Hybrid slabs made of carbon-fiber-reinforced polymer (CFRP) and concrete provide a solution that takes advantage of the strength properties of both materials. The performance of the system strongly depends on the CFRP–concrete interaction. This study investigates the shear behavior in the interface of the two materials. Eight full-scale experiments were carried out to characterize the interface shear response of these hybrid elements using different connection solutions. An untreated surface is compared to a surface with aggregates, with a novel system comprising a flexible, straight glass fiber mesh and an inclined glass fiber mesh. The experimental results show that the fabric connection improves the friction between materials and is responsible for the pseudo-plastic performance of the specimens. The inclined mesh produces a more uniform tightening effect compared to the straight mesh. In simulations via the finite element method, we used an adjusted frictional model to reproduce the experiments. Within the last six decades, many reinforced concrete structural elements have been developed under different design code regulations and using different construction techniques. They require maintenance, retrofitting, or even strengthening; see, for example, Colajanni et al. . In addiRegarding hybrid beams, they are mainly used for bridge applications; see Zou et al. . Hulatt Given that most of the FRP–concrete hybrid structures use FRP pultruded beams, it is important to highlight the work by Bank , who invFam and Skutezky  investigAl-Amery and Roberts  introducHence, there is much research interest on hybrid FRP–concrete structures, but previous studies mainly addressed bridges or cross sections composed of pultruded beams and concrete. There are few studies specifically conducted on hybrid slabs of thin CFRP laminates and even fewer on the mechanical connection between the materials.In this paper, we aim to investigate the interface shear mechanical response of hybrid CFRP sheet–concrete slabs characterized by the use of connectors such as bonded particles or a high-strength glass fiber mesh. Experimental and numerical analyses of these elements are included and compared in order to validate and analyze the performance. The connection of hybrid CFRP–concrete using a flexible material is a novel idea that is compared to the traditional roughening method using aggregates. Moreover, it has the advantage of connecting materials without the use of any steel bolts, avoiding the problem of corrosion. Finally, the manufacture of these slabs seems to be very simple and competitive in the construction market.3 of Portland cement with continuous 0 to 12 mm limestone aggregates and plasticizer. It was mixed with a water/cement ratio of 0.6, reaching a compressive strength below 25 MPa.All specimens were cast using commercial (FIASA HS-25) dry concrete  distributed in 25 kg bags. It was composed of 300 kg/mThe strength of the concrete was estimated using a non-destructive Schmidt impact hammer . Six repetitions were conducted on each specimen to estimate the average value of the compressive strength according to the ASTM method . Table 1CFRP sheets were manufactured using the traditional hand layout process on a mold of a thin steel sheet with a top-hat shape. The material was unidirectional carbon fiber Masterbrace FIB 300/50 . Each CFRP sheet had three plies with orientation [0°/90°/0°]. Epoxy resin Resoltech 1204  was brushed over every ply using a fiber/resin ratio (by weight) of 1. After impregnating the fibers, a counter mold was placed over them, and some weight was applied to it for a 48 h period to guarantee uniform impregnation. Tensile tests were conducted on eight samples extracted from the manufactured CFRP sheets according to the ASTM test  with a s2 and an average tensile strength of 45 kN/m. The mesh had a grid distribution of 25 × 25 mm, leaving empty spaces to mechanically lock the poured concrete. The grid was bonded to the CFRP sheet on the flat upper surfaces using a carbon fiber strip and the same resin (Resoltech 1024). The mesh was placed aligning the grid with the nerves of the slab in some specimens (straight specimens), while in others, the relative orientation between the grid and the nerves was 45° (inclined specimens).For some connections between the CFRP sheet and concrete, we used a flexible mesh made of MapeGrid (G220) glass fiber  with a weight of 225 g/mSolid particles of different sizes were used to increase the friction interface between the CFRP sheet and concrete. The dimension of those aggregates depended on the size of the specimen to ensure reliable manufacturing and presented a diameter between 0 and 4 mm for sand and between 5 and 12 mm for gravels. The amount of aggregates was measured by weight using 300 g of gravel and 150 g of sand, and aggregates were randomly distributed on the surface of the CFRP sheet. The aggregates were bonded by brushing the surface of CFRP with Resoltech 1024 and dropping them on.Eight hybrid specimens designed for direct shear testing were manufactured. The specimen geometry consisted of two parts with different lengths, as shown in A hydraulic jack with manual control  was placed between the two blocks of the specimen. One of the concrete blocks acted as a reaction wall while the other failed under a pushing force. The stability of the system relied on the shear stresses between the two materials. The shear test setup is shown in Force was uniformly applied through a steel loading tool (U80 steel profile)  that increased the contact area between the jack and the tested block in order to avoid local concrete damage. The applied force was increased gradually, and it was continuously measured with a 10 kN UC9 load cell . Two LVDT sensors with a range of 20 mm and 0.02% linearity were placed on each side to measure the relative displacement between the smaller block and the CFRP sheet. A data acquisition system recorded all data simultaneously.All specimens failed at the surface contact of the CFRP and concrete. The smallest block resisted up to a maximum value of force and then physically separated from the CFRP sheet. In the case of samples N and A, the failure was sudden and the load dropped instantaneously. Minor friction due to the roughness of the surfaces remained, but only for very low load values. For samples A-SM and A-IM, the failure was progressive. The load reached a maximum and the connection started to separate, but friction related to the existence of the glass fiber mesh maintained the load value. The ultimate failure occurred with a mixed mode, combining breakage of the fibers and debonding of the mesh see .The values of failure were pretty different from those of other types of connection based on bolts. Zou et al.  observed2. Moreover, the calculation of tangential strain was performed simply by dividing the average displacement measured with LVDTs (in millimeters) by the length of the small block, which was 200 mm.The force–displacement plots are shown in From the plots in From analysis of the stress variation, it is clear that the untreated surface showed an irregular response; therefore, this technique is not recommended for practitioners. It may produce non-conformities in the execution that are more severe than those that occur with hand manufacturing. The surface treatment improved the homogeneity of the results. The mean average stresses presented two groups: Case A (aggregate connections) with a level of 15.75 kPa and Cases A-SM and A-IM (mesh connections) with levels of 44.93 kPa and 34.88 kPa, respectively. This result indicates that the loads that the connections with the meshes could withstand were larger than those in other cases. Therefore, the mechanical performance of the flexible material is more competitive than that achieved by traditional roughening with aggregates.Another significant difference could be found in the shape of the plots presented in For both samples with mesh connections, the material had a positive effect. During the loading process, after the peak load, several complex types of damage took place: cracking of the concrete, debonding of the tows and the concrete, mechanical locking of the concrete in the mesh gaps, and the breakage of threads. Nevertheless, for the A-SM, damage continued to grow, and the system was unable to withstand the applied load, losing stiffness and producing a softening effect. On the contrary, the A-IM was capable of maintaining the same load level. The reason for this pseudo-plasticity lies in the mesh position.The inclined mesh has several advantages compared to the straight mesh. Firstly, the contribution of fibers to the strength comes from a tightening effect. The strength of fibers is very high compared to the levels of load, so its contribution to the load-bearing is negligible. Hence, the placement in a non-optimal direction (in terms of only the stress response) is not a limitation. Secondly, straight fibers are distributed discontinuously; there are strands only every 25 mm and, hence, there are important gaps with no fibers. Moreover, the flexibility of the perpendicular fibers cannot produce an effective locking mechanism in the gaps. On the contrary, the inclined mesh covers the whole width with its strands and does not leave any empty spaces without fibers. Moreover, the inclined threads can produce a more effective locking mechanism in the gaps. Hence, the inclined mesh provides a uniform response that helps to maintain a high level of friction.Compared to push-out tests by other authors like Zou et al. , Gong etIn order to better understand the performance of the mesh connections, some finite element simulations were performed in order to clarify the locking mechanism and the shear response of the interface between the concrete and the CFRP sheet. Both the A-SM and A-IM cases were modeled using a general-purpose finite element software program, ABAQUS  . In the The general geometry of all numerical models was the same, and it corresponded to the shortest concrete block. The concrete block and the thin CFRP sheet were considered independent solids connected at the interface surface. Glass fiber materials were modeled as beam elements with the same sections as the primary material. These were added in the corresponding direction . Details of the aggregates and the thin layer of resin or glass fiber mesh–CFRP sheet strip connector were not explicitly represented in the model and were implicitly considered in the contact between surfaces.The CFRP sheet was under a low level of stress compared to the ultimate capacity of the material. Therefore, the material composition was defined as linearly elastic. Generally speaking, the block of concrete was not damaged; only the contact zone with the different connection systems had cracks. As this zone was limited to the contact surface, it was treated separately. Hence, the concrete block was also defined as a homogeneous, linearly elastic material.Glass fiber fabrics are defined as elastic–plastic materials. The definition of the elastic branch is based on the provider’s properties, including a Young’s modulus of 72 GPa and a Poisson coefficient of 0.3. The plastic properties of the glass fiber materials were used to fit the models, and these were intended to include all the complex effects of the three-phase connection between the concrete, fabric, and CFRP sheet: sliding of the fibers, debonding of the fabric–CFRP sheet connection, and cracking of concrete around the fabric, for the cases including glass fiber meshes. The included parameters were the yielding stress of 180 MPa and consistent mass matrix formulation to obtain the shear modulus for the case of the straight mesh (A-SM), and a yielding stress of 25 MPa, transversal stiffness of 650 MPa, and slenderness compensation value of 0.9 for the definition of the plastic behavior of the A-IM cases. All these parameters were considered carefully as they are essential for the correct fitting of the experimental results presented later on.The Young’s modulus of the CFRP was experimentally obtained by testing the samples, while the Poisson’s coefficient was taken from Munoz et al. . The YouThe average concrete compressive strength was taken from The surface contact between CFRP and concrete is a complex system. Concrete cracks, and the block also generates friction with bonded aggregates. Moreover, the mesh introduces a complex tightening system that modifies the performance dramatically, as was observed in the experiment. Therefore, modeling the details of the interaction of these elements is beyond the scope of this work; additionally, there is no experimental evidence to sustain any assumption. Hence, to model this complex interface, we used a strategy of defining contacts. This approach simplifies the model but does not lose generality, and it is supported by the empirical observations. Hence, aggregates were not considered physically in the simulation, but they indirectly participate when adjusting contact properties to the experimental observations.Two models were used to represent the concrete–CFRP sheet interface; the first was a cohesive zone model  includiThe connection of the glass fiber mesh was defined as an embedded restraint in the concrete and CFRP sheet solid elements.The concrete was modeled by linear hexahedral elements of type C3D8R—an 8-node, brick-shaped, three-dimensional element with one point of integration to reduce the computational cost. According to the assumptions, the modeling of the concrete did not require precision. The CFRP sheet was modeled by linear wedge elements of type C3D6. This element type has 6 nodes and 2 integration points. The glass fiber mesh was modeled with B31 truss elements. The concrete, CFRP, and glass fiber mesh were meshed dependently with a maximum seed dimension of 15 mm. The Hex-Sweep technique was used. If a region is swept meshable, Abaqus/CAE can generate the swept mesh on a region that has been assigned the Hex.The resulting mesh can be observed in The boundary conditions were the same for both models. The bottom surface of the CFRP was simply supported. The shear load was indirectly imposed by a uniform displacement along the specimen’s longitudinal direction for all experimentally loaded faces. Finally, the CFRP face that was coplanar with the concrete face where the displacement was imposed was fixed.The analyses were carried out using a static general procedure, obtaining the shear load as the reaction associated with the imposed displacement for all time increments. The total time-period was assumed to be one second and the maximum number of increments was defined as 100.For the assumed approach of combining a frictional model to represent the CFR–concrete interaction together with embedding the mesh to model the CFRP–mesh–concrete response, there is a consistent relationship with the achieved results. The inclination of the mesh (A-IM) allowed us to consider the tensile response of the wires of the glass fiber fabric because of their relative orientation with respect to the load. A part of this load is axially resisted by the wires, which progressively develop a nonlinear response. This process allowed the load to continuously increase, although at progressively reduced stiffness up to failure. In contrast, the mesh only contributes to resisting the applied load through the shear mechanism for the A-SM cases. Hence, when the maximum shear strength is reached, all mesh capacity is lost, and only the frictional connection between the CFRP and concrete is available to resist the applied shear load. This theoretical analysis is translated in the experimental and numerical simulation results into the clear maximum peak of the force, followed by a force decrease, culminating in a constant residual shear strength due to the concrete–CFRP sheet frictional interaction.It should be noted that the obtained shear stiffness of the specimen is very similar in both cases (A-SM and A-IM), as is the slope after yielding. However, the yielding point is, in fact, influenced by the resisting mechanism of the embedded mesh, being lower for the combined axial-shear case (A-IM) than for the pure shear case (A-SM).The numerical results in terms of force reaction vs. displacement are compared to the average curve of the experimental results for each case. It was observed that the proposed numerical model accurately predicts the mechanical response of the experimental tests for both mesh orientations.No numerical values of the fitting quality are provided because the ad hoc definition of some of the variables of the numerical model would invalidate this quantification. The fitting quality can be observed through the comparison of the full force–displacement curves in The theoretical behavior inferred for both novel connection systems considering the embedding of a flexible glass fiber mesh can be seen in Although further research is necessary to accurately fit the defining properties of these models , the description of the qualitative response in Specimens without connectors (N) and those with only aggregate connections (A) presented the weakest shear resistance. The performance was fragile in all cases, with sudden failure. The post-critical response was related to merely friction between materials, not allowing significant energy dissipation. Both connections are considered unreliable for real works, disregarding even the classical connection approach of increasing the roughness via aggregate adhesion.Embedding a flexible structural glass fiber material as a connector between the CFRP sheet and the concrete increased the shear load-bearing capacity and enhanced the post-peak shear strength, changing the failure mode from sudden to progressive. Moreover, the system with the mesh connection could dissipate much more energy than that with the aggregate connection. The curve performance of the inclined mesh showed some similarities to a bolt connection.The numerical simulations combining a frictional model and the embedding of a fabric were capable of reproducing the experimental curves. Adjustment values must be taken with caution but are consistent with the results.The numerical model explains that the orientation of the fabric plays an important role in the structural response because of the possibility of combining two resisting strategies, axial and shear, when inclined with respect to the load direction.A real locking mechanism is a complex combination including concrete cracking, debonding of fibers and concrete, sliding of fibers, locking concrete in the grid gaps, friction between concrete and FRP, and breakage of fibers. The proposed strategy simplifies this complex combination of resisting mechanisms into only two equivalent interfaces: the frictional interface between concrete and FRP and the embedded beam elements between concrete, mesh, and FRP.The achieved level of load is less than that for a traditional bolt system but it has the advantage of not using steel connectors, and it involves a very simple manufacturing process for thinner slabs.In this research, an experimental study and numerical analysis of CFRP–concrete hybrid elements subjected to in-plane interface shear tests were carried out. The mechanical responses of different CFRP–concrete connection strategies, including a novel proposal based on embedding a fiber material, were analyzed and discussed. A simplified numerical model was fitted with the experimental results. The following concluding remarks can be made:


By frequency-band extracting, we experimentally and theoretically investigate time-delay signature (TDS) suppression and entropy growth enhancement of a chaotic optical-feedback semiconductor laser under different injection currents and feedback strengths. The TDS and entropy growth are quantified by the peak value of autocorrelation function and the difference of permutation entropy at the feedback delay time. At the optimal extracting bandwidth, the measured TDS is suppressed up to 96% compared to the original chaos, and the entropy growth is higher than the noise-dominated threshold, indicating that the dynamical process is noisy. The effects of extracting bandwidth and radio frequencies on the TDS and entropy growth are also clarified experimentally and theoretically. The experimental results are in good agreements with the theoretical results. The skewness of the laser intensity distribution is effectively improved to 0.001 with the optimal extracting bandwidth. This technique provides a promising tool to extract randomness and prepare desired entropy sources for chaotic secure communication and random number generation. Semiconductor laser subject to optical feedback is an all-optical and versatile structure to produce high-dimensional chaotic signals, which provides excellent test beds for the study of nonlinear dynamics ,2,3. IntUntil now, many schemes of TDS suppression for chaotic laser have been reported, which are mainly divided into two types of approaches. The first type for TDS suppression relies on different alternative mechanisms, such as mutually coupled system ,16,17, fIn this paper, the TDS suppression and entropy growth enhancement via frequency-band extracting are investigated experimentally and theoretically in a chaotic optical-feedback semiconductor laser. At the optimal extracting bandwidth, the relationship between TDS and entropy evolution are investigated over the wide range of injection-feedback parameters. The chaotic dynamics is assessed by the noise-dominated threshold. We also experimentally and theoretically study the effects of extraction bandwidth and radio frequency on TDS and entropy growth. The experiment agrees well with the theory. The statistical distribution of chaotic laser intensity is improved at optimal extracting bandwidth, and the measured skewness of the intensity distribution is negligible. By use of this technique, desired chaotic sources can be prepared for physical random number generation and secure communication.N is the carrier density. L is the length of the external cavity and c is the speed of light. e is the electronic charge. The nonlinear optical gain is expressed as:A semiconductor laser with external optical feedback as a typical complex dynamical system can be well modeled by the Lang–Kobayashi (LK) equations . The LK The original chaotic signals are acquired and improved by a frequency-band extraction, which can effectively suppress the TDS of high-dimensional chaotic laser signals. The theoretical model of frequency-band extraction is described as follows:The common approaches to quantify the TDS are the autocorrelation function, permutation entropy and delayed mutual information. In this work, we take the peak value of the autocorrelation function (ACF) at the optical feedback delay time to quantify the TDS. The ACF is defined as follows:d and embedding delay time d is often recommended between 3 and 7 in practice. Due to time constraints, we choose PE is a robust complexity measurement based on the relative amplitude of time series values. Compared with Lyapunov exponent, strangeness of strange attractors and Kolmogorov–Sinai entropy, the advantages of using PE as a metric are its implementation simplicity, flexibility, invariance, and robustness . These aFor a given time series s) can be mapped into a unique permutation The ordinal pattern of the vector at the time (The probability distribution The unnormalized PE is defined asThen, we defined the entropy growth At the external optical-feedback delay time, the entropy growth d and indicates that the chaotic dynamics is dominated by noise. The noise limit of entropy growth is d, and it indicates that the dynamics is deterministic. For In addition, it should be noted that the entropy growth To experimentally evaluate the output signals of the chaotic laser, we first measured the power spectrum of original and extracted chaotic laser operating at bias current In order to further study the chaotic dynamics and entropy evolution, we experimentally measured the ACF and entropy growth, as shown in Then, we experimentally and theoretically investigated the influences of injection current and feedback strength on the chaotic dynamics and entropy growth and characterized the relationship between the entropy growth J and For clarity, we also studied the influences of RF frequency and extracting bandwidth on the TDS suppression of the extracted chaotic laser. The LPF bandwidth affects the minima of The frequency-band extraction not only effectively suppresses the TDS of the chaotic laser, but also improves the statistical distribution of the chaotic intensity. In summary, we theoretically and experimentally investigate the TDS suppression and entropy growth enhancement of an optical-feedback chaotic laser via frequency-band extracting. By 3 GHz effective bandwidth extracting, the TDS suppression ratio is reached to 96% with the minimum


The concept of liquid metal membranes for hydrogen separation, based on gallium or indium, was recently introduced as an alternative to conventional palladium-based membranes. The potential of this class of gas separation materials was mainly attributed to the promise of higher hydrogen diffusivity. The postulated improvements are only beneficial to the flux if diffusion through the membrane is the rate-determining step in the permeation sequence. Whilst this is a valid assumption for hydrogen transport through palladium-based membranes, the relatively low adsorption energy of hydrogen on both liquid metals suggests that other phenomena may be relevant. In the current study, a microkinetic modeling approach is used to enable simulations based on a five-step permeation mechanism. The calculation results show that for the liquid metal membranes, the flux is limited by the dissociative adsorption over a large temperature range, and that the membrane flux is expected to be orders of magnitude lower compared to the membrane flux through pure palladium membranes. Even when accounting for the lower cost of the liquid metals compared to palladium, the latter still outperforms both gallium and indium in all realistic scenarios, in part due to the practical difficulties associated with making liquid metal thin films. Hydrogen selective membranes have the potential to enable efficient and low-cost hydrogen separation and purification. Dense membranes, often based on palladium, have specifically attracted a lot of attention in this area, as they feature a relatively high flux alongside a high selectivity towards hydrogen. The relatively small size of the interstitial sites through which the permeating species should diffuse, along with favourable activity for the dissociation of hydrogen compared to other molecules enables this high selectivity for hydrogen ,2. Many Recently, the concept of liquid metal membranes was introduced, adding to the growing collection of non-palladium-based hydrogen selective membranes . It is hμm) . Hence, Despite this, the initial performance of the liquid metal membrane concept justifies further investigations to elucidate the fundamental advantages of the concept and provide a basis for optimization of these novel separators. In the current paper, the transport of hydrogen through gallium- and indium-based liquid metal membranes will be modeled and compared to palladium-based solid membranes in an effort to assess which of the liquid metals is most suited for hydrogen separation and to investigate the possibilities for increased performance by means of a rate-determining step analysis.To gain the required fundamental understanding of the processes and phenomena involved, a quantitative description of the membrane flux is essential. It is generally accepted that transport of hydrogen through a dense membrane occurs through the solution-diffusion mechanism, which features five steps , as shown schematically in In absence of a sound justification that Sieverts’ law can be directly applied, a more fundamental approach is required wherein all elementary reaction steps describing the kinetic and diffusion events are treated and wherein no approximation on a possible rate-determining step is invoked a priori. A microkinetic model built on these grounds enables the optimization of existing membranes by means of a sensitivity analysis. Such models have been published in previous works, and will be appended for use in the current study to allow for thorough analysis of the performance of gallium- and indium-based liquid metal membranes.This paper is organized as follows. First, the model is introduced and the main assumptions are outlined. Next, the model is validated based on experimental findings for solid palladium membranes. Thereafter, predictions regarding liquid metal membranes are presented, along with a validation of the calculated diffusion coefficient. The most salient finding of this study is the fact that, contrary to what was assumed in earlier works, the dissociative adsorption of hydrogen is the slowest step in the permeation mechanism in most cases. Due to this, the high diffusion coefficient of hydrogen in the liquid phase cannot be exploited and the performance of liquid metal membranes based on gallium or indium will not exceed that of the conventional palladium membrane in any realistic scenario.The microkinetic model employed in this study builds upon the work of Yen et al., which in turn is based on the work by Ward and Dao ,15,20. TAs mentioned in the introduction, it is generally accepted that hydrogen is transported through a dense membrane in the following sequential steps also see  13,15,2,215,22.Gas-phase diffusion of molecular hydrogen from the retentate bulk to the membrane surface.Dissociative adsorption of molecular hydrogen on the membrane surface at the retentate side.Subsurface penetration of atomic hydrogen.Diffusion of atomic hydrogen from the retentate side to the permeate side of the membrane.Subsurface egression of atomic hydrogen.Associative desorption of molecular hydrogen on the membrane surface at the permeate side.Gas-phase diffusion of molecular hydrogen from the membrane surface to the permeate bulk.The objective of this study is to look into the differences between palladium-based membranes and liquid metal membranes and to be able to provide a basis for optimization of the latter. This means that optimization of the separation module, to minimize external mass transfer resistances, is out of scope of the current paper. With this in mind, the first and the last step will be left out of consideration (as well as transport through the porous support), yielding the elementary reaction steps shown in It can be seen that steps 4 and 5 are the permeate-side counterparts of steps 2 and 1, respectively. This means that usually, these steps do not need to be treated separately; their kinetic description may be integrated in the description of their retentate-side counterparts . In the Following the analogy of Deveau et al., the activity coefficients were set to unity by which the rates of the different elementary reaction steps can be expressed as a function of surface coverage and concentration, as shown in Equations –(6) 20,,20,23. IEquations –(6) requIt should be noted that the diffusion coefficient of a solute in a liquid is commonly calculated through the Stokes–Einstein equation, being a less complicated approach. The diffusion coefficient was calculated in this way for liquid gallium and liquid indium, but the obtained values differed three orders of magnitude from experimental data and hence this approach was abandoned and Equation (9) was adopted instead ,25. A rea and The information available does not allow for every pre-exponential factor to be calculated directly via Equations (10) and (11). Hence, Equation  is applirequency . Alternarequency . These crequency . The curections) .(12)Λ1+N parallel trial systems with sufficiently different (randomly generated) initial values were constructed and executed. Any trial systems that converged to values containing negative surface coverages, concentrations or fluxes were obviously discarded. Moreover, cases where all values were positive but N.The given equations constitute the framework of the current model. After all chemokinetic parameters have been established, Equations –(6) may ode15s algorithm of Matlab was used, which is a variable step, variable order method based on backward difference formulas for stiff problems [N parallel trial systems is validated. It should be emphasized that it could be considered to use time-integration for all calculations in this study. However, while this method is considered to be more robust, solving using the proposed methodology is computationally faster and has the additional advantage that it can trivially be parallellized by the construction of N parallel trial systems.For validation of the computational method, the obtained solution was compared to the solution of a more robust method: time-integration. The system of equations was rewritten to differential form and was also time-integrated until the steady-state solution was reached. Herein, the system was initialized with surface coverages and concentrations of zero. The problems . For eacThe parameters required for the implementation of the microkinetic model are determined based on the following assumptions. Where applicable, justification of these assumptions is provided in this section.Liquids are assumed to be quasi-crystalline, meaning that a crystal structure can be employed in describing the liquid.There is no expansion or contraction of the lattice due to hydrogen dissolution.There is no interaction between adsorbed and dissolved species amongst themselves.The host metal contains no defects, grain boundaries, internal friction or other crystal non-idealities.The membrane is modeled as a single phase and phase transitions, such as liquid–solid, FCC interstitials always occupy octahedral sites whilst BCC interstitials always occupy tetrahedral sites. Only octahedral-octahedral jumps or tetrahedral-tetrahedral jumps are allowed. Only jumps to nearest-interstitial sites are allowed.The unit cell is assumed to expand proportionally to the temperature-dependent density.Only pure metals can be modeled, as relevant parameters are hard to obtain for alloys.The ideal gas law is valid.The energies required for the modeling of the liquid metals are determined via the Pauling Bond Valence-Modified Morse Potential (PBV-MMP) methodology by Yen et al. . Their bTo determine the relevant energies within this framework, the metal-hydrogen binding energy and the coordination numbers of the different binding states are required. The former is taken from the literature and tabulated in For the relevant coordination numbers, geometric considerations are required, which are also largely based on the work of Yen et al. . In thisctively, ,40. As fctively, ,38.This leaves two final structural parameters. Firstly, the saturation solubility of hydrogen, quations  and (21)Using the geometric considerations for the different metals, the liquid free volume can be estimated, again taking into account the non-cubic liquid metal unit cells. With this parameter, the entropy change of dissolution can be approximated. This is again done via the framework of Yen et al. . The freIn considerations regarding the entropy of adsorbed species, a different approach was adopted, assuming constrained two-dimensional motion of adsorbates on the membrane surface. In this approach, the overall adsorption entropy takes the form of Equation . The entol−1K−1 ,46. It sol−1K−1 .(22)ΔSiIt was found that the postulated approach provided a high entropy in the adsorbed state , which is close to the molecular gas-phase entropy (meaning that ten full . For reften full . This faten full .(28)ΔSiWhilst including a coverage-dependent term in the determination of parameters does complicate the process to obtain a numerical solution, implementation of Equation  results unlikely ,20,49,50Validation of the current model is complicated by the scarcity of experimental liquid metal membrane data. To overcome this complication, this study uses the broad applicability of the proposed model and taps into the abundance of data available for palladium membranes. For the initial validation, permeability data of experimental cases for self-supporting palladium membranes is used, as shown in In order to validate the current model, the permeability of a pure palladium membrane was calculated over a broad range of temperatures. Conventionally, these calculations are done by means of the Sieverts’ constant. Since this parameter is not explicitly defined in the current model, the permeability was calculated via Equation . Note thThe calculated values are in good agreement with data from the literature. This shows that the current model is able to adequately describe the hydrogen permeability of palladium membranes as a function of temperature. The calculated activation energy for permeation is fitted with a value of eability .To continue the model validation, the calculated liquid metal diffusion coefficient is compared to experimental data. For gallium, two correlations describing the diffusion coefficient of hydrogen as a function of temperature are available in the literature. The correlations differ quite significantly; the activation energy has a value of he other ,57. The For indium, there is only one source of experimental data available. Calculations for this liquid metal yield an activation energy of kJmol−1 . In the For both metals, the hydrogen diffusion coefficient is approximately an order of magnitude higher than the self-diffusion coefficient ,59. ThisFor a graphic comparison of the diffusion coefficients in the liquid metals relative to the diffusion coefficient in palladium, the calculated values for the three metals are plotted in It is anticipated that the influence of surface phenomena is greater in liquid metal membranes, as there is a significant energetic barrier present for the dissociative adsorption of hydrogen in the two liquid metals under study. In the spirit of the pioneering studies by Ward and Dao, the relative influence of the different steps in the permeation process can be made quantitative through a rate-determining step analysis . In Figuickness) ,60. The Y-axis. It is seen that for the specified thickness and over the temperature range investigated, the rate-limited flux of a gallium membrane spans 12 orders of magnitude whilst the flux of a palladium membrane spans only 9 orders of magnitude. Moreover, it can be seen that for palladium, the relevant steps are desorption and diffusion (which is in agreement with the literature), whilst for gallium and indium, adsorption and diffusion are critical steps [An initial point of interest in the rate-limiting step analysis is the difference in range of the al steps ,50. OverIn this assessment, the diffusion-limited flux was determined in the situation where To further investigate whether the diffusion-limited regime may indeed be broader, evaluation of the membrane flux as a function of thickness and temperature is done by full model calculations, shown in It can be observed that at very high temperatures, indium foils could outperform palladium foils of 100 The presented results from the microkinetic modeling study show that palladium will outperform the liquid metals under study in virtually all realistic cases. One of the few remaining advantages of gallium and indium compared to palladium would be the lower price per kilogram. The price of palladium is assumed to be EUR 64,735 per kg (from Johnson Matthey as of October 2021), whereas the price of gallium is EUR 599 per kg and the price of indium is also EUR 599 per kg . This means that both metals are 108 times as cheap as palladium. Through The data in This analysis shows that the current concept has a lot in common with the group V metals, more established non-palladium membrane materials. These metals were also praised for their high diffusion coefficient, but their catalytic activity towards the dissociative adsorption of hydrogen is lacking ,62. For Based on the results from this microkinetic modeling study, it can be concluded that liquid metal membranes for hydrogen separation based on gallium or indium will likely operate in the adsorption-limited regime. Hence, optimization of these membranes cannot be achieved through a reduction of membrane thickness. This allows for thicker, more stable, membranes, but it was shown that these liquid metal membranes will underperform supported thin-film palladium-based membranes in all realistic cases, even when accounting for the much lower cost of the liquid metals. The application of the concept of liquid metal membranes is therefore seriously hampered, similarly to membranes based on group V metals, which also lack sufficient catalytic activity for the dissociation of hydrogen. Especially when taking into account the experimental complications that were experienced in producing thin liquid metal membranes that are stable under relevant gas atmospheres, it is to be questioned whether the proposed liquid metal membranes are ever a feasible alternative for conventional palladium-based membranes.


Subsidence induced by groundwater depletion is a grave problem in many regions around the world, leading to a permanent loss of groundwater storage within an aquifer and even producing structural damage at the Earth’s surface. California’s Tulare Basin is no exception, experiencing about a meter of subsidence between 2015 and 2020. However, understanding the relationship between changes in groundwater volumes and ground deformation has proven difficult. We employ surface displacement measurements from Interferometric Synthetic Aperture Radar (InSAR) and gravimetric estimates of terrestrial water storage from the Gravity Recovery and Climate Experiment (GRACE) satellite pair to characterize the hydrological dynamics within the Tulare basin. The removal of the long-term aquifer compaction from the InSAR time series reveals coherent short-term variations that correlate with hydrological features. For example, in the winter of 2018–2019 uplift is observed at the confluence of several rivers and streams that drain into the southeastern edge of the basin. These observations, combined with estimates of mass changes obtained from the orbiting GRACE satellites, form the basis for imaging the monthly spatial variations in water volumes. This approach facilitates the quick and effective synthesis of InSAR and gravimetric datasets and will aid efforts to improve our understanding and management of groundwater resources around the world. However, subsidence induced by groundwater depletion, while causing issues such as permanent storage loss and infrastructural damage, has been difficult to quantify and predict2. The hydrodynamics of the Tulare basin are quite complicated and the important components of the geologic system are not completely characterized.The Tulare Basin is an indispensable groundwater source within the Central Valley Aquifer system, which provides drinking water for 6.5 million residents and supports an agribusiness critical for the entire nation3. The main hydrological driver of deformation in a porous medium are typically changes in the total stress minus the fluid pressure within a given aquifer, a quantity known as the effective stress. In an unconfined aquifer, the fluid pressure is moderated by the possible upward movement of the water table and the coupling to the atmosphere, forming a constant pressure boundary condition. Ground deformation is often most strongly influenced by changes in the fluid volume in a confined aquifer, where the effective pressure can build up to large values. In addition, water volume changes in an overlying unconfined aquifer are coupled to the deeper aquifer, as it exerts a downward force upon the confining layer, leading to compressive stress and inducing further compaction. Thus, gravity and deformation data can have differing sensitivities to changes in the confined and unconfined aquifers and may be used together to distinguish changes in each. The presence of long-term inelastic deformation further complicates the interpretation of surface deformation, at it is related to earlier fluid volume changes and not to current aquifer conditions5.Furthermore, the complex hydrology of the basin, with multiple sources and sinks, can cause substantial changes over periods as short as a few months. Thus, orbiting satellite-based systems are well suited for monitoring variations within the Tulare basin at various timescales. Here, we consider Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) observations, which provide estimates of line-of-sight (LOS) displacements of the Earth’s surface, and terrestrial water storage (TWS) changes gravimetrically measured from NASA’s Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (FO) missions. Both data sets are sensitive to hydrologic variations in the Tulare basin and each has its own set of factors that complicate any analysis. For example, changes in the gravity field sensed by GRACE and GRACE-FO can be traced to a variety of sources such as ground movement, soil moisture, water table variations, and snow cover. Thus, it is difficult, if not impossible, to distinguish between water mass changes in the shallow unconfined aquifer and in the underlying confined aquifer using gravitational observations alone. Observations of surface deformation have their own issues, primarily due to the complicated relationship between ground motion and hydrological changesIn this paper, we describe an approach for removing longer-term deformation and extracting monthly variations in surface deformation. These shorter-term variations provide insight into the seasonal factors influencing the aquifer and its deformation. Combining the monthly displacement data with GRACE estimates of mass changes, we develop an inverse problem for water volume changes in a simplified model of the Tulare basin consisting of an unconfined near surface aquifer and an underlying confined aquifer Fig. . We show11. In this technique, phase shifts between radar returns gathered during successive passes of an orbiting satellite are used to estimate changes in the range or the line-of-sight (LOS) displacement12. Our estimates of LOS displacement were obtained from the Sentinel radar returns using the small baseline subset (SBAS) method15. The observed displacements are dominated by long term subsidence associated with the excessive pumping of groundwater from the Tulare basin5  is currently the most widely used technique for monitoring surface deformation associated with groundwater variations and subsidence in the California Central Valley16. Two time series, for locations corresponding to the Global Positioning System stations LEMA (near the town of Lemoore) and CRCN (near the town of Corcoran), are shown in the Supplementary Figure S1, along with the daily changes obtained from the GPS observations. The InSAR LOS displacements are with respect to a reference point that is assumed to be stationary, while the GPS estimates are with respect to a reference datum such as the North American plate. After accounting for this difference we find general agreement between the InSAR and GPS estimates of line-of-sight displacement at the two stations.A three-month moving window was used to compute mean displacements and standard errors for each time series, as shown in Fig. 6. As is clearly seen in Figs. 11. This uplift spreads laterally in February, March, and April, joining to form a larger northwestern region trend along the deeper Tulare basin. Interestingly, the trend of both the GPS and InSAR LOS displacements are positive throughout 2017 . These increases stand in contrast to the significant downward slopes observed in the years 2015, 2016, and 2018.The Sentinel-1 mission had a repeat time of 12 to 24 days through the entire observational period, and the derived line-of-sight displacement is resolved at a spatial resolution of 90 mThough we will only analyze a subset of the LOS estimates shown in Fig. This is followed by two months of reduced uplift and even subsidence in some areas of the Tulare basin in June and July, though the region of the largest uplift in April and May is still rising. The area of uplift parallels that observed for April of 2019 and plotted in Fig. 18. In particular, it is not possible to distinguish between changes in the shallow unconfined aquifer and the deeper confined aquifer with satellite-based gravity data. There have been several discussions and comparisons of InSAR and GPS data to GRACE estimates of mass variations over time22. The two panels Fig. 26- leading to the large-scale anomalies in Fig. 27. Thus, the wet year of 2017 is not well sampled and we must look at a later time, such as after June 2018, in order to conduct a joint inversion.While the InSAR line-of-sight displacements are likely to be the most sensitive to fluid pressure and corresponding effective stress changes within the confined aquifer, GRACE gravity observations are influenced by water mass changes everywhere in the Tulare basinAn example of current GRACE estimates, corresponding to mass changes during March in 2019, are plotted in Fig. 28   28  mission planned for 2023, there should be even better constraints on temporal changes in the Tulare basin in the future. Longer wavelength L-band data, such as the ALOS-PALSAR observations36 can improve imaging in highly vegetated regions but they did not have sufficient temporal resolution for this study.More work is necessary to substantiate and fully understand these results, and to determine the most important contributions to ground deformation. For example, continued monitoring is needed in order to determine if the patterns observed around April of 2017 and 2019 are truly periodic seasonal changes driven by the groundwater hydrology. Detailed modeling of the flow and the propagation of subsurface fluid pressure changes will help in understanding the dynamics of these results and other observations28. However, due to factors such as layering, it is frequently true that the vertical permeability is an order of magnitude less than the horizontal permeability so that other parts of the basin may contain partially confined aquifers, particularly over short time intervals. The underlying sequence of layers collectively forms a confined aquifer and effective stress changes within this volume lead to changes in the vertical location of any overlying deformable boundaries, such as the ground surface. The upper boundary of the confined aquifer is subject to a downward force, due to the weight of the overlying sediments and water, including soil moisture and snow, and sediment volumes. It is also subject to any changes in effective stress within the confined aquifer itself. The relationship between a change in the confining pressure 37B is Skempton’s coefficient34. We will assume that the mass of the overlying solid material is constant and that only the overlying water volume is changing, so thatg is the gravitational constant, and Our analysis is based upon the simplified model of the Tulare basin outlined in Fig. 40. A finite incremental change in solid volume for the i-th grid block, obtained from the InSAR observations, is noted by We can estimate the solid volume changes equation  we can w26. To mitigate these issues we use the mascons to generate gravitational changes at a height above the Earth’s surface. We use a height of 6000 meters as that is the lateral dimensions of our grid blocks for the inversion. An additional increase in elevation will also increase the sensitivity of the gravity values to changes that are outside of the Tulare basin. Thus, we solve a forward problem and calculate the gravity changes at a height of 6000 meters and then use these changes as data for an inverse problem for water volume changes in the confined and unconfined aquifers31. Such Green’s functions have proven useful in the analysis of airborne gravity and gravity gradiometry data32. The inverse problem for the water volume changes, compatible with the InSAR volume change estimates, involves solving the linear system defined by equations ..26. To mSupplementary Information.


Demonstration of gastric endoscopic submucosal dissection using the pocket-creation method at the angle along the lesser curvature and fornix. However, the stomach has a wide lumen that makes gastric ESD difficult in some locations. In difficult locations in the stomach, sometimes a distant or a vertical approach toward the muscularis is unavoidable and results in lengthy procedure times, the occurrence of adverse events, and a low-quality resected specimen. Unlike colorectal ESD, changing the patient’s position during the procedure is very difficult during gastric ESD when the patient is under conscious sedation. Use of the traction method and a multibending endoscope are viable options to facilitate ESD in difficult circumstances.The pocket-creation method (PCM) is a novel strategy to achieve safe and high-quality ESD.www.VideoGIE.org).Even in the wide lumen of the stomach, a stable antegrade approach can be obtained using the PCM. We here present 2 representative cases of gastric superficial lesions resected by ESD with the PCM (First, a minimal mucosal incision is made at least 5 mm from the edge of the tumor . Second,A 70-mm flat lesion was located at the angle along the lesser curvature A. In theA 12-mm elevated lesion was located at the fornix A. In theThe greatest advantage of the PCM in gastric ESD is stabilization in the pocket at any location in the stomach. When the conventional method is used, the difficulty of gastric ESD is strongly influenced by the location, unlike in other alimentary organs with narrow lumens, such as the esophagus and colorectum. To resect lesions located along the lesser curvature at the angle and fornix, retroflexion is generally necessary using the conventional method. However, retroflexion can make approaching the lesion difficult, and sometimes a distant approach is unavoidable. With a distant approach, endoscopists have to protrude the sheath of the endoknife in the gastric lumen, leading to rough and unstable movements. In such a situation, submucosal dissection without visualization of blood vessels or the muscularis increases the risk of bleeding and perforation. Even if the endoscopic approach is straightforward, a vertical approach is inevitable at the gastric angle and fornix. The vertical approach makes dissection difficult and increases the risk of damaging the muscularis. The PCM enables an antegrade approach regardless of the location and without need for special devices such as a multibending endoscope or traction tools.,There are some reports about the usefulness of the PCM in overcoming other challenging situations, such as complicated anatomy and submucosal fibrosis. A gastric neoplasm involving the pyloric ring is among the difficult situations encountered in ESD of gastric lesions. The submucosa under the tumor must be dissected, getting over the firm and high muscularis at the pyloric ring; then the endoscope approach becomes vertical to the sphincter and the tip of the endoscope goes into the lesion, resulting in damage to the specimen. In addition, severe submucosal fibrosis leads a low en bloc resection rate, lengthy procedure time, and increased adverse events.,In the pocket-opening procedure in the final stage of PCM, loss of stabilization creates a difficult situation in some locations. We always deal with this by starting to open the pocket from the gravity side in a step-by-step manner.In this video, we illustrated 2 cases that would be difficult using the conventional method because of their location. However, the PCM is not only useful for conquering lesions at difficult locations but also for resecting routine lesions more easily. The PCM is a simple technique to achieve safe ESD, facilitating a tangential approach that enables retrieval of a specimen with a thick submucosal layer by selecting the dissection level. Although gastric ESD is widely performed at many institutions, endoscopists struggle to resect superficial gastric lesions under difficult conditions. Gastric ESD using the PCM can be performed with a uniform strategy, regardless of the location of the lesion, and it is more straightforward for the operator than conventional methods. We believe that the PCM is a universal strategy for gastric ESD.


In this paper, a multiband noncontact temperature-measuring microwave radiometer system is developed. The system can passively receive the microwave signal of the core temperature field of the human body without removing the clothes of the measured person. In order to accurately measure the actual temperature of multilayer tissue in human core temperature field, four frequency bands of 4–6 GHz, 8–12 GHz, 12–16 GHz, and 14–18 GHz were selected for multifrequency design according to the internal tissue depth model of human body and the relationship between skin depth and electromagnetic frequency. Used to measure the actual temperature of human epidermis, dermis, and subcutaneous tissue, a small and highly directional multiband angular horn antenna was designed for the radiometer front end. After the error analysis of the full-power microwave radiometer, a novel hardware architecture of the microwave interferometric temperature-measuring radiometer is proposed, and it is proven that the novel interferometric microwave radiometer has less error uncertainty through theoretical deduction. The experimental results show that the maximum detection sensitivity of the novel interferometric microwave temperature-measuring radiometer is 215 mV/dBm, and the temperature sensitivity is 0.047 K/mV. Compared with the scheme of the full-power radiometer, the detection sensitivity is increased 7.45-fold, and the temperature sensitivity is increased 13.89-fold. At present, temperature measurement can be divided into contact temperature measurement and noncontact temperature measurement. As a representative of contact temperature measurement, the mercury thermometer has the advantages of high accuracy and stable performance, but its measurement speed is slow and cross-infection is possible . NoncontBecause clothing has a very weak attenuation effect on microwave signals, a radiometer in the microwave band can passively receive the microwave signal of human body temperature radiation through clothing, which allows measuring the true temperature of the human body. Microwave radiometers can also provide real-time, noncontact temperature monitoring for intensive care unit patients at appropriate distances, reducing the number of times healthcare workers come into contact with patients. Especially in high-risk infectious wards, the probability of infection can be greatly reduced . In addiA microwave radiometer can passively receive the electromagnetic wave radiated by the human body . After tIn 2015, Pi et al. used a C-band receiver to match a 4 GHz monopole antenna for contact and noncontact measurement of water temperature. In contact measurement, the temperature sensitivity was 0.051 K/mV . In the From 2000 to 2004, Hand et al. designed a five-band Dicke radiometer system to monitor the temperature of infants’ central brain ,19,20. AIn 2013, Wang Bin designed a Ka-band AC radiometer to measure human skin temperature by matching a direct detection receiver with a Cassegrain antenna . In 2019In 2018, Ubaichin et al. adopted an S-band full-power microwave radiometer . Due to The technical route of the overall scheme proposed in this paper is shown in Considering that the human body is made up of many tissues, each with a different medium, its dielectric constant, conductivity, and oxygen content in red blood cells will affect electromagnetic signals during noncontact human body temperature measurement . The penIn order to detect the temperature of the three layers of human skin tissue, and considering the noncontact method of human body temperature detection, this paper designed a pyramidal horn antenna for the front end of the microwave temperature-measuring radiometer. In this paper, the angular horn antenna was connected to the rectangular waveguide, and the open surface of the waveguide was gradually enlarged. By changing the matching relationship between the waveguide and the free space, the reflection coefficient of energy was reduced. Thus, the microwave signal of human body temperature radiation could be better received.The angular cone horn antenna is formed by the gradual expansion of the feed waveguide at a certain angle. Antenna schematic diagram of E-plane and H-plane are shown in The optimum unconstrained directivity occurs when To design a small, highly directional antenna that can measure the temperature of the core tissues of the human body. In this paper, half-power beam width and antenna direction is taken as the constraint condition . TherefoIn the process of antenna design, the beam angle When k, and the approximate coefficients of the functions are known.The directivity When The directivity When According to the above three situations, On the basis of the antenna size calculated above, this paper used COMSOL Multiphysics software to carry out the simulation design. The simulation results of the antenna index measured in each frequency band are shown in In Following design, a third-party organization was invited to make the antenna according to the designed 3D CAD drawings using machine tool cutting. The process is shown in Previous studies on microwave radiometer temperature measurement mainly adopted a full-power structure. In the existing literature, a full-power radiometer with high sensitivity in a single band was mainly implemented. Therefore, a multiband full-power microwave temperature-measuring radiometer was first constructed in this paper. The architecture of the multiband full-power microwave temperature-measuring radiometer included a multiband angular horn antenna, low-noise amplifier (LNA), cavity filter, RMS power detector, and analog-to-digital converter (ADC). The block diagram and prototype are shown in In order to verify the feasibility of the full-power microwave radiometer, a complex correlator was added to the structure of the full-power microwave radiometer to obtain the output correlator circle . The maiBecause the full-power microwave radiometer uses an RMS power detector to realize the detection function, and because an analog complex correlator has higher theoretical accuracy than a digital complex correlator and is more suitable for circuits with wider system bandwidth, the full-power microwave temperature-measuring radiometer was designed to use an additive analog complex correlator . A blockIn this paper, sinusoidal excitation was added to the front end of the complex correlator for frequency domain simulation, and the actual device parameters were introduced into the simulation model for simulation. The phase was swept at a 0°–360° phase difference and fixed frequency, and the points corresponding to the data were plotted and combined to form a complex correlation circle with the in-phase correlation component and orthogonal correlation component as coordinates. The shape and center position of the generated complex correlator can intuitively reflect whether the internal circuit of the complex correlator is distorted. The complex correlation circle generated by the ideal complex correlator has no deviation in its center and no distortion in its shape . Figure In order to ensure the accuracy and authenticity of the simulation results, a vector network analyzer was used to measure the S-parameters of each module and connection line in the microwave radiometer during the verification process. The corresponding SNP file was added to the simulation system of the full-power microwave radiometer. T under standard resistance can be solved. At the same time, the input power can be calculated by substituting the corresponding temperature T into Equation (13) of thermal noise.In this paper, a phase scanning simulation was carried out when the input end of microwave radiometer was connected to a 50It can be seen from the simulation results that the shape of the generated correlator circle was changed, which means that the complex correlator constructed with a full-power structure was not ideal.It can be seen from An additive analog complex correlator is composed of power splitter, orthogonal coupler, diode square law detector, and differential amplifier. A 0° power splitter is used, and the phase of each power splitter on the output phase reference surface should be strictly equal. The phase of signal input terminal IN of the 3 dB orthogonal coupler is equal to that of the direct terminal 0, and the phase difference between the signal input terminal IN and the direct terminal 0 and coupling terminal −90 is 90°. Diode square law detectors are used to detect power. The differential amplifier is used to subtract the differential mode signal of two signals and to amplify the common mode signal.Based on the principle in It can be obtained from When the radiometer uses a wide-band thermal emitter input, the response is integrated over the entire bandwidth of the receiver. For the additive analog complex correlator, the output results of the additional amplitude error and phase error are expressed asThe power splitter PWR1 and 3 dB orthogonal couplers HYB1, HYB2, and HYB3 in the complex correlator are assumed to be unbalanced in power and phase. By setting the phase difference of the output of two ports of the power splitter PWR1 as The phase differences in the 3 dB orthogonal coupler HYB1 are Furthermore, assuming that all parts of the microwave front end of the interferometric correlator are ideal except the analog complex correlator, then Suppose that the DC component has been removed by certain means. Then,For the case where When the input of the multiplicative analog complex correlator is as shown in Equation (14), signals The power splitter PWR1 and 3 dB orthogonal coupler HYB1 in the complex correlator are assumed to be unbalanced in power and phase. By setting the phase difference of output of two ports of power splitter PWR1 as When the signal is transmitted to 3 dB orthogonal coupler HYB1, the phase difference between the coupling port and the through port is If only the phase error exists in the real and imaginary parts of the analog complex correlator, it can be obtained according to Equations (16) and (27).Compared with Equations (26) and (31), the phase error of the multiplicative complex correlator depends only on the power splitter and a coupler. Compared with the additive complex correlator, the phase error is smaller, and the temperature uncertainty is also smaller.Considering the influence of the unbalance on the microwave radiometer, this paper selected an interferometric microwave radiometer based on multiplicative complex correlator for the design of the prototype, and a novel interferometric microwave radiometer is proposed. The measured signal enters the receiver through the antenna and is divided into two signals of the same amplitude through the power divider. One signal is down-converted by a mixer, while the other signal is down-converted by a mixer and then phase-shifted by a phase shifter. Then, the two signals are correlated in the analog complex correlator, and the DC signal in its output is the power value of the measured signal.At the same time, the effect of a nonideal transmission line on the complex correlator system was considered. In this paper, a wideband orthogonal demodulator was used to replace the multiplicative analog complex correlator circuit. Because the phase shifter and mixer were integrated in the orthogonal demodulator, the error caused by different insertion loss of transmission line could be reduced while complex correlation operation was realized.In this paper, the signal amplified and filtered by the multistage low-noise amplifier was connected to the power divider, which was divided into two identical half-power signals. A programmable phase shifter was added to one of the input signals to realize the correction of the input phase error. Then, the signal was input to the orthogonal demodulator for complex correlation operation. Then, a differential amplifier was used to suppress the common-mode signal, and a low-pass filter was used to filter the high-frequency component of the signal, so as to obtain the voltage response signal representing the human body temperature. Finally, the amplitude was collected by ADC analog-to-digital converter.According to the multi-cascade noise figure formula of the receiver,In order to verify the feasibility of the novel interferometric microwave radiometer, the relevant characteristics of the novel interferometric microwave radiometer were also simulated. The modeling and simulation verification of the novel interferometer analog complex correlator was carried out through ADS, as shown in In the verification process, the vector network analyzer was used to measure the S parameters of each module and connection line in the novel interferometric analog complex correlator. The corresponding SNP file was derived, and the novel interferometric analog complex correlator was simulated in ADS. In the simulation process, the harmonic simulation control was used to scan the phase of the novel interferometric analog complex correlator to verify its correlation characteristics. The simulation result is shown in It can be seen from the scanning results that the output complex correlation circle of the novel interference structure had no obvious deformation and center shift; hence, the performance index of the novel interference structure could meet the design requirements.For comparing the performance of two kinds of microwave radiometers, the sensitivity of temperature measurement and the detection of the two systems were further tested.In order to ensure the accuracy of the temperature sensitivity tests of the microwave radiometer, the rectangular waveguide antenna was sealed in an aluminum barrel. The antenna was directly facing the water for measurement in the external environment, and the antenna port was surrounded by absorbing medium ,32. The Since the detection characteristics of the microwave radiometer were similar in the four operating bands, only the 12–16 GHz operating band was tested here. The corresponding multichannel switch was adjusted to the corresponding frequency band, and then the output voltage changes of the two microwave temperature radiometers were recorded in real time by controlling the water temperature in the bucket. The measured results of the novel interferometric microwave temperature-measuring radiometer are shown in Two kinds of radiometer systems were used to measure the water temperature. The sensitivity of the full-power microwave temperature radiometer reached 0.653 K/mV. The sensitivity of the novel interferometric microwave temperature radiometer could reach 0.047 K/mV, which was 13.89-fold higher than that of the full-power radiometer. Therefore, the novel interferometric microwave temperature radiometer could capture smaller temperature changes and had higher measurement sensitivity.In order to determine the detection sensitivity of both kinds of microwave temperature-measuring radiometers, the input end of the radiometer was added to a high-frequency microwave signal source that could generate any frequency within 0.01–15 GHz through the addition of 60 dB attenuator, to simulate the output signal of the human body in four working frequency bands. Through power scanning of the signal source of the microwave radiometer, we could see the change in output voltage values when the input power of the microwave radiometer changed. These results indicated the detection sensitivity of the microwave radiometer. A larger detection sensitivity denotes a better sensitivity performance of the microwave radiometer.In this paper, two kinds of microwave temperature-measuring radiometers were used to carry out power scanning on their input terminals, and their output voltage changes were recorded when the input power changed. In the actual measurement process, the ratio of the output voltage and input power of the full-power microwave temperature radiometer was linear. The maximum detection sensitivity was 29 mV/dBm at 12 GHz. The ratio of the output voltage to input power of the novel interferometric microwave temperature radiometer was larger than that of the full-power microwave temperature radiometer. When the detection sensitivity was evaluated at 13 GHz, the maximum detection sensitivity was 215 mV/dBm, which was 7.454-fold higher than that of the full-power type. Therefore, the novel interferometric microwave temperature radiometer had better detection characteristics.The multiband noncontact temperature measurement microwave radiometer system designed in this paper can penetrate clothing or human tissue to passively receive microwave signals from the internal radiation of the human body. It can provide a technique for noncontact detection, treatment, and monitoring of severe diseases. The innovation and conclusions of this paper are described below.In this paper, a multiband noncontact microwave radiometer system covering the core temperature field of human body based on the tissue depth model and the relationship between skin depth and electromagnetic frequency was proposed. According to the relationship between human skin depth and electromagnetic wave frequency, four frequency bands of 4–6 GHz, 8–12 GHz, 12–16 GHz and 14–18 GHz were selected for design. The ratio of the half-power beam width to antenna directivity was taken as the constraint condition. By sacrificing the H-plane beam angle appropriately, small and highly directional angular horn antennas of four frequency bands were designed and manufactured by simulation. Each antenna had a frequency range of 4 GHz.Through the simulation of a full-power microwave radiometer and an analysis of the maladjustment in the additive analog complex correlator, it was found that the nonideality of the device in an additive analog complex correlator would lead to distortion of the output complex correlation circle. On the basis of an analysis of the relationship between temperature measurement error and the uncertainty of the full-power microwave radiometer, a novel hardware structure of an interferometric microwave radiometer was proposed. The experimental results showed that the maximum detection sensitivity of the novel interferometric microwave temperature radiometer was 215 mV/dBm and the temperature sensitivity was 0.047 K/mV. Compared with the full-power microwave temperature radiometer, the detection sensitivity was increased 7.45-fold, and the temperature sensitivity was increased 13.89-fold.Nevertheless, the design needs to be improved in the future. Firstly, it needs to be adapted to more application scenarios. Secondly, the novel interferometric microwave radiometer prototype needs to be integrated so as to realize a miniaturized handheld multiband noncontact microwave radiometer system. Thirdly, the performance of all bands of the human core temperature field were not tested, and all frequency band indices of the full-power radiometer and the novel interferometric radiometer should be compared experimentally. Lastly, as the environment also affects the measurement results, the novel interferometric microwave temperature radiometer prototype should be implemented in controlled temperature conditions to shield the whole machine, thereby reducing the uncertainty of the temperature measurement and improving its sensitivity.


Apis mellifera, indicating a substantial involvement of the antennal lobe, the first olfactory neuropil, in the processing of mechanical stimuli. Clean air pulses generate a complex pattern of glomerular activation that provides a code for stimulus intensity and dynamics with a similar level of stereotypy as observed for the olfactory code. Overlapping the air pulses with odor stimuli reveals a superposition of mechanosensory and odor response codes with high contrast. On the mechanosensitive signal, modulations were observed in the same frequency regime as the oscillatory motion of the antennae, suggesting a possible way to detect odorless airflow directions. The transduction of mechanosensory information via the insect antennae has so far been attributed primarily to Johnston’s organ in the pedicel of the antenna. The possibility that the antennal lobe activation by clean air originates from Johnston’s organ could be ruled out, as the signal is suppressed by covering the surfaces of the otherwise freely moving and bending antennae, which should leave Johnston’s organ unaffected. The tuning curves of individual glomeruli indicate increased sensitivity at low-frequency mechanical oscillations as produced by the abdominal motion in waggle dance communication, suggesting a further potential function of this mechanosensory code. The discovery that the olfactory system can sense both odors and mechanical stimuli has recently been made also in mammals. The results presented here give hope that studies on insects can make a fundamental contribution to the cross-taxa understanding of this dual function, as only a few thousand neurons are involved in their brains, all of which are accessible by in vivo optical imaging.In insects, neuronal responses to clean air have so far been reported only episodically in moths. Here we present results obtained by fast two-photon calcium imaging in the honey bee  Mechanosensory information underlies a variety of behaviors in insects, including negative geotaxis, flight navigation, and social interaction. Among the various mechanosensory receptors all over the insect’s body , the antHowever, in rodents, the involvement of the olfactory system in mechanosensation has recently been discovered. Patch-clamp recording from the olfactory epithelium of mice showed responses of olfactory sensory neurons to mechanical stimuli , which wAn identical mechanism in insects is not self-evident, as their olfactory receptors do not belong to the same class, their proteins are inversely oriented within the plasma membrane of the olfactory receptor neurons (ORNs) . The recApis mellifera the antennal lobe consists of 160 network nodes called glomeruli, each invaded by the dendrites of a single class of ORNs only. Glomeruli are interlinked by local neurons and their stereotyped activation patterns encode odor identity and concentration . A small rectangular window was cut into the cuticula above the AL. The glands and trachea covering the AL were moved aside and fura2-dextran, a calcium-sensitive fluorescent dye (Thermo-Fisher Scientific) dissolved in distilled water was injected into the antenno-cerebralis tracts, postero-lateral to the α-lobe using a pulled glass capillary. After the injection, the cuticula was fixed in its original position using n-eicosane (Sigma Aldrich). The bees were stored in a dark, cool, and humid place for 15–20 h to let the dye diffuse into the AL.Honey bees were prepared following a well-established protocol . The beeJust before the imaging session, antennae were blocked with a drop of n-eicosane on the pedicel leaving the flagellum free to move. The cuticular window, the trachea, and the glands were removed from the antennal lobe region. A silicone adhesive  was used to cover the brain and a rectangular plastic foil was attached frontal to the window to separate the antennae from the immersion water for the objective lens.The two-photon microscope  was illuminated by a Ti:Sa laser . The laser was tuned to 780 nm for fura-2 excitation. All images were acquired with a water immersion objective . Fluorescence was collected in epi-configuration, selected by a dichroic mirror, filtered with a band-pass filter centered at 525 nm and with a 70 nm bandwidth (Chroma Technology), and detected by a photomultiplier tube (Hamamatsu Photonics). The laser power was limited to about 10 mW to reduce photodamage on the specimen, maintaining a good signal-to-noise ratio (SNR) .The stimulus generator for controlled air and odor pulse delivery was custom built . Pure aiz-stack of the antennal lobe was acquired at a spatial resolution of 512 × 512 pixels and a layer interval of 2 μm to perform the morphological identification of glomeruli.The image acquisition was synchronized to the stimulus protocol at a frame rate of 10.083 fps. The image of 128 × 128 pixels with a digital zoom factor of 3.8 covers a field of view of 280 μm. The fluorescence intensity was recorded with a depth of 13 bits. In addition to the functional images, a F/F = −[F(t) − Fb]/Fb × 100, where Fb is the average fluorescence signal in the 3 s pre-stimulus period. This is a measure for the neuronal firing rate . Recordings were analyzed via custom python scripts. Images were background subtracted and binarized, and the antennae were identified via connected component analysis. Antenna images were then skeletonized, and the flagellum axis was obtained via the Hough transform. Its angle was measured against the head axis, which was obtained by polygonal fitting the head contour.The clean air stimuli  were genExposed to repeated airflow stimuli , clear aBut beyond previously reported activation , also stTo test the code’s stereotypy, the individual glomeruli were identified via the AL atlas  and the Confronting single glomerular responses to both fluxes shows that on average the glomerular activation amplitude is proportional to the airflow intensity in case of excitatory responses, glomerular inhibition remained constant . The gloA particular case of signal modulation is shown in Next, responses elicited by a superposition of mechanical and odor stimuli were tested by injecting 3-Hexanol (3Hex) into the air stream , an odorTo verify the origin of both signals, the flagella of three of the imaged bees were coated with a thin layer of silicone, leaving them free to move. The observed mechanosensory response was now highly attenuated, whereas the odor response was as strong as before although with slower response dynamics .Next, a potential role of the AL mechanosensation in the waggle dance communication was tested, where dancer bees communicate angle and distance of a food source by wing beating and abdominal oscillations to dance followers . MichelsThe dependence of the glomerular activity on the modulation frequency of the airflow was tested by a variation of the winglet oscillation. Experiments were repeated with a weak airflow and oscillation frequencies of 4, 12, 24, and 30 Hz. The results show that the modulatory effect saturates at 24 Hz with no further increase at 30 Hz, while at lower frequencies the effect decreases proportionally .Since a bee during waggle dance also produces oscillations at higher frequencies around 200–400 Hz via wing beating, the sensitivity of the AL also to these signals was tested by exposing the bees to comparable stimuli produced by a loudspeaker ramping frequency from 40 up to 6,000 Hz. No glomerular response to any of these stimuli was observed.Until now, the honey bee antennal lobe was thought to be activated only by olfactory stimuli. The influence of airflow on the responses was exclusively attributed to a modulation of the odor concentration. The data presented here show that airflow stimulates the antennal lobe even in the absence of odorants. The extent of the responses, involving almost all glomeruli, is a fundamental difference from the sparse odor response patterns. This confirms the corresponding conclusions of e.g., to detect wind speed and direction during flight. One of the two airflow velocities (HF = 1.8 m/s) was chosen to resemble typical flight speeds, so the high sensitivity to this stimulus underlines the suitability for this purpose. The tonic nature of the mechanosensitive responses suggests that glomeruli may record wind speed persistently during flight. Regarding the tonic character of the mechanosensitive responses, our results deviate from those of The complexity of the response patterns ranging from high excitation to complete inhibition of projection neuron activity suggests that this is not a simple background effect without functional relevance. The highly dynamic nature of the signal and, above all, the stereotypy of the combinatorial code makes it likely that the encoded information is used, The oscillatory modulations on the mechanosensory responses were found to be in the same frequency window as the azimuthal motion of the antennae that was measured by a high-speed camera. From a physical point of view, the reorientation of the flagella would change the direction under which the airflow hits the hair-like sensilla and would strongly modulate their degree of motion. It is the projection angle between wind direction and sensillum axis, that quantifies the strength of the force acting on it, reaching from zero when sensilla that are aligned in parallel and downwind to a maximum for orthogonal orientation. This seems to produce a direction-dependent signal modulation. Bees might use this direction sensitivity not only to detect odor gradients, as cockroaches do via position-dependent activation along the antennae , but alsThe simultaneous presentation of an odor stimulus with the air pulse showed that the chemical signal was perceived without a loss of contrast nor of dynamic range compared to experiments where instead of an air pulse a continuous carrier stream is used . On the The experiments with bees whose antenna surfaces were coated with silicon, without restricting the flagella movement, showed that odor responses were temporally delayed and mechanosensory responses strongly suppressed. This is a further argument against the possibility that the responses to the air pulses originate from odor impurities, which in that case should be equally delayed but not suppressed. It also suggests that the sources for the mechanosensory signal are likely located in the olfactory sensilla hairs on the antenna surface and are activated by changes in sensilla position, motion, or shape. The resulting mechanical forces may cause conformational changes directly in the olfactory receptors and/or could modulate an electrical coupling between different olfactory neurons within one sensillum  by changThis motion was strongly damped by the silicon coating and accordingly, there was no mechanical activation. Odor molecules were nevertheless able to diffuse toward the chemoreceptors although with strongly reduced velocities, which explains the delay in odor response signals. If the origin of the antennal lobe activation were Johnston’s organ neurons, a response to mechanical stimuli should have been observed, as the flagellum was free to move, and the stretch-sensitive JONs were hardly affected by the coating.Alternative sensory modalities such as hygro- or thermosensation are highly unlikely to be the origin of this signal. Apart from the fact that such sensory modalities have never been reported from the honey bee antennal lobe, in cockroaches and Drosophila, only a few peripheral glomeruli showed hygro- or thermosensitivity , whereasWhen adding a periodic low-frequency modulation to the airflow the sensitivity to the signal was found to increase in several glomeruli. The frequency dependence of this effect suggests that this might be tuning to frequencies as they occur during the waggle dance communication. The response to oscillations reaches a maximum at 24 Hz, a frequency that was reported to provide the most efficient transfer of information during the waggle dance . This frIn summary, these results provide the first evidence for parallel coding of odor and mechanical stimuli in the honey bee AL. In contrast to previous studies that have suggested Johnston’s organ as the primary organ for antennal mechanoreception, the here provided data suggest that the glomerular response code might contribute considerably to it, especially at lower frequencies corresponding to modulation of wind direction during flight or abdominal motion during waggle dance.This study suggests that our view on the insect olfactory system, which has expanded considerably over the last decades , needs te.g., mechanoreception in crayfish (Also the additive nature of the mechanical and the olfactory code confirms findings in mice. Air pulses enhanced the firing frequency of individual neurons weakly stimulated by odorants . This micrayfish  and criccrayfish , in the crayfish , and in crayfish . A firstcrayfish .Along the same line, In conclusion, one can safely say that dual coding of odors and mechanical stimuli is another of the many conserved features of the olfactory system between insects and mammals . This prThe raw data supporting the conclusion of this article will be made available by the authors, without undue reservation.ET designed the study, developed the methodology, acquired and analyzed the data. LL acquired the data and contributed to the data analysis. GS analyzed the antenna motion data. AH contributed to the data analysis and provided the funding and instrumentation. All authors contributed to the preparation of the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


This article presents an investigation of heat transfer in a porous medium adjacent to a vertical plate. The porous medium is subjected to a magnetohydrodynamic effect and suction velocity. The governing equations are nondepersonalized and converted into ordinary differential equations. The resulting equations are solved with the help of the finite difference method. The impact of various parameters, such as the Prandtl number, Grashof number, permeability parameter, radiation parameter, Eckert number, viscous dissipation parameter, and magnetic parameter, on fluid flow characteristics inside the porous medium is discussed. Entropy generation in the medium is analyzed with respect to various parameters, including the Brinkman number and Reynolds number. It is noted that the velocity profile decreases in magnitude with respect to the Prandtl number, but increases with the radiation parameter. The Eckert number has a marginal effect on the velocity profile. An increased radiation effect leads to a reduced thermal gradient at the hot surface. Porous media are used in several applications involving a wide range of scientific and engineering fields. These diverse applications have motivated many researchers to explore the characteristics of porous media when subjected to various phenomena. Certain phenomena, such as heat transfer and fluid flow, have resulted in many scientific research articles explaining the meticulous details pertaining to heat transfer inside porous media. This number of articles is justified due to the varied applications where porous media play an important role. For example, foams that have several engineering applications are a form of porous media. Iasiello et al.  studied In recent years, interest in porous media has evolved to include recent trends such as entropy generation. This trend has gained momentum particularly due to the desire to design equipment that can perform by consuming less energy while also reducing waste. Many efforts have been made to understand entropy generation associated with various processes. For instance, Sayed and Abdel-Wahed  investigEntropy generation is an unwanted element that must be reduced to the greatest possible extent to enhance the performance of devices with respect to their energy consumption. Owing to its numerous applications, it is of paramount importance to understand the entropy characteristics of a porous medium with MHD adjacent to a hot vertical plate. This article is novel for its study of entropy generation in a porous medium adjacent to a vertical plate subjected to suction velocity, and magneto hydrodynamics have not been previously reported to the best of our knowledge. Thus, the current work is an attempt in that particular direction.x and y directions are considered along with the horizontal and vertical directions. The properties of the fluid are considered to be constant, apart from the density that allows the natural convection of fluid to take place. The temperature variation is considered only in the body-force term. The governing equations can be given as:The problem under investigation belongs to a steady flow of viscous, incompressible fluid across a porous medium bounded by a vertical plate, as shown in Continuity equation:Momentum equation:Energy equation:o is the constant suction velocity normal to the plate.The continuity (1) leads to:Using the Rosseland hypothesis ,37 as:In view of Equations (4)–(6), the Equations (2) and (3) can be shown to have the form as:The related boundary conditions of present problem are given as:The following non-dimensional parameters are usedSubstituting the above non-dimensional parameters into Equation (7) and (8) yields:The boundary conditions take the formThe entropy generated inside the porous medium due to various factors can be described as (16)Sg=kEquation (16) includes the entropy generation due to conductive and radiative heat transfer, viscous effects and the magnetic effectThe non-dimensional form of entropy can be deduced asThe first term in Equation (17) represents the entropy generation due to heat transfer; the second term highlights the fluid flow entropy; and the last term shows the entropy generated due to an applied magnetic field, which can be individually shown as−5. The results are compared to available data to ascertain the accuracy of the current methodology. The comparison is shown in The physical insight of the problem under investigation can be obtained by solving Equations (12), (13) and (17). These equations are solved numerically by the finite difference method. The outcome of the solution is the velocity and temperature profiles, along with the entropy generation. These equations are further simplified by converting them into first-order ordinary differential equations that make them easier to solve. The domain is divided into 1000 points in order to obtain the desired accuracy of 10The investigation was carried out with respect to various parameters involved in the governing equations, including the Prandtl number, radiation parameter, permeability parameter, Grashof number, viscous dissipation parameter, magnetic parameter, Eckert number, Reynolds number, and Brinkman number. The results are plotted in terms of velocity, the temperature profile in the porous domain, as well as entropy generation with respect to heat transfer, fluid flow, and magnetic effects.f), and viscous dissipation parameter (D) are shown in This section describes the temperature variations in the porous domain due to various parameters. Entropy is a term that describes the disorder or usefulness of energy in any process. Thus, the entropy presents an overview of how efficient a process is by reducing its irreversibility. The lesser the irreversibility, the better the system performance. Entropy can be generated due to various factors such as heat transfer, fluid flow, and magnetic effect. This section is devoted to understanding the different types of entropy generation associated with the current problem. The individual entropy is listed for three terms arising of Equation (17), which are thermal entropy (ST), fluid flow entropy (SF), and magnetic-field-related entropy (SM).The velocity profile is affected, to a greater extent, by the Prandtl number, Grashof number, radiation parameter, magnetic parameter, and permeability parameter, whereas the impact of the Eckert number, form-drag coefficient, and viscous dissipation parameter is significantly less.The velocity profile decreases owing to the Prandtl number and magnetic parameter. However, a reverse trend is observed with respect to the radiation parameter, permeability parameter, and Grashof number.The temperature profile decreases with increasing Prandtl number, whereas it increases with increase in the radiation parameter.The entropy generation increases with an increase in the Reynold’s number, Brinkman number, and radiation parameterThe fluid entropy dominates compared to thermal and magnetic entropy.The fluid and thermal entropy sharply decrease near the vertical plate, whereas magnetic entropy produces a different profile than the fluid and thermal entropy.The present article investigated heat transfer behavior in a fixed porous domain adjacent to the permeable vertical plate subjected to suction velocity and magnetic effects. The analysis was carried out with respect to entropy generation due to various parameters. This work revealed the following concluding points: