This paper presents a novel self-localization technique for mobile robots using a central catadioptric camera. A unified sphere model for the image projection is derived by the catadioptric camera calibration. The geometric property of the camera projection model is utilized to obtain the intersections of the vertical lines and ground plane in the scene. Different from the conventional stereo vision techniques, the feature points are projected onto a known planar surface, and the plane equation is used for depth computation. The 3D coordinates of the base points on the ground are calculated using the consecutive image frames. The derivation of motion trajectory is then carried out based on the computation of rotation and translation between the robot positions. We develop an algorithm for feature correspondence matching based on the invariability of the structure in the 3D space. The experimental results obtained using the real scene images have demonstrated the feasibility of the proposed method for mobile robot localization applications. To make the mobile robot have the ability to navigate autonomously, it is commonly equipped with various sensors for environment perception. Thus, the sensing techniques are essential to many mobile robot navigation applications, such as the self-localization, obstacle detection and avoidance, human–machine interaction, and object handling, etc. In the past few decades, a number of techniques and algorithms have been proposed to accomplish these tasks. The technological development mainly depends on the types of sensors adopted for mobile robot navigation. Currently, some widely used sensors include sonars, laser rangefinders, odometers, GPS , infrared sensors, and cameras. Nevertheless, GPS is usually not applicable to indoor environments and some satellite signal denied areas. This might include the application scenarios for extra-planetary rovers and under-ground robots.The ultrasonic sonar sensor is one of the most adopted low-cost sensing devices. It is commonly used for distance sensing of the surrounding environment. However, there are some critical drawbacks such as the slow response compared to other sensors and less accurate measurements for corners and short distances. On the other hand, the laser rangefinder is probably the fastest and more accurate commercial device for depth perception. In addition to the high cost, its sensing distance range is usually limited to one-dimensional and requires extra mechanisms for multi-dimensional scans. Moreover, the laser-based technology is not able to deal with highly reflective or transparent surfaces such as glass. The odometer uses the optical encoder on the wheel to calculate the travel distance of the mobile robot. It is generally a built-in device for the wheeled robots, but the error accumulation due to the proprioceptive sensing nature makes the drifting inevitable for long range movement. Thus, the odometry is usually combined with the information from other devices, such as sonar or camera, and utilizes the sensor fusion techniques to improve the localization accuracy. There also exists an indoor self-localization technique based on the ambient magnetic field . It has In this work, we present a self-localization technique for mobile robots using an omnidirectional vision system. A catadioptric camera is adopted for image acquisition of the surroundings in an indoor environment. The vertical features are extracted from the image sequences, and the 3D information is derived based on the catadioptric image formation model. Different from the conventional stereo vision techniques, the feature points are projected onto a known planar surface and the plane equation is used for depth computation. The self-localization is then calculated using multiple 3D features and the imaging geometry. Furthermore, the 2D environment map and robot motion trajectory can be constructed by matching the static environment features among the image frames sequentially. Compared to other sensing techniques, such as using lidar for depth measurement, the vision-based methods adopt low-cost camera equipment for data acquisition. The acquired images can also provide rich information for other recognition and human-machine interaction tasks.As illustrated in The omnidirectional vision systems have been widely adopted in the mobile robot research for simultaneous localization and mapping (SLAM) . In addiThe self-localization of mobile robots is still an ongoing research topic due to the uncertainties of sensor data and a dynamic world. A few techniques cooperated with environment settings, such as the use of UWB (ultra-wideband) beacons and RFID tags, have been proposed in the past few decades ,10. In aAmong various vision-based localization approaches in the existing literature, the ground plane has been successfully adopted for many applications. In , Simond Nowadays, an increasing number of mobile robots adopt a single omnidirectional camera for environment perception to take advantage of its large field of view. However, this makes the self-localization a more difficult task by using the omnidirectional images. Marques et al. designed a self-localization method using pre-calibrated image distortion parameters to warp the omnidirectional image for computation . Liu et To localize the mobile robot using only an onboard catadioptric vision system, it is required to construct the camera projection model so that the 3D scene points can be projected onto the image plane. Thus, the catadioptric camera calibration has to be carried out first to establish the geometric representation. In the last decades, several types of omnidirectional cameras have been designed, and corresponding calibration techniques have also been proposed. This work follows Mie’s presentation for the catadioptric camera model construction . Since tThe unified sphere projection model for the catadioptric camera is illustrated in K with the focal length s, and the aspect ratio r. Based on the camera projection model, an image pixel The above projection involves a generalized camera projection matrix Now, suppose a feature point is given on an omnidirectional image, it can be back-projected onto the sphere using the unified projection model. Each point on the sphere can also be thought as a line radiated from the center. After the catadioptric camera is calibrated, the robot motion is represented with the camera coordinates, as shown in To formulate the derivation of mobile robot self-localization, we first establish the geometric constraint of a single catadioptric camera with a sphere model and ground features. The unified sphere imaging model, the ground plane, and a vertical line representing the feature in the scene are depicted in quations –4) with withXw gh is the height between the ground plane and the projection center  of the vertical structures on the ground. The intersection points between the vertical 3D lines and the ground satisfy the geometric constraints, and will be used to derive the corresponding 3D positions using the calibrated sphere camera model and Equations –8). How. How8). The mobile robot localization is accomplished by the position estimation using two consecutive frames. Thus, it is required to find the correspondence matching of the base points between two images. In this work, we do not use the SIFT descriptor  for robuCurrent Data and Past Data correspond to the current and previous image frames, respectively. The first case in To facilitate the line matching between the image frames, we consider the situations as shown in T and the The conventional stereo matching techniques utilize the disparities obtained from the multi-view cameras to calculate the 3D information. In this paper, only a single omnidirectional camera is used for the acquisition of image sequences. The base points identified in the images are back-projected to the unit vectors on the unified sphere calibrated with the catadioptric camera model. The 3D coordinates of the feature points are then derived from the intersections of the vector extensions and the ground plane equation for robot position estimation. As illustrated in on (SVD) . Given mThe proposed techniques have been carried out in the indoor environment for real-world applications. Our mobile platform for the experiment consists of a wheeled robot (U-Bot) equipped with an omnidirectional camera as shown in In the first experiment, the ground plane segmentation and vertical line identification are carried out in the indoor environment. The performance of the proposed method is evaluated by measuring the Euclidean distances in the motion trajectory with respect to the mobile robot. For the error analysis, we first verify the similarity of vertical edge features and then compute the errors on the individual lines. As shown in the previous section, the correctness of vertical feature extraction and base point derivation depends on the ground region detection. There might be some errors introduced by the stability of the image acquisition. In this paper, we present an approach for the self-localization of mobile robots using a single catadioptric camera. A new technique for vertical line detection and base point identification for the structured environment is proposed. The geometric invariants from the catadioptric image formation are used to perform the base point matching in the image sequence. The derivation of motion trajectory is then carried out based on the computation of rotation and translation between two consecutive robot positions. Our main contributions in this work include the theoretic derivation and framework validation on using a single catadioptric camera for mobile robot localization in structured environments. The experimental results obtained using the real scene images have demonstrated the feasibility of the proposed method. Since the images acquired from the omnidirectional camera contain rich information. In addition to mobile robot self-localization, the future work will focus on the object recognition during navigation. The visual surveillance and human–machine interaction will also be investigated for industrial applications.


Quantifying the distribution of nanomaterials in complex samples is of great significance to the toxicological research of nanomaterials as well as their clinical applications. Radiotracer technology is a powerful tool for biological and environmental tracing of nanomaterials because it has the advantages of high sensitivity and high reliability, and can be matched with some spatially resolved technologies for non-invasive, real-time detection. However, the radiolabeling operation of nanomaterials is relatively complicated, and fundamental studies on how to optimize the experimental procedures for the best radiolabeling of nanomaterials are still needed. This minireview looks back into the methods of radiolabeling of nanomaterials in previous work, and highlights the superiority of the “last-step” labeling strategy. At the same time, the problems existing in the stability test of radiolabeling and the suggestions for further improvement are also addressed. Nanotechnology has emerged rapidly during the past years in a broad range of product domains. It provides opportunities to manipulate or develop materials at nanoscale dimensions for a wide variety of applications , where cIn general, the methods for NMs measurement in biological samples depend on the chemical composition and peculiarities of the structure of NMs, and there is no universal technique to date suitable for all NMs. Among those techniques developed for NMs quantification and imaging :γ spectrometry, scintillation counting, PET and SPECT. For example, radioactive 141Ce labeling and HPGE γ spectrometry were used to quantify the distribution of ceria nanoparticles (NPs) in rat after intratracheal injection, and a detection limit better than 1 pg/g was achieved 3 and 141Ce(NO3)3, and 68Ga in the core of IONPs. The as-synthesized radioactive NMs have almost, if not totally, the same physicochemical properties as the unlabeled NMs. Therefore, incorporation strategy is also called intrinsic radiolabeling method in some previous reports  means. For example, MoS2 NPs were radiolabeled with 64Cu with the help of bifunctional p-SCN-Bn-NOTA  or chemical  or indirect  chemical bond formation between the radiometals and the NMs surface, the complex is incubated in simulated body fluids  for several hours or overnight, and then the detached radiometals are collected and quantified by means of centrifugation, chromatography, or liquid chromatography  The protonation of chelator’s carboxyl and amine groups may compromise the helation .in vivo  The newly formed bond between the linkage group of bifunctional chelating agent and the NMs is too weak to maintain stability 3) When the chelators are not linked to the surface atoms of NMs, but to the small molecules that constitute the surface coating of NMs through hydrogen bonding or amphiphilic self-assembly, then the chelator-radiometal complexes may detach from the surface of NMs together with the coating molecules .in vivo  The chelators are directly linked to the surface atoms of NMs, but the superficial layer of NMs undergo a decomposition Classic methods for labeling NMs with radiometals rely on the functionalization of NMs surface with traditional metal ion chelators. Radiochemists have long been committed to synthesizing and improving bifunctional chelating agents, with a chelator (like polyaminocarboxylate groups) at one end and a chemically-reactive linkage group at the other end . When thin vivo, the chemically adsorbed radiometals may also undergo a detachment in the manners similar to those shown in Besides chelator-based radiolabeling, surface chemical adsorption of radiometals is simple and easy to implement, and has received great attention as a chelator-free radiolabeling method. In the existing examples , the NMsin vivo, we here propose several improvements: 1) We should continue to improve bifunctional chelating agents with pH-insensitive stabilities of both the chelation and the linkage. 2) If we want to radiolabel degradable NMs via surface derivatization but do not want to hinder the degradation of the NMs, we could encapsulate the NMs with a mesoporous shell or long organic chains with a high degree of cross-linking, and then connect the radionuclides and the NMs coating through strong and pH-insensitive bonds. 3) Only when the NMs to be radiolabeled could remain undegraded in vivo for a long time, can we directly connect the radiometals to the surface atoms of NMs through strong and pH-insensitive bonds. 4) The ex vivo measurement of the radiolabeling stability should be conducted not only in the simulated neutral body fluids, but also in the artificial lysosomal fluid. In short, we must pay attention to the differences in metabolism between nanomaterials and molecules, as well as the resulting different requirements for radiolabeling. Furthermore, the introduction of a higher level of automations and even artificial intelligence in the design and practice of radiolabeling will definitely bring new options for the radiotracing study of NMs (Based on the above discussion on the causes of radiometal detachment y of NMs .via derivatization strategy. Meanwhile, we emphasize here a pH-related detachment of radionuclides from the NMs that has been underappreciated previously. Since the radiolabeled NMs will encounter a low pH milieu soon after exposure, radiochemical stability in acidic environment is essential for radiolabeling. This minireview also calls for a careful re-examination of the previous radiotracing results, as well as further optimization on the radiolabeling methods for NMs.To sum up, this minireview looks back into the methods for NMs radiolabeling, and highlights the superiority of the “last-step radiolabeling”


A universal C*-algebra of gauge invariant operators is presented, describing the electromagnetic field as well as operations creating pairs of static electric charges having opposite signs. Making use of Gauss’ law, it is shown that the string-localized operators, which necessarily connect the charges, induce outer automorphisms of the algebra of the electromagnetic field. Thus they carry additional degrees of freedom which cannot be created by the field. It reveals the fact that gauge invariant operators encode information about the presence of non-observable gauge fields underlying the theory. Using the Gupta-Bleuler formalism, concrete implementations of the outer automorphisms by exponential functions of the gauge fields are presented. These fields also appear in unitary operators inducing the time translations in the resulting representations of the universal algebra. We construct in this article an extension of the universal C*-algebra of the electromagnetic field in Minkowski space, presented in . It inclOur restriction to static (infinitely heavy) charges greatly simplifies the analysis since such charges can sharply be localized; the localization properties of dynamical charges with finite masses are more fuzzy . Yet theExtending arguments in , we willThe principal point in our investigation consists of the demonstration that the string-localized operators, connecting the charges, define outer automorphisms of the subalgebra of the electromagnetic field. This will be established by different means, firstly in the abstract framework and then by exhibiting a representation of the algebra, based on the Gupta-Bleuler formalism and an abelian algebra of operators creating static charges. Within the present general setting our results corroborate the claim made in  that gaugauge bridges between static charges. In Sect. Our article is organized as follows. In the subsequent section we establish our notation and recall the definition of the universal algebra In this section we recall the definition and basic properties of the universal C*-algebra ic field , show hointrinsic vector potential g with compact support and vanishing divergence, F is given by g is any solution of the equation F.The unitary elements of the algebra, describing exponentials of the V(ag) that generate a *-algebra For the sake of mathematical rigor, one describes the formal exponentials of the intrinsic vector potential by symbols The first relation  expresseLet us mention as an aside that the preceding relations are a straightened version of corresponding  relations presented in . ExampleAs is shown in , there eF underlying our framework. In a second step we will recast the heuristic structures rigorously in terms of the universal algebra.We shall show now that the algebra F determines the electric current J by the inhomogeneous Maxwell equation,dh denotes the exterior derivative (the curl) of h. Noticing that h. The value of these charges can be changed by maps of the intrinsic vector potential of the formThe electromagnetic field r around Turning to the details, we fix a Lorentz frame and a corresponding canonical coordinate system. Given any spacetime point r from c. This feature amounts to the known fact that charge measurements in a region can be replaced by flux measurements at its surface.For the corresponding intrinsic vector potential In the next step we exhibit linear maps g and m have compact support. We shall refer to Given For the proof that the maps Let Since the kernel fixed by the Pauli-Jordan function r from c. Taking into account the support properties of The remaining step is based on standard arguments, which we briefly recall. One first notices that the replacement of r around In order to determine the values in wave Eq. , we may solution  thereforV(g) with We turn now to the algebraic consequences of these observations. For the definition of pair creating automorphisms, we revert to the group of unitaries elations  to 2.3)\documentelations  to (2.3)P the equality Now, given any real linear map elations  and hencWe identify now the unitary exponential functions of the local charge operators with the symbols relation . Pickingic field , where aW(m), where W(m) has the algebraic properties of a unitary exponential function of some local generator with localization properties determined by the support of m. One can also consistently extend the action of the Poincaré transformations P to the group The construction of an algebra, containing unitary elements implementing the action of g to Eq. . We proc cf. Eq. . These grelation .VW, where We then proceed to the semi-direct product s is an arbitrary real scalar test function and the asterisk m of elements in Whereas the algebra i.e. their adjoint action implements the automorphism In order to obtain gauge invariant unitaries which implement the action of elations  and  with regular densities m. Such densities are obtained by choosing in relation . They are not separately defined in these representations, but become meaningful in gauge invariant combinations. This fact provides an alternative argument that gauge bridges between static charges cannot be constructed by means of only the electromagnetic field.Our arguments are based on the Gupta-Bleuler formalism. Although we are dealing with gauge invariant operators, the Gupta-Bleuler fields are needed in order to obtain concrete representatives of the abstract unitaries We briefly sketch the well-known construction of the Gupta-Bleuler framework, cf. for example , 13. Letw being any scalar test function,U(P) are elements of the weak closure of One can identify now the generating elements of the abstract algebra elations , this idelations  and  charges. We have also avoided the discussion of infrared problems by considering only neutral pairs of charges which are localized at finite spatial distances. These restrictions allowed us to focus on the impact of the electric charges on the electromagnetic field.The upshot of the present investigation is the insight that, as a consequence of Gauss’ law, the modifications of the electromagnetic field caused by electric charges cannot be described by operations involving only the electromagnetic field. Within our framework, it found its expression in the fact that the gauge bridges between charges induce outer automorphisms of the universal algebra. We have therefore enlarged this algebra to a bigger C*-algebra, containing localized unitary operators implementing these automorphisms. Noticing that these unitaries are not gauge invariant, we have added charged field operators, describing the static matter. Their combination with the unitaries inducing gauge bridges leads to well localized gauge invariant operators, which describe within the C*-algebraic framework bi-localized static charges.By making use of the Gupta-Bleuler formalism, we have seen that the adjoint action of the unitary operators creating gauge bridges can be represented by exponential functions of non-observable gauge fields. In this manner gauge fields make their appearance within the framework of the gauge invariant universal algebra. The adjoint action of these non-observable unitaries also leads to physically meaningful representation of the universal algebra, in accordance with the empirical fact that the presence of electric charges has no adverse effects on the energetic properties of the electromagnetic field. Since we had modeled the charged matter as being static it was, however, meaningless to discuss its energetic properties as well.We conclude this article with some remarks on recent related work by Mund, Rehren and Schroer , 11. TheThe views advocated by these authors are not in conflict with the present results. In contrast to their approach, we have put forward the localization properties of physical operations, such as the creation of charged pairs, without alluding from the outset to the idea of pushing compensating charges to infinity. Having worked with C*-algebras, we have avoided the usage of indefinite metric formalisms as well. Our excursion to the Gupta-Bleuler formalism was conducted merely for the sake of illustration. Thus in view of recent progress in the formulation of dynamical C*-algebras, cf. , 2 and r


The sea surface temperature (SST) is a crucial parameter system in climate monitoring. Satellite remote sensing is currently the most common approach for measuring long-term and large-area sea surface temperatures. The SST data measured by the satellite radiometer include the sea surface skin temperature (SSTskin) at a depth of approximately 10 μm. Satellite remote sensing measurement data must be compared and validated with on-site measured data. There are various solutions for on-site measuring instruments; the essential components are usually infrared radiation sensors with radiation output. This paper uses an ordinary integrated infrared thermometer without a radiation output function to remotely measure the sea surface temperature to achieve a high-precision measurement. The scheme of integrating infrared thermometers to measure the sea surface temperature is investigated in this paper. Based on Planck’s formula, the bidirectional conversion relationship between temperature and radiation in a certain band is established. The experimental system introduced in this paper uses an integrated infrared thermometer to measure the small blackbody and the target in a cyclic measurement system. We combine it with the sea surface emissivity characteristics and eliminate the influence of sky background radiation on the sea surface to obtain the actual amount of radiation on the sea surface, from which we obtain the actual radiation amount on the sea surface. Accurate SST can be calculated from the actual amount of radiation at the sea surface. The temperature measurement accuracy can reach 0.1 K, allowing it to meet on-site temperature measurement requirements, as well as the comparison measurement requirements confirmed by satellite remote sensing on-site data. There are relatively few products available for sensors with a temperature measurement accuracy of 0.1 K on the market, and temperature measurement equipment with a temperature measurement accuracy of 0.1 K is relatively expensive. Cost is one of the important factors to consider when using in bulk, especially as global warming increases the need for ocean monitoring. The scheme proposed in this paper is beneficial to reduce the volume and weight of measuring instruments, reduce the cost, and promote the large-scale combined application of sea surface temperature change monitoring. To meet the requirements for the accuracy of satellite SST data in climate data records, high-precision SST on-site measurement data are required to verify the satellite data ,2,3. DueMost of the above-mentioned radiometer remote sensing temperature measurement instruments are radiation measurement sensors with radiation output. The main feature common to all is that the temperature sensor takes measurements related to radiation. Subsequent circuits and firmware programs use this radiation measurement as the main parameter to invert the target temperature. These sensors are characterized by a complex structure, large volume, and relatively high price. The measurement scheme discussed in this paper adopts a different from the traditional scheme, using an inexpensive integrated infrared temperature sensor instead of an infrared radiometer. This integrated infrared temperature sensor can only output the measured temperature, but it has a simple structure, a small size, and a relatively affordable price. For the installation of sea surface temperature measurement equipment on every scientific buoy, offshore oil platform, and long-distance freighter, cost is a factor to consider. If the commercially available integrated infrared temperature measurement sensor is directly aimed at the sea surface, temperature measurement can also be carried out, but the accuracy is not adequate. Using an integrated infrared temperature sensor instead of an infrared radiometer to measure high precision sea surface temperature, compared with the traditional radiometer temperature measurement scheme, requires a series of calculations. The specific method is to obtain the radiation corresponding to the temperature of each measurement target through calculation. Combined with other radiation relationships that affect the sea surface temperature, the quantity of radiation relating to sea surface temperature is obtained, and the sea surface temperature value corresponding to the radiation amount is calculated. The Stefan–Boltzmann law integrates Planck’s formula in all wavebands to obtain the relationship between temperature and radiation amount in all wavebands. Since the wavelength range of the integrated infrared temperature sensor is not the whole band, this paper theoretically deduces the bidirectional relationship between temperature and radiation within the band range of the infrared thermometer. Through theoretical analysis and experimental verification, the real-time blackbody calibration scheme is adopted to improve the measurement accuracy of the integrated temperature sensor, from 0.5 to 0.1 K, which can better complete the measurement of SST. This precision can meet the temperature measurement requirements of environmental scientists, as well as satellite remote sensing field data verification requirements.The scheme in this paper uses the infrared temperature sensor MLX90614 and the pyroelectric integrated infrared radiometer KT19 to take seawater temperature and sky temperature, respectively. We established a bidirectional conversion relationship between temperature and radiation, and calculated the radiation corresponding to the temperature. According to the principle of sea surface temperature measurement, the radiation of seawater surface temperature is obtained, and finally the seawater surface temperature corresponding to the radiation is calculated.The Planck formula proposed the law of blackbody radiation: at any temperature, the relationship between the emissivity of the blackbody electromagnetic radiation and the wavelength of electromagnetic radiation isAccording to the equation, When Planck’s formula represents the amount of blackbody radiation at any single wavelength at any temperature. By integrating the Planck formula with wavelength T dIn the above formula, The denominator of an integral part of Equation  is expanRearrangeIn this case, the integration by parts method is used to solve the definite integralAt this time, ×1 and ×2 are not complicated and are variables containing temperature. The wavelength range of the infrared thermometer used in this paper is 5.5–14 Combined with the temperature acquisition range of this paper, which is about 173–323 K, calculate the amount of the radiation corresponding to the temperature directly output by the infrared thermometer. The calculation relationship is shown in The second step is to fit the functional relationship between temperature and radiation. The functional relationship fitted in this paper will be used on embedded devices. Considering the processing capability of the embedded system, the relationship between temperature and radiation is fitted, and the accuracy of the fitted relationship is within ±0.005 K. The relationship between radiation and temperature is as follows:The relationship between temperature and radiation is bidirectional. This paper will also use the relationship with the known radiation to find the temperature, as follows:B = LB(T) represents the function relation from temperature to radiation amount, and the fitting function and algorithm error curve are shown in Furthermore, The data directly detected by the integrated infrared thermometer are the temperature values. The corresponding radiation value is obtained through the above-fitting function. Combined with the relationship between the radiation of each part of the seawater surface described in the following chapters, the real seawater surface radiation amount is obtained. Finally, the inverse operation function relationship is used to calculate the sea surface temperature.When the temperature measurement equipment deployed on the sea or on the mobile platform measures the sea surface temperature, the observed temperature not only includes the actual sea surface temperature, but is also affected by other factors, such as the sky and air . The radIt can be seen from Lsky is the radiation amount of a single wavelength when infrared temperature measuring equipment observes the sky. B  (13)SseaTsea. According to the relationship between temperature and radiation amount, Ssea(LB(Tsea) represents the radiation amount measured by the temperature measuring equipment within the band range of 5.5–14 Tsky, Ssky(LB(Tsky), which is convenient for further calculation. After substitution, the formula can be written:It can be seen intuitively from the formula that, for the temperature measuring equipment, to measure the sea surface temperature accurately, it is necessary to obtain the radiation measurement values of sea surface radiation and atmospheric radiation. For the integrated infrared thermometer used in this paper, the measured output value is the temperature value, which needs to be converted in combination with the fitting function mentioned above. The actual output signal of the integrated infrared thermometer observed on the sea surface is T = B).The actual sea surface temperature is obtained from the inverse operation function The above is the basic principle of using an integrated infrared thermometer to measure sea surface temperature instead of other equipment.This work used the MLX90614 infrared thermometer, which integrates the infrared induction thermopile detector chip and the signal processing dedicated integrated chip. The official information of the MLX90614 infrared thermometer states that the accuracy of this thermometer reaches 0.5 K, and the resolution is 0.02 K . The algBased on the temperature measurement principle mentioned above, when observing the surface temperature of seawater, it is necessary to obtain the temperature of the seawater and the sky. Errors can be caused by rapid changes in atmospheric radiation due to different types and heights of clouds and different radiation temperatures, so ideally both sea and sky temperatures should be obtained simultaneously, or the time difference between sea and sky measurements must be small . As a soBefore formally measuring the water surface, carry out a standard blackbody calibration. Aim the device to a standard blackbody radiation source, which is a standard blackbody imported from Canada LR TECH INC., model BB-ASSIST II. The parameter accuracies of the standard blackbody official data are as follows: the radiation temperature stability is less than ±0.005 K, and the temperature display accuracy is 0.1 °C. In the experiment, the standard blackbody is set to 25 °C (296.15 K), and the measurement is started after the temperature stable. During the measurement, the temperature of the standard blackbody has been keptat 25.02 °C (296.17 K). The specific process uses the embedded system to control the rotation of the motor equipped with the infrared thermometer, and each time the infrared thermometer needs to be aligned with the ambient-temperature blackbody, the blackbody, and the standard blackbody to take the temperature, correct the accuracy of infrared thermometers in real-time and eliminate the influence of environmental factors.The figures above show the output of all measurement data when using standard blackbody calibration. A circulating constant temperature water tank was used to simulate the seawater surface in the laboratory for theoretical verification. The constant temperature water tank was placed in the natural environment so that the water surface was affected by the radiation from the sky. After the temperature stabilizes, the angle of the integrated infrared thermometer to observe the water surface is set to 45 degrees. The equipment used to measure the sky temperature was KT19, and the measurement angle was also set to 45 degrees. At the same time, the high-precision thermometer FLUKE1524 was used to measure the water surface, in order to obtain the reference temperature of the water surface.The above figures show the output of all measurement data when the laboratory uses a circulating constant temperature water tank to simulate the seawater surface for theoretical verification. This paper focuses on integrating infrared thermometers to measure sea surface temperature. Based on Planck’s formula, the bidirectional relationship between temperature and radiation in the band range is established. The pyroelectric integrated infrared thermometer in the traditional solution can be replaced by an integrated infrared thermometer that only outputs temperature. The temperature measured by the integrated infrared thermometer is converted from the temperature-radiation amount relationship, and the radiation amount is calculated.In this paper, we built an experimental system to test and verify the above temperature measurement scheme, using the MLX90614 integrated infrared temperature measurement sensor and two small black bodies with different temperatures. The small blackbody corrects the sensor in real time and adds a motor with a controllable rotational position to switch the measurement angle of the sensor. First, the experimental system conducts temperature measurement experiments on the BB-ASSIST II standard blackbody. The temperature measurement bias of the integrated temperature sensor without real-time calibration to the standard blackbody is −0.150, and the standard deviation is 0.083. After using the measurement method proposed in this paper, the temperature measurement bias of the measured standard blackbody is 0.007, and the standard deviation is 0.013. Then, the water temperature measurement experiment of the circulating constant temperature water tank under the natural sky radiation environment is carried out. The radiation amount is calculated after using the measurement method proposed in this paper, combined with the relationship between water surface radiation, sky radiation, and water temperature. Finally, the temperature at 10 um of the sea surface is obtained from the radiation–temperature relationship; the temperature measurement bias of the water body surface is 0.002, and the standard deviation is 0.039. It can be seen that the scheme in this paper has a significant effect on improving the measurement accuracy of the integrated temperature sensor.The main shortcoming of this paper is that the whole system does not use all infrared temperature measurement sensors, and the sensor Heitronics KT19 is used alone to measure the radiation of the sky. The MLX90614 infrared temperature measurement sensor has a large temperature measurement deviation for the sky and cannot accurately measure the low-temperature background radiation of the sky. In the following work, a suitable integrated temperature sensor will be selected to replace the KT19, to obtain smaller device volume and better cost performance.


Escherichia coli we here investigate the (Euclidean) distances covered by the edges in the TRN when its nodes are embedded in the real space of the circular chromosome. Our work is motivated by ’wiring economy’ research in Computational Neuroscience and starts from two contradictory hypotheses: (1) TFs are predominantly employed for long-distance regulation, while local regulation is exerted by chromosomal structure, locally coordinated by the action of structural proteins. Hence long distances should often occur. (2) A large distance between the regulator gene and its target requires a higher expression level of the regulator gene due to longer reaching times and ensuing increased degradation (proteolysis) of the TF and hence will be evolutionarily reduced. Our analysis supports the latter hypothesis.In the transcriptional regulatory network (TRN) of a bacterium, the nodes are genes and a directed edge represents the action of a transcription factor (TF), encoded by the source gene, on the target gene. It is a condensed representation of a large number of biological observations and facts. Nonrandom features of the network are structural evidence of requirements for a reliable systemic function. For the bacterium  Instrumental in this progress is the formal representation of gene regulation as a network of gene-gene interactions mediated by TFs, which allowed identifying some design principles underlying this class of biological processes. Among these are the role of small regulatory devices like coherent feedforward loops ensuring noise buffering4, feedback loops and incoherent feedforward loops implementing adaptation to long-term stimulation5, groups of genes under a common regulation as a suitable structure to run temporal programs7, as well as the functional relevance of a hierarchical organization of the interactions8.Approaches from Systems Biology have led to remarkable progress in understanding bacterial gene regulation6 that preceded their mechanistic interpretation as noise-buffering devices in the coherent case and ’pulse generators’ in the incoherent case.One of the remarkable conceptual approaches put forward by network science is the possibility to ask in a systematic fashion about the nonrandom features of a given network. In this way, diverse systems can be compared on a quantitative level using unified statistical tools. Provided a suitable null model is used, such nonrandom features can often be associated with functional requirements of the network and/or an optimization installed in the network by some evolutionary pressure. It was for instance the statistical observation of a high abundance of feedforward loops in gene regulatory networks13. This challenge, among others, has to date prevented for example the creation of predictive models of bacterial gene expression patterns and the achievement of a mechanistic understanding of bacterial gene regulation. Relating the network representation with the chromosomal organization in real space is a decisive step along this way.However, we are far from a comprehensive understanding of bacterial gene regulation. In particular accumulating evidence points to the need of considering the regulatory network as a spatially embedded structure, where the spatial organization of the circular bacterial chromosome contributes to the overall regulation of genes15. Figure The fact that the transcriptional regulatory network (TRN) needs to be considered as a spatially embedded network is particularly clear for a bacterium, as there transcription and translation are not localized in different cellular compartments. This allows us to leverage methods from network science, designed for the analysis of spatially embedded networks, for an even further-reaching statistical investigation of these nonrandom features16 first studied the spatial embedding of the transcriptional regulatory network and interpreted some of its nonrandom features from a biological perspective. In addition to this early work, a lot is already known about the nonrandom features of this spatially embedded network. Regulated and non-regulated genes have markedly different statistical distributions along chromosome17. Genomic distances among target genes of the same TF are smaller than expected at random16. The chromosomal axis defined by the origin of replication and the terminus of replication (Ori-Ter axis) is an important organizer of gene activity13 and also shows up in statistical properties of the TRN13. In contrast to other spatially embedded networks, the TRN does not show a systematic decrease of link density with genomic distance15. Genomic neighborhood and TRN explain gene expression patterns in a complementary fashion, suggesting a buffering mechanism between two types of regulation, one related to the TRN and the other to chromosomal structure11. We here extend this line of investigation by studying the interplay of network features and spatial organization and their correlation with gene expression levels.The pioneering work by Warren and ten WoldeE. coli chromosome shows a circular structure18 that shades the view of a highly condensed nucleoid19. Local heterogeneities are observed along this circle. Its circular shape fluctuates in time and from cell to cell, however with a variation of not more than 30% in width and length (perimeter), supporting an average picture of a circular chromosome18. We can expect the position of genes in the circular chromosome to be evolutionarily optimized. One functional aspect to this positioning of genes is the implementation of temporal programs via the order of genes locally on chromosome12. This is apparent in the organization of groups of genes in operons  and other aspects of the clustering of genes on smaller or larger chromosomal scales23.Direct imaging of the 27.A still unexplored level of evolutionary optimization is the wiring economy of the TRN. The hypothesis of a parsimonious usage of ’wiring’  in a network, due to construction, maintenance, and  transportation costs, has been intensely discussed in Neuroscience, where the notion of ’wiring economy’, i.e., the minimization of the total wiring length  with regard to the signal transportation efficiency, has been introducedPhysarum polycephalum28 and brain networks on the level of cortical areas27. This is achieved by addressing the statistical question, whether the distances in space spanned by the edges of the network (often referred to as the ’wiring’ of the network) are typically larger or smaller than expected at random. We also compare these observations with the signaling capabilities of the network (below defined as ’regulatory span’) and discuss the biological implications of these observations . We define the regulatory span as the percentage of nodes directly or indirectly reached by each TF. One might formulate refined versions of this regulatory span, e.g., by weighting direct and indirect targets differently.In order to assess the wiring economy of the TRN, we resort to methods developed and applied in the context of the cellular network formed for nutrient transportation by the slime mould 30 and locally stabilized by the binding of structural proteins or nucleoid-associated proteins (NAPs)31. This hypothesis suggests that dedicated TFs are more likely to be associated with long-distance regulation, rather than short-distance regulation, leading to the expectation of high total wiring length .The local regulation of genes takes place via chromosomal structure, as determined by the distribution of supercoiling energy along the chromosomelow total wiring length . At the same time, this hypothesis—due to the hypothesized evolutionary pressure on the number of produced TFs—would also suggest a discernible correlation between distance and gene expression level.The limiting factor for the regulation of genes via TFs is the cost of producing sufficient numbers of each individual TF to reach its targets , thus favoring more proximal targets and hence the expectation of Two distinct hypotheses can be formulated:E. coli.Here we test these two broad, general pictures of the wiring economy of bacterial gene regulation against data for the bacterium As a first step, we investigate, whether the spatial distances covered by the edges of the network (wiring lengths) and the average number of processing steps from source nodes (regulators) to target nodes (regulated genes) are larger or smaller than expected at random.We perform our analysis on the TRN and the coregulatory network  of E. coli see Fig. a, b. To As seen in Figs. We investigate this nonrandom property of the embedded network also by performing all the analyses using genomic distance instead of wiring length (see Methods) to account for one-dimensional sliding of TFs along the DNA. The results are consistent with the observation in Fig. It is conceivable that setting constraints in numerically generating networks to prevent self-regulation may create a bias towards higher wiring length at randomized networks . We studied the impact of this constraint and found no significant impact on wiring lengths  have the highest wiring lengths . As in Warren et al. In terms of processing steps, Fig. By going beyond direct links, the number of processing steps, as well as the regulatory span reveal, to what extent a transcription factor (source node) potentially affects systemic components further downstream of the direct regulation. This comparison of number of processing steps and regulatory span suggests a clear overall picture: In order to ensure a lean and efficient network, the number of descendants is low, but the number of processing steps is enhanced.The number of processing steps of the real CRN is higher than expected at random Fig. c, d. HowSummarizing these observations, the TRN—the ’hardware’ implementing regulation—unites efficient processing (lower-than-random average number of processing steps), very efficient wiring  at the expense of parallelized information distribution (lower-than-random regulatory span). The CRN—the structure underlying coherent activity patterns—is spatially compact (lower-than-average wiring), but shows less efficient processing (higher-than-random average number of processing steps), suggesting the possibility to decouple sub-patterns of activity.32 and Berg et al.33, it is acknowledged that proteins could find their target sites via a combination of one-dimensional sliding along the DNA and three-dimensional diffusion through the cytoplasm. It is also known that for the 1D component of the search process, the search time of a TF can depend on the initial position of the TF, i.e., the position of the regulator gene34. The average search time is estimated to be faster if a TF could find its target site via 1D sliding (≈0.3 sec) rather than a combination of 1D sliding and 3D diffusion (≈150 min)21. Moreover, degradation of TFs (proteolysis) is expectedly present . Assuming a first-order kinetics, the degradation is exponential with time.The effect of distance on the efficiency and reliability of transcriptional regulation has long been studied. Since the work by Riggs et al.35. Efficiency and consistency of gene regulation depend on how close the regulator gene is to the site on DNA the TF has to bind, i.e., the promoter region of the regulated gene21. Pulkkinen and Metzler showed in their study35 that the effect of the distance on the regulation efficiency is significant, i.e., the shorter the distance, the stronger and faster the response. It was also claimed that for efficient gene regulation, the TF concentrations should be high, and the high TF concentrations can be reached through gene proximity. These constraints promote the colocalization of the regulator genes and their targets on the genome. Similarly, at the operon level, the fact that the coregulated operons tend to colocalize is also highlighted by Warren and ten Wolde16 by comparing the network with randomly created ones.The distance between the regulator gene and the regulated gene affects the speed and reliability of transcriptional regulation in bacterial cells substantially36.Prompted by this collection of indirect evidence relating source-target distances with gene expression and by our result of a strong preference in the TRN of short source-target distances, we now analyze the rate of gene transcription, which provides a measure of the network transcriptional regulation capacity, and its relationship with the spatial distance between the regulator and regulated genes by investigating the correlation between the TRN wiring economy and the expression levels of TFs. We use a highly structured RNA-seq dataset, which contains 278 gene expression profilesp values of all profiles: < 1.18 × 10−4, average = 1.31 × 10−6). Considering the significant correlation, it can be argued that with the effect of limiting noise and increasing reliability, the wiring economy is enhanced. Long-distance and correspondingly long wiring length are associated with an increase in gene expression level.We investigate the possible relationship between wiring length and the expression level of the regulator genes (source genes in the TRN). The total wiring length of the outgoing edges from each regulator and the expression level of each regulator are found to be significantly correlated  and network structure , it is not possible to disentangle the various contributions. Correlation between expression levels and total wiring length is highest among the quantities we analyzed, but also (in descending order) maximal wiring length, the out-degree, and the average wiring length show highly significant positive correlations with gene expression levels , but it is nevertheless informative to look in more detail at the relationship between the gene expression levels and distances expected from general considerations. The object relating these two quantities is the reaching time of a transcription factor with respect to its target site. A starting point for a corresponding theoretical framework is outlined in Supplementary Text Regulons37 and the recently introduced iModulons36. Regulons are defined as groups of genes regulated by one regulator37. The concept of iModulons denotes gene sets that represent independently modulated signal processing units derived by applying independent component analysis to RNA-seq datasets. Genes are grouped into such sets by observing patterns in the transcriptome expression data. Specifically, iModulon detection involves blind source separation, i.e., the separation of environmental conditions and internal regulation via unsupervised machine learning.As an application of our spatially embedded view of the bacterial gene regulatory network, we use our framework to disentangle the biological nature and function of two related categories: the standard 36 the authors find that the iModulons are similar to, but distinct from, Regulons. Around 66% of the identified iModulons have significant overlaps with Regulons. Here we show that the embedded-network perspective allows us to uncover different organizational principles behind these two types of regulatory units in bacterial gene regulation. In order to evaluate iModulons from the perspective of embedded networks, we employ the (larger) network compiled in the original iModulon publication36, rather than the standard RegulonDB network from ref. 38. Figure In Sastry et al.Our analysis shows that from a regulatory perspective , iModulons are unspecific in their spatial organization, while Regulons are spatially localized. In the case of coregulation  both units are spatially tightly clustered . These nonrandom features of Regulons and iModulons are further evidence of the involvement of space in the organization of bacterial gene regulation. Furthermore, the embedded-network analysis reveals a discriminating feature between the two types of regulatory units: Regulons are spatially compact in regulation (as evidenced by the shorter than-random wiring length of the corresponding TRN subgraphs) and compact in co-activation (as indicated by the shorter-than-random wiring length of the corresponding CRN subgraphs). On the other hand, iModulons show a low wiring economy in regulation, but a substantial wiring economy in co-activation.Several technicalities make this investigation of TRNs challenging: (1) It is not clear, whether this statistical analysis should be performed on the level of genes or the level of operons. We do both and find that the results are quite similar, suggesting that the organization of bacterial genes into operons is not directly affecting the wiring economy of these networks. (2) It is not clear, whether the relevant network for the discussion of wiring economy is the TRN with its regulatory interactions or rather the CRN with its links representing associations of genes due to common regulation. Again we perform our analysis on both networks.38 assume that substantial parts of the network are still missing. We can only address this limitation by continuing to monitoring the features analyzed here in future versions of the TRN, when they appear .A limitation of our analysis is that even in the case of a well-investigated model organism, like E. coli, our knowledge about transcriptional regulation is incomplete. In fact, current estimates in RegulonDBA crucial step in such an investigation is the choice of the null model. A null model here is the ensemble of random graphs the original network is contrasted with. A null model is characterized by the set of network properties it preserves. Clearly, when the null model is too different from the original network, then almost any network property will seem nonrandom. One therefore needs to be very explicit in the construction of the null model, which features of the original network are preserved and which are randomized. In addition, discarding through randomization different features of the original network can provide further insight into the driving mechanisms behind the identified nonrandom features.40 and employed in ref. 6 and ref. 41. Even though the exact degree sequence of the graph is preserved, higher-order network properties like modularity are destroyed. When assessing for example the small subgraph distribution of a random modular graph with standard switch randomization as a null model, an artifactual nonrandom distribution of small subgraphs would be observed42. (2) Assigning random chromosomal positions to all genes without altering the network. This null model is particularly relevant for the assessment of wiring economy, as the distances covered by each link in the network are efficiently randomized. However, this particular null model does not preserve the highly nonuniform gene density across the circular chromosome. (3) Randomly positioning genes, but retaining the original list of gene positions (iterative gene swapping). In this case, both the network and gene density are conserved, but distances are still randomized.Here we opted for three null models: (1) Degree-preserving switch randomization. This method has been developed in ref. 43.We explored a fundamental principle of bacterial gene regulation, namely its spatial embedding. For both the transcriptional regulatory network (TRN) and the coregulatory network (CRN), we investigated their wiring economy, a concept popular in the analysis of neural connectivity patterns. We find high wiring economy  in the transcriptional regulatory network of the bacterium E. coli, suggesting an evolutionary pressure to avoid long-distance regulation. We can hypothesize that this evolutionary pressure is due to the cost of producing mRNAs, as high mRNA levels are required to diffusively reach distal regulatory targets. This interpretation is confirmed by the scaling of average transcriptome levels (as measured in RNA-seq experiments) with the distance between the source and target genes in the TRN. Future works could take benefit from single-cell RNA sequencing in situ that are developed and will soon be routinely availableOur findings suggest that gene expression levels need to be corrected for source-target distances before functional interpretation. This can have implications for the statistical assessment of differentially expressed genes and for network inference algorithms operating on transcriptome profiles.Our two initial hypotheses do not conflict with each other. Even though our results show strong support for one hypothesis, the other hypothesis (enhanced long-distance regulation by TFs) may also be valid while being just masked by the much stronger nonrandom feature of high wiring economy. Detecting such nonrandom features on multiple scales would require a careful statistical assessment of the whole probability distribution of genomic distances between a TF and its target genes. This calls for a new class of null models capable of preserving the nonrandom network features on one scale, in order to quantify nonrandom features on a different scale.44), where the spatial organization is far more complex and its regulatory contribution, though undisputed, is hard to quantitatively assess.The results presented here can serve as a starting point for a range of further investigations: validating these findings in other bacterial systems, a step currently impeded by the lack of detailed, high-quality data on TRNs in other organisms; extension to eukaryotic organisms  or operons (operon level) and directed edges represent the transcriptional regulation between these nodes. In the gene level TRN, for instance, since the gene 38, a comprehensive database that provides information on transcriptional regulations of E. coli K-12. To create a directed simple graph, multiple interactions between the nodes and the interactions originating and ending in the same operon  are removed from the network. The resulting TRNs consist of 4601 interactions between 1841 genes on the gene level and 1942 interactions between 910 operons on the operon level.We compile the TRN using the dataset from RegulonDB v10.5We assume that the chromosome is circularly embedded in 2D space. The polar coordinates of the nodes on a unit circle are calculated using the positions of the genes along the chromosome in terms of base pairs.47. Figure We also perform our analysis on the CRN of E. coli on gene and operon levels. In the CRN, nodes are the genes/operons, as in the TRN, but edges are the links between pairs of genes/operons coregulated by a third gene/operon. The simple undirected coregulatory graph is the representation of the coregulated pairs. Such a CRN visualizes the capacity of connected units to display a coherent pattern of activity. A statistical comparison of the CRN and TRN representations of the gene regulatory system has been, for example, performed in ref. 48.We use the NetworkX Python package for the creation and manipulation of the regulatory networkswiring length, serves as a proxy for the time spent in diffusing through the cytoplasm. One-dimensional sliding along the DNA is investigated by calculating the arc length between the centers of the nodes, i.e., genomic distance.Considering the chromosome to be circularly embedded in 2D space, the spatial (Euclidean) distance between the centers of the nodes, i.e., The total wiring length is computed as the sum of wiring lengths for all edges in the network. The same applies to the total genomic distance. Note that in contrast to the chromatin organization in eukaryotic organisms, here the genomic distance  and the spatial distance (in space) are related: A high genomic distance implies a high spatial distance.processing steps. Regarding CRNs (simple undirected graphs), the average number of steps is defined as the average number of steps of the largest connected component. A schematic illustration of these performance indicators is given in Fig. In a simple directed graph (TRN), the average number of steps along the shortest paths for all source and target node pairs is denoted as the number of regulatory span. Regulatory span is the average number of reachable nodes from regulators (directly or indirectly) compared to the total number of nodes in a network. Note we do not compute the regulatory span for the CRN, as it is not a meaningful quantity there, due to the undirected nature of this network.Another measure to evaluate graph connectivity is the 40, i.e., edge swapping, to create uniformly distributed directed random networks preserving in- and out-degrees. We keep the node positions fixed and randomize the edges by swapping .The number of swaps required to create a random graph and the number of random graphs are determined by comparing the results of various combinations. We varied the number of null model graphs between 100 and 4000 checking for the robustness of our results. Results are shown for 1000 random graphs. We use the edge swap algorithm also to create randomized undirected CRNs. In this method, we randomize the edges of the original CRN by swapping. This method is denoted as “Edge Swap Random CRN" in the Results. The second method employed to generate a randomized CRN has two steps. First, we generate a randomized TRN using the edge swap method, and second, we build the CRN of the randomized TRN. This null model acknowledges the TRN as the ’hardware’ from which the relational structure, the CRN, is derived. The arguments in favor of this null model are similar to those motivating randomization of metabolite-centric metabolic networks on the level of the bipartite (metabolite-reaction) graph (see ref. nth generated network as the input (reference) network to generate the (n+1)st network. Then, we build the CRN of each randomized TRN to check the consistency of the randomized CRNs. The aim is to test whether employing randomized networks as a base model affects the difference between the original and the randomized networks’ wiring lengths. If the randomization model is biased, the average total wiring length of the generated graphs are expected to be significantly different than the generated ones observed in Fig. As an additional consistency check for our data analysis pipeline, we create a randomized TRN (referred to in the following as ’base model’) and perform all analysis steps on this network, with the expectation that no nonrandom features will be discovered. Specifically, we generate randomized TRNs using the The second method employed to generate random networks is the node swapping method. Two nodes  are selected randomly, and the positions of the selected nodes are swapped. We perform on average 100 swaps per node. In this method, the set of node positions, as well as the interactions between the nodes, are preserved, i.e., the source and target nodes of the edges remain the same  without altering the interactions between nodes. As in the node swapping case, the source and target nodes of the edges remain the same (Supplementary Fig. 36. RNA-seq provides a time-averaged and population-averaged estimate of the mRNA level of each gene.We use the Precise dataset, which offers 278 high-quality E. coli RNA-seq expression profiling datasets from over 15 studies. The dataset contains 20% of RNA-seq datasets available in NCBI GEO33 for E. coli K-12 MG1655 and BW25113Supplementary Information


The objective of the present work is to show the potential of in situ measurements for the investigation of nanoparticles production in turbulent spray flames. This is achieved by considering multiple diagnostics to characterize the liquid break-up, the reactive flow and the particles production in a spray burner for TiO Synthesis in turbulent spray flames is today considered as a valuable alternative for large-scale production of nanoparticles with a relatively low cost. Laboratory-scale spray flame reactors ,10,11,12In this framework, the present study aims to prove the feasibility and the great interest of in situ measurements when investigating nanoparticles production in a laboratory-scale spray flame reactor. The burner consists of a spray nozzle where the liquid fuel is atomized by an annular flow of oxygen, a circular pilot premixed ethylene/air flame and a coflow of pure NThree main processes characterize the flame: (a) the break-up of the liquid jet, (b) the turbulent reactive flow, and (c) the production of the particles. The spatial localization of these three processes is here provided using in situ experimental measurements, classically used in combustion research: (a) shadowgraphy and light scattering for the liquid phase, (b) flame luminosity, CH* and OH* chemiluminescences to characterize the combustion process, and (c) light scattering to localize TiOThe paper is organized as follows. First, the experimental setup is described by presenting the flame synthesis burner and the different optical diagnostics considered in this work. Then, the potentials and the difficulties in applying shadowgraphy and light scattering to the characterization of nanoparticles flame synthesis are discussed. Finally, results are presented by looking at the three different processes that characterize nanoparticles’ flame synthesis.The burner  studied in the present work is the same as used in ,3,4,5,15The obtained flame is visualized in The optical setup used to perform shadowgraphy, light scattering and emission measurements is schematically presented in A YAG Surelite 400 mJ Continuum laser at 532 nm wavelength is used for the light scattering on the solid particles. A set of two lenses creates a laser sheet of 70 mm height and about 300 A second Teledyne Princeton PIMAX camera equipped with a Sodern UV lens 100F/2.8 is used for measurements of flame global spontaneous emission as well as CH* and OH* emissions. The spatial resolution is 95 Time-averaged results for all measurements are obtained by subtracting the background and considering 500 images.Several phenomena can be visualized using the shadowgraphy measurements as illustrated in In the reactive case, with the injection of TTIP, spots of light due to diffraction of partially transparent TiOSince the shadography measurements provide line-of-sight-integrated information, light scattering measurements were also performed to investigate spray and TiOThe main processes occurring during the flame synthesis, schematically presented in Thanks to shadowgraphy and light scattering measurements, the presence of liquid can be investigated. When looking at the instantaneous results of It should be noted that some differences are observed between the two techniques. In particular, a dense cylindrical liquid jet seems to be detected by light scattering whereas the atomization seems to occur more rapidly from shadowgraphy results. However, it has to be reminded that the two systems neither present the same sensitivity nor the same resolution of the liquid structures. Moreover, line-of-sight-integrated measurements are provided by shadowgraphy, whereas light scattering gives access to planar information. Finally, light scattering results may be affected by the fact that both spray and TiOTime-averaged shadowgraphy and light scattering results are presented in Even if a more detailed characterization of the performances of these techniques in the context of flame synthesis is desirable, some common conclusions on the spray process can already be drawn. First, high fluctuations of the spray position are observed (not shown). Second, results are not symmetric, possibly due to the difficulty in obtaining a perfect centering of the liquid injection syringe in the dispersion system. Third, TiOThe combustion process is investigated here by analyzing images of flame global spontaneous emission  as well Looking at the instantaneous global emission results, Results are quite different between the two cases with and without injection of TTIP, indicating that the addition of TTIP has a non-negligible effect on global spontaneous emission, as already deduced from  of TTIP b, the maTime-averaged fields of OH* and CH* chemiluminescences are presented in Classically, time-averaged line-of-sight integrated results could be transformed using an Abel-inversion to obtain 2-D planar information. Since the investigated flame is not quite axis-symmetric, as can be deduced by looking for example at the CH* results in injector , it can injector b and aloinjector a. Then, Far downstream of the burner (The objective of the present work was to demonstrate the interest in in situ optical diagnostics classically used in combustion research for the investigation of TiOShadowgraphy measurements showed that it was possible to simultaneously localize the liquid phase and the nanoparticles. Light scattering results allowed to characterize the TiO


In the study of rock mechanics, the variation of rock mechanical characteristics in high-temperature environments is always a major issue. The discrete element method and Voronoi modeling method were used to study the mechanical characteristics and crack evolution of granite specimens subjected to the high temperature and uniaxial compression test in order to study the internal crack evolution process of granite under the influence of high temperatures. Meanwhile, dependable findings were acquired when compared to experimental outcomes. A modified failure criterion was devised, and a Fish function was built to examine the evolution behavior of tensile and shear cracks during uniaxial compression, in order to better understand the evolution process of micro-cracks in granite specimens. Shear contacts occurred first, and the number of shear cracks reached its maximum value earliest, according to the findings. The number of tensile contacts then rapidly grew, whereas the number of shear cracks steadily declined. Furthermore, it was found that when temperature rises, the number of early tensile cracks grows. This study develops a fracture prediction system for rock engineering in high-temperature conditions. Deterioration of the mechanical properties of crystalline rocks due to temperature variations is always a problem in the field of rock mechanics, as thermal attack induces new microcracks or enlarges existing microcracks. The physical and mechanical properties of rocks after heat treatment have been investigated extensively ,4,5,6,7,Along with the experimental investigations of the mechanical properties of rocks, extensive numerical studies have also been conducted to simulate rock behaviour. The discrete element method (DEM) has been used extensively for the numerical simulation of rock and rock mass, as the finite element method is not able to model the development of cracking and slope failure by slip. Abe (2016) analysed the elastic properties, such as the Young’s modulus and Poisson’s ratio of a DEM material, and found that the influence of damage on the Poisson’s ratio and Young’s modulus depends on the coefficient of friction between crack surfaces under compression . Li and The grain-based method (GBM) has also recently been used to study the mechanical properties of rocks. Bahrani and Kaiser 2016) used GBM to investigate the influence of specimen size on the strength of intact rocks and rocks with defects in unconfined conditions . They fo used GBMA solution to the problem of obtaining a realistic ratio of unconfined compressive strength (UCS) to tensile strength was proposed for use in Universal Distinct Element Code (UDEC) . A list Thermal damage should also be considered in numerical simulations. A coupled thermo-mechanical model can be built using the combined finite-discrete element method (FDEM). A thermal cracking example has previously been assessed and model predictions compared with experimental results verifying the correctness of the coupled model in dealing with the problem of thermal cracking . HoweverIn this work, a novel approach was used to investigate the discreteness of rock materials after thermal treatment using the Voronoi method in UDEC. The findings related to mechanisms of fracture initiation and the relationship between shear cracking and tensile cracking will be discussed. The mechanical characteristics of rock specimens tested after high-temperature exposure in a laboratory were used to investigate the macroscopic and microscopic mechanical behavior of rock specimens from the Fujian province, China. The result provides a significant method and effective parameters for rock engineering subjected to high temperatures.In this study, the Voronoi method was selected to build a random joint model with a width of 50 mm and a height of 100 mm. How cracks appear and develop was studied by observing changes in the modelled contacts.In addition, “fully deformable” blocks were used in the UDEC model which allowed for internal deformation of each block. Although early discrete element algorithms believed that blocks were rigid, the importance of block deformability is increasingly acknowledged, notably in stability assessments of subterranean entrances and seismic response models of buried structures. In this study, deformable blocks were chosen to model the granite specimens after high-temperature exposure.Models with a block edge size of 2.5 mm were built as shown in Crack initiation in the laboratory specimens occurred well before the UCS was reached. In the numerical simulation in UDEC, cracking at low loads was expected to occur along the contact surfaces as the blocks deform elastically. Consequently, an elastic model with thermal parameters was selected to model the elastic response of the granite material. The parameters required for the model include the density, bulk modulus, shear modulus, thermal conductivity, specific heat, and thermal expansion. The density, bulk modulus, and shear modulus were obtained from experimental results which have already been published . The thef is a multiplication factor, usually set as 10; K and G are the bulk and shear moduli, respectively; and ∆Zmin is the smallest width of an adjoining zone in the normal direction, see The contact behavior was described using a Coulomb slip model with residual strength properties. The values for cohesion and friction at initial contact were based on the results of a tri-axial compression test and were modified for use in UDEC. It was assumed that contact locations lose their cohesion and friction when the failure occurs. Values for the normal and shear stiffnesses of the contacts were calculated using the method proposed in the UDEC manual. The equation for calculating the fictitious joint normal stiffness and the joint shear stiffness from the equivalent stiffness, expressed in stress-per-distance units of a zone, is of the following form :(1)kn=ksThe simulated results of the uniaxial test in UDEC before and after calibration are shown in The stress-strain relationship for the uniaxial compression of granite after thermal damage was examined in two ways. The results for the 1000 °C thermal damage sample will be used as an example to explain the two methods here. In UCS measured 56.39 MPa in the lab, while expected values were 64.50 MPa shown in . The expIn the analysis, the difference arises because the joints in the models are different. Discreteness is modelled using the Voronoi method in the models, and the different distribution of elements within each model influences the calculation results. The results for the 1000 °C models are very similar to the laboratory results . The theThermal damage causes thermal stress in a rock-type material. In a rock-type material, thermal damage creates thermal stress. The high temperature and post-cooling behavior of rocks will be compared using the 1000 °C heating cycle as an example. The estimated stress–strain relationships for granite at 1000 °C and granite cooled to room temperature are shown in According to Gao et al. (2016), the failure status of a contact at a specific loading stage in the UDEC Graphical Interface is dependent on the stress across the contact at that moment . As a reIf the shear force of a joint equals the shear limit, then the contact is regarded as a shear crack. If the normal force or shear force of a joint equals zero, then the contact is regarded as a tensile crack. Once contact is considered to have undergone shear failure or tensile failure, fracture occurs.τs is the shear stress, c is the cohesion, and φ is the frictional angle. Under this new criterion, contacts with a shear force greater than or equal to the shear limit τmax are recorded as shear cracks. If the normal force of a joint equals zero, then the contact is regarded as a tensile crack.It is unsuitable to use this criterion to model shear cracking, as the contact is no longer considered to be a shear contact once the shear force exceeds the limit. Therefore, a modified criterion is proposed in this paper in which contacts which meet the condition of Equation (2) are deemed to be shear cracks,As a result, there is a shift in the kind of failure represented in the model, where shear contacts become tensile contacts. This result is in general agreement with the results of Kazerani 2013) and Gao (2013) who used triangular meshes in UDEC, although their results were slightly different 3 and Gao. HoweverTo investigate the effect of heat treatment on the development of shear cracks and tensile cracks, the percentage of tensile contacts as a function of strain during uniaxial compression testing after heat treatment at different temperatures is shown in Although UDEC provides its own embedded criterion, users can create their Fish function to determine contact failure types. Based on the judging criterion contained in UDEC, a modified criterion, see Equation (2), was developed and a Fish function was written to extract information about shear and tensile contact failures. However, to verify whether the initial cracking which occurs during the uniaxial compression of granite is due to shear or tensile loading, additional numerical simulations may be required. With the criterion established in this paper, shear cracks rather than tensile cracks appear first. Furthermore, it was found that heat treatment affects the development of shear cracks and tensile cracks, and the transition of shear cracks to tensile cracks.(1)If the material has a non-negligible high porosity, the porosity needs to be considered in the UDEC modelling process.(2)In this research, the model established by Voronoi method can obtain the result which is more consistent with the actual situation after the thermal-mechanical coupling operation. Meanwhile, this method can be used to study the evolution or rock crack after thermal treatment.(3)According to the modified contact statistics method, shear contact first occurs in granite specimen, and part of shear contacts turns into tensile contacts when the shear contact approaches the peak value.(4)The thermal effect will lead to the advance of tensile contact. The higher the treatment temperature is, the higher the initial number of tensile contact is. The shear contact has the opposite rule.A numerical model for describing rock behavior under uniaxial compressive loading after heat treatment was established using the Voronoi method in UDEC. The model predictions were compared with the experimental results previously obtained by Chen et al. (2017) and an acceptable agreement was achieved. A modified criterion was proposed to differentiate between shear cracks and tensile cracks. From the results of these numerical investigations, the following conclusions can be drawn: