At present, research on spinal shortening is mainly focused on the safe distance of spinal shortening and the mechanism of spinal cord injury, but there is no research on the biomechanical characteristics of different shortening distances. The purpose of this study was to study the biomechanical characteristics of spine and internal fixation instruments at different shortening distances by the finite element (FE) method.An FE model of lumbar L1-S was established and referred to the previous in vitro experiments to verify the rationality of the model by verifying the Intradiscal pressure (IDP) and the range of motion (ROM) of the motion segment. Five element models of spinal shortening were designed under the safe distance of spinal shortening, and the entire L3 vertebra and both the upper and lower intervertebral discs were resected. Model A was not shortened, while models B-E were shortened by 10%, 20%, 30% and 50% of the vertebral body, respectively. Constraining the ROM of the sacrum in all directions, a 7.5 N ·m moment and 280 N follower load were applied on the L1 vertebra to simulate the motion of the lumbar vertebrae in three planes. The ROM of the operated segments, the Von Mises stress (VMS) of the screw-rod system, the VMS of the upper endplate at the interface between the titanium cage and the L4 vertebral body, and the ROM and the IDP of the adjacent segment (L5/S) were recorded and analysed.All surgical models showed good stability at the operated segments (L1-5), with the greatest constraint in posterior extension (99.3-99.7%), followed by left-right bending (97.9-98.7%), and the least constraint in left-right rotation (84.9-86.3%) compared with the intact model. The VMS of the screw-rod system and the ROM and IDP of the distal adjacent segments of models A-E showed an increasing trend, in which the VMS of the screw-rod system of model E was the highest under flexion (172.5 MPa). The VMS of the endplate at the interface between the cage and L4 upper endplate of models A-E decreased gradually, and these trend were the most obvious in flexion, which were 3.03, 2.95, 2.83, 2.78, and 2.61 times that of the intact model, respectively.When performing total vertebrae resection and correcting the spinal deformity, if the corrected spine has met our needs, the distance of spinal shortening should be minimized to prevent spinal cord injury, fracture of internal fixations and adjacent segment disease (ASD). Since MacEwen et al. reported a series of neurological symptoms in 74 patients with spinal deformities after spinal orthopedic surgery in 1975, surgeons have begun to realize that excessive stretch of the spinal cord may cause damage to the nervous system . After tThe spinal cord, which is segmentally tethered to the spine through the spinal cord tether and nerve root, is relaxed due to the decrease in tension caused by the shortening of the spinal column, but with the increase in the shortening distance, many neurological complications will occur . TherefoHowever, to the best of our knowledge, there have been no finite element studies related to spinal shortening. Therefore, this study intended to evaluate the biomechanical characteristics of different shortening distances of the spine at a safe distance by finite element analysis.Data from the L1-S lumbar spine FE model were collected from a healthy adult male volunteer . The volunteer had no previous history of trauma or fracture. Any spinal diseases were excluded by clinical imaging examination to establish a normal intact FE model. The volunteer was recruited by the Spinal Surgery Department of Tianjin Hospital and signed informed consent forms in accordance with the relevant regulations, which were submitted to the Ethics Committee for approval. A 64-slice spiral computed tomography scanner  was used to obtain the tomographic image data of the L1-S vertebrae with a 0.625 mm interslice interval in DICOM format. The image data were imported into Mimics 20.0  to create a 3D surface model of the L1-S vertebrae and then into 3-Matic 12.0 software  in STL format to perform wrapping and smoothing operations, remove excess triangular patches, and initially establish the structure of intervertebral disc and nucleus pulposus for exporting into Geomagic Studio 12.0 . After smoothing and accurate surface processing, the model was imported into Hypermesh 2017  for mesh division and ligament construction and finally into Abaqus 2019  for model assembly, material property definition and finite element analysis.As shown in As shown in Fig. To validate the rationality of the model, the in vitro verification method of Renner et al. was implemented , in whicThe boundary conditions and loads of the FE model were loaded in ABAQUS software. In all the FE models, the bottom of the sacrum was constrained in all degrees of freedom, and a compressive preload of 280 N was applied on the upper surface of the L1 vertebra to simulate part of the body weight of the lumbar vertebrae , 30. A pIn this study, the biomechanical characteristics of the different surgical methods were analysed by measuring and calculating the ROM of operated segments, the VMS of the screw-rod system, the VMS at the interface between the titanium cage and the L4 upper endplate, and the ROM and IDP of the distal adjacent segment (L5/S).In this study, the rationality of the FE model was verified by referring to the experimental method reported by Renner et al. By applying the same load and boundary conditions, the ROM of each vertebral segment of L1-S and the IDP of L4/5 were measured and compared with previous research results –28. The As shown in Fig. The ROM of L5/S for the different models under loading conditions is shown in Fig. The IDP trend and stress distribution of L5/S under all loading conditions of the different models are shown in Figs. As shown in Fig. The maximum VMS trend of the posterior rods of each surgical model and the stress distribution under flexion are shown in Figs. The spinal shortening technique is often used in congenital spinal deformities, benign and malignant invasive tumours, spinal fracture and dislocation, tethered cord syndrome and other diseases , 31–33. Then, we evaluated the ability of the model to resist the motion of the operated segments by using the structural stiffness of the model. In this study, the structural stiffness of models A-E increased significantly and had a similar trend. Because the biomechanical assessment of intervertebral fusion was not possible, successful intervertebral fusion was considered according to the FDA definition of bridging trabecular bone between fusion segments, a translational activity less than 3 mm, and an ROM less than 5 degrees . Liang eSpinal fusion surgery accelerates the onset of ASD by increasing intervertebral mobility and mechanical stress, resulting in severe back pain, radicular symptoms, or neurogenic intermittent claudication, which can seriously affect people’s daily lives –43. It hIn vertebral fusion, we should not only consider the possibility of bone graft nonfusion and adjacent segment disease but also consider the risk of vertebral bone destruction and cage subsidence at the interface between the cage and vertebral body. In this study, except for the extensional loading condition, the endplate stress of all surgical models at the interface between the cage and L4 upper endplate was greater than that of the intact model, and the stress showed a downwards trend in models A-E. The reason may be that the internal fixation and posterior structure of the vertebral body limit the extension movement of the spine, thus affecting the VMS of the endplate. It was previously reported that the failure strength of cortical bone was between 90 and 200 MPa . Our stuAlthough the results of this study show that spinal shortening technique has certain advantages in the stability of fusion segments and the reduction of endplate stress, the spinal shortening technique still has certain limitations in clinical application. In children, the growth of non-fusion segments during the growth of the spine may reestablish the tension of the spinal cord, it may affect the annual 1 mm growth retardation of the spinal fusion segments, and even lead to crankshaft deformities . MoreoveThere were some limitations in this study. The finite element model data in this study were only based on a 24-year-old adult male, and this study was without statistical analysis, which is a common defect of finite element analysis. At the same time, this study simplified the finite element model, and the material properties of each structure were assumed to be isotropic, which cannot more accurately reflect the biomechanical changes of the lumbar structure. Second, previous studies on the mechanism of acute spinal shortening and spinal cord injury were often based on animal experiments, in which the selected segments were equivalent to the human thoracolumbar vertebrae or the middle and lower thoracic vertebrae to simulate the actual situation in the human body The results of this study suggested that under the condition of ensuring the safety of the spinal cord, with the increase in the spinal shortening distance, it increased the stress of the internal rods and ROM and IDP of the adjacent distal segment, although it reduced the stress of the endplate at the interface between the titanium cage and L4 upper endplate and provided a slight advantage for the stability of the fusion segments. Therefore, when spinal correction meets our needs during surgery, the distance of spinal shortening should be reduced as much as possible to prevent spinal cord injury, internal rod fracture and the occurrence of ASD.


A novel, low-cost, sensitive microwave microfluidic glucose detecting biosensor incorporating molecularly imprinted polymer (MIP) is presented. The sensing device is based on a stub resonator to characterize water glucose solutions. The tip of one of the stubs is coated with MIP to increase the selectivity of the sensor and hence the sensitivity compared to the uncoated or to the coated with non-imprinted polymer (NIP) sensor. The sensor was fabricated on a FR4 substrate for low-cost purposes. In the presence of the MIP, the sensor loaded with a glucose solution ranging from 50 mg/dL to 400 mg/dL is observed to experience an absorption frequency shift of 73 MHz when the solutions flow in a microfluidic channel passing sensing area, while the lower limit of detection (LLD) of the sensor is discovered to be 2.4 ng/dL. The experimental results show a high sensitivity of 1.3 MHz/(mg/dL) in terms of absorption frequency. Diabetes is one of the four main noncommunicable diseases and has become one of the fastest growing diseases in the world. It will be the seventh leading cause of death worldwide by 2030 . The IntBiosensing technologies are constantly being examined, and two types of optical [2O2 to detect and measure glucose. Nevertheless, GOD can be damaged by some chemical substances and detergents or changes in its optimal environment. Indeed, those GOD-based glucose sensors are always vulnerable to deactivation due to chemical deformation and possible thermal changes during fabrication, storage, or even while using [Monitoring blood glucose level is important in managing diabetes and maintaining it in a safe range (between 80–120 mg/dL) is essential.  optical  and elec optical  biosenso optical ,6,7. TheTherefore, many researchers have tried to demonstrate the feasibility of alternative sensing methods for precise and reliable glucose monitoring. Considerable studies proposed microwave sensors for glucose level detection. The capability of microwave-based sensors to non-destructively distinguish and measure the parameters inside the liquid sample volumes make it a great alternative to the invasive daily glucose monitoring techniques. Microwave biosensors also offer high sensitivity and real-time monitoring . AnotherResearchers proposed several configurations based on planar technology for resonant frequency-based glucose sensors . The priTherefore, technical improvements are required to increase sensitivity and selectivity while reducing size and cost. Accordingly, synthetic receptors and molecular imprinting to develop such synthetic receptors can potentially reduce and/or removing limitations of enzyme . MoleculThe molecularly imprinting process usually involves starting the polymerization of monomers in the presence of a template molecule that is extracted later, which leaves complementary cavities. These polymers have an affinity for the original molecule. The molecular imprinting schematic illustration is shown in This paper presents a novel, simple, inexpensive, non-enzymatic, and sensitive characterization method by introducing a microfluidic integrated MIP-coated microwave biosensor capable of quantifying glucose concentration. A glucose imprinted polymer film is synthesized and applied as a selective coating on a stub resonator, and a microfluidic system is integrated on the top of the sensing area to control the flow of the liquid for an accurate dielectric measurement. Changes in resonant frequency due to glucose variation in the transmitted signal are analyzed.The model of the proposed sensor can be seen in The same stub structure was built to use as a reference, without the MIP, to validate the measurements. The reference stub was constructed face to face with the sensing one to simplify the fabrication of the channel and flow of the aqueous solutions in the sensing region. It allows us to measure both responses simultaneously: the distance between two microstrips is 17 mm, and the tips of two stubs are 7 mm apart. Each microstrip was soldered to two subminiature version A (SMA) connectors as input and output RF ports. Two duplicated sensors from the same fabrication process were elaborated to validate the performance of the biosensor at several attempts.The microfluidic system was designed, and 3D printed by a high-resolution SLA/DLP 3D printer  to provide a specific volume of the solution in the sensing area. It was glued with transparent epoxy on the top of both stub resonators at the center to seal the sensing area and prevent leakage. To track the flow visually, a transparent photo resin was chosen to create the microfluidic system. It was printed with a length of 40 mm, a width of 15 mm, and a height of 4 mm. Two pairs of inlets and outlets were designed with a diameter of 2 mm and placed 18 mm apart. At the bottom of the housing, two channels were designed with a depth of 1 mm and a length of 18 mm to be filled with the glucose solutions to be characterized.In order to analyze the performance of the sensor in terms of frequency responses, Ansys Electronics Desktop was utilized as a 3D EM simulator. The unloaded sensors were designed to operate at 7 GHz, and a shift towards lower frequencies was expected when the liquid under test flowed in the sensing region at the tip of the stub resonator due to the high relative permittivity of water A general illustration of an open stub resonator is shown in The input impedance of the resonator was calculated as in Equation (1) which is extracted from the mathematical model of the open stub resonator .(1)Zin=S12, S21) were calculated by converting the ABCD matrix in Equation (2) to S-parameter in Equation (3). Hence,Then, the S-parameters of the open stub resonator (S-parameter of Equation (3) simplifies in Equation (4),A normalized characteristic of impedance and impedance of resonator were considered From Equation (5), an ideal infinite attenuation or notch is obtained when the electrical length of the open stub resonator is a quarter-wave (h) of the substrate, the conductor Width (W), and the frequency (f). The capacitance :By changing the electromagnetic properties, such as the relative permittivity of the materials constituting or surrounding the resonator, the amount of energy stored in it and its losses can vary dramatically. To measure changes in permittivity due to varying concentrations of glucose, MIP was used as a selective receptor to trap target analytes, and microfluidic channels were incorporated in the sensor where the solutions flowed in, and a change in permittivity was sensed. The variation of concentrations of biomolecules attached to the MIP changes the permittivity, thus resulting in changes in the total capacitance and a shift in the resonant frequency according to Equation (7). The microfluidic device enables the water glucose solution to effortlessly pass the sensing area through the channels in the selected region where MIP was coated to study the changes in permittivity.Acrylic acid (AA);Poly (methyl methacrylate) (PMMA);Ethylene glycol dimethacrylate (EGDMA);4,4′-Azobis (4-cyanopentanoic acid) (ACPA);Dimethyl sulfoxide (DMSO).In this research, all the chemicals utilized were analytical-reagent grade and acquired from Sigma Aldrich Co.  The chemicals used in this project are listed below:Both the MIP and the NIP were prepared by adapting procedures described in the literature ,25. The (1) An amount of 1.0 mmol (69 µL) of AA, called a functional monomer, and 0.25 mmol (0.045 g) of glucose, used as a template, were dissolved in 5 mL DMSO, and stirred for 1 h. In another flask, 4.0 mmol (0.79 g) of EGDMA and 0.0050 g of ACPA were stirred for 1 h and then mixed with the former solution. Nitrogen gas was bubbled for 15 min to remove dissolved oxygen; (2) polymerization was initiated by exposure to UV light (wavelength of 385 nm and 405 nm) for 15 min; and (3) bulk polymers were washed with water to remove any non-polymerized monomers and solvents. (4) The MIP was dried by heating at 60 °C for 12 h and (5) then milled with mortar and pestle to make a fine powder. The same procedure was repeated to prepare the non-imprinted polymer (NIP); however, without adding the template (glucose) as a control to determine the selectivity of the MIP. (6) The polymer powders were mixed with a solution of 5% PMMA (Adhesion) in Acetone. The ratio of PMMA to MIP (or NIP) powders was 50:50. (7) A certain amount (20 µL) of the mixed solution was applied to the tip of the Stub resonator. Due to the rapid vaporization, a thin layer of MIP (or NIP) was formed on the sensor’s surface. (8) To evaporate the remaining solvent, the sensor was heated at 60 °C for 24 h. (9) The final step was to remove the template (glucose) from the MIP by washing the coated senor with DI water for 5 h. In order to deposit MIP and NIP accurately in the desired position (tip of the stub resonator) in sensors, a thin film of Kapton was utilized as a mask, shown in A series of 5 water glucose solutions were prepared with glucose concentrations varying between 50 mg/dL and 400 mg/dL. The experiment was performed after the water glucose solutions rested for about 12 h to establish the anomeric equilibrium. The solutions were measured several times in both sensors (MIP-NIP and MIP-uncoated): right after resting, 1 h after the first measurement, the subsequent measurement was performed after 3 h of rest from the first attempt, and the last measurement was carried out after 24 h of rest. The glucose solutions were pumped one by one through the channel with the aid of a peristaltic pump. While the solution kept flowing continuously at a rate of 5 mL/min in each procedure, three sets of data were collected: right after injecting the solution on sensor, 5 min, and 10 min after the first measurement. After each measurement, DI water was pumped into the channel to wash it and remove absorbed glucose from the MIP. To avoid any shift in the dielectric properties of the glucose solutions, the temperature was maintained constant at 20 °C.S21 scattering parameter was used to characterize the glucose concentration. The performance of the proposed biosensor was characterized in terms of its S-parameters using a performance vector network analyzer (VNA)  in a two- ports configuration after the SOLT calibration up to 20 GHz. The measurement resolution is 0.1 dB, 1 Hz, and 0.5° in terms of magnitude, frequency, and phase, respectively. The device under test (DUT) was connected to the VNA ports via coaxial cables. All experiments were carried out under normal laboratory environment conditions. In this experiment, In the process, each time, first, the response of the sensor with an empty flow channel was measured, then the flow channel was filled with DI water continuously as a reference and also to wash the glucose from the MIP between each experiment to verify the reproducibility and repeatability of the study, and finally, filled with solutions with various glucose concentrations. The flow of the solutions was controlled using a pump.The simulated and measured frequency response of the unloaded sensor (empty flow channel) (in yellow) and the measured frequency response of the loaded flow channel where DI passes the sensing area on top of the stub (in blue) compared to the simulation, up to 10 GHz, are demonstrated in The reflection and transmission coefficients of the MIP-coated biosensor in the frequency range between 2 to 6 GHz are plotted in In this study, we applied the fabricated MIP on two duplicated sensors to validate the performance of the biosensor at several attempts with different masses of MIP. These sensors were tested and the sensitivity in terms of a shift in the absorption peak due to changes in glucose concentrations was verified. Both main and duplicate sensors showed the same behavior in detecting different glucose concentrations in solutions which demonstrated the reproducibility of the sensor, as can be seen in the Frequency response of both main and duplicate senor in The calibration curves of both main and duplicate MIP-coated sensors were constructed by plotting the absorption peak shift versus the glucose concentrations in In order to verify the proposed sensing principle, the procedure mentioned above was performed in uncoated and NIP-coated stub resonators. A set of measurements were performed using the same concentrations of glucose solutions, and the transmitted signal was recorded. As expected, the frequency response of the uncoated and NIP coated sensing devices, in the absence of the template cavities (glucose), did not change with the flow of the same glucose solutions of 100 mg/dL and 400 mg/dL in the flow channel, as demonstrated in To verify the selectivity of the MIP-coated sensor, solutions of glucose and two epimers of glucose, named mannose and galactose, were studied. The experiment was followed by the flow of the mannose and galactose solutions ranging from 100 mg/dL to 300 mg/dL in the channel. The frequency response of the MIP-coated sensor did not change with the flow of the solutions, even by increasing the concentration of the mannose and galactose, as demonstrated in Furthermore, to examine the repeatability and stability of the responses, the 100 mg/dL glucose solution was pumped continuously into the flow channel for 75 min, and the transmitted signal was recorded at the interval of 15 min. The results on Although the studied range of glucose concentrations (50–400 mg/dL) covers most of the glucose levels in the human body, the linear response of the proposed biosensor confirmed that solutions with various concentrations can easily be measured after appropriate dilution. Blood glucose level measurement is a challenging task, and there are many factors affecting measurement accuracy that need to be considered when a real-life glucose range measurement is concerned. 2 = 0.9839) within the range of 50–400 mg/dL, while the lower limit of detection (LLD) of the sensor is discovered to be 2.4 ng/dL. Our sensing device differentiates the glucose variation regardless of the mass of MIP and is effectively selective toward glucose compared to similar compounds. In addition, it requires a small volume of samples (40 µL) and is highly sensitive (1.3 MHz/(mg/dL)) compared to other similar approaches. This capacity will help us to miniaturize the sensor. Moreover, the combination of molecularly imprinted technology and a microwave resonator that can be fabricated easily at a low cost, provides the opportunity to make a passive and battery-less sensing device for point-of-care monitoring purposes.The proposed MIP-coated open stub resonator biosensor is developed as an inexpensive and sensitive sensing device that detects variation in glucose concentration in the solution by measuring shifts in the absorption peak. Acrylic acid (AA) is selected as a suitable functional monomer, and 4,4′-Azobis (4-cyanopentanoic acid) (ACPA) is chosen as a fast initiator. Furthermore, the frequency response of the stub resonator shifts due to the varying glucose concentrations, which demonstrates an excellent linear correlation (R


The goal of this research is to accurately extract the parameters of the photovoltaic cells and panels and to reduce the extracting time. To this purpose, the barnacles mating optimizer algorithm is proposed for the first time to extract the parameters. To prove that the algorithm succeeds in terms of accuracy and quickness, it is applied to the following photovoltaic cells: monocrystalline silicon, amorphous silicon, RTC France, and the PWP201, Sharp ND-R250A5, and Kyocera KC200GT photovoltaic panels. The mathematical models used are single and double diodes. Datasets for these photovoltaic cells and panels were used, and the results obtained for the parameters were compared with the ones obtained using other published methods and algorithms. Six statistical tests were used to analyze the performance of the barnacles mating optimizer algorithm: the root mean square error mean, absolute percentage error, mean square error, mean absolute error, mean bias error, and mean relative error. The results of the statistical tests show that the barnacles mating optimizer algorithm outperforms several algorithms. The tests about the computational time were made using two computer configurations. Using the barnacles mating optimizer algorithm, the computational time decreases more than 30 times in comparison with one of the best algorithms, hybrid successive discretization algorithm. The increases in the demand for electric and thermal energy, the political issues, and the supply, especially with natural gas, have led to an accelerated price growth in recent times. Additionally, the fight against climate change also creates a new perspective for renewable energy, especially for the electric energy produced by photovoltaic panels.According to the report (the newest) presented in , from 20Knowing the photovoltaic cells and panel parameters is vital for the researchers, manufacturers, and photovoltaic systems designers . The curSome papers reviewed the method used to extract the parameters of the photovoltaic cells and panels. Cotfas et al. discussed 35 methods to extract the PV parameters, pros, and cons. Most of them are analytical, but two metaheuristic algorithms, particle swarm optimization and genetic algorithms, are discussed . Humada By analyzing the review papers and the specialized literature, several algorithms were selected to compare the results with the ones provided by the barnacles mating optimizer algorithm (BMOA) considering the accuracy and the extracting time, which implicitly means the number of iterations necessary for the algorithm to extract the parameters.The shuffled complex evolution (SCE) algorithm is part of the mathematical group. It uses four concepts: the combination of random and deterministic approaches, clustering, systematic evolution, and competitive complex evolution CCE, which is the critical component of SCE . PatternImperialist competitive algorithm (ICA)  is part The physics group contains some algorithms, such as the simulated annealing algorithm (SA) , where tThe biology group contains a lot of algorithms, both simple and hybrid. The first algorithm was the genetic algorithm (GA) which is based on selection, crossover, and mutation ,25,26. JThe analytical five-point method (5P) is used for comparison due to its good performance, being one of the best analytical methods for photovoltaic cell parameters extraction .Implementing a new metaheuristic algorithm for the first time to extract the five or seven parameters of three photovoltaic cells and for three photovoltaic panels, barnacles mating optimizer algorithm (BMOA);Comparison of the results obtained using BMOA with the algorithms chosen using the statistical tests and the number of iterations;Comparison of the results when the number of the epochs and the population are changed;Analyzing the computational time necessary to extract the parameters of photovoltaic cells and panels function of the computer configuration;BMOA is an algorithm that provides excellent results for the statistical test applied compared with the algorithms from the specialized literature;The extracting time is reduced more than 30 times when the barnacles mating optimizer algorithm (BMOA) is used in comparison with SDA algorithm, so the BMOA algorithm comes to fill the gap for the algorithms with high accuracy and a short time to extract the parameters of the photovoltaic cells and panels.The novelty and contributions of this paper are:The paper is structured in four sections: introduction, method and algorithm description, results and discussions, and conclusion.The SDM and DDM models are used in this paper to extract the parameters of the monocrystalline silicon, amorphous silicon, RTC France photovoltaic cells, Sharp ND-R250A5, PWP201, and Kyocera KC200GT photovoltaic panel.phI, the reverse saturation current I0, the series resistance sR, the shunt resistance shR, and the ideality factor of diode n.TV = kT/q is thermal voltage, q = 1.60217646 × 10−19 is electric elementary charge, k = 1.3806503 × 10−23 is Boltzmann constant, and T is temperature of the photovoltaic device.The single diode model (SDM) allows for the determination of five parameters using Equation (1) the photogenerated current The SDM model is used to extract the parameter when necessary, fast response, and a low manufacturing cost .pN represents the number of the photovoltaic cells connected in parallel, sN represents the number of the photovoltaic cells connected in series, index (1) is for the diffusion mechanism, and (2) is for the generation-recombination mechanism. If pN and sN are equal 1, Equation (2) becomes DDM model for photovoltaic cells.The two-diode model considers the diffusion and generation-recombination mechanism which takes place in the photovoltaic cells and panels. The DDM model provides very good results, and it must be used for low irradiation levels and to have a high curve fitting accuracy . The matMany metaheuristic algorithms are used to extract the parameters of the photovoltaic cells and panels to increase the accuracy of their analysis and characterization.Sulaiman et al. analyzing the barnacles’ mating action, developed the Barnacles Mating Optimizer (BMO) Algorithm. It is a metaheuristic optimization algorithm .Step 1: Initialize the optimization algorithm with respect to the population size, length of the penis, upper and lower bound, and so on;Step 2: Perform the objective function calculation for each and every barnacle;Step 3: Perform sorting in descending order from the largest length of the penis to the shortest; the optimal result is position on the top population;Step 4: Perform the iteration processWhile (epoch < Max epoch),Based on the dad and mom selection equation, choose the dad and mom of barnacles.If explored, DadBarnacles and MomBarnacles = length of penis set value (LP).For each variable,Generate off-springend forelse if explored DadBarnacles and MomBarnacles > LPfor each variable,generate off-spring Equation (8)end forend ifif the solution is out of boundaries, obtain the current barnaclescompute objective functionperform sorting and updating processe = e + 1end whilereturn as the optimal solution.Step 5: Record the result and end.C is the control variables numbers, and t is the number of barnacles.Candidate solution (3):n is the variable.Upper and lower bounds ((4) and (5)):Selection of Dad and Mom Barnacles:x is the normal distributed pseudo random number  and y is provided by Equation (9):LP is the Length of the PenisBarnacles off-spring generation:rand is the random number between 0 and 1. The proposed BMO algorithm-based PV cell/panel parameters extraction pictorial overview is illustrated in Process of sperm cast:The proposed BMOA set parameter values are tabulated in p represents the number of the measurement points, icI is the calculated current, and imI is the measured current.The goal is to extract the PV parameter (five or seven) with better accuracy and minimize the errors between the measured data and calculated ones. The objective function is defined as the minimization of the RMSE and the mathematical equation presented in Equation (11).The statistical errors are computed between calculated and measured current using the Equations (12)–(16). The following statistical metrics are used: mean absolute percentage error (MAPE), mean square error (MSE), mean absolute error (MAE), mean bias error (MBE), and mean relative error (MRE).Six datasets from the specialized literature are used to study the performance of the BMOA algorithm in accuracy, the number of iterations, and computational time for three commercial photovoltaic cells: monocrystalline silicon, amorphous silicon, and RTC France, and three photovoltaic panels: PWP201, Sharp ND-R250A5, and Kyocera KC200GT.2.Monocrystalline silicon photovoltaic cell is a commercial one sized 3 cm × 3 cm, and the current–voltage characteristic was measured at 27 °C under illumination at 1000 W/mI, V) pairs, the calculated current using SMD and DDM models, and the errors are presented in The  pairs, the calculated current using SMD and DDM models, and the errors are presented in The parameters of the amorphous silicon photovoltaic cell extracted for both models using BMOA algorithm and the range considered for each parameter is presented in RMSE calculated using the BMOA algorithm is higher than the one calculated with SDA in the case of the SDM, but it is lower than the five parameters method. PSDA for DDM has better results than BMOA for RMSE, MSE, MAE, and MBE, as seen in The extracted parameters are presented in The current–voltage characteristics measured and calculated are presented in 2 illumination. The  pairs, the calculated current using SMD and DDM models, and the errors are presented in The dataset for the RTC photovoltaic cell  is the mThe extracted parameters of the RTC silicon photovoltaic cell using BMOA algorithm are shown for both models in The BMOA algorithm delivers better results for RMSE than PS, ICA, MPCOA, SA, EEGWA, GA, and 5P in the case of the SDM model and PS, ICA, SA, and EEGWA in the case of DDM model. The HSDA and PSDA have better results. The values for all statistical tests are presented in The extracted parameters are presented in The current–voltage characteristics measured and calculated are presented in 2 illumination.The dataset for the PWP201 photovoltaic panel  and the The extracted parameters of the PWP201 photovoltaic panel using BMOA algorithm are shown for both models in The BMOA algorithm delivers better results for RMSE than PS, FPA, MPCOA, SA, EEGWA, and 5P in the case of the SDM model; PS, CPSO, TVACPSO, and SA in the case of DDM model. The HSDA provides better results. For SDM model, the RMSE is almost equal for GPSO and WDOWOAPSO to the one provided by BMOA. The values for all statistical tests are presented in The extracted parameters are presented in −03 and 5 × 10−03, than DDM, for which the variation is −8 × 10−03 and 6 × 10−03. This is reflected in the RMSE, which is higher for the DDM model than SDM model.The current–voltage characteristics measured and calculated are presented in 2 illumination.The dataset for the Sharp ND-R250A5 photovoltaic panel  and the The extracted parameters of the Sharp ND-R250A5 photovoltaic panel using the BMOA algorithm are shown for both models in The BMOA algorithm has lower results for RMSE than HSDA and GCPSO in the case of the SDM and DDM model, and better than 5P in the case of SDM model. The values for all statistical tests are presented in The extracted parameters are presented in The current–voltage characteristics, measured and calculated, are presented in 2 illumination.The dataset for the Kyocera KC200GT photovoltaic panel  and the The extracted parameters of the Kyocera KC200GT photovoltaic panel using the BMOA algorithm are shown for both models in The statistical test shows very good results for BMOA algorithm in comparison with ICA and WDO for both models: SDM and DDM. The HSDA provides better results. The values for all statistical tests are presented in The extracted parameters are presented in The current–voltage characteristics measured and calculated are presented in Two computer configurations were used to extract the parameters of the photovoltaic cells and panels. The first is an HP laptop with AMD Ryzen 5 3550H processor, 8 GB RAM, 2100 Mhz, and 4 GB NVIDIA GeForce GTX 1650, and the second is an Asus Computer with following features: CPU: Intel i9, 10 Core (s), 3.6 GHz 20 MB; GPU: NVIDIA GeForce RTX 3080Ti 12 GB; RAM: 32 GB. The computing time for both configurations and models for each photovoltaic cell and panel is presented in The SDA, PSDA, and HSDA algorithms provided some of the best results to extract the parameters of the photovoltaic cells and panels. The time for the SDA and HSDA is almost 5 min, even though the number of iterations is low, 4, using a computer with an 8-thread I7 processor at 1.9 GHz. The time decreases more than six times if parallelization is used, PSDA, the time to end becomes 46 s . In the BMOA algorithm used to extract the parameters of the photovoltaic cells and panels uses 1000 iterations, as seen in The influence of the number of epochs and the population is studied for each photovoltaic cell and panel. There are four cases considered: 1000 epochs with 250, 30 and 15 populations and 500 epochs with 250 populations for each photovoltaic device, and for SDM and DDM models, as seen in Comparing the results of the five statistical tests for the two cases, 1000 epochs with 250 populations and 500 epochs with 250 populations, a worsening can be observed if the number of epochs decreases from 1000 to 500, as well as a reduction in the extracting time of the parameters from 1.5 to 2 times.The variations in the epochs or the population provide weaker results in comparison with the initial case, which considers 1000 epochs and 250 populations for the monocrystalline silicon photovoltaic cell, as seen in The decreasing population number leads to improving the RMSE for the SDM model in the case of the amorphous photovoltaic cell. The case 1000 epochs and 15 populations provides the best results for both models, as seen in The case 1000 epochs and 30 populations provides the best results for both models of the RTC photovoltaic cell, as seen in For the SDM model of the PWP201 photovoltaic panel the best results for RMSE are provided by 1000 epochs and 250 populations. For the DDM model, the best results for RMSE are obtained if it uses 1000 epochs and 30 populations, as seen in The same behavior is observed when the population number decreases for the Sharp ND-R250A5 photovoltaic panel as for the amorphous photovoltaic cell, see For Kyocera KC200GT photovoltaic panel an improvement in RMSE is observed only in the case 1000 epochs and 15 populations, for the DDM model. The initial case, 1000 epochs and 250 populations, has the best results, as seen in The calculated values for the current voltage pairs and for the parameters of each photovoltaic cell or panels in the four cases considered are provided in supplementary files, as seen in Barnacles mating optimizer algorithm (BMOA) is applied for the first time to extract the intrinsic parameters of three photovoltaic cells: monocrystalline silicon commercial, amorphous silicon, RTC France, PWP201, Sharp ND-R250A5, and Kyocera KC200GT photovoltaic panels, five or seven, in the function of the mathematical model used.The accuracy provides the performance of the barnacles mating optimizer algorithm in the extraction of the photovoltaic cells and panels parameters. The accuracy of the BMOA algorithm is better than GA and 5P in the case of the monocrystalline silicon photovoltaic cell; 5P in the case of the amorphous silicon photovoltaic cell; PS, ICA, MPCOA, SA, EEGWA, GA, and 5P in the case of the RTC silicon photovoltaic cell; PS, FPA, MPCOA, SA, EEGWA, CPSO, TVACPSO, and 5P, and almost equal for GPSO and WDOWOAPSO in the case of PWP201 photovoltaic panel; 5P in the case of the Sharp ND-R250A5 photovoltaic panel; and ICA and WDO in the case of the Kyocera KC200GT photovoltaic panel.The barnacles mating optimizer algorithm uses a low number of iterations. This leads to a very short computation time. So, in comparison with the hybrid successive discretization algorithm, the computational time for the barnacles mating optimizer algorithm decreases more than 30 times and 9 times in comparison with parallelized successive discretization algorithm. The reduction in the number of epochs decreases the computational time, but RMSE is worse. Considering the improvement in computational time and worsening in accuracy, this can be a solution for the industrial process. The computational time can be reduced more using the right number for the population with improvements in the results of the statistical tests, especially for RMSE.All of these make the barnacles mating optimizer algorithm an excellent candidate that can be successfully used to extract the photovoltaic cells and panel parameters.Although the barnacles mating optimizer algorithm offers very good accuracy for extraction of the photovoltaic cells and panels parameters using the current–voltage characteristic, developing a hybrid algorithm based on BMOA will be the goal for future works. This will lead to an increase in accuracy so that the new hybrid algorithm is among the best. Additionally, these two algorithms will be applied to extract the parameters for the multijunction photovoltaic cells under natural sunlight and in concentrated light.


In full-arch implant rehabilitations, when the anterior screw abutment channel compromises the aesthetic of the patient, the OT-Bridge system used with its Seeger rings may provide the necessary retention of the prosthesis. However, no studies have evaluated the forces generated at the Seeger level during loading. This Finite Element Analysis aims to investigate the mechanical behavior of Seeger rings in a mandibular model with four implants and an OT-Bridge system, used without one or two anterior prosthetic screws. A 400 N unilateral load was virtually applied on a 7 mm distal cantilever. Two different variables were considered: the constraint conditions using two or three screws instead of four and the three different framework materials . The FEA analysis exhibited tensile and compressive forces on the Seeger closest to the loading point. With the resin framework, a tension force on abutment 3.3 generates a displacement from 5 to 10 times greater than that respectively expressed in metal framework materials. In a full-arch rehabilitation with four implants, the case with three prosthetic screws seems to be a safer and more predictable configuration instead of two. Considering the stress value exhibited and the mechanical properties of the Seeger, the presence of only two prosthetic screws could lead to permanent deformation of the Seeger in the screwless abutment closest to the loading point. Nowadays, completely edentulous jaws can be restored by using removable and fixed prosthetic solutions ,2,3,4. TThe connection between implants and prosthesis may foresee the use of different types of abutments ,10,11,12An important clinical issue, arising with “screw-retained” rehabilitations, especially in the case of severely resorbed jaws, is the presence of a buccal screw access channel that constitutes an anesthetic problem in the anterior area of the mouth. This issue could be managed with a “cemented-retained” solution, although the advantages of the screw-retained prosthesis are lost. Another way to solve this problem could be using angulated abutment but only for less than a 30° disparallelism .Retaining the benefits of a screw-in prosthesis, the OT-Bridge system may represent a solution in the absence of one or two anterior prosthetic screws when a full-arch implant rehabilitation is used. The stability of the OT-Bridge system is provided by both the posterior screws and the interlocking system between the acetal Seeger, inserted in the extragrade abutment, and the subequatorial region of the OT-Equator attachments .In this way, the OT-Bridge system has been tested and studied ,15,16,17Finite Element Analysis (FEA), as a digital engineering simulation, has been largely used in implant and prosthetic dentistry to study the mechanical behavior of the different parts ,19. The In this study, regarding the use of the OT-Bridge system for full-arch implant rehabilitations where possible esthetic issues could arise from the buccal screw channel made in the prosthesis; we tried to assess some data to understand the forces expressed at the Seeger level. As Seeger ring in the OT-Bridge system has the function of retaining the prosthesis when it is applied alone, without the screw, it is important to know the type and entity of forces expressed at this level during chewing.This FEA aims to study the amount of forces generated at the Seeger rings applied in an All-on-Four mandible rehabilitation. Two constraint conditions were established using three different framework materials—resin, titanium and Co-Cr—applying a loading on a distal cantilever. The absences of one (constraint condition 1—CC1) or two anterior screws (constraint condition 2—CC2) were studied to understand their effect on the stability of this simulated All-on-Four rehabilitation.An epoxy resin model of the mandible already described in a previous article  was initAccording to the “All-on-Four” protocol , four imUsing an appropriate software program , the implant fixtures, the OT-Bridge abutments and the prosthetic framework were designed. The framework was modeled and drawn with a constant thickness of 4.8 × 5.5 mm and connected to the extragrade abutments .Constraint condition 1 (CC1): 3 screws on 4 implants: 3 joints have been inserted: 2 at the level of the mandibular body to block the mandible in space and 1 at the level of the screwless abutment (4.3).Constraint condition 2 (CC2): 2 distal screws present on 4 implants: 4 joints have been inserted: 2 at the level of the mandibular body to block the mandible in space and 2 at the level of the 2 screwless abutments (3.3 and 4.3).Then, two different constraint conditions were applied for evaluating the mechanical behaviour of the system:Glass fiber reinforced resin ;Titanium alloy ;Cobalt-chromium  .Three different materials were used for the prosthetic framework: CC1 (3 inserted screws) with resin frameworkCC2 (2 inserted screws) with resin frameworkCC1 with titanium frameworkCC2 with titanium frameworkCC1 with Cr-Co frameworkCC2 with Cr-Co frameworkCombining the three different framework materials with each configuration, a total of six different study models were obtained:https://www.ansys.com/it-it accessed on 20 April 2022).A vertical load of 400 N on a 7 mm distal cantilever was applied distally to the implant fixture in 3.5 position. Then, for each framework, the forces generated at the screwless abutments were measured and compared under the two different constraint conditions using ANSYS software  than those generated in CC1 (99 N) and compared to those at 4.3.With the titanium framework , switchiIn the Cr-Co framework  the resuFor the 3.3 abutment on the XY plane, significantly increased forces were generated during CC2 compared to the abutment in position 4.3 in CC1.Between the three types of frameworks in CC1, the highest forces were expressed by the Cr-Co (112.37 N) and the titanium framework (109.59 N) at 4.3 abutment. On the other hand, the resin framework generated the highest forces in CC2 at the abutment 3.3 (330.92 N).In the literature, aesthetic and mechanical problems for fixed implant prostheses have been described ,26,27,28This Finite Element Analysis aims to study the entity and direction of forces generated at the Seeger level in a full-arch implant mandibular rehabilitation using the OT-Bridge system in the absence of one (CC1) or two (CC2) anterior prosthetic screws and with three different framework materials.From the data obtained, changing the framework material and removing one or two screws resulted in significantly different reaction force values. The load, in absence of the two anterior screws, generates tensile and compressive forces on the Seeger at the mesial abutments and a significant increase in the forces on the XY plane closest to the loading point. This could be explained by the type of loading that resulted in a bending moment at the farthest abutments and a compression at the closest abutment from the loading area.In the resin framework, a horizontal displacement is generated at 3.3 abutment; the movement created is about five times greater than that in the titanium one and about 10 times greater than that in the Co-Cr framework. This could be due to the different rigidity of the material which, as in other studies, demonstrated an increased stability in cases of higher rigidity ,32. In aA similar pattern of force distribution was also observed in the titanium and Co-Cr frameworks; however, the entity of the forces changed according to the degree of the material rigidity. This is inversely related to the force absorption of the material, which released those forces at the Seeger level of the prosthetic framework. In the titanium framework, for CC2, the resulting force at 4.3 is 20 N less than in CC1, but for the Cr-Co framework they are quite equal (112 N in CC1 and 119 N in CC2). This indicates that the Seeger ring closest to the loading point absorbed more stress than a screw, reducing at the same time the entity of the force expressed at the other Seeger ring.In this view, considering direction, modulus and intensity of the reaction forces and the ratio of these forces to Young’s modulus, which is proportional to displacement, the Seeger ring of the screwless abutment closer to the loading area (abutment in position 3.3) may be deformed. The deformation is quite reliable because of the intensity of the forces generated on the XY plane and on the Z-axis, related to the material of the Seeger that is an acetalic resin.In constraint condition 1 (CC1), the resulting forces expressed at the abutment in position 4.3 are higher for the Cr-Co framework than the other two materials. Although during CC2 the resin framework and the titanium framework expressed a reduction of 45 and 20 N, respectively, but for the Cr-Co framework a little increase was observed. This could be explained by the absence of elasticity in the Co-Cr material, which leads to poor absorption of the resulting forces by the framework.In constraint condition 2 (CC2), the highest force values for the abutment in position 3.3 have been observed in the resin framework (330 N) and the lowest in the Co-Cr framework (280 N); this is indicative of the major stability expressed by the Co-Cr framework because of its high rigidity.Finally, the presence of three instead of four prosthetic screws seems to be a safe and predictable configuration, regardless of the material used for the framework, as the forces expressed could be counteracted by the Seeger ring, and framework disinsertion is quite improbable. As the compression force generated along the Z-axis was seen for all three of the materials, the highest intensity of forces was found with the resin framework due to lower mechanical properties. In this type of framework, significantly larger displacements were generated, especially, on the XY plane, probably leading to permanent deformation of the acetalic Seeger instead of the titanium or the Co-Cr one.Then, it is important to consider the biomechanical response of the Seeger ring in light of the framework material used. In fact, the type of framework material, depending on the different Young’s modulus, influences the tension and deformation forces expressed at the Seeger level. This could lead to Seeger ring deformation, fracture and possibly prosthetic disinsertion, in cases of screwless abutment.The limits of this Finite Element Analysis mainly involved the virtual nature of the study. The absence of an in vivo environment involving the presence of saliva or other oral fluids makes necessary a clinical implementation of this study. The results were also conditioned by the parameters used such as prosthetic framework materials and loading conditions. Variations of those factors may lead to different forces in terms of direction, intensity and displacements and also the biomechanical behavior of the prosthetic components may be different. In addition, the mandibular constraints, which were inserted at the level of the mandibular body and not in the mandibular condyles, the design of the jawbone and of the prosthetic framework and the analysis of only one loading condition led to caution in the interpretation of these initial results. The screwed abutment has been considered fixed without the effect of the constraint forces which could dissipate in a different way the forces on the other abutments. This is the reason why the condition with all four of the screws inserted was not studied.In addition, the effects of the preload torque of the screws were not considered and the materials from a mechanical point of view were supposed to be linear, elastic and isotropic.In conclusion, the OT-Bridge system with an All-on-Four rehabilitation seems to be stable and safe in absence of one anterior screw (CC1). The stress was higher for the Co-Cr framework; however, its results are more balanced compared with the other two materials, especially in CC2. This could prevent the deformation of the Seeger and of the framework, favoring the stability of the prosthetic rehabilitation. Among the results of this study, prosthetic rehabilitations with an aesthetic screw channel could be managed with the absence of one prosthetic screw using the OT-Bridge system. These results are also conditioned by constraints and other simplifying assumptions; the variation of these parameters certainly leads to a variation of forces in terms of direction, intensity and displacements. In addition, the screwless abutment was assumed as a single block with the Seeger, but the acetalic Seeger propriety, which is elastic, has not been considered.Therefore, based on these assumptions, further in vitro and in vivo studies are needed to verify the results obtained and to test the effective biomechanical behaviour and resistance of the Seeger ring. Interesting opportunities in implant patients can be reached with the All-on-Four rehabilitation using the OT-Bridge system.


The unit operating mileage, the unit station area, and the per capita carbon emission intensity were 2.1 kg CO2e/km, 132.5 kg CO2e/m2, and 0.6 kg CO2e per capita (13th Five-Year Plan Period), respectively. By continually promoting the low-carbon operation of the subway, the cumulative carbon savings could reach 0.1 Mt CO2e (2022–2035).The huge energy consumption of metro operations has become a significant challenge faced by the urban public transportation sector to achieve low-carbon development. Using Shenzhen as an example, this study has made efforts to quantify the metro’s energy consumption and carbon emission intensity during the operation phase by using the Life Cycle Assessment approach. Furthermore, this study evaluates the actions that can be taken to reduce energy consumption and emissions. A comparative analysis between metros and other public transportation modes has also been conducted. The results show that the annual carbon emissions from the metro’s operation phase in Shenzhen city increased from 63,000 t CO Coping with global warming is a major focus in today’s world. In its 14th Five-Year Plan, China proposed the goal of “achieving peak carbon by 2030 and striving to achieve carbon neutrality by 2060”. The implementation of the “double carbon” goal is of great strategic significance for promoting a comprehensive green transformation of China’s economy and society and building a harmonious symbiotic development between humans and nature.Transportation is a significant source of greenhouse gas emissions. According to the data released by the International Energy Agency (IEA), the energy consumption of the global transportation sector was 21% in 2018, and the carbon emissions it generated made up about 23% .As one of the rapidly developing cities in China, due to the rapid expansion of the transportation industry and the growth of the urban population (from 8.3 in 2005 to 17.6 million in 2020), Shenzhen is facing major environmental challenges that are similar to other megacities in China . Given tSo far, most studies have focused on the environmental impacts of public transportation systems ,11 and hSome studies have carried out research on the characteristics of carbon emissions in the field of transportation at different scales. Mao et al. 2021) describe a metro development model at the global scale, building a material inventory and determining the actual carbon emissions of 219 cities throughout the world that have metro systems 21 descri. At the As an important part of urban public transportation, the metro has been designated a cleaner commuting mode; its low carbon emissions have become one of its defining characteristics . By compFrom the life-cycle perspective, operational activities are the main source of greenhouse gas emissions from metros. Li et al. (2018) pointed out that the carbon emissions in the metro construction stage accounts for less than 4.6%, the operational stage accounts for 92.1%, and the maintenance stage accounts for 3.4% . Therefo2 equivalent (CO2e) as the environmental impact assessment index, takes the metro operational stage as the research object, constructs a carbon emissions assessment method for the metro operational stage, and quantitatively analyzes energy consumption and the carbon emission intensity and level for metro operation. By comparing these indicators with those of other public transportation systems (buses and taxis) in Shenzhen and with the metro operations in other cities, the carbon emissions level of Shenzhen Metro operation is clarified. Finally, using the scenario analysis method, the carbon emissions of Shenzhen Metro in the operational period of 2022 to 2035 and the degree of achievable carbon emission reduction by implementing energy-saving and emission-reduction measures are predicted. The research results can provide theoretical methods and data references for researchers related to reducing the carbon emissions of the metro system, as well as a theoretical basis and data support for green and low-carbon transformation in the transportation field and a scientific formulation of the energy-saving management policies of the metro system by relevant government departments.Therefore, with the aim of meeting this unmet need, this study adopts the life-cycle assessment (LCA) method, selects the COLCA is a quantitative analysis method of evaluating the potential comprehensive environmental impact of a product (or service or activity) from raw material mining to final disposal . This me2 equivalent (CO2e) as the environmental impact assessment index in order to assess the environmental impacts of metros in the operational stage from the perspective of the whole life cycle. The system boundary of the metro operational stage includes the driving traction system and the station operation system, as shown in Following the principles of ISO 14040/44 ,40, this2), and unit passenger capacity (per capita).In LCA research, environmental impact assessment needs to be carried out in terms of functional units, which can quantify the selected products and determine their functional characteristics according to the ISO 14040/44 series of standards. During the operation of the metro, the energy consumption and carbon emissions of the driving traction and station operation systems are quite different. In order to compare the metro operations of different cities and cases and make the results applicable to future research, the driving traction and the station operation during the metro operational stage are expressed as unit operating mileage (1 km), unit operating area (1 m2e); 2e/kWh).The carbon emissions in the metro operational stage are the sum of the carbon emissions generated by the electricity consumption of the equipment and systems in the driving traction system and of the station operation system, as shown in Equation (1).This study selected Shenzhen Metro as a case study. The data types and source details of the operational stage are shown in In 2019, about 68.1% of China’s electricity came from fossil-fuel energy generation . Electri2e) in 2005 to 1.72 billion kWh (1.3 Mt CO2e); in other words, carbon emissions increased by a multiple of about 21. The historically accumulated carbon emissions of the Shenzhen Metro are 9.5 Mt CO2e. From 2005 to 2021, the carbon emissions of the metro station operation system and the driving traction system accounted for 49% and 51%, respectively. It can be seen from 2e and 65,000 t CO2e in 2010 to 333,000 t CO2e and 289,000 t CO2e in 2012, respectively. According to the analysis, the carbon emission factor of electricity from 2005 to 2021 showed little change from one year to the next. The reason for the significant increases in carbon emissions during these years is the increases in the operating mileage and number of stations of the Shenzhen Metro, with the opening of new metro lines and extension lines in 2011, 2016, and 2020 (as shown in The carbon emissions of the metro during operation are positively correlated with the intensity of electricity consumption. As shown in 2e/km) (see 2 (132.5 kg CO2e/m2), respectively.The overall trend of carbon emissions per unit operating mileage of the Shenzhen Metro remained relatively stable during 2005–2021 (as shown in /km) see , and the/km) see . The ene2e per capita) during the “12th Five-Year Plan Period” to 0.8 kWh per capita (0.6 kg CO2e per capita) during the “13th Five-Year Plan Period”. However, these trends were not steady: there were fluctuations in 2011 and 2020 due to the influences of external factors. In 2011, new lines were opened, and extension lines were added, increasing the operating mileage, the number of stations, and passenger volume by 3.4 times, 2.4 times, and 2.8 times, respectively, over those values for 2010. Additionally, electricity consumption grew faster than passenger volume in 2011. In late 2020, although the metro operation mileage reached 411.5 km and the number of stations reached 242, the COVID-19-induced drop in passenger volume caused the per capita energy consumption and the carbon emissions of the Shenzhen Metro operation to increase.In addition, passenger volume has an impact on the energy consumption of metro operations. An increase in passenger volume will induce demand for more metro services, leading to an increase in the number of trains and the frequency of the operation of the station equipment . Passenger volume will also affect the passenger-carrying rate of the trains: the traction energy consumption when the train is fully loaded or overloaded is about 5.7% higher than when there are few passengers . This inBased on Shenzhen Rail Transit Network Planning (2016–2035), Shenzhen Urban Rail Transit Phase IV Construction Planning, and its adjustment scheme (2017–2022), this research characterized the general situation of Shenzhen Metro planning and construction lines in the short term, medium term, and long term and then forecast the operating mileage and the number and scale of stations in the Shenzhen Metro system over the period of 2022–2035. Then, based on the electricity consumption per unit mileage and per unit station area, the electricity consumption required for metro operation in the future was estimated , Scenario II (Moderate), and Scenario III (Optimistic) are estimated to be 1.61, 1.42, and 1.25 Mt CO2e. Compared with the benchmark scenario, the carbon emission reductions are 0.83 Mt CO2e, a decrease of about 24%. Scenario II (Moderate) is better than either Scenario I (Conservative) or the benchmark scenario in terms of both energy conservation and emissions reduction; the carbon emissions of Scenario II (Moderate) in 2035 are expected to be 2.38 Mt CO2e, about 1.11 Mt CO2e lower than in the benchmark scenario, a decrease of about 32%. Scenario III (Optimistic) has the highest proportion of energy-saving measures of all the scenarios; the carbon emissions in 2035 are estimated to be 2.10 Mt CO2e, a carbon emission reduction of 1.39 Mt CO2e, or 40%, compared to the benchmark scenario value.Compared with the benchmark scenario, Scenario I (Conservative) improves the proportion of energy-saving measures and alleviates the growth trend of carbon emissions to a certain extent. In 2035, the carbon emissions of Scenario I (Conservative) are expected to be 2.65 Mt COIn summary, compared to the benchmark scenario, Scenario I (Conservative), Scenario II (Moderate), and Scenario III (Optimistic) can all achieve some degree of carbon emission reduction by implementing energy-saving measures and reasonably optimizing and continuously promoting energy-saving and emission-reduction schemes for the Shenzhen Metro operation, helping to control the growth of carbon emissions.2e); 2e per capita). Taking the regional characteristics into consideration, this study adopted the local per capita carbon emission index of Shenzhen; that is, the emissions from buses and taxis are 0.54 kg CO2e per capita [2e per capita [In addition to the metro, buses and taxis are the other main types of urban public transportation in China, as reflected in the annual total passenger flow data for various vehicles from 2010 to 2021, which can be found in the monthly statistical report of Shenzhen transportation operation indicators (2010–2021) . At the r capita  and 1.38r capita , respect2e per capita and 0.54 kg CO2e per capita, respectively. The per capita carbon emissions of the metro are slightly higher than those of the bus network, and the per capita carbon emissions of taxis are about 2.5 times those of the metro or bus networks; these are similar to the passenger volume and carrying rate of rental cars. According to the existing literature [2e/km (not including the carbon emissions of metro stations), which is much higher than those of the bus network (1.1 kg CO2e/km) or taxis (0.3 kg CO2e/km), because the metro operating environment, carrying space, and other factors require high electricity consumption per km of metro operation, resulting in increased carbon emissions.From the perspective of the carbon emission intensity of the Shenzhen public transportation system, the per capita carbon emissions of the metro and bus networks are 0.6 kg COterature ,51 and t2e. In general, the carbon emissions of bus transportation have been declining year by year over the past decade for two reasons: Shenzhen Metro line’s increased share of passenger volume  has come at the expense of a drop in bus passenger volume and hence in the decreased operation of buses; and the bus system has been investing in new, more efficient, and greener types of energy [The carbon emissions from the three main types of urban public transportation from 2010 to 2021 are shown in f energy . The oveThe metro, new green-energy buses, and taxis are generally considered to be green transportation modes because they generate no direct emissions during their operational stage. However, according to the above calculation results, the operation of the urban public transportation system, especially the metro, will consume a great deal of electricity, and thus the metro has gradually become the main contributor of emissions from urban public transportation. Therefore, considering the upstream production stage of electricity, the metro, green-energy buses, and taxis are not necessarily absolutely green transportation modes because the electricity used in Shenzhen does not come entirely from clean energy . The envMetros are an important part of an urban public transportation system and one of the main sources of carbon emissions . In this study, the results of energy consumption and carbon emission intensity during metro operations in Shenzhen in 2021 were compared with those from some domestic cities . The per capita energy consumption and carbon emissions are directly related to the total electricity consumption and passenger volume of a metro. The size of the metro system, in turn, affects the total energy consumption, and the passenger volume is also affected by the geographical layout of the lines.Overall, in 2021, the Chinese national metro operation consumed 21.3 billion kWh of electricity, and the total carbon emissions were about 19.1 Mt COFrom the comprehensive data shown in (1)Formulate and implement relevant energy conservation and emission-reduction policies and standards in the field of urban public transportation. In terms of energy conservation and emission reduction, Shenzhen has made great efforts to build green-energy infrastructure and promote energy conservation, such as the Shenzhen Green Building Promotion Measures and the Shenzhen Special Economic Zone Green Building Regulations. However, there are no relevant policies or measures for energy conservation and emission reduction in the transportation field. Construction and transportation have always been high resource- and energy-consuming industries, and the environmental burden they bring to society cannot be ignored. Therefore, the introduction of energy-saving and emission-reduction policies and standards is necessary, and they are guaranteed to promote the low-carbon transformation of urban public transportation systems.(2)2e) are similar to those of buses (0.54 kg CO2e) and are much lower than those of taxis (1.38 kg CO2e). Furthermore, the per capita carbon emissions curve of the metro shows a downward trend, indicating that the metro will play a vital role in reducing carbon emissions from urban public transportation in the future. In addition, at present, the full load rate of the Shenzhen Metro is relatively low. If the metro line layout can be well aligned with people’s travel needs, the metro’s share of passenger traffic can be further improved. Taking Tokyo, Japan, as an example, the construction of a compact metro is conducive to the sustainable development of a city [Reasonably plan the layouts of metro lines and improve the efficiency of metro transportation. Compared with foreign cities such as London and New York, metro construction in China started late, beginning in Shenzhen, for example, in the late 1990s. The study results show that the per capita carbon emissions of the Shenzhen Metro (0.6 kg COf a city . Therefo(3)2e (Scenario III in 2035). Clean energy generation plays an important role in the low-carbon transformation of transportation. In particular, photovoltaic systems can be widely used on the roofs of stations and depots to share energy consumption for the operation of station lighting systems. The photovoltaic electricity generation system can generate up to 47.106 million kWh of electricity per year, and the emission reduction is about 289,000 tCO2e (Scenario III in 2035). In the future, more clean energy technologies should be explored, especially photovoltaic electricity generation systems (such as perovskite photovoltaic (PV) cells) [Optimize the energy structure, improve the efficiency of thermal power generation and clean transformation, increase the proportion of new clean energy, and realize the zero-carbon transformation of energy. Although the electricity consumed by metro operations does not directly produce greenhouse gases, metro energy utilization can be improved, and the upstream production of this electricity also needs to be considered. Optimizing the energy structure can reduce emissions by up to 32% per year, with a reduction of about 1.35 Mt CO) cells) ,57, to i(4)Promote energy-saving and emission-reduction technologies and schemes. The result shows that the energy-saving equipment used in Shenzhen’s Metro , as well as photovoltaic electricity generation technology and regenerative braking energy recovery technology , can achieve a significant carbon emission reduction effect. The research results show that photovoltaic electricity generation technology can generate 50 million kWh per year, regenerative braking energy recovery technology can recover 190 million kWh per year, and energy-saving lamps, frequency-conversion air conditioners and frequency-conversion escalators can save 1.18 billion kWh per year (Scenario III in 2035). However, since energy-saving and emission-reduction technology have not yet been fully implemented in the Shenzhen Metro, the use of emission-reduction technology should be further expanded in the future.With the development of the Guangdong–Hong Kong–Macao Greater Bay Area, the metro, as an important tool for solving urban traffic congestion, will continue to increase its number of stations, vehicle and passenger volumes, and operating mileage . The carThe methods proposed in this study and the quality of the inventory data used have some limitations. First, the current analysis is limited to energy consumption and carbon emissions and lacks consideration of the end-point environmental impacts. In future research, the terminal environmental impacts under regional characteristics should be discussed in order to fully understand the environmental characteristics of the metro. Secondly, for the statistical data on the energy consumption of the metro system, the influence of uncertain factors has not been considered, and more accurate base statistics should be obtained. Then, the carbon emission factor of electricity generation should be selected to be as close as possible to the China Southern Power Grid in Shenzhen. Finally, the boundary of the research system of this study was relatively narrow, considering only the operational stage of the metro, and the calculation method only considered the per capita carbon emissions due to data unavailability. The design and construction stages should be taken into account in future studies.2e in 2005 to 1.3 Mt CO2e in 2021, and the historically accumulated carbon emissions were 9.5 Mt CO2e. (2) The overall energy consumption and carbon emission intensity of the Shenzhen Metro both show a downward trend (except for the energy consumption per unit station area), but it has achieved no advantage compared to the national average levels, and there is still room for improvement in both emission and consumption reduction. (3) The Shenzhen Metro has gradually become the main contributor to carbon emissions in the urban public transportation system. In 2021, the carbon emissions of Shenzhen Metro operation accounted for about 56.1% of the total emissions from the urban public transportation system. (4) An advanced low-carbon model (from conservative to optimistic scenarios) can significantly alleviate the rapid growth of carbon emissions of Shenzhen Metro. The maximum carbon emission reduction rate could reach 40% per year (2035), and the cumulative carbon savings from 2022 to 2035 could reach 0.1 Mt CO2e. Therefore, in order to realize a green and low-carbon transformation in the field of transportation, large cities should optimize their energy structure as soon as possible, increase the proportion of clean energy generation, and realize a zero-carbon transformation of energy use, while also further promoting energy-saving and emission-reduction technologies and schemes, especially in their metro systems. In addition, megacities should prioritize the development of metros and plan the layout of metro lines to maximize their use and their transportation efficiency. The methods and results of this study can provide a reference for the development of low-carbon transportation systems in other megacities in China.With the rapid expansion of the transportation industry and the growth of urban populations, the low-carbon development of urban public transport systems faces major challenges. Metro operation not only consumes a lot of energy but also intensifies potential environmental risks. Based on the LCA method, this study constructed a carbon emission calculation method for the operation phase of the metro system, comprehensively evaluated the carbon emission level and the effectiveness of energy conservation and emission reduction during the operational phase of the Shenzhen Metro from two aspects, station lighting systems and the driving traction, and explored its characteristics from three aspects: station area, traffic traction, per capita energy consumption, and carbon emission intensity. At the same time, other public transportation modes and the metro operation of typical domestic cities were compared and analyzed so as to provide support for green, low-carbon transformation in the transport field and the formulation of energy-saving management policies for the metro system. The main contributions of this study were: (1) the results of the life-cycle analysis show that the total carbon emissions of Shenzhen Metro operation maintained continuous growth from 2005 to 2021, from 63,000 t CO