The efficient transmission of images,which plays a large role inwireless communication systems,poses a significant challenge in the growth of multimedia technology.High-quality images require well-tuned communication ...The efficient transmission of images,which plays a large role inwireless communication systems,poses a significant challenge in the growth of multimedia technology.High-quality images require well-tuned communication standards.The Single Carrier Frequency Division Multiple Access(SC-FDMA)is adopted for broadband wireless communications,because of its low sensitivity to carrier frequency offsets and low Peak-to-Average Power Ratio(PAPR).Data transmission through open-channel networks requires much concentration on security,reliability,and integrity.The data need a space away fromunauthorized access,modification,or deletion.These requirements are to be fulfilled by digital image watermarking and encryption.This paper ismainly concerned with secure image communication over the wireless SC-FDMA systemas an adopted communication standard.It introduces a robust image communication framework over SC-FDMA that comprises digital image watermarking and encryption to improve image security,while maintaining a high-quality reconstruction of images at the receiver side.The proposed framework allows image watermarking based on the Discrete Cosine Transform(DCT)merged with the Singular Value Decomposition(SVD)in the so-called DCT-SVD watermarking.In addition,image encryption is implemented based on chaos and DNA encoding.The encrypted watermarked images are then transmitted through the wireless SC-FDMA system.The linearMinimumMean Square Error(MMSE)equalizer is investigated in this paper to mitigate the effect of channel fading and noise on the transmitted images.Two subcarrier mapping schemes,namely localized and interleaved schemes,are compared in this paper.The study depends on different channelmodels,namely PedestrianAandVehicularA,with a modulation technique namedQuadratureAmplitude Modulation(QAM).Extensive simulation experiments are conducted and introduced in this paper for efficient transmission of encrypted watermarked images.In addition,different variants of SC-FDMA based on the Discrete Wavelet Transform(DWT),Discrete Cosine Transform(DCT),and Fast Fourier Transform(FFT)are considered and compared for the image communication task.The simulation results and comparison demonstrate clearly that DWT-SC-FDMAis better suited to the transmission of the digital images in the case of PedestrianAchannels,while the DCT-SC-FDMA is better suited to the transmission of the digital images in the case of Vehicular A channels.展开更多
Small signal equivalent circuit model and modulation properties of vertical cavity surface emitting lasers(VCSEL's) are presented.The modulation properties both in analytic equation calculation and in circuit mo...Small signal equivalent circuit model and modulation properties of vertical cavity surface emitting lasers(VCSEL's) are presented.The modulation properties both in analytic equation calculation and in circuit model simulation are studied.The analytic equation calculation of the modulation properties is calculated by using Mathcad program and the circuit model simulation is simulated by using Pspice program respectively.The results of calculation and the simulation are in good agreement with each other.Experiment is performed to testify the circuit model.展开更多
It is well known that subtle changes in structure and tissue composition of articular cartilage can lead to its degeneration. The present paper puts forward a modified layered inhomogeneous triphasic model with four p...It is well known that subtle changes in structure and tissue composition of articular cartilage can lead to its degeneration. The present paper puts forward a modified layered inhomogeneous triphasic model with four parameters based on the inhomogeneous triphasic model proposed by Narmoneva et al. Incorporating a piecewise fitting optimization criterion, the new model was used to obtain the uniaxial modulus Ha, and predict swelling pattern for the articular cartilage based on ultrasound-measured swelling strain data. The results show that the new method can be used to provide more accurate estimation on the uniaxial modulus than the inhomogeneous triphasic model with three parameters and the homogeneous mode, and predict effectively the swell- ing strains of highly nonuniform distribution of degenerated articular cartilages. This study can provide supplementary information for exploring mechanical and material properties of the cartilage, and thus be helpful for the diagnosis of osteoarthritis-related diseases.展开更多
Based on the features extracted from generalized autoregressive (GAR) model parameters of the received waveform, and the use of multilayer perceptron(MLP) neural network classifier, a new digital modulation recognitio...Based on the features extracted from generalized autoregressive (GAR) model parameters of the received waveform, and the use of multilayer perceptron(MLP) neural network classifier, a new digital modulation recognition method is proposed in this paper. Because of the better noise suppression ability of the GAR model and the powerful pattern classification capacity of the MLP neural network classifier, the new method can significantly improve the recognition performance in lower SNR with better robustness. To assess the performance of the new method, computer simulations are also performed.展开更多
This paper presents the construction of an active suspension control of a one-wheel car model using fuzzy reasoning and a disturbance observer. The one-wheel car model to be treated here can be approximately described...This paper presents the construction of an active suspension control of a one-wheel car model using fuzzy reasoning and a disturbance observer. The one-wheel car model to be treated here can be approximately described as a nonlinear two degrees of freedom system subject to excitation from a road profile. The active control is designed as the fuzzy control inferred by using single input rule modules fuzzy reasoning, and the active control force is released by actuating a pneumatic actuator. The excitation from the road profile is estimated by using a disturbance observer, and the estimate is denoted as one of the variables in the precondition part of the fuzzy control rules. A compensator is inserted to counter the performance degradation due to the delay of the pneumatic actuator. The experimental result indicates that the proposed active suspension system improves much the vibration suppression of the car model. Key words One-wheel car model - Active suspension system - Single input rule modules fuzzy reasoning - Pneumatic actuator - Disturbance observer Document code A CLC number TH16展开更多
Based on the membrane-based absorption experiment of CO2 into water, shell-side flow distribution and mass transfer in a randomly packed hollow fiber module have been analyzed using subchannel model and unsteady penet...Based on the membrane-based absorption experiment of CO2 into water, shell-side flow distribution and mass transfer in a randomly packed hollow fiber module have been analyzed using subchannel model and unsteady penetration mass transfer theory. The cross section of module is subdivided into many small cells which contains only one hollow-fiber. The cross sectional area distribution of these cells is presented by the normal probability density distribution function. It has been obtained that there was a most serious non-ideal flow in shell side at moderate mean packing density, and the large amount of fluid flowed and transferred mass through a small number of large voids. Thus mass transfer process is dominated by the fluid through the larger void area. The mass transfer process in each cell is described by the unsteady penetration theory. The overall mass transfer coefficient equals to the probability addition of the mean mass transfer coefficient in each cell. The comparisons of the values calculated by the model established with the empirical correlations and the experimental data of this work have been done.The predicted overall mass transfer coefficients are in good agreement with experimental data.展开更多
To improve the global search ability of particle swarm optimization (PSO), a multi-population PSO based on pyramid model (PPSO) is presented. Then, it is applied to solve the layout optimization problems against t...To improve the global search ability of particle swarm optimization (PSO), a multi-population PSO based on pyramid model (PPSO) is presented. Then, it is applied to solve the layout optimization problems against the background of an international commercial communication satellite (INTELSAT-Ⅲ) module. Three improvements are developed, including multi-population search based on pyramid model, adaptive collision avoidance among particles, and mutation of degraded particles. In the numerical examples of the layout design of this simplified satellite module, the performance of PPSO is compared to global version PSO and local version PSO (ring and Neumann PSO). The results show that PPSO has higher computational accuracy, efficiency and success ratio.展开更多
The reverse osmosis process has been applied in large industrial fields (water treatment, food industry, biotechnology, and ect.). Despite, this progress more investigation are required to optimize the reverse osmos...The reverse osmosis process has been applied in large industrial fields (water treatment, food industry, biotechnology, and ect.). Despite, this progress more investigation are required to optimize the reverse osmosis process. The present paper deals the modeling of mass transfer in a cavity limited by a semi-permeable membrane. Mass conservation and momentum balances are developed, dimensionless and control volume method has been applied. The velocity and concentration profiles versus the Reynolds number and Sherwood are studied. The results show that the permeability of the membrane decreases as function of the transversal (radial) component of the velocity. The axial (tangential) component of the velocity presents a good stability along the thickness of the cavity; this phenomenon can be attributed to the zero gradient of the tangential velocity. These preliminary results show that the phenomenon of the concentration polarization affects the mass transfer coefficient in a channel. Current study has considered the cavity without a promoter of the turbulence; whereas, the design of the spacer has an important role on mass transfer coefficient in the reverse osmosis module. Our next interest is the integration of the spacer in the cavity, and the study of the effect of its design on the concentration and velocity profiles and the mass transfer coefficient through the reverse osmosis membrane.展开更多
The state space average model and the large signal models of Pulse Skip Modulation (PSM) mode are given in this paper. Farther more, based on these models and simulations of PSM converter circuits, the analysis of t...The state space average model and the large signal models of Pulse Skip Modulation (PSM) mode are given in this paper. Farther more, based on these models and simulations of PSM converter circuits, the analysis of the characteristics of PSM converter is described in this paper, of which include efficiency, frequency spectrum analysis, output voltage ripple, response speed and interference rejection capability. Compared with PWM control mode, PSM converter has high efficiency, especially with fight loads, quick response, good interference rejection and good EMC characteristic. Improved PSM slightly, it could be a kind of good independent regulating mode during the whole operating process for a DC-DC converter. Finally, some experimental results are also presented in this paper.展开更多
he paper focuses on the turbulence modulation problem in gas–particle flow with the use of probability density function(PDF) approach. By means of the PDF method, a general statistical moment turbulence modulation ...he paper focuses on the turbulence modulation problem in gas–particle flow with the use of probability density function(PDF) approach. By means of the PDF method, a general statistical moment turbulence modulation model without considering the trajectory difference between two phases is derived from the Navier–Stokes equations. A new turbulence production term induced by the dispersed-phase is analyzed and considered. Furthermore, the trajectory difference between two media is taken into account. Subsequently, a new k–ε turbulence modulation model in dilute particle-laden flow is successfully set up. Then, the changes to several terms, including the turbulence production, dissipation, and diffusion terms, are well described consequently. The promoted model provides a more probable explanation for the modification of particles on the turbulence. Finally, we applied the model to simulate a gas–particle turbulence flow case in a wall jet, and found that the simulation results agree well with the experimental data.展开更多
We improved the thermal equivalent-circuit model of the laser diode module(LDM) to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal p...We improved the thermal equivalent-circuit model of the laser diode module(LDM) to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal parameters and the transient junction temperature of the LDM are modeled and obtained according to the temperature of the thermistor integrated in the module.Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines,and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.展开更多
MEMS swallowable capsule is a novel technology in the non-invasive surgery. This technology provides a way to diagnose directly into the deep intestinal where the traditional invasive technology implemented, such as X...MEMS swallowable capsule is a novel technology in the non-invasive surgery. This technology provides a way to diagnose directly into the deep intestinal where the traditional invasive technology implemented, such as X-Ray, endoscopy. It is a key for us to locate and track the position of a MEMS capsule in clinical applications. To solve this problem, we implemented a magnetic sensor module based on the scalar form of the magnetic dipole model,which was designed with very small size (5.2 * 2. 1 * 1.2 em) and easy to assemble to satisfy the system requirement. Here we discuss in detail the principle of magnetic dipole model, rules of selecting sensor and functions of the module. Some trials are established to test the characteristic of the module. The results of the Cm experiment demonstrates that the module follows the rules of the new magnetic dipole model form.展开更多
Solar Photovoltaic is a very promising solution that can greatly contribute in solving the increasing global energy demand. In both rural and urban areas, photovoltaic modules are in some instances installed close to ...Solar Photovoltaic is a very promising solution that can greatly contribute in solving the increasing global energy demand. In both rural and urban areas, photovoltaic modules are in some instances installed close to telecommunication antennas or voltage transformers which generate important magnetic fields in their vicinity. The question is whether or not these magnetic fields affect the performances of the photovoltaic installations. This article presents a modelling study of external magnetic field effect on the electrical parameters of a photovoltaic module. The photocurrent, the photovoltage, the electric power, the series and the shunt resistances of the photovoltaic module, made up of ideal cells, are deduced from those of a silicon solar cell. Then, the I-V and P-V curves are plotted and the theoretical values of the electrical parameters of the photovoltaic module are deduced. The series and shunt resistances of the photovoltaic module are calculated using well known equations and the previous electrical parameters. The results show the negative effect of magnetic field on the performance of a solar photovoltaic module.展开更多
A new procedure of trial variational wave functional is proposed for investigating the mass renormalization and the local structure of the ground state of a one-dimensional quantum sine-Gordon model with linear spatia...A new procedure of trial variational wave functional is proposed for investigating the mass renormalization and the local structure of the ground state of a one-dimensional quantum sine-Gordon model with linear spatial modulation, whose ground state differs from that without modulation. The phase diagram obtained in parameters plane shows that the vertical part of the boundary between soliton lattice phase and incommensurate (IC) phase with vanishing gap sticks at , the IC phase can only appear for and the IC phase regime is enlarged with increasing spatial modulation in the case of definite parameter . The transition is of the continuous type on the vertical part of the boundary, while it is of the first order on the boundary for .展开更多
Renewable energy sources are gaining popularity,particularly photovoltaic energy as a clean energy source.This is evident in the advancement of scientific research aimed at improving solar cell performance.Due to the ...Renewable energy sources are gaining popularity,particularly photovoltaic energy as a clean energy source.This is evident in the advancement of scientific research aimed at improving solar cell performance.Due to the non-linear nature of the photovoltaic cell,modeling solar cells and extracting their parameters is one of the most important challenges in this discipline.As a result,the use of optimization algorithms to solve this problem is expanding and evolving at a rapid rate.In this paper,a weIghted meaN oF vectOrs algorithm(INFO)that calculates the weighted mean for a set of vectors in the search space has been applied to estimate the parameters of solar cells in an efficient and precise way.In each generation,the INFO utilizes three operations to update the vectors’locations:updating rules,vector merging,and local search.The INFO is applied to estimate the parameters of static models such as single and double diodes,as well as dynamic models such as integral and fractional models.The outcomes of all applications are examined and compared to several recent algorithms.As well as the results are evaluated through statistical analysis.The results analyzed supported the proposed algorithm’s efficiency,accuracy,and durability when compared to recent optimization algorithms.展开更多
Vector control schemes have recently been used to drive linear induction motors(LIM)in high-performance applications.This trend promotes the development of precise and efficient control schemes for individual motors.T...Vector control schemes have recently been used to drive linear induction motors(LIM)in high-performance applications.This trend promotes the development of precise and efficient control schemes for individual motors.This research aims to present a novel framework for speed and thrust force control of LIM using space vector pulse width modulation(SVPWM)inverters.The framework under consideration is developed in four stages.To begin,MATLAB Simulink was used to develop a detailed mathematical and electromechanical dynamicmodel.The research presents a modified SVPWM inverter control scheme.By tuning the proportional-integral(PI)controller with a transfer function,optimized values for the PI controller are derived.All the subsystems mentioned above are integrated to create a robust simulation of the LIM’s precise speed and thrust force control scheme.The reference speed values were chosen to evaluate the performance of the respective system,and the developed system’s response was verified using various data sets.For the low-speed range,a reference value of 10m/s is used,while a reference value of 100 m/s is used for the high-speed range.The speed output response indicates that themotor reached reference speed in amatter of seconds,as the delay time is between 8 and 10 s.The maximum amplitude of thrust achieved is less than 400N,demonstrating the controller’s capability to control a high-speed LIM with minimal thrust ripple.Due to the controlled speed range,the developed system is highly recommended for low-speed and high-speed and heavy-duty traction applications.展开更多
Integrated electro-absorption-modulated distributed feedback laser diodes(EMLs)are attracting much interest in optical communications for the advantages of a compact structure,low power consumption,and high-speed modu...Integrated electro-absorption-modulated distributed feedback laser diodes(EMLs)are attracting much interest in optical communications for the advantages of a compact structure,low power consumption,and high-speed modulation.In integrated EML,the microwave interaction between the distributed feedback laser diode(DFB-LD)and the electro-absorption modulator(EAM)has a nonnegligible influence on the modulation performance,especially at the high-frequency region.In this paper,integrated EML was investigated as a three-port network with two electrical inputs and a single optical output,where the scattering matrix of the integrated device was theoretically deduced and experimentally measured.Based on the theoretical model and the measured data,the microwave equivalent circuit model of the integrated device was established,from which the microwave interaction between DFB-LD and EAM was successfully extracted.The results reveal that the microwave interaction within integrated EML contains both the electrical isolation and optical coupling.The electrical isolation is bidirectional while the optical coupling is directional,which aggravates the microwave interaction in the direction from DFB-LD to EAM.展开更多
Despite the advances in combinatorial or synthetic chemis- try and bioinformatics, recent literature has demonstrated the relevance of nature and biomass as a source of new molecules to treat different pathologies, i....Despite the advances in combinatorial or synthetic chemis- try and bioinformatics, recent literature has demonstrated the relevance of nature and biomass as a source of new molecules to treat different pathologies, i.e., bioactive com- pounds obtained from Ecteinascidia turbinate to treat some types of cancer or rapamycin from Streptomyces hygroscop- icus to prevent organ rejection after transplant. This trend will continue simply due to the fact that Mother Nature has been synthesizing molecules for millions of years. In our lab- oratory, we have characterized several compounds obtained from natural sources and that possess important neuronal effects,展开更多
It is adopted the single-diode solar cell model and extended for a PV module. The current vs. voltage (I-V) characteristic based on the Lambert W-function was used. The estimation parameters for the simulation approac...It is adopted the single-diode solar cell model and extended for a PV module. The current vs. voltage (I-V) characteristic based on the Lambert W-function was used. The estimation parameters for the simulation approach of the photovoltaic (PV) module make use of Levenberg-Marquardt method. It was considered an industrial polycrystalline silicon photovoltaic (PV) module and the simulated results were compared with the experimental ones extracted from a specific datasheet. The I-V characteristic for the analysed PV module and its maximum output power are investigated for different operating conditions of incident solar radiation flux and temperature, as well as parameters related to the solar cells material and technology (series resistance, shunt resistance and gamma factor). The analysis gives indications and limitations for design and optimization of the performance for industrial PV modules. This study can be implemented in any type of PV module.展开更多
基金the Deanship of Scientific Research,Princess Nourah bint Abdulrahman University,through the Program of Research Project Funding After Publication,Grant No.(44-PRFA-P-131).
文摘The efficient transmission of images,which plays a large role inwireless communication systems,poses a significant challenge in the growth of multimedia technology.High-quality images require well-tuned communication standards.The Single Carrier Frequency Division Multiple Access(SC-FDMA)is adopted for broadband wireless communications,because of its low sensitivity to carrier frequency offsets and low Peak-to-Average Power Ratio(PAPR).Data transmission through open-channel networks requires much concentration on security,reliability,and integrity.The data need a space away fromunauthorized access,modification,or deletion.These requirements are to be fulfilled by digital image watermarking and encryption.This paper ismainly concerned with secure image communication over the wireless SC-FDMA systemas an adopted communication standard.It introduces a robust image communication framework over SC-FDMA that comprises digital image watermarking and encryption to improve image security,while maintaining a high-quality reconstruction of images at the receiver side.The proposed framework allows image watermarking based on the Discrete Cosine Transform(DCT)merged with the Singular Value Decomposition(SVD)in the so-called DCT-SVD watermarking.In addition,image encryption is implemented based on chaos and DNA encoding.The encrypted watermarked images are then transmitted through the wireless SC-FDMA system.The linearMinimumMean Square Error(MMSE)equalizer is investigated in this paper to mitigate the effect of channel fading and noise on the transmitted images.Two subcarrier mapping schemes,namely localized and interleaved schemes,are compared in this paper.The study depends on different channelmodels,namely PedestrianAandVehicularA,with a modulation technique namedQuadratureAmplitude Modulation(QAM).Extensive simulation experiments are conducted and introduced in this paper for efficient transmission of encrypted watermarked images.In addition,different variants of SC-FDMA based on the Discrete Wavelet Transform(DWT),Discrete Cosine Transform(DCT),and Fast Fourier Transform(FFT)are considered and compared for the image communication task.The simulation results and comparison demonstrate clearly that DWT-SC-FDMAis better suited to the transmission of the digital images in the case of PedestrianAchannels,while the DCT-SC-FDMA is better suited to the transmission of the digital images in the case of Vehicular A channels.
文摘Small signal equivalent circuit model and modulation properties of vertical cavity surface emitting lasers(VCSEL's) are presented.The modulation properties both in analytic equation calculation and in circuit model simulation are studied.The analytic equation calculation of the modulation properties is calculated by using Mathcad program and the circuit model simulation is simulated by using Pspice program respectively.The results of calculation and the simulation are in good agreement with each other.Experiment is performed to testify the circuit model.
基金supported by the National Natural Science Foundation of China(10772018,30872720)
文摘It is well known that subtle changes in structure and tissue composition of articular cartilage can lead to its degeneration. The present paper puts forward a modified layered inhomogeneous triphasic model with four parameters based on the inhomogeneous triphasic model proposed by Narmoneva et al. Incorporating a piecewise fitting optimization criterion, the new model was used to obtain the uniaxial modulus Ha, and predict swelling pattern for the articular cartilage based on ultrasound-measured swelling strain data. The results show that the new method can be used to provide more accurate estimation on the uniaxial modulus than the inhomogeneous triphasic model with three parameters and the homogeneous mode, and predict effectively the swell- ing strains of highly nonuniform distribution of degenerated articular cartilages. This study can provide supplementary information for exploring mechanical and material properties of the cartilage, and thus be helpful for the diagnosis of osteoarthritis-related diseases.
文摘Based on the features extracted from generalized autoregressive (GAR) model parameters of the received waveform, and the use of multilayer perceptron(MLP) neural network classifier, a new digital modulation recognition method is proposed in this paper. Because of the better noise suppression ability of the GAR model and the powerful pattern classification capacity of the MLP neural network classifier, the new method can significantly improve the recognition performance in lower SNR with better robustness. To assess the performance of the new method, computer simulations are also performed.
文摘This paper presents the construction of an active suspension control of a one-wheel car model using fuzzy reasoning and a disturbance observer. The one-wheel car model to be treated here can be approximately described as a nonlinear two degrees of freedom system subject to excitation from a road profile. The active control is designed as the fuzzy control inferred by using single input rule modules fuzzy reasoning, and the active control force is released by actuating a pneumatic actuator. The excitation from the road profile is estimated by using a disturbance observer, and the estimate is denoted as one of the variables in the precondition part of the fuzzy control rules. A compensator is inserted to counter the performance degradation due to the delay of the pneumatic actuator. The experimental result indicates that the proposed active suspension system improves much the vibration suppression of the car model. Key words One-wheel car model - Active suspension system - Single input rule modules fuzzy reasoning - Pneumatic actuator - Disturbance observer Document code A CLC number TH16
基金Supported by the Hi-Tech. Research and Development Program of China (863) (2002AA649280, 2002AA304030), National Natural Science Foundation of China (No. 20206002), Beijing NOVA program (H013610250112), University Postdoctrate Research Foundation of Chin
文摘Based on the membrane-based absorption experiment of CO2 into water, shell-side flow distribution and mass transfer in a randomly packed hollow fiber module have been analyzed using subchannel model and unsteady penetration mass transfer theory. The cross section of module is subdivided into many small cells which contains only one hollow-fiber. The cross sectional area distribution of these cells is presented by the normal probability density distribution function. It has been obtained that there was a most serious non-ideal flow in shell side at moderate mean packing density, and the large amount of fluid flowed and transferred mass through a small number of large voids. Thus mass transfer process is dominated by the fluid through the larger void area. The mass transfer process in each cell is described by the unsteady penetration theory. The overall mass transfer coefficient equals to the probability addition of the mean mass transfer coefficient in each cell. The comparisons of the values calculated by the model established with the empirical correlations and the experimental data of this work have been done.The predicted overall mass transfer coefficients are in good agreement with experimental data.
基金This project is supported by National Natural Science Foundation of China (No.50275019, No.50335040, No.50575031).
文摘To improve the global search ability of particle swarm optimization (PSO), a multi-population PSO based on pyramid model (PPSO) is presented. Then, it is applied to solve the layout optimization problems against the background of an international commercial communication satellite (INTELSAT-Ⅲ) module. Three improvements are developed, including multi-population search based on pyramid model, adaptive collision avoidance among particles, and mutation of degraded particles. In the numerical examples of the layout design of this simplified satellite module, the performance of PPSO is compared to global version PSO and local version PSO (ring and Neumann PSO). The results show that PPSO has higher computational accuracy, efficiency and success ratio.
文摘The reverse osmosis process has been applied in large industrial fields (water treatment, food industry, biotechnology, and ect.). Despite, this progress more investigation are required to optimize the reverse osmosis process. The present paper deals the modeling of mass transfer in a cavity limited by a semi-permeable membrane. Mass conservation and momentum balances are developed, dimensionless and control volume method has been applied. The velocity and concentration profiles versus the Reynolds number and Sherwood are studied. The results show that the permeability of the membrane decreases as function of the transversal (radial) component of the velocity. The axial (tangential) component of the velocity presents a good stability along the thickness of the cavity; this phenomenon can be attributed to the zero gradient of the tangential velocity. These preliminary results show that the phenomenon of the concentration polarization affects the mass transfer coefficient in a channel. Current study has considered the cavity without a promoter of the turbulence; whereas, the design of the spacer has an important role on mass transfer coefficient in the reverse osmosis module. Our next interest is the integration of the spacer in the cavity, and the study of the effect of its design on the concentration and velocity profiles and the mass transfer coefficient through the reverse osmosis membrane.
基金Supported by the National Natural Science Foundation of China (No.60436030)
文摘The state space average model and the large signal models of Pulse Skip Modulation (PSM) mode are given in this paper. Farther more, based on these models and simulations of PSM converter circuits, the analysis of the characteristics of PSM converter is described in this paper, of which include efficiency, frequency spectrum analysis, output voltage ripple, response speed and interference rejection capability. Compared with PWM control mode, PSM converter has high efficiency, especially with fight loads, quick response, good interference rejection and good EMC characteristic. Improved PSM slightly, it could be a kind of good independent regulating mode during the whole operating process for a DC-DC converter. Finally, some experimental results are also presented in this paper.
基金Project supported by the National Natural Science Foundation of China(Grant No.51176044)
文摘he paper focuses on the turbulence modulation problem in gas–particle flow with the use of probability density function(PDF) approach. By means of the PDF method, a general statistical moment turbulence modulation model without considering the trajectory difference between two phases is derived from the Navier–Stokes equations. A new turbulence production term induced by the dispersed-phase is analyzed and considered. Furthermore, the trajectory difference between two media is taken into account. Subsequently, a new k–ε turbulence modulation model in dilute particle-laden flow is successfully set up. Then, the changes to several terms, including the turbulence production, dissipation, and diffusion terms, are well described consequently. The promoted model provides a more probable explanation for the modification of particles on the turbulence. Finally, we applied the model to simulate a gas–particle turbulence flow case in a wall jet, and found that the simulation results agree well with the experimental data.
基金Project supported by the Key Program of the National Natural Science Foundation of China (Grant No. 60938002)the Special-funded Program on National Key Scientific Instruments and Equipment Development of China (Grant No. 2012YQ06016501)the Tianjin Research Program of Application Foundation and Advanced Technology,China (Grant No. 11JCYBJC04900)
文摘We improved the thermal equivalent-circuit model of the laser diode module(LDM) to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal parameters and the transient junction temperature of the LDM are modeled and obtained according to the temperature of the thermistor integrated in the module.Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines,and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.
文摘MEMS swallowable capsule is a novel technology in the non-invasive surgery. This technology provides a way to diagnose directly into the deep intestinal where the traditional invasive technology implemented, such as X-Ray, endoscopy. It is a key for us to locate and track the position of a MEMS capsule in clinical applications. To solve this problem, we implemented a magnetic sensor module based on the scalar form of the magnetic dipole model,which was designed with very small size (5.2 * 2. 1 * 1.2 em) and easy to assemble to satisfy the system requirement. Here we discuss in detail the principle of magnetic dipole model, rules of selecting sensor and functions of the module. Some trials are established to test the characteristic of the module. The results of the Cm experiment demonstrates that the module follows the rules of the new magnetic dipole model form.
文摘Solar Photovoltaic is a very promising solution that can greatly contribute in solving the increasing global energy demand. In both rural and urban areas, photovoltaic modules are in some instances installed close to telecommunication antennas or voltage transformers which generate important magnetic fields in their vicinity. The question is whether or not these magnetic fields affect the performances of the photovoltaic installations. This article presents a modelling study of external magnetic field effect on the electrical parameters of a photovoltaic module. The photocurrent, the photovoltage, the electric power, the series and the shunt resistances of the photovoltaic module, made up of ideal cells, are deduced from those of a silicon solar cell. Then, the I-V and P-V curves are plotted and the theoretical values of the electrical parameters of the photovoltaic module are deduced. The series and shunt resistances of the photovoltaic module are calculated using well known equations and the previous electrical parameters. The results show the negative effect of magnetic field on the performance of a solar photovoltaic module.
文摘A new procedure of trial variational wave functional is proposed for investigating the mass renormalization and the local structure of the ground state of a one-dimensional quantum sine-Gordon model with linear spatial modulation, whose ground state differs from that without modulation. The phase diagram obtained in parameters plane shows that the vertical part of the boundary between soliton lattice phase and incommensurate (IC) phase with vanishing gap sticks at , the IC phase can only appear for and the IC phase regime is enlarged with increasing spatial modulation in the case of definite parameter . The transition is of the continuous type on the vertical part of the boundary, while it is of the first order on the boundary for .
基金This research is funded by Prince Sattam BinAbdulaziz University,Grant Number IF-PSAU-2021/01/18921.
文摘Renewable energy sources are gaining popularity,particularly photovoltaic energy as a clean energy source.This is evident in the advancement of scientific research aimed at improving solar cell performance.Due to the non-linear nature of the photovoltaic cell,modeling solar cells and extracting their parameters is one of the most important challenges in this discipline.As a result,the use of optimization algorithms to solve this problem is expanding and evolving at a rapid rate.In this paper,a weIghted meaN oF vectOrs algorithm(INFO)that calculates the weighted mean for a set of vectors in the search space has been applied to estimate the parameters of solar cells in an efficient and precise way.In each generation,the INFO utilizes three operations to update the vectors’locations:updating rules,vector merging,and local search.The INFO is applied to estimate the parameters of static models such as single and double diodes,as well as dynamic models such as integral and fractional models.The outcomes of all applications are examined and compared to several recent algorithms.As well as the results are evaluated through statistical analysis.The results analyzed supported the proposed algorithm’s efficiency,accuracy,and durability when compared to recent optimization algorithms.
基金The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through Large Groups Project under grant number(RGP.2/111/43).
文摘Vector control schemes have recently been used to drive linear induction motors(LIM)in high-performance applications.This trend promotes the development of precise and efficient control schemes for individual motors.This research aims to present a novel framework for speed and thrust force control of LIM using space vector pulse width modulation(SVPWM)inverters.The framework under consideration is developed in four stages.To begin,MATLAB Simulink was used to develop a detailed mathematical and electromechanical dynamicmodel.The research presents a modified SVPWM inverter control scheme.By tuning the proportional-integral(PI)controller with a transfer function,optimized values for the PI controller are derived.All the subsystems mentioned above are integrated to create a robust simulation of the LIM’s precise speed and thrust force control scheme.The reference speed values were chosen to evaluate the performance of the respective system,and the developed system’s response was verified using various data sets.For the low-speed range,a reference value of 10m/s is used,while a reference value of 100 m/s is used for the high-speed range.The speed output response indicates that themotor reached reference speed in amatter of seconds,as the delay time is between 8 and 10 s.The maximum amplitude of thrust achieved is less than 400N,demonstrating the controller’s capability to control a high-speed LIM with minimal thrust ripple.Due to the controlled speed range,the developed system is highly recommended for low-speed and high-speed and heavy-duty traction applications.
基金This work was supported by the National Key Research and Development Program of China under Grant No.2018YFE0201900the National Natural Science Foundation of China under Grants No.61927821 and No.61875240the Joint Research Fund of Ministry of Education of China under Grant No.6141A02022436.
文摘Integrated electro-absorption-modulated distributed feedback laser diodes(EMLs)are attracting much interest in optical communications for the advantages of a compact structure,low power consumption,and high-speed modulation.In integrated EML,the microwave interaction between the distributed feedback laser diode(DFB-LD)and the electro-absorption modulator(EAM)has a nonnegligible influence on the modulation performance,especially at the high-frequency region.In this paper,integrated EML was investigated as a three-port network with two electrical inputs and a single optical output,where the scattering matrix of the integrated device was theoretically deduced and experimentally measured.Based on the theoretical model and the measured data,the microwave equivalent circuit model of the integrated device was established,from which the microwave interaction between DFB-LD and EAM was successfully extracted.The results reveal that the microwave interaction within integrated EML contains both the electrical isolation and optical coupling.The electrical isolation is bidirectional while the optical coupling is directional,which aggravates the microwave interaction in the direction from DFB-LD to EAM.
文摘Despite the advances in combinatorial or synthetic chemis- try and bioinformatics, recent literature has demonstrated the relevance of nature and biomass as a source of new molecules to treat different pathologies, i.e., bioactive com- pounds obtained from Ecteinascidia turbinate to treat some types of cancer or rapamycin from Streptomyces hygroscop- icus to prevent organ rejection after transplant. This trend will continue simply due to the fact that Mother Nature has been synthesizing molecules for millions of years. In our lab- oratory, we have characterized several compounds obtained from natural sources and that possess important neuronal effects,
基金This research was conducted under the research project“High-performance tandem heterojunction solar cells for specific applications(SOLHET)”,funded by the Research Council of Norway(RCN),project no.251789 the Romanian Executive Agency for Higher Education,Research,Development and Innovation Funding(UEFISCDI),project no.34/2016 and 35/2016,through the M-Era.net program.
文摘It is adopted the single-diode solar cell model and extended for a PV module. The current vs. voltage (I-V) characteristic based on the Lambert W-function was used. The estimation parameters for the simulation approach of the photovoltaic (PV) module make use of Levenberg-Marquardt method. It was considered an industrial polycrystalline silicon photovoltaic (PV) module and the simulated results were compared with the experimental ones extracted from a specific datasheet. The I-V characteristic for the analysed PV module and its maximum output power are investigated for different operating conditions of incident solar radiation flux and temperature, as well as parameters related to the solar cells material and technology (series resistance, shunt resistance and gamma factor). The analysis gives indications and limitations for design and optimization of the performance for industrial PV modules. This study can be implemented in any type of PV module.