The objective of this paper is to introduce the piecewise constant method in gait design of a planar,under actuated,five-link biped robot model and to discuss the advantages and disadvantages.The piecewise constant me...The objective of this paper is to introduce the piecewise constant method in gait design of a planar,under actuated,five-link biped robot model and to discuss the advantages and disadvantages.The piecewise constant method transforms the dynamic optimal control problem into a static problem.展开更多
The fluid-coupled discrete element method(DEM)and the constant volume method as two types of discrete modeling methods for fundamental study of undrained responses of granular materials,have been discussed by many res...The fluid-coupled discrete element method(DEM)and the constant volume method as two types of discrete modeling methods for fundamental study of undrained responses of granular materials,have been discussed by many researchers.The fluid-coupled DEM,which couples the motions of discrete particles with pore fluid movements,is theoretically robust although it requires a large amount of computation time.As a substitution for the complex fluid-coupled DEM,the constant volume method simulates an undrained condition for a saturated granular material by simply preserving the total volume of a granular assembly without considering interactions between fluids and particles;hence,the validity of its results is questionable.In this paper,the undrained behaviors of granular assemblies simulated using the aforementioned two methods are compared.Based on a comparison of both macroscopic and microscopic responses given by the two methods,it is demonstrated that the constant volume method may reasonably simulate the responses of a loose saturated granular material with very coarse grains,which has a high permeability,and thus a rapid pore pressure equalization.However,it is ineffective in simulating the responses of a loose material with fine components due to its failure to capture the process of a slow dissipation of the excess pore pressure among the individual pores.With regard to the dense material adopted,similar behaviors at the early and intermediate shearing stages given by the two methods are displayed.展开更多
Segmentation of three-dimensional(3D) complicated structures is of great importance for many real applications.In this work we combine graph cut minimization method with a variant of the level set idea for 3D segmenta...Segmentation of three-dimensional(3D) complicated structures is of great importance for many real applications.In this work we combine graph cut minimization method with a variant of the level set idea for 3D segmentation based on the Mumford-Shah model.Compared with the traditional approach for solving the Euler-Lagrange equation we do not need to solve any partial differential equations.Instead,the minimum cut on a special designed graph need to be computed.The method is tested on data with complicated structures.It is rather stable with respect to initial value and the algorithm is nearly parameter free.Experiments show that it can solve large problems much faster than traditional approaches.展开更多
In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the（E, T） phase diagram of the studied pr...In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the（E, T） phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.展开更多
Vanadium battery has fast and large capacity charge and discharge characteristics, and the concentration and stability of the battery electrolyte are the key to the electrolyte performance. In actual, with higher acid...Vanadium battery has fast and large capacity charge and discharge characteristics, and the concentration and stability of the battery electrolyte are the key to the electrolyte performance. In actual, with higher acidity and higher concentration of the vanadium battery electrolyte, the ion-pair is dominant. The ion-pair dissociation constant is one of the important thermodynamic data related to battery performance. The vanadyl sulfate conductivity in aqueous solution was determined using the conductance method at 298.15K. Using the origin data fitting, the limiting molar conductance is obtained, and then by the improved Ostwald dilution law and the Davies equation, the activity coefficient is solved so as to obtain the ionic strength of the true solution. Using the Fuoss method, the dissociation constant of vanadyl sulfate ion-pair was calculated. At last, the vanadyl sulfate limiting molar conductance (Λ <sub> 0 </sub>) is 174.8251748 S·dm<sup>2</sup>·mol<sup>?1</sup>, and the vanadyl sulfate ion-pair dissociation constant K <sub>d</sub> is 0.002636367, and then other thermodynamic properties can be studied.展开更多
The photoplethysmogram(PPG) of a pulse wave,similar in appearance to the arterial blood pressure(ABP) waveform,contains rich information about the cardiovascular system.The decay time constant RC,equal to the product ...The photoplethysmogram(PPG) of a pulse wave,similar in appearance to the arterial blood pressure(ABP) waveform,contains rich information about the cardiovascular system.The decay time constant RC,equal to the product of peripheral resistance R and total arterial compliance C,is a meaningful cardiovascular model parameter in vascular assessment.Using or ameliorating the existing ABP methods does not achieve a satisfactory estimation of RC from the PPG volume pulse(VRC).Thus,a novel non-iterative shape method(NSM) of evaluating VRC is introduced in this paper.The mathematic expression between a novel,readily available morphological parameter called the area difference ratio(ADR) and VRC was established.As it was difficult to calculate VRC from the complicated expression analytically,we recommend estimating it using a piecewise linear interpolation criterion.Also,since the effect of the PPG magnitude is eliminated in the calculation of ADR,precaliberation or normalization is dispensable in the NSM.Results of human experiments indicated that the NSM was computationally efficient,and the simulation experiments confirmed that the NSM was theoretically available for ABP.展开更多
Laser ablation coupled with inductively coupled plasma-mass spectrometry (LA-ICP-MS) calibration was conducted with multiple spot analyses on eleven intact rock samples using both an internal standard (IS) method and ...Laser ablation coupled with inductively coupled plasma-mass spectrometry (LA-ICP-MS) calibration was conducted with multiple spot analyses on eleven intact rock samples using both an internal standard (IS) method and a modified constant-sum (MCS) method. Methods were then compared for reported bulk elemental composition of the rocks. The MCS method was based on the sum of eight major elements, which is spatially more stable than one single major ele-ment as used in the IS method, and is quite constant among different rock samples. Calibrations were performed with standard reference materials NIST SRM 610, 612, 614, and 616. Little difference was found between using a single standard and a set of standards, because of the good linearity shown by the reference materials. Comparison of the two calibration methods shows that the MCS method produced better and more stable results than the IS method for heterogeneous samples. With the MCS method, approximately 94% to 95% of the total measurements are within the range of ±100% relative deviation, compared with 82% to 86% with the IS method. The IS method resulted insubstantial overestimations for some rock samples (e.g., 648% for Basalt BCR-2 using NIST SRM 610 as the calibration standard), while the largest deviation with the MCS method was 216% for U in Eagle Ford shale #80 sample. For Quartz latite QLO-1, a relative homogeneous sample, the IS method generated slightly better results than the MCS method. Regardless of method, spatially heterogeneous distribution of elements in the intact rock at the scale of the laser spot is considered to be the main reason for the large relative deviations seen in our work compared to published results.展开更多
We consider the psychophysical experiments in which the test subject’s binary reaction is determined by the prescribed exposure duration to a stimulus and a random variable subjective threshold. For example, when a s...We consider the psychophysical experiments in which the test subject’s binary reaction is determined by the prescribed exposure duration to a stimulus and a random variable subjective threshold. For example, when a subject is exposed to a millimeter wave beam for a prescribed duration, the occurrence of flight action is binary (yes or no). In experiments, in addition to the binary outcome, the actuation time of flight action is also recorded if it occurs;the delay from the initiation time to the actuation time of flight action is the human reaction time, which is not measurable. In this study, we model the random subjective threshold as a Weibull distribution and formulate an inference method for estimating the human reaction time, from data of prescribed exposure durations, binary outcomes and actuation times of flight action collected in a sequence of tests. Numerical simulations demonstrate that the inference of human reaction time based on the Weibull distribution converges to the correct value even when the underlying true model deviates from the inference model. This robustness of the inference method makes it applicable to real experimental data where the underlying true model is unknown.展开更多
The elastic constants of Al single crystal were calculated by ab initio method for calibration. Three deformation directions were selected in order to obtain the different constants of c 11 , c 12 and c 44 . The cohes...The elastic constants of Al single crystal were calculated by ab initio method for calibration. Three deformation directions were selected in order to obtain the different constants of c 11 , c 12 and c 44 . The cohesion energy curves of the three deformation directions were calculated. The results of the second order partial differential at the equilibrium point of the cohesion energy curve provide the elastic constants of the Al single crystal. The changes of crystal symmetry and lattice can lead to the deviations of the calculated cohesion energy curves and the accurate elastic constants can not be obtained, but when the correction is taken into calculation, the calculated results are very close to the literature data. It is very difficult to obtain the elastic constants of thin films by experiment and the data from the handbook are scattered in a large scale. However, the elastic constants calculated by this method can be served as a standard. Though the errors of TiN elastic constants calculated by this method are a little higher than that for Al, the results are acceptable. [展开更多
According to the appearing of isosbestic point in the absorption spectra of Ho/Y-Tribromoarsenazo (TBA)systems,the complexation reaction is considered to be M+nL=ML_n.A method has been proposed based on it for calcula...According to the appearing of isosbestic point in the absorption spectra of Ho/Y-Tribromoarsenazo (TBA)systems,the complexation reaction is considered to be M+nL=ML_n.A method has been proposed based on it for calculating the mole fraction of free complexing agent in the solutions from spectral data.and two linear regression formula have been introduced to determine the composition,the molar absorptivity,the conditional stability constant of the complex and the concentration of the complexing agent. This method has been used in Ho-TBA and Y-TBA systems.Ho^(3+)and Y^(3+)react with TBA and form 1: 2 complexes in HCl-NaAc buffer solution at pH 3.80.Their molar absorptivities determined are 1.03×10~8 and 1.10×10~8 cm^2·mol^(-1),and the conditional stability constants(logβ_2)are 11.37 and 11.15 respectively.After considering the pH effect in TBA complexing,their stability constants(log β_2^(ahs))are 43.23 and 43.01. respectively.The new method is adaptable to such systems where the accurate concentration of the complexing agent can not be known conveniently.展开更多
The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion ...The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion is the main focus of researches due to its promising potential as the electrical source. This paper presents the constant voltage method of control where the output of the converter is maintained constant irrespective of the variations in the irradiance with the high step-up isolated efficient single switch DC-DC converter for the solar PV systems. Constant voltage method of control uses the array of photovoltaic systems as its energy source. The output of the Solar PV systems is nonlinear and has its dependency on temperature and irradiance by which the panel voltage and current varies with the variation in irradiance. Constant voltage control method always operates in such a way that the converter voltage is tried to be maintained constantly to the reference voltage which is set by the user. The system used here utilizes high step single switch isolated DC-DC converter and monitors the voltage continuously by varying the duty cycle to maintain the converter voltage always constant. As a way of improving the performance, both the open and closed loop analysis is done where the closed loop analysis uses the PI controller for its performance. The model is implemented in MATLAB and it accepts the irradiance as the input and outputs the constant voltage from the converter and the feasibility of the proposed converter topology is confirmed with experimental results of the prototype model.展开更多
We proposed an empirical equation for a fine-structure constant: . Then, . where m<sub>p</sub> and m<sub>e</sub> are the rest mass of a proton and the rest mass of an electron, respectively. In...We proposed an empirical equation for a fine-structure constant: . Then, . where m<sub>p</sub> and m<sub>e</sub> are the rest mass of a proton and the rest mass of an electron, respectively. In this report, using the electrochemical method, we proposed an equivalent circuit. Then, we proposed a refined version of our own old empirical equations about the electromagnetic force and gravity. Regarding the factors of 9/2 and π, we used 3.132011447 and 4.488519503, respectively. The calculated values of T<sub>c</sub> and G are 2.726312 K and 6.673778 × 10<sup>-11</sup> (m<sup>3</sup>⋅kg<sup>-1</sup>⋅s<sup>-2</sup>).展开更多
A dynamic Bayesian error function of material constants of the structure is developed for thin-walled curve box girders. Combined with the automatic search scheme with an optimal step length for the one-dimensional Fi...A dynamic Bayesian error function of material constants of the structure is developed for thin-walled curve box girders. Combined with the automatic search scheme with an optimal step length for the one-dimensional Fibonacci series, Powell＇s optimization theory is used to perform the stochastic identification of material constants of the thin-walled curve box. Then, the steps in the parameter identification are presented. Powell＇s identification procedure for material constants of the thin-walled curve box is compiled, in which the mechanical analysis of the thin-walled curve box is completed based on the finite curve strip element （FCSE） method. Some classical examples show that Powell＇s identification is numerically stable and convergent, indicating that the present method and the compiled procedure are correct and reliable. During the parameter iterative processes, Powell＇s theory is irrelevant with the calculation of the FCSE partial differentiation, which proves the high computation efficiency of the studied methods. The stochastic performances of the system parameters and responses axe simultaneously considered in the dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step length is solved by adopting the Fibonacci series search method without the need of determining the region, in which the optimized step length lies.展开更多
In this paper the elastic constants of graphite at elevated temperature were experimentally investigated by using the virtual fields method （VFM）. A new method was presented for the characterization of mechanical pr...In this paper the elastic constants of graphite at elevated temperature were experimentally investigated by using the virtual fields method （VFM）. A new method was presented for the characterization of mechanical properties at elevated temperature. The three-point bending tests were performed on graphite materials by an universal testing machine equipped with heating fumace. Based on the heterogeneous deformation fields measured by the digital image correlation （DIC） technique, the elastic constants were then extracted by using VFM. The measurement results of the elastic constants at 500℃ were obtained. The ef- fect on the experimental results was also analyzed. The successful results verify the feasibility of using the proposed method to measure the properties of graphite at high temperature, and the proposed method is believed to have a good potential for further applications.展开更多
The purpose of this paper is to reduce the error when measuring high dielectric constant materials.In this paper,the reason why the error introduced is analyzed firstly.Then,with HFSS,the method of choosing the size o...The purpose of this paper is to reduce the error when measuring high dielectric constant materials.In this paper,the reason why the error introduced is analyzed firstly.Then,with HFSS,the method of choosing the size of cavity and the dimension of dielectric materials is proposed.And several error correction curves are provided for measuring high dielectric constant materials.Finally,the experiment is conducted to validate the feasibility of our analysis.展开更多
A new method,dual-series linear regression method,has been used to study the complexation equilibrium of praseodymium(Pr^(3+))with tribromoarsenazo(TBA)without knowing the accurate concentra- tion of the complexing ag...A new method,dual-series linear regression method,has been used to study the complexation equilibrium of praseodymium(Pr^(3+))with tribromoarsenazo(TBA)without knowing the accurate concentra- tion of the complexing agent TBA.In 1.2 mol/L HCl solution, Pr^(3+)reacts with TBA and forms 1:3 com- plex,the conditional stability constant(lgβ_3)of the complex determined is 15.47,and its molar absorptivity(ε_3^(630))is 1.48×10~5 L·mol^(-1)·cm^(-1).展开更多
In order to make the power level angle(PLA)have the same bijection relationship with the thrust when the environment changes before operational limit exceedance,and ensure the pilot's ability of unrestricted throt...In order to make the power level angle(PLA)have the same bijection relationship with the thrust when the environment changes before operational limit exceedance,and ensure the pilot's ability of unrestricted throttle movement as well as the safety of the engine,a method used to design a constant thrust power schedule was proposed.The research was based on a simulink turbofan engine model and the results were organized as look-up tables in different structures with limitations.Simulation was done to confirm the validity and demonstrate the effectiveness of the schedule obtained with the approach.The constant thrust takeoff schedule,constant thrust idle schedule and constant thrust part power schedule with the present constant thrust control(CTC)method were proved to be valid.The results can be applied to this specific engine but the method can be applied to any areoengine and can be even extended to the unmanned plane.展开更多
A new method is proposed for determining the composition and stability constant of coordination compounds of the form M m R n ; it can be used to differentiate mono and poly nuclear coordination compounds. ...A new method is proposed for determining the composition and stability constant of coordination compounds of the form M m R n ; it can be used to differentiate mono and poly nuclear coordination compounds. The equation derived is lg( A i/(A max - A i) m)=n lg c′ R+lg( m·β(c M/A max ) ( m -1) ). The method is based on Bent French limited logarithm method. The demonstration of the proposed method has yielded correct results for Sc 3+ chlorophosphonazo Ⅲ system and Fe 3+ Chromazurol S system.展开更多
This paper studies the consensus control of multiagent systems with binary-valued observations.An algorithm alternating estimation and control is proposed.Each agent estimates the states of its neighbors based on a pr...This paper studies the consensus control of multiagent systems with binary-valued observations.An algorithm alternating estimation and control is proposed.Each agent estimates the states of its neighbors based on a projected empirical measure method for a holding time.Based on the estimates,each agent designs the consensus control with a constant gain at some skipping time.The states of the system are updated by the designed control,and the estimation and control design will be repeated.For the estimation,the projected empirical measure method is proposed for the binary-valued observations.The algorithm can ensure the uniform boundedness of the estimates and the mean square error of the estimation is proved to be at the order of the reciprocal of the holding time(the same order as that in the case of accurate outputs).For the consensus control,a constant gain is designed instead of the stochastic approximation based gain in the existing literature for binary-valued observations.And,there is no need to make modification for control since the uniform boundedness of the estimates ensures the uniform boundedness of the agents’states.Finally,the systems updated by the designed control are proved to achieve consensus and the consensus speed is faster than that in the existing literature.Simulations are given to demonstrate the theoretical results.展开更多
文摘The objective of this paper is to introduce the piecewise constant method in gait design of a planar,under actuated,five-link biped robot model and to discuss the advantages and disadvantages.The piecewise constant method transforms the dynamic optimal control problem into a static problem.
基金The authors would like to express their acknowledgments to Dr.Timothy Topper for his insightful com。
文摘The fluid-coupled discrete element method(DEM)and the constant volume method as two types of discrete modeling methods for fundamental study of undrained responses of granular materials,have been discussed by many researchers.The fluid-coupled DEM,which couples the motions of discrete particles with pore fluid movements,is theoretically robust although it requires a large amount of computation time.As a substitution for the complex fluid-coupled DEM,the constant volume method simulates an undrained condition for a saturated granular material by simply preserving the total volume of a granular assembly without considering interactions between fluids and particles;hence,the validity of its results is questionable.In this paper,the undrained behaviors of granular assemblies simulated using the aforementioned two methods are compared.Based on a comparison of both macroscopic and microscopic responses given by the two methods,it is demonstrated that the constant volume method may reasonably simulate the responses of a loose saturated granular material with very coarse grains,which has a high permeability,and thus a rapid pore pressure equalization.However,it is ineffective in simulating the responses of a loose material with fine components due to its failure to capture the process of a slow dissipation of the excess pore pressure among the individual pores.With regard to the dense material adopted,similar behaviors at the early and intermediate shearing stages given by the two methods are displayed.
基金support from the Centre for Integrated Petroleum Research(CIPR),University of Bergen, Norway,and Singapore MOE Grant T207B2202NRF2007IDMIDM002-010
文摘Segmentation of three-dimensional(3D) complicated structures is of great importance for many real applications.In this work we combine graph cut minimization method with a variant of the level set idea for 3D segmentation based on the Mumford-Shah model.Compared with the traditional approach for solving the Euler-Lagrange equation we do not need to solve any partial differential equations.Instead,the minimum cut on a special designed graph need to be computed.The method is tested on data with complicated structures.It is rather stable with respect to initial value and the algorithm is nearly parameter free.Experiments show that it can solve large problems much faster than traditional approaches.
基金Supported by National Natural Science Committee and Chinese Engineering Physics Institute Foundation(10576013)Natural Science Foundation of Henan Province(0611053200)Natural Science Study Foundation of Henan University(06YBZR028)
文摘In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the（E, T） phase diagram of the studied product can be obtained.In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.
基金financially supported by the National Natural Science Foundation of China(No.21273152)
文摘Vanadium battery has fast and large capacity charge and discharge characteristics, and the concentration and stability of the battery electrolyte are the key to the electrolyte performance. In actual, with higher acidity and higher concentration of the vanadium battery electrolyte, the ion-pair is dominant. The ion-pair dissociation constant is one of the important thermodynamic data related to battery performance. The vanadyl sulfate conductivity in aqueous solution was determined using the conductance method at 298.15K. Using the origin data fitting, the limiting molar conductance is obtained, and then by the improved Ostwald dilution law and the Davies equation, the activity coefficient is solved so as to obtain the ionic strength of the true solution. Using the Fuoss method, the dissociation constant of vanadyl sulfate ion-pair was calculated. At last, the vanadyl sulfate limiting molar conductance (Λ <sub> 0 </sub>) is 174.8251748 S·dm<sup>2</sup>·mol<sup>?1</sup>, and the vanadyl sulfate ion-pair dissociation constant K <sub>d</sub> is 0.002636367, and then other thermodynamic properties can be studied.
基金Project (No.81070885) supported by the National Natural Science Foundation of China
文摘The photoplethysmogram(PPG) of a pulse wave,similar in appearance to the arterial blood pressure(ABP) waveform,contains rich information about the cardiovascular system.The decay time constant RC,equal to the product of peripheral resistance R and total arterial compliance C,is a meaningful cardiovascular model parameter in vascular assessment.Using or ameliorating the existing ABP methods does not achieve a satisfactory estimation of RC from the PPG volume pulse(VRC).Thus,a novel non-iterative shape method(NSM) of evaluating VRC is introduced in this paper.The mathematic expression between a novel,readily available morphological parameter called the area difference ratio(ADR) and VRC was established.As it was difficult to calculate VRC from the complicated expression analytically,we recommend estimating it using a piecewise linear interpolation criterion.Also,since the effect of the PPG magnitude is eliminated in the calculation of ADR,precaliberation or normalization is dispensable in the NSM.Results of human experiments indicated that the NSM was computationally efficient,and the simulation experiments confirmed that the NSM was theoretically available for ABP.
文摘Laser ablation coupled with inductively coupled plasma-mass spectrometry (LA-ICP-MS) calibration was conducted with multiple spot analyses on eleven intact rock samples using both an internal standard (IS) method and a modified constant-sum (MCS) method. Methods were then compared for reported bulk elemental composition of the rocks. The MCS method was based on the sum of eight major elements, which is spatially more stable than one single major ele-ment as used in the IS method, and is quite constant among different rock samples. Calibrations were performed with standard reference materials NIST SRM 610, 612, 614, and 616. Little difference was found between using a single standard and a set of standards, because of the good linearity shown by the reference materials. Comparison of the two calibration methods shows that the MCS method produced better and more stable results than the IS method for heterogeneous samples. With the MCS method, approximately 94% to 95% of the total measurements are within the range of ±100% relative deviation, compared with 82% to 86% with the IS method. The IS method resulted insubstantial overestimations for some rock samples (e.g., 648% for Basalt BCR-2 using NIST SRM 610 as the calibration standard), while the largest deviation with the MCS method was 216% for U in Eagle Ford shale #80 sample. For Quartz latite QLO-1, a relative homogeneous sample, the IS method generated slightly better results than the MCS method. Regardless of method, spatially heterogeneous distribution of elements in the intact rock at the scale of the laser spot is considered to be the main reason for the large relative deviations seen in our work compared to published results.
文摘We consider the psychophysical experiments in which the test subject’s binary reaction is determined by the prescribed exposure duration to a stimulus and a random variable subjective threshold. For example, when a subject is exposed to a millimeter wave beam for a prescribed duration, the occurrence of flight action is binary (yes or no). In experiments, in addition to the binary outcome, the actuation time of flight action is also recorded if it occurs;the delay from the initiation time to the actuation time of flight action is the human reaction time, which is not measurable. In this study, we model the random subjective threshold as a Weibull distribution and formulate an inference method for estimating the human reaction time, from data of prescribed exposure durations, binary outcomes and actuation times of flight action collected in a sequence of tests. Numerical simulations demonstrate that the inference of human reaction time based on the Weibull distribution converges to the correct value even when the underlying true model deviates from the inference model. This robustness of the inference method makes it applicable to real experimental data where the underlying true model is unknown.
文摘The elastic constants of Al single crystal were calculated by ab initio method for calibration. Three deformation directions were selected in order to obtain the different constants of c 11 , c 12 and c 44 . The cohesion energy curves of the three deformation directions were calculated. The results of the second order partial differential at the equilibrium point of the cohesion energy curve provide the elastic constants of the Al single crystal. The changes of crystal symmetry and lattice can lead to the deviations of the calculated cohesion energy curves and the accurate elastic constants can not be obtained, but when the correction is taken into calculation, the calculated results are very close to the literature data. It is very difficult to obtain the elastic constants of thin films by experiment and the data from the handbook are scattered in a large scale. However, the elastic constants calculated by this method can be served as a standard. Though the errors of TiN elastic constants calculated by this method are a little higher than that for Al, the results are acceptable. [
文摘According to the appearing of isosbestic point in the absorption spectra of Ho/Y-Tribromoarsenazo (TBA)systems,the complexation reaction is considered to be M+nL=ML_n.A method has been proposed based on it for calculating the mole fraction of free complexing agent in the solutions from spectral data.and two linear regression formula have been introduced to determine the composition,the molar absorptivity,the conditional stability constant of the complex and the concentration of the complexing agent. This method has been used in Ho-TBA and Y-TBA systems.Ho^(3+)and Y^(3+)react with TBA and form 1: 2 complexes in HCl-NaAc buffer solution at pH 3.80.Their molar absorptivities determined are 1.03×10~8 and 1.10×10~8 cm^2·mol^(-1),and the conditional stability constants(logβ_2)are 11.37 and 11.15 respectively.After considering the pH effect in TBA complexing,their stability constants(log β_2^(ahs))are 43.23 and 43.01. respectively.The new method is adaptable to such systems where the accurate concentration of the complexing agent can not be known conveniently.
文摘The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion is the main focus of researches due to its promising potential as the electrical source. This paper presents the constant voltage method of control where the output of the converter is maintained constant irrespective of the variations in the irradiance with the high step-up isolated efficient single switch DC-DC converter for the solar PV systems. Constant voltage method of control uses the array of photovoltaic systems as its energy source. The output of the Solar PV systems is nonlinear and has its dependency on temperature and irradiance by which the panel voltage and current varies with the variation in irradiance. Constant voltage control method always operates in such a way that the converter voltage is tried to be maintained constantly to the reference voltage which is set by the user. The system used here utilizes high step single switch isolated DC-DC converter and monitors the voltage continuously by varying the duty cycle to maintain the converter voltage always constant. As a way of improving the performance, both the open and closed loop analysis is done where the closed loop analysis uses the PI controller for its performance. The model is implemented in MATLAB and it accepts the irradiance as the input and outputs the constant voltage from the converter and the feasibility of the proposed converter topology is confirmed with experimental results of the prototype model.
文摘We proposed an empirical equation for a fine-structure constant: . Then, . where m<sub>p</sub> and m<sub>e</sub> are the rest mass of a proton and the rest mass of an electron, respectively. In this report, using the electrochemical method, we proposed an equivalent circuit. Then, we proposed a refined version of our own old empirical equations about the electromagnetic force and gravity. Regarding the factors of 9/2 and π, we used 3.132011447 and 4.488519503, respectively. The calculated values of T<sub>c</sub> and G are 2.726312 K and 6.673778 × 10<sup>-11</sup> (m<sup>3</sup>⋅kg<sup>-1</sup>⋅s<sup>-2</sup>).
基金Project supported by the National Natural Science Foundation of China(Nos.10472045,10772078, and 11072108)the National High-Tech Research and Development Program of China(863 Program) (No.2007AA11Z106)
文摘A dynamic Bayesian error function of material constants of the structure is developed for thin-walled curve box girders. Combined with the automatic search scheme with an optimal step length for the one-dimensional Fibonacci series, Powell＇s optimization theory is used to perform the stochastic identification of material constants of the thin-walled curve box. Then, the steps in the parameter identification are presented. Powell＇s identification procedure for material constants of the thin-walled curve box is compiled, in which the mechanical analysis of the thin-walled curve box is completed based on the finite curve strip element （FCSE） method. Some classical examples show that Powell＇s identification is numerically stable and convergent, indicating that the present method and the compiled procedure are correct and reliable. During the parameter iterative processes, Powell＇s theory is irrelevant with the calculation of the FCSE partial differentiation, which proves the high computation efficiency of the studied methods. The stochastic performances of the system parameters and responses axe simultaneously considered in the dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step length is solved by adopting the Fibonacci series search method without the need of determining the region, in which the optimized step length lies.
基金supported by the National Natural Science Foundation of China(11232008,91216301,11227801,and 11172151)the Tsinghua University Initiative Scientific Research Program,and the Major Basic Research Program of Beijing Institute of Technology(2011CX01030)
文摘In this paper the elastic constants of graphite at elevated temperature were experimentally investigated by using the virtual fields method （VFM）. A new method was presented for the characterization of mechanical properties at elevated temperature. The three-point bending tests were performed on graphite materials by an universal testing machine equipped with heating fumace. Based on the heterogeneous deformation fields measured by the digital image correlation （DIC） technique, the elastic constants were then extracted by using VFM. The measurement results of the elastic constants at 500℃ were obtained. The ef- fect on the experimental results was also analyzed. The successful results verify the feasibility of using the proposed method to measure the properties of graphite at high temperature, and the proposed method is believed to have a good potential for further applications.
文摘The purpose of this paper is to reduce the error when measuring high dielectric constant materials.In this paper,the reason why the error introduced is analyzed firstly.Then,with HFSS,the method of choosing the size of cavity and the dimension of dielectric materials is proposed.And several error correction curves are provided for measuring high dielectric constant materials.Finally,the experiment is conducted to validate the feasibility of our analysis.
文摘A new method,dual-series linear regression method,has been used to study the complexation equilibrium of praseodymium(Pr^(3+))with tribromoarsenazo(TBA)without knowing the accurate concentra- tion of the complexing agent TBA.In 1.2 mol/L HCl solution, Pr^(3+)reacts with TBA and forms 1:3 com- plex,the conditional stability constant(lgβ_3)of the complex determined is 15.47,and its molar absorptivity(ε_3^(630))is 1.48×10~5 L·mol^(-1)·cm^(-1).
文摘In order to make the power level angle(PLA)have the same bijection relationship with the thrust when the environment changes before operational limit exceedance,and ensure the pilot's ability of unrestricted throttle movement as well as the safety of the engine,a method used to design a constant thrust power schedule was proposed.The research was based on a simulink turbofan engine model and the results were organized as look-up tables in different structures with limitations.Simulation was done to confirm the validity and demonstrate the effectiveness of the schedule obtained with the approach.The constant thrust takeoff schedule,constant thrust idle schedule and constant thrust part power schedule with the present constant thrust control(CTC)method were proved to be valid.The results can be applied to this specific engine but the method can be applied to any areoengine and can be even extended to the unmanned plane.
文摘A new method is proposed for determining the composition and stability constant of coordination compounds of the form M m R n ; it can be used to differentiate mono and poly nuclear coordination compounds. The equation derived is lg( A i/(A max - A i) m)=n lg c′ R+lg( m·β(c M/A max ) ( m -1) ). The method is based on Bent French limited logarithm method. The demonstration of the proposed method has yielded correct results for Sc 3+ chlorophosphonazo Ⅲ system and Fe 3+ Chromazurol S system.
基金supported by the National Natural Science Foundation of China(61803370,61622309)the China Postdoctoral Science Foundation(2018M630216)the National Key Research and Development Program of China(2016YFB0901902)
文摘This paper studies the consensus control of multiagent systems with binary-valued observations.An algorithm alternating estimation and control is proposed.Each agent estimates the states of its neighbors based on a projected empirical measure method for a holding time.Based on the estimates,each agent designs the consensus control with a constant gain at some skipping time.The states of the system are updated by the designed control,and the estimation and control design will be repeated.For the estimation,the projected empirical measure method is proposed for the binary-valued observations.The algorithm can ensure the uniform boundedness of the estimates and the mean square error of the estimation is proved to be at the order of the reciprocal of the holding time(the same order as that in the case of accurate outputs).For the consensus control,a constant gain is designed instead of the stochastic approximation based gain in the existing literature for binary-valued observations.And,there is no need to make modification for control since the uniform boundedness of the estimates ensures the uniform boundedness of the agents’states.Finally,the systems updated by the designed control are proved to achieve consensus and the consensus speed is faster than that in the existing literature.Simulations are given to demonstrate the theoretical results.
