A new type of brushless DC motor has been developed by using a square wave rare earth permanent magnet synchronous motor with its double loop control circuit. The double loop control scheme of the drive system yie...A new type of brushless DC motor has been developed by using a square wave rare earth permanent magnet synchronous motor with its double loop control circuit. The double loop control scheme of the drive system yields a combination of desired characteristics including simplified control structure, small ripple torque, high speed accuracy, wide operating speed range, and fast dynamic response. Experimental results confirm excellent characteristics of the motor.展开更多
Surface wave methods are becoming increasingly popular in many geotechnical applications and in earthquake seismology due to their noninvasive characteristics.Inverse surface wave dispersion curves are a crucial step ...Surface wave methods are becoming increasingly popular in many geotechnical applications and in earthquake seismology due to their noninvasive characteristics.Inverse surface wave dispersion curves are a crucial step in most surface wave methods.Many inversion methods have been applied to surface wave dispersion curve inversion,including linearized inversion and nonlinearized inversion methods.In this study,a hybrid inversion method of Damped Least Squares(DLS) with Very Fast Simulated Annealing(VFSA) is developed for multi-mode Rayleigh wave dispersion curve inversion.Both synthetic and in situ fi eld data were used to verify the validity of the proposed method.The results show that the proposed method is superior to the conventional VFSA method in aiming at global minimum,especially when parameter searching space is adjacent to real values of the parameters.The advantage of the new method is that it retains both the merits of VFSA for global search and DLS for local search.At high temperatures,the global search dominates the runs,while at a low temperatures,the local search dominates the runs.Thus,at low temperatures,the proposed method can almost directly approach the actual model.展开更多
-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coeffic...-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.展开更多
This is a continued work in studying the wave propagation in a magneto-electroelastic square column (MEESC). Based on the analytic dispersive equation, group velocity equation and steady-state response obtained in o...This is a continued work in studying the wave propagation in a magneto-electroelastic square column (MEESC). Based on the analytic dispersive equation, group velocity equation and steady-state response obtained in our previous paper 'Steady-state response of the wave propagation in a magneto-electro-elastic square column' published in CME, the dynamical behavior of MEESC was studied in this paper. The unlimited column is an open system. The transientstate response in the open system subjected by arbitrary external fields was derived when the propagating wave pursuing method was introduced.展开更多
Least squares migration can eliminate the artifacts introduced by the direct imaging of irregular seismic data but is computationally costly and of slow convergence. In order to suppress the migration noise, we propos...Least squares migration can eliminate the artifacts introduced by the direct imaging of irregular seismic data but is computationally costly and of slow convergence. In order to suppress the migration noise, we propose the preconditioned prestack plane-wave least squares reverse time migration (PLSRTM) method with singular spectrum constraint. Singular spectrum analysis (SSA) is used in the preconditioning of the take-off angle-domain common-image gathers (TADCIGs). In addition, we adopt randomized singular value decomposition (RSVD) to calculate the singular values. RSVD reduces the computational cost of SSA by replacing the singular value decomposition (SVD) of one large matrix with the SVD of two small matrices. We incorporate a regularization term into the preconditioned PLSRTM method that penalizes misfits between the migration images from the plane waves with adjacent angles to reduce the migration noise because the stacking of the migration results cannot effectively suppress the migration noise when the migration velocity contains errors. The regularization imposes smoothness constraints on the TADCIGs that favor differential semblance optimization constraints. Numerical analysis of synthetic data using the Marmousi model suggests that the proposed method can efficiently suppress the artifacts introduced by plane-wave gathers or irregular seismic data and improve the imaging quality of PLSRTM. Furthermore, it produces better images with less noise and more continuous structures even for inaccurate migration velocities.展开更多
This paper reports on the development of a novel electrochemical assay for cadmium (II) in natural water, which involves the use of disposable hydroxyapatite modified platinum electrode (HAP/Pt). Cadmium (II) was prec...This paper reports on the development of a novel electrochemical assay for cadmium (II) in natural water, which involves the use of disposable hydroxyapatite modified platinum electrode (HAP/Pt). Cadmium (II) was preconcentrated on the surface of the modified electrode and adsorbed onto HAP and oxidized at E = –680 mV. The HAP-modified platinum electrode exhibited superior performance in comparison to the plati- num electrode and surprisingly, yielded a higher electrochemical response. The best defined anodic peak was obtained with 0.2 mol L-1 KNO3 pH 5.0 after 25 min of accumulation time. Using these conditions, the cali- bration plot was linear over the range 1 × 10?8 to 5 × 10?6 mol L-1 Cd2+. The precision was examined by car- rying out eight replicate measurements at a concentration of 2.5 ×10?5 mol L-1;the coefficient of variation was 2.9%. The method was applied to the determination of the analyte in river water samples. The interfere- ence of other metal ions on the voltammetric response of Cd(II) was studied. The HAP films was clearly ob- served in the SEM images and characterized by X-ray diffraction, IR spectroscopy and chemical analysis.展开更多
Cerium contained conversion films were deposited on LC4 aluminum alloy usingsquare wave pulse (SWP) in a CeCl_3 solution with KMnO_4 as the oxidant. Energy dispersivespectroscopy (EDS) and scanning electron microscopy...Cerium contained conversion films were deposited on LC4 aluminum alloy usingsquare wave pulse (SWP) in a CeCl_3 solution with KMnO_4 as the oxidant. Energy dispersivespectroscopy (EDS) and scanning electron microscopy (SEM) were adopted to study the composition andthe morphology of the film. It is found that the film is composed of Al, Zn, Cu, and small amount ofcerium. The polarization curves of the specimens treated with SWP technique measured in 3.5% (massfraction) NaCl solution reveal that the film thus formed inhibits both the anodic and cathodicprocess of the corrosion of the specimen. The immersion tests of treated specimens in 3.5% NaClsolution indicate that the corrosion resistance of the SWP treated specimen is better than that ofthe untreated and is equivalent to or even better than that of the traditionally electro-chemicallytreated specimens.展开更多
This paper reported a compact system of capacitively coupled contactless conductivity detection (C4D) based on the square wave excitation voltage for capillary electrophoresis, and it exhibited excellent sensitivity...This paper reported a compact system of capacitively coupled contactless conductivity detection (C4D) based on the square wave excitation voltage for capillary electrophoresis, and it exhibited excellent sensitivity at the optimal frequency of 198 kHz. The feasibility and sensitivity of this detector was demonstrated by simultaneous detection of thirteen ions including alkali, alkaline earth and heavy metal ions. And the detection limits (S/N 3) were in the range of 0.2-1μmol/L for Mn^2+, K^+, Na^+, Mg^2+, Ca^2+, Li^+, Ba^2+, and 7-25 μmol/L for Ni^2+, Cu^2+, Cd^2+, Pb^2+, Co^2+, Zn^2+.展开更多
Significant wave height is an important criterion in designing coastal and offshore structures.Based on the orthogonality principle, the linear mean square estimation method is applied to calculate significant wave he...Significant wave height is an important criterion in designing coastal and offshore structures.Based on the orthogonality principle, the linear mean square estimation method is applied to calculate significant wave height in this paper.Twenty-eight-year time series of wave data collected from three ocean buoys near San Francisco along the California coast are analyzed.It is proved theoretically that the computation error will be reduced by using as many measured data as possible for the calculation of significant wave height.Measured significant wave height at one buoy location is compared with the calculated value based on the data from two other adjacent buoys.The results indicate that the linear mean square estimation method can be well applied to the calculation and prediction of significant wave height in coastal regions.展开更多
The vibration suppression of the finite plate with square steel beams is studied using traveling wave method. The finite plate with square beams is modeled as the coupling systems between the plate flexural motion and...The vibration suppression of the finite plate with square steel beams is studied using traveling wave method. The finite plate with square beams is modeled as the coupling systems between the plate flexural motion and the flexural and torsional motions for the square beams. The vibration response at any position of the coupling structure can be obtained by wave method. Numerical results show that comparing to finite element method (FEM), not only the low frequency but also the medium-high frequency vibration response of the finite plate with square beam can be effectively calculated by wave method. The suppression effect can be increased as the square beam is located at one-third of the length of plate or increasing the height of the beam. The study provides reference for arranged square beams applying to vibration suppression of ship and train structures.展开更多
In wind power system,the randomness of wind energy increases the probability of components fault.once the switch fault of the PWM rectifier is detected,it will lead to the distortion of the motor voltage and current w...In wind power system,the randomness of wind energy increases the probability of components fault.once the switch fault of the PWM rectifier is detected,it will lead to the distortion of the motor voltage and current waveform,the increase of torque ripple,the fluctuation of filter capacitor voltage,and the increase of harmonic content,which will affect the control performance and operation safety of the system.A common fault in a three-phase PWM rectifier is the open-circuit fault of the switch.This paper analyzes the current waveform distortion of the square wave motor when the rectifier switch fault,and proposes different fault-tolerant control strategies for different situations of switch fault,include single,double and triple switches fault.This method is based on several special driving modes under power generation situation of square wave motor.The strategy is easy to implement and does not need to change the circuit topology.It can realize fault-tolerant control of switch faults in the same side half bridge or the same bridge arm of the three-phase PWM rectifier.The effectiveness of the proposed fault-tolerant strategy is verified by simulation and experiment at the end of the article.展开更多
A method for determination of lactose in food samples by Osteryoung square wave voltammetry (OSWV) was developed. It was based on the nucleophilic addition reaction between lactose and aqua ammonia. The carbonyl gro...A method for determination of lactose in food samples by Osteryoung square wave voltammetry (OSWV) was developed. It was based on the nucleophilic addition reaction between lactose and aqua ammonia. The carbonyl group of lactose can be changed into imido group, and this increases the electrochemical activity in reduction and the sensitivity. The optimal condition for the nucleophilic addition reaction was investigated and it was found that in NH4C1-NH3 buffer of pH 10.1, the linear range between the peak current and the concentration of lactose was 0.6-8.4 mg L-l, and the detection limits was 0.44 mg L- 1. The proposed method was applied to the 'determination of lactose in food samples and satisfactory results were obtained.展开更多
The electrochemical behaviour and electrode reaction mechanism of ziram (zinc-dimethyl dithiocarbamate) on a hanging mercury drop electrode were investigated in Britton-Robinson (B-R) buffer by using cyclic and sq...The electrochemical behaviour and electrode reaction mechanism of ziram (zinc-dimethyl dithiocarbamate) on a hanging mercury drop electrode were investigated in Britton-Robinson (B-R) buffer by using cyclic and square wave voltammetry (SWV). Based on these studies a voltammetric method for determination of ziram wasdeveloped and applied to determine the ziram in synthetic and spiked vegetable samples, satisfactory results were obtained in both cases.展开更多
The moisture content measurement of human skin is a significant way to assess skin conditions and diagnose diseases that influence skin function.The necessity of evaluating the efficacy of a cosmetic product makes it ...The moisture content measurement of human skin is a significant way to assess skin conditions and diagnose diseases that influence skin function.The necessity of evaluating the efficacy of a cosmetic product makes it important to improve the accuracy and reproducibility of the measurement.A pair of interdigitated gold electrodes was fabricated on the printed circuit board (PCB) substrate and utilized directly in contact with the measured skin.A square-wave voltage at a single frequency was applied to the electrodes and the corresponding response current was measured to get the equivalent impedance of human skin.Since it's easy to generate and control a square-wave signal by digital electric circuits,this method is suitable to be used in the portable application.The experimental results indicate that good repeatability and satisfied accuracy can be obtained by this method.展开更多
A 2D square lattice is studied. By using the continuum approximation, we set up the differential equations of motion for an arbitrary particle in the square lattice which subjects to an external periodic substrate pot...A 2D square lattice is studied. By using the continuum approximation, we set up the differential equations of motion for an arbitrary particle in the square lattice which subjects to an external periodic substrate potential. The exact solitary waves of the system are found for special cases. We conclude that the adhesive force f and the angle between propagation directions of upper and lower layers can affect these waves.展开更多
In this paper, the heat, resolvent and wave kernels associated to the Schr?dinger operator with multi-inverse square potential on the Euclidian space Rn are given in explicit forms.
It is well known that the dynamic response of the structure to an earthquake excitation is affected by the interaction with the foundation and the soil.The expansion of informatics and development of the computer capa...It is well known that the dynamic response of the structure to an earthquake excitation is affected by the interaction with the foundation and the soil.The expansion of informatics and development of the computer capacities has helped the scientists to develop numerical models for approximate solutions of big variety of problems related to SSI(Soil Structure Interaction).Many of those problems involve domain-coupling.In this paper we built numerical model,based on finite differences and we investigate the accuracy of the numerical model depending upon the size of the square domain around the source.We tested eight different square sizes and we analyzed their accuracy regarding to five different wave periods.The results give recommendations for the implementation of the domain-coupling algorithm.展开更多
Conventional shot-gather migration uses a cross-correlation imaging condition proposed by Clarebout (1971), which cannot preserve imaging amplitudes. The deconvolution imaging condition can improve the imaging ampli...Conventional shot-gather migration uses a cross-correlation imaging condition proposed by Clarebout (1971), which cannot preserve imaging amplitudes. The deconvolution imaging condition can improve the imaging amplitude and compensate for illumination. However, the deconvolution imaging condition introduces instability issues. The least-squares imaging condition first computes the sum of the cross-correlation of the forward and backward wavefields over all frequencies and sources, and then divides the result by the total energy of the forward wavefield. Therefore, the least-squares imaging condition is more stable than the classic imaging condition. However, the least-squares imaging condition cannot provide accurate results in areas where the illumination is very poor and unbalanced. To stabilize the least-squares imaging condition and balance the imaging amplitude, we propose a novel imaging condition with structure constraints that is based on the least-squares imaging condition. Our novel imaging condition uses a plane wave construction that constrains the imaging result to be smooth along geological structure boundaries in the inversion frame. The proposed imaging condition improves the stability of the imaging condition and balances the imaging amplitude. The proposed condition is applied to two examples, the horizontal layered model and the Sigsbee 2A model. These tests show that, in comparison to the damped least-squares imaging condition, the stabilized least-squares imaging condition with structure constraints improves illumination stability and balance, makes events more consecutive, adjusts the amplitude of the depth layers where the illumination is poor and unbalanced, suppresses imaging artifacts, and is conducive to amplitude preserving imaging of deep layers.展开更多
文摘A new type of brushless DC motor has been developed by using a square wave rare earth permanent magnet synchronous motor with its double loop control circuit. The double loop control scheme of the drive system yields a combination of desired characteristics including simplified control structure, small ripple torque, high speed accuracy, wide operating speed range, and fast dynamic response. Experimental results confirm excellent characteristics of the motor.
基金International Science&Technology Cooperation Program of China under Grant No.2011DFA71100the National Key Technology R&D Program under Grant No.2014BAK03B01the National Basic Research Program of China(973 Program)under Grant No.2007CB714201
文摘Surface wave methods are becoming increasingly popular in many geotechnical applications and in earthquake seismology due to their noninvasive characteristics.Inverse surface wave dispersion curves are a crucial step in most surface wave methods.Many inversion methods have been applied to surface wave dispersion curve inversion,including linearized inversion and nonlinearized inversion methods.In this study,a hybrid inversion method of Damped Least Squares(DLS) with Very Fast Simulated Annealing(VFSA) is developed for multi-mode Rayleigh wave dispersion curve inversion.Both synthetic and in situ fi eld data were used to verify the validity of the proposed method.The results show that the proposed method is superior to the conventional VFSA method in aiming at global minimum,especially when parameter searching space is adjacent to real values of the parameters.The advantage of the new method is that it retains both the merits of VFSA for global search and DLS for local search.At high temperatures,the global search dominates the runs,while at a low temperatures,the local search dominates the runs.Thus,at low temperatures,the proposed method can almost directly approach the actual model.
文摘-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.
基金supported by the National Natural Science Foundation of China(No.10572001).
文摘This is a continued work in studying the wave propagation in a magneto-electroelastic square column (MEESC). Based on the analytic dispersive equation, group velocity equation and steady-state response obtained in our previous paper 'Steady-state response of the wave propagation in a magneto-electro-elastic square column' published in CME, the dynamical behavior of MEESC was studied in this paper. The unlimited column is an open system. The transientstate response in the open system subjected by arbitrary external fields was derived when the propagating wave pursuing method was introduced.
基金supported by the National Science and Technology Major Project(No.2016ZX05014-001-008)the National Key Basic Research Program of China(No.2014CB239006)+2 种基金the National Natural Science Foundation of China(Nos.41104069 and 41274124)the Open foundation of SINOPEC Key Laboratory of Geophysics(No.33550006-15-FW2099-0033)the Fundamental Research Funds for Central Universities(No.16CX06046A)
文摘Least squares migration can eliminate the artifacts introduced by the direct imaging of irregular seismic data but is computationally costly and of slow convergence. In order to suppress the migration noise, we propose the preconditioned prestack plane-wave least squares reverse time migration (PLSRTM) method with singular spectrum constraint. Singular spectrum analysis (SSA) is used in the preconditioning of the take-off angle-domain common-image gathers (TADCIGs). In addition, we adopt randomized singular value decomposition (RSVD) to calculate the singular values. RSVD reduces the computational cost of SSA by replacing the singular value decomposition (SVD) of one large matrix with the SVD of two small matrices. We incorporate a regularization term into the preconditioned PLSRTM method that penalizes misfits between the migration images from the plane waves with adjacent angles to reduce the migration noise because the stacking of the migration results cannot effectively suppress the migration noise when the migration velocity contains errors. The regularization imposes smoothness constraints on the TADCIGs that favor differential semblance optimization constraints. Numerical analysis of synthetic data using the Marmousi model suggests that the proposed method can efficiently suppress the artifacts introduced by plane-wave gathers or irregular seismic data and improve the imaging quality of PLSRTM. Furthermore, it produces better images with less noise and more continuous structures even for inaccurate migration velocities.
文摘This paper reports on the development of a novel electrochemical assay for cadmium (II) in natural water, which involves the use of disposable hydroxyapatite modified platinum electrode (HAP/Pt). Cadmium (II) was preconcentrated on the surface of the modified electrode and adsorbed onto HAP and oxidized at E = –680 mV. The HAP-modified platinum electrode exhibited superior performance in comparison to the plati- num electrode and surprisingly, yielded a higher electrochemical response. The best defined anodic peak was obtained with 0.2 mol L-1 KNO3 pH 5.0 after 25 min of accumulation time. Using these conditions, the cali- bration plot was linear over the range 1 × 10?8 to 5 × 10?6 mol L-1 Cd2+. The precision was examined by car- rying out eight replicate measurements at a concentration of 2.5 ×10?5 mol L-1;the coefficient of variation was 2.9%. The method was applied to the determination of the analyte in river water samples. The interfere- ence of other metal ions on the voltammetric response of Cd(II) was studied. The HAP films was clearly ob- served in the SEM images and characterized by X-ray diffraction, IR spectroscopy and chemical analysis.
基金This work was financially supported by the National Natural Science Foundation of China (No. 59771067) and the National Key Laboratory of New Metal Materials.
文摘Cerium contained conversion films were deposited on LC4 aluminum alloy usingsquare wave pulse (SWP) in a CeCl_3 solution with KMnO_4 as the oxidant. Energy dispersivespectroscopy (EDS) and scanning electron microscopy (SEM) were adopted to study the composition andthe morphology of the film. It is found that the film is composed of Al, Zn, Cu, and small amount ofcerium. The polarization curves of the specimens treated with SWP technique measured in 3.5% (massfraction) NaCl solution reveal that the film thus formed inhibits both the anodic and cathodicprocess of the corrosion of the specimen. The immersion tests of treated specimens in 3.5% NaClsolution indicate that the corrosion resistance of the SWP treated specimen is better than that ofthe untreated and is equivalent to or even better than that of the traditionally electro-chemicallytreated specimens.
基金support from the National Natural Science Foundation of China(No.20475018)the Key Program of Guangdong Natural Science Foundation(No.05103552)
文摘This paper reported a compact system of capacitively coupled contactless conductivity detection (C4D) based on the square wave excitation voltage for capillary electrophoresis, and it exhibited excellent sensitivity at the optimal frequency of 198 kHz. The feasibility and sensitivity of this detector was demonstrated by simultaneous detection of thirteen ions including alkali, alkaline earth and heavy metal ions. And the detection limits (S/N 3) were in the range of 0.2-1μmol/L for Mn^2+, K^+, Na^+, Mg^2+, Ca^2+, Li^+, Ba^2+, and 7-25 μmol/L for Ni^2+, Cu^2+, Cd^2+, Pb^2+, Co^2+, Zn^2+.
基金support for this study was provided by the National Natural Science Foundation of China (No.40776006)Research Fund for the Doctoral Program of Higher Education of China (Grant No.20060423009)the Science and Technology Development Program of Shandong Province (Grant No.2008GGB01099)
文摘Significant wave height is an important criterion in designing coastal and offshore structures.Based on the orthogonality principle, the linear mean square estimation method is applied to calculate significant wave height in this paper.Twenty-eight-year time series of wave data collected from three ocean buoys near San Francisco along the California coast are analyzed.It is proved theoretically that the computation error will be reduced by using as many measured data as possible for the calculation of significant wave height.Measured significant wave height at one buoy location is compared with the calculated value based on the data from two other adjacent buoys.The results indicate that the linear mean square estimation method can be well applied to the calculation and prediction of significant wave height in coastal regions.
基金National Natural Science Foundation of China ( No. 10972065) Natural Science Foundation of Heilongjiang Province of China( No. ZD200905)
文摘The vibration suppression of the finite plate with square steel beams is studied using traveling wave method. The finite plate with square beams is modeled as the coupling systems between the plate flexural motion and the flexural and torsional motions for the square beams. The vibration response at any position of the coupling structure can be obtained by wave method. Numerical results show that comparing to finite element method (FEM), not only the low frequency but also the medium-high frequency vibration response of the finite plate with square beam can be effectively calculated by wave method. The suppression effect can be increased as the square beam is located at one-third of the length of plate or increasing the height of the beam. The study provides reference for arranged square beams applying to vibration suppression of ship and train structures.
文摘In wind power system,the randomness of wind energy increases the probability of components fault.once the switch fault of the PWM rectifier is detected,it will lead to the distortion of the motor voltage and current waveform,the increase of torque ripple,the fluctuation of filter capacitor voltage,and the increase of harmonic content,which will affect the control performance and operation safety of the system.A common fault in a three-phase PWM rectifier is the open-circuit fault of the switch.This paper analyzes the current waveform distortion of the square wave motor when the rectifier switch fault,and proposes different fault-tolerant control strategies for different situations of switch fault,include single,double and triple switches fault.This method is based on several special driving modes under power generation situation of square wave motor.The strategy is easy to implement and does not need to change the circuit topology.It can realize fault-tolerant control of switch faults in the same side half bridge or the same bridge arm of the three-phase PWM rectifier.The effectiveness of the proposed fault-tolerant strategy is verified by simulation and experiment at the end of the article.
基金supported from the National Natural Science Foundation (No.20562009)the State Key Laboratory of Electroanalytical Chemistry of Changchun Applied Chemical Institute (No.2004-3)+1 种基金the Jiangxi Provincial Natural Science Foundation (No.0620041)the Program for Changjiang Scholar and Innovative Research Team in Universities (No.0540).
文摘A method for determination of lactose in food samples by Osteryoung square wave voltammetry (OSWV) was developed. It was based on the nucleophilic addition reaction between lactose and aqua ammonia. The carbonyl group of lactose can be changed into imido group, and this increases the electrochemical activity in reduction and the sensitivity. The optimal condition for the nucleophilic addition reaction was investigated and it was found that in NH4C1-NH3 buffer of pH 10.1, the linear range between the peak current and the concentration of lactose was 0.6-8.4 mg L-l, and the detection limits was 0.44 mg L- 1. The proposed method was applied to the 'determination of lactose in food samples and satisfactory results were obtained.
基金the financial support of this study by the National Natural Science Foundation of China (No.20562009)the Jiangxi Province Natural Science Foundation (No.0620041)+1 种基金the State Key Laboratories of Electroanalytical Chemistry of Changchun Applied Chemical Institute (No.SKLEAC2004-3)Chemo/Biosensing and Chemometrics of Hunan University (No.2005-22).
文摘The electrochemical behaviour and electrode reaction mechanism of ziram (zinc-dimethyl dithiocarbamate) on a hanging mercury drop electrode were investigated in Britton-Robinson (B-R) buffer by using cyclic and square wave voltammetry (SWV). Based on these studies a voltammetric method for determination of ziram wasdeveloped and applied to determine the ziram in synthetic and spiked vegetable samples, satisfactory results were obtained in both cases.
文摘The moisture content measurement of human skin is a significant way to assess skin conditions and diagnose diseases that influence skin function.The necessity of evaluating the efficacy of a cosmetic product makes it important to improve the accuracy and reproducibility of the measurement.A pair of interdigitated gold electrodes was fabricated on the printed circuit board (PCB) substrate and utilized directly in contact with the measured skin.A square-wave voltage at a single frequency was applied to the electrodes and the corresponding response current was measured to get the equivalent impedance of human skin.Since it's easy to generate and control a square-wave signal by digital electric circuits,this method is suitable to be used in the portable application.The experimental results indicate that good repeatability and satisfied accuracy can be obtained by this method.
基金supported by National Natural Science Foundation of China under Grant No. 10575082the Natural Science Foundation of Gansu Province under Grant No. 3ZS061-A25-013the Natural Science Foundation of Northwest Normal University under Grant No. NWNU-KJCXGC-03-17
文摘A 2D square lattice is studied. By using the continuum approximation, we set up the differential equations of motion for an arbitrary particle in the square lattice which subjects to an external periodic substrate potential. The exact solitary waves of the system are found for special cases. We conclude that the adhesive force f and the angle between propagation directions of upper and lower layers can affect these waves.
文摘In this paper, the heat, resolvent and wave kernels associated to the Schr?dinger operator with multi-inverse square potential on the Euclidian space Rn are given in explicit forms.
文摘It is well known that the dynamic response of the structure to an earthquake excitation is affected by the interaction with the foundation and the soil.The expansion of informatics and development of the computer capacities has helped the scientists to develop numerical models for approximate solutions of big variety of problems related to SSI(Soil Structure Interaction).Many of those problems involve domain-coupling.In this paper we built numerical model,based on finite differences and we investigate the accuracy of the numerical model depending upon the size of the square domain around the source.We tested eight different square sizes and we analyzed their accuracy regarding to five different wave periods.The results give recommendations for the implementation of the domain-coupling algorithm.
基金financially supported by Important National Science and Technology Specific Projects of China(Grant No. 2011ZX05023-005-005)
文摘Conventional shot-gather migration uses a cross-correlation imaging condition proposed by Clarebout (1971), which cannot preserve imaging amplitudes. The deconvolution imaging condition can improve the imaging amplitude and compensate for illumination. However, the deconvolution imaging condition introduces instability issues. The least-squares imaging condition first computes the sum of the cross-correlation of the forward and backward wavefields over all frequencies and sources, and then divides the result by the total energy of the forward wavefield. Therefore, the least-squares imaging condition is more stable than the classic imaging condition. However, the least-squares imaging condition cannot provide accurate results in areas where the illumination is very poor and unbalanced. To stabilize the least-squares imaging condition and balance the imaging amplitude, we propose a novel imaging condition with structure constraints that is based on the least-squares imaging condition. Our novel imaging condition uses a plane wave construction that constrains the imaging result to be smooth along geological structure boundaries in the inversion frame. The proposed imaging condition improves the stability of the imaging condition and balances the imaging amplitude. The proposed condition is applied to two examples, the horizontal layered model and the Sigsbee 2A model. These tests show that, in comparison to the damped least-squares imaging condition, the stabilized least-squares imaging condition with structure constraints improves illumination stability and balance, makes events more consecutive, adjusts the amplitude of the depth layers where the illumination is poor and unbalanced, suppresses imaging artifacts, and is conducive to amplitude preserving imaging of deep layers.