In order to reduce the energy consumption and subsequent air pollution of coal-fired power station, based on the analysis to size and density distribution of particles from the recirculating load of the classifier of ...In order to reduce the energy consumption and subsequent air pollution of coal-fired power station, based on the analysis to size and density distribution of particles from the recirculating load of the classifier of pulverizer, the separation experiment on sampling material from power plant with a dilute phase fluidized bed to remove pyrite and other minerals and numerical simulation on the separation process were done. The results show that the minimum fluidization velocity is 1.62 cm/s. Pyrite and other minerals in the material are separated. Ash of the upper and bottom layer material account for 33.34% and 73.42% respectively and sulfur content occupy 1.12% and 8.96% respectively. Scanning electron microscopy and spectroscopy tests show that sulfur in the bottom material exist in the form of pyrite. Numerical simulation on the flow field form of the dilute phase separation bed with gas-solid two phase and particle motion verifies the experimental results.展开更多
On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests o...On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.展开更多
Rock experiment results indicate that the load/unload response ratio (LURR) of rocks expressed via strain energy may have singular or negative value after the stress in the rock reaches its maximum before rock failure...Rock experiment results indicate that the load/unload response ratio (LURR) of rocks expressed via strain energy may have singular or negative value after the stress in the rock reaches its maximum before rock failure or when the rock goes into the strain-weakening phase. The universality of this phenomenon is discussed. Expressed via strain or strain energy and the travel time of P wave, the variation form of the reciprocal of LURR during the process of rock failure preparation is derived. The results show that after a sharp decrease the reciprocal of LURR reaches its minimum when the main fracture of the rock is about to appear. This feature can be taken as an indication that the rock main fracture is impending.展开更多
The effects of shock loading on the morphology,grain growth during heating and phase transforma- tion of ZrO_2 have been investigated.It is shown that shock loading may be efficiently used to modify submicron ceramic ...The effects of shock loading on the morphology,grain growth during heating and phase transforma- tion of ZrO_2 have been investigated.It is shown that shock loading may be efficiently used to modify submicron ceramic powders with nanocrystalline structure.After shock loading,the critical diameter of ZrO_2 particles transformed from tetragonal to monoclinic decreased due to stored strain energy. Annealing of powders resulted in reversible transformation to the tetragonal without considerable grain growth up to 1200℃.展开更多
Aiming at the complex electromagnetic transient process of EMU passing by phase-separation with electric load in high-speed railway, mechanism of overvoltage caused by switching off, overvoltage caused by switching on...Aiming at the complex electromagnetic transient process of EMU passing by phase-separation with electric load in high-speed railway, mechanism of overvoltage caused by switching off, overvoltage caused by switching on and impact current is analyzed systematically in this article. π-type equivalent circuit of feeding section is put forward in the analysis of overvoltage mechanism. Overvoltage and overcurrent model of passing by phase-separation with electric load are also built. Correctness of mechanism was validated by simulation. In addition, the methods to solve the influence on substations, transformers and protection devices in this process are put forward, which provides a new idea on passing by phase-separation with electric load technology.展开更多
One of the very important functions of three-phase inverter is to maintain the symmetric three-phase output voltage when the three-phase loads are unbalanced. Although the traditional symmetrical component decomposing...One of the very important functions of three-phase inverter is to maintain the symmetric three-phase output voltage when the three-phase loads are unbalanced. Although the traditional symmetrical component decomposing and superimpose theory can keep the voltage balance through compensating the positive-, negative- and zero-sequence components of the output voltage of inverter, however, this method is time-consuming and not suitable for control. Aiming at high power medium frequency inverter source, a P+Resonant (Proportion and Resonant) controller which ensured a balanced three phase output voltage under unbalanced load is proposed in this paper. The regulator was proved to be applicable to both three-phase three-wire system and three-phase four-wire system and developed two methods of realization. The simulation results verified that this method can suppressed effectively the output voltage distorted caused by the unbalanced load and attained a high quality voltage waveforms.展开更多
Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport....Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport. By incorporating these counteracting driving forces in a phase-averaged manner, the theoretically-based quasi-steady formula of Wang （2007） is modified to predict the magnitude and direction of net cross-shore total load transport under the coaction of wave and current. The predictions show an excellent agreement with the measurement data on medium and fine sand collected by Dohmen-Janssen and Hanes （2002） and Schretlen （2012） in a full-scale wave flume at the Coastal Research Centre in Hannover, Germany. The modified formula can predict the net onshore transport of fine sand in sheet flows. In particular, it can predict the net offshore transport of medium sand in rippled beds through enlarged bed roughness, as well as the net offshore transport of fine-to-coarse sand in sheet flows with the aid of a new criterion to judge the occurrence of net offshore transport.展开更多
This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag partic...This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag particularly for nonlinear load. In case of single phase distribution line with nonlinear load, the complexity of controller’s design becomes more serious issue. The present single phase and/or three phase theories applicable to DVR shows poor response to restore voltage sag in case of nonlinear load due to presence of harmonics. Hence restoration of voltage sag in single phase nonlinear load connected system has been a serious concern. Therefore, new controller for DVR has been proposed incorporating effective design concept for fundamental component extraction in case of nonlinear load. The single phase SRFT based main controller for DVR works on two separate closed path viz. feed forward path for quick transient response and feedback path for reducing the steady state error. Moreover, pre-sag mitigation strategy of DVR has been adapted through these two aforementioned paths. Complete design of proposed controller is based on phasor analysis. It also consist of proportional integral (PI) controller to reduce the error in the DC-link voltage during compensation time. The controller performance has been verified in MATLAB Simulink for both types (linear and nonlinear) of load. The results obtained indicates that the proposed controller is effective in its performance.展开更多
The technique of hydrothermal stripping from mixed aqueous-organic systems is a promising method for synthesizing oxide ceramic powders for high-performance applications. Some factors influencing heterogeneous hydroth...The technique of hydrothermal stripping from mixed aqueous-organic systems is a promising method for synthesizing oxide ceramic powders for high-performance applications. Some factors influencing heterogeneous hydrothermal stripping with water from iron-loaded organic phase of naphthenic acidisooctyl alcoholkerosene, such as initial concentrations of iron and naphthenic acid, concentration of Fe2O3 搒eed, temperature and time, were investigated. Based on the experimental results, the rate equation was established. Nano-ferric oxide powders were obtained by the technique of hydrothermal stripping from the iron-loaded organic phase. The results suggest that the heterogeneous hydrothermal stripping proceeds in 3 steps: adsorption of naphthenic acid dimers and naphthenic complex of iron onto the surface of seed? hydrolysis of adsorbed complex of iron, and condensation of hydrolyzed complex. The process activation energy is 115 kJ/mol and the heterogeneous hydrothermal stripping is controlled by a chemical reaction (the hydrolysis of naphthenic complex of iron).展开更多
The surface oxide film cracking behavior of Fe-30Ni-20Cr alloy under in-phase and out-of-phase synchronizing thermal cycling with mechanical cycling was studied.Surface oxide film cracking along the grain boundary und...The surface oxide film cracking behavior of Fe-30Ni-20Cr alloy under in-phase and out-of-phase synchronizing thermal cycling with mechanical cycling was studied.Surface oxide film cracking along the grain boundary under in-phase overlapping was creep predominant fracture mechanisms.Strongly induced slip lines preceding were accompanied by the surface oxide film cracking under Out-of phase,and the shear cracking was dominant mode.Negative mean stress could counteract a part of the tensile component of alternative stress,so as to delay the cracking process under in-phase,but positive mean stress overlapping the tensile alternative stress could accelerate the cycling cracking process under out-of-phase.展开更多
The biaxial tensile tests were carried out to investigate the deformation behavior and yield loci of dual-phase （DP） steel sheets under biaxial tensile conditions. The true stress-true strain curves of DP steel shee...The biaxial tensile tests were carried out to investigate the deformation behavior and yield loci of dual-phase （DP） steel sheets under biaxial tensile conditions. The true stress-true strain curves of DP steel sheets for different loading ratios were obtained, and the experimental yield loci were determined based on the equivalent plastic work principle. The experimental yield loci were compared to the theoretical yield loci based on Hi1148, Hi1190, Hi1193, Hosford, Barlat89, Yld2000-2d and Gotoh yield criteria. It is found that Yld2000-2d yield criterion can describe the general trends of experimental yield loci of DP steel sheets with comparably higher accuracy. Hosford criterion has the maximum error for DP590, whereas Hi1148 and Barlat89 have the maximum errors for DP780 and DP980.展开更多
Non-iterative analysis of indentation results allows for the detection of phase transitions under load and their transition energy. The closed algebraic equations have been deduced on the basis of the physically found...Non-iterative analysis of indentation results allows for the detection of phase transitions under load and their transition energy. The closed algebraic equations have been deduced on the basis of the physically founded normal force ?depth3/2 relation. The precise transition onset position is obtained by linear regression of the FN = kh3/2 plot, where k is the penetration resistance, which also provides the axis cuts of both polymorphs of first order phase transitions. The phase changes can be endothermic or exothermic. They are normalized per μN or mN normal load. The analyses of indentation loading curves with self-similar diamond indenters are used as validity check of the loading curves, also from calibration standards that exhibit previously undetected phase-transitions and are thus incorrect. The phase-transition energies for fused quartz are determined from the loading curves from instrument provider handbooks. The anisotropic behavior of phase transition energies is studied for the first time. Quartz is a useful test object. The reasons for the packing-dependent differences are discussed on the basis of the local crystal structure under and around the inserting tip.展开更多
Z-source inverter can boost the voltage of the DC-side, allow the two switches of the same bridge arm conducting at the same time and it has some other advantages. The zero-sequence current flows through the fourth le...Z-source inverter can boost the voltage of the DC-side, allow the two switches of the same bridge arm conducting at the same time and it has some other advantages. The zero-sequence current flows through the fourth leg of the three-phase four-leg inverter so the three-phase four-leg inverter can work with unbalanced load. This paper presents a Z-source three-phase four-leg inverter which combines a Z-source network with three-phase four-leg inverter. The circuit uses simple SPWM modulation technique and the fourth bridge arm uses fully compensated control method. The inverter can maintain a symmetrical output voltage when the proposed scheme under the unbalanced load.展开更多
Co-phase power supply system can solve the problems of power quality of heavy unbalanced three phase, large harmonics and reactive power and cancel neutral section in electric railway power supply system. In order to ...Co-phase power supply system can solve the problems of power quality of heavy unbalanced three phase, large harmonics and reactive power and cancel neutral section in electric railway power supply system. In order to do further research, a co-phase power supply test system is proposed. By mean of analyzing on structures and principles of YNvd transformer, integrated power flow controller (IPFC) and simulation load, establishing control strategy on IPFC and simulation load, the system is simulated dynamically. The results illustrate that the scheme can well simulate co-phase system, and the negative sequence is eliminated, harmonic and reactive power are real-timely compensated in system.展开更多
基金supported financially by the National Natural Science Foundation of China (Nos. 51074156 and 50921002)
文摘In order to reduce the energy consumption and subsequent air pollution of coal-fired power station, based on the analysis to size and density distribution of particles from the recirculating load of the classifier of pulverizer, the separation experiment on sampling material from power plant with a dilute phase fluidized bed to remove pyrite and other minerals and numerical simulation on the separation process were done. The results show that the minimum fluidization velocity is 1.62 cm/s. Pyrite and other minerals in the material are separated. Ash of the upper and bottom layer material account for 33.34% and 73.42% respectively and sulfur content occupy 1.12% and 8.96% respectively. Scanning electron microscopy and spectroscopy tests show that sulfur in the bottom material exist in the form of pyrite. Numerical simulation on the flow field form of the dilute phase separation bed with gas-solid two phase and particle motion verifies the experimental results.
基金Funded by the National Natural Science Foundation of China (No.50878054)
文摘On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.
基金Key project from China Seismological Bureau (9691309020301) State Natural Sciences Foundation of China (19732060).
文摘Rock experiment results indicate that the load/unload response ratio (LURR) of rocks expressed via strain energy may have singular or negative value after the stress in the rock reaches its maximum before rock failure or when the rock goes into the strain-weakening phase. The universality of this phenomenon is discussed. Expressed via strain or strain energy and the travel time of P wave, the variation form of the reciprocal of LURR during the process of rock failure preparation is derived. The results show that after a sharp decrease the reciprocal of LURR reaches its minimum when the main fracture of the rock is about to appear. This feature can be taken as an indication that the rock main fracture is impending.
文摘The effects of shock loading on the morphology,grain growth during heating and phase transforma- tion of ZrO_2 have been investigated.It is shown that shock loading may be efficiently used to modify submicron ceramic powders with nanocrystalline structure.After shock loading,the critical diameter of ZrO_2 particles transformed from tetragonal to monoclinic decreased due to stored strain energy. Annealing of powders resulted in reversible transformation to the tetragonal without considerable grain growth up to 1200℃.
文摘Aiming at the complex electromagnetic transient process of EMU passing by phase-separation with electric load in high-speed railway, mechanism of overvoltage caused by switching off, overvoltage caused by switching on and impact current is analyzed systematically in this article. π-type equivalent circuit of feeding section is put forward in the analysis of overvoltage mechanism. Overvoltage and overcurrent model of passing by phase-separation with electric load are also built. Correctness of mechanism was validated by simulation. In addition, the methods to solve the influence on substations, transformers and protection devices in this process are put forward, which provides a new idea on passing by phase-separation with electric load technology.
文摘One of the very important functions of three-phase inverter is to maintain the symmetric three-phase output voltage when the three-phase loads are unbalanced. Although the traditional symmetrical component decomposing and superimpose theory can keep the voltage balance through compensating the positive-, negative- and zero-sequence components of the output voltage of inverter, however, this method is time-consuming and not suitable for control. Aiming at high power medium frequency inverter source, a P+Resonant (Proportion and Resonant) controller which ensured a balanced three phase output voltage under unbalanced load is proposed in this paper. The regulator was proved to be applicable to both three-phase three-wire system and three-phase four-wire system and developed two methods of realization. The simulation results verified that this method can suppressed effectively the output voltage distorted caused by the unbalanced load and attained a high quality voltage waveforms.
基金supported by the National Natural Science Foundation of China(Grant No.51179211)
文摘Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport. By incorporating these counteracting driving forces in a phase-averaged manner, the theoretically-based quasi-steady formula of Wang （2007） is modified to predict the magnitude and direction of net cross-shore total load transport under the coaction of wave and current. The predictions show an excellent agreement with the measurement data on medium and fine sand collected by Dohmen-Janssen and Hanes （2002） and Schretlen （2012） in a full-scale wave flume at the Coastal Research Centre in Hannover, Germany. The modified formula can predict the net onshore transport of fine sand in sheet flows. In particular, it can predict the net offshore transport of medium sand in rippled beds through enlarged bed roughness, as well as the net offshore transport of fine-to-coarse sand in sheet flows with the aid of a new criterion to judge the occurrence of net offshore transport.
文摘This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag particularly for nonlinear load. In case of single phase distribution line with nonlinear load, the complexity of controller’s design becomes more serious issue. The present single phase and/or three phase theories applicable to DVR shows poor response to restore voltage sag in case of nonlinear load due to presence of harmonics. Hence restoration of voltage sag in single phase nonlinear load connected system has been a serious concern. Therefore, new controller for DVR has been proposed incorporating effective design concept for fundamental component extraction in case of nonlinear load. The single phase SRFT based main controller for DVR works on two separate closed path viz. feed forward path for quick transient response and feedback path for reducing the steady state error. Moreover, pre-sag mitigation strategy of DVR has been adapted through these two aforementioned paths. Complete design of proposed controller is based on phasor analysis. It also consist of proportional integral (PI) controller to reduce the error in the DC-link voltage during compensation time. The controller performance has been verified in MATLAB Simulink for both types (linear and nonlinear) of load. The results obtained indicates that the proposed controller is effective in its performance.
基金Supported by the National Natural Science Foundation of China (No.: 59934080)
文摘The technique of hydrothermal stripping from mixed aqueous-organic systems is a promising method for synthesizing oxide ceramic powders for high-performance applications. Some factors influencing heterogeneous hydrothermal stripping with water from iron-loaded organic phase of naphthenic acidisooctyl alcoholkerosene, such as initial concentrations of iron and naphthenic acid, concentration of Fe2O3 搒eed, temperature and time, were investigated. Based on the experimental results, the rate equation was established. Nano-ferric oxide powders were obtained by the technique of hydrothermal stripping from the iron-loaded organic phase. The results suggest that the heterogeneous hydrothermal stripping proceeds in 3 steps: adsorption of naphthenic acid dimers and naphthenic complex of iron onto the surface of seed? hydrolysis of adsorbed complex of iron, and condensation of hydrolyzed complex. The process activation energy is 115 kJ/mol and the heterogeneous hydrothermal stripping is controlled by a chemical reaction (the hydrolysis of naphthenic complex of iron).
基金Acknowledgments This work has benefited from the use of 1） Los Alamos Neutron Science Facility at Los Alamos National Laboratory and 2） ISIS Pulsed Neutron and Muon Source at Rutherford-Appleton Laboratory. The financial support of the National Science Foundation＇s 1） International Materials Institutes （IMI） under DMR-0231320, 2） Integrative Graduate Education and Research Training （IGERT） under DGE-9987548, 3） Combined Research and Curriculum Development （CRCD） under EEC-9527527 and EEC-0203415, and 4） Major Research Instrumentation （MRI） under DMR-0231320 at the University of Tennessee with Dr HUBER C, Dr Van HARTESVELDT C J, Dr DUTTA D, Dr JENNINGS W, Dr G0LDBERG L, Ms P0ATS M, and Dr B0ULDIN C R as the Program Directors, is greatly appreciated. Additional funding for this project was gratefully received from the Tennessee Advanced Materials Laboratory, with Prof. PLUMMER E W as the Director.
文摘The surface oxide film cracking behavior of Fe-30Ni-20Cr alloy under in-phase and out-of-phase synchronizing thermal cycling with mechanical cycling was studied.Surface oxide film cracking along the grain boundary under in-phase overlapping was creep predominant fracture mechanisms.Strongly induced slip lines preceding were accompanied by the surface oxide film cracking under Out-of phase,and the shear cracking was dominant mode.Negative mean stress could counteract a part of the tensile component of alternative stress,so as to delay the cracking process under in-phase,but positive mean stress overlapping the tensile alternative stress could accelerate the cycling cracking process under out-of-phase.
基金This research was funded by National Natural Science Foundation of China （51275026） and State Key Laboratory of Development and Application Technology of Automotive Steels （Bao Steel Y 12ECEQ07Y）.
文摘The biaxial tensile tests were carried out to investigate the deformation behavior and yield loci of dual-phase （DP） steel sheets under biaxial tensile conditions. The true stress-true strain curves of DP steel sheets for different loading ratios were obtained, and the experimental yield loci were determined based on the equivalent plastic work principle. The experimental yield loci were compared to the theoretical yield loci based on Hi1148, Hi1190, Hi1193, Hosford, Barlat89, Yld2000-2d and Gotoh yield criteria. It is found that Yld2000-2d yield criterion can describe the general trends of experimental yield loci of DP steel sheets with comparably higher accuracy. Hosford criterion has the maximum error for DP590, whereas Hi1148 and Barlat89 have the maximum errors for DP780 and DP980.
文摘Non-iterative analysis of indentation results allows for the detection of phase transitions under load and their transition energy. The closed algebraic equations have been deduced on the basis of the physically founded normal force ?depth3/2 relation. The precise transition onset position is obtained by linear regression of the FN = kh3/2 plot, where k is the penetration resistance, which also provides the axis cuts of both polymorphs of first order phase transitions. The phase changes can be endothermic or exothermic. They are normalized per μN or mN normal load. The analyses of indentation loading curves with self-similar diamond indenters are used as validity check of the loading curves, also from calibration standards that exhibit previously undetected phase-transitions and are thus incorrect. The phase-transition energies for fused quartz are determined from the loading curves from instrument provider handbooks. The anisotropic behavior of phase transition energies is studied for the first time. Quartz is a useful test object. The reasons for the packing-dependent differences are discussed on the basis of the local crystal structure under and around the inserting tip.
文摘Z-source inverter can boost the voltage of the DC-side, allow the two switches of the same bridge arm conducting at the same time and it has some other advantages. The zero-sequence current flows through the fourth leg of the three-phase four-leg inverter so the three-phase four-leg inverter can work with unbalanced load. This paper presents a Z-source three-phase four-leg inverter which combines a Z-source network with three-phase four-leg inverter. The circuit uses simple SPWM modulation technique and the fourth bridge arm uses fully compensated control method. The inverter can maintain a symmetrical output voltage when the proposed scheme under the unbalanced load.
文摘Co-phase power supply system can solve the problems of power quality of heavy unbalanced three phase, large harmonics and reactive power and cancel neutral section in electric railway power supply system. In order to do further research, a co-phase power supply test system is proposed. By mean of analyzing on structures and principles of YNvd transformer, integrated power flow controller (IPFC) and simulation load, establishing control strategy on IPFC and simulation load, the system is simulated dynamically. The results illustrate that the scheme can well simulate co-phase system, and the negative sequence is eliminated, harmonic and reactive power are real-timely compensated in system.
