This paper deals with the investigation of the power absorption in helicon plasma excited through a half-helix antenna driven at 13.56 MHz. The simulations were carried out by means of a code,HELIC. They were carried ...This paper deals with the investigation of the power absorption in helicon plasma excited through a half-helix antenna driven at 13.56 MHz. The simulations were carried out by means of a code,HELIC. They were carried out by taking into account different inhomogeneous radial density profiles and for a wide range of plasma densities, from 10^（11） cm^（-3） to 10^（13） cm^（-3）. The magnetic field was 200, 400, 600 and 1000 G. A three-parameter function was used for generating various density profiles with different volume gradients, edge gradients and density widths. The density profile had a large effect on the efficient Trivelpiece–Gould（TG） and helicon mode excitation and antenna coupling to the plasma. The fraction of power deposition via the TG mode was extremely dependent on the plasma density near the plasma boundary. Interestingly, the obtained efficient parallel helicon wavelength was close to the anticipated value for Gaussian radial density profile.Power deposition was considerably asymmetric when the n/B_0 ratio was more than a specific value for a determined density width. The longitudinal power absorption was symmetric at approximately n_0 =10^（11） cm^（-3）, irrespective of the magnetic field supposed. The asymmetry became more pronounced when the plasma density was 10^（12） cm^（-3）. The ratio of density width to the magnetic field was an important parameter in the power coupling. At high magnetic fields, the maximum of the power absorption was reached at higher plasma density widths. There was at least one combination of the plasma density, magnetic field and density width for which the RF power deposition at both side of the tube reached its maximum value.展开更多
A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The...A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The structure of the cycle is simple which comprises evaporator,turbine,regenerator(desorber),absorber,pump and throttle valves for both diluted solution and vapor.And it is of high efficiency,because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation,which can match the sensible exothermal heat resource and the cooling water simultaneously.Orthogonal calculation was made to investigate the influence of the working concentration,the basic concentration and the circulation multiple on the cycle performance,with 85-110 ℃ heat resource and 20-32 ℃ cooling water.An optimum scheme was given in the condition of 110 ℃ sensitive heat resource and 20 ℃ cooling water,with the working concentration of 0.6,basic concentration of 0.385,and circulation multiple of 5.The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%,respectively.The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle(SRC) and 12.7% higher than that of ORC(R134a) under the optimized situation.展开更多
A multi-body wave energy converter,consisting of three floats and modeled as a two body problem,is optimised to enhance its mean absorbed power using the Response Surface Optimisation Method.The optimisation focuses o...A multi-body wave energy converter,consisting of three floats and modeled as a two body problem,is optimised to enhance its mean absorbed power using the Response Surface Optimisation Method.The optimisation focuses on two input parameters namely;the floats’diameters and the spacing,in various sea states and at different PTO dampings.A frequency domain analysis is performed for the WEC model scaled at 1∶50 in regular and irregular waves.Obtained results are validated against numerical and experimental data available in the literature.Validations show good agreement against the unmoored model’s added mass,radiation damping,response amplitude operator,mean absorbed power and,capture width ratio.The sea states selected for optimisation are represented by a JONSWAP wave spectrum with,a range of significant wave heights(0.04 to 0.06 m)and a range of peak periods(0.8 to 1.3 s).This corresponds to(2 to 3 m)significant wave heights and(5.6 to 9.2 s)peak periods in full scale.Results show that the optimised WEC model demonstrates good and consistent enhancement of its mean absorbed power and capture width ratio.展开更多
Using an one-dimensional slab model, we have studied the electron energy distribution, the anomalous skin effect, and power absorption in the solenoidal-inductively-coupled argon discharge under low pressures (≤ 1.33...Using an one-dimensional slab model, we have studied the electron energy distribution, the anomalous skin effect, and power absorption in the solenoidal-inductively-coupled argon discharge under low pressures (≤ 1.33 Pa). The electron energy distribution function and rf electromagnetic field in the plasma are determined self-consistently by the linearized Bolztmann equation incorporating with the Maxwell equations. The numerical results show that, at low pressures, the electron energy distribution function exhibits a non-Maxwellian distribution with a long high-energy tail. The anomalous skin effect is greatly enhanced under low pressures and the negative power absorption is also obtained.展开更多
Presented is a theoretical study of double-clad Er-doped fiber power amplifier(EDFA). Two kinds of double clad fibers(DCF) with rectangular and "flower" inner clad shapes are studied, and these fibers have d...Presented is a theoretical study of double-clad Er-doped fiber power amplifier(EDFA). Two kinds of double clad fibers(DCF) with rectangular and "flower" inner clad shapes are studied, and these fibers have different coupling constants and propagation losses. We calculate the effective pump power absorption ratio along the fiber with different coupling constants from the first cladding to the doped core and with different propagation losses for the power in the inner cladding. Then the gains of the double clad Er-doped fiber amplifiers versus fiber lengths are calculated using the EDFA model based on propagation and rate equations of a homogeneous, two-level medium.展开更多
Structure, improvements and experiment results of a vertical three-channel far- in- frared （FIR） hydrogen cyanide （HCN） laser interferometer, operated routinely in EAST to measure the electron density profile, are...Structure, improvements and experiment results of a vertical three-channel far- in- frared （FIR） hydrogen cyanide （HCN） laser interferometer, operated routinely in EAST to measure the electron density profile, are presented. Moreover, a five-channel deuterium cyanide （DCN） laser interferometer was developed successfully. Some key issues confronted in development, including the economization of working gas and the solution to atmospheric absorption, are resolved and described in detail.展开更多
The study was conducted to determine the influence of gratering and fermentation parameters on the physicochemical quality of starch obtained from two cassava varieties in Sierra Leone (i.e., SLICASS 11 and SLICASS 6)...The study was conducted to determine the influence of gratering and fermentation parameters on the physicochemical quality of starch obtained from two cassava varieties in Sierra Leone (i.e., SLICASS 11 and SLICASS 6). Fresh cassava roots harvested from the Department of Agricultural Engineering were peeled, washed and grated before fermentation and starch extraction. Fermentation was carried out under separate aerobic and anaerobic conditions for a period of Seven days. Physicochemical analyses were conducted at the Postharvest Food and Bioprocess Engineering Laboratory of the Department of Agricultural and Bio-System Engineering, Njala University to determine the solubility, water absorption capacity and swelling power of starch extracts obtained from various experimental treatments. Fermentation method and duration had significant effects on the solubility, water absorption capacity (WAC) and swelling power (SP) of starch extracts. Maximum solubility and WAC were recorded on the fifth day, for both cassava varieties tested, with apparent significant difference resulting from the two gratering bands (i.e., with 1.5-inch nail hole and 4-inch nail hole sizes, respectively). While swelling power increased consistently with temperature for starch obtained from SLICASS-11 variety, an irregular pattern was observed for SLICASS-6 variety. A multiple correlation analysis proposes a significant and weak correlation between temperature, WAC (+0.150) and swelling power (+0.048). Also multiple correlation analyses suggest a significant correlation between fermentation period, the functional properties of starch extracts obtained from both fermentation methods and cassava varieties (i.e., solubility (−0.226), water absorption capacity (+0.301) and swelling power (+0.329)).展开更多
The absorption cycle is a promising technology for harnessing low-temperature heat,playing a crucial role in achieving the objectives of carbon peaking and carbon neutrality.As a significant element in distributed ene...The absorption cycle is a promising technology for harnessing low-temperature heat,playing a crucial role in achieving the objectives of carbon peaking and carbon neutrality.As a significant element in distributed energy systems,the absorption cycle can utilize various types of low-grade heat to fulfill cooling,heating,and electrical energy demands.Therefore,it can be employed in diverse settings to unleash its substantial energy-saving potential.However,the widespread adoption of the absorption cycle is limited to specific scenarios.Hence,further efforts are needed to enhance its technological maturity,gain societal acceptance,and expand its application scope.Focusing on the utilization of different low-grade heat,this paper provides an overview of significant advancements in the application research of various absorption cycles,such as the absorption refrigeration cycle,absorption heat pump,absorption heat transformer,and the absorption power cycle.According to current research,absorption cycles play a critical role in energy conservation and reducing carbon dioxide emissions.They can be applied to waste heat recovery,heating,drying,energy storage,seawater desalination,refrigeration,dehumidification,and power generation,leading to substantial economic benefits.The paper also outlines the primary challenges in the current application of the absorption cycle and discusses its future development direction.Ultimately,this paper serves as a reference for the application research of the absorption cycle and aims to maximize its potential in achieving global carbon neutrality.展开更多
This paper presents a P-Q coordination based highvoltage ride through(HVRT) control strategy for doubly fed induction generators(DFIGs) based on a combined Q-V control and P-V de-loading control. The active/reactive p...This paper presents a P-Q coordination based highvoltage ride through(HVRT) control strategy for doubly fed induction generators(DFIGs) based on a combined Q-V control and P-V de-loading control. The active/reactive power injection effect of DFIG on transient overvoltage is firstly analyzed and the reactive power capacity evaluation of DFIG considering its de-loading operation is then conducted. In the proposed strategy, the reactive power limit of DFIG can be flexibly extended during the transient process in coordination with its active power adjustment. As a result, the transient overvoltage caused by DC bipolar block can be effectively suppressed. Moreover, key outer loop parameters such as Q-V control coefficient and deloading coefficient can be determined based on the voltage level of point of common coupling(PCC) and the available power capacity of DFIG. Finally, case studies based on MATLAB/Simulink simulation are used to verify the effectiveness of the proposed control strategy.展开更多
文摘This paper deals with the investigation of the power absorption in helicon plasma excited through a half-helix antenna driven at 13.56 MHz. The simulations were carried out by means of a code,HELIC. They were carried out by taking into account different inhomogeneous radial density profiles and for a wide range of plasma densities, from 10^（11） cm^（-3） to 10^（13） cm^（-3）. The magnetic field was 200, 400, 600 and 1000 G. A three-parameter function was used for generating various density profiles with different volume gradients, edge gradients and density widths. The density profile had a large effect on the efficient Trivelpiece–Gould（TG） and helicon mode excitation and antenna coupling to the plasma. The fraction of power deposition via the TG mode was extremely dependent on the plasma density near the plasma boundary. Interestingly, the obtained efficient parallel helicon wavelength was close to the anticipated value for Gaussian radial density profile.Power deposition was considerably asymmetric when the n/B_0 ratio was more than a specific value for a determined density width. The longitudinal power absorption was symmetric at approximately n_0 =10^（11） cm^（-3）, irrespective of the magnetic field supposed. The asymmetry became more pronounced when the plasma density was 10^（12） cm^（-3）. The ratio of density width to the magnetic field was an important parameter in the power coupling. At high magnetic fields, the maximum of the power absorption was reached at higher plasma density widths. There was at least one combination of the plasma density, magnetic field and density width for which the RF power deposition at both side of the tube reached its maximum value.
基金Project(50976022) supported by the National Natural Science Foundation of ChinaProject(BY2011155) supported by Science and Technology Innovation and Transformation of Achievements of Special Fund of Jiangsu Province, China
文摘A simplified dual-pressure ammonia-water absorption power cycle(DPAPC-a) using low grade energy resources is presented and analyzed.This cycle uses turbine exhaust heat to distill the basic solution for desorption.The structure of the cycle is simple which comprises evaporator,turbine,regenerator(desorber),absorber,pump and throttle valves for both diluted solution and vapor.And it is of high efficiency,because the working medium has large temperature difference in evaporation and small temperature difference in absorptive condensation,which can match the sensible exothermal heat resource and the cooling water simultaneously.Orthogonal calculation was made to investigate the influence of the working concentration,the basic concentration and the circulation multiple on the cycle performance,with 85-110 ℃ heat resource and 20-32 ℃ cooling water.An optimum scheme was given in the condition of 110 ℃ sensitive heat resource and 20 ℃ cooling water,with the working concentration of 0.6,basic concentration of 0.385,and circulation multiple of 5.The thermal efficiency and the power recovery efficiency are 8.06 % and 6.66%,respectively.The power recovery efficiency of the DPAPC-a is 28.8% higher than that of the steam Rankine cycle(SRC) and 12.7% higher than that of ORC(R134a) under the optimized situation.
文摘A multi-body wave energy converter,consisting of three floats and modeled as a two body problem,is optimised to enhance its mean absorbed power using the Response Surface Optimisation Method.The optimisation focuses on two input parameters namely;the floats’diameters and the spacing,in various sea states and at different PTO dampings.A frequency domain analysis is performed for the WEC model scaled at 1∶50 in regular and irregular waves.Obtained results are validated against numerical and experimental data available in the literature.Validations show good agreement against the unmoored model’s added mass,radiation damping,response amplitude operator,mean absorbed power and,capture width ratio.The sea states selected for optimisation are represented by a JONSWAP wave spectrum with,a range of significant wave heights(0.04 to 0.06 m)and a range of peak periods(0.8 to 1.3 s).This corresponds to(2 to 3 m)significant wave heights and(5.6 to 9.2 s)peak periods in full scale.Results show that the optimised WEC model demonstrates good and consistent enhancement of its mean absorbed power and capture width ratio.
文摘Using an one-dimensional slab model, we have studied the electron energy distribution, the anomalous skin effect, and power absorption in the solenoidal-inductively-coupled argon discharge under low pressures (≤ 1.33 Pa). The electron energy distribution function and rf electromagnetic field in the plasma are determined self-consistently by the linearized Bolztmann equation incorporating with the Maxwell equations. The numerical results show that, at low pressures, the electron energy distribution function exhibits a non-Maxwellian distribution with a long high-energy tail. The anomalous skin effect is greatly enhanced under low pressures and the negative power absorption is also obtained.
基金Foundation of Beijing Jiaotong University(2005RC034)
文摘Presented is a theoretical study of double-clad Er-doped fiber power amplifier(EDFA). Two kinds of double clad fibers(DCF) with rectangular and "flower" inner clad shapes are studied, and these fibers have different coupling constants and propagation losses. We calculate the effective pump power absorption ratio along the fiber with different coupling constants from the first cladding to the doped core and with different propagation losses for the power in the inner cladding. Then the gains of the double clad Er-doped fiber amplifiers versus fiber lengths are calculated using the EDFA model based on propagation and rate equations of a homogeneous, two-level medium.
文摘Structure, improvements and experiment results of a vertical three-channel far- in- frared （FIR） hydrogen cyanide （HCN） laser interferometer, operated routinely in EAST to measure the electron density profile, are presented. Moreover, a five-channel deuterium cyanide （DCN） laser interferometer was developed successfully. Some key issues confronted in development, including the economization of working gas and the solution to atmospheric absorption, are resolved and described in detail.
文摘The study was conducted to determine the influence of gratering and fermentation parameters on the physicochemical quality of starch obtained from two cassava varieties in Sierra Leone (i.e., SLICASS 11 and SLICASS 6). Fresh cassava roots harvested from the Department of Agricultural Engineering were peeled, washed and grated before fermentation and starch extraction. Fermentation was carried out under separate aerobic and anaerobic conditions for a period of Seven days. Physicochemical analyses were conducted at the Postharvest Food and Bioprocess Engineering Laboratory of the Department of Agricultural and Bio-System Engineering, Njala University to determine the solubility, water absorption capacity and swelling power of starch extracts obtained from various experimental treatments. Fermentation method and duration had significant effects on the solubility, water absorption capacity (WAC) and swelling power (SP) of starch extracts. Maximum solubility and WAC were recorded on the fifth day, for both cassava varieties tested, with apparent significant difference resulting from the two gratering bands (i.e., with 1.5-inch nail hole and 4-inch nail hole sizes, respectively). While swelling power increased consistently with temperature for starch obtained from SLICASS-11 variety, an irregular pattern was observed for SLICASS-6 variety. A multiple correlation analysis proposes a significant and weak correlation between temperature, WAC (+0.150) and swelling power (+0.048). Also multiple correlation analyses suggest a significant correlation between fermentation period, the functional properties of starch extracts obtained from both fermentation methods and cassava varieties (i.e., solubility (−0.226), water absorption capacity (+0.301) and swelling power (+0.329)).
基金financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA0400000)the National Key R&D Program of China(Grant No.2023YFB4005404)+1 种基金the National Natural Science Foundation of China(Grant No.52241601)the R&D Program of Institute of New Energy Dongguan(Grant No.2025-ZDBS-01)。
文摘The absorption cycle is a promising technology for harnessing low-temperature heat,playing a crucial role in achieving the objectives of carbon peaking and carbon neutrality.As a significant element in distributed energy systems,the absorption cycle can utilize various types of low-grade heat to fulfill cooling,heating,and electrical energy demands.Therefore,it can be employed in diverse settings to unleash its substantial energy-saving potential.However,the widespread adoption of the absorption cycle is limited to specific scenarios.Hence,further efforts are needed to enhance its technological maturity,gain societal acceptance,and expand its application scope.Focusing on the utilization of different low-grade heat,this paper provides an overview of significant advancements in the application research of various absorption cycles,such as the absorption refrigeration cycle,absorption heat pump,absorption heat transformer,and the absorption power cycle.According to current research,absorption cycles play a critical role in energy conservation and reducing carbon dioxide emissions.They can be applied to waste heat recovery,heating,drying,energy storage,seawater desalination,refrigeration,dehumidification,and power generation,leading to substantial economic benefits.The paper also outlines the primary challenges in the current application of the absorption cycle and discusses its future development direction.Ultimately,this paper serves as a reference for the application research of the absorption cycle and aims to maximize its potential in achieving global carbon neutrality.
基金jointly supported by the National Natural Science Foundation of China (No.51677165,No.51837004)the National Key R&D Program of China (No.2017YFB0902000)。
文摘This paper presents a P-Q coordination based highvoltage ride through(HVRT) control strategy for doubly fed induction generators(DFIGs) based on a combined Q-V control and P-V de-loading control. The active/reactive power injection effect of DFIG on transient overvoltage is firstly analyzed and the reactive power capacity evaluation of DFIG considering its de-loading operation is then conducted. In the proposed strategy, the reactive power limit of DFIG can be flexibly extended during the transient process in coordination with its active power adjustment. As a result, the transient overvoltage caused by DC bipolar block can be effectively suppressed. Moreover, key outer loop parameters such as Q-V control coefficient and deloading coefficient can be determined based on the voltage level of point of common coupling(PCC) and the available power capacity of DFIG. Finally, case studies based on MATLAB/Simulink simulation are used to verify the effectiveness of the proposed control strategy.
