In this paper, a new design method for high performance octave-band stripline circulator is given. The optimum design program is given by a construction with double-Y junction aided by a section of quarter-wavelength ...In this paper, a new design method for high performance octave-band stripline circulator is given. The optimum design program is given by a construction with double-Y junction aided by a section of quarter-wavelength impedance transformer. All the calculation is simpler than that given by Y. S. Wu, et al[1-7]. Typical performances of the 2-4GHz Y-junction stripline circulator are insertion loss 0.35dB (max), isolation 21dB (min), VSWR 1.25 (max). An octave low-loss and high isolation performance is demonstrated without the need of repeated design cycles.展开更多
基于HYCOM(Hybrid Coordinate Oceanic Circulation Model),以OFES(OGCM for the Earth Simulator)资料为参考,分析了KPP、MY2.5、KT三种不同混合方案对北太平洋西边界流系的模拟结果的影响。结果表明:三种不同混合方案模拟的上层海洋...基于HYCOM(Hybrid Coordinate Oceanic Circulation Model),以OFES(OGCM for the Earth Simulator)资料为参考,分析了KPP、MY2.5、KT三种不同混合方案对北太平洋西边界流系的模拟结果的影响。结果表明:三种不同混合方案模拟的上层海洋平均流场与OFES资料相似,但在流向和流幅上略有差异,其中KPP方案模拟的流速与OFES资料最为接近,MY2.5方案次之,KT方案与其差别最大。通过代表性断面上流速的对比分析,对模式就北赤道流、棉兰老流、棉兰老潜流、黑潮的模拟效果进行比较,KPP方案模拟的效果同前人的观测和研究最为接近。分析了北赤道流,棉兰老流,棉兰老潜流,黑潮的流量的季节变化特征,其中KPP方案与OFES资料计算的棉兰老流和棉兰老潜流的季节变化特征与前人描述比较一致,表现为春强秋弱。KPP方案和OFES资料的计算结果表明,北赤道流和棉兰老流大致上是同向变化的,而在冬季棉兰老流同黑潮的变化基本上是一致的。展开更多
In order to investigate the effect of sampling frequency and time on pressure fluctuations, the three-dimensional unsteady numerical simulations were conducted in a circulating water pump. Through comparison of turbul...In order to investigate the effect of sampling frequency and time on pressure fluctuations, the three-dimensional unsteady numerical simulations were conducted in a circulating water pump. Through comparison of turbulence models with hydraulic performance experiment, SST k-co model was confirmed to study the rational determination of sampling frequency and time better. The Fast Fourier Transform （FFT） technology was then adopted to process those fluctuating pressure signals obtained. On these bases, the characteristics of pressure fluctuations acting on the tongue were discussed. It is found that aliasing errors decrease at higher sampling frequency of 17 640 Hz, but not at a lower sampling frequency of 1 764 Hz. Correspondingly, an output frequency range ten-times wider is obtained at 17 640 Hz. Compared with 8R, when the sampling time is shorter, the amplitudes may be overvalued, and the frequencies and amplitudes of low-frequency fluctuations can not be well predicted. The frequencies at the tongue are in good agreement with the values calculated by formula and the frequency compositions less than the blade passing frequency are accurately predicted.展开更多
A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agen...A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agent and different Si O2/Al2O3 molar ratios of 3.1, 3.4, and 3.8. The mechanical, thermo-physical properties and microstructure of the foam geopolymers before and after exposure to elevated temperature of 800, 1000, and 1200 ℃ were investigated. The specimen with Si O2/Al2O3 molar ratio of 3.8 exhibits the highest compressive strength, better microstructure and dimension stability before and after firing. Carnegeite, nepheline, and zeolite crystalline phases appearing after exposure may contribute to the good post-exposure strength. Low weight foam geopolymer using CFA can increase strength and maintain higher stability as high as 1000 ℃.展开更多
Abstract:The aim of this research is to design and operate a 10 kW hot chemical-looping gasification(CLG)unit using Fe2O3/Al2O3as an oxygen carrier and saw dust as a fuel.The effect of the operation temperature on gas...Abstract:The aim of this research is to design and operate a 10 kW hot chemical-looping gasification(CLG)unit using Fe2O3/Al2O3as an oxygen carrier and saw dust as a fuel.The effect of the operation temperature on gas composition in the air reactor and the fuel reactor,and the carbon conversion of biomass to CO2and CO in the fuel reactor have been experimentally studied.A total60 h run has been obtained with the same batch of oxygen carrier of iron oxide supported with alumina.The results show that CO and H2concentrations are increased with increasing temperature in the fuel reactor.It is also found that with increasing fuel reactor temperature,both the amount of residual char in the fuel reactor and CO2concentration of the exit gas from the air reactor are degreased.Carbon conversion rate and gasification efficiency are increased by increasing temperature and H2production at 870℃reaches the highest rate.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and BET-surface area tests have been used to characterize fresh and reacted oxygen carrier particles.The results display that the oxygen carrier activity is not declined and the specific surface area of the oxygen carrier particles is not decreased significantly.展开更多
Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing me...Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber. The fluid mesh distortion was controlled by the CEL language, and the fluid struc^tre interaction mathematical model was established. The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique. The local sensitive computational area was meshed by prismatic grid, which could reduce the negative volume problem during the simulation. The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads. Flow characteristic and dynamics characteristic were obtained. The pressure distribution and the displacement of circulation value were obtained, and the acceleration curve of circulation valve was simulated and analyzed. The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber, which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.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
In order to optimize plastic viscosity of 18 mPa·s circulating micro-bubble drilling fluid formula,orthogonal and uniform experimental design methods were applied,and the plastic viscosities of 36 and 24 groups o...In order to optimize plastic viscosity of 18 mPa·s circulating micro-bubble drilling fluid formula,orthogonal and uniform experimental design methods were applied,and the plastic viscosities of 36 and 24 groups of agent were tested,respectively.It is found that these two experimental design methods show drawbacks,that is,the amount of agent is difficult to determine,and the results are not fully optimized.Therefore,multiple regression experimental method was used to design experimental formula.By randomly selecting arbitrary agent with the amount within the recommended range,17 groups of drilling fluid formula were designed,and the plastic viscosity of each experiment formula was measured.Set plastic viscosity as the objective function,through multiple regressions,then quadratic regression model is obtained,whose correlation coefficient meets the requirement.Set target values of plastic viscosity to be 18,20 and 22 mPa·s,respectively,with the trial method,5 drilling fluid formulas are obtained with accuracy of 0.000 3,0.000 1 and 0.000 3.Arbitrarily select target value of each of the two groups under the formula for experimental verification of drilling fluid,then the measurement errors between theoretical and tested plastic viscosity are less than 5%,confirming that regression model can be applied to optimizing the circulating of plastic-foam drilling fluid viscosity.In accordance with the precision of different formulations of drilling fluid for other constraints,the methods result in the optimization of the circulating micro-bubble drilling fluid parameters.展开更多
A construction method based on the p-plane to design high-girth quasi-cyclic low-density parity-check （QC-LDPC） codes is proposed. Firstly the good points in every line of the p-plane can be ascertained through filt...A construction method based on the p-plane to design high-girth quasi-cyclic low-density parity-check （QC-LDPC） codes is proposed. Firstly the good points in every line of the p-plane can be ascertained through filtering the bad points, because the designed parity-check matrixes using these points have the short cycles in Tanner graph of codes. Then one of the best points from the residual good points of every line in the p-plane will be found, respectively. The optimal point is also singled out according to the bit error rate （BER） performance of the QC-LDPC codes at last. Explicit necessary and sufficient conditions for the QC-LDPC codes to have no short cycles are presented which are in favor of removing the bad points in the p-plane. Since preventing the short cycles also prevents the small stopping sets, the proposed construction method also leads to QC-LDPC codes with a higher stopping distance.展开更多
The liquid ion exchange method, solid salt melt method and dry-wet circulation method were used to prepare natural porous antimicrobial materials with natural minerals, such as zeolite, spilite, palygorskite and montm...The liquid ion exchange method, solid salt melt method and dry-wet circulation method were used to prepare natural porous antimicrobial materials with natural minerals, such as zeolite, spilite, palygorskite and montmorillonite, respectively. Atomic absorption spectrum and X-ray diffraction analysis were carried out to investigate the effects of Ag^＋ , Cu^2＋ and Zn^2＋ on antimicrobial abilities of natural porous minerals, and the effect of preparation method on ion exchange capacity of antimicrobial material, respectively. The results show that for the ion exchange capacity, clay mineral is higher than fibrous mineral, i.e. both zeolite and montmorillonite are higher; the antimicrobial ability of material with Ag^＋ is the bests the exchange capacities of materials with Cu^2＋ or Zn^2＋ are all higher, but the antimicrobial ability of Cu^2＋ is better than that of Zn^2＋ .展开更多
Many geotechnical structures,such as the subgrade of high-speed railway,are extremely sensitive to micro deformations.As one of the most commonly used indexes in China to evaluate the potential swelling level of expan...Many geotechnical structures,such as the subgrade of high-speed railway,are extremely sensitive to micro deformations.As one of the most commonly used indexes in China to evaluate the potential swelling level of expansive soils,the effectiveness and accuracy of free swelling ratio should be highly required.However,due to the deficiency of geotechnical test regulations for the free swelling ratio test,non-negligible variation difference is often observed among the test results of the same type of soil samples.Thus,a series of laboratory tests are conducted to figure out the influences of soil particle size,initial soil temperature,and wet-dry circulation on the free swelling ratio of expansive soils.The results show that the initial soil temperature exerts an obvious influence on free swelling ratio and a relative weak influence on soil mass of expansive soil with the micro soil particle size(d<0.075 mm),and the correlation becomes unclear when soil particle size is within the range of 0.075 mm≤d<0.500 mm.A larger particle size of expansive soils induces a larger free swelling ratio and soil mass in the soil measuring cup regardless of initial soil temperature.However,the enlarging amplitude decreases as the particle size of expansive soils increases.There is a progressive enlargement of free swelling ratio at the first two wet-dry cycles and then it attenuates gradually when the number of wetdry cycles further increases.展开更多
The start-up of external circulationadded internal circulation(IC) reactor was finished in 26 d, 32 d fewer than that of IC reactor. To evaluate the influence of the added external circulation on the development of gr...The start-up of external circulationadded internal circulation(IC) reactor was finished in 26 d, 32 d fewer than that of IC reactor. To evaluate the influence of the added external circulation on the development of granular sludge, the characteristics of the granular sludge taken from the two tested laboratory-scale reactors during start-up were studied. The results show that the added external circulation can enhance biomass granulation, accelerate granule development and improve sludge characteristics. At the end of start-up, the granular size of sludge in external circulation-added IC reactor greatly increases with a size distribution much better than that of sludge in IC reactor. The granular sludge originated from external circulationadded IC reactor contains more extracellular polymers and has a greater settling velocity than that from IC reactor. Methanogenic activity of the granular sludge from the external circulationadded IC reactor started 26 d ago reaches 358.23mL·g -1 ·d -1 , 1.66 and 1.20 times as great as that of the sludge from the IC reactor started 26 d and 58 d ago respectively.展开更多
The existing constructions of quasi-cyclic low-density parity-check （QC-LDPC） codes do not consider the problems of small stopping sets and small girth together in the Tanner graph, while their existences will lead ...The existing constructions of quasi-cyclic low-density parity-check （QC-LDPC） codes do not consider the problems of small stopping sets and small girth together in the Tanner graph, while their existences will lead to the bit error rate （BER） performance of QC-LDPC codes being much poorer than that of randomly constructed LDPC codes even decoding failure. To solve the problem, some theorems of the specific chosen parity-check matrix of QC-LDPC codes without small stopping sets and small girth are proposed. A novel construction for QC-LDPC codes with long block lengths is presented by multiplying mmin or the multiple of mmin, which is the minimum order of the identity matrix for the chosen parity-check matrix. The simulation results show that the specific chosen parity-check matrix of QC-LDPC codes can effectively avoid specified stopping sets and small girth and exhibit excellent BER performance than random LDPC codes with the same longer codes length.展开更多
文摘In this paper, a new design method for high performance octave-band stripline circulator is given. The optimum design program is given by a construction with double-Y junction aided by a section of quarter-wavelength impedance transformer. All the calculation is simpler than that given by Y. S. Wu, et al[1-7]. Typical performances of the 2-4GHz Y-junction stripline circulator are insertion loss 0.35dB (max), isolation 21dB (min), VSWR 1.25 (max). An octave low-loss and high isolation performance is demonstrated without the need of repeated design cycles.
文摘基于HYCOM(Hybrid Coordinate Oceanic Circulation Model),以OFES(OGCM for the Earth Simulator)资料为参考,分析了KPP、MY2.5、KT三种不同混合方案对北太平洋西边界流系的模拟结果的影响。结果表明:三种不同混合方案模拟的上层海洋平均流场与OFES资料相似,但在流向和流幅上略有差异,其中KPP方案模拟的流速与OFES资料最为接近,MY2.5方案次之,KT方案与其差别最大。通过代表性断面上流速的对比分析,对模式就北赤道流、棉兰老流、棉兰老潜流、黑潮的模拟效果进行比较,KPP方案模拟的效果同前人的观测和研究最为接近。分析了北赤道流,棉兰老流,棉兰老潜流,黑潮的流量的季节变化特征,其中KPP方案与OFES资料计算的棉兰老流和棉兰老潜流的季节变化特征与前人描述比较一致,表现为春强秋弱。KPP方案和OFES资料的计算结果表明,北赤道流和棉兰老流大致上是同向变化的,而在冬季棉兰老流同黑潮的变化基本上是一致的。
基金Project supported by the Priority Academic Development Program of Jiangsu Higher Education Institutions, ChinaProject(CXZZ12_0680) supported by Postgraduate Innovation Foundation of Jiangsu Province, ChinaProject(12JDG082) supported by the Advanced Talent Foundation of Jiangsu University, China
文摘In order to investigate the effect of sampling frequency and time on pressure fluctuations, the three-dimensional unsteady numerical simulations were conducted in a circulating water pump. Through comparison of turbulence models with hydraulic performance experiment, SST k-co model was confirmed to study the rational determination of sampling frequency and time better. The Fast Fourier Transform （FFT） technology was then adopted to process those fluctuating pressure signals obtained. On these bases, the characteristics of pressure fluctuations acting on the tongue were discussed. It is found that aliasing errors decrease at higher sampling frequency of 17 640 Hz, but not at a lower sampling frequency of 1 764 Hz. Correspondingly, an output frequency range ten-times wider is obtained at 17 640 Hz. Compared with 8R, when the sampling time is shorter, the amplitudes may be overvalued, and the frequencies and amplitudes of low-frequency fluctuations can not be well predicted. The frequencies at the tongue are in good agreement with the values calculated by formula and the frequency compositions less than the blade passing frequency are accurately predicted.
基金Project(20120023110011) supported by Doctoral Program of Higher Education of ChinaProjects(2009KH09,2009QH02) supported by the Fundamental Research Funds for the Central Universities of China
文摘A comparative study of the influence of elevated temperature on foam geopolymer using circulating fluidized bed combustion fly ash（CFA） was reported. Foam geopoymers were prepared with different amounts of foam agent and different Si O2/Al2O3 molar ratios of 3.1, 3.4, and 3.8. The mechanical, thermo-physical properties and microstructure of the foam geopolymers before and after exposure to elevated temperature of 800, 1000, and 1200 ℃ were investigated. The specimen with Si O2/Al2O3 molar ratio of 3.8 exhibits the highest compressive strength, better microstructure and dimension stability before and after firing. Carnegeite, nepheline, and zeolite crystalline phases appearing after exposure may contribute to the good post-exposure strength. Low weight foam geopolymer using CFA can increase strength and maintain higher stability as high as 1000 ℃.
基金Supported by the National Natural Science Foundation of China(51076154)National Key Technology Research&Development Program of 12 th Five-year of China(2011BAD15B05)
文摘Abstract:The aim of this research is to design and operate a 10 kW hot chemical-looping gasification(CLG)unit using Fe2O3/Al2O3as an oxygen carrier and saw dust as a fuel.The effect of the operation temperature on gas composition in the air reactor and the fuel reactor,and the carbon conversion of biomass to CO2and CO in the fuel reactor have been experimentally studied.A total60 h run has been obtained with the same batch of oxygen carrier of iron oxide supported with alumina.The results show that CO and H2concentrations are increased with increasing temperature in the fuel reactor.It is also found that with increasing fuel reactor temperature,both the amount of residual char in the fuel reactor and CO2concentration of the exit gas from the air reactor are degreased.Carbon conversion rate and gasification efficiency are increased by increasing temperature and H2production at 870℃reaches the highest rate.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and BET-surface area tests have been used to characterize fresh and reacted oxygen carrier particles.The results display that the oxygen carrier activity is not declined and the specific surface area of the oxygen carrier particles is not decreased significantly.
基金Project(51275542) supported by the National Natural Science Foundation of Chinaproject(CDJXS12110010) supported by the Fundamental Research Funds for the Central Universities of China
文摘Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber. The fluid mesh distortion was controlled by the CEL language, and the fluid struc^tre interaction mathematical model was established. The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique. The local sensitive computational area was meshed by prismatic grid, which could reduce the negative volume problem during the simulation. The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads. Flow characteristic and dynamics characteristic were obtained. The pressure distribution and the displacement of circulation value were obtained, and the acceleration curve of circulation valve was simulated and analyzed. The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber, which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.
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.
基金Project(50304010) supported by the National Natural Science Foundation of China
文摘In order to optimize plastic viscosity of 18 mPa·s circulating micro-bubble drilling fluid formula,orthogonal and uniform experimental design methods were applied,and the plastic viscosities of 36 and 24 groups of agent were tested,respectively.It is found that these two experimental design methods show drawbacks,that is,the amount of agent is difficult to determine,and the results are not fully optimized.Therefore,multiple regression experimental method was used to design experimental formula.By randomly selecting arbitrary agent with the amount within the recommended range,17 groups of drilling fluid formula were designed,and the plastic viscosity of each experiment formula was measured.Set plastic viscosity as the objective function,through multiple regressions,then quadratic regression model is obtained,whose correlation coefficient meets the requirement.Set target values of plastic viscosity to be 18,20 and 22 mPa·s,respectively,with the trial method,5 drilling fluid formulas are obtained with accuracy of 0.000 3,0.000 1 and 0.000 3.Arbitrarily select target value of each of the two groups under the formula for experimental verification of drilling fluid,then the measurement errors between theoretical and tested plastic viscosity are less than 5%,confirming that regression model can be applied to optimizing the circulating of plastic-foam drilling fluid viscosity.In accordance with the precision of different formulations of drilling fluid for other constraints,the methods result in the optimization of the circulating micro-bubble drilling fluid parameters.
基金supported by the National Natural Science Foundation of China (60572093)Specialized Research Fund for the Doctoral Program of Higher Education (20050004016)
文摘A construction method based on the p-plane to design high-girth quasi-cyclic low-density parity-check （QC-LDPC） codes is proposed. Firstly the good points in every line of the p-plane can be ascertained through filtering the bad points, because the designed parity-check matrixes using these points have the short cycles in Tanner graph of codes. Then one of the best points from the residual good points of every line in the p-plane will be found, respectively. The optimal point is also singled out according to the bit error rate （BER） performance of the QC-LDPC codes at last. Explicit necessary and sufficient conditions for the QC-LDPC codes to have no short cycles are presented which are in favor of removing the bad points in the p-plane. Since preventing the short cycles also prevents the small stopping sets, the proposed construction method also leads to QC-LDPC codes with a higher stopping distance.
文摘The liquid ion exchange method, solid salt melt method and dry-wet circulation method were used to prepare natural porous antimicrobial materials with natural minerals, such as zeolite, spilite, palygorskite and montmorillonite, respectively. Atomic absorption spectrum and X-ray diffraction analysis were carried out to investigate the effects of Ag^＋ , Cu^2＋ and Zn^2＋ on antimicrobial abilities of natural porous minerals, and the effect of preparation method on ion exchange capacity of antimicrobial material, respectively. The results show that for the ion exchange capacity, clay mineral is higher than fibrous mineral, i.e. both zeolite and montmorillonite are higher; the antimicrobial ability of material with Ag^＋ is the bests the exchange capacities of materials with Cu^2＋ or Zn^2＋ are all higher, but the antimicrobial ability of Cu^2＋ is better than that of Zn^2＋ .
基金Project(2016M591957) supported by the China Postdoctoral Science FoundationProjects(51878667,51678571)supported by the National Natural Science Foundation of ChinaProject(2017XKQY050) supported by the Fundamental Research Funds for the Central Universities,China。
文摘Many geotechnical structures,such as the subgrade of high-speed railway,are extremely sensitive to micro deformations.As one of the most commonly used indexes in China to evaluate the potential swelling level of expansive soils,the effectiveness and accuracy of free swelling ratio should be highly required.However,due to the deficiency of geotechnical test regulations for the free swelling ratio test,non-negligible variation difference is often observed among the test results of the same type of soil samples.Thus,a series of laboratory tests are conducted to figure out the influences of soil particle size,initial soil temperature,and wet-dry circulation on the free swelling ratio of expansive soils.The results show that the initial soil temperature exerts an obvious influence on free swelling ratio and a relative weak influence on soil mass of expansive soil with the micro soil particle size(d<0.075 mm),and the correlation becomes unclear when soil particle size is within the range of 0.075 mm≤d<0.500 mm.A larger particle size of expansive soils induces a larger free swelling ratio and soil mass in the soil measuring cup regardless of initial soil temperature.However,the enlarging amplitude decreases as the particle size of expansive soils increases.There is a progressive enlargement of free swelling ratio at the first two wet-dry cycles and then it attenuates gradually when the number of wetdry cycles further increases.
文摘The start-up of external circulationadded internal circulation(IC) reactor was finished in 26 d, 32 d fewer than that of IC reactor. To evaluate the influence of the added external circulation on the development of granular sludge, the characteristics of the granular sludge taken from the two tested laboratory-scale reactors during start-up were studied. The results show that the added external circulation can enhance biomass granulation, accelerate granule development and improve sludge characteristics. At the end of start-up, the granular size of sludge in external circulation-added IC reactor greatly increases with a size distribution much better than that of sludge in IC reactor. The granular sludge originated from external circulationadded IC reactor contains more extracellular polymers and has a greater settling velocity than that from IC reactor. Methanogenic activity of the granular sludge from the external circulationadded IC reactor started 26 d ago reaches 358.23mL·g -1 ·d -1 , 1.66 and 1.20 times as great as that of the sludge from the IC reactor started 26 d and 58 d ago respectively.
基金supported by the National Natural Science Foundation of China (60572093)Specialized Research Fund for the Doctoral Program of Higher Education (20050004016)
文摘The existing constructions of quasi-cyclic low-density parity-check （QC-LDPC） codes do not consider the problems of small stopping sets and small girth together in the Tanner graph, while their existences will lead to the bit error rate （BER） performance of QC-LDPC codes being much poorer than that of randomly constructed LDPC codes even decoding failure. To solve the problem, some theorems of the specific chosen parity-check matrix of QC-LDPC codes without small stopping sets and small girth are proposed. A novel construction for QC-LDPC codes with long block lengths is presented by multiplying mmin or the multiple of mmin, which is the minimum order of the identity matrix for the chosen parity-check matrix. The simulation results show that the specific chosen parity-check matrix of QC-LDPC codes can effectively avoid specified stopping sets and small girth and exhibit excellent BER performance than random LDPC codes with the same longer codes length.
