The thermal stress-induced deformation issue of receiver is crucial to the performance and reliability of a parabolic-trough(PT) concentrating solar power(CSP) system with the promising direct steam generation(DSG) te...The thermal stress-induced deformation issue of receiver is crucial to the performance and reliability of a parabolic-trough(PT) concentrating solar power(CSP) system with the promising direct steam generation(DSG) technology.The objective of the present study is to propose a new-type receiver with axially-hollow spiral deflector and optimize the geometric structure to solve the above issue.To this end,optical-flow-thermal multi-physics coupling models have been established for the preheating,boiling and superheating sections of a typical PT-DSG loop.The simulation results show that our proposed new-type receiver demonstrates outstanding comprehensive performance.It can minimize the circumferential temperature difference through the spiral deflector while lower the flow resistance cost through the axially hollow structure at the same time.As quantitatively evaluated by the temperature uniformity improvement(ε_(ΔT)) and the performance evaluation criteria(PEC),different designs are achieved based on different optimal schemes.When ε_(ΔT)is of primary importance,the optimal design with torsional ratio of 1 is achieved,with ε_(ΔT)=25.4%,25.7%,41.5% and PEC=0.486,0.878,0.596corresponding to preheating,boiling,superheating sections,respectively.When PEC is of primary importance,the optimal design with torsional ratio of 6-6.5 is achieved,with PEC=0.950,2.070,0.993 and ε_(ΔT)=18.2%,13.3 %,19.4% corresponding to preheating,boiling,superheating sections,respectively.展开更多
Based on the analyses of foraminifer and accelerator mass spectrometer radiocarbon dating in DGKS9603 core from mid-Okinawa Trough close to bottom, oscillation curve, which expressed the relation between the surface w...Based on the analyses of foraminifer and accelerator mass spectrometer radiocarbon dating in DGKS9603 core from mid-Okinawa Trough close to bottom, oscillation curve, which expressed the relation between the surface water temperature and the depth, has been obtained by using foraminifer analysis and calculation of FP-12E transfer function. The whole core indicated seven cold phases and eight warm phases. Obvious expression of low展开更多
Through silicon via （TSV）-TSV coupling is detrimental to the performance of three-dimensional （3D） integrated circuits （ICs） with the major negative effect of introducing coupling noise. In order to obtain an ac...Through silicon via （TSV）-TSV coupling is detrimental to the performance of three-dimensional （3D） integrated circuits （ICs） with the major negative effect of introducing coupling noise. In order to obtain an accurate estimation of the coupling level from TSV-TSV in the early design stage, this paper first proposes an impedance- level model of the coupling channel between TSVs based on a two-port network, and then derives the formula of the coupling coefficient to describe the TSV-TSV coupling effect. The accuracy of the formula is validated by comparing the results with 3D full-wave simulations. Furthermore, a design technique for optimizing the coupling between adjacent coupled signal TSVs is proposed. Through SPICE simulations, the proposed technique shows its feasibility to reduce the coupling noise for both a simple TSV-TSV circuit and a complicated circuit with more TSVs, and demonstrates its potential for designers in achieving the goal of improving the electrical pertbrmance of3D ICs.展开更多
In view of the fact that most college English teachers in China invest a great deal of time andeffort responding to students’ writing,but find students improve so little in their writing skills,I ventureto put forwar...In view of the fact that most college English teachers in China invest a great deal of time andeffort responding to students’ writing,but find students improve so little in their writing skills,I ventureto put forward an alternative way of teaching writing in the paper,that is,teaching writing throughsmall group conferencing.Compared with the traditional teaching methods,small group conferencing hasfollowing advantages:(1)Saving evaluation time;(2)Providing better feedback;(3)Helping studentscritique their writing,etc.Since many empirical studies and teaching practices demonstrate that smallgroup conferencing is an effective and efficient way of teaching writing,we have good reason to believethat it will become widespread in the college English teaching in China.展开更多
Tunnel though coal seam is one of the most difficult tunnels since its risk of coal and gas outburst and the complex geological conditions.According to the directional cutting of water jet and the characteristic of th...Tunnel though coal seam is one of the most difficult tunnels since its risk of coal and gas outburst and the complex geological conditions.According to the directional cutting of water jet and the characteristic of the coal seam and rock mass,this paper presents a new method of tunnelling though coal seam assisted by water jet slotting,which can be divided into improving permeability of coal seam and directional cracking in the rock mass.The mechanism of improving permeability of coal seam was stated,and the crack criterion of rock during blasting was established based on fracture theory.Then,the evolution law of pressure wave and the crack propagation were simulated by FEM software ANSYS/LS-DYNA,the results show that the shape of the crush zone formed by stress wave is different between the normal borehole blasting and the slotted borehole blasting,and the tension is the main factor which let crack propagation.What is more,for normal borehole blasting,the tension concentration occurred along the direction of 45 degrees and let crack expand,while for slotted borehole blasting the tension concentration occurred along the direction of 0 degrees and 90 degrees,and the maximum tension along the direction of 0 degrees is larger than the maximum tension along the direction of 90 degrees,and the main crack expand along the direction of 0 degrees,which prove that the existence of the slot play a good role of orientation for directional cracking.展开更多
Poverty alleviation through employment promotion is to promote the poor households to get rid of poverty through promoting employment to increase income. It is the most effective and direct way out of poverty. Dongchu...Poverty alleviation through employment promotion is to promote the poor households to get rid of poverty through promoting employment to increase income. It is the most effective and direct way out of poverty. Dongchuan District, located in the alpine valley area of northeastern Yunnan, is a typical extreme poverty-stricken county in China. Under its jurisdiction, Awang Town is a mountainous township with a wide area of poverty and an extreme poverty. The incidence of poverty in 2015 reached 35.39%. In recent years, through the implementation of various policies to combat poverty, combined with the advantages as a traditional "hometown of migrant labor", focusing on employment- promoting poverty alleviation work, Awang Town has made certain achievements in poverty alleviation work. By the end of 2018, the poverty rate in the town fell to 0.57%, marking a major victory in the town s fight against poverty. Through field investigations, this article summarizes the main practices of Awang Town to carry out employment-promoting targeted poverty alleviation, analyzes the poverty alleviation achievements and successful experience of the town s employment-promoting targeted poverty alleviation work and discusses the promotion and application of this model so as to provide reference Yunnan Province and other poverty-stricken areas to carry out employment-promoting poverty alleviation.展开更多
本文探讨 even if与 even though 在外延意义、内涵意义和社会意义方面的语义差:even if表示“让步”与“条件”两个基本意义,even though 仅表示“让步”的基本意义;even if 分句无标记地表现为“不知是否是事实”和“非事实性”的涵义...本文探讨 even if与 even though 在外延意义、内涵意义和社会意义方面的语义差:even if表示“让步”与“条件”两个基本意义,even though 仅表示“让步”的基本意义;even if 分句无标记地表现为“不知是否是事实”和“非事实性”的涵义,有标记地表现为事实性的涵义;even though 分句无标记地表现为“事实性”与“拟事实性”的涵义;英国英语中多用even if,美国英语中多用 even though。文章认为,它们的语义差是无标记的,它们的同义是有标记的。展开更多
基金financially supported by the National Natural Science Foundation of China (52176202)the Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory (41200101)。
文摘The thermal stress-induced deformation issue of receiver is crucial to the performance and reliability of a parabolic-trough(PT) concentrating solar power(CSP) system with the promising direct steam generation(DSG) technology.The objective of the present study is to propose a new-type receiver with axially-hollow spiral deflector and optimize the geometric structure to solve the above issue.To this end,optical-flow-thermal multi-physics coupling models have been established for the preheating,boiling and superheating sections of a typical PT-DSG loop.The simulation results show that our proposed new-type receiver demonstrates outstanding comprehensive performance.It can minimize the circumferential temperature difference through the spiral deflector while lower the flow resistance cost through the axially hollow structure at the same time.As quantitatively evaluated by the temperature uniformity improvement(ε_(ΔT)) and the performance evaluation criteria(PEC),different designs are achieved based on different optimal schemes.When ε_(ΔT)is of primary importance,the optimal design with torsional ratio of 1 is achieved,with ε_(ΔT)=25.4%,25.7%,41.5% and PEC=0.486,0.878,0.596corresponding to preheating,boiling,superheating sections,respectively.When PEC is of primary importance,the optimal design with torsional ratio of 6-6.5 is achieved,with PEC=0.950,2.070,0.993 and ε_(ΔT)=18.2%,13.3 %,19.4% corresponding to preheating,boiling,superheating sections,respectively.
文摘Based on the analyses of foraminifer and accelerator mass spectrometer radiocarbon dating in DGKS9603 core from mid-Okinawa Trough close to bottom, oscillation curve, which expressed the relation between the surface water temperature and the depth, has been obtained by using foraminifer analysis and calculation of FP-12E transfer function. The whole core indicated seven cold phases and eight warm phases. Obvious expression of low
基金supported by the National Natural Science Foundation of China(No.61334003)
文摘Through silicon via （TSV）-TSV coupling is detrimental to the performance of three-dimensional （3D） integrated circuits （ICs） with the major negative effect of introducing coupling noise. In order to obtain an accurate estimation of the coupling level from TSV-TSV in the early design stage, this paper first proposes an impedance- level model of the coupling channel between TSVs based on a two-port network, and then derives the formula of the coupling coefficient to describe the TSV-TSV coupling effect. The accuracy of the formula is validated by comparing the results with 3D full-wave simulations. Furthermore, a design technique for optimizing the coupling between adjacent coupled signal TSVs is proposed. Through SPICE simulations, the proposed technique shows its feasibility to reduce the coupling noise for both a simple TSV-TSV circuit and a complicated circuit with more TSVs, and demonstrates its potential for designers in achieving the goal of improving the electrical pertbrmance of3D ICs.
文摘In view of the fact that most college English teachers in China invest a great deal of time andeffort responding to students’ writing,but find students improve so little in their writing skills,I ventureto put forward an alternative way of teaching writing in the paper,that is,teaching writing throughsmall group conferencing.Compared with the traditional teaching methods,small group conferencing hasfollowing advantages:(1)Saving evaluation time;(2)Providing better feedback;(3)Helping studentscritique their writing,etc.Since many empirical studies and teaching practices demonstrate that smallgroup conferencing is an effective and efficient way of teaching writing,we have good reason to believethat it will become widespread in the college English teaching in China.
基金Financial support for this work,provided by the National Basic Research of China(2014CB239203)the National Natural Science Foundation of China(51474158)+1 种基金also supported by Program for New Century Excellent Talents in University(NCET-12-0424)The authors would like to thank the State Key Laboratory of Coal Mine Disaster Dynamics and Control and Hubei Key Laboratory of Waterjet Theory&New Technology.
文摘Tunnel though coal seam is one of the most difficult tunnels since its risk of coal and gas outburst and the complex geological conditions.According to the directional cutting of water jet and the characteristic of the coal seam and rock mass,this paper presents a new method of tunnelling though coal seam assisted by water jet slotting,which can be divided into improving permeability of coal seam and directional cracking in the rock mass.The mechanism of improving permeability of coal seam was stated,and the crack criterion of rock during blasting was established based on fracture theory.Then,the evolution law of pressure wave and the crack propagation were simulated by FEM software ANSYS/LS-DYNA,the results show that the shape of the crush zone formed by stress wave is different between the normal borehole blasting and the slotted borehole blasting,and the tension is the main factor which let crack propagation.What is more,for normal borehole blasting,the tension concentration occurred along the direction of 45 degrees and let crack expand,while for slotted borehole blasting the tension concentration occurred along the direction of 0 degrees and 90 degrees,and the maximum tension along the direction of 0 degrees is larger than the maximum tension along the direction of 90 degrees,and the main crack expand along the direction of 0 degrees,which prove that the existence of the slot play a good role of orientation for directional cracking.
基金Supported by Construction Project of Party Branch Secretary’s Studio of "Double Leader" Teachers in Colleges and Universities of the Ministry of Education of ChinaProject of Party Construction Research of Yunnan University of Finance and Economics
文摘Poverty alleviation through employment promotion is to promote the poor households to get rid of poverty through promoting employment to increase income. It is the most effective and direct way out of poverty. Dongchuan District, located in the alpine valley area of northeastern Yunnan, is a typical extreme poverty-stricken county in China. Under its jurisdiction, Awang Town is a mountainous township with a wide area of poverty and an extreme poverty. The incidence of poverty in 2015 reached 35.39%. In recent years, through the implementation of various policies to combat poverty, combined with the advantages as a traditional "hometown of migrant labor", focusing on employment- promoting poverty alleviation work, Awang Town has made certain achievements in poverty alleviation work. By the end of 2018, the poverty rate in the town fell to 0.57%, marking a major victory in the town s fight against poverty. Through field investigations, this article summarizes the main practices of Awang Town to carry out employment-promoting targeted poverty alleviation, analyzes the poverty alleviation achievements and successful experience of the town s employment-promoting targeted poverty alleviation work and discusses the promotion and application of this model so as to provide reference Yunnan Province and other poverty-stricken areas to carry out employment-promoting poverty alleviation.
文摘本文探讨 even if与 even though 在外延意义、内涵意义和社会意义方面的语义差:even if表示“让步”与“条件”两个基本意义,even though 仅表示“让步”的基本意义;even if 分句无标记地表现为“不知是否是事实”和“非事实性”的涵义,有标记地表现为事实性的涵义;even though 分句无标记地表现为“事实性”与“拟事实性”的涵义;英国英语中多用even if,美国英语中多用 even though。文章认为,它们的语义差是无标记的,它们的同义是有标记的。
