From the situations about the incomes and life quality of the urban and rural residents,the thesis briefly introduces the status quo of the urban-rural income gap and explores the impact of the income gap on social ec...From the situations about the incomes and life quality of the urban and rural residents,the thesis briefly introduces the status quo of the urban-rural income gap and explores the impact of the income gap on social economy:firstly,it hampers economic development;secondly,it is detrimental to the social development.Then the thesis analyzes the role of a sound social security in narrowing urban-rural income gap:at first,it broadens the institutional environment of improving the agricultural efficiency;secondly,it eliminates the uncertainties influencing the farmers' income;thirdly,it improves the farmers' capacity to increase income;at last,it enhances the farmers' consciousness of wealth.Next the thesis inquires into the problems existing in the system of rural social security:the first problem is more obviously fragmented system;the second is inadequate security projects and narrower coverage;the third is an obvious lack of equality in urban and rural security;the fourth is even less sound management system;the last is the lagging of legislation.Afterwards the thesis proposes the countermeasures and suggestions to improve the system of rural social security and narrow urban-rural income gap:firstly,to integrate the social security system in rural areas;secondly,to perfect security projects and enhance the security system;thirdly,to integrate the administrative management of social security;at last,to enforce the legal system.展开更多
By using the data concerning China's urban-rural residents' income gap from 1978 to 2010,this paper mainly researches the application of several kinds of models in predicting China's urban-rural residents&...By using the data concerning China's urban-rural residents' income gap from 1978 to 2010,this paper mainly researches the application of several kinds of models in predicting China's urban-rural residents' income gap.By conducting empirical analysis,we establish ARIMA prediction model,grey prediction model and quadratic-polynomial prediction model and conduct accuracy comparison.The results show that quadratic-polynomial prediction model has excellent fitting effect.By using quadratic-polynomial prediction model,this paper conducts prediction on trend of China's urban-rural residents' income gap from 2011 to 2013,and the prediction value of income gap of urban-rural residents in China from 2011 to 2013 is 14 173.20,15 212.92 and 16 289.67 yuan respectively.Finally,on the basis of analysis,corresponding countermeasures are put forward,in order to provide scientific basis for energy planning and policy formulation:first,strengthen government's function of public service,coordinate resources,and strive to provide an equal opportunity of development for social members,so as to promote people's welfare and promote social equality;second,breach industrial monopoly and bridge income gap between employees in monopoly industry and general industry;last but not the least,support,encourage and call for government to establish social relief fund,adjust residents' income distribution from the non-governmental perspective,and endeavor to promote the income level of low-income class.展开更多
The urban-rural income gap is widening,which has become a bottleneck restricting China's economic and social development.It is the current outstanding problems in the harmonious development of the society.Community S...The urban-rural income gap is widening,which has become a bottleneck restricting China's economic and social development.It is the current outstanding problems in the harmonious development of the society.Community Supported Agriculture(CSA) is one of the most important forms of sustainable agriculture and it has received the attention in recent years.This paper first introduces the rise and development of CSA in China,and discuss the impact of CSA on urban-rural income gap in China preliminarily in order to provide ideas for improving the farmers' income and narrowing the income gap between urban and rural areas.展开更多
Taking Shouguang City in Shandong Province as an example, this article researches the mutual relationship between urban-rural income and employment of rural labor forces, and conducting cointegration test and Granger ...Taking Shouguang City in Shandong Province as an example, this article researches the mutual relationship between urban-rural income and employment of rural labor forces, and conducting cointegration test and Granger causality test on the variable sequences using statistical data. The results show that the average annual income of rural labor forces influences the income per capita of rural residents, and there is a Granger causality relationship between the income per capita of rural residents and urban employees' average wage. Engaging in production concerning agriculture, forestry, animal husbandry and fishery makes the total income per capita in rural areas of Shouguang City higher than the average wage of urban residents in Shouguang City, even in Weifang City. The comparative advantage in terms of income causes the city to loose attraction to rural residents in Shouguang City. The comparative advantage drives more rural labor forces in Shouguang City to engage in primary industry, thereby greatly reducing the pressure of employment and transfer of rural labor forces. Finally important following measures are put forward to promote employment and on-the-spot transfer of rural labor forces: vigorously propel agricultural industrialization; increase rural residents' income; improve the living conditions for rural residents.展开更多
There are two important problems of urban-rural relationship in China nowadays: the accelerated urbanization process and an enlarged urban-rural gap. The researchers can be divided into two schools according to their...There are two important problems of urban-rural relationship in China nowadays: the accelerated urbanization process and an enlarged urban-rural gap. The researchers can be divided into two schools according to their emphasis. One emphasizes particularly the urban development, and the other pays attention to the urban-rural income gap. However, there is a very strong association between urbanization rate and urban-rural inequality. As far as it goes, there is a paradox between urbanization and urban-rural inequality in China. This main reason lies' in the different temporal and spatial scales chosen by the scholars. Making use of correlative analysis and wavelet method, this paper rethinks and sums up the commonly evolving characteristics and trends between urbanization and urban-rural gap from 1950s to now. There is an intensively positive correlation between urbanization and urban- rural consumption gap. In general, with the acceleration of urbanization, urban-rural gap of China has undergone three stages of cyclical fluctuations. The rapid urbanization results in the increase of urban-rural highly risky. In addition, the special stage of urbanization is the other reason that expands urban-rural gap.展开更多
In recent years,with the rapid advancement of information technology and the widespread proliferation of the Internet,digital technology has been reshaping the value chains of traditional industries and giving rise to...In recent years,with the rapid advancement of information technology and the widespread proliferation of the Internet,digital technology has been reshaping the value chains of traditional industries and giving rise to entirely new business models and industrial forms.Technologies such as the Internet,big data,and artificial intelligence are being applied across various sectors,while new formats like e-commerce,the sharing economy,and online education are flourishing.These developments have driven new consumption patterns and employment methods.The rapid rise of the digital economy not only boosts production efficiency and economic growth but also influences the income distribution between urban and rural areas to some extent.This paper begins by examining the current state and characteristics of the digital economy and then analyzes its impact on the urban-rural income gap.Additionally,it offers countermeasures and recommendations for narrowing this gap,providing theoretical support for promoting common prosperity.展开更多
Inequality in distribution has become an issue of public concern in China. Incomes of the Chinese people have grown year after year ever since the reform and opening era began in the late 1970s. Meanwhile, the income ...Inequality in distribution has become an issue of public concern in China. Incomes of the Chinese people have grown year after year ever since the reform and opening era began in the late 1970s. Meanwhile, the income gap between urban and rural residents has widened constantly, from 1.8:1 in the mid-1980s to 3.2:1 in 2003. In a report entitled Analysis and Forecast of China's Social Conditions 2004-2005, experts with the Chinese Academy of Social Sciences listed the widening income gaps as the second most serious of the six problems China is facing. The report notes that such gaps have kept widening not only between individual workers in the same profession but also between workers in different industries and regions. In view of this, the national economic work conference held in early January called for effort to improve the order of income distribution and readjust the distribution of national wealth in an appropriate manner. How to view the problem of inequality in distribution as we see now? How the divide of the rich and the poor affects the improvement of human rights? What should be done to narrow the gap between the rich and the poor? We have dis- cussed these questions with two leading social scientists in China, Sun Guohua, pro- fessor of law at the Renmin University of China and Prof. Hu Angang of Qinghua University, a noted expert in study of the conditions in China.展开更多
Firstly,this paper conducts theoretical analysis and current situation analysis,and then proposes research hypotheses.Secondly,using spatial Dubin model and partial differential method,it empirically studies the impac...Firstly,this paper conducts theoretical analysis and current situation analysis,and then proposes research hypotheses.Secondly,using spatial Dubin model and partial differential method,it empirically studies the impact of industrial structure advancement and rationalization on the urban-rural income gap.The results show that:(1)Both industrial structure and urban-rural income gap have significant spatial dependence;(2)The increase in the industrial structure rationalization will narrow the urban-rural income gap in local region,while its spillover effect on neighboring areas is not obvious.(3)The impact of the industrial structure advancement on the urban-rural income gap is not linear.It is first expanded and then narrowed.The industrial structure advancement in the Yangtze River Delta will generally narrow the urban-rural income gap at this stage.Finally,this paper put forward relevant suggestions.展开更多
By introducing a source term into the Laplace equation, a two-dimensional fully nonlinear time-domain numerical wave flume (NWF) is developed to investigate the resonance induced by the interaction between waves and...By introducing a source term into the Laplace equation, a two-dimensional fully nonlinear time-domain numerical wave flume (NWF) is developed to investigate the resonance induced by the interaction between waves and multiple objects with narrow gaps. In the numerical model, the fully nonlinear kinematic and dynamic boundary conditions are satisfied on the instantaneous free surface and the constant artificial damping is employed in the gaps to approximate the viscous dissipation due to vortex motion and flow separation. The computational domain is discretized using a higher-order boundary element method (HOBEM). The proposed model is firstly validated against the published experimental data and numerical results of the wave height in the narrow gap between two boxes, the wave heights in the two gaps of three boxes, and wave loads on the boxes. Then, the extensive numerical experiments are performed to study the influences of the number of the boxes and the gap spacing on the resonant frequency, reflected and transmitted wave heights and wave loads on the boxes.展开更多
In this work, a tandem narrow gap gas metal arc welding( GMA W) system was developed to improve the efficiency in welding of thicker materials, which are mostly used in shipbuilding and nuclear power plant. A specia...In this work, a tandem narrow gap gas metal arc welding( GMA W) system was developed to improve the efficiency in welding of thicker materials, which are mostly used in shipbuilding and nuclear power plant. A special welding torch was desgined, where the two wires are fed through the bent contact tip to point to each side of narrow gap groove. Effect of wire distance and bent angle of contact tip on weld bead shape is studied. The experimental results show that defect free weld bead can be obtained when the wire distarwe is 5 mm and bent angle of contact tip is 10% Finally, tandem narrow gap GMAW of 65 mm thick low carbon steel was successfully carried out with one pass per layer. The obtained weld cross-section photo indicates that there is no defect of lack of side fusion or slag inclusion.展开更多
In this paper, the droplet transfer in oscillating arc narrow gap gas metal arc ( GMA ) welding was studied. According to the experimental results, the oscillating arc has effect on the droplet transfer mode. The dr...In this paper, the droplet transfer in oscillating arc narrow gap gas metal arc ( GMA ) welding was studied. According to the experimental results, the oscillating arc has effect on the droplet transfer mode. The droplet transfer frequency in narrow gap groove is higher than that in bead-on-plate welding. Because of the change of arc location in narrow gap groove, the droplet transfer in oscillating arc narrow gap changes regularly. The droplet transfer frequency near groove sidewall is higher than that at the middle of narrow gap groove.展开更多
Magnetic semiconductors have been demonstrated to work at low temperatures, but not yet at room temperature for spin electronic applications. In contrast to the p-type diluted magnetic semiconductors, n-type diluted m...Magnetic semiconductors have been demonstrated to work at low temperatures, but not yet at room temperature for spin electronic applications. In contrast to the p-type diluted magnetic semiconductors, n-type diluted magnetic semiconductors are few. Using a combined method of the density function theory and quantum Monte Carlo simulation, we briefly discuss the recent progress to obtain diluted magnetic semiconductors with both p- and n-type carriers by choosing host semiconductors with a narrow band gap. In addition, the recent progress on two-dimensional intrinsic magnetic semiconductors with possible room temperature ferromangetism and quantum anomalous Hall effect are also discussed.展开更多
Based on the time-domain higher-order boundary element method(HOBEM), a two-dimensional numerical wave flume is developed to investigate solitary wave interaction with two rectangular boxes with a narrow gap.In the nu...Based on the time-domain higher-order boundary element method(HOBEM), a two-dimensional numerical wave flume is developed to investigate solitary wave interaction with two rectangular boxes with a narrow gap.In the numerical model, the fully nonlinear boundary conditions are satisfied on the free surface, the mixed Eulerian-Lagrangian method is adopted to track the transient water surface and the fourth-order Runga-Kutta method is used to predict the velocity potential and wave elevation on the free surface. The acceleration potential technique is used to compute the transient wave forces along the wetted object surface. A piston-type wavemaker is used to generate solitary waves. The proposed model is validated by comparing the simulated wave run-up and the wave loads with the published experimental and numerical results of the reflection of a solitary wave from a vertical wall. Then, numerical experiments are performed to study the effects of the narrow gap and the size of each box on the wave run-ups at the two sides of the two-box system and in the narrow gap between two boxes, and the wave loads on the two boxes. The interaction between double solitary waves with a time interval between them with a two-box system is also investigated.展开更多
In this paper,the microstructure of narrow gap laser welded joint of 45 mm Ti6321 titanium alloy was characterized.The microstructure characteristics of Laser self-fusion and laser-multi-pass-narrow-gapfilling layer w...In this paper,the microstructure of narrow gap laser welded joint of 45 mm Ti6321 titanium alloy was characterized.The microstructure characteristics of Laser self-fusion and laser-multi-pass-narrow-gapfilling layer were observed by metallographic microscope,and the phase morphology was analyzed by transmission electron microscope.The results show that the joint was obtained using the laser-multipass-narrow-gap welding,and no volumetric defect is observed.The weld grain of self fusion welded bead tends to be equiaxed with lots of needleα’,and the width of weld metal needleα’was 0.4μm.The heat affected zone is columnar crystal with lamellarα,and The width of heat affected zonelamellarαwas 2–4μm with a large number of dislocation tangles.The weld grains of laser-multi-pass-narrow-gap filler bead are coarse columnar grains with staggered acicularα’,and the width of acicularα’in weld metal is less than 1μm with number of dislocations.The heat affected zone is thick lamellar microstructure with a width of 2–4μm with a large number of dislocation entanglement and packing.The microstructure evolution law is related with heating temperature and cooling rate.展开更多
The influence of rotating speed on metal transfer and the wire metal speed was studied in the high rotating speed arc narrow gap welding.The results indicate that the high rotating speed arc has benefit on the metal t...The influence of rotating speed on metal transfer and the wire metal speed was studied in the high rotating speed arc narrow gap welding.The results indicate that the high rotating speed arc has benefit on the metal transfer,and that with the rotating speed increasing,the droplet volume decreases.It is shown that the rotating speed has little influence on the wire metal speed with DC electrode positive polarity(DCEP),but the melting speed decreases with increasing of rotating speed in DC electrode negative polarity(DCEN).展开更多
Multi-layer narrow-gap welding of thick S32101 duplex stainless steel was conducted using laser welding with beam wobble process.The phase transition,grain size,phase proportion and crystal texture of welded joint wer...Multi-layer narrow-gap welding of thick S32101 duplex stainless steel was conducted using laser welding with beam wobble process.The phase transition,grain size,phase proportion and crystal texture of welded joint were also studied and compared with gas metal arc welding process.The microhardness and tensile strength were measured and fracture surface was analyzed to evaluate the mechanical properties of welded joints.The results showed that beam wobble technology improved the misalignment of laser beam and filler wire in narrow groove and helped to avoid incomplete fusion defects.Compared to arc welding process,the groove size and heat input were reduced,while welding efficiency was increased.The faster cooling rate and lower temperature gradient of laser wobble welding favored grain refinement,while the austenite content in weld zone decreased.Both the beam wobble and swing arc were conducive to stir weld pool,optimizing the weld microstructure and joint formation.The microstructural variance in various weld passes was caused by the heat input and heat dissipation ability.The microhardness of laser welded joint was lower,while the tensile strength and elongation percentage were higher.The fracture surface of arc welded joint was featured with shallower dimples and cleavage steps.展开更多
Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving ar...Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving arc have been developed to increase heating effect of arc to the sidewalls. In this work, a new approach Without weaving arc is attempted to ensure the penetration of sidewall, and ultra-narrow gap welding with the gap of less than 5 mm was executed successfully. In this approach, the width of gap is decreased further, so that the sidewalls are made within range of arc heating to obtain the enough heat. In order to prevent the arc from being attracted by sidewall and going up along the sidewalls, two pieces of flux bands consisting of the specified aggregates are adhered to the sidewalls to constrain the arc. In addition, when flux band being heated by the arc, slag and gases are formed to shield the arc and the weld pool. This technique was tested on the welding experiment of pipeline steel with thickness of 20 mm. The involved welding parameters were obtained, that is, the width of gap is 4 mm, the welding current 250 A, and the heat input 0. 5 kJ/mm, the width of heat-affected zone is 1 -2 mm.展开更多
The slag-free self-shielded flux-cored wire was fabricated to apply for the narrow gap welding.The results showed that narrow gap welding shows lower welding spatter compared with hardfacing except under voltage of 30...The slag-free self-shielded flux-cored wire was fabricated to apply for the narrow gap welding.The results showed that narrow gap welding shows lower welding spatter compared with hardfacing except under voltage of 30 V and current of 260 A.The deposition efficiency keeps over 90%for both 12 mm and 8 mm narrow gap welding.For 12 mm narrow gap welding,when the voltage is 28 V and the current is 264 A(or 286 A),no pores are found in the narrow gap weld.In the continuous welding process,manganese vapor,aluminum vapor and CO continuously generate to form gasbag and occupy the narrow gap space,thus protecting the droplet and molten pool from the invasion of air.展开更多
A series of experiments of tandem narrow gap GMAW for flat welding position were carried out. The arc behavior and metal transfer process were observed by a high-speed photography system. The effects of the welding pa...A series of experiments of tandem narrow gap GMAW for flat welding position were carried out. The arc behavior and metal transfer process were observed by a high-speed photography system. The effects of the welding parameters on the metal transfer were investigated. The results show that the arc behavior and metal transfer process of tandem narrow gap GMA W are different from these of bead-on-plate tandem GMA W. The arc behavior and metal transfer process are influenced by the distance between the two wires, the peak voltage, the pulse frequency and the peak time. With the increase of the distance between the two wires, the metal transfer mode gradually transforms from one pulse-multi droplets into one pulse-one droplet, and the average welding current increases. With the increase of the peak voltage, pulse frequency or peak time, the metal transfer mode transforms from one pulse-one droplet into one pulse-multi droplets, and the arc tends to occur between the wire and the sidewall.展开更多
基金Supported by Jiangxi Social Sciences Project(08SH035)Key Project of National Social Sciences Fund(08AZD005)
文摘From the situations about the incomes and life quality of the urban and rural residents,the thesis briefly introduces the status quo of the urban-rural income gap and explores the impact of the income gap on social economy:firstly,it hampers economic development;secondly,it is detrimental to the social development.Then the thesis analyzes the role of a sound social security in narrowing urban-rural income gap:at first,it broadens the institutional environment of improving the agricultural efficiency;secondly,it eliminates the uncertainties influencing the farmers' income;thirdly,it improves the farmers' capacity to increase income;at last,it enhances the farmers' consciousness of wealth.Next the thesis inquires into the problems existing in the system of rural social security:the first problem is more obviously fragmented system;the second is inadequate security projects and narrower coverage;the third is an obvious lack of equality in urban and rural security;the fourth is even less sound management system;the last is the lagging of legislation.Afterwards the thesis proposes the countermeasures and suggestions to improve the system of rural social security and narrow urban-rural income gap:firstly,to integrate the social security system in rural areas;secondly,to perfect security projects and enhance the security system;thirdly,to integrate the administrative management of social security;at last,to enforce the legal system.
文摘By using the data concerning China's urban-rural residents' income gap from 1978 to 2010,this paper mainly researches the application of several kinds of models in predicting China's urban-rural residents' income gap.By conducting empirical analysis,we establish ARIMA prediction model,grey prediction model and quadratic-polynomial prediction model and conduct accuracy comparison.The results show that quadratic-polynomial prediction model has excellent fitting effect.By using quadratic-polynomial prediction model,this paper conducts prediction on trend of China's urban-rural residents' income gap from 2011 to 2013,and the prediction value of income gap of urban-rural residents in China from 2011 to 2013 is 14 173.20,15 212.92 and 16 289.67 yuan respectively.Finally,on the basis of analysis,corresponding countermeasures are put forward,in order to provide scientific basis for energy planning and policy formulation:first,strengthen government's function of public service,coordinate resources,and strive to provide an equal opportunity of development for social members,so as to promote people's welfare and promote social equality;second,breach industrial monopoly and bridge income gap between employees in monopoly industry and general industry;last but not the least,support,encourage and call for government to establish social relief fund,adjust residents' income distribution from the non-governmental perspective,and endeavor to promote the income level of low-income class.
文摘The urban-rural income gap is widening,which has become a bottleneck restricting China's economic and social development.It is the current outstanding problems in the harmonious development of the society.Community Supported Agriculture(CSA) is one of the most important forms of sustainable agriculture and it has received the attention in recent years.This paper first introduces the rise and development of CSA in China,and discuss the impact of CSA on urban-rural income gap in China preliminarily in order to provide ideas for improving the farmers' income and narrowing the income gap between urban and rural areas.
文摘Taking Shouguang City in Shandong Province as an example, this article researches the mutual relationship between urban-rural income and employment of rural labor forces, and conducting cointegration test and Granger causality test on the variable sequences using statistical data. The results show that the average annual income of rural labor forces influences the income per capita of rural residents, and there is a Granger causality relationship between the income per capita of rural residents and urban employees' average wage. Engaging in production concerning agriculture, forestry, animal husbandry and fishery makes the total income per capita in rural areas of Shouguang City higher than the average wage of urban residents in Shouguang City, even in Weifang City. The comparative advantage in terms of income causes the city to loose attraction to rural residents in Shouguang City. The comparative advantage drives more rural labor forces in Shouguang City to engage in primary industry, thereby greatly reducing the pressure of employment and transfer of rural labor forces. Finally important following measures are put forward to promote employment and on-the-spot transfer of rural labor forces: vigorously propel agricultural industrialization; increase rural residents' income; improve the living conditions for rural residents.
文摘There are two important problems of urban-rural relationship in China nowadays: the accelerated urbanization process and an enlarged urban-rural gap. The researchers can be divided into two schools according to their emphasis. One emphasizes particularly the urban development, and the other pays attention to the urban-rural income gap. However, there is a very strong association between urbanization rate and urban-rural inequality. As far as it goes, there is a paradox between urbanization and urban-rural inequality in China. This main reason lies' in the different temporal and spatial scales chosen by the scholars. Making use of correlative analysis and wavelet method, this paper rethinks and sums up the commonly evolving characteristics and trends between urbanization and urban-rural gap from 1950s to now. There is an intensively positive correlation between urbanization and urban- rural consumption gap. In general, with the acceleration of urbanization, urban-rural gap of China has undergone three stages of cyclical fluctuations. The rapid urbanization results in the increase of urban-rural highly risky. In addition, the special stage of urbanization is the other reason that expands urban-rural gap.
文摘In recent years,with the rapid advancement of information technology and the widespread proliferation of the Internet,digital technology has been reshaping the value chains of traditional industries and giving rise to entirely new business models and industrial forms.Technologies such as the Internet,big data,and artificial intelligence are being applied across various sectors,while new formats like e-commerce,the sharing economy,and online education are flourishing.These developments have driven new consumption patterns and employment methods.The rapid rise of the digital economy not only boosts production efficiency and economic growth but also influences the income distribution between urban and rural areas to some extent.This paper begins by examining the current state and characteristics of the digital economy and then analyzes its impact on the urban-rural income gap.Additionally,it offers countermeasures and recommendations for narrowing this gap,providing theoretical support for promoting common prosperity.
文摘Inequality in distribution has become an issue of public concern in China. Incomes of the Chinese people have grown year after year ever since the reform and opening era began in the late 1970s. Meanwhile, the income gap between urban and rural residents has widened constantly, from 1.8:1 in the mid-1980s to 3.2:1 in 2003. In a report entitled Analysis and Forecast of China's Social Conditions 2004-2005, experts with the Chinese Academy of Social Sciences listed the widening income gaps as the second most serious of the six problems China is facing. The report notes that such gaps have kept widening not only between individual workers in the same profession but also between workers in different industries and regions. In view of this, the national economic work conference held in early January called for effort to improve the order of income distribution and readjust the distribution of national wealth in an appropriate manner. How to view the problem of inequality in distribution as we see now? How the divide of the rich and the poor affects the improvement of human rights? What should be done to narrow the gap between the rich and the poor? We have dis- cussed these questions with two leading social scientists in China, Sun Guohua, pro- fessor of law at the Renmin University of China and Prof. Hu Angang of Qinghua University, a noted expert in study of the conditions in China.
文摘Firstly,this paper conducts theoretical analysis and current situation analysis,and then proposes research hypotheses.Secondly,using spatial Dubin model and partial differential method,it empirically studies the impact of industrial structure advancement and rationalization on the urban-rural income gap.The results show that:(1)Both industrial structure and urban-rural income gap have significant spatial dependence;(2)The increase in the industrial structure rationalization will narrow the urban-rural income gap in local region,while its spillover effect on neighboring areas is not obvious.(3)The impact of the industrial structure advancement on the urban-rural income gap is not linear.It is first expanded and then narrowed.The industrial structure advancement in the Yangtze River Delta will generally narrow the urban-rural income gap at this stage.Finally,this paper put forward relevant suggestions.
基金The National Natural Science Foundation of China under contract Nos 51179028,51222902 and 51221961the New Century Excellent Talents in University of China under contract No.NCET-13-0076
文摘By introducing a source term into the Laplace equation, a two-dimensional fully nonlinear time-domain numerical wave flume (NWF) is developed to investigate the resonance induced by the interaction between waves and multiple objects with narrow gaps. In the numerical model, the fully nonlinear kinematic and dynamic boundary conditions are satisfied on the instantaneous free surface and the constant artificial damping is employed in the gaps to approximate the viscous dissipation due to vortex motion and flow separation. The computational domain is discretized using a higher-order boundary element method (HOBEM). The proposed model is firstly validated against the published experimental data and numerical results of the wave height in the narrow gap between two boxes, the wave heights in the two gaps of three boxes, and wave loads on the boxes. Then, the extensive numerical experiments are performed to study the influences of the number of the boxes and the gap spacing on the resonant frequency, reflected and transmitted wave heights and wave loads on the boxes.
文摘In this work, a tandem narrow gap gas metal arc welding( GMA W) system was developed to improve the efficiency in welding of thicker materials, which are mostly used in shipbuilding and nuclear power plant. A special welding torch was desgined, where the two wires are fed through the bent contact tip to point to each side of narrow gap groove. Effect of wire distance and bent angle of contact tip on weld bead shape is studied. The experimental results show that defect free weld bead can be obtained when the wire distarwe is 5 mm and bent angle of contact tip is 10% Finally, tandem narrow gap GMAW of 65 mm thick low carbon steel was successfully carried out with one pass per layer. The obtained weld cross-section photo indicates that there is no defect of lack of side fusion or slag inclusion.
基金They also thank the National Natural Science Foundation of China for its financial support
文摘In this paper, the droplet transfer in oscillating arc narrow gap gas metal arc ( GMA ) welding was studied. According to the experimental results, the oscillating arc has effect on the droplet transfer mode. The droplet transfer frequency in narrow gap groove is higher than that in bead-on-plate welding. Because of the change of arc location in narrow gap groove, the droplet transfer in oscillating arc narrow gap changes regularly. The droplet transfer frequency near groove sidewall is higher than that at the middle of narrow gap groove.
基金supported by NSFC (Grant No. Y81Z01A1A9)CAS (Grant No. Y929013EA2)+3 种基金UCAS (Grant No.110200M208)the Strategic Priority Research Program of CAS (Grant No. XDB28000000)the National Key R&D Program of China (Grant No.11834014)Beijing Municipal Science & Technology Commission (Grant No. Z181100004218001)
文摘Magnetic semiconductors have been demonstrated to work at low temperatures, but not yet at room temperature for spin electronic applications. In contrast to the p-type diluted magnetic semiconductors, n-type diluted magnetic semiconductors are few. Using a combined method of the density function theory and quantum Monte Carlo simulation, we briefly discuss the recent progress to obtain diluted magnetic semiconductors with both p- and n-type carriers by choosing host semiconductors with a narrow band gap. In addition, the recent progress on two-dimensional intrinsic magnetic semiconductors with possible room temperature ferromangetism and quantum anomalous Hall effect are also discussed.
基金The National Natural Science Foundation of China under contract Nos 51679036,51222902 and 51490672the Program for New Century Excellent Talents in University under contract No.NCET-13-0076
文摘Based on the time-domain higher-order boundary element method(HOBEM), a two-dimensional numerical wave flume is developed to investigate solitary wave interaction with two rectangular boxes with a narrow gap.In the numerical model, the fully nonlinear boundary conditions are satisfied on the free surface, the mixed Eulerian-Lagrangian method is adopted to track the transient water surface and the fourth-order Runga-Kutta method is used to predict the velocity potential and wave elevation on the free surface. The acceleration potential technique is used to compute the transient wave forces along the wetted object surface. A piston-type wavemaker is used to generate solitary waves. The proposed model is validated by comparing the simulated wave run-up and the wave loads with the published experimental and numerical results of the reflection of a solitary wave from a vertical wall. Then, numerical experiments are performed to study the effects of the narrow gap and the size of each box on the wave run-ups at the two sides of the two-box system and in the narrow gap between two boxes, and the wave loads on the two boxes. The interaction between double solitary waves with a time interval between them with a two-box system is also investigated.
基金supported by the Luoyang Ship Material Institute's Scientific and Technological Innovation Project(LW190801)Zhengzhou Luoyang and Xinxiang Independent Innovation Demonstration Area(Porject No.201200211400).
文摘In this paper,the microstructure of narrow gap laser welded joint of 45 mm Ti6321 titanium alloy was characterized.The microstructure characteristics of Laser self-fusion and laser-multi-pass-narrow-gapfilling layer were observed by metallographic microscope,and the phase morphology was analyzed by transmission electron microscope.The results show that the joint was obtained using the laser-multipass-narrow-gap welding,and no volumetric defect is observed.The weld grain of self fusion welded bead tends to be equiaxed with lots of needleα’,and the width of weld metal needleα’was 0.4μm.The heat affected zone is columnar crystal with lamellarα,and The width of heat affected zonelamellarαwas 2–4μm with a large number of dislocation tangles.The weld grains of laser-multi-pass-narrow-gap filler bead are coarse columnar grains with staggered acicularα’,and the width of acicularα’in weld metal is less than 1μm with number of dislocations.The heat affected zone is thick lamellar microstructure with a width of 2–4μm with a large number of dislocation entanglement and packing.The microstructure evolution law is related with heating temperature and cooling rate.
文摘The influence of rotating speed on metal transfer and the wire metal speed was studied in the high rotating speed arc narrow gap welding.The results indicate that the high rotating speed arc has benefit on the metal transfer,and that with the rotating speed increasing,the droplet volume decreases.It is shown that the rotating speed has little influence on the wire metal speed with DC electrode positive polarity(DCEP),but the melting speed decreases with increasing of rotating speed in DC electrode negative polarity(DCEN).
基金supported by the Science and Technology Innovation Program of Hunan Province(2022RC1060 and 2022GK4046)。
文摘Multi-layer narrow-gap welding of thick S32101 duplex stainless steel was conducted using laser welding with beam wobble process.The phase transition,grain size,phase proportion and crystal texture of welded joint were also studied and compared with gas metal arc welding process.The microhardness and tensile strength were measured and fracture surface was analyzed to evaluate the mechanical properties of welded joints.The results showed that beam wobble technology improved the misalignment of laser beam and filler wire in narrow groove and helped to avoid incomplete fusion defects.Compared to arc welding process,the groove size and heat input were reduced,while welding efficiency was increased.The faster cooling rate and lower temperature gradient of laser wobble welding favored grain refinement,while the austenite content in weld zone decreased.Both the beam wobble and swing arc were conducive to stir weld pool,optimizing the weld microstructure and joint formation.The microstructural variance in various weld passes was caused by the heat input and heat dissipation ability.The microhardness of laser welded joint was lower,while the tensile strength and elongation percentage were higher.The fracture surface of arc welded joint was featured with shallower dimples and cleavage steps.
文摘Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving arc have been developed to increase heating effect of arc to the sidewalls. In this work, a new approach Without weaving arc is attempted to ensure the penetration of sidewall, and ultra-narrow gap welding with the gap of less than 5 mm was executed successfully. In this approach, the width of gap is decreased further, so that the sidewalls are made within range of arc heating to obtain the enough heat. In order to prevent the arc from being attracted by sidewall and going up along the sidewalls, two pieces of flux bands consisting of the specified aggregates are adhered to the sidewalls to constrain the arc. In addition, when flux band being heated by the arc, slag and gases are formed to shield the arc and the weld pool. This technique was tested on the welding experiment of pipeline steel with thickness of 20 mm. The involved welding parameters were obtained, that is, the width of gap is 4 mm, the welding current 250 A, and the heat input 0. 5 kJ/mm, the width of heat-affected zone is 1 -2 mm.
基金supported by China Postdoctoral Science Foundation Funded Project(Grant No.2016M601753)Natural Science Foundation of Jiangsu Province(Grant No.BK20201453)Major Projects of Natural Science Research in Colleges and Universities in Jiangsu(Grant No.19KJA460009).
文摘The slag-free self-shielded flux-cored wire was fabricated to apply for the narrow gap welding.The results showed that narrow gap welding shows lower welding spatter compared with hardfacing except under voltage of 30 V and current of 260 A.The deposition efficiency keeps over 90%for both 12 mm and 8 mm narrow gap welding.For 12 mm narrow gap welding,when the voltage is 28 V and the current is 264 A(or 286 A),no pores are found in the narrow gap weld.In the continuous welding process,manganese vapor,aluminum vapor and CO continuously generate to form gasbag and occupy the narrow gap space,thus protecting the droplet and molten pool from the invasion of air.
基金This research is supported by National Natural Science Foundation of China (Grant No. 51275109).
文摘A series of experiments of tandem narrow gap GMAW for flat welding position were carried out. The arc behavior and metal transfer process were observed by a high-speed photography system. The effects of the welding parameters on the metal transfer were investigated. The results show that the arc behavior and metal transfer process of tandem narrow gap GMA W are different from these of bead-on-plate tandem GMA W. The arc behavior and metal transfer process are influenced by the distance between the two wires, the peak voltage, the pulse frequency and the peak time. With the increase of the distance between the two wires, the metal transfer mode gradually transforms from one pulse-multi droplets into one pulse-one droplet, and the average welding current increases. With the increase of the peak voltage, pulse frequency or peak time, the metal transfer mode transforms from one pulse-one droplet into one pulse-multi droplets, and the arc tends to occur between the wire and the sidewall.