Gastric cancer poses a significant public health problem, especially in the Far East, due to its high incidence in these areas. Surgical treatment and guidelines have been markedly different in the West, but nowadays ...Gastric cancer poses a significant public health problem, especially in the Far East, due to its high incidence in these areas. Surgical treatment and guidelines have been markedly different in the West, but nowadays this debate is apparently coming to an end. Laparoscopic surgery has been employed in the surgical treatment of gastric cancer for two decades now, but with controversies about the extent of resection and lymphadenectomy. Despite these difficulties, the apparent advantages of the laparoscopic approach helped its implementation in early stage and distal gastric cancer, with an increase on the uptake for distal gastrectomy for more advanced disease and total gastrectomy. Nevertheless, there is no conclusive evidence about the laparoscopic approach yet. In this review article we present and analyse the current status of laparoscopic surgery in the treatment of gastric cancer.展开更多
Improving vehicle fuel consumption,performance and aerodynamic efficiency by drag reduction especially in heavy vehicles is one of the indispensable issues of automotive industry.In this work,the effects of adding app...Improving vehicle fuel consumption,performance and aerodynamic efficiency by drag reduction especially in heavy vehicles is one of the indispensable issues of automotive industry.In this work,the effects of adding append devices like deflector and cab vane corner on heavy commercial vehicle drag reduction were investigated.For this purpose,the vehicle body structure was modeled with various supplementary parts at the first stage.Then,computational fluid dynamic(CFD) analysis was utilized for each case to enhance the optimal aerodynamic structure at different longitudinal speeds for heavy commercial vehicles.The results show that the most effective supplementary part is deflector,and by adding this part,the drag coefficient is decreased considerably at an optimum angle.By adding two cab vane corners at both frontal edges of cab,a significant drag reduction is noticed.Back vanes and base flaps are simple plates which can be added at the top and side end of container and at the bottom with specific angle respectively to direct the flow and prevent the turbulence.Through the analysis of airflow and pressure distribution,the results reveal that the cab vane reduces fuel consumption and drag coefficient by up to 20 % receptively using proper deflector angle.Finally,by adding all supplementary parts at their optimized positions,41% drag reduction is obtained compared to the simple model.展开更多
Based on research studies currently being carried out at Dalian University of Technology, some important aspects for the earthquake safety assessmcnt of concrete dams are reviewed and discussed. First, the rate-depend...Based on research studies currently being carried out at Dalian University of Technology, some important aspects for the earthquake safety assessmcnt of concrete dams are reviewed and discussed. First, the rate-dependent behavior of concrcte subjected to earthquake loading is examined, emphasizing the properties of concrete under cyclic and biaxial loading conditions. Second, a modified four-parameter Hsieh-Ting-Chen viscoplastic consistency model is developed to simulate the rate-dependent behavior of concrete. The earthquake response of a 278m high arch dam is analyzed, and the results show that the strain-rate effects become noticeable in the inelastic range, Third, a more accurate non-smooth Newton algorithm for the solution of three-dimensional frictional contact problems is developed to study the joint opening effects of arch dams during strong earthquakes. Such effects on two nearly 300m high arch dams have been studied. It was found that the canyon shape has great influence on the magnitude and distribution of the joint opening along the dam axis. Fourth, the scaled boundary finite element method presented by Song and Wolf is employed to study the dam-reservoir-foundation interaction effects of concrete dams. Particular emphases were placed on the variation of foundation stiffness and the anisotropic behavior of the foundation material on the dynamic response of concrete dams. Finally, nonlinear modeling of concrete to study the damage evolution of concrete dams during strong earthquakes is discussed. An elastic-damage mechanics approach for damage prediction of concrete gravity dams is described as an example. These findings are helpful in understanding the dynamic behavior of concrete dams and promoting the improvement of seismic safety assessment methods.展开更多
Since 1978, the bulk of foreign direct investment （FDI） has gone to the south-eastern coastal areas in China, with only a small portion received inland. With the launch of the Western Development Strategy in 2000 an...Since 1978, the bulk of foreign direct investment （FDI） has gone to the south-eastern coastal areas in China, with only a small portion received inland. With the launch of the Western Development Strategy in 2000 and the Central China Rising Strategy in 2004, the choice of investment locations has expanded to inland areas. Based on panel data covering 98 inland cities from 1999 to 2005, this study identifies location preference variables for FDI invested in China＇s inland areas, and finds that well-established factors such as natural resources and low labor costs are not important factors in determining FDI locations within China＇s inland. Instead, policy incentives and industrial agglomeration are the most important factors. The findings of the present study have policy implications for both host country authorities and multinational corporations.展开更多
AIM: To investigate the therapeutic effects of Guiyuanfang and bone marrow stem cells (BMSCs) on rats with liver fibrosis.METHODS: Liver fibrosis model was induced by carbon tetrachloride, ethanol, high lipid and asse...AIM: To investigate the therapeutic effects of Guiyuanfang and bone marrow stem cells (BMSCs) on rats with liver fibrosis.METHODS: Liver fibrosis model was induced by carbon tetrachloride, ethanol, high lipid and assessed biochemically and histologically. Liver function and hydroxyproline contents of liver tissue were determined.Serum hyaluronic acid (HA) level and procollagen Ⅲ level were performed by radioimmunoassay. The VG staining was used to evaluate the collagen deposit in the liver.Immunohistochemical SABC methods were used to detect transplanted BMSCs and expression of urokinase plasminogen activator (uPA).RESULTS: Serum transaminase level and liver fibrosis in rats were markedly reduced by Guiyuanfang and BMSCs. HA level and procollagen Ⅲ level were also reduced obviously,compared to model rats (HA: 47.18±10.97 ng/mL,48.96±14.79 ng/mL; PCⅢ: 22.48±5.46 ng/mL, 26.90±3.35ng/mL; P＜0.05).Hydroxyproline contents of liver tissue in both BMSCs group and Guiyuanfang group were far lower than that of model group (1 227.2±43.1 μg/g liver tissue, 1390.8±156.3 μg/g liver tissue; P＜0.01). After treatment fibrosis scores were also reduced. Both Guiyuanfang and BMSCs could increase the expression of uPA. The transplanted BMSCs could engraft, survive, and proliferate in the liver.CONCLUSION: Guiyuanfang protects against liver fibrosis.Transplanted BMSCs may engraft, survive, and proliferate in the fibrosis livers indefinitely. Guiyuanfang may synergize with BMSCs to improve recovery from liver fibrosis.展开更多
This paper investigates the impact of foreign direct investment （FDI） and exports on urbanization in China. Using prefecture city-level panel data covering China ＂s 262 prefecture cities for the period 2004-2013 an...This paper investigates the impact of foreign direct investment （FDI） and exports on urbanization in China. Using prefecture city-level panel data covering China ＂s 262 prefecture cities for the period 2004-2013 and employing a dynamic panel system generalized method of moments model with instrumental variable regression techniques, our study finds that FDI and exports have, on average, played a significantly positive role in China＇s urbanization. However, the impacts of FDl and exports on urbanization vary across regions. FDI has a positive and significant impact on urbanization in the coastal region but has no impact on urbanization in the inland region. Exports have a positive and significant impact on urbanization in both the coastal and inland regions, but the effect is much larger in the coastal region than in the inland region. The results imply that further attracting FDI inflows and promoting exports will contribute to China＇s urbanization, especially for the inland region.展开更多
Several hundred species of bacteria inhabit the gut, and affect its cell biology, morphology and homeostasis. Many bacteria are however potential pathogens, especially if the integrity of the epithelial barrier is phy...Several hundred species of bacteria inhabit the gut, and affect its cell biology, morphology and homeostasis. Many bacteria are however potential pathogens, especially if the integrity of the epithelial barrier is physically or functionally breached. Conversely, the interaction between host and commensal microbes can confer important health benefits. This has led to commercial and public interest in ＇probiotics＇, live microbes principally taken as food supplements. Might probiotics also be used in disease therapy？ Experimental evidence that probiotics modulate gut physiology, particularly barrier integrity and immunological function, underpins exciting new gastroenterological research. We discuss below the scientific basis for probiotic effects and present a critical perspective for their use in relation to gastrointestinal disease.展开更多
To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoir...To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussees. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimentalp-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including： soil plastification at an early stage of loading, ＂pinching＂ behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. （1974） for sand, is also presented.展开更多
The present study considers how education affects off-farm job participation and wages. We use a nationally representative dataset from a survey conducted in 5 provinces, 101 villages and 808 households by the authors...The present study considers how education affects off-farm job participation and wages. We use a nationally representative dataset from a survey conducted in 5 provinces, 101 villages and 808 households by the authors in early 2005. The empirical results show that educational attainment, skill training and years of experience of rural residents have positive, statistically significant effects on off-farm employment. The average return to a year of education is 7percent, which is higher than those observed in previous studies. We also find the return to an additional year of schooling to be higher for post-junior high schooling than for junior high and below schooling： 11.8 versus 3.2 percent. We conclude that not only does education still pays off in rural China, but also the rate of return to education is increasing over time.展开更多
There is some disagreement in the published literature regarding the definition and the measurement of housing bubbles in China. Extending the analytical framework of Black et al. （2006）, the present paper measures ...There is some disagreement in the published literature regarding the definition and the measurement of housing bubbles in China. Extending the analytical framework of Black et al. （2006）, the present paper measures the housing bubbles of China＇s 35 major cities from the second quarter of 1999 to the second quarter of 2010. The results indicate that the housing bubbles in China＇s 35 major cities were relatively small in the sample interval, but the bubbles in eastern metropolises, such as Beijing, Shanghai, Shenzhen, Hangzhou and Ningbo, have been relatively big since 2005. The changing tendency of housing bubbles in most cities highly corresponds with the changes in real estate policies. This paper decomposes the housing bubbles of the 35 cities, and finds a great proportion of irrational bubbles rather than rational intrinsic bubbles generated by price speculation. Based on empirical analysis, this paper proposes policy recommendations for preventing the generation and expansion of housing bubbles.展开更多
A new approach to evaluate the extreme value distribution （EVD） of the response and reliability of general multi-DOF nonlinear stochastic structures is proposed. The approach is based on the recently developed proba...A new approach to evaluate the extreme value distribution （EVD） of the response and reliability of general multi-DOF nonlinear stochastic structures is proposed. The approach is based on the recently developed probability density evolution method, which enables the instantaneous probability density functions of the stochastic responses to be captured. In the proposed method, a virtual stochastic process is first constructed to satisfy the condition that the extreme value of the response equals the value of the constructed process at a certain instant of time. The probability density evolution method is then applied to evaluate the instantaneous probability density function of the response, yielding the EVD. The reliability is therefore available through a simple integration over the safe domain. A numerical algorithm is developed using the Number Theoretical Method to select the discretized representative points. Further, a hyper-ball is imposed to sieve the points from the preceding point set in the hypercube. In the numerical examples, the EVD of random variables is evaluated and compared with the analytical solution. A frame structure is analyzed to capture the EVD of the response and the dynamic reliability. The investigations indicate that the proposed approach provides reasonable accuracy and efficiency.展开更多
Non-renewable fuel sources have been the predominant energy sources and a significant source of foreign exchange income for Nigeria,while at the same time there is a severe problem of electricity inconsistency and per...Non-renewable fuel sources have been the predominant energy sources and a significant source of foreign exchange income for Nigeria,while at the same time there is a severe problem of electricity inconsistency and persistent power blackouts in Nigeria.The research aims to end the concern for deficient energy use,and to encourage energy efficiency and sustainability.Nigeria has not maximized the advantages of renewable energy after the denationalisation of its electricity industry despite the current transformation in the power industry and the rising demand for renewable energy supply.The research adopts a doctrinal legal approach with a library-based legal research technique with a comparative legal method.It reveals that the absence of a comprehensible legal regime with encouragement for the use of renewable energy is the fundamental element causing the slow utilization of renewable energy as a substitute source of energy in Nigeria.It is suggested that,among other reforms,there is a need for a comprehensible legal regime on renewable energy and the encouragement of strict implementation of energy regulatory strategies and policies with incentives for the application of renewable energy sources in Nigeria.展开更多
In this paper,the dynamic stress concentration and scattering of SH-waves by bi-material structures that possess an interface elliptic cavity are investigated.First,by using the complex function method,the Green's...In this paper,the dynamic stress concentration and scattering of SH-waves by bi-material structures that possess an interface elliptic cavity are investigated.First,by using the complex function method,the Green's function is constructed.This yields the solution of the displacement field for an elastic half space with a semi-elliptic canyon impacted by an anti-plane harmonic line source loading on the horizontal surface.Then,the problem is divided into an upper and lower half space along the horizontal interface,regarded as a harmony model.In order to satisfy the integral continuity condition, the unknown anti-plane forces are applied to the interface.The integral equations with unknown forces can be established through the continuity condition,and after transformation,the algebraic equations are solved numerically.Finally,the distribution of the dynamic stress concentration factor(DSCF)around the elliptic cavity is given and the effect of different parameters on DSCF is discussed.展开更多
Massive segmental bone loss due to chronic osteomyelitis represents a considerable challenge to orthopedic surgeons and is a limb threatening condition.The only option available in such a clinical situation is segment...Massive segmental bone loss due to chronic osteomyelitis represents a considerable challenge to orthopedic surgeons and is a limb threatening condition.The only option available in such a clinical situation is segment transport using the Ilizarov technique of distraction osteogenesis;yet the most common problem in cases of bone transport with the Ilizarov technique in massive bone loss,is the long duration of the fixator.In addition to autologous bone grafting,several mechanical,biologic,and external physical treatment modalities may be employed to promote bone formation and maturation during segment transport in osteomyelitis patients.Mechanical approaches include compressive loading of the distraction regenerate,increased frequency of small increments of distraction,and compression-distraction.Intramedullary nailing and hemicorticotomy can reduce the time in external fixation;however,these techniques are associated with technical difficulties and complications.Exogenous application of low-intensity pulsed ultrasound or pulsed electromagnetic fields may shorten the duration of external fixation.Other promising modalities include diphosphonates,physician-directed use(off-label use)of bone morphogenetic proteins,and local injection of bone marrow aspirate and platelet gel at the osteotomy site.Well-designed clinical studies are needed to establish safe and effective guidelines for various modalities to enhance new bone formation during distraction osteogenesis after segment transfer.展开更多
Changdao Island,a hidden gem in east China’s Shandong Province,features breathtaking nature.As the sun cuddles the horizon,the island’s azure sky provides a flawless backdrop to an exquisite panorama.Jagged cliffs c...Changdao Island,a hidden gem in east China’s Shandong Province,features breathtaking nature.As the sun cuddles the horizon,the island’s azure sky provides a flawless backdrop to an exquisite panorama.Jagged cliffs carved by centuries of endless waves stand guard along the shoreline,their rocky silhouettes seemingly frozen in time,summoning ancient majesty.Against this dramatic backdrop,flocks of seagulls take flight,their ivory wings catching the golden hues of the sun,creating an enchanting ballet in the sky.The air is filled with the gentle cries of these graceful birds,enhancing the island’s serenity.This harmonious blend of nature’s elements,from the sapphire sea to the towering cliffs and the mesmerizing flight of seagulls,makes Changdao Island an artistic masterpiece painted by the hand of mother nature herself.展开更多
This study uses an event study methodology to examine how the Chinese market reacts to announcements of involvement in corporate social responsibilitY （CSR） by Southern Weekend （a Chinese newspaper）for Chinese fir...This study uses an event study methodology to examine how the Chinese market reacts to announcements of involvement in corporate social responsibilitY （CSR） by Southern Weekend （a Chinese newspaper）for Chinese firms from 2008 to 2012. Our results show significant and pcsitive market reactions, supporting the instrumental stakeholder theory. We attribute the positive market response to social capital development and real growth options related to the CSR involvement by the Chinese firms.展开更多
Using 1987-2006panel data for China, we explore the dynamics of the skill premium. The present paper focuses on the skill premium as an explanation for why income differences are so large in China. Our empirics show t...Using 1987-2006panel data for China, we explore the dynamics of the skill premium. The present paper focuses on the skill premium as an explanation for why income differences are so large in China. Our empirics show that： the rise in the relative supply of skilled labor results in an increase, instead of a decrease, in the skill premium; domestic investment is not complementary with skill formation; the skill premium is higher in more developed provinces; economic openness facilitates an increase in the skill premium; whether foreign direct investment induces skill-based technology change or not, it drives up the skill premium. An array of policy prescriptions for reducing income differences and ensuring sustained economic growth are provided.展开更多
文摘Gastric cancer poses a significant public health problem, especially in the Far East, due to its high incidence in these areas. Surgical treatment and guidelines have been markedly different in the West, but nowadays this debate is apparently coming to an end. Laparoscopic surgery has been employed in the surgical treatment of gastric cancer for two decades now, but with controversies about the extent of resection and lymphadenectomy. Despite these difficulties, the apparent advantages of the laparoscopic approach helped its implementation in early stage and distal gastric cancer, with an increase on the uptake for distal gastrectomy for more advanced disease and total gastrectomy. Nevertheless, there is no conclusive evidence about the laparoscopic approach yet. In this review article we present and analyse the current status of laparoscopic surgery in the treatment of gastric cancer.
文摘Improving vehicle fuel consumption,performance and aerodynamic efficiency by drag reduction especially in heavy vehicles is one of the indispensable issues of automotive industry.In this work,the effects of adding append devices like deflector and cab vane corner on heavy commercial vehicle drag reduction were investigated.For this purpose,the vehicle body structure was modeled with various supplementary parts at the first stage.Then,computational fluid dynamic(CFD) analysis was utilized for each case to enhance the optimal aerodynamic structure at different longitudinal speeds for heavy commercial vehicles.The results show that the most effective supplementary part is deflector,and by adding this part,the drag coefficient is decreased considerably at an optimum angle.By adding two cab vane corners at both frontal edges of cab,a significant drag reduction is noticed.Back vanes and base flaps are simple plates which can be added at the top and side end of container and at the bottom with specific angle respectively to direct the flow and prevent the turbulence.Through the analysis of airflow and pressure distribution,the results reveal that the cab vane reduces fuel consumption and drag coefficient by up to 20 % receptively using proper deflector angle.Finally,by adding all supplementary parts at their optimized positions,41% drag reduction is obtained compared to the simple model.
基金National Natural Science Foundation of China Under Grant No.50139010
文摘Based on research studies currently being carried out at Dalian University of Technology, some important aspects for the earthquake safety assessmcnt of concrete dams are reviewed and discussed. First, the rate-dependent behavior of concrcte subjected to earthquake loading is examined, emphasizing the properties of concrete under cyclic and biaxial loading conditions. Second, a modified four-parameter Hsieh-Ting-Chen viscoplastic consistency model is developed to simulate the rate-dependent behavior of concrete. The earthquake response of a 278m high arch dam is analyzed, and the results show that the strain-rate effects become noticeable in the inelastic range, Third, a more accurate non-smooth Newton algorithm for the solution of three-dimensional frictional contact problems is developed to study the joint opening effects of arch dams during strong earthquakes. Such effects on two nearly 300m high arch dams have been studied. It was found that the canyon shape has great influence on the magnitude and distribution of the joint opening along the dam axis. Fourth, the scaled boundary finite element method presented by Song and Wolf is employed to study the dam-reservoir-foundation interaction effects of concrete dams. Particular emphases were placed on the variation of foundation stiffness and the anisotropic behavior of the foundation material on the dynamic response of concrete dams. Finally, nonlinear modeling of concrete to study the damage evolution of concrete dams during strong earthquakes is discussed. An elastic-damage mechanics approach for damage prediction of concrete gravity dams is described as an example. These findings are helpful in understanding the dynamic behavior of concrete dams and promoting the improvement of seismic safety assessment methods.
基金the Resaerch Program of Chinese Economy Open Mode under the Innovation Base of Philosophy and Social Science,China Economic Research of Project 985 at the Renmin University of China
文摘Since 1978, the bulk of foreign direct investment （FDI） has gone to the south-eastern coastal areas in China, with only a small portion received inland. With the launch of the Western Development Strategy in 2000 and the Central China Rising Strategy in 2004, the choice of investment locations has expanded to inland areas. Based on panel data covering 98 inland cities from 1999 to 2005, this study identifies location preference variables for FDI invested in China＇s inland areas, and finds that well-established factors such as natural resources and low labor costs are not important factors in determining FDI locations within China＇s inland. Instead, policy incentives and industrial agglomeration are the most important factors. The findings of the present study have policy implications for both host country authorities and multinational corporations.
基金Supported by the National Natural Science Foundation of China, No. 30271663
文摘AIM: To investigate the therapeutic effects of Guiyuanfang and bone marrow stem cells (BMSCs) on rats with liver fibrosis.METHODS: Liver fibrosis model was induced by carbon tetrachloride, ethanol, high lipid and assessed biochemically and histologically. Liver function and hydroxyproline contents of liver tissue were determined.Serum hyaluronic acid (HA) level and procollagen Ⅲ level were performed by radioimmunoassay. The VG staining was used to evaluate the collagen deposit in the liver.Immunohistochemical SABC methods were used to detect transplanted BMSCs and expression of urokinase plasminogen activator (uPA).RESULTS: Serum transaminase level and liver fibrosis in rats were markedly reduced by Guiyuanfang and BMSCs. HA level and procollagen Ⅲ level were also reduced obviously,compared to model rats (HA: 47.18±10.97 ng/mL,48.96±14.79 ng/mL; PCⅢ: 22.48±5.46 ng/mL, 26.90±3.35ng/mL; P＜0.05).Hydroxyproline contents of liver tissue in both BMSCs group and Guiyuanfang group were far lower than that of model group (1 227.2±43.1 μg/g liver tissue, 1390.8±156.3 μg/g liver tissue; P＜0.01). After treatment fibrosis scores were also reduced. Both Guiyuanfang and BMSCs could increase the expression of uPA. The transplanted BMSCs could engraft, survive, and proliferate in the liver.CONCLUSION: Guiyuanfang protects against liver fibrosis.Transplanted BMSCs may engraft, survive, and proliferate in the fibrosis livers indefinitely. Guiyuanfang may synergize with BMSCs to improve recovery from liver fibrosis.
文摘This paper investigates the impact of foreign direct investment （FDI） and exports on urbanization in China. Using prefecture city-level panel data covering China ＂s 262 prefecture cities for the period 2004-2013 and employing a dynamic panel system generalized method of moments model with instrumental variable regression techniques, our study finds that FDI and exports have, on average, played a significantly positive role in China＇s urbanization. However, the impacts of FDl and exports on urbanization vary across regions. FDI has a positive and significant impact on urbanization in the coastal region but has no impact on urbanization in the inland region. Exports have a positive and significant impact on urbanization in both the coastal and inland regions, but the effect is much larger in the coastal region than in the inland region. The results imply that further attracting FDI inflows and promoting exports will contribute to China＇s urbanization, especially for the inland region.
文摘Several hundred species of bacteria inhabit the gut, and affect its cell biology, morphology and homeostasis. Many bacteria are however potential pathogens, especially if the integrity of the epithelial barrier is physically or functionally breached. Conversely, the interaction between host and commensal microbes can confer important health benefits. This has led to commercial and public interest in ＇probiotics＇, live microbes principally taken as food supplements. Might probiotics also be used in disease therapy？ Experimental evidence that probiotics modulate gut physiology, particularly barrier integrity and immunological function, underpins exciting new gastroenterological research. We discuss below the scientific basis for probiotic effects and present a critical perspective for their use in relation to gastrointestinal disease.
基金EU Fifth Framework Program: Environment, Energy and Sustainable Development Research and Technological Development Activity of Generic Nature: The Fight Against Natural and Technological Hazards, Research Project QUAKER Under Contract No. EVG1–CT–2002–00064
文摘To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussees. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimentalp-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including： soil plastification at an early stage of loading, ＂pinching＂ behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. （1974） for sand, is also presented.
基金the National Natural Science Foundation of China (No.7 0225003)the World Bank+1 种基金the Ford Foundationthe Canadian International Development Agency
文摘The present study considers how education affects off-farm job participation and wages. We use a nationally representative dataset from a survey conducted in 5 provinces, 101 villages and 808 households by the authors in early 2005. The empirical results show that educational attainment, skill training and years of experience of rural residents have positive, statistically significant effects on off-farm employment. The average return to a year of education is 7percent, which is higher than those observed in previous studies. We also find the return to an additional year of schooling to be higher for post-junior high schooling than for junior high and below schooling： 11.8 versus 3.2 percent. We conclude that not only does education still pays off in rural China, but also the rate of return to education is increasing over time.
基金supported by the National Natural Science Foundation of China(No.71173223)the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(No.10XNF049)
文摘There is some disagreement in the published literature regarding the definition and the measurement of housing bubbles in China. Extending the analytical framework of Black et al. （2006）, the present paper measures the housing bubbles of China＇s 35 major cities from the second quarter of 1999 to the second quarter of 2010. The results indicate that the housing bubbles in China＇s 35 major cities were relatively small in the sample interval, but the bubbles in eastern metropolises, such as Beijing, Shanghai, Shenzhen, Hangzhou and Ningbo, have been relatively big since 2005. The changing tendency of housing bubbles in most cities highly corresponds with the changes in real estate policies. This paper decomposes the housing bubbles of the 35 cities, and finds a great proportion of irrational bubbles rather than rational intrinsic bubbles generated by price speculation. Based on empirical analysis, this paper proposes policy recommendations for preventing the generation and expansion of housing bubbles.
基金National Natural Science Foundation of China for Innovative Research Groups Under Grant No. 50321803 National Natural Science Foundation of China for Young Scholars Under Grant No. 10402030
文摘A new approach to evaluate the extreme value distribution （EVD） of the response and reliability of general multi-DOF nonlinear stochastic structures is proposed. The approach is based on the recently developed probability density evolution method, which enables the instantaneous probability density functions of the stochastic responses to be captured. In the proposed method, a virtual stochastic process is first constructed to satisfy the condition that the extreme value of the response equals the value of the constructed process at a certain instant of time. The probability density evolution method is then applied to evaluate the instantaneous probability density function of the response, yielding the EVD. The reliability is therefore available through a simple integration over the safe domain. A numerical algorithm is developed using the Number Theoretical Method to select the discretized representative points. Further, a hyper-ball is imposed to sieve the points from the preceding point set in the hypercube. In the numerical examples, the EVD of random variables is evaluated and compared with the analytical solution. A frame structure is analyzed to capture the EVD of the response and the dynamic reliability. The investigations indicate that the proposed approach provides reasonable accuracy and efficiency.
文摘Non-renewable fuel sources have been the predominant energy sources and a significant source of foreign exchange income for Nigeria,while at the same time there is a severe problem of electricity inconsistency and persistent power blackouts in Nigeria.The research aims to end the concern for deficient energy use,and to encourage energy efficiency and sustainability.Nigeria has not maximized the advantages of renewable energy after the denationalisation of its electricity industry despite the current transformation in the power industry and the rising demand for renewable energy supply.The research adopts a doctrinal legal approach with a library-based legal research technique with a comparative legal method.It reveals that the absence of a comprehensible legal regime with encouragement for the use of renewable energy is the fundamental element causing the slow utilization of renewable energy as a substitute source of energy in Nigeria.It is suggested that,among other reforms,there is a need for a comprehensible legal regime on renewable energy and the encouragement of strict implementation of energy regulatory strategies and policies with incentives for the application of renewable energy sources in Nigeria.
文摘In this paper,the dynamic stress concentration and scattering of SH-waves by bi-material structures that possess an interface elliptic cavity are investigated.First,by using the complex function method,the Green's function is constructed.This yields the solution of the displacement field for an elastic half space with a semi-elliptic canyon impacted by an anti-plane harmonic line source loading on the horizontal surface.Then,the problem is divided into an upper and lower half space along the horizontal interface,regarded as a harmony model.In order to satisfy the integral continuity condition, the unknown anti-plane forces are applied to the interface.The integral equations with unknown forces can be established through the continuity condition,and after transformation,the algebraic equations are solved numerically.Finally,the distribution of the dynamic stress concentration factor(DSCF)around the elliptic cavity is given and the effect of different parameters on DSCF is discussed.
文摘Massive segmental bone loss due to chronic osteomyelitis represents a considerable challenge to orthopedic surgeons and is a limb threatening condition.The only option available in such a clinical situation is segment transport using the Ilizarov technique of distraction osteogenesis;yet the most common problem in cases of bone transport with the Ilizarov technique in massive bone loss,is the long duration of the fixator.In addition to autologous bone grafting,several mechanical,biologic,and external physical treatment modalities may be employed to promote bone formation and maturation during segment transport in osteomyelitis patients.Mechanical approaches include compressive loading of the distraction regenerate,increased frequency of small increments of distraction,and compression-distraction.Intramedullary nailing and hemicorticotomy can reduce the time in external fixation;however,these techniques are associated with technical difficulties and complications.Exogenous application of low-intensity pulsed ultrasound or pulsed electromagnetic fields may shorten the duration of external fixation.Other promising modalities include diphosphonates,physician-directed use(off-label use)of bone morphogenetic proteins,and local injection of bone marrow aspirate and platelet gel at the osteotomy site.Well-designed clinical studies are needed to establish safe and effective guidelines for various modalities to enhance new bone formation during distraction osteogenesis after segment transfer.
文摘Changdao Island,a hidden gem in east China’s Shandong Province,features breathtaking nature.As the sun cuddles the horizon,the island’s azure sky provides a flawless backdrop to an exquisite panorama.Jagged cliffs carved by centuries of endless waves stand guard along the shoreline,their rocky silhouettes seemingly frozen in time,summoning ancient majesty.Against this dramatic backdrop,flocks of seagulls take flight,their ivory wings catching the golden hues of the sun,creating an enchanting ballet in the sky.The air is filled with the gentle cries of these graceful birds,enhancing the island’s serenity.This harmonious blend of nature’s elements,from the sapphire sea to the towering cliffs and the mesmerizing flight of seagulls,makes Changdao Island an artistic masterpiece painted by the hand of mother nature herself.
基金the National Natural Science Foundation of China(Approval No.71031003)
文摘This study uses an event study methodology to examine how the Chinese market reacts to announcements of involvement in corporate social responsibilitY （CSR） by Southern Weekend （a Chinese newspaper）for Chinese firms from 2008 to 2012. Our results show significant and pcsitive market reactions, supporting the instrumental stakeholder theory. We attribute the positive market response to social capital development and real growth options related to the CSR involvement by the Chinese firms.
基金the National Science Foundation of China (No.70673072 and 70203008)the National Social Science Foundation (No.06 BJL 039) for financial support.
文摘Using 1987-2006panel data for China, we explore the dynamics of the skill premium. The present paper focuses on the skill premium as an explanation for why income differences are so large in China. Our empirics show that： the rise in the relative supply of skilled labor results in an increase, instead of a decrease, in the skill premium; domestic investment is not complementary with skill formation; the skill premium is higher in more developed provinces; economic openness facilitates an increase in the skill premium; whether foreign direct investment induces skill-based technology change or not, it drives up the skill premium. An array of policy prescriptions for reducing income differences and ensuring sustained economic growth are provided.
