林毅夫（1990）提出了解释中国农业集体化运动失败的博弈论假说，林的这一阵弈论假说在国际上引起了争论，董和道（Dong and Dow，1993）在论文《自由退礼能减少生产队中的偷懒吗？》对林的博弈论假说提出了挑战，文中指出，合作社成员...林毅夫（1990）提出了解释中国农业集体化运动失败的博弈论假说，林的这一阵弈论假说在国际上引起了争论，董和道（Dong and Dow，1993）在论文《自由退礼能减少生产队中的偷懒吗？》对林的博弈论假说提出了挑战，文中指出，合作社成员之间的相互偷懒策略只有在对退出施加一定成本的条件下才是有效的，否则偷懒者将选择退社以逃避惩罚，本文沿着董和道的模型继续分析，得出的结论具有戏剧性：（1）合作社的成功与退社槛无关，无论是林的假说还是Dong ＆ Dow的结论都是片面的，中国集体化运动的失败主要归因于政策失误。（2）在解决当前中国“三农”问题方面，农村集体合作经济是一种有效的组织形式，而家庭联产承包责任制只是一种次优选择。展开更多
Anti-globalization trends are in play in the US and Western Europe where electorates are recalcitrant to allow immigrants into their societies, national sovereignty is sought in certain geographic areas, and the natio...Anti-globalization trends are in play in the US and Western Europe where electorates are recalcitrant to allow immigrants into their societies, national sovereignty is sought in certain geographic areas, and the national mood seeks to suppress newly rising countries' trade and development. The continuation of economic downturn in Western countries is reinforced by their internal wealth gap and external competition. As capitalism's demand for profit is now being critiqued along with the emergent profit prospects to be delivered by pending technological progress, the temper of the times could temporarily slow down but not reverse globalization. Timely discussions about reform of international economic order and about an effective national development model should seek sustainable solutions for healthy, stable globalization and development of the world economy.展开更多
This article focuses on the development and content of an empowerment programme for staff members at a service centre. An empowerment programme for staffworking with retired volunteers can bring about better knowledge...This article focuses on the development and content of an empowerment programme for staff members at a service centre. An empowerment programme for staffworking with retired volunteers can bring about better knowledge and understanding of elderly persons. This can lead to the target group being ideally managed and understood. The personnel work and interact on a daily basis with retired volunteers. The empowering programme includes matters such as the life circumstances of retired volunteers, the value that retired volunteers have, for the functioning of the service centre, the reasons for utilising retired volunteers, what volunteers expect of staff members, and the motivation of retired volunteers to be involved in the various activities of a service centre for the elderly to benefit the staff members themselves. By presenting and evaluating the empowerment programme, staff members will be able to become functional units in utilising elderly volunteers to the fullest possible in order to benefit the staff members, the retired volunteers, and the community at large.展开更多
New embeddings of some weighted Sobolev spaces with weights a(x)and b(x)are established.The weights a(x)and b(x)can be singular.Some applications of these embeddings to a class of degenerate elliptic problems of the f...New embeddings of some weighted Sobolev spaces with weights a(x)and b(x)are established.The weights a(x)and b(x)can be singular.Some applications of these embeddings to a class of degenerate elliptic problems of the form-div(a(x)?u)=b(x)f(x,u)in?,u=0 on??,where?is a bounded or unbounded domain in RN,N 2,are presented.The main results of this paper also give some generalizations of the well-known Caffarelli-Kohn-Nirenberg inequality.展开更多
Aims Grasslands are globally threatened by climate changes and unsustainable land-use,which often cause transitions among alternative stable states,and even catastrophic transition to desertification.Spatial vegetatio...Aims Grasslands are globally threatened by climate changes and unsustainable land-use,which often cause transitions among alternative stable states,and even catastrophic transition to desertification.Spatial vegetation patch configurations have been shown to signify such transitions at large spatial scale.Here,we demonstrate how small-scale patch configurations can also indicate state transitions.Methods The whole spatial series of degradation successions were chosen in alpine grasslands characterized as seven typical communities.Patch numbers,and perimeter and cover of each patch were recorded using adjacent quadrats along transects in each type of the communities.Species abundance within each patch was measured.Important Findings Across seven grazing-induced degradation stages in the world’s largest expanse of grassland,from dense ungrazed turf to bare black-soil crust,patch numbers and perimeters first increased as patch cover decreased.Numbers and perimeters then decreased rapidly beyond an intersection point at 68%of initial continuous vegetation cover.Around this point,the vegetation fluctuated back and forth between the sedge-dominated grassland breaking-up phase and the forb-dominated phase,suggesting impending shift of grassland state.This study thus demonstrates how ground-based small-scale vegetation surveys can provide a quantitative,easy-to-use signals for vegetation degradation,with promise for detecting the catastrophic transition to desertification.展开更多
In this paper, the author studies the regularity of solutions to the Dirichlet problem forequation Lu = f, where L is a second order degenerate elliptic operator in divergence form inΩ, a bounded open subset of Rn (n...In this paper, the author studies the regularity of solutions to the Dirichlet problem forequation Lu = f, where L is a second order degenerate elliptic operator in divergence form inΩ, a bounded open subset of Rn (n ≥ 3).展开更多
Community detection in networks has been studied extensively in the last decade. Many criteria, expressing the quality of the partitions obtained, as well as a few exact algorithms and a large number of heuristics hav...Community detection in networks has been studied extensively in the last decade. Many criteria, expressing the quality of the partitions obtained, as well as a few exact algorithms and a large number of heuristics have been proposed. The parsimony criterion consists in minimizing the number of edges added or removed from the given network in order to transform it into a set of disjoint cliques.Recently Zhang, Qiu and Zhang have proposed a weighted parsimony model in which a weight coefficient is introduced to balance the numbers of inserted and deleted edges. These authors propose rules to select a good value of the coefficient, use simulated annealing to find optimal or near-optimal solutions and solve a series of real and artificial instances. In the present paper, an algorithm is proposed for solving exactly the weighted parsimony problem for all values of the parameter. This algorithm is based on iteratively solving the problem for a set of given values of the parameter using a row generation algorithm. This procedure is combined with a search procedure to find all lowest breakpoints of the value curve(i.e., the weighted sum of inserted and deleted edges). Computational results on a series of artificial and real world networks from the literature are reported. It appears that several partitions for the same network may be informative and that the set of solutions usually contains at least one intuitively appealing partition.展开更多
The purpose of this paper is to study the asymptotic behavior of the positive solutions of the problem tu- △u=au-b（x）up in Ω×R＋,u（0）=u0,u（t ）｜ Ω=0, as p→ ＋∞, where Ω is a bounded domain, and b（x...The purpose of this paper is to study the asymptotic behavior of the positive solutions of the problem tu- △u=au-b（x）up in Ω×R＋,u（0）=u0,u（t ）｜ Ω=0, as p→ ＋∞, where Ω is a bounded domain, and b（x） is a nonnegative function. The authors deduce that the limiting configuration solves a parabolic obstacle problem, and afterwards fully describe its long time behavior.展开更多
文摘林毅夫（1990）提出了解释中国农业集体化运动失败的博弈论假说，林的这一阵弈论假说在国际上引起了争论，董和道（Dong and Dow，1993）在论文《自由退礼能减少生产队中的偷懒吗？》对林的博弈论假说提出了挑战，文中指出，合作社成员之间的相互偷懒策略只有在对退出施加一定成本的条件下才是有效的，否则偷懒者将选择退社以逃避惩罚，本文沿着董和道的模型继续分析，得出的结论具有戏剧性：（1）合作社的成功与退社槛无关，无论是林的假说还是Dong ＆ Dow的结论都是片面的，中国集体化运动的失败主要归因于政策失误。（2）在解决当前中国“三农”问题方面，农村集体合作经济是一种有效的组织形式，而家庭联产承包责任制只是一种次优选择。
文摘Anti-globalization trends are in play in the US and Western Europe where electorates are recalcitrant to allow immigrants into their societies, national sovereignty is sought in certain geographic areas, and the national mood seeks to suppress newly rising countries' trade and development. The continuation of economic downturn in Western countries is reinforced by their internal wealth gap and external competition. As capitalism's demand for profit is now being critiqued along with the emergent profit prospects to be delivered by pending technological progress, the temper of the times could temporarily slow down but not reverse globalization. Timely discussions about reform of international economic order and about an effective national development model should seek sustainable solutions for healthy, stable globalization and development of the world economy.
文摘This article focuses on the development and content of an empowerment programme for staff members at a service centre. An empowerment programme for staffworking with retired volunteers can bring about better knowledge and understanding of elderly persons. This can lead to the target group being ideally managed and understood. The personnel work and interact on a daily basis with retired volunteers. The empowering programme includes matters such as the life circumstances of retired volunteers, the value that retired volunteers have, for the functioning of the service centre, the reasons for utilising retired volunteers, what volunteers expect of staff members, and the motivation of retired volunteers to be involved in the various activities of a service centre for the elderly to benefit the staff members themselves. By presenting and evaluating the empowerment programme, staff members will be able to become functional units in utilising elderly volunteers to the fullest possible in order to benefit the staff members, the retired volunteers, and the community at large.
基金supported by National Natural Science Foundation of China (Grant Nos. 11171092, 11571093 and 11371117)
文摘New embeddings of some weighted Sobolev spaces with weights a(x)and b(x)are established.The weights a(x)and b(x)can be singular.Some applications of these embeddings to a class of degenerate elliptic problems of the form-div(a(x)?u)=b(x)f(x,u)in?,u=0 on??,where?is a bounded or unbounded domain in RN,N 2,are presented.The main results of this paper also give some generalizations of the well-known Caffarelli-Kohn-Nirenberg inequality.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)(grant no.2019QZKK0302)the National Key Research and Development Program(2016YFC0501802,2016YFC0501803)the National Natural Science Foundation of China(41671263,41730752).
文摘Aims Grasslands are globally threatened by climate changes and unsustainable land-use,which often cause transitions among alternative stable states,and even catastrophic transition to desertification.Spatial vegetation patch configurations have been shown to signify such transitions at large spatial scale.Here,we demonstrate how small-scale patch configurations can also indicate state transitions.Methods The whole spatial series of degradation successions were chosen in alpine grasslands characterized as seven typical communities.Patch numbers,and perimeter and cover of each patch were recorded using adjacent quadrats along transects in each type of the communities.Species abundance within each patch was measured.Important Findings Across seven grazing-induced degradation stages in the world’s largest expanse of grassland,from dense ungrazed turf to bare black-soil crust,patch numbers and perimeters first increased as patch cover decreased.Numbers and perimeters then decreased rapidly beyond an intersection point at 68%of initial continuous vegetation cover.Around this point,the vegetation fluctuated back and forth between the sedge-dominated grassland breaking-up phase and the forb-dominated phase,suggesting impending shift of grassland state.This study thus demonstrates how ground-based small-scale vegetation surveys can provide a quantitative,easy-to-use signals for vegetation degradation,with promise for detecting the catastrophic transition to desertification.
文摘In this paper, the author studies the regularity of solutions to the Dirichlet problem forequation Lu = f, where L is a second order degenerate elliptic operator in divergence form inΩ, a bounded open subset of Rn (n ≥ 3).
文摘Community detection in networks has been studied extensively in the last decade. Many criteria, expressing the quality of the partitions obtained, as well as a few exact algorithms and a large number of heuristics have been proposed. The parsimony criterion consists in minimizing the number of edges added or removed from the given network in order to transform it into a set of disjoint cliques.Recently Zhang, Qiu and Zhang have proposed a weighted parsimony model in which a weight coefficient is introduced to balance the numbers of inserted and deleted edges. These authors propose rules to select a good value of the coefficient, use simulated annealing to find optimal or near-optimal solutions and solve a series of real and artificial instances. In the present paper, an algorithm is proposed for solving exactly the weighted parsimony problem for all values of the parameter. This algorithm is based on iteratively solving the problem for a set of given values of the parameter using a row generation algorithm. This procedure is combined with a search procedure to find all lowest breakpoints of the value curve(i.e., the weighted sum of inserted and deleted edges). Computational results on a series of artificial and real world networks from the literature are reported. It appears that several partitions for the same network may be informative and that the set of solutions usually contains at least one intuitively appealing partition.
基金Project supported by Fundaco para a Ciência e a Tecnologia (FCT) (No. PEst OE/MAT/UI0209/2011)supported by an FCT grant (No. SFRH/BPD/69314/201)
文摘The purpose of this paper is to study the asymptotic behavior of the positive solutions of the problem tu- △u=au-b（x）up in Ω×R＋,u（0）=u0,u（t ）｜ Ω=0, as p→ ＋∞, where Ω is a bounded domain, and b（x） is a nonnegative function. The authors deduce that the limiting configuration solves a parabolic obstacle problem, and afterwards fully describe its long time behavior.
