Aggregating Smallholder Farmers in Emerging Economies

The agricultural sector plays an important role in emerging economies even though most farmers are trapped in the poverty cycle owing to their smallholdings. Aggregating farmers through formal or informal cooperatives (coops) can enable them to: (i) reduce production cost; (ii) increase/stabilize process yield; (iii) increase brand awareness; (iv) eliminate unnecessary intermediaries; and (v) eliminate price uncertainty. To examine whether these effects will benefit the members of such aggregation when they compete with other individual farmers, we present separate models to capture the essence of these five effects. For each effect, we find that it is beneficial for a farmer to be part of the aggregation only when the size of the aggregation is below a certain threshold. Also, while certain effects are beneficial to the market as a whole, other effects are hurtful due to higher market price and/or lower production quantity.     

西藏山南地区民居院门文化刍议

西藏的建筑艺术是祖国建筑艺术宝库里的珍品,而西藏山南地区的民居院门艺术更是西藏建筑艺术的精品,堪称藏区一绝。笔者经调查研究西藏山南地区民居院门的结构、功能、理念、装饰和民俗,发现其承载着丰富多彩的民族文化内涵。     

城乡因素在老年人抑郁症状影响模型中的调节效应

抑郁症状是衡量老年人心理健康水平的有效指标。本研究采用2006年中国城乡老年人生活状况追踪调查10%数据,运用探索性因素分析、多元线性回归和结构方程模型等方法考察中国老年人的总体抑郁水平,比较抑郁水平的城乡及年龄差异,并对老年人抑郁症状及影响因素进行探索。结果显示,我国老年人抑郁症状较轻,心理健康处于良好水平。农村老年人抑郁症状较城镇老年人明显。健康水平、经济状况、社会支持可有效地预测老年人的抑郁症状。城乡在影响因素模型中起调节效应,健康水平和经济状况对老年人抑郁水平的影响作用受城乡因素的影响,对于农村老年人,经济状况的影响作用大于健康水平;在城镇老年人中表现出完全相反的模式。对于不同的老年人群,应采取有针对性的政策和措施,方能有效减缓老年人抑郁症状,促进心理健康。     

Approximation and Exact Algorithms for Constructing Minimum Ultrametric Trees from Distance Matrices

An edge-weighted tree is called ultrametric if the distances from the root to all the leaves in the tree are equal. For an n by n distance matrix M, the minimum ultrametric tree for M is an ultrametric tree T = (V, E, w) with leaf set {1,..., n} such that d_T(i, j) M[i, j] for all i, j and is minimum, where d_T(i, j) is the distance between i and j on T. Constructing minimum ultrametric trees from distance matrices is an important problem in computational biology. In this paper, we examine its computational complexity and approximability. When the distances satisfy the triangle inequality, we show that the minimum ultrametric tree problem can be approximated in polynomial time with error ratio 1.5(1 + log n), where n is the number of species. We also develop an efficient branch-and-bound algorithm for constructing the minimum ultrametric tree for both metric and non-metric inputs. The experimental results show that it can find an optimal solution for 25 species within reasonable time, while, to the best of our knowledge, there is no report of algorithms solving the problem even for 12 species.     

Optimal Pricing and Rebate Strategies in a Two‐Level Supply Chain

For many product categories, manufacturers and retailers often offer rebates to stimulate sales. Due to certain adverse effects, however, some manufacturers and retailers are contemplating the elimination of their rebate programs. This paper sheds light on the debate about the value of rebate programs by presenting a model for evaluating the conditions under which a firm should offer rebates in a competitive environment. Specifically, we consider a two‐level supply chain comprising one manufacturer and one retailer. Each firm makes three decisions: the regular (wholesale or retail) price, whether or not to offer rebates, and the rebate value should the firm decide to launch a rebate program. We determine the equilibrium of a vertical competition game between the manufacturer (leader) and the retailer (follower), and we provide insights about how competition affects the conditions under which a firm should offer rebates in equilibrium.     

积极情绪的社会功能及其对团队创造力的影响:隐性知识共享的中介作用

情绪是创造力的重要前因变量。当前研究指出,情绪通过认知路径作用于个体创造力,情绪通过动机路径间接作用于创造力。但是很少有研究涉及情绪的社会功能通过人际互动路径作用于团队创造力,即情绪会影响团队成员的隐性知识共享从而作用于创造力。本文采用问卷调查法,通过对57个团队(包含538个团队成员)的调查,从团队层次探讨了个体积极情绪的社会功能通过隐性知识共享作用于团队创造力。研究结果表明:在团队层次,控制了团队成员积极情绪均值后,内在动机均值则不再对团队创造力有显著预测作用;在控制了内在动机均值的情况下,积极情绪均值还能显著影响团队创造力,而隐性知识共享完全中介了积极情绪均值与团队创造力之间的关系。本文的结论对研发团队的创造力管理有一定现实意义。     

网络口碑对游客旅游目的地选择的影响研究

本文从网络口碑的视角研究社区留言对游客旅游目的地选择的影响,以浙江省2007年的各大旅游景区全年接待人数的数据和国内两个旅游网站上的网络口碑信息为样本,运用多元回归法研究了网络口碑数量、口碑态度和口碑质量与旅游景区接待数量之间的关系。研究结果表明,网络评论、旅游博客的数量以及图片数量等与景区接待量具有显著的正相关关系,而评论评分和评论的质量等与景区接待量的正向关系不显著。