给定度序列图的覆盖成本和反向覆盖成本的研究

具有n个顶点且度序列为(m,2,…,2,1,…,1)(1的重数为m)的连通图不止一个(这些图均为树),而每个树对应唯一一个段序列(l₁,l₂,…,l_m).通过对任意一树移动最长段的悬挂点到最短段悬挂点的方式得到另一树,比较前后两树的覆盖成本和反向覆盖成本,给出了具有最小覆盖成本和反向覆盖成本的极树,并且进一步给出了取得最小覆盖成本和反向覆盖成本的顶点.     

凹形树突状PtCu纳米催化剂的合成及对甲醇的电催化

以邻苯二胺为表面活性剂,通过水热釜法一步制备凹形树突状PtCu双金属纳米催化剂(PtCu NCDs)。PtCu NCDs在电催化甲醇氧化(MOR)的应用中表现出非常高的活性和很强的抗有毒中间体作用。PtCu NCDs对于甲醇氧化的质量活性为(0.53 A·mg^-1 Pt)是商业Pt/C(0.26 A·mg^-1 Pt)的2.04倍。从比活性的CV曲线图对比发现PtCu NCDs(1.07 mA·cm^-2)是商业Pt/C(0.55 mA·cm^-2)的1.95倍。而且,PtCu NCDs(2.76)比商业Pt/C催化剂(1.02)表现出更高的I_f/I_b比值。这些优异的电催化活性可能归功于PtCu NCDs特殊的凹形树突状形貌。     

长三角地区房地产市场是如何实现"去库存"的?

长三角地区在全国房地产"库存"的背景下,实现了房地产市场的不断向好.对长三角地区有关面板数据进行实证研究,实证结果表明房地产开发投资、医院床位数、工业生产总值与人均房地产成交面积呈正相关.城镇人口数,中、长期贷款利率与人均房地产成交面积呈负相关,高收入城市比低收入城市人均房地产成交面积低14.%,教育支出和城镇居民总的可支配收入对人均房地产成交面积影响不显著.     

数量折扣契约下基于成本分担的供应链突发事件协调应对

突发事件会增加供应链成本,如何进行成本分担是决定供应链能否协调应对突发事件的重要因素.用参数分别描述市场需求剧增时增加的生产成本和市场需求剧减时发生的多余产品处理成本,在数量折扣契约基础上,研究突发事件发生后制造商的最优批发价格和零售商的最优订货量,分析其影响因素比较突发事件发生前后包括市场剧增与市场剧减两种情况下的差异,并给出了数值算例.结果表明,成本分担系数和市场需求分布及其变化都会影响最优批发价格和最优订货量,只要根据市场需求变化相应调整契约参数并合理分担由突发事件增加的成本,通过数量折扣契约供应链就能够协调应对突发事件.     

Analysis of the mean squared derivative cost function

In this paper, we investigate the mean squared derivative cost functions that arise in various applications such as in motor control, biometrics and optimal transport theory. We provide qualitative properties, explicit analytical formulas and computational algorithms for the cost functions. We also perform numerical simulations to illustrate the analytical results. In addition, as a by‐product of our analysis, we obtain an explicit formula for the inverse of a Wronskian matrix that is of independent interest in linear algebra and differential equations theory. Copyright © 2017 John Wiley & Sons, Ltd.     

丙烯酸水溶液聚合法制备PTFE/PAA/Nafion膜及其性能

采用廉价的多孔聚四氟乙烯(PTFE)膜作为基底, 用少量的Nafion与PTFE膜复合可制备低成本的质子膜. 但疏水性的PTFE膜与亲水性的Nafion膜结合性不佳. 基于此, 本文对疏水性的PTFE膜材料表面进行设计, 先采用丙烯酸对疏水性的PTFE膜表面进行亲水性改性, 再喷涂亲水性Nafion膜, 完成低成本PTFE/PAA/Nafion膜的制备. 实验结果表明, 改性前的PTFE膜材料水接触角为150°, 改性后的膜接触角变为55.6°, 亲水性大幅上升, 膜的机械强度和尺寸稳定性(断裂强度为25.2 MPa, 80 ℃下的溶胀率为11.9%)均优于Nafion117膜, 而 Nafion用量则节省了60%. PTFE/PAA/Nafion膜具有高质子导通率(80 ℃下达到131.9 mS/cm), 接近于Nafion117膜, 最大功率密度可以达到404.2 mW/cm².     

THE THEORETICAL COST OF SEQUENTIAL AND PARALLEL ALGORITHMS FOR SOLVING LINEAR SYSTEMS OF EQUATIONS

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Evaluating impacts of fish stock enhancement and biodiversity conservation actions on the livelihoods of small‐scale fishers on the Beijiang River,China

Inappropriate development and overexploitation have seriously degraded aquatic resources in China. Stakeholders identified three fish stock enhancement and biodiversity conservation scenarios for the Beijiang River: S1, increased fish restocking; S2, no fishing season and habitat conservation; and S3, strict pollution control. Potential impacts of these actions on the livelihoods of fishers were evaluated using applied economic modeling. Baseline costs and benefits came from logbooks from 30 fishers and a survey of 90 households in three villages. The financial net benefit for a household was US$1583 (￥11,160) annually, representing a 142% and 387% return on capital and operating costs, respectively. Larger catches associated with S1 and S2 generated a net benefit of US$1651 and US$1822, respectively. Strict pollution control resulting in higher catches (+20%) and lower operating costs (?20%) would increase the net benefit by 15.9% to US$1835 annually. Pollution control would benefit other resource users and is a prerequisite for ecological restoration. Recommendations for Resource Managers

• Stringent pollution control measures are essential to conserve aquatic biodiversity and enhance the livelihoods of fishers but will require considerable public and private sector investment.
• Enhanced fish stocks in the Beijiang River could benefit poor livelihoods but may not be sufficient to lift households out of poverty, aged fishers require government assistance to diversify their livelihoods, access alternative urban employment, and survive with dignity.
• Adopting the economic modeling approach presented here could enable responsible authorities to simultaneously evaluate fish stock enhancement and biodiversity conservation options.
• Broader application of the approach presented here could help ensure small‐scale inland fisheries are managed sustainably and aquatic ecosystems are restored and protected by 2020, in line with Target 6 of the United Nations’ Convention on Biological Diversity Strategic Plan for Biodiversity.

     

考虑溯源系统应用的优质农产品双渠道供应链决策研究

优质农产品溯源系统的引入,既能提升有效供给、缩短流通时间,又能降低流通中的数量损耗和价值损失,由此带来了双渠道供应链系统在投资、销售、定价等方面的系列决策问题。考虑制造商开辟电子渠道、从溯源系统降低流通损耗和提高质量出发,分别构建制造商主导型的双渠道供应链决策模型。通过对比分析应用前后各成员在投资、定价及销售方面的最优策略,得到相关的核心边界值。数值仿真结果表明:核心边界值主要与双重损耗的改善程度及其他参数相关,各成员及系统接受溯源系统的应用成本不同,应用成本对各渠道销量的影响程度亦不相同,但各成员调整定价的应用成本边界值是一致的。