水资源短缺风险因子的筛选模型

水资源短缺评价首先需要确定指标体系,投影寻踪模型与灰色关联度法相结合,可以有效地筛选出水资源短缺风险因子,为进一步进行风险评价奠定了基础,同时也为制定风险的防范措施和对策提供了理论依据.综合应用这两种模型,对北京市2001～2009年的水资源短缺风险进行研究,结果表明:降水量、日照时数、雨日数、单位GDP污水排放量、人均GDP、工业总产值占有率、污水处理率和水循环使用率这8个指标是北京市水资源短缺的主要风险因子.     

Recent developments in Dual Resource Constrained (DRC) system research

Real world manufacturing systems are usually constrained by both machine and human resources. Human operators are often the constraining resource and transfer between workstations to process jobs when required. This kind of system is known as a Dual Resource Constrained (DRC) system and presents additional technical challenges which must be considered during planning and scheduling. These technical challenges can be categorised into the five main dimensions of job release mechanisms, job dispatching, worker flexibility, worker assignment and transfer costs. This paper aims to provide an overview of recent developments in DRC research concerned with each of these areas and also discusses some possible approaches to solving the resource scheduling problem in a DRC system. The focus is on materials published after 1995 and up to 2009. Previous reviews on DRC systems are commented on and followed by a review of recent works associated with each of the five dimensions of DRC system research. Advancements made and new methodologies proposed are discussed and future research directions are identified.     

LMI优化问题的择一性定理与对偶

考虑目标函数是线性函数约束条件为线性矩阵不等式的LMI优化问题,讨论了LMI优化问题中的四个择一性定理.每种类型的择一性定理包含两个线性不等式和(或)等式系统,一个原始系统和一个对偶系统.弱择一性定理说明两系统中至多只有其一有解;基于凸集分离理论得到的强择一性定理说明两系统有且仅有其一有解.并在此基础上推导了LMI优化...     

盐湖资源开发利用进展

本世纪头十年里,国际上再度掀起盐湖资源开发热潮。这很大程度上是由于锂的开发热带动的,同时也是和钾肥的广泛施用、价格一路走高有关。南美安第斯高原地区盐湖蕴藏世界70%以上的锂资源,且卤水锂、钾、硼浓度高。该地区极度干旱,少雨多风,非常适合采用卤水盐田蒸发的节能浓缩工艺技术。老的盐湖开发企业则在钾肥需求的带动下,稳步发展。在我国,新疆罗布泊和青海柴达木盆地盐湖则钾锂镁硼产品多元化,经营多元化取得长足进步。本文对近十年来,国内外盐湖开发的新动向做了概括介绍,特别着重于南美"锂三角"地区这一新的生长点。     

NUMERICAL METHOD AND APPLICATION FOR THREEDIMENSIONAL NONLINEAR SYSTEM OF DYNAMICS OF FLUIDS IN POROUS MEDIA

For the system of multilayer dynamics of fluids in porous media, the second order upwind finite difference fractional steps schemes applicable to parallel arithmetic are put forward. Some techniques, such as calculus of variations, energy method, multiplicative commutation rule of difference operators, decomposition of high order difference operators and prior estimates are adopted. Optimal order estimates are derived to determine the error in the second order approximate solution. These methods have already been applied to the numerical simulation of migration-accumulation of oil resources.     

基于非同步替代光谱定标的地表下垫面影响分析

对760nm附近的氧气吸收带,选用植被、枯萎植被、人工地物、沙地和雪地五种典型地表类型,基于模拟数据进行非同步替代光谱定标方法的误差分析,比较不同地表类型得到的光谱定标准确度,为高光谱成像仪的非同步替代光谱定标提供定标图像选择策略.结果表明:运用两种光谱匹配方法——光谱角度匹配和欧氏距离法得到的定标误差基本一致;730~800nm的地表反射率曲线标准差在0.05nm以内时,定标误差集中在±0.5nm范围内;人工地物类型中个别地物如橄榄绿光泽涂料和植被大面积覆盖的图像数据不适合用于非同步替代光谱定标.     

线性增长限制下一类三阶边值问题的可解性

考察了一类含一阶和二阶导数的三阶边值问题的可解性.非线性项f满足线性增长的限制.通过构造适当的Banach空间并利用Leray-Schauder非线性抉择证明了一个存在定理.     

Biobased polyurethanes from polyether polyols obtained by ionic‐coordinative polymerization of epoxidized methyl oleate

A series of poly(ether urethane) networks were synthesized from polyether polyols obtained by ionic‐coordinative polymerization of epoxidized methyl oleate (EMO) using 4,4′‐methylenebis(phenyl isocyanate) or l ‐lysine diisocyanate as coupling agents. Moreover, a variety of segmented poly(ether urethane) networks with different hard segment contents were obtained using 1,3‐propanediol as the chain extender. The materials were characterized by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis, and tensile properties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Unsaturated,biobased polyesters and their cross‐linking via radical copolymerization

Biobased, unsaturated polyesters derived from isosorbide, maleic anhydride, and succinic acid were synthesized and characterized. The presence of maleic anhydride units in the structure of the polyesters allowed converting them into cured coatings by radical copolymerization with crosslinking agents such as 2‐hydroxyethyl methacrylate, N‐vinyl‐2‐pyrrolidinone, acrylic acid or methacrylamide. The investigated polyesters were obtained via bulk polycondensation, catalyzed by titanium(IV) n‐butoxide. 2D NMR and MALDI‐Tof‐MS spectroscopy proved that this polymerization resulted in isomerization of maleic acid units into fumaric ones and in the formation of slightly branched structures by the reaction of isosorbide (end) groups with main chain unsaturated bonds. Moreover, some double bonds proved to have reacted with the condensation by‐product water. The resulting polyesters displayed the expected correlation between variables such as molecular weight and content of unsaturated bonds and their T_g values. Since the thermal properties of the obtained polyesters were appropriate for coating applications, the polymers were crosslinked with unsaturated monomers by radical copolymerization. The crosslinking process was studied using FTIR spectroscopy and by measurements of the soluble part of the cured coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2885–2895, 2010