LEARNING BY DOING IN THE PRESENCE OF AN OPEN ACCESS RENEWABLE RESOURCE: IS GROWTH SUSTAINABLE?

ABSTRACT. We examine the relationship between growth, resource abundance and trade when the natural resource is renewable and open access and there is inter‐industry learning by doing. We find growth is not sustainable in the closed economy and can be sustained in the open economy only so long as the labor forced engaged in resource extraction shrinks over time. Comparisons of steady state welfare in autarky and free trade reveal that for very high or low world prices of the resource‐based good, it is possible for the economy to gain from trade. However if the price is intermediate, it may instead lose.     

Patient mix optimization in tactical cardiothoracic surgery planning: a case study

Cardiothoracic surgery planning involves different resourcessuch as operating theatre (OT) time, medium care beds, intensivecare beds and nursing staff. Within cardiothoracic surgery differentcategories of patients can be distinguished with respect totheir requirements of resources. The mix of patients is, therefore,an important aspect of decision making for the hospital to managethe use of these resources. A master OT schedule is used atthe tactical level of planning for deriving the weekly OT plan.It defines for each day of a week the number of OT hours availableand the number of patients operated from each patient category.We develop a model for this tactical level planning problem,the core of which is a mixed integer linear program. The modelis used to evaluate scenarios for surgery planning at tacticalas well as strategic levels, demonstrating the potential ofinteger programming for providing recommendations for change.     

Polyesters by lipase-catalyzed polycondensation of unsaturated and epoxidized long-chain α,ω-dicarboxylic acid methyl esters with diols

Long-chain, symmetrically unsaturated α,ω-dicarboxylic acid methyl esters (C₁₈, C₂₀, C₂₆) were obtained by the catalytic metathetical condensation of 9-decenoic, 10-undecenoic, and 13-tetradecenoic acid methyl esters, respectively, with the homogeneous Grubbs catalyst bis(tricyclohexyl phosphine) benzylidene ruthenium dichloride dissolved in methylene chloride. The dicarboxylic acid esters were epoxidized chemoenzymatically with H₂O₂/methyl acetate with Novozym 435^®, an immobilized lipase B from Candida antarctica. Polyesters from symmetrically unsaturated or epoxidized α,ω-dicarboxylic acid methyl esters with 1,3-propanediol or 1,4-butanediol, respectively, were achieved by enzymatic polycondensation with the same biocatalyst applied. With 1,3-propanediol as a substrate, the linear unsaturated and epoxidized polyesters had molecular weights of 1950–3300 g/mol and melting points of 47–75 °C, whereas with 1,4-butanediol as a substrate, the resulting polyesters showed higher molecular weights, 7900–11,600 g/mol, with similar melting points of 55–74 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1601–1609, 2001     

国际互联网与沸石相关的化学化工信息资源

介绍了Internet上与沸石和天然沸石有关的化学化工信息资源,并初步讨论国际互联网和国内互联网上沸石信息量。     

Intrinsic Relations of Bipartite Quantum Resources in Tripartite Systems

Quantum resources play crucial roles for displaying superiority in many quantum communication and computation tasks. To reveal the intrinsic relations hidden in these quantum resources, many efforts have been made in recent years. In this work, the correlations of the tripartite W‐type states based on bipartite quantum resources are investigated. The inter‐relations among the degree of coherence, concurrence, Bell nonlocality, and purity are presented. Considering Bell nonlocal and Bell local (satisfied the Clauser–Horne–Shimony–Holt inequality) states for the two‐qubit subsystems derived from the tripartite W‐type states, exact lower and upper boundaries of the degree of coherence versus concurrence are obtained. Interestingly, exact relation among the degree of coherence, concurrence, and purity is obtained. Moreover, coherence is also closely related to entanglement in two specific scenarios: the tripartite W‐type state under decoherence and a practical system for a renormalized spin‐1/2 Heisenberg model.     

Synthesis and Characterization of Bagasse Poly(methyl methacrylate) Graft Copolymer

Summary: Graft copolymerization of methyl methacrylate (MMA) was carried out on bagasse fibers in an aqueous medium using ceric ammonium nitrate (CAN) as initiator under a neutral atmosphere. In order to obtain the optimum condition for graft copolymerization, the effects of initiator concentration, temperature, time of reaction, and monomer concentration were studied. The maximum grafting percent was found to be 122%. The bagasse grafted poly(methyl methacrylate) was characterized by FTIR and its thermal behavior was characterized by TGA.     

科学开发我国的盐湖资源

随着我国经济的持续发展和国家西部大开发战略的有力实施,我国盐湖资源正处于大规模开发的新阶段。本文阐述了国内外盐湖开发的相关技术与钾肥、锂盐和镁工业的发展状况,并按照资源综合利用的开发要求和可持续发展的原则,对科学开发我国盐湖资源开发的有关问题提出了建议。     

Development of Hemp Fibre – PP Nonwoven Composites

Summary: Nonwoven mats from hemp and polypropylene fibres in various proportions were produced and hot pressed to make composite material. The effect of hemp fibre content and anisotropy in nonwoven mats resulting from the carding technology were examined on the basis of the three-point bending, tensile and impact properties of the resultant composite materials. Because of the hydrophilic nature and poor dimensional stability of cellulosic fibres due to swelling, the effect of water sorption on mechanical performances was also investigated. Optimal mechanical properties were achieved in composites made from 40–50% of hemp fibre by weight. As it was expected, better mechanical properties were found in the specimens cut from the composite sheets parallel to the direction of carding. A strong decrease in three point bending properties was noticed after immersing the composite samples in distilled water for 19 days, while the impact strength increased. Double carding of raw materials resulted in a decreased anisotropy in composite material.     

宁波市高校校园植物现状调查与评价

在对宁波市4所高校校园植物种质资源进行全面调查的基础上,分析了绿化植物的种类、数量、应用频率、植物物种丰富度等,结果表明：这些高校校园共有207种植物,隶属于90科199属,其中乔木45种,占22％;灌木45种,占22％;藤本13种,占6％;草本104种,占50％．人工栽培的绿化植物111种,占植物总数的54％：而杂草有87种,占42％,比例较大,其中薇草（Humulus scandens）、加拿大一枝黄花（Solidago canadensis）、牛筋草（Eleusine indica）对其他植物和校园景观产生了严重影响．校园植物资源丰富度指数为16．86．整体上校园的植物资源较丰富,但绿化结构简单,乔木和草本绿化植物种类较少,校园树种组成类同者较多,种类单一．建议加大植物种类的引种,提高植物种类的丰富度,使校园绿化体系发挥更好的生态效益和景观效果．     

区域水土资源可持续利用评价的脉冲耦合神经网络(PCNN)模型模糊算法的构建与应用——以中国三江平原为例

针对三江平原水土资源区域特点,选择了20个指标,建立了水土资源评价指标体系和标准;对脉冲耦合神经网络模型(PCNN模型)进行了改进,提出基于模糊算法的F-PCNN模型,动态阈值等于区域水土资源评价标准的等级范围,省略了不必要的参数,减少了模型的复杂度,并应用于三江平原水土资源评价中.分析结果表明三江平原创业农场水土资源可持续利用评价等级为Ⅱ级,说明水土资源开发和利用较合理,可持续发展能力较强.应用结果说明F-PCNN模型在三江平原水土资源可持续利用评价中是可行的,既拓展了PCNN的应用领域,又为解决水土资源的分类、评价问题提供了新的思路和方法.