聚苯乙烯海南自然气候暴露后的老化现象

采用直接气候暴露、玻璃板下暴露和百页窗下暴露三种自然老化方法研究了聚苯乙烯(PS)外观、力学性能和熔体流动速率在海南自然老化过程中的变化,考察了光、热、氧、水对PS老化的影响。结果表明,PS在海南的自然老化以断链反应为主,分子量的下降与太阳辐照强度密切相关;老化过程中,由于试样温度变化所产生的内应力是影响PS力学性能的重要因素;水对PS的各项性能不产生大的影响。     

关于医学摄影的性质与价值属性的思考

传统摄影技术在数字化进程的影响下,发生了"革命",计算机数码影像技术在医院被广泛应用,医学摄影这个带有明显行业性质色彩的摄影门类,这几年迅速从摄影界脱颖而出。医学摄影作为医学科学和摄影技术相结合的产物,在医学科学领域有很高的实用价值,特别是在临床、科研、教学以及学术交流方面应用的十分广泛。虽然,医学摄影有行业特殊性,但是作为一个摄影门类,它又带有摄影的共性,不是孤立而存在,它与科技摄影、新闻摄影、艺术摄影、广告摄影等其它摄影门类有着不可分割的相互渗透关系,其价值属性也由此呈现多元化。作为医学摄影工作者不仅要懂得什么是医学摄影,还要认识医学摄影的价值属性,让手中的"武器"既发挥社会作用,也产生经济效益。     

纳米二氧化硅表面改性及其补强天然胶乳研究

简述了纳米二氧化硅的表面结构、表面改性机理及方法,介绍国内外对纳米二氧化聩表面化学改性及纳米二氧化硅改性天然橡胶复合材料的制备工艺进行详述,最后对纳米二氧化硅改性天然胶乳存在的问题和发展方向进行了展望。     

Catalytic behavior of hybrid Co/SiO2-(medium-pore) zeolite catalysts during the one-stage conversion of syngas to gasoline

The catalytic properties of 10-MR (membered ring) zeolites (ZSM-5, MCM-22, IM-5, ITQ-2, all with a similar Si/Al ratio of ca. 15) in hybrid Co/SiO₂-zeolite catalysts for the direct conversion of syngas to mainly high-octane gasoline-range hydrocarbons has been studied under typical Fischer-Tropsch (FT) conditions: 250 °C, 2.0 MPa, and H₂/CO = 2. Special emphasis has been given to the deactivation behavior and the characterization of the amount and nature of the carbonaceous deposits formed by a combination of techniques (elemental analysis, TGA (thermogravimetric analyses), GC–MS, and DR (diffuse reflectance) UV–vis spectroscopy). The presence of the medium-pore zeolite increases the gasoline yield by about 20–50%, depending on the particular zeolite, and enhances the formation of branched products with respect to the base Co/SiO₂ catalyst, which is explained by the promotion of isomerization and cracking of long-chain (C₁₃₊) n-paraffins formed on the FT component. The initial zeolite activity is mostly determined by the surface acidity rather than by the total amount of Brønsted acid sites, pointing out to the existence of limitations for the diffusion of the long-chain n-paraffins through the 10-MR channels under FT conditions. Thus, ITQ-2 bearing the largest surface area presents the highest initial yield of branched gasoline-range products, followed by ZSM-5, IM-5, and MCM-22. All zeolites experience a loss of activity with TOS, particularly during the initial reaction stages. This deactivation is governed by the morphological and structural properties of the zeolite, which finally determine the amount and location of the coke species, and not by the acidity.     

基于约束三次样条插值函数及其应用

提出了一种新的约束三次样条插值算法,该算法把样条插值的光滑性和线性插值的优越性有机结合在一起,克服越界现象,得到的插值函数更能反映实际问题的特性。     

THE DUAL NATURE OF HYDROPEAKING RIVERS: IS ECOPEAKING POSSIBLE?

Philosophically, the natural flow regime concept is tremendously appealing; however, its application can be challenging for many biologists without the expertise or resources to handle such approaches on their own. This is particularly true on hydropeaking rivers, where incorporating natural flow is sometimes challenging. Additional challenges include our limited understanding of how individual flow components relate to geomorphic and ecological processes. Supplementary to environmental flow approaches is understanding that many hydropeaking rivers are ecologically two different rivers in one: the low flow and high peaking flow. Taxa that require a narrow range of water velocities or cannot withstand rapid changes in discharge would likely be eliminated or competitively disadvantaged under such harsh environmental conditions. As the low and peak flows diverge, the two rivers become increasingly different ecologically, and there will likely be fewer taxa that can withstand such abiotic variability. Deviations from a natural flow regime may result in new constraints on certain fishes and invertebrates, but this does not necessarily mean a loss of productive fish habitat. Viewing hydropeaking rivers as two rivers in one and the risks associated with high to low flow ratios may serve as a more practical and useful perspective towards maintaining altered yet productive rivers while representing a step towards improving the management river ecosystems. © Her Majesty the Queen in Right of Canada 2013.     

仿自然鱼道的一般布置原则及数值模拟研究

拟建的阁山水库会阻断鱼类的洄游通道,为解决鱼类上溯问题,将同时布置仿自然鱼道。基于 仿自然鱼道的一般布置原则,建立了适合研究仿自然鱼道数值模拟的ＣＦＤ模型,并通过物理模型试验研 究成果进行了模型验证和率定。在此基础上对鱼道不同的障碍物布置尺寸和间距开展了优化比较,通 过研究鱼道内的流速分布及流量等水力参数,确定了较合理的障碍物布置形式。研究表明,增大障碍物 的尺寸和减小障碍物的间距均可以增强对水流的阻碍作用。综合分析后推荐本鱼道工程障碍物布置的 较合理形式为:高2．0ｍ,长4．0ｍ,宽2．5ｍ,间距10ｍ。此布置形式在设计工况下,鱼道内的流速范围 为0．3ｍ／ｓ～1．2ｍ／ｓ,主流明确,能够满足各种鱼类的上溯要求。     

Protection through property: from private to river-held rights

ABSTRACT

This article explores how private owners can protect bodies of water through private property rights. It compares the use of conventional property rights in the Netherlands and New Zealand with a novel approach whereby a New Zealand river owns itself.     

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液化天然气（ＬＮＧ）以其清洁性、经济性在２１世纪的世界能源平衡中将会取得更为重要的地位,特别是在中国这样的发展中国家。文章在简要介绍世界ＬＮＧ工业发展历程的基础上,对当前世界ＬＮＧ工业的基础建设等技术、经济现状作了较为详细的介绍,通过对大量数据的整理,结合权威机构的预测,论述了世界ＬＮＧ工业发展趋势和前景。同时还对该工业涉及的经济问题作了基本描述。结合最新资料,提供了中国发展ＬＮＧ工业的前景规划。     

西部开发借鉴国外天然气资源合理利用的研讨

着重从技术和经济性等方面较系统地介绍了南非的Sasol公司的天然气化学合成燃油及其他化学产品的技术 ,同时对这一技术在全球的应用现状及发展趋势进行了综述 ,并结合国内天然气资源的开发合理利用提出了一些建议 ,希望为我有关单位了解国外在这方面的先进经验、合理规划和整体布局我国自然资源的开发和利用 ,特别对西部天然气开发项目能起到积极有益的借鉴和参考作用。