Hydrogeological responses in tropical mountainous springs

This study presents a hydrogeochemical analysis of spring responses (2013–2017) in the tropical mountainous region of the Central Valley of Costa Rica. The isotopic distribution of δ¹⁸O and δ²H in rainfall resulted in a highly significant meteoric water line: δ²H?=?7.93·δ¹⁸O?+?10.37 (r^2? =?0.97). Rainfall isotopic composition exhibited a strong amount-dependent seasonality. The isotopic variation (δ¹⁸O) of two springs within the Barva aquifer was simulated using the FlowPC program to determine mean transit times (MTTs). Exponential-piston and dispersion distribution functions provided the best-fit to the observed isotopic composition at Flores and Sacramento springs, respectively. MTTs corresponded to 1.23?±?0.03 (Sacramento) and 1.42?±?0.04 (Flores) years. The greater MTT was represented by a homogeneous geochemical composition at Flores, whereas the smaller MTT at Sacramento is reflected in a more variable geochemical response. The results may be used to enhance modelling efforts in central Costa Rica, whereby scarcity of long-term data limits water resources management plans.     

对当前开发模压全息技术的一些看法

本文介绍了模压全息的新应用,提供了制作模压全息的新技术和有关设备。     

中国城市公共交通行业技术效率实证研究

本文选取1999-2004年间中国城市公共交通行业的面板数据,在Cobb-Douglas函数的基础上运用随机边界法对我国城市公共交通行业的技术效率进行了考察,并从时间、地域、交通工具类型和客运规模方面,分析了该行业的效率差异及其产生原因,旨在为该行业的未来发展和管制改革提供决策依据。研究结果表明,我国城市公共交通行业技术效率情况为:近几年虽有小幅上升,但基数总体不高;东部地区技术效率偏高;客运量大和拥有轨道交通的省市的技术效率较高。     

径向渡越时间振荡器的初步实验研究

 对径向渡越时间振荡器进行了实验研究，在非最优化条件下得到了辐射功率大于30MW、主频为3.66GHz的微波，同时研究了微波功率随电压、电流的变化，所得结果和规律与理论分析和数值模拟基本相符。     

Challenges and Development Opportunities for Catalytic Technologies in Petrochemical Industry in the 21st Century

The propellent drive and development opportunities for future catalytic technologies in petrochemical industry in the 21st century are reviewed in this paper. It focuses on the following five aspects:(1) The environmentally-friendly catalytic technologies, such as new technologies for the production of organic chemicals changing the raw material and synthetic process, the chemicals production replacing phosgene and hydrogen cyanide toxicant, and the conversion and utilization of organic wastes etc.(2) Utilization and development of cheaper light alkanes, for example, the chemical use of natural gas and the development technologies of methane chain, the production of acetic acid, ethylene and vinyl chloride from selective oxidation of ethane, as well as the manufacture of acrolein and acrylonitrile from the oxidation and ammoxidation of propane.(3) The new propylene-plus technologies of the low value higher olefins, such as catalytic cracking of C4,C5 olefins and metathesis of C4 olefin.(4) The technologies of high selective oxidation, e.g. production of propylene oxide with TS-1 molecular sieve, oxidation process by lattice oxygen and direct oxidation of benzene to phenol etc.(5) Development and application of novel catalytic materials, especially, mesopore molecular sieve materials for a larger molecule reaction, zeolite catalyst with MWW structure for alkylation of benzene and propylene, ionic liquid, and membrane reactor catalyst etc.Meanwhile,the challenging research subjects for future industrial catalysis and the several viewpoints for development strategy of new catalytic technologies are proposed. These viewpoints are as follows:(1) Catalysis discipline must be integrated with many other disciplines and should be multidisciplinary and transdisciplinary.(2) New preparation methods of catalytic materials must be originally developed.(3) The instrumentation having better time resolution and spatial resolution and applying under reaction conditions must be improved further.(4) Fundamental research for catalysis and catalytic theory must be enhanced.(5) Catalysis science must be closely integrated with catalytic reaction engineering.(6) Knowledge innovation and technical progress must be accelerated.(7) Scientific and technological co-operation between academic, industrial circles and public organization having a common interest in catalysis must be intensified.     

电磁轨道炮性能的数值模拟

 本文介绍一种简单的数值计算模拟，它可以模拟轨道炮的主要性能。模型中考虑了由于炮膛壁烧蚀引起的电枢等离子体质量的增加和各种阻力的影响。这些阻力包括弹丸与壁之间的摩擦力，等离子体粘性及空气阻力等。用一个经验关系表征它们的影响。我们把等离子体等效成一个可变电阻负载，而不管它与电离度有关性质的细节。数值计算结果与实验结果比较表明符合程度是满意的。     

A Coverage Model for Improving Public Transit System Accessibility and Expanding Access

Accessible and efficient service are vital features of well-utilized public transit systems. Modeling approaches to support the evaluation of transit operations for management and planning are essential for continued improvement. A hybrid coverage model is developed in this paper for simultaneously expanding service access and increasing accessibility. This paper discusses the use and integration of this model in a geographic information system environment for strategic planning. Analysis is presented for public transit service in Brisbane, Australia. The structured model provides flexibility in developing viable policies for addressing system improvements and service expansion, all of which are likely to promote increased utilization of public transit.     

The elixir of life: using a maintenance, repair and replacement model based on virtual and operating age in the water industry

Processing equipment in the water industry is subject to decayand requires maintenance, repair and eventual replacement. Thechallenge of competition within the water industry and the accompanyingregulatory regime requires that actions be integrated and costeffective. This is an industry, which has considerable dataon the failure of its equipment, but until recently very fewmodels of the maintenance process have been built. This paper describes the context of this problem for cleanwater processing where the equipment is that required to purifywater. It proposes a model based on the virtual and operatingage of the components. The operating age reflects the true ageof the equipment while the virtual age allows for the cumulativeeffect of maintenance actions performed on the equipment. Themodel also allows for different types of equipment by describingdegradation by Cox's proportional hazards model. Thus the specialfeatures of the equipment and environment in which the equipmentoperates are described by a set of characteristics, which modifythe hazard rate of the failure time of the equipment. This approachusing Cox's model with virtual and operating age can be appliedto other processing industries including the gas industry andthe ‘dirty water’ side of the water industry. The model is formulated as a stochastic dynamic programmingor Markov decision process and the form of the optimal policyis determined. This shows that repair and replacement shouldonly be performed when the equipment has failed and describesgeneral conditions when replacement is appropriate. The optimalpolicy is calculated numerically using the value iteration algorithmfor a specific example based on data on failure.     

轻工业纤维素生物质过程残渣能源化技术

以农产品为原料的轻工业大都是典型的流程工业,在通过转化过程将原料转化为食品、饮料、添加剂、调味料、纸和中成药等产品的同时产生被称为过程残渣的固体废物与废料,如白酒糟、酒精糟、醋糟、甘蔗渣、中药渣、油粕、酱渣、菌渣和造纸黑液可熔渣等。这些残渣产生于特定的生产过程,富含纤维素、蛋白质或木质素,因此代表一种已经被集中的生物质资源。它们同时含水50%—80%、易腐烂变质、甚至呈弱酸碱性,因此是重要的环境污染源。本文着眼于轻工生物质过程残渣的高值化利用,分析指出富含纤维素的白酒糟、醋糟、甘蔗渣、中药渣、茶渣和造纸边角料等适合作为生物质能源而被转化利用,并根据资源特征提出了可能的技术路线。通过分别对热化学路线涉及的脱水干燥、燃烧发电与气化发电技术和集成乙醇发酵、沼气发酵的复合转化技术进行技术综述,最后针对不同规模的富含纤维素轻工生物质过程残渣能源化提供了技术选择建议。     

化工,石油产品及硅酸盐分析

本文是《分析试验室》定期评述中“化工、石油产品及硅酸盐分析”课题的第六次评述，它评述了１９９５年７月至１９９７年６月国内关于化工产品、石油产品、硅酸盐的分析进展情况，共引用文献６７５篇。