空气-地源双热源复合热泵低温制热特性实验研究

为缓解单一空气源热泵低温供热性能差的突出问题,设计了空气-地源双热源复合热泵系统。实验研究结果表明,即使在室外-15℃的超低温环境温度工况下,利用少量的低温地下水,复合热泵的制热量较单一空气源热泵提高近50%;能效比提高40%以上。     

Renewable chain transfer agents for metallocene polymerizations: The effects of chiral monoterpenes on the polyolefin molecular weight and isotacticity

Monoterpenes were used as renewable chain transfer agents and polymerization solvents for metallocene/methylaluminoxane (MAO) catalysis. The polymerization of 1‐hexene, ethylene, and propylene in d‐limonene, hydrogenated d‐limonene and α‐pinene is reported. As detected by ¹H NMR analysis of the alkene region, chain transfer to d‐limonene yielded a higher percentage of trisubstituted alkenes. Size exclusion chromatography detected a decrease in molecular weight values resulting from chain transfer to d‐limonene. The [mmmm] pentads for isotactic polypropylene were characterized by ¹³C NMR and FTIR spectroscopy. Propylene polymerizations with the Et(Ind)₂ZrCl₂/MAO and Me₂Si(Ind)₂ZrCl₂/MAO catalyst systems in d‐limonene gave [mmmm] pentad values as high as 0.97. For the Et(Ind)₂ZrCl₂/MAO catalyst system at 0 °C, the mol fraction of [mmmm] pentads increased from 0.86 to 0.94 upon switching the solvent from toluene to d‐limonene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3150–3165, 2007     

Covalent modification of multiwalled carbon nanotubes with a low molecular weight chitosan

Covalent modification of shortened multiwalled carbon nanotubes (MWNTs) with a natural low molecular weight chitosan (LMCS) was accomplished by the nucleophilic substitution reaction. The LMCS modified MWNTs (MWNT-LMCS) were characterized by FTIR, solid-state 13C NMR, and XPS spectroscopies, thermogravimetric analysis, and transmission electron microscopy. The results revealed that amino and primary hydroxyl groups of the LMCS participated mainly in the formation of the MWNT-LMCS conjugates. The MWNT-LMCS consists of 58 wt.% LMCS, and about four molecular chains of the LMCS were attached to 1000 carbon atoms of the nanotube sidewalls. As a novel derivative of the MWNTs, the MWNT-LMCS not only solved in DMF, DMAc and DMSO, but also in aqueous acetic acid solution.     

信息资源的开发与检索

信息资源建设是信息研究的一个重要课题,也是知识创新的一个途径。立足实际情况,讲述了制定信息资源开发的原则、如何合理配置信息资源和如何采集电子文献与网上信息资源及建立信息导航库。给出了push技术、WWW信息挖掘技术和网上信息直接检索等3种信息资源的开发技术。论述了网络时代信息检索的特点及变化和引进全文检索数据库的重要性及网上信息直接检索方式的实现。     

Analysis of the third European survey on working conditions with composite indicators

A composite indicator Working conditions for comparing European countries is constructed from data of the Third European Survey on Working Conditions. The main findings are as follows: (a) European countries differ with respect to working conditions statistically more significantly than with respect to earnings; it implies a quite accurate discrimination threshold in ranking countries with respect to working conditions, (b) working conditions and earnings positively correlate over the whole of Europe but correlate little within single countries; it indicates at the prevailing role of national determinants over professional or social specificities as contributing to the average working conditions, and (c) earnings play no essential role in subjective estimations, including job satisfaction, which mainly depends on working conditions; consequently, more attention should be paid to improving the latter.     

Numerical simulation and application of three-dimensional oil resources migration-accumulation of fluid dynamics in porous media

Numerical simulation of oil migration and accumulation is to describe the history of oil migration and accumulation in basin evolution. It is of great value in evaluation of oil resources and determination of the location and amount of oil deposits. Based on such actual conditions as the effects of fluid mechanics in porous media and 3-dimensional geology characteristics, a kind of modified method of second order upwind finite difference fractional steps implicit interactive scheme was put forward. As for the actual problem of Dongying hollow, Huimin hollow, Tanhai region and Yangxin hollow in Shengli Petroleum Oil Field, a numerical simulation test was carried out, and the result is basically coincident with the actual conditions. For the model problem, optimal order estimates were derived. Thus the well-known problem on oil resources was solved. Supported by the National Basic Research Program of China (Grant No. 1999032803), the National Program for Tackling Key Problems (Grant No. 20050200069), the National Natural Science Foundation of China (Grant Nos. 10771124 and 10372052), and the Doctorate Foundation of the Ministry of Education of China (Grant No. 20030422047)     

DOES A RENEWABLE NATURAL RESOURCE USUALLY HAVE MANY NEAR‐OPTIMAL ALLOCATION PATHS?

ABSTRACT. Utilizing a deterministic single‐species computational renewable natural resource model, it is found that there exist many dynamic allocation paths near‐optimal to the efficient path, where the latter maximizes conventionally‐defined social welfare. Some alternative paths involve substantial trading of surplus over time among market participants and hold different implications for income distribution. Universality of findings cannot be asserted, but the results are intuitively plausible and suggest that multiple near‐optimal allocation paths may exist in related models as well. Existence of many near‐optimal paths holds significant implications for theory and policy.     

The economics of water resources for the generation of electricity and other uses

An optimal control approach is used to analyze the tradeoff between the use of water resources for electricity generation versus other economic uses (irrigation, industry, etc.). For that purpose, a dynamic model is presented which establishes relationships between economic growth, water resources management, and energy policy in the context of the aforementioned tradeoff, in an economy whose energy matrix is heavily dependent upon hydroelectric power. Among other results, the analysis establishes that in the market, the price of water for non-energy uses should be twice the price of the energy goods, indicating the necessity of substituting other sources of energy for hydroelectric power.     

Basin-wide cooperative water resources allocation

The Cooperative Water Allocation Model (CWAM) is designed within a general mathematical programming framework for modeling equitable and efficient water allocation among competing users at the basin level and applied to a large-scale water allocation problem in the South Saskatchewan River Basin located in southern Alberta, Canada. This comprehensive model consists of two main steps: initial water rights allocation and subsequent water and net benefits reallocation. Two mathematical programming approaches, called the priority-based maximal multiperiod network flow (PMMNF) method and the lexicographic minimax water shortage ratios (LMWSR) technique, are developed for use in the first step. Cooperative game theoretic approaches are utilized to investigate how the net benefits can be fairly reallocated to achieve optimal economic reallocation of water resources in the second step. The application of this methodology to the South Saskatchewan River Basin shows that CWAM can be utilized as a tool for promoting the understanding and cooperation of water users to achieve maximum welfare in a river basin and minimize the potential damage caused by water shortages, through water rights allocation, and water and net benefit transfers among water users under a regulated water market or administrative allocation mechanism.     

两端固定资源连续分配问题的区间根式解算法证明

对两端固定资源连续分配问题,动态规划解法过程复杂.针对目标函数及约束条件均为线性函数的此类问题,给出一个根式解的算法证明,将针对点的根式解的算法推广到区间的根式解,使该根式解的算法真正具有实用性.