胡杨对非确定性输水响应的生态表征

采用参照对比、实地调查、定点观测的方法,对新疆塔里木河下游长期干旱胁迫输水后不同地下水条件下胡杨生长量、生长势、开花结实以及更新响应的生态表征进行分析。结果表明：输水后一定时段内,胡杨一级枝年轮生长量随地下水埋深增加而降低,可以明确标定输水的响应时间、响应范围和响应程度;随着输水的进行,不同地下水条件胡杨年轮生长量逐步趋近;胡杨大树枯枝比与地下水埋深相关良好,是衡量胡杨生态恢复明确、易测的指标：输水后胡杨在一定范围发生更新,但更新范围、更新方式、更新苗长势及开花结实和保持种子活力所需的地下水条件仍爱输水方式、输水量和输水时间的限制。     

建构跨学科的中国环境与资源社会学

环境社会学与自然资源社会学是关于社会与自然界相互关系的两个主要研究传统。目前关于这两个分支学科的讨论主要是局限在美国学术界内,而其对于其它国家环境和社会研究学科建设的借鉴作用尚未引起足够的重视,这正是本文在中国的学术背景中提出环境社会学与自然资源社会学相互融合问题的原因所在。环境社会学在中国正处于重要的学科建设阶段,垮学科的中国环境与资源社会学在投身中国"资源节约型、环境友好型"社会的建设中完全有希望实现环境社会学与自然资源社会学的实质融合。     

傈僳族垂直农业的生态人类学研究——以云南省迪庆州维西县同乐村为例

云南省迪庆藏族自治州维西傈僳族自治县叶枝镇同乐村是澜沧江流域典型的傈僳族村寨,也是联合国教科文组织命名的生态文化村。同乐村的傈僳族在长期的历史发展中,根据海拔差异创造了一套行之有效的垂直农业系统。该系统最大程度的利用了自然资源,保证了本民族的基本生活需要。本文应用生态人类学的适应理论,利用参与观察法、深度访谈法等人类学田野调查方法,对同乐村傈僳族的垂直农业系统进行了研究。研究表明,傈僳族对生态环境的适应不仅表现在最大程度的利用自然资源,而且形成了一套与之相适应的传统文化体系。但随着滇西北经济社会的发展,同乐村傈僳族垂直农业系统和传统文化体系受到了极大的挑战。只有正确处理经济社会发展与垂直农业系统及与之相适应的传统文化体系之间的关系才能实现经济发展和文化保护同步进行,走一条农业可持续发展之路。     

秦岭自然保护区群成本效益研究(Ⅱ)——成本效益预测

本研究在秦岭自然保护区群成本效益计量研究成果的基础上,对成本效益进行进一步分析及预测。运用统计软件SPSS17.0结合十余种拟合曲线,根据秦岭自然保护区群中7个国家级自然保护区的成本效益截面数据,尝试性地进行了综合效益及三大成本之间关系曲线拟合。研究结果表明：根据模型拟合优度R2大小及显著水平Sig.判断,最终得出了成本效益之间的关系式。即三个拟合函数分别是：①综合效益（Qt）与直接保护成本（Xa）的函数曲线方程为：Qt=-68.244＋870.688Xa-2493.849Xa2＋2304.879Xa3;②综合效益（Qt）与间接保护成本（Xb）的函数曲线方程为：Qt=17.844e1.986Xb;③综合效益（Qt）与机会保护成本（Xc）的函数曲线方程为：Qt=-78.157＋104.775Xc-32.953Xc2＋3.296Xc3。本研究结果可以为国家有关部门进行保护区投资做有益的帮助,同时为陕西省自然保护区保护政策的完善做理论支撑。     

基于农户行为响应的农村居民点整合模式探析——以重庆市合川区兴坝村为例

农村居民点整合作为合理组织和有效配置农村土地资源、改善农村人居环境、促进农业规模经营和提升土地价值的重要手段,对其进行研究具有重要实践意义和理论价值。本研究运用相关行为科学的理论,构建了一个模型对农村居民点整合中农户行为响应的决策过程进行模拟,运用参与式农村评估对模拟过程进行农户调研,结合农户自身资源特征、住房情况与生计发展意愿分析不同类型农户的响应程度,根据不同类型农户农村居民点响应程度的差异凝练出兴坝村农村居民点的4种整合模式：农业发展型整合方式、兼业型整合方式、非农发展型整合方式和保留型整合方式。     

A theory for decoupling lossless coupled tapered lines with applications to directional couplers

A simple theory is presented for decoupling a pair of lossless coupled nonuniform transmission lines (CNUTL), with a common return and supporting TEM waves, into two lossless nonuniform transmission lines (NUTL). This theory is independent of the port terminations, symmetry conditions, etc. The method directly relates the line parameters of the lossless CNUTL's to those of the decoupled lines and vice versa; further, the matrix parameters of the CNUTL's as a four-port are explicitly expressed in terms of those of the decoupled lines as two-ports. This theory is then utilized to study the applications of CNUTL's as directional couplers.It is shown that for CNUTL's to behave as a codirectional coupler, each of the decoupled lines should be a proportional line, while for contradirectional coupler action, the two decoupled lines have to be duals of each other. The coupling response of the codirectional coupler is found to be periodic, while the phase shift between coupled and transmitted signals varies linearly with frequency. The coupling response of various contradirectional couplers with smooth transition at one of the ends, for which the decoupled lines are “basic NUTL's with hyperbolic solutions”, are studied in detail. It is shown that all these couplers have a high-pass response and that the CNUTL's with “hyperbolic cosine squared lines” as decoupled lines have the best response of all the CNUTL's considered.     

Sum and product separabilities of multivariable functions and applications

Necessary and sufficient conditions for reducibility of certain classes of multivariable polynomials are considered. The special case when a polynomial in that class can be factored into a finite product of single variable polynomials is investigated. A set of necessary and sufficient conditions for decomposing a multivariable p.r.f. into a sum of single variable p.r.f.'s is given. Examples to illustrate applications of sum and product separabilities of functions are given.     

Feedback factorizing control of 3-D transfer functions via a canonical state-space model

The problem factorizing (separating) the transfer function of a given SISO 3-D discrete system, ie of a system depending on three independent variables, is considered. The 3-D system is assumed to be available in its transfer function representation, which is converted to a canonical state-space model by a simple inspection procedure. Then applying state-feedback to this canonical model we choose the feedback matrix gain (under certain conditions) such that the transfer function of the closed-loop system has the desireed factorized form, ie a product of three 1-D transfer functions each one being dependent on a single variable. The method is illustrated by a nontrivial numerical example.     

Some aspects of science education in Britain: a comparative study

This article gives a broad picture of science education in Britain, starting with school pupils of about 11 years of age and concluding at the Ph.D. level. In the main it considers the education system from the point of view of students preparing for professional scientific work in basic and applied research as well as those who will leave the system at first degree level for a variety of occupations, ranging from school teaching to development and marketing posts in industry. The article is not directly concerned with the education and training of engineers and technologists. The British system is compared briefly with the educational patterns of several western European countries and the USA.     

The diffusion of moisture in sorbent solids part II. activated alumina

Ordinary and thermal diffusion of moisture in activated alumina are investigated using a new diffusion cell design and scheme of analysis reported earlier. The specific form of the mass flux equation has a pronounced effect on the magnitude of the associated thermal diffusion ratio. In the case of activated alumina-moist air, if a partial pressure gradient is used, then the thermal diffusion term is small if not zero.Free, Knudsen and surface diffusion all play a part in the diffusion through activated alumina. However, surface diffusion makes the major contribution and for this reason the model in this case can be simplified to a two parameter surface model.The activation energy for surface diffusion is constant and is approximately equal to the mean isosteric heat of absorption. In addition, mean pore radius, turtuosity, and other physical constants are computed from the least square fit of experimental data. Furthermore, the model is theoretically consistent over the entire concentration range (0≦ C_A ≦ C_Asat).A new fact about activated alumina (Grade F1) it that it does not transfer moisture in a nonisothermal condition so long as the partial pressures of moisture on the two sides of the pellet are the same. There appears to be no previous report of this fact in the periodical literature.