Effective dimensionality of cuprate superconductors

A novel optical method for accurate monitoring of the carrier densityN in layered conductors is introduced. It is applied to several cuprate superconductors, and it is found thatT _c doesnot scale withN. However, if the closely spaced pairs or triplets of CuO₂ planes were coupled together to act as distinct metallic slabs, the relevant variable could ben, theslab carrier density. Indeed, we found thatT _c does scale nicely withn. This suggests that high-T _c superconductivity is effectively a two-dimensional phenomenon; it can occur in a cuprate slab which is only one unit cell thick. Finally, estimates are obtained for the length scales of localization of charge carriers:d 8 Å andd 2 Å in all the cuprates under study.     

大型引调水工程自动化系统设计综述

结合我国大型引调水工程建设情况。逐一描述了南水北调东线工程（江苏省段及山东省段）、南水北调中线工程及河北省南水北调配套工程的自动化系统设计情况．进而分析了各大型引调水工程自动化系统在管理机构设置、调度控制方式、系统结构及功能模块配置、通信传输网络结构等方面的不同,为全面提升河北省南水北调配套工程自动化系统设计提出借鉴经验,具有现实意义及应用价值。     

Excel回归分析拟合河流水位-流量关系

Excel集数据分析、数据计算、图文处理功能为一身,包含了大量的与多变量回归分析相关的函数和工具。利用Excel回归分析拟合河流水位-流量关系的方法比Origin、 MATLAB等专业数据分析软件更为简单实用。文章依据某水文站水位-流量实测数据,以Excel提供的5种趋势预测类型,分别阐述河流水位-流量关系Excel回归分析的方法和步骤,并利用拟合优度参数对拟合结果进行了检验和分析。     

加窗傅里叶变换在谐波分析中的应用

针对稳定状态下的电能质量信号,采用一种组合余弦窗的汉宁窗,将该窗函数与快速傅里叶变换相结合进行电能质量中的谐波分析,并利用Matlab7.0进行仿真验证,发现将窗函数与快速傅里叶变换相结合,在很大程度上能减少谐波泄漏,有效减弱谐波之间的干扰,有利于测量到较为精确的电能信号的幅值和相位.     

Bolt support mechanism based on elastic theory

Mechanical model of anchorage surrounding rock considering tray effect was established based on elastic theory, in order to study the mechanism of bolt supporting. Elastic solutions of normal force at point in the interior of a semi-infinite solid were obtained by means of classical displacement function method in elasticity. The factors which influence stress of bolted surrounding rock, such as the length of bolt and tray effect, were analyzed. The absolute value of stress along bolt axes decreased rapidly with an increase in radical distance and the maximum appeared near ends of bolt. With increasing radical distance, the value of radical stress changed from positive to negative roughly and then increased to zero, with maximum at the middle of bolt. The evolution of hoop stress as radical distance increasing was similar with stress along bolt axes. With an increase in depth, the radical effect ranges of all normal stress components were reduced. These suggest that the effect from tray on stress along bolt axes of bolted surrounding rock could be neglected, except near surface of surrounding rock.     

Reservoir Operation Optimization: A Nonstructural Solution for Control of Seepage from Lar Reservoir in Iran

Abstract

In this paper, the results of utilizing a deterministic dynamic programming model for operation of Lar Reservoir in Iran are discussed. This reservoir has experienced extensive seepage from the start of its operation. The optimization model consists of a three-step cycle, which began with the optimization of reservoir operation for a given set of streamflows. The optimal policies are then analyzed in a regression procedure to obtain a set of operating rules. After the first run, operating rules from the previous run were placed as a new constraint on the water releases with some pre-assigned tolerance and the cycle continues. The model also consisted of mathematical functions for modeling the seepage from Lar Reservoir as a function of storage head in the reservoir. The loss function in the model was also modified in order to incorporate parameters that reduce the seepage. Results of different scenarios showed the significant effect of optimal policies on reduction of seepage and increasing the reliability of water supply to Tehran Metropolitan Area. A pumping station was also proposed to utilize the inactive part of the reservoir, in access of over 100 MCM, in order to reduce the seepage. The effectiveness of different pumping capacities to reduce the seepage was also investigated.     

Water productivity and water footprint: misguided concepts or useful tools in water management and policy?

Water productivity (WP) and water footprint (WFP) are popular concepts in research and discourses on water management. Yet there are concerns about their theoretical validity and practical value. This paper shows that the water production function, the concept with a sound theoretical foundation, is the basis for WP. Total WFP is the reciprocal of WP. The practical value of WP and WFP depends on the context of water use and stress. Maximizing WP, not a panacea to all water problems, mainly suits arid rainfed areas. In other regions, economic and marginal WP for increasing overall production should take precedence in water management and policy decisions.     

水的生态服务功能内涵与 评价方法初探

从水的生态服务功能的机理出发,深入剖析了其内涵与水的两层次生态服务结构,并在此基础上构建评价水的生态服务功能的指标体系,介绍了评价流域水的生态服务功能的主要方法;最后提出了维系流域水的生态服务功能主要思路与手段,为水的生态服务功能研究提供了新思路与新方法。     

“500”供水闸联动稳控系统应用分析

本文介绍了＂500＂水库供水闸联动稳控及水务综合管理系统的设计原则、结构功能、智能控制、运行管理的情况,以为其他供水项目的自动化系统建设提供参考。