APPLICATION OF CRITICAL PATH METHOD TO WATER RESOURCES PLANNING1

ABSTRACT. The task of resource management, in this case water resources, is rapidly becoming more complex, particularly because decision making is often contingent upon various prior activities and sets of data. Comprehensive planning is required in order to prevent misallocation of resources or mismanagement in resource development. Such planning involves five general phases which are applicable to any problem faced by society: (1) problem identification; (2) formulation of alternatives; (3) evaluation of alternatives; (4) implementation; (5) review. There have been many attempts to simplify the planning process and effectively carry out these five phases. The experience of the Alberta Water Resources Division has been that the Critical Path Method is one of the most useful tools available today for planning. It involves two basic steps: (1) preparation of a network diagram which (a) identifies all the activities necessary for the completion of a project, (b) correctly sequences these activities, (c) allocates resources; and (2) mathematical computations for scheduling the activities. In other words, this approach breaks a task down into smaller units or activities for easier organization, scheduling, and performance for eventual completion of the project. This paper will illustrate the effectiveness of the Critical Path Method by discussing its application to actual water resources projects.     

基于重整化群理论的采空区煤柱群临界失稳概率研究

为对房柱式采空区煤柱群安全稳定性进行客观评价,以概率分析为手段结合重整化群理论,深入研究了煤柱个体与相邻煤柱之间的荷载传递规律及煤柱群-顶板系统临界稳定性。得出结论:重整化群理论可适用于采空区煤柱群稳定性分析,确定煤柱群临界概率范围为0.147≤p*≤0.333;煤柱失稳荷载传递过程中的损失程度可用荷载传递系数α衡量,临界破坏概率p*随着荷载传递系数α的增加而递减;针对不同工况,需通过试验或现场实测获得传递系数α,才能准确的确定煤柱临界概率p*。     

初始几何缺陷对埋地管道屈曲临界载荷影响研究

管道初始几何缺陷与屈曲临界载荷间的关系已经成为新的研究方向。利用有限元方法对管道初始几何缺陷与临界载荷的关系进行研究,建立管道模型,在特征值屈曲分析基础上,输入不同比例的几何缺陷,逐个分析管道模型中节点的横向位移情况。结果显示,当几何缺陷达到一定程度时,屈曲临界载荷明显降低,且与初始几何缺陷具有线性相关性,利用Matlab对结果作线性拟合,给出了修正后的屈曲临界载荷公式。     

平板膜生物反应器临界通量测定方法研究

临界通量在膜污染控制中是一个非常重要的概念.本文采用通量阶梯式递增法测定平板膜生物反应器的临界通量,在此基础上考察了不同测定参数对临界通量的影响.结果表明,测定临界通量过程中,当初始启动通量小于临界通量时,其对临界通量的测定值影响不大;当通量阶梯递增量增大时,临界通量的测定结果变小;当测定间隔时间段变长时,临界通量的测定结果相应变小.在测定临界通量时,推荐以下测定参数:通量阶梯递增量不大于4 L/(m2·h),测定间隔时间段取15～30 min;初始启动通量的选择要适宜,太大可能导致试验结果的误差.     

流域水环境污染模拟及关键源区鉴别——以义乌江流域为例

以义乌江流域为研究区,应用SWAT模型模拟流域的径流、泥沙与水质过程,在分析流域内水文过程与污染负荷(总氮、总磷)时空分布特征的基础上,采用单位面积负荷指数法确定各子流域的氮磷流失强度,并划分5个等级,进而识别水环境污染的关键源区。结果表明：1)生活污染源是义乌江流域水环境污染的主要来源,氮磷的输入占比分别为52.7%和61.9%;2)氮、磷污染负荷排放主要集中在3—7月,分别占全年的66%和63%,高负荷强度区主要集中在义乌市城西街道、佛堂镇、东阳江镇和双溪乡;3)义乌江流域的关键源区为18个子流域中的4个子流域。基于流域水环境污染定量模拟识别,建立了关键污染源区的识别方法,可为高污染负荷流域的水环境污染防控提供参考。     

我国自然生态系统氮沉降临界负荷评估

过量的氮沉降引起了一系列环境问题并导致生物多样性损失,因此评估当前生态系统氮沉降临界负荷对区域氮管理及其污染控制至关重要.利用稳态质量平衡法估算了当前我国自然生态系统的氮沉降临界负荷,并与氮沉降数据对比,获取了我国超过氮沉降临界负荷的生态系统空间分布情况.结果表明,6%的地区氮沉降临界负荷大于56 kg·(hm²·a)^-1,67%的地区氮沉降临界负荷在14～56 kg·(hm²·a)^-1之间,27%的地区氮沉降临界负荷小于14 kg·(hm²·a)^-1.氮沉降临界负荷较高的区域主要分布在青藏高原东部、内蒙古东北部和南部部分地区.氮沉降临界负荷较低的区域主要分布在青藏高原西部、西北地区和东南部分地区.氮沉降超过临界负荷的区域约占我国的21%,主要分布在东南和东北部分地区.东北、西北和青藏高原地区超临界负荷值普遍低于14 kg·(hm²·a)^-1.因此,未来这些超过氮沉降临界负荷地区的氮素管理和控制更为值得关注.     

Assessment of the risk of excess sulfur input into terrestrial ecosystems of the Kola Peninsula

The tolerance of terrestrial ecosystems of the Kola Peninsula to atmospheric deposition of acid-forming sulfur compounds and the risk of their excess input into these ecosystems have been assessed on the basis of the critical load concept. The most sensitive ecosystems (critical sulfur load <400 equiv/ha per year) occupy 58% of the total area of the peninsula. These are mainly pine, spruce, and birch forests (including open and crooked birch forests) growing on podzols formed on sandy boulder-pebble glacial deposits. The zones of ecological risk cover the northwestern and central parts of the peninsula near the Pechenganikel and Severonikel combined works (20% of the total area).