考虑多地层相变的地铁联络通道三维冻结温度场数值模拟

地铁联络通道冻结法施工地层一般为多地层,各地层相变潜热具有差异性,尤其是富水卵砾石层差异较大,目前分析普遍考虑单一地层或极少数地层相变潜热,难以反映真实情况。依托南宁地铁联络通道冻结法施工工程,建立三维瞬态导热模型,并考虑多地层相变潜热,对联络通道的冻结温度场进行探究。结果表明,积极冻结约20 d,冻结圆柱逐渐增加并开始交圈;冻结43.22 d后,冻结帷幕的平均温度下降至-10℃以下。现场温度实测值与数值模拟结果温降趋势基本一致,与模型试验相差较远。     

不同初始损伤白砂岩高温处理后的力学性能研究

通过进行不同初始损伤程度白砂岩在不同等级高温处理后的力学试验,分析了温度和初始损伤对白砂岩的杨氏模量、峰值应力和显微结构等方面的影响。试验结果表明:随着温度的升高,受到初始损伤的白砂岩试件的杨氏模量和抗压强度都呈下降的趋势,初始损伤越大,高温对白砂岩造成的影响越大。通过显微镜观察到随着温度的升高,试块的晶体变小,颗粒的破坏更为破碎,岩屑更多。此外,通过对试验数据的整理,建立了不同初始损伤等级和不同温度等级下白砂岩的本构关系曲线。     

Evaluating Projects and Assessing Sustainable Development in Imperfect Economies

We are interested in three related questions:(1) How should accounting prices be estimated?(2) How should we evaluate policy change in animperfect economy? (3) How can we check whetherintergenerational well-being will be sustainedalong a projected economic programme? We do notpresume that the economy is convex, nor do weassume that the government optimizes on behalfof its citizens. We show that the same set ofaccounting prices should be used both forpolicy evaluation and for assessing whether ornot intergenerational welfare along a giveneconomic path will be sustained. We also showthat a comprehensive measure of wealth,computed in terms of the accounting prices, canbe used as an index for problems (2) and (3)above. The remainder of the paper is concernedwith rules for estimating the accounting pricesof several specific environmental naturalresources, transacted in a few well knowneconomic institutions.     

Open access,common property and scarcity rent in fisheries

Open access resources are frequently not managed efficiently, resulting in falling stock levels and a declining income for fishermen. In the late 1970's, the policy response to this problem was the implementation of 200-mile fishing zones, which enabled the European Union to formulate and implement the Common Fisheries Policy, aimed at (among other things) conservation and distribution of available stocks. In Germany, this shift from an open access regime towards a common property regime had favourable outcomes. The trend of falling prices was reversed. The conclusion was that intertemporal efficiency had increased as a result of (inter)governmental policy. Apparently, a wedge was formed between price and marginal harvesting costs, implying that scarcity rent had returned as a component of prices.     

Teams, Firms and the Evolution of Profit Seeking Behavior

Even as advances in information theory over the last quarter century have cast increasing doubt on the proposition that firms successfully maximize profits, the objective of profit maximization continues to be an axiomatic feature of the neoclassical theory of the firm. This paper attempts to improve our understanding firms by treating the objective function as an open question. Specifically, an ontogenetic thought experiment is undertaken to address the question of what differentiates production teams from firms by asking why team members would sell their control rights to a principal, thereby transforming the team into a firm. What results is an account of the emergence of the objective of profit seeking. Profit seeking emerges endogenously as a more fit alternative than the objective of value maximization, which is less capable of coping with uncertainty through purposive adaptation.     

Trade and Renewable Resources in a Second Best World: An Overview

We provide an overview and introduction to the emerging field of trade and renewable resources, and discuss the potential impact of trade liberalization on welfare and resource conservation. A key factor determining the effect of trade reform is the institutional context or property rights regime, and our survey is organized such that it loosely follows the development of new insights with respect to institutions in this literature. This implies a transition from the benevolent planners model to the polar opposite benchmark of open access in the 1990s. Currently the pendulum is swinging back towards management and regulation, but institutions are treated as endogenous. We discuss and compare various key models in some detail and search for common ground between protagonists and antagonists of free trade. Paper based on Keynote address by Erwin Bulte, 12th Annual Conference of the European Association of Environmental and Resource Economists, Bilbao (Spain), June 28–30, 2003.     

Competition and Regulation in Franchise Bidding

In this work we show that the separation property identified in the franchise bidding literature depends strictly on the hypothesis of coincidence of the regulator's beliefs with those of the competing firms. Nevertheless, in many contexts it is more truthful to hypothesize that the regulator's information is vaguer than that of the producers, so we introduce the possibility that the regulator is dealing with a double informational asymmetry as compared to the firms. In this case, the separation property is no longer valid, and the optimal tariff becomes a decreasing function of the degree of competition exercised during the auction.     

对禁止风景旅游区整体租赁的几点看法

在当前对风景旅游区的产权制度改革中,整体租赁模式运用广泛但争议颇大。本文运用产权理论和旅游相关理论,通过对风景名胜区整体租赁模式的分析,对建设部“禁止风景旅游区整体租赁”的规定提出了几点看法,希望能给我国风景旅游区的制度改革提供参考。     

我国经济体制改革的回顾与展望

我国经济体制改革已有28个年头,取得了四大成就:一是市场经济引进多元化竞争;二是经济高速增长;三是人民生活水平普遍提高;四是中国的国际影响力和竞争力在提升.我国在深化改革中面临诸多的体制性障碍和结构性矛盾,可归纳为四大滞后:一是政府职能转变滞后;二是产权制度改革滞后;三是配套改革滞后;四是经济增长方式的改革滞后.我们要清楚地认识当前的形势,解放思想,坚定信心,做深化改革的促进派.     

Sharing a River

A group of agents located along a river have quasi-linear preferences over water and money. We ask how the water should be allocated and what money transfers should be performed. The core lower bounds require that no coalition should get less than the welfare it could achieve by using the water it controls. The aspiration upper bounds demand that no coalition enjoy a welfare higher than what it could achieve in the absence of the remaining agents. Exactly one welfare distribution satisfies the core lower bounds and the aspiration upper bounds: it is the marginal contribution vector corresponding to the ordering of the agents along the river. Journal of Economic Literature Classification Numbers: D62, C71.