降雨条件下边坡暂态饱和区形成条件与演化特征数值分析

为分析降雨入渗条件下边坡暂态饱和区形成条件与演化特征,开展不同坡度条件下边坡降雨入渗数值模拟计算,分析降雨条件下边坡暂态饱和区形成条件,研究降雨强度、饱和渗透系数、坡度等多因素对边坡暂态饱和区演化特征的影响。研究结果表明,降雨条件下边坡暂态饱和区的形成条件为：①降雨强度大于等于岩土体饱和渗透系数;②降雨入渗进入饱和状态土控制入渗阶段。降雨条件下,降雨入渗影响区、暂态饱和区均持续向下扩展;降雨停止后,地下水位线以上的岩土体孔隙水压力、体积含水气量持续降低,且地下水位线不断升高。降雨强度小于岩土体饱和渗透系数时,降雨入渗影响区扩展速率与降雨强度呈正相关;降雨强度大于等于岩土体饱和渗透系数时,降雨入渗影响区、暂态饱和区扩展速率受降雨强度影响较小。降雨期间,降雨入渗影响区、暂态饱和区扩展速率与饱和渗透系数随深度的变化率δ_kz呈正相关,孔隙水压力峰值与δ_kz呈负相关;降雨停止后,地下水位线、孔隙水压力峰值与δ_kz呈正相关。降雨初期,降雨入渗影响区面积、孔隙水压力峰值与坡度呈正相关;降雨后期及降雨停止后,降雨入渗影响区面积、暂态饱和区面积、地下水位线高度与坡度呈负相关。     

砾石土质条件下葡萄滴灌生育期土壤含水率变化规律研究

为探究酿酒葡萄在砾石土质条件下的土壤含水率变化规律及合理灌溉制度,选取贺兰山东麓砾石土典型试验区,以五年生赤霞珠品种为研究对象,设计2 550、2 850、3 225、3 600 m3/hm24个不同定额的灌水处理,应用TDR土壤水分剖面仪和土壤水势仪,监测生育期滴灌前后不同土层含水率与水势变化,针对监测数据从灌水处理整体与单个生育期不同角度进行分析,研究酿酒葡萄在砾石土条件下不同滴灌定额土壤含水率变化规律,最终提出生育期适宜灌溉制度。研究结果表明:随着灌溉定额的增加,土壤含水率在0~40cm土层范围内变化较明显;不同深度土层土壤水势变化规律与灌溉定额的大小有关;1m深土壤水分蓄存比并不是随着灌水量的增加而增大,而是当灌水量达到某一定额时,随着灌水量的增加,土壤水分蓄存比减小,砾石土单次灌水量高于300 m3/hm2时,土壤水分蓄存比较低,易产生深层渗漏。     

硅藻土对上海潮土和黄泥土耕作性能改良的试验研究

采用硅藻土对上海两种农业土进行改良试验研究,分析了不同硅藻土体积比对上海潮土和黄泥土稠度指标、水稳定性大团聚体含量和击实性能的影响。试验表明:塑、液限值与硅藻土含量相关系数为0.981*、0.971*,并且硅藻土对塑、液限的影响与土的粘性聚合体含量成反比;硅藻土可以明显增加两种土中粒径大于0.25 mm的大团聚体的含量;硅藻土可以显著提高两种土的最优含水率并降低最大干密度,且相关性系数分别为0.993*、-0.999**。由此说明,硅藻土可以提高上海农业土的疏松度和保水性能。     

Efficient markets and Bayes’ rule

Summary. A series of financial anomalies motivated the development of new theories that modify the rational expectations ideal. Two possibilities have been systematically explored. The literature on behavioral finance relaxes the assumption that agents form beliefs according to the laws of probability and assume, instead, that simpler heuristic rules are used. Another stream of the literature assumes that agents process information according to Bayescontent/pn08kthu7f55c2vn/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> rule, but do not posses sufficient information to know the true data generating process. In this paper, Bayesian and Behavioral agents coexist and trade in a standard dynamic asset pricing model. A long-standing conjecture is demonstrated. It is shown that, under suitable assumptions, Bayesian agents drive Behavioral, non-Bayesian agents out of the market. Hence, asset prices are eventually determined under the Bayesian paradigm.Received: 3 June 2004, Revised: 17 September 2004, JEL Classification Numbers: D83.Preliminary versions have circulated under the titles content/pn08kthu7f55c2vn/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">Markets Favor Bayesian Modelscontent/pn08kthu7f55c2vn/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> and content/pn08kthu7f55c2vn/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">Market Selection of Empirical Models under Limited Information.content/pn08kthu7f55c2vn/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> I thank Larry Blume, David Easley, Larry Epstein, Armando Gomes, Bruce Hansen, Lars Hansen, Richard Kihlstrom, Grace Koo, George Mailath, Werner Ploberger, Andrew Postlewaite and Shakeeb Khan for useful comments. I also thank participants at the NBER GE meetings, Evolutionary Finance conference in Zurich, Latin American Meetings of the Econometric Society, Stanford Institute for Theoretical Economics, the Instituto de Matematica Pura e Aplicada, the theory seminar at Brown, Chicago, Harvard-MIT, Minnesota, Penn and Wisconsin. I gratefully acknowledge the financial support from the National Science Foundation Grant SES 0109650.     

上市公司资产减值方向信息含量研究——来自沪深两市2003年的经验证据

我国新颁布的《企业会计准则第8号——资产减值》规定,存货等已确认的资产减值不得转回。针对新准则对资产减值单向计提的规定,本文从资产减值准备计提方向研究上市公司资产减值的信息含量,发现资产减值的计提方向存在信号显示作用。这表明资产减值准备方向传递了公司未来前景的信息,全面取缔资产减值准备的转回将减少资产减值的部分信息含量。     

A note on the projection properties of Hadamard matrices obtained by the first Payley construction

We show that the projections on four factors of an arbitrary orthogonal array of strength 2 allow the estimation of main effects and two-factor interactions when all other effects are assumed to be zero, if those projections satisfy the bounds given by Weilcontent/c9lbcy286wrv25l3/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s theorem. The only exceptions are the Hadamard matrices of orders 16 and 24. A consequence is again the estimability of main effects and two-factor interactions for the projections on four factors of the first Payley construction for arbitrary run size.     

On the evolutionary edge of altruism: a game-theoretic proof of Hamilton’s rule for a simple case of siblings

We offer a game-theoretic proof of Hamiltoncontent/1xpg6xbd1m9h4fqx/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s rule for the spread of altruism. For a simple case of siblings, we show that the rule can be derived as the outcome of a one-shot prisonercontent/1xpg6xbd1m9h4fqx/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s dilemma game between siblings.JEL Classification: A13, C70, D64Correspondence to: Oded Stark, ZEF, University of Bonn, Walter-Flex-Strasse 3, 53113 Bonn, GermanyWe are indebted to an anonymous referee and to Uwe Cantner for helpful comments and suggestions. Partial financial support from the National Institute on Aging (grant RO1-AG13037) and from the Humboldt Foundation is gratefully acknowledged.     

Voting in assemblies of shareholders and incomplete markets

Summary. An economy with two dates is considered, one state at the first date and a finite number of states at the last date. Shareholders determine production plans by voting - one share, one vote - and at content/k90tqkjk7q2f135n/199_2004_Article_537_TeX2GIFEqu1.gif" alt="$\rho$" align="middle" border="0"> -majority stable stock market equilibria, alternative production plans are supported by at most content/k90tqkjk7q2f135n/199_2004_Article_537_TeX2GIFEqu2.gif" alt="$\rho \times 100$" align="middle" border="0"> percent of the shareholders. It is shown that a content/k90tqkjk7q2f135n/199_2004_Article_537_TeX2GIFEqu3.gif" alt="$\rho$" align="middle" border="0"> -majority stable stock market equilibrium exists if content/k90tqkjk7q2f135n/199_2004_Article_537_TeX2GIFEqu4.gif" alt="$$ \rho\ \geq\ \dfrac{S-J}{S-J + 1}, $$" align="middle" border="0"> where S is the number of states at the last date and J is the number of firms. Moreover, an example shows that content/k90tqkjk7q2f135n/199_2004_Article_537_TeX2GIFEqu5.gif" alt="$\rho$" align="middle" border="0"> -majority stable stock market equilibria need not exist for smaller content/k90tqkjk7q2f135n/199_2004_Article_537_TeX2GIFEqu6.gif" alt="$\rho$" align="middle" border="0"> content/k90tqkjk7q2f135n/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s.Received: 23 December 2002, Revised: 14 June 2004, JEL Classification Numbers: D21, D52, D71, G39. Correspondence to: Hervé CrésThe authors are grateful to an anonymous referee for helpful comments and suggestions. Financial support from the Danish Research Councils and hospitality of HEC is gratefully acknowledged by Mich Tvede and support from Fondation HEC is gratefully acknowledged by Hervé Crés.     

The effect of a magazine’s free digital content on its print circulation: Cannibalization or complementarity?

We examine how offering digital content affects demand for print magazines. Using a searchable website archive, we measure the digital content offered by a sample of US consumer magazines from 1996 to 2001. We find strong evidence that digital content cannibalizes print sales. On average, a magazine’s print circulation declines about 3–4% when it offers a website. However, the effect varies with the type of digital content offered. Offering digital access to the entire contents of the current print magazine reduces print sales by about 9%. We find no evidence that digital content complements print magazines. These results are robust to including controls for unobserved magazine, category, and time effects, as well as controls for the impact of contemporaneous price changes and other factors.     

粘土水泥复合浆材强度研究

通过室内试验,研究了水灰比、龄期、粘土加量、压滤效应等对粘土水泥浆材结石无侧限抗压强度的影响。分析试验结果表明,粘土水泥浆无侧限抗压强度和浆液水灰比随着龄期的变化规律呈指数关系。在完全压滤作用下,抗压强度随着压力的增大而大幅提高,且强度随龄期呈二次多项式规律变化,如在0.8 MPa压力作用下,粘土水泥浆材结石28 d无侧限抗压强度增大3倍左右;抗压强度随着粘土加量的增大而减小,粘土加量在50%~60%间出现大幅下降。研究表明,在注浆工程中采用粘土水泥浆材时,应尽可能创造条件产生较充分的压滤效应,控制粘土加量不超过50%,水灰比在2∶1左右,可以获得足够的强度指标。适量添加粘土,这类浆材完全可以用于注浆加固工程中。