稻鳅共生种养模式试验研究

[目的]稻鳅共生是典型的稻田综合利用模式,符合生态农业发展方向。通过对稻鳅共生生态系统的生理生态学机制开展试验研究,为进一步推广稻鳅共生种养模式提供科学依据。[方法]采用田间试验方法,以水稻单作为对照,研究了不同泥鳅养殖密度下的稻鳅共生对水稻农艺性状、土壤理化性质、水稻产量构成的影响,并对稻鳅共生种养模式进行了经济效益分析。[结果]与对照处理相比,水稻长势在株高、有效分蘖率、根长等方面有一定提高。养殖田水稻株高增高了3%,有效分蘖率提高了8%~11%,根长提高了8.8%~31.3%。在土壤理化性质方面,与对照相比,土壤容重降低了7.1%~21.2%,孔隙度增加了4.1%~14.7%。实验前后养殖田内土壤有机质增加了3.5%~26.5%,对照田降低了2.5%~5.8%。土壤肥力(氮、磷、钾)减少,但减少幅度小于对照处理。稻鳅共生种养模式下水稻产量提高了5%~25%,同时稻田增收泥鳅1 725~3 375kg/hm2,净收入为1.836 0万~2.307 0万元/hm2,经济效益提高了3.65~4.84倍。稻鳅共生种养模式中泥鳅的养殖密度为30万尾/hm2时稻田的生态效益和经济效益最佳。[结论]稻鳅共生有效改善了土壤理化性质,促进了水稻的生长,提高了稻田产量和产值。     

Estimating yield curves of the U.S. Treasury securities: An interpolation approach

Following the approach of interpolation, this paper proposes the multiple exponential decay model to fit yield curves for both the U.S. TIPS market and the conventional Treasury security market. Several estimation methods, including the unconstrained/constrained nonlinear minimization, quadratic programming, and the iterative linear least squares, are applied to estimate the unknown parameters according to different curve‐fitting purposes. Comparisons between the proposed model and the alternatives show that the multiple exponential decay successfully (1) adapts to a variety of shapes associated with yield curves, (2) (partially) keeps in line with the economic interpretations of Nelson–Siegel summarized by Diebold and Li ( 2006 ), and (3) dominates the competing models in curve‐fitting performance measured by mean fitted‐price errors over the sample period. In addition, the exact specification of a nonparametric interpolation model is pinned down by applying three statistical tools, which enable us to jointly take into account validity, optimality, and parsimoniousness of the proposed model.     

Some Potential Linkages for Input-Output Analysis with Flow-of-Funds

Three major, interrelated accounting statements, at the frontiers of quantitative economic analysis, are three interrelated systems, namely: (1) National income and product accounts (NIPA), (2) The input-output tableaux, (IO), and (3) flow-of- funds accounts (FF). The third-mentioned system is somewhat less available and used in only limited areas of macroeconomic analysis. This paper is mainly concerned with use of FF accounting systems. This system shows where financial resources originate, and where they go in support of real capital formation. In this respect, interest rates and other market-based financial rates are of key importance. While much macroeconomic analysis is based on the rates that fit the yield curve, showing the interest rate structure over various maturities of debt associated with a given degree of risk. In contrast, the FF accounts throw light on the whole spectrum of interest rates, across maturities and debt qualities. For example, in analysis of the real estate market and funding of capital formation there, it is important to have a full understanding of the course of mortgage rates of different maturities and qualities. In short, it is necessary to develop a full appreciation of supply and demand forces in the mortgage market, which often is not obviously related to movements of the operative rate for monetary policy, such as very short-term inter bank rates or call money rates. This paper attempts to provide material from the flow-of-funds accounts that would make it possible to analyze the movement of relevant mortgage rates or whatever other rates are needed to understand the financing of capital formation in real estate.     

On the test of the correction mechanism for mis-pricing between assets using a statistical yield spread model

This paper investigates the existence of a correction mechanism for mis-pricing between Japanese stock and bond. By this correction mechanism we mean that when deviations occur from the equilibrium levels of the expected return differentials between stock and bond — the risk premium differentials, the market will tend to correct the mis-pricing and bring the expected return differentials back to the equilibrium levels. We assume that the yield spread between the predicted earnings price ratio of stock and the yield to maturity of bond reflects the risk premium between stock and bond, and estimate the equilibrium risk premium differentials and mis-prices between stock and bond by modelling their behaviors with a statistical yield spread model (SYS). Empirical results strongly indicate the existence of the mis-pricing correction mechanism, suggesting the inefficiency of securities markets.     

汇率波动模型与人民币汇率调整新趋势

文章对四种汇率波动模型进行简要介绍与说明,指出中国渐进式的改革和开放决定了入世后人民币汇率的制度调整也应是渐进式的,现阶段人民币汇率制度的选择应实行目标区汇率制。     

Modeling Conditional Yield Densities

Given the increasing interest in agricultural risk, many have sought improved methods to characterize conditional crop-yield densities. While most have postulated the Beta as a flexible alternative to the Normal, others have chosen nonparametric methods. Unfortunately, yield data tends not to be sufficiently abundant to invalidate many reasonable parametric models. This is problematic because conclusions from economic analyses, which require estimated conditional yield densities, tend not to be invariant to the modeling assumption. We propose a semiparametric estimator that, because of its theoretical properties and our simulation results, enables one to empirically proceed with a higher degree of confidence.     

钢板桩围堰在水位变动区和软弱地基中的应用

利用钢板桩作围堰,在水位变动区和软弱地基条件下,采取一定刚度的围护设施来满足深基坑的施工需要;成功地运用了一种既施工简便、节约材料又确保安全的围护结构。根据软土的特点和钢板桩的柔性特征,通过采用模拟基坑开挖过程,按照板桩墙围护结构的设计计算方法进行围堰设计,并通过实际施工中一定的控制措施和对围堰内力、变形监测,确保相邻建筑物和自身结构施工的安全。根据实际运用的效果监测表明,采用的钢板桩围堰,是可行而又较优的一种方案。     

中国股市波动与经济波动的传递性研究

基于1994~2004年度的月份数据,对股市波动与经济波动的关系进行研究。我们采用Schwert(1989)的12阶自回归模型对各经济变量序列的波动性进行估计,并进一步通过Granger因果检验和冲击反应函数考察各波动序列之间的内在关系。检验结果表明:在Granger因果检定中,股市波动并未受到总体经济波动的影响,说明股市在一定程度上反映了当前的经济信息;股市波动与经济波动的冲击反应函数则显示,股市波动与经济波动之间的影响大体在6~8个月以内传递完毕。     

信息不对称、信息披露与股票价格波动——兼论管理会计信息披露的市场效应

当前对市场有效性的研究只重视会计盈余或某一类市场效应,而缺乏从信息披露制度的整体角度研究披露效果。我们从信息披露的幅度、频率和结构角度对其提高公司透明度的贡献进行了验证,结果表明:上市公司信息披露的幅度越大、频率越快,越有助于降低市场关于公司的信息不对称水平;管理会计信息披露是投资者迫切需要的,在统计上显示出其能显著降低公司的信息不对称水平。     

汇率波动、货币错配与银行稳定:理论及经验分析

伴随着经济的开放,汇率波动对银行经营的影响亦越来越大.本币贬值会改变企业和银行的资产负债状况,加剧银行危机.汇率波动与银行脆弱性的理论基础来自三种观点:道德风险论、原罪论和承诺问题论.在本币升值的情况下,银行资产的货币错配可能引发银行危机.我国人民币存在持续的升值压力,随着资本项目的进一步开放,利益驱动下的货币错配将大量暴露在汇率变动的风险中.