城市自然排烟隧道竖井高度优化设计

自然排烟隧道火灾烟气排放效果与竖井高度密切相关。文章利用火灾模拟软件FDS对7种不同高度竖井的排烟效果进行模拟计算,分析了烟气蔓延长度、烟气层高度、2 m高处温度、2 m高处能见度、2 m高处CO浓度的变化规律。模拟结果表明:7种隧道排烟竖井高度均满足人员疏散要求,考虑地面美观和施工成本,推荐竖井高度值为4.5 m。     

复杂环境下爆破振动衰减规律的研究

岩石地基爆破开挖会引起爆破振动,爆破振动是造成周围建筑物裂隙、坍塌的主要影响因素,如何准确预测爆破振动对施工安全与施工进度影响意义重大.以广西某项目部分爆破施工工程为例,分别运用线性、非线性两种回归分析方法对爆区附近建筑物、构筑物处的爆破振动峰值速度进行了模型预测,依据模型预测结果,调整后续爆破方案,对爆破振动速度进行测试,测试结果表明测试值接近于预测值且均小于预测值,并且明显小于安全允许值,对同类工程有一定的指导作用.分析结果表明:运用该分析方法所得到的振动速度预测模型具有较高的拟合精度保障,且第二种分析方法以其6％以内的高精度优势,使之更加适用该工程的拟合.     

公路路基填筑施工过程稳定性分析

地质复杂区的公路工程建设难度较大,施工过程中路堤的变形较大、稳定性较差,严重影响工程的施工安全。基于此,本文以S358青阳段工程为研究对象,基于固结理论计算获得公路填筑的临界高度。通过有限元软件建立三维路堤模型,模拟路堤填筑全过程,获得了路堤填筑过程中的竖向位移、塑性区以及塑性点发展规律,进一步基于强度折减法获得路堤安全稳定性系数。研究表明,该公路工程填筑的临界高度为4.1m,填筑高度低于临界值时,竖向位移增长速率仅为6.7mm/m,当填筑高度高于临界值时,竖向位移增长速率显著提升;路堤填筑过程中,路堤潜在滑动面逐渐发展,塑性区从坡脚处逐渐扩大至路堤表面;当路堤填筑超过临界值后,塑性点数量明显变多,且扩散至路堤表面,从而路堤的安全稳定性系数显著降低。本文研究内容和方法可为类似工程提供一定的经验。     

我国短期利率均值回复假设的实证研究

本文以银行间和交易所的1日及7日回购利率为研究对象,利用Va-sicek、CIR、CKLS利率模型检验了它们的均值回复特征,并使用TARCH、EGARCH、PARCH及ANTI-GARCH模型验证了它们的均值回复速度和条件方差的双重不对称性.发现当这4种利率处于较高水平时,其回落速度较慢,波动性较大;当处于较低水平时,其反弹速度较快,波动性较小.这种均值回复特征又以交易所市场更为明显,其回调速度明显高于银行间同类利率.     

通货膨胀阻碍了金融发展与经济增长吗?——基于一个门槛回归模型的新检验

本文基于门槛回归模型,以通货膨胀率作为外生的门槛变量,探讨在不同门槛值下,金融发展对经济增长的影响效果。研究发现:尽管金融发展作为弱外生变量在整体上并没有显著地促进经济增长,但是二者之间存在通货膨胀的门槛效果,当通胀率高于3·9%(或6·5%)时,金融发展对经济增长有显著影响;但在通胀率低于门槛值时,金融发展对经济增长的影响不显著;而在较低(高)通胀率的情况下,资本(劳动)对经济增长的促进作用显著。整体而言,通货膨胀与经济增长存在反向关系。     

南宁市城市污水厂污泥填埋实验研究

为解决南宁市城市污水处理厂污泥处置能力不足的问题,以南宁市江南污水处理厂污泥填埋为实验对象,研究污泥按"飞灰"标准进入垃圾填埋场飞灰区单独填埋和进入垃圾填埋场与垃圾混合填埋的可能性。经过实验研究,江南污水处理厂污泥的重金属含量、二噁英含置均远低于填埋要求,但由于含水率较高,其力学强度均不能满足填埋要求。当污泥与石灰及土按照5:1:4的比例固化后,其抗压强度最高可达850 kPa,远高于填埋要求,同时本次研究还对污泥进行了最佳含水率实验,检测出当污泥含水率为21.4%的时候,拥有最佳抗压强度。     

库内降雨下的尾矿库坝体浸润线变化规律研究

通过库内模拟降雨条件下的堆坝模型实验,研究了在库内降雨条件下坝体的浸润线变化规律,实验结果表明:库内水位的变化对浸润线的影响比较明显,坝体整体的浸润线高度随着库内水位的上升而不断上升;浸润线高度变化存在滞后于水位高度的现象,干滩面远端和干滩面中部处的浸润线高度变化滞后于水位高度不是太明显,在干滩面近端和坝体外坡处的浸润线高度滞后于库内水位高度比较明显,当库内水流渗流至干滩面近端和坝体外坡时,滞后现象逐渐消失,浸润线上升速率和水位上升速率基本一致。     

一种基于FPGA的实时人脸检测系统设计

针对Rein Lien Hsu提出的加入亮度补偿后的椭圆肤色模型在亮度较高和较低的区域容易误判的问题,提出了根据亮度值来分段选择椭圆长短半轴参数值的改进方法,MATLAB实验仿真表明改进后的算法比原始椭圆模型算法具有更高的适用性和准确性,搭建的FPGA系统能够满足人脸的实时检测需求。     

基于历史航迹的航空器高度改变点数据挖掘模型

为分析航空器飞行中高度变化特征,对航空器历史航迹数据的深入挖掘,识别航空器历史航迹高度改变点,本文建立了一种基于最小二乘法的航空器历史航迹点自适应可扩展拟合池模型.该模型可分析航空器高度剖面并解析高度改变轨迹点,并以此分析管制员高度指令及发布时机.用监视数据对本文模型进行验证,结果表明,该模型能效地检测航空器历史航迹,并识别出高度变化点,识别效率及正确率与初始拟合池池长及步长值相关,当初始拟合池池长为4,步长为1,能达到较高的识别效率及正确率.     

“稳增长”需要强力“促改革”

2013年以来，我国经济增速承接了2011年以来连续回落的态势，继2012年第二季度之后连续5个季度低于8％（近5个季度分别为7．6％、7．4％、7．9％、7_7％和7．5％）。自2000年以来，我国仅有10个季度GDP增长率低于8％，而近期就占了一半，且呈持续状态。对于近期我国经济增速持续放缓的态势，我们既不能反应过度，也不能掉以轻心。也就是说，既不能为盲目追求高速度而重拾大规模扩张性政策，也不能不要速度，而应该认真分析经济增速明显回落的各种可能原因，有针对性地采取措施，避免经济增长的大起大落。特别是要高度警惕和防控财政经济运行中存在的主要风险和不确定因素，切实以实质性改革化解财政经济风险，保持经济更长时间的平稳较快发展。     

Vertical Disintegration

With economies of scale, a vertically integrated firm can lower its upstream cost by supplying downstream competitors. The competitors may strategically choose not to purchase from the integrated firm, unless the latter's price for the intermediate good is sufficiently lower than those of alternative suppliers. In a simple model of dynamic scale economies through learning by doing, equilibrium vertical disintegration occurs if and only if total industry profit is higher under vertical separation than under integration. The model bridges a logical gap in George Stigler's classic theory on vertical organization, and sheds light on the widely observed phenomenon of vertical disintegration .     

Value Chain Envy: Explaining New Entry and Vertical Integration in Popular Music*

abstract The concepts of value creation, value capture, and value protection are employed to explain new entry and vertical integration. It is posited that if, at one stage of the value system, the share of value captured is disproportionally higher than the share of value created, value chain envy will ensue. This value chain envy will result in new entry and vertical integration towards that desirable stage provided that the means of value protection available to the incumbents can be overcome. Within the popular music industries, the value created at the stage of music publishing has diminished steadily over the course of the 20th century, but the value captured has remained high. This has triggered value chain envy both inside and outside of the value system. The data presented in this paper show high levels of vertical integration into that stage originating primarily from the stages upstream in the value system, while the level of new entry has been comparatively low. At the same time, the data indicate that the recent introduction of new information communication technologies (ICT) have not significantly affected the levels of new entry and vertical integration into music publishing.     

基于区域能量的图像融合

图像融合的目的在于将多幅图像信息加以综合,消除图像信息之间存在的冗余和矛盾,以形成对目标的清晰、完整、准确的信息描述。在小波域图像融合的范畴内,本文提出一种基于区域能量的图像融合方法,在对图像进行小波分解后,低频采用绝对值取大法,而高频采用基于区域能量的融合策略。仿真结果表明本文结果明显优于文中对比实验的结果,其中熵、互信息参数高于对比方法的融合结果。     

复合地基上钢筋混凝土板的冲击应变分析

为研究三江源地区复合地基上的钢筋混凝土板在冲击荷载作用下的变形特征,本文建立了地基与钢筋混凝土板冲击接触作用的分析模型.地基采用Extended Drucker-Prager模型,钢筋混凝土板使用Concrete Damage Plasticity损伤塑性本构模型.采用显式有限元分析方法计算了特殊地基与板的相互作用的位...     

The Value Relevance of Financial Accounting Information in a Transition Economy: The Case of the Czech Republic

ABSTRACT

The paper investigates the value relevance of accounting information in the Czech Republic in 1994–2001. Value relevance is understood as the ability of financial statement information to capture or summarise information that affects share values and empirically tested as a statistical association between market values and accounting values. The objective of the study is to investigate the validity of the value relevance methodology by finding an accounting setting where the results of value relevance tests might be predicted unambiguously. If the results of these tests confirm the predicted results, the validity of the value relevance methodology might be assumed. A transition economy represented by the Czech Republic provides such an institutional and accounting setting. It might be assumed that value relevance of accounting information is lower in a transitional economy than in a well-developed market economy. It can also be assumed that the value relevance increases over time as a result of the progress in transition. The results of the study confirm these predicted results and give thus supportive evidence of the validity of the value relevance methodology.     

Learning by doing,endogenous discounting and economic development

In this paper, we focus on a growth model where the discount rate is decreasing in capital accumulation and endogenous growth is made possible through learning by doing, knowledge accumulation being a by-product of gross investment. In such a model, the utility function has to be restricted to take positive values implying that the elasticity of marginal utility is lower than one. The presence of endogenous discounting generates a steady-state of stagnation which can be saddle-path stable or unstable depending on the marginal productivity of knowledge. In the case of long run growth, the fact that the elasticity of marginal utility is lower than one implies the existence of two asymptotic balanced growth paths: the one with the higher growth rate being a saddle point while the one with the lower growth rate not being a saddle point. We also study the optimal solution which is characterized by a unique balanced growth path. The policy consists as usual in subsidizing investment in order to internalize the externality.     

我国房地产上市公司绩效测算与比较

为了解我国房地产企业的绩效状况,以经济增加值作为绩效的代表指标,选取沪深A股91家房地产上市公司为样本,测算其2001-2012年绩效并开展产业内外的对比分析。结果显示：（1）2001—2012年,以经济增加值衡量的样本房地产上市公司绩效均值为0．99,不同房地产上市公司之间绩效差异程度较大,低于平均绩效水平的样本公司数量较多,样本公司的绩效均值在2006年以前为负,2006年以后为正;（2）房地产上市公司的绩效均值高于建筑业上市公司但低于制造业上市公司,不同所有权结构、地域和主营业务的公司绩效均值差异较大。     

Mixture Models of Missing Data

This paper proposes a general framework for the analysis of survey data with missing observations. The approach presented here treats missing data as an unavoidable feature of any survey of the human population and aims at incorporating the unobserved part of the data into the analysis rather than trying to avoid it or make up for it. To handle coverage error and unit non-response, the true distribution is modeled as a mixture of an observable and of an unobservable component. Generally, for the unobserved component, its relative size (the no-observation rate) and its distribution are not known. It is assumed that the goal of the analysis is to assess the fit of a statistical model, and for this purpose the mixture index of fit is used. The mixture index of fit does not postulate that the statistical model of interest is able to account for the entire population rather, that it may only describe a fraction of it. This leads to another mixture representation of the true distribution, with one component from the statistical model of interest and another unrestricted one. Inference with respect to the fit of the model, with missing data taken into account, is obtained by equating these two mixtures and asking, for different no-observation rates, what is the largest fraction of the population where the statistical model may hold. A statistical model is deemed relevant for the population, if it may account for a large enough fraction of the population, assuming the true (if known) or a sufficiently small or a realistic no-observation rate.     

Prediction in the lognormal regression model with spatial error dependence

In the context of the lognormal regression model with spatial error dependence, the present study examines correction of a bias in prediction. If interest lies in the predicted mean value of the dependent variable, antilogarithmic transformation of the predicted mean value of the regressand produces a bias. In order to correct such a transformation bias, we derive several alternative predictors by extending some of the predictors suggested for the lognormal regression model with spherical disturbances. Behaviors of our predictors are described in a theoretical manner, and their performances are assessed in an experimental manner. Extension of an asymptotically unbiased predictor is shown to be useful.     

Predicting the portfolio risk of high-dimensional international stock indices with dynamic spatial dependence

The spatial dependence of assets, which relates to similarities in economic, political, or cultural systems and other aspects, has been confirmed through empirical research; however, spatial dependence has rarely been applied to financial risk measurement. To fill this gap in the literature, a dynamic spatial GARCH-copula (sGC) model is proposed in this paper to evaluate the portfolio risk of international stock indices. In this model, a spatial GARCH is used as the marginal distribution and vine copula is adopted as the joint distribution of indices. Then, the proposed model is applied empirically to assess portfolio risk. Results show that, first, the proposed risk prediction model with spatial dependence outperforms a model neglecting spatial effects per the Kupiec test, Z test and Christoffersen test. Risk prediction during periods of economic stability is also more accurate than during times of crisis. Second, risk measures for models with spatial dependence are higher than those without such dependence but lower than for vine copula models. Third, models including either spatial dependence or vine copulas alone exhibit relatively poor performance. Fourth, the model involving extreme value theory (EVT) generates the greatest value at risk to pass the Kupiec test, Z test and Christoffersen test; however, this model is not suitable for characterizing international indices with EVT based on negative values of the shape parameters of estimates. Findings offer important implications for personal investors, institutional investors, and national regulatory authorities.