浅析影响混凝土质量的相关因素

混凝土的质量常以28天强度作为衡量指标,并逐渐形成追求强度的倾向,以为加大水泥用量和采用早强水泥总有利于质量,并排斥使用粉煤灰等矿物掺和料和引气剂,这些都对混凝土的结构带来极为不利的影响。对于现代混凝土来说,提高强度比较容易,为此,施工人员应该深入了解混凝土的特点,并在混凝土结构施工过程中对混凝土原材料的选用与混凝土配合比参数严加控制,本文介绍了影响混凝土质量的因素。     

The composite iteration algorithm for finding efficient and financially fair risk-sharing rules

We consider the problem of finding an efficient and fair ex-ante rule for division of an uncertain monetary outcome among a finite number of von Neumann–Morgenstern agents. Efficiency is understood here, as usual, in the sense of Pareto efficiency subject to the feasibility constraint. Fairness is defined as financial fairness with respect to a predetermined pricing functional. We show that efficient and financially fair allocation rules are in one-to-one correspondence with positive eigenvectors of a nonlinear homogeneous and monotone mapping associated to the risk sharing problem. We establish relevant properties of this mapping. On the basis of this, we obtain a proof of existence and uniqueness of solutions via nonlinear Perron–Frobenius theory, as well as a proof of global convergence of the natural iterative algorithm. We argue that this algorithm is computationally attractive, and discuss its rate of convergence.     

辽宁省大学生亚健康现状及成因研究

以辽宁省6所不同类型院校的1 200名学生为研究对象,对他们的亚健康现状和影响因素进行了调查,可以看出我省大学生亚健康检出率略高于其他省份。影响辽宁省大学生亚健康症状的主要因素:对自身健康的关注度不够、饮食不规律、缺少合理的睡眠和适当的体育锻炼、闲暇时间睡懒觉及上网聊天打游戏;学校相关部门对学生身体状况的重视程度不够,缺少家人的影响与监督;大学生对未来前程的担忧和就业的压迫感、对自身工作能力的不自信。     

Semiparametric estimation of multi-asset portfolio tail risk

When correlations between assets turn positive, multi-asset portfolios can become riskier than single assets. This article presents the estimation of tail risk at very high quantiles using a semiparametric estimator which is particularly suitable for portfolios with a large number of assets. The estimator captures simultaneously the information contained in each individual asset return that composes the portfolio, and the interrelation between assets. Noticeably, the accuracy of the estimates does not deteriorate when the number of assets in the portfolio increases. The implementation is as easy for a large number of assets as it is for a small number. We estimate the probability distribution of large losses for the American stock market considering portfolios with ten, fifty and one hundred assets of stocks with different market capitalization. In either case, the approximation for the portfolio tail risk is very accurate. We compare our results with well known benchmark models.     

Cost-benefit analysis of airport security: Are airports too safe?

This paper assesses the risks and cost-effectiveness of measures designed to further protect airport terminals and associated facilities such as car parks from terrorist attack in the U.S., Europe, and the Asia-Pacific area. The analysis considers threat likelihood, the cost of security measures, hazard likelihood, risk reduction and expected losses to compare the costs and benefits of security measures to decide the optimal security measures to airports. Monte-Carlo simulation methods were used to propagate hazard likelihood, risk reduction and loss uncertainties in the calculation of net benefits that also allows probability of cost-effectiveness to be calculated. It is found that attack probabilities had to be much higher than currently observed to justify additional protective measures. Overall, then, it is questionable whether special efforts to further protect airports are sensible expenditures. Indeed, some relaxation of the measures already in place may well be justified.     

Risk regulation,community pressure and the use of management accounting in managing climate change risk: Australian evidence

This exploratory study is amongst the first to investigate how companies perceive the regulation of carbon emissions and the pressure exerted by the community in an environment characterised by risk and uncertainty. Semi-structured interviews were conducted among 39 executives who were directly involved in carbon emissions management in 18 large listed Australian companies. Consistent with Prospect Theory, we find that decision-makers are threat biased and are more likely to take immediate actions when climate change issues are framed as threats as opposed to opportunities. From the interview data, it is seen that managers use management accounting techniques as a risk management tool in mitigating risks associated climate change issues. Furthermore, this use of management accounting appears to be driven primarily by the protection of economic interests, regulatory pressure and reputational pressure. The study provides insights into how perceptions of climate change uncertainties and external pressure for disclosure of emissions information influence companies to use management accounting in managing climate change risk.     

基于层次分析的农业企业竞争力研究

农业是具有天然弱质性的产业,不但表现出对自然条件的高度依赖,而且还很难抵御市场风险的影响,故此从事农业的企业竞争力相对比较低下。针对这一状况,以层次分析作为研究方法,结合农业企业自身特点,通过对影响农业企业竞争力的因素进行排序、分析,找出适合其发展的拓宽融资渠道,加快人才培养措施建议。     

EXTREME VALUE THEORY IN FINANCE: A SURVEY

Extreme value theory is concerned with the study of the asymptotic distribution of extreme events, that is to say events which are rare in frequency and huge in magnitude with respect to the majority of observations. Statistical methods derived from it have been employed increasingly in finance, especially for risk measurement. This paper surveys some of those main applications, namely for testing different distributional assumptions for the data, for Value‐at‐Risk and Expected Shortfall calculations, for asset allocation under safety‐first type constraints, and for the study of contagion and dependence across markets under conditions of stress.     

Credibilistic risk aversion

In the probabilistic risk aversion approach, risks are presumed as random variables with known probability distributions. However, in some practical cases, for example, due to the absence of historical data, the inherent uncertain characteristic of risks or different subject judgements from the decision-makers, risks may be hard or not appropriate to be estimated with probability distributions. Therefore, the traditional probabilistic risk aversion theory is ineffective. Thus, in order to deal with these cases, we suggest measuring these kinds of risks as fuzzy variables, and accordingly to present an alternative risk aversion approach by employing credibility theory. In the present paper, first, the definition of credibilistic risk premium proposed by Georgescu and Kinnunen [Fuzzy Inf. Eng., 2013, 5, 399–416] is revised by taking the initial wealth into consideration, and then a general method to compute the credibilistic risk premium is provided. Secondly, regarding the risks represented with the commonly used LR fuzzy intervals, a simple calculation formula of the local credibilistic risk premium is put forward. Finally, in a global sense, several equivalent propositions for comparative risk aversion under the credibility measurement are provided. Illustrated examples are presented to show the applicability of the theoretical findings.     

How locus of control shapes intention to reuse mobile apps for making hotel reservations: Evidence from chinese consumers

This study unveils the cognitive mechanism that locus of control (LOC) dimensions (internal control, chance control, and control by powerful others) predict intention to reuse mobile apps for making hotel reservations. The predictions are assumed through the unified theory of acceptance and use of technology (UTAUT) anchors and perceived risk. Drawn from an online survey with 457 Chinese participants, results show direct positive predictions of intention to reuse from UTAUT anchors including performance expectancy, effort expectancy, social influence, and facilitating conditions. Perceived risk also negatively predicts intention. Effort expectancy mediates the links between internal/chance control and intention, whereas perceived risk mediates only the latter link. Facilitating conditions mediate the relationship between control by powerful others and intention. This study contributes to existing research by distinguishing the mechanisms that underpin LOC dimensions and technology re-adoption. Practitioners are recommended to improve booking apps by addressing the concerns of users with different LOC.