利用GPS资料分析可降水量研究

地基GPS技术已被公认为观测大气水汽最有潜力的手段.探讨利用区域GPS网探测可降水量时最佳网外辅助站个数的选取,在最佳网外辅助站个数的基础上,验证地基GPS探测可降水量的精度.研究结果表明,利用区域GPS网监测大气水汽时可选用2～3个网外辅助站,GPS监测大气可降水量变化与地面实际降水量有很强的相关性.     

鄱阳湖水质时空相关性及其因素分析

利用2011年鄱阳湖监测点全年的水环境参数数据,基于相关系数法,对鄱阳湖污染物时空相关性及时空变化规律进行了研究。结果表明,鄱阳湖水质存在时空相关性,枯水期空间分异性较大,1月份TR值最大,这与鄱阳湖水位变化相关;鄱阳湖南北湖区空间分异性从主湖区都昌处沿远离都昌方向分别向北部、南部地区随着距离的增大而逐渐减少,其中监测点L7的PR值最小,这主要受到周溪地区珍珠蚌类水产养殖的影响。     

Mandatory and Voluntary Disclosures: Dynamic Interactions

Firms sometimes obtain soft private information about growth prospects along with hard information about current or past performance. In this environment, we find that optimizing disclosures over multiple periods yields nonlinear stock price reactions following both voluntary and mandatory disclosures. Further, we derive several predictions about distinct short‐run and long‐run effects of disclosures and nondisclosures on security prices. Under specified conditions, when the volatility of the firm's earnings increases, the average contemporaneous and prospective post‐mandatory‐disclosure market premia (for voluntary disclosures over nondisclosures) rise, while farther‐in‐future market discounts (for such voluntary disclosures) also become larger. Our analysis moreover predicts that both the disclosure probability and the information content of nondisclosures can increase in the persistence of earnings.     

A note on optimal expected utility of dividend payments with proportional reinsurance

In this paper, we consider the problem of maximizing the expected discounted utility of dividend payments for an insurance company that controls risk exposure by purchasing proportional reinsurance. We assume the preference of the insurer is of CRRA form. By solving the corresponding Hamilton–Jacobi–Bellman equation, we identify the value function and the corresponding optimal strategy. We also analyze the asymptotic behavior of the value function for large initial reserves. Finally, we provide some numerical examples to illustrate the results and analyze the sensitivity of the parameters.     

International Equity Index and Currency Futures: Commodity Currencies or Emerging Versus Developed Markets?

Equity index futures in both emerging and developing markets that are net commodity exporters are strongly linked to their respective currency futures markets. Unconditional correlations among equity and currency futures are the highest for these net basic materials producers in both emerging and developed markets. Granger causality tests also indicate that stock market returns are more strongly related to currency futures returns for commodity-exporting countries. Additionally, conditional correlations among currency and equity futures returns are the strongest for commodity-producing countries in both emerging and developed economies. Volatility spillover analysis provides consistent results. The overall results indicate that the status of a country as a net importer or exporter of raw materials is more important to the relationship between equity and currency futures than whether it is an emerging or developed economy.     

Do students’ perceptions matter? A study of the effect of students’ perceptions on academic performance

Prior accounting education literature documents that students typically associate accounting subjects with negative perceptions, but there are also recent suggestions that the stereotype of the accountant has positive associations. These perceptions of accounting are likely to affect students’ attitudes towards learning and, consequently, influence their performance. We examine the relationship between students’ perceptions and students’ performance. The present study involved undergraduate and graduate students enrolled in management accounting subjects. Our findings indicate that students’ performance is negatively affected by the negative perceptions of accounting that students bring to the subject. Our findings also suggest that positive perceptions of accounting held by students at the end of the semester have a positive impact on students’ performance.     

波动率区制依赖性特征：中国官方外汇市场和外汇黑市的结构分析(1981～2006)

本文采用了MSIH-VECM模型分析了1981～2006年间我国官方外汇市场与外汇黑市的区制依赖性的结构特征。实证结果表明,所使用的非线性模型要优于传统的线性VECM模型,并能有效地捕捉到结构上的突变。本文的研究还发现,我国的官方外汇市场和外汇黑市存在长期的稳定关系。最后,通过区制状态的划分。对政府在各区制下应采取何种政策提出建议。     

自耦变压器讲授方法探讨

采用改变正方向标示的方法,分析导出自耦变压器中电压、电流、功率的平衡关系和基本方程式,这种讲授方法更便于读者学习。     

基于PLS-SEM的水利工程施工安全分析

为了有效预防和减少事故发生,运用基于偏最小二乘的结构方程模型,针对水利工程进行施工风险分析。结合水利工程施工的特点,设定12个显变量与4个潜变量,建立水利工程施工风险评价模型,通过调查问卷的形式收集原始数据,应用SPSS软件对问卷数据进行信度与效度分析,再利用SmartPLS2.0软件进行循环迭代以及PLS回归分析,得到模型的载荷系数与拟合指标。计算结果表明,企业影响与组织机构、施工现场与技术措施、人员素质与操作违规、安全管理与安全监督之间的影响最大。该模型不仅描述变量间的因果关系,更能有效量化安全指标影响程度,在工程实际应用中有一定的借鉴意义。     

粉煤灰中残留氨检测方法的影响因素分析

为了准确地检测出粉煤灰中残留的氨含量,分析了纳氏分光光度法、中和滴定法和氨气敏电极法检测粉煤灰中残留氨含量的主要影响因素,探讨了这3种检测方法的主要影响因素的最佳值选取,研究了3种方法结果的相关性。结果表明:影响纳氏分光光度法的主要因素为浸提剂、浸提固液比和浸提时间,最佳值选取分别为0.05 mol/L H₂SO₄、1∶10和30 min;影响中和滴定法的主要因素为吸收溶液、氢氧化钠加入量和蒸馏时间,最佳值选取分别为0.05 mol/L H₂SO₄、0.2 g和30 min;影响氨气敏电极法的主要因素为提取液和搅拌时间,最佳值选取分别为去离子水和[10,25] min。同时,这3种方法检测结果的相关性较好。研究成果探究了适用于有效定量检测粉煤灰中残留氨的方法,为控制和限定粉煤灰中残留氨提供检测基础。