对《钻井液用消泡剂评价程序》标准的认识和建议

评价和衡量消泡剂性能优劣的主要技术指标是钻井液密度恢复率。石油天然气行业标准SY/T5560—92《钻井液用消泡剂评价程序》对钻井液密度恢复率的作出了比较详细的测试规定和要求。根据在实际工作中的摸索总结,建议变发泡后和消泡后钻井液密度的测试方法由密度计测试为体积计算。     

Markov regime-switching Beta-t-EGARCH

We suggest a Markov regime-switching (MS) Beta-t-EGARCH (exponential generalized autoregressive conditional heteroscedasticity) model for U.S. stock returns. We compare the in-sample statistical performance of the MS Beta-t-EGARCH model with that of the single-regime Beta-t-EGARCH model. For both models we consider leverage effects for conditional volatility. We use data from the Standard Poor’s 500 (S&P 500) index and also a random sample that includes 50 components of the S&P 500. We study the outlier-discounting property of the single-regime Beta-t-EGARCH and MS Beta-t-EGARCH models. For the S&P 500, we show that for the MS Beta-t-EGARCH model extreme observations are discounted more for the low-volatility regime than for the high-volatility regime. The conditions of consistency and asymptotic normality of the maximum likelihood estimator are satisfied for both the single-regime and MS Beta-t-EGARCH models. All likelihood-based in-sample statistical performance metrics suggest that the MS Beta-t-EGARCH model is superior to the single-regime Beta-t-EGARCH model. We present an application to the out-of-sample density forecast performance of both models. The results show that the density forecast performance of the MS Beta-t-EGARCH model is superior to that of the single-regime Beta-t-EGARCH model.     

The maximum entropy mortality model: forecasting mortality using statistical moments

ABSTRACT

The age-at-death distribution is a representation of the mortality experience in a population. Although it proves to be highly informative, it is often neglected when it comes to the practice of past or future mortality assessment. We propose an innovative method to mortality modeling and forecasting by making use of the location and shape measures of a density function, i.e. statistical moments. Time series methods for extrapolating a limited number of moments are used and then the reconstruction of the future age-at-death distribution is performed. The predictive power of the method seems to be net superior when compared to the results obtained using classical approaches to extrapolating age-specific-death rates, and the accuracy of the point forecast (MASE) is improved on average by 33% respective to the state-of-the-art, the Lee–Carter model. The method is tested using data from the Human Mortality Database and implemented in a publicly available R package.     

Lognormal Approximation of Complex Path-Dependent Pension Scheme Payoffs

Abstract

This paper analyzes an explicit return smoothing mechanism which has recently been introduced as part of a new type of pension savings contract that has been offered by Danish life insurers. We establish the payoff function implied by the return smoothing mechanism and show that its probabilistic properties are accurately approximated by a suitably adapted lognormal distribution. The quality of the lognormal approximation is explored via a range of simulation-based numerical experiments, and we point to several other potential practical applications of the paper's theoretical results.     

Mixed tempered stable distribution

In this paper, we introduce a new parametric distribution, the mixed tempered stable. It has the same structure of the normal variance–mean mixtures but the normality assumption gives way to a semi-heavy tailed distribution. We show that, by choosing appropriately the parameters of the distribution and under the concrete specification of the mixing random variable, it is possible to obtain some well-known distributions as special cases. We employ the mixed tempered stable distribution which has many attractive features for modelling univariate returns. Our results suggest that it is flexible enough to accommodate different density shapes. Furthermore, the analysis applied to statistical time series shows that our approach provides a better fit than competing distributions that are common in the practice of finance.     

One for all and all for one: privatization and Universal Service provision in the postal sector

Universal Service provision has a special role for the public utilities sector in many Organization for Economic Co-operation and Development (OECD) countries. These public utilities have largely been subject to privatization during the last 3 decades. Efficiency effects of privatization are widely documented while the impacts on the quality and accessibility of the Universal Service are not much examined. By using a unique dataset on privatization for 21 countries over the period 1980–2007 for the postal sector, we are able to show that privatization, in particular formal privatization, has led to a decrease in the quality of the Universal Service.     

中国省际城镇职工工资收入分布演进的时空特征

运用Kernel密度估计方法和空间马尔科夫链分析方法,并将空间因素纳入分析框架中,对1978—2009年期间中国省际城镇职工工资收入分布演进的时空特征进行了分析。研究结果表明:从时间动态性看,中国省际城镇职工工资收入的差距正逐步固化和深化,多俱乐部收敛特征明显、贫困陷阱问题日益突出;从空间动态性看,近邻效应对省际城镇职工工资收入分布演进存在一定影响,多数省份的工资收入水平向邻区的平均工资收入水平演进。     

1990－2015年三峡库区重庆段水田时空分布及演变特征

目的 水田作为三峡库区重要的耕地类型与湿地景观,对保障该区的粮食和生态安全起到了不可替代的作用。分析水田的时空分布及演变特征,为农业结构调整、水田经营政策的制定以及保障库区生态系统的安全提供一定的理论基础。方法 文章基于三峡库区重庆段1990年、2005年、2015年土地利用图像,利用ArcGIS和FRAGSTATS软件,运用土地利用转移矩阵、核密度估计以及景观指数模型等方法,分析三峡库区重庆段在不同时段水田的时空分布与演变特征。结果 2015年三峡库区重庆段水田面积为5 267.94 km²,占耕地总面积的26.70 %,平均坡度为11.87°,其中丘陵地区水田面积分最大,不同区县间水田面积差异显著。（2）近25 年草地、建设用地和水田间发生显著转移,1990—2005年水田主要转向旱地,2005—2015年水田主要转向建设用地,且转出面积大于转入面积,水田的总面积持续减少。（3）近25年来三峡库区重庆段水田面积的核密度分布呈现“西密东疏”“南密北疏”的分布格局。1990年水田分布的聚集区表现为江津和长寿2个核心分布带;2005—2015年江津的核密度值由高密度区转变为低密度区,水田分布的聚集区仅剩长寿核心分布带。（4）在7种土地利用类型中,水田的景观优势度居于中间位置,随着水田面积不断减少,水田景观的破碎化进一步扩大。结论 从粮食安全和生态保护的角度出发,未来产业结构调整和高标准农田建设中,必须稳定一定数量和质量的水田面积,充分发挥水田的生产和生态功能。     

碳密度与投资率的因果关系——对中国1980～2009年数据的实证研究

为应对国际金融危机的冲击,国务院4万亿元巨额投资计划出台,碳密度的反弹也随之见诸报端。在这样的背景下,文章运用格兰杰因果检验对我国1980～2009年投资率和碳密度的数据进行分析。检验结果表明,投资率和碳密度之间存在单向因果关系,投资率是碳密度的格兰杰原因。最后从我国的投资现状出发,提出展望与建议。     

汉宜高速铁路路基石灰改良土填筑施工的质量控制

为满足列车高速运行时路基强度、变形以及路基工后沉降的要求,在缺乏优质填料的情况下,新建武汉至宜昌高速铁路路基回填采用石灰改良土来改善土的结构,提高承载力,以满足工程需要,并降低成本,缩短工期,取得较好的经济效益。本文就土料料源、石灰质量、灰剂量、含水量四方面以及现场施工工艺来分析石灰改良土的施工质量控制要点。