山东省生态用地变化及驱动因素影响评价

［目的］研究第二次土地利用现状调查以来山东省生态用地变化特点及驱动因素，评价各类驱动因素对生态用地的影响程度，为科学编制区域空间规划，保护和合理利用生态用地提供参考。［方法］文章构建了全省生态用地转移矩阵，归纳了影响生态因素变化的主要驱动因素，提出了驱动力指数计算方法，定量分析和比对了各驱动因素对生态用地的影响。［结果］2009—2017年生态用地共计转出2048万hm2，占生态用地总面积的472%； 转入316万hm2，占生态用地总面积的072%。8年来全省生态用地净减少1732万hm2，占2009年生态用地总面积的400%。生态用地的流向以耕地最多，向城镇村及工矿用地流出次之，向设施农用地的流出也有较大面积。［结论］（1）在影响生态用地变化的六大驱动因素中，耕地开发和城镇村工矿占用的驱动力指数最高，非耕农业占用对生态用地的变化有一定影响。（2）六大因素中城镇村工矿占用对当地生态环境的破坏力最强。     

Covariance breakdowns and connectedness of crude oil futures markets with non-synchronous data

ABSTRACT

This article identifies the breakdowns in the covariance of three benchmark crude oil futures markets (WTI, Brent and Dubai) and investigates the changes of market connectedness across the breakdown periods. As the crude oil futures are traded in different regions, this article eliminates the non-synchronous trading data by employing the Vector Moving Average structure and the Bayesian data augmentation approach, which keeps the integrity of original data without changing its properties. The results show that there are significant breaks in the covariance structure of crude oil futures markets. The breakdown periods are consistent with the periods when the market volatilities are at high level and the returns are volatile. The changes of market connectedness are independent of the covariance states, which supports the globalization hypothesis for the crude oil market. The results also suggest that there is more information flow out of the WTI than to the WTI during the sample period, particularly during the breakdown periods in 2008–2009.     

绍兴市土地利用时空变化研究

[目的]探讨经济发达地区土地利用变化时空规律,为城市发展提供合理土地利用政策,同时优化土地利用结构以支持经济可持续发展。[方法]通过遥感影像获取长时间序列的土地利用数据,探讨近30多年来绍兴市的土地利用变化,进一步利用土地利用动态变化模型,对绍兴市土地利用变化过程、趋势、变化轨迹进行了深入分析。[结果](1)绍兴市土地利用在1980~2000年相对稳定,在2000年后变化强度逐年增强,2005~2015年土地利用转化量增多和类型多样。绍兴市东北部平原和县区核心区域是经济发达地区土地利用变化的活跃区域,主要是其他类型土地向建设用地转移;(2)1980~2015年绍兴市土地利用变化轨迹主要受到人口增长和GDP增长的影响。[结论]城市化的发展和人口的迅速增长,使城市人口和土地面积迅速增加,造成城市边缘的农业用地转化成了建设用地。经济的发展、科技的进步及政府政策的制定,改变了人们的生活和工作方式,进而影响土地利用类型。     

Cost–consequence analysis of a hemostatic matrix alone or in combination for spine surgery patients

Background: A five-year retrospective database analysis comparing the use of Floseal¹ flowable topical hemostat alone (F) and in combination with gelatin/thrombin (F?+?G/T) to achieve hemostasis and control surgical bleeding showed higher resource utilization for F?+?G/T cases relative to F matched pairs during spinal surgery. Lower resource use in the F group was characterized by shorter hospital length of stay and surgical time as well as fewer blood transfusions and less hemostat agent used per surgery.

Objective: To evaluate the cost–consequence of using F compared to F?+?G/T in minor, major and severe spinal surgery from the US hospital perspective.

Methods: A cost–consequence model was developed using the US hospital perspective. Model inputs include clinical inputs from the literature, cost inputs (hemostatic matrices, blood product transfusion, hospital stay and operating room time) from the literature, and an analysis of annual spine surgery volume (minor, major and severe) using the 2012 National Inpatient Sample (NIS) database. Costs are reported in 2017?US dollars. One-way and probabilistic sensitivity analyses address sources of variability in the results.

Results: A medium-volume hospital (130 spine surgeries per year) using F versus F?+?G/T for spine surgeries is expected to require 85 less hours of surgical time, 58 fewer hospital days and 7 fewer blood transfusions in addition to hemostat volume savings (F: 1?mL, thrombin: 1994?mL). The cost savings associated with the hospital resources for a medium-volume hospital are expected to be $317,959 (surgical hours?=?$154,746, hospital days?=?$125,237, blood transfusions?=?$19,023, hemostatic agents?=?$18,953) or $2445 per spine surgery.

Conclusions: The use of F versus F?+?G/T could lead to annual cost savings for US hospitals performing a low to high volume of spinal surgeries per year.     

采用目标假设的三被动式传感器数据关联算法

被动式传感器目标跟踪是多传感器多目标跟踪领域的一个重要研究方向。针对三被动式传感器多目标定位系统全局最优数据关联的三维分配问题，在允许传感器漏检和虚警的情况下，通过分析拉格朗日松弛算法，提出一种假定真实目标的快速收敛算法。该算法通过粗关联假定真实目标并重新修改代价矩阵，然后进行细关联，使得拉格朗日松弛算法在保证关联精度的前提下有效地提高了收敛速度。理论分析和实验结果表明，该算法提高了数据关联的速度,并在一定程度上提高了关联准确率。     

Is there a diversification “cost” of Shari’ah compliance? Empirical evidence from Malaysian equities

Islamic equity portfolios work with a smaller investment universe given the filtering of non-Shari’ah compliant stocks. It has been theoretically argued that this culminates in suboptimal portfolio diversification, which in turn adversely affects risk-adjusted returns. We offer empirical evidence that such a conceived portfolio diversification “penalty” is far from a foregone conclusion, at least empirically. Our results tend to indicate that Islamic portfolios are not invariably handicapped in terms of portfolio diversification. We also explored dimensions that may account for differences in the relative investment performance between Islamic and conventional portfolios, such as portfolio constraints, short selling and market conditions. We believe this paper is among the first to apply substantial empirical analysis specifically with respect to the portfolio diversification perspective on Islamic equity investments.     

空间目标的联合矩阵束极点估计

极点作为谐振区雷达目标的最主要电磁特性，具有很大的空间目标识别前景。但是在使用频域观测数据提取目标极点时，存在虚假极点和估计精度问题。针对上述问题，首先通过加窗和截断改进了后时响应信号的获取流程，抑制了虚假极点影响；然后采用最小描述长度法（MDL）估计极点个数，避免了定阶错误引起的虚假极点；最后采用联合矩阵束法估计极点，有效减少了单角度数据估计极点时存在的遗漏极点和虚假极点问题。FEKO软件验证表明，所提算法具有更高的精度和抗噪能力。     

Heteroskedasticity-consistent covariance matrix estimators for spatial autoregressive models

In the presence of heteroskedasticity, conventional test statistics based on the ordinary least squares (OLS) estimator lead to incorrect inference results for the linear regression model. Given that heteroskedasticity is common in cross-sectional data, the test statistics based on various forms of heteroskedasticity-consistent covariance matrices (HCCMs) have been developed in the literature. In contrast to the standard linear regression model, heteroskedasticity is a more serious problem for spatial econometric models, generally causing inconsistent extremum estimators of model coefficients. This paper investigates the finite sample properties of the heteroskedasticity-robust generalized method of moments estimator (RGMME) for a spatial econometric model with an unknown form of heteroskedasticity. In particular, it develops various HCCM-type corrections to improve the finite sample properties of the RGMME and the conventional Wald test. The Monte Carlo results indicate that the HCCM-type corrections can produce more accurate results for inference on model parameters and the impact effects estimates in small samples.     

Factor state–space models for high-dimensional realized covariance matrices of asset returns

We propose a dynamic factor state–space model for high-dimensional covariance matrices of asset returns. It makes use of observed risk factors and assumes that the latent integrated joint covariance matrix of the assets and the factors is observed through their realized covariance matrix with a Wishart measurement density. For the latent integrated covariance matrix of the assets we impose a strict factor structure allowing for dynamic variation in the covariance matrices of the factors and the residual components as well as in the factor loadings. This factor structure translates into a factorization of the Wishart measurement density which facilitates statistical inference based on simple Bayesian MCMC procedures making the approach scalable w.r.t. the number of assets. An empirical application to realized covariance matrices for 60 NYSE traded stocks using the Fama–French factors and sector-specific factors represented by Exchange Traded Funds (ETFs) shows that the model performs very well in- and out of sample.     

中国省域入境旅游发展的空间计量建模与影响因素效应研究

空间计量模型在旅游研究中已得到有效应用,解决了旅游产业发展中的一些实际问题,但还需进一步改进与完善。文章以中国省域入境旅游发展为着眼点,增设扩散转移矩阵为模型因变量滞后的空间权重矩阵,以反映入境旅游在中国省域之间的客流人数扩散转移实际情况,同时从最为全面的广义嵌套空间模型入手,引入旅游研究空间计量模型系统,并以区域入境旅游发展影响因素为模型自变量,构建了入境旅游发展的最优空间计量模型,最后对模型显著自变量的直接效应、溢出效应、总效应进行评估分析,给出区域入境旅游发展建议。结果显示:模型自变量出现显著消极效应的影响因素几乎为酒店供应,加强旅游资源建设和经济水平发展始终是入境旅游发展的重要途径,而开放程度已对东部省域的影响较为微弱,对中部和西部省域则起到很好的积极效应,同时交通设施在中部省域呈现出非常强劲的溢出效应。