剖线强度梯度变化的作物软硬变化区精确划分

[目的]软硬变化区的划分是进行遥感变化检测技术识别农作物的基础。为解决人工判读方法中存在人为主观因素影响以及自动判别和交互式判别方法对不同研究区的适用性问题,该文提出基于剖线梯度变化(Profile based Gradient Change Magnitude,PGCM)进行软硬变化区划分的方法。[方法]该研究选择破碎农业景观种植区域为研究区,计算拔节期Quick Bird影像和播种期模拟影像两个时相的变化强度,从作物地块内部向外绘制剖线,利用剖线强度的梯度变化确定硬变化区(Hard change region,HCR)、软变化区(Soft change region,SCR)和未变化区(Non change region,NCR)3者间的划分阈值。[结果]从识别结果来看,PGCM能够有效在地块边界处探测到软变化像元,进而确定HCR、SCR。像元分辨率在5~60 m不同尺度下,识别HCR区混入比例为11%~16%,混入比例随着分辨率下降而降低;NCR区混入比例为3%~4%,受分辨率尺度影响不大;SCR区识别比例为74%~86%,识别精度较高,识别结果与冬小麦空间分布结果保持一致。[结论]PGCM方法能够自动、便捷地确定阈值,摆脱人工判定的主观性,有效地划分出HCR、SCR和NCR 3个区域,为进一步HCR、SCR区内的作物识别提供基础。     

Bayesian selection of technology assumptions for the transformation from supply-use to input–output tables

ABSTRACT

In the construction of input–output models from supply-use tables, technology assumptions disambiguate how an industry uses inputs in the production recipe of multiple outputs. This paper uses Bayes' theorem to select technology assumptions, taking into account empirical observations. The paper presents a formulation to explore hybrids between product and industry technology assumptions in product-by-product tables. We then present Markov chain Monte-Carlo techniques to implement the Bayesian method for selecting technology assumptions. We apply the method in a case study using Eurostat supply-use tables of 2004 and 2005, exhibiting a volume of secondary products of less than 13%, and 59 products and industries per country. The results show that the choice of technology is not important, given that there is no strong evidence in favour of any of them.     

基于数字图像处理技术的再生混凝土数值模拟

为了研究骨料形态对再生混凝土材料力学性能的影响,基于势能原理的基面力元法,利用图像处理技术和MATLAB软件,建立了再生混凝土真实骨料细观模型。应用FORTRAN分析软件对再生混凝土试件进行单轴拉伸试验的数值模拟,研究了真实骨料细观模型再生混凝土宏观应力-应变曲线变化规律和试件的破坏形态。结果显示,真实骨料模型得到的宏观应力-应变曲线和试验曲线吻合度较高,骨料形状对试件的破坏形态影响较小。模型可真实地模拟再生混凝土在单轴拉伸作用下的损伤破坏过程,准确地反映试件的实际骨料形态。     

Impact of foreign direct investment on greenhouse gas emissions in agriculture of developing countries

This research analyses the impact of foreign direct investment on greenhouse gas emissions in the agriculture sector of developing countries. Panel data from 63 developing countries for the period 2005 to 2014 was used to estimate a dynamic econometric model by applying a system‐generalised method of moments. The empirical results indicate a positive impact of foreign direct investment in agriculture on the carbon dioxide equivalent emission intensity in developing countries. The results provide weak support for the pollution havens hypothesis and imply the importance of coordination between foreign direct investment and environmental policies.     

Work motivation and public service motivation: disentangling varieties of motivation and job satisfaction

Research on motivation in the public sector has used public service motivation (PSM) and self-determination theory (SDT) interchangeably. This paper compares both theories, develops hypotheses pertaining to their assumptions, and empirically tests them in two public offices in Switzerland. We then explore their relationship with job satisfaction as an indicator of predictive validity. We find that SDT and PSM display conceptual differentiation and SDT has a strongest relationship to job satisfaction. However, moderation analysis suggests that employees with high levels of PSM have more stable job satisfaction compared to their low-PSM counterparts.     

Exploring heritage tourism performance improvement for making sustainable development strategies using the hybrid-modified MADM model

Industrial heritage tourism has become increasingly popular in recent years. However, strategies for improving the industrial heritage tourism development-related performances are still an underdeveloped research topic academically. Therefore, this study’s purpose is to explore the feasibility performance-improving strategies using a hybrid-modified multiple attribute decision-making (MADM) based on the DEMATEL technique in constructing the influential network relation map (INRM) and in determining the influential weights of DANP. Then, the modified VIKOR method is combined with the influential weights of DANP, performance gaps were identified, and then the most effective strategies for improving tourism development-related performance at industrial heritage sites can be generated using INRM. Finally, an empirical real case study of a rehabilitated gold-mining site of Taiwan is used to demonstrate the effectiveness of the hybrid-modified MADM model. According to the results, the decision-makers should highly prioritize improving high-priority criteria such as ‘social usefulness’, ‘resource integration’, ‘destination policy and development’, ‘economic development’, ‘cultural links’, ‘cultural learning’, and ‘natural landscape resources’ in advance to successfully achieving the aspired performance levels. Additionally, this study suggests meaningful industrial heritage tourism performance improvement strategies that have been rehabilitated throughout the world.     

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.     

中国区域农业科技资源配置能力及比较优势研究*——基于省级农业科学院视角

[目的]通过测算各地区农业科技资源的配置能力,分析其比较优势并找出不足以便弥补差距,促进各区域农业科技配置能力的提高,为各地区农业经济的发展提供支持。省级农业科学院作为各省市规模最大、综合实力最强的农业科研机构,是农业科技创新的重要主体之一,分析其科技资源配置能力具有重要的现实意义。[方法]基于2009—2016年相关数据,遴选了有代表性的评价指标体系,运用突变级数法计算农业科技资源配置能力,运用NRCA模型定量分析农业科技资源配置效益的比较优势。[结果]山东农业科学院科技资源配置能力位居全国第一,甘肃、江苏、青海农业科学院分别在农业科技人力、物力、财力资源方面具有明显的比较优势。[结论]省级农业科学院科技资源配置能力区域差异十分明显,但区域格局变化不大,且大致与各地区经济实力相吻合;农业科技资源配置能力较高的农业科学院大多在农业科技物力资源配置效益方面具有比较优势,在农业科技人力、财力资源配置效益方面不具备比较优势。     

基于多软件平台的机电液一体化虚拟试验方法

提出一种针对复杂机电液系统的虚拟仿真试验方法,分别在ADAMS、AMESim、MATLAB/Simulink软件中建立机械子系统、液压子系统和控制子系统模型,并基于软件间接口技术,建立动态数据共享通道,实现系统的全面仿真分析,为系统设计与优化、控制策略选择等提供依据.该方法对于复杂机电液系统仿真分析具有普遍适用性,对缩短产品开发周期、降低产品研发成本、减轻仿真工作复杂性具有重要意义.     

Deal characteristics and M&A performance: How do hospitality firms fare?

The global hospitality industry has experienced significant consolidation in the past several decades. While evidence in the general business literature suggests that the target firm shareholders gain instead of the acquiring firm shareholders, some studies in the hospitality industry have suggested that mergers and acquisitions (M&As) are also beneficial to acquiring firms. Using a comparative study design and a comprehensive sample over 41 years, we empirically examine whether M&As create more value in the hospitality industry than in other industries and whether certain deal characteristics may explain the potential performance differential. Overall, we find that M&As in the hospitality industry outperform M&As in non-hospitality sectors. When examining deal attributes, we find that relative size of target, cash method of payment, and an unlisted target are characteristics positively related to merger performance and help explain some of the performance differential. We contribute theoretically and empirically to the literature by demonstrating that industry and deal effects play an important role in M&A performance.