平面连杆机构的优化设计

利用单变参数（辅助角）按最佳传动角及最大行程速度变化系数对曲柄摇杆机构进行优化设计，提高了机构设计质量，方法实用可行。     

开放式投资基金稳健投资模式的实证研究

在马柯维茨均值—方差模型的基础上,引入了流动性因素和稳健因子,综合考虑了收益、风险和流动性等因素对投资组合的影响,探索了稳健型投资模式的构建方式,并利用股市数据进行了实证分析。     

葫芦岛市耕地数量变化及其驱动力研究

以1998-2007年的统计资料为基础,分析了葫芦岛市近10年的耕地数量变化特点,并通过主成分分析法,对引起耕地数量变化的驱动力进行了研究。结果表明,经济发展、人口增长以及农业科技进步是影响葫芦岛市耕地数量变化的三大驱动力,并据此提出了葫芦岛市的耕地保护对策。     

葫芦岛市耕地数量变化及其驱动力研究

以1998-2007年的统计资料为基础,分析了葫芦岛市近10年的耕地数量变化特点;通过主成分分析法,对引起耕地数量变化的驱动力进行了研究。结果表明,经济发展、人口增长以及农业科技进步是影响葫芦岛市耕地数量变化的三大驱动力;据此提出了葫芦岛市的耕地保护对策。     

Matching method to paradigm in strategy research: limitations of cross‐sectional analysis and some methodological alternatives

A central focus of empirical research in strategic management has been to understand the relationships associated with the structure–strategy–performance paradigm. To examine these relationships, investigators have relied extensively on cross‐sectional methods that embody the implicit assumption that model parameters are stable across firms and over time. Yet, many of the theoretical constructs used in strategic management have clear firm‐ and time‐specific components. Hence, it might be expected that the parameters of the relationships investigated empirically will vary across firms and over time. Whereas recent research has raised concerns about the use of cross‐sectional analysis when parameters vary over time, little attention has been given to the issue of parameter variability across firms. Given the focus of strategy researchers on firm‐level effects and the predominant reliance on cross‐sectional analysis, accounting for across‐firm variability is a significant methodological issue. Failure to account for such variability can lead to biased parameter estimates and incorrect inferences. This paper argues for the adoption of alternative methods that can overcome the limitations of a cross‐sectional analysis and it offers guidance on how researchers can proceed to use these alternative methods to explicitly incorporate or test for variation in model parameters across firms or over time. Copyright © 1999 John Wiley & Sons, Ltd.     

Heterogeneity in the determinants of length of stay across middle age and senior age groups in thermal tourism

ABSTRACT

Water has been seen as a healing source of life for centuries. Even the placebo effect of thermal therapies increases consumers’ well-being. Especially with easy traveling options demand for thermal therapies are on the rise. Users of thermal therapies are mostly composed of seniors. Even though age groups in the senior market have heterogeneous needs, managers assume them to be homogenous. Measuring thermal tourism demand by the length of stay, this study analyzed the determinants affecting the length of stay of older thermal tourists. The length of stay is predicted to have been affected by age, purchasing power, physical distance, and seasonal preferences. Even though all of the above have an effect on the length of stay, we find that age is the main determinant deciding the duration. These results may serve as a starting point for policymakers and tourism managers to tailor strategies to increase income streams associated with length of stay.     

长江中游城市群旅游与经济发展空间差异演化及互动关系

搜集了2000—2017年长江中游城市群29个城市的相关数据,探索长江中游城市群旅游与经济发展的空间差异变化及其互动关系,结果发现:(1)长江中游城市群的旅游增长速度大于经济增长速度,且旅游增长速度区域差异大于经济增长速度的区域差异。(2)长江中游城市群旅游发展的不平衡性大于经济发展的不平衡性,旅游和经济的基尼系数及重心在不同区域的变化趋势不同,在不同的时间段内两者的变化方向也不同,既有同向变化,也有反向变化。(3)整个长江中游城市群经济发展的平衡性对旅游发展的平衡性无显著影响,而旅游发展的平衡性会影响到区域经济发展的平衡性,长江中游城市群、武汉城市圈的旅游与经济发展的不平衡性呈负相关关系。     

Speed-profile-based road segmentation for accident occurrence modelling for hilly terrains

Modelling the accident occurrences per unit length of the road requires segmentation of road stretch. In the case of hilly terrains, homogeneity-based approach results in extremely small sections thus creating a biased accident data. This result is due to the high variations in geometry along the length of the road stretch. Constant length sections do not consider the effect of road's characteristics, hence may lead to undesirable results. It is hypothesized that the speed profile of a vehicle moving in free-flow conditions is governed by the road geometry as well as the road side environment. In this paper, a new methodology based on speed profile of a test vehicle (passenger car) has been proposed for segmenting a road stretch passing through hilly terrain. Comparative analysis of the results obtained from the constant length segmentation approach and the proposed approach shows that the later approach is producing statistically better results. Relatively more parameters were found to be statistically significant in the model based on speed-profile-based segmentation. Grade length, which could be one of the major parameters in hilly terrains, was found to be statistically significant only in the model based on speed-profile-based segmentation.     

兰州市土地综合承载力的空间异化特征及其机理分析

土地综合承载力是社会、经济、环境的协调作用的中介和协调程度的表征,其空间异化研究能够有效地为多样化与区域适应性的土地利用政策的制定提供依据。通过构建土地资源综合承载力指标,从城市个体空间异化视角,采用熵值法确定权重,对兰州市土地资源承载力空间特征及其机理进行了剖析研究。研究认为,地均固定资产投资（0.102）、经济密度（0.088）指标所占比重较大,经济技术是兰州市土地综合承载力稳定发展的最主要因素;兰州市土地综合承载力指数总体变化呈现出“东南高、西北低”的空间分异特征;高承载力区主要受到经济技术条件的支撑,而榆中、皋兰等县低承载力区域,其主要受制于自然、经济环境多方面的限制。     

基于销售商利润的生鲜食品最优变异度研究

为保证生鲜食品安全性,对生鲜食品的监管、销售和购买提供参考依据,基于销售商预期利润最大化,以生鲜食品变异度为决策变量建立优化模型,分析得出由最佳销售期、消费者能够接受质量水平对应最小和最大天数、质量水平的边际收益和控制质量变异的成本参数共同决定的最优变异度,以及上述因素对最优变异度的影响,并利用数值算例验证结论,最后分别针对监管部门、销售商和消费者给出了建议。