Optimal route decision with a geometric ground-airborne hybrid model under weather uncertainty

Adverse weather is the dominant cause of delays in the National Airspace System (NAS). Since the future weather condition is only predictable with a certain degree of accuracy, managing traffic in the weather-affected airspace is a challenging task. In this paper, we propose a geometric model to generate an optimal combination of ground delay and route choice to hedge against weather risk. The geometric recourse model (GRM) is a strategic Probabilistic Air Traffic Management (PATM) model that generates optimal route choice, incorporating route hedging and en-route recourse to respond to weather change: hedged routes are routes other than the nominal or the detour one, and recourse occurs when the weather restricted airspace becomes flyable and aircraft are re-routed to fly direct to the destination. Among several variations of the GRM, we focus on the hybrid Dual Recourse Model (DRM), which allows ground delay as well as route hedging and recourses, when the weather clearance time follows a uniform distribution. The formulation of the hybrid DRM involves two decision variables - ground delay and route choice - and four parameters: storm location, storm size, maximum storm duration time, and ground-airborne cost ratio. The objective function has two components: expected total ground delay cost and expected total airborne cost. We propose a solution algorithm that guarantees to find the global optimum of the hybrid-DRM. Based on the numerical analysis, we find that ground-holding is effective only when combined with the nominal route. Otherwise, it is optimal to fly on the route determined by the DRM without ground delay. We also find the formula of the threshold ground-airborne cost ratio, which we call the Critical Cost Ratio (CCR), that determines the efficacy of ground delay: the higher the CCR, the more effective the strategies involving ground delay. We conclude that both ground delay and route hedging should be considered together to produce the best ATM decisions.     

应用技术型高校创业教育的对策研究

随着知识经济型时代的到来,大学生的就业形势也越来越严峻,作为培养应用技术型人才的高校而言,其创业教育也势必跟上时代的步伐。为此,本文将详细分析当前我国应用技术型高校创业教育存在的问题,并对此提出相应的解决对策及建议。     

预钻式旁压试验在哈尔滨地铁一期工程中的应用

本文通过哈尔滨地铁一期工程的实例,介绍了预钻式旁压试验在工程中的现场操作,成果分析及应用。     

关于提高党的领导干部能力建设问题几点思考

提高党的执政能力,重点在于加强党的各级领导干部的能力建设,从宏观与微观两个层面认识提高领导紧迫性,处理好干部能力建设中的整体与个体、德与才、内因与外因、书本知识与实践经验,党的建设与经济建设的辩证关系,才能把握方向,突出重点,取得实效。     

Exploratory and exploitative innovation: To what extent do the dimensions of individual level absorptive capacity contribute?

Individuals are considered the frontline that allows firms to learn from external sources. However, a firm can only benefit from individual efforts if it understands to what extent the dimensions of individual-level absorptive capacity are related to its innovation strategy. A firm's innovation strategy is characterized by the notions of exploration and exploitation, which result in either radical or incremental innovation. This study examines the driving factors of individual-level absorptive capacity regarding a firm's exploration versus exploitation strategy. Using quantitative data from 104 individuals, partial least squares structural equation modeling (PLS-SEM) analysis was conducted, verifying individuals' competencies in identifying external knowledge as a trigger for both exploratory and exploitative innovation. Consequently, these specific abilities also contribute to organizational ambidexterity. Furthermore, the results show the dichotomous contribution of individual competencies in assimilating external knowledge. While exploratory innovation thrives with individual assimilation efforts, realization of exploitative innovation is not significantly related to these efforts. Ultimately, individuals' competencies in utilizing external knowledge are significantly related to neither exploratory nor exploitative innovation. Moreover, this study provides means for managers to systematically position individuals in the external search process.     

Technological diversity,knowledge flow and capacity,and industrial innovation

ABSTRACT

This article examines the effect of technological diversity, knowledge flow and capacity on industrial innovation performance. We suggest that there is an inverse U-shaped relationship between technological diversity and industrial innovation performance. Moreover, knowledge flow and knowledge capacity are hypothesised as negatively moderating the effect of technological diversity on industrial innovation performance. We use negative binomial regression to test the hypotheses in a panel data of 360 industry-year cases and the findings support our prediction. Managerial implications and future research directions are discussed.     

英语专业高年级阶段的主要教学任务

教育部批准实施的新的《高等学校英语专业教学大纲》将英语本科四年的学习划分为低年级和高年级两个阶段，并明确了两个阶段不同的教学任务。在高年级阶段的主要教学任务是进一步提高语言技能。加强文化教学，提高文化素养，提升综合能力。     

Traffic density,congestion externalities,and urbanization in China

ABSTRACT

Although there is an abundant regional literature analyzing traffic congestion, only a few studies have explored extending such analysis with spatial effects. This study uses a dynamic spatial Durbin model and city-level panel data for the period 2003–14 to investigate the spatial spillover effects of traffic congestion on urbanization in China. The results show that there is an inverted ‘U’-shaped relationship between urbanization and traffic density in local and neighbouring cities, and congestion effects have appeared. In the short and long run, the spatial effects of traffic congestion have become an important force restricting the effective promotion of urbanization in China.     

Vector network equilibrium problems with capacity constraints of arcs

In this paper, we study a (weak) vector equilibrium principle with capacity constraints of arcs and common arcs in some different paths. We obtain some necessary and sufficient conditions for a (weak) vector minimum cost flow. By virtue of a (weak) Δ-equilibrium principle, we also derive some necessary and sufficient conditions for a weak vector equilibrium flow.     

Effect of driver,roadway, collision,and vehicle characteristics on crash severity: a conditional logistic regression approach

The aim of the study is to examine the factors that appear to have a higher potential for serious injury or death of drivers in traffic accidents in Turkey, such as collision type, roadway surface, vehicle speed, alcohol/drug use, and restraint use. Driver crash severity is the dependent variable of this study with two categories, fatal and non-fatal. Due to the binary nature of the dependent variable, a conditional logistic regression analysis was found suitable. Of the 16 independent variables obtained from Turkish police accident reports, 11 variables were found most significantly associated with driver crash severity. They are age, education level, restraint use, roadway condition, roadway type, time of day, collision location, collision type, number and direction of vehicles, vehicle speed, and alcohol/drug use. This study found that belted drivers aged 18–25 years involving two vehicles travelling in the same direction, in an urban area, during the daytime, and on an avenue or a street have better chances of survival in traffic accidents.