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81.
Yosuke Hanawa Yuya Higashikawa Naoyuki Kamiyama Naoki Katoh Atsushi Takizawa 《Journal of Combinatorial Optimization》2018,36(4):1299-1314
A dynamic network introduced by Ford and Fulkerson is a directed graph with capacities and transit times on its arcs. The quickest transshipment problem is one of the most fundamental problems in dynamic networks. In this problem, we are given sources and sinks. Then the goal of this problem is to find a minimum time limit such that we can send the right amount of flow from sources to sinks. In this paper, we introduce a variant of this problem called the mixed evacuation problem. This problem models an emergent situation in which people can evacuate on foot or by car. The goal is to organize such a mixed evacuation so that an efficient evacuation can be achieved. In this paper, we study this problem from the theoretical and practical viewpoints. In the first part, we prove the polynomial-time solvability of this problem in the case where the number of sources and sinks is not large, and also prove the polynomial-time solvability and computational hardness of its variants with integer constraints. In the second part, we apply our model to the case study of Minabe town in Wakayama prefecture, Japan. 相似文献
82.
Jidan Huang Feifeng Zheng Yinfeng Xu Ming Liu 《Journal of Combinatorial Optimization》2018,35(1):216-223
In this work we investigate the online over-list MapReduce processing problem on two identical parallel machines, aiming at minimizing the makespan. Jobs are revealed one by one, and each job consists of one map task and one reduce task. The map task can be arbitrarily split and processed on both machines simultaneously, while the reduce task has to be processed on a single machine and it cannot be started unless the map task has been completed. We first show that the general case of the problem reduces to the classical two machine online scheduling model with an optimal competitive ratio of 3/2. For a special case where the map task is at least as long as the reduce task, we prove that no online algorithm can be less than 4/3-competitive. An optimal Greedy algorithm with a matching competitive ratio is proposed as well. 相似文献
83.
A central problem in compressed sensing is the construction of sensing matrices. In this paper, we show how to construct sensing matrices by using semilattices, and give many examples of sensing matrices constructed from specific semilattices. Moreover, we show that the new construction for some examples with small parameters gives better sensing matrices compared with previously known constructions. 相似文献
84.
Retraining of staff is a compulsory managerial function in many organisations and often requires planning for a large number of employees. The large scale of this problem and various restrictions on the resultant assignment to classes make this planning challenging. The paper presents a complexity analysis of this problem together with linear and nonlinear mathematical programming formulations. Three different column generation based optimisation procedures and a large neighbourhood search procedure, incorporating column generation, are compared by means of computational experiments. The experiments used data typical to large electricity distributors. 相似文献
85.
Luigi Lepore Francesco Paolone Domenico Rocco Cambrea 《Journal of Management and Governance》2018,22(4):829-862
Research on the effect of ownership structure on firm performance shows no convergent evidence concerning the sign and form of the above-mentioned relationship. Similarly, there is no homogeneous evidence documenting family ownership concentration is always positively or negatively correlated with firm value, or irrelevant. This paper analyses whether and how the de facto investor protection provided by the judicial system affects the relationship between corporate performance and ownership structure in 1314 firms operating in four European countries (Germany, France, Italy, and Spain) over a five-year period, 2010–2014. Moreover, we analyse whether judicial system efficiency influences if and how family firms in the controlling coalition collude for expropriating minority shareholders. Our findings show that the level of shareholder protection, derived from judicial efficiency, is relevant to the relationship between ownership structure and firm performance, thus corroborating literature in that institutional contexts matter in explaining such relations. The results suggest the need for more efficient external mechanisms of corporate governance to facilitate investment in equity capital, thus decreasing the country risk perceived by investors. 相似文献
86.
QiJie Xiao 《Public Organization Review》2018,18(2):207-221
Control often weakens autonomy in organizational theories. While many scholars focus on the paradox of control and autonomy, few pay attention to how an organization obtains both control and autonomy. By exploring Zhangjiakou Internal Immigrant Organization, this study finds two mechanisms can contribute to the balanced combination of control and autonomy. First, managers play ambidextrous official-merchant roles, which means superiors take both bureaucratic and autonomous management styles. Second, members have dual organizational goals for both political status and network support. In conclusion, the successful combination is shaped by the subjective interaction between the government, superior managers and subordinate members. 相似文献
87.
To analyse the role of self-efficacy in goal setting in public administrations, this study combines goal-setting theory, public service motivation literature and cognitive theory. Using partial least squares structural equation modelling (PLS-SEM), survey data from 105 German civil servants are analysed. The results underline the role of goal setting (represented by goal difficulty and specificity) in determining the self-efficacy of public servants. Public service motivation and goal specificity both increase public servants’ work performance; however, the effects of goal difficulty are negatively mediated by the employee’s self-efficacy. That finding reflects the central role of self-efficacy, which should not be ignored in the goal-setting processes of public administrations. 相似文献
88.
Aage Bøttger Sørensen 《Social science research》1975,4(1):65-92
Properties of measures and models of social mobility are analyzed in relation to the conceptualization of mobility. Two main objectives of mobility research are identified. One is the study of determinants of occupational achievement, the other is the study of mobility as a characteristic of social systems. It is shown that the realization of both objectives is hindered by a failure of commonly used models and measures of mobility to separate out the various individual and structural factors responsible for mobility. 相似文献
89.
This study considers an evacuation problem where the evacuees try to escape to the boundary of an affected area, which is convex, and a grid network is embedded in the area. The boundary is unknown to the evacuees and we propose an online evacuation strategy based on the Fibonacci sequence. This strategy is proved to have a competitive ratio of 19.5, which is better than the best previously reported result of 21. 相似文献
90.
Florian Pausinger 《Journal of Combinatorial Optimization》2017,33(4):1378-1394
We present tight upper and lower bounds for the traveling salesman path through the points of two-dimensional modular lattices. We use these results to bound the traveling salesman path of two-dimensional Kronecker point sets. Our results rely on earlier work on shortest vectors in lattices as well as on the strong convergence of Jacobi–Perron type algorithms. 相似文献