We study the structural properties of Pakistan railway network (PRN), where railway stations are considered as nodes while edges are represented by trains directly linking two stations. The network displays small world properties and is assortative in nature. Based on betweenness and closeness centralities of the nodes, the most important cities are identified with respect to connectivity as this could help in identifying the potential congestion points in the network.

The structure and properties of public transportation networks have great implications in urban planning, public policies, and infectious disease control. This study contributes a weighted complex network analysis of travel routes on the national highway network of Pakistan. The network is responsible for handling 75 percent of the road traffic yet is largely inadequate, poor, and unreliable. The highway network displays small world properties and is assortative in nature. Based on the betweenness centrality of the nodes, the most important cities are identified as this could help in identifying the potential congestion points in the network. Keeping in view the strategic location of Pakistan, such a study is of practical importance and could provide opportunities for policy makers to improve the performance of the highway network.

In the distributed and horizontally integrated manufacturing environment found in agile manufacturing, there is a great demand for new product development methods that are capable of generating new customized assembly designs based on mature component designs that might be dispersed at geographically distributed partner sites. To cater for this demand, this paper addresses the methodology for complex assembly variant design in agile manufacturing. It consists in fundamental research in two parts: (i) assembly modeling; and (ii) assembly variant design methodology. This paper, the first of a two-part series, presents the assembly variant design system architecture and the assembly modeling methodology. First, a complementary assembly modeling concept is proposed with two kinds of assembly models, the hierarchical assembly model and the relational assembly model. The first explicitly captures the hierarchical and functional relationships between constituent components whereas the second explicitly captures the mating relationships at the form-feature-level. These models are complementary in the sense that each of them models only a specific aspect of assembly-related information but together they include the required assembly-related information. They are further specialized to accommodate the features of assembly variant design. As a result, two kinds of assembly models, the assembly variants model and the assembly mating graph are generated. These assembly models serve as the basis for assembly variant design which is discussed in the companion paper.

In the first paper of this two-part series, the assembly variant design system architecture and complementary assembly methodology were presented. The general complementary assembly models, hierarchical assembly model and relational assembly model, are established which were further specified as the Assembly Variants Model (AVM) and the Assembly Mating Graphs (AMGs) respectively to cater for the needs for assembly variant design. This paper discusses the assembly variant design methodology which is based on these assembly models. The matching components are searched and retrieved from the AVM and then the constraint groups are identified by manipulating the AMGs. Then the assembly variant design process is formulated as a mixed-integer (linear or non-linear) programming problem which is solved using a standard solver or heuristic. This methodology provides a systematic approach to facilitate the variant design of complex assembly products in the agile manufacturing environment. Finally, a prototype system is developed and examples are presented.

Zheng, S.; Wang, A.; Mohmand, Y.T., and He, Y., 2017. Path optimum algorithm for container relocation problems in port terminals worldwide. The container relocation problem (CRP) is concerned with emptying a cluster of identical containers stacked in one bay where every container is given a fixed extractive sequence with the fewest number of relocations. Such a typical problem has been examined in this paper. This research differs from previous studies in the following aspects: First, the retrieval paths of the CRP is proposed and its nondeterministic polynomial-time-hardness has been proved. Moreover, a mathematical model is presented that can provide the theoretical basis for the current research. Since the feasible retrieval paths are numerous, heuristic rules are presented to effectively reduce the resolution space. In addition, a new path optimum algorithm (POA) based upon heuristics is proposed to find the optimal solution for any-scale instances in a shorter central processing unit run time. Numerical experiments and comparisons with the other algorithms from the literature show the superiority, high efficiency, robustness, and accuracy of this algorithm. As competition among coastal and inland container ports has become fierce, POA can be used to increase port handling efficiency and facilitate the decision making regarding container port infrastructure planning, and contribute to coastal research worldwide.