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This study analyzes the political viability of the Russia-North Korea-South Korea (RNS) gas pipeline project. This analysis demonstrates that North Korea’s fourth nuclear test in January 2016 changed the dynamic of the project. Before the test, when inter-Korean relations were good, South Korea and Russia could make efforts to secure political support for the project. However, after the fourth nuclear test, this was no longer the case. As North Korea’s nuclear power status became more evident, this nuclear problem began to have profound implications for U.S. security. In response, Washington not only led the UN Security Council to impose very severe sanctions against North Korea, but also placed its own sanctions on the country. These sanctions began to contain provisions that could prevent the implementation of the pipeline project. In addition to these sanctions, the U.S. sanctions against Russia in 2017 over its intervention in the U.S. election and aggression against Ukraine also contained clauses that could hamper it. Therefore, unless the U.S. lifts or eases all of these sanctions, South Korea and Russia are unwilling to take any concrete actions to secure political support for the RNS pipeline project. Based on this analysis, this paper argues that the U.S. now holds the most important key to its political viability.

In a railroad system, train pathing is concerned with the assignment of trains to links and tracks, and train timetabling allocates time slots to trains. In this paper, we present an optimization heuristic to solve the train pathing and timetabling problem. This heuristic allows the dwell time of trains in a station or link to be dependent on the assigned tracks. It also allows the minimum clearance time between the trains to depend on their relative status. The heuristic generates a number of alternative paths for each train service in the initialization phase. Then it uses a neighborhood search approach to find good feasible combinations of these paths. A linear program is developed to evaluate the quality of each combination that is encountered. Numerical examples are provided.

In this article, the influence of gluing-solution layout on the gluing-solution distribution at the final stage of solidification process in a realistic railway ballast is investigated. A unified Cauchy stress model, with an asymptotic time-dependent viscosity, is proposed to account for the coupled antithixotropic and shear-thickening features of gluing solutions. Realistic railway ballast is accomplished by using the vertexidentification technique, in which regulations for gravel composition in ballast practice are followed.A network and matrix layouts of gluing solution are applied. Flow characteristics and time-dependent solidification of the gluing solution in the multiconnected conducts spanned by the gravels are simulated by using a finite-element code. Although more concrete lateral and vertical gluing adhesions among the gravels can be accomplished by spreading gluing solution in the network arrangement, the gluing-solution distribution obtained by pouring gluing solution in the matrix layout is relatively localized and limited. For a better pointwise gravel-gravel adhesion, gluing solution in a network arrangement is pronounced to be an a priori gluing practice. [ABSTRACT FROM AUTHOR]

This paper analyzes the potential risks of the Russia-North Korea-South Korea (RNS) gas pipeline, comparing it with the Russia-Ukraine-Europe (RUE) pipeline. I argue that the possibility of disputes is much higher in the RNS case. Furthermore, I propose that the South Korean government opt to import liquefied natural gas by ship directly from Russia if contingency plans in the case of gas supply disruptions in the RNS pipeline are not available. [ABSTRACT FROM AUTHOR]

Simulation of granular particles is an important tool in many fields. However, simulation of particles of complex shapes remains largely out of reach even in two-dimension. One of the major hurdles is the difficulty in representing particles in an efficient, flexible, and accurate manner. By representing particles as convex polyhedrons which are themselves the intersection of a set of half spaces, we develop a method that allows one to efficiently carry out key operations, including particle–particle and particle–container wall overlapping detection, precise identification of the overlapping region, particle shifting, particle rotation, and others. The simulation of packing 1,000 particles into a container takes only a few minutes with this approach. We further demonstrate the potential of this approach with a simulation that re-generates the “Brazil nut” phenomenon by mixing and shaking particles of two different sizes. [ABSTRACT FROM AUTHOR]

This research presents an optimization heuristic to solve the horizontal alignment of a highway segment. The iterative heuristic works in two stages. The first stage uses a neighborhood search approach to find a good piecewise linear line that approximates the highway alignment. The second stage further adjusts the alignment so that the external and code requirements are accurately satisfied. Both stages manipulate the piecewise linear line with a neighborhood search heuristic, and use a mixed integer program (MIP) to ensure that the piecewise linear line crosses the control areas and avoids the restricted ones. The optimal objective function value returned by the MIP is used to compare the quality between different piecewise linear lines. The lengths of each line segment are properly constrained in the MIP to ensure that curves can be correctly deployed. Starting from an initial feasible solution the process gradually improves the alignment through iterations. Computational examples are provided. [ABSTRACT FROM AUTHOR]

This research develops a model to solve for the three-dimensional alignment of a highway segment. Code requirements are taken into consideration, and mechanisms for maintaining heavy vehicle speeds are embedded in the model. The model brings the highway alignment close to certain preferred points, and avoids restricted areas when required. Horizontal alignment is composed of design elements, including tangent segments, circular curves, and clothoid curves. Vertical alignment is represented by lines and vertical curves. Both alignments are highly compatible with code requirements in practice. The three-dimensional alignment is obtained through an iterative process. With each iteration, a new horizontal alignment was obtained through a slight adjustment of the current alignment. Subsequently, a corresponding vertical alignment was developed by solving a series of linear mixed integer optimization problems. The entire solution process was divided into three stages with different tasks, and the accuracies in each stage carefully set to achieve efficiency. Some computational examples are provided. [ABSTRACT FROM AUTHOR]

Presents a mathematical model that solves for a set of optimal highway vertical grades for a given horizontal alignment. Comparison of the mathematical model to previous models; Definition of the vertical profile of a highway; Factors taken into consideration while designing the vertical profile of a highway.