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Construction of Turkmenistan’s East–West (EW) gas pipeline was completed in December 2015 when signs of the country’s severe economic decline were becoming increasingly evident. This paper examines...

Influence of gravel segregation on gluing solution distribution in a realistic railway ballasts is investigated numerically. The rheological characteristics of the gluing solution are accounted for by using a coupled elasto-visco-plastic stress model with an asymptotic time increasing viscosity. The realistic railway ballast is accomplished by using the vertex identification technique, in which the regulations of the gravel composition in ballast practice are followed. Specifically, a uniformly distributed one and a segregated one induced by the difference in gravel size and gravel shape are generated. The rheological model of the gluing solution and twofold ballasts are incorporated into the finite element code of ANSYS $$^{\copyright }$$ to study the flow characteristics and time-dependent solidification of the gluing solution. Relatively concrete vertical and lateral gravel–gravel adhesion in twofold ballasts can be generated by using denser network arrangement of the gluing solution; the vertical penetration in the uniform ballast is slightly deeper than that in the segregated ballast, while a slightly reverse tendency in the lateral extension near the upper and central parts appears. However, the difference in the solidified gluing solution distributions in both ballasts is essentially insignificant, indicating that the influence of the gravel segregation needs not necessary to be taken into account in gluing practice when percolation is not taken into account.

For a passenger railway system with a published timetable, train timetable adherence and punctuality are critical performance indicators. Compared with other resource allocation methods, timetable adjustment is a relatively cost-effective approach for improving timetable adherence. The insertion of appropriate time supplement and buffer time into a timetable to reduce delays as well as their propagation can improve punctuality. However, to appropriately distribute available supplement/buffer time is a challenging task, especially for real-world cases. Moreover, a very robust timetable may not necessarily be a good choice, since ideal punctuality might come at the cost of large time slacks. In this study, we propose a simulation-based approach that embeds a linear programming model to effectively adjust the time supplement and buffer time in a given passenger railway timetable to reduce the average delay. The proposed solution approach is empirically applied to instances of various sizes. It is shown that the heuristic can quantify the relationship between timetable efficiency and robustness, which helps railway operators select their ideal balance between these two important yet conflicting issues. Further, numerical studies with a real timetable demonstrate that the timetable can achieve better punctuality with an even lower time supplement after adjustment, and the insights observed in this work have not only academic value but also value for practitioners in their preparation of timetables.

The primary aim of this paper is to explain the 2009 Russia-Ukraine gas conflict. In particular, it attempts to identify the causal mechanisms between their interdependence in the gas sphere and the gas conflict. The paper first shows that existing theories in the study of international relations have limitations in accounting for that conflict. Therefore, a theoretical framework drawing insights from Armstrong's model on dependence-political compliance and Crescenzi's exit model is proposed to explain it. Relying on this framework, this paper demonstrates that the 2009 Russia-Ukraine gas conflict took place through two critical causal mechanisms. In the contexts of the 2008 global financial crisis and Ukraine's anti-Russian policy, Russia and Ukraine both considered issues involved in the gas trade such as debts, prices, transit tariffs, and Ukraine's pipeline system to be very important. Therefore, when Russia issued demands with economic threats, Ukraine refused to comply.

The demand for container terminal yards is growing significantly faster than the supply of available land; therefore, containers are typically stacked high to better utilize the land space in container yards. However, in the process of container retrieval, non-productive reshuffling may be required to relocate the containers that are stacked on top of the target container. Container retrieval is directly related to the operational efficiency of terminals. Because the industry has become increasingly competitive, it has become critical to introduce a systematic approach to retrieving containers. In this study, we develop a heuristic that can generate feasible working plans for rail-mounted gantry cranes (RMGC) in container yards to minimize the number of container movements while taking the RMGC working time into consideration. The methodology takes into consideration the case that containers are grouped in terms of their retrieval order. Multi-lift RMGC models also are studied. Comprehensive numerical experiments reveal that the method runs faster than other methods published in the literature by several orders of magnitude; additionally, our method is able to solve instances larger than practical use. The number of movements approaches a theoretical lower bound, and the numerical results clearly demonstrate the tradeoff between the number of movements and the working time, and provide useful insights for yard planning.

This paper applies two hypotheses regarding weak state foreign policy to analyze the opportunities and risks in Turkmenistan’s quest to diversify its gas export routes, especially since 2006. The first hypothesis, related to opportunities, is that competition among major powers over the allegiance of weak states strengthens their bargaining power. The second hypothesis, related to risks, is that the diversification policies of weak states in times of decreasing competition among great powers incur the danger of simply replacing an old master with a new one. I argue that while the first hypothesis is useful in explaining the opportunities of Turkmenistan’s diversification policies, especially before early 2009, the second hypothesis is helpful in accounting for the risks of these policies after early 2009. In other words, competition among four major powers, Russia, China, the EU, and India, over Turkmenistan’s gas pipeline system before early 2009 strengthened the country’s bargaining power. In contrast, Turkmenistan’s diversification policies in times of fading competition after early 2009 have left it increasingly exposed to the potential risk of replacing its old master, Russia, with a new one, China.

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.

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 vertex-identification 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 ...

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. These important tasks were traditionally done manually, but there is an increasing move toward automated software based on mathematical models and algorithms. Most published models in the literature either focus on train timetabling only, or are too complicated to solve when facing large instances. In this paper, we present an optimization heuristic that includes both train pathing and train timetabling, and has the ability to solve real-sized instances. This heuristic allows the operation time of trains to depend on the assigned track, and also lets the minimum headway between the trains to depend on the trains’ relative status. It generates an initial solution with a simple rule, and then uses a four-step process to derive the solution iteratively. Each iteration starts by altering the order the trains travel between stations, then it assigns the services to the tracks in the stations with a binary integer program, determines the order they pass through the stations with a linear program, and uses another linear program to produce a timetable. After these four steps, the heuristic accepts or rejects the new solution according to a Threshold Accepting rule. By decomposing the original complex problem into four parts, and by attacking each part with simpler neighborhood-search processes or mathematical programs, the heuristic is able to solve realistic instances. When tested with two real-world examples, one from a 159.3 km, 29-station railroad that offers 44 daily services, and another from a 345 km, eight-station high-speed rail with 128 services, the heuristic obtained timetables that are at least as good as real schedules.

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.

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.

This paper examines why there is no multinational regime governing resource extraction in the East China Sea. After comparing the East China Sea case with the partially successful regime governing Caspian Sea resources, we suggest two explanatory variables: relative power relations and trust factors.

(2005). Toward a New International Regime for the Caspian Sea. Problems of Post-Communism: Vol. 52, No. 3, pp. 37-48.

This study examines the approach of five Caspian coastal states ‐ Russia, Iran, Azerbaijan, Kazakhstan, and Turkmenistan‐toward the legal regime regarding the Caspian Sea in the 1990s. In particular, it tests the neorealist hypothesis regarding relative gains in explaining the approach of those five Caspian coastal states. This study demonstrates that concerns about relative gains matter, but not universally. Azerbaijan and Kazakhstan consistently pursued relative gains strategy. Yet, in the cases of three other Caspian states, Russia, Iran, and Turkmenistan, concerns about relative gains were not critical in determining the policy direction of these states.

In practice, the task of designing the vertical alignment of a highway is done manually by an experienced engineer. As a result, the work is both time and resource consuming and relies heavily on human expertise. This work presents a mathematical model that solves for a set of optimal highway vertical grades for a given horizontal alignment. In addition to construction costs, facts considered by this model include earthwork balance and traffic speed in both directions. Code requirements and design practice are also considered. A three-layered heuristic is developed to solve the model. In the first layer, a neighborhood search heuristic is used to determine the locations where grade can change. The second layer sets penalty terms for sections where speed is undesirable, and the third layer solves a mixed integer program that has very few or no 0-1 integer variables. Computational testing on a 2-km road segment shows that the model yields good solutions.

In this paper we propose a model to calculate an optimal vertical alignment of an interchange with a given horizontal layout. The vertical profiles of all ramps in the interchange are solved simultaneously. The problem is formulated as a mixed integer program. A heuristic that can solve the problem very efficiently is also proposed. The model and heuristic were tested by applying the technique to a real life example, a full system interchange with 4 legs and 8 ramps. Comparison of the computational results with the real layout, which was designed by a major consulting firm, indicates that the model produces designs close to those of human experts.

Planning for the operation of a railway system is a very complicated task. At the center stage of this planning work is timetabling. In this work we present TrainWorld, a powerful, sophisticated software system that, among other capabilities, is able to solve for high-quality timetables for real-sized, complicated railways. Testing with Taiwan Railways Administration (TRA) data demonstrates the ability of TrainWorld in solving for real-world timetables. The TRA system has 224 stations, approximately three-quarters of the 1085Km railway are double-tracked, and the rest are single-tracked. The system offers close to 1000 daily services in its 18-hour operation hours. Some busy stations carry more than 280 services a day, resulting in an eight-minute average headway between trains. TrainWorld is able to solve a timetable for such a system in approximately 70 hours, and the result is close to the real timetable.Copyright © 2013 by ASME

Railway system operation is a very complicated task and must be supported by the coordination of several systems including engineering, transportation, locomotive maintenance and management, ticket system and passengers service, etc. Ideally, a modern railway enterprise information system should be an integrated, consisted, and site-opened database to support railway system operation. However, multiple isolated applications instead of one integrated enterprise information system are often formed due to historical factors such as independent departments, budgetary constraint and application requirements diversification. Take Taiwan Railways Administration (TRA) as an example, four major departments have their own support systems and databases that store critical planning and operational data. Those systems are isolated and can hardly communicate with each other. As a result, most cross-systems information analyses or data reference for decision making are done manually, which significantly affect the organizational efficiency of TRA. To address the aforementioned issues, a railway decision support platform (RDSP) for integrating the legacy systems (databases) is proposed in this paper. RDSP is designed to be a railway enterprise information system that supports the critical functions of data warehouse and decision support. Furthermore, RDSP is built by integrating the existing legacy systems rather than by building it from scratch. A data bridging system (HDBS) including four modules are design and implemented, input module for connecting the external data sources, output module for exporting integrated report or dumping data by predefined criteria for other systems, configuration module with a web-based user interface for setting up the periodic operations of data input or output tasks, and DB connection module for connecting external databases. Various types of railway system data are designed in RDSP schema and collected, including facilities, timetable, train services records, tickets, centralized traffic control (CTC) system records, and automatic train protection (ATP) system records. RDSP provides a system framework to integrate many isolated island-style databases that currently exist in TRA, and can form a cross-enterprise database that serves as the primary and only data platform. To demonstrate the efficacy of the RDSP, a spatiotemporal ticket-selling analysis report, a train delay cause analysis report, and a timetable planning software (TrainWorld) are designed on top of it. In the future, RDSP will play a major supportive role in infrastructure maintenance, operations, decision support, and planning.

This paper examines the influence of fund flow on fund performance in US domestic equity funds from 1993 to 2008. We find that fund flow has an asymmetric influence on fund performance. Inflow will significantly push up simultaneous fund performance, whereas outflow does not significantly result in negative risk-adjusted returns. We also find suggestive evidence that the outperformance of funds experiencing inflow comes from flow-driven purchase, which means that funds with inflow may expand existing positions and create positive price pressure in overlapping positions.

In this paper we present computational testing results on very large scale random assignment problems. We consider a fully dense assignment problem with 2n nodes. Some conjectured or derived properties regarding fully dense assignment problems including the convergence of the optimal objective function value and the portion of nodes assigned with their kth best arc have been verified for networks up to n = 100,000 in size. Also we demonstrate the power of our approach in solving very large scale assignment problems by solving a one million node, one trillion arc random assignment problem.

In this paper, we present a computer model that can simulate the packing process and estimate the maximum density of granular material. We use three-dimensional ellipsoids as a surrogate to simulate natural particles. The model first fills the ellipsoids into a container, and then adjusts them to reach a higher density. A special process is derived to prevent deadlocking as the particles move downward. We develop algorithms to test for contacts between a given ellipsoid and a container wall or another ellipsoid. A sampling process was used to determine the average density of the packed material. This process is simple and can be used to estimate the average density at any part of the container. We verify the effectiveness of the model by testing it against analytical results for a special case, and also with particle distribution derived from a real-life standard sand. Both results are very promising.