• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.501-514
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• 2015

Earthwork is a basic operation for all forms of civil works and affects construction time, cost and productivity. It is a mechanized operation that needs various construction equipment as a group and uses a lot of fuel for construction equipment. But, the problem is that earthwork operation is usually performed by equipment operator's heuristic and intuition, which can cause low productivity, high fuel consumption, and high carbon dioxide emission. As one of solutions for this problem, the fleet management system for construction equipment is suggested for effective earthwork planning, optimal equipment allocation, efficient machine operation, fast information exchange, and so forth. The purpose of this research is to suggest core methods for developing the equipment fleet management system. The methods include 3D solid parametric model generation, soil distribution using Cctree data structure, equipment fleet construction and equipment fleet operation. A simulation test is performed to verify the effectiveness of the equipment fleet management system in terms of equipment operating ratio, fuel usage, and $CO_2$ emission.

• Korea Trade Review
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• v.48 no.3
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• pp.69-88
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• 2023

This study analyzes the dynamic characteristics of cargo volume (demand), ship fleet (supply), and freight rate (price) of container, dry bulk, and tanker shipping markets by using the VAR and VECM models. This analysis is expected to enhance the statistical understanding of market dynamics, which is perceived by the actual experiences of market participants. The common statistical patterns, which are all shown in the three shipping markets, are as follows: 1) The Granger-causality test reveals that the past increase of fleet variable induces the present decrease of freight rate variable. 2) The impulse-response analysis shows that cargo shock increases the freight rate but fleet shock decreases the freight rate. 3) Among the three cargo, fleet, and freight rate shocks, the freight rate shock is overwhelmingly largest. 4) The comparison of adjR² reveals that the fleet variable is most explained by the endogenous variables, i.e., cargo, fleet, and freight rate in each of shipping markets. 5) The estimation of co-integrating vectors shows that the increase of cargo increases the freight rate but the increase of fleet decreases the freight rate. 6) The estimation of adjustment speed demonstrates that the past-period positive deviation from the long-run equilibrium freight rate induces the decrease of present freight rate.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.171-172
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• 2015

Vinalines is actually known as not only one of Vietnam's state-sponsored economic giants but also the largest shipowner by tonnage in Vietnamese shipping industry. Therefore, a question of how to improve business performance of the corporation is always received deep attention by Vietnamese government, specially after the seriously economic scandal of Vinalines in a last few years. Among development strategies, the study focuses on short-term one in which Vinalines is recommended to restructure its own fleet in order to optimize performance of fleet operation and minimize costs while meeting the customer's shipping demand in near future. The first section is of introduction. Via method of statistical data analysis, section 2 brings to readers a panorama about the development profile and the current situation of development of Vinalines. In section 3, the authors use linear programming for setting a cost-minimization model optimizing Vinalines fleet structure based on available statistics and forecast information by Vinalines. The optimization problem is solved by applying AIMMS software in section 4. Finally, some conclusions and proposals by authors for the development of Vinalines are given.

• Journal of Korean Institute of Industrial Engineers
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• v.35 no.2
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• pp.150-159
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• 2009

The heterogeneous fleet vehicle routing problem(HVRP) is a variant of the classical vehicle routing problem in which customers are served by a heterogeneous fleet of vehicles with various capacities, fixed costs and variable costs. We propose a new conceptual HVRPCR(HVRP with customer restriction) model including additional customer restrictions in HVRP. In this paper, we develop hybrid particle swarm optimization(HPSO) algorithm with 2-opt and node exchange technique for HVRP. The solution representation is a n-dimensional particle for HVRP with N customers. The decoding method for this representation starts with the transformation of particle into a priority list of customer to enter route and limit of vehicle to serve each customer. The vehicle routes are then constructed based on the customer priority list and limit of vehicle to serve. The proposed algorithm is tested using 8 benchmark problems and it consistently produces high-quality solutions, including new best solutions. The numerical results show that the proposed algorithm is robust and efficient.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.179-184
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• 2002

We consider the heterogeneous fleet vehicle routing problem (HVRP), a variant of the classical vehicle routing problem (VRP). The HVRP differs from the classical VRP in that it deals with a heterogeneous fleet of vehicles having various capacities, fixed costs, and variables costs. Therefore the HVRP is to find the fleet composition and a set of routes with minimum total cost. We give an integer programming formulation of the problem and propose an algorithm to solve it. Although the formulation has exponentially many variables, we can efficiently solve the linear programming relaxation of it by using the column generation technique. To generate profitable columns we solve a shortest path problem with capacity constraints using dynamic programming. After solving the linear programming relaxation, we apply a branch-and-bound procedure. We test the proposed algorithm on a set of benchmark instances. Test results show that the algorithm gives best-known solutions to almost all instances.

• Strategy21
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• s.41
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• pp.5-29
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• 2017

The Mahan's seapower theory has been the basis of US Navy to date as it can enjoy the supremacy status in all of the seas of the world. His theory is very straightforward. A nation can be a great country in the world just through the use of maritime commerce that could be protected by a strong and powerful navy. Mahan's theory on seapower was substantiated in the Spanish-American War with respect to how important the naval power is. The best thing to make US a great nation was to make sure that flow of international trade is smooth, and the unhindered trade could be made possible only by the destruction of enemy's fleet that may obstruct the SLOCs. That's why Mahan insisted that a strong navy was needed and a decisive battle by the navy's fleet at sea should be encouraged as a way of ensuring the safety of the SLOCs. The newly-arrived Trump administration seems to be in line with the Mahan's theory seapower in its policy on naval forces structure. It is expected that US will continue to support the Pivot to Asia policy that has been adopted by the previous administration through an increase in its naval fleet forces. The number of US navy ships will be 355 in 2030, rendering it much more powerful navy than before. The catch phrase "3rd Fleet Forward" proposed by the president Trump indicates that two carrier strike groups will be present in the Asia Pacific region, being able to make the confrontation between US and China more tense than before. The presence of the US naval forces in the area may function as some sort of pressure against China that Trump insisted had been responsible for the closure of 60,000 factories and the loss of 3,000,000 jobs in the United States.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.6
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• pp.812-818
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• 2002

Spatio-temporal distributions of nighttime fishing fleet are descirbed with the aid of geographic information system(GIS) technology in the East/Japan Sea, using daily mean composite images of the Defense Meteorological Satellite Program(DMSP) /Operational Linescan System(OLS) in 1993. We selected a study area from $30^{\circ} N to 44^{\circ} N in latitude and from 124^{\circ} E to 142^{\circ}$ E in longitude in order to describe the monthly and seasonal changes of nighttime fishing fleet. The GIS software package Image Analyst (ArcView 3) are used to analyze spatio-temporal distributions of fishing nut. And the OLS images of nighttime visible band provide useful information about the spatio-temporal distribution of the fishing nut. Density areas of nighttime fishing fleet are around Tsushima/korea Strait. the east coast of the Korea Peninsula, the coast of Honshu, and around Yamato Bank.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.257-264
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• 2003

The international oil majors have been reducing the size of their own oil tanker fleet since from the beginning of 1980s. Like international oil majors, the Korean refineries are getting more dependent on tanker chartering than tanker ownership for their oil transportation since 1990s. They also prefer spot charter to time charter and this kind of trend continue up to today. Consequently, this paper attempted to find out factors influencing changes in tanker fleet composition. To attain the object, a empirical study is adopted using the ten decision making factors derived from the preceeding study. The findings are that MARPOL and OPA 90, and transportation cost are the most important factors influencing on oil tanker fleet composition.

• ETRI Journal
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• v.37 no.2
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• pp.273-282
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• 2015

Vehicle-to-grid presents a mechanism to meet the key requirements of an electric power system, using electric vehicles (EVs) when they are parked. The most economic ancillary service is that of frequency regulation, which imposes some constraints regarding the period and duration of time the vehicles have to be connected to the grid. The majority of research explores the profitability of the aggregator, while the perspective of the EV fleet owner, in terms of their need for usage of their fleet, remains neglected. In this paper, the optimal allocation of available vehicles on a day-ahead basis using queuing theory and fuzzy multi-criteria methodology has been determined. The proposed methodology is illustrated on the daily scheduling of EVs in an electricity distribution company.

• Proceedings of the Society of Korea Industrial and System Engineering Conference
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• 2002.05a
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• pp.209-215
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• 2002

In this paper, we propose a freight and fleet optimization model under CVO environment. The model is a kind of multi commodity network flow model based on Vehicle Routing Problem(VRP) and Vehicle Scheduling Problem(VSP), and considering operations and purposes of CVO. The main purpose of CVO is the freight and fleet management to reduce logistics cost and to Improve in vehicle safety. Thus, the objective of this model is to minimize routing cost of all the vehicle and to find the location of commodities which have origin and destination. We also present some computing test results.