• Journal of the Society of Naval Architects of Korea
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• v.35 no.3
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• pp.71-78
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• 1998

Recently, modern long-stroke diesel engines with small number of cylinders have been installed for energy saving and simpler maintenance. These kinds of low speed diesel engine produce large torsional vibration in the shafting, which induces the excessive vibratory stresses in the shafting and large propeller thrust variation. This thrust variation excites vibrations of the shafting and superstructure in the longitudinal direction. Up to now the deteriministic analysis of coupled vibration of marine shafting system has been performed. In this paper probabilistic analysis method of the marine diesel propulsion shafting system under coupled axial and torsional vibrations is presented. For the purpose of this work, the torsional and axial vibration excitations of engine and propeller are assumed to be probabilistic while the lateral excitation is assumed to be deterministic. The probabilistic analysis is based on a response surface and Monte-Carlo simulation. Numerical results based on the proposed method are compared with results calculated using the conventional deterministic analysis method. The results obtained make it clear that the proposed method gives a substantial increase in information about shafting behaviour as compared with the deterministic method.

• Journal of Fisheries and Marine Sciences Education
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• v.6 no.2
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• pp.190-197
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• 1994

In this paper, 2513 marine casualties occurred in Korean waters, during 1989-1993, were analysed by the Multivariate Data Analysis Method. The main results obtained were as follows : 1. Moat of marine casualties resulted from the human factors such as careless operation and insufficient engine maintenance. Engine trouble accounted for main patten of accidents and great number of accidents occurred in fishing vessels. 2. From the point of view of the damage of human life and properties, accidents took place in cargo ships, passenger ships and tankers were serious, but in fishing vessels, those were not so serious. 3. Grounding, collision mainly resulted from careless operation, however flooding and capsizing were much affected by bad weather and material defect.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.10
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• pp.544-551
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• 2015

This study was conducted to determine the LCC of apartment complexes with district heating and a cogeneration system. For the purpose of analyzing LCC according to the size of the apartment complex, 500, 1,500, and 4,000-unit model apartments were selected. Analysis was performed on the design of the heating system and the life cycle cost including total construction cost, maintenance and operation cost for the duration of the project period (15 years). According to the calculated results, 1) The initial cost of the cogeneration system for 500, 1,500, and 4,000-unit apartments is higher than that of the district heating system by 20%, 13%, and 12%, respectively. 2) In the case of the cogeneration system, the payback period by electric generation was found to be 5.21, 4.92 and 4.47 years, and saving cost was calculated to be 29 billion won, 94 billion won and 262 billion won after the payback period for 500, 1,500, and 4,000-unit apartments, respectively. 3) The LCC values of the cogeneration system were 1.12, 1.07 and 1.06 times larger than those of the district system according to the size of the apartment complex. In this study, the district heating system was found to be more efficient than the cogeneration system in terms of LCC reduction. 4) District heating is affected by fuel bills, so energy efficiency should be improved through recovering waste heat (incineration heat, etc.). Also, district cooling should be provided according to heat use to keep the temperature high in winter and low in summer.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.46-53
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• 1999

As of July 1999, i,185 lomocotives(excluding metropolitan area electric locomotives) are in Korean National Railroad(KNR). With this limited number of resources assigning locomotives to each trains of timetable is very important in the entire railway management point of view because schedule can be regarded as goods in transportation industry. On a simple rail network, it is rather easier to assign proper locomotives to trains with the experience of operating experts and get optimal assignment solution. However, as the network is getting bigger and complicated, the number of trains and corresponding locomotives will be dramatically increased to rover all the demands required to service all of the trains in timetable. There will be also numerous operational constraints to be considered. Assigning proper locomotives to trains and building optimal cyclic rotations of locomotive routings will result in increasing efficiency of schedule and giving a guarantee of more profit. The purpose of this study is two fold: (1) we consider a planning-level locomotive scheduling problem with the objective of minimizing the wasting cost under various practical constraints and (2) development of implementation prototype program of its assigning result. Not like other countries, i.e. Canada, Sweden, Korean railroad operates on n daily schedule basis. The objective is to find optimal assignment of locomotives of different types to each trains, which minimize the wasting cost. This problem is defined on a planning stage and therefore, does not consider operational constraints such as maintenance and emergency cases. Due to the large scale of the problem size and complexity, we approach with heuristic methods and column generation to find optimal solution. The locomotive scheduling prototype consists of several modules including database, optimization engine and diagram generator. The optimization engine solves MIP model and provides an optimal locomotive schedule using specified optimization algorithms. A cyclic locomotive route diagram can be generated using this optimal schedule through the diagram generator.

• Advances in materials Research
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• v.8 no.2
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• pp.117-135
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• 2019

The lifetime of a gas turbine combustor is typically limited by the durability of its liner, the structure that encloses the high-temperature combustion products. The primary objective of the combustor thermal design process is to ensure that the liner temperatures do not exceed a maximum value set by material limits. Liner temperatures exceeding these limits hasten the onset of cracking which increase the frequency of unscheduled engine removals and cause the maintenance and repair costs of the engine to increase. Hot gas temperature prediction can be considered a preliminary step for combustor liner temperature prediction which can make a suitable view of combustion chamber conditions. In this study, the temperature distribution of ceramic panels for a V94.2 gas turbine combustor subjected to realistic operation conditions is presented using three-dimensional finite difference method. A simplified model of alumina ceramic is used to obtain the temperature distribution. The external thermal loads consist of convection and radiation heat transfers are considered that these loads are applied to flat segmented panel on hot side and forced convection cooling on the other side. First the temperatures of hot and cold sides of ceramic are calculated. Then, the thermal boundary conditions of all other ceramic sides are estimated by the field observations. Finally, the temperature distributions of ceramic panels for a V94.2 gas turbine combustor are computed by MATLAB software. The results show that the gas emissivity for diffusion mode is more than premix therefore the radiation heat flux and temperature will be more. The results of this work are validated by ANSYS and ABAQUS softwares. It is showed that there is a good agreement between all results.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.62-80
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• 2021

The requirements for the next-generation propulsion system and for a good propellant have been summarized. The characteristics and effectiveness of kerosene, hydrogen, and methane, which are the fuels that are mainly attracting attention in Korea and abroad, were compared with each other. As a result of the comparison, methane was evaluated to be more advantageous than other fuels in reliability, cost, reusability, maintenance, eco-friendliness, safety, lifespan, technical difficulties, engine cycle selection, application of common bulkhead, and non-disassembly/reassembly delivery. And in terms of performance, the specific impulse of methane is higher than that of kerosene, so the efficiency of the launch vehicle can be increased. Methane's properties incluidng eco-friendliness, low-temperature combustion, long life, and maintenability make it beneficial for reuse and for the development of multi-purpose engines.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.97-102
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• 2012

Alternate alternating current (AAC) is used in nuclear power plants (NPPs) in order to cope with station black outs (SBOs). AAC has been provided using diesel engine drive types in Korea's NPPs. The structure of gas turbine generators (GTGs) is simpler than that of diesel generators (DGs), and GTGs have the advantage of longer maintenance intervals. However, GTG-AAC was not used in NPPs in Korea because of the lack of operation/maintenance experience. The purpose of this paper is to analyze the safety of APR+ considering a diversity of AAC types. This paper analyzes reliability data, mechanical specifications of DGs and GTGs, and the sensitivity of core damage frequency to the ACC type.

• Convergence Security Journal
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• v.23 no.2
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• pp.67-74
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• 2023

An elevator is a mechanical and electronic device composed of about 20,000 various parts, and is systematically operated with a close relationship with each other. By intuitively understanding this complex elevator structure and efficiently recognizing the operating model, it will be possible to increase the understanding of the elevator system and the efficiency of maintenance. The existing elevator management system is a process of collecting and understanding information based on data generated from elevators, and has a structure that lacks efficiency in expressing and managing real-world information during elevator maintenance. Therefore, this paper proposes a simulator framework that can operate efficiently based on the actual elevator model. By constructing the recognition of specific objects through a 3D-based service model and visualizing the operation process, it will be possible to enhance the understanding of the structure and operation required for elevator operation. To this end, the core components of the elevator system are identified, the relationship between them and the operating method are visualized, and a simulator is implemented. Based on this, it will be possible to provide a realistic information management and operating environment in virtual space and real platform.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.14-23
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• 1998

The present study investigates numerically particle laden flow through compressor cascade. In general, a lot of turbine engines are affected by various particles which are suspending in the atmosphere. Especially in the case of aircraft aviating in volcanic, industrial and desert region including many particles, each components of engine system are damaged severely. That damage modes are erosion of compressor binding and rotor path components, partial or total blockage of cooling passage and engine control system degradation.. Initial damages can not be serious but cumulation of damages influences on safety of aircraft control and economical maintenance cost of engine system can be increased. When dust, materials and volcanic particles in the atmosphere flow in the compressor, it is necessary to predict damaged and deposited region of compressor blades. To the various flow inlet angle, predictions of particles trajectory in compressor cascade by Lagrangian method are presented and impulses by impaction of particles at blade surface are calculated. By the definition of particle deposition efficiency, characteristics of particles impact are considered quantitatively. With these prediction and experimental data, erosion rates are predicted for two materials - ceramic, soft metal - on compressor blade surface. Improvements like coating of blade surface could be found, by above prediction.

• Environmental and Resource Economics Review
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• v.32 no.4
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• pp.217-238
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• 2023

Currently, automobile tax in Korea is imposed by multiplying the vehicle's engine displacement by a certain tax rate. However, the need for revision is being raised as it is pointed out that the current system does not reflect the immediate task of reducing greenhouse gas emissions. Accordingly, this study focuses on the positive relationship between engine displacement and CO₂ emissions, and seeks to calculate an appropriate automobile tax rate considering average CO₂ emissions. To this end, first, we estimated the average annual CO₂ emissions (kg/vehicle) for each engine displacement using the average CO₂ emissions for each vehicle displacement as of 2020. Next, multiple scenarios were analyzed considering the standard tax rate at $75 per ton of CO₂ emissions proposed by the IMF (2019). In particular, we compared the case of imposing a uniform carbon tax of $75 and the case of imposing a progressive tax based on CO₂ emissions by displacement. According to the results, it was confirmed that the uniform tax rate proposed by the IMF is difficult to apply to Korea as it is due to the impact of a decrease in tax revenue, and a tax scheme needs to be designed appropriately considering maintenance of tax revenue according to the current automobile tax, greenhouse gas reduction effect, and automobile tax reform trends in developed countries. For example, in the case of the K3 (1,598cc) of Kia Motors, a representative compact car sold in Korea, if we compare the tax burdens for each tax scenario, the tax burden will be about 220,000 KRW under the current system, about 79,000 KRW under the uniform tax rate, about 83,000 KRW under the progressive tax rate, and about 240,000 KRW under the progressive tax rate similar to the UK tax system, respectively. In this way, this study identified the current statuses of automobile registration and tax in Korea, and automobile tax reform trends in major developed countries, and analyzed the impact of automobile tax reform considering engine displacement and CO₂ emissions, focusing on the tax burden of the people.