• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.536-541
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• 2012

An instrumented pod has been developed to measure the aeroacoustic environment as well as the conventional data such as load, vibration, and aerodynamic heating of fighters during flight tests, confirming to the recently developed external pod design for fighters. This study presents the development of the measurement system in detail, being the first indigenous effort in its kind. The pod was designed to meet the requirements of the MIL-HDBK-1763 and MIL-STD-810 Method 515, which are the base to determine the locations and range of sensors. The Endevco 8510B-2 was selected as the sensor to withstand the harsh environment during the flight tests. In order to assess the integrity of the fabricated pod design, a ground run-up test of a KF-16 has been conducted with the pod installed at Station 5. The test results show that the system works well but the sound level exceeds the predetermined sensor range. The sensor range has been readjusted for flight test performed later.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.396-410
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• 2020

The design and the construction are carried out by installation of new caissons on the back or the front of existing caissons to increase the stability of existing caisson breakwater. In this study, we use the eigenfunction expansion method to analyze the effects of wave structure interaction when new porous dual circular caissons are installed on the back or the front of existing breakwater. The porous dual circular caisson which consisting of a porous outer cylinder circumscribing an impermeable inner cylinder is one type of seawater exchanging breakwater. The comparison of numerical results between present method and Sankarbabu et al. is made, and the wave force and the wave run-up acting on each porous dual circular caisson are calculated for various parameters by considering the wave structure interaction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.463-472
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• 2009

The aim of this study is to examine the effect of beach curvature on wave fields in coastal area with Submerged Breakwaters using the 3D numerical model that is able to simulate directly interaction of WAve Structure Sandy beach (LES-WASS-3D). At first, the adopted model was validated through the comparison with an existing experimental data and showed fairly nice agreement. And then, the numerical simulations have been performed to investigate the effect of according to the variation of beach curvature. Based on the numerical results, the wave height, mean surface elevation, mean flow around submerged breakwaters and longshore distributions of run-up height have been discussed in relation to the variation of beach curvature.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.632-637
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• 2010

Natural gas, a fossil fuel contained mostly of methane, is one of the cleanest alternative fuels. It can be used in the form of compressed gas(CNG) or liquefied natural gas(LNG) to cars and trucks. And, dedicated natural gas vehicles are designed to run on natural gas only, while Bi-fuel vehicles can also run on gasoline or CNG, especially, bi-fuel can be defined as the simultaneous combustion of two fuels. In this study, converted gasoline marine system to CNG Bi-fuel system which is made up of injector, regulator, tank and ECU is converted. And estimated the fuel system and engine power compared the result with gasoline engine is estimated. As a result, CNG engine shows low exhaust emissions but maxium power is 7% reduced compared to gasoline engine.

• The Journal of Industrial Distribution & Business
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• v.9 no.3
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• pp.19-29
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• 2018

Purpose - This study empirically analyses the changes in unemployment rates to understand push factors of generating wage pressure and how it affects the aggregate demand in Korea and the United States. We use a structural macroeconomic model which is centered on the labor market and simultaneously explains the natural rate of unemployment and deviations. Research design, data and methodology - We attempt to empirically analyse the unemployment rates through two countries to analyse the economic effects of real wages and aggregate demand between 2000 and 2016. We introduce having estimated the whole model that the growth of unemployment into the part caused by each of these factors. Results - The results of this study show that in the long run, there is not only a natural level of employment but also a natural level of real demand are positively related. in the short run, demand can vary from bring about changes in employment by means of price or wage surprises. Conclusions - The pressure of demand in the labor market shows up strongly in both countries. The estimated labor-demand equation are consistent with this framework and generally have well defined real wage and demand effects.

• Journal of the Korean Operations Research and Management Science Society
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• v.18 no.1
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• pp.119-126
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• 1993

We study a manufacturing process that is quite common in semiconductor wafer fabrication of semiconductor chip production. A machine is used to process a job consisting of J wafers. Each job requires a setup, and the i$_{th}$ setup for a job is sucessful with probability P$_{i}$. The setup is prone to failure, which results in the loss of expensive wafers. Therefore, a tiral run is first conducted on a small batch. If the set up is successful, the test is passed and the balance of the job can be processed. If the setup is unsuccessful, the exposed wafers are lost to scrap and the mask is realigned. The process then repeats on the balance of the job. We call this as send-ahead policy and consider general policies in which the number of wafers that are sent shead depend on the cost of the raw wafer, the sequence of success probabilities, and the balance of the job. We model this process and determine the expected number of good wafers per job,the expected time to process a job, and the long run average throughput. An algorithm to minimize the cost per good wafer subject to a demand constraint is provided.d.d.

• Journal of the Korean Society of Systems Engineering
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• v.10 no.1
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• pp.33-41
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• 2014

New design concept of Reactor Coolant System (RCS) including a reactor assembly for the SMR is introduced in this work. An exploration of new type of reactor that is advanced from proposed SMRs is performed by using systems engineering approach. In this point of view project structured on three main phases; needs analysis (NA), concept exploration (CE), and concept definition (CD). Main objectives as an output of the CE stage are a small size, low cost, shortening the schedule, and enhancing safety. The SMRs usually have a small size requirement. In order to meet the size requirement and to achieve a productivity, in other words, easiness to manufacture, this paper suggests an integrated PWR design concept through researching predecessors. Although the integrated PWR concept provides many advantages, it has disadvantages that composite of maintenance and a low availability problem. Therefore, this paper comes up with a run-to-fail design concept based on modular design to address the maintenance problem and to maximize the availability of SMRs as well as to be compatible with the overall-SMRs including Barge Mounted(BM)type.

• Journal of The Korean Association of Information Education
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• v.5 no.2
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• pp.230-239
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• 2001

Programming education is an important part of the ICT education field, and helps to increase the ability of analyzing, logical thinking, and solving procedural problems. Unfortunately, there is very little chance to learn computer programming nowadays. In addition, students have to install the translating program of the programming language they wish to study. In this paper, we describe the system we designed and implemented on the Internet, which can offer the setting to make programs to run on the WWW. Students can make, edit and run programs on the WWW though they did not set up the language translator program on their local computers.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.101-106
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• 2002

This paper presents an experimental investigation of high speed machining of dies and molds. Several critical issues involved with the high speed machining of QRO90 tool steel of hardness up to HRc62, have been studied and explained from a detail analysis of experimental observations. The experiments were performed using ball end mills. The effect of different process parameters on tool life and surface finish produced was also investigated. The cutting parameters involved were; cutting speeds in the range of 100 to 40 / m/min, axial depth of cut from 0.1 to 0.5mm, pick feed of 0.1 to 0.5mm. Run out and acceleration signals were observed during the experiment to investigate cutting slates. Compressed air and flood coolant were used and the effect of coolant on tool life was also determined.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.6
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• pp.614-619
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• 2009

The STW(servo track writing) system which is the process of writing servo signals on disks before assembling in drives uses the spindle motor-chuck mechanism to realize low cost because the spindle motor-chuck mechanism has merit which can simultaneously write multi-disk by piling up disks in hub. Therefore, when the spindle motor-chuck mechanism of horizontal type operates in high rotation speed it is necessary to reduce the effect of RRO(repeatable run-out) and NRRO(non-repeatable run-out) to achieve the high precision accuracy of nano-meter level during the STW process. In this paper, we analyzed that the slip in assembly surfaces can be caused by the mechanical tolerance and clamping force in hub-chuck mechanism and can affect NRRO performance. We designed springs for centering and clamping considering centrifugal force by the rotation speed and assembly condition. The experimental result showed NRRO performance improves about 30 % than case of weak clamping force. The result shows that the optimal design of the spindle motor-chuck mechanism can effectively reduce the effect of NRRO and RRO in STW process.