• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.15-21
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• 2008

The advantages of prefabricated vertical drains over conventional sand drains include their relatively low costs, less disturbance to the soil mass, the easinees of installation, and their flexibility which ensures the integrity of the drains during installation. This study tested the change of discharge capacities with respect to the hydraulic gradients for each lateral pressure. From the test results, as increases the overburden pressure, the clay soil is being consolidated, and also lateral pressure to the PVD specimen is increased. Therefore, the discharge capacity is decreased. The size of opening space in the core of PVDs is proportionally related to the discharge capacity. The numerical analysis was performed with utilizing computer simulation with considering field conditions. The results of numerical analysis are compared well with the field measurements.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.2
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• pp.72-80
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• 1998

Most cellsite are operated by 3-sector system in these days. Due to the weak propagating signal caused by peculiar topography, there exist weak or shadow regions. To solve this problem, we need double beam in a sector, thus we have to design 4-sector cellisite even if investment cost and maintenance cost gets high. We propose here using the dual TX-ANT instead of designing 4-sector cellsite to reduse investment cost and to improve call quality. We choose YangPeong and Gepo cellisite in Seoul and DuckCheon cellsite in Pusan to run the experiments. And we verified the practicality by comparing data before and before and after the installation of dual TX-ANT.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1099-1103
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• 2013

A combat vehicle needs to have an air-conditioning unit. Accordingly, new combat systems have tended to apply an integrated heating, cooling, and ventilating system. The air conditioning unit used depends on the combat vehicle's purpose of use. In this study, we studied an air-conditioning unit for an armored combat vehicle as a special use and military specification and tried to improve the air-conditioning unit's performance.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.427-437
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• 2019

The purpose of this study is to improve construction cost, time, and field management when constructing a road on soft soil foundation by eliminating extra-banking of subgrade layer after completion of the consolidation process. The subgrade layer was pre-constructed before the soft ground improvement. And then it was confirmed by the field test that the compaction effect was maintained or not after consolidation settlement. As a result of the experiment, all subgrade layers were kept constant except for the top subgrade layer. So it would be advantageous to secure economical and practical in road construction if subgrade layers were constructed exclusive of the top subgrade layer.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.2
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• pp.40-47
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• 2009

In this paper, current industrial trend of simulator development which is widely spreaded and performed in globally is introduced. Usage of satellite simulator is becoming an essential choice since the complexity of satellite and mission is being continuously increased. Satellite simulation brings reduction of satellite development cost and of period which is consumed by test on satellite development for various phases. Further more, it can be used to reduce the development period of satellite since developed resource and knowledge is possible to be delivered to next program effectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1700-1704
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• 2004

In this paper a novel power converter for some notches generation in the point of common coupling is described. The magnitude, width, polarity, and position of the notches generated by the proposed scheme can be varied arbitrary with simple control. The scheme has good features of simple structure, high reliability, low cost, high efficiency, and the capability of arbitrary several notches generation. The converter can be used for the test of custom power devices such as UPS, DVR, active power filter, etc. The circuit operation is described and the usefulness of the scheme is verified through simulations.

• Journal of Applied Reliability
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• v.18 no.3
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• pp.229-239
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• 2018

Purpose: There is a difficulty in Environmental Stress Screening (ESS) test design for weapon system's electrical/electronic components/products in small and medium-sized enterprises. To overcome this difficulty, I propose an easy ESS test design approach algorithm that is optimized with only one environment tolerance design information parameter (${\Delta}T$). Methods: To propose the mass production weapon system ESS test design for cost-effective optimization, I define an optimum cost-effective mathematical model ESS test algorithm model based on modified MIL-HDBK-344, MIL-HDBK-2164 and DTIC Technical Report 2477. Results: I clearly confirmed and obtained the quantitative data of ESS effectiveness and cost optimization along our ESS test design algorithm through the practical case. I will expect that proposed ESS test method is used for ESS process improvement activity and cost cutting of mass production weapon system manufacturing cost in small and medium-sized enterprises. Conclusion: In order to compare the effectiveness of the proposed algorithm, I compared the effectiveness of the existing ESS test and the proposed algorithm ESS test based on the existing weapon system circuit card assembly for signal processing. As a result of the comparison, it was confirmed that the test time was reduced from 573.0 minutes to 517.2minutes (9.74% less than existing test time).

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.26-37
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• 2007

A virtual engine test based on "Numerical test cell" can extremely reduce the time and cost for the development of a hardware by coupling multidisciplinary analysis. This paper introduces the development activities of full engine simulation programs in U.S.A. and Europe, with the their related techniques(the engineering models, the simulation environment and high performance computing) based on the NPSS(Numerical Propulsion System Simulation). NASA Glenn research conte. leads the development efforts of NPSS by assembling the current codes and improving their Auctions. VIVACE(Value Improvement through a Virtual Aeronautical Collaborative Enterprise), a consortium of universities, research centers and companies in Europe, is developing the PROOSIS(PRopulsion Object Oriented Simulation Software). The capability for the domestic development is also estimated by surveying the current status.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.34-39
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• 2015

In this paper, a design of an offset Cassegrain antenna is proposed for Ku and Ka dual-band without increasing the antenna size. For Efficiency of computation and implementation, the frequency selectivity surface (FSS) of reflecting the Ka-band signal and passing the Ku-band is provided for the sub-reflector instead of the main reflector. The proposed FSS hyperboloid sub-reflector is the periodic structure of a unit cell comprising octagon metal rings embedded in the multiple layers. The proposed design is verified for 19 GHz and 45 GHz bands by the use of precise electromagneitc-field simulations.

• The Journal of the Korea Contents Association
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• v.3 no.3
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• pp.63-73
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• 2003

Today, in exponential growth of internet, the importance of file caching which could reduce the sun load, the volume of network traffic, and the latency of response has emerged. Actually, in one network, the traffic has reduced by using the cache and this means that file caching can improve the internet environment by cost a fraction of link upgrades. In this paper, we address a dynamic cache group configuration policy, to solve the scalable problem. The simulation result shows that the cache group using our proposal policy reduces the latency of response time and it means that out cache group configuration is more scalable than the static cache configuration.