• Journal of Bio-Environment Control
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• v.16 no.3
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• pp.210-216
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• 2007

A study was conducted to find mechanism and spray characteristics of a mini-sprinkler with downward spray to develop a new design type to be able to prevent drop water. The experiments were executed in a plastic greenhouse to minimize the effect of the wind. Data was collected at five different operation pressures and at 4 different raiser heights. Spray characteristics of the sprinkler such as effective radius, effective area, mean application depth, absolute maximum application depth, effective maximum application depth and coefficient of variation were determined. In order to analyze the mechanism and packing supporter of sprinkler, the numerical simulation using ABAQUS was performed. The optimum pressure for preventing drop water was determined.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.34-39
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• 2007

In this paper, the FEM result has been presented for a sealing safety between a valve packing and a valve seat during a open and close operation in a LPG cylinder. The sealing operation of a LPG valve is completed when the valve packing in which is made by a nylon-66 polymer is to stop a LP gas flow, which flows out from the outlet of a brass pipe in a LPG cylinder. The contact sealing mechanism of the valve may be classified by a flat contact of an unused valve packing and a circular groove contact of an used valve packing in a current LPG valve. Based on the FEM and experimental investigations the sealing force, 4.9 MPa for a flat contact mode of the unused valve packing is a little high compared to that of the used valve packing, which shows a circular groove contact geometry against a valve seat. But these sealing pressures for two contact modes are very low compared to the ultimate strenath 83 MPa of the nylon-66 and this may be designed with a excess strength of the valve.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.94-95
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• 2020

This paper introduces the mix design and performance evaluation of Ultra-High Performance Concrete (UHPC). The concrete mixture is designed to achieve a densely compacted cementitious matrix via the modified Andreasen & Andersen particle packing model. The compressive strengths of UHPC designed by this method reached 154MPa. The relationship between packing theory and compressive strength of UHPC is discussed in this paper.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.3
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• pp.59-65
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• 2019

In many industries, particle packing is adopted quite frequently. In the particle packing process, the Discrete Element Method (DEM) can analyze the multi-collision of particles efficiently. Two types of contact models are frequently used for the DEM. One is the linear spring model, which has the fastest calculation time, and the other is the Hertz-Mindlin model, which is the most frequently used contact model employing the DEM. Meanwhile, very tiny particles in the micrometer order are used in modern industries. In the micro length order, surface force is important to decreased particle size. To consider the effect of surface force in this study, we performed a simulation with the Hertz-Mindlin model and added the Johnson-Kendall-Roberts (JKR) theory depicting surface force with surface energy. In addition, three contact models were compared with several parameters. As a result, it was found that the JKR model has larger residual stress than the general contact models because of the pull-off force. We also validated that surface force can influence particle behavior if the particles are small.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.335-338
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• 1992

To purpose of this study is to design and manufacturing of packing gland using CAD/CAM system. The computer system used in this study was constructed with CPU 80386, RAM memory 4M, VGA graphic card. We was composed with CAD/CAM system, with interface PC and NC milling machine. By using develop program, we designed packing gland and it's manufactured. The basic structure of automatic production system for packing gland was established.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1994.06a
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• pp.65-71
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• 1994

유압 실린더용 유패킹의 접촉력, 접촉폭, 돌출발생 임계압력을 밀봉간극에 대하여 유한요소법을 이용하여 수치적으로 해석하였다. 초기 간섭량이 증가함에 따라 접촉력 및 접촉폭은 급격하게 증가하였다. 그러나 유압이 작용하는 상태에서 밀봉간극이 감소하면 시일의 돌출현상이 발생하는 임계압력은 보다 가파르게 증가함을 확인하였다. 초기 간섭량에 의한 접촉력으로 부터 유압 실린더의 누설에 관련된 사용 최저 유압을 연계하여 갑섭량이 설계되어야하고, 돌출발생 임계압력으로 부터는 사용 최고유압과 관련하여 간극이 설계되어야 하므로 이에 대한 수치해석적 설계자료를 제시하였다. 특히 시일립부의 접촉면을 나타내는 축방향에 따라서 접촉력 분포는 시일립 선단부와 돌출현상에 따른 상호 복잡한 결과의 중요성을 제시하였다. 이 결과는 윤활해석을 위한 탄성유체윤활 해석시 입력자료로 사용될 수 있어 실제 유막두께 해석 및 유동해석을 통하여 누설량 예측 등에 이용될 수 있는 설게자료이다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.137-142
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• 2006

제철소 후판공장에서는 두꺼운 슬라브(Slab)를 압연하여 사각형태의 철판인 날판(Mother Plate)을 생산하고, 이를 주문(Plate) 사이즈에 맞게 다시 절단을 하게 된다. 이때 동일 슬라브라 하더라도 압연방법에 따라 다양한 사이즈의 날판을 생산할 수 있다. 여기에서 다루고 있는 후판 날판설계 문제는 주어진 주문을 대상으로 최소 개수의 슬라브를 사용하여 생산하는 문제를 말한다. 이를 위해 최적의 날판 사이즈를 결정하고, 각 날판에 주문들을 배치하게 된다. 본 논문에서는 후판 날판설계문제를 two-stage guillotine cutting problem의 변이로 모델을 세우고, 이를 위한 효율적인 휴리스틱을 제시하였다. 그리고 실 데이터를 대상으로 컴퓨터 실험을 통해 휴리스틱을 효율성을 검정하였다.

• Informatization Policy
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• v.24 no.4
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• pp.68-78
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• 2017

Malicious codes are currently becoming more complex and diversified, causing various problems spanning from simple information exposure to financial or psychologically critical damages. Even though many researches have studied using reverse engineering to detect these malicious codes, malicious code developers also utilize bypassing techniques against the code analysis to cause obscurity in code understanding. Furthermore, rootkit techniques are evolving to utilize such bypassing techniques, making it even more difficult to detect infection. Therefore, in this paper, we design the analysis process as a more agile countermeasure to malicious codes that bypass analysis techniques. The proposed analysis process is expected to be able to detect these malicious codes more efficiently.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.1
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• pp.59-65
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• 1999

In this paper, we design a entorpy encoder of HDTV/DTV encoder blocks on the basis of MPEG-II. The designed entropy encoder outputs its bit stream at 9Mbps bit rate inserting zero-stepping block to protect the depletion of buffer in case that the generated bit stream is stored in buffer and uses not only PROM bit combinational circuit to solve the problem of critical path, and packer block, one of submerge, is designed to packing into 24 bit unit using barrel shifter, and it is constructed to blocks of header information encoder, input information delay, submerge, and buffer control. Designed circuits is verified by VHDL function simulation, as a result of performing P&R with Gate compiler that apply $0.8{\mu}m$ Gate Array specification, pin and gate number of total circuits has been tested to each 235 and about 120,000.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2352-2360
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• 2007

Due to the friction characteristics of cylinders and the rail of a passenger car, in the elevator actuated with hydraulic systems, there exist dead zones, which can not be controlled by a PID controller. In this paper, the friction characteristics of a cylinder is examined, which may cause the abrupt increase of the acceleration in the zero-costing speed region. To overcome the drawbacks of a PID controlled hydraulic elevator system, a zooming fuzzy logic controller is designed and finally an improved hybrid fuzzy controller is proposed. The effectiveness of the proposed control scheme are shown by simulation and experimental results, which the proposed fuzzy hybrid control method yields good control performance not only in the zero-crossing speed region but also in the overall control region including steady-state region.