• 한국정밀공학회지
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• 제34권2호
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• pp.145-150
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• 2017

Air brake valves are widely used in automotive braking systems and the Korean automobile industry depends on importing them. Therefore, we should develop the technical expertise for their domestic production. In this study, air brake valves were analyzed that can be used in a variety of automobiles. Computational fluid dynamics analysis, static structural analysis, and hyper-elastic analysis were carried out. Before production of an air brake valve system, the performance of different parts has to be evaluated, for instance by using finite element analysis. The structural stability of the product can be determined using static dynamics. The compression behavior of the O-ring is predictable by nonlinear hyper elastic analysis, although errors are possible due to one-way loading. This simulation study can both save time and reduce costs compared to the development of experimental prototypes.

• International Journal of Quality Innovation
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• 제6권2호
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• pp.59-89
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• 2005

Manufacturing Resources Planning (MRPII) is one kind of manufacturing information system that can help manufacturing companies gain competitive advantages. It is estimated that more than one hundred MRPII systems are available in the market, many of them are mature enough to solve most operational issues in accordance with users' requirements. More often than not, many of these systems provide more functions than a company expects. Manufacturing companies worldwide have attempted to implement these MRPII systems, however, many companies experienced failure (Turbide, 1996) due to managerial rather than technical issues. The authors propose an approach utilising a roadmap to integrate BPR and the MRPII implementation in order to overcome this difficulty. A detail road map is developed to guide this implementation, which is designed using a hierarchical analysis technique known as Integrated DEFinition Method (IDEF). IDEF is a systematic manufacturing management and integration-modeling tool. The proposed approach is implemented and illustrated using a reference company and the results indicated that 66% reduction in errors for maintaining the bills of materials system; 99% reduction in time to carry out material requirement planning; and 70% reduction in time previously taken for non-productive discussions.

• 터널과지하공간
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• 제24권1호
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• pp.21-31
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• 2014

심부 5 km 내외에 고압의 유체 주입에 의하여 인공저류층을 형성한 후 지열유체를 순환 생산하여 지열발전을 하는 인공저류층 지열시스템의 실현 가능성을 판단하기 위해 다양한 지역에서 인공저류층 지열시스템 실증연구가 진행되고 있다. 본 기술보고는 영국 Rosemanowes 에서 진행된 EGS 실증연구와 호주 Cooper Basin에서 2002년 이래 진행되고 있는 EGS 적용 사례를 소개하여 해당 지역에서 진행된 연구의 경험, 오류, 시사점 등을 정리하고, 향후 한국에서의 실증연구에 활용하고자 작성되었다.

• The Korean Journal of Pain
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• 제1권2호
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• pp.199-202
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• 1988

Secure fixation is essential for continous epidural catheterization on a long-term-basis. Adhesive tape or surgical knots were commonly used for those patients, but the surgical knot method has a tendency to cause strangulation of catheter. Another invasive technique, subcutaneous tissue tunnelling is more safe than other methods but requires sophisticated technique and time. We employed a simple device using a blood transfusion set for patients who have epidural catheters placed safely un their backs. In 120 patients treated for postoperative and chronic pain by means of this technique, the results were as follows: 1) Five of 120 patients (4.2%) developed backache and pruritus, but there were no instances of respiratory depression, local infection and headache. 2) Nine of 120 patients (7.5%) failed booster-injections, but two cases were due to be non-technical errors. 3) The duration of fixation was 1~3 days in most cases (85%), the longest being for 21 days.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.454-456
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• 1987

A more specialized area of transient evaluations is transmission line fault-detecting and protection system. During the first cycle or two following a power system fault, a high-speed protective relay is expected to make a decision as to the severity or location of the fault, usually based on 60 Hz information, i.e. the phase and magnitude of 60 Hz voltage or current signals. It is precisely at this time however that the signal is badly corrupted by noise, in the form of a de offset or frequencies above 50 Hz. One of several possible sources of transients in protection measuring signals is in the primary system for which protection is required in its response to the impact of short circuit fault on-set. Other sources are in the primary voltage and current transducers from which protection signals are derived, and, often of particular importance, in the interface circuits between the transducer secondaries and the comparator and measuring elements of the protection system. However, the noise signals that will be described in this paper are due to the main power system only and do not include errors due to current or voltage transducers.

• 대한전자공학회논문지
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• 제27권2호
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• pp.39-46
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• 1990

본 논문에서는 Tschebyscheff 다항식 이론을 이용하여 상대적 전류 분포비가 1:2:2:1이 되도록 구형마이크로스트립패치 어레이 안테나를 설계 제작 하였으며, 이에 대하여 이론적 해석과 실험을 통하여 검증하였다. 보다 정확한 공진주파수를 구하기 위하여 급전선로와 전력 분배 선로를 포함한 등가회로망을 구성하여 전송선로 모델법으로 해석하였다. 프린징효과에 의한 공진주파수, 반사손실에 따른 공진주파수와 실험에 의한 공진주파수를 각각 비교 검토한 결과 오차가 거의 없이 일치됨이 확인되었다. 또한 Tschebuscheff 배열에 의한 어레이 안테나의 첨예한 합성복사 전력패턴이 측정치와 잘 일치하였다.

• Nuclear Engineering and Technology
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• 제47권5호
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• pp.546-558
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• 2015

Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

• Journal of Electrical Engineering and information Science
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• 제2권6호
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• pp.95-105
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• 1997

In this paper, we have studied about design and fabrication of the actively shielded superconducting MRI magnet. Nonlinear optimization methods are usually used to find optimum coil configurations. However the selection of initial coil configurations is very difficult. In case bad initial data are used, it is even impossible to find optimum coil configurations which satisfy predefined constraints. We have developed computer optimization program which consists of two steps. Initial coil configurations are easily selected through linear optimization in the first step and optimum coil configurations are found through nonlinear optimization in the second step. We have also studied about superconducting shim coils to cancel error fields caused by coil fabrication errors. Many researchers published design concepts of shim coil. However all these studies are for shim coil design using filamentary coils with single turn, Shim coils with multi-turns should be used to produce enough field strength to cancel error fields. We have developed computer program for the design of shim coils which have proper thickness and length. An actively shielded superconducting MRI magnet with a small warm bore was fabricated and four sets of superconducting shim coils were equipped. The magnetic field distributions were measured and field correction was carried out using shim coils.

• 대한인간공학회지
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• 제30권1호
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• pp.117-125
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• 2011

While human error happens repeatedly in the semiconductor industry in Korea, which has brought a tremendous loss from manpower, welfare etc., there are limitations to human error prevention activities. When a semiconductor company introduces new machines and facilities from Japan or Germany, the companies often do not consider human factors in the design. Also, semiconductor companies are so occupied with promoting increased productivity, their attention to human errors has been pushed aside. Negative aspects of technical exchange associated with safety management are one aspect of the industry's nature. A semiconductor company recently began acknowledging on the back of TQM(Total Quality Management) that human error has a decisive effect on the safety. There are a number of uncontrollable and hard to handle event sets because the nature of these events with a human error may often be threatened or very intensive. It is strongly required that systemic studies should be performed to grasp the whole picture of a current situation for hazard factors. This study aims to examine the human error approach through the case of human error prevention field activities in a semiconductor industry compared with the activities and experience in nuclear power plants.

• 한국BIM학회 논문집
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• 제9권2호
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• pp.11-20
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• 2019

The use of drones and laser scanners have the potential to drastically reduce the time and costs of conventional techniques employed for field survey of cultural heritage buildings. Moreover, point cloud data can be utilized to create an as-built Building Information Model (BIM), providing a repository for consistent operations information. However, BIM creation is not a requisite for heritage buildings, and their technological possibilities and barriers have not been documented. This research explored the processes required to convert a heritage university building to a BIM model, using existing off-the-shelf software applications. Point cloud data was gathered from drones for the exterior, while a laser scanner was employed for the interior of the building. The point clouds were preprocessed and used as references for the geometry of the building elements, including walls, slabs, windows, doors, and staircases. The BIM model was subsequently created for the individual elements using existing and custom libraries. The model was used to extract 2D CAD drawings that met the requirements of Korea's heritage preservation specifications. The experiment showed that technical improvements were needed to overcome issues of occlusion, modeling errors due to modeler's subjective judgements and point cloud data cleaning and filtering techniques.