• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.124-132
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• 2003

This paper described the structural design and the fabrication procedure of KSR-III composite pressure tank. The type of the composite pressure tank was COPV(Composite Overwrapped Pressure Vessel). A non-load sharing liner was made of aluminum 6061-0 and the liner provided a helium gas seal. The composite pressure tank was winded using T700 carbon/epoxy on the liner. Because the aluminum liner was thin, multiple cure cycles were applied to the filament winding technique. The multiple cure cycles prevented the liner-cylinder from losing a circular shape. A fitting force at the metallic boss was spread to the carbon fiber by a boss ring. The boss ring also prevented a local deformation at the boss part.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1077-1084
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• 2002

Optimum tool design is carried out fur a multi-stage rectangular cup deep-drawing and ironing process with the large aspect ratio. Finite element simulation is carried out to investigate deformation mechanisms with the initial design made by an expert. The analysis considers the deep drawing process with ironing for the thickness control in the cup wall. The analysis reveals that the difference of the drawing ratio within the cross section and the irregular contact condition produce non-uniform metal flow to cause wrinkling and severe extension. For remedy, the modification guideline is proposed in the design of the tool and the process. Analysis results confirm that the modified tool design not only improves the quality of a deep-drawn product but also reduces the possibility of failure. The numerical result shows fair coincidence with the experimental one. After tryouts of the tool shape, the rectangular cup has been produced in the transfer press.

• Proceedings of the Korean Association for Survey Research Conference
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• 2001.04a
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• pp.59-71
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• 2001

We investigate design-based variance estimation methods of homogeneous linear estimator for population total under stratified multi-stage sampling. One method is unbiasedly estimating the first stage variance and the second stage variance separately in each stratum. And another is sub-sampling method that estimating the first stage variance only by using sub-sample selected from the second stage sample so that resulting estimator is unbiased for the total variance. The first is useful when the second stage unbiased estimator is available and the second is when the second stage variance is not estimable. For each case, we proposed a form of non-negative unbiased variance estimator. We expect the proposed variance estimation methods can be effectively used for many practical surveys.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.23-27
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• 1997

This paper introduces the structural design optimization of a high speed machining center using multi-step optimization combined with G.A.(Genetic Algorithm) and Weighted Method. In this case, the design problem is to find out the best design variables which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously. Dimensional thicknesses of the thirteen structural members of the machine structure are adopted as design variables. The first step is the cross-section configuration optimization, in which the area moment of inertia of the cross-section for each structural member is maximized while its area is kept constant The second step is a static design optimization, In which the static compliance and the weight of the machine structure are minimized under some dimensional and safety constraints. The third step IS a dynamic design optimization, where the dynamic compliance and the structure weight are minimized under the same constraints. After optunization, static and dynamic compliances were reduced to 62.3% and 95.7% Eorn the initial design, while the weight of the moving bodies are also in the feaslble range.

• Survey Research
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• v.2 no.1
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• pp.59-71
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• 2001

We investigate design-based variance estimation methods of homogeneous linear estimator for population total under stratified multi-stage sampling. One method is unbiasedly estimating the first stage variance and the second stage variance separately in each stratum. And another is sub-sampling method that estimating the first stage variance only by using sub-sample selected from the second stage sample so that resulting estimator is unbiased for the total variance. The first is useful when the second stage unbiased estimator is available and the second is when the second stage variance is not estimable. For each case, we proposed a form of non-negative unbiased variance estimator. We expect the proposed variance estimation methods can be effectively used for many practical surveys.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.292-294
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• 2021

In this study, we designed an authentication method that can perform authentication again by loading authentication data using a blockchain and comparing it with the authentication data in the future. To this end, after passing through the conventional ID and password input method and the widely used ARS authentication method, authentication is performed using biometric data stored in each user's terminal. After going through these steps, we chose a method of comparing the previously stored chain data with the recently authenticated data to perform final authentication and then reloading the authenticated data into the chain data. It is expected that this study will be able to suggest various authentication methods.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.04a
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• pp.107-117
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• 1997

알루미늄 합금 형단조에서 재결정없이 미세하고 균일한 아결정 조직을 얻으려면 T-'$\varepsilon$ 공간상의 조직상태도에 근거한 제어된 변형조건하에서 열간 가공해야 한다. 균일 변형을 위해서는 다단계 공정 설계가 필수적인데, 각 단계에서 제품의 어느 요소에서나 가공변수의 변화량($\Delta$T,$\Delta$$\varepsilon$,$\Delta$'$\varepsilon$ )이 최소화가 되도록 금형을 정교하게 설계하고 가공변수를 정밀 제어해야 한다. 알루미늄 합금 7175로서 균일 변형 단조를 적용한 결과 균일하고 안정된 아결정 구조를 얻을 수 있었으며, 이는 특히 ST 방향의 연신률을 크게 향상시킨다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.375-379
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• 1998

음성 언어 자료의 확보 및 활용을 위해서는 다양한 소프트웨어의 도움이 필요하다. 본 논문에서는 본 연구실에서 설계 및 개발한 PC용 Workbench에 대하여 기술한다. Workbench는 음성 언어 자료의 확보를 위한 텍스트 처리 모듈들과 음성 데이터의 처리를 위한 신호처리 모듈들로 구성되어 있다. Workbench에 포함된 모듈로는 텍스트를 자동 읽기 변환하는 철자 음운 변환기, 발성 목록 선정 모듈, 끝점 검출기를 이용한 음성 데이터 편집 모듈, 끝점 검출기를 이용한 음성 데이터 편집 모듈, 다단계 레이블링 시스템, 텍스트에서 원하는 음운 환경을 포함하고 있는 문자열을 다양한 조건으로 검색할 수 있는 음운 환경 검색기를 포함하고 있다.

• Journal of the Korean Association of Geographic Information Studies
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• v.1 no.2
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• pp.67-79
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• 1998

Most GIS applications are read-intensive on a large number of spatial objects and when the spatial objects are composite objects, the contained objects within the composite objects are also accessed. In GIS applications, creation, deletion, and update operations on spatial objects occur very rarely, but once they occur they deal with a large number of spatial objects. This paper proposes the concept of the multi-level pre-fetch query to retrieve a large number of spatial objects efficiently, and the functionality of the deferred-flush on the newly created persistent objects into the database with the optimal performance, and presents the design and implementation details of those ideas into an object-oriented DBMS BADA-III while considering these characteristics of GIS applications. The multi-level pre-fetch query retrieves the objects that satisfy the query and the objects that are contained within the objects up to the level specified by users, and registers the retrieved objects on the client cache. The deferred-flush flushes a large number of composite objects that are created by the application with a minimal overhead of the server and a minimal number of communications between the client and the server. These two functionality are suitable for the applications that search or create a large number of composite objects like GIS applications.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.515-525
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• 2000

The purpose of this paper was to develop size & shape optimization programming algorithm of plane trusses. The optimum techniques applied in this study were extended penalty method of Sequential Unconstrained Minimization Techniques(SUMT) and direct search method with multi-variables proposed by Hooke & Jeeves. Upper mentioned two methods were used iteratively at each level of size and shape optimization routines. The design variables of size optimization were circular steel tube(structural member) diameter and thickness, those of shape optimization were joint coordinates, and the objective function was represented as total weight of truss. During the optimum design, two level procedures of size and shape optimization were interacted iteratively until the final optimum values were attained. At the previous studies about shape optimization of truss, the member sectional areas and coordinates were applied as design variables. So that they could not apply the buckling effect of compression member. In this paper, actual sizes of member and nodal coordinates are used as design variables to consider the buckling effect of compression member properly.