• 한국강구조학회 논문집
• /
• 제18권6호
• /
• pp.717-726
• /
• 2006

교량의 보강공법으로 주로 사용되는 외부강봉을 이용한 후인장공법은 적용범위가 넓고 교량의 극한 및 항복에 대한 강성을 증가시켜 휨 보강 효과가 뛰어나지만, 모재접합부의 응력집중, 비효율적인 하중분배, 고정앵커부설치, 유지관리의 어려움 등의 단점이 있다. 본 연구는 기존의 외부강봉을 이용한 후인장공법이 가지는 단점을 보완하고 강판접합공법의 장점을 접목한 새로운 개념의 보강공법으로 커버플레이트의 열변형 특성을 이용한 다단계 프리스트레싱 보강공법을 제안하고자 한다. 커버플레이트의 열변형 특성을 이용한 다단계 프리스트레싱 보강공법은 커버플레이트를 다단계로 가열하여 가열단계별로 거더의 하부플랜지에 고장력볼트로 접합한 뒤, 열원을 제거하여 발생하는 다단계 수축력을 보강에 필요한 프리스트레싱력으로 이용하는 보강공법이다. 커버플레이트의 다단계 프리스트레싱에 의한 보강효과는 커버플레이트의 온도분포와 가열구간에 따라 결정되므로 본 연구에서는 커버플레이트의 열전달 모형실험 및 강거더 모형 실험을 통하여 커버플레이트의 열전달해석과 프리스트레스 도입효과를 분석하였으며, 단경간 강거더 교량을 대상으로 제안된 보강공법의 효율성 및 적용성을 검토하였다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1991년도 추계학술발표회 논문집 지반공학에서의 컴퓨터 활용 COMPUTER UTILIZATION IN GEOTECHNICAL ENGINEERING
• /
• pp.289-311
• /
• 1991

Analysis of supported excavation system by Elasto-Plastic Isoparametric Finite Element Method and Elasto-Plastic Beam Method have been conducted for the simulation of stepwise underground excavation. Conventional methods, fixed Supported Beam and Spring Supported Beam method, also have been examined and compared with the results of elasto-plastic beam method and field data. Except unavoidable result of upward ground settlement near the top of retaining wall and relatively high bending moment of wall at each excavation level, satisfactory results have been derived using elasto-plastic isopara metric finite element method. The results from elasto-plastic beam analysis program, developed by the author, are proved to be fit field data in acceptable variance as shown in the paper. Displacement and bending moment, of the wall by conventional methods, both fixed supported beam and spring supported beam, are always underestimated than field data, and attention must be given that the diffence increases with deeper excavation depth and lower horizontal subgrade reaction of the ground.

• 품질경영학회지
• /
• 제48권1호
• /
• pp.51-68
• /
• 2020

Purpose: The primary objective of this research is to develop the optimal operating conditions as well as their associated design spaces for a Cryogenic Submerged Arc Welding(SAW) process by improving its quality and productivity simultaneously. Methods: In order to investigate functional relationships among quality characteristics and their associated control factors of an SAW process, a stepwise design of experiment(DoE) method is proposed in this paper. Based on the DoE results, not only a multi-dimensional design space but also a safe operating space and normal acceptable range(NAR) by integrating statistical confidence intervals were demonstrated. In addition, the optimal operating conditions within the proposed NAR can be obtained by a robust optimal design method. Results: This study provides a customized stepwise DoE method (i.e., a sequential set of DoE such as a factorial design and a central composite design) for Cryogenic SAW process and its statistical analysis results. DoE results can then provide both the main and interaction effects of input control factors and the functional relationships between the input factors and their associated output responses. Maximizing both the product quality with high impact strength and the productivity with minimum processing times simultaneously in a case study, we proposed a design space which can provide both acceptable productivity and quality levels and NARs of input control factors. In order to confirm the optimal factor settings and the proposed NARs, validation experiments were performed. Conclusion: This research may provide significant contributions and applications to many SAW problems by preparing a standardization of the functional relationship between the input factors and their associated output response. Moreover, the proposed design space based on DoE and NAR methods can simultaneously consider a number of quality characteristics including tradeoff between productivity and quality levels.

• 한국강구조학회 논문집
• /
• 제20권2호
• /
• pp.247-258
• /
• 2008

본 연구에서는 다단계 온도프리스트레싱이 도입된 강재보의 정적거동을 평가하기 위하여 H형강 시험체에 다단계 온도프리스트레싱을 도입한 후 정적 재하시험을 수행하였다. 도입한 온도 프리스트레싱력들의 차이 및 강재보와 커버플레이트 이음 형태에 따른 영향을 비교하기 위하여, 커버플레이트의 두께 및 커버플레이트와 강재보의 이음형식에 따라 높이 400mm, 길이 6,000mm의 시험체를 제작하였다. 정적재하 실험결과, 커버플레이트와 H형강을 볼트 이음하여 프리스트레싱한 시험체는 온도프리스트레싱이 도입되지 않은 시험체와 비교하여 항복하중은 13~18%, 강성은 27~34% 증가하였고, 볼트 및 용접 이음한 시험체는 항복하중이 18~29%, 강성이 43 ~51% 증가하는 것으로 나타났다. 또한 다단계 프리스트레싱의 도입으로 하중재하상태에서 시험체에 작용하는 응력상태가 다단계로 나타났다. 따라서 다단계 프리스트레싱의 도입은 강재보의 항복하중 및 강성을 증가시킬 수 있고, 단면 효율 및 프리스트레싱 효율의 증대가 가능할 것으로 판단된다.

• 한국멀티미디어학회논문지
• /
• 제25권5호
• /
• pp.670-675
• /
• 2022

This study proposes an improved binarization method to improve image recognition rate. The research goal is to minimize the information loss that occurs during the binarization process, and to transform the object of the original image that cannot be determined through the transformation process into an image that can be judged. The proposed method uses a stepwise segmentation method of an image and divides blocks using prime numbers. Also, within one block, a trapezoidal type of fuzzy is applied. The fuzzy trapezoid is binarized by dividing the brightness histogram area into three parts according to the degree of membership. As a result of the experiment, information loss was minimized in general images. In addition, it was found that the converted binarized image expressed the object better than the original image in the special image in which the brightness region was tilted to one side.

• 한국지능시스템학회논문지
• /
• 제12권6호
• /
• pp.524-530
• /
• 2002

본 연구에서는 Sugeno-type 퍼지시스템을 이용하여 계단형 퍼지 이동 슬라이딩 평면을 구성하고 이를 이용한 슬라이딩 모드제어방식을 제안한다 이 퍼지시스템은 위상평면 상에서 상태오차벡터가 이루는 각도와 원점과의 거리를 입력으로 가지며 출력으로 1차 선형방정식을 갖는다. 이 퍼지 슬라이딩 평면을 이용하여 초기 상태를 이 평면상에 위치시키고 이 슬라이딩 평면을 회전시키거나 이동시킴으로써 도달시간을 줄이고 추적시간을 줄인다. 제안된 이동 슬라이딩 평면은 개념적으로 계단형의 이산적인 형태를 가지지만 이 평면이 퍼지시스템으로 구성되기 때문에 연속으로 이동하는 특징을 나타낸다. 제안된 퍼지 슬라이딩 평면에 대한 슬라이딩 모드의 동특성이 안정함을 증명하며 이를 2차 예제시스템을 이용하여 그 타당성을 보인다.

• Structural Engineering and Mechanics
• /
• 제54권1호
• /
• pp.87-103
• /
• 2015

This paper focuses on an analytical research on the critical buckling load of cylindrical shells with stepwise variable wall thickness under axial compression. An arctan function is established to describe the thickness variation along the axial direction of this kind of cylindrical shells accurately. By using the methods of separation of variables, small parameter perturbation and Fourier series expansion, analytical formulas of the critical buckling load of cylindrical shells with arbitrary axisymmetric thickness variation under axial compression are derived. The analysis is based on the thin shell theory. Analytic results show that the critical buckling load of the uniform shell with constant thickness obtained from this paper is identical with the classical solution. Two important cases of thickness variation pattern are also investigated with these analytical formulas and the results coincide well with those obtained from other authors. The cylindrical shells with stepwise variable wall thickness, which are widely used in actual engineering, are studied by this method and the analytical formulas of critical buckling load under axial compression are obtained. Furthermore, an example is presented to illustrate the effects of each strake's length and thickness on the critical buckling load.

• 반도체디스플레이기술학회지
• /
• 제11권2호
• /
• pp.63-69
• /
• 2012

As decreasing size of chips, the need of wafer level packaging is increased in semi-conductor and display industries. Temperature uniformity is a crucial factor in vacuum soldering process to guarantee quality of bonding between chips and wafer. In this paper, a stepwise iterative algorithm has been suggested to obtain output profile of each heat source. Since this algorithm is based on open-loop stepwise iterative experimental technique, it is easier to implement and cost effective than real time feedback controls. Along with some experiments, it was shown that the suggested algorithm can remarkably improve temperature uniformity of wafer during whole heating process compared with the ordinary manual trial-and error method.

• 성인간호학회지
• /
• 제20권3호
• /
• pp.489-499
• /
• 2008

Purpose: The purpose of this study was to assess the importance and contribution of 9 nursing outcomes and their indicators that could be applied to cerebrovascular patients. Methods: Data were collected from 175 neurosurgical nurses working at two university affiliated hospitals and five secondary hospitals located in Gwang-ju. The Fehring method was used to estimate outcome content validity(OCV) and outcome sensitivity validity(OSV) of nursing outcomes and their indicators. Stepwise regression was used to evaluate relationship between outcome and its indicators. Results: The core outcomes identified by the OCV were Tissue Perfusion: Cerebral, Nutritional Status, Neurological Status, and Wound Healing: Primary Intention, whereas highly supportive outcomes identified by the OSV were Oral Health, Self-Care: ADL, and Nutritional Status. All the critical indicators selected for Fehring method were not included in stepwise regression model. By stepwise regression analysis, the indicators explained outcomes from 19% to 52% in importance and from 21% to 45% in contribution. Conclusion: This study identified core and supportive outcomes and their indicators which could be useful to assess the physical status of cerebrovascular patients. Further research is needed for the revision and development of nursing outcomes and their indicators at neurological nursing area.

• 대한산업공학회지
• /
• 제40권6호
• /
• pp.628-641
• /
• 2014

Stepwise efficiency improvement in data envelopment analysis (DEA)-based benchmarking is a realistic and effective method by which inefficient decision making units (DMUs) can choose benchmarks in a stepwise manner and, thereby, effect gradual performance improvement. Most of the previous research relevant to stepwise efficiency improvement has focused primarily on how to stratify DMUs into multiple layers and how to select immediate benchmark targets in leading levels for lagging-level DMUs. It can be said that the sequence of benchmark targets was constructed in a myopic way, which can limit its effectiveness. To address this issue, this paper proposes an optimization approach to the construction of a sequence of benchmarks in DEA-based benchmarking, wherein two optimization criteria are employed : similarity of input-output use patterns, and proximity of input-output use levels between DMUs. To illustrate the proposed method, we applied it to the benchmarking of 23 national universities in South Korea.