• Smart Structures and Systems
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• 제15권6호
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• pp.1521-1542
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• 2015

The use of shape memory alloys (SMAs) in dynamical systems has an increasing importance in engineering especially due to their capacity to provide vibration reductions. In this regard, experimental tests are essential in order to show all potentialities of this kind of systems. In this work, SMA springs are incorporated in a dynamical system that consists of a one degree of freedom oscillator connected to a linear spring and a mass, which is also connected to the SMA spring. Two types of springs are investigated defining two distinct systems: a pseudoelastic and a shape memory system. The characterisation of the springs is evaluated by considering differential calorimetry scanning tests and also force-displacement tests at different temperatures. Free and forced vibration experiments are made in order to investigate the dynamical behaviour of the systems. For both systems, it is observed the capability of changing the equilibrium position due to phase transformations leading to hysteretic behaviour, or due to temperature changes which also induce phase transformations and therefore, change in stiffness. Both situations are investigated by promoting temperature changes and also pre-tension of the springs. This article shows several experimental tests that allow one to obtain a general comprehension of the dynamical behaviour of SMA systems. Results show the general thermo-mechanical behaviour of SMA dynamical systems and the obtained conclusions can be applied in distinct situations as in rotor-bearing systems.

• Structural Engineering and Mechanics
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• 제69권3호
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• pp.269-281
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• 2019

This work addresses a three-dimensional nonlinear structural analysis of the constructive phases of a cable-stayed segmental concrete bridge using The Finite Element Method through ANSYS, version 14.5. New subroutines have been added to ANSYS via its UPF customization tool to implement viscoelastoplastic constitutive equations with cracking capability to model concrete's structural behavior. This numerical implementation allowed the use of three-dimensional twenty-node quadratic elements (SOLID186) with the Element-Embedded Rebar model option (REINF264), conducting to a fast and efficient solution. These advantages are of fundamental importance when large structures, such as bridges, are modeled, since an increasing number of finite elements is demanded. After validating the subroutines, the bridge located in Rio de Janeiro, Brazil, and known as "Ponte do Saber" (Bridge of Knowledge, in Portuguese), has been numerically modeled, simulating each of the constructive phases of the bridge. Additionally, the data obtained numerically is compared with the field data collected from monitoring conducted during the construction of the bridge, showing good agreement.

• 조명전기설비학회논문지
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• 제25권12호
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• pp.11-20
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• 2011

PSALI is referred to the supplementary lighting for the interior lighting under the daily lighting situation, and pursuant to the pertinent regulations in energy savings design standard and others in recent architecture works, the importance thereof has been increasing gradually coupled with the energy performance index (EPI), energy savings plan and the like as well as expansion of submittal and implementation policies. However, this type of PSALI studies indeed have a number of limitations since it has surrounding environmental conditions in direction, season, region, climate, time, opening rate, window area ratio, actual index, reflection rate of finishing materials and others in the architecture work as well as frequent changes in interior lighting environment for variables in daily light volume flowing into the interior, and others. Therefore, this study has analyzed existing advance research cases to produce the actual-sized model and scaled-down model, and installed the artificial lighting of LED light source possible to reproduce with same capability on both models. As a result of comparison and analysis of the artificial lighting with the key light, it has certain level of error rate from the scaled down lighting device in certain rate and actual model butit was noticeably significant within specific scope.

• 시스템엔지니어링학술지
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• 제20권spc1호
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• pp.1-11
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• 2024

Today, the importance of test and evaluation of defense systems is increasing day by day. In performing efficient defense systems test works, process improvement based on quantitative management is essential. The purpose of this paper is to present the results of process improvement for the defense systems test works of the test organization based on quantitative management activities. As a methodology to confirm process improvement performance, the 'MPM(Managing Performance and Measurement)' practice area of the CMMI model was applied. The quantitative management model for defense systems test works was developed so that it could be practically applied not only to the entire test organization but also to the organization at the department level that actually performs the test work. Finally, the application cases of the quantitative management model for defense system test works and the results of process improvement were described.

• 한국음향학회지
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• 제31권7호
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• pp.449-460
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• 2012

발전소 건설 시에 설치된 지하매설 배관이 대부분 20년 이상 경과됨에 따라서 지하매설 배관의 누설탐지의 중요성이 점차 부각되고 있다. 본 논문의 목적은 발전소와 같이 매설배관 주변에 회전체 기계잡음이 존재하는 경우에 배관의 누설위치 추정성능을 개선하기 위한 방법을 연구하는 것이며, 이러한 목적을 달성하기 위하여 주파수영역에서 배관 주변의 회전체 기계잡음을 효과적으로 제거할 수 있는 방법을 제안하였다. 또한 상호스펙트럼의 위상정보를 이용하여 배관의 누설위치를 추정하는 방법을 제안하였다. 제안된 방법의 타당성 평가를 위하여 실험을 수행하였으며, 실험결과 회전체에서 발생하는 주기적인 잡음성분을 제거함으로써, 배관 누설을 탐지하는 상호상관함수기법의 성능을 개선할 수 있음을 확인하였다.

• 대한기계학회논문집B
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• 제33권2호
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• pp.69-78
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• 2009

Cavitating flow simulation is of practical importance for many hydraulic engineering systems, such as pump, turbine, nozzle, injector, etc. In the present work, a solver for cavitating flow has been developed and applied to simulate the flows past axisymmetric cylinders. Governing equations are the two-phase Navier-Stokes equations, comprised of continuity equation of liquid and vapor phase. The momentum equation is in the mixture phase. The solver employed an implicit, dual time, preconditioned algorithm in curvilinear coordinates. Computations were carried out for three axisymmetric cylinders: hemispherical, ogive, and caliber-0 forebody shape. Then, the present calculations were compared with experiments and other numerical results to validate the present solver. Also, the code has shown its capability to accurately simulate the re-entrant jet phenomena and ventilated cavitation. Hence, it has been found that the present numerical code has successfully accounted for cavitating flows past axisymmetric cylinders.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.33-36
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• 2006

As the computing environment is rapidly improved, the interests of CFD are gradually focused on large-scale computation over complex geometry. Keeping pace with the trend, essential computational tools to obtain solutions of complex aerospace flow analysis and design problems are examined. An accurate and efficient flow analysis and design codes for large-scale aerospace problem are presented in this work. With regard to original numerical schemes for flow analysis, high-fidelity flux schemes such as RoeM, AUSMPW+ and higher order interpolation schemes such as MLP (Multi-dimensional Limiting Process) are presented. Concerning the grid representation method, a general-purpose basis code which can handle multi-block system and overset grid system simultaneously is constructed. In respect to design optimization, the importance of turbulent sensitivity is investigated. And design tools to predict highly turbulent flows and its sensitivity accurately by fully differentiating turbulent transport equations are presented. Especially, a new sensitivity analysis treatment and geometric representation method to resolve the basic flow characteristics are presented. Exploiting these tools, the capability of the proposed approach to handle complex aerospace simulation and design problems is tested by computing several flow analysis and design problems.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.681-691
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• 2017

본 연구는 2016년 충청남도 천안에서 개최된 대한민국 국제농기계자재박람회(영문약칭, KIEMSTA)를 토대로 참가업체의 관점에서 실증적 분석을 수행한 연구이다. 선행 연구를 바탕으로 참가 업체의 참가 목적에 대한 중요도와 참가 목적이 실제로 달성되었는지에 대한 여부를 판단하는 성취도에 관한 15가지의 동일 항목이 선정되었다. 본 연구는 2016년도 KIEMSTA에 참가한 국내 및 국외 453개 업체를 대상으로 실시하였으며, 그 중 유효성이 확보된 258개 업체를 대상으로 최종분석을 실시하였다. 분석을 위해 중요도-성취도 분석(IPA)의 결과를 토대로 도출되는 2차원의 사분면으로 유의미한 영역의 차이를 구분하여 정리하였다. 연구결과를 구체적으로 살펴보면 다음과 같다. 과잉영역(현상유지영역)에는 경쟁사의 제품의 정보수집, 자사의 능력전시, 자사의 전시경험 향상, 마케팅 영업팀 훈련, 유지영역(유지 강화영역)에는 기존 고객과의 관계유지, 시장정보 수집, 자사의 경쟁력 파악, 신제품 소개, 마케팅 영업팀의 고객소통능력 강화, 저순위영역(점진적 개선영역)에는 새로운 미래전망의 발견, 해외시장의 수출기회 파악, 박람회 미참가 기업대비 경쟁력 강화, 마지막으로 집중영역(중점적 개선영역)에는 매출증대, 핵심 의사결정자와의 만남, 신시장 개척과 같은 항목이 나타났다.

• 한국건설관리학회논문집
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• 제15권3호
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• pp.103-112
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• 2014

최근 건설 프로젝트 규모의 대형화, 복잡화로 인해 관리기술의 난이도가 상승하고 있으며, 이에 따른 리스크도 함께 증가하고 있어 프로젝트 관리기술 향상에 대한 필요성이 증가하고 있다. 이 같은 문제점을 해결하기 위하여 건설공사에서 우선적으로 건설사업관리(Construction Management)제도를 도입하였으나 국내 건설 산업의 경우 업역별 분리발주가 이루어지고 있어 프로젝트 전반에 걸쳐 건설사업관리제도의 기능이 제대로 작동되지 않고 있는 실정이다. 이 같은 부분적 사업관리제도의 운영은 향후 스마트그리드, 인텔리전트 빌딩 등과 같은 융 복합화 사업에 있어 많은 제약을 받을 수 있다. 국내 건설 프로젝트 관리기술의 향상을 위해서는 현 사업관리제도의 이질성을 극복할 수 있는 업역별 사업관리기술 역량을 확보하고, 협업 능력 저해 요소를 발견하여 이를 해결해야 한다. 이에 본 연구에서는 IPA모델을 활용하여 건설 전기공사의 사업관리제도 업무역량 차이를 분석하고, 프로젝트의 효율적인 운영을 위한 전기공사 사업관리제도 도입 방안을 모색하고자 한다.

• 한국지능시스템학회논문지
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• 제25권6호
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• pp.607-614
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• 2015

본 논문은 항공기 정비사의 핵심역량 16개에 대하여 정비능력향상을 목적으로 FSM을 이용하여 구조분석을 실시하여 최상층 3개, 중간층 3개, 하위층 10개로 분류되는 계층별 구조를 핵심역량간의 연결상태와 중요도를 파악하였다. 또한 항공기 정비사의 핵심역량은 업무를 통해서 정비품질 및 생산성이 향상될 수 있다는 관점에서 핵심역량과 업무를 퍼지관계를 이용하여 100명의 항공기 정비사의 설문을 통하여 퍼지관계행렬을 구하여 업무를 평가하는 기준으로 사용하고자 하였다. 본 논문에서는 모델링데이터 100개와 체킹데이터 67개를 사용하여 모델의 유효성을 보였다.