• Journal of Welding and Joining
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• 제32권3호
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• pp.1-10
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• 2014

The efficient application of any welding process depends on the understanding of associated process parameters influence on the weld quality. The weld quality includes the weld bead dimensions, temperature distribution, metallurgical phases and the mechanical properties. A detailed review on the experimental and numerical approaches to understand the parametric influence of a single wire submerged arc welding (SAW) and multi-wire SAW processes on the final weld quality is reported in two parts. The first part deals with the experimental approaches which explain the parametric influence on the weld bead dimensions, metallurgical phases and the mechanical properties of the SAW weldment. Furthermore, the studies related to statistical modeling of the present welding process are also discussed. The second part deals with the numerical approaches which focus on the conduction based, and heat transfer and fluid flow analysis based studies in the present welding process. The present paper is the first part.

• 한국조경학회지
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• 제49권2호
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• pp.1-16
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• 2021

조경의 설계 행위는 설계가의 사고체계 내에서 형성되는 개념과 그것이 형상화되는 구체적인 재현 그리고 이를 실질적인 재료로 구축하는 일련의 과정으로 이루어지며, 이러한 디자인 프로세스는 4차 산업혁명 시대의 컴퓨터 기술과 IT 생태계의 비약적인 발전으로 많은 변화를 마주하고 있다. 컴퓨터 테크놀로지는 산업 초기에 수학적 계산(calculation)과 입력 데이터의 시각적 표현(graphic representation on display) 등 비교적 단순한 목적으로 개발되었다. 하지만 ibm과 매킨토시(macintosh)를 시작으로 개인용 컴퓨터(personal computer)의 성공적인 보급 이후 프로그램 언어와 하드웨어가 급속히 발전하고, 알고리즘(algorithm) 및 응용 소프트웨어가 전문화되면서 컴퓨터의 활용 목적이 사회 전반에 걸쳐 매우 다양해졌다. 본 연구는 이러한 디지털 사회 맥락의 변화를 바탕으로 컴퓨테이셔널 디자인(computational design), 파라메트릭 디자인(parametric design) 및 알고리즘 디자인(algorithm design) 등의 새로운 설계 방법들이 조경 설계 과정에서 어떠한 기능과 역할을 할 수 있는지에 관한 현황 및 쟁점을 진단하였으며, 그중 최근 가장 주목받는 파라메트릭 테크놀로지를 적극적으로 이용하는 디자인 방법론에 집중해 연구를 진행했다. 우선 현대 조경 및 건축 전반에서 파라메트릭 디자인의 주요 개념 및 특징들에 대해 살펴 논의의 근거를 마련했다. 그리고 이를 바탕으로 조경 분야에서 파라메트릭 디자인 활용에 관한 선행 연구를 분석하고, 조경 설계 회사들의 실제 활용 현황에 대해 분석했다. 그 결과, 조경 분야에서 파라메트릭 디자인 활용에 관한 연구는 연구의 수나 다양성 측면에서 타 분야와 비교했을 때 아직 충분한 논의가 진행되지 않은 것을 확인할 수 있었고, 사용 현황 분석에서는 최근 국외 조경 회사들을 중심으로 새로운 테크놀로지를 적극적으로 활용하려는 다양한 움직임이 조사되었다. 마지막으로 이러한 논의를 바탕으로 조경 설계 분야에서 파라메트릭 디자인 활용의 구체적인 사례 및 추후 다양한 가능성에 대해 검토했다.

• Structural Monitoring and Maintenance
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• 제4권1호
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• pp.33-52
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• 2017

A cantilever beam with a breathing crack is studied to improve the breathing crack identification sensitivity by the parametric optimization of sample entropy and wavelet transformation. Crack breathing is a special bi-linear phenomenon experienced by fatigue cracks which are under dynamic loadings. Entropy is a measure, which can quantify the complexity or irregularity in system dynamics, and hence employed to quantify the bi-linearity/irregularity of the vibration response, which is induced by the breathing phenomenon of a fatigue crack. To improve the sensitivity of entropy measurement for crack identification, wavelet transformation is merged with entropy. The crack identification is studied under different sinusoidal excitation frequencies of the cantilever beam. It is found that, for the excitation frequencies close to the first modal frequency of the beam structure, the method is capable of detecting only 22% of the crack depth percentage ratio with respect to the thickness of the beam. Using parametric optimization of sample entropy and wavelet transformation, this crack identification sensitivity is improved up to 8%. The experimental studies are carried out, and experimental results successfully validate the numerical parametric optimization process.

• 기술경영경제학회:학술대회논문집
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• 기술경영경제학회 2004년도 제24회 동계학술대회 논문집
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• pp.222-245
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• 2004

This paper has an intention of proposing useful parametric tables of each industry group within Korea. These parametric tables can be insightful criteria for those who are dealing with the exact valuation of company, technology or industry through Real Option Analysis (ROA) since the identification of the movement of underlying asset is the very first step to be done. To give the exact estimations of parameters and the most preferred model in each industry group, we cover topics on ROA, stochastic process, and parametric estimation method like Generalized Method of Moments (GMM) and Maximum Likelihood Estimation (MLE). Additionally, specific industry groups, such as, Internet service group and mobile telecommunication service group defined independently in this paper are also examined in terms of its property of movement with the suggesting of the most fitting stochastic model.

• Wind and Structures
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• 제20권1호
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• pp.75-93
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• 2015

This work is focused on a parametric numerical study of the barrier's bar inclination shelter effect in crosswind scenario. The parametric study combines mesh morphing and design of experiments in automated manner. Radial Basis Functions (RBF) method is used for mesh morphing and Ansys Workbench is used as an automation platform. Wind barrier consists of five bars where each bar angle is parameterized. Design points are defined using the design of experiments (DOE) technique to accurately represent the entire design space. Three-dimensional RANS numerical simulation was utilized with commercial software Ansys Fluent 14.5. In addition to the numerical study, experimental measurement of the aerodynamic forces acting on a vehicle is performed in order to define the critical wind disturbance scenario. The wind barrier optimization method combines morphing, an advanced CFD solver, high performance computing, and process automaters. The goal is to present a parametric aerodynamic simulation methodology for the wind barrier shelter that integrates accuracy and an extended design space in an automated manner. In addition, goal driven optimization is conducted for the most influential parameters for the wind barrier shelter.

• Structural Engineering and Mechanics
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• 제33권2호
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• pp.239-255
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• 2009

In the companion paper, a simple but effective analysis procedure termed an Improved Modal Pushover Analysis (IMPA) is proposed to estimate the seismic capacities of multi-span continuous bridge structures on the basis of the modal pushover analysis, which considers all the dynamic modes of a structure. In contrast to previous studies, the IMPA maintains the simplicity of the capacity-demand curve method and gives a better estimation of the maximum dynamic response in a bridge structure. Nevertheless, to verify its applicability, additional parametric studies for multi-span continuous bridges with large differences in the length of adjacent piers are required. This paper, accordingly, concentrates on a parametric study to review the efficiency and limitation in the application of IMPA to bridge structures through a correlation study between various analytical models including the equivalent single-degree-of-freedom method (ESDOF) and modal pushover analysis (MPA) that are usually used in the seismic design of bridge structures. Based on the obtained numerical results, this paper offers practical guidance and/or limitations when using IMPA to predict the seismic response of a bridge effectively.

• 소음진동
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• 제6권5호
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• pp.661-669
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• 1996

Proposed is an aero-acoustic performance prediction method of axial fan. The fan aerodynamic performance is predicted by combining pitch-averaged quasi 3-D flow analysis with pressure loss models for blade boundary layer and wake, secondary flow, endwall boundary layer and tip leakage flows. Fan noise is assumed to be radiated as dipole distribution type, and its generation is assumed to be mainly due to the vortex street shed from blade trailing edge. The fluctuating pressure and lift on the blade surface are analyzed by incorporating the wake vortex stree shed from blade trailing edge. The fluctuating pressure and lift on the blade surface are analyzed by incorporating the wake vortex street model with thin airfoil theory. The aero-acoustic performance prediction results by the present method are in good agreement with the measured results of several axial fans. With the present prediction method, parametric studies are carried out to investigate the effects of blade chord length and spacing on the efficiency and the noise level of fan. In the case of lightly loaded fan, both efficiency improvement and noise reduction can be achieved by decreasing chord length or by increasing blade specing. However, when fan is designed at highly loaded condition, the noise reduction by increasing blade spacing penalizes the attaninable efficiency of fan.

• 응용통계연구
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• 제31권3호
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• pp.343-352
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• 2018

설명변수가 주어졌을 때 반응변수의 평균적인 추세뿐만 아니라 극단적인 지역에서의 추세에 대해서 추정하고 싶거나 반응변수 분포의 일반적인 탐색을 위해서는 분위수 회귀분석과 평률 회귀분석을 사용할 수 있다. 본 논문에서는 평률 회귀모형의 추정을 위한 모수적 방법과 비모수적 방법의 성능을 비교하고자 한다. 이를 위해 각 추정 방법을 소개하고 여러 상황의 모의실험 및 실제자료에의 적용을 통해 비교 분석을 실시하였다. 모형에 따라 성능 차이가 있는데 자료의 형태가 복잡하여 변수 간의 관계를 유추하기 힘들 경우 비모수적으로 추정한 평률 회귀분석모형이 더욱 좋은 결과를 보였다. 일반적인 회귀분석의 경우와 달리 평률의 경우 후보가 되는 모수 모형을 상정하기 어렵다는 측면에서 볼 때, 비모수적 방법의 사용이 추천될 수 있다.

• 한국지진공학회논문집
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• 제15권6호
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• pp.1-10
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• 2011

이 연구는 중공 프리스트레스트 콘크리트 교각의 P-M 상관도에 대한 매개변수 분석을 수행한 결과를 제시하고 있다. 다수의 매개변수 중에 콘크리트 압축강도, PS 강재량, 유효프리스트레스, $D_s/D_o$, 그리고 $D_i/D_o$를 선택하여 P-M 상관도에 미치는 영향을 중점적으로 다루었다. 준정적 실험을 통해서 중공 프리스트레스트 콘크리트 교각 실험체의 강도와 연성도를 평가하였다. 실험 및 해석결과와 각 코드를 기준으로 비교한 P-M상관도의 결과는 서로 다른 차이를 나타내었으며 AASHTO-LRFD는 근접한 값을 보여주었다. 무차 원화한 P-M 상관도를 중공 프리스트레스트 콘크리트 교각의 저항능력을 예측하기 위하여 제시하였다.

• Steel and Composite Structures
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• 제28권1호
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• pp.99-110
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• 2018

In this paper, a new size-dependent quasi-3D plate theory is presented for wave dispersion analysis of functionally graded nanoplates while resting on an elastic foundation and under the hygrothermaal environment. This quasi-3D plate theory considers both thickness stretching influences and shear deformation with the variations of displacements in the thickness direction as a parabolic function. Moreover, the stress-free boundary conditions on both sides of the plate are satisfied without using a shear correction factor. This theory includes five independent unknowns with results in only five governing equations. Size effects are obtained via a higher-order nonlocal strain gradient theory of elasticity. A variational approach is adopted to owning the governing equations employing Hamilton's principle. Solving analytically via Fourier series, these equations gives wave frequencies and phase velocities as a function of wave numbers. The validity of the present results is examined by comparing them with those of the known data in the literature. Parametric studies are conducted for material composition, size dependency, two parametric elastic foundation, temperature and moisture differences, and wave number. Some conclusions are drawn from the parametric studies with respect to the wave characteristics.