• Structural Engineering and Mechanics
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• 제8권5호
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• pp.453-464
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• 1999

Safety monitoring systems of structures generally resort to detecting possible changes of dynamic system parameters. Sensitivity analysis of these dynamic system parameters may implement these techniques. Conventional structural eigenvalue problems are discussed in the scope of those systems with deterministic parameters. Large and flexible structures, such as suspension bridges, actually possess stochastic material properties and these random properties unavoidably affect the dynamic system parameters. The sensitivity matrix of structural modal parameters to basic design variables has been established in this paper. Moreover, second order statistics of natural frequencies due to the randomness of material properties have been discussed. It is concluded from numerical analysis of a modem suspension bridge that although the second order statistics of frequencies are small relatively to the change of basic design variables, such as density of mass and modulus of elasticity, the sensitivities of modal parameters to these variables at different locations change in magnitude.

• 여성건강간호학회지
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• 제16권4호
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• pp.317-325
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• 2010

Purpose: This study was to examine the differences in health belief variables and HPV (Human Papillomavirus) knowledge in Pap smears according to the stages of change using Trans-theoretical Model (TTM) among married nurses. Methods: The research design was a cross sectional survey. Participants were 387 married nurses working in general hospital located metropolitan city. Measurement variables were perceived threatening, perceived severity, benefits of Pap, HPV knowledge and stages of the change in Pap smear. Results: Classified stages were pre-contemplation 3.9%, contemplation 17.8%, relapsing 29.5%, action 31.0%, and maintenance 17.8%. Accuracy rate of HPV knowledge were low ranging from 15% to 45%. Among the variables, perceived threatening (F=3.56, p=.007), perceived severity (F=9.73, p<.001) and HPV knowledge (F=7.52, p<.001) were significantly different by stages of change. Conclusion: Application of TTM to Pap smears was efficient to know the nurse's level of health behaviors, Health belief variables and HPV knowledge were main factors to identify the stages of change. The continuation of Pap smears and the education in relation to HPV knowledge should be encouraged for married nurses.

• Advances in Computational Design
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• 제4권1호
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• pp.15-32
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• 2019

One of the efficient and useful tools to achieve the optimal design of structures is employing the sensitivity analysis in the finite element model. In the numerical optimization process, often the semi-analytical method is used for estimation of derivatives of the objective function with respect to design variables. Numerical methods for calculation of sensitivities are susceptible to the step size in design parameters perturbation and this is one of the great disadvantages of these methods. This article uses complex variables method to calculate the sensitivity analysis and combine it with discrete sensitivity analysis. Finally, it provides a new method to obtain the sensitivity analysis for linear structures. The use of complex variables method for sensitivity analysis has several advantages compared to other numerical methods. Implementing the finite element to calculate first derivatives of sensitivity using this method has no complexity and only requires the change in finite element meshing in the imaginary axis. This means that the real value of coordinates does not change. Second, this method has the lower dependency on the step size. In this research, the process of sensitivity analysis calculation using a finite element model based on complex variables is explained for linear problems, and some examples that have known analytical solution are solved. Results obtained by using the presented method in comparison with exact solution and also finite difference method indicate the excellent efficiency of the proposed method, and it can predict the sustainable and accurate results with the several different step sizes, despite low dependence on step size.

• 대한조선학회논문집
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• 제53권1호
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• pp.54-61
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• 2016

This paper defines the design constraint in consideration of the dynamic characteristics and stability in the longitudinal direction of a supercavitating vehicle. Available range of the design variables is calculated by numerical simulation and the cavity modeling of vehicle dynamics is performed first. Configuration parameters of the supercavitating vehicle to determine the vehicle dynamics and characteristics of the cavity are defined as design variables. Design constraints are supercavitation, trim velocity, stability and vehicle dynamics in transition phase. Numerical results show that in accordance with the change of the design variables, the proposed design constraints reflect the physical characteristics of the supercavitating vehicle. This research finds the design region where the constraints of supercavity and the trim velocity are satisfied, and the stability analysis refines the design results by excluding the region where the stability is not guaranteed. The stability analysis is particularly important for a vehicle with the short fin span.

• 대한기계학회논문집A
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• 제37권6호
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• pp.821-826
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• 2013

구조물의 최적설계 시 설계변수의 값이 변화할 때 모드전환이 일어날 수 있다. 만약 이 모드전환을 추적하지 않으면 최적설계를 위한 고유진동수나 모드는 설계자가 의도하지 않은 모드로 평가될 수 있다. 따라서 설계변수의 값이 변화할 때마다 의도한 고유진동수와 모드의 동일성을 유지할 수 있도록 모드추적이 적용되어야 한다. 또한 설계변수가 불확실성을 포함하고 있는 설계 문제의 경우, 이를 고려한 신뢰성 기반 최적설계를 수행해야 한다. 본 연구에서는 압축기를 지지하는 관절스프링의 한 부품인 압축 코일스프링의 모드추적을 고려한 신뢰성기반 최적설계를 수행한다. 모드추적 기법은 최적화 기법들과 연동이 쉬운 다중응답접근법 기반 크리깅 메타모델을 이용하며, 신뢰성해석 기법은 크리깅 메타모델 기반 몬테카를로 추출법을 이용한다.

• 한국자동차공학회논문집
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• 제8권2호
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• pp.120-128
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• 2000

At the initial design stage of a new vehicle, the chassis layout has the most important influence on the overall vehicle performance. Most chassis designers have achieved the target performances by trial and error method as well as individual knowhow. Accordingly, a general procedure for determining the optimum location of suspension hard points with respect to the kinematic characteristics needs to be developed. In this paper, a method to optimize the toe angle in the double wishbone type front suspension of the four-wheel-drive vehicle is presented using the design of experiment, multibody dynamic simulation, and optimum design program. The handling performances of two full vehicle models having the initial and optimized toe angle are compared through the single lane change simulation. The sensitive design variables with respect to the kinematic characteristics are selected through the experimental design sensitivity analysis using the perturbation method. An object function is defined in terms of the toe angle among those kinematic characteristics. By the design of experiment and regression analysis, the regression model function of toe angle is obtained. The design variables which make the toe angle optimized ae extracted using the optimum design program DOT. The single lane change simulation and test of the full vehicle model are carried out to survey the handling performances of vehicle with toe angle optimized. The results of the single lane change simulation show that the optimized vehicle has the more improved understeer tendency than the initial vehicle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1159-1161
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• 2005

This study uses a design of experiments to explain correlations between the objective function and design variables. Analysis of means, analysis of variance and table of orthogonal array were carried out. The change of shape design variable for TFLM based on the table of orthogonal array is made. Therefore this study carried to decide design variables for maximizing thrust force of TFLM. we showed improved design variables.

• 한국소음진동공학회논문집
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• 제15권7호
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• pp.775-780
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• 2005

This study uses a characteristic function to explain correlations between the objective function and design variables. Analysis of means and table of orthogonal array were carried out. The change of shape of diaphragm, thickness of diaphragm and voice coil weight based on the table of orthogonal array Is made. Therefore this study carried to decide design variables for minimizing 1st natural frequency and maximizing 2nd natural frequency of diaphragm using design of experiments and characteristic function with constraints. we showed improved design variables.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권4호
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• pp.219-225
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• 2000

This paper presents the shape optimization considering the uncertainty of design variable to find robust optimal solution that has insensitive performance to its change of design variable. Stochastic finite element method (SFEM) is used to treat input data as stochastic variables. It is method that the potential values are series form for the expectation and small variation. Using correlation function of their variables, the statistics of output obtained form the input data distributed. From this, design considering uncertainty of design variables.

• 한국BIM학회 논문집
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• 제5권1호
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• pp.35-43
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• 2015

Existing pedagogical issues of digital design including BIM have been focused not on potential of Digital Design but on skills of BIM or digital modeling tool. Kinetic facade can move or change material state to react surrounding environment conditions. It is a suitable design object for teaching principle of Performance Oriented Digital Design. Variables of movements affect multi-criteria of performances of kinetic facade, so different design approach from fixed facade design should be explored. Kinetic facade design process is proposed to study pedagogical issues of Performance Oriented Digital Design in this paper. Through Kinetic facade design process, students can understand conditions, variables, and performances of digital design.