• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1994.10a
• /
• pp.763-767
• /
• 1994

The measured vibration on a machine or a structure is shaped by the excitation waveform and the path transfer function. Mechanism diagnostics tends to focus on retrieving source featurce by minimzing the effects of the structural path, while in structural diagnostics we are more interested in minimizing source effects and retrieving path parameters. In structural diagnostics, therefore, there are experimental issues of gathering data that are independent source effects and finding a transfer function signature that reveals structural defects. This paper describes how the transfer function can be obtained more accurately by experiment using the compatibility relationship which is newly discovered.

• Journal of the Korean Society of Combustion
• /
• v.13 no.2
• /
• pp.1-6
• /
• 2008

An experimental study of the flame response in a turbulent premixed combustor has been conducted with room temperature, atmospheric pressure inlet conditions using premixed natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable speed siren. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function as a function of the modulation frequency. Of particular interest is the effect of flame structure on the flame response predictions and measurements. The results show that both the gain and the phase of flame transfer function are closely associated with the flame length and structure, which is dependent upon the upstream flow perturbation as well as equivalence ratio in the current study.

• Clinical and Experimental Pediatrics
• /
• v.56 no.3
• /
• pp.101-106
• /
• 2013

Despite developments in surgical techniques and other interventions, right ventricular (RV) failure remains an important clinical problem in several congenital heart diseases (CHD). RV function is one of the most important predictors of mortality and morbidity in patients with CHD. RV failure is a progressive disorder that begins with myocardial injury or stress, neurohormonal activation, cytokine activation, altered gene expression, and ventricular remodeling. Pressure-overload RV failure caused by RV outflow tract obstruction after total correction of tetralogy of Fallot, pulmonary stenosis, atrial switch operation for transposition of the great arteries, congenitally corrected transposition of the great arteries, and systemic RV failure after the Fontan operation. Volume-overload RV failure may be caused by atrial septal defect, pulmonary regurgitation, or tricuspid regurgitation. Although the measurement of RV function is difficult because of many reasons, the right ventricle can be evaluated using both imaging and functional modalities. In clinical practice, echocardiography is the primary mode for the evaluation of RV structure and function. Cardiac magnetic resonance imaging is increasingly used for evaluating RV structure and function. A comprehensive evaluation of RV function may lead to early and optimal management of RV failure in patients with CHD.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.39 no.4
• /
• pp.363-369
• /
• 2002

In this paper, it could improved on the arbitrary nonlinear function learning approximation which have the wavelet neural network based on Adaptive Neuro-Fuzzy Inference System(ANFIS) and the multi-resolution Analysis(MRA) of the wavelet transform. ANFIS structure is composed of a bell type fuzzy membership function, and the wavelet neural network structure become composed of the forward algorithm and the backpropagation neural network algorithm. This wavelet composition has a single size, and it is used the backpropagation algorithm for learning of the wavelet neural network based on ANFIS. It is confirmed to be improved the wavelet base number decrease and the convergence speed performances of the wavelet neural network based on ANFIS Model which is using the wavelet translation parameter learning and bell type membership function of ANFIS than the conventional algorithm from 1 dimension and 2 dimension functions.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.1
• /
• pp.119-125
• /
• 2005

The current automotive is seeking the improvement of performance, the prevention of environmental pollution and the saving of energy resources according to miniaturization and lightweight of the components. And the variance analysis on the basis of structure analysis and DOE is applied to the lower control am. We have proposed a statistical design model to evaluate the effect of structural modification by performing the practical multi-objective optimization considering weight, stress and fatigue lift. The lower control arm is performed the fatigue analysis using the load history of real road test. The design model is determined using the optimization of acquired load history with the fatigue characteristic. The characteristic function is made use of the optimization according to fatigue characteristics to consider constrained function in the optimization of DOE. The structure optimization of a lower control arm according to fatigue characteristics is performed. And the optimized design variable is D=47 m, T=36mm, W=12 mm. In the real engineering problem of considering many objective functions, the multi-objective optimization process using the mathematical programming and the characteristic function is derived an useful design solution.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• 2007.11a
• /
• pp.151-156
• /
• 2007

2006년부터 VE 대상프로젝트가 확대되고, 기본설계와 실시설계단계에 각 1회씩 설계VE를 적용토록 규정되어 설계단계별로 VE가 각각 적용되는 프로젝트가 늘어나고 있다. 그리고 원가절감과 성능향상으로 프로젝트 가치를 높인 설계VE 사례도 많아지고 있다. 하지만 기본설계와 실시설계단계의 조건에 적합한 VE 수행방안에 대한 연구가 미진하고 참여자들의 경험과 이해가 부족하여 단계별 설계VE를 효율적으로 수행하는데 많은 어려움이 있다. 본 연구에서는 기본설계단계와 실시설계단계로 나누어 VE를 수행한 실무사례를 분석하여 기능정의와 아이디어 창출간의 연관관계 및 각 설계단계에서 기능정의를 수행할 때 발생하는 문제점을 도출하였다. 문제점을 해결하고 효과적인 설계VE를 수행하기 위하여 다음과 같은 개선방안을 제시하였다. 첫째, 설계프로세스의 흐름에 맞추어 기본설계에는 공간기능에 대하여하고 실시설계에는 부위에 대하여 기능정의를 수행한다. 이때 상위의 레벨에는 하위의 레벨의 기능정의가 연계되는 기능분류체계 (FBS : Function Breakdown Structure)를 제안하였다. 둘째, 기본설계와 실시설계단계의 기능정의를 수행하는 프로세스 (FDP : Function Definition Process)를 제안하였다. 셋째, 실시설계단계에서는 부위별 요구 성능 평가 매트릭스 (EFM : Element Function Matrix)를 적용하여 기능정의와 아이디어 창출이 연계되도록 하였다. 설계VE의 주요 부분인 기능정의 과정에 대한 문제점을 도출하여 해결방안을 제시함으로써, 보다 효과적인 설계VE의 수행을 기대할 수 있다.

• Wind and Structures
• /
• v.16 no.2
• /
• pp.157-178
• /
• 2013

Output-only modal parameter identification is based on the assumption that external forces on a linear structure are white noise. However, harmonic excitations are also often present in real structural vibrations. In particular, it has been realized that the use of forced acceleration responses without knowledge of external forces can pose a problem in the modal parameter identification, because an external force is imparted to its impulse acceleration response function. This paper provides a three-stage identification procedure as a solution to the problem of harmonic and white noise excitations in the acceleration responses of a linear dynamic system. This procedure combines the uses of the mode indicator function, the complex mode indication function, the enhanced frequency response function, an iterative rational fraction polynomial method and mode shape inspection for the correlation-related functions of the force-embedded acceleration responses. The procedure is verified via numerical simulation of a five-floor shear building and a two-dimensional frame and also applied to ambient vibration data of a large-span roof structure. Results show that the modal parameters of these dynamic systems can be satisfactorily identified under the requirement of wide separation between vibration modes and harmonic excitations.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.7
• /
• pp.535-540
• /
• 2019

The coupling between different models for MDO (Multi-disciplinary Optimization) greatly increases the complexity of the computational framework, while at the same time increasing CPU time and memory usage. To overcome these difficulties, POD (Proper Orthogonal Decomposition) and RBF (Radial Basis Function) are used to solve the optimization problem of determining the thickness of composites and sandwich cores when composite sandwich structures are used as aircraft wing skin materials. POD and RBF are used to construct surrogate models for the wing shape and the load data. Optimization is performed using the objective function and constraint function values which are obtained from the surrogate models.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.33 no.12
• /
• pp.53-62
• /
• 2017

Many gradient-based mathematical methods have been developed and are in use for structural size optimization problems, in which the cross-sectional areas or sizing variables are usually assumed to be continuous. In most practical structural engineering design problems, however, the design variables are discrete. The main objective of this paper is to propose an efficient optimization method for structures with discrete-sized variables based on the harmony search (HS) meta-heuristic algorithm that is derived using penalty function. The recently developed HS algorithm was conceptualized using the musical process of searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient search so that derivative information is unnecessary. In this paper, a discrete search strategy using the HS algorithm with a static penalty function is presented in detail and its applicability using several standard truss examples is discussed. The numerical results reveal that the HS algorithm with the static penalty function proposed in this study is a powerful search and design optimization technique for structures with discrete-sized members.

• Journal of the Korea Management Engineers Society
• /
• v.23 no.4
• /
• pp.87-103
• /
• 2018

This paper introduces the method to develop two main types of the fuzzy OEE (Overall Equipment Effectiveness) models via triangular membership function for measuring uncertainty. The fuzzy OEE includes model type 1 and model type 2. The model type 1 is used when the theoretical machine speed only reflects the time loss whereas model type 2 is used when the actual machine speed reflects both time and speed loss. Model type 2 has shown to perform a lower availability rate and a higher performance rate compared to model type 1. In addition, the fuzzy UPH (Unit Per Hour) which is derived from using the fuzzy OEE is presented to satisfy demand uncertainty. The fuzzy UPH can easily measure the fuzzy tact time and cycle time by reciprocating itself. Finally, this study demonstrates the fuzzy OEE models using IVIFS (Interval-Valued Intuitionistic Fuzzy Set) based on the characterization via membership function, non-membership function and hesitant function. For the purpose of analyzing the fuzzy system OEE, the OEE for each machine of plant structure is considered triangular interval-valued intuitionistic fuzzy number. Regardless of plant structure, the validity degree of fuzzy membership function of system OEE decreases when the number of machine with worst value of the validity degree increases. Corresponding examples are presented in this paper for practitioner to understand the applicability and practicability of the proposed fuzzy OEE methods.