• Structural Engineering and Mechanics
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• 제86권4호
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• pp.547-571
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• 2023

To deeply probe the actual earthquake level and fragility of typical reinforced concrete (RC) structures under multiple intensity grades, considering diachronic measurement building stock samples and actual observations of representative catastrophic earth shocks in China from 1990 to 2010, RC structures were divided into traditional RC structures (TRCs) and bottom reinforced concrete frame seismic wall masonry (BFM) structures, and the empirical damage characteristics and mechanisms were analysed. A great deal of statistics and induction were developed on the historical experience investigation data of 59 typical catastrophic earthquakes in 9 provinces of China. The database and fragility matrix prediction model were established with TRCs of 4,122.5284×104 m² and 5,844 buildings and BFMs of 5,872 buildings as empirical seismic damage samples. By employing the methods of structural damage probability and statistics, nonlinear prediction of seismic vulnerability, and numerical and applied functional analysis, the comparison matrix of actual fragility probability prediction of TRC and BFM in multiple intensity regions under the latest version of China's macrointensity standard was established. A novel nonlinear regression prediction model of seismic vulnerability was proposed, and prediction models considering the seismic damage ratio and transcendental probability parameters were constructed. The time-varying vulnerability comparative model of the sample database was developed according to the different periods of multiple earthquakes. The new calculation method of the average fragility prediction index (AFPI) matrix parameter model has been proposed to predict the seismic fragility of an areal RC structure.

• Nuclear Medicine and Molecular Imaging
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• 제42권2호
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• pp.153-163
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• 2008

다중영상기기는 1990년대 초에 처음 개발되어 현재 주요 영상 장비 회사에서 상품으로 개발되어 판매되고 있다. 단순한 소프트웨어적인 정합과 융합을 통해 해부학적 영상과 기능적 영상의 상호 보완하는 단계에서 발전하여 하드웨어적으로 정합하는 하드웨어의 개발은 새로운 연구의 시작이다. 다중영상기기의 발전 이전에는 해부학적 구조를 보여주는 영상 장비와 기능적 영상을 표현하는 장비가 각각 고 분해능과 고 해상도로 많은 발전을 이루어 왔다. 현재는 각 영상 장비의 특징을 살려 효과적으로 결합시킨 다중영상기기의 개발이 활발하게 이루어지고 있다. 다중영상기기는 단순하게 두 장비를 결합시키는 개념에서 기능적 영상에서 필요한 감쇠 보정을 하면서 동시에 해부학적 위치를 융합 영상 형태로 표현하는 새로운 영상 장비로 발전하고 있다 다중영상기기의 특징을 살릴 수 있는 프로토콜이 개발되고 하드웨어적으로도 상호 보완적으로 결합되고 있다. 실제로 PET/CT와 같은 다중영상기기는 임상적으로 중요한 역할을 하고 있으며 PET 영상기기를 대체하고 있다. PET/CT 스캐너는 PET에서 나오는 기능적 영상과 CT에서 나오는 해부학적 영상뿐만 아니라 융합 영상을 함께 보여 주므로 임상적으로 유용한 정보를 제공하고 있다. 현재 SPECT/CT는 아직 보급이 많이 되지 않았으나 PET/CT와 같이 임상적으로 유용한 SPECT와 CT 장비가 결합된 상품들이 나오고 있어 그 시장이 점점 성장할 것으로 기대된다. 다중영상기기는 각각의 단독 영상장비에서 갖고 있는 문제뿐만 아니라 두 영상 장비를 결합시키므로 인해 새로운 문제들이 발생하고 있다. 대표적으로 호흡에 의한 움직임, 조영제의 영향, 금속 물질의 영향과 환자의 피폭에 관한 문제가 있다. 이를 해결하기 위해 새로운 프로토콜과 프로세싱 방법이 개발되고 있다. 뇌를 동시에 촬영할 수 있는 PET/MR의 개발은 뇌 과학에 많은 발전을 줄 것으로 기대된다. PET/MR의 개발은 PET/CT 에서 촬영한 영상의 일부분을 대체할 것으로 예상된다. MR 영상이 CT 영상보다 우수한 분해능을 보이는 분야에서는 PET/MR을 이용한 검사와 연구가 활발하게 진행될 것으로 보인다. 해부학적 영상과 기능적 영상을 결합시킨 융합 영상을 함께 제공하는 다중영상기기는 환자의 질병을 진단뿐만 아니라 치료 후의 효과를 보는데 있어서 중요한 역할을 할 것으로 기대된다. 또 앞으로 검사 목적에 맞는 다양한 다중영상기기의 개발이 이루어질 것으로 기대된다.

• 한국광학회지
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• 제17권6호
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• pp.564-568
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• 2006

반도체 광증폭기에 기반을 둔 이득포화특성을 이용하여 XOR, AND, OR 논리 게이트를 동시에 구현하는 다기능 전광 논리소자를 설계하고 구현하였다. 상용화된 프로그램인 VPI Component $Maker^{TM}$을 사용하여 시뮬레이션을 수행하였고 10 Gbit/s의 입력 신호를 사용하여 XOR, AND, OR 논리동작을 동시에 구현하는 다기능 전광 논리소자를 구현하였다.

• Korean Chemical Engineering Research
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• 제62권1호
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• pp.44-52
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• 2024

복잡한 화학공정을 관리하기 위한 목적으로 도입된 공정안전관리(PSM: process safety management)제도는 그간 화학사고 예방에 기여해 왔으나, 최근에는 그 한계를 드러내고 있다. 최근 중대산업사고가 증가하고 있으며 특히 2020년 이후 비정상 작업에서 중대산업사고가 급증하였다. 효과적인 PSM 운영 방안이 필요한 시점이다. 본 연구에서는 비선형적이고 복잡한 상호작용을 모형화하여 인적오류 및 사고 발생 과정을 이해하고 예측하는데 유용한 기법인 기능공명분석기법(FRAM: Functional Resonance Analysis Method)을 활용하여 비정상 작업에서 발생한 사고 사례를 분석하고 나아가 일반적인 PSM 비정상 작업 수행 과정에 대한 분석을 수행함으로써, PSM 운영 과정에서 FRAM이 효과적으로 활용될 수 있음을 검토하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.620-626
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• 2004

For general nonlinear processes, it is difficult to control with a linear model-based control method and nonlinear controls are considered. Among the numerous approaches suggested, the most rigorous approach is to use dynamic optimization. Many general engineering problems like control, scheduling, planning etc. are expressed by functional optimization problem and most of them can be changed into dynamic programming (DP) problems. However the DP problems are used in just few cases because as the size of the problem grows, the dynamic programming approach is suffered from the burden of calculation which is called as 'curse of dimensionality'. In order to avoid this problem, the Neuro-Dynamic Programming (NDP) approach is proposed by Bertsekas and Tsitsiklis (1996). To get the solution of seriously nonlinear process control, the interest in NDP approach is enlarged and NDP algorithm is applied to diverse areas such as retailing, finance, inventory management, communication networks, etc. and it has been extended to chemical engineering parts. In the NDP approach, we select the optimal control input policy to minimize the value of cost which is calculated by the sum of current stage cost and future stages cost starting from the next state. The cost value is related with a weight square sum of error and input movement. During the calculation of optimal input policy, if the approximate cost function by using simulation data is utilized with Bellman iteration, the burden of calculation can be relieved and the curse of dimensionality problem of DP can be overcome. It is very important issue how to construct the cost-to-go function which has a good approximate performance. The neural network is one of the eager learning methods and it works as a global approximator to cost-to-go function. In this algorithm, the training of neural network is important and difficult part, and it gives significant effect on the performance of control. To avoid the difficulty in neural network training, the lazy learning method like k-nearest neighbor method can be exploited. The training is unnecessary for this method but requires more computation time and greater data storage. The pH neutralization process has long been taken as a representative benchmark problem of nonlin ar chemical process control due to its nonlinearity and time-varying nature. In this study, the NDP algorithm was applied to pH neutralization process. At first, the pH neutralization process control to use NDP algorithm was performed through simulations with various approximators. The global and local approximators are used for NDP calculation. After that, the verification of NDP in real system was made by pH neutralization experiment. The control results by NDP algorithm was compared with those by the PI controller which is traditionally used, in both simulations and experiments. From the comparison of results, the control by NDP algorithm showed faster and better control performance than PI controller. In addition to that, the control by NDP algorithm showed the good results when it applied to the cases with disturbances and multiple set point changes.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.24-34
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• 2005

The automobile seat must satisfy various safety regulations for the passenger's safety. In many design practices, each component is independently designed by concentrating on a single related regulation. However, since multiple regulations can be involved in a seat component, there may be design confliction among the various safety regulations. Therefore, a new design methodology is required to effectively design an automobile seat. The axiomatic approach is employed for considering multiple regulations. The Independence Axiom is used to define the overall flow of the seat design. Functional requirements (FRs) are defined by safety regulations and components of the seat are classified into groups which yield design Parameters (DPs). The classification is carried out to have independence in the FR-DP relationship. Components in a DP group are determined by using orthogonal away of the design of experiments (DOE). Numerical analyses are utilized to evaluate the safety levels by using a commercial software system for nonlinear transient finite element analysis.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1549-1553
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• 2008

A molecular imprinted polymer (MIP) using (+)catechin ((+)C) as a template and acrylamide (AM) as a functional monomer was prepared. Acetonitrile was used as the porogen with ethylene glycol dimethacrylate (EGDMA) as the crosslinker and 2,2'-azobis(isobutyronitrile) (AIBN) as the initiator. The adsorption isotherms in the MIP were measured and the parameters of the equilibrium isotherms were estimated by linear and nonlinear regression analyses. The linear equation for original concentration and adsorpted concentrations was then expressed, and the adsorption equilibrium data were correlated into Langmuir, Freundlich, quadratic, and Langmuir Extension isotherm models. The mixture compounds of (+)C and epicatechin (EC) show competitive adsorption on specific binding sites of the (+)catechin-MIP. The adsorption concentrations of (+)C, epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG), on the (+)catechin-molecular imprinted polymer were compared. Through the analysis, the (+)catechin-molecular imprinted polymer showed higher adsorption ability than blank polymer which was synthesized molecular imprinted polymer without (+)catechin. Furthermore, the competitive Langmuir isotherms were applied to the mixture compounds of (+)C and EC.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제22권1호
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• pp.29-62
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• 2018

We investigate a class of HIV infection models with two kinds of target cells: $CD4^+$ T cells and macrophages. We incorporate three distributed time delays into the models. Moreover, we consider the effect of humoral immunity on the dynamical behavior of the HIV. The viruses are produced from four types of infected cells: short-lived infected $CD4^+$T cells, long-lived chronically infected $CD4^+$T cells, short-lived infected macrophages and long-lived chronically infected macrophages. The drug efficacy is assumed to be different for the two types of target cells. The HIV-target incidence rate is given by bilinear and saturation functional response while, for the third model, both HIV-target incidence rate and neutralization rate of viruses are given by nonlinear general functions. We show that the solutions of the proposed models are nonnegative and ultimately bounded. We derive two threshold parameters which fully determine the positivity and stability of the three steady states of the models. Using Lyapunov functionals, we established the global stability of the steady states of the models. The theoretical results are confirmed by numerical simulations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.548-553
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• 2001

Recently, much attention is imposed on the design of the fuel assemblies in the Pressurized Light Water Reactor (PWR). Spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water and protects the system from the external impact loads. Various space grids have been proposed and new designs are also being created. In this research, a new spacer grid is designed by the axiomatic approach. The Independence Axiom is utilized for the design. For conceptual design, functional requirements (FRs) are defined and corresponding design parameters (DPs) are found to satisfy FRs in sequence. Overall configuration and shapes are determined in this process. Detail design is carried out based on the result of the axiomatic design. For the detail design, the system performances are evaluated by using linear and nonlinear finite element analysis. The dimensions are determined by optimization. Some commercial codes are utilized for the analysis and design.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1623-1630
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• 2002

Recently, much attention is imposed on the design of the fuel assemblies in the Pressurized Light Water Reactor (PWR). Spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water, and maintains a coolable geometry from the external impact loads. In this research, a new shape of the spacer grid is designed by the axiomatic approach. The Independence axiom is utilized for the design. For conceptual design, functional requirements (FRs) are defined and corresponding design parameters (DPs) are found to satisfy FRs in sequence. Overall configuration and shapes are determined in this process. Detail design is carried out based on the result of the axiomatic design. For the detail design, the system performances are evaluated by using linear and nonlinear finite element analysis. The dimensions are determined by optimization. Some commercial codes are utilized for the analysis and design.