• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1999년도 춘계학술대회 논문집
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• pp.47-52
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• 1999

In this paper we propose new approximate method for the performance analysis of closed-loop production system with unreliable machines and random processing times. The approximate method decomposes the production system consisting of K machines into a set of K subsystems, each subsystem consisting of two machines separated by a finite buffer. Then, each subsystem is analyzed by analyzing method n isolation. The population constraint of the closed-loop production system is taken into account by prescribing that the sum of average buffer level in the subsystems is equal to the number of customers in the closed-loop production system,. We establish a set of equations that characterizes unknown parameters of the servers in the subsystems. An iterative procedure is then used to determine the unknown parameters. Experimental results show that these methods provide a good estimation of the throughput.

• 대한산업공학회지
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• 제25권2호
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• pp.240-253
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• 1999

In this paper we propose new approximate methods for the performance analysis of closed-loop production systems with unreliable machines and random processing times. Each approximate method decomposes the production system consisting of K machines into a set of K subsystems, each subsystem consisting of two machines separated by a finite buffer. Then, each subsystem is analyzed by three different analyzing methods in isolation. The population constraint of the closed-loop production system is taken into account by prescribing that the sum of average buffer levels in the subsystems is equal to the number of customers in the closed-loop production system. We establish a set of equations that characterize unknown parameters of the servers in the subsystems. An iterative procedure is then used to determine the unknown parameters. Experimental results show that these methods provide a good estimation of the throughput.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1253-1255
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• 1993

Double Injection(DI) switching devices consist of p+ and n+ contact separated by a nearly intrinsic semiconductor region containing deep trap. The FEM is chosen as a simulation method for DI switching device, because of the advantage in local mesh refinement and computer memory comparing with other methods. And Scharfetter-Gummel(S-G) scheme is applied, with which an accurate-seven point Gaussian Quadrature rule is combined. The existance of deed trap requires the modification of conventional equation set. So recombination rate equation is modified and a new equation is included in the equation set which conventionally consists of Poisson equation and current continuity equations.

• 정보처리학회논문지D
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• 제18D권3호
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• pp.197-204
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• 2011

방송 신호를 수신하여 TV 등의 디스플레이 장치로 전달하는 셋톱박스는 다른 가전과는 다르게 대기모드, 즉 저전력모드가 존재하지 않는다. 이는 기술적 제약과 운용상의 이유로 인한 것이다. 현재 셋톱박스의 전원을 리모컨으로 끄면 방송을 시청하는 온모드 대비 80~90%의 높은 소비전력을 보인다. 이는 1W 미만으로 동작하는 다른 가전에 비해 월등히 높은 것이다. 국내 및 해외 선진국들은 셋톱박스의 에너지 효율을 높이고자 하는 정책을 시행하고 있다. 본 논문에서는 셋톱박스의 에너지 효율을 개선하고자 저전력 셋톱박스를 설계하고 진행 중인 개발에 대해 기술한다. 저전력 모드를 지원하는 SoC, 전원 모드를 구분하여 동작하도록 하는 시스템 하드웨어 및 소프트웨어, 그리고 방송사와의 연동을 통한 전원관리를 이루는 미들웨어 등이 핵심 개발 내용이다. 그리고 이를 통해 이룰 수 있는 에너지 소비 절감 효과를 보인다.

• 대기
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• 제25권1호
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• pp.51-66
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• 2015

This study was conducted to perform various sensitivity experiments using WRF (Weather Research and Forecasting) model in order to determine the effects of terrains of the Korean Peninsula and the land-sea thermal contrast on the formation and development of the convergent cloud band for the cases of 1 February 2012. The sensitivity experiments consist of the following five ones: CNTL experiment (control experiment), and TMBT experiment, BDMT experiment and ALL experiment that set the terrain altitude of Taeback Mountains and Northern mountain complex as zero, respectively, and the altitude of the above-mentioned two mountains as zero, and LANDSEA experiment that set to change the Korean Peninsula into sea in order to find out the land-sea thermal contrast effect. These experiment results showed that a cold air current stemming from the Siberian high pressure met the group of northern mountains with high topography altitude and was separated into two air currents. These two separated air currents met each other again on the Middle and Northern East Sea, downstream of the group of northern mountains and converged finally, creating the convergent cloud band. And these experiments suggested that the convergent cloud band located on the Middle and Northern East Sea, and the cloud band lying on the southern East sea to the coastal waters of the Japanese Island facing the East Sea, were generated and developed by different dynamical mechanisms. Also it was found that the topography of Taeback Mountains created a warm air advection region due to temperature rise by adiabatic compression near the coastal waters of Yeongdong Region, downstream of the mountains. In conclusion, these experiment results clearly showed that the most essential factor having an effect on the generation and development of the convergent cloud band was the topography effect of the northern mountain complex, and that the land-sea thermal contrast effect was insignificant.

• 한국전문물리치료학회지
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• 제21권4호
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• pp.56-66
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• 2014

For maintaining adequate psychometric properties when reducing the number of items from an instrument, item level psychometrics is crucial. Strategies such as low item correlation or factor loadings, using classical test theory, have traditionally been advocated. The purpose of this study is to describe the development of a new short form assessing the impact of low back pain on physical activity. Rasch measurement model has been applied to the International Classification of Functioning, Disability and Health Activity Measure (ICF-AM). One hundred and one individuals with low back pain aged 19-89 years (mean age: $48.1{\pm}17.3$) who live in the community were participated in the study. Twenty-seven items of lifting/carrying construct of the ICF-AM were analyzed. Ten items were selected from the construct to create a short form. Item elimination criteria include: 1) high or low mean square (out of the range: .6-1.4 for the fit statistics), 2) similar item calibrations to adjacent items, 3) person separation value, and item-person map for potential gap in person ability continuum. All 10 items of the short form fit to the Rasch model except one item (i.e., carrying toddler on back). Despite its high infit and outfit statistics (1.90/2.17), the item had to be reinstated due to potential gaps at the upper extreme of person ability level. The short form had a slightly better spread of person ability continuum compared to the entire set of item. The created short form separated individuals with low back pain into nearly 4 groups, while the entire set of items separated the individuals into 6 groups. The findings prompted multidimensional models for better explanation of the lifting/carrying domain. The item level psychometrics based on the Rasch model can be useful in developing short forms with rationally retained items.

• 한국기계기술학회지
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• 제20권6호
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• pp.924-928
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• 2018

The objective of this study is to solve a problem that is occurred during the spline machining of tubular shaft yoke in both side IMS module. In order to simulate the problem, the movement direction of upper die was set as standard case and error case. The material of tubular shaft yoke was set to S20C as refer to the analysis library. The movement directions of upper die were separated with standard case and error case. The error case was set to simulate the problem in the spline machining of tubular shaft yoke. In order to solve the problem, the outer radius of upper die were modelled from 9.40mm to 9.44mm. The simulation results were analyzed and compared in terms of effective stress, metal flow line and folding phenomena characteristics. In case of the outer radius of upper die was 9.42mm, it was observed a relatively uniform effective stress distribution and had a straight metal flow line.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.57-58
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• 2022

Concrete mix design is used as essential data for the quality of concrete, analysis of structures, and stable use of sustainable structures. However, since most of the formulation design is established based on the experience of experts, there is a lack of data to base it on. are suffering Accordingly, in this study, the purpose of this study is to build a predictive model to use the concrete mixing factor as basic data for calculation using the DNN technique. As for the data set for DNN model learning, OPC and ternary concrete data were collected according to the presence or absence of admixture, respectively, and the model was separated for OPC and ternary concrete, and training was carried out. In addition, by varying the number of hidden layers of the DNN model, the prediction performance was evaluated according to the model structure. The higher the number of hidden layers in the model, the higher the predictive performance for the prediction of the mixing elements except for the compressive strength factor set as the output value, and the ternary concrete model showed higher performance than the OPC. This is expected because the data set used when training the model also affected the training.

• International Journal of Aeronautical and Space Sciences
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• 제17권3호
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• pp.296-314
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• 2016

This paper presents experimental and computational investigations of synthetic jets with a circular exit for improving flow control performance. First, the flow feature and vortex structure of a multiple serial circular exit were numerically analyzed from the view point of flow control effect under a cross flow condition. In order to improve separation control performance, experimental and numerical studies were conducted according to several key parameters, such as hole diameter, hole gap, the number of hole, jet array, and phase difference. Experiments were carried out in a quiescent condition and a forced separated flow condition using piezoelectrically driven synthetic jets. Jet characteristics were compared by measuring velocity profiles and pressure distributions. The interaction of synthetic jets with a freestream was examined by analyzing vortical structure characteristics. For separation control performance, separated flow over an airfoil at high angles of attack was employed and the flow control performance of the proposed synthetic jet was verified by measuring aerodynamic coefficient. The circular exit with a suitable hole parameter provides stable and persistent jet vortices that do beneficially affect separation control. This demonstrates the flow control performance of circular exit array could be remarkably improved by applying a set of suitable hole parameters.

• 복식문화연구
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• 제7권1호
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• pp.1-12
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• 1999

Analysis of Customer Characteristics on Environment-Friendly Clothing Products The purpose of this study is to analyze the characteristics of the environment-friendly customers in Korean fashion market. The study is analyzed through questionary paper to the domestic female group of more than or equal to age of twenty living in Seoul. The collected questionary paper is analyzed with SPSS/PC/sub +/ program and the method of statistical analysis used for this study is frequency analysis, factor analysis, cluster analysis, t-test, and crosstab analysis. The result of analysis of the characteristics of the environment -friendly customers involves the following: Firstly, there were no significant difference in the demographic characteristics between the environment-friendly customer group and non-environment-friendly customers group. Secondly, environment-friendly customers had more environmental programs, had seen and heard more environmental program through current news from TV, newspapers, and magazines, and had more interest in recycling or separated collecting of garbage, and been doing better recycling or separated collecting. These serial processes of research, have the meaning in confirming that segmented market for environment-friendly customers exists in the domestic fashion market, and these will not only set up the basis of research on the market of environment-friendly fashion product but also be able to contribute to propose future direction of research.