• 한국항해항만학회지
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• 제40권5호
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• pp.345-351
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• 2016

This study presents a system dynamics methodology to evaluate quantitatively the effect of the Korean government's development policy, such as tax reductions, on the industrial economy. System dynamics is often perceived as an optimized means to identify the dynamic inter-relationships among various factors of development policies, and in particular the industrial characteristics and uncertainties of the coastal shipping industry. The results of simulations used in this study shows that the impact of development policies such as tax reductions would increase shipping demand for about 4 years, and that tax incentives could raise the demand volume for cabotage cargo from 5.26 to 11.11%, through the available freight-down by 90~95% points. The system dynamics approach used in this paper represents an initial attempt to use this methodology in studies of the coastal shipping industry. On the basis of our simulations, the industrial effects of other development policies, such as ship financing support, investment of social overhead, or crew supply, could also be analyzed effectively. Additionally, it should be possible to extend these results by developing a comprehensive model encompassing these various analyses.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.11-15
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• 2005

공중발사 방식은 일반적인 지상발사와 비교해 볼 때 많은 장점을 지니고 있다. 그러나 공중발사 로켓의 형상은 모선에 장착 시 많은 제한이 따르기 때문에 여러 해석분야를 통합한 시스템 설계가 필요하다. 시스템 설계는 순차적 최적화와 MDF 기법을 이용하여 수행되었다. 해석 모듈은 임무분석, 단배분, 추진해석, 형상, 중량해석, 공력해석, 궤적해석을 포함한다. 두 가지 기법 중 MDF 기법을 이용하였을 때 더 좋은 결과를 도출하였다. 시스템 최적화 결과 총 중량 1244.91 kg. 위성중량 7.5 kg, 총 길이 6.18m, 지름 0.60 m을 지닌 초음속 공중발사 로켓이 설계되었다.

• ETRI Journal
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• 제40권4호
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• pp.537-545
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• 2018

In this paper, we present a comprehensive analytical study of the symbol error rate (SER) of single-carrier frequency-division multiple access (SC-FDMA) with zero-forcing frequency domain equalization (ZF-FDE) over a Rayleigh fading channel. SC-FDMA is considered as a potential waveform candidate for fifth-generation (5G) radio access networks (RANs). First, the $N_C$ fold convolution of the noise distribution of an orthogonal frequency-division multiplexing (OFDM) system is computed for each value of the signal-to-noise ratio (SNR) in order to determine the noise distribution of the SC-FDMA system. $N_C$ is the number of subcarriers assigned to a user or the size of the discrete Fourier transform (DFT) precoding. Here, we present a simple alternative method of calculating the SER by simplifying the $N_C$ fold convolution using time and amplitude scaling properties. The effects of the $N_C$ fold convolution and SNR over the computation of the SER of the SC-FDMA system has been separated out. As a result, the proposed approach only requires the computation of the $N_C$ fold convolution once, and it is used for different values of SNR to calculate the SER of SC-FDMA systems.

• 한국시스템다이내믹스연구
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• 제8권1호
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• pp.173-186
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• 2007

This research consists of (1) building (or molding) the Dynamics Simulation Model on Return Policy mainly used in publications, phonographs, and computer industry; which are seen used in supply chain contract known as effective control mechanism under the varied supply chain situations, and (2) analyzing the effects that return rates and seller's contract parameters have in the outcome of the model and (3) observing how the effectiveness of Return Policy changes under such circumstances where the buyer's sales ability and the seller's risk inclination are taken into account. Thus, the main purpose of this research lies in analyzing what exactly are the effects (and or outcome) that sales ability and risk inclination have in Return Policy, and additionally by conducting comprehensive research on Supply Chain Policy Dynamics Simulation Model, we will try to prove that not only the Systems Dynamics approach is highly contributive in supply chain management but also that it will serve as a foothold in future research. As a result of the research, supply chain achievement level turned out to be high when Return Policy is enforced, and the achievement level was even higher when seller's sales ability was taken into consideration along with the Return Policy. On the other hand, the achievement level decreased when the seller had risk aversive tendencies.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.1186-1190
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• 1995

This paper is focused on the formulation of explicit closed-form functions describing the performance measures of the general flexible manufacturing system (FMS)according to the strategy of material handling system(MHS). the performance measures such as the production rate, the production lead-time and the utilization rate of the general FMS are expressed, respectively, as the explicit closed-form functions of the part processing time, the service rate of the material handling system (MHS) and the number of machine tools in the FMS. For this, the gensral FMS is presented as a generalized stochastic Petri net model, then, the moment generating function (MGF) based approach is applied to obtain the steady-state probabity formulation. Based on the steady-state formulation, the explicit closed-form functions for performance measures of the probability FMS can be obtained. Finally, the analytical results are compared with the Petri net simulation results to verify the validity of the suggested method. The paper is of significance in the sense that it provides a comprehensive formula for performance measures of the FMS even to the industry engineers and academic reademic resuarchers who have no background on Markov chain analysis method or Petrinet modeling

• 대한산업공학회지
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• 제43권3호
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• pp.164-175
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• 2017

Dual response surface optimization (DRSO) attempts to optimize mean and variability of a process response variable using a response surface methodology. In general, mean and variability of the response variable are often in conflict. In such a case, the process engineer need to understand the tradeoffs between the mean and variability in order to obtain a satisfactory solution. Recently, a Posterior preference articulation approach to DRSO (P-DRSO) has been proposed. P-DRSO generates a number of non-dominated solutions and allows the process engineer to select the most preferred solution. By observing the non-dominated solutions, the DM can explore and better understand the trade-offs between the mean and variability. However, the non-dominated solutions generated by the existing P-DRSO is often incomprehensive and unevenly distributed which limits the practicability of the method. In this regard, we propose a modified P-DRSO using multiple objective genetic algorithms. The proposed method has an advantage in that it generates comprehensive and evenly distributed non-dominated solutions.

• 한국항공우주학회지
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• 제33권12호
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• pp.26-32
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• 2005

공중발사 방식은 일반적인 지상발사와 비교해 볼 때 많은 장점을 지니고 있다. 그러나 공중발사 로켓의 형상은 모선에 장착 시 많은 제한이 따르기 때문에 여러 해석분야를 통합한 시스템 설계가 필요하다. 시스템 설계는 순차적 최적화와 MDF 기법을 이용하여 수행되었다. 해석 모듈은 임무분석, 단배분, 추진해석, 형상, 중량해석, 공력해석, 궤적해석을 포함한다. 두 가지 기법 중 MDF 기법을 이용하였을 때 더 좋은 결과를 도출하였다. 시스템 최적화 결과 총 중량 1244.91kg, 위성중량 7.5kg, 총 길이 6.36 m, 지름 0.60m을 지닌 초음속 공중발사 로켓이 설계되었다.

• Geomechanics and Engineering
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• 제15권2호
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• pp.755-767
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• 2018

This paper uses a finite element based approach to provide a comprehensive understanding to the behaviour and the design performance of buried uPVC pipes with different diameters. It also investigates pipes with good and poor haunch support and proposes minimum safe wall thicknesses for these pipes. The results for pipes with good haunch support showed that the maximum pipe wall stress and deformation increase as the diameter increased. The results for pipes with poor haunch support showed an increase in the dependency of the developed vertical displacement on the haunch support as the diameter or the backfill height increased. Additionally, poor haunch support was found to increase the soil pressure, with the effect increasing as the diameter increased. The design of uPVC pipes for both poor and good haunch support was found to be governed by critical buckling. A key outcome is a new design chart for the minimum wall thickness, which enables the robust and economic design of buried uPVC pipes. Importantly, the methodology adopted in this study can also be applied to the design of flexible pipes manufactured from other materials, buried under different conditions and subjected to different loading arrangements.

• Asian Journal for Public Opinion Research
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• 제1권3호
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• pp.217-231
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• 2014

This study begins with a review of commonly discussed dimensions of public risk perception that may influence public opinion toward risks. Factors that have been revealed by the literature to have substantial impact on risk perception, such as demographic background, trust, and media environment, are also discussed. Meanwhile, we evaluate two well-known research models in the realm of risk analysis: 1) the psychometric paradigm, and 2) the social amplification of risk framework (SARF). Based on a literature review, this study suggests that, besides the psychological and social approach, models of risk perception and risk communication research should shift to a more comprehensive one by considering the interrelations between laypeople and the environment. This study proposes a research model from the perspective of social cognitive theory (SCT) as a potential framework for future studies: 1) in the societal environment, individuals' risk perception and information seeking behavior, which is determined by risk perception will be influenced by trust in regulators and interpersonal trust; 2) in the media environment, individuals' risk perception and information seeking behavior will be influenced by individuals' perceived information characteristics. Knowledge about risk accumulated through information seeking will change risk perception in a longitudinal process.

• 한국기술사회:학술대회논문집
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• 한국기술사회 1995년도 제25회 한일기술사 합동 심포지엄 한국편 자료(2차)
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• pp.23-29
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• 1995

Green landscape plan to the riverfront area of the Han River The Han River, one of the symbolic elements in metropolitan Seoul, structures an axis of waterscape as the openspace crossing east to west of the city of Seoul. As riverside urban motorway(88 Olympic motorway) and riverside public park were constructed by the Han River Comprehensive Development Project in 1986, the necessity of general plan for the in-stallation of envirommental facility belt to conserve living enviroument is being required with relation to, dense residential areas closed to the river Therefore, the goal of the study is to provide better riverview and to increase environmental purifi-cation ability as a large scale waterscape axis by the preparation of landscape plan to the riverfront area of Han River, In order to achieve the goal, the study deals with sectional speciality, the introduction of landscape assessment techniques and ecological approach to given environment. As unity is kept through whole waterfront area, the area is divided into 9 zoning sections to study development methods for each section, and themes for speciality are given to each section, and the. sort of plants which can be symboliged to the area is selected. Also, the planting methods for harmony with the type of road structure and riverscape is offered. Though the study may give significane to the image and the function of riverside road, in con-clusion, the characteristic ecological approach to the river is so limited that has not been reflected enough on the plan. It is expected that the study should be continued, and long-term riverfront openspace plan, environmentally sustainable, should be arepared.