• 산업경영시스템학회지
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• 제24권66호
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• pp.69-77
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• 2001

The management of return flows induced by the various forms of reuse of products and materials in industrial production processes has received growing attention throughout this decade. As one of the developing countries in the world trade market, we have to apply the reverse logistics system considering an environment seriously, and to implement reverse logistics activities abreast with the forward logistics system of a companies. Therefore, the objective of this study was to discuss what the reverse logistics system of Environmentally Conscious Logistics Systems(ECLS) is by introducing a case study.

• The Journal of Korean Physical Therapy
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• 제32권6호
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• pp.378-382
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• 2020

Purpose: This study aimed to examine the effects of forward head posture on the flexion-relaxation ratio (FRR) and muscle activity during sustained neck flexion and to investigate the correlation between craniovertebral angle and FRR. Methods: Nineteen subjects participated in this study and were allocated to a forward head posture (FHP) group or a non-forward head posture (NFHP) group. Craniovertebral angle (CVA) and FRR were measured in all subjects, and all participants performed a standardized cervical flexion-extension movement in two phases: Phase I, sustained cervical full flexion for 5s; and Phase II, cervical extension with the return to the starting position for 5s. The value of CVA has calculated three times, and the value of FRR was measured three times in order to obtain the mean value. Results: FRR values in the FHP and NFHP group were significantly different (p<0.05). Phase I was significantly different, but the Phase II was not significantly different between the FHP and NFHP group (p>0.05). There was a significant correlation between the muscle activity of Phase I and CVA (p<0.05). However, FRR and the muscle activity of the Phase II were not a significant correlation with the CVA (p>0.05). Conclusion: FHP increases the muscle activity of the cervical erector spinae during sustained neck flexion and reduces FRR, which can cause fatigue in the cervical erector spinae. In addition, for those with a smaller CVA, muscle activity of the cervical erector spinae is increased during sustained neck flexion, which can increase neck muscle tension.

• 디지털융복합연구
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• 제13권11호
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• pp.45-55
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• 2015

본 연구에서는 종합주가지수와 코스닥지수, 문화콘텐츠 산업과 관련이 높은 오락 문화, 디지털콘텐츠 지수를 이용하였다. 지난 2004년 3월에서 2015년 7월까지 총 597주 동안 각각의 주가지수 및 수익률 동향을 파악하였다. 각 주가지수의 수익률, 변동성, 상관관계, 동조화현상 등을 비교 분석하여 콘텐츠관련 주식들이 투자가치가 있는지 살펴보았다. 향후 문화콘텐츠 산업의 높은 성장 가능성을 보았을 때 관련 주식들의 투자 가능성에 기대를 걸어보았다. 분석 결과 지난 2008년도 글로벌 금융위기 이후 문화콘텐츠 관련 주식들이 더 높은 상승률을 보여주었다. 최근 문화콘텐츠 산업에 대한 관심이 높아지면서 점점 투자가치 메리트가 증가하고 있음을 볼 수 있었다. 향후 문화콘텐츠 산업이 계속 발전할 것으로 예상되어 이들 기업에 대한 투자자들의 많은 관심이 이어지면서 문화콘텐츠관련 기업들의 투자가치 상승에 많은 기대를 걸어본다.

• 한국정보통신학회논문지
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• 제11권8호
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• pp.1564-1573
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• 2007

현재 사용 중인 프린터의 토너에 부착된 토너 잔량 검출 회로는 PCB 회로기판을 사용함으로써 부피가 비교적 큰 상태이므로 보다 경량 소형화된 프린트에 사용하기에는 부적합하다. 본 연구에서는 이와같은 소형화된 회로를 one chip함으로써 경쟁력이 있는 제품을 개발한다. 2005년 이후 출시 된 프린터에 사용되는 토너에는 칩이 필수적으로 부착되어야 한다. 따라서 앞으로의 재생시장에서 사용될 칩의 수요는 점점 커질 것이다. 세계적인 레이저 프린터 메이커들이 프린터에서 사용되는 토너카트리지의 정보를 관리하여 고객 서비스를 한다는 취지로 프린터에 부착되는 칩으로 인해 재생토너의 생산이 불가능하다. 본 연구에서는 재생토너를 생산하기 위해 필수적으로 부착되는 칩을 개발한다.

• Industrial Engineering and Management Systems
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• 제15권1호
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• pp.63-76
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• 2016

Multiperiod portfolio selection problem attracts more and more attentions because it is in accordance with the practical investment decision-making problem. However, the existing literature on this field is almost undertaken by regarding security returns as random variables in the framework of probability theory. Different from these works, we assume that security returns are uncertain variables which may be given by the experts, and take absolute deviation as a risk measure in the framework of uncertainty theory. In this paper, a new multiperiod mean absolute deviation uncertain portfolio selection models is presented by taking transaction costs, borrowing constraints and threshold constraints into account, which an optimal investment policy can be generated to help investors not only achieve an optimal return, but also have a good risk control. Threshold constraints limit the amount of capital to be invested in each stock and prevent very small investments in any stock. Based on uncertain theories, the model is converted to a dynamic optimization problem. Because of the transaction costs, the model is a dynamic optimization problem with path dependence. To solve the new model in general cases, the forward dynamic programming method is presented. In addition, a numerical example is also presented to illustrate the modeling idea and the effectiveness of the designed algorithm.

• 대한전자공학회논문지TC
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• 제44권6호
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• pp.31-39
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• 2007

본 논문에서는 코드분할다중접속방식을 사용하는 이동통신 시스템에서 기지국의 순방향 송신전력 및 파일롯 전력 등 RF 파라미터를 실시가 또는 주기적으로 측정하여 분석함으로써 시스템의 장애를 미연에 방지하고 셀커버리지 확대, 가입자 수용용량 증가 등 최적의 서비스 품질을 확보하고 투자효율을 극대화하기 위한 방안을 제시하였다. 순방향 전력 측정에서는 디텍터 내의 국부발진기 주파수를 가변함으로써 모든 채널의 송신출력을 측정할 수 있도록 하였다. 채널전력의 측정에 의하여 통화량 증가에 따른 송신출력의 변화를 관찰할 수 있으며, 순방향 $E_c/I_o$ 와의 비교를 통하여 파일롯 채널의 전력을 유추함으로써 대전력증폭기 등 송신부 모듈의 열화를 판독할 수 있도록 하였다. 일련의 모든 측정에는 CDMA 레벨디텍터에 의한 정밀 계측에 이은 정확한 분석이 이루어져야 하므로 변조방식 차이에서 오는 Crest factor 가 상이함으로 인한 측정상의 오차를 극복할 수 있도록 설계하였다.

• ETRI Journal
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• 제27권3호
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• pp.243-249
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• 2005

A mobile antenna for multimedia communications with Ku-band geostationary satellite KOREASAT-3 and JSAT-2A is presented. The forward link of the satellite communication is 11.7 to 12.75 GHz, and the return link is 14.0 to 14.5 GHz. The mobile antenna is designed to be a stair structure using 24 active phased array elements in order to provide a low profile, and to be at a non-periodic array distance using the genetic algorithm. Also, the designed antenna uses the double beam forming method for stable satellite tracking. The fabricated mobile antenna is examined using various experiments to confirm its capability for practical application. From the measured results, the fabricated mobile antenna system is confirmed to have a good performance.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1758-1763
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• 2004

This paper focuses on congestion control for ATM network with uncertain time-variant delays. The time-variant delays can be distinguished into two distinct components. The first one is represented by time-variant queueing delays in the intermediate switches that are occurred in the return paths of RM cells. The next one is a forward path delay. It is solved by the VBR model which quantifies the data propagation from the sources to the switch. Robust $H_8$ control is studied for solving congestion problem with norm-bounded time-varying uncertain parameters. The suitable robust $H_8$ controller is obtained from the solution of a convex optimization problem through LMI technique.

• 대한산업공학회지
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• 제16권2호
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• pp.71-79
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• 1990

In this paper, the Double Shortest Arborescence & Merging method is presented as an efficient heuristic algorithm for the Public Vehicle Routing Problem which is to find the minimum total cost routes of M or less vehicles to traverse the required arcs(demand streets) at least once and return to their starting depot on a directed network. Double Shortest Arborescence which consists of forward shortest aborescence and backward one informs M or less shortest routes to traverse all required arcs. The number of these routes is reduced to M or less by merging routes. The computational experiment based on randomly generated networks reports that this algorithm is efficient.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2161-2163
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• 2004

This paper focuses on congestion control for ATM network with uncertain time-variant delays. The time-variant delays can be distinguished into two distinct components. The first one that is represented by time-variant queueing delays in the intermediate switches is occurred in the return paths of RM cells. The next one is a forward path delay. It is solved by the VBR Model which quantifies the data propagation from the sources to the switch. Robust $H_{\infty}$ control is studied for solving congestion problem with norm-bounded time-varying uncertain parameters. The suitable robust $H_{\infty}$ controller is obtained from the solution of a convex optimization problem including terms of LMIs.