• Industrial Engineering and Management Systems
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• 제12권3호
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• pp.172-180
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• 2013

We herein consider a stochastic multi-item inventory management problem in which a warehouse sells multiple items with stochastic demand and periodic replenishment from a supplier. Inventory management requires the timing and amounts of orders to be determined. For inventory replenishment, trucks of finite capacity are available. Most inventory management models consider either a single item or assume that multiple items are ordered independently, and whether there is sufficient space in trucks. The order cost is commonly calculated based on the number of carriers and the usage fees of carriers. In this situation, we can reduce future shipments by supplementing items to an order, even if the item is not scheduled to be ordered. On the other hand, we can reduce the average number of items in storage by reducing the order volume and at the risk of running out of stock. The primary variables of interest in the present research are the average number of items in storage, the stock-out volume, and the number of carriers used. We formulate this problem as a multi-objective optimization problem. In a numerical experiment based on actual shipment data, we consider the item shipping characteristics and simulate the warehouse replenishing items coordinately. The results of the simulation indicate that applying a conventional ordering policy individually will not provide effective inventory management.

• Structural Engineering and Mechanics
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• 제41권4호
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• pp.559-573
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• 2012

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

• 조명전기설비학회논문지
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• 제23권8호
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• pp.124-129
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• 2009

최근 생활수준의 향상과 세계적인 녹색성장 정책으로 환경에 대한 관심이 고조되어, 전력분야에서도 환경친화적인 설비가 요구되어 지고 있다. 이에 따라 전력용 변압기도 소음저감에 대한 연구가 진행되어, 최근 55[dBA]급 154[kV] 저소음 변압기가 개발되었다. 저소음 변압기는 소음레벨은 저감되었지만, 중량 및 부피의 증가, 고무댐퍼의 적용 등이 변화가 있다. 이로 인하여 현장적용시 시험, 수송, 설치 및 운용 등에 대한 면밀한 검토가 필요한 실정이다. 따라서 본 논문에서는 효과적인 현장적용을 위해 소음레벨 기준치, 수송중량, 설치공간, 장기운용에 대한 사항을 검토하였다.

• Korea-Australia Rheology Journal
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• 제12권1호
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• pp.83-92
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• 2000

In resin transfer molding (RTM) process, preplaced fiber mat is set up in a mold and thermoset resin is injected into the mold. An important interest in RTM process is to minimize cycle time without sacrificing part quality or increasing cost. In this study, the numerical simulation and optimization process in filling stage were conducted in order to determine the optimum gate locations. Control volume finite element method (CVFEM) was used in this numerical analysis with the coordinate transformation method to analyze the complex 3-dimensional structure. Experiments were performed to monitor the flow front to validate simulation results. The results of numerical simulation predicted well the experimental results with every single, simultaneous and sequential injection procedure. We performed the optimization analysis for the sequential injection procedure to minimize fill time. The complex geometry of an automobile bumper core was chosen. Genetic algorithm was used in order to determine the optimum gate locations with regard to 3-step sequential injection case. These results could provide the information of the optimum gate locations in each injection step and could predict fill time and flow front.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1896-1897
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• 2007

Medical equipment of high frequency has been presently applied to various parts of human body and novel treatment effects have been shown by it. Recently there are many cases that high frequency apparatus has been used in dermatology as the interest in beauty has been growing. Especially used in skin, blood volume is increased by keeping surface temperature of skin at around $43^{\circ}C$ and domodex folliculorum are treated by applying high electric field. It is the aspect we consider that increasing blood volume and domodex folliculorum treatment take effect on hair loss. In this study, high frequency electrotherapy apparatus was proposed to be applied to hair loss treatment. For that, human body was experimented with varying output voltage and frequency. The adjustable switching signal for treatment was obtained from 100[kHz] to 1000[kHz] by using DSP. Stable output specific was also obtained by feedback control to protect human body. The best hair growth conditions were the output voltage of 1.2[kV], the frequency of near 300[kHz] and the maximum current of 2[mA]. We apply this high frequency electrotherapy apparatus to two bald men, 46-year-old and 45-year-old. After treatment for a month they had thick and strong hair.

• 무역상무연구
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• 제75권
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• pp.95-116
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• 2017

The global financial crisis has slowed overall growth in the global economy. In addition, uncertainty is increasing in the world economy due to the Trade protectionism, sluggish world trade, and a rise in the rate of interest caused by expansion of fiscal spending by major countries. In this study, we analyzed various factors affecting the container import and export volume, which has a high correlation with export and import of commodities in international trade. In particular, we will examine how exchange rate fluctuations and domestic and overseas economic conditions affect container imports and exports. For the empirical analysis, monthly time series data were used from January 2000 to January 2017. We use the Error Correction Model (VECM) for the empirical analysis and the GARCH model for the exchange rate fluctuation. As a result, container export and import volume had a negative relationship with exchange rate and exchange rate volatility, which had a positive effect on domestic and international economic conditions. However, the effects are different before and after the financial crisis.

• 한국산학기술학회논문지
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• 제17권6호
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• pp.560-565
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• 2016

본 연구에서는 공매도관련 거래활동이 주가하락요인으로 작용하는지를 파악하기 위해서 국내 주식시장의 자료를 활용하여 실증분석하였다. 표본 분석기간은 2005년 1월부터 2016년 3월까지이며, 이 기간 동안의 공매도거래비율을 기준으로 상위 10%, 상위 25%, 상위 50% 주식을 대상으로 각각 포트폴리오로 구성하여, 이 포트폴리오를 대상으로 분석하였다. 매도거래활동이 많이 이루어진 포트폴리오의 가치-가중 수익률과 해당 포트폴리오의 공매도거래활동과의 관계를 살펴본 것이다. 종속변수는 포트폴리오의 가치-가중 수익률에서 시장수익률을 뺀 고유수익률이다. 시장수익률은 KOSPI 지수 수익률과 KOSDAQ 지수 수익률의 시가총액 가중수익률로 사용한다. 종속변수는 포트폴리오의 공매도거래비중, 대차거래비중, 대차잔량비율 등을 사용한다. 종속변수들의 안정성을 위해서 각 변수를 차분하였다. 본 연구의 결과, 공매거래비중(${\Delta}SVR$), 대차거래비중(${\Delta}LVR$), 대차잔량비율(${\Delta}LIR$) 등과 같은 공매도관련 활동변수들은 주가고유수익률에 부(-)의 영향을 미치고 있음을 보였다. 따라서 공매도관련 활동은 주가하락을 초래한다고 할 수 있다. 공매도활동을 모두 설명변수로 추정한 결과의 공통점은 대차거래비중이나 대차잔량비율이 주가하락에 영향을 미치지만, 공매거래비중은 통계적으로 유의한 영향이 없다는 것이다. 이는 대차거래활동이 공매도활동보다 주가하락에 더 큰 영향을 미치고 있다는 것을 의미한다.

• 동의신경정신과학회지
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• 제34권3호
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• pp.235-245
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• 2023

Objectives: The aim of this study was to analyze public and researcher interests in suicide and related illnesses and acupuncture and acupressure treatment using Google Trends and some electronic databases. Methods: Search results for keywords "suicide," "acupuncture," "acupressure," and several illnesses related to suicide were analyzed in Google Trends from January 2004 to June 2023. Illnesses included anxiety, depression (including major depressive disorder), schizophrenia, bipolar disorder, post- traumatic stress disorder (PTSD), eating disorder (including anorexia nervosa and bulimia nervosa), substance use disorder, autism spectrum disorder, personality disorder (including borderline person- ality disorder), and chronic pain. Search results were extracted using relative search volume (RSV) scores between 0 and 100. Search terms were also searched in online databases, including PubMed, CNKI, and OASIS, to estimate the number of related studies, and descriptive analysis was conducted. Results: Google Trends analysis showed a strong positive correlation between the RSVs of "suicide and depression," "acupuncture and chronic pain," and "acupressure and PTSD." The electronic database search results produced numerous studies published on "suicide and depression," "acupuncture and depression," and "acupressure and anxiety." High interest in "suicide and depression," "acupuncture and chronic pain," and "acupressure and anxiety" was seen among the public and researchers. Interest in "suicide and chronic pain," "acupuncture and eating disorder," and "acupressure and PTSD" was higher in the public than among researchers, while "anxiety and suicide" and "anxiety and acu- puncture" showed opposite trends. Conclusions: The results of this research enable an understanding of public and researcher interest in suicide, acupuncture, acupressure, and suicide-related illnesses. The results also provide a basis for fu- ture research and examining public health implications in Korean medicine.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제3권2호
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• pp.101-108
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• 2014

최근 들어, 소셜 네트워크 서비스를 통한 멀티미디어 콘텐츠의 열람과 공유가 보편화됨에 따라, 사용자의 관심이나 특징에 부합되는 콘텐츠의 효과적 제공에 대한 욕구가 높아지고 있다. 특히, 생성되는 콘텐츠의 방대한 양을 고려할 때 적합한 콘텐츠의 효과적 선택이 사용자의 만족도를 크게 좌우하게 된다. 예를 들어, 사람간의 관계에 기반하여 관심 콘텐츠를 제공하는 방법의 경우 신뢰성이 어느 정도 보장되기 때문에, 사용자의 효과적인 열람이 가능하다. 대표적인 소셜 네트워크 서비스인 Facebook에서 제공하는 Facebook 페이지는 관심사에 대한 콘텐츠를 획득할 수 있는 공간이지만, 사용자는 제공되는 콘텐츠의 양이 너무 많아 원하는 목적에 맞게 콘텐츠를 획득하기 어렵다. 본 논문에서는, 개인 사용자의 관심에 따라 Facebook 페이지 콘텐츠를 순위별로 선정하여 대표 콘텐츠를 제공하는 기법을 제안한다. 사용자 간의 친밀도를 이용해 사용자를 관심 분야에 따라 그룹화하고, 그룹화 된 사용자들에게 Facebook 페이지 콘텐츠를 중요도 순위별로 선택하여 사용자에 제공한다. 마지막으로 실험을 통해 제안된 기법의 성능을 보인다.

• 한국가스학회지
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• 제25권2호
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• pp.28-33
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• 2021

최근 친환경 자동차에 대한 관심이 높아짐에 따라 공해물질을 배출하지 않는 수소연료전지 차량에 대한 관심과 구매가 증가하고 있다. 최근 정부의 수소에너지 보급정책에 따라 수소충전소의 확충과 핵심부품의 국산화를 지원하고 있다. 본 연구에서는 그중에서도 수소 유량제어 밸브의 차압에 따른 유동특성을 연구하였다. 차압이 높아 짐에 따라 질량유량과 유량계수는 체적유량과 다른 경향을 보임을 확인하였다. 그리고 병목 구간에서의 노즐효과로 인해 수소온도에 영향을 주게되고, 밀도의 변화를 일으켜 질량유량에 영향을 주게 되는 것을 확인 하였다.