• 대한산업공학회지
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• 제29권4호
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• pp.312-320
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• 2003

Recently there is a growing interest in mobile cellular network providing multimedia service. However, the link bandwidth of mobile cellular network is not sufficient enough to provide satisfactory services to users. To overcome this problem, an adaptive framework has been proposed. In this study, we propose a new method of estimating DPR(Degradation Period Ratio) in an adaptive multimedia network where the bandwidth of ongoing call can be dynamically adjusted during its lifetime. DPR is a QoS(Quality of Service) parameter which represents the ratio of allocated bandwidth below a pre-defined target to the whole service time of a call. We improve estimation method of DPR using DTMC(Discrete Time Markov Chain) model by calculate mean degradation period, degradation probability more precisely than in existing studies. Under Threshold CAC(Call Admission Control) algorithm, we present analytically how to guarantee QoS to users and illustrate the method by numerical examples. The proposed method is expected to be used as one of CAC schemes in guaranteeing predefined QoS level of DPR.

• 항공우주시스템공학회지
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• 제16권5호
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• pp.94-101
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• 2022

본 논문에서는 해외수출용 유도무기체계에 탑재되는 MEMS 관성측정기의 특성과 탑재되는 유도무기체계의 운용 환경 분석을 통해서 신뢰성 입증을 위한 관성측정기 가속계수를 도출하고, 이를 기반으로 관성측정기 수명 시험을 설계하였다. 또한 설계된 수명 시험을 토대로 관성측정기 3조에 대한 수명 시험 수행을 통해 12년의 목표 수명을 입증하였다.

• 한국환경보건학회지
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• 제36권6호
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• pp.456-464
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• 2010

Recently, heavy metals contamination of the agricultural soil and crops surrounding mining areas has been identified as one of the most serious environmental problems in South Korea. The Ministry of the Environment in Korea conducted a Preliminary National Environmental Health Survey (PNEHS) in abandoned metal mines in 2007. The priority for a subsequent detailed examination was ranked from the results of PNEHS. The studied mine which was ranked as being of the highest priority is located in the midwestern part of Korea and was operated from 1911 to 1985. In this study, the contamination levels of the heavy metals in the abandoned metal mine were investigated. From the results, the average daily dose (ADD), target hazard quotient (THQ) and target cancer risk of the heavy metals were evaluated. The concentration of arsenic (As) in all of the tailings from the mine was higher than its countermeasure standard of Korea. In particular, the highest concentration of As, 330 mg/kg, was up to 15 times higher than its countermeasure standard. The average concentration of As in agricultural soils was higher than the warning standard of Korea, and higher than its countermeasure standard at six sites. The average concentrations of the analyzed heavy metals in agricultural soil were below the warning standard, but concentrations of cadmium (Cd) and lead (Pb) at 4 sites were higher than its warning standard. The average concentration of As in surface water exceeded the warning standard of Korea. The value of the THQ of As for the tailings was higher than the health protection standard 1. The value of THQ of As for the farmlands was lower than the standard, while the hazard index (HI) of As was higher than the standard. The value of target cancer risk (TCR) of As, $6.44{\times}10^{-4}$, were higher than the health protection standard of a lifetime risk for TCR at $1{\times}10^{-6}$. This suggests that the residents around the metal mines are exposed to As pollution with a carcinogenic risk.

• 대한환경공학회지
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• 제37권6호
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• pp.349-356
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• 2015

본 연구는 부산연근해에서 서식하는 저서어류 체내의 미량금속에 의한 인체 위해 영향을 정량적으로 평가하기 위하여 수행되었다. 부산의 용호부두 인근에서 채취 된 4종의 식용저서어류 넙치, 우럭, 쥐치, 밑달갱이 조직내의 미량금속(trace metals)의 함량을 ICP-MS를 이용하여 분석하였다. 그리고 이를 토대로 어류섭취를 통한 미량금속의 인체 노출량을 파악하고, 이로 인한 잠재적 인체 위해도 평가를 수행하였다. 4종의 어류 조직 내 미량금속의 평균함량은 Li, Cr, Ni, Cu, Zn, As, Cd, Pb이 각각 $0.005{\pm}0.009$, $0.77{\pm}0.30$, $0.29{\pm}0.34$, $0.49{\pm}0.14$, $15.96{\pm}2.52$, $10.62{\pm}4.67$, $0.001{\pm}0.002$, $0.045{\pm}0.06mg/kgdw$으로 나타났다. 이 지역에서 채취된 어류의 섭취로 인한 표준체중(60 kg)의 국민에 대한 노출평가 결과 Cu, Zn은 PMTDI (provisional maximum tolerable daily intake)의 0.0032, 0.054-0.18%, As, Cd, Pb는 PTWI (provisional tolerable weekly intake)값의 13, 0.0041, 0.020%로 나타나 합동식품첨가물전문가위원회(The Joint FAO/WHO Expert Committee on Food Additives, JFCFA)에서 권고하는 각원소의 제한섭취량에 비하여 매우 낮은 수준이었다. 그리고 독성(비발암)위해도 평가 결과는 모두 HI (hazard index)지수가 1 이하로 장기간 섭취하여도 안전한 것으로 나타났으며, 4종의 모든 어류섭취로 인한 As의 노출로 인한 초과 발암 위해도도 10만명 당 1명 이하로 나타나 역시 장기섭취로 인한 발암 확률도 무시할 만한 수준인 것으로 나타났다.

• 드라이브 ㆍ 컨트롤
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• 제17권2호
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• pp.19-27
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• 2020

The purpose of this study was to suggest design criteria for the HMT (hydro-mechanical transmission) of a 55 kW-class agricultural tractor, develop a simulation model, and evaluate its performance such as axle rotational speed, tractor speed, and power transmission efficiency. In this study, the HMT comprised a compound planetary gear and a HSU (hydro-static unit), and the compound planetary gear comprised two planetary gear sets. The HMT has three gear stages, and the maximum tractor speed was selected as 40 km/h. The simulation time was set at 2736 hours considering the lifetime of the tractor, and the simulation was performed for each gear stage at the engine-rated power conditions. As a result of the simulation, the axle rotational speeds for each gear stage were 39, 77, and 158 rpm, respectively. The range of tractor speed for each gear stage were 1.05-10.22 km/h, 10.74-20.17 km/h, and 20.70-41.40 km/h, respectively. The APE (absolute percentage gear) for the tractor's maximum speed between target value and simulation results were 2.20%, 0.85%, and 3.50%, respectively. Also, the power transmission efficiency for each gear stage were 0-75%, 72-81%, and 69-81%, respectively. The simulation results for the power transmission efficiency of the HMT were similar with the results of the previous research. This was a basic study on the development of the HMT for an agricultural tractor. In future studies, it is necessary to develop a tractor platform and evaluate the performance. The comparison between the simulation model and the HMT tractor should be performed.

• 한국가구학회지
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• 제20권4호
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• pp.358-373
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• 2009

Probability based design(PBD)method has some advantages against current design methods. First, it can provide the quantitative values for the structural safety or capacity through the reliability index, $^{\beta}$. That presented the certainty on the corresponding structure for the designer or user, also that permitted the broad consideration in the safety of structures. In addition, it can give the quantitative lifetime of the related structure in the calculation process of target reliability index. Also, incidental economical efficiency can be expected because decrease of required structural material can be obtained by using the practical material data. Unlikely current deterministic structural design methods, main advantage is the reflection of real condition in the structural design process by application of the data with not small clear specimen but structural size material. Advanced countries, namely America, Canada, Europe, Australia and New Zealand already converted from allowable stress design(ASD) method to PBD method and used as a standard wooden structures code in the late 1980s and 1990s. Other domestic constructions standards such as the steel or concrete constructions accepted and used the PBD methods already. Accordingly, wooden structural design method also should be converted from deterministic ASD to probabilistic LRFD(Load and resistance factor design) in order to keep pace with worldwide demands for PBD. Hence, to suggest the reason of introduction the PBD in domestic wooden structural design and analysis, a brief example was used to show the different reliability index by using the different design methods. Definition, merits and demerits of deterministic ASD and probabilistic LRFD were followed. Also the three examples were presented to show the similarity and differences between ASD and LRFD. Finally, connection problems that might cause a disputation in wooden structural design and analysis were broadly examined.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제16권12호
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• pp.1234-1238
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• 2010

최근 센서 네트워크를 이용하여 이동 객체의 정보를 모니터링 하는 응용에 대한 연구가 활발하게 이루어지고 있다. 네트워크 전체 영역에서 대상 객체가 원하는 밀도로 분포하는 영역을 찾아내는 밀도 질의는 객체 모니터링 응용의 한 분야이다. 본 논문에서는 에너지 효율적인 질의 처리를 위한 동종 센서 기반의 인-네트워크 밀도 질의 처리 기법을 제안한다. 제안하는 기법은 밀도 질의 처리의 정확도를 높이고, 에너지 소비를 최소화하기 위한 가능성 기반 예상 지역 선정 기법과 센싱 영역 면적 기반 결과 보정 기법을 수행한다. 제안하는 기법의 우수성을 보이기 위해 시뮬레이션을 통해 기존에 제안된 밀도 질의 처리 기법과의 성능을 비교하였다. 그 결과 기존 기법에 비해 질의 처리를 위한 에너지 소모는 약 92% 감소하였고, 그에 따른 네트워크 생존 시간이 증가하였다. 덧붙여, 기존 기법보다 제안하는 기법의 질의 결과가 더 높은 정확도를 보장한다.

• 한국강구조학회 논문집
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• 제20권2호
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• pp.259-268
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• 2008

본 논문에서는 교량의 유지관리를 위하여 생애주기 성능 및 비용을 고려한 최적 유지관리 전략 수립 기법을 개발하였다. 제안된 기법을 이용하여 교량을 구성하는 부재수준뿐만 아니라 교량 시스템수준에서도 최적 유지관리 전략의 생성이 가능한 프로그램을 개발하였다. 실제 공용중인 강교량에 개발된 프로그램을 적용하여 부재 및 시스템 수준의 생애주기분석을 수행하고 각 수준에서 생성된 유지관리전략을 비교 고찰하여 그 적용성을 검토하였다. 부재 및 시스템 수준의 유지관리전략을 비교한 결과, 교량을 구성하고 있는 유지관리 대상 모든 부재를 고려한 교량시스템 수준에서의 분석을 통해 유지관리 전략을 수립하는 것이 보다 합리적이며 실제적인 것으로 판단된다.

• Asian-Australasian Journal of Animal Sciences
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• 제14권10호
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• pp.1483-1496
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• 2001

Small ruminants form an important economic and ecological niche in small farm systems and agriculture. Their current low level of contribution is dismal, and is not commensurate with the potential capacity for higher levels of production. The context for productivity enhancement and increased socio-economic contribution relates to large sizes of small ruminant populations; wide distribution across various agro-ecological zones and production systems; and diversity of breeds, where 66% of all goat and 57% of sheep breeds in Asia are found in China, India and Pakistan. The advantages and disadvantages of small ruminants over larger ruminants are enumerated with reference to adaptation and environment, small size, production systems and products and interactions with the environment. Discussion focuses especially on efficiency of meat production and niche markets for higher-priced goat meat, and inefficient marketing systems given an estimated 40-45% loss of income to farmers presently. Increasing the quantity of meat produced is related to live weight and the total number of animals at Slaughter, which in turn, depend on the total number of offsprings weaned and lifetime productivity. At the national level, priority attention is essential to build up numbers in concerted breeding programmes, selection for efficiency of reproduction and meat production, and improvements to make traditional markets and marketing systems to respond to the changing environmental and consumer preferences. Post-production systems are neglected and improvements are associated with collection, handling, marketing, slaughter facilities and consumer requirements. Potential opportunities to expand and benefit from integrating small ruminants into annual and perennial cropping systems remain largely unexplored. Important development imperatives include choice of species and better use of available breeds, appropriate production systems that match available feed resources, and linkages between production, products and by-products to markets. Affirmative action is necessary, backed by official policy support, institutional commitment and increased resource use, that can target poverty and directly benefit the poor, and shift subsistence production to a more market-oriented opportunity. These efforts together constitute the challenges for both the owners and producers of small ruminants in the immediate future, as also the will to accelerate increased productivity, improve their livelihoods and promote rural growth.

• 한국정보과학회논문지:시스템및이론
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• 제36권5호
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• pp.422-428
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• 2009

플래시 메모리는 부피가 작고, 가볍고, 소비전력이 낮으며 입출력이 빨라 최근 소형기기의 저장 장치로 널리 사용이 되고 있다. 그러나 플래시 메모리는 지움 연산을 수반하는 가비지 컬렉션을 수행해야 한다. 지움 연산은 속도가 느리고, 각 블록마다 지움 연산 횟수가 제한이 있다. 따라서 본 논문에서는 지움 연산 횟수와 각 블록의 지움 횟수 편차를 줄이는데 초점을 맞춘 균등화 정책을 제안한다. 따라서 플래시 메모리의 페이지 사용률에 기반을 둔 두 가지 가비지 컬렉션 수행 모드를 정의하고 그리고 각 모드에 대해 다른 지움 비용을 계산하여 전체 지움 연산 횟수와 각 블록의 지움 횟수 편차를 최소화하는 가비지 컬렉션 기법을 제안한다. 추가로 가비지 컬렉션 연산 시간을 최소화하기 위해 그룹 관리 기법을 제안해 보다 빠른 수행 시간을 가질 수 있도록 한다. 실험 결과 제안하는 정책은 기존의 Greedy 와 CAT 기법의 장점들을 동시에 나타내었고, 지움 횟수 편차를 평균 85% 감소 시켰고 가비지 컬렉션 수행 시간을 최대 6% 단축 시켰다