• 한국신뢰성학회지:신뢰성응용연구
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• 제11권3호
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• pp.293-303
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• 2011

Reliability Prediction using MIL-HDBK-217F has some restrictions due to its one modeling basis. One of the restrictions is caused by selecting one operating environment of a system, which is chosen regardless of its detailed conditions, e.g., external impact and vibration. Especially, an equipment, which is installed on a mobile vehicle though its movement is quasi-static, is controversial to designate its environment as ground mobile($G_M$), rather than ground fixed($G_F$). In this paper, failure rates were compared, which are computed using several moving time rates to total operating time. RiAC-HDBK-217Plus was used as the basic calculation model. In addition, $G_F$ conditioned failure rate was evaluated by comparing with that under $G_M$ environment but fixed state.

• 공업화학
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• 제19권2호
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• pp.209-213
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• 2008

바이오매스 폐기물로부터 수소를 생산하기 위하여 1 m 높이와 10.2 cm의 외경을 갖는 고정층 가스화 반응기를 이용하였다. 촉매를 첨가하지 않은 나왕톱밥과 촉매를 혼합한 나왕톱밥이 시료로 사용되었다. 고정층 가스화 실험 변수로써 온도와 촉매가 공정운전에 미치는 영향을 파악하였다. 반응온도가 $400^{\circ}C$에서 $700^{\circ}C$ 범위에서 온도변화에 따른 생성기체 조성의 변화는 온도증가에 따라 수소 생성량이 증가하였으며, 수소, 일산화탄소와 메탄의 생성분율은 탄산나트륨($Na_2CO_3$)과 탄산칼륨($K_2CO_3$) 촉매 사용에 의해서 증가하였다. 또한, 탄산나트륨 촉매는 탄산칼륨 촉매에 비하여 수소생산 효율에 보다 효과적인 것으로 판명되었다.

• 한국멀티미디어학회논문지
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• 제12권12호
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• pp.1778-1786
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• 2009

Many sensor network applications have been developed for smart home, disaster management, and a wide range of other applications. These applications, however, generally assume a fixed base station as well as fixed sensor nodes. Previous research on sensor networks mainly focused on efficient transmission of data from sensors to fixed sink nodes. Recently there has been active research on mobile sink nodes, sink mobility is one of the most comprehensive trends for information gathering in sensor networks, but the research of an environment where both fixed sink nodes and mobile sinks are present at the same time is rather scarce. This paper proposes a scheme for context-aware by ubiquitous devices with the sink functionality added through fixed sinks under a previously-built, cluster-based multi-hop sensor network environment. To this end, clustering of mobile devices were done based on the fixed sinks of a previously-built sensor network, and by using appropriate fixed sinks, context gathering was made possible. By mathematical comparison with TTDD routing protocol, which was proposed for mobile sinks, it was confirmed that performance increases by average 50% in energy with the number of mobile sinks, and with the number of movements by mobile devices.

• 한국통신학회논문지
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• 제31권10B호
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• pp.929-935
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• 2006

When the Internet phone service, generally PC-to-Phone, first entered into the telecommunications service market, no regulatory issues were arisen to manage the service within the regulatory framework because of it's low quality, no phone number assignment and etc. However, almost the same quality, more applications and cheaper price compared with the fixed telecommunications service, have changed the regulator's policy allowing Internet phone service within market mechanism. While incumbent fixed telecommunications service enterprises had given with tremendous duties to continue the job categorized 'facilities-based telecommunication service provider', and which can be unreasonable and unfair if Internet phone service enterprises are allowed to enter into the fixed telecommunications market without any regulation. Thus, new regulatory framework has worked for the Internet phone service named the VoIP service generally in the fixed telecommunications market. Recently, VoIP is provided not only in the fixed telecommunications market but also in the mobile market as Wi-Fi phone is feasible in the wireless LAN environment. Furthermore, bundled service of Wi-Fi and cellular phone service will be launched soon, and the next version will be the mobile VoIP service operating like a cellular phone service. Hence, we will meet similar situation when the VoIP sewice enters into the fixed telecommunications service market. And, in this paper, we prospect the regulatory issues arising when the wireless or mobile VoIP service enterprises enter the mobile market, by analyzing possible scenarios.

• 한국물환경학회지
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• 제24권3호
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• pp.328-332
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• 2008

This research was about T-N removal efficiency of oxic reactor in which fixed media submerged from Membrane BNR(An+Ax+Ox) process. This experiment was implemented by using fixed media and changing DO concentration in the oxic reactor. Nitrification efficiencies of all modes were more than 98%. When no media was in the oxic reactor, T-N removal efficiency was only 47.4%, while it were shown from 60.3% to 67.4% with packed media, which indicated improved efficiency of 27~42%. The removal efficiencies of TCOD and BOD were more than 89%, 98% respectively, which could satisfy the guideline of advanced sewage reclamation by Department of Environment. When DO concentration in the packed oxic-media tank was 0.5~1.0 mg/L, T-N removal efficiency was low, which resulted from insufficient nitrification in the oxic reactor. Therefore, DO concentration of bulk solution needs to be kept more than 1.0 mg/L to induce higher nitrification efficiency in the reactor in which media was submerged. Also, the selection of DO concentration is important to prevent media from being clogged.

• Geomechanics and Engineering
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• 제32권5호
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• pp.523-540
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• 2023

The failure of slope can cause remarkable damage to either human life or infrastructures. Stabilizing piles are widely utilized to reinforce slope as a slip-resistance structure. The workability of pile-stabilized slopes is affected by various parameters. In this study, the performance of earth slope reinforced with piles and the behavior of piles under static load, by shear reduction strength method using the finite difference software (FLAC^3D) has been investigated. Parametric studies were conducted to investigate the role of pile length (L), different pile distances from each other (S/D), pile head conditions (free and fixed head condition), the effect of sand density (loose, medium, and high-density soil) on the pile behavior, and the performance of pile-stabilized slopes. The performance of the stabilized slopes was analyzed by evaluating the factor of safety, lateral displacement and bending moment of piles, and critical slip mechanism. The results depict that as L increased and S/D reduced, the performance of slopes stabilized with pile gets better by raising the soil density. The greater the amount of bending moment at the shallow depths of the pile in the fixed pile head indicates the effect of the inertial force due to the structure on the pile performance.

• 한국유기농업학회지
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• 제30권4호
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• pp.471-483
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• 2022

This study analyzed management situations of two organizations that have produced environment-friendly agricultural and processed meat products. 'A' farming corporation sells environment-friendly agricultural products like as grains, vegetables, fruits and processing foods. 'B' agricultural corporation processes and sells environment-friendly processed meat products, specially organic and antibiotic-free beef products. Recently, members and production areas of 'A' farming corporation have decreased because of their aging and labor shortage. And Indices for the management analysis are stability ratio, activity ratio and profitability ratio. Stability ratio indices are debt ratio, net worth ratio, fixed ratio and current ratio. Activity ratio ones include fixed assets turnover and net worth turnover. And profitability ratio is showed through return on investment, net return on sales and return on equity.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.676-682
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• 2018

WSN을 포함하는 IoT 세상이 발전할수록, IoT를 적용하는 주위환경에 따라 정보를 센싱하는 센서 시스템의 수가 매우 가변적이다. 이러한 복잡한 환경에서 각각의 센서 시스템들에 대한 보안을 수행하기 위하여 보안모듈들도 가변적으로 증감을 수행해야 한다. 이러한 문제점은 시스템 효율성과 해킹/크래킹을 고려하였을 경우, 하드웨어/소프트웨어적인 구현을 어렵게 한다. 그러므로 본 논문은 이러한 문제점을 해결하기 위하여 센싱 노드들의 수와 상관없이 일정한 주기를 가지는 의사난수를 발생시키며 이상현상을 탐지할 수 있는 기능을 가진 고정 길이 탭을 가진 의사 난수 발생기(FLT: Pseudo-random Number Generator with Fixed Length Tap unrelated to the variable sensing nodes) 구조를 제안하였다. 제안된 FLT-LFSR 구조는 IoT 환경에서 하드웨어/소프트웨어 구현에 대하여 보안레벨 및 전체 데이터 포맷팅을 일정하게 유지시킬 수 있도록 하였다. 그러므로 제안된 FLT-LFSR 구조는 센서 시스템 구현의 용이성 및 센싱 노드들의 수와 상관없이 네트워크의 확장성을 강조할 수 있도록 하였다.

• 한국IT서비스학회지
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• 제4권1호
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• pp.107-115
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• 2005

As Real Time Enterprise (RTE) has been spotlighted since the year of 2002, some advanced companies have been implementing the paradigm of RTE to its legacy systems and the number of the companies has been growing. However, the network infrastructures mainly based on fixed telecommunications network make the results of the RTE implementations fall short of their expectations. In this paper, we propose to construct the fixed-mobile convergence (FMC) environment to achieve RTE. The convergence infrastructure will improve user accessibility to all kinds of data and will encourage the users to interact with the systems.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권5호
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• pp.75-81
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• 2012

In this study, remediation of heavy metal contaminated soil was attempted by the electrokinetic process equipped with fixed or swappable electrode. Copper was more effectively removed with EDTA than citric acid. Zinc was much more removed than copper with both detergents. When electrokinetic with fixed electrode and detergents were applied to the contaminated soil, copper was removed about 28.52%~35.25% and zinc was removed about 63.44%~71.48%. When electrokinetics with swappable electrode and detergents were applied to the contaminated soil, the pseudo-first order reaction constants was higher about 16~50% than with fixed electrode in the case of zinc. It is conclusive that electrokinetics with swappable electrode could be an effective method for the remediation of heavy metal contaminated soil.