• 한국물환경학회지
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• 제22권1호
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• pp.116-121
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• 2006

Fundamental investigations have been carried out to find the applicability of manganese nodule as an adsorbent of nickel ion with an intention that nickel can be secured in manganese nodule along with the treatment of wastewater. The average content of manganese in nodules which used in the experiments was about 27%. The content of nickel in manganese nodules was observed to increase up to 4 times higher with comparison to its original value after adsorption. When the initial concentration of nickel ion in artificial wastewater was lower than 500 mg/L, its adsorbed amount on manganese nodule was shown to increase continuously. However, no more than about 82 mg/L of nickel was attained at higher initial nickel ion concentration than 500 mg/L. The adsorption of nickel ion was increased with temperature under experimental conditions and as the size of manganese nodule particles became smaller more nickel ion was adsorbed on adsorbent. Regarding the effect of pH, the adsorption of nickel ion was more hindered as the solution became acidic. Adsorption behavior of nickel ion on manganese nodule was found to follow the Freundlich model well and kinetic analysis showed that the adsorption reaction of nickel ion was second order. Thermodynamic parameters for the nickel ion adsorption were estimated on the basis of thermodynamic equations and they were in good agreement with experimental results.

• 농촌지도와개발
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• 제17권3호
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• pp.527-548
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• 2010

The objective of this study is to suggest the developmental tasks for the successful fostering the Farmer's Study Group which have been guided by the agricultural extension work since 1994 in Korea. The 3,278 farmers study groups with 148,420 memberships have been organized in field of grains, cash crop, horticulture, livestock, improving living conditions, food processing and so on. Although the number of study groups have rapidly expanded, there also are tasks to be secured for their successful development in terms of (a) desirable phase of the study groups and goals of its fostering, (b) managements / administration of them, (c) long-term tasks to be reviewed. With regard to the desirable phase of the study groups and goals of its fostering, they should secure differential mission and the way of works compare to the other farmer's groups. Also, there should be consensus on the proper number of study groups to be fostered with a agricultural technical center at local level. With regard to the managements / administration of the study groups, there should be the different support, assistance and guidance according to the developmental level of the groups. For these, there should be evaluation works on the groups, and guidance manuals for the extension workers. Also extension works should facilitate the establishment of networks among groups over the counties. Finally, to establish the nationwide association in hierarchy and to make the cooperative works with similar farmer's group, doing the value-added activities rather than mere information exchange, and the introduction of capacity building programs for the extension workers are long-term tasks needed to review for the successful fostering study groups.

• 대한치과보철학회지
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• 제39권3호
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• pp.297-305
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• 2001

Statement of problem. There have been previous studies about instability according to screw material by means of calculating preload in tightening screw or recording of the torque necessary to loosen screw after tightening screw. Purpose. The purpose of this study was to evaluate screw joint stability through the analysis of fitness at the mating thread surfaces between implant and screw after tightening screws made of different materials. Material and methods. In this study, screws were respectively used to secure a cemented abutment to a hexlock implant fixture; teflon coated titanium alloy screw and titanium alloy screw(Steri-Oss), gold-plated gold-palladium alloy screw and titanium alloy screw(Implant Innovation), gold screw and titanium screw(AVANA Dental Implant System). Each abutment screw was secured to the implant with recommended torque value using a digital torque controller. Each screw was again tightened after 10minutes. All samples were cross sectioned with sandpaper and polished. Then samples were evaluated with an scanning electron microscope analysis. Results. In titanium alloy screw, irregular contact and relatively large gap was present at mating thread surface. Also in teflon-coated titanium screw, incomplete seating and only partially contact was present at the mating thread surface. In gold-plated gold-palladium alloy screw, relatively close and tight contact without the presence of large gap was present by existing of gold coating at the mating thread surfaces. In gold alloy screw, relatively small gap between the mating components was seen. Conclusions. This result suggested that gold plated gold-palladium alloy screw and gold alloy screw achieved a greater degree of contact at the mating thread surfaces compared to titanium alloy screw and teflon-coated titanium alloy screw.

• 한국게임학회 논문지
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• 제11권6호
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• pp.115-125
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• 2011

최근 스마트폰 사용자의 급격한 증가는 스마트폰게임 시장의 큰 성장을 가져왔으며 고 부가가치 시장으로서의 입지를 굳히고 있다. 이에 새롭게 부각되는 스마트폰게임에 대한 다각적인 연구가 야기되고 있으나 기존 연구가 스마트폰 이전의 휴대폰을 대상으로 연구가 대부분 이루어져 스마트폰 중심의 새로운 확장 연구가 필요한 실정이다. 따라서 선행연구를 통해 도출한 스마트폰게임의 구매영향요인을 토대로 구매의도, 구매행동, 만족, 추천, 지속사용 간의 영향관계를 알아봄으로서 추천과 지속사용에 영향을 미치는 핵심 요인을 도출하고자 하였다. 이를 위해 스마트폰 사용자 커뮤니티 등을 통해 수집한 설문응답자료 293부를 분석에 이용하였으며 변인들 간의 영향관계 분석에 이점을 가진 구조방정식 모델을 채택하였다. 본 연구를 통하여 얻은 핵심 요인들은 차후 스마트폰게임 관련 비즈니스 시장에서 좀 더 효율적으로 개발을 수행하고 보다 가시적인 성과를 거둘 수 있는 유용한 시사를 제공해 줄 수 있을 것이다.

• 조명전기설비학회논문지
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• 제23권2호
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• pp.27-35
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• 2009

본 연구에서는 먼저 도시적 특성의 분석을 토대로 안양시를 6개 지역으로 구분하였으며 지역별 구분에 따른 야간의 조도 휘도의 실측조사 및 야간이용자 패턴 조사를 통하여 야간경관의 문제점을 도출하였다. 야간경관 연출개념으로는 지역별 문제점 분석에 따른 개선방안과 예술적 가치를 창출하는 개념을 적용하여 예술도시로서의 안양의 이미지를 고양시키고자 하였으며 야간조명의 괌형과 통일성 확보를 위해 지역별 점진적 변화를 빛의 조닝의 개념으로 선정하였다. 특히, 건축물의 높이에 따른 건축물 기준선을 통해 주변 건축물과 조화된 단계적인 스카이라인을 연출하여 자연경관 등과 조화로운 조망권을 확보하도록 하였으며 지역 특성에 따라 가로등 및 가로시설물의 조도, 높이, 램프형태, 배열방식 등의 야간 조명환경의 개선방향을 추가로 제시하였다.

• 한국건설관리학회논문집
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• 제12권2호
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• pp.101-110
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• 2011

사회기반시설물 중 교량은 다른 시설물보다 열악한 환경에 노출되며, 파손 등이 발생할 경우 훨씬 심각한 결과를 야기할 수 있으므로 일정 수준 이상의 안전에 관한 성능을 반드시 유지하여야 한다. 하지만 향후 교량의 유지관리를 위한 예산 및 인적자원은 더욱 한정되어 갈 것이다. 자산관리기법은 이러한 한정된 자원으로 효율적인 교량의 유지관리를 위한 중요한 대안이 될 수 있다. 자산관리기법을 적용하기 위해서는 교량이 제공하는 서비스의 수준(Level of Service; LOS)을 평가하기 위한 방법이 결정되어야 하며, LOS는 성능척도(Performance Measures; PM)를 통해 정량적으로 결정될 수 있다. 본 논문은 교량 자산관리를 위한 PM을 개발하였으며, PM을 활용한 LOS 평가 방법을 정립하였다. 이러한 LOS 평가 결과를 활용하여 자산관리 대상, 항목 등을 결정할 수 있으며, 효율적이고 합리적인 교량의 자산관리관련 의사결정을 도울 수 있을 것으로 판단된다.

• 한국재료학회지
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• 제30권7호
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• pp.376-382
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• 2020

CeO₂ nanoparticles, employed in a lot of fields due to their excellent oxidation and reduction properties, are synthesized through a solvothermal process, and a high specific surface area is shown by controlling, among various process parameters in the solvothermal process, the type of solvent. The synthesized CeO₂ nanoparticles are about 11~13 nm in the crystallite size and their specific surface area is about 65.38~84.65 ㎡/g, depending on the amount of ethanol contained in the solvent for the solvothermal process; all synthesized CeO₂ nanoparticles shows a fluorite structure. The dispersibility and microstructure of the synthesized CeO₂ nanoparticles are investigated according to the species of dispersant and the pH value of the solution; an improvement in dispersibility is shown with the addition of dispersants and control of the pH. Various dispersing properties appear according to the dispersant species and pH in the solution with the synthesized CeO₂ nanoparticles, indicating that improved dispersing properties in the synthesized CeO₂ nanoparticles can be secured by applying dispersant and pH control simultaneously.

• 한국해양공학회지
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• 제35권5호
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• pp.327-335
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• 2021

Microcracks can rapidly grow and develop in high-strength steels used in offshore structures. It is important to render these microcracks harmless to ensure the safety and reliability of offshore structures. Here, the dependence of the aspect ratio (As) of the maximum depth of harmless crack (a_hlm) was evaluated under three different conditions considering the threshold stress intensity factor (Δk_th) and residual stress of offshore structural steel F690. The threshold stress intensity factor and fatigue limit of fatigue crack propagation, dependent on crack dimensions, were evaluated using Ando's equation, which considers the plastic behavior of fatigue and the stress ratio. a_hlm by peening was analyzed using the relationship between Δk_th obtained by Ando's equation and Δk_th obtained by the sum of applied stress and residual stress. The plate specimen had a width 2W = 12 mm and thickness t = 20 mm, and four value of As were considered: 1.0, 0.6, 0.3, and 0.1. The a_hlm was larger as the compressive residual stress distribution increased. Additionally, an increase in the values of As and Δk_th(l) led to a larger a_hlm. With a safety factor (N) of 2.0, the long-term safety and reliability of structures constructed using F690 can be secured with needle peening. It is necessary to apply a more sensitive non-destructive inspection technique as a non-destructive inspection method for crack detection could not be used to observe fatigue cracks that reduced the fatigue limit of smooth specimens by 50% in the three types of residual stresses considered. The usefulness of non-destructive inspection and non-damaging techniques was reviewed based on the relationship between a_hlm, a_NDI (minimum crack depth detectable in non-destructive inspection), a_{cr N} (crack depth that reduces the fatigue limit to 1/N), and As.

• 한국기후변화학회지
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• 제7권4호
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• pp.477-484
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• 2016

In general, $CH_4$ concentrations generated in combustion facilities are known to be ppm units. In most cases, $CH_4$ samples are collected in Tedlar bags and transported to laboratories for analysis. Considering this fact, in the present study, an attempt was made to find out how long samples can be stored in cases where they are kept in bags and transported as a preliminary study for sampling. According to the results of the experiment using simulated gases (1 ppm, 5 ppm, 10 ppm) in Tedlar bag, $CH_4$ was safe up to 240 hr which is the full time. In the case of simulated gases are containing 4 kind gases ($N_2$, $CO_2$, $CH_4$, and $N_2O$). Field samples (samples of obtained by collecting combustion facilities' exhaust gases) are known to contain highly reactive substances (for example NOx, SOx, and VOCs) and may affect each other. In the present study, one site sample was secured from each of a bituminous coal combustion facility and an LNG combustion facility and whether the concentrations of $CH_4$ gas would change over time (24 hr, 96 hr, 144 hr, 192 hr) was checked. Since site samples could not be analyzed on the day of collection, an experiment was started 24 hr after the time point of sampling to analyze the samples. As with the results of analysis of the simulated gas (240 hr), the results of analysis using the site sample indicated that it could be stored for the full study period 192 hr. Therefore, it was judged that if 192 hr would be taken after sampling before the sample would be analyzed, the concentration value should be reliable.

• 융합보안논문지
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• 제18권3호
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• pp.141-148
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• 2018

본 연구는 경비안전시스템 이용자들의 안전욕구와 생활만족을 살펴보기 설문조사를 실시하였다. 설문내용은 "안전욕구, 이용만족, 생활만족"으로 구성하였다. 분석 결과 Chronbach's Alpha 계수가 안전욕구 0.897, 이용만족 0.888, 생활만족 0.887로 산출되어 측정항목들이 내적 일관성을 확보한 것으로 파악되었다. 판별타당성 검증에서 AVE와 CR 수치가 모두 기준치인 0.6와 0.8 이상으로 산출되어 본 연구에 사용된 변수들의 집중타당성이 대체로 확보된 것으로 파악되었다. 가설검증결과 표준화 계수가 '안전욕구 ⇨ 이용만족'은 0.993으로, '이용만족 ⇨ 생활만족'은 0.453으로 산출되어 두 가설이 양(+)인 관계로 산출되었다. 검증 결과 이용자들의 안전욕구가 높을수록 이용만족이 높을 것이고, 이용만족이 높을수록 생활만족이 높을 것으로 분석되었다.