• 한국환경과학회지
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• 제19권12호
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• pp.1447-1454
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• 2010

In this study, the detection limits of lower fatty acids in air were investigated by using Dynamic SPME(Solid Phase Micro-Extraction), i.e. improved Head Space - SPME method(HS-SPME). This Dynamic SPME, called SPDE(Solid Phase Dynamic Extraction), is the analytical method for volatile compounds in air with the extraction by using a stainless steel needle of which inner surface is coated with adsorption material and following the gas chromatographic analysis by inserting the needle into a injection port of GC and subsequently, desorption of the volatile compounds into a gas-chromatographic column. Extraction was carried out by passing the sample air through the needle with a suction pump which has been used for a detection tube. The result of measurement for the 6 lower fatty acids showed that the detection limits ranged from 0.10 ppm to 0.44 ppm and the linear correlation coefficients were over 0.99. Relative standard deviations obtained from 5 analytical repetition of a ca. 1.6 ppm standard mixture were in the range of 1.87%~2.47%. This method has been shown to be a adequate for the measuring C2~C5 fatty acids in air in the concentrations of over several hundreds ppb.

• 대한환경공학회지
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• 제31권6호
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• pp.442-448
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• 2009

예혼합 분무화염의 유적군 연소 기구를 평가하기 위하여 레이저 가시화법, MICRO (multi-color integrated Cassegrain receiving optics) 및 PDA (phase Doppler anemometer) 광학계측 시스템을 이용하여 동시 시계열 계측을 실시하였다. 또한 유적군의 군연소수를 실험적으로 산출하여 이론해석에 적용하였을 경우 실제로 관찰되는 군연소 형태와 일치하는지에 대하여 검토하였다. 유적군 단면화상에 의해 확인된 모든 유적군에 대하여 실험적으로 군연소수 $G_c$를 산출한 결과 주로 내부 군연소와 외부 군연소로 분류되었으며 이론해석과 일치하였다. 또한 실제 관찰된 군연소 형태와 그 유적군의 군연소수를 이론해석에 적용한 경우에 군연소 형태가 일치하는 경우와 일치하지 않는 경우가 있었다. 일치하지 않는 원인은 군연소수를 유적의 기하학적 배치만으로 결정한 것이나 현상의 3차원성이 측정 결과에 영향을 미친 것이라고 생각되어진다.

• 한국물환경학회지
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• 제24권6호
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• pp.793-800
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• 2008

Recently domestic drinking water industry has recognized membrane-based technology as a promising alternative for water treatment. To ensure successful application of membrane processes, the integrity of membrane systems should be maintained. According to US EPA guidance, the pressure decay test based on the bubble point theory is recommended to detect any membrane defection of which size is close to the smallest diameter of Cryptosporidium oocysts, $3{\mu}m$. Proper implementation of the pressure decay test is greatly affected by initial test pressure, and the interpretation of the test results is associated with upper control limit. This study is conducted to investigate various factors affecting determination of initial test prtessure and upper control limit, including membrane-based parameters such as pore shape correction factor, surface tension and contact angle, and system-based parameters, such as volumetric concentration factor and total volume of system. In this paper, three different hollow fibers were used to perform the pressure decay test. With identical initial test pressure applied, their pressure decay tendency were different from each other. This finding can be explained by the micro-structure disparity of those membranes which is verified by FESEM images of those membranes. More specifically, FESEM images revealed that three hollow fibers have asymmetry, deep finger, shallow finger pore shape, respectively. In addition, sensitivity analysis was conducted on five parameters mentioned above to elucidate their relation to determination of initial test pressure and upper control limit. In case of initial pressure calculation, the pore shape correction factor has the highest value of sensitivity. For upper control limit determination, system factors have greater impact compared to membrane-based parameters.

• Structural Engineering and Mechanics
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• 제39권3호
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• pp.303-316
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• 2011

Experimental tests have shown that glass exhibits very different strengths when tested under biaxial and uniaxial conditions. This paper presents a study on the effects of biaxial stresses on the notional ultimate strength of glass. The study involved applying the theory of elasticity and finite element analysis of the Griffith flaw in the micro scale. The strain intensity at the tip of the critical flaw is used as the main criterion for defining the limit state of fracture in glass. A simple and robust relationship between the maximum principal stress and the uniaxial stress to cause failure of the same glass specimen has been developed. The relationship has been used for evaluating the strength values of both new and old annealed glass panels. The characteristic strength values determined in accordance with the test results based on 5% of exceedance are compared with provisions in the ASTM standard.

• 한국주거학회논문집
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• 제8권3호
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• pp.209-218
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• 1997

The residential street is an area in which the residential function clearly predominates over any provisions for traffic. Therefore schoud it serve as a living space for the inhabitants. But in reccent times have motorists become lord and master through development and use according to the measure of automobile. As a result is being falling-off in the quality of residential environment particularly serious. This study have illustrated specially the environmental pollution (air pollution, micro climate. water balance and soil pollution) which the analysis of research data in foreign countrys. With that have this study proposed on the measures of the environmental friendly construction in residental street.

• 대한환경공학회지
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• 제38권8호
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• pp.420-427
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• 2016

본 연구는 미세기포를 이용하여 하천 및 호수의 퇴적물 내 영양염류 제어 가능성을 살펴보고자 하였다. 이를 위해 실제 호수에서 퇴적물을 채취하여 용출 특성 실험 및 기포를 이용한 퇴적물 및 영양염류 제거 실험을 수행하였다. 연구에 사용된 퇴적물의 입도분석 결과, 점토와 실트(<0.075 mm)비율은 약 7.7%, 모래(0.075~4.75 mm)는 약 67.8%, 자갈은(${\geq}4.75mm$) 약 24.5%로 나타났다. 총질소(T-N), 총인 (T-P), 강열감량은 각각 2,790~3,260 mg/kg, 261~311 mg/kg, 4.1~9.6%로 나타났다. 퇴적물의 입도별 T-N과 T-P을 분석한 결과, 입도가 클수록 퇴적물의 T-N와 T-P 함량은 감소하는 경향을 나타냈다. 이는 입도가 클수록 비표면적이 작아져 흡착되는 오염물질량이 줄어들기 때문으로 판단된다. 기포의 특성에 따른 퇴적물의 제거효율을 분석한 결과, 압력 6기압, 순환률 30%, 응집제 주입량 15 ppm의 조건으로 실험을 수행하였을 때 퇴적물의 제거율이 19.9%로 가장 높게 나타났다. 이 때의 T-N, T-P의 제거효율도 21.4, 22.6%로 가장 높게 나타났다. 운전조건을 고정시키고 기포 주입횟수를 증가시키면서 T-N과 T-P의 제거효율을 살펴본 결과, 주입횟수 2회까지 T-N과 T-P의 제거효율은 높았으나, 3회부터는 제거효율이 낮아짐에 따라 주입횟수가 증가하더라도 제거효율에는 큰 변화를 보이지 않았다. 그리고 미세입자가 제거된 퇴적물의 영양염류 용출량은 미세입자를 제거하지 않은 퇴적물의 용출량보다 약 20.1~64.3% 정도 감소함을 알 수 있었다. 이를 통해 미세기포를 퇴적물에 반복적으로 주입하는 방안은 퇴적물 및 퇴적물에서의 영양염류 용출을 제어하는 효과적인 방안으로써 가능성이 있음을 확인할 수 있었다.

• Asia pacific journal of information systems
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• 제5권1호
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• pp.236-257
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• 1995

Not much attention has been paid to the characteristics of successful MIS in small business in Korea. This study compares the characteristics of successful MIS with those of less successful MIS of manufacturing industry in Korea in terms of micro level, macro level, and personal level. The micro level consists of those variables relating to the system development and maintenance while the macro level consists of the environmental variables relating to the information systems. The personal level measures a personal EDP experience. A mail survey was sent to small manufacturing companies to collect the data for the hypothesis tests. And 81 usable questionnaires were returned for data analysis. This study performs the validity of the categorization of variables in terms of three levels. The results shows that this categorization is appropriate but the personal level. As the personal experiences of EDP in Korea used to come up with those of the organization, the variables in the personal level have high correlations with those in the macro level in empirical testing. As the personal level, however, is different dimension from the macro level in theoretical aspect, the level is maintained separately throughout the study. The data were analyzed with MANOVA and two group discriminant analysis. The analyses reveal that the characteristics of successful MIS are different from those of less successful MIS in terms of three levels. And the micro level is more important than the macro level to develop successful MIS. That is because the organizations have relatively few experience in dealing with information systems, they have not developed unique information systems which are adjusted to their organizational characteristics. Those findings seems to be important determinants of success for the MIS in a firm.

• Advances in Energy Research
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• 제4권2호
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• pp.121-146
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• 2016

This study is concerned with the analysis of two renewable technologies for electric energy production: wind energy and photovoltaic energy. The two technologies were assessed and compared by economic point of view, by using selected indicators characterized by a clear calculation approach, requirement of information easy to be collected, clear, but even complete, interpretation of results. The used economic indicators are Levelized Cost of Energy, $CO_2$ abatement cost and fossil fuel saving specific cost; these last two specifically aimed at evaluating the different capabilities that renewable technologies have to cut down direct $CO_2$ emissions and to avoid fossil fuel extraction. The two technologies were compared also from the environmental point of view by applying Life Cycle Assessment approach and using the environmental impact categories from the Eco-indicator'95 method. The economic analysis was developed by taking into account different energy system sizes and different geographic areas in order to compare different European conditions (Italy, Germany and Denmark) in term of renewable resource availability and market trend. The environmental analysis was developed comparing two particular types of PV and wind plants, respectively residential and micro-wind turbine, located in Italy. According to the three calculated economic indicators, the wind energy emerged as more favorable than PV energy. From the environmental point of view, both the technologies are able to provide savings for almost all the considered environmental impact categories. The proposed approach, based on the use of economic and environmental indicators may be useful in supporting the policies and the decision making procedures concerned with the promotion and use of renewables, in reference to the specific geographic, economic and temporal conditions.

• 대한환경공학회지
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• 제35권5호
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• pp.363-370
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• 2013

소수력발전은 하수처리장 에너지 자립을 위한 효과적인 대안이다. 본 연구는 유량변동이 크고 유효낙차가 낮은 중소형 하수처리장(기흥레스피아) 적용을 위해 피치조절형 세미카플란(semi-kaplan) 마이크로수력발전의 적용 타당성을 평가하였다. 가변피치 semi-kaplan 수차는 유량조절을 위한 가이드베인은 생략하고 피치조절형 런너를 장착하여 기계적 결함은 줄이면서 유량변동이 큰 처리장에 특화된 기술이다. 마이크로수력발전 시스템은 설계조건(유량 0.35 $m^3/s$, 유효낙차 4.7 m)에서 90.2%의 수차효율 달성이 가능하였고 발전용량은 13.4 kW로 산정되었다. 설비가동률 74%로 가동 시 연간 약 86.8 MWh 에너지 생산을 통해 2.1%의 에너지 자립이 가능하고 이는 연간 49톤의 $CO_2$ 감축효과와 맞먹는다. 경제성 평가결과 초기 건설공사비가 200,000,000원 이하인 경우에는 내부수익률은 6.1%, 순현가는 15,539,000원, 편익-비용률은 1.08, 투자회수년은 15.5년으로 경제성이 충분한 것으로 나타났다.

• Computers and Concrete
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• 제33권6호
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• pp.725-738
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• 2024

This study presents a macro-modeling procedure for nonlinear finite element analysis of reinforced and prestressed concrete panels under blast loading. The analysis procedure treats cracked concrete as an orthotropic material based on a smeared rotating crack model within the context of total-load secant stiffness-based formulation. A direct time integration method compatible with the analysis formulation is adapted to solve the dynamic equation of motion. Considerations are made to account for strain rate effects. The analysis procedure is verified by modeling 14 blast tests from various sources reported in the literature including a blast simulation contest. The analysis results are compared against those obtained from experiments, simplified single-degree-of-freedom (SDOF) methods, and sophisticated hydrocodes. It is demonstrated that the smeared crack macro-modeling approach is a viable alternative analysis procedure that gives more information about the structural behavior than SDOF methods, but does not require detailed micro-modeling and extensive material characterization typically needed with hydrocodes.