• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.30-35
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• 2008

This paper describes a fault detection and diagnosis (FDD) system developed for the heat source apparatus in building air-conditioning system. As HVAC&R systems in building become complex and instrumented with highly automated controllers, the processes and systems get more difficult for the operator to understand and detect the mal-functions. Poorly maintained, degraded, and improperly controlled equipment wastes an estimated 15% to 30% of energy used in commercial building. When operating a complex facility, FDD system is beneficial in equipment management to provide the operator with tools which can help in decision making for recovery from a failure of the system. Automated FDD for HVAC&R system has the potential to reduce energy and maintenance costs and improves comfort and reliability. Over the last decade there has been considerable research for developing FDD system for HVAC&R equipment. However, they are being made too much of a theoretical study, so only a small of FDD methods are deployed in the field. This study deduced an actual defect source for the heat source apparatus and suggested a low price FDD method which is ready to be deployed in the field.

• 한국대기환경학회지
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• 제24권1호
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• pp.72-82
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• 2008

Benzene is a very harmful and toxic compound known as human carcinogen by all routes of exposure. Owing to the risky feature of benzene, several countries such as Japan, UK and EU have established the ambient air quality standard and protect from that risk of it. Korea also has designated it as one of the criteria air pollutants and established the concentration limit ($5\;{\mu}g/m^3$) in the air and is going to apply the standard from 2010. Benzene is emitted from various sources such as combustion plants, production processes, waste treatment facilities and also automobiles. Mobile source is known as one of the major emission sources of benzene. In this study, we estimated the domestic emissions of benzene from mobile source and compared the results with those of advanced countries. Mobile source was divided into 2 categories, Le., on-road source and non-road source. The total emissions of benzene from mobile source were estimated as 3,106 tons/yr and 1,612 tons/yr was emitted from on-road source and 1,494 tons/yr was from non-road source. Emission ratio of benzene from on-road source showed that 80.0% was from passenger cars, 10.1% was from taxis, 7.2% was from light-duty vehicles, 2.5% was from heavy-duty vehicles and 0.2% was from buses. In the case of non-road source, the distribution showed that 66.3% was from construction machineries, 14.5% was from locomotives, 11.7% was from ships, 7.1% was from agriculture equipments and 0.5% was from aircrafts. The cold-start emissions were estimated as 942 tons/yr and this value was almost 1.5 times greater than that for hot engine emissions (608 tons/yr). In addition, the fuel-based distribution was 65.9%, 31.1% and 2.8% from gasoline, LPG and diesel vehicles, respectively. The emission ratio from mobile source occupied 65% and 30% of total benzene emissions in USA and UK, respectively. In case of Korea, the emission ratio of benzene from mobile source occupied 29% (15% from on-road source, 14% from non-road source) which showed similar value with UK.

• 한국세라믹학회지
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• 제12권4호
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• pp.3-8
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• 1975

Hydration processes of the rapid hardening cement clinkers, which were synthesized from domestic alunite for major alumina source, limestone, kaolin and fluorite, were investigated by means of x-ray diffraction analysis, thermal analysis and microscopic observation etc. The clinkers were composed mainly of alite, calcium fluroaluminate (C11A7.CaF2) minerals. While the hydratio processes of the clinkers are altered by concentration of SO3 in the paste, calcium aluminate hydrates such as C4AH13, CAH10 and calcium monosulfate hydrate (C3A.CaSO4.12H2O) are formed at first and then some of them are transformed into ettringite(C3A.3CaSO4.32H2O) within 30~60 min. when the concentration of SO3 in the paste are enough. However the formed ettringite are changed slowly into calcium monosulfate hydrate as the concentration of SO3 become lowered, and the paste is hardened with these close-packed minerals. When the content of SO3 in clinker is so enough, calcium sulfoaluminate hydrates are found without any addition of anhydrite or hemi-hydrite.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.416-422
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• 2010

Estimating condition of geotechnical structures are difficult because of nonlinear time dependency and seasonal effects. Measuring data of structure failure is highly variable in time and space, and a unique approach cannot be defined to model structure movements. Characteristics of movements are obtained by using a statistical method called Principal Component Analysis(PCA). The PCA is a non-parametric method to separate unknown, statistically uncorrelated source processes from observed mixed processes. Instead, since the "best" mathematical relationship is estimated for given data sets of the input and output measured from target systems. As a consequence, this method is advantageous in modeling systems whose geomechanical properties are unknown or difficult to be measured.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.25-26
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• 2011

In this paper, we investigated the effect of various annealing processes on the electrical characteristics of oxide thin film transistors (TFTs). When we annealed the TFT devices before and after source/drain (S/D) process, we could observe the different electrical characteristics of oxide TFTs. When we annealed the TFTs after deposition of transparent indium zinc oxide S/D electrodes, the annealing process decreased the contact resistance but increased the resistivity of S/D electrodes. The field effect mobility, subthreshold slope and threshold voltage of the oxide TFTs annealed before and after S/D process were 5.83 and 4.47 $cm^2$/Vs, 1.20 and 0.82 V/dec, and 3.92 and 8.33 V respectively. To analyze the differences, we measured the contact resistances and the carrier concentrations using transfer length method (TLM) and Hall measurement.

• Environmental Engineering Research
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• 제19권1호
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• pp.1-8
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• 2014

Natural organic matter (NOM) is a primary component of fouling in low-pressure membrane filtration, either solely, or in concert with colloidal particles. Various preventive measures to interfere with NOM fouling have been developed and extensively tested, such as coagulation, oxidation, ion exchange, carbon adsorption, and mineral oxide adsorption. Therefore, this article aims to conduct a literature review covering the topics of low-pressure membrane processes, NOM characteristics and fouling behaviors, and diverse fouling control strategies. In-depth explanations and discussion are made regarding why some treatment options are able to remove NOM from source water, but do not reduce fouling. This review provides insight for hybridized membrane processes with respect to NOM removal and fouling mitigation in water treatment.

• 한국통신학회논문지
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• 제18권5호
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• pp.757-772
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• 1993

본 논문에서는 영상 이해를 위한 지식 베이스 시스템에 있어서 핵심적 기능을 수행하게 되는 저급 지식원과 중급 지식원의 추출에 관한 것으로 화소 영역에 적용되는 저급 처리 과정으로 영역 분할 처리과정, 방향 영상 변환과정, 형태 정보 추출 과정, 영역 특징량 추출과정으로 구성되며 중급 처리 과정으로 특징 베이스 분류, 기하학적 토큰 관계성, 인지적 조직과 집단화 과정으로 구성되어 있다.

• The Korean Journal of Ceramics
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• 제5권4호
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• pp.395-399
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• 1999

MgO/metal nanocomposite powder mixtures were prepared by solution chemical processes to obtain suitable structure for ceramic/metal nanocomposites. Nickel or cobalt nitrate, as a source of metal dispersion, was dissolved into alcohol and mixed with magnesia powder. After calcined in air, these powders were reduced by hydrogen. Densified nanocomposites were successively obtained by Pulse Electric Current Sintering (PECS) process. The dispersed metal partical size depended on temperature and time in calcination and reduction processes. The phase analyses in the synthesized powders as a functioni of temperature were tracked using a dynamic high temperature X-ray diffractioni (HTXRD) system. Phase and crystallite size analyses were done using X-ray diffractioni and TEM. The MgO/metal nanocomposites were successfully fabricated, and ferromagnetic responses with enhanced coercive force were also investigated for these composites.

• 한국생산제조학회지
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• 제20권5호
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• pp.517-522
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• 2011

Most of SEM is double condenser lens system. Two condenser lenses are required to provide the high demagnification ratios necessary for forming nanometer probes. The thin lens concept provides a highly useful basis for preliminary calculations in a broad range of situations. It is an easy way to understand the electron beam paths in column. Demagnification is easily calculated by this method. In this paper, we present design processes for condenser lens's demagnification by using thin lens combination model. Also, we verify the reliability of our design processes by comparing the modeled demagnification with these of corrected condenser lens.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 추계학술발표회
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• pp.161-166
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• 2002

Bioremediation of trace metals in groundwater may require the manipulation of redox conditions via the injection of a carbon source. To simulate the numerous biogeochemical processes that will occur during the bioremediation of trace-metal-contaminated aquifers, a reactive transport model has been developed. The model consists of a set of coupled mass balance equations, accounting for advection, hydrodynamic dispersion, and a kinetic formulation of the biological or chemical transformations affecting an organic substrate, electron acceptors, corresponding reduced species, and trace metal contaminants of interest, uranium in this study. The redox conditions of the domain are characterized by estimating the pE, based on the concentrations of the dominant terminal electron acceptor and its corresponding reduced specie. This pE and the concentrations of relevant species we then used by a modified version of MINTEQA2, which calculates the speciation/sorption and precipitation/dissolution of the species of interest under equilibrium conditions. Kinetics of precipitation/dissolution processes are described as being proportional to the difference between the actual and calculated equilibrium concentration.