• 대한전기학회논문지
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• 제43권6호
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• pp.951-957
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• 1994

We present a new model for the series resistance of inverted-staggered amorphous silicon (a-Si) thin film transistors (TFT's) by employing the current spreading under the source and the drain contacts as well as the space charge limited current model. The calculated results based on our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which have been verified successfully by the experimental measurements.

• 한국대기환경학회지
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• 제6권2호
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• pp.135-146
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• 1990

The purpose of the study was to identify sources of particulate matters statistically and to estimate the mass contribution quantitatively in the Pusan metropolitan area. Then, the study has used the TTFA (target transformation factor analysis) model, a receptor model, to apportion aerosol mass with the raw data of 106 ambient samples characterized by 24 heavy metal variables. The TTFA was extensively applied to generate source profiles and their aerosol mass contributions. Though a couple of sources were not identified, four to seven sources were able to be extracted at 3 different sites (Jang Rim-Dong, Kwang Bok-Dong, and Kwang An-Dong) in Pusan area and finally mass conributions could be calculated.

• 대기
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• 제24권3호
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• pp.317-329
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• 2014

Eddy covariance data have been analyzed to investigate the influence of surface heterogeneity on turbulent transfer over farmland and industrial sites near Nakdong river, Korea, where both large and small scale heterogeneities co-exist. For this purpose, basic turbulent statistics, quadrant analysis and multi-resolution decomposition have been analyzed during the daytime. Basic turbulent statistics were compared with typical turbulent statistics in the surface layer. Such comparisons were in close agreement for momentum and heat at both sites but not for water vapor at industrial site. The correlation coefficient between water vapor and vertical velocity ($r_{wq}$) is relatively low and skewness of water vapor ($sk_q$) is very low at industrial site, possibly due to limited water source. For heat at both sites and water vapor at farmland, the quadrant analysis show similar behavior to that over homogeneous site but for water vapor at industrial site, the presence of river and limited water source at industrial site seems to influence on water vapor transfer by coherent eddy motion by increasing sweep contribution and decreasing ejection contribution. Multi-resolution decomposition analysis shows that large scale heterogeneity leads to low $r_{Tq}$ at large averaging time regardless of season at both sites and there are seasonal changes of $r_{Tq}$ in mid-averaging times at industrial site, possibly due to seasonal change of trees and grasses near the site.

• 한국물환경학회지
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• 제37권1호
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• pp.20-31
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• 2021

In this study, an analysis of the characteristics of organic matter and nitrogenous oxygen demand (NOD) of 17 sewage effluent and wastewater treatments was conducted. High CODMn and carbonaceous biological oxygen demand (CBOD) concentrations were observed in the livestock treatment plants (LTP), wastewater treatment plants(WTP), and night soil treatment plants (NTP), but the highest NOD concentration and contribution rates of NOD to BOD5 were found in sewage treatment plants (STP). There was no significant difference in the CBOD/CODMn ratio for each of the six pollution source groups, but the LTPs, WTPs, and NTPs all showed relatively high CODMn concentrations in their effluent samples, indicating that they are facilities which discharge large amounts of refractory organic matter. The seasonal change of NOD in all facilities' effluent was found to be larger than the seasonal change of CBOD, and data results also revealed an elevation of NOD and NH3-N concentration from December to February, when the water temperature was low. There was no significant difference in NH3-N concentration in relation to pollution source group (p=0.08, one-way ANOVA), but the STP, which had a high NOD contribution rate to BOD5 of 48%, showed a high correlation between BOD5 and NOD (r2=0.95, p<0.0001). These results suggest that the effect of NOD on BOD5 is an important factor to be considered when analyzing STP effluent.

• 한국물환경학회지
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• 제35권1호
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• pp.43-54
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• 2019

The objective of this study was to assess the effect of policies on water quality management based on the changes in pollutants and water quality in Special Water Preservation Area (SWPA) of Lake Paldang watershed from 1990 to 2016. The population, total sewage and flow rate of wastewater in SWPA continuously increased from 1990 to 2016, while the location of new facilities for industrial and livestock facilities has been restricted. However, unlike the buffer zone in which industrial and livestock facilities were continuously reduced after implementing of TMDL, it was found that the effect of land-use regulations on industrial and livestock facilities in SWPA were mitigated by the increase in the size of large facilities. Since 1999 when the emission standard of public sewage treatment plants (STP) was changed, the water quality of Lake Paldang has increased despite the increase of pollutant source. Since emission standard of STP changed in 2012 (BOD 5 mg/L, TP 0.2 mg/L), BOD concentration in Lake Paldang has also improved to the level of water quality in the early 1990s where as TP concentration has remained at its lowest since 1990. BOD and TP average discharge concentration of 43 STP (${\geq}500m^3/day$) in 2016 have been maintained $1.7{\pm}0.7mg/L$ and $0.06{\pm}0.02mg/L$ respectively. While the discharged load of STP in SWPA was decreased by the concentration management, the contribution rate to the total discharged load of non-point pollutants increased to 70 % in 2015, and the contribution rate to the point discharged load of individual treatment facilities increased to 80 %.

• Asia pacific journal of information systems
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• 제25권3호
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• pp.473-499
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• 2015

The limited literature on Open Source Software (OSS) customers' adoption does not provide explanations on how OSS services are adopted by customers in the presence of functionally superior commercially licensed software (CLS). This paper aims to uncover the process that shapes customer satisfaction of OSS services in comparison to CLS. Expectation Disconfirmation Theory (EDT) is adapted and integrated with pre implementation factor model that influences software customers' expectations including cost, reputation, and experience. The constructed research model is empirically validated using a field survey of OSS and CLS database management system (DBMS) customers in Korea. The theoretical contribution of the paper lies on the application of EDT to explain the wide adoption of OSS DBMS services in the presence of functionally superior CLS DBMSs. Furthermore, this paper integrates EDT with pre-implementation factors for customers' expectations, which has been considered a limitation of the theory. Among the practical contributions, this study draws attention to the substantive differences between OSS and CLS customers' expectations. Additionally, it offers initial explanations for the differences in customer behavior for OSS and CLS and the way that customers' expectations and actual performance are mingled together to form customer satisfaction.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.639-639
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• 2013

In this research we report the significant contribution of the as-spun multi-walled carbon nanotube (MWCNT) on the x-ray images formation using a low tube voltage x-ray source. The MWCNT, which was used for the fabrication of the spun CNT, was grown using a microwave plasma-enhanced chemical vapor deposition machine. Electrical-optics simulation software was utilized to determine the electron field emission trajectory of the triode-structure-as-spun CNT-based x-ray source. It was shown that a significant amount of converging electrons hit the target anode producing a clear x-ray image. These x-ray images where produced at a small amount of anode current of 0.67 mA at a tube voltage of 5 kV with the gate voltage of 0 V. Also, comparisons of the radiographs at various exposure times of the sample where analyzed with and without an x-ray dose filter. Results showed that spatially-resolved images were formed using the as-spun CNT at a low tube voltage with a $54-{\mu}m$ Al x-ray filter. This study can be used for low-voltage medical applications.

• 한국멀티미디어학회논문지
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• 제13권8호
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• pp.1171-1182
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• 2010

본 논문에서는 특정 시점, 특정 장소의 대기 중에 발생하는 악취의 발생원을 추적하기 위한 악취분류 및 악취원 분석 방법을 제안한다. 이를 위해 악취원별 대표패턴의 생성이 필요하다. 이에 주요 악취원에서 측정한 67개의 악취를 악취 대표패턴으로 생성하였다. 또한, 여러 악취가 대기 중에서 섞였을 경우를 고려하여 2~3개의 악취들을 조합하여 복합 악취 대표패턴을 생성하였고, pseudo inverse method를 이용하여 악취에 대한 악취원들의 가중치를 계산하였다. 그 결과 해당 악취를 발생시킨 악취원들과 악취에 대한 기여도를 알아낼 수 있었다. 이러한 본 연구의 성과는 악취 관련 민원해결에 기여할 것으로 전망된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.807-814
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• 2004

Land seismic reflection survey has been increasingly demanded in various civil engineering works because of its own ability to delineate layers, water table, to detect cavities or fracture zones, to estimate seismic velocities of each layer. However, our shallow subsurface structures are very complex. The relatively thin layer(mostly soil) to the wavelength directly followed by a basic rock with high impedance used to generate complicated surface waves, kind of channel waves with high amplitude that is dominate in entire seismograms and hence the useful reflection events will be almost hopelessly immersed in the undesired surface waves. Thus, it would seem that the use of traditional seismic survey could not be likely to provide in itself a satisfactory information about our exploration targets. This paper hence introduces an efficient measuring strategy illustrating a properly controlled arrangement of the vertical single force sources commonly used, yielding a very sharply elongated form of P-energy with a minimum of S radiation energy, what we call, P-beam source. Abundant experiments of physical modeling showed that in that way the surface waves could be enormously reduced and the reflection events would be additive and thus reinforced. Examples of field data are also illustrated. The contribution of P-beam source will be great in civil engineering area as well as in general geological exploration area.

• 한국소음진동공학회논문집
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• 제19권4호
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• pp.347-354
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• 2009

Frequency analysis is one of the most useful way to analyze response signal for the purpose of grasping the dynamic characteristics of system through Fourier transformation. Although it is very effective way for frequency analysis, it is hard to analyze out a specific sound or vibration component which is correlated with others. In this thesis, source contribution analysis tool for NI-PXI equipment is developed with LabVIEW using coherences of MISO(multiple-input single-output) model. For the purpose of examining propriety of developed tool, simulation is performed with several correlated signals that have different frequency range. After checking the OCF(ordinary coherence function) and PCF(partial coherence function) of the each signal for concerned frequency domain, an experiment is conducted on an evaporator that cause the principal noise of a refrigerator. This developed tool will be expected to build up more convenient and serviceable measurement system.