• Journal of Korean Society for Atmospheric Environment
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• v.9 no.2
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• pp.132-139
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• 1993

TCM has been used for many environmental impact assessments and many case studies in Korea. TCM was applied to urbvan areas and rolling terrains. But original TCM was developed for rural area, and this model could not reflect the characteristcs of these study sites. This paper analyzed the characteristics of TCM, and modified the algorithm of area source, and modified the vertical wind speed profile exponents and diffusion parameter to make it applicable in urban area. In the process of modification, an important error in area source calculation of original TCM program was found. So that was corrected as follows. $$ Before modification $QC = 0.79788456^*(0.5^*GRID)^**BA/(U(IA, IRUN)^*AA^*BA TCM09310$ After modification $QC = 0.79788456^*(500^*GRID)^**BA/(U(IA, IRUN)^*AA*BA) modified$ $$ Then original TCM and modified TCM-urban mode were compared, and it was found that predicted mean value by original TCM was 7 times higher than observed mean value. But mean value by modified TCM-urban mode was very similar to observed value.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.312-314
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• 2000

The electric wave propagation characteristics of electromagnetic field by induction current shows a nonlinear distinction in the metal but linear on air. This paper is written about the magnetic transmission distinction in the metalic tube, which wrapped the center axis by the same direction. The electromagnetic field made by the transmission signal is transferred from the transmission coil area toward the receiving coil by the magnetic diffusion. So, it is different magnetic flux around the coil with one in the remote field area. Analyzing such a complex magnetic characteristic, we verified this theory by the vector analysis and presented eddy current mechanism and analytical model about magnetic distribution in the remote field area. This magnetic distribution rate in metal body will be very useful in the nondestructive inspection of the eddy current in remote field which is recently rising as a new technology.

• International Area Studies Review
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• v.21 no.1
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• pp.97-117
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• 2017

This research highlights the process of adopting cloud computing technology from users' perspective. Concentrating on perceived mechanism from employees side that lead to job performance at work. Cloud computing, the new player in our modern business environment, authors employ diffusion of innovation theory to capture how this new technology affect employees in workplace in terms of job performance. Education for this new system and managerial support by firm were used as moderating variable to test dependent variable, job performance. Research was done through survey from total 284 people working in metropolitan area at South Korea. The result shows that cloud computing system affect positively on work efficiency, and the extent of diffusion factors that influence from the most to least are as follow: 1. Users' Skill, 2. System Quality, 3. Information Quality, 4. Group Awareness, 5. Attitude towards New System. To test diffusion factors of cloud computing and job performance, South Korean people actually felt that cloud computing help their job performance and the extent of diffusion factors that influence from the most to least are as follow: 1. Users' Skill, 2. System Quality, 3. Information Quality, 4. Attitude towards New System, 5. Group Awareness. As for diffusion factors of cloud computing and productivity, result proved that cloud computing really helps firms, and the extent of diffusion factors that influence from the most to least are as follow: 1. Information Quality, 2. Attitude towards New System, 3. Group Awareness, 4. System Quality, 5. Users' Skill. Two moderating variables, employee education and managerial support were tested to prove whether these two variables affect the job performance and the result displays positive affect for both two factors. To conclude, adopting cloud computing helps firms by increase employees' work efficiency and job performance. In order to accelerate the process employees education really matters because users' skill is the most crucial among diffusion factors.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.7
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• pp.345-350
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• 2016

This research suggests the keyword filtering about disaster and the method of detecting area in real-time event detecting system by analyzing contents of twitter. The diffusion of smart-mobile has lead to a fast spread of SNS and nowadays, various researches based on studying SNS are being processed. Among SNS, the twitter has a characteristic of fast diffusion since it is written in 140 words of short paragraph. Therefore, the tweets that are written by twitter users are able to perform a role of sensor. By using these features the research has been constructed which detects the events that have been occurred. However, people became reluctant to open their information of location because it is reported that private information leakage are increasing. Also, problems associated with accuracy are occurred in process of analyzing the tweet contents that do not follow the spelling rule. Therefore, additional designing keyword filtering and the method of area detection on detecting real-time event process were required in order to develop the accuracy. This research suggests the method of keyword filtering about disaster and two methods of detecting area. One is the method of removing area noise which removes the noise that occurred in the local name words. And the other one is the method of determinating the area which confirms local name words by using landmarks. By applying the method of keyword filtering about disaster and two methods of detecting area, the accuracy has improved. It has improved 49% to 78% by using the method of removing area noise and the other accuracy has improved 49% to 89% by using the method of determinating the area.

• Korean Journal of Remote Sensing
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• v.32 no.5
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• pp.471-482
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• 2016

This paper presents an extraction method for water body which uses block-based image partitioning and extension of water body boundaries to improve the performance of supervised classification for water body extraction. The Mahalanobis distance image is created by computing the spectral information of Normalized Difference Water Index (NDWI) and Near Infrared (NIR) band images over a training site within the water body in order to extract an initial water body area. To reduce the effect of noise contained in the Mahalanobis distance image, we apply mean curvature diffusion to the image, which controls diffusion coefficients based on connectivity strength between adjacent pixels and then extract the initial water body area. After partitioning the extracted water body image into the non-overlapping blocks of same size, we update the water body area using the information of water body belonging to water body boundaries. The update is performed repeatedly under the condition that the statistical distance between water body area belonging to water body boundaries and the training site is not greater than a threshold value. The accuracy assessment of the proposed algorithm was tested using KOMPSAT-2 images for the various block sizes between $11{\times}11$ and $19{\times}19$. The overall accuracy and Kappa coefficient of the algorithm varied from 99.47% to 99.53% and from 95.07% to 95.80%, respectively.

• Korean Journal of Radiology
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• v.24 no.6
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• pp.553-563
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• 2023

Objective: Functional magnetic resonance imaging (fMRI) and diffusion tensor imaging-derived tractography (DTI-t) contribute to the localization of language areas, but their accuracy remains controversial. This study aimed to investigate the diagnostic performance of preoperative fMRI and DTI-t obtained with a simultaneous multi-slice technique using intraoperative direct cortical stimulation (DCS) or corticocortical evoked potential (CCEP) as reference standards. Materials and Methods: This prospective study included 26 patients (23-74 years; male:female, 13:13) with tumors in the vicinity of Broca's area who underwent preoperative fMRI and DTI-t. A site-by-site comparison between preoperative (fMRI and DTI-t) and intraoperative language mapping (DCS or CCEP) was performed for 226 cortical sites to calculate the sensitivity and specificity of fMRI and DTI-t for mapping Broca's areas. For sites with positive signals on fMRI or DTI-t, the true-positive rate (TPR) was calculated based on the concordance and discordance between fMRI and DTI-t. Results: Among 226 cortical sites, DCS was performed in 100 sites and CCEP was performed in 166 sites. The specificities of fMRI and DTI-t ranged from 72.4% (63/87) to 96.8% (122/126), respectively. The sensitivities of fMRI (except for verb generation) and DTI-t were 69.2% (9/13) to 92.3% (12/13) with DCS as the reference standard, and 40.0% (16/40) or lower with CCEP as the reference standard. For sites with preoperative fMRI or DTI-t positivity (n = 82), the TPR was high when fMRI and DTI-t were concordant (81.2% and 100% using DCS and CCEP, respectively, as the reference standards) and low when fMRI and DTI-t were discordant (≤ 24.2%). Conclusion: fMRI and DTI-t are sensitive and specific for mapping Broca's area compared with DCS and specific but insensitive compared with CCEP. A site with a positive signal on both fMRI and DTI-t represents a high probability of being an essential language area.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.594-602
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• 2010

Since the requirement of the high density integration and thin package technique of semiconductor have been increasing, the main package type of semiconductor will be a chip scale package (CSP). The changes of diffusion coefficient and moisture content ratio of epoxy resin systems according to the change of liquid type epoxy resin and fillers for CSP applications were investigated. The epoxy resins used in this study are RE-304S, RE310S, and HP-4032D, and Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The micro-sized and nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these epoxy molding compound (EMC) according to the change of filler size. The temperature of glass transition (Tg) of these EMC was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these EMC according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these EMC were calculated in terms of modified Crank equation based on Ficks' law. An increase of diffusion coefficient and maximum moisture absorption ratio with Tg in these systems without filler can be observed, which are attributed to the increase of free volume with Tg. In the EMC with filler, the changes of Tg and maximum moisture absorption ratio with the filler content can be hardly observed, however, the diffusion coefficients of these systems with filler content show the outstanding changes according to the filler size. The diffusion via free volume is dominant in the EMC with micro-sized filler; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the EMC with nano-sized filler.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.4
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• pp.261-270
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• 1992

To investigate the flow patterns and diffusions in the Taean coastal waters of the eastern Yellow Sea, hydraulic and numerical experiments of tidal currents and diffusions of dye and cooling water were performed during spring tide along with field observations. Flow patterns obtained by the hydraulic and numerical experiments approximately coincide with those of the field observations. In the fold observations of tidal current, currents flow southwestward during the ebb tide, while currents flow northeastward during the flood tide. and the maximum velocity is 2.13 ㎧ toward WSW direction. The Eulerian diffusion coefficient estimated from field measmements of current is 7.82$\times$10$^{5}$ $\textrm{cm}^2$/s. Diffusion coefficients obtained from the area of dye plume in the model are given by the expression 0.18 $r^{4}$3/, and the coefficients have the range of 10$^{5}$ ~10$^{6}$ $\textrm{cm}^2$/s. These values are similar to the Eulerian diffusion coefficient estimated fram field measurements. Diffusion coefficients obtained in the hydraulic model are one to two orders higher than those obtained in the Onsan Bay in the eastern waters and two to three orders higher than those obtained in the Chinhae Bay in the southern waters of the Korean Peninsula. Diffusion patterns of cooling water by numerical experiments are similar to those of dye plume by hydraulic experiments. Both hydraulic and numerical experiment results of diffusions of dye plume and cooling water in the Taean coastal waters, have shown that the diffusion during the ebb tide is more prevalent than one during the flood tide.

• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.539-546
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• 2016

It is over 12 years since the launch of Korea Train eXpress (KTX) services. Demand for the KTX has been on the increase continuously but few studies have been produced related to this phenomenon. KTX passenger demand has been constantly increasing due to influencing factors such as the expansion of network, rise of oil prices, etc. In this study, our main focus is to verify that there are other types of elements that are causing an increase in KTX demand; our approach looks at changes in social and psychological aspect that have occurred due to the reduction of travel time and cost, as well as the imposition of a five-day workweek. In other words, we considered diffusion theory in the marketing area, which affects product selection and purchasing attitudes, as a key factor that is causing passenger demand to increase. That is to say that it is hypothesized that the demand for travel on the KTX has increased due to the train's utility, which is spread by the diffusion effect Therefore, the Bass diffusion model was applied to explain the dramatic increase in KTX passenger demand. Based on this foundation, it was also discussed how certain marketing strategies that incorporate the diffusion effect should be considered variously for sustainable management of rail transportation, while considering a steady passenger demand.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.59-66
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• 2000

To investigate the optimum brazing condition, variation of bonded structure and mechanical properties of novel brazed pure Al with bonding condition (brazing temperature, time and Si/flux ratio) was studied. A basic study of the bonding mechanism was also examined. The optimum brazing condition was obtained at $590^{\circ}$ for 2 minutes and the bonded structure showed that it is composed of almost entirely eutectic Al-Si with near eutectic composition. At higher brazing temperature $630^{\circ}$, hypoeutectic Al-Si structure was observed in the bonded area and resulted in erosion of base metal. The thickness of eutectic layer formed in optimum brazing temperature increased linearly with the square root of time, showing a general diffusion controlled process. The ultimate tensile strength of bonded joint brazed at an optimum brazing condition was about 60% of base metal and its fracture surface showed a brittle mode.