• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1495-1498
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• 2002

The constrained average method is one of dither methods which combines edge emphasis and grayscale rendition to provide legibility of textual region and proper quality of continuous tone region. How-ever, image quality of continuous tone region is insufficient compared to other dither methods, such as ordered dither methods or the error diffusion method. The constrained average method uses a uniform distribution function to decide number of lit pixels related to the average intensity in a picture area. However, actual distribution of continuous tone region is closer to the Laplacian distribution or triangle distribution. In this paper, we introduce various probability distributions and the actual luminance distribution to decide the threshold value of the constrained average method in order to improve image quality of dithered image.

• Carbon letters
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• v.7 no.1
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• pp.9-18
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• 2006

Activated carbons were obtained by activating wild cherry stones with different concentrations of phosphoric acid or zinc chloride at different temperatures. The adsorption of $N_2$ at 77 K and of $CO_2$ at 273 K was followed and the data were analyzes by considering different adsorption models. The activated carbons obtained measured high surface area with the most of the surface in all samples located in micropores. Fair agreement was found between the nitrogen surface areas calculated from the BET-, t-, ${\alpha}$- and DR- methods, although the first three are based on surface coverage whereas the latter is based on micropore filling. The carbon dioxide surface areas calculated by the DA equation were smaller than the comparable nitrogen areas. This was ascribed to domination of surface coverage mechanism, the absence of activated diffusion process. Based on this explanation the $CO_2$-surface areas as calculated by DA equation should be taken with great reservation.

• Journal of Information Technology Applications and Management
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• v.13 no.1
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• pp.95-116
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• 2006

Many SMEs have adopted ASP models which have brought various benefits to SMEs such as decreasing the total cost, using new IT technology, enhancing the maintenance, and implementing the information systems rapidly. Ministry of Information and Communication had implemented the ASP diffusion project for the ASP venders and SMEs between 2001 and 2003. As results of this project, various industries adopted the ASP applications of which the performance was enhanced, and then the competitiveness of the ASP vendors in Korea was increased. The purpose of this study is to make a strategy of the penetration into China market for ASP services which have competitive advantages. This study uses various research methods such as questionnaire survey, visiting SMEs in china and making interviews. This study shows the current status of Chines ASP market, the several cases of using ASP services, and questionnaire analyses(service recognition, service requirement and factors and infrastructure, business environment and supporting organizations etc) of ASP demand. And finally this study proposes several strategic considerations in entering China market and suggests several support policies for supporting Korean ASPs.

• ETRI Journal
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• v.11 no.2
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• pp.109-119
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• 1989

Based on the 2-dimensional charge-control simulation[4], a purely analytical model for MODFET's is proposed. In this model, proper treatment of the diffusion effect in the 2-DEG transport due to the gradual channel opening along the 2-DEG channel was made to explain the enhanced mobility and increased thershold voltage. The channel thickness and gate capacitance are experssed as functions of gate vlotage including subthreshold characteristics of the MODFET's analytically. By introducing the finite channel opening and an effective channel-length modulation, the slope of the saturation region of the I-V curves was modeled. The smooth transition of the I-V curves from linear-to-saturation region of the I-V curves was possible using the continuous Troffimenkoff-type of field-dependent mobility. Furthermore, a correction factor f was introduced to account for the finite transtition section forming between the GCA and the saturated section. This factor removes the large discrepanicies in the saturation region fo the I-V curves presicted by existing 1-dimensional models. The fitting parameters chosen in our model were found to be predictable and vary over relatively small range of values.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.547-550
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• 2004

We present a multiscale scheme which describes the dynamic pictures of atoms in the multiple length-scale systems. Large-scale atomic systems are reduced to coarse grained system by the quasicontinuum, of which the dynamic pathways are rendered by the action-derived molecular dynamics proved effective for multiple time-scale problems such as rare events. Adatom diffusions on the metal (001) surface are selected for our numerical examples. The energy barriers of the diffusions and the real dynamic trajectories of the adatoms are calculated.

• Nuclear Engineering and Technology
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• v.32 no.6
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• pp.549-558
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• 2000

A transient model for hydrogen generation in molten metal-water interactions was developed with separate models for two stages of coarse mixing and stratification. The model selves the mechanistic equations (heat and mass transfer correlation, heat conduction equation and the concentration diffusion equation) of each stage with non-zero boundary conditions. Using this model, numerical simulations were performed for single droplet experiments in the Argonne National Laboratory tests and for FITS tests that simulated dynamic fragmentation and stratification. The calculation results of hydrogen generation showed better agreement to the experiment data than those of previous works. It was found from the analyses that the steam concentration to be reached at the reaction front might be the main constraint to the extent of the metal droplet oxidized. Also, the hydrogen generation rate in the coarse mixing stage was the higher than that in the stratification stage. The particle size was the most important factor in the coarse mixing stage to predict the amount of hydrogen generation.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.252-256
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• 1999

In this research, the performance predictions of the submersible mixer were investigated. The variation of the performance characteristics by changing the impeller design parameters were discussed through the flow calculation results by using a commercial program, FLUENT. The performance of the submersible mixers is related to the velocity diffusion profiles downstream of the impeller and also the required input motor power to mix the fluid. In this study, the various design parameters such as the number of blade, the hub and tip diameters, the impeller blade profiles and revolution speed of the blades were taken for the fixed values. The blade sweep direction, the chord length distribution along with the radius of the blade and the inlet blade angle were changed to make different testing models. The flow calculation results show the effect of the changed design parameters on the performance of the submersible mixers and also give some helpful information for designing more efficient submersible mixers.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.199-202
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• 2008

It is well-known fact that tidal difference between the ebb and flow in Yellow Sea is about 9 m so that it has largest value in the world. This wide range of tide level enables Yellow Sea water to intrude into main stream of Han River. However, the study of the tidal reach of Han River has not been carried out thoroughly since North and South Koreas share this region so that topography data and physical measurement are lacking. In this study, to examine the reverse flow and dispersion behavior by tidal effect at the tidal reach of Han River, 2-D river analysis models were applied. RMA-2 was applied to calculate the horizontal velocities and water surface elevation. With the results of velocities and water depth, RAM4, which is 2-D advection-dispersion model based on FEM was simulated to analyze the horizontal transport behavior of BOD.

• Asia pacific journal of information systems
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• v.9 no.4
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• pp.125-142
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• 1999

The increased investment in technological innovations makes the investigation of factors affecting technology adoption more interesting. Several perspectives have been proposed to explain the determinants of information technology adoption. While the traditional innovation diffusion research streams try to explain and predict adoption behavior with the adopter's perceptions about the characteristics of the innovation itself, critical mass theorists argue that adoption behavior as a collective action is based on what their business partners are doing and whether there exists enough critical mass to justify the investment. Drawing on theses two perspectives, this study investigates the decision criteria in the adoption of information technology as innovation and factors affecting the decision criteria. The survey results reveal that the adoption behavior is affected both by innovation characteristics and by critical mass's activity. Correlation analysis, t-test, and stepwise regression models also show that as the environmental uncertainty is getting higher, adoption decision is affected more by what others are doing, and that highly competitive organizations seem to play the role of critical mass.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.380-383
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• 2019

인터넷의 급속한 발전은 네트워크를 통해 많은 정보를 흘러가도록 만들었다. 그 정보들 중에는 다른 시스템이나 사용자에게 루머나 바이러스와 같은 좋지 않은 정보를 포함하는 경우도 있는데, 이에 대비해서 이런 악성정보가 더 많이 퍼져나가지 않도록 다양한 보안방법들이 제안되었다. 본 논문에서는 이를 위해 정보를 처음 퍼뜨린 근원을 추정해 나가는 문제를 고려한다. 특히, 기존의 이 문제를 다룬 많은 연구에서와는 다르게 본 연구에서는 정보가 시간이 지남에 따라, 혹은 근원으로부터 멀어짐에 따라 그 전파력이 감쇠되는 여러 가지 정보확산 모델을 고려한 후, 각각의 모델에서 트리기반 추정법을 사용하여 정보의 근원을 얼마나 잘 탐지해 내는지에 대해 살펴본다.