• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.540-546
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• 2013

Using the free volume of van der Waals equation, Carnahan-Starling equation for hard spheres, Wilson equation for nonrandom mixing of solution, NRTL equation and our equation, several new equations of states for pure gases are derived. Using these equations, compressibility factors for pure gases are calculated and compared with Nelson-Obert generalized compressibility factor charts. The equation of states using the concept of molecular nonrandom distribution gave better results than those of molecular random distribution. This shows that the molecular nonrandom distribution makes considerable effect on the equation of states.

• Polymer(Korea)
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• v.32 no.3
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• pp.193-198
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• 2008

Sibutramine is a highly crystalline and poorly water soluble drug as the appetite depressant for obesity treatment. In order to increase water solubility of sibutramine, microspheres including sibutramine were prepared by solid dispersion method using a spray dryer. The crystallinity and morphology of the prepared microspheres were confirmed by SEM and XRD. The morphology of micro spheres has gradually changed into spherical shape as increasing evaporation rate of solvent. According to XRD analysis, crystallinity of sibutramine in micro spheres was decreased by below 10%. Release behavior of microspheres was investiaged at pH 1.2, pH 6.8, and solubility of the sibutramine was significantly different depending on pH. The hard capsule showed fast release of sibutramine comparing with the tablet. These results demonstrated that the pharmaceutical preparation is able to control the release behaviors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.689-695
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• 2016

The performance of proton exchange membrane fuel cells (PEMFC) is strongly related to the water flow and accumulation in the gas diffusion layer (GDL) and catalyst layer. Understanding the behavior of fluid from the characteristics of the media is crucial for the improvement of the performance and design of the GDL. In this paper, a numerical method is proposed to calculate the design parameters of the GDL, i.e., permeability, tortuosity, and effective diffusivity. The fluid flow in a channel filled with randomly packed hard spheres is simulated to validate the method. The flow simulation was performed by lattice Boltzmann method with bounce back condition for the solid volume fraction in the porous media, with different values of porosities. Permeability, which affects the flow, was calculated from the average pressure drop and the velocity in the porous media. Tortuosity, calculated by the ratio the average path length of the randomly injected massless particles to the thickness of the porous media, and the resultant effective diffusivity were in good agreement with the theoretical model. The suggested method can be used to calculate the parameters of real GDL accurately without any modification.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.10a
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• pp.7-7
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• 1997

During sintering of very porous green bodies, as obtained by compaction of hard powders - such as tungsten carbide or ceramics - or by injection moulding, important shrinkage occurs. Due to heterogeneous green density field, gravity effects, friction on the support, thermal gradients, etc., this shrinkage is often non-uniform, which' may induce significant shape changes. As the ratio of compact dimension to powder size is very high, the mechanics of continuum is relevant to model such phenomena. Thus numerical techniques, such as the finite element method can be used to simulate the sintering process and predict the final shape of the sintered part. Such type of simulation has much been developed in the last decade firstly for hot isostatic pressing and next for die compaction. Finite element modelling has been recently applied to free sintering. The simulation of sintering should be based on constitutive equations describing the thermo-mechanical behaviour of the material under any state of stress and any temperature which may arise within the sintering body. These equations can be drawn either from experimental data or from micromechanical models. The experiments usually consist in free sintering and sinter-forging tests. Indeed applying more complex loading conditions at high temperature under controlled atmosphere is delicate. Micromechanical models describe the constitutive behaviour of aggregates of spheres from the deformation of two-sphere contact either by viscous flow or grain boundary diffusion. Such models are not able to describe complex microstructure and mechanisms as observed in real materials but they can give some basic information on the formulation of constitutive equations. Practically both experimental and theoretical approaches can be coupled to identify the constitutive equations. Such procedure has been performed for modelling the sintering of compacts obtained by die pressing of a mixture of tungsten carbide and cobalt powders. The constitutive behaviour of this material during sintering has been described by a linear viscous constitutive model, whose functions have been fitted from results of free sintering and sinter-forging experiments. This model has next been introduced in ABAQUS finite element code to simulate the sintering of heterogeneous green compacts of various geometries at constant temperature. Examples of simulations are shown and compared with experiments.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.2
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• pp.74-79
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• 2017

Purpose Proton therapy can deliver an optimal dose to tumor while reducing unnecessary dose to normal tissue as compared the conventional photon therapy. As proton beams are irradiated into tissue, various positron emitters are produced via nuclear fragmentation reactions. These positron emitters could be used for the dose verification by using PET. However, the short half-life of the radioisotopes makes it hard to obtain the enough amounts of events. The aim of this study is to investigate the effect of off-line PET imaging scan time on the PET image quality. Materials and Methods The various diameters of spheres (D=37, 28, 22 mm) filled with distilled water were inserted in a 2001 IEC body phantom. Then proton beams (100 MU) were irradiated into the center of the each sphere using the wobbling technique with the gantry angle of $0^{\circ}$. The modulation widths of the spread out bragg peak were 16.4, 14.7 and 9.3 cm for the spheres of 37, 28 and 22 mm in diameters respectively. After 5 min of the proton irradiation, the PET images of the IEC body phantom were obtained for 50 min. The PET images with different time courses (0-10 min, 11-20 min, 21-30 min, 31-40 min and 41-50 min) were obtained by dividing the frame with a duration of 10 min. In order to evaluate the off-line PET image quality with the different time courses, the contrast-to-noise ratio (CNR) of the PET image calculated for each sphere. Results The CNRs of the sphere (D=37 mm) were 0.43, 0.42, 0.40, 0.31 and 0.21 for the time courses of 0-10 min, 11-20 min, 21-30 min, 31-40 min and 41-50 min respectively. The CNRs of the sphere (D=28 mm) were 0.36, 0.32, 0.27, 0.19 and 0.09 for the time courses of 0-10 min, 11-20 min, 21-30 min, 31-40 min and 41-50 min respectively. The CNR of 37 mm sphere was decreased rapidly after 30 min of the proton irradiation. In case of the spheres of 28 mm and 22 mm, the CNR was decreased drastically after 20 min of the irradiation. Conclusion The off-line PET imaging time is an important factor for the monitoring of the proton therapy. In case of the lesion diameter of 22 mm, the off-line PET image should be obtained within 25 min after the proton irradiation. When it comes to small size of tumor, the long PET imaging time will be beneficial for the proton therapy treatment monitoring.

• Korean journal of communication and information
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• v.61
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• pp.74-97
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• 2013

Asia is developing rapidly in 21st century. Human and material exchanges between Korea and Asian countries have greatly increased. Korea entered the multicultural society. It became important for Korean people to understand Asia more correctively. Korean media can play a key role for this. In this point, I analyzed 1786 news contents reported in 2011 by four Korean newspapers(Chosun Ilbo, Dong-A Ilbo, Hankyoreh newspaper, Kyungh Kyunghyang Daily News), to see differences of Asia and West news aspect and its reason, focusing on news topic, amount of news, news tone and foreign media sources. In amount of news, the percent of West(54.3%) was higher than that of Asia news(45.7%). In news tone, negative news were the most in Asia news, but the least in West news. Korean newspaper showed more positive attitude to West than Asia. 1786 news were classified into seven topics(morality and justice, politics, economics and science, society, diplomacy and national defense, human interest, people). In news amount of seven topics, Korean newspapers reported hard news like morality and justice more than soft news like human interest about Asia. However they reported many soft news about West besides hard news. In news topics and tone, hard news showed negative tone most and soft news showed neutral or positive tone most. As a result, Korean news showed the negative attitude to Asia and the positive to West. Among five main sources(media, government, private organization, individual and material), only media source affected the differences of news attitude to Asia and West. Asia media source took the more positive attitude to Asia than West. West media took the negative attitude to Asia most and the neutral attitude to West most. Korean newspapers used West media as main sources in the news of all areas except East Asia. As a result, Korean newspapers showed the West-centered-attitude and reported the negative news more than neutral and positive about Asia. It was suggested that Korean newspapers had better increase Asia news in diverse spheres by the direct reporting of the correspondent and the more use of Asia media through the internet.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.1
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• pp.54-60
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• 2010

Purpose: Nuclear medicine manufacturers provide various softwares which shorten imaging time using their own image processing techniques such as UlatraSPECT, ASTONISH, Flash3D, Evolution, and nSPEED. Seoul National University Hospital has introduced softwares from Siemens and Philips, but it was still hard to understand algorithm difference between those two softwares. Thus, the purpose of this study was to figure out the difference of two softwares in planar images and research the possibility of application to images produced with high energy isotopes. Materials and Methods: First, a phantom study was performed to understand the difference of softwares in static studies. Various amounts of count were acquired and the images were analyzed quantitatively after application of PIXON, Siemens and ASTONISH, Philips, respectively. Then, we applied them to some applicable static studies and searched for merits and demerits. And also, they have been applied to images produced with high energy isotopes. Finally, A blind test was conducted by nuclear medicine doctors except phantom images. Results: There was nearly no difference between pre and post processing image with PIXON for FWHM test using capillary source whereas ASTONISH was improved. But, both of standard deviation(SD) and variance were decreased for PIXON while ASTONISH was highly increased. And in background variability comparison test using IEC phantom, PIXON has been decreased over all while ASTONISH has shown to be somewhat increased. Contrast ratio in each spheres has also been increased for both methods. For image scale, window width has been increased for 4~5 times after processing with PIXON while ASTONISH showed nearly no difference. After phantom test analysis, ASTONISH seemed to be applicable for some studies which needs quantitative analysis or high contrast, and PIXON seemed to be applicable for insufficient counts studies or long time studies. Conclusion: Quantitative values used for usual analysis were generally improved after application of the two softwares, however it seems that it's hard to maintain the consistency for all of nuclear medicine studies because result images can not be the same due to the difference of algorithm characteristic rather than the difference of gamma cameras. And also, it's hard to expect high image quality with the time shortening method such as whole body scan. But it will be possible to apply to static studies considering the algorithm characteristic or we can expect a change of image quality through application to high energy isotope images.

• The Korean Journal of Archival Studies
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• no.5
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• pp.111-148
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• 2002

Digitalization of public administration information shall be accelerated more. When information exists both in the form of electronic and paper record, even the disclosure of paper record make it possible the access to public administration information itself, but there may some needs for the disclosure of electronic record in applicant's situation. Similarly, when only electronic record exists, there may be some problem about whether to disclose the record as print-out or as being electronic format itself. Thus, the method and format of disclose are very sensitive issues, and it is very important to clarify who has the competence to decide the method and format of disclosure, applicant or the public agency. In making any record available to an applicant under the EFOIA in America, the public agency shall provide the record in any form or format requested by the applicant, if the record is readily reproducible by the agency in that form or format. And for the convenience of the applicant with sensory disability, the AIA in Canada also permits the right to access to information in an alternative format. It is desirable also in our country that disclosure of information is done by public agencies in the format that applicant wants, as possible. In the meantime, we should consider the costs and technological restrictions corresponding to the change of format of information to the format that applicant specifies. In the case of electronic record, efforts required for searching cause some hard problems. Information disclosure system requires disclosure of record that exists at the demand point, and creation of new record that does not exist at that them is not required on the public agency. For the search of electronic information, we need some code or program. So, if we evaluate that act of coding or programming as creation of new record, demand on disclosure of electronic record becomes impossible, in fact. Therefore, when we include electronic record as the object of information disclosure system, we need to clarify the degree of reasonable efforts for searching the information included in that record, as long as possible, although it is very difficult problem. Also, we should consider the way to make it permitted to demand the disclosure of electronic record by FAX or E-mail. Disclosure of electronic record itself by E-mail is not generalized yet, even in America or Canada. There are many technological and legal problems to solve, before permitting or enforcing the disclosure of electronic record by E-mail. But, it is desirable to expand the method of disclosure to including disclosure by E-mail in possible spheres. Also, as well as disclosure on demands, we need to expand electronic access to information, so far as possible, in the process of information offer.

• The Journal of the Korea Contents Association
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• v.19 no.9
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• pp.67-80
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• 2019

Augmented Reality (AR) is a crucial technology in the Fourth Industrial Revolution that can revolutionize the existing Information and Communication Technology (ICT) market and powerfully create a new market However, it is hard to find the clear answer for AD/PR strategies in the rapidly changing AR market. Thus this research explores the big picture of the AR industry as it pertains to Politics, Economy, Social, and Technology through in-depth interview with seven AR experts who are leading the domestic AR market. The research also analyzes the AR market's Strengths, Weaknesses, Opportunities, and Threats. Furthermore, it looks for strategies to vitalize the advertising and PR industry by analyzing the Contents, Platform, Network, and Devices of the AR ecosystem. The results of the research indicate a need for the government's strengthened policy of supporting the AR market, fostering of pace-setting killer contents, connecting services of several industries through AR platforms, strengthening the network of communication systems such as through 5G, and the commercialization and industrialization of domestic devices in order to vitalize the AR industry in its marketing and PR spheres. Therefore, this research suggests measures to revitalize the marketing and PR industries of the AR ecosystem, which has only recently gotten to its developing stage and provides an academic as well as practical foundation for future research in the field of AR.

• Journal of Korea Game Society
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• v.4 no.3
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• pp.11-20
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• 2004

Virtual reality that we have seen from the movies in 80's and 90's is hawing near based on the rapid progress of science together with a computer technology. Various virtual reality system developments (such as VRML, HMD FishTank, Wall Type, CAVE Type, and so on) and the advancement of those systems make for the embodiment of virtual reality that gives more sense of the real. Virtual reality is so immersive that makes people feel like they are in that environment and enable them to manipulate without experiencing the environment at first hand that is hard to experience in reality. Virtual reality can be applied to the spheres, such as education, high-level programming, remote control, surface exploration of the remote satellite, analysis of exploration data, scientific visualization, and so on. For some connote examples, there are training of a tank and an aeroplane operation, fumiture layout design, surgical operation practice, game, and so on. In these virtual reality systems, the actual operation of the human participant and virtual workspace are connected each other to the hardware that stimulates the five senses adequately to lend the sense of the immersion. There are still long way to go, however, before long it will be possible to have the same feeling in the virtual reality as human being can have by further study and effort. In this thesis, the basic definition, the general idea, and the kind of virtual reality were discussed. Especially, CAVE typed in reality that is highly immersive was analyzed in definition, and then the method of VR programming and modeling in the virtual reality system were suggested by showing the restoration process of Kyongbok Palace (as the content of the original form of the culture) that was made by KISTI(Korea Institute of Science and Technology Information) in 2003 through design process in virtual reality system. Through these processes, utilization of the immersive virtual reality system was discussed and how to take advantage of this CAVE typed virtual reality system at the moment was studied. In closing the problems that had been exposed in the process of the restoration of the cultural property were described and the utilization plan of the virtual reality system was suggested.