• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.900-906
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• 2004

Solid oxide fuel cells have a limitation in their low-temperature application due to the low ionic conductivity of electrolyte materials and difficulties in thin film formation on porous gas diffusion layer. These problems can be solved by improvement of ionic conductivity through controlled nanostructure of electrolyte and adopting nanoporous electrodes as substrates which have homogeneous submicron pore size and highly flattened surface. In this study, ultra-thin oxide films having submicron thickness without gas leakage are deposited on nanoporous substrates. By oxidation of metal thin films deposited onto nanoporous anodic alumina substrates with pore size of $20nm{\sim}200nm$ using dc-magnetron sputtering at room temperature, ultra-thin and dense ionic conducting oxide films with submicron thickness are realized. The specific material properties of the thin films including gas permeation, grain/gran boundaries formation, change of crystalline structure/microstructure by phase transition are investigated for optimization of ultra thin film deposition process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.59-66
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• 2008

This paper presents a spectrum sharing and allocation problem in multiple network operators(NOs). Most of previous works as to dynamic spectrum allocation(DSA) schemes have presented the DSA gain achieved by utilizing the time or regional variations in traffic demand between multi-network operators(NOs). In this paper, we introduce the functionalities required for the entities related with the spectrum sharing and allocation and propose a spectrum allocation algorithm while considering the long-term priority(or fairness) between NOs, the prioritybetween multiple class services, and the urgent bandwidth request. It was shown that the proposed algorithm with priorities between multiple class services could sustain better satisfaction ratio(SR) than the fixed allocation schemes or one without priority under different traffic patterns. Therefore, we conclude that the proposed DSA with priorities between multiple class services and network operators could provide the fairness between service classes of network operators and effective negotiation procedure for urgent bandwidth request by users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.45-54
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• 2010

This paper studies the design of a multiuser multiple-input multiple-output (MIMO) system, where a base station (BS) transmits independent messages to multiple users. The remarkable "dirty paper coding (DPC)" result was first presented by Costa that the capacity does not change if the Gaussian interference is known at the transmitter noncausally. While several implementable DPC schemes have been proposed recently for single-user dirty-paper channels, DPC is still difficult to implement directly in practical multiuser MIMO channels. In this paper, we propose a network channel matrix triangulation (NMT) algorithm for utilizing interference known at the transmitter. The NMT algorithm decomposes a multiuser MIMO channel into a set of parallel, single-input single-output dirty-paper subchannels and then successively employs the DPC to each subchannel. This approach allows us to extend practical single-user DPC techniques to multiuser MIMO downlink cases. We present the sum rate analysis for the proposed scheme. Simulation results show that the proposed schemes approach the sum rate capacity of the multiuser MIMO downlink at moderate signal-to-noise ratio (SNR) values.

• Journal of Korean Society of Archives and Records Management
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• v.24 no.2
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• pp.113-137
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• 2024

In this study, considering the National Memorial of the Korean Provisional Government as a "Larchiveum," the researchers attempted to develop a classification system that can comprehensively categorize various types of materials and propose a method of providing an online service. To this end, as a case study, the researchers examined the classification system structure and contents of the National Archives of Korea, National Assembly Archives, and Archives of Korean History of the National Institute of Korean History, which are the current material collection institutions of the Korean Provisional Government. Regarding online services, apart from the three institutions above, the Imperial War Museum and the Hoover Institution at Stanford University were also explored. Through the implications derived from the case analysis of domestic and foreign institutions, a basic hierarchical classification system by provenance for the materials held by the institution was established, and a multi-classification system was presented according to the classification criteria of "by type, by era, and by subject." In addition, methods of applying the developed classification system to online services were proposed.

• Journal of Chest Surgery
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• v.30 no.12
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• pp.1197-1204
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• 1997

Between April 1981 and June 1996, 65 patients had aortic root replacement at our institution. Disease entities were pure aortic annuloectasia in 31 patients(47.7%), Stanford type A aortic dissection with annuloectasia in 8(43.1%), atherosclerotic aneurysm with aortic regurgitation in 4(6.2%), and paravalvular leakage after aortic valve replacement in 2(3.1 %). 34 patients(52.3%) had the clinical stigmata of the Marfan syndrome. The operative procedures were Bentall operation in 61 patients(93.8%); 3 of conventional procedure and 58 of Cabrol's modification, aortic valve-sparing operation in 2(3.1 %), and root replacement with homograft in 2(3.1%). Hospital deaths occurred in 3 patients(4.8%) because of uncontrolled bleeding(1) and bypass weaning failure due to low cardiac output(2), and all had emergency operation with Cabrol's procedure. Postoperative complications developed in 19(29.2%) patients and most of them were transient. Surviving 62 patients have been followed up to cumulative total 315.0 patient-years(mean 60.2 $\pm$42.4 months). Late deaths occurred in 7 patients(11.3%), aneurysmal changes of remaining aorta were detected in 12 patients(19.4%). Actuarial survival rate at 10 years was 72.0 $\pm$ 9.7%, and the subsequent aortic operation-free rate at 10 years was 68.0$\pm$ 8.9% In a multivariate analysis, Marfan syndrome, emergency operation, preoperative dissection, combined arch replacement, and total circulatory arrest emerged as significant risk factors for hospital death or subsequent aortic operation. Over 60 years of age was the only risk factor for late death. Our 16 years'cummulative experience shows that aortic root replacement, mainly by means of Cabrol's procedure, can be applied successfully to variety of aortic root disease. However, long-term follow up will be needed to determine the late result of aortic valve-saving operation and root replacement with homograft. When dissection is present or the distal native aorta is diseased in'Marfan patients, close follow-up is necessary because of the subsequent aneurysmal change of remaining aorta.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.679-682
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• 2005

Negative-differential conductance (NDC) characteristics as well as negative-differential trans-conductance (NDT) characteristics have been observed in the room temperature I-V characteristics of Field-induced Inter-band Tunneling Effect Transistors (FITETs). These characteristics have been explained with inter-band tunneling physics, from which, inter-band tunneling current flows when the energy bands of degenerately doped regions align, and it does not flow when they don't. FITET is an SOI device and the body region is not directly connected to the external terminal. Therefore, Fermi energy in the body region is determined by electrical coupling among four regions - gate, source, drain and substrate. So, a quasi Fermi energy of the majority carriers in the floating body region can be changed by external voltages, and this causes the energy band movements in the body region, which determine whether the energy bands between degenerately doped junctions aligns or not. This is a key point for an explanation of NDT and NDC characteristics. In this paper, a quasi Fermi energy movement in the floating body region of FITET was investigated by a device simulation. This result was applied for the description of relation between quasi Fermi energy in the body region and external gate bias voltage.

• Journal of Chest Surgery
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• v.40 no.11
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• pp.733-744
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• 2007

Background: There is a controversy regarding the pathogenesis and management principle of an acute intramural hematoma (IMH) of the aorta, Recent studies have reported intimal defects in many patients diagnosed with IMH, and suggested that intimal defects play important roles in the pathogenesis, progression of the pathology, and prognosis. Material and Method: This study reviewed the preoperative and postoperative computed tomography (CT) scan images of 36 patients who underwent surgical treatment for Stanford type A acute IMH of the aorta. The surgical findings were also reviewed retrospectively from the medical records. Result: In 15 patients (41.7%), the findings suggestive of the intimal defects were found in the preoperative CT. During the operation, 20 patients (72.2%) were found to have small intimal defects in the ascending aorta or the arch, of which 13 patients (50.5%) did not have the CT findings suggestive of intimal defects. In 17 patients, the intimal defects were located in the aortic arch or distal ascending aorta, where a gross examination would have been impossible without total circulatory arrest. In all patients, the intimal defects identified were included in the resected aortic segment, or locally closed. Follow-up CT at 4 months or longer after surgery showed that the IMH in the descending aorta had disappeared or was markedly improved. Conclusion: Most patients undergoing surgical treatment for acute type A IMH had intimal defects. This suggests that a large proportion of IMH might have a similar pathogenic mechanism as classic dissection. Consequently, it is believed that those two entities of acute aortic syndrome should be treat-ed using the same principles.

• Molecules and Cells
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• v.38 no.7
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• pp.643-650
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• 2015

The use of conditioned medium from mesenchymal stem cells may be a feasible approach for regeneration of bone defects through secretion of various components of mesenchymal stem cells such as cytokines, chemokines, and growth factors. Mesenchymal stem cells secrete and accumulate multiple factors in conditioned medium under specific physiological conditions. In this study, we investigated whether the conditioned medium collected under hypoxic condition could effectively influence bone regeneration through enhanced migration and adhesion of endogenous mesenchymal stem cells. Cell migration and adhesion abilities were increased through overexpression of intercellular adhesion molecule-1 in hypoxic conditioned medium treated group. Intercellular adhesion molecule-1 was upregulated by microRNA-221 in mesenchymal stem cells because microRNAs are key regulators of various biological functions via gene expression. To investigate the effects in vivo, evaluation of bone regeneration by computed tomography and histological assays revealed that osteogenesis was enhanced in the hypoxic conditioned medium group relative to the other groups. These results suggest that behavioral changes of endogenous mesenchymal stem cells through microRNA-221 targeted-intercellular adhesion molecule-1 expression under hypoxic conditions may be a potential treatment for patients with bone defects.

• Journal of Ginseng Research
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• v.38 no.3
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• pp.167-172
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• 2014

Background: Roles of immune reaction and toll-like receptor-4 (TLR-4) have widely been established in the pathogenesis of alcoholic liver disease (ALD). Methods: We evaluated the biologic efficacy of Korean Red Ginseng (KRG), urushiol, and probiotics (Lactobacillus rhamnosus R0011 and Lactobacillus acidophilus R0052) in mouse models of ALD. Sixty C57BL/6 mice were equally divided into six feeding groups for 10 weeks: normal diet, alcohol, control, alcohol + KRG, alcohol + urushiol, and alcohol + probiotics. Alcohol was administered via a LiebereDeCarli liquid diet containing 10% alcohol. TLR-4 expression, proinflammatory cytokines, and histology, as well as the results of liver function tests were evaluated and compared. Results: No between-group differences were observed with regard to liver function. TLR-4 levels were significantly lower in the KRG, urushiol, and probiotics groups than in the alcohol group ($0.37{\pm}0.06ng/mL$, $0.39{\pm}0.12ng/mL$, and $0.33{\pm}0.07ng/mL$, respectively, vs. $0.88{\pm}0.31ng/mL$; p < 0.05). Interleukin-$1{\beta}$ levels in liver tissues were decreased among the probiotics and KRG groups. The tumor necrosis factor-${\alpha}$ level of liver tissue was decreased in the KRG group. Conclusion: The pathological findings showed that alcohol-induced steatosis was significantly reduced by KRG and urushiol. As these agents improve immunologic capacity, they may be considered in potential anti-ALD treatments.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.4
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• pp.27-43
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• 2020

Recently, there has been growing interest in entrepreneurial universities. Accordingly, this study discussed the paradigm shift from traditional university roles to entrepreneurial universities and conducted case analysis of Oxford University, Stanford University and Berlin Institute of Technology from the perspective of ambidextrous strategies of universities. Universities are emphasizing the importance of academic capitalism through market activities as well as the educational and research-oriented role to adapt and survive the rapidly changing uncertain environment. Therefore, many studies related to this have been conducted. This paper discusses the background and necessity of the transformation from traditional universities to entrepreneurial universities, and applies the case of a university that has been successful in transforming into an entrepreneurial universities and creating excellent outcome in terms of ambidextrous strategy. Specifically, this study examined the structural, contextual, and leadership perspectives as a antecedents for ambidextrous strategy. This paper expects not only to introduce cases but also to be used as reference for adapting to future paradigm shifts to entrepreneurial universities and setting the direction of universities.