• Journal of KIISE
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• v.44 no.7
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• pp.658-667
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• 2017

The demand for large-scale storage systems has continued to grow due to the emergence of multimedia, social-network, and big-data services. In order to improve the response time and reduce the load of such large-scale storage systems, DRAM-based in-memory cache systems are becoming popular. However, the high cost of DRAM severely restricts their capacity. While the method of compressing cache entries has been proposed to deal with the capacity limitation issue, compression and decompression, which are technically difficult to parallelize, induce significant processing overhead and in turn retard the response time. A selective compression scheme is proposed in this paper for in-memory file system caches that rapidly estimates the compression ratio of incoming cache entries with their Shannon entropies and compresses cache entries with low compression ratio. In addition, a description is provided of the design and implementation of an in-kernel in-memory file system cache with the proposed selective compression scheme. The evaluation showed that the proposed scheme reduced the execution time of benchmarks by approximately 18% in comparison to the conventional non-compressing in-memory cache scheme. It also provided a cache hit ratio similar to the all-compressing counterpart and reduced 7.5% of the execution time by reducing the compression overhead. In addition, it was shown that the selective compression scheme can reduce the CPU time used for compression by 28% compared to the case of the all-compressing scheme.

• Journal of Information Technology Applications and Management
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• v.30 no.2
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• pp.45-57
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• 2023

Efforts to build metaverse platform services and expand profit structure are developing in a more realistic direction. The metaverse, which has been centered on 'creation and economy' and 'discovery', will evolve into an 'experience' metaverse, creating tangible business effects where satisfaction with the user experience leads directly to purchase. In this paper, the condition of the avatar used as a medium of economic activity between the metaverse platformer and the user and the business utilization plan were sought. In addition, a new 'metaverse business model' was proposed based on 'experience, discovery, creation and economy', and in particular, it was intended to lay the foundation for the experience metaverse to further develop in the form of 'business experience'. In addition, a survey was conducted on the 'application of metaverse service and avatar' targeting the MZ generation, the main customer base of the current metaverse service. In order to provide a service that satisfies the user, it was concluded that the appearance of the avatar needs to be changed according to the purpose and function. Accordingly, we propose an 'selective switch mode' that can change the avatar's appearance at the desired timing according to the 'experience' and 'purchase purpose' of each metaverse service area. In addition, by strategically utilizing the 'Digilog' psychology, we believe that it will be possible to promote the influx of new users while increasing the loyalty of existing users to the platform. Through the establishment of 'avatar purchase system' by 'selective switch mode' and 'avatar decorating system' by 'digilog' strategy, the experience metaverse, which has been focused on 'digital twin experience' so far, is As it develops into 'business experience', it is expected that the user experience can be further satisfied.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.112-116
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• 2000

This paper presents anisotropic ethcing characteristics of single-crystal silicon in tetramethylammonium hydroxide(TMAH):isopropyl alcohol(IPA) solutions containing pyrazine. With the addition of IPA to TMAH solutions, etching characteristics are exhibited that indicate an improvement in flatness on the etching front and a reduction in undercutting, but the etch rate on (100) silicon is decreased. The (100) silicon etch rate is improved by the addition of pyrazine. An etch rate on (100) silicon of $0.8\;{\mu}m/min$, which is faster by 13 % than a 20 wt.% solution of pure TMAH, is obtained using 20 wt.% TMAH:0.5 g/100 ml pyrazine solutions, but the etch rate on (100) silicon is decreased if more pyrazine is added. With the addition of pyrazine to a 25 wt.% TMAH solution, variations in flatness on the etching front were not observed and the undercutting ratio was reduced by 30 ~ 50 %.

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.17-28
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• 2007

Indium and gallium have emerged as useful metals in organic synthesis as a result of its intriguing chemical properties of reactivity, selectivity, and low toxicity. Although indium belongs to a main metal in group 13, its first ionization potential energy is very low and stable in H2O and O2. Therefore, indium-mediated organic reactions are of our current interest. On the basis of these properties of indium, many efficient indium-mediated organic reactions have been recently developed, such as the addition reactions of allylindium to carbonyl and iminium groups, the indium-mediated synthesis of 2-(2-hydroxyethyl)homoallenylsilanes, the indiummediated allylation of keto esters with allyl halides, sonochemical Reformatsky reaction using indium, the indium-mediated selective introduction of allenyl and propargyl groups at C-4 position of 2-azetidinones, the indium-mediated Michael addition and Hosomi-Sakurai reactions, the indium-mediated β-allylation, β- propargylation and β-allenylation onto α,β-unsaturated ketones, the highly efficient 1,4-addition of 1,3-diesters to conjugated enones by indium and TMSCl, and the intramolecular carboindation reactions. Also, we found gallium-mediated organic reactions such as addition reactions of propargylgallium to carbonyl group and regioselective allylgallation of terminal alkynes.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.45-48
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• 2000

The use of multi-level modulation scheme in the wireless LAN(Local Area Networks) system requires an accurate channel estimation. In this paper, we present sequential least squares(LS) channel estimation scheme based on decision-directed channel tracking scheme. The proposed scheme improves the performance of the conventional LS estimator for wireless LAN. In addition, its structure is suitable for the high-rate wireless LAN. Simulation results show that the proposed scheme achieves about IdB Packet Error Rate(PER) gain compared to the LS scheme in a frequency selective channel.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3382-3384
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• 2010

A new synthetic route to ($\pm$)-aspidospermidine was devised, starting from the cycloadduct of 3-ethyl-5-bromo-2-pyrone with vinyl sulfide through a tandem conjugate addition-alkylation sequence. The requisite 3-ethyl-5-bromo-2-pyrone was prepared via the C3-selective Pd-catalyzed coupling reaction with $Et_3Al$-dimethylaminoethanol complex.

• Transactions of the Society of Information Storage Systems
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• v.3 no.1
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• pp.43-46
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• 2007

The fabrication of metal nanostructures by a combination of atomic force microscopy nanomachining on a thin polymer resist, metal coating and lift-off is reported. Nanodots with sizes and nanowires with widths ranging between 50 and 100 nm have been successfully created. The present work exemplifies the feasibility and effectiveness of using a single-layer resist in comparison with a two-layer resist. In addition, the localized surface plasmon resonance peaks of the metal nanostructures have been measured and the selective growths of zinc oxide nanowires on the metal nanostructures are demonstrated.

• Korean Journal of Biological Psychiatry
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• v.26 no.2
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• pp.33-38
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• 2019

Psychiatric disorder as dysfunctional behavioural syndrome is a paradoxical phenomenon that is difficult to explain evolutionarily because moderate prevalence rate, high heritability and relatively low fitness are shown. Several evolutionary genetic models have been proposed to address this paradox. In this paper, I explain each model by dividing it into selective neutrality, mutation-selection balance, and balancing selection hypothesis, and discuss the advantages and disadvantages of them. In addition, the feasibility of niche specialization and frequency dependent selection as the plausible explanation about the central paradox is briefly discussed.

• Bulletin of the Korean Chemical Society
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• v.3 no.4
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• pp.149-152
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• 1982

A new convenient method for the reduction of carboxylic acids to the corresponding alcohols via acyloxyborohydrides was explored. Acyloxyborohydrides, prepared from the reaction of various carboxylic acids and sodium borohydride, underwent reduction to the corresponding alcohols readily by the addition of dimethyl sulfate or Lewis acids, such as boron trifluoride etherate and triphenyl borate, presumably through acyloxyboranes. By utilizing this procedure, aliphatic and aromatic acids are rapidly and quantitatively reduced to the corresponding alcohols in terahydrofuran either at room temperature (or at $65^{\circ}$). This procedure provides selective reduction of carboxylic acids in the presence of halogen, nitro, and heterocyclic rings such as furan and thiophene.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4757-4761
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• 2012

LED chip on board(COB) package has been fabricated using aluminum substrate and aluminum anodization process. An alumina layer, used as a dielectric in COB substrate, is produced on aluminum substrate by selective anodization process. Also, selective anodization process makes it possible to construct a thermal via with a fully-filled via hole. Two types of the COB package are fabricated in order to analyze the effects of their substrate types on thermal resistivity and luminous efficiency. The aluminum substrate with the thermal via shows more improved measurement results compared with the alumina substrate. These results demonstrate that selective anodization process and thermal via can increase heat dissipation of COB package in this work. In addition, it is proved experimentally that these parameters also can be enhanced using efficient layout of multiple chip in the COB package.