• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.174-181
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• 2007

In this study, $SiO_2/poly(ethylene-co-vinyl$ alcohol)(EVOH) hybrid coating materials with gas barrier property could be produced using sol-gel method. The biaxially oriented polypropylene (BOPP) substrate with surface pretreatment was coated with the prepared hybrid sols containing various inorganic silicate component by a spin coating method. Crystallization behavior of the hybrids was investigated in terms of analysis of X-ray diffraction and cooling thermogram from DSC experiment. From the morphological observation of the $SiO_2/EVOH$ hybrid gel, it was confirmed that there existed an optimum content of inorganic silicate precursor, Tetraethylorthosilicate (TEOS), to produce hybrid materials with dense microstructure, exhibiting uniformly dispersed silica particles with average size below 100 nm. When TEOS was added at below or above the optimum content, particle clusters with large domain were observed, resulting in phase separation. This morphological result was found to be in good agreement with that of oxygen permeability of the hybrid coated films. In the case of film coated with hybrid prepared from addition of 0.01 - 0.02mol of TEOS, a remarkable improvement in barrier property could be obtained, however, with the addition of TEOS more than 0.04 mol, the barrier property was dramatically reduced because of phase separation and micro-crack formation on the film surface.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.101-112
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• 1995

In order to construct a feature map-based phoneme classification system for speech recognition, two procedures are usually required. One is clustering and the other is labeling. In this paper, we present a phoneme classification system based on the Kohonen's Self-Organizing Feature Map (SOFM) for clusterer and labeler. It is known that the SOFM performs self-organizing process by which optimal local topographical mapping of the signal space and yields a reasonably high accuracy in recognition tasks. Consequently, SOFM can effectively be applied to the recognition of phonemes. Besides to improve the performance of the phoneme classification system, we propose the learning algorithm combined with the classical K-mans clustering algorithm in fine-tuning stage. In order to evaluate the performance of the proposed phoneme classification algorithm, we first use totaly 43 phonemes which construct six intra-class feature maps for six different phoneme classes. From the speaker-dependent phoneme classification tests using these six feature maps, we obtain recognition rate of $87.2\%$ and confirm that the proposed algorithm is an efficient method for improvement of recognition performance and convergence speed.

• Journal of Korea Spatial Information System Society
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• v.8 no.2 s.17
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• pp.91-107
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• 2006

To handling the extreme situation that must manage positional information of a very large volume, at least millions of moving objects. A cluster-based sealable distributed computing system architecture, called the GALIS which consists of multiple data processors, each dedicated to keeping records relevant to a different geographical zone and a different time zone, was proposed. In this paper, we proposed a valid time management and time-zone shifting scheme, which are essential in realizing the long-term location data subsystem of GALIS, but missed in our previous prototype development. We explain how to manage valid time of moving objects to avoid ambiguity of location information. We also describe time-zone shifting algorithm with three variations, such as Real Time-Time Zone Shifting, Batch-Time Zone Shifting, Table Partitioned Batch-Time Zone Shifting, Through experiments related with query processing time and CPU utilization, we show the efficiency of the proposed time-zone shifting schemes.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.176-183
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• 2016

This study relates to a polymer electrolyte membrane for improved performance fuel cell, were researched with respect to properties required for driving a fuel cell. The bis(4-fluorophenyl)phenyl phosphine oxide was sulfonated using fuming sulfuric acid. Synthetic hydrophilic oligomer and the hydrophobic oligomer and the block copolymers were prepared via aromatic nucleophilic substitution polycondensation. A block copolymer structure and degree of sulfonation was analyzed by $^1H$-NMR and gel permeation chromatography(GPC) analysis. Thermal stability was confirmed by thermogravimetric analysis(TGA), block copolymer was stable at high temperature(>$200^{\circ}C$), The ion conductivity was measured in order to demonstrate the performance of fuel cell. Synthesis membrane was the increase of temperature was improved conductivity up to 58 mS/cm due to the influence of the developed ion clusters. The phase separation of the polymer was observed to make AFM analysis.

• 대한공업교육학회지
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• v.34 no.1
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• pp.19-43
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• 2009

An ideology what a modern society seeks is lifelong employment through lifelong learning. The single word which draws the attainment is lifelong vocational competency development. This study is designed for exploring its possibility and limit of a redesign of it, and tries to propose efficiently a redesign idea of a vocational educational path. To this end, it was analyzed by a subject for a national human resource foundation plan and a lifelong bocational competency development foundation plan. In addition to that, it was covered a structure and content analysis of main laws and regulations which are a base of policy making. An educational path could be divided into an area of formal education system, an area of workplace for labors, and an area of lifelong vocational competency development. And the insights were drawn by pulling apart an operational situation of main organizations and a recurrent process of the educational path. The redesign plan of a vocational education path we did analyze to activate lifelong vocational competency development system is deduced as following. Firstly, it should be re-organized with a direction towards an effective manpower training to be linked with skills and demands required by an industry. Secondly, it should be generalized for a model of recurrence between work and learning and its alternation for lifelong vocational competency development. Thirdly, it should create a cluster in the region for lifelong vocational competency development so that it is to form an efficient network to have a division of labor and its liaison with cooperative relationship.

• Polymer(Korea)
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• v.24 no.6
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• pp.886-892
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• 2000

Poly(4-vinyl phenol) (PVPh) was neutralized by LiOH and PVPh ionomers (PVPh-Li) with different Li neutralization extents were synthesized. The variation in $T_{g}$ with Li neutralization was determined by DSC and the results show that the $T_{g}$ increases by 3.$8^{\circ}C$ per Li mol%. When comparing this result with the 3.$2^{\circ}C$ per Na mol% reported for poly (styrene-co-hydroxy styrene), the greater value for PVPh-Li may be due to a strong interaction between unneutralized free -OH and -OLi produced. No distinct small angle X-ray scattering (SAXS) peak was observed for these PVPh ionomers in bulk. In the 50/50 blend of PVPh-Li with PVPh, the miscibile blend was obtained when the Li neutralization in PVPh-Li was 10 mol%. On the contrary, the 50/50 PVPh-Li/PMMA was immiscible when the Li neutralization was 5 mol%. It can be concluded that, even if the starting blend is miscible owing to hydrogen bonding, the miscibility of blend becomes diminished by introducing small amount of ion groups into one of the constituent polymers and the blend can be immiscible as long as any new strong intermolecular ion-dipole interaction is not generated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.277-288
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• 2013

3GPP LTE-Advanced (Third Generation Partnership Project Long Term Evolution-Advanced) as a next generation mobile communication standard introduced small base stations such as femto cells or pico cells, and D2D (Device-to-Device) communications between mobiles in the proximity in order to satisfy the needs of rapidly growing wireless data traffic. A diverse range of topics has been studied to solve various interference situations which may occur within a single cell. In particular, an introduction of a small base station along with D2D communication raises important issues of how to increase the channel capacity and frequency efficiency in HetNets (Heterogeneous Networks). To this end, we propose in this paper methods to manage the interference between the macro cell and other small cells in the HetNet to improve the frequency efficiency. The proposed CCN (Cluster Coordinator Node)-assisted ICI (Inter-Cell Interference) avoidance methods exploit the CCN to control the interference in HetNet comprising of an MeNB (Macro enhanced Node-B) and a large number of small cells. A CCN which is located at the center of a number of small cells serves to avoid the interference between macro cell and small cells. We propose methods of resource allocation to avoid ICI for user equipments within the CCN coverage, and evaluate their performance through system-level computer simulations.

• Journal of Internet Computing and Services
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• v.10 no.4
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• pp.87-103
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• 2009

Grid computing is an expanded technology of distributed computing technology to use low-cost and high-performance computing power in various fields. Although the purpose of Grid computing focuses on large-scale resource sharing, innovative applications, and in some case, high-performance orientation, it has been used as conventional distributed computing environment like clustered computer until now because Grid middleware does not have common sharable information system. In order to use Grid computing environment efficiently which consists of various Grid middlewares, it is necessary to have application-independent information system which can share information description and services, and expand them easily. Thus, in this paper, we propose a semantic information system framework based on web services and ontology for Grid computing environment, called WebSIS. It makes application and middleware developer easy to build sharable and extensible information system which is easy to share information description and can provide ontology based platform-independent information services. We present efficient ontology based information system architecture through WebSIS. Discovering appropriate resource for task execution on Grid needs more high-level information processing because Grid computing environment is more complex than other traditional distributed computing environments and has various considerations which are needed for Grid task execution. Thus, we design and implement resource information system and services by using WebSIS which enables high-level information processing by ontology reasoning and semantic-matching, for automation of task execution on Grid.

• Journal of Korea Spatial Information System Society
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• v.7 no.3 s.15
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• pp.119-130
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• 2005

A spatial data warehouse is a system that stores geographical information as a subject oriented, integrated, time-variant, non-volatile collection for efficiently supporting decision. This system consists of a builder and a spatial data warehouse server. A spatial data warehouse server suspends user services, stores transferred data in the data repository and constructs index using stored data for short response time. Existing methods that construct index are bulk-insertion and index transfer methods. The Bulk-insertion method has high clustering cost for constructing index and searching cost. The Index transfer method has improper for the index reconstruction method of a spatial data warehouse where periodic source data are inserted. In this paper, the efficient index reconstruction method using a partial index in a spatial data warehouse is proposed. This method is an efficient reconstruction method that transfers a partial index and stores a partial index with expecting physical location. This method clusters a spatial data making it suitable to construct index and change treated clusters to a partial index and transfers pages that store a partial index. A spatial data warehouse server reserves sequent physical space of a disk and stores a partial index in the reserved space. Through inserting a partial index into constructed index in a spatial data warehouse server, searching, splitting, remodifing costs are reduced to the minimum.

• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.377-382
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• 2012

CdS thin films have been widely used as a buffer layer of CIGS semiconductor solar cells to reduce the lattice mismatch between transparent electrode and absorber layer. In order to prepare the CdS films with high transparency and low resistivity, they were deposited by varying Cd concentration with the constant S concentration in the solution using chemical bath deposition method. They were analyzed in terms of structural, optical and electrical properties of CdS films according to the $[S^{2-}]/[Cd^{2+}]$ ratio. In the case of Cd concentration higher than S concectration, CdS thin films were formed mainly by cluster- by-cluster formation due to the homogeneous reaction between Cd and S in the solution. Therefore the grain size increased and the transmittance decreased. On the other hand, in the case of Cd concentration lower than S concentration, CdS films were formed by heterogeneous reaction on the substrate rather than in the solution. The CdS films have the grains with the uniform circular shape of a few hundreds ${\AA}$. As the Cd concentration increased in the solution, the $[S^{2-}]/[Cd^{2+}]$ ratio decreased and the resistivity decreased by the increase in the carrier concentration due to the formation S vacancy by the excess Cd.