• Polymer(Korea)
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• v.39 no.2
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• pp.346-352
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• 2015

Polyalphaolefin (PAO) is a synthetic lubricant that is superior to mineral-based lubricants in the terms of physical and chemical characteristics such as low pour point, high viscosity index (VI), and thermal and oxidation stability. Several kinds of PAOs have been synthesized by using 1-pentene, 1-hexene, 1-octene, or 1-dodecene as monomer with three kinds of aluminum-based Lewis acid catalysts via cationic polymerization. The control of the catalytic performance and physical properties of PAO such like molecular weight, kinematic viscosity, pour point, and viscosity index was done by changing polymerization parameters. The alkyl aluminum halide-based catalysts show better catalytic activity than that of the conventional $AlCl_3$ catalyst. The microstructure of PAO was investigated by means of TOF-MS (time of flightmass spectroscopy) analysis in order to elucidate the correlation between the performances of the lubricant (VI, pour point) and the molecular structure of PAO. The VI of PAO increases with increases in the carbon number of ${\alpha}$-olefin. In other words, the performances of PAO as a lubricant strongly depended on the branch length of PAO.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.2
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• pp.47-54
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• 2016

This study aims to analyze the accuracy for feasibility study of Network-RTK(VRS) surveying inside and outside of Korean CORS network. The southwest coast of Korea where some part of mainland and islands are outside of CORS network is chosen as the test area. To evaluate the accuracy of VRS surveying at surveying points, several Unified Control Points (UCPs) inside and outside of Korean CORS network were selected as the points in the test area. The feasibility of VRS surveying was analyzed by investigating the errors related to the location of points inside and outside of CORS network and the difference of 3-dimensional coordinates observed on different date. As the results of this study, the orthometric height errors of points outside of CORS network based on KNGeoid14 were improved about 5.0 cm in RMSE in comparison with KNGeoid13. The height errors of VRS surveying were considered to be less relevant to the results from PDOP and number of satellites (GPS and GLONASS). However, the orthometric errors caused by the geoidal height of KNGeoid and the ellipsoidal height of VRS surveying at points located outside of CORS network need to be addressed carefully for control surveying. When a point surveyed twice on different date, the difference of the ellipsoidal height of the point outside of CORS network was larger than that of the point inside of CORS network.

• Journal of IKEEE
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• v.25 no.1
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• pp.174-179
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• 2021

An Edwards curve cryptography (EdCC) core supporting point scalar multiplication (PSM) on Edwards curves of Edwards25519 and Edwards448 was designed. For area-efficient implementation, finite field multiplier based on word-based Montgomery multiplication algorithm was designed, and the extended twisted Edwards coordinates system was adopted to implement point operations without division operation. As a result of synthesizing the EdCC core with 100 MHz clock, it was implemented with 24,073 equivalent gates and 11 kbits RAM, and the maximum operating frequency was estimated to be 285 MHz. The evaluation results show that the EdCC core can compute 299 and 66 PSMs per second on Edwards25519 and Edwards448 curves, respectively. Compared to the ECC core with similar structure, the number of clock cycles required for 256-bit PSM was reduced by about 60%, resulting in 7.3 times improvement in computational performance.

• Journal of the Korean Institute of Rural Architecture
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• v.23 no.4
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• pp.1-12
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• 2021

Recently, the use of unmanned aerial vehicles (UAVs) is increasing in the field of land information acquisition and terrain exploration through high-altitude aerial photography. High-altitude aerial photography is suitable for large-scale geographic information collection, but has the disadvantage that it is difficult to accurately collect small-scale geographic information. Therefore, this study used low-altitude UAV to monitor changes in small rural spaces around rural resources, and the results are as follows. First, the low-altitude aerial imagery had a very high spatial resolution, so it was effective in reading and analyzing topographic features. Second, an area with a large number of aerial images and a complex topography had a large amount of point clouds to be extracted, and the number of point clouds affects the three-dimensional quality of rural space. Third, 3D mapping technology using point cloud is effective for monitoring rural space and rural resources because it enables observation and comparison of parts that cannot be read from general aerial images. In this study, the possibility of rural space analysis of low-altitude UAV was verified through aerial photography and analysis, and the effect of 3D mapping on rural space monitoring was visually analyzed. If data acquired by low-altitude UAV are used in various forms such as GIS analysis and topographic map production it is expected to be used as basic data for rural planning to maintain and preserve the rural environment.

• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.172-178
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• 2023

When the mobile device moves from the coverage of one access point to the radio coverage of another access point it needs to maintain its connection with the current access point before it successfully discovers the new access point, this process is known as handoff. During handoff the acceptable delay a voice over IP application can bear is of 50ms whereas the delay on medium access control layer is high enough that goes up to 350-500ms. This research provides a suitable methodology on medium access control layer of the IEEE 802.11 network. The medium access control layer comprises of three phases, namely discovery, reauthentication and re-association. The discovery phase on medium access control layer takes up to 90% of the total handoff latency. The objective is to effectively reduce the delay for discovery phase to ensure a seamless handoff. The research proposes a scheme that reduces the handoff latency effectively by scanning channels prior to the actual handoff process starts and scans only the neighboring access points. Further, the proposed scheme enables the mobile device to scan first the channel on which it is currently operating so that the mobile device has to perform minimum number of channel switches. The results show that the mobile device finds out the new potential access point prior to the handoff execution hence the delay during discovery of a new access point is minimized effectively.

• Archives of Pharmacal Research
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• v.4 no.1
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• pp.43-51
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• 1981

The effect of some alcohols on the riboflavin derivatives in non-polar solvent was studied by various spectroscopic method in order to support the view point that alcohol may directly interect with the isoalloxazine moiety of FAD, the coenzyme of D-amino-acid oxidase. The most possible association complex between alcohol and riboflavin is the 1:1 complex through the 2-C carbonyl function of the isollaxazine ring nd the hydroxyl proton of alcohol. It is appeared that methanol has a larger association constant than any other alcohols, and the association constant decreases with the carbon number increases and being bulkier in the alkyl group of alcohols.

• ETRI Journal
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• v.35 no.3
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• pp.469-479
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• 2013

This paper proposes an efficient computation-aware mode decision and search point (SP) allocation algorithm for spatial and quality scalabilities in Scalable Video Coding. In our proposal, a linear model is derived to allocate the computation for macroblocks in enhancement layers by using the rate distortion costs of the base layer. In addition, an adaptive SP decision algorithm is proposed to decide the number of SPs for motion estimation under the constraint of the allocated computation. Experiment results demonstrate that the proposed algorithm allocates the computation resource efficiently and outperforms other works in rate distortion performance under the same computational availability constraint.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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• pp.156-159
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• 1993

In this paper, computerized BEAM (brain electrical activity map) was implemented for objective and quantitative multichannel EEG analysis. BEAM is calculated by 4 point Interpolation method and number of elements are 5140. Representation methods of BEAH are two. One is dot density method which classify brain electrical potential 9 levels by dot density and the other is color method which classify brain electrical 12 levers by different colors. In this BEAM, instantaneous change and average energy distribution over any arbitrary time interval of brain electrical activity could be observed and analyzed easily.

• Journal of the Korean Wood Science and Technology
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• v.18 no.3
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• pp.26-33
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• 1990

To study the wood quality factors of Populus nigra $\times$ maxmowiczii known a rapidly growing species, the variations of green moisture contents, bulk density, wood fibre dimensions, microfibril angles, and number of leaf knot in stem wood were investigated. The heartwood contained a higher moisture content than the corresponding sapwood. Bulk density in radial patterns variations decrease outward from the pith, then increase toward the bark. The wood-fiber length and diameters had somewhat smaller values than on Populus alba $\times$ glandulosa or Populus euramericana. The microfibril angles decreased rapidly toward the outside, and their mean values were about 16 degree. The grain angles run nearly parallel to the cell axies. Number of leaf knot showed a fluctural change above ground level to a point near the base of the crown and then increased rapidly to the top of tree and average number of leaf knot varied exclusively from tree to tree.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.5
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• pp.19-32
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• 2012

The purpose of this study is to quantitatively measure the view target and the view area through the selection of landscape control point by selecting Jimyeong-dong Dong-gu and Yeongyeong-dong Buk-gu Daegu, which are planned as the large scale housing complex development area, as the target places. It is very meaningful that from the simulation based on this measurement, the improvement methods are attempted to be suggested at the project level. The results of this study are as follows. First, the total number of viewing targets derived from the literature analysis for the selection of the viewing targets was 24, and finally derived main viewing targets were 4 places. Second, the total number of selection criteria of the derived landscape control point was 15, and these were re-categorized as prospect, accessibility and publicness according to the common property. The preliminary LCPs were selected by measuring the publicness and accessibility, and because of the said measurement, a total of 43 preliminary LCPs were selected. The final LCPs were selected by estimating the prospect of the selected preliminary LCPs, and as a result of estimation, a total of 29 final LCPs were selected. Finally, the total number of evaluation indicators derived from literature analysis was 26. Because of the valuation by the landscape control point, it was found that the 2 view areas were the I grade, 3 areas were II grade and 3 areas were the V grade, the lowest grade among 29 view areas. From the analysis on problems for the improvement methods, 4 improvement-indicators including the diversity of land mosaic were selected for the view area-1 without considering the development project drawing. In addition, for the view area-2 with considering the development project drawing, the landscape as the scenery forests was well formed, and the arrangement of architectures for the security of view corridor was right angle arrangement, and their floor number was 10.