• Membrane Journal
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• v.16 no.4
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• pp.303-312
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• 2006

The asymmetric hybrid membranes of polyethersulfone (PES) and $ZrO_2$ nanoparticles were prepared via new one-step procedure combining simultaneously the phase-inversion method and the sol-gel technique. The optimum contents of $Zr(PrO)_4\;and\;HNO_3$ catalyst were determined by the adsorption experiments of phosphate anion onto the resulting hybrid membranes. The maximum adsorption of phosphate anion is obtained at the conditions of 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES and 30 mL $HNO_3$ addition per 1 mL $Zr(PrO)_4$. Variation of morphology, performance and incorporated $ZrO_2$ amount of the resulting hybrid membranes were discussed and determined using SEM, pure water flux, TGA, ICP, XRD and contact angle measurements. Increasing $Zr(PrO)_4$ addition into casting solution, pure water flux is increased and $ZrO_2$ amount in the hybrid membrane is maximized at the conditions 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES. The prephosphatation of PES-$ZrO_2$ hybrid membrane was studied to modify the surface characteristics of membrane. Ultrafiltration of bovine serum albumin (BSA) solution was performed in a dead-end cell using both a bare (non-phosphated) and a phosphated hybrid membrane. It is revealed that both the permeate flux and BSA rejection were increased as about 40% by prephosphatation of hybrid membrane. These results may be explained on the basis of the increase of membrane hydrophilicity, which was determined from contact angle measurements.

• Radiation Oncology Journal
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• v.7 no.2
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• pp.305-311
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• 1989

Fletcher-Suit colpostat has an internal structure to reduce dose to bladder and rectum. Some programs were developed to calculate dose at any point in water in three dimension around the colpostat containing Cs-137 tube, to find the shielding effect to dose by the internal structure, and to draw isodose curves and iso-shielding effect curves. Computer was an IBM compatible AT with EGA card and language was MS-Basic V6.0, Material, shape and geometry of the strucure, tube and colpostat were considered in algorithm for calculation of dose. Dose rates per unit mg. Ra. eq. in water calculated by a program were stored in auxiliary memory devices and retrieved in another programs. Isodose curves on medial side shrinked. Dose distribution was not symmetric about a transverse axis bisecting the colpostat. Reduction of dose was more excessive on top side than on bottom. Iso-shielding effect curve showed that the shielding effect was higher on top side than on bottom, and that there was shielding effect over almost all area of medial side. Such results were related to both shifted position of tube in the colpostat and asymmetric distribution of active source in the tube. Maximum of shielding effect was $49\%$ on top side and $44\%$ on bottom side. The direction of iso-shielding effect curve was generally radial from the center of active source. In treatment planning using Fletcher-Suit colpostat, the internal structure should be considered to find precise doses to bladder and rectum, etc.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.165-165
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• 2010

$1.55\;{\mu}m$ 대역의 레이저 다이오드를 제작하기 위해, InP(001) 기판에 InAlGaAs 물질을 장벽층으로 하는 InAs 양자점 구조를 분자선증착기 (MBE)를 이용하여 성장하고 구조 및 광학적 특성을 Double Crystal X-ray Diffraction (DCXRD), Atomic Force Microscopy (AFM), Photoluminescence (PL)을 이용하여 평가하였다. 일반적으로 InAlGaAs 물질은 고유한 상분리 현상 (Phase Separation)이 나타나는 특성이 있으며, 이는 양자점 성장에 중요한 요인으로 작용할 수 있다. 이러한 InAlGaAs 물질의 상분리 현상을 기판온도 ($540^{\circ}C$, $555^{\circ}C$, $570^{\circ}C$)를 비롯한 성장변수를 변화시켜 제어하고 InAs 양자점 형성에 어떠한 영향을 미치는지를 분석하였다. 540의 성장온도에서 InP(001) 기판에 격자정합한 InAlGaAs 장벽층이 성장온도를 $570^{\circ}C$로 증가시킬 경우 기판에 대하여 인장 응력 (Tensile Strain)을 받는 구조로 변화되었다. 인장응력을 받는 InAlGaAs 장벽층을 Ga Flux 양을 조절하여 격자정합한 InAlGaAs 층을 형성할 수 있었다. AFM을 통한 표면 형상 분석 결과, 서로 다른 기판온도에서 성장한 InAlGaAs 물질이 InP(001) 기판에 격자정합 조건일지라도 표면의 거칠기 (Surface Roughness)는 매우 다른 양상을 보였고 InAs 양자점 형성에 직접적으로 영향을 주었다. $570^{\circ}C$에서 성장한 InAlGaAs 위에 형성한 InAs 양자점의 가로방향 크기를 세로방향 크기로 나눈 비율이 1.03으로서, 555와 $540^{\circ}C$의 1.375 와 1.636와 비교할 때 모양 대칭성이 현저히 개선된 것을 알 수 있다. 상분리 현상이 줄어 표면 거칠기가 좋은 InAlGaAs 위에 양자점을 형성할 때 원자들의 이동도가 상대적으로 높아 InAs 양자점의 크기가 증가하고, 밀도가 감소하는 현상이 나타났다. 또한 InAlGaAs 장벽층이 InP(001) 기판을 기준으로 응력 (Compressive 또는 Tensile)이 존재하는 경우, InAs 양자점 모양이 격자정합 조건 보다 비대칭적으로 변하는 특성을 보여 주었다. 이로부터, 대칭성이 개선된 InAs 양자점 형성에 InAlGaAs 장벽층의 표면 거칠기와 응력이 중요한 변수로 작용함을 확인 할 수 있었다. PL 측정 결과, 발광파장은 $1.61\;{\mu}m$로 InAs 양자구조 형상에 따라 광강도 (Intensity), 반치폭 (Line-width broadening) 등이 변화 되었다.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.63-68
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• 2009

Purpose: TiN films were deposited on sus304 by unbalanced magnetron sputtering system which was designed and developed as unbalancing the strength of the magnets in the magnetron electrode. The effect of oxygen incorporation in the fabrication of deposited films was investigated. Methods: The cross sections of deposited films on Silicon wafer were observed by SEM to measure the thickness of the films, the components of the surface of the films were identified by XPS survey spectra, the compositional depth-profile of deposited films was examined by an XPS apparatus. Results: From the data of XPS depth profile of films, it could be seen that the element O as well as the elements Ti and N present in the surface of the film and the relative percentage of the element O was constant at 65 at.% with respect to the depth of film. Conclusions: The color change with thickness of the films had something to do with the change of Ti $ 2p_{3/2}$ peak intensity and shape mixed of $ TiO_2$, TiN, $ TiO_{x}N_{y}$ compound.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.57-62
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• 2009

Purpose: TiN films were deposited on sus304 by unbalanced magnetron sputtering system which was designed and developed as unbalancing the strength of the magnets in the magnetron electrode. The color and hardness of deposited TiN films was investigated. Methods: The cross sections of deposited films on silicon wafer were observed by SEM to measure the thickness of the films, the components of the surface of the films were identified by XPS, the components of the inner parts of the films were observed by XPS depth profiling. XPS high resolution scans and curve fittings of deposited films were performed for quantitative chemical analysis, Vickers micro hardness measurements of deposited films were performed with a nano indenter equipment. Results: The colors of deposited films gradually changed from light gold to dark gold, light violet, and indigo color with increasing of the thickness. It could be seen that the color change come from the composite change of three compound,$TiO_{x}N_{y}$, $TiO_2$, TiN. Especially, the composite change of$TiO_{x}N_{y}$ compound was thought to affect the color change with respect to thickness. Conclusions: Deposited films had lower than the value of general TiN film in Vickers hardness, which was caused by mixing three TiN, $TiO_2$,$TiO_{x}N_{y}$ compound in the deposited films. The increasing and decreasing of micro hardness with respect to thickness was thought to have something to do with the composite of TiN in the films.

• Journal of Internet Computing and Services
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• v.16 no.5
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• pp.19-27
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• 2015

Due to the advantages of fast read/write operation and low power consumption, SSD(Solid State Drive) is now widely adopted as storage device of smart phone, laptop computer, server, etc. However, the shortcomings of SSD such as limited number of write operations and asymmetric read/write operation lead to the problem of shortened life span of SSD. Therefore, the block replacement policy of SSD used as cache for HDD is very important. The existing solutions for improving the lifespan of SSD including the LARC scheme typically employ the LRU algorithm to manage the SSD blocks, which may increase the miss rate in SSD due to the replacement of frequently used block instead of rarely used block. In this paper we propose a novel block replacement scheme which considers the block reuse interval to effectively handle various data read/write patterns. The proposed scheme replaces the block in SSD based on the recency decided by reuse interval and age along with hit ratio. Computer simulation using workload trace files reveals that the proposed scheme consistently improves the performance and lifespan of SSD by increasing the hit ratio and decreasing the number of write operations compared to the existing schemes including LARC.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.274-280
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• 2014

Polysulfone (PSf) hollow fiber membranes were prepared via the nonsolvent induced phase separation technique. The cosolvent of ${\gamma}$-butyrolactone (GBL) was added to the polymer solution containing a mixture of PSf and N,N-dimethylacetamide (DMAc). Water was utilized as a precipitation nonsolvent. The morphology of prepared membranes was investigated using a field emission scanning electron microscopy. The fabricated membrane showed a typical asymmetric structure such as the dense layer on the porous support layer by the addition of GBL to the polymer solution. As the concentration of GBL increased, the asymmetric porous structure was shown to be more intensified. It was thought that the added GBL played a role of enhancing the liquid-liquid phase separation of the polymer solution, since the cosolvent of GBL might change the thermodynamic solubility parameter of the doping solution. Permeation properties through the prepared hollow fiber membranes were characterized by measuring the pure water flux and the solute rejection using $0.05{\mu}m$ polystyrene latex (PSL) beads. Experimental results revealed that the use of PEG as the internal coagulant enhanced the pure water flux up to 130 times compared to the use of EG while the rejection of the PSL beads decreased only 5%.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.4
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• pp.444-451
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• 1999

The effect of individual density on the growth and survival of Laminaria japonica was experimentally evaluated. Four density treatments of young sporophytes (0.63 cm In maximum length) grown in the laboratory were transplanted to the southeastern coast of Korea and their survivorship and growth rate were measured twice a month from January to July, 1996. Plants showed higher survivorship at low density. Final densities at three lowest densities were similar, ranging from 34 to 38 inds${\cdot}100 cm^{-2}$. Planis at the highest density, however, suffered greater decline than at lower densities, and only 21 plants remained at the end of this study. Mean frond size (length and width) fluctuated throughout the study period at four densities. During the first two mouths after outplanting, mean frond size was negatively correlated with initial density, However, the size was density independent after three months. As stand density increased, size-frequency distribution through time tended to be more positively skewed. The 10 largest plants grew faster in frond size and attained larger size in the lower density. There was a positive relationship between plant size and relative growth rate (or survival). The slope of yield-density (Y-D) relationships at four densities ranged from -0.060 to -0.137. The study suggests that density can strongly affect the survival and growth of this alga. The density-dependent survival and growth patterns, however, were not strictly consistent with those of terrestrial plants.

• Journal of KIISE:Information Networking
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• v.27 no.3
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• pp.348-359
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• 2000

Most of the important real time multimedia applications require multipoint transmissions. To support these applications in ATM based Intermet environments, it is important to provide efficient IP multicast transportations over ATM networks. IETF proposed MARS(Multicast Address Resolution Server) as the service architecture to transport connectionless IP multicast flows over connection oriented ATM VCs. MARS assumes UNI3.0/3.1 signalling. Since UNI3.0/3.1 does not provide any means for receivers to request a join for a multicast ATM VC, MARS provides overlay service to relay join request from IP multicast group members to the sources of the multicast group. Later on, ATM Forum standardized UNI4.0 signalling which is provisioned with a new signalling mechanism called LIJ(Leaf Initiated Join). LIJ enables receivers to directly signal the source of an ATM VC to join. In this paper, we propose a new service architecture providing IP multicast flow transportation over ATM networks deploying UNI4.0 signalling. The proposed architecture is named UNI4MARS. It comprises service components same as those of the MARS. The main functionality provided by the UNI4MARS is to provide source information to the receivers so that the receivers may exploit LIJ to join multicast ATM VCs dynamically. The implementation overhead of UNI4MARS and that of MARS are compared by a course of simulations. The simulation results show that the UNI4MARS supports the dynamic IP multicast group changes more efficiently with respect to processing, memory and bandwidth overhead.

• Journal of Korean Society of Forest Science
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• v.73 no.1
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• pp.21-32
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• 1986

This study was done to classify 15 species in the genus Acer through tracking of the changing shape of the vascular branch from the base part to the terminal part of petiole by the anatomical method. The basic vascular branches were 3 ea, except A. mandshuricum 3-4 ea. The vascular bundle was separated, moved and connected from the base part to the terminal part of petiol, the number of separated vascular branch was 11-32 ea., the number of connected vascular branch was 0-17 ea., and the ratio of the separated vascular branch to the connected was 0.00-8.00. The maximum number of vascular branch in No, 39 of cross section part was observed in 12 species; A. ginnala and A. buergerianum were No. 11, A. truncatum and A. platanoides were No. 13, A. saccharium was No. 26. The number of the connected vascular branches with the main vascular branch were 0-6, while the number of the separated vascular branch were 0-7. On the ratio of separation to connection of the base vascular branch; "A", "B" and "C", the symmetrical shapes on the basis of "B" were A>BC, AB>C shape. The classical groups by the development of main vascular branch formation were obtained 7 groups of "a" through "g" shape. Especially, A. negundo and A. saccharinum were shown to have central vascular branches with unique changing patterns.