• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.1023-1032
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• 2004

It is generally known that handoff delay degrades the QoS by packet drop, packet delay and jitter. Moreover. handoff highly effects on QoS in beyond 3G system because not only micro cells for achieving high capacity and fast moving nodes induce the frequent handoff but also hard handoff must be carried out in OFDM system. Therefore, study on a handoff algorithm for guaranteeing QoS is required. Related works on handoff for beyond 3G system mainly focused on reducing the L3 handoff delay or packet loss. That is, these schemes try to compensate L2 delay rather directly eliminate it. However, remained 1.2 delay degrades QoS, especially delay-sensitive realtime traffic. Therefore, we proposed the seamless handoff algorithmwhich can minimize the L2 handoff delay.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.640-645
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• 2010

This paper describes the power generating property of hydrothermally grown ZnO nanorods on a flexible polyethersulfone (PES) substrate. The piezoelectric currents generated by the ZnO nanorods were measured when bending the ZnO nanorod by using I-AFM, and the measured piezoelectric currents ranged from 60 to 100 pA. When the PtIr coated tip bends a ZnO nanorod, piezoelectrical asymmetric potential is created on the nanorod surface. The Schottky barrier at the ZnO-metal interface accumulates elecntrons and then release very quickly generating the currents when the tip moves from tensile to compressed part of ZnO nanorod. These ZnO nanorods were grown almost vertically with the length of 300-500 nm and the diameter of 30-60 nm on the Ag/Ti/PES substrate at $90^{\circ}C$ for 6 hours by hydrothermal method. The metal-semiconductor interface property was evaluated by using a HP 4145B Semiconductor Parameter Analyzer and the piezoelectric effect of the ZnO nanorods were evaluated by using an I-AFM. From the measured I-V characteristics, it was observed that ZnO-Ag and ZnO-Au metal-semiconductor interfaces showed an ohmic and a Schottky contact characteristics, respectively. ANSYS finite element simulation was performed in order to understand the power generation mechanism of the ZnO nanorods under applied external stress theoretically.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.309-317
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• 2011

Research on elderly suicide has increased since 2000. It indicates that elderly suicide is receiving a great attention as a part of elderly problems, and policy efforts are needed. However, most of existing research on elderly suicide focused on factors of elderly suicide. Therefore discussion about suicidal prevention measures is staying on general and suggestive level. As a result, this study is trying to seek effective prevention strategies of elderly suicide through systematic analysis of suicidal factors and sporadic policy proposals presented in existing research. To achieve this, the relevant research papers among academic journals registered with Korea Research Foundation are analyzed. According to the results, while the ordinary elderly tended to require macro level of intervention, the potential-risky elderly were inclined to need all of micro and moderate level of prevention efforts. Above all, secondary prevention must be more emphasized in moderate level. In the future direction of research, based on prevention strategies as stated above, it is recommended to entail discussion of what kind of a specific program and policy should be invented and how it should be operated.

• Composites Research
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• v.17 no.3
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• pp.1-7
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• 2004

In the vacuum assisted RTM (VARTM) process that has become the center of attention for manufacturing massive composite structures, a good evacuation of air in the fiber preform is recognized as the prime factor. The microvoids, or the dry spots, are formed as a result of improper gate/vent locations and the mold geometry. The non-uniform resin velocity at the flow front leads to the formation of microvoids in the fibers, whereas the air in the microvoids can migrate along with the resin flow during mold filling. The residual air in the internal voids of a composite structure may cause a degradation of the mechanical properties as well as the structural failure. In this study, a unified macro- and micro analysis methods were developed to investigate the formation and transport of air in resin during VARTM process. A numerical simulation program was developed to analyze the three-dimensional flow pattern as well as the macro- and microscopic distribution of air in a composite part fabricated by VARTM process.

• The Journal of Korean Society of Virology
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• v.30 no.1
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• pp.83-99
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• 2000

A defective HIV-1 helper virus DNA, pHyPC, was assembled by deleting the RNA packaging signal, env, nef and the 3'LTR sequences. HIV-1 like virus particles that carry the HIV-1 receptor, CD4 were generated by co expression of pHyPC and plasmid DNAs encoding different chimeric CD4 proteins. The CD4 particles, sharing the CD4 ectodomain, precisely fused to different membrane anchors. CD4(+) particles specifically bound to HIV-1 Env expressing cells, but any signs of infection into these cells were not detected. Binding was only partially blocked by either polyclonal anti-CD4 antibodies or by high concentrations of soluble CD4. Surprisingly, CD4(+) particles also adsorbed to HeLa, CHO, NIH3T3 and COS-7 cells in the absence of HIV-1 Env expression. Adsorption was comparable in strength and speed to the highly specific CD4-Env interaction. CD4(-) particles exhibited only background levels of binding. Cell binding was CD4. dependent, but it was independent of the cell type from which the CD4(+) particles originated. Interestingly, CD4-dependent/Env-independent binding was only found when CD4 was present on virus particles. This suggests that the micro-environment of CD4 on virus particles uniquely expose this new cell binding activity. Its high affinity could explain in part why infection of Env(+) cells by CD4(+) particles was not detected. Further experiments will be required to evaluate whether this strong membrane interaction could represent one step in the multiple-step viral entry process.

• 보존과학연구
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• s.24
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• pp.187-213
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• 2003

Sungseonsa Temple site in Chungju city in Chungcheongbuk-doProvince is written in "Goryeosa" as a building for Queen Sinmyeongsunseong, the mother of Gwangjong in AD 954 in Goryeo Dynasty. The museum in Chungcheong University takes charge of the excavation for 3 times from 2000 to 2002 and identified that its construction was carried out till Joseon Dynasty. Among the iron artifacts from the first excavation such as a weeding hoe, a hand knife, a lock, two nails and a plow which had conservation treatments, the sample was collected. Its micro-structure and method of manufacture were investigated. Excavation report for those artifacts has not published yet, therefore, the date of each artifacts is not clearly confirmed. The samples were collected from each part of the objects and then embedded in epoxy resin and etched with nitric acid. The examination of its microstructure is carried out under the microscope and the hardness values were measured by Vickers hardness tester. From the results, some artifacts show different manufacture method sin the each parts. The forming processes of the iron weeding hoe and the iron sickle are similar but the blade of iron weeding hoe was strengthened by carbonization whereas the blade of the iron sickle was done by quenching. The hand knife and the nails were produced through almost same methods and shows similar microstructures. The hand knife seems to be made by repeated beating and folding in low temperature resulting in fine crystallization, but the nail shows large crystallization due to processes in high temperature. Lock is made of white cast iron, that does not show any heat treatment.

• Nuclear Engineering and Technology
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• v.4 no.4
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• pp.331-339
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• 1972

For the syntheses of tritium labelled polystyrene, the basic material for the preparation of tritium luminous compound, various methods of labelling such as Tesla discharge, Wilzbach exposure, gamma irradiation, and U V. irradiation were compared in view of getting high specific activity-product. The obtained polystyrene-T(G) by the method of Tesla discharge and by the method of U. V. irradiation had specific activity of 1～1.2 mCi/mg, and these two methods were the most encouraging. Mixing of 1 part of polystyrene-T(G) with 4 parts of ZnS:Cu phosphor, in weight, appeared to be the most suitable ratio in tile preparation of luminous compound in luminosity point of view. When 30 mg. of obtained luminescent mixture was applied on steel plate by using 1 ml. of the selected binder (i.e., 1g of commercial varnish in 100m1. of benzene) the luminosity maximum was ca. 20 micro Lambert. The prepared luminous compound was confirmed to be practically applicable for mine marker or dark-room light source.

• Korean Journal of Veterinary Research
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• v.31 no.3
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• pp.259-264
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• 1991

The proteins of the race horse erythrocyte membrane were analysed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate(SDS-PAGE), and their relations to the fast erythrocyte sedimentation rate(ESR) of the race horse were investigated. The erythrocyte sedimentation rate of race horse were very fast compared with the human one(33 times <$90^{\circ}-plastic-ESR/30m$> and 25 times <$90^{\circ}-micro-ESR/30m$> as fast as the human one) are reported previously. Although the general protein profiles of the race horse erythrocyte membranes were almost similar to that of human, band 3 content was showing higher in race horse (34.7%) than in human (25.3%). The glycoprotein profiles of the race horse erythrocyte membranes revealed by periodic acid Schiff's(PAS) stain showed a marked difference from that of human. The PAS-1(glycophorin) and PAS-2(sialoglycoprotein) present in human erythrocyte memo brane were almost absent from the Holstein and race horse erythrocyte membranes, but PAS-2 was more in only race horse from that of human. Instead, the bovine erythrocyte membranes showed a strong PAS-B near the origin of the electrophorograms and the race horse erythrocyte membranes showed a strong PAS-negative band near the end of the electrophorograms, which is named as PAS-E in this study. These results suggest that the fast sedimentation rate of race horse erythrocyte is due in part to the presence of more band 3 protein fraction and PAS-E glycoproteins in the race horse erythrocytes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1289-1297
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• 2005

The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Serpentine Laminating Micromixer (SLM) in the present study, Part 1. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: splitting/recombination and chaotic advection. The splitting and recombination (in other term, lamination) mechanism is obtained by the successive arrangement of 'F'-shape mixing units in two layers. The chaotic advection is induced by the overall three-dimensional serpentine path of the microchannel. Chaotic mixing performance of the SLM was fully characterized numerically. To compare the mixing performance, a T-type micromixer which has the same width, height and length of the SLM was also designed. The three-dimensional numerical mixing simulations show the superiority of the SLM over the T-type micromixer. From the cross-sectional simulation results of mixing patterns, the chaotic advection effect from the serpentine channel path design acts favorably to realize the ideal lamination of fluid flow as Re increases. Chaotic mixing mechanism, proposed in this study, could be easily integrated in Micro-Total-Analysis-System, Lab-on-a-Chip and so on.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.111-118
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• 2004

The work presented in this paper concerns the aerodynamic characteristics and compression wave generated in a tunnel when a high speed train enters it. A large number of solutions have been proposed to reduce the amplitude of the pressure gradient in tunnels and some of the most efficient solutions consist of (a) addition ofa blind hood, (b) addition of inclined part at the entrance, and (c) holes in the ceiling of the tunnel. These are numerically studied by using the three-dimensional unsteady compressible Euler equation solver with ALE, CFD code, based on FEM method. Computational results showed that the smaller inclined angle leads to the lower pressure gradient of compression wave front. This study indicated that the most efficient slant angle is in the range from $30^{\circ}$ to $50^{\circ}$. The maximum pressure gradient is reduced by $26.81\%$ for the inclined angle of $30^{\circ}$ as compared to vertical entry. Results also showed that maximum pressure gradient can be reduced by $15.94\%$ in blind hood entry as compared to $30^{\circ}$ inclined tunnel entry. Furthermore, the present analysis showed that inclined slant angle has little effect on aerodynamic drag. Comparison of the pressure gradient between the inclined tunnel hood and the vertical entry with air vent holes indicated that the optimum inclined tunnel hood is much more effective way in reducing pressure gradient and increasing the pressure rise time.