• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5B
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• pp.500-511
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• 2003

To prevent performance degradation of TCP due to packet losses in the smooth handoff by the route optimization extension of Mobile IP protocol, a buffering of packets at a base station is needed. A buffering of packets at a base station recovers those packets dropped during handoff by forwarding buffered packets at the old base station to the mobile user. But, when the mobile user moves to a congested base station in a new foreign subnetwork, those buffered packets forwarded by the old base station are dropped and the wireless link utilization performance degrades due to increased congestion by those forwarded packets. In this paper, considering the case that a mobile user moves to a congested base station in a new foreign subnetwork, we propose an Implicit Priority Packet Forwarding to improve TCP performance in mobile networks. In the proposed scheme, the old base station marks a buffered packet as a priority packet during handoff. In addition, RED (Random Early Detection) at the new congested base station does not include priority packets in queue size and does not drop those packets randomly based on average queue size. Simulation results show that wireless link utilization performance of mobile hosts can be improved without modification to Mobile IP protocol by applying proposed Implicit Priority Packet Forwarding.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.518-527
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• 2004

In this study, SiC whiskers were grown in porous alumina substrate in order to enhance the filtering efficiency, performance, and durability by controlling pore morphology. This experiment was performed by Chemical Vapor Infiltration (CVI) in order to obtain the whiskers on the inside of pores as well as on the surface of porous the A1$_2$O$_3$ substrate. The deposition behavior was changed remarkably with the deposition position, temperature, and input gas ratio. First, the mean diameter of whisker was decreased as the position of observation moved into the inside of substrate due to the reactant gas depletion effect'. Second, the deposition temperature caused the changes of the deposition type such as debris, whiskers and films and the change in morphology affect the various properties. When SiC films were deposited. the gas permeability and the specific surface area decreased. However, the whisker showed the opposite result. The whiskers increase not only the specific surface area and minimizing pressure drop but also mechanical strength. Therefore it is expected that the porous alumina body which deposited the SiC whisker is the promising material for the filter trapping the particles.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.86-91
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• 2004

$LiCoO_2$ cathode powders with round particle shaped and nano grain sized of 70-300nm were synthesized by a mechanochemical method. The surface of Li-Co precursor prepared by freeze drying method was modified by $K_2SO_4$ coating and ball milling was used for the coating process. The precursor was crystallized to high temperature form of $LiCoO_2$ at $800^{\circ}C$ and the grain growth was inhibited by the $K_2SO_4$ coating effect. The $K_2SO_4$ coating was not decomposed at $800^{\circ}C$ and prevented the contact in the Li-Co precursor particles. The nano-sized $LiCoO_2$ powder had tetragonal phase and it affected the Li diffusion through the surface of particles. It means that the anode materials for hight performance battery should be satisfied not only small particle size but phase contol on the surface of particles. In this study, the powder characteristics and rate capabilities were compared with a commercial powder and the nano-sized $LiCoO_2$ powder fabricated by the mechanochemical method. And the crucial factor which affects on battery performance was also examined.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.81-85
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• 2004

Nanoporous materials with nanometer-sized pores, are of great interest in the various applications such as selective adsorbents, heterogeneous catalysts and catalyst supports because of their high porosity, surface area, and size selective adsorption properties. This study is aimed to prepare nanoporous catalytic materials on the basis of two-dimersional clay by pillaring of $SiO_2$ sol particles. $SiO_2$ Pillared Montmorillonite (Si-PILM) was prepared by ion exchanging the interlayer $Ni^{2+}$ ions of clay with $SiO_2$ nano-sized particles of which the surface was modified with nicked polyhydroxy cations sach as $Ni_4(OH)_4^{4+}$. Nano-sized $SiO_2$ particles were formed by the controlled hydrolysis of tetraethyl orthosilicate (TEOS). Upon pillaring of $Ni^+$-modified $SiO_2$ nano particles between the clay layers, the basal spacing was expanded largely to $45{\AA}$ and the extremely large specific surface area ($S_{BET}$) of $760m^2/g$ was obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.1
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• pp.279-285
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• 2017

The study on 'support for V2V(Vehicle to Vehicle) services based on LTE sidelink' has been carried out in 3GPP RAN working group. The conventional LTE sidelink technology is not adequate for high speed V2V communications because the conventional DM-RS(Demodulation Reference signal) structure is developed for pedestrian environment. While the typical speed of pedestrian environment is 3km/h, that of V2V communications is 120 km/h and the information on channel estimation is not sufficient with legacy DM-RS structure. In this paper, improved DM-RS structures for V2V communications that have rapid channel variation are introduced and the performance of channel estimation accuracy is analyzed. Simulation results show that the performance improvement of channel estimation can be achieved based on extended sub-carrier spacing structure resulted from reduced inter-carrier interference. However, the extended sub-carrier spacing requires the longer cyclic prefix and higher overhead. As a results of considerations on DM-RS modification, the sub-carrier spacing is maintained and the high density of DM-RS is applied for V2V communications.

• The korean journal of orthodontics
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• v.44 no.4
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• pp.195-202
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• 2014

Objective: A low-viscosity resin (infiltrant) was used to inhibit the progression of white spot lesions (WSLs) and resolve associated esthetic issues. An alternative pretreatment was explored to increase the pore volume of the surface layer of the WSLs. Also, the penetration effects of the infiltrant were evaluated for various pretreatments. Methods: Sixty two artificial lesions were fabricated on bovine teeth. As a positive control, 15% HCl gel was applied for 120 seconds. Further, 37% $H_3PO_4$ gel was applied for 30 seconds using three methods. The samples were divided as follows: $H_3PO_4$ only group, $H_3PO_4$ sponge group, and $H_3PO_4$ brush group. The acid was gently rubbed with the applicators (i.e., a sponge or brush) throughout the application time. To compare the effects of resin infiltration, twenty paired halves of specimens were treated with an infiltrant (ICON$^{(R)}$). Results: Thicknesses of the removed surface layers and infiltrated areas were evaluated by confocal laser scanning microscope. The positive control and the 37% $H_3PO_4$ brush group failed to show significant differences in the removed thickness (p > 0.05); however, the mean percentage of the infiltrated area was higher in the 37% $H_3PO_4$ brush group ($84.13{\pm}7.58%$%) than the positive control ($63.51{\pm}7.62%$, p < 0.001). Scanning electron microscope observations indicate higher pore volumes for the 37% $H_3PO_4$ brush group than for the positive control. Conclusions: Application of 37% $H_3PO_4$ with a brush for 30 seconds increased the pore volume of WSL surface layers and the percentage of infiltrated areas in comparison to the use of 15% HCl for 120 seconds.

• Journal of Aquaculture
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• v.16 no.3
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• pp.159-164
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• 2003

Effect of the benthic echiurid Urechis unicinctus juveniles on the chemical characteristics of organically enriched sediment, as well as the individual survival rate and growth in various sediments, was investigated in this study to ascertain the effectiveness of U. unicinctus in the bioremediation of organically polluted sediment. The content of acid volatile sulfide (AVS) in the sediment of three coastal areas was 0.4±0.1 mg/gㆍdry sediment in Seonso, 0.1±0.01 mg/gㆍdry sediment in Myo-do, 0.02±0.01 mg/gㆍdry sediment in Dolsan-do, respectively. 500 juveniles with average body length of 1.2±0.3 mm were bred in these sediments. After 30 days, the AVS content of three places decreased to 0.29±0.3, 0.08±0.01 and 0.0l±0.01 mg/gㆍdry. After 60 days, the content was 0.23±0.03, 0.0l±0.01, 0.0l±0.01 mg/gㆍdry. The AVS content in the control (sediment from Seonso without juveniles) was 0.39±0.75 mg/gㆍdry sediment (after 30 days) and 0.45±0.01 mg/gㆍdry sediment (after 60 days). At the same time, the chemical oxygen demand (COD) and total ingition loss (TIL) of these sediments showed the same trend with that of AVS. Furthermore, 60 days later, the survival rate and growth of juveniles were 71.2%, 11.1±l.0 mm in Seonso, 89.8%, 12.0±1.3 mm in Myo-do and 81.6%, 11.9±1.9 mm in Dolsan-do. It was suggested that U. unicinctus can survive better in less polluted environment. Under different U. unicinctus juvenile density (100, 300, 500, 700, 900 individuals), after 60 days cultivation, the AVS content decreased from 0.4±0.1, 0.4±0.1, 0.4±0.3, 0.4±0.3, 0.4±0.3 mg/gㆍdry to 0.4±0.2, 0.3±0.2, 0.2±0.1, 0.2±0.1, 0.2±0.1 mg/gㆍdry. Therefore, the higher the density of juveniles, the greater the effect in improving the sediment. In comparison to different initial AVS concentration (0.40±0.01, 0.35±0.01, [I can't find a reference to this number above], 0.29±0.02, [I can't find a reference to this number above], 0.18±0.03, [I can't find a reference to this number above], 0.06±0.02 mg/gㆍdry sediment [I can't find a reference to this number above] and the control 0.0±0.0[I can't find a reference to this number above]), after 30 days cultivation with 500 juveniles, the AVS content was 0.29±0.03, 0.19±0.0, 0.15±0.01, 0.12±0.02, 0.05±0.0mg/gㆍdry and 0(control). After 60 days cultivation, the content was 0.23±0.03, 0.12±0.4, 0.10±0.01, 0.18±0.03, 0.06±0.02 mg/gㆍdry and 0 (control). Use % decrease in AVS content to state: The impact of U. unicinctus on the sediments was greater with higher concentrations of AVS. The results of this study indicate that U. unicinctus is effective in the biological treatment of sediments polluted by AVS and other organics.

• Journal of the Korea Society of Computer and Information
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• v.20 no.6
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• pp.13-20
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• 2015

A genuine product authentication framework and genuine distinction algorithm based on design QR code is proposed in this paper. The proposed framework consists of design QR code, a smart phone application for authentication, and a server system. Design QR code is a shape-modification of conventional QR code according to manufacturer's and/or product's need. In the design QR code, information about manufacturer and product is written. The written information can be read with general QR code reader, however, the content is transformed with authentication code, used in the first step authentication, and the meaning cannot be inferred. The application conducts the first step authentication and sends the resulting information to the server system for the second step authentication. The server system decides the genuinity using look-up history. The proposed framework can improve the authentication effect while minimizing the additional costs by managing the history through the server system. The proposed framework has proven to be effective in actual use, such as that used for the management of garbage bags in Ansan city.

• The Korean Journal of Malacology
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• v.27 no.1
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• pp.15-27
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• 2011

This study was performed to observe ultrastructure of the gill and to ascertain the effect of salinity on histopathological and ultrastructural changes in the gill of the Japanese clam, Corbicula japonica. Experimental period was 7 days. Experimental groups consisted of control, 5, 10, 20 psu. $LC_{50}$ (96 h.) by the probit was 19.55 psu. Mortality was significantly different from the control (p < 0.05). Inner demibranch of the gill of C. japonica was wider 1.37 times than outer demibranch (p < 0.001). The filament zone on the plica can be distinguished by the six epithelial celll cell; frontal ciliated epithelium ($7{\mu}m$), latero-frontal ciliated epithelium ($5{\mu}m$), postlatero-frontal epithelim ($3{\times}8{\mu}m$), and lateral ciliated epithelium ($5{\mu}m$) in the frontal zone, endothelial cellin the intermediate zone, and abfrontal cell in the abfrontal zone. It had one type of secretory cell that was filled with fibrous substances of low electron density. The gill of C. japonica exposed to 5 psu for 7 days was observed partially disappearance of the cilia, and glycogen granule in the filament. In the 10 psu, gill appeared partially modification of epithelial cell and destruction of the glycocalyx. Gill exposed to 20 psu was extended nuclus of the ciliated epithelial cell, destruction of the organelles, and observed glycogen granules infiltration and numerous vacuoles. Moreover, more than 50% filaments were observed that come out chitinous rod from disappearance of epithelial cell in the filament. Therefore, the destruction of the cilia and epithelial cell induce physiological activity and it may be leading directly to death.

• Polymer(Korea)
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• v.30 no.2
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• pp.168-174
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• 2006

To utilize as highly functional scaffolds for tissue engineering by improving hydrophobicity and cell compatibility of the exist polymer scaffolds, the biodegradable poly(L-lactic acid) (PLLA) films and scaffolds having the optimal hydrophilicity were prepared by in situ plasma treatment and grafting of a carboxyl acid-containing monomer, acrylic acid (AA) in the chamber. From the results of surface analyses, surface-modified nonporous PLLA film and dual pore scaffold surfaces showed high hydrophilicity due to the decrease in contact angle and the increase in carboxylic groups as compared with untreated PLLA control. In particular, among various surface modification methods, Ar(argon)+AA+AA sample prepared by Ar plasma and then acrylic acid treatments displayed lower contact angle and more carboxylic groups thar Ar/AA and Ar+TP(thermal polymerization) samples, indicating that Ar+AA+AA sample was optimally treated for improving its hydrophilicity. In the cases of surface modified nonporous PLLA films and dual pore scaffolds, the adhesion and proliferation of chondrocytes increased with increasing their hydrophilicity.