• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.262-265
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• 2015

In modern society, the spread of computers and smart phones, the Internet has become part of life. Therefore, the most places, wired/wireless router is installed. Crackers can attack the user to use the router by exploiting network vulnerabilities. therefore, the administrator is able to try cracker variety of attacks sloppy router, vaccine is installed also computer and smartphone users, appearance and address of the usual Internet is not deer medium and similar. In this paper, we look at a method for preventing in each attack seen for typical network attacks.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1289-1301
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• 2004

Direct numerical simulation (DNS) of strongly-heated air flows moving upward in a vertical tube has been conducted to investigate the effect of gas property variations on turbulence modification. Three heating conditions(q$_1$$^{+}$=0.0045, 0.0035 and 0.0018) are selected to reflect the experiment of Shehata and McEligot (1998) at the inlet bulk Reynolds numbers of 4300 and 6000. At these conditions, the flow inside the heated tube remains turbululent or undergoes a transition to subturbulent or laminarizing flow. Consequently, a significant impairment of heat transfer occurs due to the reduction of flow turbulence. The predictions of integral parameters and mean profiles such as velocity and temperature distributions are in excellent agreement with the experiment. The computed turbulence data indicate that a reduction of flow turbulence occurs mainly due to strong flow acceleration effects for strongly-heated internal gas flows. Thus, buoyancy influences are secondary but not negligible especially for turbulent flow at low heating condition. Digital flow visualization also shows that vortical structures rapidly decay as the heating increases.s.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1807-1812
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• 2004

Sinusoidal wavy channel is one of the most commonly used devices in the industry for achieving mixing and heat transfer. Here we report on results obtained from the DNS of flow inside the wavy channel performed using the finite volume technique. As a primary stage to obtain the optimal design for heat transfer and mixing, this study observed the basic flow structures in a wavy channel. The mass flow rate is kept constant with friction Reynolds number of $Re_{\tau}$ = 140 . Time- and space-averaged and instantaneous flow fields are illustrated to observe the flow structures. Although the direct comparison of results between turbulent wavy and flat channel is somehow difficult due to the different flow phenomena derived from different configuration, here the mean streamwise velocity and RMS of velocities at same $Re_{\tau}$ of two different channels are compared. The basic difference between wavy and flat channel flow is the existence of small scale wall vortices along the walls in a wavy channel. These vortices make flow more complex, which will accompany the increase of heat transfer, pressure drop and drag.

• Journal of the Korean Chemical Society
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• v.29 no.3
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• pp.304-310
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• 1985

Effect of spermine on the susceptibility of calf thymus nucleohistone to DNase 1, in relation to the structural change of the nucleohistone, and cooperativity of the interaction of the nucleohistone with DNase 1 was investigated. Dansylated nucleohistone, in which the histone moiety had been derivatized by dansylation, was also used to investigate functional roles of the histone moiety on the cooperativity. The data here indicate the possibility that the nucleohistone, in contrast with the DNA, may not undergo monomolecular condensation, whereas intermolecular aggregation and enhancement of the positive cooperativity of the interaction of nucleohistone with DNase 1 may be brought about by spermine. The interaction of the DNS-nucleohistone with DNase 1 showed negative cooperativity. Based on the data here, it can be speculated that the cooperativity of the nucleohistone is influenced by the histone moiety of the nucleohistone.

• Microbiology and Biotechnology Letters
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• v.18 no.1
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• pp.35-38
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• 1990

$\alpha$-D-Glucosidase inhibitor purified in a pure form was amorphous powder which gave a single spot at Rf value 0.12-0.71 with various developing solvent systems on silica gel thin layer chromatography, and melting point was 154.3-155.3$^{\circ}C$. It was disolved in water, formic acid and ethylene glycol monoethyl ether, and was very high hygroscopic substance. Biochemical reaction of the substance was positive to phenol sulfuric acid, ninhydrin, silver nitrate-sodium hydroxide, but negative to DNS reagent. Acid hydrolysis gave fructose and acid as sole sugar and amino acid constituents respectively. Moelcular weight of the inhibitor was estimated to be 1,050 by Shphadex G-25 column chromatography.

• Journal of Mechanical Science and Technology
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• v.20 no.2
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• pp.262-270
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• 2006

Direct numerical simulations (DNS) of turbulent channel flows up to $Re_{\tau}=1270$ are performed to investigate an elliptic feature and strain rate field on cross sections of coherent fine scale eddies (CFSEs) in wall turbulence. From DNS results, the CFSEs are educed and the strain rate field around the eddy is analyzed statistically. The principal strain rates (i.e. eigenvalues of the strain rate tensor) at the CFSE centers are scaled by the Kolmogorov length $\eta$ and velocity $U_k$. The most expected maximum (stretching) and minimum (compressing) eigenvalues at the CFSE centers are independent of the Reynolds number in each $y^+$ region (i. e. near-wall, logarithmic and wake regions). The elliptic feature of the CFSE is observed in the distribution of phase-averaged azimuthal velocity on a plane perpendicular to the rotating axis of the CFSE $(\omega_c)$. Except near the wall, phase-averaged maximum $(\gamma^{\ast}/\gamma_c^{\ast})$ and minimum $(\alpha^{\ast}/\alpha_c^{\ast})$ an eigenvalues show maxima on the major axis around the CFSE and minima on the minor axis near the CFSE center. This results in high energy dissipation rate around the CFSE.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.212-214
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• 2014

홍보용 LED 전광판의 경우 표준이 제정되어 있는 도로 전광판과는 달리 획일화된 기준 없이 설치한 것들이 많아 관리를 위한 시스템의 규격이 체계적으로 규정 되어 있지 않으며 통일된 시스템 구축체계를 정의하기 쉽지 않아 제작 비용적인 측면에서 낭비가 발생한다. 이러한 관리 측면의 문제점을 해결해야 한다는 요구사항에 스마트폰을 통하여 전자 제품을 제어하는 유비쿼터스 시대적 요구사항을 결합하여 모바일 상에서 실시간 원격으로 제어할 수 있는 LED 전광판 통합 관리/제어 시스템을 제안한다. 통일된 시스템을 제안함으로써 서로 다른 규격을 일일이 맞추는 낭비를 줄일 수 있으며, 모바일 기능을 강화함으로써 전광판에서 재생하는 저작물의 배포 및 서비스 구조 관리, 제어 등의 측면에서 신뢰성 있고 효율적인 LED 전광판 시스템 관리를 할 수 있을 것으로 기대한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.437-443
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• 2007

In this paper, the design of URL structures and managements for UFID(Unique feature Identification) based wireless communications is presented with the combination of GIS and URL address informations. As a result of IPv6 based UFID wireless communications, new methods for URI(Uniform Resource Identifier) informations and UFID communication systems are proposed with a 6byte coded 128-bit IPv6 DNS system for the presentation of 1,500,000 korean buildings.

• Nuclear Engineering and Technology
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• v.42 no.6
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• pp.608-619
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• 2010

A multi-scale analysis of water-cooled reactor thermalhydraulics can be used to take advantage of increased computer power and improved simulation tools, including Direct Numerical Simulation (DNS), Computational Fluid Dynamics (CFD) (in both open and porous mediums), and system thermalhydraulic codes. This paper presents a general strategy for this procedure for various thermalhydraulic scales. A short state of the art is given for each scale, and the role of the scale in the overall multi-scale analysis process is defined. System thermalhydraulic codes will remain a privileged tool for many investigations related to safety. CFD in porous medium is already being frequently used for core thermalhydraulics, either in 3D modules of system codes or in component codes. CFD in open medium allows zooming on some reactor components in specific situations, and may be coupled to the system and component scales. Various modeling approaches exist in the domain from DNS to CFD which may be used to improve the understanding of flow processes, and as a basis for developing more physically based models for macroscopic tools. A few examples are given to illustrate the multi-scale approach. Perspectives for the future are drawn from the present state of the art and directions for future research and development are given.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.143-145
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• 2022

With the spread of the Internet around the world, devices connected to the Internet are gradually increasing. In addition, the number of distributed reflection service attacks (DrDoS), an attack that maliciously requests large responses by deceiving IPs as if the attacker was a victim, using vulnerabilities in application protocols such as DNS, NTP, and CLDAP, is increasing rapidly. It is believed that the security threat of distributed reflection service attacks will not disappear unless ISPs establish appropriate countermeasures to IP Spoofing. Therefore, this paper describes the security threat and response status of distributed reflection service attacks based on IP Spoofing.