• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.50-56
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• 2008

Experimental results for forced convection condensation of Refrigerant-22 and ternary Refrigerant-407C(HFC-32/125/134a 23/25/52 wt%) which is being considered as a substitute R-22 inside a horizontal micro-fin tube are presented. The test section was horizontal double-tube counterflow condenser with a length 4,000 mm micro-fin tube, having 8.53 mm ID, 0.2 mm fin height and 60 fins. The range of parameters of mass velocity were varied from 102.1 to 301.0 kg/(m2.s) and inlet quality 1.0. At the given experimental conditions. the average heat transfer coefficients for R-407C were lower than that for R-22 at a micro-fin tube. Over the mass velocity range tested. the PF(penalty factor) for R-22, R-407C were lower than the increasing ratio of heat transfer area by fins, and the EF(enhancement factor) for R-22, R-407C were higher than the increasing ratio of heat transfer area by fins.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1467-1480
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• 2016

This paper proposes "A Black Hole Detection Protocol Design based on a Mutual Authentication Scheme on VANET." It consists of the Mutual Authentication Scheme (MAS) that processes a Mutual Authentication by transferring messages among a Gateway Node, a Sensor Node, and a User Node and the Black Hole Detection Protocol (BHDP) which detects a Non-Authentication Node by using the Session Key computed in the MAS and a Black Hole by using the Broadcasting Table. Therefore, the MAS can reduce the operation count of hash functions more than the existing scheme and protect a privacy from an eavesdropping attack and an information exposure by hashing a nonce and user's ID and password. In addition, the MAS prevents a replay attack by using the randomly generated nonce and the time stamp. The BHDP improves Packet Delivery ratio and Throughput more than the AODV with Black hole by 4.79% and 38.28Kbps. Also, it improves Packet Delivery ratio and Throughput more than the IDSAODV by 1.53% and 10.45Kbps. Hence it makes VANET more safe and reliable.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.505-510
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• 2007

Greenhouses should be heated during nights and co Id days in order to fit growth conditions in greenhouses. Ground source heat pump(GSHP) or geothermal heat pump system(GHPs) is recognized to be outstanding heating and cooling system. Horizontal GSHP system is typically less expensive than vertical GSHP system but requires wide ground area to bury ground heat exchanger (GHE). In this study, a horizontal GSHP system with thermal storage tank was installed in greenhouse and investigated as performance characteristics. In the daytime, heating load of greenhouse is very small or needless because solar radiation increases inner air temperature. The results of study showed that the heating coefficient of performance of the heat pump($COP_h$) was 2.9 and the overall heating coefficient of performance of the system($COP_{sys}$) was 2.4. Heating energy cost was saved 76% using the horizontal GSHP system with thermal storage tank.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.189-192
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• 2008

Turbulent coherent structure near rod-roughened wall are investigated by analyzing the database of direct numerical simulation of turbulent boundary layer. The roughness sublayer id defined as two-point correlations are not independent of streamwise locations around roughness. The roughness sublayer based on the two-point spatial correlation is different from that given by one-point statistics. Quadrant analysis and probability-weighted Reynolds shear stress indicate that turbulent structures are not affected by surface roughness above the roughness sublayer defined by the spatial correlations. The conditionally-averaged flow fields associated with Reynolds shear stress producing Q2/Q4 events show that though turbulent vortices are affected in the roughness sublayer, these are very similar at different streamwise locations above the roughness sublayer. The Reynolds stress producing turbulent vortices in the log layer have almost the same geometrical shape as those in the smooth wall-bounded turbulent flows. This suggests that the mechanism by which the Reynolds stress is produced in the log layer has not been significantly affected by the present surface roughness.

• The Transactions of the Korea Information Processing Society
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• v.7 no.2S
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• pp.608-620
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• 2000

A web based E-mail system consists of serves which supply mail accounts and service, and clients which take part of interfacing with users. The web browsers such as Netscape Navigator and Internet Explorer are the popular clients. Users who cannot afford to get an E-mail id in general mail servers are, therefore, able to reach a e-mailing service in the web environment by using client programs in connection with a mail server. Although the quality of service has been upgraded a lot in recent days, it doesn't provide with satisfactory services anymore. In this paper, we intend to design a mail agent system based on the web environment. Through this system we could reach a convenient user interface based on Internet Explorer and could easily access administratory environment on the basis of NT Server 4.0. Using the service engine dominent in mail agent system, it could provide with convenient user interfacing tools like responding the absence of users, mail filtering and refusing messages, etc. And it would ultimately make possible a constant system security, by preventing system failure phenomena caused by extraordinary uses beyond its capability.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10b
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• pp.278-283
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• 2006

결정 트리는 큰 가설 공간을 가지고 있어 유연하고 강인한 성능을 지닐 수 있다. 하지만 결정트리가 학습 데이터에 지나치게 적응되는 경향이 있다. 학습데이터에 과도하게 적응되는 경향을 없애기 위해 몇몇 가지치기 알고리즘이 개발되었다. 하지만, 데이터가 속성 축에 평행하지 않아서 오는 공간 낭비의 문제는 이러한 방법으로 해결할 수 없다. 따라서 본 논문에서는 다변수 노드를 사용한 선형 분류기를 이용하여 이러한 문제점을 해결하는 방법을 제시하였으며, 결정트리의 성능을 높이고자 지지 벡터 머신을 도입하였다(SVMDT). 본 논문에서 제시한 알고리즘은 세 가지 부분으로 이루어졌다. 첫째로, 각 노드에서 사용할 속성을 선택하는 부분과 둘째로, ID3를 이 목적에 맞게 바꾼 알고리즘과 마지막으로 기본적인 형태의 가지치기 알고리즘을 개발하였다. UCI 데이터 셋을 이용하여 OC1, C4.5, SVM과 비교한 결과, SVMDT는 개선된 결과를 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.736-752
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• 2010

We propose a novel collision-avoidance algorithm for the active type RFID regarding an indoor tracking system. Several well-known collision avoidance algorithms are analyzed considering the adequacy for the indoor tracking system. We prove the superiority of the slotted ALOHA in comparison with CSMA for short and fixed length packets like an ID message in RFID. Observed results show that they are not applicable for active type RFID in terms of energy efficiency. Putting these all together, we propose a dedicated collision avoidance algorithm considering the unique features of the indoor tracking system. The proposed method includes a scheduled tag access period (STAP) as well as a random tag access period (RTAP) to address both of the static and dynamic characteristics of the system. The system parameters are determined through a quantitative analysis of the throughput and energy efficiency. Especially, some mathematical techniques have been deployed to obtain the optimal slot count for RTAP. Finally, simulation results are provided to illustrate the performance of the proposed method with variations of the parameters.

• YAKHAK HOEJI
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• v.46 no.2
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• pp.124-128
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• 2002

The nitrone-based free radical trapping reagent, $\alpha$-phenyl-n-tert-butyl nitrone (PBN) has been proposed as therapeutic agent for stroke. We used this for model drug of development of new drug for neuroprotection. The purpose of this study was to evaluate the blood-brain barrier (BBB) permeability of PBN in Sprague-Dawly (SD) rats. The BBB transport of PBN was investigated in SD rats using internal carotid artery perfusion (ICAP) method at a rate of 4 mι/min for 15 second. We also obtained pharmacokinetic parameters of PBN using single intravenous injection technique. When we estimated BBB permeability of PBN with ICAP method, the brain volume of distribution of PBN was 60.0 $\pm$ 12.0 $\mu\textrm{g}$/ι. The brain uptake of PBN after IV injection at 120 min was 0.15 $\pm$ 0.01%ID/g. The PBN was transported to the brain through the BBB well in rats, because PBN is small molecule (MW 177) and lipid-soluble (log P 1.23) compound.

• International Commerce and Information Review
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• v.13 no.4
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• pp.81-100
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• 2011

With the smart device deployment, the interest in NFC technology is increasing. In this study, to be successful in NFC based business commercialization, we present main factors affecting success of NFC based e-commerce business model. To this end, we conduct NFC and business models, case study methodology through literature review. And then, we suggest representative NFC e-commerce business model cases, and practices that affect the success or failure of the six factors are derived Derived factors are based on inductive learning to apply the technology to create a case study table, and decision trees to bring it, NFC-based commerce business models need to be successful at the strategic implications are present.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.247-247
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• 2010

DLC(diamond-like carbon)는 비정질 고상 탄소의 하나로 다이아몬드의 유사한 높은 경도, 내마모성, 윤활성, 전기절연성, 화학적 안정성을 가지고 있는 재료이다. 이러한 우수한 특성 때문에 DLC는 박막의 형태로 여러 종류의 보호코팅에 많이 응용되고 있다. DLC의 광범위한 응용에 있어 가장 큰 문제점은 박막이 갖는 높은 잔류응력과 이에 따른 기판과의 낮은 접착성으로 알려져 있다. 최근 연구에 의하면, plasma pre-treatment를 통해 PTFE기판에 DLC박막의 adhesion strength를 증진 시킬 수 있다고 보고하였다. 또한 ion beam technique를 이용하여 잔류응력을 줄이고 기판과의 접착력을 높일 수 있다는 것도 보고 되었다. 이에 기인하여 pre-treatment가 DLC합성에 잔류응력을 낮추고 기판과의 접착성을 높이는 효과를 보일 것이라고 가정하고 연구하였다. 본 연구에서 pre-treatment가 Diamond-like Carbon의 stainless steel 합성시 stress와 adhesion에 어떤 효과가 있는지 알아보기 위해, pre-treatment시와 synthesis of DLC film시에 13.56MHz 150W RF플라즈마 화학기상 증착 (RF-PECVD) 법을 통해 합성되었다. pre-treatment시에 H2(80 sccm), O2(10 sccm), N2(20 sccm)의 가스 종류를 다르게 하였고, synthesis of DLC film시에는 CH4 (20 sccm), H2 (80 sccm)가스의 유량을 고정하였다. 합성된 DLC 박막은 Contact Angle Analyze, Raman spectroscopy, Scratch tester를 이용하여 접촉각, D peak Position, G peak Position, ID/IG ratio, 접착력을 측정하였다.