• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.798-803
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• 2005

This paper describes a design of AES(Advanced Encryption Standard)-based CCMP core for IEEE 802.1li wireless LAN security. To maximize its performance, two AES cores ate used, one is for counter mode for data confidentiality and the other is for CBC(Cipher Block Chaining) mode for authentication and data integrity. The S-box that requires the largest hardware in AES core is implemented using composite field arithmetic, and the gate count is reduced by about $20\%$ compared with conventional LUT(Lookup Table)-based design. The CCMP core designed in Verilog-HDL has 13,360 gates, and the estimated throughput is about 168 Mbps at 54-MHz clock frequency. The functionality of the CCMP core is verified by Excalibur SoC implementation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.21-25
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• 2017

The umbilical system used for launch vehicle is to connect all ground supply lines (Pneumatic, hydraulic and electrical) to launch vehicle and disconnect those at few second before launch vehicle lift-off (or simultaneously with launch vehicle lift-off). During launch preparation stage, all umbilical shall be securely connected and also at separation stage, separation of all umbilical line shall be guaranteed. Therefore finding an appropriate connection force is a key factor on development of umbilical system. According to these design requirement, various kind of umbilical system has been developed from early stage of space development till today. In this paper, various kind of umbilical system developed so far is introduced according to its feature and operational concept. Also, umbilical system used for KSLV-II is introduced

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1085-1091
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• 2006

For an experiment in this paper, designed test bed to secure confidentiality of data and safe transmission that Mobile node exchanges in Mobile network. And, For IPsec use that support basically in MIPv6, modeling and experimented IKEv2 protocol that is used for reliable authentication key management and distribution between End Point. When Mobile node handoff in Mobile network, analyzed effect that authentication key re-exchange and limited bandwidth that happen often get in key exchange. And studied about Performance and latency about authentication setting and exchange process that use multi interface. To conclusion, when Mobile node transmits using IPSec, re-authentication of key confirmed that re-setting by limit of bandwidth that existent Mobile network has can be impossible. According to other result, proposed MN's multi interface is expected to minimise key exchange latency by hand-off when transmit IPSec.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.367-370
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• 2005

This paper describes a design of AES(Advanced Encryption Standard)-based CCMP core for IEEE 802.11i wireless LAN security. To maximize its performance, two AES cores are used, one is for counter mode for data confidentiality and the other is for CBC(Cipher Block Chaining)mode for authentication and data integrity. The S-box that requires the largest hardware in AES core is implemented using composite field arithmetic, and the gate count is reduced by about 25% compared with conventional LUT(Lookup Table)-based design. The CCMP core designed in Verilog-HDL has 15,450 gates, and the estimated throughput is about 128 Mbps at 50-MHz clock frequency). The functionality of the CCMP core is verified by Excalibur SoC implementation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.812-818
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• 2009

A MOV(Main Oxidizer shutoff Valve) controls the flow rate of liquid oxygen into the rocket combustor by opening and shutting operations piloted by a pneumatic force. In order to improve the effective design for sealing parts of poppet and piston assemblies, the poppet assembly has been designed to be just contacted with the piston assembly. However, to avoid a gap at the poppet/piston contact surface and to evaluate the MOV operating performance, an analyze on the force balance during the closing motion have been performed. For the accuracy of the analysis, the friction forces and the hydraulic forces have been respectively obtained by experiments and CFD analysis. Through the analysis, some important design parameters such as the spring constant, poppet friction and orifice size in the force balance have been introduced and the required operation performance of the MOV has been proved feasible.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.12-19
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• 2022

Cathode open-type PEMFC (Proton Exchange Membrane Fuel Cells) stacks, which are widely used in small transport-type PEMFC, have a problem with poor durability. Through the accelerated durability test of the 13-cell PEMFC stack, we tried to find the cause of the degradation of the stack and to contribute to the improvement of the durability of the cathode open stack. A hydrogen/air boundary is formed during start-up/shut-down (SU/SD) due to the structural problem of the cathode open stack in which the cathode is open to the atmosphere and it is difficult to maintain airtightness, thereby deteriorating the cathode. In this study, it was possible to evaluate the durability in a relatively short time by reducing the 54% of the initial performance by repeating SU/SD 1,800 times on the cathode open stack. After dismantling the stack, each cell was divided into two and the performance was analyzed. Overall, the anode outlet MEA, which facilitates air inflow, showed more severe electrode deterioration than the inlet MEA, confirming that the hydrogen/air boundary formation during SU/SD is the main cause of degradation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.782-789
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• 2020

The demand for the development of rolling stock technology to maintain the best performance in various climatic environments has increased to expand the overseas market of rolling stock. In this study, international and domestic standards that must be applied to build a harsh climatic environment test system were investigated and compared. The way of improvement for domestic standards is proposed. The wind velocities and temperatures are specified in the UIC, EN, and IEC standards for climatic wind tunnel, and EN 50125-1 provides the velocity test up to 180km/h, the largest wind speed. UIC and EN provide the lowest temperature of -45℃, and IEC 62498-1 provides the highest temperature 55℃. The solar radiation test was specified up to 1200W/m2 in the UIC, EN, and IEC. The IEC, EN, and KS R 9145 provide the water tightness standards, which are different from each other in water capacity, pressure, and methods. The snow test method was not well specified. KRTS-VE-Part 31 provides pressurization test methods. The airtightness standards for high-speed rolling stock are defined and regulated for internal pressure change rate in UIC 660 and 779-11. The domestic standard for the wind tunnel test was not well prepared, and the solar radiation test and snow test do not exist in Korea. Therefore, it is necessary to improve domestic standards to an international level for the climatic wind tunnel test of rolling stock.

• Journal of the Korean Wood Science and Technology
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• v.40 no.1
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• pp.10-18
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• 2012

A high airtightness is required for the residential spaces constructed recently to save cooling and heating energy through improving insulation performance. Because the chances to release steam formed by human activity in building and inflow of water vapor in outdoor air to residential space are reduced, the natural humidity control performance of interior materials has become more important. In this study, hygroscopic performance of thermo-physically treated wood (Pinus koraiensis) was estimated. At various relative humidity condition, the water vapor adsorption and desorption rates of wooden materials were measured as well as equilibrium moisture content. Effects of roughness and surface microstructure as physical factors and functional groups as chemical factors on the hygroscopicity were analyzed. It is expected that the results from this study and further study of measuring moisture generation in residential spaces could contribute to install a system for evaluating the hygrothermal performance of wooden building.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.182-188
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• 2016

A decoy is a weapon system that can protect vessels from an enemy's torpedo. Thus, the decoy should be able to operate in the field without any failure. Because the decoy can be inoperable once its sealing is broken and water permeates inside the system, the hermetic sealing capability considering the operational environment is mandatory. To be hermetically sealed, a rubber-type O-ring is generally used in a decoy system. The sealed performance of rubber-type products, however, tends to age and deteriorate with time. Therefore, the O-ring needs to be maintained or changed periodically. This paper proposes a method to estimate the proper maintenance period using the hardness and elongation percentage, which represents the performance of the O-ring product and test data from Accelerated Life Test (ALT) of the product. The O-ring used in this paper is a NBR type, and the temperature was chosen to be the main accelerating factor as referenced in many studies. The criteria for the failure of the O-ring was set for the product to be 50% degraded compared to the initial performance. In addition, the Korean standard KS M 6518 was adopted and referenced for the preparation of test samples and the calculation of estimates. The O-ring's predicted life was simulated by analyzing the test results from a computer program, and the optimized maintenance period for the product was determined.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.72.2-72.2
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• 2010

평판형 고체산화물 연료전지 스택의 고온 밀봉 구조에 대하여 설명하고 스택 운전 후 사후 분석을 통하여 밀봉재와 금속 분리판의 계면반응에 대하여 고찰하였다. 대표적인 고온 밀봉재인 Barium-Silicate 계 결정화 유리와 Fe-Cr 계 금속 분리판은 스택의 작동온도인 $700{\sim}850^{\circ}C$ 에서 고온 반응을 통하여 계면에 반응생성물을 형성하는 것이 확인되었다. 이러한 계면반응은 장기 운전시 SOFC 스택 성능 저하의 원인이 되고, 열 싸이클(작동온도${\leftrightarrow}$상온)을 가하면 계면반응 생성물이 delamination 되어 밀봉구조가 파괴되어 수명을 단축시키게 된다. 계면반응은 Fe-Cr 계 금속 분리판의 산화물인 Cr 산화물, Fe 산화물이 밀봉유리 소재와 반응을 일으키는 것이 주요 원인으로 판명되었다. SOFC 스택에서 열 싸이클시 계면반응에 의하여 기밀도가 감소하는 현상이 확인되었으며, 밀봉 구조의 어느 부분에서 계면반응이 진행되는지 관찰하였다. 이러한 계면반응을 막기 위해서는 금속 분리판과 밀봉유리 사이에 계면반응을 억제하는 보호층을 형성하는 방법이 효과적이다. 본 연구에서는 보호층으로서 밀봉유리 및 Fe-Cr 계 금속 분리판과의 계면반응성이 낮고 열팽창 계수가 비슷한 Yttria Stabilized Zirconia 층을 APS(Atmospheric Plasma Spray) 공정을 이용하여 형성하였다. 밀봉유리/YSZ 보호층/금속분리판은 gas-tight 한 밀봉 구조를 형성하였으며, YSZ 보호층은 밀봉유리와 Fe-Cr 계 금속 분리판 소재와 계면반응을 효과적으로 억제하는 것이 확인되었다.