• 한국군사과학기술학회지
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• 제7권3호
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• pp.21-29
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• 2004

Numerical analysis of aerodynamic heating for KPSAM is performed using aerodynamic heating model suitable to KPSAM, which has complex flow field resulting from the spike attached to the dome, such as large separation area and the strong shock/boundary layer interaction region around reattachment point on the dome. The aerodynamic heating model is validated and modified through the comparison between the flight test measurement and the thermal analysis results. TFD temperature sensors are installed on the dome to measure surface temperature during the flight. Computation results, obtained from the heat transfer analysis on the sensors, agree well with flight test data. The aerodynamic heating model provides heat transfer rate into surface as a boundary condition of unsteady 1D/axisymmetric thermal analysis on the missile structure. The axisymmetric thermal analysis using FLUENT is more versatile than the 1D analysis and can be applied to the heating problem related with complex structures and multi-dimensional heat transfer problems such as prediction of temperature rise at contact surface of different materials.

• 한국수소및신에너지학회논문집
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• 제31권2호
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• pp.202-209
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• 2020

In methanol steam reforming, commercial catalysts in the form of pellets are mainly used, but there are limitations to directly apply them to underwater weapon systems that require shock resistance and heat transfer characteristics. In this study, to overcome this problem, a multi-layer cup structure (MLCS) was applied to support a pellet type catalyst. The characteristics of pellet catalyst supported by MLCS and the pellet catalyst supported by conventional structure (CS) were compared by the reforming experiment. In the case of MLCS, a high methanol conversion rate was shown in the temperature range 200 to 300℃ relative to the CS manufactured with the same catalyst weight as MLCS. CS shown similar characteristics to MLCS when it manufactured in the same volume as MLCS by adding an additional 67% of the catalyst. In conclusions, MLCS can not only reduce catalyst usage by improving heat transfer characteristics, but also support pellet catalyst in multiple layers, thus improving shock resistance characteristics.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권9호
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• pp.2399-2418
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• 2023

The paper focuses on investigating secure transmission in wireless powered communication networks (WPCN) that involve multiple energy-constrained relays and one energy-constrained source. The energy is harvested from a power beacon (PB) while operating in the presence of a passive eavesdropper. The study primarily aims to achieve energy-efficient secure communications by examining the impact of channel estimation on the secrecy performance of WPCN under both perfect and imperfect CSI scenarios. To obtain practical insights on improving security and energy efficiency, we propose closed-form expressions for secrecy outage probability (SOP) under the linear energy harvesting (LEH) model of WPCN. Furthermore, we suggest a search method to optimize the secure energy efficiency (SEE) with limited power from PB. The research emphasizes the significance of channel estimation in maintaining the desired performance levels in WPCN in real-world applications. The theoretical results are validated through simulations to ensure their accuracy and reliability.

• 한국분말재료학회지
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• 제13권4호
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• pp.269-277
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• 2006

[ ${\beta}-W(W_3O)$ ] oxide layer on the surface of each W(tungsten) nanopowder produced by the electric explosion of wire(EEW) process were formed during the 1vol.% air passivation process. The oxide layer hindered sintering densification of compacts during SPS process. The oxide phase was reduced to the pure W phase during SPS. The W nanopowder's compacts treated by the hydrogen reduction showed high sintered density of 94.5%. after SPS process at $1900^{\circ}C$.

• 전기학회논문지
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• 제65권2호
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• pp.342-348
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• 2016

We propose an obstacle detection algorithm for unmanned ground vehicle on uneven terrain. The key ideas of the proposed algorithm are the use of two-layer laser range data to calculate the gradient of a target, which is characterized as either ground or obstacles. The proposed obstacle detection algorithm includes 4-steps: 1) Obtain the distance data for each angle from multiple lidars or a multi-layer scan lidar. 2) Calcualate the gradient for each angle of the uneven terrain. 3) Determine ground or obstacle for each angle on the basis of reference gradient. 4) Generate a new distance data for each angle for a virtual laser scanner. The proposed algorithm is verified by various experiments.

• 정보보호학회논문지
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• 제17권6호
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• pp.41-56
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• 2007

본 논문에서는 국내 무선인터넷 표준 플랫폼 규격인 WIPI(Wireless Internet Platform for Interoperability)에 적합한 Specification 기반의 침입탐지시스템을 제안한다. 시스템을 제안함에 있어서는 경량의 단순화된 코드, C와 자바 등의 다양한 언어 수용성 그리고 하드웨어 독립성을 고려하였다. 제안한 침입탐지시스템은 WIPI HAL(Handset Adaptation Layer)의 주요 AP 대상으로 침입을 탐지하는 알고리즘에 기반하고 있으며, HAL API에 추가 가능한 형태의 mIDS(mobile Intrusion Detection System) API 그룹을 프로토타입으로 정의하였고, 자바 라이브러리와 WIPI 에뮬레이터를 이용한 시뮬레이션을 통해 적용 가능성을 증명하였다.

• 정보보호학회논문지
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• 제20권5호
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• pp.99-110
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• 2010

네트워크 대역폭 소모 위주로 발생했던 DDoS 공격이 최근에는 웹서비스 대상 응용계층에서의 DDoS 공격 위주로 발생하고 있다. 응용계층 DDoS 공격은 Source IP당 발생하는 트래픽이 감소하고 정상 사용자의 트래픽과 유사한 형태로 진화하고 있어 기존 Threshold 기반 탐지기법으로 대응하기 어렵다. 본 논문에서는 발생 가능한 Get Flooding의 모든 유형을 도시하고, 간단하면서도 강력한 3가지 대응 메커니즘을 제시한다. 특허, 제안된 메커니즘은 현재까지 발생한 모든 DDoS 공격도구를 탐지 및 차단할 수 있으며, 성능분석 결과 상용 환경에 적용할 수 있을 것으로 예상된다.

• Rapid Communication in Photoscience
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• 제3권2호
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• pp.32-34
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• 2014

We report the performance improvement of electrochromic devices for modulating the transmittance contrast of long wavelength infrared light between 1.5 and 5.0 ${\mu}m$ based on a double layer of conducting polymers. The device, fabricated with poly(3-hexylthiophene) (P3HT) and poly(3,4-ethylenedioxythiophene) (PEDOT) as the first and second layers, respectively, showed an transmittance contrast of 60% with a response rate under 5 s, which is greater than the transmittance contrast of cells based on only P3HT or PEDOT (approximately 40%).

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2014년도 제50차 하계학술대회논문집 22권2호
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• pp.227-229
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• 2014

플래시 메모리는 빠른 처리 속도, 비휘발성, 저 전력, 강한 내구성 등으로 인해 최근 스마트폰, 태블릿, 노트북, 컴퓨터와 같은 여러 분야에서 많이 사용하고 있다. 최근 기존에 사용하던 NAND 플래시가 미세화 기술의 한계에 봉착함에 따라 기존 2차원 구조의 NAND플래시를 대처할 장치로 3차원 수직구조 NAND 플래시 메모리(3D Vertical NAND)가 주목받고 있다. 기존의 플래시 메모리는 데이터를 효율적으로 삽입/삭제/검색하기 위해 B-tree와 같은 색인기법을 필요로 한다. 플래시 메모리 상에서 B-tree 구현에 관한 기존 연구로서는 BFTL(B-Tree Flash Translation Layer)기법이 최초로 제안되었다. 현재 3차원 V-NAND 구조의 플래시 메모리가 시작품으로 제작되어 머지않아 양산 될 예정이다. 본 논문에서는 향후 출시될 3차원 구조의 플래시 메모리에 적합한 Octree 기반의 파일시스템을 제안한다.

• Journal of Power Electronics
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• 제13권3호
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• pp.362-368
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• 2013

Commercial home appliances using remotely controlled systems consume electric power while in standby mode to prepare for receiving a remote turn-on signal. The proposed power system can significantly reduce standby power consumption without increasing cost. Furthermore, since a Electronic Double Layer Capacitor (EDLC) is used as an auxiliary power storage element, the life cycle is longer and system reliability can be better than with existing approaches. When the energy of the EDLC is not sufficient for turning on the appliance, the power system charges the EDLC without affecting the main system. The proposed power system is verified with a commercial LCD TV and a 3.93mW standby consumption is obtained. This standby consumption can be regarded as zero standby equipment according to the IEC-62031 standard.