• 한국음향학회지
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• 제42권3호
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• pp.203-213
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• 2023

의료용 초음파 영상 시스템에서, 영상점의 밖에서 오는 신호가 초음파 수신 집속 과정에서 완전히 제거되지 않으면 부엽을 발생시킨다. 부엽의 시간 신호가 영상점에서 오는 시간 신호(주엽)와 같이 중첩되어 나타나면 시간 영역에서 필터 처리를 이용하여 완전히 제거하기 어렵다. 그러나 수신 집속 과정에서 시간 -채널 신호를 푸리에 변환하면, 주엽과 부엽의 신호는 주파수 스펙트럼 영역에서 공간적으로 분리가 된다. 따라서 스펙트럼 영역에서 계산한 주엽과 부엽의 신호크기를 이용하여 크기 가중치를 계산하여 영상에 곱함으로써 부엽을 억제하였다. 그리고 주엽과 부엽의 스펙트럼이 인접할 때, 주엽과 부엽 스펙트럼 사이의 거리에 따라 거리 가중치를 적용하였다. 64 채널 선형 트랜스듀서를 사용하는 5 MHz의 초음파 영상 시스템에서 점확산 영상과 다른 밝기의 낭종을 가지는 스페클 영상을 합성하고 가중치를 적용하여 초음파 영상을 계산하였다. 점반사체 영상에서 해상도의 변화 없이 부엽이 크게 줄어들었으며 낭종 영상에서 대조도가 크게 개선됨을 컴퓨터 시뮬레이션으로 확인하였다.

• 전력전자학회논문지
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• 제11권3호
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• pp.233-238
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• 2006

전력 외란을 해결하기 위해서는 전력 계통의 전원 측과 부하 측 양단에서 전력 성분의 측정이 요구된다. 본 논문은 전원 측과 부하 측 양단에서 동시에 전력 성분을 측정하고 분석할 수 있는 DSP(디지털 신호 처리 장치) 기반의 다채널(전압 8채널, 전류 10채널) 전력 성분 측정 시스템을 제안하였다. 개발된 시스템은 YOKOGAWA 2558을 이용하여 전압과 전류를 보정한 후, 전력 계통 현장에서 실험하였다.

• Korean Journal of Hydrosciences
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• 제6권
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• pp.67-79
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• 1995

The reattachment of buoyant efflluent to a shore in a crossflow is investigated experimentally. The effluent is prodeced by discharging heated water through a projected side channel into a confined crossflow of the same depth. In the projecting effluent, the size of recirculating region, which is formed by deflected thermal plume on the lee of the effluent, tends to increase, but the maximum temperature decreases in the direction of the crossflow and it has more uniform transverse spreading compared to non-projected type. The heat flux across the crossflow is found to be independent of the projceted length of the side channel under relatively high buoyancy flux on the contrary to low buoyancy flux. The reattachment of th effluent can be specified by both velocity ratio and densimetric Froude number, whereas only the velocity ratio is governing factor to the reattachment of the effluent in the case of non-projecting type.

• Journal of information and communication convergence engineering
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• 제12권4호
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• pp.237-245
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• 2014

In this study, software-based countermeasures against a side-channel cryptanalysis of the Rabbit stream cipher were developed using Moteiv's Tmote Sky, a popular wireless sensor mote based on the Berkeley TelosB, as the target platform. The countermeasures build upon previous work by improving mask generation, masking and hiding other components of the algorithm, and introducing a key refreshment scheme. Our contribution brings improvements to previous countermeasures making the implementation resistant to higher-order attacks. Four functional metrics, namely resiliency, robustness, resistance, and scalability, were used for the assessment. Finally, performance costs were measured using memory usage and execution time. In this work, it was demonstrated that although attacks can be feasibly carried out on unprotected systems, the proposed countermeasures can also be feasibly developed and deployed on resource-constrained devices, such as wireless sensors.

• 정보보호학회논문지
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• 제23권3호
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• pp.561-566
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• 2013

본 논문은 Torus-Based-Cryptosystem 중 $T_2(p)$ 에서 부채널공격을 방지하는 효율적인 지수 연산방법을 제안한다. 제안한 지수 연산방법은 일반적인 지수 연산보다 더 효율적일 뿐만 아니라 제곱과 곱셈 연산의 계산량 차이를 없게하여 SPA 공격에 안전하다. 또한 상군(quotient group)의 특성을 이용하여 지수 연산시 메시지를 난수화하여 제1차 DPA 공격도 방어할 수 있다.

• Journal of Communications and Networks
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• 제10권4호
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• pp.437-443
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• 2008

The randomized projective coordinate (RPC) method applied to a pairing computation algorithm is a good solution that provides an efficient countermeasure against side channel attacks. In this study, we investigate measures for increasing the efficiency of the RPC-based countermeasures and construct a method that provides an efficient RPC-based countermeasure against side channel attacks. We then apply our method to the well-known $\eta_T$ pairing algorithm over binary fields and obtain an RPC-based countermeasure for the $\eta_T$ pairing; our method is more efficient than the RPC method applied to the original $\eta_T$ pairing algorithm.

• 정보보호학회논문지
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• 제12권4호
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• pp.99-114
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• 2002

실행시간이나 전력 소모량 분석 등과 같은 부가채널 공격에 안전하면서도 보다 효율적인 새로운 타원곡선 상수배 알고리즘을 제안한다. 먼저 기존 방식들을 분석하여 잠재적인 문제점들을 지적하고, 이런 문제점들을 제거할 수 있는 간단한 $\pm$1-이진 부호화 방식을 제안한다. 또한 제안 부호화 방식을 이용한 이진 및 고정 윈도우 알고리즘을 기술하고 안전성과 효율성을 분석한다.

• 반도체디스플레이기술학회지
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• 제12권4호
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• pp.21-25
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• 2013

This paper is for enhancing the breakdown voltage of MHEMTs with an InP-etchstop layer. The fully removed recess structure in the drain side of MHEMT shows that the breakdown voltage enhances from 2 V to 4 V in the previous work. This is because the surface effect at the drain side decreases the channel current and the impact ionization in the channel at high drain voltage. In order to increase the breakdown voltage at the same asymmetric gate-recess structure, the InGaAs channel structure is replaced with the InGaAs/InP composite channel in the simulation. The simulation results with InGaAs/InP channel show that the breakdown voltage increases to 6V in the MHEMT as the current decreases. In this paper, the simulation results for the InGaAs/InP channel are shown and analyzed for the InGaAs/InP composite channel in the MHEMT.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1147-1152
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• 2009

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the zigzag channel PCHE using diffusion bonding technology by numerical analysis. PCHE of five types are designed, which are zigzag channel angle $180^{\circ}$, $160^{\circ}$, $140^{\circ}$, $120^{\circ}$ and $100^{\circ}$. The zigzag PCHE was numerically investigated for Reynolds number in a range of $150{\sim}800$. The temperatures of the hot side were performed at $80^{\circ}C$ while that of the cold side was conducted at $20^{\circ}C$. The results show that the performance of heat transfer rate for zigzag channel $100^{\circ}$ increases about 11.5% compared to that of zigzag channel $180^{\circ}$. On the other hand, the performance of pressure drop for zigzag channel $100^{\circ}$ is remarkably higher than that of zigzag channel $180^{\circ}$, about 1.4 times.

• 설비공학논문집
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• 제21권9호
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• pp.475-482
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• 2009

The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the zigzag channel PCHE using diffusion bonding technology by numerical analysis. PCHE of five types are designed, which are zigzag channel angle 180$^{\circ}$, 160$^{\circ}$, 140$^{\circ}$, 120$^{\circ}$ and 100$^{\circ}$. The zigzag PCHE was numerically investigated for Reynolds number in a range of 150$\sim$800. The temperatures of the hot side were performed at 80$^{\circ}$ while that of the cold side was conducted at 20$^{\circ}C$. The results show that the performance of heat transfer rate for zigzag channel 100$^{\circ}$ increases about 11.5% compared to that of zigzag channel 180$^{\circ}$. On the other hand, the performance of pressure drop for zigzag channel 100$^{\circ}$ is remarkably higher than that of zigzag channel 180$^{\circ}$, about 2.4 times.