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디지털 현미경 홀로그래피 기법을 이용한 마이크로 액체 제트 유동에 관한 실험적 연구
이한얼(Haneol Lee),이재호(Jaiho Lee),신원규(Weon Gyu Shin) 한국가시화정보학회 2018 한국가시화정보학회지 Vol.16 No.1
In this study, the effect of injection pressure on the column diameter and droplet velocity of liquid jet with the weakly turbulent Rayleigh-like breakup mode is experimentally studied using digital microscopic holography (DMH). The injection nozzle has the diameter of 50 μm and injection pressure is varied from 0.1 to 0.4 MPa. When the micro liquid jet is injected into still air, the double-pulsed holograms was recorded on a CCD sensor and numerically reconstructed in order to obtain well focused images. In this study, the liquid column diameter from 50 μm orifice nozzle is shown to be changed slightly but the droplet velocity is increased proportionally as the injection pressure is increased.
이한얼(Haneol Lee),오남수(Namsoo Oh),로드리그 휴고(Hugo Rodrigue) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
In this study, an inflatable gripper made with plastic films based on pouch motors is introduced. Pouch motor is an actuator which makes contraction in the longitudinal direction while expanding in the lateral direction when pressure is applied to the pouch. If the length of both ends of the pouch motor is limited to less than total length, overlap occurs between two inflated pouches makes forces outwards. And if this of one side is limited, pouches of unfixed side cannot maintain the overlap, so it can make bending angles. The gripper consists of two pouch motors based on this principle. First chamber makes bending motion by inflating. Second chamber is constrained to the unfixed side of the first chamber. It prevents the first chamber being released by the load and makes forces higher. Single actuator made with PE tubes with a width of 50 mm and a thickness of 0.05 mm can bends about 360 degrees and sustains over 1 kg loads at 10 kPa. Bending angles and forces of the gripper at the same pressure can be varied by changing the length of constraint or size of pouches.
이한얼(Haneol Lee),김휘강(Huy Kang Kim) 한국정보보호학회 2021 정보보호학회논문지 Vol.31 No.4
커널을 변조하는 루트킷과 같은 악성코드가 만약 메모리 분석을 회피하기 위한 메커니즘을 추가하게 될 경우, 분석이 어려워지거나 불가능하게 되면서 분석가의 판단에 악영향을 미칠 수 있다. 따라서 향후 고도화된 커널 변조를 통해 탐지를 우회하는 루트킷과 같은 악성코드에 선제적으로 대응하고자 한다. 이를 위해 공격자의 관점에서 윈도우 커널에서 사용되는 주요 구조체를 분석하고, 커널 객체를 변조할 수 있는 방법을 적용하여 메모리 덤프 파일에 변조를 진행하였다. 변조 결과 널리 사용되는 메모리 분석 도구에서 탐지가 되지 않는 것을 실험을 통해 확인하였다. 이후 분석가의 관점에서 변조 저항성의 개념을 사용하여 변조를 탐지할 수 있는 소프트웨어 형태로 만들어 기존 메모리 분석 도구에서 탐지되지 않는 영역에 대해 탐지 가능함을 보인다. 본 연구를 통해 선제적으로 커널 영역에 대해 변조를 시도하고 정밀 분석이 가능하도록 인사이트를 도출하였다는 데 의의가 있다 판단된다. 하지만 정밀 분석을 위한 소프트웨어 구현에 있어 필요한 탐지 규칙을 수동으로 생성해야 한다는 한계점이 존재한다. Malware, such as a rootkit that modifies the kernel, can adversely affect the analyst’s judgment, making the analysis difficult or impossible if a mechanism to evade memory analysis is added. Therefore, we plan to preemptively respond to malware such as rootkits that bypass detection through advanced kernel modulation in the future. To this end, the main structure used in the Windows kernel was analyzed from the attacker’s point of view, and a method capable of modulating the kernel object was applied to modulate the memory dump file. The result of tampering is confirmed through experimentation that it cannot be detected by memory analysis tool widely used worldwide. Then, from the analyst’s point of view, using the concept of tamper resistance, it is made in the form of software that can detect tampering and shows that it is possible to detect areas that are not detected by existing memory analysis tools. Through this study, it is judged that it is meaningful in that it preemptively attempted to modulate the kernel area and derived insights to enable precise analysis. However, there is a limitation in that the necessary detection rules need to be manually created in software implementation for precise analysis.