(A)Study on the meaning acceptance of concealed image : based on my works

학위논문(석사)--서울대학교 대학원 :서양화과 서양화전공,2005.Maste

A study on the localization strategy of LG Electronics

Maste

위치 및 이동성 분석을 활용한 이동컴퓨팅 시스템의 성능 개선에 관한 연구

학위논문(박사) - 한국과학기술원 : 전산학부, 2016.8 ,[iv, 67 p. :]Today, as mobile communication and computing technologies are significantly improving, many people enjoy the convenience of mobile application services through portable devices, such as smart-phones and tablet computers. Based on these advances, we are approaching the era of the Internet-of-Things (IoT) in which light-weight computing substrates are installed in real world objects so that they become parts of the Internet world. In an effort to realize the vision of the IoT, this dissertation proposes to exploit user location and mobility-related features to improve the performance of wireless mobile computing systems. Specifically, it explores the following two issues. As the first result of this dissertational research, we present a new distributed hash table (DHT) for wireless mobile environments, especially for when a higher level of mobility and membership dynamics occur together. In this DHT paradigm, a publish/look-up process consists of a sequence of spatial motion tracking of the rendezvous node that is responsible for directory information. Thus, we name the protocol Motion-MiX-DHT (MX-DHT). As opposed to conventional topology-based DHT schemes that suffer from frequent disconnections of the logical topology caused by user mobility, MX-DHT provides robust publish/look-up paths exploiting one-hop encounter records as the milestones for motion tracking. This is inspired by two mobility-related features: the mobility capacity effect and motion-mix property. By leveraging the mobility capacity effect, which implies mobility-assisted data dissemination, motion tracking is successfully done with a low-cost search-and-forward process. Join/leave operation also consists of a low-cost one-hop signaling process depending on the motion-mix property. Consequently, in high-speed mobility and dynamic membership environments, MX-DHT achieves a significant reduction in the communication costs of publish/look-up and join/leave operations as compared to conventional mobile DHT schemes. An extensive set of experiments showed that MX-DHT is a cost-effective solution to providing various distributed services (e.g., domain name service, P2P file sharing, distributed file system, cloud storage, and so on) in a wide range of wireless mobile networks with dynamic mobility and membership changes (e.g., vehicular or human-carried device networks). The second focus of this dissertation is developing an analytical method to estimate the mean cell-sojourn time in 2-tier heterogeneous (e.g., macro/pico, macro/femto or macro/Wi-Fi) networks, which have been widely used to increase the capacity density of mobile systems. In heterogeneous networks, accurate estimation of the mean cell- sojourn time is critical for evaluating the performance of the network and its applications. It is especially important to analyze the cell- sojourn times of mobile users, as they reside in different network tiers: either macro-cell-only or small-cell-covered areas. However, because small cells are deployed in an irregular manner, it is difficult to derive the analytical mean cell sojourn time in a macro-cell-only area. We propose a novel approach to resolve this difficulty. Based on the location distribution features of general random walk mobility, we developed a simple but effective trick that approximates a heterogeneous network to a discrete grid so that it becomes tractable, making it possible to derive the analytical mean sojourn time in the macro-cell-only area. Simulation results confirm that the proposed method has excellent accuracy for general random walk mobility models, including random waypoint, Brownian motion, and Levy walk. In this dissertational research, user location and mobility-related properties such as mobility capacity effect, motion-mix property, and uniform location distribution feature, play important roles to achieve the above contributions. Considering that these features are satisfied well in various user mobility models including random waypoint, Brownian motion, Manhattan, urban vehicular, and Levy walk, our proposed works can be applicable to a wide range of mobile computing services. MX-DHT can be used as a data discovery/sharing protocol for autonomous local ad hoc communication. And, our cell sojourn time estimation method may contribute to optimize infrastructured wireless Internet access. By interworking these technologies, flexible pervasive Internet connectivity can be established so that we can realize various IoT services.한국과학기술원 :전산학부

A Clinic Decision Support System on Macintosh HyperCard and Excel

For the strategic management of the small and/or mid sized clinics, the introduction of the clinic information system is necessary. Currently there are not many information systems for the clinics, yet. In this study, we have developed a clinic information system (CLINSYS) as a guiding prototype and suggested the development directions of the total integrated clinic decision support system. For the better user interface and easy communication. the object-oriented language Macintosh Hyper-Card and Excel are used as the developing tools. And as a part of the integrated decision system, an expert system to consult about the urine test and the blood test interpretation has been developed using the Macintosh spreadsheet Excel

Bandwidth efficient key management for secure multicast in clustered wireless networks

학위논문(석사) - 한국과학기술원 : 전산학전공, 2009.2, [ v, 42 p. ]무선 통신 기술의 발달로 인해 앞으로는 다양한 종류의 멀티캐스트 기반 서비스가 클러스터화된 무선 네트워크를 통하여 이루어질 것으로 예상된다. 보안성을 제공하는 멀티캐스트 서비스의 경우 암호화에 사용하는 그룹키의 관리가 중요한 문제가 된다. 따라서 다양한 종류의 그룹키 관리 기법들이 계속해서 제안되고 있다. 대표적인 그룹키 관리 기법 중 하나인 트리 기반 그룹키 관리 기법은 키 분배 센터가 전송해야 하는 키 갱신 메시지의 수를 효과적으로 줄인다는 장점을 지니고 있지만, 키 갱신 메시지를 전달하는데 실제로 소모되는 네트워크 대역폭을 정확히 고려하지 않고 있다. 본 논문은 그룹 멤버쉽이 동적으로 변하는 클러스터화된 무선 네트워크 환경에서 트리 기반 그룹키 관리 기법을 사용했을 때 키 갱신을 위한 대역폭 소모량을 효율적으로 절감할 수 있는 방법을 제시하고 있다. 컴퓨터 시뮬레이션을 통한 실험은 제안하는 방법이 기존의 기법들에 비해 매우 우수한 대역폭 절감 능력을 지니고 있음을 보여주고 있다. 본 논문에서 제시하는 그룹키 관리 기법은 향후 클러스터화된 무선 네트워크 상에서 대규모의 컨텐츠를 제공하는 멀티캐스트 어플리케이션에 효과적으로 결합되어 사용될 수 있을 것이다.한국과학기술원 : 전산학전공