Different applications have different security sensitivities, which are determined by subjective judgment in the process of security research on Internet of Things(IOT). This paper presents a Security Model of IOT Based on Hierarchy(BHSM-IOT), which can be used to analyze the topology structure, predict the attack source and attack type and determine the application level of security domain, so that appropriate safety technical configuration can be made. The model is applied in a wisdom campus system of a university, and result proves that it is helpful for the managers to construct a more safe and stability system for the students and teachers with the model.

Data replication is widely used to hide network latency, enhance response time and improve interaction experience in real-time collaboration. Users can operate on data replicas unconstrainedly, which results in consistency maintenance problems of these replicas. Aiming at the problem, this paper introduces the challenges of consistency maintenance according to the features and requirements of real-time collaboration applications. By analyzing representative key techniques of operation transformation, address space transformation and WOOT, it elaborates the challenging problems such as Undo and String transformation, and details how these key techniques are applied in the transparent adaptation from single-user applications to collaborative ones, Web 2.0 and mobile collaboration environments.

Green computing is a new kind of computing mode to promote the scientific and technological improvement and sustainable social development. It is the focus of international competition and concerns national politics, economics and social safety. It involves system architecture, system software, parallel and distributed computing and computer network. Under the premise of guaranteeing computing efficiency, reliability and providing pervasive service, it aims to realize low power. The new kind of computing mode, which is new computer system architecture-oriented and cloud computing-included, through building energy awareness computing system, Internetworking environment, and computing service system, provides low power supporting environment for personalized, diversified information service mode.