Xi Chen

Bio: Xi Chen is an academic researcher from Tsinghua University. The author has contributed to research in topics: Wireless sensor network & HVAC. The author has an hindex of 11, co-authored 29 publications receiving 315 citations.

A new gradient-based routing protocol in wireless sensor networks

Abstract: A new gradient-based routing protocol is proposed in this paper. It takes into account the minimum hop count and remaining energy of each node while relaying data from source node to the sink. The optimal routes can be established autonomously with our protocol. A simple acknowledgement scheme, which can be implemented without extra overheads, is proposed. Our protocol also employs data aggregation to save transmission energy. To handle the frequent change of the topology of the network, one scheme for topology update is provided. At last, simulation results illustrate the effect of system parameters on the protocol performance.

Long-Term Scheduling for Cascaded Hydro Energy Systems With Annual Water Consumption and Release Constraints

Abstract: Long-term scheduling for cascaded hydro energy systems is very important for low carbon energy production. It aims at determining the water release over a planning horizon to meet water resource requirements and the system demands for electric power. The problem is challenging in view of the complicated and stochastic system dynamics, nonlinear marginal cost, coupled hydraulic constraints, and the large problem size. In this paper we formulate the long-term scheduling problem of cascaded hydro energy systems with annual consumption and release constraints as a finite horizon constrained Markov decision process (CMDP), and develop a new rollout algorithm to optimize the policies. Numerical results demonstrate the effectiveness and the efficiency of the formulation and the new algorithm.

Coverage problems in sensor networks: A survey

Abstract: Sensor networks, which consist of sensor nodes each capable of sensing environment and transmitting data, have lots of applications in battlefield surveillance, environmental monitoring, industrial diagnostics, etc. Coverage which is one of the most important performance metrics for sensor networks reflects how well a sensor field is monitored. Individual sensor coverage models are dependent on the sensing functions of different types of sensors, while network-wide sensing coverage is a collective performance measure for geographically distributed sensor nodes. This article surveys research progress made to address various coverage problems in sensor networks. We first provide discussions on sensor coverage models and design issues. The coverage problems in sensor networks can be classified into three categories according to the subject to be covered. We state the basic coverage problems in each category, and review representative solution approaches in the literature. We also provide comments and discussions on some extensions and variants of these basic coverage problems.

Sustainable Queuing-Network Design for Airport Security Based on the Monte Carlo Method

Abstract: The design of airport queuing networks is a significant research field currently for researchers. Many factors must to be considered in order to achieve the optimized strategies, including the passenger flow volume, boarding time, and boarding order of passengers. Optimizing these factors lead to the sustainable development of the queuing network, which currently faces a few difficulties. In particular, the high variance in checkpoint lines can be extremely costly to passengers as they arrive unduly early or possibly miss their scheduled flights. In this article, the Monte Carlo method is used to design the queuing network so as to achieve sustainable development. Thereafter, a network diagram is used to determine the critical working point, and design a structurally and functionally sustainable network. Finally, a case study for a sustainable queuing-network design in the airport is conducted to verify the efficiency of the proposed model. Specifically, three sustainable queuing-network design solutions are proposed, all of which not only maintain the same standards of security, but also increase checkpoint throughput and reduce passenger waiting time variance.