Zhongwei Li

Multi-agent trust-based intrusion detection scheme for wireless sensor networks

Abstract In order to achieve both a higher detection rate and a lower false positive rate of internal node intrusion detection in layer-cluster wireless sensor networks, an intrusion detection scheme based on the use of both a multi-agent system and a node trust value is proposed. In this scheme, the multi-agent model framework is established in both the cluster heads and the ordinary sensor nodes to perform intrusion detection. First, various, typical node trust attributes are defined and Mahalanobis distance theory is used to judge whether these attributes are normal. Second, the node trust value is calculated and updated based on the combination of the Beta distribution and a tolerance factor. Finally, node intrusion detection is realized. Simulation results demonstrate that the modified scheme has a higher detection rate and a lower false positive rate, even when several types of intrusions are present.

A Survey on Key Pre-distribution Scheme of Distributed WSNs

Key management scheme is one of the hot issues in the research field of wireless sensor networks (WSNs). In this article, the evaluation criteria of key management scheme according to the features of WSNs are analyzed, the description and comparison of existing key pre-distribution schemes in distributed WSNs are given, and finally the future direction of WSNs key managements development is proposed.

Design optimization of key components’ spatial position of unilateral axle counting sensor

Purpose The unilateral axle counting sensor is an important railway signal device that detects a train. For efficient and stable detection, the amplitude of induced electromotive force and its changes must be big enough. Therefore, the purpose of this study is to find a way to design and optimize the sensor structure quickly and accurately. Design/methodology/approach With the help of extensive electromagnetic field calculations, the study puts forward a modified model based on the finite element method, establishes an independent air domain around the sensor, wheel and the railway and adopts a unique grid division method. It offers a design optimization method of the induction coil angles and its spatial location with respect to the excitation coil by using the combination weighting algorithm. Findings The modified modeling method can greatly reduce the number of finite element mesh and the operation time, and the method can also be applied to other areas. The combination weighting algorithm can optimize the structure of the sensor quickly and accurately. Originality/value This study provides a way to design and optimize the structure of the sensor and a theoretical basis for the development. The results can improve and expand the technology of the axle counting sensor.

A Survey on Intrusion Detection System for Advanced Metering Infrastructure

The security issues of smart grid have drawn more and more attention in the recent years. As a foundational part of smart grid, the cyber and physical security of advanced metering infrastructure (AMI) is of critical importance. Various securing solutions for AMI have been proposed, most of which based on cryptographic technology. However, as learned from experiences in IT environment, intrusion detection system (IDS) can dynamically monitoring the status of network-based systems and provide supplementary defensive capability besides the conventional static solutions, such as encryption, authentication, firewall, etc. In this paper, we analyze the potential threats in AMI and investigate the current academic approaches on intrusion detection systems and techniques for AMI. Then we give some recommendations in designing and deploying a practical AMI-IDS, and propose a comprehensive distributed IDS architecture suitable for AMI. In addition, the existing research problems and challenges are concluded to promote the future progress in this field.

Configuration analysis and optimization on multipolar Galatea trap

Multipolar Galatea magnetic trap simulation model was established with the finite element simulation software COMSOL Multiphysics. Analyses about the magnetic section configuration show that better magnetic configuration should make more plasma stay in the weak magnetic field rather than the annular magnetic shell field. Then an optimization model was established with axial electromagnetic force, weak magnetic field area and average magnetic mirror ratio as the optimization goals and with the currents of myxines as design variables. Select appropriate weight coefficients and get optimization results by applying genetic algorithm. Results show that the superiority of the target value of typical application parameters, including the average magnetic mirror can reduce more than 5%, the weak magnetic field area can increase at least 65%, at the same time, axial electromagnetic force acting on the outer myxines can be reduced to less than 50 N. Finally, the results were proved by COMSOL Multiphysics and the results proved the optimized magnetic trap configuration with more plasma in the weak magnetic field can reduce the plasma diffusion velocity and is more conducive for the constraint of plasma.

Quasi-Equilibrium Model for Separating the Plasma and the Conductor in the Galatea Device

In order to study the plasma distribution around the conductor coil in Galatea device, a 1-D plasma dynamic model of the linear topological Galatea device is established in this paper, and the static equilibrium analytical solution of this model is derived. The analytical results show that in the vicinity of the conductor coil, the closer to the conductor coil, the greater the plasma pressure is, which causes collision losses due to the plasma concentration on the surface of conductor coil. Therefore, absolute static balance does not exist near the conductor coil. Based on this fact, this paper introduces a quasi-equilibrium model with the plasma separated from the conductor coil by changing its carrying current form. The proposed method is verified by a simulation model established in COMSOL, and the simulation results show that the plasma can be separated from the conductor coil when an increasing current passes through the conductor coil. At the end of this paper, the effects on the separation efficiency of time-varying current with different increasing rate are also given. The duration of the quasi-equilibrium is also analyzed.

Design Optimization of Multipole Galatea Trap Coils by Multiple Population Genetic Algorithm

In order to improve the performance of multipole Galatea traps, this paper proposes an optimized method for the design of coil parameters. Based on an accurate magnetic field model, key parameters describing the multipole Galatea magnetic trap configuration were analyzed to establish an optimization model using the axial electromagnetic force, weak magnetic field area, and average magnetic mirror ratio as the optimization goals with the coil current as the design variable. Applying the improved multiple population genetic algorithm (MPGA), which has a strong searching ability and a fast convergence speed, enables production of optimization results following selection of the appropriate weight coefficients. Results confirm that optimization design results from MPGA are consistent with the design goals for different weight coefficients. In addition, the performance of multipole Galatea magnetic traps with optimization coil parameters was improved. Finally, the results from finite-element simulation software proved the validity and feasibility of the proposed method.

Analysis to Space Location Between Excitation Coil and Induction Coil of Unilateral Axle Counting Sensor

Introduces a kind of unilateral axle counting sensor and analysis the sensors working principle and the signals generation procedure, and gets the value of the induction electromotive force by simulation software at the same time. Finally, the rule of induction electromotive force difference changes along with the changing of coil position is given.

Study on Ethernet Communication Strategy for Electric Energy Data Acquisition System

As Ethernet technology is being matured and perfect, Ethernet also show the advantage of its application in industrial control field because of its good reliability and real-time performance. After introducing calculation method of basic power parameter briefly, the Ethernet communication strategy between smart meter and acquisition terminal in the electric energy data acquisition system is studied for the date communication requirements of energy data acquisition. The rule of data transfer regulation, and formulation method of Modbus/TCP protocol based on DLT 645, hardware design and software design of Ethernet communication interface are given. The test showed communication is stabilized, and the transmission efficiency of electric energy data meet requirement.

Analysis of the Steady State Characteristics and Regulation Strategies of the Frequency in the Northwest Power Grid

Using frequency data of the Northwest Power Grid from Feb. 15th to 28th, 2013 that is measured by PMU-light units in Shandong University, the steady state characteristics of frequency are analyzed in this paper. Duration and number of low-frequency and high-frequency events are listed. Statistics of daily highest, lowest and average frequency values are given. Ensemble averaged frequency values are calculated. Characteristics of steady-state frequency in the Northwest Power Grid are summarized and influence factors of frequency are discussed. The influence of the proportion of wind power on the frequency quality is simulated. The necessity of the application of a new frequency control method called DFR (Demand as Frequency Controlled Reserve) in the Northwest Power Grid is discussed.