Time synchronization is required in wireless sensor networks in order to improve its performance. This improvement could be noticed in terms of energy, storage, computation, shared resources or bandwidth. One of the main applications in WSNs has been to decrease the energy consumption. A wireless network can save energy with this feature, but if this synchronization is corrupted, it could cause a worse behavior. Firstly, we will analyze which are the most important time synchronization issues. Then, a secure time synchronization method will be presented for group-based wireless sensor networks to avoid malicious attacks. The synchronization technique is based on a system model for secure intra-group synchronization. This system will use simple messages, where nodes of each group will exchange several parameters like time stamps, groupID, etc. in order to make a secure system. The system proposed has high scalability, due to group-based feature, while saves energy thanks to the designed synchronization technique. In order to test our proposal we will simulate several situations to show the performance of our synchronization algorithm.

关键词：传感器；时间同步

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Models that account for the progression of nation-building and the impacts of the instruments of national power -- Diplomacy, Informational, Military, and Economic effects -- are rare. This research proposes the development of such a model. Through the derivation of state indices for the operational variables of Political, Military, Economic, Social, Infrastructure, and Information, a functional form of a system of differential equations is developed to account for the interactions between the state indices and instruments of national power. This methodology is a mean-field inverse problem which solves for the coefficients of the differential equations in a data- driven manner. Publicly available data are used to develop the indices and describe the instruments of national power. Applying mean-field theory allows the differential equations to be solved through a nonlinear program that derives minimum error-producing coefficients. An application of the model is derived for Operation Iraqi Freedom to demonstrate the utility as well as the effects of various alternate strategies, using the dynamics captured in the model. This modeling approach offers a potentially significant capability for analyzing and planning future Stabilization, Security, Transition, and Reconstruction Operations (STTRO).

关键词：模型；安全；微分方程

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The concept of forward secrecy is extended to wireless sensor networks where it is frequent that nodes run out of energy and new nodes join the network. However it should not be able to retrieve the previous session key or some crucial information. In 2011 Hagras et al. proposed a key management scheme for heterogeneous wireless sensor networks, which satisfies confidentiality, authentication, integrity and unforgetability but lacks forward secrecy. In this paper, the shortcomings of the victim scheme has been extricated and repaired with the help of Elliptic Curve Discrete logarithm problem (ECDLP). An elliptic curve based signcryption key management scheme has been proposed which includes forward secrecy.

关键词：传感器；签名；密钥

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Wireless sensor networks (WSNs) have generated immense interest among researches for the last few years motivated by several theoretical and practical challenges. The increase in interest is mainly attributed to new applications designed with large scale networks consisting of devices capable of performing computations on the sensed data and finally processing the data for transmitting to remote locations. Providing security to WSNs plays a major role as these networks are generally deployed in inaccessible terrain and also for their communication being in the wireless domain. These reasons impose security mechanisms to be employed on the highly vulnerable sensor networks that are robust enough to handle attacks from adversaries. WSNs consist of nodes having limited resources and therefore classical security measures applicable in traditional networks cannot be applied here. So the need of the hour is using systems that lie within the boundary of the sensor nodes resource potential as well competent enough to handle attacks. Intrusion detection is one such defense used in sensor networks having the ability to detect unknown attacks and finding means to thwart them. Researches have found intrusion detection system (IDS) to be very much compatible in sensor networks. Therefore intrusion detection holds a very prominent research area for researchers. So familiarity with this promising research field will surely benefit the researchers. Keeping this in mind we survey the major topics of intrusion detection in WSNs. The survey work presents topics such as the architectural models used in the different approaches for intrusion detection, different intrusion detection techniques and highlights intrusion detection methods applicable for the different layers in sensor networks. The earlier achievements in intrusion detection in WSNs are also summarized along with more recent works and existing problems are discussed. We also give an insight into the possible directions for future work in intrusion detection involving different aspects in sensor networks.

关键词：无线传感器；问题；挑战；方法

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Today, medical knowledge is expanding so rapidly that clinicians cannot follow all progress any more. This is one reason for making knowledge-based systems desirable in medicine. Such systems can give a clinician a second opinion and give them access to new experience and knowledge. Recent advances in Artificial Intelligence (AI) offers methods and techniques with the potential of solving tasks previously difficult to solve with computer-based systems in medical domains. This chapter is especially concerned with diagnosis of stress-related dysfunctions using AI methods and techniques. Since there are large individual variations between people when looking at biological sensor signals to diagnose stress, this is a worthy challenge. Stress is an inevitable part of our human life. No one can live without stress. However, long-term exposure to stress may in the worst case cause severe mental and/or physical problems that are often related to different kind of psychosomatic disorders, coronary heart disease etc. So, diagnosis of stress is an important issue for health and well-being. Diagnosis of stress often involves acquisition of biological signals for example finger temperature, electrocardiogram (ECG), electromyography (EMG) signal, skin conductance (SC) signals etc. and is followed by a careful analysis by an expert. However, the number of experts to diagnose stress in psycho-physiological domain is limited. Again, responses to stress are different for different persons. So, interpreting a particular curve and diagnosing stress levels is difficult even for experts in the domain due to large individual variations. It is a highly complex and partly intuitive process which experienced clinicians use when manually inspecting biological sensor signals and classifying a patient. Clinical studies show that the pattern of variation within heart rate i.e., HRV signal and finger temperature can help to determine stress-related disorders. This chapter presents a signal pre-processing and feature extraction approach based on electrocardiogram (ECG) and finger temperature sensor signals. The extracted features are used to formulate cases in a case-based reasoning system to develop a personalized stress diagnosis system. The results obtained from the evaluation show a performance close to an expert in the domain in diagnosing stress.

关键词：传感器；生物；案例

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In present era of railways transportation the presence of the railway signal system in railway networks makes the train control system much easier & safer. Today the all railway signal systems are based on electrical devices. In this paper we propose a new signal system for railway network which will be based on wireless sensor devices. Proposed frame work helps the train control mechanism to control the train even in low visibility weather condition like dust, haze, snow, heavy rain, fogginess conditions. In this paper we proposed the idea and the framework for the new wireless sensor device based signal system which can be implemented in modification in existing current signal systems.

关键词：传感器；铁路信号；框架

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Wireless sensor network (WSN) technology promises to have a high potential to tackle environmental challenges and to monitor and reduce energy and greenhouse gas emissions. Indeed, WSNs have already been successfully employed in applications such as intelligent buildings, smart grids and energy control systems, transportation and logistics, and precision agriculture. All these applications generally require the exchange of a large amount of data and the localization of the sensor nodes. Both these two tasks can be particularly energy-hungry. Since sensor nodes are typically powered by small batteries, appropriate energy saving strategies have to be employed so as to prolong the lifetime of the WSNs and to make their use attractive and effective. To this aim, the study of data compression algorithms suitable for the reduced storage and computational resources of a sensor node, and the exploration of node localization techniques aimed at estimating the positions of all sensor nodes of a WSN from the knowledge of the exact locations of a restricted number of these nodes, have attracted a large interest in the last years. In this chapter, we discuss how multi-objective evolutionary algorithms can successfully be exploited to generate energy-aware data compressors and to solve the node localization problem. Simulation results show that, in both the tasks, the solutions produced by the evolutionary processes outperform the most interesting approaches recently proposed in the literature.

关键词：传感器；多目标

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Image sensors have become significant due to the high demand from different applications. Charge-Coupled Device (CCD) and Complementary Metal-Oxide Semiconductor (CMOS) image sensors are two different technologies used for capturing images digitally. Both types of imagers are fabricated in silicon and convert light into electronic signals for processing. Section 3.1 of this chapter discusses briefly the CCDs and CMOS image sensors. Section 3.2 gives an overview of the photodetection in silicon. The different types of photodiodes used to sense the light intensity are discussed. Section 3.3 discusses the basic types of pixels commonly used in CMOS image sensors. The advantages and disadvantages of each type are elaborated. Section 3.4 discusses the performance parameters of the CMOS image sensors and section 3.5 presents the peripheral circuits used in conventional CMOS image sensors. Section 3.6 describes the design of a 128×128 pixel CMOS image sensor chip with in-pixel analog memory and a 1-bit dynamic memory in a standard 0.18μm 1-poly-3-metal CMOS CIS (CMOS Image Sensor) process. The characterization and measurement results of the image sensor are also presented in section 3.7.

关键词：图像传感器；CMOS

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This chapter has presented the background to power system dynamics, as appropriate for use in a modelling study of a power system. The complexities of the models depend on the type of transient and the system being investigated. Since we are mostly concerned about the frequency control of the power system, more effort has been placed on the active power flow in the system. Generally, the components of the power system that influence the electrical torque include the network state before and after the transient, the loads and their characteristics, the synchronous generator, the speed governor and other supplementary controls such as tie-line power flows.

关键词：电力系统；动态

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In the future, technology will be hidden in the environment and invisible to the user but, at the same time, responsive and adaptive to user interaction and environmental variations [1]. For example, smart buildings will become aware of the presence of people and of their needs: thanks to this, temperature and light conditions will be adapted automatically for the best comfort and optimal power consumption. The realization of such a vision requires a technology that can sense, process and respond to external stimuli, both human and environmental, coming from many spots of a large environment, such as a room, a house or a whole building. An answer to such needs may come from WSNs. These are networks that consist of a large number of energy-autonomous nodes deployed into the environment to collect physical data.

关键词：传感器；集成

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