Search

The secure authenticated key establishment between nodes in Wireless Sensor Networks (WSNs) has not been fully solved in the existing schemes. It’s a good idea to apply the Diffie-Hellman protocol to address it perfectly, but the existing authenticated Diffie-Hellman (ADH) protocols are not perfect because their authentication are partial or delayed. In this paper, we first present a concept of full authentication and propose a new fully authenticated Diffie-Hellman (FADH) prototype with light-certificate-based authentication. And then based on the theory of elliptic curve cryptography, we construct the TinyADH (Tiny Authenticated Diffie-Hellman) protocol with applying the FADH in WSNs. Compared with the existing similar solutions, TinyADH has lower communication overload, is easier to implement into existing standards, and more secure under equivalent computational complexity. The experimental results show that using this scheme for a successful key agreement between two nodes averagely takes about 54 seconds on TelosB. Moreover, the simulation results indicate that repeated key agreement can improve the secure connectivity rate. However, considering the cost performance ratio, it is advisable to take 2 runs of the negotiation. [ABSTRACT FROM AUTHOR]

The addition of massive machine type communication (mMTC) as a category of Fifth Generation (5G) of mobile communication, have increased the popularity of Internet of Things (IoT). The sensors are one of the critical component of any IoT device. Although the sensors posses a well-known historical existence, but their integration in wireless technologies and increased demand in IoT applications have increased their importance and the challenges in terms of design, integration, etc. This survey presents a holistic (historical as well as architectural) overview of wireless sensor (WS) nodes, providing a classical definition, in-depth analysis of different modules involved in the design of a WS node, and the ways in which they can be used to measure a system performance. Using the definition and analysis of a WS node, a more comprehensive classification of WS nodes is provided. Moreover, the need to form a wireless sensor network (WSN), their deployment, and communication protocols is explained. The applications of WS nodes in various use cases have been discussed. Additionally, an overlook of challenges and constraints that these WS nodes face in various environments and during the manufacturing process, are discussed. Their main existing developments which are expected to augment the WS nodes, to meet the requirements of the emerging systems, are also presented. [ABSTRACT FROM AUTHOR]

We study spectrum allocation for terahertz (THz) band communication (THzCom) systems, while considering the frequency and distance-dependent nature of THz channels. Different from existing studies, we explore multi-band-based spectrum allocation with adaptive sub-band bandwidth (ASB) by allowing the spectrum of interest to be divided into sub-bands with unequal bandwidths. Also, we investigate the impact of sub-band assignment on multi-connectivity (MC) enabled THzCom systems, where users associate and communicate with multiple access points simultaneously. We formulate resource allocation problems, with the primary focus on spectrum allocation, to determine sub-band assignment, sub-band bandwidth, and optimal transmit power. Thereafter, we propose reasonable approximations and transformations, and develop iterative algorithms based on the successive convex approximation technique to analytically solve the formulated problems. Aided by numerical results, we show that by enabling and optimizing ASB, significantly higher throughput can be achieved as compared to adopting equal sub-band bandwidth, and this throughput gain is most profound when the power budget constraint is more stringent. We also show that our sub-band assignment strategy in MC-enabled THzCom systems outperforms the state-of-the-art sub-band assignment strategies and the performance gain is most profound when the spectrum with the lowest average molecular absorption coefficient is selected during spectrum allocation. [ABSTRACT FROM AUTHOR]

In modern life, there is invisible data being continuously generated, data that if collected and processed can detect risks and changes and enable us to mitigate their effect. Thus, there is an essential need to sense everything around us in order to make better use of it. This lead us to an era known as “sensing-era” in which wireless sensor networks (WSN) play a vital role in the monitoring of natural and artificial environments. Indeed, the collection and transmission of huge amounts of redundant data by sensor nodes will lead to a faster consumption of their limited battery power, which is sometimes difficult to replace or recharge, reducing the overall lifetime of the network. Therefore, an effective way to increase lifetime by saving energy is to reduce the amount of transmitted data by eliminating redundancy along the path to the sink. In this paper, we propose a Zoom-In Zoom-Out (ZIZO) mechanism aimed to minimize data transmission in WSN. ZIZO works on two WSN levels: on the sensor level where we propose a compression method called index-bit-encoding (IBE) in order to aggregate similar readings before sending them to the second network level, e.g. cluster-head (CH). The CH searches then for correlation among node data in order to optimize the sampling rate of the sensors in the cluster through a process called sampling rate adjustment (SRA). We evaluate the performance of our mechanism based on both simulations and experiments while the obtained results are compared to other existing techniques, and we show reduced energy consumption by up to 90% in some cases. [ABSTRACT FROM AUTHOR]

As we connect more microcontrollers to the Internet and employ them to control the physical world around us, their reliability and security are increasingly important. Many microcontrollers provide limited facilities for hardware isolation, and real-time OSes offer custom APIs, that require coupling applications into the ecosystem and abstractions of that specific OS to leverage isolation. This article investigates the use of software sandboxing of applications to support isolation for resource-constrained devices. Toward this, we detail the design of eWASM, a processes abstraction that adapts a popular sandbox, Wasm, for microcontrollers. eWASM provides a runtime to constrain memory accesses and control flow, enabled by our aWsm Wasm compiler. We discuss and evaluate its multiple implementations that effectively trade time and space, optimizing for the constraints of embedded systems. This enables popular languages (e.g., C) to be effectively sandboxed by software. We demonstrate performance within 40% of native C on Polybench. We believe this is a practical and compelling result for many IoT domains, and it represents the first compiled sandboxing environment for microcontrollers. We show that restrictions of the current Wasm specification lead to significant memory consumption and provide suggestions for the creation of an embedded-specific Wasm variant. [ABSTRACT FROM AUTHOR]

Brushless doubly fed reluctance machines (BDFRM) are an attractive option for megawatt-scale turbo-electric propulsion systems due to use of a partially rated power converter, reduced maintenance, and absence of permanent magnets. Conventional design approach of a BDFRM uses equal electrical loadings on both stators and an initial phase offset $\delta$ of $\pi /2$ between the two stator currents. However, this approach leads to poor torque density because the machine saturates even before the stator reaches the current density limit. This article proposes an approach to maximize the torque density by finding appropriate electrical excitations on both stator windings for chosen machine dimensions as well as for specific flux density, current density, and grid voltage limits. A single-objective optimization problem is formulated. The optimized solution establishes that an initial phase offset $\delta$ of $2\pi /3$ produces 75% more torque as compared to the conventional $\delta = \pi /2$ design. The new design allows a higher stator currents injection without saturating the machine. The results are verified through extensive simulations using a finite element model. Operating with the optimized design also leads to higher machine efficiency and better power factor on the secondary stator, thus reducing the converter rating. [ABSTRACT FROM AUTHOR]

A nondestructive evaluation technique for determining complex permittivities and permeabilities of uniaxial anisotropic sheet media is presented. An existing technique, the two-flanged waveguide measurement technique (tFWMT), has demonstrated good results for the nondestructive electromagnetic characterization of isotropic materials. This article extends the tFWMT for uniaxially anisotropic materials and presents the experimental determination of the permittivity and permeability of uniaxially anisotropic media. The measured scattering parameters are compared to theoretical scattering parameters, and the complex permittivity and permeability are extracted using a nonlinear least squares method. To find theoretical scattering parameters, Love’s equivalence principle and the spectral-domain Green’s function are used to form a set of coupled magnetic-field integral equations (MFIEs). This set of coupled MFIEs is solved utilizing the method of moments. To validate the new method, electromagnetic characterization of two honeycomb materials is made by using the two-flanged waveguides measurement technique and the results are compared to those obtained using the established methods. [ABSTRACT FROM AUTHOR]

With the increased uncertainty in the power system operation due to growing penetration of highly intermittent energy sources such as wind power, the need for the impact assessment of the renewable penetration on system operating risk and the quantification of benefits of using energy storage technologies is more than ever. A recovery-risk-analysis-based analytical framework for operating risk assessment of wind-integrated bulk power system following a major contingency disturbance is presented in this paper. Two new indices that quantify the recovery risk profile of the bulk power system and its load delivery points following major disturbances are introduced in this paper. The indices obtained from the proposed framework quantify the impact of increasing wind penetration on the system operating risk and the reliability benefits of using fast-responding energy storage system such as flywheel energy storage systems. The proposed methodology is illustrated through several case studies carried out in a test system. [ABSTRACT FROM AUTHOR]

The future Internet of Things (IoT) networks are expected to be composed of a large population of low-cost devices communicating dynamically with access points or neighboring devices to communicate small bundles of delay-sensitive data. To support the high-intensity and short-lived demands of these emerging networks, we propose an efficient MAC paradigm for IoT (EMIT). Our paradigm bypasses the high overhead and coordination costs of existing MAC solutions by employing an interference-averaging strategy that allows users to share their resources simultaneously. In contrast to the predominant interference-suppressing approaches, EMIT exploits the dense and dynamic nature of IoT networks to reduce the spatio-temporal variability of interference to achieve low-delay and high-reliability in service. This paper introduces foundational ideas of EMIT by characterizing the global interference statistics in terms of single-device operation and develops power-rate allocation strategies to guarantee low-delay high-reliability performance. A significant portion of our work is aimed at validating these theoretical principles in experimental test beds and simulations, where we compare the performance of EMIT with a CSMA-based MAC protocol. Our comparisons confirm the beneficial characteristics of EMIT and reveal significant gains over CSMA strategies in the case of IoT traffic. [ABSTRACT FROM AUTHOR]

This paper presents a droop-based distributed control strategy for multithree-phase machines that provides augmented controllability during power sharing transients. The proposed strategy is able to mitigate the mutual interactions among different sets of windings without controlling any subspace variable, also offering a modular and redundant design. On the contrary, in a centralized configuration, subspaces would be controlled using the vector space decomposition, but fault tolerance and reliability levels required by the stricter regulations and policies expected in future transportation systems would not be satisfied. The proposed method is analytically compared against the state-of-the-art power sharing technique and equivalent models and control design procedures have been derived and considered in the comparison. Uncontrolled power sharing transients and their effects on mutual couplings among isolated sets of windings have been compared against the proposed regulated ones. Experimental results on a 22-kW nine-phase multithree-phase synchronous machine rig validate the design procedures showing good agreement with the expected performances. [ABSTRACT FROM AUTHOR]

Avalanche photodiodes are fabricated and characterized using a single diffusion fabrication process with the surface patterned by selective area growth prior to diffusion. Raster mapping of the photocurrent near the breakdown voltage is used to characterize the electric field distribution in the multiplication layer. Devices fabricated with the precursor CBrCl3 introduced during selective area epitaxy show a smoother surface morphology and effective edge breakdown suppression, while those fabricated without CBrCl3 have a rougher surface morphology and exhibit evidence of premature edge breakdown at the corners of the device along specific crystal orientations. Comparison of the dark current–voltage curves below breakdown shows a reduction in dark current associated with the use of CBrCl3, as well as with the inclusion of floating guard rings in the device design. [ABSTRACT FROM AUTHOR]

Techniques for parameter determination of induction and doubly fed induction machines are well established. However, these techniques do not apply directly to the brushless doubly fed reluctance machine (BDFRM). Even though the mathematical model for this machine is like that of a double-fed induction machine, the complexity of the machines magnetic fields due to differing winding pole numbers interacting with a reluctance rotor preclude standard testing. Very high leakage inductances affect the use of the normal locked rotor test, and nonsinusoidal air gap fluxes complicate modeling for stand still frequency domain and time domain testing. This paper examines the validity of a combination of testing and analysis techniques, including open circuit and pulse testing, which were eventually used to determine the BDFRM inductance parameters over a range of operating points. The accuracy of the results are validated by machine testing and comparison with the finite element analysis machine design. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid estimation and identification (HEI) method for identifying the load model parameters of voltage-dependent loads along with estimating the system states. The parameters of voltage-dependent load models are identified using multiple snapshots consecutively gathered through supervisory control and data acquisition system. The proposed HEI method imposes no additional cost to the installed metering devices or communication network. Mathematical aspects of the proposed HEI method are analytically proved and a four-step approach is presented for implementing it. Comprehensive numerical experiments and statistical analysis are presented to demonstrate the effectiveness of the proposed method for both load model identification and state estimation. [ABSTRACT FROM AUTHOR]

The doubly fed induction machine has been traditionally adopted in adjustable-speed ac power generation drives in order to take advantage of the reduced rating for the power electronic interface. Aside this well-established application where the doubly fed induction generator (DFIG) is controlled by a back-to-back converter, recent literature records a growing interest toward un-conventional DFIG drives for dc power generation, combining DFIG high control freedom with simplified power electronic interfaces to achieve an overall cheap and fully controllable system. Despite several concepts have been demonstrated on small-scale rigs, there is a lack of systematic comparison among different topologies and control solutions. This paper bridges this gap by providing a review of recent topologies, their control, design and performance, and operation issues. As major novelties, this paper includes off-spec performance comparison of different torque-ripple mitigation strategies, discussion of sizing requirements for generator and power electronics, fundamental aspects of the behavior under voltage dips, and priorities and challenges for future research on the subject. [ABSTRACT FROM AUTHOR]

Investment of charging facilities is facing deficit problems in many countries at the initial development stage of plug-in electric vehicles (PEVs). In this paper, we study the charging facility planning problem faced by a PEV charging station investor who aims to serve PEV customers with random behaviors and demands (but follow a series of predicted distributions) with lower economic costs of both charging facilities and practical operation. First, we design a multiple-charger multiple-port charging (MCMP) system which provides the capability of scheduling a limited quantity of chargers to serve more PEVs. Second, we further develop a general two-stage stochastic programming model to plan the MCMP system inside a PEV parking lot with consideration of coordinated charging. Third, we classify MCMP stations according to three different connecting patterns between chargers and parking spaces. Fourth, the general planning model is simplified (as a reference) based on the classification. Finally, we complement our analysis through case studies. [ABSTRACT FROM AUTHOR]

This paper presents a new concept and approach for topology control and switching in distribution systems by extending the traditional circuit switching to laterals and single-phase loads. Voltage unbalance and other key performance indicators including voltage magnitudes, line loading, and energy losses are used to characterize and demonstrate the technical value of optimizing system topology on a per-phase basis in response to feeder conditions. The near-optimal per-phase topology control is defined as a series of hierarchical optimization problems. The proposed approach is applied to IEEE 13-bus and 123-bus test systems for demonstration, which included the impact of integrating electric vehicles (EVs) in the test circuit. It is concluded that the proposed approach can be effectively leveraged to improve voltage profiles with electric vehicles, the extent of which depends on the performance of the base case without EVs. [ABSTRACT FROM AUTHOR]

The use of wireless sensor network for industrial applications has attracted much attention from both academic and industrial sectors. It enables a continuous monitoring, controlling, and analyzing of the industrial processes, and contributes significantly to finding the best performance of operations. Sensors are typically deployed to gather data from the industrial environment and to transmit it periodically to the end user. Since the sensors are resource constrained, effective energy management should include new data collection techniques for an efficient utilization of the sensors. In this paper, we propose adaptive data collection mechanisms that allow each sensor node to adjust its sampling rate to the variation of its environment, while at the same time optimizing its energy consumption. We provide and compare three different data collection techniques. The first one uses the analysis of data variances via statistical tests to adapt the sampling rate, whereas the second one is based on the set-similarity functions, and the third one on the distance functions. Both simulation and real experimentations on telosB motes were performed in order to evaluate the performance of our techniques. The obtained results proved that our proposed adaptive data collection methods can reduce the number of acquired samples up to 80% with respect to a traditional fixed-rate technique. Furthermore, our experimental results showed significant energy savings and high accurate data collection compared to existing approaches. [ABSTRACT FROM PUBLISHER]

Increasing wind power (WP) integration is forcing conventional units to go through more frequent and significant cycling operations, which would accelerate wear and tear to unit components and eventually affect the unit's lifespan. In this context, this paper proposes a hierarchical scheme to control the power of plug-in electric vehicles (PEVs) to mitigate unit ramp cycling (URC) operations. A general-form representation of the URC operation is proposed for the first time. At the top level of the hierarchical scheme, a system net load variation range (NLVR) is constructed first to capture the uncertainty in WP forecasts, and then the PEV power is scheduled to reshape the NLVR so as to minimize the URC operations that can be caused by the possible net load realizations in the NLVR. Based on updated WP forecasts, the middle-level dispatch model exempts overscheduled anti-URC regulation onus on PEVs to promote PEV charging. At the bottom level, a decentralized PEV charging control strategy is used to implement the PEV power dispatch instruction. Simulation results verify that the proposed scheme can avert the URC operations effectively, while preserve most of the desired PEV charging energy. Simulation results also show that the proposed scheme is more capable of withstanding WP forecast errors compared with its deterministic version and a benchmark scheme. [ABSTRACT FROM PUBLISHER]

Objective: The goal of this paper is to automatically segment perivascular spaces (PVSs) in brain from high-resolution 7T magnetic resonance (MR) images. Methods: We propose a structured-learning-based segmentation framework to extract the PVSs from high-resolution 7T MR images. Specifically, we integrate three types of vascular filter responses into a structured random forest for classifying voxels into two categories, i.e., PVS and background. In addition, we propose a novel entropy-based sampling strategy to extract informative samples in the background for training an explicit classification model. Since the vascular filters can extract various vascular features, even thin and low-contrast structures can be effectively extracted from noisy backgrounds. Moreover, continuous and smooth segmentation results can be obtained by utilizing patch-based structured labels. Results: The performance of our proposed method is evaluated on 19 subjects with 7T MR images, with the Dice similarity coefficient reaching 66%. Conclusion: The joint use of entropy-based sampling strategy, vascular features, and structured learning can improve the segmentation accuracy. Significance: Instead of manual annotation, our method provides an automatic way for PVS segmentation. Moreover, our method can be potentially used for other vascular structure segmentation because of its data-driven property. [ABSTRACT FROM PUBLISHER]

This paper proposes a new design procedure for a bidirectional dc/dc LCL converter for potential megawatt range applications, including mobile mining equipment. This type of dc/dc converters employ two dc/ac converters and a passive LCL filter instead of a traditional high-frequency transformer. The exclusion of the transformer eliminates the core losses, while the switching losses are minimized by using soft switching operation. The proposed design method is different from previous publications as it ensures zero reactive power circulation, minimizes the size of the biggest capacitor, ensures stable and robust operation, and offers a good tradeoff between the capacitor size and the fault current in the converter under a dc fault condition. In addition to the proposed design, a simple and effective control strategy is proposed, which is based on single phase $pq$ theory. The converter design and control have been evaluated by a digital simulation in EMTP-RV software environment for a 100 MW 300 kV/20 kV converter. Experimental validation has been carried out on a laboratory 200W 100V/20V prototype converter. [ABSTRACT FROM AUTHOR]

Sensor nodes are small and low-cost portable devices that are connected wirelessly to form a wireless sensor network. Sensor nodes are typically powered by a chemical battery source that has a load-dependent finite lifetime. Most applications require wireless sensor networks to operate reliably for an extended period of time beginning with their deployment. To ensure both the longevity of a wireless sensor network via power management techniques and development of a self-powered sensor node, it is important to understand a sensor node’s operational energy consumption. It is well understood that wireless sensor network lifetime has a strong functional dependence on sensor node lifetime. This paper presents the development of a stochastic model to capture the expected energy consumption of a schedule-driven sensor node per cycle of operation by utilizing renewal theory, random stopping criteria, and Wald’s inequality. The model captures the expected energy consumed due to generic operation of a schedule-driven sensor node when an external event occurs (i.e., node level activities) and energy consumed due to carrier sense multiple access/collision avoidance medium access control protocol (i.e., retransmission attempts, channel listening, and other network level activities). The stochastic energy model is used to compute the expected lifetime and cycle lifetime of the sensor node. This paper also computes the deterministic energy bounds corresponding to the minimum and maximum energy consumption of a sensor node per cycle of operation. Analytical and numerical model validations are performed and presented. [ABSTRACT FROM PUBLISHER]