bluuebunny/crossref_metadata_2025 huggingface dataset:
International Health and the Limits of its Global Influence: Bhutan and the Worldwide Smallpox Eradication Programme
Authors: Bhattacharya Sanjoy
Published: September 2013

Histories of the global smallpox eradication programme have tended to concentrate on the larger national formations in Africa and Asia. This focus is generally justified by chroniclers by the fact that these locations contributed a major share of the world’s annual tally of variola, which meant that international agencies paid a lot of attention to working with officials in national and local government on anti-smallpox campaigns in these territories. Such historiographical trends have led to the marginalisation of the histories of smallpox eradication programmes in smaller nations, which are presented either in heroic, institutional tropes as peripheral or as being largely shorn of sustained campaigns against the disease. Using a case study of Bhutan, a small Himalayan kingdom sandwiched between India and China, an effort is made to reclaim the historical experiences in small national entities in the worldwide smallpox eradication programme. Bhutan’s experience in the 1960s and 1970s allows much more in addition. It provides us with a better understanding of the limited powers of international agencies in areas considered politically sensitive by the governments of powerful nations such as India. The resulting methodological suggestions are of wider historical and historiographical relevance.
Statutory Sentencing Reform in Israel: Exploring the Sentencing Law of 2012
Authors: Roberts Julian V , Gazal-Ayal Oren
Published: September 2013

In 2012 the Knesset approved a new sentencing law. Israel thus became the latest jurisdiction to introduce statutory directions for courts to follow in sentencing. The approach of the United States to structuring judicial discretion often entails the use of a sentencing grid with presumptive sentencing ranges. In contrast, the Sentencing Act of Israel reflects a less prescriptive method: it provides guidance by words rather than numbers. Retributivism is clearly identified as the penal philosophy underpinning the new law, which takes a novel approach to promoting more proportionate sentencing. Courts are directed to construct an individualised proportionate sentencing range appropriate to the case in hand. Once this is established, the court then follows additional directions regarding factors and principles related to sentencing. Although other jurisdictions have placed the purposes and principles of sentencing on a statutory footing, this is the first such legislative declaration in Israel. The statute also contains a methodology to implement a proportional approach to sentencing as well as detailed guidance on sentencing factors. This article describes and explores the new Sentencing Act, making limited comparisons to sentencing reforms in other jurisdictions – principally England and Wales, New Zealand and the United States. In concluding, we speculate on the likely consequences of the law: will it achieve the goals of promoting more consistent and principled sentencing?
Successful use of a military-grade haemostatic agent for a major head and neck bleed
Authors: Crunkhorn R , Burnham R , Walton G
Published: September 2013

Background:

Major haemorrhage is a catastrophic complication occurring in 3–4 per cent of head and neck cancer patients. Massive haemorrhage also causes 50 per cent of preventable deaths in combat situations. There has been a surge of interest in the development of effective haemostatic products in the military, with chitosan being one such product.

Case report:

A 48-year-old lady presented with a life-threatening head and neck bleed. She was known to have a malignant peripheral nerve sheath sarcoma originating from the left parapharyngeal space. Bleeding was successfully controlled with the application of Celox™ granules, a chitosan-based product currently used in the military.

Conclusion:

This paper describes the first known use of a military haemostatic agent to control a malignant head and neck bleed. Celox granules can be poured directly onto a wound to enhance haemorrhage control. The suggested mechanism of action and reports of current uses of haemostatic agents are described.
The Nature of Verbal Memory Impairment in Multiple Sclerosis: A List-Learning and Meta-analytic Study
Authors: Lafosse Jose M. , Mitchell Sandra M. , Corboy John R. , Filley Christopher M.
Published: September 2013

The primary purpose of this study was to test the hypothesis that multiple sclerosis (MS) patients have impaired acquisition rather than a retrieval deficit. Verbal memory impairment in MS was examined in 53 relapsing-remitting MS patients and 31 healthy controls (HC), and in a meta-analysis of studies that examined memory functioning in MS with list-learning tasks. The MS group demonstrated significantly lower acquisition and delayed recall performance than the HC group, and the meta-analysis revealed that the largest effect sizes were obtained for acquisition measures relative to delayed recall and recognition. Our data argue against a retrieval deficit as the sole explanation for verbal memory impairment in MS, and make a consistent case for the position that deficient acquisition contributes to the memory dysfunction of MS patients. Deficient acquisition may result from demyelination in relevant white matter tracts that reduces encoding efficiency as a result of impaired speed of information processing. (JINS, 2013,19, 995–1008)
Metabolic engineering of cyanobacteria for the production of hydrogen from water
Authors: Rögner Matthias
Published: September 2013

Requirements concerning the construction of a minimal photosynthetic design cell with direct coupling of water-splitting photosynthesis and H2 production are discussed in the present paper. Starting from a cyanobacterial model cell, Synechocystis PCC 6803, potentials and possible limitations are outlined and realization strategies are presented. In extension, the limits of efficiency of all major biological components can be approached in a semi-artificial system consisting of two electrochemically coupled half-cells without the physiological constraints of a living cell.
Evolving protocells to prototissues: rational design of a missing link
Authors: Mantri Shiksha , Sapra K. Tanuj
Published: September 2013

Realization of a functional artificial cell, the so-called protocell, is a major challenge posed by synthetic biology. A subsequent goal is to use the protocellular units for the bottom-up assembly of prototissues. There is, however, a looming chasm in our knowledge between protocells and prototissues. In the present paper, we give a brief overview of the work on protocells to date, followed by a discussion on the rational design of key structural elements specific to linking two protocellular bilayers. We propose that designing synthetic parts capable of simultaneous insertion into two bilayers may be crucial in the hierarchical assembly of protocells into a functional prototissue.
all-trans-Retinoic acid improves immunocompetence in a murine model of lipopolysaccharide-induced immunosuppression
Authors: Martire-Greco Daiana , Landoni Veronica I. , Chiarella Paula , Rodriguez-Rodrigues Nahuel , Schierloh Pablo , Rearte Barbara , Isturiz Martin A. , Fernandez Gabriela C.
Published: September 2013

Secondary infections due to post-sepsis immunosuppression are a major cause of death in patients with sepsis. Strategies aimed at restoring immune functions offer a new perspective in the treatment of sepsis. In the present study, we used LPS (lipopolysaccharide)-immunosuppressed mice to analyse the effects of ATRA (all-trans retinoic acid) on different immune parameters. The IS (immunocompromised) group had decreased lymphocyte and increased MDSC (myeloid-derived suppressor cell) counts in lymph nodes. They also had an impaired in vitro T-cell proliferation, mediated by MDSCs. ATRA administration restored T-cell proliferation, which was associated with a decreased number of live MDSCs. The IS group treated with ATRA had an increased number of CD4+ and CD8+ T-cells. ATRA partially improved the primary humoral immune response, even when immunosuppression was established first and ATRA was administered subsequently. Our results demonstrate that ATRA restores immunocompetence by modulating the number of leucocytes and the survival of MDSCs, and thus represents an additional potential strategy in the treatment of the immunosuppressive state of sepsis.
Spectral efficiency optimisation in amplify and forward relay network with diversity using adaptive rate and adaptive power transmission
Authors: Taki Mehrdad
Published: September 2013

In this study, new transmission schemes are designed for the spectral efficiency optimisation in the amplify and forward relay network with diversity. The proposed schemes utilise both adaptive rate and adaptive power transmission with individual average power constraints for the relay and the transmitter. To obtain an analytical insight into the network performance, schemes with continuous rate adaptation are designed at first. Next, transmission schemes with discrete rate and power adaptation are developed for practical systems. An amplify–forward relaying scenario with diversity is considered in which signals at the destination are received from both the transmitter and the relay. Albeit, the schemes could be simplified for the network without diversity in which there is no path for the signal from the transmitter to the receiver. Schemes with constant power transmission are also designed and analysed. Numerical evaluations show that there is a considerable performance gain in using adaptive power transmission compared to the constant power scheme at the cost of a reasonable complexity increase.
Maximum likelihood algorithms for joint estimation of synchronisation impairments and channel in multiple input multiple output–orthogonal frequency division multiplexing system
Authors: Jose Renu , Hari K.V.S.
Published: September 2013

Maximum likelihood (ML) algorithms, for the joint estimation of synchronisation impairments and channel in multiple input multiple output–orthogonal frequency division multiplexing (MIMO–OFDM) system, are investigated in this work. A system model that takes into account the effects of carrier frequency offset, sampling frequency offset, symbol timing error and channel impulse response is formulated. Cramér–Rao lower bounds for the estimation of continuous parameters are derived, which show the coupling effect among different impairments and the significance of the joint estimation. The authors propose an ML algorithm for the estimation of synchronisation impairments and channel together, using the grid search method. To reduce the complexity of the joint grid search in the ML algorithm, a modified ML (MML) algorithm with multiple one‐dimensional searches is also proposed. Further, a stage‐wise ML (SML) algorithm using existing algorithms, which estimate less number of parameters, is also proposed. Performance of the estimation algorithms is studied through numerical simulations and it is found that the proposed ML and MML algorithms exhibit better performance than SML algorithm.
Signal‐to‐noise ratio optimisation for multi‐input multi‐output relay systems with direct source–destination path
Authors: Shariat Mohammad Hassan , Biguesh Mehrzad , Gazor Saeed
Published: September 2013

The authors consider a relay communication system, where all nodes are equipped with multi‐input multi‐output antennas, and there is a direct path/channel between the source and the destination. Assuming a linear non‐regenerative relaying, the relay matrix is designed by maximising the signal‐to‐noise ratio of the system. The authors derive the optimum relaying matrix for different power constraints in the relay, including the fixed relay power constraint and constraint on the maximum transmitting power from the relay. Under the constraint of fixed total transmit power, they derive the optimum power budgets of the relay and source that only depend on four positive quantities. They prove that there always exists a rank‐one relaying matrix, which transmits signal in one‐dimensional subspace and leaves the other subspaces clean. In addition, when the quality of the source–destination (SD) channel is poor, this matrix is the best rank‐one relaying transform that maximises mutual information between the source and the destination. Finally, they conclude that the relaying is beneficial only if the link quality for the source–relay is twice better than that of the SD, where the link quality is proportional to the ratio of the channel power gain to the received noise variance.
Difference sets‐based compressive sensing as denoising method for narrow‐band power line communications
Authors: Matanza Javier , Alexandres Sadot , Rodriguez‐Morcillo Carlos
Published: September 2013

The present work analyses and compares two of the most popular specifications for data transmission over power line networks: PoweRline Intelligent Metering Evolution (PRIME) and G3‐power line communication (G3‐PLC). A simulation model has been built using Matlab software in order to evaluate their respective performances with special focus on impulsive noise environments. For this purpose, Middleton's Class‐A noise model was used in conjunction with measured noise parameters reported in the literature for the narrow‐band spectrum. The performance is measured in terms of bit error rate versus signal to noise ratio. Simulation results show how G3‐PLC outperforms PRIME when the channel is impaired by such type of noise. Moreover, although the use of compressive sensing to cancel impulsive noise in communications has already been proposed in other studies, this paper details a modification based on Partial Fourier Matrix indexing according to difference sets. Results from simulations report an almost complete cancellation of the impulsive noise effects. An advantage of this technique is that no redundancy is added to the message; therefore no decrement in the transmission rate is experienced.
Performance analysis of cooperative virtual multiple‐input–multiple‐output in small‐cell networks
Authors: Zheng Kan , Xin Xuemei , Liu Fei , Xiang Wei , Dohler Mischa
Published: September 2013

With the advent of small‐cell networks (SCNs) to support growing wireless data volumes and thus reduced cell sizes, cooperative communications are significantly facilitated. Applicable to Third Generation Partnership Project long‐term evolution‐A, the authors propose a novel channel/queue‐aware user pairing and scheduling scheme in a cooperative virtual multiple‐input–multiple‐output (VMIMO) system. The queueing performance of the VMIMO system with the scheduling scheme is analysed based on the finite‐state Markov model (FSMM), and compared with that of non‐cooperative systems. Bounds on the average queuing delay of users are derived by using a semi‐definite programming (SDP) approach. The presented analyses are validated through comparing the analytical and simulation results. It is found that the introduced VMIMO pairing process is able to significantly reduce service delays, bringing on a positive impact of cooperative techniques on next generation wireless systems.
Constructive robust model predictive control for constrained non‐linear systems with disturbances
Authors: He De‐feng , Ji Hai‐bo , Yu Li
Published: September 2013

This study presents a new robust model predictive control (MPC) scheme for constrained continuous‐time non‐linear systems subject to unknown but bounded disturbances. The performance index is a function on disturbance‐free state and input profiles, and the predictions are parameterised by an analytic controller with a small number of adjustable parameters. In particular, input‐to‐state stable control Lyapunov functions techniques are used to construct a variation of Freeman's formula with some tunable parameters, which yields an MPC with guaranteed input‐to‐state stability in some estimated invariant sets w.r.t the disturbance. It is further derived that the MPC here is inverse optimal for a class of dynamic game problems and has a sector margin (0.5, ∞). Finally, two numerical examples are used to illustrate the performance and effectiveness of the results obtained here.
Eigenvalue assignment in linear descriptor systems via output feedback
Authors: Zhang Biao
Published: September 2013

An approach for eigenvalue assignment in linear descriptor systems via output feedback is proposed. Sufficient conditions in order that a given set of eigenvalues is assignable are established. Parametric form of the desired output feedback gain matrix is also given. The approach assigns the full number of generalised eigenvalues, guarantees the closed‐loop regularity and overcomes the defects of some previous works.
Robust pole placement for second‐order linear systems using velocity‐plus‐acceleration feedback
Authors: S. Abdelaziz Taha Helmy
Published: September 2013

This paper considers the robust pole assignment problem using combined velocity and acceleration feedbacks for matrix second‐order linear systems. The necessary and sufficient conditions which ensure solvability are derived. Based on recently developed parametric solution to the eigenstructure assignment problem by velocity‐plus‐acceleration feedback, a new technique is described to perform robust pole placement for second‐order systems. The available degrees‐of‐freedom offered by the velocity‐plus‐acceleration feedback in selecting the associated eigenvectors are utilised to improve robustness of the closed‐loop system. The main advantage of the described approach is that the problem is tackled in the second‐order form without transformation into the first‐order form. Finally, several examples are introduced to demonstrate the effectiveness of the proposed approach.
A decoupled controller design approach for formation control of autonomous underwater vehicles with time delays
Authors: Yang Huizhen , Wang Chuanfeng , Zhang Fumin
Published: September 2013

Formation control for a group of autonomous underwater vehicles (AUVs) is challenging due to the complex systems dynamics and time delay in the cooperative feedback loops. This paper introduces a decoupled design procedure, so that formation controllers designed for particle dynamics can be generalised to formation controllers for fully actuated AUVs with six‐degree‐of‐freedom dynamic models for motions in three‐dimensional space. The orientation control and the translation control are first decoupled following a standard inner–outer loop approach. Then, a geometric approach is followed to separate the translation dynamics into formation shape dynamics and formation centre dynamics. Coupling terms between the two portions of the dynamics are treated as perturbations and are tolerated by a robust formation‐keeping controller. The controller is also robust to constant bounded time delays. This decoupling procedure simplified the entire design process comparing with other existing approaches with similar goals. Both rigorous theoretical analysis and simulation results are presented to justify the effectiveness of this method.
Distributed mixed continuous‐discrete receding horizon filter for multisensory uncertain active suspension systems with measurement delays
Authors: Song Il Young , Shin Vladimir
Published: September 2013

This study presents a new robust filtering method in modelling an active multisensory suspension system with measurement delays and parameteric uncertainties in a state‐space dynamical model. To achieve good performance of the system, a new distributed fusion receding horizon filtering frameworks are constructed to couple the continuous dynamics with the multisensory discrete measurements, and to coordinately deal with the parametric uncertainty and time‐delays. The novel filtering algorithm is proposed based on the receding horizon strategy, standard mixed continuous‐discrete Kalman filtering and discrete Kalman filtering for systems with time‐delays in order to achieve high estimation accuracy and stability under parametric uncertainties. The key theoretical contributions of this study are the derivation of the error cross‐covariance equations between the local receding horizon filters in order to compute the optimal matrix fusion weights. The high accuracy and efficiency of the new filter are demonstrated through its implementation and performance and then compared to the existing vehicle active suspension system.
Computing an invariance kernel with target by computing Lyapunov‐like functions
Authors: She Zhikun , Xue Bai
Published: September 2013

Reachability analysis and viability theory play an important role in control synthesis and trajectory analysis of constrained dynamical systems, many methods are known for computing them in low‐dimensional non‐linear systems, but these well‐known methods rely on gridding the state space and hence suffer from the curse of dimensionality. In this study, for systems whose dynamics are described by polynomials, a method based on semi‐definite programming is proposed to estimate an invariance kernel with target as large as possible by iteratively searching for Lyapunov‐like functions. The proposed methodology is scalable, since the size of the semi‐definite programming problem to be solved grows linearly with the system dimension. We test the method on two interesting examples and compare them with some existing methods, the results show that our method is more efficient.
Contour matching using the affine‐invariant support point set
Authors: Wang Wei , Jiang Yongmei , Xiong Boli , Zhao Lingjun , Kuang Gangyao
Published: September 2013

Moment has been widely used for contour matching. To use the moment to achieve contour matching under affine transformations, the affine‐invariant support point set (SPS) should be constructed first. Then, a novel method of acquiring SPS based on the contour projection (SPS‐CP) is proposed here. For an arbitrary selected contour point, the contour is projected onto the line vertical to the vector connecting the contour centroid and the selected point, and the contour points with the sampled projection values are picked up to form the SPS‐CP of the point. SPS‐CP which captures the global structure of the contour is stably affine‐invariant. Experiments on synthetic and real data demonstrate that moments generated from SPS‐CP outperform those generated from SPSs sampled by uniform spacing or affine length.
Implementation of distribution static compensator for power quality enhancement using learning vector quantisation
Authors: Arya Sabha Raj , Singh Bhim
Published: September 2013

An implementation of a three‐phase distribution static compensator (DSTATCOM) using learning vector quantisation (LVQ) control algorithm is presented for compensation of loads in a distribution system. The DSTATCOM is used for harmonics elimination, load balancing and reactive power compensation with self‐supporting dc bus in distribution system. The LVQ‐based control algorithm is used for extraction of fundamental weighted values of active and reactive power components of load currents which are required for estimation of reference supply currents. It is based on a double supervisory system where each weighted vector is modified by input weights. The input weights are trained outputs of the first stage learning weights. It is needed for accurate estimation of compensation currents from the voltage source converter (VSC) used in DSTATCOM. A prototype of the VSC‐based DSTATCOM is developed using a digital signal processor to validate the proposed control approach and its performance is studied under a steady state and dynamic conditions. The performance of the DSTATCOM is found satisfactory with the proposed control algorithm under linear and non‐linear loads which are commonly used in the distribution system. The dc bus voltage of the VSC of DSTATCOM has a negligible effect on varying loads.
Probabilistic evaluation of failure risk of transmission line surge arresters caused by lightning flash
Authors: Shariatinasab Reza , Ajri Farid , Daman‐Khorshid Hadiseh
Published: September 2013

Transmission line surge arresters (TLAs) are vital elements for protection of power networks against the lightning surges. The proper selection of TLAs leads to a reduction of the lightning‐related outages as well as the costs imposed to the power utility, because of the undelivered energy and damage to the equipment. The selection of the optimal arrester depends on how well its stresses can be estimated. Although a ground flash very frequently consists of multiple strokes, it is usual to consider only a single lightning stroke to calculate the lightning‐related failures. A probabilistic method is presented for risk calculation that considers multiple strokes of each lightning flash to estimate the annual outage rate of TLAs. In the presented method, once the equivalent wave of the flash is computed, the probability of arrester failure is estimated by means of two indices, including total charge and maximum energy stress by the flash, separately. The energy stress caused by the flash is calculated using a few electromagnetic transient program (EMTP) simulations. Then, the obtained results from EMTP simulation are utilised to estimate the probability of failure. The accurate evaluation of failure probability of arresters permits the power utility to select the optimal arresters, considering a desirable average life.
Laboratory simulation of naturally polluted high‐voltage transmission line insulators
Authors: Gouda Osama E. , El Dein Adel Z.
Published: September 2013

This study represents experimental techniques for testing the high‐voltage polluted insulators under conditions simulating the natural environment. International Electrotechnical Commission (IEC) fog method is used for testing the insulators of type π‐ϕ‐E4.5, but it does not simulate the desert pollution environments. For that reason, other two suggested techniques are added to explain the performance of the polluted insulators under dew and under simultaneous fog and dew, respectively. The leakage current bursts are recorded in each test type. Also the effect of the wetting method of the insulators under testing on the flashover voltage is investigated. The results of the three types of tests are compared with each other, under different surface layer conductivities. It is concluded that the analysis of leakage current bursts can be used to monitor the severity of pollution on the electrical network.
Lossy and lossless image encoding using multi‐scale recurrent pattern matching
Authors: Graziosi Danillo Bracco , Rodrigues Nuno Miguel , da Silva Eduardo A.B. , de Carvalho Murilo B. , de Faria Sérgio Manuel Maciel
Published: September 2013

In this study, the authors investigate the use of multi‐scale recurrent pattern matching paradigm for lossless image compression. The multi‐scale multidimensional parser (MMP) algorithm is a successful implementation of this paradigm for lossy image compression, and can naturally perform lossless compression since it was first derived from a Lempel–Ziv lossless scheme. However, neither its recently adopted coding tools had been adapted for lossless coding nor a thorough analysis of its performance had been carried out. In this work, the authors evaluate MMP's lossless compression capability, proposing modifications for some of its predictions modes, as well as the inclusion of an adaptive prediction mode based on least squares. The residual information is also coded with well‐known techniques used in lossless compression. Experimental results for MMP show that the algorithm achieves a good performance for images such as computed generated graphics and scanned documents, whereas keeping a competitive performance for natural images. Since the algorithm's structure is exactly the same for lossless and lossy compression, the obtained results suggest that MMP is able to achieve a high compression performance for a wide range of images and rates, from lossy to lossless, without any prior analysis of the image to be coded.
Spatio‐temporal video contrast enhancement
Authors: Celik Turgay
Published: September 2013

A video contrast enhancement algorithm which automatically enhances the contrast of a video using spatial and temporal information is proposed. The algorithm is based on the observation that the contrast in a video frame can be improved by increasing the grey‐level differences between each pixel of the video frame and its neighbouring pixels. Furthermore, such an improvement should be smooth in between consecutive video frames so that continuum of contrast improvement is achieved. A two‐dimensional (2D) histogram of a video frame is constructed using mutual relationship between each pixel and its neighbouring pixels. For each video frame, a 2D target histogram is computed by considering 2D histogram of the video frame, 2D uniformly distributed histogram, and the 2D histograms of forward and backward neighbouring video frames. The contrast enhancement of the video frame is achieved by mapping the diagonal elements of the 2D input histogram to the diagonal elements of the 2D target histogram. The proposed algorithm is easy to implement and is thus suitable for real‐time contrast enhancement applications.
Integration of ultra‐wideband planar baluns into the Eleven feed
Authors: Raza Hasan , Yang Jian , Pantaleev Miroslav
Published: September 2013

Integration of decade bandwidth baluns into the Eleven feed faces many challenges. The authors present a compact, low‐loss and low‐cost integration solution to the ultra‐wideband balun feeding network for the dual‐polarised Eleven feed in this study. The design procedures are described in detail. Evaluation of the balun integration based on the BOR1 (Body of Revolution type1) efficiency is introduced. Numerical simulations and measurements are presented for verifying the design.
Generalised correction to the Friis formula: quick determination of the coupling in the Fresnel region
Authors: Kim Ilkyu , Xu Shenheng , Rahmat‐Samii Yahya
Published: September 2013

A simple yet effective correction term to the Friis formula is presented to improve its accuracy in the Fresnel region. Based on the concept of gain reduction factor, the proposed asymptotic term with an empirical coefficient can be widely applied to a variety of antennas without lengthy calculations. The information required in the computation is only the antenna gain, separation and wavelength for the boresight scenarios. Case studies of several representative antennas using full‐wave simulations show that the accuracy of the estimated power transmission levels between two antennas in the Fresnel region can be improved by up to 2–5 dB, for both boresight and off‐axis cases. Measurement results using two horn antennas also confirm the validity of the proposed correction term.
Power recycling concept applied to distributed amplification
Authors: Ng‐Molina Francisco Y. , Martín‐Guerrero Teresa M. , Camacho‐Peñalosa Carlos
Published: September 2013

A novel distributed amplifier structure based on a power recycling scheme is proposed. It allows the amplifier gain to be enhanced while providing optimum output power and a perfect input match within a moderate bandwidth. The ideal performance of this novel distributed amplifier, called the power recycling distributed amplifier, is analysed. Limitations introduced by mismatch and losses in the gate line have also been assessed. A prototype of such an amplifier has been designed, manufactured and measured. The experimental results demonstrate its viability as an optimum class‐A active power combiner with enhanced gain and excellent input match.
Physically‐based indicator for identifying ultra‐wideband indoor channel condition
Authors: Mucchi Lorenzo , Sorrentino Antonio , Carpini Alessio , Migliaccio Maurizio , Ferrara Giuseppe
Published: September 2013

In this study, a model based on the generalised‐K (GK) distribution is proposed for identifying ultra‐wideband (UWB) indoor channel profiles. In particular, an index (γ‐index) based on a proper combination of GK parameters is proposed to unambiguously and effectively distinguish among line‐of‐sight (LOS) and non‐LOS propagation conditions. This clear distinction is achieved by defining two non‐overlapping sets which correspond to the two well‐defined profiles. The technique is user‐friendly since it does not call for any complex estimation process. Comparison among the results achieved by both real measurements and IEEE.802.15.4a channel model simulations confirm the soundness of the employed method and the effectiveness of the proposed γ‐index.
Inductor‐less envelope modulated radio frequency power amplifier using stacked amplifiers and envelope shaping
Authors: Watkins Gavin
Published: September 2013

An envelope modulated radio frequency (RF) power amplifier (PA) is presented using a ‘stacked amplifiers’ modulator. The modulator combines the efficiency of class G with the convenience of a charge pump. Since it is a single band modulator, no large inductors or transformers are required. A two level prototype has been developed and tested with a 7.5 dB peak‐to‐average power ratio 1.4 MHz bandwidth long term evolution (LTE) signal. Envelope shaping was used to improve linearity. Individually the modulator achieved between 54 and 60% efficiency, dependant on the envelope shaping function. When combined with a suitable class E PA, 40% DC to RF efficiency was achieved at 1.38 W output power with the 1.4 MHz LTE signal.
Reduced DC voltage source flying capacitor multicell multilevel inverter: analysis and implementation
Authors: Sadigh Arash Khoshkbar , Dargahi Vahid , Abarzadeh Mostafa , Dargahi Saeedeh
Published: September 2013

Voltage source multicell multilevel converters (VSMMCs) have been extensively exploited in medium‐voltage high‐power fed industrial applications. One of the typical breeds of the VSMMCs is flying‐capacitor multicell converter (FCMC). This study presents an improved configuration for FCMCs, accompanied by its analysis, modelling and implementation. The main advantage of the proposed converter, in comparison with the conventional one, is that the number and voltage rating of the required dc voltage sources are halved in the improved topology which results in reducing the cost, size, installation area and weight of the FCMCs effectively. This amelioration is attained by adding four power switches to the conventional topology of an FCMC without making any amendments to the number and voltage rating of high‐frequency power‐switches and flying capacitors (FCs). The proposed switching and control methodology for the adopted FCMC is based on the phase‐shifted carrier pulse width modulation technique with applying some amendments; therefore the natural balancing phenomenon of the FC voltages, one of the critical advantages of the FCMCs, is preserved in the proposed VSMMC. Experimental measurements taken from the 3‐cell‐four‐level and 4‐cell‐five‐level laboratory prototype systems of the proposed converter are presented in order to validate and corroborate the effectiveness and advantages of the proposed topology, its switching and suggested control strategy. Furthermore, experimental studies are accomplished on an 8‐cell‐nine‐level prototype system of the proposed FCMC to peruse its feasibility and viability for higher number of cells and voltage levels. In addition, comparison of the proposed converter with the other types of multilevel converters is carried out to underline the advantages of the proposed structure profoundly.
Control of variable pitch and variable speed direct‐drive wind turbines in weak grid systems with active power balance
Authors: Yuan Xibo , Li Yongdong
Published: September 2013

In the case of operating in a weak grid system, when wind power becomes a significant portion of the power system or even the sole energy source, the wind power generators and converters are expected to help maintain the grid voltage. The grid‐side converter needs to work as a voltage source to help regulate the terminal (grid) voltage amplitude and frequency by adjusting the reactive power and active power flow, respectively. For a direct‐drive permanent magnet synchronous generator with a full power converter, the active power must be provided by the captured wind power. The active power flow between the source (captured wind power) and the grid (load) must be balanced by actively controlling the generator speed and wind turbine pitch angle. In the study, the coordinated control of generator speed and blade pitch angle is proposed together with a dc‐link voltage controller. A model of the grid‐side converter operating as a voltage source has been built and the strategy regarding voltage and frequency regulation is presented. Simulation is carried out with different wind and load profile. The results show the wind energy can help support the weak grid and power the local grid in stand‐alone mode as well.
Power optimisation of a point absorber wave energy converter by means of linear model predictive control
Authors: Richter Markus , Magaña Mario E. , Sawodny Oliver , Brekken Ted K.A.
Published: September 2013

This study presents a model predictive control (MPC) scheme for a wave energy converter (WEC); in particular, for a buoy‐type point absorber. The WEC is a two‐body system which is taut‐moored to the sea floor with three cables. Much research has been done recently to achieve optimal operation of WECs. The goal is to maximise the power conversion without violating system limits. In practice, there are physical constraints on position, velocity and the power take‐off (PTO) force. MPC is a promising and beneficial approach to achieve this goal. It poses a control formulation including constraints in a natural way. Furthermore, MPC can exploit predictions for the sea motion a standard MPC approach always needs a reference trajectory. For one‐body point absorber, an optimal velocity trajectory can be calculated. However, an optimal trajectory is not easily available for the two‐body case. The proposed formulation in the presented work does not require an optimal trajectory. For this reason it is possible to apply this MPC scheme to a two‐body model as well. This work demonstrates that the proposed control algorithm optimises the power extraction without violating the system constraints. Finally, the performance of MPC is compared to linear passive load control through simulation.
Mitigation of power system oscillation caused by wind power fluctuation
Authors: Su Chi , Hu Weihao , Chen Zhe , Hu Yanting
Published: September 2013

Wind power is increasingly integrated in modern power grids, which brings new challenges to the power system operation. Wind power is fluctuating because of the uncertain nature of wind, whereas wind shear and tower shadow effects also cause periodic fluctuations. These may lead to serious forced oscillation when the frequencies of the periodic fluctuations are close to the natural oscillation frequencies of the connected power system. By using modal analysis and time‐domain simulations, this study studies the forced oscillation caused by the wind shear and tower shadow effects. Three forced oscillation mitigation controllers are proposed and compared. A model of direct‐drive‐full‐convertor‐based wind farm connected to the IEEE 10‐machine 39‐bus system is adopted as the test system. The calculations and simulations are conducted in DIgSILENT PowerFactory 14.0. Results are presented to show the effectiveness of the controllers in mitigating the forced oscillation.
Determination of characteristic parameters of battery energy storage system for wind farm
Authors: Zhang Kun , Mao Chengxiong , Xie Junwen , Lu Jiming , Wang Dan , Zeng Jie , Chen Xun , Zhang Junfeng
Published: September 2013

Integrating a battery energy storage system (BESS) with a wind farm can smooth power fluctuations from the wind farm. Battery storage capacity (C), maximum charge/discharge power of battery (P) and smoothing time constant (T) for the control system are three most important parameters that influence the level of smoothing (LOS) of output power transmitted to the grid. The economic cost (EC) of a BESS should also be taken into consideration when determining the characteristic parameters of BESS (C, P). In this study, an artificial neural network‐based long‐term model of evaluated BESS technical performance and EC is established to reflect the relationship between the three parameters (C, P, T) and LOS of output power transmitted to the grid, the EC of BESS. After that, genetic algorithm is used to find optimal parameter combination of C, P and T by optimising the objective function derived from the mathematical model constructed. The simulation results of the example indicate that the parameter combination of C, P and T obtained by the proposed method can better not only meet the technical demand but also achieve maximum economic profit.
Shaft speed ripples in wind turbines caused by tower shadow and wind shear
Authors: De Kooning Jeroen D.M. , Vandoorn Tine L. , Van de Vyver Jan , Meersman Bart , Vandevelde Lieven
Published: September 2013

Wind turbines are an important source of renewable energy. Although the amount of wind turbine installations has known a considerable increase in recent years, technological improvements are still needed to increase their efficiency. An important subject is the presence of vibrations. For instance, ripples can be present in the torque and shaft speed, which can be caused by turbulence of the air flow, resonance or mechanical problems. Furthermore, tower shadow and wind shear are able to cause significant torque oscillations. In literature, a mathematical model of the torque oscillations has been presented for three‐bladed horizontal‐axis upwind turbines. However, it remains unclear what the impact is of these torque oscillations on the shaft speed. When ripples are present in the shaft speed, they affect the back‐electromotive force and electrical power of the generator and could propagate further in the system. Therefore this study investigates whether this effect is large enough to have a considerable impact on the system. The turbine inertia and size are both relevant parameters in this research. However, it will be shown by mathematical proof that the relative amount of shaft speed ripples caused by tower shadow and wind shear is independent of the turbine size.
Control of doubly‐fed induction generator for wind energy in network context
Authors: Bejaoui Mouna , Marinescu Bogdan , Slama‐belkhodja Ilhem , Monmasson Eric
Published: September 2013

This study investigates a novel control methodology for the doubly‐fed induction generators (DFIGs) in the real situation of wind energy generation when the machine is connected to a power system. The machine speed, DC voltage, active and reactive grid powers have been controlled using a reduced‐order representation of the DFIG coupled to the grid. This framework allows several methods for the synthesis of the regulator. A state‐feedback controller is designed based on the linear quadratic method. This regulator is tested in comparison with the standard vector control approach and the more recent flux magnitude angle control via simulations performed with Simulink and SimPowerSystem Toolbox of MATLAB.
Modulation effect and inverse synthetic aperture radar imaging of rotationally symmetric ballistic targets with precession
Authors: Pan Xiao‐yi , Wang Wei , Liu Jin , Ma Liang , Feng De‐jun , Wang Guo‐yu
Published: September 2013

The modulation effect of rotationally symmetric ballistic targets (BTs) with precession is concerned. To further approach the actual case, the modulation in amplitude and Doppler is considered in the radar backscattering and revealed by short‐time Fourier transform (STFT). The results indicate that the micro‐Doppler (m‐D) effect induced by periodical precession is not represented as a sinusoidal modulation on the edge of BTs as usual, and the amplitude modulation may lead to discontinuity of time–frequency curve. The phenomenon in STFT is confirmed by both simulated and real data from a BT model with precession measured in the microwave anechoic chamber. Based upon the measured data, inverse synthetic aperture radar imaging results have been obtained by smoothed pseudo Wigner‐Ville time–frequency distribution.
Non‐cooperative target recognition in multistatic radar systems
Authors: Stinco Pietro , Greco Maria S. , Gini Fulvio , Manna Mario La
Published: September 2013

The ability to recognise quickly and reliably non‐cooperative targets is a primary issue in modern radar systems. The use of multistatic radars has already been demonstrated to improve sensibly the recognition capacity of a radar system, through the exploitation of its inherent spatial diversity, given by the presence of multiple observation channels. This calls for the development of suitable fusion strategies for efficiently combining the signals arising from multiple channels of the network. In this study, the authors define a multistatic classification algorithm where the information on the target class is provided by the sensors of the system and the final decision is made using a fusion rule that combines the decisions coming from each channel of the radar network. A suitable selection is made to favour the channels with better performance. The numerical analysis demonstrates the superior performance of the proposed algorithm over the classical fusion rule, that takes into account only the effect of the energy path loss, in terms of probability of correct classification.
Sparse subband fusion imaging based on parameter estimation of geometrical theory of diffraction model
Authors: Tian Biao , Chen Zengping , Xu Shiyou
Published: September 2013

This study focuses on sparse subband fusion imaging. A method based on high‐precision parameter estimation of geometrical theory of diffraction (GTD) model is given. Considering the incoherence problem in each subband data, a coherent processing method is adopted in the paper. Based on an all‐pole model, it makes use of the phase difference of pole and scattering coefficient between each sub‐band to effectively estimate the incoherent components. After coherent processing, the high and low frequency subband data can be expressed as a uniform all‐pole model. The gapped‐data amplitude and phase estimation algorithm is adopted to fill up the gapped band. Finally, fusion data is gained by high precision parameter estimation of GTD‐all‐pole model with full‐band data, such as scattering center number, scattering center type and amplitude. The experimental results of simulated data with fixed‐points indicate that the resolution of one‐dimensional (1D) range profile and 2D inverse synthetic aperture radar (ISAR) image based on this method is better than that of each sub‐band. In this way, the validity of the proposed method is proved.
Wright–Fisher dynamics on adaptive landscape
Authors: Jiao Shuyun , Xu Song , Jiang Pengyao , Yuan Bo , Ao Ping
Published: September 2013

Adaptive landscape, proposed by Sewall Wright, has provided a conceptual framework to describe dynamical behaviours. However, it is still a challenge to explicitly construct such a landscape, and apply it to quantify interesting evolutionary processes. This is particularly true for neutral evolution. In this work, the authors study one‐dimensional Wright Fisher process, and analytically obtain an adaptive landscape as a potential function. They provide the complete characterisation for dynamical behaviours of all possible mutation rates under the influence of mutation and random drift. This same analysis has been applied to situations with additive selection and random drift for all possible selection rates. The critical state dividing the basins of two stable states is directly obtained by the landscape. In addition, the landscape is able to handle situations with pure random drift, which would be non‐normalisable for its stationary distribution. The nature of non‐normalisation is from the singularity of adaptive landscape. In addition, they propose a new type of neutral evolution. It has the same probability for all possible states. The new type of neutral evolution describes the non‐neutral alleles with 0%. They take the equal effect of mutation and random drift as an example.