bluuebunny/crossref_metadata_2025 huggingface dataset:
Using the fragment molecular orbital method to investigate agonist–orexin-2 receptor interactions
Authors: Heifetz Alexander , Aldeghi Matteo , Chudyk Ewa I. , Fedorov Dmitri G. , Bodkin Mike J. , Biggin Philip C.
Published: April 2016

The understanding of binding interactions between any protein and a small molecule plays a key role in the rationalization of affinity and selectivity and is essential for an efficient structure-based drug discovery (SBDD) process. Clearly, to begin SBDD, a structure is needed, and although there has been fantastic progress in solving G-protein-coupled receptor (GPCR) crystal structures, the process remains quite slow and is not currently feasible for every GPCR or GPCR–ligand complex. This situation significantly limits the ability of X-ray crystallography to impact the drug discovery process for GPCR targets in ‘real-time’ and hence there is still a need for other practical and cost-efficient alternatives. We present here an approach that integrates our previously described hierarchical GPCR modelling protocol (HGMP) and the fragment molecular orbital (FMO) quantum mechanics (QM) method to explore the interactions and selectivity of the human orexin-2 receptor (OX2R) and its recently discovered nonpeptidic agonists. HGMP generates a 3D model of GPCR structures and its complexes with small molecules by applying a set of computational methods. FMO allows ab initio approaches to be applied to systems that conventional QM methods would find challenging. The key advantage of FMO is that it can reveal information on the individual contribution and chemical nature of each residue and water molecule to the ligand binding that normally would be difficult to detect without QM. We illustrate how the combination of both techniques provides a practical and efficient approach that can be used to analyse the existing structure–function relationships (SAR) and to drive forward SBDD in a real-world example for which there is no crystal structure of the complex available.
Homing to solid cancers: a vascular checkpoint in adoptive cell therapy using CAR T-cells
Authors: Ager Ann , Watson H. Angharad , Wehenkel Sophie C. , Mohammed Rebar N.
Published: April 2016

The success of adoptive T-cell therapies for the treatment of cancer patients depends on transferred T-lymphocytes finding and infiltrating cancerous tissues. For intravenously transferred T-cells, this means leaving the bloodstream (extravasation) from tumour blood vessels. In inflamed tissues, a key event in extravasation is the capture, rolling and arrest of T-cells inside blood vessels which precedes transmigration across the vessel wall and entry into tissues. This depends on co-ordinated signalling of selectins, integrins and chemokine receptors on T-cells by their respective ligands which are up-regulated on inflamed blood vessels. Clinical data and experimental studies in mice suggest that tumour blood vessels are anergic to inflammatory stimuli and the recruitment of cytotoxic CD8+ T-lymphocytes is not very efficient. Interestingly, and somewhat counter-intuitively, anti-angiogenic therapy can promote CD8+ T-cell infiltration of tumours and increase the efficacy of adoptive CD8+ T-cell therapy. Rather than inhibit tumour angiogenesis, anti-angiogenic therapy ‘normalizes’ (matures) tumour blood vessels by promoting pericyte recruitment, increasing tumour blood vessel perfusion and sensitizing tumour blood vessels to inflammatory stimuli. A number of different approaches are currently being explored to increase recruitment by manipulating the expression of homing-associated molecules on T-cells and tumour blood vessels. Future studies should address whether these approaches improve the efficacy of adoptive T-cell therapies for solid, vascularized cancers in patients.
Regulation of calcium and phosphoinositides at endoplasmic reticulum–membrane junctions
Authors: Dickson Eamonn J. , Jensen Jill B. , Hille Bertil
Published: April 2016

Effective cellular function requires both compartmentalization of tasks in space and time, and coordination of those efforts. The endoplasmic reticulum's (ER) expansive and ramifying structure makes it ideally suited to serve as a regulatory platform for organelle–organelle communication through membrane contacts. These contact sites consist of two membranes juxtaposed at a distance less than 30 nm that mediate the exchange of lipids and ions without the need for membrane fission or fusion, a process distinct from classical vesicular transport. Membrane contact sites are positioned by organelle-specific membrane–membrane tethering proteins and contain a growing number of additional proteins that organize information transfer to shape membrane identity. Here we briefly review the role of ER-containing membrane junctions in two important cellular functions: calcium signalling and phosphoinositide processing.
Targeting the tumour profile using broad spectrum chimaeric antigen receptor T-cells
Authors: Navai Shoba A. , Ahmed Nabil
Published: April 2016

A variety of distinct and redundant mechanisms support tumour propagation and survival. Tumour parenchyma consists of a variety of geographically diverse cells with varying genetic expression among subclonal populations. Additionally, the solid tumour microenvironment consists of a dense network of stromal, vascular and immune cells altered by a number of mechanisms not only to tolerate but often to enhance cancer growth. The limited spectrum of chimaeric antigen receptor (CAR) T-cell specificity in the face of this dynamic landscape is one of the greatest challenges facing CAR T-cell therapy for solid tumours. Thus targeting multiple cancer-specific markers simultaneously could result in improved efficacy by broadening the therapeutic reach to include multiple subclonal populations of the tumour parenchyma as well as elements of the tumour microenvironment. Over the last 10 years, we and others have developed multiplex platforms that target the tumour profile rather than single tumour-restricted antigens. These platforms introduce a new dimension that may be key to the successful development of T-cell therapies for solid tumours and to the mitigation of relapses due to antigen escape.
Autophagic degradation of peroxisomes in mammals
Authors: Zientara-Rytter Katarzyna , Subramani Suresh
Published: April 2016

Peroxisomes are essential organelles required for proper cell function in all eukaryotic organisms. They participate in a wide range of cellular processes including the metabolism of lipids and generation, as well as detoxification, of hydrogen peroxide (H2O2). Therefore, peroxisome homoeostasis, manifested by the precise and efficient control of peroxisome number and functionality, must be tightly regulated in response to environmental changes. Due to the existence of many physiological disorders and diseases associated with peroxisome homoeostasis imbalance, the dynamics of peroxisomes have been widely examined. The increasing volume of reports demonstrating significant involvement of the autophagy machinery in peroxisome removal leads us to summarize current knowledge of peroxisome degradation in mammalian cells. In this review we present current models of peroxisome degradation. We particularly focus on pexophagy–the selective clearance of peroxisomes through autophagy. We also critically discuss concepts of peroxisome recognition for pexophagy, including signalling and selectivity factors. Finally, we present examples of the pathological effects of pexophagy dysfunction and suggest promising future directions.
GPCR–styrene maleic acid lipid particles (GPCR–SMALPs): their nature and potential
Authors: Wheatley Mark , Charlton Jack , Jamshad Mohammed , Routledge Sarah J. , Bailey Sian , La-Borde Penelope J. , Azam Maria T. , Logan Richard T. , Bill Roslyn M. , Dafforn Tim R. , Poyner David R.
Published: April 2016

G-protein-coupled receptors (GPCRs) form the largest class of membrane proteins and are an important target for therapeutic drugs. These receptors are highly dynamic proteins sampling a range of conformational states in order to fulfil their complex signalling roles. In order to fully understand GPCR signalling mechanisms it is necessary to extract the receptor protein out of the plasma membrane. Historically this has universally required detergents which inadvertently strip away the annulus of lipid in close association with the receptor and disrupt lateral pressure exerted by the bilayer. Detergent-solubilized GPCRs are very unstable which presents a serious hurdle to characterization by biophysical methods. A range of strategies have been developed to ameliorate the detrimental effect of removing the receptor from the membrane including amphipols and reconstitution into nanodics stabilized by membrane scaffolding proteins (MSPs) but they all require exposure to detergent. Poly(styrene-co-maleic acid) (SMA) incorporates into membranes and spontaneously forms nanoscale poly(styrene-co-maleic acid) lipid particles (SMALPs), effectively acting like a ‘molecular pastry cutter’ to ‘solubilize’ GPCRs in the complete absence of detergent at any stage and with preservation of the native annular lipid throughout the process. GPCR–SMALPs have similar pharmacological properties to membrane-bound receptor, exhibit enhanced stability compared with detergent-solubilized receptors and being non-proteinaceous in nature, are fully compatible with downstream biophysical analysis of the encapsulated GPCR.
Efficacy and toxicity management of CAR-T-cell immunotherapy: a matter of responsiveness control or tumour-specificity?
Authors: Alonso-Camino Vanesa , Harwood Seandean Lykke , Álvarez-Méndez Ana , Alvarez-Vallina Luis
Published: April 2016

Chimaeric antigen receptor (CAR)-expressing T-cells have demonstrated potent clinical efficacy in patients with haematological malignancies. However, the use of CAR-T-cells targeting solid tumour-associated antigens (TAAs) has been limited by organ toxicities related to activation of T-cell effector functions through the CAR. Most existing CARs recognize TAAs, which are also found in normal tissues. CAR-T-cell-mediated destruction of normal tissues constitutes a major roadblock to CAR-T-cell therapy, and must be avoided or mitigated. There is a broad range of strategies for modulating antigen responsiveness of CAR-T-cells, with varying degrees of complexity. Some of them might ameliorate the acute and chronic toxicities associated with current CAR constructs. However, further embellishments to CAR therapy may complicate clinical implementation and possibly create new immunogenicity issues. In contrast, the development of CARs targeting truly tumour-specific antigens might circumvent on-target/off-tumour toxicities without adding additional complexity to CAR-T-cell therapies, but these antigens have been elusive and may require novel selection strategies for their discovery.
Armored CAR T-cells: utilizing cytokines and pro-inflammatory ligands to enhance CAR T-cell anti-tumour efficacy
Authors: Yeku Oladapo O. , Brentjens Renier J.
Published: April 2016

Chimaeric antigen receptor (CAR) T-cells are T-cells that have been genetically modified to express an artificial construct consisting of a synthetic T-cell receptor (TCR) targeted to a predetermined antigen expressed on a tumour. Coupling the T-cell receptor to a CD3ζ signalling domain paved the way for first generation CAR T-cells that were efficacious against cluster of differentiation (CD)19-expressing B-cell malignancies. Optimization with additional signalling domains such as CD28 or 4-1BB in addition to CD3ζ provided T-cell activation signal 2 and further improved the efficacy and persistence of these second generation CAR T-cells. Third generation CAR T-cells which utilize two tandem costimulatory domains have also been reported. In this review, we discuss a different approach to optimization of CAR T-cells. Through additional genetic modifications, these resultant armored CAR T-cells are typically modified second generation CAR T-cells that have been further optimized to inducibly or constitutively secrete active cytokines or express ligands that further armor CAR T-cells to improve efficacy and persistence. The choice of the ‘armor’ agent is based on knowledge of the tumour microenvironment and the roles of other elements of the innate and adaptive immune system. Although there are several variants of armored CAR T-cells under investigation, here we focus on three unique approaches using interleukin-12 (IL-12), CD40L and 4-1BBL. These agents have been shown to further enhance CAR T-cell efficacy and persistence in the face of a hostile tumour microenvironment via different mechanisms.
Multipath mitigation strobe for global navigation satellite system receivers
Authors: Liu Zhe , Huang Long , Tang Xiaomei , Wang Feixue
Published: April 2016

A multipath mitigation strobe for binary phase shift keying and binary offset carrier signals in the global navigation satellite system is presented, which consists of three element rectangular pulses. By shrinking the gate width of the third rectangular pulse, the proposed method exhibits better multipath performance than the conventional tracking methods and has approximately the same performance as the optimal linear s‐curve.
Feedforward joint frequency and timing estimation scheme for M‐CPFSK signals
Authors: Xie Xu , Xu Zhengguang
Published: April 2016

A non‐data‐aided synchronisation technique is proposed for M‐ary continuous phase frequency shift keying signals, which has a feedforward structure and is suitable for burst‐mode transmissions. The proposed scheme is to estimate the carrier frequency offset, carrier phase and symbol timing, whose performances are investigated by simulations and compared with the modified Cramer–Rao bounds. It turns out that the estimation accuracies of the frequency offset and timing offset are close to the theoretical limits in high signal‐to‐noise ratio.
Printed monopole antennas on uniaxial substrate: theory and simulation
Authors: Bhattacharjee S. , Kshetrimayum R.S. , Bhattacharjee R.
Published: April 2016

The performance of printed monopole antennas (PMAs) on uniaxial substrate is studied and the same is theoretically analysed using spectral domain immittance approach. Using immittance approach, field components of unit current source is evaluated first and then directivity is also calculated. The theoretical values of the far‐field radiation pattern and directivity of uniaxial substrate based rectangular PMAs are validated by high frequency structure simulator (HFSS), whereas return loss is calculated using HFSS.
Ergodic secrecy capacity for downlink multiuser networks using switch‐and‐examine combining with post‐selection scheduling scheme
Authors: Yang Maoqiang , Zhang Bangning , Huang Yuzhen , Guo Daoxing , Yi Xu
Published: April 2016

A novel threshold‐based scheduling scheme for multiuser downlink wiretap networks is addressed, which consist of a base station (BS), multiple legitimate users and multiple eavesdroppers. Particularly, the active scenario is concentrated, where BS has access to the channel state information for the eavesdropper's channel. In doing so, new exact and asymptotic closed‐form expressions for the ergodic secrecy capacity are derived for multiuser downlink networks using switch‐and‐examine combining with post‐selection scheduling at legitimate users and maximum ratio combining at the eavesdroppers. Moreover, the high signal‐to‐noise ratio slope and power offset are also given to explicitly characterise the impact of main link and wiretap link on the ergodic secrecy capacity. Simulation results show the effect of key parameters such as the number of legitimate users and eavesdroppers, switching threshold on the secrecy performance of the considered wiretap network.
Diode triggered ESD power clamp circuit with accurate discharge duration
Authors: Yang Zhaonian , Zhang Yue , Yang Yuan , Yu Ningmei
Published: April 2016

A new diode triggered power clamp circuit is proposed. It adopts diode strings to detect electrostatic discharge event and avoid mis‐triggering. By considering the amount of ESD charges in different power‐on ESD events, a compensation circuit with a new turn‐off mechanism is presented to accurately control the discharge duration, and this mechanism is validated by simulation. The circuit is fabricated in a 0.18 μm 1.8 V CMOS process, and the ESD performance is verified by the transmission line pulse measurement.
Generation of OAM radio beams with modified uniform circular array antenna
Authors: Yuan Tiezhu , Cheng Yongqiang , Wang Hong‐Qiang , Qin Yuliang
Published: April 2016

A modified uniform circular array is analysed and configured to generate radio waves carrying orbital angular momentum (OAM). The relationship between OAM mode and array parameters is derived mathematically. Results show that the produced OAM mode can be altered arbitrarily by changing the exciting frequency when the array is fixed. Moreover, the OAM mode is associated with elevation angle, offering the potential of elevation resolution for radar imaging.
Optimisation of FeICIC for energy efficiency and spectrum efficiency in LTE‐advanced HetNets
Authors: Merwaday A. , Güvenç I.
Published: April 2016

Until recently, spectral efficiency (SE) has been considered as the major key performance indicator of cellular networks. Nowadays, green evolution is becoming a major trend and the telecom industry is concerned about the energy costs and carbon footprint of their network infrastructure. These concerns will get more critical in the future due to the increasing base station densities. In such a scenario, minimising the network energy consumption while maximising the data sent to the users becomes crucial for the sustained operation of the network. In this letter, stochastic geometry is used to analyse the energy efficiency (EE) and SE in a two‐tier long‐term evolution‐advanced heterogeneous network (HetNet). Range expansion and further‐enhanced inter‐cell interference coordination which have been standardised in third generation partnership project Release‐11 are considered. System parameters of the HetNet are optimised and the trade‐offs associated between EE and SE of the network are studied.
Near‐field shielding measurement of small shield cans in metallic mobile devices for RF interference analysis
Authors: Park H.H. , Lim J.‐D. , Park H.‐B. , Kim J.
Published: April 2016

A novel near‐field shielding measurement method is presented for small shield cans used in modern mobile devices with metallic cases. To effectively capture electromagnetic leakage through the shield cans at the very near‐field region, a stripline mounted on a test board is utilised similar to the integrated circuit stripline method. Using simulation and measurement, it is verified that the proposed method is more accurate and effective than the conventional gigahertz transverse electromagnetic (GTEM) cell measurement method for shielding evaluation of small shield cans used in metallic mobile devices from an radio‐frequency interference point of view.
Passive quantisation error extraction in continuous‐time delta–sigma modulators
Authors: Han C. , Maghari N.
Published: April 2016

A new method for quantisation error extraction in continuous‐time delta–sigma modulators (CTDSMs) is proposed. The proposed method avoids the use of additional active components such as transconductors and opamps and uses only passive components. Instead, the virtual ground of the second stage integrator is used as a summing node and is utilised to extract the quantisation error. Thus, multi‐stage CTDSM can be implemented in a power and area efficient way.
Set of uniquely decodable codes for overloaded synchronous CDMA
Authors: Singh Amiya , Amini Arash , Singh Poonam , Marvasti Farokh
Published: April 2016

In this study, the authors consider the designing of a new set of uniquely decodable codes for uncoded synchronous overloaded code division multiple access for the number of codes exceeding the assigned code length. For the construction, the proposed recursive method at iteration‐k generates a matrix that can be classified into k orthogonal subsets of different dimensions. Out of them, all besides the largest (binary Hadamard) one are ternary in nature. There resides an inbuilt twin tree structured cross‐correlation hierarchy that facilitates an advantageous balance between the auto and intergroup cross‐correlation for the signatures in a subset. This opportunity is further leveraged by the proposed multi‐stage detector to maintain the uniquely decodable (errorless) nature of the matrices for noiseless transmission. The simple logic of matched filtering serving as the basic designing block of the decoder provides an enormous saving over the complexity of optimum maximum likelihood decoder. For the noisy channel, the authors derive the theoretical expression of the average bit error rate for the individual subset. Moreover, the authors explain the role of the two factors (cardinality of the subset, and net level of interference) in being responsible for the non‐uniformity in the order of their error performance.
Adaptive fractional‐order non‐singular fast terminal sliding mode control for robot manipulators
Authors: Nojavanzadeh Donya , Badamchizadeh Mohammadali
Published: April 2016

In this study, an adaptive fractional‐order terminal sliding mode controller is proposed for controlling robot manipulators with uncertainties and external disturbances. An adaptive tuning method is utilised to deal with uncertainties which upper bounds are unknown in practical cases. Fast convergence is achieved using non‐singular fast terminal sliding mode control. Also, fractional‐order controller is used to improve tracking performance of controller. After proposing a new stable fractional‐order non‐singular and non‐linear switching manifold, a sliding mode control law is designed. The stability of the closed‐loop system is proved by Lyapunov stability theorem. Simulation results demonstrate the effectiveness and high‐precision tracking performance of this controller in comparison with integer‐order terminal sliding mode controllers.
Precise vehicle speed measurement for law enforcement applications based on calibrated camera with parallel standard patterns
Authors: Eslami Hamed , Raie Abolghasem , Faez Karim
Published: April 2016

Common VSM (vehicle speed measurement) methods lack either necessary precision and/or flexibility to be used conveniently in law enforcement applications. In this study, a new method is proposed for simultaneous camera calibration and VSM compensating for these problems. The contribution of this study is to give a solution to the degeneracy problem of the Zhang's algorithm while dealing with parallel planar patterns and using the calibration data to estimate vehicle's speed. In applications like estimating the vehicle's speed in straight roads in which the license plates are parallel to each other, the number of linearly independent equations is reduced to 2 and the method cannot be used. In this study, the degeneracy problem of the Zhang's algorithm in dealing with parallel patterns is solved. Using orthonormal properties of all rotation vectors, the number of linearly independent equations is increased from 2 to 5 and camera calibration and VSM are performed simultaneously. Results of implementing this algorithm on real images taken by law enforcement cameras show that the proposed method can estimate the vehicle's speed with a mean of errors less than 1.22 km/h and consequently is proper for law enforcement applications.
Adaptive controller with an improved high‐frequency injection technique for sensorless synchronous reluctance drive systems
Authors: Pan Pin‐Chia , Liu Tian‐Hua , Madawala Udaya K.
Published: April 2016

This paper proposes an adaptive controller with an improved high‐frequency injection method for sensorless synchronous reluctance drive systems. A mathematical model is presented to show that the use of a high‐frequency injection method that takes into account the effects of unequal mutual‐inductances and the influence of speed reduces the rotor position estimation error. The adaptive speed control algorithm offers improved transient performance in comparison to typical proportional–integral (PI) controllers that are employed in sensorless drive systems. To demonstrate the viability, the proposed adaptive controller and the modified high‐frequency injection method are implemented using a TMS‐320F‐28335A digital signal processor to control a 500 W prototype synchronous reluctance motor drive. Experimental results are presented to show that the transient, load disturbance, and tracking responses of the proposed drive system are superior in comparison to a drive that uses a PI controller. Both experimental and theoretical analyses clearly indicate that the proposed high‐frequency injection method with an adaptive speed‐loop controller offers improved performance in adjustable speed synchronous reluctance drive systems.
Electromagnetic vibration noise analysis of transformer windings and core
Authors: Jingzhu Hu , Dichen Liu , Qingfen Liao , Yang Yan , Shanshan Liang
Published: April 2016

Analyses of transformer electromagnetic vibration noise are presented in this study. A finite element model is established which combines transient electromagnetic field analysis, mechanical field analysis and acoustic analysis to calculate the sound pressure level of the radiated noise around the transformer. Transient electromagnetic field analysis is performed to get the Lorentz, reluctance magnetic forces and magnetostriction according to Maxwell theory and virtual displacement principle. Mutual influence of strain and magnetisation has been considered. The main frequency components of harmonic electromagnetic excitations are analysed by Fourier transformation so as to carry out the harmonic response analysis and obtain the nodes displacements of the windings and core. The noise distribution is further calculated by acoustic analysis based on the achieved vibration data. Comparison of calculated results and measured data verifies that the combined noise calculating model is applicable for transformer noise prediction.
Analysis and design of a high‐speed permanent magnet characteristic actuator using eddy current effect for high‐voltage vacuum circuit breaker
Authors: Fang Shuhua , Xia Miao , Lin Heyun , Ho Siulau
Published: April 2016

This study proposes a high‐speed permanent magnet actuator (HSPMA) for high‐voltage vacuum circuit breaker (VCB). The HSPMA comprises mainly of an eddy current repulsion force actuator and a permanent magnet (PM) actuator. The structural saliency of HSPMA is described and its control principle is elaborated in details. Finite element method is used and the eddy current is included in the computation of the electro‐magnet fields of the HSPMA. The system equations, which couples the magnet field to circuit and mechanical equations, are built in ANSOFT Maxwell and Circuit Editor in this study of the making and breaking procedures of the HSPMA. The simulated characteristics show the design meets the requirement of the high‐voltage VCB. The optimal thickness of the eddy current plate is 10 mm. The capacitor also has an economic optimal value of 10,000 µF. The simulated results indicate that the HSPMA has a sound characteristic when compared with circuit breakers with only PM actuator.
Evaluation of saliency tracking as an alternative for health monitoring in PMSM‐drives under non‐stationary conditions
Authors: Arellano‐Padilla Jesus , Sumner Mark , Gerada Chris
Published: April 2016

This paper evaluates the capability of saliency tracking to assess the health condition of permanent magnet synchronous motor (PMSM) drives operating under non‐stationary conditions. The evaluated scheme is based on saliency tracking methods, which are associated to the accurate sensorless control of AC drives without zero speed limitations. In this work two representative saliency tracking architectures are evaluated: high frequency (HF) injection, and PWM transient excitation. Although a monitoring approach based on HF injection was previously reported, a comparative study to evaluate the most representative saliency tracking schemes to assess health condition in drives was still missing. The aim of this work is to fill out this gap by evaluating and comparing two saliency‐based monitoring schemes (one based on HF‐injection and the other based on PWM transient excitation) to evaluate their performance in the presence of inter‐turn winding faults. Simulation and experimental results are presented which confirm that both schemes offer excellent detection capabilities and that are suitable for drives operating under nonstationary conditions including standstill operation.
Non‐linear circuit based model of permanent magnet synchronous machine under inter‐turn fault: a simple approach based on healthy machine data
Authors: Belguerras Lamia , Arellano‐Padilla Jesus , Arumugam Puvaneswaran , Hamiti Tahar , Mezani Smail , Gerada Chris
Published: April 2016

The paper proposes a fast dynamic mathematical model to evaluate the performances of saturated permanent magnet synchronous machines (PMSMs) under stator winding's inter‐turn fault. The parameters of the model can be determined using only manufacturer's data of the healthy machine. Two surface mounted PMSMs have been considered to investigate the validity of the proposed approach; with distributed and concentrated winding. It has been shown that the proposed model predicts the fault current with a reasonable accuracy compared with the non‐linear finite elements analyses and to the experimental results. This model can be incorporated in a global simulation environment of power electronic of electrical device since the computation time is very short.
Hybrid excitation synchronous machine finite simulation model based on experimental measurements
Authors: Mbayed Rita , Salloum Georges , Monmasson Eric , Gabsi Mohamed
Published: April 2016

This paper presents a finite simulation model of the hybrid excitation synchronous machine taking into consideration the saturation effect, the iron losses and including higher‐order electromagnetic force harmonics. Simulation and experimental testing prove that the advanced model represents more accurately the machine especially when compared with the basic Park model built with sinusoidal waveform assumption. The main contribution of the work is that only few experimental measurements are needed in order to implement the advanced model.
Temperature rise of a dry‐type transformer with quasi‐3D coupled‐field method
Authors: Liu Chao , Ruan Jiangjun , Wen Wu , Gong Ruohan , Liao Caibo
Published: April 2016

A quasi‐3D coupled‐field method is introduced and applied on a ventilated dry‐type transformer to study temperature rise of windings in this study. A simplified 3D model was first established to calculate energy loss of core and velocity distribution in a plane above the lower yoke. Then two accurate 2D models were built up to figure out energy losses in the windings. With a combination of indirect and sequential coupling, energy losses of both windings and core were used as heat source, and velocities for both 2D models were applied as boundary condition for analysing fluid‐thermal field. Final results of temperature rise were calculated with temperature rise of two 2D models. In the end, numerical results were compared with experimental data to prove the effectiveness of this method.
Integrated motor drives: state of the art and future trends
Authors: Abebe Robert , Vakil Gaurang , Lo Calzo Giovanni , Cox Thomas , Lambert Simon , Johnson Mark , Gerada Chris , Mecrow Barrie
Published: April 2016

With increased need for high power density, high efficiency and high temperature capabilities in aerospace and automotive applications, integrated motor drives (IMD) offers a potential solution. However, close physical integration of the converter and the machine may also lead to an increase in components temperature. This requires careful mechanical, structural and thermal analysis; and design of the IMD system. This study reviews existing IMD technologies and their thermal effects on the IMD system. The effects of the power electronics position on the IMD system and its respective thermal management concepts are also investigated. The challenges faced in designing and manufacturing of an IMD along with the mechanical and structural impacts of close physical integration is also discussed and potential solutions are provided. Potential converter topologies for an IMD like the matrix converter, two‐level bridge, three‐level neutral point clamped and multiphase full bridge converters are also reviewed. Wide band gap devices like silicon carbide and gallium nitride and their packaging in power modules for IMDs are also discussed. Power modules components and packaging technologies are also presented.
Application of stator shifting to five‐phase fractional‐slot concentrated winding interior permanent magnet synchronous machine
Authors: Abdel‐Khalik Ayman S. , Ahmed Shehab , Massoud Ahmed
Published: April 2016

In many applications, interior permanent magnet synchronous machines (IPMSMs) with fractional slot concentrated windings (FSCWs) are considered promising candidates in terms of higher power density and efficiency. In addition, employing a multiphase stator winding improves the drive train availability and increases reliability. This study investigates the effect of applying stator shifting to five‐phase FSCW winding IPMSMs to suppress the effect of the slot harmonics by doubling the number of slots. In this case, the winding coil pitch will be two, which stands as a compromise between single‐tooth and distributed winding topologies. This highly improves the air gap flux distribution, significantly reduces both rotor core and magnet eddy current losses, and increases saliency ratio and reluctance torque component. Moreover, an improved performance under fault conditions, in terms of lower torque ripple, and core and magnet losses, adds to the main advantages of this technique. Various slot/pole combinations suitable for five‐phase machines are investigated. A full simulation case study based on two‐dimensional finite element analysis is applied to the 20‐slot/18‐pole stator with single‐tooth winding under both healthy and open‐circuit phase fault cases.
Cogging force mitigation techniques in a modular linear permanent magnet motor
Authors: Tootoonchian Farid , Nasiri‐Gheidari Zahra
Published: April 2016

Modular linear doubly salient permanent magnet motors are well adapted to linear propulsion systems because of their distinct characteristics, such as high efficiency and power density, reduced maintenance and initial cost, low noise and permanent magnet (PM) leakage flux, and fault tolerance capability. However, such motors suffer from high cogging thrust. In this study, various techniques based on previously proposed methods for PM machines are applied on the studied motor and evaluated by using non‐linear three‐dimensional time‐stepping finite element analysis; three novel, optimised techniques are then presented. The techniques presented are based on the minimisation of the variation in air‐gap reluctance relative to the displacement. The PM volume and average air‐gap length are kept constant in all optimisations. Since the average thrust and thrust ripples under load condition may be affected by cogging reduction techniques, these values are presented for all given techniques. The results show that the proposed techniques not only maintained the average thrust under various loads but also significantly suppressed the thrust ripples for different average thrusts and cogging forces.
Experimental study on inter‐laminar short‐circuit faults at random positions in laminated magnetic cores
Authors: Hamzehbahmani Hamed , Anderson Philip , Jenkins Keith , Lindenmo Magnus
Published: April 2016

Inter‐laminar short‐circuit faults between the laminations of electrical machines, and other magnetic devices, have been one of the major challenges for the suppliers and customers of electrical steels. Extra power losses caused by inter‐laminar faults depend on many factors including the location of the fault points. In this study, fundamental definitions and concepts of inter‐laminar short‐circuit faults, effect of inter‐laminar faults on configuration of the magnetic cores and FEM verification are presented. Experimental works were performed to study the effect of inter‐laminar faults with different configurations on the total power loss to distinguish and locate the critical and destructive faults. In the relevant studies, artificial short circuits of different configurations were applied between laminations of packs of four Epstein size laminations of 3% grain oriented silicon steel. Extra power losses caused by the inter‐laminar faults were measured and the results were analysed.
Ultra‐fast axial and radial scaling of synchronous permanent magnet machines
Authors: Stipetic Stjepan , Zarko Damir , Popescu Mircea
Published: April 2016

Scaling laws are used when the size of a certain machine design with known performance needs to be adjusted for a new application with known requirements, or when a machine design is geometrically scaled and one needs to determine its performance. Scaling laws derived in this study allow one to quickly and accurately recalculate parameters of a geometrically scaled permanent magnet machine. They basically consist of two separate important scaling procedures: axial scaling and radial scaling. The third and inevitable scaling procedure is rewinding, which is used to adjust the winding for a required voltage level. Exact but simple analytical equations for the various parameters (torque, power, losses, mass, resistance, inductance, efficiency etc.) of the machine are derived using three independent scaling factors, one for each scaling procedure. Special attention is given to the inclusion of end‐winding influence and three‐dimensional permanent magnet loss effects. Algorithms for fast determination of winding parameters for a given voltage and fast determination of scaling factors for scaling based on the torque requirement with stack length limitation are presented. All derived scaling equations are numerically validated using two state‐of‐the‐art motor design software packages with automated extraction of parameters based on finite‐element calculations.
Synthesis and optimisation of new wideband symmetrical six‐port junction
Authors: Chagtmi Nadia , Boulejfen Noureddine , Darragi Ramzi , Ghannouchi Fadhel M.
Published: April 2016

In this study, the authors propose a new approach for the synthesis of wideband symmetrical six‐port junctions. The suggested approach is based on a novel microstrip topology that can be optimised using genetic algorithm. The proposed approach has been numerically validated through the synthesis of single and double cell six‐port junctions. As an experimental validation single and double cell six‐port junctions with centre frequencies of 2.5 and 5.3 GHz, respectively, have been realised and measured. The obtained experimental results have revealed the performance of the proposed synthesis approach, its robustness and its superiority compared to the conventional empirical design techniques.
Design of dual band and dual‐polarised dual band SIW cavity backed bow‐tie slot antennas
Authors: Mukherjee Soumava , Biswas Animesh
Published: April 2016

A novel design technique to implement dual band substrate integrated waveguide (SIW) cavity backed planar slot antenna is presented. The proposed antenna uses a combination of multiple SIW cavities of different size connected through coupling window in the common sidewall of the cavities. The cavities are loaded with long bow tie shaped slots to achieve higher bandwidth of the antenna. The placement of long bow tie slots helps to generate multiple hybrid modes which can be tuned by varying slot dimensions. First, two SIW cavities loaded with bow‐tie slots are used to excite four closely placed hybrid modes in X band (8–12 GHz) to realise dual band response with a bandwidth of 600 MHz (7.2%) and 888 MHz (8.74%) and a gain of 5.3 and 4.4 dBi, respectively. The design is further extended using a set of four SIW cavities arranged as two pair of coupled SIW cavities along with bow‐tie slots and placed in orthogonal orientation to implement dual band dual polarised slot antenna while maintaining its planar configuration. The proposed antenna exhibits a bandwidth of 390 MHz (3.9%) and 790 MHz (7.29%) with a gain of 6.1 and 5.4 dBi, respectively.
Planar millimetre‐wave antenna simultaneously producing four orbital angular momentum modes and associated multi‐element receiver array
Authors: Vourch Clement J. , Allen Ben , Drysdale Timothy D.
Published: April 2016

The authors present the design and simulation of a planar Bull's eye antenna that can simultaneously produce four orbital angular momentum (OAM) modes with up to 2.4 GHz impedance bandwidth at 60 GHz. OAM modes l = ±3, ±13 are produced simultaneously by two ring resonators in the centre of the antenna. The peak gain is 13.1 (8.1) dBi at ±10 (±25) degrees for mode l = ±3 (±13), with all modes present over a 30° angular range (15–45° from the boresight). For reception and demultiplexing, the authors use a discretely sampled partial aperture receiver (DSPAR), and show algebraically that such systems can achieve ideal mode orthogonality in cases where existing partial aperture receivers cannot. The authors present a DSPAR design to complement the Bull's eye antenna, needing only four simple receiving elements and hence more readily scaling to work over longer link distances than systems relying on horn antennas with integrated spiral phase plates.
Dual band complementary split‐ring resonator‐loaded printed dipole antenna arrays for pattern diversity multiple‐input–multiple‐output applications
Authors: Sarkar Debdeep , Saurav Kushmanda , Srivastava Kumar Vaibhav
Published: April 2016

In this study, a dual‐band multiple‐input–multiple‐output (MIMO) antenna with pattern diversity is designed, targeting at the 2.4 GHz wireless local area network and 1.8 GHz global system of mobile communication application bands. The proposed scheme utilises arrays of printed dipoles fed with signals of equal amplitude but different input‐phase values to achieve diverse radiation patterns in the operating frequency bands. The printed dipoles are loaded with complementary split‐ring resonators to obtain one additional lower‐frequency resonance, ensuring simultaneous miniaturisation and dual‐band characteristics. The impedance, radiation and diversity performances of the proposed MIMO configuration are analysed by full‐wave simulations in ANSYS high‐frequency structure simulator. It is observed that both the antennas in the MIMO configuration cover the common frequency range of 1.7–1.8 and 2.25–2.5 GHz, with satisfactory average gain and stable radiation pattern in the working bands. Experimental results on the fabricated structure are in good agreement with simulation results, confirming validity of the proposed concept.
Triple band frequency selective surface design for global system for mobile communication systems
Authors: Döken Bora , Kartal Mesut
Published: April 2016

As a result of the enormous increase in mobile phone usage throughout the world, mobile phone base stations are located in almost everywhere nowadays. Many scientific studies have investigated possible health symptoms of mobile systems radiation. The globally recognised organisations have started to release maximum radio‐frequency (RF) exposure levels that are regarded as safe. An efficient approach to decrease the RF exposure levels inside the buildings is to transform building walls to a frequency selective surface which filters out global system for mobile communication signals but allows the others, such as radio and television signals. This study proposes a new frequency selective surface element geometry which leads to a minimum 20 dB attenuation in 900, 1800 and 2100 MHz mobile communication bands according to Swiss electromagnetic radiation prevention limit values (NISV, 23 December 1990). High‐frequency structure simulator software is used for simulation and design purposes. Due to a given good insight into the resonance characteristics of the FSS structures, it is benefited from the equivalent circuit model in the optimisation process. Achieved results show that the proposed FSS element geometry has a stable frequency response with minimum 20 dB of attenuation levels for transverse‐electric (TE) and transverse‐magnetic (TM) polarisations when the angle of incident wave is varied from 0° to 60°.
Modified rectifications for improving the charge equalisation performance of series‐connected battery stack
Authors: Hua Chih‐Chiang , Fang Yi‐Hsiung , Chen Yen‐Liang
Published: April 2016

Two modified rectifications for improving the charge equalisation performance of series‐connected battery stack are proposed in this study. Not only high reliability can be achieved because only one power switch is required, but also the control circuit is simple due to no voltage sensors. In addition, high efficiency can be achieved because of zero‐voltage‐switching. In this study, two modified rectifications are presented to eliminate the voltage differences between the odd and even batteries, which are not removed by the conventional methods, and reduce the number of transformer windings and diodes. Hence, the cost, size and complexity of the system can be reduced. The circuit topology and operation analysis of the proposed equaliser are described in detail. Finally, the simulations and experimental results are provided to demonstrate the performance of the proposed charge equaliser.
Offset‐free feedback linearisation control of a three‐phase grid‐connected photovoltaic system
Authors: Errouissi Rachid , Al‐Durra Ahmed , Muyeen S.M.
Published: April 2016

In this study, a state feedback control law is combined with a disturbance observer to enhance disturbance rejection capability of a grid‐connected photovoltaic (PV) inverter. The control law is based on input–output feedback linearisation technique, while the existing disturbance observer is simplified and adopted for the system under investigation. The resulting control law has a proportional–integral (PI)/almost PI–derivative‐like structure, which is convenient for real‐time implementation. The objective of the proposed approach is to improve the DC‐bus voltage regulation, while at the same time control the power exchange between the PV system and the grid. The stability of the closed‐loop system under the composite controller is guaranteed by simple design parameters. Both simulation and experimental results show that the proposed method has significant abilities to initiate fast current control and accurate adjustment of the DC‐bus voltage under model uncertainty and external disturbance.
Cooperative security communications design with imperfect channel state information in wireless sensor networks
Authors: Gong Xiangwu , Long Hang , Dong Feihong , Yao Qing
Published: April 2016

Relay strategies can increase coverage range and improve reliability for power‐limited sensors. In this study, cooperative jamming schemes are investigated for security communications in two‐hop multi‐sensors relay networks where a passive eavesdropper can wiretap the relay channels in both hops. The normally inactive nodes can be used as cooperative jamming sources to confuse the eavesdropper. Artificial noise (AN) is maximised to degrade the signal‐to‐interference‐plus‐noise ratio (SINR) level at the eavesdropper, while satisfying the individual power constraint of each relay sensor and SINR constraint at the desired receiver. Assuming that CSI is perfect, relay beamforming weights can be obtained by solving a second‐order cone programming problem. However, the available CSI is impossible to be perfect in practice. Therefore, a robust beamforming scheme is also presented. The transmit power used for AN is maximised, while satisfying the power constraint of each relay sensor and worst‐case SINR constraint at the desired receiver under a bounded spherical region for the norm of the CSI error vector from the relays to the destination. Robust beamforming weight vector can be obtained by using S‐procedure and rank relaxation techniques. The benefits of the proposed schemes are shown in simulation results.