bluuebunny/crossref_metadata_2025 huggingface dataset:
Full‐polarisation three‐dimensional pattern synthesis for conformal conical arrays with dynamic range ratio constraint by using the initialisations based on equivalence theorem
Authors: Zhang Yunxiang , Zhao Zhiqin , Nie Zaiping , Liu Qing Huo
Published: August 2015

To design three‐dimensional (3D) conformal conical arrays with desired 3D co‐polarisation and cross‐polarisation radiation patterns, a pattern synthesis method based on equivalent principle and trust region method is presented. Dynamic range ratio (DRR) of element excitations is taken into consideration. An analytical function is utilised to constrain DRR and avoid discontinuity of objective function. Owing to the optimisation is based on very good initial currents distribution, the optimisation procedure is very fast. The analytical gradient and Hessian matrix expressions of the objective function are derived. This also improves the optimisation efficiency compared with using the finite difference methods to solve gradient and Hessian matrix. To demonstrate the effectiveness of this proposed method, a conformal conical array with 454 elements has been designed. The amplitude and phase excitations were optimised by using the proposed method.
Valuing large‐scale solar photovoltaics in future electricity generation portfolios and its implications for energy and climate policies
Authors: Vithayasrichareon Peerapat , MacGill Iain F.
Published: August 2015

This study examines the potential role of large‐scale photovoltaics (PV) generation in addressing the economic, energy security and environmental challenges facing the electricity industry. A Monte‐Carlo‐based generation portfolio modelling tool is employed to examine the value and impacts of different PV penetrations in future electricity generation portfolios under future uncertainty and multiple industry objectives of minimising expected future costs, cost uncertainty and CO2 emissions. The Australian National Electricity Market (NEM) facing highly uncertain future fossil‐fuel prices, carbon price, plant capital costs and electricity demand was used as a case study. Hourly PV generations across diverse locations were simulated for different penetration levels. Modelling results show that, with relatively modest carbon prices, increased PV penetration leads to not only reductions in cost uncertainties and greenhouse gas emissions, but also the overall industry generation costs. This would greatly enhance the value and thus encourage investment in large‐scale solar PV, even when the transmission cost estimates were included. The value of PV generation in future generation portfolios is also influenced by the mix of generation technologies. The findings from this study can assist in energy and climate policy decision making in the electricity industry, particularly with regard to large‐scale PV generation and carbon pricing.
Range migration compensation in static digital‐beamforming‐on‐receive radar
Authors: Brennan Paul V. , Rahman Samiur , Lok Lai Bun
Published: August 2015

Range migration is a well‐known, and readily compensable, phenomenon in synthetic‐aperture radar. Under certain circumstances, it may also afflict phased array radar systems based on fixed antenna elements, but there is little or no literature on its occurrence in this type system, nor how it may be addressed. This study sets out to define the conditions in which range migration is a significant issue in phased array radar systems and how it may be mitigated, in particular concentrating on step frequency and frequency‐modulated continuous‐wave radar for which range migration is not so easily addressed. Results are presented to validate the approach based both on simulation and experimental data from ground‐penetrating radar systems performing two‐dimensional through‐ice imaging in Antarctica.
Target recognition in synthetic aperture radar images via non‐negative matrix factorisation
Authors: Cui Zongyong , Cao Zongjie , Yang Jianyu , Feng Jilan , Ren Hongliang
Published: August 2015

This study proposes a novel non‐negative matrix factorisation (NMF) variant L1/2‐NMF after visualisation and analysis of the process of target recognition via NMF for synthetic aperture radar (SAR) images. NMF has been applied to obtain pattern feature in SAR images. This study considers the intrinsic character and the physical meaning of NMF feature when applied for SAR automatic target recognition. At the base of obtaining the linear relationship between the sample to be recognised and the train samples, the whole recognition process is detailed and vividly visualised. Meanwhile, lots of researches have been done to improve NMF methods by enforcing sparse constraint with L1‐norm, such as non‐negative sparse coding (NNSC), local NMF and sparse NMF. Compared with L1‐norm, L1/2‐norm has been shown to have a more natural sparseness. In this study, a novel variant of NMF with L1/2 constraint, called L1/2‐NMF is proposed, and is carried out a thorough study by applying it in SAR target recognition. Experimental results on MSTAR public database show that both the basis and coding matrices obtained by L1/2‐NMF have higher sparseness than those obtained by NMF, NNSC and NMF with sparseness constraints (NMFsc). The recognition results demonstrate that the L1/2‐NMF outperforms NNSC, NMFsc and non‐smooth NMF.
Textural feature extraction based on time–frequency spectrograms of humans and vehicles
Authors: Shi Xiaoran , Zhou Feng , Liu Lei , Zhao Bo , Zhang Zijing
Published: August 2015

Extraction of features and subsequent classification of ground moving targets, especially humans and vehicles, are topics of great relevance for the theoretical research and practical application in the signal processing of the ground surveillance radar. Through the time–frequency analysis of ground moving target, the energy distribution of spectrogram can be regarded as a kind of image texture. On the basis of this, a novel method for the feature extraction of micro‐motion targets is proposed in this study. In the proposed method, the spectrograms of targets’ echoes are first obtained through the short‐time Fourier transform. To improve the precision of features extracted, a pre‐processing based on the spectrogram is followed to enhance image features. On the basis of targets’ spectrograms, the entropy, third‐order moment of statistical histogram and directionality features are extracted finally as jointly effective features of micro‐motion targets. The support vector machine (SVM) is utilised to classify the ground moving targets and a high probability of correct classification is obtained. The experimental results under different signal‐to‐noise ratio and training sample number conditions verify the validity and robustness of the proposed method.
Real‐valued sparse representation for single snapshot direction‐of‐arrival estimation in shipborne high‐frequency surface wave radar
Authors: Wang Zhongbao , Xie Junhao , Zhou Gongjian , Ji Zhenyuan , Quan Taifan
Published: August 2015

By exploiting the intrinsic sparsity of the spatial spectrum for a given resolution cell of range and Doppler, this study introduces the recently developed sparse representation approaches for direction‐of‐arrival estimation in shipborne high‐frequency surface wave radar (HFSWR). These approaches can reconstruct the sparse signal and obtain high‐resolution spatial spectrum with a small number of snapshots or even single snapshot. A generalised real‐valued sparse representation, which seeks to replace the complex‐valued problem with a real one, is proposed to reduce the computational complexity and improve the resolution probability and the estimation accuracy. The advantage of the proposed method is demonstrated by theoretical analysis and numeral simulations. Furthermore, validation of the proposed method is verified by the experiment of shipborne HFSWR on the Yellow Sea of China.
Fast algorithm based on superpixel‐level conditional triplet Markov field for successive‐approximation resistor image segmentation
Authors: Wu Yan , Wang Fan , Zhang Qingjun , Niu Fanglong , Li Ming
Published: August 2015

Conditional random field (CRF) is a useful tool for optical and remote sensing image segmentation for its ability of incorporating the feature and texture information. However, its application is restricted in successive‐approximation resistor (SAR) image segmentation, since SAR images often contain complex non‐stationary contents. The triplet Markov field (TMF) model improves the non‐stationary image segmentation ability by introducing an auxiliary field to characterise different stationary parts in non‐stationary image. Combining the advantages of CRF and TMF, the pixel‐level conditional TMF (CTMF) had been proposed. To further improve the segmentation efficiency, a superpixel‐level CTMF (SL‐CTMF) is proposed in this study. The superpixel representation comes from the improved TurboPixels algorithm and the superpixel representation has better performance in edge location. The auxiliary field U in SL‐CTMF is reconstructed on superpixels. With the superpixel‐level feature and texture information, the unary and pairwise potentials are derived. Finally, SL‐CTMF is applied to real SAR image segmentation with the maximum posterior marginal inference. The experimental results demonstrate the accuracy and the efficiency of the proposed method on SAR images.
Multi‐frequency high frequency surface wave radar based on phase offset
Authors: Zhang Lan , Wu Xiongbin , Liu Jianfei , Yao Chunyu , Li Wang
Published: August 2015

Multi‐frequency high frequency surface wave radar (MHFSWR) shows good capability of anti‐interference, sea‐state information extraction and target detection. The authors develop a new technique to produce a specified Doppler frequency offset on the echoes spectra for each operating frequency in simultaneous MHFSWR system. The radar transmits frequency modulated interrupted continuous wave signals with different linear phase offsets which are counted up from sweep cycle to sweep cycle. After the echoes being demodulated, the signals of different operating frequencies from same range can be distinguished by the preset frequency offsets in a single Doppler spectrum, though they are indiscernible in the A‐Scope display. In the receiver, both the data transmission channel and the signal processing channel of different operating frequency, including digital down‐conversion, data rate conversion and range–Doppler transform, are shared significantly reducing the hardware cost and system complexity. The simulation results and the initial observations obtained by the radar verify the feasibility of the proposed technique. This technique is applicable in monostatic radars, bistatic radars and networking radars to apply multi‐frequency observations simultaneously.
Knowledge‐based design of space–time transmit code and receive filter for a multiple‐input–multiple‐output radar in signal‐dependent interference
Authors: Karbasi Seyyed Mohammad , Aubry Augusto , Carotenuto Vincenzo , Naghsh Mohammad Mahdi , Bastani Mohammad Hassan
Published: August 2015

The authors deal with the robust design of multiple‐input–multiple‐output (MIMO) space–time transmit code (STTC) and space–time receive filter (STRF) for a point‐like target embedded in signal‐dependent interference. Specifically, they assume that the radar exploits knowledge provided by dynamic environmental database, to roughly predict the actual scattering scenario. Then, they devise an iterative method to optimise the (constrained) STTC and the (constrained) STRF which sequentially improves the worst‐case (over interfering scatterers statistics) signal‐to‐interference‐plus‐noise ratio (SINR). Each iteration of the algorithm is handled via solving two (hidden) convex optimisation problems. The resulting computational complexity is linear with the number of iterations and polynomial with the sizes of the STTC and the STRF. At the analysis stage, they assess the performance of the proposed algorithm in terms of the achieved SINR. They show that properly exploiting the spatial degrees of freedom offered by the MIMO system, it is possible to obtain considerable SINR gains with respect to the conventional single‐input–single‐output system. Moreover, their results highlight the capability of the proposed method to robustify the performance of the designed system against possible knowledge inaccuracies.
Recognition of humans based on radar micro‐Doppler shape spectrum features
Authors: Ricci Roberto , Balleri Alessio
Published: August 2015

In this study, a feature extraction algorithm is presented which automatically generates a set of shape spectrum features based on the cadence velocity diagram of the human micro‐Doppler signature. Recognition performance between humans undertaking the same activity is assessed on a set of experimental data collected with a continuous wave radar operating at X‐band using a Naïve Bayesian classifier and a shape‐similarity‐spectrum classifier. Recognition performance is analysed as a function of key parameters, such as the dwell time on the target and the size of the training set, to investigate the level of robustness of the proposed features. Results show that high level recognition performance can be achieved for both the walking and running activities.
Efficient architecture and hardware implementation of coherent integration processor for digital video broadcast‐based passive bistatic radar
Authors: Shan Tao , Liu Shengheng , Zhang Yimin D. , Amin Moeness G. , Tao Ran , Feng Yuan
Published: August 2015

In this study, the problem of efficient implementation of a coherent integration processor in passive bistatic radars (PBRs) in the presence of range migration is addressed. The authors present a coherent integration architecture for PBR, which consists of a frequency‐domain pulse compression module to reduce the overall runtime for the computation of the cross‐ambiguity function, and an efficient decimated keystone transform module based on the chirp z‐transform to compensate the range migration. The proposed architecture is then implemented in a hybrid central processing unit plus graphic processing unit scheme. Real measurement data are used to verify the superior integration performance and reduced computational complexity achieved by the proposed scheme.
Motion feature extraction from inverse synthetic aperture radar image time‐series: a sparse and low‐rank approach
Authors: Wang Zelong , Zhu Jubo , Niu Wei , Liu Jiying
Published: August 2015

Motion information of the non‐cooperative targets observed by inverse synthetic aperture radar (ISAR) is an important feature for target recognition. Owing to the addition of time dimension, ISAR image time‐series are effective carriers about motion features; however, motion feature extraction is not robust enough for the restriction of ISAR imaging and traditional feature point extraction methods. In this study, the authors propose a novel method called as sparse and low‐rank approach for motion feature extraction from ISAR image time‐series. This method first models the ISAR image time‐series as a mixed matrix composed of a low‐rank matrix and a sparse matrix, which correspond to the low‐rank structure of the static feature points and the sparse structure of the dynamic feature points, respectively. Then these feature points can be separated by sparse and low‐rank matrices decomposition to prepare for estimation of motion parameters, such as precession angle and precession period of the targets. The results of experimental validation suggest that the new approach is more robust than traditional methods.
Accelerating search based on truncated convolution for rapid detection of linear frequency modulated signals
Authors: Cao Huawei , Fu Tuo , Gao Meiguo
Published: August 2015

This study investigates the problem of rapid detection of linear frequency modulated signals. An accelerating search algorithm is proposed based on the classical dechirp method. The fast Fourier transform operation is substituted with the truncated convolution in the dechirp method, and then a compatible search strategy is presented. The computational load of the proposed method is reduced. With the increasing length of the input signal, the presented method enhances the computational efficiency more obviously. Both the theoretical analysis and simulation results show that the detection performance of this method is desirable in the case of low signal‐to‐noise ratio; thus, it could be a competitive candidate for applications in engineering practices.
Discrimination of human targets for radar surveillance via micro‐Doppler characteristics
Authors: McDonald Michael Kenneth
Published: August 2015

An approach is examined for reducing false alarms during detection of human targets via radar surveillance from moving platforms. The ability to distinguish between human target and clutter discrete micro‐Doppler signatures is quantified using simulated and real data collected using the DORC X‐band wideband experimental airborne radar. Signal processing methodologies to extract key target signature characteristics are discussed along with separability of target classes and classifier performance.
Aspect angle dependence and multistatic data fusion for micro‐Doppler classification of armed/unarmed personnel
Authors: Fioranelli Francesco , Ritchie Matthew , Griffiths Hugh
Published: August 2015

This study discusses the analysis of multistatic micro‐Doppler signatures and related features to distinguish and classify unarmed and potentially armed personnel. The application of radar systems to distinguish different motion types has been previously proposed and this work aims to further investigate the applicability of this in more scenarios. Real data have been collected using a multistatic radar system in a series of experiments involving several individuals performing different movements. Changes in classification accuracy as a function of different aspect angle between the direction in which the target faces and the line‐of‐sight of the radar nodes are analysed. Multiple data fusion methodologies are proposed, showing that significant improvement of the classification accuracy can be achieved when using separate classification at each node followed by a voting procedure to reach the final decision. This is beneficial especially at those aspect angles for which micro‐Doppler detection is less favourable.
Design of multiple‐input multiple‐output transmit waveform and receive filter for extended target detection
Authors: Karbasi Seyyed Mohammad , Radmard Mojtaba , Nayebi Mohammad Mahdi , Bastani Mohammad Hassan
Published: August 2015

It is presumed that using multiple antennas at the transmit and receive sides can improve the radar's performance. One such improvement can be achieved in the detection of extended targets. However, in such multiple‐input multiple‐output systems, proper design of the transmit signals is an obstacle that can have significant influence on the performance. In this study, enforcing the peak‐to‐average‐ratio (PAR) constraint, the authors consider the problem of transmit space‐time code and receive space‐time filter design of such a system detecting extended targets. In addition, the power allocation among the different antennas is another degree of freedom that should be optimised under a total power constraint. Here, the authors derive a constrained optimisation procedure for transmit code, receive filter and transmit powers, which sequentially improves the signal‐to‐interference plus noise ratio of the system.
System parameter optimisation for moving target detection and imaging in multi‐band synthetic aperture radar based on genetic algorithm
Authors: Wang Jinwei , Zhou Feng , Tao Mingliang , Zhang Zijing , Sun Guangcai
Published: August 2015

To overcome the shortcomings of the conventional moving target detection method in single‐channel synthetic aperture radar (SAR), this study proposes a novel method for moving target detection in single‐channel multi‐band SAR. In this method, according to the detectable velocity in different bands, the genetic algorithm is applied to optimise the choice of radar band parameters, for example, wavelength and pulse repetition frequency. With the obtained optimal parameter combinations, the multi‐band SAR system could achieve the highest velocity detection rate and the maximal bands utilisation rate. Then, moving target detection, imaging and location could be accomplished with the radon transform and the deramp method. Finally, simulation results are presented to demonstrate the effectiveness and feasibility of the proposed method.
Debiased converted position and Doppler measurement tracking with array radar measurements in direction cosine coordinates
Authors: Jinbin Fu , Jinping Sun , Songtao Lu , Xuwang Zhang
Published: August 2015

With the advantage that antenna pattern and scanning features can be described conveniently in phased array radar, direction cosine coordinates (COS) is widely used. Unfortunately, measurements reported in the COS are non‐linear relative to the target states described in the Cartesian coordinates. In addition, it has been proved by the theory and practice that the tracker can perform better by making full use of the Doppler measurement. This study mainly focuses on dealing with the position and Doppler measurement in the COS. Firstly, a pseudo measurement constructed by the product of range measurement and Doppler measurement is utilized to reduce the high non‐linearity between the target state and the Doppler measurement. Then, via taking the fourth‐order terms of a Taylor series expansion, the consistent estimation of converted measurements errors is obtained based on current measurements. Finally, in order to process the converted position measurements and pseudo measurement sequentially, Cholesky decomposition is exploited to decorrelate the converted position and pseudo measurement errors. Simulation results illustrate that the filter presents a higher estimation accuracy of target states, whether the target is moving or static. Furthermore, compared with unscented Kalman filter, the calculation load of the proposed filter is reduced significantly.
Multiband FM‐based passive bistatic radar: target range resolution improvement
Authors: Zaimbashi Amir
Published: August 2015

FM‐based passive bistatic radars (PBRs), exploiting a single broadcasted channel, have limited range resolution due to low modulation bandwidth and high dependence on the content broadcasted from an FM station. This may be alleviated by exploiting multiple broadcasted channels from a single transmitter. To reach these goals, the authors formulate the problem of detecting a target in the presence of interference signals, such as receiver noise, direct signal, multipath/clutter echoes, and interfering targets, as a composite hypothesis test. So, they derive a multiband uniformly most powerful invariant test. In the proposed detector, they analytically show how the exploitation of the multiple broadcasted channels can improve the target range resolution. The false alarm rate and detection probability of the proposed detector are also derived in the closed‐form expressions. Finally, they provide some simulation examples to validate the authors’ theoretical analysis. Simulation results show that a multiband PBR system offers advantages in terms of coherent combined diversity gain and target range resolution improvement as compared to a single band PBR system.
Target tracking with a two‐scan data association algorithm extended for the hybrid target state
Authors: Khan Uzair , Song Taek Lyul
Published: August 2015

This study develops a two‐scan data association algorithm for the hybrid target state, which consists of the target trajectory state and the target existence state. The proposed method uses the sliding window‐based approach for the multi‐scan data association. It updates the target existence state by considering all the feasible multi‐scan target existence events in the sliding window. The proposed method also updates the target trajectory state by calculating the joint association events in the sliding window. Performance of the proposed algorithm is compared with that of the integrated track splitting algorithm and the integrated probabilistic data association algorithm for various conditions.
Connecting gravity turn guidance dynamics to near planar missile motion geometry
Authors: Danchick Roy
Published: August 2015

The dynamic pressure on a rocket body caused by atmospheric drag must be kept small to prevent the missile from breaking up during its trajectory in the earth's lower atmosphere. Gravity turn guidance minimises this dynamic pressure load on the body structure by aligning the rocket's thrust in the direction opposite to the drag force, along the direction of the missile's inertial velocity relative to the inertial velocity of the earth's atmosphere. In this study, the authors first show why the trajectories of ballistic missiles under gravity turn guidance are accurately approximated by motion that is closely confined to an earth‐centred, earth‐fixed plane. They then introduce a new cylindrical coordinate trajectory profile model that exploits this inherent near planar motion. It is shown that this model interpolates the numerically integrated solution to the rocket equations of motion down to centimetres of position accuracy and tenths of centimetres per second in velocity error.
Class‐modular multi‐layer perceptron networks for supporting passive sonar signal classification
Authors: Souza Filho João B.O. , de Seixas José Manoel
Published: August 2015

The automatic classification of passive sonar signals in real time is an extremely useful tool for supporting sonar operators decision making during submarine missions. An appealing architecture for the development of accurate, flexible, modular and real‐time classification systems is the class‐modular multi‐layer perceptron (CM‐MLP). However, for this task, several design parameters have to be tuned and a more extensive guideline about how to conduct this process is missing in the literature. This work aims at discussing the main design phases related to the development of CM‐MLP systems for passive sonar signal classification. For each phase, several approaches are discussed and their cost‐effectiveness is experimentally evaluated using statistical significance tests. This analysis is based on real signals produced by 8 vessel classes and acquired by an omnidirectional hydrophone in a shallow water environment, during 263 experimental runs of 34 ships. Results show that some design parameters significantly affect the accuracy of the classification system, especially the complexity of each module. An accuracy of 84.4% is achieved by using tuned design parameters.
Squint model interferometric ISAR imaging based on respective reference range selection and squint iteration improvement
Authors: Tian Biao , Zou Jiangwei , Xu Shiyou , Chen Zengping
Published: August 2015

Aiming at interferometric inverse synthetic aperture radar (InISAR) imaging on squint model, a new method based on respective reference range selection (RRRS) and squint iteration improvement (SII) is proposed in this study. The influence of squint model mainly includes two aspects, namely accessional phase and image distortion. The three‐dimensional (3D) imaging results are degraded greatly with the increment of squint angle by using traditional InISAR imaging algorithm. On the basis of the RRRS, the image registration is well achieved. Then, after a few times of SII and distortion correction, the performance of 3D reconstruction was improved. Simulation results confirmed the effectiveness of the proposed method.
Research on lightning surge overvoltage of convertor station with 500 kV hot‐standby circuit breakers
Authors: Fan Youping , Wu Lihui , Qiu Huimin , Wen Wu , Liu Songkai , Qian Hai , Chen Dong
Published: August 2015

This study introduces a circuit breaker flashover accident caused by lightning strokes in a row of Xingren convertor station in Guizhou. To find out the reason of the flashover and whether fault circuit breaker insulation coordination can meet requirements under multiple lightning strikes, the overvoltage condition of hot‐standby circuit breakers under lightning surge is calculated and checked by using EMTP and full‐scale high impulse voltage test of the fault circuit breaker is conducted for the first time. Owing to the hot‐standby state of the circuit breaker, the flashover accident is more likely to happen when lightning surge invades the substation or convertor station again. Measures to improve the hot‐standby circuit breakers’ lightning withstand level are proposed and by simulating analysis, the measure combined installing a line arrester at a tower of the inlet line and installing an arrester near a certain breaker on the line proves to be effective.
Influence of altitude on radio interference level of AC power lines based on corona cage
Authors: He Wang‐ling , He Jun‐jia , Wan Bao‐quan , Chen Yu‐chao , Pei Chun‐ming , Chen Yu‐long
Published: August 2015

To investigate the effect of altitude on radio interference (RI) of AC power lines, a corona cage test system was used to measure the RI excitation function values of different bundle conductors in different altitude locations, such as Wuhan 23 m, Jingyuan 1408 m, Xining 2261 m, Gonghe 2943 m and Yangbajain 4300 m. Then, the RI curves with different altitudes, bundle numbers and subconductor diameters were obtained. The analysis and comparison show that the actual RI altitude correction values fall in between the range of 1 dB/300 m and 40(1 − σ/σ0) when the altitude below 3200 m, which is widely used as Italian correction term and Westinghouse correction term, respectively. Above this altitude, they are not applicable to predict the correction values. In this study, an RI correction term is proposed from the test results, which are fitted well for different altitude regions <4300 m.
Characterisation system for the evaluation of digital partial discharge measuring instruments
Authors: Hu Yue , Chiampi Mario , Crotti Gabriella
Published: August 2015

A characterisation system is developed to evaluate the performances of the digital partial discharge measuring instruments (PDMIs) that implement complex analysis functions, such as PD pattern classification and identification. The system can reproduce PD patterns, obtained from mathematical models or experiments on artificial defects or on‐site measurements. The structure of the system and the characterisation of the generated charge sequences are discussed. The potentiality of the developed characterisation system has been proved in the evaluation of the advanced features of some digital PDMIs.
Eddy current sensor based velocity and distance estimation in rail vehicles
Authors: Hensel Stefan , Strauß Tobias , Marinov Marin
Published: August 2015

The precise localisation of rail vehicles is fundamental to the development and employment of more efficient train control systems in security, logistics and disposition applications. A key element of this is the exact and reliable velocity and distance estimation. The popular satellite navigation (global navigation satellite systems) and visual odometry, based on optical systems, tend to fail in the rough environment of rail application scenarios. This study describes an approach to making a precise distance estimate using an innovative eddy current sensor system. This is achieved through the combination of an augmented cross‐correlation approach to highly accurate velocity estimation. That is subsequently employed to determine the travelled distance based on counting rail clamps in a spatial transformed space. This approach relies on recursive state estimation of the dynamic states and a statistical assessment of the counted rail clamps for the purpose of outlier rejection. The proposed methods are compared and evaluated in a quantitative way on the basis of experimental data. The results prove that the proposed approach can improve the accuracy and reliability of velocity measurement and relative position detection.
Feature extraction of SF6 thermal decomposition characteristics to diagnose overheating fault
Authors: Tang Ju , Pan Jianyu , Yao Qiang , Miao Yulong , Huang Xiujuan , Zeng Fuping
Published: August 2015

This study examines how byproducts from thermal decomposition of sulfur fluoride (SF6) can be measured and applied to diagnose an overheating fault occurring in SF6 insulated equipment. Using a series of experiments performed on a SF6 thermal fault simulation system, the thermal decomposition characteristics of SF6 were obtained for temperatures below 400°C. Based on these results, the formation rate was extracted to indicate the progress of the thermal fault’s development, and the characteristic component ratio was used to identify the type and severity of the thermal fault. The relationship of the fault temperature and the formation rate along with the correlation between the characteristic ratio and the fault temperature were studied. The results show that: the formation rate of the components effectively reflects the severity and development trend of the thermal fault; by integrating the IEC standard 60480‐2004, the obtained thermal fault maximum safe time (TMS) can accurately indicate the largest safe time when thermal fault happens; component characteristic ratios C(SO2)/C(SO2F2) and C(SO2F2+SOF4)/C(SOF2) can be used to evaluate whether the fault type is a thermal fault; and the thermal correlation ratio (TR) can be employed to recognize the temperature value from 300°C to 400°C.
Planetary gearbox fault diagnostic method using acoustic emission sensors
Authors: Yoon Jae , He David
Published: August 2015

In this study, a new acoustic emission (AE) sensor‐based planetary gearbox (PGB) fault diagnosis method is presented. The method includes a heterodyne‐based AE data acquisition system, empirical mode decomposition (EMD)‐based AE signal analysis method, and computation of condition indicators (CIs) for PGB fault diagnosis. The heterodyne technique is hardware‐implemented to downshift the sampling frequency of AE signals at a rate compatible to vibration analysis. The sampled AE signals are processed using EMD to extract PGB fault features and compute the CIs. The CIs are input into supervised learning algorithms for PGB fault diagnosis. The method is validated on a set of seeded localised faults on all gears: sun gear, planetary gear, and ring gear. The validation results have shown a promising PGB fault diagnostic performance using the presented method.
Adaptive Gauss–Hermite filter for non‐linear systems with unknown measurement noise covariance
Authors: Dey Aritro , Sadhu Smita , Ghoshal Tapan Kumar
Published: August 2015

A non‐linear adaptive state estimator based on the Gauss–Hermite (GH) quadrature rule has been proposed to suit non‐linear signal models where the measurement noise covariance remains unknown. The proposed algorithm which may be used for both parameter and state estimation incorporates online adaptation of the measurement noise covariance (R) following maximum‐likelihood estimation‐based method. The GH quadrature approach has been considered so that the proposed filter may inherit the enhanced estimation accuracy as exhibited by its non‐adaptive counterpart. The proposed adaptation algorithm, in contrast to some other reported methods, automatically ensures positive definiteness of the adapted measurement noise covariance. The efficacy of the adaptive algorithm over the non‐adaptive GH filter has been demonstrated using Monte Carlo simulation and two case studies. Performance comparison has also been carried out with respect to adaptive unscented Kalman filter with the help of same case studies.
Research on biomechanical compatibility for the artificial anal sphincter based on rectal perception function reconstruction
Authors: Zan Peng , Zhao Jie , Yang Lihong
Published: August 2015

To treat the anal incontinence, a new artificial anal sphincter is put forward. Aiming at the rectal perception function reconstruction and the mechanical compatibility for artificial anal sphincter, this paper regards the huge mobile contraction wave in the typical rectal pressure contraction waves as the main signal of defecation. Meanwhile, by extracting features of rectal pressure signals with the help of wavelet packet analysis, and by adopting the Davies Bouldin index (DB) optimal algorithm, rectal perception function reconstruction is realised through predicting the defecation by means of the SVM classifier. In order to avoid the rectal ischemia necrosis, a three‐dimensional finite element model for the rectum and artificial anal sphincter is constructed, with the purpose of analysing the viscoelasticity of the rectum. Then, prony series is deduced by utilising the constitutive equation of rectum, and finite element analysis for artificial anal sphincter is conducted by simulating the contraction and relaxation of the sphincter to generate load. At last, the shift and the stress distribution for the rectum at the time of being oppressed are obtained. This simulative experiment result shows that the artificial anal sphincter can highly accurately predict the defecation and it features favorable biomechanical compatibility.
Measurement method of charge densities at ground level under high‐voltage direct current conductor
Authors: Zou Zhilong , Cui Xiang , Lu Tiebing
Published: August 2015

Ions generated by corona discharge of high‐voltage direct current (HVDC) transmission lines exist in the space between conductors and the ground. Electric field strength, ion current density, and space charge density are significant electromagnetic environment parameters of HVDC transmission lines. To measure the charge densities at ground level under the HVDC power lines, an aspirator‐type charge meter is designed and utilised. The charge meter is calibrated in the ionised field generated by parallel metal mesh and plate. Charge densities on the ground under the unipolar HVDC conductor are measured by the calibrated devices in the laboratory. Experimental results show that reasonable agreement between measured data by the devices and the ones by field mills and ion current plates could be obtained, which establishes a foundation to research the charge characteristics of ions near the ground.
One‐pot strategy for biomimetic synthesis of zein‐conjugated silver sulphide nanospheres in ethanol solution
Authors: Zhang Li , Du Xian , Yang Guangrui , Zhang Qiuxia , Qin Dezhi
Published: August 2015

Water‐soluble Ag2S nanospheres embedded in a zein matrix were successfully synthesised by a simple, controllable protein‐assisted method in ethanol solutions. The morphology and size of products were tunable through controlling the concentration of zein. X‐ray diffraction and energy‐dispersive X‐ray spectrum results showed that the obtained samples were a pure monoclinic phase of Ag2S. The Ag2S nanoparticles were homogeneously surrounded by protein molecules observed from a high‐resolution transmission microscopy image. There was strong chemical interaction between the Ag2S nanocrystals and the functional groups of zein molecules, which has been confirmed by Fourier transform infrared and thermogravimetry analysis measurements. The band gap of zein‐conjugated Ag2S nanocrystals showed obvious blue shift in ultraviolet‐visible spectra compared with bulk materials because of the quantum size effect.
Formation of silver nanoparticles induced by ultrasonically treated sodium dodecyl benzene sulphonate
Authors: Zhang Shun , Yang Keli , Liu Quansheng
Published: August 2015

A simple and novel method for the synthesis of silver nanoparticles (AgNPs) was investigated, using only ultrasonically treated aqueous solutions of sodium dodecyl benzene sulphonate (UT‐SDBS) as both reducing and stabilizing agents at 100°C. The obtained AgNPs were characterised by their size and morphology. The results have shown that well‐dispersed AgNPs were produced with a narrow size distribution of about 3–9 and 2–13 nm using AgAc and AgNO3 as precursors, respectively. The intermediates generated in the UT‐SDBS solution served as the reducing radicals. The reduction ability of intermediates was determined by the ultrasonic time of SDBS. Most of the intermediates were produced in the first 1 h of ultrasonic irradiation, the reduction ability of UT‐SDBS‐1h was sufficient at this stage. However, by increasing the ultrasonic time to 8 h resulted in further decomposition of intermediates and in the decrease of its reduction ability.
Synthesis of magnetic graphene composites for preconcentraton trace amounts of malachite green and crystal violet from water
Authors: Zhong Yaping , Wang Xue , He Yu , Ge Yili , Song Gongwu
Published: August 2015

Graphene/silica magnetic nanocomposites are synthesised and introduced as new and reusable adsorbents for rapid and high‐efficiency preconcentraton trace amounts of dye pollutants in water. This method is simple, fast, cheap and non‐toxic. The optimum adsorption conditions for the preconcentraton of crystal violet (CV) and malachite green (MG) are investigated and the adsorption mechanisms are also discussed. The regeneration and reuse experiments showed the good reusability of the as‐prepared adsorbent. In addition, this method was successfully applied to the preconcentraton of trace amounts of MG and CV from water samples, which presages more opportunities for application in environmental and material sciences.
Negative differential resistance in graphene nanoribbon superlattice field‐effect transistors
Authors: Chang Sheng , Zhao Lei , Lv Yawei , Wang Hao , Huang Qijun , He Jin
Published: August 2015

Different from researches in two‐terminal nanoscale graphene structures, the negative differential resistance (NDR) phenomenon in graphene nanoribbon superlattice (GNSL) field‐effect transistors (FETs) is studied in this reported work. Numerical analyses of two types of GNSL FETs with different gate voltages reveal that NDR occurs in some ‘Z’‐type GNSL FETs under some gate voltages, which develops NDR research compared with the traditional two‐terminal nanoscale structures. Based on these results, two trends are observed: the 3m + 2 series GNSL FETs easily exhibit NDR, whereas it is more difficult to achieve this phenomenon with narrow FETs. This phenomenon is explained by the transmission coefficient as well as ab‐initio calculations of the energy levels, where the entire channel of the FET is considered as a supercell. Through this analysis, the effect of gate control on energy‐level localisation is uncovered, and a heterojunction‐like explanation is proposed. This new explanation bridges the gap between a novel structure's physical analysis and the general semiconductor device concept, which can also provide inspiration for improving our understanding of novel nanostructure devices.
Quantum stopping times stochastic integral in the interacting Fock space
Authors: Kang Yuanbao
Published: August 2015

Following the ideas of Hudson [J. Funct. Anal. 34(2), 266-281 (1979)] and Parthasarathy and Sinha [Probab. Theory Relat. Fields 73, 317-349 (1987)], we define a quantum stopping time (QST, for short) τ in the interacting Fock space (IFS, for short), Γ, over L2(ℝ+), which is actually a spectral measure in [0, ∞] such that τ([0, t]) is an adapted process. Motivated by Parthasarathy and Sinha [Probab. Theory Relat. Fields 73, 317-349 (1987)] and Applebaum [J. Funct. Anal. 65, 273-291 (1986)], we also develop a corresponding quantum stopping time stochastic integral (QSTSI, for abbreviations) on the IFS over a subspace of L2(ℝ+) equipped with a filtration. As an application, such integral provides a useful tool for proving that Γ admits a strong factorisation, i.e., Γ = Γτ] ⊗ Γ[τ, where Γτ] and Γ[τ stand for the part “before τ” and the part “after τ,” respectively. Additionally, this integral also gives rise to a natural composition operation among QST to make the space of all QSTs a semigroup.
Electron collisions with methyl-substituted ethylenes: Cross section measurements and calculations for 2-methyl–2-butene and 2,3-dimethyl–2-butene
Authors: Szmytkowski Czesław , Stefanowska Sylwia , Zawadzki Mateusz , Ptasińska-Denga Elżbieta , Możejko Paweł
Published: August 2015

We report electron-scattering cross sections determined for 2-methyl–2-butene [(H3C)HC = C(CH3)2] and 2,3-dimethyl–2-butene [(H3C)2C = C(CH3)2] molecules. Absolute grand-total cross sections (TCSs) were measured for incident electron energies in the 0.5–300 eV range, using a linear electron-transmission technique. The experimental TCS energy dependences for the both targets appear to be very similar with respect to the shape. In each TCS curve, three features are discernible: the resonant-like structure located around 2.6–2.7 eV, the broad distinct enhancement peaking near 8.5 eV, and a weak hump in the vicinity of 24 eV. Theoretical integral elastic (ECS) and ionization (ICS) cross sections were computed up to 3 keV by means of the additivity rule (AR) approximation and the binary-encounter-Bethe method, respectively. Their sums, (ECS+ICS), are in a reasonable agreement with the respective measured TCSs. To examine the effect of methylation of hydrogen sides in the ethylene [H2C = CH2] molecule on the TCS, we compared the TCS energy curves for the sequence of methylated ethylenes: propene [H2C = CH(CH3)], 2-methylpropene [H2C = C(CH3)2], 2-methyl–2-butene [(H3C)HC = C(CH3)2], and 2,3-dimethyl–2-butene [(H3C)2C = C(CH3)2], measured in the same laboratory. Moreover, the isomeric effect is also discussed for the C5H10 and C6H12 compounds.
Magneto-structural transformations via a solid-state nudged elastic band method: Application to iron under pressure
Authors: Zarkevich N. A. , Johnson D. D.
Published: August 2015

We extend the solid-state nudged elastic band method to handle a non-conserved order parameter, in particular, magnetization, that couples to volume and leads to many observed effects in magnetic systems. We apply this formalism to the well-studied magneto-volume collapse during the pressure-induced transformation in iron—from ferromagnetic body-centered cubic (bcc) austenite to hexagonal close-packed (hcp) martensite. We find a bcc-hcp equilibrium coexistence pressure of 8.4 GPa, with the transition-state enthalpy of 156 meV/Fe at this pressure. A discontinuity in magnetization and coherent stress occurs at the transition state, which has a form of a cusp on the potential-energy surface (yet all the atomic and cell degrees of freedom are continuous); the calculated pressure jump of 25 GPa is related to the observed 25 GPa spread in measured coexistence pressures arising from martensitic and coherency stresses in samples. Our results agree with experiments, but necessarily differ from those arising from drag and restricted parametrization methods having improperly constrained or uncontrolled degrees of freedom.
Strong field coherent control of molecular torsions—Analytical models
Authors: Ashwell Benjamin A. , Ramakrishna S. , Seideman Tamar
Published: August 2015

We introduce analytical models of torsional alignment by moderately intense laser pulses that are applicable to the limiting cases of the torsional barrier heights. Using these models, we explore in detail the role that the laser intensity and pulse duration play in coherent torsional dynamics, addressing both experimental and theoretical concerns. Our results suggest strategies for minimizing the risk of off-resonant ionization, noting the qualitative differences between the case of torsional alignment subject to a field-free torsional barrier and that of torsional alignment of a barrier-less system (equivalent to a 2D rigid rotor). We also investigate several interesting torsional phenomena, including the onset of impulsive alignment of torsions, field-driven oscillations in quantum number space, and the disappearance of an alignment upper bound observed for a rigid rotor in the impulsive torsional alignment limit.