bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical characterization of INTS3 and C9ORF80, two subunits of hNABP1/2 heterotrimeric complex in nucleic acid binding
Authors: Vidhyasagar Venkatasubramanian , He Yujiong , Guo Manhong , Talwar Tanu , Singh Ravi Shankar , Yadav Manisha , Katselis George , Vizeacoumar Franco J. , Lukong Kiven E. , Wu Yuliang
Published: November 2017

Human nucleic acid-binding protein 1 and 2 (hNABP1 and hNABP2, also known as hSSB2 and hSSB1 respectively) form two separate and independent complexes with two identical proteins, integrator complex subunit 3 (INTS3) and C9ORF80. We and other groups have demonstrated that hNABP1 and 2 are single-stranded (ss) DNA- and RNA-binding proteins, and function in DNA repair; however, the function of INTS3 and C9OFR80 remains elusive. In the present study, we purified recombinant proteins INTS3 and C9ORF80 to near homogeneity. Both proteins exist as a monomer in solution; however, C9ORF80 exhibits anomalous behavior on SDS–PAGE and gel filtration because of 48% random coil present in the protein. Using electrophoretic mobility shift assay (EMSA), INTS3 displays higher affinity toward ssRNA than ssDNA, and C9ORF80 binds ssDNA but not ssRNA. Neither of them binds dsDNA, dsRNA, or RNA : DNA hybrid. INTS3 requires minimum of 30 nucleotides, whereas C9OFR80 requires 20 nucleotides for its binding, which increased with the increasing length of ssDNA. Interestingly, our GST pulldown results suggest that the N-terminus of INTS3 is involved in protein–protein interaction, while EMSA implies that the C-terminus is required for nucleic acid binding. Furthermore, we purified the INTS3–hNABP1/2–C9ORF80 heterotrimeric complex. It exhibits weaker binding compared with the individual hNABP1/2; interestingly, the hNABP1 complex prefers ssDNA, whereas hNABP2 complex prefers ssRNA. Using reconstituted heterotrimeric complex from individual proteins, EMSA demonstrates that INTS3, but not C9ORF80, affects the nucleic acid-binding ability of hNABP1 and hNABP2, indicating that INTS3 might regulate hNABP1/2's biological function, while the role of C9ORF80 remains unknown.
Mechanism of activation of SGK3 by growth factors via the Class 1 and Class 3 PI3Ks
Authors: Malik Nazma , Macartney Thomas , Hornberger Annika , Anderson Karen E. , Tovell Hannah , Prescott Alan R. , Alessi Dario R.
Published: November 2017

Derailment of the PI3K-AGC protein kinase signalling network contributes to many human diseases including cancer. Recent work has revealed that the poorly studied AGC kinase family member, SGK3, promotes resistance to cancer therapies that target the Class 1 PI3K pathway, by substituting for loss of Akt kinase activity. SGK3 is recruited and activated at endosomes, by virtue of its phox homology domain binding to PtdIns(3)P. Here, we demonstrate that endogenous SGK3 is rapidly activated by growth factors such as IGF1, through pathways involving both Class 1 and Class 3 PI3Ks. We provide evidence that IGF1 enhances endosomal PtdIns(3)P levels via a pathway involving the UV-RAG complex of hVPS34 Class 3 PI3K. Our data point towards IGF1-induced activation of Class 1 PI3K stimulating SGK3 through enhanced production of PtdIns(3)P resulting from the dephosphorylation of PtdIns(3,4,5)P3. Our findings are also consistent with activation of Class 1 PI3K promoting mTORC2 phosphorylation of SGK3 and with oncogenic Ras-activating SGK3 solely through the Class 1 PI3K pathway. Our results highlight the versatility of upstream pathways that activate SGK3 and help explain how SGK3 substitutes for Akt following inhibition of Class 1 PI3K/Akt pathways. They also illustrate robustness of SGK3 activity that can remain active and counteract physiological conditions or stresses where either Class 1 or Class 3 PI3K pathways are inhibited.
Microvesicles derived from human Wharton's Jelly mesenchymal stem cells ameliorate ischemia–reperfusion-induced renal fibrosis by releasing from G2/M cell cycle arrest
Authors: Chen Wenxia , Yan Yongbin , Song Chundong , Ding Ying , Du Tao
Published: November 2017

Studies have demonstrated that microvesicles (MVs) derived from human Wharton's Jelly mesenchymal stromal cells (hWJMSCs) could ameliorate renal ischemia/reperfusion injury (IRI); however, the underlying mechanisms were not clear yet. Here, MVs were isolated and injected intravenously into rats immediately after ischemia of the left kidney, and Erk1/2 activator hepatocyte growth factor (HGF) or inhibitor U0126 was administrated. Tubular cell proliferation and apoptosis were identified by Ki67 or terminal-deoxynucleotidyl transferase-mediated nick end labeling immunostaining. Masson's tri-chrome straining and alpha-smooth muscle actin staining were used for assessing renal fibrosis. The mRNA or protein expression in the kidney was measured by quantitative reverse transcription-PCR or Western blot, respectively. The total collagen concentration was also determined. In vitro, NRK-52E cells that treated with MVs under hypoxia injury and with HGF or U0126 administration were used, and cell cycle analysis was performed. The effects of hWJMSC-MVs on enhancing the proliferation and mitigating the apoptosis of renal cells, abrogating IRI-induced fibrosis, improving renal function, decreasing collagen deposition, and altering the expression levels of epithelial–mesenchymal transition and cell cycle-related proteins in IRI rats were found. In vitro experiment showed that hWJMSC-MVs could induce G2/M cell cycle arrest and decrease the expression of collagen deposition-related proteins in NRK-52E cells after 24 or 48 h. However, U0126 treatment reversed these effects. In conclusion, MVs derived from hWJMSCs ameliorate IR-induced renal fibrosis by inducing G2/M cell cycle arrest via Erk1/2 signaling.
Distinct RNA-unwinding mechanisms of DEAD-box and DEAH-box RNA helicase proteins in remodeling structured RNAs and RNPs
Authors: Gilman Benjamin , Tijerina Pilar , Russell Rick
Published: November 2017

Structured RNAs and RNA–protein complexes (RNPs) fold through complex pathways that are replete with misfolded traps, and many RNAs and RNPs undergo extensive conformational changes during their functional cycles. These folding steps and conformational transitions are frequently promoted by RNA chaperone proteins, notably by superfamily 2 (SF2) RNA helicase proteins. The two largest families of SF2 helicases, DEAD-box and DEAH-box proteins, share evolutionarily conserved helicase cores, but unwind RNA helices through distinct mechanisms. Recent studies have advanced our understanding of how their distinct mechanisms enable DEAD-box proteins to disrupt RNA base pairs on the surfaces of structured RNAs and RNPs, while some DEAH-box proteins are adept at disrupting base pairs in the interior of RNPs. Proteins from these families use these mechanisms to chaperone folding and promote rearrangements of structured RNAs and RNPs, including the spliceosome, and may use related mechanisms to maintain cellular messenger RNAs in unfolded or partially unfolded conformations.
Autophagy in the context of the cellular membrane-trafficking system: the enigma of Atg9 vesicles
Authors: Noda Takeshi
Published: November 2017

Macroautophagy is an intracellular degradation system that involves the de novo formation of membrane structures called autophagosomes, although the detailed process by which membrane lipids are supplied during autophagosome formation is yet to be elucidated. Macroautophagy is thought to be associated with canonical membrane trafficking, but several mechanistic details are still missing. In this review, the current understanding and potential mechanisms by which membrane trafficking participates in macroautophagy are described, with a focus on the enigma of the membrane protein Atg9, for which the proximal mechanisms determining its movement are disputable, despite its key role in autophagosome formation.
Gaussian approach versus Dolph‐Chebyshev synthesis of pencil beams for linear antenna arrays
Authors: Buttazzoni G. , Vescovo R.
Published: November 2017

A very simple and fast method for the synthesis of pencil beams with linear antenna arrays of equally spaced elements is presented. The proposed procedure starts selecting the desired pencil beam as a Gaussian function. This is very convenient for two reasons: first, the continuous line‐source distribution that exactly produces the desired pencil beam (i.e. the Fourier transform of it) is in turn a Gaussian function and is immediately calculated. Second, a suitable weighted sampling of this distribution gives the excitations of the array elements in closed form. Two numerical examples reveal the good performances of the proposed approach, also in comparison with the classical method by Dolph‐Chebyshev. It is shown that the synthesised array factors well approximate the desired pencil beams in real time, in particular ensuring a very good behaviour in the side lobe regions. Furthermore, the ‘dynamic range ratio’ of the excitations, defined as the ratio between the maximum and the minimum amplitude of the excitations, is very low and close to unity when the array length is sufficiently small.
Denoising different types of acoustic partial discharge signals using power spectral subtraction
Authors: Hussein Ramy , Shaban Khaled Bashir , El‐Hag Ayman H.
Published: November 2017

Measuring acoustic emission (AE) of partial discharge (PD) phenomena can be adopted to estimate the condition of power transformers. However, the environmental noise encountered with AE of PD measurements negatively affects the accuracy of PD localisation and classification. Thus, efficient signal denoising techniques are required for noise suppression and hence, better detection accuracy. This study deals with white noise and it is a continuation of a previously published work that deals with random noise. The published work addresses the random noise suppression using a method named, power spectral subtraction denoising (PSSD). This study applies PSSD to the PD signals contaminated with white noise and uses a novel scheme of noise power spectrum density estimation. Multiple types of AE signals are examined including signals produced by corona, surface, parallel, and void PDs. Synthetic and real data demonstrate the superiority of the proposed method over the wavelet shrinkage denoising method as it can more effectively eliminate white noise and preserve signals of low signal‐to‐noise ratio.
Augmenting NOx reduction in diesel exhaust by combined plasma/ozone injection technique: a laboratory investigation
Authors: Madhukar Apeksha , Rajanikanth Bangalore S.
Published: November 2017

With the advent of non‐thermal plasma technique for diesel exhaust treatment attention is being focused on reducing oxides of nitrogen (NOx) both from stationary as well as automobile sources. In this work, an attempt has been made to enhance NOx reduction only by utilising a plasma/ozone injection approach without resorting to additional treatments based on catalysts/adsorbents. It was observed that cascading ozone injection with discharge plasma enhances the reduction of NOx as high as 95% for the specific energy of 123 J/l. In the long run, this plasma‐only based approach may be beneficial or a possible alternative for catalyst/adsorbent based NOx treatments. The results have been discussed and a comparative analysis has been made with respect to individual plasma and ozone injection treatment.
Performance analysis of multi‐pair two‐way amplify‐and‐forward relaying with imperfect CSI over Ricean fading channels
Authors: Sun Xiaoli , Xu Kui , Xu Youyun
Published: November 2017

This study investigates the spectral efficiency (SE) and energy efficiency (EE) of a multipair two‐way massive multiple‐input multiple‐output amplify‐and‐forward relaying system over Ricean fading channels. Both maximum‐ratio combining/maximum ratio transmission and zero‐forcing transmission/zero‐forcing reception beamforming matrices are considered at the relay with imperfect channel state information (CSI). The asymptotic signal‐to‐interference‐plus‐noise ratio expressions (in the number of relay antennas M) are derived. Moreover, four power scaling schemes are proposed and the asymptotic SE and EE based on the proposed power scaling schemes are obtained analytically. Theoretical analyses and simulation results show that with imperfect CSI when M tends to infinity, the transmit power should be scaled down to different proportions for the Ricean channel with and without line‐of‐sight components to maintain a desirable rate. However, when M tends to infinity, SE is independent of the Ricean K‐factor with perfect CSI.
Synchronisation algorithm for OFDM/OQAM systems based on zero autocorrelation code
Authors: Qian Xuewen , Deng Yansha , Deng Honggui , Zhang Chaoyang , Du Jie
Published: November 2017

In this study, the authors first propose a sequence with the impulse‐like autocorrelation property named zero autocorrelation code (ZAC) for orthogonal frequency division multiplexing (OFDM) based on offset quadrature amplitude modulation (OQAM) systems. The ZAC sequence can be generated by many prototype filters such as physical layer for dynamic spectrum access and cognitive radio and isotropic orthogonal transform algorithm filters. Thus, it has a wide application range. The authors then propose a synchronisation algorithm based on the ZAC. The proposed algorithm only needs two symbols to compose the preamble while existing algorithms need at least four symbols. They further assess the synchronisation performances via computer simulation. The simulation results show that the proposed algorithm can achieve better performance in terms of root mean square error of the timing and frequency offset estimation, with a 10 dB improvement on timing offset estimation performance over Saeedi‐Sourck's algorithm when signal‐to‐noise ratio is 0 dB.
Cyclic switching weighted bit‐flipping decoding for low‐density parity‐check codes
Authors: Wang Yige , Wu Guilong
Published: November 2017

A cyclic switching weighted bit‐flipping (CS‐WBF) decoding algorithm for low‐density parity‐check (LDPC) codes is proposed in this study. By carefully choosing two selection criteria of the bit to flip and cyclically switching from one criterion to the other according to some rules during decoding, the proposed scheme can effectively break decoding loops, which often appear for weighted bit‐flipping (WBF) algorithms and greatly degrade decoding performance. Simulation results show that CS‐WBF provides 0.7–1.3 dB coding gain over various simple improved WBF algorithms, such as reliability ratio‐based WBF and improved modified WBF, with almost the same complexity for both regular and irregular LDPC codes. Compared with WBF algorithms that break decoding loops and the belief propagation‐based algorithm, CS‐WBF can also provide a better complexity‐performance trade‐off.
Modelling and performance analysis of mmWaves and radio‐frequency based 3D heterogeneous networks
Authors: Bachtobji Soumaya , Omri Aymen , Bouallegue Ridha , Raoof Kosai
Published: November 2017

This study introduces a three‐dimensional (3D) model for K‐tier heterogeneous networks (HetNets) in order to evaluate the performance of using millimetre wave (mmWave) and radio‐frequency (RF) bands. The model is based on 3D stochastic geometry that describes the different cells' positions in the network with realistic constraints. Based on the 3D model, the successful transmission probability, the average throughput, and the average bit error rate expressions of down‐link HetNets are detailed and derived for both considering bands. Using numerical results, the analytical derived expressions are evaluated, and the advantages of using mmWave and RF bands for HetNets are investigated.
An energy‐efficient joint antenna and user selection algorithm for multi‐user massive MIMO downlink
Authors: Olyaee Maryam , Eslami Mohsen , Haghighat Javad
Published: November 2017

Massive multiple‐input multiple‐output (MIMO) technology employs hundreds of antennas at the base station (BS) of a cellular system. Activating hundreds of antennas requires hundreds of radio‐frequency (RF) chains that lead to high cost and high energy consumption. Antenna selection techniques reduce the number of RF chains while curtailing the resulting performance loss. In this study, the authors consider massive‐MIMO downlink with zero‐forcing (ZF) precoding in a single cell. In ZF precoding with antenna selection, the number of users must always be less than or equal to the number of selected antennas, which may require adopting user selection (scheduling) algorithms. They propose a joint user and antenna selection algorithm to increase BS's energy efficiency (EE) and show that its performance is very close to that of the optimum exhaustive‐search based scheme. Using an analytical approximation for EE of the proposed scheme in asymptotically large numbers of users region, they find the optimum number of antennas to be selected.
Robust fault detection filter design for interconnected systems subject to packet dropouts and structure changes
Authors: Li Jian , Wu Chun‐Yu , Su Qingyu
Published: November 2017

The problem of robust fault detection (FD) filter design for interconnected systems, and the problems of both packet dropouts and disconnected interconnections in these subsystems are studied. By modelling instances of disconnected interconnections among subsystems and packet dropouts in the measurement channel into independent subsystems, this study proposes a switched scheme that combines mode‐dependent average dwell time with event‐driven switching. A filter in which the FD system is exponentially stable and achieves a weighted performance can be derived from the optimal method of convex linear matrix inequalities. An example is given to demonstrate the effectiveness of the proposed method.
Multi‐instance multi‐label learning of natural scene images: via sparse coding and multi‐layer neural network
Authors: Zhang Hu , Wu Wei , Wang Ding
Published: November 2017

The classification of natural scene images is multi‐instance multi‐label (MIML) for many labels that exist in a natural scene image. The traditional method of solving MIML is to degenerate it into single‐instance single‐label learning (SISL). However, the precision of the method could decrease due to information loss during the degeneration process. How to reasonably solve the MIML problem is key to obtaining high accuracy in this research area. An MIML algorithm based on instances via combining sparse coding with a deep neural network is proposed. First, an instance‐based sparse representation with dictionary learning is adopted. Second, an MIML description model based on a deep network is proposed, which can realise parameter self‐learning in combination with sparse representations. Third, the residuals of the sparse representation are introduced to the deep neural network. The results of the experiments show that the method outperforms a number of state‐of‐the‐art approaches.
Review of constraints on vision‐based gesture recognition for human–computer interaction
Authors: Chakraborty Biplab Ketan , Sarma Debajit , Bhuyan M.K. , MacDorman Karl F
Published: November 2017

The ability of computers to recognise hand gestures visually is essential for progress in human–computer interaction. Gesture recognition has applications ranging from sign language to medical assistance to virtual reality. However, gesture recognition is extremely challenging not only because of its diverse contexts, multiple interpretations, and spatio‐temporal variations but also because of the complex non‐rigid properties of the hand. This study surveys major constraints on vision‐based gesture recognition occurring in detection and pre‐processing, representation and feature extraction, and recognition. Current challenges are explored in detail.
Foreground extraction for freely moving RGBD cameras
Authors: Junejo Imran N. , Ahmed Naveed
Published: November 2017

In this study, the authors propose a novel method to perform foreground extraction for freely moving RGBD cameras. Although the field of foreground extraction or background subtraction has been explored by the computer vision researcher community since a long time, the depth‐based subtraction is relatively new and has not been extensively addressed as of yet. Most of the current methods make heavy use of geometric reconstruction, making the solutions quite restrictive. In this study, the authors make a novel use of RGB and depth data: from the RGB frame, they first extract corner features and then represent these features with the histogram of oriented gradients (HoG) descriptor. They then train a non‐linear SVM on these HoG descriptors. During the test phase, they make use of the fact that the foreground object has a distinct depth ordering with respect to the rest of the scene. Hence, they use the positively classified features from accelerated segment test (FAST) features on the test frame to initiate a region growing algorithm to obtain an accurate foreground segmentation from the depth data alone. The authors demonstrate the proposed method on six datasets, and demonstrate encouraging quantitative and qualitative results.
Using mel‐frequency audio features from footstep sound and spatial segmentation techniques to improve frame‐based moving object detection
Authors: Roshan Aditya , Zhang Yun
Published: November 2017

Moving object detection in video streams is a challenging and integral part of computer vision which is used in surveillance, traffic and site monitoring, and navigation. Compared with the background‐based techniques, frame differencing technique is computationally inexpensive. However, frame differencing technique only detects the boundary of a moving object. Due to changing light conditions, shadows, poor contrast between object and background, and a slow‐moving object, object detection rate from frame differencing technique reduces. This is because the number of noisy frames and frames with missing/partially detected object increases. Application of large kernel size morphological operations fails to remove noise as they might remove the boundary (or part) of a moving object. In this study, the authors propose a methodology to improve the frame differencing technique using footstep sound generated by a moving object. Audio recorded with the video system is processed and footstep sound is detected using audio features computed as mel‐frequency cepstral coefficients. Number of frames within each footstep sound are counted and processed. Spatial segmentation is used to find the moving object in noisy frames. A missing or partially detected object is recovered by modelling an ellipse using a moving object from other neighbourhood frames.
Space vector pulse width modulation control techniques for a five‐phase quasi‐impedance source inverter
Authors: Abduallah Ahmad Anad , Meraj Mohammed , Al‐Hitmi Mohammed , Iqbal Atif
Published: November 2017

This study proposes space vector modulation (SVM) techniques for a five‐phase quasi‐impedance source inverter. Five different SVM methods are elaborated utilising four active neighbouring (from two different lengths group) and a zero space vector to synthesise the reference voltage with the aim of obtaining sinusoidal output voltage waveforms. The main objective of the developed SVM methods is to reduce total harmonic distortion (THD) in the output voltage waveform while simultaneously boosting the DC link voltage. Shoot‐though period is computed according to the required boost in the DC voltage and spread in a switching cycle. Five different schemes are developed based on the shoot‐through application in a number of inverter legs. A comprehensive comparative study of the proposed SVM techniques is carried out based on various obtained characteristics such as the shoot‐through duty ratio, boost factor, voltage gain, THD and efficiency. Theoretical analysis and simulation results are validated using experimental approach.
Online diagnostic method of open‐switch faults in PWM voltage source rectifier based on instantaneous AC current distortion
Authors: Shi Tiancheng , He Yigang , Deng Fangming , Tong Jin , Wang Tao , Shi Luqiang
Published: November 2017

The three‐phase pulse‐width modulating (PWM) voltage source rectifier (VSR) system is widely used because of its advantages in performance. Numerous studies show that power semiconductors are significant contributors to the overall failure rate of power converters. This study presents an online diagnosis method for a single open‐switch fault of a three‐phase PWM VSR, because existing research mainly focuses on fault diagnosis of inverters. The proposed method employs current distortion to diagnose faults in a convenient and simple way. It requires no extra hardware but only AC current signals, which are available in the control system and can be embedded into the existing driving software as a subroutine without excessive computational effort. The proposed method offers high diagnostic effectiveness and reliability. Experimental results show that the proposed method can diagnose the faulty switch at low currents as well as under abrupt load transient conditions without false alarms. Furthermore, the average diagnostic time of this method is only 1.8 ms.
Colour image encryption algorithm using one‐time key and FrFT
Authors: Gao Zhenguo , Chen Danjie , Zhang Wei , Cai Shaobin
Published: November 2017

A novel chaos‐based colour image encryption algorithm is proposed, which adopts a one‐time key mechanism based on message‐digest algorithm 5 (MD5) value of the input plain image. The algorithm combines several key technologies including fractional Fourier transform (FrFT), MD5, and global scrambling. Using fast digital discrete FrFT, the algorithm develops the complex data manipulating potentials of FrFT efficiently; meanwhile, keeps the size of the cipher image un‐changed, thus eliminates the requirement on double storage space to store complex values of cipher image. Exploiting the intrinsic robustness of FrFT, the algorithm achieves high robustness to pixel errors and noise attacks. Experimental results show that the algorithm achieves better pixel change rate and unified average change intensity, and is efficient, effective, and robust to attacks.
Compact Rotman lens‐fed slot array antenna with low sidelobes
Authors: Liu Yi , Yang Hu , Jin Zusheng , Zhao Fei , Zhu Jiang
Published: November 2017

A slot array in substrate‐integrated waveguide (SIW) technology fed by a microstrip Rotman lens is proposed. This compact multibeam antenna is designed in two layers using a novel transition based on double‐stepped coupling slots on the broad wall of SIWs. Compared with a rectangular transverse coupling slot, this transition is broadband and its coupling power can be controlled for low‐sidelobe applications. The radiating part is a 10 × 10 slot array and the beam‐forming network can generate seven beams with good coverage from −30° to 30° in the azimuthal plane. To validate the proposed concept, an antenna prototype is implemented at 10 GHz. The frequency response and measured radiation patterns are in good agreement with simulated results provided by full wave simulation software. Experimental results show that the sidelobe level is lower than −21 dB for the central beam in both H and E planes and better than −18 dB for the edge beams.
Dual‐band platform‐mounted HF/VHF antenna design using the characteristic mode theory
Authors: Li Mingjian , Behdad Nader
Published: November 2017

The design of a dual‐band antenna mounted on a military platform is presented. The antenna operates in both high‐frequency (HF) and very‐high‐frequency (VHF) bands and consists of two half‐loops mounted on the platform. When the two half‐loops are excited differentially, they act as coupling elements exciting the platform dominant characteristic mode. This generates a horizontally polarised radiation with maximum radiation towards to zenith. Due to the presence of the platform, the antenna bandwidth is increased compared with that of an isolated antenna. When the two half‐loops are excited in the common mode, they behave as an ultra‐wideband antenna with monopole‐like radiation in the VHF band. A diplexer is used to achieve dual‐band operation, which allows the antenna operating at both bands simultaneously. A 60:1 scaled antenna prototype and its feed network is fabricated and characterised. At the lower band, the antenna exhibits an impedance bandwidth of 2.8% for a voltage standing wave ratio (VSWR) better than 2.25:1 and a directional radiation pattern with horizontal polarisation. At the higher band, the antenna exhibits a VSWR better than 2.25:1 and monopole‐like radiation characteristics across 2:1 bandwidth. The impact of the presence of a realistic ground plane on the antenna performance is also studied and discussed.
235 GHz on‐chip antenna with miniaturised AMC loading in 65 nm CMOS
Authors: Zhu Hua , Li Xiuping , Feng Weiwei , Xiao Jun , Zhang Jianhua
Published: November 2017

In this study, an on‐chip antenna with miniaturised artificial magnetic conductor (AMC) structure loading is designed and fabricated in the 65 nm complementary metal oxide semiconductor process at 235 GHz. The proposed on‐chip antenna consists of a double‐layer dipole and miniaturised AMC with wide bandwidth and low‐backward radiation. A quarter square loop structure for the miniaturised AMC is designed and analysed by the current and electric field distributions. The simulation results show that the miniaturised AMC has a similar resonant frequency and lower reflection loss compared with the original one. The die area of the proposed antenna is . The measurement of the −10 dB impedance bandwidth is 81 GHz (200–281 GHz). The gain of the antenna is up to 0 dBi at 235 GHz. By loading the miniaturised AMC, the on‐chip antenna can obtain higher gain, wider bandwidth than that loading the original one. Good agreement can be well observed between the simulated and measured results.
Highly compact size serpentine‐shaped multiple‐input–multiple‐output fractal antenna with CP diversity
Authors: Abed Amer T.
Published: November 2017

A novel multiple‐input–multiple‐output fractal antenna was proposed in this study. The proposed antenna consisted of two symmetrical radiating elements placed on opposite sides to achieve spatial diversity with a highly compact size (8 × 8 × 0.8 mm3). Each radiating element is configured by a process of three iterations, and an additional semi‐crescent structure scaled down in each iteration placed in a cascade arrangement. This arrangement generated circularly polarised radiation with an axial ratio bandwidth of (2.2–3.2) GHz, which was about 24% of the entire operational range of (0.1–4.3) GHz that can be used for many wireless communications such as long‐term evolution, radio‐frequency identification, wireless fidelity, and worldwide interoperability for microwave access applications. The envelope correlation coefficient, mutual coupling, circular polarisation (CP), and current distribution were studied and analysed to improve the design process. Compared to other related antennas, the proposed antenna can improve many radiation characteristics such as diversity (left‐hand CP) and (right‐hand CP), wide axial ratio bandwidth, and acceptable gain in a small antenna size.
Increasing the reliability of wind turbines using condition monitoring of semiconductor devices: a review
Authors: Moeini Rana , Tricoli Pietro , Hemida Hassan , Baniotopoulos Charalampos
Published: November 2017

The majority of electrical failures in wind turbines occur in the generator‐side semiconductor devices. This is due to temperature swings affecting the layers of insulated‐gate bipolar transistors in different ways; these effects are aggravated by the variation of wind speed. The implementation of accurate on‐line condition monitoring mainly relies on on‐line tracking of the temperature variation of components. The maximum temperature stress is observed at the junction terminal of the devices, which cannot be easily measured. Additionally, it is difficult to track the exact dynamic of temperature due to the slow response of sensors. Thus, several methods have been presented in the technical literature to estimate the junction temperature of the semiconductor devices. Each method has merits and disadvantages in terms of accuracy and complexity, as failure mechanisms have their own effects on the variation of junction temperature and some or all of the electrical parameters. Therefore, detection algorithms have to determine the root cause of the temperature variation. This study comparatively reviews the condition monitoring methods presented so far and gives directions on the future steps that should be addressed by research in this area.
Indirect boost matrix converter and low‐voltage generator for direct drive wind turbines
Authors: Singh Akanksha , Mirafzal Behrooz
Published: November 2017

Here, a new topology for direct drive wind turbines (DDWTs) with a new power electronics interface and a low‐voltage generator is presented. In the presented power electronics interface, the grid‐side converter is replaced by a boost current source inverter (CSI) which eliminates the required dc‐bus capacitors, resulting in an increase in the system lifetime. The inherently required dc‐link inductor for this topology is eliminated by utilising the synchronous inductance of the permanent magnet synchronous generator. The control technique used for the developed DDWT is described here. The boost CSI enables conversion of a low dc voltage to a higher line‐to‐line voltage creating an indirect boost matrix converter, and thus, enabling the implementation of a low‐voltage generator. This further enables a reduction in the number poles required in direct drive wind generators. The feasibility of the proposed generator‐converter topology for DDWTs and its controllers are verified through simulations and experimental results on a laboratory scale 1.5 kW, 240 V set‐up.
Time synchronisation for multi‐static radar via microwave and troposcatter
Authors: Liuv Jiye , Chen Xihong
Published: November 2017

Time synchronisation is one of the key issues to realise remote detection for multi‐static radar. With the condition that the receivers are commonly located at different distances from the transmitter, a high‐precision time synchronisation scheme for multi‐static radar with mixed microwave and troposcatter channels is proposed. In order to prove the feasibility of transmitting pulse signals in microwave channel, the jitter of the signals has been tested, and the transmission loss of the troposcatter channel has been calculated. Finally, the accuracy of the proposed model is analysed, which shows that the proposed scheme is feasible and can be a backup for time synchronisation for multi‐static radar.
Multi‐objective reactive power optimisation approach for the isolated grid of new energy clusters connected to VSC‐HVDC
Authors: Yin Shengli , Wu Linlin , Song Wei , Wang Xiao
Published: November 2017

It is known that reactive power optimisation is of great significance to improve the electrical power quality. How the security, reliability, and economy of the system can be effectively improved by reactive power optimisation has attracted the attention of scholars. In this study, according to the characteristics of an isolated grid of the new energy clusters connected to voltage source converter‐based high‐voltage direct current, the multi‐objective reactive power optimisation model, which takes the network loss, and the reactive power margin of new energy clusters into consideration, is established. In particular, the maximisation of reactive power margin of new energy clusters is chosen as one goal, thus the response speed of voltage control can be effectively improved, and the preventive control of transient voltage stability of new energy clusters will be realised. Afterwards, using the weighted method the multi‐objective optimisation model can be transformed into a single‐objective optimisation model and the particle swarm algorithm is utilised to obtain the optimal solution. Finally, the simulation results show that the reactive power optimisation approach proposed can effectively reduce the network loss of the system, increase the reactive power margin of the new energy clusters, and improve the quality of the system voltage.
Positive and negative sequence control of DFIG based wind turbines and its impact on grid voltage profile concerning converter control capability
Authors: Yan Lun , Yuan Xiaoming
Published: November 2017

As grid‐connected doubly fed induction generator (DFIG) based wind turbines have become a significant power source, in order to meet grid code and ensure its safe operation during asymmetrical grid faults, many improved control algorithms have been developed for the rotor‐side converter (RSC). However, most of them did not take the RSC control capability constraint into account and may cause overcurrent problem in the rotor side under serve asymmetric faults. In this study, first a new positive and negative sequence current control scheme for the RSC is designed so that DFIG can operate well during serve asymmetrical faults. Then, due to the RSC capability constraint, the controllable regions of DFIG are analysed while the limitation of DFIG is given. Based on the controllable regions and limitation of DFIG, the limitation and division strategies between DFIG rotor positive and negative sequence current are also developed theoretically. Finally, a typical system of a 45 MW DFIG‐based wind farm connected to power system is used to verify the effectiveness of the developed rotor positive and negative sequence current limitation and division strategies and study their impact on grid voltage profile during various asymmetrical faults in Matlab/Simulink software.
Few‐layer graphene doped with boron to enhance ammonium hydroxide vapour detection at low temperature
Authors: Ahmadi Shahrokh , Afzalzadeh Reza
Published: November 2017

Few‐layer graphene and multilayer graphene are grown using atmospheric pressure chemical vapour deposition method with polystyrene as a solid carbon source on copper foil. These experimentations demonstrate that the sensor made of few layer graphene compared to multilayer graphene shows 12.5 times higher sensitivity to the vapour of ammonium hydroxide. Doping of a few layer graphene by boron is done by using boric acid as a solid precursor. The sensitivity of the few layer graphene sensor after 20 min has increased by 4.7 times when the graphene layer was doped with boron atoms (∼2.1%) for ammonium hydroxide detection. Selectivity of the boron doped sensor for ammonium hydroxide is about 16 times more than the presence of ethanol and methanol vapours. All measurements were done at room temperature and in air ambient. Atomic force microscopy, X‐ray photoelectron spectroscopy and Raman spectroscopy have been used for characterisation of the layers. The dynamic response of the sensor is well fitted with Freundlich isotherm.
Stellar streams as gravitational experiments
Authors: Thomas G. F. , Famaey B. , Ibata R. , Renaud F. , Martin N. F. , Kroupa P.
Published: November 2017

Kinematically cold tidal streams of globular clusters (GC) are excellent tracers of the Galactic gravitational potential at moderate Galactocentric distances, and can also be used as probes of the law of gravity on Galactic scales. Here, we compare for the first time the generation of such streams in Newtonian and Milgromian gravity (MOND). We first computed analytical results to investigate the expected shape of the GC gravitational potential in both frameworks, and we then ran N-body simulations with the Phantom of Ramses code. We find that the GCs tend to become lopsided in MOND. This is a consequence of the external field effect which breaks the strong equivalence principle. When the GC is filling its tidal radius the lopsidedness generates a strongly asymmetric tidal stream. In Newtonian dynamics, such markedly asymmetric streams can in general only be the consequence of interactions with dark matter subhalos, giant molecular clouds, or interaction with the Galactic bar. In these Newtonian cases, the asymmetry is the consequence of a very large gap in the stream, whilst in MOND it is a true asymmetry. This should thus allow us in the future to distinguish these different scenarios by making deep observations of the environment of the asymmetric stellar stream of Palomar 5. Moreover, our simulations indicate that the high internal velocity dispersion of Palomar 5 for its small stellar mass would be natural in MOND.
Abundance of SiC2
in carbon star envelopes
Authors: Massalkhi S. , Agúndez M. , Cernicharo J. , Velilla Prieto L. , Goicoechea J. R. , Quintana-Lacaci G. , Fonfría J. P. , Alcolea J. , Bujarrabal V.
Published: November 2017

Context. Silicon carbide dust is ubiquitous in circumstellar envelopes around C-rich asymptotic giant branch (AGB) stars. However, the main gas-phase precursors leading to the formation of SiC dust have not yet been identified. The most obvious candidates among the molecules containing an Si–C bond detected in C-rich AGB stars are SiC2, SiC, and Si2C. To date, the ring molecule SiC2 has been observed in a handful of evolved stars, while SiC and Si2C have only been detected in the C-star envelope IRC +10216.

Aim. We aim to study how widespread and abundant SiC2, SiC, and Si2C are in envelopes around C-rich AGB stars, and whether or not these species play an active role as gas-phase precursors of silicon carbide dust in the ejecta of carbon stars.

Methods. We carried out sensitive observations with the IRAM 30 m telescope of a sample of 25 C-rich AGB stars to search for emission lines of SiC2, SiC, and Si2C in the λ 2 mm band. We performed non-LTE excitation and radiative transfer calculations based on the LVG method to model the observed lines of SiC2 and to derive SiC2 fractional abundances in the observed envelopes.

Results. We detect SiC2 in most of the sources, SiC in about half of them, and do not detect Si2C in any source except IRC +10216. Most of these detections are reported for the first time in this work. We find a positive correlation between the SiC and SiC2 line emission, which suggests that both species are chemically linked; the SiC radical is probably the photodissociation product of SiC2 in the external layer of the envelope. We find a clear trend where the denser the envelope, the less abundant SiC2 is. The observed trend is interpreted as evidence of efficient incorporation of SiC2 onto dust grains, a process that is favored at high densities owing to the higher rate at which collisions between particles take place.

Conclusions. The observed behavior of a decline in the SiC2 abundance with increasing density strongly suggests that SiC2 is an important gas-phase precursor of SiC dust in envelopes around carbon stars.
Design and performance of dual-polarization lumped-element kinetic inductance detectors for millimeter-wave polarimetry
Authors: McCarrick H. , Jones G. , Johnson B. R. , Abitbol M. H. , Ade P. A. R. , Bryan S. , Day P. , Essinger-Hileman T. , Flanigan D. , Leduc H. G. , Limon M. , Mauskopf P. , Miller A. , Tucker C.
Published: November 2017

Aims. Lumped-element kinetic inductance detectors (LEKIDs) are an attractive technology for millimeter-wave observations that require large arrays of extremely low-noise detectors. We designed, fabricated and characterized 64-element (128 LEKID) arrays of horn-coupled, dual-polarization LEKIDs optimized for ground-based CMB polarimetry. Our devices are sensitive to two orthogonal polarizations in a single spectral band centered on 150 GHz with Δν∕ν = 0.2. The 65 × 65 mm square arrays are designed to be tiled into the focal plane of an optical system. We demonstrate the viability of these dual-polarization LEKIDs with laboratory measurements.

Methods. The LEKID modules are tested with an FPGA-based readout system in a sub-kelvin cryostat that uses a two-stage adiabatic demagnetization refrigerator. The devices are characterized using a blackbody and a millimeter-wave source. The polarization properties are measured with a cryogenic stepped half-wave plate. We measure the resonator parameters and the detector sensitivity, noise spectrum, dynamic range, and polarization response.

Results. The resonators have internal quality factors approaching 1 × 106. The detectors have uniform response between orthogonal polarizations and a large dynamic range. The detectors are photon-noise limited above 1 pW of absorbed power. The noise-equivalent temperatures under a 3.4 K blackbody load are <100 μK √s. The polarization fractions of detectors sensitive to orthogonal polarizations are >80%. The entire array is multiplexed on a single readout line, demonstrating a multiplexing factor of 128. The array and readout meet the requirements for 4 arrays to be read out simultaneously for a multiplexing factor of 512.

Conclusions. This laboratory study demonstrates the first dual-polarization LEKID array optimized specifically for CMB polarimetry and shows the readiness of the detectors for on-sky observations.
Seasonal infertility in pigs: what have we achieved and where are we up to?
Authors: King R. H.
Published: November 2017

The most common manifestations of seasonal infertility are delayed puberty, prolonged weaning to oestrus intervals and a reduced farrowing rate brought about by increased returns to oestrus, including a proportionally higher incidence of irregular returns to oestrus. Over the past 40 years, there has been considerable investment in Australian pig research that has generated extensive knowledge about the physiological mechanisms behind seasonal infertility. While some of the physiological mechanisms allowing the expression of seasonal infertility still remain unclear, a number of possible intervention strategies have been developed and investigated to ameliorate the effects of seasonal infertility in commercial production. For commercial pork producers, there is considerable information available that is based on both research and practical experience, which the farmers can use to identify strategies to minimise the impact of seasonal infertility on the farm. The industry still provides some support to research and development efforts to address seasonal infertility, although, in the future, it may be more targeted to identifying interventions to ameliorate the impact of seasonal infertility in affected herds, rather than undertaking intensive studies into the possible mechanisms and reasons behind this very complex syndrome.