bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation template matching CPA method
Authors: Akalp Kuzu E. , Tangel A.
Published: June 2016

An improved decision mechanism to the previously advertised correlation power analysis (CPA) type of attack which is applied on the Montgomery ladder exponentiation steps of the Application‐Specific Integrated Circuit (ASIC) RSA implementation is proposed. As the nature of this previous attack, for each m‐bit sized windows of the key bits, ratios of the correlation values of the correct type vector with all the other candidate vectors must also exist between the peak value of the correlation curve of the correct type vector and of the other candidate vectors. As a novelty, proposed method uses this property; namely, it searches the closest matching between these ratios to decide the correct bit type vector. It is experimentally and theoretically shown that this decision mechanism requires lesser number of traces to extract the correct key bit types compared with the previous CPA type attack. Also this decision methodology can be used to improve the effectiveness of other possible CPA type of attacks which construct power leakage models for more than one bit.
Energy‐efficient network cooperation joint resource configuration in multi‐RAT heterogeneous cognitive radio networks
Authors: Feng Li , Kuang Yujun , Fu Xinchuang , Dai Zeyang
Published: June 2016

A novel energy efficiency (EE)‐oriented cognitive spectrum sharing scheme in heterogeneous cognitive radio networks, called energy‐efficient cognitive cooperation (ECC) is proposed, in which the primary system release a part of its radio spectrum to the secondary system in exchange for secondary user (SU) served as a relay to assist the transmission of the primary user (PU) traffic. On the basis of ECC scheme, an EE maximisation non‐convex problem for SUs is formulated under the circuit power consumption and the QoS requirements as well as power constraints. By virtue of parametric Dinkelbach's algorithm and golden section search method, an efficient resource allocation algorithm is developed. Simulation results show that our proposals attain significantly higher EE compared with the non‐cooperation transmission without sacrificing the performance of PU's QoS, and thus, a ‘win‐win’ situation is achieved.
Superior execution time design of optimal (Wiener) time‐frequency filter
Authors: Ivanović V.N. , Jovanovski S. , Radović N.
Published: June 2016

Completely pipelined signal adaptive multicycle hardware design of the optimal time‐frequency (TF) filter is developed and verified. The design retains all desirable characteristics of the corresponding recently proposed signal adaptive solution with the optimised time and hardware requirements, but additionally improves the execution time – for a clock cycle per each TF point performed within the estimation, resulting in the improvement of up to 50% in terms of points lying outside the instantaneous frequency of the estimated signal.
5.3 GHz 42% PAE class‐E power amplifier with 532 mW/mm2 power area density in 180 nm CMOS process
Authors: Alsuraisry H. , Wu M.‐H. , Huang P.‐S. , Tsai J.‐H. , Huang T.‐W.
Published: June 2016

A 5.3 GHz high‐efficiency and low‐cost class‐E power amplifier (PA) implemented in a 180 nm CMOS process is presented. Cascode configuration is utilised in the class‐E PA to achieve high efficiency due to its high gain property and low drain‐to‐source parasitic capacitor. Through the trade‐off between inductance and inductor loss, an optimised RF choke inductor for fully integrated class‐E PA design can be selected to achieve high efficiency while maintaining compact circuit size. The class‐E CMOS PA demonstrates the highest Power Added Efficiency (PAE) of 42% and greatest power area density of 532 mW/mm2 in 0.263 mm2 chip area to date.
Integrated visual sensor with 2D/3D imaging and in‐situ proximity sensing for mobile devices
Authors: Choi J. , Choi O.
Published: June 2016

A low‐power visual sensor for low‐light 2D imaging, proximity sensing, and 3D depth imaging is presented; it is applicable to smart sensing applications such as user recognition under dark conditions, gesture sensing, and extended user interface/user experience (UI/UX) in mobile devices. With integrated background suppression circuits, the sensor provides in‐situ proximity sensing that generates a background‐cancelled proximity map while capturing 2D images. In addition, 3D depth images are provided based on stereo matching with two 2D images from the visual sensor and the existing camera module. The prototype sensor was fabricated with a 0.11 μm 1P4M CMOS image sensor (CIS) process. The power consumption is 1.98 mW (at 15 fps) from the sensor and 9.38 mW (at 16 ms on‐time) from the infrared LED.
Parallel capacitive temperature micro‐sensor for passive wireless sensing applications
Authors: Ren Qing‐Ying , Wang Li‐Feng , Huang Qing‐An
Published: June 2016

The parallel capacitive temperature micro‐sensor is designed and fabricated based on the metal multi‐user MEMS processes. The interdigitated capacitors parallelly connected with the plane capacitor are used as the temperature sensing structures. Thermal expansion of the top layer cause the out‐of‐plane deformation, and introduce horizontal and vertical displacements of the structure, which leads to the capacitance variation. Top metal layer is the cascaded bent beam with interdigitated end, which is used as the interdigitated capacitors. Polysilicon layer paired with metal layer to form the plane capacitor. Experimental results show that the sensor provides an average sensitivity of 32.45 fF/°C in the 0–100°C range. It is also demonstrated that the temperature sensor can be integrated with an inductor to form an LC passive wireless sensor, which provides a sensitivity of 46.61 kHz/°C in the whole temperature range.
Fuzzy‐entropy threshold based on a complex wavelet denoising technique to diagnose Alzheimer disease
Authors: Lazar Prinza , Jayapathy Rajeesh , Torrents‐Barrena Jordina , Mol Beena , Mohanalin  , Puig Domenec
Published: June 2016

The presence of irregularities in electroencephalographic (EEG) signals entails complexities during the Alzheimer's disease (AD) diagnosis. In addition, the uncertainty presented on EEG raises major issues in the improvement of the classification rate. The multi‐resolution analysis through an optimum threshold will likely achieve better results in distinguishing AD and normal EEG signals. Hence, a fuzzy‐entropy concept defined in a complex multi‐resolution wavelet has been proposed to obtain the most appropriate threshold. First, the complex coefficients are fuzzified using a Gaussian membership function. Afterwards, the ability of the proposed fuzzy‐entropy threshold has been compared with traditional thresholds in complex wavelet domain. Experimental results show that the authors’ methodology produces a higher signal‐to‐noise ratio and a lower root‐mean‐square error than traditional approaches. Moreover, a neural network scheme is performed along several features to classify AD from normal EEG signals obtaining a specificity of 87.5%.
Effects of non‐uniform quantisation on the interference mitigation using multi‐cell multiple‐input and multiple‐output‐coordinated beamforming
Authors: Chang Wenson , Chang Chih‐Hao
Published: June 2016

In recent years, coordinated beamforming (CBF) has attracted considerable attention because of its effectiveness in intercell interference (ICI) mitigation. To facilitate the operations of CBF for the frequency‐division duplex mode, efficient channel state information (CSI) exchanges through backhaul links are necessary. In previous studies, uniform quantisation of CSI has been generally assumed in feedback schemes. Statistically, however, uniform quantisation may not be optimal from the viewpoint of the ICI in CBF, which is mainly caused by the quantisation error (QE). This study proposes a low‐complexity cumulative distribution function (CDF)‐based non‐uniform quantisation method with a limited number of feedback bits for applying more quantisation levels to represent feedback CSI, which occurs with higher probability. This is because a more accurate representation of frequent CSI can lead to a lower QE for reducing the ICI level in most cases. To prove the effectiveness of the proposed CDF‐based quantisation scheme, the ICI in the considered two‐cell CBF scenario was analysed using several feedback bits. The simulation results proved the higher transmission rate, particularly in cases with fewer feedback bits.
Measurements and modelling for D2D indoor wideband MIMO radio channels at 5 GHz
Authors: Zhao Xiongwen , Li Shu , Liang Xiaolin , Wang Qi , Hentilä Lassi , Meinilä Juha
Published: June 2016

Based on the indoor wideband multiple‐input multiple‐output (MIMO) device‐to‐device (D2D) measurements at 5 GHz with 100 MHz bandwidth carried out in University of Oulu, Finland, this study investigates the characteristics of indoor D2D radio channels with the same antenna height when both of the transceivers are moving or one end is fixed. The received power for the D2D channel is investigated by using double‐ and multiple‐Rayleigh distributions. It turned out that the received powers follow joint Rayleigh and double‐Rayleigh distribution as well as approximately Rayleigh distribution in non‐line‐of‐sight and line‐of‐sight scenarios, respectively. The angular distributions and their correlation of the angle‐of‐arrival and angle‐of‐departure in the azimuth and elevation planes are investigated in order to build three‐dimension model of Doppler power spectra and compare with the measurements. The channel parameters are derived from the measurements and compared with WINNER A1 scenario to find the differences between the D2D and conventional fixed‐to‐mobile (CF2M) channels. From the results, one can find the differences between the D2D and CF2M radio channels and better understand the physics for the D2D channel. Meanwhile, the channel parameters derived herein are important in the link and system level simulations for indoor D2D radio systems.
Public safety users’ priority‐based energy and time‐efficient device discovery scheme with contention resolution for ProSe in third generation partnership project long‐term evolution‐advanced systems
Authors: Kaleem Zeeshan , Li Yunpeng , Chang KyungHi
Published: June 2016

A device‐to‐device (D2D) discovery scheme is key enabler for proximity‐based services in third generation partnership project long‐term evolution‐advanced systems for public safety (PS) and general LTE scenarios. The deployment of D2D networks results in severe co‐channel interference between conventional cellular users and D2D users, and faces proximity interference management challenges because of the co‐existence of multiple D2D users. We propose a time and energy‐efficient contention‐resolving device discovery resource allocation (TEECR‐DDRA) scheme that has the capability to enhance the success ratio for discovery of D2D users by reducing collisions among users. Moreover, the proposed TEECR‐DDRA scheme has the ability to prioritise PS users to meet their QoS and latency requirements. Furthermore, multi‐channel slotted ALOHA with energy sensing can be used to increase the probability of successful discovery of non‐PS users. This ability helps to reduce the discovery time of PS users under disaster scenarios, and also reduces the energy consumption of non‐PS users by minimising the number of beacon retransmissions. System‐level simulations show that the proposed TEECR‐DDRA scheme performs remarkably well under D2D network. Compared with the conventional random access scheme, the proposed scheme almost doubles the discovery range and significantly improves the success ratio for discovery of D2D users.
Local altruistic coalition formation game for spectrum sharing and interference management in hyper‐dense cloud‐RANs
Authors: Sun Youming , Wang Jinlong , Sun Fenggang , Zhang Zongsheng
Published: June 2016

In this study, the authors investigate the spectrum sharing and interference management in hyper‐dense cloud radio access networks (C‐RANs). The authors formulate this problem as a local altruistic coalition formation game (LACF) with externalities. Different from previous studies considering maximising individual small cell's throughput, the authors’ purpose is to maximise the social welfare, i.e. the sum satisfaction of remote radio heads (RRHs) with diverse traffic types. The authors design a local altruistic utility function for RRH, i.e. each RRH cares about not only his own interest but also his neighbours’. They make autonomous decisions, finally shaping the entire RRHs into multiple disjoint coalitions. In addition, joint transmission coordinated multi‐point technology is considered within coalition to mitigate interference. Then, the authors propose a distributed coalitional formation algorithm based on modified recursive core to obtain the final stable coalition partition. Furthermore, the system stability, convergence and complexity of the proposed algorithm are analysed. Numerical results show that the proposed algorithm outperforms the classical and non‐cooperation schemes in the perspective of both social welfare and individual fairness. To be specific, the average rate per RRH of the authors’ proposed scheme is superior to the classical and non‐cooperation cases by 20 and 25% in hyper‐dense scenario, respectively.
Performance analysis of multirelay RF energy harvesting cooperative networks with hardware impairments
Authors: Do Nhu Tri , da Costa Daniel Benevides , An Beongku
Published: June 2016

In this study, the authors analyse the outage performance of multirelay decode‐and‐forward cooperative networks subject to two joint practical issues of wireless communications, namely, energy constraints and transceiver hardware impairment (HI). To deal with energy constraints at relay nodes, radio‐frequency (RF) energy harvesting (EH) technique is adopted. Considering the joint impacts of RF EH technique and HI, two relay selection schemes, namely, harvested energy‐based relay selection (HEbS) scheme and channel quality‐base relay selection (CQbS) scheme are proposed. Tight closed‐form approximate expressions for the outage probability of each scheme are derived and corroborated through Monte Carlo simulations. Some representative performance comparisons are carried out and show that the diversity order achieved by the HEbS scheme is 1 and is independent of the number of relays, K, whereas that achieved by the CQbS scheme is K, which is full diversity.
Analysis and design of diverse electromagnet type actuators for moulded case circuit breaker
Authors: Park Hyeon‐Jeong , Jung Hyun‐Kyo , Ro Jong‐Suk
Published: June 2016

Recently, remote‐controllable actuators for circuit breaker (CB) have attracted attention for the smart grid electric power system. In this study, diverse kinds of remote‐controllable electromagnetic actuator for CB are precisely investigated to give a guideline for the selection of the effective actuator according to numerous voltage level of CB. In case of a low‐voltage level of CB, the separated permanent‐magnet actuator (SPMA) is verified in this research as the most suitable actuator through the comparison with diverse electromagnetic actuators. The SPMA is designed for the 225AF moulded case CB by using the proposed optimisation method, which the authors termed as a multi‐step optimisation strategy.
Image decomposition‐based blind image deconvolution model by employing sparse representation
Authors: Chen Huasong , Wang Qinghua , Wang Chunyong , Li Zhenhua
Published: June 2016

Conventional blind restoration methods often take consideration of images as a whole. However, an image may have different types of components, and each component has different morphology and properties. Using one model only can capture one part of images effectively, but fail to represent the others; the processing results by using conventional methods would lose some important features. In this study, a new sparse prior‐based blind image deconvolution model has been proposed by employing commonly considered image decomposition strategy which separates an image into cartoon (piecewise‐smooth part) and texture (the oscillating pattern part). On the basis of the different properties of cartoon and texture, it, respectively, regularises the texture with the sparsity of discrete cosine transform domain, and the cartoon with a combined term including framelet‐domain‐based sparse prior and a quadratic regularisation. Then a double alternating split Bregman iteration is proposed to address the proposed minimisation problem. It has been demonstrated that images can be recovered with high quality and more abundant features by authors’ proposed algorithm than other popular deblurring methods.
Saliency and depth‐based unsupervised object segmentation
Authors: He Hu
Published: June 2016

This study demonstrates an unsupervised segmentation algorithm for video sequences acquired from a moving camera with results comparable to semi‐supervised (interactive) methods. The authors employ depth cues from multiple views stereo to enhance the hypothesis of a potential object based on saliency scores. The resulting object and background hypotheses are then used to model foreground and background distributions for a graph‐cut‐based segmentation. The authors’ graph‐cut framework simultaneously optimises over depth and colour information to produce automatically segmented objects in challenging unstructured scenes. They refer to this saliency and depth‐based segmentation method as ‘SDCut’. The proposed method is fully automatic without requiring any intervention. Experiments demonstrate that their method can achieve accurate segmentation results which are comparable with several well‐known human interactive semi‐supervised segmentation methods.
Vanishing point detection using random forest and patch‐wise weighted soft voting
Authors: Fan Xue , Riaz Irfan , Rehman Yawar , Shin Hyunchul
Published: June 2016

Variations in road types and its ambient environment make the single image based vanishing point detection a challenging task. In this study, a novel and efficient vanishing point detection method is proposed by using random forest and patch‐wise weighted soft voting. To eliminate the noise votes introduced by background region and to reduce the workload of voting stage, random forest based valid patch extraction technique is developed, which distinguishes the informative road patches from the background noise. To prepare training data for the random forest, a training patch generation method is proposed, and a variety of road relevant features are introduced for training patch representation. Since the traditional pixel‐wise voting scheme is time consuming and imprecise, a patch‐wise weighted soft voting scheme is proposed to generate a more precise voting map and to further reduce the computational complexity of voting stage. The experimental results on the benchmark dataset show that the proposed method reveals a step forward in performance. The authors’ approach is about 6 times faster in detection speed and 5.6% better in detection accuracy than the generalised Laplacian of Gaussian filter based method, which is a well‐known state‐of‐the‐art approach.
Scene‐adaptive single image dehazing via opening dark channel model
Authors: Liu Xin , Zhang He , Tang Yuan Yan , Du Ji‐Xiang
Published: June 2016

Many traditional dark channel prior based haze removal schemes often suffer from the colour distortion and generate halo artefacts in the remote scenes. To tackle these issues, the authors present an efficient scene‐adaptive single image dehazing approach via opening dark channel model (ODCM). First, the authors detect the image depth information and separate it into close view and distant view. Then, an ODCM is proposed to optimise the whole atmospheric veil, in which the values of close view are regularised by a minimum channel image while the distant parts are estimated by an appropriate lower constant. Accordingly, the transmission map can be further optimised by guide filter and smoothed by domain transform filter. Finally, the haze degraded image can be well restored by the atmosphere scattering model. The extensive experiments have shown that the proposed image dehazing approach has significantly increased the perceptual visibility of the scene and achieved a better colour fidelity visually.
Multilevel framework to handle object occlusions for real‐time tracking
Authors: Cai Yingfeng , Wang Hai , Chen Xiaobo , Chen Long
Published: June 2016

This study proposes an efficient method to handle the object occlusions seen in monocular traffic image sequences. The motivation of this study is different methods perform differently in occlusion segmentation and the authors’ idea is to use a situation‐driven approach to aggregate different methods in order to get a good performance. This study classifies occlusion into four categories according to the foreground situation and a multilevel occlusion handling framework is utilised. First, the image segmentation algorithm based on convex hull analysis is utilised for intra‐frame level occlusion segmentation. The segmentation algorithm is established by the compactness ratio and interior distance ratio of the foreground. Second, an online sample‐based classification algorithm is utilised for tracking level occlusion segmentation. Training samples are extracted from the historical frames before occlusion and testing samples are extracted from the current frame by an adaptive searching strategy. The segmentation of occlusion is transferred into the online classification of testing samples. Such algorithm is established by the similarity and coherence of target's property between continuous frames. Experiments on video sequences illustrate the good performance of the proposed method under different conditions with low computational cost.
Wideband tunable common‐mode suppression filter based on varactor‐loaded slot‐ring resonator for high‐speed differential signals
Authors: Chen Jian‐Xin , Zhou Wen‐Jun , Yang Wen‐Wen , Zhang Xue‐Feng , Bao Zhi‐Hua
Published: June 2016

In this study, a varactor‐loaded slot‐ring resonator (SRR) is investigated and applied in the design of tunable common‐mode (CM) suppression filter for high‐speed differential signals. Two tunable capacitors (realised by two kinds of varactors) with different values are symmetrically added to the SRR. Under the stepped‐width structure of the SRR, the frequency‐tuning principle is studied. It can be found that the fundamental resonant frequency ffund can be shifted up and down by properly controlling the respective values of the two loaded capacitors, i.e. bi‐directional tuning. As a result, the tuning range of ffund can be greatly enlarged, approximately double that of the traditional tunable resonator. Meanwhile, the employed stepped‐width SRR is useful not only for miniaturising the circuit size, but also further increasing the tuning range of ffund. By etching the proposed SRRs on the ground plane underneath the differential microstrip line, two wideband tunable CM‐suppression filters using one and three SRR units, respectively, are designed, and their simulated and measured results showing good agreement are presented. It is found that the CM stopband frequency can be tuned from 0.78 to 1.52 GHz, while the differential signals still keep good signal integrity in eye‐pattern observation.
Revisiting and improvement of thru‐reflect‐line calibration for accurate measurement of substrate integrated waveguide components
Authors: Chen Haidong , Che Wenquan , Chao Yue , Feng Wenjie , Wu Ke
Published: June 2016

Thru‐reflect‐line (TRL) calibration method were reviewed and the related kits based on substrate integrated waveguide (SIW) were re‐examined, designed, and compared for measurements of SIW circuits. Different types of calibration kits were discussed and the design guidelines were provided. Filters working at 5 and 10 GHz were designed for the verification purpose of these calibration kits. Meanwhile, the TRL calibration method based on uniform SIW‐coaxial transitions was proposed, which shows improved measurement accuracy.
Stacked microstrip linear array with highly suppressed side‐lobe levels and wide bandwidth
Authors: Dzagbletey Philip Ayiku , Kim Kwang‐Seon , Byun Woo‐Jin , Jung Young‐Bae
Published: June 2016

A 1 × 7 microstrip linear antenna array has been designed with parasitic patches in the 28.0 GHz sub‐millimetre wave frequency band for fifth‐generation mobile communication. A relatively large bandwidth and gain region has been investigated between a separation distance of 0.07λg in a two layer electromagnetically coupled rectangular patch antenna The one dimensional linear array was fabricated and measured to have an impedance bandwidth of <−14.7 dB in a 2.1 GHz range; which is comparable with commercial designs but with reduced design complexity. Side‐lobe levels were realised at <−18.31 dB with antenna gains of up to 14.71 dBi.
Analysis of a loop type ground radiation antenna based on equivalent circuit model
Authors: Zahid Zeeshan , Kim Hyeongdong
Published: June 2016

A loop type ground radiation antenna has been analysed using an equivalent circuit model in this study. The proposed circuit model has been selected in such a way that the design parameters of the ground radiation antenna can be mapped onto the circuit. To demonstrate the accuracy of the model, a specific ground radiation antenna is designed in a full wave electromagnetic simulator and the equivalent circuit model of the antenna is optimised in a circuit simulator. The simulation results of the circuit simulator and full wave simulator are compared. Expressions of return loss and input impedance of the equivalent model have also been obtained. The proposed circuit model can be used to develop insight and describe the behaviour of the network parameters of the antenna.
Fault tolerant‐topology and controls for a three‐level hybrid neutral point clamped‐flying capacitor converter
Authors: Ben Abdelghani Hafedh , Bennani Ben Abdelghani Afef , Richardeau Frédéric , Blaquière Jean‐Marc , Mosser Franck , Slama‐Belkhodja Ilhem
Published: June 2016

This study details a three‐level hybrid fault‐tolerant converter. The definition of an original decoupling solution between the fourth flying capacitor (FC) leg and the three neutral point (NP) clamped‐based phases overcomes topology hybridisation issues. Under normal conditions, a control strategy of the FC‐based leg leads to a converter NP voltage balance, and decreases the DC side capacitors’ volume and cost. Under fault conditions, the presented fault isolation and converter reconfiguration strategies generate a post‐fault converter, which is able to operate safely with the added FC‐based leg. The proposed topology is an interesting trade‐off between converter fault‐tolerant capability and its complexity and offers the ability to be simply reconfigured and controlled in the case of switch fault occurrence. Two operation modes under fault conditions are presented and their performances are shown and discussed through simulation results and first experimental tests.
Short‐term wind speed forecasting using wavelet transformation and AdaBoosting neural networks in Yunnan wind farm
Authors: Shao Haijian , Wei Haikun , Deng Xing , Xing Song
Published: June 2016

Wind speed presents a potential seasonal pattern revealed by the self‐similarity in wavelet periodogram with various scales. The corresponding seasonal pattern will promote the improvement of the short‐term wind speed forecasting accuracy. In this study, a novel method for short‐term wind speed forecasting using wavelet transformation (WT) and AdaBoost technique is proposed to analyse the wind speeds distribution features and promote the model configuration. Power spectrum and seasonal pattern analysis using the WT are presented to investigate the wind speeds feature distribution based on the scalogram percentage of energy distribution in different seasons. This procedure contributes to perfecting the investigation of wind speed seasonal pattern characteristics over time and promotes the sample division by computing the statistics measurement based on the estimated frequencies interval. The model order estimation based on the information criteria is processed to reflect the systems dynamical sustainability between the current outputs and historical data. Finally, the experiments based on the real data from Yunnan wind farm are given to verify the effectiveness of the proposed approach.
M, the conservative power quantity based on the flow of energy
Authors: Castro‐Núñez Milton , Londoño‐Monsalve Deysy , Castro‐Puche Róbinson
Published: June 2016

The reactive power in non‐sinusoidal circuits is determined here from an energy analysis instead of using the non‐sinusoidal apparent power S. In the first of the two energy analyses, circuits previously examined by the currents’ physical components power theory are re‐examined using the principle of conservation of energy, the balance principle of the reactive power and the concept of reactive power compensation. This energy analysis yields a reactive power value substantiated by the aforementioned principles and power theory but it also suggests a value of S that differs from its traditional definition. The energy analysis performed with the circuit analysis technique based on geometric algebra, its GN domain power theory and M, a conservative power quantity based on the flow of energy, confirms the reactive power value attained in the former analysis. More importantly, M clarifies three intriguing issues about S: its value, its physical significance and whether this quantity can lead to erroneous conclusions. These, and previous results, demonstrate that the reactive power should be assessed on the energy flow but a multidimensional mathematical framework is needed to better understand energy flow in non‐sinusoidal circuits.
Progress toward steady-state tokamak operation exploiting the high bootstrap current fraction regime
Authors: Ren Q. L. , Garofalo A. M. , Gong X. Z. , Holcomb C. T. , Lao L. L. , McKee G. R. , Meneghini O. , Staebler G. M. , Grierson B. A. , Qian J. P. , Solomon W. M. , Turnbull A. D. , Holland C. , Guo W. F. , Ding S. Y. , Pan C. K. , Xu G. S. , Wan B. N.
Published: June 2016

Recent DIII-D experiments have increased the normalized fusion performance of the high bootstrap current fraction tokamak regime toward reactor-relevant steady state operation. The experiments, conducted by a joint team of researchers from the DIII-D and EAST tokamaks, developed a fully noninductive scenario that could be extended on EAST to a demonstration of long pulse steady-state tokamak operation. Improved understanding of scenario stability has led to the achievement of very high values of βp and βN, despite strong internal transport barriers. Good confinement has been achieved with reduced toroidal rotation. These high βp plasmas challenge the energy transport understanding, especially in the electron energy channel. A new turbulent transport model, named TGLF-SAT1, has been developed which improves the transport prediction. Experiments extending results to long pulse on EAST, based on the physics basis developed at DIII-D, have been conducted. More investigations will be carried out on EAST with more additional auxiliary power to come online in the near term.
Engineered band structure for an enhanced performance on quantum dot-sensitized solar cells
Authors: Jin Bin Bin , Wang Ye Feng , Wei Dong , Cui Bin , Chen Yu , Zeng Jing Hui
Published: June 2016

A photon-to-current efficiency of 2.93% is received for the Mn-doped CdS (MCdS)-quantum dot sensitized solar cells (QDSSCs) using Mn:ZnO (MZnO) nanowire as photoanode. Hydrothermal synthesized MZnO are spin-coated on fluorine doped tin oxide (FTO) glass with P25 paste to serve as photoanode after calcinations. MCdS was deposited on the MZnO film by the successive ionic layer adsorption and reaction method. The long lived excitation energy state of Mn2+ is located inside the conduction band in the wide bandgap ZnO and under the conduction band of CdS, which increases the energetic overlap of donor and acceptor states, reducing the “loss-in-potential,” inhibiting charge recombination, and accelerating electron injection. The engineered band structure is well reflected by the electrochemical band detected using cyclic voltammetry. Cell performances are evidenced by current density-voltage (J-V) traces, diffuse reflectance spectra, transient PL spectroscopy, and incident photon to current conversion efficiency characterizations. Further coating of CdSe on MZnO/MCdS electrode expands the light absorption band of the sensitizer, an efficiency of 4.94% is received for QDSSCs.
Critical role of morphology on the dielectric constant of semicrystalline polyolefins
Authors: Misra Mayank , Mannodi-Kanakkithodi Arun , Chung T. C. , Ramprasad Rampi , Kumar Sanat K.
Published: June 2016

A particularly attractive method to predict the dielectric properties of materials is density functional theory (DFT). While this method is very popular, its large computational requirements allow practical treatments of unit cells with just a small number of atoms in an ordered array, i.e., in a crystalline morphology. By comparing DFT and Molecular Dynamics (MD) simulations on the same ordered arrays of functional polyolefins, we confirm that both methodologies yield identical estimates for the dipole moments and hence the ionic component of the dielectric storage modulus. Additionally, MD simulations of more realistic semi-crystalline morphologies yield estimates for this polar contribution that are in good agreement with the limited experiments in this field. However, these predictions are up to 10 times larger than those for pure crystalline simulations. Here, we show that the constraints provided by the surrounding chains significantly impede dipolar relaxations in the crystalline regions, whereas amorphous chains must sample all configurations to attain their fully isotropic spatial distributions. These results, which suggest that the amorphous phase is the dominant player in the context, argue strongly that the proper polymer morphology needs to be modeled to ensure accurate estimates of the ionic component of the dielectric constant.
Eigenvalue asymptotics for Dirac–Bessel operators
Authors: Hryniv Rostyslav O. , Mykytyuk Yaroslav V.
Published: June 2016

In this paper, we establish the eigenvalue asymptotics for non-self-adjoint Dirac–Bessel operators on (0, 1) with arbitrary real angular momenta and square integrable potentials, which gives the first step for solution of the related inverse problem. The approach is based on a careful examination of the corresponding characteristic functions and their zero distribution.
Avoiding fractional electrons in subsystem DFT based ab-initio molecular dynamics yields accurate models for liquid water and solvated OH radical
Authors: Genova Alessandro , Ceresoli Davide , Pavanello Michele
Published: June 2016

In this work we achieve three milestones: (1) we present a subsystem DFT method capable of running ab-initio molecular dynamics simulations accurately and efficiently. (2) In order to rid the simulations of inter-molecular self-interaction error, we exploit the ability of semilocal frozen density embedding formulation of subsystem DFT to represent the total electron density as a sum of localized subsystem electron densities that are constrained to integrate to a preset, constant number of electrons; the success of the method relies on the fact that employed semilocal nonadditive kinetic energy functionals effectively cancel out errors in semilocal exchange–correlation potentials that are linked to static correlation effects and self-interaction. (3) We demonstrate this concept by simulating liquid water and solvated OH• radical. While the bulk of our simulations have been performed on a periodic box containing 64 independent water molecules for 52 ps, we also simulated a box containing 256 water molecules for 22 ps. The results show that, provided one employs an accurate nonadditive kinetic energy functional, the dynamics of liquid water and OH• radical are in semiquantitative agreement with experimental results or higher-level electronic structure calculations. Our assessments are based upon comparisons of radial and angular distribution functions as well as the diffusion coefficient of the liquid.
Kinetic modeling of E-to-H mode transition in inductively coupled hydrogen plasmas
Authors: Nishida K. , Mattei S. , Mochizuki S. , Lettry J. , Hatayama A.
Published: June 2016

Radio Frequency (RF) Inductively Coupled Plasmas (ICPs) are widely known for their two discharge modes, i.e., H-mode and E-mode, where the dynamics of the plasmas are completely different from each other. We have performed a kinetic simulation of a hydrogen plasma discharge in order to clarify the discharge mechanism and the E-to-H transition of the RF ICPs. The numerical simulation results, such as the time variations of spatial distribution of electron density and the power dissipated in the plasma, show the characteristic changes of the plasma dynamics due to E-to-H mode transition. Especially, the drastic change during the mode transition has been observed in the time evolution of the electron energy distribution function (EEDF). The EEDF deviates from a Maxwellian distribution before/after the transition and the deviation is more significant in the E-mode phase. These results indicate the importance of kinetic modeling for the physical understanding of E-to-H transition.
Low-energy phase change memory with graphene confined layer
Authors: Zhu Chengqiu , Ma Jun , Ge Xiaoming , Rao Feng , Ding Keyuan , Lv Shilong , Wu Liangcai , Song Zhitang
Published: June 2016

How to reduce the Reset operation energy is the key scientific and technological problem in the field of phase change memory (PCM). Here, we show in the Ge2Sb2Te5 based PCM cell, inserting an additional graphene monolayer in the Ge2Sb2Te5 layer can remarkably decrease both the Reset current and energy. Because of the small out-of-plane electrical and thermal conductivities of such monolayer graphene, the Set resistance and the heat dissipation towards top TiN electrode of the modified PCM cell are significantly increased and decreased, respectively. The mushroom-typed larger active phase transition volume thus can be confined inside the underlying thinner GST layer, resulting in the lower power consumption.
Tuning the tetrahedrality of the hydrogen-bonded network of water: Comparison of the effects of pressure and added salts
Authors: Prasad Saurav , Chakravarty Charusita
Published: June 2016

Experiments and simulations demonstrate some intriguing equivalences in the effect of pressure and electrolytes on the hydrogen-bonded network of water. Here, we examine the extent and nature of equivalence effects between pressure and salt concentration using relationships between structure, entropy, and transport properties based on two key ideas: first, the approximation of the excess entropy of the fluid by the contribution due to the atom-atom pair correlation functions and second, Rosenfeld-type excess entropy scaling relations for transport properties. We perform molecular dynamics simulations of LiCl–H2O and bulk SPC/E water spanning the concentration range 0.025–0.300 molefraction of LiCl at 1 atm and pressure range from 0 to 7 GPa, respectively. The temperature range considered was from 225 to 350 K for both the systems. To establish that the time-temperature-transformation behaviour of electrolyte solutions and water is equivalent, we use the additional observation based on our simulations that the pair entropy behaves as a near-linear function of pressure in bulk water and of composition in LiCl–H2O. This allows for the alignment of pair entropy isotherms and allows for a simple mapping of pressure onto composition. Rosenfeld-scaling implies that pair entropy is semiquantitatively related to the transport properties. At a given temperature, equivalent state points in bulk H2O and LiCl–H2O (at 1 atm) are defined as those for which the pair entropy, diffusivity, and viscosity are nearly identical. The microscopic basis for this equivalence lies in the ability of both pressure and ions to convert the liquid phase into a pair-dominated fluid, as demonstrated by the O–O–O angular distribution within the first coordination shell of a water molecule. There are, however, sharp differences in local order and mechanisms for the breakdown of tetrahedral order by pressure and electrolytes. Increasing pressure increases orientational disorder within the first neighbour shell while addition of ions shifts local orientational order from tetrahedral to close-packed as water molecules get incorporated in ionic hydration shells. The variations in local order within the first hydration shell may underlie ion-specific effects, such as the Hofmeister series.
Investigations of the contact bounce behaviors and relative dynamic welding phenomena for electromechanical relay
Authors: Ren Wanbin , He Yuan , Jin Jianbing , Man Sida
Published: June 2016

Dynamic welding, being the principal mechanism of sticking failure, correlates closely with the contact bounce of electromechanical relay. The typical waveforms of dynamic contact force and contact voltage at making and breaking process are obtained with the use of a new designed test rig. The variations in bounce time, bounce numbers, last bounce duration, and relevant welding force are investigated in the electrical endurance test. It is determined that the welding strength and the welding probability are increased with the reduced stationary force. The degradation physical mechanism is present to better understand the relationship between dynamic welding and operation characteristics of electromechanical relay.
Generalized flexibility-rigidity index
Authors: Nguyen Duc Duy , Xia Kelin , Wei Guo-Wei
Published: June 2016

Flexibility-rigidity index (FRI) has been developed as a robust, accurate, and efficient method for macromolecular thermal fluctuation analysis and B-factor prediction. The performance of FRI depends on its formulations of rigidity index and flexibility index. In this work, we introduce alternative rigidity and flexibility formulations. The structure of the classic Gaussian surface is utilized to construct a new type of rigidity index, which leads to a new class of rigidity densities with the classic Gaussian surface as a special case. Additionally, we introduce a new type of flexibility index based on the domain indicator property of normalized rigidity density. These generalized FRI (gFRI) methods have been extensively validated by the B-factor predictions of 364 proteins. Significantly outperforming the classic Gaussian network model, gFRI is a new generation of methodologies for accurate, robust, and efficient analysis of protein flexibility and fluctuation. Finally, gFRI based molecular surface generation and flexibility visualization are demonstrated.
Dielectrophoresis of a surfactant-laden viscous drop
Authors: Mandal Shubhadeep , Bandopadhyay Aditya , Chakraborty Suman
Published: June 2016

The dielectrophoresis of a surfactant-laden viscous drop in the presence of non-uniform DC electric field is investigated analytically and numerically. Considering the presence of bulk-insoluble surfactants at the drop interface, we first perform asymptotic solution for both low and high surface Péclet numbers, where the surface Péclet number signifies the strength of surface convection of surfactants as compared to the diffusion at the drop interface. Neglecting fluid inertia and interfacial charge convection effects, we obtain explicit expression for dielectrophoretic drop velocity for low and high Péclet numbers by assuming small deviation of drop shape from sphericity and small deviation of surfactant concentration from the equilibrium uniform distribution. We then depict a numerical solution, assuming spherical drop, for arbitrary values of Péclet number. Our analyses demonstrate that the asymptotic solution shows excellent agreement with the numerical solution in the limiting conditions of low and high Péclet numbers. The present analysis shows that the flow-induced redistribution of the surfactants at the drop interface generates Marangoni stress, owing to the influence of the surfactant distribution on the local interfacial tension, at the drop interface and significantly alters the drop velocity at steady state. For a perfectly conducting/dielectric drop suspended in perfectly dielectric medium, Marangoni stress always retards the dielectrophoretic velocity of the drop as compared with a surfactant-free drop. For a leaky dielectric drop suspended in another leaky dielectric medium, in the low Péclet number limit, depending on the electrical conductivity and permittivity of both the liquids, the Marangoni stress may aid or retard the dielectrophoretic velocity of the drop. The Marangoni stress also has the ability to move the drop in the opposite direction as compared with a surfactant-free drop. This non-intuitive reverse motion of the drop is observed for drops with less viscosity and for particular values of electrical conductivity and permittivity ratios. In the high Péclet number limit, the surfactants completely immobilize the fluid velocity at the drop interface. As a result, the drop behaves like a solid sphere. Further, it is also demonstrated that the flow-induced non-uniform distribution of surfactants always increases the deformation of the drop as compared with a uniformly coated drop which is due to the decreased (or increased) interfacial tension near the poles of the drop for prolate (or oblate) type deformation.
Effect of inter-species selective interactions on the thermodynamics and nucleation free-energy barriers of a tessellating polyhedral compound
Authors: Escobedo Fernando A.
Published: June 2016

The phase behavior and the homogeneous nucleation of an equimolar mixture of octahedra and cuboctahedra are studied using thermodynamic integration, Gibbs-Duhem integration, and umbrella sampling simulations. The components of this mixture are modeled as polybead objects of equal edge lengths so that they can assemble into a space-filling compound with the CsCl crystal structure. Taking as reference the hard-core system where the compound crystal does not spontaneously nucleate, we quantified the effect of inter-species selective interactions on facilitating the disorder-to-order transition. Facet selective and facet non-selective inter-species attractions were considered, and while the former was expectedly more favorable toward the target tessellating structure, the latter was found to be similarly effective in nucleating the crystal compound. Ranges for the strength of attractions and degree of supersaturation were identified where the nucleation free-energy barrier was small enough to foretell a fast process but large enough to prevent spinodal fluctuations that can trap the system in dense metastable states lacking long-range order. At those favorable conditions, the tendency toward the local orientational order favored by packing entropy is amplified and found to play a key role seeding nuclei with the CsCl structure.