bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine control over the morphology and photocatalytic activity of 3D ZnO hierarchical nanostructures: capping vs. etching
Authors: Mujtaba Jawayria , Sun Hongyu , Fang Fang , Ahmad Mashkoor , Zhu Jing
Published: June 2015

ZnO 3D hierarchical structures with different morphologies can be selectively synthesized at room temperature by using potassium hydroxide and citric acid as an etchant and capping agent, respectively.
A facile approach for achieving an effective dual sorption ability of Si/SH/S grafted sodium montmorillonite
Authors: Chen Hsuan-Hsuan , Thirumavalavan Munusamy , Lin Fang-Yu , Lee Jiunn-Fwu
Published: June 2015

In this study, sodium montmorillonite was functionalized with SH, S and Si functional groups using four different soil modifiers for an effective uptake of both organic and inorganic pollutants.
Synthesis of 5,10,15,20-tetrakis[4-(naphthalen-2-yloxycarbonyl)phenyl]porphyrin (TNBP) and its complexes with zinc and cobalt and an investigation of the photocatalytic activity of nanoFe3O4@ZrO2–TNBP
Authors: Ghafuri Hossein , Movahedinia Zahra , Rahimi Rahmatollah , Esmaili Zand Hamid Reza
Published: June 2015

5,10,15,20-Tetrakis[4-(naphthalen-2-yloxycarbonyl)phenyl]porphyrin and its porphyrin complexes with zinc and cobalt and nanoFe3O4@ZrO2–TNBP photocatalysts were synthesized with high yields and the structure and morphology were fully characterized.
Unique synthesis of novel octahedral micro/nano-hierarchical LiFePO4 cages as an enhanced cathode material for lithium-ion batteries
Authors: Li Wenxiang , Zhang Huijuan , Mu Yanping , Liu Li , Wang Yu
Published: June 2015

Novel monodisperse LiFePO4 cages with an octahedral micro/nano-hierarchical structure have been synthesized for the first time through a simple and controllable solvothermal approach followed by high-temperature calcination.
Synthesis of planar dibenzo[de,op]bistetracene derivatives for organic field-effect transistor applications: substituent effect on crystal packing and charge transport property
Authors: Wu Tien-Lin , Kuo Chi-Hsien , Lin Bo-Chao , Tao Yu-Tai , Hsu Chao-Ping , Liu Rai-Shung
Published: June 2015

A series of dibenzo[de,op]bistetracene derivatives is synthesized and their single-crystal FET devices show a hole mobility from 0.045 cm2 V−1 s−1 up to 1.19 cm2 V−1 s−1, due to the effect of substituents on the crystal packing/electronic coupling.
Highly efficient acido-triggered reversible luminescent and nonlinear optical switch based on 5-π-delocalized-donor-1,3-di(2-pyridyl)benzenes
Authors: Nisic Filippo , Colombo Alessia , Dragonetti Claudia , Fontani Mattia , Marinotto Daniele , Righetto Stefania , Roberto Dominique , Williams J. A. Gareth
Published: June 2015

A highly efficient acido-triggered reversible luminescent and nonlinear optical switch based on 5-π-delocalized-donor-1,3-di(2-pyridyl)benzenes is presented.
The ICF, Relationship-Centred Care and Research Outcome Measurement: Carol Frattali's Impact on Aphasia Research
Authors: Worrall Linda , Wallace Sarah
Published: June 2015

Outcome measurement was a major focus of Carol Frattali's work. This article describes three aphasia research initiatives that have followed from her early publications. The first is the application of the World Health Organization (WHO) International Classification of Functioning, Disability and Health (ICF) to aphasia. The Living with Aphasia: A Framework for Outcome Measurement (A-FROM) is a reinterpretation of the ICF specifically as it applies to aphasia. The Assessment for Living with Aphasia (ALA) is an assessment that is derived from the A-FROM. The second initiative is the program of research that has described aphasia and aphasia rehabilitation from the patient perspective. Using qualitative methodologies, this research has highlighted the need for relationship-centred care in aphasia services. Finally, a current project is described that seeks to gain international consensus on a core outcome set for aphasia treatment research. This will help researchers combine data in effectiveness studies. To achieve the best outcomes for people with aphasia, there is a need to realize Carol Frattali's vision and ensure the continued use of unifying frameworks, relationship-centered practice, consumer-focused research, and consistent outcome measurement practices.
Support vector data description using privileged information
Authors: Zhang Wenbo
Published: June 2015

Support vector data description (SVDD) is a data description method which gives the target data set a hypersphere‐shaped description and can be used for one‐class classification or outlier detection. To further improve its performance, a novel SVDD called SVDD+ which introduces the privileged information to the traditional SVDD is proposed. This privileged information, which is ignored by the classical SVDD but often exists in human learning, will optimise the training phase by constructing a set of correcting functions. The performance of SVDD+ on data sets from the UCI machine learning repository and radar emitter recognition is demonstrated. The experimental results indicate the validity and advantage of this method.
Investigation of carbon dioxide adsorption effects on graphene nanoribbon conductance
Authors: Akbari E. , Buntat Z. , Enzevaee A.
Published: June 2015

A novel method is employed for the derivation of an analytical model for a carbon‐dioxide (CO2) gas sensor based on graphene nanoribbon (GNR) conductance variation. The capacitance gradient created between the channel and the gate of a field effect transistor device is employed as an important property in the interpretation. Gas concentration and its effect on capacitance are incorporated as a modelling platform. In another attempt to model the electrical conductance in GNRs, an intelligent artificial neural network scheme is used in the modelling stage. A satisfactory agreement is presented by comparison between the empirical data extracted from a study conducted by Yoon et al. and the proposed models.
One‐dimensional adiabatic circuits with inherent charge recycling
Authors: Khorami A. , Sharifkhani M.
Published: June 2015

A new switching method for the stabilisation of a one‐dimensional capacitor array tank for the stepwise charging of a load capacitor is presented. In this method, the tank capacitor configuration is rearranged in a circular manner once the charging process of a load capacitor finishes and before the charging process of a new load capacitor begins. Unlike previously reported methods, this method does not require backward switching for the stabilisation of tank capacitor voltages. Hence, the proposed method reduces the number of charging process steps by a factor of up to 2 compared with the conventional method. Moreover, since the tank recycles its charge inherently, the capacitive load can retain its charge after the charging process finishes without the problem of instability. Systematic MATLAB simulation, post‐layout simulation in 0.18 μm technology and a fabricated printed circuit board prove the benefits of the proposed method and the provided analytical derivations.
Computationally efficient colour image warping for real‐time video applications
Authors: Ryoo Jung Rae , Kim Bong Kyu , Doh Tae‐Yong
Published: June 2015

Each pixel in a full‐colour image has three colour values, and warping of the colour image requires three times the computational load of a greyscale image. A new colour image warping is proposed for enhancing computational efficiency in real‐time video applications. Considering that a colour filter array (CFA) is commonly utilised in an image sensor, the raw CFA image obtained from the image sensor is warped before colour reconstruction. The computational load is only one third of the conventional colour image warping.
30 GHz bandwidth 850 nm VCSEL with sub‐100 fJ/bit energy dissipation at 25–50 Gbit/s
Authors: Haglund E. , Westbergh P. , Gustavsson J.S. , Haglund E.P. , Larsson A. , Geen M. , Joel A.
Published: June 2015

A high‐speed and energy‐efficient oxide‐confined 850 nm vertical‐cavity surface‐emitting laser (VCSEL) for optical interconnects is presented. A record‐high modulation bandwidth of 30 GHz is reached for a 3.5 µm oxide aperture VCSEL, with 25 GHz bandwidth already at a bias current of 1.8 mA. The high bandwidth at low currents enables energy‐efficient transmission with a dissipated heat energy in the VCSEL of <100 fJ/bit at 25, 40 and 50 Gbit/s.
Quasi‐maximum feasible subsystem for geometric computer vision problems
Authors: Yu Chanki , Ju Da Young , Lee Sang Wook
Published: June 2015

A robust fitting algorithm for geometric computer vision problems under the L∞‐norm optimisation framework is presented. It is essentially based on the maximum feasible subsystem (MaxFS) but it overcomes the computational limitation of the MaxFS for large data by finding only a quasi‐maximum feasible subset. Experimental results demonstrate that the algorithm removes outliers more effectively than the other parameter estimation methods recently developed when the outlier‐to‐inlier ratio in a data set is high.
Easily fabricated 60 GHz WR15/MSL transition to measure apparent reflection coefficient of differentially fed patch antennas
Authors: Hamouda C. , Poussot B. , Villegas M. , Laheurte J.‐M.
Published: June 2015

A new procedure to measure the apparent reflection coefficient of differential patch antennas at 60 GHz is described. The measurement method makes use of two WR15/microstrip‐line (MSL) transitions which are simple to realise. The experimental results are compared with simulated results. This comparison emphasises the limited effect of transition losses on measurement accuracy.
Area‐efficient video transform for HEVC applications
Authors: Chen Yuan‐Ho , Liu Chieh‐Yang
Published: June 2015

A hardware design capable of supporting high‐efficiency video coding (HEVC) inverse transform (IDCT) is developed for a 32‐point transform unit using a single one‐dimensional (1D) transform core with two transposed memories to reduce area overhead. The proposed 1D core employs two calculation paths to obtain high throughput and is able to calculate first‐dimensional (1st‐D) and second‐dimensional (2nd‐D) transformations simultaneously along two parallel paths. The results from a practical implementation of the chip demonstrate that the proposed design presents the smallest circuit area among existing 2D transform cores.
Buried‐heterostructure mid‐infrared quantum cascade lasers fabricated by non‐selective regrowth and chemical polishing
Authors: Chang C.‐C. , Kirch J.D. , Buelow P. , Boyle C. , Kuech T.F. , Lindberg D. , Earles T. , Botez D. , Mawst L.J.
Published: June 2015

A novel fabrication method of buried‐heterostructure (BH) mid‐infrared quantum cascade lasers (QCLs) by using non‐selective regrowth of iron‐doped indium phosphide (InP) (Fe:InP), around deeply etched laser ridges, via metal‐organic chemical vapour deposition (MOCVD) and planarisation via chemical polishing is reported. Owing to better heat dissipation, the fabricated 4.75 μm emitting QCLs exhibit about three‐fold enhancement in maximum output power under continuous‐wave operation at room temperature (T = 20°C) compared with that from lasers without the regrown InP. The demonstrated fabrication method provides a more flexible route to realising BH QCLs by removing strict requirements on the etched‐ridge sidewall profile, as well as on the physical dimensions of the dielectric mask for the regrowth via MOCVD. The method can be further employed for making large‐emitting aperture, closely packed arrays of QCLs, with planarised geometry, for coherent‐power scaling.
Ultra‐compact lumped element cross‐over
Authors: Arigong Bayaner , Zhou Mi , Ren Han , Shao Jin , Ding Jun , Kim Hyoungsoo , Zhang Hualiang
Published: June 2015

A novel ultra‐compact wide‐band microwave cross‐over using lumped components is presented for the first time. The proposed cross‐over is composed by inductors and capacitors, and the explicit design equations are derived based on the even–odd mode method. The size of the proposed cross‐over is 1 × 1 cm2, and the bandwidth is 20–30%. Full‐wave electromagnetic simulations are performed and an experimental prototype is fabricated to demonstrate the novel design concept. The measurement results match well with the theoretical and numerical results.
Way to design an orthogonal frequency‐division multiple access‐base station receiver disturbed by a narrowband interfering cognitive radio signal
Authors: Poveda Héctor , Ferré Guillaume , Grivel Eric
Published: June 2015

This study deals with an interweave cognitive‐radio (CR) system, where an uplink orthogonal frequency‐division multiple access system is considered for the primary users (PUs). Our purpose is to estimate the PU carrier frequency offsets (PU‐CFOs) as well as the channels to estimate the transmitted symbols. However, in wideband wireless communications, the PU received‐signal spectrum usually exhibits a localised fading because of the multipath propagation channel. When the PU faded frequencies are used by the CR system, the PU system is contaminated by a CR narrowband interference (CR‐NBI). In that case, if a Kalman filter (KF)‐based approach is used for the estimations of the CFOs and the channels, the state‐space representation does not necessarily take into account the CR‐NBI; this hence has a negative impact on the algorithm performance. Therefore the authors propose to make this solution more robust to the CR‐NBI by detecting when it appears and disappears to avoid using the data disturbed by the CR‐NBI. The authors’ contribution is to assume that the CR‐NBI is because of the transmission of contiguous blocks and to propose various criteria based on the covariance matrix of the KF innovation.
Variable bit rate video traffic prediction based on kernel least mean square method
Authors: Haghighat Nasser , Kalbkhani Hashem , Shayesteh Mahrokh G. , Nouri Mehdi
Published: June 2015

In this study, the problem of variable bit rate (VBR) video traffic prediction is addressed. VBR traffic prediction is necessary in dynamic bandwidth allocation for multimedia quality of service control strategies. Autoregressive (AR) models have been widely used in VBR traffic prediction where the least mean square (LMS)‐based methods were utilised for parameter estimation. However, they are ineffective when the traffic is dynamic in nature. In this study, using the Brock, Dechert, and Scheinkman (BDS) test, it is shown that the video traffic is non‐linear. Kernel is an efficient tool to convert non‐linear data into linear one in a higher‐dimensional space. The kernel LMS (KLMS) method is proposed to forecast the next frame sizes of I, B and P frames as well as the next group‐of‐pictures (GOP) size of video traffic. Extensive simulations were performed on different video traces where different performance metrics were considered. KLMS results were very close to those of the Wiener–Hopf optimum solution and better than the results of commonly used normalised LMS and other algorithms such as the least mean kurtosis (LMK), wavelet LMK, adaptive network fuzzy inference system (ANFIS) and neural networks.
Performance evaluation of decode‐and‐forward dual‐hop asymmetric radio frequency‐free space optical communication system
Authors: Anees Sanya , Bhatnagar Manav R.
Published: June 2015

In this study, the error performance and the capacity analysis is performed for the decode‐and‐forward based dual‐hop asymmetric radio frequency‐free space optical communication (RF‐FSO) system. The RF link is characterised by Nakagami‐m fading and the FSO link is characterised by path loss, Gamma–Gamma distributed turbulence and pointing error. For this mixed RF‐FSO cooperative system, novel closed‐form mathematical expressions are derived for cumulative distribution function, probability density function and moment generating function of the equivalent signal‐to‐noise ratio in terms of Meijer‐G function. Using these channel statistics, new finite power series based analytical expressions are obtained for the outage probability, the average bit error rate for various binary and M ‐ary modulation techniques and the average channel capacity of the considered system in terms of Meijer‐G function. As a special case, the analytical framework can also be obtained for channel statistics and performance metrics of dual‐hop mixed Rayleigh–Gamma–Gamma system. Simulation results validate the proposed mathematical analysis. The effects of fading, turbulence and pointing error are studied on the outage probability, average bit error rate and channel capacity of the asymmetric RF‐FSO system.
Performance of multiuser scheduling in free space optical systems over atmospheric turbulence channels
Authors: Zhalehpour Sasan , Uysal Murat
Published: June 2015

In this study, the authors consider a multiuser multiple‐input multiple‐output (MU‐MIMO) free space optical (FSO) communication system and investigate the performance of various scheduling protocols which provide different degrees of tradeoff between throughput and fairness. In the MU‐MIMO FSO system under consideration, the central node and each user node are equipped with multiple transmit and receive apertures and equal gain combining is employed at the receiver side. Round robin, opportunistic round Robin, select‐max and m th best user selection scheduling protocols are employed. The authors derive closed‐form outage probability expressions for each scheduling protocol over log‐normal turbulence channels assuming non‐equidistant placement of users. The authors further present Monte Carlo simulations to confirm the accuracy of derived expressions.
Temperature dependent state‐of‐charge estimation of lithium ion battery using dual spherical unscented Kalman filter
Authors: Aung Htet , Low Kay Soon
Published: June 2015

Accurate and reliable state‐of‐charge (SOC) estimation is an important task for battery management system in a satellite. Ambient temperature is one of the significant factors that affect SOC estimation. Since satellite operates at different temperatures throughout the orbit, it must be taken care of accordingly to safeguard the battery performance and reliability. Moreover, SOC estimation depends on battery model accuracy as well. The battery parameters are affected by temperature, SOC, charging and discharging rates. Hence, the parameters need to be updated accordingly to improve the battery model and the SOC estimation accuracy. In this study, a SOC estimation method and online parameter updating using a dual square root unscented Kalman filter based on unit spherical unscented transform is proposed. The proposed method has been validated experimentally and the results are compared with extended Kalman filter and unscented Kalman filter based on unit spherical unscented transform. Experimental results have shown that the proposed method has better performance in terms of lower root mean square error and absolute maximum error.
Few-cycle pulses from a graphene mode-locked all-fiber laser
Authors: Purdie D. G. , Popa D. , Wittwer V. J. , Jiang Z. , Bonacchini G. , Torrisi F. , Milana S. , Lidorikis E. , Ferrari A. C.
Published: June 2015

We combine a graphene mode-locked oscillator with an external compressor and achieve ∼29 fs pulses with ∼52 mW average power. This is a simple, low-cost, and robust setup, entirely fiber based, with no free-space optics, for applications requiring high temporal resolution.
3D Numerical simulation of high current vacuum arc in realistic magnetic fields considering anode evaporation
Authors: Wang Lijun , Huang Xiaolong , Jia Shenli , Deng Jie , Qian Zhonghao , Shi Zongqian , Schellenkens H. , Godechot X.
Published: June 2015

A time-dependent 3D numerical model considering anode evaporation is developed for the high current vacuum arc (VA) under a realistic spatial magnetic field. The simulation work contains steady state 3D numerical simulation of high current VA considering anode evaporation at nine discrete moments of first half wave of 50 Hz AC current, transient numerical simulation of anode activity, and realistic spatial magnetic field calculation of commercial cup-shaped electrodes. In the simulation, contact opening and arc diffusion processes are also considered. Due to the effect of electrode slots, the simulation results of magnetic field and temperature of anode plate exhibit six leaves shape (SLS). During 6–8 ms, the strong evaporation of anode surface seriously influence the parameter distributions of VA. Ions emitted from anode penetrate into arc column and the axial velocity distribution on the anode side exhibits SLS. The ions emitted from anode surface have the same temperature with anode surface, which cool the arc plasma and lead to a relative low temperature area formed. The seriously evaporation of anode leads to the accumulation of ions near the anode, and then the current density is more uniform.
Accurate ab initio potential energy surface, thermochemistry, and dynamics of the F− + CH3F SN2 and proton-abstraction reactions
Authors: Szabó István , Telekes Hajnalka , Czakó Gábor
Published: June 2015

We develop a full-dimensional global analytical potential energy surface (PES) for the F− + CH3F reaction by fitting about 50 000 energy points obtained by an explicitly correlated composite method based on the second-order Møller–Plesset perturbation-F12 and coupled-cluster singles, doubles, and perturbative triples-F12a methods and the cc-pVnZ-F12 [n = D, T] basis sets. The PES accurately describes the (a) back-side attack Walden inversion mechanism involving the pre- and post-reaction (b) ion-dipole and (c) hydrogen-bonded complexes, the configuration-retaining (d) front-side attack and (e) double-inversion substitution pathways, as well as (f) the proton-abstraction channel. The benchmark quality relative energies of all the important stationary points are computed using the focal-point analysis (FPA) approach considering electron correlation up to coupled-cluster singles, doubles, triples, and perturbative quadruples method, extrapolation to the complete basis set limit, core-valence correlation, and scalar relativistic effects. The FPA classical(adiabatic) barrier heights of (a), (d), and (e) are −0.45(−0.61), 46.07(45.16), and 29.18(26.07) kcal mol−1, respectively, the dissociation energies of (b) and (c) are 13.81(13.56) and 13.73(13.52) kcal mol−1, respectively, and the endothermicity of (f) is 42.54(38.11) kcal mol−1. Quasiclassical trajectory computations of cross sections, scattering (θ) and initial attack (α) angle distributions, as well as translational and internal energy distributions are performed for the F− + CH3F(v = 0) reaction using the new PES. Apart from low collision energies (Ecoll), the SN2 excitation function is nearly constant, the abstraction cross sections rapidly increase with Ecoll from a threshold of ∼40 kcal mol−1, and retention trajectories via double inversion are found above Ecoll = ∼ 30 kcal mol−1, and at Ecoll = ∼ 50 kcal mol−1, the front-side attack cross sections start to increase very rapidly. At low Ecoll, the indirect mechanism dominates (mainly isotropic backward-forward symmetric θ distribution and translationally cold products) and significant long-range orientation effects (isotropic α distribution) and barrier recrossings are found. At higher Ecoll, the SN2 reaction mainly proceeds with direct rebound mechanism (backward scattering and hot product translation).
Figure correction of a metallic ellipsoidal neutron focusing mirror
Authors: Guo Jiang , Yamagata Yutaka , Morita Shin-ya , Takeda Shin , Kato Jun-ichi , Hino Masahiro , Furusaka Michihiro
Published: June 2015

An increasing number of neutron focusing mirrors is being adopted in neutron scattering experiments in order to provide high fluxes at sample positions, reduce measurement time, and/or increase statistical reliability. To realize a small focusing spot and high beam intensity, mirrors with both high form accuracy and low surface roughness are required. To achieve this, we propose a new figure correction technique to fabricate a two-dimensional neutron focusing mirror made with electroless nickel-phosphorus (NiP) by effectively combining ultraprecision shaper cutting and fine polishing. An arc envelope shaper cutting method is introduced to generate high form accuracy, while a fine polishing method, in which the material is removed effectively without losing profile accuracy, is developed to reduce the surface roughness of the mirror. High form accuracy in the minor-axis and the major-axis is obtained through tool profile error compensation and corrective polishing, respectively, and low surface roughness is acquired under a low polishing load. As a result, an ellipsoidal neutron focusing mirror is successfully fabricated with high form accuracy of 0.5 μm peak-to-valley and low surface roughness of 0.2 nm root-mean-square.
Hom-structures on finite-dimensional simple Lie superalgebras
Authors: Yuan Jixia , Liu Wende
Published: June 2015

A Hom-structure on a Lie superalgebra is an even linear mapping which twists the super Jacobi identity. In this paper, using Kac’s classification theorem and a reduction method, we show that finite-dimensional simple Lie superalgebras over the complex field ℂ admit only the trivial Hom-structures, that is, the scalar mappings.
Single spin optically detected magnetic resonance with 60–90 GHz (E-band) microwave resonators
Authors: Aslam Nabeel , Pfender Matthias , Stöhr Rainer , Neumann Philipp , Scheffler Marc , Sumiya Hitoshi , Abe Hiroshi , Onoda Shinobu , Ohshima Takeshi , Isoya Junichi , Wrachtrup Jörg
Published: June 2015

Magnetic resonance with ensembles of electron spins is commonly performed around 10 GHz, but also at frequencies above 240 GHz and in corresponding magnetic fields of over 9 T. However, experiments with single electron and nuclear spins so far only reach into frequency ranges of several 10 GHz, where existing coplanar waveguide structures for microwave (MW) delivery are compatible with single spin readout techniques (e.g., electrical or optical readout). Here, we explore the frequency range up to 90 GHz, with magnetic fields of up to ≈3 T for single spin magnetic resonance in conjunction with optical spin readout. To this end, we develop MW resonators with optical single spin access. In our case, rectangular 60–90 GHz (E-band) waveguides guarantee low-loss supply of microwaves to the resonators. Three dimensional cavities, as well as coplanar waveguide resonators, enhance MW fields by spatial and spectral confinement with a MW efficiency of 1.36mT/W. We utilize single nitrogen vacancy (NV) centers as hosts for optically accessible spins and show that their properties regarding optical spin readout known from smaller fields (<0.65 T) are retained up to fields of 3 T. In addition, we demonstrate coherent control of single nuclear spins under these conditions. Furthermore, our results extend the applicable magnetic field range of a single spin magnetic field sensor. Regarding spin based quantum registers, high fields lead to a purer product basis of electron and nuclear spins, which promises improved spin lifetimes. For example, during continuous single-shot readout, the 14N nuclear spin shows second-long longitudinal relaxation times.
Study of localized structures of kinetic Alfvén wave and generation of turbulence
Authors: Kumari Anju , Sharma R. P. , Yadav Nitin
Published: June 2015

Localization of kinetic Alfvén waves (KAW) due to ponderomotive nonlinearity can be regarded as an important mechanism for heating the space plasmas. The present paper investigates the effect of background density fluctuations on the formation of large amplitude localized structures and turbulent spectrum of KAW applicable to magnetopause. The dynamical equations are derived, taking into account the ponderomotive nonlinearity of the KAW as well as the background fluctuations which are in the form of ion acoustic waves. The system is studied numerically as well as semi-analytically. The results reveal that the presence of density fluctuations affects the formation of localized structures. These fluctuations affecting the localization of KAW may also affect heating and acceleration of plasma. Respective turbulent scaling for the different amplitude of background fluctuations has also been studied. The relevance of the numerical results has been discussed with the THEMIS observations near the magnetopause [C. Chaston et al., Geophys. Res. Lett. 35, L17S08 (2008)].
On the role of surface rheology in a magnetohydrodynamic swirling flow
Authors: Delacroix Jules , Davoust Laurent
Published: June 2015

The original coupling between the surface rheology of a liquid metal surface and a supporting annular Couette magnetohydrodynamic (MHD) flow is theoretically and numerically investigated in this paper, in the general layout of the classical annular viscometer, as developed by Mannheimer and Schechter [“An improved apparatus and analysis for surface rheological measurements,” J. Colloid Interface Sci. 32, 195–211 (1970)]. The purely hydrodynamic interplay between the main azimuthal flow (induced by a rotating floor) and the secondary overturning flow (generated by centrifugation) is found to be strongly affected by both surface viscous shear and surface viscous dilatation. When the flow is subjected to an outer vertical magnetic field, the impact of varying interface boundary conditions (through the surface shear and dilatational viscosities) at the gas/liquid interface profoundly alters the MHD flow topology. Particularly, when centrifugation competes with electromagnetic effects, advection of the main flow by the secondary flow is proved to affect significantly the core MHD flow, leading to a variety of atypical MHD flow patterns.
Giant enhancement of light emission from nanoscale Bi2Se3
Authors: Vargas Anthony , Liu Fangze , Kar Swastik
Published: June 2015

Bi2Se3 is a well-known room temperature topological insulator with a gapless surface state and ∼300 meV bulk band-gap, and as such has never been proposed to possess light-emitting properties. Here, we report prominent light emission in the visible region via photoluminescence (PL) measurements of chemical vapor deposition grown Bi2Se3 nanoplates with an average thickness and effective diameter of tens of nanometers. When excited using 488 nm (2.54 eV) laser light, these nanoscale Bi2Se3 platelets show a strong photoluminescence response in the Eph ∼ 2.1–2.3 eV region, with significant enhancement of light emission compared to bulk level emission. After annealing samples at 200 °C for 4 h, PL intensity increased by a factor of 2.4 to 3 for nanoscale Bi2Se3.
Evolution of Kelvin-Helmholtz instability at Venus in the presence of the parallel magnetic field
Authors: Lu H. Y. , Cao J. B. , Zhang T. L. , Fu H. S. , Ge Y. S.
Published: June 2015

Two-dimensional MHD simulations were performed to study the evolution of the Kelvin-Helmholtz (KH) instability at the Venusian ionopause in response to the strong flow shear in presence of the in-plane magnetic field parallel to the flow direction. The physical behavior of the KH instability as well as the triggering and occurrence conditions for highly rolled-up vortices are characterized through several physical parameters, including Alfvén Mach number on the upper side of the layer, the density ratio, and the ratio of parallel magnetic fields between two sides of the layer. Using these parameters, the simulations show that both the high density ratio and the parallel magnetic field component across the boundary layer play a role of stabilizing the instability. In the high density ratio case, the amount of total magnetic energy in the final quasi-steady status is much more than that in the initial status, which is clearly different from the case with low density ratio. We particularly investigate the nonlinear development of the case that has a high density ratio and uniform magnetic field. Before the instability saturation, a single magnetic island is formed and evolves into two quasi-steady islands in the non-linear phase. A quasi-steady pattern eventually forms and is embedded within a uniform magnetic field and a broadened boundary layer. The estimation of loss rates of ions from Venus indicates that the stabilizing effect of the parallel magnetic field component on the KH instability becomes strong in the case of high density ratio.
A model study of assisted adiabatic transfer of population in the presence of collisional dephasing
Authors: Masuda Shumpei , Rice Stuart A.
Published: June 2015

Previous studies have demonstrated that when experimental conditions generate non-adiabatic dynamics that prevents highly efficient population transfer between states of an isolated system by stimulated Raman adiabatic passage (STIRAP), the addition of an auxiliary counter-diabatic field (CDF) can restore most or all of that efficiency. This paper examines whether that strategy is also successful in a non-isolated system in which the energies of the states fluctuate, e.g., when a solute is subject to collisions with solvent. We study population transfer in two model systems: (i) the three-state system used by Demirplak and Rice [J. Chem. Phys. 116, 8028 (2002)] and (ii) a four-state system, derived from the simulation studies of Demirplak and Rice [J. Chem. Phys. 125, 194517 (2006)], that mimics HCl in liquid Ar. Simulation studies of the vibrational manifold of HCl in dense fluid Ar show that the collision induced vibrational energy level fluctuations have asymmetric distributions. Representations of these asymmetric energy level fluctuation distributions are used in both models (i) and (ii). We identify three sources of degradation of the efficiency of STIRAP generated selective population transfer in model (ii): too small pulse areas of the laser fields, unwanted interference arising from use of strong fields, and the vibrational detuning. For both models (i) and (ii), our examination of the efficiency of STIRAP + CDF population transfer under the influence of the asymmetric distribution of the vibrational energy fluctuations shows that there is a range of field strengths and pulse durations under which STIRAP + CDF control of population transfer has greater efficiency than does STIRAP generated population transfer.
Phase transition behavior and defect chemistry of [001]-oriented 0.15Pb(In1/2Nb1/2)O3-0.57Pb(Mg1/3Nb2/3)O3-0.28PbTiO3-Mn single crystals
Authors: Liu Xing , Fang Bijun , Deng Ji , Deng Hao , Yan Hong , Yue Qingwen , Chen Jianwei , Li Xiaobing , Ding Jianning , Zhao Xiangyong , Luo Haosu
Published: June 2015

The ferroelectric single crystals 0.5 mol. % Mn-doped 0.15Pb(In1/2Nb1/2)O3-0.57Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PIMNT-Mn) with rhombohedral perovskite structure were grown by a modified Bridgman method. Dielectric performance analysis reveals that the as-grown PIMNT-Mn single crystals exhibit complex dielectric behavior after polarization, in which the dielectric constant depends on frequency apparently around the ferroelectric phase transition temperatures TR-M and Tm. The temperature and electric-field induced ferroelectric phase transitions were investigated by the temperature dependent unipolar strain curves. The electric-field induced discontinuous ferroelectric phase transitions at elevated temperatures exhibit first-order like phase transition character. The converse piezoelectric constant (d33), maximum strain value (Smax%), and longitudinal electrostrictive coefficient (Q) increase considerably when the temperature approaches the ferroelectric phase transition temperatures TR-M and TM-T. The complex impedance curves (Z″-Z′) present typical semicircle shapes from 425 °C to 550 °C. The activation energy calculated by the Arrhenius law is 0.86 eV, indicating that the high-temperature conduction mechanism is dominated by the extrinsically formed oxygen vacancies.
Fe2: As simple as a Herculean labour. Neutral (Fe2), cationic (Fe2+), and anionic (Fe2−) species
Authors: Kalemos Apostolos
Published: June 2015

We have studied 175 molecular states of the Fe2 diatomic by constructing full potential energy curves dissociating to the ground Fe(5D) + Fe(5D) and first excited Fe(5D) + Fe(5F) dissociation channels by multireference configuration interaction methods and large basis sets. The ground X9Σg− and the first excited 7Σu− states have been detailed by a multitude of plain and explicitly correlated F12 methods at both the valence and core-valence computational levels. The potential curves of most of the states present strong interactions/avoided crossings that trigger a severe non adiabatic behavior. For reasons of completeness, the ground states of the charged Fe2−,+ species have also been considered.
Characterization of a new electrostatic storage ring for photofragmentation experiments
Authors: Pedersen H. B. , Svendsen A. , Harbo L. S. , Kiefer H. V. , Kjeldsen H. , Lammich L. , Toker Y. , Andersen L. H.
Published: June 2015

We describe the design of and the first commissioning experiments with a newly constructed electrostatic storage ring named SAPHIRA (Storage Ring in Aarhus for PHoton-Ion Reaction Analysis). With an intense beam of Cu− at 4 keV, the storage ring is characterized in terms of the stored ion beam decay rate, the longitudinal spreading of an injected ion bunch, as well as the direct measurements of the transverse spatial distributions under different conditions of storage. The ion storage stability in SAPHIRA was investigated systematically in a selected region of its electrical configuration space.
Pressure-induced reversible phase transition in thiourea dioxide crystal
Authors: Wang Qinglei , Yan Tingting , Wang Kai , Zhu Hongyang , Cui Qiliang , Zou Bo
Published: June 2015

The effect of high pressure on the crystal structure of thiourea dioxide has been investigated by Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) in a diamond anvil cell up to 10.3 GPa. The marked changes in the Raman spectra at 3.7 GPa strongly indicated a structural phase transition associated with the distortions of hydrogen bonding. There were no further changes up to the maximum pressure of 10.3 GPa and the observed transition was completely reversible when the system was brought back to ambient pressure. This transition was further confirmed by the changes of ADXRD spectra. The high-pressure phase was indexed and refined to an orthorhombic structure with a possible space group Pbam. The results from the first-principles calculations suggested that this phase transition was mainly related to the changes of hydrogen-bonded networks in thiourea dioxide.
Tunable solid acoustic metamaterial with negative elastic modulus
Authors: Hou Zhilin , Assouar Badreddine M.
Published: June 2015

We report in this letter on a tunable solid acoustic metamaterial with negative elastic modulus by means of piezoelectric composite. The theoretical formulae for one-dimensional layer-stacked metamaterial embedding a piezoelectric material by means of external shunted inductors are presented. The acoustic band structure of the composite is calculated by the transfer matrix method. Results show that a band gap can be opened and tuned by the resonant behavior of the LC circuit. It is found further by the formulae that piezoelectric material with large piezoelectric constant and small elastic modulus will be beneficial for opening a wide band gap. The effective elastic constant of the system is also calculated by the unit-cell-boundary-averaging method. Result shows that the system behaves as an effective medium with a negative elastic modulus. This property is quite different from the typical solid metamaterial achieved by dispersing heavy inclusions coated with a soft layer into a matrix for which only the negative mass density can be obtained.
Antiferromagnetic order induced by gadolinium substitution in Bi2Se3 single crystals
Authors: Kim S. W. , Vrtnik S. , Dolinšek J. , Jung M. H.
Published: June 2015

Magnetic topological insulators can serve as a fundamental platform for various spin-based device applications. We report the antiferromagnetic order induced by the magnetic impurity dopants of Gd in GdxBi2−xSe3 and the systematic results with varying the Gd concentration x ( = 0.14, 0.20, 0.30, and 0.40). The antiferromagnetic order is demonstrated by the magnetic susceptibility, electrical resistivity, and specific heat measurements. The anomaly observed at TN = 6 K for x ≥ 0.30 shifts towards lower temperature with increasing the magnetic field, indicative of antiferromagnetic ground state. The Gd substitution into Bi2Se3 enables not only tuning the magnetism from paramagnetic to antiferromagnetic for high x (≥ 0.30) but also giving a promising candidate for antiferromagnetic topological insulators.
Bulk- and layer-heterojunction phototransistors based on poly [2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] and PbS quantum dot hybrids
Authors: Song Xiaoxian , Zhang Yating , Wang Ran , Cao Mingxuan , Che Yongli , Wang Jianlong , Wang Haiyan , Jin Lufan , Dai Haitao , Ding Xin , Zhang Guizhong , Yao Jianquan
Published: June 2015

The responsivity (R) of a thin film photodetector is proportional to the product of its photo-induced carrier density (n) and mobility (μ). However, when choosing between layer heterojunction (LH) and bulk heterojunction (BH) field-effect phototransistors (FEpTs), it is still unclear which of the two device structures is more conducive to photodetection. A comparison study is performed on the two structures based on polymer and PbS quantum dot hybrids. Both devices exhibit ambipolar behavior, with μE ≈ μH = 3.7 cm2 V−1 s−1 for BH-FEpTs and μH = 36 cm2 V−1 s−1 and μE = 52 cm2 V−1 s−1 for LH-FEpTs. Because of the improvements in μ and the channel order degree (α), the responsivity of LH-FEpTs is as high as 101 A/W, which is as much as two orders of magnitude higher than that of BH-FEpTs (10−1A/W) under the same conditions. Although the large area of the BH improves both the exciton separation degree (β) and n in the BH-FEpT, the lack of an effective transport mechanism becomes the main constraint on high device responsivity. Therefore, LH-FEpTs are better candidates for use as photo detectors, and a “three-high” principle of high α, β, and μ is found to be required for high responsivity.

At the request of the authors, this article is being retracted effective 23 February 2017.
Origin of green luminescence in hydrothermally grown ZnO single crystals
Authors: Čížek J. , Valenta J. , Hruška P. , Melikhova O. , Procházka I. , Novotný M. , Bulíř J.
Published: June 2015

Combining photoluminescence and positron annihilation studies of hydrothermally grown ZnO crystals with stoichiometry varied by controlled annealing enabled us to clarify the origin of green luminescence. It was found that green luminescence in ZnO has multiple origins and consists of a band at 2.3(1) eV due to recombination of electrons of the conduction band by zinc vacancy acceptors coupled with hydrogen and a band at 2.47(2) eV related to oxygen vacancies. The as-grown ZnO crystals contain zinc vacancies associated with hydrogen and exhibit a green luminescence at 2.3(1) eV. Annealing in Zn vapor removed zinc vacancies and introduced oxygen vacancies. This led to disappearance of the green luminescence band at 2.3(1) eV and appearance of a green emission at higher energy of 2.47(2) eV. Moreover, the color of the crystal was changed from colorless to dark red. In contrast, annealing of the as-grown crystal in Cd vapor did not remove zinc vacancies and did not cause any significant change of green luminescence nor change in coloration.
The effect of multi-rank domain pattern on the polarization response of BaTiO3 crystal during electric field loading
Authors: Li Y. W. , Li F. X.
Published: June 2015

A barium titanate crystal, which consists of a region with sparse a-c domain pattern and two regions with dense domain pattern, was specially prepared. During the in-plane bipolar electric field loading, this specimen showed double polarization versus electric field (P-E) loops. To understand the origin of the observed double P-E loops, polarization responses of these regions were measured separately. It was found that the region with sparse a-c domain pattern showed typical P-E loop; however, the regions with dense domain pattern were very stable, and hardly any remnant polarizations were observed. Further analysis demonstrated that the double P-E loops might be caused by incompatible domain switching in the specimen during electric field loading.
Microbial phytase improves performance and bone traits in broilers fed diets based on soybean meal and containing lupin meal
Authors: Kaczmarek S. A. , Cowieson A. J. , Hejdysz M. , Rutkowski A.
Published: June 2015

A completely randomised design study with a 3 × 2 factorial arrangement was conducted. A total of 480 male broiler chickens were used to determine the influence of phytase addition, plant protein source [soybean meal, soybean meal + 200 g/kg of blue lupin meal (Lupinus angustifolius L.) or soybean meal + 200 g/kg yellow lupin meal (Lupinus luteus L.)] on performance of broiler chickens, ileal calcium (Ca), phosphorus (P) and protein digestibility, tibia bone characteristics and nitrogen-corrected apparent metabolisable energy. All diets were deficient in Ca, available P as well as lysine and total sulfur amino acids. Birds fed different protein sources were characterised by similar bodyweight gain and feed intake during the whole trial but feed conversion ratio was higher when birds were fed supplemented with yellow lupin meal (P < 0.05). Phytase improved bodyweight gain and feed conversion ratio regardless of protein source (P < 0.05). Diets supplemented with 200 g/kg blue or yellow lupin meal were found to be lower in nitrogen-corrected apparent metabolisable energy than soybean meal diets (P < 0.05). Birds fed diets supplemented with phytase were characterised by higher utilisation of Ca and P than birds whose feed was not supplemented with phytase (P < 0.05). Tibia bone ash as well as Ca content was similar across protein sources (P > 0.05), whereas tibia P content was lower when soybean meal or blue lupin meal was used (P < 0.05). Birds fed diets supplemented with blue lupin meal were characterised by the highest tibia P content (P < 0.05). Birds fed phytase-supplemented diets were characterised by higher tibia Ca and P content irrespective of protein source.
Syntheses and Structures of Homodinuclear (Na–Na) and Heterodinuclear (Cu–Na, Cu–K) Metal Complexes
Authors: Jia Rui , Gao Ting , Chen Ruoxi , Yang Yu , Gao Po , Wang Yan , Yan Pengfei
Published: June 2015

The study of polynuclear metal complexes has gained great recognition over the last decade owing to their fascinating topological structures, various properties, and potential applications as functional solid materials in luminescence, catalysis, and magnetic materials. A large number of heterodinuclear 3d–4f and 3d–3d′ complexes have been widely studied due to their functional applications. To our knowledge, structurally characterised heterodinuclear (3d–Na, 3d–K) and homodinuclear (Na–Na) metal complexes are rare. Three metal complexes, [CuIINaI(HL1)2(SbF6)]n (1), [CuIIKI(HL1)2(PF6)]n (2), and [Na2(H2L2)2] (3), were synthesised by two kinds of ligands, o-vanillin (HL1) and N,N′-ethylene-bis(3-methoxysalicylideneimine) (H2L2). The structures of heterodinuclear complexes 1 and 2 are both one-dimensional chain structures, including transition metal ions (CuII) and main group metal ions (NaI and KI). However, the complex 3, as a homodinuclear metal complex, only has one kind of centre, a NaI ion. The structures of complexes 1–3 were determined by single crystal X-ray crystallographic studies.