bluuebunny/crossref_metadata_2025 huggingface dataset:
Driver's fatigue expressions recognition by combined features from pyramid histogram of oriented gradient and contourlet transform with random subspace ensembles
Authors: Zhao Chihang , Zhang Xiaozheng , Zhang Bailing , Dang Qian , Lian Jie
Published: May 2013

Human‐centric driver fatigue monitoring systems (DFMS) with integrated sensing, processing and networking aim to find solutions for traffic accidents and other relevant issues. A novel, efficient combined features extraction approach from Pyramid Histogram of Oriented Gradients (PHOG) and contourlet transform (CT) for fatigue expression descriptions of vehicle drivers is proposed, and a random subspace ensemble (RSE) of linear perception (LP) classifiers as the base classifier is then exploited for the classification of three predefined fatigue expressions classes, namely, awake expressions, moderate fatigue expressions and severe fatigue expressions. Holdout and cross‐validation experiments are created, and the results show that combined features by RSE of LP classifiers outperform the other seven classifiers, that is, PHOG features by LP classifier, CT features by LP classifier and combined features by five individual LP classifiers. With combined features and RSE of LP classifiers, the average classification accuracies of three fatigue expression classes are over 92% in both the holdout and cross‐validation experiments. Among the three fatigue expression classes, the class of severe fatigue expressions is the most difficult to recognise, and the classification accuracy is over 84% in both the holdout and cross‐validation experiments, which shows the effectiveness of the proposed feature extraction method and RSE of LP classifiers in developing DFMS.
Method for estimating the energy consumption of electric vehicles and plug‐in hybrid electric vehicles under real‐world driving conditions
Authors: Shankar Ravi , Marco James
Published: May 2013

This study presents a novel framework by which the energy consumption of an electric vehicle (EV) or the zero‐emissions range of a plug‐in hybrid electric vehicle (PHEV) may be predicted over a route. The proposed energy prediction framework employs a neural network and may be used either ‘off‐line’ for better estimating the real‐world range of the vehicle or ‘on‐line’ integrated within the vehicle's energy management control system. The authors propose that this approach provides a more robust representation of the energy consumption of the target EVs compared to standard legislative test procedures. This is particularly pertinent for vehicle fleet operators that may use EVs within a specific environment, such as inner‐city public transport or the use of urban delivery vehicles. Experimental results highlight variations in EV range in the order of 50% when different levels of traffic congestion and road type are included in the analysis. The ability to estimate the energy requirements of the vehicle over a given route is also a pre‐requisite for using an efficient charge blended control strategy within a PHEV. Experimental results show an accuracy within 20–30% when comparing predicted and measured energy consumptions for over 800 different real‐world EV journeys.
Coexistence of fast‐scale and slow‐scale instability in ĆUK power factor correction AC–DC pre‐regulators under non‐linear current‐mode control
Authors: ParvathyShankar Deivasundari , Govindarajan Uma , Mallapu Gopinath Umamaheswari , Anbukumar Kavitha
Published: May 2013

Power factor correction (PFC) converters using conventional control strategies have been reported tremendously as exhibiting slow‐ and fast‐scale bifurcations. This study investigates the fast‐scale and slow‐scale instabilities in a PFC ĆUK converter under non‐linear carrier (NLC) control, which is proved advantageous compared with other conventional control strategies. It is found that the fundamental periodic orbit loses its stability via period‐doubling bifurcation and later bifurcates to chaos. Bifurcation studies of NLC controlled higher‐order converters have not been reported so far in literature. Computer simulations as well as experimental investigations are performed to study the qualitative behaviour of the system under variations of different parameters. It is found that both the fast‐ and slow‐scale instabilities may cause distortion in the line current and degrade the supply power factor. The results offer useful information of parameter space for the design and operation of the converter in the desired fundamental stable regime.
Selective harmonic elimination pulse‐width modulation of modular multilevel converters
Authors: Konstantinou Georgios , Ciobotaru Mihai , Agelidis Vassilios
Published: May 2013

The modular multilevel converter (MMC) is the state‐of‐the‐art for multilevel converter topologies. This study presents the operation of the MMC using the multilevel selective harmonic elimination pulse‐width modulation (MSHE‐PWM) technique. MSHE‐PWM offers tight control of the low‐order harmonics and the lowest switching frequency for the power semiconductors among all modulation techniques. A comprehensive analysis of the modulation methods for the MMC leads to two different modulation patterns for MSHE‐PWM. A method for selecting the number of sub‐modules in the phase‐legs of the converter is also proposed in this study. Simulation results for both patterns are provided and verified through matching experimental results from a single phase 11‐level laboratory prototype.
Wireless battery chargers for portable applications: design and test of a high‐efficiency power receiver
Authors: Boscaino Valeria , Pellitteri Filippo , Rosa La , Capponi Giuseppe
Published: May 2013

In this study, the authors present a 5 W wireless battery charger for handheld devices. Efficiency‐related issues are addressed. A power receiver architecture which improves power conversion efficiency is proposed. Design hints are provided for further applications. Comparison with a conventional architecture is provided as well. Laboratory prototypes of both the proposed and the conventional architectures have been realised. Both prototypes are tested by using the same power transmitter to perform a valuable comparison. As shown by the experimental results, in the receiver side power conversion efficiency is increased up to 99% thanks to the proposed solution.
Three‐phase four‐leg flying‐capacitor multi‐level inverter‐based active power filter for unbalanced current operation
Authors: Zhang Li , Waite Michael J. , Chong Benjamin
Published: May 2013

This study describes a new application of flying capacitor multi‐level inverters whereby a three‐phase, four‐leg three‐level inverter is used for harmonic current cancellation and unbalanced current compensation in a four‐wire system. A direct three‐dimensional‐pulse‐width modulation (3D‐PWM) scheme is developed to deal with the increased state redundancy in the four‐leg flying capacitor multi‐level inverter. Test results show much superior performance in the four‐leg case, which may allow the use of smaller DC supply capacitors. A new modified dead–beat current control algorithm is proposed and combined successfully with the 3D‐PWM modulation technique in a hardware demonstrator of a complete active filter.
Implementation of a soft switching DC/DC converter without reverse recovery loss for rectifier diodes
Authors: Lin Bor‐Ren , Jhong Jian‐Yo
Published: May 2013

This study presents an interleaved soft switching converter to achieve ripple current reduction, zero‐voltage switching (ZVS) turn‐on for MOSFETs and zero‐current switching (ZCS) turn‐off for fast recovery diodes. Active snubber circuit is used in the proposed circuit to absorb the energy stored in the leakage inductor and to achieve ZVS turn‐on for power switches. The resonant tank composed of the leakage inductor and the resonant capacitor at the secondary side is used to achieve ZCS turn‐off for all rectifier diodes. The reverse recovery loss on rectifier diodes can be eliminated. Thus, the low‐cost fast recovery diodes can be used at the secondary side. The interleaved pulse‐width modulation scheme is used to control two converter cells in order to achieve load sharing and input ripple current reduction. Experiments with a 400 W prototype, verifying the effectiveness of the proposed converter, are described.
Numerical study of a slip-link model for polymer melts and nanocomposites
Authors: Del Biondo Diego , Masnada Elian M. , Merabia Samy , Couty Marc , Barrat Jean-Louis
Published: May 2013

We present a numerical study of the slip link model introduced by Likhtman for describing the dynamics of dense polymer melts. After reviewing the technical aspects associated with the implementation of the model, we extend previous work in several directions. The dependence of the relaxation modulus with the slip link density and the slip link stiffness is reported. Then the nonlinear rheological properties of the model, for a particular set of parameters, are explored. Finally, we introduce excluded volume interactions in a mean field such as manner in order to describe inhomogeneous systems, and we apply this description to a simple nanocomposite model. With this extension, the slip link model appears as a simple and generic model of a polymer melt, that can be used as an alternative to molecular dynamics for coarse grained simulations of complex polymeric systems.
Electron and hole mobilities at a Si/SiO2 interface with giant valley splitting
Authors: Niida Yoshitaka , Takashina Kei , Ono Yukinori , Fujiwara Akira , Hirayama Yoshiro
Published: May 2013

We examine the electron mobility and hole mobility at the Si/buried oxide (BOX) interface at which the valley splitting of the electron system is strongly enhanced, and compare the values observed to those at a standard Si/thermal oxide (T-SiO2) interface in the same silicon-on-insulator device. In contrast to the electron mobility, which is lower at the Si/BOX interface, the hole mobility at the Si/BOX interface is found to be slightly higher than that at the Si/T-SiO2 interface.
Tungsten-incorporation induced red-shift in the bandgap of gallium oxide thin films
Authors: Rubio E. J. , Ramana C. V.
Published: May 2013

Tungsten (W) incorporated Ga2O3 films were produced by co-sputter deposition. W-concentration was varied by the applied sputtering-power. The structure and optical properties of W-incorporated Ga2O3 films were evaluated using X-ray diffraction, scanning electron microscopy, and spectrophotometric measurements. No secondary phase formation was observed in W-incorporated Ga2O3 films. W-induced effects were significant on the structure and optical properties of Ga2O3 films. The bandgap of Ga2O3 films without W-incorporation was ∼5 eV. Red-shift in the bandgap was noted with increasing W-concentration indicating the electronic structure changes in W-Ga2O3 films. A functional relationship between W-concentration and optical property is discussed.
The structures of neutral transition metal doped silicon clusters, Sin
X (n = 6−9; X = V, Mn)
Authors: Claes Pieterjan , Ngan Vu Thi , Haertelt Marko , Lyon Jonathan T. , Fielicke André , Nguyen Minh Tho , Lievens Peter , Janssens Ewald
Published: May 2013

We present a combined experimental and theoretical investigation of small neutral vanadium and manganese doped silicon clusters SinX (n = 6−9, X = V, Mn). These species are studied by infrared multiple photon dissociation and mass spectrometry. Structural identification is achieved by comparison of the experimental data with computed infrared spectra of low-lying isomers using density functional theory at the B3P86/6-311+G(d) level. The assigned structures of the neutral vanadium and manganese doped silicon clusters are compared with their cationic counterparts. In general, the neutral and cationic SinV0,+ and SinMn0,+ clusters have similar structures, although the position of the capping atoms depends for certain sizes on the charge state. The influence of the charge state on the electronic properties of the clusters is also investigated by analysis of the density of states, the shapes of the molecular orbitals, and NBO charge analysis of the dopant atom.
Doubly electron-attached and doubly ionized equation-of-motion coupled-cluster methods with 4-particle–2-hole and 4-hole–2-particle excitations and their active-space extensions
Authors: Shen Jun , Piecuch Piotr
Published: May 2013

The full and active-space doubly electron-attached (DEA) and doubly ionized (DIP) equation-of-motion coupled-cluster (EOMCC) methods with up to 4-particle–2-hole (4p-2h) and 4-hole–2-particle (4h-2p) excitations are developed. By examining bond breaking in F2 and low-lying singlet and triplet states in the methylene, (HFH)−, and trimethylenemethane biradicals, we demonstrate that the DEA- and DIP-EOMCC methods with an active-space treatment of 4p-2h and 4h-2p excitations reproduce the results of the analogous full calculations at the small fraction of the computer effort, while improving the DEA/DIP-EOMCC theories truncated at 3p-1h/3h-1p excitations.
Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on adsorbate diffusion and dehydrogenation at vanadium oxide substrate
Authors: Gruber M. , Hermann K.
Published: May 2013

We discuss the details of important steps of the selective catalytic reduction (SCR) of NOx at model V2O5(010) substrate. First, diffusion processes at the substrate surface are considered where hydrogen and ammonium, NH4, are used as examples. Hydrogen diffusion, a prerequisite for water formation involving substrate oxygen, is described by diffusion paths between adjacent surface oxygen sites. Corresponding energy barriers are determined mainly by the flexibility and the amount of distortion of the oxygen atoms which participate in the O–H–O bridge formation at the transition state. Further, diffusion of sub-surface oxygen to fill surface oxygen vacancies of the V2O5(010) substrate has been considered and results in reactive surface sites which have not been discussed so far. NH4 diffusion at the V2O5(010) surface can be described as a combined tumbling and rotation process characterized by quite low diffusion barriers which make the adsorbate rather mobile. Finally, hydrogenation and dehydrogenation of different NHx species at the V2O5(010) substrate surface are studied where special emphasis is given to the influence of surface reduction simulated locally by oxygen vacancies. The results confirm experimental findings of the presence of both NH2 and NH4 species after ammonia adsorption at the V2O5(010) surface.
Adhesion and friction control localized folding in supported graphene
Authors: Zhang K. , Arroyo M.
Published: May 2013

Graphene deposited on planar surfaces often exhibits sharp and localized folds delimiting seemingly planar regions, as a result of compressive stresses transmitted by the substrate. Such folds alter the electronic and chemical properties of graphene, and therefore, it is important to understand their emergence, to either suppress them or control their morphology. Here, we study the emergence of out-of-plane deformations in supported and laterally strained graphene with high-fidelity simulations and a simpler theoretical model. We characterize the onset of buckling and the nonlinear behavior after the instability in terms of the adhesion and frictional material parameters of the graphene-substrate interface. We find that localized folds evolve from a distributed wrinkling linear instability due to the nonlinearity in the van der Waals graphene-substrate interactions. We identify friction as a selection mechanism for the separation between folds, as the formation of far apart folds is penalized by the work of friction. Our systematic analysis is a first step towards strain engineering of supported graphene, and is applicable to other compressed thin elastic films weakly coupled to a substrate.
Polymer-dispersed liquid crystal doped with carbon nanotubes for dimethyl methylphosphonate vapor-sensing application
Authors: Lai Yu-Tse , Kuo Jui-Chang , Yang Yao-Joe
Published: May 2013

This paper proposes a sensitive gas sensor composed of polymer-dispersed liquid crystal (PDLC) for dimethyl methylphosphonate (DMMP) detection. The sensing element comprises a PDLC sensing film doped with carbon nanotubes (CNT-PDLC) and a planar interdigital electrode pair. The concentration of DMMP exposed to the CNT-PDLC material is detectable by measuring the change in conductivity of the material. Compared to conventional LC-based sensors, the proposed PDLC device is robust against mechanical shocks, and can fully operate with a simple read-out circuit. The sensor response is linear for gas concentrations from 5 to 250 ppm, and the response time is approximately 125 s.
Thermal nonlinear coherent states on a flat space and on a sphere
Authors: Bagheri H. , Mahdifar A.
Published: May 2013

In this paper, we first define thermal nonlinear coherent states on a sphere and show that these states are essentially two-mode squeezed nonlinear coherent states of the sphere at zero temperature. Then we consider quantum statistical properties of the thermal sphere nonlinear coherent states. In particular, we investigate temperature effects on transition of the constructed states from nonclassical states to classical ones. By using the Mandel parameter, we obtain a transition temperature and show that this transition temperature increases by increasing the curvature of the physical space. It turns out that, increasing curvature of the space provides nonlinear coherent states with nonclassical properties in higher temperature ranges.
Water nanodroplets: Predictions of five model potentials
Authors: Kazachenko Sergey , Thakkar Ajit J.
Published: May 2013

Putative global minima for five intermolecular potential energy models are reported for water clusters (H2O)n with n ⩽ 55. The models studied include three empirical, pairwise-additive potential energy surfaces, TIP4P, TIP4P-Ew, and TIP4P/2005, which use fixed point charges and rigid monomers. The other two, TTM2.1-F and AMOEBA, are polarizable, include non-additive inductive effects, have flexible monomers, and were parametrized, at least partially, using ab initio data. The n = 51 cluster has the same structure and is exceptionally stable for all five potentials. A structured inner core can be seen in cage clusters with n > 37. Periplanar rings, branched rings, and coils are among the structural motifs of the inner core.
Non-linear eigensolver-based alternative to traditional SCF methods
Authors: Gavin B. , Polizzi E.
Published: May 2013

The self-consistent procedure in electronic structure calculations is revisited using a highly efficient and robust algorithm for solving the non-linear eigenvector problem, i.e., H({ψ})ψ = Eψ. This new scheme is derived from a generalization of the FEAST eigenvalue algorithm to account for the non-linearity of the Hamiltonian with the occupied eigenvectors. Using a series of numerical examples and the density functional theory-Kohn/Sham model, it will be shown that our approach can outperform the traditional SCF mixing-scheme techniques by providing a higher converge rate, convergence to the correct solution regardless of the choice of the initial guess, and a significant reduction of the eigenvalue solve time in simulations.
Non-volatile switching characteristics in wet-deposited Ag2Se/GeSe double layers for resistive random access memory applications
Authors: Nam Ki-Hyun , Kim Jang-Han , Cho Won-Ju , Chung Hong-Bay
Published: May 2013

The resistance switching characteristics of resistive random access memory (ReRAM) based on amorphous GeSe thin films have been demonstrated by using Al/Ag2Se/GeSe/Pt structure. The Ag2Se layer that serves as the metal ionic source of GeSe switching medium was formed by a very simple wet-deposition process in AgNO3 solution. The X-ray diffraction and Auger electron spectroscopy analysis revealed the existence of the Ag2Se layer. As a result, an extremely low-voltage set/reset operation of less than 0.2 V, a high on-off resistance ratio larger than 103, good endurance characteristics, and excellent long-term reliability were achieved by the proposed Ag2Se/GeSe bilayered ReRAMs using the wet-deposition process.
Low-field induced giant magnetocaloric effect in TmCuAl compound
Authors: Mo Zhao-Jun , Shen Jun , Yan Li-Qin , Wu Jian-Feng , Wang Li-Chen , Lin Jing , Tang Cheng-Chun , Shen Bao-Gen
Published: May 2013

A giant low field reversible magnetocaloric effect has been observed in TmCuAl compound around 4 K, which is the boiling point of helium. The maximum value of magnetic entropy change (−ΔSMmax) and adiabatic temperature change (ΔTadmax) is 17.2 J/Kg K and 4.6 K without thermal and field hysteresis loss, for field changes of 0–2 T, respectively. Especially, the giant value of −ΔSMmax (12.2 J/Kg K) is obtained for a field change of 0-1 T. The results indicate that the TmCuAl compound could be considered as a good candidate material for low-temperature and low-field magnetic refrigerant.
Differential interference contrast microscopy using light-emitting diode illumination in conjunction with dual optical traps
Authors: Battle C. , Lautscham L. , Schmidt C. F.
Published: May 2013

Differential interference contrast (DIC) microscopy is a common mode of biological light microscopy used to achieve maximal resolution and contrast with label-free, weakly absorbing specimens such as cells. Maintaining the polarization state of the illuminating light is essential for the technique, and this requirement can conflict with optical trapping. We describe how to optimize DIC imaging using a light-emitting diode illumination source in a microscope while integrating a dual optical trap into the set up. Every time a polarized light beam reflects off or transmits through a dichroic mirror in the beam path, its polarization state will change if it is not polarized exactly parallel (p) or perpendicular (s) to the plane of incidence. We observe wavelength-dependent optical rotation and depolarization effects in our illumination light upon reflection from/transmission through dichroic mirrors in the beam path, resulting in significant degradation of image quality. We describe a method to compensate for these effects by introducing quarter-waveplates and a laser clean-up filter into the imaging pathway. We show that this approach achieves a full recovery of image quality.
Absolute photo-destruction and photo-fragmentation cross section measurements using an electrostatic ion beam trap
Authors: Aviv O. , Kafle B. , Chandrasekaran V. , Heber O. , Rappaport M. L. , Rubinstein H. , Schwalm D. , Strasser D. , Toker Y. , Zajfman D.
Published: May 2013

We describe a technique to measure absolute photo-induced cross sections for cluster anions stored in an electrostatic ion beam trap (EIBT) with a central deflector. The setup allows determination of total photo-destruction cross sections as well as partial cross sections for fragmentation and electron detachment. The unique properties of this special EIBT setup are investigated and illustrated using small \documentclass[12pt]{minimal}\begin{document}${\rm Al}_n^-$\end{document} Al n− clusters.
Size dependent magnetic and dielectric properties of nano CoFe2O4 prepared by a salt assisted gel-combustion method
Authors: Vasundhara K. , Achary S. N. , Deshpande S. K , Babu P. D. , Meena S. S. , Tyagi A. K.
Published: May 2013

In this communication, we report the preparation and properties of nano-CoFe2O4 by gel combustion in presence of KCl and subsequent heat treatments. The products were characterized by X-ray diffraction, Infrared spectroscopy, and Mössbauer Spectroscopy. Spinel type structure with all Fe in 3+ oxidation states was confirmed from the XRD and Mossbauer spectroscopy. The average crystallite sizes of the studied samples were about 6 and 50 nm. Low temperature magnetic and dielectric properties of the samples were studied by superconducting quantum interference device magnetometry and ac-impedance spectroscopy. The field and temperature dependent magnetization studies indicated superparamagnetic nature for 6 nm sample and ferromagnetic nature for 50 nm sample. The temperature-dependent dielectric properties measured over a wide range of frequencies indicated an increasing trend of dielectric permittivity with the decrease in crystallite size. Variable range polaron hopping conduction was observed in both samples.
A nuclear magnetic resonance spectrometer concept for hermetically sealed magic angle spinning investigations on highly toxic, radiotoxic, or air sensitive materials
Authors: Martel L. , Somers J. , Berkmann C. , Koepp F. , Rothermel A. , Pauvert O. , Selfslag C. , Farnan I.
Published: May 2013

A concept to integrate a commercial high-resolution, magic angle spinning nuclear magnetic resonance (MAS-NMR) probe capable of very rapid rotation rates (70 kHz) in a hermetically sealed enclosure for the study of highly radiotoxic materials has been developed and successfully demonstrated. The concept centres on a conventional wide bore (89 mm) solid-state NMR magnet operating with industry standard 54 mm diameter probes designed for narrow bore magnets. Rotor insertion and probe tuning take place within a hermetically enclosed glovebox, which extends into the bore of the magnet, in the space between the probe and the magnet shim system. Oxygen-17 MAS-NMR measurements demonstrate the possibility of obtaining high quality spectra from small sample masses (∼10 mg) of highly radiotoxic material and the need for high spinning speeds to improve the spectral resolution when working with actinides. The large paramagnetic susceptibility arising from actinide paramagnetism in (Th1−xUx)O2 solid solutions gives rise to extensive spinning sidebands and poor resolution at 15 kHz, which is dramatically improved at 55 kHz. The first 17O MAS-NMR measurements on NpO2+x samples spinning at 55 kHz are also reported. The glovebox approach developed here for radiotoxic materials can be easily adapted to work with other hazardous or even air sensitive materials.
Polarization dependence of absorption by bound electrons in self-assembled quantum dots
Authors: Ameen Tarek A. , El-Batawy Yasser M.
Published: May 2013

In this paper, the effects of the incident light polarization on the bound to continuum linear absorption coefficient of quantum dot devices have been investigated. The study is based on the effective mass theory and the Non Equilibrium Green's Function formalism. For the bound to continuum component of the absorption coefficient, both of in-plane and perpendicular polarization effects are studied for different sizes of conical quantum dots. Generally, decreasing the dot's dimensions results in an increase of the in-plane polarized light absorption and in moving the absorption peak towards longer wavelengths. On the other hand, decreasing the dot's dimensions results in a decrease of the perpendicularly polarized light absorption coefficient and in moving the absorption peak towards longer wavelengths.
Thermal conductivity of low temperature grown vertical carbon nanotube bundles measured using the three-ω method
Authors: Vollebregt Sten , Banerjee Sourish , Beenakker Kees , Ishihara Ryoichi
Published: May 2013

The thermal conductivity of as-grown vertical multi-walled carbon nanotubes (CNT) bundles fabricated at low temperature (500 °C) was measured using a vertical 3ω-method. For this, CNT were selectively grown inside an oxide opening and sandwiched between two metal electrodes. The validity of the method was confirmed by both measurements as simulations. The measured thermal conductivity of 1.7-3.5 W/mK is significantly lower than values reported before, which is caused by the low quality of the tubes. This clearly indicates that tube quality will be essential when integrating CNT.
Energy resolved X-ray grating interferometry
Authors: Thuering T. , Barber W. C. , Seo Y. , Alhassen F. , Iwanczyk J. S. , Stampanoni M.
Published: May 2013

Although compatible with polychromatic radiation, the sensitivity in X-ray phase contrast imaging with a grating interferometer is strongly dependent on the X-ray spectrum. We used an energy resolving detector to quantitatively investigate the dependency of the noise from the spectral bandwidth and to consequently optimize the system—by selecting the best energy band matching the experimental conditions—with respect to sensitivity maximization and, eventually, dose. Further, since theoretical calculations of the spectrum are usually limited due to non-ideal conditions, an energy resolving detector accurately quantifies the spectral changes induced by the interferometer including flux reduction and beam hardening.
Effect of germanium fraction on the effective minority carrier lifetime in thin film amorphous-Si/crystalline-Si1xGex/crystalline-Si heterojunction solar cells
Authors: Abdul Hadi Sabina , Hashemi Pouya , DiLello Nicole , Polyzoeva Evelina , Nayfeh Ammar , Hoyt Judy L.
Published: May 2013

The effect of germanium fraction on the effective minority carrier lifetime (τeff) for epitaxial Si1-xGex layers is extracted using measurements on amorphous(a) Si(n+)/crystalline(c)-Si1-xGex(p)/crystalline(c)-Si(p+) heterojunction solar cells with x = 0.25, 0.41 and 0.56. The τeff extracted for Si0.75Ge0.25 is ∼1 μs, decreasing to ∼ 40 ns for Si0.44Ge0.56. In addition, the band-gap voltage offset (Woc) increases from 0.5 eV for Si to 0.65 eV for 56% Ge indicating an increase in non-radiative recombination consistent with the reduction in effective lifetime.
Anomalous circular photogalvanic effect of the spin-polarized two-dimensional electron gas in Mg0.2Zn0.8O/ZnO heterostructures at room temperature
Authors: Duan J. X. , Tang N. , Ye J. D. , Mei F. H. , Teo K. L. , Chen Y. H. , Ge W. K. , Shen B.
Published: May 2013

A spin-related photocurrent with swirly distribution and anomalous dependence of the total spin-related photocurrent on the incident angle were observed on spin-polarized two-dimensional gas in a Mg0.2Zn0.8O/ZnO heterostructure under illumination of circular polarized light at room temperature. The ferromagnetic two-dimensional Rashba model was adopted to interpret the results. It is demonstrated that a radial spin current induced by the gradient of the spin-polarized electron density is the origin of the anomalousness. This spin current only exists in spin polarized systems.
Study of the effects of guide field on Hall reconnection
Authors: Tharp T. D. , Yamada M. , Ji H. , Lawrence E. , Dorfman S. , Myers C. , Yoo J. , Huang Y.-M. , Bhattacharjee A.
Published: May 2013

The results from guide field studies on the Magnetic Reconnection Experiment (MRX) are compared with results from Hall magnetohydrodynamic (HMHD) reconnection simulation with guide field. The quadrupole field, a signature of two-fluid reconnection at zero guide field, is modified by the presence of a finite guide field in a manner consistent with HMHD simulation. The modified Hall current profile contains reduced electron flows in the reconnection plane, which quantitatively explains the observed reduction of the reconnection rate. The present results are consistent with the hypothesis that the local reconnection dynamics is dominated by Hall effects in the collisionless regime of the MRX plasmas. While very good agreement is seen between experiment and simulations, we note that an important global feature of the experiments, a compression of the guide field by the reconnecting plasma, is not represented in the simulations.
First-principles study of temperature-dependent diffusion coefficients: Hydrogen, deuterium, and tritium in α-Ti
Authors: Lu Yong , Zhang Ping
Published: May 2013

We report the prediction of temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium atoms in α-Ti using transition state theory. The microscopic parameters in the pre-factor and activation energy of the impurity diffusion coefficients are obtained from first-principles total energy and phonon calculations including the full coupling between the vibrational modes of the diffusing atom with the host lattice. The dual occupancy case of impurity atom in the hcp matrix is considered, and four diffusion paths are combined to obtain the final diffusion coefficients. The calculated diffusion parameters show good agreement with experiments. Our numerical results indicate that the diffusions of deuterium and tritium atoms are slower than that of the hydrogen atom at temperatures above 425 K and 390 K, respectively.
Ferromagnetic bubble clusters in Y0.67Ca0.33MnO3 thin films
Authors: Kim Jeehoon , Haberkorn N. , Kim Suenne , Civale L. , Dowden P. C. , Movshovich R.
Published: May 2013

We studied the ferromagnetic domains and the presence of phase coexistence in a Y0.67Ca0.33MnO3 thin film with a combination of magnetic force microscopy and magnetization measurements. Our results show that the spin glass-like behavior, reported previously for this system, could be attributed to frustrated interfaces of the bubble-like ferromagnetic clusters embedded in a non-ferromagnetic matrix. We found temperature dependent changes of the magnetic domains at low temperatures, which suggest a non-static Mn3+/Mn4+ ratio.
Large magnetocaloric effect and refrigerant capacity near room temperature in as-cast Gd5Ge2Si2−xSnx compounds
Authors: Carvalho A. Magnus G. , Tedesco J. C. G. , Pires M. J. M. , Soffner M. E. , Guimarães A. O. , Mansanares A. M. , Coelho A. A.
Published: May 2013

Large values of isothermal entropy change (ΔST) and refrigerant capacity have been found in Gd5Ge2Si2−xSnx compounds. Values of the order of 20 J kg−1 K−1 for −ΔST were obtained in as-cast samples when submitted to a magnetic field variation of 2 T. First-order-magneto-structural transition is induced by the substitution of silicon by tin and it is shifted to lower temperatures with the tin content. It means that the magnetocaloric effect on this series can be properly tuned to a specific practical thermodynamic cycle, including near room temperature range.
Probing the dynamic responses of individual actin filaments under fluidic mechanical stimulation via microfluidics
Authors: Cheng Chao-Min , Yang Chung-Yao , Kim YongTae , LeDuc Philip R.
Published: May 2013

Herein, we demonstrate an easy-to-handle approach that employs a combination of microcurvilinear flow and fluorescence microscopy for probing the dynamic responses of individual synthesized actin filaments. We observed morphological changes of single actin filaments with different spatiotemporal responses when they were elongated with rotation or underwent significant bending during fluidic shear stress, and found that they may initially increase their curvature but then start releasing the external force immediately thereafter. Our approach allowed us to visibly examine the dynamic responses of individual actin filaments under simultaneous forces of rotation and elongation, as well as bending resulting from fluidic shear stress.
Tailoring spin-orbit torque in diluted magnetic semiconductors
Authors: Li Hang , Wang Xuhui , Doǧan Fatih , Manchon Aurelien
Published: May 2013

We study the spin orbit torque arising from an intrinsic linear Dresselhaus spin-orbit coupling in a single layer III-V diluted magnetic semiconductor. We investigate the transport properties and spin torque using the linear response theory, and we report here: (1) a strong correlation exists between the angular dependence of the torque and the anisotropy of the Fermi surface; (2) the spin orbit torque depends nonlinearly on the exchange coupling. Our findings suggest the possibility to tailor the spin orbit torque magnitude and angular dependence by structural design.
Probing hot electron transport across an epitaxial Schottky interface of SrRuO3/Nb:SrTiO3
Authors: Roy S. , Kamerbeek A. M. , Rana K. G. , Parui S. , Banerjee T.
Published: May 2013

SrRuO3 (SRO), a conducting transition metal oxide, is commonly used for engineering domains in BiFeO3. Oxide devices can be envisioned by integrating SRO with an oxide semiconductor as Nb doped SrTiO3 (Nb:STO). Using a three-terminal device configuration, we study vertical transport in a SRO/Nb:STO device at the nanoscale and find local differences in transport which originate due to the high selectivity of SRO growth on the underlying surface terminations in Nb:STO. This causes a change in the interface energy band characteristics and is explained by the differences in the spatial distribution of the interface-dipoles at the local Schottky interface.
19 μm quantum cascade infrared photodetectors
Authors: Zhai Shen-Qiang , Liu Jun-Qi , Wang Xue-Jiao , Zhuo Ning , Liu Feng-Qi , Wang Zhan-Guo , Liu Xi-Hui , Li Ning , Lu Wei
Published: May 2013

Two InP based InGaAs/InAlAs photovoltaic quantum cascade detectors operating at peak wavelengths of 18 μm and 19 μm using different electronic transport mechanisms are reported. A longitudinal optical phonon extraction stair combined with energy mini-steps are employed for electron transport, which suppresses the leakage current and results in high device resistance. Altogether, this quantum design leads to 15 K peak responsivity of 2.34 mA/W and Johnson noise limited detectivity of 1 × 1011 Jones at 18 μm.
Monolithic integration of light-emitting diodes and power metal-oxide-semiconductor channel high-electron-mobility transistors for light-emitting power integrated circuits in GaN on sapphire substrate
Authors: Li Z. , Waldron J. , Detchprohm T. , Wetzel C. , Karlicek R. F. , Chow T. P.
Published: May 2013

We report the demonstration of monolithically integrated light-emitting diodes (LEDs) and power metal-oxide-semiconductor channel high-electron-mobility transistors (HEMTs) in GaN. The structure comprised a direct epitaxial integration of layers typical for a GaN-based LED grown directly on top of the layers of a GaN-based HEMT. The layers were then fabricated into a serially connected pair of GaN LED and metal-oxide-semiconductor-gated 0.3 μm-channel HEMT by exposing the LED/HEMT epitaxial layers in selective area etching. The resulting monolithically integrated circuit shows a full gate voltage modulation of the light output power. This demonstrates compatibility of group-III nitride LED and HEMT processes.
Communication: State-to-state photodissociation study by the two-color VUV-VUV laser pump-probe time-slice velocity-map-imaging-photoion method
Authors: Gao Hong , Song Yu , Jackson William M. , Ng C. Y.
Published: May 2013

We demonstrate that combining two independently tunable vacuum ultraviolet (VUV) lasers and the time-slice velocity-map-imaging-photoion (VMI-PI) method allows the rovibronically state-selected photodissociation study of CO in the VUV region along with the state-selective detection of product C(3P0,1,2) using the VUV-UV (1+1′) resonance-enhanced photoionization and the VUV Rydberg autoionization methods. Both tunable VUV lasers are generated based on the two-photon resonance-enhanced four-wave mixing scheme using a pulsed rare gas jet as the nonlinear medium. The observed fine-structure distributions of product C(3PJ), J = 0, 1, and 2, are found to depend on the CO rovibronic state populated by VUV photoexcitation. The branching ratios for C(3P0) + O(3PJ): C(3P0) + O(1D2), C(3P1) + O(3PJ): C(3P1) + O(1D2), and C(3P2) + O(3PJ): C(3P2) + O(1D2), which were determined based on the time-slice VMI-PI measurements of C+ ions formed by J-state selective photoionization sampling of C(3P0,1,2), also reveal strong dependences on the spin-orbit state of C(3P0,1,2). By combining the measured branching ratios and fine-structure distributions of C(3P0,1,2), we have determined the correlated distributions of C(3P0,1,2) accompanying the formation of O(1D2) and O(3PJ) produced in the VUV photodissociation of CO. The success of this demonstration experiment shows that the VUV photodissociation pump-VUV photoionization probe method is promising for state-to-state photodissociation studies of many small molecules, which are relevant to planetary atmospheres as well as fundamental understanding of photodissociation dynamics.
Communication: Pressure fluctuations in isotropic solids and fluids
Authors: Wittmer J. P. , Xu H. , Polińska P. , Weysser F. , Baschnagel J.
Published: May 2013

Comparing isotropic solids and fluids at either imposed volume or pressure, we investigate various correlations of the instantaneous pressure and its ideal and excess contributions. Focusing on the compression modulus K, it is emphasized that the stress fluctuation representation of the elastic moduli may be obtained directly (without a microscopic displacement field) by comparing the stress fluctuations in conjugated ensembles. This is made manifest by computing the Rowlinson stress fluctuation expression Krow of the compression modulus for NPT-ensembles. It is shown theoretically and numerically that Krow|P = Pid(2 − Pid/K) with Pid being the ideal pressure contribution.
Length of stay variations between rural and urban patients with acute myeloid leukemia: a case-matched study
Authors: Heinz Sean J. , Milliken Sam
Published: May 2013

Background.
Keeping patients in hospital longer than medically necessary is costly and occupies resources that could be better utilised. If patients from regional areas remain in hospital longer because of logistical issues such as transport and accommodation, then there is an argument for establishing or expanding appropriate medical services for rural areas. However, if the length of stay (LOS) for rural and urban patients is similar, it could be surmised that current logistic services appropriately meet demand.

Methods.
This study reviews the cases of 40 patients with acute myeloid leukemia. This disease was selected as patients are generally required to travel to a metropolitan hospital for treatment, regardless of location. Twenty patients resided within the Sydney metropolitan area and 20 lived in rural New South Wales. Each of the 20 metropolitan patients were case-matched (1 : 1) with 20 rural patients with reference to sex, specific acute myeloid leukemia subtype (by World Health Organisation ICD-10 classification), and age.

Results.
Following statistical non-parametric (t-test) analysis, rural and urban medians were found to be very similar with a high t-value and small mean (urban median = 29, rural median = 29.5, t-value = 0.722, m = –0.95, s.d. = 15.236, two-tailed P = 0.789, 95% CI = –7.89, 5.99). This demonstrates that there was no statistically significant difference between mean LOS for rural or urban patients after case-matching, a conclusion supported by qualitative analysis of the data.

Conclusion.
Logistical issues are therefore unlikely to keep rural patients with AML in hospital beyond their immediate medical treatment.

What is known about this topic?
A United States-based study found that LOS in hospital for rural patients with human immunodeficiency virus was one-third longer than for urban patients across each of the 6 years analysed (from 1998 to 2003). However it was noted that after adjusting for covariates such as age and sex, differences between LOS for rural and urban residents were not of statistical significance.

What does this paper add?
This paper provides evidence that current services are utilised appropriately by demonstrating that rural and urban patients spend on average the same amount of time in hospital. Factors such as lack of transport or accommodation are therefore unlikely to keep rural patients in hospital beyond their immediate medical requirements. This paper adds to the limited research base within the Australian context.

What are the implications for practitioners?
It appears that support organisations adequately fulfil the needs of rural patients in the discharge process. LOS does not appear to correlate with the distance of residence from hospital. Practitioners should continue to support and encourage such support networks.
Polyoxometalate Insertion into Cu–pz Porous and Cu-bim Knighthead Coordination Polymers: [{Cu4(pz)5.5}{Cu2(2,2'-bim)3}0.5{P2W18O62}]·H2O
Authors: Xu Yanglei , Wu Jiang , Yu Kai , Su Zhanhua , Wang Chunxiao , Wang Chunmei , Zhou Baibin
Published: May 2013

The structure of crystallised {[Cu4(pz)5.5][Cu2(2,2′-bim)3]0.5[P2W18O62]}·H2O (1) (pz = pyrazine, bim = biimidazole) is reported. The crystal structure is characterised by cage-like pores [Cu8(pz)11]8+ of Cu ions linked through pz ligands. [P2W18O62]6– polyanions are capsulated into cage-like pores of [Cu8(pz)11]8+, forming ‘hamburger’-like units. Furthermore, the three-dimensional framework in 1 is achieved via copper-pyrazolate layers, binuclear copper-biimidazole subunits, and Dawson-type polyoxometalate clusters. The electrochemical properties of compound 1 were also studied in detail.
Stable Molecular Complex of Squaric Acid with 2-(Quinuclidinium)propionate
Authors: Dega-Szafran Zofia , Katrusiak Andrzej , Szafran Miroslaw
Published: May 2013

Squaric acid (3,4-dihydroxy-3-cyclobuten-1,2-dione, H2SQ) forms a complex with 2-(quinuclidinium)propionate (QNPr). In crystals, the molecules of H2SQ and zwitterions of QNPr are bridged by two strong non-equivalent O–H⋯O hydrogen bonds of 2.476(2) and 2.482(1) Å. The complex is investigated by X-ray diffraction, FTIR, and NMR techniques, and the results are supported by density functional theory calculations. The solid-state aggregation is consistent with the NMR results, recorded for an aqueous solution, and is also reproduced for the structure optimized at the B3LYP/6-311++G(d,p) level of theory. The calculated IR frequencies for the optimized structure have been used for the assignment of the experimental FTIR spectrum, where the broad absorption at ~2400 cm–1 corresponds to the short asymmetric OH⋯O bonds.
Systematic revision and reappraisal of the Kakaducarididae Bruce (Crustacea : Decapoda : Caridea) with the description of three new species of Leptopalaemon Bruce & Short
Authors: Short John W. , Humphrey Christopher L. , Page Timothy J.
Published: May 2013

The freshwater shrimp family Kakaducarididae Bruce, 1993 is revised and its familial status reappraised using morphological characters and the results of a complementary molecular study (Page et al. 2008). Based on combined morphological–molecular data, the Kakaducarididae is synonymised with the Palaemonidae Rafinesque, 1815 and the monotypic genus Kakaducaris Bruce, 1993 is synonymised with Leptopalaemon Bruce & Short, 1993. The Texan cave shrimp, Calathaemon holthuisi (Strenth, 1976), provisionally included in the Kakaducarididae by Bruce (1993), is re-assigned back to the Palaemonidae. Leptopalaemon is re-diagnosed and three new species, L. gibbosus, sp. nov., L. gudjangah, sp. nov. and L. magelensis, sp. nov., are described from the north-western edge of the Arnhem Land plateau/escarpment complex, Northern Territory, Australia. The two previously described species, L. gagadjui Bruce & Short, 1993 and L. glabrus (Bruce, 1993), comb. nov. are re-diagnosed. A key to the five presently recognised Leptopalaemon species is provided.