bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancing Speech Intelligibility: Interactions Among Context, Modality, Speech Style, and Masker
Authors: Van Engen Kristin J. , Phelps Jasmine E. B. , Smiljanic Rajka , Chandrasekaran Bharath
Published: April 2014

Purpose

The authors sought to investigate interactions among intelligibility-enhancing speech cues (i.e., semantic context, clearly produced speech, and visual information) across a range of masking conditions.

Method

Sentence recognition in noise was assessed for 29 normal-hearing listeners. Testing included semantically normal and anomalous sentences, conversational and clear speaking styles, auditory-only (AO) and audiovisual (AV) presentation modalities, and 4 different maskers (2-talker babble, 4-talker babble, 8-talker babble, and speech-shaped noise).

Results

Semantic context, clear speech, and visual input all improved intelligibility but also interacted with one another and with masking condition. Semantic context was beneficial across all maskers in AV conditions but only in speech-shaped noise in AO conditions. Clear speech provided the most benefit for AV speech with semantically anomalous targets. Finally, listeners were better able to take advantage of visual information for meaningful versus anomalous sentences and for clear versus conversational speech.

Conclusion

Because intelligibility-enhancing cues influence each other and depend on masking condition, multiple maskers and enhancement cues should be used to accurately assess individuals' speech-in-noise perception.
Exclusive OR circuit for optical signals using combined technology of photonics and electronics
Authors: Takiguchi K.
Published: April 2014

A novel exclusive OR circuit with a simple configuration for binary signals, which is composed of a balanced photodetector and an intensity modulator, is proposed. Two input optical signals into the balanced detector produce an electrical signal to drive the modulator. The modulator outputs an optical exclusive OR signal of the two input optical signals. The primary operation is demonstrated by evaluating the circuit with 10 Gbit/s signals.
Collaborative demonstration of optical‐layer service‐differentiation and load‐balancing in intelligent optical network
Authors: Guo Junhu , Xu Chongfeng , Li Hui , Ji Yuefeng , Zhao Yongli , Zhang Jie
Published: April 2014

Optical‐layer service‐differentiation (Diff‐Serv) and load‐balancing abilities are achieved by collaborative implementation of OpenFlow (OF) switches and intelligent optical adapt unit (IOAU) prototypes. Experimental demonstration shows that by adapting OF‐switches as edge routers, optical‐layer Diff‐Serv can be realised by mapping services of different priorities into different lightpaths. Thus, optical fibre is service‐aware rather than merely a blind pipe. In addition, the load‐balancing function of the IOAU can be used to gain reasonable wide area network (WAN) link utilisation. By combining these two abilities, many interesting experimental scenarios and meaningful upper layer applications can be devised.
Real‐time load disaggregation algorithm using particle‐based distribution truncation with state occupancy model
Authors: Wong Yung Fei , Drummond T. , Şekercioğlu Y.A.
Published: April 2014

A new particle‐based distribution truncation method with a duration‐dependent hidden semi‐Markov model for non‐intrusive appliance load monitoring is presented. Unlike earlier works, the approach keeps track of a set of states without prematurely pruning away intermediately ranked states. It also enables appliance state duration characteristics to be incorporated in a straightforward manner. Results show that the approach outperforms both the Viterbi algorithm and conventional particle‐filtering methods.
Suppression of self‐pulsing in Yb fibre lasers coupled with external Fabry‐Pérot cavity
Authors: Lee J.S. , Kim J.W.
Published: April 2014

A simple technique to suppress self‐pulsing behaviour in a fibre laser employing a two‐mirror Fabry‐Pérot external feedback cavity is reported. Feedback provided by the external Fabry‐Pérot cavity enforces the fibre laser to oscillate in the selected longitudinal modes, resulting in robust laser operation without self‐pulsing. This technique has been successfully applied to a double‐clad Yb fibre laser, yielding a stable continuous‐wave output of up to 9.8 W at 1050 nm. The advantages of this technique and the prospects of further improvement are discussed.
Fast motion estimation for HEVC with directional search
Authors: Yang Shih‐Hsuan , Jiang Jia‐Ze , Yang Hsien‐Jie
Published: April 2014

The new high‐efficiency video coding (HEVC) standard is becoming popular owing to its excellent rate‐distortion performance especially for emerging high‐resolution applications. In HEVC more flexible coding options and partitioning types are provided for prediction units (PUs) and consequently motion estimation (ME) is more involved than previous video‐coding standards. The existing fast ME algorithms, including the test zone search provided in the HEVC reference software, cannot generate high‐quality video with reasonable computational complexity. A new fast integer‐pixel ME algorithm for HEVC is presented. Starting with the initial motion vector obtained by the advanced motion vector prediction, the proposed directional search extends three search paths from the initial motion vector and considers the highly probable horizontal or vertical movement. Compared to the test zone search, the proposed method saves, on average, 60% time in integer‐pixel ME with negligible rate‐distortion degradation.
Analysis of electromagnetic interference under different types of near‐field environments
Authors: Jeon Sangbong , Park Seungkeun , Kwon Jong‐Hwa , Kim Dongho
Published: April 2014

The effect of different interferences on a victim wireless device in electric and magnetic near‐field (NF) environments is investigated. Using a four‐port transverse electromagnetic (TEM) cell, those NF environments are generated by varying wave impedance in the cell, which can be done by applying an external interference signal. As a measure of interference, the bit error rate performance of the victim device is chosen, which shows both NF environments have significant but distinctive interference effects on the victim device.
High-pressure cell for neutron diffraction with in situ pressure control at cryogenic temperatures
Authors: Jacobsen Matthew K. , Ridley Christopher J. , Bocian Artur , Kirichek Oleg , Manuel Pascal , Khalyavin Dmitry , Azuma Masaki , Attfield J. Paul , Kamenev Konstantin V.
Published: April 2014

Pressure generation at cryogenic temperatures presents a problem for a wide array of experimental techniques, particularly neutron studies due to the volume of sample required. We present a novel, compact pressure cell with a large sample volume in which load is generated by a bellow. Using a supply of helium gas up to a pressure of 350 bar, a load of up to 78 kN is generated with leak-free operation. In addition, special fiber ports added to the cryogenic center stick allow for in situ pressure determination using the ruby pressure standard. Mechanical stability was assessed using finite element analysis and the dimensions of the cell have been optimized for use with standard cryogenic equipment. Load testing and on-line experiments using NaCl and BiNiO3 have been done at the WISH instrument of the ISIS pulsed neutron source to verify performance.
Gedanken densities and exact constraints in density functional theory
Authors: Perdew John P. , Ruzsinszky Adrienn , Sun Jianwei , Burke Kieron
Published: April 2014

Approximations to the exact density functional for the exchange-correlation energy of a many-electron ground state can be constructed by satisfying constraints that are universal, i.e., valid for all electron densities. Gedanken densities are designed for the purpose of this construction, but need not be realistic. The uniform electron gas is an old gedanken density. Here, we propose a spherical two-electron gedanken density in which the dimensionless density gradient can be an arbitrary positive constant wherever the density is non-zero. The Lieb-Oxford lower bound on the exchange energy can be satisfied within a generalized gradient approximation (GGA) by bounding its enhancement factor or simplest GGA exchange-energy density. This enhancement-factor bound is well known to be sufficient, but our gedanken density shows that it is also necessary. The conventional exact exchange-energy density satisfies no such local bound, but energy densities are not unique, and the simplest GGA exchange-energy density is not an approximation to it. We further derive a strongly and optimally tightened bound on the exchange enhancement factor of a two-electron density, which is satisfied by the local density approximation but is violated by all published GGA's or meta-GGA’s. Finally, some consequences of the non-uniform density-scaling behavior for the asymptotics of the exchange enhancement factor of a GGA or meta-GGA are given.
Repulsively driven frequency-increased-generators for durable energy harvesting from ultra-low frequency vibration
Authors: Tang Qiaochu , Yang Yongliang , Li Xinxin
Published: April 2014

An electromagnetic kinetic energy harvester has been developed, which can convert ultra-low-frequency motion and vibration energy into electrical power. This harvester employs a two-stage vibratory structure to collect low-frequency kinetic energy and effectively transfer it into electric power by using a pair of high-frequency resonant generators. Non-contact magnetic repulsive force is herein utilized for the 1st-stage sliding vibrator to drive the 2nd-stage resonators into frequency-up-conversion resonance. The non-contact actuation is helpful for durable and long-life working of the device. The prototyped device is fabricated and the design is well confirmed by experimental test. The harvester can be well operated at the frequency as low as 0.25 Hz. Under driving acceleration of 1 g at 0.5 Hz, the miniaturized harvester can generate a peak power of 4.42 mW and an average power of 158 μW.
Onset of simple liquid behaviour in modified water models
Authors: Prasad Saurav , Chakravarty Charusita
Published: April 2014

The transition to simple liquid behaviour is studied in a set of modified hybrid water models where the potential energy contribution of the Lennard-Jones dispersion-repulsion contribution is progressively enhanced relative to the electrostatic contribution. Characteristics of simple liquid behaviour that indicate the extent to which a given system can be mapped onto an inverse power law fluid are examined, including configurational energy-virial correlations, functional form of temperature dependence of the excess entropy along isochores, and thermodynamic and excess entropy scaling of diffusivities. As the Lennard-Jones contribution to the potential energy function increases, the strength of the configurational energy-virial correlations increases. The Rosenfeld-Tarazona temperature dependence of the excess entropy is found to hold for the range of state points studied here for all the hybrid models, regardless of the degree of correlating character. Thermodynamic scaling is found to hold for weakly polar fluids with a moderate degree of energy-virial correlations. Rosenfeld-scaling of transport properties is found not to be necessarily linked with the strength of energy-virial correlations but may hold for systems with poor thermodynamic scaling if diffusivities and excess entropies show correlated departures from the isomorph-invariant behaviour characteristic of approximate inverse power law fluids. The state-point dependence of the configurational energy-virial correlation coefficient and the implications for thermodynamic and excess entropy scalings are considered.
A robust and well shielded thermal conductivity device for low temperature measurements
Authors: Toews W. H. , Hill R. W.
Published: April 2014

We present a compact mechanically robust thermal conductivity measurement apparatus for measurements at low temperatures (<1 K) and high magnetic fields on small high-purity single crystal samples. A high-conductivity copper box is used to enclose the sample and all the components. The box provides protection for the thermometers, heater, and most importantly the sample increasing the portability of the mount. In addition to physical protection, the copper box is also effective at shielding radio frequency electromagnetic interference and thermal radiation, which is essential for low temperature measurements. A printed circuit board in conjunction with a braided ribbon cable is used to organize the delicate wiring and provide mechanical robustness.
Real-time x-ray scattering study of the initial growth of organic crystals on polymer brushes
Authors: An Sung Yup , Ahn Kwangseok , Kim Doris Yangsoo , Lee Hyun-Hwi , Cho Jeong Ho , Lee Dong Ryeol
Published: April 2014

We studied the early-stage growth structures of pentacene organic crystals grown on polymer brushes using real-time x-ray scattering techniques. In situ x-ray reflectivity and atomic force microscopy analyses revealed that at temperatures close to the glass transition temperature of polymer brush, the pentacene overlayer on a polymer brush film showed incomplete condensation and 3D island structures from the first monolayer. A growth model based on these observations was used to quantitatively analyze the real-time anti-Bragg x-ray scattering intensities measured during pentacene growth to obtain the time-dependent layer coverage of the individual pentacene monolayers. The extracted total coverage confirmed significant desorption and incomplete condensation in the pentacene films deposited on the polymer brushes. These effects are ascribed to the change in the surface viscoelasticity of the polymer brushes around the glass transition temperature.
Mechanism of oil detachment from hybrid hydrophobic and hydrophilic surface in aqueous solution
Authors: Zhang Peili , Xu Zhen , Liu Qian , Yuan Shiling
Published: April 2014

In this paper, the detachment mechanism of alkane molecules from one hybrid hydrophobic and hydrophilic solid surface was studied by molecular dynamics simulation. First, some alkyl chains were linked through C–O bonds with silica surface to get one half-hydrophobic one, and the other half-hydrophilic area was still same as silica surface, thus one modified hybrid hydrophobic and hydrophilic silica surface was constructed. Second, some alkane molecules were adsorbed on the hybrid surface to get one whole hydrophobic oil layer, and the detachment mechanism of alkane molecules on the surface was discussed in aqueous solution using molecular dynamics. The simulated results showed that the key to the detachment of alkane molecules is the formation of water channel in oil layer between water phase and solid surface. In the detachment process, water molecules can penetrate oil layer to the silica surface through the strong H-bonding interaction among water molecules in water channel, and soon these molecules can form a gel layer along the silica surface by fast diffusion under the H-bonding interaction and electrostatic interaction between water molecules and silica surface. At last, the half-hydrophilic area on hybrid surface becomes hydrophilic again after the oil layer's detachment, and alkane molecules aggregate on the modified surface linked the alkyl chains. For the hybrid surface, some of alkane molecules insert into the interstice among the alkyl chains, and thus the oil drop cannot be dispatched thoroughly from the surface linked alkyl chains in aqueous solution. Our results showed that the detachment mechanism of oil from hybrid surface is different, compared with the whole pure hydrophilic surface.
Mesoscale properties of clay aggregates from potential of mean force representation of interactions between nanoplatelets
Authors: Ebrahimi Davoud , Whittle Andrew J. , Pellenq Roland J.-M.
Published: April 2014

Face-to-face and edge-to-edge free energy interactions of Wyoming Na-montmorillonite platelets were studied by calculating potential of mean force along their center to center reaction coordinate using explicit solvent (i.e., water) molecular dynamics and free energy perturbation methods. Using a series of configurations, the Gay-Berne potential was parametrized and used to examine the meso-scale aggregation and properties of platelets that are initially random oriented under isothermal-isobaric conditions. Aggregates of clay were defined by geometrical analysis of face-to-face proximity of platelets with size distribution described by a log-normal function. The isotropy of the microstructure was assessed by computing a scalar order parameter. The number of platelets per aggregate and anisotropy of the microstructure both increases with platelet plan area. The system becomes more ordered and aggregate size increases with increasing pressure until maximum ordered state at confining pressure of 50 atm. Further increase of pressure slides platelets relative to each other leading to smaller aggregate size. The results show aggregate size of (3–8) platelets for sodium-smectite in agreement with experiments (3–10). The geometrical arrangement of aggregates affects mechanical properties of the system. The elastic properties of the meso-scale aggregate assembly are reported and compared with nanoindentation experiments. It is found that the elastic properties at this scale are close to the cubic systems. The elastic stiffness and anisotropy of the assembly increases with the size of the platelets and the level of external pressure.
The intensity of forbidden torsional transitions in electronic spectra of molecules with a 6-fold barrier: Application to toluenes
Authors: Virgo Edwina A. , Gascooke Jason R. , Lawrance Warren D.
Published: April 2014

Franck-Condon forbidden transitions involving methyl rotor modes are seen in the S1 ← S0 spectrum of toluene and toluene-like molecules. The strongest of these rotor transitions (m″ = 1 → m′ = 2, m″ = 0 → m′ = 3a1″, and m″ = 1 → m′ = 4) have been shown by Walker et al. [J. Chem. Phys. 102, 8718 (1995)] to gain intensity through the rotor equivalent of the Herzberg-Teller mechanism. Despite the m″ = 0 → m′ = 3a2″ transition being forbidden in this formalism, it is sporadically observed. We show that this transition derives oscillator strength from incomplete mixing of the −3 and +3 free rotor basis states due to torsion-rotation coupling. Calculations demonstrate that this mechanism quantitatively explains the intensities observed for toluene, including their temperature dependence. Because the −3/+3 mixing is weakest when the torsional barrier height, V6, is small, the m″ = 0 → m′ = 3a2″ transition increases in intensity as |V6| decreases. The temperature and |V6| dependencies explain why reports of the 0 → 3a2″ transition have been intermittent. The torsion-rotation coupling mechanism is predicted to also give significant intensity to m = 0 → m = 6a2′ transitions relative to m = 0 → m = 6a1′ transitions and to provide intensity to 0 → 3a2 transitions in molecules with a 3-fold (V3) barrier. Comparison between the observed and calculated rotor band contours shows, unexpectedly, that the 3a1″ constants fail to predict the 3a2″ contour despite these two states being derived from the same free rotor basis states. Comparison with the observed spectrum also reveals differences in the separation of the S1 3a2″ and 3a1″ levels. The V6 value determined from analysis of the high resolution, rotationally resolved m″ = 0 → m′ = 3a1″ spectrum overestimates the 3a2″–3a1″ separation by 0.6 cm−1. We postulate that this may be due to torsion-vibration coupling. The observed toluene torsion-rotation contours have been modeled to provide estimates of the rotational constants for several of the torsional states.
Direct numerical simulations of transition and turbulence in smooth-walled Stokes boundary layer
Authors: Ozdemir Celalettin E. , Hsu Tian-Jian , Balachandar S.
Published: April 2014

Stokes boundary layer (SBL) is a time-periodic canonical flow that has several environmental, industrial, and physiological applications. Understanding the hydrodynamic instability and turbulence in SBL, therefore, will shed more light on the nature of such flows. Unlike its steady counterpart, the flow in a SBL varies both in space and time, which makes hydrodynamic instability and transition from laminar to turbulent state highly complicated. In this study, we utilized direct numerical simulations (DNS) to understand the characteristics of hydrodynamic instability, the transition from laminar to turbulent state, and the characteristics of intermittent turbulence in a smooth SBL for $Re_\Delta$ReΔ in the range of 500–1000. Simulation results show that nonlinear growth plays a critical role on the instability at $Re_\Delta = 500$ReΔ=500 and 600. However, the nonlinear growth does not warrant sustainable transition to turbulence and the outcome is highly dependent on the amplitude and spatial distribution of the initial velocity disturbance in addition to $Re_\Delta $ReΔ. Simulation results at $Re_\Delta = 500$ReΔ=500 confirm that instability and subsequent transitional flow will eventually decay. At $Re_\Delta = 600$ReΔ=600 nonlinear growth recurs at every modulation period but such transition does not evolve into fully developed turbulence at any time in the modulation cycle. At $Re_\Delta = 700$ReΔ=700, the flow shows features of fully developed turbulence during some modulation periods and the transitional character of $Re_\Delta = 600$ReΔ=600 at the remaining. Therefore, we conclude that flow in the range of $Re_\Delta = 600$ReΔ=600–700 is to be classified as self-sustaining transitional flow. For higher Reynolds number the flow indeed exhibits features of fully developed boundary layer turbulence for a portion of the wave period, which is known as the intermittently turbulent regime in the literature.
Flame surface statistics of constant-pressure turbulent expanding premixed flames
Authors: Saha Abhishek , Chaudhuri Swetaprovo , Law Chung K.
Published: April 2014

In this paper we investigate the local flame surface statistics of constant-pressure turbulent expanding flames. First the statistics of local length ratio is experimentally determined from high-speed planar Mie scattering images of spherically expanding flames, with the length ratio on the measurement plane, at predefined equiangular sectors, defined as the ratio of the actual flame length to the length of a circular-arc of radius equal to the average radius of the flame. Assuming isotropic distribution of such flame segments we then convolute suitable forms of the length-ratio probability distribution functions (pdfs) to arrive at the corresponding area-ratio pdfs. It is found that both the length ratio and area ratio pdfs are near log-normally distributed and shows self-similar behavior with increasing radius. Near log-normality and rather intermittent behavior of the flame-length ratio suggests similarity with dissipation rate quantities which stimulates multifractal analysis.
Quantification of pore size distribution using diffusion NMR: Experimental design and physical insights
Authors: Katz Yaniv , Nevo Uri
Published: April 2014

Pulsed field gradient (PFG) diffusion NMR experiments are sensitive to restricted diffusion within porous media and can thus reveal essential microstructural information about the confining geometry. Optimal design methods of inverse problems are designed to select preferred experimental settings to improve parameter estimation quality. However, in pore size distribution (PSD) estimation using NMR methods as in other ill-posed problems, optimal design strategies and criteria are scarce. We formulate here a new optimization framework for ill-posed problems. This framework is suitable for optimizing PFG experiments for probing geometries that are solvable by the Multiple Correlation Function approach. The framework is based on a heuristic methodology designed to select experimental sets which balance between lowering the inherent ill-posedness and increasing the NMR signal intensity. This method also selects favorable discrete pore sizes used for PSD estimation. Numerical simulations performed demonstrate that using this framework greatly improves the sensitivity of PFG experimental sets to the pores’ sizes. The optimization also sheds light on significant features of the preferred experimental sets. Increasing the gradient strength and varying multiple experimental parameters is found to be preferable for reducing the ill-posedness. We further evaluate the amount of pore size information that can be obtained by wisely selecting the duration of the diffusion and mixing times. Finally, we discuss the ramification of using single PFG or double PFG sequences for PSD estimation. In conclusion, the above optimization method can serve as a useful tool for experimenters interested in quantifying PSDs of different specimens. Moreover, the applicability of the suggested optimization framework extends far beyond the field of PSD estimation in diffusion NMR, and reaches design of sampling schemes of other ill-posed problems.
Finite barrier corrections to the PGH solution of Kramers' turnover theory
Authors: Pollak Eli , Ianconescu Reuven
Published: April 2014

Kramers [Physica 7, 284 (1940)], in his seminal paper, derived expressions for the rate of crossing a barrier in the underdamped limit of weak friction and the moderate to strong friction limit. The challenge of obtaining a uniform expression for the rate, valid for all damping strengths is known as Kramers turnover theory. Two different solutions have been presented. Mel'nikov and Meshkov [J. Chem. Phys. 85, 1018 (1986)] (MM) considered the motion of the particle, treating the friction as a perturbation parameter. Pollak, Grabert, and Hänggi [J. Chem. Phys. 91, 4073 (1989)] (PGH), considered the motion along the unstable mode which is separable from the bath in the barrier region. In practice, the two theories differ in the way an energy loss parameter is estimated. In this paper, we show that previous numerical attempts to resolve the quality of the two approaches were incomplete and that at least for a cubic potential with Ohmic friction, the quality of agreement of both expressions with numerical simulation is similar over a large range of friction strengths and temperatures. Mel'nikov [Phys. Rev. E 48, 3271 (1993)], in a later paper, improved his theory by introducing finite barrier corrections. In this paper we note that previous numerical tests of the finite barrier corrections were also incomplete. They did not employ the exact rate expression, but a harmonic approximation to it. The central part of this paper, is to include finite barrier corrections also within the PGH formalism. Tests on a cubic potential demonstrate that finite barrier corrections significantly improve the agreement of both MM and PGH theories when compared with numerical simulations.
Implementation and analysis of an innovative digital charge amplifier for hysteresis reduction in piezoelectric stack actuators
Authors: Bazghaleh Mohsen , Grainger Steven , Cazzolato Ben , Lu Tien-Fu , Oskouei Reza
Published: April 2014

Smart actuators are the key components in a variety of nanopositioning applications, such as scanning probe microscopes and atomic force microscopes. Piezoelectric actuators are the most common smart actuators due to their high resolution, low power consumption, and wide operating frequency but they suffer hysteresis which affects linearity. In this paper, an innovative digital charge amplifier is presented to reduce hysteresis in piezoelectric stack actuators. Compared to traditional analog charge drives, experimental results show that the piezoelectric stack actuator driven by the digital charge amplifier has less hysteresis. It is also shown that the voltage drop of the digital charge amplifier is significantly less than the voltage drop of conventional analog charge amplifiers.
Numerical and experimental investigations on the interaction of light wire-array Z-pinches with embedded heavy foam converters
Authors: Xiao Delong , Ding Ning , Ye Fan , Ning Jiamin , Hu Qingyuan , Chen Faxin , Qin Yi , Xu Rongkun , Li Zhenghong , Sun Shunkai
Published: April 2014

The interaction of a light tungsten wire-array Z-pinch with an embedded heavy foam converter, whose mass ratio is typically less than 0.16, is numerically analyzed and experimentally investigated on the 1.3 MA “QiangGuang I” facility. Computational results show that this implosion process can be divided into three stages: acceleration of the tungsten wire-array plasma, collision, and stagnation. The tungsten plasma is accelerated to a high speed by the J × B force and interacts weakly with the foam plasma in the first stage. Strong energy conversions take place in the second collision stage. When the high speed tungsten plasma impacts on the foam converter, the plasma is thermalized and a radial radiation peak is produced. Meanwhile, a shock wave is generated due to the collision. After the shock rebounds from the axis and meets the W/Foam boundary, the plasma stagnates and the second radial radiation peak appears. The collision and stagnation processes were observed and the two-peak radial radiation pulse was produced in experiments. Increasing the wire-array radius from 4 mm to 6 mm, the kinetic energy of the tungsten plasma is increased, causing a stronger thermalization and generating a higher first radiation peak. Experimental results also showed a higher ratio of the first peak to the second peak in the case of larger wire-array radius. If we add a thin CH film cover onto the surface of the embedded foam converter, the first radiation peak will be hardly changed, because the acceleration of the tungsten plasma is not evidently affected by the film cover. However, the second radiation peak decreases remarkably due to the large load mass and the corresponding weak compression.
Surface forces: Surface roughness in theory and experiment
Authors: Parsons Drew F. , Walsh Rick B. , Craig Vincent S. J.
Published: April 2014

A method of incorporating surface roughness into theoretical calculations of surface forces is presented. The model contains two chief elements. First, surface roughness is represented as a probability distribution of surface heights around an average surface height. A roughness-averaged force is determined by taking an average of the classic flat-surface force, weighing all possible separation distances against the probability distributions of surface heights. Second the model adds a repulsive contact force due to the elastic contact of asperities. We derive a simple analytic expression for the contact force. The general impact of roughness is to amplify the long range behaviour of noncontact (DLVO) forces. The impact of the elastic contact force is to provide a repulsive wall which is felt at a separation between surfaces that scales with the root-mean-square (RMS) roughness of the surfaces. The model therefore provides a means of distinguishing between “true zero,” where the separation between the average centres of each surface is zero, and “apparent zero,” defined by the onset of the repulsive contact wall. A normal distribution may be assumed for the surface probability distribution, characterised by the RMS roughness measured by atomic force microscopy (AFM). Alternatively the probability distribution may be defined by the histogram of heights measured by AFM. Both methods of treating surface roughness are compared against the classic smooth surface calculation and experimental AFM measurement.
Electric double layer for a size-asymmetric electrolyte around a spherical colloid
Authors: Kim Eun-Young , Kim Soon-Chul
Published: April 2014

We have studied the structure of a size-asymmetric electrolyte on charged colloids by a density functional perturbation theory. The hard-sphere contribution has been approximated as the direct pair correlation function with the coupling parameter, whereas the electronic contribution has been approximated as the mean-spherical approximation in the bulk phase. The calculated results for the ionic density distributions and mean electrostatic potentials are in very good agreement with the computer simulations over a wide range of colloid sizes and electrolyte concentrations. The present theory provides better structural results than the hypernetted-chain equation based on the mean spherical approximation. We have confirmed that the overcharging appears when the counterions are larger than the coions. The overcharging disappears everywhere when the electrostatic repulsion becomes strong enough, while the charge reversal is observed when the coions are larger than the counterions, and the reversal effect appears for a size-asymmetric electrolyte at high surface charge densities. The charge reversal occurs even for the point of zero charge, mainly due to the depletion force between two ions. The present theory is able to provide interesting insights about the charge reversal and overcharging phenomena occurring at the interface.
Atomic shell structure from the Single-Exponential Decay Detector
Authors: de Silva Piotr , Korchowiec Jacek , Wesolowski Tomasz A.
Published: April 2014

The density of atomic systems is analysed via the Single-Exponential Decay Detector (SEDD). SEDD is a scalar field designed to explore mathematical, rather than physical, properties of electron density. Nevertheless, it has been shown that SEDD can serve as a descriptor of bonding patterns in molecules as well as an indicator of atomic shells [P. de Silva, J. Korchowiec, and T. A. Wesolowski, ChemPhysChem 13, 3462 (2012)]. In this work, a more detailed analysis of atomic shells is done for atoms in the Li–Xe series. Shell populations based on SEDD agree with the Aufbau principle even better than those obtained from the Electron Localization Function, which is a popular indicator of electron localization. A link between SEDD and the local wave vector is given, which provides a physical interpretation of SEDD.
Superposition of super-integrable pseudo-Euclidean potentials in N = 2 with a fundamental constant of motion of arbitrary order in the momenta
Authors: Campoamor-Stursberg R.
Published: April 2014

It is shown that for any \documentclass[12pt]{minimal}\begin{document}$\alpha ,\beta \in \mathbb {R}$\end{document}α,β∈R and \documentclass[12pt]{minimal}\begin{document}$k\in \mathbb {Z}$\end{document}k∈Z, the Hamiltonian \documentclass[12pt]{minimal}\begin{document}$H_{k}=p_{1}p_{2}\break-\alpha q_{2}^{(2k+1)}q_{1}^{(-2k-3)}-\frac{\beta }{2} q_{2}^{k}q_{1}^{(-k-2)}$\end{document}Hk=p1p2−αq2(2k+1)q1(−2k−3)−β2q2kq1(−k−2) is super-integrable, possessing fundamental constants of motion of degrees 2 and 2k + 2 in the momenta.
Intermittent dynamics and logarithmic domain growth during the spinodal decomposition of a glass-forming liquid
Authors: Testard Vincent , Berthier Ludovic , Kob Walter
Published: April 2014

We use large-scale molecular dynamics simulations of a simple glass-forming system to investigate how its liquid-gas phase separation kinetics depends on temperature. A shallow quench leads to a fully demixed liquid-gas system whereas a deep quench makes the dense phase undergo a glass transition and become an amorphous solid. This glass has a gel-like bicontinuous structure that evolves very slowly with time and becomes fully arrested in the limit where thermal fluctuations become negligible. We show that the phase separation kinetics changes qualitatively with temperature, the microscopic dynamics evolving from a surface tension-driven diffusive motion at high temperature to a strongly intermittent, heterogeneous, and thermally activated dynamics at low temperature, with a logarithmically slow growth of the typical domain size. These results elucidate the microscopic mechanisms underlying a specific class of viscoelastic phase separation.
Communication: Conical intersections between vibrationally adiabatic surfaces in methanol
Authors: Dawadi Mahesh B. , Perry David S.
Published: April 2014

A set of seven conical intersections (CI’s) in methanol between vibrationally adiabatic surfaces is reported. The intersecting surfaces represent the energies of the two asymmetric CH stretch vibrations regarded as adiabatic functions of the torsion and COH bend angles. The ab initio data are well described by an extended Zwanziger and Grant (E ⊗ e) model [J. W. Zwanziger and E. R. Grant, J. Chem. Phys. 87, 2954 (1987)] that might also be regarded as an extension of the XHL model [L.-H. Xu, J. T. Hougen, and R. M. Lees, J. Mol. Spectrosc. 293–294, 38 (2013)]. The CI's illuminate the role of geometric phase in methanol. More generally, they suggest the importance of energy transfer processes localized near the CI’s.
Alternative current conduction mechanisms of organic-inorganic compound [N(CH3)3H]2ZnCl4
Authors: Ben Bechir M. , Karoui K. , Tabellout M. , Guidara K. , Ben Rhaiem A.
Published: April 2014

[N(CH3)3H]2ZnCl4 has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH3)3H]2ZnCl4 hybrid compound is crystallized at room temperature (T ≈ 300 K) in the orthorhombic system with Pnma space group. Five phase transitions (T1 = 255 K, T2 = 282 K, T3 = 302 K, T4 = 320 K, and T5 = 346 K) have been proved by DSC measurements. The electrical technique was measured in the 10−1-107 Hz frequency range and 233–363 K temperature interval. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC electrical conduction in [N(CH3)3H]2ZnCl4 is analyzed by different processes, which can be attributed to several models: the correlated barrier hopping model in phase I, the overlapping large polaron tunneling model in phase II, the quantum mechanical tunneling model in phase IV, and the non-overlapping small polaron tunneling model in phases III, V, and VI. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.
Density functional theory study of chemical sensing on surfaces of single-layer MoS2 and graphene
Authors: Mehmood F. , Pachter R.
Published: April 2014

In this work, density functional theory (DFT) calculations have been used to investigate chemical sensing on surfaces of single-layer MoS2 and graphene, considering the adsorption of the chemical compounds triethylamine, acetone, tetrahydrofuran, methanol, 2,4,6-trinitrotoluene, o-nitrotoluene, o-dichlorobenzene, and 1,5-dicholoropentane. Physisorption of the adsorbates on free-standing surfaces was analyzed in detail for optimized material structures, considering various possible adsorption sites. Similar adsorption characteristics for the two surface types were demonstrated, where inclusion of a correction to the DFT functional for London dispersion was shown to be important to capture interactions at the interface of molecular adsorbate and surface. Charge transfer analyses for adsorbed free-standing surfaces generally demonstrated very small effects. However, charge transfer upon inclusion of the underlying SiO2 substrate rationalized experimental observations for some of the adsorbates considered. A larger intrinsic response for the electron-donor triethylamine adsorbed on MoS2 as compared to graphene was demonstrated, which may assist in devising chemical sensors for improved sensitivity.
Vertically integrated metal-clad/silicon dioxide-shell microtube arrays for high-spatial-resolution light stimuli in saline
Authors: Sakata M. , Nakamura T. , Matsuo T. , Goryu A. , Ishida M. , Kawano T.
Published: April 2014

Microdevices composed of integrated microscale light source arrays are powerful tools in optogenetic applications. Herein, we prepared vertically aligned 3-μm inner diameter silicon dioxide (SiO2) tube-based optical light waveguide arrays. To increase the locality of the light stimuli through the tube, we also fabricated metal-cladded SiO2 tubes using iridium (Ir). After filling the tube with a saline solution, the saline-core/Ir-clad/SiO2-shell waveguide exhibited light stimuli without spreading. With a 532-nm wavelength, the half-power width of the light intensity measured 10 μm above the tube tip was 3 μm, while that of the saline/SiO2-shell waveguide was 9.6 μm, which was more than three times wider. Such high-spatial-resolution optical light stimuli will offer a new class of optogenetic applications, including light stimuli for specific regions of a neuron (e.g., axons or dendrites).
Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air
Authors: Che Xueke , Nie Wansheng , Shao Tao , Tian Xihui , Hou Zhiyong , He Haobo , Zhou Penghui , Zhou Siyin , Yang Chao
Published: April 2014

Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.
Morphology and structure evolution of tin-doped indium oxide thin films deposited by radio-frequency magnetron sputtering: The role of the sputtering atmosphere
Authors: Nie Man , Mete Tayfun , Ellmer Klaus
Published: April 2014

The microstructure and morphology evolution of tin-doped indium oxide (ITO) thin films deposited by radio-frequency magnetron sputtering in different sputtering atmospheres were investigated by X-ray diffraction, X-ray reflectivity, and atomic force microscopy. The surface roughness w increases with increasing film thickness df, and exhibits a power law behavior w ∼ dfβ. The roughness decreases with increasing O2 flow, while it increases with increasing H2 flow. The growth exponent β is found to be 0.35, 0.75, and 0.98 for depositions in Ar/10%O2, pure Ar, and Ar/10%H2 atmospheres, respectively. The correlation length ξ increases with film thickness also with a power law according to ξ ∼ dfz with exponents z = 0.36, 0.44, and 0.57 for these three different gas atmospheres, respectively. A combination of local and non-local growth modes in 2 + 1 dimensions is discussed for the ITO growth in this work.
Study of the shape of an optical window in a super-resolution state by electromagnetic-thermal coupled simulation: Effects of melting of an active layer in an optical disc
Authors: Sano Haruyuki , Shima Takayuki , Kuwahara Masashi , Fujita Yoshiya , Uchiyama Munehisa , Aono Yoshiyuki
Published: April 2014

We performed a multi-physics simulation for the propagation of electromagnetic waves and heat conduction in a super-resolution optical disc that includes an active layer of InSb. Because the change in the optical constant of InSb due to the phase transition is taken into account, the melting of the active layer can be realistically simulated in our calculation. It was found that in the case of an incident light power (P) of 2 mW, a profile of the electric field intensity transmitted through the InSb layer has an asymmetric shape with a narrow peak. This beam-narrowing was suggested to be an essential mechanism of the super-resolution, because a narrower light beam allows the detection of a smaller pit structure than the optical diffraction limit. This beam-narrowing was found to be originating from a small molten region produced in the InSb layer, which works as a mask for light exposure.
Probing high-frequency dynamics of a single ferromagnetic flake using a broadband micro-loop permeameter
Authors: Neige J. , Ledieu M. , Le Bihan T. , Estrade E. , Adenot-Engelvin A.-L. , Belleville P. , Vukadinovic N.
Published: April 2014

The permeability spectra of single NiFeMo flakes have been measured within the frequency range 10 MHz–20 GHz using a high-sensitivity micro-permeameter, which we have developed. It is shown that the permeability spectrum of single flakes exhibits two resonance lines at 45 MHz and 2.8 GHz and resembles the one of flake-shaped particle composites. These two excitations exist whatever the geometrical irregularity of the flake. In addition, a comparison with the permeability spectrum of a square-shaped element suggests that the shouldering appearing in the low-frequency side of the high-frequency resonance could be attributed to domain wall resonances.
Inner surface flash-over of insulator of low-inductance high-voltage self-breakdown gas switch and its application
Authors: Zhang Hong-bo , Liu Jin-liang
Published: April 2014

In this paper, the inner surface flash-over of high-voltage self-breakdown switch, which is used as a main switch of pulse modulator, is analyzed in theory by employing the method of distributed element equivalent circuit. Moreover, the field distortion of the switch is simulated by using software. The results of theoretical analysis and simulation by software show that the inner surface flash-over usually starts at the junction points among the stainless steel, insulator, and insulation gas in the switch. A switch with improved structure is designed and fabricated according to the theoretical analysis and simulation results. Several methods to avoid inner surface flash-over are used to improve the structure of switch. In experiment, the inductance of the switch is no more than 100 nH, the working voltage of the switch is about 600 kV, and the output voltage and current of the accelerator is about 500 kV and 50 kA, respectively. And the zero-to-peak rise time of output voltage at matched load is less than 30 ns due to the small inductance of switch. The original switch was broken-down after dozens of experiments, and the improved switch has been worked more than 200 times stably.
Electrothermally actuated microelectromechanical systems based omega-ring terahertz metamaterial with polarization dependent characteristics
Authors: Ho Chong Pei , Pitchappa Prakash , Lin Yu-Sheng , Huang Chia-Yi , Kropelnicki Piotr , Lee Chengkuo
Published: April 2014

We present the design, simulation, fabrication, and characterization of a continuously tunable Omega-ring terahertz metamaterial. The tunability of metamaterial is obtained by integrating microactuators into the metamaterial unit cell. Electrothermal actuation mechanism is used to provide higher tuning range, larger stroke, and enhanced repeatability. The maximum achieved tuning range for the resonant frequency is around 0.30 THz for the input power of 500 mW. This shows the potential of using electrothermally actuated microactuators based tunable metamaterial design for application such as filters, absorbers, sensors, and spectral imagers.