bluuebunny/crossref_metadata_2025 huggingface dataset:
Moist convection and its upscale effects in simulations of the Indian monsoon with explicit and parametrized convection
Authors: Willetts P. D. , Marsham J. H. , Birch C. E. , Parker D. J. , Webster S. , Petch J.
Published: December 2016

In common with many global models, the Met Office Unified Model (MetUM) climate simulations show large errors in Indian summer monsoon rainfall, with a wet bias over the equatorial Indian Ocean, a dry bias over India, and with too weak low‐level flow into India. The representation of moist convection is a dominant source of error in global models, where convection must be parametrized, with the errors growing quickly enough to affect both weather and climate simulations. Here we use the first multi‐week continental‐scale MetUM simulations over India, with grid spacings that allow explicit convection, to examine how convective parametrization contributes to model biases in the region.

Some biases are improved in the convection‐permitting simulations with more intense rainfall over India, a later peak in the diurnal cycle of convective rainfall over land, and a reduced positive rainfall bias over the Indian Ocean. The simulations suggest that the reduced rainfall over the Indian Ocean leads to an enhanced monsoon circulation and transport of moisture into India. Increases in latent heating associated with increased convection over land deepen the monsoon trough and enhance water vapour transport into the continent. In addition, delayed continental convection allows greater surface insolation and, along with the same rain falling in more intense bursts, generates a drier land surface. This increases land–sea temperature contrasts, and further enhances onshore flow. Changes in the low‐level water vapour advection into India are dominated by these changes to the flow, rather than to the moisture content in the flow. The results demonstrate the need to improve the representations of convection over both land and oceans to improve simulations of the monsoon.
Confidence interval estimation for electromechanical mode parameters obtained from stochastic subspace identification
Authors: Jia Yong , He Zhengyou , Liao Kai
Published: December 2016

Electromechanical modes estimated from ambient measurement signals are always subjected to statistical uncertainties. For evaluating the quality of the obtained results, it is necessary to know the respective confidence intervals of the mode estimates. A perturbation method for computing the variances of mode parameters (frequencies, damping ratios) obtained from covariance‐driven stochastic subspace identification of multiple synchrophasors is presented in this paper. The variance estimates are achieved by using the first‐order sensitivity of the mode parameter estimates to perturbations of the system matrixes, whose covariances are derived from the measured signals. The confidence interval estimation method is validated by Monte Carlo simulations with the two‐area system and the New England system. The comparison results between the mean values of the estimated variances and empirical sample variances of the estimated mode parameters show that it is feasible to estimate the confidence intervals of the mode parameters using a single set of multiple signals. The proposed method is further validated with field‐measured signals from the Western Electricity Coordinating Council system. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
A comparison of the wound rotor and nested‐loop rotor brushless doubly fed generator
Authors: Jia Lei , Wang Xuefan
Published: December 2016

Both the wound rotor and the nested‐loop rotor can realize the coupling with the power winding (PW) and control winding. And the two types of rotors in a brushless doubly fed generator (BDFG) can realize variable‐speed, constant‐frequency generation. In this paper, the two types BDFG are compared through finite element analysis and experiments. From the finite element simulation results, it can be seen that the air gap flux density harmonic contents, PW line voltage harmonic contents, and the core loss of the nested‐loop rotor BDFG are higher than those of the wound‐rotor BDFG. In the experiments, the efficiency of the wound rotor BDFG is slightly lower than that of the nested‐loop rotor BDFG when the rotor speed is below the natural synchronous speed and is much higher than that of the nested‐loop rotor BDFG when the rotor speed is above the natural synchronous speed. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Torque regulation of multiphase induction motors under symmetrical fault condition
Authors: Zheng Xiaoqin , Wang Dong
Published: December 2016

Multiphase induction motors are popular for electric ship propulsion systems because of their superior fault‐tolerant capability. In this paper, a torque regulation method for multiphase induction motors with symmetrical fault is investigated under the precondition of constant current amplitude. On the basis of parameter recalculation, the relationships between the torque, input voltage magnitude, and frequency are analyzed by using the equivalent circuit. The maximum torque and the corresponding input voltage magnitude and frequency are predicted. Finally, the developed torque regulation method is validated by experimental test on a 45‐kW prototype 15‐phase induction machine under a symmetrical 5‐phase open‐circuit condition. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Design of smiling‐face‐shaped band‐notched UWB antenna
Authors: Liu Han , Yin Chengyou , Huang Ye
Published: December 2016

A novel smiling‐face‐shaped band‐notched ultra‐wideband (UWB) antenna is designed in this paper. First, antenna bandwidth is broadened by adding a pair of small semi‐circular stubs (ears) and etching a pair of symmetrical C‐shaped slots (eyes), a triangular slot (nose), and a U‐shaped slot (mouth) on the patch. Second, by adjusting the length of the ground plane and creating a stepped slot on the ground plane, antenna bandwidth covers 3–12 GHz. Third, a pair of L‐shaped slots (hands) is etched on the ground plane to create a notch, which can effectively suppress the interference signal in worldwide interoperability for microwave access (WiMAX) (3.4–3.6 GHz) and satellite C band (3.7–4.2 GHz). Lastly, the proposed antenna is fabricated and measured. The measured results indicate the proposed antenna has good performance and can be widely used in UWB systems. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Energy‐aware congestion control scheme in opportunistic networks
Authors: Zhang Feng , Wang Xiaoming , Li Peng , Zhang Lichen
Published: December 2016

In opportunistic networks, a congestion phenomenon may occur if the remaining buffer of a node cannot accept any arrival message. Energy is consumed by dropping the messages stored in the buffer to provide space for new messages. In order to reduce and balance the energy consumption of nodes during congestion in opportunistic networks, a novel congestion control scheme is proposed. Nodes dynamically update their residual energy level and query the residual energy level of their neighbors in current local environment and adjust their threshold ratio using the learning automata principle while moving around. Nodes will only receive messages whose remaining TTL (time to live) proportion of initial TTL is larger than the threshold ratio when congestion occurs. Simulation results show that the Epidemic routing protocol with the proposed congestion control scheme can efficiently reduce and balance energy consumption among nodes. Also, the routing performances such as delivery ratio, overhead ratio, and deliver latency are improved. Furthermore, the network lifetime is obviously improved since much more energy is left. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Europe Since 1945
Authors: Wegs J. Robert , Ladrech Robert
Published: December 2016

As Europe has expanded its influence in world economic and political affairs, there has been an increased need to understand how Europe recovered from the devastation of World War II to become a major world player. This concise history offers a comprehensive overview of Europe's political, social, economic and cultural developments since 1945.

J. Robert Wegs and Robert Ladrech balance a narrative of the major events and personalities of the post-war political scene with a critical assessment of key issues and themes, such as:

– The development of the welfare state

– European integration and the European Union

– The Cold War

– The rise and fall of the Soviet Empire

– The political-economic turmoil in eastern Europe since 1989

– The place of Europe in the globalisation of the world's political-economic affairs

The text also features further reading sections at the end of each chapter to aid more detailed study, and is enhanced throughout with tables, maps and illustrations.

Written for students and general readers alike, this thoroughly revised, updated and expanded new edition is an ideal introduction for anyone with an interest in the history and politics of post-war Europe, east and west.
From Phase Behavior to Understand the Dominant Mechanism of Alkali‐Surfactant‐Polymer Flooding in Enhancing Heavy Oil Recovery
Authors: Wei Bing , Lu Laiming , Pu Wanfen , Jiang Feng , Li Kexing , Sun Lin , Jin Fayang
Published: December 2016

The primary objective of this work was to understand the dominant mechanism(s) of alkali‐surfactant‐polymer (ASP) flooding in enhancing heavy oil recovery. Chemical formulations were first optimized based on phase behavior studies. The data indicated that alkali and surfactant created a synergistic effect at the oil/water interface, which further decreased the interfacial tension (IFT) and improved the emulsification. However, it was also found that the addition of alkali was detrimental to the viscous properties of the chemical systems and caused the ultimate oil recovery to decrease. In other words, the macroscopic sweep efficiency as a result of viscosity was the primary factor determining the overall recovery of heavy oil followed by emulsification, which was verified by the phase behavior of the effluent. Based on the experimental results, we found that for this targeted heavy oil reservoir, surfactant‐polymer (SP) flooding was more appropriate than ASP flooding and it was not necessary to decrease the IFT to the ultralow level (10−3mN/m) using alkali. Through chemical flooding, the incremental oil recovery was increased up to 27% of original oil in place, indicating the potential of this technique in heavy oil reservoirs.
The Structured Interview for Insight and Judgment in Dementia: Development and validation of a new instrument to assess awareness in patients with dementia
Authors: Parrao Teresa , Brockman Simone , Bucks Romola S. , Bruce David G. , Davis Wendy A. , Hatch Katherine K. , Leavy Tammy L. , Axten Christine A.P. , Starkstein Sergio E.
Published: December 2016

Introduction

Poor insight about their cognitive and functional deficits is highly prevalent in patients with Alzheimer's disease (AD); however, there is a lack of reliable, valid instrumentation to measure this construct. The aim of this study was to develop and validate a semistructured interview to assess insight and judgment in patients with AD and to provide information regarding the assessment of competency and risk in this population.

Methods

We validated the Structured Clinical Interview for Insight and Judgment in Dementia (SIJID) in a consecutive series of 124 patients with probable AD. The following psychometric properties were evaluated: internal consistency, test‐retest reliability, interrater reliability, and convergent and predictive validity.

Results

The SIJID demonstrated high test‐retest, interrater reliability and also showed strong discriminant and convergent validity. It showed good predictive validity based on 1‐year follow‐up information of the patient's clinical outcomes, with a significant association between higher SIJID total scores at baseline, and more severe neuropsychiatric symptoms and more severe caregiver distress at follow‐up. Moreover, higher scores of dangerous behaviors at baseline were significantly correlated with a higher frequency of hospitalization and placement in residential care 1 year later.

Conclusion

The SIJID is a reliable and valid instrument to assess insight and judgment in patients with AD and is a valuable tool for assessing presence and severity of dangerous behaviors, determining risk, and providing critical information for the assessment of competency.
Microwave-assisted deep eutectic solvent extraction coupled with headspace solid-phase microextraction followed by GC-MS for the analysis of volatile compounds from tobacco
Authors: Nie Jing , Yu Guowei , Song Zhiyu , Wang Xiajun , Li Zuguang , She Yuanbin , Lee Mawrong
Published: December 2016

Microwave-assisted deep eutectic solvent extraction coupled with SPME to determine the volatile compounds in tobacco samples.
MoS2 quantum-dots as a label-free fluorescent nanoprobe for the highly selective detection of methyl parathion pesticide
Authors: Fahimi-Kashani Nafiseh , Rashti Ali , Hormozi-Nezhad M. Reza , Mahdavi Vahideh
Published: December 2016

A reliable, simple, and sensitive fluorescence method was developed for the determination of methyl parathion (MP) in rice using MoS2 quantum dots (QDs).
Determination of phenolic acids in a range of Irish whiskies, including single pot stills and aged single malts, using capillary electrophoresis with field amplified sample stacking
Authors: White Blánaid , Smyth Malcolm R. , Lunte Craig E.
Published: December 2016

Phenolic acids in Irish whiskeys were determined using CE-UV with field amplified sample stacking. Length of aging and prior use of cask influenced phenolic acid profiles.
Modulation of charge carrier pathways in CdS nanospheres by integrating MoS2 and Ni2P for improved migration and separation toward enhanced photocatalytic hydrogen evolution
Authors: Choi Jiha , Amaranatha Reddy D. , Han Noh Soo , Jeong Seonghyun , Hong Sangyeob , Praveen Kumar D. , Song Jae Kyu , Kim Tae Kyu
Published: December 2016

This work demonstrates a design strategy for CdS/MoS2@Ni2P as hydrogen production photocatalyst.
Titanium dioxide modified with various amines used as sorbents of carbon dioxide
Authors: Kapica-Kozar Joanna , Piróg Ewa , Kusiak-Nejman Ewelina , Wrobel Rafal J. , Gęsikiewicz-Puchalska Andżelika , Morawski Antoni W. , Narkiewicz Urszula , Michalkiewicz Beata
Published: December 2016

Among sorbents prepared through hydrothermal treatment, TEPA-modified TiO2demonstrates the highest adsorption capacity (1.63 mmol CO2g−1) and also shows good stability and regenerability after multiple cycles of operation.
Ligand and solvent effects in the formation and self-assembly of a metallosupramolecular cage
Authors: Adarsh N. N. , Chakraborty Amarnath , Tarrés Màrius , Dey Surjendu , Novio Fernando , Chattopadhyay Basab , Ribas Xavi , Ruiz-Molina Daniel
Published: December 2016

A metallosupramolecular cage and a one-dimensional coordination polymer have been synthesized and structurally characterized by single crystal X-ray diffraction.
A highly active chiral (S,S)-bis(oxazoline) Pd(ii) alkyl complex/activator catalytic system for vinyl polymerization of norbornene in air and water
Authors: Huang Yingda , He Jianyun , Liu Zhanxiong , Cai Guilong , Zhang Shaowen , Li Xiaofang
Published: December 2016

The air/water-tolerant chiral Pd alkyl complexes/borate systems promote the norbornene polymerization both in air and water using unpretreated technical grade solvent and monomer with extremely high activity up to 1.7 × 109 g PNB per molPd per h.
Oxygen and carbon dioxide dual gas-responsive homopolymers and diblock copolymers synthesized via RAFT polymerization
Authors: Jiang Xue , Chun Feng , Lu Guolin , Xiaoyu Huang
Published: December 2016

This article reports a new strategy to prepare homopolymers with CO2 and O2 responsiveness via the installation of CO2- and O2-responsive functionalities in the same repeated unit.
EuSn2As2: an exfoliatable magnetic layered Zintl–Klemm phase
Authors: Arguilla M. Q. , Cultrara N. D. , Baum Z. J. , Jiang S. , Ross R. D. , Goldberger J. E.
Published: December 2016

We synthesize EuSn2As2, the first exfoliatable layered magnetic Zintl–Klemm phase that features van der Waals bonding between neighboring layers.
Enhanced visible-light photocatalytic hydrogen production activity of three-dimensional mesoporous p-CuS/n-CdS nanocrystal assemblies
Authors: Vamvasakis Ioannis , Trapali Adelais , Miao Jianwei , Liu Bin , Armatas Gerasimos S.
Published: December 2016

Mesoporous assemblies of p-CuS/n-CdS nanocrystal junctions with high surface areas and uniform pores demonstrate a high performance and stability in photocatalytic hydrogen generation from water using visible light.
Structural stability and thermoelectric properties of cation- and anion-doped Mg2Si0.4Sn0.6
Authors: Andersen Henrik L. , Zhang Jiawei , Yin Hao , Iversen Bo B.
Published: December 2016

The structural stability of undoped and doped (Sb, Bi, Ca, Zn) Mg2Si0.4Sn0.6 is investigated by high resolution synchrotron PXRD and related to measured physical properties, revealing a stabilizing effect of cation doping.
Fabrication of morphology-preserved microporous carbon from a zeolitic-like porous coordination polymer
Authors: Zhou Bihang , Hua Yinying , Cheng Fujun , Duan Jingui , Chen Lingyun , Jin Wanqin
Published: December 2016

A new zeolitic-like microporous coordination polymer (PCP), [Zn2(L)·2H2O]·xguest, was firstly converted to morphology-preserved carbon rods with exclusive micropores and a large surface area for selective gas capture.
The direct decarboxylative allylation of N-arylglycine derivatives by photoredox catalysis
Authors: Duan Yingqian , Zhang Muliang , Ruzi Rehanguli , Wu Zhongkai , Zhu Chengjian
Published: December 2016

The direct decarboxylative allylation of N-arylglycine derivatives has been accomplished via visible-light photoredox catalysis.
Asymmetric synthesis of trifluoromethyl-substituted 3,3′-pyrrolidinyl-dispirooxindoles through organocatalytic 1,3-dipolar cycloaddition reactions
Authors: Huang Wei-Jie , Chen Qing , Lin Ning , Long Xian-Wen , Pan Wei-Gao , Xiong Yan-Shi , Weng Jiang , Lu Gui
Published: December 2016

A series of trifluoromethylated 3,3′-pyrrolidinyl-dispirooxindoles were constructedviaasymmetric [3 + 2] cycloaddition.
De novo synthesis of alkyne substituted tryptophans as chemical probes for protein profiling studies
Authors: Nair R. N. , Rosnow J. J. , Murphree T. A. , Bowden M. E. , Lindemann S. R. , Wright A. T.
Published: December 2016

Old is Gold: a de novo approach for alkynylated tryptophans.
An Aberrant Abductor Digiti Minimi Muscle Crossing Guyon's Canal
Authors: Nam YongSeok , Hwang SeungHwan , Eo SuRak
Published: December 2016

Anomalous hypothenar muscles in the wrist are relatively common with 47% prevalence, and their possible consequences associated with Guyon's canal are well known. The accessory of the abductor digiti minimi muscle (ADM) is known to be one of the causes of ulnar tunnel syndrome or ulnar artery thrombosis. A unique ADM was found in the volar wrist region of an 87-year-old male cadaver passing through Guyon's canal.
Comparative Effectiveness of Intranasal Dexmedetomidine–Midazolam versus Oral Chloral Hydrate Targeting Moderate Sedation during Pediatric Transthoracic Echocardiograms
Authors: Fett Jordan , Hackbarth Richard , Boville Brian , Olivero Anthony , Davis Alan , Winters John
Published: December 2016

Objective To compare efficacy and safety of two moderate sedation regimens for transthoracic echocardiography (TTE): intranasal dexmedetomidine–midazolam (DM) versus oral chloral hydrate (CH) syrup.

Method This was a retrospective cohort of 93 children under 4 years of age receiving moderate sedation with either DM or CH for TTE from January 2011 through December 2014.

Measurements and Main Results Forty-nine patients received oral CH and 44 received the intranasal combination of DM. The demographics between groups were similar except the DM patients were slightly older and heavier (each p < 0.05). Failure rate between groups did not reach statistical significance (CH 14.3% vs. DM 6.8%; p = 0.324). Total sedation to discharge time was similar between groups (CH 89.4 minutes vs. DM 89.6 minute; p = 0.97). Cardiopulmonary data did reveal a significantly lower heart rate (101.9 vs. 91.7; p < 0.001) and respiratory rate (23.4 vs. 21.0, p = 0.03) in the DM group, but no difference in blood pressure measurements or echo determined shortening fraction.

Conclusion These data support the use of intranasal DM as a safe and efficacious method of moderate sedation for children undergoing TTE.
Global sensitivity analysis in stochastic simulators of uncertain reaction networks
Authors: Navarro Jimenez M. , Le Maître O. P. , Knio O. M.
Published: December 2016

Stochastic models of chemical systems are often subjected to uncertainties in kinetic parameters in addition to the inherent random nature of their dynamics. Uncertainty quantification in such systems is generally achieved by means of sensitivity analyses in which one characterizes the variability with the uncertain kinetic parameters of the first statistical moments of model predictions. In this work, we propose an original global sensitivity analysis method where the parametric and inherent variability sources are both treated through Sobol’s decomposition of the variance into contributions from arbitrary subset of uncertain parameters and stochastic reaction channels. The conceptual development only assumes that the inherent and parametric sources are independent, and considers the Poisson processes in the random-time-change representation of the state dynamics as the fundamental objects governing the inherent stochasticity. A sampling algorithm is proposed to perform the global sensitivity analysis, and to estimate the partial variances and sensitivity indices characterizing the importance of the various sources of variability and their interactions. The birth-death and Schlögl models are used to illustrate both the implementation of the algorithm and the richness of the proposed analysis method. The output of the proposed sensitivity analysis is also contrasted with a local derivative-based sensitivity analysis method classically used for this type of systems.
Laser-driven gel microtool for single-cell manipulation based on temperature control with a photothermal conversion material
Authors: Hayakawa T. , Kikukawa M. , Maruyama H. , Arai F.
Published: December 2016

We propose a laser-driven hybrid gel microtool for stable single-cell manipulation. The microtool is made of a microbead dyed with multiwalled carbon nanotubes (MWNT) and thermosensitive poly (N-isopropylacrylamide) gel coating. The gel adheres to cells at high temperatures but not at low temperatures. We can manipulate single cells without direct laser irradiation by adhering the cells to the gel on the microtool using the cell-adhesion property of the gel. The microtool is heated by trapping it with optical tweezers to make its surface cell-adhesive during the manipulation. Furthermore, we can control the optical heating property of the microtool by dyeing the microbeads with MWNT ink. The laser-heating-induced temperature increase of the microtool can be controlled from 4.2 °C to 23.5 °C by varying the concentration of MWNT ink. We succeeded in fabricating the proposed microtool and demonstrated single-cell transportation using the microtool without direct laser irradiation of the cell.
Hyperfine interactions and internal rotation in methanol
Authors: Lankhaar Boy , Groenenboom Gerrit C. , van der Avoird Ad
Published: December 2016

We present a rigorous derivation of the nuclear spin-rotation and spin-torsion coupling terms in the hyperfine Hamiltonian for molecules with internal rotation. Our formulas differ from the expressions derived by Heuvel and Dymanus [J. Mol. Spectrosc. 47, 363 (1973)], which these authors used and which were also applied recently by others to interpret experimental hyperfine spectra of such molecules. In the present work, our theoretical results are applied to methanol. We calculate the nuclear spin-spin magnetic dipole-dipole interactions and the nuclear contribution to the spin-torsion coupling vectors from the nuclear coordinates as functions of the internal rotation angle γ, compute the spin-rotation coupling tensors by ab initio electronic structure methods also as functions of γ, and obtain the missing parameters for the electronic contribution to the spin-torsion coupling from a fit to measured spectra. The resulting hyperfine Hamiltonian is then used to compute hyperfine transition frequencies and intensities for twelve torsion-rotation transitions in methanol. With the use of the ab initio calculated spin-rotation coupling parameters without any modification, and physically reasonable values for the spin-torsion coupling parameters from the fit, we find good agreement with all of the measured spectra.
Kinetic growth mode of epitaxial GaAs on Si(001) micro-pillars
Authors: Bergamaschini Roberto , Bietti Sergio , Castellano Andrea , Frigeri Cesare , Falub Claudiu V. , Scaccabarozzi Andrea , Bollani Monica , von Känel Hans , Miglio Leo , Sanguinetti Stefano
Published: December 2016

Three-dimensional, epitaxial GaAs crystals are fabricated on micro-pillars patterned into Si(001) substrates by exploiting kinetically controlled growth conditions in Molecular Beam Epitaxy. The evolution of crystal morphology during growth is assessed by considering samples with increasing GaAs deposit thickness. Experimental results are interpreted by a kinetic growth model, which takes into account the fundamental aspects of the growth and mutual deposition flux shielding between neighboring crystals. Different substrate pattern geometries with dissimilar lateral sizes and periodicities of the Si micro-pillars are considered and self-similar crystal structures are recognized. It is demonstrated that the top faceting of the GaAs crystals is tunable, which can pave the way to locally engineer compound semiconductor quantum structures on Si(001) substrates.
Nanopipe formation as a result of boron impurity segregation in gallium nitride grown by halogen-free vapor phase epitaxy
Authors: Kimura Taishi , Aoki Yuko , Horibuchi Kayo , Nakamura Daisuke
Published: December 2016

The work reported herein demonstrated that nanopipes can be formed via a surfactant effect, in which boron impurities preferentially migrate to semipolar and nonpolar facets. Approximately 3 μm-thick GaN layers were grown using halogen-free vapor phase epitaxy. All layers grown in pyrolytic boron nitride (pBN) crucibles were found to contain a high density of nanopipes in the range of 1010 to 1011 cm−2. The structural properties of these nanopipes were analyzed by X-ray rocking curve measurements, transmission electron microscopy, and three-dimensional atom probe (3DAP) tomography. The resulting 3DAP maps showed nanopipe-sized regions of boron segregation, and these nanopipes were not associated with the presence of dislocations. A mechanism for nanopipe formation was developed based on the role of boron as a surfactant and considering energy minima. A drastic reduction in the nanopipe density was achieved upon replacing the pBN crucibles with tantalum carbide-coated carbon crucibles. Consequently, we have confirmed that nanopipes can be formed solely due to surface energy changes induced by boron impurity surface segregation. For this reason, these results also indicate that nanopipes should be formed by other surfactant impurities such as Mg and Si.
Highly ordered horizontal indium gallium arsenide/indium phosphide multi-quantum-well in wire structure on (001) silicon substrates
Authors: Han Yu , Li Qiang , Lau Kei May
Published: December 2016

We report the characteristics of indium gallium arsenide stacked quantum structures inside planar indium phosphide nanowires grown on exact (001) silicon substrates. The morphological evolution of the indium phosphide ridge buffers inside sub-micron trenches has been studied, and the role of inter-facet diffusion in this process is discussed. Inside a single indium phosphide nanowire, we are able to stack quantum structures including indium gallium arsenide flat quantum wells, quasi-quantum wires, quantum wires, and ridge quantum wells. Room temperature photoluminescence measurements reveal a broadband emission spectrum centered at 1550 nm. Power dependent photoluminescence analysis indicates the presence of quasi-continuum states. This work thus provides insights into the design and growth process control of multiple quantum wells in wire structures for high performance nanowire lasers on a silicon substrate with 1550 nm band emission.
Design of a metamaterial slow wave structure for an O-type high power microwave generator
Authors: Yurt Sabahattin C. , Fuks Mikhail I. , Prasad Sarita , Schamiloglu Edl
Published: December 2016

We describe a new O-type high power microwave oscillator that uses a metamaterial slow wave structure (MSWS) supporting waves with negative dispersion. The MSWS comprises periodically alternating, oppositely oriented split ring resonators (SRRs) connected to a metal tube where the distance between the rings is much less than a wavelength of the radiation generated. The SRRs provide negative permeability μ. The diameter of the metal tube is such that the generated oscillations are below cutoff for a regular waveguide with the same dimension, thus providing negative permittivity ε. A tubular electron beam propagates coaxially through this structure. The interaction space is coupled with the outer coaxial channel through gaps between the SRRs. Radiation is extracted in an endfire manner at the end of the outer channel via a conical horn section. Using particle-in-cell (PIC) simulations, it was found that the electron beam in the interaction space forms a sequence of trapped electron bunches by the synchronous operating wave. The output parameters of this oscillator for an applied voltage U = 400 kV, electron beam current I = 4.5 kA, and guide axial magnetic field B = 2 T are radiation power P = 260 MW, radiation frequency f = 1.4 GHz, and electronic efficiency η = 15% when the total SWS length L consisting of 12 split rings is 34.5 cm. The output radiation pattern corresponds to a TE21-like hybrid mode. This article presents details on the simulations of this novel structure and computational and experimental cold tests of a prototype structure in preparation for experimental hot tests.
Scrape-off layer modeling with kinetic or diffusion description of charge-exchange atoms
Authors: Tokar M. Z.
Published: December 2016

Hydrogen isotope atoms, generated by charge-exchange (c-x) of neutral particles recycling from the first wall of a fusion reactor, are described either kinetically or in a diffusion approximation. In a one-dimensional (1-D) geometry, kinetic calculations are accelerated enormously by applying an approximate pass method for the assessment of integrals in the velocity space. This permits to perform an exhaustive comparison of calculations done with both approaches. The diffusion approximation is deduced directly from the velocity distribution function of c-x atoms in the limit of charge-exchanges with ions occurring much more frequently than ionization by electrons. The profiles across the flux surfaces of the plasma parameters averaged along the main part of the scrape-off layer (SOL), beyond the X-point and divertor regions, are calculated from the one-dimensional equations where parallel flows of charged particles and energy towards the divertor are taken into account as additional loss terms. It is demonstrated that the heat losses can be firmly estimated from the SOL averaged parameters only; for the particle loss the conditions in the divertor are of importance and the sensitivity of the results to the so-called “divertor impact factor” is investigated. The coupled 1-D models for neutral and charged species, with c-x atoms described either kinetically or in the diffusion approximation, are applied to assess the SOL conditions in a fusion reactor, with the input parameters from the European DEMO project. It is shown that the diffusion approximation provides practically the same profiles across the flux surfaces for the plasma density, electron, and ion temperatures, as those obtained with the kinetic description for c-x atoms. The main difference between the two approaches is observed in the characteristics of these species themselves. In particular, their energy flux onto the wall is underestimated in calculations with the diffusion approximation by 20%–30%. This discrepancy can be significantly reduced if after the convergence of coupled plasma-neutral calculations, the final computation for c-x atoms is done kinetically.
Effect of collisions on the two-stream instability in a finite length plasma
Authors: Sydorenko D. , Kaganovich I. D. , Ventzek P. L. G. , Chen L.
Published: December 2016

The instability of a monoenergetic electron beam in a collisional one-dimensional plasma bounded between grounded walls is considered both analytically and numerically. Collisions between electrons and neutrals are accounted for the plasma electrons only. Solution of a dispersion equation shows that the temporal growth rate of the instability is a decreasing linear function of the collision frequency which becomes zero when the collision frequency is two times the collisionless growth rate. This result is confirmed by fluid simulations. Practical formulas are given for the estimate of the threshold beam current which is required for the two-stream instability to develop for a given system length, neutral gas pressure, plasma density, and beam energy. Particle-in-cell simulations carried out with different neutral densities and beam currents demonstrate a good agreement with the fluid theory predictions for both the growth rate and the threshold beam current.
The characteristics of an intense laser beam propagating in a corrugated plasma channel
Authors: Tian Jian-Min , Tang Rong-An , Hong Xue-Ren , Yang Yang , Wang Li , Zhou Wei-Jun , Xue Ju-Kui
Published: December 2016

The propagation of an intense laser beam in a corrugated plasma channel is investigated. By using the source-dependent expansion technique, an evolution equation of the laser spot size is derived. The behaviors including aperiodic oscillation, resonance, beat-like wave, and periodic oscillation with multipeak are found and analyzed. The formula for the instantaneous wave numbers of these oscillations is obtained. These theoretical findings are confirmed by the final numerical simulation.
A physics package for rubidium atomic frequency standard with a short-term stability of 2.4 × 10−13 τ−1/2
Authors: Hao Qiang , Li Wenbing , He Shengguo , Lv Jianfeng , Wang Pengfei , Mei Ganghua
Published: December 2016

In this article, a new type of physics package with high signal to noise ratio for a rubidium atomic frequency standard is reported. To enhance the clock transition signal, a slotted tube microwave cavity with a field orientation factor of 0.93 and an absorption cell with the diameter of 30 mm were utilized in design of the cavity-cell assembly. Based on the spectral analysis of the three commonly used rubidium spectral lamps, the spectral lamp filled with Xe gas was chosen as the optical pumping source for its small line shape distortion. To suppress the shot noise of the signal, a band pass interference filter was used to filter out Xe spectral lines from the pumping light. A desk system of the rubidium frequency standard with the physics package was realized, and the short-term stability of the system was predicted and tested. The measured result is 2.4 × 10−13 τ−1/2 up to 100 s averaging time, in good agreement with the predicted one.
Molecular doping of MoS2 transistors by self-assembled oleylamine networks
Authors: Lockhart de la Rosa César J. , Phillipson Roald , Teyssandier Joan , Adisoejoso Jinne , Balaji Yashwanth , Huyghebaert Cedric , Radu Iuliana , Heyns Marc , De Feyter Steven , De Gendt Stefan
Published: December 2016

Thin MoS2 films continue to be of key interest for numerous applications; however, effective doping and high metal to MoS2 contact resistance are challenges for future applications. We report on the self-assembly of oleylamine on top of MoS2 thin-films and the effective doping of MoS2 thin-film field effect transistors by oleylamine. Atomic force microscopy revealed that oleylamine organizes in lamellae domains on MoS2 thin films with similar characteristics of those previously observed on highly ordered pyrolytic graphite. A carrier concentration increase from 7.1 × 1011 cm−2 up to 1.9 × 1013 cm−2 at 0 V gate voltage is achieved together with a reduction of the contact resistance by a factor of 5 when using gold as metal contact. Furthermore, this non-covalent doping proves to be removable and reproducible among different flakes and does not degrade the electron mobility. Thus, this work opens the path for future works on controlling the doping of MoS2 by proper selection of the self-assembled species.
Si clusters are more metallic than bulk Si
Authors: Jackson Koblar , Jellinek Julius
Published: December 2016

Dipole polarizabilities were computed using density functional theory for silicon clusters over a broad range of sizes up to N = 147 atoms. The calculated total effective polarizabilities, which include contributions from permanent dipole moments of the clusters, are in very good agreement with recently measured values. We show that the permanent dipole contributions are most important for clusters in the intermediate size range and that the measured polarizabilities can be used to distinguish between energetically nearly degenerate cluster isomers at these sizes. We decompose the computed total polarizabilities α into the so-called dipole and charge transfer contributions, αp and αq, using a site-specific analysis. When the per-atom values of these quantities are plotted against N−1/3, clear linear trends emerge that can be extrapolated to the large size limit (N−1/3→0), resulting in a value for αN of 30.5 bohrs3/atom that is significantly larger than the per-atom polarizability of semiconducting bulk Si, 25.04 bohrs3/atom. This indicates that Si clusters possess a higher degree of metallicity than bulk Si, a conclusion that is consistent with the strong electrostatic screening of the cluster interiors made evident by the analysis of the calculated atomic polarizabilities.
A power series revisit of the PBE exchange density-functional approximation: The PBEpow model
Authors: Brémond Éric
Published: December 2016

PBEpow is a power series extension of the Perdew–Burke–Ernzerhof (PBE) exchange generalized gradient approximation. This novel variant is constructed by an inductive determination of the power series coefficients to fulfill physical fundamental constants in the slowly and rapidly varying density limits. When combined with the PBE correlation, PBEpow significantly improves the estimation of molecular covalent interactions such as energies of atomization reactions and keeps the line of performance of PBE for noncovalent interactions. More generally this work provides new insights about how to improve the modeling of short- and long-range interactions at the generalized gradient approximation level without the help of any kind of empirical parameterization.
Stabilizing a graphene platform toward discrete components
Authors: Mzali Sana , Montanaro Alberto , Xavier Stéphane , Servet Bernard , Mazellier Jean-Paul , Bezencenet Odile , Legagneux Pierre , Piquemal-Banci Maëlis , Galceran Regina , Dlubak Bruno , Seneor Pierre , Martin Marie-Blandine , Hofmann Stephan , Robertson John , Cojocaru Costel-Sorin , Centeno Alba , Zurutuza Amaia
Published: December 2016

We report on statistical analysis and consistency of electrical performances of devices based on a large scale passivated graphene platform. More than 500 graphene field effect transistors (GFETs) based on graphene grown by chemical vapor deposition and transferred on 4 in. SiO2/Si substrates were fabricated and tested. We characterized the potential of a two-step encapsulation process including an Al2O3 protection layer to avoid graphene contamination during the lithographic process followed by a final Al2O3 passivation layer subsequent to the GFET fabrication. Devices were investigated for occurrence and reproducibility of conductance minimum related to the Dirac point. While no conductance minimum was observed in unpassivated devices, 75% of the passivated transistors exhibited a clear conductance minimum and low hysteresis. The maximum of the device number distribution corresponds to a residual doping below 5 × 1011 cm−2 (0.023 V/nm). This yield shows that GFETs integrating low-doped graphene and exhibiting small hysteresis in the transfer characteristics can be envisaged for discrete components, with even further potential for low power driven electronics.
Load characteristics of wireless power transfer system with different resonant types and resonator numbers
Authors: Zhang Yiming , Zhao Zhengming , Chen Kainan , Fan Jun
Published: December 2016

Wireless Power Transfer (WPT) has been the research focus and applied in many fields. Normally power is transferred wirelessly to charge the battery, which requires specific load characteristics. The load characteristics are essential for the design and operation of the WPT system. This paper investigates the load characteristics of the WPT system with different resonant types and resonator numbers. It is found that in a WPT system with series or LCL resonance under a constant voltage source, the load characteristic is determined by the number of inductors. Even number of inductors results in a constant current characteristic and odd number constant voltage characteristic. Calculations, simulations, and experiments verify the analysis.
Unsaturated magnetoconductance of epitaxial La0.7Sr0.3MnO3 thin films in pulsed magnetic fields up to 60 T
Authors: Niu Wei , Wang Xuefeng , Gao Ming , Xia Zhengcai , Du Jun , Nie Yuefeng , Song Fengqi , Xu Yongbing , Zhang Rong
Published: December 2016

We report on the temperature and field dependence of resistance of La0.7Sr0.3MnO3 thin films over a wide temperature range and in pulsed magnetic fields up to 60 T. The epitaxial La0.7Sr0.3MnO3 thin films were deposited by laser molecular beam epitaxy. High magnetic field magnetoresistance curves were fitted by the Brillouin function, which indicated the existence of magnetically polarized regions and the underlying hopping mechanism. The unsaturated magnetoconductance was the most striking finding observed in pulsed magnetic fields up to 60 T. These observations can deepen the fundamental understanding of the colossal magnetoresistance in manganites with strong correlation of transport properties and magnetic ordering.
Anisotropic electronic states in the fractional quantum Hall regime
Authors: Ciftja Orion
Published: December 2016

Recent experiments indicate the presence of new anisotropic fractional quantum Hall states at regimes not anticipated before. These experiments raise many fundamental questions regarding the inner nature of the electronic system that leads to such anisotropic states. Interplay between electron mass anisotropy and electron-electron correlation effects in a magnetic field can create a rich variety of possibilities. Several anisotropic electronic states ranging from anisotropic quantum Hall liquids to anisotropic Wigner solids may stabilize due to such effects. The electron mass anisotropy in a two-dimensional electron gas effectively leads to an anisotropic Coulomb interaction potential between electrons. An anisotropic interaction potential may strongly influence the stability of various quantum phases that are close in energy since the overall stability of an electronic system is very sensitive to local order. As a result there is a possibility that various anisotropic electronic phases may emerge even in the lowest Landau level in regimes where one would not expect them. In this work we study the state with filling factor 1/6 in the lowest Landau level, a state which is very close to the critical filling factor where the liquid-solid transition takes place. We investigate whether an anisotropic Coulomb interaction potential is able to stabilize an anisotropic electronic liquid state at this filling factor. We describe such an anisotropic state by means of a liquid crystalline wave function with broken rotational symmetry which can be adiabatically connected to the actual wave function for the corresponding isotropic phase. We perform quantum Monte Carlo simulations in a disk geometry to study the properties of the anisotropic electronic liquid state under consideration. The findings indicate stability of liquid crystalline order in presence of an anisotropic Coulomb interaction potential. The results are consistent with the existence of an anisotropic electronic liquid state in the lowest Landau level.
Increased boron content for wider process tolerance in perpendicular MTJs
Authors: Pellegren J. P. , Furuta M. , Sundar V. , Liu Y. , Zhu J.-G. , Sokalski V.
Published: December 2016

Perpendicular CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) prepared from (Co25Fe75)1−xBx alloys are found to have better annealing stability when made with 30at% boron relative to a more typical 20at% boron. A comparison of film-level properties shows that perpendicular magnetic anisotropy (PMA) increases significantly for 30at%B, while the range of electrode thicknesses that maintain a perpendicular easy axis also increases. Because capping layer interdiffusion has been previously suggested to play a role in the breakdown of PMA with annealing temperature, we have isolated its effect by studying the annealing process of thin Ta/CoFeB(2nm)/Ta trilayers. Through analysis of the decrease in Curie temperature during annealing, we can infer that higher boron content indeed suppresses growth of the intermixed CoFeB-Ta dead layer. For device structures and processing conditions where interdiffusion is a limiting factor, increasing boron content is shown to result in substantially improved tunneling magnetoresistance (TMR).
Anomalous dielectric relaxation with linear reaction dynamics in space-dependent force fields
Authors: Hong Tao , Tang Zhengming , Zhu Huacheng
Published: December 2016

The anomalous dielectric relaxation of disordered reaction with linear reaction dynamics is studied via the continuous time random walk model in the presence of space-dependent electric field. Two kinds of modified reaction-subdiffusion equations are derived for different linear reaction processes by the master equation, including the instantaneous annihilation reaction and the noninstantaneous annihilation reaction. If a constant proportion of walkers is added or removed instantaneously at the end of each step, there will be a modified reaction-subdiffusion equation with a fractional order temporal derivative operating on both the standard diffusion term and a linear reaction kinetics term. If the walkers are added or removed at a constant per capita rate during the waiting time between steps, there will be a standard linear reaction kinetics term but a fractional order temporal derivative operating on an anomalous diffusion term. The dielectric polarization is analyzed based on the Legendre polynomials and the dielectric properties of both reactions can be expressed by the effective rotational diffusion function and component concentration function, which is similar to the standard reaction-diffusion process. The results show that the effective permittivity can be used to describe the dielectric properties in these reactions if the chemical reaction time is much longer than the relaxation time.