bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization‐based power management of a wind farm with battery storage
Authors: Borhan Hoseinali , Rotea Mario A. , Viassolo Daniel
Published: September 2012

This paper presents an optimization‐based control strategy for the power management of a wind farm with battery storage. The strategy seeks to minimize the error between the power delivered by the wind farm with battery storage and the power demand from an operator. In addition, the strategy attempts to maximize battery life. The control strategy has two main stages. The first stage produces a family of control solutions that minimize the power error subject to the battery constraints over an optimization horizon. These solutions are parameterized by a given value for the state of charge at the end of the optimization horizon. The second stage screens the family of control solutions to select one attaining an optimal balance between power error and battery life. The battery life model used in this stage is a weighted Amp‐hour throughput model. The control strategy is modular, allowing for more sophisticated optimization models in the first stage or more elaborate battery life models in the second stage. The strategy is implemented in real time in the framework of model predictive control. Copyright © 2012 John Wiley & Sons, Ltd.
Virtual inertia for variable speed wind turbines
Authors: Zeni Lorenzo , Rudolph Andreas Jakob , Münster‐Swendsen Janus , Margaris Ioannis , Hansen Anca Daniela , Sørensen Poul
Published: September 2012

Inertia provision for frequency control is among the ancillary services that different national grid codes will likely require to be provided by future wind turbines. The aim of this paper is analysing how the inertia response support from a variable speed wind turbine (VSWT) to the primary frequency control of a power system can be enhanced. Unlike fixed speed wind turbines, VSWTs do not inherently contribute to system inertia, as they are decoupled from the power system through electronic converters. Emphasis in this paper is on how to emulate VSWTs inertia using control of the power electronic converter and on its impact on the primary frequency response of a power system. An additional control for the power electronics is implemented to give VSWTs a virtual inertia, referring to the kinetic energy stored in the rotating masses, which can be released initially to support the system's inertia. A simple Matlab/Simulink model and control of a VSWT and of a generic power system are developed to analyse the primary frequency response following different generation losses in a system comprising VSWTs provided with virtual inertia. The possibility of substituting a 50% share of conventional power with wind is also assessed and investigated. The intrinsic problems related to the implementation of virtual inertia are illustrated, addressing their origin in the action of pitch and power control. A solution is proposed, which aims at obtaining the same response as for the system with only conventional generation. The range of wind speeds near the power limitation zone seems to be the most critical from a primary response point of view. The theoretical reasons behind this are elucidated in the paper. Copyright © 2012 John Wiley & Sons, Ltd.
Effects of Vehicle Size on Pedestrian Injury Pattern and Severity: Prospective Study
Authors: AlEassa Essa M. , Eid Hani O. , Abu‐Zidan Fikri M.
Published: September 2012

Background

The type of injuries caused by sport utility vehicles may be different from those caused by small passenger cars. We studied prospectively the effects of the offending vehicle type and design on severity and pattern of pedestrian injuries.

Methods

All injured pedestrians admitted to the two major trauma centers of Al‐Ain city were studied prospectively during the period of April 2006 to October 2007. Patients were classified into two groups according to the offending vehicle type: small vehicle and sport utility vehicle. These two groups were compared regarding the distribution of injury and its severity.

Results

The anatomical distribution of injury in a descending order were the lower extremities (56.3, 67 %), head (53.8, 57.1 %), face (37.5, 57.1 %), and upper extremities (32.5, 28.6 %) in small vehicle and sport utility vehicle groups, respectively. No significant statistical difference has been found between the two groups regarding the anatomical distribution and severity.

Conclusions

The vehicle size and design did not affect the anatomical injury distribution and severity in our setting. High‐impact speed may overcome the vehicle type when it comes to injury severity and pattern of distribution.
From overlooking to concealed: predator avoidance in an apex carnivore
Authors: Wam H. K. , Eldegard K. , Hjeljord O.
Published: September 2012

Many prey species select bed sites that reduce the risk of being caught off guard. We investigated bed sites used by an apex predator (gray wolf, Canis lupus) before and after individuals were approached by humans (N = 48 trials). On 9 out of 10 days, the unprovoked wolves rested at sites high in the terrain with a good overview (overlooking sites). After being approached, they resettled on more concealed sites lower in the terrain. Solitary yearlings used less overlooking sites than adults both before and after disturbance. The study provides experimental evidence that wolves’ behavioural response to approaching humans is analogous to predator avoidance in prey species.
An alternative mechanism for shade adaptation: implication of allometric responses of three submersed macrophytes to water depth
Authors: Fu Hui , Yuan Guixiang , Cao Te , Ni Leyi , Zhang Meng , Wang Shengrui
Published: September 2012

Allometric scaling models describing size‐dependent biological relationships are important for understanding the adaptive responses of plants to environmental variation. In this study, allometric analysis was used to investigate the biomass allocation and morphology of three submerged macrophytes (Potamogeton maackianus, Potamogeton malaianus and Vallisneria natans) in response to water depth (1.0 and 2.5 m) in an in situ experiment. The three macrophytes exhibited different allometric strategies associated with distinct adjustments in morphology and biomass allocation in response to varying water depths. In deeper water, after accounting for the effects of plant size, P. maackianus and P. malaianus tended to enhance light harvesting by allocating more biomass to the stem, increasing shoot height and specific leaf area. V. natans tended to allocate more biomass to the leaf than to the basal stem (rosette), showing a higher leaf mass ratio and shoot height in deeper water. The three species decreased biomass allocation to roots as water depth increased. The main effect of water depth treatments was reduced light availability, which induced plastic shoot or leaf elongation. This shows that macrophytes have evolved responses to light limitation similar to those of terrestrial plants.
Encounters between medical specialists and patients with medically unexplained
physical symptoms; influences of communication on patient outcomes and use of health
care: a literature overview
Authors: Weiland Anne , De Kraats Rianne E. Van , Blankenstein Annette H. , Van Saase Jan L. C. M. , Van der Molen Henk T. , Bramer Wichor M. , Van Dulmen Alexandra M.
Published: September 2012

None
The Knowledge Intuition and the Ability Hypothesis
Authors: Ren Huiming
Published: September 2012

ABSTRACT: I argue that the Ability Hypothesis cannot really accommodate the knowledge intuition that drives the knowledge argument and therefore fails to defend physicalism. When the thought experiment is run with, instead of Mary, an advanced robot Rosemary, for whom there presumably is no distinction between knowledge-how and knowledge-that, proponents of the Ability Hypothesis would have to give a far-fetched and counterintuitive explanation of why Rosemary wouldn’t learn anything new upon release.
THE ROW OF HEADS: A PHILOSOPHICAL TRAGEDY
Authors: Ben-Yami Hanoch
Published: September 2012

Curtain. On the stage there's a row of about forty heads, of natural size, on a long and narrow white board roughly chest height, arranged facing the audience with equal spaces between them from near the left end of the stage to near its right end. The heads are all identical apart from two features. First, the leftmost head is completely bald, the rightmost head has lots of hair on its scalp, and the amount of hair on the heads increases gradually and uniformly from left to right, so that it is hard to discern a difference between any two consecutive heads. Secondly, the colour of the heads changes from bright red on the left to bright orange on the right, again so gradually that it is hard to discern a difference between any two consecutive heads. Apart from the row of heads the stage is empty, with dark background.
Activation of IP3 receptors requires an endogenous 1-8-14 calmodulin-binding motif
Authors: Sun Yi , Rossi Ana M. , Rahman Taufiq , Taylor Colin W.
Published: September 2012

Binding of IP3 (inositol 1,4,5-trisphosphate) to the IP3-binding core (residues 224–604) of IP3Rs (IP3 receptors) initiates opening of these ubiquitous intracellular Ca2+ channels. The mechanisms are unresolved, but require conformational changes to pass through the suppressor domain (residues 1–223). A calmodulin-binding peptide derived from myosin light chain kinase uncouples these events. We identified a similar conserved 1-8-14 calmodulin-binding motif within the suppressor domain of IP3R1 and, using peptides and mutagenesis, we demonstrate that it is essential for IP3R activation, whether assessed by IP3-evoked Ca2+ release or patch-clamp recoding of nuclear IP3R. Mimetic peptides specifically inhibit activation of IP3R by uncoupling the IP3-binding core from the suppressor domain. Mutations of key hydrophobic residues within the endogenous 1-8-14 motif mimic the peptides. Our results show that an endogenous 1-8-14 motif mediates conformational changes that are essential for IP3R activation. The inhibitory effects of calmodulin and related proteins may result from disruption of this essential interaction.
Uncertainty evaluation for the gauge blocks calibration using the modified DMDM gauge block interferometer
Authors: Zivkovic V. , Zelenika S. , Stefanovic G.
Published: September 2012

This paper presents the evaluation of the uncertainty for the length measurement of gauge blocks by optical interferometry. In order to improve the gauge block calibration method and to decrease measurement uncertainty the old Zeiss-Kösters gauge block interferometer has been modified and improved by DMDM (Directorate of Measures and Precious Metals of Serbia). The main modification of the interferometer covers introduction of two laser sources, as new wavelength standards, as well as new hardware system and interferometer software, developed to completely automate the calibration process. The validation of the new measurement procedure details the uncertainty budget. The measurement method and model equation, which serves as the basis for the uncertainty evaluation is described. The uncertainty evaluation is performed in accordance with the document JCGM 100:2008-Evaluation of measurement data – Guide to the expression of uncertainty in measurement (GUM).
Evaluation of metrology technologies for free form surfaces
Authors: Arámbula K. , Siller H.R. , De Chiffre L. , Rodríguez C.A. , Cantatore A.
Published: September 2012

This research work describes a novel approach for comparing different technologies for
free form surface metrology: computerized tomography (CT), photogrammetry and coordinate
measuring machines (CMM). The comparison has the aim of providing relevant information for
the selection of metrology equipment when measuring free form components. Results
demonstrate that there is the imperative need to assess the uncertainty and
reproducibility of CT and photogrammetry measurements by applying some calibration
procedures taking into account some recommendations for work piece alignment. This article
also deals with costs issues, required standards, and necessary additional information
when selecting inspection equipment.
Measurement uncertainty evaluation of automatic Tan Delta and resistivity test set for transformer oil
Authors: Mandavgade N.K. , Jaju S.B. , Lakhe R.R.
Published: September 2012

Quality of transformer oil plays vital role in the performance of transformer in electrical appliances. Measurement uncertainty is a general concept associated with any measurement and can be used in professional decision processes as well as judging attributes in many domains, both theoretical and experimental. As the tolerances applied in industrial production become more demanding, the role of measurement uncertainty becomes more important when assessing conformity to these tolerances. Measurement uncertainty plays a central role in quality assessment and quality standards. In an effort to meet national, international and commercial accreditation requirements, users of transformer oil testing machines must establish adequate methods of determining calibration and test measurement uncertainties. Determining measurement uncertainty for transformer oil testing equipments and test data can be a very complex process. Many factors affect the uncertainty of test data produced by testing machines. In this paper, the concepts associated with the procedure for estimation of uncertainty is discussed and the application of these for the determination of uncertainty in transformer oil testing equipments in government testing labs is illustrated. The objective of this study is to develop a methodology for determining the result of measurement concerning electrical properties of transformer oil and their respective uncertainties.
Generation of 656 nm coherent red-light by frequency-doubled
Nd:YLiF4/β-BaB2O4 laser for a compact
silver atoms optical clock
Authors: Loisel J.-P. , Topsu S. , Chassagne L. , Alayli Y. , Dahoo P.R. , Juncar P.
Published: September 2012

We describe an efficient continuous-wave diode-pumped Nd:YLiF4 laser
oscillating on the σ-polarized
4F3/2-4I13/2
transition at λω = 1312 nm. With a simple
linear cavity laser, we reached an intracavity power of 310 W at λ = 1312
nm for 16 W of absorbed pump power
(λp ~ 806 nm). A 0.25 W of tunable
radiation (λ2ω = 656−658 nm) was obtained
by intracavity second-harmonic generation (SHG) with a 5 × 5 × 7
mm3β-BaB2O4 crystal. Up to 10 mW of
tunable single-frequency operation was observed using a 200 μm thin fused
silica intracavity solid etalon. The optimal waist for a maximum conversion efficiency has
been calculated theoretically using Boyd and Kleiman model. For the 1312–656 nm SHG, we
found a walk-off parameter B = 8.99 and an optimal waist of 25
μm. Comparing to the experimental measurement of the optimal waist, we
found a relative discrepancy of 2.84 × 10-2. This laser is dedicated to the
spectroscopic study of silver atoms trapped in a buffer-gas-free paraffin coated Pyrex
cell that will be used in a compact atomic optical clock.
The influence of geometrical tolerances of Vickers indenter on the accuracy of measured hardness
Authors: El-Sherbiny M. , Hegazy R. , Ibrahim M. , Abuelezz A.
Published: September 2012

This paper reports work carried out to determine the influence of the Pyramidal indenter geometrical errors and tolerances on the accuracy of Vickers hardness measurements. The angle between the opposite faces and line of conjunction of nine indenters were measured by the optical comparator. The influence of the indenter geometry on the hardness accuracy is investigated. Three calibrated reference hardness test blocks were used to check the Vickers hardness test using the nine selected indenters. The results show that the geometrical error of the indenters (specially the angles) considerably affects the accuracy of the hardness measurement. Finite element analysis of the indentation process into metallic test pieces was conducted. Comparison of the experimental results with the numerical findings was discussed. Errors in the experimental values are correlated with measured tolerances in the angles between faces.
A low noise single-transistor transimpedance preamplifier for Fourier-transform mass spectrometry using a T feedback network
Authors: Lin Tzu-Yung , Green Roger J. , O’Connor Peter B.
Published: September 2012

A novel single-transistor transimpedance preamplifier has been introduced for improving performance in Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry. A low noise junction field-effect transistor (JFET), BF862, is used as the main amplification stage of this trans-impedance preamplifier, and a T-shaped feedback network is introduced as both the feedback and the gate biasing solutions. The T feedback network has been studied using an operational amplifier (Op Amp), AD8099. Such a feedback system allows ∼100-fold less feedback resistance at a given transimpedance, hence preserving bandwidth, which is beneficial to applications demanding high gain. The single-transistor preamplifier yields a tested transimpedance of ∼104 Ω (80 dBΩ) in the frequency range between 1 kHz and 1 MHz (mass-to-charge ratio, m/z, of around 180-180k for a 12-T FT-ICR system), with a low power consumption of ∼6 mW, which implies that this preamplifier is well suited to a 12-T FT-ICR mass spectrometer. In trading noise performance for higher trans-impedance, an alternative preamplifier design, an AD8099 preamplifier with the T feedback network, has also been studied with a capability of ∼106 Ω (120 dBΩ) transimpedance in the same frequency range. The resistive components in the T feedback network reported here can be replaced by complex impedances, which allows adaptation of this feedback system to other frequency, transimpedance, and noise characteristics for applications not only in other mass spectrometers, such as Orbitrap, time-of-flight (TOF), and ion trap systems, but also in other charge/current detecting systems such as spectroscopy systems, microscopy systems, optical communication systems, or charge-coupled devices (CCDs).
Rapid preparation of electron beam induced deposition Co magnetic force microscopy tips with 10 nm spatial resolution
Authors: Belova L. M. , Hellwig Olav , Dobisz Elizabeth , Dan Dahlberg E.
Published: September 2012

Magnetic force microscope Co spike tips with lateral magnetic resolution of 10 nm have been prepared. The Co spikes are grown by electron beam induced deposition of Co from Co2(CO)8 gas precursor. The high resolution Co spikes are fabricated at the spot of a tightly focused electron beam on the tip of commercial atomic force microscope cantilevers. Qualitative investigations indicate that a spike grown on a planar base of Co improves the signal to noise.
Spectroscopic refractive indices of monoclinic single crystal and ceramic lutetium oxyorthosilicate from 200 to 850 nm
Authors: Jellison Gerald E. , Specht Eliot D. , Boatner Lynn A. , Singh David J. , Melcher Charles L.
Published: September 2012

The four real values of the dielectric function tensor of the monoclinic crystal Lu2SiO5 or lutetium oxyorthosilicate (LSO) have been determined using generalized ellipsometry from 200 to 850 nm. The three principal values are fit to the Sellmeier model and they indicate that the band gap of LSO is less than ∼9 eV. The off-diagonal element ε12 is non-zero over the entire spectrum, but it is very close to zero for wavelengths longer than ∼400 nm, indicating that structurally monoclinic LSO is nearly optically orthorhombic in this wavelength region. The spectroscopic dielectric functions of three isotropic ceramic LSO samples are presented, which are consistent with the dielectric functions of single-crystal LSO when the effects of optical density are included. As a comparison, the dielectric functions are also determined using relativistic electronic structure and optical calculations based on the recently developed potential functional of Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)].
Nonlinear dynamo in a short Taylor–Couette setup
Authors: Nore C. , Guermond J.-L. , Laguerre R. , Léorat J. , Luddens F.
Published: September 2012

It is numerically demonstrated by means of a magnetohydrodynamics code that a short Taylor–Couette setup with a body force can sustain dynamo action. The magnetic threshold is comparable to what is usually obtained in spherical geometries. The linear dynamo is characterized by a rotating equatorial dipole. The nonlinear regime is characterized by fluctuating kinetic and magnetic energies and a tilted dipole whose axial component exhibits aperiodic reversals during the time evolution. These numerical evidences of dynamo action in a short Taylor–Couette setup may be useful for developing an experimental device.
Competitive fragmentation pathways of acetic acid dimer explored by synchrotron VUV photoionization mass spectrometry and electronic structure calculations
Authors: Guan Jiwen , Hu Yongjun , Zou Hao , Cao Lanlan , Liu Fuyi , Shan Xiaobin , Sheng Liusi
Published: September 2012

In present study, photoionization and dissociation of acetic acid dimers have been studied with the synchrotron vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. Besides the intense signal corresponding to protonated cluster ions (CH3COOH)n·H+, the feature related to the fragment ions (CH3COOH)H+·COO (105 amu) via β-carbon-carbon bond cleavage is observed. By scanning photoionization efficiency spectra, appearance energies of the fragments (CH3COOH)·H+ and (CH3COOH)H+·COO are obtained. With the aid of theoretical calculations, seven fragmentation channels of acetic acid dimer cations were discussed, where five cation isomers of acetic acid dimer are involved. While four of them are found to generate the protonated species, only one of them can dissociate into a C–C bond cleavage product (CH3COOH)H+·COO. After surmounting the methyl hydrogen-transfer barrier 10.84 ± 0.05 eV, the opening of dissociative channel to produce ions (CH3COOH)+ becomes the most competitive path. When photon energy increases to 12.4 eV, we also found dimer cations can be fragmented and generate new cations (CH3COOH)·CH3CO+. Kinetics, thermodynamics, and entropy factors for these competitive dissociation pathways are discussed. The present report provides a clear picture of the photoionization and dissociation processes of the acetic acid dimer in the range of the photon energy 9–15 eV.
Phase slips and dissipation of Alfvenic intermediate shocks and solitons
Authors: Laveder D. , Passot T. , Sulem P. L.
Published: September 2012

The time evolution of a rotational discontinuity, characterized by a change of the magnetic-field direction by an angle Δθ such that π<|Δθ|<2π and no amplitude variation, is considered in the framework of asymptotic models that, through reductive perturbative expansions, isolate the dynamics of parallel or quasi-parallel Alfvén waves. In the presence of viscous and Ohmic dissipation, and for a zero or sufficiently weak dispersion (originating from the Hall effect), an intermediate shock rapidly forms, steepens and undergoes reconnection through a quasi gradient collapse, leading to a reduction of |Δθ| by an amount of 2π, which can be viewed as the breaking of a topological constraint. Afterwards, as |Δθ|<π, the intermediate shock broadens and slowly dissipates. In the case of a phase jump |Δθ|>3π, which corresponds to a wave train limited on both sides by uniform fields, a sequence of such reconnection processes takes place. Differently, in the presence of a strong enough dispersion, the rotational discontinuity evolves, depending on the sign of Δθ, to a dark or bright soliton displaying a 2π phase variation. The latter is then eliminated, directly by reconnection in the case of a dark soliton, or through a more complex process involving a quasi amplitude collapse in that of a bright soliton. Afterwards, the resulting structure is progressively damped. For a prescribed initial rotational discontinuity, both quasi gradient and amplitude collapses lead to a sizeable energy decay that in the collisional regime is independent of the diffusion coefficient η but requires a time scaling like 1/η. In the non-collisional regime where dissipation originates from Landau resonance, the amount of dissipated energy during the event is independent of the plasma β, but the process becomes slower for smaller β.
Heavy-ion emission from short-pulse laser-plasma interactions with thin foils
Authors: Sinenian N. , Fiksel G. , Frenje J. A. , Freeman C. G. , Manuel M. J.-E. , Casey D. T. , Nilson P. M. , Stoeckl C. , Theobald W. , Meyerhofer D. D. , Petrasso R. D.
Published: September 2012

A Thomson parabola ion spectrometer, implemented on the Laboratory for Laser Energetics Multi-Terawatt laser facility, has been used to study heavy-ion acceleration from ultra-intense laser-plasma interactions. These studies were conducted using 20 μm-thick flat foil targets with on-target intensities of 4−5×1019 W-cm−2. Several charge states of energetic heavy ions were accelerated from the rear of Al and Cu foils in the presence of hydrocarbon contaminants. In contrast to previous work, we show that the mean and maximum energies of each heavy-ion species scale linearly with only the charge of the ion, and not the charge-to-mass ratio, implying that the space-charge is not readily depleted as ions expand. It has been shown previously and observed here that the maximum heavy-ion energies are lower than that of protons, though a fundamental explanation for this discrepancy has not been provided. We show how a two-temperature electron distribution, observed in these experiments, explains these observations.
The effect of the top electrode interface on the hysteretic behavior of epitaxial ferroelectric Pb(Zr,Ti)O3 thin films with bottom SrRuO3 electrode
Authors: Pintilie L. , Pasuk I. , Negrea R. , Filip L. D. , Pintilie I.
Published: September 2012

The hysteretic behavior of the epitaxial Pb(Zr,Ti)O3 thin films with different top metal electrodes is studied, with emphasis on the influence of the leakage current and trap generation current on the shape of the loop as well as on the magnitude of the measured polarization. Cu, Pt, and SrRuO3 were used as top contacts and important differences were observed for measurements performed in both dynamic and static modes, although the contacts were deposited on the same epitaxial Pb(Zr,Ti)O3 film grown on SrRuO3/SrTiO3 substrate. A peculiar behavior was observed especially for the static hysteresis loops where, depending of the top contact, the loop is influenced mainly by the leakage current (Pt) or by the trap generation current (Cu and SrRuO3). The last one can contribute with an additive charge, having a linear dependence on the applied voltage, as suggested by the simple model developed to explain the abnormally high values of the dielectric constant extracted from the linear part of the static hysteresis loop. It is concluded that the properties of the top electrode interface can significantly impact the hysteretic behavior of the ferroelectric films.
Vortex dynamics in triangular-shaped confining potentials
Authors: Vogel Andreas , Corinna Niemann Anna , Stenner Charlotte , Drews André , Im Mi-Young , Fischer Peter , Meier Guido
Published: September 2012

Triangular-shaped permalloy microstructures in the vortex magnetization state are studied via transmission soft x-ray microscopy, broadband-ferromagnetic resonance measurements, and micromagnetic simulations. The vortex chirality can be controlled via the direction of a saturating in-plane magnetic field applied before nucleation of the vortex state. The resonance frequencies of vortex gyration are probed for different equilibrium positions within the magnetic structure to determine the shape of the asymmetric confining potential. The experimental results are shown to coincide with micromagnetic simulations.
A pseudo-matched filter for chaos
Authors: Cohen Seth D. , Gauthier Daniel J.
Published: September 2012

A matched filter maximizes the signal-to-noise ratio of a signal. In the recent work of Corron et al. [Chaos 20, 023123 (2010)], a matched filter is derived for the chaotic waveforms produced by a piecewise-linear system. This system produces a readily available binary symbolic dynamics that can be used to perform correlations in the presence of large amounts of noise using the matched filter. Motivated by these results, we describe a pseudo-matched filter, which operates similarly to the original matched filter. It consists of a notch filter followed by a first-order, low-pass filter. We compare quantitatively the matched filter's performance to that of our pseudo-matched filter using correlation functions. On average, the pseudo-matched filter performs with a correlation signal-to-noise ratio that is 2.0 dB below that of the matched filter. Our pseudo-matched filter, though somewhat inferior in comparison to the matched filter, is easily realizable at high speed (>1 GHz) for potential radar applications.
An analytical model of computing ion energy distributions for multiple frequencies capacitive discharges
Authors: Zhou Zhuwen , Linghu Rongfeng , Deng Mingsen , Xiong Deyong
Published: September 2012

We have developed an analytical multi-frequency model, which results in accurate multi-peaks of the ion energy distributions (IEDs) for the given control parameters. The model can analytically calculate and predict the IEDs multiple peaks and energy width with necessary plasma parameters. This model can also predict the IEDs from multiple frequencies' drives at any voltage, the associated results are compared with particle-in-cell (PIC) simulations. The IED at a surface is an important parameter for processing in multiple radio frequencies driven capacitive discharges. The analytical model is developed for the IED in a low pressure discharge based on a linear transfer function that relates the time-varying sheath voltage to the time-varying ion energy response at the surface. This model is in good agreement with PIC simulations over a wide range of multiple frequencies driven capacitive discharge excitations.
Frequency analysis of a step dynamic pressure calibrator
Authors: Choi In-Mook , Yang Inseok , Yang Tae-Heon
Published: September 2012

A dynamic high pressure standard is becoming more essential in the fields of mobile engines, space science, and especially the area of defense such as long-range missile development. However, a complication arises when a dynamic high pressure sensor is compared with a reference dynamic pressure gauge calibrated in static mode. Also, it is difficult to determine a reference dynamic pressure signal from the calibrator because a dynamic high pressure calibrator generates unnecessary oscillations in a positive-going pressure step method. A dynamic high pressure calibrator, using a quick-opening ball valve, generates a fast step pressure change within 1 ms; however, the calibrator also generates a big impulse force that can lead to a short life-time of the system and to oscillating characteristics in response to the dynamic sensor to be calibrated. In this paper, unnecessary additional resonant frequencies besides those of the step function are characterized using frequency analysis. Accordingly, the main sources of resonance are described. In order to remove unnecessary frequencies, the post processing results, obtained by a filter, are given; also, a method for the modification of the dynamic calibration system is proposed.
Nanodomain structures formation during polarization reversal in uniform electric field in strontium barium niobate single crystals
Authors: Shur V. Ya. , Shikhova V. A. , Ievlev A. V. , Zelenovskiy P. S. , Neradovskiy M. M. , Pelegov D. V. , Ivleva L. I.
Published: September 2012

We have studied the ferroelectric nanodomain formation in single crystals of strontium barium niobate Sr0.61Ba0.39Nb2O6 using piezoelectric force microscopy and Raman confocal microscopy. The nanodomain structures have been created by application of the uniform electric field at room temperature. Four variants of nanodomain structure formation have been revealed: (1) discrete switching, (2) incomplete domain merging, (3) spontaneous backswitching, and (4) enlarging of nanodomain ensembles. Kinetics of the observed micro- and nanodomain structures has been explained on the basis of approach developed for lithium niobate and lithium tantalate crystals.
Procedure for numerical integration of the magnetocaloric effect
Authors: Moore J. D. , Skokov K. P. , Liu J. , Gutfleisch O.
Published: September 2012

When the magnetocaloric effect is obtained using indirect or direct techniques, the result is the isothermal entropy change ΔSiso(T,ΔH) or the adiabatic temperature change ΔTad(T,ΔH). Evaluation of the linking relation dTad=−(T/Cp)×dSiso (Cp, specific heat; T, temperature) as a way to determine the magnetocaloric effect, however, is typically not performed because it requires detailed knowledge of Cp(T,H). Here, we outline the procedure for numerical integration of the magnetocaloric effect—this is important for a physics understanding and as a practical guide on implementing the procedure. The process is notably different than the well-known method used to calculate ΔSiso from the Maxwell equation. We test the procedure by using it to calculate Cp (with dTad and dSiso as input data) and comparing it with directly measured Cp, finding excellent agreement for both first-order transition in LaFe11.6Si1.4 and second-order transition in Gd. We establish the merits and limitations of the method. In particular, the presence of a demagnetizing effect in experimental data can reduce accuracy of the method. The procedure can be applied to accurately model the magnetocaloric effect in a magnetic cooling cycle.
Spectroscopic analysis of Al and N diffusion in HfO2
Authors: Lysaght P. S. , Woicik J. C. , Sahiner M. A. , Price J. , Weiland C. , Kirsch P. D.
Published: September 2012

X-ray photoelectron core level spectroscopy, secondary ion mass spectroscopy, spectroscopic ellipsometry, and extended x-ray absorption fine structure measurements have been employed to distinguish the effects of Al and N diffusion on the local bonding and microstructure of HfO2 and its interface with the Si substrate in (001)Si/SiOx/2 nm HfO2/1 nm AlOx film structures. The diffusion of Al from the thin AlOx cap layer deposited on both annealed and unannealed HfO2 has been observed following anneal in N2 and NH3 ambient. Both N2 and NH3 subsequent anneals were performed to decouple incorporated nitrogen from thermal reactions alone. Causal variations in the HfO2 microstructure combined with the dependence of Al and N diffusion on initial HfO2 conditions are presented with respect to anneal temperature and ambient.
Charge carrier dynamics and interactions in electric force microscopy
Authors: Lekkala Swapna , Hoepker Nikolas , Marohn John A. , Loring Roger F.
Published: September 2012

In electric force microscopy, a charged atomic force microscope tip in vacuum senses a fluctuating electrical force generated by the sample. Such measurements can in principle probe electrical noise generated by moving charge carriers in an organic semiconductor. We present a theory of cantilever frequency fluctuations in electric force microscopy, driven by coupled charge carrier dynamics and dielectric fluctuations. The connection between observable frequency fluctuations in electric force microscopy and the Casimir-Lifshitz force is described. This classical electrodynamic calculation is based on Maxwell's equations coupled to diffusive carrier transport. The effects of carrier transport and inter-carrier interactions on the spectrum of cantilever frequency noise are elucidated. We find that a simplified model of freely diffusing carriers can overestimate cantilever frequency noise by several orders of magnitude because of the neglect of interactions. Electric force microscopy measurements on an organic field effect transistor are reported and qualitatively interpreted in terms of the suppression of electrical noise from charge carriers by Coulomb interactions.
Highly conductive p-type amorphous oxides from low-temperature solution processing
Authors: Li Jinwang , Tokumitsu Eisuke , Koyano Mikio , Mitani Tadaoki , Shimoda Tatsuya
Published: September 2012

We report solution-processed, highly conductive (resistivity 1.3–3.8 mΩ cm), p-type amorphous A-B-O (A = Bi, Pb; B = Ru, Ir), processable at temperatures (down to 240 °C) that are compatible with plastic substrates. The film surfaces are smooth on the atomic scale. Bi-Ru-O was analyzed in detail. A small optical bandgap (0.2 eV) with a valence band maximum (VBM) below but very close to the Fermi level (binding energy EVBM = 0.04 eV) explains the high conductivity and suggests that they are degenerated semiconductors. The conductivity changes from three-dimensional to two-dimensional with decreasing temperature across 25 K.
Degenerate parallel conducting layer and conductivity type conversion observed from p-Ge1−ySny (y = 0.06%) grown on n-Si substrate
Authors: Ryu Mee-Yi , Yeo Y. K. , Ahoujja M. , Harris Tom , Beeler Richard , Kouvetakis John
Published: September 2012

Electrical properties of p-Ge1−ySny (y = 0.06%) grown on n-Si substrate were investigated through temperature-dependent Hall-effect measurements. It was found that there exists a degenerate parallel conducting layer in Ge1−ySny/Si and a second, deeper acceptor in addition to a shallow acceptor. This parallel conducting layer dominates the electrical properties of the Ge1−ySny layer below 50 K and also significantly affects those properties at higher temperatures. Additionally, a conductivity type conversion from p to n was observed around 370 K for this sample. A two-layer conducting model was used to extract the carrier concentration and mobility of the Ge1−ySny layer alone.
Enhanced sampling molecular dynamics simulation captures experimentally suggested intermediate and unfolded states in the folding pathway of Trp-cage miniprotein
Authors: Shao Qiang , Shi Jiye , Zhu Weiliang
Published: September 2012

The ability of molecular dynamics simulation to capturing the transient states within the folding pathway of protein is important to the understanding of protein folding mechanism. In the present study, the integrated-tempering-sampling molecular dynamics (ITS-MD) simulation was performed to investigate the transient states including intermediate and unfolded ones in the folding pathway of a miniprotein, Trp-cage. Three force fields (FF03, FF99SB, and FF96) were tested, and both intermediate and unfolded states with their characteristics in good agreement with experiments were observed during the simulations, which supports the hypothesis that observable intermediates might present in the folding pathway of small polypeptides. In addition, it was demonstrated that FF03 force field as combined with ITS-MD is in overall a more proper force field than the others in reproducing experimentally recorded properties in UVRS, ECD, and NMR, Photo-CIDNP NMR, and IR T-jump experiments, and the folding/unfolding thermodynamics parameters, such as ΔGU, ΔCp, and ΔHU (Tm). In summary, the present study showed that using suitable force field and energy sampling method, molecular dynamics simulation could capture the transient states within the folding pathway of protein which are consistent with the experimental measurements, and thus provide information of protein folding mechanism and thermodynamics.
Influence of indium content and temperature on Auger-like recombination in InGaN quantum wells grown on (111) silicon substrates
Authors: Galler B. , Drechsel P. , Monnard R. , Rode P. , Stauss P. , Froehlich S. , Bergbauer W. , Binder M. , Sabathil M. , Hahn B. , Wagner J.
Published: September 2012

High-efficiency InGaN-based light-emitting diodes have been grown on (111) silicon substrates and investigated with regard to efficiency and carrier lifetime as a function of current density. Using a single quantum well active layer ensures a well-defined active volume which enables the precise determination of the recombination coefficients in the ABC rate model for different emission wavelengths and junction temperatures. Good agreement of the resulting C values with calculated Auger coefficients is found both with respect to absolute value as well as their dependence on bandgap energy and temperature.
Enhancement of room temperature ferromagnetism in Mn-implanted Si by He implantation
Authors: Chen Jihong , Guo Liping , Liu Congxiao , Luo Fengfeng , Li Tiecheng , Zheng Zhongcheng , Jin Shuoxue , Yang Zheng
Published: September 2012

Room temperature ferromagnetism in Mn-implanted p-Si was enhanced dramatically by implantation of He. A 75 nm end-of-range region was found in the sample, with large scale and inhomogeneous damaging but preserved Si lattice periodicity. The end-of-range region shows an intrinsic magnetization of ∼100 emu/cm3. High resolution transmission electron microscopy and x-ray photoelectron spectroscopy measurements indicate that the spin polarization of Si dangling bonds rather than Mn impurity was the major source for the enhanced magnetism.
Mean first-passage time for random walks in general graphs with a deep trap
Authors: Lin Yuan , Julaiti Alafate , Zhang Zhongzhi
Published: September 2012

We provide an explicit formula for the global mean first-passage time (GMFPT) for random walks in a general graph with a perfect trap fixed at an arbitrary node, where GMFPT is the average of mean first-passage time to the trap over all starting nodes in the whole graph. The formula is expressed in terms of eigenvalues and eigenvectors of Laplacian matrix for the graph. We then use the formula to deduce a tight lower bound for the GMFPT in terms of only the numbers of nodes and edges, as well as the degree of the trap, which can be achieved in both complete graphs and star graphs. We show that for a large sparse graph, the leading scaling for this lower bound is proportional to the system size and the reciprocal of the degree for the trap node. Particularly, we demonstrate that for a scale-free graph of size N with a degree distribution P(d) ∼ d−γ characterized by γ, when the trap is placed on a most connected node, the dominating scaling of the lower bound becomes N1−1/γ, which can be reached in some scale-free graphs. Finally, we prove that the leading behavior of upper bounds for GMFPT on any graph is at most N3 that can be reached in the bar-bell graphs. This work provides a comprehensive understanding of previous results about trapping in various special graphs with a trap located at a specific location.
Defect specific photoconductance: Carrier recombination through surface and other extended crystal imperfections
Authors: Kamieniecki Emil
Published: September 2012

The analysis of carrier recombination through defects using a unified approach, common to all extended defects independent of their dimensionality is presented. The considered crystal defects include surface, grain boundaries, dislocations, and clusters of crystal defects and impurities. It is shown that, at low carrier injection levels, carrier recombination through extended defects is controlled by the electrostatic potential barrier formed at the defects. The barrier model is applied to the analysis of the photoconductance in the defect controlled regions. Unlike in the case of recombination through point defects in the bulk, which is characterized by the linear dependence of the steady-state photoconductance on the light intensity and exponential decay of the photoconductance after cessation of the illumination, the photoconductance associated with recombination through extended defects under depletion conditions exhibits logarithmic dependence on the light intensity and characteristic logarithmic decay after cessation of the illumination. The predictions of the “barrier-controlled recombination” model are compared with the measurements of photoconductance in electronic grade silicon. Differentiation between time dependences of the photoconductance decay associated with recombination through the point defects and through the extended crystal imperfections is used as a basis of the defect specific photoconductance (DSPC) methodology. It is shown that DSPC allows for the separation of the bulk and surface characteristics without any additional surface treatments, enabling electrical characterization of both bulk and thin-film wafer structures critical for photovoltaic (PV) solar cell and high-brightness light emitting diode (HB-LED) manufacturing. The comparison of the “barrier-controlled recombination” and standard diffusion model based on surface recombination velocity is discussed.
Platinum thickness dependence of the inverse spin-Hall voltage from spin pumping in a hybrid yttrium iron garnet/platinum system
Authors: Castel V. , Vlietstra N. , Ben Youssef J. , van Wees B. J.
Published: September 2012

We show the experimental observation of the platinum thickness dependence in a hybrid yttrium iron garnet/platinum system of the inverse spin-Hall effect from spin pumping, over a large frequency range and for different radio-frequency powers. From the measurement of the voltage at the resonant condition and the resistance of the normal metal layer, a strong enhancement of the ratio of these quantities has been observed, which is not in agreement with previous studies on the NiFe/platinum system. The origin of this behaviour cannot be fully explained by the spin transport model that we have used and is therefore still unclear.
Dynamical regimes due to technological change in a microeconomical model of production
Authors: Hamacher K.
Published: September 2012

We develop a microeconomical model to investigate the impact of technological change onto production decisions of suppliers—modeling an effective feedback mechanism of the market. An important property—the time horizon of production planning—is related to the Kolmogorov entropy of the one-dimensional maps describing price dynamics. We simulate this price dynamics in an ensemble representing the whole macroeconomy. We show how this model can be used to support ongoing research in economic growth and incorporate the obtained microeconomic findings into the discussion about appropriate macroeconomic quantities such as the production function—thus effectively underpinning macroeconomics with microeconomical dynamics. From there we can show that the model exhibits different dynamical regimes (suggesting “phase transitions”) with respect to an order parameter. The non-linear feedback under technological change was found to be the crucial mechanism. The implications of the obtained regimes are finally discussed.
Interface mediated ferromagnetism in bulk CuO/Cu2O composites
Authors: Gao Daqiang , Zhang Zhipeng , Yang Zhaolong , Xue Desheng
Published: September 2012

In this letter, we report the interface-related room temperature ferromagnetism in bulk CuO/Cu2O composites which were synthesized by heat-decomposing or oxidation methods with the CuO and Cu2O as the precursors, respectively. Magnetic measurement results indicate that all the CuO/Cu2O composites show obvious room temperature ferromagnetism, while the samples with the pure CuO and Cu2O phases are paramagnetic. What is more, the ferromagnetism can be tuned by changing the phase rations of the CuO and Cu2O in the composites. The observed ferromagnetism in CuO/Cu2O composites is considered to be related to the interface between CuO and Cu2O phases.
15% efficient Cu(In,Ga)Se2 solar cells obtained by low-temperature pulsed electron deposition
Authors: Rampino S. , Armani N. , Bissoli F. , Bronzoni M. , Calestani D. , Calicchio M. , Delmonte N. , Gilioli E. , Gombia E. , Mosca R. , Nasi L. , Pattini F. , Zappettini A. , Mazzer M.
Published: September 2012

An approach to low-cost production of Cu(In,Ga)Se2 (CIGS) solar cells based on pulsed electron deposition (PED) has achieved a crucial milestone. Lab-scale solar cells with efficiencies exceeding 15% were obtained by depositing CIGS from a stoichiometric quaternary target at 270 °C and without any post-growth treatment. An effective control of the p-doping level in CIGS was achieved by starting the PED deposition with a layer of NaF tailored to generate the optimum Na diffusion. These results show that PED is a promising technology for the development of a competitive low-cost production process for CIGS solar cells.