bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring the Advantage of Kalman-Weighted Averaging for Auditory Brainstem Response Hearing Evaluation in Infants
Authors: Cone Barbara , Norrix Linda W.
Published: February 2015

Purpose

The purposes of this study were to (a) measure the effects of Kalman-weighted averaging methods on auditory brainstem response (ABR) threshold, latency, and amplitude; (b) translate lab findings to the clinical setting; and (c) estimate cost savings when ABRs can be obtained in nonsedated infants.

Method

ABRs were recorded in 40 adults with normal hearing during induced motor noise conditions using the Kalman-weighted averaging method implemented on a commercial system, the Vivosonic Integrity (Vivosonic Inc., Toronto, Ontario, Canada). The device was then used to test 34 infants in awake and asleep states. The advantages of the Kalman-weighted averaging method were modeled in terms of time saved for conducting an ABR evaluation.

Results

Kalman-weighted ABR threshold estimates were 6–7 dB lower than with conventional methods during induced motor noise. When used to obtain ABRs in infants who were awake, the number of sweeps required to obtain a result was significantly greater than that required for a sleeping infant but well within the range for clinical application.

Conclusions

The use of Kalman-weighted averaging provides a measurable advantage over conventional methods and may reduce costs for the pediatric audiology practice.
Comparison of Performance of Older Adults on Two Tests of Temporal Resolution
Authors: Vaidyanath Ramya , Yathiraj Asha
Published: February 2015

Purpose

Gap-detection thresholds have been reported to vary depending on the type of stimuli used. The current study compared the performance of older adults on 2 tests of temporal resolution, one with random gaps and the other with gaps in the center of a noise signal. The study also determined which of the 2 tests was able to detect more temporal resolution deficits in older individuals.

Method

Two tests of temporal resolution, the Gap Detection Test (GDT; Shivaprakash, 2003) and the Gaps-In-Noise test (GIN; Musiek et al., 2005), were administered to 31 older adults with near normal hearing, aged 55 to 70 years. The order in which the tests were administered was randomized.

Results

The gap-detection thresholds obtained using GIN were significantly higher than those obtained using GDT. The difference in thresholds was ascribed to the randomness with which gaps were interspersed within noise segments in the 2 tests. More individuals failed on GIN than GDT. The older adults with high-frequency hearing loss obtained poorer gap thresholds than those with normal hearing.

Conclusion

The results indicated that older individuals failed GIN more often compared to GDT. This was attributed to the differences in stimuli and procedure used in the 2 tests.
Speech-Language Pathologists' Knowledge and Attitudes Regarding Lesbian, Gay, Bisexual, Transgender, and Queer (LGBTQ) Populations
Authors: Hancock Adrienne , Haskin Gregory
Published: February 2015

Purpose

The cultures and service needs of lesbian, gay, bisexual, transgender, and queer (LGBTQ) minority groups are relevant to speech-language pathologists (SLPs). In particular, transgender individuals seeking communication services from SLPs in order to improve quality of life require culturally and clinically competent clinicians. Knowledge and attitudes regarding a population are foundational stages toward cultural competency (Turner, Wilson, & Shirah, 2006). The purpose of this research is to assess LGBTQ knowledge and attitudes among aspiring and practicing SLPs.

Method

An online survey was completed by 279 SLPs from 4 countries.

Results

Mean accuracy scores on LGBTQ culture questions were near 50%. Self-ratings indicated more comfort than knowledge, with generally positive feelings toward LGBTQ subgroups. Transgender communication is within SLPs' scope of practice, yet 47% indicated such services were not addressed in their master's curriculum, and 51% did not know how to describe transgender communication therapy. When respondents were asked to indicate priority of 10 LGBTQ topics for a continuing education seminar, communication masculinization/feminization best practice and case examples had the highest mean priority scores.

Conclusion

There is a need to promote LGBTQ cultural competence within speech-language pathology. This study provides direction for improving LGBTQ cultural competence among SLPs.
The Efficacy of Recasts in Language Intervention: A Systematic Review and Meta-Analysis
Authors: Cleave Patricia L. , Becker Stephanie D. , Curran Maura K. , Van Horne Amanda J. Owen , Fey Marc E.
Published: February 2015

Purpose

This systematic review and meta-analysis critically evaluated the research evidence on the effectiveness of conversational recasts in grammatical development for children with language impairments.

Method

Two different but complementary reviews were conducted and then integrated. Systematic searches of the literature resulted in 35 articles for the systematic review. Studies that employed a wide variety of study designs were involved, but all examined interventions where recasts were the key component. The meta-analysis only included studies that allowed the calculation of effect sizes, but it did include package interventions in which recasts were a major part. Fourteen studies were included, 7 of which were also in the systematic review. Studies were grouped according to research phase and were rated for quality.

Results

Study quality and thus strength of evidence varied substantially. Nevertheless, across all phases, the vast majority of studies provided support for the use of recasts. Meta-analyses found average effect sizes of .96 for proximal measures and .76 for distal measures, reflecting a positive benefit of about 0.75 to 1.00 standard deviation.

Conclusion

The available evidence is limited, but it is supportive of the use of recasts in grammatical intervention. Critical features of recasts in grammatical interventions are discussed.

Supplemental Material

https://doi.org/10.23641/asha.6170231
Variable data‐window‐size recursive least‐squares algorithm for dynamic system identification
Authors: Cho Hyeonwoo , Yu Son‐Cheol
Published: February 2015

A variable data‐window size for the recursive least‐squares algorithm is proposed. Using the window‐size selection criterion, the window size can be suitably adjusted for the conditions of the system parameters to be estimated.
Flexible and low‐complexity bit‐reversal scheme for serial‐data FFT processors
Authors: Yu Chu
Published: February 2015

A simple yet flexible bit‐reversal hardware scheme applicable to variable‐length fast Fourier transform (FFT) processors to facilitate the continuous flow of serial data is presented. The proposed design employs a length‐N two‐port register file (N is the processing size of the FFT), and a simple address generator to perform variable‐length bit‐reversal operations on the input or output of the FFT processor. This enables the conversion of bit‐reversed data to the natural order. The proposed scheme is superior to the existing technologies because of its ability to process a continuous‐flow input sequence and its applicability to variable‐length FFT processors without the need for a shuffling mechanism on the input and output memory ports. The proposed design is particularly suitable for applications involving bit‐reversal operations on large‐point FFT processors.
High‐speed two‐step single‐slope ADC using multi‐sampling with partial conversion
Authors: Kim Jong‐Boo , Hong Seong‐Kwan , Kwon Oh‐Kyong
Published: February 2015

A multi‐sampling method with partial conversion for a low‐noise and high‐speed analogue‐to‐digital converter (ADC) is proposed. The proposed multi‐sampling method divides the total bits of an ADC into upper and lower bits, and only repeats the lower bit conversion using the two‐step ADC architecture. This partial conversion decreases the A/D conversion time, along with noise reduction by multi‐sampling. The proposed method with pseudo‐multi‐sampling or correlated multi‐sampling for lower bit conversion reduces the number of clock cycles by 99.7 or 98.8%, respectively, compared with the conventional multi‐sampling method.
Semi‐modular delay model revisited in context of relative timing
Authors: Park Hoon , He Anping , Roncken Marly , Song Xiaoyu
Published: February 2015

A new definition of semi‐modularity to accommodate relative timing constraints in self‐timed circuits is presented. While previous definitions ignore such constraints, the new definition takes them into account. The difference on a design solution for a well‐known speed‐independent circuit implementation of the Muller C element and a set of relative timing constraints that renders the implementation hazard free is illustrated. The old definition produces a false semi‐modularity conflict that cannot exist due to the set of imposed constraints. The new definition correctly accepts the solution.
Quantum‐inspired hybrid medical ultrasound images despeckling method
Authors: Fu Xiaowei , Wang Yi , Chen Li , Dai Yun
Published: February 2015

A novel medical ultrasound despeckling method combining quantum‐inspired bilateral filtering and wavelet thresholding is proposed. An adaptive bilateral filter under the framework of quantum signal processing is exploited in this method and used as a pre‐processing step. Then wavelet thresholding, on the assumption that the signal and noise coefficients in the wavelet domain are subject to generalised Laplace distribution and Gaussian distribution, respectively, is applied to the pre‐filtered image. Experiments show that the proposed method can obtain a better speckle noise reduction performance while retaining high‐contrast features such as edges.
SEU reliability evaluation of 3D ICs
Authors: Li Huiyun , Hu Xiaobo , Shao Cuiping , Zhou Jianbin , Xu Guoqing
Published: February 2015

The single‐event‐upset (SEU) reliability is a concern for three‐dimensional (3D) integrated circuits (ICs), mainly due to the carrier mobility change caused by thermo‐mechanical stress from through‐silicon vias (TSVs) and the shallow trench isolation (STI). A systematic evaluation method is proposed to identify the vulnerability within 3D ICs at design time. The evaluation flow involves the TSV/STI stress‐aware mobility variation calculation, sensitive region marking, insertion of excitation signals and then the simulation of the 3D ICs. This method is able to help 3D IC designers to evaluate and enhance the SEU reliability at design time.
Eight‐element UWB‐MIMO array with three distinct isolation mechanisms
Authors: Saleem R. , Bilal M. , Bajwa K.B. , Shafique M.F.
Published: February 2015

An eight‐element multiple‐input–multiple‐output (MIMO) antenna array for ultra‐wideband (UWB) communication is reported. The proposed array contains eight antenna elements having annular ring slots in the middle of each element and tapered feed lines for impedance matching. The defected ground planes are introduced on the back of these antenna elements. Moreover, closed‐loop frequency selective surfaces are introduced to achieve enhanced isolation between antenna pairs. A quad‐strip connected circular arc decoupling structure is also used to enhance the isolation among particular antenna elements. These decoupling structures provide isolation of 20 dB over most of the desired UWB spectrum. The proposed UWB‐MIMO array has dimensions of 60 × 93 mm2. The proposed design is suitable for integration with system‐in‐package applications and provides ease of connectivity on all four sides.
Fragment‐type UHF RFID tag embedded in QR barcode label
Authors: Han Jiangxiao , Wang Gang , Sidén Johan
Published: February 2015

The fragment‐type appearance of two‐dimensional barcodes provides the hint of embedding a fragment‐type ultra‐high frequency radio frequency identification (UHF RFID) tag into the barcode. In this reported work, genetic algorithm searching is used to select which modules in a quick response (QR) barcode should be metalised and connected to form the RFID tag antenna. The design is demonstrated by embedding a 915 MHz UHF RFID tag in a QR barcode label of dimensions 14.5 × 14.5 mm on a single‐sided PCB.
Hybrid cooperation for machine‐to‐machine data collection in hierarchical smart building networks
Authors: Luan Xi , Zheng Zijie , Wang Tianyu , Wu Jianjun , Xiang Haige
Published: February 2015

Machine‐to‐machine (M2M) communication plays an important role in various kinds of intelligent networks. In this study, a hybrid cooperation scheme for data collection in hierarchical smart building networks (SBN) is proposed under the framework of M2M communications. The hierarchical network structure means that the data collection process is carried out via multi‐layer communications. In the first layer, smart metres organise themselves into clusters and send information to the cluster‐heads. Then all cluster‐heads forward the received information to the base station automatically in the second layer. In particular, the roles of cluster‐head can be acted by either fixed nodes or user terminals in the building, and this endow a hybrid cooperation mode to the data collection process. To construct the network structure and utilise the resources efficiently, the authors first provide some theoretical analysis on the influence of network structure and bandwidth constraints. Then a distributed scheme for joint structure formation and subband allocation is proposed based on coalitional game theory. Furthermore, for the feasibility of this scheme in practical applications, some improvements of the proposed scheme have also been made at last. The advantages of the proposed scheme are verified by simulation results.
Evolutionary Prisoner's Dilemma in updating fuzzy linguistic model to damp power system oscillations
Authors: Vakula V. S. , Padmaja A. , Sudha K. Rama
Published: February 2015

This study presents a novel technique to extract and update the rules of fuzzy linguistic model (FLM). The interrelations between inputs and outputs of a FLM are assigned using payoff matrix through Prisoner's Dilemma (PD). These interrelations are updated by updating the payoff matrix through Evolutionary Algorithm based PD to propose Evolutionary Algorithm based fuzzy Prisoner's Dilemma linguistic model (FPDLM). The effect of evolutionary algorithm based FPDLM as power system stabiliser is tested on single machine infinite bus system and also multi machine system.
Recovering the modular multilevel converter from a cleared or isolated fault
Authors: Li Tan , Zhao Chengyong
Published: February 2015

The modular multilevel converter (MMC) is one of the best potential candidates for high‐voltage direct current (HVDC). Various kinds of faults may occur in an MMC‐HVDC system. The system should be restarted by deblocking the converter after a temporary fault is cleared or a fault is isolated, thus recovering the power transmission as soon as possible. This study analyses the recovery process after the converter is deblocked. The analysis shows that the capacitor voltages of the three upper arms or the three lower arms can be rebalanced quickly, and the power transmission and the DC voltage can be recovered with the original main controller. However, the speed of rebalancing the capacitor voltages of the upper arm and the lower arm depends on the arm resistance, the modulation index and so on, and is probably slow. To improve the damping characteristic of the MMC, a dedicated supplementary controller is proposed based on the concept of ‘virtual arm resistance’. Time‐domain simulation studies based on PSCAD/EMTDC are performed to verify the analysis and the proposed controller.
Novel pilot protection principle for high‐voltage direct current transmission lines based on fault component current characteristics
Authors: Gao Shuping , Song Guobing , Ma Zhibin , Jin Xingfu
Published: February 2015

For high‐voltage direct current (HVDC) transmission systems, the transient fault current characteristics are that: if the fault point is over the line, the fault component current measured at both converter stations would be increased and they have the same changing direction. If the fault point is beyond the line, the fault component current measured at one converter station is increasing and the fault component current measured at the other converter station is decreasing, so they have the opposite changing direction. According to this characteristic, a novel pilot protection principle for HVDC transmission line based on fault component current is proposed here. The principle proposed has no limitation to the sampling frequency. A fault, whether it occurs in the line or beyond the line, can be effectively identified only using the fault component current at both converter stations. At the same time, the setting criterion of the fault component current is also given. The simulation results show that the new method can identify the faults reliably and rapidly. The study is promising to have significant theoretical and practical value.
Instantaneous positive‐sequence current applied for detecting voltage sag sources
Authors: Polajžer Boštjan , Štumberger Gorazd , Dolinar Drago
Published: February 2015

This study proposes a method for detecting voltage‐sag sources, using only the measurements of line currents. Instantaneous symmetrical components are introduced for accommodating the transient nature of voltage sag events, where a magnitude and phase change in the instantaneous positive‐sequence current is used as a criterion. The proposed method is compared with conventional phasor‐based methods known from the literature. All the discussed methods for voltage sag source detection, both the already known and the proposed ones, were evaluated by applying extensive simulations, laboratory tests and field testing. When compared with the phasor‐based methods, the proposed method showed faster response, a higher degree of confidence and superior effectiveness, especially for transient voltage sag events in networks with distributed generation and active loads.
Quasi‐oppositional harmony search algorithm and fuzzy logic controller for load frequency stabilisation of an isolated hybrid power system
Authors: Tarkeshwar Mahto , Mukherjee Vivekananda
Published: February 2015

The studied isolated hybrid distributed generation (IHDG) model of this paper consists of a wind turbine generator and a diesel engine generator. This work presents a study for improving both frequency and power deviation profiles of the studied IHDG model with the help of capacitive energy storage (CES) unit. A novel derivative‐free meta‐heuristic method, termed as quasi‐oppositional harmony search (QOHS) algorithm, is applied to determine the optimal frequency and power deviation responses by tuning the tunable parameters of the studied IHDG model. The two fuzzy logic controllers (FLCs) are used (one at diesel unit and the other at wind generator side) to generate the output levelling frequency and power command. Each fuzzy control has two inputs, either frequency or power deviation and their respective derivatives. The two proposed FLCs are designed with QOHS algorithm for the studied CES equipped IHDG model. Performance study of the model has been carried out under different perturbation conditions. The results presented in this study demonstrate that minimum frequency and power deviations have been achieved by using the two proposed FLCs for the CES equipped studied IHDG model.
Fast algorithm for estimating power frequency phasors under power system transients
Authors: Yang Liming , Jiao Zaibin , Kang Xiaoning , Song Guobing , Suonan Jiale
Published: February 2015

Power frequency phasors are widely used in the measurement, analysis, control and protection of power systems. When disturbances occur in such systems, power frequency phasors must be estimated quickly to ensure an accurate restoration to normal operation. Hence, a fast and accurate estimation algorithm would be a significantly useful tool. In consideration of the composition of transient signals in power systems, a novel algorithm for power frequency phasor estimation is proposed. Based on the double matrix pencil method, a unitary reference matrix of complex‐valued exponential signals is formed. The power frequency phasor estimation is then transformed to a brief multiplication of matrices. Thus, the QR decomposition, generalised eigenvalue calculation, and secondary estimation can be avoided and no complex multiplication is introduced. Therefore, the computational efficiency of the proposed method is improved compared with previous estimation techniques. Analytical and experimental investigations show that the proposed algorithm can extract power frequency phasors accurately, stably and quickly under power system transients.
Carboxymethyl chitosan‐assisted uniformly anchored Pd nanoparticles on carbon nanotubes for methanol electrooxidation in alkaline media
Authors: Tang Wanli , Gan Lang , Wu Bohua , Mao Liqiu , Yin Dulin
Published: February 2015

A carboxymethyl chitosan (CMC)‐assisted method is developed for the preparation of a palladium (Pd) nanoparticles (NPs)/carbon nanotubes (CNTs) nanohybrid. The addition of a small amount of CMC to the reaction solution leads to the production of well‐crystallised metallic Pd NPs with small diameter and uniformly dispersed on CNTs. The obtained Pd NPs supported on CNTs show enhanced catalytic activity and stability for the electrochemical oxidation of methanol in alkaline media. The as‐developed Pd NPs/CNTs nanohybrid is a highly promising catalyst for use in fuel cell technology.
Numerical study on the stability of weakly collisional plasma in E×B fields
Authors: Horký M. , Miloch W. J.
Published: February 2015

Plasma stability in weakly collisional plasmas in the presence of E×B fields is studied with numerical simulations. Different types of ion-neutral collisions are considered in a fully magnetized regime. We study the influence of ion-neutral collisions and the role of collision types on the stability of plasma. It is found that the stability of plasma depends on the type of ion-neutral collisions, with the plasma being unstable for charge exchange collisions, and stable for the elastic scattering. The analysis focuses on the temporal evolution of the velocity phase space, RMS values of the potential fluctuations, and coherent structures in potential densities. For the unstable case, we observe growth and propagation of electrostatic waves. Simulations are performed with a three-dimensional electrostatic particle in cell code.
Radiation hydrodynamics modeling of the highest compression inertial confinement fusion ignition experiment from the National Ignition Campaign
Authors: Clark D. S. , Marinak M. M. , Weber C. R. , Eder D. C. , Haan S. W. , Hammel B. A. , Hinkel D. E. , Jones O. S. , Milovich J. L. , Patel P. K. , Robey H. F. , Salmonson J. D. , Sepke S. M. , Thomas C. A.
Published: February 2015

The recently completed National Ignition Campaign (NIC) on the National Ignition Facility (NIF) showed significant discrepancies between post-shot simulations of implosion performance and experimentally measured performance, particularly in thermonuclear yield. This discrepancy between simulation and observation persisted despite concerted efforts to include all of the known sources of performance degradation within a reasonable two-dimensional (2-D), and even three-dimensional (3-D), simulation model, e.g., using measured surface imperfections and radiation drives adjusted to reproduce observed implosion trajectories [Clark et al., Phys. Plasmas 20, 056318 (2013)]. Since the completion of the NIC, several effects have been identified that could explain these discrepancies and that were omitted in previous simulations. In particular, there is now clear evidence for larger than anticipated long-wavelength radiation drive asymmetries and a larger than expected perturbation seeded by the capsule support tent. This paper describes an updated suite of one-dimensional (1-D), 2-D, and 3-D simulations that include the current best understanding of these effects identified since the NIC, as applied to a specific NIC shot. The relative importance of each effect on the experimental observables is compared. In combination, these effects reduce the simulated-to-measured yield ratio from 125:1 in 1-D to 1.5:1 in 3-D, as compared to 15:1 in the best 2-D simulations published previously. While the agreement with the experimental data remains imperfect, the comparison to the data is significantly improved and suggests that the largest sources for the previous discrepancies between simulation and experiment are now being included.
Enhancing conductivity of metallic carbon nanotube networks by transition metal adsorption
Authors: Ketolainen T. , Havu V. , Puska M. J.
Published: February 2015

The conductivity of carbon nanotube thin films is mainly determined by carbon nanotube junctions, the resistance of which can be reduced by several different methods. We investigate electronic transport through carbon nanotube junctions in a four-terminal configuration, where two metallic single-wall carbon nanotubes are linked by a group 6 transition metal atom. The transport calculations are based on the Green’s function method combined with the density-functional theory. The transition metal atom is found to enhance the transport through the junction near the Fermi level. However, the size of the nanotube affects the improvement in the conductivity. The enhancement is related to the hybridization of chromium and carbon atom orbitals, which is clearly reflected in the character of eigenstates near the Fermi level. The effects of chromium atoms and precursor molecules remaining adsorbed on the nanotubes outside the junctions are also examined.
Role of compositional fluctuations and their suppression on the strain and luminescence of InGaN alloys
Authors: Pantzas Konstantinos , Patriarche Gilles , Troadec David , Kociak Mathieu , Cherkashin Nikolay , Hÿtch Martin , Barjon Julien , Tanguy Christian , Rivera Thomas , Suresh Sundaram , Ougazzaden Abdallah
Published: February 2015

Advanced electron microscopy techniques are combined for the first time to measure the composition, strain, and optical luminescence, of InGaN/GaN multi-layered structures down to the nanometer scale. Compositional fluctuations observed in InGaN epilayers are suppressed in these multi-layered structures up to a thickness of 100 nm and for an indium composition of 16%. The multi-layered structures remain pseudomorphically accommodated on the GaN substrate and exhibit single-peak, homogeneous luminescence so long as the composition is homogeneous.
Measurement of internal defects in aluminum using a nano-granular in-gap magnetic sensor
Authors: Ozawa T. , Yabukami S. , Totsuka J. , Koyama S. , Hayasaka J. , Wako N. , Arai K. I.
Published: February 2015

Techniques for identifying defects in metals are very important in a wide variety of manufacturing areas. The present paper reports an eddy current testing method that employs a nano-granular in-gap magnetic sensor (GIGS) to detect internal defects in aluminum boards. The GIGS consists of a tunnel magnetoresistive film with nanometer sized grains and two yokes. In the presence of an external magnetic field, the nano-granular film exhibits only a small change in resistance due to the tunnel magnetoresistive effect. However, by placing it between two yokes, the magnetic flux can be greatly concentrated, thus increasing the change in resistance. The GIGS is a magnetic-field sensor that exploits this principle to achieve enhanced sensitivity. Moreover, because it has a cross-sectional yolk area of just 80 μm × 0.5 μm, it achieves outstanding spatial resolution. In the present study, it is used in combination with an eddy-current method in order to detect internal defects in aluminum. In this method, an excitation coil is used to apply an AC magnetic field perpendicular to the aluminum surface. This induces eddy currents in the metal, which in turn give rise to an AC magnetic field, which is then measured by the GIGS. The presence of defects in the aluminum distorts the eddy current flow, causing a change in the magnitude and distribution of the magnetic field. Such changes can be detected using the GIGS. In the present study, the proposed method was used to successfully detect indentations with diameters of 5 mm on the rear surface of an aluminum plate.
Enhanced carrier collection efficiency and reduced quantum state absorption by electron doping in self-assembled quantum dot solar cells
Authors: Li Tian , Lu Haofeng , Fu Lan , Tan Hark Hoe , Jagadish Chennupati , Dagenais Mario
Published: February 2015

Reduced quantum dot (QD) absorption due to state filling effects and enhanced electron transport in doped QDs are demonstrated to play a key role in solar energy conversion. Reduced QD state absorption with increased n-doping is observed in the self-assembled In0.5Ga0.5As/GaAs QDs from high resolution below-bandgap external quantum efficiency (EQE) measurement, which is a direct consequence of the Pauli exclusion principle. We also show that besides partial filling of the quantum states, electron-doping produces negatively charged QDs that exert a repulsive Coulomb force on the mobile electrons, thus altering the electron trajectory and reducing the probability of electron capture, leading to an improved collection efficiency of photo-generated carriers, as indicated by an absolute above-bandgap EQE measurement. The resulting redistribution of the mobile electron in the planar direction is further validated by the observed photoluminescence intensity dependence on doping.
The R-matrix of quantum doubles of Nichols algebras of diagonal type
Authors: Angiono Iván , Yamane Hiroyuki
Published: February 2015

Let H be the quantum double of a Nichols algebra of diagonal type. We compute the R-matrix of 3-tuples of modules for general finite-dimensional highest weight modules over H. We also calculate a multiplicative formula for the universal R-matrix when H is finite dimensional. We show the unicity of a PBW basis (or a Lusztig-type Poincaré-Birkhoff-Witt basis) with a given convex order.
Spatially resolved study of polarized micro-photoluminescence spectroscopy on single GaAs nanowires with mixed zincblende and wurtzite phases
Authors: Mukherjee Amlan , Ghosh Sandip , Breuer Steffen , Jahn Uwe , Geelhaar Lutz , Grahn Holger T.
Published: February 2015

Localized and polarized photoluminescence spectra are observed in single GaAs nanowires with mixed zincblende and wurtzite phases, grown using molecular beam epitaxy. For low excitation intensities, the photoluminescence emission exhibits narrow spectral features predominantly polarized perpendicular to the nanowire axis. For high excitation intensities, the photoluminescence spectra transform into dominant broadened features, which exhibit different peak energies and polarization properties. The strongly polarized emission at high excitation intensities is identified as being due to a spatially direct transition in wurtzite sections of the nanowires. The analysis, including band structure calculations suggests that carriers in the wurtzite sections diffuse into regions where the average low-temperature peak emission energy and crystal field parameter are 1.535 eV and 20 meV, respectively.
A rigorous two-dimensional model for the stripline ferromagnetic resonance response of metallic ferromagnetic films
Authors: Lin Z. , Kostylev M.
Published: February 2015

In this work, we constructed a two-dimensional numerical model for calculation of the stripline ferromagnetic resonance (FMR) response of metallic ferromagnetic films. We also conducted numerical calculations by using this software. The calculations demonstrated that the eddy current contribution to the FMR response decreases with a decrease in the stripline width. The most important manifestations of the conductivity (eddy current) effect are excitation of the higher-order standing spin waves across the film thickness in the materials for which the standing spin wave peaks would be absent in cavity FMR measurements and strong dependence of the off-resonance series conductance of the stripline on the stripline width. Whereas the contribution of the eddy currents to the stripline FMR response can be very significant, because wide striplines (100 μm+) are conventionally used for the FMR measurements, it is negligible in the case of excitation of spin waves, just because very narrow stripline transducers (0.5–5 μm wide) are required in order to excite spin waves in metallic ferromagnetic films in a noticeable frequency/applied field range.
Carrier depletion and electrical optimization of gallium arsenide plasmonic solar cell with a rear metallic grating
Authors: Shang Aixue , Li Xiaofeng
Published: February 2015

Plasmonic nanostructures have been extensively considered for photovoltaics due to the outstanding light-trapping capability; however, the intrinsic processes of carrier transport, recombination and collection have seldom been concerned. We report a complete optoelectronic investigation for plasmonic gallium arsenide solar cells (SCs) with a rear silver grating, by especially quantifying the plasmonics-induced photocurrent loss. It is found that, although the plasmonic design shows indeed much improved output photocurrent, its potential in improving the performance of SCs has not been fully exploited since a lot of energy has been wasted in the form of carrier depletion. A further design which electrically separates the plasmonic nanostructure from the core PN junction is verified to be an effective solution in improving the electrical performance of the SCs. The complete optoelectronic consideration is expected to advance the design of plasmonic SCs for thin-film and high-efficiency.
Evolution of magnetic properties and microstructure of Hf2Co11B alloys
Authors: McGuire Michael A. , Rios Orlando
Published: February 2015

Amorphous Hf2Co11B alloys produced by melt-spinning have been crystallized by annealing at 500–800 °C, and the products have been investigated using magnetization measurements, x-ray diffraction, and scanning electron microscopy. The results reveal the evolution of the phase fractions, microstructure, and magnetic properties with both annealing temperature and time. Crystallization of the phase denoted HfCo7, which is associated with the development of coercivity, occurs slowly at 500 °C. Annealing at intermediate temperatures produces mixed phase samples containing some of the HfCo7 phase with the highest values of remanent magnetization and coercivity. The equilibrium structure at 800 °C contains HfCo3B2, Hf6Co23, and Co, and displays soft ferromagnetism. Maximum values for the remanent magnetization, intrinsic coercivity, and magnetic energy product among the samples are approximately 5.2 kG, 2.0 kOe, and 3.1 MGOe, respectively, which indicates that the significantly higher values observed in crystalline, melt-spun Hf2Co11B ribbons are a consequence of the non-equilibrium solidification during the melt-spinning process. Application of high magnetic fields during annealing is observed to strongly affect the microstructural evolution, which may provide access to higher performance materials in Zr/Hf-Co hard ferromagnets. The crystal structure of HfCo7 and the related Zr analogues is unknown, and without knowledge of atomic positions powder diffraction cannot distinguish among proposed unit cells and symmetries found in the literature.
Pressure driven ferroelectric to paraelectric transition in Sr doped BaTiO3
Authors: Basu Abhisek , Jana Rajesh , Mandal Guruprasad , Chandra Amreesh , Mukherjee Goutam Dev
Published: February 2015

High pressure Raman spectroscopy, X-ray diffraction, and dielectric measurements have been carried out in Ba1−xSrxTiO3 (x = 0.05 and 0.1). Detailed structural analysis revealed a single phase transition from tetragonal P4mm to cubic Pm3m symmetry. Increase in Sr ion concentration resulted in decrease in the phase transition pressure. The dielectric measurements showed considerable lowering of transition pressure which has been attributed to bulk behaviour of the material.
Spin wave excitation in yttrium iron garnet films with micron-sized antennas
Authors: Khivintsev Y. V. , Filimonov Y. A. , Nikitov S. A.
Published: February 2015

In this paper, we explore spin waves excitation in monolithic structures based on yttrium iron garnet (YIG) films with micro-sized antennas. Samples based on plain and patterned YIG film were fabricated and tested for tangential bias field geometries. We observed spin wave excitation and propagation with wave numbers up to 3.5 × 104 rad/cm. The corresponding wavelength is thus shorter more than by one order of magnitude compared to previous experiments with such films. For the sample with a periodic array of nanotrenches, we observed the effect of the shape anisotropy resulting in the shift of the spin wave propagation band in comparison to the unpatterned YIG film. Our results are very promising for the exploitation of short spin waves in YIG and provide great opportunity for significant miniaturization of YIG film based microwave devices.
Temporal and spectral shaping of broadband terahertz pulses in a photoexcited semiconductor
Authors: Shalaby Mostafa , Peccianti Marco , Cooke David G. , Hauri Christoph P. , Morandotti Roberto
Published: February 2015

Transmission through a photoexcited semiconductor is used to temporally and spectrally shape a terahertz (THz) pulse. By adjusting the optical pump-THz probe delay, we experimentally introduce a polar asymmetry in the pulse profile as large as 92%. To shape the spectrum, we apply the same technique after strongly chirping the terahertz pulse. This leads to significant reshaping of the spectrum resulting in a 52% upshift of its median value. The pulse shaping techniques introduced here are of particular importance for temporal and spectral shape-sensitive THz nonlinear experiments.
Magnetic field control of the neutral and charged exciton fine structure in single quantum dashes emitting at 1.55 μm
Authors: Mrowiński P. , Musiał A. , Maryński A. , Syperek M. , Misiewicz J. , Somers A. , Reithmaier J. P. , Höfling S. , Sęk G.
Published: February 2015

We investigated the neutral and charged exciton fine structure in single InAs/InGaAlAs/InP quantum dashes emitting at 1.55 μm using polarization-resolved microphotoluminescence in a magnetic field. Inverted spin configuration of horizontally [1–10] and vertically [110] polarized transitions has been observed. An in-plane magnetic field of up to 5 Tesla has been applied to tailor the fine structure, and eventually to reduce the splitting of the bright exciton states down to zero. This inverted structure has been observed for all the investigated excitons, making it a characteristic feature for this class of nanostructures with the largest splitting reduction of 170 μeV.
High-efficiency THz modulator based on phthalocyanine-compound organic films
Authors: He Ting , Zhang Bo , Shen Jingling , Zang Mengdi , Chen Tianji , Hu Yufeng , Hou Yanbing
Published: February 2015

We report a high efficiency, broadband terahertz (THz) modulator following a study of phthalocyanine-compound organic films irradiated with an external excitation laser. Both transmission and reflection modulations of each organic/silicon bilayers were measured using THz time-domain and continuous-wave systems. For very low intensities, the experimental results show that AlClPc/Si can achieve a high modulation factor for transmission and reflection, indicating that AlClPc/Si has a superior modulation efficiency compared with the other films (CuPc and SnCl2Pc). In contrast, the strong attenuation of the transmitted and reflected THz waves revealed that a nonlinear absorption process takes place at the organic/silicon interface.
Identification of spin wave modes in yttrium iron garnet strongly coupled to a co-axial cavity
Authors: Lambert N. J. , Haigh J. A. , Ferguson A. J.
Published: February 2015

We demonstrate, at room temperature, the strong coupling of the fundamental and non-uniform magnetostatic modes of an yttrium iron garnet ferrimagnetic sphere to the electromagnetic modes of a co-axial cavity. The well-defined field profile within the cavity yields a specific coupling strength for each magnetostatic mode. We experimentally measure the coupling strength for the different magnetostatic modes and, by calculating the expected coupling strengths, we are able to identify the modes themselves.
Communication: Automatic code generation enables nuclear gradient computations for fully internally contracted multireference theory
Authors: MacLeod Matthew K. , Shiozaki Toru
Published: February 2015

Analytical nuclear gradients for fully internally contracted complete active space second-order perturbation theory (CASPT2) are reported. This implementation has been realized by an automated code generator that can handle spin-free formulas for the CASPT2 energy and its derivatives with respect to variations of molecular orbitals and reference coefficients. The underlying complete active space self-consistent field and the so-called Z-vector equations are solved using density fitting. The implementation has been applied to the vertical and adiabatic ionization potentials of the porphin molecule to illustrate its capability.
Crystalline ZrTiO4 gated p-metal–oxide–semiconductor field effect transistors with sub-nm equivalent oxide thickness featuring good electrical characteristics and reliability
Authors: Wu Chao-Yi , Hsieh Ching-Heng , Lee Ching-Wei , Wu Yung-Hsien
Published: February 2015

ZrTiO4 crystallized in orthorhombic (o-) phase was stacked with an amorphous Yb2O3 interfacial layer as the gate dielectric for Si-based p-MOSFETs. With thermal annealing after gate electrode, the gate stack with equivalent oxide thickness (EOT) of 0.82 nm achieves high dielectric quality by showing a low interface trap density (Dit) of 2.75 × 1011 cm−2eV−1 near the midgap and low oxide traps. Crystallization of ZrTiO4 and post metal annealing are also proven to introduce very limited amount of metal induced gap states or interfacial dipole. The p-MOSFETs exhibit good sub-threshold swing of 75 mV/dec which is ascribed to the low Dit value and small EOT. Owing to the Y2O3 interfacial layer and smooth interface with Si substrate that, respectively, suppress phonon and surface roughness scattering, the p-MOSFETs also display high hole mobility of 49 cm2/V-s at 1 MV/cm. In addition, Ion/Ioff ratio larger than 106 is also observed. From the reliability evaluation by negative bias temperature instability test, after stressing with an electric field of −10 MV/cm at 85 °C for 1000 s, satisfactory threshold voltage shift of 12 mV and sub-threshold swing degradation of 3% were obtained. With these promising characteristics, the Yb2O3/o-ZrTiO4 gate stack holds the great potential for next-generation electronics.
Magneto-plasmonics on perpendicular magnetic CoPt–Ag nanostructures with ZnO intermediate thin layers
Authors: Yamane H. , Takeda K. , Kobayashi M.
Published: February 2015

The magneto-optical properties of perpendicular magnetic Co80Pt20–Ag nanostructures formed on Ru underlayer were investigated under polar Kerr measurement conditions. The nanostructures consisting of CoPt layers and Ag fine grains had two magnetic regions with different coercivities. ZnO intermediate thin layers improved the perpendicular magnetic properties and promoted the surface agglomeration of Ag to form the nanostructure. In the CoPt–Ag nanostructures, the antiparallel magnetic alignment of the CoPt layers on the Ag grains and Ru underlayer produced an increase in the Kerr rotation angle, and it was explained by the phase reversal in Kerr rotation for the CoPt layer on the Ag grains. These magneto-optical behaviors (enhancement and phase reversal in Kerr rotation) were attributed to the influence of the localized surface plasmon resonance of Ag grains on CoPt layers.
Interface/border trap characterization of Al2O3/AlN/GaN metal-oxide-semiconductor structures with an AlN interfacial layer
Authors: Liu Shenghou , Yang Shu , Tang Zhikai , Jiang Qimeng , Liu Cheng , Wang Maojun , Shen Bo , Chen Kevin J.
Published: February 2015

We report the interface characterization of Al2O3/AlN/GaN MOS (metal-oxide-semiconductor) structures with an AlN interfacial layer. A thin monocrystal-like interfacial layer (AlN) is formed at the Al2O3/GaN to effectively block oxygen from the GaN surface and prevent the formation of detrimental Ga-O bonds. The suppression of Ga-O bonds is validated by X-ray photoelectron spectroscopy of the critical interface. Frequency-dispersion in C-V characteristics has been significantly reduced, owing to improved interface quality. Furthermore, using the conventional conductance method suitable for extracting the interface trap density Dit in MOS structures, Dit in the device with AlN was determined to be in the range of 1011–1012 eV−1 cm−2, showing one order of magnitude lower than that without AlN. Border traps near the gate-dielectric/GaN interface were identified and shown to be suppressed by the AlN interfacial layer as well.
Investigation of Sn surface segregation during GeSn epitaxial growth by Auger electron spectroscopy and energy dispersive x-ray spectroscopy
Authors: Tsukamoto Takahiro , Hirose Nobumitsu , Kasamatsu Akifumi , Mimura Takashi , Matsui Toshiaki , Suda Yoshiyuki
Published: February 2015

The mechanism of Sn surface segregation during the epitaxial growth of GeSn on Si (001) substrates was investigated by Auger electron spectroscopy and energy dispersive X-ray spectroscopy. Sn surface segregation depends on the growth temperature and Sn content of GeSn layers. During Sn surface segregation, Sn-rich nanoparticles form and move on the surface during the deposition, which results in a rough surface owing to facet formation. The Sn-rich nanoparticles moving on the surface during the deposition absorb Sn from the periphery and yield a lower Sn content, not on the surface but within the layer, because the Sn surface segregation and the GeSn deposition occur simultaneously. Sn surface segregation can occur at a lower temperature during the deposition compared with that during postannealing. This suggests that the Sn surface segregation during the deposition is strongly promoted by the migration of deposited Ge and Sn adatoms on the surface originating from the thermal effect of substrate temperature, which also suggests that limiting the migration of deposited Ge and Sn adatoms can reduce the Sn surface segregation and improve the crystallinity of GeSn layers.
The Diaspora Within: Himalayan Youth, Education-Driven Migration, and Future Aspirations in India
Authors: Smith Sara H , Gergan Mabel
Published: February 2015

Economic change has driven parents across the Indian Himalayan Region to send their children to major Indian cities for higher education. Himalayan students' urban experience and understanding of the nation is profoundly shaped by the movement between the Himalayan context and the foreign experience of Indian city life. We draw on interviews with students to discuss their experiences in the sometimes liberating and sometimes hostile cities of India. In their perceived cultural and racialized difference, we argue, Himalayan students form a diaspora within their own nation, and we suggest that attention to their micropractices of belonging and movement between home and city is critical to understanding India as a nation-state. Here, we suggest that education-driven migration to urban centers results in challenging spaces of encounter, and that minority students cope with these encounters both by forging diasporic ties with those from their homeland and other marginalized Himalayan students, and by building a cosmopolitan sensibility that reaches beyond India's borders. Our research is based primarily on a set of twenty interviews conducted in 2011 in Delhi, Sikkim, and Leh, Ladakh, but is informed by our ongoing work on the topic, and on our previous and continuing research on family politics in Ladakh and in Sikkim on youth politics and development.