bluuebunny/crossref_metadata_2025 huggingface dataset:
Scalable route to CH3NH3PbI3 perovskite thin films by aerosol assisted chemical vapour deposition
Authors: Bhachu D. S. , Scanlon D. O. , Saban E. J. , Bronstein H. , Parkin I. P. , Carmalt C. J. , Palgrave R. G.
Published: October 2014

An industrially relevant, scalable deposition route to high quality MAPI films is reported.
Revealing Al evaporation-assisted functions in solution-processed ZnO thin film transistors
Authors: Kang Tae Sung , Kim Tae Yoon , Yoon Kap Soo , Kim Jong Min , Im Hyun Sik , Hong Jin Pyo
Published: October 2014

Impregnated Al atoms inside the ZnO layer form Al–O bonds with oxygen ions and may reduce the concentration of weakly bonded oxygen as well as the space charge region, significantly reducing the polar ZnO surface.
Performance improved by point‐contact electrodes and SiO2/SiNX layers at rear
Authors: Wang Sheng‐Shih , Ho Jyh‐Jier , Chen Duo‐Sheng , Ho Jia‐Show , Du Chen‐Hsun , Tsai Song‐Yeu , Hung Hsien‐Seng , Wang Kang L.
Published: October 2014

The rear point‐contact fabricated through the laser‐opening technique for mass production was applied on the photovoltaic cells. Laser opening, different layers for passivation (SiO2) and protection (SiNX) were employed to investigate their impact on the performances of solar cells. The SiNX layer protects the SiO2 layer from being burnt through by aluminium paste at the co‐firing step. A conversion efficiency (η) of 16.91% with an open‐circuit voltage of 628 mV was obtained for the optimal cell, a stack structure with SiO2 and SiNX layers, which also achieves a lower contact resistance of 6.66 mΩ·cm2 and a higher light‐beam‐induced current of 80.77 mA/cm2. The optimal cell also showed longer lifetime and 3–4% increased quantum efficiency in the visible wavelength range. Therefore, the developed process has simplicity and reliability, is fast and cost‐effective and could be applied to industrial applications.
Hybrid STAP approach of direct data domain algorithm and adaptive localised domain transformation for discrete interference suppression in non‐homogeneous clutter
Authors: Yang Xiaopeng , Sun Yuze , Liu Yongxu , Long Teng
Published: October 2014

A hybrid space–time adaptive processing (STAP) approach of the direct data domain (DDD) algorithm and adaptive localised domain transformation is proposed for discrete interference suppression in non‐homogeneous clutter which is inevitable in actual airborne radar applications. In the proposed method, the adaptive localised domain transformation matrix is firstly formed by the DDD weighting vectors in angle‐Doppler directions to suppress discrete interference. Afterwards, the adaptive localised domain transformation matrix is applied to the conventional STAP method to suppress the residual clutter. The proposed method is verified based on the actual airborne radar data.
Normally‐off vertical‐type mesa‐gate GaN MOSFET
Authors: Won Chul‐Ho , Kim Ki‐Won , Kim Dong‐Seok , Kang Hee‐Sung , Im Ki‐Sik , Jo Young‐Woo , Kim Do‐Kywn , Kim Ryun‐Hwi , Lee Jung‐Hee
Published: October 2014

A vertical‐type mesa‐gate GaN metal–oxide semiconductor field‐effect transistor (MOSFET) has been fabricated. The mesa‐gate structure can be easily achieved by a single deep etch to the n+‐GaN which is the drain of the device, whereas the trench‐gate structure, the commonly used structure for the vertical‐type MOSFETs, requires an additional etching process to define the gate region. The mesa‐gate GaN MOSFET exhibited a normally‐off operation with the threshold voltage of 3 V, a normalised drain current of ∼ 55 mA/mm and a high on/off current ratio of 108.
Efficient calculation of information reduction factor for tracking in clutter
Authors: Hill R.D. , Tough R.J.A.
Published: October 2014

A reformulation of the information reduction factor (IRF) for tracking in the presence of measurement uncertainty is presented. A simple integral representation is employed to derive an expression for the IRF that can be calculated without approximation in terms of one‐dimensional integrals. This significantly reduces the computational requirements of the calculation and is relevant to the offline calculation of tracking performance and the selection of detection thresholds to optimise tracking accuracy. A comparison with Monte Carlo integration shows that the new technique is approximately 380 times faster.
AC response of 0.35 µm CMOS triple‐junction photodetector
Authors: Schidl S. , Zimmermann H.
Published: October 2014

A vertically stacked triple‐junction photodiode (PD) is characterised for its suitability for sensor applications which demand a high speed. The proposed PD is implemented in a 0.35 µm CMOS process without process modifications. The AC performance of the detector is characterised at three wavelengths, blue (410 nm), green (520 nm) and red (675 nm). The measurements are carried out with a high dynamic range to fully characterise possible interactions between the different wavelengths (cross‐coupling mechanisms).
Noise figure reduction by port decoupling for dual circular polarised microstrip antenna
Authors: Khan M. , Warnick K. F.
Published: October 2014

A planar dual circular polarised (CP) feed is highly desirable for dish‐type satellite communication terminals, but isolation between ports is typically poorer for CP microstrip antennas than for linearly polarised elements. Mutual coupling between the output ports of a dual CP planar feed can affect the equivalent noise temperature of the satellite ground terminal receiver. A port decoupling network is designed for a single‐layer dual CP microstrip antenna to increase the isolation to >20 dB between the antenna ports while maintaining CP quality. The effect of decoupling for the single‐layer dual CP feed on the performance of a high sensitivity dual polarised receiver for satellite communication applications is analysed.
InAs/GaAs p–i–p quantum dots‐in‐a‐well infrared photodetectors operating beyond 200 K
Authors: Park M.S. , Jain V. , Lee E.H. , Kim S.H. , Pettersson H. , Wang Q. , Song J.D. , Choi W.J.
Published: October 2014

High‐temperature operating performance of p–i–p quantum dots‐in‐a‐well infrared photodetectors (QDIPs) is successfully demonstrated. The optically active region consists of 10 layers of p‐doped self‐assembled InAs quantum dots (QDs) asymmetrically positioned in In0.15Ga0.85As quantum wells (QWs). The dark current is suppressed by an incorporated superlattice (SL) structure composed of 10 pairs of AlGaAs/GaAs heterostructure. The very low recorded dark current makes the fabricated p–i–p QDIPs suitable for high‐temperature operation. The measured photoresponse reveals broad mid‐wave infrared (MWIR) detection up to 200 K.
Block‐windowed burst OFDM: a high‐efficiency multicarrier technique
Authors: Nunes J. , Bento P. , Gomes M. , Dinis R. , Silva V.
Published: October 2014

A block‐windowed burst orthogonal frequency division multiplexing (OFDM) technique which is a multicarrier technique with power spectral density similar to the filtered OFDM approach, since it also employs smoother, non‐rectangular windows, is presented. However, it does not need a cyclic prefix, which means the overall power and spectral efficiencies are higher. An appropriate receiver for typical time‐dispersive channels, allowing 2 dB of gain relatively conventional OFDM schemes is also presented.
Perceptual sharpness metric based on human visual system
Authors: Gao Shaoshu , Wang Yanjiang , Jin Weiqi , Zhang Xiaodong
Published: October 2014

Sharpness is an important quality attribute influencing image quality. Existing sharpness assessment models have not given sufficient consideration to the human visual system, especially the human luminance masking effect. On the basis of an isotropic local contrast model, an objective perceptual sharpness assessment model is proposed combined with the human luminance masking effect. Experimental results show that the proposed perceptual sharpness metric provides better predictions than four existing sharpness metrics and can evaluate image perceptual sharpness effectively.
Uplink outage performance of linear cellular networks with non‐uniform user distribution
Authors: Khan A. , Fanaei M. , Jamalipour A.
Published: October 2014

The Wyner model has been extensively used in the literature for analysing cellular networks. Recent studies show that when compared with a grid‐based model, this simple model fails to capture key features of a cellular network under different scenarios. Without increasing complexity, a linear network model which uses an average user distance and considers a non‐uniform user distribution scenario within cells is proposed. Simulation results show that despite the simplicity, the proposed model can provide a close insight when compared with a grid‐based model.
Two‐stage hot‐carrier‐induced degradation of p‐type LDMOS transistors
Authors: Chen Jone F. , Chen Tzu‐Hsiang , Ai Deng‐Ren
Published: October 2014

Hot‐carrier‐induced device degradation of high‐voltage p‐type lateral diffused metal–oxide semiconductor (LDMOS) transistors is investigated. A two‐stage linear region drain current (IDlin) shift (IDlin shift increases rapidly at the beginning of stress but tends to saturate when the stress time is longer) is observed. Technology computer‐aided‐design simulations and direct current current–voltage measurement results suggest that the decrease of residual fabrication interface traps (NIT) leads to an initial increase in IDlin shift. On the other hand, two competing mechanisms, i.e. increase in NIT generation and increase in electron trapping, are responsible for the saturated IDlin shift when the stress time is longer.
Fractional order constant modulus blind algorithms with application to channel equalisation
Authors: Shah S.M. , Samar R. , Naqvi S.M.R. , Chambers J.A.
Published: October 2014

A novel methodology is developed for blind equalisation where the output of the linear filter is passed through a nonlinear fractional update term derived from the cost function using fractional calculus. The final weights update is a combination of the conventional constant modulus algorithm (CMA) weights and a fractional update part. As an improvement over the traditional approach, the new fractional strategy helps capture the parameters of the model at a faster rate while keeping the error small. The algorithm is applied for the blind equalisation of flat and frequency‐selective channels. To assess the suitability of the proposed technique, different fractional orders and step sizes are used; the performance metric considered is the mean squared error for a quadrature phase shift keying transmission scheme. The simulation results show that the proposed technique outperforms the conventional CMA, exhibits faster convergence and yields an improved steady‐state response.
Millimetre‐wave broadband waveguide‐based power combiner using lossy planar lines
Authors: Xiaoqiang Xie , Qiang Zhou , Dawei Li
Published: October 2014

A lossy waveguide‐based power combiner is proposed for broadband low‐loss symmetrically combining with good port matching and isolation at millimetre‐wave frequencies. In the combiner, lossy planar transmission lines are used to provide attenuation to even‐mode excitations and to achieve broadband low‐loss power combining with good port matching and isolation. The experimental results show that the lossy waveguide‐based power combiner has a loss of about 0.14 dB and a reflection coefficient and isolation of about –15 dB in 26.5–40 GHz, respectively. The lossy waveguide‐based power combiner can be used in a multi‐way power amplifying–combining system to obtain millimetre‐wave broadband high solid‐state power with high efficiency and good stability.
Low‐voltage quadrature LC oscillator with fast start‐up
Authors: Roy A.G. , Mayaram K. , Fiez T.S.
Published: October 2014

A novel low‐voltage quadrature inductor–capacitor (LC) oscillator is presented. The proposed oscillator is immune to the phase ambiguity problem encountered in quadrature oscillators. Simulations show that the proposed oscillator can obtain a phase noise of −150 dBc/Hz at 10 MHz offset for a 5 GHz centre frequency and a figure‐of‐merit (FoM) of 195 dBc/Hz. The proposed oscillator has a superior start‐up performance compared to other low‐voltage quadrature LC oscillator architectures.
Colour interpolation using adaptive window for Bayer colour filter array
Authors: Kim Yonghoon , Kim Kibaek , Jeon Gwanggil , Jeong Jechang
Published: October 2014

Most demosaicking solutions focus on improving the accuracy of direction estimation for interpolation, and they achieve a highly precise gradient estimation performance. Direction estimation techniques achieve great improvement in objective image quality; however, in terms of subjective image quality there are remaining demosaicking problems to solve. An adaptive window algorithm to reduce demosaicking artefacts by exploiting the colour similarity of neighbouring pixels is introduced. Experimental results confirm that the proposed method produces the best colour peak signal‐to‐noise ratio and FSIM performance, and achieves great improvement in subjective image quality.
Fabrication and measurement of graphene p–n junction with two top gates
Authors: Liu Jingping , Safavi‐Naeini Safieddin , Ban Dayan
Published: October 2014

A graphene device with two top gates has been fabricated and measured for the first time. The thickness of the gate dielectric is 60 nm. The measurement results indicate that the externally applied gate biases can dope the underneath graphene to either p‐ or n‐type, forming an induced p–n junction. The current–voltage (I–V) curve measurement results also indicate that there is no nonlinear phenomenon in a weakly induced graphene p–n junction. This graphene p–n junction can potentially be used for terahertz wave generation.
Chipless RFID tag using RF MEMS switch
Authors: Attaran A. , Rashidzadeh R. , Muscedere R.
Published: October 2014

A new chipless radio‐frequency identification (RFID) tag using the micro‐electro‐mechanical system (MEMS) technology is presented. The tag can operate at the conventional UHF band for RFID applications and can be implemented using a basic fabrication process. In the presented scheme, MEMS switches are used as programmable elements to support the communication between the tag and RFID interrogators.
Bio‐signal acquisition circuit with high signal‐to‐noise ratio for u‐healthcare system
Authors: Nam Ilku , Kang Hongseok , Woo Doo Hyung
Published: October 2014

The testing of a monolithic bio‐signal acquisition circuit with an analogue negative feedback loop for ubiquitous healthcare (u‐healthcare) and the monitoring of physical activity is described. The large low‐frequency signal is effectively rejected by the proposed circuit, allowing the dynamic range of the more valuable signals to be improved. The proposed circuit has been designed and fabricated using a 0.18 μm 1‐poly 6‐metal CMOS process. Using an analogue negative feedback loop with a dual‐gain filter, the proposed method provides an average signal‐to‐noise ratio 8.1 dB higher than that of the conventional method.
Electrical localisation of full open defects in comb–meander–comb structures
Authors: Arumí D. , Rodríguez‐Montañés R. , Figueras J.
Published: October 2014

Test structures are key elements to characterise and identify the main contributors to yield loss in wiring structures. Among such monitors, comb–meander–comb structures have been widely used owing to their simplicity and reduced number of pads. With continuous scaling of dimensions and use of copper in interconnections, open defects has arisen as the most common defect affecting the interconnection, focusing thus on an important part of the research effort. In fact, present electrical methodologies are able to detect, localise and predict the resistance of weak (resistive) opens. However, such methodologies are not able to locate full opens. This lack of information may be useful for faster ramp‐up and yield improvement, among others. In this context, a simple electrical methodology to predict the location of full opens in comb–meander–comb structures is presented. Experimental measurements carried out in a 65 nm technology die corroborate the feasibility of the approach.
Minimum energy channel codes for molecular communications
Authors: Bai Chenyao , Leeson Mark S. , Higgins Matthew David
Published: October 2014

Owing to the limitations of molecular nanomachines, it is essential to develop reliable, yet energy‐efficient communication techniques. Two error correction coding techniques are compared under a diffusive molecular communication mechanism, namely, Hamming codes and minimum energy codes (MECs). MECs, which previously have not been investigated in a diffusive channel, maintain the desired code distance to keep reliability while minimising energy. Results show that MECs outperform the Hamming codes, both in aspects of bit error rate and energy consumption.
One million fps digital holography
Authors: Xia P. , Awatsuji Y. , Nishio K. , Matoba O.
Published: October 2014

Digital holography at the rate of 1 000 000 frames per second (fps), which is the fastest speed in digital holography to the best of knowledge, has been achieved. High‐speed recording of digital holography needs a high‐speed camera. However, the number of available pixels is very small in general, due to the characteristics of the high‐speed camera. Then, to record the hologram with such a small number of pixels and obtain a clear phase image of the object, parallel phase‐shifting digital holography (PPSDH) was adopted. This technique was used to successfully obtain images of the phase variation of electrical discharging phenomenon at the rate of 1 000 000 fps.
Compact slotted semi‐circular antenna for implantable medical devices
Authors: Li Rongqiang , Xiao Shaoqiu
Published: October 2014

A novel, compact, semi‐circular, implantable, planar‐inverted‐F antenna (PIFA) is presented for the medical implant communications services (MICSs) band (402–405 MHz). By cutting three arc‐shaped slots in a semi‐circular patch, the proposed antenna can obtain effective size reduction. The total volume of the proposed antenna, including substrate and superstrate, is about 151 mm3. A bandwidth of 25 MHz is obtained at return loss of 10 dB. In addition, the radiation and specific absorption rate (SAR) performance of the antenna are examined and characterised.
Multi‐carrier transmission of vectorial modulation schemes using electronic transceivers at 588 GHz
Authors: Ducournau G. , Szriftgiser P. , Bacquet D. , Zaknoune M. , Kassi R. , Lampin J.‐F.
Published: October 2014

A reported is presented on the first communication system using vectorial modulation schemes above 500 GHz. Using Schottky‐based electronic technologies at 588 GHz, potentialities of high‐level multi‐carrier modulation schemes for wireless links are analysed. The wireless link is composed of an emitter with a sub‐harmonic mixer for up‐conversion from 294 to 588 GHz and carrier modulation. A pumped zero‐bias detector is used at reception. Mono‐carrier signalling is realised using an up to 32‐symbol modulation scheme and multi‐carrier terahertz transmission is also achieved using several modulation schemes in parallel.
Power factor correction in switched mode power supply for computers using canonical switching cell converter
Authors: Singh Shikha , Bist Vashist , Singh Bhim , Bhuvaneswari Gurumoorthy
Published: October 2014

This study presents a novel power factor correction (PFC) technique using a canonical switching cell (CSC) converter applicable to multi‐output switched mode power supply (SMPS) used in personal computers (PCs). The CSC converter at the front end of this single‐phase fed SMPS operates in discontinuous conduction mode that offers inherent PFC for wide range of varying input voltages. It is cascaded to an isolated half‐bridge multi output dc–dc converter for obtaining multiple dc voltages that are stiffly regulated and isolated from each other as per the requirement of the PC. The proposed SMPS is designed, modelled and its performance is investigated under steady state and dynamic operating conditions for varying input voltages and loads. It is found that the proposed design is able to offer excellent power factor and low total harmonics distortion at the utility interface as shown in investigations carried on simulation and experimental studies. A comparison of conventional SMPS with proposed PFC‐based SMPS vividly brings out the merits of the latter. Further, a comparison is made with other types of front end converters to investigate the relative merits and demerits of the CSC converter over other front end converters.
Evaluation and analysis of transformerless photovoltaic inverter topology for efficiency improvement and reduction of leakage current
Authors: Cha Woo‐Jun , Kim Kyu‐Tae , Cho Yong‐Won , Lee Sung‐Ho , Kwon Bong‐Hwan
Published: October 2014

In transfomerless photovoltaic (PV) grid‐connected inverter application, to reduce leakage current and to increase efficiency, many inverter topologies have been proposed. The method for increasing efficiency and reducing leakage current is evaluated and analysed in the present study. The operation of transfomerless PV inverter topologies with high‐performance such as full‐bridge, H5, H6, HERIC and paralleled‐buck topology is analysed to calculate switching losses, conduction losses and free‐wheeling losses. Device total losses for inverter topology are calculated according to the switching frequency and the output power. Also, a novel high‐frequency model of inverter topology is proposed using the leg voltage and high‐frequency equivalent circuit. The relation between the parasitic capacitor voltage and its leakage current is explained using the proposed high‐frequency model. Also, the magnitude of the high‐frequency voltage in the parasitic capacitor is derived mathematically. Efficiency of the several inverter topology according to the output power is compared and the leakage current is analysed using a novel high‐frequency model. Finally, the efficiency and leakage current analysis are verified by simulation tool and 3 kW prototype.
Development and Clinical Evaluation of MatrixMANDIBLE Subcondylar Plates System (Synthes)
Authors: Cortelazzi Roberto , Altacera Mario , Turco Monica , Antonicelli Viviana , De Benedittis Michele
Published: October 2014

In this article, authors report the different steps of development and clinical validation of MatrixMANDIBLE Subcondylar Plates (Synthes, Soletta, Switzerland), a specialized osteosynthesis system developed by Synthes during the past 4 years. Between 2009 and 2013, a total of 62 patients were treated for subcondylar and condylar neck fractures via a preauricular or retromandibular/transparotid approach. The MatrixMANDIBLE Subcondylar Plates System consists of a Trapezoidal Plate, a three-dimensional (3D) 4-hole 1.0-mm plate for smaller fracture areas, the Lambda Plate, a 7-hole 1.0-mm linear plate which mimics the two miniplates technique, and the Strut Plate, a 3D 1.0-mm plate with great versatility of employment. All devices satisfy the principles of a functionally stable osteosynthesis as stated by Champy et al. None of the plates broke and no macroscopic condylar displacement was noted on radiological follow-up. Clinical and functional parameters assessed at 6 months postoperative (mandibular range of motion, pain, dental occlusion) were almost restored. MatrixMANDIBLE Subcondylar Plates System (Synthes) has proved to provide sufficient mechanical stiffness and anatomically accurate fracture reduction to avoid major postoperative drawbacks of subcondylar and condylar neck fractures.
Bifacial solar cell with SnS absorber by vapor transport deposition
Authors: Wangperawong Artit , Hsu Po-Chun , Yee Yesheng , Herron Steven M. , Clemens Bruce M. , Cui Yi , Bent Stacey F.
Published: October 2014

The SnS absorber layer in solar cell devices was produced by vapor transport deposition (VTD), which is a low-cost manufacturing method for solar modules. The performance of solar cells consisting of Si/Mo/SnS/ZnO/indium tin oxide (ITO) was limited by the SnS layer's surface texture and field-dependent carrier collection. For improved performance, a fluorine doped tin oxide (FTO) substrate was used in place of the Mo to smooth the topography of the VTD SnS and to make bifacial solar cells, which are potentially useful for multijunction applications. A bifacial SnS solar cell consisting of glass/FTO/SnS/CdS/ZnO/ITO demonstrated front- and back-side power conversion efficiencies of 1.2% and 0.2%, respectively.
Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy
Authors: Schwanke C. , Golnak R. , Xiao J. , Lange K. M.
Published: October 2014

A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl2 aqueous solution by X-ray absorption and emission spectroscopy is presented.
Thermal plasma processed ferro-magnetically ordered
face-centered cubic
iron at room temperature
Authors: Raut Suyog A. , Kanhe Nilesh S. , Bhoraskar S. V. , Das A. K. , Mathe V. L.
Published: October 2014

Here, we report tailor made phase of iron nanoparticles using homogeneous gas phase condensation process via thermal plasma route. It was observed that crystal lattice of nano-crystalline iron changes as a function of operating parameters of the plasma reactor. In the present investigation iron nanoparticles have been synthesized in presence of argon at operating pressures of 125–1000 Torr and fixed plasma input DC power of 6 kW. It was possible to obtain pure fcc, pure bcc as well as the mixed phases for iron nanoparticles in powder form as a function of operating pressure. The as synthesized product was characterized for understanding the structural and magnetic properties by using X-ray diffraction, vibrating sample magnetometer, and Mössbauer spectroscopy. The data reveal that fcc phase is ferromagnetically ordered with high spin state, which is unusual whereas bcc phase is found to be ferromagnetic as usual. Finally, the structural and magnetic properties are co-related.
Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation
Authors: Bréchignac Philippe , Garcia Gustavo A. , Falvo Cyril , Joblin Christine , Kokkin Damian , Bonnamy Anthony , Parneix Pascal , Pino Thomas , Pirali Olivier , Mulas Giacomo , Nahon Laurent
Published: October 2014

Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory.
Structural and dielectric properties of laser ablated BaTiO3 films deposited over electrophoretically dispersed CoFe2O4 grains
Authors: Barbosa J. G. , Gomes I. T. , Pereira M. R. , Moura C. , Mendes J. A. , Almeida B. G.
Published: October 2014

Thin film nanocomposites with mixed connectivity, composed by CoFe2O4 grains, deposited by electrophoresis on Si|Pt substrates, and subsequently covered by a laser ablation deposited BaTiO3 layer were prepared with different cobalt ferrite concentrations. Their structure presented a combination of BaTiO3, with its tetragonal and the orthorhombic phases coexisting at room temperature, and CoFe2O4 with the cubic spinel structure. The cobalt ferrite nanograins were under in-plane tensile stress, while the BaTiO3 phase was under in-plane compressive stress. The dielectric measurements showed that as the barium titanate grain size decreased, its ferroelectric Curie temperature shifted to lower temperatures relative to the bulk. This grain size dependent TC shift was associated and modeled by a core-shell structure of BaTiO3 grains in the films, with a tetragonal core and cubic shell. Additionally, a diffuse tetragonal-orthorhombic phase transition was observed and, in agreement with Raman spectroscopy results, associated to the coexistence of barium titanate orthorhombic and tetragonal phases in the room temperature region. This led to the formation of polar nanoclusters with random polarization orientations, which induced a frustrated phase transition between the tetragonal and orthorhombic phases of barium titanate in the films.
Liquid–solid phase transition of hydrogen and deuterium in silica aerogel
Authors: Van Cleve E. , Worsley M. A. , Kucheyev S. O.
Published: October 2014

Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H2 and D2 in an ∼85%-porous base-catalyzed silica aerogel. We find that liquid–solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ∼4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H2 and D2 confined inside the aerogel monolith. Results for H2 and D2 are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.
Rolling motion of an elastic cylinder induced by elastic strain gradients
Authors: Chen Lei , Chen Shaohua
Published: October 2014

Recent experiment shows that an elastic strain gradient field can be utilized to transport spherical particles on a stretchable substrate by rolling, inspired by which a generalized plane-strain Johnson-Kendall-Roberts model is developed in this paper in order to verify possible rolling of an elastic cylinder adhering on an elastic substrate subject to a strain gradient. With the help of contact mechanics, closed form solutions of interface tractions, stress intensity factors, and corresponding energy release rates in the plane-strain contact model are obtained, based on which a possible rolling motion of an elastic cylinder induced by strain gradients is found and the criterion for the initiation of rolling is established. The theoretical prediction is consistent well with the existing experimental observation. The result should be helpful for understanding biological transport mechanisms through muscle contractions and the design of transport systems with strain gradient.
Width dependent transition of quantized spin-wave modes in Ni80Fe20 square nanorings
Authors: Banerjee Chandrima , Saha Susmita , Barman Saswati , Rousseau Olivier , Otani YoshiChika , Barman Anjan
Published: October 2014

We investigated optically induced ultrafast magnetization dynamics in square shaped Ni80Fe20 nanorings with varying ring width. Rich spin-wave spectra are observed whose frequencies showed a strong dependence on the ring width. Micromagnetic simulations showed different types of spin-wave modes, which are quantized upto very high quantization number. In the case of widest ring, the spin-wave mode spectrum shows quantized modes along the applied field direction, which is similar to the mode spectrum of an antidot array. As the ring width decreases, additional quantization in the azimuthal direction appears causing mixed modes. In the narrowest ring, the spin-waves exhibit quantization solely in azimuthal direction. The different quantization is attributed to the variation in the internal field distribution for different ring width as obtained from micromagnetic analysis and supported by magnetic force microscopy.
Doping concentration driven morphological evolution of Fe doped ZnO nanostructures
Authors: Sahai A. , Kumar Y. , Agarwal V. , Olive-Méndez S. F. , Goswami N.
Published: October 2014

In this paper, systematic study of structural, vibrational, and optical properties of undoped and 1-10 at.% Fe doped ZnO nanostructures, synthesized adopting chemical precipitation route, has been reported. Prepared nanostructures were characterized employing an assortment of microscopic and spectroscopic techniques, namely Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) Spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Micro-Raman Spectroscopy (μRS), and UV-visible and Photoluminescence (PL) spectroscopy. With Fe incorporation, a gradual morphological transformation of nanostructures is demonstrated vividly through SEM/TEM characterizations. Interestingly, the morphology of nanostructures evolves with 1–10 at. % Fe doping concentration in ZnO. Nanoparticles obtained with 1 at. % Fe evolve to nanorods for 3 at. % Fe; nanorods transform to nanocones (for 5 at. % and 7 at. % Fe) and finally nanocones transform to nanoflakes at 10 at. % Fe. However, at all these stages, concurrence of primary hexagonal phase of Zn1-xFexO along with the secondary phases of cubic ZnFe2O4 and rhombohedric Fe2O3, is revealed through XRD analysis. Based on collective XRD, SEM, TEM, and EDX interpretations, a model for morphological evolution of nanostructures was proposed and the pivotal role of Fe dopant was deciphered. Furthermore, vibrational properties analyzed through Raman and FTIR spectroscopies unravel the intricacies of formation and gradual enhancement of secondary phases with increased Fe concentration. UV-visible and PL spectroscopic analyses provided further insight of optical processes altering with Fe incorporation. The blue shift and gradual quenching of visible photoluminescence with Fe doping was found in accordance with structural and vibrational analyses and explicated accordingly.
Design of a broadband ultra-large area acoustic cloak based on a fluid medium
Authors: Zhu Jian , Chen Tianning , Liang Qingxuan , Wang Xiaopeng , Jiang Ping
Published: October 2014

A broadband ultra-large area acoustic cloak based on fluid medium was designed and numerically implemented with homogeneous metamaterials according to the transformation acoustics. In the present work, fluid medium as the body of the inclusion could be tuned by changing the fluid to satisfy the variant acoustic parameters instead of redesign the whole cloak. The effective density and bulk modulus of the composite materials were designed to agree with the parameters calculated from the coordinate transformation methodology by using the effective medium theory. Numerical simulation results showed that the sound propagation and scattering signature could be controlled in the broadband ultra-large area acoustic invisibility cloak, and good cloaking performance has been achieved and physically realized with homogeneous materials. The broadband ultra-large area acoustic cloaking properties have demonstrated great potentials in the promotion of the practical applications of acoustic cloak.
A nonlinear model for magnetoacoustic waves in dense dissipative plasmas with degenerate electrons
Authors: Masood W. , Jahangir R. , Eliasson B. , Siddiq M.
Published: October 2014

The properties of nonlinear fast magnetoacoustic waves in dense dissipative plasmas with degenerate electrons are studied theoretically in the framework of the Zabolotskaya-Khokhlov (ZK) equation for small but finite amplitude excitations. Shock-like solutions of the ZK equation are obtained and are applied to parameters relevant to white dwarf stars.
A study of self organized criticality in ion temperature gradient mode driven gyrokinetic turbulence
Authors: Mavridis M. , Isliker H. , Vlahos L. , Görler T. , Jenko F. , Told D.
Published: October 2014

An investigation on the characteristics of self organized criticality (Soc) in ITG mode driven turbulence is made, with the use of various statistical tools (histograms, power spectra, Hurst exponents estimated with the rescaled range analysis, and the structure function method). For this purpose, local non-linear gyrokinetic simulations of the cyclone base case scenario are performed with the GENE software package. Although most authors concentrate on global simulations, which seem to be a better choice for such an investigation, we use local simulations in an attempt to study the locally underlying mechanisms of Soc. We also study the structural properties of radially extended structures, with several tools (fractal dimension estimate, cluster analysis, and two dimensional autocorrelation function), in order to explore whether they can be characterized as avalanches. We find that, for large enough driving temperature gradients, the local simulations exhibit most of the features of Soc, with the exception of the probability distribution of observables, which show a tail, yet they are not of power-law form. The radial structures have the same radial extent at all temperature gradients examined; radial motion (transport) though appears only at large temperature gradients, in which case the radial structures can be interpreted as avalanches.
Efficient and accurate laser shaping with liquid crystal spatial light modulators
Authors: Maxson Jared M. , Bartnik Adam C. , Bazarov Ivan V.
Published: October 2014

A phase-only spatial light modulator (SLM) is capable of precise transverse laser shaping by either functioning as a variable phase grating or by serving as a variable mask via polarization rotation. As a phase grating, the highest accuracy algorithms, based on computer generated holograms (CGHs), have been shown to yield extended laser shapes with <10% rms error, but conversely little is known about the experimental efficiency of the method in general. In this work, we compare the experimental tradeoff between error and efficiency for both the best known CGH method and polarization rotation-based intensity masking when generating hard-edged flat top beams. We find that the masking method performs comparably with CGHs, both having rms error < 10% with efficiency > 15%. Informed by best practices for high efficiency from a SLM phase grating, we introduce an adaptive refractive algorithm which has high efficiency (92%) but also higher error (16%), for nearly cylindrically symmetric cases.
Strain-modulation of spin-dependent transport in graphene
Authors: Cao Zhen-Zhou , Li Guan-Qiang , Hou Jin , Cheng Yan-Fu
Published: October 2014

We investigate strain modulation of the spin-dependent electron transport in a graphene junction using the transfer matrix method. As an analogy to optics, we define the modulation depth in the electron optics domain. Additionally, we discuss the transport properties and show that the modulation depth and the conductance depend on the spin-orbit coupling strength, the strain magnitude, the width of the strained area, and the energy of the incident electron. The conductances of the spin-down and spin-up electrons have opposite and symmetrical variations, which results in the analogous features of their modulation depths. The maximum conditions for both the modulation depth and the electron spin upset rate are also analyzed.
Regarding the Néel relaxation time constant in magnetorelaxometry
Authors: Leliaert J. , Coene A. , Crevecoeur G. , Vansteenkiste A. , Eberbeck D. , Wiekhorst F. , Van Waeyenberge B. , Dupré L.
Published: October 2014

Magnetorelaxometry (MRX) is a sensitive measurement technique frequently employed in biomedical applications for imaging magnetic nanoparticles (MNP). In this article, we employ a first principles model to investigate the effects of different iron oxide MNP sample properties on the Néel relaxation time constant τN in magnetorelaxometry. Using this model, we determined that dipolar interactions start to have an impact on the MRX signal from Fe concentrations of 100 mmol/l and result in a smaller τN. Additionally, the micromagnetic damping constant, closely related to τN, was found to be between 0.0005 and 0.002 by comparison to an MRX measurement of iron oxide particles. This is significantly lower compared to the bulk value of 0.07 for this material.
Band structure and transport studies of copper selenide: An efficient thermoelectric material
Authors: Tyagi Kriti , Gahtori Bhasker , Bathula Sivaiah , Auluck S. , Dhar Ajay
Published: October 2014

We report the band structure calculations for high temperature cubic phase of copper selenide (Cu2Se) employing Hartree-Fock approximation using density functional theory within the generalized gradient approximation. These calculations were further extended to theoretically estimate the electrical transport coefficients of Cu2Se employing Boltzmann transport theory, which show a reasonable agreement with the corresponding experimentally measured values. The calculated transport coefficients are discussed in terms of the thermoelectric (TE) performance of this material, which suggests that Cu2Se can be a potential p-type TE material with an optimum TE performance at a carrier concentration of ∼4−6×1021cm−3.
Air-stable short-wave infrared PbS colloidal quantum dot photoconductors passivated with Al2O3 atomic layer deposition
Authors: Hu Chen , Gassenq Alban , Justo Yolanda , Devloo-Casier Kilian , Chen Hongtao , Detavernier Christophe , Hens Zeger , Roelkens Günther
Published: October 2014

A PbS colloidal quantum dot photoconductor with Al2O3 atomic layer deposition (ALD) passivation for air-stable operation is presented. Two different types of inorganic ligands for the quantum dots, S2− and OH−, are investigated. PbS/S2− photoconductors with a cut-off wavelength up to 2.4 μm are obtained, and a responsivity up to 50 A/W at 1550 nm is reported. The corresponding specific detectivity is ∼3.4 × 108 Jones at 230 K. The 3-dB bandwidth of the PbS/S2− and PbS/OH− photodetectors is 40 Hz and 11 Hz, respectively.
Highly textured oxypnictide superconducting thin films on metal substrates
Authors: Iida Kazumasa , Kurth Fritz , Chihara Masashi , Sumiya Naoki , Grinenko Vadim , Ichinose Ataru , Tsukada Ichiro , Hänisch Jens , Matias Vladimir , Hatano Takafumi , Holzapfel Bernhard , Ikuta Hiroshi
Published: October 2014

Highly textured NdFeAs(O,F) thin films have been grown on ion beam assisted deposition-MgO/Y2O3/Hastelloy substrates by molecular beam epitaxy. The oxypnictide coated conductors showed a superconducting transition temperature (Tc) of 43 K with a self-field critical current density (Jc) of 7.0×104 A/cm2 at 5 K, more than 20 times higher than powder-in-tube processed SmFeAs(O,F) wires. Albeit higher Tc as well as better crystalline quality than Co-doped BaFe2As2 coated conductors, in-field Jc of NdFeAs(O,F) was lower than that of Co-doped BaFe2As2. These results suggest that grain boundaries in oxypnictides reduce Jc significantly compared to that in Co-doped BaFe2As2 and, hence biaxial texture is necessary for high Jc.
Buckling of microtubules: An insight by molecular and continuum mechanics
Authors: Zhang Jin , Meguid S. A.
Published: October 2014

The molecular structural mechanics method has been extended to investigate the buckling of microtubules (MTs) with various configurations. The results indicate that for relative short MTs the shear deformation effect, rather than the nonlocal effect, is mainly responsible for the limitation of their widely used Euler beam description and the observed length-dependence of their bending stiffness. In addition, the configuration effect of MTs is also studied and considered as an explanation for the large scattering of the critical buckling force and bending stiffness observed in existing experiments. This configuration effect is also found to mainly originate from the geometry of the MTs and is mainly determined by the protofilament number.
Quantum dot ternary-valued full-adder: Logic synthesis by a multiobjective design optimization based on a genetic algorithm
Authors: Klymenko M. V. , Remacle F.
Published: October 2014

A methodology is proposed for designing a low-energy consuming ternary-valued full adder based on a quantum dot (QD) electrostatically coupled with a single electron transistor operating as a charge sensor. The methodology is based on design optimization: the values of the physical parameters of the system required for implementing the logic operations are optimized using a multiobjective genetic algorithm. The searching space is determined by elements of the capacitance matrix describing the electrostatic couplings in the entire device. The objective functions are defined as the maximal absolute error over actual device logic outputs relative to the ideal truth tables for the sum and the carry-out in base 3. The logic units are implemented on the same device: a single dual-gate quantum dot and a charge sensor. Their physical parameters are optimized to compute either the sum or the carry out outputs and are compatible with current experimental capabilities. The outputs are encoded in the value of the electric current passing through the charge sensor, while the logic inputs are supplied by the voltage levels on the two gate electrodes attached to the QD. The complex logic ternary operations are directly implemented on an extremely simple device, characterized by small sizes and low-energy consumption compared to devices based on switching single-electron transistors. The design methodology is general and provides a rational approach for realizing non-switching logic operations on QD devices.
Temperature dependence of non-radiative energy transfer in hybrid structures of InGaN/GaN nanorods and F8BT films
Authors: Smith R. M. , Liu B. , Bai J. , Wang T.
Published: October 2014

Hybrid organic/inorganic white light emitting structures have been fabricated based on a combination of high efficiency InGaN/GaN multiple quantum well (MQW) nanorod arrays and a yellow emitting co-polymer F8BT, leading to a minimised separation between them in order to achieve high efficiency non-radiative energy transfer (NRET). The NRET efficiency has been found 6.7 times higher at room temperature than at 7 K. This is attributed to the existence of strong exciton localization the InGaN MQWs, which can undergo thermally activated delocalization at high temperatures. The enhanced NRET efficiency is not only due to the delocalized MQW excitons, but also enhanced by the increased exciton diffusion at higher temperatures. This behaviour highlights the potential for high efficiency NRET in down-conversion hybrid white light emitting diodes operating at room temperature.