bluuebunny/crossref_metadata_2025 huggingface dataset:
Negative‐order ridge substrate integrated waveguide coupled‐resonator filter
Authors: Yang Qingshan , Zhang Yunhua
Published: February 2014

A negative‐order resonator (NOR) based on a ridge substrate integrated waveguide (RSIW) structure and its application to a coupled‐resonator filter (CRF) is investigated. The NOR is realised by etching an interdigital slot on the ridge surface of the original RSIW to achieve the composite right/left‐handed (CRLH) characteristics, which makes the resonator exhibit the unique property of negative‐order resonances. The −1st‐order resonance can be generated with a much lower resonant frequency than that of the original RSIW resonator with the same size. Thus, miniaturisation can be achieved by using this NOR structure. Besides, the non‐radiative property of the CRLH RSIW structure would help in avoiding radiation loss and electromagnetic interference to the other circuits, which is a better choice in guided‐wave applications than other open radiative CRLH structures. Electric coupling is adopted between the neighbouring resonators in the filter design. This CRF shows the advantages of a low‐profile, compact size, non‐radiation as well as easy integration with other planar circuits.
Nonlinear limit of alternative method to 2 × 2 MIMO for LTE RoF system
Authors: Kanesan T. , Rajbhandari S. , Giacoumidis E. , Aldaya I.
Published: February 2014

Owing to the limited cell size of eNodeB (eNB), the relay node has emerged as an attractive solution for the long‐term evolution (LTE) system. The nonlinear limit of the alternative method to multiple‐input and multiple‐output (MIMO) based on frequency division multiplexing (FDM) for orthogonal FDM (OFDM) is analysed over varying transmission spans. In this reported work, it is shown that the degradation pattern over the linear, intermixing and nonlinear propagation regions is consistent for the 2 and the 2.6 GHz bands. The proposed bands experienced a linear increase in the error vector magnitude (EVM) for both the linear and the nonlinear regions proportional to the increasing transmission spans. In addition, an optical launch power between −2 and 2 dBm achieved a significantly lower EVM than the LTE limit of 8% for the 10–60 km spans.
Simple approach to determining parameters of noncommensurate sampling for optimal pseudo‐noise code phase delay discrimination
Authors: Jin Xiaojun , Xu Zhaobin , Zhang Chaojie , Jin Zhonghe
Published: February 2014

Noncommensurate sampling is an effective solution for improving the tracking performance of digital code tracking loops. So far there has been a lack of a generalised method for designing the parameters of this sampling scenario. A simple approach to choosing the parameters of noncommensurate sampling is presented, which is based on the analysis of the quantitative relationship among the chip phase delay discrimination, the sampling ratio and the correlation length. Numerical and simulation results show that optimal phase delay discrimination and thereby superior tracking accuracy can be achieved with the proposed approach. This approach is especially suitable for precision ranging applications, and can be extended to other applications involving accurate signal tracking in digital equipment.
Variability analysis of interconnect structures including general nonlinear elements in SPICE‐type framework
Authors: Biondi A. , Manfredi P. , Vande Ginste D. , De Zutter D. , Canavero F.G.
Published: February 2014

A stochastic modelling method is developed and implemented in a SPICE framework to analyse variability effects on interconnect structures including general nonlinear elements.
Virtual network embedding with discrete particle swarm optimisation
Authors: Wang Li , Qu Hua , Zhao Jihong , Guo Ya
Published: February 2014

Network virtualisation is organised as a fundamental technology for eradicating the ossified architecture of the Internet. Virtual network embedding (VNE) instantiates virtual networks on a substrate network to carry as many services as possible, which is an optimisation problem. VNE with discrete particle swarm optimisation (DPSO) is proposed, which models VNE and abstracts its constraints, modifies PSO into DPSO, adapts the characters of VNE and obtains the optimal solution to map virtual networks onto a substrate network.
Required Cauer network order for modelling of thermal transfer impedance
Authors: Davidson J.N. , Stone D.A. , Foster M.P.
Published: February 2014

Impedance spectroscopy, a technique for analysing electroceramics, is applied to the two‐port form of the Cauer network which is commonly used as a thermal circuit analogue. The transfer impedance spectra of the Cauer network representations of a single material are presented as Nyquist plots for a range of network orders. The results demonstrate that a model with four or more resistor‐capacitor elements is required to accurately model a single material. The effect of taking a measurement at different points within a single material is then reported and four elements are similarly required between the heat source and the measurement. The existing modelling techniques, which often use only one element per material block, are shown to be especially inaccurate. By using these findings, a design engineer can produce a better thermal model of a complete system by making an informed compromise between the model's accuracy and complexity.
Symbol error rate analysis of transmit beamforming systems under delayed and limited feedback
Authors: Lee Donghun , Jeong Byung Jang
Published: February 2014

The symbol error rate (SER) analysis of a transmit beamforming system is investigated under delayed and limited feedback. Using the Lauricella hypergeometric series, the exact closed‐form expressions of the transmit beamforming for SER with M‐ary phase shift keying and quadrature amplitude modulation is derived under the delayed and limited feedback.
Structure tensor based in‐loop filter for depth video coding
Authors: Hu Jinhui , Hu Ruimin , Wang Zhongyuan
Published: February 2014

A structure tensor based in‐loop filter to remove the compression artefacts in depth video coding is proposed. Instead of involving all neighbouring depth pixels in the joint filtering process, the algorithm chooses one neighbouring depth pixel as the filter output from a reliable neighbour region which is adaptively determined by a structure tensor analysis. It can effectively reduce the negative influence of the non‐similar neighbouring depth pixels and improve the quality of the synthesised virtual views. The experimental results show that the proposal is more effective in improving the depth video coding efficiency.
Radio frequency signals synthesised from independent cryogenic sapphire oscillators
Authors: Hartnett J.G. , Parker S.R. , Ivanov E.N. , Povey T. , Nand N.R. , le Floch J.‐M.
Published: February 2014

The phase noise and frequency stability measurements of 1 GHz, 100 MHz and 10 MHz signals are presented which have been synthesised from the 11.2 GHz outputs of two nominally identical independent cryogenic microwave sapphire oscillators.
Multilayer, low‐parasitic, interconnection scheme for advanced submillimetre‐wave GaN circuits
Authors: Margomenos A. , Shinohara K. , Regan D.C. , Corrion A.L. , Brown D.F. , Tang Y. , Butler C. , Schmitz A. , Robinson J.F. , Kim S. , McGuire C. , Micovic M.
Published: February 2014

A multilayer, low‐parasitic interconnection scheme for highly scaled GaN high electron mobility transistors is reported. The fabrication process offers three Au interconnects embedded in benzocyclobutene (BCB) dielectric, with an integrated air‐box in the active area in order to minimise the gate parasitic capacitances. With the addition of the air‐box, it is demonstrated that the performance of the BCB encapsulated device is similar to that of a non‐encapsulated device. Furthermore, by utilising the multilayer interconnection scheme a low‐loss (0.75 dB) 3 dB tandem coupler operating from 140 to 220 GHz is demonstrated.
Method to improve efficiency of human detection using scalemap
Authors: Bae Guntae , Kwak Sooyeong , Byun Hyeran , Park Daeyong
Published: February 2014

An efficient method is introduced for detecting humans in surveillance video. The method improves the performance of multiscale human detection through the use of a scalemap, and does not require knowledge of the camera parameters or the use of additional devices. A scalemap is a map that links each position in the observed image to the optimal detection scale. The proposed method efficiently reduces the computational costs by estimating the scale of interest and the region of interest based on the scalemap, while maintaining the accuracy of the detection. It is experimentally shown through an experiment that the proposed method can improve both the accuracy and the efficiency of real‐world surveillance videos.
Wideband ceiling mount omnidirectional antenna for indoor distributed antenna system applications
Authors: Zhou Lei , Jiao Yong‐Chang , Qi Yhong , Weng Zbin , Ni Tao
Published: February 2014

A wideband omnidirectional vertical polarised antenna is presented. By incorporating a shorted coupling top loading structure over two cross‐connected monopole antennas, an enhanced impedance bandwidth of 152% is achieved. The prototype antenna operates from 650 to 4500 MHz, with a reflection coefficient <−15 dB, a 2–6 dBi antenna gain with a very stable vertical radiation pattern and <3.5 dB horizontal pattern ripples. The proposed antenna can be widely used in indoor distributed antenna systems (DASs), such as GSM900, GSM1800, UMTS2100 and the enhanced TD‐LTE (up to 3.5 GHz) bands. The simulated and the measured return loss and radiation pattern results show good agreement.
Terahertz wireless communication using GaAs transistors as detectors
Authors: Tohmé L. , Blin S. , Ducournau G. , Nouvel P. , Coquillat D. , Hisatake S. , Nagatsuma T. , Pénarier A. , Varani L. , Knap W. , Lampin J.‐F.
Published: February 2014

The detection of high data‐rate wireless communication using a terahertz‐frequency carrier, and a GaAs transistor as a detector, is reported. Communications are investigated around 0.2 and 0.3087 THz. For the first time, an error‐free transmission at data rates up to 8.2 Gbit/s is demonstrated, using a carrier frequency of 0.3087 THz.
Small‐size high‐selectivity bandstop filter with coupled‐line stubs for dual‐band applications
Authors: Wang Weimin , Liao Mengbi , Wu Yongle , Liu Yuanan
Published: February 2014

A novel coupled‐line stub is proposed for the design of a novel dual‐band small‐size bandstop filter (BSF). This kind of coupled‐line dual‐band BSF features a compact and simple structure, flexible frequency‐ratio adjustment and high selectivity. To verify the proposed circuit structure and design approach, a microstrip example has been fabricated and measured. The measured results show a good agreement with the simulated responses.
Dynamic ternary CAM for hardware search engine
Authors: Vinogradov V. , Ha Joowan , Lee Changhyuk , Molnar A. , Hong Sang Hoon
Published: February 2014

A five‐transistor dynamic ternary content addressable memory (CAM) is presented for high‐density data search applications. The data path and the search path are separated to avoid unwanted capacitive coupling at the storage node. To increase the data retention time, the data lines are grounded and dummy search lines are implemented for refresh operations. The proposed CAM cell is fabricated using a 130 nm CMOS process, and occupies an area of 8.99 μm2. A prototype array of 64 × 128 search memory has a retention time of 2.84 ms at room temperature with a 1.2 V supply voltage. The hardware search performance is compared with a conventional software‐based search scheme, running on two different systems with clock frequencies of more than an order of magnitude faster. The hardware search engine exhibits comparable search speeds while dissipating only 149 mW.
Self‐contained compact transmitter for high‐rate data transmission
Authors: Salehi M. , Manteghi M.
Published: February 2014

A new technique to realise a high‐rate data transmission through electrically small antennas is presented. In this technique, the fundamental resonant frequency of a single‐mode antenna is modulated by feeding the antenna with a switched capacitor with a switching signal controlled by baseband digital data. The antenna operates completely in the transient state and a DC power source is used to excite the fundamental resonances, and therefore no RF source is required.
CPW‐fed low‐profile directional antenna operating in low microwave band for wideband medical diagnostic systems
Authors: Mobashsher A.T. , Abbosh A.
Published: February 2014

Medical diagnostic systems demand wideband antennas with directive radiation patterns. In addition, portable systems require low profile and light weight antennas to be incorporated. These necessities of modern microwave‐based diagnostic systems are addressed in this reported work. The antenna is built with two simple thoroughly printed structures connected to each other using two copper walls, forming a loop‐like geometry. The top element is capacitively loaded with a pair of symmetrically placed slots and fed with a coplanar waveguide (CPW). The antenna works like a small loop in the lower resonating mode and as a folded‐dipole in the higher modes. The antenna exhibits a 109% bandwidth with stable radiation patterns of an about 9 dB front‐to‐back ratio over most of the band with only a profile of 0.05λ (λ = wavelength at the lowest frequency). The measured and the simulated results show that the proposed antenna is suitable for wideband medical imaging systems.
300°C operation of normally‐off AlGaN/GaN MOSFET with low leakage current and high on/off current ratio
Authors: Xu Zhe , Wang Jinyan , Cai Yong , Liu Jingqian , Yang Zhen , Li Xiaoping , Wang Maojun , Yang Zhenchuang , Xie Bin , Yu Min , Wu Wengang , Ma Xiaohua , Zhang Jincheng , Hao Yue
Published: February 2014

300°C operation of a normally‐off AlGaN/GaN metal‐oxide semiconductor field‐effect transistor (MOSFET) is successfully demonstrated, which is fabricated using a self‐terminating gate recess etching technique. At 300°C, by employing a 15 nm‐thick Al2O3 as the gate dielectric deposited by atomic layer deposition, the fabricated normally‐off MOSFET exhibits a threshold voltage (Vth) of 3.2 V, a low off‐state leakage current of ∼10−7 A/mm and a low forward gate leakage current of ∼10−7 A/mm. Thus, a high on/off current ratio of ∼ 106 is obtained. Furthermore, the normally‐off MOSFET also exhibits small variations in terms of its Vth from room temperature to 300°C with a maximum relative variation of 6.7% in a such temperature range. These results make this normally‐off AlGaN/GaN MOSFET very promising for high‐temperature digital electronics.
Design of USB dongle antenna for WLAN applications using theory of characteristic modes
Authors: Elghannai E.A. , Rojas R.G.
Published: February 2014

A compact universal serial bus (USB) antenna design for wireless USB dongle application is presented. The use of the theory of characteristic modes (CMs) to design such an antenna is novel and leads to a systematic antenna design scheme. The physical insight that the CM offers is of great importance for designing such an antenna. The systematic placing of reactive loads on the antenna body plays a key role in matching the antenna at the desired frequency bands. The proposed antenna's overall size is (48 × 10 mm) and it can serve the WLAN IEEE 802.11 a/b/g/n bands (2.4/5.5 GHz). It could also be used for the Bluetooth and LTE applications.
Refractive index calculation from echo interference in pulsed terahertz spectroscopy
Authors: Sanjuan F. , Vidal B.
Published: February 2014

A method for calculating the average refractive index of a sample using transmission terahertz time‐domain spectroscopy in a single measurement is presented. The refractive index is derived from the analysis of the frequency‐domain interference caused by Fabry‐Pérot reflections in the sample through the discrete Fourier transform of the spectrum module. This approach is simple and fast (not requiring a reference measurement), improves sensitivity over direct time‐domain analysis and allows the derivation of the refractive index in a specific frequency window. The method can also be used to identify unwanted reflections in the experimental setup.
Design of broadband microwave absorber using honeycomb structure
Authors: Choi Won‐Ho , Shin Jae‐Hwan , Song Tae‐Hoon , Lee Woo‐Yong , Lee Won‐Jun , Kim Chun‐Gon
Published: February 2014

A novel broadband microwave absorber design concept using a honeycomb sandwich structure is proposed. Unlike the conventional microwave absorbing honeycomb sandwich structure, the newly proposed design concept uses the transverse direction of a honeycomb structure with a coated lossy material. When the incident waves reach the inside of the honeycomb coated with the lossy material, multiple scattering occurs inside the honeycomb due to the two different refractive indices. Then, the trapped electromagnetic (EM) waves lose energy due to the coated lossy walls. Thus, the honeycomb structure can be used in the transverse direction and the effective thickness in terms of the incident EM waves becomes very large. This considerable thickness represents a very effective way to sufficiently attenuate the trapped waves. This way, a lightweight and broadband absorber could be implemented without use of a magnetic material and without any limitations on the thickness.
Shield can mounting clip design for robust and enhanced shielding effectiveness in mobile devices
Authors: Song Eakhwan , Park Hyun H.
Published: February 2014

A small metallic shield enclosure, commonly called a shield can, is an indispensable component of modern mobile devices in reducing electromagnetic interference. A sophisticated clip design utilising an embossing technique and a furrow structure for mounting shield cans on printed circuit boards in mobile devices is proposed in order to enhance the robustness and effectiveness of the shield cans. The proposed design is validated by radiated spurious emission measurement and three‐dimensional field simulation.
Two‐layer motion estimation algorithm for video coding
Authors: Paramkusam A.V. , Reddy V.S.K.
Published: February 2014

A novel two‐layer motion estimation which searches motion vectors on two layers with partial distortion measures in order to reduce the overwhelming computational complexity of motion estimation (ME) in video coding is proposed. A layer is an image which is derived from the reference frame such that the summation of a block of pixels in the reference frame determines the point of a layer. It has been noted on different video sequences that many motion vectors on the layers are the same as those searched on the reference frame. Experimental results on a wide variety of video sequences show that the proposed algorithm achieves both fast speed and good motion prediction quality when compared with the state‐of‐the‐art fast block matching algorithms.
Terahertz quantum cascade lasers with >1 W output powers
Authors: Li Lianhe , Chen Li , Zhu Jingxuan , Freeman J. , Dean P. , Valavanis A. , Davies A.G. , Linfield E.H.
Published: February 2014

Terahertz (THz) frequency quantum cascade lasers emitting peak powers of >1 W from a single facet in the pulsed mode are demonstrated. The active region is based on a bound‐to‐continuum transition with a one‐well injector, and is embedded into a surface‐plasmon waveguide. The lasers emit at a frequency of ∼3.4 THz and have a maximum operating temperature of 123 K. The maximum measured emitted powers are ∼1.01 W at 10 K and ∼420 mW at 77 K, with no correction made to allow for the optical collection efficiency of the apparatus.
Valley current mode pulse train control technique for switching DC–DC converters
Authors: Sha Jin , Xu Jianping , Zhong Shu , Liu Shuhan
Published: February 2014

To eliminate the low‐frequency oscillation phenomenon in pulse train controlled switching DC–DC converters operating in continuous conduction mode (CCM), a valley current mode pulse train control technique is proposed. The experimental results show that by using the proposed control technique, the low‐frequency oscillation in the pulse train (PT) controlled CCM switching DC–DC converter can be eliminated, while the great robustness and excellent transient performance of the traditional PT control technique can be retained.
Quantitative imaging of numerically realistic human head model using microwave tomography
Authors: Jalilvand M. , Wu Chuanren , Schmid J. , Zwick T.
Published: February 2014

Microwave tomography (MWT) is exploited for the detection of haemorrhagic stroke by using a nonlinear iterative imaging algorithm. An anatomically realistic two‐dimensional (2D) head model is simulated using a finite difference time‐domain numerical solver. By using an iterative optimisation algorithm based on the Gauss–Newton approach, the head model with an artificially embedded stroke region modelled as blood is successfully reconstructed through a blind reconstruction procedure (i.e. no a priori information about the shape or the dielectric properties of the model is assumed). It is observed that beginning from a homogeneous guess similar to the background material, right after the first iteration the shapes of the layers are clearly distinguished and the values of the dielectric properties converge to the actual values after only 10 iterations.
Ultra‐wideband, high‐dynamic range, low loss GaN HEMT mixer
Authors: Kang J. , Kurdoghlian A. , Margomenos A. , Moyer H.P. , Brown D. , McGuire C.
Published: February 2014

An ultra‐wideband double‐balanced resistive mixer with high dynamic range (IIP3) is reported. The mixer is designed and fabricated using HRL Laboratory's GaN high electron mobility transistor (HEMT) (T2) process and it utilises a series resistor‐capacitor circuit network termination to the device gate, in order to achieve resonance‐free broadband conversion loss and high dynamic range. The measured conversion loss from 3 to 40 GHz is between 5.5 and 8.5 dB at 1 GHz intermediate frequency. Large signal testing at 15 GHz showed a 1 dB gain compression point (P1dB) of 22 dBm.
Sub‐THz characterisation of multi‐walled carbon nanotube thin films using vector network analyser
Authors: Puthukodan S. , Dadrasnia E. , Vinod V.K.T. , Nguendon H.K. , Lamela H. , Ducournau G. , Lampin J.‐F. , Garet F. , Coutaz J.‐L. , Lee D.‐M. , Baik S.
Published: February 2014

A vector network analyser is used to study the electrical properties of multi‐walled carbon nanotube (MWCNT) thin films deposited on a fused quartz substrate in the sub‐terahertz (THz) frequency ranges of 220–325 GHz (WR3.4) and 325–500 GHz (WR2.2). The experiment is performed in free space. The complex permittivity of the MWCNT thin films is extracted using the Nicholson‐Ross‐Weir method. The refractive index and conductivity are then determined from the extracted permittivity. The method is validated by comparison with values obtained using THz time‐domain spectroscopy.
Adaptive face modelling for reconstructing 3D face shapes from single 2D images
Authors: Maghari Ashraf , Venkat Ibrahim , Liao Iman Yi , Belaton Bahari
Published: February 2014

Example‐based statistical face models using principle component analysis (PCA) have been widely deployed for three‐dimensional (3D) face reconstruction and face recognition. The two common factors that are generally concerned with such models are the size of the training dataset and the selection of different examples in the training set. The representational power (RP) of an example‐based model is its capability to depict a new 3D face for a given 2D face image. The RP of the model can be increased by correspondingly increasing the number of training samples. In this contribution, a novel approach is proposed to increase the RP of the 3D face reconstruction model by deforming a set of examples in the training dataset. A PCA‐based 3D face model is adapted for each new near frontal input face image to reconstruct the 3D face shape. Further an extended Tikhonov regularisation method has been employed to reconstruct 3D face shapes from a set of facial points. The results justify that the proposed adaptive PCA‐based model considerably improves the RP of the standard PCA‐based model and outperforms it with a 95% confidence level.
Analytical approach for placement and sizing of distributed generation on distribution systems
Authors: Elsaiah Salem , Benidris Mohammed , Mitra Joydeep
Published: February 2014

An analytical method for placement and sizing of distributed generation on power distribution systems for loss reduction is introduced. The proposed analytical method is developed based on a new formulation for the power flow problem, which is non‐iterative, direct, and involves no convergence issues even for systems with high R/X branch ratios. Further, this power flow solution is extremely useful whenever fast and repetitive power flow estimations are required. A priority list based on loss sensitivity factors is developed to determine the optimal locations of the candidate distributed generation units. Sensitivity analysis is performed to estimate the optimal size and power factor of the candidate distributed generation units. Various types of distributed generators (DGs) have been dealt with and viable solutions are proposed to reduce total system loss. The proposed method has been tested on 33‐bus and 69‐bus distribution systems, which are extensively used as examples in solving the placement and sizing problem of DGs. Exhaustive power flow routines are also performed to verify the sizes obtained by the analytical method. The test results show that the proposed analytical method could lead to optimal or near‐optimal solution, while requiring lower computational effort.
Simple power electronic controller for photovoltaic fed grid‐tied systems using line commutated inverter with fixed firing angle
Authors: Binu Ben Jose D.R. , Ammasai Gounden N. , Ravishankar Jayashri
Published: February 2014

A power electronic interface with maximum power point tracking (MPPT) for grid connected photovoltaic (PV) systems using an integrated cascade boost converter (ICBC) and line commutated inverter (LCI) has been proposed. The variable dc voltage of the PV array is fed as input to the ICBC and the output voltage of the ICBC is maintained constant with the firing angle of the LCI being fixed at an appropriate value greater than 90°. The interesting feature of this scheme is that, it is not mandatory that the constant dc‐link voltage should be more than the peak value of the grid voltage. As the array voltage is now boosted and fixed at the dc link, any variation in the PV output power is reflected in the variation of the dc‐link current and hence only one parameter (the dc‐link current) sensing is required for the MPPT. Furthermore, the proposed controller has made it possible to dispense with the step up transformer between the LCI and the utility grid. The complete scheme has been constructed and experiments have been conducted on an 84 V, 10 A PV array feeding power to a three‐phase 230 V utility grid and the experimental results are compared with the MATLAB simulation results. The steady‐state analysis of the overall system and the experimental results confirm the validity of the proposed controller and the efficacy of the analysis.
Amperometric biosensor for cholesterol based on novel nanocomposite array gold nanoparticles/acetone‐extracted propolis/multiwall carbon nanotubes/gold
Authors: Molaei Rahim , Sabzi Reza Emamali , Farhadi Khalil , Kheiri Farshad , Forough Mehrdad
Published: February 2014

In this reported work, the electrochemical behaviour of gold electrodes modified with gold nanoparticles, acetone‐extracted propolis, multiwall carbon nanotubes and cholesterol oxidase was established for the detection of hydrogen peroxide by using cyclic voltammetry and amperometric techniques. The obtained results confirmed that the current enzymatic biosensor exhibits a fast, highly sensitive, and cost‐effective detection of cholesterol. Cholesterol in the concentration range of 0.15–0.55 mmol l−1 was determined with a detection limit of 4.9 × 10−5 mol l−1 by the amperometric method, and the sensitivity of the proposed method was found to be 17.38 µA/mmol l−1. Normal electroactive species such as ascorbic acid and glucose in the presence of the constant concentration of cholesterol in the samples do not interfere with the determination.
Segmented scintillation detectors with silicon photomultiplier readout for measuring antiproton annihilations
Authors: Sótér A. , Todoroki K. , Kobayashi T. , Barna D. , Horváth D. , Hori M.
Published: February 2014

The Atomic Spectroscopy and Collisions Using Slow Antiprotons experiment at the Antiproton Decelerator (AD) facility of CERN constructed segmented scintillators to detect and track the charged pions which emerge from antiproton annihilations in a future superconducting radiofrequency Paul trap for antiprotons. A system of 541 cast and extruded scintillator bars were arranged in 11 detector modules which provided a spatial resolution of 17 mm. Green wavelength-shifting fibers were embedded in the scintillators, and read out by silicon photomultipliers which had a sensitive area of 1 × 1 mm2. The photoelectron yields of various scintillator configurations were measured using a negative pion beam of momentum p ≈ 1 GeV/c. Various fibers and silicon photomultipliers, fiber end terminations, and couplings between the fibers and scintillators were compared. The detectors were also tested using the antiproton beam of the AD. Nonlinear effects due to the saturation of the silicon photomultiplier were seen at high annihilation rates of the antiprotons.
Non-parabolicity and band gap re-normalisation in Si doped ZnO
Authors: Treharne R. E. , Phillips L. J. , Durose K. , Weerakkody A. , Mitrovic I. Z. , Hall S.
Published: February 2014

A combinatorial methodology, developed for the rapid optimisation of sputtered transparent conducting oxides, was applied to Si doped ZnO. A wide range of compositions have been explored over a single sample to determine an optimum composition, with respect to the minimisation of resistivity, of x = 0.65% wt. SiO2. A fundamental investigation of the conduction band non-parabolicity yields values of me0=0.35m0 and C = 0.3 eV−1 for the conduction band minimum effective mass and the non-parabolicity factor, respectively. The variation of extracted band gap values with respect to dopant concentration provided an estimate of the magnitude of re-normalization effects. A model is proposed to describe the carrier transport behaviour for a degenerate polycrystalline semiconductor by accounting for the tunnelling of carriers through grain boundaries.
Excitation transfer pathways in excitonic aggregates revealed by the stochastic Schrödinger equation
Authors: Abramavicius Vytautas , Abramavicius Darius
Published: February 2014

We derive the stochastic Schrödinger equation for the system wave vector and use it to describe the excitation energy transfer dynamics in molecular aggregates. We suggest a quantum-measurement based method of estimating the excitation transfer time. Adequacy of the proposed approach is demonstrated by performing calculations on a model system. The theory is then applied to study the excitation transfer dynamics in a photosynthetic pigment-protein Fenna-Matthews-Olson (FMO) aggregate using both the Debye spectral density and the spectral density obtained from earlier molecular dynamics simulations containing strong vibrational high-frequency modes. The obtained results show that the excitation transfer times in the FMO system are affected by the presence of the vibrational modes; however, the transfer pathways remain the same.
Analysis of the microwave, terahertz, and far infrared spectra of monodeuterated methanol CH2DOH up to J = 26, K = 11, and o1
Authors: Coudert L. H. , Zemouli M. , Motiyenko R. A. , Margulès L. , Klee S.
Published: February 2014

The first theoretical approach aimed at accounting for the energy levels of a non-rigid molecule displaying asymmetric-top asymmetric-frame internal rotation is developed. It is applied to a line position analysis of the high-resolution spectrum of the non-rigid CH2DOH molecule and allows us to carry out a global analysis of a data set consisting of already available data and of microwave and far infrared transitions measured in this work. The analysis is restricted to the three lowest lying torsional levels (e0, e1, and o1), to K ⩽ 11, and to J ⩽ 26. For the 8211 fitted lines, the unitless standard deviation is 2.4 and 103 parameters are determined including kinetic energy, hindering potential, and distortion effects parameters.
A deterministic thermostat for controlling temperature using all degrees of freedom
Authors: Patra P. K. , Bhattacharya B.
Published: February 2014

We propose a new thermostat that uses all the phase space variables for controlling temperature and thus differs from the existing thermostats that control either the kinetic (e.g., Nose Hoover) or the configurational (e.g., Braga Travis) degrees of freedom. Our thermostat is a special case of the set of equations proposed by Kusnezov et al. [Ann. Phys. 204, 155 (1990)] and is derived using the extended system method. We show that it generates a canonical phase-space distribution. The performance of the thermostat is compared with those of Nose-Hoover kinetic thermostat and Braga-Travis configurational thermostat for a system (i) in thermal equilibrium, (ii) subjected to sudden temperature changes, and (iii) in steady state non-equilibrium under thermal conduction. We observe that all three thermostats perform similarly for systems in equilibrium. However, our thermostat performs the best in the thermal conduction problem by generating a consistent temperature profile across the conduction length. We expect this thermostat to be useful in other non-equilibrium scenarios as well.
Electron pair emission detected by time-of-flight spectrometers: Recent progress
Authors: Huth Michael , Chiang Cheng-Tien , Trützschler Andreas , Schumann Frank O. , Kirschner Jürgen , Widdra Wolf
Published: February 2014

We present results for electron coincidence spectroscopy using two time-of-flight (ToF) spectrometers. Excited by electron impact, the energy and momentum distribution of electron pairs emitted from the Cu(111) surface are resolved and a spectral feature related to the Shockley surface state is identified. By combining the two ToF spectrometers with a high-order harmonic generation light source, we demonstrate double photoemission spectroscopy in the laboratory that required synchrotron radiation in the past. Utilizing this setup, we report results for (γ,2e) on NiO(001) on Ag(001) excited with light at 30 eV photon energy.
Electrostatic correlations on the ionic selectivity of cylindrical membrane nanopores
Authors: Buyukdagli Sahin , Ala-Nissila T.
Published: February 2014

We characterize the role of electrostatic fluctuations on the charge selectivity of cylindrical nanopores confining electrolyte mixtures. To this end, we develop an extended one-loop theory that can account for correlation effects induced by the surface charge, nanoconfinement of the electrolyte, and interfacial polarization charges associated with the low permittivity membrane. We validate the quantitative accuracy of the theory by comparisons with previously obtained Monte-Carlo simulation data from the literature, and scrutinize in detail the underlying forces driving the ionic selectivity of the nanopore. In the biologically relevant case of electrolytes with divalent cations such as CaCl2 in negatively charged nanopores, electrostatic correlations associated with the dense counterion layer in the channel result in an increase of the pore coion density with the surface charge. This peculiarity analogous to the charge inversion phenomenon remains intact for dielectrically inhomogeneous pores, which indicates that the effect should be observable in nanofiltration membranes or DNA-blocked nanopores characterized by a low membrane permittivity. Our results show that a quantitatively accurate consideration of correlation effects is necessary to determine the ionic selectivity of nanopores in the presence of electrolytes with multivalent counterions.
All-electrical time-resolved spin generation and spin manipulation in n-InGaAs
Authors: Stepanov I. , Kuhlen S. , Ersfeld M. , Lepsa M. , Beschoten B.
Published: February 2014

We demonstrate all-electrical spin generation and subsequent manipulation by two successive electric field pulses in an n-InGaAs heterostructure in a time-resolved experiment at zero external magnetic field. The first electric field pulse along the [11¯0] crystal axis creates a current-induced spin polarization (CISP) which is oriented in the plane of the sample. The subsequent electric field pulse along [110] generates a perpendicular magnetic field pulse leading to a coherent precession of this spin polarization with 2-dimensional electrical control over the final spin orientation. Spin precession is probed by time-resolved Faraday rotation. We determine the build-up time of CISP during the first field pulse and extract the spin dephasing time and internal magnetic field strength during the spin manipulation pulse.
A mixing-length model for side layers of magnetohydrodynamic channel and duct flows with insulating walls
Authors: Boeck Thomas , Krasnov Dmitry
Published: February 2014

We propose a simple extension of Prandtl's classical mixing-length model for channel flow in order to describe the effects of a uniform spanwise magnetic field. The mixing length is assumed to be constrained by an additional length scale called the Joule damping length. It is based on the friction velocity and the Joule damping time. The limitation of mixing length is implemented by using the harmonic mean of the wall distance and the Joule damping length. Near the wall, the model captures the combined linear-logarithmic dependence of velocity on the wall distance observed in direct numerical simulations. It also provides a satisfactory prediction for the overall velocity distribution for different Reynolds and Hartmann numbers. The velocity profile of turbulent side layers in magnetohydrodynamic duct flows in a strong field can also be computed with the help of the model provided that the Hartmann layers are already laminar.
Change in magnetic and structural properties of FeRh thin films by gold cluster ion beam irradiation with the energy of 1.67 MeV/atom
Authors: Koide T. , Saitoh Y. , Sakamaki M. , Amemiya K. , Iwase A. , Matsui T.
Published: February 2014

The effect of energetic cluster ion beam irradiation on magnetic and structural properties of FeRh thin films have been investigated. The cluster ions used in the present studies consist of a few gold atoms with the energy of 1.67 MeV/gold atom. Saturation magnetization of the sample irradiated with Au3 cluster ion beam (280 emu/cc) is larger than that for the irradiated sample with Au1 ion beam (240 emu/cc) for the same irradiation ion fluence. These results can also be confirmed by the X-ray magnetic circular dichroism (XMCD) measurement; the XMCD signal for Au3 cluster ion irradiation is larger than that for Au1 ion irradiation. Since the ion beam irradiation induced magnetization of FeRh is significantly correlated with the amount of the lattice defects in the samples, cluster ion beam irradiation can be considered to effectively introduce the lattice defects in B2-type FeRh rather than the single ion beam. Consequently, cluster ion irradiation is better than single ion irradiation for the viewpoint of saturation magnetization, even if the same irradiation energy is deposited in the samples.
Magnetic tweezers for manipulation of magnetic particles in single cells
Authors: Ebrahimian H. , Giesguth M. , Dietz K.-J. , Reiss G. , Herth S.
Published: February 2014

Magnetic tweezers gain increasing interest for applications in biology. Here, a setup of magnetic tweezers is introduced using micropatterned conducting lines on transparent glass slides. Magnetic particles of 1 μm diameter were injected in barley cell vacuoles using a microinject system under microscopic control. Time dependent tracking of the particles after application of a magnetic field was used to determine the viscosity of vacuolar sap in vivo relative to water and isolated vacuolar fluid. The viscosity of vacuolar sap in cells was about 2-fold higher than that of extracted vacuolar fluid and 5 times higher than that of water.
Octahedral rotations in strained LaAlO3/SrTiO3 (001) heterostructures
Authors: Fister T. T. , Zhou H. , Luo Z. , Seo S. S. A. , Hruszkewycz S. O. , Proffit D. L. , Eastman J. A. , Fuoss P. H. , Baldo P. M. , Lee H. N. , Fong D. D.
Published: February 2014

Many complex oxides display an array of structural instabilities often tied to altered electronic behavior. For oxide heterostructures, several different interfacial effects can dramatically change the nature of these instabilities. Here, we investigate LaAlO3/SrTiO3 (001) heterostructures using synchrotron x-ray scattering. We find that when cooling from high temperature, LaAlO3 transforms from the \documentclass[12pt]{minimal}\begin{document}$Pm\bar{3}m$\end{document}Pm3¯m to the Imma phase due to strain. Furthermore, the first 4 unit cells of the film adjacent to the substrate exhibit a gradient in rotation angle that can couple with polar displacements in films thinner than that necessary for 2D electron gas formation.
Enhanced mechanical properties and large magnetocaloric effects in bonded La(Fe, Si)13-based magnetic refrigeration materials
Authors: Zhang Hu , Sun YuJie , Niu E , Hu FengXia , Sun JiRong , Shen BaoGen
Published: February 2014

Bonded La(Fe, Si)13 magnetic refrigeration materials have been prepared, and the microstructure, mechanical properties, and magnetocaloric effect (MCE) of bonded LaFe11.7Si1.3C0.2Hx have been investigated systematically. Bonded materials show porous architecture, and the mechanical properties increase with the increase of epoxy resin content, which could fill more pores and boundaries and thus enhance the binding force between different particles. Bonded LaFe11.7Si1.3C0.2H1.8 with 3 wt. % epoxy resin exhibits a compressive strength of 162 MPa, 35% higher than that of bulk compound. The mass magnetic entropy change (ΔSM) remains nearly unchanged while the volumetric ΔSM reduces due to the decrease of density in bonded materials. For a low magnetic field change of 2 T, the maximum ΔSM value of bonded LaFe11.7Si1.3C0.2H1.8 is ∼10.2 J/kg K and ∼54.7 mJ/cm3 K, which is larger than those of some magnetocaloric materials in the same temperature range. Enhanced mechanical properties and great MCE suggest that bonded La(Fe, Si)13-based materials could be promising candidates of magnetocaloric materials for practical applications of magnetic refrigeration.
Hot spot generation in energetic materials created by long-wavelength infrared radiation
Authors: Chen Ming-Wei , You Sizhu , Suslick Kenneth S. , Dlott Dana D.
Published: February 2014

Hot spots produced by long-wavelength infrared (LWIR) radiation in an energetic material, crystalline RDX (1,3,5-trinitroperhydro-1,3,5-triazine), were studied by thermal-imaging microscopy. The LWIR source was a CO2 laser operating in the 28-30 THz range. Hot spot generation was studied using relatively low intensity (∼100 W cm−2), long-duration (450 ms) LWIR pulses. The hot spots could be produced repeatedly in individual RDX crystals, to investigate the fundamental mechanisms of hot spot generation by LWIR, since the peak hot-spot temperatures were kept to ∼30 K above ambient. Hot spots were generated preferentially beneath RDX crystal planes making oblique angles with the LWIR beam. Surprisingly, hot spots were more prominent when the LWIR wavelength was tuned to be weakly absorbed (absorption depth ∼30 μm) than when the LWIR wavelength was strongly absorbed (absorption depth ∼5 μm). This unexpected effect was explained using a model that accounts for LWIR refraction and RDX thermal conduction. The weakly absorbed LWIR is slightly focused underneath the oblique crystal planes, and it penetrates the RDX crystals more deeply, increasing the likelihood of irradiating RDX defect inclusions that are able to strongly absorb or internally focus the LWIR beam.
Ultra-wideband microwave imaging of breast cancer tumors via Bayesian inverse scattering
Authors: Fouda A. E. , Teixeira F. L.
Published: February 2014

We develop a new algorithm for ultra-wideband (UWB) microwave imaging of breast cancer tumors using Bayesian inverse scattering. A key feature of the proposed algorithm is that constitutive properties of breast tissues are reconstructed from scattered UWB microwave signals together with the confidence level of the reconstruction. Having such confidence level enables minimization of both false alarms and missed detections. Results from the application of the proposed algorithm demonstrate the accuracy in estimating both location and permittivity of breast tumors without the need for a priori knowledge of pointwise properties of the background breast tissue.
Intrinsic subtypes of high-grade bladder cancer reflect the hallmarks of breast cancer biology
Authors: Damrauer Jeffrey S. , Hoadley Katherine A. , Chism David D. , Fan Cheng , Tiganelli Christopher J. , Wobker Sara E. , Yeh Jen Jen , Milowsky Matthew I. , Iyer Gopa , Parker Joel S. , Kim William Y.
Published: February 2014

Significance

The identification of molecular subtype heterogeneity in breast cancer has allowed a deeper understanding of breast cancer biology. We present evidence that there are two intrinsic subtypes of high-grade bladder cancer, basal-like and luminal, which reflect the hallmarks of breast biology. Moreover, we have developed an accurate gene set predictor of molecular subtype, the BASE47, that should allow the incorporation of subtype stratification into clinical trials. Further clinical, etiologic, and therapeutic response associations will be of interest in future investigations.
Helicity and singular structures in fluid dynamics
Authors: Moffatt H. Keith
Published: February 2014

Significance

This paper covers aspects of the dynamics of fluids that are of central importance for (
i
) the origin of planetary and astrophysical magnetism, and (
ii
) the determination of stable magnetic field configurations used in thermonuclear fusion reactors like the tokamak. The technique of magnetic relaxation also has implications for the theory of tight knots, an emerging field of research with applications in polymer physics and molecular biology. The final section on slow viscous flows has relevance for the design of micro- and nanofluid devices, and for the understanding of mixing processes in chemical engineering and in geophysics.