bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Ho3+ doping on the temperature sensing behavior of Er3+–Yb3+ doped La2CaZnO5 phosphor
Authors: Kumar Vijay , Som S. , Dutta S. , Das Subrata , Swart H. C.
Published: September 2016

Er3+/Yb3+ and Er3+/Ho3+/Yb3+ codoped La2CaZnO5 phosphors were prepared by the combustion synthesis method. The Er3+/Yb3+-codoped sample exhibited strong green and red UC emissions. The phosphors are suitable for future applications in thermometry.
A universal strategy for direct immobilization of intact bioactivity-conserved carbohydrates on gold nanoparticles
Authors: Wang Xiao , Xu Jiying , Wang Yuanyuan , Wang Fuyi , Chen Yi
Published: September 2016

Carbohydrate-functioned gold nanoparticles have been highlighted for sensing complicated carbohydrates but their performance is far from ideal due to the lack of bioaffinity-conserved ways to function the particles with intact carbohydrates.
A novel Fe–La-doped hierarchical porous silica magnetic adsorbent for phosphate removal
Authors: Wang Chun , Zheng Xudong , Zhang Fusheng , Huang Yongqiang , Pan Jianming
Published: September 2016

A novel Fe–La modified magnetic hierarchical porous silica was synthesized by an impregnation method to adsorb phosphate in aquatic ecology.
Blue thermally activated delayed fluorescence from a biphenyl difluoroboron β-diketonate
Authors: Daly Margaret L. , DeRosa Christopher A. , Kerr Caroline , Morris William A. , Fraser Cassandra L.
Published: August 2016

Optical properties of biphenyl difluoroboron β-diketonates were studied in poly(lactic acid) (PLA) blends.
The treatment of phenolic contaminants from shale gas drilling wastewater: a comparison with UV-Fenton and modified UV-Fenton processes at neutral pH
Authors: Chen Wenjing , Zou Changjun , Li Xiaoke , Li Lu
Published: September 2016

In this study, the treatment efficiency of phenolic contaminants from drilling wastewater was evaluated with three different UV-Fenton processes.
Solvation and surface effects on polymorph stabilities at the nanoscale
Authors: Belenguer A. M. , Lampronti G. I. , Cruz-Cabeza A. J. , Hunter C. A. , Sanders J. K. M.
Published: September 2016

We explore the effects of particle size and solvent environment on the thermodynamic stability of two pairs of polymorphs subjected to ball-mill neat grinding (NG) and liquid assisted grinding (LAG).
Correction: Anti-biofouling ability and cytocompatibility of the zwitterionic brushes-modified cellulose membrane
Authors: Liu Pingsheng , Chen Qiang , Li Li , Lin Sicong , Shen Jian
Published: September 2016

Correction for ‘Anti-biofouling ability and cytocompatibility of the zwitterionic brushes-modified cellulose membrane’ by Pingsheng Liu et al., J. Mater. Chem. B, 2014, 2, 7222–7231.
Combined RF coils for brain imaging at 7 T with receive and transmit resonators
Authors: Yoo H.
Published: August 2016

MRI has the potential to produce clear anatomic, as well as functional, images of the human body. However, the ability to diagnose is limited by signal‐to‐noise ratio (SNR) and the resolution of current medical systems. To remove the challenges prevalent due to the use of high‐field scanners, dedicated RF coils are used. Transverse electromagnetic (TEM) coils have the advantage of providing a homogeneous magnetic field throughout the region, but with a low SNR, while surface coils have the advantage of providing a higher SNR, but with low homogeneity. The research discussed combines both advantages into one by utilising transmit‐only TEM RF coils (8‐channel) along with receive‐only surface coils (varying in number) to obtain good homogeneity, as well as significant SNR improvements, from MRI throughout the human brain.
1.2 V CMOS temperature compensated logarithmic converter based on translinear circuit
Authors: Bai Chunfeng , Wu Jianhui
Published: September 2016

With the help of proposed translinear circuit, intrinsic temperature coefficient of logarithmic converter is compensated by that of a proportional‐to‐absolute‐temperature current source in bandgap reference, which contributes to the proposed fully integrated logarithmic converter. Using a 0.13 μm CMOS technology with 1.2 V single supply, the proposed logarithmic converter exhibits less than 350 ppm temperature coefficient with a 0.5–1.2 V input range.
Broadband design of planar circular tag antenna for UHF RFID system
Authors: Lu J.H. , Zheng G.T.
Published: September 2016

A planar broadband circular tag antenna operated at ultra‐high frequency (UHF) band for radio‐frequency identification (RFID) system is proposed. By adding a pair of T‐arc‐shaped strips and parasitic step strips, excitation of multi‐resonant modes can approximate reach with the operating half‐power band from 848 to 963 MHz, which covers the required bandwidth for worldwide UHF RFID (860–960 MHz) system. Moreover, the measured read distance of this design can reach 3.8 m, and exhibits good unidirectional radiation patterns in the X–Z and X–Yplanes.
Hysteresis versus PSM of ideal memristors, memcapacitors, and meminductors
Authors: Biolek Z. , Biolek D. , Biolkova V.
Published: September 2016

The classical fingerprint of the ideal memristor with differentiable constitutive relation has recently been extended with a piece of knowledge that the area of the pinched hysteresis loop of a memristor driven by sinusoidal signal with fixed amplitude and increasing frequency disappears with an integer power of the frequency. This fingerprint is extended to the memcapacitor and meminductor, and it is also shown that the way the hysteresis disappears can be determined directly from the behaviour of the parameter versus state map (PSM) of the element in the neighbourhood of the initial operating point.
Experimental investigation on through‐wall imaging based on non‐linear inversions
Authors: Meng Qingyang , Ye Dexin , Huangfu Jiangtao , Li Changzhi , Ran Lixin
Published: September 2016

Through‐wall imaging (TWI) is a challenging topic in the area of inverse scattering problem based microwave imaging. A TWI solution based on non‐linear inversion algorithms is experimentally investigated. Experiments are performed using a setup with the object surrounded by a closed wall. The inversion is based on a twofold subspace‐based optimisation method, and the results show that the location, shape, size, and dielectric constant of the object can be successfully retrieved from the measured scattering data. This is the first experimental demonstration of TWI of objects behind a closed wall using a non‐linear inversion algorithm. These results imply the potential of TWI for practical applications.
SAR image segmentation based on analysing similarity with clutter spatial patterns
Authors: Zhao Xiaohui , Jiang Yicheng , Wang Wen‐Qin
Published: September 2016

An image segmentation method is proposed based on exploiting the spatial patterns in synthetic aperture radar (SAR) images. First, a similarity map is constructed for evaluating the similarity between the spatial pattern of the SAR image and the reference clutter images. Then, a segmentation threshold is selected based on the similarity map. Finally, image segmentation is achieved by preserving pixels that have larger similarity values. The superiority of the proposed method is verified by the experimental results for high‐resolution SAR images.
Design of robust fractional‐order lead–lag controller for uncertain systems
Authors: Gogani Khiabani Ataollah , Babazadeh Reza
Published: September 2016

In this study, a new method for designing fractional‐order robust lead–lag controllers in order to ensure robust stability in uncertain systems with unstructured uncertainty, has been presented. In this method, at first by the use of pole placement and solving Diophantine equation, a fractional‐order controller, which has a new form, is designed in order to stabilise the nominal system. Then a constrained optimisation problem is solved, in which, the cost function consists of the numerator and denominator coefficients of the proposed fractional‐order controller and the constraints are the robust stability conditions. Finally, the parameters of the robust fractional‐order controller are acquired. This method is implemented on an unstable system and simulation results are presented.
Stability of neutral type fractional delay systems and its relation with stability of time‐delay and discrete systems
Authors: Mesbahi Afshin , Haeri Mohammad
Published: September 2016

The bounded‐input bounded‐output stability of fractional delay systems of neutral type is investigated in this study. The proposed method calculates the number of unstable poles of the system for each delay value. All time‐delay intervals in time‐delay space where system is stable are precisely determined. The stability of systems with not only indefinitely large values of time‐delay, but also with multiple poles on the imaginary axis has been studied. The proposed method is employed for investigating the stability of a fractional delay system when its fractional orders approach to the integer numbers or zero. It is proved that simple case of neutral types and time‐delay systems have the same conditions for the independent stability. Two numerical examples are provided to illustrate the proficiencies of the proposed method.
Data‐driven model based design and analysis of antenna structures
Authors: Ulaganathan Selvakumar , Koziel Slawomir , Bekasiewicz Adrian , Couckuyt Ivo , Laermans Eric , Dhaene Tom
Published: September 2016

Data‐driven models, or metamodels, offer an efficient way to mimic the behaviour of computation‐intensive simulators. Subsequently, the usage of such computationally cheap metamodels is indispensable in the design of contemporary antenna structures where computation‐intensive simulations are often performed in a large scale. Although metamodels offer sufficient flexibility and speed, they often suffer from an exponential growth of required training samples as the dimensionality of the problem increases. In order to alleviate this issue, a Gaussian process based approach, known as Gradient‐Enhanced Kriging (GEK), is proposed in this work to achieve cost‐efficient modelling of antenna structures. The GEK approach incorporates adjoint‐based sensitivity data in addition to function data obtained from electromagnetic simulations. The approach is illustrated using a dielectric resonator and an ultra‐wideband antenna structures. The method demonstrates significant accuracy improvement with the less number of training samples over the Ordinary Kriging (OK) approach which utilises function data only. The discussed technique has been favourably compared with OK in terms of computational cost.
Compact 3D‐loop antenna with bandwidth enhancement for WWAN/LTE mobile‐phones applications
Authors: Wu Di , Cheung Sing Wai , Yuk Tung Ip
Published: September 2016

This study presents a 3D‐loop antenna for wireless‐wide‐area network/long‐term evolution (WWAN/LTE) operation. The size is compact and low profile and so the antenna is suitable for mobile‐phone applications. The loop itself generates four resonant modes. Three parasitic elements are placed closely to the 3D‐meandered loop radiator to generate three more resonant modes. These resonant modes form a dual‐band, a lower band and a wide upper band, to cover many current mobile standards. The antenna performance, in terms of impedance bandwidth, efficiency, peak gain and radiation pattern, is studied using simulation. The antenna is also fabricated and the prototyped antenna is measured using the Satimo StarLab system. The measured results of the antenna inside a phone case on a phantom hand and phantom head in the data mode and talk mode, respectively, (defined by the Cellular Telephone Industries Association) are also presented. The measured efficiencies are subsequently used to estimate the total‐radiated powers (TRPs). Results show that the TRPs in all covered standards meet the strictest over‐the‐air testing requirement of Vodafone.
Wideband stacked maltese cross‐shaped DR antenna for WiMAX and WLAN applications
Authors: Sharma Abhishek , Biswas Animesh
Published: September 2016

A new maltese cross‐shaped dielectric resonator (DR) antenna is presented and analysed as a wideband radiator. The antenna comprises of maltese cross‐shaped DR, arranged in a stacked configuration and centrally fed by a coaxial probe. The proposed antenna radiates such as an electric monopole, generating omnidirectional linearly polarised fields. Three modes: namely, TM01δ, TM02δ, and TM03δ are simultaneously excited and merged in the composite structure to obtain a wide bandwidth of 59.5% [for voltage standing wave ratio≤2], covering frequency range from 3.15 to 5.82 GHz. The radiation pattern of the proposed antenna is fairly stable throughout the operating band with the measured peak gain varies from 3.27 to 6.09 dBi. A prototype of the proposed antenna is built and tested. Both the simulations and experimental results are presented and discussed. The proposed antenna is suitable candidate for worldwide interoperability for microwave access (3.5 GHz) and wireless local area network (3.65 GHz/4.9 GHz/5 GHz) applications. Moreover, it can also be used for lower European ultra‐wideband frequency band (3.4–5 GHz) applications.
Acoustic shooter localisation using a network of asynchronous acoustic nodes
Authors: Hengy Sébastien , Duffner Pascal , DeMezzo Sébastien , Heck Stéphane , Gross Laurent , Naz Pierre
Published: September 2016

The present study focuses on the acoustical detection and localisation of shots using a network of wireless asynchronous acoustic nodes. The first sections describe the detection and classification schemes of the developed real‐time acoustic nodes and the asynchronous shooter localisation principle. This localisation method is evaluated in free field and in complex propagation conditions, where obstacles affect the propagation of the muzzle blast and shock waves. More than 600 shots with calibre 5.56 to 12.7mm weapons at distances varying from 100 to 800 m constitute the database used for the evaluation of the localisation performance. It shows that the localisation of shooters in complex environments is possible when the group of acoustic nodes is near to the shot trajectory.
IT-Sicherheit: Vorsicht vor Wohlfühl-Verkäufern
Authors: Humpert-Vrielink Frederik
Published: September 2016

Nach den Attacken mit Erpresser-Software rüsten derzeit viele Kliniken ihre IT-Abteilungen technisch massiv auf. Doch im Kampf um bessere IT-Sicherheit greift dieser Aktionismus ohne ein umfassendes IT-Risikomanagement viel zu kurz.
Digitale Archivierung: Raus damit!
Authors: König Romy
Published: September 2016

Weg mit dem Papier, sagen sich viele Kliniken, und stellen auf digitale Archive um. Doch nicht nur das: Einige vertrauen ihre Unterlagen Hostinganbietern an – und lagern ihr Archiv gleich ganz aus. Der Vorteil: Weniger Sorge um rechtliche Vorgaben.
Reha-Investor Waterland: „Der deutsche Gesundheitsmarkt ist sehr attraktiv“
Authors: Rössing Sabine
Published: September 2016

Carsten Rahlfs ist Partner beim niederländischen Finanzinvestor Waterland, der seit Jahren massiv in den deutschen Reha-Markt investiert. Im Interview spricht er über die Gründe für das Engagement und warum die Niederländer weiter zukaufen werden.
Wachsende Nachfrage
Authors: Mewis Dirk
Published: September 2016

Um 11,6 Prozent legte der Gesamtumsatz der produzierenden Medizintechnikunternehmen in Deutschland im vergangenen Jahr zu. Dabei ist die Branche in Deutschland extrem innovativ und hat sehr kurze Produktzyklen. Rund ein Drittel ihres Umsatzes erzielen die deutschen Medizintechnikhersteller mit Produkten, die nicht älter als drei Jahre sind. Wer sind die Spezialisten für chirurgische Instrumente, Endoskope, Gelenkprothesen und optische Geräte? Warum wächst die Nachfrage nach Medizintechnik? Antworten auf diese Fragen finden sie in dieser Branche kompakt. Lesen sie außerdem welche Innovationen deutsche Medizintechnikunternehmen so erfolgreich machen.
Medizintechnik: Meister der Innovationen
Authors: Mewis Dirk
Published: September 2016

Deutsche Medizintechnikhersteller erzielen rund ein Drittel ihres Umsatzes mit Produkten, die nicht älter als drei Jahre sind. Denn Digitalisierung und Effizienzdruck verändern die Branche grundlegend.
Projektmanagement: Denn erstens kommt es anders
Authors: Thalmayr Maria
Published: September 2016

Leben ist, was passiert, während man ganz andere Pläne macht. Darum sollten Projektmanager auf mögliche Störungen vorbereitet sein. Sie brauchen genug zeitlichen Puffer und vor allen Dingen auch Werkzeuge, um auf unvorhergesehene Ereignisse reagieren zu können.
Vanessa Gürkan: Vertraut mit Verantwortung
Authors: Wenzel Kirsten
Published: September 2016

Sie hat die gesundheitsökonomische Schule von Peter Oberender absolviert, ist mit Mitte 20 ins Asklepios-Management eingestiegen und heute Klinikchefin in Sebnitz. Abgehoben ist Vanessa Gürkan trotzdem nicht. Schon gar nicht, wenn es um ihre Mitarbeiter geht.
ÖVKT-Tagung in Pörtschach – 27. bis 29. September: Superkräfte fürs Krankenhaus
Authors: Thalmayr Maria
Published: September 2016

„Ein jeder hat heute Superkräfte, mehr Macht als der Präsident der Vereinigten Staaten vor 20 Jahren. Sie können jede Frage beantworten, Millionen Menschen auf der Stelle eine Nachricht schicken, einfach unglaubliche Dinge tun, …“
Enhanced hole boring with two-color relativistic laser pulses in the fast ignition scheme
Authors: Yu Changhai , Deng Aihua , Tian Ye , Li Wentao , Wang Wentao , Zhang Zhijun , Qi Rong , Wang Cheng , Liu Jiansheng
Published: September 2016

A scheme of using two-color laser pulses for hole boring into overdense plasma as well as energy transfer into electron and ion beams has been studied using particle-in-cell simulations. Following an ultra-short ultra-intense hole-boring laser pulse with a short central wavelength in extreme ultra-violet range, the main infrared driving laser pulse can be guided in the hollow channel preformed by the former laser and propagate much deeper into an overdense plasma, as compared to the case using the infrared laser only. In addition to efficiently transferring the main driving laser energy into energetic electrons and ions generation deep inside the overdense plasma, the ion beam divergence can be greatly reduced. The results might be beneficial for the fast ignition concept of inertial confinement fusion.
Aerogel Cherenkov detector for characterizing the intense flash x-ray source, Cygnus, spectrum
Authors: Kim Y. , Herrmann H. W. , McEvoy A. M. , Young C. S. , Hamilton C. , Schwellenbach D. D. , Malone R. M. , Kaufman M. I. , Smith A. S.
Published: August 2016

An aerogel Cherenkov detector is proposed to measure the X-ray energy spectrum from the Cygnus—intense flash X-ray source operated at the Nevada National Security Site. An array of aerogels set at a variety of thresholds between 1 and 3 MeV will be adequate to map out the bremsstrahlung X-ray production of the Cygnus, where the maximum energy of the spectrum is normally around 2.5 MeV. In addition to the Cherenkov radiation from aerogels, one possible competing light-production mechanism is optical transition radiation (OTR), which may be significant in aerogels due to the large number of transitions from SiO2 clusters to vacuum voids. To examine whether OTR is a problem, four aerogel samples were tested using a mono-energetic electron beam (varied in the range of 1–3 MeV) at NSTec Los Alamos Operations. It was demonstrated that aerogels can be used as a Cherenkov medium, where the rate of the light production is about two orders magnitude higher when the electron beam energy is above threshold.
Dynamic unified RANS-LES simulations of high Reynolds number separated flows
Authors: Mokhtarpoor Reza , Heinz Stefan , Stoellinger Michael
Published: September 2016

The development of hybrid RANS-LES methods is seen to be a very promising approach to enable efficient simulations of high Reynolds number turbulent flows involving flow separation. To contribute to further advances, we present a new, theoretically well based, dynamic hybrid RANS-LES method, referred to as DLUM. It is applied to a high Reynolds number flow involving both attached and separated flow regimes: a periodic hill flow is simulated at a Reynolds number of 37 000. Its performance is compared to pure LES, pure RANS, other hybrid RANS-LES (given by DLUM modifications), and experimental observations. It is shown that the use of this computational method offers huge cost reductions (which scale with Re/200, Re refers to the Reynolds number) of very high Reynolds number flow simulations compared to LES, it is much more accurate than RANS, and more accurate than LES, which is not fully resolved. In particular, this conclusion does also apply to the comparison of DLUM and pure LES simulations on rather coarse grids, which are often simply required to deal with simulations of very high Reynolds number flows: the DLUM provides mean velocity fields which are hardly affected by the grid, whereas LES velocity fields reveal significant shortcomings. We identified the reason for the superior performance of our new dynamic hybrid RANS-LES method compared to LES: it is the model’s ability to respond to a changing resolution with adequate turbulent viscosity changes by ensuring simultaneously a physically correct turbulence length scale specification under the presence of interacting RANS and LES modes.
Analogue saturation limit of single and double 10 mm microchannel plate photomultiplier tubes
Authors: Milnes J. S. , Conneely T. M. , Horsfield C. J.
Published: September 2016

Photek are a well-established supplier of microchannel plate (MCP) photomultiplier tubes (PMTs) to the inertial confinement fusion community. The analogue signals produced at the major inertial confinement fusion facilities cover many orders of magnitude, therefore understanding the upper saturation limit of MCP-PMTs to large low rate signals takes on a high importance. Here we present a study of a single and a double MCP-PMT with 10 mm diameter active area. The saturation was studied for a range of optical pulse widths from 4 ns to 100 ns and at a range of electron gain values: 103 to 104 for the single and 104 to 106 for the double. We have shown that the saturation level of ∼1.2 nC depends only on the integrated charge of the pulse and is independent of pulse width and gain over this range, but that the level of charge available in deep saturation is proportional to the operating gain.
Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes
Authors: Zhai Zhao-Hui , Zhong Sen-Cheng , Li Jun , Zhu Li-Guo , Meng Kun , Li Jiang , Liu Qiao , Peng Qi-Xian , Li Ze-Ren , Zhao Jian-Heng
Published: September 2016

Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ∼400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.
Transient motion of and heat transfer in a rarefied gas between plane parallel walls with different surface properties
Authors: Doi Toshiyuki
Published: September 2016

Transient motion of and heat transfer in a rarefied gas between plane parallel walls with different surface properties are studied based on kinetic theory. It is assumed that one wall is a diffuse reflection boundary and the other wall is a Maxwell-type boundary, and the transient behavior of the gas caused by a sudden heating of one of the walls is studied. The linearized Boltzmann equation for a hard-sphere molecular gas is numerically studied using the modified hybrid scheme of the characteristic coordinate and finite difference methods, to correctly describe the discontinuities in the velocity distribution function. The transient motion of the gas from an early time stage to the final time-independent state is studied over a wide range of the mean free path and the accommodation coefficient of the boundary. Between the two transient flows caused by the heating of the respective walls, the values of the heat flow on the heated wall are different, whereas those on the unheated wall coincide identically. This property, which is a consequence of the symmetric relation of the linearized Boltzmann equation, is numerically confirmed over a wide range of the mean free path. The long time behavior of the heat flow on the walls is quite similar to that of the shear stress in the Couette flow problem, whereas a distinct wavy behavior is observed in an early time stage.
Phase diagram of a model of the protein amelogenin
Authors: Haaga Jason , Pemberton Elizabeth , Gunton J. D. , Rickman J. M.
Published: August 2016

There has been considerable recent interest in the self-assembly and phase behavior of models of colloidal and protein particles with anisotropic interactions. One example of particular interest is amelogenin, an important protein involved in the formation of dental enamel. Amelogenin is primarily hydrophobic with a 25-residue charged C-terminus tail. This protein undergoes a hierarchical assembly process that is crucial to mineral deposition, and experimental work has demonstrated that the deletion of the C-terminus tail prevents this self-assembly. A simplified model of amelogenin has been proposed in which the protein is treated as a hydrophobic sphere, interacting via the Asakura-Oosawa (AO) potential, with a tethered point charge on its surface. In this paper, we examine the effect of the Coulomb interaction between the point charges in altering the phase diagram of the AO model. For the parameter case specific to amelogenin, we find that the previous in vitro experimental and model conditions correspond to the system being near the low-density edge of the metastable region of the phase diagram. Our study illustrates more generally the importance of understanding the phase diagram for proteins, in that the kinetic pathway for self-assembly and the resulting aggregate morphology depends on the location of the initial state in the phase diagram.
Surface-potential-based physical compact model for graphene field effect transistor
Authors: Wang Lingfei , Peng Songang , Wang Wei , Xu Guangwei , Ji Zhuoyu , Lu Nianduan , Li Ling , Jin Zhi , Liu Ming
Published: August 2016

A surface potential based physical compact model for a graphene field effect transistor is proposed, including Boltzmann transport and thermally activated transport. We verified it by the experiments and Gummel symmetry test, showing good accuracy and continuity over a wide range of operation regions. Coded in Verilog-A, this model provides physics-based consistent DC and AC characteristics, which can be easily embedded into a vendor CAD tool to simulate circuits. Based on this model, a direct insight into the relationship between physical parameters and circuit performances can be achieved.
Intra-grain conduction of self-doped polyaniline
Authors: Usami Yuki , Imamura Kentaro , Akai Tomoki , Che Dock-Chil , Ohoyama Hiroshi , Kobayashi Hikaru , Matsumoto Takuya
Published: August 2016

The conduction behavior of ultrathin films (about 10 nm thick) composed of self-doped water-soluble polyaniline sulfonate (SPAN) was investigated using nano-gap electrodes under vacuum conditions. The conductance was found to be ohmic even in the high field regime up to 105 V cm−1 over a temperature range of 10–300 K. The temperature dependence of the conductance indicated that SPAN gave the extremely high value of localization length (L) = 300 nm without secondary doping, in comparison with conventional polyaniline. We propose that SPAN forms long-range highly crystalline metallic grains, and we observed intra-grain conduction due to some grains directly bridging the two nano-gap electrodes at low temperature. We conclude that inter-grain conduction becomes dominant as the temperature increases.
Lifting a large object from an anisotropic porous bed
Authors: Karmakar Timir , Raja Sekhar G. P.
Published: September 2016

An analytical study of two dimensional problem of lifting an object from the top of a fully saturated rigid porous bed is discussed. It is assumed that the porous bed is anisotropic in nature. The flow within the gap region between the object and the porous bed is assumed to be governed by Stokes equation while the flow within the porous bed is governed by Brinkman equation. The breakout phenomenon for different kinds of soil is reported. The effect of mechanical properties like anisotropic permeability, grain diameter size, and porosity on streamlines, velocity, and force is analyzed. Relevant comparison with C. C. Mei, R. W. Yeung, and K. F. Liu [“Lifting a large object from a porous bed,” J. Fluid. Mech. 152, 203–215 (1985)] and Y. Chang, L. H. Huang and F. P. Y. Yang [“Two-dimensional lift-up problem for a rigid porous bed,” Phys. Fluids, 27, 053101 (2015)] is done.
High reflectance dielectric distributed Bragg reflectors for near ultra-violet planar microcavities: SiO2/HfO2 versus SiO2/SiNx
Authors: Réveret F. , Bignet L. , Zhigang W. , Lafosse X. , Patriarche G. , Disseix P. , Médard F. , Mihailovic M. , Leymarie J. , Zúñiga-Pérez J. , Bouchoule S.
Published: September 2016

SiO2/SiNx and SiO2/HfO2 distributed Bragg reflectors for the ultra-violet (λ = 360 nm–380 nm) are compared through their structural and optical properties. The SiO2/HfO2 system exhibits a lower interface roughness, higher reflectance, larger stop band, and lower penetration depth than SiO2/SiNx. A cavity quality factor of 3700 at about 360 nm is measured on a passive SiO2/HfO2-based planar microcavity. Compared with values obtained in the literature for the near UV range, the latter is rather large. Micro-reflectance measurements have been performed on a series of passive microcavities with increasing cavity thickness to determine the residual absorption in the SiO2 and HfO2 layers. Absorption coefficients of 30 (k = 0.86 × 10−4) and 160 cm−1 (k = 4.59 × 10−4) near λ ∼ 360 nm have been extracted for SiO2 and HfO2, respectively. Transfer-matrix simulations taking into account the residual absorption show that microcavity quality factors up to 8000 can be expected at 360–380 nm with this material system. Such values are well-suited for the fabrication of UV-vertical cavity surface emitting lasers or microcavity polariton lasers operating at room temperature.
First-principles calculations of high-pressure phase transition of TiO2 during decompression: From baddeleyite-type TiO2 to α-PbO2-type TiO2
Authors: Murata Hidenobu , Taniguchi Takashi , Tanaka Isao
Published: August 2016

First-principles calculations were used to investigate the phase transition from baddeleyite-type to α-PbO2-type TiO2 during decompression. An intermediate structure was found, and its space group is Pbc21, which is polarized along [001]. The phase transition was mainly caused by oxygen diffusion, which has low activation energy for the phase transition. The activation energy increased as the pressure decreased. These results suggest that rapid decompression and preventing oxygen diffusion would be an effective way of recovering baddeleyite-type TiO2.
Stability of Brillouin flow in the presence of slow-wave structure
Authors: Simon D. H. , Lau Y. Y. , Greening G. , Wong P. , Hoff B. , Gilgenbach R. M.
Published: September 2016

Including a slow-wave structure (SWS) on the anode in the conventional, planar, and inverted magnetron, we systematically study the linear stability of Brillouin flow, which is the prevalent flow in crossed-field devices. The analytic treatment is fully relativistic and fully electromagnetic, and it incorporates the equilibrium density profile, flow profile, and electric field and magnetic field profiles in the linear stability analysis. Using parameters similar to the University of Michigan's recirculating planar magnetron, the numerical data show that the resonant interaction of the vacuum circuit mode and the corresponding smooth-bore diocotron-like mode is the dominant cause for instability. This resonant interaction is far more important than the intrinsic negative (positive) mass property of electrons in the inverted (conventional) magnetron geometry. It is absent in either the smooth-bore magnetron or under the electrostatic assumption, one or both of which was almost always adopted in prior analytical formulation. This resonant interaction severely restricts the wavenumber for instability to the narrow range in which the cold tube frequency of the SWS is within a few percent of the corresponding smooth bore diocotron-like mode in the Brillouin flow.
The charge imbalance in ultracold plasmas
Authors: Chen Tianxing , Lu Ronghua , Guo Li , Han Shensheng
Published: September 2016

Ultracold plasmas are regarded as quasineutral but not strictly neutral. The results of charge imbalance in the expansion of ultracold plasmas are reported. The calculations are performed by a full molecular-dynamics simulation. The details of the electron velocity distributions are calculated without the assumption of electron global thermal equilibrium and Boltzmann distribution. Spontaneous evolutions of the charge imbalance from the initial states with perfect neutrality are given in the simulations. The expansion of outer plasma slows down with the charge imbalance. The influences of plasma size and parameters on the charge imbalance are discussed. The radial profiles of electron temperature are given for the first time, and the self-similar expansion can still occur even if there is no global thermal equilibrium. The electron disorder induced heating is also found in the simulation.
Interface-mediated ferroelectric patterning and Mn valency in nano-structured PbTiO3/La0.7Sr0.3MnO3
Authors: Krug Ingo P. , Doganay Hatice , Nickel Florian , Gottlob Daniel M. , Schneider Claus M. , Morelli Alessio , Preziosi Daniele , Lindfors-Vrejoiu Ionela , Laskowski Robert , Barrett Nick
Published: September 2016

We employed a multitechnique approach using piezo-force response microscopy and photoemission microscopy to investigate a self-organizing polarization domain pattern in PbTiO3/La0.7Sr0.3MnO3 (PTO/LSMO) nanostructures. The polarization is correlated with the nanostructure morphology as well as with the thickness and Mn valence of the LSMO template layer. On the LSMO dots, the PTO is upwards polarized, whereas outside the nanodots, the polarization appears both strain and interface roughness dependent. The results suggest that the electronic structure and strain of the PTO/LSMO interface contribute to determining the internal bias of the ferroelectric layer.
The annealing effects on the micro-structure and properties of RuMoC films as seedless barrier for advanced Cu metallization
Authors: Zou Jianxiong , Liu Bo , Jiao Guohua , Lu Yuanfu , Dong Yuming , Li Qiran
Published: September 2016

100 nm thick RuMoC films and 5 nm thick RuMoC films with Cu capping have been deposited on Si(111) by magnetron co-sputtering with Ru and MoC confocal targets. The samples were subsequently annealed at temperatures ranging from 450 to 650 °C in vacuum at a pressure of 3 × 10−4 Pa to study the annealing effects on the microstructures and properties of RuMoC films for advanced seedless Cu metallization applications. The sheet resistances, residual oxygen contents, and microstructures of the RuMoC films have close correlation with the doping contents of Mo and C, which can be easily controlled by the deposition power ratio of MoC versus Ru targets (DPR). When DPR was 0.5, amorphous RuMoC film (marked as RuMoC II) with low sheet resistances and residual oxygen contents was obtained. The fundamental relationship between the annealing temperatures with the microstructures and properties of the RuMoC films was investigated, and a critical temperature point was revealed at about 550 °C where the components and microstructures of the RuMoC II films changed obviously. Results indicated that below 550 °C, the RuMoC II films remained amorphous due to the well-preserved C-Ru and C-Mo bonds. However, above 550 °C, the microstructures of RuMoC II films transformed from amorphous to nano-composite structure due to the breakage of Ru-C bonds, while the supersaturated solid solution MoC segregated out along the grain boundaries of Ru, thus hindering the diffusion of Cu and O atoms. This is the main mechanism of the excellent thermal stability of the RuMoC films after annealing at high temperatures. The results indicated great prospects of amorphous RuMoC films in advanced seedless Cu metallization applications.
Role of spin-transfer torques on synchronization and resonance phenomena in stochastic magnetic oscillators
Authors: Accioly Artur , Locatelli Nicolas , Mizrahi Alice , Querlioz Damien , Pereira Luis G. , Grollier Julie , Kim Joo-Von
Published: September 2016

A theoretical study on how synchronization and resonance-like phenomena in superparamagnetic tunnel junctions can be driven by spin-transfer torques is presented. We examine the magnetization of a superparamagnetic free layer that reverses randomly between two well-defined orientations due to thermal fluctuations, acting as a stochastic oscillator. When subject to an external ac forcing, this system can present stochastic resonance and noise-enhanced synchronization. We focus on the roles of the mutually perpendicular damping-like and field-like torques, showing that the response of the system is very different at low and high frequencies. We also demonstrate that the field-like torque can increase the efficiency of the current-driven forcing, especially at sub-threshold electric currents. These results can be useful for possible low-power, more energy efficient applications.
Free-end adaptive nudged elastic band method for locating transition states in minimum energy path calculation
Authors: Zhang Jiayong , Zhang Hongwu , Ye Hongfei , Zheng Yonggang
Published: September 2016

A free-end adaptive nudged elastic band (FEA-NEB) method is presented for finding transition states on minimum energy paths, where the energy barrier is very narrow compared to the whole paths. The previously proposed free-end nudged elastic band method may suffer from convergence problems because of the kinks arising on the elastic band if the initial elastic band is far from the minimum energy path and weak springs are adopted. We analyze the origin of the formation of kinks and present an improved free-end algorithm to avoid the convergence problem. Moreover, by coupling the improved free-end algorithm and an adaptive strategy, we develop a FEA-NEB method to accurately locate the transition state with the elastic band cut off repeatedly and the density of images near the transition state increased. Several representative numerical examples, including the dislocation nucleation in a penta-twinned nanowire, the twin boundary migration under a shear stress, and the cross-slip of screw dislocation in face-centered cubic metals, are investigated by using the FEA-NEB method. Numerical results demonstrate both the stability and efficiency of the proposed method.
Precision atomic beam density characterization by diode laser absorption spectroscopy
Authors: Oxley Paul , Wihbey Joseph
Published: September 2016

We provide experimental and theoretical details of a simple technique to determine absolute line-of-sight integrated atomic beam densities based on resonant laser absorption. In our experiments, a thermal lithium beam is chopped on and off while the frequency of a laser crossing the beam at right angles is scanned slowly across the resonance transition. A lock-in amplifier detects the laser absorption signal at the chop frequency from which the atomic density is determined. The accuracy of our experimental method is confirmed using the related technique of wavelength modulation spectroscopy. For beams which absorb of order 1% of the incident laser light, our measurements allow the beam density to be determined to an accuracy better than 5% and with a precision of 3% on a time scale of order 1 s. Fractional absorptions of order 10−5 are detectable on a one-minute time scale when we employ a double laser beam technique which limits laser intensity noise. For a lithium beam with a thickness of 9 mm, we have measured atomic densities as low as 5 × 104 atoms cm−3. The simplicity of our technique and the details we provide should allow our method to be easily implemented in most atomic or molecular beam apparatuses.
Fragmentation network of doubly charged methionine: Interpretation using graph theory
Authors: Ha D. T. , Yamazaki K. , Wang Y. , Alcamí M. , Maeda S. , Kono H. , Martín F. , Kukk E.
Published: September 2016

The fragmentation of doubly charged gas-phase methionine (HO2CCH(NH2)CH2CH2SCH3) is systematically studied using the self-consistent charge density functional tight-binding molecular dynamics (MD) simulation method. We applied graph theory to analyze the large number of the calculated MD trajectories, which appears to be a highly effective and convenient means of extracting versatile information from the large data. The present theoretical results strongly concur with the earlier studied experimental ones. Essentially, the dication dissociates into acidic group CO2H and basic group C4NSH10. The former may carry a single or no charge and stays intact in most cases, whereas the latter may hold either a single or a double charge and tends to dissociate into smaller fragments. The decay of the basic group is observed to follow the Arrhenius law. The dissociation pathways to CO2H and C4NSH10 and subsequent fragmentations are also supported by ab initio calculations.
Optical fiber-based photocathode
Authors: Căsăndruc Albert , Bücker Robert , Kassier Günther , Miller R. J. Dwayne
Published: September 2016

We present the design of a back-illuminated photocathode for electron diffraction experiments based on an optical fiber, and experimental characterization of emitted electron bunches. Excitation light is guided through the fiber into the experimental vacuum chamber, eliminating typical alignment difficulties between the emitter metal and the optical trigger and position instabilities, as well as providing reliable control of the laser spot size and profile. The in-vacuum fiber end is polished and coated with a 30 nm gold (Au) layer on top of 3 nm of chromium (Cr), which emits electrons by means of single-photon photoemission when femtosecond pulses in the near ultraviolet (257 nm) are fed into the fiber on the air side. The emission area can be adjusted to any value between a few nanometers (using tapered fibers) and the size of a multi-mode fiber core (100 μm or larger). In this proof-of-principle experiment, two different types of fibers were tested, with emission spot diameters of 50 μm and 100 μm, respectively. The normalized thermal electron beam emittance (TE) was measured by means of the aperture scan technique, and a TE of 4.0 π nm was measured for the smaller spot diameter. Straightforward enhancements to the concept allowed to demonstrate operation in an electric field environment of up to 7 MV/m.
Directive and enhanced spontaneous emission using shifted cubes nanoantenna
Authors: Bahari B. , Tellez-Limon R. , Kante B.
Published: September 2016

Recent studies have demonstrated that nano-patch antennas formed by metallic nanocubes placed on top of a metallic film largely enhance the spontaneous emission rate of quantum emitters due to the confinement of the electromagnetic field in the small nanogap cavity. The popularity of this architecture is, in part, due to the ease in fabrication. In this contribution, we theoretically demonstrate that a dimer formed by two metallic nanocubes embedded in a dielectric medium exhibits enhanced emission rate compared to the nano-patch antenna. Furthermore, we compare the directivity and radiation efficiency of both nanoantennas. From these characteristics, we obtained information about the “material efficiency” and the coupling mismatch efficiency between a dipole emitter and the nanoantenna. These quantities provide a more intuitive insight than the Purcell factor or localized density of states, opening new perspectives in nanoantenna design for ultra-directive light emission.
Picosecond X-ray streak camera dynamic range measurement
Authors: Zuber C. , Bazzoli S. , Brunel P. , Fronty J.-P. , Gontier D. , Goulmy C. , Raimbourg J. , Rubbelynck C. , Trosseille C.
Published: September 2016

Streak cameras are widely used to record the spatio-temporal evolution of laser-induced plasma. A prototype of picosecond X-ray streak camera has been developed and tested by Commissariat à l’Énergie Atomique et aux Énergies Alternatives to answer the Laser MegaJoule specific needs. The dynamic range of this instrument is measured with picosecond X-ray pulses generated by the interaction of a laser beam and a copper target. The required value of 100 is reached only in the configurations combining the slowest sweeping speed and optimization of the streak tube electron throughput by an appropriate choice of high voltages applied to its electrodes.
High-resolution 2-D Bragg diffraction reveal heterogeneous domain transformation behavior in a bulk relaxor ferroelectric
Authors: Pramanick Abhijit , Stoica Alexandru D. , An Ke
Published: September 2016

In-situ measurement of fine-structure of neutron Bragg diffraction peaks from a relaxor single-crystal using a time-of-flight instrument reveals highly heterogeneous mesoscale domain transformation behavior under applied electric fields. It is observed that only ∼25% of domains undergo reorientation or phase transition contributing to large average strains, while at least 40% remain invariant and exhibit microstrains. Such insights could be central for designing new relaxor materials with better performance and longevity. The current experimental technique can also be applied to resolve complex mesoscale phenomena in other functional materials.
Amoebic gill disease: a growing threat
Authors: Johnson-Mackinnon Jessica , Oldham Tina , Nowak Barbara
Published: August 2016

The risk of disease outbreaks is predicted to increase due to climate change. For farmed fish an example is amoebic gill disease (AGD). While initially reported only in farmed salmonids in Washington State, USA, and Tasmania, Australia, it has now become an issue for Atlantic salmon farming worldwide and affects a range of other farmed marine fish species. Local high temperature anomalies and a lack of rainfall have been associated with the outbreaks of AGD. This worldwide presence is at least partly due to the cosmopolitan nature of the parasite and its low host-specificity. The disease can be treated using freshwater or hydrogen peroxide baths, but the treatments increase the cost of salmon production. Management of AGD contributes 20% to production costs of Atlantic salmon in Tasmania.