Energy and spatial response of silicon strip detectors to X-rays

This paper describes an experimental investigation of the energy and spatial response of silicon strip detectors used for X-ray measurements. The measurements of single strip amplitude distributions have been performed for a p⁺–n silicon strip detector irradiated with X-rays for different detector bias voltages and for two measurements geometries (with the detector irradiated from either the strip side or from the ohmic contact side). The measured amplitude distributions have been compared with those obtained from simulations using the developed simulation package. The spatial response of the detector has been measured by scanning an edge across the strips and measuring the corresponding strip count rate. The measured spatial response has been compared with that obtained from simulations.     

Electrically tunable mid-infrared antennas based on VO2

A large change in optical constants of phase-change vanadium dioxide enables active control over the transmission and reflection properties of structures incorporating VO₂. In this paper, we demonstrate electrically tunable mid-infrared strip array antennas based on metal–insulator transition of vanadium dioxide. The antennas consist of an interdigitated metal strip array separated from a metallic ground plane by a film of vanadium dioxide. The interdigitated metal strips serve as both antennas and electrodes. As the insulator-to-metal phase transition of vanadium dioxide is induced with applied voltages, resonance of the strip antenna array redshifts with reduced absorbance before it is eventually switched off. A tuning magnitude of 30% in reflectivity is measured at 25.5 THz. Our measurements of sample temperature reveal that tuning mechanism of the antennas is primarily thermal in nature. The demonstrated electrical tuning of mid-infrared antennas could be used for reconfigurable bolometric sensing, camouflaging and modulation of infrared radiations.     

Structures, varistor properties, and electrical stability of ZnO thin films

In this letter, we report the structures, varistor properties, and electrical stability of ZnO thin films deposited by the gas discharge activated reaction evaporation (GDARE) technique. The X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements showed that the thin films thus prepared have polycrystalline structures with the preferred orientation along the (002) plane whose surface consists of ZnO aggregates with sizes of 50-200 nm. The ZnO thin films deposited by GDARE and annealed at 250 °C for 2 h have strong nonlinear varistor-type I-V characteristics. The nonlinear coefficient (α) of a single-layered ZnO thin film sample was 33 and that of a triple-layered sample obtained by the many-time deposition was 62. The varistor voltages (V_1mA) of the two samples are found rather close each other. Under a DC bias of 0.75 V_1mA and a temperature of 150 °C these thin films exhibit good electrical stability with a degradation rate coefficient K_T of 0.05 mA/h^1/2.     

Development of a 60 Hz Power Standard Using SNS Programmable Josephson Voltage Standards

We are implementing a new standard for 60 Hz power measurements based on precision sinusoidal reference voltages from two independent programmable Josephson voltage standards (PJVS): one for voltage and one for current. The National Institute of Standards and Technology PJVS systems use series arrays of Josephson junctions to produce accurate quantum-based DC voltages. Using stepwise-approximation synthesis, the PJVS systems produce sinewaves with precisely calculable RMS voltage and spectral content. We present measurements and calculations that elucidate the sources of error in the RMS voltage that are intrinsic to the digital-synthesis technique and that are due to the finite rise times and transients that occur when switching between the discrete voltages. Our goal is to reduce all error sources and uncertainty contributions from the PJVS synthesized waveforms to a few parts in 10 ⁷ so that the overall uncertainty in the AC-power standard is a few parts in 10⁶     

STRIP DISTRIBUTED TRANSFER FUNCTION METHOD FOR ANALYSIS OF PLATES

A semi-analytical method, called the strip distributed transfer function method, is developed for analysis of plate structures that are composed of rectangular plates. In the method, a rectangular plate (substructure) is divided into a number of strips; the response of each strip is interpolated in the unknown nodal line displacements, which are functions of the strip longitudinal co-ordinate and time. The nodal line displacements are determined in an exact and closed form by the distributed transfer functions that are defined along the strips. Synthesis of the substructures using the strip distributed transfer functions yields accurate prediction of the static and dynamic response, natural frequencies and buckling loads of the structure. The proposed method is compared with some existing techniques in numerical examples.     

Nonequilibrium Electron Cooling by NIS Tunnel Junctions

We discuss the theoretical framework to describe quasiparticle electric and heat currents in NIS tunnel junctions in the dirty limit. The approach is based on quasiclassical Keldysh-Usadel equations. We apply this theory to diffusive NIS^′S tunnel junctions. Here N and S are respectively a normal and a superconducting reservoirs, I is an insulator layer and S^′ is a nonequilibrium superconducting lead. We calculate the quasiparticle electric and heat currents in such structures and consider the effect of inelastic relaxation in the S^′ lead. We find that in the absence of strong relaxation the electric current and the cooling power for voltages eV<Δ are suppressed. The value of this suppression scales with the diffusive transparency parameter. We ascribe this suppression to the effect of backtunneling of nonequilibrium quasiparticles into the normal metal.     

Interpretation of conduit voltage measurements on the poloidal field insert sample using the CUDI–CICC numerical code

The results of simulations with the CUDI–CICC code on the poloidal field insert sample (PFIS) tested in the SULTAN test facility are presented. The interpretations are based on current distribution analysis from self-field measurements with Hall sensor arrays and current sharing measurements. The possible variation in voltage–current (VI) curves among the sub-cables in the PFIS caused by the cable self-field and joint non-uniformity is a principal issue for the evaluation of the strand-to-cable performance. The cable transverse voltages, initiated by current non-uniformity in a cabled conductor, can affect the shape of the longitudinal VI curve. The basic cable data are obtained by petal-to-conduit contact resistance and conduit resistivity measurements under transverse cyclic load in the Twente Cryogenic Cable Press. We assessed the impact of the conduit, the sub-cable resistive barrier wraps and the location of the voltage taps on the measured voltage, and some comparisons were carried out with experimental runs on the PFIS. The outcome confirms that the transverse voltages, caused by current redistribution, do affect the shape of the VI transition. This effect seems particularly important in short sample tests. Moreover, it is demonstrated that the location of the voltage taps can affect the experimentally obtained VI curve and solutions for most accurate measurement of the VI are discussed in the paper. The numerical model, CUDI–CICC covers the final cabling stage of inter-petal interactions only, by which the possible role of intra-petal non-uniformities is ignored, although recognized as potentially relevant.     

Surface acoustic wave reflection from diamond-like carbon thin film reflecting arrays on LiNbO3 substrates

Surface acoustic wave (SAW) reflection from diamond-like carbon (DLC) strip reflecting arrays on Y-Z LiNbO₃ is investigated. The reflection from DLC strips with triangular cross section has been observed. Reflection increases in alternating DLC and Al strips in 90° reflecting arrays in comparison with pure Al structures. The values of reflection coefficient per period in the slanted reflecting arrays are estimated to be about 1.0% for pure DLC strips (height to wavelength ratio equal to 0.02), 2% for uniform Al coating on DLC reflecting arrays, and 3.5% for alternating DLC and Al strips. This value is higher than that for pure Al strips by about 0.7%. Reflection properties are briefly discussed, and preparation technique is presented     

An experimental analysis of drawing characteristics of a dual-phase steel through a round drawbead

The sheet drawing characteristics of a dual-phase steel (DP600) through a round drawbead are determined experimentally using strip drawing tests. For this purpose, a drawbead simulator is designed and integrated with a standard tensile testing machine. Drawing tests are conducted with steel strips cut from 1 mm thickness blanks. The strip geometries, thickness strains, pulling forces and clamping forces are measured during drawing through a round drawbead of 5 mm bead and shoulder radius. The drawbead force parameters and thinning strains are determined from measurements. The experiments are repeated with conventional draw-quality sheets (DC06) of the same thickness for the purpose of establishing a benchmark database. A comparison of calculated drawing characteristics between two types of steels indicates the significant differences in terms of drawbead force parameters. In addition, analysis of experimental data demonstrated bead penetration, clamping force and material flow stress as the dominant factors on drawbead restraint force and blank thinning deformation for both materials. The results of experimental analyzes for both steel types can employed as model input curves for equivalent drawbead models in FE process simulations.     

Effect of chemical termination of self-assembled organic monolayers on the tip induced local anodic oxidation of silicon(100)

We evaluated the scanning probe microscope based anodization process of silicon(100) terminated by organic monolayers of the same thickness but with different surface properties. The surface energy of these monolayers with its dispersive and polar component was determined by contact angle measurements. We discovered that the anodization oxide characteristics depend ceteris paribus clearly on the surface properties of the sample. With an increased polar component, and therefore hydrophilic character of the surface, the formed oxide structures became broader and thinner. On the other hand a hydrophilic surface allowed the generation of oxide structures at higher tip velocities and lower applied voltages. The absolute amount of formed oxide is independent of the monolayer indicating a dominating influence of initially formed oxide on the following oxidation process.     

Nanoscale Quantum Solvation of para-H2 Around the Linear OCS Molecule Inside 4He Droplets

We present a microscopic analysis of the quantum solvation structures of para-H₂ around the OCS molecule when embedded in low temperature ⁴He droplets. The structures of clusters containing M=5 and 6 para-H₂ molecules are compared with corresponding structures for M=1 (OCS-H₂ complex) and M=17 (a full solvation shell), as well as with the clusters in the absence of helium. We find that the helium has negligible effect on the structures for the small and large OCS(H₂) _M clusters, but that it modifies the cluster structure for M=6. We discuss implications of these resugts for the onset of superfluidity in the solvating hydrogen shell and for spectroscopic measurements.     

Precipitation in vanadium bearing ultralow carbon strip steels

Abstract

Two novel ultralow carbon (ULC) steels were investigated, one based on combined vanadium and titanium additions and the second based on titanium only additions. Grain size and mechanical property measurements have been performed on continuously annealed specimens previously subjected to 80% cold rolling reduction on both strip steel grades. The recrystallisation and grain coarsening characteristics of annealed ULC strips have been studied. The amount of precipitated species, under equilibrium conditions, at various annealing temperatures has also been calculated using MT-DATA thermodynamic modelling software. Transmission electron microscopy characterisation coupled with EDX study of the precipitation sequences on continuous annealing strips was also performed. Precipitate studies of the novel ULC steels confirmed the major role of TiC precipitates in retarding the recrystallisation behaviour of ULC strip steels. The role of vanadium addition in ULC steel grades in reducing the recrystallisation temperature of ULC strip steels was also identified.     

Mechanical properties of laminated bamboo strips from Gigantochloa Scortechinii/polyester composites

In this study, the mechanical properties of culm fiber composites with various thicknesses from the inner through the outer layer of bamboo strips were investigated. This study utilized a specific type of bamboo species named Gigantochloa Scortechinii (Buluh Semantan), which was collected from the Bukit Larang village in Melaka, Malaysia. In these experiments, unsaturated polyester (UP) and bamboo fiber (BF) strips were prepared through the hand lay-up technique using 3 mm thick aluminum mould. The composite bamboo strips were prepared in 1.5–2.5 mm thicknesses. The weight of the inner, middle and outer bamboo parts varied from a minimum of 0.742 g to a maximum of 2.600 g. The specimens were then characterized using several techniques including tensile, flexural, hardness, and impact tests. The results indicated that the properties of the middle part of the bamboo strips improve as the bamboo strip thickness increases due to the incorporation of unsaturated polyesters. However, the hardness properties increase for the outer layer of the laminate. These findings suggest that bamboo strips, based on unsaturated polyesters, yield excellent mechanical properties and are a viable alternative to composite-based reinforcing fibers.     

Relating crash frequency and severity: Evaluating the effectiveness of shoulder rumble strips on reducing fatal and major injury crashes

To approach the goal of “Toward Zero Deaths,” there is a need to develop an analysis paradigm to better understand the effects of a countermeasure on reducing the number of severe crashes. One of the goals in traffic safety research is to search for an effective treatment to reduce fatal and major injury crashes, referred to as severe crashes. To achieve this goal, the selection of promising countermeasures is of utmost importance, and relies on the effectiveness of candidate countermeasures in reducing severe crashes. Although it is important to precisely evaluate the effectiveness of candidate countermeasures in reducing the number of severe crashes at a site, the current state-of-the-practice often leads to biased estimates. While there have been a few advanced statistical models developed to mitigate the problem in practice, these models are computationally difficult to estimate because severe crashes are dispersed spatially and temporally, and cannot be integrated into the Highway Safety Manual framework, which develops a series of safety performance functions and crash modification factors to predict the number of crashes. Crash severity outcomes are generally integrated into the Highway Safety Manual using deterministic distributions rather than statistical models. Accounting for the variability in crash severity as a function geometric design, traffic flow, and other roadway and roadside features is afforded by estimating statistical models. Therefore, there is a need to develop a new analysis paradigm to resolve the limitations in the current Highway Safety Manual methods. We propose an approach which decomposes the severe crash frequency into a function of the change in the total number of crashes and the probability of a crash becoming a severe crash before and after a countermeasure is implemented. We tested this approach by evaluating the effectiveness of shoulder rumble strips on reducing the number of severe crashes. A total of 310 segments that have had shoulder rumble strips installed during 2002–2009 are included in the analysis. It was found that shoulder rumble strips reduce the total number of crashes, but have no statistically significant effect on reducing the probability of a severe crash outcome.     

Eddy currents in a transverse MRI gradient coil

A transverse gradient coil (x- or y-coil) of an MRI-scanner is modeled as a network of curved circular strips placed at the surface of a cylinder. The current in this network is driven by a time-harmonic source current. The low frequency applied allows for an electro-quasi-static approach. The strips are thin and the current is assumed to be uniformly distributed in the thickness direction. For the current distribution in the width direction of the strips, an integral equation is derived. Its logarithmically singular kernel represents inductive effects related to the occurrence of eddy currents. For curved circular strips of width much smaller than the radius of the cylinder one may locally replace the curved circular strip by a tangent plane circular strip. This plane geometry preserves the main characteristics of the transverse current distribution through the strips. The current distribution depends strongly on the in-plane curvature of the strips. The Petrov–Galerkin method, using Legendre polynomials, is applied to solve the integral equation and shows fast convergence. Explicit results are presented for two examples: a set of 1 strip and one of 10 strips. The results show that the current distributions are concentrated near the inner edges and that resulting edge-effects, both local and global, are non-symmetric. This behavior is more apparent for higher frequencies and larger in-plane curvatures. Results have been verified by comparison with finite-element results.     

Electrical conduction mechanisms of metal nanoclusters embedded in an amorphous Al2O3 matrix

We present the synthesis and electrical characterization of amorphous nanocomposite layers made of metallic nanoclusters embedded in an alumina matrix (nc-Co:Al₂O₃). The nanostructured materials were fabricated using a pulsed laser deposition (PLD)-derived method based on a nano-cluster generator coupled with a conventional PLD system for host medium co-deposition. The films were subjected to a detailed structural study carried out using high-resolution transmission electron microscopy and atomic force microscopy. The clusters inserted in the alumina matrix are metallic, well crystallized and possess an fcc structure with an average diameter centered at ∼ 2 nm. Dielectric constant and electrical conduction mechanisms of nc-Co:Al₂O₃ layers integrated in metal-insulator-metal capacitive structures were studied for different doping levels and for a broad temperature range (303-473 K). It was concluded that the dielectric constant in the films depends on the doping levels while the major electrical conduction mechanisms are best described by the space charge limited currents formalism, in which the current density J on an applied voltage V follow a power-law dependence (J ∼ Vⁿ) at applied voltages higher than ∼ 2 V. Such composite may find immediate applications as dielectric layers with controlled discharging conduction paths in Radio Frequency-Micro-Electro-Mechanical Systems capacitive structures.     

Low-k film damage-resistant CO chemistry-based ash process for low-k/Cu interconnection in flash memory devices

In this paper, CO chemistry-based ash processes have been suggested to reduce carbon depletion and moisture absorption from plasma discharges for low-k/Cu interconnection in 40 nm-node Flash memory. We analyzed ash processes utilizing Fourier transform infrared spectroscopy (FTIR), k-value measurements, and sidewall-shrinking profile measurements based on a cross-sectional scanning electron microscope (SEM) image obtained before and after filling trench with Cu. In an effort to better understand the role of ash processes in ultra-narrow capacitors, we also evaluated the distribution of breakdown voltages as a function of voltage for trench-patterned wafers. In this paper, we successfully found that low-damage ash processes for low-k/Cu interconnection by adopting CO chemistry-based ash process.     

Andreev Reflection and Granular Superconductivity Features Observed in Mesoscopic Samples Using Amorphous Tungsten Carbide Superconductors

Point-contact Andreev reflection and magnetoresistance measurements were done using amorphous tungsten carbide (WC _x ) superconductors. Superconducting tips as well as microwires were grown directly under a focused Ga⁺-ion beam (FIB) on pre-patterned samples. Using e-beam lithography, the electrical contacts were prepared later using a special geometry. Current?Cvoltage measurements as a function of temperature and magnetic field clearly showed the signatures of Andreev reflection. We observed anomalies in the differential conductivity at voltages above the energy gap values. These anomalies can be well understood as due to a weak-link formation with narrow band properties contributing in parallel at the interfaces of the contacts. We also observed Andreev oscillations as a function of magnetic field similar to those found recently in specially prepared normal?Csuperconducting?Cnormal nanostructures and multigraphene samples. In some of the structures, we were able to produce interfaces in which clear granular behavior in a certain temperature region was observed, such as, for example, an anomalous field hysteresis loop compatible with the existence of granular superconductivity, similar to that found also in thin mesoscopic graphite samples.     

Impact response of an anti-plane crack in a FGPM bonded to a homogeneous piezoelectric strip

A finite crack under transient anti-plane shear loads in a functionally graded piezoelectric material (FGPM) bonded to a homogeneous piezoelectric strip is considered. It is assumed that the electroelastic material properties of the FGPM vary continuously according to exponential functions along the thickness of the strip, and that the two layered strips is under combined anti-plane shear mechanical and in-plane electrical impact loads. The analysis is conducted on the electrically unified crack boundary condition. Laplace and Fourier transforms are used to reduce the mixed boundary value problems to Fredholm integral equations of the second kind in the Laplace transform domain. Then, a numerical Laplace inversion is performed and the dynamic intensities are obtained as functions of time and geometric parameters, which are displayed graphically.     

The influence of the strip width on the performance of a strip detector

In high energy physics experiments strip detectors are used for vertex determination. The strip geometry of such detectors has up to now been symmetrical, with the strip width and interspacing equalling each other. However, nothing is known about the exact importance of this geometry. Therefore, a theoretical and an experimental study was made of the influence of the strip width on a strip detector's performance. Firstly, the potential and electric field distributions in the neighbourhood of the strips were calculated, which enabled the influence of parameters such as detector geometry, bias voltage and surface charge to be investigated. Secondly, test devices were designed and fabricated. These devices, in which both the pitch and the strip width were varied, were tested on their electrical behaviour as well as on their interaction with radiation.The main conclusion to be drawn from this research is that the position precision is independent of the strip width, while the electrical characteristics are not. Small strips are preferable, with the minimum determined by the technological possibilities.