Sweep Direction Research Articles

Surface Modification of Aluminium Alloys with Laser Shock Processing

An adequate residual stress variation and frequently also improved corrosion resistance of a material are key requirements for usability of numerous machine components in various applications. The aim of the investigation conducted was to determine optimum Laser Shock Processing (LSP) parameters for aluminium specimens in order to obtain the desired residual stress variation and improved corrosion resistance. LSP treatment was performed with a Q-switched Nd:YAG laser with a wavelength of 1064 nm. In order to statistically confirm the optimum process parameters, a factorial design was applied, in which the first experimental factor was pulse density, i.e. 900 and 2500 pulses/cm2, the second factor was the type of material used, i.e. aluminium alloys AlMgSiPb and AlSi1MgMn and the third factor was the direction of LSP surface sweep, i.e. longitudinal and transversal direction. The experiments made confirmed a characteristic influence of the first factor representing different pulse densities. An analysis of residual stresses confirmed that in processing with 2500 pulses/cm2 the highest compressive residual stresses were obtained. Potentiodynamic corrosion testing confirmed that the higher pulse density resulted in a stronger shift of pitting potential, which provided higher corrosion resistance.

Electrical Characterization of Wafer-Bonded Germanium-on-Insulator Substrates Using a Four-Point-Probe Pseudo-Metal–Oxide–Semiconductor Field-Effect Transistor

The electrical characteristics of wafer-bonded non-doped germanium-on-insulator (GOI) substrates were investigated using a four-point-probe pseudo-metal–oxide–semiconductor field-effect transistor. Annealing the wafer-bonded GOI substrates in vacuum strongly influenced their electrical characteristics. GOI samples annealed at temperatures below 500 °C exhibited n-channel depletion transistor operation, whereas GOI samples annealed at temperatures between 550 and 600 °C exhibited p-channel depletion transistor operation. The carrier mobility strongly depended on the sweep direction of the gate voltage; this characteristic disappeared after annealing at temperatures above 550 °C. The dependence of the electrical characteristics on the annealing temperature is explained in terms of the influence of the defect states on energy band bending near the interface.

Sweep direction and efficiency of the swept-frequency two pulse phase modulated scheme for heteronuclear dipolar-decoupling in solid-state NMR

We present here a bimodal Floquet theoretical and experimental investigation of the direction of sweep in the swept-frequency two pulse phase modulated (SW f -TPPM) scheme used for heteronuclear dipolar decoupling in solid-state NMR. The efficiency of the decoupling turns out to be independent of the sweep direction.

Performance characterisation for two radio frequency identification inventory readers within a university library environment

Performance testing is an integral aspect of Radio Frequency Identification (RFID) application, with users’ anticipation of near 100% accuracy rate. A review of a number of academic research databases has shown sparse empirical research on RFID testing in a library environment. This study investigates factors that may affect the read rate of an inventory reader in a library. The factors investigated in this study were read distance, tag location, number of sweeps and sweep direction. This methodology applied a systematic approach to investigate the performance of two inventory readers using design of experiment. A 2k–1 fractional factorial experiment, where k is the number of factors investigated, was used to determine the relationship between independent factors (k = 5) and the performance of the RFID reader, measured by the read rate. It is anticipated that the findings may help researchers and library practitioners to understand and further investigate methods to optimise the performance of the reader and spur the need for investigation of other factors.

In-depth analysis of transient errors of inline IV measurements

Abstract Silicon solar cells are prone to transient effects during fast acquisition of the illuminated IV parameters, as it is commonly carried out using industrial cell testers. It is known that the IV curve sweep time and direction have a significant impact on the measured fill factor and open circuit voltage. Within this contribution, the hysteresis effect on the fill factor and the open circuit voltage are investigated for different types of industrially fabricated silicon solar cells. This investigation is carried out on two different, commonly used, flash-based cell testers.

Asymmetry of the latent heat signature in b-axis oriented single crystal Gd5Si2Ge2

ABSTRACTA 100 micron fragment of a b-axis oriented single crystal Gd5Si2Ge2 has been studied using microcalorimetry, enabling the separate measurement of the heat capacity and the latent heat. The sample was taken from the same crystal previously studied with Hall probe imaging, which showed that the phase transition is seeded by a second phase of Gd5Si1.5Ge1.5 nanoplatelets on the increasing field sweep direction only. The multiple transition features observed in the latent heat signature suggests a nucleation size of approximately 20 μm, consistent with the lengthscale suggested by Hall imaging. The difference in nucleation and growth process with field sweep direction is clearly identified in the latent heat. We show that the latent heat contribution to the entropy change is of the order of 50% of the total entropy change and unlike other systems studied, the transition does not broaden (and the latent heat contribution does not diminish significantly) as magnetic field and temperature are increased within the parameter range explored in these experiments.

Real-time collision culling of a million bodies on graphics processing units

We cull collisions between very large numbers of moving bodies using graphics processing units (GPUs). To perform massively parallel sweep-and-prune (SaP), we mitigate the great density of intervals along the axis of sweep by using principal component analysis to choose the best sweep direction, together with spatial subdivisions to further reduce the number of false positive overlaps. Our algorithm implemented entirely on GPUs using the CUDA framework can handle a million moving objects at interactive rates. As application of our algorithm, we demonstrate the real-time simulation of very large numbers of particles and rigid-body dynamics.

An Ultrathin Forming-Free $\hbox{HfO}_{x}$ Resistance Memory With Excellent Electrical Performance

Abstract-A forming-free 3-nm-thick HfOx, resistive memory device is demonstrated. The percolation threshold of insulatingto-conductive transition in the ultrathin HfOx, can be lowered by using the Ti capping layer with an adequate post metal annealing. By the reaction between Ti and HfOx,, oxygen ions are depleted from the oxide, and conductive percolative paths, which consist of charged oxygen vacancies, are formed. Without any forming step, the memory can operate with stable bipolar resistance switching by initial positive or negative voltage sweep. Possible scenarios of switching mechanism for the initial state of the device with different sweep directions are proposed. This forming-free device also exhibits an on/off ratio of about ten and excellent memory performances, including high speed (~10 ns), low operation voltages ( 106 cycles), good nonvolatile property (500 min at 85 °C), and 2-b switching per cell.

Cat's behavioral sensitivity and cortical spatiotemporal responses to the sweep direction of frequency-modulated tones

Neural responses to frequency modulated (FM) sweeps have been well investigated in single-units using electrophysiological recording methods. However, rare psychophysical experiments were conducted to investigate behavioral discrimination of FM-sweeps in the same species used in physiological experiments. Also, the previous studies have not focused on how the population of cortical neurons works together to encode the direction of FM-sweeps. To investigate the relation between the behavioral perception of FM direction and the population coding, we examined the cat's capability to discriminate the upward and downward FM-sweeps and recorded the neural responses to the same stimuli from the primary auditory cortex (A1) in different awake cats. We found that cats showed high performance to detect the change of direction of FM-sweeps, which linearly swept between 0.1 and 16kHz in 40–160ms duration; however, the behavioral performance obviously deteriorated when the sweeps were shortened to 10–20ms. Physiological results indicated that the upward sweeps elicited a temporal sequence of responses among the A1 neurons, in which neurons tuning to low-frequencies responded earlier and those tuning to high-frequencies later, while the response sequence was reversed when A1 was driven by the downward sweeps. The rank-order of response latencies could provide a reliable discrimination of the FM direction, and the discrimination performance paralleled with the cat's behavioral performance. Our result suggests that the relative response timings in A1 contain enough information used by subsequent processing stages to make the decision of FM direction.

Effects of Moisture on Pentacene Field-Effect Transistors with Polyvinylpyrrolidone Gate Insulator

We report the effects of moisture on the electrical characteristics of pentacene field-effect transistors (FETs) with the polyvinylpyrrolidone (PVPy) gate insulator. For the condition of relative humidity below 40%, the pentacene FET exhibited a stable operation without a shift in the threshold voltage upon a gate voltage sweep direction. With increasing the relative humidity above 50%, the threshold voltage shifted critically toward the positive direction, accompanied by significant degradations in the field-effect mobility and the subthreshold slope. These moisture-induced characteristic degradations could be substantially recovered by the low-temperature annealing process under a base pressure of 2 × 10−3 Torr.

Enhanced Sequential Carrier Capture into Individual Quantum Dots and Quantum Posts Controlled by Surface Acoustic Waves

Individual self-assembled quantum dots and quantum posts are studied under the influence of a surface acoustic wave. In optical experiments we observe an acoustically induced switching of the occupancy of the nanostructures along with an overall increase of the emission intensity. For quantum posts, switching occurs continuously from predominantly charged excitons (dissimilar number of electrons and holes) to neutral excitons (same number of electrons and holes) and is independent of whether the surface acoustic wave amplitude is increased or decreased. For quantum dots, switching is nonmonotonic and shows a pronounced hysteresis on the amplitude sweep direction. Moreover, emission of positively charged and neutral excitons is observed at high surface acoustic wave amplitudes. These findings are explained by carrier trapping and localization in the thin and disordered two-dimensional wetting layer on top of which quantum dots nucleate. This limitation can be overcome for quantum posts where acoustically induced charge transport is highly efficient in a wide lateral matrix-quantum well.

Effects of sweep VEP parameters on visual acuity and contrast thresholds in children and adults

There are many parameters that may impact the thresholds obtained with sweep visually evoked potentials (sVEP), yet a number of these parameters have not been systematically studied, and there is no recognised standard for sVEP recording. In this study, the effects of electrode placement, temporal frequency, sweep direction, presence of a fixation target, stimulus area, and sweep duration on visual acuity (VA) and contrast thresholds of the sVEP were investigated. Additionally, the effect of these parameters on the number of viable threshold readings obtained from five active electrodes was investigated. Participants were six children (aged 6-8 years) and six adults (aged 17-30 years) with normal vision. Binocular sVEP VA and contrast thresholds were measured for two electrode placements (ISCEV and PowerDiva) of five active electrodes, three temporal frequencies (6, 7.5, and 10 Hz), two sweep directions (low to high and high to low), presence or absence of a fixation target, three stimulus areas, and three sweep durations. There were differences between adults and children with respect to visual acuity, the adults having better VA than the children (p = 0.033 in experiment 2). Overall, there were more viable readings at 7.5 Hz than at either 10 or 6 Hz (p = 0.0014 for VA and 0.001 for contrast thresholds). The adults performed better (in terms of viable readings) with the fixation target than without it (p = 0.04). The smallest stimulus size used gave rise to fewer viable readings in both adults and children (p = 0.022 for VA and 0.0001 for contrast thresholds). The other parameters (electrode placement, sweep direction and sweep duration) did not give rise to significant differences. A temporal frequency of 7.5 Hz, a stimulus area of 4° or larger for VA and 10° or larger for contrast thresholds, and the use of a fixation target gave more viable readings, and may be indicated for future application. Consideration of the number of viable readings showed more differences between parameters than the actual thresholds, and it is suggested that more readings presumably would yield more reliable threshold measurements.

Intrinsic doping and gate hysteresis in graphene field effect devices fabricated onSiO2 substrates

We have studied the intrinsic doping level and gate hysteresisof graphene-based field effect transistors (FETs) fabricated overSi/SiO2 substrates. It was found that the high p-doping level of graphene in some as-prepareddevices can be reversed by vacuum degassing at room temperature or abovedepending on the degree of hydrophobicity and/or hydration of the underlyingSiO2 substrate. Charge neutrality point (CNP) hysteresis, consisting of the shift of thecharge neutrality point (or Dirac peak) upon reversal of the gate voltage sweepdirection, was also greatly reduced upon vacuum degassing. However, another type ofhysteresis, consisting of the change in the transconductance upon reversal of thegate voltage sweep direction, persists even after long-term vacuum annealing at200 °C, whenSiO2 surface-bound water is expected to be desorbed. We propose a mechanismfor this transconductance hysteresis that involves water-related defects,formed during the hydration of the near-surface silanol groups in the bulkSiO2, that can act as electron traps.

Facilitatory Mechanisms Shape Selectivity for the Rate and Direction of FM Sweeps in the Inferior Colliculus of the Pallid Bat

The inferior colliculus (IC) of the pallid bat has a large percentage of neurons that respond selectively to the rate and direction of the bat's echolocation pulse, a downward FM sweep. Three underlying mechanisms have been previously described. Here we describe a fourth mechanism, facilitation, that shapes selectivity for both sweep rate and direction. The neurons studied are termed FM specialists, because they do not respond to tones. Most were selective for the downward sweep direction, and this preference was expressed even when presented with narrowband, 1 kHz sweeps that crossed only a fraction of their excitatory receptive fields. This selectivity was also expressed in response to two tones delayed in time, termed two-tone facilitation (TTF). Direction-selective neurons showed a greatly facilitated response when a higher-frequency tone preceded a lower-frequency tone, simulating conditions in a downward sweep. The degree of temporal asymmetry in facilitation accurately predicted direction selectivity. When the spectral difference between the two tones was increased, the best delay also increased and could be used to predict a neuron's preferred sweep rate. To determine whether TTF alone created rate and direction selectivity, low- and high-frequency inhibitory sidebands, which can also shape selectivity, were eliminated from sweeps. In most cases, selectivity persisted. These results support the idea of spectral delay lines that produce an overlap and summation of excitatory inputs only when a dynamic stimulus traverses a receptive field in one direction at a specific velocity.

Multiple mechanisms shape selectivity for FM sweep rate and direction in the pallid bat inferior colliculus and auditory cortex

The inferior colliculus and auditory cortex of the pallid bat contain a large percentage of neurons that are highly selective for the direction and rate of the downward frequency modulated (FM) sweep of the bat's echolocation pulse. Approximately 25% of neurons tuned to the echolocation pulse respond exclusively to downward FM sweeps. This review focuses on the finding that this selectivity is generated by multiple mechanisms that may act alone or in concert. In the inferior colliculus, selectivity for sweep rate is shaped by at least three mechanisms: shortpass or bandpass tuning for signal duration, delayed high-frequency inhibition that prevents responses to slow sweep rates, and asymmetrical facilitation that occurs only when two tones are presented at appropriate delays. When acting alone, the three mechanisms can produce essentially identical rate selectivity. Direction selectivity can be produced by two mechanisms: an early low-frequency inhibition that prevents responses to upward sweeps, and the same asymmetrical two-tone inhibition that shapes rate tuning. All mechanisms except duration tuning are also present in the auditory cortex. Discussion centers on whether these mechanisms are redundant or complementary.

Calibration algorithm for Fourier transform spectrometer with thermal instabilities

Complex domain calibration is an efficient method to correct the amplitude and phase of a spectrum obtained from a Fourier transform spectrometer. This method is, however, not directly applicable in the occurrence of a zero path difference (ZPD) shift between a scene interferogram and calibration blackbody interferograms. This situation is likely to happen for a system with thermal instabilities. It is found that a ZPD shift smaller than 1 sampling point can cause a large disagreement between the spectra evaluated from the two interferometer sweep directions. We have developed an algorithm for a complex calibration in the presence of ZPD shifts. The restricting aspect of the real-time capability is taken into account.

The dominance of inhibition in the inferior colliculus

Almost all of the processing that occurs in the various lower auditory nuclei converges upon a common target in the central nucleus of the inferior colliculus (ICc) thus making the ICc the nexus of the auditory system. A variety of new response properties are formed in the ICc through the interactions among the excitatory and inhibitory inputs that converge upon it. Here we review studies that illustrate the dominant role inhibition plays in the ICc. We begin by reviewing studies of tuning curves and show how inhibition shapes the variety of tuning curves in the ICc through sideband inhibition. We then show how inhibition shapes selective response properties for complex signals, focusing on selectivity for the sweep direction of frequency modulations (FM). In the final section we consider results from in vivo whole-cell recordings that show how parameters of the incoming excitation and inhibition interact to shape directional selectivity. We show that post-synaptic potentials (PSPs) evoked by different signals can be similar but evoke markedly different spike-counts. In these cases, spike threshold acts as a non-linear amplifier that converts small differences in PSPs into large differences in spike output. Such differences between the inputs to a cell compared to the outputs from the same cell suggest that highly selective discharge properties can be created by only minor adjustments in the synaptic strengths evoked by one or both signals. These findings also suggest that plasticity of response features may be achieved with far less modifications in circuitry than previously supposed.

P‐102: Hysteresis Suppression of Thin‐Film Transistors with Poly (Vinyl Alcohol) Insulator on Flexible Stainless Steel Substrate

AbstractThe Hysteresis effects can be suppressed in flexible thin‐film transistors with poly (vinyl alcohol) insulator without crosslinking agent. The characteristic of hysteresis was greatly reduced by SiO2 nano‐particle in PVA solution. The TFTs were fabricated by using a‐IGZO as active layer at room temperature. The TFTs exhibited stable performance with field effect mobility (∼10.81 Vs/cm2), high on/off current ratios (∼106), and low threshold voltage (∼−1V) on planarized stainless steel substrate. The transfer curve which measured from various sweep ranges in two different sweep directions suggested that the hysteresis has been successfully suppressed.

Hysteresis effect on traps of Si 3N 4 sensing membranes for pH difference sensitivity

The mechanism of different pH sensitivities on single and stacked layer silicon nitride (Si 3N 4)-electrolyte insulator semiconductor (EIS) structures was investigated for the application of an inorganic ion sensitive field effect transistor (ISFET) and reference field effect transistor (REFET) pair. The capacitance–voltage ( C– V) hysteresis effect of the EIS structures was measured. In addition, pH sensitivity was evaluated with different sweep directions and ranges of the substrate bias. Based on the hysteresis results, a pH-dependent trapping effect was found to decrease the pH sensitivity on a single Si 3N 4 sensing membrane EIS structure.

Magnetoresistance in a hybrid ferromagnetic/semiconductor device

Ballistic transport of a two-dimensional electron gas (2DEG) in a rectangle shaped wire, subjected to a local nonhomogeneous magnetic field that results from an in-plane magnetized ferromagnetic (FM) strip deposited above the 2DEG, is investigated theoretically. We found a positive magnetoresistance (MR), which exhibits hysteresis behavior with respect to the direction of the magnetic field sweep, in agreement with a recent experiment. This positive MR can be tuned by applying a gate voltage to the FM strip.