Hysteresis Thresholding Research Articles

Room temperature memory operation of a single InAs quantum dot layer in a GaAs∕AlGaAs heterostructure

Room temperature (RT) memory operation of a single InAs quantum dot (QD) layer serving as floating gate is demonstrated. In an in-plane gated quantum-wire transistor, the charge state of the self-assembled InAs QDs is controlled by the applied gate voltage. Due to the floating-gate function of the QDs on a nearby transport channel, threshold hysteresis exceeding 200mV and storage times of several minutes are observed. The RT operation is attributed to an optimized positioning of the QDs at the site of a local minimum in the AlGaAs conduction band.

Molecular Mechanism of Water Bridge Buildup: Field-Induced Formation of Nanoscale Menisci

We perform molecular dynamics calculations to describe, at the molecular level, the formation of a water bridge induced by an electric field. Restriction of orientational degrees of freedom (confinement) of water dipoles at the interfaces leads to a polarizability that depends on the shape of the water system, that is, droplet versus pillar. Above a threshold field of 1.2 V nm(-1), the competition between orientational confinement and electric field leads to the sudden formation of a water pillar. The formation of a water bridge is marked by a first order discontinuity in the total energy of the system. The simulations offer a molecular explanation for the threshold voltage and hysteresis behavior observed in the formation of nanoscale liquid bridges with a force microscope.

A Method to Estimate the Horizontal Handover Decision Effect on Indoor Wireless Conversational Video Quality

One of the most interesting and valuable services considered in fixed mobile convergence is video telephony. The success of this conversational video service will depend on the conversational video quality achieved in the multicell wireless indoor scenarios. One of the essential elements in the quality is the effect of the horizontal handovers in the conversational video. This paper analyzes the handover decision based on the probability calculation of handover events in the case of relative signal strength with hysteresis threshold (RSSHT) approach, and it proposes a new handover decision mechanism, variable hysteresis, to avoid unnecessary handovers. The paper presents the impact of the number of handovers and their duration time on the video's effective frame rate. Moreover, the effect of video stream modification during a short handover is also analyzed. Probability and handover duration approaches are combined and a new simple method for video quality evaluation is caused by the handovers in multicell indoor WLAN scenarios. Finally, the model proposed has been applied to a real office scenario.

Dynamics of capillary condensation in bistable optical superlattices

The optical transmission through a porous superlattice is modulated by capillary condensation and evaporation of ethanol. The system exhibits optical bistability, with the two stable states characterized by a different amount of liquid ethanol in the pores. Switching between states is controlled by the input power of the incident light beam. By tuning the input power at various speeds, we study the dynamics of condensation and evaporation and study the behavior of the hysteresis and switching thresholds. We find that the time response of the system is limited by the condensation process, which is faster in pores with lower radius. We also report on the dependence of the hysteresis loop on vapor concentration.

Real-Time Modeling of 3-D Soccer Ball Trajectories From Multiple Fixed Cameras

In this paper, model-based approaches for real-time 3-D soccer ball tracking are proposed, using image sequences from multiple fixed cameras as input. The main challenges include filtering false alarms, tracking through missing observations, and estimating 3-D positions from single or multiple cameras. The key innovations are: 1. incorporating motion cues and temporal hysteresis thresholding in ball detection; 2. modeling each ball trajectory as curve segments in successive virtual vertical planes so that the 3-D position of the ball can be determined from a single camera view; and 3. introducing four motion phases (rolling, flying, in possession, and out of play) and employing phase-specific models to estimate ball trajectories which enables high-level semantics applied in low-level tracking. In addition, unreliable or missing ball observations are recovered using spatio-temporal constraints and temporal filtering. The system accuracy and robustness are evaluated by comparing the estimated ball positions and phases with manual ground-truth data of real soccer sequences.

Channel estimation and physical layer adaptation techniques for satellite networks exploiting adaptive coding and modulation

AbstractThe exploitation of adaptive coding and modulation techniques for broadband multi‐beam satellite communication networks operating at Ka‐band and above has been shown to theoretically provide large system capacity gains. In this paper, the problem of how to accurately estimate the time‐variant channel and how to adapt the physical layer taking into account the effects of estimator errors and (large) satellite propagation delays is analyzed, and practical solutions for both the forward and the reverse link are proposed. A novel pragmatic solution to the reverse link physical layer channel estimation in the presence of time‐variant bursty interference has been devised. Physical layer adaptation algorithms jointly with design rules for hysteresis thresholds have been analytically derived. The imperfect physical layer channel estimation impact on the overall system capacity has been finally derived by means of an original semi‐analytical approach. Through comprehensive system simulations for a realistic system study case, it is showed that the devised adaptation algorithms are able to successfully track critical Ka‐band fading time series with a limited impact on the system capacity while satisfying the link outage probability requirement. Copyright © 2008 John Wiley & Sons, Ltd.

Line defects and temperature effects in liquid crystal tunable planar Bragg gratings

Liquid crystal tunable planar Bragg Gratings produced by Direct UV Writing are capable of wavelength tuning of over 100GHz. However, such devices exhibit non-linear tuning curves with threshold points and hysteresis. We show that these effects are due to the formation of disclination structures in the liquid crystal and discuss the role of electrode defects and sample temperature on wavelength tuning.

Bias Voltage Controlled Memory Effect in In-Plane Quantum-Wire Transistors With Embedded Quantum Dots

The drain-current through GaAs/AlGaAs quantum-wire transistors (QWTs) with InGaAs quantum dots (QDs) exploited as floating gates is studied for temperatures up to 150 K. It is found that the threshold hysteresis between the up sweep and the down sweep of the gate voltage decreases with increasing bias voltage and is suppressed at a critical bias voltage. It is proposed and demonstrated that these QWTs show logic OR-gate functionality with the option to store the corresponding logic state by switching the bias voltage to zero. The authors explain this behavior by a bias voltage dependent efficiency of the gate to control differently the QDs and the quantum wire

Memory inhibition in quantum‐wire transistors controlled by quantum dots

AbstractCurrent‐voltage characteristics of in‐plane gated quantum‐wire transistors with embedded InGaAs quantum dots are studied at low temperatures. Due to the floating gate function of the quantum dots, for small bias voltages a threshold hysteresis of up to 0.9 V is observed between the up sweep and the down sweep of the gate voltage. With increasing bias the threshold hysteresis decreases, is even suppressed for a critical bias voltage and inverts its sign for higher biasing. We associate this bias controlled memory function to a bias voltage dependent gate efficiency of the quantum‐wire transistor. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Bayesian Operating Point of the Canny Edge Detector

We have investigated the operating point of the Canny edge detector which minimizes the Bayes risk of misclassification. By considering each of the sequential stages which constitute the Canny algorithm, we conclude that the linear filtering stage of Canny, without postprocessing, performs very poorly by any standard in pattern recognition and achieves error rates which are almost indistinguishable from a priori classification. We demonstrate that the edge detection performance of the Canny detector is due almost entirely to the postprocessing stages of nonmaximal suppression and hysteresis thresholding.

Electro-optical performance of polymer stabilized cholesteric texture cell: The influence of chiral dopant and monomer concentration

Reverse-mode polymer stabilized cholesteric texture (PSCT) cells with various chiral dopant and monomer concentrations were fabricated. Experimental results indicate that the chiral dopant concentration and the monomer concentration significantly influence the threshold voltage and hysteresis of the cells. The chiral dopant and monomer deform the hysteresis loop. Increasing the monomer concentration reduces the width of the hysteresis loop of the reverse-mode PSCT cell.

Self-gating controlled pronounced threshold hysteresis in electron Y-branch switch with quantum dots

A novel compact, monolithic memory device based on Y-branched junctions with embedded quantum dots is demonstrated. Up sweeps and down sweeps of the voltage difference between the branches lead to a pronounced threshold hysteresis exceeding 0.5 V. It is concluded that the charge state of the quantum dots and thus the hysteresis is also controlled by the self-gating in an electron Y-branch switch.

Light-induced thermal hysteresis and intensity thresholds in molecular switcheable solids, by mean-field macroscopic master equation approach: Discussion of the experimental data obtained for Co–Fe Prussian Blue Analogues

Abstract The mean-field macroscopic master equation (MFMME) provides a convenient first approach to the static and dynamic properties of photo-switcheable molecular solids under irradiation. The MFMME static approach is formally equivalent to those of the Ising-like or regular solution models in mean-field (or Bragg) approximation. In addition to the previously described light-induced instability of the low-temperature photo-stationary states [A. Desaix, O. Roubeau, J. Jeftic, J.G. Haasnoot, K. Boukheddaden, E. Codjovi, J. Linares, M. Nogues, F. Varret, Eur. Phys. J. B6 (1998) 183], the MFMME approach also provides an easy access to the intensity threshold values involved in photo-switching experiments performed in the thermal hysteresis loop [N. Shimamoto, S. Ohkoshi, O. Sato, K. Hashimoto, Chem. Lett. 4 (2002) 486–487; H.W. Liu, K. Matsuda, Z.Z. Gu, K. Takahashi, A.L. Cui, R. Nakajima, A. Fujishima, O. Sato, Phys. Rev. Lett. 90 (2203) 167403; E. Freysz, S. Montant, S. Letard, and JF Letard, Chem. Phys. Lett. 394 (2004) 318] and to the reversible mechanism suggested in [H.W. Liu, K. Matsuda, Z.Z. Gu, K. Takahashi, A.L. Cui, R. Nakajima, A. Fujishima, O. Sato, Phys. Rev. Lett. 90 (2203) 167403]. The kinetic aspects of photo-switching are also accounted for. The light-induced thermal hysteresis loop of a photomagnetic Prussian Blue Analogue is reported for the first time, and the resulting value for the threshold intensity is discussed.

Soft breakdown enhanced hysteresis effects in ultrathin oxide silicon-on-insulator metal-oxide-semiconductor field effect transistors

The impact of oxide soft breakdown location on threshold voltage hysteresis in partially depleted silicon-on-insulator metal-oxide-semiconductor field effect transistors with an ultrathin oxide (1.6nm) is investigated. Two breakdown enhanced hysteresis modes are identified. In a drain-edge breakdown device, excess holes result from band-to-band tunneling flow to the floating body, thus causing threshold voltage variation in drain bias switching. In contrast, in a channel breakdown device, enhanced threshold hysteresis is observed during gate bias switching because of increased valence band electron tunneling. Our findings reveal that soft breakdown enhanced hysteresis effect can be a serious reliability issue in silicon-on-insulator devices with floating body configuration.

Throughflow variability during snowmelt in a forested mountain catchment, coastal British Columbia, Canada

AbstractThis study documented the spatial and temporal variability of outflow from a forested hillslope segment during snowmelt at a small mountain catchment in south coastal British Columbia, Canada. A pit 5 m wide was established just upslope from the stream channel. Outflow from the organic horizon was intercepted and measured by a single trough, and outflow from the mineral horizons was measured separately for three adjacent sections. Throughflow exhibited non‐steady‐state behaviour involving shifting allocations of flow amongst different sections of the outflow pit, as well as threshold effects and hysteresis in the relationship between pit outflow and water table elevation. Most of the pit outflow originated from the mineral horizons, indicating that throughflow was the dominant pathway by which water was delivered to the stream channel. Direct precipitation and snowmelt onto near‐stream saturated areas can account for less than 20% of the total outflow from the hillslope segment. Throughflow from the mineral sections consistently peaked either at the same time as or earlier than stream flow from the 150‐ha catchment during diurnal snowmelt cycles, indicating that throughflow appears to respond rapidly enough to contribute to snowmelt‐induced peak stream flow. Pit outflow cannot be extrapolated reliably to the catchment scale on the basis of simple length‐ or area‐based ratios. Copyright © 2004 John Wiley & Sons, Ltd.

Multi‐scale Feature Extraction on Point‐Sampled Surfaces

Abstract We present a new technique for extracting line‐type features on point‐sampled geometry. Given an unstructuredpoint cloud as input, our method first applies principal component analysis on local neighborhoods toclassify points according to the likelihood that they belong to a feature. Using hysteresis thresholding, we thencompute a minimum spanning graph as an initial approximation of the feature lines. To smooth out the featureswhile maintaining a close connection to the underlying surface, we use an adaptation of active contour models.Central to our method is a multi‐scale classification operator that allows feature analysis at multiplescales, using the size of the local neighborhoods as a discrete scale parameter. This significantly improves thereliability of the detection phase and makes our method more robust in the presence of noise. To illustrate theusefulness of our method, we have implemented a non‐photorealistic point renderer to visualize point‐sampledsurfaces as line drawings of their extracted feature curves.

Robust edge detection

Edge detection is an important issue in computer vision and image understanding systems. Most conventional techniques have assumed Gaussian noise, and their performance could decrease with the departure of noise distribution from normality. In this paper, we present an edge detection approach using robust statistics. The edge structure is first detected by a robust one-way design model, and then localized by a robust contrast test. Finally, hysteresis thresholding is applied to yield the output edge map. To evaluate its performance, experiments were carried out on synthetic and real images corrupted with both Gaussian noise and a mixture of Gaussian and impulsive noise. The results show that the performance of the proposed edge detector is stable and reliable under severe impulsive noise conditions.

Field emission properties of porous diamond-like films produced by chemical vapor deposition

The field emission properties of “porous diamond-like” carbon structures have been characterized. A hot filament chemical vapor deposition system fed with ethyl alcohol vapor diluted in helium was used to deposit the samples. Morphological analysis by field emission scanning electron microscopy revealed that they had a highly porous structure, which was attributed to the modification of the kinetics of the carbon deposition process due to the presence of helium as a buffer gas. Micro-Raman spectroscopy showed two peaks in the graphene and microcrystalline graphite frequencies and a new peak at 1620 cm−1. Low threshold fields (Et) and hysteresis in the current versus voltage characteristic have been observed, and a model to explain the hysteresis is proposed.

Large threshold hysteresis in a narrow AlGaAs/GaAs channel with embedded quantum dots

Self-assembled InGaAs quantum dots have been grown by molecular-beam epitaxy in the spacer of AlGaAs/GaAs modulation-doped heterostructures. The wafer has been further processed by electron-beam lithography and etching techniques in order to realize 70 nm wide channels controlled by lateral side gates. It is found that the drain current threshold differs by up to 2 V with respect to down and up sweeps of the gate voltage. The large hysteresis is attributed to charging and discharging of the quantum dots in the spacer and persists up to 260 K.

Computer-aided diagnosis scheme for detection of polyps at CT colonography.

Colon cancer is one of the leading causes of cancer deaths in the United States. However, most colon cancers can be prevented if precursor colonic polyps are detected and removed. An advanced computer-aided diagnosis (CAD) scheme was developed for the automated detection of polyps at computed tomographic (CT) colonography. A region encompassing the colonic wall is extracted from an isotropic volume data set obtained by interpolating CT colonographic scans along the axial direction. Polyp candidates are detected with computation of three-dimensional (3D) geometric features that characterize polyps, followed by extraction of polyps with hysteresis thresholding and fuzzy clustering using these geometric features. The number of false-positive findings is reduced by extracting 3D texture features from polyp candidates and applying quadratic discriminant analysis to the candidates. This CAD scheme was applied in 71 patients who underwent CT colonography, 14 of whom had colonoscopically confirmed polyps (n = 21). At by-patient analysis, sensitivity was 100%, with an average false-positive rate of 2.0 per patient. At by-polyp analysis, the scheme detected 90% of the polyps at the same false-positive rate. This CAD scheme permits accurate detection of suspicious lesions and thus has the potential to reduce radiologists' interpretation time and improve their diagnostic accuracy in the detection of polyps at CT colonography.