Dependent Threshold Research Articles

Multilevel Image Thresholding for Image Segmentation using Hybrid Algorithm

Image thresholding is an extraction method of objects from a background scene, which is used most of the time to evaluate and interpret images because of their advanced simplicity, robustness, time reduced, and precision. The main objective is to distinguish the subject from the background of the image segmentation. As the ordinary image segmentation threshold approach is computerized costly while the necessity for optimization techniques are highly recommended for multi-tier image thresholds. Level object segmentation threshold by using Shannon entropy and Fuzzy entropy maximized with hGSA-PS. An entropy maximization of hGSA-PS dependent multilevel image thresholds is developed, where the results are best demonstrated in PSNR, misclassification, structural similarity index and segmented image quality compared to the Firefly algorithm, adaptive cuckoo search algorithm and the search algorithm gravitational.

Sub-nanosecond threshold switching dynamics in GeSb2Te4 phase change memory device

Conventional Ge–Sb–Te based phase change memory (PCM) devices offer promising attributes, including fast non-volatile memory operations, higher endurance and sub-ns re-crystallization/re-amorphization capabilities for the next generation high speed non-volatile memory. The threshold switching process in the amorphous phase of the PCM device enables breakdown of electrical resistance followed by rapid flow of device current, leading to Joules heating induced crystallization, known as SET operation. The speed of SET operation is, therefore, governed by voltage dependent threshold switching dynamics and the delay time (td) characteristics at the timescale of nanoseconds. Although GeSb2Te4 offers faster crystal growth velocity, realization of fast threshold switching capabilities remains unexplored. In this work, the ultrafast threshold switching dynamics of a prototypical GeSb2Te4 PCM device are investigated. The present experimental results demonstrate an exponential reduction of td upon increasing the applied voltage (VA) above its threshold voltage (VT). The td has been reduced to a strikingly lower value of 0.5 ns for VA of 1.6 times of VT, which enables faster SET operation within 3 ns as evidenced by a permanent change in the device resistance. These experimental findings of sub-nanosecond threshold switching dynamics and faster SET operation in the GeSb2Te4 device pave a way for designing a PCM device with ns programming speed for future electronics.

Insights on heterogeneity in blinking mechanisms and non-ergodicity using sub-ensemble statistical analysis of single quantum-dots.

Photo-luminescence (P-L) intermittency (or blinking) in semiconductor nanocrystals (NCs), a phenomenon ubiquitous to single-emitters, is generally considered to be temporally random intensity fluctuations between "bright" ("On") and "dark" ("Off") states. However, individual quantum-dots (QDs) rarely exhibit such telegraphic signals, and yet, a vast majority of single-NC blinking data are analyzed using a single fixed threshold which generates binary trajectories. Furthermore, while blinking dynamics can vary dramatically over NCs in the ensemble, the extent of diversity in the exponents (mOn/Off) of single-particle On-/Off-time distributions (P(tOn/Off)), often used to validate mechanistic models of blinking, remains unclear due to a lack of statistically relevant data sets. Here, we subclassify an ensemble of QDs based on the emissivity of each emitter and subsequently compare the (sub)ensembles' behaviors. To achieve this, we analyzed a large number (>1000) of blinking trajectories for a model system, Mn+2 doped ZnCdS QDs, which exhibits diverse blinking dynamics. An intensity histogram dependent thresholding method allowed us to construct distributions of relevant blinking parameters (such as mOn/Off). Interestingly, we find that single QD P(tOn/Off)s follow either truncated power law or power law, and their relative proportion varies over subpopulations. Our results reveal a remarkable variation in mOn/Off amongst as well as within subensembles, which implies multiple blinking mechanisms being operational amongst various QDs. We further show that the mOn/Off obtained via cumulative single-particle P(tOn/Off) is distinct from the weighted mean value of all single-particle mOn/Off, evidence for the lack of ergodicity. Thus, investigation and analyses of a large number of QDs, albeit for a limited time span of a few decades, are crucial to characterize the spatial heterogeneity in possible blinking mechanisms.

Modeling of rigidity dependent CORSIKA simulations for GRAPES-3

The GRAPES-3 muon telescope located in Ooty, India records 4x10^9 muons daily. These muons are produced by interaction of primary cosmic rays (PCRs) in the atmosphere. The high statistics of muons enables GRAPES-3 to make precise measurement of various sun-induced phenomenon including coronal mass ejections (CME), Forbush decreases, geomagnetic storms (GMS) and atmosphere acceleration during the overhead passage of thunderclouds. However, the understanding and interpretation of observed data requires Monte Carlo (MC) simulation of PCRs and subsequent development of showers in the atmosphere. CORSIKA is a standard MC simulation code widely used for this purpose. However, these simulations are time consuming as large number of interactions and decays need to be taken into account at various stages of shower development from top of the atmosphere down to ground level. Therefore, computing resources become an important consideration particularly when billion of PCRs need to be simulated to match the high statistical accuracy of the data. During the GRAPES-3 simulations, it was observed that over 60% of simulated events don't really reach the Earth's atmosphere. The geomagnetic field (GMF) creates a threshold to PCRs called cutoff rigidity Rc, a direction dependent parameter below which PCRs can't reach the Earth's atmosphere. However, in CORSIKA there is no provision to set a direction dependent threshold. We have devised an efficient method that has taken into account of this Rc dependence. A reduction by a factor ~3 in simulation time and ~2 in output data size was achieved for GRAPES-3 simulations. This has been incorporated in CORSIKA version v75600 onwards. Detailed implementation of this along the potential benefits are discussed in this work.

New insights into the threshold behavior of a 9–12% Cr ferritic/martensitic steel – Separation and quantification of crack closure mechanisms

The energy transition and the associated increase in the share of regenerative energies require flexible power plant operation to compensate fluctuations in residual load. As a result of the decreasing dwell times at constant high temperatures, the significance of fatigue damage gains in importance. At present, existing design codes are of limited validity for this new loading scenario. This necessitates the development of adapted design codes based on damage tolerance concepts. For this reason the frequency dependent threshold behavior of the ferritic/martensitic steel X20CrMoV12-1 was investigated in a temperature range from 300 °C to 600 °C. In order to exploit the maximum lifetime of a component without compromising safety, detailed knowledge on active crack closing mechanisms is of elementary importance. Therefore, a general experimental approach for separation and quantification of crack closure mechanisms and their impact on crack propagation threshold values was developed. By this methodology, both the influence of temperature and corrosion on the threshold can be separated and quantified despite superposition of several mechanisms. The only application criterion of this procedure is SR ≪ 1, because roughness induced crack closure has to be negligible small. If roughness induced crack closure cannot be neglected, the methodology developed in this study has to be modified by models which quantify the influence of roughness induced crack closure.

Interaction between leukocyte aldo-keto reductase 1C3 activity, genotypes, biological, lifestyle and clinical features in a prostate cancer cohort from New Zealand.

IntroductionAldo-keto reductase 1C3 (AKR1C3) is known for multiple functions including its catalytic activity towards producing extra-testicular androgen. The present study is towards understanding interaction between biological, lifestyle and genetic impacts of AKR1C3 and their influence on clinical factors in a prostate cancer (PC) cohort from New Zealand (NZ).MethodCharacteristics of 516 PC patients were collected from the Auckland Regional Urology Facility, NZ. These men were genotyped for the AKR1C3 rs12529 single nucleotide polymorphism (SNP). The leukocyte AKR1C3 activity was measured in a sub-cohort. Variability of leukocyte AKR1C3 activity between biological, lifestyle and clinical features as well as correlation between biological and clinical features were assessed with and without genetic stratification.ResultsThe leukocyte AKR1C3 activity was associated with age at diagnosis (0.51 vs 0.34 μM coumberol units for >69y vs ≤69y, P = 0.03); and with anatomic stage/prognostic grouping among the AKR1C3 rs12529 CC genotype carriers (0.50 vs 28 μM coumberol units among low- and high-risk groups respectively, P = 0.02). Significant correlation between leukocyte AKR1C3 activity and age at PC diagnosis was also observed (correlation coefficient 0.20 and P = 0.02). Ever- smoking impacted both age and PSA at PC diagnosis among AKR1C3 rs12529 GG and CG genotype carriers respectively. Age at diagnosis significantly correlated with PSA at diagnosis in the main (correlation coefficient 0.29, and P<0.001) and sub-cohorts (correlation coefficient 0.24, and P = 0.01); and those carrying the AKR1C3 rs12529 CG and GG genotypes in both the main (correlation coefficient 0.30, and P<0.001 and correlation coefficient 0.35, and P<0.001 respectively) and sub-cohorts (correlation coefficient 0.43, and P<0.001 and correlation coefficient 0.39, and P = 0.06 respectively); but not with those carrying the CC genotype.ConclusionsAge dependent PSA thresholds in PC screening could have been valid only in men carrying the AKR1C3 rs12529 CG and GG genotypes in this NZ cohort.

Pressure Induced Nanoparticle Phase Behavior, Property, and Applications.

Nanoparticle (NP) high pressure behavior has been extensively studied over the years. In this review, we summarize recent progress on the studies of pressure induced NP phase behavior, property, and applications. This review starts with a brief overview of high pressure characterization techniques, coupled with synchrotron X-ray scattering, Raman, fluorescence, and absorption. Then, we survey the pressure induced phase transition of NP atomic crystal structure including size dependent phase transition, amorphization, and threshold pressures using several typical NP material systems as examples. Next, we discuss the pressure induced phase transition of NP mesoscale structures including topics on pressure induced interparticle separation distance, NP coupling, and NP coalescence. Pressure induced new properties and applications in different NP systems are highlighted. Finally, outlooks with future directions are discussed.

FFLSD - Fast Fog and Low Stratus Detection tool for large satellite time-series

Fast Fog and Low Stratus Detection (FFLSD) is a processing tool enabling detection of fog and low stratus (FLS) on very large time-series of Meteosat Second Generation data. We combine approaches for FLS detection by day and night into one homogeneous and efficient processing tool. The main unification improvements are: (1) consistent spatial tiling instead of various pixel clustering approaches, (2) uniform generation of sun and viewing angle dependent thresholds for individual tiles, (3) flexible study areas instead of area dependence, (4) parallel raster processing using the Open Computing Language (OpenCL), (5) and efficient algorithms for complex processing steps like histogram generation and analysis.As a result, users are enabled to generate products like long-term FLS climatologies with reasonable resources and short processing times. FFLSD is available as open source and allows reuse and extensions for other tasks.

Cell Cycle Inhibitor Whi5 Records Environmental Information to Coordinate Growth and Division in Yeast

Proliferating cells need to evaluate the environment to determine the optimal timing for cell cycle entry, which is essential for coordinating cell division and growth. In the budding yeast Saccharomyces cerevisiae, the commitment to the next round of division is made in G1 at the Start, triggered by the inactivation of the inhibitor Whi5 through multiple mechanisms. However, how a cell reads environmental condition and uses this information to regulate Start is poorly understood. Here, we show that Whi5 is a key environmental indicator and plays a crucial role in coordinating cell growth and division. We found that under a variety of nutrient and stress conditions, the concentration of Whi5 in G1 is proportional to the doubling time in the environment. Thus, under a poorer condition a longer doubling time results in a higher Whi5 concentration, which in turn delays the next cell cycle entry to ensure sufficient cell growth. In addition, the coordination between division and the environment is further fine-tuned in G1 by environmentally dependent G1 cyclin-Cdk1 contribution and Whi5 threshold at Start. Our results show that Whi5 serves as an environmental ‘memory’ and that the cell adopts a simple and elegant mechanism to achieve an adaptive cellular decision making.

Near-saddle-point-energy photoionization microscopy images of Stark states of the magnesium atom

Photoionization microscopy (PM) is a photoelectron imaging method based on the measurement of the electron current probability density in the case of photoionization of an atom in an external uniform static electric field. The resolution of PM is high enough for observing the quantum oscillatory spatial structure of the outgoing electron flux. We examine the Stark states of the magnesium atom and focus on PM features which are specific to the energy range just above the saddle-point energy. Particularly, the existence of $m$-dependent saddle-point thresholds is clearly demonstrated by following the evolution of the recorded angular distributions with energy. Furthermore, the outer inflection point radii of the radial distributions of the images are generally found to increase with energy monotonically but occasionally abruptly, signaling parabolic channel openings (above which these channels are converted to continua). This observation is in accord with recently reported quantum mechanical PM calculations for hydrogenic systems. More importantly, there are a number of nonmonotonic variations (local maxima) of the outer inflection point. The latter are attributed to the local emergence of an intensity halo at the outer part of the images, a feature relevant to the excitation of quasibound Stark states (resonances). The emergence of the halo for a given resonance is found to depend on the static electric field strength. These observations along with the difficulties in observing resonant effects on the recorded images of nonhydrogenic atoms, such as the medium-size magnesium atom, are discussed in detail.

Onset of magnetic reconnection in a collisionless, high- plasma

In a magnetized, collisionless plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase in the magnetic-field strength in such a plasma thus leads to an increase in the thermal pressure perpendicular to the field lines. Above a$\unicode[STIX]{x1D6FD}$-dependent threshold (where$\unicode[STIX]{x1D6FD}$is the ratio of thermal to magnetic pressure), this pressure anisotropy drives the mirror instability, producing strong distortions in the field lines on ion-Larmor scales. The impact of this instability on magnetic reconnection is investigated using a simple analytical model for the formation of a current sheet (CS) and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a CS in a collisionless plasma, coupled with the low threshold for the mirror instability in a high-$\unicode[STIX]{x1D6FD}$plasma, imply that the geometry of reconnecting magnetic fields can differ radically from the standard Harris-sheet profile often used in simulations of collisionless reconnection. As a result, depending on the rate of CS formation and the initial CS thickness, tearing modes whose growth rates and wavenumbers are boosted by this difference may disrupt the mirror-infested CS before standard tearing modes can develop. A quantitative theory is developed to illustrate this process, which may find application in the tearing-mediated disruption of kinetic magnetorotational ‘channel’ modes.

Robustness of Griffiths effects in homeostatic connectome models

I provide numerical evidence for the robustness of the Griffiths phase (GP) reported previously in dynamical threshold model simulations on a large human brain network with N=836733 connected nodes. The model, with equalized network sensitivity, is extended in two ways: introduction of refractory states or by randomized time-dependent thresholds. The nonuniversal power-law dynamics in an extended control parameter region survives these modifications for a short refractory state and weak disorder. In case of temporal disorder the GP shrinks and for stronger heterogeneity disappears, leaving behind a mean-field type of critical transition. Activity avalanche size distributions below the critical point decay faster than in the original model, but the addition of inhibitory interactions sets it back to the range of experimental values.

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Nanostructured TiO2 and graphene-based materials constitute components of actual interest in devices related to solar energy conversion and storage. In this work, we show that a thin layer of electrochemically reduced graphene oxide (ECrGO), covering nanostructured TiO2 photoelectrodes, can significantly improve the photoactivity. In order to understand the working principle, ECrGO/TiO2 photoelectrodes with different ECrGO thicknesses were prepared and studied by a set of photoelectrochemical measurements. Methanol in alkaline conditions was employed as effective hole acceptor probe to elucidate the electronic phenomena in the electrode layers and interfaces. These studies underline the hole accepting properties of ECrGO and reveal the formation of a p-n junction at the interface between ECrGO and TiO2. It is shown for the first time that the resulting space charge region of about 10 nm defines the operational functionality of the ECrGO layer. Films thinner than the space charge region act as hole transport layer (HTL), which efficiently transfers holes to the liquid interface thus leading to enhanced photoactivity. Thicker films however act as hole blocking layer (HBL), resulting in a systematic decrease of the photoactivity. The finding of a thickness dependent threshold value for the operation of ECrGO as HTL and HBL is of general interest for the fabrication of optoelectronic devices with improved performance.

Synchronization of heterogeneous oscillator populations in response to weak and strong coupling

Synchronous behavior of a population of chemical oscillators is analyzed in the presence of both weak and strong coupling. In each case, we derive upper bounds on the critical coupling strength which are valid for arbitrary populations of nonlinear, heterogeneous oscillators. For weak perturbations, infinitesimal phase response curves are used to characterize the response to coupling, and graph theoretical techniques are used to predict synchronization. In the strongly perturbed case, we observe a phase dependent perturbation threshold required to elicit an immediate spike and use this behavior for our analytical predictions. Resulting upper bounds on the critical coupling strength agree well with our experimental observations and numerical simulations. Furthermore, important system parameters which determine synchronization are different in the weak and strong coupling regimes. Our results point to new strategies by which limit cycle oscillators can be studied when the applied perturbations become strong enough to immediately reset the phase.

Rate dependent ductility and damage threshold: Application to Nickel-based single crystal CMSX-4

A phenomenological damage model is proposed to account for the strain rate dependency of the damaging processes at high temperature. Mechanical softening during tertiary creep and monotonic tension are modeled by an isotropic scalar internal variable D, whose evolution is described using a rate damage law dD/dt=⋯ governed by visco-plasticity and accounting for the enhancement by stress triaxiality. A novel rate sensitive damage threshold is introduced in order to reproduce the rate dependency of the onset of damaging processes. Damage evolution is coupled with the visco-plasticity model developed by the same authors for single crystal superalloys and accounting for microstructural evolution (like γ'-rafting and coarsening) in Desmorat et al. (2017). The curves presented in this article are identified at 1050 °C for the Ni base single crystal superalloy CMSX-4 but the proposed rate sensitive threshold modeling can be applied to other alloys showing a rate sensitive damage onset, as for example the single crystal superalloys MC2 but also the polycrystalline aggregate AD 730™.

Diameter dependent threshold voltage modification of resistive state switching in organometallic single nanowire devices (diameter ∼ 10–100 nm)

Reversible electrical resistive state switching (ERSS) and memory effects have been investigated for a wide range of organometallic compounds and device configurations where the underlying mechanism is still not fully explored. We synthesized single nanowires (NWs) of organometallic charge transfer complexes between pre-fabricated electrodes with diameter (d) 10 ≤d≤ 100 nm, and their ERSS properties have been systematically investigated at 300 K, encompassing versatile measurement techniques. The thinnest NW with d ∼ 10 nm switched to its low resistive state with very low applied voltage. It appeared as metallic in the switched state as confirmed by its current-voltage characteristics and temperature (T) dependent resistivity for 100 ≤T≤ 300 K. Supported by a theoretically simulated model, we proposed a possible mechanism for the single metallic filament formation in an almost defect-free 10 nm wire in its switched state considering the migration of metal ions created by a strong electric field between two very closely spaced electrodes. We also experimentally demonstrated that the diameter dependence of the threshold voltage (Vth) for switching follows a power law (Vth∝dδ) which is independent of the electrode configurations, measurement techniques and growth mechanism. The results explained the strategies to engineer the ERSS properties of single NW devices and might be beneficial for further research and development.

Interfacial energy band bending and carrier trapping at the vacuum-deposited MAPbI3 perovskite/gate dielectric interface

We report energy band bending of methylammonium lead halide (MAPbI3) perovskite film in contact with indium-tin-oxide (ITO) surface using photoelectron spectroscopy in air (PESA) and ultraviolet photoelectron spectroscopy (UPS) measurements. MAPbI3 perovskite films were vacuum-deposited using co-evaporation of methylammonium iodide (CH3NH3I, MAI) and lead iodide (PbI2) powders. Using PESA and UPS, the highest occupied molecular orbital levels were measured varying the thickness of the perovskite films. Substantial energy band bending close to the ITO surface was not observed. The vacuum-deposited perovskite films feature ambipolar carrier transport from field effect current measurements. Particularly, the threshold voltage for electron conduction was −20 and 25 V for the forward and reverse gate scans, exhibiting significant current hysteresis. The magnitude of the threshold voltage, far away from zero gate voltage, implies that interface trapping rather than energy band bending dominate the threshold voltage. In other words, perovskite/gate dielectric interface trap states for electrons modulate the magnitude of the threshold voltage. Our work provides insights into the origin of gate voltage dependent threshold voltage in perovskite FETs minimizing the contribution from ion migration based on the observation of ambipolar carrier transport at room temperature for vacuum deposited perovskite films.

Solid-Core Fiber Spectral Broadening at Its Limits

Broadband optical spectra are employed in ultrafast time-resolved studies, seeding of tunable parametric amplifiers, and selectively addressing transitions in absorption spectroscopy. A strong extension of spectral bandwidth is commonly achieved in nonlinear fiber by means of self-phase modulation. In terms of energy scalability and achievable bandwidth, the method is, however, limited by the damage threshold of the core material. Here, we study spectral broadening in four different single-mode normal dispersive photonic crystal fibers length of 8–10 cm. They are pumped by a thin-disk oscillator emitting 250 fs pulses at peak powers close to the critical power of silica. We demonstrate mode-field diameter-dependent broadening factors from 19 to 51, which are obtained at power spectral densities from 200 to 5 mW/nm. We explain the results by a relation between peak power and broadening factor. This will serve as a fiber selection guideline transferable to lasers emitting at wavelengths different from 1030 nm. In addition, we examine to which extend prechirp leads to energy scalability of spectral broadening in solid-core fiber. By contrast to previous reports, we point out that the applicability of the technique is strongly limited through the requirement of bell-shaped input pulses and the pulse duration dependent material damage threshold.

An echo state network algorithm based on recursive least square for electrocardiogram denoising

Electrocardiogram (ECG) is easily submerged in noise of the complex environment during remote medical treatment, and this affects the intelligent diagnosis of cardiovascular diseases. Considering this situation, this paper proposes an echo state network (ESN) denoising algorithm based on recursive least square (RLS) for ECG signals. The algorithm trains the ESN through the RLS method, and can automatically learn the deep nonlinear and differentiated characteristics in the noisy ECG data, and then the network can use these characteristic to separate out clear ECG signals automatically. In the experiment, the proposed method is compared with the wavelet transform with subband dependent threshold and the S-transform method by evaluating the signal-to-noise ratio and root mean square error. Experimental results show that the denoising accuracy is better and the low frequency component of the signal is well preserved. This method can effectively filter out complex noise and effectively preserve the effective information of ECG signals, which lays a foundation for the recognition of ECG signal feature waveform and the intelligent diagnosis of cardiovascular disease.

Nanoserpents: Graphene Nanoribbon Motion on Two-Dimensional Hexagonal Materials.

We demonstrate snake-like motion of graphene nanoribbons atop graphene and hexagonal boron nitride ( h-BN) substrates using fully atomistic nonequilibrium molecular dynamics simulations. The sliding dynamics of the edge-pulled nanoribbons is found to be determined by the interplay between in-plane ribbon elasticity and interfacial lattice mismatch. This results in an unusual dependence of the friction-force on the ribbon's length, exhibiting an initial linear rise that levels-off above a junction-dependent threshold value dictated by the pre-slip stress distribution within the slider. As part of this letter, we present the LAMMPS implementation of the registry-dependent interlayer potentials for graphene, h-BN, and their heterojunctions that were used herein, which provides enhanced performance and accuracy.