Cutoff Region Research Articles

Characterization of compressive fracture strain based on bilinear strain paths

This study proposes the compressive fracture characterization method using bilinear strain paths: pre-tension and compression. Compressive ductile fracture exhibits extremely large strain, which has been regarded as being difficult to be measured. Large deformation under compressive loading makes the shape of a specimen barreled and changes the stress triaxiality rapidly. Due to these complicated and large strains, compressive fracture strain can be considered to be within the so-called cut-off region where no fracture occurs. In order to enable compression tests to be easier, an approach that can lower the range of fracture strain is needed. Uniaxial tensile deformation is a strain path that induces the growth of voids inside ductile materials and leads to ductility reduction. Ductile materials subjected to pre-tensile loading before compressive loading can show the premature compressive fracture. A ductile fracture model capable of predicting the cut-off region is selected for ductile fracture loci of the bilinear paths and implemented into the numerical simulation with different pre-tensile strain levels. The verification of the proposed characterization method is performed by comparing experimental data and simulation results for fractured specimen shapes and load-displacement curves.

A plant based electrochemical device with transistor like behavior

Since its invention, transistor has become the fundamental building block of virtually all of today’s integrated circuits which constitute the electronics technology. In the present letter, we report the vegetal version of a self-powered electrochemical transistor, i.e., a device with an inherent energy source which exhibits energy-converting and amplifying-modulating properties. Surprisingly, at the interface constituted by the surface of an n-type germanium sample and a vegetal slice it become apparent that the surface of the n-type germanium passing anodic current acts as a multiplying collector for holes. Experimental transconductance characteristics show well-defined the cut-off, active and saturation regions. Likewise, since the collector is itself part of an electrolytic cell, device incorporates its own power supply. Thereby, it is able to reproduce an analogical AC signal via the DC electrolytic cell voltage. Furthermore, one of the most outstanding properties of the transistors is their DC current gain (hFE), which for commercially available small-signal transistors typically ranges 50–350, and for medium power transistors 15–70. The proposed device presents an hFE of 70 and 40 for the potato and apple based transistors respectively. Genuinely, this approach opens an alternative route for the development of a novel green electronics based on self-powered vegetative devices. Genuinely, this approach opens an alternative route for the development of a novel green electronics based on self-powered vegetative devices which could works as sensing devices for monitoring living plants during sow and harvest.

Solvent-vapor-triggered crystallization of a ZIF-90 membrane with versatile separation properties towards light hydrocarbons

Membrane separation has been well acknowledged as a forward-looking technology for hydrocarbon separation. Zeolitic imidazole framework-90 (ZIF-90) with effective pore size of 5.0 Å is a promising membrane material for hydrocarbon separation. Owing to the enormous challenges facing the fabrication process, the research on the ZIF-90 polycrystalline membrane is fairly underexplored. Herein we report a solvent-vapor-triggered crystallization strategy for the production of ZIF-90 membranes. The resultant ZIF-90 membrane had a typical polycrystalline membrane structure where the regular ZIF-90 grains propagated inside the whole porous support. Intriguingly, the membrane displayed two obvious sharp cut-off regions falling between the C3H6/C3H8 and n-C4H10/i-C4H10 gas pairs, respectively. The ZIF-90 membrane achieved ultrafast and selective permeation of C3H6 from the C3H6/C3H8 mixture. The C3H6 flux was about 3.4 kg·m−2·h−1 which was comparable to the commercial NaA zeolite membrane for organic solvent dehydration. Further, the distinctive gas transport kinetic nature enabled the ZIF-90 membranes to exclude i-C4H10 and thus harvest unprecedented n-/i-C4H10 separation ability in high-temperature regions. As the temperature elevated from 25 to 150 °C, the n-C4H10 permeance was enhanced from 3.0 × 10−9 to 12 × 10−9 mol·m−2·s−1·Pa−1 and the n-C4H10/i-C4H10 separation factors was improved from 63 to 95, respectively. The high permeance and permselectivity at industrially relevant high temperatures and pressures make ZIF-90 membrane attractive for industrial light hydrocarbon separation.

Optical and Electrical Properties of AlGaN-Based High Electron Mobility Transistors and Photodetectors with AlGaN/AlN/GaN Channel-Stacking Structure.

High channel current of the high electron mobility transistors (HEMTs) and high relative responsivity of the photodetectors (PDs) were demonstrated in the AlGaN/AlN/GaN channel-stacking epitaxial structures. The interference properties of the X-ray curves indicated high-quality interfaces of the conductive channels. The AlGaN/AlN/GaN interfaces were observed clearly in the transmission electron microscope micrograph. The saturation I ds currents of the HEMT structures were increased by adding a number of channels. The conductive properties of the channel-stacking structures corresponded to the peaks of the transconductance (g m) spectra in the HEMT structures. The depletion-mode one- and two-channel HEMT structures can be operated at the cutoff region by increasing the reverse V gs bias voltages. Higher I ds current in the active state and lower current in the cutoff state were observed in the two-channel HEMT structure compared with one- and three-channel HEMT structures. For the channel-stacking metal-semiconductor-metal photodetector structures, the peak responsivity was observed at almost 300 nm incident monochromic light, which was increased by adding a number of channel layers. The channel current of the HEMT devices and the photocurrent in the PD devices were increased by adding a number of two-dimensional electron gas (2DEG) channels. By using a flat gate metal layer, the two-channel AlGaN/AlN/GaN HEMT structures exhibited a high I ds current, a low cutoff current, and a high peak g m value and have the potential for GaN-based power devices, fast portable chargers, and ultraviolet PD applications.

Se4+ doped CsPbX3 (X=Cl/Br, Br, Br/I, I) perovskite quantum dot glasses for long wavelength pass filters with deep energy level quenching mechanism

CsPbX3 (X = Cl/Br, Br, Br/I, I) perovskite quantum dots (QDs) glasses have enormous application potential in the field of long wavelength pass (short wavelength cutoff) filters. In this work, the CsPbX3 (X = Cl/Br, Br, Br/I, I) QDs doped with Se4+ were prepared in the borogermanate glass matrix. To quench strong exciton emission of QDs, the CsPbX3 (X = Cl/Br, Br, Br/I, I) perovskite QDs glasses were doped with Se4+ at different concentrations of 0, 0.05 %, 0.1 % and 0.2 %, respectively. The nanocrystal structure, transmittance, optical density, photoluminescence (PL), PL excitation and PL decay have been investigated. The working wavelength of filters has been extended to wide range from 440 nm to 650 nm. The samples have large optical density in cutoff region, excellent steepness in the transition region, and high transmittance in transmission region. As Se4+ concentration increases, the PL intensity is quenched and the PL lifetime is decreased obviously for CsPbX3 QDs glasses, whereas the absorption and transmittance characteristics for filters are less affected. The quenching mechanism is attributed to nonradiative recombination by deep energy level traps. The Se4+ doped CsPbX3 QDs glasses can meet requirements for the long wavelength pass filters.

A 43.5dB Gain Unipolar a-IGZO TFT Amplifier with Parallel Bootstrap Capacitor for Bio-signals Sensing Applications.

In this paper, a high gain amplifier with phase compensation loop is presented. A structure of parallel gate cross-coupled transistors to both ends of differential pair drain and source is designed to improves the load impedance, which obtains sufficient gain and further reduces power consumption. A novel capacitor bootstrap load circuit is proposed. The capacitor bootstrap topology is constructed by the drain source resistance of the transistor working in the cut-off region, where the gate source parasitic capacitor of the transistor is in parallel with the bootstrap capacitor rather than the existing series structure, thereby only a small bootstrap capacitor is required. By avoiding the use of large capacitors, chip area can be effectively reduced without compromising performance such as gain and bandwidth. The amplifier is fabricated using 10-μm n-type a-IGZO TFT technology. Measurement results show that the proposed amplifier achieves a voltage gain of 43.5dB and a common mode rejection ratio of 61.2dB while maintaining low power consumption. The amplifier also exhibits a -3dB bandwidth covering 0.4~2.1KHz, encompassing major bioelectric frequency bands. A real-time ECG signal was successfully captured using the fabricated TFT amplifier and gel electrodes. It has great potential in flexible sensing and acquisition applications such as electro cardiogram (ECG), electro encephalogram (EEG), pulse detection, and other wearable applications.

A Convolutional-Transformer Model for FFR and iFR Assessment From Coronary Angiography.

The quantification of stenosis severity from X-ray catheter angiography is a challenging task. Indeed, this requires to fully understand the lesion's geometry by analyzing dynamics of the contrast material, only relying on visual observation by clinicians. To support decision making for cardiac intervention, we propose a hybrid CNN-Transformer model for the assessment of angiography-based non-invasive fractional flow-reserve (FFR) and instantaneous wave-free ratio (iFR) of intermediate coronary stenosis. Our approach predicts whether a coronary artery stenosis is hemodynamically significant and provides direct FFR and iFR estimates. This is achieved through a combination of regression and classification branches that forces the model to focus on the cut-off region of FFR (around 0.8 FFR value), which is highly critical for decision-making. We also propose a spatio-temporal factorization mechanisms that redesigns the transformer's self-attention mechanism to capture both local spatial and temporal interactions between vessel geometry, blood flow dynamics, and lesion morphology. The proposed method achieves state-of-the-art performance on a dataset of 778 exams from 389 patients. Unlike existing methods, our approach employs a single angiography view and does not require knowledge of the key frame; supervision at training time is provided by a classification loss (based on a threshold of the FFR/iFR values) and a regression loss for direct estimation. Finally, the analysis of model interpretability and calibration shows that, in spite of the complexity of angiographic imaging data, our method can robustly identify the location of the stenosis and correlate prediction uncertainty to the provided output scores.

Enhancing harmonic brightness near the cutoff region by using laser pulses with a small positive chirp.

Efficient enhancement of harmonic brightness near the cutoff region is achieved by employing laser pulses with a small positive chirp in theory, where the laser intensity and frequency near the peak of the laser pulse are almost unchanged relative to the chirp-free field. The improvement of harmonic brightness is achieved under the condition that the ionization probability is almost unchanged. Through the analysis of the harmonics contributed by the rising and falling parts of the laser pulse, we have uncovered a "frequency compensation" mechanism that leads to an enhanced harmonic brightness near the cutoff region. Under appropriate chirp parameters, the harmonics contributed by the rising and falling parts can be constructively interfered in a smaller frequency range with greater intensity, thereby obtaining harmonics with good monochromaticity and high brightness. This study explains the mechanism of harmonic brightness enhancement from a new perspective, and provides a new idea for harmonic regulation without changing the ionization.

Multiphonon scattering formula of dynamic structure factors for classical Debye solids.

A semianalytic formula of the dynamic structure factor S(k,ω) for classical Debye solids over the entire wave-number (k) and frequency (ω) range is constructed by taking into account multiphonon thermal diffuse scattering up to infinite order. The formula adopts Gaussian approximations to the spatial and time decay of the multiphonon part of the displacement correlation function. Numerical illustrations for isotropic polycrystals reveal that, as k increases, sharp peaks due to one-phonon normal scattering in the hydrodynamic regime (k→0) are replaced by diffuse spectra consisting of umklapp scattering and multiphonon continuum; approach toward the ideal-gas spectra in the large-k limit is proven from analytic properties of the multiphonon term. When k coincides with a Bragg reflection point, total thermal diffuse scattering S_{TDS}(k,ω) exhibits a 1/ω divergence as ω→0, which in turn gives rise to a logarithmic enhancement of the corresponding static structure factor S_{TDS}(k). Overall accuracy of the theory is confirmed through the exact zeroth-order frequency-moment sum rule between S_{TDS}(k,ω) and S_{TDS}(k); agreement with the second-order sum rule is shown to be satisfactory except for the vicinity of the Debye cutoff region.

Ductile fracture of LYP225 steel: Effects of stress states and loading histories

This paper presents the experimental and modeling studies of the ductile fracture initiation of LYP225 steel, considering the stress state and loading history dependency. The monotonic material tests, including the notched round bars (NRBs), flat grooved plates (FGPs), and the shear plates (SPs), confirm the prominent stress state dependency of the ductile fracture. The increased stress triaxiality will significantly reduce the fracture strain, and the shear effect quantified by the Lode angle parameter will degrade the deformability under similar triaxiality. The Hosford-Coulomb fracture criterion can well characterize the relationship between fracture strain and stress state variables. Regarding the cyclic loading, a generalized expression of the cut-off region is proposed to consider the temporarily frozen damage accumulation under compression applied. In addition, the premature cyclic fracture initiation predicted by the monotonic fracture criterion highlights the necessity of considering the loading history effect. Based on the plastic strain memory surface, a reduced factor is introduced for the lower damage accumulation rate under cyclic loading. By comparing the testing and predicted plastic deformation corresponding to fracture initiation, the proposed fracture model is validated under different stress states and loading protocols, as indicated by the low average percentage errors of 4.02% for monotonic loading and 16.7% for cyclic loading.

Tunability of Half Cycle Cutoff Harmonics with Inhomogeneously Enhanced Laser Pulse

For homogeneous driving, half cycle harmonics and its corresponding half cycle cutoff (HCO) show prominent spectral features, allowing one to produce an isolated attosecond pulse with suitable filtering, or vice versa the retrieval of the driving pulse itself. The temporal profile and spatial dependence of the inhomogeneously enhanced field are two important factors that determine the high harmonic generation (HHG) near a plasmonic nanostructure. This leads us to the question of how the HHG spectra and, in particular, the corresponding half cycle harmonics modify with different types of inhomogeneously enhanced fields. To elucidate this, we have made a comparative study of the HHG in three different types of inhomogeneously enhanced laser pulses by employing the time-dependent Schrödinger equation in one dimension. Within our chosen parameter range, the HCO in cutoff and mid-plateau regimes shift towards higher order with the increase of strength of the inhomogeneity in isotropic case. In anisotropic inhomogeneity, the cutoff HCO shifts towards the higher order but the mid-plateau HCO shifts towards lower order with the increase of strength of inhomogeneity. With increasing carrier envelope phase (CEP), the enhanced HCO in the lower-order harmonic region shifts towards higher orders. This shift is nearly linear from near the above threshold to mid-plateau region and becomes saturated in the near cutoff region. The harmonic spectra is modulo-π periodic for the isotropic inhomogeneity and it is modulo-2π periodic for the anisotropic inhomogeneity. This extension of periodicity increases the tunability of the enhanced HCO harmonics with CEP in the anisotropic inhomogeneity than the CEP tuning of the HCO harmonics in the isotropic inhomogeneity or vice versa the retrieval of CEP.

Wind Resource Assessment over the Hellenic Seas Using Dynamical Downscaling Techniques and Meteorological Station Observations

The current work focuses on establishing the parameters that influence the wind’s behavior over the Aegean and Ionian Seas and estimating the wind potential in the region based on long-term historic climate data. Combining a downscaling technique performed with the well-founded WRF-ARW computational algorithm and a number of simultaneous meteorological station time series, an attempt is made to investigate how regional changes may affect low-altitude wind speed distribution at hub height (100 m a.s.l.). The provided time-series coastal data span the entire region of interest from north to south. WRF-ARW v.3.9 is utilized to associate the geostrophic wind distribution obtained from long-term Copernicus ERA5 wind data with the localized wind potential over lower altitudes. Evaluation and correlation of the observational data to the predicted wind climate are performed, and the statistical differences that arise are investigated. High-accuracy wind resource potential maps are thus obtained in the region. Also, a few distinctive flow patterns are identified, such as wind speed cut-off regions and very high wind speed distributions, which are presented in specific southern regions of the Aegean Sea.

Frequency-Scanning Leaky-Wave Array Antenna With Extended Scanning Range for Millimeter-Wave Imaging

In this letter, we propose a frequency scanning leaky-wave array antenna with a significantly increased scanning range. The proposed structure consists of a pair of rectangular waveguide fed leaky-wave slot array antennas that are designed to achieve focusing in the backward and forward quadrants at 26.5 GHz and 23 GHz respectively. A total scanning range of about 73˚ is achieved by the structure simply by changing the frequency. The focusing gain between the backward and forward quadrants varies from 23 dBi to 25 dBi with the operation of the two waveguides separated by exploiting the cutoff region of one waveguide, operating with negative phase constant, and the endfire radiation of the other waveguide, operating with a positive phase constant, allowing the use of a single feed for both waveguides.

Improving the accuracy for amplitude and frequency of analytical equation of single-ended ring oscillators based on circuit and transistor parameters

PurposeThis paper aims to find a closed-form expression for the frequency and amplitude of single-ended ring oscillators when transistors experience all regions.Design/methodology/approachIn this paper, the analytical relationships presented for ring oscillator amplitude and frequency are approximately derived due to the nonlinear nature of this oscillator, taking into account the differential equation that governs the ring oscillator and its output waveform.FindingsIn the case where the transistors experience the cut-off region, the relationships presented so far have no connection between the frequency and the dimensions of the transistor, which is not valid in practice. The relationship is presented for the frequency, including the dimensions of the transistor. Also, a simple and approximately accurate relationship for the oscillator amplitude is provided in this case.Originality/valueThe validity of these relationships has been investigated by analyzing and simulating a single-ended oscillator in 0.18 µm technology.

Automatic Street Light Control System

Abstract: Automatic Street Light Control System is a simple yet powerful concept, which uses transistor as a switch. By using this system manual works are 100% removed. It automatically switches ON lights when the sunlight goes below the visible region of our eyes. This is done by a sensor called infrared sensor (IR) which senses the light actually like our eyes. It automatically switches OFF lights whenever the sunlight comes, visible to our eyes. By using this system energy consumption is also reduced because nowadays the manually operated street lights are not switched off even the sunlight comes and also switched on earlier before sunset. In this project, no need of manual operation like ON time and OFF time setting. This project clearly demonstrates the working of transistor in saturation region and cut-off region.

A 38.5-fJ 14.4-ns Robust and Efficient Subthreshold-to-Suprathreshold Voltage-Level Shifter Comprising Logic Mismatch-Activated Current Control Circuit

This brief presents a robust and energy-efficient voltage level shifter (VLS) for wide-range conversion from the subthreshold to the suprathreshold regime. The proposed VLS contains a new logic mismatch detection circuit to address the exist contention current of the conversion stage. A power reducer circuit is introduced to increase the drivability of pull-up and pulldown devices in linear and cut-off regions and further energyconsuming improvement. The proposed VLS is simulated using a 0.18-lm process, the minimal convertible voltage is 0.2 V (deep subthreshold region) for the input signal. Post-layout simulation considering process voltage temperature (PVT) variations proves the proposed VLS outperforms previous designs in several aspects. The results report the consuming energy of 38.5 fJ per transition, a static power of 73.4 pW, and a delay of 14.4 ns when converting range is 0.4 V to 1.8 V. The proposed VLS occupies a 59.98-lm2 silicon area.

Automatic Street Light On and Off Using LDR

Abstract: Automatic Street Light Control System is a simple yet powerful concept, which uses transistor as a switch. By using this system manual works are 100% removed. It automatically switches ON lights when the sunlight goes below the visible region of our eyes. This is done by a sensor called Light Dependant Resistor (LDR) which senses the light actually like our eyes. It automatically switches OFF lights whenever the sunlight comes, visible to our eyes. By using this system energy consumption is also reduced because nowadays the manually operated street lights are not switched off even the sunlight comes and also switched on earlier before sunset. In this project, no need of manual operation like ON time and OFF time setting. This project clearly demonstrates the working of transistor in saturation region and cut-off region. The working of relay is also known.

Experimental observations of communication in blackout, topological waveguiding and Dirac zero-index property in plasma sheath

Abstract The plasma sheath causes the spacecraft’s communication signal to attenuate dramatically during the re-entry period, which seriously threatens the astronauts. However, valid experimental protocols have not been obtained hitherto. To realize the propagation of electromagnetic waves in negative permittivity background of the plasma sheath, alumina columns are embedded in the plasma background to form plasma photonic crystals, which can support the coupling of evanescent waves between the alumina columns. We experimentally demonstrate the realization of communication in blackout scenario by achieving a complete passing band in the plasma cutoff region. For high frequency communications in the plasma sheath, electromagnetic wave propagation based on topological edge states is also experimentally demonstrated. Furthermore, we realize a triply-degenerate Dirac cone formed dynamically at the center of the Brillouin zone by modulating the electron density, where electromagnetic wave exhibits high transmittance and does not experience phase accumulation at the Dirac point. Our work thus not only provides an effective approach to overcome the communication blackout problem, but the design can also be served as a promising experimental platform to explore topological electromagnetic phenomena.

Improving the Accuracy for Amplitude and Frequency of Analytical Equation of Single-ended Ring Oscillators Based on Circuit and Transistor Parameters

The analytical relationships presented for amplitude and frequency of the ring oscillator are derived approximately due to the nonlinear nature of this oscillator. In the case where the transistors experience the cut-off region, the relationships presented so far have no connection between the frequency and the dimensions of the transistor, which is not valid in practice. In this paper, considering the circuit’s governing equation and the ring oscillator’s output waveform, a relation for the frequency is presented, including the dimensions of the transistor. Also, a simple and approximately accurate relationship for the oscillator amplitude is provided in this case. The validity of these relationships has been investigated by analyzing and simulating a single-ended oscillator in 0.18μm technology.

Generation and application of four-wave mixing in collinear high harmonic generation

We describe a thorough study of the wave-mixing procedure in the extreme ultraviolet (XUV) region involving three laser fields (800 nm, 1400 nm and 1860 nm). In addition to the phase matched HHG spectrum generated by an 800-nm laser (driving field), non-integer order wave-mixing spectra are produced when the driving field and the control field (1400 nm or 1860 nm) are collinearly focused into krypton gas. In addition, the simultaneous presence of three laser fields generates resolvable four-wave mixing (FWM) frequencies that clearly indicate the contribution of each control field. We also discuss an application of the FWM scheme to extend the HHG cutoff region and generate the XUV quasi-continuum spectrum.