Saturation Region Research Articles

Modeling and Online Adaptation of ALOHA for Low-Power Wide-Area Networks (LPWANs)

Unslotted ALOHA protocol has been adopted as a channel access mechanism in commercial low-power wide-area networks (LPWANs), such as Sigfox and long-range (LoRa) alliance. This work examines the throughput and random access (RA) delay distribution of unslotted ALOHA systems by considering exponential random backoff (ERB) or uniform random backoff (URB) algorithm. We further characterize the operating region of the systems as unsaturated stable, bistable, and saturated regions in terms of the new packet arrival and retransmission rates. To run the system stably with the maximum throughput, we propose a Bayesian online backoff algorithm that estimates the number of backlogged devices. Its performance is compared with other algorithms, such as particle filter (PF)-based algorithm, binary exponential backoff (BEB) algorithm, and the algorithm of exploiting exact backlog size information. Through extensive simulations, it is demonstrated that the performance of the proposed algorithm is very close to the upper bound and robust to time-varying traffic condition.

Hierarchical Model Predictive Control for Autonomous Collision Avoidance of Distributed Electric Drive Vehicle with Lateral Stability Analysis in Extreme Scenarios

This paper proposes an active collision avoidance controller based on a hierarchical model predictive control framework for distributed electric drive vehicles (4IDEV) considering extreme conditions. In this framework, a two-layer strategy is developed. The upper layer is the path replanning controller based on nonlinear MPC (nMPC), from which a collision-free path including the optimal lateral displacement and yaw angle can be obtained in real-time while encountering the obstacles. The lower layer is the path tracking controller based on hybrid MPC (hMPC), and the coordinated control inputs (yaw moment and the front wheel steering angle) are solved by a Mixed-Integer Quadratic Programming (MIQP) with the piecewise affine (PWA) tire model considering tire saturation region. Moreover, to improve the lateral stability when tracking, the stable zone of lateral stability in the high-risk condition is analyzed based on the phase portrait method, by which the constraints of vehicle states and inputs are derived. The verification is carried out on the MATLAB and CarSim co-simulation platform, and the simulation results show that the proposed active collision avoidance controller can track the reference path accurately and prevent vehicle instability in extreme scenarios.

Deep Kronecker neural networks: A general framework for neural networks with adaptive activation functions

We propose a new type of neural networks, Kronecker neural networks (KNNs), that form a general framework for neural networks with adaptive activation functions. KNNs employ the Kronecker product, which provides an efficient way of constructing a very wide network while keeping the number of parameters low. Our theoretical analysis reveals that under suitable conditions, KNNs induce a faster decay of the loss than that by the feed-forward networks. This is also empirically verified through a set of computational examples. Furthermore, under certain technical assumptions, we establish global convergence of gradient descent for KNNs. As a specific case, we propose the Rowdy activation function that is designed to get rid of any saturation region by injecting sinusoidal fluctuations, which include trainable parameters. The proposed Rowdy activation function can be employed in any neural network architecture like feed-forward neural networks, Recurrent neural networks, Convolutional neural networks etc. The effectiveness of KNNs with Rowdy activation is demonstrated through various computational experiments including function approximation using feed-forward neural networks, solution inference of partial differential equations using the physics-informed neural networks, and standard deep learning benchmark problems using convolutional and fully-connected neural networks.

Investigation of the Persistence Conductivity and Photoelectric Characteristics in Detectors with Interdigital Electrodes Based on β‐Ga2O3

Herein, the electrical and photoelectric characteristics of solar‐blind UV detectors based on β‐Ga2O3 films with interdigital electrodes are presented. The sensors with interdigital electrodes have interelectrode spacing d = 5, 10, 30, and 50 μm. The structures exhibit high sensitivity to ultraviolet radiation with a wavelength of λ = 254 nm. The detectors with the smallest interelectrode spacing (5 μm) demonstrate the highest photocurrent value. The detectors have a saturation region on the current–voltage characteristics under UV irradiation, which shifts to the region of lower voltages with decreasing interelectrode spacing. A mechanism to explain the presence of the saturation region on the I–V characteristic is proposed. The sensors exhibit high value of a persistence photoconductivity, which decreases exponentially with an estimated value of the time constant t 1 = 59–63 s.

Extension of a Group Contribution Method to Predict Viscosity Based on Momentum Transport Theory Using a Modified Peng–Robinson EoS

In this work, a semitheoretical model based on the momentum transport theory is generalized through the development of a group contribution method. Viscosity data for temperatures between 13.95 and 950 K and pressures from 1.00 × 10–3 bar up to 1.00 × 104 bar were used to develop and to validate the model. To perform viscosity calculations, the model requires density and residual enthalpy that were obtained from a modified Peng–Robinson equation of state. Also, the model has one adjustable parameter that can be estimated form the group contribution method. Viscosity was calculated for 256 substances including 95 non-polar and 161 polar compounds. In total, 23 organic families were considered. Average deviations below 6.67% were calculated. The performance of the model was compared with those of other models reported in the literature. Calculations were carried out to include the saturation and single-phase regions. In general, it can be considered that the proposed model describes viscosity adequately using only one adjustable parameter.

Analysis of zero-temperature coefficient behavior on vertically stacked double nanosheet nMOS devices

This work presents an experimental study of the zero-temperature coefficient (ZTC) bias point of vertically stacked gate-all-around (GAA) double nanosheet nMOS devices (GAA-NS) for different dimensions, operating in linear and saturation regions. The experimental data is also compared to a simple analytical ZTC model in order to better understand which electrical parameters impact the ZTC behavior. The variation of the threshold voltage with the temperature (ΔVTH/ΔT) and temperature transconductance degradation factor (c) are the two important aspects that most impact the gate to source voltage at ZTC (VZTC). Although the ZTC behavior of the GAA-NS nMOS devices studied in this paper is well described by the simple analytical ZTC model in linear region, at high drain bias, factors such as series resistance and carrier saturation velocity play a significant influence in the ZTC performance of GAA-NS nMOS devices examined in this study.

ROLE OF THE THIRD MISSION OF THE BRANCH UNIVERSITY IN THE DEVELOPMENT OF THE REGIONAL ECONOMY

Subject. The problem of the development of the regional economy is of great importance for all participants living and working within the borders of the territory. Each subject of the ecosystem should contribute to the development of the region in proportion to financial stability, receiving image and investment bonuses. In this article, the algorithm of the influence of the branch university on the rate of improvement of the welfare of the population in the Omsk region is considered. In the article, the authors prove the hypothesis that the achievements of university science are a key factor in the development of the region in the conditions of a new knowledge economy and limited human and financial resources. Methodology. Methods of induction and deduction, analysis and generalization were used in the process of studying the problem of the development of the regional economy. Results. Five global trends were identified for the development of higher education and science at Omsk State Agrarian University named after P.A. Stolypin. Project competencies have been developed – both traditional and expected, as well as frontier development of IT solutions. The desire for collaboration with other organizations and the creation of an effective ecosystem of external relations is proved. The course of implementation of “digital” projects at Omsk State Agrarian University named after P.A. Stolypin is analyzed. Conclusions. It is concluded that a collaborative approach to the interaction of all institutions within the regional economy is applicable for an industrially saturated region, will effectively solve the issue of national environmental and food security, will become a new vector of development.

Deposition and Characterization of Innovative Bulk Heterojunction Films Based on CuBi2O4 Nanoparticles and Poly(3,4 ethylene dioxythiophene):Poly(4-styrene sulfonate) Matrix

This work presents the deposition and study of the semiconductor behavior of CuBi2O4 nanoparticles (NPs) with an average crystallite size of 24 ± 2 nm embedded in poly(3,4 ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) films. The CuBi2O4 NP bandgap was estimated at 1.7 eV, while for the composite film, it was estimated at 2.1 eV, due to PEDOT:PSS and the heterojunction between the polymer and the NPs. The charge transport of the glass/ITO/PEDOT:PSS-CuBi2O4 NP/Ag system was studied under light and dark conditions by means of current–voltage (I–V) characteristic curves. In natural-light conditions, the CuBi2O4 NPs presented electric behavior characterized by three different mechanisms: at low voltages, the behavior follows Ohm’s law; when the voltage increases, charge transport occurs by diffusion between the NP–polymer interfaces; and at higher voltages, it occurs due to the current being dominated by the saturation region. Due to their crystalline structure, their low bandgap in films and the feasibility of integrating them as components in composite films with PEDOT:PSS, CuBi2O4 NPs can be used as parts in optoelectronic devices.

AlGaN/GaN HEMT pH Sensor Simulation Model and Its Maximum Transconductance Considerations for Improved Sensitivity

In this work, AlGaN/GaN high electron mobility transistor (HEMT) pH sensing simulation model is presented along with the sensitivity analysis to different pH values of an electrolyte by considering charged adsorbates systematically. Investigations were performed by studying the effect of pH values on device transfer characteristics and a smooth operation is observed with good pH resolution. The output current sensitivity is analyzed from both linear and saturation regions highlighting the response obtained at different drain bias. The device intricacies and sensing mechanism is also explained and demonstrated by analyzing the channel conductance, conduction band, potential profile and coupling capacitance along with the charge distribution profile at various interfaces using ATLAS Silvaco device simulation tool. The pH of solution is modelled by incorporating charged adsorbates as interface charge density at oxide-semiconductor interface in HEMT for the first time to best of our knowledge. The voltage sensitivity (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sub> ) of 110 mV/pH was observed which is ~2 times beyond Nernst limit of sensitivity (59 mV/pH) and the current sensitivity (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</sub> ) is 17 mA/mm/pH which is 3 orders higher than silicon based devices. The effects of region of operation is also reported with a maximum upto 8 times higher sensitivity being observed in terms of maximum transconductance (g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) considerations and a near zero maximum g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> was found to be optimum condition for higher sensitivity operation in reference electrode free configuration. Therefore high sensitive response along with better biocompatibility of AlGaN/GaN HEMT paves its way in next generation biosensing applications.

Movement Aware Smart Street-lights for Efficient Energy Utilisation

Now a days, energy is an essential resource as the number of energy resources are sinking day by day. Movement Aware Smart Street light is a simple yet powerful concept, which uses transistor as a switch and replaces the manual system. It instantly switches the lights ON when the sunlight goes below the visible region. As energy is the scarcest source, this requires finding innovative ways to use it efficiently. Big cities consume a large amount of electricity and it is required to save energy by operating the street-lights at the time of need. In this paper, an effective method of street-light operation is presented which detects the sun set and sun rise alongside detection of vehicle movement on roads to utilise the energy only when it is required. Furthermore, a system is proposed which reduces energy consumption by replacing manually operated street-lights as they are not switched OFF even the sunlight appears and also switched ON earlier before sunset. The proposed mehtod has saved the municipal utility budget by 35% - 45% through energy saving. This paper also discussed the elimination of manual operation like ON time and OFF time setting and clearly demonstrates the working of transistor in saturation region and cut-off region.

HPA Linearization for Next Generation Broadcasting Systems With Fast Convergence-Digital Predistortion

The Last decade saw significant growth in the digital terrestrial television (DTT) subscribers. The High peak-to-average power ratio (PAPR) of the transmitted signal is implied by the large fluctuations in its amplitude, which is a serious issue in the contemporary and next generation DTT broadcasting systems. These large fluctuations prevent feeding the high power amplifier (HPA) at an operating point near its non-linear (NL) saturation region, thereby lowering its power efficiency. For a better future, energy-efficient green communications is the need of hour. This paper focuses on digital predistortion (DPD), which is among the widely used techniques for HPA linearization in order to minimize the NL effects. DPD technique requires a feedback signal. This paper proposes a novel adding signal-based digital predistortion, where the output of the HPA is gradually linearized by adding a signal at the input in an iterative manner. By Taylor series approximation, the DPD problem can be posed as a convex one. We prove that a tighter upper bound exists for the convergence factor and instead of directly solving the convex problem, we pick a convergence factor value within its bounds that offers a good trade-off between convergence speed and residual error value. The simulation results show that the proposed technique can quickly linearize the HPA with good convergence.

Detection of the initial region of the current transformer core saturation

In the first part of the paper the detailed analysis of the existing current transformer (CT) saturation detection methods with their classification is presented. A new saturation detection method has been proposed in second part of the paper. Mathematical description of the method is given. In the next section of the paper a CT model with test scheme is presented. To identify the reliability of proposed method against nose and remanent flux density experiments have been produced in the fourth section. Comparative analysis between proposed and existing methods is also given. Finally, in conclusion a detailed description of the method is given regarding its behavior with respect to remanent flux and noise

Observation of source/drain bias-controlled quantum transport spectrum in junctionless silicon nanowire transistor

We investigate the influence of source and drain bias voltages (V DS) on the quantum sub-band transport spectrum in the 10-nm width N-typed junctionless nanowire transistor at the low temperature of 6 K. We demonstrate that the transverse electric field introduced from V DS has a minor influence on the threshold voltage of the device. The transverse electric field plays the role of amplifying the gate restriction effect of the channel. The one-dimensional (1D)-band dominated transport is demonstrated to be modulated by V DS in the saturation region and the linear region, with the sub-band energy levels in the channel (E channel) intersecting with Fermi levels of the source (E fS) and the drain (E fD) in turn as V g increases. The turning points from the linear region to the saturation region shift to higher gate voltages with V DS increase because the higher Fermi energy levels of the channel required to meet the situation of E fD = E channel. We also find that the bias electric field has the effect to accelerate the thermally activated electrons in the channel, equivalent to the effect of thermal temperature on the increase of electron energy. Our work provides a detailed description of the bias-modulated quantum electronic properties, which will give a more comprehensive understanding of transport behavior in nanoscale devices.

Performance Optimization of Analog Circuits in Negative Capacitance Transistor Technology

Negative Capacitance Field-Effect Transistor (NC-FET) is one of the emerging technology for the future ultra-low power circuits. NC-FET incorporates a ferroelectric layer within the transistor gate stack, which provides an internal voltage amplification. However, Negative Differential Resistance (NDR), which occurs at thick ferroelectric can deteriorate NC-FET devices in which the drain current, in the saturation region, decreases with drain voltage increase. This noticeably harms the figure of merits of circuits, especially when it comes to analog applications.This work presents a detailed analysis on the correlation between ferroelectric thickness and NDR effects using well-calibrated TCAD infrastructure for 14 nm FDSOI. For the first time, a novel extension length modulation technique is proposed to mitigate NDR effects effectively. Our technique allows designers to optimize the combination of ferroelectric thickness and extension length in which NDR effects are well suppressed, thereby maximizing the performance and gain of analog circuits.

Dicyano-Imidazole: A Facile Generation of Pure Blue TADF Materials for OLEDs.

A series of dicyano-imidazole-based molecules with thermally activated delayed fluorescence (TADF) properties were synthesized to obtain pure blue-emitting organic light-emitting diodes (OLEDs). The targeted molecules used dicyano-imidazole with a short-conjugated system as the electron acceptor to strong intermolecular π-π interactions, and provide a relatively shallow energy level of the lowest unoccupied molecular orbital (LUMO). The cyano group was selected to improve imidazole as an electron acceptor due to its prominent electron-transporting characteristics. Four different electron donors, that is, 9,9-dimethyl-9,10-dihydroacridine (DMAC), 10H-spiro(acridine-9,9'-fluoren) (SPAC), and 9,9-diphenyl-9,10-dihydroacridine (DPAC), were used to alternate the highest occupied molecular orbital (HOMO) energy level to tune the emission color further. The crowded molecular structure in space makes the electron donor and acceptor almost orthogonal, reducing the energy gap (ΔEST ) between the first excited singlet (S1 ) and the triplet (T1 ) states and introducing significant TADF property. The efficiencies of the blue-emissive devices with imM-SPAC and imM-DMAC obtained in this work are the highest among the reported imidazole-based TADF-OLEDs, which are 13.8 % and 13.4 %, respectively. Both of Commission Internationale de l'Eclairage (CIE) coordinates are close to the saturated blue region at (0.17, 0.18) and (0.16, 0.19), respectively. Combining these tailor-made TADF compounds with specific device architectures, electroluminescent (EL) emission from sky-blue to deep-blue could be achieved, proving their great potential in EL applications.

Fabrication and Characterization of In0.9Ga0.1O EGFET pH Sensors

In this study, the In0.9Ga0.1O sensing membrane were deposited by using the RF magnetron sputtering at room temperature and combined with commercial MOSFETs as the extended gate field effect transistor (EGFET) pH sensors. The sensing performance of the In0.9Ga0.1O EGFET pH sensors were measured and analyzed in the pH value of range between 2 to 12. In the saturation region, the pH current sensitivity calculated from the linear relationship between the IDS and pH value was approximately 56.64 μA/pH corresponding to the linearity of 97.8%. In the linear region, the pH voltage sensitivity exhibited high sensitivity and linearity of 43.7 mV/pH and 96.3%, respectively. The In0.9Ga0.1O EGFET pH sensors were successfully fabricated and exhibited great linearity. The analyzed results indicated that the In0.9Ga0.1O was a robust material as a promising sensing membrane and effectively used for pH sensing detection application.

Impact Phenomena of Metallic Microparticles under Breakdown Voltages in Vacuum Interrupters

This paper studies the impact phenomena of the metallic microparticles with the vacuum gap in the range of 10–50 mm under different breakdown voltages in vacuum interrupters. The results show that for the vacuum gap 10–40 mm, the average impact velocities of the microparticles increase linearly with the increase of the vacuum gap, and the impact could damage the cathode surface, which would cause irregularities and give high local field enhancement, finally it may lead to vacuum breakdown. For the vacuum gap 40–50 mm, the average impact velocities of the microparticles are thought to enter the saturation region and remain nearly constant. The impact could cause more metal vapor, which may lead to developing gradually into the vacuum breakdown. Furthermore, the materials with the higher yield stress will cause more obvious fractures and broken phenomena on the edge of the craters, which would have an influence on the vacuum breakdown.

Moisture Distribution during Water Absorption of Ordinary Portland Cement Mortars Obtained with Low-Field Unilateral Magnetic Resonance.

Moisture distribution in cement-based materials is important from the durability point of view. In the present study, a portable three-magnet array with an elliptical surface radio frequency coil was used to undertake magnetic resonance measurements of moisture content in ordinary Portland cement mortar and concrete samples. Measurements along the length of the samples during capillary water absorption produced moisture content profiles that were compared with reference profiles acquired using a magnetic resonance imaging instrument. Profiles obtained with the three-magnet array were similar in shape and in penetration depth to those acquired with magnetic resonance imaging. The correlation coefficient between the moisture content measured with both techniques was r2 = 0.97. Similar values of saturated permeability of the mortars with identical w/c ratio were computed with the Hydrus 1D software based on the moisture content profiles. Additionally, inverse Laplace transformation of the signal decays provided the water-filled pore size distribution in saturated and unsaturated regions of the samples. The three-magnet array was successfully used to acquire nuclear magnetic resonance signal from a concrete sample, which was not possible with the magnetic resonance imaging instrument using the single-point imaging technique.

Highlight-aware two-stream network for single-image SVBRDF acquisition

This paper addresses the task of estimating spatially-varying reflectance (i.e., SVBRDF) from a single, casually captured image. Central to our method is a highlight-aware (HA) convolution operation and a two-stream neural network equipped with proper training losses. Our HA convolution, as a novel variant of standard (ST) convolution, directly modulates convolution kernels under the guidance of automatically learned masks representing potentially overexposed highlight regions. It helps to reduce the impact of strong specular highlights on diffuse components and at the same time, hallucinates plausible contents in saturated regions. Considering that variation of saturated pixels also contains important cues for inferring surface bumpiness and specular components, we design a two-stream network to extract features from two different branches stacked by HA convolutions and ST convolutions, respectively. These two groups of features are further fused in an attention-based manner to facilitate feature selection of each SVBRDF map. The whole network is trained end to end with a new perceptual adversarial loss which is particularly useful for enhancing the texture details. Such a design also allows the recovered material maps to be disentangled. We demonstrate through quantitative analysis and qualitative visualization that the proposed method is effective to recover clear SVBRDFs from a single casually captured image, and performs favorably against state-of-the-arts. Since we impose very few constraints on the capture process, even a non-expert user can create high-quality SVBRDFs that cater to many graphical applications.

A rail-to-rail CMOS amplifier with improved current efficiency for MEMS geophone applications

In this study, a two-stage rail-to-rail amplifier with improved current efficiency is presented for microelectric mechanical system (MEMS) geophone applications, when operating in the saturated region. With the proposed recycling current method in the input stage, the amplifier gains improved unity-gain bandwidth (GBW) and DC gain with little power consumption. Based on the SMIC 180 nm process, the simulation results demonstrate that the proposed amplifier achieves rail-to-rail input/output, 92 dB DC gain and 4.8 MHz GBW with 1.2 V supply voltage.