Inverse Characteristics Research Articles

Tuning Threshold Voltage of Electrolyte-Gated Transistors by Binary Ion Doping.

Electrolyte-gated transistors (EGTs) operating at low voltages have attracted significant attention in widespread applications, including neuromorphic devices, nonvolatile memories, chemical/biosensors, and printed electronics. To increase the practicality of the EGTs in electronic circuits, systematic control of threshold voltage (Vth), which determines the power consumption and noise margin of the circuits, is essential. In this study, we present a simple strategy for systematically tuning Vth to almost half of the operating potential range of the EGT by controlling the electrochemical doping of electrolyte ions into organic p-type semiconductors. The type of anion in the ionogel determines Vth as well as other transistor characteristics, such as the subthreshold swing and mobility, because the positive hole carriers are the majority carriers. More importantly, Vth can be finely controlled by binary anion doping using ionogels with two anions with varying molar fractions at a fixed cation. In addition, the binary anion doping successfully controls the inversion characteristics of ion-gated inverters. As unlimited combinations of ion pairs are possible for ionogels, this study opens a route for controlling the device characteristics to expand the practicality and applicability of ionogel-based EGTs for next-generation ionic/electronic devices.

Analysis of fog and inversion characteristics and prediction of fog and associated meteorological parameters using NWP model over sub-urban Bangalore

Analysis of fog and inversion characteristics and prediction of fog and associated meteorological parameters using NWP model over sub-urban Bangalore

A novel method to avoid the sintering shrinkage of Al2O3-Cr cermets formed by direct ink writing

The three-dimensional (3D) printed ceramic body often shrinks considerably after thermal processing, which seriously affects the forming accuracy of the final formed parts. In this report, the Al2O3-Cr parts were prepared by 3D direct ink writing. After sintering, the final formed parts have no shrinkage and expanded slightly compared with the green body. Cr plays an important role in this process. The oxidation of Cr causes volume expansion to make up for the sintering shrinkage of the ceramic matrix. The Al2O3-Cr cermet ink exhibits shear-thinning and viscoelastic inversion characteristics, indicating suitability for direct ink writing. A series of printed compacts with different metal and ceramic ratios were sintered at 1600 ℃. The related mechanical properties and microstructure of Al2O3-Cr parts prepared by 3D direct ink writing were investigated. The data of XPS and SEM indicate that Cr reacts with oxygen in the system to produce Cr2O3 during sintering, resulting in the sintered part's volume expansion. This new method provides a good strategy for controlling and eliminating the shrinkage of cermet parts during sintering.

A multi-objective peak regulation transaction optimization and benefits coordination model for multi-sources coupling system considering flexible load response

Based on the intermittent output and inverse peak regulation characteristics of wind power, a multisource peak regulation transaction optimization model that considers the feasibility of combining thermal power, energy storage, and demand response for both power generation and consumption is proposed in this paper. First, a multisource peak regulation transaction cost model is established by considering flexible load participation in peak regulation and price- and incentive-based demand responses. Subsequently, with the objective of minimizing both the peak regulation cost and wind curtailment rate, a reduced half gradient membership function is selected to transform the multiobjective model. Finally, by analyzing the roles of the different subjects in multisource peak regulation transactions, a compensation mechanism based on the Shapley method is designed, and a local power grid in northeast China is chosen as the simulation object. The results show the following: (1) When the thermal power generators (TPGs) transit from regular peak regulation to deep peak regulation, the wind curtailment rate decreases by 5.10%, and the peak regulation cost increases by $ 0.793 × 106. This indicates that the peak regulation cost of the TPGs and the income of the on-grid wind power need to be balanced. (2) When the energy storage and the demand response are combined for peak regulation, both the peak load regulation cost and wind curtailment rate reach the optimal values, decreasing by $ 0.642 × 106 and 5.72%, respectively, showing cooperative optimization. However, the TPGs require a higher regulation cost, whereas the other subjects achieve incremental benefits. (3) The compensation mechanism assists each subject in obtaining incremental benefits depending on the contribution rate. With the strengthening of the peak regulation of the TPGs, more energy storage and demand response output are introduced to meet the urgent peak regulation requirement, which leads to increased regulation revenue and optimal dispatching. In summary, the proposed transaction and compensation mechanism of multisource peak regulation can be used to balance the peak regulation ability and contributions of different subjects and establish the optimal peak regulation scheme.

Post-test debris characterisation of molten corium interaction with sacrificial material in a scaled down core catcher

Core catchers are being installed in advanced light water reactors after TMI and Fukushima. The core catchers are designed to stabilise and cool molten corium within the reactor containment for a long time, reducing the risk of core meltdown. Some core catchers use sacrificial material to lower the specific volumetric heat release of the molten corium. The low density oxidic component of molten pool migrate to the top layer of the core catcher after melt-sacrificial material interaction. The high density metallic component migrate to the bottom layer. In the event that the core catcher is top flooded, this prevents metallic components from reacting with water and generate hydrogen. Post experimental analysis of the cooled stratified melt pool was performed. The experimental scaled down core catcher used reactor the prototypic sacrificial material while maintaining the actual reactor flooding conditions. About 550 kg of simulant corium was melted at about 2500 °C using heat of thermite reaction. The core catcher vessel was partially filled with sacrificial bricks. After the test, solidified debris samples from different locations of the core catcher model were analysed for density and SEM-EDS for quantitative and qualitative characterisation. Post-test analysis showed the melt inversion characteristics.

Investigation of the characteristics and mechanisms of the layer inversion in binary liquid–solid fluidized beds with coarse particles

This paper adopts an optimized Euler–Lagrange method proposed in our previous work to study the characteristics and formation mechanisms of layer inversion in binary liquid–solid fluidized beds (LSFBs) with coarse particles. The LSFBs are formed in a cylindrical pipe with a diameter of 50 mm and a length of 0.6 m and consist of two species of coarse particles with different sizes: 6 mm glass spheres (species 1) and 10 mm glass spheres (species 2) with the particle density of 2600 kg/m3. First, the characteristics of the layer inversion of LSFBs with coarse particles are qualitatively analyzed. The positions of species 1 and species 2 are converted during layer inversion. Second, the changes in the trajectory and volume fraction of two species of particles are quantitatively investigated. Finally, the formation mechanisms of layer inversion with coarse particles are analyzed. The results show that the relative magnitude of the fluid–solid interaction force and the gravity is the main reason for determining the layer inversion of binary coarse particles of different sizes. The collision force is to balance the net force of the particle–fluid interaction force and the net gravity, so that the fluidized bed is in relative equilibrium. In addition, through the analysis of the evolution of the network of contact forces, the constraint of the wall on coarse particles is discussed during the layer inversion.

In situ stress inversion and fracture characteristics around local fault in deep heterogeneous strata

The southeast Sichuan in China is a key area for deep shale gas exploration. However, shale gas exploration in deep heterogeneous strata is greatly affected by in situ stress. Faults caused by tectonic movement strongly change the distribution of in situ stress. Inversion and prediction of in situ stress have become an important research hotspot in the field of resource exploitation. Based on the geological structure evolution and experimental data, the boundary stress iterative inversion method is used to inverse the in situ stress field of deep heterogeneous strata containing shale gas reservoirs, and the fracture characteristics around local fault are analyzed by fracture mechanics theory. The research shows that the stress field has the characteristics of non-uniform distribution under the influence of fault, and there is obvious stress concentration and deflection of principal stress direction around the fault. And magnitude and direction of stress are affected by the internal friction angle of the fault zone and the formation depth in different tectonic periods. Through the analysis and calculation of the plastic strain and stress intensity factors, it can be inferred that the cracks will propagate at the terminal portion of the fault. The research is important to guide engineering for the adjustment of resource exploitation scheme.

Coordination of Ultrafast Solid-State Circuit Breakers in Radial DC Microgrids

This article proposes a comprehensive method for optimal coordination of ultrafast solid-state circuit breakers (SSCBs) in radial dc microgrids. The proposed method consists of two consecutive steps. In the first step, SSCBs are optimally coordinated for overload, short circuit, and instantaneous protections. Inverse time-current characteristics (ITCC) curves are formulated to systematically coordinate SSCBs. The trip curve of each SSCB includes overload, short-circuit, and instantaneous profiles. In determining overload protection, the thermal capability of SSCBs is considered; while the short-circuit and instantaneous tripping profiles are realized based on short circuit thermal capability and ultrafast response time of SSCBs. Coordination time interval (CTI) is included between upstream and downstream SSCBs to achieve selectivity. To avoid miscoordination in practice, CTI is chosen by incorporating the SSCBs’ metal-oxide varistor (MOV) conduction time interval during turn-off process and dc current measurement error. In the second step, the operating speed of the protective scheme is optimized by applying distance-based secondary protection (DBSP). The DBSP is used to minimize the tripping time when short circuit faults occur close to upstream SSCBs. This significantly reduces the consumed energy by faults, prevents damage, reduces absorbed energy by SSCBs, and enhances the safety of operators. The proposed coordination removes the need for communication links between SSCBs and presents high reliability. A 400-V dc microgrid benchmark with photovoltaic (PV) and energy storage systems (ESSs) is examined as a case study in simulation. Besides, experiments are conducted in a 400-V dc system to evaluate the effectiveness and accuracy of the DBSP.

Sensitivity enhancement analysis of frequency tuned-SAW resonator with temperature for sensor applications

Cooling of quartz-SAW devices leads to a noticeable increase in sensitivity. However, the effect of heating on the output characteristics of quartz-SAW resonators in terms of sensitivity has not yet been studied. Here we examine the inverse parabolic temperature characteristics of a quartz-SAW resonator in order to study the effect of temperature rise on the sensitivity. Various characteristics of a quartz SAW resonator are measured such as frequency shifts, phase, and group delay by Vector Network Analyzer (VNA) over a temperature range of 5 °C to 150 °C. It is shown that the sensitivity could be increased at certain combinations when the operating frequency (fo) is tuned away from the centre frequency (fc) along with temperatures higher or lower than room temperature. Sensitivity increases up to 24-fold was achieved when T > 120 °C and fo > fc. This study of temperature tuning of SAW device will be useful for enhancing the sensitivity in various SAW sensing applications for various industrial purposes.

An enhanced approach for joint configuration of a robot performing in a repetitive task

Human-Centric Manufacturing considers the integration of the industrial automation systems with human capabilities. It combines the strength, speed, repeatability and precision of automation with the intelligence, flexibility and skill of human operators. This advanced manufacturing concept strongly emphasis on human-assisted robotic operation. Recently, the interest in the human-robot cooperative industrial robot which can work together with human through physical interaction in the same space has increased. The direct teaching technology for human-robot cooperation enables an operator who is not used to robot programming to control the robot easily by teaching the task trajectory directly. However, because of the industrial robot inverse kinematics characteristics, there are multiple different inverse kinematics solutions in configure space. The planned trajectory based on the track points selected by the operator may be not efficient enough for the task. Hence, optimizing the joint configurations of a robot in a repetitive task becomes one of the increasingly important issues. In this paper, a mathematical model of the robotic joint configurations based on graph theory is developed, which takes into account repeat task constraints. An enhanced approach for the joint configuration of a robot in a repetitive task is proposed. It leads to the reduction of computational complexity and computing time. A numerical experiment and a case study of the optimization of time consumption in an industrial repetitive task are reported to show the effectiveness of the proposed approach.

Inversion invasions: when the genetic basis of local adaptation is concentrated within inversions in the face of gene flow.

Across many species where inversions have been implicated in local adaptation, genomes often evolve to contain multiple, large inversions that arise early in divergence. Why this occurs has yet to be resolved. To address this gap, we built forward-time simulations in which inversions have flexible characteristics and can invade a metapopulation undergoing spatially divergent selection for a highly polygenic trait. In our simulations, inversions typically arose early in divergence, captured standing genetic variation upon mutation, and then accumulated many small-effect loci over time. Under special conditions, inversions could also arise late in adaptation and capture locally adapted alleles. Polygenic inversions behaved similarly to a single supergene of large effect and were detectable by genome scans. Our results show that characteristics of adaptive inversions found in empirical studies (e.g. multiple large, old inversions that are FST outliers, sometimes overlapping with other inversions) are consistent with a highly polygenic architecture, and inversions do not need to contain any large-effect genes to play an important role in local adaptation. By combining a population and quantitative genetic framework, our results give a deeper understanding of the specific conditions needed for inversions to be involved in adaptation when the genetic architecture is polygenic. This article is part of the theme issue 'Genomic architecture of supergenes: causes and evolutionary consequences'.

Surface temperature inversion characteristics in dissimilar valleys, Yukon Canada

Permafrost distribution in high-latitude continental mountains is a product of both latitudinal and elevationally controlled attributes. Frequently occurring surface-based temperature inversions (SBIs) significantly modify surface lapse rates (SLRs) annually. We aim to identify and quantify patterns of SBI characteristics in two proximal yet morphologically and vegetatively dissimilar central Yukon valleys. Elevational transect analysis is applied by using sensors in valley bottoms and 100 m upslope to determine in situ SLRs for the study period (August 2017 – August 2021). SLRs were shown to vary significantly between these dissimilar valleys. Climate reanalysis products (ClimateNA and Globsim) underestimated or almost entirely missed the presence of strong SBIs which produce annual average SLRs that range from 0.46 to 1.2 °C 100 m−1. The magnitude of these hyper-inversions was grossly underpredicted by previous surface air temperature modelling that attempted to account for SBIs across Yukon. Our results support the previously conceptualized framework that strong SBIs influence surface air temperatures and the pattern of permafrost distribution.

Fractional-Order PIλDμ Controller Using Adaptive Neural Fuzzy Model for Course Control of Underactuated Ships

For the uncertainty caused by the time-varying modeling parameters with the sailing speed in the course control of underactuated ships, a novel identification method based on an adaptive neural fuzzy model (ANFM) is proposed to approximate the inverse dynamic characteristics of the ship in this paper. This model adjusts both its own structure and parameters as it learns, and is able to automatically partition the input space, determine the number of membership functions and the number of fuzzy rules. The trained ANFM is used as an inverse controller, in parallel with a fractional-order PIλDμ controller for the course control of underactuated ships. Meanwhile, the sine wave curve and the sawtooth wave curve are considered as the input learning samples of ANFM, respectively, and the inverse dynamics simulation experiments of the ship are carried out. Two different ANFM structures are obtained, which are connected in parallel with the fractional-order PIλDμ controller respectively to control the course of ship. The simulation results show that the proposed method can effectively overcome the influence of uncertainty of ship modeling parameters, track the desired course quickly and effectively, and has a good control effect. Finally, comparative experiments of four different controllers are carried out, and the results show that the FO PIλDμ controller using ANFM has the advantages of small overshoot, short adjustment time, and precise control.

Modelling and performance testing of a digital over-current relay enhanced designed model

Introduction. The over-current relay is widely used to protect distribution and transmission electrical systems against excessive currents occurring due to short circuit or overload conditions. Many works have been carried out in the field of models simulation design of digital over-current relays in the literature, but unfortunately many of them are more complex design models, have very slow execution time and only work in simple faults cases. Purpose. The purpose of this work is to present the performance of a modified and improved model of a digital over-current relay designed in Simulink/MATLAB environment with more simplified design, faster execution time, and able to operate under more complex fault conditions. Methodology. Before starting tests, modelling of over-current relay is presented in details, of which the basic logics of the proposed model to implement inverse and instantaneous characteristics are well explained. Afterwards, various tests are carried out for the performance analysis of the enhanced designed relay model in terms of: operating speed for eliminating faults that has arisen, ability to distinguish between a fault current and load starting current, capacity distinguish between real and temporary fault currents, the way to manage variable faults over time, and the degree of harmony between primary protection relay and back-up protection relay. Originality. The originality of our proposed work consists in the development and improvement of a digital over-current relay model designed in Simulink/MATLAB environment in such way that it becomes able to operate under new harsh test conditions. This developed designed model is implemented and applied in a 400V radial distribution power system with a load that causes a starting current. Results. The obtained values of simulation are compared with the theoretically calculated values and known existing models. The obtained results after various tests validate the good performance of our enhanced designed model.

РОЗРОБКА МОДЕЛІ СТРУМОВОГО РЕЛЕЙНОГО ЗАХИСТУ В ПАКЕТІ MATLAB/SIMULINK

Based on MATLAB / SIMULINK, a model of a radial network with one-way power supply and three radial lines with a complex load at the end of each line is built. The model allows you to study the relationship of processes in the network in the case of normal operation, and in the case of possible damage at different distances from the power supply. The proposed model of the current protection device consists of a three-phase current meter, a switching element and a display. In the dialog box of the device, the primary current of the transformer current, the mains voltage frequency, the multiplicity of the protection tripping current and the tripping time multiplier are set, and the type of the standard curve of the protection tripping time characteristic is selected. A protection device with inverse time delay characteristics measures the RMS value of three-phase AC. The switch-off signal is given from the output of the relay protection device, depending on the time delay. The display shows the operating time of the device, primary and secondary currents and setpoint multiplicity. The performance of the device was evaluated by a three-phase short circuit. As a result of research it is established that the offered model of the relay protection device confirms correct behavior of the relay of the maximum current in various operating modes of a network. The behavior of the protection device indicates that the proposed model can be used in further work to develop algorithms for current protection of lines. To improve the model of the device, it is necessary to investigate the influence of simulation parameters, such as data on power sources, power lines, load and type of damage on the parameters of the protection device. The scientific novelty is the the developed models of the electric network and the device of the maximum current protection with all inverse characteristics of endurance of time provided by the ANSI / IEEE and IEC standards. The practical significance of the work is the possibility of using the model to test the selectivity and sensitivity of protection in the event of changes in network parameters in a wide range and in the case of research in the development and improvement of relay protection devices and training.

Experimental Study on the Accumulation Characteristics and Mechanism of Landslide Debris Dam

According to physical model tests, we analyzed the accumulation characteristics of landslide dams formed under three different slope characteristics, namely, uniform slope, parallel slope, and intersecting slope and investigated the accumulation mechanisms of the debris dams. The relationship between slope types and accumulation characteristics was also explored using the tracer particle analysis method. The damming process and accumulation mechanism of the landslide dam were changed with slope conditions, which lead to the difference in the accumulation characteristics of the dam, especially in transverse cross-sectional shape and grain size distribution. The transverse cross-sectional shape of the landslide dams formed by different slope conditions can be divided into three categories: the flat pattern, unidirectional pattern, and undulating pattern. The characteristics of the slope body are closely related to those of the landslide dam with respect to debris distribution. The debris distributions in the longitudinal and transverse directions of the slope body are consistent with those in the longitudinal and sliding regions of the dam. A general inverse grading characteristic of debris gains occurs in the vertical direction of landslide dams. For the uniform and parallel slopes, obvious inverse grading distribution is induced by overall-starting initiation of the slope body and strong vertical infiltration of the fine sands during the movement. However, inverse grading distribution is generated by the effects of pushing–climbing and lateral infiltration that existed among particles caused by a layered-starting mode for the intersecting slope body. This study provides a basis for the prediction of landslide dam formation and backtracks the initial structure of the slope.

Further Generalization and Approximation of Fractional-Order Filters and Their Inverse Functions of the Second-Order Limiting Form

This paper proposes a further generalization of the fractional-order filters whose limiting form is that of the second-order filter. This new filter class can also be regarded as a superset of the recently reported power-law filters. An optimal approach incorporating constraints that restricts the real part of the roots of the numerator and denominator polynomials of the proposed rational approximant to negative values is formulated. Consequently, stable inverse filter characteristics can also be achieved using the suggested method. Accuracy of the proposed low-pass, high-pass, band-pass, and band-stop filters for various combinations of design parameters is evaluated using the absolute relative magnitude/phase error metrics. Current feedback operational amplifier-based circuit simulations validate the efficacy of the four types of designed filters and their inverse functions. Experimental results for the frequency and time-domain performances of the proposed fractional-order band-pass filter and its inverse counterpart are also presented.

Characteristics of Temperature and Humidity Inversions Based on High-Resolution Radiosonde Observations at Three Arctic Stations

AbstractThe Global Climate Observing System Reference Upper-Air Network (GRUAN) with high-vertical-resolution radiosonde data at three Arctic stations and European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data (ERA5) were used to investigate the characteristics of multiple temperature inversions (TI) and humidity inversions (HI) in this study. It is found that surface-based inversion (SBI) at two coastal stations exists throughout the whole year, mainly due to the surface cooling in cold months, advection warm months, and the orography of the stations. The seasonal variation of surfaced-based HI (SBHI) frequency is similar to that of SBI, and its intensity is greater in summer because of the larger air moisture content. The frequency of the first elevated TI (EI1) and HI (EHI1) are both higher than that of the surface-based ones. The second elevated TI/HI layer (EI2/EHI2) is shallower and weaker than that of the EI1/EHI1. At two coastal stations, EI1 caused by warm advection is thicker and stronger than that caused by subsidence. At the station farther from the coast, EI1 caused by subsidence is higher, thinner, and stronger. The top height and depth of the EHI2 both show seasonal variations, with larger values in the cold months. EHI1 tends to be formed by the TI, whereas EHI2 is dominant by humidity advection at all studied stations. HI under the influence of TI is usually thicker and stronger than that formed by humidity advection. The coexistence of EI and EHI is the most frequent inversion structure at these stations.

Predistortion Approaches Using Coefficient Approximation and Bidirectional LSTM for Nonlinearity Compensation in Visible Light Communication

A Light-Emitting Diode (LED) has a nonlinear characteristic, and it contains fundamental limitations for the performance of Visible Light Communication (VLC) systems in indoor environments when using intensity modulation with Orthogonal Frequency Division Multiplexing (OFDM). In this paper, we investigate this nonlinear characteristic with analysis and proposal. At first, we identified the LED nonlinear characteristics in terms of bit-error performances. After analysis, we propose initial predistortion schemes to mitigate the nonlinearity matters. In the predistortion schemes, the nonlinear distortion compensation model contains predistortion features with the LED inverse characteristics. Considering a Direct-Current-biased Optical OFDM (DCO-OFDM) system, we compared the Bit-Error Rate (BER) performances with and without compensation via simulations. The performance on the LED with the compensation showed LED nonlinearity could significantly improve the bit-error performance. In addition, with consideration that the predistortion model is insufficient to represent LED distortion, we investigated possible opportunities of distortion correction using Bidirectional Long Short-Term Memory (BLSTM), one of the leading deep learning approaches. Its result showed promising improvement of the distortion compensation as well.

Reference modification for trajectory tracking using hybrid offline and online neural networks learning

In this paper, we propose a hybrid offline/online neural networks learning method, which combines complementary advantages of two types of neural networks (NNs): deep NN (DNN) and single-layer radial basis function NN (RBFNN). Firstly, after analyzing the mechatronic system’s model, we select reasonable features as the input of the DNN to learn the inverse dynamic characteristics of the closed-loop system offline, so as to establish the mapping between the desired trajectory and the reference trajectory of the system. The trained DNN is used to generate a new reference trajectory and compensate for the tracking error in advance, which can speed up the convergence of online learning control based on RBFNN. This reference trajectory is further modified iteratively when the tracking task is repeated. For this purpose, a single-layer RBFNN model is established, and an online learning algorithm is developed to update the RBFNN parameters. The proposed hybrid offline/online NN method can improve the tracking performance of mechatronic systems by modifying the reference trajectory on top of the baseline controller without affecting the system stability. To verify the effectiveness of this method, we conduct experiments on a piezoelectric drive platform.