Rise Time Tr Research Articles

On the structure dynamic response induced by the dam-break surge impact using multivariate copulas

In this study, the dam-break induced surge impact pressure data on a vertical wall are used to investigate the corresponding structure dynamic response. Both the hydrodynamic and structure parameters are confirmed to be crucial in assessing the structure dynamic responses. The surge peak pressure pk, the pressure rise time Tr, the surge impact duration Td, and the structure natural period Tn are considered to establish the statistical model. The present study determines the dependencies among these parameters which describe the structure dynamic response due to the complexity of dam breaking. Accordingly, two multivariate copulas, i.e., the Gaussian copula and the Vine copula, are used to simulate the statistical properties of the maximum dynamic amplification factor ψm, allowing a better understanding of the dependencies and correlations among different parameters. The tail dependence of variable pairs (pk, Tr) and (pk, ψm) are not significant, while the variable pairs (Tr, ψm) and (Td/Tn, ψm) show lower and upper tail dependence. With respect to the experiment data, simulation using the Gaussian copula shows good results regarding variable pairs of symmetric dependence structures, whereas the Vine copula is more suitable for variable pairs of asymmetric dependence structures.

Analysis and Performance Validation of CRONE Controllers for Speed Control of a DC Motor

In recent decades controllers play a major role for an efficient control and reliable operation of an industrial process. Hence in this paper, a special kind of Commande Robuste d’Ordre Non Entier (CRONE) controller is designed for controlling the speed of DC Motor (DCM). The proper design procedure of two generations CRONE control strategies named as First-Generation CRONE (FGC) and Second-Generation CRONE (SGC) controllers are implemented through the transfer function of armature-controlled DCM. Simulations are performed on MATLAB software in order to investigate the servo responses of two designed CRONE controllers, besides the results are presented in terms of settling time(ts), rise time(tr), Integral Square Error (ISE) and Integral Absolute Error (IAE). In addition, the relay PI controller is designed and the simulation results are presented for comparison purpose. It is evident from the comparing results that the SGC controller is superior for effective process control.

Subduction Interface Earthquake Rise-Time Scaling Relations

ABSTRACT The slip duration in a fault plane, also known as the rise time (Tr), is determined in finite-fault rupture models (FFRMs) through the analysis of seismic source inversions using strong ground-motion (SGM) records and teleseismic data. For subduction interface earthquakes (megathrust), models exist that provide estimates for Tr values. The finite-source rupture model database and National Earthquake Information Center databases include FFRMs that allow for the extension of source-scaling relations. Currently, Tr versus seismic moment (M0) scaling relations specifically derived for large megathrust earthquakes in the near-source region are scarce. The relationship between stress drop and M0 is not straightforward; therefore, the logarithmic distribution of stress drop among earthquakes of different magnitudes (Mw) appears to be constant or self-similar. This self-similarity refers to a symmetry of the time-dependent fields, which remain unchanged under certain scale transformations in space and time characterized by similarity exponents and a function of the scaled variable, called the scaling function. In this study, Tr scaling has been conducted using 45 FFRMs derived from large megathrust earthquakes (Mw≥7.3) obtained from the previously mentioned databases. The scaling relation derived from the FFRMs based on SGM records closely approximates log(Tr)=const+1/3log(M0), which agrees with the self-similarity assumption for earthquake ruptures. On the other hand, the scaling relation obtained from the teleseismic dataset exhibits a smaller slope, indicating that the teleseismic data may overestimate source time characteristics compared with SGM data from seismic stations located close to the source.

Performance and Properties of a Ti-Al Composite Anodic Oxide Film on AC-Etched Al Foil

AC-etched aluminum foils for an Al electrolytic capacitor were covered with a TiO2 film by a sol–gel coating and then anodized to 25 V in an ammonium adipate solution. The structure, properties, and performance of the anodic oxide films were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), electrochemical impedance measurements (EIS), a general digital LCR meter, a TV characteristic tester, and multicycle pulse charging–discharging. It was found that the anodizing of aluminum coated with TiO2 films led to the formation of Al-Ti composite anodic oxide films, which consist of an outer Al-Ti composite oxide layer and an inner Al2O3 layer on the metal substrate. The capacitance (C25V) of the anodic oxide films formed on specimens with a TiO2 coating was about 10% larger than without a TiO2 coating. The specific resistance (Rox) of the Al-Ti composite film measured by EIS was lower than the blank one, accounting for a greater increase in the rise time (Tr) and a slight reduction in the withstand voltage (Vt). After hydration and a multicycle pulse charging–discharging destructive test, the Al-Ti composite anodic oxide film maintained the same good, comprehensive dielectric properties and performance as the blank one, thereby proving to be promising for acting as dielectric layers.

Modified Flower Pollination Optimization Based Design of Interval Type-2 Fuzzy PID Controller for Rotary Inverted Pendulum System

The Type 2 Fuzzy Logic System (T2FLS) is an enhanced form of the classical Fuzzy Logic System (FLS). The T2FLS based control technics demonstrated a lot of improvements for the past few decades. This is based on the advantage of its membership function (MF). Many experimental studies indicated the superiority of Type 2 Fuzzy Logic Controller (T2FLC) over the ordinary Type 1 Fuzzy Logic Controller (T1FLC), particularly in the event of non-linearities and complex uncertainties. However, the organized design method of T2FLCs is still an interesting problem in the control engineering community. This is due to the difficulties in computing the parameters associated it. A novel application of the Modified Flower Pollination (MFP) optimization algorithm in the design of T2FL is presented. The optimized Cascade Interval Type 2 Fuzzy PID Controller (IT2FPIDC) structure is proposed in this study. The best values of the parameters of the antecedent MFs and the PID gains of IT2FPIDC are found using the MFP algorithm. The MFP optimization technique was used because of its lower computational effort and high convergence speed, in view of the higher number of variables to be optimized in cascaded IT2FPIDC. The MFP-based Type-1 Fuzzy Proportional Integral Derivative Controller (T1FPIDC) is compared with the proposed MFP-based cascade-optimized IT2FPIDC. The rotary inverted pendulum (RIP) which is a non-minimum phase, non-linear, and unstable system is employed as a benchmark for testing the proposed controller. Balance and trajectory-tracking controls of the RIP are considered. Furthermore, the disturbance rejection ability of the proposed controller is analysed. The presented control methos is evaluated on the RIP manufactured by Quanser over many simulations and real-world experiments. The performance characteristics considered are steady state error (Ess), settling time (ts), maximum overshoot (Mp) and rise time (tr). The improvement of the effectiveness and robustness proposed controller in the presence of load disturbance, noise effects and parameter variation is shown.

LMIs-Based LPV Control of Quadrotor with Time-Varying Payload

Applications of a quadrotor with payload, particularly for chemical spraying, have increased in recent times. The variation in payload mass over time causes a change in the moments of inertia (MOI). Moreover, large tilt angles are required for fast reference tracking and external disturbance rejection. These variations in plant parameters (i.e., mass and inertia) and large tilt angles can degrade the control scheme’s performance and stability. This article proposes a linear matrix inequalities (LMIs)-based linear parameter varying (LPV) control scheme for a quadrotor subject to time-varying mass, time-varying inertia, mass flow rate, and large tilt angles. The control strategy is designed by solving LMIs derived from quadratic H∞ performance and D-stability. The robust stability and quadratic H∞ performance are assessed by LMIs. The efficacy of the proposed methodology is established using numerical simulations, and its performance is compared to the linear time-invariant (LTI) H∞ design with pole placement constraints. The results obtained show that the LPV control scheme gives better tracking performance in the presence of time-varying parameters, noise, and external disturbances without actuator saturation. In comparison to the LTI design technique, the proposed LPV scheme improves the rise time (tr), settling time (ts), and mean squared error (MSE) by up to 14%, 15%, and 30%, respectively. Moreover, smooth transitions are observed in the tilt angles and control signals with the LPV scheme, contrary to the LTI controller, which exhibits significant oscillations.

Band Gap Engineering of AlYN Films for Solar-Blind Ultraviolet Photodetection

Aluminum nitride (AlN) has been proven as a potential photoelectric material with high breakdown field strength, excellent thermal conductivity, and stable physical properties. However, its ultrawide intrinsic band gap (6.2 eV) prohibits the direct application of AlN as an optical absorption layer for solar-blind ultraviolet (SBUV) detectors. To solve this problem, AlYN thin films with a SBUV absorption cut-off edge of 264 nm were prepared first by energy band engineering using yttrium (Y) as the dopant, based on which a photovoltaic detector with a p-Gr/i-AlYN/n-Si structure was fabricated and exhibited excellent performance of SBUV detection at 0 V bias, including an extremely short rise time (tr) of 20 ms, a decay time (td) of 60 ms, an ultrahigh detectivity (D*) of 5.09 × 1012 Jones, a responsivity (R) of 13 mA/W, a maximum external quantum efficiency (EQE) of 6.69%, and a rejection ratio (R255nm/R310nm) of 245. This work has great value as a reference for the preparation of high-performance AlN-based SBUV detectors.

Dual Mode Symmetrical Proportional Resonant Controlled Quadratic Boost Converter for PMSM-Drive

Power electronics-based converters have been widely used in several applications, specifically electric propulsion systems. Ongoing advancements in converters have led to high-gain Quadratic Boost Converters (QBC) which control Permanent Magnet Synchronous Motor (PMSM) drive. In this work, a novel scheme is employed, particularly a three-phase inverter between QBC and PMSM operated by a dual-mode controller strategy. Precisely, the novelty of this work is to use the quadratic boost converter to control the PMSM drive by applying different control strategies. This work also demonstrates the simulation of two different current control strategies applied to a Semi-Converter (SC) fed QBC based on PMSM-based EV. It also presents the strategy, inquiry, and model of SC-based QBC three-phase inverter (TPI) fed PMSM with symmetrical operated PI (Proportional Integral), FOPID (Fractional Order Proportional Integral Derivative), and PR (Proportional Resonant) controllers. The simulated results offer a significant improvement in PMSM parameters compared with the PI-PI framework, notably voltage, speed, and torque against source disturbances. Further, the PR-PR control approach provides better time-domain parameters than the PI-PI control strategy (including the least rise time (Tr) of 1.15 s, peak time (Tp) of 2.38 s, settling time (Ts) of 4.12 s, and steady-state error (Ess) of 4.89 s). Furthermore, the experimental module is designed to test the effectiveness of the proposed control strategies and was found to be more advantageous in dual mode symmetric PR-PR controlled SC-based QBC-TPI fed PMSM.

Fuzzy Logic Control and PID Controller for Brushless Permanent Magnetic Direct Current Motor: A Comparative Study

Electrical machines based on permanent magnet material excitations have been applied in many sectors since they are distinguished by their high torque-to-size ratio and offer high efficiency. Brushless permanent magnetic direct current (BLPMDC) motors are one type of these machines. They are preferable over conventional DC motors. one of the main challengings of the BLPMDC motor drives is the inherited feature of nonlinearity. Therefore, a conventional PID controller would not be an efficient choice for the speed control of such motors. The object of this paper is to design an efficient speed control for the BLPMDC motor. The proposed controller is based on the Fuzzy logic technique. MATLAB/ Simulink has been employed to design and test the drive system. Simulations were carried out for three cases, the first without a controller, the other using conventional control, and the third using expert systems. The results proved the possibility of improving the engine's working performance using the control systems. They also proved that the adoption of expert systems is better than the traditional nonlinear systems. The simulation response shows that the Rise Time(tr) at PID equals 66.306ms, while it equals 19.530ms for the Fuzzy logic controller. Moreover, Overshoot for PID and Fuzzy logic controller are 6.989% and 1.531%, respectively. On the other hand, undershoot is equal to 1.788% and 11.924% for PID and Fuzzy logic controller, respectively.

Closed-loop vagus nerve stimulation for heart rate control evaluated in the Langendorff-perfused rabbit heart

Persistent sinus tachycardia substantially increases the risk of cardiac death. Vagus nerve stimulation (VNS) is known to reduce the heart rate, and hence may be a non-pharmacological alternative for the management of persistent sinus tachycardia. To precisely regulate the heart rate using VNS, closed-loop control strategies are needed. Therefore, in this work, we developed two closed-loop VNS strategies using an in-silico model of the cardiovascular system. Both strategies employ a proportional-integral controller that operates on the current amplitude. While one control strategy continuously delivers stimulation pulses to the vagus nerve, the other applies bursts of stimuli in synchronization with the cardiac cycle. Both were evaluated in Langendorff-perfused rabbit hearts (n = 6) with intact vagal innervation. The controller performance was quantified by rise time (Tr), steady-state error (SSE), and percentual overshoot amplitude (%OS). In the ex-vivo setting, the cardiac-synchronized variant resulted in Tr = 10.7 ± 4.5 s, SSE = 12.7 ± 9.9 bpm and %OS = 5.1 ± 3.6% while continuous stimulation led to Tr = 10.2 ± 5.6 s, SSE = 10 ± 6.7 bpm and %OS = 3.2 ± 1.9%. Overall, both strategies produced a satisfying and reproducible performance, highlighting their potential use in persistent sinus tachycardia.

A novel proposal for all optical 1-bit comparator based on 2D linear photonic crystal

We employ seven optical waveguides based on two-dimensional linear photonic crystal (LPhC) to realize an all optical comparator (AOCMP). The proposed 1-bit AOCMP has a very simple structure with a footprint of 356 μm2 which is composed of 31 × 33 cubic lattice of silicon rods immersed in air. This LPhC comparator comprises two input ports and two output ports. The functionality of the proposed 1-bit AOCMP is based on constructive and destructive interference phenomenon of optical beams and phase shift keying technique. The finite difference time domain (FDTD) procedure based on Yee’s Algorithm is used to compute the propagation of optical waves in this structure. The FDTD simulation results of suggested 1-bit AOCMP indicate that the minimum and maximum values of the normalized power at ON and OFF states for output ports are 62% and 10%, respectively. Also, the ON–OFF contrast ratio, bit rate, rise and fall times (Tr and Tf) of the suggested design are about 7.92 dB, 2.22 Tb/S, 0.15 ps and 0.05 ps, respectively.

Squeeze-Type Piezoelectric Inkjet Printhead Actuating Waveform Design Method Based on Numerical Simulation and Experiment.

The piezoelectric inkjet printing technique has been commonly used to produce conductive graphics. In this paper, a trapezoidal waveform design method for squeeze-type piezoelectric inkjet printhead is presented to provide a modified steady ejection and optimal droplet shape, in which a coupled multi-physics model of a piezoelectric inkjet printhead is developed. This research describes the effects of parameters, including rising time tr, falling time tf, and dwelling time td, of the trapezoidal waveform on the pressure at the nozzle through numerical simulations. These parameters are initially optimized based on numerical simulations and further optimized based on experimental results. When the printhead is actuated by the optimized waveform with the tr = 5 µs, td = 10 µs, and tf = 2 µs, the droplets are in optimal shape, and their size is about half the diameter of the nozzle. The experimental results validate the efficacy of this waveform design method, which combines numerical simulation and experiment, as well as demonstrating that ink droplet formation can be studied from the point of pressure variation at the nozzle.

Analysis of Multilayer Graphene Nanoribbon Interconnects Constrained by Structural Edge Roughness and Corrugated Surface Dielectric

The transient response, 3 dB bandwidth, and relative stability of undoped‐ and doped‐multilayer graphene nanoribbon (MLGNR) interconnects are investigated based on the mean free path (MFP) model incorporating scatterings induced by structural roughness of edges and corrugation of dielectric surface (viz., SiC, BN, and SiO2). The impact of scattering phenomenon on undoped‐MLGNRs (viz., horizontal top‐contact (HTC) and vertical top‐contact) and doped HTC‐MLGNR is analyzed, and the obtained results are compared with smooth and rough copper (Cu) interconnects at the 13 nm technology node. An ABCD parameter model for transmission lines considering the decoupling technique is employed to analyze three capacitively coupled interconnect lines. The results show that, while Cu interconnects outperform MLGNR variants in terms of step response and 3 dB bandwidth, MLGNR interconnects are more stable than Cu counterparts. Moreover, Li‐doped HTC‐MLGNR interconnects with edge roughness on SiO2 leads to slow and sluggish step response, particularly demonstrating a 1250.4% increase in rise time (tr) and 92.56% decrease in 3 dB bandwidth compared to smooth Cu. However, Li‐doped HTC‐MLGNR without edge roughness on SiC exhibits a 94.7% improvement in tr compared to smooth Cu. Hence, patterning GNRs with smooth edges and less degree of dielectric corrugation is necessary for MLGNR on SiO2 to outperform Cu counterparts.

Hetero-radial MgO capped TiO2 nanowire arrays as a deep UV and self-powered photodetector

Nanowires acts as a potential component in photodetectors (PDs) owing to its superior capacity to generate morphology-dependent broad absorption spectrum. In this study, we have demonstrated an efficient self-powered PD based on the radial heterostructure of the MgO capping layer on top of TiO2 nanowires (RHNWs). RHNWs are highly sensitive under deep ultraviolet (UV) illumination when compared to TiO2-MgO axial heterostructure nanowires (AHNWs) PD. The finite-difference time-domain (FDTD) method is used to simulate electric field distribution, absorption spectra and generation rate profile of the structures. The RHNWs device possesses two times lower leakage current (∼ 1.78 × 10−9 A) than AHNWs (∼ 3.84 ×10−9 A) at – 1.5 V. Theoretical analysis shows a higher photoconductive gain for RHNWs (∼ 12) than the corresponding AHNWs device (∼ 9.9). Maximum photoresponsivity of ∼ 18 A/W has been observed for RHNWs with a sharp rise time (Tr) ∼ 0.12 s and fall time (Tf) ∼ 0.13 s at 200 nm (– 9 V) and the device also behaves like a self-powered PD under white light illumination.

Specific Design Features of Charge Sensitive Amplifiers on Arsenide-Gallium Master Slice

For the production of integrated analog circuits with a small-scale integration, which are developed to operate at temperatures up to minus 200 ℃ and/or with absorbed dose of gamma radiation up to 5 Mrad, a gallium arsenide master slice has been created. The following types of active elements are used in this master slice: DpHEMT with gate dimensions 100 ηm/0,2 ηm and 10 ηm/0,2 ηm; p-n-p HBT, they were chosen for realization of most common analog circuits of operational amplifiers, comparators, voltage followers. Despite the small number of available DpHEMT with high transconductance for circuit synthesis and volt-ampere characteristics features of DpHEMT experimental samples, which exclude use of those transistors at low drain current, master slice give opportunity for developing charge-sensitive amplifiers (CSA) circuits with only one type of active elements – DpHEMT. At the same time, correct choice of the operating point of transistors provide development of low-noise, high-speed CSAs with better parameters than silicon CSAs for sensors with internal capacitance up to 100 pF. So, developed on GaAs master slice CSA with head DpHEMTs and ratio of the gate width to its length, equal to W/L = 2000 and W/L = 3000, characterized by current consumption ICC = 5,46 mA and ICC = 5,25 mA, rise time tR = 10,7 ns and tR = 9,6 ns, equivalent noise charge ENC = 3960 el, and ENC = 3700 el. with sensor capacitance of 50 pF, while the CSA with a head silicon p-channel junction field-effect transistor has W/L = 3870, ICC = 6,99 mA, tR = 27,7 ns, ENC = 5360 el. with the same sensor capacitance.

VO2 thin film based highly responsive and fast VIS/IR photodetector

The VO2 (M1) thin film has attracted significant attention due to its abrupt semiconductor to metal transition (SMT) near room temperature and diverse optoelectronic applications. In this work, pure VO2 (M1) phase thin film has been grown on the silicon substrate using a pulsed laser deposition technique. The Raman spectroscopy results confirmed the deposition of pure VO2 (M1) phase thin film. The X-ray photoelectron spectroscopy (XPS) showed that the deposited vanadium oxide thin film is mainly composed of VO2. The field emission scanning electron microscopy (FESEM) showed a smooth, continuous, and well-covered surface morphology. The elemental composition analysis of the deposited thin film using energy-dispersive X-ray spectroscopy (EDX) exhibited the presence of V and O in the deposited thin film. The VO2 (M1) thin-film device with a simple planar structure displayed resistance change of more than two orders of magnitude with increasing and decreasing temperature displaying a sharp semiconductor to metal transition (SMT) behavior with a transition width of ∼10 °C and transition temperature of ∼67 °C; a property associated with VO2 (M1). The photo-detection results of the VO2 (M1) based device revealed a better response upon illumination with 650 nm light at 0.15 mW/cm2 compared to 980 nm light at 0.34 mW/cm2. The rise time (tr) and fall time (tf) of ∼1.57 and ∼1.64 ms were achieved upon illumination with 650 nm light at 0.15 mW/cm2 while ∼1.67 and ∼4.12 ms upon illumination with 980 nm light at 0.34 mW/cm2. The photo-responsivity has been measured as ∼353 mA/W and ∼78 mA/W for 650 nm and 980 nm light, respectively. The response time and responsivity of the phase pure VO2 (M1) thin film for the Visible and IR light has been significantly improved compared to the earlier reported vanadium dioxide thin films based photodetectors.

Dynamic Characteristics and Successive Start-Up Control Strategy Optimization of Pumped Storage Units under Low-Head Extreme Conditions

With inherent ‘S’ characteristics and the one-tunnel-with-two-units arrangement of the pump-turbine, hydraulic transient changes in the successive start-up process are complex, and the optimal control is difficult. This paper aims to study the dynamic characteristics and successive start-up control strategy optimization of two hydraulic couplings pumped storage units (PSUs) under low-head extreme conditions. Firstly, an accurate model of two hydraulic coupling PSUs’ successive start-up is established. Based on this model, the influence of the interval time of successive start-up on the dynamic characteristics of PSUs is carried out. It is shown that the change of the interval time of the successive start-up (ΔT) of the two PSUs has a significant impact on the dynamic response stability of the low-head start-up. If ΔT is more than 40 s, the hydraulic oscillation and speed fluctuation of the PSUs deteriorate. Secondly, with the different controller parameters for the two PSUs, a novel multi-objective optimization scheme with fractional order PID controller (FOPID) is proposed to figure out the best control scheme for the successive start-up. Furthermore, selecting the sum of the rise time (Tr) of the rotating speed of two PSUs and the sum of the integral time absolute error (ITAE) of two PSUs is the objective. Meanwhile, the optimization scheme of PID with different parameters (PIDDP) is used to compare and verify the optimization method proposed in this paper. The results for this extreme condition indicate that FOPID has more significant advantages in optimizing the instability of the successive start-up process, with the better Pareto front, and the optimized scheme has a more stable dynamic transition process of flow, water hammer pressure, and rotational speed.

Dual-step photocarrier injection by mixture layer of ZnO QDs and MoS2 NPs on hybrid PdAu NPs

Hybrid UV-photodetector (PD) design consisted of various compatible nano-material systems are drawing significant research interests due to their improved device tunability and functionality. A hybrid ZnO–MoS2/HNP UV-PD design is demonstrated by the mixture layer of zinc oxide (ZnO) quantum dot (QD) and molybdenum di-sulfate (MoS2) nanoparticles (NPs) on the plasmonic hybrid PdAu NP template. The proposed design exhibits an excellent photocurrent of 1.45×10−3 A under the 54.9 mW/mm2 at ± 10 V due to a dual step enhancement of photo-carrier injection. It then leads to the significantly improved performance factors of photo-responsivity 1430 mA/mm2 and detectivity 4.50 × 1010 jones at 0.34 mW/mm2. The rise time (Tr) and fall time (Tf) of 3.37 and 0.35 s are obtained for the ZnO–MoS2/HNP PD. The demonstrated performance factors indicate that the hybrid ZnO–MoS2/HNP UV-PD platform is one of the best UV-PDs as summarized in Table 1.

Utilizing zinc oxide nanorods/polyaniline heterojunction as a flexible self-powered ultraviolet photodetector

In the face of the impending energy crisis, developing photoelectronic devices with broadband activity and self-powered characteristics are crucial. Hence, a flexible self-powered ultraviolet photodetector based on sandwiched layers of Zinc oxide nanorods (ZnO) and polyaniline network (Pani) between polyethylene terephthalate (PET) plates along with copper electrodes (PZH) has been fabricated and studied. I–V-T characteristics of the flexible device showed nonlinear rectifying behavior at different temperatures, the formation of an inhomogeneous Schottky contact in ZnO-Pani interface, and the Richardson constant of 30.4 A cm−2 K−2 which is attributed to the ZnO. I–V curves of the device under different directions of ultraviolet light illumination have exhibited nonlinear rectifying behavior, high contrast ratio, and short-circuit current at zero bias voltage which imply the self-powered nature. The PZH exhibited various favorable photoresponsivity (RPh), acceptable response speed, and high photocurrent under different directions and power densities of the UV light. The results showed RPh and rise time (tR) of the device improved about 30% under light illumination from the Pani side than that of opposite direction, while best fall time obtained under light illumination from the ZnO side. The long-term stability, significant photoresponse properties, and simultaneous improvement of tR, RPh and photocurrent; offer our flexible hand-made device as a reliable self-powered photodetector with the broad-wide application and optimal efficiency. Finally, the possible mechanism to improve device performance under two direction of the light illumination through applying a standard thermionic emission-diffusion model and energy band diagram was discussed in detail.

Mathematical Parameters Calculation of Double Exponential Function by a New Numerical Method

Background: Lightning electromagnetic pulse (LEMP) and high-altitude electromagnetic pulse (HEMP) are widely described by three physical parameters (rise time tr, full-width at halfmaximum pulse width tw, and maximum electric field strength E0). These pulse shapes are often given by a double exponential form concerning four mathematical parameters, namely α, β, k and Ep. Objective: The transformation from physical parameters into mathematical parameters is necessary in waveform simulation and is traditionally accomplished by linear fit functions regarding the two groups of parameters. However, traditional methods commonly rely on data analysis and calculation. In order to obtain the mathematical parameters more concisely and clearly. Methods: In this paper, a numerical method to calculate the mathematical parameters by solving nonlinear equations with three key constraints is proposed. Firstly, we establish the nonlinear system of equations regarding four variables, namely t1, t2, α and β. Then, three constraints are given to converge the solutions of the equations. Lastly, select the minimal value of the convergent solution of each equation. Results: Comparing the solutions obtained by our proposed method to the iterated ones, the overall relative error is less than 2×10-8. Conclusion: The results show that our proposed method not only simplifies the transformation from physical parameters to mathematical parameters, but also keeps the solutions high accurate.