Polynomial Curve Fitting Technique Research Articles

Impact of Source Resistance on Linearity of AlGaN/GaN HEMTs at Ka-Band

The impact of the source resistance (RS) on the linearity of AlGaN/GaN high electron mobility transistors (HEMTs) measured by the two-tone test is investigated in this study. The theoretical analysis of the third-order intermodulation (IM3) and the third-order intercept point (IP3) of the devices was performed based on the equivalent circuit approach and the polynomial curve fitting technique. The results revealed that the suppression of IM3 level and thus the improvement of IP3 were achieved for the device with a larger RS. For the experimental verifications, three types of AlGaN/GaN HEMTs were fabricated with different layout structures and air-bridge architectures corresponding to different RS values, which were then extracted by the cold-FET method. It is concluded that a device with a shorter length of middle source pad (LMS) and a side-type air-bridge architecture tends to have a larger RS value. In this study, the 4 × 50–20 device with LMS of 20 um and a side-type air-bridge architecture demonstrated the best-measured linearity performance at 30 GHz due to the largest RS.

STRESS DISTRIBUTION IN THE HOLLOW STIFFENED HYBRID LAMINATED COMPOSITE PANELS IN SHIP STRUCTURES UNDER SINUSOIDAL LOADING

A simplified hollow stiffened hybrid laminated plate model has been developed for the marine structures. The detailed stress analysis through the thickness of the stiffened plate based on the higher order shear deformation theory has been carried out under sinusoidal loading. The hybrid laminates are made by wrapping the GFRP laminates with CFRP at the outermost layers of the stiffened panel. This hybridization technique can be an optimum solution from the point of view of cost reduction as well as enhancement of strength properties. The layer-wise stresses for the stiffened plate have been calculated in the present paper. A 3D polynomial curve fitting technique has been used to obtain higher accuracy and consistency in the computation of stresses. The computer code has been developed using MATLAB considering the plates as eight noded isoparametric plate bending element and the stiffener has been modeled as three noded isoparametric beam element. The stiffened panel has also been analysed using the ANSYS14.0 software package considering 2D model. The results obtained from the present formulation have been compared with those available in the published literature to validate the present formulation. The stiffened panels made of GFRP, CFRP and GFRP-CFRP hybrid laminates have been studied here. An extensive parametric study has been carried out with varying fibre content in the laminates.

BreaCNet: A high-accuracy breast thermogram classifier based on mobile convolutional neural network.

The presence of a well-trained, mobile CNN model with a high accuracy rate is imperative to build a mobile-based early breast cancer detector. In this study, we propose a mobile neural network model breast cancer mobile network (BreaCNet) and its implementation framework. BreaCNet consists of an effective segmentation algorithm for breast thermograms and a classifier based on the mobile CNN model. The segmentation algorithm employing edge detection and second-order polynomial curve fitting techniques can effectively capture the thermograms' region of interest (ROI), thereby facilitating efficient feature extraction. The classifier was developed based on ShuffleNet by adding one block consisting of a convolutional layer with 1028 filters. The modified Shufflenet demonstrated a good fit learning with 6.1 million parameters and 22 MB size. Simulation results showed that modified ShuffleNet alone resulted in a 72% accuracy rate, but the performance excelled to a 100% accuracy rate when integrated with the proposed segmentation algorithm. In terms of diagnostic accuracy of the normal and abnormal test, BreaCNet significantly improves the sensitivity rate from 43% to 100% and specificity of 100%. We confirmed that feeding only the ROI of the input dataset to the network can improve the classifier's performance. On the implementation aspect of BreaCNet, the on-device inference is recommended to ensure users' data privacy and handle an unreliable network connection.

Fast Maximum Torque per Ampere (MTPA) Angle Detection for Interior PMSMs using Online Polynomial Curve Fitting

For interior permanent magnet synchronous machines (IPMSMs), maximum torque per ampere (MTPA) control aims to find the MTPA angle to maximize the control objective (the ratio of output torque to stator current). This article proposes a novel online polynomial curve fitting technique for fast and accurate MTPA angle detection, which is motivated by the fact that the objective increases before MTPA angle and decreases after MTPA angle. This article proposes a polynomial-based objective model and identifies the polynomial parameters from a few test data for direct MTPA angle calculation. The proposed approach can avoid the time-consuming search process resulting in fast detection speed in comparison to existing search-based methods. In implementation, the current angle is set to a few test values to obtain the data for online curve fitting and MTPA angle calculation, in which there is no need of machine inductances and PM flux linkage. Moreover, the proposed polynomial model is analyzed to obtain the number of test data required for fast and accurate MTPA angle detection. The proposed approach is validated with extensive experiments and comparisons with existing methods on a laboratory IPMSM.

Petro-physical properties of Marcellus shale samples and their impact on CO2 adsorption: Equilibrium, kinetics, and empirical modeling study

The correlation of CO2 adsorption characteristics with the associated shale samples mineralogy, at various total organic contents, are essential for CO2 sequestration, improved oil recovery, and gas storage operations. In this work, Marcellus shale samples from the U.S.A are studied for their CO2 adsorption capacities in term of equilibrium and kinetics. A series of analyses, including total organic carbon content, X-ray diffraction, Fourier Transform Infra-red Spectroscopy, Field Emission Scanning Electron Microscopy, temperature-programmed desorption, and N2/CO2 adsorption were performed. Gravimetric adsorption technique with magnetic suspension balance at 298 K and up to 20 bars is used to conduct isothermal adsorption and desorption measurements. Considerable organic contents of ≈ 3-18 wt% are observed. Clay minerals such as calcite, illite, kaolinite and smectite are identified with up to 50 wt% ratio of some samples. Porosity and pore distribution analysis illustrate that the samples are mostly mesoporous with hysteresis supporting bottleneck or open ended-shaped pores. The temperature-programmed adsorption encouraged the phenomenon of chemisorption. Though, equilibrium isotherm modelling supported physical and chemical, heterogeneous, and multilayer adsorption. The kinetic investigation by double exponential model shows different rate of adsorption, which can be due to mineralogical alteration, physical properties or organic content. A new empirical model is developed to study the effect of relative pressure and porosity on the adsorption capacity using polynomial curve fitting technique. The model will help to predict the adsorption uptake at different operating pressures and porosity for future studies. The study can demonstrate insightful findings related to CO2 separation, sequestration and gas production for enhanced hydrocarbons recovery.

Influence of self-heating on the millimeter-wave and terahertz performance of MBE grown silicon IMPATT diodes

The influence of self-heating on the millimeter-wave (mm-wave) and terahertz (THz) performance of double-drift region (DDR) impact avalanche transit time (IMPATT) sources based on silicon (Si) has been investigated in this paper. The dependences of static and large-signal parameters on junction temperature are estimated using a non-sinusoidal voltage excited (NSVE) large-signal simulation technique developed by the authors, which is based on the quantum-corrected drift-diffusion (QCDD) model. Linear variations of static parameters and non-linear variations of large-signal parameters with temperature have been observed. Analytical expressions representing the temperature dependences of static and large-signal parameters of the diodes are developed using linear and 2nd degree polynomial curve fitting techniques, which will be highly useful for optimizing the thermal design of the oscillators. Finally, the simulated results are found to be in close agreement with the experimentally measured data.

On the Development of a Modified Triangular Patch Antenna Array for 4.9 GHz Public Safety WLAN

The present paper reports on the development of a Novel Patch Antenna Array for 4.9 GHz Public Safety WLAN applications. In today’s era of advanced technology, high speed video surveillance is very crucial from security point of view. Public safety surveillance services below 1 GHz are mainly used in voice surveillance services, whereas 4.9 GHz Public Safety WLAN is used for video surveillance services. Accordingly, in this work, 2×2 element antenna array is designed on FR4 substrate using modified triangular patch antenna element with improved gain to the tune of 6.69 dBi. In this research work, biologically inspired Whale Optimization method is used in combination with polynomial curve-fitting technique for the optimization of three different geometrical dimensions of the patch antenna element. The optimized element is further modified geometrically by corner rounding and cut in feed to improve its performance including gain. The proposed antenna array resonates at 4.9 GHz covering 120 MHz bandwidth with an achievement of -15.87 dB reflection coefficient and high gain. Results of simulation study are validated with measured results. The uniqueness of the proposed design lies in the achievement of a large gain using simple patch antenna array designed on readily available low cost FR4 substrate making very easy fabrication. Such an attempt has been rarely reported in the literature. However, the results of present investigations are quite convincing.

Node density optimisation using composite probabilistic sensing model in wireless sensor networks

Network coverage is a measure of efficiency that signifies the extent to which the deployed nodes collectively cover the network area. It is a fundamental and critical quality of service (QoS) parameter for designing wireless sensor networks (WSNs). Various sensing models are reported which can be used to predict the coverage fraction for a given number of nodes in a predetermined network area. However, each of these reported models consider a subset of parameters. In this study, a novel formulation and hence a new model, composite probabilistic sensing model (CPSM) is proposed which combines the cumulative effects of all the possible factors, thus resulting in a realistic study. Further, the model is revisited to estimate the optimal density of randomly deployed nodes required to attain the desired network area coverage. An exhaustive parametric study is carried out and the results obtained are used to empirically derive a formula based on regression analysis using least square polynomial curve fitting technique. The formulation can be readily and accurately used to design any practical WSN system.

Structured-illumination reflectance imaging coupled with phase analysis techniques for surface profiling of apples

Three-dimensional (3-D) geometry information is valuable for fruit quality evaluation. This study was aimed at exploring an emerging structured-illumination reflectance imaging (SIRI) system, coupled with phase analysis, for reconstructing surface profiles of fruit. Phase-shifted sinusoidal patterns, distorted by the fruit geometry, were acquired and processed through phase demodulation, phase unwrapping and other post-processing procedures to obtain phase difference maps relative to the phase of a reference plane. The phase maps were then transformed into height profiles based on phase-to-height calibrations. A reference plane-based approach, in conjunction with the curve fitting technique using polynomials of order 3 or higher, was utilized for phase-to-height calibrations, which achieved superior accuracies with the root-mean-squared errors (RMSEs) of 0.027–0.033 mm for a height measurement range of 0–91 mm. The 3rd-order polynomial curve fitting technique was further tested on two reference blocks with known heights, resulting in relative errors of 3.75% and 4.16%. Tests of the calibrated system for reconstructing the surface of apple samples showed that surface concavities (i.e., stem/calyx regions) could be readily discriminated from bruising defects from both the phase difference images and reconstructed height profiles. This study has laid a foundation for using SIRI for reconstructing the 3-D geometry, and thus expanded the capability of the technique for quality evaluation of horticultural products. Further research is needed to utilize the phase analysis techniques for detecting surface concavities of apples, and optimize the phase demodulation and unwrapping algorithms for faster and more reliable detection.

Visualization of Performance of Bubble Sort in Worst Case in Personal Computer using Polynomial Curve Fitting Technique

Bubble sort is one of the simple sorting algorithms. In this study, the researchers had used polynomial curve fitting technique to visualize the performance of Bubble sort in the worst case in a personal computer. To identify the best fit (i) R square, (ii) Adjusted R square, (iii) Root mean square error, (iv) Akaike information criterion (AIC) and (v) Bayesian information criterion (BIC) had been used. The Bubble sort algorithm in the worst case had been implemented using C programming language and the algorithm had been run for data size two thousand five hundred (2500) to data size twenty thousand (20000) with an interval of five hundred (500). For each data size one hundred (100) observations (execution time in seconds) had been recorded and for each data size the median value of the observations (execution time in seconds) had been calculated. Thus, the researchers had calculated thirty six (36) data points (data size versus median value of execution time in seconds). The polynomial curve fitting had been tried and tested on these thirty six (36) data points (data size versus median value of execution time in seconds). In total twenty four (24) models starting from linear model to polynomial of degree 24 had been employed in this study to identify the best model and among these models “Polynomial of degree 2” model had been identified as the best model. Keywords: Polynomial curve fitting; Bubble sort; AIC; BIC; Performance visualization

Analysis of Crimping of Large Diameter Welding Pipe

Crimping is widely used in production of large diameter submerged-arc welding pipes. Traditionally, the designers obtain the technical parameters for crimping from experience or trial-errors by experiments. To tackle this problem, a theoretical analytical model is proposed to analysis crimping forming process. In this paper, taking the crimping of X80 steel Φ1219mm×22mm×12000mm welding pipe for instance, the theoretical analytical model is constructed by quadratic polynomial curve fitting technique and mechanics theory. And it is verified by a comparison with experiment results. Thus, the presented model of this research provides an effective path to design crimping parameters.

High thermal stability and low hysteresis dispersion AlGaN/GaN MOS-HEMTs with zirconia film design

Gate structure of AlGaN/GaN metal–oxide–semiconductor high electron mobility transistors (MOS-HEMTs) on silicon substrates has been developed using electron-beam evaporated high-permittivity (high-k) zirconium oxide layer (ZrO2). As a gate insulator, this structure has been investigated and compared with the conventional GaN HEMTs. From the measured capacitance–voltage (C–V) curve, the dielectric constant of ZrO2 was 20.7 and the voltage shift of C–V hysteresis phenomena can be reduced to 7.2mV after high temperatures annealing. The crystalline structures of ZrO2 at different annealing temperatures were observed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The ZrO2 thin film achieved a better thermal stability after high temperatures annealing. Moreover, the MOS-HEMTs with ZrO2 gate insulator layer markedly improved its gate leakage current and microwave performances. The device linearity was also improved due to its flat and wide transconductance (gm) distribution which was analyzed by polynomial curve fitting technique. Load–pull and flicker noise measurements showed that ZrO2 MOS-HEMT had a higher output power at high input swing and low surface density. Therefore, ZrO2 was a potential candidate high-k material for the gate insulator on GaN-based MOS-HEMT for it exhibited a better thermal stability and reliability at high power applications.

Demographic Changes, Financial Markets, and the Economy

It seems natural that the shifting composition of a nation’s population ought to influence GDP growth and perhaps also capital markets returns. As the baby boomers have aged, many people have studied past demographic data in an effort to extract indications for the future influence of the boomers on many aspects of the economy. We extend this body of literature by analyzing the effect of demographic changes on three measures of great importance for countries all over the world: real per capital PPP-adjusted GDP growth, stock market excess returns, and bond market excess returns. We confirm what others have already demonstrated, but we extract markedly more statistical significance by adapting a polynomial curve-fitting technique pioneered by Fair and Dominguez (1991), to this new purpose. In our work, we find that a growing roster of young adults (age 15–49) is very good for GDP growth, a growing roster of older workers is a little bad for GDP growth, and a growing roster of young children or senior citizens is very bad for GDP growth. We find surprisingly powerful results when we apply the same technique for exploring the links between demography and capital markets returns, net of the strong and well-documented effects of valuation and yield levels. Stocks perform best when the roster of people age 35–59 is particularly large, and when the roster of people age 45–64 is fast-growing. Bonds follow a similar pattern, with an age-shift: they’re best when the roster of people age 50–69 is growing quickly. We carry out three different forms of robustness checks, each of which provides statistical significance in different ways: applying different country weights, testing alternative demographic variables, and confirming GDP results on out-of-sample countries. It would be dangerous to forecast the future based on these results. Tacitly, we would be assuming that past relationships between demography and either GDP growth or capital market returns will hold unaltered in the future. However, given the high levels of statistical significance in the historical relationships, it is too tempting to resist exploring the possible implications for future GDP growth and capital market returns. These implications—with all the caveats that must necessarily be offered—are sobering, to say the least.

Low Hysteresis Dispersion La2O3 AlGaN ∕ GaN MOS-HEMTs

metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) using electron-beam evaporated high-dielectric-constant (high-) lanthanum oxide layer as the gate insulator have been investigated and compared with the traditional GaN HEMTs. The dielectric constant of the insulator layer developed in this study was 13.1. In addition, a negligible hysteresis voltage shift in the capacitance–voltage curves can be obtained after high temperature annealing. The compositions and the crystalline structures of with different annealing temperatures were observed by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The thin film achieved a good thermal stability after 200, 400, and postdeposition annealing owing to its high binding energy characteristics. Moreover, the gate leakage current of a traditional metal gate GaN HEMT can be suppressed for 1 order of magnitude after inserting a insulator between Ni and AlGaN, resulting in a better pulsed-mode operation. The device linearity was also improved due to its flat and wide transconductance distribution, which was analyzed by a polynomial curve-fitting technique. Therefore, is a potential candidate high- material for the gate insulator to enhance the GaN-based field effect transistor performance while scaling down the device dimension and device reliability at high power operation.

Computer animation in mobile phones using a motion capture database compressed by polynomial curve-fitting techniques

The aim of this paper is to efficiently implement motion-capture-based computer animation in mobile phones. Motion-capture-based computer animation is made from a large motion capture database stored in memory. Unfortunately mobile phones have little memory. To adapt motion-capture-based computer animation to the small memories of mobile phones, we revise a commercial motioncapture-based computer animation process to use a reduced motion capture database. To obtain a reduced motion capture database, we design a simple polynomial curve-fitting-based motion capture database reduction method. This approach preserves the smoothness of motion in the motion capture data, and does not overload the low computational capability of mobile phones. To further enhance performance, we optimize the degree of the polynomial fitting function. Using the developed approach we demonstrate an example implementation of motion-capture-based computer animation in a commercial mobile platform. Many motion data compression methods are already known, however this is the first attempt to specialize motion data compression for low performance architecture, mobile embedded system.

A NEW METHOD TO AVOID CROWDING PHENOMENON IN EXTRACTING THE PERMITTIVITY OF FERROELECTRIC THIN FILMS

In this paper, a new method is proposed to avoid crowding phenomenon in extracting the permittivity of ferroelectric thin films. Polynomial curve fitting technique is used to determine the filling factor while the thickness of the thin film is very small. Conformal mapping (CM) combining with partial capacitance approach (PTA) is used to obtain the relationshipbetween the effective p ermittivity of multiplayer coplanar waveguide (CPW) and the permittivity of each layer. A CPW with a thin film layer is simulated and the permittivity of thin film is extracted, the results show that, by using the proposed method, the crowding phenomenon can be avoided successfully and the permittivity of thin films can be extracted accurately.

Transmission line distance relaying using a variable window short-time Fourier transform

This paper presents a new approach for transmission line protection using a variable window short-time Fourier transform known as S-transform. The S-transform (ST) is a time–frequency spectral localization method, similar to short-time Fourier transform (STFT), but with a Gaussian window whose width scales inversely, and whose height scales linearly with the frequency. The change in spectral energy of the ST of the current and voltage signals provide the information regarding fault detection. After the fault detection, the impedance to the fault point is calculated using the estimated phasors of the faulted current and voltage signals which provide accurate results even with noisy conditions. Also, the fault location is calculated using polynomial curve fitting technique with a devised index obtained from the ratio of spectral energy of the voltage and current signals, respectively.

Improving the performance of model-based damage detection methods through the use of an updated analytical model

The advantages of finite-element model updating in association with a model-based method for structural damage localisation are investigated. An approach designed to identify and locate delamination damages in carbon fibre reinforced polymers is used. The method is based on a correlation between measured damage-induced modal damping variations from an elasto-mechanic structure and the corresponding data from a numerical model in order to derive information on the damage location. Using a numerical model enables to locate damage in a three-dimensional structure from experimental data obtained with only a single response sensor. To acquire sufficiently accurate experimental data a polynomial curve fitting technique is used to extract damping parameters from measured frequency responses. It will be shown that in order to achieve a good localisation precision the numerical model must retain a high degree of accuracy and physical consistency.

A Displacement and Velocity Measurement Technique Using Millimeter-Wave Sensor

In this paper, a millimeter-wave sensor is presented for measurement of displacement and velocity. By using monolithic microwave integrated circuits and digital quadrature sampling signal-processing scheme, the sensor operating at 60 GHz is implemented. Polynomial curve-fitting technique is used for the error correction. Digital quadrature mixer is also configured as a phase-detecting processor, which enables low Doppler frequency to be measured with high resolution. Measured displacement results indicate resolution and maximum error of 10 μm and 30 μm, respectively, and measured speed is as low as 30 mm/s, corresponding to 6.6 Hz in Doppler frequency, with an estimated velocity resolution of 3.3 mm/s. To the best of our knowledge, the attained resolution and maximum error are the best reported results.

A hybrid method for generator tripping

Generator tripping is one of the most effective approaches to enhance the transient stability of a power system. In this paper, an online prediction method of transient stability and an offline analysis method of generator tripping are studied respectively. First, a polynomial curve fitting technique is employed to improve the online prediction accuracy of system stability. Then, a shell program is developed to automatically generate and update look-up tables for generator tripping. Based on these, a hybrid method is proposed. It uses the look-up tables to determine generator tripping requirements and before sending out generator tripping signals, instability is confirmed by online prediction of system stability. Simulation results show that this hybrid method can avoid unnecessary generation shedding.