Order Polynomial Fit Research Articles

Muscle Activation Frequency Relationship with Cost of Transport at Increasing Walking Speed in Preliminary Study Reveals Interplay of Both Active and Passive Dynamics

Metabolic cost plays a critical role in gait biomechanics, particularly in rehabilitation. Several factors influence metabolic cost during walking. Therefore, this study aimed to examine the relationship between metabolic cost and muscle activity, focusing on the frequency of EMG signals during walking. We recruited nine participants (five male and four female, age range 20–48 years) who walked for four minutes at six different speeds (ranging from 1.8 to 5.9 mph). EMG data were collected from the dominant lower leg muscles, specifically the lateral gastrocnemius (GAS-L) and the anterior tibialis (AT). Oxygen respiration was measured using open-circuit spirometry. Energy expenditure was estimated as the cost of transport (COT). The EMG data were analyzed using frequency domain features, such as the area under the curve of power spectral density (PSD-AUC) and the maximal distance between two points before and after the peak of the power spectral density curve (MDPSD). The results indicated that PSD-AUC is a better measure than MDPSD for understanding the relationship between activation frequency and COT. PSD-AUC demonstrated an increasing curvilinear trend (R2 = 0.93 and 0.77, second order polynomial fit), but the AT displayed higher variability. MDPSD exhibited more nonlinearity (R2 = 0.17–28, second order polynomial fit), but MDPSD demonstrated statistically significant differences (p < 0.05, t-test independent) in frequency between the GAS-L (64–237 Hz) and AT (114–287 Hz) during slow walking. Additionally, the relationship between COT and PSD-AUC revealed a U-shaped curve, suggesting that high COT is a function of both active and passive dynamics during walking. These findings will be valuable in rehabilitating individuals who suffer from gait-related disorders, especially those related to muscle inefficiency.

Filling up the water quality database to assess the water quality levels and self-cleaning capacities

The one of water resource’s functions is the self-renewable capacity about quality, quantity and energy. To assess the level or fluctuat trend of water resource functions, a complete set of continuous and representative data is needed. The water quality monitoring of environment management is implementing continuous in Ho Chi Minh City. Because of many causes, the water quality data set is asynchronous by years and observation locations. It causes the many difficulties to researches, studies as the assessment of water’s self-cleaning capacity. With the support of two interpolations equations (the Highest order polynomial fitting Curve Function (HopCEF) and Multivariable Regression Correlative Function (MrCEF)) and GIS tool, the water quality and self-cleaning capacity distributions are zoned/mapped with the fully and continuously data set. The research of water quality and self-cleaning capacity is implemented with the filled quality data set period 2012 – 2022 for urban inner canal system in HCMC. Based on the assessment’s results and the mapped distribution of levels, the fluctuations the quality and self-cleaning capacity of inner canal system are made high visualization. And they are a valuable basis for planning and decision making on the solutions of management agencies in HCMC.

Characterizing the Myoarchitecture of the Supraspinatus and Infraspinatus Muscles With MRI Using Diffusion Tensor Imaging.

The societal cost of shoulder disabilities in our aging society keeps rising. Providing biomarkers of early changes in the microstructure of rotator cuff (RC) muscles might improve surgical planning. Elevation angle (E1A) and pennation angle (PA) assessed by ultrasound change with RC tears. Furthermore, ultrasounds lack repeatability. To propose a repeatable framework to quantify the myocyte angulation in RC muscles. Prospective. Six asymptomatic healthy volunteers (1 female aged 30 years; 5 males, mean age 35 years, range 25-49 years), who underwent three repositioned scanning sessions (10 minutes apart) of the right infraspinatus muscle (ISPM) and supraspinatus muscle (SSPM). 3-T, T1-weighted and diffusion tensor imaging (DTI; 12 gradient encoding directions, b-values of 500 and 800 s/mm2 ). Each voxel was binned in percentage of depth defined by the shortest distance in the antero-posterior direction (manual delineation), i.e. the radial axis. A second order polynomial fit for PA across the muscle depth was used, while E1A described a sigmoid across depth: . Repeatability was assessed with the nonparametric Wilcoxon's rank-sum test for paired comparisons across repeated scans in each volunteer for each anatomical muscle region and across repeated measures of the radial axis. A P-value <0.05 was considered statistically significant. In the ISPM, E1A was constantly negative, became helicoidal, then mainly positive across the antero-posterior depth, respective at the caudal, central and cranial regions. In the SSPM, posterior myocytes ran more parallel to the intramuscular tendon ( ), while anterior myocytes inserted with a pennation angle ( ). E1A and PA were repeatable in each volunteer (error < 10%). Intra-repeatability of the radial axis was achieved (error < 5%). ElA and PA in the proposed framework of the ISPM and SSPM are repeatable with DTI. Variations of myocyte angulation in the ISPM and SSPM can be quantified across volunteers. 2 TECHNICAL EFFICACY: Stage 2.

Design, performance evaluation and calibration of an indirectly-excited piezoelectric wind energy harvester via a double-bluffbody exciter

Using piezoelectric wind energy harvester to harvest energy from fluids has been an effective way to power wireless sensing systems in the last decade. In order to solve the problems of low reliability, poor environmental adaptability and narrow operating bandwidth of existing piezoelectric wind energy harvesters, a piezoelectric wind energy harvester with a double-bluffbody exciter (DE-PWEH) is proposed in this research. By summarizing the disadvantages of traditional piezoelectric wind energy harvester with upwind structure, a downwind structure was adopted to improve the ability of PWEH to adapt to high wind speed environment. In order to further improve the reliability of the DE-PWEH, a wind isolation structure and an indirect excitation structure was adopted, which means the piezoelectric element was installed inside a cylindrical shell. Therefore, this 2-DOF indirectly excited DE-PWEH could possess both high reliability and broad working bandwidth. To verify the principle feasibility and design regarding the proposed DE-PWEH, a prototype of the DE-PWEH was fabricated and tested in terms of output and operating bandwidth. The results showed that the relative size and position of the adjustable plate and cylindrical shell brought significant effects on the output and operating bandwidth. When the distance-diameter ratio was 0.6, the width-diameter ratio was 1 and the height ratio was 1, the maximum output voltage was 90.35 V and the critical wind speed was 0.96 m/s. The maximum increase of the critical wind speed was 550%, and the minimum was −85.67%. With a wind speed of 15 m/s and the optimal load resistance of 2000 kΩ, a maximum power of 2.57 mW was attained. In order to quantitatively study the performance of DE-PWEH, a data fitting method based on polynomial was proposed for the first time to calibrate PWEH performance. The sixth order polynomial fitting equation can be used to characterize the output characteristics of DE-PWEH. And in practice, 80 LEDs in series were successfully driven by the DE-PWEH. The DE-PWEH could charge the 470 μF, 1000 μF, 2200 μF and 3000 μF commercial capacitors to 2 V in 60 s, 128 s, 340 s, and 400 s, respectively.

Quantitative and qualitative prediction of sulfur content in diesel by near infrared spectroscopy

This study explored the application of near infrared spectroscopy for quantitative and qualitative prediction of sulfur content in diesel fuel in the range of 10.3–1038.0 mg kg−1. The original spectra were preprocessed through various methods such as decentralization, normalization, multivariate scattering correction, and a smoothing (15-point window with second order polynomial fit). The performances of models based on partial least squares (PLS) regression, the bootstrapping soft shrinkage (BOSS), competitive adaptive reweighted sampling and Monte Carlo uninformative variable elimination algorithms in quantitative analysis of diesel samples were compared. The model for quantitative prediction of sulfur content in diesel samples using the BOSS-PLS algorithm had the highest performance and accuracy with a RMSEP of 36.20 mg kg−1 and r2 of 0.98 using a Savitzky-Golay second derivative. Diesel fuel samples were classified into five groups according to the sulfur content for qualitative analysis. The interval PLS method was then used to determine the characteristic spectra of the diesel samples. The experimental results indicated that the discriminant partial least squares qualitative analysis model had the highest performance with the characteristic spectrum from 12,493 to 10,892 cm−1, with 92.04% accuracy.

Coastal tides measurement in Indonesia using GNSS-Reflectometry

The important role of coastal areas in human life and their vulnerability to natural hazards such as sea level rise, make continuous monitoring of coastal ecosystem rehabilitation concerning the local sea level is urgently required. Conventional tide observation using a tide gauge sensor measures a local sea level relative to the land. Unfortunately, the effects of deformation and land subsidence around tidal stations make local tide observations irrelevant to measure absolute sea level rise. Currently, an alternative method is being developed accordingly. The method utilizes Global Navigation Satellite Systems (GNSS) signal, known as GNSS-Reflectometry (GNSS-R), to observe the tide. This research aimed to observe the sea level from the reflection of the GNSS signal. Tidal observation using GNSS-R was carried out in four Geospatial Information Agency’s tidal stations, i.e., Morotai, Piru, Tehoru, and Pasangkayu. The tide was determined based on the dominant frequency of a multipath signal, which is obtained by separating the composite signal from the direct one using 3rd order polynomial fitting. The combination of GPS and GLONASS at the L1 and L2 frequencies resulted in tide observations with an RMSE value of 18 cm. The result is 90% correlated with tidal observation using tide gauge sensor. The residual of main tidal constituent vector in both semidiurnal and diurnal components ranged from 0.01 to 0.02 m. This means that the tide prediction generated from the GNSS-R observation is statistically similar to the prediction generated from the tide gauge sensor.

Changchun SLR data analysis using different techniques

The aim of the present study is to investigate three different techniques for fitting the SLR data observed from the Changchun observatory in China which is characterized by its huge amount of data points and to examine which of the three techniques is more proper for fitting such kind of data. The first technique is the interpolation using the Chebyshev polynomial for fitting the total number of satellite laser ranging (SLR) data points. The second technique is the spline technique which is used for matching continuous intervals for fitting the SLR data. The third technique is the method, which is used at Changchun observatory, known as the Iterative 4th order polynomial fit. The three techniques are applied to 100 samples; 50 samples for the satellite LAGEOS I and the other 50 samples for the satellite Starlette that were observed during the first quarter of 2018. From the obtained results, it is found that the first two techniques, namely the Chebyshev polynomial and Spline techniques provide better standard deviation in comparison to the Iterative 4th order polynomial fit technique that is used at Changchun observatory, with merit to Spline technique over the Chebyshev polynomial.

Ultra-low wide bandwidth vibrational energy harvesting using a statically balanced compliant mechanism

Structure design of ultra-low wide bandwidth vibrational energy harvesters remains an open issue. In this research, a statically balanced compliant mechanism (SBCM) is proposed, dynamically modelled, and experimentally demonstrated to address this need. This SBCM is designed based on the concept of stiffness compensation between a linear component with positive-stiffness (two double parallelograms in parallel) and a nonlinear component with negative-stiffness (two sets of post-buckled fixed-guided compliant beams in parallel). A design guideline of the SBCM starting from using rapid-design stiffness compensation equation is provided for reasonably approximate and accurate results. Subsequently, a dynamic analytical model of the displacement response of the SBCM to harmonic base excitation has been derived based on the averaging method. The nonlinear force-displacement relationship of the system was obtained through nonlinear finite element analysis (FEA) simulations in this regard and a 5th order polynomial fit was chosen taking only odd terms into account. The accuracy of this analytical model is confirmed by numerical analysis. Next, a prototype of the SBCM was fabricated and its applicability to piezoelectric vibrational energy harvesters (PVEHs) was demonstrated by integrating piezoelectric capacitors made of PVDF films with compliant beams of the SBCM to generate electric outputs in response to the bending of the beams. Static balancing is achieved over a continuous displacement range of 2 mm around the origin. Bi-stability and mono-stability were observed with the same prototype by adjusting the length of the positive-stiffness beams. Under static-balancing condition, the SBCM is able to respond to a wide range of ultra-low frequencies with low accelerations, which has been established experimentally, analytically and numerically. In dynamic experiments, the steady-state relative displacement amplitude H is 2.9 mm under an excitation condition of 6 Hz and 0.1g (1g=9.8 m/s2), and it reaches a maximum of 9.4 mm under 12.75 Hz and 0.25 g. A 30%-Hmax frequency bandwidth is introduced to assess the nonlinear dynamic performance of the SBCM from a mechanical perspective. The maximum experimental 30%-Hmax bandwidth of the structure is 6.75 Hz (from 6 Hz to 12.75 Hz) at 0.25 g and the corresponding theoretical value is 8.73 Hz (from 3.34 Hz to 12.07 Hz). Under the same excitation condition, it is shown that the maximum relative displacement amplitude deceases as the jump-down frequency increases. In addition, super-harmonic and sub-harmonic oscillations are observed in the dynamic experiments. The SBCM can provide a practical structural solution for harvesting energy from a range of vibrational scenarios (e.g. ocean waves, human motions and bridge vibrations) with ultra-low wide bandwidth frequencies and weak accelerations. The concept of SBCM is suitable to be combined with various energy conversion principles and is not limited to piezoelectric sources alone. When miniaturized, the SBCM concept can be of particular interest to researchers active in energy harvesting for microelectromechanical systems (MEMS) technology.

A correlation approach for the calculation of thermal conductivity of nanofluids as a function of dynamic viscosity

A correlation approach for the calculation of thermal conductivity of nanofluids as a function of dynamic viscosity is presented in this paper due to the significance of the nanofluids in energy systems. Available experimental data of relevant literature are used in terms of second order polynomial fit of the least-squares sense through the commercial software of MATLAB. The data belong to a variety of nanoparticles used in water (W) and ethylene glycol (EG)/ethylene glycol-water (EG-W) base fluids. Graphical plots of relative thermal conductivity, kr and relative dynamic viscosity, µr are given as a function of nanoparticle volume fraction φ as a common route. The fitted equations are used to calculate kr and µr in an extended range of 0% ≤ φ ≤ 55%. The validity range is given as a temperature range T of 20–50 °C and nanoparticle size range of 5–100 nm. The proposed non-dimensional equations of kr = kr (µr) for W-based and EG/EG-W-based nanofluids have a severe difference indicating the major influence of base fluid. It is possible to calculate kr with the known or estimated value of µr or vice versa as a solid contribution the state of art. The correlations also reflect the influence of viscosity on thermal enhancement of nanofluids as a physical fact of practice provided.

Fading and residual responses for thermoluminescent dosimetry of silica beads irradiated using a high-dose electron-beam

Thermoluminescent (TL) glow-curves of 10 different coloured Toho Japan bead types have been obtained using a Risø TL/OSL reader studied for a fading period of 6 months as well as for residual dosimetry for fading up to 16 months after irradiation. For the entirety of the delay period studied the Frosted beads showed the largest TL response followed by Pink and Rose beads. Pink beads showed the best fit to the second order polynomial fit applied to the observed fading. In a more detailed dose curve fitted for a 6 month delay between irradiation and readout in order to determine the nature of the TL response as a function of increasing dose, it was found to follow the same trend for all bead colours. The residual TL response was also studied for beads that showed a large TL response. In these studies all colours showed similar dose response curves to those for the 1st readout, with Pink beads showing the best agreement to the fit applied to model fading.

Zero-crossing temperature of ultra-stable optical reference cavity measured by optical transition spectrum

In an experimental system of &lt;sup&gt;87&lt;/sup&gt;Sr atomic optical lattice clock, the free-running 698 nm diode laser is locked in an ultra-stable optical reference cavity to obtain the ultra-stable narrow linewidth laser with good short-term frequency stability. The ultra-stable optical reference cavity, which is usually composed of glass material doped with titanium dioxide for ultra-low thermal expansion coefficient and two highly reflective fused quartz mirrors, is called ULE cavity. The cavity length is prone to being affected by mechanical vibration, temperature change, airflow, etc. The stability of the cavity length determines the stability of the final laser frequency. Near the room temperature, there exists a special temperature point for the ultra-low expansion glass material, at which temperature its thermal expansion coefficient becomes zero, which is called the zero-crossing temperature. At the zero-crossing temperature, the length of the ULE cavity is not sensitive to the temperature fluctuation, reaching a minimum value, and the laser locked to the ULE cavity has a minimum frequency drift. In order to reduce the influence of temperature on the laser frequency instability, the zero-crossing temperature of the ultra-stable optical reference cavity of 698 nm ultra-stable narrow linewidth laser system is measured by using the clock transition spectrum of the strontium atomic optical lattice clock. The frequency drift and frequency instability of the 698 nm ultra-stable narrow linewidth laser system at zero-crossing temperature are measured by using the change of the in-loop locked clock frequency of strontium atomic optical lattice clock. By scanning the atomic clock transition frequencies at different temperatures, the clock transition spectra at different temperatures are obtained. The second order polynomial fitting of the central frequency of the clock transition spectrum with the change curve of temperature is carried out, and the zero-crossing temperature of the 698 nm ultra-stable narrow linewidth laser system ULE cavity is measured to be 30.63 ℃. At the zero-crossing temperature, the 698 nm ultra-stable narrow linewidth laser frequency is used for in-loop locking of &lt;sup&gt;87&lt;/sup&gt;Sr atomic optical lattice clock. The linear drift rate of the ULE cavity in the 698 nm ultra-stable narrow linewidth laser system is measured to be 0.15 Hz/s, and the frequency instability of the 698 nm ultra-stable narrow linewidth laser system is 1.6 × 10&lt;sup&gt;–15&lt;/sup&gt; at an average time of 3.744 s. The determination of ULE cavity zero-crossing temperature for the 698 nm ultra-stable narrow linewidth laser system is of great significance in helping to not only improve the instability of the laser system, but also increase the instability of &lt;sup&gt;87&lt;/sup&gt;Sr optical lattice clock system. In the future, we will improve the temperature control system of the ULE cavity in the 698 nm clock laser system, enhancing the temperature control accuracy of the ULE cavity and reducing the measurement error, thus achieving a more accurate zero-crossing temperature and further improving the frequency instability of the 698 nm ultra-stable narrow linewidth laser system.

Nonuniform Carrier Heating Induced Nonlinear Electron Transport Properties in Asymmetrically Necked InAs Mesa Structures

IntroductionTerahertz (THz) wave has been very attractive light for scientific and practical applications such as light source for characterizing fundamental physics on ultra-fast carrier dynamics in semiconductors and imaging applications in the submillimeter wavelength regime. Therefore, there have been studied on various kind of emitting and detecting methods on THz waves in this quarter century. So far, we also have proposed simple and low-cost THz wave source with InAs thin films grown on GaAs substrates combining with a time-domain spectroscopy system [1, 2]. In case of THz detectors, there are not so many techniques which enable to detect THz wave at room temperature with high responsivity without biasing. For example, square-law field rectifier detectors, such as Schottky diodes and InGaAs-based bow-tie diodes, respond to THz electric field at room temperature with no external power supply [3]. Nonlinear current-voltage characteristics of the latter technique is based on unique operation principle which is generated by nonuniform carrier heating in asymmetric bow-tie shaped planar structures. Since InAs possesses one of the highest electron mobility at room temperature among semiconductors, this material based thin films will be hopeful candidate for detecting THz waves by fabricating this unique nonlinear device structures on them. In this paper, we devise utilizing InAs THz wave emitter thin films to base material for asymmetrically necked bow-tie mesa structures for the THz detector. As a first step of this idea, nonlinear current-voltage characteristics of these devices are presented. We especially discuss on the curvature of current-voltage characteristic at zero-bias point which is closely related to the sensitivity on square-law detection for THz wave.ExperimentalNominally undoped InAs thin films were epitaxially grown on semi-insulating GaAs (100) substrate by molecular beam epitaxy. For improving the crystal quality of InAs channel layer, 150 nm thick InAs buffer layer was directly grown with gradually changing growth temperature from 300 to 500°C on GaAs substrate. An 1 µm think InAs channel layer was grown on this buffer layer at 450°C. This growth condition is same as that of THz emitter InAs films we have reported [2]. The patterning of asymmetric bow-tie mesa structure was carried out by photo lithography and phosphoric acid based wet chemical etching. After defining mesa structures, in order to investigate the film thickness dependence on nonlinear current properties, some samples were performed recess etching for InAs channel, which were made each thickness to be 265 nm, 435 nm, 625 nm and 835 nm. Finally, non-alloyed ohmic contact metals of Ti/Pt/Au (50/30/170 nm) were deposited by electron-beam evaporation technique and defined by lift-off. The structure of asymmetric bow-tie diode and the measurement configuration are shown in Fig. 1. Current-voltage characteristics were measured by using Keithley 4200A-SCS system at room temperature.Results and Conclusion Typical current-voltage characteristic of the investigated InAs asymmetric bow-tie diode is represented in Fig. 2, which was the result measured with the sample of 265 nm thick InAs channel. It showed clear asymmetric current-voltage characteristic depended on the polarity of applied voltage, which was considered originated from nonlinear carrier transport related to non-uniform carrier heating in asymmetric mesa structure. In order to evaluate the nonlinearity of current-voltage curve at zero-biased point, the zero-biased curvature coefficient γ was calculated, which is given by the formula written in Fig. 3. A fifth order polynomial fit was utilized to current-voltage curves in determining the curvature. As shown in Fig. 3, the zero-bias curvature clearly depended on thickness of InAs thin film. The highest zero-bias curvature of 0.12 V-1 was obtained in the thinnest sample. In addition, this value was about 2.2 times larger than that of the GaAs/AlGaAs heterostructure-based asymmetric bow-tie diode which had the same shape and size (not shown here). These results indicate that the InAs thin film for THz radiation has possibility to be applied to square-law detection device for THz wave. The details of nonlinearity which depends on mesa shape and size and comparison between InAs based structures and that of GaAs/AlGaAs will be discussed at the conference.

Displacement-free stereoscopic phase measuring deflectometry based on phase difference minimization.

In this paper, we propose a phase difference minimization algorithm to measure the specular surface shape in a displacement-free stereoscopic phase measuring deflectometry (PMD) system. The presented system is capable of solving the height-normal ambiguity appearing in a PMD system without moving any system component. Both the surface normal and the absolute height are simultaneously obtained by implementing phase difference minimization between the phase distributions in the LCD screen and the camera image plane. In particular, phase difference minimization is performed by using a second order polynomial fitting iteration method. Bi-cubic sub-pixel interpolation combined with 2D Fourier integration is used to reconstruct the surface. Finally, the performance of the proposed stereoscopic PMD system is verified by measuring the surface shapes of different mirrors and performing repeatability tests.

Exercising hybrid statistical tools GA-RSM, GA-ANN and GA-ANFIS to optimize FDM process parameters for tensile strength improvement

The properties of functional parts printed by additive manufacturing are highly dependent on various process parameters of the machine. The process parameters can be optimized by hybrid statistical tools to enhance the objective function. The present study investigates the tensile strength of Dogbone American Society for Testing and Materials (ASTM)-D638-V standardized parts fabricated by FDM 3D printer, using poly lactic acid (PLA) plus material. The test specimens were fabricated by varying three parameters: infill density (20–100%), speed (50–150mm/s) and temperature (190–210°C). For the parametric combination, response surface methodology (RSM) based central composite design (CCD) matrix was developed using second order polynomial fitting model. The maximum tensile strength of testing specimens on UNITEK-94100 universal testing machine (UTM) was recorded as 45.27MPa. Further, hybrid optimization techniques like genetic algorithm-artificial neural network (GA-ANN), genetic algorithm-response surface methodology (GA-RSM) and genetic algorithm-adaptive neuro fuzzy interface system (GA-ANFIS) are deployed to optimize these process parameters. Among these tools, the maximum accuracy of 99.89% obtained with GA-ANN which results in optimized parameters as infill density 100%, temperature 210°C, and speed 124.778mm/s to achieve the maximum tensile strength of 47.0212MPa. The results of this examination will facilitate the added substance producing units to choose the optimize factor value of input factors for FDM parts fabrication with improved mechanical properties. The hybrid developed models could be proposed for precise prediction and optimization of other process parameters and results for any industrial application problems.

Quantification of fabric in cemented granular materials

Abstract We perform a set of tomographic studies on polymer bonded frictional granular material to systematically characterize the structure through quantification of the relative orientation of its constituents. A three-dimensional network is constructed by considering the centroid of granules as vertex and polymer bridge as a link. We present the spatial distribution of coordination numbers in the network, which indicates the degree of bonding by the number of bridges per grain. Further, we quantify the network using microfabric tensors for each vertex. The spatial distribution of eigenvectors of these microfabric tensors suggests that the bridges align themselves, preferentially, along the direction of gravity. Further, a spherical distribution of direction of links is presented along with a second order polynomial fit. We construct ellipsoid fabric chains by traversing the path of optimally aligned dominant eigenvectors of microfabric tensors. This chain traverses the direction along which contacts orient themselves maximally.

High Accuracy Homodyne Interferometric Method for Wide Dynamic Range Applications

In this paper a new method for the detection of optical phase in passive homodyne interferometers, with high accuracy and wide dynamic range is presented. Unlike the traditional and more recent methods, which use between 3 and 6 harmonic components to calculate the modulation index, the proposed method uses only 2 harmonic components. Because of this, the method has higher accuracy in the presence of noise compared to other methods known in the literature. Further, the method has the advantage of not requiring knowledge of the phase of the excitation signal. The numerical implementation is simple, since it uses a 3rd order polynomial fit for the calculation of the modulation index. For the experimental verification of the method, a configuration based on an unbalanced Mach-Zehnder interferometer (MZI) was used, which resulted in a dynamic range for the modulation index from 8.38 to 16.76 rad. It is important to note that these limits can be easily expanded by means of adaptations of the optical and electronic setup depending on the characteristics of the excitation signal. The proposed method can be used in several applications, such as pressure measurements, vibration, displacement, etc.

Research of intelligent segment-fitting algorithm for increasing the measurement accuracy of quadrant detector in straightness measuring system

In this paper, we propose an intelligent segment-fitting algorithm to increase the measurement accuracy of quadrant detector (QD) in straightness measuring system. Add-subtract algorithm and polynomial fitting are usually adopted to acquire the estimate of the spot projected on QD. The accuracy of QD is limited by the nonlinear relationship between the spot position and its estimate. In order to obtain higher accuracy, the polynomial fitting order must be higher with more calculation amounts, so the new algorithm is designed to optimize the nonlinearity. Through the specific method mentioned in the new algorithm, the whole measurement range of QD can be divided into several segments intelligently. And the data in each segment and between adjacent segments can be simply expressed by the third order polynomial fitting and linear interpolation. The experiment results verified that the algorithm could increase the measurement accuracy with good real-time performance. Within the measurement range of ±250 μm, the residual RMSE of the QD using the proposed algorithm, compared with that using the third order polynomial fitting, was reduced more than 80%, and the calculation amount was reduced to about 1/4 of that using the seventh order polynomial fitting.

Investigation of PPLN Waveguide Uniformity via Second Harmonic Generation Spectra

Experimental data collection methods and a corresponding numerical model are presented to investigate the quality of waveguide fabrication in nonlinear optics. The method utilises white light interferometry and standard image recognition techniques to calculate a waveguide propagation constant function. This enables comparison of a numerical second harmonic spectrum in quasi-phasematched materials, such as periodically poled lithium niobate, with the waveguide’s experimental phasematching spectrum. Using the presented method, a 3rd order polynomial fit to waveguide ridge width is demonstrated to be in good agreement with experimental phasematching spectra. The presented technique provides a nondestructive route to discriminate between issues in fabrication steps in nonlinear waveguide design.

Polynomial Augmented Extended Kalman Filter to Estimate the State of Charge of Lithium-Ion Batteries

In battery-electric vehicles, an accurate knowledge of the current state of charge (SOC) of the battery is crucial for safe and efficient operation. Offset-free SOC estimation for Lithium-ion batteries (LIB) during operation still is a challenging problem, due to the uncertain output nonlinearity present in battery models. In battery management systems employed in such vehicles, the age- and cycle-dependent relationship between the open circuit voltage (OCV) and the state of charge of each cell (SOC) can be kept track of using lookup tables. Between the scattered data points, linear interpolation is often used. Another common approach is to switch between models, each with a different piecewise polynomial fit of low order. In this contribution, a single polynomial fit of a higher order with state-dependent coefficients for the whole SOC-OCV range is proposed, so as to avoid switching and facilitate usage of Taylor-based linearization algorithms like in the extended Kalman filter. While the polynomial order is high, the number of parameters is only three; the parameters are estimated and updated by the Kalman filter itself. This augmentation of the observer's state vector with said polynomial parameters is inspired by the idea of an increased “stochastization,” introducing redundancy that aids to achieve a more accurate SOC estimation. In this sense, the algorithm can be described as a model-adaptive extended Kalman estimator. Two variants of a polynomial EKF are investigated: polynomial EKF with output and with state nonlinearity models. Their performances are compared in real experiments using a dedicated test bench based on a Samsung ICR18650-26F cell, demonstrating the effectiveness of the algorithms. The variant that includes the terminal voltage in the state vector, i.e. the state nonlinearity variant of the EKF, shows better result, also compared to the existing literature.

Load separability and ηpl factor determination for CT specimen of Zr-2.5Nb pressure tube material

For fracture testing of pressure tubes, specimens are machined directly from the pressure tube without disturbing its curvature. The compact tension (CT) specimens thus obtained are called curved compact tension (CCT) specimens. Apart from being curved, the CCT specimens do not satisfy width/thickness criteria as mentioned in ASTM E1820-15. In spite of these differences, CCT specimens use the same ηpl and χpl factors as that of standard CT specimens for fracture toughness evaluation. In this work, 17 mm wide blunt notched CT specimens of different crack length obtained from a Zr-2.5Nb pressure tube, which were not meeting the thickness criteria, were used to investigate load separation and to evaluate the ηpl factor experimentally. Load separation existed between a/W of 0.45 and 0.70. The ηpl factor had a constant value of 2.078 in this range when calculated using the load separation method by power law fit. The ηpl factor calculated using a third order polynomial fit passing through the origin showed linear increase with b/W similar to but marginally lower than standard CT specimen.