Average Absolute Value Research Articles

A frequency-based parameter for rapid estimation of magnitude

This study introduce a new frequency parameter called tau_{text{fcwt}}, which can be used to estimate earthquake magnitude on the basis of the first few seconds of P-waves, using the waveforms of earthquakes occurring in Japan. This new parameter is introduced using continuous wavelet transform as a tool for extracting the frequency contents carried by the first few seconds of P-wave. The empirical relationship between the logarithm of tau_{text{fcwt}} within the initial 4 s of a waveform and magnitude was obtained. To evaluate the precision of tau_{text{fcwt}}, we also calculated parameters tau_{text{p}}^{ hbox{max} } and tau_{text{c}}. The average absolute values of observed and estimated magnitude differences (|M_{text{est}} - M_{text{obs}} |) were 0.43, 0.49, and 0.66 units of magnitude, as determined using tau_{text{p}}^{ hbox{max} }, tau_{text{c}}, and tau_{text{fcwt}}, respectively. For earthquakes with magnitudes greater than 6, these values were 0.34, 0.56, and 0.44 units of magnitude, as derived using tau_{text{p}}^{ hbox{max} }, tau_{text{c}}, and tau_{text{fcwt}}, respectively. The tau_{text{fcwt}} parameter exhibited more precision in determining the magnitude of moderate- and small-scale earthquakes than did the tau_{text{c}}-based approach. For a general range of magnitudes, however, the tau_{text{p}}^{ hbox{max} }-based method showed more acceptable precision than did the other two parameters.

Analysis of climate change in Dnipropetrovsk Region

The decision about writing this article was made after familiarization with the "Brief Climatic Essay of Dnepropetrovsk City (prepared based on observations of 1886 – 1937)" written by the Head of the Dnipropetrovsk Weather Department of the Hydrometeorological Service A. N. Mikhailov.
 The guide has a very interesting fate: in 1943 it was taken by the Nazis from Dnipropetrovsk and in 1948 it returned from Berlin back to the Ukrainian Hydrometeorological and Environmental Directorate of the USSR, as evidenced by a respective entry on the Essay's second page.
 Having these invaluable materials and data of long-term weather observations in Dnipro city we decided to analyze climate changes in Dnipropetrovsk region.
 The article presents two 50-year periods, 1886-1937 and 1961-2015, as examples. Series of observations have a uniform and representative character because they were conducted using the same methodology and results processing.
 We compared two main characteristics of climate: air temperature and precipitation.
 The article describes changes of average annual temperature values and absolute temperature values. It specifies the shift of seasons' dates and change of seasons' duration.
 We studied the changes of annual precipitation and peculiarities of their seasonable distribution. Apart from that peculiarities of monthly rainfall fluctuations and their heterogeneity were specified.
 Since Dnipro city is located in the center of the region the identified tendencies mainly reflect changes of climatic conditions within the entire Dnipropetrovsk region.

Is the Cobb technique the most reliable and valid to assess the scoliotic deformity?

Introduction Adolescent idiopathic scoliosis (AIS) is a 3D deformity of the spine commonly assessed on frontal X-rays using the Cobb technique. Some authors have found this technique to be poorly representative of the extent of the deformity, suggesting that the Ferguson and Centroid techniques, could better characterize this deformity. The aim was to evaluate the reliability and validity of different measurement techniques of the scoliotic deformity. Material and methods Seventy-three subjects with AIS (55F, age: 14 years [9–18]) underwent full body biplanar X-rays with 3D spinal reconstructions. The subjects were stratified into 4 groups with increasing Cobb values: Gr1 [10–20°] – n = 20, Gr2 [20–40°] – n = 20, Gr3 [40–70°] – n = 20, Gr4 [> 70] – n = 13. 2D frontal X-rays were used to measure the Cobb, Ferguson and Centroid angles digitally using a software, and manually on a film using a goniometer. 3D reconstructions were used to calculate the frontal, sagittal and axial deformity indices (FDI, SDI, ADI: averages of absolute values of upper endplate inclinations or axes of each vertebra in the scoliotic segment, in corresponding plane), which were considered as gold standard for deformity evaluation. Reliability was assessed by measuring each parameter twice manually then digitally, by 3 operators. Intraclass correlation coefficient (ICC) and reproducibility variance (SR) for each parameter were evaluated. As for the validity, stepwise multiple linear regressions (SMLR) were used to investigate which measurement technique is the most representative of the deformity indices in the 3 planes. Results Overall, the SR was higher for the manual technique regardless of the method, and increased with Cobb angle. In Gr1 to 3, the Cobb method showed the lowest SR (2.2°, 2.8°, 3.6° in Gr1 to 3) compared to the Ferguson and Centroid methods (from 2.6° to 4.8° and 3.8° to 5.4°). In Gr4, the Ferguson method showed the lowest SR (5.8° for Ferguson vs. 7.6° for Cobb and 10° for Centroid). The SMLR models found that the only determining factor for all techniques was the FDI. The slope of the linear regressions between the FDI and each parameter was: 1.9 for Ferguson (R2 = 0.94), 2.79 for Centroid (R2 = 0.93) and 2.97 for Cobb (R2 = 0.95). Discussion The Cobb was the most reliable and representative of the 3D deformity and shows that it would better differentiate between spines with different curvatures (highest correlation slope). Although some studies had criticized the Cobb angle for inadequately representing the scoliotic deformity, this study revealed that the Cobb was the most appropriate measurement technique to assess the 3D scoliotic deformity.

FUSION OF LANDSAT- 8 THERMAL INFRARED AND VISIBLE BANDS WITH MULTI-RESOLUTION ANALYSIS CONTOURLET METHODS

Abstract. Land surface temperature image is an important product in many lithosphere and atmosphere applications. This image is retrieved from the thermal infrared bands. These bands have lower spatial resolution than the visible and near infrared data. Therefore, the details of temperature variation can't be clearly identified in land surface temperature images. The aim of this study is to enhance spatial information in thermal infrared bands. Image fusion is one of the efficient methods that are employed to enhance spatial resolution of the thermal bands by fusing these data with high spatial resolution visible bands. Multi-resolution analysis is an effective pixel level image fusion approach. In this paper, we use contourlet, non-subsampled contourlet and sharp frequency localization contourlet transform in fusion due to their advantages, high directionality and anisotropy. The absolute average difference and RMSE values show that with small distortion in the thermal content, the spatial information of the thermal infrared and the land surface temperature images is enhanced.

An acoustic method for flow rate estimation in agricultural sprayer nozzles

The cost of current flow rate measurement devices is quite high compared to the cost of low-end microphones. This circumstance, together with the fact that common agricultural sprayers have more than 50 nozzles, makes the use of current flow rate measurement devices cost-prohibitive. That considered, this article examines, by proposing one particular method, the feasibility of using microphones as flowmeters for nozzle tips in agricultural sprayers. The proposed method consists of the following stages: (i) acquisition of the digital acoustic data sequence, (ii) signal preprocessing, (iii) frequency domain transformation using Fast Fourier Transform (FFT) analysis, (iv) in-band power calculation, (v) power normalization, and (vi) regression or curve fitting. This method was assessed in an in-lab sprayer test bench employing 11 commercial nozzle tips at several operating flow rates within or close to those recommended by the manufacturers. The experimental results yielded, for all the tested nozzle tips, average absolute and relative Root Mean Square Error (RMSE) values always below 0.08 liters per minute (lpm) and 5%, respectively, while the overall mean absolute and relative RMSE values were lower than 0.05lpm and 2.5%. Furthermore, for each tested nozzle tip, the Maximum Absolute Error (MAE) was always bounded below 0.3lpm, being the absolute error lower than 0.15lpm for 95% of the time. The accuracies when employing a high-end microphone instead of a low-end one presented no statistically significant differences. These results provide strong evidence of the feasibility of accurately estimating the nozzle tip flow rate in real time based on acoustic signals. Moreover, no significant improvements are to be expected by using a high-end microphone instead of a low-end one. However, there are still some issues that should be tackled in order to enable the application of this method in real agricultural settings.

The Method of Random Skewers

Ecological and evolutionary studies are often concerned with the properties of covariance matrices. The method of random skewers (RS method) has been used compare a matrix to an a priori vector or to compare two matrices. The method involves multiplying a matrix by many random vectors drawn from a uniform distribution over all possible vector directions. The comparisons are usually made using the average angle (or cosine) of the response vectors to an a priori vector or to the response vectors corresponding from another matrix. Angles are usually constrained to the interval 0°–90° because the distribution of response vectors is bipolar bimodal. The size of the average angle or cosine depends strongly on the relative sizes of the eigenvalues (especially the first). The distribution of angles between pairs of response vectors from two covariance matrices is more complicated because it depends on the differences in orientation of the eigenvectors and the relative sizes of the eigenvalues of the both matrices. The average absolute value of the angles between these pairs of response vectors depends on the relative sizes of the eigenvalues of the matrices making it difficult to interpret its meaning without knowledge of the eigenvalues and eigenvectors of the two matrices. Thus, it is simpler to just directly compare matrices in terms of these quantities.

Efficient estimation of acid gases (CO2 and H2S) absorption in ionic liquids

This work presents the application of computer based models including radial basis function neural network optimized by particle swarm optimization method (PSO-RBF), multilayer perceptron neural network (MLP-NN), least square support vector machine optimized by coupled simulated annealing (CSA-LSSVM) and adaptive neuro-fuzzy inference system trained by hybrid method (Hybrid-ANFIS) for prediction of solubility of CO2 and H2S in ionic liquids (ILs). A high-valued data base including 2930 data points for 39 CO2-IL systems and 664 data points for 14 H2S-ILsystems were collected to develop the models with acceptable generality. The input parameters of the models are temperature, pressure, molecular weight of IL and several structural related parameters of ILs. The performance of the developed models was evaluated by using statistical quality measure approaches. Moreover, the predictions of the developed models are compared with the predictions of a thermodynamic model based on Peng-Robinson equation of state (EoS). Results show that the developed models provide accurate predictions with reasonable errors. However, the CSA-LSSVM model provides better predictions for both CO2-IL and H2S-IL systems with average absolute relative deviation values of 1.97% and 0.13%, respectively. Moreover, the predictions of the developed models are found better and effective than the predictions of the thermodynamic model. Results of this work also show that the solubility of CO2 and H2S in ILs could be well correlated by structural related parameters of ILs.

A Novel Protocol to Monitor Trace Levels of Selected Polycyclic Aromatic Hydrocarbons in Environmental Water Using Fabric Phase Sorptive Extraction Followed by High Performance Liquid Chromatography-Fluorescence Detection

Fabric phase sorptive extraction (FPSE) combines the advanced material properties of sol–gel derived microextraction sorbents and the flexibility and permeability of fabric to create a robust, simple and green sample preparation device. It simultaneously improves the extraction sensitivity and the speed of the extraction by incorporating high volumes of sponge-like, porous sol–gel hybrid inorganic–organic sorbents into permeable fabric substrates that are capable of extracting target analytes directly from both simple and complex aqueous sample matrices. For the first time, this technique was applied to the trace-level determination of selected polycyclic aromatic hydrocarbons (PAHs) in environmental water samples using a non-polar sol–gel C18 coated FPSE media. Several extraction parameters were optimized to improve the extraction efficiency and to achieve a high detection sensitivity. Validation tests of spiked samples showed good linearity for four selected PAHs (R2 = 0.9983–0.9997) over a wide range of concentrations (0.010–10 ng/mL). Limits of detection (LODs) and quantification (LOQs) were measured at pg/mL levels; 0.1–1 pg/mL and 0.3–3 pg/mL, respectively. Inter- and intra-day precision tests showed variations of 1.1%–4.1% for four selected PAHs. Average absolute recovery values were in the range of 88.1%–90.5% with relative standard deviations below 5%, surpassing the values predicted by the recovery prediction model. Finally, the developed FPSE-HPLC-FLD protocol was applied to analyze 8 environmental water samples. Out of four selected PAHs, fluoranthene (Flu) and phenanthrene (Phen) were the most frequently detected in four samples, at concentrations of 5.6–7.7 ng/mL and 4.1–11 ng/mL, respectively, followed by anthracene (Anth) and pyrene (Pyr) in two samples. The newly developed FPSE-HPLC-FLD protocol is simple, green, fast and economical, with adequate sensitivity for trace levels of four selected PAHs and seems to be promising for routine monitoring of water quality and safety.

Experimental investigation of slip velocity and dispersed phase holdup in a Kühni extraction column

AbstractSlip velocity in the solvent extraction columns is the relative velocity of drops with respect to the continuous phase and defines as the sum of the linear velocities of the two phases. In this research, slip velocity and dispersed phase holdup in a pilot plant‐scale Kühni extraction column has been investigated experimentally. The effects of operating parameters including rotor speed, continuous and dispersed phase flow rates, and mass transfer direction have been examined. An empirical correlation is presented to predict slip velocity in Kühni extraction column as a function of physical properties of the chemical test systems, operating conditions, and geometry of the column. The overall average absolute values of relative error for holdup and slip velocity are 8.75% and 10.50%, respectively. Optimum values of the constants for the correlations were obtained via genetic algorithm method. The result of the empirical correlation was compared with experimental data and with previous correlations. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

How Accurately The Smartwatch Measures Steps?

Wearable activity trackers are getting popular in the fitness market to track individual’s activity level and several research studies have examined the validity of popular wearable activity trackers. However, there is still limited research regarding the validity of smart watch. PURPOSE: The present study was to systemically examine the validity of the Apple watch for measuring steps. METHODS: Healthy individuals (mean ± SD; age = 23.5 ± 13.4 years; body mass index = 26.8 ± 4.2 kg·m2) participated in the study. The participants were asked to wear the apple watch while normal walking, fast walking and running for one lap on an indoor track (i.e., 200-meter track). The actual steps were manually tallied by researchers using a hand tally counter and the steps on the watch were recorded before and after each test, step counts from the apple watch were compared with manually counted steps. Pearson correlation was calculated to identify the measurement relationship between the counted steps and the recorded steps from the apple watch. Mean absolute percentage error (MAPE) were calculated to examine the measurement error of the Apple watch steps. A dependent t-test was performed to the significant mean differences between counted steps and recorded steps from the apple watch. RESULTS: Total step counts (means ± SD) for counted steps were 222.3±82.5 for normal walking, 198.2±55.7 for fast walking, and 185.9±35.7. Recorded steps from the apple watch were 216.9±77.7 for normal walking, 198.2±55.7 for fast walking, and 188.4±37.9 for running. Pearson correlations were r=.96 (p=.001) for normal walking, r=.83 (p=.000) for fast walking, and r=.93 (p=.000) for running, respectively. Corresponding mean absolute error rates (computed as the average absolute value of the individuals’ errors) were 6.1 ±6.6%, 8.8±11.2%, and 4.3±5.8%, for normal walking, fast walking, and running, respectively. Dependent sample t-tests indicated that there is no significant difference (t(35)=.989, p=.359) between the counted steps and the recorded steps from apple watch. CONCLUSION: The results demonstrate that the apple watch accurately measures steps on normal walking and running conditions compared to the manually counted steps. However, further research is needed to with more sample size and various populations. Words: 1972/2000

Constitutive Modeling of Warm Deformation Flow Curves of an Eutectoid Steel

The capabilities of the commonly encountered Johnson-Cook and Arrhenius-type constitutive equations to describe the warm deformation flow curves of an eutectoid steel undergoing dynamic spheroidization have been compared based on the warm compression test data. Warm compression tests were conducted over the temperature range 620-770 °C and strain rates in the range of 0.01-10 s−1. The average absolute relative error values for the Johnson-Cook and Arrhenius-type constitutive equations were 44.03 and 6.50%, respectively, thereby showing that the Arrhenius-type constitutive equation is to be preferred. It is also shown that in contrast to the Arrhenius-type constitutive equation, the softening caused by dynamic spheroidization cannot be modeled using the Johnson-Cook equation.

The effect of cyano groups on the solubility of carbon dioxide in ionic liquids containing cyano groups in anion

The solubility of carbon dioxide (CO2) was investigated using three ionic liquids containing different numbers of cyano groups in the anion, 1-hexyl-3-methylimidazolium tricyanomethanide ([c6mim][C(CN)3]), 1-hexyl-3-methylimidazolium dicyanamide ([c6mim][N(CN)2]), and 1-hexyl-3-methylimidazolium thiocyanate ([c6mim][SCN]). The CO2 solubilities were determined by measuring the bubble point pressures of the CO2+ionic liquid mixtures at temperatures ranging from 303.15 to 373.15 K and pressure up to 105MPa. The experimental results showed that the solubilities of CO2 in ionic liquids increased with pressure, decreased with temperature, and increased with the length of the alkyl chains in the cation. Furthermore, a higher CO2 solubility was achieved in the ionic liquid with more cyano groups in the anion. The experimental data were correlated with the Peng-Robinson equation of state (PR-EoS), using the conventional van der Waals one fluid mixing rule and the modified Lydersen-Joback-Reid method. The average absolute deviation values of pressure (AAD-P) were 0.0658 for CO2+[c6mim][SCN], 0.0633 for CO2+[c6mim][N(CN)2], and 0.0761 for CO2+[c6mim][C(CN)3] system.

Predicting Flow Stress of Four Types of Microalloyed Forging Steel at High Temperature by Artificial Neural Network Model

Artificial neural network (ANN) gets a lot of applications in predicting flow stress of steels at high temperature. However, few studies have been devoted to simultaneously predict flow stress of several steels by ANN. The purpose of this paper is to determine the effect of ANN on simultaneously predicting flow stress of several steels. Based on the results of previous compression experiments of four types of microalloyed forging steel, using the mass percentage of major chemical composition of the steels, such as as C, Mn, Si and V, and deformation temperature, strain rate and strain as input variables, a three-layers back propagation neural network was established as the constitutive model for them. Standard statistical methods were employed to quantitatively measure the accuracy of predicted results by the model. The calculated correlation coefficient and the average relative error absolute value between the predicted values by the model and experimental values were 0.9982 and 2.4181%, respectively. In addition, the relative error between the two kinds of values was calculated, and for more than 89% samples, the relative error was within ± 5%. The results show that the developed constitutive model can predict the flow stress of the four types of microalloyed forging steel accurately and simultaneously.

The categorical perception of Mandarin tones by children with speech development disorders

Objective To investigate the perception of Mandarin′s tones by children with speech development disorders so as to provide a theoretical basis for clinical rehabilitation. Methods Thirty children with speech development disorders (DPDs) aged 4 to 6 were matched with 30 healthy counterparts as a control group. Both groups underwent the tone perception experiment, which included tone identification and discrimination tasks. The speech stimuli were 11 computer-simulated voices expressing a continuum of sounds from Mandarin speech ranging from /ba/ to /ba/. The two groups were compared in their ability to identify and differentiate the tones. Results Both groups showed typical S-shaped identification curves in a category pattern. The category boundaries of the control group were between stimulus steps 6 and 7, significantly different from those of the experimental group where the boundary fell between stimulus steps 5 and 6. On the distinguishing curve, both groups presented obvious peak values. The stimulus steps of the peaks and the crossing points of the identification curves were consistent. In addition, the average absolute value (b1) of the identification curve and the peaks′ degree of steepness (DP) of the DPD group′s distinguishing curve were significantly lower than those of the control group. At the same time, the average boundary width (Wcb) was significantly higher than that of the control group. Conclusion Children with speech development disorders perceive Mandarin tones with categories different from those of normal children. They may have difficulty in perceiving tones, which might be an important factor leading to pronunciation errors. Key words: Tones; Speech development; Categorical perception; Mandarin

レンズ型二重空気膜構造の強風時の応答性状の把握と内圧設定手法の提案

Pneumatic structure resists external force by increasing internal air-pressure. In particular, lenticular pneumatic structure are strongly sealed. With this structure it is expected that stress suddenly changes with volume change. For this reason, the supposition of internal air-pressure uniformity may lead to an unsafe situation. In addition, the setting method of internal air-pressure on the basis of structural behavior of lenticular pneumatic structure has not been established. This paper examined the parameters as aspect ratios of rectangular panels. Firstly, dynamic data was collected through wind tunnel tests using both a rigid and a flexible model for the purpose of understanding the wind pressure coefficient under strong winds and the dynamic behavior of fluctuating internal air-pressure. Next, a time-history wind response analysis was performed to evaluate the fluctuating internal air-pressure under strong winds, and then compared with the results of flexible model by the wind tunnel test. Finally, a methodology for setting the internal air-pressure was proposed based on the data obtained from the static and the dynamic numerical analysis. The results of these studies revealed the following. The wind tunnel test using the rigid model showed mostly suction pressure over the entire surface in all parameters. In addition, when the turbulence intensity of air flows increased, the average absolute value of the coefficient of wind force became small. In the wind tunnel test using the soft elastic model, volumes increased and internal air-pressure decreased because the entire surface experienced suction pressure. It was compared to the numerical analysis data using a potential-based fluid and the results of the wind tunnel test using soft elastic model. The numerical analysis value corresponded with the experimental value. Through method of setting internal air-pressure in the case of aspect ratio of 1, it indicated that setting internal air-pressure is possible by accounting for internal air-pressure and membrane stress under uniformly distributed load.

Accuracy of various intraocular lens power calculation formulas in steep corneas

Purpose:To compare the accuracy of four different intraocular lens (IOL) power calculation formulas for eyes with mean keratometry values greater than 46 diopters (D).Methods:Forty five eyes from 45 patients who were candidates for senile cataract surgery with mean keratometry values greater than 46 D were included. Calculation of the IOL power was performed by the Lenstar. The implanted IOL in all cases was Acrysof SA60AT. The average absolute value of the differences between the actual and predicted spherical equivalent (SE) of the postoperative refractive error (mean absolute error: MAE) was calculated using 4 formulas (Haigis, Holladay 1, Hoffer Q, and SRK/T) with optical IOL constants from the User Group for Laser Interference Biometry constants.Results:The MAE was smallest in the SRK/T formula (0.39 D ± 0.35) followed by those of the Holladay 1 (0.44 D ± 0.32), Haigis (0.45 D ± 0.35) and Hoffer Q (0.5 D ± 0.38) formulas. However, there was no statistically significant difference between the MAE among different formulas. The SRK/T formula predicted more eyes within ± 0.5 D of the SE (77.8%) compared to other formulas.Conclusion:In eyes with steep corneas, there were no statistically significant differences among the accuracies of the four common IOL power calculation formulas.

Reliable prediction of adsorption isotherms via genetic algorithm molecular simulation.

Conventional molecular simulation techniques such as grand canonical Monte Carlo (GCMC) strictly rely on purely random search inside the simulation box for predicting the adsorption isotherms. This blind search is usually extremely time demanding for providing a faithful approximation of the real isotherm and in some cases may lead to non-optimal solutions. A novel approach is presented in this article which does not use any of the classical steps of the standard GCMC method, such as displacement, insertation, and removal. The new approach is based on the well-known genetic algorithm to find the optimal configuration for adsorption of any adsorbate on a structured adsorbent under prevailing pressure and temperature. The proposed approach considers the molecular simulation problem as a global optimization challenge. A detailed flow chart of our so-called genetic algorithm molecular simulation (GAMS) method is presented, which is entirely different from traditions molecular simulation approaches. Three real case studies (for adsorption of CO2 and H2 over various zeolites) are borrowed from literature to clearly illustrate the superior performances of the proposed method over the standard GCMC technique. For the present method, the average absolute values of percentage errors are around 11% (RHO-H2), 5% (CHA-CO2), and 16% (BEA-CO2), while they were about 70%, 15%, and 40% for the standard GCMC technique, respectively.

Analyses of determination conditions of n-GaN dislocation density by triple-axis X-ray diffraction

Dislocation densities of two hydride vapor phase epitaxy-grown hexagonal GaN samples, which are Si doped and unintentionally doped respectively, are determined by triple-axis X-ray diffractometry and van der Pauw variable temperature Hall-effect measurement. The dislocation densities of these two samples should be at the same level from the X-ray testing, the -FWHM (full width at half maximum) values of all corresponding reflections for these two samples are almost the same. But from the Hall-effect measurements, the dislocation density values should be different from each other remarkably, because the unintentionally doped sample belongs to Mott transition material, while the Si-doped one does not. This fact indicates that the X-ray testing is perhaps inaccurate under some conditions, although the triple-axis X-ray diffractometry is a highly suitable technique for discriminating different kinds of structural defects such as edge and screw dislocations that lead to characteristic broadening of symmetric and asymmetric Bragg reflection. The experimental result obtained so far (say, for hot-electron bolometer) shows that the dislocation density value from mobility fitting model is in good accordance with that from -FWHM fitting using Srikant method. The anomaly that the dislocation density from -FWHM fitting is much lower than that from mobility fitting for the same sample (sample 59#), indicates that dislocations located in grain boundary may not be tested by triple-axis X-ray diffractometry. According to mosaic model, the layer is assumed to consist of single crystallites, called mosaic blocks, which are assumed to be slightly misoriented with respect to each other. The out-of-plane rotation of the block perpendicular to the surface normal is of the mosaic tilt, and the in-plane rotation around the surface normal is of the mosaic twist. The average absolute values of tilt and twist angles are directly related to the FWHM values of the corresponding distributions of crystallographic orientations. So, the X-ray testing can determine the average orientation of the grains with the same interplanar distance, excluding the information about the grain boundary at which X-ray cannot interfere because of disdortion of lattice. The experimental results and calculation analyses indicate that the dislocation density value from Srikant model is accurate when the ratio of twist angle to tilt angle exceeds 2.0, or the magnitude of the lateral coherence length is larger than 1.5 m.

An observer-based digital control system for individually management of active and reactive power of dual-active-bridge DC/DC converter

AbstractThis paper proposes an observer-based digital control system to manage active and reactive powers in a Dual-Active-Bridge converter. Since they are proportional to the direct and the quadrature components of the transferred current, Id and Iq, respectively, the power management is realized by regulating the two current components. An observer is designed to estimate them from the feedback voltage and the average absolute value of the transferred current. Since all the feedback signals for the observer are DC quantities, the sampling speed is not necessary to be very high. A digital controller is then synthesized to regulate Id and Iq at desired values. In the control system, the bridge shift angle is used to handle Iq, meanwhile the switching frequency is variable to manipulate Id. The current command for Id is calculated from the desired active power, meanwhile, by assigning a positive value for Iq control loop, soft turn on is easily achieved. The performance of the observer as well as the digit...

Consensus of Switched Multiagent Systems under Relative State Constraints

The consensus problem is presented for the switched multiagent system (MAS), where the MAS is switched between continuous- and discrete-time systems with relative state constraints. With some standard assumptions, we obtain the fact that the switched MAS with relative state constraints can achieve consensus under both fixed undirected graphs and switching undirected graphs. Furthermore, based on the absolute average value of initial states, we propose sufficient conditions for consensus of the switched MAS. The challenge of this study is that relative state constraints are considered, which will make the consensus problem much more complex. One of the main contributions is that, for the switched MAS with relative state constraints, we explore the solvability of the consensus problem. Finally, we present two simulation examples to show the effectiveness of the results.