Homogeneous Coefficients Research Articles

An improved distributed scatterers extraction algorithm for monitoring tattered ground surface subsidence with DSInSAR: A case study of loess landform in Tongren county

In order to effectively detect the detailed subsidence of tattered ground surface composed of many small fragments with the distributed scatterer interferometric synthetic aperture radar (DSInSAR) technique, a fast and accurate distributed scatterer extraction (FADSE), as an improved distributed scatterers extraction algorithm, is proposed and demonstrated in this paper. The emphasis of FADSE is on the improvement of accuracy of extracted DSs and detection efficiency as well. For the purpose, nonparametric estimation and parametric estimation methods are combined into FADSE to fast identify as many accurate statistically homogeneous pixels (SHP) as possible. Then the thresholds of homogeneous pixel number and coherence coefficient are adjusted to select DSs from SHPs. The validation of FADSE was performed in the case of loess subsidence detection in Tongren county, Qinghai Province of China, using 20 Sentinel-1A SAR images acquired between February 2016 and June 2017. Moreover, FADSE was compared with the Kolmogorov-Smirnov algorithm and Fast Statistically Homogeneous Pixel Selection method. Results show that FADSE is capable of efficiently extracting more DSs that are accurate and the detailed subsidence of tattered ground surface can be accurately detected.

Vector Autoregressive Models with Spatially Structured Coefficients for Time Series on a Spatial Grid

We propose a parsimonious spatiotemporal model for time series data on a spatial grid. Our model is capable of dealing with high-dimensional time series data that may be collected at hundreds of locations and capturing the spatial non-stationarity. In essence, our model is a vector autoregressive model that utilizes the spatial structure to achieve parsimony of autoregressive matrices at two levels. The first level ensures the sparsity of the autoregressive matrices using a lagged-neighborhood scheme. The second level performs a spatial clustering of the non-zero autoregressive coefficients such that nearby locations share similar coefficients. This model is interpretable and can be used to identify geographical subregions, within each of which, the time series share similar dynamical behavior with homogeneous autoregressive coefficients. The model parameters are obtained using the penalized maximum likelihood with an adaptive fused Lasso penalty. The estimation procedure is easy to implement and can be tailored to the need of a modeler. We illustrate the performance of the proposed estimation algorithm in a simulation study. We apply our model to a wind speed time series dataset generated from a climate model over Saudi Arabia to illustrate its usefulness. Limitations and possible extensions of our method are also discussed.

Analysis of the effect of surface topography on lubrication using heterogeneous multiscale method

In this paper, flow factors considering the roughness of the different orientation angles and different wavelengths are obtained from the derived form of the homogenization coefficient, which is calculated by a heterogeneous multiscale inverse approach. The influence of anisotropic roughness on the flow factors is investigated. When the angle is equal to 45°, the span flow is maximum. The flow factor curves happen to overlap when the wavelength ratio is less than 4 with double cosine roughness. To verify the flow factors, film pressures are calculated by a finite element heterogeneous multiscale method (FE-HMM) without considering the flow factors. Then, by comparing the results with solutions of a finite difference method, the FE-HMM method gets the results that are needed, and with a shorter time of calculation. The pressure curve is greatest when the orientation angle is 45° with a double cosine roughness, which is caused by the asperity number and the span flow. The pressure distributions of the cosine roughness and double cosine roughness are different as the orientation angle changes.

Study on multiple fingerprint profiles control and quantitative analysis of multi-components by single marker method combined with chemometrics based on Yankening tablets

In this study, we explored the quality consistent evaluation method of Yankening Tablets (YKNT) from different manufacturers by using multiple fingerprint profiles, including dual-wavelength ultra-high performance liquid chromatography (UPLC) serial fingerprint and Fourier Transform Infrared Spectroscopy (FT-IR) fingerprint, combined with quantitative analysis of multi-components by single marker (QAMS) method. In the Average method of systematic quantified fingerprint method (AMSQFM), three fingerprint parameters of macro qualitative similarity (Sm-UPLC-FTIR), macro quantitative similarity (Pm-UPLC-FTIR), and the variation coefficient of fingerprint homogeneity (αUPLC-FTIR) were calculated based on the ratio method. The Sm-UPLC-FTIR values of all the samples were greater than 0.80, the αUPLC-FTIR values were less than 0.20, and the Pm-UPLC-FTIR values range from 72.8% to 119.8%. Method validation results showed the established fingerprint method had good precision, solution stability, and method repeatability, all samples could be roughly divided into different levels. The contents of berberine (BBR) and baicalin (BCL) measured by the calibration curve method (CCM) and QAMS method were compared, and t-test results (Pvalue > 0.05) indicated there was no significant difference between the two methods, which showed that QAMS could accurately quantify the markers of the YKNT. The explanatory ability (R2Y) values of BBR and BCL in the PLS model were both greater than 0.94, and the root mean square error of estimation (RMSEE) and root mean square error of prediction (RMSEP) values were both less than 2.5, indicating that the established model was reliable. Hierarchical cluster analysis divided all samples into four categories. This research made a major contribution to the quality consistent evaluation of Traditional Chinese Medicine (TCM) and food.

Quantitative characterize binder blending and diffusion in recycled asphalt mixture: An environmental-friendly solution using wooden cube and 3D fluorescence image technology

Due to the undetermined extent of blending phenomena between virgin and reclaimed asphalt, the use of reclaimed asphalt pavement (RAP) is limited. Currently, there is no universally accepted method and uniform terms for the quantification of blending phenomena. To this end, this paper proposed a new method based on 3D fluorescence image technology (3D-FIT) by using laser scanning confocal microscope. Natural asphalt and wooden cube were used to prepare RAP under laboratory aging for specific needs, styrene-butadiene-styrene (SBS) as fluorescent particles from SBS modified asphalt were employed to trace and quantify the blending phenomena. Subsequently, the steps of standardized pretreatment on wooden cube were developed, such as correction of asphalt content, autofluorescence elimination, attenuation correction etc. Under this new method, two suggested parameters including degree of blending, homogenization coefficient were proposed, both of which depends on the fluorescence intensity decay function, homogenization coefficient was defined to describe the homogenization of virgin and reclaimed asphalt. Moreover, the concepts on degree of blending and degree of RAP binder mobilization were distinguished. Compared with existing methods, the combination of fluorescent particles and laser scanning confocal microscope (LSCM) can perform three-dimensional observation and quantitative characterization for blending phenomena. It also provides a new attempt to analyze and evaluate blending and diffusion on the interface between asphalt and aggregate.

Matroid connectivity and singularities of configuration hypersurfaces

Consider a linear realization of a matroid over a field. One associates with it a configuration polynomial and a symmetric bilinear form with linear homogeneous coefficients. The corresponding configuration hypersurface and its non-smooth locus support the respective first and second degeneracy scheme of the bilinear form. We show that these schemes are reduced and describe the effect of matroid connectivity: for (2-)connected matroids, the configuration hypersurface is integral, and the second degeneracy scheme is reduced Cohen–Macaulay of codimension 3. If the matroid is 3-connected, then also the second degeneracy scheme is integral. In the process, we describe the behavior of configuration polynomials, forms and schemes with respect to various matroid constructions.

Quantitative homogeneity assessment of particle reinforced magnesium-lithium composite ingot by homogeneity factors

A method based on dimensionless homogeneity factors (homogeneity coefficient ζ and deviation rate η) was proposed to assess the homogeneity of particle reinforced magnesium-lithium matrix composite industrial-sized ingot. The effectiveness of the method was investigated, and the correlation between microstructure homogeneity and mechanical properties was explored through the assessment of YAl2p/LA143 ingot. The results show that the method can effectively assess the homogeneity degree of composite ingot through homogeneity factors. The homogeneity of YAl2p/LA143 ingot is affected by some assessment indexes with ζ lower than 90% and η higher than 30% such as grain size, reinforcement distribution, tensile strength and elongation. With the increase of homogeneity coefficient of YAl2 particles distribution (ζPD), the tensile strength and elongation of composite ingot increase exponentially, and the yield strength increases linearly.

The steel plate curvature analytic modeling for the snake rolling with the same roll diameters

The snake rolling can keep the plate shape well, and the larger shear strain produced by the snake rolling is conducive to the deformation penetrating into the center of the heavy plate. So it provides a new method for producing the high-performance heavy steel plate. However, there is little research on the plate curvature modeling which is the key to achieve the snake rolling process. The deformation region was divided into four different zones at most which was depended on the positions of the two neutral points, and this number could be dropped to three or two in some other conditions. It was divided into three different cases according to the neutral point position: I, II, III and IV; I, II and IV; II and IV. The unit pressure and the accumulated shear strain deviation between the top and bottom portions of the plate with every case were established, and the plate curvature caused by shear strain was calculated on this basis. The plate curvature caused by the axial strain was also calculated according to the flow criterion. The approximations are corrected by a fitting coefficient E. The homogeneity coefficient E was introduced during the plate curvature modeling process to make the model more accurate. Then the total plate curvature model was established. The simulation of snake rolling process is carried out by using ANSYS LS-DYNA, and the plate curvature results are compared with the theoretical method. The results showed that the maximum and minimum relative error of the model was 11.61% and 0.28% compared to the simulation method, which can be applied for the online plate curvature control application with the effect of some self-learning methods. The plate curvature affecting law with the different process parameters (roll offset, roll speed ratio, rolling reduction, plate thickness and so on) was obtained in this paper. The research about the plate curvature modeling will provide important references for the heavy steel plate snake rolling production.

Method of optimization of geometric transformations of design surfaces of a man’s jacket

The article considers the mechanism of combining 3D and 2D-design methods based on the combination of modules of 3D-digital modification of the morphological structure of the body and 2D-generation of sweep details of the jacket. The mechanism of formation of the integrated design system for transformation of a surface of a body into silhouette designs on the basis of geometrical modeling has been offered. The selection of optimal divisions of the mannequin surface on the basis of identification of zones of stable deformations of the grid with regular topology is theoretically substantiated. Has been shown that the maximum compression deformation in the range of overall dimensions characterizes the parametric levels of darts in the product design. The affine transformations by the operation “shift” of the mannequin surface scan into three basic silhouettes of the jacket design were experimentally investigated. Parametrical transformation of silhouette designs have been realized by schemes of designs and the reference book of standard movements. Homogeneity of details’ construction of the sketch project of interchangeable models system has been estimated by coefficients of constructive homogeneity of silhouette designs and technological homogeneity of model functional knots. The algorithm of formation of the integrated design system of 3D and 2D-design is developed and its practical application on an example of the development of a series of interchangeable models of a jacket is shown.

First-order linear partial differential equations using the GeoGebra and GeoGebra 3D graphing calculator

In this paper we will show, through various examples of how are the animated solutions of certain linear partial differential equations of the first order with constant homogeneous coefficients through GeoGebra applets designed for a first course of Partial Differential Equations for the engineering careers of the University of Antofagasta-Chile

The long-term dynamics of the old-growth structure in the National Nature Reserve Badínsky prales

The main goal of this paper was to evaluate structure dynamics in the fir-beech, old-growth forest Badínsky prales. Measurements were taken on four permanent research plots (0.5 ha each) between 1970 and 2018, typically in ten-year intervals. In order to assess long-term structure dynamics, this study used basic stand characteristics and selected structural indices – the relative density (RD), coefficient of homogeneity (H), and structural complexity index (SCI). Species composition was quantified by the relative importance value (RIV), and a detrended correspondence analysis was carried out for the visualisation of long-term changes. The long-term mean of the stand volume reached 634 ± 99 m3·ha−1, and the mean of the basal area was 36.6 ± 4.0 m2·ha–1. Calculated values of the coefficient of homogeneity (1.46–2.54) were similar to values in other old-growth forests with a comparable tree species composition. An increasing trend in beech RIV values was observed; on the other hand, fir RIV values fell by approximately 20%–25%. In 2018, maximal values of the basal area, stand volume and relative density were recorded. These high values may indicate better growth conditions due to climate change, as well as fewer disturbance events in the last few decades.

Monetary Policy Independence and Bond Yield in Developing Countries

This paper investigates the impact of monetary policy independence shock on bond yield by allowing for heterogeneous coefficients in the model based on panel data for 19 developing countries using quarterly data from 1991 to 2016. First, we estimate the model using conventional panel VAR estimation with the assumption of homogeneous coefficients across countries. Second, by performing Chow and Roy-Zellner tests to check the homogeneity assumption, we find that the assumption does not hold in the model. Third, we apply a meangroup estimation for panel VAR as a solution for heterogeneity panel model. The results reveal that central bank independence is effective in reducing bond yield with the maximum at period 6 after the shock. Shock one standard deviation bond yield has a negative effect on consumption and investment. We determine that central bank independence has a contradictory effect on real activity; a negative effect on consumption but a positive influence on investment for the first two years after the shock. Additionally, we split our sample into three groups to make the subgroups pool. Our empirical result shows that monetary policy independence shock reduces bond yield. Meanwhile, the response of economic activity to bond yield varies for all three groups.

Study of HCAP-PC to Enhance Process Efficiency for Age-Hardened Aluminum Alloys Based on Grey Relational Analysis

A multi-pass equal-channel angular pressing (helical channel angular pressing-parallel channel, HCAP-PC) is proposed to enhance process efficiency and avoid plastic deformation damage during the preparation of ultrafine-grained age hardened aluminum alloys. Multiple shear and twist deformations are provided at the single extrusion channel. The channel parameters were optimized by using grey relational analysis (GRA). An orthogonal L16-4-5 test array containing five factors (ψ, ϕ, γ, m and the length of L1 section) and four levels was collected to investigate the influence of channel parameters on the effective strain, the effective stress, the amount of damage and the deformation homogeneity coefficients. Based on the GRA, the grey relational coefficients and the grey relational grades were calculated to report the significant channel parameters which affect the extrusion quality and efficiency. Furthermore, according to the results of segregated grey relational grades, the contribution orders from high to low were listed as ψ, ϕ, γ, m and L1. The extrusion experiments were carried out with aluminum alloy 2024 after solid solution treatment and at the HCAP-PC die with geometry of ψ 20°, ϕ 90°, γ 73°, m 1.35 and 1d. The ultrafine-grained age hardened aluminum alloys were prepared and the process time was decreased to less than 120 min.

A homogeneous approach to testing for Granger non-causality in heterogeneous panels

This paper develops a new method for testing for Granger non-causality in panel data models with large cross-sectional (N) and time series (T) dimensions. The method is valid in models with homogeneous or heterogeneous coefficients. The novelty of the proposed approach lies in the fact that under the null hypothesis, the Granger-causation parameters are all equal to zero, and thus they are homogeneous. Therefore, we put forward a pooled least-squares (fixed effects type) estimator for these parameters only. Pooling over cross sections guarantees that the estimator has a sqrt{NT} convergence rate. In order to account for the well-known “Nickell bias”, the approach makes use of the well-known Split Panel Jackknife method. Subsequently, a Wald test is proposed, which is based on the bias-corrected estimator. Finite-sample evidence shows that the resulting approach performs well in a variety of settings and outperforms existing procedures. Using a panel data set of 350 U.S. banks observed during 56 quarters, we test for Granger non-causality between banks’ profitability and cost efficiency.

Study on the particle morphology, powder characteristics and hydration activity of blast furnace slag prepared by different grinding methods

This paper compares and studies the particle morphology, particle size distribution (PSD) characteristics, powder characteristics and hydration characteristics of ground granulated blast furnace slag prepared by a ball mill and a vertical roller mill. Both types of slag particles are found to comply with the Rosin–Rammler–Bennett (RRB) distribution model. The degree of sphericity of the blast furnace slag powder particles decreases with the particle size and is lower when produced by vertical roller milling than by ball milling; the differences in particle morphology mainly exist at the 0–3 μm particle grade. For the same specific surface area, ball-milled slag powder has a higher angle of repose, natural bulk density and tapped bulk density than does vertical-roller-milled slag powder. Both slag powders are categorized as Coulomb solids, which exhibit cohesiveness and high flow resistance. Ball-milled slag powder has better hydration activity than that of vertical-roller-milled slag powder. The difference in the homogeneity coefficients of the two powders is important to the obvious differences in the particle characteristics and hydration activities of the ball-milled and vertical-roller-milled slags.

Method of Evaluating Residual Stresses in the Product Material

The method of evaluating the level of residual surface stresses in the products without the loss of their integrity at elastoplastic strains and under static and cyclic loading by scattering of hardness characteristics is proposed. Residual surface stress levels are assessed not by absolute hardness values but by the state of material structure. Its homogeneity coefficient in the Weibull distribution, characterizing the scattering of large-scale hardness data, was taken as a calculated structure damage parameter and evaluated by the LM-hardness method based on direct multiple independent hardness measurements. The estimation of residual stresses is built upon the correlation relation between the material structure damage and residual stresses. By comparing the measured parameters of structure homogeneity, charactering their damage level in the region of residual stresses, with the structure parameter in the region free from them, their level is determined. In the absence of such a region, residual stresses are evaluated by comparing the homogeneity parameter of the product element in their region with that of a reference sample made of the same material and subject to the same operating loads as the examined product. The product quality can be estimated by the regions of high residual stress concentrations, comparing the parameters obtained in its different characteristic sections. Correlation relations, determining the values of residual stresses, are found from preliminary experimental tests of the material specimens by constructing the structural parameter – stress diagram at a preset loading step. The structure parameter is measured by scattering its large-scale hardness measurements.

Mısır ve Ceviz Arazilerinde Kurulu Damla Sulama Sistemlerinde Bazı Performans Ölçütlerinin Belirlenmesi

Bu çalışma, 2017-2018 yıllarında Kırklareli ilinde mısır ve ceviz yetiştiriciliğinde kullanılan 15 adet çiftçi arazisindeki damla sulama sistemlerinde bazı performans ölçütlerini tespit etmek amacıyla yürütülmüştür. Çalışmanın yürütüldüğü işletmelerdeki damla sulama sistemlerinde, sulama eş dağılımının (CU) %82- 96, damlatıcı değişim katsayıları (Cv) 0.02-0.21, istatistiksel eş dağılım katsayıları (Us), %79-99, sistem su çıkış türdeşliği katsayıları (Eua) ise %82-99 arasında değişmiştir. Buna göre, test edilen damla sulama sistemlerinin bazılarında ilk projeleme, kurulum ve işletiminde bazı kriterlerin uygun olmadığı tespit edilmiştir. Bunlardan bazıları, lateral hatlarının gereğinden çok fazla uzun seçilmesi, kullanılan malzemelerin yeterli kalitede olamaması, filtrasyon sisteminin uygun seçilmemesi, uygun olmayan damlatıcı debi seçimi ve işletme basınçlarının 1.0-1.5 atmosferin çok altında olması sayılabilir. Ölçülen bu parametreler toprakta su dağılımı, etkin su kullanımı ve verim ile doğrudan ilişkili olması nedeniyle, sistem kurulmadan önce toprak ve bitki özellikleri esas alınmalı ve sistem tekniğe uygun işletilmelidir. Ayrıca sistemi kullananların yeterli eğitimi alarak deneyimlerini artırmaları sistemlerin sürdürülebilir kullanımı ve en yüksek yararın sağlanması bakımından önemlidir.

Instrumental Variable Estimation of Large Panel Data Models with Common Factors

This article introduces the xtivdfreg command in Stata, which implements a general Instrumental Variables (IV) approach for estimating large panel data models with unobserved common factors or interactive effects, as developed by Norkute et al. (2020) and Cui et al. (2020a). The underlying idea of this approach is to project out the common factors from exogenous co-variates using principal components analysis, and run IV regression using de-factored co-variates as instruments. The resulting method is valid for models with homogeneous or heterogeneous slope coefficients, and has several advantages relative to existing popular approaches. In addition, the xtivdfreg command extends the IVDF approach in two major ways. Firstly, the algorithm accommodates estimation of unbalanced panels. Secondly, the algorithm permits highly flexible instrumentation strategies. It is shown that when one imposes zero factors, the xtivdfreg command can replicate the results of the popular ivregress Stata command. Notably, xtivdfreg also permits estimation of the two-way error components panel data model with heterogeneous slope coefficients.

The impact of dose delivery time on biological effectiveness in proton irradiation with various biological parameters

The purpose of this study is to evaluate the sublethal damage (SLD) repair effect in prolonged proton irradiation using the biophysical model with various cell-specific parameters of (α/β)x and T1/2 (repair half time). At present, most of the model-based studies on protons have focused on acute radiation, neglecting the reduction in biological effectiveness due to SLD repair during the delivery of radiation. Nevertheless, the dose-rate dependency of biological effectiveness may become more important as advanced treatment techniques, such as hypofractionation and respiratory gating, come into clinical practice, as these techniques sometimes require long treatment times. Also, while previous research using the biophysical model revealed a large repair effect with a high physical dose, the dependence of the repair effect on cell-specific parameters has not been evaluated systematically. Biological dose [relative biological effectiveness (RBE)×physical dose] calculation with repair included was carried out using the linear energy transfer (LET)-dependent linear-quadratic (LQ) model combined with the theory of dual radiation action (TDRA). First, we extended the dose protraction factor in the LQ model for the arbitrary number of different LET proton irradiations delivered sequentially with arbitrary time lags, referring to the TDRA. Using the LQ model, the decrease in biological dose due to SLD repair was systematically evaluated for spread-out Bragg peak (SOBP) irradiation in a water phantom with the possible ranges of both (α/β)x and repair parameters ((α/β)x =1-15Gy, T1/2 =0-90min). Then, to consider more realistic irradiation conditions, clinical cases of prostate, liver, and lung tumors were examined with the cell-specific parameters for each tumor obtained from the literature. Biological D99% and biological dose homogeneity coefficient (HC) were calculated for the clinical target volumes (CTVs), assuming dose-rate structures with a total irradiation time of 0-60min. The differences in the cell-specific parameters resulted in considerable variation in the repair effect. The biological dose reduction found at the center of the SOBP with 30min of continuous irradiation varied from 1.13% to 14.4% with a T1/2 range of 1-90min when (α/β)x is fixed as 10Gy. It varied from 2.3% to 6.8% with an (α/β)x range of 1-15Gy for a fixed value of T1/2 =30min. The decrease in biological D99% per 10min was 2.6, 1.2, and 3.0% for the prostate, liver, and lung tumor cases, respectively. The value of the biological D99% reduction was neither in the order of (α/β)x nor prescribed dose, but both comparably contributed to the repair effect. The variation of HC was within the range of 0.5% for all cases; therefore, the dose distribution was not distorted. The reduction in biological dose caused by the SLD repair largely depends on the cell-specific parameters in addition to the physical dose. The parameters should be considered carefully in the evaluation of the repair effect in prolonged proton irradiation.

Pestisit Uygulamaları İçin Optimize Edilmiş Koşullarda Sprey Karakteristiklerinin Belirlenmesi

Agriculture is a large and serious sector developing on a global basis. An important research subject in agriculture is the pesticide applications performed by spraying method. One of the objectives of spray application technologies is to provide using at the recommended dosage of pesticides at the right time by using the appropriate application techniques in order to reduce the level of pest or disease factors at crop production. In this study, the effects of flow parameters on droplet diameter of single hollow-cone nozzle used on conventional sprayers were investigated. For this purpose, three different nozzle-surface distances (70 cm, 85 cm, 100 cm), three different operational pressure (6 bar, 8 bar, 10 bar) and three different nozzle orifice diameters were determined as flow parameters under conditions of constant speed and spray angle. The experiments were carried out in duplicate at different times. After spray application, the droplet spot images obtained from the water sensitive paper surfaces were processed and the volumetric diameter and homogeneity values ​​were determined. In order to examine the effect of the flow parameters on droplet diameter, the charts were drawn and the variations were interpreted. In general, the characteristic droplet diameters were decreased and the homogeneity coefficient increased on the conditions of the same nozzle orifice diameter and spray distance as the operational pressure increased. Comparing nozzle orifice diameters for the same operational pressure and spraying distance, it was observed that the droplet diameter increased for the nozzles with large orifice diameter and the homogeneity value deteriorated.