Homogeneous Fragments Research Articles

Particular Strength Criteria for Microstructural Analysis of Masonry

This study presents a set of "particular" strength criteria of the constituent elements of masonry as a composite material constituted by homogeneous fragments of heterogeneous materials (brick and mortar) and contact interface (shear and normal adhesive strength). This paper proposes the expressions for calculate the values of each particular strength criterion used for the discrete modelling of masonry. The results were obtained based on the experimental study of stresses and failure modes in masonry specimens, mortar samples and brick units. There are determined a set of 8 particular strength criteria, which correspond to the actual work of the masonry constituent elements. Their use in the structural micromodelling of masonry allows to determine the body contact interactions, track the gradual accumulation of local stresses, exclude from the calculation model the elements in which a particular strength criterion has been exceeded, and modelling the degradation process.

Mechanical Properties and Microstructures of Highly Fe-Containing Al–Mg–Si Alloys Processed by Severe Plastic Deformation under High Pressure

In this study, A6022-based Al–Mg–Si alloys with three additional Fe contents are processed by high-pressure torsion (HPT) and high-pressure sliding (HPS). Both processes yield a similar tensile strength exceeding 400 MPa. Fe intermetallics were finely and homogeneously fragmented to an average size of ∼2 µm by the HPT process. The high tensile strength is attributed to such a fine and homogeneous fragmentation of Fe intermetallics. It is also demonstrated that the finely fragmented Fe intermetallics play an important role to maintain finer grain size even after solution treatment.

Influence of Scan orientation Strategy on microstructural and tensile characteristics of Inconel 718 fabricated by DMLS process

Metal additive manufacturing, particularly direct metal laser sintering (DMLS), is dominating all mechanical and manufacturing segments with its compelling growth. Several studies have shown that the build orientation of the Additive Manufacturing (AM) process has a substantial impact on the mechanical properties. In this study, different IN718 specimens with varying Scan Strategy (SS) were produced using direct metal laser sintering (DMLS). The effects on mechanical parameters and microstructures were examined and it was found that specimen B (90 & 67 deg orientation) displayed ultimate tensile strength (UTS), 8.37 percent higher than specimen C (90 deg orientation), and 5.36 percent higher than specimen A (67 deg orientation) due to a superior rate of elemental enrichment. Similarly, the percentage elongation of specimen C is 19 % greater than that of specimen B and 15 % greater than that of specimen A. Images of the specimens' fractured surface, elemental segregation, and columnar pattern growth obtained using a scanning electron microscope (SEM) and an optical microscope (OM). The fracture surfaces of tensile specimens C & A displayed homogeneous fragmentation with deep concave pits and equi-dimensional failures, although the fragmented part of specimen B showed an intermetallic formation with lower plastic deformation that is brittle in nature.

Retrospective technology of segmentation and classification for GARCH models based on the concept of the $ \epsilon $-complexity of continuous functions

<abstract><p>We consider a retrospective segmentation and classification problem for GARCH models. Segmentation is the partition of a long time series into homogeneous fragments. A fragment is homogeneous if only one mechanism generates it. The points of "concatenation" of homogeneous segments we call (by analogy with the term used in the stochastic literature) points of disorder or change-points. We call classification the separation of two relatively short time series generated by different mechanisms. By classification, we mean the way in which two groups of time series with unknown generating mechanism (in particularly, generated by GARCH models) can be distinguished, and the new time series can be assigned to the class. Our model free technology is based on our concept of $ \epsilon $-complexity of individual continuous functions. This technology does not use information about the time series generation mechanism. We demonstrate our approach on time series generated by GARCH models. We present simulations and real data analysis results confirming the effectiveness of the methodology.</p></abstract>

In Vitro Comparison of Two Electromagnetic Shockwave Generators: Low-Pressure Wide Focus vs High-Pressure Small Focus- Impact on Initial Stone Fragmentation and Final Stone Comminution.

Context: Recently developed concepts for higher efficacy extracorporeal shockwave lithotripsy with low-pressure wide focus systems resulting in finer fragmentation of the calculi. Objective: To compare two different electromagnetic shockwave sources (low-pressure wide focus [Xinin Lithotripter, XL] vs high-pressure small focus [Siemens Lithoskop, SL]) by sound field measurements and in vitro fragmentation. Evidence Acquisition: The CS-2012A XX-ES lithotripter (self-focusing electromagnetic shockwave generator with concave spherical curved electrical coil; XL) was compared to the (SL) (electromagnetic generator with a flat electric coil with an acoustical lens). Different sound field measurements were performed using a fiber-optic hydrophone. Measurements at three different power settings (XL: 8.0, 9.3, and 10.3 kV and SL: Level 1, 5, and 8). Ten AST stones and 15 BegoStones (9.3 kV, Level 3) with a frequency of 90/minute (SL) and 20/minute (XL). Number of impulses to the first crack and for complete stone comminution (residual fragments <2 mm) was documented. Results: The median number of shockwaves for the first crack in AST stones with the XL was 12 (10-14) and 7 with the SL (6-9). Complete disintegration was accomplished after 815 (782-824) shockwaves with XL and 702 (688-712) with SL. The difference was not statistically significant. The median number of shockwaves to produce the first crack in BegoStones was 524 (504-542) with XL and only 151 (137-161) with SL. Numbers of shockwaves for complete disintegration did not differ significantly (XL: 2518 vs SL: 2287). Using a wide focus with low pressure shows more homogeneous disintegration. Conclusion: Two stone models showed significant differences regarding form and time of the initial fragmentation. Impulses for stone comminution did not differ significantly. The advantages of a low-pressure wide-focus system include minimal trauma and a homogeneous fragment size but is more time consuming. High-pressure small-focus systems are clinically effective.

Improved AEB algorithm combined with estimating the adhesion coefficient of road ahead and considering the performance of EHB

This paper proposes an improved autonomous emergency braking (AEB) algorithm intended for intelligent vehicle. Featuring a combination with the estimation of road adhesion coefficient, the proposed approach takes into account the performance of electronic hydraulic brake. In order for the accurate yet fast estimate of road ahead adhesion coefficient, the expectation maximization framework is applied depending on the reflectivity of ground extracted by multiple beams lidar in four major steps, which are the rough extraction of ground points based on 3 σ criterion, the accurate extraction of ground points through principal component analysis (PCA), the main distribution characteristics of ground as extracted using the expectation maximum method (EM) and the estimation of road adhesion coefficient via joint probability. In order to describe the performance of EHB, the response characteristics, as well as the forward and adverse models of both braking pressure and acceleration are obtained. Then, with two typical roads including single homogeneous road and fragment pavement, the safe distance of improved AEB is modeled. To validate the algorithm developed in this paper, various tests have been conducted. According to the test results, the reflectivity of laser point cloud is effective in estimating the road adhesion coefficient. Moreover, considering the performance of EHB system, the improved AEB algorithm is deemed more consistent with the practicalities.

Morphology and Function of Myocardium and Skin Microcirculation 24 Hours after Clozapine Poisoning

Aim of the study: to evaluate the effect of sublethal dose of clozapine on the rat cardiovascular system 24 hours after administration of the drug.Materials and methods. The experiments were carried out on 17 male Wistar rats weighing 220-270 g. Under general anesthesia with sevoflurane, the animals of Group I were enterally given 0.9% NaCl solution, Group II animals received clozapine in a dose of 150 mg/kg diluted in 2.0 ml of NaCl solution 0.9%, Group III animals were given clozapine in a dose of 150 mg/kg diluted in 2.0 ml of 40% ethanol. Blood pressure (BP), heart rate (HR), skin microcirculation using laser Doppler flowmetry (LDF), NADH and FAD+ fluorescence were estimated 24 hours after the drug administration. After euthanasia, autopsy with sampling of internal organs for morphological study was done. Then paraffin heart sections with subsequent H&amp;E staining were made, which were studied using the Nikon Eclipse Ni-U light microscope.Results. Spectral analysis of local skin blood flow fluctuations showed that clozapine reduced Amax and amplitude in all frequency ranges of active microcirculation regulatory system in comparison with the controls. No differences in blood gases and acid-base status were seen between the groups of animals 24 hours after administration of the drugs. However, the animals from clozapine groups (II and III) had lower hemoglobin and hematocrit than in the control group.Histological examination of rat hearts in groups II and III revealed congested venules, haemorrhages by dia-pedeses, perivascular and interstitial edema. The signs of blood stasis and marginalization of granulocytes were noted in the vascular lumen. Irregular staining of myocardium due to cardiomyocytes with hypereosinophilic and occasionally homogeneous cytoplasm, fragmentation and deformations of cardiac cells were revealed. Car-diomyocytic nuclei were polymorphic and irregularly stained, and perinuclear edema was observed.Conclusions. The results of the study demonstrate the toxic effect of clozapine manifesting as progressive myocardial alteration and disordered central and peripheral circulation. However, control of bradycardia, restored skin perfusion and metabolic improvement (diagnosed by NADH fluorescence and blood acid-base status) after 24 hours may be due to the activation of compensatory mechanisms, particularly through changes in neurogenic and humoral regulation of homeostasis.

Morphological and Molecular Characterization of Dicrocoelium spp. Isolates from Sheep, Goat and Cattle in the West of Iran

DICROCELIOSIS is a prevalent parasitic disease in ruminants and in humans and is accidental caused by different species of Dicrocoelium spp. This study aimed to evaluate the morphological characteristics and molecular parameters of Dicrocoelium spp. isolated from livers of slaughtered sheep, goat, and cattle in three provinces in west of Iran from Feb 2018 to Feb 2019. In the present study, 45 infected livers with Dicrocoelium were collected (each province 15 and each host 5 infected liver). After morphological examination, the molecular evaluation was carried out for the ribosomal DNA (partial 5.8S, complete ITS2 and partial 28S genes) using PCR and PCR-RFLP techniques. Morphological analysis revealed that all specimens belonged to Dicrocoelium dendriticum. There were profound morphometric variations among D. dendriticum from different hosts and sampling areas, but no statistically significant differences was found (P>0.001). The sequencing analysis of obtained fragments in GeneBank showed 96% to 100% similarity within homogeneous fragments in the database. The obtained sequences were also registered in Gene Bank with the accession numbers, MN831473, MN831474 and MN831475. Additionally, all PCR-RFLP products revealed two similar fragments (319bp and 271 bp) in all examined samples. According to the present study, haplotype A was shown to be the predominant haplotype of D. dendriticum in the west of Iran.

Preparation of High-Elongation and High-Toughness Poly(l-lactide) Using Multi-Arm Methyl-β-Cyclodextrin-Poly(l-lactide)

We synthesized 3–16 armed methyl-β-cyclodextrin-poly(l-lactide) (MCD-PLLA) polymers, and then blended them with PLLA. The addition of MCD-PLLA with 9 or 12 arms to PLLA dramatically increased the elongation at break (E) and toughness (UT) of PLLA with little affecting its Tg and tensile strength. The highest E and UT were obtained to be 127% and 6.85 GJ/m3, respectively, for PLLA blends containing these MCD-PLLAs. It was confirmed that the MCD-PLLA served as a nucleation agent for PLLA, inducing PLLA chains to form smaller and more uniform-sized crystallites compared with pure PLLA. The homogeneous fragmentation of these small and uniform-sized crystallites during tensile deformation consequently resulted in such a remarkable increase in E and UT. In contrast, the addition of MCD-PLLAs with more than 12 arms to PLLA decreased its E and UT mainly due to preferential crystallization by themselves.

Scattering Patterns of Orthogonally Polarized Light Components for Statistically Rotationally Invariant Mosaic Birefringent Layers

Using the method of two-point generalized Mueller matrices and the phase screen approximation, we have studied the relationship between the shape of the angular spectra of linearly polarized components of light scattered by randomly inhomogeneous layers of a birefringent material and the correlation structural characteristics of the layers. For statistically rotationally invariant layers, the structural conditions for three types of scattering patterns of linearly polarized components have been revealed: (i) patterns invariant with respect to the azimuthal rotation by 180°, (ii) patterns invariant with respect to the azimuthal rotation by 90°, and (iii) patterns possessing a circular symmetry. For mosaic birefringent layers consisting of homogeneous fragments with different azimuthal orientations of their optic axes, a relationship between the correlation structural properties of the layer and the shape of the scattering pattern of polarized components has been determined. In particular, conditions for the observation of crosslike four-lobed scattering patterns in crossed and parallel polarizers have been determined and the structural characteristic that is responsible for the orientation of such a scattering pattern with respect to the direction of polarization of the incident light has been found. The inferences that were derived have been supported by experimental data and results of numerical simulations.

Картины рассеяния ортогонально поляризованных компонент света для статистически вращательно-инвариантных мозаичных двулучепреломляющих слоев

AbstractUsing the method of two-point generalized Mueller matrices and the phase screen approximation, we have studied the relationship between the shape of the angular spectra of linearly polarized components of light scattered by randomly inhomogeneous layers of a birefringent material and the correlation structural characteristics of the layers. For statistically rotationally invariant layers, the structural conditions for three types of scattering patterns of linearly polarized components have been revealed: (i) patterns invariant with respect to the azimuthal rotation by 180°, (ii) patterns invariant with respect to the azimuthal rotation by 90°, and (iii) patterns possessing a circular symmetry. For mosaic birefringent layers consisting of homogeneous fragments with different azimuthal orientations of their optic axes, a relationship between the correlation structural properties of the layer and the shape of the scattering pattern of polarized components has been determined. In particular, conditions for the observation of crosslike four-lobed scattering patterns in crossed and parallel polarizers have been determined and the structural characteristic that is responsible for the orientation of such a scattering pattern with respect to the direction of polarization of the incident light has been found. The inferences that were derived have been supported by experimental data and results of numerical simulations.

Characterization of Complex Image Spatial Structures Based on Symmetrical Weibull Distribution Model for Texture Pattern Classification

Texture pattern classification has long been an essential issue in computer vision (CV). However, texture is a kind of perceptual concept of human beings in scene observation or content understanding, which cannot be defined or described clearly in CV. Visually, the visual appearance of the complex spatial structure (CSS) of texture pattern (TP) generally depends on the random organization (or layout) of local homogeneous fragments (LHFs) in the imaged surface. Hence, it is essential to investigate the latent statistical distribution (LSD) behavior of LHFs for distinctive CSS feature characterization to achieve good classification performance. This work presents an image statistical modeling-based TP identification (ISM-TPI) method. It firstly makes a theoretical explanation of the Weibull distribution (WD) behavior of the LHFs of the imaged surface in the imaging process based on the sequential fragmentation theory (SFT), which consequently derives a symmetrical WD model (SWDM) to characterize the LSD of the TP’s SS. Multidirectional and multiscale TP features are then characterized by the SWDM parameters based on the oriented differential operators; in other words, texture images are convolved with multiscale and multidirectional Gaussian derivative filters (GDFs), including the steerable isotropic GDFs (SIGDFs) and the oriented anisotropic GDFs (OAGDFs), for the omnidirectional and multiscale SS detail exhibition with low computational complexity. Finally, SWDM-based TP feature parameters, demonstrated to be directly related to the human vision perception system with significant physical perception meaning, are extracted and used to TP classification with a partial least squares-discriminant analysis- (PLS-DA-) based classifier. The effectiveness of the proposed ISM-TPI method is verified by extensive experiments on three texture image databases. The classification results demonstrate the superiority of the proposed methods over several state-of-the-art TP classification methods.

Texture pattern classification based on probability density function estimation of the image spatial structure feature with symmetrical weibull distribution model

Automatic texture pattern classification (ATPC) has long been an essential issue in computer vision. However, ATPC is still a challenging task since texture is a subjective conception, which is difficult to be expressed concisely by the existing computational models. The visual appearance of the imaged texture pattern (TP) visually depends on the random organization of local homogeneous fragments (LHFs) in it. Hence, it is essential to investigate the latent statistical distribution (LSD) behavior of LHFs for the texture image spatial structural feature (TISSF) characterization and expression to achieve a good performance of ATPC. We presented a probability density function estimation (PDFE)-based ATPC scheme, termed PDFE-ATPC. We demonstrated the Weibull distribution (WD) behavior of LHFs by the sequential fragmentation theory to explain the LSD of the TISSFs. To obtain the multiscale and multi-orientation detail expression of the TISSFs, we introduced an oriented Gaussian derivative filter (OGDF)-based TISSF characterization method, including the steerable isotropic Gaussian derivative filters (SIGDFs) and the oriented anisotropic Gaussian Derivative filters (OAGDFs). Successively, the LSDs of the filter responses were characterized omnidirectionally by a symmetrical WD model (SWDM) and the SWDM-based TISSF parameters, demonstrated to be directly related to the human vision perception (HVP) system, were extracted and applied to the ATPC with a spline regression-based classifier. Effectiveness of the proposed PDFE-ATPC method was verified by extensive experiments on three different texture image databases and compared with four commonly-used statistics-based texture classification methods.

Influence of lactic acid on the catalytic performance of MDABCO for ring-opening polymerization of l-lactide

A series of metal organic frameworks (MOFs) MDABCO (M=Co, Ni, Cu, Zn; DABCO=1,4-diazabicyclo[2.2.2]octane) are utilized as catalysts for the bulk ring-opening polymerization of l-lactide. The catalytic activity varies in the order CuDABCO, NiDABCO<ZnDABCO, CoDABCO. By adding lactic acid, we unexpectedly observed enhanced catalytic activity. The combined use of lactic acid and ZnDABCO during polymerization results in a highly active polymerization system, along with the gradual change of MOFs structure caused by an increased acid concentration. Compared to related homogeneous fragments, such as zinc nitrate and 1,4-diazabicyclo[2.2.2]octane, ZnDABCO is found to afford highly isotactic polylactide, which would be ascribed to the unique structural properties of MOFs.

The Largest Fragment of a Homogeneous Fragmentation Process

We show that in homogeneous fragmentation processes the largest fragment at time $t$ has size $e^{-t \Phi'(\bar{p})}t^{-\frac32 (\log \Phi)'(\bar{p})+o(1)},$ where $\Phi$ is the L\'evy exponent of the fragmentation process, and $\bar{p}$ is the unique solution of the equation $(\log \Phi)'(\bar{p})=\frac1{1+\bar{p}}$. We argue that this result is in line with predictions arising from the classification of homogeneous fragmentation processes as logarithmically correlated random fields.

One-Sided FKPP Travelling Waves for Homogeneous Fragmentation Processes

In this paper, we introduce an analogue of the classical one-sided FKPP equation in the context of homogeneous fragmentation processes. The main result of the present paper is concerned with the existence and uniqueness of one-sided FKPP travelling waves in this setting. In addition, we prove some analytic properties of such travelling waves. Our techniques make use of fragmentation processes with killing, an associated product martingale as well as various properties of Levy processes. This paper is mainly concerned with general fragmentation processes, but we also devote a section to related considerations regarding fragmentations with a finite dislocation measure, where we obtain a stronger result than for fragmentation processes with an infinite jump activity over finite time horizons. Furthermore, we discuss the relation of our problem to similar questions in the setting of branching Brownian motions, which provides a motivation for our approach.

Quality-Related Monitoring and Grading of Granulated Products by Weibull-Distribution Modeling of Visual Images with Semi-Supervised Learning.

The topic of online product quality inspection (OPQI) with smart visual sensors is attracting increasing interest in both the academic and industrial communities on account of the natural connection between the visual appearance of products with their underlying qualities. Visual images captured from granulated products (GPs), e.g., cereal products, fabric textiles, are comprised of a large number of independent particles or stochastically stacking locally homogeneous fragments, whose analysis and understanding remains challenging. A method of image statistical modeling-based OPQI for GP quality grading and monitoring by a Weibull distribution(WD) model with a semi-supervised learning classifier is presented. WD-model parameters (WD-MPs) of GP images’ spatial structures, obtained with omnidirectional Gaussian derivative filtering (OGDF), which were demonstrated theoretically to obey a specific WD model of integral form, were extracted as the visual features. Then, a co-training-style semi-supervised classifier algorithm, named COSC-Boosting, was exploited for semi-supervised GP quality grading, by integrating two independent classifiers with complementary nature in the face of scarce labeled samples. Effectiveness of the proposed OPQI method was verified and compared in the field of automated rice quality grading with commonly-used methods and showed superior performance, which lays a foundation for the quality control of GP on assembly lines.

Visual Perception-Based Statistical Modeling of Complex Grain Image for Product Quality Monitoring and Supervision on Assembly Production Line.

Computer vision as a fast, low-cost, noncontact, and online monitoring technology has been an important tool to inspect product quality, particularly on a large-scale assembly production line. However, the current industrial vision system is far from satisfactory in the intelligent perception of complex grain images, comprising a large number of local homogeneous fragmentations or patches without distinct foreground and background. We attempt to solve this problem based on the statistical modeling of spatial structures of grain images. We present a physical explanation in advance to indicate that the spatial structures of the complex grain images are subject to a representative Weibull distribution according to the theory of sequential fragmentation, which is well known in the continued comminution of ore grinding. To delineate the spatial structure of the grain image, we present a method of multiscale and omnidirectional Gaussian derivative filtering. Then, a product quality classifier based on sparse multikernel–least squares support vector machine is proposed to solve the low-confidence classification problem of imbalanced data distribution. The proposed method is applied on the assembly line of a food-processing enterprise to classify (or identify) automatically the production quality of rice. The experiments on the real application case, compared with the commonly used methods, illustrate the validity of our method.

Compensated fragmentation processes and limits of dilated fragmentations

A new class of fragmentation-type random processes is introduced, in which, roughly speaking, the accumulation of small dislocations which would instantaneously shatter the mass into dust, is compensated by an adequate dilation of the components. An important feature of these compensated fragmentations is that the dislocation measure $\nu$ which governs their evolutions has only to fulfill the integral condition $\int_{\mathit{p}}$ (1-$\mathit{p}_{1}$)$^{2}\nu$(d$\mathbf{p}$ < $\infty$, where $\mathbf{p}$ = ($\mathit{p}_{1}$,…) denotes a generic mass-partition. This is weaker than the necessary and sufficient condition $\int_{\mathit{p}}$ (1-$\mathit{p}_{1}$)$^{2}\nu$(d$\mathbf{p}$ < $\infty$ for $\nu$ to be the dislocation measure of a homogeneous fragmentation. Our main results show that such compensated fragmentations naturally arise as limits of homogeneous dilated fragmentations, and bear close connections to spectrally negative Levy processes.

Toward Automated Quality Classification via Statistical Modeling of Grain Images for Rice Processing Monitoring

AbstractComputer vision-based rice quality inspection has recently attracted increasing interest in both academic and industrial communities because it is a low-cost tool for fast, non-contact, nondestructive, accurate and objective process monitoring. However, current computer-vision system is far from effective in intelligent perception of complex grainy images, comprised of a large number of local homogeneous particles or fragmentations without obvious foreground and background. We introduce a well known statistical modeling theory of size distribution in comminution processes, sequential fragmentation theory, for the visual analysis of the spatial structure of the complex grainy images. A kind of omnidirectional multi-scale Gaussian derivative filter-based image statistical modeling method is presented to attain omnidirectional structural features of grain images under different observation scales. A modified LS-SVM classifier is subsequently established to automatically identify the processing rice q...