Computational modelling and experimental characterisation of heterogeneous materials

Heterogeneous materials can exhibit behaviour under load that cannot be described by classical continuum elasticity. Beams in bending can show a relative stiffening as the beam depth tends to zero, a size effect. Size effects are recognised in higher order continuum elastic theories such as micropolar elasticity. The drawback of higher order theories is the requirement of addition constitutive relations and associated properties that are often difficult to establish experimentally. Furthermore the finite element method, of great benefit in classical elasticity, has shown limitations when applied to micropolar elasticity. The determination of additional constitutive properties and the computational modelling of micropolar elasticity will be discussed in the context of a model heterogeneous material loaded in simple 3 point bending. The model material was created by drilling holes in aluminium bar in a regular pattern, with the hole axis normal to the plane of bending. The bending tests show that a size effect is present. These results are compared against modelling the detailed beam geometries in the finite element package ANSYS, which again shows the size effect. These two bending test are used to extract the additional micropolar elastic material properties. A comparison is then made against analytical solutions,numerical solutions using a micropolar beam finite element and a micropolar plane stress control volume method.It will be shown that the need for extensive experimental testing to determine the additional constitutive properties may not be necessary with the appropriate use of numerical methods

Random Projections For Large-Scale Regression

Fitting linear regression models can be computationally very expensive in large-scale data analysis tasks if the sample size and the number of variables are very large. Random projections are extensively used as a dimension reduction tool in machine learning and statistics. We discuss the applications of random projections in linear regression problems, developed to decrease computational costs, and give an overview of the theoretical guarantees of the generalization error. It can be shown that the combination of random projections with least squares regression leads to similar recovery as ridge regression and principal component regression. We also discuss possible improvements when averaging over multiple random projections, an approach that lends itself easily to parallel implementation.Comment: 13 pages, 3 Figure

A Mechanism for Ferrimagnetism and Incommensurability in One-Dimensional Systems

A mechanism for ferrimagnetism in (1+1)-dimensions is discussed. The ferrimagnetism is cased by interactions described by operators with non-zero conformal spin. Such interactions appear in such problems as the problem of tunneling between Luttinger liquids and the problem of frustrated spin ladder. I present exact solutions for a representative class of models containing such interactions together with a simple mean field analysis. It is shown that the interactions (i) dynamically generate static oscillations with a wave vector dependent on the coupling constant, (ii) give rise to a finite magnetic moment at $T = 0$ accompanied by the soft mode with a non-relativistic ({\it ferromagnetic}) dispersion $E \sim k^2$, (iii) generate massive (roton) modes.Comment: replaced by the extended version, references adde

Ultramorphology of the ventriculus of nectarivorous, granivorous and omnivorous species of passerine birds

The objective of this study was to investigate the effect of disparate diets on the ventriculi of three species of similar sized granivorous, nectarivorous and omnivorous passerine birds. A total of twelve birds were captured with mist net under license and ventriculi from these birds were processed for light and electron microscopy. Nectarivorousventriculus had thin, poorly developed muscle and sac-like in shape while the granivorous gizzard had the thick, well developed muscle with the classical shape of biconvex lens and the omnivorous gizzard was intermediate. The wall of the ventriculus consisted of mucosal, submucosal , muscularis and inconspicuous serosal layers. Tunica muscularis, the most prominent layer of the wall was thickest in granivore, thinnest in nectarivore , and intermediate in omnivore. The mucosal glands were individual, tubular units with slightly expanded basal ends, demarcated from each other by dense connective tissue and opened individually into the lumen of the organ. Each glandular unit consisted of basal, chief, endocrine, neck and surface epithelial cells.The chief cells of the glandular units produced the "tubular” portion of the cuticle while the neck and surface epithelial cells produced the "surface” portion of the cuticle and the merger of these two portions formed the gastric cuticle, a protein mucopolysaccharide complex. The overlaying gastric cuticle (luminal cuticle) of the ventriculus was hard, tough, and sieve-like in the granivore, soft and jelly-like in the nectarivore and intermediate in the omnivore. The structural adaptations of the ventriculi of these three species to their various diets are discussed. There is need for more studies to be done on composition and functional morphology of the cuticle in aves.Keywords: Morphology, Ventriculus, Gizzard, Passerine Bird

Isometric Sliced Inverse Regression for Nonlinear Manifolds Learning

[[abstract]]Sliced inverse regression (SIR) was developed to find effective linear dimension-reduction directions for exploring the intrinsic structure of the high-dimensional data. In this study, we present isometric SIR for nonlinear dimension reduction, which is a hybrid of the SIR method using the geodesic distance approximation. First, the proposed method computes the isometric distance between data points; the resulting distance matrix is then sliced according to K-means clustering results, and the classical SIR algorithm is applied. We show that the isometric SIR (ISOSIR) can reveal the geometric structure of a nonlinear manifold dataset (e.g., the Swiss roll). We report and discuss this novel method in comparison to several existing dimension-reduction techniques for data visualization and classification problems. The results show that ISOSIR is a promising nonlinear feature extractor for classification applications.[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子

Tests of sunspot number sequences: 3. Effects of regression procedures on the calibration of historic sunspot data

We use sunspot group observations from the Royal Greenwich Observatory (RGO) to investigate the effects of intercalibrating data from observers with different visual acuities. The tests are made by counting the number of groups RB above a variable cut-off threshold of observed total whole-spot area (uncorrected for foreshortening) to simulate what a lower acuity observer would have seen. The synthesised annual means of RB are then re-scaled to the full observed RGO group number RA using a variety of regression techniques. It is found that a very high correlation between RA and RB (rAB > 0.98) does not prevent large errors in the intercalibration (for example sunspot maximum values can be over 30 % too large even for such levels of rAB). In generating the backbone sunspot number (RBB), Svalgaard and Schatten (2015, this issue) force regression fits to pass through the scatter plot origin which generates unreliable fits (the residuals do not form a normal distribution) and causes sunspot cycle amplitudes to be exaggerated in the intercalibrated data. It is demonstrated that the use of Quantile-Quantile (“Q Q”) plots to test for a normal distribution is a useful indicator of erroneous and misleading regression fits. Ordinary least squares linear fits, not forced to pass through the origin, are sometimes reliable (although the optimum method used is shown to be different when matching peak and average sunspot group numbers). However, other fits are only reliable if non-linear regression is used. From these results it is entirely possible that the inflation of solar cycle amplitudes in the backbone group sunspot number as one goes back in time, relative to related solar-terrestrial parameters, is entirely caused by the use of inappropriate and non-robust regression techniques to calibrate the sunspot data

Electronic Structures of Quantum Dots and the Ultimate Resolution of Integers

The orbital angular momentum L as an integer can be ultimately factorized as a product of prime numbers. We show here a close relation between the resolution of L and the classification of quantum states of an N-electron 2-dimensional system. In this scheme, the states are in essence classified into different types according to the m(k)-accessibility, namely the ability to get access to symmetric geometric configurations. The m(k)-accessibility is an universal concept underlying all kinds of 2-dimensional systems with a center. Numerical calculations have been performed to reveal the electronic structures of the states of the dots with 9 and 19 electrons,respectively. This paper supports the Laughlin wave finction and the composite fermion model from the aspect of symmetry.Comment: Two figure

Enterovirus and Bacterial Evaluation of Mississippi Oysters

The numbers of enteric viruses and fecal coliform bacteria in oysters and water samples collected along the Mississippi Gulf coast during 1979 were determined. Ten viral isolates, representing members of the poliovirus group, were identified from an approved oyster harvesting site. The number of virus isolations increased to 51 when oysters were collected from a prohibited harvesting location. The majority of isolates were identified as poliovirus type 1 or 2, coxsackievirus B3 and B4, and echovirus type 24. Fecal coliforms in water samples collected at approved and prohibited locations confirmed the classification assigned to each area by the Mississippi State Board of Health. The numbers of fecal coliforms in oyster samples collected at the identical sites did not reflect the levels observed in water samples. There was no positive correlation between indicator bacteria in the water column and the number of viruses in the shellfish examined. These results imply that viral analyses of shellfish may be needed as an adjunct to bacteriological analyses so that shellfish safety is verified

Enterovirus and Bacterial Evaluation of Mississippi Oysters

The numbers of enteric viruses and fecal coliform bacteria in oysters and water samples collected along the Mississippi Gulf coast during 1979 were determined. Ten viral isolates, representing members of the poliovirus group, were identified from an approved oyster harvesting site. The number of virus isolations increased to 51 when oysters were collected from a prohibited harvesting location. The majority of isolates were identified as poliovirus type 1 or 2, coxsackievirus B3 and B4, and echovirus type 24. Fecal coliforms in water samples collected at approved and prohibited locations confirmed the classification assigned to each area by the Mississippi State Board of Health. The numbers of fecal coliforms in oyster samples collected at the identical sites did not reflect the levels observed in water samples. There was no positive correlation between indicator bacteria in the water column and the number of viruses in the shellfish examined. These results imply that viral analyses of shellfish may be needed as an adjunct to bacteriological analyses so that shellfish safety is verified

A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants