A new meshless “fragile points method” and a local variational iteration method for general transient heat conduction in anisotropic nonhomogeneous media. Part II: Validation and discussion

Abstract

In the first part of this two-paper series, a new computational approach is presented for analyzing transient heat conduction problems in anisotropic nonhomogeneous media. The approach consists of a truly meshless Fragile Points Method (FPM) being utilized for spatial discretization, and a Local Variational Iteration (LVI) scheme for time discretization. In the present article, extensive numerical results are provided as validations, followed by a discussion on the recommended computational parameters. The FPM?+?LVIM approach shows its capability in solving 2?D and 3?D transient heat transfer problems in complex geometries with mixed boundary conditions, including preexisting cracks. Both functionally graded materials and composite materials are considered. It is shown that, with appropriate computational parameters, the FPM?+?LVIM approach is not only accurate, but also efficient, and has reliable stability under relatively large time intervals.     

Chemical characteristics of oils from naked and husk seeds of Cucurbita pepo L.

Pumpkin seed oils from naked and husk pumpkin seeds, produced by an industrial process and by laboratory extraction, were evaluated for fatty acid composition, tocopherol, sterol and squalene content. The major fatty acids in the oils from both varieties were oleic, linoleic and palmitic acid, followed by stearic acid. The ratios of monounsaturated to polyunsaturated fatty acids for husk and naked seed oils were about 0.60 and 0.75, respectively. Analysis of tocopherols in industrially pressed and laboratory‐extracted oils showed that husk seed oils had higher amounts of total tocopherols than naked seed oils. Oils extracted in the laboratory had higher amounts of tocopherols than industrial oils. Pumpkin seed oil, in general, had a high level of squalene, which was higher in husk seed oils than in naked seed oils and in extracted than in pressed oils. The total amount of sterols was higher in husk than in naked seed oils and in extracted oil samples. The main sterols were Δ7‐sterols and their content was similar in all samples, but the content of Δ5‐sterols was higher in oil samples of husk pumpkin seed and in extracted than in pressed oils.     

Morphometric characteristics of choroid plexus epithelial cells in cases with significantly different psammoma bodies' presence

Objectives: Taking into the consideration the fact that psammoma bodies have never been observed in stroma of any other organ as aging change, the aim of our research was to prove some structural similarities of choroids plexus and tumors psammoma bodies, and their possible connection with choroids plexus epithelial cells atrophy. Materials and Methods: We used 30 cadavers' right lateral ventricle central parts of choroid plexus as material. Tissue samples were routinely processed for the applied histochemical and immunohistochemical stainings. ImageJ software was used for morphometric analysis. Results: Cluster analysis showed the presence of two significantly different groups. The first group included the cases with sparse psammoma bodies and milder epithlelial atrophy with dome cells and vacuoles presence in older cases. The second group included the cases with numerous psammoma bodies and more severe epithelial atrophy, significant cystic formations and epithelial flattening presence, even in younger cases. Immunohistochemical analysis showed positive reaction of psammoma bodies and choroid plexus stroma on S100 protein. Application of S100 A8/A9 marker showed partial positive psammoma bodies' reaction and significant presence of S100 A8/A9 positive cells in choroid plexus blood vessels and stroma, especially, in cases with psammoma bodies' positive reaction on this marker. Conclusions: So, presence of more numerous psammoma bodies' might be associated with more severe choroids plexus epithelial cells atrophy. Immunohistochemical analysis showed psammoma bodies' positive reaction on S100 protein and the presence of S100 A8/A9 positive cells in stroma of cases with psammoma bodies' positive reaction on this marker. Microsc. Res. Tech., 2009. © 2008 Wiley‐Liss, Inc.     

Sensitivity analysis of frequency response functions of composite sandwich plates containing viscoelastic layers

In the scope of structural dynamics, sensitivity analysis is a very useful tool in a number of numerical procedures such as parameter identification, model updating, optimal design and uncertainty propagation. In this paper the formulation of first-order sensitivity analysis of complex frequency response functions (FRFs) is developed for composite sandwich plates composed by a combination of fiber-reinforced and elastomeric viscoelastic layers, in arrangements that are frequently used for the purpose of noise and vibration attenuation. Although sensitivity analysis is a well known numerical technique, the main contribution intended for this study is its extension to viscoelastic structures, which are characterized by frequency- and temperature-dependent material properties and, thus, require particularly adapted analytical and numerical procedures. Due to the fact that finite element discretization has become the most used method for dynamic analysis of complex structures, the sensitivity analysis addressed herein is based on such models, being computed from the analytical derivatives of the FRFs with respect to a set of design parameters, such as fiber orientations and layer thicknesses. Also, a procedure for evaluating the sensitivity of the FRFs with respect to temperature of the viscoelastic material is suggested. After discussion of various theoretical aspects, including a parameterization scheme of the structural matrices with respect to the design variables, first-order response derivatives are calculated for a composite plate with inherent structural damping, and for a composite sandwich plate with a viscoelastic core. The results are compared to those obtained from first-order finite-difference approximations.     

Compensation of the temperature-dependent offset drift of a Hall sensor

We present a method to cancel the offset of a Hall sensor and compensate its temperature-dependent drift. We adapt and improve a compensation technique based on a correction using the input voltage. A more accurate compensation for the temperature drift is obtained by an offset calibration at two different temperatures. To decrease the calibration time, we propose a procedure for fast heating of the sensor. It consists of forcing a current pulse through a p-n junction of the sensor. Since the resistance of a forward-biased diode is small, this principle is compatible with low-voltage applications. After correction, the resulting offset is less than two percent of the initial offset over the temperature range −10 to +60°C. The corresponding residual equivalent offset is lower than 250 μT.     

In vivo adenoviral vector-mediated gene transfer into balloon-injured rat carotid arteries

Homozygotes for the dsy1 desynaptic mutant of maize show massive failure of chiasma maintenance during diplotene and diakinesis. Although some chiasmata persist until anaphase I in most microsporocytes expressing this mutant, homozygotes are completely or nearly completely sterile, owing apparently to disjunctive irregularities. Pachytene synaptic errors and some synaptic failure also are found, but recombination nodules are common in homologously synapsed regions, and equational separation of a heterozygous knob into univalents or open arms at diakinesis clearly demonstrates that chiasma failure occurs following crossing-over. A wider than normal synaptonemal complex central region and uniform apparent weakness of central region cross connections to spreading procedures strongly suggest the presence of a genetic lesion in a synaptonemal complex central region component. The dsy1 mutant may provide an especially important source of material for molecular studies on the nature of chiasma maintenance mechanism.     

Integral equation method for solution of boundary value problems of structural mechanics,Part II. Elliptic partial diffeerential equations

The method presented in Part I of this paper¹ is extended to problems governed by a system of partial differential equations. The basic clarity and simplicity of the method is preserved. The domain of integration is covered by a net of orthogonal (not necessarily equidistant) straight lines. Choosing again highest derivatives with respect to each of the co-ordinates as unknowns, it is possible to reduce the problem to a system of integral equations along the lines of the adopted net. The subsequent procedure is basically the same as in Part I. The results prove to be of remarkable accuracy even for very coarse nets.