Computational Simulation and 3D Virtual Reality Engineering Tools for Dynamical Modeling and Imaging of Composite Nanomaterials

An adventure at engineering design and modeling is possible with a Virtual Reality Environment (VRE) that uses multiple computer-generated media to let a user experience situations that are temporally and spatially prohibiting. In this paper, an approach to developing some advanced architecture and modeling tools is presented to allow multiple frameworks work together while being shielded from the application program. This architecture is being developed in a framework of workbench interactive tools for next generation nanoparticle-reinforced damping/dynamic systems. Through the use of system, an engineer/programmer can respectively concentrate on tailoring an engineering design concept of novel system and the application software design while using existing databases/software outputs.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

On the Contributions of Pavel Andreevich Zhilin to Mechanics

This paper is dedicated to the memory of Pavel A. Zhilin (1942-2005), the great Russian scientist in the field of Rational Mechanics. He was educated and worked at the State Polytechnical University in St. Petersburg (Russian Federation), formerly known as the Polytechnical Institute. As Head of the Department of Theoretical Mechanics he supervised sixteen PhD theses (Candidate of Science theses) and six higher doctorates (Habilitations or Doctor of Science theses), some of them are shown on Fig. 2. His scientific interests covered various branches of Mechanics and Theoretical Physics. In his research he strived to pave a way based on Rational Mechanics to areas which are traditionally not associated with Mechanics, such as Physics of Microstructures and Electrodynamics. The paper gives a brief summary of the scientific biography and the main results obtained by Pavel A. Zhilin1

Stress-strain state and wear modelling for fuel rod – grid contact

The paper presents an approach for effective solution of the stress-strain state and wear prediction problem for the case of contact between fuel rod and grid surfaces of a nuclear reactor. Boundary-initial value elastic-plastic problem statement, due to the quasi-static character of the forced oscillations, which was approved by eigen frequencies analysis, was reduced to boundary one. The influence of inhomogeneous temperature field and varying pressure in the outer surface of fuel rod’s shell are considered. For this, a sequence of special procedures for searching the most effective ways of numerical simulation with limited computational resources was considered. The method of weighted residuals and the finite difference method were used to solve the problem of nonlinear forced oscillations under periodic loading of the fuel rod, described as beam under bending. The analytical solution for the fuel rod’s shell displacements in thermo-elasticity problem is obtained, approximated for spatial case and added to the general three-dimensional Finite Element model. The same procedure was adopted for the maximum amplitude values of the displacements which were obtained in the geometrically nonlinear beam problem solution. After that the general elastic-plastic contact problem of the interaction between the fuel rod and the grid surfaces was solved, taking into account preliminary obtained stress distributions achieved by temperature and amplitude displacements influence. The theory of plasticity of an isotropic material with isotropic hardening was used as a model. The limits of linear solutions for beam deflections as well as deflection dependencies upon time are demonstrated and analyzed. The numerically obtained distributions of strains and stresses are presented. By use of the obtained maximum stress values an attempt for the wear estimation in contact zone was done and the fuel rod’s operating time without critical wear during the contact with the grid surface was determined. The obtained results may be considered as corresponding to practical operating data.Представлено підхід до ефективного розв’язання задачі прогнозування напружено-деформованого стану та зношування для випадку контакту поверхонь твелу та трубної дошки ядерного реактора. Початково-крайову пружно-пластичну постановку задачі внаслідок квазістатичного характеру вимушених коливань, який підтверджено аналізом власних частот, приведено до граничної. Розглянуто вплив неоднорідного температурного поля та змінного тиску на зовнішній поверхні оболонки твелу. Для цього було розглянуто послідовність спеціальних процедур для пошуку найбільш ефективних способів чисельного моделювання з обмеженими обчислювальними ресурсами. Методом зважених відхилів і методом скінченних різниць розв’язано задачу про нелінійні вимушені коливання при періодичному навантаженні твелу, що описується як балка при згині. Аналітичний розв’язок для переміщень оболонки твелу в задачі термопружності апроксимовано для просторового випадку та додано до загальної тривимірної моделі МСЕ. Така ж процедура була прийнята для максимальних значень амплітуди переміщень, отриманих у розв’язуванні задачі геометрично нелінійного згину балки. Після цього розв’язано загальну пружно-пластичну контактну задачу взаємодії поверхонь твелу та трубної дошки з урахуванням попередньо отриманих розподілів напружень, обумовлених доданими температурними та амплітудними переміщеннями. Як модель використано теорію пластичності ізотропного матеріалу з ізотропним зміцненням. Продемонстровано та проаналізовано межі лінійних розв’язків для прогинів балки, а також залежності прогину від часу. Наведено чисельно отримані розподіли деформацій і напружень. За отриманими максимальними значеннями напружень була зроблена спроба оцінювання зношування в зоні контакту та визначено час роботи твелу без критичного зносу під час контакту з поверхнею трубної дошки. Отримані результати можливо вважати такими, що відповідають практичним експлуатаційним даним

Cyclic creep damage in thin-walled structures

Thin-walled structural elements are often subjected to cyclic loadings. This paper presents a material model describing creep behaviour under high-cycle loading conditions (N greater than or equal to 5 x 10(4)-10(5)). Assuming that the load can be split into two joint acting parts (a static and a superposed, rapidly varying small cyclic component), the asymptotic expansion of two time-scales has been applied to the governing equations of the initial-boundary value creep problem. The system of equations determine two problems. The first is similar to the creep problem by quasi-static loading. The second is the problem of forced vibrations. Both the problems are coupled by constitutive equations. The model is applied to the simulation of the cyclic creep damage behaviour of thin-walled structural elements. The results are discussed for two special numerical examples (a conical shell and a circular plate). The simulations show that the creep and the damage rates as well as the failure time are strongly sensitive to the redistribution of the stress state cycle asymmetry parameter A(s). The values of A(s) increase during the creep process. For particular cases of the loading frequency, A(s) can exceed the critical value. In this case the material model must be extended in order to consider the creep-fatigue damage interaction

Microhabitats of benthic foraminifera - a static concept or a dynamic adaption to optimize food aquisition?

In situ observations of microhabitat preferences of living benthic foraminifera are presented from sediments of the Norwegian-Greenland Sea, the upwelling area off northwestern Africa and the shallow-water Kiel Bight (Baltic Sea). Certain foraminiferal species (e.g.Cibicidoides wuellerstorfi andRupertina stabilis) can be regarded as strictly epibenthic species, colonizing elevated habitats that are strongly affected by bottom water hydrodynamics. Large epibenthic foraminifera (e.g.Rhabdammina abyssorum andHyperammina crassatina) colonize the sediment surface in areas where strong bottom currents occur and might have by virtue of their own size an impact on the small-scale circulation patterns of the bottom water. Motile species changing from epifaunal to infaunal habitats (e.g.Pyrgo rotalaria, Melonis barleeanum, Elphidium excavatum clavatum, Elphidium incertum, Ammotium cassis andSphaeroidina bulloides) are regarded here as highly adaptable to changes in food availability and/or changing environmental conditions. This flexible behaviour is regarded as a dynamic adaptation to optimize food acquisition, rather than a static concept leading to habitat classification of these ubiquitous rhizopods

An acceptor-substrate binding site determining glycosyl transfer emerges from mutant analysis of a plant vacuolar invertase and a fructosyltransferase

Glycoside hydrolase family 32 (GH32) harbors hydrolyzing and transglycosylating enzymes that are highly homologous in their primary structure. Eight amino acids dispersed along the sequence correlated with either hydrolase or glycosyltransferase activity. These were mutated in onion vacuolar invertase (acINV) according to the residue in festuca sucrose:sucrose 1-fructosyltransferase (saSST) and vice versa. acINV(W440Y) doubles transferase capacity. Reciprocally, saSST(C223N) and saSST(F362Y) double hydrolysis. SaSST(N425S) shows a hydrolyzing activity three to four times its transferase activity. Interestingly, modeling acINV and saSST according to the 3D structure of crystallized GH32 enzymes indicates that mutations saSST(N425S), acINV(W440Y), and the previously reported acINV(W161Y) reside very close together at the surface in the entrance of the active-site pocket. Residues in- and outside the sucrose-binding box determine hydrolase and transferase capabilities of GH32 enzymes. Modeling suggests that residues dispersed along the sequence identify a location for acceptor-substrate binding in the 3D structure of fructosyltransferases

USDA Plant Genome Research Program

The U.S. Congress appropriated funds in 1991 for the USDA Plant Genome Research Program, four years after its initial conception in 1987. The goal of the USDA Plant Genome Research Program is to improve plants (agronomic, horticultural, and forest tree species) by locating marker DNA or genes on chromosomes, determining gene structure, and transferring genes to improve plant performance with accompanying reduced environmental impact to meet marketplace needs and niches. The Plant Genome Research Program is one program with two parts: National Research Initiative and Plant Genome Database (PGD). The PGD is now a real and functioning information and data resource for agricultural and other plant science genome researchers, and it is in the public domain. Additional progress is given according to major plant groups. The PGD is a suite of several information products produced at the National Agricultural Library (NAL) in collaboration with the Agricultural Research Service and Forest Service species coordinators