scholarly journals Prediction of initial shape of functionally graded ceramic pre-forms for near-net-shape sintering

2003 ◽  
Vol 35 (1) ◽  
pp. 5-12 ◽  
Author(s):  
A.L. Maximenko ◽  
Der Biest ◽  
E.A. Olevsky
Keyword(s):  
Numerical Procedure ◽  
Continuum Theory ◽  
Functionally Graded ◽  
Theoretical Determination ◽  
Initial Shape ◽  
Ceramic Components ◽  
Near Net Shape ◽  
The Difference ◽  
The Continuum

Sintering of macroscopically inhomogeneous ceramic components is always accompanied by shape distortions due to the difference in shrinkage rates of powder elements. The objective of the present investigation is the theoretical determination of initially distorted shapes of the green bodies needed to provide near-net-shape sintered components. Calculations are based on a finite element implementation of the continuum theory of sintering. In this theory, sintering is considered as a creep under the influence of the compressive ?sintering stress?. To predict the initial shapes of the components the ?inverse? numerical procedure is used when the component is assumed to swell from the final shape to the initial one under the influence of the pressure equal (with the exception of sign) to the sintering stress.

Molecular Simulation of Viscous Flow

2006 ◽  
Author(s):  
M. H. Hamedi ◽  
M. Ghassemi
Keyword(s):  
Contact Angle Hysteresis ◽  
Constitutive Relations ◽  
Numerical Procedure ◽  
Atomic Scale ◽  
Missing Information ◽  
Governing Equations ◽  
Molecular Dynamics Calculations ◽  
Molecular Aspects ◽  
The Continuum

Sometimes the continuum equations of fluid mechanics must be completed by information about processes occurring at microscopic seals. For example, we can consider the formulation of boundary conditions, the resolution of singular solutions of the governing equations, and the determination of constitutive relations. In such situations, molecular dynamics calculations can be simulated at the atomic scale and provide the missing information. We review the numerical procedure and then discuss several recent applications of this technique. We consider the validity of lubrication theory at very short distances, the smoothing of corner singularities for both Newtonian and non-Newtonian fluids, and some molecular aspects of wetting phenomena, particularly contact angle hysteresis.

Mechanism of Ion Transport in Cooled and Supercooled Water at High Pressure

1983 ◽  
Vol 22 ◽  
Author(s):  
M. Nakahara ◽  
N. Takisawa ◽  
J. Osugi
Keyword(s):  
Room Temperature ◽  
Pressure Coefficient ◽  
Water Structure ◽  
Continuum Theory ◽  
Supercooled Water ◽  
Ionic Mobility ◽  
Dielectric Friction ◽  
Friction Theory ◽  
The Difference ◽  
The Continuum

ABSTRACTAs predicted by the Hubbard-Onsager continuum dielectric friction theory for ionic mobility in solution, the observed pressure coefficient of the difference ζ between the observed ionic drag coefficient and the Stokes law friction (4πηR), is negative for the small ion Li+ even at low temperatures where the water structure is highly developed. For the large ion Cs+, however, it is positive at any temperature in contrast to the theoretical prediction, its magnitude being larger at lower temperatures and pressures. The anomaly is shown also by the medium-sized ion K+ below room temperature. The passing-through-cavities (PTC) mechanism has been proposed to explain the limitations of the continuum theory.

scholarly journals PREDICTION OF THE ANTICLASTIC SHAPE CHANGES OF HYBRID COMPOSITE MATERIAL

2010 ◽  
Vol 16 (2) ◽  
pp. 222-229 ◽  
Author(s):  
Andris Baikovs ◽  
Kārlis Rocēns
Keyword(s):  
Composite Material ◽  
Calculation Model ◽  
Initial Shape ◽  
Reinforced Plastic ◽  
Glass Fibre Reinforced Plastic ◽  
Bending Radius ◽  
Glass Fibre Reinforced ◽  
The Difference ◽  
Moisture Conditions

In search of structurally better and aesthetically more attractive solutions of the erection of various structures, non‐standard anticlastic elements are used more frequently. Therefore preservation of the initial shape of timber composite material sheets by using of reinforced plastic reinforcement has been investigated. Calculation model for determination of the thickness of rational reinforcement anticlastic sheet, which provides change of the original bending radius under variable moisture conditions (Baikovs and Rocens, 2006) within the limits of preferable intervals is developed by authors and using finite element method, calculations and modelling of sheet deformations are carried out with software package ANSYS v.11 (henceforth FEM) and by developed analytical method. Comparative research of the results calculated with the FEM and developed calculation model showed that the difference between results in the three cases investigated, when the composite timber material is reinforced on the top, bottom and both sides for the most of the cases does not exceed 3.3%. An opportunity to provide the original shape of anticlastic timber composite material sheets by using glass fibre reinforced plastic reinforcement under variable moisture conditions and not exceeding the difference of 5% has been demonstrated. Santrauka Ieškant ivairiu konstrukciju statiniu konstrukciškai geresniu ir estetiškai patrauklesniu sprendiniu, dažniausiai naudojami nestandartiniai antiklastiniai elementai. Todel buvo tyrinetas medienos kompozitines medžiagos lakštu pradinio pavidalo išsaugojimas naudojant sustiprinta plastiko armatūra. Skaičiuojamasis modelis, padedantis nustatyti racionaliai armuoto antiklastinio lakšto stori, kuris pakeičia pradini lenkimo spinduli kintamomis dregmes salygomis (Baikovs, Rocens 2006) tarp priimtinu intervalu ribu, yra sukurtas autoriu ir, taikant baigtiniu elementu metoda, lakšto deformaciju skaičiavimai bei modeliavimas atlikti kompiuteriniu programu paketu ANSYS v. 11 (toliau ‐ FEM) ir pagal sukurta analitini metoda. Rezultatu, apskaičiuotu su FEM ir pagal sukurta analitini modeli, lyginamasis tyrimas parode, kad skirtumas tarp triju tirtu atveju, kai medienos kompozitine medžiaga yra armuota viršuje, apačioje ir iš abieju pusiu, rezultatai daugeliu atveju neviršija 3,3%. Parodyta galimybe suteikti originalu pavidala antiklastiniams medienos kompozitiniams lakštams naudojant stiklo pluoštu sustiprinto plastiko armatūra ivairiomis dregmes salygomis ir neviršijant 5% skirtumo.

Analytical responses of functionally graded beam under moving mass using Caputo and Caputo–Fabrizio fractional derivative models

2020 ◽  
Vol 26 (19-20) ◽  
pp. 1859-1867 ◽  
Author(s):  
Ibrahim M Abu-Alshaikh ◽  
Amro A Almbaidin
Keyword(s):  
Fractional Derivative ◽  
Functionally Graded ◽  
Beam Deflection ◽  
Moving Mass ◽  
Functionally Graded Beam ◽  
The Laplace Transform ◽  
Voigt Model ◽  
The Difference ◽  
Euler Bernoulli Beam

In this article, a functionally graded simply supported Euler–Bernoulli beam subjected to moving mass is considered in which the beam-damping is described using fractional Kelvin–Voigt model. A comparison between Caputo and Caputo–Fabrizio fractional derivatives for obtaining the analytical dynamic response of the beam is carried out. The equation of motion is solved by the decomposition method with the cooperation of the Laplace transform. Two verification studies were performed to check the validity of the solutions. The results show that the grading order, the velocity of the moving mass and the fractional derivative order have significant effects on the beam deflection, whereas the difference between the results of the two fractional derivative models is expressed by the determination of the correlation coefficient.

The Theory of Osmosis

2003 ◽  
Author(s):  
Larry D. Howlett
Keyword(s):  
Osmotic Pressure ◽  
Atmospheric Pressure ◽  
Traditional Theory ◽  
Theoretical Determination ◽  
Concentration Difference ◽  
Capillary Action ◽  
The Difference ◽  
Basic Equations ◽  
Thermodynamic Derivation

A fresh view for explaining the process of osmosis and the phenomenon of osmotic pressure is presented. The process of osmosis was identified and modeled more than 100 years ago. Others have unsuccessfully challenged the original model developed by J.H. van’t Hoff. We revisit the basic equations and assumptions used in the thermodynamic derivation of the osmosis model. And, we propose a small but significantly different view of the traditional theory of osmosis. From this new view of osmosis and the osmosis experiment, we conclude that osmosis occurs at atmospheric pressure. In cellular membranes, flow from the solvent to the solution is related to the vapor pressure difference determined from the concentration difference with Raoult’s law. Furthermore, we suggest that osmotic pressure as determined from the osmosis experiment is related to both the solution properties and the membrane characteristics. We suggest that the difference between experimental and theoretical determination of osmotic pressure can be attributed to capillary action that may occur in some man made membranes.

scholarly journals Influence of the continuum determination method on the mean transmission in the Lyα forest

2016 ◽  
Vol 6 (1) ◽  
pp. 34-40 ◽  
Author(s):  
O. Torbaniuk
Keyword(s):  
Determination Method ◽  
Quasar Spectra ◽  
The Mean ◽  
The Difference ◽  
The Continuum

Determination of the initial flux, or continuum, in the quasar spectra prior to its absorption by the intergalactic HI is nontrivial problem and it affects the precision of the mean transmission in the Lyα forest, <F>(z). The results of comparison of the <F>(z) values obtained using different methods of the continuum determination are presented in this paper. This analysis was conducted using the most complete compilation of the <F>(z) data from the literature. It was found that the values of the <F>(z) obtained with the manually determined continuum are systematically higher than those obtained from extrapolated continuum. The difference varies from 5% at z=2 up to 33% at z=4.5, respectively.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

THE SUBJECT FIELD OF INSTITUTIONAL EDUCATION: THE SENSE AND PROSPECTS OF DEVELOPMENT IN UKRAINE

2020 ◽  
pp. 25-38
Author(s):  
Irina Mordous
Keyword(s):  
Decisive Role ◽  
Subject Field ◽  
National Education ◽  
Progressive Development ◽  
Separate Area ◽  
Economic Transformations ◽  
The Difference ◽  
The Individual ◽  
Political Economic

The development of modern civilization attests to its decisive role in the progressive development of institutions. They identified the difference between Western civilization and the rest of the world. Confirmation of the institutional advantages of the West was its early industrialization. The genesis and formation of institutionalism in its ideological and conceptualmethodological orientation occurs as a process alternative to neoclassic in the context of world heterodoxia, which quickly spread in social science. Highlighting institutional education as a separate area of sociocultural activity is determined by the factor of differentiation of institutional theory as a whole. A feature of institutional education is its orientation toward the individual and his/her transformation into a personality. The content of institutional education is revealed through the analysis of the institution, which includes a set of established customs, traditions, ways of thinking, behavioral stereotypes of individuals and social groups. The dynamics of socio-political, economic transformations in Ukraine requires a review of the foundations of national education and determination of the prospects for its development in the 21st century in the context of institutionalism.

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