Modele de comportement mecanique d'element combustible dans un assemblage PWR

Irradiated fuel in pressurized water reactors (PWRs) frequently displays rod bowing, due to two kinds of assymmetry. The first originates in the fabrication of the sheath, causing eccentricity, ovalization and thickness non-uniformity. The other comes from in-pile fuel element conditions such as off-line grids compressing the rods, circumferential thermal gradients on the sheath, and pellet-clad interactions.The MAC code was developed for parametric studies of some of these effects. It shows that:In the case of fuel rods undergoing compressive forces by the spacer grids the usual friction forces are unable to bow the rods significantly, except when the rods are blocked by the spacer grid springs.In some assembly configurations, the temperature difference between adjacent rods is able to bow them, requiring an increase in number of spacer grids.Localized pellet-clad interactions may cause significant bowing, particularly when they occur near the grids.     

One-dimensional collision: An interactive graphics program

An interactive program with output to a graphical terminal has been developed for use in an undergraduate physics laboratory. The program computes and draws “snapshots” of one dimensional elastic collisions from data chosen by the student. The aim of the program is to come to a better understanding of the physics of collisions as seen from laboratory and center of mass reference frames. Great stress is laid upon the properties of the latter.     

A Two-Dimensional Heat Transfer Model for Thermal Barrier Coating Average Thermal Conductivity Computation

ABSTRACT

The present article is devoted to quantifying the contribution of pores and cracks in the decrease of the effective thermal conductivity of thermal barrier coatings (TBCs). A finite-difference-based model is used for the computation of heat transfer through a porous structure. Each pixel of a binary picture describing the pore network is interpreted as a cell of integration of the heat conduction equation. A thermal gradient is applied and a large system of linear Equations is subsequently derived. Since it has a strong influence on the required CPU time, particular attention is given to the solving procedure.     

Synthesis of ZnO nanostructure films by thermal evaporation approach and their application in dye-sensitized solar cells

Zinc oxide (ZnO) films were prepared successfully by simple thermal evaporation of zinc acetate dihydrate at low temperature onto FTO (fluorine-doped tin oxide) glass substrates coated with thin ZnO seed layer. The synthetic parameter such as temperature was found to determine the morphology of nanostructures. ZnO nanorod (NR) and nanoparticle (NP) films have been synthesized at 245 and 350 °C, respectively, for 6 h. The dye-sensitized solar cells (DSSCs) were fabricated using the ZnO nanostructure films as photosensitized electrodes. A maximum photoelectric conversion efficiency (PCE) of 1.56%, and short-circuit photocurrent density of 5.12 mA/cm² were achieved with the ZnO NP-based DSSC. The PCE increase was ascribed to the reduced recombination loss and prolonged electron lifetime according to electrochemical impedance spectroscopy (EIS).     

Artificial neural networks implementation in plasma spray process: Prediction of power parameters and in-flight particle characteristics vs. desired coating structural attributes

Artificial neural networks (ANN) were implemented to predict atmospheric plasma spraying (APS) process parameters to manufacture a coating with the desired structural characteristics.The specific case of predicting power parameters to manufacture grey alumina (Al₂O₃-TiO₂, 13% by wt.) coatings was considered. Deposition yield and porosity were the coating structural characteristics.After having defined, trained and tested ANN, power parameters (arc current intensity, total plasma gas flow, hydrogen content) and resulting in-flight particle characteristics (average temperature and velocity) were computed considering several scenarios. The first one deals at the same time with the two structural characteristics as constraints. The others one deals with one structural characteristic as constraint while the other is fixed at a constant value.     

Measurement of thermal conductivity of epoxy resins during cure

This work reports the development of a methodology for the measurement of thermal conductivity of thermosetting polymers during their cure. The study addresses the reliability and robustness of the method through FEA modeling and testing using a noncuring material with known thermal conductivity. The thermal conductivity and its evolution during the cure has been measured for three widely used aerospace epoxy resins, namely, RTM6, 890RTM, and the XU3508/XB3473 system as function of cure temperature. A constitutive model expressing the dependence of thermal conductivity on the degree of cure and temperature has been established. The device developed here can measure thermal conductivity of epoxy resin with accuracy up to 3%. © 2018 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47015.     

22层框架楼房定向爆破拆除倒塌过程分析

河源市龙川县远东花园4号楼为22层框架结构楼房,系违章建筑需爆破拆除.紧挨楼房5 m处有一栋3层别墅,别墅的围墙与待拆除楼房只有0.5 m,需防止楼房产生后座.根据周围环境条件,采用定向倾倒的方式爆破拆除,采用梯形爆破缺口,爆破高度13.5 m.为确定最佳延期时间,用ANSYS/LS-DYNA对排间延期时间300 ms...     

Zur Frage des Kupfergehaltes der Milch und einiger Milchpr?parate

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