Coupled Mechanical and Chemical Damage in Calcium Leached Cementitious Structures

Long-term durability of concrete structures must be faced both from the point of view of cracking and physical degradations. In this paper, the relevance and the sensitivity of an existing constitutive relation aimed at modeling mechanical and chemical damage is examined. This constitutive relation is based on a scalar continuum damage model. The chemical degradation mechanism is calcium leaching. It is observed that the model predictions, i.e., the lifetime of cement-based beams subjected to leaching, are very sensitive on the tensile strength and fracture energy of the sound material. The existing model predicts the response of bending beams subjected to various states of leaching prior to any mechanical loading. The simulation of the size effect tests shows that the mechanical internal length and the damage threshold of the material cannot be considered to be constant. The internal length ought to decrease and the damage threshold should increase.     

Microscopic noise modeling and macroscopic noise models: how good aconnection? [FETs]

Based on the active line concept, a novel approach for the calculation of the high frequency noise performance of field effect transistors (FET) is proposed. By using a simple analytical theory, the FET small signal equivalent circuit as well as the macroscopic noise sources and their correlation are calculated for different two-port terminations. Values of the usual dimensionless noise parameters P, R, C, gate noise temperature T_g and drain noise temperature T _d are then given and discussed. By comparison with a more realistic numerical modeling of the noise performance, the validity of the analytical noise model is discussed. The validity of Pospieszalski's noise model and its relations with Pucel's one is emphasized     

Validation de séquences de test fonctionnel de microprocesseurs

The qualification ofVLSI circuits is usually performed by the mean of functional testing sequences, some of them very complex. The performance of these sequences is often quite unknown, and it is difficult to link them with a reject rate. This work shows the possibility to describe a complex integrated circuit as a cartesian graph ; then, having the functional sequence going over this graph, it provides the ability to get test reject rates. It is obvious that such a validation of test sequences could improve the usual process of components standardization.     

Experimental aspects of the thermochemical conversion of solar energy; Decarbonation of CaCO3

High temperature endothermic reactions as well as heating of chemically inert materials were performed with small solar furnaces (power: 2 kW) in specially designed reactors. These reactors—fluid bed and rotary kiln—allow continuous processing at high temperature.The treatment temperatures of fluidized inert materials (Silica, Chamotte, Ilmenite) may vary from 600° to 1300°C according to their nature and their radiative properties and also to the gas velocity, the particle diameters and the bed weight. Temperature homogeneity can be reached in a rather large volume. Thermal conversion efficiency can reach 0.35 with Ilmenite at 1250°C even though the experiment is conducted at a laboratory scale.A strong thermal gradient exists in materials treated in the rotary kiln, for example there can be temperature distribution from 1500°C at the opening of the furnace to 300°C at the bottom. Because of the cavity effect temperature is only slightly dependent on the thermal radiative properties of materials. Thermal conversion efficiency for this set-up is of the order of 0.1–0.3.The study of decarbonation of CaCO₃ showed that conversion of solar energy to thermochemical energy is a viable proposition: conversion yields of 0.1 are reached for total decomposition and over 0.15 for partial (75%) decomposition. It is seen from these laboratory scale experiments that great improvements can be made.     

L'Entra?nement à l'empathie et le style de valorisation.

Hypothesized that empathy training is effective and that the individual who values being expressive (active) in his/her environment will learn that skill more easily than the impressive (passive) individual. 29 undergraduate psychology students participated in a training program for enhancing helping relations skills. Three measures of empathy were administered both before and after training: an index of communication, an index of discrimination, and interviews rated on R. R. Carkhuff's (1969) empathy scale. Values were measured using the Questionnaire des Valeurs d'éducation (J. Perron, 1974). Outcome measures supported the efficiency of the training program, but the expressive values were negatively correlated with the learning of empathy. The ceiling effect in the results and their implications for the Carkhuff model are discussed. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quasi-stationäres verhalten von wandernden brennzonen

During the performance of a fast exothermic reaction in a catalyst bed, the complete chemical reaction can occur in a very short moving reaction zone, which frequently only ranges over a few pellet diameters. Experimental examinations, made by Wicke and Vortmeyer, on the behavior of such a moving reaction zone resulted in the following fact: through variation of the flow velocity u in axial direction of the bed, this zone can optionally be moved. If the conditions of the reaction are time constant, and the reactor is sufficiently long on both sides, a quasi-stationary axial movement of this reaction zone appears. This movement is characterized through a constant velocity w. For these quasi-stationary dynamics, the diffusion model's equations are approximately solved. From these, the velocity w of the moving reaction zone can be determined as a function of all parameters of reaction and reactor. This can be done in a very distinct way by means of a graph.     

Mise en evidence d'un transfert d'energie de type Gd3+ → Tb3+ dans les phases Sr2Gd1−xTbxGaO5

Energy transfer from optically excited Gd³⁺ ions to Tb³⁺ ions is reported in Sr₂Gd_1?xTb_xGaO₅. It is illustrated by the comparison of the emission and excitation spectra of Sr₂GdGaO₅ and of Sr₂Gd_0,995Tb_0,005GaO₅ between 77 and 300 K.     

Secretory pathways in animal cells: With emphasis on pancreatic acinar cells

Studies over the past three decades have clearly established the existence of at least two distinct pathways for the intracellular transport and release of secretory proteins by animal cells. These have been identified as the regulated and constitutive pathways. Many observations have indicated that in certain cells, such as those of the exocrine pancreas and parotid glands at least, these pathways coexist in the same cells. Although the general scheme of protein transport within these pathways is well established, many fundamental aspects of intracellular transport remain to be unraveled. How are proteins transported through the endoplasmic reticulum? How are the transitional vesicles formed and what are the underlying mechanisms involved in their fusion with the cis-Golgi cisterna? Even the general mode of transfer through the Golgi stack is debated: Is there a diffusion through the stack by flow through intercisternal tubules and openings or is there a vesicle transfer system where membrane quanta hop from one cisterna to the other? What is the fate of secretory proteins in the trans-Golgi area and by what mechanisms is a fraction of newly synthesized molecules of a given secretory protein released spontaneously while the majority of such nascent molecules are diverted into a secretory granule compartment? In this review, we have examined these and other aspects of intracellular transport of secretory proteins using pancreatic acinar cells as our reference model and we present some evidence to support the existence of a paragranular pathway of secretion associated with secretory granule maturation.     

Secure implementation of identification systems

In this paper we demonstrate that widely known identification systems, such as the public-file-based Feige-Fiat-Shamir scheme, can be insecure if proper care is not taken with their implementation. We suggest possible solutions. On the other hand, identity-based versions of the Feige-Fiat-Shamir scheme are conceptually more complicated than necessary.Gilles Brassard's research is supported in part by Canada's NSERC. A part of this research was done while Yvo Desmedt was sponsored by NFWO (the Belgian NSF). A later part was done while he was visiting professor at the Département IRO, Université de Montréal. A part of his research is now supported by NSF Grants NCR-9004879 and NCR-9106327. This research was done while Jean-Jacques Quisquater was at the late Philips Research Laboratory, Belgium. Parts of this research were presented at Crypto '86, Crypto '87, and Securicom '88.