Shape optimal design using B-splines

Shape optimal design of an elastic structure is formulated using a design element technique. It is shown that Bezier and B-spline curves, typical of the CAD philosophy, are well suited to the definition of design elements. Complex geometries can be described in a very compact way by a small set of design variables and a few design elements. Because of the B-splines flexibility, it is no longer necessary to piece design elements together in order to agree with the shape complexity, nor to restrict the shape variations. Moreover, the additional optimization constraints that are most often needed to avoid unrealistic designs when the shape variables are the nodal coordinates of a finite element mesh, are automatically taken into account in the new formulation. An analytical derivation of the sensitivity analysis will be established, giving rise to numerical efficiency. It will be seen that the resulting optimization problem does not involve highly nonlinear functions with respect to the shape variables, so that simple mathematical programming algorithms can be applied to solve it. Some numerical examples are offered to demonstrate the power and generality of the new approach presented in this paper.     

Behavior of nickel-base superalloy single crystals under thermal-mechanical fatigue

The thermal-mechanical fatigue behavior of AM1 nickel-base superalloy single crystals is studied using a cycle from 600 °C to 1100 °C. It is found to be strongly dependent on crystallo-graphic orientation, which leads to different shapes of the stress-strain hysteresis loops. The cyclic stress-strain response is influenced by variation in Young’s modulus, flow stress, and cyclic hardening with temperature for every crystallographic orientation. The thermalmechanical fatigue life is mainly spent in crack growth. Two main crack-initiation mechanisms occur, depending on the mechanical strain range. Oxidation-induced cracking is the dominant damage mechanism in the lifetime of interest for turbine blades.     

Activation of the uncoupling protein by fatty acids is modulated by mutations in the C-terminal region of the protein

The transport properties of the uncoupling protein (UCP) from brown adipose tissue have been studied in mutants where Cys304 has been replaced by either Gly, Ala, Ser, Thr, Ile or Trp. This position is only two residues away from the C-terminus of the protein, a region that faces the cytosolic side of the mitochondrial inner membrane. Mutant proteins have been expressed in Saccharomyces cerevisiae and their activity determined in situ by comparing yeast growth rates in the presence and absence of 2-bromopalmitate. Their bioenergetic properties have been studied in isolated mitochondria by determining the effects of fatty acids and nucleotides on the proton permeability and NADH oxidation rate. It is revealed that substitution of Cys304 by non-charged residues alters the response of UCP to fatty acids. The most effective substitution is Cys for Gly since it greatly enhances the sensitivity to palmitate, decreasing threefold the concentration required for half-maximal stimulation of respiration. The opposite extreme is the substitution by Ala which increases twofold the half-maximal concentration. We conclude that the C-terminal region participates in the fatty acid regulation of UCP activity. The observed correlation between yeast growth rates in the presence of bromopalmitate and the calculated activation constants for respiration in isolated mitochondria validates growth analysis as a method to screen the in situ activity of UCP mutants.     

Superconductivity above the temperature of liquid nitrogen

The discovery of superconductivity in certain copper oxides above liquid nitrogen temperature and the attendant publicity are put in perspective. The nature of the oxide superconductors is examined. Their fabrication and physical properties are discussed. Present research directions are described     

A laboratory validation study of the diagnostic mode of the Autoset system for sleep-related respiratory disorders

We performed a validation study of the diagnostic mode of the Autoset system (ResMed, Australia) on a group of 44 snorers (10 women). We compared the result of the Autoset's automatic analysis of nasal airflow (using nasal prongs) to those of an in-laboratory polysomnographic study with a Fleisch facemask pneumotachograph. For the first 29 patients, the Autoset software was set to recognize only apneas; for the remaining 15, the software was modified to recognize both apneas and hypopneas. Relative to polysomnography, the Autoset overestimated the number of apneas. Oral breathing or displacement of the nasal prongs partially explained these differences. A significant correlation was found between the apnea indices (AI) assessed by the two methods (r = 0.98). For an AI of 20/hour the Autoset was 100% sensitive and 88% specific. The Autoset significantly underestimated the number of hypopneas compared to the polysomnograph with pneumotachograph (62.9 +/- 4.7 vs. 85.5 +/- 73.1, P = 0.04), although for an apnea-hypopnea index of 20, Autoset was 100% sensitive and 88% specific. The lack of linearity of Autoset's volume evaluation at low volumes could explain most of the differences. Our results indicate that the Autoset system, in its diagnostic mode, is a useful tool for identifying patients with significant obstructive sleep apnea syndrome. The system is less useful in patients with mild to moderate sleep disordered breathing, where it may give erroneous results.     

Shape sensitivity analysis using low- and high-order finite elements

A general procedure to perform the sensitivity analysis for the shape optimal design of elastic structures is proposed. The method is based on the implicit differentiation of the discretized equilibrium equations used in the finite element method (FEM). The so-called semianalytical approach is followed, that is, finite differences are used to differentiate the finite element matrices. The technique takes advantage of the geometric modeling concepts typical of the computer-aided design (CAD) technology used in the creation of a compact design model. This procedure is largely independent of the types of finite elements used in the analysis and has been implemented in ah-version andp-version finite element program. Very accurate and stable shape sensitivity derivatives were obtained from both programs over a wide range of finite difference step sizes. It is shown that the method is computationally efficient, general, and relatively easy to implement. Some classical shape optimal design problems have been solved using the CONLIN optimizer supplied with these gradients.     

Smoke data from the Cone Calorimeter for comparison with the room fire test

Smoke production in the full–scale room fire test ISO 9705 (Commonly referred to as the Room Corner Test) and in the Cone Calorimeter ISO 5660 has been analysed for three sets of building products comprising a total of 28 products. The smoke production may be critical for the fire classification of surface products since some products produce large amounts of smoke in the room fire test even if they do not reach flashover within 20 min. Several smoke parameters in the Cone Calorimeter and the room fire test have been analysed. Good correlations have been obtained when the products are divided into two groups: products with more than 10 min to flashover in the room fire test and those with less than 10 min. These two time categories correspond to the two heat output levels in the room fire test: 100 kW for the first 10 min and then 300 kW up to 20 min. For products with more than 10 min to flashover the average rate of smoke production and the total smoke production seem to be useful parameters for predictions of smoke release in the room fire test. Both parameters have good correlations between data from the Cone Calorimeter and the room fire test. For products with less than 10 min to flashover no parameter seems to give useful predictions. For all products evaluated together, the correlations are not so good, but the same regression lines as for products with more than 10 min might be used as a first rough estimate. In this case the total smoke production in the Cone Calorimeter could be used to estimate the total smoke production in the room fire test for different building products, independent of their estimated time to flashover. It is suggested that the average rate of smoke production and the total smoke production from the Cone Calorimeter is reported in addition to the mass-based specific extinction area. This will be helpful in predicting smoke release in the room fire test and will also make the data on smoke release analogous to those on heat release.     

Connaissance des résultats et contr?le spatiotemporel dans une tache d'anticipation-co?ncidence chez des enfants de 6 à 10 ans.

Studied the effects of knowledge of results (KR), either spatial or temporal, on performance of a coincidence-timing task among Canadian children. Human subjects: 90 male and female Canadian children (aged 6–10 yrs). Ss were divided into 3 age groups (mean age 6.8 yrs, 8.3 yrs, and 10.2 yrs). Each age group was divided into 3 experimental groups: 1 group received spatial KR, 1 group received temporal KR, and 1 group received no KR during practice sessions for a coincidence-timing task. The task consisted of moving an object horizontally with the hand to a spot corresponding to the movement of a visual stimulus. The object was to reach the correct spot at the same time as the visual stimulus, which came from either the right or the left at speeds of 100 or 152 cm/s. The results were analyzed according to Ss' age, speed of stimulus, direction of stimulus, type of KR training, and whether or not the S's object arrived before or after the visual stimulus. A multivariate analysis of variance (MANOVA) was used. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Incidence of the dehydration step on the electrochemical behaviour of 3-hydroxy 2-one benzodiazepine compounds (oxazepam and lorazepam) in aqueous acid media at the mercury electrode

The hypothesis of an e.c.e. mechanism may justify the electrochemical behaviour observed for the reduction at the mercury electrode of two benzodiazepinones: oxazepam $\text{1}$ and lorazepam $\text{1′}$.In aqueous acid medium, the first step $\text{2}$ would consist in the grossly irreversible reduction of the imine bond (2F mol^?1).The chemical rate limiting step of the overall e.c.e. mechanism (4 F mol^?1) would consist in an acid-catalysed dehydration of an intermediate $\text{2}$ yielding a species $\text{3}$ which undergoes a disproportionation reaction with the hydrated species $\text{2}$ generated in the first step. The following values of k′ (k_exp = k′.(H⁺)) were determined for the rate constant of the chemical rate limiting step: oxazepam $\text{1}$:k′ = (1.0 ± 0.1) 10⁶ s^?1; lorazépam $\text{1′}$ = (7.1 ± 0.5)10⁴s^?1.     

Stabilisation électrique de films résistants en zinc pulvérisé

Zinc sputtered thin films show, after aging, an electric resistance of high fidelity versus the variations of electric field and temperature; fractionned sputtering introduces no disturbance in the evolution of electrical resistance. Data are in qualitative agreement with the consequences of Laville Saint Martin's theories.