Laminar round jet diffusion flame buoyant instabilities: Study on the disappearance of varicose structures at ultra-low Froude number

At very low Froude number, buoyancy instabilities of round laminar jet diffusion flames disappear (except for small tip oscillations referred to as flickering) and those flames look stable and smooth. This study examines the contributions of the different phenomena in the flow dynamics that may explain this effect. It is observed that, at ultra-low Froude/Reynolds numbers, the material influenced by buoyancy is the plume of the flame and not the flame itself (reaction zone) that is short. Therefore, the vorticity creation zone does not profit from the reaction neighbourhood promoting a sharp gradient of density. Expansion and stretch are also important as they push vorticity creation terms more inside the flame and closer to the burner rim compared to moderate Froude flames. In these latter, the vorticity is continuously created around the flame reaction zone, along its developed height and closer to the vertical direction (in average).     

Effect of health status evaluated at arrival on growth in milk-fed veal calves: A prospective single cohort study

The objective of this prospective single cohort study was to determine the effect of health status at arrival on growth in milk-fed veal calves. Upon arrival at the veal facility, calves were evaluated using a standardized health scoring system and weighed, and the supplier of the calf was recorded. The calves were followed until slaughter, when the hot carcass weight (HCW) was reported. To calculate average daily gain (ADG), the HCW was transformed into an estimated live weight, weight at arrival was subtracted, and this value was divided by the number of days on feed. A mixed linear regression model was created to evaluate the association of health status on arrival with the ADG throughout the production period. A total of 4,825 calves were evaluated at arrival; however, due to inconsistent HCW data from one slaughter plant, and 357 calves dying during the production period, 2,283 calves were used for analysis. In the final model, 7 variables were significantly associated with ADG. Housing location within the farm, method of calf procurement (drover or auction-derived calves versus direct delivery from local farms) and having a higher body weight at arrival were associated with a higher ADG. The season of arrival (summer or fall compared with winter) and being dehydrated at arrival were associated with a lower ADG. Days on feed was also significant in the multivariable model and had a quadratic relationship with ADG. The associations identified suggest that there may be value in scoring dehydration and body weight at arrival to a veal facility.     

Reliability based design optimization using response surfaces in application to multidisciplinary systems

Traditionally, reliability based design optimization (RBDO) is formulated as a nested optimization problem. For these problems the objective is to minimize a cost function while satisfying the reliability constraints. The reliability constraints are usually formulated as constraints on the probability of failure corresponding to each of the failure modes or a single constraint on the system probability of failure. The probability of failure is usually estimated by performing a reliability analysis. The difficulty in evaluating reliability constraints comes from the fact that modern reliability analysis methods are themselves formulated as an optimization problem. Solving such nested optimization problems is extremely expensive for large scale multidisciplinary systems which are likewise computationally intensive. In this research, a framework for performing reliability based multidisciplinary design optimization using approximations is developed. Response surface approximations (RSA) of the limit state functions are used to estimate the probability of failure. An outer loop is incorporated to ensure that the approximate RBDO converges to the actual most probable point of failure. The framework is compared with the exact RBDO procedure. In the proposed methodology, RSAs are employed to significantly reduce the computational expense associated with traditional RBDO. The proposed approach is implemented in application to multidisciplinary test problems, and the computational savings and benefits are discussed.     

Property‐averaging applied to determination of volume contraction in binary‐solid liquid‐fluidized beds

This communication examines experimental information from the literature on the volume contraction that can occur when two monocomponent particle species that have a diameter ratio and a buoyancy‐corrected density ratio on opposite sides of unity are subjected to liquid fluidization as a binary mixture. Attempts are made to predict this volume contraction by applying monocomponent bed expansion equations using averaged properties of the binary solids. It was found that this method works better if the equations are anchored to experimental monocomponent voidages by the fractional bed volume change that they predict than if the equations are used directly. However, greater prediction accuracy can be achieved by correlation of the adjustable parameter G of the Westman, Am Ceramic Soc, 19 , 127–129, (1936) equation, originally applied to binary packed beds.     

X-Ray Micro-Calorimeter Based on Si Thermistors for X-Ray Astronomy: Design and First Measurements

X-ray Astronomy provides a unique window on a wide variety of astrophysical phenomena. The currently operating X-ray space observatories perform X-ray spectral imaging with the use of CCDs. When available, cryogenic X-ray microcalorimeter arrays will far outperform CCDs in terms of spectral resolution, energy bandwidth and count rate. Experience has been gained with Infra-Red bolometer arrays at CEA-LETI (Grenoble) in collaboration with the CEA-SAp (Saclay); taking advantage of this background, we are now developing an X-ray spectro-imaging camera for the next generation space astronomy missions, using silicon technology (implanted and high temperature diffused thermistors). Each pixel of this array detector is made of a tantalum absorber bound, by indium bump hybridization, to a silicon thermistor. The absorber array is bound to the thermistor array in a single automatic step. The thermo-mechanical link, provided by hybridization, is being improved in terms of thermal capacitance. Finally, our main effort is in developing arrays of silicon thermistors with negligible excess 1/f noise. The thermistor has been simulated with the 2D simulator ATHENA (SILVACO International). We studied the effects of the implants and their thermal treatment on both vertical and lateral dopant distributions at the edges of the thermistor. Prototypes have been created following the procedure optimized by the ATHENA simulation. We present the status of the development and results of measurements performed on these four main building blocks required to create a detector array up to 32×32 pixels in size.      

Optical constants of electroplated Bi2Te3 films by Mueller matrix spectroscopic ellipsometry

We synthesized polycrystalline Bi_2 + xTe_3 − x (− 0.2< x <0.2) thin films by electrodeposition in acidic medium. Since Bi₂Te₃-like structure may be uniaxially anisotropic due to its rhombohedral crystallographic system, we investigated their optical behavior using ex and in situ Mueller matrix spectroscopic ellipsometry in the wavelength range of 470 to 830 nm (1.5-2.6 eV). We found that room-temperature electroplated polycrystalline appears optically isotropic and that no depolarization effect occurs from the first steps of growth until several micrometers thick films. Additional ex situ measurements permit to obtain their optical constants from far-ultraviolet to near-infrared (190-2100 nm).     

Total lipid content, fatty acids and 4-desmethylsterols accumulation in developing fruit of Pistacia lentiscus L. growing wild in Tunisia

This research has determined oil, fatty acid and sterol contents of the Tunisian Pistacialentiscus (Lentisc) fruits during maturation. Low oil accumulation was observed during the first 35 days after the fruiting (DAF) date (from 1.83% to 2.57%). After that, two phases were distinguished (35th until the 60th and 105th to the 145th DAF), where the rate of oil accumulation increased significantly. At the last stage of maturation, the lentisc fruits had the highest percentage of lipid content, 42.54%. The changing profile of fatty acids during maturation had been marked mainly by an increase in oleic acid content (from 19.49% to 50.72%) paralleling a decrease in linoleic acid content (from 42.5% to 21.75%). At the 15th DAF, the alpha-linolenic acid was found with a maximum of 13.81%. At full maturity, the main fatty acids were oleic acid, followed by palmitic and linoleic acid. Other fatty acids were present in trace proportions, such as palmitoleic, stearic, linolenic, gadoleic and arachidic acid. In all stages of ripening only four sterols were identified and quantified. β-Sitosterol was the major 4-desmethylsterol in samples tested, followed by campesterol. Cholesterol and stigmasterol were detected in trace amounts. During the first stage of ripening, the amount of total sterols was about 5.19/100 g of oil. It decreased to 0.43/100 g in the last stage. Sitosterol and campesterol showed nearly the same profile during the ripening of P. lentiscus fruit which could be linked to the relation between these compounds during their biosynthesis.     

Work function tuning for flexible transparent electrodes based on functionalized metallic single walled carbon nanotubes

We present a method to control the work function of metallic carbon nanotube transparent electrodes by functionalization of the random network with metallic nanoparticles. Flexible functionalized electrodes with high transparency (～90%) can be obtained with work function values ranging from ～4.6 up to ～5.1 eV, depending on the nature of the nanoparticles. The work function values were obtained by comparative in situ Kelvin probe force microscopy under ultra high vacuum and ultraviolet photoelectron spectroscopy measurements. Interestingly, by appropriate choice of the metal source for functionalization, work function engineering can lead to work function values higher or lower than that for pristine metallic nanotubes. This could be of great interest for adjusting the work function of transparent electrodes to active layers in many optoelectronics devices.     

Use of Multi-response Modelling to Investigate Mechanisms of β-Carotene Degradation in Dried Orange-Fleshed Sweet Potato During Storage: from Carotenoids to Aroma Compounds

In order to give insight into β-carotene degradation mechanism during the storage of dried orange-fleshed sweet potato, and particularly into the role of isomers and norisoprenoids formation, multi-response kinetic modelling was applied. Determination of degradation compounds were carried out by HPLD-DAD and SPME-GC-MS as a function of time between 10 and 40 °C and at four water activities from 0.13 to 0.76. Kinetic modelling was developed assuming first-order reactions and by using mass balance. Eight compounds, namely, two isomers (9-cis- and 13-cis-β-carotene), two β-carotene epoxides (β-carotene 5,6 and 5,8 epoxide) and four volatile compounds (β-cyclocitral, β-ionone, 5,6-epoxy-β-ionone and dihydroactinidiolide), were integrated into two theoretical reaction schemes. The different models were discriminated according to goodness of fit to experimental data. This work showed that: (1) the formation of cis-isomers from β-carotene preceded oxidation, (2) β-cyclocitral arose directly from β-carotene scission while the other norisoprenoids resulted from β-carotene epoxide degradation, (3) cis-isomers were high reactive compounds. Temperature had a major influence on reaction rates k while water activities only impacted k at values under 0.51. Therefore, multi-response modelling is not only a tool to predict β-carotene degradation but a interesting way to select the appropriate degradation scheme based on the different options presented in literature.