CATHARE 2 V2.5_2: A single version for various applications

This paper presents the new capabilities of CATHARE 2 as a multi-purpose multi-reactor concept system code. The CATHARE 2 code was originally devoted to best estimate calculations of thermal-hydraulic transients in Water-Cooled Reactors such as PWR, VVER or BWR. Recently, in the framework of the Generation IV International Forum, CEA launched several feasibility studies of future advanced reactor concepts including Gas-Cooled Reactors, Sodium-Cooled Fast-Breeder Reactors, Supercritical Water-Cooled Reactors. The 2-fluid model with non-condensable gases transport equations was first easily extended to Gas-Cooled Reactor applications with very few modifications. At the same time CEA seized opportunity to use CATHARE 2 to perform studies for non-nuclear industrial applications such as cryogenic rocket engines. New capabilities were implemented allowing passage from supercritical pressure to subcritical conditions and these features were then easily applied to Supercritical Water-Cooled Reactors. New developments were also necessary to extend the code to Sodium-Cooled Reactors. CATHARE 2 can now describe several circuits with various fluids either in single-phase gas or liquid, or in two-fluid conditions possibly with noncondensable gases, which allows simulating any kind of reactor concept and any kind of accidental transient.The development method for the extension to new fluids is presented with an overview of the most striking functional and modelling features that have been implemented in the new CATHARE 2 V2.5_2 version to be released mid-2009 for industrial applications.     

Sustainable GQDs for potential application in engineering using corn powder as green precursor

Abstract

An alternative way to produce Graphene Quantum Dots (GQDs) economically is proposed in this study where corn powder was used as a green precursor to fabricate GQDs in a hassle less one-step route. These GQDs showed a stable, size-dependent in aqueous solution. The size of GQDs obtained from this work is approximately measure from 0.21 to 5.20?nm. The XRD patterns showed a broad peak at 22?Å. Furthermore, the UV-vis absorption spectrum has a broad peak around the range of 250–350?nm which is ascribed to the typical absorption of n-π* transition of the carbonyl groups. The said sample also exhibited bright green photoluminescence under an UV light. The Raman spectra displayed a D band around 1375?cm^?1 and G band around 1578?cm^?1. The performed analysis confirms that the GQDs by this method has a similar result compared to the other methods. This suggests that corn powder as a precursor can be used to fabricate GQDs in a simplistic and environment-friendly way for potential application in sensors, very large scale integration and energy generation technology.     

Effect of metakaolin and foundry sand on the near surface characteristics of concrete

This paper deals with the effect of foundry sand (FS) and metakaolin (MK) on the near surface characteristics of concrete. A control concrete having cement content 450 kg/m³ and w/c of 0.45 was designed. Cement was replaced with three percentages (5%, 10%, and 15%) of metakaolin weight, and fine aggregates were replaced with 20% foundry sand. Tests were conducted for initial surface absorption, sorptivity, water absorption and compressive strength at the ages of 35, 56, and 84 days.Test results indicated that with the increase in MK content from 5% to 15%, there was a decrease in the initial surface absorption, decrease in the sorptivity till 10% metakaolin replacement. But at 15% MK replacement an increase in sorptivity was observed. All mixtures showed low water absorption characteristic i.e. less than 10%. Compressive strength shared an inverse relation with sorptivity. Higher MK replacements of 15% are not helpful in improving inner core durability, even though it helps in improving surface durability characteristics. Inclusion of foundry sand resulted in reduction in compressive strength. This aspect cements the findings that addition of FS causes permeability of concrete to increase causing in an increase in sorptivity and water absorption of concrete.     

A decision aided channel estimation scheme

In this letter, we address the problem of mobile radio channel estimation at high channel efficiency using a small number of training symbols. A decision aided channel estimation scheme is proposed for slow fading multipath DS-CDMA channels. The approach is an extension of single-user least-square channel estimation. It is demonstrated that, due to the suggested channel estimate updating algorithm, the proposed scheme improves the channel estimation accuracy significantly.     

Atomic layer deposition on biological macromolecules: metal oxide coating of tobacco mosaic virus and ferritin

Decoration of nanoparticles, in particular biomolecules, gathered high attention in recent years.(1-7) Of special interest is the potential use of biomolecules as templates for the fabrication of semiconducting or metallic nanostructures.(1-7,26) In this work we show the application of atomic layer deposition, a gas-phase thin film deposition process, to biological macromolecules, which are frequently used as templates in nanoscale science, and the possibility to fabricate metal oxide nanotubes and thin films with embedded biomolecules.(1-13).     

Properties of self-compacting mortar made with various types of sand

Higher cement and fines content is needed in self-compacting mortars (SCMs) to increase their flowability and stability. Different inert fillers and supplementary cementitious materials are usually added. The use of sands rich in fines may be a cost effective alternative source of filler. This paper presents the results of an experimental study on the rheological and mechanical properties of self-compacting mortars (SCMs) made with various types of sands: crushed sand (CS), river sand (RS), dune sand (DS) and a mixture of different sands. The mini-slump flow, V-funnel flow time and viscosity measurement tests were used to study the rheological properties. The experimental results indicate that the rheological properties and strength improve with mixtures of crushed and river sands but decrease with mixtures of crushed and dune sands especially for higher dune sand content. Crushed sand with (10–15%) of limestone fines can be used successfully in production of SCM with good rheological and strength properties. However, a reduction in compressive strength with increasing dune sand content (up to 50%) in mortar with binary and ternary sands was observed.     

Flavor Comparison of Natural Cheeses Manufactured in Different Countries

Abstract: The objective of this study was to determine the main flavor components of different natural aged cheese types from various countries and determine whether a unique sensory characteristic exists within specific countries for European cheeses. The flavor of 152 cheeses from Estonia, France, Italy, Germany, Holland, Austria, England, Greece, Ireland, Spain, Switzerland, Sweden, Belgium, and Denmark were described during 4 independent studies. The sensory data from these studies were combined. The cheeses were sorted according to milk type and texture, and flavor characteristics of these groups were described. The main flavor characteristics of the cheeses tested were salty, sweet, sour, astringent, biting, pungent, sharp, nutty, musty/earthy, dairy fat, buttery, and dairy sweet. The cluster analysis divided the cheeses into 4 clusters: clusters 1 and 2 were sour, dairy sour, salty, astringent, biting, and varied in buttery (cluster 1) and sharp notes (cluster 2). Cluster 1 and 2 were mainly composed of French cheeses, while clusters 3 and 4 represented cheeses from various countries. Cluster 3 and 4 were sweet, with cooked milk and nutty characteristics and varied from buttery (cluster 3) to sharp notes (cluster 4). Cheeses from some countries, for example, France and Estonia, generally exhibited common sensory characteristics within the specific country, but cheeses from some other countries, such as Italy, varied widely, and seemed to have no common sensory theme. Most regional cheese standards are not specific about flavor profiles and these results suggest it may be possible to start a further characterization of cheeses in some countries. Practical Application: This research shows the main flavor characteristics of certain types of cheeses manufactured in various countries. The information may be useful to cheese manufacturers, product developers, food scientists, cheese connoisseurs, and government officials to better understand the flavor classification of cheeses from various countries.     

Compressive strength and shrinkage of mortar containing various amounts of mineral additions

Three mineral additions largely used in cementitious materials were tested in order to follow the shrinkage behaviour for 1 year of observation when they substitute a part of cement. The tests were carried out on standardized mortars specimen where cement was replaced by 5%, 15% and 25% of limestone, 10%, 20%, 30% of natural pozzolan and 10%, 30% and 50% of slag. The substitution of cement by 10%, 20% and 30% of limestone powder, natural pozzolan and slag respectively involves an optimal improvement of compressive strength of mortar. The separate quantification of the autogeneous and drying shrinkage development shows the effective contribution of each addition on microstructure modification and of the additional hydrates production. The microstructure was improved in the presence of limestone and of a moderate rate of slag, whereas it remains normal with natural pozzolan. The replacement rate of an active addition lower than 10% led to an additional hydrates production. This overproduction which accompanies the autogeneous shrinkage is more pronounced when cement is largely replaced by limestone. The evolutions of strength and shrinkage of mortars follow the same tendency from where it is easier to find a linear relationship giving the shrinkage deformation according to the compressive strength.