Showing papers by "Congrès International d'Architecture Moderne published in 2009"

Modeling study of gas-turbine combustor emission

Abstract: On the base of the three-dimensional CFD simulation a simple reactor model to predict the pollutant formation in a combustor operating in a diffusion mode was built. This reactor model has been validated against NO x emission measured for model aero-engine combustor using both methane and kerosene as a fuel. It was shown that the predicted NO x emission index strongly depends on the applied reaction mechanism. The NO x emission indices calculated for methane-fueled and kerosene-fueled combustor using the developed reactor model and extended detailed reaction mechanisms for CH 4 /air and C 10 H 22 /air mixtures are consistent well with the experimental data. The developed model was used to estimate the emission of different species involving sulfur compounds (SO 2 and SO 3 ), carbon oxide, and unburned hydrocarbons depending on power setting of gas-turbine aviation engine.

The political undertones of building national health research systems – reflections from The Gambia

Abstract: In developing countries building national health research systems is a movement similar to a political leadership contest. Increasingly, political campaigns to select leaders depend less on ideologies and political messages and more on promising change that will promptly improve the quality of life of the voters. In this process the benefits and risks of every action and statement made by the candidates are carefully assessed. Approaches currently promoted to strengthen health research within ministries of health in developing countries place emphasis on implementing logical steps towards building national health research systems including developing a national health research policy and strategic plan, conducting a situational analysis of research in the country, setting a national health research agenda, establishing research ethics and scientific committees, and building human and institutional capacity for health research management and conduct. Although these processes have successfully improved the standards of health research in some settings, many developing countries struggle to get the process going. One reason is that this approach does not deal with basic questions posed within a ministry of health, namely, "What is the political benefit of the ministry assuming control of the process?" and "What are the political implications for the ministry if another institution spearheads the process?" Seen from the perspective of non-governmental organizations, academic institutions and donors trying to support the processes of strengthening national health research systems, one of the foremost activities that needs to be undertaken is to analyze the political context of national health research and, on that basis, plan and implement appropriate political health research advocacy initiatives. This includes the development of explicit messages on the political benefits to the leadership in the ministry of health of their role in the conduct, management and dissemination of health research within the country. Civil society organizations, with links to both government and non-governmental organizations, are well placed to play the role of advocates. It is only through broad and active participation of stakeholders that the process of developing effective and sustainable national health research systems will truly become a national movement inspired, led and sustained by ministries of health.

Antioxidant power, bacteriostatic activity, and characterization of white grape pomace extracts by HPLC–ESI–MS

Abstract: Polyphenolic fractions obtained from white grape pomace by aqueous extraction were analyzed to determine their antioxidant power (DPPH and TBARS methods), bacteriostatic activity, the effect of particle size on total extractable polyphenols (expressed as gallic acid equivalents (GAE)), and to characterize by HPLC–ESI–MS. The extraction of polyphenols from Albarino variety grape pomace was performed both on lab-scale and on pilot-plant scale using particles sizes of <1 mm, 3–5 mm and entire particle. Lab-scale assays showed that the lower the particle size the higher the raw extract (RE) percentage (%w/w), which values were 21.3 ± 0.37% (SD), 12.6 ± 0.38%, and 6.6 ± 0.44%, respectively. Several fractions were obtained from RE, either as result of applying liquid–liquid partition or gel permeation chromatography. The antiradical activities of the fractions were lower than that of gallic acid (17.8 ± 0.1 mg GAE/mol DPPH) but similar to that of catechin or procyanidin B2 (46.0 ± 2.3 mg GAE/mol DPPH and 52.3 ± 6.3 mg GAE/mol DPPH). Several fractions showed bacteriostatic activity both at 50 and at 100 mg/L. Total aerobic bacterial enumeration (TABE, log UFC/cm2) of treated samples revealed a significant lower TABE than that for control. HPLC–ESI–MS studies demonstrated that fractions V and VI included monomers, dimers, and trimers of procyanidins, few of them galloylated. Fraction VII contained several oligomers and galloylated procyanidins.

Numerical experiment on conformal mapping of doubly connected regions onto a disk with a slit

Abstract: We present a method for computing the conformal mapping function of doubly connected regions bounded by two closed Jordan curves onto a disk with a concentric circular slit of radius . Our mapping procedure consists of two parts. First we solve a system of integral equations on the boundary of the region we wish to map. The system of integral equations is based on a boundary integral equation involving the Neumann kernel discovered by the authors satisfied by , , and , where is a fixed interior point with predetermined. The boundary values of are completely determined from the boundary values of through a boundary relationship. Discretization of the integral equation leads to a system of non-linear equations. Together with some normalizing conditions, a unique solution to the system is then computed by means of an optimization method called the Lavenberg-Marquadt algorithm. Once we have determined the boundary values of , we use the Cauchy integral formula to compute the interior of the regions. Typical examples for some doubly connected regions show that numerical results of high accuracy can be obtained for the conformal mapping problem when the boundaries are sufficiently smooth

Simultaneous Extraction and Cleanup Method Based on Pressurized Solvent Extraction for Multiresidue Analysis of Pesticides in Complex Feed Samples

Abstract: The development of a multiresidue method based on pressurized solvent extraction (PSE) to determine a large number of pesticides (mostly pyrethroids and organochlorines) in cattle feed is described. As far as we know, this is the first work dedicated to the PSE of many of the target pesticides from animal feed. A mixed level fraction design was performed to investigate the influence of several operational variables on the PSE procedure; integrated cleanup strategies were also assessed allowing the direct chromatographic analysis of the extracts. Method accuracy was evaluated by the analysis of a certified reference material (BCR-115) and different fortified cattle feed samples. Most analytes were recovered in the range of 70-110%, with relative standard deviations generally lower than 15%. Limits of detection (LODs) were below the maximum residue levels (MRLs) set by the European Union for animal feed and main crops used in the preparation of feedingstuffs. The applicability of the proposed method was demonstrated by the analysis of real cattle feed samples collected from 23 dairy farms located in Galicia (NW Spain).

Simulation of the rate of turbulent homogeneous combustion using the “quasi-laminar” approach

Abstract: The possibility is considered of using a bulk (“quasi-laminar”) model of combustion for describing the rate of propagation of flame front in a turbulent flow of homogeneous fuel-oxidizer mixture. It is demonstrated that the analytical relation for the rate of propagation of flame front, obtained using a bulk model of combustion, agrees well with the available experimental data. Bulk and front models of combustion, as well as an original reduced model of kinetics of methane-air mixture, are used for calculating a V-flame. Two-dimensional calculations of an axisymmetric low-emission combustion chamber are performed using the bulk model of combustion and two reduced kinetic schemes. Comparison is made of calculation and experimental data.

Investigation of the photochemical behaviour of pyrethroids lacking the cyclopropane ring by photo-solid-phase microextraction and gas chromatography/mass spectrometry.

Abstract: The characterization of by-products arising from the UV photodegradation of two insecticide pyrethroids lacking the cyclopropane ring (flucythrinate and fenvalerate) has been investigated by gas chromatography coupled with mass spectrometry (GC/MS). Twenty photoproducts were tentatively identified mainly based on the interpretation of the experimental mass spectra or by using reference mass spectra. Some of these compounds had not previously been detected. Furthermore, the generation of some of the photoproducts might be a matter for concern due to their potential toxicity. The corresponding photodegradation routes, including postulation of the intermediate radicals, have also been proposed. These photodegradation studies were performed by photo-solid-phase microextraction (photo-SPME) in which the SPME fibre was exposed to light after extraction of the target analytes from aqueous solutions. The degradation kinetics of the investigated pyrethroids and the photoformation-photodegradation curves of the photoproducts generated in situ were also monitored through the ion chromatograms obtained for different irradiation times and the corresponding mass spectra.

Application of taguchi's design of experiment in performance analysis of destination sequence distance vector (DSDV) routing protocol in mobile ad hoc networks

Abstract: Numerous routing protocols for mobile ad hoc networks (MANETs) have been designed in process information delivery from a source node to a destination node. In this paper, the Taguchi's design of experiment (TDE) has been applied to investigate the performance of Destination Sequence Distance Vector (DSDV) routing protocol in MANETs. The effects of network parameters namely terrain sizes, node speeds, network sizes, transmission ranges, transmission rates, pause times and the number of maximum connections on packet delivery ratio and routing overhead in medium scale ad hoc networks have been done through simulation experiments. Through this study, we can rank these factors that may affect packet delivery ratio and routing overhead. The response performance was analyzed based on signal-to-noise ratio and analysis of variance (ANOVA). The results revealed that the transmission range was the most influential factor on the packet delivery ratio, followed by terrain size and transmission rate. The network size had the greatest effect on routing overhead, followed by the transmission range.

Numerical Conformal Mapping via a Fredholm Integral Equation using Fourier Method

Abstract: An interpolation formula based on Fourier method for the numerical solution of a Fredholm integral equation related to conformal mapping of a simply connected region onto a unit disc is presented. The integral equation involves the Neumann kernel. The numerical results obtained from the interpolation formula based on Fourier method are then compared with the numerical results obtained from the interpolation formula based on Nystrom’s method. Numerical comparison shows that the interpolation formula based on Nystrom’s method gives better performance. Numerical implementations on some test regions are presented.

Experimental investigation of a surface discharge in focused beam of microwave radiation at wavelength of 2.5cm and 8.9cm

Abstract: Microwave generator feeds trough waveguide horn-shaped antenna, forming by dielectric radio transparent lens and spherical metal mirror the focused beam of radiation. Radiation is vertical linearly polarized. The dielectric plane layers of varied thickness and substance are being located in the focus of radiation. The surface of layer is parallel to electric field vector. If needed, half-wavelength metal thin initiator is located in surface of layer. Influence of dielectric layer on breakdown and discharge processes is investigated. The properties of surface discharge are studied.