Investigation of passive shock wave-boundary layer control for transonic airfoil drag reduction

The passive drag control concept, consisting of a porous surface with a cavity beneath it, was investigated with a 12-percent-thick circular arc and a 14-percent-thick supercritical airfoil mounted on the test section bottom wall. The porous surface was positioned in the shock wave/boundary layer interaction region. The flow circulating through the porous surface, from the downstream to the upstream of the terminating shock wave location, produced a lambda shock wave system and a pressure decrease in the downstream region minimizing the flow separation. The wake impact pressure data show an appreciably drag reduction with the porous surface at transonic speeds. To determine the optimum size of porosity and cavity, tunnel tests were conducted with different airfoil porosities, cavities and flow Mach numbers. A higher drag reduction was obtained by the 2.5 percent porosity and the 1/4-inch deep cavity

Enhancement of voip and video streaming performance over IEEE802.11e WLAN

There are various versions of IEEE802.11 WLAN in the market, and each applies different modulation technique and operates in different frequency bands. For example, the IEEE 802.11 b version provides data rates up to 11 Mb/s on the wireless medium, applying complementary code keying (CCK) and direct sequence spread spectrum (DSSS) as modulation technique. It operates in the industrial, scientific, and medical (ISM) band at 2.4 GHz. On the other hand, the IEEE 802.11 a version operates in the unlicensed 5 GHz band, and provides data rates up to 54 Mb/s on the wireless medium, applying the multicarrier technique orthogonal frequency-divi sion multiplexing (OFDM) as the modulation technique [1]. The 802.11 g version applies the same multicarrier modulation technique as 802.11 a, but operates in the 2.4 GHz ISM band like 802.11 b. However, due to channel conditions and protocol overhead, the maximum achievable throughput on the MAC layer is less than the data rate available on the wireless medium for the mentioned IEEE 802.11 version

A Topological Study of Chaotic Iterations. Application to Hash Functions

International audienceChaotic iterations, a tool formerly used in distributed computing, has recently revealed various interesting properties of disorder leading to its use in the computer science security field. In this paper, a comprehensive study of its topological behavior is proposed. It is stated that, in addition to being chaotic as defined in the Devaney's formulation, this tool possesses the property of topological mixing. Additionally, its level of sensibility, expansivity, and topological entropy are evaluated. All of these properties lead to a complete unpredictable behavior for the chaotic iterations. As it only manipulates binary digits or integers, we show that it is possible to use it to produce truly chaotic computer programs. As an application example, a truly chaotic hash function is proposed in two versions. In the second version, an artificial neural network is used, which can be stated as chaotic according to Devaney

On the Link Between Strongly Connected Iteration Graphs and Chaotic Boolean Discrete-Time Dynamical Systems

Chaotic functions are characterized by sensitivity to initial conditions, transitivity, and regularity. Providing new functions with such properties is a real challenge. This work shows that one can associate with any Boolean network a continuous function, whose discrete-time iterations are chaotic if and only if the iteration graph of the Boolean network is strongly connected. Then, sufficient conditions for this strong connectivity are expressed on the interaction graph of this network, leading to a constructive method of chaotic function computation. The whole approach is evaluated in the chaos-based pseudo-random number generation context

A Parallel Incremental Learning Algorithm for Neural Networks with Fault Tolerance

URL : http://vecpar.fe.up.pt/2008/papers/46.pdfInternational audienceThis paper presents a parallel and fault tolerant version of an incremental learning algorithm for feed-forward neural networks used as function approximators. It has been shown in previous works that our incremental algorithm builds networks of reduced size while providing high quality approximations for real data sets. However, for very large sets, the use of our learning process on a single machine may be quite long and even sometimes impossible, due to memory limitations. The parallel algorithm presented in this paper is usable in any parallel system, and in particular, with large dynamical systems such as clusters and grids in which faults may occur. Finally, the quality and performances (without and with faults) of that algorithm are experimentally evaluated

LE DEFICIT IMMUNITAIRE COMMUN VARIABLE (A PROPOS DE 6 CAS)

Common variable immunodeficiency (CVID) is a constitutional deficit in the antibody. It can be of transmission recessive, dominating or related to X. The CVID is the only being able to appear at the adulthood. The fundamental cause of this disorder remains unknown. The disease is characterized by the heterogeneity of the clinical picture and the immunological characteristic Our study’s goal is to present un discuss 6 cases of CVID hospitalized at the clinical Immunology Unit, of the Pediatry I department in the child hospital of Casablanca, between March 1998 and March 2004. The mean age at the first clinical symptoms is 11 years. Our six patients, suffered from recurrent pneumonias, the recurrent sinusitis, the chronic diarrhea with failure to thrive and granulomatous disease. They all had a hypogammaglobulinemia, the taking in charge consisted in an infections episode treatment as well as a nutrition rehabilitation with intravenous immunoglobulin antibiotic prophylaxis and a respiratory kinesitherapy. Our set was characterized by the severity of the clinical phenotype, especially by the therapeutic means insufficiency, and the delay of the diagnostic. A considerable effort should be achieved in order to make doctors more sensitive, tools of diagnosis and the hold in charge.Le déficit immunitaire commun variable (DICV) est un déficit primitif en anticorps, de transmission récessive, dominante ou liée à l’X, et qui peut se révéler à l’âge adulte. Son mécanisme moléculaire est encore inconnu. Le diagnostic est caractérisé par une hétérogénéité du tableau clinique et immunologique. L’objectif de notre travail est de présenter et discuter 6 cas de DICV, hospitalisés à l’unité d’immunologie clinique de la Pédiatrie I à l’hôpital d’Enfants de Casablanca, sur 6 ans (1998 – 2004). L’âge moyen de début des symptômes est de 11 ans. Nos 6 malades avaient présenté des broncho-pneumopathies à répétitions, des infections ORL, des diarrhées chroniques avec retentissement staturo-pondéral, et un cas de sarcoïdose. Ils avaient présenté tous une hypogammaglobulinémie globale. La prise en charge a consisté en un traitement des épisodes infectieux, une perfusion des immunoglobulines, une antibioprophylaxie et une kinésithérapie respiratoire. Le tableau clinique de nos malades reste sévère du fait du retard du diagnostic et de l’insuffisance des moyens thérapeutiques ; c’est pourquoi un effort doit être réalisé, afin de sensibiliser les médecins, pour établir un diagnostic précoce et une prise en charge adéquate

Microstructure Effects on the Machinability of AM-Produced Superalloys

This paper discusses the microstructure effects on the machinability of Inconel 718 by conducting machining tests on an additively manufactured (AM) workpiece with a strongly textured grain structure and a wrought workpiece incorporating a finer and more equiaxed grain structure. The AM workpiece was produced as a thin tube using Laser Melting Powder Bed Fusion and optimal processing conditions for this alloy. A lathe was used to conduct instrumented orthogonal machining tests on the two workpiece materials under dry cut and coolant conditions using a semisynthetic emulsion coolant. The process parameters studied were feed from 0.05 to 0.15 mm/rev and cutting speed from 60 to 120 m/min with a cut time of 2 sec duration for each process condition. Measures for each process condition included cutting forces in the feed and main cut direction, and images of chip forms were obtained. The grain structures of the workpiece materials were characterized using Electron Back Scattered Diffraction (EBSD). New findings suggest that grain structures can significantly affect the machinability of the superalloy at a higher feed for all cutting speeds studied, and insights into the cause are discussed. Other important findings comment on the effectiveness of the coolant as a lubricant for reducing friction in machining

Trends in adult asthma hospitalization: gender-age effect

BACKGROUND: Hospital admissions due to asthma are a reliable source of information on the morbidity of the disease which, after the increase observed in the last quarter of the last century, shows a declining trend in the last few years. The aim of this study was to look at hospital admission trends due to asthma in our community and analyze some of its associated factors. METHODS: Retrospective analysis of all hospital admissions involving adults aged 15 years and older with asthma as the primary or secondary diagnosis (if the first diagnosis was respiratory failure or respiratory infection) in Public Health Service hospitals in the Galician region of Spain between the years 1995-2009 (total 24,766 admissions). RESULTS: The majority of patients admitted were female (71%), over 60 years of age (64%), and admission occurred predominantly in the winter months. The hospitalization rate due to asthma tripled over the period studied, this being mainly accounted for by women aged over 60 years. Mean hospital stay was 9.2 days, longer in older patients or those admitted over the weekend. CONCLUSIONS: A significant increase in hospital admissions due to asthma over the last few years has been observed in our community, mainly involving older women. The mean stay seems long, increasing with patients' age and admission over the weekend