Drag coefficients in hydraulic channel

Mestrado de dupla diplomação com a Université Libre de TunisExperimental information is extremely useful in solving problems involving flow over bodies, as well as for determination of design parameters in aerodynamics and hydrodynamics, the drag coefficient being one of the most relevant as it allows to quantify the drag forces, that is, the total resistance of a body being dragged by a fluid. In this context, water tunnels have become indispensable research tools as they allow simulations involving all the complexity of a real flow in a fast and economical way, and together with experimental techniques of dimensional analysis, allow to standardize the coefficients in technical norms and with wide acceptance for different flow regimes and models of different geometric shapes, among which we can highlight the plates, bars, discs, cylinders, and hydrodynamic bodies. experimental tests were carried out to perform several measurements of hydrodynamic drag allowing a comparative study based on empirical drag coefficients in the literature for smooth cylinders.Informação experimental é extremamente útil para a resolução de problemas envolvendo fluxo sobre corpos, bem como para a determinação de parâmetros de projeto em aerodinâmica e hidrodinâmica, sendo o coeficiente de arrasto um dos mais relevantes, uma vez que permite quantificar as forças de arrasto, ou seja, a resistência total de qualquer corpo a ser arrastado por um fluido. Neste contexto, os túneis de água tornaram-se ferramentas de investigação indispensáveis, pois permitem simulações envolvendo toda a complexidade de um fluxo real de forma rápida e económica, e juntamente com técnicas experimentais de análise dimensional, permitem normalizar os coeficientes em normas técnicas com ampla aceitação para diferentes regimes de fluxo e modelos de diferentes formas geométricas, entre os quais podemos destacar as placas, barras, discos, cilindros e corpos hidrodinâmicos, todos com elevada aplicabilidade. Assim, neste trabalho, foram realizados ensaios experimentais para várias medições de arrasto hidrodinâmico, permitindo um estudo comparativo baseado em coeficientes de arrasto empíricos na literatura para cilindros lisos, e posterior comparação com diferentes graus de rugosidade no mesmo modelo. Consequentemente, foi também possível obter perceções sobre a viabilidade do equipamento, as suas principais limitações, bem como expandir e conciliar a teoria dos fluxos externos com a prática laboratorial

Global rational stabilization of a class of nonlinear time-delay systems

The present paper is mainly aimed at introducing a novel notion of stability of nonlinear time-delay systems called Rational Stability. According to the Lyapunov-type, various sufficient conditions for rational stability are reached. Under delay dependent conditions, we suggest a nonlinear time-delay observer to estimate the system states, a state feedback controller and the observer-based controller rational stability is provided. Moreover, global rational stability using output feedback is given. Finally, the study presents simulation findings to show the feasibility of the suggested strategy

Effect of pre-germination treatments on the dormancy breaking and early growth performance of bitter kola (Garcinia kola- (heckel) in south southern Nigeria

The demand for bitter kola (Garcinia kola) is high in Nigeria market but the population of the species is low both in the wild and home gardens. Rapid deforestation, heavy exploitation in the natural forest and difficulties associated with its germination occasioned by seed dormancy have been blamed. The study on enhancing germination and early growth of Garcinia kola was conducted using Complete Randomized Design (CRD) with three treatments and a control. The control was made of untreated seeds (T1) while the treatments included nicked seeds soaked in water for 24 hours (T2), seeds from fermented pods (T3), and seeds from fresh pods (T4). Seed germination tests were carried out after pre treatment using 16 seeds for each treatment anf the control in the nursery site of the Cross River University of Technology (CRUTECH, Obubra campus) in South southern Nigeria.. The result showed that cutting seeds at the opposite end to the radicle (nicking) was the most suitable pre-sowing treatment to increase seed germination and early growth performance of Garcinia kola. Treating the seeds with mechanical scarification (nicking) significantly enhanced germination (P<0.001) and significantly influenced seedlings growth (P<0.05). The highest mean values of 8, 14.65 cm and 5 were obtained for germination count, plant height and leaf number respectively from nicked seeds soaked in water for 24 hours. Dormancy in Garcinia kola seeds can be removed by nicking the seeds and soaking in cold water for a day.Keywords: Germination, growth, seed nicking, pre-treatment, dormanc

Nonlinear Modulation of Wave Propagation in Spherical Shell Model and Modified Zhang Model Using Free Space Model as a Bench-Mark

This paper presents nonlinear modulation of wave propagation in spherical shell model (SSM) and modified Zhang model (MZM) using free space model (FSM) as a bench-mark. A typical non-linearity is the change in the dielectric constant due to electromagnetic (EM) wave field that propagates through a medium. By modulation, we mean the characteristic departure of EM waves’ propagation in both media as opposed to the free space propagation. Maxwell’s equations were used to derive the basic equation that govern the propagation of electromagnetic waves in nonlinear media. The equations of the models were found to be nonlinear and their solution were obtained numerically using Runge-Kutta scheme implemented in Matlab software. The spatial EM wave profile graphic displays were supplemented by the symmetric spatial Fast Fourier Transform (FFT) analysis. The symmetric implementation of the FFT meant that the actual number of modes present in any solution was half the number of observed spikes. The free space model (FSM) showed periodic propagation for all frequencies ( examined corresponding to a wavenumber per frequency. The result only serves to give some level of confidence that the algorithm performed well. The MZM supports a variety of characteristics. There are amplitude amplifications or wave steeping, lossless or solitary propagation and multiplicity of modes for all frequencies examined. However, at the fundamental frequency , the SSM is capable of exhibiting amplitude amplification without attenuation. The EM wave propagation characteristics of the MZM and SSP showed that materials which could be fabricated according to this model would be very useful as EM wave guides as they could support waves without losses as opposed to the present known commercial optical fibers. Keywords: Nonlinear modulation, Wave propagation, Spatial Electromagnetic wave

F-door spaces and F-submaximal spaces

[EN] Submaximal spaces and door spaces play an enigmatic role in topology. In this paper, reinforcing this role, we are concerned with reaching two main goals: The first one is to characterize topological spaces X such that F(X) is a submaximal space (resp., door space) for some covariant functor Ff rom the category Top to itself. T0, and FH functors are completely studied. Secondly, our interest is directed towards the characterization of maps f given by a flow (X, f) in the category Set, such that (X,P(f)) is submaximal (resp., door) where P(f) is a topology on X whose closed sets are exactly the f-invariant sets.Dridi, L.; Lazaar, S.; Turki, T. (2013). F-door spaces and F-submaximal spaces. Applied General Topology. 14(1):97-113. doi:10.4995/agt.2013.1621.SWORD9711314

Submaximal and door compactifications

AbstractIn this paper, a characterization is given for compact door spaces. We, also, deal with spaces X such that a compactification K(X) of X is submaximal or door.Let X be a topological space and K(X) be a compactification of X.We prove, here, that K(X) is submaximal if and only if for each dense subset D of X, the following properties hold:(i)D is co-finite in K(X);(ii)for each x∈K(X)∖D, {x} is closed.If X is a noncompact space, then we show that K(X) is a door space if and only if X is a discrete space and K(X) is the one-point compactification of X

Co-infection and morphometrics of three clinostomatids (Digenea: Clinostomatidae) in Tilapia guinensis Bleeker, 1862 from Opi lake, Nigeria

Co-infection and morphometrics of helminth parasites of Tilapia guinensis in Opi Lake (GPS N06.75275*, E007.49104*), were studied from (Nov 2007– Oct 2008) using multiple fishing gear techniques; cast nets, hook and line, and seine nets (150 mm – 200 mm). The parasites recovered were C. tilapiae, C. complanatum and E. heterostomum. The prevalence was low, indicative of parasitic infection in the wild. Prevalence of (33.9 %) was recorded in C. complanatum, (7.2 %) in E. heterostomum and (12.6 %) in C. tilapiae. But high mean intensity was suggestive of heavy parasite burden; C. complanatum (4.8), C. tilapiae (2.8), and E. heterostomum (5.1). Morphometrics of the parasites showed no significance difference in the distance between oral and ventral suckers. However, they differed in all other parts significantly (p < 0.05). In the rank-abundance curve for parasite communities, C. complanatum was most abundant (pi 0.63). Differential parasitic effects were due to selection for relatively better adaptiveness to host’s microhabitats, more population size, better host location, and larger body size. Consequently, this resulted in a trade-off between larger morphometric parts and population size among the parasite

Increasing knowledge and attitudes of adolescents related to sexual and reproductive health by using audio-visual media during the covid-19 pandemic

Adolescence is a developmental stage from the transition to adulthood. A cognitive problem that affects adolescence namely the lack of knowledge about reproductive health. The purpose of this study was to explain the effectiveness of health education using audio-visual methods on students' knowledge and attitudes about adolescent reproductive health during the COVID-19 pandemic. This research uses a quasi-experimental design. The results obtained from the 75 respondents who filled out the questionnaire showed that the attitude of the students on the pre-test score was 60,00 and the post-test was 63,45, whereas the students' knowledge on the pre-test score was 15,89 and the post-test is 17,20. From the results of the research carried out with the Wilcoxon test that the Asymp. Sig (2-tailed) is worth 0,0001 where the value is less than <0.005, therefore the hypothesis was accepted. Using audiovisual media is that it will add more real material content and will increase memory retention due to media that is much interesting and easy to remember by the individual, factors that can influence knowledge and attitudes related to reproductive and sexual health in adolescents are knowledge, attitudes and the individual's environment in processing the information obtained. Therefore there is a significant effect of health education with audiovisual methods on increasing the knowledge and attitudes of adolescents related to reproductive and sexual health

Physiochemical properties of mixed twin clay deposits in Awgbu used for pottery and possible structural applications

The practice of mixing Asha clay and Ajagworo clay deposit at Ngene-Agu site in the ratio of 3:1 by Awgbu women for pottery business is investigated. Physical (Atterberg limits) properties, elemental content, compressive strength, water absorption and characterization for individual and mixed clays were carried out. The result obtained shows that between 700 0C and 1100 0C, the compressive strength of Asha clay and Ajagworo clay derived burnt bricks did not individually meet the Nigeria specifications for structural development, while that of the mixed clay derived burnt bricks satisfied the minimum strength requirement of ∙ / at 1000 0C and above. The result also showed that the mixed clay derived burnt bricks has the least values for porosity of ∙ and water absorption at varying temperatures. This has proved that the practice by Awgbu women of mixing Asha and Ajagworo in the ratio of 3:1 raised the compressive strength to ∙ / and lowered the water absorption to a minimum value of ∙ %. This work has shown that the Awgbu mixed clay can be used for structural development in Anambara State and Nigeria.Keywords: Awgbu mixed clay, Compressive strength, Water Absorption, Porosity and Structural developmen