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A Study on the Estimation of Prefabricated Glass Fiber Reinforced Concrete Panel Strength Values with an Artificial Neural Network Model
Get PDFIn this study, artificial neural networks trained with swarm based artificial bee colony optimization algorithm was implemented for prediction of the modulus of rapture values of the fabricated glass fiber reinforced concrete panels. For the application of the ANN models, 143 different four-point bending test results of glass fiber reinforced concrete mixes with the varied parameters of temperature, fiber content and slump values were introduced the artificial bee colony optimization and conventional back propagation algorithms. Training and the testing results of the corresponding models showed that artificial neural networks trained with the artificial bee colony optimization algorithm have remarkable potential for the prediction of modulus of rupture values and this method can be used as a preliminary decision criterion for quality check of the fabricated products
Natural Convection in a Square Cavity: Numerical Study for Different values of Prandtl Number
Get PDFA numerical study of natural convection in a square cavity subjected to the thermals boundary conditions on the sidewalls is presented and discussed. The fluid is Newtonian and equations governing the flow field and the heat transfer are given in dimensionless form. The finite volume method was adopted to solve the algebraic system. Influence of the Prandtl and the Rayleigh numbers on heat transfer and the flow field is illustrated and discussed as the stream functions, isotherms, horizontal velocity, local and average Nusselt numbers. Results indicate that improved heat transfer is more pronounced with increasing Rayleigh number. In particular, at low Rayleigh numbers, the flow field is slightly pronounced with increasing Prandtl number and decreases by increasing the Rayleigh number. In contrast, the heat transfer is not affected by variations of Prandtl number at low Rayleigh numbers and decrease with increasing the Prandtl number especially for very high Rayleigh numbers
Mathematical Analysis of a New Design for Cascade Solar Still
Get PDFFresh water available on earth is very scared. Yet the demand of fresh water is incessantly increasing, due to population growth and rapid industrialization. According to the United Nations, in 2025, 63% of the world’s population will be living in scarce water areas. The provision of freshwater is becoming a gradually more important issue in many areas of the world. Oceans are the only available source for large amount of water. Ocean water presents high salinity, so there is a need to desalinate ocean water for everyday consumption. Solar stills are widely used in solar desalination for being very simple devices, easy to fabricate and require only few maintenance. In this paper, a new approach to design a solar still absorber plate was developed and the effect of this design on the productivity was investigated theoretically. A mathematical model was developed to calculate the theoretical productivity of the solar still. The energy balance equations for the various elements of the solar still are formulated and numerically solved using the dynamic simulation program Matlab/SimulinkTM. The performance of the still was investigated. The results show that the thermal performance of a modified stepped solar still can be considerably improved through new introduced modifications
Wall-Pressure Fluctuations of Modified Turbulent Boundary Layer with Riblets
Get PDFAn experimental investigation was carried out to study the response of a turbulent pressure drop fluctuations to longitudinal groove riblets, involved two configurations being triangular and spaced triangular grooves with height 600, 800, 1000 μm and peak to peak spacing 1000 μm and 2000 μm respectively. Experiments were therefore performed at free stream velocity up to 0.44 m/sec, which were corresponding to Reynolds number (Re) 53000. The development of the obtained turbulent layer downstream of the grooves was then compared with the results from the corresponding smooth-wall case. To conclude, the effect of the spaced triangular riblets on the turbulent characteristics seemed to be more pronounced than the effects of the triangular riblets
Mathematical Modeling of Two Dimensional Ferrofluid Flow in Thermal and Buoyant Conditions in a Trough
Get PDFThe present problem addresses a thermally driven two-dimensional, buoyant flow in a vessel with the application of magnetic field directed in the radial and tangential direction. In the present study, a trough filled with ferrofluid is heated along the center strip by an applied heat flux. Thereby the convection pattern along with the heat distribution is observed. The half of the trough dynamics is calculated with the symmetric plane in the center. On the surface of the bowl, penalty function is applied to enforce the no-slip boundary condition. This problem is then modelled and the results are obtained for flow velocity, vorticity, density and temperature distribution. The results are then compared in the same scenario but in the absence of magnetic field
Longitudinal Vibration Analysis of Marine Riser During Installation and Hangoff in Ultra Deepwater
Get PDFThis paper is concerned with the problem of longitudinal vibration of a 3,000 m long disconnected drilling riser during installation and hangoff operation. The natural frequency, amplitude of vibration displacement and vibration force of longitudinal vibration have been determined with consideration of the damping effect of the sea water. Results show the natural frequency of riser under these two situations are both decrease with the increase of water depth. The natural frequency of riser in installation operation is bigger than that in hangoff operation. The vibration displacement in hangoff configuration is bigger than that in installation while the vibration force in hangoff configuration is smaller than that in installation configuration. Under the condition of resonance, the vibration displacement increase along riser from top end to the bottom end while the vibration force increase along riser from riser bottom end to the top end
Atomic Exponential Basis Function Eup(<i>x,ω</i>) - Development and Application
Get PDFThis paper presents exponential Atomic Basis Functions (ABF), which are called Eup(x,ω). These functions are infinitely differentiable finite functions that unlike algebraic up(x) basis functions, have an unspecified parameter - frequency w. Numerical experiments show that this class of atomic functions has good approximation properties, especially in the case of large gradients (Gibbs phenomenon). In this work, for the first time, the properties of exponential ABF are thoroughly investigated and the expression for calculating the value of the basis function at an arbitrary point of the domain is given in a form suitable for implementation in numerical analysis. Application of these basis functions is shown in the function approximation example. The procedure for determining the best frequencies, which gives the smallest approximation error in terms of the least squares method, is presented
Structural and Optical Properties of Graphene Oxide Prepared by Modified Hummers’ Method
Get PDFGraphene oxide was synthesized from graphite flakes using modified Hummers’ method. The interlayer spacings of graphite, graphite oxide and graphene oxide were measured using X-ray diffraction technique. The C/O atomic ratios of graphite oxide and graphene oxide were calculated from XPS measurements. The transformation of graphite to graphite oxide and finally to graphene oxide was clearly observed from the micro-Raman spectroscopy data and was confirmed from the FESEM micrographs. UV-VIS-NIR spectrophotometer was used to study the absorbance of graphene oxide and reduced graphene oxide samples. Finally, the chemically reduced graphene oxide was heat-treated in air to obtain chemically modified graphene
Analytical Estimation of Radar Cross Section of Infinitely Long Conducting Cylinder Coated with Metamaterial
Get PDFAerospace structures can be approximately modeled as a combination of canonical structures such as cylinder, cone and ellipsoid. Thus the RCS estimation of such canonical structures is of prime interest. Furthermore metamaterials possess peculiar electromagnetic properties which can be useful in modifying the RCS of structures. This paper is aimed at calculating the RCS of an infinitely long PEC circular cylinder coated with one or two layers of metamaterial. The incident and scattered fields of coated cylinder are expressed in terms of series summation of Bessel and Hankel functions. The unknown coefficients of summation are obtained by applying appropriate boundary conditions. The computations are carried out for both principal polarizations. The computed results are validated against the numerical-based method of moments. Further, the variation of RCS of the metamaterial coated PEC cylinder with material parameters, frequency, aspect angle and polarization is analyzed
Lamin A/C Regulates Endothelial Glucocorticoid Receptor Nuclear Translocation in Response to Cyclic Stretch
Get PDFThe glucocorticoid receptor (GR) has multiple phosphorylation sites that can be activated by MAPKs, which have been previously shown to be activated in response to cyclic stretch in endothelial cells. It is possible therefore that physiological and/or pathological degree of cyclic stretch may also initiate phosphorylation-induced changes in GR subcellular localization as we previously showed with shear stress. However, little is known about the effects of cyclic stretch on glucocorticoid receptor (GR) activity in endothelial cells. We used control and lamin shRNA BAECs and subjected them to ligand (dexamethasone) treatment, physiological stretch (10% at 1 Hz), or pathological stretch (20% at 1 Hz or 10% at 2 Hz), in order to evaluate GR nuclear translocation in endothelial cells with and without lamin A/C as well as potential upstream protein regulators of GR subcellular movement during cyclic stretch. Upon exposure to pathological degrees of stretching, control shRNA BAECs showed greater nuclear concentration of GR at each time point compared to when they were stretched at physiological parameters. The response of GR in lamin-deficient cells to cyclic stretching was relatively non-existent compared to that observed in control shRNA cells. Our results suggest that in cells with lamin A/C, cyclic stretch activates GR through the JNK pathway, and ERK has some inhibitory role on GR nuclear translocation. DUSP proteins become upregulated in response to stretch as a result of GR activation (DUSP1) or by stretch-induced MAPK signaling. In lamin-deficient cells, only the combination of cyclic stretch and p38 inhibition was able to induce marginal nuclear translocation. Increased MAPK phosphorylation due to lamin A/C absence could drive DUSP expression as a negative feedback mechanism. Upregulation of the cytoplasmic DUSP6 suggests a significant role of ERK in reducing GR sensitivity to mechanical strain