In this work, an experimental investigation has been done for heat transfer by natural-convection through a horizontal concentric annulus with porous media effects. The porous structure in gap spacing consists of a glass balls and replaced by plastic (PVC) balls with different sizes. The outer surface of outer tube is isothermally cooled while the outer surface of inner tube is heated with constant heat flux condition. The inner tube is heated with different supplied electrical power levels. Four different radius ratios of annulus are used. The effects of porous media material, particles size and annulus radius ratio on heat dissipation in terms of average Nusselt number have been analyzed. The experimental results show that the average Nusselt number increases with increasing annulus radius ratio and particle diameter for same porous media material. Furthermore, two empirical correlations of average Nusselt number with average Rayleigh number for glass and PVC particles are developed. The present experimental results are compared with previously works and good correspondence is showed. |
. In recent years, Bitcoin has become the most widely used blockchain platform in business and finance. The goal of this work is to find a viable prediction model that incorporates and perhaps improves on a combination of available models. Among the techniques utilized in this paper are exponential smoothing, ARIMA, artificial neural networks (ANNs) models, and prediction combination models. The study's most obvious discovery is that artificial intelligence models improve the results of compound prediction models. The second key discovery was that a strong combination forecasting model that responds to the multiple fluctuations that occur in the bitcoin time series and Error improvement should be used. Based on the results, the prediction a
... Show MoreThis study had succeeded in producing a new graphical representation of James abacus called nested chain abacus. Nested chain abacus provides a unique mathematical expression to encode each tile (image) using a partition theory where each form or shape of tile will be associated with exactly one partition.Furthermore, an algorithm of nested chain abacus movement will be constructed, which can be applied in tiling theory.
The process of transformation from the central economy to a free economy requires restructuring the economy according to a new economic philosophy that relies on activating the role of private economic activity in which private and medium-sized institutions occupy an essential axis for their active role in the economies of all countries, especially those countries that have directed towards the market mechanism and sector leadership. The special process of economic development and the role that commercial banks can play in advancing the financing of these projects by establishing specialized business incubators for financing.
What encouraged countries to pay attention to these institutions is the ease of
... Show MoreThe aim of this study was to investigate the effectiveness of binary solvent for regeneration of spent lubricating oil by extraction-flocculation process. The regeneration was investigated by bench scale experiments by using locally provided solvents (Heavy Naphtha, n-Butanol, and iso-Butanol). Solvents to used oil, mixing time, mixing speed and temperatures were studied as operating parameters. The performance on three estimated depended key parameters, namely the percentage of base oil recovered (Yield), percent of oil loss (POL), and the percent of sludge removal (PSR) were used to evaluate the efficiency of the employed binary solvent on extraction process. The best solvent to solvent ratio for binary system were 30:70 for Heavy Naph
... Show MoreIn this work, we have investigated optical properties of the thermally evaporation PbS/CdS thin films. The optical constant such as (refractive index n, dielectric constant εi,r and Extinction coefficient κ) of the deposition films were obtained from the analysis of the experimental recorded transmittance spectral data. The optical band gap of PbS/CdS films is calculate from (αhυ)1/2 vs. photon energy curve.
A Mini-TEA CO2 laser system was designed and operated to obtain a pulse at 10.6 μm. Output energy of 30 mJ, with preionization pins, and pulse duration of 100ns were obtained. While an output energy of 6mJ and pulse duration of 100 ns in absence of pre-ionization were obtained. The system was operated with Ernest profile main-discharge electrodes. Dependencies of supply voltage and output laser energy on the pressure inside laser cavity were investigated as well as dependencies of supply voltage and output energy on the main capacitor(8CO2 : 8N2 : 82He :2CO). Efficiency of was calculated to be 4.4%.
In this work, the effect of different particle size on the nonlinear optical properties of silver nanoparticles in de-ionized water was studied. The experimental observation of the far field diffraction patterns by CCD camera in two and three dimensions. The maximum change of nonlinear refractive index and the relative phase shift were calculated. The self-defocusing technique was used with a continuous-wave radiation from DPSS Blue laser .The wavelength is 473 nm with an output power of 270 mW. All the Ag colloids samples containing the sizes 15, 30, 50, and 70 nm of silver nanoparticles used in the study were chemically prepared. It was found that the nonlinear refractive index is a particle size dependent and of the order of 10-7 cm2/
... Show MoreNeonatal sepsis refers to the bacterial bloodstream infections of the newborn during the neonatal period as usually the first twenty-eight days of life. The current study was done in the laboratories of AL-Batool Teaching Hospital for Gynecology and Pediatrics in Baqubah, Diyala Governorate, including 140 blood specimens collected from the neonates admitted to the hospital with suspected sepsis, the ages of the both groups was ranged from 1 day to 28 days. Out of the total cultured samples, 32.14% (45 of 140) were positive and 67.86% (95 of 140) were negative blood culture. 45 of 140 samples were negative to the blood culture chosen as control group. The results showed highest isolates were Coagulase Negative Staphylococcus (CoNS) 19 (42.2%
... Show MoreThe rotor dynamics generally deals with vibration of rotating structures. For designing rotors of a high speeds, basically its important to take into account the rotor dynamics characteristics. The modeling features for rotor and bearings support flexibility are described in this paper, by taking these characteristics of rotor dynamics features into standard Finite Element Approach (FEA) model. Transient and harmonic analysis procedures have been found by ANSYS, the idea has been presented to deal with critical speed calculation. This papers shows how elements BEAM188 and COMBI214 are used to represent the shaft and bearings, the dynamic stiffness and damping coefficients of journal bearings as a matrices have been found
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