Previously, many empirical models have been used to predict corrosion rates under different CO2 corrosion parameters conditions. Most of these models did not predict the corrosion rate exactly, besides it determined effects of variables by holding some variables constant and changing the values of other variables to obtain the regression model. As a result the experiments will be large and cost too much. In this paper response surface methodology (RSM) was proposed to optimize the experiments and reduce the experimental running. The experiments studied effects of temperature (40 – 60 °C), pH (3-5), acetic acid (HAc) concentration (1000-3000 ppm) and rotation speed (1000-1500 rpm) on CO2 corrosion performance of the regression model calculated by RSM. The experiments were conducted in saturated solution of CO2 with 3.5 % NaCl solution. STATISTICA program version 10 was used for data analysis. In conclusion a quadratic model is proposed to predict the effect of mentioned variables in CO2 environment.
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An experimental investigation based on thirty three simple pullout cylinder specimens was conducted to study the bond-slip trend between concrete and steel reinforcement. Plain and deformed steel reinforcement bars were used in this investigation. The effect of bar diameter, concrete compressive strength and development length on bond-slip relation was detected. The results showed that the bond strength increases with increasing of compressive strength and with decreasing of bar diameter and development length. A nonlinear regression analysis for the experimental results yields in a mathematical correlation to predict the bond strength as a function of concrete compressive strength, reinforcing bar diameter and its yield stress. The minimum
... Show MoreThis paper studies the effects of stiffeners on shear lag in steel box girders with stiffened flanges. A three-dimensional linear finite element analysis using STAAD.Pro V8i program has been employed to evaluate and determine the actual top flange stress distribution and effective width in steel box girders. The steel plates of the flanges and webs have been modeled by four-node isoparametric shell elements, while the stiffeners have been modeled as beam elements. Different numbers (4, 8, and 15) for the steel stiffeners have been used in this study to establish their effects on the shear lag and longitudinal stresses in the flange. Using stiffeners reduced the magnitude of the top flange longitudinal stresses about 40%, but did
... Show MoreThe wake potential and wake phenomena for swift proton in an amorphous carbon target were studied by utilising various dielectric function formalisms, including the Drude dielectric function, the Drude–Lorentz dielectric function and quantum dielectric function. The Drude model results exhibited a damped oscillatory behaviour in the longitudinal direction behind the projectile; the pattern of these oscillations decreases exponentially in the transverse direction. In addition, the wake potential extends slightly ahead of the projectile which also depends on the proton coordinate and velocity. The effect of electron binding on the wake potential, characterised by the ratio to 0.1, has been studied alongside the Drude–Lorentz dielectric
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In this paper , the CO2 laser receiver system is designed and studied, with wavelength laser 10.6 ?m in room temperature , and to evaluate the performance and discussion it via the package of optical design (ZEMAX), from its output the Spot Diagram is measured through RMS ,and from the Ray fan plot , the aberrations is found which is the normal error for the best focus named (under corrected ) , the other output was the Geometric Encircled Energy in the spot diagram . and found that the radius of spot diagram at 80% (R80%) from the total energy ,and focal shift .The designed system have high efficiency and low cost .
Background: Hemorrhoids are one of the most
common surgical conditions .Conventional
haemorrhoidectomy was the traditional operation for
the treatment of hemorrhoids. Other modalities of
treatment had been used as an alternative operations
including CO2 laser haemorrhoidectomy.
Objectives: To determine the outcome of treatment
of hemorrhoids by using CO2 laser
haemorrhoidectomy and its advantages over
conventional surgery
Methods: This is a retrospective comparative
interventional study of 1024 case of third degree
haemorhoids selected out of 1300 case of
hemorrhoids of different degrees, admitted to
ALKINDY, ALYERMOUK teaching hospitals and
ABD ALMAGEED private hospital, from May 1998
to J
Cerium oxide CeO2, or ceria, has gained increasing interest owing to its excellent catalytic applications. Under the framework of density functional theory (DFT), this contribution demonstrates the effect that introducing the element nickel (Ni) into the ceria lattice has on its electronic, structural, and optical characteristics. Electronic density of states (DOSs) analysis shows that Ni integration leads to a shrinkage of Ce 4f states and improvement of Ni 3d states in the bottom of the conduction band. Furthermore, the calculated optical absorption spectra of an Ni-doped CeO2 system shifts towards longer visible light and infrared regions. Results indicate that Ni-doping a CeO2 system would result in a decrease of the band gap. Finally,
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