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Search Results: 1 - 10 of 224836 matches for " Gh. R. Rashed "
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Electrochemical and Oxidation Behavior of Yttria Stabilized Zirconia Coating on Zircaloy-4 Synthesized via Sol-Gel Process
S. Rezaee,Gh. R. Rashed,M. A. Golozar
International Journal of Corrosion , 2013, DOI: 10.1155/2013/453835
Abstract: Sol-gel 8?wt.% Yttria Stabilized Zirconia (YSZ) thin films were prepared on zirconium (zircaloy-4?alloy) by dip-coating technique followed by heat treating at various temperatures (200°C, 400°C, and 700°C) in order to improve both electrochemical corrosion and high temperature oxidation properties of the substrate. Differential thermal analysis and thermogravimetric analysis (DTA-TG) revealed the coating formation process. X-ray diffraction (XRD) was used to determine the crystalline phase structure transformation. The morphological characterization of the coatings was carried out using scanning electron microscopy (SEM). The electrochemical behavior of the coated and uncoated samples was investigated by means of open circuit potential, Tafel, and electrochemical impedance spectroscopy (EIS) in a 3.5?wt.% NaCl solution. The homogeneity and surface appearance of coatings produced was affected by the heat treatment temperature. According to the corrosion parameters, the YSZ coatings showed a considerable increase in the corrosion resistance, especially at higher heat treatment temperatures. The coating with the best quality, from the surface and corrosion point of view, was subjected to oxidation test in air at 800°C. The coated sample presented a 25% reduction in oxidation rate in comparison with bare substrate. 1. Introduction Because of many excellent bulk properties like low thermal neutron capture cross section, favorable mechanical properties and good corrosion resistance even at high temperatures, zirconium and its alloys are widely used in nuclear reactors as fuel cladding and as reactor structural elements, chemical engineering, and lately in biomedical applications. For fuel cladding applications, the alloys of choice are zircaloy-2 (Zr-2) and zircaloy-4 (Zr-4). In fuel deep geological repository, used fuel bundles and the associated Zr cladding are encapsulated in durable containers and the containers are sealed in an engineered vault at a depth of hundreds of meters in a stable low permeability rock mass. Ground water composition especially in crystalline and sedimentary rock types contains NaCl. In a failed container, zirconium is in contact with NaCl solution [1–4]. So, they are somehow subject to corrosion and their specific surface properties (e.g., corrosion, oxidation, etc.) should be improved [2, 4]. Surface modification of materials permits independent optimization of bulk and surface properties. Among all surface modification techniques such as chemical vapor deposition [5, 6], physical vapor deposition [7], plasma [8], ion
The Environmental Impacts of Kabd Landfill on the Soil and Groundwater in Kuwait: A Case Study  [PDF]
Ahmed R. Al Rashed
International Journal of Geosciences (IJG) , 2018, DOI: 10.4236/ijg.2018.95016
Abstract: The environmental impacts of the Kabd Landfill on the soil and groundwater in Kuwait were evaluated. Physical and chemical analyses were carried out on thirty pairs of surface, subsurface soil and five groundwater samples. The groundwater samples are collected from boreholes nearby and downstream of the landfill while the soil samples collected along six profiles. The groundwater samples were geochemically analyzed to determine the total dissolved solids, cations, anions and heavy metals, particularly Iron (Fe), Copper (Cu), zinc (Zn), Cadmium (Cd), Nickel (Ni), Chromium (Cr) and Aluminum (Al), Lithium (Li), Boron (B), Fluoride (F) and Vanadium (V). The soil samples were geochemically analyzed to determine concentration of Cadmium (Cd), Lead (Pb), Nickel (Ni), Iron (Fe), Aluminum (Al) and organics. The results show that the soil and groundwater are contaminated with high TDS, Na, Ca, Mg, Cl, SO4 and heavy metals, especially Ni, Cd, Cu, Al, V and F. The heavy metal concentrations in both the soil and groundwater samples are compared to the World Health Organization (WHO) standard permissible limits. The results revealed that the Zn, Li, B and Fe metals are below the WHO limits for consumption. The soil lithology, natures of dumping, the depth of quarry and the depth to the groundwater level play roles in leachate generation and groundwater contaminations. Such leachate may be originated from the capillary fringe water, moisture content and rising water table, due to its close level at the bottom of the waste disposal site. The organic strength of the soil was reduced due to waste decomposition and continuous gas
Obstructive Sleep Apnea
R. Rashed,F. Heravi
Journal of Dentistry of Tehran University of Medical Sciences , 2006,
Abstract: Sleep apnea, and particularly obstructive sleep apnea, is a common disorder that is characterized by a repetitive, partial or complete cessation of air flow, associated with oxyhemoglobin desaturation and an increased effort to breath. In recent years,orthodontists have been interested and involved in the management of this disordersince it has been shown that oral appliance therapy can be an effective treatment approach for obstructive sleep apnea (OSA). The purpose of this article is to present a review of OSA by describing this disorder, its diagnosis, currently available treatmentmodalities and, in particular, the role of oral appliance therapy in its treatment.
"The Effects of Temperature and PH on Settlability of Activated Sludge Flocs"
Gh Ghanizadeh,R Sarrafpour
Iranian Journal of Public Health , 2001,
Abstract: The effluent quality of a sewage treatment plant using activated sludge process and finally secondary treatment depends on the flocculation efficiency and settling of the flocs. The survey of various treatment processes in water and wastewater treatment shows that temperature and pH are the important factors affecting efficiency of flocculation and settling properties. This study was performed to determine the effects of pH and temperature on settling of the flocs in activated sludge process. It was carried out for three months in two phases, using mixed liquor suspended solids (MLSS), obtained from aeration tank from one of wastewater treatment plants in Tehran. In the primary phase, the temperature of samples was increased from 15°C to 35°C. As a result, the sludge volume index (SVI) and effluent suspended solids increased and consequently, COD removal percent decreased. In the second phase, the pH was increased from 5.7 to 9. As a result, SVI and effluent suspended solids decreased and COD removal percent increased.
Neonatal Jaundice
GH.R Walizadeh
Iranian Journal of Pediatrics , 1985,
Abstract: This article gives an account of the origins and metabolism of billirubin as well as causes of physiologic and pathologic hyperbilirubinemias in the newborn infant. The usual methods of the treatment, I.e., blood exchange transfusion, phototherapy and enzyme induction are discussed and their benefits and complications elucidated.
The Normal Newborn
GH.R Walizadeh
Iranian Journal of Pediatrics , 1990,
Abstract: The neonatal period is a very sensitive and in respect to the later life of the individual extremely important phase of life. Disturbances of adaptation to extrauterine life, intrauterine disease and congenital malformations can and should be detected and treated properly by routine and regular examination of newborn infants. Otherwise, these diseases and malformations may cause unfavorable and painful sequelae for the related individual possibly lasting a life long. Therefore, it is imperative to distinguish transient and harmless findings from relevant pathological disturbances. Evaluation of the specific neonatal reflexes and motor reactions makes it possible to determine the gestational age, and in sick infants, they can be used to assess the medical and neurological status
Anthropometrical Measurements in Iranian Neonates
GH.R Walizadeh
Iranian Journal of Pediatrics , 1985,
Abstract: To obtain standard norms for Iranian neonates, weight, length, head circumference and chest circumference are measured in 13,988 (8208 males and 6780 females) successively born, clinically normal neonates in a maternity unit in Tehran during the first 24 hours after birth. The statistical examination showed following results (Methods): Weight: Males 3215.83±547.83 grams. Females 3114.31±510.40 grams. Length: Males 51.16±2.65 cm. Females 50.46±2.49 cm. Head circumference: Males 34.57±1.65 cm. Females 33.98±1.59 cm. Chest circumference: Males 32.79±2.18 cm. Females 32.55±2.07 cm. These figures compared with the American norms show that Iranian neonates are somewhat lighter in weight (Boys -5%, girls -7%), but in respect to length, head circumference and chest circumference show no significant differences.
GH.R Khatami
Iranian Journal of Pediatrics , 1985,
Abstract: Amebiasis, caused by Entamoeba histolytica, may be an acute or chronic disease. The organism is a protozoan and exists as trophozoite and in cystic form. The trophozoite remains harmless after colonization in the large intestine. The infection involves most frequently cecum and ascending colon and less frequently the rectosigmoid. Asymptomatic intraluminal Amebiasis is the most frequent form of infection. The diagnosis of Amebiasis is missed in more than 40% of the infected children as the physicians seldom think of it. If stool cultures and rectoscopy are negative for Amebiasis, serologic tests should be performed. Amebic colitis has to be differentiated from ulcerative colitis, corhn's disease and bacillary dysentery. Prophylactic measures consist of boiling of the drink water and eradication of the enteral Amebiasis. Nitroimidazole (Metronidazole) and its more recent derivative imidazole are effective in all three kinds of infection, i.e. itraluminal, intramural and systemic (Hepatic) Amebiasis.
Neonatal Asphyxia
GH.R Walizadeh
Iranian Journal of Pediatrics , 1986,
Abstract: Neonatal Asphyxia may impose a major risk on the life and well-being of the newborn infant. The recognition of the four phases of Asphyxia at birth, I.e., primary hyperpnea, primary apnea secondary hyperpnea and secondary apnea, is of importance in employment of the appropriate treatment. The causes of Asphyxia may be operative intrauterine, natally or postnatally. Apgar score is a practical means of estimating the grade of severity of neonatal Asphyxia and its outcome. The treatment should employ mechanical ventilation, medical suppression of the convulsions and correction of the acidosis.
Neonatal Sepsis and Meningitis
GH.R Walizadeh
Iranian Journal of Pediatrics , 1986,
Abstract: This article discusses the etiology, predisposing factors, clinical signs, therapy and prognosis of the neonatal septicemia and meningitis. Beta-hemolytic streptococcus of group B has been reported as the most frequent infectious agent in the recent years, the next being E.coli. The natural humoral and cellular immune immaturity of newborns and particularly premature predisposes the newborn infant to the infection. Early onset septicemia has a higher mortality rate while late onset sepsis has a better prognosis. The therapy of choice consists in a combination of a penicillin and an aminoglycoside till the results of cultures and antibiograms are reported.
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