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Search Results: 1 - 10 of 3306 matches for " Mustafa Doruk "
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Determination of Susceptibility to Intergranular Corrosion of UNS 31803 Type Duplex Stainless Steel by Electrochemical Reactivation Method
Mehmet Emin Ar?kan,Rafet Ar?kan,Mustafa Doruk
International Journal of Corrosion , 2012, DOI: 10.1155/2012/651829
Abstract: Specimens taken from a hot-rolled cylindrical duplex stainless steel (DSS) bar with 22% Cr grade were solution annealed at C and then aged at C from 100 to 31622?min for sensitization treatment. Double loop electrochemical potentiodynamic reactivation and standard weight loss immersion acid tests were conducted. The solution-annealed samples were found unsensitized. Those samples aged for 100 and 316?min were less sensitized whereas samples aged for 1000?min and especially those aged for 3162, 10000, and 31622?min were heavily sensitized. The degree of sensitization (DOS) can be attributed to higher contribution of chromium- and molybdenum-depleted areas resulting from intermetallic phases. 1. Introduction Generally, duplex stainless steels (DSS) are Fe-Cr-Ni alloys having an approximately volumetric fraction of 50% ferrite and 50% austenite in their microstructures. Their main feature is that they compromise the favorable corrosion resistance of austenitic stainless steels with good mechanical properties [1–4]. In duplex stainless steels undesirable phases such as intermetallic phases (sigma and chi), carbides, and nitrides may exist if the manufacturing processes are not carefully controlled. High levels of elements stabilizing ferrite, such as chromium, molybdenum, and silicon, can promote the formation of sigma phase . Sigma phase is a hard and brittle intermetallic phase, which is generally formed between 600 and 950°C with rapid formation kinetics [5–7]. Additional phases found in duplex stainless steels can include chi , laves , and [8]. The nucleation sites for and phases are grain boundaries, incoherent twin boundaries, and dislocations. Duplex stainless steels are susceptible to sensitization due to the precipitation of additional phases when heated in a temperature range of 600–950°C. These phases have a reverse effect on the corrosion and mechanical properties [6, 7]. A substantial depletion of Cr and Mo due to a copious precipitation of and phases results in a decrease of the corrosion properties [9]. There are several test methods for determining the sensitization to intergranular corrosion. Weight loss acid test was first standardized, and the test procedure was presented in ASTM A262-91 [10]. Corrosion rate is determined by measuring the weight loss of the sample. Another test method of measuring the degree of sensitization to intergranular corrosion involves electrochemical reactivation of the steel samples as defined in ASTM G108-94 [11]. This reactivation process is named as electrochemical potentiodynamic reactivation (EPR) and has
Determination of Susceptibility to Intergranular Corrosion of UNS 31803 Type Duplex Stainless Steel by Electrochemical Reactivation Method: A Comparative Study
Mehmet Emin Ar?kan,Rafet Ar?kan,Mustafa Doruk
International Journal of Corrosion , 2012, DOI: 10.1155/2012/478508
Abstract: In the present study as in our previous studies (Arikan and Doruk, 2008 and Arikan et al., 2012), similar specimens taken from a hot rolled cylindrical duplex stainless steel (DSS) bar with 22% Cr grade were solution annealed at 1050°C and then aged at 800°C from 100 to 31622?min for sensitization treatment. Double loop electrochemical potentiodynamic reactivation and standard weight loss immersion acid tests were conducted. The solution annealed samples were found unsensitized. The samples aged for 100?min were less sensitized whereas samples aged for 316?min and more time were sensitized. The degree of sensitization (DOS) can be attributed to higher contribution of chromium and molybdenum depleted areas that result from intermetallic phases. However, especially the samples aged from 3162 to 31622?min have revealed chromium replenishment. Consequently, the degree of sensitization was lowered in comparison to the results obtained in previous studies. 1. Introduction Generally, duplex stainless steels (DSS) are Fe-Cr-Ni alloys having an approximately volumetric fraction of 50% ferrite and 50% austenite in their microstructures. Their main feature is that they compromise favorable corrosion resistance of austenitic stainless steels with good mechanical properties [1–4]. However, duplex stainless steels are susceptible to the precipitation of some phases that affect both the corrosion and the mechanical properties. These phases may be formed during the solidification of the alloy or in subsequent heat treatments or plastic deformation processes or even due to ageing processes during its use, causing a marked effect upon the workability and the useful life of the material [5]. One of the possible phases to be formed is the sigma phase ( ), a hard and brittle intermetallic compound, rich in Cr and Mo, which is formed from ferrite [6]. This phase has deleterious effect upon both mechanical and the corrosion properties [7]. In most of the duplex stainless steels sigma phase is formed between 600°C and 950°C and its precipitation becomes faster between 700°C and 900°C. The embrittlement of some alloys due to the sigma phase precipitation may occur in very short times, of the order of 3?min [7–9]. Brandi and Padilha [10] and Maehara et al. [11] found the sigma phase precipitation in duplex stainless steels that as the amount of sigma phase increases the amount of ferrite decreases, until its total consumption. According to this result it was concluded that the sigma phase is formed from the ferrite. The proposed mechanism for this formation [10, 11] is the
kinci nesil trombosit konsantrasyonunun klinik uygulamalar
?smail Doruk Ko?yi?it,Mustafa Tunal?,Hakan ?zdemir,Yasemin Kartal
Cumhuriyet Dental Journal , 2012, DOI: 10.7126/cdj.2012.1238
Abstract: The therapeutic use of autologous platelet-rich fibrin constitutes a relatively new biotechnology that has been a breakthrough in the stimulation and acceleration of soft-tissue and bone healing. The efficiency of this process lies in the local and continuous delivery of a wide range of growth factors and proteins, mimicking the needs of the physiological wound healing and reparative tissue processes. Platelet-rich fibrin (PRF) belongs to a new generation of platelet concentrates, with simplified processing and without biochemical blood handling. This easy protocol allows the production of leukocyte and platelet-rich fibrin clots starting from autologous blood samples. PRF is used especially in clinical Periodontal and Oral and Maxillofacial Surgery applications. The significance of the PRF is gradually increasing Keywords: Platelet, Autogenous Fibrine, Growth hormone. ZET Trombositten zengin otojen ürünlerin tedavi amac ile kullan lmas , güncel bir yakla m olarak dikkati ekmektedir. Sert ve yumu ak doku iyile melerinde kullan lan ve ok e itli büyüme fakt rleri ve proteinlerin kontrollü sal n mlar n i eren bu preparatlar n do al yara iyile mesi i in gerekli olan maddeleri yo un olarak i erdikleri bilinmektedir. Platelet-rich fibrin (PRF), yeni jenerasyon trombositten zengin otojen ürün olarak bilinmektedir. Kolay uygulanabilir ve biyokimyasal herhangi bir i lem gerektirmeyen PRF protokolü, ki inin kendisinden al nan kan rneklerinden l kositten ve trombositten zengin bir otolog biyomateryal elde edilmesine izin vermektedir. Di Hekimli inde zellikle Periodontoloji ve A z, Di ve ene Cerrahisi’ndeki klinik uygulamalarda kullan lmaya ba lanan PRF’nin nemi giderek artmaktad r.
The “Other” Neglected Diseases in Global Public Health: Surgical Conditions in Sub-Saharan Africa
Doruk Ozgediz ,Robert Riviello
PLOS Medicine , 2008, DOI: 10.1371/journal.pmed.0050121
Abstract:
Discourse of Mobbing in Turkish Press
Ece Karado?an Doruk
Online Journal of Communication and Media Technologies , 2011,
Abstract: Mobbing (Psychological violence in working place) has been researched especially by the scientists making researches in organizational communication for last 20-25 years. In Turkey, mobbing concept is a newer research field. In this study, how the news regarding mobbing has been given in Turkish press will be analyzed with Van Dijk s discourse analysis.How the news regarding mobbing has taken place in Turkish press will be analyzed by applying Van Dijk s discourse analysis. From the year of 1997 when the news related to the mobbing appeared to today, what kinds of differences happened in news discourses especially with taking place of mobbing in Turkish Criminal Law, will be analyzed.
SDRE Based Attitude Control Using Modified Rodriguez Parameters
R. Ozgur Doruk
Physics , 2011,
Abstract: The purpose of this paper is to present an application of the State Dependent Riccati Equation (SDRE) method to satellite attitude control where the satellite kinematics is modeled by Modified Rodriguez Parameters (MRP). The SDRE methodology is applicable on special forms of nonlinear systems where satellite model is one of the candidates. It is not easy to find an analytical solution from the SDRE. Thus point wise solutions are interpolated with respect to the operating conditions. The point wise solutions are obtained from the MATLAB algorithms which are derived from the positive definite solutions of the SDRE. The global stability analysis is difficult due to the nature of the methodology. The resultant attitude controllers outside the breakpoints (the selected operating conditions for interpolation) are suboptimal. The performance of the designs is examined by simulations on MATLAB - Simulink environment. The simulation results show that, the designed attitude controllers are working satisfactorily even in the presence of inertial uncertainties.
Control of the repetitive firing in the squid giant axon using electrical fields
Resat Ozgur Doruk
Quantitative Biology , 2011,
Abstract: In this research, the aim is to develop a repetitive firing stopper mechanism using electrical fields exerted on the fiber. The Hodgkin - Huxley nerve fiber model is used for modeling the membrane potential behavior. The repetitive firing of the nerve fiber can be stopped using approaches based on the control theory where the nonlinear Hodgkin - Huxley model is used to achieve this goal. The effects of the electrical field are considered as an additive quantity over the equilibrium potentials of the cell membrane channels. The study is a representative of an experimental application.
Is There a Role for Intravitreal Triamcinolone Acetonide Injection in the Treatment of Purtscher-Like Retinopathy? Report of Two Cases  [PDF]
Hasan Can Doruk, Ali Osman Saatci, Aylin Yaman
Open Journal of Ophthalmology (OJOph) , 2014, DOI: 10.4236/ojoph.2014.44023
Abstract: We hereby described two cases with unilateral Purtscher-like retinopathy. The first case occurred following an uneventful spontaneous vaginal delivery. The second case had no discernable cause despite having meticulous systemic work-up. Both eyes had low presenting visual acuity of hand movements and 20/200 consecutively. We elected to inject 1 mg triamcinolone acetolamide in-travitreally for the treatment. Though, there was some subjective visual and clinical improvement within time in both patients, we were not convinced that intravitreal injection was superior to no treatment approach.
Statistical Evaluation of Anthropometric Measures and Oral Health Status in Terms of Diet, Smoking and Brushing Habits  [PDF]
Rukiye Dagalp, Sema P. Aka, Itir Aydintug, Doruk Iper
Health (Health) , 2019, DOI: 10.4236/health.2019.114035
Abstract: Introduction and Objective: The aim of this research was to find out the interaction of anthropometric measurements particularly body mass and oral health status of Turkish young adult nationals regionally, depending on the effects of diet (food and fluid consumption), smoking and tooth brushing habits, which were determined by using the body mass index (BMI) and dental health index (DMFT). Material and Methods: The BMI and DMFT of 202 cases, with an age average 22.5 years, were recorded through physical and clinical examinations. Statistical evaluation of the data was checked by Cronbach’s Alpha Reliability Scale and performed by analysis of variance, Somer’s d and Pearson Chi-Square statistics, Poisson Regression and Odds Ratio analysis. Results: The results showed that the mean of BMI was at the optimum level (21.52) for all cases. The DMFT was higher for underweight females and for overweight males. The mean of DMFT according to sexes seemingly had no significant difference; however, females had 8.6% more DMFT than males. When the risk factors of dental caries were evaluated, the DMFT was found as 19.3% more for cases consuming high carbohydrate foods, 4.5% more for high beverage consumption and 18% more for smokers. Conclusions: In conclusion, tooth brushing 3 or more times a day is necessary to decrease the DMFT and tooth brushing 3 times a day as opposed to 1 or 2 times shows significant difference regarding oral health.
Approach to Fall in Elderly Population
Mehmet Ilkin Naharci,Huseyin Doruk
TAF Preventive Medicine Bulletin , 2009,
Abstract: Falls are one of the geriatric syndromes which occur commonly and significantly increase morbidity and mortality rates in elderly. The incidence of falls increases with age. Falls usually occur when impairments in cognitive, behavioral, and executive function begin. The incidence of fall is between 30 and 40 percent of community-dwelling people and approximately 50 percent of individuals in the long-term care setting over the age of 65 years. Fracture (hip, arm, wrist, pelvis), head trauma or major lacerations, as defined serious wounding, occur 10-25% of elderly cases. Fall is overlooked in clinical examination due to various reasons; the patient never mentions the event to a doctor; there is no injury at the time of the fall; the doctor fails to ask the patient about a history of falls; or either doctor or patient erroneously believes that falls are an inevitable part of the aging process. Elderly give not usually any self-information about fall, for this reason, all older patients should be asked at least once per year about falls and should be assessed in terms of balance and gait disorders. There are many distinct causes for falls in old people. Falls in older individuals occur when a threat to the normal homeostatic mechanisms that maintain postural stability is superimposed on underlying age-related declines in balance, ambulation, and cardiovascular function. This factor may be an acute illness (eg, fever, water loss, arrhythmia), a new medication, an environmental stress (eg, unfamiliar surrounding), or an unsafe walking surface. The elderly person can not cope with happened additional stress. To prevent and decrease the frequency of falls, effective approaches are medical interventions, environmental modifications, education-exercise programs, and assisted device. Detection and amelioration of risk factors can significantly reduce the rate of future falls. The assessment of fall, causing mobility restriction, use of nursing home, and treating independent live in elderly, are very important. and needs further studies. [TAF Prev Med Bull. 2009; 8(5): 437-444]
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