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RISS 인기검색어
- 검색키워드
- 저자 : Erdogdu, Sakir (검색결과 5 건)
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Erdogdu, Sakir,Kandil, Ufuk,Nayir, Safa Techno-Press 2019 Advances in concrete construction Vol.8 No.2
In this study, the mechanical properties of reactive powder concrete (RPC) with a constant cement to silica fume ratio of 4 were investigated. In the experimental program, reactive powder concretes with steel fiber at different ratios were produced. Five productions using quartz sand with a maximum grain size of 0.6 mm were performed. A superplasticizer with a ratio of 3% of the cement was used for all productions. $40{\times}40{\times}160mm$ prismatic specimens were prepared and tested for flexural and compression. The specimens were exposed to two different curing conditions as autoclave and standard curing condition. Autoclave exposure was performed for 3 hours under a pressure of 2 MPa. It was observed that the compressive strength of concrete, along with the flexural strength exposed to autoclave was quite high compared to the strength of concretes subjected to standard curing. The results obtained indicated that the compressive strength, along with the flexural strength of autoclaved concrete increased as the amount of cement used increases. Approximately 15% increase in flexural strength was achieved with a 4% steel fiber addition. The maximum compressive strength that has been reached is over 210 MPa for reactive powder concrete for the same steel fiber ratio and with a cement content of $960kg/m^3$. The relationship between compressive strength and flexural strength of reactive powder concrete exposed to both curing conditions was also identified.
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BETCHOV-DA RIOS EQUATION BY NULL CARTAN, PSEUDO NULL AND PARTIALLY NULL CURVE IN MINKOWSKI SPACETIME
Melek Erdogdu,Yanlin Li,Ayse Yavuz 대한수학회 2023 대한수학회보 Vol.60 No.5
The aim of this paper is to investigate Betchov-Da Rios equation by using null Cartan, pseudo null and partially null curve in Minkowski spacetime. Time derivative formulas of frame of $s$ parameter null Cartan, pseudo null and partially null curve are examined, respectively. By using the obtained derivative formulas, new results are given about the solution of Betchov-Da Rios equation. The differential geometric properties of these solutions are obtained with respect to Lorentzian causal character of $s$ parameter curve. For a solution of Betchov-Da Rios equation, it is seen that null Cartan $s$ parameter curves are space curves in three-dimensional Minkowski space. Then all points of the soliton surface are flat points of the surface for null Cartan and partially null curve. Thus, it is seen from the results obtained that there is no surface corresponding to the solution of Betchov-Da Rios equation by using the pseudo null $s$ parameter curve.
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A GEOMETRIC APPROACH TO TIMELIKE FLOWS IN TERMS OF ANHOLONOMIC COORDINATES
Ays¸e Yavuz,Melek Erdogdu 호남수학회 2022 호남수학학술지 Vol.44 No.2
This paper is devoted to the geometry of vector fields and timelike flows in terms of anholonomic coordinates in three dimensional Lorentzian space. We discuss eight parameters which are related by three partial differential equations. Then, it is seen that the curl of tangent vector field does not include any component in the direction of principal normal vector field. This implies the existence of a surface which contains both s − lines and b − lines. Moreover, we examine a normal congruence of timelike surfaces containing the s − lines and b − lines. Considering the compatibility conditions, we obtain the Gauss-Mainardi-Codazzi equations for this normal congruence of timelike surfaces in the case of the abnormality of normal vector field is zero. Intrinsic geometric properties of these normal congruence of timelike surfaces are obtained. We have dealt with important results on these geometric properties.
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Mertsoylu, Huseyin,Muallaoglu, Sadik,Besen, Ayberk Ali,Erdogdu, Suleyman,Sezer, Ahmet,Sedef, Ali Murat,Kose, Fatih,Arican, Ali,Ozyilkan, Ozgur Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.17
Background: The aim of this study was to assess the epidemiological and clinicopathological characteristics of primary extranodal non-Hodgkin's lymphoma (pENL) patients, focusing on treatment and survival outcome. Materials and Methods: Between October 2003 and March 2012, 802 patients with non-Hodgkin's lymphoma (NHL) were diagnosed and treated in two different cancer centers of Southern Turkey. Results: pENL, constituted 12.4% (100/802) of all NHL studied during this period. Median age of the patients was 56 years (range 17-87 years) and the male: female distribution was 3:2. Eighty-five of 100 patients (85%) were in stage I/II, 9/100 (9%) in stage III, whereas 6/100 (6%) were in stage IV. Head and neck constituted the most common site (51/100, 51%), followed by gastrointestinal tract (GIL) (37/100, 37%), and cerebrum (CL) (5/100, 5%). Diffuse large B cell lymphoma (DLBCL) was the most common histological type, observed in 53% of patients, followed by marginal zone extranodal lymphoma (13%). Most of patients (76%) received a CHOP containing regimen. Complete remission (CR) were achieved in 71% of patients. The median follow-up duration of all patients was reported as 37.6 months (range, 0.8-165 months). This period was reported as 137.5 months (range, 117.5-1578.6 months) in gastrointestinal lymphoma (GIL) patients, 119.0 months (range, 91.8-146.1 months) in head and neck lymphoma (HNL) patients, and 18.4 months (range, 12.6-24.1 months) in cerebral lymphoma (CL) patients. Conclusions: Head and neck, and the gastrointestinal tract were the two most common extranodal sites observed. Histologically DLBC accounted for the majority of cases. Most patients were on earlier stages, had low-low intermediate IPI scores and had a favorable prognosis.
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Pozzolanic properties of trachyte and rhyolite and their effects on alkali-silica reaction
Baki, Vahiddin Alperen,Nayir, Safa,Erdogdu, Sakir,Ustabas, Ilker Techno-Press 2021 Advances in concrete construction Vol.11 No.4
The alkali-silica reaction (ASR) is a highly complex chemical reaction which causes damage to concrete and thus adversely affects the durability and service life. Significant damage can occur in concrete structures due to cracking because of the chemical reactions taking place. Various mineral and chemical additives have been used so far to mitigate ASR and/or to reduce its adverse effects. In this study, ground trachyte and rhyolite provided from Rize-Çağrankaya region, Turkey, were used to investigate their effectiveness in controlling ASR-induced damage by substituting them with cement at certain ratios. In this context, initially the possible use of trachyte and rhyolite as pozzolanas was determined in accordance with BS EN 450-1 and TS 25 standards by considering their pozzolanic activities and then their effectiveness in mitigating the ASR was evaluated as per ASTM C 1567-13. In experimental study, blends of trachyte and rhyolite were prepared by substituting them by cement at 25%, 35%, and 50% percentage. Totally 7 mixes were prepared and three samples of 25×25×285 mm mortar bars were prepared from each batch. The length changes of the mortar bars were determined at the end of 3, 7, 14 and 28 days of exposure. SEM, along with XRD analyses were performed to examine and elementally determine the ASR products that have been formed. The results obtained have shown that ground trachyte and rhyolite used in this study can be used as pozzolanas in concrete and they can also significantly mitigate ASR-induced damage as the substitution ratio increases.
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