Çok Duvarlı Karbon Nanotüplerin Serbest Titreşimi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Bu çalışmada, basit destekli çok duvarlı karbon nanotüplerin titreşimi genelleştirilmiş kayma deformasyon teorisi kullanılarak incelenmiştir. Çözümlerde parabolik kayma deformasyon teorisi (PKDT) kullanılmıştır. Timoshenko kiriş teorisinden farklı olarak mevcut teori kiriş alt ve üst yüzeyindeki sınır şartlarını sağlar ve böylelikle kayma düzeltme çarpanına gerek yoktur. Serbest titreşim frekansları ve genlik oranları bulunmuş ve önceki çalışmalarla kıyaslanmıştır. Sonuçlar PKDT ile Euler teorisi arasında önemli bir farkın olduğunu göstermektedir. Kayma deformasyonu özellikle yüksek modlar için önem kazanmaktadır.In this study, free vibration of simply supported multi-walled carbon nanotubes (CNTs) was investigated by using the generalized shear deformation-beam theory (GSDBT). Parabolic shear deformation theory (PSDT) is used in the specific solutions. Unlike Timoshenko beam theory present theory satisfies zero traction boundary conditions on the upper and lower surface of the structures so there is no need to use a shear correction factor. Free vibration frequencies and amplitude ratios were obtained and results are compared with previous studies. Shear deformation effects are important especially for higher modes

Eksenel Fonksiyonel Derecelenmiş Kirişlerin Titreşim Ve Burkulma Analizi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Fonksiyonel Derecelendirilmiş Kirişler, plaklar ve kabuklarda istenilen doğrultuda malzeme özellikleri değiştirilebildiği için mühendislik uygulamalarında kullanımı son yıllarda gittikçe artmıştır. Bu derecelendirme ile kompozit malzeme içerisinde gerilme dağılımları sürekli bir hale getirilebilmektedir.Bu çalışmada eksenel fonksiyonel derecelendirilmiş kirişlerin, değişik sınır koşullarındaki titreşim ve burkulma davranışları incelenmektedir. Kritik burkulma yükü ve frekanslar Ritz Metodu yardımıyla bulunmaktadır. Yer değiştirmeler basit cebirsel fonksiyonlar olarak ele alınmıştır. Malzeme özellikleri eksen doğrultusunda bir fonksiyona uygun değiştirilerek, değişik malzeme özellikleri ve değişik fiziksel sonuçlar elde edilmiştir

Buckling and Vibration of In-Plane Loaded Simply Supported Symmetrically Laminated Rectangular Thin Com-Posite Plates

DergiPark: 246274trakyafbdBu çalışmada, tek eksenli düzlem-içi üniform yükler etkisindeki tüm kenarları basit destekli simetrik açı-lı-katmanlı kompozit plakların titreşim frekansları verilmiştir. Düzlem-içi yükler incelenen plakların kritik burkulma yüklerinin belirli oranları olarak seçilmiştir. Basit destekli açılı-katmanlı kompozit plakların burkul-ma ve titreşim problemlerine analitik bir çözüm bulmak mümkün olmadığından, problemin çözümünde yer de-ğiştirme bileşeninin trigonometrik olarak seçildiği Ritz yöntemi kullanılmıştır. Sonuçların doğruluğunu göster-mek amacıyla yakınsama çalışmaları verilmiştir. Elyaf yönlenme açısı, katman sayısı, kenar oranları ve farklı malzemelerin düzlem-içi yüklü kompozit plakların titreşimi üzerindeki etkileri araştırılmıştır.In this study, accurate numerical results are presented for the vibration frequencies of uniform uniax-ially in-plane loaded simply supported, rectangular, angle-ply laminated plates. In-plane loads are chosen as certain ratios of the critical buckling loads of the plates investigated. The Ritz method, along with the dis-placement component assumed in the form of a double sine series, is applied in order to solve the vibration and buckling problems of angle–ply laminated plates, which can not be solved analytically. Convergence studies are presented to demonstrate the accuracies of the results and the effects of fiber orientation angle, side ratios and different materials on the frequencies of in-plane loaded composite plates are investigated

Three Dimensional Vibration of an Isotropic Plate Enclosed in a Rigid Body

In this study, vibration of plates embedded in a rigid enclosure has been investigated analytically for the first time in the literature. It is assumed that the isotropic plate is always in contact with outer enclosure. Therefore, the normal displacement at a boundary surface is constrained but tangential displacement at a surface is allowed. The displacement field is assumed in trigonometric function form. This analytical solution is the only available exact solution of three-dimensional isotropic plate. Numerical results were presented for various geometrical parameters. It is believed that the present formulation and the results can be used as a benchmark for the numerical methods where the exact solution is not possible

Quercus pyrenaica honeydew honey with high phenolic contents cause dna damage, apoptosis, and cell death through generation of reactive oxygen species in gastric adenocarcinoma cells

Many studies have shown that honey with high phenolic contents prevents cancer formation. Furthermore, recent studies have demonstrated that honey can be used for the treatment of cancer as well as cancer prevention. Antineoplastic effects of honey are often associated with their antioxidant phenolic contents. However, very few studies have dealt with the association of phenolic contents of honeys in terms of antiproliferative effects. The aim of this study was, therefore, to elucidate the cytotoxic, genotoxic, apoptotic, and reactive oxygen species (ROS) generating effects of honey samples on the basis of their phenolic and flavonoid contents. Fourteen different honey varieties were collected from various parts of Turkey, and their characteristics regarding total phenols, flavonoids, and antioxidant contents were determined to test their effects on gastric cancer cells (AGS). For convenience, 2 honey varieties were selected, namely, Ida Mountains Quercus pyrenaica honeydew honey (QPHH-IM) having the highest phenolic and antioxidant content and Canakkale multifloral honey (MFH-C) with the lowest phenolic and antioxidant content. Levels of 11 different phenolic compounds in QPHH-IM and MFH-C samples were determined by LC-MS/MS. AGS cells were incubated with different concentrations of QPHH-IM and MFH-C for 24 hours, then the cell viability, DNA damage, apoptosis, and generation of ROS were determined. We found that QPHH-IM had more cytotoxic, genotoxic, and apoptotic effects than that of MFH-C. We think that these effects are probably related to pro-oxidant activities due to the high phenolic contents present. Therefore, further research on high-phenolic honey may contribute to the future development of cancer therapeutics

The acorn honey used for a published study was mistakenly listed as quercus pyrenaica and should be corrected to quercus species

A critical review letter1 was published concerning the article “Quercus pyrenaica honeydew honey effects on gastric adenocarcinoma cells” published in Integrative Cancer Therapies in 2019.2 According to the letter, the authors reported that the Quercus pyrenaica mentioned in the study was neither found in Mount Ida nor within the borders of Turkey as stated in the study, therefore the results obtained in the study may belong to another Quercus species

A Real-Life Turkish Experience of Ruxolitinib in Polycythemia Vera

Introduction:Ruxolitinib is a small -molecule inhibitor of the JAK1/2 pathway. This study aimed to reveal the results and side-effect profile of the use of ruxolitinib as a treatment option in polycythemia vera (PV).Methods:A total of 34 patients with PV from 18 different centers were included in the study. The evaluation of the response under treatment with ruxolitinib was determined as a reduction in spleen volume (splenomegaly size: ≥35%) by imaging and control of hematocrit levels (≤45%) compared to baseline.Results:While the number of patients in which a reduction in spleen volume and hematocrit control was achieved was 19 (55.9%) at 3 months of treatment, it was 21 (61.8%) at 6 months. Additionally, while the number of side effects was negatively correlated with the reduction in spleen volume (Spearman’s rho: -0.365, p=0.034), a decrease in the hematocrit level was positively correlated (Spearman’s rho: 0.75, p=0.029). Those without a reduction in spleen volume experienced more constipation (chi-square: 5.988, Fisher’s exact test: p=0.033).Conclusion:This study shed light on the use of ruxolitinib in PV and the importance of splenomegaly on studies planned with larger patient groups

Katmanlı Kompozit Plaklar İçin Yeni Bir Kayma Deformasyon Teorisi: Aydogdu Modeli

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2010Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2010Katmanlı kompozit plaklar için üç boyutlu çözüm sonuçlarından hareket ile yarı-ters elastisite yöntemi ile yeni bir kayma deformasyon teorisi geliştirilmiştir. Yeni model plak alt ve üst yüzeylerinde kayma deformasyonunun sıfır olma şartını sağlamakta ve kalınlık doğrultusundaki kayma gerilmelerinin dağılımını yaklaşık olarak parabolik formda elde etmektedir. Elde edilen sonuçlar literatür ile kıyaslanarak mevcut teorinin geçerliliği gösterilmiştir.A new shear deformation theory is developed for composite plates using three dimensional results by semi-inverse method. New model satisfies zero shear deformation conditions on the plate top and bottom surfaces and gives approximately parabolic shear stress along the thickness direction. Validity of present theory is shown by comparing present results with existing results in literatüre

Dişli taslakları üretiminde üretim yöntemi optimizasyonu

Bir makine elemanını farklı üretim yöntemiyle üretmek mümkündür. Üretim yönteminin seçilmesinde mekanik özellikler, üretim hızı, ekonomiklik gibi pek çok kriterin incelenmesi gerekmektedir. Bu çalışmada, dişli pompaların dişli taslaklarının üretiminde uygun üretim yöntemi araştırması yapılmıştır. Dişli taslak üretiminde talaşlı şekil verme, kapalı kalıpta dövme, sürtünme kaynağı ve ekstrüzyon gibi üretim yöntemleri kullanılabilir. Bu çalışmada talaşlı şekil verme ve kapalı kalıpta dövme yöntemleri ile üretilen dişli taslakları üretim zamanı, malzeme kayıpları ve yorulma özellikleri açısından kıyaslanmaktadır. Çalışmanın sonuçları işleme zamanı ve malzeme kayıpları açısından kapalı kalıpta dövme yönteminin daha üstün olduğunu, yorulma dayanımı açısından kritik kesitte plastik şekil değişiminin etkisi fazla olmadığından büyük bir farkın olmadığını göstermektedir.It is possible to manufacture a machine element with different method. When selecting a manufacturing method many criterion should be evaluated. In this study, optimum manufacturing method was experimented for producıng gear blanks of gear pumps. It manufacturing of gear blanks; machining, closed die forging, extrusion friction welding can be used. In this study, gear blanks which were produced with machining and closed die forging were compared in manufacturing time, lost and fatigue limit. In, conclusion closed die forging showed better result in manufacturing time and material lost. Two methos are nearly similar in fatigue experiment results because closed die forging has not any effect in critical cross section

Three dimensional mechanical buckling of FG plates with general boundary conditions

The mechanical buckling analysis of rectangular functionally graded plates under different axial loadings is considered. The analysis is based on the small strain elasticity theory with different boundary conditions. The material properties of the plate vary through the thickness direction according to a simple power law. Three dimensional buckling solutions are obtained using the Ritz method with Chebyshev polynomials as assumed displacement functions. The convergence and comparison studies are presented and effects of the different material composition and the plate geometry (side-side ratio, side-thickness ratio) on the critical buckling loads and mode shapes are investigated. (c) 2012 Elsevier Ltd. All rights reserved