Konik Tipi Viskoelastik Helislerin Farklı Yüklemeler Altındaki Dinamik Davranışı

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Bu çalışmanın amacı, Timoshenko çubuk kuramına dayalı karışık sonlu eleman formülasyonu kullanılarak daire kesitli konik tipi doğrusal viskoelastik helislerin düzgün yayılı yük etkisinde dinamik davranışını araştırmaktır. Doğrusal viskoelastik malzemenin kayma modülü standart model ile tanımlanmış ve Poisson oranı elastik alınmıştır. Sonlu eleman çözümlemesi Laplace uzayında gerçekleştirileceği için, viskoelastik malzeme özellikleri karşıgelim ilkesi kullanılarak belirlenmiş ve. Laplace uzayında elde edilen sonuçlar, geliştirilmiş Durbin dönüşüm algoritması kullanılarak zaman uzayına taşınmıştır. Örnek problemlerde iki farklı sınır koşulu kullanılmıştır: bir ucundan tutulu diğer ucu serbest helis ve iki ucu tutulu helis. Her iki durum için adım ve impulsif tiplerinde (dikdörtgen, sinüzoidal, dik üçgen ve üçgen formlarında olmak üzere) düşeyde etkiyen dinamik yayılı yüklemeler etkisindeki helislerin dinamik davranışı incelenmiştir.The objective of this study is to investigate the dynamic behavior of a linear viscoelastic conical type helical bar having a solid circular cross-section subjected to vertical distributed loading by using the mixed finite method based on Timoshenko beam theory. It is assumed that, the linear viscoelastic material exhibits the standard type of distortional behavior while having elastic Poisson's ratio. The finite element analysis is carried out in Laplace space, the material properties are implemented into the formulation through the use of the correspondence principle. The results are transformed back to the time domain numerically by using of the Modified Durbin's transformation algorithm. Two different cases of boundary conditions are considered in the sample problems: helix fixed from one end (cantilevered) and helix fixed from two ends. For each case, the dynamic responses of the helices are determined for step and impulsive types (having rectangular, sinusoidal, right triangular and triangular forms) of dynamic vertical distributed loadings

Effects of standard diets from different sources on growth and some organ parameters of rats

ΔΕΝ ΔΙΑΤΙΘΕΤΑΙ ΠΕΡΙΛΗΨΗThis study aims to determine the effects of open and closed formulated standard diets supplied from different sources on growth performance and internal organ development of laboratory rats. Five-week-old 32 Wistar rats were used. A special control group diet was produced in accordance with the criteria determined by the National Research Council (NRC) (1995). Three different most preferred commercial open and closed-formula diets produced by international and local companies were used as trial groups’ diets. The experiment was carried out for 12 weeks. Weekly feed consumption, body weight change, internal organ weight, intestinal organ weigths and lengths, intestinal villi heigth and crypt depth were measured in groups. The body weight values of the control group and the first group fed with open-formula diet were found at the highest level (P <0.05). The control group diet had a positive effect on small intestine villi heigth and crypt depth (P <0.05). The nutrient contents and energy values of the diets of experimental groups were determined as different from the commercial firm notifications. As a result of the research, it is concluded that the diets prepared with open-formula give more reliable results in the growth performance and development of internal organs of Wistar rats

Fıçı Tipi Doğrusal Viskoelastik Helislerin Dinamik Davranışı

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Bu çalışmada, viskoelastik parametrelerin dairesel kesitli fıçı (barrel) tipi doğrusal viskoelastik helislerin dinamik davranışı üzerindeki etkileri Timoshenko çubuk kuramını esas alan bir karışık sonlu eleman algoritması kullanılarak incelenmiştir. Helisin iki ucundan tutulu ve dinamik olarak adım tipinde düzgün yayılı yük etkisinde olduğu varsayılmıştır. Doğrusal viskoelastik malzemede, kayma şekil değiştirmelerinin standart modele ve hacimsel şekil değiştirmelerinin ise Kelvin modele uygun davranış gösterdiği kabul edilmiş ve karşıgelim ilkesi kullanılarak malzeme özellikleri çözüm algoritmasına eklenmiştir. Helis probleminin çözümü Laplace uzayında gerçekleştirilmiş ve sonuçlar geliştirilmiş Durbin dönüşüm algoritması kullanılarak zaman uzayına taşınmıştır. Doğrusal viskoelastik fıçı tipi helislerin dinamik davranışına ait sayısal sonuçlar detaylı olarak irdelenmiştir.In this study, the effects of viscoelastic parameters on the dynamic behavior of a linear viscoelastic circular cross-sectioned barrel type helix is investigated by using the mixed finite element method based on the Timoshenko beam theory. The helix is assumed to be fixed from both ends and subjected to dynamic step type of vertical distributed loading. The linear viscoelastic material exhibits standard type of distortional behavior and Kelvin type of bulk compressibility, and, the material properties are implemented into the formulation through the use of the correspondence principle. The solutions of the helix problem are obtained in the Laplace space and the results are transformed back to the time domain numerically by means of the Modified Durbin's transformation algorithm. Numerical results for the dynamic behavior of linear viscoelastic barrel type helix are discussed extensively

Viskoelastik Eliptik Düzlem Çubukların Dinamik Analizi

Konferans Bildirisi-- İstanbul Teknik Üniversitesi, Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2017Conference Paper -- İstanbul Technical University, Theoretical and Applied Mechanical Turkish National Committee, 2017Bu çalışmanın amacı, Timoshenko çubuk kuramına dayalı karışık sonlu eleman formülasyonunu kullanarak, farklı sınır koşulları ve çubuk kesitlerine sahip doğrusal viskoelastik eliptik kirişlerin düzgün yayılı yük etkisinde dinamik davranışını incelemektir. Doğrusal viskoelastik malzemenin kayma modülü standart model ile tanımlanmış ve Poisson oranının elastik olduğu kabul edilmiştir. Sonlu eleman çözümleri Laplace uzayında gerçekleştirileceği için, viskoelastik malzeme özellikleri karşıgelim ilkesi kullanılarak belirlenmiş ve Laplace uzayında elde edilen sonlu eleman sonuçları, geliştirilmiş Durbin dönüşüm algoritması kullanılarak zaman uzayına taşınmıştır. Problemlerde iki farklı sınır koşulu kullanılmıştır: iki ucundan rijit tutulu ve konsol. Net alanları birbirine eşit olan farklı kesitler seçilmiştir: dairesel ve iki farklı oryantasyona sahip eliptik kesit geometrisi. Farklı sınır koşulları ve kesit türlerinin eliptik düzlem kirişin elastik ve viskoelastik davranışına olan etkisi detaylı olarak incelenerek özgün örnek olarak literatüre sunulmuştur.The objective of this study is to investigate the dynamic behavior of a linear viscoelastic elliptical beam having different types of boundary conditions and cross-sections subjected to vertical distributed loading by using the mixed finite method based on Timoshenko beam theory. It is assumed that, the linear viscoelastic material exhibits the standard type of distortional behavior while having elastic Poisson's ratio. The finite element analysis is carried out in Laplace space, the material properties are implemented into the formulation through the use of the correspondence principle. The results are transformed back to the time domain numerically by using of the Modified Durbin's transformation algorithm. Two different types of boundary conditions are considered in the problems: fixed-free, fixed-fixed. Different types of cross-sections keeping the net area equal to each other are selected: circular and two different elliptically oriented cross sections. The effect of different types of boundary conditions and cross-sections on the behavior of elastic and viscoelastic elliptical planar beam is investigated in detail and the examples are presented as original examples for the literature

Dynamic group key agreement for resource-constrained devices using blockchains

Dynamic group key agreement (DGKA) protocols are one of the key security primitives to secure multiparty communications in decentralized and insecure environments while considering the instant changes in a communication group. However, with the ever-increasing number of connected devices, traditional DGKA protocols have performance challenges since each member in the group has to make several computationally intensive operations while verifying the keying materials to compute the resulting group key. To overcome this issue, we propose a new approach for DGKA protocols by utilizing Hyperledger Fabric framework as a blockchain platform. To this end, we migrate the communication and verification overhead of DGKA participants to the blockchain network in our developed scheme. This paradigm allows a flexible DGKA protocol that considers resource-constrained entities and trade-offs regarding distributed computation. According to our performance analysis, participants with low computing resources can efficiently utilize our protocol. Furthermore, we have demonstrated that our protocol has the same security features as other comparable protocols in the literature

Definitive hypofractionated radiotherapy for early glottic carcinoma: experience of 55Gy in 20 fractions

Introduction: A wide variety of fractionation schedules have been employed for the treatment of early glottic cancer. The aim is to report our 10-year experience of using hypofractionated radiotherapy with 55Gy in 20 fractions at 2.75Gy per fraction. Methods: Patients treated between 2004 and 2013 with definitive radiotherapy to a dose of 55Gy in 20 fractions over 4 weeks for T1/2 N0 squamous cell carcinoma of the glottis were retrospectively identified. Patients with prior therapeutic minor surgery (eg. laser stripping, cordotomy) were included. The probabilities of local control, ultimate local control (including salvage surgery), regional control, cause specific survival (CSS) and overall survival (OS) were calculated. Results: One hundred thirty-two patients were identified. Median age was 65 years (range 33–89). Median follow up was 72 months (range 7–124). 50 (38 %), 18 (14 %) and 64 (48 %) of patients had T1a, T1b and T2 disease respectively. Five year local control and ultimate local control rates were: overall - 85.6 % and 97.3 % respectively, T1a - 91.8 % and 100 %, T1b - 81.6 and 93.8 %, and T2 - 80.9 % and 95.8 %. Five year regional control, CSS and OS rates were 95.4 %, 95.7 % and 78.8 % respectively. There were no significant associations of covariates (e.g. T-stage, extent of laryngeal extension, histological grade) with local control on univariate analysis. Only increasing age and transglottic extension in T2 disease were significantly associated with overall survival (both p <0.01). Second primary cancers developed in 17 % of patients. 13 (9.8 %) of patients required enteral tube feeding support during radiotherapy; no patients required long term enteral nutrition. One patient required a tracheostomy due to a non-functioning larynx on long term follow up. Conclusions: Hypofractionated radiation therapy with a dose of 55Gy in 20 fractions for early stage glottic cancer provides high rates of local control with acceptable toxicity

Current source converter based STATCOM: Operating principles, design and field performance

This paper describes the operating principles, design and field performance of two-level, three-leg device commutated current source converter (CSC) topology based Static Synchronous Compensator (STATCOM), which is developed for medium voltage industry applications. In the paper, the relationship between the reactive power and the control variables is obtained, harmonic minimization techniques applicable to CSC are investigated, and then Selective Harmonic Elimination Technique is applied for the elimination of the 5th, 7th, 11th and 13th harmonics in CSC line current. The design principles of the input filter are also set out. Considerations for optimum sizing of STATCOM in common industry applications are described with the design objective of maximum utilization of power semiconductors. Two CSC based STATCOMs, which are rated at +/- 500 kVAr and 0-1500 kVAr capacitive are implemented and applied to industry. Field results are also given in the paper in order to validate the operating principles and design criteria

Effects of Distributed Air-Gaps in the Iron-Core of Shunt Reactors on Inductance Components and Losses

In this paper, effects of dividing the air-gap in the iron-core of shunt reactors into several discrete gaps on inductance parameters of the equivalent circuit, core losses and gap losses are investigated. This is achieved by both analytical calculations and Finite Element Method based analyses. A new method called Moving Strip Method is also introduced to estimate the gap loss in the iron-core of shunt reactors having discretely distributed small air-gaps relative to those with large air-gaps. Theoretical results are verified by experiments carried out on an optimized shunt reactor. Results obtained in this work show that leakage inductance component in the equivalent circuit of the reactor can be brought to an absolute minimum and gap loss owing to fringing flux can be reduced significantly by distributing a large air-gap in the reactor core into several discretely distributed small air-gaps. These will simplify the design procedure of shunt reactors which will be used in utility grid applications. Copyright (c) 2012 Praise Worthy Prize S.r.l. - All rights reserved