Optimal control of a linear system subject to partially specified input noise

One of the most basic problems in control theory is that of controlling a discrete-time linear system subject to uncertain noise with the objective of minimising the expectation of a quadratic cost. If one assumes the noise to be white, then solving this problem is relatively straightforward. However, white noise is arguably unrealistic: noise is not necessarily independent and one does not always precisely know its expectation. We first recall the optimal control policy without assuming independence, and show that in this case computing the optimal control inputs becomes infeasible. In a next step, we assume only knowledge of lower and upper bounds on the conditional expectation of the noise, and prove that this approach leads to tight lower and upper bounds on the optimal control inputs. The analytical expressions that determine these bounds are strikingly similar to the usual expressions for the case of white noise

Eksenel Yüklü Çatlak İçeren Kirişlerde Titreşim Probleminin Nümerik Analizi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2010Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2010Kusurlu yapılarda bulunan çatlağın, yapının mukavemetine ve dinamik özelliklerine etkisi oldukça fazla olmakta ve yapı dayanımında bir düşüşe neden olmaktadır. Makine ve inşaat mühendisliği uygulamalarında yapılar bazı durumlarda eksenel yük altında çalışmaktadırlar, dolayısı ile çatlağın boyutu ve yerinin yanında uygulanan eksenel yükün de yapının titreşim özelliklerine olan etkisinin tespiti önem arz etmektedir. Bu çalışmada eksenel yüklü, ilerlemeyen düzlem çatlak içeren dikdörtgen kesitli kirişlerin titreşim davranışları araştırılmıştır. Kirişlerin burkulma yükü ve doğal frekanslarının hesaplanması için sonlu elemanlar metodu kullanılmıştır. Yapılardaki çatlaklar çeşitli şekillerde modellenebilmekte olup, bu çalışmada kullanılan model kütlesiz yay modelidir. Yayın rijitliği, kırılma mekaniği teorileri kullanılarak hesaplanan gerilme yığılma faktörü ve şekil değiştirme enerjisi salıverinim oranlarına bağlı olarak bulunan esneklik matrisinin tersi alınarak türetilmiştir. Çalışmadan elde edilen sonuçlar ile literatürde bulunan sonuçlar karşılaştırılmış ve sonuçlar arasında iyi bir uyum görülmüştür. Bu da önerilen metodun güvenilir ve etkili olduğunu göstermiştir.A crack in a defected structure, affects the strength and dynamical properties of the whole structure and consequently results in a degradation in the structural resistance. In the mechanical and civil engineering applications, the structures sometimes are subjected to axial loading. Therefore, besides the crack ratio and locations, the influence of the applied axial force on the dynamical characteristics of the structure should also be determined. This study investigates the vibration analysis of single nonpropagating edge cracked beams subjected to axial loading. The finite element method is used to determine the buckling loads and natural frequencies of the beams. There are various modelling types of the damage. For uniform beams, a physical model of a massless spring is used to represent the local flexibility introduced by the crack in this study. The stiffness of the spring is derived from the lineer elastic fracture mechanics theory as the inverse of the compliance matrix calculated using the stress intensity factors and strain energy release rate expressions. The results of current study and those in the literature are compared and good agreements have been found. It is showed that proposed method is reliable and effective

Consensus report for workshop on ⇜early diagnosis and intervention in cerebral Palsy” Turkey’s approach to babies at risk and suggestions 1. National congress on babies at risk (1-4 March 2018, the Ankara Hotel)

The workshop on “Early Diagnosis and Intervention in Cerebral Palsy” aimed to reflect the current situation of and the challenges encountered in the early diagnosis and intervention in cerebral palsy in babies at risk, in order to raise awareness in the corresponding community by putting forth suggestions for providing solutions to these problems, and also, to provide a model suggestion suitable for the whole country. In the direction of these purposes, problems encountered in the prenatal, natal, and postnatal periods, and the corresponding suggestions were discussed, and vital topics concerning numerous disciplines, especially for the postnatal period, were emphasized in the workshop. With the aim of providing a solution to the current problems in the country regarding the matter, by employing an interdisciplinary approach, the establishment of Monitoring Centers for the Babies at Risk was proposed, and a model for these centers was created. Implications derived from this workshop will establish a foundation for the creation of a special strategic plan for the early diagnosis and intervention in cerebral palsy for the babies at risk. Copyright © 2018 by Türkiye Klinikleri