Optimal motion control and vibration suppression of flexible systems with inaccessible outputs

This work addresses the optimal control problem of dynamical systems with inaccessible outputs. A case in which dynamical system outputs cannot be measured or inaccessible. This contradicts with the nature of the optimal controllers which can be considered without any loss of generality as state feedback control laws for systems with linear dynamics. Therefore, this work attempts to estimate dynamical system states through a novel state observer that does not require injecting the dynamical system outputs onto the observer structure during its design. A linear quadratic optimal control law is then realized based on the estimated states which allows controlling motion along with active vibration suppression of this class of dynamical systems with inaccessible outputs. Validity of the proposed control framework is evaluated experimentally

Physically based deformable object modeling and soft tissue deformation

Bilgisayar destekli sanal ameliyat benzetimleri ve farklı alanlardaki uygulamaları, birçok parametrenin olası en doğru biçimde belirlendiği ve uygulandığı matematiksel modellerle mümkündür. Bu parametreler benzetimi yapılacak biyolojik yapıların geometrik sınırlarının, organ özelliklerinin, farklı kuvvetler altındaki davranışlarının ve en önemlisi dokuya ait malzeme parametrelerinin olası en doğru biçimde belirlenmesi ile elde edilir. Bu çalışma yumuşak dokuların doğrusal olmayan, viskoelastik davranışlarının matematiksel olarak modellenmesi ve önerilen bu modelin sonlu elemanlar yöntemi kullanılarak sayısal olarak çözülmesine odaklanmıştır. Örnek organ olarak seçilen insan karaciğerine ait malzeme katsayıları, hastane ortamında canlı dokular üzerinde yapılan deney sonuçları kullanılarak doğrusal olmayan eniyileme yöntemi ile elde edilmiştir. Uygulanan genel yaklaşımlardan farklı olarak benzetim sonuçlarının çözümden önce yani modelleme aşamasında yapılan ön basitleştirmelerden etkilenmemesi ilkesi benimsenmiştir. Bu nedenle, modelleme aşamasında uygulanan ve gerçeklikten uzaklaşılması ile sonuçlanan geleneksel basitleştirme adımları uygulanmamış, bu yaklaşım yerine tam çözümü veren benzetim sonuçları üzerinde model indirgeme teknikleri uygulanmıştır. İlk aşama olarak yumuşak dokuların önemli özelliklerini içeren bir model önerilmiş, sonrasında oluşturulan bu model sonlu elemanlar yöntemi kullanılarak analiz edilmiştir. Analiz sonrası elde edilen sonuçlar bir sonraki aşamada kullanılmak üzere saklanmıştır. İkinci adımda saklanan sonuçlar üzerinde Karhunen Loeve model indirgeme yöntemi kullanılarak, ilk adımda elde edilen sonuçlara yakın değerleri gerçek zamanlı sunabilen bir çözüm elde edilmiştir. Son adımda ise basitleştirilmemiş model ile indirgenmiş model sundukları hızlar ve sonuçların doğrulukları açısından karşılaştırılmıştır. Anahtar Kelimeler: Yumuşak dokular, sonlu elemanlar yöntemi, model indirgeme, viskoelastisite.As indicated by The Institute of Medicine Report, 44,000 to 98,000 people die annually as a result of procedure mistakes in surgery. The main reason cited was the young surgeons' insufficient experience of new techniques before facing real-world surgical operations. With the use of virtual surgery, surgeons have the opportunity to test different critical surgical procedures in a low- cost, ethically sound environment. The virtual surgery simulators equipped with physically based modeling engines are outstanding candidates for the simulation of deformable human organs. The real time soft tissue simulation has gained a great interest recently as a result of advancements in areas such as surgery planning and the surgical simulations. Linear deformation models may not provide the required accuracy in such areas whilst nonlinear models do not serve the real time needs. Therefore, there is a common need for a computationally simplified yet accurate, nonlinear, large deformable viscoelastic model of soft tissues to be used in these real time applications. Computer aided surgery and surgery simulation applications require accurate form and feature description as well as proper material and behavior descriptions of the biological tissues in a mathematically formulated model. This study focuses on mathematical formulation and numerical implementation of a nonlinear viscoelastic model of soft tissues using Finite Element Method (FEM). As an object, a human liver is selected in our study. The necessary material parameters are extracted from results of in vivo material tests on human liver using a nonlinear optimization method. Due to the technology limitations, today's physics based surgery simulators are forced to use different simplification methods to obtain satisfactory visual effects and response time in delivering an acceptable visual and haptic user experience. Thus, previous approaches to this problem involve techniques in the simplification of the mathematical models prior to obtain the necessary numerical solutions. The model simplification is necessary to achieve the required computational speeds however; these simplifications will inevitably result in reduced accuracy. Unlike the above mentioned approaches, our research is based on the opposite view that accuracy should not unduly influenced due to premature model simplifications prior to the analysis. Therefore, simplification step that is applied in the modeling phase, resulting in inaccurate outcome, is displaced to be applied after the solution phase. This aims to limit the degradation of already calculated values. As the first step, a complete soft tissue model is created. Subsequently this model is analyzed using Finite Element Method (FEM) and the results are stored and are used as the input to the next stage. Then, the Karhunen-Loeve decomposition technique is used to simplify the previously obtained data resulting in the final simulated model. Simplification technique is necessary to achieve acceptable real-time update rates due to the computing power available. Finally, a complete (unsimplified) model is compared with the simplified model in terms of accuracy and speed. Since soft tissues undergo large deformations under applied load and required volume preservation behavior, the use of linear strain tensor is not suitable for the accurate modeling of the resulting large deformations involved. Limitation of using a linear strain tensor is overcome by the use of nonlinear Green strain tensor in our customized FEM code. Standard material tests on human liver reveal the material nonlinearity relationship between applied forces and the resulting displacements. This nonlinear behavior is necessitated the use of hyperelastic strain energy density function in our FEM implementation. Viscoelastic behavior is also a predominant feature of soft tissues that must be included in any soft tissue deformation simulation. Therefore, the quasi-linear viscoelastic behavior of a human liver is added to our implementation to provide for this need. To implement time dependent viscoelastic behavior in improved the reduced order model, the surface nodes and its neighboring nodes are determined inside the Radius of Influence (ROI). Then, a constant unit force is applied to each of surface nodes for a period of 20 seconds. It is assumed that the creep response of the soft tissue lasts for 20 seconds due to the limitations of data storage and higher computational costs. Our proposed model, when employed, results in a final constitutive equation that successfully produces accurate results while catering for the whole previously mentioned phenomenon namely; geometric and material nonlinearity, volume preservation, viscoelasticity. Keywords: Real-time simulation; deformable models; model order reduction; nonlinear simulations; soft tissue; viscoelasticity

Recursive learning of image parameters and restoration of images using EM based learning algorithm

Birçok klasik görüntü onarım tekniği bulanıklık işlevinin bilindiği varsayımı altında çalışır. Ancak, gerçek hayat problemlerinde sadece gözlem verisi elde edilebilmekte bozucu sistemler hakkında yeterli bilgi sağlanamamaktadır. Bu yüzden görüntü onarımının ilk adımı bozucunun öğrenilmesi (tanınması) işlemidir. Geçmişte, görüntü ve bulanıklık parametrelerinin öğrenilmesi Enbüyük Olabilirlik (EO) problemi olarak ele alınmış ve Beklenti Enbüyükleme (BE) yordamı ile çözülmüştür. Özellikle BE yordamının E adımında kapalı yapıda bir çözüm bulunması bu yordamı daha cazip bir hale getirmektedir. Görüntü ve bulanıklık parametrelerinin tüm görüntü verisi kullanılarak öğrenilmesi geçmişte çalışılmış olmakla birlikte, parametrelerin yinelemeli BE’ye dayalı öğrenilmesi daha önce çalışılmamıştır. Yinelemeli teknikler dinamik işlem yetenekleri sayesinde tüm veri üzerinde işlem yapan yöntemlere nispetle çok daha az bellek ihtiyacı duyarlar. Daha az bellek ihtiyacı ise özellikle görüntü işleme alanında çok önemlidir. Bu çalışmada yeni bir eşzamanlı yinelemeli parametre öğrenme ve görüntü onarım yöntemi sunulmuştur. Dinamik Bayesçi Ağ (DBA) yapısında yeni bir çözüm önerilmiştir. Sunulan yöntem EO parametre tanıma ve durum kestirimi için en iyi Kalman yumuşatma ifadelerini içerir. Kalman yumuşatma ifadelerinin yoğun hesaplama gerektirmesi sebebi ile Kalman süzgeç yaklaşıklığı kullanılmıştır. Aynı zamanda, onarılmış görüntü eş zamanlı olarak bu süzgeç çıkışından elde edilmektedir. Görüntü ve bulanıklık parametrelerinin BE öğrenme problemi kapalı yapıda çözümlenmesi başarılmıştır.  Yöntemin başarımı gerçek görüntüler üzerinde yapılan benzetim ve denemeler ile verilmiştir.  Anahtar Kelimeler: Beklenti enbüyükleme, bulanıklık ve görüntü tanıma, yinelemeli işleme, kalman yumuşatma ve süzgeçleme.The image restoration problem can be defined as the general problem of estimating the ideal image from its blurred and noisy version. Many classical image restoration techniques have been reported under the assumption that the blur operation is exactly known. In real life applications, the corruption mechanism of any system is not known because only observed data is available, so it is necessary to handle uncertain events and observations. The image restoration problem is in general ill-posed; a small perturbation on the given data produces large deviations in the solution. The direct inversion of the blur transfer function usually has a large magnitude at high frequencies, therefore excessive amplification of noise results at those frequencies. Clearly, this is not an acceptable solution for noisy images. To overcome the noise sensitivity problem of the inverse filter, some filters have been developed based on the least-squares structure. The Wiener filter is based on batch processing which is usually implemented in the frequency domain. The Kalman filter is based on recursive processing which is usually implemented in the spatial domain. Both solutions only work when blur, image and noise parameters are known. The first step for image restoration is the identification of degradation. Consequently, modeling uncertain relationships among many kinds of variables and learning (identification) such variables are important topics. The blur and image parameter identification problem was formerly formulated as a constrained Maximum Likelihood (ML) estimation procedure which was based on optimizing the probability density function (pdf) of the observed image with respect to the unknown parameters. But, the direct optimization of the likelihood function is not feasible, because of its highly nonlinear character. The Expectation Maximization (EM) algorithm is a very popular and widely used algorithm for the computation of ML estimates. There are two steps in EM algorithm, as E (Expectation) and M (Maximization). The EM algorithm finds the conditional expectation of the log-likelihood of complete data given the observed incomplete data. In the E-step, the conditional expectation of the "hidden variables" is calculated.  In the M-step, this expectation is maximized with respect to the parameters. The advantage of the EM method is such that it avoids operating directly on the nonlinear likelihood function. The EM algorithm becomes more attractive if its maximization step can be formulated analytically. Even though batch processing of the EM based blur identification and restoration problem needs large memory size, recursive techniques allow dynamic processing with modest storage requirements. Although the EM learning was applied to learning of unknown image and blur parameters based on batch image processing before, recursive EM learning of unknown image and blur parameters has not been studied as much as necessary. Many time series models, including the Hidden Markov Models (HMM) and Kalman Filter Models (KFM) used in filtering and control applications, can be viewed as examples of Dynamic Bayesian Network DBNs. Since, a Bayesian Network is a graphical way to represent a particular factorization of joint distribution; we propose that state space image model can be represented as a DBN. In this work, we introduce a new simultaneous recursive parameter learning and image restoration method based on the ML parameter identification and state estimation for images. We present a new formulation which is given in a Dynamic Bayesian Network (DBN) framework. We focus on the problem of learning the parameters of a Bayesian network. This technique incorporates optimal Kalman smoothing equations for ML parameter identification and state estimation. The use of Kalman filtering instead of Kalman smoothing is employed because of the computationally extensive processing of smoothing. In addition, a restored image is obtained simultaneously as the output of the Kalman filter. We manage to solve the EM learning problem for image and blur parameters in closed form. Although our proposed method processes huge data, because of the recursive structure it does not need large size storage. Performance evaluation of the method is given based on experiments carried out upon real images.  Keywords: Expectation-Maximization, Blur and Image Identification, Recursive Processing,  Kalman Smoothing and Filtering

Assessment of the Prevalence of Pulp Stones in a Sample of Turkish Central Anatolian Population

Objective. The aim of this study was to determine the prevalence of pulp stones (PS) in a Turkish dental patient population with respect to sexes and dental localization in relation between sex and this anomaly. Materials Methods. A retrospective study was performed using bitewing radiographs of 814 patients ranging in age from 15 to 65. All data (age, sex, and location) was obtained from the files. These patients were analyzed for pulp stones. Descriptive characteristics of sexes, jaws, and dental localization were recorded. The Pearson chi-squared test was used. Results. Of the patients, 462 (56.8%) were female and 352 (43.2%) were male. Sixty (12%) had one or more teeth that contained pulp stones. Pulp stones were identified in 518 (63.6%) of the subjects and in 2391 (27.8%) of the teeth examined. Pulp stone occurrence was significantly more common in the females than in males. With the increasing of age, the prevalence of pulp stones increased. Molars had statistically more pulp stones than premolars. Pulp stones were significantly more common in the maxilla compared with mandible. Conclusion. Prevalence of pulp stones in Turkish population was 27.8% but further larger-scale studies are required to assess its prevalence in the general population to compare it with other ethnic groups

Practical review of the place of social networks in our daily life and their effect on today’s youth,

In this study, we practically reviewed the negative effects of social networks on today’s youth which became somewhat indispensable to them. The study was based on the university students attending public and private universities and the high-school students. The number of participants included in the study is 894 individuals in total. The study was completed in an eight month period. Within this period, specific student groups were asked to fill in a survey composed of eighty questions on their own free will and choices. While the survey had two sections, the 60 questions in the first section were prepared in a 5-point Likert scale. In the first section, questions towards the use of social networks were answered. The last 20 questions were demographic which were arranged as multiple-choice questions. The data from the survey were analyzed via the statistical program SPSS 15. The results of the analysis and findings were presented as tables and explanations at the end of the study. This study contributes to the understanding of social status and problems experienced by today’s youth related to the social networking web pages. At the end of the research, we came to the conclusion that social networks had a negative effect on the youth

Molecular and pomological diversity among pomegranate (Punica granatum L.) cultivars in Eastern Mediterranean region of Turkey

Pomegranate (Punica granatum L.) is an important fruit species for Turkey where many cultivars are being cultivated. In this study, we determined the fruit characteristics and RAPD band patterns of sixlocal cultivars from Hatay, Turkey. Our results demonstrated that there is a great level of morphological variation. The principle component analysis of 18 quantitative fruit characteristics revealed that fruitweight, aril number/fruit, peel color and soluble solids/acidity ratio are important traits for discriminating the cultivars tested. The UPGMA cluster of fruit characteristics indicated that ‘Katýrbaý’and ‘Kan narý’ were similar to each other and they were separated from rest of the cultivars. Twenty-two RAPD primers generated total of 106 reproducible bands 22% of which were polymorphic. The UPGMAdendrogram of RAPD data showed that ‘Tatlý nar’ and ‘erife’ were very closely related while ‘ncekabuk’ is distinct from the other cultivars. As a result, discrepancies were detected between morphological and molecular data. Therefore, we confirmed that diversity among the fruitcharacteristics were not good indication of genetic relatedness while molecular tools are valuable to study such similarities

Combined approach of density functional theory and quantum Monte Carlo method to electron correlation in dilute magnetic semiconductors

We present a realistic study for electronic and magnetic properties in dilute magnetic semiconductor (Ga,Mn)As. A multi-orbital Haldane-Anderson model parameterized by density-functional calculations is presented and solved with the Hirsch-Fye quantum Monte Carlo algorithm. Results well reproduce experimental results in the dilute limit. When the chemical potential is located between the top of the valence band and an impurity bound state, a long-range ferromagnetic correlations between the impurities, mediated by antiferromagnetic impurity-host couplings, are drastically developed. We observe an anisotropic character in local density of states at the impurity-bound-state energy, which is consistent with the STM measurements. The presented combined approach thus offers a firm starting point for realistic calculations of the various family of dilute magnetic semiconductors.Comment: 5 pages, 4 figure

7-17 Yaş Arası Farklı Gelişimsel Özellikleri Olan Çocuklara Sahip Ailelerin Stresle Başa Çıkma Yöntemlerinin İncelenmesi

Zihinsel ve bedensel yetersizlik, hiperaktivite ve davranış bozuklukları ve ortopedik ve travmatolojik rahatsızlıklar sadece duruma maruz kalan bireyleri değil onların aile üyelerini de birçok açıdan (ekonomik, sosyal, duygusal vb.) etkilemektedir. Bu durum aile üyelerinde stres faktörünü artırıcı bir unsur olmaktadır. Stres başa çıkılması gereken ciddi bir sorundur. Aksi taktirde ebeveynlerin içinde bulundukları aşırı stres onların daha da yıpranmalarına ve daha ciddi sağlık problemleriyle karşılaşmalarına neden olabilmektedir. Bu bağlamda araştırmada, 7-17 yaş arası özel gereksinime ihtiyacı olan (Zihinsel ve bedensel yetersizlik/hiperaktivite ve davranış bozukluğu, ortopedik ve travmatolojik rahatsızlık tanısı almış) çocukları olan ailelerin psikolojik iyi olma ve başa çıkma yöntemlerinin incelenmesi ve bazı değişkenler açısından (çocuğun yaşı, engel türü, anne babanın cinsiyeti, eğitim düzeyi vb.) farklılaşmaların ortaya koyulması amaçlanmıştır. Katılımcılara ilk bölümünde, Katılımcıların ve çocuklarının demografik ve betimleyici özelliklerinin, ikinci bölümde ise ebeveynlerin başa çıkma yöntemlerinin ele alındığı bir anket uygulanmıştır. Toplanan verilerin analizi kapsamında betimleyici istatistikler ile ebeveynlerin stresle başa çıkma durumlarının bazı değişkenler açısından farklılıklarının tespitine yönelik ANOVA testinden yararlanılmıştır. Araştırma sonunda, ebeveynlerin sosyo-ekonomik, yaş, eğitim ve cinsiyet değişkenlerinin ve çocukların cinsiyet ve yaş değişkenlerinin ebeveynlerin stresle başa çıkma durumlarında etkili olduğu sonucuna ulaşılmıştır

Post-contrast FLAIR imaging in a patient with posterior reversible encephalopathy syndrome (PRES).

We herein present a case of delayed enhancement of CSF on fluidattenuated inversion recovery (FLAIR) imaging in a patient with posterior reversible encephalopathy syndrome (PRES). In our case despite the settled clinical setting of PRES initial MR scan was negative and on repeated FLAIR imaging increased CSF signal intensity was more conspicuous than subtle cortical involvement

Comparative Istanbul example regarding attitudes of the students preparing for university exam towards mathematics and computer

The purpose of this study is to determine mathematics and computer attitudes of the students preparing for university exam. In this sense, the questionnaire was performed on a total of 250 people. Cronbach’s alpha analysis was applied for the reliability of the questions prepared, and the reliability coefficient was found 0.920. Factor analysis, regression test, chi-square, t test and one-way Anova tests were utilized in the analysis of data obtained In summary, it has been concluded that the success average of the participants for math lesson is high and their daily internet use is 4 hours and above. The students have stated that the technology increases their success in their lessons but they waste their time with internet use instead of using their time to prepare university exam. The parents of the students have put forward their negative concerns about the use of technology due to the worries for the exam