Winkler Zemine Oturan Elastik İki Tabaka İçin Sürekli Temas Probleminin Sonlu Elemanlar Yöntemi Kullanılarak Çözümü

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Bu çalışmada, düzgün yayılı yük ile yüklenmiş ve Winkler zemine oturan birbirine yapışık elastik iki tabakanın sürekli temas problemi sonlu elemanlar yöntemi kullanılarak çözülmüştür. Çözümde tabakaların kütle kuvvetleri ihmal edilmiştir. Problem düzlem hal için incelendiğinden z ekseni doğrultusundaki kalınlık birim olarak alınmıştır. Problemin sonlu eleman modeli ANSYS paket programı kullanılarak oluşturulmuş ve iki boyutlu analizi yapılmıştır. En büyük normal gerilmeler simetri ekseni üzerinde meydana geldiğinden, bu eksende oluşan sx ve sy gerilmeleri çeşitli boyutsuz büyüklükler için elde edilmiştir. Son olarak bulunan sonuçlar literatürdeki analitik sonuçlarla karşılaştırılarak doğrulanmıştır.In this paper, a continuous contact problem for two bonded elastic layers resting on a Winkler foundation and loaded by uniformly distributed load is solved using finite element method. Body forces of elastic layers are neglected in the problem. Thickness in z-direction is taken to be unit. The finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. By reason of the fact that maximum value of the normal stress is on the symmetry axis, sx and sy stresses on the symmetry axis are determined for various dimensionless quantities. Finally, the results obtained from finite element method are verified by comparison with the analytical results

Receding contact problem for two elastic layers resting on a Winkler foundation

In this study, receding contact problem for two elastic layers resting on a Winkler foundation and loaded by means of a rigid circular punch is considered. The elastic layers have different heights and elastic constants. External load is applied to the upper elastic layer by means of a rigid circular punch and the lower elastic layer rests on a Winkler foundation. The problem is solved under the assumptions that the contact between elastic layers, and between the rigid punch and the upper elastic layer are frictionless and the effect of gravity forces is neglected. Since the contact between two bodies is assumed to be frictionless, then only compressive normal tractions can be transmitted in the contact areas. General equations of stresses and displacements which are required for the solution of the problem are obtained by using the theory of elasticity and the integral transform techniques. Using integral transform technique and boundary conditions of the problem, the problem is reduced to a system of singular integral equations in which the contact stresses and areas are the unknown functions. The system of singular integral equations is solved numerically by making use of appropriate Gauss-Chebyshev integration formulas and an iterative scheme is employed to obtain the correct contact half-areas that satisfies the equilibrium conditions. Numerical results for the contact stresses and the contact areas are given for various dimensionless quantities

Acute carpal tunnel syndrome caused by tenosynovial effusion due to calcium pyrophosphate deposition

Acute carpal tunnel syndrome mostly occurs secondary to trauma. While storage diseases may cause symptoms of progressive nerve compression on a chronic basis, in some cases, they may present with acute onset symptoms. 77 years old female patient without known history of any rheumatic and chronic diseases was admitted to our clinic with pain and numbness. After physical examination and further interventions, surgery was performed with a pre-diagnosis of acute carpal tunnel syndrome. The patient was referred to the rheumatology department when the pathological examination of the samples taken during surgery was consistent with pseudogout

Temas Probleminin Sonlu Elemanlar Yöntemi Ile 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 çalışmada, düzgün yayılı yük ile yüklenmiş ve yarım düzleme oturan elastik iki tabakanın temas problemi sonlu elemanlar yöntemi kullanılarak çözülmüştür. Çözümde tabakaların kütle kuvvetleri ihmal edilmiştir. Problem düzlem hal için incelendiğinden z ekseni doğrultusundaki kalınlık birim olarak alınmıştır. Problemin sonlu eleman modeli ANSYS paket programı kullanılarak oluşturulmuş ve iki boyutlu analizi yapılmıştır. Çeşitli boyutsuz büyüklükler için normal gerilmeler elde edilmiş ve bulunan sonuçlar literatürdeki analitik sonuçlarla karşılaştırılarak doğrulanmıştır.In this paper, a contact problem for two elastic layers resting on a elastic half plane and loaded by uniformly distributed load is solved using finite element method. Body forces of elastic layers are neglected in the problem. Thickness in z-direction is taken to be unit. The finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. By reason of the fact that maximum value of the normal stress is on the symmetry axis, x and y stresses on the symmetry axis are determined for various dimensionless quantities. Finally, the results obtained from finite element method are verified by comparison with the analytical results

Proximal tibiofibular joint arthrodesis due to recurrent giant ganglion cyst causing peroneal nerve palsy

Ganglion cysts are masses that we encounter frequently in our daily practice, usually in the upper extremity, less frequently in the lower extremities, and rarely cause compression symptoms. We present a case of a massive ganglion cyst of the lower limb causing peroneal nerve compression, managed with excision and proximal tibiofibular joint arthrodesis to prevent recurrence.Examination and radiological imaging of a 45-year-old female patient who was admitted to our clinic showed new-onset weakness in right foot movements and numbness on the dorsum of the foot and lateral cruris, a mass consistent with a ganglion cyst expanding the muscle was detected in the peroneus longus muscle. In the first surgery, the cyst was carefully resected. After three months, the patient came with a repeated mass on the lateral side of the knee. After confirmation of the ganglion cyst with clinical examination and MRI, a second surgery was planned for the patient. In this stage, we performed a proximal tibiofibular arthrodesis for the patient. Her symptoms recovered during the early follow-up period and no recurrence occurred during the two years of the follow-up period.Although the treatment of ganglion cysts seems easy, it can sometimes be challenging. We think that arthrodesis may be a good treatment option in recurrent cases

The use of external fixator and iliac crest bone graft in traumatic metacarpal bone defect

Introduction: Metacarpal bone fractures often lead to significant shortening in the phalanges; it can be caused by variable conditions, ranging from idiopathic, and infective to traumatic causes. There are very rare reports of metacarpals shortening in idiopathic primary hypoparathyroidism cases in the literature. Traumatic metacarpal shortening differs from congenital agenesis [2]. This condition leads to both functional and cosmetic limitations which affect the patient's quality of life. Case report: A 22-year-old male patient was admitted to our outpatient clinic with a traumatic left-hand fracture that caused a bone defect in the second metacarpal shaft leading to bone loss, shortening and flexion limitation in the second finger of the left hand, and a flexion contracture in the first metacarpophalangeal joint. For the treatment plan, an external fixator was set on the second metacarpal of the left hand for a 23 mm elongation over a period of 58 days, elongation rate was organized as 1 mm/day. After achieving the planned elongation, another operation was planned for the reconstruction of the bone defect that has occurred due to trauma in the second metacarpal bone. An osteotomy was performed for extracting an iliac crest graft and inserting it into the bone defect after debridement of scar tissue. For the first metacarpophalangeal joint, an arthrodesis was performed through the use of plate and screws. Multiple studies have showed a common complication of pin tract infections, which were controlled with oral antibiotics and local wound care [10, 11]. Proper alignment and union were achieved with early, stable fracture fixation of low-velocity gunshot wounds of the metacarpal. With early rehabilitation, treatment was provided without an increase in morbidity. [11]. Conclusion: It is possible to obtain acceptable surgical results when the method of fixation of the defect with autograft is used after lengthening with external fixator in pseudoarthrosis with metacarpal defect

Examining the contact problem of a functionally graded layer supported by an elastic half-plane with the analytical and numerical methods

This study offers a comparative study of the analytical and numerical methods for investigating a contact problem. The contact problem comprises a functionally graded layer supported by a half-plane and loaded with a distributed load from the top surface. First, the analytical and numerical solutions to the problem are acquired by utilizing a theory of elasticity and finite element method, respectively. The problem is transformed into a system of integral equations in which the contact stress is an unknown function. The solution of the integral equation was achieved with Gauss–Jacobi integration formulation. The finite element model of the problem is created using ANSYS software, and the two-dimensional analysis of the problem is performed. Results were obtained from the samples for different material properties and loading conditions. The distributed load width and non-homogeneity parameters significantly impact on contact mechanics. The results indicate that the contact area and the contact stress obtained from finite element method (FEM) are close to the analytical results. As a result, acceptable error rates were obtained. Finally, this study provides evidence of a good agreement between the two methods

False negative effect of high triglycerides concentration on vitamin D levels: A big data study

Background: Inaccurate test results may be a reason why vitamin D deficiency is seen as a common problem worldwide. Interferences from the sample matrix during testing are the most important factors in measurement errors. In this study, the relationship between triglycerides and total cholesterol levels and vitamin D levels in Turkey was investigated. Methods: The 25-hydroxyvitamin D test results and lipid test results studied in Turkey in 2021 were compared. Data were obtained from the Ministry of Health National Health Database. Simultaneously, 25-hydroxyvitamin D, triglyceride, and total cholesterol levels were studied, and 1,135,644 test results were taken as the basis. Results: In the group of patients with total cholesterol levels between 0-10.33 mmol/L, the proportion of patients below 20 mg/L ranged from 56.8% to 61.8%. In the patient group with cholesterol between 10.36-259 mmol/L, the rate of patients with less than 20 mg/L was between 70.8-100%, while the rate of patients with cholesterol above 100 mg/L was 0%. The mean 25-hydroxyvitamin D level was 20.1 mg/L in the patient group with a total cholesterol level between 0-10.33 mmol/L, and 16 mg/L in the patient group with a cholesterol level above 10.36 mmol/L. The mean 25-hydroxyvitamin D level was 20.11 mg/L in the patient group with triglycerides 0-10.16 mmol/L, and the 25-hydroxyvitamin D level was 12.28 mg/L in the patient group with triglycerides 10.17-113 mmol/L. The proportion of patients with vitamin D levels above 100 mg/L was found to be 0% in the group of patients with triglycerides above 10.17-113 mmol/L. Conclusions: According to this study, there is a risk of toxicity when administering vitamin D therapy in patients with high cholesterol and triglycerides levels. This study is the first of this size in the literature. High triglycerides and cholesterol levels can cause inaccurate measurement of vitamin D levels, so care should be taken when evaluating these tests

The effect of vitamin D status on non-alcoholic fatty liver disease: a population-based observational study

Introduction: The effect of vitamin D status on steatosis has not been fully elucidated. In this study, we planned to investigate this interaction using a large-scale population-based cohort. Material and methods: Patients diagnosed with simple steatosis (K76.0) and non-alcoholic steatohepatitis (NASH) (K75.8) by using the International Classification of Diseases 10th Revision (ICD-10) coding system, and who had 25-hydroxyvitamin D (25OHD) measurements at the diagnosis, were included in the study. Control group comprised subjects without liver diseases. Age, gender, alanine aminotransferase (ALT) and 25OHD levels, and the date of the measurements were recorded. Results: We compared ALT and 25OHD measurements between the patient and control groups, and between the simple steatosis and NASH subgroups. 25OHD levels were lower and ALT levels were higher in the patient group (p < 0.001, effect size = 0.028, and p < 0.001, effect size = 0.442, respectively). Logistic regression analysis showed that when 25OHD levels decrease by 1 ng/dL, it increases the risk of being in the patient group by 3.7%. Conclusion: Our results suggest that vitamin D status may be related to the development of non-alcoholic fatty liver disease (NAFLD). Although this relationship is weak, it may be important in the pathogenesis of steatosis

Perceptual Approaches in Image and Video Analysis

Recent advances in digital technology enabled the use of multimedia in various fields of our lives. Education, health, security, entertainment, business and many other sectors started using all kinds of multimedia material for their benefits to provide better services. In order to utilize the full potential of such material and enable their effective consumption in those areas, accurate analysis and understanding of the multimedia content is essential. Content based multimedia analysis aims to provide this insight through various computer algorithms and extract relevant information to support different fields. When designing such algorithms, in order to lead to practical solutions, it is essential to keep in mind that both performance and efficiency are of significant importance. Considering the fact that humans have remarkable ability in analyzing visual content, this thesis presents algorithms for image and video analysis by taking the perspective of human visual perception.The algorithms presented in this thesis follow the perceptual rules proposed by Gestalt Psychology, which suggests that our perceptions are based on the emergent properties that result from the organization of individual percepts. Such a stance is often overlooked – if not ignored – in content analysis algorithms, and the offered solutions are generally based on analyzing individual components only. This typically results in either inadequate or overcomplicated solutions. By following the perceptual organization rules defined by Gestalt Psychology, it has been shown in this thesis that content analysis can be performed in a significantly more efficient and effective manner. These improvements are revealed in miscellaneous topics, such as color content description, image segmentation, object recognition and video shot change detection.The main contribution of this thesis is to demonstrate the significance of taking a perceptual standpoint in image and video content analysis. This significance can be examined through the benefits it brings in, namely the improvements in performance and efficiency. Performance improvements in this thesis are realized in the aforementioned fields, specifically by attaining more accurate characterization of the color composition of an image, more precise segmentation of the objects, higher accuracy in recognizing objects and higher accuracy in detecting shot boundaries in a video. Achieving such improvements via simple and lightweight algorithms without over complicating or over engineering the underlying problem proves the efficiency of the proposed algorithms. Algorithms presented in this thesis are evaluated according to both criteria, i.e. performance and efficiency, and it will be shown in the thesis that they achieve exceptional results when compared to the state of the art. In other words, describing the color content of an image, segmenting an image into meaningful objects, recognizing objects and detecting shot changes in a video are all successfully accomplished with minimal effort – just as we humans perform such tasks