Değişken Kalınlıklı Dönel Simetrik Dairesel Plakların Doğrusal Olmayan Analizi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Değişken kalınlıklı dönel simetrik dairesel plakların geometrik doğrusal olmayan eğilme analizi sayısal olarak yapıldı. Çevresi boyunca ankastre dairesel plağın düzgün yayılı transvers yük altındaki davranışı incelendi. Plak malzemesinin homojen ve izotrop olduğu kabul edildi. Sayısal hesaplarda kullanılan sıradan (adi) diferansiyel denklem takımının çözümü için sonlu farklar ve Newton-Raphson yöntemleri kullanıldı. Plak kalınlığının sabit ve değişken olması durumları incelenerek orta noktadaki çökme değeri için literatürdeki değerlerle karşılaştırma yapıldı.Geometrically nonlinear analysis of axisymmetric circular plates of variable thickness was made numerically. Clamped circular plate under uniform transverse pressure was investigated. The material of the plate was assumed to be homogeneous and isotropic. Finite difference and Newton-Raphson methods were used to solve the system of ordinary differential equations. The central deflection of the plate was compared with the solutions in the literature for both uniform and varying thickness

İlkel Kusurlu Dairesel Plakların Geometrik Doğrusal Olmayan Analizi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2008Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2008Bu çalışmada doğrusal değişen dönel simetrik yük etkisindeki ilkel kusurlu dairesel plakların geometrik doğrusal olmayan analizi sayısal yöntemlerle incelenmiştir. Sabit kalınlıklı dairesel plağın modellemesinde sığ küresel kabuk denklemleri kullanılmıştır. Doğrusal olmayan formdaki sıradan diferansiyel denklemler sonlu farklar yöntemiyle cebirsel denklemlere dönüştürülmüş, doğrusal olmayan yapıdaki cebirsel denklemler de Newton- Raphson yöntemiyle çözülmüştür. Plak kenarı boyunca ankastre (A) ve sabit (S) mesnetlenme durumları incelenmiştir. Yer değiştirme ve kesit tesirlerinin plak üzerindeki dağılımında, ilkel kusur parametresinin ve Poisson oranının etkisi incelenmiştir. Bu çalışmada elde edilen bulgular, Kirchhoff-Love plak teorisinin (KLPT) baz alındığı kusursuz dairesel plakların incelendiği çalışmalarla karşılaştırılmış ve uyumlu sonuçlar elde edildiği görülmüştür.Geometrically nonlinear analysis of initially imperfect circular plates subjected to a linearly varying axisymmetrical load was investigated in this study by numerical methods. Shallow spherical shell equations were used in the modelling of the circular plate of uniform thickness. By the finite difference method, nonlinear ordinary differential equations were transformed to nonlinear algebraical equations which were solved by the Newton-Raphson method. Two cases were considered: clamped (A), and simply supported (S) along the plate perimeter. The influence of the parameter of initial imperfection and the Poisson’s ratio on displacements and stress resultants was examined. The results obtained in this study were compared with those based on the Kirchhoff-Love plate theory (KLPT), and good agreement was obtained

Sığ Küresel Kabukların Doğrusal Olmayan 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 dairesel sığ küresel kabukların geometrik doğrusal olmayan eğilme analizi sayısal olarak yapılmaktadır. Enine kayma şekil değiştirmesinin göz önüne alındığı çalışmada kabuk malzemesinin homojen ve izotrop olduğu kabul edilmektedir. Ankastre veya basit mesnetli olmak üzere iki mesnetlenme hali araştırılmaktadır. Kabuk kalınlığı sabittir. Dönel simetrik düzgün yayılı dış basınç altında konik açısının, kabuk kalınlığının ve yükleme bölgesi parametresinin çökme ve kesit tesirleri üzerindeki etkileri araştırılmaktadır. Analiz sonlu farklar yöntemiyle yapılmaktadır. Doğrusal olmayan cebirsel denklemlerin çözümünde Newton-Raphson yöntemi kullanılmaktadır.Geometrically nonlinear bending of circular shallow spherical shells is investigated numerically. Transverse shear deformation is considered in the study. Material of the shell is assumed homogeneous and isotropic. Clamped or simply supported shells are examined. The thickness of the shell is uniform. The influences of the conical angel, the thickness of the shell, and the parameter of loading zone on the deflection and on the stress resultants are studied. The analysis is made by means of the finite difference method. Newton-Raphson method is employed in the solution of the nonlinear algebraic equations

Profit-oriented disassembly-line balancing

As product and material recovery has gained importance, disassembly volumes have increased, justifying construction of disassembly lines similar to assembly lines. Recent research on disassembly lines has focused on complete disassembly. Unlike assembly, the current industry practice involves partial disassembly with profit-maximization or cost-minimization objectives. Another difference between assembly and disassembly is that disassembly involves additional precedence relations among tasks due to processing alternatives or physical restrictions. In this study, we define and solve the profit-oriented partial disassembly-line balancing problem. We first characterize different types of precedence relations in disassembly and propose a new representation scheme that encompasses all these types. We then develop the first mixed integer programming formulation for the partial disassembly-line balancing problem, which simultaneously determines (1) the parts whose demand is to be fulfilled to generate revenue, (2) the tasks that will release the selected parts under task and station costs, (3) the number of stations that will be opened, (4) the cycle time, and (5) the balance of the disassembly line, i.e. the feasible assignment of selected tasks to stations such that various types of precedence relations are satisfied. We propose a lower and upper-bounding scheme based on linear programming relaxation of the formulation. Computational results show that our approach provides near optimal solutions for small problems and is capable of solving larger problems with up to 320 disassembly tasks in reasonable time

Acquired QT interval prolongation and ventricular arythmias associated with brucellosis: A case report and review of literature

SummaryBrucellosis is a zoonosis caused by Brucella species and usually involves the lymphoreticular system. Cardiovascular involvement is rare but fatal. Endocarditis is the most common cardiovascular manifestation of brucellosis. Herein we report a case of brucellosis with a presentation of acquired QT prolongation and ventricular tachycardia without a clear clinical picture of endocarditis and myocarditis

Determination of right ventricular dysfunction using the speckle tracking echocardiography method in patients with obstructive sleep apnea

Background: The speckle tracking echocardiography (STE) method shows the presence of right ventricular (RV) dysfunction before the advent of RV failure and pulmonary hypertension in patients with cardiopulmonary disease. We aimed to assess subclinical RV dysfunction in obstructive sleep apnea (OSA) using the STE method. Method: Twenty-one healthy individuals and 58 OSA patients were included. According to severity as determined by the apnea&#8211;hypopnea index (AHI), OSA patients were examined in three groups: mild, moderate and severe. RV free wall was used in STE examination. Results: Right ventricle strain (ST %) and systolic strain rate (STR-S 1/s) were decreasing along with the disease severity (ST &#8212; healthy: &#8211;34.05 &#177; &#8211;4.29; mild: &#8211;31.4 &#177; &#8211;5.37; moderate: &#8211;22.75 &#177; &#8211;4.89; severe: &#8211;20.89 &#177; &#8211;5.59; p < 0.003; STR-S &#8212; healthy: &#8211;2.93 &#177; &#8211;0.64; mild: &#8211;2.85 &#177; &#8211;0.73; moderate: &#8211;2.06 &#177; &#8211;0.43; severe: &#8211;1.43 &#177; &#8211;0.33; p < 0.03). Correlated with the disease severity, the RV early diastolic strain rate (STR-E) was decreasing and the late diastolic strain rate was increasing (STR-E &#8212; healthy: 2.38 &#177; 0.63; mild: 2.32 &#177; 0.84; moderate: 1.66 &#177; 0.55; severe: 1 &#177; 0.54; p < 0.003; STR-A &#8212; healthy: 2.25 &#177; 0.33; mild: 2.32 &#177; 0.54; moderate: 2.79 &#177; 0.66; severe: 3.29 &#177; 0.54; p < 0.03). The STR-E/A ratio was found to be in a decreasing trend along with the disease severity (healthy: 1.08 &#177; 0.34; mild: 1.06 &#177; 0.46; moderate: 0.62 &#177; 0.22; severe: 0.34 &#177; 0.23; p < 0.03). Conclusions: Subclinical RV dysfunction can be established in OSA patients even in the absence of pulmonary hypertension and pathologies which could have adverse effects on RV functions. In addition to the methods of conventional, Doppler and tissue Doppler echocardiography, using the STE method can determine RV dysfunction in the subclinical phase. (Cardiol J 2012; 19, 2: 130&#8211;139

Temperature-dependent nonlinear analysis of shallow shells: A theoretical approach

The paper presents a theoretical formulation for the computation of temperature-dependent nonlinear response of shallow shells with single and double curvatures subjected to transverse mechanical loads while being exposed to through-depth non-uniform heating regimes such as those resulting from a fire. The material nonlinearity arises from taking into consideration the degradation of the material elastic behaviour at elevated temperatures under quasi-static conditions. Two types of boundary conditions are considered, both of which constrain the transverse deflections and allow the rotations about the edge axis to be free. One of the boundary conditions permits lateral translation (laterally unrestrained) and the other one does not (laterally restrained). A number of examples are solved for shallow shells under different types of loading conditions including: an exponential "short hot" fire leading to a high temperature over a relatively short duration; and an exponential "long cool" fire of lower temperature over a longer duration. The limits of the shallow shell equations are investigated through comparison studies. Results show that while current numerical approaches for analysis of laterally restrained shallow shells are often computationally intensive, the proposed approach offers an adequate level of accuracy with a rapid convergence rate for such structures.The Edinburgh Research Partnership in Engineering (ERPE)

C-REACTIVE PROTEIN LEVELS IN OBSTRUCTIVE SLEEP APNEA PATIENTS

Amaç: Obstrüktif Uyku Apne Sendromu (OUAS)'u olan hastalarda C-Reaktif Protein (CRP)'in erken ateroskleozun saptanmasında kullanılması. Yöntemler: Çalışmaya Dokuz Eylül Üniversitesi Tıp Fakültesi uyku bozukluğu polikliniğine başvuran, yaşları 20-66 arasında olan toplam 45 obez hasta alındı. Hastaların cinsiyet, yaş, boy, kilo değerleri saptandı. Vücut kitle indeksleri, bel / kalça oranları hesaplandı. Polisomnografi tetkiki yapıldı. OUAS'u olan hasta grubu ve OUAS'u olmayan kontrol grubu olarak iki gruba ayrıldı. Her iki grup hastadan açlık venöz kan örneği alınarak yüksek duyarlılıklı CRP düzeyleri ve lipid profilleri çalışıldı. B-mode dopler ultrasonografiyle karotis intima madia kalınlıkları ölçüldü. Bulgular: Kontrol grubunda yd-CRP düzeyleri 0,22 (0,01-0,57) mg/dl, OUAS'lı hasta grubundaysa 0,30 (0,05-1,52) mg/dl olarak bulundu, iki grup arasında istatiksel olarak anlamlı fark saptanmadı (p=0,300). Karotis İntima Media Kalınlığı (KİMK) ölçümleri değerlendirildiğinde her iki grup arasında istatistiksel olarak anlamlı fark saptandı (p=0,01). Bel / kalça oranları belirlenip, abdominal obezite açısından değerlendirildiğinde iki grup arasında istatistiksel olarak anlamlı fark gözlendi (p&lt;0,01). AKŞ, TK ve LDL-K düzeylerinde de anlamlı fark saptandı (p=0,049, p=0,01 ve p=0,03). Sonuç: OUAS'lı hastalarda abdominal obezite, AKŞ, TK ve LDL-K düzeylerinde istatistiksel olarak anlamlı fark saptanması OUAS metabolik sendrom ilişkisi için varolan kanıtları doğruladı. Bununla birlikte, ölçülen CRP düzeylerinin OUAS'u hastalarında erken aterosklerozun gösterilmesinde iyi bir gösterge olmayabileceği belirlendi. Objective: To determine whether CRP can detect subclinic atherosclerosis in obstructive sleep apnea patients. Methods: Ages between 20-66, 45 obese patient who was have application to D.E.Ü. Medical Faculty sleep laboratory recruited to study. We determine sex, age, height and weight for all patients and calculate body mass index, waist / hip raito. Polisomnographia was done. Patient's divided in to two group's, whose PSG detected OSA constitute patients group and whose PSG not detected OSA constitude control group. We obtained fasting venous blood sample and measure HSCRP and lipid profiles. Carotis intima media thickness measured with B-mode doppler ultrasonography. Results: HSCRP found 0,22 (0,01-0,57) mg/dl in control group and 0,30 (0,05-1,52) mg/dl in OSA patients group, we didn't detect statistical significancy (p=0,300). When Carotid İntima Media Thickness (CIMT) measurements evaluated for each group, statistical significancy find (p=0,01). WHR determined and evaluated for abdominal obesity, statistical significancy found between two group (p&lt;0,01). Also significant differece detected for FBG, TK and LDL-K (p=0,049, p=0,01 and p=0,03). Conclusion: Detected significant difference for abdominal obesity, FBG, TK and LDL-K levels in OSA patients confirmed existing evidence of relation eith sleep apnea and metabolic syndrome. Although we determined, measured HSCRP levels may not be a good marker for presenting subclinic atherosclerosis in OSA patients