Modeling the Evaporation of Drying Sessile Droplets with Buoyancy Driven Internal Convection

Droplet evaporation is a fundamental phenomenon encountered in diverse applications such as inkjet printing, DNA mapping, film coating, and electronics cooling. Modeling the evaporation process of a sessile droplet is complicated because of the coupling of several physical phenomena occurring in different phases and various magnitudes such as the buoyant convection of the liquid in millimeter size droplets and that of the surrounding air/water vapor mixture, in the order of meters. In this study, the theoretical framework presented previously for the steadily fed droplets [Int J Therm Sci, 158 (2020) 106529] is extended to resolve the evaporation of drying droplets with a pinned contact line. Based on the quasi-steady-state assumption, buoyant convection inside the droplet and diffusive-convective transport of vapor in the gas domain are modeled. As a test case, drying process of a water droplet with a 68° initial contact angle on a heated substrate is simulated and the predictions of the model are interpreted

Increased fat graft survival with mesenchymal stem cell recruiting effect of PRP: in vitro and in vivo study of application techniques

Aim: Adding platelet-rich plasm (PRP) or mesenchymal stem cells are the most accepted methods to increase fat graft’s permanence. However, there is no consensus on timing and whether the effect of stem cells or PRP is observed more in the recipient area or in the donor area. It is aimed to present the application method and localization of PRP to be combined with fat graft to increase the survival. Material and Methods: in vitro part: Fat grafts were kept in a medium containing PRP. Cell output from the fat graft to the Petri dishes was examined every day. The time to recruit the maximum number of stem cells to the medium was determined (day 10). in vivo part: Eight group of rats were received PRP in different concentrations either to recipient or donor areas of fat grafts. After ten days, fat grafts were transferred to the recipient area. Ninety days after the transfer, histopathological examination and immunohistochemical staining were performed. Results: The group which had received the full-dose PRP to the recipient area showed the highest cellular integrity and vascularity (p< 0.05). Vascularity was superior in the half-dose PRP group compared to the control group (p< 0.05); cellular integrity did not increase. Donor site groups did not show increase in cellular integrity. Conclusion: Although PRP starts to increase fat graft permanence by increasing vascularity, it acts by preserving the cellular integrity of the fat cells as the concentrations increase. The PRP injection to the recipient area 10 days before fat grafting may provide higher survival rates

Ağır ticari kamyonlarda kullanılan kampana frenlerin ses ve titreşim analizleri

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2018Includes bibliographical references (leaves: 42-43)Text in English; Abstract: Turkish and EnglishHeavy commercial duty vehicles have been used to for many years. High energy dissipation is required to stop these types of vehicles. Selection of brake type is related with the brake resists to this physical and environment conditions and also comfortability of drivers and passengers. Brake squeal is the most common costumer complaint for brake systems. This problem is main interest and tackled in many ways. In this thesis, vibration characteristics of the heavy commercial duty brake system, which is a drum brake, is studied by Finite Element Method to analyze the brake squeal. Natural frequencies and mode shapes of drum and shoe which are in frictional contact are determined by using ANSYS. Block Lanczos solver is preferred for this analysis. Experimental modal tests are accomplished to compare finite element results with experimental ones. Then, the noise characteristics of the brake system are obtained by performing a series dynamometer tests. In these experiments, four parameters are selected to investigate the decreasing and eliminating the noise. The selected parameters are deceleration rate, pressure, temperature and friction coefficients. The results are presented in tables and graphs.Ağır ticari görev araçları uzun yıllardan beri kullanılmaktadır. Bu tür araçları durdurmak için yüksek enerji dağılımı gereklidir. Fren tipinin seçimi, frenin bu fiziksel ve çevre koşullarına; ayrıca sürücü ve yolcuların konforu ile ilgilidir. Fren sistemleri için fren çığlığı en yaygın müşteri şikayetidir. Bu sorun ana ilgi konusudur ve birçok yönden ele alınmaktadır. Bu tez çalışmasında, tamburlu freni olan ağır ticari fren sisteminin titreşim karakteristikleri, fren çığlığını incelemek için Sonlu Elemanlar Yöntemi ile çalışılmıştır. Sürtünmeli temasta olan tambur ve balataların doğal frekansları ve titreşim şekilleri ANSYS kullanılarak belirlenmştir. Bu analiz için Block Lanczos çözücü tercih edilmiştir. Sonlu eleman sonuçlarını deneysel olanlarla karşılaştırmak için deneysel modal testler gerçekleştirilmiştir. Ardından, fren sisteminin gürültü karakteristikleri bir dizi dynamometer testi yapılarak elde edilmiştir. Bu deneylerde, gürültüyü azaltmak ve ortadan kaldırmak için dört parametre seçilmiştir. Seçilen parametreler yavaşlama hızı, basınç, sıcaklık ve sürtünme katsayılarıdır. Elde edilen sonuçlar tablo ve grafiklerde sunulmuştur

Oluklu bir ısı borusunun kanatçığındaki yoğuşmanın modellenmesinde yeni bir yaklaşım.

Phase-change passive heat spreaders have the capability of carrying large amounts of heat from a heat source to a heat sink creating a small temperature difference. One common type of the passive heat spreaders is the heat pipes. The liquid flow inside a heat pipe is driven by the capillary pressure gradient created by a wick structure on the inner wall, which may be in the form of grooves, sintered grains or wire meshes. In the literature, grooved heat pipes are the most studied ones for modeling and experimentation due to their relatively simple geometry and ease of manufacturing. During the operation of a grooved heat pipe, continuous thin film condensation occurs on the fin top surfaces between two consecutive grooves and the condensate flows into the grooves. Modeling thin film condensation is crucial for an accurate estimation of grooved heat pipe performance. In the current study, a novel approach is developed to model the condensation and associated liquid flow in a fin-groove system. Conservation of mass and momentum equations, augmented Young-Laplace equation and Kucherov-Rikenglaz equation are solved simultaneously to calculate the film thickness profile. Differently from the numerical models in the literature, in this new approach the fin-groove corner is kept inside the solution domain and the effect of disjoining pressure is taken into account. The results reveal that the disjoining pressure may become effective for some cases and creates a textit{slope break} in the free surface of the liquid at the fin-groove corner. The current study presents the first numerical model which resolves the corner region and shows the effect of disjoining pressure on the thin film condensation in a fin-groove system. Furthermore, a parametric study is performed and the effects of geometric and thermophysical parameters on the condensation performance are discussed. Lastly, the thin film condensation in non-perpendicular fin-grooves, where the grooves are not rectangular but have inclined walls, is investigated and the effect of fin-groove corner on the condensation is presented.Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Mechanical Engineering

Ağır ticari kamyonlarda kullanılan kampana frenlerin ses ve titreşim analizleri

Thesis (Master)--Izmir Institute of Technology, Mechanical Engineering, Izmir, 2018Includes bibliographical references (leaves: 42-43)Text in English; Abstract: Turkish and EnglishHeavy commercial duty vehicles have been used to for many years. High energy dissipation is required to stop these types of vehicles. Selection of brake type is related with the brake resists to this physical and environment conditions and also comfortability of drivers and passengers. Brake squeal is the most common costumer complaint for brake systems. This problem is main interest and tackled in many ways. In this thesis, vibration characteristics of the heavy commercial duty brake system, which is a drum brake, is studied by Finite Element Method to analyze the brake squeal. Natural frequencies and mode shapes of drum and shoe which are in frictional contact are determined by using ANSYS. Block Lanczos solver is preferred for this analysis. Experimental modal tests are accomplished to compare finite element results with experimental ones. Then, the noise characteristics of the brake system are obtained by performing a series dynamometer tests. In these experiments, four parameters are selected to investigate the decreasing and eliminating the noise. The selected parameters are deceleration rate, pressure, temperature and friction coefficients. The results are presented in tables and graphs.Ağır ticari görev araçları uzun yıllardan beri kullanılmaktadır. Bu tür araçları durdurmak için yüksek enerji dağılımı gereklidir. Fren tipinin seçimi, frenin bu fiziksel ve çevre koşullarına; ayrıca sürücü ve yolcuların konforu ile ilgilidir. Fren sistemleri için fren çığlığı en yaygın müşteri şikayetidir. Bu sorun ana ilgi konusudur ve birçok yönden ele alınmaktadır. Bu tez çalışmasında, tamburlu freni olan ağır ticari fren sisteminin titreşim karakteristikleri, fren çığlığını incelemek için Sonlu Elemanlar Yöntemi ile çalışılmıştır. Sürtünmeli temasta olan tambur ve balataların doğal frekansları ve titreşim şekilleri ANSYS kullanılarak belirlenmştir. Bu analiz için Block Lanczos çözücü tercih edilmiştir. Sonlu eleman sonuçlarını deneysel olanlarla karşılaştırmak için deneysel modal testler gerçekleştirilmiştir. Ardından, fren sisteminin gürültü karakteristikleri bir dizi dynamometer testi yapılarak elde edilmiştir. Bu deneylerde, gürültüyü azaltmak ve ortadan kaldırmak için dört parametre seçilmiştir. Seçilen parametreler yavaşlama hızı, basınç, sıcaklık ve sürtünme katsayılarıdır. Elde edilen sonuçlar tablo ve grafiklerde sunulmuştur

Obtaining functional vasculer structures by prefabricated tubularized capsule flaps

Teknolojinin gelişmesi ile ortaya çıkan kompleks yaralanmaların başarı ile onarılabilmesi için kompleks rekonstrüktif ameliyatlara gereksinim duyulmaktadır. Eksik olanın benzeri ile onarımı temel prensibi doğrultusunda hastaya özel kompozit dokular oluşturmak ve bunları mikrovasküler cerrahi metotlarla aktarmak mümkündür.Ciddi arter yaralanmaları, fonksiyon açısından yetersiz damarların replasmanı, prefabrike flep cerrahisinde pedikül implantasyonu veya uzatılması gibi durumlarda fonksiyonel vasküler yapılara ihtiyaç duyarız. Günümüzde bu amaçla otojen arter ve ven greftleri ya da sentetik materyaller kullanılmaktadır. Çalışmamızda bu ihtiyacı karşılayabilen kişinin kendi dokusundan elde edilen ve herhangi bir donör alan morbiditesi olmayan fonksiyonel yapılar elde etmeye çalıştık.Çalışmada toplam 30 adet erişkin Yeni Zelanda tavşanı kullanıldı. Tavşanlar 10'arlı 3 gruba ayrıldı. Tavşan femoral arterinde oluşturulacak 2 cmlik defekttin replasmanı için birinci ve ikinci gruplarda tübülarize kapsül flepleri oluşturuldu. Üçüncü gruptaki arter defekti ise juguler venden alınan ven grefti ile onarıldı. Birinci ve ikinci grupta tübülarize kapsül flebi oluşturmak için 3 cm uzunluğunda ve 3 mm çapa sahip yuvarlak şekilli silikon rodlar inguinal bölgeye yerleştirildi. İkinci gruba ek olarak silikon rodun her iki ucuna juguler venden alınan halka şeklinde greftler yerleştirildi. Dördüncü haftanın sonunda oluşan tüp şekilli kapsül flepleri femoral arterde meydana getirilen defektin onarımında kullanıldı. Tüm gruplar patens, akım hızları açısından ki kare testi ve tek yönlü varyans analizi ile değerlendirildi. Her üç grubunda erken ve geç dönem patens oranları ve geç dönem akım hızları arasında istatistiksel olarak anlamlı fark olmadığı gözlendi.Bu yöntemle insanda herhangi bir donör alan morbiditesi olmaksızın ve biyouyumluluğu tam olan ve daha az maliyetli fonksiyonel vasküler yapı elde edilebilecektir. Prefabrike tübülarize kapsül fleplerinin konvansiyonel yöntemlere alternatif olarak vasküler defektlerin onarımında kullanılabileceği gösterilmiştir.Complex reconstructive procedures are required for successful repair of complicated injuries through improvements in technology. It is possible to compose patient specific composite tissues and transfer these tissues with microsurgical methods depending on the basic principle that ?like with like.?We need functional structures in cases such as pedicle implantation or lengthening in prefabricated flap surgery, serious arterial injuries and replacement of functionally insufficient vessels. Recently, autogenous arterial and vein grafts or synthetic materials are used for this purpose. The aim of this study is to produce functional structures that can be obtained from one person?s own self tissue without causing donor site morbidity.We used 30 adult New Zealand rabbit. They are divided into three groups consisting of ten rabbits in each group. In the first and second groups tubularized capsule flaps are formed for the replacement of femoral arterial defect 2 cm in length. The arterial defect in the third group is repaired with vein graft taken from jugular vein. In order to form tubularized capsule flap, round shaped silicon rods which are 3 cm in length and 3 mm in width are placed to the inguinal region. Tube shaped capsule flaps are used in the repair of the defect in the femoral artery at the end of the forth week. All groups are evaluated with Chi- Square Test and One-Way Analysis of Variance for patency and flow velocity. There was no statistically significant factor in early and late phase patency rates and late phase flow velocity in the three groups.By the help of this method it will be possible to obtain functional vascular structures with maximum biocompatibility and minimum cost without causing any donor site morbidity. In this study we showed that prefabricated tubularized capsule flaps can be utilized in repair of vascular defects as an alternative way to conventional methods

Uyumlu sıklaştırılabilen üçgen ağlar üzerinde en küçük kareler spektral eleman yöntemi kullanılarak sıkıştırılamaz akış benzetimleri yapılması..

The main purpose of this study is to develop a flow solver that employs triangular grids to solve two-dimensional, viscous, laminar, steady, incompressible flows. The flow solver is based on Least Squares Spectral Element Method (LSSEM). It has p-type adaptive mesh refinement/coarsening capability and supports p-type nonconforming element interfaces. To validate the developed flow solver several benchmark problems are studied and successful results are obtained. The performances of two different triangular nodal distributions, namely Lobatto distribution and Fekete distribution, are compared in terms of accuracy and implementation complexity. Accuracies provided by triangular and quadrilateral grids of equal computational size are compared. Adaptive mesh refinement studies are conducted using three different error indicators, including a novel one based on elemental mass loss. Effect of modifying the least-squares functional by multiplying the continuity equation by a weight factor is investigated in regards to mass conservation.M.S. - Master of Scienc

Idiopathic scrotal calcinosis: A review of the literature with seven cases

Objective: Scrotal calcinosis is a rare benign disease characterized by calcified nodules on the scrotum skin. In this article, seven patients who were diagnosed as idiopathic scrotal calcinosis were reviewed with the relevant literature. Methods: Seven patients who were operated for scrotal calcinosis between 2007 and 2015 were included in the study. Patients’ age, admission symptoms, accompanying symptoms, duration of symptoms, size and number of masses, type of anesthesia, type of treatment, duration of hospitalization, complications and disease recurrence were evaluated. Results: All patients presented with a painless mass in the scrotum and their ages ranged from 18 to 67 years (mean 34.2 years). The mean time from the onset of the disease to the time of admission was 2.5 years (range, 6 months-9 years). The masses ranged from 2 mm to 40 mm. There were no pathological findings in the systemic examinations except the lesions in the scrotum. One patient was operated under local anesthesia, three patients under spinal anesthesia and three patients under general anesthesia. The patients were removed from follow up at their own request after 12 months. No recurrence was observed during the follow up period. Conclusion: Although there are various theories about the etiology of the disease, its etiology is still controversial and the disease is considered idiopathic