Mikrokanal İçinde Parçacık Hareketinin Sınır Eleman Yöntemi İle Analizi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2013Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2013Bir mikrokanal içinde akışkanın hareketi ile birlikte parçacık hareketinin modellenmesi, özellikle son dönemlerde çip-üstü-laboratuar teknolojilerindeki gelişme ve yeniliklere paralel olarak, giderek daha fazla önem kazanmaktadır. Özellikle birden fazla parçacığın birbirleri ile etkileşimli olarak hareketlerinin modellenmesi, deneme yanılma ile yapılması çok zor olan bazı özel tasarımların ortaya çıkmasını sağlayabilmektedir. Ancak, özellikle sonlu eleman yöntemi ve benzeri çözüm bölgesini hacimsel olarak ayrıklaştıran sayısal yöntemler ile çözüm, özellikle de birden fazla parçacığın hareketi söz konusu olduğunda, oldukça zor olmaktadır. Bu çalışmanın temel amacı, mikrokanal içinde hareket eden akışkanın içinde yüzer parçacıkların hareketinin sınır eleman yöntemi ile modellenmesidir. Sınır eleman yönteminin sadece sınır bölgesini ayrıklaştıran yapısı dolayısı ile modelleme hem kolaylaşmakta hem de parçacık hareketi sırasında tekrar ayrıklaştırma işlemi çok daha basit olarak yapılabilmektedir. Aynı zamanda, çözüm bölgesi içi ayrıklaştırılmadığından dolayı ve çözüm bölgesi içinde bünye denklemleri sayısal değil, analitik olarak karşılanıyor olması dolayısı ile tekrar ayrıklaştırma işlemi sırasında bir sayısal kayıp söz konusu olmamaktadır. Oluşturulan formülasyon, parçacık hareketini modellemeye yöneliktir. Parçacık hareketi, sınır koşullarında hareketi tanımlamaya yönelik değişikliklerin tanımlanması ile doğrudan parçacığın ağırlık merkezinin hızı cinsinden elde edilmekte ve elde edilen hızdan açık adım (explicit) ile zaman integrasyonu kullanılarak parçacık yörüngesi belirlenmektedir. Formülasyon iki boyutta elde edilmiştir; ancak üç boyuta kolaylıkla uygulanabilir. Parçacık şeklinin herhangi bir önemi olmamakla birlikte, uygulama problemlerinde (parametrik olarak ifade edilmeleri daha kolay olması dolayısı ile) sadece dairesel ve elips geometriler kullanılmıştır. Çözülen örnekler yapılan formülasyonun, en azından iki boyutlu problemler söz konusu olduğunda, oldukça iyi sonuçlar verdiğini göstermektedir. Anahtar kelimeler: mikro-akışkanlar-dinamiği, Stokes denklemi, sınır eleman yöntemi, parçacık hareket

Computational Modeling of Vehicle Radiators Using Porous Medium Approach

A common tool for the determination of thermal characteristics of vehicle radiators is the experimental testing. However, experimental testing may not be feasible considering the cost and labor-time. Basic understanding of the past experimental data and analytical/computational modeling can significantly enhance the effectiveness of the design and development phase. One such computational modeling technique is the utilization of computational fluid dynamics (CFD) analysis to predict the thermal characteristics of a vehicle radiator. However, CFD models are also not suitable to be used as a design tool since considerable amount of computational power and time is required due to the multiple length scales involved in the problem, especially the small-scale geometric details associated with the fins. Although fins introduce a significant complexity for the problem, the repetitive and/or regular structure of the fins enables the porous medium based modeling. By porous modeling, a memory and time efficient computational model can be developed and implemented as an efficient design tool for radiators. In this work, a computational methodology is described to obtain the hydrodynamic and thermal characteristics of a vehicle radiator. Although the proposed methodology is discussed in the context of a vehicle radiator, the proposed methodology can be implemented to any compact heat exchanger with repetitive fin structures which is an important problem for many industrial applications

Interplay of transport mechanisms during the evaporation of a pinned sessile water droplet

Droplet evaporation has been intensively investigated in past decades owing to its emerging applications in diverse fields of science and technology. Yet the role of transport mechanisms has been the subject of a heated debate, especially the presence of Marangoni flow in water droplets. This work aims to draw a clear picture of the switching transport mechanisms inside a drying pinned sessile water droplet in both the presence and absence of thermocapillarity by developing a comprehensive model that accounts for all pertinent physics in both phases as well as interfacial phenomena at the interface. The model reveals a hitherto unexplored mixed radial and buoyant flow by shedding light on the transition from buoyancy induced Rayleigh flow to the radial flow causing the coffee ring effect. Predictions of the model excellently match previous experimental results across varying substrate temperatures only in the absence of Marangoni flow. When thermocapillarity is accounted for, strong surface flows shape the liquid velocity field during most of the droplet lifetime and the model starts to overestimate evaporation rates with increasing substrate temperature

The Moss Flora of Akdağ Mountain (Amasya, Turkey)

The moss flora of Akdağ Mountain (Amasya, Turkey) was investigated. At the result of identifications of 1500 moss specimens, collected from the research area, 178 taxa belonging to 69 genera and 26 families were determined. Among them, 94 taxa are new for A3 grid square according to the Turkey grid system which was adopted by Henderson. The location data of Grimmia crinitoleucophaea Cardot and Barbula enderesii Garov. are the first records for Turkey, and Encalypta spathulata Müll. Hal., Schistidium dupretii (Thér.) W. A. Weber, Weissia condensa var. armata (Thér. & Trab.) M. J. Cano, Ros & J. Guerra, Tortella bambergeri (Schimp.), Barbula enderesii Garov., Hedwigia ciliata var. leucophaea Bruch & Schimp., and Campyliadelphus elodes (Lindb.) Kanda are recorded for the second time to the byroflora of Turkey

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

The effect of three different sets method used in resistance training on hypertrophy and maximal strength changes

Background and Study Aim. To compare the effects of three different sets method, which is frequently used in resistance training, on strength and hypertrophy values. Materials and Methods. Thirty-three young male athletes with similar daily activities and nutrient intakes at the Fitlife fitness center in Sakarya were included in the study. Participants were randomly divided into three different groups as Modified German Volume Training (MGVT) (n=11, 21.5 ± 2.4 years), Super Set (SS) (n=11, 22.4 ± 2.9) and Giant Set (GS) (n=11, 23.0 ± 4.3 years). The study was started with a total of thirty-three people, but two participants in the Giant set group were excluded from the measurements because they left the study due to personal reasons. Strength, muscle thickness and cross-sectional area (CSA) measurements were made in the upper extremity muscles before and after the six-week training period.    Results. After six weeks of training, significant increases were observed in the cross-sectional area and thickness (p0,05).   Conclusions. Modified German Volume Training (MGVT), Super Set (SS) and Giant Set (GS) methods reveal that there is no difference between the set methods in the 1 Repetition Maximum (1RM) strength and hypertrophy development of young male individuals who do not have a history of resistance exercise but have completed the adaptation period, and that there is an improvement in all set methods

FIRTINA VADİSİ (ÇAMLIHEMŞİN, RİZE) Buxus sempervırens L. TOPLUMLARININ YAYILIŞ GÖSTERDİĞİ ALANLARIN KARAYOSUNU (MUSCI) FLORASI

Kaçkar Dağları’nın kuzey yamaçlarında yer alan Fırtına Vadisi’nde Buxus sempervirens L.’in saf veya diğer bazı odunsu taksonlarla oluşturduğu meşcerelerdeki karayosunu (musci) florası araştırılmıştır. 2005 yılı Haziran ve Ağustos aylarında toplanan karayosunu örneklerinin değerlendirilmesi sonucunda 18 familya ve 34 cinse ait 47 takson tespit edilmiştir. Araştırma alanında bulunan karayosunlarından 6 tanesi ( Tetraphis pellucida Hedw., Dicranoweisia crispula (Hedw.) Milde, Dicranodontium denudatum (Brid.) E.Britton var. denudatum, Oncophorus virens (Hedw.) Brid., Pseudoleskeella nervosa (Brid.) Nyholm, Eurhynchium schleicheri (R.Hedw.) Jur.) Henderson (1961) tarafından uygulanan Türkiye kareleme sistemine göre A4 karesi için yeni kayıttır. Araştırma alanında içerdiği takson sayısı en yüksek olan ilk 5 familya; Dicranaceae (7), Hypnaceae (6), Brachytheciaceae (5), Mniaceae (5), Polytrichaceae (4) dir. İçerdiği takson sayısı en yüksek olan cinsler ise Plagiomnium (4), Polytrichum (3), Hypnum (3) dur. Araştırma alanından toplanan karayosunu örneklerinin yaşam formları, tercih ettikleri substrat ve nemlilik gibi ekolojik özellikleri Dierßen (2001)’e göre ve yaşam formlarına ait bilgiler de Mägdefrau (1982)’ye göre düzenlenmiş olup, bu bilgilerin ışığında taksonların ekolojik tercihleri ele alınmıştır. Anahtar Kelimeler: Fırtına Vadisi, Buxus sempervirens, Karayosunu florası, Rize

Reliability and validity of the multi-point method and the 2-point method's variations of estimating the one-repetition maximum for deadlift and back squat exercises

This study aimed at examining the concurrent validity and reliability of the multi-point method and the two-point method's variations for estimating the one-repetition maximum (1RM) in the deadlift and squat exercises and to determine the accuracy of which optimal two loads can be used for the two-point method protocol. Thirteen resistance-trained men performed six sessions that consisted of two incremental loading tests (multi-point method: 20-40-60-80-90% and two-point method variations: 40-60%, 40-80%, 40-90%,60-80%, 60-90%) followed by 1RM tests. Both the multi-point method and the two-point method load variations showed reliable results for 1RM estimation (CV < 10%) squat and deadlift exercises. Session-session reliability was found to be low in deadlift (ICC: 0.171-0.335) and squat exercises (ICC: 0.235-0.479) of 40-60% and 60-80% in two-point methods. Deadlift (ICC: 0.815-0.996) and squat (ICC: 0.817-0.988) had high session-to-session reliability in all other methods. Regarding the validity of deadlift exercise, the multipoint method (R2 = 0.864) and two variations of the two-point method (R2 = 0.816 for 40-80%, R2 = 0.732 for 60-80%) showed very large correlations, whereas other two variations of the two-point method (R2 = 0.945 for 40-90%, R2 = 0.914 for 60-90%) showed almost perfect correlations with the actual 1RM. Regarding the validity of squat exercise, the multi-point method (R2 = 0.773) and two variations of the two-point method (R2 = 0.0847 for 60-80%, R2 = 0.705 for 40-90%) showed very large correlations, whereas 40-60% variation showed almost perfect correlation (R2 = 0.962) with the actual 1RM. In conclusion, whereas both the multi-point method and the two-point method load variations showed reliable results, the multiple-point method and most of the two-point methods' load variations examined in this research provided an accurate (from large-moderate to perfect) estimate of the 1RM. Therefore, we recommend using the multi-point method and especially the two-point methods variations including higher relative loads to estimate 1RM

Oxidative stress of crystalline lens in rat menopausal model

Purpose: To evaluate lenticular oxidative stress in rat menopausal models. Methods: Forty Wistar female albino rats were included in this study. A total of thirty rats underwent oophorectomy to generate a menopausal model. Ten rats that did not undergo oophorectomy formed the control group (Group 1). From the rats that underwent oophorectomy, 10 formed the menopause control group (Group 2), 10 were administered a daily injection of methylprednisolone until the end of the study (Group 3), and the remaining 10 rats were administered intraperitoneal streptozocin to induce diabetes mellitus (Group 4). Total oxidant status (TOS), total antioxidant capacity (TAC), and oxidative stress index (OSI) measurements of the crystalline lenses were analyzed. Results: The mean OSI was the lowest in group 1 and highest in group 4. Nevertheless, the difference between the groups was not statistically significant in terms of OSI (p > 0.05). The mean TOS values were similar between the groups (p > 0.05), whereas the mean TAC of group 1 was significantly higher than that of the other groups (p < 0.001). Conclusions: Our results indicate that menopause may not promote cataract formation