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The Capability Study of Practical Working Fluids in the Desktop-Cpu Cooling System
No full textInternational Symposium on Convective Heat and Mass Transfer (CONV) -- JUN 05-10, 2022 -- Izmir, TURKEYThis work was aimed to investigate the cooling capability of different practical working fluid; deionized water, coolant (ethylene glycol and deionized water), nanofluid (Copper/deionized water and Copper/coolant) in the CPU liquid-cooling system. Three different nanofluid concentrations were applied in both Cu/deionized water and Cu/coolant as 0.86%w/w, 1.71%w/w, and 2.57%w/w. The liquid-cooling system was installed inside a desktop personal computer. The computer was placed in the room controlled in three temperatures: 22, 26 and 30 Celsius. The CPU was controlled to operate at the maximum operation condition by the program; Cinebench R15 trademark, in 1 hour for each experiment, three repeating investigations for each working fluid were conducted. When each working fluid was applied to the cooling system, the values of CPU surface temperatures, the liquid temperatures and electricity consumption were recorded and compared with the original CPU cooling system combining of the heat sink and fan. From the experimental results, the highest average CPU surface temperature occurred at 67.45, 70.72 and 73.80 Celsius, respective;y, when the heat sink and fan were applied, while the original cooling system consumed power at 0.0900 kWh. The liquid cooling system using the 2.57%w/w copper-water nanofluid resulted in the lowest CPU surface temperature at 45.76, 54.40 and 55.26 Celsius, respectively and the average electricity consumption was at 0.0993 kWh. The efficiency information of the CPU cooling system could be used in selecting the appropriate cooling system fluid which decreases the CPU surface temperatures and results in an extended use of the computer.Office of the Ministry of Higher Education, Science, Research and Innovation; Thailand Science Research and Innovation through the Kasetsart University Reinventing University Program; Faculty of Science and Engineering, Kasetsart University, Chalermphrakiat Sakon Nakhon Province CampusThis work was financially supported by the Office of the Ministry of Higher Education, Science, Research and Innovation; and the Thailand Science Research and Innovation through the Kasetsart University Reinventing University Program 2021, as well as the research funding supported by Faculty of Science and Engineering, Kasetsart University, Chalermphrakiat Sakon Nakhon Province Campus. Thank you, all research members, SMART team, as well as, Nattakarn Ladjanthuek, Tanupat Kunasakulpakdee, Paradorn Onnog, Wasin Chatsakunphanit, Witsanu Sittibak, Sahatsawat Chaiyo and Sittiporn Boonsin
Yüksek Hizli Akislarda Asimetrik Üç Boyutlu Sok Tahmin Algoritmasi Gelistirilmesi
No full textShock waves are formed as a result of the combination of disturbances around vehicles moving at supersonic speeds. These waves are generally characterized by sudden and discontinuous changes in pressure, temperature, and density in the medium. CFD applications are frequently used in solving complex problems with strong gradients, such as shock phenomena. Nowadays, one of the main focuses of CFD is to solve complex problems in a minimum amount of time while maintaining the fidelity of the analyses. For supersonic and hypersonic flow problems, an effective way is to generate a suitable computational mesh that is refined and aligned along the strong gradient regions, like the shock waves. In addition, correct prediction of the shock shape is required to use the fast flow prediction methods, which are frequently used in design problems. Therefore, different approaches have been developed in the literature to determine the shock shapes. Some of the common approaches can be presented as analytical equation-based methods that can only be used for simple geometries, methods based on the inverse solution of simplified conservation equations, and mesh adaptation methods based on predetermined solutions. In this study, a faster model than previously defined methods in the literature was developed to accurately predict stationary shock waves around high-speed aircraft without the use of expensive CFD simulation or simulation examination costs. First of all, the validation studies of open-source SU2 v7.1.1 software, which is used in CFD applications, were performed on spherically blunt-nosed geometries at different angles of attack (0, 5, 10.25). Mesh-independent solutions were determined by using Spalart-Allmaras and SST SST k-w turbulence models. As a result of the calculations, it was observed that the CFD results agree well with the experimental data. Two and three-dimensional shock shape prediction algorithms were examined in detail within the scope of the thesis. The 2D shock shape prediction method mainly consists of three parts, which are: detached shock prediction with Billig experimental hyperbola curves; attached shock prediction with analytical shock-expansion equations; and a sonic line correction process using the CFD correction factor. The 3D shock prediction method is basically designed as an application of the 2D methodology on surface streamlines. In order to calculate the surface streamlines, the geometry is expressed with a surface mesh. After that, the free flow velocity is reflected on the surface, and the fluid kinematic equations are solved over the surface mesh. The calculated shock points are expressed as 3D shock geometry, and the shock shape prediction process is complete. Validation studies were performed for 2D and 3D shock shape prediction algorithms. In validation studies, 2D and 3D algorithms were compared with HAD and experimental results using ogive and spherically blunt-nosed geometries. CFD analyses were performed at Mach 5 for ogive and Mach 3, 5, 8 for blunt-nosed geometries. Free stream conditions for analyses were examined at angles of attack of 0, 5, 10 degrees. The shock shape determined from the CFD analysis and the shock geometry obtained as a result of the algorithm were compared using their the vertical distance with respect to the geometry exposed to the flow. As a result of the 2D and 3D investigations, almost no difference was observed in the ogive geometry, while it was observed that the percentage differences increased as the angles of attack increased in the conical geometry comparisons. While the maximum difference was calculated as approximately %1 in 2D validation studies, the difference can increase up to %4 in 3D studies. In addition to the comparison with the CFD calculations, when the 3D shock shape prediction method was compared with the experimental shock shape, it was observed that the errors increase with the angle of attack as determined from the CFD comparisons. The maximum error between the experimental data and the model was calculated as %3.Şok dalgaları, ses üstü hızlarda hareket eden araçlar etrafında bozuntuların birleşimi sonucu oluşmaktadır. Bu dalgalar genelde ortamda ani ve süreksiz basınç, sıcaklık ve yoğunluk değişimleri ile karakterize edilmektedir. HAD uygulamaları şok fenomeni gibi yüksek gradyan barındıran karmaşık problemlerin çözümünde sıklıkla kullanılmaktadır. Günümüzde ise HAD temel odaklarından biri analiz doğruluklarını muhafaza ederek, minimum zamanda karmaşık çözümlemeler yapabilmektir. Bu kapsamda ses üstü hızlar içeren problemlerde en etkili yöntemlerden biri şok fenomeni gibi yüksek gradyan barındıran bölgelerde uygun çözüm ağı boyutunun kullanılması ve çözüm ağının uygun şekilde hizalanmasıdır. Buna ek olarak şok şeklinin doğru tahmini, tasarım problemlerinde sıklıkla kullanılan hızlı akış tahmin metotlarının kullanılabilmesi için gereklidir. Bu doğrultuda literatürde şok şeklinin belirlenmesi amacıyla farklı yaklaşımlar geliştirilmiştir. Yaklaşımlardan bazıları sadece basit geometriler için kullanılabilen analitik denklemler tabanlı yöntemler, basitleştirilmiş korunum denklemlerinin tersine çözümüne dayalı yöntemler ve önceden belirlenmiş çözümlere dayalı çözüm ağı adaptasyonu yöntemleri olarak örneklendirilebilir. Bu tez çalışması, herhangi bir pahalı HAD simülasyonu ve inceleme maliyeti olmadan, yüksek hızlı hava araçları etrafında durağan şok dalgalarını doğru ve literatürde tanımlı yöntemlerden daha hızlı tahmin edebilecek bir model oluşturulmasını amaçlamaktadır. Çalışmalar kapsamında öncelikle HAD uygulamalarında kullanılan açık kaynaklı SU2 v7.1.1 yazılımı doğrulama çalışmaları, küresel küt burunlu geometriler üzerinde farklı hücum açılarında (0, 5, 10.25) yapılmıştır. Spalart-Allmaras ve SST k-w türbülans modelleri kullanılarak, çözüm ağından bağımsız sonuçlar elde edilmiştir. Hesaplamalar sonucunda analiz sonuçlarının deneysel veriler ile uyumlu olduğu gözlemlenmiştir. İki ve üç boyutlu şok şekli tahmin algoritmaları tez kapsamında detaylı olarak incelenmiştir. 2B şok şekli tahmin yöntemi temel olarak Billig deneysel hiperbol eğrileri ile ayrık şok tahmini, analitik şok-genişleme denklemleri ile bitişik şok tahmini ve HAD düzeltme faktörü kullanımı ile sonik çizgi ve Mach dalgaları düzeltme işlemlerinden oluşmaktadır. 3B şok tahmini yöntemi ise temelde 2B tahmin yönteminin yüzey akım çizgileri üzerinde uygulanması sonucu oluşturulmaktadır. Yüzey akım çizgilerinin hesaplanabilmesi için geometri yüzey çözüm ağı ile ifade edilmektedir. Ardından serbest akış hızı yüzey üzerine yansıtılarak, çözüm ağı üzerinden akışkan kinematik denklemleri çözümlenmektedir. Hesaplanan şok noktaları 3B bir yüzey haline getirilerek, şok şekli tahmin edilmektedir. 2B ve 3B şok şekli tahmin algoritmaları üzerinde doğrulama çalışmaları yapılmıştır. Çalışmalar kapsamında 2B ve 3B algoritmalar, ogive geometrisi ve küresel küt burunlu konik geometriler kullanımı ile HAD analiz sonuçları ve deneysel veriler ile karşılaştırılarak, incelenmiştir. Bu kapsamda kurgulanan HAD analizleri ogive için Mach 5; küt burunlu konik geometriler için ise Mach 3, 5, 8'de yapılmıştır. Serbest akış koşulları, 0, 5, 10 derece hücum açılarında incelenmiştir. HAD analizleri sonucunda elde edilen şok şekli ve algoritma sonucunda elde edilen şok geometrisinin, akışa maruz kalan geometri ile dik mesafeleri karşılaştırılmıştır. 2B ve 3B karşılaştırmalarda ogive geometrisinde neredeyse fark gözlemlenmezken, konik geometri karşılaştırmalarında yüzde farkların hücum açısı arttıkça arttığı gözlemlenmiştir. 2B geçerleme çalışmalarında maksimum fark yaklaşık %1 olarak hesaplanırken, 3B çalışmalarda fark %4 değerine kadar çıkabilmektedir. HAD çözümleri ile karşılaştırmalara ek olarak, 3B şok şekli tahmin yöntemi deneysel şok şekliyle karşılaştırıldığında ise benzer şekilde hücum açısı ile birlikte hatalar artmaktadır. Deneysel veriler ile geliştirilen algoritma arasındaki maksimum hata değeri %3 'tür
Kütlesi Optimize Edilmiş Kuş Çarpmasına Dayanıklı Polikarbonat Kanopi Yapısı Geliştirilmesi
No full textBu çalışmada, kuş çarpmasına dayanaklı, kütlesi merkezi deformasyona bağlı olarak optimize edilmiş kanopi yapısı elde edilmesi amaçlanmıştır. Çalışma kapsamında öncelikle kuşun modellenmesi, ardından kanopi malzemesi olarak kullanılacak polikarbonatın çarpışma modelinin oluşturulması ve son olarak ise farklı eğrilik yarıçaplarındaki katmanlı kanopi yapısının kütlesinin, merkezi deformasyonuna bağlı olarak optimizasyonu çalışması yapılmıştır. Kuş modelinin oluşturulmasında ucu yarı küresel silindir SPH kuş modelinin gerçek çarpışma durumuna en yakın sonucu verdiği görülmüş ve analizlerde bu model kullanılmıştır. Literatürden elde edilen SPH metodu ile kuşun sonlu elemanlar modelinin ve yine literatürden elde edilen polikarbonat plakanın çarpışma modelinin doğrulama çalışmaları yapılmış, doğrulanan modeller kullanılarak R=∞, R=1.25, R=0.75 ve R=0.5 metre eğrilik yarıçaplarındaki 5 katmanlı bir kanopi panel tasarımının kütlesi merkezi deformasyonuna bağlı olarak genetik algoritma kullanılarak optimize edilmiştir. Yapılan çalışmalar sonucunda R=∞ tasarımı için %3.2, R=1.25 tasarımı için %5.2, R=0.75 tasarımı için %0.53, R=0.5 tasarımı için %0.54 kütlede azalma elde edilmiştir
On the Tradeoff Between Network Lifetime and K-Connectivity Reliability in Uwsns
No full textUnderwater wireless sensor networks (UWSNs) are utilized for a wide range of monitoring and surveillance applications. Lifetime maximization and maintenance of network reliability are among the most important considerations in the deployment of UWSNs. k-connectivity is a robust approach for reinforcing reliability. However, maintaining k disjoint paths from each sensor node to the BS, inevitably, results in extra energy dissipation, which reduces the network lifetime (NLT). Yet, there is no systematic exploration to determine the extent of lifetime reduction due to the increase in the k value, in the literature, to the best of our knowledge. In this study, we create an optimization framework to be able to explore the tradeoff between NLT and k-connectivity-based reliability in UWSNs. Through the optimal solutions of the proposed optimization model for a large set of salient parameters, we characterize the interplay between lifetime and k-connectivity. Our analysis reveals that the k value to be maintained in a UWSN can affect the NLT significantly.This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) 3001 under Project 113E470.Scientific and Technological Research Council of Turkey (TUBITAK) [113E470
Design and Numerical Analysis of Locally-Resonant Meta-Lattice Structure for Vibration Attenuation
No full textASME 2022 International Mechanical Engineering Congress and Exposition, IMECE 2022 -- 30 October 2022 through 3 November 2022 -- 186577Meta-materials are artificial materials that perform superior properties in addition to natural behavior. Regardless of their chemical properties, metamaterials show high performance due to their geometric orientation. There are mechanical metamaterials that are used in vibration and acoustic fields, the main subject of which is wave transmission. The propagation of mechanical waves, which can cause problems such as structural damage, fatigue, poor performance, and discomfort in the industry, can be prevented or reduced by using meta-materials. Mechanical waves of various frequencies can be reduced or eliminated by locally resonant metamaterials obtained by adding various masses to viscoelastic materials. Metamaterials can be designed by modifying various lattice structures. Higher performance metamaterials are designed in this study by modifying the lattice structures used in the literature for vibration isolation. Finite element analyzes are carried out to show the transmissibility performance of the designed meta-lattice structures. Copyright © 2022 by ASME.We would like to express our special gratitude to Simofis, Boğaziçi Yazılım, and especially Berkay Çevik from Simofis for his assistance with Simcenter 3D analyzes
Understanding Hajj Travel: a Dynamic Identity Perspective
No full textThe present study brings an explanation for how tourist–pilgrims construct, deconstruct, and reconstruct their identities throughout the Hajj travel. The study focuses on the embodied, symbolic, and experiential aspects of this experience, creating idiosyncratic meanings for individuals. This travel is conceptualized as a religious endeavor and a consumptive-touristic activity at the same time, studied within a cultural context shaped by social, religious, and individual values, which is called the Consumer Culture Theory. This study also presents a new perspective by decomposing the pilgrim–tourist continuum and negating the opposite ends of pure tourists and pure pilgrims. Qualitative methodology is employed to provide a deeper understanding and a thicker explanation. In-depth interview data is collected from 38 individuals, in addition to findings gathered from prolonged observation of religious settings and several social media accounts. Findings draw attention to different groups of pilgrim–tourists, named as Mortals, Cleaners, Journalists, and Seekers. Findings also indicate that each individual can illustrate the characteristics of different groups, and that self-transformation can interactively occur among different groups of pilgrim–tourists. Identity appears as an ongoing project to be negotiated in the Hajj context, intertwined with the leisure aspect of this religious/touristic encounter. © 2021 Informa UK Limited, trading as Taylor ; Francis Group
Role of Melatonin in Tlr4-Mediated Inflammatory Pathway in the Mtpt-Induced Mouse Model
No full textNeuroinflammation has an essential role in various neurodegenerative diseases including Parkinson's disease (PD). Microglial activation as a result of neuroinflammation exacerbates the pathological consequences of the disease. The toxic effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes alpha-synuclein (alpha-synuclein) accumulation, which leads to dopaminergic neuron death in the MPTP-induced mouse model. Toll-like receptor 4 (TLR4) stimulates release of cytokine through NF-kB by activating glial cells, thus resulting in the death of dopaminergic neurons. Melatonin has the ability to cross the blood-brain barrier and protect neurons through anti-inflammatory properties. We hypothesized that melatonin could suppress TLR4-mediated neuroinflammation, decrease cytokine release due to the inflammatory response, and reduce dopaminergic neuron loss in the MPTP-induced mouse model. In the MPTP-induced mouse model, we aimed to assess the neuroinflammatory responses caused by TLR4 activation as well as the effect of melatonin on these responses. Three-month-old male C57BL/6 mice were randomly divided into five groups; Control (Group-C), Sham (Group-S), Melatonin-treated (Group-M), MPTP-injected (Group-P), and MPTP + melatonin-injected (Group-P + M). MPTP toxin (20 mg/kg) was dissolved in saline and intraperitoneally (i.p.) injected to mice for two days with 12 h intervals. The total dose per mouse was 80 mg/kg. Melatonin was administered (20 mg/kg) intraperitoneally to Group-M and Group-P + M twice a day for five days. Eight days after starting the experiment, the motor activities of mice were evaluated by locomotor activity tests. The effects on dopamine neurons in the SNPc was determined by tyrosine hydroxylase (TH) immunohistochemistry. TLR4, alpha-synuclein, and p65 expression was evaluated by immunostaining as well. The amount of TNF-alpha in the total brain was evaluated by western blot analysis. In our results seen that locomotor activity was lower in Group-P compared to Group-C. However, melatonin administration was improved this impairment. MPTPcaused decrease in TH immuno-expression in dopaminergic neurons in Group-P. TLR4 (p 0.001), alpha-synuclein (p 0.001), and p65 (p 0.01) immuno-expressions were also decreased in Group-P+M compared to Group-P (using MPTP). TNF-alpha expression was lower in Group-C, Group-S, Group-M, and Group-P+M, when compared to Group-P (p 0.0001) due to the absence of inflammatory response. In conclusion, our study revealed that melatonin administration reduced alpha-synuclein aggregation and TLR4mediated inflammatory response in the MPTP-induced mouse model.This study was supported by Akdeniz University Scientific Research Projects with project number TYL-2018-3972 and a Master of Science thesis of Sendegul YILDIRIM.Akdeniz University Scientific Research ProjectsAkdeniz University [TYL-2018-3972
Siyaset Bilimi Açısından Bir Değerlendirme Şeyh Bedreddin İsyanı; Sufi ve Siyaset
No full textThis thesis study deals with a series of rebellions that broke out in Western Anatolia and Southern Balkans in 1416 by focusing on the complex nature of the state, religion and societal relations. In this respect, the 1416 Revolt of Sheikh Bedreddin offers a very productive framework in terms of understanding religion, culture and state relations. Naturally, the claim of understanding mentioned here should include that the event in question first requires a multifaceted evaluation. The 1416 Revolts, which took place on a state order that has not yet been fully institutionalized and a social structure reminiscent of a mosaic of identities, makes it necessary to make inferences far beyond the individual-based judgmental view that classical Ottoman historical sources constantly emphasize and the romantic Bedreddin readings that started with Nazım Hikmet in the Republic period. Therefore, this study will try to go deeper into social events by adopting a methodological approach at first hand. Yet, as could be seen in the main text, it is not easy to make a clear distinction between the religious and the political, between the pile of accidental events and the conscious social protests. In some cases, such intertwinements, which are thought to be gone beyond, might constitute the basis of explaining social events. However, I propose to read the aforementioned incident by placing it on a line of historical perpetuity, through appropriate examples of comparison. The origins of the Safavid Iran State or the Babai Revolts will be the examples that is going to be frequently mentioned as a touchstone in this context. Thus, in the case of the pre-modern period, we will be able to see more easily that Sufistic distinctive structures were also directly part of political organizations.Bu tez çalışması, 1416 tarihinde Batı Anadolu ve Güney Balkanlar'da patlak veren bir dizi isyanı devlet, din ve toplum ilişkilerinin karmaşık sarmalına odaklanarak ele almaktadır. Bu yönüyle Şeyh Bedreddin İsyanı din, kültür ve devlet ilişkilerini anlamak bakımından oldukça verimli bir çerçeve sunmaktadır. Elbette burada bahsedilen anlama iddiası, bahsi geçen hadisenin öncelikle çok yönlü bir değerlendirme gerektirdiğini içermelidir. Henüz tam anlamıyla kurumsallaşamamış bir devlet düzeni ve adeta kimlikler mozaiğini anımsatan bir toplumsal yapı üzerinde gerçekleşen 1416 İsyanları, klasik Osmanlı tarih kaynaklarının sürekli olarak vurguladığı bireysel temelli yargılayıcı bakışın ve Cumhuriyet döneminde Nazım Hikmet ile başlayan ideolojik ve romantik Bedreddin okumalarının çok ötesinde çıkarımlar yapmayı gerekli kılmaktadır. Dolayısıyla bu çalışma ilk elden, metodolojik bir tutum benimseyerek sosyal hadiselerin zeminine inmeyi teklif edecektir. Zira ana metinde görüleceği üzere dini olanla siyasi olanın, tesadüfi hadiseler yığınıyla bilinçli toplumsal karşı çıkışların arasında net bir ayrım yapmak hiçte kolay değildir. Bazı durumlarda ise, aşılması gerektiği düşünülen bu tür iç içe geçişler, sosyal olayları açıklayabilmenin esasını teşkil edebilmektedir. Bununla birlikte uygun karşılaştırma örnekleri üzerinden, bahsi geçen hadiseyi bir tarihsel süreklilik hattına oturtarak okumayı teklif ediyorum. Babai İsyanı ya da Safevi Devleti'nin kökenleri konusu bu bağlamda mihenk taşı niteliğinde sıkça anılacak örnekler durumunda olacaktır. Böylece sufi veya sufi-meşrep yapıların modern- öncesi dönem söz konusu olduğunda, aynı zamanda doğrudan politik organizasyonların bir parçası haline geldiğini daha kolay görebileceğiz
Deviant Behaviors at Work
No full textThrough order and discipline, we expect to have better functioning organizations. However, even though some strong sanctions are placed against those who do not obey workplace norms, rules and regulations, some employees, individually or in groups, may still attempt to commit deviant acts. With Hawthorne studies, we had come to realize that individuals in the workplace may show deviant behaviors that do not serve organizational goals. Even though some studies reveal that not all deviant behaviors are negative, such as organizational citizenship behavior, the outcomes of negative deviance in organizations bring serious costs to the effectiveness and competitiveness of organizations. This chapter of the book will give an overview of deviant behaviors in organizations, reviewing the related literature (performing a meta-analysis) in order to identify and classify the types of deviant behaviors. Additionally, the chapter aims at presenting their antecedents (common reasons, if any) and consequences, as well as discussing how to reduce deviant behaviors and their costs, or when to ignore specific deviances, and specifically how to deal with the negative organizational behaviors presented. © 2023 H. Cenk Sözen and H. Nejat Basım
