72 research outputs found
Droplet evaporation dynamics on surfaces
No full textDroplet evaporation governs many man-made and natural processes. Hence, it has been widely studied by many scientists over the past century. With the recent advancements in nanotechnology, many surfaces for two phase heat transfer have been developed including hydrophobic, biphilic and lubricantinfused surfaces. However, evaporation of droplets on these surfaces have not been explored in depth. Traditionally, evaporation on surfaces was characterized by observing the temporal size changes of a droplet. Yet, the transient nature coupled with the significant mass transfer governed gas dynamics occurring at the droplet three-phase contact line make the classical method crude. To accurately investigate evaporation dynamics on surfaces, we present a novel steady measurement technique. By utilizing a piezoelectric dispenser to feed microscale droplets (20 ≤ ≤ 400 μm) to a larger evaporating droplet at a prescribed frequency, we can create variable-sized droplets on any surface and study their evaporation rates by modulating the droplet addition frequency. Using our steady method, we studied evaporation of water and low surface tension fluids on surfaces including functional, biphilic, biconductive and lubricant-infused surfaces. We elucidated the physics governing the droplet evaporation process for each studied surface and working fluid. Furthermore, we developed an original high-speed focal-shift imaging technique to study droplet mobility on the interface. Our results not only shed light into the evaporation physics of droplets on different surfaces but also provides new avenues and strong experimental platforms for the study of phase change heat transfer processes that enable the decoupling of the intricate and length-scale dependent balance played by internal and external flows and binary-mixture dynamics, and the visualization of the interfacial dynamics.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-05-01The student, Ahmet Gunay, accepted the attached license on 2019-04-12 at 18:06.The student, Ahmet Gunay, submitted this Dissertation for approval on 2019-04-12 at 18:10.This Dissertation was approved for publication on 2019-04-15 at 13:19.DSpace SAF Submission Ingestion Package generated from Vireo submission #13602 on 2019-08-22 at 16:21:14Made available in DSpace on 2019-08-23T20:47:22Z (GMT). No. of bitstreams: 2
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Orchestrating learning during implementation of a 3D virtual world
No full textKarakus Yilmaz, Turkan/0000-0002-5809-3962; Baydas Onlu, Ozlem/0000-0002-5812-7085WOS: 000383915700002There are many issues to be considered when designing virtual worlds for educational purposes. In this study, the term orchestration has acquired a new definition as the moderation of problems encountered during the activity of turning a virtual world into an educational setting for winter sports. A development case showed that community plays a key role in both the emergence of challenges and in the determination of their solutions. The implications of this study showed that activity theory was a useful tool for understanding contextual issues. Therefore, instructional designers first developed relevant tools and community-based solutions. This study attempts to use activity theory in a prescriptive way, though it is known as a descriptive theory. Finally, since virtual world projects have many aspects, the variety of challenges and practical solutions presented in this study will provide practitioners with suggestions on how to overcome problems in future.Turkish Science and Technology Institution Project [111K516]This study was conducted as part of the "Effects of Virtual and Multimedia Environments on Interest and Awareness Towards Winter Sports" project [number "111K516"], supported by the Turkish Science and Technology Institution Project
Modeling, fabrication and optimization of optically transparent - thermally insulating silica aerogels for solar thermal applications
No full textSolar thermal energy conversion has the potential to reduce greenhouse gas emissions via the offset of fossil fuel burning power generation methods. By capturing the suns energy and using it to heat steam as part of a Rankine cycle, electrical energy can be renewably produced. Furthermore, solar thermal collectors have high potential for domestic heating when deployed at the rooftop scale, reducing fossil fuel consumption used for home heating needs. The efficiency of these solar applications is highly dependent on the ability of the collecting device to absorb the incoming solar energy, and minimize thermal losses to the environment. Current techniques utilize vacuum tubes to eliminate convective losses, in combination with selective surfaces (high absorptivity in the solar spectrum, and low emissivity in the infra-red (IR)) to minimize thermal re-radiation. Here, we present an alternate approach that operates at atmospheric pressures with simple, black, absorbing surfaces. An Optically Transparent Thermally Insulating (OTTI) layer was assumed to be coated on the back side of the black, broadband absorber. This absorber was assumed to have perfect transparency and opacity in the solar spectrum and Infra-Red (IR), respectively. In order to provide a deeper understanding of the link between the optimum OTTI layer material properties and the overall solar thermal efficiency, we developed a coupled radiative-conduction heat transfer (HT) model used to predict how the investigated OTTI layers will behave when they are used as solar thermal absorbers. The optimum properties that were obtain were then incorporated into the HT model to study the thermal performance under various optical concentrations (1 – 20 suns), solar thermal absorber temperatures (20 – 200°C), and external heat transfer coefficients (10 – 100 W/m2K). The results showed potential solar thermal conversion efficiencies of ≈90% can be attained by utilizing OTTI layers as insulators in the solar thermal absorbers. To check if a material to have the assumed material properties can be fabricated, silica aerogels were procured, synthesized and characterized. Due to their naturally high and low transmissivities in the solar and IR spectrums, respectively, silica based aerogels coated on the back with highly absorbing (black) surfaces offer a potential solution to create simple and inexpensive solar thermal absorbers. To test our hypothesis, we fabricated tetramethyl orthosilicate (TMOS) and tetraethyl orthosilicate (TEOS) based silica aerogels. The formed gels were aged for 3 weeks and dried using a carbon dioxide supercritical point dryer. The obtained aerogel optical properties were characterized using ultraviolet-visible (UV-Vis) and Fourier Transform Infrared (FTIR) spectroscopy, showing spectrally averaged (0 < λ < 2.7 µm) transmissions of ≈87% for a sample thickness of 4mm. To minimize the effect the O-H group transmission reduction occurring in the solar spectrum, we modified the baseline aerogels to be hydrophobic with a silane treatment to shield the exposed hydroxyl groups on the surface. Hydrophobic modification resulted in an increase of the spectrally averaged transmissions to ≈ 94%. This study sheds light on the applicability of silica aerogels on black coatings as ideal solar thermal absorbers and offers insights into new avenues for performance improvement of solar thermal energy systems.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-05-01The student, Ahmet Gunay, accepted the attached license on 2016-04-25 at 15:18.The student, Ahmet Gunay, submitted this Thesis for approval on 2016-04-25 at 15:31.This Thesis was approved for publication on 2016-04-27 at 09:14.DSpace SAF Submission Ingestion Package generated from Vireo submission #9484 on 2016-07-07 at 13:50:50Made available in DSpace on 2016-07-07T20:28:01Z (GMT). No. of bitstreams: 3
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The Efficiency Analysis of Non-life Insurance Companies Active in Turkey
No full textThis paper evaluates the technical effi ciencies of non-life insurance companies, which are active in Turkey in 2007, using Data Envelopment Analysis (DEA). DEA, which is a nonparametric method, facilitates to examine different input-output components. DEA is a
management evaluation tool that assists in identifying the most efficient and ineffi cient decision making units (DMUs) in the best practice frontier. In this study, as inputs of 23 non-life insurance companies, the number of agents, the number of brokers, fi xed assets,
shareholders’ equity and as outputs the investment incomes, premiums received are used. Empirical results of BCC and CCR models, which are DEA models, show that the most efficient insurance company is RAY
Dark matter and dark energy solutions using by observational evidence
No full text33rd International Physics Congress of the Turkish-Physical-Society (TPS) -- SEP 06-10, 2017 -- Bodrum, TURKEYIn this study, we examine dark energy, dark matter and baryonic matter in FRW by observational evidences. Also we study our model by considering possible dark energy candidates such as Phantom energy. Obtained solutions show that dark energy candidate may be phantom energy depending on accuracy of today's observation.Turkish Phys So
CREATION OF THE GEOINFORMATION MAP OF HISTORICAL AND NATURAL MONUMENTS IN THE TERRITORY OF THE NORTHEAST SLOPE OF CAUCASUS WITHIN THE AZERBAIJAN TERRITORY
No full textIn this report the author describes the geographical information system of historical monuments and natural conditions aimed at promotion of innovative planning of the tourist sector of the economy
Technical Problems Experienced in the Transformation of Virtual Worlds into an Education Environment and Coping Strategies
No full textResearch into virtual worlds demonstrates that to successfully use virtual world platforms in different disciplines, certain limitations and potential difficulties of these platforms must be overcome. The current study extends previous research by investigating problems in integrating virtual worlds in education with a longitudinal observation of two cases and in perspectives of designers, practitioners and administrators. The purpose of this study was both to determine technical problems encountered by practitioners and designers who create environments in 3D virtual worlds for a certain purpose and to suggest practical strategies for these problems. In the study, designers experimented with two different 3D virtual world platforms for one year, to design and create learning environments. To collect the research data, interview records and design diaries in which the designers and practitioners noted problems that they encountered during two virtual world projects. The results indicate that the technical problems has not aroused only related the problems and those problems influenced several pedagogical issues like motivation of students and guidance in the environments. Our findings should be beneficial both to virtual world designers and to users who wish to use these environments in broad range of fields
Dynamic Ambulance Deployment to Reduce Ambulance Response Times Using Geographic Information Systems: A Case Study of Odunpazari District of Eskisehir Province, Turkey
No full textAbstractBackground and ObjectiveAmbulances should always reach patients in the shortest time possible whenever they are called upon so as to increase patient survival chances especially in cardiac related medical cases. The placement of ambulances directly affects the time ambulances reach patients. The objective of the study was to find optimal stations to deploy ambulances so as to reduce ambulance response times and increase patient survival chances as a result.Data and MethodsTo reduce ambulance response times for Odunpazari district, the study employed system status management technique and maximal coverage location problem optimization model, to deploy ambulances according to ambulance demand and ensure maximum ambulance demand coverage is realized with a small ambulance fleet size, respectively. ArcGIS network analyst location allocation tool was used to find optimal ambulance stations from where ambulance demand areas can be reached within 5minutes of drive time. Four different ambulance deployment plans were modeled for periods ranging from 00:00 to 06:00hrs, 06:00 to 12:00hrs, 12:00 to 18:00hrs and 18:00 to 24:00hrs. The study used a total of 20,260 ambulance demand calls’ data for Odunpazari district collected from January 1st to December 31st 2014.ResultsThe Odunpazari district fleet of 17 ambulances was deployed differently for every six hours; between 00:00 to 06:00hrs, 06:00 to 12:00hrs, 12:00 to 18:00hrs and 18:00 to 24:00hrs to match ambulance demand and as a result, 77.6% of ambulance demand areas were located within 5minutes of drive time from the nearest ambulance station.ConclusionThe study found out that moving ambulances closer to ambulance demand areas reduces ambulance response times and dynamic ambulance deployment is by far a more effective ambulance deployment strategy than static ambulance deployment
About the Teaching Strategies of Modality in the Classroom
No full textThe article investigates the modality of verbs, words, expressions, and the methodology of teaching them in the auditorium. First of all, the author gives some information about the category of modality. She states the opinions of different scientists about the modality in different languages. For instance, the names of the scientists who investigated the category of modality such as O. Musayev, F. Jahangirov, I. Crilova, Y. Slinin, Y. Zvereva, I. Rickman and others have been referred to in the article. She gives the division of the modal verbs according to O. Musayev’s classification in the English language. They are: primary modal verbs, and secondary modal verbs. Each of these modal verbs has been analyzed through the examples by the author. Besides modal verbs, there are words, expressions which can express modality too. These facts are also stated in the article. The author considers it noteworthy to mention that the usage of modality of words, expressions is not generally found in the textbooks which are studied in the auditorium of Azerbaijani students. For this reason this usage of modality is considered to be challenging by the students as they don’t have much information about them. So, she gives the methodology of teaching modality in the auditorium. The methodology can be helpful for the lecturers to teach the category of modality. The examples used by the author can illustrate the exact model of the modal words, expressions, etc
A Method for Supporting Smoking Cessation in Adolescents: Peer Education
No full textSmoking is the most important cause of disability, death and preventable illness in Turkey and all over the world. According to the Global Youth Survey, smoking prevalence among young people increased from 9.4% in males and 3.5% in females in 2003 to 10.2% and 5.3% in 2009. Cigarette smoking affects a large part of the society with increasing frequency among young people. Therefore, the tobacco industry targets youth and women. The decrease in the starting age of smoking will cause longer term exposure to the harmful effects of cigarettes. Adolescents start smoking due primarily to a desire to imitate adults, peer pressure, affectation and easy access to cigarettes. Peer group has a great impact on both risky and safe behaviours of an adolescent. Adolescents want to be independent in their behaviours, attitudes and interests. They want to have activities with friends without prior permission and explanation. Peer education aims to use peer influence in the positive way, as peers can be positive models for behaviour. The increase in tobacco consumption among adolescents in the recent years has increased the importance of peer education. The purpose of this article is to explain how to use peer education in changing the cigarette smoking behaviours of adolescents. © 2014 by Turkish Thoracic Society
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