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Öğe AC hot wire measurement of thermophysical properties of nanofluids with 3? method(2008) Turgut A.; Sauter C.; Chirtoc M.; Henry J.F.; Tavman S.; Tavman I.; Pelzl J.We present a new application of a hot wire sensor for simultaneous and independent measurement of thermal conductivity k and diffusivity ? of (nano)fluids, based on a hot wire thermal probe with ac excitation and 3? lock-in detection. The theoretical modeling of imaginary part of the signal yields the k value while the phase yields the ? value. Due to modulated heat flow in cylindrical geometry with a radius comparable to the thermal diffusion length, the necessary sample quantity is kept very low, typically 25µl. In the case of relative measurements, the resolution is 0.1% in k and 0.3% in ?. Measurements of water-based Aerosil 200V nanofluids indicate that ultrasound treatment is more efficient than high pressure dispersion method in enhancing their thermal parameters. © EDP Sciences/ Societé Italiana di Fisica/Springer-Verlag 2008.Öğe Assessment of modulated hot wire method for thermophysical characterization of fluid and solid matrices charged with (nano)particle inclusions(Institute of Physics Publishing, 2010) Chirtoc M.; Henry J.F.; Turgut A.; Tavman I.; Hadjov K.; Schuchmann H.P.; Sauter C.; Antoniow J.S.; Fudym O.; Tavman S.Recently we reported on simultaneous thermal conductivity k and thermal diffusivity a measurement of liquids and in particular of nanofluids in a configuration using an ac excited hot wire combined with lock-in detection of the third harmonic (3? method) [1]. The conductive wire is used as both heater and sensor. The requirements for the asymptotic validity of the line heat source model are fulfilled at low modulation frequencies below a few Hz. The study of the relative sensitivity of signal amplitude and phase to changes in k and a indicates that there is an optimum frequency range for accurate and stable results. We extend by up to two decades the feasible frequency range for 3? measurements by considering various more elaborate models for the heat transfer between the wire and the fluid. Finally we show that the same ac hot wire method can be applied to soft solid, composite materials. We measured the k enhancement of a poly(ethylene vinyl acetate) EVA polymer matrix charged with various fractions of graphite. © 2010 IOP Publishing Ltd.Öğe The effects of temperature and muscle composition on the thermal conductivity of frozen meats(2010) Kumcuoglu S.; Turgut A.; Tavman S.Thermal conductivity values of meat samples with moisture contents between 4.73 and 79.47% (wet basis) and fat contents between 1.44 and 93.17% (wet basis) were measured at temperatures ranging from-30 to 25C using the line heat source probe method. Thermal conductivities of frozen meat samples were higher than the ones in the unfrozen state. Measured thermal conductivity values were mathematically interpreted as a function of temperature, moisture, protein and fat contents by application of nonlinear regression analysis for frozen samples. Measured thermal conductivities were compared with the models given in the literature. Levy's model provided more accurate predictions than the others in the frozen state and parallel model showed the best predictions in the unfrozen state. For unfrozen state, thermal conductivity was found to increase with moisture content and decrease with fat content, although in the frozen state, thermal conductivity increases with decreasing temperature. © 2010 The Author(s). Journal compilation © 2010 Wiley Periodicals, Inc.Öğe Experimental study on thermal conductivity and viscosity of water-based nanofluids(2010) Tavman I.; Turgut A.; Chirtoc M.; Hadjov K.; Fudym O.; Tavman S.Thermal conductivity and viscosity of deionized water-based TiO 2, SiO2, and Al2O3 nanofluids were investigated for various volume fractions of nanoparticles content and at different temperatures. A 3? technique was developed for measuring thermal conductivity of nanofluids. The theory and the experimental setup of the 3? measuring system is explained; a conductive wire is used as both heater and sensor in this system. At first, the system is calibrated using water with known thermophysical properties. Measured results showed that the effective thermal conductivity of nanofluids increases as the concentration of the particles increases but not anomalously as indicated in the majority of the literature and this enhancement is very close to the Hamilton-Crosser model; also this increase is independent of the temperature. The effective viscosities of these nanofluids increase by the increasing particle concentration and decrease with an increase in temperature, and cannot be predicted by the Einstein model. © 2010 Begell House, Inc.Öğe First step toward a better trauma management: Initial results of the northern Izmir trauma registry system for children [Çocuklarda daha iyi travma yönetimi için ilk adım: Kuzey İzmir Travma Kayıt Sistemi’nin ilk sonuçları](Turkish Association of Trauma and Emergency Surgery, 2019) Öztan M.O.; Anıl M.; Anıl A.B.; Yaldız D.; Uz İ.; Turgut A.; Köse I.; Acar K.; Sofuoğlu T.; Akbulut G.BACKGROUND: Trauma is an important health problem in children, and improvement in trauma care on the national level is possible only through the knowledge gathered from trauma registry systems. This information is not available in our country, because there is no current trauma registry system in the hospitals. Our aim in this paper is to explain the trauma registry system we have developed and to present the first year’s data. METHODS: The planned trauma registry system was integrated into the emergency department registry system of 14 hospitals in the Izmir province. The data of pediatric patients with multiple trauma have been recorded automatically through the registry system. Demographics, vital signs, mechanism, the type of trauma, anatomical region, Injury Severity Score (ISS), Pediatric Trauma Score (PTS), Glasgow Coma Scale (GCS) score, the length of hospital stay, and the need for blood transfusion/endotracheal intubation/surgery/ hospitalization were evaluated by the patient transfer status and outcome. RESULTS: At the end of one year, a total of 356 pediatric major trauma patients were included in the study. The most common type of trauma was blunt trauma (91.9%), and the most common mechanism was vehicle-related traffic accident (28.1%). In the group with the Glasgow Outcome Scale ?3; the age was greater, ISS was higher, and PTS was lower. Motorcycle accidents, sports injuries, and penetrating injuries were more frequent in this group. All scores were significantly different between direct and transferred patients. The referral time to the hospital of the transferred patients was longer than directly admitted patients, but the results were not different. CONCLUSION: Pediatric major trauma is an important cause of mortality and morbidity, and our trauma registry system, which is a successful example abroad, is insufficient in our country. We hope that the trauma registry system we planned and the pilot application we started will be expanded to include other hospitals throughout the country with the aim of developing a national registry system. © 2019 Turkish Association of Trauma and Emergency Surgery.Öğe Intra- and inter-observer reliability of Laredo classification system in Legg–Calvé–Perthes Disease(Springer-Verlag France, 2019) Erkus S.; Turgut A.; Kalenderer O.; Yuksel K.The purpose of the current study was to investigate intra- and inter-observer reliability of arthrographic Laredo classification system in Perthes disease. Forty-seven patients were included in this cross-sectional descriptive study. Patients’ age, gender, physical findings and hip arthrographs were collected from hospital medical records. Two different sets of power point slides were prepared in which the order of cases was randomized and blinded. Observers were divided into three groups according to their surgical experience (9 residents, 10 seniors, 10 pediatric orthopedists), and they assessed two times 1 month’s intervals. Statistical analysis was performed by using the SPSS v21. Inter- and intra-observer reliabilities were calculated using intra-class correlation coefficient, weighted kappa and percentage agreement. Percentage agreement of Laredo classification was about 50% for all groups (residents, seniors and pediatric orthopedists); intra-observer reliabilities were excellent, excellent and fair, respectively. Inter-observer reliability of Laredo classification for each set was found to be excellent for all groups. Length of experience did not correlated significantly with the level of intra-observer agreement. As a conclusion, our results showed that Laredo’s arthrographic classification system’s intra-observer reliability is at least at a fair level and inter-observer reliability is at an excellent level. We believe that this classification system is valuable for an orthopedic surgeon who deals with the treatment of Perthes disease. © 2019, Springer-Verlag France SAS, part of Springer Nature.Öğe Measurement of thermal conductivity of edible oils using transient hot wire method(2009) Turgut A.; Tavman I.; Tavman S.Thermal conductivities of three different edible oils, namely sunflower oil, corn oil and olive oil, were measured at temperatures 25, 40, 60, and 80°C. The measurements were carried out using a hot wire probe method. The calibration of the probe was performed using 0.3% agar gel with water and glycerin. In general, thermal conductivities of oils used in this study are found to be decreasing with temperature. The values of thermal conductivity measured are quite near to each other, the highest and the lowest being respectively 0.168 W/m K for sunflower oil at 25°C and 0.152 W/m K for corn oil at 80°C.Öğe Preparation and mechanical properties of graphite filled HDPE nanocomposites(2011) Sarikanat M.; Sever K.; Erbay E.; Güner F.; Tavman I.; Turgut A.; Seki Y.; Özdemir I.Purpose: The design and manufacture of lightweight polymer composites with high electrical and thermal conductivity have been a research focus in recent years. In this study, tensile strength and modulus of elasticity of nanocomposites formed by high density polyethylene (HDPE) matrix and graphite powder filler material were determined. Design/methodology/approach: In this study the conductive filler was graphite with an average particle size of 400 nm and purity of 99.9%, the matrix material was high density polyethylene (HDPE) with a density of 0.968 g/cm3 and a melt index of 5.8 g/10 min, supplied by Petkim A.Ş.- Izmir. Nanocomposites containing up to 30 weight percent of graphite powder filler material were prepared by mixing them in a Brabender Plasticorder at 180°C for 15 minutes. Tensile strength and modulus of elasticity of nanocomposites formed were determined as functions of graphite powder content. Findings: An increase in tensile strength and modulus of elasticity was observed with increasing graphite powder content from 0 to 6%. However, for further increasing the graphite content, tensile strength decreases while modulus of elasticity continued to increase in the composite. Practical implications: Since natural graphite (NG) has a high electrical conductivity at room temperature, it is considered an ideal candidate for manufacturing conductive polymer composites. The recent advancement of nano-scale compounding technique enables the preparation of highly electrically conductive polymeric nanocomposites with low loading of conductive fillers. Nanocomposites may offer enhanced physical features such as increased stiffness, strength, barrier properties and heat resistance, without loss of impact strength in a very broad range of common synthetic or natural polymers. Originality/value: To see the effect of conducting fillers on mechanical properties of HDPE based nanocomposites, graphite particle 400 nm in size were used. © International OCSCO World Press.Öğe Size effects of graphene nanoplatelets on the properties of high-density polyethylene nanocomposites: Morphological, thermal, electrical, and mechanical characterization(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2020) Evgin T.; Turgut A.; Hamaoui G.; Spitalsky Z.; Horny N.; Micusik M.; Chirtoc M.High-density polyethylene (HDPE)-based nanocomposites incorporating three different types of graphene nanoplatelets (GnPs) were fabricated to investigate the size effects of GnPs in terms of both lateral size and thickness on the morphological, thermal, electrical, and mechanical properties. The results show that the inclusion of GnPs enhance the thermal, electrical, and mechanical properties of HDPE-based nanocomposites regardless of GnP size. Nevertheless, the most significant enhancement of the thermal and electrical conductivities and the lowest electrical percolation threshold were achieved with GnPs of a larger lateral size. This could have been attributed to the fact that the GnPs of larger lateral size exhibited a better dispersion in HDPE and formed conductive pathways easily observable in scanning electron microscope (SEM) images. Our results show that the lateral size of GnPs was a more regulating factor for the above-mentioned nanocomposite properties compared to their thickness. For a given lateral size, thinner GnPs showed significantly higher electrical conductivity and a lower percolation threshold than thicker ones. On the other hand, in terms of thermal conductivity, a remarkable amount of enhancement was observed only above a certain filler concentration. The results demonstrate that GnPs with smaller lateral size and larger thickness lead to lower enhancement of the samples' mechanical properties due to poorer dispersion compared to the others. In addition, the size of the GnPs had no considerable effect on the melting and crystallization properties of the HDPE/GnP nanocomposites. © 2020 Evgin et al.Öğe Thermal conductivity and viscosity measurements of water-based TiO 2 nanofluids(2009) Turgut A.; Tavman I.; Chirtoc M.; Schuchmann H.P.; Sauter C.; Tavman S.In this study, the thermal conductivity and viscosity of TiO 2 nanoparticles in deionized water were investigated up to a volume fraction of 3% of particles. The nanofluid was prepared by dispersing TiO 2 nanoparticles in deionized water by using ultrasonic equipment. The mean diameter of TiO 2 nanoparticles was 21 nm. While the thermal conductivity of nanofluids has been measured in general using conventional techniques such as the transient hot-wire method, this work presents the application of the 3? method for measuring the thermal conductivity. The 3? method was validated by measuring the thermal conductivity of pure fluids (water, methanol, ethanol, and ethylene glycol), yielding accurate values within 2%. Following this validation, the effective thermal conductivity of TiO 2 nanoparticles in deionized water was measured at temperatures of 13 °C, 23 °C, 40 °C, and 55 °C. The experimental results showed that the thermal conductivity increases with an increase of particle volume fraction, and the enhancement was observed to be 7.4% over the base fluid for a nanofluid with 3% volume fraction of TiO 2 nanoparticles at 13 °C. The increase in viscosity with the increase of particle volume fraction was much more than predicted by the Einstein model. From this research, it seems that the increase in the nanofluid viscosity is larger than the enhancement in the thermal conductivity. © 2009 Springer Science+Business Media, LLC.
