Çağlar Duvarcı, Özlem
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Duvarci, Ozlem C.
Duvarci, Ozlem
Duvarci, Ö. Çaǧlar
Duvarci, OC
Duvarci, O. Caglar
Duvarcı, Özlem
Duvarci, Ozlem Caǧlar
Caglar Duvarci, Ozlem
Caglar, Ozlem
Çağlar, Özlem
Duvarci, O. C.
Duvarci, Ozlem
Duvarci, Ö. Çaǧlar
Duvarci, OC
Duvarci, O. Caglar
Duvarcı, Özlem
Duvarci, Ozlem Caǧlar
Caglar Duvarci, Ozlem
Caglar, Ozlem
Çağlar, Özlem
Duvarci, O. C.
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ozlemduvarci@iyte.edu.tr
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03.02. Department of Chemical Engineering
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Current Staff
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3GOOD HEALTH AND WELL-BEING
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4QUALITY EDUCATION
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6CLEAN WATER AND SANITATION
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7AFFORDABLE AND CLEAN ENERGY
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8DECENT WORK AND ECONOMIC GROWTH
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
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10
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455
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9
Documents
11
Citations
444
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14
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7
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12147/6986
Supervised MSc Theses
2
Supervised PhD Theses
1
WoS Citation Count
335
Scopus Citation Count
342
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0
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1
WoS Citations per Publication
23.93
Scopus Citations per Publication
24.43
Open Access Source
13
Supervised Theses
3
| Journal | Count |
|---|---|
| Journal of Food Engineering | 2 |
| Journal of Cereal Science | 2 |
| Food Engineering Series | 1 |
| Handbook of Food Engineering | 1 |
| Key Engineering Materials | 1 |
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14 results
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Now showing 1 - 10 of 14
Book Part Citation - WoS: 12Linear and Non-Linear Rheological Properties of Foods(Taylor & Francis, 2019) Duvarcı, Özlem; Doğan, Hülya; Yazar, Gamze; Çağlar Duvarcı, Özlem; Doğan, Hülya; Kokini, Jozef L.[No abstract available]Article Citation - WoS: 27Citation - Scopus: 29Non-Linear Rheological Properties of Soft Wheat Flour Dough at Different Stages of Farinograph Mixing(Kerschensteiner Verlag GmbH, 2016) Yazar, Gamze; Duvarcı, Özlem; Tavman, Şebnem; Kokini, Jozef L.During mixing of wheat flour doughs, the distribution of the gluten network changes as a result of continuously applied large deformations. Especially gliadin, changes its distribution in the whole network during mixing. It is possible to fundamentally explain the role of molecular changes in more detail using large amplitude oscillatory measurements (LAOS) in the non-linear region. Therefore, the purpose of this study is to understand the effect of mixing on the non-linear fundamental rheological behavior of soft wheat flour dough using LAOS. Dough samples were obtained at 4 different phases of the Farinograph mixing and LAOS tests were done on each of them. LAOS tets give in depth intracycle understanding of rheology. All samples showed strain stiffening S and shear thinning T behavior at large strains previously not known in the cereal rheology community. Increasing mixing time (phase 1 to phase 4) and decreasing frequency resulted in retardation in the break of strain stiffening as strain increases. The strain stiffening behavior started to decrease for the dough samples at the 3rd and the 4th phases of mixing. LAOS data enabled us to describe the non-linear rheological changes occurring both in the viscous part largely attributed to the starch matrix and elastic part largely attributed to the gluten network components of the soft wheat flour dough under large deformations.Doctoral Thesis Rheological Behavior of Nanocrystalline / Submicron Ceramic Powder Dispersions(Izmir Institute of Technology, 2009) Çağlar Duvarcı, Özlem; Çiftçioğlu, MuhsinSeveral rheometric techniques were applied to submicron and nano ceramic powder dispersions systematically in this study. The rheological behavior of the dispersions was determined by steady shear and dynamic shear rheology. Dynamic shear rheological techniques are scarcely used for the characterization of ceramic powder dispersions contrary to polymers.The flow behaviors of the submicron and nano dispersions were found to be dependent on the solids content and fructose concentration. The submicron alumina, nano alumina, and nano titania dispersions in fructose solution showed shear thinning behavior and were fitted to the Herschel-Bulkley model.The dynamic shear rheology measurements showed that the solid part of the dispersions was dominant over the liquid part for both submicron and nano powder dispersions. The elastic modulus was higher than the viscous modulus in stress and frequency sweep measurements. The elastic moduli of the dispersions with solids content lower than 40 vol% were dependent on the angular frequency which indicated a gel-like behavior. However, the elastic moduli of the dispersions with 40 vol% solids were independent of angular frequency which indicated a solid like behavior. Further increase in fructose content had significant effects on both steady shear and dynamic shear rheological behavior of the dispersions regardless of particle size. The submicron and nano ceramic powder dispersions can be prepared by using fructose for the regulation of the rheological behavior of ceramic powder dispersions. The characterization of powder surfaces is essential for the effective adsorption of fructose.Article Citation - WoS: 41Citation - Scopus: 42Non-Linear Rheological Behavior of Gluten-Free Flour Doughs and Correlations of Laos Parameters With Gluten-Free Bread Properties(Elsevier Ltd., 2017) Yazar, Gamze; Çağlar Duvarcı, Özlem; Tavman, Şebnem; Kokini, Jozef L.Predicting loaf volume development of gluten free baked products to have similar properties to wheat products remains a challenge and there is no good marker for loaf volume. Large Amplitude Oscillatory Shear (LAOS) flow experiments and baking tests were conducted on rice, buckwheat, quinoa, and soy flour doughs to understand if there is any correlation between the non-linear rheological properties and loaf volume. The challenging water absorption capacities were determined by matching the η* vs. frequency data of the gluten free flours with that of the soft wheat flour dough with moisture content at 500 BU. 110%, 90%, 85%, and 160% water levels were found as optimal for rice, buckwheat, quinoa, and soy flour, respectively. The comparison of elastic Lissajous-Bowditch curves showed that the stronger non-linearities were seen at low frequencies and the wider the loop, the weaker the structure and the more structural breakdown with an order of soft wheat, soy, buckwheat, quinoa and rice flour doughs. Secondary loops have been observed in viscous Lissajous-Bowditch curves which are related to the strong non-linearities in elastic stress. The distributions of elastic and viscous LAOS parameters showed that soy dough has the closest rheological performance to wheat dough among other dough samples, which has the highest protein content. GL ′ and GM ′ values at 10 rad/s and 200% strain showed the best correlation among all LAOS parameters with the loaf volume. The strain stiffening/softening property e3/e1 complemented the mechanistic explanations which were offered using GL ′ and GM ′ values.Article Citation - WoS: 63Citation - Scopus: 70Laos Behavior of the Two Main Gluten Fractions: Gliadin and Glutenin(Elsevier Ltd., 2017) Yazar, Gamze; Çağlar Duvarcı, Özlem; Tavman, Şebnem; Kokini, Jozef L.Crude gliadin and glutenin fractions were studied using Large Amplitude Oscillatory measurements. LAOS measurements were carried out at three different frequencies (20, 10, 1 rad/sec) between the strain values of 0.01–200%. The beginning of non-linearity for glutenin occurred at ∼2.5%, while an initial region of strain hardening was observed for gliadin (2.5–10%) at 1 rad/sec frequency and up to 15% at the higher frequencies applied. Lissajous curves showed in the elastic analysis of both fractions glutenin was more elastically dominated since Lissajous curves were narrower, while for gliadin the ellipses were much broader suggesting more fluid-like behavior and each ellipse depended on the magnitude of frequency. Decreasing frequency increased the viscous behavior of both glutenin and gliadin in the non-linear region, but the change in gliadin was much more pronounced. Gliadin molecules only display intramolecular disulfide bonds creating a great deal of mobility whereas for glutenin molecules, which contain both intermolecular and intramolecular disulfide bonds, the strong network structure formed by this molecular arrangement results in very pronounced strain stiffening.Article Citation - WoS: 54Citation - Scopus: 58Effect of Mixing on Laos Properties of Hard Wheat Flour Dough(Elsevier Ltd., 2016) Yazar, Gamze; Çağlar Duvarcı, Özlem; Tavman, Şebnem; Kokini, Jozef L.Large Amplitude Oscillatory Shear (LAOS) tests were conducted at strains ranging from 0.01% to 200% and different frequencies (20, 10, 1, and 0.1 rad/sec) on hard wheat flour dough samples obtained from the different phases of Farinograph mixing: 1) at the first peak, 2) 5 min after the first peak, 3) 12 min after the first peak, 4) at the 20th min. All samples showed strain stiffening and shear thinning behavior in large strains. The gluten network is the origin of strain stiffening behavior and the rearrangement of the suspended starch matrix is the origin of shear thinning behavior. LAOS enables us to independently deconvolute these two events offering new insights into the structural origins of rheological properties in the non-linear region. Dough samples started to show strain softening and shear thickening after giving a peak around 100% strain due to the onset of the breakdown of the gluten network.Article Citation - WoS: 44Citation - Scopus: 50Thermal Behaviour of a Zeolitic Tuff(Elsevier Ltd., 2007) Çağlar Duvarcı, Özlem; Akdeniz, Yelda; Özmıhçı Ömürlü, Filiz; Ülkü, Semra; Balköse, Devrim; Çiftçioğlu, MuhsinNatural zeolites undergo structural changes after heating which open their possible use in different fields, related to their chemical and physical properties, such as building stone, lightweight aggregate, ceramic foam, concrete bricks, tiles, porcelain stoneware and additive in puzzolonic cements. In this study, thermal behavior of zeolitic tuff quarried from Gördes-Manisa, region of Turkey was investigated. Zeolitic rocks were first reduced to 2 μm and pellets were prepared by dry-pressing. The pellets were heated for 30 min in the temperature range of 200-1200 °C. Heating the tuff up to 600 °C did not cause any structural change detectable by X-Ray powder diffraction (X-Ray), Fourier Transform Infrared Spectroscopy (FTIR) and thermal characterization methods with regard to the original sample, while further increase in the temperature caused structural breakdown of zeolitic tuff. The appearance of the broad low intensity peaks in X-Ray diffraction diagrams indicated most probably a partial transformation of crystal structure into an amorphous structure. The Scanning Electron Microscopy (SEM) micrographs showed that the crystals seen in the original rock sample were broken during grinding and pressing processes. The crystal structure disappeared above 1000 °C and the spherical pores was observed at 1200 °C. Chemical composition of the zeolitic tuff did not change significantly with respect to temperature. The highest density (2.28 g/cm3) and hardness (387 Hv) were obtained by sintering the pellets at 1000 °C for 30 min.Article Citation - WoS: 19Citation - Scopus: 17Preparation and Characterization of Nanocrystalline Titania Powders by Sonochemical Synthesis(Elsevier Ltd., 2012) Çağlar Duvarcı, Özlem; Çiftçioğlu, MuhsinNanocrystalline mesoporous titania powders were synthesized by hydrolyzing titanium isopropoxide in ethanol-water mixtures which were ultrasonically treated without using any templates or chemicals. Titanium isopropoxide-ethanol mixture was added dropwise to a water-ethanol mixture placed in an ultrasonic bath. The properties of the sonochemically synthesized powder were compared with those of the powders prepared without ultrasonic treatment along with Degussa P-25 titania powder. The phase structure, crystallite size, surface area, particle size, powder density were determined and sintering behavior was analyzed in this work. The nanotitania powder prepared during ultrasonic induced hydrolysis (TiO 2-U) was determined to be formed from a mixture of anatase and brookite phases at 25°C. The brookite phase in nanotitania powder prepared without ultrasonic treatment (TiO 2-NoU) was detected at 70°C. The anatase-rutile phase transformation was completed in the 500-700°C range for both powders. The average crystallite sizes of the powders at 25°C were determined as 10 and 5nm for TiO 2-NoU and TiO 2-U, respectively. The surface area decreased from 238 to106m 2/g for TiO 2-NoU and from 287 to 82m 2/g for TiO 2-U when the calcination temperature was increased from 200 to 500°C. The evolution of the N 2 adsorption-desorption behavior with calcination temperature and the corresponding pore size distributions/volumes was attributed to the formation of closely packed submicron aggregates during powder synthesis and calcination. The sintering behavior was concluded to be controlled by 7-10nm crystallites and the submicron aggregates. The determination of the densification behavior of titania powders prepared by different methods with various levels of dopants may prove to be very useful for a better understanding of the phase/pore structure evolution which is crucial for a significant number of applications.Conference Object Preparation and Characterization of Nanocrystalline Titania(Türk Seramik Derneği, 2001) Çağlar, Özlem; Çiftçioğlu, Muhsin; Güden, MustafaNanokristal seramikler, ileri seramiklerin gelecekteki uygulamalannda önemli etkileri olabilecek özgün kimyasal, fiziksel ve mekanik özelliklere sahiptir. Bu çalışmada, tItanyum; izopropoksit'ten titan seramikleri hazırlanması ve karakterizasyonu incelendi. Şekillendirilmiş yapılar 650-850 C aralığında hava ortamında sinterlendi. Sol-jel prosesi ve jellerin kontrollü kurutulması ile elde edilen seramiklerin yoğunluklan teorik yoğrunluğun %79-99' u olarak bulundu. Sollar, jeller ve çökertme yöntemleriyle hazırlanan tozlardan preslenen peletlerin sinterlerne işlemi öncesi ve sonrası yoğunlukları sırasıyla teorik yoğunluğun %40-52 ve %55-83' ü olarak bulundu.Conference Object Citation - WoS: 5Citation - Scopus: 5Preparation and Microstuructural Development of Nanocrystalline Titania and Alumina(Trans Tech Publications, 2004) Çağlar Duvarcı, Özlem; Çiftçioğlu, Muhsin; Güden, Mustafa; Arıkut, G.The preparation of nanocrystalline titania and alumina was investigated by sol-gel methods using titanium isopropoxide, boehmite and aluminum isopropoxide. Various drying control chemical additives like oxalic acid, acetic acid and polyacrylic acid were used for modifying the drying behaviour and shrinkage of the gels. The sintered densities of the ceramics prepared by sol-gel processing and the dried gels were in the 79-99% of theoretical density for rutile. The green and sintered densities of the pellets prepared by uniaxial pressing of powders derived from sols, gels and precipitation techniques for titania were in the 40-52% and 55-83% respectively. The titania ceramics were observed to experience anatase-rutile phase transformation upon heat treatment at 650oC. The grain size of the sintered ceramics at 650oC was determined to be about 26 nm. Grain size of titania increased to 213 nm. at 850oC. The mechanical properties of these nanocrystalline ceramics were investigated by using microhardness testing.