18 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 10 / 18
Öğe N-type InP Schottky diodes with organic thin layer: Electrical and interfacial properties(Journal of Vacuum Science & Technology B, 2010-03) Güllü, Ömer; Turut, AbdulmecitThe rectifying junction characteristics of methyl red (MR) organic film on n-type InP substrate have been studied. It has been observed that MR-based structure shows an excellent rectifying behavior and that the MR film increases the effective barrier height by influencing the space charge region of the n-type InP. The barrier height and ideality factor values for this structure have been obtained as 0.75 eV and 1.93 from the forward bias current-voltage characteristics, respectively. By using capacitance-voltage characteristics at 1 MHz, the barrier height and the carrier concentration values have been calculated as 0.93 eV and 5.13×1015 cm−3, respectively. The energy distributions of the interface states and their relaxation times have been determined from the forward bias capacitance-frequency and conductance-frequency characteristics. Moreover, it was seen that both the interface-state density and the relaxation time of the interface states decreased with bias voltage from experimental results.Öğe The changes in the serum, liver, kidney protein and genomic DNA profiles in rats treated with 7,12-Dimethylbenz(A) anthracene and Plantago major L.(RJPBCS, 2014-01) Berber, İsmet; Ekin, Suat; Levent, Abdulkadir; Oto, Gökhan;In the study, the changes in the serum, liver, kidney protein and genomic DNA profiles in Wistar albino rats administrated to 7,12-dimethylbenz(a)anthracene (DMBA) and Plantagomajor L. were investigated. SDS-PAGE profiling of the serum proteins showed that the levels of two proteins molecular weighing 140.8 kDa and 46.8 kDa were significantly lower on the 0th day of treatment than on the 60th day of application in the groups. Furthermore, two proteins (34.5 and 22.3 kDa) were solely present in DMBA-treated liver cell lysates. On the contrary, the kidney protein profiles did not show significant banding variations in groups. Genomic DNA analysis also confirmed that DNA extracted from liver and kidney cells did not fragment in any of the groups after the 60th study day. The proteins 34.5 and 22.3 kDa in liver cell lysates at the 60th day in DMBA-treated group could be extra-prognostic indicators for severe DMBA toxicity.Öğe Dimension and insulation thickness optimization of circular flat plate solar collectors(Energy Education Science and Technology, 2011) Argunhan, ZekiIn this study, expressions for optimum radius of a circular flat plate solar collector and the optimum insulation thickness distribution are derived by using the concept of solar gain, which maximizes the life-cycle savings. For the specified condition the optimum radius has been found as 2.14 m and the optimum insulation thickness distribution on back of collectors has been formulized. The insulation material thickness distribution has been determined by performing a detailed dimensional analysis; therefore heat loss is minimized, and results are presented in graphics.Öğe The effects of injection pressure on the engine performance characteristics of a CI engine fueled with canola oil-diesel blends(Energy Education Science and Technology Part A: Energy Science and Research, 2012-01) Aydın, HüseyinThe usage of vegetable oils in diesel engines has some negative effects especially on engine performance. Therefore vegetable oils can not be used as pure form or with high percentages in diesel fuel in unmodified diesel engines. Some of the engine operation conditions should be improved by modifying engine operation systems for this purpose. The effects of injection pressure on engine performance of a diesel engine, by using two different blends of vegetable oil (canola oil) in diesel fuel (DF) having a concentration of 20% (O20) and 50% (O50) vegetable oil, were studied in the present work. The injection pressure was changed from 200 MPa to 220 MPa. Tests were made at fully loaded engine and different speeds of engine operation. In the experiments, the engine power, torque, brake specific fuel consumption (Bsfc), mass fuel consumption rate, brake thermal efficiency and exhaust gas temperature of the test engine have been investigated. Results revealed that the increased injection pressure can significantly promote performance parameters of diesel engine with using vegetable oil without any modification either in oil or in engine itself. The improved results of experiments have been given as graphics in this paper.Öğe Influence of yogurt adding on physicochemical and sensorial properties of some lettuce types(WFL Publisher, 2013) Tarakçı, Zekai; Uǧur, Atnan; Temiz, Hasan; Dağ, BeşirThe aim of this study was to investigate the effects of adding yogurt and roasting treatment on some physicochemical, L*, a* and b* colour values and organoleptic acceptability properties of lettuce types. The 10 different lettuce varieties included kasam, mangano, robinson, olenka, arapsaçi{dotless}, red leaf, lolorosso, red salat, palamet and salanova were used. After cleaning and cutting into 0.5 mm, the lettuces were roasted with equal amount added yogurt for about 5 min and then applied to the mixing process. There were significant differences in dry matter and pH values between the lettuces added yogurt and raw lettuces. While dry matter of lettuces was increased significantly with yogurt, the pH levels were decreased. The whiteness values (L*) for lettuces have caused significant differences by adding yogurt and roasting applications. L* values of control sample without lettuces were significantly higher than the samples prepared by adding yogurt to lettuces. Lettuce types had a significant effect on the L* colour of samples. The lettuces were a significant a* color values between before and after roasting. After adding yogurt to lettuces; b* values of kasam, robinson and olenka colour values were significantly higher than the other samples prepared by adding yogurt to lettuce types. The lowest overall acceptability scores were detected for olenka, robinson and lolorosso lettuce types while the highest overall acceptability scores were detected for arapsaci, red salat and salanova lettuce types, which were common use in Turkish meals.Öğe Effects of natural hard shell particles on physical, chemical, mechanical and thermal properties of composites(SAGE Journals, 2021-05-31) Çelik, Yahya Hışman; Çelik, Kadir Serdar; Kılıçkap, ErolShelled herbal foods are widely consumed. The evaluation of the shells of these foods is important due to their features such as low cost, ease of recycling and environmental friendliness. In this study, hazelnut shell (HS), pistachio shell (PS), and apricot kernel shell (AKS) were brought to powder particles by grinding to dimensions of 300–425 µm. Some of the powder particles were converted into ash at 900°C. The amounts of cellulose, ash, humidity, and metal in these particles via chemical analyses were determined, while their structural properties via X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analyses. Composite materials were produced by adding 15 wt.% to the polyester matrix material from these powder particles and ashes. Compression strength, hardness, specific weight, and thermal conductivity of these composites were analyzed. The lowest and highest humidity, ash, cellulose, hemicellulose, and lignin ratios in powders showed differences depending on the type of powders. The amount of Sn and K in the HS, PS, and AKS powders were close to each other, while the amount of Ca, Na, Mg, Fe, Mn, Cu, Zn and Si was higher in AKS powder. The reinforcement adding to the polyester increased the compression strength, hardness, specific weight and thermal conductivity properties.Öğe Biodiesel production from raw cottonseed oil and its characterization(Energy Education Science and Technolgy Part A, 2011-07) Altun, Şehmus; Yaşar, Fevzi; Öner, CengizIn this study, raw cottonseed oil of Turkish origin was transesterified using methyl alcohol and an alkali catalyst to obtain the cottonseed oil methyl ester. The obtained cottonseed oil methyl ester was analyzed by gas chromatography (GC) for determining the fatty acid composition. The fuel-related properties of cottonseed oil methyl ester, cold filter plugging point, cloud point, kinematic viscosity, density, cetane index, flash point, distillation, sulfur content and heating value were determined and compared with those of petroleum diesel fuel and international biodiesel standards. From gas chromatograph analysis, it was found that the cottonseed oil methyl ester has the more amount of total unsaturated FA, therefore, it showed better cold-flow properties than more saturated ones, as expected. Moreover, the fuel-related properties of cottonseed oil methyl ester were within the specified standardsÖğe Second Law analysis in concentric heat exchangers with vortex flow generators(Energy Education Science and Technology, 2011) Argunhan, Zeki; Çakmak, Gülşah; Yıldız, Cengiz; Behçet, RasimIn the present study, the experimental results of heat transfer of a concentric tube heat exchanger were analyzed with respect to Second Law of Thermodynamics to reach the geometric optimal design of the heat exchangers. In order to increase the heat transfer, the vortex generators were placed in the entrance of the inner pipe of the heat exchanger. These vortex generators are 60 mm in diameter having six angled (55°, 65°, 75°, 90°) winglets. The winglets have one rectangular slot in each and are 2×7 mm in dimensions. Experiments were carried out with different Reynolds Numbers. Air as hot fluid and water as cold fluid were passed through the inner pipe and outer pipe of the concentric tube heat exchanger, respectively. The variations of the efficiency and Entropy Generation Number with respect to Reynolds Number are shown in graphics, and the results were discussed.Öğe The effect of rotary type turbulator placed in entrance of heat exchanger on heat transfer and frictional loss(Energy Education Science and Technology, 2011) Argunhan, Zeki; Behçet, Rasim; Yakut, Ali KemalIn this study, improving heat transfer in heat exchangers with paralel flow is gained by using swirl flow. For this purpose, a propeller type of turbulator was placed in the entrance of interior pipe of heat exchanger with paralel flow and the effect of turbulator on the heat transfer and friction losses in steady conditions was experimentally investigated. The effect of production of turbulance for improvement of heat transfer in interior pipe flows and the effects of turbulator on heat transfer and pressure drop are experimentally researched by placing a propeller type of turbulator at the entrance of heat exchanger to produce swirl air flow. In experiment setup, water was used as the fluid on which the heat was transferred and air was used as the fluid from which heat was transferred to the water. By usage of datas obtained from experimental measurements were calculated for Reynolds number ranging from 8000 to 24000 necessary relationships effet on heat transfer and pressure drop. In comparison with empty pipe it was seen that the heat transfer increased at range between 25,5%- 50,3% and the friction losses increased 5 times. Besides, by analyzing the system exergy, the dependence of non-dimensional exergy loss on Reynolds number was drawn to investigate whether this improvement technique is advantageous thermodynamically or not. When comparing the exergy losses in empty pipe and the pipe with a turbulator at approximately same Reynolds numbers, it was seen that exergy loss is 15% higher for empty pipe than that for the pipe with the turbulator. As a result of that information, the improvement technique was proved to be advantageous in thermodynamic manner too. By the usage of turbulator that results in the partial recovery of loss energy, it was proven that the improvement technique was thermodynamically advantageousÖğe Effect of swirl generators with different sized propeller on heat transfer enhancement(Energy Education Science and Technology, 2011) Argunhan, Zeki; Yıldız, Cengiz; Çakmak, GülşahIn this study, the swirl flow that is one of the passive methods is used for increasing the heat transfer coefficient in the concentric heat exchangers. For this purpose, propeller type swirl generators were prepared to test in the experiments. So, the effect of propellers placed in the inner pipe of the concentric heat exchangers on the heat transfer and pressure drop was investigated experimentally. Experiments were undertaken for the Reynolds Number range of 4000-12000 and for both parallel and counter-flow. It is shown that, the propellers rotated freely with the effect of fluid flowed in the inner pipe are swirling flow generator and they have improved heat transfer. In addition that up to 50% enhancements could be accomplished in heat transfer rates with the swirl generators compared to without the swirl generators. In the parallel flow mode, the enhancement was 10% lower than that of counter-flow at the same Reynolds number. On the other hand the pressure losses increase approximately 3 times more than the empty tube related to Reynolds numbers and propeller sizes. As an outcome of the study, the results showed that a rather smaller size but the same capacity heat exchanger could be proposed by using these elements imposing swirling to the fluid flowing through inner pipe.
