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Filtreler
Bulunan: 39 Adet 0.002 sn
Koleksiyon [8]
Tam Metin [2]
Yayın Türü [2]
Yazar [20]
Yayın Yılı [14]
Konu Başlıkları [20]
Yayıncı [2]
Yayın Dili [2]
Dergi Adı [1]
Membrane potentials for linearly varying fixed charges

Genç, Ayten

Article | 2009 | Turkish Journal of Engineering and Environmental Sciences33 ( 1 ) , pp.73 - 81

The membrane potentials for asymmetric membranes where fixed charges varied linearly with position were evaluated from the numerical solutions of Nernst-Planck flux and Donnan potential equations. The evaluated membrane potentials were compared with the results obtained from the conventional TMS theory where the fixed charge concentration in the membrane was assumed to be uniform. In the comparison, the number of fixed charges was kept constant by defining an average for the fixed charge concentration. The numerical results showed that the membrane potential increased in magnitude when the distributions of fixed charges at the membr . . .ane-solution interfaces were unequal. In addition, the deviation from TMS theory increased more as the charge difference at the interfaces increased. © TÜBİTAK Daha fazlası Daha az

Mechanical properties of spray cast 7XXX series aluminium alloys

Salamcı, Elmas

Other | 2002 | Turkish Journal of Engineering and Environmental Sciences26 ( 4 ) , pp.345 - 352

Mechanical properties of spray deposited and extruded 7xxx series aluminium alloys were investigated in peak aged condition. To study the influence of Zn additions on the mechanical behaviour of spray deposited materials, three alloy compositions were selected, namely: SS70 (11.5% Zn), N707 (10.9% Zn) and 7075 (5.6% Zn). After ageing treatment, notched and unnotched specimens of spray deposited alloys were subjected to tensile tests at room temperature. Experimental results showed that the SS70 alloy exhibited the highest strength. Spray deposited Al alloys showed a very high strength as compared to conventionally processed 7xxx ser . . .ies Al alloys. Compared with the PM processed 7xxx series Al alloys, fracture toughness values of these alloys were higher. Mechanical properties of spray deposited and extruded 7xxx series aluminium alloys were investigated in peak aged condition. To study the influence of Zn additions on the mechanical behaviour of spray deposited materials, three alloy compositions were selected, namely: SS70 (11.5% Zn), N707 (10.9% Zn) and 7075 (5.6% Zn). After ageing treatment, notched and unnotched specimens of spray deposited alloys were subjected to tensile tests at room temperature. Experimental results showed that the SS70 alloy exhibited the highest strength. Spray deposited Al alloys showed a very high strength as compared to conventionally processed 7xxx series Al alloys. Compared with the PM processed 7xxx series Al alloys, fracture toughness values of these alloys were higher Daha fazlası Daha az

Directionality in the mechanical properties of spray cast and extruded 7XXX series aluminium alloys

Salamci E.

Article | 2003 | Turkish Journal of Engineering and Environmental Sciences27 ( 3 ) , pp.169 - 176

Three 7xxx series aluminium SS70, N707 and 7075 alloys have been produced by the spray deposition process. The alloys were extruded and subsequently heat treated in the T6 and T7 temper conditions. Texture analysis of as-received and solution treated alloys revealed and fibre textures leading to higher mechanical properties in the longitudinal direction. Anisotropic behaviour was observed in these alloys. In addition, the influence of recrystallizing, heat treatment, stretching, and processing techniques (IM, PM and spray casting) as well as techniques of forming (extrusion, rolling and forging) on the anisotropic behaviour of the . . . 7xxx series aluminium alloys was examined Daha fazlası Daha az

Relations between coal properties and spontaneous combustion parameters

Kaymakçi E. | Didari V.

Article | 2002 | Turkish Journal of Engineering and Environmental Sciences26 ( 1 ) , pp.59 - 64

The results of linear and multiple regression analyses to determine the relationship between spontaneous combustion parameters (derived from time-temperature curves obtained from laboratory tests) and coal parameters (obtained from proximate, ultimate and petrographic analyses) have been explained. The linear regression analyses have shown that ash (A), volatile matter (VM), carbon (C), hydrogen (H), exinite (E), inertinite (I) and mineral matter (MM) are the major factors affecting spontaneous combustion. According to the multiple regression analyses, these major factors are volatile matter, carbon, hydrogen, nitrogen (N), oxygen ( . . .O), sulphur (S) and inertinite. As a result of this study, some empirical equations have been derived using statistical models Daha fazlası Daha az

Bir Stirling motorunda ısıtıcı ve soğutucu boyutlarının belirlenmesi için bir matematik model

Yücesu, Hüseyin Serdar

Article | 1999 | Turkish Journal of Engineering and Environmental Sciences23 ( 2 ) , pp.105 - 120

Bu araştırmada bir Stirling motorunun ısıtıcı ve soğutucusunda hız ve sıcaklık dağılım eğrileri sonlu farklar yöntemiyle incelenmiştir. Kararlı çalışma şartlarında, 300 K soğuk kaynak ve 1000 K sıcak kaynak sıcaklığı ve 750 d/d motor hızı için motorun termodinamik analizleri yapılarak sıkıştırma ve genişleme periyodu boyunca ısıtıcı ve soğutucu içerisine giren iş gazı kütlesi miktarları hesaplanmış, yoğunluk ve kütle miktarı değişimi kullanılarak hız ve sıcaklık profilleri oluşturulan bir Fortran bilgisayar programı yardımı ile belirlenmiştir. Peryodik akış şartlarında yapılan hesaplamalarda sıkıştırma ve genişleme periyotları süres . . .ince ortalama gaz sıcaklığı ve ısı taşınım katsayıları da hesaplanmıştır. Deneysel çalışmalarda ölçülen sıcaklıklar hesaplamalarda sınır şartları olarak kullanılmıştır. Yapılan hesaplama sonucunda lmm kanal genişliği için ısıtıcı boyu 12 cm ve soğutucu boyu 14 cm olarak belirlenmiştir. In this study the dimensions of the heater and cooler of a Stirling engine are estimated by simulating the velocity and temperature fields in the heater and cooler using finite difference method. For an engine working at steady conditions, at the 300 K cold and 1000 K hot sources temperatures and 750 rpm engine speed a thermodynamic analysis is performed and the local values of mass, density and pressure are determined relative to crank angle. The cyclic period is divided into 10 degree sub periods and using the mass flow obtained from thermodynamic analysis, the velocity profiles, temperature profiles, average temperature and heat transfer coefficient distribution are calculated for each sub period. In the calculations the gas temperature measured at the inlet and outlet of heater are used as boundary condition. As the result considering 1 mm channel width, 12 cm length for heater and 14 cm length for cooler were determined Daha fazlası Daha az

Geometric accuracy testing of Ikonos Geo-product mono imagery using different sensor orientation models

Büyüksalih, Gürcan | Oruç, Murat | Koçak, Güven

Other | 2003 | Turkish Journal of Engineering and Environmental Sciences27 ( 5 ) , pp.347 - 360

This paper addresses the metric accuracy potential of Ikonos Geo imagery for 2D geopositioning. For this, alternative sensor orientation models including rational functions, satellite orbital modelling and ter-rain relief-corrected affine transformation were used since the Ikonos camera model and the information for external parameters are not provided to the users. Test results arising from the application of these alternative models in a Zonguldak testfield confirm that Ikonos Geo-scenes can yield 2D geopositioning to pixel and in some cases even sub-pixel, accuracy. The paper describes the Zonguldak testfield, discusses geopositi . . .oning approaches in the 2D adopted and reports on the geometric accuracy obtained with different sensor orientation models. This paper addresses the metric accuracy potential of Ikonos Geo imagery for 2D geopositioning. For this, alternative sensor orientation models including rational functions, satellite orbital modelling and ter-rain relief-corrected affine transformation were used since the Ikonos camera model and the information for external parameters are not provided to the users. Test results arising from the application of these alternative models in a Zonguldak testfield confirm that Ikonos Geo-scenes can yield 2D geopositioning to pixel and in some cases even sub-pixel, accuracy. The paper describes the Zonguldak testfield, discusses geopositioning approaches in the 2D adopted and reports on the geometric accuracy obtained with different sensor orientation models Daha fazlası Daha az

Effect of alloying elements to aluminium on the wettability of AL/SiC system

Candan E.

Article | 2002 | Turkish Journal of Engineering and Environmental Sciences26 ( 1 ) , pp.1 - 5

The wettability at a liquid Al-alloy/SiC interface was evaluated by the sessile drop method at 750°C. The wetting angle, ?, of a sessile drop on SiC substrate decreased with the addition of Pb, Mg and Ca to pure aluminium. The reduction in ? of the Al-Pb alloy was proportional to the reduction in surface tension, ?lv of aluminium, whereas in Al-Mg and Al-Ca alloys the reduction in ? was greater than the reduction in ?lv of Al. This was attributed to reactions that took place at the Al-alloy/SiC interface. Scanning electron microcopy (SEM) analysis showed that severe interactions had taken place at the interfaces of Al-Mg alloy/SiC a . . .nd Al-Ca alloy/SiC Daha fazlası Daha az

A computer-controlled triaxial swelling test apparatus

Bilir, M. Erdinç | Müftüoğlu, Yadigar V. | Sarı, Dursun

Other | 2004 | Turkish Journal of Engineering and Environmental Sciences28 ( 4 ) , pp.269 - 280

To avoid the problems encountered during and after the construction of engineering structures built within swelling rocks or soils, data related to swelling stresses and strains should be used in the design stage. For an effective design, it is important that the data used for this purpose should be derived from triaxial swelling tests. In this article, a re-designed and computer-controlled triaxial swelling test apparatus is introduced. Due to the limited amount of test equipment, the work associated with triaxial swelling tests has been rather limited and consequently a test standard has not been developed yet. The computer-contro . . .lled triaxial swelling test apparatus has made tedious swelling tests easier and thus it has provided better possibilities for the investigation of the triaxial swelling behavior of soils and rocks. To avoid the problems encountered during and after the construction of engineering structures built within swelling rocks or soils, data related to swelling stresses and strains should be used in the design stage. For an effective design, it is important that the data used for this purpose should be derived from triaxial swelling tests. In this article, a re-designed and computer-controlled triaxial swelling test apparatus is introduced. Due to the limited amount of test equipment, the work associated with triaxial swelling tests has been rather limited and consequently a test standard has not been developed yet. The computer-controlled triaxial swelling test apparatus has made tedious swelling tests easier and thus it has provided better possibilities for the investigation of the triaxial swelling behavior of soils and rocks Daha fazlası Daha az

On the radiological character of a coal-fired power plant at the town of Çatalağzı, Turkey

Aytekin, Hüseyin | Baldık, Rıdvan

Other | 2008 | Turkish Journal of Engineering and Environmental Sciences32 ( 2 ) , pp.101 - 105

This paper presents a study performed on the radiological character of the Çatalağzı Thermal Power Plant (ÇTPP/ÇATES), on the west Black Sea coast of Turkey. Natural radioactivity distribution of the terrestrial radionuclides $^{238}U$, $^{232}Th$, and $^{40}K$ of surface soil samples around the ÇTPP was analyzed. The average radioactivity concentrations for $^{232}Th$, $^{238}U$, and $^{40}K$ for soil samples were 39.7, 30.5, and 378.7 Bq $kg^{-1}$, respectively. $^{238}U$ and $^{40}K$ concentrations are lower than the world average values, 35 Bq $kg^{-1}$ and 400 Bq $kg^{-1}$, respectively, and the $^{2 . . .32}Th$ concentration is higher than the world average value, 30 Bq $kg^{-1}$. This paper presents a study performed on the radiological character of the Çatalağzı Thermal Power Plant (ÇTPP/ÇATES), on the west Black Sea coast of Turkey. Natural radioactivity distribution of the terrestrial radionuclides $^{238}U$, $^{232}Th$, and $^{40}K$ of surface soil samples around the ÇTPP was analyzed. The average radioactivity concentrations for $^{232}Th$, $^{238}U$, and $^{40}K$ for soil samples were 39.7, 30.5, and 378.7 Bq $kg^{-1}$, respectively. $^{238}U$ and $^{40}K$ concentrations are lower than the world average values, 35 Bq $kg^{-1}$ and 400 Bq $kg^{-1}$, respectively, and the $^{232}Th$ concentration is higher than the world average value, 30 Bq $kg^{-1}$ Daha fazlası Daha az

Evaluation of a modified Jeffreys type model for viscoelastic fluids

Kopaç M.

Article | 1999 | Turkish Journal of Engineering and Environmental Sciences23 ( 1 ) , pp.49 - 57

In this study using some existing constitutive equations, a modified Jeffreys type model with retardation time is developed which is successful with the experimental data for simple shear flow and shear free flow. Nonlinear regression analysis based on Marquardt Algorithm is used for determination of material parameters for simple shear flow. The general form of the modified model is reduced by using the simple shear flow conditions and Oldroyd derivative for cartesian coordinates. In the determination of material parameters of the modified model is used experimental data of Leider and Lilleleht(1973) for viscometric functions. When . . . viscometric functions of the modified model is compared with viscometric functions of the existing constitutive equations which use the material parameters of Leider and Lilleleht(1973), viscometric functions of the modified model is found to be more successful.In this study using some existing constitutive equations, a modified Jeffreys type model with retardation time is developed which is successful with the experimental data for simple shear flow and shear free flow. Nonlinear regression analysis based on Marquardt Algorithm is used for determination of material parameters for simple shear flow. The general form of the modified model is reduced by using the simple shear flow conditions and Oldroyd derivative for cartesian coordinates. In the determination of material parameters of the modified model is used experimental data of Leider and Lilleleht (1973) for viscometric functions. When viscometric functions of the modified model is compared with viscometric functions of the existing constitutive equations which use the material parameters of Leider and Lilleleht (1973), viscometric functions of the modified model is found to be more successful Daha fazlası Daha az

Effect of coating thickness on electrode life in the spot welding of galvanized steels

Müftüoğlu, Fisun | Keskinel, Tuna

Article | 2007 | Turkish Journal of Engineering and Environmental Sciences31 ( 3 ) , pp.183 - 187

This study examined the effect of coating thickness on electrode life and nugget strength. Uncoated and galvanized steel sheets supplied from Ere˘gli Iron and Steel Factories Co. (Erdemir) with similar chemical compositions having different coating weights (100, 180, and 275 g/m2) were welded using resistance spot welding under constant welding parameters. Electrode force used during spot welding operation was 7.3 kN under 6.5 kA of constant welding current and 2 s welding time. After welding operations, shearing tests were applied to selected specimens and the nugget diameters were measured. Experimental results showed tha . . .t as the coating thickness increased the electrode life and the strength of the weld nugget decreased. This study examined the effect of coating thickness on electrode life and nugget strength. Uncoated and galvanized steel sheets supplied from Ere˘gli Iron and Steel Factories Co. (Erdemir) with similar chemical compositions having different coating weights (100, 180, and 275 g/m2) were welded using resistance spot welding under constant welding parameters. Electrode force used during spot welding operation was 7.3 kN under 6.5 kA of constant welding current and 2 s welding time. After welding operations, shearing tests were applied to selected specimens and the nugget diameters were measured. Experimental results showed that as the coating thickness increased the electrode life and the strength of the weld nugget decreased Daha fazlası Daha az

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