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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

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

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

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

Salamcı, Elmas

Other | 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. 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

The effects of cutting tool coating on the surface roughness of AISI 1015 steel depending o cutting parameters

Gökkaya, Hasan | Nalbant, Muammer

Article | 2006 | Turkish Journal of Engineering and Environmental Sciences30 ( 5 ) , pp.307 - 316

The effects of a number of cutting tool coating materials on the surface quality of workpieces, depending on various cutting parameters, were investigated. AISI 1015 steel was processed without cooling on a lathe using 4 different cemented carbide cutting tools, i.e. uncoated, coated with AlTiN and coated with TiAlN using the PVD technique, and one with 3-layer coatings (outermost being TiN) applied by the CVD technique. Among the cutting parameters, the depth of cut was kept constant (2.5 mm) while the cutting speed and feed rate were changed. Five cutting speeds (50, 73, 102, 145, 205 m/min) and 2 feed rates (0.24 and 0.32 mm/rev) . . . were used during the machining process. Coating type, feed rate and cutting speed have different effects on surface roughness. In the experiments, less average surface roughness was obtained by using a 3-layer coated tool coated outermost with TiN. The lessening of cutting speed by about 33% improves the surface roughness by about 26%, and increasing the cutting speed by about 310% resulted in an improvement of about 69%. The effects of a number of cutting tool coating materials on the surface quality of workpieces, depending on various cutting parameters, were investigated. AISI 1015 steel was processed without cooling on a lathe using 4 different cemented carbide cutting tools, i.e. uncoated, coated with AlTiN and coated with TiAlN using the PVD technique, and one with 3-layer coatings (outermost being TiN) applied by the CVD technique. Among the cutting parameters, the depth of cut was kept constant (2.5 mm) while the cutting speed and feed rate were changed. Five cutting speeds (50, 73, 102, 145, 205 m/min) and 2 feed rates (0.24 and 0.32 mm/rev) were used during the machining process. Coating type, feed rate and cutting speed have different effects on surface roughness. In the experiments, less average surface roughness was obtained by using a 3-layer coated tool coated outermost with TiN. The lessening of cutting speed by about 33% improves the surface roughness by about 26%, and increasing the cutting speed by about 310% resulted in an improvement of about 69% Daha fazlası Daha az

Experimental investigation of vegetable oil usage as alternative fuel in diesel engines [Dizel Motorlarinda Alternatif Yakit OlaraK Bitkisel Yag Kullaniminin Deneysel Incelenmesi]

Yücesu H.S. | Altin R. | Çentinkaya S.

Article | 2001 | Turkish Journal of Engineering and Environmental Sciences25 ( 1 ) , pp.39 - 49

In this experimental study, the effect of the usage of vegetable oils, as alternative fuels, on engine performance and exhaust emissions in a single cylinder diesel engine were investigated. No 2-D diesel fuel and nine different oils (raw sunflower oil, raw cottonseed oil, raw soybean oil, and sunflower methyl ester, cottonseed methyl ester, soybean methyl ester, obtained from the raw oils respectively and refined opium poppy oil, rapeseed and corn oil) were used. In order to determine emission and performance characteristics, the engine was tested with full load-varied speed and constant speed-varied load tests. Chemical and physic . . .al properties of the raw oils were improved by transesterification. Test results showed that, when using vegetable oils, the engine performance and NO? are lower, and smoke density is higher than the engine performance in which No 2-D diesel fuel is used. The engine performance with the methyl ester fuels is higher than that with the raw oils and are close to diesel fuel performance Daha fazlası Daha az

Cladding of high Mn steel on low C steel by explosive welding

Acarer M. | Gülenç B.

Article | 2003 | Turkish Journal of Engineering and Environmental Sciences27 ( 6 ) , pp.431 - 434

High Mn steel containing about 16% Mn was cladded to a low C steel by explosive welding. The experimental results showed that the bonding interface has a wavy morphology; the welding interface has the characteristics of both sharp transition and local melted zones between 2 metals. Hardness increased near the welding interface due to excess plastic deformation in the explosion area and phase transformation from ? (f.c.c.) to ? (b.c.c.).

Effect of material parameters on rate-type constitutive equations in accelerated flow of viscoelastic fluids [Viskoelastik akiskanlarin ivmeli akisinda malzeme parametrelerinin turev tipli bunye denklemlerine etkisi]

Kopaç M. | Topuz A. | Arikol M.

Article | 1998 | Turkish Journal of Engineering and Environmental Sciences22 ( 6 ) , pp.495 - 502

The effect of material parameters on three rate-type constitutive equations (White-Metzner, Oldroyd 3-constant and Kopac-Arikol) used successfully according to the literature was investigated. The flow along the symetry axis of a converging-diverging flow channel was considered. In order to determine the effect of material parameters appearing in constitutive equations, the tensorial expressions of the models were reduced to the axis of symmetry, using derivative operators of models and flow kinematics. Arikol's values (1976, 1985) were used for the velocity and initial viscosity values appearing in reduced nonlinear ordinary differ . . .antial equations. The reduced constituve equations were solved numerically using the 4th order Runge-Kutta method. In these calculations, velocity and the 1st and 2nd derivatives of velocity were used as input in the equations. Solving the constitutive equations for 3 different values of the material parameters, the normal stress differences were determined along the axis of symmetry. The sum of squares between the calculated normal stress values and Arikol's(1976, 1985) experimental values were determined. As a result, the material parameters, sensitive and non-sensitive, were determined in each of the constitutive equations.The effect of material parameters on three rate-type constitutive equations (White-Metzner, Oldroyd 3-constant and Kopac-Arikol) used successfully according to the literature was investigated. The flow along the symmetry axis of a converging-diverging flow channel was considered. In order to determine the effect of material parameters appearing in constitutive equations, the tensorial expressions of the models were reduced to the axis of symmetry, using derivative operators of models and flow kinematics. Arikol's values (1976, 1985) were used for the velocity and initial viscosity values appearing in reduced nonlinear ordinary differential equations. The reduced constitutive equations were solved numerically using the 4th order Runge-Kutta method. In these calculations, velocity and the 1st and 2nd derivatives of velocity were used as input in the equations. Solving the constitutive equations for 3 different values of the material parameters, the normal stress differences were determined along the axis of symmetry. The sum of squares between the calculated normal stress values and Arikol's (1976, 1985) experimental values were determined. As a result, the material parameters, sensitive and non-sensitive, were determined in each of the constitutive equations Daha fazlası Daha az

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