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Item The Frenet and Darboux instantaneous rotation vectors of curves on time-like surface(1996)In this paper, depending on the Darboux instantaneous rotation vector of a solid perpendicular trihedron in the Minkowski 3-space $R_1^3=[R^3, (+,+,-)]$ the Frenet instantaneous rotation vector was stated for a space-Eke curve (c) with the principal normal n being a time-like vector. The Darboux instantaneous rotation vector for the Darboux trihedron was found when the curve (c) is on a time-Eke surface. Some theorems and results giving the relations between two frames were stated and proved.Item Examination of temperature distribution as a result of hard-brazing of two different materials by finite elements method(1996)Knowing the temperature effect on machine construction is the first step at material selection and planing machine parts exposed to temperature effect above, normal conditions. Since joining processes such as welding and hard-brazing were done at high temperatures, abrupt variations in temperature distributions take place. Because of these temperature variations inner structure and shape changes occur in material. If two different materials are joint, these problem becomes more important due to mismatch of physical properties of materials joint. Because of this reason, temperature distribution must be known at these kind of joinings. In this study only the temperature distribution calculations around the joining zone were carried out. In the future step the thermal stress and residual stress distributions during and after joining process will be calculated. For this purpose steel-brass material couple were chosen and the materials as thin plates were hard-brazed. The joining parts of this material couple were heated upto hard- brazing temperature and then cooled in air. In this numeric study finite elements method was used and the programming language was chosen Fortran77. In modelling two dimensionel four nodes rectangular elements were selected.Item Comparing artificial neural networks ( ANN ) image compression technique with different image compression techniques(1996)In this paper it is presented that, 256x256 16 gray level images can be compressed fast and efficiently by using neural networks . Compression results were compared with the other methods according to mean square error (MSE) and visual of the image and it is seen that by further works on ANN the images can be compressed better.Item Deacidification of high acid olive oil by immobilized lipase(1996)The acidity reduction of high acid oils prior to refining could be an attractive application for industry. In this study the enzymatic deacidification degummed and dewaxed olive oil with a high free fatty acid content, catalysed by an immobilized lipase was optimzed (Novozym 435). The optimum amount of substrate for synthesizing trigliycerides was the necessary stoichiometric amount of fatty acid and glycerol. The mixing was performed with a mechanical stirrer and the dehydration was performed by vacuum pump or by bubbling dry nitrogen. The dehydration rate was faster than the deacidification rate. The four parameters chosen for this experimental plan: pressure, temperature, and the amounts of glycerol and enzyme in the reaction mixture. The use of glycerol more than theortical amount did not affect the rate of deacidification. The stoichiometric amount of glycerol was sufficient for the deacidification of high acid olive oil. Maintaining low pressure is very important for the removal of water which is formed during the esterification reaction. Either, the reaction is conducted at 20 mm Hg or the dehydration is performed by bubbling dry nitrogen. The optimum amount of immobilized enzyme necessary for the deacidification reaction was determined and 10:1 ratio of oil: immobilized enzyme appeared to be satisfactory. The effect of temperature on the deacidification of high acid olive oil was investigated (between $40- 70^o$C). The reaction temperature influenced the rate of deacidification. The optimum operation temperature was found to be $60^o$C. At $70^o$C the deacidification decreased with increasing incubation time due to enzyme deactivation occuring at this temperature.Item The Frenet and Darboux instantaneous rotation vectors for curves on space-like surface(1996)In this paper , considering the Darboux instantaneous rotation vector of a solid perpendicular trihedron in the Minkowski 3-space $R_1^3$ , the Frenet instantaneous rotation vector was stated for the Frenet trihedron of a space -like space curve (c) with the binormal b being a time-like vector. The Darboux deri¬vative formulas and the Darboux instantaneous rotation vector were found when the curve (c) is on a space -like surface , A fundamental relation , as a base for the geometry of space-like surfaces, was obtained among the Darboux vectors of the parameter curves $(c_1)$ , $(C_2)$ and an arbitrary curve (c) on a space-like surface.Item Steady state relations of plasma zinc to copper and iron plasma levels in children(1996)In 153 randomly selected children with no clinical and laboratory findings of acute infection, the mean (± SEM) fasting plasma zinc, iron and copper levels (0.699± 0.028 mg/L, 1.553+ 0.083 mg/L and 1.012+0.039 mg/L, respectively) were pair-assessed on an atomic absorption spectrophotometer. A significant simple linear relation was found between plasma zinc (PIZn) and iron (PIFe) levels and the regression equation was plasma (PIZn)=0.602+0.062(PIFe), p<0.022, r=0.184. However, the polynomial parabolic relation between zinc and iron was not found significant. Whereas, a significant polynomial parabolic relation was found between plasma zinc and copper (PICu) and the regression equation was (PIZn)=0.411+0.471 (PICu)-0.154(PICu) 2 p<0.024, r=0.220. In addition, a significant multiple relation with a constant was found between plasma zinc, copper and iron levels and the regression equation was PIZn=0.476+0.121(PICu)+0.158(PIFe) p<0.008, r=0.249. and without a constant the regression equation was PIZn- -0.160(PICu)+0.184(PIFe). In conclusion, in children at steady state, when plasma zinc level was high the plasma iron level was also found high; whereas, plasma copper level was found low.Item Relation between Darboux instantaneous rotation vectors of curves on a time-like surface(1996)In this study, a fundamental relation , as a base for the geometry of the time-like surfaces, among the Darboux vectors of an arbitrary time-like curve (c) on a time-like surface and the parameter curves $(c_1)$ and $(c_2)$ in the Minkowski 3-space $R_1^3$ was founded.Item The study mapping for directed space-like and time-like lines in Minkowski 3-space $R^3_1$(1996)In this study, the E. Study mapping was defined for the space-like and time-like lines in the Minkowski 3-space $R_1^3$. Hence, there is one to one correspondence between directed space-like (resp.,time-like) lines of $R_1^3$ and ordered pair of vectors (a ,$a_0$ ) such that < a,a >=1 (resp., < a,a>= -1) and <a,$a_0$ >=0Item The finite element analysis of buckling of laminated rectangular reinforced concrete plates with circular hole(1996)In this investigation an approach buckling analysis for simply supported rectangular reinforced concrete plates under uniaxial compression are developedThe objective of this investigation is to compare buckling load of the reinforced plate with circular hole and without hole. A laminated composite plate is considered. The finite element models for with central circular hole and without hole are designed. The composite materials and composite laminates materials approach are discussed. The solution of the problem by computer program coded in FORTRAN is explained and numerical example is given.Item The effect of FAD on erythrocyte glutathione reductase activity in undialyzed uremic patients and healthy subjects(1997)The eryrocyte glutathione reductase (GSSG-R) activity with and without FAD supplementation (Act. A and Act B, respectively) was studied in 24 undialyzed uremic patients and 25 healty subjects. Mean erytrocyte GSSG-R activity from normal subjects was 5039+-1.43 U/g Hb (the active form). After the addition of FAD to the hemolysates, this increased to 7.79+-1.07 U/g Hb, an increase of 1.88+-0.84 U/g Hb (the inactive from) (p<0.001). In patients with FAD supplementation, erytrocyte GSSG-R activity increased from 9.26+-1.19 U/g Hb to 10.06+-1.06 U/g Hb, an increased of0.80+-0.76 U/g Hb (p<0.01). In addition, there were significant positive correlations between the enzyme activities and plasma urea level, and negative correlations between the enzyme activities and hemoglobin concentrations in patients, but not in the controls. It was included that further cross-sectional in vivo studies should be made to determine whether riboflavin administration may or nat be useful in preventing renal anemia.Item How to improve weaning food(1997)The weaning food prepared by cereals and winter or summer vegetables in the 'baby kitchen of the hospital and recom¬mended to be cooked at home by 'housewives was studied in view of trace element and mineral compositions. Trace elements were assayed on an atomic absorption spectrophotometer (Perkin Elmer 2380) and the minerals on a flame photometer. Different combinations of foliated and bulbous vegetables were used in winter and summer months on a common basis of cereals and legumes. The mean (± SEM) mineral and trace element contents in the infant vegetable dish did not differ significantly when prepared at home with winter and summer vegetables. According to ESPGAN criteria, iron was found in appropriate amounts, copper and zinc were.found low, but manganese was found high. In the present study chicken fat is introduced for shortening, since its long-chain polyunsaturated fatty acid profile is very close to that of human milk. In conclusion, to improve a weaning food of cereals, foliated and bulbous vegetables could be possible if chicken fat is used for shortening; since chicken fat profile is very close to that of human milk while sustaining breast feeding at least twice a day to compansate its zinc shortage.Item An investigation of deep drawing of low carbon steel sheets and applications in artificial neural networks(1997)In this study, the deep drawability of SAE 6114, being a low carbon steel, was investigated. The materials with thickness varying from 0.67 mm to 2 mm were subjected to tensile tests and then R (average vertical anisotropy coefficient) and n (stain hardening exponent) values were determined. At the same time, h (the height of the cup) and F (the reaction force) values of the materials were found by subjecting them to Erichsen test. A sheet with 2 mm thickness was cold rolled in 6 different deformation ratios and the tests were applied to it. Results obtained from the tests were compared with each other and ANN application was performed for these results. It was proved that, there was an ANN solution to obtain new values of % deformation rate and thickness properties of deep drawing of low carbon steel sheets which were found by experiment. The obtained values satisfied our estimation.Item A generalized approach to coupled nonlinear vibration of continuous systems(1997)A mathematical model covering many practical vibration problems of continuous systems has been proposed. The equations of motion consist of two nonlinearly coupled partial differential equations. The quadratic and cubic nonlinearities as well as the linear part of the equations are represented by arbitrary operators. A perturbation approach (method of multiple time scales) has been applied directly to the partial differential equations. The responses as well as the amplitude and phase modulation equations are found for the case of primary resonances of the external excitation and one-to-one internal resonances between the natural frequencies of the equations. The coefficients of the amplitude and phase modulation equations are calculated in their most general form. Results are then applied to a nonlinear cable vibration problem having small sag-to-span ratios.Item Oral konstraseptif kullanan kadınlarda artmış kardeş kromatid değişimi ve mitotik indeks sıklığı(1997)! OBJECTIVE: In this study, we tried to investigate acute mutagenic effects of monophasic oral j contraceptives in standard doses on sister chromatid exchange and Mitotic index. i STUDY DESING: 35 women using oral contraceptives for three months were included into the study. I They were given 0,03 mg of ethinyl estradiol and 0,3 mg of norgestrel continuously for three weeks i and 75 mg ferrous for the fourth week. Sister chromatid exchange and mitotic index frequencies were recorded from peripheral blood leucocytes in a blinded fashion. RESULTS: Frequencies determined at the end of the third month were significantly increased (p<0.001). These rates reclined to normal level in three months with the witdrawal of the contraceptive pills. CONCLUSION: Our results suggested that estrogen and progesteron or their metabolites in standard- dose oral contraceptives, might have a potential reversible mutagenic effect on cell-division and DNA and this effect lasts for some time after the pills have been stopped. Having a baby after a period of contraception with hormonal contraceptives may require considering a interval time of a few months. (Gynecol Obstet Reprod Med 1997; 3:439-441)Item Application of the Hall-Petch relation to microhardness measurement on AA 1030, Cu, CuSn7, CuZn30 and 6114 alloys(1997)In this experimental study, the strip formed specimens made from aluminum alloy 1030, pure Cu, CuSn7, CuZaSO and low carbon steel 6114 were cold worked to different ratios. To be able to determine the microhardaess values of the materials, the micmhardaess tests were applied. Grain sizes of the materials were determined by the Heyn method using metal microscope. The hardness of materials, H, is dependent on the grain diameter, d, in a similar way as in the flow stress in the Hall-Petch relation: $H=H_o+K_Hd^{-1/2}$ where $H_o$ and $K_H$ are constants. The microhardness of the materials is found to vary with the grain size according to the Hall-Petch equation with reasonable accuracy.Item Three dimensional stress analysis in the crowned human teeth(1997)The stress distribution on a maudibular right second premolar tooth was investigated by using a three dimensional finite element model. Three crowns cast in different materials were subjected to a simulated biting force of 100 N with six different postures. The distribution of compressive and tensile stresses on cole and apex was evaluated by using a computer program. The stress component in transverse direction on the cole with porcelain crown was found to be most compatible with enamel when compared with other materials.Item Tuberculin skin test reactivity in right-handed and left-handed children(1997)A study of tuberculin sensitivity was performed on 387 healthy children aged 11-15 to test the hypothesis that non-right handedness is associated with immunological abnormalities. The size of tuberculin indurance was compared in right-handed and left-handed children. Our results demonstrated that there is no significant difference in the size of tuberculin induration between right-handed and left -handed children. We conclude that tuberculin sensitivity is not related to hand perference.