Showing papers by "Istanbul Technical University published in 1991"
TL;DR: In this paper, the authors proposed two different methods for the assessment of the initial soluble inert COD fraction and summarized their comparative evaluation for five different industrial wastes characterizing pulp and paper, meat processing, antibiotics, textile and dairy effluents.
133 citations
TL;DR: Pyridinium ions of appropriate reduction potential E red 1 2 are capable of oxidizing carbon-centred free radicals to carbocations that can initiate the polymerization of various compounds as discussed by the authors.
78 citations
TL;DR: A survey of hourly averages of observations of the interplanetary medium, made by satellites close to the Earth (i.e. at 1 a.u.) in the years 1963-1986, is presented in this paper.
75 citations
TL;DR: In this paper, new formulae have been developed for estimating the calorific values of Turkish lignites from their proximate analyses data and all the correlations were obtained using least squares regression analysis.
70 citations
TL;DR: In this article, a study was made of boron removal from Kizildere/Turkey geothermal waste water using the Boron selective resin Amberlite IRA 743.
60 citations
TL;DR: In this paper, a canonical representation for piecewise-affine maps has been developed, which extends the canonical representation proposed by L.O. Chua and S.M. Hang (Proc. IEEE, vol.65, no.6, p.915-29, 1977).
Abstract: A canonical representation for a rather general class of piecewise-affine maps has been developed. This canonical representation extends the canonical representation proposed by L.O. Chua and S.M. Hang (Proc. IEEE, vol.65, no.6, p.915-29, 1977) into PWA (piecewise-affine) partitions, which arise frequently in driving-point, transfer characteristics, and state equations. Thus, a universal canonical representation that is capable of characterizing circuit equations, state equations, and driving-point and transfer characteristics of piecewise-affine circuits in a compact global analytic form has been obtained. The canonical forms developed seem to be promising tools for computational purposes as well as for analytical studies of PWA circuits. >
55 citations
TL;DR: In this article, the symmetry groups associated with a system of balance equations of arbitrary order involving n independent and N dependent variables are discussed by employing exterior calculus, and the infinitesimal generators of symmetry groups are components of isovectors fields of the closed ideal of certain exterior differential forms corresponding to an equivalent first order system of equations.
45 citations
TL;DR: In this paper, the block copolymer structure was elucidated by means of extraction by appropriate solvents, GPC analysis, and IR and NMR spectral measurements, and the mechanisms for initiation and possible termination for systems involving benzoin-type initiators were discussed in the light of results from studies of composition of the blockcopolymerization mixture.
Abstract: Block copolymers of styrene and methyl methacrylate were prepared by means of azo-benzoin initiators. In the first stage, prepolymers were synthesized by using these initiators. Photoactive prepolymers containing benzoin end groups were employed in the second stage for block copolymerization. The block copolymer structure was elucidated by means of extraction by appropriate solvents, GPC analysis, and IR and NMR spectral measurements. Mechanisms for initiation and possible termination for systems involving benzoin-type initiators are discussed in the light of results from studies of composition of the block copolymerization mixture. Structure and efficiency of the formation of the block copolymers depend greatly on both the relative reactivities of the photochemically derived radicals and the termination mode of polymerization.
39 citations
TL;DR: In this paper, a non-linear, physically realizable, discrete runoff model is developed on the basis of the descriptive knowledge of catchment operation, and applied for monthly runoff generation.
36 citations
31 citations
TL;DR: In this paper, the authors used Ce(IV) with poly(ethylene glycol) having azo and hydroxyl functions to yield acrylamide-block copolymers with azo linkages in the main chains.
TL;DR: In this article, the pitting potential of AISI 304 stainless steels was investigated in neutral chloride solutions between 10 and 70°C and molybdate ion additions were between 0.01 and 0.1 M.
TL;DR: In this paper, the authors used Holographic Interferometry (HI) and clip gage measurements to find the normal and shear traction applied to the propagating crack faces.
TL;DR: In this paper, the electrocatalytic oxidation of ethylene glycol has been investigated on platinum-palladium alloy electrodes of different compositions in alkaline aqueous solution, and the surface characteristics of the alloys in contact with electrolytic solution have been studied using cyclic voltammetry.
TL;DR: In this paper, shape sensitivity expressions for linear piezoelectric structures with coupled mechanical and elastic fields were derived by adopting the quasielectrostatic approximation for these inherently anisotropic materials, the adjoint variable method of optimization and the material derivative formulation of shape variations.
Abstract: Shape sensitivity expressions are derived for linear piezoelectric structures with coupled mechanical and elastic fields. By adopting the quasielectrostatic approximation for these inherently anisotropic materials, the adjoint variable method of optimization and the material derivative formulation of shape variations are used in a systematic procedure to evaluate the total variation of a general performance criterion with respect to shape variations. The material (total) derivative of the adopted integral functional is found in terms of primary and adjoint quantities, as well as the deformation velocity field. Since the structure is assumed to undergo dynamic response, domain integrations evaluated at the initial time are also needed in this formulation.
TL;DR: In this paper, it was shown that the differential calculus of Wess and zumino for the quantum hyperplane is intimately related to the q-difference operator acting on then-dimensional complex space.
Abstract: It is shown that the differential calculus of Wess and zumino for the quantum hyperplane is intimately related to theq-difference operator acting on then-dimensional complex space ℂ
n
. An explicit transformation relates the variables and theq-difference operators on ℂ
n
to the variables and the quantum derivatives on the quantum hyperplane. For real values of the quantum parameterq, the consideration of the variables and the derivatives as hermitean conjugates yields a quantum deformation of the Bargmann-Segal Hilbert space of analytic functions on ℂ
n
. Physically such a system can be interpreted as the quantum deformation of then dimensional harmonic oscillator invariant under the unitary quantum groupU
q
(n) with energy eigenvalues proportional to the basic integers. Finally, a construction of the variables and quantum derivatives on the quantum hyperplane in terms of variables and ordinary derivatives on ℂ
n
is presented.
TL;DR: In this article, the estimate of reservoir capacity required to meet a prescribed demand for a given model of annual inflows is a random variable and the probability distribution and parameters of this ideal reservoir capacity are determined by simulation experiments using synthetic streamflow series generated by four different models.
TL;DR: In this article, the esterification of castor oil with oleic acid was investigated in view of the reaction kinetics under various conditions, and the reaction was carried out at 200°C, 225°C and 250°C by using equivalent proportions of the reactants.
Abstract: In this study, esterification of castor oil with oleic acid was investigated in view of the reaction kinetics under various conditions. Potassium hydroxide,p-toluenesulfonic acid and tin chloride (SnCl22H2O) were used as catalysts. Reaction was carried out at 200°C, 225°C and 250° C by using equivalent proportions of the reactants. For tin chloride, experimental data fitted the second-order rate equation, while for the other catalysts the obtained data fitted the third-order rate equation.
TL;DR: In this paper, the exterior calculus is used to construct symmetry groups associated with the quasi-linear wave equation u u = [ f ( u x, u t, u, x, t )] x.
Abstract: Thc symmetry groups associated with the quasi-linear wave equation u u = [ f ( u x , u t , u , x , t )] x are investigated by employing techniques of the exterior calculus. Certain special cases corresponding to particular choices of the function f are studied in detail and some similarity solutions (invariant solutions) are constructed explicitly.
TL;DR: In this article, the dynamic stability of radially stiffened annular plates with both edges subjected to in-plane forces is studied and the instability regions are determined for a wide range of exciting frequencies with different boundary conditions by varying the number and size of the stiffeners.
TL;DR: In this article, the authors investigated the contributions of thermal expansion and diffusion to the dissipation rate of atoms in the atomizer. But the authors did not consider the effect of the number of gaseous atoms present at any time.
TL;DR: In this paper, the preparation and characteristics of thiol-modified silica and its application to the preconcentration and determination of trace amounts of copper and cadmium by flame atomic absorption spectrometry are described.
Abstract: The preparation and characteristics of thiol-modified silica and its application to the preconcentration and determination of trace amounts of copper and cadmium by flame atomic absorption spectrometry are described. For the preparation of modified silica, the untreated silica suspended in methanol was impregnated with 3-(trimethoxysilyl)-1-propanethiol to obtain thiol-modified silica and the methanol was evaporated under vacuum. The residual silica was dried at 150°C and washed with distilled water until the washings appeared clear. The surface area of thiol-modified silica was 410m2/g, whereas the copper capacity was about 0.022mmolCu/g silica. Batch and column methods were used for the separation and concentration of the above-mentioned metals. These metals were quantitatively retained on the adsorbent at acidic media. In the batch method, the effects of pH, shaking time and the kind of buffer on adsorption of copper and cadmium were investigated. The shaking time of 30min was sufficient for a quantitative adsorption of the metals. In the column and batch procedures, both copper and cadmium adsorbed on the modified silica were quantitatively recovered with 2M hydrochloric acid. Sodium chloride (up to 1%) had no effects on the recoveries.
TL;DR: In this paper, a generalized theory of thermoelasticity is used, with thermal relaxation predicting finite wave speeds for thermal disturbances, and curves are plotted denoting the variations of normal stresses with time at different locations and variations of stresses along the thicknesses of the composite bodies at different times.
TL;DR: In this article, the Goynuk and Seyitomer oil shales overlie coal seams and an investigation of their geochemistry by solid-state and high-resolution nuclear magnetic resonance, infra-red spectroscopy and gas chromatography/mass spectrometry of the extracted bitumen suggests a classification as immature Type I kerogens.
Abstract: The Goynuk and Seyitomer oil shales overlie coal seams. An investigation of their geochemistry by solid-state and high-resolution nuclear magnetic resonance, infra-red spectroscopy and gas chromatography/mass spectrometry of the extracted bitumen suggests a classification as immature Type I kerogens. However, the n-alkane distribution is consistent with a substantial input from terrestrial plants.
TL;DR: In this paper, the probability density function and parameters of the critical period length are determined for normally and lognormally distributed annual flows for various levels of regulation and a range of reservoir sizes.
TL;DR: In this article, thermal splitting of secondary fatty acid esters of castor oil was investigated to determine the reaction kinetics under various conditions, and the results fitted the first-order rate equation for the catalyzed and non-catalyzed reactions.
Abstract: In this study, thermal splitting of secondary fatty acid esters of castor oil was investigated to determine the reaction kinetics under various conditions. Zinc oxide,p toluenesulfonic acid and sulfuric acid were used as catalysts. Reactions were carried out at 260, 270, and 280°C. Experimental data fitted the first-order rate equation for the catalyzed and noncatalyzed reactions. In addition to the kinetic investigation, the splitting (pyrolysis) mixture was evaluated in the preparation of a synthetic drying oil. For this purpose, the mixed fatty acids of linseed, sunflower andEcballium elaterium seed oils were used in the esterification stage of the process. Pyrolysis mixtures were converted to drying oils by combining the liberated acids with equivalent amounts of glycerol. The oils thus obtained show good drying oil properties.
TL;DR: In this article, the use of Raman frequency shifts of non-soft modes to provide detailed predictions of the critical behaviour of specific heat up to within a fraction of a degree of a second order (or weakly first order) phase transition is illustrated.
TL;DR: In this article, the effect of pH, temperature, salinity and ethoxylated sulfonate addition on adsorption was studied in order to elucidate the mechanisms governing polymer readsorption.
TL;DR: The similarity equation for the nonlinear Schrodinger equation is equivalent to the σ form of the Painleve IV equation given by M. Jimbo and T. Miwa as mentioned in this paper.
Abstract: In this short communication it is shown that the similarity equation for the nonlinear Schrodinger equation is equivalent to the σ form of the Painleve IV equation given by M. Jimbo and T. Miwa.