Showing papers by "Istanbul Technical University published in 1987"

Interactive Compromise Programming

Abstract: The purpose of this paper is to introduce a solution method for multiple objective linear programming (MOLP) problems. The method, called interactive compromise programming (ICP), offers a practical solution to MOLP problems by combining judgement with an automatic optimization technique in decision-making. This is realised by using the method of compromise programming and the method of a two-person zero-sum game in an iterative way. The method is illustrated by a numerical example.

Polymerization of n-butyl vinylether initiated by polymeric peroxycarbamates and active polystyrenes

Abstract: The free radical promoted cationic polymerization of n-butyl vinylether (BVE) was achieved by thermal decomposition of polymeric peroxycarbamates (PPC) or active polystyrene (APS), having fragments of PPC in the presence of diphenyliodonium hexafluorophosphate (Ph2I+ PF) or silver tetrafluoroborate (AgBF4). Polymerizations were accompanied by phase separation. Formation of block copolymers, mainly in the solid phase, was evidenced by NMR spectroscopy. Polymer samples obtained by this procedure contained only a very small fraction of block copolymer structure due to the phase separation and very effective chain transfer reactions predominating the cationic polymerization of BVE. Durch die thermische Zersetzung von polymeren Peroxycarbamaten (PPC) oder von mit Anteilen von PPC aktivierten Polystyrolen (APS) wurde in Gegenwart von Diphenyljodoniumhexafluorophosphat (Ph2I+ PF) oder von Silbertetrafluoroborat (AgBF4) die durch freie Radikale promovierte kationische Polymerisation von n-Butylvinylather (BVE) erreicht. Wahrend der Polymerisation wurde eine Phasenseparation beobachtet. Die im wesentlichen in der festen Phase gebildeten Blockcopolymeren wurden mittels NMR-Spektroskopie nachgewiesen. Die so gewonnenen Polymerproben enthielten infolge dieser Phasenseparation und der bei der kationischen Polymerisation des BVE dominierenden Kettentransferreaktion nur sehr kleine Anteile an Blockcopolymeren.

Determination of the Overall Heat Transfer Coefficient of the Building Envelope from the Bioclimatic Comfort Point of View

Abstract: This new method to determine the optimum overall heat transfer coefficients for the opaque components of the building envelope in respect to orientation, window characteristics and transparency ratio, is based on the comfort values of the inner surface temperatures of the facade elements. The inner surface temperatures of the transparent components are calculated initially assuming window characteristics and climatic conditions. The inner surface temperatures for the opaque parts can be calculated from the inner surface temperatures of the transparent components, transparency ratios and the comfort value of the inner surface temperatures of the facade elements. The optimum values of the heat transfer coefficients f or the opaque components are determined from these and the sol-air temperatures.

An iterative method to optimize the operation of reservoir systems

Abstract: Optimization of long-term operation of real-world reservoir systems by dynamic programming has been studied. Computer time requirements make it necessary to use iterative methods in the case of multi-reservoir systems. State-incremental dynamic programming provides a reasonable rate of convergence for serial systems when initial policies are suitably chosen. A new method is proposed that combines dynamic programming with successive approximations and state-incremental dynamic programming. Incremental sequential dynamic programming is especially useful for systems of complex configuration which cannot be optimized with other iterative methods due to very slow convergence. Choices of initial policy, state increment, and the number of states to be considered in each iteration are investigated in two case studies.

Determination of kinetic parameters of ethyl methacrylate polymerization by using the dead-end procedure

Abstract: Kinetics of polymerization of ethyl methacrylate initiated by 2,2′-azoisobutyronitrile (AIBN) was studied applying the “dead-end” theory. This theory is appropriate to examine the solution polymerization of this monomer in benzene at θ > 60°C. Radical polymerizations of ethyl methacrylate were carried out at 60–110°C. By using the procedures of the dead-end theory, the rate of decomposition and the initiator efficiency of AIBN were determined. Kinetic parameters of the solution polymerization of ethyl methacrylate were calculated and the results were compared with the literature values.

Chemistry of Sulphide Mineral Flotation

Abstract: Chemistry of sulphide mineral flotation by xanthates has been reviewed and discussed with respect to hydrophibization by collector coating and depressing effects of hydroxyl, cyanide and sulphide ions. The collection mechanism in Galena-Oxygen-Xanthate Flotation System has been elucidated electro-chemically by the use of electrode potentials. It is concluded that there is a limiting range of Eh and pH where flotation is possible. Finally, silver sulphide electrode was utilized to control the activity of xanthate ion during flotation of oxidized lead minerals after sulphidization. The continuous control of sulphide and xanthate ions has been found practical to achieve reproducible results during flotation of an oxidize lead-zinc ore containing cerussite, smithsonite and hydrozincite.

Spatial Point Processes and Clustering Tendency in Exploratory Data Analysis

Abstract: Discriminating among random, clustered and regular arrangements of multidimensional patterns (data) is an important problem in exploratory data analysis, statistical pattern recognition and image processing. Clustering methods have been used extensively for this purpose. However, clustering algorithms will locate and specify clusters in data even non are present. It is therefore appropriate to measure the clustering tendency or randomness of a pattern set before subjecting it to a clustering algorithm. Spatial point process models are alternatives to structures obtained from cluster analysis and are a means for objectifying observed data. We survey the work that has been done in developing measures of clustering tendency, with special attention to distance-based methods. We review several models for spatial point processes with an eye towards identifying potential research problems in applying such models to clustering tendency. The successes and failures of these methods are discussed as well as suggestions and directions for future study.

The elastic torsion problem for a nonhomogeneous and transversely isotropic half-space

Abstract: The statical Reissner-Sagoci problem for nonhomogeneous transversely isotropic elastic half-space is investigated. The modulus of rigidity is assumed asCii(r,z)=μiirβf(z),i=4, 6 and β≧0, where μii are constants. The expressions for stresses, displacement and torque are given. The analysis is based on the assumption that the tangential displacement is prescribed within the areaz=0,r≦1 and shearing stress is zero in the outside arear>1,z=0. The integral equation which is obtained is solved in the case whenf(z)=cosh2kz and β≧0, wherek is a constant.

Earthquake-resistant design according to the most unfavourable seismic direction under combined internal forces

Abstract: In this study it has been shown that, in the case of linear theory, the combined internal forces corresponding to each seismic direction lie on an ellipsoid having internal forces chosen as the set of axes. A method is proposed to obtain the most unfavourable results easily, in the neighbourhood of the several unfavourable points without actually determining the ellipsoid. The design can be carried out using linear, as well as non-linear, theory. Two examples are given to illustrate the application of the proposed method.

Constitutive Relationships for Soil Dynamics

Abstract: The main intention in this paper is to give a brief overview of the constitutive relationships developed to model cyclic behavior of soils In doing this the constitutive equations formulated and implemented in various numerical analysis methods are classified under two categories; nonlinear elastic and elasto-plastic In the last section of the paper, as an example to the elasto-plastic constitutive relationships, a brief description and an application of an endochronic constitutive equations developed to model cyclic simple shear behavior of cohesive soils is presented