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Publication Metadata only 1,3-bis(gamma-aminopropyl)tetramethyldisiloxane modified epoxy resins: curing and characterization(Elsevier, 1998) Department of Chemistry; Department of Chemistry; Yılgör, Emel; Yılgör, İskender; Researcher; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; 40527; 24181Incorporation of siloxane oligomers with reactive organofunctional terminal groups, such as amine, epoxy and carboxy, into the structure of epoxy networks, provides improvements in the fracture toughness, water absorption and surface properties of the resultant systems. 1,3-bis(gamma-aminopropyl) tetramethyldisiloxane (DSX) was used as a model curing agent and modifier in bis(4-aminocyclohexyl)methane (PACM-20) cured diglycidyl ether of bisphenol-A (DGEBA) based epoxy resins. Curing reactions followed by differential scanning calorimetry indicated faster reaction rates between DSX and DGEBA as compared with PACM-20 and DGEBA. Mechanical characterization of the modified products showed improvements in tensile and impact strengths as expected. Glass transition temperatures of these materials showed a decrease with an increase in DSX content.Publication Metadata only A comparison of stochastic and interval finite elements applied to shear frames with uncertain stiffness properties(Elsevier, 1998) Elishakoff, I; Department of Mathematics; Köylüoğlu, Hasan Uğur; Teaching Faculty; Department of Mathematics; College of Sciences; N/AStructural uncertainties are modelled using stochastic and interval methods to quantify the uncertainties in the response quantities. Through a suitable discretization, stochastic and interval finite element methods are constructed. A comparison of these methods is illustrated using a shear frame with uncertain stiffness properties.Publication Metadata only A decomposition model for continuous materials flow production systems(Taylor & Francis, 1997) Yeralan, Sencer; Department of Business Administration; N/A; Tan, Barış; Faculty Member; N/A; Department of Business Administration; College of Administrative Sciences and Economics; N/A; 28600; N/AThis study presents a general and flexible decomposition method for continuous materials flow production systems. The decomposition method uses the station model developed in the first part of this study (Yeralan and Tan 1997). The decomposition method is an iterative method. At each iteration the input and output processes of the station model are matched to the most recent solutions of the adjacent stations. The procedure terminates when the solutions converge and the conservation of materials flow is satisfied. The decomposition method does not alter the station parameters such as the breakdown, repair, and service rates. This method can be used to analyse a wide variety of production systems built from heterogeneous stations. The properties of the decomposition method are studied for the series arrangement of workstations. The convergence and uniqueness of the decomposition method are discussed. The method is compared to other approximation methods. The complexity of the decomposition method is empirically investigated and is shown to be in the order of N-2 where N is the number of stations in the line, irrespective of the buffer capacities.Publication Metadata only A direct method for the inversion of physical systems(Institute of Physics (IOP) Publishing, 1994) Caudill, Lester F.; Rabitz, Herschel; Department of Mathematics; Aşkar, Attila; Faculty Member; Department of Mathematics; College of Sciences; 178822A general algorithm for the direct inversion of data to yield unknown functions entering physical systems is presented. of particular interest are linear and non-linear dynamical systems. The potential broad applicability of this method is examined in the context of a number of coefficient-recovery problems for partial differential equations. Stability issues are addressed and a stabilization approach, based on inverse asymptotic tracking, is proposed. Numerical examples for a simple illustration are presented, demonstrating the effectiveness of the algorithm.Publication Metadata only A new antiaromatic compound: 1,4-biphenylenequinone synthesis and trapping reactions(American Chemical Society (ACS), 1997) Kılıç, Hamdullah; Balcı, Metin; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129N/APublication Metadata only A new lamellar morphology of a hybrid amorphous liquid crystalline block copolymer film(American Chemical Society (ACS), 1999) Sentenac, D; Demirel, AL; Lub, J; de Jeu, WH; Department of Chemistry; Demirel, Adem Levent; Faculty Member; Department of Chemistry; College of Sciences; 6568N/APublication Metadata only A solution method for linear and geometrically nonlinear MDOF systems with random properties subject to random excitation(Elsevier, 1998) Micaletti, RC; Çakmak, Ahmet Ş.; Nielsen, Søren R.K.; Department of Mathematics; Köylüoğlu, Hasan Uğur; Teaching Faculty; Department of Mathematics; College of Sciences; N/AA method for computing the lower-order moments of response of randomly excited multi-degree-of-freedom (MDOF) systems with random structural properties is proposed. The method is grounded in the techniques of stochastic calculus, utilizing a Markov diffusion process to model the structural system with random structural properties. The resulting state-space formulation is a system of ordinary stochastic differential equations with random coefficients and deterministic initial conditions which are subsequently transformed into ordinary stochastic differential equations with deterministic coefficients and random initial conditions, This transformation facilitates the derivation of differential equations which govern the evolution of the unconditional statistical moments of response. Primary consideration is given to linear systems and systems with odd polynomial nonlinearities, for in these cases there is a significant reduction in the number of equations to be solved. The method is illustrated for a five-story shear-frame structure with nonlinear interstory restoring forces and random damping and stiffness properties. The results of the proposed method are compared to those estimated by extensive Monte-Carlo simulation.Publication Metadata only A station model for continuous materials flow production systems(Taylor & Francis, 1997) Yeralan, S; Department of Business Administration; Tan, Barış; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 28600This study develops a station model for continuous flow production systems. The most prominent use of the model is as a building block for a general and flexible decomposition method to analyse and design continuous materials flow production systems. Station breakdown and a finite capacity buffer are considered. Station inference caused by the blocking and starving phenomena is included in the station model. We assume that the time to station breakdown and station repair are exponentially distributed while the buffer is neither empty nor full. No restrictive assumptions are made about the distributions of the station breakdown and repair times when the station is blocked or starved, that is, while the buffer remains empty or remains full. The production rate and the expected level of the buffer are given in closed form. Numerical results that show the effects of the input parameters on the production rate along with an overview of the decomposition methods are presented.Publication Metadata only A test for reverse causality in the democratic peace relationship(Sage, 1999) Shi, Yuhang; Department of International Relations; Mousseau, Michael; Faculty Member; Department of International Relations; College of Administrative Sciences and Economics; N/ASeveral studies have suggested the possibility of reverse causation in the 'democratic peace' relationship: that the well-known extreme rarity of wars between democratic nations may be partially or wholly explained by a negative impact of war on democracy. Three kinds of war-on-regime effects are discussed. Anterior effects are regime changes that occur in preparation for wars; concurrent effects are those that occur during the course of a war; and posterior effects are regime changes that occur after a war concludes. Because studies have shown that democratic nations are rarely, if ever, on opposite sides in wars at their start, it is argued that reversed causation may affect the presence of causation from democracy to peace only if nations tend to become more autocratic as they prepare for impending wars. This proposition is examined with the observation of war events involving geographic neighbors or major powers, worldwide, from 1816 to 1992. With interrupted time-series analysis, it is found that nations are about as likely to become more institutionally autocratic as they are to become more democratic in the periods before the onset of wars. Moreover, this pattern holds even for the smaller subset of nations estimated to be democratic in the periods before major wars. These results indicate that studies of regime type and war participation have not been underspecified due to possible reverse causation before the onset of wars, and thus support the notion that the direction of causation in the democracy and war relationship is unidirectional from democracy to peace.Publication Metadata only An analytical formula for variance of output from a series-parallel production system with no interstation buffers and time-dependent failures(Pergamon-Elsevier Science Ltd, 1998) Department of Business Administration; Tan, Barış; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 28600This paper presents a method to determine the mean and the variance of the amount of materials produced in a fixed time interval by a continuous materials flow production system with N stations in series and M stations in parallel and no interstation buffers. Unreliable stations with exponential failure and repair times, time dependent failures, and deterministic processing times are considered. Closed-form expressions for the asymptotic mean and variance of the amount of materials produced per unit time are given for series, parallel, and series-parallel production systems with identical stations. It is shown that the distribution of the amount of materials produced in a fixed time is asymptotically normal. By using this property, effects of variability on the due-date performance are investigated by considering the probability of meeting a customer order on time. Numerical experiments that explore some relationships among performance measures and production system parameters are also presented.