Research Outputs
Permanent URI for this communityhttps://hdl.handle.net/20.500.14288/2
Browse
67 results
Search Results
Publication Open Access A class of Banach algebras whose duals have the Schur property(TÜBİTAK, 1999) Mustafayev, H.; Department of Mathematics; Ülger, Ali; Faculty Member; Department of Mathematics; College of SciencesCall a commutative Banach algebra A a γ-algebra if it contains a bounded group Λ such that aco(Λ) contains a multiple of the unit ball of A. In this paper, first by exhibiting several concrete examples, we show that the class of γ-algebras is quite rich. Then, for a γ-algebra A, we prove that A* has the Schur property iff the Gelfand spectrum Σ of A is scattered iff A* = ap(A) iff A* = Span(Σ).
Publication Metadata only A class of banach algebras whose duals have the schur property(Scientific and Technical research Council of Turkey - TUBITAK/Türkiye Bilimsel ve Teknik Araştırma Kurumu, 1999) Mustafayev, Heybetkulu; Department of Mathematics; Ülger, Ali; Faculty Member; Department of Mathematics; College of Sciences; N/ACall a commutative Banach algebra A a γ-algebra if it contains a bounded group Λ such that aco(Λ) contains a multiple of the unit ball of A. In this paper, first by exhibiting several concrete examples, we show that the class of γ-algebras is quite rich. Then, for a γ-algebra A, we prove that A* has the Schur property iff the Gelfand spectrum Σ of A is scattered iff A* = ap(A) iff A* = Span(Σ).Publication Metadata only A computational study of the reactivity of diethenylnaphthalenes towards anionic polymerization(Royal Soc Chemistry, 1999) Akın, Fatma Ahu; Erdem, Safiye Sağ; Nugay, Turgut; Aviyente, Viktorya; Department of Physics; Reşat, Haluk; Faculty Member; Department of Physics; College of Sciences; N/ADiethenyl, di(1-methylethenyl), and di(1-phenylethenyl) naphthalenes are known to be difunctional initiators used in the synthesis of thermoplastic elastomers. Semiempirical (AM1, PM3) and ab initio calculations (HF/6-31G, HF/6-31G*) have been carried out to determine the reactivity of these compounds towards anionic polymerization. For this purpose, geometrical parameters, electrostatic potentials, and frontier orbitals have been analyzed. Reaction paths starting from the diethenylnaphthalenes and reaching the proposed products have been studied, and transition structures along the paths have been located. The minimum energy conformers were determined through a conformational search around single bonds for a series of diethenylnaphthalenes. We have attempted to predict how the location of the vinyl groups affects the reactivity of diethenylnaphthalenes. Our results have revealed that the most suitable difunctional initiators for anionic polymerization are the compounds where the substituents lie away from the naphthalene bridge. We have also found that in some cases the substituents are conjugated with each other and di(1-phenylethenyl)naphthalenes are more reactive th an diethenylnaphthalenes which in turn are more reactive than di(1-methylethenyl)naphthalenes towards anionic polymerization.Publication Metadata only A cross-language evaluation of the Kintsch and Van Dijk model of text comprehension(Psychology Press, 1996) Department of Psychology; Gülgöz, Sami; Faculty Member; Department of Psychology; College of Social Sciences and Humanities; 49200N/APublication Metadata only A dynamic analysis of market entry rates in a global industry: a community ecology perspective(Emerald, 1999) Çavuşgil, S. Tamer; Department of Business Administration; Tunalı, Ayşegül Özsomer; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 108158States that it is critical that incumbent firms understand the processes that enhance or inhibit entry of new firms into their industry. A new entrant into an industry may create additional demand by legitimizing the technology/products, and/or may share the existing market by drawing buyers away from incumbents. An analysis of market entry rates is especially important in new, high technology industries where sub‐groups of firms pursue different technology and global market diversification strategies because such sub‐groups may have asymmetrical cross‐effects on entry rates of new firms. Suggests a community ecology approach to assessing the impact of industry density on new firm entry rates. The framework is demonstrated by applying it to the global personal computer industry during the period of 1977‐1992. Results suggest that density has a nonmonotonic positive effect, while the firm‐level variables of technological strategy and market expansion strategies have a monotonic positive effect on new firm entry rates.Publication Metadata only A faster simulation method for the stochastic response of hysteretic structures subject to earthquakes(Elsevier, 1996) Çakmak, Ahmet Ş.; Nielsen, Søren R.K.; Department of Mathematics; Köylüoğlu, Hasan Uğur; Teaching Faculty; Department of Mathematics; College of Sciences; N/AA semi-analytical forward-difference Monte Carlo simulation procedure is proposed for the determination of the lower order statistical moments and the joint probability density function of the stochastic response of hysteretic non-linear multi-degree-of-freedom structural systems subject to nonstationary gaussian white noise excitation, as an alternative to conventional direct simulation methods. The method generalizes the so-called Ermak-Allen algorithm developed for simulation applications in molecular dynamics to structural hysteretic systems. The proposed simulation procedure rely on an assumption of local gaussianity during each time step. This assumption is tantamount to various linearizations of the equations of motion. The procedure then applies an analytical convolution of the excitation process, hereby reducing the generation of stochastic processes and numerical integration to the generation of random vectors only. Such a treatment offers higher rates of convergence, faster speed and higher accuracy. The procedure has been compared to the direct Monte Carlo simulation procedure, which uses a fourth-order Runge-Kutta scheme with the white noise process approximated by a broad band Ruiz-Penzien broken line process. The considered system was a multi-dimenensional hysteretic shear frame, where the constitutive equation of the hysteretic shear forces are described by a bilinear hysteretic model. The comparisons show that significant savings in computer time and accuracy can be achieved.Publication Metadata only A new class of adiabatic cyclic states and geometric phases for non-Hermitian Hamiltonians(Elsevier Science Bv, 1999) N/A; Department of Mathematics; Mostafazadeh, Ali; Faculty Member; Department of Mathematics; College of Sciences; 4231For a T-periodic non-Hermitian Hamiltonian H(t), we construct a class of adiabatic cyclic states of period T which are not eigenstates of the initial Hamiltonian H(O). We show that the corresponding adiabatic geometric phase angles are real and discuss their relationship with the conventional complex adiabatic geometric phase angles. We present a detailed calculation of the new adiabatic cyclic states and their geometric phases for a non-Hermitian analog of the spin 1/2 particle in a precessing magnetic field.Publication Metadata only A theoretical study of structural defects in conjugated polymers(Elsevier Science Sa, 1999) Yurtsever, Mine; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129Accurate ab-initio calculations are performed for pyrrole and thiophene oligomers bonded through alpha and beta carbons. The thermodynamical stabilitiy of all possible binding types including the branched forms of tetramers and pentamers are compared. Employing the probabilities obtained from these calculations, a Monte Carlo type growth scheme is applied to predict branching as functions of the chain length and temperature. A high degree of branching for polypyrrole is reported whereas the linear chains dominate the structure of polythiophene.Publication Metadata only Agile manufacturing and management of variability(Wiley-Blackwell, 1998) Department of Business Administration; Tan, Barış; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 28600In this study, the relationship between agile manufacturing and management of variability is discussed. First, the key concepts of agility and agile manufacturing are introduced. These key concepts are then related to the management of variability. Previous studies on the modeling of variability of manufacturing systems are reviewed. Then the effects of variability of the structure of the production system, and also the processing time variability on the performance of a manufacturing system are studied by utilizing a simple model of a synchronous production line with identical stations and random processing times. Numerical results that examine the effects of the coefficient of variation of service time and the number of stations on the variability of the cycle time are also given.Publication Metadata only Alternative polynomial and holomorphic Dunford-Pettis properties(Scientific and Technical research Council of Turkey - TUBITAK/Türkiye Bilimsel ve Teknik Araştırma Kurumu, 1999) Department of Mathematics; Freedman, Walden; Faculty Member; Department of Mathematics; College of Sciences; N/AAlternatives to the Polynomial Dunford-Pettis property and the Holomorphic Dunford-Pettis property, called the PDP1 and HDP1 properties, respectively, are introduced. These are shown to be equivalent to the DP1 property, an alternative Dunford-Pettis property previously introduced by the author, thus mirroring the equivalence of the three original properties. © TÜBİTAK.