Publications without Fulltext
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
Browse
176 results
Search Results
Publication Metadata only Time-dependent diffeomorphisms as quantum canonical transformations and the time-dependent harmonic oscillator(Iop Publishing Ltd, 1998) N/A; Department of Mathematics; Mostafazadeh, Ali; Faculty Member; Department of Mathematics; College of Sciences; 4231Quantum canonical transformations corresponding to time-dependent diffeomorphisms of the configuration space are studied. A special class of these transformations which correspond to time-dependent dilatations is used to identify a previously unknown class of exactly solvable time-dependent harmonic oscillators. The Caldirola-Kanai oscillator belongs to this class. For a general time-dependent harmonic oscillator, it is shown that choosing the dilatation parameter to satisfy the classical equation of motion, one obtains the solution of the Schrodinger equation. A simple generalization of this result leads to the reduction of the Schrodinger equation to a second-order ordinary differential equation whose special case is the auxiliary equation of the Lewis-Riesenfeld invariant theory. The time-evolution operator is expressed in terms of a positive red solution of this equation in a closed form, and the time-dependent position and momentum operators are calculated.Publication Metadata only Time series evidence on the saving-investment relationship(Routledge, 1996) Barkoulas, J; Murphy, R; Department of Economics; Filiztekin, Alpay; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 4010The long-run saving-investment correlation for the 24 OECD countries is re-examined using the Johansen procedure. It is found that saving and investment rates are not correlated in the long run for the majority of OECD countries. In the countries where cointegration is found, the Gonzalo-Granger common factor analysis suggests that saving is the driving force of the cointegrated system.Publication Metadata only Syndicated lending under asymmetric creditor information - Correction(Elsevier, 1996) Cadot, O; Department of Business Administration; Banerjee, Saugata; Researcher; Department of Business Administration; College of Administrative Sciences and Economics; N/AThis paper explores how asymmetric information about borrower quality among syndicated lenders alters the incentive to refinance illiquid borrowers. We use a model in which lenders enter the market sequentially in two rounds of lending. Between the two rounds, a shock separates borrowers into good ones and bad ones, and early entrants acquire information about individual borrower type, while late entrants know only the distribution of borrower types. The asymmetric information structure gives rise to both signalling and screening issues. We show that self-selecting contracts do not exist, and that there is always a pooling Perfect Bayesian Equilibrium in which late entrants lend to both good and bad types, without borrower type being exposed before final clearing at the terminal time. Based on this framework, we argue that prior to the 1982 international debt crisis, it was possible for banks with heavy exposure to troubled debtors to attract rational newcomers in syndicated loans which were, with positive probability, bailout loans.Publication Metadata only Chaos in rotating triatomic clusters(Editions Physique, 1997) Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129Lyapunov exponent distributions of rotating triatomic Lennard-Jones clusters are calculated to analyze the effects of the vibrational and rotational motion on the extent of chaotic behavior. Initial momentum components are assigned to atoms either to rotate the clusters around symmetry axes or to generate random angular momenta. In both cases, it is seen that the initial kinetic energy assigned to vibrational modes is the dominant factor which determines the degree of chaos.Publication Metadata only Efficient continuous-wave radiatively cooled Cr4+: forsterite lasers at room temperature(Optical Soc Amer, 1998) Department of Physics; Sennaroğlu, Alphan; Faculty Member; Department of Physics; College of Sciences; 23851Results of a detailed experimental investigation aimed at reducing the thermal loading problem in a cw Cr4+:forsterite laser at elevated temperatures are presented. From a Cr4+:forsterite crystal with a differential absorption coefficient of 0.57 cm(-1), as much as 900 mW of cw output power has been obtained at 1.26 mu m and at a crystal boundary temperature of 15 degrees C with an absorbed pump power of only 4.5 W at 1.06 mu m. No chopping of the the pump beam was necessary. An efficient radiative cooling technique was further employed to cool the laser and no subsequent power fading was observed. To the author's knowledge, the measured absorbed power slope efficiency of 29.5% represents the highest cw power performance reported to date: from a Cr4+:forsterite laser pumped by a Nd:YAG laser around room temperature. The role of the low differential absorption coefficient in the reduction of thermal loading is further elucidated by presenting comparative cw power performance data with a second Cr4+:forsterite crystal having a differential absorption coefficient of 1.78 cm(-1) in the temperature range between 12 and 35 degrees C. Finally, some interesting multipulse effects of the laser observed in the millisecond regime during quasi-cw operation at 50% duty cycle are described.Publication Metadata only Finite-capacity scheduling-based planning for revenue-based capacity management(Elsevier Science Bv, 1997) Department of Business Administration; Akkan, Can; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; N/AFinite-capacity scheduling can be argued to be a crucial component of revenue-based capacity management. In that case, one way to plan production is to reserve portions of capacity for incoming customer orders as they arrive, in real-time. In such a planning method, the way these work-orders are scheduled affects the useable capacity, due to fragmentation of the time-line. Assuming the work-orders are rejected if they cannot be inserted into the existing schedule, we develop heuristics to minimise the present-value of the cost of rejecting orders and inventory holding cost due to early completion. We perform simulation experiments to compare the performance of these heuristics in addition to some common heuristics used in practice.Publication Metadata only Cost uncertainty, taxation, and irreversible investment(Springer-Verlag Berlin, 1999) Demers, FS; Demers, M; Department of Economics; Altuğ, Sumru; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; N/AWe examine the impact of learning about the unknown costs of investment on irreversible investment decisions, and show that the presence of:learning increases the endogenous cost of adjustment and depresses investment. We demonstrate convergence of the state of information and capital stock to the ergodic set. Once learning is complete, in-contrast to the exogenous cost-of-adjustment model, a mean-preserving increase in risk raises the endogenous marginal adjustment cost, reducing investment and the steady-state capital stock. We use data on the U.S. economy to study the impact of uncertainty and risk in the determinants of the costs of investing. Among our Salient findings is that increases in uncertainty have a much larger impact quantitatively on investment than increases in risk. Thus, if firms are unsure about various aspects of the stochastic environment that they face, the reduction in investment is much larger compared to the case in which there are increases in the riskiness in the price of capital or Other determinants of the costs of investing.Publication Metadata only Interior energy focusing within an elasto-plastic material(Pergamon-Elsevier Science Ltd, 1996) Tadi, M; Rabitz, H; Kim, YS; Prevost, JH; McManus, JB; Department of Mathematics; Aşkar, Attila; Faculty Member; Department of Mathematics; College of Sciences; 178822In this paper we consider the problem of focusing acoustic energy within a subsurface volume in a solid by means of a designed surface pattern, and ask how that focusing is affected by plastic yield of the material. Surface force patterns that yield efficient subsurface acoustic focusing have been designed using optimal control theory, based on a linear elastic model of a solid. The acoustic waves generated by these forces then are propagated, via numerical algorithms, in a model solid that exhibits plastic yield. Numerical results indicate that as the amplitude of the force increases, yield begins to develop at the focus, with the formation of an expanding region of permanent plastic deformation. Despite the occurrence of yield near the focus, acoustic energy still can be delivered to the focal volume with good efficiency.Publication Metadata only Strategic context of organizational market information processes within the multinational corporation(amer Marketing assoc, 1996) Department of Business Administration; N/A; Gençtürk, Esra; Faculty Member; N/A; Department of Business Administration; College of Administrative Sciences and Economics; N/A; N/A; N/AN/APublication Metadata only Comparison between difference-frequency generation and parametric fluorescence in quasi-phase-matched lithium niobate stripe waveguides(IEEE, 1996) Baldi, P.; El Hadi, K.; De Micheli, M. P.; Ostrowsky, D.B.; Department of Physics; Sundheimer, Michael; Faculty Member; Department of Physics; College of Sciences; N/ATuning curves and gain are two relevant parameters for integrated optical parametric oscillators. We show in this paper that they can be determined with a good precision without building a high-finesse cavity by measurement of the optical parametric fluorescence and difference-frequency generation. In the first part of this paper, we compare theoretically the guided optical parametric fluorescence and the guided difference-Frequency generation in the quasi-phase matching configuration. In the second part, we compare experimental results on optical parametric fluorescence in the 1.2-2.2-μm region and optical difference-frequency generation from a 1.55-μm laser diode using a pump wavelength between 775-795 nm in quasi-phase-matched lithium niobate stripe waveguides. This comparison shows that the gain measured by both methods is identical, but, while parametric fluorescence allows us to obtain the quasi-phase-matching curve, the difference-frequency generation gives a simpler and more accurate measurement of the gain. The combination of these two techniques provides therefore a powerful tool for evaluating the different fabrication processes of the nonlinear waveguides, without actually fabricating a parametric oscillator.