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51.
S.M. Kostritskii R.F. Tavlykaev R.V. Ramaswamy Yu.N. Korkishko V.A. Fedorov 《Photonics Technology Letters, IEEE》2004,16(10):2260-2262
We have realized broad-band distributed Bragg reflectors with photorefractive gratings recorded at 441.6 nm in channel Ti : Cu : LiNbO/sub 3/ waveguides. Proton-assisted copper exchange is used to enable a high level of copper doping and, thereby, achieve an extremely large modulation of refractive index (/spl ges/ 5/sup */10/sup -4/) within a photorefractive grating. Experimental structures demonstrate reflectivities up to 17% with full-width at half-maximum bandwidths in excess of 1.2 nm at center wavelengths around 1.55 /spl mu/m. 相似文献
52.
Ramakrishna Ramaswamy 《Chemical physics》1984,88(1):7-16
A method of analysing classical trajectory data, based on recently derived scaling principles, is applied to a model atom-triatom collinear collision system. Apart from the utility of the scaling idea in extending trajectory computations, the analysis of the scaling coefficients in terms of transition probabilities increases the scope of the classical scaling theory as a means of obtaining (at the very least) qualitative quantum-mechanical information from classical trajectories. As an useful adjunct, the method of continuous quantization is applied to generate approximate transition probabilities. These results are semiquantitative; thus a combination of classical scaling and continuous quantization affords a powerful means of modeling complex collision cases with a minimum of computational effort. 相似文献
53.
54.
In this work, a two-dimensional thermosolutal convection flow under a sinusoidal gravity modulation (g-jitter) field is studied
to understand the effects of the periodic source on flow field, as well as heat and mass transfer mechanisms. A semi-implicit
projection finite element method is adopted to solve the transient Navier–Stokes, energy and species concentration equations.
The fingering regime and the diffusive regime are explored for a series of gravity modulation frequencies. Two types of flow
evolution, synchronous and subharmonic responses, are obtained for different frequencies. Distribution of unstable responses
for the singly unstable condition is in agreement with the literature predict. The results show that heat and mass transfer
rates are affected by the response type. For a subharmonic variation flow field, the overall Nusellt number and Sherwood number
exhibit larger values. In addition, the augmenting condition in combining thermally driving force and solutally driving force
is analyzed for a practical crystal material and displays a different response distribution from those in the fingering regime
and the diffusive regime.
Received on 19 February 2001 / Published online: 29 November 2001 相似文献
55.
56.
Summary The method described is a simple procedure for separating gas oil boiling range petroleum fraction into its aromatic hydrocarbons of the mono-, di- and trinucleartype. This is accomplished by gradient elution through an alumina adsorption column under established/standardised conditions. Characterisation is performed by UV-absorption. The method can be used also for investigating aromatic hydrocarbon structures from other petroleum fractions.
Einfaches Verfahren zur chromatographischen Trennung und Bestimmung von mono-, di- und tricyclischen aromatischen Kohlenwasserstoffen in schwereren Erdölfraktionen
Zusammenfassung Zur Trennung der Erdölfraktion vom Siedebereich des Gasöls in die ein-, zwei- und dreikernigen aromatischen Bestandteile wird eine Gradientenelution an einer Aluminiumoxidsäule unter standardisierten Bedingungen angewendet. Zur Charakterisierung dienen UV-spektrometrische Messungen. Das Verfahren kann auch zur Untersuchung von Aromaten aus anderen Erdölfraktionen eingesetzt werden.相似文献
57.
S. G. Ravi Kumar P. A. Aswatha Narayana K. N. Seetharamu B. Ramaswamy 《国际流体数值方法杂志》1989,9(9):1165-1177
The velocity correction algorithm is used in the finite element method to solve forced convection problems between parallel plates with a triangular step, for Reynolds numbers up to 1000. Equal-order interpolation functions for velocity, pressure and temperature are used. The solutions show a smooth variation of pressure. The streamfunction, isotherms, isobars and velocity profiles are presented for a typical Reynolds number of 500. The skin friction and heat transfer results are presented for Reynolds numbers up to 1000. 相似文献
58.
The kinetics of oxidation of thiosulfate to tetrathionate by trans-dihydroxotetraoxoosmate(VIII) in aqueous alkaline media have been studied. The oxidation follows a rate expression where KOs is the formation constant of trans-dihydroxotetraoxoosmate (VIII), and K2 and k3, respectively, represent the formation constants of the intermediate complex involving Os(VIII) and S2O and its decomposition constant. The KOs, K2, and k3 values have been computed to be (19.5 ± 3) dm3/mol, (6.12 ± 0.5) and (3.32 ± 0.3) × 10?1 dm3/mol s at 303 K, and I = 0.32 mol/dm3, respectively. The rate law is consistent with a mechanism envisaging the equilibrium formation of an intermediate complex involving Os(VIII) and S2O, followed by a rate-determining decomposition of the complex with concomitant electron transfer. 相似文献
59.
Sakai’s method of analysing logft values has been extended to higher excited states in even-even nuclei. Within the context of the rather limited data an enhancement in the matrix element is observed for transitions to 2″+, 2?+ and 4′+ and 4″+ levels. 相似文献
60.
Lu S.C.H. Ramaswamy D. Kumar P.R. 《Semiconductor Manufacturing, IEEE Transactions on》1994,7(3):374-388
The problem of reducing the mean and variance of cycle time in semiconductor manufacturing plants is addressed. Such plants feature a characteristic reentrant process flow, where lots repeatedly return at different stages of their production to the same service stations for further processing, consequently creating much competition for machines. We introduce a new class of scheduling policies, called Fluctuation Smoothing policies. Unanimously, our policies achieved the best mean cycle time and Standard Deviation of Cycle Time, in all the configurations of plant models and release policies tested. As an example, under the recommended Workload Regulation Release policy, for a heavily loaded Research and Development Fabrication Line model, our Fluctuation Smoothing policies achieved a reduction of 22.4% in the Mean Queueing Time, and a reduction of 52.0% in the Standard Deviation of Cycle Time, over the baseline FIFO policy. These conclusions are based on extensive simulations conducted on two models of semiconductor manufacturing plants. The first is a model of a Research and Development Fabrication Line. The second is an aggregate model intended to approximate a full scale production line. Statistical tests are used to corroborate our conclusions 相似文献