Photorefractive Four-Wave Mixing Switches Utilizing Pockels Effect -Longitudinal and Lateral Switches-

We carried out detailed calculations for photorefractive wave-mixing switches based on one of three crystals with high electro-optic coefficients, namely, BaTiO₃, Strontium Barium Niobate (SBN (0.75)), and Potasium Sodium Strontium Barium Niobate (KNSBN). A comparison of results for the three crystals shows that a 0_-cut BaTiO³ crystal is suitable for a longitudinal switch and requires a voltage of about 80 for a 2-mm-thick crystal to induce sufficient phase mismatch. The electrodes must be transparent for the incident and diffracted beams. A 45_-cut SBN (0.75) crystal, however, is suitable for a lateral switch and requires a voltage of about 150 for a 1-mm-wide crystal. The electrodes do not need to be transparent.     

Composite polymeric electrolytes based on PMMA-LiCF3SO3-SiO2

Preliminary results on the mechanical, optical and electrical properties of composite gel electrolytes (CGEs) with fumed silica (SiO₂) as a filler added to gel polymeric electrolyte (GPE) based on PMMA, LiCF₃SO₃ and PC are presented in this paper. Added fumed silica is seen to enhance the mechanical properties of the GPE without changing the conductivity significantly. The high ionic conductivity (×10⁻³ S/cm), high transmission in the visible region and nominal variance of conductivity and viscosity over a wide temperature window show that these CGEs are potential electrolytes for electrochromic windows (ECWs).     

Interferences in Photodetachment of a Negative Molecular Ion

The photodetachment of a negative molecular ion is studied theoretically using a two-center model. The detached electron wave function is obtained as a superposition of two coherent waves originating from each center. The photo-detached electron flux is evaluated on a screen placed at a large distance from the negative molecular ion. The electron flux on the screen displays strong interferences, the peak positions are related to the distance between the two centers in the negative molecular ion. We a/so obtained a simple analytical formula for the total photodetachment cross section. It approaches one and two times of the cross section for the one-center system in the high and lowphoton energy limits respectively.     

A quasilinearization method for a class of integro-differential equations with mixed nonlinearities

We develop an extended form of the quasilinearization method for an initial value problem involving a nonlinear integro-differential equation with mixed nonlinearities, occurring in distributed-infective and distributed-contact models. In fact, a monotone sequence of iterates converging uniformly and quadratically to a solution of the problem is obtained. Some interesting observations are presented.     

Low noise double pass L-band erbium-doped fiber amplifier

A new double pass long wavelength band erbium-doped fiber amplifier with enhanced noise figure characteristics is demonstrated. The noise figure is improved by about 2.6 dB with the incorporation of broadband conventional-band fiber Bragg grating (FBG) in between the two segments of erbium-doped fiber. By incorporating both the pre-amplifier and the FBG, the noise figure is further improved, which varies from 4.0 to 5.0 dB in the flat gain region from 1570 to 1600 nm. The gain varies from 32.0 to 33.4 dB within this region. The new amplifier with high gain and low noise figure can be useful as an inline amplifier in a wavelength division multiplexing transmission system.     

Thermal analysis of renal stones

The chemical composition of 200 renal stones, collected from Taxila, Rawalpindi and Islamabad regions in Pakistan, was determined by thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The thermal curves show weight losses at various temperatures indicating dehydration and decomposition phenomena of renal stones. Results were compared with qualitative data obtained by IR analysis which confirmed the chemical composition of various stones in the solid state. The thermal curves helped in the differentiation of various kinds of water held by stones and their chemical composition was obtained by weight loss during pyrolysis. It was found that 26.5% of the stones were pure whewellite, 3% weddellite, 13% uric acid anhydrous, 7.5% struvite, 2.5% ammonium acid urate, 0.5% cystine and 47% stones had mixed composition. In the mixed state the most frequent combinations were those of calcium oxalate with uric acid (14.5%) and with phosphates (27.5%).

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Zusammenfassung Mittels TG und DTA wurde die chemische Zusammensetzung von 200 Nierensteinen untersucht, die in den Gebieten Taxila, Rawalpindi und Islamabad in Indien gesammelt wurden. Die Thermogramme zeigen Masseverluste bei verschiedenen Temperaturen, die auf Dehydratation und Zersetzung der Nierensteine hinweisen. Die Ergebnisse wurden mit den qualitativen Resultaten aus der IR-Analyse verglichen, welche die chemische Zusammensetzung der verschiedenen Steine im festen Zustand bekräftigte. Die Thermogramme halfen bei der Unterscheidung von verschieden gebundenem Wasser, ihre chemische Zusammensetzung wurde durch Gewichtsverlust bei der Pyrolyse bestimmt. Man fand, daß 26.5 % der Steine aus reinem Whewellit bestanden, 3 % aus Weddellit, 13 % aus anhydrierter Harnsäure, 7.5 % aus Struvit, 2.5 % aus Ammmoniumhydrogenurat, 0.5 % aus Cystin und 47 % der Steine hatten eine gemischte Zusammensetzung. Die häufigsten Kombinationen der Mischzusammensetzungen waren Calciumoxalat mit Harnsäure (14.5 %) und mit Phosphaten (27.5 %).

     

A solution procedure for the discrete time, cost and quality tradeoff problem using electromagnetic scatter search

Decisions concerning a project’s expedition, traditionally involved considerations regarding time and cost tradeoff. It was recently suggested that the quality of a project should also be taken into considerations. In this paper, we propose a meta-heuristic solution procedure for the discrete time, cost and quality tradeoff problem. This problem involves the scheduling of project activities in order to minimize the total cost of the project while maximizing the quality of the project and also meeting a given deadline. We apply a so called electromagnetic scatter search to solve this problem. In this process, we initially generate a population of feasible solutions. In so doing, we use frequency memory to well sample the feasible region. A number of these solutions are then selected and improved locally. The improved solutions are then combined to generate new set of solutions. The combination process utilizes attraction–repulsion mechanisms borrowed from the electromagnetism theory. The whole process is stopped when no significant improvement in the set of solutions are observed. The validity of the proposed solution procedure is demonstrated, and its applicability is tested on a randomly generated large and complex problem having 19,900 activities.