Experimental Study Of Multi-Hole Cooling For Integrally-Woven, Ceramic Matrix Composite Walls For Gas Turbine Applications

In this paper, multi-hole cooling is studied for an oxide/oxide ceramic specimen with normal injection holes and for a SiC/SiC ceramic specimen with oblique injection holes. A special purpose heat transfer tunnel was designed and built, which can provide a wide range of Reynolds numbers (10(5)similar to 10(7)) and a large temperature ratio of the primary flow to the coolant (up to 2.5). Cooling effectiveness determined by the measured surface temperature for the two types of ceramic specimens is investigated. It is found that the multi-hole cooling system for both specimens has a high cooling efficiency and it is higher for the SiC/SiC specimen than for the oxide/oxide specimen. Effects on the cooling effectiveness of parameters including blowing ratio, Reynolds number and temperature ratio, are studied. In addition, profiles of the mean velocity and temperature above the cooling surface are measured to provide further understanding of the cooling process. Duplication of the key parameters for multi-hole cooling, for a representative combustor flow condition (without radiation effects), is achieved with parameter scaling and the results show the high efficiency of multi-hole cooling for the oblique hole, SiC/SiC specimen. (C) 2008 Elsevier Ltd. All rights reserved.

Synthesis Of Plastic Zr-Based Bulk Metallic Glass Matrix Composites By The Copper-Mould Suction Casting And The Bridgman Solidification

Zr-based bulk metallic glass matrix composites with the composition of Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.(5) were synthesized by the copper-mould suction casting and the Bridgman solidification. The composite, containing a well-developed flowery beta-Zr dendritic phase, was obtained by the Bridgman solidification with the withdrawal velocity of 0.8 mm/s and the temperature gradient of 45 K/mm, and the ultimate strength of 2050 MPa and fracture plastic strain of 14.6% of the composite were achieved, which was mainly interpreted by the homogeneous dispersion of bcc beta-Zr phase in the glass matrix. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.

Micromachining Of Passive Planar Micromixer On Poly (Methyl Methacrylate) Substrate With Excimer Laser Ablation

Excimer laser ablation technique was introduced into this work to fabricate a passive planar micromixer on the PMMA substrate. T-junction shaped and width-changed S-shaped microchannels were both designed in this micromixer to enhance mixing effect. The mixing experiment of distilled water and Rhodamine B with injection flow rate of 500 and 1,500 mu m/s validates the mixing effectivity of this micromixer, and indicates the feasibility of excimer laser ablation in the microfabrication of mu-TAS device.

MODIFIED DIRECT TWOS-COMPLEMENT PARALLEL ARRAY MULTIPLICATION ALGORITHM FOR COMPLEX MATRIX OPERATION

A direct twos-complement parallel array multiplication algorithm is introduced and modified for digital optical numerical computation. The modified version overcomes the problems encountered in the conventional optical twos-complement algorithm. In the array, all the summands are generated in parallel, and the relevant summands having the same weights are added simultaneously without carries, resulting in the product expressed in a mixed twos-complement system. In a two-stage array, complex multiplication is possible with using four real subarrays. Furthermore, with a three-stage array architecture, complex matrix operation is straightforwardly accomplished. In the experiment, parallel two-stage array complex multiplication with liquid-crystal panels is demonstrated.

MODIFIED ENGAGEMENT METHOD FOR MATRIX OPERATION

We describe a modified engagement method for matrix operation based on a two-dimensional crossed-ring interconnection network, Our method incorporates fewer steps than that reported by Bocker et al. [Appl. Opt. 22, 804 (1983)], and its performance is found to be the most efficient (minimum steps) in comparison with other systolic and/or engagement methods for matrix operation. Thus, it may be helpful for other optical and electronic implementations of matrix operations. One compact optoelectronic integrity approach for implementing the modified engagement method is briefly described. (C) 1995 Optical Society of America

ABCD matrix for reflection and refraction of Gaussian beams at the surface of a parabola of revolution

We report the formulation of an ABCD matrix for reflection and refraction of Gaussian light beams at the surface of a parabola of revolution that separate media of different refractive indices based on optical phase matching. The equations for the spot sizes and wave-front radii of the beams are also obtained by using the ABCD matrix. With these matrices, we can more conveniently design and evaluate some special optical systems, including these kinds of elements. (c) 2005 Optical Society of America

Simple ABCD matrix method for evaluating optical coupling system of laser diode to single-mode fiber with a lensed-tip

In this paper, we present a simple technique to determine the coupling efficiency between a laser diode and a lensed-tip based on the ABCD transformation matrix method. We have compared our analysis technique to that of previous work and have found that the presented method is reliable in predicting the coupling efficiency of lensed-tip and has the advantage of simplicity of coupling efficiency calculation even by a pocket calculator. The results can be useful for designing coupling optics. (c) 2005 Elsevier GmbH. All rights reserved.

Passive Q-switching of short-length Tm3+-doped silica fiber lasers by polycrystalline Cr2+:ZnSe microchips

We demonstrate passive Q-switching of short-length double-clad Tm3+-doped silica fiber lasers near 2 mu m pumped by a laser diode array (LDA) at 790 nm. Polycrystalline Cr2+:ZnSe microchips with thickness from 0.3 to 1 mm are adopted as the Q-switching elements. Pulse duration of 120 ns, pulse energy over 14 mu] and repetition rate of 53 kHz are obtained from a 5-cm long fiber laser. As high as 530 kHz repetition rate is achieved from a 50-cm long fiber laser at similar to 10-W pump power. The performance of the Q-switched fiber lasers as a function of fiber length is also analyzed. (c) 2008 Elsevier B.V. All rights reserved.

Tm3+/Er3+/Yb3+-codoped oxyhalide tellurite glasses as materials for three-dimensional display

Blue, green and red emissions through frequency upconversion and energy transfer processes in Tm3+/Er3+/Yb3+-codoped oxyhalide tellurite glass under 980 nm excitation are investigated. The intense blue (476 nm), green (530 and 545 nm) and red (656 nm) emissions are simultaneously observed at room temperature. The blue (476 nm) emission was originated from the (1)G(4)->H-3(6) transition of Tm3+. The green (530 and 545 nm), and red (656 nm) upconversion luminescences were identified from the H-2(11/2)->I-4(15/2), S-4(3/2)->I-4(15/2), and F-4(9/2)->I-4(15/2) transitions of Er3+, respectively. The energy transfer processes and possible upconversion mechanisms are evaluated. (C) 2005 Elsevier B.V. All rights reserved.

Investigation on nonradiative decay of the (Er3+I13/2)-I-4 -> I-4(15/2) transition in different tellurite glass matrix

Three kinds of Er3+-doped tellurite glasses with different hydroxyl groups are prepared by the conventional melt-quenching method. Infrared spectra are measured to estimate the exact content of OH- groups in samples. The maximum phonon energy in glasses are obtained by measuring the Raman scattering spectra. The strength parameters Omega(t) (t = 2, 4, 6) for all the samples are calculated and compared. The nonradiative decay rate of the Er3+ I-4(13/2) -> I-4(15/2) transition are calculated for the glass samples with different phonon energy and OH- group contents. Finally, the effect of OH- groups on fluorescence decay rate of Er3+ is analysed, the constant KOH-Er Of TWN, TZPL and TZL glasses are calculated to be 9.2 x 10(-19) cm(4)s(-1), 5.9 x 10(-19) cm(4)s(-1), and 3.5 x 10(-19) cm(4)s(-1), respectively.

Transparent colloid containing upconverting nanocrystals: An alternative medium for three-dimensional volumetric display

We report an alternative medium of transparent upconverting colloid containing lanthanide ion doped NaYF4 nanocrystals for three-dimensional (3D) volumetric display. The colloids exhibit tunable upconversion luminescence with a wide spectrum of colors by adjusting the doping concentrations of the nanocrystals and the compositions of the colloids. Our preliminary experimental result indicates that an upconverting colloid-based 3D volumetric display using a convergent, near infrared laser beam to induce a localized luminescent spot near the focus is technically feasible. Therefore arbitrary 3D objects can be created inside the upconverting colloid by use of computer controlled 3D scanning systems. (C) 2008 Optical Society of America

Design and fabrication of color filters for projection display system

Color filters are key components in an optical engine projection display system. In this paper, a new admittance-matching method for designing and fabricating the high performance filters is described, in which the optimized layers are limited to the interfaces between the stack (each combination of quarter-wave-optical-thickness film layers is called a stack) and stack, or between stack and substrate, or between stack and incident medium. This method works well in designing filters containing multiple stacks such as UV-IR cut and broadband filters. The tolerance and angle sensitivity for the designed film stacks are analyzed. The thermal stability of the sample color filters was measured. A good result in optical performance and thermal stability was obtained through the new design approach. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

Matrix analysis of an anisotropic optical thin film

Based on Maxwell's equations, standard boundary conditions are imposed on resultant electric- and magnetic-field vectors at interfaces, and the propagating characteristics of extraordinary waves, such as the forward- and backward-propagating directions of wave vectors, rays and their corresponding refractive indices are determined in a uniaxially birefringent thin film. Furthermore, 2 x 2 characteristic matrices of a birefringent thin film are derived including multiple reflections for the extraordinary wave.

Design and fabrication of color filters for projection display system

Color filters are key components in an optical engine projection display system. In this paper, a new admittance-matching method for designing and fabricating the high performance filters is described, in which the optimized layers are limited to the interfaces between the stack (each combination of quarter-wave-optical-thickness film layers is called a stack) and stack, or between stack and substrate, or between stack and incident medium. This method works well in designing filters containing multiple stacks such as UV-IR cut and broadband filters. The tolerance and angle sensitivity for the designed film stacks are analyzed. The thermal stability of the sample color filters was measured. A good result in optical performance and thermal stability was obtained through the new design approach. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

Analysis of characteristic matrix for a uniaxially birefringent thin film

As the principal section consistent with the principal plane, electromagnetic propagation in a uniaxially birefingent thin film can be described with a concise 2 x 2 characteristic matrix, in which the refractive indices of the forward and backward propagating extraordinary rays are different and dependent. In this letter, based on Huygen's construction, the refractive indices and effective optical admittances of the forward and backward propagating extraordinary rays are discussed further, and the 2 x 2 characteristic matrix is simplified. Furthermore, the input optical admittance, reflectance and transmittance of assembly is presented, just as an isotropic thin film. The result can be extended to the general case of multilayer uniaxially birefringent thin films with their optic axes in the incident plane. Copyright (c) EPLA, 2007.