Improvement In Figure Of Merit Research Articles

Dielectric Properties of MultilayeredBa0.5Sr0.5TiO3 Thin Films Deposited on ITO-CoatedCorning 1737 Glass by rf Magnetron Sputtering

A new stacking method via variation of substrate temperature in rfmagnetron sputter is used to fabricate polycrystalline/polycrystallineBa0.5Sr0.5TiO3 thin films with higher dielectricconstant, higher breakdown strength and lower leakage current densitiesthan those prepared by a conventional deposition method. The improvedfigure of merit G (ε0εrEb) of theBa0.5Sr0.5TiO3 thin films implies that they are afeasible insulation layer for thin film electroluminescent devices.

TU-C-I-609-07: Optimization of a Real Time Dual-Energy Subtraction Technique Based On a Flat Panel Detector

Purpose: To determine the optimal x-ray spectra for dual-energy subtraction with a flat panel detector (FPD), and to quantify the effects of dynamic filtration and FPD gain settings on image quality, tube loading, patient exposure, and overall system performance. Method and Materials: A simulation study was performed using available empirically determined data of x-ray spectra. The lungs and mediastinum of the chest were modeled with 12.5 cm and 20 cm thick regions of Lucite, respectively. Coronary calcification was modeled with a 1 mm thickness of bone-equivalent plastic. The FPD was modeled as an ideal detector with a 600 micron thick layer of CsI. Scatter was not considered in this study. Low and high energy images were normalized to a desired energy deposit in the detector dependent on FPD gain. A figure-of-merit (FOM) was used t6o quantify the overall system performance. The effects of various silver filter thicknesses (0–1000 microns), high to low energy image signal ratios (1–8), and two dual-energy noise reduction algorithms were evaluated for their effect on image quality, patient entrance exposure, tube loading, and FOM improvement. Results: As the thickness of the high-energy filter increased, image contrast, contrast-to-noise ratio, FOM and tube loading increased. Patient exposure was reduced by approximately 10% for the range of filter thicknesses studied. The FOM was maximized with a FPD signal ratio of approximately 3 without application of dual-energy noise reduction. However, dual gain operation did not show any improvement after noise reduction. Conclusion: An optimal dynamic filter combined with dual-energy noise reduction can improve the system FOM by a factor of 5. There is no further improvement in the system FOM when dual detector gain is used in conjunction with dual-energy noise reduction.

Improvement in material figure of merit of PLZT by samarium substitution

The paper reports dielectric and pyroelectric properties of samarium substituted PLZT. The polycrystalline samples with chemical formula Pb0.925-xSmxLa0.075(Zr0.2Ti0.8)0.981O3 with x varying from 0 to 0.02 were prepared by conventional dry ceramic method. XRD analysis shows all the compositions to be single phase with tetragonal structure. Room temperature dielectric constant increases marginally with x while dielectric loss is found to decrease appreciably. Pyroelectric coefficient improves with x. The sample with x = 0.015 exhibited the maximum value of material figure of merit in this series of compositions.

Preparation of high-density small grain size compacts of lead tin telluride

High-density compacts of lead tin telluride with grain sizes,L, in the range 25<L<60 µm, 10<L<25 µm, 5<L<10 µm andL<5 µm and with good mechanical properties have been prepared using a two-stage pressing technique. Preliminary measurements of the thermoelectric transport properties of cold-compacted and hot-pressed material are reported. The lattice thermal conductivity decreases with a reduction in grain size. In the cold-compacted material this reduction more than offsets the accompanying reduction in the electrical power factor and results in a significant improvement in the thermoelectric figure of merit.

Piezoelectric and electrostrictive transducers, sensors, actuators, and smart materials

This talk will discuss recent developments in large area acoustic sensors that become possible using composite piezoelectric transducers. The design rules for the composites will be briefly reviewed and the immense improvement in figure of merit that can be encompassed will be delineated. The development of materials for agile switching transducer arrays will be discussed and electrostrictive materials described that can be controlled for both phase and amplitude in transmit and receive modes. Polarization control in the electrostrictive family of electroceramics permits both direct dc field control and a pulsed charge control mode with memory capability so that large arrays can be rapidly switched by a limited number of supplies. In actuator systems, the development of multilayer actuator materials will be traced and new possibilities for ultrahigh‐strain materials discussed. The theme will again be electrical polarization control to exploit the large dimension changes that occur in domain and phase change antiferroelectrics and ferroelectrics. In the composite systems, a logical extension of current work is to explore possible systems that incorporate both sensor and responder in the same material coupled together by active solid‐state electronics. Systems that seek to control elastic compliance in this manner will be discussed and preliminary measurements of the controlled response presented. Extension of this concept to alternative systems will be considered.

Multichip Module Designs for High Performance Applications

A package performance bottleneck is developing because of the inability to densely wire single chip modules together on the printed wiring board. An array processor, constructed by means of various high performance packaging techniques, demonstrates that multichip modules of even modest size can give dramatic improvements in the packaging figure of merit.

Transient response of two-terminal networks

The maximum possible increase in gain/rise-time for a 2-terminal network with shunt capacitance is shown to be 2.75 compared with the parallel RC case; the overall gain/rise-time figure for a cascade of n such stages is also deduced. As such networks would have a large amount of overshoot, those having a monotonic response to a stepfunction current drive are next considered. Improvement in figure of merit is shown to be greatest with complex poles and zeros, and the case of three poles, two of which are conjugate complex, is discussed in some detail. Finally, modifications are made to a network with three poles having a monotonic response so as to produce improved risetime at the expense of a small amount of overshoot; e.g. a figure of merit of 1.90 can be obtained with 1% overshoot.