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83 results on '"Valdmanis, J. A."'

3. Electro-optical Probing Of Terahertz Integrated Circuits

Author

Bhasin, K. B, Romanofsky, R, Whitaker, J. F, Valdmanis, J. A, Mourou, G, and Jackson, T. A

Subjects
Electronic Components And Circuits
Abstract

Electro-optical probe developed to perform noncontact, nondestructive, and relatively noninvasive measurements of electric fields over broad spectrum at millimeter and shorter wavelengths in integrated circuits. Manipulated with conventional intregrated-circuit-wafer-probing equipment and operated without any special preparation of integrated circuits. Tip of probe small electro-optical crystal serving as proximity electric-field sensor.

Published
1990

14. External electro-optic probing of millimeter-wave integrated circuits

Author

Whitaker, J. F, Valdmanis, J. A, Jackson, T. A, Bhasin, K. B, and Romanofsky, R

Subjects
Electronics And Electrical Engineering
Abstract

An external, noncontact electro-optic measurement system, designed to operate at the wafer level with conventional wafer probing equipment and without any special circuit preparation, has been developed. Measurements have demonstrated the system's ability to probe continuous and pulsed signals on microwave integrated circuits on arbitrary substrates with excellent spatial resolution. Experimental measurements on a variety of digital and analog circuits, including a GaAs selectively-doped heterostructure transistor prescaler, an NMOS silicon multiplexer, and a GaAs power amplifier MMIC are reported.

Published
1989

17. Technology and Applications of Terahertz Imaging Non-Destructive Examination: Inspection of Space Shuttle Sprayed On Foam Insulation.

Author

Zimdars, David, Valdmanis, J. A., White, Jeffrey S., Stuk, G., Williamson, S., Winfree, William P., and Madaras, Eric I.

Subjects
*SPACE shuttles, *IMAGING systems, *SCANNING systems, *SYNTHETIC products, *OPTOELECTRONIC devices
Abstract

The implementation of terahertz (THz) imaging for non-destructive evaluation shows great promise in 2 and 3 dimensional non-contact inspection of non-conductive materials such as plastics, foam, composites, ceramics, paper, wood and glass. THz imaging employs safe low power non-ionizing electromagnetic pulses, which produce images with lateral resolution <200 microns, and depth resolution <50 microns. We demonstrate the detection of voids and disbonds intentionally incorporated within the sprayed on foam insulation of a space shuttle external tank mock-up segment using time domain THz imaging. Recently, highly integrated turn-key THz imaging systems have been introduced commercially. An industrially hardened THz scanning system which has been deployed to scan the space shuttle tank with small remote THz transceiver on a 30 meter fiber optic umbilical, is described. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2005
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18. 100-GHz Electro-Optic S-Parameter Characterization of High-Electron-Mobility Transistors

Author

MICHIGAN UNIV ANN ARBOR ULTRAFAST SCIENCE LAB, Frankel, M. Y., Whitaker, J. F., Mourou, G. A., Valdmanis, J. A., Smith, P. M., MICHIGAN UNIV ANN ARBOR ULTRAFAST SCIENCE LAB, Frankel, M. Y., Whitaker, J. F., Mourou, G. A., Valdmanis, J. A., and Smith, P. M.

Abstract

Progress in the research of modern semiconductor devices has advanced their response frequencies above 400 GHz. Such performance exceeds the conventional, purely electronic test instrumentation bandwidth, with the major limitations being imposed by the connectors and waveguides that are required for signal coupling to the device under test. This lack of convenient and accurate high-bandwidth device characterization methods imposes a serious obstacle to progress in semiconductor device development and utilization.

Published
1992

20. Imaging through scattering media with holography

Author

Leith, E., primary, Chen, C., additional, Chen, H., additional, Chen, Y., additional, Dilworth, D., additional, Lopez, J., additional, Rudd, J., additional, Sun, P.-C., additional, Valdmanis, J., additional, and Vossler, G., additional

Published
1992
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34. Effect of biomass high-frequency pre-treatment on combustion characteristics

Author

Barmina, I., Lickrastina, A., Purmalis, M., Zake, M., Valdmanis, R., Valdmanis, J., Alexandr Arshanitsa, Solodovnik, V., and Telisheva, G.

Subjects
lcsh:Computer engineering. Computer hardware, lcsh:TP155-156, lcsh:TK7885-7895, lcsh:Chemical engineering
Abstract

Combustion characteristics of microwave (2.45 GHz) pre-treated biomass (wood) pellets are investigated experimentally with the aim to find out the effect of pellets pre-treatment on the biomass composition and the feasibility of their thermo-chemical conversion. A complex study of the main combustion characteristics of the pre-treated biomass samples was carried out using a thermo-gravimetric method and a pilot–scale combustion test facility. The study includes time dependent measurements of mass loss at the primary stage of biomass gasification, variations of the flame temperature and heat production rate, combustion efficiency and composition of pollutants. The results have shown that the low-temperature microwave pre-treatment of wood pellets enriches the biomass carbon content from 50 % to ~ 60 % (d.b.) for biomass pre-treated for 180 s accompanied by the increasing higher heating values (HHV) from 19.9 up to 23.4 MJ/kg. The microwave pre-treatment promotes a faster thermal decomposition of biomass pellets with an enhanced heat energy production (up to 30 %) and a correlating increase of the volume fraction of CO2 in the products up to 25-28 %, while the mass fraction of the main volatiles (CO and H2) in the products decreases, indicating a more complete combustion of the volatiles. The shear of the char combustion stage increases with the increasing pre-treatment time. The data of thermo-gravimetric analysis coincide with the results of the pilot-scale tests.

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