JLA Vol:2 Iss:1 (Simultaneous Measurement of Temperature and Size of Droplets in the Micrometer Range)

Authors:
N. Roth
K. Anders
A. Frohn
Institut fu¨r Thermodynamik der Luft‐ und Raumfahrt, Universita¨t Stuttgart, Pfaffenwaldring 31, D‐7000 Stuttgart 80, Federal Republic of Germany

A new optical instrument for simultaneous measurements of temperature and size of periodically generated droplets is described. With this instrument, basic phenomena such as droplet evaporation or combustion can be studied. The droplets, which are produced with a vibrating orifice droplet generator, can be injected into different environments to study, for example, evaporation in a rarefied media or combustion in a hot environment. To determine evaporation o...

JLA Vol:2 Iss:1 (Novel Speckle Velocimeter Using the Double Clipping Cross‐Correlation Method)

Authors:
H. Kitajima
T. Yoshida
N. Nakatsuka
T. Yamashita
Central R&D Lab., Omron Tateisi Electronics Co., Shimokaiinji, Nagaokakyo, Kyoto 617, Japan

A new speckle velocimeter using the cross‐correlation method was developed. Its optical system achieved wide working distance range of ±5mm and small measuring errors for various materials. Furthermore the realtime correlation processor for the clipped signals makes the cross‐correlation method applicable to in‐line measurement in factories.

JLA Vol:2 Iss:1 (Spray Characterization of a NASA MOD‐1 Nozzle)

Authors:
Dennis R. Alexander
Diego F. F. Gutierrez
Center for Electro‐Optics, University of Nebraska‐Lincoln (UNL), Lincoln, Nebraska, U.S.A.

An aerometrics Phase Doppler Particle Analyzer with Frequency Shifting (PDPA/FS) and a Laser Imaging and Video Processing System (LI/VPS) were used to perform a detailed analysis of the spray characteristics of a NASA MOD‐1 air assist nozzle. These results were compared to the results obtained using an earlier version of a Phase Doppler Particle Analyzer (P/DPA). The spray plume was analyzed under two sets of operating conditions. For Case I, a water pressure of 105 psia (723.95 kPa) and a...

JLA Vol:2 Iss:1 (The Clinical Status of Low Energy Laser Therapy in 1989)

Authors:
Jeffrey R. Basford
Department of Physical Medicine and Rehabilitation, Mayo Clinic and Foundation, Rochester, MN, U.S.A. 55902

Low energy laser therapy has gained varying acceptance as a treatment for a broad range of soft tissue, musculoskeletal and neurological conditions. A controversial, but surprisingly large body of research with cell cultures suggests that laser irradiation can nondestructively alter cellular processes. Unfortunately, animal and human studies are often contradictory and difficult to evaluate due to differing study designs. As a result, the clinical effectiveness of low energy laser therapy remains debatable. Nevertheless, the findings are intriguing a...

JLA Vol:2 Iss:1 (Laser Laparoscopy Contamination)

Authors:
Douglas E. Ott
420 Charter Blvd. Macon, Georgia 31210

JLA Vol:2 Iss:1 (Interaction of Excimer Laser Radiation with Solids)

Authors:
Walter W. Duley
Kevin Dunphy
Grant Kinsman
Stephen Mihailov
Laser Processing Laboratory, York University, 4700 Keele St., North York, Ontario, Canada M3J 1P3

We review the nature of the interactions that occur when excimer laser radiation impacts on different materials. The physical processes that occur during such interactions can be traced by subsequent physical and chemical analysis of the interface following the irradiation. We illustrate this approach with data obtained for a variety of materials including Cu, Al, polyimide and foamed polystyrene. We also discuss the processes that initiate material removal in transparent (wide ban...

JLA Vol:1 Iss:4 (Laser System for Dulling Work Roll by Q‐Switched Nd:YAG Laser)

Authors:
K. Minamida
J. Suehiro
T. Toshimitu
T. Kawamoto
R & D Laboratories‐I, Central R & D Bureau, Nippon Steel Corporation, 1618 Ida, Nakahara‐ku, Kawasaki 211, Japan

A new dulling system for the work rolls used to roughen the surface of cold‐rolled steel sheet has been developed. Such sheets are used in various products, such as outer panels of automobiles, and decorative outer plates of electric appliances. In this process, several pulsed laser beams generated by Q‐switched Nd:YAG lasers produce small craters with rims around them. This process includes a longitudinal scanning system...

JLA Vol:1 Iss:4 (Recent Developments in Laser Melt/Particle Injection Processing)

Authors:
K. P. Cooper
Geo‐Centers, Inc., 10903 Indian Head Highway, Fort Washington, Maryland 20744

P. Slebodnick
Naval Research Laboratory, Washington, D.C. 20375.

Investigations into crack formation in particle injected surfaces and into microstructural evolution during cladding were some of the recent developments in laser melt/particle injection processing. Both surface modification techniques involved blowing powder particles into a melt pool formed by a laser beam. When the particulate materials were metal carbides composite surface layers were formed and the thermal stresses that developed during cooling of the carbide injected layer resulted in th...

JLA Vol:1 Iss:4 (Optical Methods in Flow Visualization)

Authors:
Wen‐Jei Yang
Yi Chen
Department of Mechanical Engineering and Applied Mechanics, The University of Michigan, Ann Arbor, Michigan 48109

Optical techniques for flow visualization are presented, including light‐sheet flow visualization, shadowgraphy, schlieren method, interferometry, holography, speckle photography, laser‐induced fluorescence and thermography. The principles of these methods are briefly described and the examples of their applications to flow visualization are given.

JLA Vol:1 Iss:4 (The Use of High‐Frequency Pulsed Laser Diodes in Fringe Type Laser Doppler Anemometry)

Authors:
D. Dopheide
H. Pfeifer
M. Faber
G. Taux
Physikalisch Technische Bundesanstalt (PTB), D‐3300 Braunschweig, Bundesallee 100, Germany

The benefits obtained by using pulsed laser diodes with repetition rates much higher than the Doppler frequency are described and the advantages over cw‐ and long‐pulse operation are shown. These benefits are achieved by several characteristics of pulsed laser operation. First, in pulsed mode the time‐averaged number of photons may be considerably higher than in cw‐mode. Second, for some of the LDA data acquisition systems the laser pulses can be synchronized with the sampl...