ABSTRACT
We discuss a method for measuring electro-optic coefficients by measuring diffraction from a tunable grating. The method involves measuring the changes in the diffraction pattern of a reflection grating, where applied electric fields of alternating direction induce changes in the index of refraction through the electro-optic effect. For certain geometries, these applied fields cause period-doubling effects that produce new peaks in the diffraction pattern. Numerically calculated diffraction patterns are presented for the assumptions of both homogeneous and inhomogeneous fields. Peak splitting, as a function of both the number of slits illuminated and the induced change in the index of refraction, is observed and discussed. Finally, the usefulness of our method for the measurement of electro-optic coefficients is discussed.
ABSTRACT
A modular infrared spectrometer with microsampling and cryosampling capabilities has been designed, constructed, and tested. The main design features and preliminary results are discussed, and some strengths of the final instrument, when used in the optical characterization of superconducting materials, are presented.
ABSTRACT
The dependence of the optical attenuation on the fiber coating has been measured for a sensor fiber subjected to periodic microbending. The dependence on the spectral characteristics of the selected light sources is also addressed and the proper source/coating combination is discussed. Results indicate that the proper selection of this combination is of crucial importance in the design, development, and performance of fiber optic sensors in which intensity modulated microbending transducers are considered. A combination of a short wavelength for the light source and a fiber coated with a hard, elastomeric material seems to be the optimal selection for enhancing the sensitivity in controlled microbending experiments with applications to fiber optic sensors. The highest sensitivity to microbending was obtained for a nylon coated fiber and using a He-Ne laser at 632.8 nm.
ABSTRACT
The effect of neuromuscular stimulation of the quadriceps femoris combined with continuous passive motion (CPM) on the active extension range of motion and force of patients with total knee arthroplasty was investigated. The experimental group received three one-hour periods of electric stimulation per day in the extension cycle of the continuous passive motion. The control group received continuous passive motion without quadriceps electric stimulation. Both groups engaged in physical therapy consisting of active range of motion, quadriceps femoris setting, flexion and extension stretches, and ambulation. Manual goniometry and tensiometry were used to evaluate knee active extension range of motion and quadriceps strength. Upon dismissal, the stimulated group was able to generate more force at 90 degrees, 35 degrees, 20 degrees, and terminal extension of the involved knee, but none of these values was found to be statistically significant. Active extension range of motion of the stimulated group on dismissal showed a significant decrease in active extension lag (degrees) as compared to the control group. The experimental group averaged ten days in the hospital as compared to 12.5 for the control group, and subjectively noted decreased pain during stimulation.
Subject(s)
Electric Stimulation Therapy/methods , Exercise Therapy/methods , Knee Prosthesis/rehabilitation , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Muscle Contraction , ThighABSTRACT
The attenuation of optical power in a graded-index multimode fiber subjected to periodic microdistortions has been measured. The noncommunication fiber (designated the sensor fiber) had a small numerical aperture and a large core diameter, resulting in a large coupling wavelength and an enhanced sensitivity to microdistortion forces. The linewidth of the fundamental attenuation peak is in excellent agreement with that predicted by theory without the need to introduce a correlation length. The amplitude and force dependence of the attenuation measured at the fundamental peak is also in excellent agreement with theory. The inferred distortion force versus distortion amplitude curve is a straight line, as predicted by elasticity theory.
