78,067 research outputs found
Non-contact torsion transducer based on the measurement of Moire patterns using plastic optical fibres
An angular and displacement sensor that uses a polymer optical fiber and Moire patterns is demonstrated. Moire fringes are generated using two transparent superimposed planar gratings placed in front of an optical mirror. Moire patterns with periods ranging from 0.4 to 2 mm have been obtained in this way with 1mm-diameter plastic optical fibers for torsion angles ranging from 10° to 20° have been compared with theoretical calculations and a good agreement has been confirmed. Measuring the period length and the number of periods, both the relative angle between the gratings and the displacement of the fiber with respect to the mirror are obtained. With this technique very low angles can be measured with a very high resolution. The sensor principle has been successfully checked in the laboratory. Finally, the effect of employing different plastic fibers is also discussed. Besides, other possible applications of this measurement technique are presented and discussed
Non-contact friction between nanostructures
We calculate the van der Waals friction between two semi-infinite solids in
normal relative motion and find a drastic difference in comparison with the
parallel relative motion. The case of the good conductors is investigated in
details both within the local optic approximation, and using a non-local optic
dielectric approach. We show that the friction may increase by many order of
magnitude when the surfaces are covered by adsorbates, or can support
low-frequency surface plasmons. In this case the friction is determined by
resonant photon tunneling between adsorbate vibrational modes, or surface
plasmon modes. The theory is compared to atomic force microscope experimental
data.Comment: Published in PR
Electromagnetic Non-contact Gears: Prelude
We calculate the lateral Lifshitz force between corrugated dielectric slabs
of finite thickness. Taking the thickness of the plates to infinity leads us to
the lateral Lifshitz force between corrugated dielectric surfaces of infinite
extent. Taking the dielectric constant to infinity leads us to the conductor
limit which has been evaluated earlier in the literature.Comment: 7 pages, 2 figures, Contribution to Proceedings of 9th Conference on
Quantum Field Theory Under the Influence of External Conditions (QFEXT09),
Norman, OK, September 21-25, 200
Non-contact Vital Signs Monitor
An apparatus for measuring simultaneous physiological parameters such as heart rate and respiration without physically connecting electrodes or other sensors to the body. A beam of frequency modulated continuous wave radio frequency energy is directed towards the body of a subject. The reflected signal contains phase information representing the movement of the surface of the body, from which respiration and heartbeat information can be obtained. The reflected phase modulated energy is received and demodulated by the apparatus using synchronous quadrature detection. The quadrature signals so obtained are then signal processed to obtain the heartbeat and respiratory information of interest.Georgia Tech Research Corporatio
Non-contact temperature measurement requirements
The Marshall Space Flight Center is involved with levitation experiments for Spacelab, Space Station, and drop tube/tower operations. These experiments have temperature measurement requirements, that of course must be non-contact in nature. The experiment modules involved are the Acoustic Levitator Furnace (ALF), and the Modular Electromagnetic Levitator (MEL). User requirements of the ALF and drop tube are presented. The center also has temperature measurement needs that are not microgravity experiment oriented, but rather are related to the propulsion system for the STS. This requirement will also be discussed
Non-Contact Friction for Ion-Surface Interactions
Non-contact friction forces are exerted on physical systems through
dissipative processes, when the two systems are not in physical contact with
each other, or, in quantum mechanical terms, when the overlap of their wave
functions is negligible. Non-contact friction is mediated by the exchange of
virtual quanta, with the additional requirement that the scattering process
needs to have an inelastic component. For finite-temperature ion-surface
interactions, the friction is essentially caused by Ohmic resistance due to the
motion of the image charge moving in a dielectric material. A conceivable
experiment is difficult because the friction force needs to be isolated from
the interaction with the image charge, which significantly distorts the ion's
flight path. We propose an experimental setup which is designed to minimize the
influence of the image charge interaction though a compensation mechanism, and
evaluate the energy loss due to non-contact friction for helium ions (He+)
interacting with gold, vanadium, titanium and graphite surfaces. Interactions
with the infinite series of mirror charges in the plates are summed in terms of
the logarithmic derivatives of the Gamma function, and of the Hurwitz zeta
function.Comment: 9 pages; ReVTeX; accepted for publication in Eur.Phys.J.
Non-contact Microelectronic Device Inspection Systems And Methods
Non-contact microelectronic device inspection systems and methods are discussed and provided. Some embodiments include a method of generating a virtual reference device (or chip). This approach uses a statistics to find devices in a sample set that are most similar and then averages their time domain signals to generate the virtual reference. Signals associated with the virtual reference can then be correlated with time domain signals obtained from the packages under inspection to obtain a quality signature. Defective and non-defective devices are separated by estimating a beta distribution that fits a quality signature histogram of inspected packages and determining a cutoff threshold for an acceptable quality signature. Other aspects, features, and embodiments are also claimed and described.Georgia Tech Research Corporatio
Non-contact ultrasonic detection of angled surface defects
Non-destructive testing is an important technique, and improvements are constantly needed. Surface defects in metals are not necessarily confined to orientations normal to the sample surface; however, much of the previous work investigating the interaction of ultrasonic surface waves with surface-breaking defects has assumed cracks inclined at 90° to the surface. This paper explores the interaction of Rayleigh waves with cracks which have a wide range of angles and depths relative to the surface, using a non-contact laser generation and detection system. Additional insight is acquired using a 3D model generated using finite element method software. A clear variation of the reflection and transmission coefficients with both crack angle and length is found, in both the out-of-plane and in-plane components. The 3D model is further used to understand the contributions of different wavemodes to B-Scans produced when scanning a sample, to enable understanding of the reflection and transmission behaviour, and help identify angled defects. Knowledge of these effects is essential to correctly gauge the severity of surface cracking
Adsorbate induced enhancement of electrostatic non-contact friction
We study the non-contact friction between an atomic force microscope tip and
a metal substrate in the presence of bias voltage. The friction is due to
energy losses in the sample created by the electromagnetic field from the
oscillating charges induced on the tip surface by the bias voltage. We show
that the friction can be enhanced by many orders of magnitude if the ads orbate
layer can support acoustic vibrations. The theory predicts the magnitude and
the distance dependence of friction in a good agreement with recent puzzling
non-contact friction experiment \cite{Stipe}. We demonstrate that even an
isolated adsorbate can produce high enough friction to be measured
experimentally.Comment: Published in PR
- …