摘要:
A method and apparatus for correcting errors in an electronic digital timepiece that includes an oscillator which has a 2.sup.n frequency output, an n-stage frequency divider for reducing the oscillator output frequency to a time keeping frequency, and means for displaying the count of the time keeping frequency. The error E in the time of the timepiece for an arbitrary period of time T is determined. A computer computes a new adjustment value N+(2.sup.n-m +N)E/T where N is the preceding adjustment value and m is a nonnegative integer less than n. Then the 2.sup.n-m divisor of the first n-m stages of the n-stage frequency divider is adjusted in an amount equal to the new adjustment value. In first and second embodiments of the invention the timepiece is synchronized with a time standard at the beginning of the period of time T. In the first embodiment of the invention the timepiece user observes E (the difference between the time standard and the timepiece time at the end of the period T) and then operates a selected switch to correct the time of the timepiece and to obtain a count for E. In the second embodiment of the invention, the user operates a switch at the beginning of T and at the end of T and a count for E is obtained electronically.
摘要:
A material characteristic measurement approach measures an internal state of a material by measuring the nonlinear shift in velocity induced by different acoustic energies. The technology for implementing this measurement approach is relatively simple, robust, permits portable measurements, does not require that an unloaded initial condition of the material be measured or otherwise known in order to determine a characteristic of the material, can be applied using one or more transducers, and does not require physical contact with the material. Some example material characteristics include a residual stress existing without any external mechanical force applied, applied stress, a fatigue state, age, an interference-fit fastener stress, bio-activity, a nanostructure mixture of the material, a heat treatment of the material, a cross-linking of polymers in the material, a bio-growth organization of the material, a clotting factor of blood or blood-like material, a cure of an adhesive or sealant material, or the microstructure of the material.
摘要:
A multilayer object having multiple layers arranged in a stacking direction is evaluated for imperfections such as voids, delaminations and microcracks. First, an acoustic wave is transmitted into the object in the stacking direction via an appropriate transducer/waveguide combination. The wave propagates through the multilayer object and is received by another transducer/waveguide combination preferably located on the same surface as the transmitting combination. The received acoustic wave is correlated with the presence or absence of imperfections by, e.g., generating pulse echo signals indicative of the received acoustic wave, wherein the successive signals form distinct groups over time. The respective peak amplitudes of each group are sampled and curve fit to an exponential curve, wherein a substantial fit of approximately 80-90% indicates an absence of imperfections and a significant deviation indicates the presence of imperfections. Alternatively, the time interval between distinct groups can be measured, wherein equal intervals indicate the absence of imperfections and unequal intervals indicate the presence of imperfections.
摘要:
A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.
摘要:
A broadband megahertz range electrostatic acoustic transducer for use in a liquid environment. A liquid-tight enclosure 11 which includes a metallic conducting membrane 18 as part of its outside surface has a means 19 inside the liquid-tight enclosure for applying a tension to the membrane and for mounting an electrode 23 such that the flat end of the electrode is approximately parallel to the membrane. The invention includes structure and a method for ensuring that the membrane 18 and the flat end of the electrode 23 are exactly parallel and a fixed predetermined distance from each other.
摘要:
Acoustic temperature measurement at a remote location is provided. An acoustic source transmits acoustic radiation to an acoustic receiver along an acoustic path. The path passes through or near the remote location. The temperature is non-uniform along the path. A change in an integrated acoustic delay between the source and receiver along the path is measured. This acoustic delay can be either a phase velocity delay or a group velocity delay. The temperature at the remote location is determined by relating the measured change in integrated acoustic delay to the remote location temperature with a combined thermal-acoustic model. The combined model relates temperature to acoustic propagation velocity along the path. The combined model preferably includes temperatures of the source and receiver locations, and a heat source geometry at the remote location.
摘要:
A multilayer object having multiple layers arranged in a stacking direction is evaluated for imperfections such as voids, delaminations and microcracks. First, an acoustic wave is transmitted into the object in the stacking direction via an appropriate transducer/waveguide combination. The wave propagates through the multilayer object and is received by another transducer/waveguide combination preferably located on the same surface as the transmitting combination. The received acoustic wave is correlated with the presence or absence of imperfections by, e.g., generating pulse echo signals indicative of the received acoustic wave, wherein the successive signals form distinct groups over time. The respective peak amplitudes of each group are sampled and curve fit to an exponential curve, wherein a substantial fit of approximately 80-90% indicates an absence of imperfections and a significant deviation indicates the presence of imperfections. Alternatively, the time interval between distinct groups can be measured, wherein equal intervals indicate the absence of imperfections and unequal intervals indicate the presence of imperfections.
摘要:
A heat source such as a magnetic induction/eddy current generator remotely heats a region of a surface of a test structure to a desired depth. For example, the frequency of the heating source can be varied to heat to the desired depth. A thermal sensor senses temperature changes in the heated region as a function of time. A computer compares these sensed temperature changes with calibration standards of a similar sample having known disbond and/or inclusion geography(ies) to analyze the test structure. A plurality of sensors can be arranged linearly to sense vector heat flow.
摘要:
A device and method are provided which non-destructively detect crack length and crack geometry in thin metallic plates. A non-contacting vibration apparatus produces resonant vibrations without introducing extraneous noise. Resulting resonant vibration shifts in cracked plates are correlated to known crack length in plates with similar resonant vibration shifts. In addition, acoustic emissions of cracks at resonance frequencies are correlated to acoustic emissions from known crack geometries.
摘要:
A method and apparatus are provided for acoustophoresis, i.e., the separation of species via acoustic waves. An ultrasonic transducer applies an acoustic wave to one end of a sample container containing at least two species having different acoustic absorptions. The wave has a frequency tuned to or harmonized with the point of resonance of the species to be separated. This wave causes the species to be driven to an opposite end of the sample container for removal. A second ultrasonic transducer may be provided to apply a second, oppositely directed acoustic wave to prevent undesired streaming. In addition, a radio frequency tuned to the mechanical resonance and coupled with a magnetic field can serve to identify a species in a medium comprising species with similar absorption coefficients, whereby an acoustic wave having a frequency corresponding to this gyrational rate can then be applied to sweep the identified species to one end of the container for removal.