Measurement Of Small Displacements Research Articles

Elastographic imaging

Elastographic imaging

Radiographic evaluation of osseous displacement following intra-articular fractures of the distal radius: Reliability of plain radiography versus computed tomography

This study evaluated the reliability of plain radiography versus computed tomography (CT) for the measurement of small (< 5 mm) intra-articular displacements of distal radius fracture fragments. The plain radiographs and CT scans of 19 acute intra-articular distal radius fractures were used by 5 independent observers, using 2 standardized techniques, to quantify incongruity of the articular surface in a blinded and randomized fashion. Repeat measurements were performed by the same observers 2-4 weeks later, allowing determination of intraclass correlation coefficients (ICC) as a measure of intraobserver and interobserver agreement. The average maximum gap displacement on plain radiographs was 2.1 mm (range, 0.0-15.0 mm, lateral view) and on CT images was 4.9 mm (range, 0.7-17.3 mm, axial view). The average maximum step displacement on plain radiographs was 0.9 mm (range, 0.0-6.4 mm, lateral view) and on CT images was 1.2 mm (range, 0.0-6.0 mm, sagittal view). More reproducible values determining step and gap displacement were obtained when the arc method of measurement was used on CT scans (ICC values, .69-.97) as compared to the longitudinal axis method for plain radiographs (ICC values, .30-.50). For measured displacements of 2 mm or more, our data demonstrated poor correlation between measurements made on CT images and those made on plain radiographs (gap or step displacement > 2 mm, K = 0.21; step displacement > 2 mm, K = 0.21). Thirty percent of measurements from plain radiographs significantly underestimated or overestimated displacement compared to CT scan measurements. From these data, we conclude that CT scanning data, using the arc method of measurement, are more reliable for quantifying articular surface incongruities of the distal radius than are plain radiography measurements.

Magnetosensors based on semiconductor microwires

Some aspects of the technology of semiconductor and semimetal microwires (MW) with glass coating are described. Two types of MW magnetosensing elements (magnetoresistive and galvanomagnetorecombination) are proposed and obtained on the basis of Ge, Bi, InSb and their alloys. Such MW magnetoelements with various constructive variants allowed us to use them for the design and fabrication of new magnetosensors and transducers. The design and the characteristics of some MW magnetosensors, enabling the measurement of turn angles, small and large displacements, and electric charges, are analyzed.

Large deformation mechanical testing of biological membranes using speckle interferometry in transmission II: Finite element modeling

In holography and speckle interferometry the measurement range is generally limited by the greatest number of fringes that can be resolved in a single image. As a result these techniques have been generally confined to small displacement measurement applications. In the case of out-of-plane measurements one can overcome this limitation by simply adding incremental measurements at individual detector pixels. In the case of in-plane measurements, however, summing incremental measurements is not a straightforward procedure since the interference pattern moves laterally across the detector as the material deforms. We describe a modeling technique based on finite elements which solves this problem. In combination with a full field method such as holography or speckle interferometry, it provides a very sensitive measurement technique with dense spatial sampling and large dynamic range. Experimental results of speckle interferometry operating in transmission to measure in-plane displacements of biological membranes are presented, where total material displacements are of the order of millimeters. The results also demonstrate how the finite strain tensor is calculated analytically from the data at any point on the material.

Internal tissue displacement measurement based on ultrasonic wave Doppler signal digital detection and its application to fetal movement monitoring.

We have developed a fetal movement monitoring system based on small displacement measurement of internal tissues. When ultrasonic pulses are transmitted to the fetus, the reflected ultrasonic waves which have a Doppler frequency shift due to the fetal movements are detected by using an ultrasonic pulsed Doppler technique. In this paper, we propose a displacement measurement method for internal tissues which is based on the Doppler signal digital detection technique. In the method, the received ultrasonic RF signals are sampled with a sampling frequency of four times higher than the centre frequency of the ultrasonic waves; the Doppler frequency shift signals are derived using digital signal processing. From the detected signals, the internal displacements are estimated using the arc-tangent method. The basic algorithm of the detection method has already been used in the area of blood flow sensing, however, we apply the algorithm to the displacement measurement of internal tissues. The comparison between the proposed method and the conventional method is presented. The fetal movement quantitative monitoring system based on the method which has been constructed is shown.

Automated fetal breathing movement detection from internal small displacement measurement.

We have previously proposed a method to measure small displacements of internal tissue which is based on an ultrasonic pulsed Doppler technique. The Doppler frequency shift of the ultrasonic waves due to the tissue movement is detected using a modified quadrature detector, and the displacement of the internal tissue is estimated by using an arctangent method. Based on the algorithm, we have constructed a quantitative monitoring system for fetal breathing movement. The fetal breathing movement is a rhythmic movement of the fetal diaphragm and it is recorded as a nearly sinusoidal displacement with a repetition frequency from 0.5 Hz to 2 Hz. In this paper, an automated fetal breathing movement detection algorithm for the displacement data observed by using the small displacement measurement system is proposed. This method uses a modified autocorrelation technique for detecting the displacement due to the fetal breathing movement. The method is applied to five fetuses of late pregnancy and the result is compared with the manual detection.

Remote measurement of small displacements using a CD pickup head

The recording and analysis of heart beats and other sounds produced naturally by the human fetus provides a valuable and non-invasive metric of fetal well-being. Vibrations initiated by fetal heart beats are heavily attenuated as they propagate through the intervening tissue to the surface of the maternal abdomen. Successful recording of these vibrations must allow for their microscopic amplitude and the high compliance of the maternal abdomen. Thus the ideal recording transducer presents no inertial load to the skin surface and there is no vibration attenuation* With the goal of designing an improved fetal sound ‘microphone’ an optical displacement measL~rement technique has been investigated. Using optical techniques in recording sub-millimetre displacements offers the possibility of precise measurements, insensitivity to electrical interference and the potential for remote sensing. The Compact Disc (CD) pickup head integrates a coherent light source, optics including an objective lens with built in actuator, and a photodiode array. This is within a compact package and available at comparatively low cost. As they are normally only available as a ‘spares item’ technical information is difficult to obtain. The purpose of this note is to describe a simple working system, easily constructed, to promote experimentation in using CD pickups for distance measurement. The interface circuit described is designed for a Sony pickup (KSSZlOA). However, only trivial modifications are required for it to be used with CD pickups from other manufacturers. A system in which a beam of light is directed at a mirror and reflected onto a photodiode provides a convenient technique for remote distance measurement. When suitably configured, displacement of the mirror modulates the amplitude of the photodiode output. In this way relative displacement of the mirror is determined from the photodiode output. The same principle is utilised in compact disc (CD) players in order to maintain the CD pickup head at a fixed distance, (to within microns), above the CD surface. This principle is again used here to describe use of a CD pickup to measure small displacements of a reflecting surface.

Tissue Displacement Measurement Using Ultrasonic Wave Adaptive Digital Detection Method

We have developed an internal small-displacement measurement system based on the ultrasonic wave pulsed Doppler technique. In the system, the ultrasonic wave Doppler frequency shift due to tissue movement is detected by using either an analog-type quadrature detector or digital detection algorithm. In this paper, we propose an adaptive digital detection algorithm which can derive a Doppler frequency shift signal with higher precision and with higher signal-to-noise ratio than the conventional method. The comparison between the proposed method and the conventional method is shown through both numerical analysis and basic experimentation.

Magneto-optical high resolution measurement of small displacements between light beams of different color

The magneto-optical Kerr-effect of a 40 nm thin iron film is used to modulate light beams of different color (e.g., red and green) up to 100 kHz. Yielding a resolution of 35 nm at a total light power of 5 /spl mu/W, the displacement between the two focal points of these beams is measured by the time difference of the corresponding photo diode signals. The relation between the time and a locally defined magnetization reversal of the film is achieved by a ferrite C-yoke with gradient pole shoes and the rectangular hysteresis of the iron film. Besides various optical measurement applications, the method is foremost useful for studying the atmospheric refraction, where the dispersion of the refractive index leads to small angles (/spl ap/1 /spl mu/rad) between light beams of different wavelengths.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of small angular displacement by a modified moire technique

Small angle measurement using a modified moiré interference technique is reported. The range of angle measurement for 25-μm pitch gratings is about ± 25 μrad and the accuracy of measurement is of the order of 0.2 μrad with a time constant of 0.1 s. A piezoelectric transducer (PZT) is used for angular displacement. The angular sensitivity under the present experimental conditions is found to be of the order of 21.8 mV/μrad.

An experimental investigation of contact bounce in medium duty contacts

An investigation of the parameters influencing the dynamics of electrical contact bounce under medium current loading (1-30 A) was carried out. A new measurement system which offers an improvement in the monitoring of mechanism dynamics is presented. The system is based on the measurement of small impact displacements using an infrared optical method. In addition, the measurement of impact forces has been achieved using a piezoelectric film (PVDF). The results show the effect of current loading and the associated thermal softening on the impact and the separation characteristics occurring during contact bounce. >

Two-frequency displacement measurement interferometer based on a double-heterodyne technique

A two-frequency laser heterodyne interferometer has been implemented for small displacement measurement. The displacement signal is detected by using a double-heterodyne technique. Vibration amplitudes at 1 kHz on the order of 1 nm and smaller can be detected.

Measurement of small angular displacements with a flat-parallel glass plate.

A new, simple method is presented for the accurate measurement of small angular displacements. An incident laser diode beam on a flat-parallel glass plate was reflected at the front and the rear surface of the plate, and the interference pattern of two reflected beams was measured with a one-dimensional image sensor and a microcomputer, After the running average of the interference pattern signals was computed numerically to reduce spatial noise on the interference pattern, interference peak positions and angular displacements were estimated. The small angular displacements thus obtained were found to be in approximate agreement with a theory.

Measurement of small displacements by speckle holography

A speckle holography technique is discussed for measuring small displacements of objects. It is based on the sensitivity of the diffracted light intensity from a mutual shift between the hologram and the reconstructed speckle wave. The proposed method allows the measurement of both an object's lateral and longitudinal displacement without changing the arrangement of the apparatus. This set-up allows continuous measurements to be taken.

Improvement of young's fringes' visibility in speckle photography by use of BSO-PROM device

For real time measurements of small displacements and deformations, dependence of the Young's fringes' visibility on an applied voltage to a BSO-PROM device, which is used as a recording device of the specklegram in the speckle photography, has been investigated. It is experimentally shown that the Young's fringes' visibility is improved by changing the applied voltage to the PROM device in the readout operation. This improvement is useful to accurate measurements of displacements in the speckle photography when the amount of the exposure is small and will be able to shorten cycle times of measurements.

Composite Grating For Moire Interferometry

This paper presents the theoretical background and experimental verification of a new composite grating with two different grating frequencies, which was developed for simultaneous measurements of small and large displacements in a single specimen using moire interferometry. A composite grating with line frequencies of 1200 and 300 lines/mm was used to study the changes in the displacement field and the approximate J-integral values of a 5152-H32 aluminum, single-edge-notched specimen under increasing load.

Experimental determination of the center of resistance of the upper first molar in a macerated, dry human skull submitted to horizontal headgear traction

Laser speckle interferometry, recently developed for noninvasive measurement of small displacement (microns), was used to study the movement of maxillary molars submitted to extraoral traction. Using an antenna-headgear at different horizontal levels, loadings of 700 gm were applied perpendicular to the long axes of these teeth. Bodily movement was observed when the traction line passed slightly occlusal to the trifurcation of the roots. Therefore, the center of resistance of the upper molar was experimentally localized at this level. Laser speckle interferometry proved to be a promising technique for dental research.

Parametric converters for detection of small harmonic displacements

We discuss the construction and operation of a superconducting microwave cavity parametric converter suitable for the measurement of small harmonic displacements. Displacements of one endwall of the cavity produced by a piezoelectric ceramic and of order δx = 3 × 10 −17 cm have been detected. Such a device is presently used to search for anomalous long range interactions of a beam of stored high energy particles.

Cosmic and geophysical noise in measurements of small displacements

Cosmic and geophysical noise in measurements of small displacements

Application of optical heterodyning methods for precision measurements of small displacements

Application of optical heterodyning methods for precision measurements of small displacements