Fast Measurement Technique Research Articles

In vivo R1‐enhancement mapping of canine myocardium using ceMRI with Gd(ABE‐DTTA) in an acute ischemia‐reperfusion model

To demonstrate the usefulness of normalized DeltaR1 (DeltaR1(n)) mapping in myocardial tissue following the administration of the contrast agent (CA) Gd(ABE-DTTA). Ischemia-reperfusion experiments were carried out in 11 dogs. The method exploited the relatively long tissue lifetime of Gd(ABE-DTTA), and thus no fast R1 measurement technique was needed. Myocardial perfusion was determined with colored microspheres (MP). With varying extent of ischemia, impaired wall motion (WM) and lower DeltaR1(n) values were detected in the ischemic sectors, as opposed to the nonischemic sectors where normal WM and higher DeltaR1(n) were observed. Based on the DeltaR1(n), data from the myocardial perfusion assay and the DeltaR1(n) maps were compared in the ischemic sectors. A correlation analysis of these two parameters demonstrated a significant correlation (R = 0.694, P < 0.005), validating the DeltaR1(n)-mapping method for the quantitation of ischemia. Similarly, pairwise correlations were found for the MP, DeltaR1(n), and wall thickening (WT) values in the same areas. Based on the correlation between DeltaR1(n) and MP, DeltaR1(n) maps calculated with a pixel-by-pixel resolution can be converted to similarly high-resolution myocardial perfusion maps. These results suggest that the extent of the severity of ischemia can be quantitatively represented by DeltaR1(n) maps obtained in the presence of our CA.

A New Measurement and Testing Procedure Based on Thermoelasticity for Motorcycle Frame Prototype Development

Motorcycle frames are mechanical components that need to be optimised in terms of performance and costs but with a limited amount of resources compared to, for example, car frames. Fatigue testing of the component is required for qualification and this is typically performed by using rotating drums with steps or servo-controlled hydraulic actuator based test benches. Therefore a fast and simple measurement and testing technique that operates during the fatigue tests will be a very useful tool. In this paper the possibility of analysing these components by measuring the stress levels and stress concentration in critical parts by thermoelasticity is investigated. The development of a multibody model, useful to simulate the typical working conditions of the motorcycle frame, is also described.

Characteristics and physical mechanisms of positive bias and temperature stress-induced drain current degradation in HfSiON nMOSFETs

Drain current degradation in HfSiON gate dielectric nMOSFETs by positive gate bias and temperature stress is investigated by using a fast transient measurement technique. The degradation exhibits two stages, featuring a different degradation rate and stress temperature dependence. The first-stage degradation is attributed to the charging of preexisting high-k dielectric traps and has a log(t) dependence on stress time, whereas the second-stage degradation is mainly caused by new high-k trap creation. The high-k trap growth rate is characterized by two techniques, namely 1) a recovery transient technique and 2) a charge-pumping technique. Finally, the effect of processing on high-k trap growth is evaluated.

A new fast parallel statistical measurement technique for computational cosmology

Higher order cumulants of point processes require significant computational effort to calculate, particularly when evaluated using standard methods such as counts-in-cells. While newer techniques based on tree algorithms are more efficient, they still suffer from shot noise problems in homogeneous systems. We present a new algorithm for calculating higher order moments using Fourier methods. A filtering technique is used to suppress noise, and this approach allows us to calculate skew and kurtosis even when the point process is highly homogeneous. The algorithm can be implemented efficiently in a shared memory parallel environment provided a data-local random sampling technique is used.

A fast measurement technique of MOSFETI/sub d/-V/sub g/ characteristics

In this letter, we developed an improved ultrafast measurement method for threshold voltage V/sub th/ measurement of MOSFETs. We demonstrate I/sub d/--V/sub g/ curve measurement within 1 /spl mu/s to extract the threshold voltage of MOSFET. Errors arising from MOSFET parasitics and measurement setup are analyzed quantitatatively. The ultrafast V/sub th/ measurement is highly needed in the investigation of gate dielectric charge trapping effect when traps with short detrapping time constants are present. Application in charge trapping measurement on HfO/sub 2/ gate dielectric is demonstrated.

Dynamic speckle effect induced by an acousto-optic deflector for fast range sensing

A technique for fast distance measurements based on continuous frequency measurements of the power modulation of spatially filtered scattered light is proposed. For what is to our knowledge the first time, it is shown that the technique works when laser beam scanning is performed with an acousto-optic deflector. The most impressive feature of the proposed technique is that it works at very high scanning speed, providing an extremely fast response time. Experimental verification of the technique is demonstrated at a scanning speed as as high as 130 m/s. The proposed method of range sensing allows the design of a distance sensor possessing a response time as fast as 80 ns.

Feasibility of quantifying ecosystem–atmosphere C 18O 16O exchange using laser spectroscopy and the flux-gradient method

Stable isotopes of carbon dioxide (CO 2) can be used as natural tracers to better understand carbon cycle processes and exchange pathways between the biosphere and atmosphere. In this study, we used a tunable diode laser (TDL) technique for continuous fast measurement of the stable isotopomers C 18O 16O and C 16O 2 and their ratio, δ a. The TDL system was configured to measure mixing ratios of [C 16O 2] and [C 18O 16O] at wavenumber frequencies of 2308.225 and 2308.416 cm −1, respectively. Two-minute precision (1 standard deviation) was 0.0004, 0.09 μmol mol −1, and 0.26‰ for [C 18O 16O], [C 16O 2] and δ a, respectively. Comparison of TDL and mass spectrometry flask measurements showed relatively good agreement ( r 2 = 0.94) with a standard deviation of 0.55‰ for the residual values. Estimates of the isotope signature of ecosystem flux components over a soybean ( Glycine max) field were examined. These data represent one of the first continuous flux measurements of C 18O 16O. The isotope signature of net ecosystem CO 2 exchange at night ranged from −15 to −7‰ and during the daytime from −40 to −20‰. A simple estimate of canopy-scale photosynthetic discrimination showed significant diurnal variation and averaged 10.5‰ (±8.8‰). The large difference between the isotope signature of respiration and midday canopy photosynthesis represented significant isotopic disequilibrium. Coupled with recent advances in measuring water vapor isotopomers with the TDL technique, a new opportunity is emerging to better understand the dynamics, complex interactions, and discrimination mechanisms controlling land-atmosphere C 18O 16O exchange.

Fast distance measurements by use of dynamic speckles

A technique for fast measurements of the distance to an object's surface based on spatial filtering of dynamic speckle patterns is proposed. Exploitation of two spatial filters (Ronchi rulings) enables measurements to be independent of surface speed. Experimental verification of the technique is demonstrated at speeds of the surface as high as 50 m/s. The technique may find applications in machine-vision systems for acquisition of three-dimensional images and in control systems for on-line monitoring of fast-moving parts of industrial machines.

Full-field micro surface profilometry using digital fringe projection with spatial encoding principle

This article describes an effective full-field three-dimensional micro surface profilometer using digital fringe projection with digital micromirror device (DMD) technology and triangulation measurement principle. Fast and accurate three-dimensional measurement techniques with full-field measurement capability are thus highly demanded for sharpening product competitiveness. Traditional laser triangulation methods have difficulty in detecting the accurate centre position of projected points or lines when encountered with light scattering problems caused by the object's geometric discontinuities, such as surface boundaries or edges. The newly developed profilometer deploys a DMD to project flexible digital structured light patterns of white light onto the object to suit various inspection requirements, such as the object's size and surface condition. Micro structured light patterns can be generated by using optical zoom and collimating lens sets. Accurate system parameters of 3-D surface profilometry can be obtained by developing a calibration process based on least squares minimization. Micro 3-D contours with a large surface gradient can be reconstructed accurately and efficiently.

A thermal dissociation–chemical ionization mass spectrometry (TD‐CIMS) technique for the simultaneous measurement of peroxyacyl nitrates and dinitrogen pentoxide

We have developed a thermal dissociation–chemical ionization mass spectrometry (TD‐CIMS) technique for fast measurements of a series of peroxyacyl nitrates and dinitrogen pentoxide. Thermally generated acylperoxy radicals react with I− to produce a carboxylate ion that is unique for each parent species. NO3 resulting from the decomposition of N2O5 reacts with I− to form NO3−. The measurement technique was verified for PAN and PPN during an informal comparison with a gas chromatograph (GC) equipped with an electron capture detector (ECD) in Boulder, Colorado, during October 2002. Good agreement was obtained between the two instruments with R2 = 0.91 for PAN (n = 657) and R2 = 0.89 for PPN (n = 655). Detection limits of 7 pptv and 4 pptv were determined for PAN and PPN, respectively, for a 1 s integration period and a signal‐to‐noise ratio of 3. The TD‐CIMS simultaneously detected ambient PiBN and N2O5 + NO3 in addition to PAN and PPN during the intercomparison period. We estimate a detection limit of 3 pptv in 1 s for PiBN. PnBN would be detected at the same mass, so we cannot rule out a contribution from PnBN to our PiBN estimate. Sensitivity to MPAN was found to be lower than to PAN in laboratory experiments, but a detection limit of 10 pptv can still be achieved by integrating for 15 s. Assuming the same sensitivity as for PAN, the detection limit for the sum of N2O5 and NO3 was estimated to be 12 pptv in 1 s. The fast time response of the TD‐CIMS combined with a sensitivity and limit of detection comparable to the GC/ECD make this a promising technique for PAN flux measurements by eddy covariance. PAN uptake by different types of vegetation could be important input for global and regional ozone models, and PAN deposition to snow is of interest in polar regions.

Semiquantitative fast flow velocity measurements using catheter coils with a limited sensitivity profile.

Flow measurements can be used to quantify blood flow during MR-guided intravascular interventional procedures. In this study, a fast flow measurement technique is proposed that quantifies flow velocities in the vicinity of a small RF coil attached to an intravascular catheter. Since the small RF coil receives signal from only a limited volume around the catheter, a spatially nonselective signal reception is employed. To enhance signal from flowing blood, and suppress unwanted signal contributions from static material, a slice-selective RF excitation is used. At a velocity sensitivity of 150 cm/s, a temporal resolution of 2 x TR = 10.2 ms can be achieved. The flow measurement is combined with an automatic slice positioning to facilitate measurements during interventional procedures. The influence of the catheter position in the blood vessel on the velocity measurement was analyzed in simulations. For blood vessels with laminar flow, the simulation showed a systematic deviation between catheter measurement and true flow between -15% and 80%. In four animal experiments, the catheter velocity measurement was compared with results from a conventional ECG-triggered 2D phase-contrast (PC) technique. The shapes of the velocity time curves in the abdominal aorta were nearly identical to the conventional measurements. A relative scaling factor of 0.69-1.19 was found between the catheter velocity measurement and the reference measurement, which could be partly explained by the simulation results.

A study of the transient plasma potential in a pulsed bi-polar dc magnetron discharge

The temporal evolution of the plasma potential, Vp, in a pulsed dc magnetron plasma has been determined using the emissive probe technique. The discharge was operated in the ‘asymmetric bi-polar’ mode, in which the discharge voltage changes polarity during part of the pulse cycle. The probe measurements, with a time-resolution of 20 ns or better, were made along a line above the racetrack, normal to the plane of the cathode target, for a fixed frequency (100 kHz), duty cycle (50%), argon pressure (0.74 Pa) and discharge power (583 W). At all the measured positions, Vp was found to respond to the large and rapid changes in the cathode voltage, Vd, during the different phases of the pulse cycle, with Vp always more positive than Vd. At a typical substrate position (>80 mm from the target), Vp remains a few volts above the most positive surface in the discharge at all times. In the ‘on’ phase of the pulse, the measurements show a significant axial electric field is generated in the plasma, with the plasma potential dropping by a total of about 30 V over a distance of 70 mm, from the bulk plasma to a position close to the beginning of the cathode fall. This is consistent with measurements made in the dc magnetron. During the stable ‘reverse’ phase of the discharge, for distances greater than 18 mm from the target, the axial electric field is found to collapse, with Vp elevated uniformly to about 3 V above Vd. Between the target and this field-free region an ion sheath forms, and the current flowing to the target is still an ion current in this ‘reverse’ period. During the initial 200 ns of the voltage ‘overshoot’ phase (between ‘on’ and ‘reverse’ phases), Vd reached a potential of +290 V; however, close to the target, Vp was found to attain a much higher value, namely +378 V. Along the line of measurement, the axial electric field reverses in direction in this phase, and an electron current of up to 9 A flows to the target.The spatial and temporal measurements of Vp presented here confirm a simple picture of the evolution of Vp, predicted from previously made time-resolved mass spectroscopic measurements of the ionic component in the pulsed magnetron. This paper describes the development and characteristics of the emissive probe technique for such fast measurements, together with implications for the form of the measured transient potential profiles on the operation of the magnetron discharge. In particular, it addresses the charged particle drifts and the potential for sputtering of the walls and the anode by ion impact.

Dynamic measurement access, a new technique for fast thermal conductivity measurement

A new technique called dynamic measurement access (DMA) is presented in this article which was developed for relatively easy, fast, and accurate thermal conductivity measurements. Utilizing a commercial cryocooler adapted for this experiment, the DMA technique allows the measurement of typically 400 data points in a temperature range between 300 and 10 K, during an elapsed time of approximately 90 min. This technique provides very good precision and requires a very simple experimental setup, which is described in this article.

The determination of material parameters of microcomponents using digital holography

Progresses in microsystem technology promise a lot of new applications in industry and research. However, the increased complexity of the microsystems demand sensitive and robust measurement techniques. Fullfield and non invasive methods are desirable to get access to spatially resolved material properties and parameters. This contribution describes a simple and fast interferometric method for the analysis of shape and deformation of small objects by optical means. These quantities together with a well defined loading of the components can be the starting point for the determination of material parameters like Poisson-ratio, Young's modulus or the thermal expansion coefficient. Holographic interferometry and multiple wavelength contouring as well as multiple source point contouring are precise enough to fulfill the requests for precision and resolution in microsystem technology even on complex shaped structures with steps or gaps A new adaptive, iterative algorithm is developed and applied to the measured results that allows the numerical evaluation of the phase data to get absolute shape and deformation information in Cartesian coordinates. Surfaces with holes, gaps and steps can be registered without any ambiguities. Digital holography as the underlying holographic recording mechanism is extremely suitable for small objects and lead to simple and compact setups in which the objects’ shape as well as their deformation behavior can be recorded. Experiments using silicon microbeams and an object from fine mechanics are described to show the great potential of these fast and robust measurement techniques with respect to the determination of material parameters.

Measurement techniques for unsteady flows in turbomachines

The growing interest for unsteady flows in turbomachines over the last two decades has led to an intensive development of fast response measurement techniques, capable of resolving with high frequency phenomena related to inlet distortion, rotating stall and blade row interference effects with blade passing frequencies ranging from 3 to 30 kHz. This development was favoured by major advances in sensor technology and data acquisition systems. The paper reviews the progress in fast response measurement techniques for high speed turbomachinery and application with emphasis on fast response pressure and temperature probes and blade surface sensors including pressure, heat transfer and shear stress determination.

Multifrequency grating projection profilometry based on the nonlinear excess fraction method

Although promised to be a fast and accurate three-dimensional shape measurement technique, grating projection profilometry based on phase measurement has been frequently baffled by the difficulty in phase unwrapping. We introduce the conventional excess fraction method into profilometry and extend it to nonlinear domain. Nonlinear excess fraction method (NLEFM), on the basis of which a multifrequency grating projection profilometry is developed, can work as a robust temporal phase unwrapper, which may extend the reliable measuring range by dozens of times at no cost of accuracy. The principle of NLEFM is detailed, and experimental results are given in which complex profiles are reliably measured with the novel system.

Accurate and fast speed measurement using ramp-waveform sampling technique

A novel sampling technique for accurate and fast speed measurement is presented. Square pulses from an encoder are turned into ramps using analog electronics. They are then sampled, and linear regression is used on ramp-waveform sample points to extrapolate backward and determine the starting point of each pulse very accurately.

Fast-Bearing Measurement with a Single Ultrasonic Transducer

In conventional ultrasonic sensing, accurate ultrasonic target- bearing measurement is often regarded as difficult, due to the wide- beam angle of ultrasonic transducers. However, the accurate mea surement of distances and angles is usefulfor many robot tasks, such as obstacle avoidance and wall following. In this paper, we propose a method for extracting bearing information by using a single trans ducer in ultrasonic pulse-echo sensing, which basically exploits the dependency of the echo spectrum on bearing angle. The method em ploys a simple approach using a zero-crossing time interval of the reflected echo, and consequently is a fast measurement technique. This paper also presents experimental results on a real mobile robot and illustrates the usefulness of the ultrasonic bearing-measurement approach.

The application of a laser scanning vibrometer for dynamic characterization of large impellers

The application of a laser scanning vibrometer to detect resonance frequencies and mode shapes of large impeller rotors is illustrated. The dynamic analysis of the structure has been previously performed by means of a standard FEM code. The key to success was the ability of the laser vibrometer to detect very low vibration amplitudes (of the order of nanometers) with a high spatial resolution, inside an industrial environment, in very low testing time; all fundamentals for this application. The experimental and numerical activity presented in this work has been carried out at Nuovo Pignone together with the University of Ancona with the final purpose of establishing a new, fast measurement technique to identify, in a production industrial environment, the dynamic behaviour of large dimension impellers for centrifugal compressors.

An iterative technique for fast and accurate measurement of power system frequency

This paper describes the design, computational aspects and implementation of an iterative technique for measuring power system frequency. The technique provides accurate estimates to a resolution of 0.01-0.02 Hz for near-nominal, nominal and off-nominal frequencies in about 20 ms. Computation requirements are modest and the technique has been implemented on a modern digital signal processor. The proposed technique was extensively tested using voltage signals obtained from a dynamic frequency source and from a power system. Some test results are presented in the paper.