Real-time Measurement Technique Research Articles

Laboratory Characterization of Modified Tapered Element Oscillating Microbalance Samplers

Laboratory tests with generated aerosols were conducted to test the efficacy of two recent design modifications to the well-established tapered element oscillating microbalance (TEOM) continuous particulate matter (PM) mass monitor. The two systems tested were the sample equilibration system-equipped TEOM monitor operating at 30 °C, which uses a Nafion dryer as part of the sample inlet, and the differential TEOM monitor, which adds a switched electrostatic precipitator and uses a self-referencing algorithm to determine “true PM mass.” Test aerosols included ammonium sulfate, ammonium nitrate, sodium chloride, copper (II) sulfate, and mixed aerosols. Aerosols were generated with an atomizer or a vibrating orifice generator and were equilibrated in a 450-L slow flow chamber before being sampled. Relative humidity in the chamber was varied between 10 and 90%, and step changes in humidity were executed while generating aerosol to test the response of the instruments. The sample equilibration system-equipped TEOM monitor does reduce, but not totally eliminate, the sensitivity of the TEOM mass monitor to changes in humidity. The differential TEOM monitor gives every indication of being a very robust technique for the continuous real-time measurement of ambient aerosol mass, even in the presence of semi-volatile particles and condensable gases.

Measurement of Dynamically Changing Thermal Diffusivity by the Forced Rayleigh Scattering Method (Measurement of Gelation Process)

A measuring method of the thermal diffusivity with high temporal and spatial resolutions has been studied. The forced Rayleigh scattering method is an optical technique to measure the thermal diffusivity of solids and liquids. Based on its characteristics, this method has the applicability to become a “thermal diffusivity real-time monitoring system.” The maximum repetition rate of thermal diffusivity measurement is determined by the attenuation of an excited temperature distribution by laser heating, and a mathematical model of three-dimensional heat conduction is constructed. The temporal resolution of continuous measurements was improved to about 1 s, and the sol-gel transition of a gellan gum aqueous solution was studied to check the validity of the dynamic measurement of thermal diffusivity. Through the gelation process, the dynamical change of the thermal diffusivity was measured, and the gelation point of the solution was identified from a series of thermal diffusivity data. The results indicate the capability of the forced Rayleigh scattering method to be a real-time thermal diffusivity measurement technique for monitoring the rapidly changing process of a material.

On-line measurement of the straightness of seamless steel pipes using machine vision technique

In this paper, on-line and real-time laser visual alignment measurement technique is studied to measure the spatial straightness of large objects. The basic principle of the visual alignment measurement is detailed. The mathematics models of visual sensor, measurement system and their calibrations are presented. Based on the technique, an experiment system is developed and the straightness of a 1500 mm long seamless steel pipe is inspected. The experiment results show that the measurement technique can achieve total on-line measurement and it offers high precision and stability, which is of practical importance for the application.

Combining signal processing and machine learning techniques for real time measurement of raindrops

The data acquisition system for a new type of optical disdrometer is presented. As the device must measure sizes and velocities of raindrops as small as 0.1 mm diameter in real time in the presence of high noise and a variable baseline, algorithm design has been a challenge. The combining of standard signal processing techniques and machine learning methods (in this case, a neural network) has been essential to obtaining good performance.

Tunnelling and the Born-Oppenheimer approximation in optical lattices

We study periodic well-to-well flopping of rubidium atoms in one-dimensional grey optical lattices using a nondestructive, real-time measurement technique and quantum Monte Carlo wavefunction simulations. The observed flopping rates as well as flopping rates extracted from exact band structure calculations can largely be reproduced using adiabatic models that employ the Born-Oppenheimer approximation. The adiabatic model is greatly improved by taking into account a gauge potential that is added to the usual adiabatic light-shift potential. The validity of the adiabatic model allows us to interpret the observed flopping phenomenon as periodic well-to-well tunnelling. At low intensities and in related far-off-resonant optical lattices the adiabatic model fails. There, a weak-coupling model becomes valid, which describes the well-to-well flopping as a Rabi oscillation between weakly coupled states, but not as a tunnel effect.

A03 図示仕事のリアルタイム計測法 : その 1 : ピストンクランク機構

A03 図示仕事のリアルタイム計測法 : その 1 : ピストンクランク機構

Measurements of Primary Radical Concentrations Generated by Pulsed Laser Photolysis Using Fluorescence Detection

Details of a novel technique for direct real-time measurement of the primary radical concentrations generated in pulsed laser photolysis (PLP) experiments are presented. The method takes advantage of the large increase in fluorescence quantum yield that occurs when a nitroxide containing a suitable fluorophore couples with a carbon-centered radical. The technique is applied to PLP experiments which involve photolysis of azobisisobutyronitrile (AIBN) or azobis(methyl isobutyrate) (AIBMe) in the presence of 4-(1-naphthoyloxy)-2,2,6,6-tetramethylpiperidine-1-oxyl (NTEMPO). In these experiments, the method is shown to be capable of reliably measuring transient radical concentrations of less than 10-7 M. Various side reactions that might complicate the technique are considered and shown not to be of significance. The concentration of radicals generated per pulse is shown to have a linear dependence on [AIBN], [AIBMe], and laser energy per pulse (and is shown to be independent of [NTEMPO]) over a wide range of ...

An ion beam technique for real-time measurement of two-dimensional islands during epitaxial growth

In this paper, we describe a technique for real-time measurement of two-dimensional (2D) islands during molecular beam epitaxy, using GaAs(001) growth as the test case. In this technique, an ion beam impinges at a glancing angle relative to the sample surface, and the specularly scattered ion current is measured. The current is a quantitative probe of surface defects, e.g., adatoms and step edges, which interrupt the locally flat surface needed for a specular reflection. Nucleation is detected during the early stages of GaAs growth when the measured adatom density drops below the expected value, because of adatom self-shadowing in 2D nuclei. After deposition, there is a relatively fast current recovery – related to adatom diffusion – combined with a much slower recovery – explained by a decrease in step-edge density as the 2D island density decreases. Good fits to the recovery data were obtained by assuming power-law island coarsening.

Remote True Temperature Pyrometry of Si Wafers: Theoretical and Practical Considerations

ABSTRACTThe problems of real thermodynamic temperature measurement in semiconductor processing can be divided into fundamental and environmental. The first type arises from a-priori unknown and in process changing optical properties (emissivity) of the target wafer. Others have to do with the need to eliminate direct and indirect stray heat flux from entering into the sensor. We describe the advantages and pitfalls of various (passive and active) remote measurement methods. Experimental results of a novel emissivity independent technique for real time measurement in the range of 450–850°C with accuracy better than 1% for wafer emissivity in the range of 0.2 to 0.95 are given.

MEDICAL AEROSOLS: TECHNIQUES FOR PARTICLE SIZE EVALUATION

ABSTRACT Methods for the in-vitro measurement of the particle size distribution of aerosols from medical aerosol delivery systems, including pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs) and nebulizers, are reviewed with emphasis on their applicability both for compendial testing and for simulation of patient use. The importance of real-time measurement techniques, particularly for routine quality control testing, is also discussed, despite the current lack of a means to obtain absolute measurements of drug mass with these systems.

Novel method for real-time monitoring of non-linear transition shift

This paper presents a technique for real-time measurement of non-linear transition shift (NLTS) caused by the adjacent transition. The method is based on the harmonic elimination principle. By measuring the readout amplitude of three selected harmonics from a specific test pattern, the NLTS can be obtained from the amplitudes of the three selected harmonics. The proposed method has the advantage for real-time measurement of the NLTS. This is not true for the existing NLTS measurement techniques. Comparison of the NLTS value measured by the proposed method and the existing method shows satisfactory agreement between them. Furthermore, the proposed method has the advantage of insensitivity to the fluctuation of flying height during the reading and testing process.

Experiments with numerically controlled atomic clocks

Long term timing stability of present atomic clocks can be considerably improved by simple numerical algorithms which correct both the inherent frequency bias and the effects of supply voltage variations and outside temperature. Rubidium units are demonstrated to operate with less than 100 ns errors per week or any sensible longer interval corresponding to relative uncertainties of 10/sup -13/. Often a linear subtraction of frequency offset which can be realized by a microprocessor controlled digital delay line is sufficient. A cesium clock could be run at 10/sup -15/ level, but reliable and reasonable real-time measurement techniques do not yet exist.

A Patient-Side Technique for Real-Time Measurement of Acetylcholinesterase Activity During Monitoring of Eptastigmine Treatment

Rapid and reliable measurement of acetylcholinesterase (AChE) activity is of crucial importance to the pharmacodynamic monitoring of anticholinesterase drugs. A new assay has been developed to measure AChE from 10 microliter samples of capillary blood. AChE activity was calculated from the change in pH of the reaction medium caused by the hydrolysis of acetylcholine and measured with a highly sensitive differential pH apparatus (CL-10, Eurochem, Rome, Italy). Interference by butyrylcholinesterase was eliminated by a specific inhibitor, quinidine sulfate. The assay lasts 1 min. The coefficient of variation (CV) for replicated measurements was 2.8% (3267 U/L, n = 33). Linearity ranged from 0 to 10,000 U/L. The correlation coefficient between the new technique and Ellman's colorimetric method on washed erythrocytes was r = 0.987 (y = 1.299x - 63, n = 29). The correlation coefficient between assays on capillary and venous samples was r = 0.979 (y = 0.974x + 174, n = 47). A cross-laboratory validation study was performed in 10 centers using glycerol-stabilized hemolysates with normal and reduced AChE activity. Samples were assayed in triplicate. The within- and between-laboratory CVs for samples with normal AChE activity (6,018 U/L) were 2.2 and 8.1%, respectively. The new method was applied to a double-blind, placebo-controlled multicenter study of eptastigmine in Alzheimer patients and proved to be a simple, noninvasive, rapid, and reliable method for pharmacodynamic monitoring of this drug.

Phase-correlation techniques for quasi real-time measurement of deformations with digital speckle interferometry

A new approach of in-plane speckle-displacement analysis by binary phase-correlation evaluation is described. An optical implementation of the method based on digital speckle-pattern interferometry and one-focal-length correlator architecture that uses a liquid-crystal light valve is proposed.

Femtosecond real-time probing of reactions. VIII. The bimolecular reaction Br+I2

In this paper, we discuss the experimental technique for real-time measurement of the lifetimes of the collision complex of bimolecular reactions. An application to the atom–molecule Br+I2 reaction at two collision energies is made. Building on our earlier Communication [J. Chem. Phys. 95, 7763 (1991)], we report on the observed transients and lifetimes for the collision complex, the nature of the transition state, and the dynamics near threshold. Classical trajectory calculations provide a framework for deriving the global nature of the reactive potential energy surface, and for discussing the real-time, scattering, and asymptotic (product-state distribution) aspects of the dynamics. These experimental and theoretical results are compared with the extensive array of kinetic, crossed beam, and theoretical studies found in the literature for halogen radical–halogen molecule exchange reactions.

Cerebrospinal fluid flow. II. Physiology of respiration-related pulsations.

Cerebrospinal fluid (CSF) flow in the cerebral aqueduct and spinal canal was analysed using real-time magnetic resonance imaging measurement techniques. Respiration-induced rhythmic modulation of the cardiac-related oscillating CSF pulsation in the cerebral aqueduct and spinal canal was found. Deep inspiration was immediately followed by a marked increase in downward CSF flow in the cervical spinal canal, whereas a delay of about two heart beats was seen before downward flow from the third to the fourth ventricle increased. This pattern was also detected during yawning and was followed by a marked increase of blood flow in the internal jugular vein.

A technique for real-time measurement of Nth-order derivatives d/sup N/V/dI/sup N/

A technique for the measurement of device derivatives d/sup N/V/dI/sup N/ of arbitrary order N described. Measurement is accomplished by injecting a test current composed of the sum of N square waves into the rest device, and then multiplying the corresponding voltage change by the product of those same square waves, followed by low-pass filtering. The algorithm is implemented in real time using a mixture of analog and digital circuitry, and its application to semiconductor laser control in high-speed optical communications is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Real-time moire vibration analysis of diffusive objects

An optical moire technique for real-time metrological measurements is proposed. Temporal behavior of periodic as well as nonperiodic vibrations can be accurately determined. We demonstrate the method by measuring the mechanical vibration of a driven speaker membrane.

Automatic Method Of Real-Time Wavefront Analysis

A technique for real-time measurement of interferograms is described which circumvents the common sources of error in traditional methods of analysis. By nulling the interferometer and simultaneously measuring the phase over a rectilinear grid, error due to geometric distortion in the interferometer (which produces apparent coma terms in the analysis of straight line interferograms), uneven pupil illumination (which shifts the apparent location of the fringe peaks), and the difficulty in fitting and interpolation of polynomials to unevenly sampled pupil functions are eliminated. Data are not interpolated or artificially smoothed, so localized irregularities in the wavefront are visible in the results. Because on-line computer processing is used, contour and isometric plots are displayed less than two minutes after data taking is completed. A unique interface design permits utilization of virtually all of the information present in the input video signal. By taking thousands of measurements per minute at each point in the wavefront, and extending the measurements over several minutes, the effects of vibration and turbulence are averaged out of the data. With a reasonably stable interferometer, the effective instrument bandwidth can be reduced to .01 Hz providing worst point peak-to-peak repeatabilities of successive measurements of better than A/100. For repeatabilities of A/20, data taking times can be reduced below two seconds. Interferometry plays a central role in the fabrication, alignment, and testing of precision optics at Tropel. From the time of our initial commitment to the manufacture of complex precision optics, we have realized the need for extreme precision in the surfacing and alignment of the individual elements. In recent years as optical systems with significant glass paths have been designed, we have begun measuring and selecting glass for homogeneity. As the requirements have become more severe, the resolution of conventional interferometry has become inadequate.

Corrections [to "Error probabilities due to atmospheric noise and flat fading in HF ionospheric communication systems;" "Some techniques for the instantaneous real-time measurement of multipath and doppler spread;" and "Selective fading limitations of the Kathryn modem and some design considerations"

Presents revisions to various equations and formulas from the selected articles named above.