System Calibration Procedure Research Articles

Thermogravimetry-evolved gas analysis-mass spectrometry system for materials research

Thermal analysis is a widely used analytical technique for materials research. However, thermal analysis with simultaneous evolved gas analysis describes the thermal event more precisely and completely. Among various gas analytical techniques, mass spectrometry has many advantages. Hence, an ultra high vacuum (UHV) compatible mass spectrometry based evolved gas analysis (EGA-MS) system has been developed. This system consists of a measurement chamber housing a mass spectrometer, spinning rotor gauge and vacuum gauges coupled to a high vacuum, high temperature reaction chamber. A commercial thermogravimetric analyser (TGA: TG + DTA) is interfaced to it. Additional mass flow based gas/vapour delivery system and calibration gas inlets have been added to make it a versatile TGA-EGA-MS facility. This system which gives complete information on weight change, heat change, nature and content of evolved gases is being used for (i) temperature programmed decomposition (TPD), (ii) synthesis of nanocrystalline materials, (iii) gas-solid interactions and (iv) analysis of gas mixtures. The TPD of various inorganic oxyanion solids are studied and reaction intermediates/products are analysed off-line. The dynamic operating conditions are found to yield nanocrystalline products in many cases. This paper essentially describes design features involved in coupling the existing EGA-MS system to TGA, associated fluid handling systems, the system calibration procedures and results on temperature programmed decomposition. In addition, synthesis of a few nanocrystalline oxides by vacuum thermal decomposition, gas analysis and potential use of this facility as controlled atmosphere exposure facility for studying gas-solid interactions are also described.

Calibration, parameter estimation, and accuracy enhancement of a four-dimensional imager camera turntable system

The four-dimensional imager (4DI) system, a real-time threedimensional (3-D) imager, is a laser range data sensing system for making continuous geometric measurements of 3-D surfaces. We concentrate on the objective of improving the resolution and accuracy of this system using a camera-turntable arrangement. A fast and inexpensive method to capture dense range data for 360-deg viewing of an object is provided. After the system calibration procedure and parameter estimation operations, the method to improve the data resolution by object rotation is derived. By oversampling the object surface and then using a 3-D smoothing and resampling operation, the accuracy of the data can be improved while maintaining a given spatial resolution. The method of removing the low credibility data points is also discussed.

Ground-based lidar measurements of aerosols during ACE-2: instrument description, results, and comparisons with other ground-based and airborne measurements

A micro-pulse lidar system (MPL) was used to measure the vertical and horizontal distribution of aerosols during the Aerosol Characterization Experiment 2 (ACE-2) in June and July of 1997. The MPL measurements were made at the Izaña observatory (IZO), a weather station located on a mountain ridge (28°18’ N, 16°30’ W, 2367 m asl) near the center of the island of Tenerife, Canary Islands. The MPL was used to acquire aerosol backscatter, extinction, and optical depth profiles for normal background periods and periods influenced by Saharan dust from North Africa. System tests and calibration procedures are discussed, and an analysis of aerosol optical profiles acquired during ACE-2 is presented. MPL data taken during normal IZO conditions (no dust) showed that upslope aerosols appeared during the day and dissipated at night and that the layers were mostly confined to altitudes a few hundred meters above IZO. MPL data taken during a Saharan dust episode on 17 July showed that peak aerosol extinction values were an order of magnitude greater than molecular scattering over IZO, and that the dust layers extended to 5 km asl. The value of the dust backscatter−extinction ratio was determined to be 0.027±0.007 sr−1. Comparisons of the MPL data with data from other co-located instruments showed good agreement during the dust episode.

Development of an automated method for determining oil in water by direct aqueous supercritical fluid extraction coupled on-line with infrared spectroscopy

A direct aqueous supercritical fluid extraction (SFE) system was developed which can be directly interfaced to an infrared spectrometer for the determination of oil in water. The technique is designed to provide an environmentally clean, automated alternative to established IR methods for oil in water analysis which require the use of restricted organic solvents. The SFE-FTIR method involves minimum sample handling stages, with on-line analysis of a 500 ml water sample being complete within 15 min. Method accuracy for determining water samples spiked with gasoline, white spirit, kerosene, diesel or engine oil was 81-100% with precision (RSD) ranging from 3 to 17%. An independent evaluation determined a 2 ppm limit of quantification for diesel in industrial effluents. The results of a comparative study involving an established IR method and the SFE-FTIR method indicate that oil levels calculated using an accepted equation which includes coefficients derived from reference hydrocarbon standards may result in significant errors. A new approach permitted the derivation of quantification coefficients for the SFE-FTIR analyses which provided improved results. In situations where the identity of the oil to be analysed is known, a rapid off-line SFE-FTIR system calibration procedure was developed and successfully applied to various oils. An optional in-line silica gel clean-up procedure incorporated within the SFE-FTIR system enables the same water sample to be analysed for total oil content including vegetable oils and selectively for petroleum oil content within a total of 20 min. At the end of an analysis the SFE system is cleaned using an in situ 3 min clean cycle.

Avanced Communications Technology Satellite (ACTS) propagation campaign in North America

Ka-band propagation measurements with the Advanced Communications Technology Satellite (ACTS) are entering their fifth year of data collection. Beacon-signal levels and radiometric sky noise are being measured at 20.2 and 27.5 GHz, with supporting meteorological information, at seven experiment sites in the US and Canada, using ACTS propagation terminals (PSTs) supplied by NASA. Uniform system-calibration, data-collection and data-processing procedures and software, prescribed and developed by the NASA Propagation Experimenters (NAPEX) Group, promote commonality of the data sets and permit comparison among results from the various sites. Goals of the program are to develop basic Ka-band propagation knowledge, and to supply information needed to improve propagation-prediction models and to develop impairment-mitigation techniques. The APT sites were selected to sample a variety of North American climate regions and their associated propagation features. Statistical results from the propagation measurements are presented and compared to the predictions of new and existing prediction models. Other aspects of the measurements, including unusually strong antenna-wetting effects observed with the APTs, plus analyses related to impairment dynamics, rain-rate modeling, and clear-air effects, are discussed.

Real-time neural network based camera localization and its extension to mobile robot control.

The feasibility of using neural networks for camera localization and mobile robot control is investigated here. This approach has the advantages of eliminating the laborious and error-prone process of imaging system modeling and calibration procedures. Basically, two different approaches of using neural networks are introduced of which one is a hybrid approach combining neural networks and the pinhole-based analytic solution while the other is purely neural network based. These techniques have been tested and compared through both simulation and real-time experiments and are shown to yield more precise localization than analytic approaches. Furthermore, this neural localization method is also shown to be directly applicable to the navigation control of an experimental mobile robot along the hallway purely guided by a dark wall strip. It also facilitates multi-sensor fusion through the use of multiple sensors of different types for control due to the network's capability of learning without models.

Automation of an ultrasound velocity measurement system in high-pressure liquids

A system for the measurement of ultrasound velocity in liquids was automated to cope with variations in temperature and pressure . The following problems had to be solved: supervision and monitoring of the achievement of the required pressure and temperature, creation and reception of the signal, acquisition of the measurement points, identification of the signal received on the basis of the characteristics of a reference signal, measurement of ultrasound travel times, memorization and processing of the results. The system enables substantial savings of time compared with manual methods. The system calibration procedure is also described. Measurements of octane and pentane (which had been studied previously) are used to verify the validity of the system developed and to determine its degree of accuracy (absolute average deviation from literature data 0.1% and maximum deviation from literature data 0.25%).

A re-interpretation of the BCR/VAMAS low cycle fatigue intercomparison programme using an energy criterion

Data from a previous round robin low cycle fatigue exercise on 316L steel, 9Cr1Mo steel and IN718 alloy at 550°C and Nimonic 101 at 850°C are re-examined, emphasis being placed on material stress-strain response and associated energy expenditure rather than cycles to failure. It is shown that persistent inter-laboratory scatter in material response remains even at the very early stages of testing and that this may be due, during this period, to intrinsic microstructural behaviour as well as to imprecision in test system calibration procedures. To some extent the data may be rationalised by assuming a constant energy expenditure at failure and choosing an earlier failure criterion than the often-used 25% load drop stage. In the best case, inter-laboratory scatter was reduced by a factor 5. As before, scatter within a laboratory (repeatability) was always less than that between laboratories (reproducibility).

A Compact Testing System for Dynamic Fracture Studies

Abstract Development of a compact instrumented impacting apparatus for dynamic fracture studies designed on the lines of a swing pendulum machine is described. Salient features of the system and instrumentation calibration procedures are presented. The dynamic characteristics of the system are explained with the aid of a simple inertial model. Results of dynamic fracture experiments conducted on aluminum 6061 alloy and polymethylmethacrylate (PMMA) are discussed.

Measurement of the thermal diffusivity of thin films on substrate by the photoacoustic method

Measurements of the thermal diffusivity of thin films on substrate have been performed by the photoacoustic method. In order to examine the method we have built a new apparatus and proposed (1) a system calibration procedure using optically and thermally thick reference samples and (2) a data analysis procedure based on the RG (Rosencwaig and Gersho) theory. As a result of using a transparent photoacoustic cell, the systematic errors which are caused by stray light have been reduced. With this apparatus, measurements have been performed on platinum, titanium, and stainless steel (SUS304) thin foils (thickness form 50 to 100 µm) with three different liquid backing materials (water, glycerol, and ethyl alcohol). The reproducibility was within ±7% regardless of film thickness and substrate materials.

Automated swept-angle bistatic scattering measurements using continuous wave radar

The establishment of the IEEE Electromagnetic Modeling Software Committee and the Department of Defense sponsored Electromagnetic Code Consortium indicates the electromagnetics community is interested in validating general electromagnetic modeling software. An important part of this validation is obtaining reliable bistatic scattering measurements on canonical scatterers. The author describes a simple system well suited for such measurements. The system is capable of measuring bistatic scattering from near backscatter through forward scatter. At X-band frequencies, scattering levels of -50 dBsm in the backscattering region and -20 dBsm near forward scatter can be measured to an accuracy of +or-1 dB. This fully automated indoor system fixes the target and direction of illumination and sweeps the receive antenna to collect data as a direct function of bistatic angle. A broad band, coherent, continuous wave radar is used to obtain both amplitude and phase of the component of the total field aligned with the receive antenna polarization. The system design, calibration procedures, and measurement accuracy are considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Quantitative PIXE analysis using a scanning proton microbeam

PIXE analysis is often quoted as being simple, fast, accurate and multielemental. In practice, however, especially if a wide range of samples is analysed, the measurements are adversely affected by uncertainty about the sample matrix composition, thickness and homogeneity. This is particularly true for thick samples, where major corrections to the X-ray yield can depend on knowledge of the chemical composition of the specimen. This can often be circumvented by techniques such as determination of bulk composition by other methods, or comparison with standards, but all these additional processes add to the analysis time and complexity. In addition, it is necessary to assume that the sample composition is uniform over the full area of the beam spot, not necessarily true even for carefully homogenised materials. This paper describes how the use of a scanning proton microbeam (SPM) with simultaneous PIXE, backscattered particle spectroscopy and secondary electron detection can enhance the accuracy of PIXE analysis by allowing the selection of a uniform region of the sample and the determination of the matrix composition. System calibration procedures are described and examples of analyses of standard reference materials and experimental samples are presented.

Measurement of the Thermal Diffusivity of Thin Film on Substrate by the Photoacoustic Method. 1st Report, Examination of the Method and Measurement of Metal Thin Foils.

This paper reports the measurement of the thermal diffusivity of thin films on substrate by the photoacoustic method. In order to examine the method, we built a new apparatus and proposed (1) a system calibration procedure using thermally thick materials and (2) a data analysis procedure based on the Rosencwaig and Gersho theory (RG theory). As a result of using a transparent photoacoustic cell, the systematic error factors which were caused by stray light have been reduced. With this apparatus, measurements have been performed on platinum, titanium and stainless steel (SUS304) thin foils (thickness: 50-100μm) with three different substrate materials (water, glycerol, and ethyl alcohol). The reproducibility was within ±7% regardless of the film thickness and substrate material.

A flexible inspection system for gauging precision industrial parts

This paper presents an overview of an inspection system called Automated Robotic Visual Inspection System (ARVIS). The ARVIS system concept, hardware components, work-cell, and calibration and inspection procedures are described. Application of ARVIS is currently focused on inspecting precision industrial parts, specifically, traveling wave tube (TWT) components for avionic radar systems. The variability of parts which comprise a TWT requires a general purpose flexible inspection system that is both adaptable and programmable. ARVIS integrates robotics and computer technology together with vision processing software to achieve a flexible system.

Obtaining 3-dimensional shape of textured and specular surfaces using four-source photometry

Thephotometric stereo method is extended to four-source photometry for obtaining 3-dimensional shapes of visually textured and specular surfaces from intensity values. The table look-up approach (based on reflectance maps) for determining surface normals is shown to be of limited value in this context and a more direct method of computing these normals is used. Our method also eliminates the requirement of a preliminary system calibration procedure. The method is applied to real images as a test of its applicability.

Photoplethysmography: system calibration and light history effects.

ABSTRACTTo ensure accurate recording of vasomotor activity in the peripheral vascular system with the photoplethysmographic technique, a system calibration procedure is presented. Utilization of a calibration procedure reveals several significant sources of photocell and light source artifact. A calibration apparatus and procedure as well as data demonstrating the light history artifact and its resolution are presented.

Limitations of Today's Systems for Noise Measurement and Analysis

We have an increasing number of techniques and instruments available for solving noise-measurement problems. The selection of the instrumentation is determined by the over-all measurement objective plus the practical considerations of instrument accuracy, availability, cost, etc. The choice of microphone or vibration pickup is often determined by the nonacoustic portion of the environment. If magnetic-tape recording appears to offer advantages, one should be aware of the limited frequency and dynamic range, the subtle nonlinearity plus crosstalk on multichannel recorders. The acoustic signal may be analyzed in both the frequency and time domains with a variety of signal-detection and readout techniques. The preferred analysis system or technique would present the desired information in its simplest form. The inherent limitations of the total measurement-and-analysis system must be investigated and understood. This is accomplished by careful evaluation of the instrument manufacturer's specifications plus an over-all system checkout and calibration procedure.