Artefact and Distortion Sources in Time Correlated Single Photon Counting

ABSTRACT

Sources for artefacts and distortions in data from a time correlated single photon counting spectrometer are described and illustrated. Methods are provided to avoid these instumental problems and to correct for the residual distortions.     

Laminar and turbulent channel flow simulation using residual based variational multi-scale method

We present a residual-based isogeometric variational multiscale method to solve laminar and turbulent channel flow. Residual-based variational multiscale method is a new finite element formulation for solving turbulent flows using a large-eddy simulation type modeling. Isogeometric analysis, a new finite element method using CAD blending functions as its basis functions, is employed for higher order approximation of the solution. First, laminar flow with Re _τ 0.55 = through flat channel is considered and linear, quadratic and cubic basis functions, which are C ⁰, C ¹, and C ²-continuous across element boundaries, respectively are employed and their accuracy is presented by the comparison with analytical result. Next, same methodology is applied to the turbulent channel flow with Re_r = 180. Current results are validated by the comparison of turbulence statistics using available DNS data.     

Multipurpose Computer-Based Data Acquisition System

Abstract

A universally applicable instrument for data acquisition and manipulation is presented. Several applications are discussed spanning a wise range of experiments and time domains. Attention is given to interfacing and programming problems.     

Rolling Bearing Service Life Based on Probable Cause for Removal—A Tutorial

In 1947 and 1952 G. Lundberg and A. Palmgren developed what is now referred to as the Lundberg-Palmgren model for rolling bearing life prediction based on classical rolling-element fatigue. Today, bearing fatigue probably accounts for less than 5% of bearings removed from service for cause. A bearing service life prediction methodology and tutorial indexed to eight probable causes for bearing removal, including fatigue, are presented that incorporate strict series reliability; Weibull statistical analysis; available published field data from the Naval Air Rework Facility; and ～224,000 rolling-element bearings removed for rework from commercial aircraft engines. Bearing service life L_serv can be benchmarked and calculated to the bearing L₁₀ fatigue life as follows: L_serv = X^1/m L₁₀, where X is the number of bearings removed from service because of fatigue divided by the total of all bearings removed from service regardless of cause and m is the Weibull modulus of the bearings removed from service. The most conservative bearing L₁₀ service life calculation is obtained assuming an exponential distribution where m = 1.1. Of the ～224,000 commercial engine bearings removed from service for rework, 1,977 or 0.88% were rejected because of fatigue. From the Naval Air Rework Facility bearing data, eliminating rolling–element fatigue as a cause for removal, the L₁₀ service life of these bearings would increase by approximately 3%.     

Kinetic Interpretation of Fluorescence Decays

ABSTRACT

We review the interpretation of reconvolution analysis of single photon fluorescence decay data with regard to the time resolution achievable and sources of error encountered. Examples are presented for complex fluorescence decays in a wide range of applications including polymers, membranes, scintillators and solar collectors.     

Non-constant parameter NC tool path generation on sculptured surfaces

An algorithm for three-axis NC tool path generation on sculptured surfaces is presented. Non-constant parameter tool contact curves are defined on the part by intersecting parallel planes with the part model surface. Four essential elements of this algorithm are introduced: initial chordal approximation, true machining error calculation, direct gouge elimination, and non-constant parameter tool pass interval adjustment. A software implementation of this algorithm produces graphical output depicting the tool path superimposed over the part surface, and it outputs cutter location (CL) data for further post-processing. Several applications examples are presented to demonstrate the capabilities of the algorithm. The results of this technique are compared to those generated from a commercially available computer-aided manufacturing program, and indicate that equivalent accuracy is obtained with many fewer CL points.Notation C cutting curve - C ¹ cutting curve tangent - CC ₀,CC ₁, ... cutter contact points - d chordal deviation - /_ABC triangle - w incremental step in parameterw - ABC angle - a small quantity - l chord length - n _s ,n _p , ... normal vectors - P, P _r ,P _c ,P ₁ ,P ₂ , ... space point - Q parametric equation of a surface - R radius of a ball-end milling tool - TC ₀,TC ₁, ... tool center points - u, v, u _s ,u _c ,w, t parameters - angle - curvature - h cusp height - T machining tolerance     

Computerized Circuit for the Precise Measurement of Rapid Temperature Changes

ABSTRACT

A computerized thermistor circuit is described which uses a pulsed technique for the measurement of rapid temperature changes. Tests are detailed which demonstrate the speed (5 kHz sampling rate), precision (±0.002 °K/sample), and utility of the instrument. Software outines for calibration of the circuit and for data acquisition are described briefly.     

Global and Target Analysis of Complex Decay Phenomena

ABSTRACT:

Methodologies for the simultaneous analysis of multiple total-intensity, anisotropy, and excited-state reactions are developed. Alternatives to the standard sums-of-exponentials fitting are proposed for both anisotropy and excited-state reaction data. Both simulation studies and real-data examples show these methods to be superior to single curve analysis.     

Modification of Wiley-Mclaren Tof Analyzers for Laser Desorption

ABSTRACT

Conversion of Wiley-McLaren type TOF instruments for laser desorption is described, including laser optics, timing circuitry, postacceleration detection for high mass and data acquisition. Results are shown to illustrate signal averaging capabilities, detection limits and high mass measurements.     

Computerized Phosphorescence Decay Measurements

ABSTRACT

An on-line digital computer has been applied to phosphorescence decay studies. The computer controlled excitation timing and provided data acquisition, smoothing, and data reduction functions. Phosphorescence decay steps for mixtures could be observed over a wide time domain.     

Modification of a Vg Escalab Mk-1 Esca Spectrometer for Digital Data Acquisition and Processing

ABSTRACT

To enable signal averaging on our VG ESCALAB MK-1 spectrometer we designed a digital ramp generator with repetitive mode of operation for each selected energy analyser sweep time.

For digital data acquisition purposes we constructed a dedicated microcontrolled acquisition unit performing digitization of the ESCA spectrum in 4096 channels of 12-bit words. Data flow is controlled by a 6809 microprocessor driving a parallel interface adapter. Two RS232C serial links are provided for communication with a terminal and a mass storage unit.     

Secondary Ion Time-Of-Flight Mass Spectrometers and Data Systems

ABSTRACT

Some recent improvements to the Manitoba linear time-of-flight mass spectrometer are reviewed. A new data system gives greatly improved performance. A detector assembly with a small 45° ion mirror and separate detectors for neutral and charged particles has been added. In conjunction with the new data system, it enables measurement of correlations between neutral and charged fragments resulting from unimolecular decay in the flight tube.

A new time-of-flight spectrometer has been constructed. It is a reflecting instrument with a relatively long ion mirror. Resolution and signal/background ratio are much better than in the linear instrument, and correlation measurements can be made with considerably higher accuracy in mass determination than with the small mirror.     

Cutting path generation of linear hotwire cutter for VLM-ST

Most rapid prototyping (RP) processes adopt a solid CAD model, which will be sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; eventually, the stacked layers form a physical part of the model. A new thick-layered RP process, the transfer-type variable lamination manufacturing process using expandable polystyrene foam sheets (VLM-ST), has been developed to reduce building time by employing thick layers and to improve the surface finish of parts with a sloping surface. This paper describes the method to generate the unit shape layer (USL), the cutting path data of the four-axis hotwire cutter for the VLM-ST process. The USL is the basic unit of cutting and building in the VLM-ST process and it is also the basic unit of cutting path data of each layer. The USL includes data such as layer thickness, positional coordinates, side angles of each layer, and reference shape. The method to generate the USL is as follows: (1) the mid-slice of each layer is generated from the CAD model, (2) each mid-slice is converted into a simply-connected domain, (3) the rotation angle of the hotwire of the cutting system is calculated for each layer, and (4) the reference shape of each layer is generated for manual stacking. The procedure to generate the cutting path data of the linear hotwire cutter for VLM-ST was practically applied and verified for various three-dimensional shapes.     

GC/MS By Time-Of-Flight Mass Spectrometry: Instrumentation and Data System Developments

ABSTRACT

The ability of time-of-flight mass spectrometers to produce up to 10,000 mass spectra per second suggests that these instruments may be ideal for use in GC/MS work. For GC/TOF-MS to be a useful technique, specific improvements in TOF technology are required. To completely utilize the mass spectral data available in TOF-MS, a data system is required that can collect and manipulate these large numbers of mass spectra per second. Progress in instrumentation and data system development, at the Michigan State University/National Institutes of Health Mass Spectrometry Facility, is directed toward the maturation of GC/TOF-MS as a viable technology.     

Spatially Sampled Pressure Profile Measurements in Externally Pressurized Gas Journal Bearings

Abstract

Externally pressurized gas journal bearings (EPGJBs) are widely adopted to support high-speed rotors. This article presents novel experimental benchmark test data that enable EPGJB model validation. Axial and circumferential pressure profile measurements are presented for a 40-mm-diameter annular restrictor EPGJB operating at speeds up to 25?krpm. The corresponding rotor position, air mass flow rate, and load capacity are also measured. The effects of supply pressure, rotational speed, and load on the measured variables are presented. The measurements are in good agreement with numerical model computations. The cases in which the model deviates from the measured data are discussed in terms of compressible flow theory.     

Fortran Programs to Acquire and Process Isotopic Mass Spectrometry Data: A Conceptual Description

ABSTRACT

New FORTRAN computer programs have been written to process isotopic mass spectrometric data. A major goal of these programs was to achieve maximum flexibility in all phases of the analytical process: data acquisition, data processing, and report writing. Magnetic disk files are exploited to this end. The programs can acquire and process data from any element taken under any scanning scheme and with any desired ratios calculated. Results are stored on magnetic disks and results of similar samples can be listed in a single compact report.     

An Inexpensive Real-Time Digital Integrator Based on A Sym-1 Microcomputer for Use with High Pressure Liquid Chromatography

ABSTRACT

Details of a data acquisition system controlled by a SYM-1 single-board microcomputer are presented. The total cost of constructing the system was approximately $300. The system's variable gain amplifier coupled with a 10 bit analog-to-digital converter can be used to interface the SYM-1 to many laboratory instruments. In this report the data system is used to digitally integrate sample peaks from a high pressure liquid chromatograph.     

Computer Programs for Kinetic Analysis of Non-Isothermal Thermogravimetric Data

Abstract

In this paper, computer programs to evaluate kinetic analysis from non-isothermal thermogravimetric data are discussed. The flowcharts for all the programs are shown. These include those based on single-heating-rate and multi-heating-rate procedures. The single-heating-rate methods include the differential and integral calculations while the multi-heating-rate methods include those of Friedman and Ozawa.

It is proposed that the multi-heating-rate programs should be used as a reference to distinguish the mechanisms and the single-heating-rate programs should be used to obtain the reaction activation energy, the frequency factor values and the linear regression parameters.     

An Approach to Measure the Densities of Solids using an Artificial Neural Network

Abstract

A dedicated microcontroller based density measurement system is developed to measure densities of solids. A data acquisition system is designed and fabricated using a PIC16F877 microcontroller. To measure the weight and temperature of the sample, strain gauge and thermocouple sensors are used. A three layer neural network is used to train the data for atomic number, temperature, and density of sample using a back propagation algorithm. After training the neural network, it is used to compute the density at various temperatures.     

Dielectric Constant Measurement Using an Artificial Neural Network

Abstract

A microcontroller based measurement setup has been developed to measure dielectric constant of liquids using a PIC16F877 microcontroller. An AC Desauty's bridge network was used to compute capacitance as well as dielectric constants of liquids. This measurement system permits recording of dielectric constant of liquids at various concentrations and temperatures. The recorded data are automatically sent to a computer to enable the computer processing of such data. A three‐layer neural network was used to train the data, using a back propagation algorithm. After training the neural network, it is used to compute the dielectric constants for various concentrations of liquids.