Search Results

You are looking at 111 - 120 of 1,501 items for :

  • "calibration" x
  • All content x
Clear All

Abstract  

Wood cribs free burning tests were conducted under ISO9705 hood. From the tests, the heat release rate of these cribs was grouped as 0.5, 1.0 and 1.5 MW. This result was used to correct an empirical formula for peak heat release rate calculation. The correction achieves acceptable accuracy for the typical wood. The test result also shown heat release rate curve can be normalized by the total combustion surface of the wood crib. This can also be used to predict the HRR of wood crib of certain sizes and structures.

Restricted access

Abstract  

The advantage of using slats as e.g. NaBr, KBr, AlI3 for monitoring the fluxes of both thermal and epithermal neutrons is discussed and compared with the accepted usual methods. The main advantages are the possible use for fast determination, the use for a large range of fluxes and the lower propagation error than Zr target in the case of relatively low thermal to epithermal fluxes (>10).

Restricted access

Abstract  

Precise, absolute
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $${1 \mathord{\left/ {\vphantom {1 {\sqrt d }}} \right. \kern-\nulldelimiterspace} {\sqrt d }}$$ \end{document}
provides a simple means of interpolation and extrapolation. Experimental coincidence summation effects were determined for various nuclides and compared with calculated values. The results are found to be in good agreement with each other.
Restricted access

Abstract  

Accurately determining the amount of a radionuclide actually administered to a patient is an important aspect of quality control in nuclear medicine. In this study, in order to accurately assess the “apparent” radioactivities of radionuclides with impurities by a dose calibrator, two methods, (1) curve fitting, and (2) relative sensitivities calculation, have been employed to determine the parameter, M (relative response). From the comparisons between the measurement and re-calculated radioactivity using the M values, each method was found to have its own advantage and disadvantage, depending upon the fraction ratio of the impurity as well as the energy level of the impurity’s photons. This study might be helpful for improving the assessment of radiopharmaceuticals’ “true” activity and its “apparent” activity measured by a dose calibrator.

Restricted access

A review is given of recently developed instruments used in thermometric analysis and new methods of direct injection enthalpimetry.

Restricted access

Abstract  

It is proposed a calorimetric model that helps to understand the dependence on the sensitivity of a flow microcalorimeter with the spatial localization of the energetic dissipation. The model allows to compare the spatial localization of different studied mixtures and permits us to conclude that in the ‘rapid’ mixtures, the length that the mixture dissipation occupies and the sensitivity remain nearly constant; however, in the mixtures called ‘slow’, the mixture length increases with the injection flow. This fact produces, at the same time, a clear variation of the sensitivity.

Restricted access

A comparison of the performance of calorimeters

Application of a test and reference reaction

Journal of Thermal Analysis and Calorimetry
Authors: M. O’Neill, S. Gaisford, A. Beezer, C. Skaria, and P. Sears

Abstract  

Isothermal calorimetry is finding extensive application in a number of research areas. This popularity is reflected in the number of commercially available instruments which are capable of yielding a variety of thermodynamic and kinetic parameters. Whilst there has been much discussion of ways in which to validate any values returned from these instruments very little has been done quantitatively to compare the relative performances of different instruments. This paper highlights the use of a test and reference reaction quantitatively to compare the performance of three instruments (Thermometric TAM, THT RC and a Setaram HSDSC III); the specifications of these instruments provide a range from high-sensitivity, long equilibration time to lower-sensitivity, short equilibration time. The comparison is made through a statistical analysis of values returned for the rate constant, enthalpy of reaction and activation energy for the base catalysed hydrolysis of methyl paraben. The statistical analysis from the data set discussed here indicates that there is no significant difference between the returned thermodynamic and kinetic parameters from the TAM and RC. The analysis revealed however that the HSDSC returns values for the rate constant which are significantly different from both the TAM and RC, although it is noted that this instrument was not specifically designed to operate in a step-isothermal mode and that it was possible to apply a correction to the data. In all cases the enthalpy data returned from all instruments were statistically similar although the RC and HSDSC returned values which were, for the rate constant and activation energy, less precise than those obtained from the TAM. As well as highlighting the importance of using test and reference reactions, this study also shows that proper instrument selection is an important factor when designing a calorimetric experimental series.

Restricted access

Summary  

{\rtf1\ansi\ansicpg1250\deff0\deflang1038\deflangfe1038\deftab708{\fonttbl{\f0\froman\fprq2\fcharset238{\*\fname Times New Roman;}Times New Roman CE;}} \viewkind4\uc1\pard\f0\fs24 Multi-pass pebble bed reactors are loaded with spherical fuel pebbles that are circulated through the core until they reach a proposed burnup limit (~100,000 MWD/MTU). An HPGe detector can be used to assay the fuel on-line to ensure that the burnup limit is not breached. The potential exists for using a relative burnup indicator, which would allow the use of a relative self-calibrating approach for efficiency determination. The utilization of several fission products as built-in on-line relative calibration standards is explored using the computer codes ORIGEN2.1, MCNP4C, and SYNTH to produce simulated gamma-ray spectra of the fuel pebbles at various levels of burnup. \par }

Restricted access

Abstract  

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on strict symmetry of the twin calorimeter. This symmetry is of particular importance for temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. The heat capacities for sapphire-filled and empty aluminum calorimeters (pans) under designed cell imbalance caused by different pan-masses were measured. In addition, the positive and negative signs of asymmetry have been explored by analyzing the phase-shift between temperature and heat flow for sapphire and empty runs. The phase shifts change by more than 180° depending on the sign of the asymmetry. Once the sign of asymmetry is determined, the asymmetry correction for temperature-modulated DSC can be made.

Restricted access

Abstract  

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on the symmetry of the twin calorimeters. This symmetry is of particular importance for the temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. Three different DSC instruments capable of modulation have been calibrated for asymmetry using standard non-modulated measurements and a simple method is described that avoids potentially large errors when using the reversing heat capacity as the measured quantity. It consists of overcompensating the temperature-dependent asymmetry by increasing the mass of the sample pan.

Restricted access