Short-term exposure. This is the maximum concentration to which workers can be exposed for a period of up to 15 minutes continuously without suffering from (a) intolerable irritation, (b) chronic or irreversible tissue change, or (c) narcosis of sufficient degree to increase accident proneness, impair self-rescue, or materially reduce efficiency, provided that no more than four excursions per day are permitted, with at least 60 minutes between exposure periods, and provided the daily time-weighted value is not exceeded.  [c.260]

The remaining problem analysis technique can be applied to any feature of the network that can be targeted, such as minimum area. In Chap. 7 the approach to targeting for heat transfer area [Eq. (7.6)] was based on vertical heat transfer from the hot composite curve to the cold composite curve. If heat transfer coefficients do not vary significantly, this model predicts the minimum area requirements adequately for most purposes. Thus, if heat transfer coefficients do not vary significantly, then the matches created in the design should come as close as possible to the conditions that would correspond with vertical transfer between the composite curves. Remaining problem analysis can be used to approach the area target, as closely as a practical design permits, using a minimum (or nea minimum) number of units. Suppose a match is placed, then its area requirement can be calculated. A remaining problem analysis can be carried out by calculating the area target for the stream data, leaving out those parts of the data satisfied by the match. The area of the match is now added to the area target for the remaining problem. Subtraction of the original area target for the whole-stream data Anetwork gives the area penalty incurred.  [c.387]

Copyright 1995 by McGraw-Hill, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a data base or retrieval system, without the prior written permission of the publisher.  [c.464]

The plasma comprises free positive and negative ions generally in equilibrium at high temperature. It has a high electrical and thermal conductivity and emits photons whose frequency is characteristic of the atoms present. The polychromatic rays are analyzed by a monochromator that gives the plasma s spectrum. The elements are identified by their wavelengths and the signal intensity is proportional to the quantity of ions present in the arc. The response is linear for. 5 or 6 orders of magnitude, something which gives a large advantage to the plasma technique over atomic absorption. Furthermore, the method is multi-elemental it permits the analysis of about 70 trace elements without having to change the device.  [c.37]

The magnetic method detects changes in the earth s magnetic field caused by variations in the magnetic properties of rocks. In particular basement and igneous rocks are relatively highly magnetic and if close to the surface give rise to short wavelength, high amplitude anomalies in the earth s magnetic field (Fig. 2.7). The method Is airborne (plane or satellite) which permits rapid surveying and mapping with good areal coverage. Like the gravity technique this survey is often employed at the beginning of an exploration venture.  [c.16]

In integrated photoelasticity it is impossible to achieve a complete reconstruction of stresses in samples by only illuminating a system of parallel planes and using equilibrium equations of the elasticity theory. Theory of the fictitious temperature field allows one to formulate a boundary-value problem which permits to determine all components of the stress tensor field in some cases. If the stress gradient in the axial direction is smooth enough, then perturbation method can be used for the solution of the inverse problem. As an example, distribution of stresses in a bow tie type fiber preforms is shown in Fig. 2 [2].  [c.138]

Conventionally, a radiographic image is produced by permitting the X-ray or gamma-ray source to penetrate an object and expose a photographic film. Film radiography produces negative images which are normally viewed in static mode using a view box by a certified inspector.  [c.179]

The purpose of the nondestructive control consists in detecting local modifications of the material parameters which, by their presence can endanger the quality of the half-finished or finished products. The electromagnetic nondestructive control permits to render evident surface and subsurface discontinuities in the electroconductive material under test. The present tendency of this control is to pass from a qualitative evaluation (the presence or absence of the material discontinuities which give at the output of the control equipment a signal higher or at least equal to that coming from a standard discontinuity whose shape and severity has been prescribed by the product standards) to a quantitative one, which enables to locate as exactly as possible the discontinuity and to make predictions over its shape and severity.  [c.373]

A new design of photothermal camera permits the deteetion of surface-breaking flaws in metallic materials through an original technique of active IR thermography. The novelty of that equipment allows to reveal cracks of a few micrometers wide in a contactless way and even on rough industrial surfaees. The performances obtained on a pre-industrial demonstrator of such a camera permit to consider that this technology is an industrial alternative to conventional NDE techniques (penetrants, eddy currents, magnetics...) for fast and remote surface damages detection.  [c.393]

The eombination in a compact system of an infrared sensor and a laser as excitation source is called a photothermal camera. The surface heating is aehieved by the absorption of the focused beam of a laser. This localisation of the heating permits a three-dimensional heat diffusion in the sample to be examined. The infrared (IR) emission of the surface in the neighbourhood of the heating spot is measured by an infrared detector. A full surface inspection is possible through a video scanning of the excitation and detection spots on the piece to test (figure 1).  [c.393]

A new design of an old concept of thermal surface inspection permits the photothermal camera to be considered as an interesting alternative to NDT methods like penetrant or magnetic testing, particularly when the testing has to be made in a remote or automatic way.  [c.398]

A major advantage of radioscopy is the flexible inspection perspective that allows an optimum adjustment of beam direction and geometrical magnification to the inspection task at hand it also permits in-motion testing.  [c.436]

High performance composites and other light weight materials and components are generally a complex problem to the performance of nondestructive testing methods. X-ray refraction provides unconventional X-ray scattering techniques to meet the actual demand for improved nondestructive characterization of Advanced Materials. Due to the short wavelength of about 0.1 nm this method determines the amount of inner surfaces and interfaces within the range of micro- to nanometer dimensions. Scanning the samples across a collimated narrow incident X-ray beam permits to image micro-structures at currently 10 pm resolution of  [c.558]

The over-washing test is performed on holes perforate reference block defined in standard NFA 09.521 and permits the evaluation of the resistance to over-washing of penetrants (see figure 2, annex 1).  [c.621]

This study permitted to compare products family, on the base of normalized tests all parameters maintained constant during tests.  [c.625]

These tests permited us to define minimum requirements to obtain for our fabrication applications, and to introduce in our code minimum requirements and method to verify them.  [c.625]

A section view at defect height permits a detailed analysis. Printouts of the front panels are made by clicking.  [c.1008]

The results of corrosion surveys are received by the Surveyor in an agreed format using Forms TMl - TM8, preferably with the LR software freely issued to the approved firms. The report will highlight any areas where corrosion has gone beyond the permitted maximum diminution, which may be as low as 15% of the nominal thickness for a single item, and will also identify areas of "substantial corrosion T.e., any in excess of 75% of the permitted maximum. Corrosion in excess of that permitted means that the item has to be replaced. Any areas of corrosion deemed to be "substantial" are recorded for annual inspection. The Surveyor will review the completed report for verification and confirmation of the completeness of the thickness survey.  [c.1051]

The treatment may be made more detailed by supposing that the rate-determining step is actually from species O in the OHP (at potential relative to the solution) to species R similarly located. The effect is to make fi dependent on the value of 2 and hence on any changes in the electrical double layer. This type of analysis has permitted some detailed interpretations to be made of kinetic schemes for electrode reactions and also connects that subject to the general one of this chapter.  [c.214]

A very important but rather complex application of surface chemistry is to the separation of various types of solid particles from each other by what is known as flotation. The general method is of enormous importance to the mining industry it permits large-scale and economic processing of crushed ores whereby the desired mineral is separated from the gangue or non-mineral-containing material. Originally applied only to certain sulfide and oxide ores.  [c.471]

In Section IX, we intend to present a geometrical analysis that permits some insight with respect to the phenomenon of sign flips in an M-state system (M > 2). This can be done without the support of a parallel mathematical study [9]. In this section, we intend to supply the mathematical foundation (and justification) for this analysis [10,12], Thus employing the line integral approach, we intend to prove the following statement  [c.668]

Hydrogen sulphide is a colourless gas, b.p. 213 K, with a most unpleasant odour the gas is very toxic, but the intense odour fortunately permits very minute concentrations of the gas to be detected.  [c.282]

The classical microscopic description of molecular processes leads to a mathematical model in terms of Hamiltonian differential equations. In principle, the discretization of such systems permits a simulation of the dynamics. However, as will be worked out below in Section 2, both forward and backward numerical analysis restrict such simulations to only short time spans and to comparatively small discretization steps. Fortunately, most questions of chemical relevance just require the computation of averages of physical observables, of stable conformations or of conformational changes. The computation of averages is usually performed on a statistical physics basis. In the subsequent Section 3 we advocate a new computational approach on the basis of the mathematical theory of dynamical systems we directly solve a  [c.98]

Because of the use of the focusing method [18], more than four calculations are actually carried out for each group. However, the focusing method saves computer time by permitting the use of less extensive finite-difference grids.  [c.185]

Answers to questions in structural biology are often sought by means of long time biomolecular simulations using empirical classical mechanical force fields. Nevertheless, the shortest time scales present in the simulation have limited the integration step to 0.5-1 fs, which is many orders of magnitude smaller than the desired simulation time interval. Fairly recently the introduction of the Verlet-I [8, 9]/r-RESPA [23] impulse multiple time step (MTS) method has permitted an increase to 4 fs in the length of the longest time step. This article describes this development as well as empirical [4] and analytical [7] evidence indicating that timesteps of 5 fs or greater are not possible with the impulse MTS method (for unconstrained molecular dynamics). Nevertheless, a modification to this method - the mollified impulse method [7] - yields stable dynamics for longest timesteps as great as 7 fs.  [c.318]

A good MD algorithm permits a large time step to be used while preserving acceptable energy conservation. Major methodological progress has been made in the directions of longer time scales and larger systems size [11, 12, 13].  [c.334]

A highsophistic infrared system was described, which provides quality assureance for turbine blades and vanes. Two different infrared teehniques are implemented in the system Transmission-Thermography for testing cooling structures of turbine blades and Impulse-Video-Thermography for testing proteetion layers of turbine blades It was depicted that both techniques are leading to reliable results within shortest time and full automatically In addition to the Transmission- and Video-Impulse-Thermography for quality assurance, Video-Impulse-Thermography permits the quantification of wallthicknesses from turbine blades  [c.407]

This study has permitted the definition of the minimum requirements to be introduced in RCCM code in order to select properly the dye penetrant product family.  [c.621]

The removing penetrant test is performed on sanded and cracked reference block defined in standard NFA 09.520 ( see figure 1, annex 1) and permits the evaluation of the washability of penetrants.  [c.621]

A common method used to induce phase modulation in shearography is by use of piezoelectric materials to either change the position of Michelson interferometer mirrors [10,11] or to induce strain in a liiglily birefringent optical fibre [12]. However the voltages used to drive these materials are of the order of lOOV. The use of a birefringent wedge [13] and a split liquid crystal cell used with a glass wedge [14], have been presented as alternative methods but both feature fixed shearing distances characteristic of the wedge teclmique. The use of a liquid crystal that covers the field of view in a Michelson arrangement offers a low voltage ( 10V ac) and versatile system. Calibration of a suitable liquid crystal cell, permits phase stepping of a wide range of illuminating wavelengths, while alteration of the mirror tilt provides a variation in the amount of shear and the shearing direction.  [c.680]

The pressure equipment directive was adopted by the European Parliament and the European Council in May 1997. It harmonises the national laws of the 15 Member States of the European Union relating to equipment subject to the pressure risk. That directive is one of the series of technical harmonisation directives such as for machinery, medical devices, simple pressure vessels, gas appliances and so on, which were foreseen by the Communities programme for the elimination of technical barriers to trade. It therefore aims to ensure the free placing on the market and putting into service of the equipment concerned within the European Union and the European Economic Area. At the same time it permits a flexible regulatory environment, allowing European industry to develop new techniques increasing thereby its international competitiveness.  [c.937]

Various aspects of the experimental approach to the chemisorption bond are illustrated in the preceding sections. Modem spectroscopic and surface diffraction techniques provide a wealth of information about the chemisorbed state. Analysis of LEED intensity data permits the estimation of adsorbate-adsorbent bond lengths [147], usually 5-10% longer than in molecules having a similar bond. Bond lengths may also be obtained from XPD and SEXAFS data (see Table VIII-1) [148]. A bond energy can be obtained from temperature-programmed desorption data if coupled with knowledge of the activation energy for adsorption (Eq. XVIII-21) see Ref. 149 for the case of a heterogeneous surface. The traditional approach to obtaining bond energies is, of course, through isosteric heats of adsorption, although complications are that equilibrium may be difficult to reach and/or the surface may be heterogeneous. Some literature data compiled by Shustorovich, Baetzold, and Muetterties [ISO] are shown in Table XVIII-2. For hydrogen atom-metal bonds Q averages about 62 kcal/mol, corresponding to about 20 kcal/mol for desorption as H2. Bond energies for CO and NO run somewhat higher. Values can vary depending on the surface preparation and, of course, on the crystal plane involved if the surface is a well-defined one. Older compilations may be found in Refs. 81 and 84, and more recent ones, in Somoijai [13].  [c.712]

Ref. 205). The two mechanisms may sometimes be distinguished on the basis of the expected rate law (see Section XVni-8) one or the other may be ruled out if unreasonable adsorption entropies are implied (see Ref. 206). Molecular beam studies, which can determine the residence time of an adsorbed species, have permitted an experimental decision as to which type of mechanism applies (Langmuir-Hinshelwood in the case of CO + O2 on Pt(lll)—note Problem XVIII-26) [207,208].  [c.722]

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (508) 750-8400, fax (508) 750-4744. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, (212) 850-6011, fax (212) 850-6008, E-Mail PERMREQ W1LEY.COM.  [c.786]

Development of laser technology over the last decade or so has permitted spectroscopy to probe short-time events. Instead of having to resort to the study of reactants and products and their energetics and shuctures, one is now able to follow reactants as they travel toward products. Fast pulsed lasers provide snapshots of entire molecular processes [5] demanding similar capabilities of the theory. Thus, explicitly time-dependent methods become suitable theoretical tools.  [c.222]

The concept of biradicals and biradicaloids was often used in attempts to account for the mechanism of photochemical reactions [2,20,129-131]. A biradical (or diradical) may be defined as [132] an even-electron molecule that has one bond less than the number permitted by the standard rules of valence.  [c.388]

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic or mechanical, including uploading, downloading, printing, decompiling, recording or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without the prior written permission of the Publisher. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, (212) 850-6011, fax (212) 850-6008, E-Mail PERMREQ WTLEY.COM.  [c.763]

This permits us to denote the QCMD equations (1) in the form i = The formal solution can now be written as  [c.399]

See pages that mention the term Permits : [c.63]    [c.225]    [c.418]    [c.426]    [c.183]    [c.378]    [c.732]    [c.938]    [c.69]    [c.1200]    [c.104]    [c.341]    [c.402]   
Process safety in outsourced manufacturing operations (2000) -- [ c.0 ]