Source and radiation effects

In this chapter we have concentrated on sound propagation through a tube, and saw that even this, the simplest of all acoustic systems can be quite complicated. Another entire branch of the field of acoustics is devoted to sound propagation through three dimensional spaces, and this can be drawn on to produce a better model of radiation through the hps. As with the other refinements mentioned in this section, modelling both the source and hp losses with more realistic expressions 

In developing our model, we have attempted to balance the needs of realism with tractability. The all-pole vocal tract model that described in Section 11.3 will now be adopted for die remainder of the book as the model best suited to our purposes. In subsequent chapters, we shall in fact see that this model has some important properties that make its use particularly attractive. 

One of the key jobs in making assumptions in a model is to recognise that such assumptions have indeed been made. So long as this is done, and these assumptions are borne in mind, we should not run into too many problems when we rely on the model to deliver faithful analyses. With this in mind, we will now note the main assiunptions we have made and discuss any potential problems that might arise because of these. The following list is in approximate increasing order of severity. 

Linear filter Throughout we have assiuned that the system operates as a time invariant linear (LTI) filter of the type described in Chapter 10. While it is well known that there are many non-linear processes present in vocal tract soimd propagation, in general the linear model provides a very good approximation to these. 

Discrete tube model The number of tubes determines the granularity at which we model the real, continuously varying tube. As we saw in Section 11.3.6, the number of tubes is determined by the sampling rate, and so long as we have the correct number of tubes for the sampling rate being used, there will be no loss of accuracy. A rule of thumb is that we use one tube for every IkHz sampling rate, so that lOKHZ requires 10 tubes and so on. For a tme continuous 

All-pole modelling Only vowel and approximant soimds can be modelled with complete accuracy by aU-pole transfer functions. We will see in Chapter 12 that the decision on whether to include zeros in the model really depends on the application to which the model is put, and mainly concerns tradeoffs between accmacy and computational tractabiUty. Zeros in transfer functions can in many cases be modelled by the addition of extra poles. The poles can provide a basic model of anti-resonances, but cannot model zero effects exactly. The use of poles to model zeros is often justified because the ear is most sensitive to the peak regions in the spectrum (which are naturally modelled by poles) and less sensitive to the anti-resonance regions. Hence using just poles can often generate the required spectral envelope. One problem, however, is that as poles are used for purposes other than their natural one (to model resonances) they become harder to interpret physically, and this will have knock-on effects on, say, determining the number of tubes required, as explained above. 

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Singh, A. K. (2008). Heat source and radiation effects on magneto-convection flow of a viscoelastic fluid past a stretching sheet Analysis with Kummer s functions, Int. Comm. Heat Mass Transfer, 35, pp. 637-642, ISSN 0947-7411. 

UNSCEAR. 1982. United Nations Scientific Committee on the Effects of Atomic Radiation. Ionizing radiation Sources and biological effects. New York United Nations. 

UNSCEAR, Ionizing Radiation Sources and Biological Effects. United Nations, New York, NY (1982). 

Ionizing Radiation Sources and Biological Effects. New York, United Nations. U.S. Nuclear Regulatory Commission (1981) Technical basis for estimating fission product behaviour during LWR accidents. Report NUREG-0772, Washington, D.C. 

Some nonionizing radiation sources and their effects on human exposure along with the precautions to be taken in their usage are summarized. 

Ionizing Radiation Sources and Biological Effects, United Nations 1982. 

Term 5 This represents the rate of energy generated in V due to chemical reaction. Electrical and radiation effects can be included in this term. The source term A (not the reactant) is defined as the amount of energy generated per unit time per unit volume, i.e.,... 

In the course of reactor operation other components of the core have also been improved (e.g. the control and protection system guide tubes and rods, and the neutron source) through the use of advanced stmctural materials and optimization of the structure of the items to mitigate the influence of temperature and radiation effects, which resulted in improvements to reliability and service life. 

UNSCEAR (1982). Ionizing Radiation Sources and Biological Effects, United Nations Scientific Committee on the Effects of Atomic Radiation, 1982 Report to the General Assembly, 37th Session, Suppl. 45 (A/37/45) Annex E (United Nations, New York). 

To sum up the results of the test work, it has been shown that liquid hydrogen is much safer to handle than many other missile propellants. When accidentally mixed with air under unconfined conditions, it does not detonate, and radiation effects of any fire are less than those of more conventional fuels. On the other hand, its low initiation energy requirements and its wide flammability limits make ignition of any vapor cloud more likely, and for that reason, more care should be taken to remove all potential sources from an area where liquid hydrogen is stored or handled. 

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