Quantitative Frequency Evaluation

Guidance on performing a quantitative frequency evaluation is beyond the scope of this book. Reference 4 provides detailed guidance on frequency evaluation. 

Monaci et al. (1997) performed a lichen-biomonitoring study in Siena by means of two different methods. The pattern of air quality in the study area was examined on the basis of the in situ frequency of different species of epiphytic lichens, i.e. using their species-specific sensitivity to the complex mixture of phytotoxic pollutants in the urban environment. The distribution of trace elements was evaluated quantitatively by an analysis of thalli of a tolerant species, P. caperata, known to be a reliable bioaccumulator of persistent atmospheric pollutants. The values obtained for Al, Ba, Cr, Cu, Fe, Pb and S were significantly higher in Sienese lichens over and above controls. Traffic was found to be the major source of atmospheric pollution. The pattern of trace-elemental deposition did not always coincide with air quality. lAP values were found to reflect essentially the emission of gaseous phytotoxic pollutants in the urban environment. 

The cationic Re-H and Re-D stretching frequencies are lowered in each case in comparison to those corresponding to the neutral molecule. This experimental information can be used to evaluate quantitatively the changes in Re-H bonding and equilibrium bond distance upon removal of an electron. For all three of these molecules, Franck-Condon analysis of the observed vibrational structure indicates that the Re-H or Re-D equilibrium bond distance is lengthened by about 0.25 A on ionization. The deduction that the Re-H bond orbital is localized is confirmed by theoretical calculations. 

The acronym for chemical process quantitative risk analysis. It is the process of hazard identification followed by numerical evaluation of incident consequences and frequencies, and their combination into an overall measure of risk when applied to the chemical process industry. It is particularly applied to episodic events. It differs from, but is related to, a probabilistic risk analysis (PRA), a quantitative tool used in the nuclear industry... 

The development of a quantitative estimate of risk based on engineering evaluation and mathematical techniques for combining estimates of incident consequences and frequencies... 

The accident sequence frequencies are quantified by linking the system fault tree models together as indicated by the event trees for the accident sequence and quantified with plant-specific data to estimate initiator frequencies and component/human failure rates. The SETS code solves the fault trees for their minimal cutsets the TEMAC code quantitatively evaluates ihe cm sols and provides best estimates of component/event probabilities and frequencies. 

Chemical Process Quantitative Risk Analysis(CPQRA) The numerical evaluation of both incident consequences and probabilities or frequencies and their combination into an overall measure of risk. 

In a more quantitative sense, cause-consequence analysis may be viewed as a blend of fault tree end event tree analysis (discussed in tlie two preceding cliapters) for evaluating potential accidents. A major strengtli of cause-consequence analysis is its use as a communication tool. For example, a cause-consequence diagram displays the interrelationships between tlie accident outcomes (consequences) and Uieir basic causes. The method can be used to quantify the expected frequency of occurrence of the consequences if the appropriate chita are available. 

Accountability and transparency have several aspects reporting to and control by supervisory bodies clarity and openness of procedures criteria for decision-making and decisions made and existence of systems for complaint and appeal. Accountability and transparency can be evaluated by examining, in particular reporting requirements, external reviews of the authority s performance frequency of publications and content of website (and other means of communication between the DRA, the public and the regulated parties) bodies to which complaints are directed and appeals procedures. However, the individual details of these elements of regulation make quantitative comparison difficult. 

From the calculated building damage versus response relationship and the empirical probability of serious injury or fatality versus damage relationship discussed above, the relationship between explosion overpressure (or other effects) and probability of serious injury or fatality may be constructed in a manner that accounts for the detailed structural characteristics of plant buildings. The steps involved are similar to risk screening (Chapter 4), with the addition of detailed quantitative structural evaluation of plant buildings and detailed quantitative frequency assessment as described in the next section. 

After several cycles of the compression and expansion, the dynamic jc-A curve becomes a single closed loop, somewhat distorted from a genuine ellipsoid. In order to analyze the forms of the hysteresis loop under stationary conditions, we have measured the time trace of the dynamic surface pressure after five cycles of the compression and expansion, and then Fourier-transformed it to the frequency domain. The Fourier-transformation was adapted to evaluate the nonlinear viscoelasticity in a quantitative manner. The detailed theoretical consideration for the use of the Fourier transformation to evaluate the nonlinearity, are contained in the published articles [8,43]. 

Probability analysis Way to evaluate the likelihood of an event occurring. By using failure rate data for equipment, piping, instruments, and fault tree techniques, the frequency (number of events per unit time) can be quantitatively estimated. 

In general, risk reduction is accomplished by implementing one or more protective layers, which reduce the frequency and/or consequence of the hazard scenario. LOPA provides specific criteria and restrictions for the evaluation of protection layers, eliminating the subjectivity of qualitative methods at substantially less cost than fully quantitative techniques. LOPA is a rational, defensible methodology that allows a rapid, cost-effective means for identifying the protection layers that lower the frequency and/or the consequence of specific hazard scenarios. 

The quantitative evaluation of expected risk from potential incident scenarios. It examines both consequences and frequencies, and how they combine into an overall measure of risk. The CPQRA process is always preceded by a qualitative systematic identification of process hazards. The CPQRA results may be used to make decisions, particularly when mitigation of risk is considered. 

The quantitative dose-response assessment involves two different challenges, namely to determine the relationship between doses and the frequency of cases of cancer (i.e., potency evaluation), and to determine what statistical risk is tolerable or acceptable. This section gives a very short overview of some general aspects related to the quantitative dose-response assessment. The currently used approach by the WHO, the US-EPA, and the EU, as well as new approaches for the risk assessment of compounds that are both genotoxic and carcinogenic, are presented in Sections 6.3 and 6.4, respectively. 

An exposure assessment is the quantitative or qualitative evaluation of the amount of a substance that humans come into contact with and includes consideration of the intensity, frequency and duration of contact, the route of exposure (e.g., dermal, oral, or respiratory), rates (chemical intake or uptake rates), the resulting amount that actually crosses the boundary (a dose), and the amount absorbed (internal dose). Depending on the purpose of an exposure assessment, the numerical output may be an estimate of the intensity, rate, duration, and frequency of contact exposure or dose (the resulting amount that actually crosses the boundary). For risk assessments of chemical substances based on dose-response relationships, the output usually includes an estimate of dose (WHO/IPCS 1999). 

We have implemented the principle of multiple selective excitation (pulse sequence II in fig. 1) thereby replacing the low-power CW irradiation in the preparation period of the basic ID experiment by a series of selective 180° pulses. The whole series of selective pulses at frequencies /i, /2, , / is applied for several times in the NOE build-up period to achieve sequential saturation of the selected protons. Compared with the basic heteronuclear ID experiment, in this new variant the sensitivity is improved by the combined application of sequential, selective pulses and the more efficient data accumulation scheme. Quantitation of NOEs is no longer straightforward since neither pure steady-state nor pure transient effects are measured and since cross-relaxation in a multi-spin system after perturbation of a single proton (as in the basic experiment) or of several protons (as in the proposed variant) differs. These attributes make this modified experiment most suitable for the qualitative recognition of heteronuclear dipole-dipole interactions rather than for a quantitative evaluation of the corresponding effects. 

---