Allowing Flexibility

Flexibility can be important in setting a standard. There are various reasons why this might be the case  

We have already introduced some ways in which flexibility can be introduced into standards by adopting different types or, when a compliance target is used, by addressing the criteria outlined. If flexibility is too broad, there is a risk of bringing too little pressure to bear, and environmental improvements are seriously compromised. Other sources of flexibility include the following  

Whatever implementation measures are adopted, they will need to be explained so the approach can be justified and the decision made transparent. If the standard-setting process has been open and participatory but the implementation is opaque, then credibility is lost (to the regulator, industry, etc.), and trust is reduced (Farmer 2007). 

We must also be prepared to enforce a standard if it is important enough. It is inappropriate to use such measures to achieve what is, in effect, a permanent reduction in a standard. For example, if exceedances of a standard routinely occur and are simply accepted, then what the public might think is that compliance with an annual average concentration of 10 mg L-1 is in fact only compliance with a concentration of 20 mg L 1. If the latter is environmentally acceptable, then it should have been used as a standard in the first place. Only if they are steps on a path toward full compliance should such interim measures be tolerated (e.g., for particular hot spots or problem periods). 

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Atom types represen t the chemical environment of an atom. The atom types associated with a given force field could be hard-wired to have specific vahiesand meaning. llyperChem also allows flexible definitions of the atom types and the associated chemical en vironmen Is. Th e ch em ical en viron men t of an atom (a set of rules for defining a type) and the default rules are in a standard ASCII text file, chem.nil. included with llyperChem. You can modify this file and compile it m a binary form that llyperChem... 

Kuhni contacters (Eig. 15e) have gained considerable commercial application. The principal features are the use of a shrouded impeller to promote radial discharge within the compartments, and a variable hole arrangement to allow flexibility of design for different process applications. Columns up to 5 m in diameter have been constmcted (176). Description and design criteria for Kuhni extraction columns have been reported (177,178). 

To allow flexibility, the database manager must also perform point addition or deletion. However, the abihty to create a point type or to add or delete attributes of a point type is not normally required because, unlike other data processing systems, a process control system normally involves a fixed number of point types and related attributes. For example, analog and binary input and output types are required for process I/O points. Related attributes for these point types include tag names, values, and hardware addresses. Different system manufacturers may define different point types using different data structures. We will discuss other commonly used point types and attributes as they appear. 

Concrete and fiberglass vaults are often used, although they can be subject to environmentally induced cracks. Soil and clay liners are not allowed. Flexible hner systems have been developed that may be a cost-effective and environmentally sound alternative. State-of-the-art liner technology has overcome many of the previous problems with seams, low mechanical strength, and chemical resistance. 

The major reason most turbine motors are designed with various add-on motor sections is to allow flexibility when applying turbine motors to operational situations. 

Directives, on the other hand, are addressed to member states and require that they enact national legislation so as to achieve the objectives of the directives. Thus, a directive allows flexibility in how national legislation is enacted. In practice, national legislation will frequently refer you back to the directive, particularly when a directive contains large amounts of detailed technical requirements. 

Although the directives allow flexibility in the methods and solutions that a manufacturer may employ to fulfil the essential requirements, they promote the use of standards as the preferred method to establish conformity. Specifically, the directives stipulate that Member States shall presume compliance with the essential requirements in respect of devices that are in conformity with relevant harmonised standards. 

The procedure illustrated here, besides containing only trivial technical calculations, lacks important features that are required in production programs. Extensive error checking and recovery must be performed. The procedure must detect the occurrence of a self-referential system of formulas, which would result in attempting endless recursive calls. Access to multiple raw material and formula databases adds power to the program, but must be implemented by complex code to allow flexible control of that access. The structural and input/output statements to support these features may greatly exceed the number of statements that perform modelling calculations. 

Given the nature of this usage we have designed the software to emphasize ease of use by operators with a wide range of skills. The operating system environment has been chosen to allow flexible operation of tasks in a menu-driven environment. The task structure and the associated data structures are designed to provide an orderly flow of information and control. 

The U-tube was developed to simplify the recovery of fluids from deep boreholes and allow flexibility for post-sampling analysis (Freifeld et al. 2005 Freifeld Trautz 2006). In particular, the ability to repeatedly collect large volume multiphase samples into high pressure cylinders facilitates both real-time field analysis as well as acquisition of sample splits for future laboratory based analysis. 

Rules in the expert system are structured to allow flexibility and future expansion. For speed of execution, the IF-THEN clauses are actually executable LISP code. Tables II and III contain examples of how rules are structured. The IF clauses contain functions, called predicates. Predicates have a value of either... 

As an alternative to the preferred option, the ICH guideline allows flexibility in the choice of study designs, as long as the combination of studies chosen covers the complete reproductive cycle. This allows the toxicologist to design the reproductive toxicology package so that it is relevant to the compoimd class imder test. 

Therefore, a flexible method to evaluate physical and chemical system parameters is still needed (2, 3). The model identification technique presented in this study allows flexibility in model formulation and inclusion of the available experimental measurements to identify the model. The parameter estimation scheme finds the optimal set of parameters by minimizing the sum of the differences between model predictions and experimental observations. Since some experimental data are more reliable than others, it is advantageous to assign higher weights to the dependable data. 

ECVAM is the leading international center for alternative test method validation. Hartung et al. (29) summarized the modular steps necessary to accomplish stage 3 (test validation). The seven modular steps are (I) test definition, (2) within-laboratory variability, (3) transferability, (4) between-laboratory variability, (5) predictive capacity, (6) applicability domain, and (7) performance standards (29). Steps 2-4 evaluate the test s reliability steps 5 and 6 evaluate the relevance of the test. Successful completion of all seven steps is necessary to proceed to stage 4 (independent assessment or peer review). This modular approach allows flexibility for the validation process where information on the test method can be gathered either prospectively or retrospectively. The approach is applicable not only to in vitro test methods but also to in silico approaches (e.g., computer-based approaches such as quantitative structure-activity relationships or QSAR) and pattern-based systems (e.g., genomics and proteomics). 

Re-evaluating sample size is one example of adapting the design of the trial based on accumulating data from the trial. There is currently substantial interest in the potential of allowing flexibility in this way. These considerations come under the heading of adaptive or flexible designs. 

Stability of Standard and Sample Solutions. Appropriate stability of the standard and sample solutions will allow flexibility of the method to be used in a quality control laboratory. For example, 4-day stability of the standard and sample solutions will allow investigation if problems arise during a weekend HPLC run. 

In order to allow flexibility in operation of sequential chemical and biological stages, they do not have to be directly coupled. A storage tank or drain in between allows changes in experimental parameters to be made more independently. An alternative method is outlined in Section B 6.4. 

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