Testing difference

The characterization of probe contributes to understanding the probe behaviour and gives the probe features as well. We have illustrated though different examples how to manage to limit the measurements to what is strictly necessary. We think that many things are still to do either to simplify with automatic process system existing procedures or to imagine different tests. 

Individual comparisons using Fisher s least significant difference test are based on the following null hypothesis and one-tailed alternative hypothesis... 

Discriminant Sensory Analysis. Discriminant sensory analysis, ie, difference testing, is used to determine if a difference can be detected in the flavor of two or more samples by a panel of subjects. These differences may be quantitative, ie, a magnitude can be assigned to the differences but the nature of the difference is not revealed. These procedures yield much less information about the flavor of a food than descriptive analyses, yet are extremely useful eg, a manufacturer might want to substitute one component of a food product with another safer or less expensive one without changing the flavor in any way. Several formulations can be attempted until one is found with flavor characteristics that caimot be discriminated from the original or standard sample. 

B. J. Lockhart, M. D. Hampton, and C. J. Bryan, The Oyygen Sensitivityl Compatahility Ranking of Several Materials by Different Test Methods, ASTM Spec. Tech. Publ. 1040, ASTM, Philadelphia, Pa., 1989, pp. 93-105. 

In all antiseptic testing, it is recognized that skin and mucous membranes to which products ate appHed cannot be disinfected or sterilized but it is possible to significantly reduce the population of transient and resident pathogenic bacterial flora. AH in vivo test methods requite a deterrnination of the bacteria on the skin before and after treatment. Because of the normal variation in bacterial population of the skin of different people, a number of people must be tested in order to make a statistical analysis of the results. Different parts of the body are used for different tests. In aH of the tests the details of the protocol ate extremely important and must be strictly adhered to in order to obtain reproducible results. 

Sa.lt Spray Tests. One of the older accelerated corrosion tests is the salt spray test (40). Several modifications of this imperfect test have been proposed, some of which are even specified for particular appHcations. The neutral salt spray test persists, however, especially for coatings that are anodic to the substrate and for coatings that are dissolved or attacked by neutral salt fog. For cathodic coatings, such as nickel on steel, the test becomes a porosity test, because nickel is not attacked by neutral salt fog. Production specifications that call for 1000 hours salt spray resistance are not practical for quahty acceptance tests. In these cases, the neutral salt spray does not qualify as an accelerated test, and faster results from different test methods should be sought. 

When maldug any economic analysis, care should be taken to be certain that the efficiency ratings of all motors being considered are on the same basis. While this should not be a problem for motors rated 1 to 500 horsepower as covered by the NEMA Standards for efficiency marldug, it is common practice for several different test methods to be used when measuring the efficiency of motors rated over 500 horsepower. A particular test method may need to be selected by the test facility on the basis of available test equipment and power supply. All test methods that may be used to test any one motor will not necessarily give the same result for efficiency. 

Different tests for estimation the accuracy of fit and prediction capability of the retention models were investigated in this work. Distribution of the residuals with taking into account their statistical weights chai acterizes the goodness of fit. For the application of statistical weights the scedastic functions of retention factor were constmcted. Was established that random errors of the retention factor k ai e distributed normally that permits to use the statistical criteria for prediction capability and goodness of fit correctly. 

Many different test systems have been used to investigate the ability of chemicals to interact with components of the endocrine system. The usefulness and applicability of the available methods has been the subject of much debate. Four key texts are particularly helpful in reviewing and giving guidance on currently available test methods and strategies for testing EDs. ... 

The information obtained during the background search and from the source inspection will enable selection of the test procedure to be used. The choice will be based on the answers to several questions (1) What are the legal requirements For specific sources there may be only one acceptable method. (2) What range of accuracy is desirable Should the sample be collected by a procedure that is 5% accurate, or should a statistical technique be used on data from eight tests at 10% accuracy Costs of different test methods will certainly be a consideration here. (3) Which sampling and analytical methods are available that will give the required accuracy for the estimated concentration An Orsat gas analyzer with a sensitivity limit of 0.02% would not be chosen to sample carbon monoxide... 

EN 779 1993 in principle contains two different test methods. The filter is tested both with untreated outdoor air and with the addition of synthetic dust. In the first case, the filter s dust spot efficiency is determined, i.e., its capacity to clean normal outdoor air. In the second case, the filter s arrestance is measured, i.e., its capacity to separate synthetic dust. The average value for dust spot efficiency or arrestance during the course of the test is used for classification of the filter. 

The deflagration flame arrester must he subjected to a series of at least 10 explosion (deflagration) tests in a rig with a pipe at least 5 feet (1.5 meters) long with various mixtures of propane in air and different test conditions to test the entire spectrum of possible deflagrations. Also, a series of 3 flashback tests, using a mixture of 4.2 volume percent of propane in air, must be conducted. 

Different test methods produce numerically different results and comparisons should only be made of results using the same test method. Tests fall into three categories gravimetric tests, which measure ability to trap and retain dust those which measure staining power of contaminants before and after filtration and those measuring the concentration of a test aerosol either side of the filter by photoelectric methods. The tests which will be met most often are as follows. 

Note There are many different tests and different versions of the same test for water analysis. If there is any doubt as to method or interpretation consult a reputable water-treatment supplier. The letters ND in the table indicate not detectable. Parts per million (ppm) are also commonly used to express concentration and are essentially identical to mg/l. 

Boiling point distillation data also provides information about the quality and composition of a feed. The significance is discussed later in this chapter. Distillation indicates molecular weight and carbon number. It indicates whether the feed contains any clean products that could be sold as is. Before discussing the data, the different testing methods and their limitations should be reviewed. 

The oxygen concentration of the solution, as in many instances of corrosion, can also be critical in stress-corrosion cracking tests. Instances are available in the literature that show very markedly different test results according to the oxygen concentration in systems as widely different as austenitic steels immersed in chloride-containing phosphate-treated boiler water and aluminium alloys immersed in 3% NaCl. 

Nicolas, M. T. (1980). Solubilisation du systeme lumineux des Polynoi niens, comparaison de differents tests d activite. Biol. Cellulaire 39 5. 

Test rate and property The test rate or cross-head rate is the speed at which the movable cross-member of a testing machine moves in relation to the fixed cross-member. The speed of such tests is typically reported in cm/min. (in./min.). An increase in strain rate typically results in an increase yield point and ultimate strength. Figure 2-14 provides examples of the different test rates and temperatures on basic tensile stress-strain behaviors of plastics where (a) is at different testing rates per ASTM D 638 for a polycarbonate, (b) is the effects of tensile test-... 

Different tests are used on prototypes. As an example industry has a test where a load may be double that of a heavy person. Its two rear legs are positioned in front of an anchored board. The top of the chair has a rope or chain extending backwards to an oscillating device. The top of the chair will be pulled back to the point of almost failing backward and then released. The loaded chair will bounce on its two front legs. This cycle is repeated thousands of times. The industry test has requirements so if the chair is to be used in commercial environment its number of cycles will be many more than a noncommercial chair. 

There are destructive and nondestructive tests (NDTs) (2). Most important, they are essential for determining the performance of plastic materials to be processed and of the finished fabricated products. Testing refers to the determination by technical means properties and performances. This action, when possible, should involve application of established scientific principles and procedures. It requires specifying what requirements are to be met. There are many different tests (thousands) that can be conducted that relate to practically any material or product requirement. Usually only a few will be applicable to meet your specific application. Examples of these tests will be presented. 

There is usually more than one test method to determine a performance because each test has its own behavior and meaning. As an example there are different tests used to determine the abrasion resistance of materials. There is the popular Taber abrasion test. It determines the weight loss of a plastic or other material after it is subjected to abrasion for a prescribed number of the abrader disk rotations (usually 1000). The abrader consists of an idling abrasive speed controlled rotating wheel with the load applied to the wheel. The abrasive action on the circular specimen is subjected to a rotary motion. 

Other abrasion tests have other type actions such as back and forth motion, one direction, etc. These different tests provide different results that can have certain relations to the performance of a product that will be subjected to abrasion in service. 

Conditioning procedures of test specimens and products are important in order to obtain reliable, comparable, and repeatable data within the same or different testing laboratories. Procedures are described in various specifications or standards such as having a standard laboratory atmosphere [50 2% relative humidity, 73.4 1.8°F (23 1°C)] with adequate air circulation around all specimens. The reason for this type or other conditioning is due to the fact the temperature and moisture content of plastics can affect different properties. 

These test procedures and standards are subject to change, so it is essential to keep up to date if one has to comply with them. It may be possible to obtain the latest issue on a specific test (such as a simple tensile test or a molecular weight test) by contacting the organization that issued it. For example, the ASTM issues new annual standards that include all changes. Their Annual Books of ASTM Standards contain more than seven thousand standards published in sixty-six volumes that include different materials and products. There are four volumes specifically on plastics 08.01-Plastics 1 08.02-Plastics 11 08.03-Plastics III, and 08.04-Plastic Pipe and Building Products. Other volumes include information on plastics and RPs. The complete ASTM index are listed under different categories for the different products, types of tests (by environment, chemical resistance, etc.), statistical analyses of different test data, and so on (56,128,129). 

Hardness basically is the resistance to indentation as measured under specific conditions such as depth of indentation, load applied, and time period. Different tests relate to different hardness behaviors of plastics. They include Barcol, Brinell, durom-eter, Knoop, Mohs, Rockwell, Shore, and Vicat (2). 

Fig. 5-5 Hardness of different materials using different test methods.

In this test for transparent plastics, the loss of optical effects is measured when a specimen is exposed to the action of a special abrading wheel. In one type of test the amount of material lost by a specimen is determined when the specimen is exposed to falling abrasive particles or to the action of an abrasive belt. In another test, the loss of gloss due to the dropping of loose abrasive on the specimen is measured. The results produced by the different tests may be of value for research and development work when it is desired to improve a material with respect to one of the test methods. The variables that enter into tests of this type are... 

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