F number

Sum of squared, weighted residuals °F Number of degrees of freedom... 

The ratio F/d is the F number of the lens. For F numbers much less than unity, spherical aberration precludes reaching the ultimate diffraction-limited spot size. Therefore a practical limit for the minimum spot size obtainable is approximately the wavelength of the light. Commonly this is expressed as the statement that laser light may be focused to a spot with dimensions equal to its wavelength. 

Chapter 12 discusses the software provided with this book including the program Lambda that does the chi-squared and F-number calculations. 

The numerator is a random normally distributed variable whose precision may be estimated as V(N) the percent of its error is f (N)/N = f (N). For example, if a certain type of component has had 100 failures, there is a 10% error in the estimated failure rate if there is no uncertainty in the denominator. Estimating the error bounds by this method has two weaknesses 1) the approximate mathematics, and the case of no failures, for which the estimated probability is zero which is absurd. A better way is to use the chi-squared estimator (equation 2,5.3.1) for failure per time or the F-number estimator (equation 2.5.3.2) for failure per demand. (See Lambda Chapter 12 ),... 

Selection 2 is a similar calculation using the F-Number method (Section 2.5.3.2) 3 calculates the integral over the Chi-Squared distribution. When selected i nput the upper limit of integration... 

Schenk, R., Hessel, V., Hoemann, C., Kiss, )., Lowe, H., Schoneeld, F., Numbering-up of micro devices a first liquid-flow splitting unit, Chem. Eng. Technol. 26, 12 (2003) 1271-1280. 

Carborundum is rjsed mainly for fast work when much glass needs to be removed, and for grinding quartz. It is cheaper and harder than emery. It can be graded by particle size the coarsest normally used is 90 mesh. The medium size is about 180 mesh, and the fine about 300 mesh, with very fine of 600 and 900 mesh this last is usually unnecessary since better results can be obtained with jeweller s rouge. Carborundum is also often graded in F numbers F consists of 240 mesh and finer 2F of 280 and finer and 3F of 320 mesh and finer. Carborundum is used in the same way as emery, and has the advantage that carborundum wheels and blocks can be obtained. 

Figure 22 Stress-relaxation modulus as a function of Crystallinity at temperatures above I f Numbers on the curves are rough values of the degree of Crystallinity.

F = Number of photons emitted by Si/Number of photons absorbed by S0... 

F number F number is the ability to gather light. Smaller F numbers may be required for outdoor applications where light cannot be controlled as easily. 

Figure 10. Chromatographic pattern for organosoluble uC-labeled metabolites from [ring-14C]-molinate-treated water which contained carp for 4 days. F number represents metabolite code.

N, number of experiments f, number of examined factors d, number of dummies and n, number of center points (—) not specified ( ) assumed. 

Type and Extent of Required Examination The intent of examinations is to provide the examiner and the inspector with reasonable assurance that the requirements of the code and the engineering design have been met. For F-number 3, 4, and 5 materms, examination shall be performed after any heat treatment has been completed. 

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