Equations for predicting airborne cleanliness in non-unidirectional airflow cleanrooms

Equations are derived in this paper for predicting the airborne concentration of particles and microbe-carrying particles in non-unidirectional airflow cleanrooms during manufacturing. The equations are obtained for a variety of ventilation systems with different configurations for mixing fresh and recirculated air, air filter placements, and number and efficiency of air filters. The variables in the equations are air supply rate, airborne dispersion rate of contamination from machinery and people, surface deposition of particles from air, particle concentration in fresh makeup air, proportion of make-up air, and air filter efficiencies. The equations are amenable to relatively simple modification for the study of different cleanroom ventilation systems. The use of these equations to investigate the effect of different configurations of ventilation systems and the relative importance of the equation variables on airborne concentrations will be reported in a further paper

Calculation of airborne cleanliness and air supply rate for non-unidirectional airflow cleanrooms

Equations have been recently derived by Whyte, Lenegan and Eaton for calculating the airborne concentration of particles and microbe-carrying particles in non-unidirectional airflow cleanrooms. These equations cover a variety of ventilation systems, and contain the variables of air supply rate, airborne dispersion rate of contamination from machinery and people, surface deposition of particles from the air, concentration of contamination in fresh make-up air, proportion of fresh air, and air filter efficiencies. The relative importance of these variables is investigated in this present research paper, with particular regard to the removal efficiency, location, and number of air filters. It was shown that air filters were important in ensuring low levels of contamination in cleanrooms but the types of filters specified in current cleanroom designs were very effective in ensuring a minimal contribution to the cleanroom’s airborne contamination especially when a secondary filter is used in addition to a primary and terminal filter. The most important determinants of airborne contamination were the air supply rate and the dispersion rate of contamination within the cleanroom, with a lesser effect from deposition of airborne particles onto cleanroom surfaces. The information gathered confirmed the usefulness of the equation previously used by Whyte, Whyte, Eaton and Lenegan to calculate the air supply rate required for a specified concentration of airborne contamination

Syphon Diaphragms : A Method for Predicting Their Performance for Purposes of Instrument Design

Here, the purpose is to show that the characteristic performance of a syphon diaphragm can be predicted from a knowledge of its stiffness and of its dimensions. The proof is based on a mathematical analysis of this type of diaphragm, together with enough experimental data to prove the validity of the assumptions and the sufficiency of the analysis. Equations are developed for the performance of syphons under various conditions of loading, both for concentrated loads and for hydrostatic pressure

Spurious Eccentricities of Distorted Binary Components

I discuss the effect of physical distortion on the velocities of close binary components and how we may use the resulting distortion of velocity curves to constrain some properties of binary systems, such as inclination and mass ratio. Precise new velocities for 5 Cet convincingly detect these distortions with their theoretically predicted phase dependence. We can even use such distortions of velocity curves to test Lucy's theory of convective gravity darkening. The observed distortions for TT Hya and 5 Cet require the contact components of those systems to be gravity darkened, probably somewhat more than predicted by Lucy's theory but clearly not as much as expected for a radiative star. These results imply there is no credible evidence for eccentric orbits in binaries with contact components. I also present some speculative analyses of the observed properties of a binary encased in a non-rotating common envelope, if such an object could actually exist, and discuss how the limb darkening of some recently calculated model atmospheres for giant stars may bias my resuts for velocity-curve distortions, as well as other results from a wide range of analyses of binary stars.Comment: 14 pp, 2 tables, 12 fig; under review by Ap

What the banker expects from the accountant

What does a banker expect an audited statement to show? He expects that it will set forth a correct picture of all the assets and ail the liabilities of the company. And he expects that these various assets and liabilities will be classified and described with sufficient detail and exactness to enable him to form a satisfactory estimate of their value as a basis for granting credit

The relationship between parental education and children's schooling in a time of economic turmoil: The case of East Zimbabwe, 2001 to 2011.

Using data collected from 1998 to 2011 in a general population cohort study in eastern Zimbabwe, we describe education trends and the relationship between parental education and children's schooling during the Zimbabwean economic collapse of the 2000s. During this period, the previously-rising trend in education stalled, with girls suffering disproportionately; however, female enrolment increased as the economy began to recover. Throughout the period, children with more educated parents continued to have better outcomes such that, at the population level, an underlying increase in the proportion of children with more educated parents may have helped to maintain the upwards education trend

Calculation of air supply rates and concentrations of airborne contamination in non-UDAF cleanrooms

This article reviews a series of scientific articles written by the authors, where the following topics were investigated in relation to non-unidirectional airflow cleanrooms. (1) The air supply rate required to obtain a specified concentration of airborne contamination. (2) The calculation of concentrations of airborne contaminants in different ventilation and dispersion of contamination situations. (3) The decay of airborne contamination (a) during the ‘clean up’ test described in Annex 1 of the EU Guidelines to Good Manufacturing Practice (2008); (b) during the recovery rate test described in Annex B12 of ISO 14644-3 (2005); (c) associated with clean areas, such as airlocks, to reduce airborne contamination before a door into a cleanroom is opened. Worked examples are provided to demonstrate the calculation methods to provide solutions to the above topics

Welcome back, Polaris the Cepheid

For about 100 years the amplitude of the 4-day pulsation in Polaris has decreased. We present new results showing a significant increase in the amplitude based on 4.5 years of continuous monitoring from the ground and with two satellite missions.Comment: 5 pages; to appear in the proceedings of the "Cool Stars 15" workshop held at St Andrews, U

Rainfall record

Rainfall (including melted snow) at the Experiment Station, from August 1. 1892, to March 1, 1893