“Right-Sizing” Research Studies: Assuring Adequate, not Grossly-Overlarge Sample-Sizes

A “right-sizing” system is demonstrated that provides for: robust estimations of minimum study sample-size requirements, and efficient evaluations of alternate parameter assumptions. Importantly, ‘assumption evaluations' often result in the avoidance of grossly-oversized studies [e.g., added $10K-$1000K costs]. “Right-sizing” calculations may be quickly conducted using simple-computational tools (eg, hand calculator) during a meeting as questions arise. Built upon an understanding of the robust mechanisms underlying the Dunlap “2–2” heuristic (re: α=0.05 2-tailed, and 1-β ≥ 0.80), it is applicable to the same range of dichotomous-to-interval data, but is also generalized to broadly accommodate correlated means and a full-spectrum of alternative α, 1-β combinations. We recommend our right-sizing system to HF/E and other practitioners interested in (1) Assuring adequate study sample-sizes, and (2) Avoiding grossly oversized studies that drain critical resources.

Does Hand Calculator Use Explain Why University Students Cannot Perform Elementary Arithmetic?

In a sample of German students (125 women, 128 men) only 26.3% answered 10 mathematics problems in the D'Amore Test, fewer than Standing, et al. reported. Significant correlations were found for test and self-predicted scores but predictors were not the same in the two studies. Although there were no sex differences, women were more accurate in the mental calculations, especially if they rarely used calculators.

Faceted Design of Microscale Channels for Electrokinetic Flows

A novel methodology for designing microfluidic channels for low-dispersion, electrokinetic flows is presented. The technique relies on trigonometric relations that apply for ideal electrokinetic flows, allowing faceted channels to be designed using common drafting software and a hand calculator. Flows are rotated and stretched along the abrupt interface between adjacent regions having differing specific permeability. Two-interface systems are used to eliminate hydrodynamic rotation of bands injected into channels. Regions bounded by interfaces form faceted flow “prisms” with uniform velocity fields that can be combined with other prisms to obtain a wide range of turning angles and expansion ratios. Lengths of faceted prisms can be varied arbitrarily, simplifying chip layout and allowing the ability to select time-of-flight for a given faceted prism. The method is tested using combined experimental and computational demonstrations of flow displacers. Designs are demonstrated using two-dimensional numerical solutions of the Laplace equation. Experimental flow visualization is performed using standard epi-fluorescence microscopy techniques.

‘Natural’ Coordinates for Analysis of the Practical Stirling Cycle

The appropriate choice of coordinate system so simplifies basic cycle analysis that computation of the ideal particle trajectory diagram reduces to a straightforward graphical process. Ideal pressure, Reynolds number Nre, friction factor Cf and heat-transfer parameters Nst and N2/3pr follow in function of location and crank angle via a few steps on the hand calculator. A thermodynamic design parameter is identified which has essentially the same numerical value for such diverse Stirling engines as Philips' MP1002CA, General Motors' GPU-3 and the turn-of-the-century Kyko hot-air engine.

Intimate Thermodynamic Design of the Stirling Engine Gas Circuit without the Computer

Thermodynamic similarity conditions are cited for the gas circuit of the Stirling machine. Charts or a hand calculator become the only tools required for the design of a new machine to the detail previously calling for sophisticated software. Independent corroboration is presented.