Possible versus desirable in instructional systems: Who's driving?

This paper takes a pragmatic stance that the key to successful application of technology in education is good teaching: using technology only when it is a cost‐effective servant of pedagogy. The paper discusses some fundamental issues in the production of computer‐based materials, and considers them in the context of an on‐going evaluation of an Internet courseware project

Statement of the Labor Policy Association Before the Commission on the Future of Worker-Management Relations

Testimony_Carswell_110893.pdf: 299 downloads, before Oct. 1, 2020

Inversion of 2 wavelength Lidar data for cloud properties

The inversion of the lidar equation to derive quantitative properties of the atmosphere has continued to present considerable difficulty. The results of a study in which Klett's procedure was utilized for the analysis of cloud backscatter measurements made simulataneously at two ruby lidar wavelengths (694nm,347nmm) are presented. With one lidar system a cloud is probed at the two wavelength and the backscatter measured simulataneously by separate receivers. As a result two sigma profiles which should differ only because the wavlength dependence of the scattering. Experimental data presented to demonstrate the effects and the implications of the applications of the inversion method will be discussed

Evolution of the Ionizing Background at High Redshifts

We use a Maximum-Likelihood analysis to constrain the value and evolution of the ionizing background for 2<z<4.5, taking account of possible systematic errors. (The paper has a more detailed abstract)Comment: 12 figures (9 of those double plots), 17 pages. Accepted by MNRA

Principles for aerospace manufacturing engineering in integrated new product introduction

This article investigates the value-adding practices of Manufacturing Engineering for integrated New Product Introduction. A model representing how current practices align to support lean integration in Manufacturing Engineering has been defined. The results are used to identify a novel set of guiding principles for integrated Manufacturing Engineering. These are as follows: (1) use a data-driven process, (2) build from core capabilities, (3) develop the standard, (4) deliver through responsive processes and (5) align cross-functional and customer requirements. The investigation used a mixed-method approach. This comprises case studies to identify current practice and a survey to understand implementation in a sample of component development projects within a major aerospace manufacturer. The research contribution is an illustration of aerospace Manufacturing Engineering practices for New Product Introduction. The conclusions will be used to indicate new priorities for New Product Introduction and the cross-functional interactions to support flawless and innovative New Product Introduction. The final principles have been validated through a series of consultations with experts in the sponsoring company to ensure that correct and relevant content has been defined

CONCAP 4: A Complex Autonomous Payload (CAP) for growing organic thin films in microgravity

A GAS facility has been developed for carrying out low temperature experiments. The arrangement being used on CONCAP IV-01 is designed for thin film growth in microgravity and can process up to twelve samples per mission. The nonlinear optical oven hardware can also be made suitable for other low temperature applications, such as gradient freeze and solution growth of crystals

Direct Observational Test Rules Out Small MgII Absorbers

Recent observations suggest the incidence of strong intervening MgII absorption systems along the line-of-sight to gamma ray burst (GRB) afterglows is significantly higher than expected from analogous quasar sightlines. One possible explanation is a geometric effect, arising because MgII absorbers only partially cover the quasar continuum regions, in which case MgII absorbers must be considerably smaller than previous estimates. We investigate the production of abnormal absorption profiles by partial coverage and conclude that the lack of any known anomalous profiles in observed systems, whilst constraining, cannot on its own rule out patchy MgII absorbers. In a separate test, we look for differences in the distribution function of MgII equivalent widths over quasar continuum regions and CIII] emission lines. We show that these anomalies should be observable in any scenario where MgII absorbers are very small, but they are not present in the data. We conclude that models invoking small MgII cloudlets to explain the excess of absorbers seen towards GRBs are ruled out.Comment: Accepted for publication in MNRAS Letters. 5 pages, 2 figure

The enrichment history of the intergalactic medium: O VI in Ly-alpha forest systems at redshift z ~ 2

A search for O VI at redshifts corresponding to Ly-alpha lines in the z_em ~ 2.4 QSOs HE1122-1648 and HE2217-2818 reveals that a substantial fraction of those with H I column densities log N(HI) > 14 (cm^{-2}) are highly ionized and show some heavy element enrichment. If these two sight lines are typical, then the O VI systems contain a cosmologically significant fraction of the baryons and the metals in the universe. For most systems the temperatures derived from the line widths are too low for collisional ionization to be responsible for the O VI lines. Photoionization models with a substantial hard ultraviolet flux can reproduce the observations for densities that are in good agreement with a model assuming local, hydrostatic equilibrium and heavy element abundances in the range ~ 10^{-3} - 10^{-2} solar. Photoionization by a UV flux much softer than that predicted by Haardt & Madau (1996) for a background dominated by quasars can be ruled out. Finally, we find one system with a very low H I column density for which both photoionization and collisional ionization models yield a metallicity close to solar and a density that is inconsistent with gravitational confinement, unless the gas fraction is negligible.Comment: 16 pages, 16 figures, 7 tables. Accepted for publication in the Astrophysical Journal. Minor change

Determination of cloud microphysical properties by laser backscattering and extinction measurements

The extinction and backscattering of 514 nm laser radiation in polydisperse water droplet clouds was studied in the laboratory. Three cloud size distributions with modal diameters of 0.02, 5.0, and 12.0 microns were investigated. The relationships between the cloud optical parameters (attentuation coefficient, sigma and volume backscattering coefficient, Beta (sub pi)) and the cloud water content, C, were measured for each size distribution. It was found that a linear relationship exists between sigma and C and between beta (sub pi) and C for cloud water content values up to 3gm/cubic m. The linear relationships obtained, however, have slopes which depend on the droplet size distribution. For a given water content both sigma and beta (sub pi) increase as the modal diameter decreases. The measured data are compared with existing theoretical analyses and discussed in terms of thie application to lidar measurements of atmospheric clouds. It is concluded that the empirical information obtained can serve as a basis for quantitative lidar measurements