Instructional texts rewritten by five expert teams: Revisions and retention improvements.

700 undergraduates were tested in 3 experiments on original or rewritten versions of 52 instructional texts about Army job tasks, general science, philosophy, and history. Five experts had rewritten various sets of the texts and stated hypotheses about the efficacious features of their revisions. We tested their hypotheses and several others. Recall and recognition tests were given immediately and after a 24-hr delay. Results showed that revisions made by 3 of the 5 experts improved retention of text information. The kind and number of revisions and improvements varied across the text sets. Most expert hypotheses were not supported, and they made many revisions they were declaratively unaware of. Some of our hypotheses about the revision features were supported, but different features were effective for different sets of texts. It was concluded that some experts have effective knowledge about improving instructional text, but it exists primarily in procedural form. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

NMR Line Shape-Spin-Lattice Relaxation Correlation Study of Portland Cement Hydration

The proton free induction decay of a portland cement paste in an advanced stage of hydration can be roughly divided into three main components: (1) a component with a very short spin-spin relaxation time, T², representing the protons of the solid OH groups and the water of crystallization, (2) a component with an intermediate T, representing the bonded water in the gel phase, and (3) a third component with a relatively long T² representing the water in the micropores and layers. The dependences of the intensities, T²'s, and spin-lattice relaxation times (T¹'s) of these three components on the cement hardening time have been determined. The proton spin-lattice relaxation time of the "solid" component increases with hardening time whereas T¹ decreases for the other two components. The observed time dependence of the diffusion coefficient, D, of water in a tricalcium silicate paste supports the findings of the above correlation study.     

Impact Fracture of Thermally Tempered Glass Helicopter Windshields

In-service fracture of helicopter windshields was studied. Simulated catastrophic fracture tests were conducted by firing alumina and steel spheres onto stationary tempered and as-received glass panels. The results were studied by Hertzian analysis and modified Auerbach's relations. Thermally tempered glass shows much higher impact resistance than that estimated from superposition of residual stresses. Subcritical impact sites exhibit slow crack growth in tempered plates, eventually leading to fracture of the entire plate.     

Critical Review of the Thermophysical Properties of Fast-Reactor Fuel

This paper identifies the fuel properties for which more data are needed for fast-reactor safety analysis. In addition, a brief review is given of current research on the vapor pressure over liquid UO₂ and (U, Pu)O_2-x the solid-solid phase transition in actinide oxides, and the thermal conductivity of molten urania.     

The function of bleaching earths in the processing of palm,palm kernel and coconut oils

The results presented in the literature, which attempt to elucidate the mechanisms by which triglyceride oils are bleached by earths, are reviewed. The impact of this work and how the mechanistic proposals affect changes in oil properties are considered, with particular emphasis on the needs of the palm oil processor. Important properties include color, metals and phosphorus content and oxidative stability of the oil. Investigations made in our own laboratories have been aimed at elucidating the effect of varying physical and chemical properties of the bleaching earth on the quality of bleached and deodorized oils. Techniques used in this work are pore-size distribution, surface area, scanning and transmission electron microscopy and a variety of chemical and X-ray analysis methods. The ability to vary such parameters in montmorillonite clays by alteration of process conditions to give materials with specific performance characteristics is demonstrated. Comparisons are made between acid-activated montmorillonites and other clay types.     

Hydrodynamic loadings due to the motion of large offshore structures

A very effective non-reflecting boundary condition is proposed for the three-dimensional finite element analysis of hydrodynamic loads on offshore structures under motion due to earthquake, waves or machinery forces. The effect of surface waves is considered and the analysis is conducted in the frequency domain. The structure is assumed to be sufficiently large such that the non-linear effect of drag force is negligible. The unbounded extent of water surrounding the structure is assumed to be incompressible. The boundary condition, which is derived for the general analysis of structure-water interaction, is found to depend on the frequency of excitation, the location of the truncation boundary and the depth of water in the far field. Through some simplified numerical examples, it is shown that the proposed technique is very efficient for a wide range of the frequency of excitation. Incorporation of the boundary condition into a finite element program requires practically no extra effort.     

Optical networks for local loop applications

Some of the options for optical technology within the local loop environment are examined. In particular, passive shared access networks have been considered in some detail. These networks show great promise for delivering existing telephone services to small to medium business customers (4-30 lines) economically by the early 1990s. Extending fiber to the home will also be possible by virtue of a similar passive network infrastructure for customers requiring new broadband services beyond the single telephone line. For one-line plain old telephone service (POTS) customers, an intermediate approach of terminating the fiber network at the final network distribution point, with copper retained for the final leg, may be used prior to the provision of broadband services. A key feature of the passive optical network architecture is the use of wavelength-division multiplexing (WDM) as an upgrade strategy, allowing graceful upgrading from telephone services to multichannel high-definition television (HDTV) on gigabit/second bearers and full two-way switched broadband services employing wavelength routing across the network