The government <Emphasis Type="Italic">is</Emphasis> here to help: a small business perspective

Public-private partnerships between government and industry have been increasingly used as a vehicle for defining and executing R&D activities. Stimulus of smaller technology enterprises in particular is important, and this article explores this topic from the policy level as well as from organizations “on the ground.” The story in brief: challenges and opportunities. Editor’s Note: A hypertext-enhanced version of this article is available on-line at www.tms.org/pubs/journals/JOM/0412/Hunt-0412.html Warren H. Hunt, Jr. is technical consultant at TMS.     

The China factor: Aluminum industry impact

The emergence of China as a global economic force has influenced the technical enterprise generally and a number of industries specifically. The aluminum industry is an example, with effects on consumption and demand as well as production and supply. This article reviews these areas from both a historical and future perspective. For more information, contact W.H. Hunt, Jr., TMS, 184 Thorn Hill Road, Warrendale, PA 15086; (724) 776-9000, ext. 226; (724) 776-3770; e-mail whunt@tms.org.     

Cadmium sulfide and cadmium selenide/cadmium sulfide nanoparticles stabilized in water with poly(cysteine acrylamide)

Cysteine acrylamide (N-acryloyl L-cysteine) stabilizes CdS nanoparticles as the particles form in aqueous dispersions. Cysteine acrylamide also exchanges for citrate on the surfaces of CdSe and core/shell CdSe/CdS nanoparticles to provide greater stability. Heating of the nanoparticle dispersions polymerizes the cysteine acrylamide on the surface to form a more efficient polydentate stabilizer. The polymer-coated nanoparticle dispersions are colloidally stable even after removal of low molecular weight solutes by dialysis. Emission quantum yields of the polymer-coated CdSe and CdSe/CdS samples were 0.9% and 2.6%, respectively, after aging of the samples in light. CdSe/CdS coated with poly(cysteine acrylamide) is colloidally stable for at least two years in the dark at 5 degrees C.     

Fabrication and measurement of low-stress membrane mirrors for adaptive optics

We have fabricated low-stress membranes from single-crystal silicon for use as deformable mirrors in adaptive optics. These membranes have lower stress than membranes made from silicon nitride or other materials and therefore are capable of greater deformation than previously used membrane mirrors. Membranes were assembled into devices by flip chip bonding to electrode chips with either 256 or 1024 electrodes. We have characterized devices with static and dynamic tests and compared their performance with an analytical model. We tracked the evolution of strain in the membrane during the device's fabrication and assembly and identified sources of stress and strain in this process. We identified boron dopant concentration as a critical determinant of intrinsic stress in the membrane.     

Effect of particle asphericity on single-scattering parameters: comparison between Platonic solids and spheres

The single-scattering properties of the Platonic shapes, namely, the tetrahedron, hexahedron, octahedron, dodecahedron, and icosahedron, are investigated by use of the finite-difference time-domain method. These Platonic shapes have different extents of asphericity in terms of the ratios of their volumes (or surface areas) to those of their circumscribed spheres. We present the errors associated with four types of spherical equivalence that are defined on the basis of (a) the particle's geometric dimension (b) equal surface area (A), (c) equal volume (V), and (d) equal-volume-to-surface-area ratio (V/A). Numerical results show that the derivations of the scattering properties of a nonspherical particle from its spherical counterpart depend on the definition of spherical equivalence. For instance, when the Platonic and spherical particles have the same geometric dimension, the phase function for a dodecahedron is more similar than that for an icosahedron to the spherical result even though an icosahedron has more faces than a dodecahedron. However, when the nonspherical and spherical particles have the same volume, the phase function of the icosahedral particle essentially converges to the phase function of the sphere, whereas the result for the dodecahedron is quite different from its spherical counterpart. Furthermore, the present scattering calculation shows that the approximation of a Platonic solid with a sphere based on V/A leads to larger errors than the spherical equivalence based on either volume or projected area.     

Computation of forced convection in slow flow through ducts and packed beds—I extensions of the graetz problem

A computational study of forced convection processes in ducts and packed beds at low Reynolds numbers has been made. The results give a better understanding of these processes, especially for small Peclet numbers. It is demonstrated that two distinct forms of Nusselt numbers are relevant for low Peclet numbeRs. One, used mostly by theorists, is related to the local driving force; the other, used mostly by experimentalists, is related to easily measurable temperatures and concentrations. As an example the Graetz problem has been solved numerically over a wide range of Peclet numbers, and new asymptotes have been obtained for the region of small Peclet numbers.     

The nuclear export policy of the Reagan administration

The Reagan Administration maintains the Carter Administration's objective of non-proliferation of nuclear weapons as being fundamental to US nuclear export policy. However, it sees the USA as having another important role to play in influencing the use of nuclear power and the trading of related goods and technologies in other countries. While the Administration believes its policies will prove beneficial to the USA, there is concern that trade considerations are being given priority over preventing the proliferation of nuclear weapons.     

An improved numerical interconversion for creep compliance and relaxation modulus

An imporved method for the numerical evaluation of the convolution integral in the relationship between creep compliance and relaxation modulus is discussed. The better approximation is obtained by the assumption that both functions can be assumed to be linear within a series of increasing time intervals which do not change as the calculation progresses. The calculation is carried out on both hypothetical and real examples which substantiates its applicability and accuracy.     

Internal friction,acoustic emission and fatigue in metals for high amplitude ultrasonic frequencies

High amplitudes (strains up to 3 × 10^?3) have been used in studying internal friction, acoustic emission and fatigue in metals. The internal friction in the high amplitude range is due to breakaway of dislocations from pinning points and by the generation of Frank-Read loops which results in plastic strain. There are two plastic regions, one when the added loops are held up by the grain boundaries, and the second when the loops break through the grain boundaries. In the second region, slip bands are produced in the metal. As the amplitude increases slip bands can join up and fatigue in the metal occurs. Ultrasonic frequencies are useful for studying fatigue since a large number of cycles can occur in a reasonable time.Acoustic emission—that is, a noise in the sample associated with the dislocation motion—can be studied by putting transducers on the sample. It is shown that the emission is closely associated with the internal friction since it goes through two regions in the plastic range.