Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

liquid crystal host. Since the ultimate goal of this research is to produce interferometers capable of phase shifting at video frame
rates, we will quantify the difference in switching times between ferroelectric and nematic liquid crystals. While we have more
experience with nematic crystals, they typically switch more slowly than ferroelectric cells. As part of that effort, we will investigate
the difference in the modulation of the interferograms as a function of the type of liquid crystal in the cell. Because the temporal
switching response of a liquid crystal cell is directly related its thickness, we intend to explore techniques required to produce
cells that are as thin as possible. However, the cells must still produce a total phase shift of two pi radians.
Author (revised)
Diffraction; Liquid Crystals; Interferometers
20010024945 Naval Research Lab., Plasma Physics Div., Washington, DC USA
DSD-A Particle Simulation Code for Modeling Dusty Plasmas
Joyce, G., Naval Research Lab., USA; Lampe, M., Naval Research Lab., USA; Ganguli, G., Naval Research Lab., USA; Proceedings
of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference; December 2000, pp. 1140-1142; In English;
See also 20010024890; No Copyright; Abstract Only; Available from CASI only as part of the entire parent document
The NRL Dynamically Shielded Dust code (DSD) is a particle simulation code developed to study the behavior of strongly
coupled, dusty plasmas. The model includes the electrostatic wake effects of plasma ions flowing through plasma electrons, collisions
of dust and plasma particles with each other and with neutrals. The simulation model contains the short-range strong forces
of a shielded Coulomb system, and the long-range forces that are caused by the wake. It also includes other effects of a flowing
plasma such as drag forces. Magnetic fields may also be included in the formalism. In order to model strongly coupled dust in
plasmas, we make use of the techniques of molecular dynamics simulation, PIC simulation, and the ’particle-particle/particlemesh’
(P3M) technique of Hockney and Eastwood. We also make use of the dressed test particle representation of Rostoker and
Rosenbluth. Many of the techniques we use in the model are common to all PIC plasma simulation codes. The unique properties
of the code follow from the accurate representation of both the short-range aspects of the interaction between dust grains, and
long-range forces mediated by the complete plasma dielectric response. If the streaming velocity is zero, the potential used in the
model reduces to the Debye-Huckel potential, and the simulation is identical to molecular dynamics models of the Yukawa potential.
The model basically represents the dust as simulation particles interacting via the dressed potential. The plasma appears only
implicitly through the plasma dispersion function, so it is not necessary in the code to resolve the fast plasma time scales.
Author (revised)
Computerized Simulation; Dust; Collisions; Plasmas (Physics); Crystal Structure; Liquid Phases
20010024946 Michigan Univ., Dept. of Chemical Engineering, Ann Arbor, MI USA
Aggregation and Gelation of Anisometric Colloidal Particles: Preliminary Results and Research Plan
Solomon, Michael J., Michigan Univ., USA; Varadan, Priya, Michigan Univ., USA; Proceedings of the Fifth Microgravity Fluid
Physics and Transport Phenomena Conference; December 2000, pp. 1143-1145; In English; See also 20010024890; No Copyright;
Abstract Only; Available from CASI only as part of the entire parent document
A research plan for the study of the structure and dynamics of aggregates and gels of colloidal rods and platelets by means
of static and dynamic light scattering is presented. Studies under both quiescent and flow conditions are envisaged. For purposes
of comparison, preliminary results of the structure and dynamics of spherical colloidal gels are reported. The materials studied,
sterically stabilized spherical colloidal silica suspended in hexadecane, form stable, reversible gels that can be studied by light
scattering in the volume fraction range 0.01 - 0.10. The gels allow divergences of characteristic times at the gel point to be sensitively
probed by manipulating temperature.
Author (revised)
Aggregates; Gels; Colloids; Dynamic Characteristics; Structural Analysis
20010024947 Kansas State Univ., Dept. of Physics, Manhattan, KS USA
Gelation Kinetics in Aerosols
Sorensen, C., Kansas State Univ., USA; Chakrabarti, A., Kansas State Univ., USA; Hagemann, W., Kansas State Univ., USA;
Fischbach, D., Kansas State Univ., USA; Shi, D., Kansas State Univ., USA; Fry, D., Kansas State Univ., USA; Proceedings of
the Fifth Microgravity Fluid Physics and Transport Phenomena Conference; December 2000, pp. 1146-1147; In English; See also
20010024890; No Copyright; Abstract Only; Available from CASI only as part of the entire parent document
Our recent work has demonstrated that an aerogelation process occurs in acetylene diffusion flames and is responsible for
the formation of millimeter sized soot. This work is the first demonstration of gelation in the aerosol phase. Furthermore, our measurements
indicate that the aggregates grow too quickly (by a factor of 400) to be described by the Smoluchowski Equation (SE).
Based on our previous measurements of the rate constant in dilute aerosol systems which were in agreement with kinetic theory,
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