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Chemistry

Chemical engineering & processing

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Displaying 551 - 575 of 781

Solution and Surface Composition Gradients via Microfluidic Confinement: Fabrication of a Statistical-Copolymer-Brush Composition Gradient

June 6, 2006
Author(s)
Chang Xu, Susan E. Barnes, Tao Wu, Daniel A. Fischer, Dean M. DeLongchamp, J Batteas, Kathryn L. Beers
A simple method to generate solution gradients through microfluidic confinement is described. The solution gradient inside a microchannel was formed by varying the relative infusion rates of two solutions that differed in compositions. The establishment

Inertance Tube Optimization for Pulse Tube Refrigerators

April 27, 2006
Author(s)
Ray Radebaugh, Michael A. Lewis, Ercang Lou, John M. Pfotenhauer, G. F. Nellis, L. F. Schunk
The efficiency of regenerative refrigerators is generally maximized when the pressure and flow are in phase near the midpoint of the regenerator. Such a phase relationship minimizes the amplitude of the mass flow for a given acoustic power flow through the

Regenerator Operation at Very High Frequencies for Microcryocoolers

April 27, 2006
Author(s)
Ray Radebaugh, Agnes A. O'Gallagher
The size of Stirling and Stirling-type pulse tube cryocoolers is dominated by the size of the pressure oscillator. Such cryocoolers typically operate at frequencies up to about 60 Hz for cold-end temperatures above about 60 K. Higher operating frequencies

Relaxation Effects in Small Critical Nozzles

January 1, 2006
Author(s)
Aaron N. Johnson, C L. Merkle, Michael R. Moldover, John D. Wright
We computed the flow of four gases (He, N 2, CO 2, and SF 6) through a critical nozzle by augmenting traditional computational fluid dynamics (CFD) with a rate equation that accounts for τ relax, a species-dependent relaxation time that characterizes the

Microscale Heat Transfer at Low Temperatures

September 26, 2005
Author(s)
Ray Radebaugh
This paper discusses the fundamentals and applications of heat transfer in small space and time domains at low temperatures. The modern trend toward miniaturization of devices requires a better understanding of heat transfer phenomena in small dimensions

Microfluidic Platform for the Generation of Organic-Phase Microreactors

April 1, 2005
Author(s)
Zuzanna T. Cygan, J Cabral, Kathryn L. Beers, Eric J. Amis
Rapid prototyping photolithography of a thiolene based resin was used to fabricate microfluidic devices stable to aliphatic and aromatic organic solvents. The swelling of the thiolene resin in various organic solvents was quantified and the solvent

Development of a Microfluidic Rheometer for Complex Fluids

January 1, 2005
Author(s)
Jai A. Pathak, Robert F. Berg, Kathryn Beers
Our group has recently published a report of a combinatorial rheometer/viscometer developed in our lab, based on the princinple of a damped harmonic oscillator. In this paper, we describe a modification of this approach to scale down this viscometer to the

Refrigeration for Superconductors

September 20, 2004
Author(s)
Ray Radebaugh
Temperatures in the range of 0.05 to 80 K are required for most applications of superconductors. Refrigeration powers range from fractions of a watt for many electronic applications to kilowatts for some large magnet and power applications. This paper

A Buckling-Based Metrology for Measuring the Elastic Moduli of Polymeric Thin Films

August 1, 2004
Author(s)
Christopher Stafford, Eva Simonyi, C Harrison, Kathryn Beers, Alamgir Karim, Eric J. Amis, Mark R. VanLandingham, H C. Kim, W Volksen, R D. Miller
As technology continues towards smaller, thinner and lighter devices, more stringent demands are placed on thin polymer films as diffusion barriers, dielectric coatings, electronic packaging and so on. Therefore, there is a growing need for testing
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