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Displaying 1601 - 1625 of 1739

An Optical Sensor for Polymer Injection Molding

January 1, 2000
Author(s)
Anthony J. Bur, C L. Thomas
An optical sensor using fiber optics to access the mold cavity was used to monitor the mold filling and cooling phases of injection molding. The sensor consists of a sapphire window at the end of a sleeved ejector pin into which an optical fiber is

Direct Measurement of Valence-Charge Asymmetry by X-Ray Standing Waves

January 1, 2000
Author(s)
Joseph C. Woicik, E Nelson, P Pianetta
By detecting valence-photoelectron under condition of strong x-ray Bragg reflection, we have determined that a majority of GaAs valence charge resides on the anion sites of this heteropolar crystal, in quantitative agreement with the Ga-As bond polarity as

Factors That Affect Adhesion at the Fiber-Matrix Interface in Composites

January 1, 2000
Author(s)
Gale A. Holmes, E Feresenbet, E Pohl, Walter G. McDonough, D T. Raghavan, D Thompson
The development of methods to assess adhesion at the fiber-matrix interface in composite materials has been driven primarily by the recognition that the interface or interphase in many composite materials has a profound affect on the onset of failure in

Layer Perfection in Ultrathin InAS Quantum Wells in GaAs(001)

January 1, 2000
Author(s)
J A. Gupta, S P. Watkins, E D. Crozier, Joseph Woicik, D A. Harrison, D Jiang, I J. Pickering, B A. Karlin
X-ray diffraction (XRD), X-ray standing wave (XSW) and X-ray absorption fine structure (XAFS) measurements were used to assess the layer perfection and positions of 1 and 2 monolayer (ML) InAs quantum wells buried in GaAs(001). Photoluminescence (PL)

Model of Fatigue Damage in Strain Rate-Sensitive Composite Materials

January 1, 2000
Author(s)
S K. Lee, Tinh Nguyen, Tze J. Chuang
A Fatigue damage accumulation model based on the Paris law has been proposed for strain rate-sensitive polymer composite materials. A pre-exponent factor c 2/f and strain-rate sensitive exponent n is introduced. Numerical analysis of the model has been

Real-Time Dielectric Measurements During Extrusion of Filled Polymers

January 1, 2000
Author(s)
M M. McBrearty, Anthony J. Bur, S C. Roth
Mineral fillers are added to extend and modify physical properties of polymers. To achieve porcessing control of mixing, real-time measurements are needed. Previuos work has shown that dielectric sensors can measure concentrations of fillers in non-polar

Single Fiber Composites: A New Methodology for Determining Interfacial Shear Strength

January 1, 2000
Author(s)
Gale A. Holmes, Donald L. Hunston, Walter G. McDonough, R C. Peterson
One of the critical factors controlling the long-term performance and durability of composites in structural applications is the interfacial shear strength (IFSS). The single fiber composite (SFC) test has been viewed by many as the best test for

The Effect of Processing on Interfacial Shear Properties of Composite Materials

January 1, 2000
Author(s)
Walter G. McDonough, Joy P. Dunkers, Gale A. Holmes, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The objective of our research was to extend the use of the single fiber fragmentation test to include fast reacting resin systems and to determine the effect of gelation time on interfacial shear properties. To do this work, we developed a processing

Ordering/Displacive Phase Transformations in Ca 4 Nb 2 O 9

December 17, 1999
Author(s)
Igor Levin, Leonid A. Bendersky, Robert S. Roth, Terrell A. Vanderah
Four Ca 4Nb 2O 9=Ca(Ca1/3Nb 2/3)O 3 polymorphs based on ABO 3 perovskite-like structure were identified. These polymorphs feature three different arrangements of Ca/Nb cations on B-sites of perovskite. In three of the polymorphs, cation ordering is

Modeling Wear of Ceramics Based on Wear Maps

December 2, 1999
Author(s)
Stephen M. Hsu, M C. Shen
Ceramics are increasingly being considered for wear resistant applications. The design and prediction of ceramics wear, however are lacking behind metals. This paper addresses the ability to predict wear of ceramics by examining a large data base of four

A Novel Multiaxial Wear Tester for Accelerated Testing of Materials

December 1, 1999
Author(s)
M C. Shen, Stephen M. Hsu, John A. Tesk, A Christou
A versatile wear tester has been designed and built. The initial study showed that that with this tester, tes procedures can be developed to achieve clinically relevant simulations in a short time. With the continuously monitored force traces, this tester
Displaying 1601 - 1625 of 1739