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Displaying 1026 - 1050 of 1856

Impact of molecular mass on the elastic modulus of polystyrene thin films

July 31, 2010
Author(s)
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
Euler wrinkling was used to determine the elastic modulus at ambient temperature of polystyrene (PS) films of varying thickness and relative molecular mass (Mn). A range of Mn from 1.2 kg/mol to 990 kg/mol was examined to determine if the molecular size

Forced Assembly and Mixing of Melts via Planar Polymer Micro-Mixing

June 24, 2010
Author(s)
Doyoung Moon, Kalman D. Migler
The ability to force immiscible polymers into specific, targeted structures would enable the generation of blends with tailored performance by exploiting the intimate relationship between structure and blend properties. Here we present a strategy for the

High frequency characterization of a Schottky contact to a GaN nanowire bundle

June 16, 2010
Author(s)
Chin J. Chiang, Thomas M. Wallis, Dazhen Gu, Atif A. Imtiaz, Pavel Kabos, Paul T. Blanchard, Kristine A. Bertness, Norman A. Sanford, Kichul Kim, Dejan Filipovic
A GaN nanowire (NW) Schottky contact was characterized up to 10 GHz. Using a calibration procedure and circuit model a capacitance-voltage (CV) curve was obtained, from which a carrier concentration was calculated for the first time. These results

Tooth chipping can reveal bite forces and diets of fossil hominins

June 16, 2010
Author(s)
Paul Constantino, James J. Lee, H Chai, Bernhard Zipfel, Charles Ziscovici, Brian R. Lawn, Peter Lucas
Fossil hominin tooth enamel often exhibits antemortem edge chipping (Robinson 1954; Tobias 1967; Wallace 1973). Here we apply a simple fracture equation to estimate peak bite forces from the sizes of such chips. This equation, previously validated by

FRACTURE OF TOOTH ENAMEL FROM INCIPIENT MICROSTRUCTURAL DEFECTS

June 14, 2010
Author(s)
H Chai, James J. Lee, Brian R. Lawn
We present definitive evidence for crack growth from internal defects called 'tufts' in human enamel. Side walls of slices sawn from extracted human teeth are observed during loading to 'failure'. 'Longitudinal' and 'transverse' slices (parallel and normal

Effects of fiber gripping methods on single fiber tensile test using Kolsky bar

June 10, 2010
Author(s)
Jae Hyun Kim, Richard L. Rhorer, Haruki Kobayashi, Walter G. McDonough, Gale A. Holmes
Preliminary data by Ming Cheng et al. indicate minimal impact of strain rate on the tensile stress-strain behavior of Kevlar. However, technical issues associated with specimen preparation appear to limit the number of samples and show an undesirable

Observations of Nanobubble Formation on Carbon Nanotubes

May 28, 2010
Author(s)
Andrew J. Slifka, Damian S. Lauria, Gurpreet Singh, Roop L. Mahajan
We used an optical trap and a high-speed camera to image bubble initiation on the surface of multi-walled carbon nanotubes. The laser wavelength was 1064 nm and the average power was 100 mW. This is the first demonstration of bubble formation on individual

Mechanical properties of one-dimensional nanostructures

May 23, 2010
Author(s)
Gheorghe Stan, Robert F. Cook
The elastic mechanical properties of one-dimensional nanostructures are considered, with an emphasis on the use of contact-resonance atomic force microscopy methods to determine elastic moduli. Various methods used to determine elastic moduli of one

Core-shell composite of SiCN and multiwalled carbon nanotubes from Toluene dispersion

May 21, 2010
Author(s)
John H. Lehman, Katherine E. Hurst, Gurpreet Singh, Elisabeth Mansfield, John D. Perkins, Christopher L. Cromer
Carbon nanotubes are known to have high thermal conductivity, and in bulk form, a topology that could constitute the matrix of an inhomogeneous solid. Among the promised applications of carbon nanotubes is a composite material that is practical for thermal

A Graphical Approach for Assessing High Strength Fiber Performance

May 20, 2010
Author(s)
Walter G. McDonough, Gale A. Holmes, Amanda L. Forster, Kirk D. Rice
The design and materials used for bullet resistant body armor have evolved continuously to keep up with the threats. In this paper, a graphical approach is presented that plots the potential strain energy absorption of some common high performance fibers

High Speed Fiber Testing: The Single Fold Test

May 20, 2010
Author(s)
Haruki Kobayashi, Walter G. McDonough, Alexander J. Shapiro, Jae H. Kim, Stefan D. Leigh, Amanda L. Forster, Kirk D. Rice, Gale A. Holmes
The failure of a first responder s body armor has prompted research to assess the long-term durability and effectiveness of current and future soft body armor products. Prior work in this laboratory described a 10 % drop in tensile strength and 15 % drop

GRADED STRUCTURES FOR ALL-CERAMIC RESTORATIONS

May 17, 2010
Author(s)
Yu Zhang, H Chai, Brian R. Lawn
One failure mode of all-ceramic crown restorations is radial cracking at the cementation surface, from occlusally-induced flexure of the stiffer crown layer on the softer dentin underlayer. We hypothesize that such failure may be substantially mitigated by

Predicting the In-Service Performance of Materials Exposed to Outdoor Weathering

May 12, 2010
Author(s)
Christopher C. White, Kar T. Tan, Donald L. Hunston
Test methods were developed to duplicate the failure modes that occur to sealants during exposure in structures. The methods used a systematic approach to identify independent and synergistic effects of various aging factors on the durability of sealants

Gate Dielectrics Year-In-Review

May 3, 2010
Author(s)
Jason P. Campbell
The gate dielectrics year-in-review includes a comprehensive examination of the past year s reports which detail gate stack reliability issues and the corresponding physical mechanisms which limit the performance and lifetimes of advanced devices. The

Novel CaF2 Nanocomposite with High Strength and F Ion Release

May 3, 2010
Author(s)
Hockin D. Xu, Jennifer L. Moreau, Limin Sun, Laurence Chow
Secondary caries and restoration fracture remain the two most common problems. The objectives of this study were to develop stress-bearing, fluoride-releasing nanocomposites. Novel CaF2 nanoparticles (56-nm) were synthesized via spray-drying and
Displaying 1026 - 1050 of 1856