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Selected Works

1989

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Articles 1 - 3 of 3

Full-Text Articles in Engineering

Progress In The Development Of Hemp Protection Standards For C3i Facilities, George H. Baker, Clinton R. Gordon Apr 1989

Progress In The Development Of Hemp Protection Standards For C3i Facilities, George H. Baker, Clinton R. Gordon

George H Baker

DoD is involved in EMP standards development efforts which culminate 25 years of research. This paper previews an EMP protection standard for fixed, ground-based communication facilities. The standard uses a low-risk hardening approach which depends on an electromagnetic barrier comprised of a conducting shield to prevent harmful transients from reaching communication electronics. The standard is the first of its kind and is being instituted as MIL-STD-188-125.

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Pitch Of Complex Tones With Many High‐Order Harmonics, Adrianus J. M. Houtsma, J. Smurzynski Jan 1989

Pitch Of Complex Tones With Many High‐Order Harmonics, Adrianus J. M. Houtsma, J. Smurzynski

Jacek Smurzynski

Pitch identification and pitch discrimination experiments were performed for complex tones with missing fundamentals between 200 and 300 Hz and with many successive harmonics varying from low (below the 10th) to high (above the 25th) harmonic order. Identification performance was found to degrade with increasing harmonic order from an essentially perfect to an asymptotic level that was clearly less than perfect but much better than chance. Just‐noticeable differences in (missing) fundamental frequency were found to increase, with increasing harmonic order, from a fraction of 1 Hz to an asymptotic level of about 5 Hz. Influence of phase was found only …

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Thermal And Rheological Properties Of A Liquid-Crystalline Polyurethane, William Macknight, Peter J. Stenhouse, Enrique M. Valles, Simon W. Kantor Dec 1988

Thermal And Rheological Properties Of A Liquid-Crystalline Polyurethane, William Macknight, Peter J. Stenhouse, Enrique M. Valles, Simon W. Kantor

William MacKnight

A novel liquid-crystalline polyurethane (LCPU) was synthesized by the condensation of
2,4-toluenediisocyanate and 4,4'-bis(6-hydroxyhexoxy)biphenyl. Solution polymerization in dimethylformamide
produced intrinsic viscosities in the range 0.30-0.57 dL/g. Differential scanning calorimetry shows a crystalline
melting transition that is highly dependent on molecular weight and thermal history and a clearing transition
that is virtually independent of both. Parallel-plate rheometry results are consistent with the presence of
a liquid-crystalline phase, coexisting with a small amount of three-dimensional crystallinity, between 152 and
166 °C. Dynamic mechanical measurements reveal an unusually high elastic modulus of 180 MPa in the plateau
region above Tg, compared with 6 …

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