Acoustic emission caused by large alternating strains

By vibrating specimens at very high strains, acoustic emission has been observed under controlled conditions. Continuous emission, in the form of strong harmonic generation, has been observed for polycrystalline copper and brass. In single crystal copper, a non-harmonic, burst type, response has also been observed. For brass the internal friction and the the third harmonic were analysed in terms of the dislocation models of Granato-Lücke and Peguin et al. A dynamic dislocation multiplication mechanism is suggested for the burst type emissions.     

A folded-diagram perturbation expansion for effective operators

Linked-diagram expansions for the model-space effective operators are derived for both open-shell nuclei and closed-shell nuclei. These expansions are derived using time-dependent perturbation theory and are given as a diagrammatic series which contains folded diagrams. Our results are in general agreement with the results obtained earlier by Brandow, but the general structure of the present expansions is perhaps simpler and more convenient for calculations. The projections of the true nuclear eigenfunctions onto the model space are required for the derivation of effective operators. These projections are obtained from the solution of the model-space eigenvalue problem defined by the energy-independent effective Hamiltonian. Methods for calculating the above diagrammatic series for effective operators are discussed.     

Analysis of lower modes of vibration of rectangular plates of linearly varying thickness

The title problem is solved assuming that the thickness varies symmetrically with respect to the x-axis. The edges defined by $\text{x = ± a/2}$ are elastically restrained against rotation while the remaining edges are clamped or simply supported.Approximate expressions for four of the lower natural frequencies of vibration (including the fundamental) are given.A forced vibrations situation is also dealt with.     

W-parity, octet dominance and the breaking of chiral symmetry

It is shown that W-invariance together with octet dominance restricts the SU(3) × SU(3) symmetry breaking Lagrangian to the representations (3, ) ( ,3), (6, ) ( ,6), (8,8) and (1,8) (8,1). In a nonlinear model, this Lagrangian predicts that the T = 2, S-wave π-π scattering length is zero; and when fitted to the empirical pion and K-meson masses, it predicts a T = 0 scattering length of 0.26m_π⁻¹. Compared with the (3, ) ( ,3) model, this model gives a larger (by a factor 8/3) nucleon σ-term, in agreement with recent calculations.     

Two ADPCM Algorithms with Widely Separated Error Recovery Times

Two adaptive differential pulse code modulation (ADPCM) algorithms are discussed that provide for transmitter-receiver resynchronization when used in a non-zero error rate digital transmission medium. Novel techniques are used in the algorithms (e.g., step-size bias) and in their extensive characterization (e.g., intermodulation distortion measurements).     

Two New Sesquiterpenes 3β-Hydroxycedrol and Widdringtonia Acid II-A Co-Crystal of β-Chamigrenic Acid and Hinokiic Acid

Widdringtonia acid II, a common acidic constituent in Juniperus and Widdringtonia species, and 3β-hydroxycedrol were isolated from juniperus squamata Lamb. Widdringtonia acid II was proved to be crystals derived from the 1:1 mixture of β-chamigrenic acid and hinokiic acid. The structures of β-chamigrenic acid and 3β-hydroxycedrol were established by chemical and physical evidence. In addition three other crystalline compounds, 7-oxototarol. hinokiol, and widdrol, were also identified.