Characteristics of partially filled Helmholtz resonators

In this work we have developed a technique for the measurement of the resonance curve of Helmholtz resonators as a function of filling with beads and sands of different sizes, and water as the reference. Our measurements allowed us to observe very different behaviors of resonance frequencies and resonance half-widths as a function of the size of the sand grains and the beads. By comparing results for beads and water we were able to prove that the sound penetrates the interstitial space between the beads. This was confirmed by measurements of the resonance properties in resonators filled with spherical beads whose experimentally determined filling factor is close to the random filling factor of about 0.54. The similar behavior of the frequency and half-width of resonance of sand-filled resonators of three different sizes allowed us to suggest that sound penetrates the sand in the same way as it does the beads.Comment: 10 pages, one column, 9 figures, regular pape

Melting of regular and decoupled vortex lattices in BSCCO crystals

The angular dependence of the first-order phase transition (FOT) in the vortex lattice in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ crystals was investigated by a low frequency AC shielding technique (with the AC field $\parallel c$), in which the static-field component parallel to $c$- ($H_{\perp}$) was varied with the in-plane field $H_{\parallel}$ held constant. The linear decrease of the FOT field $H_{\perp}^{FOT}$ with increasing $H_{\parallel}$ ends at a temperature--dependent critical value of $H_{\parallel}$. A new transition, marked by the abrupt drop of the $ab$-plane shielding current, appears at this point. We draw a new phase diagram with $H_{\parallel}$ and $H_{\perp}$ field components as coordinates; this features at least two distinct regions in the vortex solid phase, that are determined by the different interplay between the pancake vortex-- and Josephson vortex lattice.Comment: 2 pages, 2 figures Paper submitted to the conference proceedings of M2S-2000 Houston, T

Axially linear slopes of composition for “delta” crystals

“Delta” crystals are solid solutions of miscible materials with large lattice parameter differences which contain high concentration gradients in one direction (parallel to a lattice plane strongly diffracting X-rays). The system GaSb-InSb has been chosen as suitable for study. By means of a “gradient projection method”, the growth of nearly linear composition profiles with relatively steep slopes of the lattice parameter (up to (Δa/ ) / Δz = 8.3% cm-1), adjustable by the temperature gradient, have been performed. However, the grown ingots were not monocrystalline due to the use of too high a growth rate

Supercooling of the high field vortex phase in single crystalline BSCCO

Time resolved magneto-optical images show hysteresis associated with the transition at the so-called ``second magnetization peak'' at B_sp in single-crystalline Bi_2Sr_2CaCu_2O_8+d. By rapid quenching of the high-field phase, it can be made to persist metastably in the sample down to fields that are nearly half B_sp.Comment: 2 pages, 2 figures Submitted to the conference proceedings of M2S-VI, February 200, Housto

Observation of correlated vortex flow in NbSe2 with magnetic decoration

Article / Letter to editorLeids Instituut Onderzoek Natuurkund

Predicting dislocation climb: Classical modeling versus atomistic simulations

The classical modeling of dislocation climb based on a continuous description of vacancy diffusion is compared to recent atomistic simulations of dislocation climb in body-centered cubic iron under vacancy supersaturation [Phys. Rev. Lett. 105 095501 (2010)]. A quantitative agreement is obtained, showing the ability of the classical approach to describe dislocation climb. The analytical model is then used to extrapolate dislocation climb velocities to lower dislocation densities, in the range corresponding to experiments. This allows testing of the validity of the pure climb creep model proposed by Kabir et al. [Phys. Rev. Lett. 105 095501 (2010)]