Optimal Algorithms for the Inhomogeneous Spiked Wigner Model

In this paper, we study a spiked Wigner problem with an inhomogeneous noise profile. Our aim in this problem is to recover the signal passed through an inhomogeneous low-rank matrix channel. While the information-theoretic performances are well-known, we focus on the algorithmic problem. We derive an approximate message-passing algorithm (AMP) for the inhomogeneous problem and show that its rigorous state evolution coincides with the information-theoretic optimal Bayes fixed-point equations. We identify in particular the existence of a statistical-to-computational gap where known algorithms require a signal-to-noise ratio bigger than the information-theoretic threshold to perform better than random. Finally, from the adapted AMP iteration we deduce a simple and efficient spectral method that can be used to recover the transition for matrices with general variance profiles. This spectral method matches the conjectured optimal computational phase transition.Comment: 17 pages, 5 figure

Centrifugal Modeling of a Pile Under Vertical Random Excitation

Data from the experimental modeling of a pile in a geotechnical centrifuge are compared with analytical results. The model pile was subjected to vertical random excitation with subsequent determination of the compliance function in the frequency domain. This compliance function was found to be consistent with theory. An absorbing boundary was used to minimize reflected wave energy from the centrifuge container boundaries

Estimated stress and friction distributions on tool rake face in the medium density fiberboard cutting process

This paper presents a model of load distribution on the cutting edge of a tool during machining Medium Density Fibreboard (MDF). A series of cutting tests has been carried out with tools having designated rake face contact lengths. Utilising the experimental data and a mechanics approach developed earlier by the third author, a model to estimate the distribution of stresses and friction on the rake face is developed. The model provides an essential step in the design and development of cutting edge geometry to prevent early edge failure and to control and reduce thermal/mechanical loading of the tool wedge

Dynamic Centrifuge Experiment on a Cantilever Retaining Wall

Seismic loads on a tall, cantilever retaining wall were studied using centrifuge modeling. An aluminum wall (55\u27 prototype) retaining dry, cohesionless backfill was subjected to two successive dynamic events. The backfill surface was horizontal and even with the top of the wall. The input motion was supplied via a servo-controlled, electro-hydraulic shake table. The input motion was roughly sinusoidal with peak horizontal accelerations of approximately 0.2g and 0.4g for the first and second dynamic events, respectively. The input motion frequency was 1 hz at prototype scale. Lateral earth pressures on the wall, wall displacement, and accelerations of the wall and backfill soil were measured. Pressure transducers were used to directly measure lateral earth pressures on the wall. The magnitudes of the lateral earth pressures were compared with values calculated using the Mononobe-Okabe method. Preliminary results indicate that calculated pressures are higher than the measured pressures

Kl4K_{l4} - Decays Beyond One Loop

The matrix elements for K\rightarrow \pi \pi \l \nu decays are described by four form factors $F,G,H$ and $R$. We complete previous calculations by evaluating $R$ at next-to-leading order in the low-energy expansion. We then estimate higher order contributions using dispersion relations and determine the low-energy constants $L_1,L_2$ and $L_3$ from data on $K_{e4}$ decays and on elastic pion scattering. Finally, we present predictions for the slope of the form factor $G$ and for total decay rates.Comment: 31 pages, LaTex, 3 figs. (two figures appended as postscript file), BUTP-94/4,ROMF2 94/0

Isospin relaxation time in heavy-ion collisions at intermediate energies

Using an isospin-dependent transport model, we have studied the isospin and momentum relaxation times in the heavy residues formed in heavy-ion collisions at intermediate energies. It is found that only at incident energies below the Fermi energy, chemical or thermal equilibrium can be reached before dynamical instability is developed in the heavy residues. Also, the isospin relaxation time is shorter (longer) than that for momentum at beam energies lower (higher) than the Fermi energy.Comment: 8 pages Latex + 2 ps Figs.; Phys. Rev. C in pres

Omnidirectional stretchable inorganic-material-based electronics with enhanced performance

Inorganic material‐based devices are well known for their high performance, excellent stability, and hence suitability for fast computation and communication. But their nonflexibility and nonstretchability often hinder their application in several emerging areas where conformability with irregular 3D surfaces is required in addition to the high performance. Herein, with honeycomb like patterns, the omnidirectional stretchability and conformability of inorganic material‐based device are demonstrated without sacrificing the performance. The simple method presented here facilitates the transfer of patterned inorganic material‐based devices from rigid poly(methyl methacrylate) (PMMA)/glass substrate onto flexible/stretchable substrate such as polydimethylsiloxane simply by placing a water droplet at the PMMA/glass interface. As a proof of concept, the intrinsically brittle indium–gallium–zinc oxide (IGZO)‐based stretchable photodetector devices are fabricated. These devices can be stretched up to 10% without performance degradation, which is a significant improvement considering the less than ≈1% fracture limit of IGZO. With Au decoration, these devices show 127‐fold higher responsivity (295.3 mA W−1) than planar IGZO devices. The higher fracture strain together with the omnidirectional stretchability underpinned by the honeycomb pattern could allow presented devices to conform to complex hemispherical surfaces such as the human eyes, thus showing significant potential for future high‐performance stretchable electronics

Low-Energy Photon-Photon Collisions to Two-Loop Order

We evaluate the amplitude for $\gamma \gamma \rightarrow \pi^0 \pi^0$ to two loops in chiral perturbation theory. The three new counterterms which enter at this order in the low-energy expansion are estimated with resonance saturation. We find that the cross section agrees rather well with the available data and with dispersion theoretic calculations even substantially above threshold. Numerical results for the Compton cross section and for the neutral pion polarizabilities are also given to two-loop accuracy.Comment: 48 pages, LaTex, 11 figs. (figures not included; available upon request from [email protected]),BUTP-93/18,LNF-93/077(P),PSI-PR-93-1

Nearest pattern interaction and global pattern formation

We studied the effect of nearest pattern interaction on a globally pattern formation in a 2-dimensional space, where patterns are to grow initially from a noise in the presence of periodic supply of energy. Although our approach is general, we found that this study is relevant in particular to the pattern formation on a periodically vibrated granular layer, as it gives a unified perspective of the experimentally observed pattern dynamics such as oscillon and stripe formations, skew-varicose and crossroll instabilities, and also a kink formation and decoration