A new agents-based model for dynamic job allocation in manufacturing shopfloors

Market-based mechanisms such as the contract net protocol (CNP) are very popular for dynamic job allocation in distributed manufacturing control and scheduling. The CNP can be deployed with different configurations of the system elements. Every configuration corresponds to a basic or a hybrid topology. The subject of topology is generally discussed in the field of “distributed systems.” Inspired from the notion of topology in the distributed systems, this paper proposes a ring-like model as a competitor for the web-like CNP-based job allocation within the concept of holonic manufacturing systems. Details of the algorithm for scheduling and assignment of jobs to resources in the ring structure is presented and its performance is compared with both CNP-based distributed model, and the centralized conventional scheduling of a real manufacturing case study involving a major turbine production plant. Comparison of performance indicators such as time and cost of operations shows that the distributed models clearly outperform the conventional practice with meaningful impact on the production economy. As a possible implementation strategy, a hybrid switching model, composed of both competing models, is proposed

An E-Learning Investigation into Learning Style Adaptivity

Abstrac

Spectrum of one dimensional p-Laplacian operator with indefinite weight

This paper is concerned with the nonlinear boundary eigenvalue problem $$-(|u'|^{p-2}u')'=\lambda m|u|^{p-2}u\qquad u \in I=]a,b[,\quad u(a)=u(b)=0,$$ where $p>1$, $\lambda$ is a real parameter, $m$ is an indefinite weight, and $a$, $b$ are real numbers. We prove there exists a unique sequence of eigenvalues for this problem. Each eigenvalue is simple and verifies the strict monotonicity property with respect to the weight $m$ and the domain $I$, the k-th eigenfunction, corresponding to the $k$-th eigenvalue, has exactly $k-1$ zeros in $(a,b)$. At the end, we give a simple variational formulation of eigenvalues

Matching domain wall configuration and spin-orbit torques for very efficient domain-wall motion

In our numerical study, we identify the best conditions for efficient domain wall motion by spin-orbit torques originating from the Spin Hall effect or Rashba effect. We demonstrate that the effect depends critically on the domain wall configuration, the current injection scheme and the symmetry of the spin-orbit torque. The best identified configuration corresponds to a N\'eel wall driven by spin Hall Effect in a narrow strip with perpendicular magnetic anisotropy. In this case, the domain wall velocity can be a factor of 10 larger than that for the conventional current-in-plane spin-transfer torque.Comment: 9 pages, 3 figures, 1 tabl

Measurement of the intrinsic damping constant in individual nanodisks of YIG and YIG{\textbar}Pt

We report on an experimental study on the spin-waves relaxation rate in two series of nanodisks of diameter $\phi=$300, 500 and 700~nm, patterned out of two systems: a 20~nm thick yttrium iron garnet (YIG) film grown by pulsed laser deposition either bare or covered by 13~nm of Pt. Using a magnetic resonance force microscope, we measure precisely the ferromagnetic resonance linewidth of each individual YIG and YIG{\textbar}Pt nanodisks. We find that the linewidth in the nanostructure is sensibly smaller than the one measured in the extended film. Analysis of the frequency dependence of the spectral linewidth indicates that the improvement is principally due to the suppression of the inhomogeneous part of the broadening due to geometrical confinement, suggesting that only the homogeneous broadening contributes to the linewidth of the nanostructure. For the bare YIG nano-disks, the broadening is associated to a damping constant $\alpha = 4 \cdot 10^{-4}$. A 3 fold increase of the linewidth is observed for the series with Pt cap layer, attributed to the spin pumping effect. The measured enhancement allows to extract the spin mixing conductance found to be $G_{\uparrow \downarrow}= 1.55 \cdot 10^{14}~ \Omega^{-1}\text{m}^{-2}$ for our YIG(20nm){\textbar}Pt interface, thus opening large opportunities for the design of YIG based nanostructures with optimized magnetic losses.Comment: 4 pages, 3 figure

Noise Probe of the Dynamic Phase Separation in La2/3Ca1/3MnO3

Giant Random Telegraph Noise (RTN) in the resistance fluctuation of a macroscopic film of perovskite-type manganese oxide La2/3Ca1/3MnO3 has been observed at various temperatures ranging from 4K to 170K, well below the Curie temperature (TC = 210K). The amplitudes of the two-level-fluctuations (TLF) vary from 0.01% to 0.2%. We use a statistical analysis of the life-times of the TLF to gain insight into the microscopic electronic and magnetic state of this manganite. At low temperature (below 30K) The TLF is well described by a thermally activated two-level model. An estimate of the energy difference between the two states is inferred. At higher temperature (between 60K and 170K) we observed critical effects of the temperature on the life-times of the TLF. We discuss this peculiar temperature dependence in terms of a sharp change in the free energy functional of the fluctuators. We attribute the origin of the RTN to be a dynamic mixed-phase percolative conduction process, where manganese clusters switch back and forth between two phases that differ in their conductivity and magnetization.Comment: 15 pages, PDF only, Phys. Rev. Lett. (in press

Electronic control of the spin-wave damping in a magnetic insulator

It is demonstrated that the decay time of spin-wave modes existing in a magnetic insulator can be reduced or enhanced by injecting an in-plane dc current, $I_\text{dc}$, in an adjacent normal metal with strong spin-orbit interaction. The demonstration rests upon the measurement of the ferromagnetic resonance linewidth as a function of $I_\text{dc}$ in a 5~$\mu$m diameter YIG(20nm){\textbar}Pt(7nm) disk using a magnetic resonance force microscope (MRFM). Complete compensation of the damping of the fundamental mode is obtained for a current density of $\sim 3 \cdot 10^{11}\text{A.m}^{-2}$, in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime.Comment: 6 pages 4 figure