Radial breathing-mode frequency of elastically confined spherical nanoparticles subjected to circumferential magnetic field

Knowledge of the vibrational properties of nanoparticles is of fundamental interest since it is a signature of their morphology, and it can be utilized to characterize their physical properties. In addition, the vibration characteristics of the nanoparticles coupled with surrounding media and subjected to magnetic field are of recent interest. This paper develops an analytical approach to study the radial breathing-mode frequency of elastically confined spherical nanoparticles subjected to magnetic field. Based on Maxwell's equations, the nonlocal differential equation of radial motion is derived in terms of radial displacement and Lorentz's force. Bessel functions are used to obtain a frequency equation. The model is justified by a good agreement between the results given by the present model and available experimental and atomic simulation data. Furthermore, the model is used to elucidate the effect of nanoparticle size, the magnetic field and the stiffness of the elastic medium on the radial breathing-mode frequencies of several nanoparticles. Our results reveal that the effects of the magnetic field and the elastic medium are significant for nanoparticle with small size.     

Enriched workflow modelling and Stochastic Branch-and-Bound

Workflow systems provide means and techniques for modelling, designing, performing and controlling repetitive (business) processes. The quality of commercial workflow systems is usually determined to a large extent by their versatility and multi-purpose application. One of the current trends in improving workflow systems lies in enriching modelling methods and techniques in order to enlarge design alternatives.The need for such advanced methods is particularly apparent in those fields in which the process duration can be determined only vaguely, but whose completion schedules are at the same time strictly enforced by a highly competitive market by means of fines and penalties. The risk of an overrun has to be weighed against the expected costs and benefits of certain measures reducing turn-around time and their combinations. Because they can help to avoid such penalties—or, at least, keep any potential losses low by identifying critical subprocesses and evaluate appropriate measures—modelling and evaluation techniques are becoming essential features of workflow systems.Methodologically, we use Stochastic Branch-and-Bound as a technique for finding “optimal” bundles of measures. A numerical study shows the benefits of this meta-approach by means of five stepwise-developed decision scenarios requiring rich modelling. Petri nets as a modelling tool and Stochastic Branch-and-Bound as an optimization technique determine for multi-mode resource constrained workflows of varying complexity an optimal workforce strategy with respect to the number of workers and their qualification.     

On scheduling around large restrictive common due windows

This paper deals with the problem of scheduling a number of jobs on a single machine around a large, restrictive common due window. We consider individual earliness and tardiness penalties for the jobs. The objective is to find an optimal schedule which jointly minimizes the sum of the earliness and tardiness penalties. This problem is intractable and hence no efficient procedure for solving large instances is expected to be found. For this reason we first introduced a mapping of the problem which takes advantage of the structural properties inherent to optimal solutions. Secondly we solved the problem under study by using this mapping and applying three meta-heuristics, namely evolutionary strategy, simulated annealing and threshold accepting. To validate the quality of these approaches, altogether 250 benchmark problems with different window sizes and positions of up to 200 jobs are examined. Furthermore small instances are solved to optimality by a mixed integer programming formulation.     

Flexible self-organization of two size-scales oxide nanotubes on Ti45Nb alloy

We report on the growth of anodic oxide nanotubes grown on a simple Ti45Nb alloy that show self-organization on two size-scales. The well-ordered nanotube layers consist of large and small diameter tubes that are arranged in an alternating two-dimensional (2D) structure. This bimodal morphology and the thickness of the nanotube layer are affected by the electrochemical conditions used. The bimodal feature can be obtained over a wide potential range (between 15 and 55 V), resulting in a linear diameter variation from 80 to 330 nm for the larger and 50–180 nm for the smaller tubes. The organization into two size-scales takes place during the first hour of the anodization process. This result of flexible two size-scale self-organization using a simple two element alloy is of significant importance not only for fundamental research but also for specific applications that can benefit from bimodal properties.     

The Tolerance of All-Optical Switching Based on Cascaded Second-Order Nonlinearity in PPLN APE Waveguide

Based on solving the couple mode equation numerically, the characterization of the signal power on the gate power was analyzed. And the relationship of the tolerance of the grating period and the bulk temperature on the interaction length was analyzed.     

Detection of low energy scattered X-rays using charged spheres

To detect low energy scattered X-ray dose below 9.5 keV simply, we have designed a low energy X-ray detector that uses multiple electrically charged conductive spheres floated by static electricity repulsion force. This detector detects the dose with the following steps (principles): (1) positive and negative ions are generated by ionization function of low energy X-rays projected in the detector; (2) those ions neutralize the electrically charged conductive spheres floated; (3) accordingly, the spheres fall; and (4) the detector detects low energy X-ray dose from the number of the conductive spheres fallen. This paper verified performance of this detector.     

Optical characteristics of semiconductor saturable absorber mirrors investigated by the reflection Z-scan technique

Recently, the semiconductor saturable absorber mirror (SESAM) has become a key component of passive mode-locked solid-state lasers. Here we present a simple method based on the reflection Z-scan technique to measure the key optical parameters of SESAM such as saturation fluence and modulation depth. The experimental results demonstrate that our method is able to perform with a high accuracy of 10⁻⁴ and a dynamic range of over four orders of magnitude.     

Vibrations of a solid sphere or shell of Functionally Graded Materials

We have solved the equation of equilibrium for torsional vibrations of a sphere in which the density and rigidity are functions of the radial distance and co-latitude. Making use of the particular forms of heterogeneity the exact frequency equations are derived. The work is motivated by the recent research activity on functionally graded materials (FGM), i.e. materials with spatially varying properties tailored to satisfy particular engineering applications.     

Couette flow in ferrofluids with magnetic field

Instability of a viscous, incompressible ferrofluid flow in an annular space between two coaxially rotating cylinders in the presence of axial magnetic field has been investigated numerically. The magnetic field perturbations in fluid in the gap between the cylinders have been taken into consideration and these have been observed to stabilize the Couette flow.