Magnetic domain walls in constrained geometries

Magnetic domain walls have been studied in micrometer-sized Fe20Ni80 elements containing geometrical constrictions by spin-polarized scanning electron microscopy and numerical simulations. By controlling the constriction dimensions, the wall width can be tailored and the wall type modified. In particular, the width of a 180 degree Neel wall can be strongly reduced or increased by the constriction geometry compared with the wall in unconstrained systems.Comment: 4 pages, 6 figure

Performance Evaluation of Vision-Based Algorithms for MAVs

An important focus of current research in the field of Micro Aerial Vehicles (MAVs) is to increase the safety of their operation in general unstructured environments. Especially indoors, where GPS cannot be used for localization, reliable algorithms for localization and mapping of the environment are necessary in order to keep an MAV airborne safely. In this paper, we compare vision-based real-time capable methods for localization and mapping and point out their strengths and weaknesses. Additionally, we describe algorithms for state estimation, control and navigation, which use the localization and mapping results of our vision-based algorithms as input.Comment: Presented at OAGM Workshop, 2015 (arXiv:1505.01065

Зміст та основні цілі стимулювання збуту на підприємстві

Стаття присвячена висвітленню сутності стимулювання підприємства, як важливої складової для забезпечення ефективного його функціонування, а також проаналізовано головні завдання, та основні переваги та недоліки заходів, які використовуються у системі стимулювання збуту. У статті розглянуто зміст стимулювання збуту продукції підприємства, його цілі та завдання. Виявлено, що стимулювання збуту ‒ це система короткострокових спонукальних заходів на тимчасовій або територіальній основі, що чинить вплив на трьох учасників ринку (споживачів, торгових посередників, торговий персонал), яка покликана стимулювати негайне здійснення покупки і прискорений збут продукції. Наведена характеристика сучасних засобів і прийомів стимулювання збуту. Розглянуто класифікацію стимулювання збуту продукції підприємства за виникненням і впливом на покупців. Дістали подальшого розвитку теоретичні положе ння стимулювання збуту, в тому числі визначення його основних напрямків.The article is devoted to highlighting the essence of stimulating the enterprise as an important component for ensuring its effective functioning, and also analyzed the main tasks and the main advantages and disadvantages of those used in the sales promotion system. The article deals with the content of sales’ promotion in the complex of product promotion, its goals and tasks. It is found that sales promotion is a system of short-term incentives on a temporary or territorial basis, affects three market part icipants (consumers, resellers, sales personnel), which is designed to stimulate immediate purchase and accelerated sales. The characteristic of modern means and methods of sales’ promotion is given. The classification of sales promotion in the work on occurrence and influence on buyers is described. The theoretical positions of sales’ promotion were furt her developed, the main directions of sales promotion were established

On a Basis for the Framed Link Vector Space Spanned by Chord Diagrams

In view of the result of Kontsevich, now often called ``the fundamental theorem of Vassiliev theory'', identifying the graded dual of the associated graded vector space to the space of Vassiliev invariants filtered by degree with the linear span of chord diagrams modulo the ``4T-relation'' (and in the unframed case, the ``1T-'' or ``isolated chord relation''), it is a problem of some interest to provide a basis for the space of chord diagrams modulo the 4T-relation. We construct the basis for the vector space spanned by chord diagrams with n chords and m distinguishable link components, modulo 4T relations for n less than or equal to 5.Comment: 25 papers, numerous png figure

Modeling and Performance Evaluation of Machining Spindle with Active Magnetic Bearings

Active magnetic bearings (AMBs) are increasingly employed in the machine tool industry to exploit their advantages over classical bearings such as high speed capability, rotation accuracy, high stiffness, and accurate displacement tracking capability. Furthermore, the possibility of on-line monitoring of the machining process (e.g., cutting force measurement, tool wear) makes AMB spindles very appealing to the High-Speed Machining (HSM) industry. Despite significant progress already reached in HSM technology, there remain numerous open challenges in modeling and control of magnetic bearings as applied to machining spindles. These include optimum control given AMB magnetic saturation levels, management of nonlinear effects, reduction of chatter, and rotor properties. This paper describes a five-degree-of-freedom, high-speed machining spindle supported on AMBs. The rotordynamic modeling and experimentally extracted transfer functions are presented and analyzed. The experimentally measured tool tip compliance is used to compare PID and mu-synthesis control schemes. The primary finding is that the achieved tool tip stiffness is substantially higher with the μ-synthesized controllers than with the best PID we were able to design

Fluctuation-Response Relations for Multi-Time Correlations

We show that time-correlation functions of arbitrary order for any random variable in a statistical dynamical system can be calculated as higher-order response functions of the mean history of the variable. The response is to a ``control term'' added as a modification to the master equation for statistical distributions. The proof of the relations is based upon a variational characterization of the generating functional of the time-correlations. The same fluctuation-response relations are preserved within moment-closures for the statistical dynamical system, when these are constructed via the variational Rayleigh-Ritz procedure. For the 2-time correlations of the moment-variables themselves, the fluctuation-response relation is equivalent to an ``Onsager regression hypothesis'' for the small fluctuations. For correlations of higher-order, there is a new effect in addition to such linear propagation of fluctuations present instantaneously: the dynamical generation of correlations by nonlinear interaction of fluctuations. In general, we discuss some physical and mathematical aspects of the {\it Ans\"{a}tze} required for an accurate calculation of the time correlations. We also comment briefly upon the computational use of these relations, which is well-suited for automatic differentiation tools. An example will be given of a simple closure for turbulent energy decay, which illustrates the numerical application of the relations.Comment: 28 pages, 1 figure, submitted to Phys. Rev.

Direct observation of domain-wall configurations transformed by spin currents

Direct observations of current-induced domain-wall propagation by spin-polarized scanning electron microscopy are reported. Current pulses move head-to-head as well as tail-to-tail walls in sub-micrometer Fe_{20}Ni_{80} wires in the direction of the electron flow, and a decay of the wall velocity with the number of injected current pulses is observed. High-resolution images of the domain walls reveal that the wall spin structure is transformed from a vortex to a transverse configuration with subsequent pulse injections. The change in spin structure is directly correlated with the decay of the velocity.Comment: 5 pages, 3 figure