553 research outputs found
The equivalent ellipsoid of a magnetized body
No full textThe equivalent ellipsoid for magnetized bodies of arbitrary shape can be determined by imposing the equality between the demagnetization factors of the two shapes of equal volume. It is shown that the 'commonsense' criterion for mapping two different shapes by imposing the equality of the demagnetization factors for equal aspect ratios often results in large errors. We propose a general method for the rigorous determination of the equivalent ellipsoid. The cases of the exact equivalent ellipsoids for discs, cylinders with elliptical cross section and prisms are worked out and discussed
Magnetostatics of the uniformly polarized torus
No full textWe provide an exhaustive description of the magnetostatics of the uniformly polarized torus and its derivative self-intersecting (spindle) shapes. In the process, two complementary approaches have been implemented, position-space analysis of the Laplace equation with inhomogeneous boundary conditions and a Fourier-space analysis, starting from the determination of the shape amplitude of this topologically non-trivial body. The stray field and the demagnetization tensor have been determined as rapidly converging series of toroidal functions. The single independent demagnetization-tensor eigenvalue has been determined as a function of the unique aspect ratio α of the torus. Throughout the range of values of the ratio, corresponding to a multiply connected torus proper, the axial demagnetization factor Nz remains close to one half. There is no breach of smoothness of Nz(α) at the topological crossover to a simply connected tight torus (α=1). However, Nz is a non-monotonic function of the aspect ratio, such that substantially different pairs of corresponding tori would still have the same demagnetization factor. This property does not occur in a simply connected body of the same continuous axial symmetry. Several self-suggesting practical applications are outlined, deriving from the acquired quantitative insight
Demagnetization factors for elliptic cylinders
No full textThe magnetometric (volume averaged) demagnetization factors for cylinders with elliptical cross section are computed using a Fourier-space approach and compared with similar results obtained with a different treatment. The demagnetization factors are given as a series expansion in the eccentricity epsilon of the elliptical cross section, where the terms up to order epsilon(10) are given explicitly as a function of the cylinder aspect ratio. Other simplified expressions, valid in restricted regimes, are also given. Two different series expansions, obtained previously and valid in particular combinations of shape parameters, are recalled and compared with the new results. After the computation of the magnetostatic and exchange-energy terms associated with a vortex closure-domain state in the elliptic cylinder, the single-domain limit, or the critical size below which the structure can support quasi-uniform magnetization, is derived and discussed
AAS227 - Synthesizing Understanding from Data with yt
No full textThis is a talk I gave at the AAS227 about yt. yt is available at yt-project.org.<div><br></div><div>While I am listed as the author of this talk, the yt community is composed of more than a hundred code contributors and mailing list participants, and we are grateful to their involvement and support.</div><div><br></div><div>Additionally, the yt project is built on other members of the scientific software ecosystem such as Jupyter, NumPy, Cython, h5py and hdf5, Matplotlib, and Sympy.</div
Correction to: Chemoradiation in elderly patients with glioblastoma from the multiinstitutional GBMmolRPA cohort: is shortcourse radiotherapy enough or is it a matter of selection?
No full textThe name of author Do Hoon Lim was incorrect in the initial online publication. The original article has been corrected
Effect of donepezil on transcranial magnetic stimulation parameters in Alzheimer's disease
No full textIntroduction: There is a need for a reliable, noninvasive biomarker for Alzheimer's disease (AD). We assessed whether short-latency afferent inhibition (SAI), a transcranial magnetic stimulation paradigm that assesses cholinergic circuits of the brain, could become such a biomarker.
Methods: Nineteen patients with AD underwent four SAI testing sessions. The timing of their usual donepezil dose was altered to create different cholinergic states for each session. This was compared to the SAI results from 20 healthy subjects.
Results: SAI was not able to distinguish the different cholinergic states assessed in our study. There appeared to be a diurnal variation in cholinergic function in the control group, which was not present in the AD cohort.
Discussion: SAI does not appear to have a role in diagnosis and assessment of AD patients. The loss of diurnal variation, however, warrants further investigation as it may provide further biochemical insights about AD
Can Cause and Effect be Distinguised by Simple Regression? ESRI Memorandum Series No. 50 (revised) 1968(?)
No full textLet data be (Xt, Yt), t = 1, 2, ..., T. We assume throughout that T is "large". We try to evolve statistical tests for identifying whether X or Y is the cause, the other variable being the effect
Scaling relationships in indentation of power-law creep solids using self-similar indenters
No full textWe use dimensional analysis to derive scaling relationships for self-similar indenters indenting solids that exhibit power-law creep. We identify the parameter that represents the indentation strain rate. The scaling relationships are applied to several types of indentation creep experiment with constant displacement rate, constant loading rate or constant ratio of loading rate over load. The predictions compare favourably with experimental observations reported in the literature. Finally, a connection is found between creep and 'indentation-size effect' (i.e. changing hardness with indentation depth or load)
Nonlinear Analysis of Oscillatory Indentation in Elastic and Viscoelastic Solids
No full textDetermining the mechanical properties at micro- and nanometer length scales using nanoindentation or atomic force microscopy is important to many areas of science and engineering. Here we establish equations for obtaining storage and loss modulus from oscillatory indentations by performing a nonlinear analysis of conical and spherical indentation in elastic and viscoelastic solids. We show that, when the conical indenter is driven by a sinusoidal force, the square of displacement is a sinusoidal function of time, not the displacement itself, which is commonly assumed. Similar conclusions hold for spherical indentations. Well-known difficulties associated with measuring contact area and correcting thermal drift may be circumvented using the newly derived equations. These results may help improve methods of using oscillatory indentation for determining elastic and viscoelastic properties of solids
Equivalent formula of S4 system & its application in NLU & TMT
No full textIn this paper we first give a brief introduction to the basic concepts of TMT and S4 system. Now a small TMT prototype is being built up in SIA which is funded by CAS. Then author presents a safest way to transform some natural language form each other which is called the duality-drived-equivalent formula that uses unambiguous-natural-language-like-4th-class-symbols and is drived out based on the duality principles. Duality-drived-equivalent formula are of absolutely correctness that needn't to consider the context, so it can be used in TMT-trustworthy machine translation-system to guarantee the correctness of MT
- …
