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排序方式: 共有192条查询结果,搜索用时 15 毫秒
21.
For a class of abstract λ-dependent boundary value problems where a local variant of generalized Nevanlinna functions appears
in the boundary condition, linearizations are constructed and their local spectral properties are investigated. 相似文献
22.
Moilanen P Talmant M Nicholson PH Cheng S Timonen J Laugier P 《The Journal of the Acoustical Society of America》2007,122(4):2439-2445
It was reported in a previous study that simulated guided wave axial transmission velocities on two-dimensional (2D) numerically reproduced geometry of long bones predicted moderately real in vitro ultrasound data on the same bone samples. It was also shown that fitting of ultrasound velocity with simple analytical model yielded a precise estimate (UTh) for true cortical bone thickness. This current study expands the 2D bone model into three dimensions (3D). To this end, wave velocities and UTh were determined from experiments and from time-domain finite-difference simulations of wave propagation, both performed on a collection of 10 human radii (29 measurement sites). A 3D numerical bone model was developed with tuneable fixed material properties and individualized geometry based on X-ray computed tomography reconstructions of real bones. Simulated UTh data were in good accordance (root-mean-square error was 0.40 mm; r(2)=0.79, p<0.001) with true cortical thickness, and hence the measured phase velocity can be well estimated by using a simple analytical inversion model also in 3D. Prediction of in vitro data was improved significantly (by 10% units) and the upgraded bone model thus explained most of the variability (up to 95% when sites were carefully matched) observed in in vitro ultrasound data. 相似文献
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In On What Matters, Derek Parfit defends a new metaethical theory, which he calls non-realist cognitivism. It claims that (i) normative judgments are beliefs; (ii) that some normative beliefs are true; (iii) that the normative concepts that are a part of the propositions that are the contents of normative beliefs are irreducible, unanalysable and of their own unique kind; and (iv) that neither the natural features of the reality nor any additional normative features of the reality make the relevant normative beliefs true. The aim of this article is to argue that Parfit’s theory is problematic because its defenders have no resources to make sense of the nature of normative truth, which is an essential element of their view. I do this by showing how the traditional theories of truth are not available for the non-realist cognitivists. 相似文献
25.
Pekka Kekäläinen Mikko Voutilainen Antti Poteri Pirkko Hölttä Aimo Hautojärvi Jussi Timonen 《Transport in Porous Media》2011,87(1):125-149
A model transport system is considered in which a pulse of tracer molecules is advected along a flow channel with porous walls.
The advected tracer thus undergoes diffusion, matrix-diffusion, inside the walls, which affects the breakthrough curve of
the tracer. Analytical solutions in the form of series expansions are derived for a number of situations which include a finite
depth of the porous matrix, varying aperture of the flow channel, and longitudinal diffusion and Taylor dispersion of the
tracer in the flow channel. Novel expansions for the Laplace transforms of the concentration in the channel facilitated closed-form
expressions for the solutions. A rigorous result is also derived for the asymptotic form of the breakthrough curve for a finite
depth of the porous matrix, which is very different from that for an infinite matrix. A specific experimental system was created
for validation of matrix-diffusion modeling for a matrix of finite depth. A previously reported fracture-column experiment
was also modeled. In both cases model solutions gave excellent fits to the measured breakthrough curves with very consistent
values for the diffusion coefficients used as the fitting parameters. The matrix-diffusion modeling performed could thereby
be validated. 相似文献
26.
Nonlinear Dynamics - Dynamic simulation of mechanical systems can be performed using a multibody system dynamics approach. The approach allows to account systems of other physical nature, such as... 相似文献
27.
Jussi Klemelä 《Probability Theory and Related Fields》2006,134(4):539-564
Estimation of a quadratic functional of a function observed in the Gaussian white noise model is considered. A data-dependent
method for choosing the amount of smoothing is given. The method is based on comparing certain quadratic estimators with each
other. It is shown that the method is asymptotically sharp or nearly sharp adaptive simultaneously for the “regular” and “irregular”
region. We consider lp bodies and construct bounds for the risk of the estimator which show that for p=4 the estimator is exactly optimal and for example when p ∈[3,100], then the upper bound is at most 1.055 times larger than the lower bound. We show the connection of the estimator
to the theory of optimal recovery. The estimator is a calibration of an estimator which is nearly minimax optimal among quadratic
estimators.
Writing of this article was financed by Deutsche Forschungsgemeinschaft under project MA1026/6-2, CIES, France, and Jenny
and AnttiWihuri Foundation. 相似文献
28.
Jussi Väisälä 《Monatshefte für Mathematik》1991,111(3):233-244
We considern-dimensional quasiconformal maps of an arbitrary domain onto a domain with specific properties and prove various results related to the Hayman-Wu theorem. 相似文献
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