103,342 research outputs found
Integration of Quantitative and Qualitative Techniques for Deformable Model Fitting from Orthographic, Perspective, and Stereo Projections
In this paper, we synthesize a new approach to 3-D object shape recovery by integrating qualitative shape recovery techniques and quantitative physics based shape estimation techniques. Specifically, we first use qualitative shape recovery and recognition techniques to provide strong fitting constraints on physics-based deformable model recovery techniques. Secondly, we extend our previously developed technique of fitting deformable models to occluding image contours to the case of image data captured under general orthographic, perspective, and stereo projections
Doing evolution in economic geography
Evolutionary approaches in economic geography face questions about the relationships between their concepts, theories, methods, politics, and policy implications. Amidst the growing but unsettled consensus that evolutionary approaches should employ plural methodologies, the aims here are, first, to identify some of the difficult issues confronting those working with different frameworks. The concerns comprise specifying and connecting research objects, subjects, and levels; handling agency and context; engaging and integrating the quantitative and the qualitative; comparing cases; and, considering politics, policy, and praxis. Second, the purpose is to articulate a distinctive geographical political economy approach, methods, and illustrative examples in addressing these issues. Bringing different views of evolution in economic geography into dialogue and disagreement renders methodological pluralism a means toward improved understanding and explanation rather than an end in itself. Confronting such thorny matters needs to be embedded in our research practices and supported by greater openness; more and better substantiation of our conceptual, theoretical, and empirical claims; enhanced critical reflection; and deeper engagement with politics, policy, and praxis
Modified Kedem-Katchalsky equations for osmosis through nano-pore
This work presents a modified Kedem-Katchalsky equations for osmosis through
nano-pore. osmotic reflection coefficient of a solute was found to be chiefly
affected by the entrance of the pore while filtration reflection coefficient
can be affected by both the entrance and the internal structure of the pore.
Using an analytical method, we get the quantitative relationship between
osmotic reflection coefficient and the molecule size. The model is verified by
comparing the theoretical results with the reported experimental data of
aquaporin osmosis. Our work is expected to pave the way for a better
understanding of osmosis in bio-system and to give us new ideas in designing
new membranes with better performance.Comment: 19 pages, 4 figure
Optimal execution strategies in limit order books with general shape functions
We consider optimal execution strategies for block market orders placed in a
limit order book (LOB). We build on the resilience model proposed by Obizhaeva
and Wang (2005) but allow for a general shape of the LOB defined via a given
density function. Thus, we can allow for empirically observed LOB shapes and
obtain a nonlinear price impact of market orders. We distinguish two
possibilities for modeling the resilience of the LOB after a large market
order: the exponential recovery of the number of limit orders, i.e., of the
volume of the LOB, or the exponential recovery of the bid-ask spread. We
consider both of these resilience modes and, in each case, derive explicit
optimal execution strategies in discrete time. Applying our results to a
block-shaped LOB, we obtain a new closed-form representation for the optimal
strategy, which explicitly solves the recursive scheme given in Obizhaeva and
Wang (2005). We also provide some evidence for the robustness of optimal
strategies with respect to the choice of the shape function and the
resilience-type
Dynamics of viscoelastic snap-through
We study the dynamics of snap-through when viscoelastic effects are present.
To gain analytical insight we analyse a modified form of the Mises truss, a
single-degree-of-freedom structure, which features an `inverted' shape that
snaps to a `natural' shape. Motivated by the anomalously slow snap-through
shown by spherical elastic caps, we consider a thought experiment in which the
truss is first indented to an inverted state and allowed to relax while a
specified displacement is maintained; the constraint of an imposed displacement
is then removed. Focussing on the dynamics for the limit in which the timescale
of viscous relaxation is much larger than the characteristic elastic timescale,
we show that two types of snap-through are possible: the truss either
immediately snaps back over the elastic timescale or it displays
`pseudo-bistability', in which it undergoes a slow creeping motion before
rapidly accelerating. In particular, we demonstrate that accurately determining
when pseudo-bistability occurs requires the consideration of inertial effects
immediately after the indentation force is removed. Our analysis also explains
many basic features of pseudo-bistability that have been observed previously in
experiments and numerical simulations; for example, we show that
pseudo-bistability occurs in a narrow parameter range at the bifurcation
between bistability and monostability, so that the dynamics is naturally
susceptible to critical slowing down. We then study an analogous thought
experiment performed on a continuous arch, showing that the qualitative
features of the snap-through dynamics are well captured by the truss model. In
addition, we analyse experimental and numerical data of viscoelastic
snap-through times reported in the literature. Combining these approaches
suggests that our conclusions may also extend to more complex viscoelastic
structures used in morphing applications.Comment: Main text 37 pages, Appendices 13 page
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