8,335 research outputs found
Reversable heat flow through the carbon nanotube junctions
Microscopic mechanisms of externally controlled reversable heat flow through
the carbon nanotube junctions (NJ) are studied theoretically. Our model
suggests that the heat is transfered along the tube section by
electrons () and holes () moving ballistically in either in parallel or
in opposite directions and accelerated by the bias source-drain voltage (Peltier effect). We compute the Seebeck coefficient , electric
and thermal conductivities and find that their magnitudes
strongly depend on and . The sign reversal of
versus the sign of formerly observed experimentally is interpreted
in this work in terms of so-called chiral tunneling phenomena (Klein paradox)
Mean encounter times for cell adhesion in hydrodynamic flow: analytical progress by dimensional reduction
For a cell moving in hydrodynamic flow above a wall, translational and
rotational degrees of freedom are coupled by the Stokes equation. In addition,
there is a close coupling of convection and diffusion due to the
position-dependent mobility. These couplings render calculation of the mean
encounter time between cell surface receptors and ligands on the substrate very
difficult. Here we show for a two-dimensional model system how analytical
progress can be achieved by treating motion in the vertical direction by an
effective reaction term in the mean first passage time equation for the
rotational degree of freedom. The strength of this reaction term can either be
estimated from equilibrium considerations or used as a fit parameter. Our
analytical results are confirmed by computer simulations and allow to assess
the relative roles of convection and diffusion for different scaling regimes of
interest.Comment: Reftex, postscript figures include
Core compressor exit stage study, 2
A total of two three-stage compressors were designed and tested to determine the effects of aspect ratio on compressor performance. The first compressor was designed with an aspect ratio of 0.81; the other, with an aspect ratio of 1.22. Both compressors had a hub-tip ratio of 0.915, representative of the rear stages of a core compressor, and both were designed to achieve a 15.0% surge margin at design pressure ratios of 1.357 and 1.324, respectively, at a mean wheel speed of 167 m/sec. At design speed the 0.81 aspect ratio compressor achieved a pressure ratio of 1.346 at a corrected flow of 4.28 kg/sec and an adiabatic efficiency of 86.1%. The 1.22 aspect ratio design achieved a pressure ratio of 1.314 at 4.35 kg/sec flow and 87.0% adiabatic efficiency. Surge margin to peak efficiency was 24.0% with the lower aspect ratio blading, compared with 12.4% with the higher aspect ratio blading
Design of helicopter rotor blades for optimum dynamic characteristics
The possibilities and limitations of tailoring blade mass and stiffness distributions to give an optimum blade design in terms of weight, inertia, and dynamic characteristics are discussed. The extent that changes in mass of stiffness distribution can be used to place rotor frequencies at desired locations is determined. Theoretical limits to the amount of frequency shift are established. Realistic constraints on blade properties based on weight, mass, moment of inertia, size, strength, and stability are formulated. The extent that the hub loads can be minimized by proper choice of E1 distribution, and the minimum hub loads which can be approximated by a design for a given set of natural frequencies are determined. Aerodynamic couplings that might affect the optimum blade design, and the relative effectiveness of mass and stiffness distribution on the optimization procedure are investigated
On worst-case investment with applications in finance and insurance mathematics
We review recent results on the new concept of worst-case portfolio optimization, i.e. we consider the determination of portfolio processes which yield the highest worst-case expected utility bound if the stock price may have uncertain (down) jumps. The optimal portfolios are derived as solutions of non-linear differential equations which itself are consequences of a Bellman principle for worst-case bounds. They are by construction non-constant ones and thus differ from the usual constant optimal portfolios in the classical examples of the Merton problem. A particular application of such strategies is to model crash possibilities where both the number and the height of the crash is uncertain but bounded. We further solve optimal investment problems in the presence of an additional risk process which is the typical situation of an insurer
Issues in the Interpretation of 180-Day Exclusivity
Congress created 180-day exclusivity for generic drug applicants in the 1984 Hatch-Waxman amendments to the Federal Food, Drug, and Cosmetic Act (FDCA) and amended it substantially in the Medicare Prescription Drug, Improvement, and Modernization Act of 2003 (MMA). The core concept of this exclusivity as it has been applied by FDA and the courts is that the first generic drug applicant to challenge an innovator\u27s patent is entitled to six months of exclusivity against subsequent patent challengers for the same innovator drug. The 180-day exclusivity provision is governed by sections 505(j)(5)(B)(iv) and 505(j)(5)(D) of the FDCA, and it is intended to encourage generic applicants to challenge innovator patents. Although the basic idea is simple and the language enacted in 1984 was correspondingly brief, over the years the provision has given rise to a substantial number of interpretive disputes, both at the agency and in the courts. The courts are still grappling with interpretation of the 1984 provision, and it is already apparent that the amended language will trigger additional disputes. An earlier article in this journal traced the history of the 180-day exclusivity provision from 1984 through its amendment in 2003 and court cases in 2004.
This article updates the earlier piece through the end of 2006 but is arranged by issue rather than in a chronology. Part II presents the original and amended statutory language. For the most part, the amended language applies only to abbreviated new drug applications (ANDAs) filed after December 8, 2003, provided there was no paragraph IV certification to the reference drug prior to that date. We refer to these as new ANDAs and to all other ANDAs as old ANDAs. Part III presents the interpretive issues that have been addressed by FDA and/or the courts and describes their resolution with respect to old ANDAs and, where different, new ANDAs
Generic Subsequence Matching Framework: Modularity, Flexibility, Efficiency
Subsequence matching has appeared to be an ideal approach for solving many
problems related to the fields of data mining and similarity retrieval. It has
been shown that almost any data class (audio, image, biometrics, signals) is or
can be represented by some kind of time series or string of symbols, which can
be seen as an input for various subsequence matching approaches. The variety of
data types, specific tasks and their partial or full solutions is so wide that
the choice, implementation and parametrization of a suitable solution for a
given task might be complicated and time-consuming; a possibly fruitful
combination of fragments from different research areas may not be obvious nor
easy to realize. The leading authors of this field also mention the
implementation bias that makes difficult a proper comparison of competing
approaches. Therefore we present a new generic Subsequence Matching Framework
(SMF) that tries to overcome the aforementioned problems by a uniform frame
that simplifies and speeds up the design, development and evaluation of
subsequence matching related systems. We identify several relatively separate
subtasks solved differently over the literature and SMF enables to combine them
in straightforward manner achieving new quality and efficiency. This framework
can be used in many application domains and its components can be reused
effectively. Its strictly modular architecture and openness enables also
involvement of efficient solutions from different fields, for instance
efficient metric-based indexes. This is an extended version of a paper
published on DEXA 2012.Comment: This is an extended version of a paper published on DEXA 201
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