6,276 research outputs found
Intellectual Property, Contracts, and Reverse Engineering After ProCD: A Proposed Compromise for Computer Software
Unobserved retailer behavior in multimarket data: joint spatial dependence in market shares and promotion variables.
Semi-empirical model for prediction of unsteady forces on an airfoil with application to flutter
A semi-empirical model is described for predicting unsteady aerodynamic forces on arbitrary airfoils under mildly stalled and unstalled conditions. Aerodynamic forces are modeled using second order ordinary differential equations for lift and moment with airfoil motion as the input. This model is simultaneously integrated with structural dynamics equations to determine flutter characteristics for a two degrees-of-freedom system. Results for a number of cases are presented to demonstrate the suitability of this model to predict flutter. Comparison is made to the flutter characteristics determined by a Navier-Stokes solver and also the classical incompressible potential flow theory
Beltrami state in black-hole accretion disk: A magnetofluid approach
Using the magnetofluid unification framework, we show that the accretion disk
plasma (embedded in the background geometry of a blackhole) can relax to a
class of states known as the Beltrami-Bernoulli (BB) equilibria. Modeling the
disk plasma as a Hall MHD system, we find that the space-time curvature can
significantly alter the magnetic/velocity decay rate as we move away from the
compact object; the velocity profiles in BB states, for example, deviate
substantially from the predicted corresponding geodesic velocity profiles.
These departures imply a rich interplay of plasma dynamics and general
relativity revealed by examining the corresponding Bernoulli condition
representing "homogeneity" of total energy. The relaxed states have their
origin in the constraints provided by the two helicity invariants of Hall MHD.
These helicities conspire to introduce a new oscillatory length scale into the
system that is strongly influenced by relativistic and thermal effects.Comment: 8 figure
Forward-backward Asymmetry and New Physics
The forward-backward asymmetry in
decay is a sensitive probe of New Physics. Previous studies have focused on the
sensitivity in the position of the zero. However, the short distance effective
couplings are in principle complex, as illustrated by
decay within the Standard Model. Allowing the effective couplings to be
complex, but keeping the and rate
constraints, we find the landscape for to be far richer than from entertaining just sign flips,
which can be explored by future high statistics experiments.Comment: RevTex 4 pages including 5 eps figures; Minor changes made,
references adde
89Y NMR Probe of Zn Induced Local Magnetism in YBa2(Cu(1-y)Zn(y))3O(6+x)
We present detailed data and analysis of the effects of Zn substitution on
the planar Cu site in YBaCuO (YBCO) as evidenced from
our Y NMR measurements on oriented powders. For we find
additional NMR lines which are associated with the Zn substitution. From our
data on the intensities and temperature dependence of the shift, width, and
spin-lattice relaxation rate of these resonances, we conclude that the spinless
Zn 3 state induces local moments on the near-neighbour () Cu
atoms. Additionally, we conjecture that the local moments actually extend to
the farther Cu atoms with the magnetization alternating in sign at subsequent
sites. We show that this analysis is compatible with ESR data taken on
dilute Gd doped (on the Y site) and on neutron scattering data reported
recently on Zn substituted YBCO. For optimally doped compounds
Y resonances are not detected, but a large % -dependent
contribution to the Y NMR linewidth is evidenced and is also attributed
to the occurence of a weak induced local moment near the Zn. These results are
compatible with macroscopic magnetic measurements performed on YBCO
samples prepared specifically in order to minimize the content of impurity
phases. We find significant differences between the present results on the
underdoped YBCO samples and Al NMR data taken on Al
substituted on the Cu site in optimally doped LaCuO. Further
experimental work is needed to clarify the detailed evolution of the impurity
induced magnetism with hole content in the cuprates.Comment: To be published in EPJB 15 pages of text and figures in eps forma
Systems of Linear Equations over and Problems Parameterized Above Average
In the problem Max Lin, we are given a system of linear equations
with variables over in which each equation is assigned a
positive weight and we wish to find an assignment of values to the variables
that maximizes the excess, which is the total weight of satisfied equations
minus the total weight of falsified equations. Using an algebraic approach, we
obtain a lower bound for the maximum excess.
Max Lin Above Average (Max Lin AA) is a parameterized version of Max Lin
introduced by Mahajan et al. (Proc. IWPEC'06 and J. Comput. Syst. Sci. 75,
2009). In Max Lin AA all weights are integral and we are to decide whether the
maximum excess is at least , where is the parameter.
It is not hard to see that we may assume that no two equations in have
the same left-hand side and . Using our maximum excess results,
we prove that, under these assumptions, Max Lin AA is fixed-parameter tractable
for a wide special case: for an arbitrary fixed function
.
Max -Lin AA is a special case of Max Lin AA, where each equation has at
most variables. In Max Exact -SAT AA we are given a multiset of
clauses on variables such that each clause has variables and asked
whether there is a truth assignment to the variables that satisfies at
least clauses. Using our maximum excess results, we
prove that for each fixed , Max -Lin AA and Max Exact -SAT AA can
be solved in time This improves
-time algorithms for the two problems obtained by Gutin et
al. (IWPEC 2009) and Alon et al. (SODA 2010), respectively
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