Results 1  10
of
882
Throughout the Milky Way’s history, a nonnegligible fraction of s...
, 2004
"... We have derived the star formation history of the Milky Way disk over the last 2 Gyr with a time resolution of 0.05 Gyr from the age distribution diagram of a large sample of open clusters comprising more than 580 objects. By interpreting the age distribution diagram using numerical results from an ..."
Abstract
 Add to MetaCart
We have derived the star formation history of the Milky Way disk over the last 2 Gyr with a time resolution of 0.05 Gyr from the age distribution diagram of a large sample of open clusters comprising more than 580 objects. By interpreting the age distribution diagram using numerical results from an extensive library of Nbody calculations carried out during the last ten years, we reconstruct the recent star formation history of the Milky Way disk. Under the assumption that the disk has never been polluted by any extragalactic stellar populations, our analysis suggests that superimposed on a relatively small level of constant star formation activity mainly in smallN star clusters, the star formation rate has experienced at least 5 episodes of enhanced star formation lasting about 0.2 Gyr with production of larger clusters. This cyclic behavior shows a period of 0.4±0.1 Gyr and could be the result of density waves and/or interactions with satellite galaxies. On the other hand, the star formation rate history from a volumelimited sample of open clusters in the solar neighbourhood appears to be consistent with the overall star formation history obtained from the entire sample. Pure continuous star formation both in
For Most Large Underdetermined Systems of Linear Equations the Minimal ℓ1norm Solution is also the Sparsest Solution
 Comm. Pure Appl. Math
, 2004
"... We consider linear equations y = Φα where y is a given vector in R n, Φ is a given n by m matrix with n < m ≤ An, and we wish to solve for α ∈ R m. We suppose that the columns of Φ are normalized to unit ℓ 2 norm 1 and we place uniform measure on such Φ. We prove the existence of ρ = ρ(A) so that ..."
Abstract

Cited by 568 (10 self)
 Add to MetaCart
that for large n, and for all Φ’s except a negligible fraction, the following property holds: For every y having a representation y = Φα0 by a coefficient vector α0 ∈ R m with fewer than ρ · n nonzeros, the solution α1 of the ℓ 1 minimization problem min �x�1 subject to Φα = y is unique and equal to α0
The Role of Intergenerational Transfers in Aggregate Capital Accumulation
 Journal of Political Economy
, 1981
"... This paper uses historical U.S. data to directly estimate the contribution of intergenerational transfers to aggregate capital accumulation. The evidence presented indicates that intergenerational transfers account for the vast majority of aggregate U.S. capital formation; only a negligible frac ..."
Abstract

Cited by 269 (11 self)
 Add to MetaCart
This paper uses historical U.S. data to directly estimate the contribution of intergenerational transfers to aggregate capital accumulation. The evidence presented indicates that intergenerational transfers account for the vast majority of aggregate U.S. capital formation; only a negligible
HeavyTailed Phenomena in Satisfiability and Constraint Satisfaction Problems
 J. of Autom. Reasoning
, 2000
"... Abstract. We study the runtime distributions of backtrack procedures for propositional satisfiability and constraint satisfaction. Such procedures often exhibit a large variability in performance. Our study reveals some intriguing properties of such distributions: They are often characterized by ver ..."
Abstract

Cited by 165 (27 self)
 Add to MetaCart
of the distribution, which is indicative of a nonnegligible fraction of relatively short, successful runs. A rapid restart strategy eliminates heavytailed behavior and takes advantage of short runs, significantly reducing expected solution time. We demonstrate speedups of up to two orders of magnitude on SAT
Variance Estimation For Imputed Survey Data With NonNegligible Sampling Fractions
"... We consider variance estimation for HorvitzThompson type estimated totals based on survey data with imputed nonrespondents and with nonnegligible sampling fractions. A method based on a variance decomposition is proposed. Our method can be applied to complicated situations where a composite of som ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
We consider variance estimation for HorvitzThompson type estimated totals based on survey data with imputed nonrespondents and with nonnegligible sampling fractions. A method based on a variance decomposition is proposed. Our method can be applied to complicated situations where a composite
Tracing Traitors
, 1994
"... We give cryptographic schemes that help trace the source of leaks when sensitive or proprietary data is made available to a large set of parties. A very relevant application is in the context of pay television, where only paying customers should be able to view certain programs. In this application ..."
Abstract

Cited by 172 (10 self)
 Add to MetaCart
probability. Since there is typically little demand for decoders which decrypt only a small fraction of the transmissions (even if it is nonnegligible), we further introduce threshold tracing schemes which can only be used against decoders which succeed in decryption with probability greater than some
The price of routing unsplittable flow
 In Proc. 37th Symp. Theory of Computing (STOC
, 2005
"... The essence of the routing problem in real networks is that the traffic demand from a source to destination must be satisfied by choosing a single path between source and destination. The splittable version of this problem is when demand can be satisfied by many paths, namely a flow from source to d ..."
Abstract

Cited by 140 (3 self)
 Add to MetaCart
showed that for linear edge latency functions the price of anarchy is exactly 4 3 under the assumption that each user controls only a negligible fraction of the overall traffic (this result also holds for the splittable case). Note that under the assumption of negligible traffic pure and mixed strategies
The Actual Effect on the Gross Measures of the System Were Negligible.
"... iono For SIM 2 the reduction is one and a half times as great. MEASUI< SIM 1 EXP. C1 SIM 2 EXP. C2 Number of Times 2RD and 2WD Executed for CIO 13119 13422 15756 Mean CPM Service Time for LPP's CPM Time Spent Servicing LPP's from CIO for 2RD and 2WD (seconds) 0 CPM Time Saved by H ..."
Abstract
 Add to MetaCart
fraction of PP requests, little further improve ment, however, seems likely. 5.4 Experiment D  All PP Overlays on
For most large underdetermined systems of equations, the minimal l1norm nearsolution approximates the sparsest nearsolution
 Comm. Pure Appl. Math
, 2004
"... We consider inexact linear equations y ≈ Φα where y is a given vector in R n, Φ is a given n by m matrix, and we wish to find an α0,ɛ which is sparse and gives an approximate solution, obeying �y − Φα0,ɛ�2 ≤ ɛ. In general this requires combinatorial optimization and so is considered intractable. On ..."
Abstract

Cited by 122 (1 self)
 Add to MetaCart
1 and we place uniform measure on such Φ. We study the underdetermined case where m ∼ An, A> 1 and prove the existence of ρ = ρ(A) and C> 0 so that for large n, and for all Φ’s except a negligible fraction, the following approximate sparse solution property of Φ holds: For every y having
Verification of a Human in the Loop Or Identification Via the Turing Test
, 1996
"... We propose using a "Turing Test" in order to verify that a human is the one making a query to a service over the web. Thus, before a request is processed the user should answer as a challenge an instance of a problem chosen so that it is easy for humans to solve but the best known programs ..."
Abstract

Cited by 75 (1 self)
 Add to MetaCart
programs fail on a nonnegligible fraction of the instances. We discuss several scenarios where such tests are desired and several potential sources for problems instances. We also dicuss the application of this idea for combatting junk mail.
Results 1  10
of
882