575 research outputs found
Group Divisible Codes and Their Application in the Construction of Optimal Constant-Composition Codes of Weight Three
The concept of group divisible codes, a generalization of group divisible
designs with constant block size, is introduced in this paper. This new class
of codes is shown to be useful in recursive constructions for constant-weight
and constant-composition codes. Large classes of group divisible codes are
constructed which enabled the determination of the sizes of optimal
constant-composition codes of weight three (and specified distance), leaving
only four cases undetermined. Previously, the sizes of constant-composition
codes of weight three were known only for those of sufficiently large length.Comment: 13 pages, 1 figure, 4 table
Optimal Memoryless Encoding for Low Power Off-Chip Data Buses
Off-chip buses account for a significant portion of the total system power
consumed in embedded systems. Bus encoding schemes have been proposed to
minimize power dissipation, but none has been demonstrated to be optimal with
respect to any measure. In this paper, we give the first provably optimal and
explicit (polynomial-time constructible) families of memoryless codes for
minimizing bit transitions in off-chip buses. Our results imply that having
access to a clock does not make a memoryless encoding scheme that minimizes bit
transitions more powerful.Comment: Proceedings of the 2006 IEEE/ACM international Conference on
Computer-Aided Design (San Jose, California, November 05 - 09, 2006). ICCAD
'06. ACM, New York, NY, 369-37
Optimal Partitioned Cyclic Difference Packings for Frequency Hopping and Code Synchronization
Optimal partitioned cyclic difference packings (PCDPs) are shown to give rise
to optimal frequency-hopping sequences and optimal comma-free codes. New
constructions for PCDPs, based on almost difference sets and cyclic difference
matrices, are given. These produce new infinite families of optimal PCDPs (and
hence optimal frequency-hopping sequences and optimal comma-free codes). The
existence problem for optimal PCDPs in , with base blocks
of size three, is also solved for all .Comment: to appear in IEEE Transactions on Information Theor
Linear Size Optimal q-ary Constant-Weight Codes and Constant-Composition Codes
An optimal constant-composition or constant-weight code of weight has
linear size if and only if its distance is at least . When , the determination of the exact size of such a constant-composition or
constant-weight code is trivial, but the case of has been solved
previously only for binary and ternary constant-composition and constant-weight
codes, and for some sporadic instances.
This paper provides a construction for quasicyclic optimal
constant-composition and constant-weight codes of weight and distance
based on a new generalization of difference triangle sets. As a result,
the sizes of optimal constant-composition codes and optimal constant-weight
codes of weight and distance are determined for all such codes of
sufficiently large lengths. This solves an open problem of Etzion.
The sizes of optimal constant-composition codes of weight and distance
are also determined for all , except in two cases.Comment: 12 page
A BIOMECHANICAL ANALYSIS FOR PROFICIENT AND LESS-PROFICIENT SUBJECTS FOR SOCCER HEADING
Soccer is one of the most popular sports and is played and watched by millions of people around the world. In heading the players intentionally strike the ball using his head; therefore it is essential to instruct them in a proper manner how to do it optimally. Our results showed that lower and upper body had a significant difference between the proficient and less proficient subjects. For upper body kinematics, the proficient subjects exerted lesser elbow angles (47.8" (1.9) than the less-proficient (58.7"(3.5)). In the case of lower bdy kinetics, the proficient subjects exerted greater ankle moment (l.g(O.2) NmlKg) than less proficient subjects (1.5(0.3)Nm/Kg). With the results obtained it became possible to create particular training programs on how to perform a skill better and therefore result in an improvement of their ability
Cost-minimizing preemptive scheduling of mapreduce workloads on hybrid clouds
MapReduce has become the dominant programming model for processing massive amounts of data on cloud platforms. More and more enterprises are now utilizing hybrid clouds, consisting of private infrastructure owned by themselves and public clouds such as Amazon EC2, to process their spiky MapReduce workloads, which fully utilize their own on-premise resources while outsourcing the tasks only when needed. With disparate workloads of different MapReduce tasks, an efficient scheduling mechanism is in need to enable efficient utilization of the on-premise resources and to minimize the task outsourcing cost, while meeting the task completion time requirements as well. In this paper, a fine-grained model is described to characterize the scheduling of heterogeneous MapReduce workloads, and an online algorithm is proposed for joint task admission control into the private cloud, task outsourcing to the public cloud, and VM allocation to execute the admitted tasks on the private cloud, such that the time-averaged task outsourcing cost is minimized over the long run. The online algorithm features preemptive scheduling of the tasks, where a task executed partially on the on-premise infrastructure can be paused and scheduled to run later. It also achieves desirable properties such as meeting a pre-set task admission ratio and bounding the worst-case task completion time, as proven by our rigorous theoretical analysis. © 2013 IEEE.published_or_final_versio
Emerging trends in polymerization-induced self-assembly
In this Perspective, we summarize recent progress in polymerization-induced self-assembly (PISA) for the rational synthesis of block copolymer nanoparticles with various morphologies. Much of the PISA literature has been based on thermally initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. Herein, we pay particular attention to alternative PISA protocols, which allow the preparation of nanoparticles with improved control over copolymer morphology and functionality. For example, initiation based on visible light, redox chemistry, or enzymes enables the incorporation of sensitive monomers and fragile biomolecules into block copolymer nanoparticles. Furthermore, PISA syntheses and postfunctionalization of the resulting nanoparticles (e.g., cross-linking) can be conducted sequentially without intermediate purification by using various external stimuli. Finally, PISA formulations have been optimized via high-throughput polymerization and recently evaluated within flow reactors for facile scale-up syntheses
Atom Interferometry tests of the isotropy of post-Newtonian gravity
We present a test of the local Lorentz invariance of post-Newtonian gravity
by monitoring Earth's gravity with a Mach-Zehnder atom interferometer that
features a resolution of about 8*10^(-9)g/Hz^(1/2), the highest reported thus
far. Expressed within the standard model extension (SME) or Nordtvedt's
anisotropic universe model, the analysis limits four coefficients describing
anisotropic gravity at the ppb level and three others, for the first time, at
the 10ppm level. Using the SME we explicitly demonstrate how the experiment
actually compares the isotropy of gravity and electromagnetism.Comment: Added outlook, corrected typos; to appear in PRL. 4 pages, 3 figure
The fine intersection problem for Steiner triple systems
The intersection of two Steiner triple systems (X,A) and (X,B) is the set A
intersect B. The fine intersection problem for Steiner triple systems is to
determine for each v, the set I(v), consisting of all possible pairs (m,n) such
that there exist two Steiner triple systems of order v whose intersection has n
blocks over m points. We show that for v = 1 or 3 (mod 6), |I(v)| = Omega(v^3),
where previous results only imply that |I(v)| = Omega(v^2).Comment: 9 page
The PBD-Closure of Constant-Composition Codes
We show an interesting PBD-closure result for the set of lengths of
constant-composition codes whose distance and size meet certain conditions. A
consequence of this PBD-closure result is that the size of optimal
constant-composition codes can be determined for infinite families of parameter
sets from just a single example of an optimal code. As an application, the size
of several infinite families of optimal constant-composition codes are derived.
In particular, the problem of determining the size of optimal
constant-composition codes having distance four and weight three is solved for
all lengths sufficiently large. This problem was previously unresolved for odd
lengths, except for lengths seven and eleven.Comment: 8 page
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