39340000
Circular chromatic numbers of Mycielski's graphs
Abstract In a search for triangle-free graphs with arbitrarily large chromatic numbers, Mycielski developed a graph transformation that transforms a graph G into a new graph μ ( G ), we now call the Mycielskian of G , which has the same clique number as G and whose chromatic number equals χ ( G )+1. Let μ n ( G )= μ ( μ n −1 ( G )) for n ⩾2. This paper investigates the circular chromatic numbers of Mycielski's graphs. In particular, the following results are proved in this paper: (1)  for any graph G of chromatic number n, χ c (μ n−1 (G))⩽χ(μ n−1 (G))− 1 2 ; (2)  if a graph G satisfies χ c (G)⩽χ(G)− 1 d with d =2 or 3, then χ c (μ 2 (G))⩽χ(μ 2 (G))− 1 d ; (3)  for any graph G of chromatic number 3, χ c ( μ ( G ))= χ ( μ ( G ))=4; (4) χ c ( μ ( K n ))= χ ( μ ( K n ))= n +1 for n ⩾3 and χ c ( μ 2 ( K n ))= χ ( μ 2 ( K n ))= n +2 for n ⩾4.
13203978
Circular Chromatic Numbers of Distance Graphs with Distance Sets Missing Multiples
Given positive integers m, k, s withm&sk, let Dm, k, srepresent the set {1, 2,? , m } \ { k, 2 k,? , sk }. The distance graph G(Z, Dm, k, s) has as vertex set all integersZ and edges connecting i and j whenever | i?j | ?Dm, k, s. This paper investigates chromatic numbers and circular chromatic numbers of the distance graphs G(Z, Dm, k,s). Deuber and Zhu and Liu have shown that?m+sk+ 1s+ 1? ??(G(Z, Dm, k,s)) ? ?m+sk+ 1s+ 1? +1whenm? (s+ 1)k. In this paper, by establishing bounds for the circular chromatic number ?c(G(Z, Dm,k , s)) of G(Z, Dm, k,s), we determine the values of ?(G(Z, Dm,k , s)) for all positive integers m, k, s and?c (G(Z, Dm, k,s)) for some positive integers m, k, s.
16953475
Fuzzy unidirectional force control of constrained robotic manipulators
The end effector of a robotic arm is required to keep a contact on the contour of the constraint surface in tasks such as deburring and grinding. Being different from contacts resulted from general mechanical pairs, such a contact is unidirectional, or equivalently, the contact force can only act along the outward normal of the constraint surface at the contact point. How to achieve this specification was not addressed explicitly in many position/force control schemes developed so far, instead it was assumed in the development of controllers. In this paper, the unidirectionality of the contact force is explicitly included in modeling and control of constrained robot system. A fuzzy tuning mechanism is developed to generate the impedance model resulted from the continuous contact made by the end effector of the robotic manipulator on the constraint surface while it is in motion. A controller is then developed based on the fuzzy rule bases and the nonlinear feedback technique. The simulation is carried out to verify the effectiveness of the approach.
6253832
Towards a more efficient implementation of OpenMP for clusters via translation to global arrays
This paper discusses a novel approach to implementing OpenMP on clusters. Traditional approaches to do so rely on Software Distributed Shared Memory systems to handle shared data. We discuss these and then introduce an alternative approach that translates OpenMP to Global Arrays (GA), explaining the basic strategy. GA requires a data distribution. We do not expect the user to supply this; rather, we show how we perform data distribution and work distribution according to the user-supplied OpenMP static loop schedules. An inspector-executor strategy is employed for irregular applications in order to gather information on accesses to potentially non-local data, group non-local data transfers and overlap communications with local computations. Furthermore, a new directive INVARIANT is proposed to provide information about the dynamic scope of data access patterns. This directive can help us generate efficient codes for irregular applications using the inspector-executor approach. We also illustrate how to deal with some hard cases containing reshaping and strided accesses during the translation. Our experiments show promising results for the corresponding regular and irregular GA codes.
27213248
Multiresolution recognition of offline handwritten Chinese characters with wavelet transform
The authors propose a novel multiresolution recognition scheme for handwritten Chinese character recognition in which an input pattern is recognized by adopting the coefficients of the wavelet transforms. It is known that wavelet representation provides a coarse-to-fine strategy. The recognition starts from the coarse scale and moves to the finer scales. After preprocessing, the wavelet transform is applied to the kanji image. Then, we make use of the coefficients with the lowest resolution to select 50 candidates from 3755 categories. In order to enhance the statistical feature of a character, we used statistical methods to reconstruct features in fine classification. With the proposed recognition system, experiments are performed on the 863 Testing System. The correct rate reaches 80.56%, which is a promising result.
6341849
Efficient Translation of OpenMP to Distributed Memory
The shared memory paradigm provides many benefits to the parallel programmer, particular with respect to applications that are hard to parallelize. Unfortunately, there are currently no efficient implementations of OpenMP for distributed memory platforms and this greatly diminishes its usefulness for real world parallel application development. In this paper we introduce a basic strategy for implementing OpenMP on distributed memory systems via a translation to Global Arrays. Global Arrays is a library of routines that provides many of the same features as OpenMP yet targets distributed memory platforms. Since it enables a reasonable translation strategy and also allows precise control over the movement of data within the resulting code, we believe it has the potential to provide higher levels of performance than the traditional translation of OpenMP to distributed memory via software distributed shared memory.
11156292
Efficient Implementation of OpenMP for Clusters with Implicit Data Distribution
This paper discusses an approach to implement OpenMP on clusters by translating it to Global Arrays (GA). The basic translation strategy from OpenMP to GA is described. GA requires a data distribution; we do not expect the user to supply this; rather, we show how we perform data distribution and work distribution according to OpenMP static loop scheduling. An inspector-executor strategy is employed for irregular applications in order to gather information on accesses to potentially non-local data, group non-local data transfers and overlap communications with local computations. Furthermore, a new directive INVARIANT is proposed to provide information about the dynamic scope of data access patterns. This directive can help us generate efficient codes for irregular applications using the inspector-executor approach. Our experiments show promising results for the corresponding regular and irregular GA codes.