On hypergraph Lagrangians

It is conjectured by Frankl and F\"uredi that the $r$-uniform hypergraph with $m$ edges formed by taking the first $m$ sets in the colex ordering of ${\mathbb N}^{(r)}$ has the largest Lagrangian of all $r$-uniform hypergraphs with $m$ edges in \cite{FF}. Motzkin and Straus' theorem confirms this conjecture when $r=2$. For $r=3$, it is shown by Talbot in \cite{T} that this conjecture is true when $m$ is in certain ranges. In this paper, we explore the connection between the clique number and Lagrangians for $r$-uniform hypergraphs. As an implication of this connection, we prove that the $r$-uniform hypergraph with $m$ edges formed by taking the first $m$ sets in the colex ordering of ${\mathbb N}^{(r)}$ has the largest Lagrangian of all $r$-uniform graphs with $t$ vertices and $m$ edges satisfying ${t-1\choose r}\leq m \leq {t-1\choose r}+ {t-2\choose r-1}-[(2r-6)\times2^{r-1}+2^{r-3}+(r-4)(2r-7)-1]({t-2\choose r-2}-1)$ for $r\geq 4.$Comment: 10 pages. arXiv admin note: substantial text overlap with arXiv:1312.7529, arXiv:1211.7057, arXiv:1211.6508, arXiv:1311.140

Multiple Access Channels with Generalized Feedback and Confidential Messages

This paper considers the problem of secret communication over a multiple access channel with generalized feedback. Two trusted users send independent confidential messages to an intended receiver, in the presence of a passive eavesdropper. In this setting, an active cooperation between two trusted users is enabled through using channel feedback in order to improve the communication efficiency. Based on rate-splitting and decode-and-forward strategies, achievable secrecy rate regions are derived for both discrete memoryless and Gaussian channels. Results show that channel feedback improves the achievable secrecy rates.Comment: To appear in the Proceedings of the 2007 IEEE Information Theory Workshop on Frontiers in Coding Theory, Lake Tahoe, CA, September 2-6, 200

A Study of Service Desk Setup in Implementing IT Service Management in Enterprises

金沢大学理工研究域電子情報学系Information Technology Service Management (ITSM) provides a framework to provide IT related services and the interaction of IT staff with users, and is often related with the British Government’s Information Technology Infrastructure Library (ITIL). ITIL offers a set of “best practices” for managing IT services and is one of the most widely accepted approaches to IT service management in the world. Recently, more and more enterprises implemented a centralized IT service management model based on the ITIL framework. However, even by adopting ITIL, most of the enterprises didn’t improve their IT service management level. Some factors become the barriers to the success of ITIL and ITSM implementation. In some cases, enterprises paid more attention to IT infrastructure setup and operation but neglect the importance of Service Desk. In this study, we first review ITSM, ITIL and Service Desk. Second, we identify a full function of new Service Desk and how to setup a good Service Desk. Enterprises should take proper measures in building a mature Service Desk to ensure successful implementation of ITSM

Numerical Study of Hypersonic Boundary Layer Receptivity Characteristics Due to Freestream Pulse Waves

A finite difference method is used to do direct numerical simulation (DNS) of hypersonic unsteady flowfield under the action of freestream pulse wave. The response of the hypersonic flowfield to freestream pulse wave is studied, and the generation and evolution characteristics of the boundary layer disturbance waves are discussed. The effects of the pulse wave types on the disturbance mode in the boundary layer are investigated. Results show that the freestream disturbance waves significantly change the shock standoff distance, the distribution of flowfield parameters and the thermodynamic state of boundary layer. In the nose area, the main disturbance modes in the boundary layer are distributed near the fundamental mode. With the evolution of disturbance along with streamwise, the main disturbance modes are transformed from the dominant state of the fundamental mode to the collective leadership state of the second order and the third order harmonic frequency. The intensity of bow shock has significant effects on both the fundamental mode and the harmonic modes in each order. The strong shear structure of boundary layer under different types of freestream pulse waves reveals different stability characteristics. The effects of different types of freestream pulse waves are significant on the distribution and evolution of disturbance modes. The narrowing of frequency band and the decreasing of main disturbance mode clusters exist in the boundary layer both for fast acoustic wave, slow acoustic wave and entropy wave

A scalable bloom filter based prefilter and hardware-oriented predispatcher

Presented in this paper a scalable bloom filter based prefilter and a hardware-oriented predispatcher pattern matching mechanism for content filtering applications, which are scalable in terms of speed, the number of patterns and the pattern length. Prefilter algorithm is based on a memory efficient multi-hashing data structure called bloom filter. According to the statistics of simulations, the filter ratio can reach up to 60% if the whole engine has been trained well. It has been showed that this engine could enhance the capabilities of general-purpose IDS solutions