云计算数据中心组网技术

本文分析云计算应用对网络架构提出的新需求,结合近两年网络技术的标准发展,介绍当前主流厂家的网络技术及他们的发展方向。     

On the rod placement theorem of Rybko and Shlosman

Given n−1 points on the real line and a set of n rods of strictly positive lengths , we get to choose an n-th point x_n anywhere on the real line and to assign the rods to the points according to an arbitrary permutation π. The rod is thought of as the workload brought in by a customer arriving at time x_k into a first in -first out queue which starts empty at − ∞. If any x_i equals x_j for i < j, service is provided to the rod assigned to x_i before the rod assigned to x_j. Let denote the set of departure times of the customers (rods). Let denote the number of choices for the location of x_n for which . Rybko and Shlosman proved that

股票定向增发、盈余管理与公司的业绩滑坡——基于应计项目操控与真实活动操控方式下的研究

本文采用了应计项目操控与真实活动操控两种模型研究了我国上市公司定向增发新股过程中盈余管理行为以及之后的业绩表现,结果发现:中国上市公司在定向增发过程中会同时使用应计项目操控与真实活动操控两种盈余管理方式;进一步研究发现应计项目盈余管理会导致上市公司定向增发后业绩的短期滑坡,真实活动盈余管理会引起公司业绩的长期滑坡,真实活动盈余管理是上市公司定向增发之后业绩滑坡的主要原因。     

两轮移动倒立摆的开关切换模糊极点配置控制器设计

为了更好地控制两轮移动式倒立摆,文章以两轮移动式倒立摆动力学数学模型为基础,设计了一种开关切换模糊极点配置控制器,利用该控制器对系统进行控制。通过一个选择型开关把模糊控制和状态反馈的极点配置控制有机的统一起来构成了开关切换模糊极点配置控制器。在Simulink中,对设计的开关切换模糊极点配置控制器进行了仿真,实现了两轮移动式倒立摆的平衡、匀速前进、匀速转弯。仿真结果说明了开关切换模糊极点配置控制器对两轮移动式倒立摆起到一定的抗干扰和理想的控制作用。     

Relighting 3D Scenes with a Continuously Moving Camera

This paper proposes a novel technique for 3D scene relighting with interactive viewpoint changes. The proposed technique is based on a deep framebuffer framework for fast relighting computation which adopts image‐based techniques to provide arbitrary view‐changing. In the preprocessing stage, the shading parameters required for the surface shaders, such as surface color, normal, depth, ambient/diffuse/specular coefficients, and roughness, are cached into multiple deep framebuffers generated by several caching cameras which are created in an automatic manner. When the user designs the lighting setup, the relighting renderer builds a map to connect a screen pixel for the current rendering camera to the corresponding deep framebuffer pixel and then computes illumination at each pixel with the cache values taken from the deep framebuffers. All the relighting computations except the deep framebuffer pre‐computation are carried out at interactive rates by the GPU.     

Statistical methods to estimate vehicle count using traffic cameras

Traffic camera has played an important role in enabling intelligent and real-time traffic monitoring and control. In this paper, we focus on establishing a correlation model for the traffic cameras’ vehicle counts and increase the spatial-resolution of a city’s vehicle counting traffic camera system by means of correlation-based estimation. We have developed two methods for constructing traffic models, one using statistical machine learning based on Gaussian models and the other using analytical derivation from the origin-destination (OD) matrix. The Gaussian-based method outperforms existing correlation coefficient based methods. When training data are not available, our analytical method based on OD matrix can still perform well. When there is only a limited number of cameras, we develop heuristic algorithms to determine the most desirable locations to place the cameras so that the errors of traffic estimations at the locations without traffic cameras are minimized. We show some improvements in the performance of our proposed methods over an existing method in a variety of simulations.

Optimal wire ordering and spacing in low power semiconductor design

A key issue for high integration circuit design in the semiconductor industry are power constraints that stem from the need for heat removal and reliability or battery lifetime limitations. As the power consumption depends heavily on the capacitances between adjacent wires, determining the optimal ordering and spacing of parallel wires is an important issue in the design of low power chips. As it turns out, optimal wire spacing is a convex optimization problem, whereas the optimal wire ordering is combinatorial in nature, containing (a special class of) the Minimum Hamilton Path problem. While the latter is ${\mathcal{NP}}A key issue for high integration circuit design in the semiconductor industry are power constraints that stem from the need for heat removal and reliability or battery lifetime limitations. As the power consumption depends heavily on the capacitances between adjacent wires, determining the optimal ordering and spacing of parallel wires is an important issue in the design of low power chips. As it turns out, optimal wire spacing is a convex optimization problem, whereas the optimal wire ordering is combinatorial in nature, containing (a special class of) the Minimum Hamilton Path problem. While the latter is -hard in general, the present paper provides an algorithm that solves the coupled ordering and spacing problem for N parallel wires to optimality. Dedicated to Prof. Martin Gr?tschel on the occasion of his 60th birthday.     

控制贴片质量关键因素的研究

贴片质量的优劣一直困扰着贴片机的使用者,影响贴片质量的因素有很多,诸如贴片机自身硬件软件条件、贴片对象的质量、贴片环境的合适程度、贴片技术的娴熟程度、贴片机操作人的人为因素等等。本文从元器件选择、贴片机结构与性能两个角度阐述了其如何影响贴片质量。以元器件尺寸、端头电极与引线电极、平整度、料带等方面细述如何选择最合适的元器件以提高贴片质量,并以吸嘴为例细述了如何选择与设置贴片机吸嘴和贴片压力来提高贴片质量。对影响贴片质量的贴片位置控制也作了一定的论述。     

On Performance of Node Placement Approaches for Hierarchical Heterogeneous Sensor Networks

This paper considers a two-tier hierarchical heterogeneous wireless sensor network using the concept of clustering. The network has two type of nodes: regular sensor nodes (litenodes or LN) with limited communications, storage, energy, and computation power; and high-end sophisticated nodes (SNs), or clusterheads, with significantly additional resources. The litenodes communicate their data to the SNs and the SNs forward all collected data to a central gateway node called the base station (BS). Our network architecture allows the LNs to reach a SN via multiple hops through other LNs. We investigate the problem of optimally placing a minimum number of sophisticated nodes to handle the traffic generated by the lite nodes, while ensuring that the SNs form a connected network using their wireless links. This placement problem is formulated and solved as multi-constraint optimization problem using well known approaches: Binary Integer Linear Programming (BILP) approach, Greedy approach (GREEDY) and Genetic Algorithm (GA) approach. It was found through simulations that BILP performed best for regular grid topologies, while GA performed better for random LN deployment. Furthermore, the effects of various parameters on the solution are also presented. The paper also proposes a HYBRID approach that uses the solutions provided by GREEDY and/or BILP as the initial solution to the GA. Using HYBRID, results comparable to original GA could be obtained in only 11.46% of the time required for the original GA. Part of the research was supported by a grant from Air Force Office of Scientific Research (AFOSR) grant No. FA9550-06-1-0103.     

Cache Hit Ratio Maximization in Device-to-Device Communications Overlaying Cellular Networks

This paper investigates the content placement problem to maximize the cache hit ratio in device-to-device(D2D)communications overlaying cellular networks.We consider offloading contents by users themselves,D2D communications and multicast,and we analyze the relationship between these offloading methods and the cache hit ratio.Based on this relationship,we formulate the content placement optimization as a cache hit ratio maximization problem,and propose a heuristic algorithm to solve it.Numerical results demonstrate that the proposed scheme can outperform existing schemes in terms of the cache hit ratio.