基于PC的大面积地形三维可视化仿真系统研究

提出了一种基于单处理器PC机的大面积地形三维可视化仿真系统建模、管理和动态调度的实现方法,较好地解决了图像的逼真度和实时性之间的矛盾。同时,为满足不同用户对系统开发的要求,提出了一种把Multigen-ParadigmVega开发平台与OpenGL技术结合使用的方法。并采用分布交互仿真技术,实现该仿真系统与其它仿真系统的互操作。     

一种基于三阶中心矩的图像边缘检测方法

利用像素邻域的三阶中心矩,可以提取图像边界。根据边缘图像灰度的众数,边缘强度图像的二值化变得非常简单,不需要手工交互。利用中国数字化虚拟人数据进行实验,结果表明,应用这种基于三阶中心矩的新方法来检测边缘的效果良好。     

建筑平面图理解中对墙体符号的识别方法

一些由图纸矢量化或者CAD软件绘制的建筑平面图只包含基本的几何图形元素如线段、弧线等,需要通过符号识别得到关于建筑结构的信息,例如墙体拓扑结构、门窗的位置、型号等。该文提出了一种对建筑平面图的墙体符号识别算法,结合建筑平面图的领域知识,首先利用几何运算从平面图中提取出构成墙体候选符号的子图,再使用逻辑方法推理确定墙体元素符号并得到完整的墙体拓扑结构信息。     

基于状态检测的TCP包过滤在Linux下的实现方法

该文主要介绍了在Linux2.4内核下基于状态转换和检测的TCP包过滤的实现方法。通过对传统全状态包过滤防火墙的改进,增加了状态转换和连接序号检查,增强了防火墙的安全性。通过日志记录异常状况,系统管理员可以采用相应的措施防止潜在的攻击。     

A Fast Spectral Method for Active 3D Shape Reconstruction

Variational energy minimization techniques for surface reconstruction are implemented by evolving an active surface according to the solutions of a sequence of elliptic partial differential equations (PDE's). For these techniques, most current approaches to solving the elliptic PDE are iterative involving the implementation of costly finite element methods (FEM) or finite difference methods (FDM). The heavy computational cost of these methods makes practical application to 3D surface reconstruction burdensome. In this paper, we develop a fast spectral method which is applied to 3D active surface reconstruction of star-shaped surfaces parameterized in polar coordinates. For this parameterization the Euler-Lagrange equation is a Helmholtz-type PDE governing a diffusion on the unit sphere. After linearization, we implement a spectral non-iterative solution of the Helmholtz equation by representing the active surface as a double Fourier series over angles in spherical coordinates. We show how this approach can be extended to include region-based penalization. A number of 3D examples and simulation results are presented to illustrate the performance of our fast spectral active surface algorithms.     

Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations.The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored.     

高强度钢干式铣削替代半精磨的试验研究

采用硬质合金刀片(YW1)和涂层刀片(YB415)进行了高强度钢的干式铣削代替半精磨试验研究。根据试验结果,确定适合加工该型号高强度钢的刀具材料和切削用量。以这两种刀片在不同切削用量条件下的耐用度、加工表面粗糙度和主切削力作为刀具加工性能的评价依据,同时研究了刀片的磨、破损机理和卷、排屑稳定性。试验结果表明:涂层刀片干铣削高强度钢的加工性能优异,工件加工表面质量达到半精磨水平。     

硅藻土胎模成形刀具设计

通过硅藻土胎模的加工实践,分析了硅藻土特点及其切削性能,设计了加工硅藻土胎模成型曲面的成形刀具,不但提高了胎模加工表面的质量,而且使硅藻土胎模成型曲面的加工效率提高了几十倍。     

压铸镁合金选择的模糊综合评判方法

合理地选择合金是进行压铸产品设计的重要环节之一。本文基于模糊综合评判原理 ,建立了压铸镁合金材料选择系统 ,快捷有效地选择出最合适的合金牌号。同时 ,以一 MP3外壳选材为例 ,具体说明系统运行过程     

水声换能器及其研究和发展

阐述了水声换能器和频响特性、指向性及不同尺寸和频率范围的换能器的多种不同的校准方法，就其优缺点进行了比较。并具体介绍我国自声学院声学所成立以来水声换能器在换能材料和声学无源材料、换能吕和基陈以及水下电声测量等3个方面的取得的研究和成果。介绍了在压电陶瓷、吸声材料、换能器各种基阵等方面取得的国内外领先成果和应用现状。最后给出我国水声换能器的发展方向及动态，对其发展前景作了展望。