Computational methods applied to oxidational wear

Theories of oxidational wear tend to involve the number of contacts (N) between sliding tribo-elements as well as the contact temperature (T_F), i.e. the temperature at the real areas of contact between these tribo-elements. This paper describes how these important parameters can be found for a given tribo-system, namely high-chromium ferritic steel pins sliding against rotating austenitic stainless steel disks, by the application of a numerical method to the analysis of the theoretical and experimental divisions of heat (DTH and DE) between tribo-elements undergoing oxidational wear. The paper then shows how one can use these values of N and T_F as inputs to a similar numerical method in order to deduce credible and consistent values for the tribological oxidation constants required for the theoretical oxidational wear rates (W_RTH) to be equal to the experimentally measured oxidational wear rates (W_REXPT) of the given tribo-system.     

Synthesis of stochastic images with given fractal dimension

Synthesis methods based on spatial-frequency filtering have been developed for fractal images for which the structure functions are power laws over a wide range of increments which is about one-quarter of the image size. It is shown that, using the Weierstrass function, only stationary processes (images) can be simulated. An algorithm for modeling fractional Brownian images is proposed and studied. It is established that the integral characteristic of the spectrum of a Brownian image with the Hurst parameter α is well approximated by a power function with an exponent 2(α+1) for α ∈ (0, 1/2] and an exponent of 3 for α ∈ (1/2, 1). Using as an examples modifications of images of samples of amorphous alloys, it is shown that statistically self-similarity images little different from the original image can be simulated. This allows one to determine to what extent the structures visualized in the images exhibit fractal properties.     

NC data generation for 6-axis machine tools to produce a helical drill

This study presents a design methodology for grinding a specific helical drill on a CNC 6-axis grinding machine. The proposed methodology comprises three steps: (1) deriving a mathematical model of the helical drill, (2) establishing the ability matrix of the multi-axis grinding machine according to Denavit-Hartenberg (D-H) notation, and (3) constructing configuration matrices to express the required grinding wheel positions and orientations while machining the flute and flank surfaces of the drill. The NC data for the motion values of each axis are obtained by equating the corresponding elements of the CNC ability matrix and the configuration matrices of the grinding wheel. To verify the proposed methodology, a designed helical drill is machined on a 6-axis CNC tool-grinding machine. The methodology presented in this study integrates the drill design and manufacturing activities, thereby making possible the implementation of a more flexible, automatic, cost efficient and controllable design and production process.     

共面二次曲线族不变量的计算方法研究

不变量是几何结构的本质描述,利用不变量进行物体识别、形状描述是计算机视觉中非常活跃的一个研究领域,其中图像中不变量特征的提取与构造是最终实现图像目标识别的关键技术之一。在基于目标不变量的复杂场景三维重建中,有时会遇到对多条共面二次曲线(二次曲线族)不变量的计算问题。从实际应用的角度出发,首先将二次曲线族表示为一个多变量矩阵,然后利用不变量理论研究二次曲线族不变量的计算方法,最后通过算法举例,给出了共面二次曲线族不变量的计算过程,并进行了算法验证。     

平面轮廓曲线数据的B样条曲线逼近算法

周期性封闭B样条曲线曲面是医学内植物设计中曲线、曲面造型的主要构造方法.介绍一种断层医学图像目标组织轮廓样条曲线建模方法.首先从断层医学序列图像中提取出目标组织的轮廓曲线,然后采用多边形逼近简化数据点,之后在满足一定控制误差的条件下,用最小二乘法通过B样条曲线逼近轮廓曲线,用尽可能少的数据量表示出各个断层的轮廓曲线,获得医学内植物设计所需的骨组织轮廓曲线模型.     

新一代天气雷达原始数据自动整理程序

按照中国气象局业务观测规范,新一代天气雷达体扫数据要求及时存储。新一代天气雷达体扫资料数据量大,手工进行压缩存盘是一项繁杂的工作。本文介绍了一种新一代天气雷达（CINRAD/CD）基数据自动压缩存贮备份程序,该程序实现了无人操作、安全可靠地多重存储备份雷达基数据资料,减少了业务上的繁杂工作。     

Bayesian estimate of the degree of a polynomial given a noisy data sample

Regression analysis is widely used to create continuous representations of discrete data-sets. When the regression model is not based on the physics underlying the data, heuristic models play a crucial role and the model choice affects the data analysis. This paper identifies the most appropriate model in terms of Bayesian selection. The result is applied to two practical examples, one of which is taken from a problem of chemical thermodynamics.     

模糊图像边缘精确定位的滤波算法

图像的边缘是图像最基本也是最重要的特征之一。实际应用中,光学系统离焦和图像传感器噪声源引起图像模糊,导致边缘自动定位算法无法精确确定边缘点。从边缘检测理论出发,根据噪声及图像模糊模型,提出了基于空间域和频域的滤波方法对模糊边缘图像去噪,从而消除模糊图像对于边缘定位的影响。实验表明,各种滤波方法对于边缘点的自动提取都具有一定的效果,离焦模糊和噪声可以得到有效抑制,尤其是频域低通滤波器能够精确地提取出模糊边缘位置。     

An investigation of segmentation methods and texture analysis applied to tomographic images of human vertebral cancellous bone

The goal of this study is to determine architectural and textural parameters on computed tomographic (CT) images, allowing us to explain the mechanical compressive properties of bone. Although the resolution (150 μm) is of the same order of magnitude as the trabecular thickness, this method enables the possibility of perfecting an in vivo peripheral CT system with an acceptable radiation dose for the patient. This study was performed on L2 vertebrae cancellous bone specimens taken after necropsy in 22 subjects aged 47–95 years (mean: 79 years). The segmentation process is a crucial point in the determination of accurate architectural parameters. In this paper the use of two different segmentation methods is investigated, based on an edge enhancement and a region growing approach. The images are compared and the architectural parameters extracted from the images segmented by both methods lead to a quantitative evaluation. The parameters are found to be globally robust towards the segmentation process, although some of them are much more sensitive to the approach used. Highly significant correlations ( P  < 0.0005) have been obtained between the two segmentation methods for all the parameters, with ρ ranging from 0.70 to 0.93. In order to improve the assessment of bone architecture, texture analysis (run length method) was investigated. New features are obtained from an image reduced to 16 grey-levels. Textural parameters in addition to architectural parameters in a multivariate regression model increase significantly ( P  = 0.01) the prediction of the maximum compressive strength (variation of r ² from 0.75 up to 0.89).     

A new method to determine the number of experimental data using statistical modeling methods

For analyzing the statistical performance of physical systems, statistical characteristics of physical parameters such as material properties need to be estimated by collecting experimental data. For accurate statistical modeling, many such experiments may be required, but data are usually quite limited owing to the cost and time constraints of experiments. In this study, a new method for determining a reasonable number of experimental data is proposed using an area metric, after obtaining statistical models using the information on the underlying distribution, the Sequential statistical modeling (SSM) approach, and the Kernel density estimation (KDE) approach. The area metric is used as a convergence criterion to determine the necessary and sufficient number of experimental data to be acquired. The proposed method is validated in simulations, using different statistical modeling methods, different true models, and different convergence criteria. An example data set with 29 data describing the fatigue strength coefficient of SAE 950X is used for demonstrating the performance of the obtained statistical models that use a pre-determined number of experimental data in predicting the probability of failure for a target fatigue life.

     

视频图像实时采集和显示系统的FPGA设计

针对视频图像信息实时采集过程中,数据量大、快速性要求高,普通的处理器芯片难以胜任的问题,本文给出一种采用FPGA的视频图像实时采集和显示系统的设计实例.通过该实例介绍了基于FPGA的视频信息采集与显示系统的设计方法,以及FPGA应用系统设计中一些难点问题的解决办法.通过IP核调用、异步FIFO数据缓冲、存储器乒乓操作等方法,利用FPGA内部资源实现了各功能模块的设计.仿真和实际测试结果表明,利用FPGA进行视频图像信息采集和显示系统设计,是降低产品体积、功耗,提高快速性、稳定性的有效途径.     

Use of centrifugal disk atomizer to produce CdS films

The use of a centrifugal disk atomizer to produce chemically sprayed CdS films is described. The film growth rate has been found to depend on substrate temperature, solution concentration, and feed rate. The films grown on glass substrates have been studied by electron microscopy and x-ray diffraction. A fine-grained wurtzite structure has been obtained.     

数字化图像技术测量凝胶电泳蛋白质含量的三种方法比较

本文基于光密度测量原理,在考虑了凝胶电泳图像数字化过程中照射光源强度、凝胶背景、摄像机等参量对蛋白质含量计算结果的影响后,提出了凝胶电泳蛋白定量测量的改进公式和实验方法,并与目前使用较多的灰度积分法、灰度积分拟合法进行了实验比较。结果显示,改进公式所得结果更接近真实值、标准差更小、且不受凝胶背景变化的影响。     

Computational approach to photonic drilling of silicon carbide

The ability of lasers to carry out drilling processes in silicon carbide ceramic was investigated in this study. A JK 701 pulsed Nd:YAG laser was used for drilling through the entire depth of silicon carbide plates of different thicknesses. The laser parameters were varied in different combinations for a well-controlled drilling through the entire thickness of the SiC plates. A drilling model incorporating effects of various physical phenomena such as decomposition, evaporation-induced recoil pressure, and surface tension was developed. Such comprehensive model was capable of advance prediction of the energy and time required for drilling a hole through any desired depth of material.     

A simple model of holography and some enhanced resolution methods in electron microscopy

A simple pictorial model of electron interference effects based on an extended representation of the autocorrelation function is described and developed. Unlike Abbe's theory of transmission imaging, the model incorporates fully the effect of the loss of phase that occurs in the detector plane. The aperture transfer function and information limit (envelope function) are also incorporated with reference to the simplest scattering geometry of Young's slits. The model is then applied to holography, the diffraction phase problem, ptychography, Wigner distribution deconvolution, conventional bright-field imaging, single side-band imaging and tilt-series reconstruction. Some of these methods require an understanding of four-dimensional integral functions, but the model reduces the problem into a projection of a two-dimensional space. It is hoped that the model will help material scientists who are not specialists in imaging and diffraction theory to understand some recent developments in advanced super-resolution imaging methods.     

离心式鼓风机常见故障及排除措施

分析了离心式鼓风机运行中轴承振动、轴承温度高等故障的几种原因,特别是着重分析了喘振的具体现象,并对以上故障提出了被实践证明行之有效的处理方法。