供水业大管径流量仪表的应用

供水行业流量仪表分为原水、出厂水、向用户供水等贸易结算和水厂内部工艺流程的流量测量／控制两大类。两类仪表性能要求不同。     

超声流量计的市场与应用

一、前言 超声技术应用于流量测量要回溯到20世纪50年代后期，60～70年代出现了一批超声流量计（简称USF）专利，70～80年代众多型号USF商品投入市场。60年代末70年代初研制出无需对被测管道动手术，外夹装超声换能器的USF，还发展多普勒效应USF。1972年外夹装式传播时间法USF商品投放市场，引起了用户极大兴趣，推动了USF的发展。     

轧机机架和轴承座的间隙及衬板材料

轧机机架和轴承座的间隙及衬板材料［加拿大］ＲｉｃｈａｒｄＣ．Ｓｃｈｒａｍａ等１前言由于对带钢形状和规格的质量要求越来越高，因此，生产时要求轧机各部分要保持准确的公差。本文描述轧机牌坊窗口和轧辊轴承座之间的间隙和公差极限，然后阐述其设计的基本原理，同时...     

Designing DSS (decision support systems) and EIS (executive information systems) applications to fit executive user needs

The effectiveness of executive information systems and decision support rests on the level of understanding, commitment and use that top management devotes to the system. The author describes new technologies that help promote executive commitment to DSS/EIS.     

Development and validation of a Monte Carlo simulation of photon transport in an Anger camera

The geometric component of the point spread function (PSF) of a gamma camera collimator can be determined analytically, and the penetration component can be calculated readily by numerical ray-tracing. A Monte Carlo simulation of photon transport which includes collimator scatter is developed. The simulation was implemented with an array processor which propagates up to 1024 photons in parallel, allowing accurate estimates of the total radial PSF in less than a day. The simulation was tested by imaging monoenergetic point sources of Tc-99m, Cr-51, and Sr-85 (140, 320, and 514 keV, respectively) on a General Electric Star Cam with low-energy, general-purpose, and medium-energy collimators. Comparisons of measured and simulated PSFs demonstrate the validity of the model and the significance of collimator scatter in the degradation of image quality.     

A nonstationary signal simulation model for continuous wave and pulsed Doppler ultrasound

A computer simulation model of the nonstationary Doppler ultrasound signals arising from pulsatile blood flow is presented. The model uses sinusoidal components that are modulated by a power spectral density function that varies over the cardiac cycle. An empirical model consisting of two exponential functions is used to represent both the continuous wave and pulsed Doppler power spectral density for normal carotid arteries. It is shown that the spectrogram speckle patterns of the synthesized Doppler signals compare very well with those clinically recorded.     

Corrections for nonuniform sampling distortions in magnetic resonance imagery

A technique for estimating and correcting nonuniform sampling distortions in magnetic resonance imagery is presented. The technique consists of first estimating the sampling grid distortion using a parametric model, and then estimating the uniformly sampled data by interpolation on the nonuniform grid. Parameterized models for two particular sampling grid distortion are presented. Maximum likelihood and maximum a posteriori estimators are developed for these distortions. Using computer simulated data, these estimators are shown to perform well.