CAD线图数据处理的灰色逐步优化GM(1,1)模型

在分析计算机辅助设计线图数据处理的技术后，通过逐步优化差商调整系数，得到了其线图数据处理的灰色模型参数估计的逐步优化模型与方法。该模型突破了传统GM(1，1)模型发展系数的禁区，克服了现有GM(1，1)模型的不足，扩展了GM(1，1)模型的应用范围。实例表明，该方法简单实用，值得在计算机辅助设计中推广使用。     

CAD设计线图处理的不确定性系统模型与方法

运用泛灰不确定性系统理论，建立了计算机辅助设计线图处理不确定性系统模型USM-1，给出了精度检验方法。编制了Matlab程序，给出了线图处理实例，并与各种灰色模型进行了比较。该模型不需要累加生成和累减生成，不仅适合于等间距建模，也适合于非等间距建模，具有精度高、使用简便等特点，可在计算机辅助设计中使用。     

CAD线图数据处理的GM(1,N)模型与方法

运用灰色系统理论，通过优化模型系数与背景取值建立了灰色多因素灰色动态GM（1，N）模型。该模型克服了现有GM（1，N）模型的不足，扩宽了GM（1，N）模型的应用范围。运用该模型的GM（1，2）、GM（1，3）线图处理实例表明该方法简单实用，值得在计算机辅助设计中推广应用。     

计算机辅助设计技术在机械设计中的应用分析

计算机辅助设计技术随着时间的发展其在机械设计中的渗透速度不断加快,计算机辅助设计技术能够借助现有优势优化机械设计环节,同时能够建立模型增强设计功能的稳定性。计算机辅助设计能够兼顾经济和社会两大因素,并促使机械设计时间不断缩短,计算机辅助设计技术不断更新,满足了不断增长的机械设计需求。     

山东双力集团股份有限公司CAPP工程的实施与应用

以山东双力集团股份有限公司计算机工艺辅助设计系统(CAPP)实施与应用的实现为例，针对计算机工艺辅助设计系统(CAPP)的需求、系统选型、实施等问题，提出了相应的方法和策略。     

基于PDM犁的智能CAD设计系统

讨论基于产品数据管理(PDM)犁的智能CAD设计系统基本框架及其3个组成部分：设计专家系统、产品数据管理和犁的计算机辅助设计。研究了各部分的功能和技术实现，设计专家系统用于犁的参数化设计过程中参数的选择和装配图装配合理性的判断，PDM主要管理犁的辅助设计相关的数据和文件以及专家系统知识。在此基础上，介绍了集成专家系统和产品数据管理犁的计算机辅助设计软件开发。     

“泵的CAD系统”通过鉴定

由江苏工学院排灌机械研究所负责的机电部基金项目“泵的CAD系统”于1992年7月7日在江苏工学院通过部级鉴定。该系统包括;(1)离心泵计算机辅助设计程序;(2)混流泵计算机辅助设计程序;(3)轴流泵计算机辅助设计程序;(4)空间导叶、径向导叶计算机辅助设计程序;(5)泵内三元粘性流动计算程序;(6)泵的图形库和数据库。     

基于AutoCAD的三维建模在数控加工上的应用研究

在机械设计和制造中，计算机辅助设计（Computer Aided Design，简称CAD）和数控加工自动编程（Automatic Programming，简称AP）被广泛的应用，使工艺设计自动化与计算机辅助设计和辅助制造一体化。借助VBA用机械加工的方法开发机械零件的三维实体造型，将造型直接数控加工出来，使机械制造高度自动化，缩短产品的开发周期，大大提高生产率，节约大量人力、物力资源。     

计算机辅助设计技术在机械设计中的应用分析

在机械设计的过程中需要计算机辅助设计技术人员利用绘图软件对机械进行设计,而绘图是机械设计的重要一环,需要设计人员不断的修改完善,才能使得机械设计更加合理,符合使用者对软件设计的要求。本文通过对机械设计中计算机辅助设计技术对机械设计的重要性、计算机辅助设计技术的应用范围以及它们的优缺点进行分析,供相关人员参考借鉴。     

浅谈计算机在农机开发与推广中的应用

随着计算机应用的普及和网络资源的迅猛发展,计算机已经渗透到人类的生产、生活中,计算机辅助设计(CAD)和计算机辅助制造(CAM)以及计算机辅助分析(CAA),己经在机械设计、加工等领域得到了广泛的应用,在我国的许多科研院所计算机辅助设计(CAD)的使用也是相当普遍的.     

Influence of likelihood function choice for estimating crop model parameters using the generalized likelihood uncertainty estimation method

Proper estimation of model parameters is required for ensuring accurate model predictions and good model-based decisions. The generalized likelihood uncertainty estimation (GLUE) method is a Bayesian Monte Carlo parameter estimation technique that makes use of a likelihood function to measure the closeness-of-fit of modeled and observed data. Various likelihood functions and methods of combining likelihood values have been used in previous studies. This research was conducted to determine the effects of using previously reported likelihood functions in a GLUE procedure for estimating parameters in a widely-used crop simulation model. A factorial computer experiment was conducted with synthetic measurement data to compare four likelihood functions and three methods of combining likelihood values using the CERES-Maize model of the Decision Support System for Agrotechnology Transfer (DSSAT). The procedure used an arbitrarily-selected parameter set as the known “true parameter set” and the CERES-Maize model to generate true output values. Then synthetic observations of crop variables were randomly generated (four replicates) by using the simulated true output values (dry yield, anthesis date, maturity date, leaf nitrogen concentration, soil nitrate concentration, and soil moisture) and adding a random observation error based on the variances of corresponding field measurements. The environmental conditions were obtained from a sweet corn (Zea mays L.) experiment conducted in 2005 in northern Florida. Results showed that the method of combining likelihood values had a strong influence on parameter estimates. The combination method based on the product of the likelihoods associated with each set of observations reduced the uncertainties in posterior distributions of parameter estimates most significantly. It was also found that the likelihood function based on Gaussian probability density function was the best among those tested. This combination accurately estimated the true parameter values, suggesting that it can be used when estimating CERES-Maize model parameters for real experiments.     

点源时间序列数据缺失值的估值不确定性分析——以小流域气象和水文数据为例

【目的】对普遍存在的时间序列缺失值进行有效估值,进而改善时间序列数据的质量。【方法】以亚热带典型小流域长期定位观测的气象(最低气温、最高气温、太阳辐射)及水文(降水量、地表径流量)数据为样本并利用计算机模拟的方法,比较了线性内插法、K-最近邻插值法、多项式插值法、样条插值法和核密度估值法5种估值方法的性能差异,分析了不同取样时间步长(日和月)及不同数据缺失量(1%、5%、10%、15%、20%)条件下对缺失值进行估值的不确定性。均方根误差(RMSE)、绝对值平均误差(MAE)和Pearson相关系数(r)3个交叉验证指标用于评估5种估值方法的性能优劣。【结果】①5种方法估值性能较好,Pearson相关系数为0.62～0.99(P<0.05),且以核密度估值法和多项式插值法的估值性能为优;②数据缺失量和取样步长增加降低了5种估值方法的估值精度;③数据集的变异系数(CV)与估值评估指标(RMSE、MAE及r)显著相关(P<0.05)。【结论】核密度估值法和多项式插值法的估值结果相对更可靠,变异系数是影响估值不确定性的重要因素。     

无速度传感器矢量控制系统的电机参数测算

针对无速度传感器矢量控制系统电机参数的自检测问题,根据异步电机的数学模型,给出了电机在静止条件下,利用单相加载、采用准同步采样算法测算电机参数的新方法;推导出计算转子等效电阻、定子等效漏感和电机等效互感的数学模型。并以7．5kw电机为例对电机的参数进行实测,以该数据设计了无速度传感器矢量控制系统。运行实验证实了该方法的实用性和有效性。     

Methods to measure Dust Production and Deposition Rates in Buildings

Two parameter estimation methods were developed for the estimation of the rates of dust production and dust deposition. Both methods could be applied to occupied livestock buildings because they do not involve the need to take measurements within the animal pens. Experiments were conducted in a laboratory chamber using talcum powder as the aerosol to test the two methods.The steady-state method depends upon being able to hold all except one of the terms in the steady-state mass balance equation constant. In these laboratory tests, the term that was changed was the dust removal efficiency of the filtration system. The estimates of dust production rate were within 1 and 15% of the measured rate in two tests, while the estimates of dust deposition rate were within 1 and 18% of the measured rate in the same two tests.The unsteady-state method involved measuring airspace dust concentration versus time. The method provided accurate estimates of dust production and dust deposition separately for the data of Wadden and Scheff but not for the experimental data collected in this project. When the experimental data were used, only the net rate of dust production could be estimated, but these estimates agreed well with measured values. In laboratory studies with talcum powder as the dust, the ratio of dust deposition to dust production varied from 60 to 86%. These findings confirmed earlier hypotheses that dust deposition is an important means of removing dust from the livestock building airspace.     

Digital elevation data for estimation of potential wetness in ridged fields—Comparison of two different methods

The aim of this study was to develop, adjust and test two different methods for the estimation of drainage area and potential wetness in ridged fields. The methods were applied to a gridded digital elevation model (DEM) of a potato field in central Sweden. Elevation data were registered by a global positioning system (GPS) receiver. A high-precision real time kinematic (RTK) system was used to record positions both horizontally and vertically. The study can be divided into four parts. First, we present the two different methods of estimating the drainage area and potential wetness. The potential wetness index used is ln(a/tan β), which is directly related to drainage area. Second, we constructed a high-accuracy DEM based on GPS-measured elevation points. We then modelled the GPS errors and the sampling errors in the DEM. Finally, we used a Monte Carlo simulation to test differences between the two methods of estimating the drainage area and potential wetness. The wetness index for the new method, which takes ridges into account, differs both statistically and visually from the first method, which does not incorporate ridges. The new method, incorporating ridges, is thus strongly recommended for hydrological modelling in ridged agricultural fields.     

Evaluation of infiltration measurements for border irrigation

A number of methods are discussed for obtaining a reasonable estimate of the infiltration function for irrigation borders. Data from ring infiltrometers are fit to power functions for infiltration rate and cumulative infiltration rate versus time and to a branch function where the infiltration rate is not allowed to go below some value (called the final infiltration rate). A volume balance within the border is used to adjust the data to give a better indication of the “average” infiltration conditions over the border. The results of Bouwer's method, which uses a series of borders as infiltrometers, were compared to the results of ring data for actual field data. Bower's method was also analyzed by developing advance and recession curves with the zero-inertia border-irrigation model with a known infiltration rate. The zero-inertia model was also used to examine the effect of different infiltration functions for specific examples (resulting from different irrigations or different estimation methods) on the application of water by surface irrigation.     

机械故障诊断的遗传—独立分量分析算法

为了解决现有独立分量分析算法需要根据源信号的峭度性质选择二次型函数的问题,提出了一种基于遗传算法的独立分量分析算法.该算法选择互信息作为优化目标,针对互信息计算较复杂的现象,对其进行了简化;采用直方图法估计信号的概率分布,解决了互信息计算问题;采用遗传算法寻找使互信息最小的分离矩阵,实现了对线性混叠信号的分离.模拟信号分离结果表明,改进独立分量分析算法的性能优于FastICA算法.将该算法应用于滚动轴承故障诊断,实验结果表明,改进独立分量分析算法成功地分离出滚动轴承声音信号.     

矩形花键滚刀齿形曲线的优化设计

提出了用优化设计方法模拟花键滚刀齿形曲线的计算模型,以齿形误差最小为目标函工保证了两段圆弧光滑连接,给出了５个设计实例,计算结果表明：与其他方法相比,本模型的设计精度最高。     

Evaluation of various quick methods for estimating furrow and border infiltration parameters

For estimating infiltration properties of surface irrigation, some ‘quick’ and easy methods have been developed. The main objective of this study was to evaluate different ‘quick’ methods and to compare the obtained results with two new methods proposed based on the Shepard one-point approach. For this purpose, data sets measured in six borders and five furrows were used for evaluating different methods. Using the volume balance equation and estimated infiltration parameters, the total infiltrated volume and advance times were predicted to evaluate the accuracy of estimated infiltration parameters. The results showed that the modified Mailapalli and Elliott and Walker methods provided the lowest errors for both furrow and border irrigations. The Elliott and Walker method predicted advance times with highest accuracy. There was very small difference between the Shepard and new proposed one-point methods. The performance of the Elliott and Walker method was slightly better than the new proposed two-point method for the experimental furrows, while a minor difference was found for the experimental borders. The results also showed that the performance of the Elliot and Walker method would be improved using binomial approximation instead of Kiefer approximation.