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921.
Near-infrared (NIR) reflectance spectroscopy was evaluated as a rapid and environmentally benign technique for the simultaneous determination of macronutrients and energy in commercially available, packaged meals. Reflectance spectra (400–2498 nm) of homogenized meals were obtained with a dispersive NIR spectrometer. Protein and moisture were measured by AOAC reference methods, total fat by a semi-automated acid hydrolysis, solvent extraction, gravimetric method and total carbohydrate calculated. Energy was calculated using Atwater factors. Using multivariate analysis software, PLS models (n = 113–115 products) were developed to relate NIR spectra of homogenized meals to the corresponding reference values. The models predicted components and energy in validation samples (n = 37–38 products), overall, with r2 of above 0.96. Ratios of deviation to performance were between 3.6 and 6.6, and indicated adequacy of the models for screening, quality control, or process control. Performance of the models varied substantially when used to predict sub-groups of meals within the validation set. 相似文献
922.
讨论被控对象非线性特性补偿的传统方法,也讨论了采用智能阀门定位器和PID非线性增益的补偿方法。 相似文献
923.
Junyong XIA Youmin HU Bo WU Tielin SHI 《Frontiers of Mechanical Engineering in China》2008,3(4):408-415
Empirical model of machine tools on thermal error has been widely researched, which can compensate for thermal error to some
extent but not suitable for thermal dynamic errors produced by dynamic heat sources. The thermoelastic phenomenon of unidimensional
heat transfer of ballscrews influenced by changeable heat sources is analyzed based on the theory of heat transfer. Two methods
for system identification (the least square system identification and BP artificial neural network (ANN) system identification)
are put forward to establish a dynamic characteristic model of thermal deformation of ballscrews. The model of thermal error
of the X axis in a feed system of DM4600 vertical miller is established with a fine identification effect. Comparing the results
of the two identification methods, the BP ANN system identification is more precise than the least square system identification. 相似文献
924.
925.
800MW机组水燃比控制方案 总被引:2,自引:0,他引:2
王存旭 《沈阳工程学院学报(自然科学版)》2005,1(1):65-67
介绍了某800MW直流炉机组协调控制系统水燃比控制方案,并对燃料校正模糊PID控制器及最小二乘煤质校正方法进行了详细分析. 相似文献
926.
One of the most problematic issues in contemporary meta-analysis is the estimation and interpretation of moderating effects. Monte Carlo analyses are developed in this article that compare bivariate correlations, ordinary least squares and weighted least squares (WLS) multiple regression, and hierarchical subgroup (HS) analysis for assessing the influence of continuous moderators under conditions of multicollinearity and skewed distribution of study sample sizes (heteroscedasticity). The results show that only WLS is largely unaffected by multicollinearity and heteroscedasticity, whereas the other techniques are substantially weakened. Of note, HS, one of the most popular methods, typically provides the most inaccurate results, whereas WLS, one of the least popular methods, typically provides the most accurate results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
927.
本文在理论分析的基础上,利用MAPLE软件研究了一类弹簧振子周期运动的特点,分析了系统参数对运动周期的影响,并借助ANSYS/LS-DYNA软件用有限元方法验证了弹簧质量系统的周期。 相似文献
928.
Tommaso Proietti 《Computational statistics & data analysis》2007,52(2):935-958
Signal extraction deals with weighting the available observations in order to estimate a latent feature of interest. A signal extraction method is linear if the feature is measured by a possibly time-varying linear combination of the available observations. Linear methods play an important role since they are well understood, easy to apply, and are a key ingredient in more elaborate nonlinear and non-Gaussian models. The focus is on the main methods for inference about parametric and semiparametric unobserved components models formulated as linear mixed models and state space models and establish the connections between best linear unbiased prediction, penalised least squares and recursive methods of signal extraction. The methods are illustrated with reference to the traditional problem of extracting the cycle and the trend from economic time series. 相似文献
929.
由自由振动响应识别非线性系统参数的一种方法 总被引:3,自引:0,他引:3
本文提出了一种由自由振动响应识别非线性系统参数的方法,即首先用直接摄动法求出系统自由振动的近似解作为数学模型,然后用最小二乘法来识别系统的物理参数.此方法具有精度高、应用方便的特点. 相似文献
930.
为解决直接合成所得1,1-二氨基-2,2-二硝基乙烯(FOX-7)存在的晶体形貌不规则,粒度分布不均匀等问题,采用激光动态法和间歇动态法分别测定了FOX-7在N,N-二甲基甲酰胺(DMF)与水(H2O)二元体系(V(DMF)∶V(H2O)=7∶3)中的溶解度和超溶解度及冷却结晶动力学数据,利用最小二乘法拟合得到了晶体成核速率与生长速率方程。结果表明,FOX-7在上述体系中溶解度方程为lnx=16.42-5019.51/T-0.45lnT;在冷却结晶过程中呈粒度无关生长模型;在成核速率与生长速率方程中,过饱和比S的指数分别为0.61与0.45,悬浮密度MT指数的为2.30,搅拌强度ωr的指数为0.22。 相似文献