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241.
To promote modern agricultural equipment level is one characteristic of constructing and developing modern agriculture in China.This paper makes up stepwise linear regression analysis model of influence factors of modern agricultural equipment level,and chooses rural labor,per capita income of rural residents,rural investment,proportion of people at secondary education level and at higher level in per hundred rural labor force and arable land area as independent variables,and total power of machine as induced variable.The major results show that the relativity of modern agricultural equipment level,rural investment and education level of peasants is remarkable,and they are the major influence factors of modern agricultural equipment level.Raising investment level of rural infrastructure construction as well as and research and development and promotion of advanced and applicable modern agricultural equipment,improving quality and education level of peasants can accelerate the development of China’s modern agricultural equipment effectively in the process of agricultural sustainable development. 相似文献
242.
H. B. Osborn L. J. Lane R. S. Kagan 《Journal of the American Water Resources Association》1971,7(3):484-494
ABSTRACT Significant parameters for predicting thunderstorm runoff from small semiarid watersheds are determined using data from the Walnut Gulch watershed in southern Arizona. Based on these data, thunderstorm rainfall is dominant over watershed parameters for predicting runoff from multiple linear regression equations. In some cases antecedent moisture added significantly to the models. A technique is developed for estimating precision of predicted values from multiple linear regression equations. The technique involves matrix methods in estimating the variance of mean predicted values from a regression equation. The estimated variance of the mean predicted value is then used to estimate the variance of an individual predicted value. A computer program is developed to implement these matrix methods and to form confidence limits on predicted values based on both a normality assumption and the Chebyshev inequality. 相似文献
243.
摘要本文采用逐步回归等方法处理了山东相公庄水准 EW、SN 向1989年1月1日至1990年9月30日的五日均值观测资料。回归分析结果表明:苍山4.4(M_L)级地震前相公庄水准 EW、SN 向均有10天左右的短临前兆异常,异常最大幅值分别为0.84mm和0.42mm,地震发生在异常达最大值的前一天,回归剩余标准差分别为±0.17mm和±0.12mm。据动态灰箱法处理的结果说明:短临异常在月均值上也有一定显示,只是幅度小些。作者认为:距震中50km左右的定点形变台,在一定条件下有可能监测到4级以上地震的短临前兆异常。 相似文献
244.
中国入境旅游市场的多元回归预测 总被引:15,自引:0,他引:15
为了准确预测我国入境旅客的规模,收集了1978~2003年中国入境游客量的值,运用多元回归分析的方法,并借助SPSS软件,对我国入境游客的规模进行了预测,建立了以预测年前3年的入境游客量为自变量的多元回归方程:X(t)=251.067 0.178(t-3)-0.441X(t-2) 1.286X(t-1).与传统预测的时间序列等方法比较,该方法模拟、预测精度更高,更符合入境游客量的变化规模,同时可通过增加每年的实际值,动态更新方程,使之更能反映游客量的变化. 相似文献
245.
地震预报的基础是要有连续可靠的高质量的观测资料。地震台站一线的工作人员对本台产出的观测资料的可靠性最有发言权,溧阳地震台的体应变观测资料在历年的全国资料质量评比中连续6年获得前三名。本文通过对江苏溧阳地震台体应变观测资料的分析研究,发现1996年11月09日在南黄海6.1级地震和1997年07月28日在南黄海5.1级地震,台湾1999年09月21日7.6级地震和2002年03月31日7.5级地震以及2001年11月14日青海8.1级地震前后,该台体应变资料有较明显的前兆异常反应,并且有一定的变化规律和异常特征,通过对这种规律的总结对地震预报有一定的参考价值,为此,我们对这种规律认真的分析总结,以提供给大家参考。 相似文献
246.
Peroxyacyl nitrates (PANs) are important secondary pollutants in ground-level atmosphere. Accurate prediction of atmospheric pollutant concentrations is crucial to guide effective precautions for before and during specific pollution events. In this study, four models based on the back-propagation (BP) artificial neural network (ANN) and multiple linear regression (MLR) methods were used to predict the hourly average PAN concentrations at Peking University, Beijing, in 2014. The model inputs were atmospheric pollutant data and meteorological parameters. Model 3 using a BP-ANN based on the original variables achieved the best prediction results among the four models, with a correlation coefficient (R) of 0.7089, mean bias error of ? 0.0043 ppb, mean absolute error of 0.4836?ppb, root mean squared error of 0.5320?ppb, and Willmott's index of agreement of 0.8214. Based on a comparison of the performance indices of the MLR and BP-ANN models, we concluded that the BP-ANN model was able to capture the highly non-linear relationships between PAN concentration and the conventional atmospheric pollutant and meteorological parameters, providing more accurate results than the traditional MLR models did, with a markedly higher goodness of R. The selected meteorological and atmospheric pollutant parameters described a sufficient amount of PAN variation, and thus provided satisfactory prediction results. More specifically, the BP-ANN model performed very well for capturing the variation pattern when PAN concentrations were low. The findings of this study address some of the existing knowledge gaps in this research field and provide a theoretical basis for future regional air pollution control. 相似文献
247.
水资源开发利用与区域经济协调管理的一种交互式模式 总被引:1,自引:0,他引:1
本文据大系统多级递阶优化控制理论,将水资源系统分解成地面水资源系统与地下水资源系统。在地面水系统中,给出了多目标开发利用管理模型;在地下水系统中,提出了地下水资源开发利用经济管理模型。区域经济涉及区域内的各种工农业和城镇生活用水部门──用水系统。对该用水系统提出了分解──协调优化管理模型。据水资源开发利用和用水系统的特点,在最高级设置总协调器来协调水资源开发利用系统与用水系统,进而提出了水资源开发利用与区域经济协调管理的一种交互式模式。 相似文献
248.
Extreme value analysis of Munich air pollution data 总被引:1,自引:0,他引:1
We present three different approaches to modelling extreme values of daily air pollution data. We fitted a generalized extreme
value distribution to the monthly maxima of daily concentration measures. For the exceedances of a high threshold depending
on the data, the parameters of the generalized Pareto distribution were estimated. Accounting for autocorrelation, clusters
of exceedances were used. To obtain information about the relationship of the exceedance of the air quality standard and possible
predictors we applied logistic regression. Results and their interpretation are given for daily average concentrations of
ozone and nitrogen dioxide at two monitoring sites within the city of Munich. 相似文献
249.
250.
Walter W. Piegorsch 《Environmental and Ecological Statistics》1994,1(2):153-162
Hierarchical models are considered for estimating the probability of agreement between two outcomes or endpoints from an environmental
toxicity experiment. Emphasis is placed on generalized regression models, under which the prior mean is related to a linear
combination of explanatory variables via a monotone function. This function defines the scale over which the systematic effects
are modelled as additive. Specific illustration is provided for the logistic link function. The hierarchical model employs
a conjugate beta prior that leads to parametric empirical Bayes estimators of the individual agreement parameters. An example
from environmental carcinogenesis illustrates the methods, with motivation derived from estimation of the concordance between
two species carcinogenicity outcomes. Based on a large database of carcinogenicity studies, the inter-species concordance
is seen to be reasonably informative, i.e. in the range 67–84%. Stratification into pertinent potency-related sub-groups via
the logistic model is seen to improve concordance estimation: for environmental stimuli at the extremes of the potency spectrum,
concordance can reach well above 90%. 相似文献