新型压电-流体混合驱动精密位移机构

提出一种新型压电驱动精密位移机构,着重介绍了其结构、工作原理和控制方法,分析了机构参数与输出性能之间的关系。该机构以压电叠堆为动力元件驱动流体,利用换向阀控制流体流向,通过执行缸两个腔体内流体置换的方法将压电叠堆的往复振动转换成执行缸的直线运动。调整电压或执行缸的参数可获得所需的进给步长和输出推力,具有精度高、易于控制、稳定性好等特点,适用于微位移以及较大行程范围内的精密进给运动。     

Optimal utilisation of natural resources for agricultural sustainability in rainfed hill plateaus of Orissa

The climatic data for 17 years from 1988 to 2004 of the rainfed hill plateaus of Kandhamal district of Orissa (India) were analyzed to find out the monthly climatic index from the calculated values of effective rainfall and evapotranspiration. The 80% dependable monthly climatic index was correlated with crop coefficient and suitable cropping period and sequences for the study area were suggested based on it. The extent of investment, net return and soil loss from agriculture were estimated as per the present condition and for the suggested cropping patterns. A mathematical model was formulated for optimal allocation of area to different crop sequences with different objectives viz. minimization of soil loss, minimization of investment and maximization of net return from agriculture and was solved using linear goal programming technique. The model suggested to take up food crops in area of 1,30,777 ha and perennial grass cover in 3223 ha with a cropping intensity of 1.61 resulting in a net return of Rs 1064.775 millions sustaining soil loss to a tune of 9489.67 thousand tons per year. The model was found to be favourable in respect of higher net return of Rs 8862.34 and lesser soil loss of 23.41 tons/ha than the corresponding present values. But more investment of Rs 4489.01 per ha was required to fulfill the objectives.     

Supporting decision-makers in estimating irrigation demand for urban street trees

Greening cities is of considerable significance to creating sustainable cities. Cost-benefit analyses have shown that urban green is not only ecologically and socially desirable but also economically advantageous. However, maintaining this urban green is becoming challenging due to changing climatic conditions. With frequent heat-waves, droughts and increasing water scarcity in many regions, it is crucial to establish systematic approaches to economise the available water used for irrigation. Currently, cities rely on rough approximations to assess irrigation demand. To address this gap, a linear time series model was developed based on soil water balance and Water Use Classifications of Landscape Species approach. The model uses publicly available data regarding trees, soil, and current and forecasted weather to estimate the irrigation demand of urban street trees on a weekly time scale. The developed model is applied in a case study of a metropolis in a moderate continental climate. The results show more distributed irrigation demand than the currently implemented soil moisture based model of the case study city. Accordingly, the model can support the decision-makers to not only assess the irrigation demand of existing trees but also help in water budgeting of new plantation under varying climatic conditions.     

Prediction of the changes on the CIELab values of fabric after chemical finishing using artificial neural network and linear regression models

Changes on the CIELab values of the dyed materials after the different chemical finishing treatments using artificial neural network (ANN) and linear regression (LR) models have been predicted. The whole structural properties of fabrics and some process data which were from fiber to the finishing parameters were accepted as inputs in these models. The networks having different structures were established, and it was also focus on the parameters which could affect the performance of the established networks. It was determined that we could successfully predict the color differences values occurring on the material after the finishing applications. In addition, we realized that some ANN parameters affected the prediction performance while establishing the models. After training ANN models, the prediction of the color difference values was also tried by linear regression models. Then, extra ANN models were established for all outputs using the parameters as inputs in the LR equations, and the prediction performances of both established models were compared. According to the results, the neural network model gives a more accurate prediction performance than the LR models.     

Relationships between rainfall characteristics and ephemeral gully erosion in a cultivated catchment in Sicily (Italy)

Recent research has shown a lack of long-term monitoring for detailed analysis of gully erosion response to climate characteristics. Measures carried out from 1995 to 2007 in a wheat-cultivated area in Raddusa (Sicily, Italy), represent one of the longest series of field data on ephemeral gully, EG, erosion. The data set collected in a surface area of almost 80 ha, permits analysis of the influence of rainfall on EG formation and development. Ephemeral gullies formed in the study area were measured on a yearly scale with a Post-Processing Differential GPS for length and with a steel tape for the width and depth of transversal sections. Ephemeral gully formation was observed for 8 years out of 12, which corresponds to a return period of 1.5 years. The measurements show strong temporal variability in EG erosion, in agreement with the rainfall characteristics. The total eroded volumes ranged between 0 and ca. 800 m³ year⁻¹, with a mean of ca. 420 m³ year⁻¹, corresponding to ca. 0.6 kg m⁻² year⁻¹. Ephemeral gully erosion in the study area is directly and mainly controlled by rainfall events. An antecedent rainfall index, the maximum value of 3-days rainfall (H_max3_d), is the rain parameter which best accounts for EG erosion. This index is used here as a simple surrogate for soil water content. An H_max3_d threshold of 51 mm was observed for EG formation. The return period of the H_max3_d threshold is almost the same as the return period for EG formation. Although a mean of seven erosive rain events were recorded in a year, EG formation and development generally occur during a single erosive event, similarly to other semiarid environments. The most critical period is that comprised between October and January, when the soil is wetter and the vegetation cover is scarce. Empirical models for EG eroded volume estimation were obtained using the data set collected at this site. A simple power-type equation is proposed to estimate the eroded volumes using H_max3_d as an independent variable. This equation shows an R² equal to 0.67 and a standard error of estimation of 0.79.     

基于线性规划模型的农业种植业结构优化研究

以土地资源、农作物需水量、肥料、乡村劳动力资源、农业机械总动力等作为农业种植业规划的约束条件,建立基于线性规划的农业种植业结构优化数学模型。以山东枣庄市为例,提出农业种植业结构优化方案,该优化方案具有实用性和合理性。     

基于回归理论分析下南瓜估重模型的研究

针对数学建模竞赛南瓜估重问题,主要运用了回归分析理论进行数值模拟。建模前,采用了简单相关分析理论审慎地剔除了线性相关的若干变量,降低了建模的复杂性。然后,分别采用了1种线性回归模型和6种二元高次多项式回归模型对相关数据进行了拟合,并由拟合出的各函数表达式分别求出各模型对应所有数据的误差。通过分析比较所得的误差,对各模型拟合的精度进行了合适地评价,并且挑选出了当前最优模型,也顺利地找到了特殊白南瓜,还为进一步的修正模型剔除了部分不合理数据。最后拟合出最优模型,该模型在假定重量误差允许范围为15．00％的前提下有高达81．25％的拟合准确率,同时又创造性地设计出“查表法”和“卷尺标重法”运用最优模型解决实际估重问题。     

江苏省如东县未来5年农业产值的预测

根据2001年至2007年如东县的农业产值统计资料,应用GM（1,1）模型和线性回归模型,预测了该县2008～2012年农业产值的发展趋势。     

西门子S7-200PLC模拟量输出在节水灌溉中的应用

该文介绍了西门子S7-200PLC模拟量输出值的对应关系、模拟量输出的处理方法,展望了其在农业节水灌溉中的应用前景,可编程控制器在现代农业中的作用有待进一步拓展。      

本溪地区近52年来温度变化特征和突变分析

根据本溪地区1958~2009年气温序列资料,运用线性回归和Mann-Kendall法,对近52年来本溪地区年和季平均气温变化特征和突变进行了分析。结果表明,近52年来本溪地区气温以增温为主,冬季增温趋势最为显著;以1988年为界,可将本溪地区分为2个阶段：1958~1988年为相对冷期,1989~2009年为相对暖期;本溪地区年和季平均气温均在20世纪80年代末发生了突变。