Operative Approach to Agricultural Drought Risk Management

In a companion paper, the agricultural drought economic risk assessment (ADERA) model was described. ADERA studies agricultural drought not only in terms of deficit soil water content and its frequency and severity (as in the traditional approach) but also in terms of net benefit reduction and vulnerability. The relationship between drought index, crop yield, and crop economic net benefit is modeled and three threshold levels are considered: the critical water content; the critical impact in terms of net benefit; and its critical return period (i.e., frequency) above which the soil-climate unit is considered unsuitable for the cultivation of a specific crop. These critical levels are used in long-term action planning as the triggers for different risk classes. The rapidity with which the critical impact is reached is considered indicative of the crop vulnerability, and real-time monitoring of the impact evolution (short-term actions) is also implemented. Initially ADERA was applied at only one point (soil-crop-climate unit), but because agricultural drought is by definition a wide area phenomenon, the model must be validated in other units and then used to evaluate the drought area extension (risk map). In this paper, generalization, demonstration, and guidance on the application of ADERA are given with reference to rainfed sunflower and sorghum crops in six soil-climate units in central Italy for which time series for yield (obtained in experimental plots where the water scarcity was the principal factor limiting the final yield) since 1978 is available. The application of ADERA made it possible to quantify the vulnerability class and the corresponding risk class for the single unit (long-term action planning). The analysis results confirm that typically for the selected crops the critical impact has a low risk and a low vulnerability. In fact sunflower and sorghum are rainfed crops widely cultivated in the area under investigation. Moreover, the results show that each risk class is present only within a specific cost range, in particular the upper and lower limits, and the size of each cost range varies according to the different units; the occurrence of a specific risk class and vulnerability level is highly correlated with the selected triggers, in particular with the critical net benefit (for an increment of which above the corresponding cost range, a given soil-climate unit can become unsuitable for the cultivation of a specific crop); the critical water content is a normal occurrence event for all the units analyzed, with the crop water stress onset date always around 40% of the growing period being a typical characteristic of the specific area, of the two crops and of the selected drought index. The practical usefulness of the impact monitoring procedure was stressed by comparing its progressive evolution in the cases of both a rainfed crop and of a rescue irrigation carried out at a selected and opportune date. In the latter case the impact was reduced below the critical level.     

突扩管条件下材料的冲刷腐蚀机理研究Ⅱ不锈钢

利用新近研制的双相流冲刷腐蚀激光多普勒实验装置,通过失重测试、表面形貌观察、局部流速流态测试和典型部位的电化学测试,研究了突护管条件下不锈钢ＡＩＳＩ３１６Ｌ在单相及含砂人工海水介质中的冲刷腐蚀机理。结果表明：冲刷腐蚀峰值发生在距突扩位置约３．０Ｄ的部位（Ｄ为粗管直径）,与切向流速扰动度的峰值位置相同。在３．０Ｄ和５．５Ｄ的部位,冲刷作用是主要的,而在回流区（１．５Ｄ）,则为氧扩散控制,不同部位的冲     

Hoek-Brown经验强度准则的修正及应用

对Hoek-Brown强度准则中岩体地质力学指标GSI和扰动参数D的评估值进行统计分析发现,不同评估者对岩体GSI值的评估有较强的一致性,而对D值的评估则呈现很高离散性．扰动参数D的评估值的离散性是岩体力学参数估计值可靠度降低的主要原因,因此,对Hoek-Brown经验强度准则而言,给出一种更为准确的D值确定方法是十分必要的．通过分析现有的岩体扰动参数确定方法的局限性以及基于声波测试理论的岩体完整性评价方法,探讨了基于声波传播速度的扰动参数D的确定方法以及在实际工程中考虑或忽略开挖扰动的基本原则,并通过有限元算例与Hoek等人的理论进行了比较．     

基于改进QPSO算法的逢低买入最优定价研究

研究逢低买入拍卖中最优定价问题。由于逢低买入拍卖中卖方期望收益函数异常复杂,常规函数极值法具有极大局限性,无法获得最优价格策略,提出一种带极值扰动算子的QPSO（Quantum-behaved Particle Swarm Optimization）算法对模型进行优化和数值计算。算例表明该算法可以快速有效地找到最优价格策略,且具有较好的全局收敛能力。     

基于改进的简化粒子群聚类算法

针对粒子群算法后期收敛速度慢、易陷入局部极值的缺点,提出一种基于粒密度和最大距离积法的简 化粒子群聚类算法.通过采用线性递减与随机分布相结合的惯性权重策略、添加极值扰动算子、优化粒子个体最优位置,使粒子群算法能够快速收敛于全局最优.再把改进后的粒子群算法与K-means算法相结合,解决K-means算法因随机初始聚类中心而导致聚类效果差、不稳定等问题.通过实验分析,该算法的聚类结果准确率更高、收敛速度更快、稳定性更强.     

一种更简化而高效的粒子群优化算法

针对基本粒子群优化(basic particle swarm optimization,简称bPSO)算法容易陷入局部极值、进化后期的收敛速度慢和精度低等缺点,采用简化粒子群优化方程和添加极值扰动算子两种策略加以改进,提出了简化粒子群优化(simple particle swarm optimization,简称sPSO)算法、带极值扰动粒子群优化(extremum disturbed particle swarm optimization,简称tPSO)算法和基于二者的带极值扰动的简化粒子群优化(ext     

考虑等离子体粘性时的扰动磁场

从只考虑粘滞效应的非理想磁流体方程组出发,先应用半解析方法进行公式推导,然后数值计算了几种非均匀等离子体压强时,圆柱等离子体轴向扰动磁场随半径和粘度的演化规律。数值模拟结果表明:轴向扰动磁场在等离子体轴线位置处的值为零,而且这个值不受等离子体粘度,波数以及压强的影响。当等离子体压强一定时,轴向扰动磁场的极大值随着粘度的增加而增大。当粘度大到一定程度时,轴向扰动磁场在轴线和壁之间出现多个极大值和极小值,这表明了等离子体粘度对轴向扰动磁场的影响十分明显。     

城市混合用地停车共享需求模型——以北京市华贸中心为例

基于停车泊位共享的思路,通过停车需求调查,分析了典型混合用地北京市华贸中心的停车需求特性,建立了基于单一用途建筑物停车需求叠加模型和停车需求共享模型,通过比较,停车共享模型计算的误差明显低于利用叠加方法的误差.     

Coupled Crop and Solid Set Sprinkler Simulation Model. II: Model Application

In this work, applications of the coupled solid set sprinkler irrigation and crop model AdorSim introduced in the companion paper are presented. The sprinkler irrigation model is based on ballistic theory, while the crop model is based on CropWat. AdorSim was used to evaluate the effect of sprinkler spacing on seasonal irrigation water use (WU) and crop yield. The most relevant results were related to the characterization of advanced irrigation scheduling strategies. The differences in crop yield and WU derived from irrigating at different times of the day were estimated for two locations strongly differing in wind speed. Irrigation guidelines were established in these locations to relate gross water use and water stress induced yield reductions. Simulations were also applied to estimate adequate wind speed thresholds for irrigation operation. In the experimental conditions, thresholds of 2.0–2.5?m?s?1 proved effective to control yield reductions and to minimize WU.     

白银炉加料量自动控制系统

介绍了白银炉计算机监测与控制系统中主要调节回路———加料量控制系统的构成、手动 /自动无扰动切换的实现及控制程序的编制。