Prediction of daily reference evapotranspiration by a multiple regression method based on weather forecast data

Prediction of daily reference evapotranspiration (ET ₀) is the basis of real-time irrigation scheduling. A multiple regression method for ET ₀ prediction based on its seasonal variation pattern and public weather forecast data was presented for application in East China. The forecasted maximum temperature (T _max), minimum temperature (T _min) and weather condition index (WCI) were adopted to calculate the correction coefficient by multilinear regression under five time-division regimes (10 days, monthly, seasonal, semi-annual and annual). The multiple regression method was tested for its feasibility for ET ₀ prediction using forecasted weather data as the input, and the monthly regime was selected as the most suitable. Average absolute error (AAE) and root mean square error (RMSE) were 0.395 and 0.522 mm d^?1, respectively. ET ₀ prediction errors increased linearly with the increase in temperature prediction error. A temperature error within 3 K is likely to result in acceptable ET ₀ predictions, with AAE and average absolute relative error (AARE) <0.142 mm d^?1 and 5.8%, respectively. However, one rank error in WCI results in a much larger error in ET ₀ prediction due to the high sensitivity of the correction coefficient to WCI and the large relative error in WCI caused by one rank deviation. Improving the accuracy of weather forecasts, especially for WCI prediction, is helpful in obtaining better estimations of ET ₀ based on public weather data.     

太行山山前平原夏玉米优化灌溉制度研究

5年田间试验研究不同气候年型下灌水次数、灌溉时间对夏玉米生育、产量和水分利用效率的影响结果表明 ,随生育期总耗水量的增加 ,夏玉米产量逐步提高 ,当耗水量增至一定程度时产量反而递减 ;而水分利用效率随耗水量的增加呈逐步递减趋势。并确定了夏玉米最优耗水量 ,建立了不同降水年型下夏玉米优化灌溉制度。     

视频监控系统在消防指挥调度中的作用

视频监控系统以其覆盖广、传输快、清晰度高等特点,广泛应用于城市预警、交通、城市管理、安防监控等诸多领域。本文主要介绍了视频监控系统在消防调度指挥中起到的辅助决策作用,可以更方便地为调度指挥提供丰富的即时信息,大大提高了出警速度,给领导辅助决策提供了帮助。     

Performance Assessment of Chlorophyll Meter to Determine When to Irrigate Wheat under Different Soil Moisture Deficit Conditions: An Initial Study

ABSTRACT

Proper irrigation timing can minimize the negative impacts that reduce crop yields. Therefore, in an initial pot experimental study, we assessed the SPAD (Soil–Plant Analysis Development)-chlorophyll meter as a tool to determine proper irrigation timing of wheat under different soil water deficit conditions in a controlled-environment greenhouse. The treatments were controlled irrigation at 100% (T₁), 70% (T₂), 50% (T₃) and 30% (T₄) of soil water content at field capacity; and the growth stages were development, mid-season and late-season. SPAD readings were measured pre-irrigation events. The results indicated that the T₃ and T₂ achieved maximum grain yield per accumulated crop evapotranspiration, i.e. water productivity (0.82 and 0.76 kg m^?3), and were at par with T₁. Moreover, the SPAD readings had a high Pearson’s correlation coefficient with crop evapotranspiration (r = 0.95; P ≤ 0.001) and wheat grain yield (r = 0.90; P ≤ 0.001), indicating that SPAD reading could be used to reliably estimate when to irrigate wheat. Therefore, T₃ and T₂ SPAD readings were averaged to estimate a target limit at which irrigation should be applied. Accordingly, the target limit was defined as >44.76 for the development stage, >50.72 for the mid-season stage, and >37.64 for the late-season stage; readings below this target limit indicate that it is time to irrigate.     

Linux进程调度策略的分析

描述了Linux的进程调度的过程,Linux采用时间片轮转和可剥夺调度优先级相结合的调度策略,它把进程分成两类:实时进程和非实时进程。实时进程总是在非实时进程之前运行。     

Comparing multipurpose forest management with timber management,incorporating timber,carbon and oxygen values: A case study

Abstract

This paper comparatively examines two forest management planning approaches: multipurpose forest management and traditional timber management, with carbon, timber and oxygen production objectives in mind. The effects of both approaches on carbon and oxygen values were estimated with an oxygen and carbon flow matrix, while timber production was modelled through a growth and yield model. The estimated values were simultaneously integrated into a linear programming model developed for this study. The objective was to maximize the net present value (NPV) of the profits of timber, oxygen and carbon under the constraints of an even flow of timber production and ending forest inventory for each planning approach. The results showed that the ecological and environmental regulations in multipurpose management substantially decreased the NPV of timber production even though they increased the NPV of carbon and oxygen flow. The results also indicated that over a 100 year planning horizon the total NPV of all forest ecosystem values including carbon, timber and oxygen is almost the same (only 1.9% reduction in multipurpose management approach) in both management approaches. Although multipurpose management creates more NPV of carbon and oxygen than timber management does, the latter provides better results in terms of timber production. It is therefore important to take into account the NPV of all apparent and quantifiable forest values in preparing forest management plans, particularly in developing new management planning approaches.     

海子水库灌区节水型灌溉制度的制定

本文介绍了中日双方专家团在海子水库灌区现场调查中,实测土壤水分特征值的方法,土壤水分曲线的制定和应用,负压计观测值的应用,计算节水型灌溉用水量和灌水间隔日数的方法,并用节水型频繁灌溉法制定了各作物的节水型灌溉制度,用这种方法制定的节水型灌溉制度要比我国过去用的常规法节水40%以上。     

基于森林空间收获问题的模拟退火算法邻域搜索技术比较

邻域搜索是当前提高启发式算法求解效率的核心技术之一,然而近期关于该搜索策略的性能却产生了较大争议。模拟退火算法作为一种典型的启发式算法,已广泛应用于一系列的林业规划问题。为此,本研究以模拟退火算法为例,系统评估2种不同邻域搜索技术在森林空间收获安排问题中的应用效果。规划模型以50年规划周期(10个规划分期)内的最大化木材收获为目标函数,以蓄积均衡收获、蓄积期末存量、单位限制模型和绿量限制等为主要约束条件。测试方法以模拟退火算法为原型,以每次优化过程中随机选择的小班数量为标准,共包括1-邻域和2-邻域2种不同的搜索技术。模拟规划数据由3个假设的栅格数据集组成,其共产生了3293个(林分Ⅰ)、29536个(林分Ⅱ)和81625个(林分Ⅲ)0-1型决策变量。研究结果表明:模拟退火算法2-邻域搜索技术能够提高各规划问题的最大目标函数值;但当规划问题的决策变量数(或小班数量)较大时(即林分数量≥3600),单纯增加邻域范围并不能提高规划问题的平均目标函数值。因此,鉴于模拟退火算法的优化结果对规划问题具有较高的敏感性,因此森林经营决策人员应慎重选择模拟退火算法邻域搜索作为相关规划问题的优化求解技术。      

改进粒子群算法在车间作业调度中的研究

车间作业调度（JSP）是典型的NP难题,传统求解方法都有各自的特色和不足。免疫系统强大的信息处理能力为人工免疫应用提供了丰富的暗示,因此,免疫算法被提出,并逐渐应用于许多工程实际。针对车间作业调度这个优化问题的难处理性,提出了基于免疫粒子群算法（IPA）的JSP求解方法。在该求解方法中,结合免疫原理和粒子群算法应用于JSP的算法流程;算法采用基于操作的编码方式;依据接种疫苗和变异、免疫选择的机制来设计算子。并通过仿真,证明了IPA算法在JSP中的有效性。