管道式喷灌系统水力计算的ESM方法

针对管道式喷灌系统的水力计算,剖析了目前采用的有限元法和Hathoot进步法等数解法的优点和局限性,结合进步法、退步法的计算思路,提出一种可以求解干管双向布置管道式喷灌系统的水力计算方法--改进步进法（ESM）.给出了详细的水力计算步骤及计算机流程图,并给出了实例.计算结果表明,ESM方法的水力学关系式准确和干管双向布置喷灌系统的水力学边界条件清晰,可有效解决干管双向布置的管道式喷灌系统的流量水头计算问题.     

水分胁迫对北京城市绿化树种水分状况和栓塞的影响

该文选取了北京3个城市绿化树种国槐、小叶黄杨和女贞为研究对象,采用便携式压力室SKYE(SKPM1400)和改良的冲洗法,分别测定了在不同水分状况下3个树种水势和导水率损失的变化规律.结果显示,3个树种忍耐低水势的能力是小叶黄杨>女贞>国槐,不同树种经抗旱锻炼后对水分胁迫的反应产生了差异.同时,不同水分条件下3个树种导水率损失变化情况有差异.     

拖拉机液压悬挂控制系统动态特性分析

本文分重分析间控泵单作用油缸系统运动规律，建立拖拉机阀控泵单作用油缸液压悬挂闭环控制系统动态特性数学模型，并加以分析，指出提高稳定性的措施，提供稳定性系统设计的理论依据．     

滚筒式穴播器的设计原理

本文探讨了滚筒式穴播器设计原则，确定主要参数选择原则，提出提高播种质量的措施，为滚筒式穴播器设计提供了理论依据。     

采用16位单片机的拖拉机电液悬挂控制系统

将原有机械式液压悬挂控制系统改装为电液式悬挂控制系统,其控制核心采用了MCS96系列16位单片机系统;对电液悬挂控制系统进行了硬件和软件设计,并在室内仿真试验台上进行了试验验证。试验结果表明,系统具有较好的调节性能,能够满足对拖拉机悬挂控制系统的静动态要求。     

水轮发电机组模糊控制PI调速器研究

根据一种简化的模糊控制算法来设计模糊控制决策表的计算机自动生成软件,即所谓的“决策软件”。这是一种把PI控制与模糊控制有机地结合在一起的方法,能够实现水轮发电机组PI调速器参数按模糊规则近似进行在线自动调整的控制。     

京西山地棕壤和淋溶褐土饱和导水率的分析

导水率Ｋ（ｈｙｄｒａｕｌｉｃｃｏｎｄｕｃｔｉｖｉｔｙ）是表示孔隙介质透水性能的综合比例系数,即单位水力势梯度下水的通量密度或渗透流速。Ｋ值是土壤颗粒大小分布、固体物质的化学组成和土壤紧实度的函数。因此,对于不同的土壤或同一土壤的不同层次Ｋ值亦可能有差...     

比例溢流阀在拉力轴承试验液压加载系统中的应用

比较了3种液压加载系统调节方式的原理和特点,介绍了该拉力轴承寿命试验装置中采用电比例溢流阀调节方式的组成及工作原理,重点分析了其在恒力加载状态经过闭环控制的工作特性.试验表明,此加载方式调节方便,加载载荷准确,系统性能稳定可靠,应用效果良好.     

Water relations of Eucalyptus nitens × Eucalyptus grandis: is there interclonal variation in response to experimentally imposed water stress?

This study tested the hypothesis that water stress increases the hydraulic efficiency of Eucalyptus nitens × E. grandis saplings as a result of osmotic and elastic adjustments. Eucalyptus nitens × E. grandis clones (NH00, NH58, NH69 and NH70) were potted in coarse river sand supplemented with a slow-release fertiliser, drip-irrigated four times daily and exposed to full sunlight for eight months. Thereafter, irrigation was withheld twice for seven consecutive days from half of the saplings of each clone, with a seven-day recovery period (regular irrigation) in-between. Relative soil moisture content did not correlate with stomatal conductance (g_s) at pre-dawn and at midday. Leaves of plants subjected to the water-stress treatment wilted in 7 d, and the reduction in g_s was significant at midday with no significant differences between clones. Stomatal conductance and all traits derived from pressure-volume graphs (e.g. osmotic potential at full turgor) were constant in the control treatment. There were no clear patterns in osmotic and elastic adjustments in both treatments. Root hydraulic conductance was constant between treatments and clones. However, water stress reduced shoot hydraulic conductance and stem hydraulic conductivity with significant interclonal effects. Plant biomass, leaf area and leaf weight ratio were significantly lower in the water-stressed plants, but there were no differences between the clones. In conclusion, the water-stress treatment did not introduce significant differences in stomatal conductance and tissue-water relations of Eucalyptus nitens × E. grandis clones. Interclonal variation in water-stress response was found in shoot hydraulic traits, and clone NH58 may be more suitable for planting across sites prone to moderate water stress.     

提高日照记录准确性的措施

暗筒式日照计是目前气象台站使用的主要日照观测设备。该文从暗筒式日照计的安装与维护、日照纸涂药、记录整理、不正常记录的处理方法以及在计算机中的录入等方面介绍了提高日照记录准确性的措施,以提高日照观测水平。