齿墩状内消能工的消能及压力特性

输水管道或泄洪洞常见的内消能方式为孔板和洞塞,结合明渠水流中的消能工形式提出了齿墩状内消能工,并通过物理模型试验对不同面积收缩比的齿墩状内消能工进行了研究,分析了它们的过流能力、消能率、压强沿程变化及脉动压强特性.结果表明:齿墩状内消能工的过流能力主要是由消能工的体型及尺寸决定的,其面积收缩比越大,消能率越低,过流能力就越强;齿墩状内消能工的时均压强在收缩段骤降,在其后部逐渐上升,而后恢复至稳定,其恢复长度基本相同;齿墩状内消能工的脉动压强最大点均出现在收缩段后1倍圆管直径范围内,随后迅速减小,逐渐趋于平稳;面积收缩比为0.471 2的齿墩状消能工的脉动强度最小,因而其抗空化性能优于其他情况,且脉动压强最大点的压强概率密度分布接近正态分布.     

电算法在引水式水电站闸坝取水枢纽泄洪消能设计中的研究与应用

通过对闸坝枢纽泄洪建筑物下游消能的各种影响因素的分析,综合考虑泄洪建筑物泄洪时对下游河床冲刷严重的问题,结合低水头闸坝枢纽一般采用的底流消能方式,提出了在传统设计方法的基础上编制电算程序的设计方案,用试算法确定了坝闸下游消能的最不利工况,并将其结果应用到程序中,对其实用性和有效性进行了验证.结果表明:该电算法能使低水头...     

应用热扩散技术对柠条锦鸡儿主根液流速率的研究

运用热扩散技术对柠条锦鸡儿根部液流速率(Fs)进行连续测定,同步进行环境要素的实时监测。选择2008年4—10月30天典型晴天日观测数据。结果表明:1)Fs在晴天日表现出典型的宽峰型正态分布,可划分为4个特征差异明显的阶段,反映了大气环境因子对液流的直接驱动效应,以及柠条锦鸡儿叶片气孔行为对液流变化的调控作用。2)液流的变化受多个环境因子共同驱动,其中潜在蒸发散(ET0)综合性强、与Fs相关紧密,是分析液流特征更为可靠的复合型环境变量。Fs与主要环境因子间的耦合关系因时段而异,在早晨启动的液流上升阶段,Fs与太阳辐射、ET0间均呈线性关系,反映了太阳辐射等因子对液流的驱动与对光合作用的激活效应,而在峰值后的下降阶段基本呈Sigmoidal-Hill函数关系;Fs随大气水分亏缺(VPD)的变化与随太阳辐射、ET0的变化趋势相反,表明VPD在达到一定值后启动气孔调节行为以及抑制过度蒸腾耗水的效应。3)柠条锦鸡儿根部Fs与主要环境要素间的变化近似同步,试验期间没有出现典型的时滞现象。4)在整个生长季的大部分时间内观测到柠条锦鸡儿根部夜间持续存在着液流现象,夜间液流量平均占全天液流量的3.83%。试验结果可例证热扩散技术在根部测定液流并用来计算灌木树种单株耗水方法的科学性与优越性。     

Mechanical Model of Steel Plate Composite Shear Walls

Based on concepts of mechanics, a mechanical model of novel type of steel plate composite shear wall is presented. The novel type of structure is formed by steel plate shear wall and T-shaped solid-web composite columns. Flexural stiffness of steel beams, lateral stiffness of the T-shaped solid-web composite columns, shear stiffness of steel plate composite shear wall and shear stiffness of beam-column connection are taken into account in the mechanical model. And the equivalent damping between steel plate and boundary is considered. Based on the deformation features of structures and the calculation hypothesis, the lateral stiffness model and the energy dissipation model of structures are developed. Meanwhile, the calculation equations of elastic ultimate and plastic ultimate of shear strength of structures are set up. The theoretical analysis results inosculate better with the results of experiment. The comparison between the result calculated from the formula and the experimental result shows that the calculation precision is high enough to meet the demand of theoretical analysis. The difference, including equivalent model, stress states, manufacturing defect and installation error, between the formula and the experiment has been further discussed.     

杏树蒸腾与降水和冠层微气象因子的关系

利用热扩散植物液流技术(TDP)测定时间步长10min的杏树蒸腾数据,结合同步观测到的降水量和果树冠层微气象因子值,分析华北低山丘陵区杏树蒸腾耗水规律及其与降水、微气象因子关系。结果表明:1)杏树蒸腾速率具有明显昼夜变化特征,在夜晚杏树蒸腾速率很低,白天随着太阳辐射强度的逐渐增加,气温逐渐升高,蒸腾速率逐渐增强;而后,太阳辐射强度减弱,温度降低,蒸腾速度减小。且在同一生长期内晴、多云天气日的蒸腾速率高于阴天天气日。2)杏树在生长季(4—9月)、非生长季(1—3月、10—12月)蒸腾耗水量分别为294.4、68.4mm,分别占全年的81.1%、18.9%。从4月起,杏树的蒸腾耗水量迅速增加,5月和6月达到全年的峰值,此后杏树耗水量逐渐减小。3)年际总降水与杏树蒸腾量的比值为1.6,大于1.0,周年降水可以满足杏树蒸腾耗水的需要,但供(降水量)求(蒸腾量)比各月间差异很大。4)回归分析表明:杏树在主要生长期内蒸腾速率与冠层净辐射、空气温度、湿度、风速等气象因子有很好的相关性(R2=0.833),各气象因子与杏树蒸腾速率的相关程度为冠层净辐射相对湿度空气温度风速。     

青稞的光合特性及光破坏防御机制

通过气体交换、荧光猝灭动力学以及反射光谱等技术研究了两个青稞(Hordeum vulgare L.)品种的光合特性及激发能分配。结果表明, 青稞的光饱和点1 000 μmol m^-2 s^-1左右。在0~500 mmol m^-2 s^-1的光强范围里, 青稞叶片的光呼吸(Pr)随着光强升高而增加; 光强超过500 mmol m^-2 s^-1以后, 光呼吸变化不明显。光呼吸占总光合的比例(P_r/P_m)随光强增强下降。随着光强增强, 光系统II开放反应中心转化效率(F_v′/F_m′), 光系统II实际光化学量子效率(Φ_PSII), 光化学猝灭系数(qP)不断降低而青稞叶片的非光化学猝灭(NPQ)持续升高, 说明越来越多的光能以热的形式耗散掉。光谱分析表明△PRI随着青稞叶片暴露于光下的时间迅速增大。因此, 光呼吸不是青稞主要的光破坏防御机制, 依赖叶黄素循环的热耗散可能是田间青稞耗散过剩光能的主要途径。     

Comparative assessment of five methods of determining sap flow in peach trees

Five different methods of determining sap flow (SF), three based on heat pulse (compensation heat pulse, New Zealand—cHP–NZ; compensation heat pulse, Greenspan/Australia—cHP–G (South oriented), and cHP–G–EW (East and West oriented, average); non-compensation heat pulse, Ariel/Israel—ncHP), one based on stem heat balance (Dynamax/USA—SHB), and another based on heat dissipation (Granier/France—HD) were compared in an experiment performed on peach trees in Northeast Spain. Two irrigation treatments (drip-irrigated) were applied: a control and a stress treatment, the latter consisting of withholding water from day 190 to 199. Between 1 and 3 different systems were installed in some trees of both, the control and stress treatments. All the techniques reflected the evolution of water stress in the stressed trees with a very similar tendency and in agreement with the evolution of predawn water potential (Ψp). Ψp correlated well with sap flow (SF) determined with all the systems (r² > 0.65) in the stress treatment, indicating that all the SF techniques detected changes in tree water status. The cHP–NZ system was the first to detect a SF reduction through the outer xylem vessels, as a response to water withholding. In control trees, daily SF rates provided by the three heat pulse and heat balance methods were well correlated with ETo and somewhat less with global radiation; all regressions improved on an hourly basis. Daily pattern and magnitude of mean SF rates monitored by the three heat pulse systems were quite similar in control trees. This was reflected by high regression coefficients when compared with each other. Higher SF rates recorded by ncHP methods in comparison with cHP–G and cHP–NZ might be attributed to technical limitations and to different sensor orientation. In an accompanying experiment, substantial differences between East and West location of the cHP–G sensors were observed, but when taking the mean value of those daily SF rates, differences between ncHP and cHP–G–EW were lower. Mean monthly crop coefficients, calculated by using SF data computed with ncHP method and soil evaporation as determined with microlysimeters, were 0.64 in July and 0.67 in August. SF systems can be used to detect plant water stress related to control, and might be useful for irrigation scheduling based on plant water status. The SF techniques analysed showed potential to better determine actual plant water necessities than other traditional methods, but a preceding calibration is needed.     

阴阳棚共用墙体不同季节的吸放热状况分析

对新近出现的阴阳结合型温室共用墙体的吸放热状况进行了测定。结果表明:休眠和通风时期,阴面的蓄热明显的低于阳面;露天生长时,阴面的吸热量在日出到8点时显著高于阳面,之后差异逐渐减小,但其吸热量始终小于阳面;不同季节,阴阳面的吸、放热量晴天均大于阴天;阳面在冬季蓄冷(2008年12月)到春季通风降温(2009年2月)期间,在测试的2点中,高度越高,蓄热量越多,散热量越少,其热量损失越小,3月份之后高度越高,蓄热量越少,散热量越多,其热量损失越大;而阴面全年中,均为高度越高,蓄热量越多,而散热量在冬季蓄冷的12月和1月时高度越高,散热量越少,其热量损失越小;而从春季通风到采收期间,则为高度越高,散热量越多,热量损失越大。     

茚虫威在金银花中的残留动态研究及安全性评价

为了探明茚虫威在金银花中的残留特性和安全性,对茚虫威在金银花中的消解动态及最终残留进行了研究。样品经乙腈提取,超高效液相色谱-串联质谱(UPLC-MS/MS)检测,外标法定量。运用所建立的方法对茚虫威在山东泰安、河北邢台、浙江杭州、湖南邵阳、广东湛江和重庆九龙坡6个试验点的金银花中的残留消解动态和最终残留进行了研究。试验结果表明:茚虫威残留量在金银花中随时间延长而递减,符合一级反应动力学方程,消解速度较快,半衰期为1.5～2.2 d,属易消解型农药。参照中国制定的茶叶中茚虫威的最大残留限量(MRL)5 mg/kg,15%茚虫威悬浮剂按推荐使用剂量90 g/hm~2,施药1次,施药后7 d,所采收的金银花中的茚虫威残留量低于5 mg/kg。研究结果可为茚虫威在金银花上的合理使用及其最大残留限量制定提供参考。