液压悬挂试验的加载误差及其补偿

通过对下支点固定式油缸加载工况下拖拉机液压悬挂装置的受力分析，推导出这种国内外常用试验台设计方案的加载误差，并给出试验数据的修正方法以补偿该项误差的影响。     

拖拉机液压提升能力试验加载方案的对比研究

综述了国内外拖拉机液压提升能力试验的几种加载方案，并就其优缺点进行了探讨，给出了一种适于基层单位进行液压提升器检测维修的经济型方案。     

梯级引水工程水位优化调度模型研究

大型引水工程整个系统在进入稳态运行后,在各站的抽水流量或首级站进口水位发生变化的情况下及时做出运行决策,调整各梯级站间的水位,达到整个系统总能耗最小的目的。针对这一问题提出了大型引水工程各梯级站水位优化调度的数学模型,并对其解法进行探讨。     

反渗透海水淡化用提升泵的设计

针对提升泵存在轴头力过大的问题,采用调整口环直径、前盖板加装辅助叶片、降低转速等方法进行轴向力平衡,对于2500 t/d反渗透海水淡化的提升泵,通过降低转速增加叶轮尺寸的方法来平衡轴向力使结构更趋合理.结合反渗透海水淡化的工艺流程,提出提升泵性能参数的确定方法.鉴于提升泵入口高压的运行环境,选择单级悬臂、双蜗壳、三推力轴承组合结构形式,采用较粗的轴径和较小的悬臂比,提高系统的稳定性.应用新型的上游泵送机械密封,通过100 h的运转试验,在较高的压力环境下运行,仍能保持良好的密封性能,且断面无接触,磨损量小,解决了高压环境下轴封反复失效的问题.     

果园作业升降平台设计与剪叉分析

利用Autodesk Inventor三维软件设计了一款轮式果园作业升降平台,其针对新式果园(即果园)采用矮砧密植种植模式,株行距2m×4m,树高3.5~4m,枝展1.5m左右。此种果园将园艺与农机结合,易于机械化作业的实现。剪叉是升降动作的主体,其稳定性是着重考虑的因素之一,剪叉的静力学性能直接影响安全性,同时剪叉固有频率与工作频率相近会对稳定性有不利影响,因而进行了静力学强度校核与模态分析。结果显示:剪叉臂静力学强度符合要求,剪叉机构的固有频率从19.686~58.965Hz逐渐变大,后期发动机选用时应当参考此结果。     

水盐胁迫下根系提水作用对土壤盐分与番茄产量的影响

为探究水盐胁迫下番茄根系发生提水作用的可能性及其对土壤盐分分布和番茄产量的影响,利用上下桶分根装置,设定上桶不同水分(W1、W2、W3表示土壤含水率为田间持水率的60%～70%、50%～60%、40%～50%)和盐分条件(S0、S1、S2表示Na Cl添加量分别为干土质量的0、0.2%、0.4%),监测分析了水盐胁迫下根系提水量、上桶盐分分布及番茄产量。结果表明:随着生育期的推进,根系提水量呈现先增加后减小的趋势,其中盐分对番茄根系提水量影响显著,在相同水分处理条件下,盐分含量越高,根系提水量越大;水盐胁迫下,上桶盐分含量与根系提水量呈线性正相关,除W1S0处理外,上桶土壤电导率在提水量达到最大时有所增加;与对照处理W1S0相比,水盐抑制了根系生长,使根系活性显著下降,同一水分处理下,随着盐分的增加,根长、根表面积及根体积减小;盐分对番茄水分生产率有显著影响,在相同水分条件下,盐分越大,水分生产率越大,7种处理中W2S2水分生产率达到最大,而其产量较对照并未显著减小,生育期提水量占需水量的17.73%。本研究对进一步理解作物在"上干下湿"的土壤水盐胁迫下充分利用土壤剖面深层水分来维持上层根系生存和提高水分生产率具有科学价值。     

新疆叶尔羌河泽普县段河道防洪工程治理对策

叶尔羌河是典型的冰雪补给型河流,水量年际变化不大,年内分配不均,洪枯流量相差悬殊,并周期性的伴有冰川湖突发洪水,泽普县全县均属于叶尔羌河流域,是叶尔羌河的主要平原灌区县之一,根据现有防洪工程的具体情况,新建1.7km上、下亚斯墩防洪堤从根本上解决泽普县段河道的防洪问题。     

Yield, growth and mortality rate of the Thai river sprat, Clupeichthys aesarnensis, in Sirinthorn Reservoir, Thailand

The Thai river sprat, Clupeichthys aesarnensis Wongratana, is a clupeid with a short life span, and supports artisanal fisheries in a number of reservoirs in the Mekong Basin. The growth parameters, mortality rates and the status of the Thai river sprat in Sirinthorn Reservoir (28 800 ha), NE Thailand (15°N; 105°E), are presented. The fishery is based on lured lift‐nets, operated 7–14 days in the new moon period, September to April each year. It was shown that the von Bertalanffy growth function (VBGF) model was L_t (mm) = 78.43[1 ? exp{?0.211[t ? (?0.7996)]}] and its growth conformed to an isometric pattern. Natural mortality rate (month^?1) was 0.13 month^?1. Total mortality rates ranged from 0.69 to 1.53 month^?1 depending on the weather and the fishing season. Recruitment was continuous throughout the year but peaked in June and July. The yield per recruit model indicated that the exploitation rate of this fishery is probably too high.     

Contribution of Adventitious Roots to Water Use Strategy of Juniperus sabina in a Semiarid Area of China

duniperus sabina Linnaeus, an evergreen shrub with prostrate life form, can effectively prevent sand moving and is an important tree species for reforestation in semiarid areas of China. It has laterally distributed adventitious roots and a deeply distributed main root system. To detect water movement between the main root system and adventitious roots, we adopted heat pulse sensors using the Heat Ratio Method, a high precision method for measuring low sap flow rates. Two sensors were implanted in each individual in the stem between the main root system and adventitious roots, and another two in lateral stems distal to all the roots. Positive sap flows during nighttime, even under saturated air moisture conditions, were detected only between the main root system and adventitious roots under drought conditions, and the rate of flow increased as drought progressed and decreased or disappeared after rain events. The results demonstrated the existence of water movement from the main root system to adventitious roots, and combined with the high contribution of nighttime sap flow to transpiration （11%-16%） the results indicate that it also involves the process of hydraulic lift, a water movement from moist subsoil to dry surface soils. Integrated water use strategy between the main root system and adventitious roots via the process of hydraulic lift of soil water maximizes water acquisition efficiency from both subsoil water and water from rain pulses on the soil surface; this increases survivability in the water-limited environment of semiarid areas.     

Stability analysis on shallow tunnel with floor lift under inclined ground by upper bound method

采用极限分析上限法,基于内外能耗守恒原理,通过构建考虑隧底隆起的斜坡地段浅埋隧道破坏模式,推导出围岩压力的计算式,并通过典型算例重点分析了典型因素对隧道围岩稳定性的影响。研究结果表明：基于泰沙基极限平衡法进行隧道围岩支护设计较为保守,不考虑隧底隆起的极限分析方法次之考虑隧底隆起极限分析方法的风险最大;斜坡地表倾角增大对浅埋隧道稳定性有着不可忽视的不利影响;围岩压力随岩土侧压力系数减小、埋深增大、断面尺寸加大而增大;岩土黏聚力增大、内摩擦角增大对提高浅埋隧道围岩稳定性有积极作用。