自吸泵启动过程气液两相流动的数值模拟

自吸泵的自吸过程是一个十分复杂的瞬态气液两相流动过程,自吸过程中气水混合及分离效果的好坏,是决定自吸泵自吸性能的关键。该文运用VOF多相流模型结合滑移网格技术,加载试验所获得启动过程中叶轮的转速变化曲线及泵出口压力变化曲线,模拟了启动过程中气液混合现象及气液分离现象,获得了气液分离室进口、回流孔、蜗壳各断面及叶轮内监测点的含气率变化曲线。结果表明,叶轮外缘出现了明显的气液混合层,气液分离室进口回流现象明显,启动过程初期泵运行的不稳定,使气液分离室进口及蜗壳隔舌处含气率出现明显的振荡,气泡在叶轮中不断地生成及溃灭是造成叶轮上监测点含气率振荡的原因。该文采用的模拟方法能够较好地模拟自吸泵启动过程内部气液两相流动,为进一步研究自吸泵内部气液混合及分离提供参考。     

机械-液压双元动力发动机锥形配流阀的优化

机械-液压双元动力输出发动机（MHPE）将传统的内燃机和柱塞泵融为一体,可同时或单独输出机械、液压2种动力。MHPE采用锥形阀配流系统,其容积效率高低直接影响MHPE的整机性能。该文以容积效率为目标函数,以锥形阀的工作条件和结构尺寸为约束条件,以MHPE锥形阀的结构参数为优化变量,建立了优化模型,并基于iSIGHT软件进行优化设计。优化结果表明,优化后系统的容积效率提高5.71%,改善程度较大。     

Vegetative Propagation of Local Fruit Trees by Air Layering in the Guinean Savannah Highlands (GSH)

Over recent decades there has been a growing interest in the attributes of non-timber forest products (NTFPs) to food security, income generation, and poverty alleviation. In the Guinean Savannah Highlands (GSH) of West Africa, species producing these products are still in wild stands where they are subjected to various pressures. To conserve these species, their domestication is required. Air layering is a low-cost propagation technique easy to use by farmers. The present study aims at evaluating the effects of the wood type (hardwood, semi-hardwood, and softwood) as well as branch diameter (Φ ≤ 6.67 cm; Φ > 6.67 cm) in the rooting ability of the marcots (air-layered propagules) of Lophira lanceolata Van Tiegh. Ex Key., Parkia biglobosa (Jacq.) Benth, Syzygium guineense var. macrocarpum Engl., Vitex doniana Sweet., Vitex madiensis Oliv., and Ximenia americana L. The experimental design was a split-plot with three replications. The rooting percentage of the marcots varied significantly from 13.5 (X. americana) to 55.85% (Lophira lanceolata; p < .001). The diameter * wood type interaction was significant (p < .05) due to the high rooting percentage obtained in large semi-hardwood cuttings (40%). Lophira lanceolata, Syzygium guineense var. macrocarpum, and Vitex madiensis were the easiest marcotting rooting species. Large branch diameters as well as semi-hardwood are suitable for layering. This information will help in developing appropriate domestication strategies.     

空中拖拉机喷雾系统及喷雾技术

摘要：空中拖拉机是当前我国农化作业效率最高的飞机之一。其先进的喷雾系统由药箱、高压泵、喷杆、喷头、加药设备及控制系统等部分组成。空中拖拉机飞行高度在平原和山区分别为树梢以上10～15m和20m以上,AT-504和AT-402B的有效喷幅分别为80m和60m。大多数雾滴直径100～200μm,雾化程度高,可以通过改变喷头角度来调整雾滴密度和大小。     

Vacuum and Air Flow for 2QXP-1 Vacuum Precision Seed Metering

Vacuum precision seed metering is the key part of vacuum seed planter. Planting performance of planter is affected by vacuum and air flow which are important parameters for choosing fan. Effects of qualification percent and miss percent on air chamber vacuum 3, 4, 5 and 6 kPa were studied at different operating speeds. The results showed that operating performance of the seed metering was excellent when air chamber vacuum was 5 and 6 kPa, which air flow was 7.4-8.0 m3·s-1 and 8.0-8.8 m3·s-1 , respectively.     

Serratospiculosis in a New Zealand Falcon (Falco novaeseelandiae)

CASE HISTORY: An adult New Zealand falcon was presented with metacarpal fractures in the left wing.

CLINICAL FINDINGS: In addition to the fractures, radiographs revealed an area of opacity in the air sacs. A few days after hospitalisation and initiation of treatment of the fractures, the bird developed signs of respiratory disease; the area of opacity was found to have increased in size and density. Treatment with antibiotics and nebulisation was commenced; the bird initially responded but respiratory signs subsequently worsened and the bird died. At necropsy, air sacculitis and bronchopneumonia were associated with numerous nematodes in the air sacs, which were morphologically consistent with Serratospiculum guttatum.

DIAGNOSIS: Serratospiculosis

CLINICAL RELEVANCE: The discovery of this parasite and the associated disease for the first time in New Zealand indicates that it should be considered in the differential diagnosis of respiratory disease in falcons and possibly other raptors in New Zealand.     

铁路罐车下装下卸可行性分析

目前,铁路罐车装卸油品方式主要以上装上卸为主,采用上卸方式易产生气阻,卸车效率低,且损耗大,易产生静电。已经成熟的汽车下装下卸技术,特别是无残油留存新型阀门技术的发展为铁路轻油罐车的改造提供了新思路。基于无残油留存新型阀门技术的工作原理,论述了铁路罐车实施下装下卸的可行性。同时,在底卸方面成熟的安全措施经验和管理规定可为铁路罐车下装下卸技术的顺利实施提供保障。铁路罐车下装下卸技术的应用,可有效解决气阻、静电等问题,降低损耗,节约投资,产生一定经济和社会效益。（图3,参6）     

Mitral valve and tricuspid valve dysplasia in a 9‐week‐old Standardbred colt

A 9‐week‐old Standardbred colt was presented for investigation of dull demeanour, exercise intolerance and heart murmurs. Cardiac auscultation revealed a grade 5/6 holosystolic murmur and a grade 5/6 pansystolic murmur over the left and right cardiac apex respectively, and an irregularly irregular cardiac rhythm. Electrocardiographic examination findings were consistent with atrial fibrillation and tachycardia. Echocardiographic examination identified marked atrioventricular regurgitation and atrial dilation bilaterally, thickening of the mitral and tricuspid valves and dilation of the pulmonary artery consistent with pulmonary hypertension. No ventricular or atrial septal defect was present. Cardiomegaly and diffuse pulmonary oedema were evident on examination of lateral thoracic radiographs. Dysplasia of the mitral and tricuspid valves, eccentric cardiomegaly and pulmonary oedema were confirmed by post mortem examination. Dysplasia of the atrioventricular valves represents a rare cause of biventricular failure in the horse.     

Determining treatment frequency for controlling weeds on traffic islands using chemical and non‐chemical weed control

Many public authorities rely on the use of non‐chemical weed control methods, due to stringent restrictions on herbicide use in urban areas. However, these methods usually require more repeated treatments than chemical weed management, resulting in increased costs of weed management. In order to investigate the efficacy of four non‐chemical weed control methods and glyphosate treatment, experiments were carried out on traffic islands in the growing seasons 2005 and 2006. Three trial sites were each divided into six treatment areas, which were either treated with glyphosate, flame, steam, hot air/flame, hot water or left untreated. The treatments were carried out at regular, predetermined intervals throughout the growing season in 2004, whereas in 2005 and 2006 how many treatments that were required to keep weed cover below a predetermined acceptance level of 2% were investigated. Percentage weed cover was measured every second week using a 75 cm × 75 cm quadrat divided into 100 squares. On the control areas, a rapid increase in weed cover was observed, whereas weed cover could be kept below 2% by 2–7 treatments per year, depending on control method. On average, the following numbers of treatments per year were required: glyphosate 2.5, hot water 3, flames 5, hot air/flames 5.5 and steam 5.5 treatments. The results demonstrate that the weed control should be adjusted to the prescribed quality for the traffic islands by regularly assessing the need for weed control. They also show that tailored treatments can reduce the number of required non‐chemical treatments per year.     

河西走廊东部冰雹的气候特征及天气特征

利用线性回归分析、Mann-Kendall检验和小波分析法,统计分析河西走廊东部1961-2010年近50 a来冰雹日数的变化规律。结果表明：河西走廊东部冰雹日数时空分布差异较大,从祁连山区到走廊平川区冰雹日数迅速递减;年冰雹日数变化总体呈下降趋势,其线性倾向率为-0.164 3 次•a-¹;一年中冰雹出现时段集中在6-9月,一日集中在12：00-18：00;冰雹持续时间在1～20 min。采用Mann Kendall检验法进行检验,河西走廊东部年冰雹日数从1985年开始减少,突变点出现在2006年,2006年后冰雹日数显著减少。在全球变暖的气候背景下,河西走廊东部冰雹日数呈减少趋势,但开始减少和显著减少的时间均滞后于年平均气温开始上升和显著上升时间。小波分析结果表明,河西走廊东部冰雹日数存在9 a的准周期变化。根据冰雹天气发生的物理机制和高低空环流配置,将冰雹出现的大尺度高空环流形势归纳为西北气流型、西风气流型、低压槽型3大类。对每种大尺度高空环流形势下700 hPa中尺度环流进一步细化,分析了每种冰雹类型的垂直环流特征及影响程度。