基于Pro/Toolkit的离心叶轮自动三维建模技术研究

离心叶轮是发动机涡轮增压机等产品的核心零件.分析了CAD环境下离心叶轮三维建模一般步骤.采用NURBS构造了离心叶轮叶片流线通用表达式,制定了离心叶轮三维模型自动生成方案,并阐述了基于Pro/Toolkit的离心叶轮三维建模的具体实现方法.在此基础上,开发软件实现了离心叶轮三维实体模型的自动生成,提高了离心叶轮的设计质量与效率.     

叶轮切割技术在井用潜水泵设计中的应用

在效率合格的情况下,井用潜水泵的叶轮扬程和流量偏高时会产生无功损耗.为保证叶轮的扬程和流量,必须降低轴功率,减少能耗,提高叶轮的效率,才能达到节能减耗的效果.基于相似理论,利用叶轮切割定律进行了叶轮切割计算,并针对250QJ125型井用潜水泵叶轮进行水力模型试验和分析.     

三元流动理论在高压离心风机设计中的应用

通过对一些林业机械用高压小比转数离心风机结构特点及其气动损失的分析,提出了改进风机叶轮结构的措施。依据三元流动理论,采用变分有限元法对叶轮叶道内的流场进行了计算,从理论上分析所采取措施的正确性,并通过试验进行了验证。     

基于CFD软件的轴流式风力灭火机叶轮性能模拟研究

利用CFD软件对轴流式风力灭火机叶轮的内部流场进行数值模拟,与风机试验台的试验数值对比,验证了数值模拟分析的正确性,得到了风机内部流场情况.通过对内部流场分析,为叶轮的结构优化提供了重要的理论依据,并对扭角和安装角调整改进,使设计方案最佳.     

离心泵流动损失分析及对其效率的影响

分析了离心泵叶轮流道内液体的流动，并根据流体力学理论将液体的流动用速度三角形表示。借助速度三角形分析了离心泵内的流动损失（其流动损失包括摩阻损失和冲击损失），进一步阐明了流动损失对离心泵效率的影响。得出了离心泵工作时排量应等于或近似等于最优排量，离心泵的效率才能最高的结论。     

“全可控涡”节能压缩机转子

“全可控涡”节能压缩机转子该项目主要用于压缩机、风机转子。通过计算机优化设计，较好地解决了叶轮内全空间流体流动的自由控制与叶片型面光滑可加工间的矛盾，能在叶片出口相对宽度很宽（ｂ２／Ｄ２０．０９－０．１１）或轴向尺寸很小（圆弧叶片叶轮）等条件下，有效...     

低比速离心式消防泵优化研究

为研究叶轮几何参数对低比速离心式消防泵轴功率的影响,利用设计软件CFturbo,采用堵塞叶轮部分流道和降低叶轮出口直径相结合的设计方法,对某型低比速离心式消防泵进行了优化,并进行了试验验证。结果表明：堵塞叶轮部分流道时,叶片加厚适合采用从骨线向两边加厚的方式;采用堵塞叶轮部分流道和降低叶轮出口直径相结合的方法,可以在保证低比速离心式消防泵性能的前提下,有效降低最大轴功率,在全流量范围内实现无过载。研究结果可为低比速离心式消防泵的无过载优化提供参考。     

离心泵叶轮非定常入流及激励特性研究现状

指出了离心泵叶轮的非定常入流特性对其流动诱发压力脉动、振动特性影响显著。对叶轮的非定常入流特性进行了全面分析,阐述了其目前研究现状,并总结了非定常入流性能的控制及改善措施。进一步展望了离心泵叶轮非定常入流特性的发展趋势,为相关研究的继续深入提供参考。     

超高比转速离心泵的高效设计

为研究叶轮结构参数对提升n_s在300～450间的超高比转速离心泵设计点效率的影响,以某超高比转速单级单吸立式离心泵为研究对象,选取叶轮出口宽度b₂、叶片进口安放角β₁、叶片出口安放角β₂和叶片包角φ为试验因素,建立L₉(4³)正交试验方案,在0.9Q_n～1.1Q_n工况内对各方案模型进行数值计算,分析各因素对泵水力性能影响的主次顺序,进而得到叶轮结构尺寸的最佳参数组合。按照最佳尺寸优化叶轮,将优化后的泵外特性试验结果与原型进行了对比分析。结果表明：(1)高效设计时超高比转速离心泵叶轮结构参数对效率影响的主次顺序为φ→b₂→β₂→β₁,影响水力性能的主要因素为φ,以便指导超高比转速离心泵的高效设计;(2)确定了高效设计时叶轮结构参数的最优水平组合;(3)优化后泵设计点效率较原型提高约4.2%,高效区扩宽至0.75Q_n～1.1Q     

罗茨鼓风机叶轮数学模型的建立

罗茨鼓风机叶轮的传统设计方法是图解法,这种方法误差较大,浪费时间,在加工过程中需要反复进行修改,而且叶轮运转时容易产生噪声,效率低.针对这一问题,根据啮合原理中求解共轭曲线的解析法来求解叶轮的共轭曲线并构建精确的数学模型,以缩短叶轮的设计时间,提高叶轮的设计效率和设计品质.     

地榆及其开发利用

对地榆的分布及其生态环境、开发利用进行了分析论述。     

呼玛县林业局野生蓝莓人工抚育技术探讨

文章详细介绍了呼玛县林业局野生蓝莓分布、生物学特性以及提高野生蓝莓产量和质量的抚育技术。     

配电系统中浪涌保护器的选择和安装

随着电子信息设备的大量应用,雷击电磁脉冲和雷电过电压对设备和系统所造成的损坏日显严重。因此,解决雷击对建筑物电子信息和配电系统所造成的损害变得十分重要。本文简要阐述了在配电系统设计中如何选择浪涌保护器。     

Importance of root growth in overcoming planting stress

Root growth is critical to the establishment of planted seedlings. Seedlings can undergo stress just after planting if root growth is not sufficient to couple the seedling to available soil water. Stress occurs when a newly planted seedling’s root system can not supply enough water to transpiring needles to maintain a proper water balance and ensure survival. Thus, a newly planted seedling’s ability to overcome planting stress is affected by its root system size and distribution, root–soil contact, and root hydraulic conductivity. This paper describes how factors of root growth and water status of newly planted seedlings are important in overcoming the phenomenon of planting stress which then allows a newly planted seedling to enter the establishment phase of development.     

喜树碱在喜树体内分布及在有害生物防治上的应用

喜树碱为重要的抗癌药物和植物源杀虫剂,主要存在于珙桐科的喜树植株体内。该文从季节性、植株组织、产地、栽培密度及环境胁迫等方面分析影响喜树碱在喜树植株中的分布情况,并对其作为杀虫剂和杀菌剂的使用情况进行了综合阐述。     

植物适应逆境胁迫研究进展

低温、干旱、土地盐碱化是影响植物生长发育的主要逆境胁迫因子。植物在逆境胁迫下的生理生化变化以及对逆境适应能力的研究是近年来研究的热点。探索如何将逆境胁迫对植物的伤害降到最低以及如何提高植物的适应性已成为研究需要解决的关键问题。研究植物的抗寒性、抗旱性、抗盐性机理,提高其耐受性,对于生态环境保护和建设具有重要意义。文中分别综述了低温胁迫、干旱胁迫、盐胁迫对植物的危害,植物耐寒性、耐旱性、耐盐性的生理生化机制,以及提高植物耐寒性、耐旱性、耐盐性的途径,展望了植物适应逆境胁迫的研究方向,以期为抗逆性植物种质的筛选和育种提供参考。     

杨树对镉胁迫的响应及抗性机制研究进展

重金属镉（Cd）污染已经成为严峻的环境问题之一,近年来将杨树作为重金属Cd植物修复物种的研究越来越多。文中从杨树生长、光合作用、抗氧化酶活性、可溶性蛋白含量和分子水平上的变化等方面综述了杨树受到Cd胁迫后的生理生化响应;阐述了杨树对土壤Cd的吸收及污染土壤中Cd在杨树体内的分布规律和杨树对Cd的抗性机制;指出杨树对土壤中重金属Cd具有较强的抗性,且这种抗性与杨树品种、树龄、土壤类型、土壤中Cd质量分数等有关;展望了对杨树Cd胁迫的深入研究方向,以期为未来关于杨树修复土壤Cd污染提供更多的理论参考。     

Mistletoe effects on Scots pine decline following drought events: insights from within-tree spatial patterns, growth and carbohydrates

Forest decline has been attributed to the interaction of several stressors including biotic factors such as mistletoes and climate-induced drought stress. However, few data exist on how mistletoes are spatially arranged within trees and how this spatial pattern is related to changes in radial growth, responses to drought stress and carbon use. We used dendrochronology to quantify how mistletoe (Viscum album L.) infestation and drought stress affected long-term growth patterns in Pinus sylvestris L. at different heights. Basal area increment (BAI) trends and comparisons between trees of three different infestation degrees (without mistletoe, ID1; moderately infested trees, ID2; and severely infested trees, ID3) were performed using linear mixed-effects models. To identify the main climatic drivers of tree growth tree-ring widths were converted into indexed chronologies and related to climate data using correlation functions. We performed spatial analyses of the 3D distribution of mistletoe individuals and their ages within the crowns of three severely infested pines to describe their patterns. Lastly, we quantified carbohydrate and nitrogen concentrations in needles and sapwood of branches from severely infested trees and from trees without mistletoe. Mistletoe individuals formed strongly clustered groups of similar age within tree crowns and their age increased towards the crown apex. Mistletoe infestation negatively impacted growth but this effect was stronger near the tree apex than in the rest of sampled heights, causing an average loss of 64% in BAI (loss of BAI was ～51% at 1.3 m or near the tree base). We found that BAI of severely infested trees and moderately or non-infested trees diverged since 2001 and such divergence was magnified by drought. Infested trees had lower concentrations of soluble sugars in their needles than non-infested ones. We conclude that mistletoe infestation causes growth decline and increases the sensitivity of trees to drought stress.     

Cattle distribution and behavior in southern-pine silvopasture versus open-pasture

Shade present in silvopasture systems could reduce heat stress associated with microclimatic conditions that characterize warm-weather portions of the year on the Coastal Plain of the Southeast USA. Objectives of this research were to: (1) quantify diurnal distribution patterns of landscape use and behavior of cattle in loblolly-pine (Pinus taeda) silvopasture versus open-pasture landscapes, and (2) relate observed differences in landscape use and cattle behavior patterns between the two pastures to differences in microclimatic conditions, and forage quantity and quality. The research was conducted in Chipley, Florida USA within a 5-ha cell of a loblolly-pine-bahiagrass (Paspalum notatum) silvopasture (tree age 20 year), and a 5-ha open bahiagrass pasture with unlimited access to an adjacent 1-ha wooded area. One-day observations of diurnal distribution and behavior of cattle were conducted in March, June, and September 2007; microclimatic conditions were measured, and forage quantity and quality were estimated within each landscape. Cattle utilized the landscape more evenly in the silvopasture versus the open-pasture and this difference was mainly attributed to reduced solar radiation recorded in the silvopasture. Grazing was the dominant behavior in the silvopasture while loafing was dominant in the open-pasture. Shade present in silvopasture appeared to reduce heat stress for cattle grazing during warm-weather portions of the year on the Coastal Plain of the Southeast USA. Further study is needed to determine how this reduction in heat stress influences cattle performance in southern-pine silvopasture, and the nature and extent of the interactions among animal distribution and behavior, microclimatic conditions, and forage characteristics in these systems.     

The search for resistance to Heterobasidion root rot in Norway spruce - old and new approaches in studies of infection biology

The paper surveys the methods used for studying the root rot in Norway spruce (Picea abies) and summarizes the major results on Heterobasidion infection, the importance of the rhizosphere, preformed and induced resistance factors, search for trees with high resistance, and on virulence factors of the fungus. New approaches are discussed regarding where to look for resistance, how to study host-parasite interaction, the importance of stress factors, and the need for short-term experiments and standardized inoculum.