Selection for adaptation in multipurpose trees and shrubs for production and function in agroforestry systems

Summary With the greater uniformity in site conditions in cultivated fields and higher levels of inputs (soil amendments and labour) for modern agroforestry systems, selection and breeding for optimal tree adaptation to site conditions and management practices call for strategies radically different from those for plantation forestry. Furthermore, specific requirements for the most efficient growth resource sharing arrangements between the tree and its companion crop call for evaluation both above-ground and below-ground tree growth characteristics in much greater details than has been the case for forestry practice.Specific adaptations in tree-soil relations are highlighted. Tree ideotype profiles are defined for a valuable fodder species (Calliandra calothyrsus) and a valuable timber species (Grevillea robusta). Results from half-sib progeny testing experiment on C. calothyrsus in alley farming system indicate differential adaptedness to frequent cutting for fodder production among the families after 6 cutting cycles (over a period of 2 years). If this differential response to frequent cutting among genotypes is confirmed, phyllomorphs which are more tolerant to this management practice could be selected for further improvement research.Excavation of 2 trees per family within G. robusta half-sib progeny testing experiments at two locations in Kenya provided the base for studying (a) variations in root growth patterns and (b) correlations between stem and root growth patterns in the background of efficient soil resource sharing strategies and of potentials for indirect selection for root growth characteristics. Analyses based on 7 categories of root growth and 7 categories of stem growth patterns involving 94 families selected in Australia and 60 families selected from landraces in Kenya indicate (a) insignificant variation among families in root growth patterns and (b) non existent or weak correlations between stem and root growth pattenrs.     

架空索道多荷重轨迹包络图的研究

根据挠度与弯矩的相似性,阐述绘制多荷重状态下架空索道荷重轨迹包络图的精确算法.通过算例比较2种近似算法相对于精确算法的挠度计算精度及荷重大小对误差的影响,同时讨论荷重数量的变化问题.     

论柔性管理与馆员职业倦怠的抑制

职业倦怠是困扰当前高校图书馆馆员的主要心理情结.在调查研究的基础上,分析了导致高校图书馆馆员产生职业倦怠的成因,指出柔性管理是抑制和消除职业倦怠的基本手段.     

关节式内骨骼气动软体驱动器的结构设计

软体驱动器具有优异的柔顺性,能适应不同形状的目标物体,且不易损伤被抓持物。为了在工业流水线上快速安全可靠地抓持诸如水果、精密元器件等不同质量、不同尺寸物体,该文介绍了一种新型关节式内骨骼气动软体驱动器,将驱动与承力功能分解,在保持柔顺性的同时,显著提高了抓持能力。推导了气压驱动下,驱动器的弯曲角度数学模型。以理论模型为基础,分析了驱动器的各项设计参数对弯曲角度的影响。以确定气压下自由端位姿作为输入条件,以驱动器整体质量最小为优化目标,优化了各参数值,并以得到的参数完成了软体驱动器的实物制造与装配,且试验获得了其弯曲角度与弯曲刚度。试验表明在最大工作压力为150 kPa时,总体误差控制在9%以内,证实了所建立驱动器理论模型的正确与有效性。驱动器的弯曲刚度在最大工作压力时达到4.50 N/rad,弯曲刚度得到大幅提高。该软体驱动器具有良好的开发和应用前景。     

Efficiency of Fund Utilization in Chongqing Districts

This paper analyzes the efficiency of fund utilization of districts of Chongqing by positive approach. It macroscopically compares the rate of capital productivity, labor productivity and integrated productivity of each districts of Chongqing, and does a time serial analyzsis on the base of the sectional analysis with data of year 1998 to 2001. Moreover, it compares the absolute value of production flexibility of each district and finds out the differences of funds utilization efficiency between these districts and gives an explanation. It shows that Chongqing should focus on improving the rate of capital productivity of its districts to develop its economy, because integrated productivity depends on the rate of capital productivity. At the end of this paper, it is pointed out that which districts Chongqing City should develop prior.     

压杆稳定计算的图解解析法

本文说明了压杆稳定计算的图解解析法的原理，分析了压杆截面设计图解解析法的使用条件，通过例题说明了求解过程。     

简支梁在动载荷作用下竖向动挠度的计算理论研究

本文对简支梁在匀速常量力和匀速脉冲力的作用下，应用结构动力学理论，对梁的动力响应给出了近似解答。     

基于局部单元模态柔度差值的木质梁模拟缺陷检测

为尽早对结构和构件的最薄弱位置进行检测和评估,避免因突然破坏而导致的灾难性事故,本文通过振动测试获取了锯材的前两阶模态振型,并利用锯材损伤前后的局部模态柔度矩阵差值提出了损伤识别指标。为了验证所构建的损伤指标的有效性,通过人工切除截面质量来模拟不同损伤程度、不同损伤位置和双损伤的情景。结果表明：损伤识别指标对不同损伤程...     

The Element Flexibility Matrix of Thin-walled Beam and Its Application

In this paper, the calculation of the space deformation of thin-walled element by "dynamic coordinate method" is explained in detail through an example. The thin-walled element with different shear-centers on one section is analyzed and calculated by this method as well, then, the element flexibility matrix is presented. Some difficulties in calculation of thin-walled structures with "plane bending theory" and "constrict twist theory" are overcome, showing the advantages of this method.     

生物质颗粒燃烧器燃料适应性试验

为深入研究生物质颗粒燃料的燃烧特性,探讨自动燃烧器的燃料适应性,该文基于PB-20型生物质颗粒燃烧器,选择了5种灰分小于25%(空气干燥基)的颗粒燃料,分别研究了燃烧工况中进料量和空气量对燃烧性能的影响。试验结果表明灰分含量大于20%的颗粒燃料燃烧不充分,工况不稳定,效率低,结渣大,易熄火,不适用于此类生物质颗粒燃烧器;灰分含量为12.40%的颗粒燃料推荐参数为进料量4 kg/h,风机转速2 600~2 800 r/min,清渣速度为3 r/min,转5 s/停35 s;灰分在7.21%的颗粒燃料推荐控制参数为进料量3~4 kg/h,风机转速2 600~2 800 r/min,清渣速度相对应为3 r/min,转5 s/停60~55 s;灰分值低于1%的颗粒燃料均以进料量3~4 kg/h,风机转速2 600~2 800 r/min,不需清渣为推荐参数。该研究总结了生物质颗粒燃烧器的燃料适用控制参数,为燃烧器的推广应用提供了数据支持。