角规测树方法的误差分析

本文利用414块人工落叶松林样地实测资料,探讨了角规测树的误差问题。研究结果表明,即使在排除了某些产生偏差因素的情况下,角规常数选择不当,仍然会产生偏小或偏大的误差。这说明角规常数的选择在角规测树中是至关重要的;并说明了角规常数的选择与其它误差相关联,是角规测树的中心问题。     

提高刷式集流环主要性能指标的研究

集流环是对旋转体进行测量时传递电信号的中间装置。集流环性能指标的好坏直接影响测量精度。刷式集流环最主要的性能指标是电刷和滑环这对接触副接触电阻变化量的大小,在这方面我们做了大量的试验研究。到目前为止,已可将接触副接触电阻变化量控制在8×10~(-5)Ω以内。     

EPIDUROGRAPHY IN THE NORMAL DOG: TECHNIC AND RADIOGRAPHIC FINDINGS

Ten clinically normal adult mongrel dogs were examined using lumbosacral epidurography in an effort to determine a reproducible technic and a normal radiographic appearance. The site of contrast medium injection was the ventral epidural space at the sacrococcygeal junction or the cranial coccygeal region. An initial dose of 0.15 ml/kg of metrizamide for the right lateral recumbent radiograph with 0.10 ml/kg additional metrizamide for additional right lateral or the subsequent dorsoventral radiographs was considered adequate. Two numerical values were observed for each normal epidurogram: the sacrovertebral angle; the ratio of the contrast medium column width to L6 body length. A statistically significant relationship between hindlimb positioning and the numerical value of the sacrovertebral angle was identified. Some advantages of epidurography for delineating the lumbosacral area are obvious: (1) it overcomes the limited value of lumbosacral area myelography; (2) it is technically easier than intraosseous vertebral venography; (3) there is minimal patient trauma; (4) there was no apparent adverse sequela to repeated contrast medium injections.     

棉纤维的微原纤螺旋角和纤维素微晶相对取向指数在植株中的分布

用Ｘ射线衍射法对棉纤维细胞壁的微原纤维旋角和纤维素微晶相对取向指数在植株中的分布规律进行了研究。结果是：微原纤螺旋角随果枝位和果节位的增加略有增加，相对取向指数随果枝位和果节位的增加略有减小。     

针叶材管胞径壁与弦壁纤丝角的差异分析

在对马尾松和日本柳杉的管胞次生壁中层径壁纤丝角与弦壁纤丝角进行测定的基础上,(?)统计分析方法,对其进行了比较分析,并进行了分布类型检验及方差和期望的检验,结果表明,针叶材管胞次生壁中层的径壁纤丝角和弦壁纤丝角不存在显著性差异。为人们在木材纤丝角的研究中只讨论弦壁纤丝角的作法,提供了必要的理论依据。     

平面应力状态下主应力与主平面对应关系研究──锐角判别法

平面应力状态下主应力方向的确定，对农业工程结构设计和理论分析都非常重要。本文提出了确定主应力方向的有效方法──锐角判别法，建立了锐角判别法准则，阐述了锐角判别法的基本原理，并进行了证明。     

论直剪试验的常见问题与对策

本文论述了直剪试验的方法及在直剪试验中常见问题，并提出相应的解决方法。     

光波在媒质分界面上的周相突变

光波遇到媒质分界面时，出现反射光和折射光，本文就反射光是否会出现周相突变π，根据菲涅耳公式作一数学上的论述。     

Water repellent cotton fabrics prepared by PTFE RF sputtering

A poly(tetrafluoroethylene) (PTFE) sputtering technique was employed to introduce water repellency onto the surfaces of commercial cotton fabrics. Sputtering power, time, and argon pressure were varied as processing parameters, when PTFE coatings were applied on the fabrics. Total 27 different samples were prepared to compare their water repellent properties, which were investigated by contact angle measurements. Morphology of the PTFE coatings were probed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Also, the extent of the coating was examined by X-ray photoelectron spectroscopy (XPS). Maximum hydrophobicity was obtained when PTFE coating was extensive enough to cover cotton fabrics almost completely, and the extensive coating was the roughest among the samples prepared in this study.     

叶片残留法测定植物提取物对绣线菊蚜的触杀作用

[目的]研究5种植物提取物对绣线菊蚜生物活性的影响。[方法]采用浸渍法,以95%乙醇为溶剂,对竹柏、小花八角、单瓣狗牙花、灯台树、辣蓼5种植物进行提取。将5种植物提取物分别稀释成1、5、10倍液,在室内用叶片残留法对绣线菊蚜进行触杀测定。[结果]5种植物的触杀效果为灯台树〉小花八角〉辣蓼〉竹柏〉单瓣狗牙花。不同浓度的5种植物提取物对绣线菊蚜的校正死亡率均无显著差异,竹柏、小花八角和辣蓼3种提取物的不同触杀时间的校正死亡率差异显著,单瓣狗牙花提取物不同触杀时间的校正死亡率差异极显著,灯台树提取物在不同触杀时间的校正死亡率无显著差异。[结论]5种植物提取物对绣线菊蚜的触杀效果相当。