植物叶片厚度日变化及其与生态因子相关性的研究

多数植物的叶片很薄、很软、充满水分,对其组织结构的研究主要集中在显微结构和亚显微结构方面.利用自主研发的YI-20010A型植物叶片厚度精密测量仪,对几种温室栽培的植物叶片进行监测,可以直接获得叶片厚度的实时变化情况.供试的5种植物叶片都在正午前后出现叶片厚度一天中的最低值.对番茄和高羊茅叶片厚度与相同时段的叶片附近的光照强度、空气温度、相对湿度三个周期性变化的生态因子的相关性进行分析,得出叶片厚度变化与光照强度有显著的负相关,与相对湿度呈显著的正相关.     

北京地区老年人人体尺寸测量

目前国内尚缺乏65岁以上老年人的人体尺寸数据,为此对113名北京地区65岁以上的老年人（包括53名男性与60名女性）进行了人体测量,获得47个尺寸参数的平均值、标准差以及各百分位数.通过比较得知,老年人男女性别之间臀部、腰部、大腿区域的围度、宽度、厚度尺寸差别较小,其他尺寸差别较大;老年人在进入65岁以后,身体尺寸变化趋于稳定.     

植物叶面物理信息检测技术研究进展

针对节能减排技术中的节水灌溉及林业碳汇量计量等问题,需对植物的生长状态进行精确的无损检测.目前的方法是依据植物生理参数与其物理参数间的关系,将不可直接测得的生理参数量转化为可直接测得的物理参数量,利用植物叶面物理信息检测技术采集植物生理信息;通过植物叶面物理信息检测技术的研究,实现了对植物叶片各物理参数(如叶片厚度、叶表温度、叶片叶绿素含量及叶表气孔等)的实时测量,建立了叶面物理参数与植物生理状态的相关数学模型.这些工作对研究环境的响应机制、植物微观生长量及植物宏观特征的精确表征具有参考价值.     

精量灌溉中的植物水分精密诊断技术

针对目前我国水资源短缺的现状,提出基于植物水分诊断检测技术的闭环反馈控制节水灌溉系统.该系统的关键技术是研究可同时精确测量叶片厚度和温度的双参数融合式传感器,厚度测量的传感器原理实验已经完成.     

中国成年人人体尺寸数据相关性研究

本文基于最新的中国成年人人体尺寸数据,开展了人体测量基础项目与5项人体关键尺寸测量项目之间的相关性研究,建立了线性回归方程,为人体尺寸测量项目的优化提供了技术支持。研究成果在人体测量工作中的应用,可有效降低人体测量工作难度,缩短工作时间,减少资金投入,为提高人体尺寸数据更新速度提供帮助。     

大型水轮机叶片快速检测的新方法

为解决大型水轮机叶片尺寸检测这一行业性难题,实现对叶片型面外型尺寸的快速检测,提出了一种基于视觉测量技术的新方法.该方法以摄影测量原理为理论基础,首先在物体表面待测位置粘贴标志点,然后从不同角度拍摄一组照片,作为测量的原始数据输入计算机中进行解析处理.在测量软件中通过对照片组进行图像检测,识别出各张照片中标志点并定位其中心,匹配同名标志点,最后根据标志点的多个二维坐标重建出对应物体点的三维坐标,从而实现对被测对象的数字化建模和测量.现场实验表明,与传统的水轮机叶片检测方法相比,该方法具有工作量小,速度快,成本低,容易实现在线检测,并且不易受现场灰尘、振动、湿度和温度变化等外界因素的干扰.     

单晶涡轮叶片合金的薄截面尺寸效应

单晶涡轮叶片合金存在明显的薄截面尺寸效应,当截面尺寸小于0.5mm时,持久寿命大幅降低,尤其是中温持久寿命.截面尺寸效应是由于试样厚度减小引起显微组织和表面完整性的变化以及实验误差综合影响所致.     

ZL114A铝合金激光-电弧复合焊接头枝晶尺寸与熔宽的关系

采用激光-电弧复合焊方法对厚度为8mm的ZL114A铝合金板进行焊接实验,焊后对接头显微组织尺寸与分布进行了分析.结果表明,在不同工艺参数得到的各焊接接头中,树枝晶尺寸与熔凝区宽度具有一定的相关性,熔凝区宽度一定枝晶尺寸一定,且树枝晶尺寸沿板厚方向从焊缝上部到根部逐渐变小,呈近似线性变化.     

国产Q460高强度钢材焊接工字形截面残余应力试验及分布模型研究

焊接残余应力是影响钢结构受压构件整体稳定性能的一种重要初始缺陷. 为研究国产Q460高强度钢材焊接工字形截面的残余应力分布, 该文采用分割法对8个不同截面尺寸和焊缝类型的截面试件进行了测量. 基于近2000组测量数据, 得到了不同试件全截面的残余应力分布和拉、压应力大小, 并研究了腹板和翼缘的板件宽厚比、板件厚度、焊缝类型以及腹板和翼缘的相关性等因素对残余应力的影响. 试验结果表明, 残余压应力的数值大小与截面尺寸直接相关而基本不受焊缝类型的影响, 残余拉应力的大小则与截面尺寸没有相关性;由于翼缘和腹板内的残余应力能够分别满足自平衡条件, 二者没有相互间的影响作用. 最后, 该文提出了能够准确描述试验结果和截面尺寸影响的国产Q460高强钢焊接工字形截面的残余应力分布模型和计算公式.     

涡轮导向叶片蜡模组焊件的测量

涡轮导向叶片蜡模组件是由三个单联叶片蜡件组焊接而成,涡轮导向叶片蜡模组件形状复杂,蜡件收缩率大,且通道公差也大,易变形,检测定位难度很大,需要检测导向叶片蜡模单件和组件安装板两侧面中心位置尺寸,安装板侧面由双斜面形成空间位置,该测量装置既实现各单件通道尺寸测量,又能满足焊接后的尺寸和焊接后各单联叶片的相互位置要求,边焊接边检查。由于蜡件熔铸成型时,每个蜡件尺寸不同,变形大,因此需要此测具克服位置尺寸公差进行测量,从结构上采用斜块涨紧,并限制蜡件叶片的理论极限位置,确保组焊接件位置,采用UG三维建模,建立三个叶片蜡件空间的焊接的位置,采用螺纹压紧机构,在设计时合理选取倒棱厚度和方向,消除其影响;斜块涨紧高度位置取在叶片中心位置,保证三联叶片准确位置,用可调式斜块限制线性移动,并有限位机构进行测量,解决了多联涡轮导向叶片蜡模组件焊接位置的测量。     

Speckle correlation photography for the study of water content and sap flow in plant leaves

The speckle pattern fluctuation in the leaf of a plant is investigated by using speckle correlation photography. The speckle correlation method is used to extract the amount of speckle pattern fluctuations. The speckle pattern fluctuations are related to the water content of the sap, which is in the veinous structure of a leaf. The speed of sap flow in veins is obtained by this method.     

基于AD598模块的圆度仪数字化改造

以Talyrond 73型圆度仪为例,详细介绍了基于AD598模块的圆度仪数字化改造方法.测试结果表明改造后的仪器在保持原有精度的前提下,实现了检测过程的自动化、数字化及可视化.     

包装薄膜厚度与阻湿性能关系的研究

薄膜厚度是影响薄膜阻湿性能的因素之一,研究二者之间关系有重要意义.通过测量不同厚度PET薄膜的透湿率,得到了PET薄膜厚度与透湿率的关系曲线,根据曲线推算出厚度与透湿率二者的函数方程.     

合金氧化膜的AES分析技术及其应用研究

根据俄歇电子能谱（AES）的深度分布图，得到不同区域的膜厚和在此区域中的元素富集因子与材料性能之间的关系。并以304不锈钢在高温水中生成的氧化膜为例，探讨膜厚和元素铬的富集因子与材料抗应力腐蚀性能之间的关系。     

Spacing of edge fractures in layered materials

Opening-mode fractures developed from a free surface in a layered material often terminate at the interface that divides the fractured layer and the underlying layer. They also display regular spacing that is of the same order of magnitude as the thickness of the fractured layer. We have investigated the stress distribution between two adjacent edge fractures as a function of the ratio of fracture spacing to thickness of the fractured layer using a two-layer elastic model with a fractured top layer. The results show that when the ratio of fracture spacing to the layer thickness changes from greater than to less than a critical value the normal stress acting perpendicular to the fractures near the free surface changes from tensile to compressive. This stress state transition precludes further infilling of fractures unless they are driven by mechanisms other than a pure extension, or there are flaws that significantly perturb the local stress field between the fractures. Hence, the critical fracture spacing to layer thickness ratio defines a lower limit for fractures driven by extension, which also defines the condition of fracture saturation. The critical value of the fracture spacing to layer thickness ratio is independent of the average strain of the fractured layer, and it increases with increasing ratio of Young's modulus of the fractured layer to that of the underlying layer. The critical value increases with increasing Poisson's ratio of the fractured layer, but it decreases with increasing Poisson's ratio of the underlying layer. For the case with the same elastic constants for the fractured layer and the underlying layer, the critical spacing to layer thickness ratio is about 3.1. Delamination between the fractured layer and the underlying layer makes the critical spacing to layer thickness ratio much greater. Infilling fractures grow more easily from flaws located near the bottom of the fractured layer than from those located near the free surface when the spacing to layer thickness ratio is less than the critical value. The propagation of an edge flaw between adjacent edge fractures is unstable, but for the flaw to propagate to the interface, its height has to be greater than a critical size, that decreases with increasing fracture spacing to layer thickness ratio. The propagation behavior of an internal flaw with its lower tip at the interface depends on the edge fracture spacing to layer thickness ratio. The propagation is unstable, when the fracture spacing to layer thickness ratio is greater than a critical value; stable, when the fracture spacing to layer thickness ratio is less than another critical value; and first unstable, then stable, and/or unstable again, when the fracture spacing to layer thickness ratio is between these two critical values.     

减振器节流阀片对阀门水击力的影响研究

针对车用减振器受地面瞬态冲击阀门容易失效的特点,提出了研究阻尼阀水击压强的重要性.建立了带有环形节流阀片的阻尼阀物理模型.通过有限元软件对节流阀片受瞬态冲击的变形时间进行了研究,得出了节流阀片受冲击的最大变形时间只与结构参数和材料特性相关,并随阀片厚度增加而减小的结论.与水击理论相结合,推导了阻尼阀水击的初始和边界条件,创建了阻尼阀水击数学模型.运用节流阀片等效厚度法则,编程分析了叠加节流阀片对水击力的影响规律,得出了在等效厚度相同的情况下,随着叠加阀片物理厚度的增加水击压强增大的结论,可以作为阻尼阀的设计参考.     

叶片厚度仪原理误差的研究

建立了叶片厚度仪的实际传动特性方程,通过与理论的线性模型比较,获得了仪器的原理误差函数式。并且分析了测量时接触变形误差对测量结果的影响问题,在此基础上提出了减小原理误差的方案,并以增加测量臂长为例论述了减小原理误差的方法.     

Packaging materials for fermented milk,part 2: solute‐induced changes and effects of material polarity and thickness on food quality

This work is a continuation of the application of a developed methodology for the selection of packaging material for a specific food product, in this case the ‘demanding’ food product: fermented milk. The effects of different packaging material parameters on the quality of fermented milk were studied. Food quality after storage was determined as a function of material polarity and pouch thickness by storing the liquid in pouches of different materials. The material polarity was varied by using laminates with polyethylene, poly(ethylene‐co‐vinyl alcohol) with two different ethylene contents and an aliphatic polyketone. The effects of pouch thickness were studied using high‐density polyethylene films of different thicknesses between 25 µm and 200 µm. The interactions between the milk product and the pouch material were analysed by oxygen and water permeability, gas chromatography–mass spectrometry and tensile testing. The CO₂ and O₂ contents in the headspace of the pouches were determined. The food quality was determined by measuring whey syneresis and the contents of Bifidobacteria, Enterobacteriaceae, yeast and mould. A trained taste panel determined the sensory properties. The content of CO₂, and consequently the sparkling taste, increased with increasing polarity and/or pouch thickness. The CO₂ content was affected more easily by changes in material polarity than by changes in pouch thickness. The increase in whey syneresis and the decrease in Bifidobacteria content with time were independent of material polarity and pouch thickness. The contents of Enterobacteriaceae, yeast and mould in the liquid were always below existing limits for foodstuffs. A newly developed method was used by which the CO₂ and O₂ permeabilities of the pouch/packaging could be estimated, using the kinetics of the gas composition in the pouch headspace. Permeability values, as estimated by the method, revealed that the CO₂ production and the O₂ consumption rates of the fermented milk were dependent on the CO₂ and O₂ headspace concentrations. An increase in permeability, determined by conventional methods, suggested that both the non‐polar and the polar polymers were plasticized by fermented milk. The plasticization was, however, modest and undetectable when the polyethylene tensile test data were analysed. Copyright © 2003 John Wiley & Sons, Ltd.