Early Responses to Acute Ozone Exposure in Two Fagus Sylvatica Clones Differing in Xeromorphic Adaptations: Photosynthetic and Stomatal Processes, Membrane and Epicuticular Characteristics

Two Fagus sylvatica L. clones were used to investigate the early responses to acute O₃ exposure (150 nL L⁻¹, i.e., 1.35× ambient hourly peak in rural Italy) and whether xeromorphic adaptations affect gas exchange, membrane, and epicuticular responses. One clone originated in a wet and temperate climate in Central Italy (Tuscany); the other clone originated in a warmer and drier climate in the southern-most part of the F. sylvatica distribution (Sicily). Because of higher base gas exchange rates, the most negative effects of O₃ exposure (gas exchange impairment, uncoupling between net photosynthesis and stomatal conductance, increased membrane lipid peroxidation) were found in the southern clone. Xeromorphic adaptations (higher epicuticular waxes and stomatal density, lower leaf wettability and size) were found in this clone. Our results suggest that xeromorphism may increase O₃ sensitivity in species not adapted to face water stress, like the mesophilic F. sylvatica, when experiments are carried out with full irrigation. We present evidence describing the relationship between gas exchange and number and status of stomata. Stomatal density and the structural damage to stomata resulting from O₃ exposure did not affect gas exchange: In fact, non-stomatal limitations to photosynthesis prevailed over stomatal limitations.     

桁架转换层设置在不同高度处结构的受力性能分析

以一个实际工程案例为背景,采用SAP2000有限元软件,建立原结构的三维有限元分析模型,通过将桁架转换层设置在第3、6、9层不同的高度,对结构施加各种荷载工况,对比建筑结构层刚度比、最大层问位移、最大层间位移角的变化。结果表明,桁架转换结构比其他形式的转换结构更为合理。转换层设置在不同高度时结构层位移曲线、层间位移角曲线变化趋势基本一致;但随着转换层高度的增加,刚度比增大,层间位移角突变增大,结构整体性越差;且转换层位置较高时,转换层附近的层间位移急剧变化,这会引起结构内力的突变,易使转换层附近几层成为薄弱点首先破坏。此外,桁架转换层具有很大的刚度,不仅能很好的满足建筑上对空间及穿越管道设备的要求,还可以有效降低水平荷载作用下结构顶点位移。     

双线盾构隧道斜交下穿既有机场高速公路的地表沉降预测模型研究*

为指导隧道盾构下穿既有建构筑物施工的变形控制,考虑隧道收敛模式和复合地层主要影响角的影响,以双线圆形盾构隧道斜交下穿既有机场高速公路为例,构建圆形隧道地层主要影响角计算方法,改进传统Peck公式,分析盾构斜交角、盾构坡角和隆起偏角的共同影响,引入地层损失率几何修正系数,并利用叠加原理建立双线盾构隧道斜交下穿既有机场高速公路的地表沉降预测模型,依托实际工程对预测模型的工程适用性进行验证。研究结果表明:本文预测模型的整体精度相比Suwansawat等预测模型提升44.15％,可预测施工影响范围内任意点的地表沉降值,相比现有模型更适用于解决双线盾构隧道斜交下穿施工的地表沉降预测问题,可为类似工程中的地表沉降变形预测及控制提供指导。     

沸石负载羟基氧化铁对铬（VI）吸附的固体浓度效应研究

本文利用沸石负载羟基氧化铁作吸附剂对六价铬进行吸附和解吸附实验。探讨了沸石负载羟基氧化铁对六价铬的吸附机制和固体浓度效应。实验结果表明：当吸附剂的用量从0.05g增加到0.2g时,在实验条件下,六价铬的吸附量从27999.493μg/g降低到8930.610μg/g,吸附剂对Cr6＋的吸附存在明显的固体浓度（Cs）效应。吸附滞后角随着Cs的增加而减小,吸附反应的可逆性增大。将实验数据分别用Languir和Freundlich吸附模型进行拟合,发现Freundlich吸附模型对实验数据拟合效果较好,表明该吸附反应以单分子层吸附为主。     

Visual Costs of the Inhomogeneity of Luminance and Contrast by Viewing LCD-TFT Screens Off-Axis

In this study the anisotropic characteristics of TFT-LCD (Thin-Film-Transistor- Liquid Crystal Display) screens were examined. Anisotropy occurs as the distribution of luminance and contrast changes over the screen surface due to different viewing angles. On the basis of detailed photometric measurements the detection performance in a visual reaction task was measured in different viewing conditions. Viewing angle (0°, frontal view; 30°, off-axis; 50°, off-axis) as well as ambient lighting (a dark or illuminated room) were varied. Reaction times and accuracy of detection performance were recorded. Results showed TFT’s anisotropy to be a crucial factor deteriorating performance. With an increasing viewing angle performance decreased. It is concluded that TFT’s anisotropy is a limiting factor for overall suitability and usefulness of this new display technology.     

Postural and Muscular Responses While Viewing Different Heights of Screen

This study aimed to examine the effects of visual display terminal (VDT) viewing angle on human postural angle and muscular activity. The participants’ neck, thoracic bending, and trunk inclination angles; and the activity of sternocleidomastoid, trapezius, splenius capitis, and erector spinae at 5 viewing angles (+40°, +20°,0°, –20°, and –40°) of a VDT screen were collected for 1 min. This study showed that neck and thoracic bending angles increased with viewing angle, while viewing angle did not significantly affect trunk inclination angle. In addition, the activity of trapezius and erector spinae increased when viewing a higher or lower VDT screen height compared with viewing a horizontal VDT screen height; however, the activity of splenius capitis decreased with viewing angle.     

Kickback risk of portable chainsaws while cutting wood of different properties: laboratory tests and deductions

Portable chainsaws are associated with substantial risk and can cause serious injury to operators, especially during kickback. This paper presents new results from research and analyses conducted regarding the impact between the different properties of wood on this occurrence. In an open area, such differences may include: wood species, humidity, temperature and the facing angle of the wood fibres in relation to the kerf and shape of the wood surface that comes in contact with the tip of the guide bar. This paper investigates chainsaw kickback including the research results on kickback and wood-cutting energy, saw chain speed and the efficiency of the chainsaw engine. It also presents conclusions drawn from the tests that can be useful for chainsaw users, showing the dependencies between the different properties of wood and the risk of injury.     

非等压下考虑渗流和剪胀的圆巷围岩弹塑性统一解

对于富水地层中深埋圆形巷道,为研究多种因素影响下巷道围岩塑性区范围和洞周位移的变化规律,对巷道围岩进行了弹塑性理论分析。对围岩应力场和渗流场进行耦合分析,基于统一强度理论和非关联流动法则,推导出多种因素影响下深埋圆形巷道围岩应力、位移和塑性区半径的解析计算式。结合工程实例进行计算分析,结果表明:中间主应力参数、围岩侧压系数、初始孔隙水压和剪胀角对围岩塑性区径向位移和塑性区范围均有显著影响,但影响规律各不相同;考虑中间主应力作用时,其他各因素的影响效应减弱。综合考虑以上各因素对围岩稳定性的影响,计算结果更加接近工程实际情况。     

基于SAPSO-BP网络模型的海洋平台落物碰撞损伤分析

为了确保海洋平台作业过程中落物坠落对甲板撞击后的结构安全,对坠落立管撞击海洋平台甲板的过程进行了非线性仿真分析。运用ANSYS/LS-DYNA建立有限元模型,对坠落立管不同撞击角度撞击海洋平台甲板进行模拟计算,得到甲板在不同工况下的损伤情况。运用1种自适应性变异的粒子群优化算法SAPSO与BP神经网络结合［1］,对海洋平台进行落物碰撞损伤分析。研究结果表明:落物与垂直方向偏离5°～10°为坠落时最危险的工况。SAPSO-BP提高了BP神经网络的拟合能力,减小了拟合误差,提高了拟合精度,验证了SAPSO-BP网络模型的实用性和可靠性。综合考虑制定适用于海洋平台落物安全的工作程序和平台及设备的防护措施,为海洋平台作业中落物风险评估和海洋平台作业安全保障提供参考。     

生物型表面活性剂在煤表面润湿吸附规律研究

为了探讨生物型表面活性剂溶液在煤表面的润湿吸附规律,选定茶皂素、蔗糖酯、无患子和脂肽这4种结构性能不同的生物型表面活性剂作为研究对象,通过对4种溶液在煤表面接触角和表面张力进行测定,研究这4种生物型表面活性剂在煤表面的铺展系数、黏附功、黏附张力等润湿吸附参数。研究结果表明:脂肽的表面张力、接触角和黏附功均低于其他3种溶液,而其铺展系数高于其他3种溶液,说明脂肽在煤表面的润湿吸附性要强于茶皂素、蔗糖酯和无患子,但是黏附性则低于茶皂素、蔗糖酯和无患子。脂肽对煤体的润湿吸附性能优于另外3种生物型表面活性剂。