Rheological behavior and mechanical properties of wood flour/high density polyethylene blends: Effects of esterification of wood with citric acid

This study explored the modifying effects of wood flour (WF) with citric acid (CA) on the rheological and mechanical properties of WF/high density polypropylene (HDPE) composites. WF was treated with CA, which acts a cross‐linking agent and melt‐blended with HDPE with a twin‐screw extruder. Injection molding was used to make tensile and impact tests samples. The rheological properties of the blends were characterized using a Haake microcompounder, torque‐, capillary‐, and rotational‐rheometer, respectively. Results show that the thermal stability of WF decreased after treatment. Compared with those of untreated composites, the tensile strength, elongation‐at‐break, and impact strength of the composites treated with 5% CA were reduced by 6%, 14%, and 16%, respectively. This reduction was attributed to embrittlement of WF, which may negatively influence the mechanical properties of the resulting composites. Scanning electron microscopy revealed better dispersion of CA‐treated WF in the composites than the untreated WF. For composites treated with 5% CA, the melt torque, viscosity, moduli, and shear stress decreased significantly, indicating an improvement in processibility. This improvement is attributed to uniform dispersion of the modified WF, as well as to better interfacial adhesion between WF and the matrix. Results suggest that treating WF with CA shows promise for improving the processibility of highly filled thermoplastic composites via extrusion/injection molding processing. POLYM. COMPOS., 37:553–560, 2016. © 2014 Society of Plastics Engineers     

Correction to: Experimental study on strength properties,fracture patterns,and permeability behaviors of sandstone containing two filled fissures under triaxial compression

Bulletin of Engineering Geology and the Environment - A correction to this paper has been published: https://doi.org/10.1007/s10064-021-02296-1     

建筑雪工程学研究方法综述

建筑雪工程学系指综合物理学、地球环境学、灾害学等交叉学科,从专业角度对建筑(群)及其周围环境冬季受降雪影响进行预测及研究,以抵御由雪灾诱发建筑物倒塌事故的一门学科。从该学科中主要的三种研究方法,即实地观测、试验研究以及数值模拟为切入点对三者的发展进行梳理与深入剖析。对于实地观测,总结了国外规范中考虑风致雪漂移和热力融雪等影响因素的研究历程与相应理论模型的建立,并指出今后我国实测工作应以对足尺建筑屋面积雪特性及其演变机理为重心;通过对近年来试验研究工作的概括总结,梳理了现今试验研究的四种手段,并明确了对应试验手段相似准则的建立与参数的选取,同时指出今后在我国建立专业风雪试验的必要性;通过对CFD数值模拟方法研究进展的回顾,总结了目前数值模拟已取得的成果与存在的不足,为考虑因素全面的新数值模拟方法的发展指明方向。     

一种测量天空亮度的新方法

本文介绍了一种测量天空亮度分布的新方法。这种方法利用视场角为180°的鱼眼镜头照相机和计算机数字图像处理系统,实现了天空亮度分布的瞬时测取和胶片密度的高效率处理。文中论述了胶片灰度与天空亮度的标定转换实验方法。引用了误差理论中的数据处理方法确定出二者间的函数关系。通过对昆明和重庆地区晴和阴天空下大量实测结果的误差处论和分析,得到了其相关系数和标准偏差的频数分布图,由此证明了这种方法的可靠性。     

湿润气候区带膨润土垫ET封顶的性能分析

ET(evapotranspiration,腾发)封顶目前主要用于少雨地区的填埋场,本文考虑1500mm的年降雨量,分析一种加膨润土垫(GCL)的新型土工复合ET封顶在湿润地区的工作性能。建立渗流-腾发耦合模型,计算此新型ET封顶和典型单层土ET封顶的地表径流量、地表蒸发量、植被蒸腾量、最终透水量,对比分析两种ET封顶内的水分运移规律及其工作性能。结果表明:新型ET封顶产生的地表径流总量多于典型单层土ET封顶;新型ET封顶通过膨润土垫的低渗透性使上部土层能够储存更多的水分用于后期腾发,其腾发量大于典型单层土ET封顶,尤其是在降雨高峰期更为明显;在该地区,总厚度1.2m的典型单层土ET封顶并不能有效阻止水分渗透到填埋场中,而新型ET封顶能够满足设计要求。     

离子质谱计及其应用

文章介绍了离子质谱计的原理及应用范围。由快原子枪装备的一台低价小型双聚焦质谱计用于离子的同位素丰度分析,微克级氮的同位素测量精度为1.5％。列举了一些应用实例,如用~(15)N、~(10)B和~(42)Ca、~(44)Ca作示踪剂研究生物学过程。     

China Drills Its First “Earth Hole“

On August 4, 2001, drilling of Kezuan-1 Well, the first continental scientific exploration well in China, was officially kicked off in Donghai County,Jiangsu Province. About 1000 people including high-ranking governmental officials and famous experts attended the drilling ceremony. Vice Chairman of the Chinese People‘s Political Consultative Conference Wan Guoquan pressed the button to start drilling of the exploration well.……     

PTT纤维染色工艺研究

采用Artelon Red系列染料对聚对苯二甲酸丙二醇酯(PTT)纤维进行染色,研究了其染色工艺,并对PTT纤维染色前后的力学性能进行了比较。结果表明:在相同温度和pH值条件下,PTT纤维对ArtelonRed AQE染料的上染率较Artelon Red W-3B染料的高;Artelon Red AQE染料,Artelon Red W-3B染料适宜的染浴温度分别为100,110℃,pH值均为7;当染色温度达到80℃后,升温速率缓和,可提高匀染效果;染色过程对PTT纤维强力的损伤影响不大。     

Image/video spatial scalability in compressed domain

Image/video compression is widely used in various applications with the advent of the Joint Photographic Expert Group (JPEG), Motion Picture Expert Group (MPEG), and H.261 standards. Hence, most visual data are stored in the compressed format. Spatial scalable encoding of visual data has several applications, including browsing visual databases, querying multimedia databases, interactive multimedia communications, etc. We propose two novel techniques, namely, format compatible (FC) discrete cosine transform (DCT) and format modified (FM) DCT to implement image/video spatial scalability directly in the DCT compressed domain. The FC-DCT technique can be used to manipulate the standard bit streams, such as JPEG, MPEG, etc., while the FM-DCT technique can be employed in a variety of applications which require fast processing. In contrast to the traditional spatial-domain techniques, the compressed-domain techniques remove the unnecessary decompression and recompression procedures, thus, they have the advantages of reduced computational complexity and storage requirements. Simulation results demonstrate that the proposed DCT-domain techniques can achieve a comparable performance at a much lower computational complexity compared to the spatial-domain techniques