几种典型木质地板材料的热重比较实验研究

利用Mettler-Toledo同步热分析仪对市场上利用率比较高的四种木质地板在不同程序控制升温,和不同气氛流量条件下的热解特性进行了研究.同时,为了更好地对地板材料的热解特性进行深入了解,以实木地板为例,验证了升温速率对热分解过程的影响.通过研究发现,四种地板样品的热解过程分为三个阶段,但每个阶段的峰值大小和峰面积各不相同.同时,气氛流量中氧气的参与使热解机理发生改变,反应时间提前,温度升高,热解速度加快.通过对比受热期间的TG、DTG和DSC曲线,确定失重范围,以及各成分的残炭百分比,可以得出四种地板材料试验成分的火灾危险性,即,实木地板的火灾危险性低于其它三种地板材料.     

矿用可移动式救生舱隔热性能研究与试验

根据救生舱舱体结构,构建舱体隔热层填充材料隔热性能测定系统;利用该系统,分别测定了硅酸铝针刺毯、复合硅酸盐毡和膨胀蛭石粉自身的隔热性能;结合舱体结构特点,制作救生舱模拟结构层;在钢板内侧粘贴铝箔,构建双层防护隔热结构;测定结果表明复合硅酸盐毡最适合作为救生舱隔热层的填充材料;利用修正函数计算出复合硅酸盐毡的厚度为100mm,对该厚度材料的隔热性能进行测定,试验结果证明其可行。     

Rare earth elements in China: Policies and narratives of reinventing an industry

After top producer China decided in 2010 to tighten its export quotas for rare earth elements (REE), major customers feared being cut off from the valuable metals. The trade dispute intensified when the EU, the USA, and Japan brought the case before the WTO. The export controls raise questions about China’s intentions and strategies. This article argues that China’s export policy should not be viewed in isolation. The export controls are embedded in a greater transformation of the strategic REE industry. Beijing promotes a broad set of policies, including industry reorganization, resource conservation, and environmental protection. Next, the article examines three narratives that may be constitutive of the Chinese policy. Findings indicate that the geopolitical narrative, which sees natural resources as instruments of power politics, can be only partly attributed to China’s REE policies. The major driving motives are domestic concerns for resource conservation and environmental protection, as well as the development of competitive downstream industries.     

可用作原料的固体废物进口可行性评价指标体系探索研究

合理利用境外的可用作原料的固体废物,可以弥补我国国内资源的相对不足,但固体废物固有的废物属性仍不可避免地会带来一定的环境负面影响。建立可用作原料的固体废物进口可行性评价体系,对于在合理利用境外废物资源的同时,保护和改善环境具有重要意义。本文论述了我国建立可用作原料的固体废物进口可行性评价体系的理论和原则,并根据影响可用作原料的固体废物进口可行性评价的因素分析,构建了可用作原料的固体废物进口可行性评价指标体系框架。     

Occupational Exposure to Harmful Chemical Substances While Processing Phenol-Formaldehyde Resins

Air pollutants emitted while processing phenol-formaldehyde resins have been investigated. Gas chromatography-mass-selective detection was used to separate and identify chemical compounds. It was determined that workers were exposed to formaldehyde in all workplaces. Besides, phenol, acetaldehyde, acrylaldehyde, 2-furaldehyde, xylene, ethylbenzene, toluene, tetrachlorethene, ethyl acetate, butyl acetate were found during the production of frictional materials; and 2-furaldehyde, phenol, naphthalene, 2-furan-methanol, polycyclic aromatic hydrocarbons (PAHs) during the production of abrasive materials. Quantitative analyses were performed with gas chromatogra-phy and high performance liquid chromatography. Assessment of occupational exposure indicated that chemical compounds emitted during the investigated processes might be dangerous for human health, mainly because of suspected carcinogenic compounds: formaldehyde and PAHs.     

A Whole Body Postural Loading Simulation and Assessment Model for Workplace Analysis and Design

Abstract

This study reports on the development and validation of a new computer model for simulating human postures at work, and assessing the reaction forces and bending moments in 43 human articulation joints. The proposed model estimates the intradiscal pressure in the vertebral column in response to external loading forces encountered during human interactions with work objects or processes. The model was implemented in a self-contained interactive software package. The simulation results compare favorably with the reported experimental data, and provide reasonable confidence in the quality of the model. Its characteristics and its applications in evaluating physical task performance are also discussed     

岸边填土地基的强度与稳定性加固

岸边混杂填土结构松散,易受地表水流等外界因素的影响,常产生地面沉陷、崩塌和整体滑移等破坏现象.对于这类地基,可先设置散粒材料增强体使其初步硬化,再利用高置换率的复合地基抗滑坝体形成护坡和阻止整体滑移的作用,最后通过低能级强夯处理,将碎石桩复合地基的单一结构改变成具有碎石二合土硬壳层的三层结构,从而可较大程度地提高地基的强度和稳定性.通过对碎石桩夯击破坏性状的分析,提出了确定抗滑复合坝体宽度和夯击处理深度的设计计算方法.     

Poly(vinyl alcohol)/Compost Composites for Biofiltration of Swine Waste Volatiles

In this study, a Poly(vinyl alcohol)(PVA)/compost composite bead is prepared and is indicated suitable as a filter material for biofiltration. The optimal preparation process is with the compost size of 16–35 mesh, the ratio of water to compost of 40 g/15 g compost, and the immersion time in the phosphate solution of 60 min. The composite bead prepared by this process is a porous spherical particle with a diameter between 2.4 and 6.0 mm and a density of 0.96 g/cm³. It contains 9.43 mg P/g dry solid and 12.1 mg N/g dry solid. The equilibrium moisture content of the composite bead bed from adsorption and holding experiments is 50.5 and 54.6% on a wet basis respectively, which is about 1.74 times higher than that of swine manure compost bed. It corresponds to the optimal filter material required and is sufficient to sustain biological activity as the composite bead adsorbs equilibrium moisture. The bulk compressive strength of the composite bead bed is about 1.15 times larger than that of swine manure compost bed to ensure even distribution of air flow and reduce the head loss as the air flow stream passed through. The pH value of the filter bed could maintain in the 6.9–7.2 range during the operation period due to the composite bead has the phosphate buffer capacity. The percentage of ethyl acetate removal could remain at over 99% for 40 days operation while the composite beads adsorbed inorganic nitrate nutrients. The pressure drop of two kind composite beads and pig manure compost filter beds are 0 and 2 mm H₂O, respectively, after operating for 40 days.     

Effect of Nanoscale SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> as the Fillers on the Mechanical Properties and Aging Behavior of Linear Low-Density Polyethylene/Low-Density Polyethylene Blends

Linear low-density polyethylene (LLDPE) was blended with low-density polyethylene (LDPE) at a fixed ratio (80 wt LLDPE and 20 wt %LDPE) and filled with nanoparticles of SiO₂ and TiO₂ at a ratio up to wt 5%, so as to develop the polymeric composites suitable to preparing the agricultural micro-irrigation pipes having good environmental adaptability. These compounds were blended using calcium stearate, polyethylene wax, and titanate coupling agent as the auxiliary dispersants, and ethylene-vinyl acetate copolymer (EVA) as the toughness improver. The LLDPE/LDPE composites filled with the nanoparticles were extruded and injected to prepare the composites specimens for the performance evaluations and micro-irrigation pipe field test. The mechanical properties, thermostability, and processibility of the injected composites were investigated. The effect of heating in an oven and irradiating by ultraviolet on the mechanical properties of the composites was explored. The environmental adaptability of the micro-irrigation pipes made of the filled LLDPE/LDPE composites was evaluated making use of long-term outdoor field test in northwest China where the arid and harsh natural conditions are of great concerns. It was found that the LLDPE/LDPE blend with the LLDPE mass fraction fixed as 80% showed balanced mechanical and thermal properties and flexibility, and was suitable to be used as the basic resin matrix. The incorporation of nano-TiO₂ contributed to effectively improving the resistance to heating and ultraviolet irradiation of the composites. The composite made from 91% basic resin matrix, 6% EVA, and 3% mixed nano-SiO₂ and TiO₂, showed balanced comprehensive properties. The micro-irrigation pipes made of this filled LLDPE/LDPE composite had good environmental adaptability and service behavior in a three-year field test and were suitable to be used in arid area.     

Kenaf/Ramie Composite for Automotive Headliner

An increasing industrial interest is applications of kenaf and ramie fiber nonwovens for making automotive interior trim parts because of their excellent strength and renewability. This paper presents a study on the manufacture and evaluation of the kenaf/ramie nonwoven composite for this automotive end use. Carding, needle-punching, and wet bonding were used to fabricate the composite. End-use performance of the composite, in terms of tensile strength, thermal conductivity, dynamic mechanical property, and bonding structure, was tested using a series of instruments in accordance with the ASTM methods. Bonding performance of the polyvinyl alcohol binder and acrylic copolymer binder was also compared. Research results revealed that the acrylic-copolymer bonded composite was significantly anisotropic in both tensile and bending deformation and the polyvinyl-alcohol bonded composite was significantly anisotropic only in bending deformation. For the acrylic-copolymer bonded composite, increase of padding times helped enhance tensile properties. The acrylic-copolymer bonded composite also exhibited a better performance in dynamic thermal mechanical deformation but indicated insignificant difference of thermal conductivity compared to the polyvinyl-alcohol bonded composite.