Kinetic and mechanism of the thermal degradation of a plywood by using thermogravimetry and Fourier-transformed infrared spectroscopy analysis in nitrogen and air atmosphere

The thermal degradation of plywood was investigated using thermogravimetric analysis (TGA) device. The TGA experiments were conducted between ambient temperature and 1000 °C for seven different heating rates: 5, 10, 15, 20, 30, 40 and 50 °C min⁻¹. The experiments were realized under inert and air atmospheres in order to characterize the plywood thermal decomposition occurring during the pyrolysis and oxidative processes. Throughout all the tests, the gaseous emissions were continuously monitored using a Fourier transformed infra-red spectrometer (FTIR). The progress in the mass, the mass-loss rate (MLR) and gas emissions data allow to propose a mechanism of the thermal decomposition of plywood with six different stages. The reactions (stages) of this mechanism is of a rate represented by a modified Arrhenius law containing four unknown kinetic parameters (A, E_a, n and ν) for each reaction. These 24 unknown parameters are determined by using the inverse optimization method of the genetic algorithms. The model developed is validated regardless of the heating rate and atmosphere (inert or air) chosen. A very good agreement is obtained between the experimental and the numerical mass loss rate evolutions.     

Investigation of emissions from heated essential‐oil‐rich fuels at 200 °C

Essential oil of fuels is closely linked with the behavior of forest fires, especially high intensity fires and eruptive fires. It is assumed that the potential reason is the large quantities of flammable gases released from essential oil‐rich fuels before pyrolysis in fire environment. However, few studies have been carried out on the hypothesis. The purpose of the present study is to investigate the emissions from essential oil‐rich fuels. The fuels were collected from three coniferous species. In the experiment, needles and twigs were heated in a vacuum oven at 200 °C, and the emissions within 15 min had been sampled using Tenax tubes. Gas chromatography–mass spectrometry served as an analytical instrument. The results showed that the emissions contained high proportion of monoterpenes, such as α‐pinene, camphene, β‐pinene, 3‐carene, and d ‐limonene. The monoterpene emissions from heated needles and twigs of Pinus pumila, Larix gmelinii, and Pinus sylvestris were 61.221, 49.606, and 37.853 µg g^?1 dry weight (needles), and 211.727, 139.957, and 121.505 µg g^?1 dry weight (twigs), respectively. Statistical analyses showed the significant differences not only among species but also between needles and twigs. Copyright © 2012 John Wiley & Sons, Ltd.     

桉木制单板层积材的抗压强度预测模型

为了研究桉木制单板层积材的抗压强度预测模型,进行了342个试件的抗压试验,分析了试件纹理角度、胶层角度对其抗压强度、弹性模量和破坏模式的影响.采用指数模型拟合试件抗压强度,并通过卡方（χ2）检验来验证该指数模型和Hankinson公式、Norris公式以及GB 50005—2003规范公式对抗压强度的拟合度.结果表明：随着试件纹理角度、胶层角度的增加,其抗压强度和弹性模量均显著下降;抗压试件的破坏模式有3种,为纤维褶皱破坏、剪切破坏和压溃破坏;指数模型、Hankinson公式和Norris公式均能较好地拟合抗压强度,而GB 50005—2003规范公式拟合的抗压强度值偏高.     

竹层积材在高温中和高温后的抗弯性能研究

为了研究竹层积材在高温中和高温后的抗弯性能,在20～225℃下对104个试样进行了三点静态抗弯测试.结果表明:随着温度的升高,高温中和高温后竹层积材的抗弯强度、弹性模量和延性系数均明显减小;相对于高温中的试样,高温后的试样抗弯强度和弹性模量均明显较高,而其延性系数则较低.根据回归分析,建立了竹层积材在高温中和高温后的相对抗弯强度与温度的关系模型,该模型预测结果与实测值吻合良好.     

气动不平衡式发射装置气水回收过程仿真与分析

当潜艇使用气动不平衡式发射装置发射鱼雷时,无泡系统的气水回收过程对潜艇的隐蔽性与艇体均衡均有直接影响。为了对无泡系统气水回收过程进行研究,建立了无泡系统的定时调节器、无泡气瓶、泄放阀等各组成部件的数学模型,并结合已有的气动不平衡发射系统的数学模型,进行了无泡系统气水回收过程的仿真。仿真结果与实际回收海水量的结果对比表明,所建立的模型基本正确,可用于气动不平衡式发射装置无泡系统的分析与论证。     

Experimental definition and its significance on the minimum safe distance of blown sand between the proposed Qinghai-Tibet Expressway and the existing Qinghai-Tibet Railway

Science China Technological Sciences - The Qinghai-Tibet Expressway is a major strategic project planned by China that will be built along the Qinghai-Tibet Engineering Corridor. At present,...     

装备战场抢修能力预测混合算法

分析了信息化条件下战场抢修的主要影响因素,研究了各环节的特点和规律,提出了运用备件保障能力算法、排队网络、层次分析法、模糊综合评判等相结合的方法,分别计算备件保障、战损修理能力、机动能力、人员素质等对战场抢修的影响程度,用指数法建立了战场抢修能力预测模型,给出了计算实例,验证了算法的实用性和合理性,为战场抢修指挥决策和模拟仿真系统的优化设计提供理论依据。     

落叶松锯材抗弯强度尺寸效应

以兴安落叶松锯材为研究对象,研究了不同目测等级下锯材尺寸与其抗弯强度之间的关系.试验选取1961根6.5、9.0和14.0 cm3种宽度尺寸的目测等级锯材,每个宽度尺寸分为高、低目测等级组,按照每组试件宽度18倍的测试跨度测试锯材的抗弯强度.利用斜率法和形状参数法确定高、低目测等级组抗弯强度5％分位值的长度与宽度的组合尺寸效应.研究结果表明,斜率法获得高、低目测等级组试件抗弯强度5％分位值的组合尺寸效应分别为0.19和0.23.     

落叶松结构用规格材分级研究

选取截面尺寸为40mm×90mm的兴安落叶松规格材为研究对象,参照GB 50005—2003对规格材进行目测分级及足尺弯曲测试,依据足尺弯曲性质设定落叶松规格材机械分级的等级边界条件,并对规格材进行机械分级.结果表明：目测分级中高等级规格材（Ⅰc~Ⅲc）的比例相对较高,落叶松规格材的主要降等缺陷为节子、轮裂/干裂和腐朽;以弹性模量为界限指标,可以将落叶松规格材划分为M14,M30和M40这3个强度等级;落叶松规格材等级强度从大到小的排列顺序为：M40,Ⅰc,M30,Ⅲc,Ⅱc,M14;机械分级后的规格材其强度性质更加稳定,规格材的价值得到明显提高.综合比较,中国商品林落叶松规格材更适合机械分级.