Photolytic degradation of decabromodiphenyl ethane (DBDPE)

The photolytic degradation of decabromodiphenyl ethane (DBDPE), an alternative flame retardant to decabromodiphenyl ether, was investigated in a variety of matrixes (n-hexane, tetrahydrofuran, methanol/water, humic acid/water, and silica gel) by irradiation under ultraviolet light and in n-hexane under natural light. Photolytic degradation of DBDPE occurs in all the matrixes investigated within the irradiation period (<320 min). The degradation experiments showed varied reaction rates, dependent on the matrixes, with increasing half-lives (t_1/2) in the order of tetrahydrofuran (t_1/2 = 6.0 min) > n-hexane (t_1/2 = 16.6 min) > humic acid/water (30 < t_1/2 < 60) > silica gel (t_1/2 = 75.9 min) > methanol/water (t_1/2 > 240 min). The reaction in tetrahydrofuran, n-hexane, and silica gel matrixes can be described by the pseudo first order kinetics. Nevertheless, the matrixes have little effect on the degradation product distributions of DBDPE. A numbers of debrominated intermediates were identified. The degradation involves the initial formation of nona-BDPEs and the subsequent decomposition of these congeners to lower brominated congeners (octa- and hepta-BDPEs) within the irradiation time. To our knowledge, the present work is the first attempt to investigate the photolytic degradation kinetics and the identification of intermediates, as well as the degradation mechanism, during the degradation of DBDPE. Further research is needed to understand the photolytic degradation pattern of DBDPE in the natural environment.     

土动力参数变异性对深软场地地表地震动参数的影响

采用等效线性化技术考虑土的动力非线性特性,利用一维波传法及SHAKE91软件计算水平成层场地的地震反应,研究了土的动剪模量比和阻尼比与剪应变幅值的关系曲线、土层剪切波速的变异性对深软场地地表峰值加速度及其反应谱的影响。结果表明:土的动剪模量比均值加1倍标准差与阻尼比均值减1倍标准差、动剪模量比均值减1倍标准差与阻尼比均值加1倍标准差的组合对地表峰值加速度的影响最为显著,但对地表加速度反应谱形状的影响不大;土层剪切波速15%的变异性对地表加速度反应谱形状有较大影响;土层剪切波速的变异性对地表加速度和反应谱的影响比动剪模量比和阻尼比变异性的影响更为显著。     

广州人群尿液有机磷阻燃剂的暴露与健康风险

针对广州480名普通群众,利用尿液作为检测基质,研究人体内有机磷酸酯阻燃剂(OPFRs)代谢物的浓度水平,暴露的潜在来源,阐明其健康风险,并与其他包括邻苯二甲酸酯在内的多种有机污染物的健康风险对比筛选出高风险污染物.结果表明,广州居民体内普遍检出OPFRs代谢物,其平均浓度为6.59ng/mL,尤其是二-β,β-氯乙基...     

有风条件下火灾自然排烟的临界失效风速分析

采用双区模拟思想对有风条件下室内火灾自然补气、自然排烟过程进行分析。引入"总风压系数"和"临界失效风速"的概念,并将其作为评价外界环境风对自然排烟过程影响程度的判定参数。总风压系数非负时,外界风的存在将提高自然排烟的效果;总风压系数为负时,外界风的存在将降低自然排烟的效果,甚至使自然排烟失效。通过对排烟口内外压差以及气体流动进行分析,发现临界失效风速正比于总风压系数绝对值的-1/2次幂,并给出了不同条件下自然排烟临界失效风速的计算方法。实际采用自然排烟方式进行火灾排烟时,应尽量避免出现总风压系数为负的情形,以防止自然排烟的失效。     

大型游乐设施运行状态测试系统及关键技术研究

系统分析游乐设施当前的测试水平,指出游乐设施运行状态测试是当前迫切需要解决的问题,并确定了加速度测试、速度测试、应力应变测试作为游乐设施运行状态测试系统的核心。结合游乐设施运行的特点,分别对以上3种核心测试技术从理论分析、设备选择、测试方法上进行了深入的研究。测试案例表明:基于以上技术测试的游乐设施运行状态测试系统是可行的,并为游乐设施检测提供了有力的技术支持。     

回转升降生物接触工艺的实验

提出了一个具有全新运转方式的新型ＲＢＣ系统－回转升降生物接触工艺。通过清水充氧实验考查了实验装置的充氧能力;通过正交试验,确定了最佳运行条件;在最佳运行条件下,研究了本工艺处理有机废水的性能和效果。     

轻亚粘土液化状态前后的剪切波波速对比观测初探

南京理工大学学生第十三宿舍桩机施工时 ,引起了轻亚粘土液化。通过对液化前后剪切波速的对比观测 ,对于 4种情况下的液化观测表明 ,随着液化程度的增加 ,剪切波速液化 (液化前 /液化后 )的比值也在增加 ,并增加到一定程度时变化值趋于稳定。     

利用宽频带速度记录的时域特征研究台风

利用福建省地震监测台网资料中有关台风前、台风期间及台风消亡的宽频带速度记录进行了分析研究,提出了用滑动时间窗内的均方根速度作为一种特征能量尺度,研究了台风形成、发展过程中振动能量的变化,统计了均方根速度与台风参数的对应关系.结果初步表明,地震监测资料可以应用于台风的监测与预报.     

由微振动记录用剥层法研究浅层S波速度结构

根据江苏华电句容发电一期2×1000 MW发电机组场地情况,布设了三角形嵌套和同心圆台阵进行微振动观测,采用空间自相关法计算频散曲线,并用剥层法反演得到该工程场地浅部的S波速度结构。反演结果与钻孔探测结果吻合较好,表明用微振动台阵记录反演浅部地壳S波速度结构在工程上是可行的。该方法具有不需要人工源,对避开噪声要求不苛刻、成本低且精度可满足工程要求等优点,故有良好的应用前景。     

Effect of initial temperature on explosion characteristics of 2, 3, 3, 3–Tetrafluoropropene

The flammability of refrigerants is a major cause of refrigerant explosion incidents. Studying the explosion characteristics of refrigerants at different initial temperatures can provide significant benefits for solving the safety problems of refrigerants under actual working conditions. This paper studied the effects of the initial temperature and refrigerant concentration on the explosion characteristics of refrigerant 2, 3, 3, 3-tetrafluoropropene (R1234yf) at 0.1 MPa. The curves of explosion characteristics with different initial temperature revealed the same variation trend ranged from 25 °C to 115 °C. Specifically, as the refrigerant concentration was raised, the peak overpressure, the maximum rate of pressure rise, and laminar burning velocity increased initially and decreased afterwards, along with maximum values at the refrigerant concentration of 7.6%. When the refrigerant concentration was 7.6%, the peak overpressure declined exponentially with the initial temperature rise, while the maximum rate of pressure rise increased linearly. The laminar burning velocity calculated from the spherical expansion method indicated that the flame propagation was gradually accelerated by the increase of initial temperature, which coincided with the change of the maximum rate of pressure rise. Meanwhile, experiments and CHEMKIN simulation results demonstrated the effects of elevated temperature from 20 °C to 50 °C on the explosion limits of R1234yf. The lower explosion limit reduced and the upper explosion limit increased with rising initial temperature. In general, R1234yf exhibited moderate combustion and lower explosion risk, compared with traditional refrigerants.