辐射热流下有限厚度PMMA着火特性研究

探究透明PMMA（聚甲基丙烯酸甲酯）厚度和4种不同恒定热流对材料表面温度、质量损失率、着火时间及着火温度的影响。利用反演模型并结合部分实验数据得到PMMA的热物性参数,将其他工况模拟结果与实验测量值及理论分析值相互对比,验证了数值模型和理论分析的准确性和可靠性。结果表明,PMMA着火时间的下降趋势随热流的增大而逐渐变缓。PMMA厚度小于3 mm时,表面温度和质量损失率随厚度增大而减小。PMMA厚度大于3 mm时,着火温度的平均值为（628±20） K,其着火特性几乎不随厚度的变化而变化,故着火温度可作为PMMA着火判据。     

Study on the thermal behavior of aluminum reticulated shell structures considering solar radiation

The aluminum dome has been more and more widely adopted in industrial and civil buildings, and the span is up to 140 m. Because the thermal expansion coefficient of aluminum with a value of 2.3×10⁻⁵ is almost two times than that of steel, the temperature change will induce significant thermal deformation and thermal stress, especially for the large span aluminum domes under solar radiation. In this paper, the solar radiation absorption coefficient was firstly measured using spectrophotometer, and then a numerical simulation method was presented and verified by test dada. To take a aluminum dome project with a span of 125 m for an example, the non-uniform temperature distribution and change under solar radiation were analyzed using the presented method, and following conclusions were obtained: (1) The thermal load is the key load for the aluminum domes, and the solar radiation has a significant effect on the thermal behavior of the aluminum domes. Therefore, the non-uniform thermal load considering solar radiation has to be considered in the future design. (2) There is a remarkable variation of member stress, and it is necessary to study the fatigue behavior of the aluminum domes under solar radiation.     

混凝土表面太阳辐射吸收率试验研究

混凝土对太阳辐射的吸收率直接影响混凝土结构内温度场分布以及温度效应。由于混凝土材料的物理力学性能离散性大,施工条件多样,使用环境千差万别,目前尚无对太阳辐射吸收率研究的系统而成熟的成果。结合太阳能利用原理和热工规范等,对不同颜色、不同粗糙度混凝土表面,进行太阳辐射吸收率的探索性试验,初步提出在考虑温度作用的混凝土结构设计中,其表面太阳辐射吸收率的建议取值。     

水泥基膨胀珍珠岩吸声材料性能研究

以普通硅酸盐水泥、轻质多孔膨胀珍珠岩为主要原料,利用物理和化学方式发泡,制备了水泥基膨胀珍珠岩多孔吸声材料.研究了制备工艺、膨胀珍珠岩掺量、发泡剂种类和掺量、试样厚度、水灰比、养护温度及压力等对材料吸声性能的影响.     

混凝土表面太阳辐射吸收系数测试研究

混凝土表面太阳辐射吸收系数是求解混凝土结构温度问题的重要参数之一.本文从热平衡的基本方程出发,提出了混凝土表面太阳辐射吸收系数的测试方法.并通过对不同表面性状混凝土试件的测试,研究了混凝土模板种类、混凝土表面色泽等因素对太阳辐射吸收系数的影响.文中给出了混凝土表面太阳辐射吸收系数的建议值,并讨论了减小结构日照温度效应的相关措施.     

外表面吸收系数对农宅室内热环境影响的模拟研究

目前,农宅的热环境调节主要以被动方式为主,太阳辐射直接影响室内热环境。太阳辐射对室内热环境影响程度与外围护结构的外表面吸收系数有关。以鄱阳湖生态经济区为基础,选取了一幢农宅,采用DeST软件,模拟分析了太阳辐射吸收系数值与室内气温的关系。研究结果可为今后建筑设计提供一定的参考。     

Characterization of thermal properties and analysis of combustion behavior of PMMA in a cone calorimeter

This paper deals with the thermal degradation of a black poly(methyl)methacrylate (PMMA) in a cone calorimeter (CC) in air with a piloted ignition. The influence of several heat fluxes (11 kW m⁻² and 12 kW m⁻², and ten values from 15 to 60 kW m⁻² in steps of 5 kW m⁻²) on PMMA sample degradation and the decomposition chemistry has been studied. Thus, thermal properties have been deduced and calculated from ignition time and mass loss rate (MLR) curves. During our experiments, among compounds quantified simultaneously by a Fourier transformed infrared (FTIR) or gas analyzer, five main species (CO₂, CO, H₂O, NO and O₂) have been encountered, regardless of the external heat flux considered. The main product concentrations allow calculation of the corresponding emission yields. Thus, mass balances of C and H atoms contained in these exhaust gases were able to be compared with those included in the initial PMMA sample. Using the standard oxygen consumption method, heat release rate (HRR), total heat release (THR) and effective heat of combustion (EHC) have been calculated for each irradiance level. Therefore, these different results (thermal properties, emission yields, HRR, THR and EHC) are in quite good accordance (same order of magnitude) with those found in previous studies.     

烧成制度对电镀渣泥防辐射功能集料性能的影响

研究了烧成制度对利用富含Cr,Zn等重金属电镀渣泥制备的防辐射功能集料矿物组成和性能的影响规律,探讨了电镀渣泥防辐射功能集料的烧成机理.采用预烧-焙烧的烧成方式成功制备出具有γ射线屏蔽性能的防辐射功能集料,其对0.662 MeV的γ射线线性衰弱系数≥0.220cm-1,单颗粒抗压强度≥5.00 MPa,表观密度为2.60g/cm3左右,重金属浸出浓度符合环境安全要求.     

磁浮轨道钢箱梁日照温度场及变形研究

磁浮轨道梁日照作用下的温度变形是轨道梁设计需考虑的重要因素,文章根据传热学与有限元理论,结合上海夏季气象参数与日照辐射半经验公式,利用ANSYS建立上海磁浮线轨道钢箱梁日照温度场三维瞬态模型,经实测构件验证,计算值与实测值吻合良好。分析磁浮轨道梁的最大竖向与横向温差发生时刻的温度梯度分布,并以指数函数为基础拟合得到对应温度梯度曲线,竖向温差拟合值略低于德国磁浮规范值,横向温差拟合值高于德国磁浮规范值。基于日照温度场分析结果,计算不同支承形式钢轨道梁的温度变形,得到磁浮轨道钢箱梁在双跨连续形式下能够较好抵抗温度变形的结论。提出磁浮轨道钢箱梁外露部分涂料的选取建议,以减小日照辐射吸收能量,从而降低截面温差及温度梯度变形。     

石墨炉原子吸收法测定水中锶

本文探讨了石墨炉原子吸收法测定水中锶的最佳仪器测量条件、测定下限，并对多种水样进行了加标回收实验和水中共存元素的干扰实验，结果表明该方法灵敏，准确，稳定性良好。     

On the influence of boundary conditions and thermal radiation on predictive accuracy in numerical simulations of indoor ventilation

Room ventilation is a well studied field, whereby ventilation is either mechanically driven or reliant on buoyancy forces driven by thermal gradients. In office spaces, where occupant comfort is important, the latter (termed displacement ventilation) is sometimes used. In many existing studies, computational methods used to simulate ventilation cases use a number of general engineering assumptions. These can include neglecting heat transfer through the walls, assuming that internal radiative transfer is negligible, or by modelling radiative sources as additional heat loads. In this study, these assumptions are systematically examined by selectively modelling certain phenomena in the simulations. In this way, the accuracy and suitability of such assumptions can be examined with reference to previous experimental work. The variation of radiative absorptivity upon the vertical temperature profile has also been investigated in order to determine the contribution of thermal re-distribution by surface radiation alone, and in addition to radiative participation from the air.     

干热干冷地区围护结构热工设计对内表面温度及室内热舒适的影响

为了分析干热干冷地区围护结构热工性能对室内热环境的影响,采用物理环境实测结合动态模拟方法对比分析了2组墙体的保温、蓄热性能对内表面温度的影响,并结合太阳辐射季节变化探究了太阳辐射吸收比对室内热舒适的影响.研究表明:实测结果与模拟结果吻合较好,对于干热干冷地区,提高围护结构蓄热性能能够降低夏季内表面温度,对冬季内表面温度...     

Photodegradation of the antibiotics nitroimidazoles in aqueous solution by ultraviolet radiation

The objective of this study was to analyze the efficacy of ultraviolet (UV) radiation in the direct photodegradation of nitroimidazoles. For this purpose, i) a kinetic study was performed, determining the quantum yield of the process; and ii) the influence of the different operational variables was analyzed (initial concentration of antibiotic, pH, presence of natural organic matter compounds, and chemical composition of water), and the time course of total organic carbon (TOC) concentration and toxicity during nitroimidazole photodegradation was studied. The very low quantum yields obtained for the four nitroimidazoles are responsible for the low efficacy of the quantum process during direct photon absorption in nitroimidazole phototransformation. The R₂₅₄ values obtained show that the dose habitually used for water disinfection is not sufficient to remove this type of pharmaceutical; therefore, higher doses of UV irradiation or longer exposure times are required for their removal. The time course of TOC and toxicity during direct photodegradation (in both ultrapure and real water) shows that oxidation by-products are not oxidized to CO₂ to the desired extent, generating oxidation by-products that are more toxic than the initial product. The concentration of nitroimidazoles has a major effect on their photodegradation rate. The study of the influence of pH on the values of parameters ? (molar absorption coefficient) and k′_E (photodegradation rate constant) showed no general trend in the behavior of nitroimidazoles as a function of the solution pH. The components of natural organic matter, gallic acid (GAL), tannic acid (TAN) and humic acid (HUM), may act as promoters and/or inhibitors of OH· radicals via photoproduction of H₂O₂. The effect of GAL on the metronidazole (MNZ) degradation rate markedly differed from that of TAN or HUM, with a higher rate at low GAL concentrations. Differences in MNZ degradation rate among waters with different chemical composition are not very marked, although the rate is slightly lower in wastewaters, mainly due to the UV radiation filter effect of this type of water.     

油氢合建站典型泄漏火灾热辐射后果模拟分析

根据油氢合建站实际运行状态识别典型火灾事故场景,建立高压氢气泄漏喷射火及油池火灾事故热辐射模型,模拟分析油氢合建站地面涉氢设施及加油设备典型泄漏火灾危害特性.结果表明:储氢区涉氢压力45 MPa、发生典型10 mm泄漏喷射火时危害范围较大,对设备及人员危害距离分别为21 m和36 m;加油枪断裂发生40～60 L/mi...     

钨钽基体—石墨炉原子吸收法测定水中铝

以钨与钽基体替代石墨管涂钽,采用直接石墨炉原子吸收法测定水中铝,该方法克服了涂钽石墨管制备繁琐和使用次数少的缺陷,且测定灵敏度高、基体干扰少、结果稳定准确,检出限可达到1．0μg／L。应用此方法测定4种水样中的铝,相对标准偏差为2．6％～5．3％,加标回收率为95％～108％。     

夏热冬冷地区住宅围护结构能耗的灵敏度分析

为得到围护结构各相关因素对建筑能耗影响的权重,采用EETP围护结构评价指标对空调、采暖能耗进行计算,分析了夏热冬冷地区上海、长沙、韶关和成都四个城市高层点式住宅围护结构各因素对空调、采暖及全年能耗的灵敏度,包括体形系数、窗墙比、遮阳系数、外墙/屋顶/外窗的传热系数、外墙/屋顶外表面的太阳辐射吸收系数。结果表明：窗墙比为25%时,墙体传热系数、体形系数和窗墙比依次是影响全年能耗的前三位主要因素,四个城市灵敏度分别为24.4%~35.8%、21.7%~32.0%和16.8%~31.1%;窗墙比为50%时,窗墙比、体形系数和遮阳系数依次是前三位主要因素,灵敏度分别为34.8%~45.6%,20.0%~44.3%和12.0%~47%;外墙和屋顶外表面太阳辐射吸收系数以及屋顶传热系数对建筑全年能耗影响均很小。     

The 24-h unsteady analysis of air flow and temperature in a real city by high-speed radiation calculation method

Heat island phenomenon is an important issue in environmental studies. Many studies involving observations and simulations have been performed. Computational Fluid Dynamics (CFD) analysis including the effects of solar radiation and longwave radiation heating/cooling are limited in the extreme conditions at midday, when solar radiation intensity are at maximum; and the 24-h unsteady analyses are not done due to the difficulties of the boundary conditions. Authors developed Computer Graphics (CG) method for calculating solar radiation and longwave radiation with high speed, and developed the 24-h unsteady analytical method from the data calculated by Weather Research and Forecasting (WRF). The integrated CFD was applied to the real city. The results showed that the integrated CFD was the useful tool to analyze the heat island phenomena.     

Decomposition of trichloroethylene and tetrachloroethylene in drinking water by a combined radiation/ozone treatment

The decomposition of small amounts (100 ppb) of tri- or perchloroethylene in drinking water has been investigated. The combined action of γ-radiation and ozone results in a considerable synergistic effect. Furthermore, the presence of ozone eliminates completely the formation of nitrite occurring under γ-irradiation alone.     

石墨炉原子吸收光谱法测定石英玻璃中痕量铁检出限的探讨

以铁元素为例,讨论了石墨炉原子吸收光谱法测定石英玻璃中痕量元素检出限的空白选择、方法检出限的常见两种测定方法和计算依据,以及样品检出限的计算与表示.一个月内,不同时间段,分五次测定至少20个样品空白,所得检出限为真实的方法检出限,可作为日常分析使用.结果表明,增加进样量和使用新的石墨管可以提高灵敏度.     

原子吸收分光光度法测定氧化锌电阻片造粒料中杂质含量

为了加强工艺质量控制,使用原子吸收分光光度法对氧化锌电阻片造粒料中杂质含量进行测定,可以了解氧化锌电阻片中杂质元素的分布情况,通过对氧化锌电阻片电性能的跟踪分析,可以得出不同杂质含量对氧化锌电阻片电性能的影响,从而也验证了我们选取杂质元素在氧化锌造粒料中的含量上限的科学性。该方法手段先进,操作方便,具有广泛推广使用的价值。