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41.
为了研究聚苯乙烯外墙保温系统火灾风险的问题,对比了3种火灾测试方法,分别是基于ISO 5660的小尺寸锥形量热计实验方法、基于ISO 9705的大尺寸实验方法和基于BS 8414的全尺寸实验方法。讨论了3种方法评测外墙保温系统火灾风险的适用性,进一步在比较分析热释放速率、临界热流强度、火蔓延情况、火灾行为以及实验后样品完整性等参数的基础上,得到了影响聚苯乙烯外墙保温系统火灾风险的关键因素。结果表明:虽然空腔的形成在此类系统火灾中不可避免,但系统保护层的严密性和完整性决定了空腔火蔓延的危险性以及聚苯乙烯在系统内的融化流动及燃烧特性。针对聚苯乙烯外墙保温系统火灾风险影响因素,进一步给出了此类系统的防火措施。 相似文献
42.
采用数值模拟技术研究了干挂石材幕墙发生燃烧情况下的火蔓延及羽流特点。通过外部高温辐射源点燃了具有4 cm厚PMMA保温层但保温材料和外层钢板间存在2 cm缝隙下的干挂石材幕墙,对模拟结果的温度场、速度场和热释放速率的分析表明其火蔓延速度较泡沫壁面低,但碳化区形状规则,蔓延路径清晰;虽然热释放速率低,但相对而言火焰高度较高,火焰宽度较小,而且其火羽流呈现点火源的特点。 相似文献
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以干化污泥作为替代燃料和造孔剂加入到以页岩为主体的原料体系中,制备出具有节能效果的多孔污泥页岩烧结墙体材料,这是提高污泥利用效率和满足村镇建筑节能建材制备的有效手段,探究了城市污泥掺量、烧结温度和烧结保温时间对烧结墙体材料试样的物理性能、力学性能的影响规律。结果表明,在采用污泥和瘠性页岩为主要原料时不能满足多孔节能烧结墙体材料挤出成型要求,而应采用压制成型工艺,当污泥掺量为15%时,烧结温度为1 050 ℃,保温时间为6 h,可以制备出性能指标优异并满足工程实用的烧结墙体材料,且污泥中的重金属可有效固溶于材料内部,气体排放也可满足国家标准中的相关指标要求,研究结果对干化污泥的利用具有较好的指导意义。 相似文献
45.
Dr R. J. Morrow M. J. Whittle Margaret B. McNay P. A. M. Raine A. A. M. Gibson Jenny Crossley 《黑龙江环境通报》1993,13(2):111-115
An attempt was made to identify all the cases of abdominal wall defects occurring in the West of Scotland over a 7-year period to determine the current incidence, prenatal diagnosis, management, and prognosis for fetuses and neonates with abdominal wall defects. Cases were identified because they presented either for prenatal diagnosis, or to the Department of Pathology following termination or spontaneous pregnancy loss, or as neonates to the Neonatal Surgical Department. The incidence of abdominal wall defects was found to be 1 in 2500 births. Exomphalos was diagnosed before birth in 66 per cent of cases, and in 30 per cent of cases it was associated with another major abnormality. There was a 20 per cent intact survival in the cases diagnosed prenatally who had no fetal anomaly and who opted to continue with the pregnancy. Gastroschisis was diagnosed before delivery in 70 per cent of cases, and in the group who continued with the pregnancy there was an intact survival of 77 per cent. Body stalk anomalies were all diagnosed prenatally and terminated. Maternal serum alpha-fetoprotein was elevated in 89 per cent of the cases with exomphalos and in 100 per cent of the cases with gastroschisis and body stalk anomalies in which it was tested. 相似文献
46.
离体培养植物细胞的表面与细胞粘连 总被引:3,自引:0,他引:3
对离体培养的胡萝卜(Daucuscarota)细胞和普通烟草(Nicotianatabacum)细胞的表面进行了扫描电镜观察.观察表明,细胞的自由表面上有很多疣突和纤丝.疣突的大小不同、形状各异,主要含果胶质;有些细胞表面出现小坑,坑中集中有许多微小颗粒.疣突相互可融合成更大的疣突或连成桥;纤丝常与疣突结合.纤丝-纤丝的交织,纤丝-疣突的交联,及疣突-疣突的融合,在细胞壁外表面构成交织的网络.同种细胞之间及异种细胞之间均可通过纤丝、疣突的交织融合而粘连.疣突分布不均一,且与细胞的分散性有关.与疏松烟草愈伤组织比较,致密烟草愈伤组织细胞的自由表面上疣突显著较多.在分化再生时,烟草愈伤组织首先致密变绿,然后才见到芽的分化及植株再生.对疣突出现、壁物质沉积与细胞粘连、细胞分化、形态建成几者之间的关系进行了讨论. 相似文献
47.
Amol Balu Mande 《International Journal of Green Energy》2019,16(3):211-227
This experimental work has been conducted to compare the performance of the modified stills with that of the conventional still. Three modified stills (S1, S2, and S3) and conventional still (S4) were fabricated, each with 0.5 m2 of the basin area. S1 and S3 had transparent double glass walls with air in between acting as insulation, whereas S2 has a single transparent wall. S4 has insulated plywood walls painted black from inside. A mixture of coco peat and charcoal was used in S1, S2, and S3, whereas there was no basin material for S4. Experiments were conducted by changing the water quantity in the solar still ranging from 5 to 10 kg. Maximum distillate output of 5.46 l/m2-d was obtained for S2, whereas it was 3.80 l/m2-d for S4 for an average solar radiation intensity of 675 W/m2 (24.3 MJ/m2-d). Use of transparent walls with troughs to collect condensate increased the condenser area by 78.4%. The distillate water cost per liter was estimated as Rs. 0.86 (0.013 US$) and Rs. 1.61 (0.025 US$) for S2 and S4, respectively. Energy payback time for S2 was estimated as 4 months. Theoretical and experimental values showed that there is a significant loss of incoming solar radiation due to wall shadow. 相似文献
48.
隧道通风数值计算中定义壁面粗糙程度的参数由粗糙高度和粗糙常数构成,参数的选取很难利用数学推导的方式进行研究。依托衢宁铁路鹫峰山隧道的施工通风项目,采用数值模拟并结合现场实测数据研究了隧道内壁面粗糙度的评定方法、取值和工程应用。结果表明:隧道壁面平均粗糙高度由隧道内实际开挖轮廓线和设计开挖轮廓线之间包络的面积与取样长度的比值确定,计算得到了隧道横断面平均粗糙高度为0. 191 m,纵向平均粗糙高度为0. 231 m;建立了粗糙常数Rc与粗糙单元间距、形状的关系,同时得到基本模型对应的Rc计算公式;基于典型理想壁面模型,以原模型面积减去理想模型的面积(绝对值)除以原模型面积所得值最小定义了最优简化模型,提出了关于壁面粗糙常数取值的计算方法,并以此计算出鹫峰山隧道壁面粗糙常数Rc为0.46。最终根据Rh和Rc的取值,采用三维数值模拟,分析了隧道内CO质量浓度不同时间段的分布规律。由于压入式通风自身的缺陷(无法突破长度瓶颈),且受现场布置及施工方式所限,通风距离超过3 000 m很难满足施工条件的需要,无法达到规定的洞内作业环境条件。因此,急需对现有的通风方式进行优化和调整。 相似文献
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50.
India ranks as the sixth largest producer of iron ore in the world. The current practice of washing iron ore in India generates as high as 18 million tonnes of tailings per year. These tailings are stored in massive ponds and pose environmental hazards. Safe disposal or utilisation of these materials thus remains a challenging task for the iron ore industry in India. The present paper describes a new development in managing these tailings by converting them into value added products such as ceramic floor and wall tiles for building application. These tiles have high strength and hardness compared to conventional tiles and conform to most of the EN standards. Energy economy and lower production costs are some other benefits. 相似文献