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401.
热-力耦合作用对建筑结构火灾安全的影响 总被引:4,自引:3,他引:1
结构火灾安全可以避免建筑物在火灾中坍塌.火灾热环境影响建筑结构的响应,传统的标准火灾环境有一定的局限性,不能完全适用于若干真实火灾场景.因此有必要开展真实火灾环境下建筑结构的热-力响应特性研究,发展有效的工程工具来设计经济安全的结构.近来,性能化的结构火灾安全设计评估方法和相应技术发展迅速,该文给出一种综合考虑热-力耦合作用的结构火灾安全设计评估方法及相应流程.首先通过建筑和燃料特性来预测可能的火灾热环境特性,然后再分析构件和结构的热响应和力学响应特性来判定结构是否会失效,以及可以降低热和力影响的预防失效措施.该文通过案例分析将该方法应用于某中庭钢结构屋顶的防火保护,得到经济合理的防火涂层设计,满足有关防火规范的安全等价要求. 相似文献
402.
城市屋面绿化生态热效应 总被引:16,自引:0,他引:16
文章在享有“火炉”这称的山城重庆夏末季节对草坪层面与水泥屋面的热特性进行了对比实测分析,研究结果表明草坪屋面具有显著的生态热效应。 相似文献
403.
碳管吸收气相色谱法测定大气中的非甲烷烃 总被引:1,自引:0,他引:1
文章研究了用碳管吸收大气中的非甲烷烃,经热解吸后,用气相色谱氢火 离子检测器进行测定的方法。本文色谱柱为玻璃微球填充柱。与其它方法比较,本法简便、快速,重现性好。 相似文献
404.
火电厂对生态环境影响的总体评价 总被引:1,自引:1,他引:0
抛弃了以往在分析污染排放物对环境影响时只对不同污染物进行单独分析的做法,从单位污染物对大气的影响和生产单位有用能的污染物排放量两方面考虑,建立了一个通用的、能综合评价各种污染物对环境总体影响的模型--能源生态效率模型,并对燃烧不同燃料火电厂的能源生态效率作了计算,对能源生态效率的影响因素进行了分析. 相似文献
405.
通过建设以火电厂为中心的生态工业园的初步研究,阐述了建设生态工业园的重要意义,详细探讨了不同产业间的资源相互最大利用的循环经济发展模式,并总结了建设生态工业园经济发展模式的经验以及可能存在的问题,为各地建设类似生态工业园提供参考. 相似文献
406.
407.
ABSTRACT: In‐reservoir thermal and ecological effects of releasing some flows over the surface spillway at Blue Mesa Reservoir, Colorado, rather than routing all releases through the hypolimnetic outlet were evaluated using a calibrated and validated one‐dimensional thermal model (CE‐THERM) with a set of ecological models. Thermal model output indicated that surface water temperatures were influenced primarily by atmospheric conditions, but the release of warmer water over the spillway resulted in a thinner epilimnion and cooler metalimnetic water temperatures. Ecological model predictions indicated that spillway releases and associated temperatures resulted in lower growth rates for young‐of‐year (YOY) kokanee salmon (Oncorhynchus nerka) in the reservoir by up to 9 percent when compared with growth rates under baseline operations with no releases over the spillway. Kokanee growth rates were reduced under spillway release scenarios because lower temperatures not only affected metabolic rates, but limited the productivity of the zooplankton as well. Thus, altering the release regime with spillway discharges could have deleterious effects on Blue Mesa's YOY kokanee. However, in other reservoirs, distributing discharges among different elevations may provide managers with a mechanism to regulate temperatures to benefit species of concern that are facing challenges imposed by environmental conditions such as global warming. 相似文献
408.
Polyisocyanurate foams were prepared from polymeric 4,4-diphenylmethane diisocyanate (MDI), soy polyol and polypropylene oxide polyol by varying isocyanate index from 110 to 350. The higher isocyanate index produced polyisocyanurate foams with higher thermal stability, improved flame resistance, tensile strength, higher modulus, and higher glass transition. Soy-based foams displayed better thermal stability, lower flammability, higher rigidity (modulus) and higher compression strength than those based on the propylene oxide polyols of the same molecular weight and functionality. 相似文献
409.
P. Louka G. Vachon J.-F. Sini P. G. Mestayer J.-M. Rosant 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):351-364
The thermal effects on the airflow within a street canyon, which are produced by the variation of direct solar heating of the street sides and ground, are examined in this article. The investigation is based on the experimental results of the Nantes'99 campaign and numerical simulations performed with the Computational Fluid Dynamics (CFD) code CHENSI using the standard k- model. The Nantes'99 experimental campaign was performed in a North-to-South oriented central street canyon of Nantes, France. It was observed that a thin thermal layer develops locally within a few centimetres from the heated wall. It is anticipated that, the convective flow close to the windward wall, which was visualised during the experiment, carries air masses from the street level upwards, where normally cleaner air is transported. Consequently, thermal effects may be important for the air quality in the street.Based on the temperature and wind flow measurements, the flow and temperature fields were simulated first in two dimensions with the CFD code CHENSI. It was found that CHENSI overestimates the thermal effects on the canyon airflow showing the main re-circulation simulated in the isothermal case to change into two counter-rotating vortices after the inclusion of the heating of the windward wall. A reason for this overestimation is possibly the temperature wall function implemented for such thin thermal boundary layers in conjunction with the limitations in grid resolution. 相似文献
410.
Poly(lactic acid) is the subject of considerable commercial development by a variety of organizations around the world. In this work, the thermal and rheological properties of two commercial-grade poly(lactic acid)s (PLAs) are investigated. A comparison of the commercial samples to a series of well-defined linear and star architecture PLAs provides considerable insight into their flow properties. Such insights are valuable in deciding processing strategies for these newly emerging, commercially significant, biodegradable plastics. Both a branched and linear grade of PLA are investigated. The crystallization kinetics of the branched polymer are inferred to be faster than the linear analog. Longer relaxation times in the terminal region for the branched material compared to the linear material manifests itself as a higher zero shear rate viscosity. However, the branched material shear thins more strongly, resulting in a lower value of viscosity at high shear rates. Comparison of the linear viscoelastic spectra of the branched material with the spectra for star PLAs suggests that the branched architecture is characterized by a span molecular weight of approximately 63,000 g/mol. The present study conclusively demonstrates that a wide spectrum of flow properties are available through simple architectural modification of PLA, thus allowing the utilization of this important degradable thermoplastic in a variety of processing operations. 相似文献