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631.
632.
Modeling the two-phase cloud evolution from instantaneous flashing release using CFD 总被引:1,自引:0,他引:1
Wei Tan Xiao LiuYujin Liu Yu BuZejun Wang 《Journal of Loss Prevention in the Process Industries》2011,24(4):420-425
Computational Fluid Dynamics (CFD) approach has been successfully applied to simulate the small-scale instantaneous flashing release experiment by Pettitt. A model for dispersion of the release event is provided based on relevant theories and existing experimental data. An application of the CFD method to the dispersion simulation is illustrated. Furthermore, a new methodology based on discrete phase model for setting computational initial conditions is provided. An initial expansion and subsequent turbulence dispersion can be characteristically identified from both volume and temperature variation of the cloud obtained by the simulation. The possible mechanism for these phenomena has also been discussed and analyzed. The study deepens the understanding of the physical process of this event and provides one more reliable tool for relevant safety systems. 相似文献
633.
大气中二次有机气溶胶估算方法研究进展 总被引:6,自引:0,他引:6
大气中二次有机气溶胶产生于光化学反应或挥发性及半挥发性有机物的气-粒转化,目前没有直接测定二次有机气溶胶的方法,一般采用间接方法估算二次有机气溶胶的贡献.通过分析对比各种二次有机气溶胶估算方法的优缺点及应用条件,认为EC示踪法操作简单,参数容易获得,但参数的不确定性高; 化学迁移模型法能详细反映二次有机气溶胶形成情况,但所需参数不易获得; 有机物受体模型示踪法,不需要模拟复杂的情况,但难于保证成分谱的准确性及可靠性.因此,在选择估算方法时应充分考虑到各种方法的局限性及适用范围,将试验观测与环境空气质量模型联合用于二次有机气溶胶估算应成为今后重要的发展方向. 相似文献
634.
Males of many tephritid fruit fly species of the genus Bactrocera show a very strong affinity to methyl eugenol (ME). An attracted male compulsively ingests ME, which is then biotransformed
before its metabolites are accumulated into the rectal gland. The glandular organ is known to serve as a reservoir for sex
pheromone in some species. Upon ME-feeding, males of the oriental fruit fly, Bactrocera dorsalis, selectively accumulated two metabolites, 2-allyl-4,5-dimethoxyphenol (DMP) and (E)-coniferyl alcohol (E-CF), in the rectal pheromone gland. We compared the profiles of phenylpropanoid metabolites accumulated
by three other species of very high economic and quarantine importance—Bactrocera invadens, Bactrocera zonata and Bactrocera correcta, with that of B. dorsalis. Males of each species were fed artificially on ME and the metabolites stored in the rectal glands were examined by means
of chromatography and spectroscopy. Similar to B. dorsalis, males of laboratory-raised B. invadens accumulated DMP and E-CF, in almost equal quantities, in the rectal sac. The sum of DMP and E-CF increased gradually with
time after ME consumption and reached as high as 150 μg/male 2 days post ME-feeding. Wild males of B. invadens captured in Kenya also possessed both the compounds in varying quantities. In contrast, males of B. zonata accumulated DMP and (Z)-coniferyl alcohol (Z-CF) in an approximate ratio of 1:1; whereas B. correcta is known to convert ME to (Z)-3,4-dimethoxycinnamyl alcohol (Z-DMC) and Z-CF also in an approximately 1:1 ratio. Thus, there are three types of binary
combinations of rectal phenylpropanoid volatiles (i.e. DMP + E-CF; DMP + Z-CF; Z-CF + Z-DMC) utilized among the four Bactrocera species. Such differences in phenylpropanoid ingredients may play a critical role in differentiating these species if encountered
in the natural habitat. In this context, the two putative sibling species—B. invadens and B. dorsalis, possess the identical subset of rectal volatiles (DMP and E-CF) in a similar proportion. Furthermore, the phylogenetic analyses
of the four Bactrocera species by comparing nucleotide sequences in the mitochondrial genes showed that B. invadens clearly belonged to the same clade as B. dorsalis species. Therefore, we consider the two as the same biological species, and certainly not distinct. 相似文献
635.
综述了近年来海洋微生物来源天然产物研究的新进展,总结了该类天然产物的开发策略.通过对样品采用不同的预处理方式、不同的分离培养基以及新的培养方法,讨论如何获得海洋来源的特有微生物和增加海洋来源微生物类群的多样性.阐述了在海洋微生物天然产物的开发过程中,采用宏基因组技术及基因组测序等手段,来发现难培养或不可培养微生物中的天然产物以及处于"沉默"状态的天然产物.最后介绍了异源生物合成、组合生物合成以及核糖体工程等技术在海洋微生物天然产物开发和改造中的应用,并举例论述了海洋微生物天然产物的开发. 相似文献
636.
Gang Xiao Baosheng Jin Mingjiang Ni Kefa Cen Yong Chi Zhongxin Tan 《Frontiers of Environmental Science & Engineering》2011,5(2):193-204
Considering high-moisture municipal solid waste (MSW) of China, a steam dried MSW gasification and melting process was proposed, the feasibility was tested, and the mass and energy balance was analyzed. Preliminary experiments were conducted using a fixed-bed drying apparatus, a 200 kg per day fluidized-bed gasifier, and a swirl melting furnace. Moisture percentage was reduced from 50% to 20% roughly when MSW was dried by slightly superheated steam of 150°C?C350°C within 40 min. When the temperature was less than 250°C, no incondensable gas was produced during the drying process. The gasifier ran at 550°C?C700°Cwith an air equivalence ratio (ER) of 0.2?C0.4. The temperature of the swirl melting furnace reached about 1240°C when the gasification ER was 0.3 and the total ER was 1.1. At these conditions, the fly ash concentration in the flue gas was 1.7 g·(Nm3)?1, which meant over 95% fly ash was trapped in the furnace and discharged as slag. 85% of Ni and Cr were bound in the slag, as well as 60% of Cu. The mass and energy balance analysis indicates that the boiler heat efficiency of an industrial MSW incineration plant reaches 86.97% when MSW is dried by steam of 200°C. The boiler heat efficiency is sensitive to three important parameters, including the temperature of preheated MSW, the moisture percentage of dried MS Wand the fly ash percentage in the total ash. 相似文献
637.
Bo Han Xiaohui Bi Yonghua Xue Jianhui Wu Tan Zhu Baogui Zhang Jianqing Ding Yuanxin Du 《Frontiers of Environmental Science & Engineering》2011,5(4):552-563
A total of 168 PM10 samples were collected during the year of 2005 at eight sites in the city of Wuxi in China. Fifteen chemical elements, three water-soluble ions, total carbon and organic carbon were analyzed. Six source categories were identified and their contributions to ambient PM10 in Wuxi were estimated using a nested chemical mass balance method that reduces the effects of colinearity on the chemical mass balance model. In addition, the concentrations of secondary aerosols, such as secondary organic carbon, sulfate and nitrate, were quantified. The spatially averaged PM10 was high in the spring and winter (123 ??g·m?3 and low in the summer-fall (90 ??g·m?3). According to the result of source apportionment, resuspended dust was the largest contributor to ambient PM10, accounting for more than 50% of the PM10 mass. Coal combustion (14.6%) and vehicle exhaust (9.4%) were also significant source categories of ambient PM10. Construction and cement dust, sulfates, secondary organic carbon, and nitrates made contributions ranging between 4.1% and 4.9%. Other source categories such as steel manufacturing dust and soil dust made low contributions to ambient PM10. 相似文献
638.
639.
640.
Marlies J Kampschreur Cristian Picioreanu Nico Tan Robbert Kleerebezem Mike S M Jetten Mark C M van Loosdrecht 《Water environment research》2007,79(13):2499-2509
Nitric oxide production was measured during nitrification in a laboratory-scale bioreactor, operated at conditions relevant to municipal nitrifying wastewater treatment plants. This study aims to determine which type of microorganism and which metabolic pathway is responsible for nitric oxide emission during nitrification. Simulation studies were used to identify which pathway is the main source of nitric oxide emission, based on the following three hypothetical pathways for nitric oxide emission: (a) nitrification, (b) denitrification by ammonia-oxidizing bacteria with ammonium as electron donor, and (c) heterotrophic denitrification. The results of the study suggest that, in a nitrifying reactor treating wastewater containing solely ammonium and nutrients, denitrification by ammonia-oxidizing bacteria is the main nitric-oxide-producing pathway. During the experiments, 0.025% of the treated ammonium is emitted as nitric oxide, independent of the aeration rate imposed. Nitrite presence and oxygen limitation were found to increase the nitric oxide emission. 相似文献