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991.
风电场风资源测量与计算的精度控制 总被引:3,自引:1,他引:2
根据多个复杂地形风电场观测操作实践和大量观测数据的计算分析,提出了对观测数据和计算质量精度控制的主要措施,包括:复杂地形测风站布设的5个原则,仪器的合理选型和设置;对由于测风仪固有的系统误差和缺测数据的插补订正可能引起的计算误差进行了定量估算,通过对大量实测数据的对比计算显示:①目前普遍采用的进口风速计的相对偏差在1.6%~5.25%之间,由此可导致轮毂高度附近的年平均风功率密度误差在5%以上,最大达13.8%;②在季风气候区、复杂地形和风的年变率较大的地区,进行缺测数据插补订正时,应选取同季或同一主导风向的数据作为插补订正的基础数据,否则可能导致其平均风功率密度相对误差达20%~50%. 相似文献
992.
京津冀地区霾成因机制研究进展与展望 总被引:9,自引:3,他引:6
为满足当前对京津冀地区霾研究和控制的迫切要求,本文梳理了近年来京津冀地区霾的长期变化特征、天气学特征、污染物来源等相关研究成果,发现:从2000年以后,京津冀地区的霾日数呈现出了下降趋势;北京细颗粒物(PM2.5)质量浓度也在总体上呈现下降的趋势,但2013年年均质量浓度仍高达89.5μg m–3,约为我国空气质量标准的3倍(35μg m–3),京津冀空气污染的形势依然严峻;近年来京津冀地区的霾污染事件频发可以归因为不利天气条件与大量污染物人为排放的共同作用;大量的研究表明,区域输送对京津冀地区霾事件的形成和维持有不可忽视的影响;京津冀地区的大气污染不再局限于一时一地,针对重污染天气的预警以及应急控制应该以区域预报为基础实现区域联动;京津冀地区独特的地理环境条件加上城市群的快速发展,形成的局地大气环流也会对局地的污染过程产生重大的影响;大气边界层内气象要素的变化对重污染发生具有显著贡献。京津冀地区的污染控制需要城市群的联动应对治理。 相似文献
993.
陈毅敏 《测绘与空间地理信息》2005,28(5):118-120
长度检定场是电磁波测距仪量值传递的主要标准,主要用于各等级电磁波测距仪的常数测定,本文根据相关的测量规范,就建场设计及其控制测量中一些技术问题作了一些分析和探讨. 相似文献
994.
Structural specific features of the sedimentary succession on the continental margin of the South Crimea in the Black Sea have been examined in the Yalta Area using geomorphologic, acoustic, and lithologic methods. Alternation of regressive and transgressive sequences has been ascertained in sediment sections formed on the shelf and in the Yalta deep-sea fan due to Quaternary oscillations of the basin level. The analysis of sediment sections resulted in revealing a leading role of sedimentary material transference from upper hypsometric levels to lower ones in the sediment accumulation. 相似文献
995.
Vassilios C. Kelessidis Cassiani Papanicolaou Antonios Foscolos 《International Journal of Coal Geology》2009,77(3-4):394-400
This review paper presents the results of an extensive study investigating whether addition of 3% w/w Greek lignite to 6.42% w/w water–bentonite suspensions, after being exposed to high temperatures, can prevent gelation and control filtration characteristics. Two different bentonites and eight lignites from different Greek basins have been used while a commercial lignite product has been used as standard. The lignite-free bentonite suspensions heated to 177 °C for 16 h (thermal aging) thicken considerably, increasing the yield stress and the yield point. Fluid consistency and flow behavior indices also change while no significant change is observed for plastic viscosity. Thermal aging of the suspensions results in unacceptably high fluid loss values.Addition of Greek lignite to water–bentonite suspensions, followed by thermal aging, provided the rheological stability of the suspensions by maintaining the low yield stress/point regardless of the type of bentonite. Some of the lignites performed as well as their commercial counterpart. No specific trends for rheological improvement have been identified with respect to various characteristics of lignites such as contents of humic, fulvic acids, humins and other parameters such as specific surface area and cation exchange capacity.Furthermore, addition of lignite in most cases provided very good filtration control of the water–bentonite suspensions after exposure to 177 °C, with some Greek lignites being superior to the commercial product. The same lignite parameters examined for rheological control, were also examined to determine their effect on fluid loss of these suspensions for both bentonites. The content of humic and fulvic acids of two groups of lignites showed weak inverse correlations with the fluid loss volumes for both bentonites, while all other parameters did not seem to directly correlate with the effectiveness of the lignites. 相似文献
996.
A strain hardening model is proposed for simulation of the shear behavior of rockfills, including the non-linear stress–strain relationship, stress-dependence of stiffness, non-linear strength envelope, and particularly the shearing contraction and dilatancy. This model utilizes the Mohr–Coulomb yield criterion, which is defined by the mobilized friction angle varying with plastic octahedral shear strain. The development of Rowe’s stress dilatancy theory is reviewed, with its limitation for rockfills highlighted. A modified solution is then proposed to derive the mobilized dilatancy angle of rockfills. Compared with large-scale triaxial testing results, it has been demonstrated that this simple model is capable of predicting the shear behavior of rockfills with fair accuracy. 相似文献
997.
Arsenic is one of the most dangerous inorganic pollutants and thus a penalty element in many base metal concentrates. Arsenic removal in sulphide flotation has been studied extensively with various approaches, including pre-oxidation of flotation pulp, Eh control during flotation and the use of selective depressants/collectors. Pre-oxidation of flotation pulp using oxidizing agents or aeration conditioning represents a simple approach in arsenic removal and was found effective in many cases. Selective flotation of arsenic minerals through Eh control has made significant advances in recent years with promising results achieved. In addition, various depressants and collectors have also been studied in arsenic removal. In this communication, the various approaches used in selective flotation of arsenic minerals are reviewed with emphasis on the development in recent years. 相似文献
998.
999.
Zefeng Li 《地震科学(英文版)》2021,34(2):177-188
Seismic networks have significantly improved in the last decade in terms of coverage density, data quality, and instrumental diversity. Moreover, revolutionary advances in ultra-dense seismic instruments, such as nodes and fiber-optic sensing technologies, have recently provided unprecedented high-resolution data for regional and local earthquake monitoring. Nodal arrays have characteristics such as easy installation and flexible apertures, but are limited in power efficiency and data storage and thus most suitable as temporary networks. Fiber-optic sensing techniques, inclu-ding distributed acoustic sensing, can be operated in real time with an in-house power supply and connected data storage, thereby exhibiting the potential of becoming next-generation permanent networks. Fiber-optic sensing techniques offer a powerful way of filling the observation gap particularly in submarine environments. Despite these technological advancements, various challenges remain. First, the data characteristics of fiber-optic sensing are still unclear. Second, it is challenging to construct software infrastructures to store, transfer, visualize, and process large amount of seismic data. Finally, innovative detection methods are required to exploit the potential of numerous channels. With improved knowledge about data characteristics, enhanced software infrastructures, and suitable data processing techniques, these innovations in seismic instrumentation could profoundly impact observational seismology. 相似文献
1000.