董家山隧道小净距段爆破控制的数值模拟   总被引：11，自引：1，他引：11  

姚勇  何川  晏启祥  李玉文 《岩土力学》2004,25(Z2):501-506

结合都-汶高速公路董家山隧道小净距段的实际情况,应用数值模拟方法,对小净距段在爆破荷载作用下的相互影响问题进行了研究.结果表明在隧道爆破施工中应对迎爆侧进行重点监控,采用合理的开挖和加固方式将有效降低爆破施工对先建隧道的不利影响.研究结论可为类似小净距段隧道的爆破设计、施工及现场监控量测提供参考.  相似文献   

Comparisons on seasonal and annual variations of δ~(18)O in precipitation     

ZHANG Xinping  YAO Tandong 《地理学报(英文版)》2004,(2)

interpretationofpaleoclimaticrecordsinicecore(Dansgaardetal.,1969;Rozanskietal.,1997;Yao,1999;Thompsonetal.,2000).SincethefirstdeepicecorewasdrilledinGreenlandin1966(Dansgaardetal.,1969),hundredsoficecoreswereobtainedsuccessivelyfromicesheetsinAntarcticaandArctic,andmountainglaciersatmid-highlatitudes,fundedbynumerousresearchprogramsonglobalclimateandenvironmentalchange.Theseicecoresprovideuniqueandvaluablefirst-handinformationinrecoveringglobalpaleoenvironmentalrecordsandforecastingfuturecl…  相似文献   

国内旅游文化开发研究综述   总被引：6，自引：0，他引：6  

赵飞  彭华  姚静 《云南地理环境研究》2004,16(2):48-52

旅游文化是一种重要的旅游资源。是旅游地可持续发展的源泉。在旅游地开发过程中，文化事项如何转化为旅游产品，即旅游文化开发是一个极具实际应用价值的研究课题。目前，国内对于旅游文化开发的研究还没有能够形成一个完整的理论研究体系，并且缺少成熟的研究方法，具体到实践中可操作性还比较弱。在查阅了国内近20年中的众多相关研究文献的基础上，试图从应用理论、开发实践、方法探索3个方面对国内的旅游文化开发研究做一个系统的总结。  相似文献   

Vertical dynamic and thermodynamic characteristics of urban lower boundary layer and its relationship with aerosol concentration over Beijing   总被引：1，自引：0，他引：1  

ZHOU Mingyu  YAO Wenqing  XU Xiangde  YU Haiqing 《中国科学D辑(英文版)》2005,48(Z2)

By utilizing observational data from a 325 m tower of the Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS) on March 19-29, 2001 and August 11-25, 2003, a comprehensive study was conducted on the vertical dynamical and thermodynamic characteristics of the urban lower boundary layer (ULBL) and its relationship with aerosol concentration over Beijing. Firstly, a comparative analysis was made on the gradient data (wind, temperature and humidity), ultrasonic data (atmospheric turbulences) and air-quality observations at different tower heights (47, 120 and 280 m). Secondly, a diagnosis was made to reveal the major features of normalized variances of velocity and temperature, turbulence kinetic energy as well as their relationship with aerosol concentrations. Furthermore, the characteristics of the ULBL vertical structure and the TSP concentration/distribution variations during a sand/dust weather process were also analyzed. The outcome of the study showed that under unstable stratification, the normalized variances of velocity (σu/u*, σv/u*, σw/u*) and temperature (σT/T*) at 47 and 120 m heights fit the Monin-Obukhov similarity (MOS) framework and the fitting formulas were given out accordingly. According to the stratification parameter (z′/L), the stable ULBL could be divided into 2 zones. With z′/L<0.1, it was a weakly stable zone and MOS framework was applicable. The other was a highly stable zone with z′/L>0.1 and the normalized velocity variances tended to increase along with higher stability, but it remained constant for normalized temperature variances. At daytime, the near-surface layer includes two heights of 47 and 120 m, while 280 m has been above it. The ULBL analysis in conjunction with a sand/dust weather process in Beijing in March 2001 indicated that the maximum concentration of Total Suspended Particulates (TSP) at 320 m reached 913.3 μg/m3 and the particles were transported from the upper to lower ULBL, which was apparently related to the development process of a low-level jet and its concomitant strong sinking motion.  相似文献   

Vertical structures of PM10 and PM 2.5 and their dynamical character in low atmosphere in Beijing urban areas     

DING Guoan  CHAN Chuenyu  GAO Zhiqiu  YAO Wenqing  LI Yoksheung  CHENG Xinghong  MENG Zhaoyang  YU Haiqing  WONG Kamhang  WANG Shufeng  MIAO Qiuju 《中国科学D辑(英文版)》2005,48(Z2)

The vertical structures and their dynamical character of PM2.5 and PM10 over Beijing urban areas are revealed using the 1 min mean continuous mass concentration data of PM2.5 and PM10 at 8, 100, and 320 m heights of the meteorological observation tower of 325 m at Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP CAS tower hereafter) on 10―26 August, 2003, as well as the daily mean mass concentration data of PM2.5 and PM10 and the continuous data of CO and NO2 at 8, 100 (low layer), 200 (middle layer), and 320 m (high layer) heights, in combination with the same period meteorological field observation data of the meteorological tower. The vertical distributions of aerosols observed on IAP CAS tower in Beijing can be roughly divided into two patterns: gradually and rapidly decreasing patterns, I.e. The vertical distribution of aerosols in calm weather or on pollution day belongs to the gradually decreasing pattern, while one on clean day or weak cold air day belongs to the rapidly decreasing pattern. The vertical distributive characters of aerosols were closely related with the dynamical/thermal structure and turbulence character of the atmosphere boundary layer. On the clean day, the low layer PM2.5 and PM10 concentrations were close to those at 8 m height, while the concentrations rapidly decreased at the high layer, and their values were only one half of those at 8 m, especially, the concentration of PM2.5 dropped even more. On the clean day, there existed stronger turbulence below 150 m, aerosols were well mixed, but blocked by the more stronger inversion layer aloft, and meanwhile, at various heights, especially in the high layer, the horizontal wind speed was larger, resulting in the rapid decrease of aerosol concentration, I.e. Resulting in the obvious vertical difference of aerosol concentrations between the low and high layers. On the pollution day, the concentrations of PM2.5 and PM10 at the low, middle, and high layers dropped successively by, on average, about 10% for each layer in comparison with those at 8 m height. On pollution days, in company with the low wind speed, there existed two shallow inversion layers in the boundary layer, but aerosols might be, to some extent, mixed below the inversion layer, therefore, on the pollution day the concentrations of PM2.5 and PM10 dropped with height slowly; and the observational results also show that the concentrations at 320 m height were obviously high under SW and SE winds, but at other heights, the concentrations were not correlated with wind directions. The computational results of footprint analysis suggest that this was due to the fact that the 320 m height was impacted by the pollutants transfer of southerly flow from the southern peripheral heavier polluted areas, such as Baoding, and Shijiazhuang of Hebei Province, Tianjin, and Shandong Province, etc., while the low layer was only affected by Beijing's local pollution source. The computational results of power spectra and periods preliminarily reveal that under the condition of calm weather, the periods of PM10 concentration at various heights of the tower were on the order of minutes, while in cases of larger wind speed, the concentrations of PM2.5 and PM10 at 320 m height not only had the short periods of minute-order, but also the longer periods of hour order. Consistent with the conclusion previously drawn by Ding et al., that air pollutants at different heights and at different sites in Beijing had the character of "in-phase" variation, was also observed for the diurnal variation and mean diurnal variation of PM2.5 and PM10 at various heights of the tower in this experiment, again confirming the "in-phase" temporal/spatial distributive character of air pollutants in the urban canopy of Beijing. The gentle double-peak character of the mean diurnal variation of PM2.5 and PM10 was closely related with the evident/similar diurnal variation of turbulent momentum fluxes, sensible heat fluxes, and turbulent kinetic energy at various heights in the urban canopy. Besides, under the condition of calm weather, the concentration of PM2.5 and PM10 declined with height slowly, it was 90% of 8 m concentration at the low layer, a little lesser than 90% at the middle layer, and 80% at the high layer, respectively. Under the condition of weak cold air weather, the concentration remarkably dropped with height, it was 70% of 8 m concentration at the low layer, and 20%―30% at the middle and high layers, especially the concentration of PM2.5 was even lower.  相似文献   

The diurnal and seasonal characteristics of urban heat island variation in Beijing city and surrounding areas and impact factors based on remote sensing satellite data     

ZHANG Jiahua  HOU Yingyu  LI Guicai  YAN Hao  YAO Fengmei 《中国科学D辑(英文版)》2005,48(Z2)

Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative.The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and large-scale construction of greenbelts can considerably reduce the UHI effect.  相似文献   

元谋人时代研究评述——兼论我国早更新世古人类时代问题   总被引：1，自引：0，他引：1  

姚海涛  邓成龙  朱日祥 《地球科学进展》2005,20(11):1191-1198

我国早更新世古人类遗址时代的确定对于认识早期人类起源、扩散与演化具有重要意义。对元谋人化石的各种年龄测定结果和认识分歧进行了综合评述。综合分析认为，在翔实的岩石地层学和古生物地层学基础上，开展高分辨率磁性地层学研究是解决包括元谋人在内的这一时期哺乳动物时代科学问题的最有效的研究途径。  相似文献   

地震灾害预测和应急模拟系统的设计与应用——以永安市城市应急系统为例   总被引：1，自引：0，他引：1  

危福泉  刘高焕  姚新  蔡宗文  洪伟 《地理研究》2005,24(5):749-756

城市防震减灾是地震潜在频发区提高自然灾害防治能力建设的重要方面。本文结合福建省永安市城市防震减灾信息管理系统的建设,探讨设计防震减灾数值模型,分析模型集成的关键技术,构建了地震风险评估、建筑物易损性评价、生命与财产损失估算、救援与救灾管理调度等模型和基于GIS开发的震害预测和应急模拟系统。该系统在福建省永安市的实际应用表明,通过对地震灾害预测结果的分析,可加强城市抗震中的薄弱环节,为灾区政府应急响应和制订对策提供决策支持辅助信息,从而显著提高城市防震减灾的综合能力。  相似文献   

273.15K下LiCl-Li2B4O7-H2O体系热力学性质的等压研究   总被引：2，自引：0，他引：2       下载免费PDF全文

杨吉民  姚燕  张爱云  宋彭生 《盐湖研究》2005,13(1):19-24

用等压法研究了273 15K下LiCl-Li2B4O7-H2O体系中纯盐水溶液(离子强度范围为LiCl0 2046～2 5055mol·kg-1,Li2B4O70 1295～0 3700mol·kg-1)以及混合盐水溶液(离子强度范围为0 0931～2 4911mol·kg-1)渗透系数和水活度;计算了LiCl-Li2B4O7-H2O体系的饱和蒸汽压,获得饱和蒸汽压、渗透系数随离子强度的变化规律。用实验数据以最小二乘法求取了LiCl和Li2B4O7纯盐参数及体系的混合盐参数,拟合的标准偏差分别为0 0077和0 026。用该模型计算的渗透系数值与实验结果取得合理的一致。同时研究结果与273 15K下LiCl-Li2SO4-H2O体系的渗透系数随离子强度变化的规律作了比较。本研究对完善低温下含锂、硼盐湖卤水体系的热力学模型和盐湖资源的综合开发利用具有重要意义。  相似文献   

日本“3·11”海啸引起的乐清湾共振研究          下载免费PDF全文

刘勇  卢文芳  应超  李新文  姚文伟 《海洋学研究》2019,37(3):31-39

本文基于TELEMAC-2D模型建立太平洋区域海啸传播模型,模拟2011年日本“3·11”海啸事件下海啸波的传播。使用实测数据对该模型进行验证,在模型验证良好的基础上分析日本“3·11”海啸事件对乐清湾的影响。通过频谱分析得到“3·11”海啸激发的乐清湾内240、180和103 min这3个主导模态的幅值及其相位。通过白噪声实验对乐清湾的固有共振特征进行估算,进一步支持了乐清湾在上述3个模态发生共振这一结论。白噪声实验还表明,海啸等海洋灾害发生时会在乐清湾湾顶及湾口处产生较大的增水,该结论对乐清湾内海洋灾害风险防范具有指导意义。  相似文献