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61.
62.
中国煤炭地质总局航测遥感局作为我国煤炭航测技术的主要单位,承担着95%以上的煤炭矿区航测成图任务,并逐步发展成为我国集航空摄影、遥感地质、地图制印、地下管线探测、地理信息技术等全面发展的空间信息产业集团:伴随着计算机技术的发展,煤炭航测技术走过了从模拟测图到解析测图,最后发展到今天的全数字测图的历程。目前煤航已拥有和掌握了IMU/DGPS辅助航空摄影技术、SAR(合成孔径雷达)成图技术、LIDAR(机载激光扫描)技术等空间数据采集最新技术。 相似文献
63.
Fu-Ping Liu Rui-Zhong Li Jin-yao Li Hui-Guo Chen Chang-Chun Yang 《Mathematical Geosciences》2008,40(7):813-829
The group time delay (GTD) formulae of quasi-total reflection of inhomogeneous P-polarized electromagnetic waves (P-PEW, whose electric field parallels to the plane of incidence), caused by the Goos–Hänchen effect, is derived by the phase shift of the wave. A numerical example where the frequency equals to 1 GHz is given. The curves of calculating results show that there are three discontinuous points at the critical angle of phase shift vector, the critical angle of attenuation vector and 90○. When the angle of incidence is equal to one of these three angles, the GTD will become infinite, and the electromagnetic wave will propagate along the interface. The GTD will be very large, when the angle of incidence is close to one of these three angles. The results indicate that there is an important relationship between the two critical angles and the conductivity and permittivity of the two strata, and that the GTD has an important relationship with the angle of incidence. These results can be used to determine the lithology of the strata and to delimit the interfaces of strata more effectively. It is suggested that this research may prove useful in electromagnetic logging analysis and, perhaps, in the design of logging instruments. 相似文献
64.
Particulate content of savanna fire emissions 总被引:9,自引:0,他引:9
Hélène Cachier Catherine Liousse Patrick Buat-Menard Annie Gaudichet 《Journal of Atmospheric Chemistry》1995,22(1-2):123-148
As part of the FOS-DECAFE experiment at Lamto (Ivory Coast) in January 1991, various aerosol samples were collected at ground level near prescribed fires or under local background conditions, to characterize the emissions of particulate matter from the burning of savanna vegetation. This paper deals with total aerosol (TPM) and carbon measurements. Detailed trace element and polycyclic hydrocarbon data are discussed in other papers presented in this issue.Near the fire plumes, the aerosols from biomass burning are primarily of a carbonaceous nature (C%70% of the aerosol mass) and consist predominantly of submicron particles (more than 90% in mass.) They are characterized by their organic nature (black to total carbon ratio Cb/Ct in the range 3–20%) and their high potassium content (K/Cb0.6). These aerosols undergo aging during their first minutes in the atmosphere causing slight alterations in their size distribution and chemical composition. However, they remain enriched in potassium (K/Cb=0.21) and pyrene, a polycyclic aromatic hydrocarbon, such that both of these species may be used as tracers of savanna burning aerosols. We show that during this period of the year, the background atmosphere experiences severe pollution from both terrigenous sources and regional biomass burning (44% of the aerosol). Daynight variations of the background carbon concentrations suggest that fire ignition and spreading occur primarily during the day. Simultaneous TPM and CO2 real-time measurements point to a temporal and spatial heterogeneity of the burning so that the ratio of the above background concentrations (TPM/CO2) varies from 2 to 400 g/kg C. Smoldering processes are intense sources of particles but particulate emissions may also be important during the rapidly spreading heading fires in connection with the generation of heavy brown smoke. We propose emission factor values (EF) for aerosols from the savanna biomass burning aerosols: EF (TPM)=11.4±4.6 and 69±25 g/kg Cdry plant and EF(Ct)=7.4±3.4 and 56±16 g C/kg Cdry plant for flaming and smoldering processes respectively. In these estimates, the range of uncertainty is mostly due to the intra-fire variability. These values are significantly lower than those reported in the literature for the combustion of other types of vegetation. But due to the large amounts of vegetation biomass being burnt in African savannas, the annual flux of particulate carbon into the atmosphere is estimated to be of the order of 8 Tg C, which rivals particulate carbon emissions from anthropogenic activities in temperate regions. 相似文献
65.
以上海某长距离急曲线顶管工程为例,通过现场实测4节管段顶进过程中的顶力,研究了顶力随顶程的变化规律,系统分析了顶进过程中顶力的主要影响因素,得到了一些有用的结论。 相似文献
66.
Koji Fujima 《Natural Hazards》2006,39(2):179-193
The hybrid numerical model had been developed to simulate a complicated 3D flow around structures generated by tsunami. In
the model, the conventional 2D model is adopted for the wide region far from structures and the 3D non-hydrostatic pressure
model is used in the limited region adjacent to structures. The applicability of the model is shown by comparisons of the
numerical results with the experimental results of the laboratory model tests and the numerical analysis results of the conventional
whole 2D simulation. In addition, the effect of a submerged structure at the opening of a breakwater is discussed from the
numerical simulations by the hybrid model. The submerged structure improves the stability of the rubble mound and reduces
the tsunami inflow into the bay, while it increases the water surface velocity around the opening of the breakwater. The increase
of surface velocity causes the increases of impulsive forces by collision with drafts and so on. 相似文献
67.
根据67个随机格网样点和分层抽样样点的耕层土壤氮素含量,在ArcGIS9.0平台上运用地统计学等方法研究了环溪河流域土壤氮素含量及其影响因素。结果表明,环溪河流域土壤全氮和碱解氮的平均含量分别为0.60g/kg和53.31mg/kg。研究区土壤全氮含量总体上呈条带状和团块状分布,其低值中心区(〈0.5g/kg)位于团结村不规则三角形区域,并以此为中心向四周增加;高值中心区(〉0.8g/kg)主要位于走马村椭圆状区域。区内土壤碱解氮其高值区(〉75mg/kg)主要分布在深弯村以西,低值区(〈33mg/kg)主要分布于窝窝店村和杨柳村一带。影响区内土壤氮素含量空间分布的因素主要是成土母质、土壤质地、土地利用方式、地貌和坡度。 相似文献
68.
Daily zenith scattered light intensity observations were carried out in the morning twilight hours using home-made UV-visible
spectrometer over the tropical station Pune (18‡31′, 73‡51′) for the years 2000–2003. These observations are obtained in the
spectral range 462–498 nm for the solar zenith angles (SZAs) varying from 87‡ to 91.5‡. An algorithm has been developed to
retrieve vertical profiles of ozone (O3) and nitrogen dioxide (NO2) from ground-based measurements using the Chahine iteration method. This retrieval method has been checked using measured
and recalculated slant column densities (SCDs) and they are found to be well matching. O3 and NO2 vertical profiles have been retrieved using a set of their air mass factors (AMFs) and SCDs measured over a range of 87–91.5‡
SZA during the morning. The vertical profiles obtained by this method are compared with Umkehr profiles and ozonesondes and
they are found to be in good agreement. The bulk of the column density is found near layer 20–25 km. Daily total column densities
(TCDs) of O3 and NO2 along with their stratospheric and tropospheric counterparts are derived using their vertical profiles for the period 2000–2003.
The total column, stratospheric column and tropospheric column amounts of both trace gases are found to be maximum in summer
and minimum in the winter season. Increasing trend is found in column density of NO2 in stratospheric, tropospheric and surface layers, but no trend is observed in O3 columns for above layers during the period 2000–2003 相似文献
69.
基于全站仪的圆形建筑物倾斜观测的方法和精度 总被引:2,自引:0,他引:2
随着建筑物的不断增高、增大,其稳定性和可靠性成为人们关注的焦点.其中建筑物的倾斜度是衡量施工技术质量的重要指标之一.而传统的观测方法如经纬仪测小角法、经纬仪投点法,由于受仪器精度和观测条件的限制,观测精度较低.拓普康全站仪独具推出的圆柱偏心测量功能为快速、准确测定圆形建筑物的倾斜量开辟了一条新途径,本文阐述了基于全站仪的圆形建筑物倾斜观测的原理和方法,并对其精度进行分析. 相似文献
70.