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131.
132.
高铁测量中的投影变形处理方法探讨 总被引:2,自引:1,他引:1
首先对长度投影综合变形情况做了分析,然后介绍投影变形的处理方法的原理,讨论了它们的优缺点,其中也提出了一些自己的看法,这对铁路测量方面具有借鉴作用。 相似文献
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135.
根据松花江流域1961-2000年观测气温、降水量资料和ECHAM5/MPI-OM模式对该流域21世纪前50 a气候变化的预估结果,分析了松花江流域1961-2000年年平均气温和年降水量变化,并对21世纪前50 a气温和降水量变化趋势进行了预估。结果表明,在全球变暖的背景下,作为中国气候变暖区域响应的先锋,松花江流域年平均气温自1980年代初持续升高,升温幅度比较显著;年降水量在1961-2000年无明显增加或减少趋势,年代际差异也不大。相对于1961-1990年的气候场,21世纪前半叶,年平均气温仍将呈明显增加趋势,到2040年代升温幅度达1℃以上,年降水量变化趋势不显著,可能微弱增加,但冬季平均气温和冬季降水量都呈增加趋势,春季降水量也为增加趋势。 相似文献
136.
Turbulent Intensities and Velocity Spectra for Bare and Forested Gentle Hills: Flume Experiments 总被引:1,自引:1,他引:0
To investigate how velocity variances and spectra are modified by the simultaneous action of topography and canopy, two flume
experiments were carried out on a train of gentle cosine hills differing in surface cover. The first experiment was conducted
above a bare surface while the second experiment was conducted within and above a densely arrayed rod canopy. The velocity
variances and spectra from these two experiments were compared in the middle, inner, and near-surface layers. In the middle
layer, and for the canopy surface, longitudinal and vertical velocity variances () were in phase with the hill-induced spatial mean velocity perturbation (Δu) around the so-called background state (taken here as the longitudinal mean at a given height) as predicted by rapid distortion
theory (RDT). However, for the bare surface case, and remained out of phase with Δu by about L/2, where L is the hill half-length. In the canopy layer, wake production was a significant source of turbulent energy for , and its action was to re-align velocity variances with Δu in those layers, a mechanism completely absent for the bare surface case. Such a lower ‘boundary condition’ resulted in longitudinal
variations of to be nearly in phase with Δu above the canopy surface. In the inner and middle layers, the spectral distortions by the hill remained significant for the
background state of the bare surface case but not for the canopy surface case. In particular, in the inner and middle layers
of the bare surface case, the effective exponents derived from the locally measured power spectra diverged from their expected
− 5/3 value for inertial subrange scales. These departures spatially correlated with the hill surface. However, for the canopy
surface case, the spectral exponents were near − 5/3 above the canopy though the minor differences from − 5/3 were also
correlated with the hill surface. Inside the canopy, wake production and energy short-circuiting resulted in significant departures
from − 5/3. These departures from − 5/3 also appeared correlated with the hill surface through the wake production contribution
and its alignment with Δu. Moreover, scales commensurate with Von Karman street vorticies well described wake production scales inside the canopy,
confirming the important role of the mean flow in producing wakes. The spectra inside the canopy on the lee side of the hill,
where a negative mean flow delineated a recirculation zone, suggested that the wake production scales there were ‘broader’
when compared to their counterpart outside the recirculation zone. Inside the recirculation zone, there was significantly
more energy at higher frequencies when compared to regions outside the recirculation zone. 相似文献
137.
针对海拔较高的城市建立或改造独立坐标系,存在着如何选择模型及各模型对长度变形的影响等问题,通过算例对常见椭球变换和比例缩放模型进行较为全面系统的分析,归纳出常见模型在不同投影带区域、不同投影面高度对长度变形的影响差异,并得出有益的结论。 相似文献
138.
The future changes in the relationship between the South Asian summer monsoon (SASM) and the East Asian summer monsoon (EASM) are investigated by using the high-emissions Shared Socioeconomic Pathway 5-8.5 (SSP5- 8.5) experiments from 26 coupled models that participated in the phase 6 of the Coupled Model Intercomparison Project (CMIP6). Six models, selected based on their best performance in simulating the upper- and lower-level pathways related to the SASM-EASM teleconnection in the historical run, can capture the positive relationship between the SASM and the rainfall over northern China. In the future scenario, the upper-level teleconnection wave pattern connecting the SASM and the EASM exhibits a significant weakening trend, due to the rainfall anomalies decrease over the northern Indian Peninsula in the future. At the lower level, the western North Pacific anticyclone is projected to strengthen in the warming climate. The positive (negative) rainfall anomalies associated with positive (negative) SASM rainfall anomalies are anticipated to extend southward from northern China to the Yangtze-Huai River valley, the Korea Peninsula, and southern Japan. The connection in the lower-level pathway may be strengthened in the future. 相似文献
139.
高永超 《测绘与空间地理信息》2017,(6):106-108
利用Arc GIS的投影变换功能进行坐标系转换,介绍了转换过程中怎样使用七参数模型、布尔莎七参数模型及计算方法,对于抬高投影面和任意中央子午线建立的地方坐标系,在转换过程中要注意哪些操作。 相似文献
140.
李玉平 《测绘与空间地理信息》2017,(2):220-221
为了满足城市建设对测绘基准的要求,需建立相对独立的平面坐标系,我国测绘法等相关法律法规对独立平面坐标系的建立及管理有着明确的要求,本文结合新疆某县城相对独立平面坐标系的建立技术方案、申报材料准备、申报组织以及发布等方面进行了详细论述,希望能为测绘同行和测绘管理单位建立城市相对独立平面坐标系起到一定的参考作用。 相似文献