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41.
Performance of Singapore Integrated Multiple Reference Station Network (SIMRSN) for RTK Positioning 总被引：1，自引：0，他引：1
Conventional RTK positioning is usable, but requires the use of a local base station. It is also restricted by the effects
of the de-correlate atmospheric refraction on the GPS signal, which limits the use of the RTK positioning up to distances
of 10–15 km from the reference station to the user. With a multiple reference station network approach, precise RTK positioning
capability may be extended for a much larger area. The Singapore Integrated Multiple Reference Station Network (SIMRSN) has
been established for this purpose. Using an existing method termed linear combination method, the multiple reference station
network corrections are generated for the user on an epoch by epoch, satellite-by-satellite basis. A residual-based adaptive
Kalman filter is proposed to improve network correction availability. The VRS concept is used to transmit corrections to the
user for RTK positioning. Field tests were conducted to demonstrate the general performance of SIMRSN. The tests confirmed
that RTK positioning within a multiple reference station network can provide the user with better than 3 cm in horizontal
position, the height accuracy is in the range of 1–7 cm, and the average TTF (Time To Fix) are 46 and 76 s during GLC station
and LPR station tests, respectively. With this highly efficient survey technique, the user needs only to be equipped with
a single GPS receiver. This reduces equipment and manpower costs compared with traditional RTK positioning using a specially
set up reference station. The multiple reference station framework also paves the way for various other applications beyond
the traditional surveying profession.
Electronic Publication 相似文献
42.
In recent years,we have entered the so-called Fourth Paradigm with the regular production of huge amount of observational data.Big data is often characterized by the three‘V's:Volume of data,Variety and Velocity.The concept of big data can potentially address some existing issues in areas of geoscience and geoengineering.Large-scale,comprehensive,multidirectional and multifield geotechnical monitoring is becoming a reality in the very near future. 相似文献
43.
Human perception to tremors during earthquakes in high-rise buildings is usually associated with psychological discomfort such as fear and anxiety. This paper presents a methodology for estimating the level of perception to tremors for occupants living in high-rise buildings subjected to ground motion excitations. Unlike other approaches based on empirical or historical data, the proposed methodology performs a regression analysis using the analytical results of two generic models of 15 and 30 stories. The recorded ground motions in Singapore are collected and modified for structural response analyses. Simple predictive models are then developed to estimate the perception level to tremors based on a proposed ground motion intensity parameter—the average response spectrum intensity in the period range between 0.1 and 2.0 s. These models can be used to predict the percentage of occupants in high-rise buildings who may perceive the tremors at a given ground motion intensity. Furthermore, the models are validated with two recent tremor events reportedly felt in Singapore. It is found that the estimated results match reasonably well with the reports in the local newspapers and from the authorities. The proposed methodology is applicable to urban regions where people living in high-rise buildings might feel tremors during earthquakes. 相似文献
44.
A series of centrifuge tests were performed to investigate the response of a free-head monopile due to cyclic lateral loading in normally consolidated clay. By linking the maximum reaction-force point of the final cycles in all tests with various amplitudes, a postcyclic reaction-force curve is obtained, which can be used to assess the postcyclic remolded lateral stiffness. To numerically analyze the tests, a strength degradation model of the clay is calibrated by the T-bar cyclic test. However, this model is T-bar-dependent, which is unable to capture the degrading behavior of the monopile stiffness. Thus, a modification approach is proposed based on the upper bound theory, and the modified model is further combined with finite element analysis to simulate the cyclic behavior of the model pile. The simulation results show similar degrading trend and consistent postcyclic remolded lateral stiffness with the model tests. This further demonstrates that the remolded lateral stiffness mainly depends on the soil remolded strength, which is one of the parameters calibrated by the T-bar tests. Based on this finding, a simplified numerical analysis is proposed, which can predict the postcyclic reaction-force curve by performing one monotonic loading instead of modeling the whole process of cyclic loading. 相似文献
45.
Large underground caverns are increasingly being considered for the construction of industrial facilities and transportation infrastructure in order to optimize the use of surface land in large urban cities. Due to the geological constraints underground, it is sometimes necessary to construct a cavern close to an existing cavern. Pillars serve as an underground support element in twin caverns, without which it is difficult to sustain the weight of the overburden materials. If the strength of a pillar is exceeded, it will fail, and the load that it carried will be transferred and thereby contribute to the collapse of the twin caverns. The lack of confinement in slender pillars also contributes to the complete collapse of pillars at relatively low stress magnitudes. From a design point of view, understanding the pillar failure mechanism and the interaction effect between twin caverns is essential. This paper presents a numerical investigation on the influence of various design parameters on twin cavern interaction. Pillar performances with respect to the changes to the maximum principal stress in the pillar, the peak vertical stress, and the peak principal stress difference in the pillar core are studied in order to examine the failure mechanisms and to identify situations in which there is significant cavern interaction and overlap of the plastic zones. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
46.
Tetsutaro Takikawa Goh Onitsuka Ken-ichi Fukudome Jong-Hwan Yoon Akihiko Morimoto Masatoshi Moku Atsushi Watanabe 《Estuaries and Coasts》2011,34(4):775-784
Horizontal, vertical and temporal distribution of a cyclonic (counterclockwise) eddy, where biological productivity is high,
downstream of the Tsushima Islands in the eastern channel of the Tsushima Straits in November 2007 was revealed using conductivity–temperature–depth
and acoustic Doppler current profiler data. The eddy had a horizontal scale of approximately 40–60 km, and the accompanying
baroclinic current was more than 15 cm s−1 at the edge of the eddy. The island-induced cyclonic eddy moved east-northeastward at about 10 km day−1 (∼10 cm s−1) along the Tsushima Warm Current and was intensified by the barotropic instability in the current shear. The cyclonic eddy
with high surface chlorophyll a concentrations intensified in the vicinity of the Tsushima Islands and was advected by the Tsushima Warm Current towards
the southwestern Japan Sea. 相似文献
47.
Acta Geotechnica - The spatial variability of the properties of natural soils is one of the major sources of uncertainties that can influence the performance of geotechnical structures. The direct... 相似文献
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