利用实时路况数据聚类方法检测城市交通拥堵点

 城市交通拥堵严重制约其网络总体效率。开展检测交通拥堵点可有效识别网络瓶颈,以整治交通拥堵现象。对此,本文提出一种新的城市交通时空拥堵点检测的方法:即采用实时路况数据,通过定义时空关联,检测时空意义上长期性、规律性交通拥堵点。本文基于DBSCAN(Density-Based Spatial Clustering of Applications with Noise)算法,以成都市为试验区,实现了这种拥堵点检测方法。试验表明,该方法可快速、有效、准确地检测出城市道路严重拥堵路段,并确定其拥堵时空范围,为交通管理、交通拥堵机理分析、交通拥堵预测等提供参考。     

Dynamic Response and Mechanical Behaviours of Geogrid for High Earth-rockfill Dams

Geotechnical and Geological Engineering - Due to the complexity of the interaction between the geogrid and the soil interface in high earth-rock dams, the method of replacing the grid with steel...     

2005年1月18日乳山ML4.3地震序列

对2005年1月18日乳山ML4.3地震序列特征及烈度分布进行了介绍, 认为乳山ML4.3地震序列是一次能量衰减较快、频度起伏衰减的主-余型地震序列, 序列本身不具有明显的前兆意义.     

Inter- and intra-annual trend analysis of water level and flow in the middle and lower reaches of the Ganjiang River,China

ABSTRACT

The Ganjiang River is the largest tributary of Poyang Lake in China, and its hydrological regime variation greatly affects the utilization of regional water resources and the ecological environment of the lake. In this study, a novel trend analysis method, the Moving Average over Shifting Horizon (MASH), was applied to investigate the inter- and intra-annual trends of flow and water level from 1976 to 2016 at the Xiajiang and the Waizhou hydrological stations in the Ganjiang River. The Significant Change Rate Method (SCRM) was proposed to determine the MASH averaging parameters. The trend analysis results show a statistically significant decrease in water level series throughout the year and the relationship of flow and water level have changed greatly at the Waizhou station. The sediment load reduction, large-scale sand mining and water level decrease of Poyang Lake are identified as the main causes for the water level decrease.     

A Simulation Study on the Evolution of Groundwater Circulation Systems in Cenozoic Basins of Northern China

Three Cenozoic basins-the Qaidam basin, the Weihe graben-type basin and the North China plain-which are different in climatic conditions, geological settings and run-off types, are selected for the study. Based on an analysis of background information of the transect along the middle-latitude region, studies of groundwater dynamics, geochemistry, simulation of water circulation of the main elements as well as isotopic chronology, the information on global changes is collected, the formation of groundwater circulation systems and their evolution under stacked impacts of natural conditions and human activities are discussed, and a correlation is made between the evolutionary features of the above systems in these basins since 25 ka B.P. All these have laid a good foundation for further generalizing the evolutionary model of land water in northern China.     

Study of Influence of Regional Geodynamic Background on Strata Behaviors in China's Tongxin Mine

Strata behaviors are mainly affected by regional geodynamic background. The influence of rock mass stress and energy distribution on strata behaviors in the Tongxin mine is studied in terms of regional tectonic movement, seismic activity and tectonic stress field. The results show that the extrusion lifting movement of Kouquan fault adjacent to the Tongxin mine results in the stress concentration in the rock of the Carboniferous coal bed and accumulation of a large amount of elastic energy and forms structural background of Tongxin mine. Due to various seismic activities in the mine area, the strain energy is known to reach much higher levels, up to 0.5×10⁸ J^1/2. Since the stratigraphic structure is sensitive to the mining operation, the strain energy could cause strong strata behaviors. A special geological structure model of the Tongxin mine is established based on the geodynamic division method. The distribution of regional structure stress field is determined by the rock mass stress analysis system. Based on this model, Tongxin mine is divided into five areas with high stress, eight areas with low stress and eight areas with gradient stress. The strong strata behaviors mostly occur in high stress areas. These results could provide guidance to predict the strength of regional or mine pressure and control strata behavior in different areas.     

Approximating constant‐Q seismic propagation in the time domain

In this study, we investigate the accuracy of approximating constant‐Q wave propagation by series of Zener or standard linear solid (SLS) mechanisms. Modelling in viscoacoustic and viscoelastic media is implemented in the time domain using the finite‐difference (FD) method. The accuracy of numerical solutions is evaluated by comparison with the analytical solution in homogeneous media. We found that the FD solutions using three SLS relaxation mechanisms as well as a single SLS mechanism, with properly chosen relaxation times, are quite accurate for both weak and strong attenuation. Although the RMS errors of FD simulations using a single relaxation mechanism increase with increasing offset, especially for strong attenuation (Q = 20), the results are still acceptable for practical applications. The synthetic data of the Marmousi‐II model further illustrate that the single SLS mechanism, to model constant Q, is efficient and sufficiently accurate. Moreover, it benefits from less computational costs in computer time and memory.     

The CCD photometric study of the newly identified RS CVn binary star DV Piscium

This paper presents new CCD BVRI light curves of the newly discovered RS CVn eclipsing binary star DV Psc. From the asymmetric light curves outside the eclipse, we find there are two depressions in the phase ranges 0.3–0.45 and 0.6–0.9, respectively. By analyzing the light curves using the Wilson–Devinney program, the four photometric solutions of the system are obtained and the starspot parameters are also derived. It turns out that the case of two spots being on the primary is most successful in reproducing the light curve distortion of DV Psc. Moreover, analysis the longitudes of spots suggests that there are two active longitude belts (one is about 90°, the other is about 270°). At the same time, on 22 November 2008, the first flare-like event was detected on DV Psc at phase 0.35 whose duration was about 13.5 min. These findings reveal that DV Psc has a high degree of magnetic activity.     

Estimating open boundary conditions from coastal tidal observations by adjoint approach

A numerical study for estimating the tidal open boundary conditions of a shelf current modrl from tb coastal tidal observations is presented. The method is based on the optimal control/adjoint method. A lrast square fitting of the model state to simulated data is used. Two ideal domains and coastlines are considered. Using the IAP shallow. water model and its adjoint model, some identical twin experiments are carried out to test efficiency and lirnilsd of the method. The results show that the adjoint method can efficiently estimate the open boundary conditions well for gulf/bay like domains. The adjoint method seems to have great potential to improve the accuracy of tide and shelf current modeling in coastal regions. Project supported hy the National Natural Science Fuundation of China (Grant No. 49376256)