The correlation between the local density of galaxies and the presence of Gamma‐Ray Bursts

In order to explore the characteristics of the environment surrounding Gamma‐Ray Bursts (GRBs), we have studied the correlation between the local density of galaxies and the presence of bursts. Using the Main Galaxy sample of the Sloan Digital Sky Survey Data Release 3 (SDSS DR3) and the Current BATSE GRB Catalog, we calculate the local surface density of galaxies within a radius of <2° surrounding each burst. It turns out that there is no correlation between the local density of galaxies and the presence of GRBs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

榆林地区景观变化探测模型

Landscape is a dynamic phenomenon that almost continuously changes. The overall change of a landscape is the result of complex and interacting natural and spontaneous processes and planned actions by man. However, numerous activities by a large number of individuals are not concerted and contribute to the autonomous evolution of the landscape in a similar way as natural processes do. There is a well-established need to detect land use and ecological change so that appropriate policies for the ;egional sustainable development can be developed. Landscape change detection is considered to be effectively repeated surveillance and needs especially strict protocols to identify landscape change. This paper developed a series of technical frameworks on landscape detection based on Landsat Thematic Mapper (TM) Data. Through human-machine interactive interpretation, the interpretation precision was 92.00% in 1986 and 89.73% in 2000. Based on the interpretation results of TM images and taking Yulin prefecture as a case study area, the area of main landscape types was summarized respectively in 1986 and 2000. The landscape pattern changes in Yulin could be divided into ten types.     

Transverse seismic kinematics of single piles by a modified Vlasov model

Within the framework of soil–pile interaction, a novel displacement scheme for the transverse kinematic response of single piles to vertically propagating S waves is proposed on the basis of the modified Vlasov foundation model. The displacement model contains a displacement function along the pile axis and an attenuation function along the radial direction. The governing equations and boundary conditions of the two undetermined functions are obtained in a coupled form by using Hamilton's principle. An iterative algorithm is adopted to decouple and solve the two unknown functions. In light of the governing equation of the pile kinematics, a mechanical model is proposed to evaluate the present method on a physical basis considering material damping. The coefficient of the equivalent Winkler spring is derived explicitly as function of the displacement decay parameter γ and soil Poisson's ratio. A parametric study is performed to investigate the effects of the soil–pile system properties on the kinematic response of single piles. The results show that the dimensionless pile length controls the transverse kinematics of piles. In terms of the theory of beams on elastic foundation, the classification limits of the dimensionless pile length may be π ∕ 4 and π, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Modelling of the retreat process of composite riverbank in the Jingjiang Reach using the improved BSTEM

Bank retreat in the Jingjiang Reach is closely related not only to the near‐bank intensity of fluvial erosion but also to the composition and mechanical properties of bank soils. Therefore, it is necessary to correctly simulate bank retreat to determine the characteristics of fluvial processes in the Jingjiang Reach. The current version of bank stability and toe erosion model (5.4) was improved to predict riverbank retreat, by inputting a dynamic water table, and calculating the approximation of the distribution of dynamic pore water pressure in the soil near the river bank face, and considering the depositional form of the failed blocks, which is assumedly based on a triangular distribution, with the slope approximately equalling the stable submerged bank slope and half of collapsed volume deposited in the bank‐toe region. The degrees of riverbank stability at Jing34 were calculated using the improved bank stability and toe erosion model. The results indicate the following trends: (a) the degrees of riverbank stability were high during the dry season and the rising stage, which led to minimal bank failure, and (b) the stability degrees were low during the flood season and the recession stage, with the events of bank collapse occurring frequently, which belonged to a stage of intensive bank erosion. Considering the effects of bank‐toe erosion, water table lag, and the depositional form of the collapsed bank soil, the bank‐retreat process was simulated at the right riverbank of Jing34. The model‐predicted results exhibit close agreement with the measured data, including the total bank‐retreat width and the collapsed bank profile. A sensitivity analysis was conducted to determine the quantitative effects of toe erosion and water table lag on the degree of bank stability. The calculated results for toe erosion indicate that the amount of toe erosion was largest during the flood season, which was a primary reason for bank failure. The influence of water table lag on the degree of stability demonstrates that water table lag was an important cause of bank failure during the recession stage.     

蓝牙室内测距模型研究与精度分析

针对低功耗蓝牙进行室内定位过程中,蓝牙信号在室内传播过程中受到多路径、反射、非视距等误差的影响,导致蓝牙信号值存在波动性、奇异值等问题,进一步导致测距误差较大。为了验证环境对信号传播的影响,本文验证了3种主要影响因素对信号值的影响,并提出3种滤波方法对采集的初始值进行预处理;根据实际环境利用最小二乘法分段拟合测距模型;根据拟合的测距模型与处理后的RSSI值,得到准确的测距信息。实验表明,利用分段拟合的测距模型和混合滤波方法处理后的强度值,测距精度得到了明显的提高。