Numerical study on wave dynamics and wave-induced bed erosion characteristics in Potter Cove, Antarctica

Wave generation, propagation, and transformation from deep ocean over complex bathymetric terrains to coastal waters around Potter Cove (King George Island, South Shetland Islands, Antarctica) have been simulated for an austral summer month using the Simulating Waves Nearshore (SWAN) wave model. This study aims to examine and understand the wave patterns, energy fluxes, and dissipations in Potter Cove. Bed shear stress due to waves is also calculated to provide a general insight on the bed sediment erosion characteristics in Potter Cove.A nesting approach has been implemented from an oceanic scale to a high-resolution coastal scale around Potter Cove. The results of the simulations were compared with buoy observations obtained from the National Data Buoy Center, the WAVEWATCH III model results, and GlobWave altimeter data. The quality of the modelling results has been assessed using two statistical parameters, namely the Willmott’s index of agreement D and the bias index. Under various wave conditions, the significant wave heights at the inner cove were found to be about 40–50 % smaller than the ones near the mouth of Potter Cove. The wave power in Potter Cove is generally low. The spatial distributions of the wave-induced bed shear stress and active energy dissipation were found to be following the pattern of the bathymetry, and waves were identified as a potential major driving force for bed sediment erosion in Potter Cove, especially in shallow water regions. This study also gives some results on global ocean applications of SWAN.     

Numerical study on wave dynamics and wave-induced bed erosion characteristics in Potter Cove,Antarctica

Wave generation, propagation, and transformation from deep ocean over complex bathymetric terrains to coastal waters around Potter Cove (King George Island, South Shetland Islands, Antarctica) have been simulated for an austral summer month using the Simulating Waves Nearshore (SWAN) wave model. This study aims to examine and understand the wave patterns, energy fluxes, and dissipations in Potter Cove. Bed shear stress due to waves is also calculated to provide a general insight on the bed sediment erosion characteristics in Potter Cove.A nesting approach has been implemented from an oceanic scale to a high-resolution coastal scale around Potter Cove. The results of the simulations were compared with buoy observations obtained from the National Data Buoy Center, the WAVEWATCH III model results, and GlobWave altimeter data. The quality of the modelling results has been assessed using two statistical parameters, namely the Willmott’s index of agreement D and the bias index. Under various wave conditions, the significant wave heights at the inner cove were found to be about 40–50 % smaller than the ones near the mouth of Potter Cove. The wave power in Potter Cove is generally low. The spatial distributions of the wave-induced bed shear stress and active energy dissipation were found to be following the pattern of the bathymetry, and waves were identified as a potential major driving force for bed sediment erosion in Potter Cove, especially in shallow water regions. This study also gives some results on global ocean applications of SWAN.

     

Density and undrained shear strength of bed sediment from ND-CPT

The density and the undrained shear strength (s _u) of bed sediments at either side of the Isahaya Bay dike in the Ariake Sea, Japan, were investigated using nuclear density cone penetration tests (ND-CPTs). The nuclear density cone penetrometer (ND-CP) was operated from a boat, conducting 71 ND-CPTs. Furthermore, 26 undisturbed samples were obtained for soil density and s _u measurements to calibrate the ND-CPT data. The results show that the density and s _u obtained from in situ with the ND-CPTs agree well with those from the laboratory tests on undisturbed samples, and the obtained density profiles show good repeatability. The vertical variation in density and s _u of the bed sediment can be obtained from the ND-CPT results. The relations between the density and s _u show that s _u increases with an increase in density, but that this relation is site specific. The values of s _u show an exponentially growing trend and the values of log s _u show a linearly increasing trend with density. The vertical distribution of the bed sediments can be described using the density values obtained with the ND-CPT.     

基于ARIMA(p,1,1)的电离层预报模型

利用ARIMA(p,1,1)对IGS发布的电离层格网数据进行逐点建模,并对线性最小方差预测(一般预测法)和修正预测两种方法的预测结果进行比较.结果表明,修正预测法在一天的短期预测时高精度点所占比例较多,但在VTEC极值点可能会出现预测值偏离实测值较大的情况;一般预测法在较长时间内的预测精度仍较好.     

基于移动定位的行为数据采集与地理应用研究

微观个体行为的研究是人文地理学者解释人文地理现象的重要视角,而个体时空数据的获取是制约行为研究的重要瓶颈之一。随着手机的普及,移动定位服务为个体时空数据的获取提供了新的技术手段。通过与人口普查、交通调查等传统移动性数据获取方法的比较,基于移动定位的时空行为数据所具有特点包括:(1)采集个体位置和移动信息真实;(2)定位精度高、信号覆盖广;(3)可持续实时动态获取移动信息;(4)可减少行为数据编码过程的信息损失,适合大规模采集。详细介绍了基于移动通信网络和手机终端的移动定位技术原理,并通过微观个体行为分析和宏观城市动态空间规划的两个典型案例,实证基于移动定位的时空行为数据在城市规划等领域的可行性和适用性。移动定位方法显示出了巨大的技术优势和应用前景,但一些重要的基础性问题仍没有解决,特别是个人的隐私保护和移动定位的地理尺度问题。现有的研究成果表明,基于移动定位数据的地理应用仍处在试验和探索阶段,新的数据获取协议、数据分析方法、地理时空模式提取方法等研究亟待展开。     

银川隐伏活动断裂工程避让问题初步研究

基于多手段多层次综合探测的结果,评估了银川隐伏活动断裂及其分支断裂未来产生地震地表破裂的可能性;通过对多种勘探剖面深浅部的衔接性分析,讨论了未来地表破裂发生的原地重复性。考虑勘探精度和前人对地震地表破裂带宽度的统计资料,确定了银川隐伏活动断裂未来地震地表破裂带的可能范围,划分了断裂附近的危险地带和不利地带,并给出了不同类型建筑物避让危险地带的建议距离,可供城市规划和建设参考。     

基于钻探的芦花台隐伏断层晚第四纪活动特征

The Luhuatai fault is one of the important buried tectonics in the Yinchuan basin. Based on the results of shallow seismic exploration, we conducted composite drilling section exploration and dating of the samples from boreholes. Some useful data was obtained, such as the depth of the upper breaking point, the latest activity age, displacement in the late Quaternary, and slip rates, etc. This study shows that the activity is different between the north and south segment along the Luhuatai fault. The north segment is a Holocene fault, while the south segment is a late mid-Pleistocene fault. From north to south along the north segment of Luhuatai fault, the activity has been enhanced, and the faulting is stronger in late Pleistocene than Holocene.     

FVCOM model estimate of the location of Air France 447

On June 1, 2009, Air France AF447 disappeared in the Equatorial Atlantic Ocean en route from Rio de Janeiro, Brazil, to Paris, France. On June 6–19, 2009, bodies and debris from the aircraft were recovered floating in the equatorial ocean. This paper describes efforts on using the global–local nested finite volume community ocean model (FVCOM) to model reversely the tracks of bodies and debris back to the time of the crash and to help searchers locate the cockpit voice and flight data recorders and learn why this tragic accident occurred. To validate the reliability and reality of FVCOM, eight surface drifters were deployed by the French Bureau d’Enquêtes et d’Analyses pour la sécurité de l’aviation civile (BEA) near the last known position in early June 2010 for a period of 3?weeks. These drifter data were used to optimize the spatial and temporal correlation scales of the adaptive sampling data assimilation method of FVCOM. Applying an optimized FVCOM system to assimilate all available drifter- and float-tracking-derived currents in May–June 2009 under three different wind conditions, we reproduced the June 2009 current fields in the area near the LKP and used these fields to reversely track bodies and debris from locations where they were found to the time when the crash occurred. Possible locations for the crashed plane were suggested based on our model results and were made available to the French investigators and the Woods Hole Oceanographic Institution REMUS autonomous underwater vehicle Operations Group who successfully located the aircraft debris field in April 2011 on the seafloor at a depth of 3,900?m.     

工程岩爆灾害判别的RBF-AR耦合模型

岩爆是深部高地应力区地下岩体工程中的主要工程地质灾害之一,其发生及烈度预测是一个复杂的不确定系统问题。为了有效预测和判别深部工程岩爆灾害,在总体考虑岩爆各影响因素的基础上,选取地下工程中岩体完整性指数、岩石单轴抗压强度、岩石单轴抗拉强度、围岩最大切向应力、围岩抗压强度与其抗拉强度的比值、围岩切向应力与围岩抗压强度比值、弹性能量指数、岩爆倾向性指数作为岩爆预测的评判指标,提出了一种基于非线性参数优化的RBF-AR岩爆预测模型。在终南山隧道竖井岩爆判别中,利用RBF-AR法进行计算,计算结果与实际情况完全一致,表明该模型在岩爆预测中的可行性和有效性。     

星载GPS相位非差观测粗差和周跳的探测与修复

提出了以历元间星载GPS载波相位观测值之差作为观测量,结合拟准检定法（QuAD）来探测和修复非差星载GPS相位观测值中的粗差和周跳的方法。利用仿真低轨卫星GPS相位观测数据,对粗差和周跳的特性进行了分析,并对探测和修复步骤与效果进行了详细说明。实验表明,该方法不仅计算简捷,而且能有效修复非差载波相位观测值中的粗差和周跳,为非差星载GPS精密单点定轨提供了良好的质量控制基础。