Bottom acoustic parameters play an important role in sound field prediction. Acoustic parameters in deep water are not well understood. Bottom acoustic parameters are sensitive to the transmission-loss （TL） data in ...Bottom acoustic parameters play an important role in sound field prediction. Acoustic parameters in deep water are not well understood. Bottom acoustic parameters are sensitive to the transmission-loss （TL） data in the shadow zone of deep water. We propose a multiple-step fill inversion method to invert sound speed, density and attenuation in deep water. Based on a uniform liquid hMf-space bottom model, sound speed of the bottom is inverted by using the long range TL at low frequency obtained in an acoustic propagation experiment conducted in the South China Sea （SCS） in summer 2014. Meanwhile, bottom density is estimated combining with the Hamilton sediment empirical relationship. Attenuation coefficients at different frequencies are then estimated from the TL data in the shadow zones by using the known sound speed and density as a constraint condition. The nonlinear relationship between attenuation coefficient and frequency is given in the end. Tile inverted bottom parameters can be used to forecast the transmission loss in the deep water area of SCS very we//.展开更多
Based on 49 digital seismograms recorded by 73 seismic stations in the Jiangsu Telemetered Seismic Network,the paper uses Atkinson's method to calculate the inelastic attenuation coefficient of the Jiangsu area. W...Based on 49 digital seismograms recorded by 73 seismic stations in the Jiangsu Telemetered Seismic Network,the paper uses Atkinson's method to calculate the inelastic attenuation coefficient of the Jiangsu area. We find that the frequency-dependent Q in the Jiangsu region is Q( f) = 272. 1·f^(0. 5575). We also use Moya's method to invert the 63 stations' site responses. The results show that the site responses of the 25 stations in Jiangsu are approximately 1 at a range between 1Hz and 20 Hz, which is consistent with their basements on rocks. The response curves of the site responses of the 14 underground stations are similar to each other. Their site responses show an amplification at low frequencies and minimization at high frequencies. The calculation of the Brune model on the waveform data of M_L≥2. 5 earthquakes from Jiangsu Digital Seismic Network between October 2010 and May 2015 in terms of seismic source parameters of 58 seismic waves shows that there are good correlations between seismic magnitude and other source parameters such as seismic moment, source radius and corner frequency, while the correlations between seismic magnitude and stress drop,and stress drop and source radius are not so good.展开更多
The problem of determining a minimum-area ellipse through three non-collinear points is discussed in this paper. We give the proof and construction of the minimum-area ellipse through three non-collinear points from t...The problem of determining a minimum-area ellipse through three non-collinear points is discussed in this paper. We give the proof and construction of the minimum-area ellipse through three non-collinear points from the geometric point of view, and present a new method of determining knots. This method replaces the chord length, which is closer to the arc length of the mini- mum-area ellipse with arc length, and avoids the occurrence of ＇oscillation＇ and ＇loops＇. We compare the new method with the uni- form method, chord length method and the centripetal method. The comparison is performed on the quality of cubic spline curves using these methods. In most cases, the result of our method is better than others.展开更多
以短历时强降水为特征的暴雨事件增多是北京地区近年来暴雨内涝频发的主要原因.为提高北京地区短历时强降水的模拟和预报能力,选用WRF(weather research and forecasting,WRF)模型中对降水模拟结果影响较为明显的3类参数化方案组成12组...以短历时强降水为特征的暴雨事件增多是北京地区近年来暴雨内涝频发的主要原因.为提高北京地区短历时强降水的模拟和预报能力,选用WRF(weather research and forecasting,WRF)模型中对降水模拟结果影响较为明显的3类参数化方案组成12组物理参数化方案组合,对北京地区具有不同中尺度环流特征的2类共8场短历时强降水事件进行模拟.基于构建的评价指标体系,评估各类参数化方案模拟北京地区短历时强降水过程的能力,评选出综合表现最好的物理参数化方案组合.研究结果表明:积云对流参数化方案对各类型强降水模拟结果的影响最大,云微物理参数化方案次之,行星边界层参数化方案的影响最小;从模拟北京地区短历时强降水过程的综合能力来看,表现较好且较稳定的方案分别为WSM6云微物理参数化方案、GD积云参数化方案和MYJ行星边界层方案;从模型模拟不同类型强降水过程的整体表现来看,模型对具有连续性降水特点且受地形抬升作用影响相对较小的第2类强降水过程的模拟效果最好,而对具有间歇性降水特点的深对流强降水过程及其相关的湿物理过程的模拟效果较差.研究结果对于提高区域强降水预警预报能力,改进模型参数化方案具有参考意义.展开更多
In this paper, we establish the boundedness of parameterized Littlewood-Paley operator μλ^＊,p and parameterized area integralμΩ^σSp with kernel satisfying the logarithmic type Lipschitz condition on the weak Ha...In this paper, we establish the boundedness of parameterized Littlewood-Paley operator μλ^＊,p and parameterized area integralμΩ^σSp with kernel satisfying the logarithmic type Lipschitz condition on the weak Hardy space.展开更多
平原地区泵闸主体的结构型式大多较为相似,而传统的二维设计仍需要逐一设计,且前期设计方案的调整,及施工图阶段的二维配筋图绘制也有大量的修改工作,使得设计效率低下。针对以上问题,考虑采用三维参数化设计来解决。即将同一类型的泵...平原地区泵闸主体的结构型式大多较为相似,而传统的二维设计仍需要逐一设计,且前期设计方案的调整,及施工图阶段的二维配筋图绘制也有大量的修改工作,使得设计效率低下。针对以上问题,考虑采用三维参数化设计来解决。即将同一类型的泵闸建立参数化模型模板,利用该模板通过修改参数可得到同一类型不同尺寸的泵闸,并可直接进行下一步的三维配筋及出图、工程量统计工作。通过某泵闸工程实例,利用BIM软件Micro Station CONNECT建立了该泵闸的参数化模型,定义好通用参数以及约束关系参数,并利用Re Station完成了模型的三维配筋设计及出图、工程量统计工作。结果表明利用三维参数化可以优化平原地区泵闸的全过程设计。展开更多
Mesh morphing is a technique which gradually deforms a mesh into another one. Mesh parameterization, a powerful tool adopted to establish the one-to-one correspondence map between different meshes, is of great importa...Mesh morphing is a technique which gradually deforms a mesh into another one. Mesh parameterization, a powerful tool adopted to establish the one-to-one correspondence map between different meshes, is of great importance in 3 D mesh morphing. However, current parameterization methods used in mesh morphing induce large area distortion, resulting in geometric information loss. In this paper, we propose a new morphing approach for topological disk meshes based on area-preserving parameterization. Conformal mapping and M？bius transformation are computed firstly as rough alignment. Then area preserving parameterization is computed via the discrete optimal mass transport map. Features are exactly aligned through radial basis functions. A surface remeshing scheme via Delaunay refinement algorithm is developed to create a new mesh connectivity. Experimental results demonstrate that the proposed method performs well and generates high-quality morphs.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11434012,41561144006,11174312 and 11404366
文摘Bottom acoustic parameters play an important role in sound field prediction. Acoustic parameters in deep water are not well understood. Bottom acoustic parameters are sensitive to the transmission-loss （TL） data in the shadow zone of deep water. We propose a multiple-step fill inversion method to invert sound speed, density and attenuation in deep water. Based on a uniform liquid hMf-space bottom model, sound speed of the bottom is inverted by using the long range TL at low frequency obtained in an acoustic propagation experiment conducted in the South China Sea （SCS） in summer 2014. Meanwhile, bottom density is estimated combining with the Hamilton sediment empirical relationship. Attenuation coefficients at different frequencies are then estimated from the TL data in the shadow zones by using the known sound speed and density as a constraint condition. The nonlinear relationship between attenuation coefficient and frequency is given in the end. Tile inverted bottom parameters can be used to forecast the transmission loss in the deep water area of SCS very we//.
基金jointly sponsored by the“Science for Earthquake Resilience(1730801)the Youth Fund Program of Earthquake Administration of Jiangsu Province,China(201405)
文摘Based on 49 digital seismograms recorded by 73 seismic stations in the Jiangsu Telemetered Seismic Network,the paper uses Atkinson's method to calculate the inelastic attenuation coefficient of the Jiangsu area. We find that the frequency-dependent Q in the Jiangsu region is Q( f) = 272. 1·f^(0. 5575). We also use Moya's method to invert the 63 stations' site responses. The results show that the site responses of the 25 stations in Jiangsu are approximately 1 at a range between 1Hz and 20 Hz, which is consistent with their basements on rocks. The response curves of the site responses of the 14 underground stations are similar to each other. Their site responses show an amplification at low frequencies and minimization at high frequencies. The calculation of the Brune model on the waveform data of M_L≥2. 5 earthquakes from Jiangsu Digital Seismic Network between October 2010 and May 2015 in terms of seismic source parameters of 58 seismic waves shows that there are good correlations between seismic magnitude and other source parameters such as seismic moment, source radius and corner frequency, while the correlations between seismic magnitude and stress drop,and stress drop and source radius are not so good.
基金Supported by the National Research Foundation for the Doctoral Program of Higher Education of China(20110131130004)Independent Innovation Foundation of Shandong University,IIFSDU(2012TB013)Ji’nan Science and Technology Development Project(No.201202015)
文摘The problem of determining a minimum-area ellipse through three non-collinear points is discussed in this paper. We give the proof and construction of the minimum-area ellipse through three non-collinear points from the geometric point of view, and present a new method of determining knots. This method replaces the chord length, which is closer to the arc length of the mini- mum-area ellipse with arc length, and avoids the occurrence of ＇oscillation＇ and ＇loops＇. We compare the new method with the uni- form method, chord length method and the centripetal method. The comparison is performed on the quality of cubic spline curves using these methods. In most cases, the result of our method is better than others.
文摘以短历时强降水为特征的暴雨事件增多是北京地区近年来暴雨内涝频发的主要原因.为提高北京地区短历时强降水的模拟和预报能力,选用WRF(weather research and forecasting,WRF)模型中对降水模拟结果影响较为明显的3类参数化方案组成12组物理参数化方案组合,对北京地区具有不同中尺度环流特征的2类共8场短历时强降水事件进行模拟.基于构建的评价指标体系,评估各类参数化方案模拟北京地区短历时强降水过程的能力,评选出综合表现最好的物理参数化方案组合.研究结果表明:积云对流参数化方案对各类型强降水模拟结果的影响最大,云微物理参数化方案次之,行星边界层参数化方案的影响最小;从模拟北京地区短历时强降水过程的综合能力来看,表现较好且较稳定的方案分别为WSM6云微物理参数化方案、GD积云参数化方案和MYJ行星边界层方案;从模型模拟不同类型强降水过程的整体表现来看,模型对具有连续性降水特点且受地形抬升作用影响相对较小的第2类强降水过程的模拟效果最好,而对具有间歇性降水特点的深对流强降水过程及其相关的湿物理过程的模拟效果较差.研究结果对于提高区域强降水预警预报能力,改进模型参数化方案具有参考意义.
基金Supported by National Natural Science Foundation of China(Grant Nos.11001266 and 11171345)Fundamental Research Funds for the Central Universities(Grant No.2009QS16)
文摘In this paper, we establish the boundedness of parameterized Littlewood-Paley operator μλ^＊,p and parameterized area integralμΩ^σSp with kernel satisfying the logarithmic type Lipschitz condition on the weak Hardy space.
文摘平原地区泵闸主体的结构型式大多较为相似,而传统的二维设计仍需要逐一设计,且前期设计方案的调整,及施工图阶段的二维配筋图绘制也有大量的修改工作,使得设计效率低下。针对以上问题,考虑采用三维参数化设计来解决。即将同一类型的泵闸建立参数化模型模板,利用该模板通过修改参数可得到同一类型不同尺寸的泵闸,并可直接进行下一步的三维配筋及出图、工程量统计工作。通过某泵闸工程实例,利用BIM软件Micro Station CONNECT建立了该泵闸的参数化模型,定义好通用参数以及约束关系参数,并利用Re Station完成了模型的三维配筋设计及出图、工程量统计工作。结果表明利用三维参数化可以优化平原地区泵闸的全过程设计。
基金Supported by the National Natural Science Foundation of China(61772379)the National Key Research and Development Program of China(2016YFB052204)
文摘Mesh morphing is a technique which gradually deforms a mesh into another one. Mesh parameterization, a powerful tool adopted to establish the one-to-one correspondence map between different meshes, is of great importance in 3 D mesh morphing. However, current parameterization methods used in mesh morphing induce large area distortion, resulting in geometric information loss. In this paper, we propose a new morphing approach for topological disk meshes based on area-preserving parameterization. Conformal mapping and M？bius transformation are computed firstly as rough alignment. Then area preserving parameterization is computed via the discrete optimal mass transport map. Features are exactly aligned through radial basis functions. A surface remeshing scheme via Delaunay refinement algorithm is developed to create a new mesh connectivity. Experimental results demonstrate that the proposed method performs well and generates high-quality morphs.
