Simulation analyses of buildings damaged in the 1995 Kobe,Japan, earthquake considering soil–structure interaction

A series of studies was conducted on three buildings of steel reinforced concrete structures with RC shear walls damaged in the 1995 Hyogo-ken Nanbu earthquake. These buildings are located in an area where structural damage centred around. Two of these buildings suffered severe damage, while the third was not structurally damaged. Our studies deal with site inspections, including micro-tremor measurement of buildings, the evaluation of input motions, and the response analyses considering soil–structure interaction. The results of simulation analyses of the two severely damaged buildings correspond to their actual damage state. From the response analyses of the one slender building with no structural damage, it was concluded that uplifting is the main reason it did not suffer any structural damage. Through these studies, the importance of soil–structure interaction and effective input motion is fully understood. Copyright © 1999 John Wiley & Sons, Ltd.     

一种IIR滤波器的FPGA设计与仿真

在分析IIR滤波器结构的基础上,借助Mat lab完成一种基于FPGA的级联型IIR滤波器的设计与实现,同时设计并生成向量文件(.vec文件),在QuartusⅡ中完成向量文件的仿真。仿真结果表明文中设计的IIR滤波器能够高效完成滤波功能,同时通过向量文件的激励引入能够增强FPGA的仿真能力。     

A tangential wind profile for simulating strong tropical cyclones with MM5

A new tangential wind profile for simulating strong tropical cyclones is put forward and planted into the NCARAFWA tropical cyclone bogussing scheme in MM5. The scheme for the new profile can make full use of the information from routine typhoon reports, including not only the maximum wind, but also the additional information of the wind speeds of 25.7 and 15.4 ms^-1 and their corresponding radii, which are usually provided for strong cyclones. Thus, the new profile can be used to describe the outer structure of cyclones more accurately than by using the earlier scheme of MM5 in which only the maximum wind speed is considered. Numerical experimental forecasts of two strong tropical cyclones are performed to examine the new profile. Results show that by using the new profile the prediction of both cyclones‘ intensity can be obviously improved, but the effects on the track prediction of the two cyclones are different. It seems that the new profile might be more suitable for strong cyclones with shifted tracks. However, the conclusion is drawn from only two typhoon cases, so more cases are needed to evaluate the new profile.     

Regular and chaotic orbits in a self-consistent triaxial stellar system with slow figure rotation

We created a self-consistent triaxial stellar system through the cold disipationless collapse of 100,000 particles whose evolution was followed with a multipolar code. The resulting system rotates slowly even though its total angular momentum is zero, i.e., it offers an example of figure rotation. The potential of the system was subsequently approximated with interpolating formulae yielding a smooth potential stationary in the rotating frame. The Lyapunov exponents could then be computed for a randomly selected sample of 3,472 of the bodies that make up the system, allowing the recognition of regular and partially and fully chaotic orbits. The regular orbits were Fourier analyzed and classified using their locations on the frequency map. A comparison with a similar non-rotating model showed that the fraction of chaotic orbits is slightly but significantly enhanced in the rotating model; alternatively, there are no significant differences between the corresponding fractions neither of partially and fully chaotic orbits nor of long axis tubes, short axis tubes, boxes and boxlets among the regular orbits. This is a reasonable result because the rotation causes a breaking of the symmetry that may increase chaotic effects, but the rotation velocity is probably too small to produce any other significant differences. The increase in the fraction of chaotic orbits in the rotating system seems to be due mainly to the effect of the Coriolis force, rather than the centrifugal force, in good agreement with the results of other investigations.     

2008年汶川地震前震源区的异常应力状态

我们收集了紫坪铺水库区域台网记录到的2004年8月16日至2008年5月12日汶川地震前发生在震中区及附近区域的486个小震震源机制资料,运用碎裂分析法对这些震源机制数据进行分析,获得了汶川地震前3年多时间内震源区应力水平随时间的演化过程.结果显示,强震发生前震源及附近区域约在2007年6月发生了应力突变,出现了2个应力异常高值区,其形成过程同时伴随着龙门山中央断裂的应力水平降低,最终强震发生在高应力区和低应力区之间的应力梯度带上.汶川地震前应力状态的演化过程,类似于实验研究中出现的非均匀断层失稳前的地震成核现象,符合地震成核的宏观表现.巴颜喀拉块体的南边界-鲜水河断裂的短基线测量也显示出,在同一时间段鲜水河断裂南段由左旋滑动转为异常的右旋错动,反映了汶川强震前整个巴颜喀拉块体有向东加速运动的异常过程.     

一次冰雹天气过程分析

对奎玛流域一次冰雹天气的分析表明，在巴尔喀什湖低槽加强东移的环流背景下，低层水汽辐合、抬升启动和层结不稳定有利于该地区强对流的发生、发展，中尺度强对流云团的形成、发展是产生这次冰雹天气的主要原因。     

北京地区一次特大强风过程边界层结构的研究

利用北京325 m气象塔资料对1993年4月9日北京地区出现的一次特大强风过程的边界层结构（风、温、风切变及阵风特征）进行了分析。随着该次大风的过境，边界层内风场出现数个风速高值中心，高度位于200～300 m，时间间隔1～3 h。伴随上层风速垂直切变和阵风特性。湍流能谱的计算结果表明了大尺度涡旋对边界层湍流微结构的影响。     

地震荷载下莫高窟围岩动态损伤特性研究

本以敦煌莫高窟为研究对象，阐述了地震荷载下洞窟围岩动态损伤的影响因素；采用动力有限元法。从地震动特性入手。分析研究了地震作用对洞窟围岩及其附属构筑物可能造成的损坏，为石窟物地震安全评估及防灾对策研究提供了依据。     

Comparison of the spatial distribution of ground motion between main shocks and strong aftershocks

Using the ground motion attenuation relation, we calculated and compared the effective peak acceleration (EPA) generated by main shocks and their strong aftershocks of 21 earthquake sequences with MS≥7 occurred in Chinese mainland and offing of China during 1966~2002. The result shows that EPA of strong aftershocks usually exceed that of main shock for 76.2% earthquake sequences and EPA of more than 50% strong aftershocks are greatly lar-ger than that of main shocks in large area, which suggests that it is necessary to take damage produced by strong aftershock into account in the probabilistic seismic hazard analysis and the seismic design.     

HD 82943行星系统的2:1共振与稳定性

用直接数值积分方法通过模拟不同的行星构型探讨了HD82943行星系统(由两颗共振的巨行星组成)的长期动力演化,同时,还研究了在相空间的轨道运动.在对系统长达107年数值积分中,发现所有的稳定轨道均与2:1共振相关联.典型地,在相同的时标内,两个共振幅角θ1和θ2同时(或其中之一)存在秤动.由于共振幅角在一定范围内的秤动,因而使两颗行星轨道半长径被约束而表现为规则运动模式.另外,利用分析模型(包含了外行星偏心率e2的因素),还讨论了对于不同取值的e2和相对近星点经度θ时,内行星在相空间的运动,并发现2:1轨道共振对于相对较小的e2以及当θ=0°时易于保持.此外,适中的e2将导致系统的两颗行星进入深度共振状态.再者,分析模型和数值计算的结果吻合得很好,两者都揭示了行星系统的2:1共振结构.