MyShake一个跨界的系统:智能手机用于地震预警

在城市地区发生的大地震可以造成重大人员伤亡,引发社会和经济灾难。地震预警(Earthquake Early Warning,EEW)可以提供秒到分钟的警报,让人们转移到安全区,使工厂停工,车辆减速和刹车。目前世界上只在少数国家使用传统的地震台网和大地测量观测网运行EEW系统。智能手机比传统地震台网更为广泛和普及,它内置了可检测地震的加速度计。我们开发了一种新的测震系统称为MyShake,它利用智能手机内置传感器来收集数据并分析地震。智能手机MyShake系统可以从日常的各种震动中检测到距手机10km或以内的5级地震。这些数据汇集到观测中心,经过一定的算法处理,可以实时测定地震的位置和震级,发出地震预警信息,证明我们的理念是可行的。对没有地震预警系统的区域,MyShake系统可提供地震预警,而对有预警系统的区域,MyShake系统是对原系统预警能力的补充和增强。此外,该系统地震波形记录可以用来提供快速地震烈度图,以评估地震对建筑物的影响,还可以获取地球内部浅层结构图像和地震破裂过程。

OSCILLATION CRITERIA FOR SECOND ORDER NONLINEAR DYNAMIC EQUATIONS WITH p-LAPLACIAN AND DAMPING

This paper concerns the oscillation of solutions of the second order nonlinear dynamic equation with p-Laplacian and damping（r（t）φ（x^△（t））^△＋p（t）φα（x^△α（t）＋q（t）f（xδ（t））=0on a time scale T which is unbounded above. Sign changes are allowed for the coefficient functions r, p and q. Several examples are given to illustrate the main results.

Deep convolutional autoencoders as generic feature extractors in seismological applications

The idea of using a deep autoencoder to encode seismic waveform features and then use them in different seismological applications is appealing.In this paper,we designed tests to evaluate this idea of using autoencoders as feature extractors for different seismological applications,such as event discrimination(i.e.,earthquake vs.noise waveforms,earthquake vs.explosion waveforms),and phase picking.These tests involve training an autoencoder,either undercomplete or overcomplete,on a large amount of earthquake waveforms,and then using the trained encoder as a feature extractor with subsequent application layers(either a fully connected layer,or a convolutional layer plus a fully connected layer)to make the decision.By comparing the performance of these newly designed models against the baseline models trained from scratch,we conclude that the autoencoder feature extractor approach may only outperform the baseline under certain conditions,such as when the target problems require features that are similar to the autoencoder encoded features,when a relatively small amount of training data is available,and when certain model structures and training strategies are utilized.The model structure that works best in all these tests is an overcomplete autoencoder with a convolutional layer and a fully connected layer to make the estimation.

数字经济对跨境服务贸易增值税征管的挑战与应对

国际上对于跨境贸易的增值税,普遍遵循消费地征税原则,实行进口国征税、出口国按照零税率退税的制度,以消除国际间的增值税重复征税。目前,国际上对于什么是跨境服务消费地及如何准确判定消费地,尚无普遍认可的适用原则,特别是在当前数字经济条件下,如何准确界定跨境服务,清晰判定服务的消费地,更是世界公认的难题。本文系统分析了数字经济对跨境服务贸易增值税征管带来的挑战,在充分吸收借鉴代表性国家做法的基础上,试图提出适合我国国情的跨境服务贸易增值税征管方案。

H∞ synchronization of chaotic Hopfield networks with time-varying delay: a resilient DOF control approach

This paper focuses on the issue of resilient dynamic output-feedback(DOF)control for H_∞synchronization of chaotic Hopfield networks with time-varying delay.The aim is to determine a DOF controller with gain perturbations ensuring that the H_∞norm from the external disturbances to the synchronization error is less than or equal to a prescribed bound.A delaydependent criterion for the H_∞synchronization is derived by employing the Lyapunov functional method together with some recent inequalities.Then,with the help of some decoupling techniques,sufficient conditions on the existence of the resilient DOF controller are developed for both the time-varying and constant time-delay cases.Lastly,an example is used to illustrate the applicability of the results obtained.