A performance predictor of beamforming versus time-reversal based far-field wireless power transfer from linear array

For far-field wireless power transfer (WPT) in a complex propagation environment, a time-reversal (TR) based WPT that can overcome the drawbacks of conventional beamforming (BF) by taking advantage of multipath has been recently proposed. However, due to the WPT performance of BF and TR depending on the complexity of the propagation environment, the performance prediction between BF versus TR would be required. We present a detailed and generalized analysis of the recently proposed performance metric referred to as the peak received power ratio (PRPR) for linear array-based WPT. Here, the effectiveness of PRPR is verified via measurement for free space and indoor scenarios. The results demonstrate that PRPR is directly related to the complexity of the propagation environment and the corresponding power transmission capability of BF and TR. That is, the higher the complexity, the greater the value of PRPR and TR outperforms BF with higher peak power given the same average transmit power and vice versa. The mode decision between BF and TR based on PRPR potentially promises efficient far-field WPT even in a dynamic propagation environment.

Earthquake dynamics constrained from laboratory experiments: new insights from granular materials

The traction evolution is a fundamental ingredient to model the dynamics of an earthquake rupture which ultimately controls, during the coseismic phase, the energy release, the stress redistribution and the consequent excitation of seismic waves. In the present paper we explore the use of the friction behavior derived from laboratory shear experiments performed on granular materials at low normal stress. We find that the rheological properties emerging from these laboratory experiments can not be described in terms of preexisting governing models already presented in literature; our results indicate that neither rate–and state–dependent friction laws nor nonlinear slip–dependent models, commonly adopted for modeling earthquake ruptures, are able to capture all the features of the experimental data. Then, by exploiting a novel numerical approach, we directly incorporate the laboratory data into a code to simulate the fully dynamic propagation of a 3–D slip failure. We demonstrate that the rheology of the granular material, imposed as fault boundary condition, is dynamically consistent. Indeed, it is able to reproduce the basic features of a crustal earthquake, spontaneously accelerating up to some terminal rupture speed, both sub– and supershear.

ANALYZING THE ROAD NETWORK STRUCTURE OF TANG-TIBET ROAD AND BUILDING A SPATIAL INFORMATION SYSTEM FOR ITS TIBET SECTION

Since the Tang Dynasty (618–907 AD), the Tang-Tibet Road has been the only way from inland China to Qinghai and Tibet, and even to other countries such as Nepal and India. It ties and bonds various ethnic groups and regions, integrates cultural memories and cross-cultural communication achievements from ancient times to the present, and witnesses the dynamic propagation of the culture. Affected by the environment, climate, and wars, Tang-Tibet Road was often impossible to travel on or through intermittently during its progressive development in history. Routes and lines of each of its sections changed from time to time; eventually, an ancient road network was formed, consisting of one trunk road, two subsidiary roads in the north and south, several branches, and scattered auxiliary routes separated from the system, among which there were both outward-oriented international passages and inward-oriented passages. Nonetheless, research on Tang-Tibet Road is insufficient at the current stage. Regarding the problems summarized based on the review of the research situation, the present work probes deeper into the network structure of Tang-Tibet Road. How historical corridor is generated and evolved is understood from a regional perspective. In particular, strategies to design a space information system for the Tibet section of Tang-Tibet Road are explained to promote the exploration and use of cultural heritages in Tibet, in an effort to preserve these heritages while developing Tibet’s society and economy.

ITDPM: An Internet Topology Dynamic Propagation Model Based on Generative Adversarial Learning

Network information propagation analysis is gaining a more important role in network vulnerability analysis domain for preventing potential risks and threats. Identifying the influential source nodes is one of the most important problems to analyze information propagation. Traditional methods mainly focus on extracting nodes that have high degrees or local clustering coefficients. However, these nodes are not necessarily the high influential nodes in many real-world complex networks. Therefore, we propose a novel method for detecting high influential nodes based on Internet Topology Dynamic Propagation Model (ITDPM). The model consists of two processing stages: the generator and the discriminator like the generative adversarial networks (GANs). The generator stage generates the optimal source-driven nodes based on the improved network control theory and node importance characteristics, while the discriminator stage trains the information propagation process and feeds back the outputs to the generator for performing iterative optimization. Based on the generative adversarial learning, the optimal source-driven nodes are then updated in each step via network information dynamic propagation. We apply our method to random-generated complex network data and real network data; the experimental results show that our model has notable performance on identifying the most influential nodes during network operation.