混合式P2P系统中基于缓存的多项查询方法研究

首先从混合式P2P网络拓扑结构出发,结合DHT思想,提出了基于DHT的层次化P2P网络模型.其次根据在文档集巨大的情况下,用户提交的查询不可能"面面俱到",实际用来回答查询的文档仅仅是文档集中很小的一部分这一思想,在层次化P2P模型的超级节点中建立了分布式缓存,运用分布式索引与缓存技术,提出一种新的方法来解决多项查询问题.即由多项查询中的某个关键字key,根据hash函数定位到负责该key的超级节点,查询该节点上的分布式索引得到缓存具体存储位置,最终将结果返回给用户,如若缓存中没有所要查询的内容,则广播该查询,同时根据系统中的历史广播查询信息来计算某个待选缓存项的利益值,利益最大的待选项加入缓存.一般针对多项查询的泛洪算法往往会造成巨大的网络信息量,提出的方法牺牲了超级节点上一小部分的存储力,缓解了多项查询造成的网络拥挤现象.同时,基于DHT的层次化P2P模型也具有很好的稳定性,不会因为大量节点的动态加入或者退出而无法进行多项查询.     

ADRC Law of Spacecraft Rendezvous and Docking in Final Approach Phase

This article addresses the high-precision coordinated control problem of spacecraft autonomous rendezvous and docking, which couple the relative position and attitude in the final approach phase. The coupled dynamics equations of the tracking-target spacecrafts is derived by using dual quaternions. Then, a cascade Active Disturbance Rejection Controller is proposed, by which the extended state observer and nonlinear error feedback law is designed, the virtual value on which the actual control volume tracking is calculated to ensure the finite time convergence of the relative position and attitude tracking errors in spite of parametric uncertainties and external disturbances. Finally, numerical simulations are performed to demonstrate that the proposed approaches, which can avoid the coupling effect and restrain the interference, can track the target spacecraft in a relatively short period of time, and the control precision can satisfy the requirements of docking.     

Performance modeling of hyper-scale custom machine for the principal steps in block Wiedemann algorithm

Solving large-scale sparse linear systems over GF(2) plays a key role in fluid mechanics, simulation and design of materials, petroleum seismic data processing, numerical weather prediction, computational electromagnetics, and numerical simulation of unclear explosions. Therefore, developing algorithms for this issue is a significant research topic. In this paper, we proposed a hyper-scale custom supercomputer architecture that matches specific data features to process the key procedure of block Wiedemann algorithm and its parallel algorithm on the custom machine. To increase the computation, communication, and storage performance, four optimization strategies are proposed. This paper builds a performance model to evaluate the execution performance and power consumption for our custom machine. The model shows that the optimization strategies result in a considerable speedup, even three times faster than the fastest supercomputer, TH2, while consuming less power.     

Investigation of fused silica glass etching using C4F8/Ar inductively coupled plasmas for through glass via (TGV) applications

Through glass via (TGV) technology is considered to be a cost effective enabler for the integration of micro electromechanical systems and radio frequency devices. Inductively coupled plasma and Bosch etching process comprise one of the most pervasive methods for through silicon via (TSV) formation. Unfortunately an equivalent process for glass etching remains elusive. In this paper, the influence of plasma etching for fused silica glass were investigated to find the best tradeoff between etch rate and profile of TGVs. The process parameters including bias power, gas flow rate, ratio of etching gases and reaction chamber pressure using Ar/C₄F₈ inductively coupled plasmas were studied. The etching results show that all these three parameters have a significant impact on the etch rate. Furthermore, the adjustment including total flow rate and ratio of Ar/C₄F₈ and chamber pressure can be used to control the via profile. Constant fused silica glass etch rate greater than 1 μm/min was obtained when chiller temperature was 40 °C with etching time of 60 min. The profile angle of TGVs with nearly 90° was also achieved.     

Creating and simulating a realistic physiological tongue model for speech production

Simulation of the tongue has important applications in biomechanics, medical science, linguistics, and graphics. The accuracy of the geometry, intrinsic structure and dynamic simulation of tongue are crucial for these applications. In this paper, we build a 3D anatomically and biomechanically accurate tongue model. For ensuring anatomical accuracy, the tongue mesh model is constructed based on accurate medical data and an interactive muscle marking method for specifying the muscle geometry and fiber arrangement. For ensuring biomechanical accuracy, a nonlinear, quasi-incompressible, isotropic, hyperelastic constitutive model is applied for describing the tongue tissues. Particularly, tongue muscles are additionally endowed with an anisotropic constitutive model, which reflects the active and passive mechanical behavior of muscle fibers. The dynamic simulation results of tongue movements subjected to certain muscle activations are presented and validated with experimental data, indicating the suitability for visual speech synthesis.     

Analysis and improvement of the quantum image matching

We investigate the quantum image matching algorithm proposed by Jiang et al. (Quantum Inf Process 15(9):3543–3572, 2016). Although the complexity of this algorithm is much better than the classical exhaustive algorithm, there may be an error in it: After matching the area between two images, only the pixel at the upper left corner of the matched area played part in following steps. That is to say, the paper only matched one pixel, instead of an area. If more than one pixels in the big image are the same as the one at the upper left corner of the small image, the algorithm will randomly measure one of them, which causes the error. In this paper, an improved version is presented which takes full advantage of the whole matched area to locate a small image in a big image. The theoretical analysis indicates that the network complexity is higher than the previous algorithm, but it is still far lower than the classical algorithm. Hence, this algorithm is still efficient.