基于竞争窗口递减因子自适应调整退避算法

包括IEEE802.11、802.15.4标准在内的许多无线网络协议都采用二进制指数退避机制管理数据的重发。在动态分布式的网络环境中,二进制指数退避算法固定的竞争窗口递减方式难以适应动态变化的网络规模。针对这一问题,提出了一种改进的回退机制,该机制通过引入竞争窗口递减因子,自适应地调整无线节点的等待时间,以实现网络吞吐量的最大化。同时,在算法实现上提出一种启发式算法以跟踪网络中竞争节点数量的改变。在IEEE 802.11DCF协议中以相同的物理层参数进行仿真,结果表明改进算法提高了网络吞吐量,降低了分组平均接入时延。     

An adaptive generation method for electrophoretic display driving waveform design

Electrophoretic display (EPD) technology is attractive when used for reading devices such as e‐paper because of its paper‐like appearance. EPD driving is more complex than other display technologies such as liquid crystal display or organic light emission diode because the driving result of a pixel strongly depends on the initial display state. The particle size and distribution in the EPD film may vary, even if the initial state is the same. Therefore, the display devices vary between different manufacturing batches. Furthermore, different display modes such as videos, pictures or documents need different driving waveforms to achieve an optimal result. EPD manufacturers need to build a customized driving waveform for every manufacturing batch. This is very inconvenient if new applications on EPD are to be developed. And the workload is huge. In this work, an adaptive method is described for automatically creating EPD driving waveforms to fit different conditions. The central idea of this method is generally adjusting the driving time and the voltage state after getting the feedback from a measurement model. In this method, a new driving waveform is used to reduce refresh time and visual flicker. The experimental results show that the proposed approach can automatically and adaptively generate an EPD driving waveform with reasonable quality.     

Letter: Solution‐processed flexible zinc‐tin oxide thin‐film transistors on ultra‐thin polyimide substrates

In this letter, solution‐processed flexible zinc‐tin oxide (Z_0.35T_0.65O_1.7) thin‐film transistors with electrochemically oxidized gate insulators (AlOx:Nd) fabricated on ultra‐thin (30 µm) polyimide substrates are presented. The AlOx:Nd insulators exhibited wonderful stability under bending and excellent insulating properties with low leakage current, high dielectric constant, and high breakdown field. The device exhibited a mobility of 3.9 cm²/V · s after annealing at 300 °C. In addition, the flexible device was able to maintain the electricity performance under various degrees of bending, which was attributed to the ultra‐thin polyimide substrate.     

Multifocus image fusion method of Ripplet transform based on cycle spinning

The curvelet transform can represent images at both different scales and different directions. Ripplet transform, as a higher dimensional generalization of the curvelet transform, provides a new tight frame with sparse representation for images with discontinuities along C² curves. However, the ripplet transform is lack of translation invariance, which causes the pseudo-Gibbs phenomenon on the edges of image. In this paper, the cycle spinning method is adopted to suppress the pseudo-Gibbs phenomena in the multifocus image fusion. On the other hand, a modified sum-modified-laplacian rule based on the threshold is proposed to make the decision map to select the ripplet coefficient. Several experiments are executed to compare the presented approach with other methods based on the curvelet, sharp frequency localized contourlet transform and shearlet transform. The experiments demonstrate that the presented fusion algorithm outperforms these image fusion works.     

QoS constraints-based energy-efficient model in cloud computing networks for multimedia clinical issues

For many applications of multimedia medical devices in clinical and medical issues, cloud computing becomes a very useful way. However, high energy consumption of cloud computing networks for these applications brings forth a large challenge. This paper studies the energy-efficient problem with QoS constraints in large-scale cloud computing networks. We use the sleeping and rate scaling mechanism to propose a link energy consumption model to characterize the network energy consumption. If there is no traffic on a link, we will let it be sleeping. Otherwise, it is activated and we divide its energy consumption into base energy consumption and traffic energy consumption. The former describes the constant energy consumption that exists when the link runs, while the later, which is a quadratic function with respect to the traffic, indicates the relations between link energy consumption and the traffic on the link. Then considering the relation among network energy consumption, number of active links, and QoS constraints, we build the multi-constrained energy efficient model to overcome the high energy consumption in large-scale cloud computing networks. Finally, we exploit the NSF and GEANT network topology to validate our model. Simulation results show that our approach can significantly improve energy efficiency of cloud computing networks.     

Integrated guidance and control design based on a reference model

In this paper, an Integrated Guidance and Control (IGC) algorithm based on a reference model is proposed for a side-jet missile. First, a IGC structure is introduced, incorporating the response characteristics of the missile control loop into the guidance loop. To describe the response characteristics, then a reference model is built. Next, with the back stepping scheme and sliding mode control algorithm, the reference model is adopted to derive a novel guidance law, which contains response parameters of missile control system to formulate the IGC design. Finally, simulations and comparisons with the time-scale separation design and an existing IGC design, are conducted to verify the proposed IGC algorithm. It can be shown that the proposed algorithm performs better against highly maneuvering target in different missile-target initial position and heading scenarios.     

给水管网抗震对策的重要度分析方法研究

针对城市给水管线不同管段在灾后对于管网整体可靠度影响的差异性,为了能够较好地评价不同管段对管网系统连接可靠度的贡献,引入失效概率重要度和关键重要度,建立了基于历史经验方法的管网可靠度及管线失效概率重要度、关键重要度计算模型。实例计算结果表明,该模型计算的管网连接可靠度结果与其他文献方法的计算结果基本一致,验证了模型的合理性、有效性。进而应用该模型计算出各段管线的失效概率重要度、关键重要度,对管线防灾等级划分,给出了管网分割方法与管网震后恢复策略。研究结果为编制给水管网抗震防灾规划、震后管网恢复计划及制定出相应的抗灾应急措施提供依据。     

SMT封装电路板三维在线检测技术

为了检测回流焊接之后SMT( Surface Mount Technology)封装电路板是否存在缺陷,设计并搭建了基于线结构光传感器的SMT封装电路板三维在线检测系统,通过线结构光扫描测量,获取SMT封装电路板表面三维数据。采用双传感器测量技术,有效减少数据丢失;研究了双传感器统一标定技术,可同时实现两个传感器的参数标定和坐标系统一。提出了自适应光条中心提取算法,对反射或散射影响而形成的光条图像噪声具有很好的抑制效果,能够提取准确的光条中心。实验表明系统测量精度可达到0.02 mm。系统测量得到的三维数据,可以为在线检测SMT封装电路板缺陷提供可靠的三维信息。