基于TDMA机制的工业无线网时间同步算法的改进与实现

基于TDMA机制的MAC层接入协议在工业控制网络的实时性保证方面具有极大的优势。然而要保证该机制微秒级的时隙调度,网络中所有的节点必须保持时间同步的高精度。针对现有的一些同步算法并不能完全满足这种高精度时间同步要求的问题,在传统的时间同步算法基础上,添加时钟漂移预测与补偿机制,改进得到一种具有同步精度高、能量消耗低等优点的同步算法--ITR(Improved Wireless Sensor Networks Time Synchronization Algorithm Based On TPSN and RBS),并在RouterBOARD493G路由节点上进行实验测试。实验结果表明ITR同步算法的平均同步误差比传统同步算法降低了约52%。     

无线自组网融网同步的实现

无线自组网内节点间的时间同步,是网络正常工作的保证。传统时间同步算法只能实现单一网络内节点的同步,无法在多个网络融合时,实现节点间的时间同步。针对该问题,文章提出一种加入融网策略的时间主从同步算法。为保证融网后的网络最优,文章还提出两种不同的IDLE(空闲)状态节点处理方案。仿真实验表明,该算法能够实现多个网络融网下的节点时间同步,方案二中的IDLE节点处理流程可以降低节点的融网时间。     

分簇式无线传感器网络睡眠调度机制研究

提出了一个容忍节点失效和时间同步误差的簇内睡眠调度算法JCSS(Intra-Cluster Sleeping scheduling),该算法不需要外部的精确时间同步机制,对不同类型的节点采用不同的调度机制,在对时间同步的估计中考虑了误差和更新.仿真实验显示在密集部署的网络环境中,该睡眠调度算法在满足网络传输性能的情况下,相对于无同步的固定时间间隔调度和有同步的固定时间间隔调度,网络生存周期分别提高了16.7%和10.5%.     

分簇型无线传感器网络时间同步机制的研究

提出了一种基于分簇型网络结构的时间同步算法。算法的主要思想是通过在簇建立阶段利用LEACH优化算法优化网络拓扑结构,降低网络的跳数,从而降低了时间同步精度由于跳数增加而导致的误差积累,为时间同步算法提供一个良好的网络结构。在LEACH优化算法中,簇首选取机制融入簇首节点的剩余能量和密度因子,并且提出了助理簇首节点用以均衡簇首节点的能量消耗。同时在时间同步阶段,采用双向时间同步机制和单向广播时间机制。实验仿真证明,提出的时间同步算法降低了网路的跳数,提高了时间同步精度,降低了节点的能量消耗,提高了网路的运行时间,具有一定的实用价值。     

一种低功耗的多跳无线传感网时间同步算法

高精度低功耗的时间同步对于无线传感网络至关重要,文中重点分析了高精度时间同步算法,发现其在多跳网络时间同步过程中由于每跳范围内所有节点均要广播时间同步包,会产生大量的冗余信息。为降低同步功耗,提出了一种新方法,通过调节发射功率,筛选出每一跳范围内的周边节点,使其完成下一跳范围的时间同步,而非周边节点只接受却不发送时间同步包。最后,针对改进的算法在OMNet++上进行了仿真实验,仿真结果表明,改进后的算法能够有效地降低全网能量消耗。     

协同作战系统的时间同步

协同作战中需要高精度的时间同步将各站点在同一时间获得的信息融合,从而获得精确的敌方目标态势图来作出相应的对策。结合传统算法TPSN中的同步封包交换及FPST中的根节点动态选取,设计在无GPS授时状态下,协同作战系统中适用的时间同步算法及具体的同步方案。保证了同步网络的健壮性及伸缩性,其理论上可达到的同步精度符合协同作战的需求。     

基于IEEE1588协议的精确时钟同步算法改进

本文详细分析了IEEE1588时钟同步的基本原理,并在此基础上给出一种改进的时间同步方法.该改进的时钟同步算法针对网络传输路径的不对称性引入加权因子,用一定时间窗内的主从时钟偏差样本的算术平均值而不是直接利用主从时钟偏差来调整从时钟,并根据算法的状态改变时间窗N的大小,同时利用方差阈值滤波的方法过滤跳变过大时钟偏差测量值,保证同步算法的稳定性.最后给出Alcatel-Lucent TSS5R系统在实验室的时间性能实验结果.实验结果表明TSS5R时钟同步具有稳定的性能,同步精度达到亚微秒级,可满足PTN产品高精度时钟同步的要求.     

无线躯体传感器网络中低能耗的时间同步算法

时间同步是无线躯体传感器网络(WBSN)的一项支撑技术.文章针对WBSN能源有限的问题,提出了一种改进的时间同步算法.该算法结合基准节点单向广播机制和成对双向消息传递机制,在保证一定同步精度的前提下,减少消息传递次数,降低通信开销,达到了低能耗的要求.最后进行仿真验证了算法性能.     

水下传感器网络时间同步技术综述

 时间同步是传感器节点协同工作的基础.水下传感器网络由于采用水声通信方式,具有不同于陆地无线传感器网络的特点,为时间同步算法研究带来了新的挑战.论文首先说明同步问题与同步算法的形式化定义,然后讨论水下传感器网络不同于陆地传感器网络的特点,并指出相关特点对于同步问题的影响;接着综述陆地传感器网络同步算法的研究进展,分析相关算法用于水下环境的不足;进而介绍水下传感器网络同步算法的研究进展,并通过仿真实验完成了相关算法的性能对比;最后总结水下传感器网络时间同步的关键问题,指出进一步的研究方向.     

分布式POS时间同步算法及软件设计

分布式POS是一种基于惯性/卫星组合技术的柔性基线多节点高精度时空测量系统,是多任务航空遥感载荷高精度成像的关键装置。为了实现分布式POS系统高精度数据融合,该文设计了分布式POS数据采集以及数据融合的时间同步算法,设计分布式POS传递对准算法,编写分布式POS数据处理电路软件,并对算法进行车载实验验证。实验结果表明,分布式POS时间同步算法实现了分布式POS各节点位置、速度、姿态信息的高精度测量。     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.