Design of Seven-core Photonic Crystal Fiber with Flat In-phase Mode for Yb: Fiber Laser Pumping

We numerically investigate the seven-core photonic crystal fiber (PCF) with the zero dispersion wavelength designed in the range of 1000 - 1080 nm, particularly suitable for the ytterbium-doped fiber laser pumping. Also, the PCFs are well designed for obtaining a flat in-phase mode by carefully adjusting the diameter of inner layer six holes, and the corresponding empirical values of fiber structure are summarized and listed. The variations of inner six holes to the amplitude of in-phase mode are further investigated, and our results show that a better tolerance can be achieved in the fiber structures with lower filling ratio configuration.

On the Sub-Critical Bifurcation of Anti-Phase and In-Phase Synchronized Vortex Shedding Forms

Transition of flows past a pair of side-by-side circular cylinders are investigated by numerical simulations and the bifurcation analysis of the numerical results. Various flow patterns behind the cylinder-pair have been identified by the gap ratio (G) and Reynolds number (Re). This study focus on transition of in-phase and anti-phase vortex shedding synchronized forms. A nested Cartesian-grid formulation, in combination with an effective immersed boundary method and a two-step fractional-step procedure, has been adopted to simulate the flows. Numerical results reveal that the in-phase and anti-phase vortex shedding flows at Re = 100 can co-exist at 2.08 ≤G≤ 2.58. Hysteresis loop with increasing/decreasing G at constant Reynolds number Re = 100 is reported.

Characteristic Surface Oxide Film Cracking Behavior of a Fe-Ni-Cr Alloy under In-phase and Out-of-phase Thermo-mechanical Fatigue

The surface oxide film cracking behavior of Fe-30Ni-20Cr alloy under in-phase and out-of-phase synchronizing thermal cycling with mechanical cycling was studied.Surface oxide film cracking along the grain boundary under in-phase overlapping was creep predominant fracture mechanisms.Strongly induced slip lines preceding were accompanied by the surface oxide film cracking under Out-of phase,and the shear cracking was dominant mode.Negative mean stress could counteract a part of the tensile component of alternative stress,so as to delay the cracking process under in-phase,but positive mean stress overlapping the tensile alternative stress could accelerate the cycling cracking process under out-of-phase.

Single-trial EEG classification using in-phase average for brain-computer interface

Communication signals should be estimated by a single trial in a brain-computer interface.Since the relativity of visual evoked potentials from different sites should be stronger than those of the spontaneous electro-encephalogram(EEG),this paper adopted the time-lock averaged signals from multi-channels as features.200 trials of EEG recordings evoked by target or non-target stimuli were classified by the support vector machine(SVM).Results show that a classification accuracy of higher than 97%can be obtained by merely using the 250–550 ms time section of the averaged signals with channel Cz and Pz as features.It suggests that a possible approach to boost communication speed and simplify the designation of the brain-computer interface(BCI)system is worthy of an attempt in this way.

Conversion of out-of-phase to in-phase order in coupled laser arrays with second harmonics

A novel method for converting an array of out-of-phase lasers into one of in-phase lasers that can be tightly focused is presented.The method exploits second-harmonic generation and can be adapted for different laser arrays geometries.Experimental and calculated results,presented for negatively coupled lasers formed in a square,honeycomb,and triangular geometries are in good agreement.

Bafang Fabric Keep up the World Demin in-phase

From Shanghai to Haining Bafang Weaving Co., Ltd., through China’s busiest high way, we saw the adverts of Bafang Fabric on the side of the road. Upon the arriving in the downtown of Haining, the huge advert of Bafang Fabric attracts your eye --"advertising plus advertising to increase strength, that is, quality, and brand ".

基于MEMS IMU的GNSS RTK/INS紧组合定位分析

本文针对复杂动态的城市环境自动驾驶规模化应用需求,提出惯性单元辅助RTK快速收敛的自动驾驶低成本、高精度定位方法。使用MEMS IMU M39和战术级IMU Pos320,通过对多组实测车载数据进行仿真中断,得到INS位置漂移误差、模糊度收敛时间、模糊度固定正确性指标,再对无惯导辅助、M39辅助模糊度固定和Pos320辅助3种情形下的模糊度固定时间和定位精度进行了统计和分析。结果表明,M39在GNSS中断5 s时可辅助RTK实现模糊度瞬时固定,中断时间为10 s时可以将RTK模糊度收敛时间压缩至1/4。MEMS IMU的加入使得RTK模糊度固定错误个数显著下降,10 cm以内高精度定位占比由62.25%提高至98.44%。试验验证了MEMS IMU辅助RTK能够加快模糊度收敛速度,提高了其在自动驾驶导航定位应用中的精度和可靠性。

自旋载体中的超紧组合GNSS接收机跟踪环路设计

自旋载体是全球导航卫星系统接收机的一种典型应用。当全球导航卫星系统载体自旋时,旋转产生的高阶动态将导致传统跟踪环路失锁;全球导航卫星系统与惯性导航系统组合可以有效补偿信号的高阶动态。因此,提出了一种利用惯性导航信息辅助卫星导航信号跟踪的超紧组合导航接收机环路设计方法,并分析了惯性导航信息辅助速率、自旋载体转速和信号载波相位误差之间的关系。通过仿真验证了所提接收机环路结构可以有效解决自旋载体接收机的信号跟踪问题,且相比于卫星导航单系统三阶环路而言,所提超紧组合环路结构可以显著提升自旋载体接收机的定位精度。

制导火箭INS辅助GNSS跟踪环路设计

为提高制导火箭全球导航卫星系统(GNSS)在高动态环境中的稳定跟踪能力,提出一种使用弹上INS辅助GNSS载波跟踪环路的方法,该方法采用INS估计GNSS的多普勒频率信息,控制GNSS跟踪环路中本地信号的载波和码发生器,进而降低高动态环境对GNSS跟踪环路的影响。仿真实验结果表明,该方法不仅能有效减小跟踪环路的相位误差和多普勒频率跟踪误差,而且可提高GNSS在高动态环境中稳定跟踪能力。

基于惯导和无时延滤波器的舰船升沉测量

在利用惯导测量舰船的升沉运动中,针对传统方法设计的高通数字滤波器存在较大的相位滞后误差(即信号处理后的时间延迟误差)问题,提出一种滤波器设计方法:通过先设计传统的无限冲激响应低通滤波器,再采用互补方法将其转换为无相位滞后的高通滤波器,解决了信号时延问题;阐述了舰船升沉测量信号处理过程,即根据舰船上惯导姿态信息和加速度计采样输出,解算并给出天向加速度,通过积分和无时延高通滤波处理,获得升沉运动信息。最后,利用海上舰船试验数据进行验证,结果表明该方法的升沉测量精度提高了一个数量级。

High-performance compensation scheme for frequency-dependent IQ imbalances in OFDM transmitter and receiver

An efficient compensation scheme combining a timedomain Gaussian elimination（GE） channel estimator and a frequency-domain GE equalizer is proposed for orthogonal frequency division multiplexing（OFDM） systems with frequencydependent in-phase and quadrature-phase（IQ） imbalances at both transmitter and receiver.Compared with the traditional least square and least mean square compensation schemes,the proposed compensation scheme achieves the same bit error rate as the ideal IQ branches by using only two training OFDM symbols instead of about 20 OFDM symbols.

采用H_∞滤波器的GPS/INS全组合导航系统研究

根据 H∞ 鲁棒滤波理论 ,提出了基于 H∞ 滤波技术的 GPS/INS全组合导航系统。该系统仅含有位置误差、速度误差和平台误差角 9维状态 ,并利用位置、速度和载波相位观测信息对全部状态进行观测 ,组成全组合导航系统 ,由 H∞ 滤波来提高系统的鲁棒性。对提出的全组合系统进行了动态仿真 ,仿真结果表明 ,该系统结构简单 ,状态估计精度高 ,系统鲁棒性好 。

A new model for life prediction of GH4133 under TMF conditions

Thermal mechanical cyclic strain tests were carried out under in-phase andout-of-phase conditions on a Nickel-base Superalloy GH4133 in the temperature range of 571-823 degC. Based on analyzing the present models of TMF (thermal mechanical fatigue) life prediction, a newmodel for predicting nickel-base superalloy TMF lifetime was proposed. TMF life of superalloy GH4133was calculated accurately based on the new model. Experimental TMF life has been compared with thecalculated results and all results fall in the scatter band of 1.5. The calculating results showthat the new model is not only simple, but also precise. This model will play great roles as lifeprediction of the metal materials and the engineering components subjected to non-isothermal serviceconditions.

Decoupled estimation of frequency-dependent IQI and channel for OFDM systems with direct-conversion transceivers

The in-phase and quadrature-phase imbalance (IQI) is one of the major radio frequency impairments existing in orthogonal frequency division multiplexing (OFDM) systems with direct-conversion transceivers. During the transmission of the communication signal, the impact of IQI is coupled with channel impulse responses (CIR), which makes the traditional channel estimation schemes ineffective. A decoupled estimation scheme is proposed to separately estimate the frequency-dependent IQI and wireless channel. Firstly, the generalized channel model is built to separate the parameters of IQI and wireless channel. Then an iterative estimation scheme of frequency-dependent IQI is designed at the initial stage of communication. Finally, based on the estimation result of IQI, the least square algorithm is utilized to estimate the channel-related parameters at each time of channel variation. Compared with the joint estimation schemes of IQI and channel, the proposed decoupled estimation scheme requires much lower training overhead at each time of channel variation. Simulation results demonstrate the good estimation performance of the proposed scheme.

Optimization of Mapping Rule of Bit-Interleaved Turbo Coded Modulation with 16QAM

Optimization of mapping rule of bit-interleaved Turbo coded modulation with 16 quadrature amplitude modulation (QAM) is investigated based on different impacts of various encoded bits sequence on Turbo decoding performance. Furthermore, bit-interleaved in-phase and quadrature phase (I-Q) Turbo coded modulation scheme are designed similarly with I-Q trellis coded modulation (TCM). Through performance evaluation and analysis, it can be seen that the novel mapping rule outperforms traditional one and the I-Q Turbo coded modulation can not achieve good performance as expected. Therefore, there is not obvious advantage in using I-Q method in bit-interleaved Turbo coded modulation.

基于载波相位平滑伪距技术的GPS/INS组合导航

给出了基于载波相位平滑伪距技术的GPS/INS组合导航的公式并进行了误差分析。用算例对该算法进行验证,结果表明:如果GPS周跳较少或不发生周跳,基于载波相位平滑伪距技术的GPS/INS组合导航的精度较伪距紧组合导航有较大的提高;反之,精度提高不显著。

SPE-LC-MS／MS检测不同水产品组织中四环素类药物残留的方法研究

采用固相萃取(SPE)结合液相色谱-串联质谱(LC-MS/MS)技术,建立了不同水产品组织中四环素类药物残留的测定方法。样品通过含EDTA的弱酸性MCI缓冲盐提取,醋酸铅沉淀蛋白,并结合正己烷和固相萃取(SPE)同时净化技术,以液相色谱-串联质谱多反应监测(MRM)离子模式定性,工作曲线法定量分析。结果表明,被测组分在对应范围内线性关系良好;方法的检出限为1.00μg/kg,定量限为5.00μg/kg;以空白鳗、鲤、海参和河豚鱼作为基质进行回收率评价,四环素、土霉素、金霉素和强力霉素等4种四环素类药物在不同加标浓度时的回收率范围为70%~100%,相对标准偏差皆小于10%(n=6)。将所建立的方法应用于实际养殖鳗中四环素类药物残留的分析,结果表明,该方法灵敏度高、重现性好,适用于不同水产生物样品中四环素类药物残留的同时检测。

低成本车载GPS/INS组合导航速度更新算法

针对低成本GPS/INS组合导航系统无法观测得到多普勒值获得速度更新的问题,介绍了相邻历元伪距差分、载波相位差分以及附加辅助信息对INS进行速度更新的过程,并对这几种算法进行了分析和比较。实测算例表明,在市区车载环境中载波相位差分易受到外界干扰,周跳频繁,速度更新不可靠;伪距差分尽管也会受到干扰,但是影响不大,速度更新精度较高;而附加辅助信息速度更新精度较低,但是这种算法在GPS不可用时,仍然能够进行速度更新。

离心萃取-紫外光谱法测定可乐饮料中咖啡因的含量

建立了一种快速、准确,溶剂消耗少的测定可乐饮料中咖啡因含量的紫外光谱分析方法,并将大相比离心萃取应用于仪器分析样品微制备过程。该方法将2mL三氯甲烷直接加入装有100μL可乐饮料的离心试管中,离心萃取3min后取清液在278nm处进行紫外光谱测定,操作简单、快速,重现性好,相对标准偏差小于3%;在3种可乐饮料中加入不同浓度的咖啡因标准溶液,回收率在96.6%～106.1%之间。线性范围为0.5～30mg/L,相关系数为0.9999;检出限为0.001mg/L。将本方法应用于市售可乐饮料中咖啡因含量分析,取得了满意的结果。

EFFECTS OF STRAIN RATIO ON THERMAL-MECHANICAL CYCLIC STRESS-STRAIN RESPONSE AND FATIGUE LIFE IN DS SUPERALLOY DZ125

The effects of strain ratio on thermal-mechanical cyclic stress-strain response and fatigue life in DS superalloy DZ125 have been studied by performing tests at various strain ratio experiments, under strain-controlled and temperature cycling from 550 to 1000℃. It is shown that thermal-mechanical cyclic stress-strain response behavior not only depend on magnitude of strain, and temperature-loading phase angle, but also strain ratio. Fatigue life at strain ratio Rε=-0.3 is longer than that of strain ratio Rε=-1.0, under in-phase thermal-mechanical loading. However, Fatigue life at strain ratio Rε=-0.3 is shorter than that of strain ratio Rε=-1.0, under out-of-phase thermal-mechanical loading. The thermal-mechanical fatigue (TMF) damage model was discussed. Results of fractography show that fatigue, creep and oxidation damage always occur during TMF. The main damage mode depends on loading wave, strain ratio and magnitude of strain.