Theory of Dynamics In-Phase Locking and Quasi-Period Synchronization in Two Mutually Coupled Multi-Quantum-Well Lasers

Abstract We study dynamics in two mutually coupling multi-quantum-well lasers. We carry out theoretical and numerical analysis of synchronization, anti-synchronization, in-phase locking in the two identical lasers but detuning, in detain. It is proved that the coupling level determines stability of the lasers by analyzing the eigenvalue equation. Critical case of locking is discussed via the phase difference equation. Quasi-period and stable states in the two lasers are investigated via varying the current, detuning and coupling level.

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.

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.

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.

中低压直流配电系统的主动保护研究

分布式发电和储能的大量接入、直流负荷的快速增长、电力电子技术的迅速发展,使得直流配电越来越受关注。直流配电系统将会成为未来配电技术的一个重要组成部分。但直流配电保护是直流配电系统快速发展的一个关键问题,亟需深入研究。针对中低压直流配电网中常见的短路、接地、环网、交直流混接、绝缘下降等典型故障类型,该文分析了这些故障的特点和发展过程,并提出了一种基于电力电子技术的主动保护方案,即将直流保护与电力电子变换器有效集成,基于变换器的拓扑结构和运行机理,保护动作逻辑与器件控制逻辑协调配合,实现快速保护和故障自然隔离。该文阐述了直流主动保护的应用场景,分析了主动保护各功能的实现原理和方法,论述了直流配电系统的短路主动保护和接地主动保护,以及直流环网、交直流混接故障的出现机理和基于主动保护的解决方法。最后通过试验进行验证,结果表明,主动保护能够有效可以实现故障的快速切断和准确隔离,从而保障系统的稳定。

Gain-Enhanced Metamaterial Based Antenna for 5G Communication Standards

Metamaterial surfaces play a vital role to achieve the surface waves suppression and in-phase reflection,in order to improve the antenna performance.In this paper,the performance comparison of a fifth generation(5G)antenna design is analyzed and compared with a metamaterial-based antenna for 5G communication system applications.Metamaterial surface is utilized as a reflector due to its in-phase reflection characteristic and high-impedance nature to improve the gain of an antenna.As conventional conducting ground plane does not give enough surface waves suppression which affects the antenna performance in terms of efficiency and gain etc.These factors are well considered in this work and improved by using the metamaterial surface.The radiating element of the proposed metamaterial based antenna is made up of copper material which is backed by the substrate,i.e.,Rogers-4003 with a standard thickness,loss tangent and a relative permittivity of 1.524 mm,0.0027 and 3.55,correspondingly.The proposed antenna with and without metamaterial surface operates at the central frequency of 3.32 GHz and 3.60 GHz,correspondingly.The traditional antenna yields a boresight gain of 2.76 dB which is further improved to 6.26 dB,using the metamaterial surface.The radiation efficiency of the proposed metamaterial-based 5G antenna is above 85%at the desired central frequency.

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.

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.

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.

Broadband ADCP digital signal processing based on CIC filter banks

The acoustic Doppler current profilers(ADCP)as a new type of flow measuring equipment,can measure the flow velocity of the channel section directly.ADCP has the advantages of short measuring time and wide measuring range.The traditional ADCP processing system uses analog method to realize demodulation and filtering,which will introduce extra errors.While digital processing system will greatly increase the computation and slow down the speed of data processing.To solve this problem,an efficient real-time broadband ADCP digital signal processing system is proposed based on the low computational cascade integrator comb(CIC)cascade and interpolated second-order polynomial(ISOP)filter banks.The digital in-phase and quadrature(IQ)demodulation,CIC filter banks,and complex autocorrelation operation steps are cascaded with a pipelined method in the system,which greatly improves the system operating speed while avoiding the high memory occupation of non-real-time systems.

变电站用低压交流环网故障的危害

从理论上对变电站用低压交流系统(以下简称"系统")的各种环网故障进行研究,分析了各种环网故障下系统的特征量以及继电保护、自动切换装置(automatic transfer switching equipment,ATS)的动作情况。得出结论:直接影响系统的环网故障类型会马上引起继电保护动作;间接影响系统的环网故障类型会引起继电保护误动,扩大故障的影响范围;多相环网故障会造成ATS不能正常投切。指出应尽快研究探测交流环网故障的方法。

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.

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.

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.

In—Phase Resonances with Generic Transmission Zeros and Eigenvectors of Hamiltonian in Models of Single Channel Transport

We investigate the phase coherent transport in a single channel system. The theory that the transmission zeros lead to abrupt phase change and in-phase resonances is confirmed numerically in two tight-binding models. After calculating the eigenvalues and eigenvectors of the Hamiltonians we also confirmed that the same symmetry of the eigenvectors also leads to the abrupt phase change and in-phase resonances that equal the transmission zero.

Hepatic steatosis with mass effect:A case report

BACKGROUND Hepatic steatosis is a common radiologic finding.Some imaging inklings are the absence of a mass effect,and there is currently no report of hepatic steatosis with mass effect.CASE SUMMARY A 23-year-old female was admitted due to a liver mass for half a month.No obvious abnormalities were found in physical and laboratory examinations.Ultrasound,computed tomography,and magnetic resonance imaging showed a huge mass between the liver and stomach with a significant mass effect,and the caudate lobe and left lobe of the liver were involved.The signal on T2-and T1-weighted fat-saturated images of the mass was significantly reduced,and the enhanced scan showed inhomogeneous enhancement.Surgical and pathological findings indicated the diagnosis of hepatic steatosis.The operation and re-review of the patient’s images showed that the lesion was supplied by the branch of the hepatic artery.The signal on T1-weighted out-of-phase images of the lesion was lower than on in-phase images,and there was no black rim cancellation artifact around the hepatic steatosis area on T1-weighted out-of-phase images.The dynamic enhancement pattern of the lesion was similar to that of the adjacent normal liver parenchyma.The above characteristics suggested that the lesion was hepatic steatosis.However,in this case,the lesion showed exogenous growth and was mass-like,with an obvious mass effect,which has not been reported previously.CONCLUSION Hepatic steatosis could grow exogenously and has an obvious mass effect.It needs to be distinguished from fat-rich tumors.The T1-weighted in-and out-of-phase images and dynamic enhanced scanning are valuable for differential diagnosis of this lesion.

会展建筑供电节能设计探讨

根据对目前设计的部分会展项目进行的部分资料的收集和整理,对具有明显的周期性及间歇性特征的会展建筑用电负荷,提出可行的两种供电系统节能运行方式:专用变压器配电及低压环网配电设计方案,并对此进行探讨。

峰峰集团通信光纤环网建设

目前峰峰集团公司的通信网采用"点到点"的PDH传输方式,存在设备的稳定性差、寿命较短、不支持环网功能等缺点,由于中国移动、电信、联通等均已大规模建设了基于同步数字体系(SDH)骨干光传输网络,且该通信光纤环网具有兼容性好、功能强、保护强的优点,故峰峰集团亦在建设通信光纤环网。介绍了通信光纤环网建设的原则及其所具有的优缺点,提出建成后的集团公司通信网络结构更为合理,层次划分更为清晰,传输质量更为稳定可靠,从而为集团公司通信网的安全稳定运行打下坚实的基础。

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 ".