Phase-matching analysis of four-wave mixing induced by modulation instability in a single-mode fiber

Four-wave mixing induced by modulation instability in a single-mode fiber is analyzed from the phase-matching point of view. For the two-channel transmission, a method is proposed to select the four-wave-mixing-induced sidebands, which is based on the proper use of a continuous-wave and a pulse as light sources. We find that a mass of sidebands are generated in the modulation instability resonance region, and the power of the sideband increases with not only the peak power of the pump pulse but also the continuous-wave power which acts as a seed. The research will provide guidance for fiber communication and sensing systems using wavelength division multiplexing technology.

The Control Technology Research of the Z-source Three-phase Four-bridge Arm Inverter

Z-source inverter can boost the voltage of the DC-side, allow the two switches of the same bridge arm conducting at the same time and it has some other advantages. The zero-sequence current flows through the fourth leg of the three-phase four-leg inverter so the three-phase four-leg inverter can work with unbalanced load. This paper presents a Z-source three-phase four-leg inverter which combines a Z-source network with three-phase four-leg inverter. The circuit uses simple SPWM modulation technique and the fourth bridge arm uses fully compensated control method. The inverter can maintain a symmetrical output voltage when the proposed scheme under the unbalanced load.

Phase dispersion of Raman and Rayleigh-enhanced four-wave mixings in femtosecond polarization beats

Based on color-locking noisy field correlation in three Markovian stochastic models, phase dispersions of the Raman- and Rayleigh-enhanced four-wave mixing （FWM） have been investigated. The phase dispersions are modified by both linewidth and time delay for negative time delay, but only by linewidth for positive time delay. Moreover, the results under narrowband condition are close to the nonmodified nonlinear dispersion and absorption of the material. Homodyne and heterodyne detections of the Raman, the Rayleigh and the mixing femtosecond difference-frequency polarization beats have also been investigated, separately.

Phase grating in a doubly degenerate four-level system

In this paper, we suggest a doubly degenerate four-level system, in which the transition takes place between the hyperfine energy 52S1/2 F = 1 and 52P3/2 F = 2 in rubidium 87 D2 line, for studying atomic phase grating based on the cross-Kerr and phase conjugation effects. The phase grating with high efficiency can be obtained by tuning phase shift Ф between the coupling and probe field, when the coupling intensity is much stronger than the strength of probe field. Under different coupling intensities, a high diffraction efficiency can be maintained. A new and simple way of implementing phase grating is presented. However, in such an atomic system, two main limitations must be taken into account. First, the independence between steady state probe susceptibility and the coupling intensity, when the population decay rate is larger than the Rabi frequency of the coupling field, cannot result in diffraction grating; second, the sample to be prepared should not be too long.

经络腧穴学课程“三段四相”创新教学改革

针对经络腧穴学课程的学习内容庞杂、基础知识缺乏临床应用、考核形式单一,以及学生的专业学习能力急需培养等问题,教学团队积极开展以学生为中心的“三段四相”课程教学改革设计与实践。“三段实施”即线上自主探索、线下任务驱动、课后交流应用;“四相整合”为线上与线下混合式教学、课程思政融入日常教学、基础课程渗透临床应用、课堂学习延伸与课外拓展。“三段四相”模式结合了丰富的线上学习资源、通畅的讨论答疑渠道、多维的评价体系,促成经络腧穴学的教学改革进一步深化。

the phase-dependent gain without inversion in a Doppler broadened open four-level system

It is shown that in a Doppler broadened open N-type four-level atomic system with spontaneously generated coherence （SGC）, the gain without inversion （GWI） is very sensitive to the variation of the relative phase between the probe field and the driving field; the atomic exit rate （R0） and the ratio （S） of the atomic injection rates have a considerable modulation effect on the phase-dependent GWI. GWI first increases and then decreases with R0 increasing; in a certain value range of S, GWI increases monotonically with S increasing; by adjusting the values of R0 and S, in an open system a much larger GWI can be obtained than in the corresponding closed system [2011 Phys. Rev. A 83 043805]. The modulation effects of R0 and S on the phase-dependent GWI in the case with the counter-propagating probe and driving fields are stronger than those in the co-propagating case, GWI in the co-propagating case is much larger than that in the counter-propagating case.

基于双闭环控制的三相四线制逆变器控制研究

三相四线制逆变器具有更好的不平衡负载驱动能力,被广泛用于不间断电源等领域。对于这种离网模式下的逆变器而言,通常使用电压电流双闭环控制模式对输出进行控制。提出一种无需坐标变换的电压电流双闭环控制,实现输出三相之间完全解耦。由于准比例谐振(Quasi Proportional Resonance,QPR)控制对交流信号的控制效果更好,因此电压外环采用QPR控制,电流内环采用比例控制。实验证明了所提控制方法的有效性。

宽增益高效率级联式四开关Buck-Boost LLC变换器

为了解决变频控制的桥臂共用型四开关Buck-BoostLLC级联变换器磁性元件设计和优化困难的问题,提出一种二次侧为特殊全桥整流结构的级联式四开关Buck-Boost LLC变换器。通过控制二次侧开关管的交叠导通时间以拓宽变换器的电压增益。该变换器可根据不同的输入电压范围工作在交叠模式和整流模式;在不改变变换器参数的条件下将增益显著提高,能够适应更宽范围的输入电压,同时保持了变换器较高的工作效率。在两种工作模式的基础上,采用移相控制使变换器所有开关管实现零电压导通(ZVS),二极管实现零电流关断(ZCS)。结合状态平面轨迹分析法,对定频控制的级联式四开关Buck-Boost LLC变换器进行模态分析,并推导两种工作模式下的输入-输出表达式和开关管的软开关实现条件。最后,通过研制一台70~280 V输入、240 W/28 V输出的实验样机,验证了理论分析的正确性。

Modulation of atomic exit and injection rates on the phase-dependent gain without inversion in a Doppler broadened open four-level system

It is shown that in a Doppler broadened open N-type four-level atomic system with spontaneously generated coherence (SGC), the gain without inversion (GWI) is very sensitive to the variation of the relative phase between the probe field and the driving field; the atomic exit rate (R0) and the ratio (S) of the atomic injection rates have a considerable modulation effect on the phase-dependent GWI. GWI first increases and then decreases with R0 increasing; in a certain value range of S, GWI increases monotonically with S increasing; by adjusting the values of R0 and S, in an open system a much larger GWI can be obtained than in the corresponding closed system [2011 Phys. Rev. A 83 043805]. The modulation effects of R0 and S on the phase-dependent GWI in the case with the counter-propagating probe and driving fields are stronger than those in the co-propagating case, GWI in the co-propagating case is much larger than that in the counter-propagating case.

备战巴黎奥运会周期我国男乒主要竞争对手技战术能力监控与分析

采用文献资料法、录像观察法、四段指标评估法、经典技术效益值评估法、数理统计法,对我国男乒队5位主要竞争对手共20场比赛的技战术能力进行监控与分析,旨在为中国男乒队备战巴黎奥运会提供参考。研究结论:张本智和的发球结合快攻打法特点鲜明,发球轮能力优于接发球轮;林昀儒的接发球技战术体系较为全面,在接抢段的得分效果最佳,接发球轮能力优于发球轮;雨果变化多端的发球旋转特点鲜明,中远台的强强对抗能力较为突出,接发球轮发挥极不稳定,发球轮能力优于接发球轮;奥恰洛夫的发球轮和接发球轮发挥均不突出,尤其在相持阶段的技战术体系运用不合理,战术灵活性较差;张禹珍的抢攻意识较强,发球抢攻为主要得分手段与技战术实施,多数在前4板内便分出胜负,相持阶段的能力为弱势阶段,发球轮能力优于接发球轮。

川蜀“衷中参西”妇科流派的“三期四步”法诊治求嗣患者的验案举隅

随着三胎政策开放,我国面临的生育形势逐渐严峻。针对目前不孕夫妇求嗣的问题,川蜀“衷中参西”妇科流派总结出“简便廉效”的不孕“三期四步”诊疗方案,强调四步排查不孕因素,三期适时辨证治疗,中西医结合,以达助孕之目的。

基于三相四桥臂电机系统架构的车载锂电池自加热系统

为解决锂电池在低温环境下输出功率降低与放电容量衰减的问题,提出了一种基于三相四桥臂电机系统架构的车载锂电池自加热系统,通过加热电池使其脱离低温状态。在逆变器中引入第四桥臂,并与车载驱动电机三相星型绕组中性点连接,形成三相四桥臂电机系统架构。结合上述电机系统架构,建立电池、电机系统及电池自加热系统等效数学模型。分析电池发热机理及开关频率对电池温升速率的影响,并结合零序电压矢量设计高频电流滞环控制策略。实验结果证明,该系统能够实现锂电池在低温环境下的快速自加热功能,脱离低温状态。

宽带卫星IP通信网络中数字调制解调技术研究

针对宽带卫星网络之间互连的协议(Internet Protocol,IP)通信网络解调过程中受到非线性通信信道影响,出现信道失真,导致通信信道误码率高的问题,提出宽带卫星IP通信网络中数字调制解调技术。利用I/Q偏压进行数字式调制,避免正交型时引起的信道间干扰。通过星座图调制信号,使其满足恒包络特性,获取星座图向量。求解调制码元中各位元的对数似然比,利用基于通道特征的解调方法,解调振幅畸变和相位畸变的星座图。根据获取的星座图星座点坐标,构建通信信道参数估计模型。使用最小二乘法估计信道参数向量修正的星座图并进行解调,使用四相移相键控解调差分检测方式修正信号幅频,达到更平稳的通信效果。由解调性能实验分析结果可知,该技术能够使解调曲线趋于一条直线,达到频域均衡的目的,且误码率最小为10-5 B,可实现通信网络的高效准确解调。

《三因极一病证方论》中天干方组方思路及应用

天干方是陈无择所创,首载于《三因极一病证方论》,是以运气理论为指导,以五行亢害承制规律为依照,运用药物四气、五味来治疗和预防岁运太过或不及而导致的人体已出现或可能出现的病证的10首方剂。其制方参照气味相和、阴阳动态平衡、五脏苦欲补泻、五行制化原则,针对岁运太过或不及,各有制方法度。治疗目的在于以偏纠偏,恢复人体气化的动态平衡。在应用时要注意识运气、观体质、辨病证,应用范畴涵盖岁运太过或不及致病和治未病。

“四关三风”穴针刺对脑卒中急性期吞咽障碍患者血清BDNF、SP、DA、5-HT及NGF的影响研究

目的:明确“四关三风”针刺治疗脑卒中急性期吞咽障碍的临床疗效,并分析其对患者血清中脑源性神经营养因子(BDNF)、P物质(SP)、多巴胺(DA)、5-羟色胺(5-HT)和神经生长因子(NGF)含量的影响。方法:选取在广州中医药大学第一附属医院神经内科病房进行住院治疗的100例卒中后急性期吞咽障碍患者,通过使用随机数字表法对所有纳入患者进行随机分组,分为对照组和治疗组,每组患者50例。两组均给予脑卒中常规治疗,除常规治疗外,对照组患者进行吞咽功能训练,治疗组在对照组基础上进行“四关三风”针刺治疗,1次/d,6 d为1个疗程,共治疗2个疗程。分别在治疗前及治疗后进行疗效评价,采用标准吞咽功能量表(SSA)、改良吞咽能力评价量表(MMASA)进行吞咽功能评定,并检测血清中BDNF、SP、DA、5-HT及NGF的含量,进行临床疗效分析。在中风两个月时采用SSA量表进行随访。结果:与治疗前比较,两周治疗后两组SSA及MMASA评分均明显改善,差异有统计学意义(P<0.05),治疗组SSA评分低于对照组,差异有统计学意义(P<0.05),MMASA评分高于对照组,差异有统计学意义(P<0.05);对照组总有效率为80.0%(40/50),治疗组总有效率为92.0%(46/50),治疗组高于对照组,差异有统计学意义(P<0.05)。与治疗前比较,治疗后两组患者血清BDNF、SP、DA、5-HT及NGF水平显著升高,差异有统计学意义(P<0.05),且治疗组高于对照组,差异有统计学意义(P<0.05)。与治疗结束时比较,卒中两个月时两组SSA评分比较均未见明显变化,差异无统计学意义(P>0.05),但治疗组SSA评分仍较对照组为低,差异有统计学意义(P<0.05)。结论:“四关三风”针刺对卒中后急性期吞咽障碍疗效确切,可显著改善患者的吞咽功能,且远期疗效较好,其机制可能与改善血清中BDNF、SP、DA、5-HT及NGF的含量有关。

何成诗教授从“结者散之”论治肺结节经验

目前肺结节检出率逐年升高,因其病因多样和潜在的恶性,容易导致过度治疗或治疗延误,这使得肺结节的防治成为临床难点、热点。何成诗教授基于“结者散之”理论,认为肺结节核心病机突出一个“结”字,包括气结、痰瘀结、毒结、多邪结;临证处方主张紧扣一个“散”字,包括益气散结、行气散结、化痰祛瘀散结、解毒散结、通络散结。从“结者散之”论治肺结节,紧扣病机,处方灵活,疗效显著,为临床论治肺结节提供了新的思路,值得借鉴。

基于同步采样SDFT的高性能单相锁相环方法研究

在电力机车及动车组的牵引传动控制系统中,网侧变流器通过锁相环获取相位信息并进行精确控制。牵引供电网电压的幅值及频率存在波动,而且网压经常出现严重畸变及含有大量谐波,复杂的电网环境对锁相环性能提出了很高的要求。文章结合同步采样,提出一种基于SDFT的高性能锁相环方法,并通过数字仿真及半实物仿真对所述方法的性能进行了验证。仿真结果表明,与其他几种主流的锁相环对比,该方法稳态锁相精度高,动态响应速度快,并有较强的谐波抑制能力与抗偏置能力,适宜在轨道交通领域应用。

基于0.18μm工艺的低纹波电荷泵电路设计及仿真分析

针对传统电荷泵较低负载能力和较高纹波的问题,基于SMIC 0.18μm CMOS工艺,设计一款四相非交叠时钟的低纹波电荷泵电路。电荷泵主体电路由2个四相时钟控制的全PMOS电荷泵交叉耦合构成;通过优化时序信号输入,降低传输管的导通电阻,减小传输损耗和尖峰脉冲,提高输出效率,同时压缩输出纹波;采用动态衬底偏置结构以消除体效应影响,提高各级升压电路的稳定性,进一步减小输出纹波。仿真结果表明,在电源电压为1.8 V、负载电流为5 mA时,电荷泵输出电压值约为5 V,上升时间约为3.67μs,电压纹波仅为5.4 mV,表明本设计可以满足高可靠堆叠闪存芯片的电压需求。

AT89C52单片机控制的步进电机驱动设计

为实现步进电机在生产应用中的精确控制、防止控制“失步”,并能够根据需求对电机工作状态灵活变动以提升生产效率和质量,本文设计四相步进电机的控制系统。该系统利用电路设计及单片机程序控制,以模拟试验的形式,先对控制电路进行线路设计,然后利用AT89C52单片机进行电机驱动控制的程序编写,具有良好的实用性和便捷性。