循环倍率对动力和液体燃料多联产系统的电与蒸汽自平衡影响分析

本文以煤气化(240万吨/年)动力,液体燃料(甲醇,醋酸,醋酐)多联产系统(串联式)为研究对象,分析了循环倍率对系统动力输出、蒸汽、液体燃料产量的影响;确定了可满足具有不同优先级的目标、达到系统动力和蒸汽自平衡的循环倍率、燃气轮机选型等关键单元和系统参数。     

两种新型芴类衍生物的三光子吸收特性研究

研究了两种新型芴类衍生物9，9_二（2_乙基已基）_2，7_二咔唑_9H_芴（简记为DCZF）和9 ，9_二（2_乙基已基）_2，7_二（2_（4_甲氧基）苯_2，1_乙烯基）芴（简记为BMOSF）在N ，N_二甲基甲酰胺（DMF）中的线性吸收和单光子荧光行为，并用脉冲宽度为38ps，重复 频率为10 Hz的1064 nm Nd：YAG脉冲激光研究了两种化合物的三光子吸收性质.结果表明： 两种新材料的最大线性吸收峰分别位于330和380nm，吸收区域覆盖了270—420 nm波段. 两种化合物的荧光带位于蓝_紫区，中心波长为369和442 nm，都具有较小的斯托克斯位移. 化合物DCZF和BMOSF的三光子吸收系数分别为γ_DCZF=678×10^{- 20} cm3/W²和γ_BMOSF=592×10^-20 cm³/W². 同时， 两种新材料还表现出明显的三光子吸收光限幅效应，当入射光强分别为8和6GW/cm²时，非线性透过率分别达到30%和45%. 关键词： 芴类衍生物 三光子吸收 光限幅 非线性透过率     

Performance enhancement on mechanical and electrical effects for on-line fiber-optic bending loss measurement

For an automatic testing of the fiber bending loss parameter, we proposed an on-line fiber optic bending loss measurement system. Many impact factors from the supporting systems, free space coupling alignment, external spatial perturbation device and the other automatic testing systems may degrade the on-line fiber-optic bending loss measurement system. We reduce those impact factors and show the mechanical and electrical improvement in this paper. The accuracy can be improved by 3–5 dB for the proposed on-line bending loss measurement system. Development of an on-line fiber-optic bending loss measurement system can provide a fast-checking solution for jump-line quality improvement on fiber-from-the-desk (FFTD) access network.     

一种大功率窄脉冲半导体激光器测试台的研制

大功率窄脉冲半导体激光器主要光电性能参数为:输出峰值光功率、阈值电流、正向电压、上升时间、峰值波长、光谱半宽、半强度角.根据激光制导系统对大功率窄脉冲激光器参数的特殊测试要求,研制一种大功率窄脉冲激光器测试平台,将小型化大功率激励器功放模块、大范围可调DC-DC模块、信号源板、激光器座、光学准直镜集成在一个平台上,与峰值功率计、光谱仪、CCD摄像机等仪器配合,可测出大功率窄脉冲激光器的峰值功率、峰值波长及波长随温度变化的漂移特性、发光芯均匀性等参数.介绍了大功率窄脉冲激光器测试台的特点,并对测试结果作了论述.     

无人值守变电站电力设备音频监测及故障诊断系统

针对智能变电站的无人值守需求及现有故障诊断系统的不足,提出一种电力设备音频监测及故障诊断系统。根据变电站电力设备音频信号信噪比较低的特点,采用具有强鲁棒性的梅尔频率倒谱系数作为判断音频信号异常的特征参数,在此基础上根据音频特征构成多样本观测序列,并采用隐马尔科夫模型进行故障诊断,通过对比对数似然估计概率的输出值确定故障类型。该方法具有实时性较强的优势,也避免了现有故障诊断方法要求较大样本容量的缺陷。实验结果表明,该故障诊断系统具有较高的识别率和鲁棒性。     

The effect of high power airborne ultrasound and microwaves on convective drying effectiveness and quality of green pepper

The effectiveness of hybrid drying based on convective drying with application of ultrasound and microwave enhancement is the main subject of the studies. The drying kinetics, energy consumption as well as the quality aspect of green pepper is analysed. It was shown that hybrid drying methods shorten significantly the drying time, reduce the energy consumption and affect positively the quality factors. Each of the analysed aspects depend on combination of the convective-ultrasound-microwave drying programs. Besides, based on the drying model elaborated earlier by one of the authors, the effects of ultrasound on convective drying assessed by such phenomena as “heating effect”, “vibration effect” and “synergistic effect” are presented.     

Theory of noise in a kilo-Hz cascaded high-energy Yb-doped nanosecond pulsed fiber amplifier

A theoretical analysis of noise in a high-power cascaded fiber amplifier is presented. Unlike the noise theory in low power communication, the noise of a high power system is redefined as the leaked output energy between pulses with coherent beat noise uncounted. This definition is more appropriate for high power usage in which the pulse energy receives more attention than the pulse shape integrity. Then the low power pre-amplifying stages are considered as linear amplification and analyzed by linear theory. In the high-power amplification stages, the inversion is assumed to recover linearly in the time interval between pulses. The time shape of the output pulse is different from that of the input signal because of different gains at the front and back ends of the pulse. Then, a criterion is provided to distinguish the nonlinear and linear amplifications based on the signal-to-noise ratio （SNR） analysis. Then, an experiment that shows that the output SNR actually drops off in nonlinear amplification is performed. The change in the noise factor can be well evaluated by pulse shape distortion.     

利用Ag@SiO_2纳米粒子等离子体共振增强发光二极管辐射功率的数值研究

金属纳米粒子利用其局域表面等离子体共振效应(LSPR),可以增强附近荧光分子的自发辐射速率,因而在光学传感、光电器件等领域中具有潜在的应用价值.金属纳米粒子的LSPR与其自身的材料、形状、尺寸以及周围环境介质密切相关,这影响着纳米粒子在具体器件中的应用.本文利用三维时域有限差分法,研究了相同体积的球形、椭球形、立方形与三棱柱形银纳米粒子对薄膜发光二极管辐射功率的影响;计算了不同形状银纳米粒子对偶极子光源辐射功率和薄膜器件光出射强度的增强,并结合LSPR效应讨论了辐射功率变化的物理机理.研究结果表明:银纳米粒子自身形状尖锐程度的增加有利于提高LSPR的共振强度;同时纳米粒子的形状影响了LSPR共振电场与薄膜器件中偶极子辐射电场之间的耦合作用,其中立方形纳米粒子因为能实现最强的耦合作用而对器件的辐射功率增强最大.在此基础上进一步讨论了不同薄膜材料对LSPR共振及光源辐射功率的影响,发现较高的材料折射率有利于增强金属纳米粒子的LSPR与器件的耦合作用,从而改善发光二极管性能.     

激光诱导击穿光谱脉冲激光功率锁定的研究

激光诱导击穿光谱(laser-induced breakdown spectroscopy,LIBS)在煤质在线监测方面展现了突出的应用前景和研究价值。针对该技术在实际应用中会由于脉冲激光功率起伏导致的长期测量稳定性差的问题,建立了闭环负反馈式脉冲激光功率锁定装置,采用激光功率负反馈信号控制和锁定Nd∶YAG激光器输出功率。实验研究了不同分光比例脉冲激光器锁定在设定输出功率,同一分光比例激光器锁定在不同输出功率以及长时间运行时的功率锁定。结果表明,不同的分光比例对激光输出功率的锁定效果影响不大,分光比例越小,稳定速度越快;同一分光比例实现激光脉冲功率不同预设值的锁定以及在长时间运行时,采用此装置进行功率锁定后,激光输出功率处于预设区间内,RSD值由自由运行时的2.4%降低至1.1%。     

分数阶傅里叶变换结合高峰均比抑制算法对CO-OFDM系统的影响分析

针对相干光正交频分复用系统中出现的高峰值平均功率比问题,提出分数阶傅里叶变换与高峰值平均功率比抑制算法相结合的方法.计算表明:随着分数阶傅里叶变换阶数的减小,信号的峰值平均功率比逐渐降低;与抑制算法结合后可进一步降低系统的峰值平均功率比,并解决抑制算法影响系统性能的问题.从结合的兼容性、抑制高峰值平均功率比效果及改善引入抑制算法后对系统的负面影响三方面进行仿真分析,结果表明:采用选择性映射算法与分数阶傅里叶变换结合后,旋转因子同为4时,峰值平均功率比高于6.6dB的概率较单一选择性映射算法低104;选取高峰值平均功率比抑制情况相近时,结合算法的时间复杂度比单一选择性映射算法降低了8倍;采用限幅算法与分数阶傅里叶变换结合的仿真情况也较单一限幅算法有很大提高,表明该算法结合的兼容性良好.