三级质量-弹簧-阻尼系统的特性分析

利用控制理论中的Lyapunov方法对三级质量-弹簧-阻尼系统进行稳定性分析,并用信号流图对系统的可控性做了讨论,结果表明此系统为不稳定系统。     

一种用于谐波检测过程中消除谐波背景方法的研究

针对可调谐半导体激光吸收光谱（TDLAS）连续检测技术中,二次谐波背景信号存在漂移的现象,提出改变激光器中心电流实时提取背景信号,以消除连续检测过程中背景信号的漂移对浓度反演的影响。依据波长调制理论推导了二次谐波背景信号的理论表达式,并分析了实际情况下影响二次谐波背景信号的因素。给出激光器在不同工作温度时电流和输出光强度之间的关系曲线,并分析了改变激光器中心电流实时提取背景信号的可行性。结合背景信号搜索方法设计了基于LabVIEW的背景信号提取流程图。设计以氨气为检测对象的TDLAS实验系统,选取了氨气的吸收谱线以及对应的吸收中心电流。在激光器电流全工作区间内只存在唯一吸收峰的情况下,确定实验中各参数的数值及搜索背景的电流范围。实验结果表明：该方法可实时提取谐波背景信号。结合线性最小二乘法拟合反演可有效地减小检测误差及背景信号对浓度反演精度的影响,提高浓度的检测精度及准确性。在连续检测实验中,反演浓度的标准差由2.688 3降到1.856 1,减小背景信号漂移对检测浓度准确性的影响,提高了连续检测的准确性。     

能够突破标准量子极限的原子双数态的制备研究

所有经典的双模(两路径)干涉仪的相位测量精度都受限于1/N/(1/2)(其中N为参与干涉测量的总粒子数),这一极限被称为经典极限或标准量子极限.量子计量学最重要的目标之一是探索如何通过量子纠缠实现超越经典极限的测量精度.双数态是一种能突破经典极限的纠缠态,它由数目相等、不可区分的自旋朝上和朝下(双模)玻色粒子组成.通过光学自发参量下转换或囚禁离子内态的操控手段已实现了不到十个光子或离子的双数态.利用玻色-爱因斯坦凝聚体中原子的自旋混合过程,近年来也能产生多达几千个原子的双数态.但是这样制备的双数态的总粒子数的随机涨落过大,限制了它们的实际应用潜力.最近,我们通过调控原子凝聚体中的量子相变,实现了超过一万个原子的双数态的确定性制备.本文简要综述这一研究进展.     

近红外微弱光信号检测镜头的研制

运用ZEMAX设计了一款大孔径、小畸变微弱光信号检测镜头,与高灵敏近红外CCD图像传感器匹配,实现了对微弱单态氧¹O₂信号的实时、快速、高准确度的检测.检测镜头相对孔径1:0.86,半像高为6.3 mm,光谱范围为1 250~1 290 nm,放大倍率为1X,畸变小于0.1%.运用AutoCAD设计光学系统的机械结构,采用双高斯对称式结构以降低成本,手动聚焦、直插式滤片切换机构方便实验的调节,检测镜头研制成功并在实验中采集到较好的微弱单态氧¹O₂信号.     

WMS的玻璃药瓶内氧气含量检测及其标定方法改进

应用激光波长调制光谱(WMS)技术,建立了一种开放光路短光程检测玻璃药瓶内氧气含量的方法。选择氧气分子位于760.885(13 142.58 cm-1)的吸收谱线,通过多次调试优化了系统相关参数,给出了实时扣背景及实时谱线校正等数据处理的方法和步骤。采集七种不同氧气含量的玻璃药瓶样本,获取相应的二次谐波信号,分别建立二次谐波峰值、半高谱峰面积与浓度的线性回归方程进行定量预测。实验结果表明,其拟合系数分别为0.996 6和0.997 8,后者相比前者的标定方法提高了0.12%。采用完全交互验证的方法来评价两个模型的预测精度,其预测的均方根误差(RMSEP)分别是0.003 1和0.002 0,后者相比前者降低了37.69%。对浓度是4%的气体样品,比较不同时间的20次测量结果,标准差分别为0.002 2和0.001 6,后者相比前者降低了27.3%,同时其测量灵敏度分别为0.198%和0.097%,后者相比前者的灵敏度提高了约51%。证明了该系统及数据处理方法对玻璃药瓶内氧气含量检测是可行的,且利用半高谱峰面积更丰富的幅值信息来反演气体浓度可以降低波峰失真影响,检测精度更高,稳定性更好。     

模型传递用于解析遥感傅里叶变换红外谱图

基于模型传递的原理,建立了一种可对存在背景干扰,谱峰严重混叠的遥感傅里叶变换红外(remote sensing Fourier transform infrared: RS-FTIR)谱图进行解析的方法。分别用4组分气体混合物的EPA红外标准谱图和RS-FTIR谱图,建立校正和预测模型,经过正交信号校正(OSC)处理后,用EPA红外谱图数据所建立的校正模型,对RS-FTIR谱图数据进行预测,得到的丙酮、甲醇、苯和三氯甲烷的均方根预测误差(RMSEP)分别为：0.008 5,0.018 0,0.064 0,0.002 8。未经OSC处理时的RMSEP依次是0.085 6,0.047 9,1.065 3,0.014 2。经优化,支集选择的方法为Kennard-Stone法,OSC在实现过程中循环次数为3时得到的预测结果最好。研究结果表明,该方法能够克服背景和校正模型给RS-FTIR监测大气污染物带来的制约。     

Main Components of Xinjiang Lavender Essential Oil Determined by Partial Least Squares and Near Infrared SpectroscopySCIEI北大核心CSCD

This work was undertaken to establish a quantitative analysis model which can rapid determinate the content of linalool, linalyl acetate of Xinjiang lavender essential oil. Totally 165 lavender essential oil samples were measured by using near infrared absorption spectrum(NIR), after analyzing the near infrared spectral absorption peaks of all samples, lavender essential oil have abundant chemical information and the interference of random noise may be relatively low on the spectral intervals of 7100-4 500 cm(-1). Thus, the PLS models was constructed by using this interval for further analysis. 8 abnormal samples were eliminated. Through the clustering method, 157 lavender essential oil samples were divided into 105 calibration set samples and 52 validation set samples. Gas chromatography mass spectrometry (GC-MS) was used as a tool to determine the content of linalool and linalyl acetate in lavender essential oil. Then the matrix was established with the GC-MS raw data of two compounds in combination with the original NIR data. In order to optimize the model, different pretreatment methods were used to preprocess the raw NIR spectral to contrast the spectral filtering effect, after analysizing the quantitative model results of linalool and linalyl acetate, the root mean square error prediction(RMSEP) of orthogonal signal transformation (OSC) was 0.226, 0.558, spectrally, it was the optimum pretreatment method. In addition, forward interval partial least squares (FiPLS) method was used to exclude the wavelength points which has nothing to do with determination composition or present nonlinear correlation, finally 8 spectral intervals totally 160 wavelength points were obtained as the dataset. Combining the data sets which have optimized by OSC-FiPLS with partial least squares(PLS) to establish a rapid quantitative analysis model for determining the content of linalool and linalyl acetate in Xinjiang lavender essential oil, numbers of hidden variables of two components were 8 in the model. The performance of the model was evaluated according to root mean square error of cross-validation (RMSECV) 9 root mean square error of prediction (RMSEP). In the model, RESECV of linalool and linalyl acetate were 0.170 and 0.416, respectively; RMSEP were 0.188 and 0.364. The results indicated that raw data was pretreated by OSC and FiPLS, the NIR-PLS quantitative analysis model with good robustness, high measurement precision; it could quickly determine the content of linalool and linalyl acetate in lavender essential oil. In addition, the model has a favorable prediction ability. The study also provide a new effective method which could rapid quantitative analysis the major components of Xinjiang lavender essential oil.     

Fiber optical parametric amplifiers in optical communication systems

The prospects for using fiber optical parametric amplifiers (OPAs) in optical communication systems are reviewed. Phase‐insensitive amplifiers (PIAs) and phase‐sensitive amplifiers (PSAs) are considered. Low‐penalty amplification at/or near 1 Tb/s has been achieved, for both wavelength‐ and time‐division multiplexed formats. High‐quality mid‐span spectral inversion has been demonstrated at 0.64 Tb/s, avoiding electronic dispersion compensation. All‐optical amplitude regeneration of amplitude‐modulated signals has been performed, while PSAs have been used to demonstrate phase regeneration of phase‐modulated signals. A PSA with 1.1‐dB noise figure has been demonstrated, and preliminary wavelength‐division multiplexing experiments have been performed with PSAs. 512 Gb/s have been transmitted over 6,000 km by periodic phase conjugation. Simulations indicate that PIAs could reach data rate x reach products in excess of 14,000 Tb/s × km in realistic wavelength‐division multiplexed long‐haul networks. Technical challenges remaining to be addressed in order for fiber OPAs to become useful for long‐haul communication networks are discussed.

     

Accurate frequency atlas of molecular iodine near 532 nm measured by an optical frequency comb generator

An optical frequency comb generator (OFCG) at 1064 nm with a modulation frequency of 2 GHz is developed for an accurate optical frequency link between iodine absorption lines near 532 nm. With the OFCG, we have measured frequency differences between seventeen ¹²⁷I₂ transitions with a measurement uncertainty of about 240 Hz (relatively 4.3×10⁻¹³), which is mainly contributed from the frequency repeatability of iodine-stabilized Nd:YAG lasers. The measured transitions provide an attractive frequency reference network and are excellent candidates for the practical realization of the meter.     

储粮害虫声信号的检测和应用

与传统的储粮害虫检测方法相比,害虫的声测报技术作为一种快速、实用的新方法,正日益受到重视,近年来,这一领域在微电子设备及计算机技术的推动下,取得了很大进展,已由最初在小容器谷物样品中钻蛀为害粮粒害虫声音的技术,发展到目前实仓多点监测储糖害虫声音的微机监控系统,实现了对储糖害虫侵害程度的量化,通过声信号识别害虫种类方面的工作也在进一步的研究中,文章综述了储糖害虫声测报领域的发展历程,最新进展及存在问题。