扫频光学相干层析成像系统的波数校正与相位测量研究

相位敏感光学相干层析成像(OCT)系统可以用于高灵敏度的相位探测,在细胞分析、材料检测等方面具有重要应用,但扫频光源的不稳定性会影响扫频OCT系统的相位测量精度.本文提出了一种基于马赫-曾德尔干涉仪(MZI)时域相位信息的波数校正方法.利用MZI时域包裹相位的互相关运算确定各采集波数序列的相对偏移量,鉴于时域包裹相位的非严格周期特征,可确定偏移量的大小不受限制.依据相对偏移量对各序列信号进行时域同步,并基于同步后的MZI时域解包裹相位实施待测干涉信号在位相域的等间隔重采样.基于所提出的波数校正方法,实施了各扫频序列波数偏移量的校正,开展了基于位相信息的光程重复性测量实验.结果表明,即使在不稳定扫频光源的前提下,也能获得高精度的相位测量结果.     

多自由度系统自然激励技术的统一模型

结构运行状态下的模态参数提取是结构健康监测系统需要解决的关键问题之一.自然激励技术的提出为大型复杂工程结构运行状态下的模态参数提取提供了一条新的途径.原始自然激励技术给出了单输入白噪声激励下利用结构位移响应的互相关函数进行模态识别的理论模型,对于多输入情况则缺乏相应的理论模型.本文在单输入理论模型的基础上进一步发展了自然激励技术:推导了多输入独立白噪声激励下多自由度系统结构位移响应的互相关函数的解析公式,并分析了它与单输入情况下互相关函数之间的关系;基于此互相关函数定义了一个新函数,证明它含有结构各阶模态信息,可以表达为一系列衰减正弦函数之和,并且各个组分正弦函数的频率等于各阶模态的有阻尼固有圆频率;提出了以新函数为核心的同时适用于单输入和多输入情况的模态识别算法,建立了自然激励技术的统一模型.     

强烈段塞流特征参数测量方法试验研究

通过对单个液塞经过管道上某一测压点时的压力信号进行理论分析,指出了压力波动曲线上的特征点与液塞相对于测压点位置之间的对应关系。根据分析结果,采用单压力信号判断法,求得了强烈段塞流的液塞运动速度、液塞长度等特征参数。与利用双平行电导探针相关法求得的结果比较发现,单压力信号判断法具有测量结果准确、不受流动介质物性限制、不干扰流场、简便实用等优点。     

多级混沌映射变参数伪随机序列产生方法研究

针对单混沌系统因计算机有限精度效应产生的混沌退化问题,提出了一种多级混沌映射变参数伪随机序列产生方法,基于该方法构建的混沌系统较单混沌系统具有伪随机序列周期大,密钥数量多,密钥空间大等优势,所产生的密码具有更高的安全性能.仿真结果表明,该方法在低复杂度条件下可以生成大量具有良好自相关和互相关特性的混沌序列,在安全领域具有良好的应用前景.     

利用脉冲负反馈压缩准分子激光脉冲

分析了准分子激光脉冲在放大过程中的展宽现象。将饱和开关技术应用于放电泵浦激光器放大腔的放大压缩,发展了脉冲负反馈饱和压缩技术。利用该技术在天光一号系统前端LPX-150激光器上成功获得能量100 mJ、脉宽10 ns的脉冲输出,其空间分布均匀性保持在3%以内。这证明该技术可与无阶梯诱导非相干技术联合使用,在保证光束均匀性基础上进行脉冲压缩。     

Multiscaling wavelet analysis of infrared and Raman data on polyethylene glycol 1000 aqueous solutions

Infrared and Raman scattering spectra of aqueous solutions of poly(ethylene glycol) with nominal weight 1000 Da have been collected and analyzed as a function of the water content both in terms of a two-state physical model and in terms of an innovative multiscale wavelet cross-correlation approach. Both the analysis procedures allow to highlight the spectral shape changes occurring when water is added to pure polymer, showing the effectiveness of the wavelet analysis. It is shown that, provided that the pure polymer spectral contribution is subtracted from the aqueous solutions spectra, the shape of the intramolecular O–H stretching band can be reproduced by a superposition of the spectrum of bulk water and of the spectrum of hydration water, i.e., the spectrum relative to the water molecules bonded to the polymer chain. The weight of the bonded-water spectrum changes with concentration furnishing a polymer hydration number value which well agrees with hydration number data, reported in literature, obtained with other techniques. On the other hand, the intramolecular infrared O–H stretching band and the low-frequency Raman spectra, for all the investigated polymeric aqueous solutions, when analyzed through a multiscale wavelet cross-correlation approach reveal that significant spectral changes are registered in the 0.00–0.46 water weight fraction range. Such complementary experimental and analytic findings suggest the picture that when the water content increases, the water molecules saturate the two lone pairs of each oxygen atom of the polymer furnishing a hydration number which agrees with previous determinations and hence supporting the validity of the wavelet approach.     

Compensation of the active-medium dispersion in a semiconductor laser with an external resonator

Measurements of the dispersion parameter (the second derivative of the wave vector with respect to the frequency) of the active waveguide layer of semiconductor lasers operating in the red region of the spectrum (0.65–0.67 μm) were performed. It was revealed that for these lasers the dispersion parameter has a value of (0.13–1.40)·10⁻²⁵ sec²/cm. It is shown that the dispersion of the active medium of a semiconductor laser with an external resonator can be compensated by inserting a quartz-glass rod into the resonator. Reported at the Second International Scientific and Technical Conference on Quantum Electronics, Minsk, November 23–25, 1998. Translated from Zhurnal Prikladnoi Spektroskoii, Vol. 66, No. 5, pp. 707–710, September–October, 1999.     

Estimation of multiple sound source directions using artificial robot ears

Estimating the direction of a sound source is an important technique used in various engineering fields, including intelligent robots and surveillance systems. In a household where a user’s voice and noises emitted from electric appliances originate from arbitrary directions in 3-D space, robots need to recognize the directions of multiple sound sources in order to effectively interact with the user.This paper proposes an ear-based estimation (localization) system using two artificial robot ears, each consisting of a spiral-shaped pinna and two microphones, for application in humanoid robots. Four microphones are asymmetrically placed on the left and right sides of the head. The proposed localization algorithm is based on a spatially mapped generalized cross-correlation function which is transformed from the time domain to the space domain by using a measured inter-channel time difference map. For validation of the proposed localization method, two experiments (single- and multiple-source cases) were conducted using male speech. In the case of a single source, with the exception of laterally biased sources, the localization was achieved with an error of less than 10°. In a multiple-source environment, one source was fixed at the front side and the other source changed its direction; from the experimental results, the error rates on the localization of the fixed and varying sources are 0% and 36.9% respectively within an error bound of 15°.     

On Optical Sensing of Alkali Halide Crystal Surfaces

The surface quality of alkali halide crystals to be used in spectroscopy and as laser components has been sensed using a computer-generated hologram together with digital image processing. FFT and two-dimensional cross-correlation analyses. Surfaces cleaved only or finished to various extents are considered as examples.     

Probing molecular mechanism of inhibitor bindings to bromodomain-containing protein 4 based on molecular dynamics simulations and principal component analysis

ABSTRACT

It is well known that bromodomain-containing protein 4 (BRD4) has been thought as a promising target utilized for treating various human diseases, such as inflammatory disorders, malignant tumours, acute myelogenous leukaemia (AML), bone diseases, etc. For this study, molecular dynamics (MD) simulations, binding free energy calculations, and principal component analysis (PCA) were integrated together to uncover binding modes of inhibitors 8P9, 8PU, and 8PX to BRD4(1). The results obtained from binding free energy calculations show that van der Waals interactions act as the main regulator in bindings of inhibitors to BRD4(1). The information stemming from PCA reveals that inhibitor associations extremely affect conformational changes, internal dynamics, and movement patterns of BRD4(1). Residue-based free energy decomposition method was wielded to unveil contributions of independent residues to inhibitor bindings and the data signify that hydrogen bonding interactions and hydrophobic interactions are decisive factors affecting bindings of inhibitors to BRD4(1). Meanwhile, eight residues Trp81, Pro82, Val87, Leu92, Leu94, Cys136, Asn140, and Ile146 are recognized as the common hot interaction spots of three inhibitors with BRD4(1). The results from this work are expected to provide a meaningfully theoretical guidance for design and development of effective inhibitors inhibiting of the activity of BRD4.