光载毫米波上变频系统的设计与研究

对光载毫米波(ROF)系统中毫米波副载波的上变频方案进行了理论分析及仿真研究。在中心站端通过30GHz的本地振荡源,采用载波抑制技术得到了差频为60GHz的光载射频信号,即在中心站实现了上变频的处理。该系统不需要在基站设置高频震荡源,大大降低了ROF系统的成本,满足了未来光无线通信系统中不断增长的载波频率的要求。同时,理论分析了中心站上变频的信号产生方法,搭建了仿真系统,结合理论分析结果,验证了该方案产生的ROF信号在光线中的传输性能及传输距离。     

浅谈色觉的数学机制

正常人眼拥有色觉功能,其目的是为了辨识不同的光辐射能谱分布。色觉的生理基础是:在视网膜上具有三类视锥细胞,它们将光信号转换成为使大脑便于分析和处理的神经电信号。由于单个视锥细胞产生的神经电信号只反映光辐射的强度信息,所以光辐射的谱信息(波长分布)须由三类视锥细胞的响应比来反映。以光辐射中的单色辐射及线性连续辐射为辨识对象,构造了光辐射辨识的数学模型。基于该模型,对用三类视锥细胞的响应比来表征光辐射的谱信息这一命题的必要性与完备性进行了理论论证。     

40Gb/s光纤传输单边带归零信号的产生和性能分析

对光的单边带归零信号（SSBRZ）的一种产生方式进行了推导.通过合理设置调制器的偏置电压，使产生的SSBRZ信号的一个边带得到更有效的抑制，而且没有引起光脉冲的变形.对其在普通单模光纤（SMF）40Gb/s传输系统中的传输进行了仿真，并和归零（RZ）信号、载波抑制的RZ（CSRZ）信号的性能相比较，结果表明：在色散完全补偿的单信道传输系统中，SSBRZ的抗非线性能力比RZ、CSRZ强.     

高能电子辐照对束测量系统的影响

在直线感应加速器束参数测量系统实验的基础上,给出了束参数测量系统的实验布局和特点,分析高能电子辐照对直线感应加速器中测量系统电子器件介电性能的影响和变化规律;进一步探讨电子器件介电性能受高能电子辐照后的抑制措施。针对电磁空间干扰情况,主要通过采用光纤传输控制信号的措施,能很好地传输窄脉冲,信号延时抖动小,达到了高速信号的可靠传输要求,利用紧凑嵌入式方法,提高了抗电磁干扰的能力,这样可以更好保护束参数测量电子器件。     

循环侧抑制网络的红外图像预处理FPGA实现研究

在红外成像预处理中,循环侧抑制网络具有很好的增强图像边缘反差、突出边框的功能。由于循环侧抑制网络处理运算的复杂性,如何实时实现循环侧抑制网络的红外图像预处理成为关键问题。根据简化的循环侧抑制网络处理算法,并结合硬件计算特点,提出一种适合于硬件实现循环侧抑制网络的并行处理结构,采用流水线设计方式在FPGA中实时实现。试验证明：该算法在FPGA内具有与视频流同步的实时性,达到了增强反差、突出边框的效果。用于图像目标实时跟踪系统时,极大地提高了目标的跟踪精度和稳定性。     

基于异步延迟采样的光通信性能监测方法

基于异步延迟采样和人工神经网络统计学习提出了一种光通信性能监测方法。通过对高速光信号进行异步延迟采样,获得信号二维幅度直方图,然后提取其中特征参数并对人工神经网络进行训练,最后以人工神经网络的预测输出实现对光信号损伤的监测。构建10 Gb/s非归零码开关键控,40 Gb/s光学双二进制码和归零码差分移相键控光通信仿真系统,并对光信噪比、色散和偏振模色散损伤进行监测。仿真结果表明,所提方法对被监测光信号的速率、码型调制格式透明,可同时准确监测多种并存的传输损伤,损伤参数监测误差小于5%。该方法具有电域处理带宽要求低、采样机制简单的特点,适用于分布式在线光性能监测。     

InGaAs单光子探测器传感检测与淬灭方式

针对InGaAs单光子雪崩光电二极管(SPAD)的光电感应特性,研究了基于门控主动式淬灭的SPAD动态偏置控制和电路实现的策略.采用门控主动淬灭控制可降低淬灭时间,有效抑制暗计数和后脉冲效应.接口感应检测电路采用标准互补金属氧化物半导体(CMOS)工艺进行制造,而SPAD则采用非标准CMOS工艺.利用铟柱互连混合封装工艺实现SPAD与感应接口电路的协同工作.在低温-30?C的条件下,实现了SPAD光触发雪崩电流信号的提取和快速淬灭.研究了感应电阻和临界检测电压对传感检测电性能的影响,并采用简单电路结构实现状态检测,实测得到的SPAD恢复时间、传输延时分别为575,563 ps,淬灭时间为1.88 ns,满足纳秒级精度传感检测应用的需要.     

无线光副载波信号的循环谱分析

以无线光通信中的副载波调制技术为背景,研究了光强调制正交相移键控信号的循环自相关和循环谱密度函数,并对实际测得的信号的循环谱和循环自相关函数进行了分析。结果表明,无线光副载波信号经过大气传输,同时受到了加性白噪声和乘性窄带随机噪声的影响,有限强度的大气湍流并未破坏正交相移键控信号的循环平稳特性。影响接收信噪比的主要因素是有用信号功率与低频噪声功率之差,通过加时间窗的方法可以有效抑制低频噪声的影响,从而提高系统接收信噪比。     

电磁干扰下时间分辨测量系统信号外触发技术

在实验的基础上给出了束参数时间分辨测量系统的实验布局和特点,分析高压电磁干扰对直线感应加速器中时间分辨测量系统外触发性能的影响和变化规律;进一步探讨系统高压电磁干扰后的抑制措施。针对电磁空间干扰情况,主要通过采用光纤传输控制信号的措施,能很好地传输窄脉冲,信号延时抖动小于2ns,达到了高速信号的可靠传输要求,采用嵌入式控制器既解决了抗电磁干扰的要求,也满足了束参数时间分辨测量系统的使用要求。     

束参数瞬态测量在复杂环境中的电磁干扰及兼容设计技术

强流电子束束参数瞬态测量系统在直线感应加速器的复杂电磁环境中会受到强电磁的干扰,主要包括:干扰特性、干扰机理、数学描述、抑制措施、防范措施等,这些干扰既针对电路又针对系统,从而对束参数瞬态测量系统测量的稳定性以及测量数据的有效性都有很大的影响。介绍时间分辨测量系统的原理,分析了瞬态脉冲干扰的成因和抑制方法,给出了束参数测量系统的实验布局和特点,进一步探讨电子器件电性能受瞬态脉冲干扰后的抑制措施,其目的是为了达到减少或消除干扰,破坏干扰信号的传输条件,从而提高整个系统的抗干扰能力及可靠性。通过采用光纤传输控制信号可以很好地传输窄脉冲,减少信号延时抖动,以达到高速信号的可靠稳定传输;利用紧凑嵌入式方法,提高了抗电磁干扰的能力,可以更好保护测量系统电子器件,提高整个系统的抗干扰能力。     

Biological image processing via Chaotic Differential Search and lateral inhibition

In this paper, we propose a hybrid biological image processing approach, which is based on Chaotic Differential Search (CDS) algorithm and lateral inhibition (LI) mechanism. We named this hybrid biological image processing approach as LI-CDS. Differential Search (DS) algorithm is a new bio-inspired optimization algorithm mimicking the migration behavior of an organism, and has been successfully used for solution of coordinate system transformation. The property of chaotic variable is integrated into DS to improve its search strategy so that it can escape from the local optimum. Furthermore, lateral inhibition mechanism, which is verified to have good effects on image edge extraction and image enhancement, is employed to pre-process images involved. In this hybrid biological image processing mechanism, our proposed LI-CDS method incorporates both advantages of chaos theory and lateral inhibition mechanism. Series of comparative experimental results by using LI-CDS, DS, CDS and Particle Swarm Optimization (PSO) demonstrate that the proposed LI-CDS performs better than the other three methods.     

结合空间侧抑制的仿生复眼模型

结合昆虫复眼运动神经具有的空间侧抑制机制,设计了一种新的复眼模型,并使用全硬件方法实现了该模型。与自相关的模拟量模型相比,该模型的数字部分采用触发响应模式,使系统具有很宽的速度测量范围;在此基础上,通过结合空间侧抑制网络,使得模型能够有效地减少背景光强不均匀、不稳定造成的错误判断。由于整个系统是完全实时并行的,所以能够处理高速运动情况。通过实验,验证了系统的可行性。     

Hybrid bio-inspired lateral inhibition and Imperialist Competitive Algorithm for complicated image matching

Bio-inspired intelligent algorithms, such as Particle Swarm Optimization (PSO) and Ant Colony Optimization (ACO), have been applied to solve image matching problems. However, due to high computational complexity and premature convergence problems associated with these methods, they have limitations in defining the global optimal matcher efficiently and accurately. To address these problems, we proposed a hybrid bio-inspired optimization approach, coupling the lateral inhibition mechanism and Imperialist Competitive Algorithm (ICA), to solve complicated image matching problems. With the adoption of the lateral inhibition mechanism, the global convergence of conventional ICA algorithms has been greatly improved. We demonstrate the efficiency and feasibility of the proposed approach by extensive comparative experiments.     

Combined confocal/en face T-scan-based ultrahigh-resolution optical coherence tomography in vivo retinal imaging

Combined confocal scanning ophthalmoscopy/en face T-scan-based ultrahigh-resolution optical coherence tomography (OCT) of the human retina in vivo is reported for the first time to our knowledge. The system uses a superluminescent diode-based broadband source, which gives an axial resolution of 3.2 microm in the retina. We demonstrate acquisition of T-scan-based OCT B-scan and simultaneous confocal/C-scan images of the human retina of large lateral size (covering a field of up to 20 degrees ) at a frame rate of 2Hz.     

Simulated human eye retina adaptive optics imaging system based on a liquid crystal on silicon device

In order to obtain a clear image of the retina of model eye, an adaptive optics system used to correct the wave-front error is introduced in this paper. The spatial light modulator that we use here is a liquid crystal on a silicon device instead of a conversional deformable mirror. A paper with carbon granule is used to simulate the retina of human eye. The pupil size of the model eye is adjustable (3--7mm). A Shack-Hartman wave-front sensor is used to detect the wave-front aberration. With this construction, a value of peak-to-valley is achieved to be 0.086Λ, where Λ is wavelength. The modulation transfer functions before and after corrections are compared. And the resolution of this system after correction (69lp/m) is very close to the diffraction limit resolution. The carbon granule on the white paper which has a size of 4.7μm is seen clearly. The size of the retina cell is between 4 and 10μm. So this system has an ability to image the human eye's retina.     

能量传递制冷机制中激光制冷的最佳泵浦频率和最大制冷效率

在能量传递型激光制冷中,对于非均匀线宽比较窄的情况,引起最大制冷效率的激发光频率不随温度的变化而变化最大制冷效率与温度呈三次暴的关系。对于非均匀线宽比较宽的情况。随着温度的降低,最佳激发光频率与非均匀线形的中心频率差越来越大,并在较低的温度下迅速拉大它们间的距离。由能量传递机制所引起的荧光制冷最大效率也随着温度的降低而越来越低,并在最后趋于零。它们随温度的降低而降低的规律与实验中得到的结论相符合。     

Persistence of structure over fluctuations in biological electron-transfer reactions

In the soft-wet environment of biomolecular electron transfer, it is possible that structural fluctuations could wash out medium-specific electronic effects on electron tunneling rates. We show that beyond a transition distance (2-3 A in water and 6-7 A in proteins), fluctuation contributions to the mean-squared donor-to-acceptor tunneling matrix element are likely to dominate over the average matrix element. Even though fluctuations dominate the tunneling mechanism at larger distances, we find that the protein fold is "remembered" by the electronic coupling, and structure remains a key determinant of electron transfer kinetics.     

Measurements of AIM for Visible Wavelength Based on Individual Eye Model

We measure and calculate the aerial image modulation （AIM） of human retina for visible wavelengths based on the individual eye model. By employing the optical design software ZEMAX, we obtain the modulation transfer function （MTF） of human eye in visible wavelengths. Using CSV-1000 and VAF-1000, the contrast sensitivity function （CSF） and the visual acuity （VA） for the same eye are measured. Then the AIM of human retina could be acquired by the relations between MTF and CSF and between MTF and VA. The AIM of human retina is independent of MTF, and the values of AIM for normal eyes （without retina disease） are similar, so the assembly average for large numbers of normal eyes can be a standard AIM curve, which is helpful for the diagnosis of diseases in the retina system.     

基于抑制性突触可塑性的反馈神经回路兴奋性与抑制性动态平衡

大脑皮层的兴奋性与抑制性平衡是维持正常脑功能的前提, 而其失衡会诱发癫痫、帕金森、抑郁症等多种神经疾病, 因此兴奋性与抑制性平衡的研究是脑科学领域的核心科学问题. 反馈神经回路是脑皮层网络的典型连接模式, 抑制性突触可塑性在兴奋性与抑制性平衡中扮演关键角色. 本文首先构建具有抑制性突触可塑性的反馈神经回路模型; 然后通过计算模拟研究揭示在抑制性突触可塑性的调控下反馈神经回路的兴奋性与抑制性可取得较高程度的动态平衡, 并且二者的平衡对输入扰动具有较强的鲁棒性; 其次给出了基于抑制性突触可塑性的反馈神经回路兴奋性与抑制性平衡机理的解释; 最后发现反馈回路神经元数目有利于提高兴奋性与抑制性平衡的程度, 这在一定程度上解释了为何神经元之间会存在较多的连接. 本文的研究对于理解脑皮层的兴奋性与抑制性动态平衡机理具有重要的参考价值.