Controllable Kerr nonlinearity with perfect transparency in the existence of spontaneously generated coherence

We investigate the Kerr nonlinearity of a V-type three-level atomic system where the upper two states decay outside to another state and hence spontaneous generated coherence may exist. It is shown that dark state and hence perfect transparency present under certain conditions. Meanwhile, the Kerr nonlinearity can be controlled by manipulation of the decay rates and the splitting of the two excited states. Therefore, enhanced Kerr nonlinearity without absorption can be obtained under proper parameters.

An in vitro biomolecular breadboard for prototyping synthetic biological circuits

Biomolecular circuit engineering is critical for implementing complex functions in vivo, and is a baseline method in the synthetic biology space. However, current methods for conducting biomolecular circuit engineering are time-consuming and tedious. A complete design-build-test cycle typically takes weeks' to months' time due to the lack of an intermediary between design ex vivo and testing in vivo. In this work, we explore the development and application of a "biomolecular breadboard" composed of an in-vitro transcription-translation (TX-TL) lysate to rapidly speed up the engineering design-build-test cycle. We first developed protocols for creating and using lysates for conducting biological circuit design. By doing so we simplified the existing technology to an affordable ($0.03/uL) and easy to use three-tube reagent system. We then developed tools to accelerate circuit design by allowing for linear DNA use in lieu of plasmid DNA, and by utilizing principles of modular assembly. This allowed the design-build-test cycle to be reduced to under a business day. We then characterized protein degradation dynamics in the breadboard to aid to implementing complex circuits. Finally, we demonstrated that the breadboard could be applied to engineer complex synthetic circuits in vitro and in vivo. Specifically, we utilized our understanding of linear DNA prototyping, modular assembly, and protein degradation dynamics to characterize the repressilator oscillator and to prototype novel three- and five-node negative feedback oscillators both in vitro and in vivo. We therefore believe the biomolecular breadboard has wide application for acting as an intermediary for biological circuit engineering.

腐蚀石英光栅为分光元件的激光照明系统研究(英文)

利用腐蚀法制作的石英光栅作为分光元件，将其应用拓展到激光景观工程领域中，产生了全新的激光景观效果．给出了一种适用于室外复杂环境用于激光景观照明系统中的光栅分光原理、制作工艺过程等，发展了采用光栅分光元件产生多种不同激光景观照明效果的控制系统，并与利用高速扫描振镜实现的激光照明系统的景观效果进行了比较．

Study on Frequency Coherence Properties of Light Beams

This paper presents a new concept of frequency coherence in the frequency-time domain to describe the field correlations between two lightwaves with different frequencies. The coherence properties of the modulated beams from lightwave sources with different spectral widths and the modes of Fabry-Wrot (FP) laser are investigated. It is shown that the lightwave and its corresponding sidebands produced by the optical intensity modulation are perfectly coherent. The measured linewidth of the beat signal is narrow and almost identical no matter how wide the spectral width of the beam is. The frequency spacing of the adjacent FP modes is beyond the operation frequency range of the measurement instruments. In our experiment, optical heterodyne technique is used to investigate the frequency coherence of the modes of FP laser by means of the frequency shift induced by the optical intensity modulation. Experiments show that the FP modes are partially coherent and the mode spacing is relatively fixed even when the wavelength changes with ambient temperature, bias current and other factors. Therefore, it is possible to generate stable and narrow-linewidth signals at frequencies corresponding to several mode intervals of the laser.

Collective excitations in coupled quantum wells

The dielectric response of a modulated three-dimensional electron system composed of a periodic array of quantum wells with weak coupling and strong coupling are studied, and the dispersions of the collective excitations and the single particle excitations as functions of wave vectors are given. It is found that for the nearly isolated multiple-quantum-well case with several subbands occupation, there is a three-dimensional-like plasmon when q(z)=0 (q(z) is the wave-vector component in the superlattice axis). There also exist intersubband collective excitations in addition to one intra-subband mode when q(z) not equal 0. The intra-subband mode has a linear dispersion relation with q(//) (the wave-vector component perpendicular to the superlattice axis) when q(//) is small. The inter-subband modes cover wider ranges in q(//) with increasing values of q(z). The energies of inter-subband collective excitations are close by the corresponding inter-subband single-particle excitation spectra. The collective excitation dispersions show obvious anisotropy in the 2D quantum limit. The calculated results agree with the experiment. The coupling between quantum wells affects markedly both the collective excitations and the single particle excitations spectra. The system shows gradually a near-three-dimensional electron gas character with increasing coupling. Copyright (C) 1996 Published by Elsevier Science Ltd

Intelligent control of avalanched photodiode to get optimal state

To improve the sensitivity of our laser radar system, we provided a set of control method for APDs (Avalanched Photodiodes) based on single-chip computer together with the circuits dealing with noise and temperature. It adjusts the voltages intelligently and maintains the APD's optimal working status.

移动机器人激光全局定位系统的算法研究

介绍了一种新型的移动机器人激光全局定位系统。重点讨论了结构化环境中移动机器人的全局定位方法 ,提出了一种新的基于最小二乘法的迭代搜索定位算法。全方位移动机器人平台上进行的定位实验 ,证实了该算法的有效性。

基于Vega Prime的多水下机器人视景仿真系统的设计与实现

介绍了一套多水下机器人三维视景仿真系统。该系统采用虚拟现实技术，利用虚拟仿真软件VegaPrime 与Visual C++.NET 2003 混合编程实现三维视景仿真。它主要用于海洋环境的模拟和多水下机器人运行时的位姿更新、碰撞检测、环境效果及各种特效的实时显示。此外，它还具有响应各种输入/输出设备的功能和通过人性化图形界面接口与用户进行交互的功能。

自主移动机器人激光全局定位系统研究

本文介绍了我们研制开发的一种用于自主移动机器人的激光全局定位系统 ,重点描述了该系统的硬件结构和工作原理 ,介绍分析了定位算法 .文章最后介绍了该定位系统在实验室条件下所进行的实验 .实验结果表明 :该系统具有较高的定位精度和抗干扰能力 ,是自主移动机器人理想的定位工具 .

激光拼焊生产线定位误差分析及其控制

对激光拼焊生产线板材定位精度进行了分析与研究。详细介绍了该系统定位装置的组成及定位原理。通过对板材自身直线度误差、定位销定位误差和对中运动误差的分析,建立了激光拼焊生产线板材定位误差模型。根据系统定位机构特点提出了过盈量作用机制来提高定位精度,通过对前后侧压紧力F1、F2以及过盈量I这3个主要参数的优化,在全自动激光拼焊生产线上实现良好的板材定位精度。对比试验验证了采用过盈量作用机制能有效减小板材定位误差,提高焊接质量。

金属粉末激光成形系统的研究

为了实现功能零件金属粉末激光快速成形的制备,研究开发了一套金属粉末激光成形系统。系统基于模块化设计思想,主要包括5个组成部分。每个模块既具备各自的特定功能,又相互协调来统一完成功能零件快速成形制备,而且系统具备高度柔性和自动控制的特点,使得操作与运转简单易行。

激光拼焊错边产生与预测建模方法

错边是评定激光拼焊质量的一个非常重要的指标,薄板构件错边的控制是激光拼焊中一个难题。针对国内首条全自动激光拼焊设备,对错边的产生以及控制方法进行了深入研究,经过大量试验确定了影响错边大小的几个主要因素,板材自身物理变形、压紧力大小与均匀性、压紧横梁变形、支撑底板平面度误差以及焊接变形的影响。通过分析以上因素对错边的影响以及各个因素之间相互关系,建立了错边预测的数学模型。试验验证了模型的正确性,从而为确定错边产生原因,提高焊接质量提供了一个有效的理论指导。

PLC在长焊缝激光拼焊系统中的应用

介绍了长焊缝激光拼焊系统的工作原理和控制要求。针对长焊缝激光拼焊的难点,提出了焊缝塑性成形原理,采用碾压轮对板材焊缝进行碾压预处理提高定位精度。阐述了牵引电机同步控制原理和碾压轮力控制原理。详细介绍了该系统的组成和工作原理,确定了以三菱PLC为核心的长焊缝激光拼焊的控制系统,说明了其硬件组成、软件设计和控制系统的抗干扰措施。

基于PLC的激光拼焊生产线控制系统设计

本文介绍了基于PLC的激光拼焊生产线控制系统。分析了激光拼焊生产工艺过程,针对激光拼焊生产过程中多工作单元相互协调和工业过程复杂等特点,开发了基于三菱PLC的控制系统,介绍了系统的软硬件设计方法。该系统能够完成上料、定位、压紧、焊接、检测、下料以及废料处理功能,实现了激光拼焊生产线的全自动化,具有较高的安全性和稳定性。

A Recurrent Cooperative/Competitive Field for Segmentation of Magnetic Resonance Brain Imagery

The Grey-White Decision Network is introduced as an application of an on-center, off-surround recurrent cooperative/competitive network for segmentation of magnetic resonance imaging (MRI) brain images. The three layer dynamical system relaxes into a solution where each pixel is labeled as either grey matter, white matter, or "other" matter by considering raw input intensity, edge information, and neighbor interactions. This network is presented as an example of applying a recurrent cooperative/competitive field (RCCF) to a problem with multiple conflicting constraints. Simulations of the network and its phase plane analysis are presented.