雾化式几何光学演示仪

使用肥皂液显示光路,由于液体的重力限制了教具的尺寸,演示效果不佳.利用雾化的方式使光路可视化,设计了雾化几何光学演示仪.设计了立体光路,通过激光光源、类平行光源、立体光源和F光源的转换,能够演示初中物理几何光学的所有实验.     

快速光固化3D打印的探究与实现

在光固化3D打印技术的基础上,搭建了基于投影仪的快速、一体化的光固化3D打印装置.自制了可见光响应的光固化树脂,并对其性质进行了吸收和红外光谱的表征.借鉴CT断层扫描原理,通过构建3D模型,使用投影仪将该3D模型每个截面以环绕方式投影至光固化树脂上,使光固化树脂聚合形成具有3D立体形貌的打印成品.该打印方案打印速度快,成品一体化性强,打印仪器简单,成本低.     

立体磁场演示实验组合教具

为了能真实、直观地演示出各种磁体周围空间的磁力线分布情况,我们制作了一套“立体磁场演示实验组合教具”,收到了很好的效果。一、器材及装置 1.透明水槽两个一个为长12cm、宽5cm、高10cm,一个为长12cm、宽8cm、高10cm,可用厚3mm的玻璃用强力胶或环氧树脂粘制,     

基于广义正交迭代算法的立体视觉定位

提出了一种新的基于广义正交迭代算法的立体视觉定位.该算法通过提取CenSurE局部特征和相应的U-SURF描述符,采用SAD方法进行子像素立体匹配,并利用U-SURF描述符匹配进行前后帧图像特征跟踪.在RANSAC框架下对匹配点进行3D-3D运动估计获得了运动参量的初始值.由于3D-3D运动估计使3D点集间欧式距离误差最小,而3D特征点坐标受噪音影响很大,因此运动估计误差也较大.本文把广义正交迭代算法应用到立体视觉定位方法中,得到使立体相机目标空间共线性误差最小的运动估计参量,由于共线性误差比3D-3D运动估计算法中的共点误差受噪音影响更小,从而大大较少了运动估计误差.仿真实验和户外真实实验表明：本文算法获得了较高的计算准确度、鲁棒性和实时性,优于传统方法.     

基于立体像素匹配的图像重构技术研究

为了解决目前全景成像技术中分辨率低的问题,提出了一种新的基于3D场景立体像素光线映射的全景图像计算机重构技术.在全景成像技术中,3D场景的每个立体像素点经全景成像系统的编码系统分别映射在一定区域的多个体元素图像的不同像素点上.在计算机重构全景图像时,根据逆光学路径原理,提出了从立体像素映射到的体元素图像区域中提取对应立体像素的多个2D像素点来重构全景图像,使重构的全景图像最大分辨率可达到传统成像方法图像分辨率的N倍（N为映射区域面积）.提出的立体像素的匹配技术大大提高了重构的计算机全景图像分辨率.     

对《自感现象实验的改进》的商榷

本刊2011年第10期刊登了《自感现象实验的改进》一文．在实验改进方案一“用‘通电自感’电路演示通、断电自感现象”中,提出用如图1（原文图3,下同）所示电路演示通、断电自感现象．笔者按文中内容操作,使用图1电路进行的通电自感实验,不能观察到原文描述的“D1滞后于D2正常发光”的演示效果．     

基于窗截取的立体元图像阵列快速生成

集成成像需要从不同角度记录三维(3D)物体的空间信息,采用计算机生成时,计算量大、时间长。针对这一问题,提出窗截取的立体元图像阵列快速生成方法。模拟真实透镜阵列的结构,建立采样模型,根据显示平台光学参数计算得出虚拟3D物体对应每个虚拟透镜元中的图像,即立体元图像,然后采用窗截取的方式生成立体元图像阵列。改变采样点和窗函数可以生成任意孔径任意排列结构的立体元图像阵列。实验搭建基于LED的集成成像显示平台,设计了与LED匹配的方形、六边形、圆形孔径的透镜阵列,选取不同类型的3D模型对比立体元图像阵列的计算时间和立体显示效果,结果表明,在不改变立体图像质量的前提下,当立体元图像的分辨率高于透镜阵列的采样率时,本文方法速度更快。     

基于广义正交迭代算法的立体视觉定位

提出了一种新的基于广义正交迭代算法的立体视觉定位.该算法通过提取CenSurE局部特征和相应的U-SURF描述符,采用SAD方法进行子像素立体匹配,并利用U-SURF描述符匹配进行前后帧图像特征跟踪.在RANSAC框架下对匹配点进行3D-3D运动估计获得了运动参量的初始值.由于3D-3D运动估计使3D点集间欧式距离误差...     

基于旋转镜法的低成本3D成像装置

利用高速旋转的平面镜将图像投射向空间的不同位置,人眼观察时由于存在视觉残留效应,就可以观察到3D投影成像.本文基于旋转平面镜法设计并制作了包含投影装置、反馈装置和配套的软件系统的低成本高分辨率和广观察范围的三维立体投影成像系统,实现了3D投影仪器的驱动和简单3D视频的制作.     

驻波实验中一个经常出现的错误

对驻波演示实验中出现的立体驻波的原因及特点进行分析,并提出改进实验的建议.     

基于Unity 3D的霍尔效应实验虚拟仿真平台设计与实现

基于Unity 3D设计了霍尔效应实验虚拟仿真平台.该平台利用3ds Max构建三维模型,并将生成的FBX文件导入Unity 3D资源管理器,使用C#语言编写脚本,控制相应模型实现各种状态的动态响应,在Windows平台上运行实现霍尔效应实验.该虚拟仿真实验平台可激发学生的兴趣,提高学生的实验技能,改善教学效果,同时,解决了目前实验教学中普遍存在的硬件资源不足、仪器设备易损坏等诸多困扰.     

The process of energy transfer between excited sodium atoms

Two experiments were carried out to test a process proposed by Allegrini et al. as a viable explanation of the fluorescence from high lying levels which is observed when sodium vapor is illuminated by resonance radiation. In the first experiment a cell with sodium vapor was illuminated by a cw dye laser tuned to the 3S → 3P transition, and the linewidth and lineshape of the fluorescence from the 3D → 3P transition were measured. In the second experiment the cell was illuminated by two pulsed lasers, one tuned to the 3S → 3P resonance and the second well off resonance with this transition. The photoionization current was measured, as was the fluorescence intensity from the 6S → 3P and 5D → 3P transitions. We conclude that the Allegrini process does not significantly contribute to the populations in the 5D, 6S and 3D states.     

Effects of the approximations of light propagation on quantitative photoacoustic tomography using two-dimensional photon diffusion equation and linearization

Quantitative photoacoustic tomography (QPAT) employing a light propagation model will play an important role in medical diagnoses by quantifying the concentration of hemoglobin or a contrast agent. However, QPAT by the light propagation model with the three-dimensional (3D) radiative transfer equation (RTE) requires a huge computational load in the iterative forward calculations involved in the updating process to reconstruct the absorption coefficient. The approximations of the light propagation improve the efficiency of the image reconstruction for the QPAT. In this study, we compared the 3D/two-dimensional (2D) photon diffusion equation (PDE) approximating 3D RTE with the Monte Carlo simulation based on 3D RTE. Then, the errors in a 2D PDE-based linearized image reconstruction caused by the approximations were quantitatively demonstrated and discussed in the numerical simulations. It was clearly observed that the approximations affected the reconstructed absorption coefficient. The 2D PDE-based linearized algorithm succeeded in the image reconstruction of the region with a large absorption coefficient in the 3D phantom. The value reconstructed in the phantom experiment agreed with that in the numerical simulation, so that it was validated that the numerical simulation of the image reconstruction predicted the relationship between the true absorption coefficient of the target in the 3D medium and the reconstructed value with the 2D PDE-based linearized algorithm. Moreover, the the true absorption coefficient in 3D medium was estimated from the 2D reconstructed image on the basis of the prediction by the numerical simulation. The estimation was successful in the phantom experiment, although some limitations were revealed.

     

Gradient- and Sensitivity-Enhanced TOCSY Experiments

A pulsed field gradient version of the sensitivity-enhanced 2D TOCSY experiment is proposed which yields high-quality spectra with improved sensitivity and a minimum of two scans pert₁increment. For rapid acquisition of 1D TOCSY spectra, the 1D DPFGSE–TOCSY experiment was modified to include phase-encoded multiple-selective excitation followed by a simple spectral editing. Combination of these two building blocks is used in a sensitivity-enhanced 2D analog of the 3D TOCSY–TOCSY experiment which provides an efficient tool for resolving severely overlapped signals of oligomers in short experimental time.     

New (15)N NMR exchange experiments for the unambiguous assignment of (1)H(N)/(15)N resonances of proteins in complexes in slow chemical exchange with free form

The potentialities of a 2D proton-detected heteronuclear exchange experiment to assign the nitrogen and amide proton resonances in a uniformly (15)N-enriched macromolecule involved in a complex, starting from the free form assignments, are demonstrated on a protein-DNA complex. This 2D experiment is further extended to a 3D experiment in the case of severe superpositions.     

三维NMR谱

３ＤＮＭＲ谱是２ＤＮＭＲ谱附加一个时间周期扩展而成，３ＤＮＭＲ共振峰的重叠降低，并且灵敏度与常规的２ＤＮＯＥＳＹ实验大体相当，采集３ＤＮＭＲ数据组所需时间太长，因此迄今为止，该方法的实际应用只局限于那些浓度相当高的样品。尽管目前还十分费时，但很可能３ＤＮＭＲ不久即可成为常规的ＮＭＲ技术。     

基于数字显微全息技术的相位光栅结构测量

以相位光栅为实验对象,开展了基于数字显微全息技术的相位物体三维显微结构信息的再现研究.在Mach-Zender透射式实验系统的基础上,分别采用显微物镜和无透镜放大方式,对相位光栅进行放大,以提高系统横向分辨率.在显微物镜放大系统中,菲涅耳近似数值再现算法与双波长技术相结合,抑制主要系统噪音,获得相位光栅的显微结构三维分布.在无透镜放大数字显微全息系统中,分别利用菲涅耳近似法和卷积方法再现原始物波前,并提出相减法消除系统主要球面误差,获得相位光栅的深度信息.实验结果与Veeco干涉仪测试结果比对表明,光栅周期和深度结构与干涉仪测试数据相符.     

Application of three-dimensional magnetic resonance image registration for monitoring hip joint diseases

The purpose of this study was to estimate the accuracy of a method in which three-dimensional (3D) magnetic resonance (MR) volume registration is used for monitoring hip joint disease. Data were analyzed using a normalized cross-correlation (NCC) algorithm involving a user-selected 3D box including the proximal femur. Most of the femoral head was not included in the 3D box because it can become deformed during the course of disease. The accuracy of registration around the femoral head was evaluated using five phantoms and clinical MR data of 17 patients with hip joint disease. In the phantom experiment, registration accuracy was evaluated using four fiducial markers attached to the femoral head. In the experiment using clinical data, registration accuracy was evaluated using a landmark in the femoral head. The registration accuracy in the phantom and clinical experiment was 0.43+/-0.18 mm (S.D.) and 1.12+/-0.46 mm (S.D.), respectively. The former is a value less than half the minimum dimension of a voxel (1.25 x 1.25 x 1.0 mm). Although the latter is slightly larger than the minimum dimension of a voxel, actual errors would be smaller because of the uncertainty in landmark localization. In conclusion, the present method based on an NCC algorithm can be used to accurately register serial MR images of the femoral heads with an error on the order of a voxel. We believe that this method is sufficiently accurate for monitoring hip joint diseases.     

A high-resolution (13)C 3D CSA-CSA-CSA correlation experiment by means of magic angle turning

It is shown in this paper that a previously reported 90 degrees sample flipping (13)C 2D CSA-CSA correlation experiment may be carried out alternatively by employing constant slow sample rotation about the magic angle axis and by synchronizing the read pulse to 13 of the rotor cycle. A high-resolution 3D CSA-CSA-CSA correlation experiment based on the magic angle turning technique is reported in which the conventional 90 degrees 2D CSA-CSA powder pattern for each carbon in a system containing a number of inequivalent carbons may be separated according to the isotropic chemical shift value. The technique is demonstrated on 1,2,3-trimethoxybenzene in which all of the overlapping powder patterns that cannot be segregated by the 2D CSA-CSA experiment are resolved successfully by the 3D CSA-CSA-CSA experiment, including even the two methoxy groups (M(1) and M(3)) whose isotropic shifts, confirmed by high-speed MAS, are separated by only 1 ppm. A difference of 4 ppm in the principal value component (delta(33)) between M(1) and M(3) is readily obtained.     

New N NMR Exchange Experiments for the Unambiguous Assignment of H/N Resonances of Proteins in Complexes in Slow Chemical Exchange with Free Form

Thepotentialities of a 2D proton-detected heteronuclear exchange experiment to assign the nitrogen and amide proton resonances in a uniformly ¹⁵N-enriched macromolecule involved in a complex, starting from the free form assignments, are demonstrated on a protein–DNA complex. This 2D experiment is further extended to a 3D experiment in the case of severe superpositions.