Echelle dif fraction grating based high-resolution spectrometer-on-chip on SiON waveguide platform

An echelle diffraction grating based high-resolution spectrometer-on-chip on silicon oxynitride (SiON) waveguide platform operated at a wavelength range of 850 nm is demonstrated. The chip comprises 120 output waveguides with 0.25-nm wavelength channel spacing and has a size of only 11 × 6 (mm). The experimental results show that the insertion loss is-14 dB, the measured adjacent channel crosstalk is less than -25 dB, the 3 dB channel bandwidth is < 0.1 nm, and the channel non-uniformity is 3 dB for 56 channels with a wavelength ranging from 838 to 852 nm.     

三维声传播模型BELLHOP3D的信息传递接口并行优化

近些年,我国对海洋不断深入的探索对复杂环境中声场的快速预报提出了越来越高的需求。BELLHOP3D是一种基于射线法的三维声传播计算模型,在海洋声学中应用十分广泛。BELLHOP3D的计算效率比其他常用模型高,但是仍然有非常大的提升空间。该文使用信息传递接口对BELLHOP3D进行粗粒度的并行优化,并行后的程序计算结果稳定可靠,并行效率高,更适合在实际应用中实现快速的声场预报。并行BELLHOP3D程序可以在https://github.com/nj-zyq/BELLHOP3D＿MPI.git下载。     

3D displays: toward holographic video displays of 3D images

As the flat panel displays (Liquid Crystal Displays, AMOLED, etc.) reach near perfection in their viewing qualities and display areas, it is natural to seek the next level of displays, including 3D displays. There is a strong surge in 3D liquid crystal displays as a result of the successful movie Avatar. Most of these 3D displays involve the employment of special glasses that allow one view perspective for each of the eyes to achieve a depth perception. Such displays are not real 3D displays. In fact, these displays can only provide one viewing perspective for all viewers, regardless of the viewer’s position. In addition, a fundamental viewing problem of focusing and accommodation exist that can lead to discomfort and fatigue for many viewers. In this paper, the authors review the current status of stereoscopic 3D displays and their problems. The authors will also discuss the possibility of using flat panels for the display of both phase and intensity of video image information, leading to the ultimate display of 3D holographic video images. Many of the fundamental issues and limitations will be presented and discussed.     

3D polarimetric purity

From our previous definition of the indices of polarimetric purity for 3D light beams [J.J. Gil, J.M. Correas, P.A. Melero and C. Ferreira, Monogr. Semin. Mat. G. de Galdeano 31, 161 (2004)], an analysis of their geometric and physical interpretation is presented. It is found that, in agreement with previous results, the first parameter is a measure of the degree of polarization, whereas the second parameter (called the degree of directionality) is a measure of the mean angular aperture of the direction of propagation of the corresponding light beam. This pair of invariant, non-dimensional, indices of polarimetric purity contains complete information about the polarimetric purity of a light beam. The overall degree of polarimetric purity is obtained as a weighted quadratic average of the degree of polarization and the degree of directionality.     

D3+D6 solution and D4+D6 solution

We make the supergravity solutions describing the branes (D3 branes and D4 branes) localized within the D6 branes in the near core region of D6 brane. From the D=11 solutions (M3 branes and M4 branes with the Z_N identifications in the transverse space) we obtain the D=10 supergravity solutions of D3 branes localized within D6 branes and D4 branes localized within D6 branes by reducing the dimension down to D=10 along a circular direction of S³ part of the transverse space. M3 brane solution leads to D=10 background representing D3 branes localized on D6 branes in the region close to the D6 branes core. M4 branes lead to the D4 branes localized on D6 branes in the region close to the D6 brane core.     

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。     

3D fast flair: a CSF-nulled 3D fast spin-echo pulse sequence

Since its introduction, the fluid attenuated inversion recovery (FLAIR) sequence has found many applications in the central nervous system (CNS), because of its heavy T₂ weighting and excellent cerebrospinal fluid (CSF) suppression. More recently fast spin-echo based variants have been developed that greatly reduce scan time; such sequences are often referred to as “fast FLAIR.” We present what we believe to be the first implementation of FLAIR using a three dimensional (3D) fast spin-echo-based pulse sequence, which combines the cerebrospinal fluid suppression and good lesion contrast of two-dimensional fast FLAIR with the advantages of a three-dimensional sequence such as higher signal-to-noise ratio (SNR) per unit time, thinner slices (giving reduced partial volume effect) and the ability to reformat the data in an arbitrary plane.     

Magnetic fields in 2D and 3D sphere

In this note we study the Landau–Hall problem in the 2D and 3D unit sphere, that is, the motion of a charged particle in the presence of a static magnetic field. The magnetic flow is completely determined for any Riemannian surface of constant Gauss curvature, in particular, the unit 2D sphere. For the 3D case we consider Killing magnetic fields on the unit sphere, and we show that the magnetic flowlines are helices with the given Killing vector field as its axis.     

3D micro-inspection goes DMD

Digital image-projection and video-projection are the classical applications of Digital Micromirror Devices (DMD) but further applications in the field of optical metrology are also possible. Operated with certain patterns, a DMD can function, for instance, as an array of pinholes that may substitute the Nipkow disk presently used for lateral scanning in confocal microscopes. The various process parameters that influence the measurement (e.g. pinhole size, pinhole shape, lateral step-size and the number of pinholes used simultaneously, etc.) can be configured easily for individual measurements by simply programming the DMD. Furthermore, price-drops for metrological precision instruments may be achieved by implementation of the mass article DMD.The paper explains the basics of DMD technology, illustrates the principle setup of a newly designed instrument, shows results achieved with it and gives examples for its application.     

3D molecular imaging SIMS

Thin monolayer and bilayer films of spin cast poly(methyl methacrylate) (PMMA), poly(2-hydroxyethyl methacrylate) (PHEMA), poly(lactic) acid (PLA) and PLA doped with several pharmaceuticals have been analyzed by dynamic SIMS using SF₅⁺ polyatomic primary ion bombardment. Each of these systems exhibited minimal primary beam-induced degradation under cluster ion bombardment allowing molecular depth profiles to be obtained through the film. By combing secondary ion imaging with depth profiling, three-dimensional molecular image depth profiles have been obtained from these systems. In another approach, bevel cross-sections are cut in the samples with the SF₅⁺ primary ion beam to produce a laterally magnified cross-section of the sample that does not contain the beam-induced damage that would be induced by conventional focussed ion beam (FIB) cross-sectioning. The bevel surface can then be examined using cluster SIMS imaging or other appropriate microanalysis technique.     

Differential 3D shape retrieval

We are presenting a differential three-dimensional (3-D) shape profiling method that is based on the combination of orthogonal fringe projection. It allows us to compute depth gradient maps in a fast and efficient manner. What we are demonstrating is that depth gradients can be computed in a simple way by measuring fringe deformation throughout a novel single-shot approach. We show the usefulness and potential applications of the proposed approach. Validation experiments are presented as well.     

透明胶膜与三维显示

最近加拿大多伦多大学的K .Iizuka博士完成了将通常使用的二维屏幕图像转化成三维立体影像 .他所使用的透明胶膜具有双折射性 ,即这种材料的折射系数并不是在所有方向上都是相同的 ;这就意味着入射光的偏振具有旋转性 .K .Iizuka博士使用的是一块 2 5 μm厚的透明胶膜 ,它在对白光的偏振方向的旋转性能方面要比一般市场所供应的胶膜好 .通常市场上供应的是一种专为特定波长设计的半波板 (half -waveplate) .从普通影像上辐射的光线 ,事实上它总是会发生偏振的 ,因此传统的三维立体图像是利用观察者所戴的偏振眼镜将左边与右边图像的偏振方…     

3D projection sideband cooling

We demonstrate 3D microwave projection sideband cooling of trapped, neutral atoms. The technique employs state-dependent potentials that enable microwave photons to drive vibration-number reducing transitions. The particular cooling sequence we employ uses minimal spontaneous emission, and works even for relatively weakly bound atoms. We cool 76% of atoms to their 3D vibrational ground states in a site-resolvable 3D optical lattice.     

Comparison of 1D, 2D and 3D quench onset simulations

Measured and simulated minimum quench energies (MQE) for short samples are doubtful when estimating disturbance tolerance of an impregnated superconducting magnet. If measurements are performed at liquid cryogen, the cooling provided by the cryogen causes MQE to be high. At a conduction-cooled system, the transverse heat conduction is neglected causing low MQE. Even though these conditions can be artificially brought closer to the ones in an impregnated magnet, it is difficult to estimate by short-sample measurement the MQE of a superconducting coil. These similar difficulties are present at simulations. On the other hand, 1D and 2D measurements and simulations can be used, e.g., to compare wires or consider effect of insulation layer thickness, but according to the results only in a rough quantitative way. In this paper, we compare MQE and normal zone propagation velocity simulations of an MgB₂ wire with 1D, 2D and 3D finite element method models to focus on the different results given by the models employing different dimensions.