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Phase angle

Jie Luo, Yuting Yang, Zhongqi Yao, Weixin Lu, Bo Hou, Zhi Hong Hang, C T Chan, Yun Lai
By using pure dielectric photonic crystals, we demonstrate the realization of ultratransparent media, which allow near 100% transmission of light for all incident angles and create aberration-free virtual images. The ultratransparency effect is well explained by spatially dispersive effective medium theory for photonic crystals, and verified by both simulations and proof-of-principle microwave experiments. Designed with shifted elliptical equal frequency contours, such ultratransparent media not only provide a low-loss and feasible platform for transformation optics devices at optical frequencies, but also enable new freedom for phase manipulation beyond the local medium framework...
November 25, 2016: Physical Review Letters
Ruilian Tang, Yan Li, Shengyi Xie, Nana Li, Jiuhua Chen, Chunxiao Gao, Pinwen Zhu, Xin Wang
Raman spectroscopy, synchrotron angle-dispersive X-ray diffraction (ADXRD), first-principles calculations, and electrical resistivity measurements were carried out under high pressure to investigate the structural stability and electrical transport properties of metavanadate MgV2O6. The results have revealed the coordination change of vanadium ions (from 5+1 to 6) at around 4 GPa. In addition, a pressure-induced structure transformation from the C2/m phase to the C2 phase in MgV2O6 was detected above 20 GPa, and both phases coexisted up to the highest pressure...
December 7, 2016: Scientific Reports
Haitao Li, Xin Ning, Wenzhuo Li
In order to improve the reliability and reduce power consumption of the high speed BLDC motor system, this paper presents a model free adaptive control (MFAC) based position sensorless drive with only a dc-link current sensor. The initial commutation points are obtained by detecting the phase of EMF zero-crossing point and then delaying 30 electrical degrees. According to the commutation error caused by the low pass filter (LPF) and other factors, the relationship between commutation error angle and dc-link current is analyzed, a corresponding MFAC based control method is proposed, and the commutation error can be corrected by the controller in real time...
December 2, 2016: ISA Transactions
Trent M Guess, Swithin Razu, Amirhossein Jahandar, Marjorie Skubic, Zhiyu Huo
The Microsoft Kinect is becoming a widely used tool for inexpensive, portable measurement of human motion with the potential to support clinical assessments of performance and function. In this study, the relative osteokinematic Cardan joint angles of the hip and knee were calculated using the Kinect 2.0 skeletal tracker. The pelvis segments of the default skeletal model were reoriented and three-dimensional joint angles were compared to a marker-based system during a drop vertical jump and a hip abduction motion...
December 5, 2016: Journal of Applied Biomechanics
Bingyi Liu, Wenyu Zhao, Yongyuan Jiang
As the two dimensional version of the functional wavefront manipulation metamaterial, metasurface has become a research hot spot for engineering the wavefront at will with a subwavelength thickness. The wave scattered by the gradient metasurface, which is composed by the periodic supercells, is governed by the generalized Snell's law. However, the critical angle that derived from the generalized Snell's law circles the domain of the incident angles that allow the occurrence of the anomalous reflection and refraction, and no free space scattering waves could exist when the incident angle is beyond the critical angle...
December 5, 2016: Scientific Reports
Ilya Belopolski, Daniel S Sanchez, Yukiaki Ishida, Xingchen Pan, Peng Yu, Su-Yang Xu, Guoqing Chang, Tay-Rong Chang, Hao Zheng, Nasser Alidoust, Guang Bian, Madhab Neupane, Shin-Ming Huang, Chi-Cheng Lee, You Song, Haijun Bu, Guanghou Wang, Shisheng Li, Goki Eda, Horng-Tay Jeng, Takeshi Kondo, Hsin Lin, Zheng Liu, Fengqi Song, Shik Shin, M Zahid Hasan
The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1-xTe2 are inversion-breaking, layered, tunable semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1-xTe2 at x=25%...
December 5, 2016: Nature Communications
Andrea P Arguelles, Christopher M Kube, Ping Hu, Joseph A Turner
Elastic wave scattering is used to study polycrystalline media for a wide range of applications. Received signals, which include scattering from the randomly oriented grains comprising the polycrystal, contain information from which useful microstructural parameters may often be inferred. Recently, a mode-converted diffuse ultrasonic scattering model was developed for evaluating the scattered response of a transverse wave from an incident longitudinal wave in a polycrystalline medium containing equiaxed single-phase grains with cubic elastic symmetry...
September 2016: Journal of the Acoustical Society of America
Jiangkun Liu, Weixing Cai, Ruola Ning
Grating-based differential phase contrast (DPC) imaging enables the use of a hospital-grade X-ray tube, but compromises the image quality due to insufficiently coherent illumination. In this research, a bench-top DPC cone beam CT (DPC-CBCT) was systematically evaluated and compared with the traditional attenuation-based CBCT in terms of contrast to noise ratio, noise property, and contrast resolution through phantom studies. In order to evaluate DPC-CBCT for soft tissue imaging, breast specimen and small animal studies were carried out...
November 30, 2016: Journal of X-ray Science and Technology
P D VanMeter, P Franz, L M Reusch, J S Sarff, D J Den Hartog
The Soft X-Ray (SXR) tomography system on the Madison Symmetric Torus uses four cameras to determine the emissivity structure of the plasma. This structure should directly correspond to the structure of the magnetic field; however, there is an apparent phase difference between the emissivity reconstructions and magnetic field reconstructions when using a cylindrical approximation. The difference between the phase of the dominant rotating helical mode of the magnetic field and the motion of the brightest line of sight for each SXR camera is dependent on both the camera viewing angle and the plasma conditions...
November 2016: Review of Scientific Instruments
Letian Guo, Jiawei Li, Tao Ba, Wenhua Huang, Hao Shao
A compact five-port waveguide structure consisting of three rectangular ports, one coaxial port, and one circular waveguide port is proposed. The three rectangular waveguides are uniformly distributed in space at angles of 120°, and the coaxial and circular waveguides are located at the top and bottom, respectively, of the rectangular waveguides. The ideal scattering matrix is derived from the symmetry properties of the structure. If the circular and coaxial ports are matched, then the entire five-port waveguide structure is automatically matched...
November 2016: Review of Scientific Instruments
R G L Vann, K J Brunner, R Ellis, G Taylor, D A Thomas
The Synthetic Aperture Microwave Imaging (SAMI) system is a novel diagnostic consisting of an array of 8 independently phased antennas. At any one time, SAMI operates at one of the 16 frequencies in the range 10-34.5 GHz. The imaging beam is steered in software post-shot to create a picture of the entire emission surface. In SAMI's active probing mode of operation, the plasma edge is illuminated with a monochromatic source and SAMI reconstructs an image of the Doppler back-scattered (DBS) signal. By assuming that density fluctuations are extended along magnetic field lines, and knowing that the strongest back-scattered signals are directed perpendicular to the density fluctuations, SAMI's 2-D DBS imaging capability can be used to measure the pitch of the edge magnetic field...
November 2016: Review of Scientific Instruments
T Akiyama, A Sirinelli, C Watts, P Shigin, G Vayakis, M Walsh
A dispersion interferometer is a reliable density measurement system and is being designed as a complementary density diagnostic on ITER. The dispersion interferometer is inherently insensitive to mechanical vibrations, and a combined polarimeter with the same line of sight can correct fringe jump errors. A proof of the principle of the CO2 laser dispersion interferometer combined with the PEM polarimeter was recently conducted, where the phase shift and the polarization angle were successfully measured simultaneously...
November 2016: Review of Scientific Instruments
Jinxiu Guo, Yu Chen, Lizhi Zhao, Ping Sun, Hongli Li, Lei Zhou, Xiayan Wang, Qiaosheng Pu
Plastic microchips have been broadly used as disposable microfluidic devices, but the poorly defined surface properties limit their application. Herein, we proved that an anionic polymer could be used as the background electrolyte (BGE) to provide a strong and stable cathodic electroosmotic flow (EOF) and modulate the electrophoretic behavior for efficient separation in relative thicker microchannels (∼75μm id). A cathodic EOF of ∼3.3×10(-4)cm(2)V(-1)s(-1) was maintained using sodium polystyrene sulfonate (PSSNa) with a molecular weight of 5×10(5) as the BGE, which ensured fluorescein isothiocyanate labeled biogenic amines (BAs) appeared ahead of other components in the electropherograms obtained with microchips of cyclic olefin copolymer...
November 23, 2016: Journal of Chromatography. A
Ming Yang, Xinlei Zhu, Yaqiong Zhang, Na Ta, Zhushi Rao
Sound source localization uses interaural time difference (ITD) or interaural intensity difference cues, and most of the methods based on ITD are limited by the aperture of array. However, a kind of parasitoid fly called Ormia ochracea with coupled ears has a remarkable ability to localize calling of crickets regardless of the fly's small body size. The structure of fly's ear is generalized, and a multi-dimensional coupled system with an acoustic sensor array is proposed. The magnification factor of the phase difference in this system, which can be used to describe the ITD changes of signals from the coupled system, is chosen as the kernel parameter to measure the effect of coupling...
November 2016: Journal of the Acoustical Society of America
Yanlong Yang, Shaohui Yan, Xianghua Yu, Manman Li, Baoli Yao
We propose a non-paraxial hollow accelerating beam, which is formed by incoherently superposing two well-designed coherent accelerating beams. Very interestingly, this incoherent superposition does not hamper the acceleration dynamics pertaining to the coherent ones, but results in a hollow intensity pattern in the cross section transverse to the circular accelerating trajectory. By a simple optimization, this hollow cross section pattern can be effectively extended to an angle close to 90°. The magnitude and the phase of the angular spectrum of the beam are given followed by a suggested scheme to generate the beam in practice...
November 28, 2016: Optics Express
Tran Quang Hung, Wai Hoe Chin, Yi Sun, Anders Wolff, Dang Duong Bang
Solid-phase PCR (SP-PCR) has become increasingly popular for molecular diagnosis and there have been a few attempts to incorporate SP-PCR into lab-on-a-chip (LOC) devices. However, their applicability for on-line diagnosis is hindered by the lack of sensitive and portable on-chip optical detection technology. In this paper, we addressed this challenge by combining the SP-PCR with super critical angle fluorescence (SAF) microlens array embedded in a microchip. We fabricated miniaturized SAF microlens array as part of a microfluidic chamber in thermoplastic material and performed multiplexed SP-PCR directly on top of the SAF microlens array...
November 12, 2016: Biosensors & Bioelectronics
Yair Rivenson, Yichen Wu, Hongda Wang, Yibo Zhang, Alborz Feizi, Aydogan Ozcan
High-resolution imaging of densely connected samples such as pathology slides using digital in-line holographic microscopy requires the acquisition of several holograms, e.g., at >6-8 different sample-to-sensor distances, to achieve robust phase recovery and coherent imaging of specimen. Reducing the number of these holographic measurements would normally result in reconstruction artifacts and loss of image quality, which would be detrimental especially for biomedical and diagnostics-related applications...
November 30, 2016: Scientific Reports
Ki Hwan Kim, Sung-Hong Park
The balanced steady-state free precession (bSSFP) MR sequence is frequently used in clinics, but is sensitive to off-resonance effects, which can cause banding artifacts. Often multiple bSSFP datasets are acquired at different phase cycling (PC) angles and then combined in a special way for banding artifact suppression. Many strategies of combining the datasets have been suggested for banding artifact suppression, but there are still limitations in their performance, especially when the number of phase-cycled bSSFP datasets is small...
November 27, 2016: Magnetic Resonance Imaging
Jingxu Zheng, Zhongyuan Luo, Lida Tan, Bin Chen
In the present study, nano-sized cuboid-shaped particles in Mg-Nd-Y are studied by means of Cs-corrected atomic-scale high-angle annular dark-field scanning transmission electron microscopy. The structure of the cuboid-shaped phase is identified to be yttrium (major component) and neodymium atoms in face-centered cubic arrangement without the participation of Mg. The lattice parameter a=5.15 Å. During isothermal aging at 225°C, Mg3(Nd,Y) precipitates adhere to surface (100) planes of the cuboid-shaped particles with the orientation relationship: $[100]_{{{\rm Mg}_{{\rm 3}} {\rm RE}}} \,/\,\,/\,[100]_{{{\rm Cuboid}}} $ and $[310]_{{{\rm Mg}_{{\rm 3}} {\rm RE}}} \,/\,\,/\,[012]_{{{\rm Cuboid}}} $ ...
November 30, 2016: Microscopy and Microanalysis
Manjunatha Reddy, Aida Huqi, Dinu Iuga, Satoshi Sakurai, Andrew Marsh, Jeffery T Davis, Stefano Masiero, Steven P Brown
The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G-quartet based assemblies are formed in chloroform depending on the nature of the cation, anion and salt concentration, as characterized by circular dichroism and time course diffusion-ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G-quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon-like assemblies as revealed by fast magic-angle spinning (MAS) NMR spectroscopy...
November 29, 2016: Chemistry: a European Journal
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