2011
2011
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Record 313 of
Title:Biased electric field analysis of a photoconductive antenna for terahertz generation
Author(s):Yang, Jian(1); Fan, Wenhui(1); Xue, Bing(1)Source: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume: 637 Issue: 1 SUPPL. DOI: 10.1016/j.nima.2010.02.048 Published: May 1, 2011Abstract:The development of terahertz (THz) science has been ongoing for decades. As such, the generation and detection of THz radiation tend to be advanced. Currently, there are two main approaches to detect THz radiation: free-space electro-optic sampling (FS-EOS) and photoconductive (PC) sampling. Among the generations, the photoconductive effect is significant in the amplitude of THz radiation, which is believed to be proportional to the magnitude of the inner electric field. In order to increase THz radiation by safely enhancing the biased electric field, simulations on the electric field distributions of several different antennas have been conducted during our research. As a result of comparing and analyzing the findings of the simulations, a specific antenna structure suitable for a much higher biased field has been designed. Furthermore, satisfactory THz radiation is expected from this antenna. ? 2010 Elsevier B.V. All rights reserved.Accession Number: 20112013983320 -
Record 314 of
Title:Design of combined magnetic field system for magnetic-bottle time-of-flight spectrometer
Author(s):Wang, Chao(1); Tian, Jinshou(1); Zhang, Meizhi(2); Kang, Yifan(3)Source: Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams Volume: 23 Issue: 7 DOI: 10.3788/HPLPB20112307.1810 Published: July 2011Abstract:Based on the primary requirement for the magnetic field system in magnetic-bottle time-of-flight spectrometer, an appropriate combined inhomogeneous magnetic field system is designed. The inhomogeneous higher magnetic field part, with the highest field of 1.2 T, is produced by the combination of a permanent magnet and a pole piece with optimized shape. The magnet, known as NdFeB magnet, is one of rare earth permanent magnets in N52. The guiding uniform magnetic field of 1.0×10-3 T is provided by solenoid, with length of 3 m and radius of 3 cm. The pitch between the pole piece and the near end of used solenoid is determined to be 5 cm, which can satisfy the actual engineering needs.Accession Number: 20113614310387 -
Record 315 of
Title:Compact equivalent-circuit model of LiNbO3 modulator for passive millimeter wave imaging system
Author(s):Qian, Feng-Chen(1,2,3); Xie, Xiao-Ping(1,3); Ye, Ya-Lin(3)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8196 Issue: DOI: 10.1117/12.900869 Published: 2011Abstract:This paper presents a compact frequency-independent equivalent-circuit model for mmW characteristics of lithium niobate (LiNbO3) optical modulator, taking the skin effect, and substrate effect into consideration. Equivalent-circuit model with only ideal lumped elements represents the broadband electrical response of LiNbO3 modulator. A 4-long ladder model is used to model the skin effect. Coupling capacitor is used to simulate the substrate coupling from the CPW to the buffer and LiNbO3 substrate. Lumped-element circuit model was cascaded to model the distributive skin effect, transmission attenuation, and substrate effect. The equivalent-circuit models are fully SPICE compatible and can be incorporated directly into common circuit simulators and microwave design tools. ? 2011 SPIE.Accession Number: 20113614296285 -
Record 316 of
Title:High power tunable picosecond green laser pulse generation by frequency doubling of an Yb-doped fiber power amplifier seeded by a gain switch laser diode
Author(s):Liu, H.J.(1); Li, X.F.(2)Source: Laser Physics Volume: 21 Issue: 12 DOI: 10.1134/S1054660X11210146 Published: December 2011Abstract:A compact tunable high power picosecond green laser pulse source based on frequency doubling of an Yb-doped fiber amplifier seeded by a gain switch laser diode has been developed. The fiber amplifier generates the picosecond infrared pulses with average power of 10.3 W, repetition rate of 1 MHz, pulse duration of 150 ps, and tunable range of 20 nm around 1064 nm. For underwater use, the tunable output infrared pulses are frequency doubled into picosecond green laser pulses, which can be tuned from 527 to 537 nm with average power of more than 1.1 W, corresponding to an overall conversion efficiency of 10.7% by a BBO nonlinear crystal. This kind of laser source will have potential application for underwater optical communication. ? Pleiades Publishing, Ltd., 2011.Accession Number: 20120314700421 -
Record 317 of
Title:Single image super resolution with high resolution dictionary
Author(s):Mu, Guangwu(1); Gao, Xinbo(1); Zhang, Kaibing(1); Li, Xuelong(2); Tao, Dacheng(2)Source: Proceedings - International Conference on Image Processing, ICIP Volume: Issue: DOI: 10.1109/ICIP.2011.6115630 Published: 2011Abstract:Image super resolution (SR) is a technique to estimate or synthesize a high resolution (HR) image from one or several low resolution (LR) images. This paper proposes a novel framework for single image super resolution based on sparse representation with high resolution dictionary. Unlike the previous methods, the training set is constructed from the HR images instead of HR-LR image pairs. Due to this property, there is no need to retrain a new dictionary when the zooming factor changed. Given a testing LR image, the patch-based representation coefficients and the desired image are estimated alternately through the use of dynamic group sparsity, the fidelity term and the non-local means regularization. Experimental results demonstrate the effectiveness of the proposed algorithm. ? 2011 IEEE.Accession Number: 20120514729838 -
Record 318 of
Title:High-precision image motion measurement applied for space camera based on hybrid opto-digital joint transform correlator
Author(s):Yi, Hongwei(1); Zhao, Hui(1,2); Li, Yingcai(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8006 Issue: DOI: 10.1117/12.900508 Published: 2011Abstract:Hybrid opto-digital joint transform correlator (HODJTC) is effective for image motion measurement, but it is different from the traditional joint transform correlator (JTC) because it only has one process of optical Fourier transform and the intermediate joint power spectrum (JPS) is directly input to a digital unit to compute the image motion. In original HODJTC, the correlation image is obtained by using a global discrete Fourier transform operator. In fact, the location of cross-correlation peak corresponding to zero image motion is known and the maximum image shift can also be estimated. Thus, the local cross-correlation image can be directly obtained by adopting a local Fourier transform operator instead. With the pixel-level location of cross-correlation peak is obtained, the up-sampling technique is introduced to relocate the peak in even higher accuracy. Both the experiments and simulations demonstrate that the RMS (root-mean-square) error of motion determination can be controlled below 0.05 pixels, which is a very promising result for real application. ? 2011 SPIE.Accession Number: 20115214642378 -
Record 319 of
Title:Face sketch-photo synthesis based on support vector regression
Author(s):Zhang, Jiewei(1); Wang, Nannan(1); Gao, Xinbo(1); Tao, Dacheng(2); Li, Xuelong(2)Source: Proceedings - International Conference on Image Processing, ICIP Volume: Issue: DOI: 10.1109/ICIP.2011.6115625 Published: 2011Abstract:The existing face sketch-photo synthesis methods trend to lose some vital details more or less. In this paper, we propose a novel sketch-photo synthesis approach based on support vector regression (SVR) to handle this difficulty. First, we utilize an existing method to acquire the initial estimate of the synthesized image. Then, the final synthesized image is obtained by combining the initial estimate and the SVR based high frequency information together to further enhance the quality of synthesized image. Experimental results on the benchmark database and our new constructed database demonstrate that the proposed method can achieve significant improvement on perceptual quality. Moreover, the synthesized face images can obtain higher recognition rate when used in retrieval system. ? 2011 IEEE.Accession Number: 20120514729833 -
Record 320 of
Title:Active optical system for any field angle zoom
Author(s):Hu, Shaolei(1,2,3); Zhao, Xin(1,2,3); Dong, Weihui(2,3); Xie, Yongjun(3)Source: Optical Engineering Volume: 50 Issue: 11 DOI: 10.1117/1.3654181 Published: November 1, 2011Abstract:We have theoretically proposed a new type of active optical zoom system. It can change the magnification of an imaging system at any field angle, namely, it can change the effective focal length at a limited region of interest and simultaneously maintain high resolution. It is comprised of two static aspheric mirrors and two deformable mirrors; furthermore, by changing the curvature of mirrors the focal length can be adjusted from-399 to-558.6 mm. The system reduces the bandwidth of data transmission and may find potential applications in high speed photography. ? 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).Accession Number: 20174104246357 -
Record 321 of
Title:Low-temperature brush-shaped large-volume plasma generated by direct current discharge at atmospheric pressure
Author(s):Sun, Aimin(1); Tang, Jie(2); Cao, Wenqing(2); Zhao, Wei(2); Duan, Yixiang(1,2)Source: IEEE Transactions on Plasma Science Volume: 39 Issue: 11 PART 1 DOI: 10.1109/TPS.2011.2132742 Published: November 2011Abstract:Low-temperature plasma is generated by glow discharge with a high direct current power supply and argon gas. A brush-shaped plasma source with large volume is obtained with a width of 15 mm, a thickness of 1 mm, and a length of about 18 mm. The source design and mechanism of the plasma generation are presented and discussed. The large-volume plasma source provides advantages in surface treatment, such as high working efficiency, sufficient utilization of the plasma gas, and natural cooling down. The characteristics of large volume, high energy density, and low temperature allow this kind of plasma source to be more suitable to practical applications. ? 2006 IEEE.Accession Number: 20114714532614 -
Record 322 of
Title:Putting images on a manifold for atlas-based image segmentation
Author(s):Cao, Yihui(1); Yuan, Yuan(1); Li, Xuelong(1); Yan, Pingkun(1)Source: Proceedings - International Conference on Image Processing, ICIP Volume: Issue: DOI: 10.1109/ICIP.2011.6116265 Published: 2011Abstract:In medical image analysis, atlas-based segmentation has become a popular approach. Given a target image, how to select the atlases with the similar shape of anatomical structure to the input image is one of the most critical factors affecting the segmentation accuracy. In this paper, we propose a novel strategy by putting the images on a manifold to analyze the intrinsic similarity between the images. A subset of atlases can be selected and the optimal fusion weights are computed in a low-dimensional manifold space. Finally, it combines the selected atlases by using the corresponding weights for image segmentation. The experimental results demonstrated that our proposed method is robust and accurate especially when a large number of training samples are available. ? 2011 IEEE.Accession Number: 20120514730322 -
Record 323 of
Title:Extending the depth of field of incoherent imaging system through wave-front coding by using composite phase masks
Author(s):Zhao, Hui(1,2); Yi, Hongwei(1); Li, Yingcai(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8004 Issue: DOI: 10.1117/12.900250 Published: 2011Abstract:Since 1995 when wave-front coding was first proposed by Dowski and Cathey, this technique has become a powerful tool to extend the DOF (depth of field) of incoherent imaging systems. By introducing a phase mask to the aperture plane, the optical transfer function (OTF) can be made insensitive to defocus and thus the key to this technique lies in the design of suitable phase masks. So far, many phase masks have been proposed to achieve the goal of DOF extension. In this paper, a new kind of phase mask, called composite phase mask, is designed by combining existing phase masks. With the optimized parameters, the composite phase mask can be made even less sensitive to defocus than any single mask. At the same time, as the number of phase masks used to generate one composite phase mask increases, the DOF extension effect can also be changed. Both the simulations and experiments demonstrate the effectiveness of the composite phase masks and the work reported also enriches the phase mask family used to realize the large DOF effect. ? 2011 SPIE.Accession Number: 20115214631759 -
Record 324 of
Title:Medical image segmentation using descriptive image features
Author(s):Yang, Meijuan(1); Yuan, Yuan(1); Li, Xuelong(1); Yan, Pingkun(1)Source: BMVC 2011 - Proceedings of the British Machine Vision Conference 2011 Volume: Issue: DOI: 10.5244/C.25.94 Published: 2011Abstract:Segmentation of medical images is an important component for diagnosis and treatment of diseases using medical imaging technologies. However, automated accurate medical image segmentation is still a challenge due to the difficulties in finding a robust feature descriptor to describe the object boundaries in medical images. In this paper, a new normal vector feature profile (NVFP) is proposed to describe the local image information of a contour point by concatenating a series of local region descriptors along the normal direction at that point. To avoid trapping by false boundaries caused by non-boundary image features, a modified scale invariant feature transform (SIFT) descriptor is developed. The number and locations of sample points for building NVFP are determined for each contour point, which are constrained by the neighboring anatomical structures and the statistical consistency of the training features. NVFP is incorporated into a model based method for image segmentation. The performance of our proposed method was demonstrated by segmenting prostate MR images. The segmentation results indicated that our method can achieve better performance compared with other existing methods. ? 2011. The copyright of this document resides with its authors.Accession Number: 20141617592823