2010
2010
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Record 253 of
Title:Excitonic optical absorption in quantum wells under intense terahertz waves polarized along the grown direction
Author(s):Li, Ying(1); Zhang, Tong-Yi(2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 7854 Issue: DOI: 10.1117/12.868906 Published: 2010Abstract:Excitonic optical absorption in quantum wells (QWs) under intense terahertz (THz) waves polarized along the grown-direction is investigated. The characteristics induced by the strong THz field in the optical absorption spectrum in the QWs near the band gap edge is analyzed by coherent wave approach. The calculated results with and without the presence of THz field are presented. It shows that the excitonic absorption peaks may split or broaden when an intense THz field is applied. The presence of an intense THz field results in the formation of replicas in the absorption spectrum. The replicas are not symmetric and presence on both sides of the main excitonic peaks due to the Coulomb interaction between electrons and holes. ? 2010 Copyright SPIE - The International Society for Optical Engineering.Accession Number: 20110213560587 -
Record 254 of
Title:A new package structure for high power single emitter semiconductor laser and performance analysis
Author(s):Zhang, Yanxin(1); Wang, Jingwei(1); Wu, Di(2); Yang, Kai(2); Ma, Youlong(3); Liu, Xingsheng(1,2)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 37 Issue: 5 DOI: 10.3788/CJL20103705.1186 Published: May 2010Abstract:A new high power single emitter laser (F-mount) is reported. This package structure is different from the commercial products structure with C-mount, and it has an advantage of higher thermal conduction. The maximum output optical power of 13.3 W through this package structure is obtained under the testing condition of continuous waves (CW) at 20°C and the laser can still work well. There was no catastrophic mirror-damage (COMD) occurred on it. The maximum output optical power of 30.8 W is obtained under the testing condition of quasi-continuous wave (QCW). Moreover, the following parameters are calculated with coefficient of wavelength-shift versus temperature of 0.278 nm/°C, thermal resistance of 3.18 K/W, the characteristic temperature of 135 K at the threshold current at room temperature, the characteristic temperature of 743 K for the differential efficiency at room temperature. It has lower thermal resistance and better heat sink capability and higher output power than commercial single emitter laser packaged with C-mount structure.Accession Number: 20102413003957 -
Record 255 of
Title:Study of the mechanisms of spectral broadening in high power
Author(s):Wang, Jingwei(1); Yuan, Zhenbang(2); Zhang, Yanxin(1); Wu, Di(3); Chen, Xu(2); Liu, Xingsheng(1,3)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 37 Issue: 1 DOI: 10.3788/CJL20103701.0092 Published: January 2010Abstract:High power semiconductor laser arrays have found increasing applications in pumping of solid state laser systems. Spectral width is one of the key factors of laser array products. Increasing the spectral accuracy by reducing the spectral width of the pump diode can improve the laser system compactness, efficiency, power, and beam quality while reducing thermal management cost in the system. The mechanisms of spectral broadening in high power semiconductor laser arrays are studied for the first time by numerical simulation and by means of spatial spectral mapping and scan acoustic microscope(SAM). The broadening of a laser spectrum is often the result of the appearance of a shoulder/tail on either or both sides of the spectrum or sometimes a double-peak or even multiple peaks occurs. It is concluded that the shoulder/tail appeared on the longer-wavelength side of the spectrum is normally caused by thermal effect while the shoulder/tail on the shorter-wavelength side of the spectrum is usually the result of thermal-stress built in the laser array. Based on the mechanism of spectral broadening in high power semiconductor laser arrays, the strategy of controlling spectral broadening is presented in this paper.Accession Number: 20101012758912 -
Record 256 of
Title:A unified tensor level set for image segmentation
Author(s):Wang, Bin(1); Gao, Xinbo(1); Tao, Dacheng(2); Li, Xuelong(3)Source: IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics Volume: 40 Issue: 3 DOI: 10.1109/TSMCB.2009.2031090 Published: June 2010Abstract:This paper presents a new region-based unified tensor level set model for image segmentation. This model introduces a three-order tensor to comprehensively depict features of pixels, e.g., gray value and the local geometrical features, such as orientation and gradient, and then, by defining a weighted distance, we generalized the representative region-based level set method from scalar to tensor. The proposed model has four main advantages compared with the traditional representative method as follows. First, involving the Gaussian filter bank, the model is robust against noise, particularly the salt- and pepper-type noise. Second, considering the local geometrical features, e.g., orientation and gradient, the model pays more attention to boundaries and makes the evolving curve stop more easily at the boundary location. Third, due to the unified tensor pixel representation representing the pixels, the model segments images more accurately and naturally. Fourth, based on a weighted distance definition, the model possesses the capacity to cope with data varying from scalar to vector, then to high-order tensor. We apply the proposed method to synthetic, medical, and natural images, and the result suggests that the proposed method is superior to the available representative region-based level set method. ? 2006 IEEE.Accession Number: 20102112951935 -
Record 257 of
Title:One-dimensional steady-state bright photovoltaic solitons in LiNbO3:Fe crystal with background illumination
Author(s):Zhang, Meizhi(1,2); Lu, Keqing(1); Cheng, Guanghua(1); Zhang, Yiqi(1,2); Li, Kehao(1,2); Zhang, Lei(1,2); Zhang, Yanpeng(3)Source: Optik Volume: 121 Issue: 6 DOI: 10.1016/j.ijleo.2008.09.020 Published: March 2010Abstract:We investigate theoretically and experimentally one-dimensional bright photovoltaic solitons in LiNbO3:Fe crystal by use of the background illumination. We find that, in LiNbO3:Fe crystal, bright photovoltaic solitons can be obtained with background illumination for κ>1, where κ is the ratio of the background illumination photovoltaic constant to the soliton optical beam's photovoltaic constant. For κAccession Number: 20100912743874 -
Record 258 of
Title:Local feature based geometric-resistant image information hiding
Author(s):Gao, Xinbo(1); Deng, Cheng(1); Li, Xuelong(2); Tao, Dacheng(3)Source: Cognitive Computation Volume: 2 Issue: 2 DOI: 10.1007/s12559-010-9033-8 Published: June 2010Abstract:Watermarking aims to hide particular information into some carrier but does not change the visual cognition of the carrier itself. Local features are good candidates to address the watermark synchronization error caused by geometric distortions and have attracted great attention for content-based image watermarking. This paper presents a novel feature point-based image watermarking scheme against geometric distortions. Scale invariant feature transform (SIFT) is first adopted to extract feature points and to generate a disk for each feature point that is invariant to translation and scaling. For each disk, orientation alignment is then performed to achieve rotation invariance. Finally, watermark is embedded in middle-frequency discrete Fourier transform (DFT) coefficients of each disk to improve the robustness against common image processing operations. Extensive experimental results and comparisons with some representative image watermarking methods confirm the excellent performance of the proposed method in robustness against various geometric distortions as well as common image processing operations. ? Springer Science+Business Media, LLC 2010.Accession Number: 20102212974925 -
Record 259 of
Title:Improvement of thermal indium sealing by metal layer growth
Author(s):Zhao, Feifei(1,2); Zhao, Baosheng(1); Li, Wei(3); Sai, Xiaofeng(1); Wei, Yonglin(1); Zou, Wei(1)Source: Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology Volume: 30 Issue: 4 DOI: Published: August 2010Abstract:The paper addressed the enhancement of wettibility of In-Sn alloy on the glass surface, modified with the different multi-layers of Cr, Ni, Cu and Ag, grown by electron beam evaporation. The interfacial microstructures and the wettibility of In-Sn alloy on the glass were characterized with scanning electron microscopy. The results show that the microstructures of the multi-layer improve the we ttibility and spreadability of In-Sn alloy on glass to a varying degree. We suggest that the glass covered with Cr/Ni/Cu/Ag multilayered films outperform that modified with other 4 types of multilayers in thermal indium sealing-better air-tightness and higher rate of the finished products.Accession Number: 20103513195201 -
Record 260 of
Title:Vibration and temperature insensitive fiber-optic current transducer
Author(s):Mu, Jie(1,2); Wang, Jia(1); Zhao, Wei(1); Xu, Jin-Tao(1)Source: Gaodianya Jishu/High Voltage Engineering Volume: 36 Issue: 4 DOI: Published: April 2010Abstract:The insensitivity to vibration and the temperature drift are two defects of the fiber-optic current transducer based on the Faraday effect, which restrict its harsh environment engineering applications. Therefore, a new scheme of fiber-optic current transducer insensible to vibration and temperature is designed and verified. Its sensing fiber coil is fabricated by the bifilar winding technique, which consists of one half-wave plate embedded in the middle of the sensing optical fiber and one quarter-wave plate rotated by 90 degrees in its input port. Theoretical analysis with Jones matrix shows that the new transducer is insensitive to vibration and temperature. Experimental results using low-frequency vibration test table and low/high temperature chamber suggest that, this new transducer can steadily measure the current from 100 to 1000 A under strong mechanical vibration at accelerations up to 20 g and frequencies from 10 to 400 Hz, with good linearity and a relative deviation of no higher than ± 0.2%. Furthermore, its temperature drift is eliminated in the temperature range of -50°C~50°C. This configuration, with simple structure, high accuracy and immunity to circumstance, is a new technique for fiber-optic current transducers design.Accession Number: 20102212974504 -
Record 261 of
Title:In-depth study on propane-air combustion enhancement with dielectric barrier discharge
Author(s):Tang, Jie(1); Zhao, Wei(1); Duan, Yixiang(2)Source: IEEE Transactions on Plasma Science Volume: 38 Issue: 12 PART 1 DOI: 10.1109/TPS.2010.2084597 Published: December 2010Abstract:Low-temperature plasmas generated from dielectric barrier discharges (DBDs) play an important role in hydrocarbon combustion reactions. In this paper, two different arrangements of coaxial cylindrical DBD reactors are designed to investigate the enhancement processes of plasma-assisted propane combustion through activating propane and air, respectively. Each reactor corresponds to one kind of activation method. With plasma being on and off, the physical appearances of the propane combustion flame are observed and compared, and the spatial distributions of the flame temperature are measured and comparatively investigated under each activation approach. In addition, some major components such as OH, CH, and $\hbox{C}-{2}$ in the combustion flame are identified using flame/plasma emission spectroscopy. The relationship of OH radical concentration with flame position is studied when plasma is on and off, and concentration profiles as well as densities of these major components in the main combustion zone are qualitatively measured and analyzed. Possible physical and chemical reaction mechanisms in the plasma and flame zones are discussed in detail under both activation ways. Experimental results suggest that propane combustion be enhanced with plasma applied on either propane or air stream. A temperature rise of about 30° C is achieved for the activation of propane, but about 50 °C is achieved for the activation of air with a 30-W plasma being applied. It denotes that some active species like O-atoms, N-atoms, and excited molecular oxygen and nitrogen produced by activating air components play a greater role than those smaller fragments and radicals generated by cracking propane in plasma-assisted combustion in our experimental conditions. ? 2006 IEEE.Accession Number: 20105113507911 -
Record 262 of
Title:Geometric distortion insensitive image watermarking in affine covariant regions
Author(s):Gao, Xinbo(1); Deng, Cheng(1); Li, Xuelong(2); Tao, Dacheng(3)Source: IEEE Transactions on Systems, Man and Cybernetics Part C: Applications and Reviews Volume: 40 Issue: 3 DOI: 10.1109/TSMCC.2009.2037512 Published: May 2010Abstract:Feature-based image watermarking schemes, which aim to survive various geometric distortions, have attracted great attention in recent years. Existing schemes have shown robustness against rotation, scaling, and translation, but few are resistant to cropping, nonisotropic scaling, random bending attacks (RBAs), and affine transformations. Seo and Yoo present a geometrically invariant image watermarking based on affine covariant regions (ACRs) that provide a certain degree of robustness. To further enhance the robustness, we propose a new image watermarking scheme on the basis of Seos work, which is insensitive to geometric distortions as well as common image processing operations. Our scheme is mainly composed of three components: 1) feature selection procedure based on graph theoretical clustering algorithm is applied to obtain a set of stable and nonoverlapped ACRs; 2) for each chosen ACR, local normalization, and orientation alignment are performed to generate a geometrically invariant region, which can obviously improve the robustness of the proposed watermarking scheme; and 3) in order to prevent the degradation in image quality caused by the normalization and inverse normalization, indirect inverse normalization is adopted to achieve a good compromise between the imperceptibility and robustness. Experiments are carried out on an image set of 100 images collected from Internet, and the preliminary results demonstrate that the developed method improves the performance over some representative image watermarking approaches in terms of robustness. ? 2006 IEEE.Accession Number: 20101712883042 -
Record 263 of
Title:Eight-channel Fourier transform computer generated holograms
Author(s):Guo, Rongli(1,2,3); Yao, Baoli(2); Han, Jun(1); Lu, Shaojun(1); Duan, Cunli(1); Wang, Fan(4)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 7848 Issue: DOI: 10.1117/12.871674 Published: 2010Abstract:A method of encoding eight objects simultaneously in a detour computer generated hologram(CGH) is proposed. In the method, we divide eight objects into two groups and multiple objects are encoded through synthesized spectrum. The simulation demonstrated the effectiveness of the method. In the reconstruction two groups of objects were reconstructed around the same diffraction order along x, y directions, respectively. The result showed that the method can improve the information capacity in a CGH efficiently. ? 2010 Copyright SPIE - The International Society for Optical Engineering.Accession Number: 20110113551000 -
Record 264 of
Title:On combining morphological component analysis and concentric morphology model for mammographic mass detection
Author(s):Gao, Xinbo(1); Wang, Ying(1); Li, Xuelong(2); Tao, Dacheng(3)Source: IEEE Transactions on Information Technology in Biomedicine Volume: 14 Issue: 2 DOI: 10.1109/TITB.2009.2036167 Published: March 2010Abstract:Mammographic mass detection is an important task for the early diagnosis of breast cancer. However, it is difficult to distinguish masses from normal regions because of their abundant morphological characteristics and ambiguous margins. To improve the mass detection performance, it is essential to effectively preprocess mammogram to preserve both the intensity distribution and morphological characteristics of regions. In this paper, morphological component analysis is first introduced to decompose a mammogram into a piecewise-smooth component and a texture component. The former is utilized in our detection scheme as it effectively suppresses both structural noises and effects of blood vessels. Then, we propose two novel concentric layer criteria to detect different types of suspicious regions in a mammogram. The combination is evaluated based on the Digital Database for Screening Mammography, where 100 malignant cases and 50 benign cases are utilized. The sensitivity of the proposed scheme is 99% in malignant, 88% in benign, and 95.3% in all types of cases. The results show that the proposed detection scheme achieves satisfactory detection performance and preferable compromises between sensitivity and false positive rates. ? 2009 IEEE.Accession Number: 20101212800234