2016
2016
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Record 121 of
Title:Nonspherical hollow α-Fe2O3 structures synthesized by stepwise effect of fluoride and phosphate anions
Author(s):Wang, Conghui(1,5); Shi, Jing(4); Cui, Xinmin(1,5); Wang, Huixiang(1,5); Wu, Jianghong(1,5); Zhang, Chenghua(1,3); Wang, Liancheng(1); Lv, Baoliang(1); Xu, Yao(2)Source: Journal of Materials Chemistry A Volume: 4 Issue: 28 DOI: 10.1039/c6ta03228a Published: 2016Abstract:Despite the significant progress in making hollow structures, it is still a challenge to synthesize some specialized hollow structures. In the present work, we obtained a new hollow hematite structure, tube-in-dodecahedron, by using the stepwise influences of fluoride and phosphate anions. Based on condition-dependent experiments, we proposed a "nucleation-aggregation-recrystallition and etching" mechanism, which also directed us to synthesize a series of hematite hollow structures, including hollow dodecahedron and hollow ellipsoid. The concentration of phosphate was found to play a decisive role in the control of these hollow structures. 0.08 mM is the critical point for keeping the top facets of dodecahedral hematite particles while 0.2 mM is the upper limit for keeping the lateral facets. The magnetic properties of these synthesized hollow hematite structures were found to be closely associated with the structures. The synthesized tube-in-dodecahedral hematite particles exhibited excellent photocatalytic reactivity toward organic dyes. ? 2016 The Royal Society of Chemistry.Accession Number: 20162902616570 -
Record 122 of
Title:Self-deployable structure designed for space telescope for microsatellite application
Author(s):Zhao, Chao(1); Li, Chuang(2); Zhou, Nan(2); Liao, Hongqiang(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9685 Issue: DOI: 10.1117/12.2242957 Published: 2016Abstract:With the gradual development of micro-satellite technology and the extension of application field of earth observation technology, researchers show more concern and attention on how to obtain high-resolution images with microsatellite platform equipped with space telescope. Such microsatellites require the space telescopes with small volume, low mass, and low cost. Deployable telescope is a good choice to meet these requirements, and it has the same capabilities as the traditional space telescope. We investigate a space telescope with smart self-deployable structure. The telescope is folded before launch, the distance between primary mirror and secondary mirror becomes short and the volume of the telescope becomes small, and the telescope extends to its working configuration after it is in orbit. The deployable structure is one of the key techniques of deployable space telescope, and this paper focuses on the design of a self-deployable structure of the secondary mirror. There are mainly three parts in this paper. Firstly, the optics of the telescope is presented, and a Ritchey-Chretien (RC) type optical system is designed. Secondly, the self-deployable structure is designed and the finite element method (FEM) is used to analyze dynamics of the extended telescope. Thirdly, an adjusting mechanism with six degrees of freedom to correct the misalignment of the secondary mirror is investigated, and the kinematics is discussed. ? 2016 SPIE.Accession Number: 20164903095205 -
Record 123 of
Title:A method for extracting urban built-up area based on RS indexes
Author(s):Qin, Ruijiao(1,2); Li, Jiansong(3); Tang, Huijun(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 10156 Issue: DOI: 10.1117/12.2247393 Published: 2016Abstract:Within administrative regions, urban built-up areas are vast stretches of constructed areas equipped with basic public facilit ies. Human act ivit ies most frequently take place within urban regions and the dynamic evolution of urbanization has caused profound variations in urban spatial structures. Conventional boundary extraction methods are complicated and require human intervention. This article innovatively proposes a vector method that combines a data-dimension compression index known as an Index-based Built-up Index (IBI) with aggregate analysis to extract vector boundaries of urban built-up areas automatically by setting a threshold value and the parameters for aggregate analysis. Datadimension compression technology is used to extract urban built-up areas using thematic bands (rather than original bands) to build indexes, which improves the precision of extraction. Areas ext racted by the methods above contains urban built-up areas, rural built-up areas, independent houses and fully bare areas. Aggregate analysis aggregates a certain range of non-Adjacent plots into a new polygon section. This method has made it easy to analyze the spatial expansion of Wuhan city from 2003 to 2013. This method avoids cumbersome process es of outlining vector boundaries by artificial visual interpretation with a better working efficiency and reduced costs than other methods, which cannot accurately determine vector boundaries to an accurate degree by manual vector quantizat ion without depending on other data or expert knowledge. Compared with t raditional boundary extraction methods, this vector method is more efficient, precise, objective, and exquisite. ? 2016 SPIE.Accession Number: 20165103154249 -
Record 124 of
Title:Stray light measurement for point source transmittance of space optical systems
Author(s):Chen, Qinfang(1); Ma, Zhen(1); Li, Xinyao(2); Pang, Zhihai(1); Xu, Liang(1); Li, Zhaohui(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9684 Issue: DOI: 10.1117/12.2243405 Published: 2016Abstract:The increased sensitivity of space-based sensors has imposed greater stray light performance goals on telescope design. To meet the demand, a stray light test station for measuring point source transmission (PST) has been built with a lower threshold and higher accuracy. The station is nearly all black with dimensions of 28m long by 8m wide by 9m high. it is coupled with a double cylindrical chamber that reflects the specular light away from the instrument under test. The chamber is a Class 6 cleanroom. The station will allow measuring the instruments with up to a 1 meters diameter, and to perform these measurements at visible and infrared wavelengths. The instrument under test will allow to scan at azimuth angles ±110°, and at elevation ±15°. The tests were performed to estimate stray light characteristics of two optical instruments. Test results demonstrated PST performance below 1×10-7 at visible wavelengths, and 1×10-6 at infrared wavelengths. ? 2016 SPIE.Accession Number: 20165003113959 -
Record 125 of
Title:Thermally accelerated ageing test of 808nm high power diode laser arrays in CW mode
Author(s):Nie, Zhiqiang(1); Wu, Di(2); Lu, Yao(1); Wu, Dhai(1); Wang, Shuna(1); Zhang, Pu(1); Xiong, Lingling(1); Li, Xiaoning(2); Shen, Zenan(2)Source: 2016 17th International Conference on Electronic Packaging Technology, ICEPT 2016 Volume: Issue: DOI: 10.1109/ICEPT.2016.7583100 Published: October 4, 2016Abstract:The reliability is the important performance of high power semiconductor laser. Thermally accelerated ageing test is an important technology of lifetime evaluation and reliability analysis. In this study, three groups of thermally accelerated ageing tests of conduction-cooled-packaged 60W 808nm high power diode laser arrays packaged by Indium solder at constant current have been carried out. Analysis of ageing data suggest the extrapolated lifetime under room temperature to value device reliability. We also analyze and discuss the degradation modes. This work can provide guidance for optimizing the chip and package structure, is helpful for improving performance and enhancing reliability of high power semiconductor lasers. ? 2016 IEEE.Accession Number: 20164502990952 -
Record 126 of
Title:Dual-wavelength synchronous mode-locked Yb:LSO laser using a double-walled carbon nanotube saturable absorber
Author(s):Feng, Chao(1); Hou, Wei(1); Yang, Jimin(1); Liu, Jie(1); Zheng, Lihe(2); Su, Liangbi(2); Xu, Jun(3); Wang, Yonggang(4)Source: Applied Optics Volume: 55 Issue: 13 DOI: 10.1364/AO.55.003639 Published: May 1, 2016Abstract:A dual-wavelength, passively mode-locked Yb:LSO laser was demonstrated using a double-walled carbon nanotube as a saturable absorber. The maximum average output power of the laser was 1.34 W at the incident pump power of 9.94 W. The two central wavelengths were 1057 and 1058 nm. The corresponding pulse duration of the autocorrelation interference pattern was about 15 ps, while the beat pulse repetition rate was 0.17 THz and the width of one beat pulse about 2 ps. When the incident pump power was above 10.25 W, a multiwavelength mode-locked oscillation phenomenon was observed. After employing a pair of SF10 prisms, a 1058.7 nm singlewavelength mode-locked laser was obtained with a pulse width of 7 ps. ? 2016 Optical Society of America.Accession Number: 20161902362739 -
Record 127 of
Title:Numerical simulation of thermo-mechanical behavior in high power diode laser arrays
Author(s):Lu, Yao(1); Nie, Zhiqiang(1); Zhang, Pu(1); Wang, Zhenfu(1); Xiong, Lingling(1); Wang, Shuna(1); Wu, Dihai(1); Liu, Xingsheng(2)Source: 2016 17th International Conference on Electronic Packaging Technology, ICEPT 2016 Volume: Issue: DOI: 10.1109/ICEPT.2016.7583094 Published: October 4, 2016Abstract:Thermal stress is an influential factor for the reliability of HPDL and their optical properties. Two packages of conduction-cooled-packaged 60W HPDL were selected as the study samples. In order to investigate what reflow factors influence thermo-mechanical of HPLD, a COS model is established. In reflow process and working process, hard solder package suffers higher thermal stress. Thermal stress mainly comes from reflow process. In reflow process, copper mount will deteriorate thermo-mechanical of hard solder package. There exists shear stress in HPLD and it will convert TE-polarized power to TM-polarized power. In working process, uniaxial normal stress along the width direction of QW is mainly influenced by coefficient expansion thermal. The displacement of HCS along growth direction is larger than that of CS, whereas the 'smile' value is smaller. 'Smile' is mainly impacted by CTE of solder and submount. ? 2016 IEEE.Accession Number: 20164502990946 -
Record 128 of
Title:Weakly supervised human fixations prediction
Author(s):Zhang, Luming(1); Li, Xuelong(2); Nie, Liqiang(3); Yang, Yi(4); Xia, Yingjie(5)Source: IEEE Transactions on Cybernetics Volume: 46 Issue: 1 DOI: 10.1109/TCYB.2015.2400821 Published: January 2016Abstract:Automatically predicting human eye fixations is a useful technique that can facilitate many multimedia applications, e.g., image retrieval, action recognition, and photo retargeting. Conventional approaches are frustrated by two drawbacks. First, psychophysical experiments show that an object-level interpretation of scenes influences eye movements significantly. Most of the existing saliency models rely on object detectors, and therefore, only a few prespecified categories can be discovered. Second, the relative displacement of objects influences their saliency remarkably, but current models cannot describe them explicitly. To solve these problems, this paper proposes weakly supervised fixations prediction, which leverages image labels to improve accuracy of human fixations prediction. The proposed model hierarchically discovers objects as well as their spatial configurations. Starting from the raw image pixels, we sample superpixels in an image, thereby seamless object descriptors termed object-level graphlets (oGLs) are generated by random walking on the superpixel mosaic. Then, a manifold embedding algorithm is proposed to encode image labels into oGLs, and the response map of each prespecified object is computed accordingly. On the basis of the object-level response map, we propose spatial-level graphlets (sGLs) to model the relative positions among objects. Afterward, eye tracking data is employed to integrate these sGLs for predicting human eye fixations. Thorough experiment results demonstrate the advantage of the proposed method over the state-of-the-art. ? 2015 IEEE.Accession Number: 20152901035155 -
Record 129 of
Title:Improvement of CO2 capture performance of calcium-based absorbent modified with palygorskite
Author(s):Shan, Liyuan(1); Li, Hui(1,2); Meng, Binglu(3); Yu, Youhai(3); Min, Yonggang(1,2)Source: Chinese Journal of Chemical Engineering Volume: 24 Issue: 9 DOI: 10.1016/j.cjche.2016.05.021 Published: September 1, 2016Abstract:Limestone can be used for CO2 capture and sequestration (CCS) in flue gas effectively. However, its CCS capability will dramatically decline after several cycles due to the surface "sintering". In this work, the limestone was modified with palygorskite to reduce sintering phenomenon between the absorbent particles during the CCS process and the carbonation rate of the limestone can be enhanced effectively. Palygorskite is a natural mineral with nano-fibrous structure which can reduce the mutual contact of limestone particles during the CCS process. The results were detected by TGA, SEM, MIP, FTIR and particle size analyzer respectively. The best CO2 capture performance of modified absorbent was 13.11% improvement with only 5?wt% palygorskite added during the CCS process after 15?cycles compared with natural absorbent. It was found that excellent microscopic structures of absorbent modified with palygorskite was created, and the surface sintering was postponed leading to CO2 capture performance enhanced under the same conditions. ? 2016 Elsevier B.V.Accession Number: 20164402970351 -
Record 130 of
Title:Weakly Supervised Multilabel Clustering and its Applications in Computer Vision
Author(s):Xia, Yingjie(1); Nie, Liqiang(2); Zhang, Luming(3); Yang, Yi(4); Hong, Richang(3); Li, Xuelong(5)Source: IEEE Transactions on Cybernetics Volume: 46 Issue: 12 DOI: 10.1109/TCYB.2015.2501385 Published: December 2016Abstract:Clustering is a useful statistical tool in computer vision and machine learning. It is generally accepted that introducing supervised information brings remarkable performance improvement to clustering. However, assigning accurate labels is expensive when the amount of training data is huge. Existing supervised clustering methods handle this problem by transferring the bag-level labels into the instance-level descriptors. However, the assumption that each bag has a single label limits the application scope seriously. In this paper, we propose weakly supervised multilabel clustering, which allows assigning multiple labels to a bag. Based on this, the instance-level descriptors can be clustered with the guidance of bag-level labels. The key technique is a weakly supervised random forest that infers the model parameters. Thereby, a deterministic annealing strategy is developed to optimize the nonconvex objective function. The proposed algorithm is efficient in both the training and the testing stages. We apply it to three popular computer vision tasks: 1) image clustering; 2) semantic image segmentation; and 3) multiple objects localization. Impressive performance on the state-of-the-art image data sets is achieved in our experiments. ? 2016 IEEE.Accession Number: 20161502223579 -
Record 131 of
Title:A kind of infrared expand depth of field vision sensor in low-visibility road condition for safety-driving
Author(s):Wang, Hui-Feng(1); Wang, Gui-Ping(1); Wang, Xiao-Yan(1); Ruan, Chi(2); Chen, Shi-Qin(1)Source: Sensor Review Volume: 36 Issue: 1 DOI: 10.1108/SR-04-2015-0055 Published: January 18, 2016Abstract:Purpose - This study aims to consider active vision in low-visibility environments to reveal the factors of optical properties which affect visibility and to explore a method of obtaining different depths of fields by multimode imaging. Bad weather affects the driver's visual range tremendously and thus has a serious impact on transport safety. Design/methodology/approach - A new mechanism and a core algorithm for obtaining an excellent large field-depth image which can be used to aid safe driving is designed and implemented. In this mechanism, atmospheric extinction principle and field expansion system are researched as the basis, followed by image registration and fusion algorithm for the Infrared Extended Depth of Field (IR-EDOF) sensor. Findings - The experimental results show that the idea we propose can work well to expand the field depth in a low-visibility road environment as a new aided safety-driving sensor. Originality/value - The paper presents a new kind of active optical extension, as well as enhanced driving aids, which is an effective solution to the problem of weakening of visual ability. It is a practical engineering sensor scheme for safety driving in low-visibility road environments. ? Emerald Group Publishing Limited.Accession Number: 20160501865982 -
Record 132 of
Title:Single-walled carbon nanotube saturable absorber for a diode-pumped passively mode-locked Nd,Y:SrF2 laser
Author(s):Li, Chun(1); Cai, Wei(1); Liu, Jie(1); Su, Liangbi(2); Jiang, Dapeng(2); Ma, Fengkai(2); Zhang, Qian(2); Xu, Jun(3); Wang, Yonggang(4)Source: Optics Communications Volume: 372 Issue: DOI: 10.1016/j.optcom.2016.04.012 Published: August 1, 2016Abstract:A reflective single-walled carbon nanotube as saturable absorber has been firstly adopted to a passively mode-locked Nd,Y:SrF2 crystal. Without any dispersion compensation, the stably mode-locked laser delivers pulses with pulse width as short as 1.7 ps, repetition rate of 107.8 MHz and center wavelength of 1056 nm. The oscillator produces maximum average output power of 319 mW corresponding with a high slope efficiency of 20.2%. The single pulse energy and the peak power are 2.96 nJ and 1.74 kW, respectively. The experimental results show that single-walled carbon nanotube is an excellent saturable absorber for mode-locked lasers. ? 2016 Published by Elsevier B.V.Accession Number: 20161702282318