| 160821. |
- Liu, Bingbing, et al.
(författare)
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Bromine doped single-walled carbon nanotubes
- 2001
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Ingår i: Nanotubes and Related Materials. - Warrendale : Materials Research Society. - 1558995439 ; , s. A13.36-
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Konferensbidrag (refereegranskat)abstract
- Raman spectra for three SWNT samples doped with Br2 were studied using different excitation energies, 2.41 eV and 1.58 eV. One sample was also studied under high pressure up to 2GPa. The vibrations in the low frequency range behave similarly for all samples. With an excitation energy of 1.58eV, additional peaks at ca 240 cm-1 and 209 cm-1 are observed. With increasing pressure, the peak at 209 cm-1 gradually softens by 2~3 cm-1 and becomes very weak at 1.7 GPa, while a new broader peak at ca 250 cm-1 remains constant up to 2 GPa. A number of high intensity overtone modes are observed under high pressure. These results indicate that the vibrations are attributed to bromine, not to the breathing modes of SWNTs, and that bromine resides in the bundles, possibly also inside tubes as a form of polymer.
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| 160822. |
- Liu, Bin, et al.
(författare)
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Compensation of Load-Dependent Position Error for A Hybrid Stepper Motor
- 2017
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Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON MECHATRONICS AND AUTOMATION (ICMA). - : IEEE. - 9781509067596 ; , s. 846-851
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Konferensbidrag (refereegranskat)abstract
- Load-dependent position error and its compensation approach in a hybrid stepper motor has been studied in this paper. With stepper motor modelling and load angle concept, low position stiffness feature for a stepper motor with open loop operation has been explained. A specific field oriented control has been proposed to maximize stepper motor position stiffness. Experimental verification shows the effectiveness of the proposed method. Results also show that stepper motor efficiency can be improved significantly by the proposed method.
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| 160823. |
- Liu, Bin, et al.
(författare)
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Cryptographic Role-Based Access Control, Reconsidered
- 2022
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Ingår i: <em>Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)</em>Volume 13600 LNCS, Pages 282 - 2892022. - Cham : Springer Science and Business Media Deutschland GmbH. - 9783031209161 ; , s. 282-289
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Konferensbidrag (refereegranskat)abstract
- In this paper, we follow the line of existing study on cryptographic enforcement of Role-Based Access Control (RBAC). Inspired by the study of the relation between the existing security definitions for such system, we identify two different types of attacks which cannot be captured by the existing ones. Therefore, we propose two new security definitions towards the goal of appropriately modelling cryptographic enforcement of Role-Based Access Control policies and study the relation between our new definitions and the existing ones. In addition, we show that the cost of supporting dynamic policy update is inherently expensive by presenting two lower bounds for such systems which guarantee correctness and secure access. © 2022, The Author(s).
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| 160824. |
- Liu, Bingchen, et al.
(författare)
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GPU-Accelerated Direct Volume Rendering of Finite Element Data Sets
- 2012
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Direct Volume Rendering of Finite Element models is challengingsince the visualisation process is performed in worldcoordinates, whereas data fields are usually defined overthe elements’ material coordinate system. In this paper wepresent a framework for Direct Volume Rendering of FiniteElement models. We present several novel implementationsvisualising Finite Element data directly without requiring resamplinginto world coordinates. We evaluate the methodsusing several biomedical Finite Element models. Our GPUimplementation of ray-casting in material coordinates usingdepth peeling is several orders of magnitude faster than thecorresponding CPU approach, and our new ray interpolationapproach achieves near interactive frame rates for high-orderfinite element models at high resolutions.
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| 160825. |
- Liu, Bingbing, et al.
(författare)
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High pressure and high temperature induced polymeric C60 nanocrystal
- 2008
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Ingår i: Diamond and related materials, vol. 17, issue 4-5. - Amsterdam : Elsevier B.V.. ; , s. 620-623
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Konferensbidrag (refereegranskat)abstract
- In this paper, C60 nanosheets with polymeric phases have been obtained under various high pressures and high temperatures, including orthorhombic and tetragonal polymeric phases. The structures have been identified and compared with those of nanorods by photoluminescence and Raman spectroscopies. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The difference of photoluminescence and Raman spectra between nanosheets and nanorods samples treated under the same conditions is probably caused by different polymerization degree in these samples because of different shapes.
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| 160826. |
- Liu, Bingbing, et al.
(författare)
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High pressure and high temperature induced polymeric C60 nanorods and their photoluminiscence properties.
- 2007
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Ingår i: Materials Research at High Pressure. - Warrendale : Maerials Research Society. - 9781558999442 ; , s. 99-103
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Konferensbidrag (refereegranskat)abstract
- We report that C60 nanorods of three polymeric phases have been synthesized under high pressure and high temperature and that the photoluminescence properties of these polymeric nanorods also have been studied. C60 nanorods were fabricated by a facile solution evaporation method. Raman spectra indicate that this material transformed into orthorhombic, tetragonal and rhombohedral polymeric phases under various high pressure and high temperature conditions. SEM measurements show that the shape of the nanorods can be kept under quasi-hydrostatic pressure condition. The photoluminescence intensity of the polymeric C60 nanorods has been enhanced compared with that of the pristine C60 nanorods. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The enhanced fluorescence with adjustable frequency for different polymeric C60 nanorods makes possible potential application in luminescent nanomaterials.
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| 160827. |
- Liu, Bingbing, et al.
(författare)
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High-pressure induced polymerization of C60 nanorods
- 2005
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Ingår i: Proceedings of the Joint 20th AIRAPT and 43rd EHPRG Conf. on High Pressure Science and Technology, Karlsruhe 2005. - 3923704496 ; , s. Nanomat-O133
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- C60 nanorods, about 200 nm in diameter and several micrometers in length and with a rectangular cross section, have been synthesized by a simple solution-growth method. Raman spectroscopy and TEM indicate that the C60 nanorods have a fcc crystalline structure similar to that of pristine C60. Nanorods were polymerized at high temperature and high pressure below 2 GPa. Two different polymeric structures, orthorhombic and tetragonal as determined by Raman spectroscopy, have been obtained under different high temperature and high pressure conditions. The high-pressure induced polymeric samples keep the original nanometer scale rod shape.
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| 160828. |
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| 160829. |
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| 160830. |
- Liu, Bilong, et al.
(författare)
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Influence of pressurization on sound insulation of curved airplane panels
- 2005
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Ingår i: 12th International Congress on Sound and Vibration 2005. - 9781627481496 ; , s. 4843-4850
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Konferensbidrag (refereegranskat)abstract
- he purpose of this paper is to investigate the pressurization effects on sound transmission through airplane panels. The airborne sound transmission through airplane panels under the condition of overpressure at one side has been investigated by measurement. The test results agree well with the theoretic prediction of infinite cylindrical shell model at high frequencies, but have considerable discrepancies at low frequencies, which, however, are ready to be explained by the influence of finiteness and stiffeners of the panel. When the frequency is higher than the ring frequency of curved panel, both test and theoretic prediction reveal that the overpressure under laboratory conditions tends to reduce the sound transmission loss at the rate of about 0.5dB/10000 Pa. while at low frequencies, say below around the ring frequency, the overpressure may increase the sound transmission loss of ring-stiffened panel, the reason of this behavior is resulted from the shift of the resonant frequencies led by the increased in-plane tension.
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