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General Solution and Fractal Localized Structures for the (2+1)-Dimensional Generalized Ablowitz-Kaup-Newell-Segur System
ZHENG Chun-Long, , ZHANG Jie-Fang,
Chin. Phys. Lett. 2002, 19 (10):
1399-1402
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Using the standard truncated Painlevé expansions, we derive a quite general solution of the (2+1)-dimensional generalized Ablowitz-Kaup-Newell-Segur (AKNS) system. Except for the usual localized solutions, such as dromions, lumps, and ring soliton solutions, etc., some special localized excitations with fractal behaviour, i.e., the fractal dromion and fractal lump excitations, are obtained by some types of lower-dimensional fractal patterns.
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Non-statistical Fluctuation of Compound Multiplicity in Nucleus-Nucleus Interactions: Evidence of Strong Intermittency
Dipak Ghosh, Argha Deb, Pasupati Mandal, Subrata Biswas, Keya Chattopadhyay, Rinku Sarkar, Ishita Dutta, Biswanath Biswas, Jayanta Roychowdhury, Jayita Ghosh, Mitali Mondal, Swarnapratim Bhattacharyya, Kanchan Kr. Patra, Swarup Ranjan Sahoo, Prabir Kr. Haldar
Chin. Phys. Lett. 2002, 19 (10):
1436-1438
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We present a study of the ‘compound multiplicity’distribution in terms of scaled factorial moments of orders 2, 3, 4, and 5 in 24Mg-AgBr interactions at 4.5 AGeV. The study reveals a strong signal of the intermittent pattern of fluctuation in the compound multiplicity distribution.
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Three-Colour Single-Mode Electroluminescence from Alq3 Tuned by Microcavities
ZHAO Jia-Min, MA Feng-Ying, LIU Xing-Yuan, LIU Yun, CHU Guo-Qiang, NING Yong-Qiang, WANG Li-Jun,
Chin. Phys. Lett. 2002, 19 (10):
1447-1449
.
Organic metal microcavities were fabricated by using full-reflectivity aluminum film and semi-transparent silver film as cavity mirrors. Unlike conventional organic microcavities, such as the typical structure of glass/DBR/ITO/organic layers/metal mirror, a microcavity with a shorter cavity length was obtained by using two metal mirrors, where DBR is the distributed Bragg reflector consisted of alternate quarter-wave layers of high and low refractive index material. It is realized that red, green and blue single-mode electroluminescence (EL) from the microcavities with the structure, glass/Ag/TPD/Alq3/Al, are electrically-driven when the thickness of Alq3 layer changes. Compared to a non-cavity reference sample whose EL spectrum peak is located at 520 nm with a full width at half maximum (FWHM) of 93 nm, the microcavity devices show apparent cavity effects. The EL spectra of red, green and blue microcavities are peaked at 604 nm, 540 nm, and 491 nm, whose FWHM are 43 nm, 38 nm, and 47 nm, respectively.
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Experimental Phenomena of Improved Ohmic Confinement Induced by Modulated Toroidal Current on the HT-7 Tokamak
MAO Jian-Shan, LUO Jia-Rong, P. Phillips, ZHAO Jun-Yu, JIE Yin-Xian, WU Zhen-Wei, HU Li-Qun, LI Jian-Gang
Chin. Phys. Lett. 2002, 19 (10):
1467-1469
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The phenomena of improved Ohmic confinement have been observed during modulation of toroidal current on the Hefei superconducting Tokamak-7 (HT-7). In the experiment, the programming ohmic heating field was modulated. A toroidal frequency-modulated current induced by modulated loop voltage was added on the plasma equilibrium current. The ratio of ac amplitude of the plasma current to the main plasma current is about 12%--30%. These improved plasma confinement phenomena include the facts that the average electron density and the central electron temperature both increase, the Dα radiation from the edge is reduced, the magnetichydrodynamics is obviously suppressed by oscillating plasma current, and the global energy confinement time increases by 27%-45%. It is found that the faster the modulation is, the more effective the improved ohmic confinement phase.
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Calculation of the Griffith Cohesive Energy of the Ni3AlBx Symmetrical Grain Boundary
ZHENG Li-Ping, ZHANG Hu-Yong, LI Dou-Xing, CUI Fu-Zhai
Chin. Phys. Lett. 2002, 19 (10):
1490-1493
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A Monte Carlo simulation, with the energetics described by the embedded atom method, has been employed to study the physical behaviour of boron atoms during relaxation of the Ni3AlBx grain boundary, It has also been used to calculate not only the peak concentrations of Ni and B and the valley concentration of Al at the grain boundary, but also the dependence of the grain boundary cohesion on the B bulk concentration. During relaxation of impure Ni3Al grain boundaries, we suggest that, as the segregating species, the B atoms either insert into interstices in the grain boundary or substitute Ni atoms. Meanwhile, as the inducing species, they induce Ni atoms to substitute for Al atoms. Calculations show that in the equilibrium, when the B bulk concentration x increases from 0.1 to 0.9, the peak concentration of B increases, the peak concentration of Ni maximizes while the valley concentration of Al minimizes at x = 0.5. The calculations also show the best cohesion of the grain boundary at x = 0.5.
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Preparation of p-n Junction Diode by B-Doped Diamond Film Grown on Si-Doped c-BN
WANG Cheng-Xin, GAO Chun-Xiao, ZHANG Tie-Chen, LIU Hong-Wu, LI Xun, HAN Yong-Hao, LUO Ji-Feng, SHEN Cai-Xia
Chin. Phys. Lett. 2002, 19 (10):
1513-1515
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A Heterojunction diode has been fabricated by boron-doped p-type diamond thin film grown epitaxially on a silicon-doped n-type cubic boron nitride bulk crystal using the conventional hot filament chemical vapor deposition method. The ohmic electrode of Ti (50 nm)/Mo (100 nm)/Au (300 nm) for the p-type diamond film and the bulk crystal of the c-BN were deposited by the rf planar magnetron method. Then the device was annealed at 410°C in air for 1 h in order to form ohmic metal alloy. The I-V characteristics of the hetero-junction diode were measured and the result indicated that the rectification ratio reached 105, and the turn-on voltage and the highest current were 7 V and 0.35 mA, respectively.
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Enhanced Electron Injection Efficiency and Electroluminescence
in Organic Light-Emitting Diodes by Using an Sn/Al Cathode
LI Feng, CHENG Gang, FENG Jing, LIU Shi-Yong
Chin. Phys. Lett. 2002, 19 (10):
1534-1536
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A series of organic light-emitting diodes (OLEDs) have been fabricated with different thickness of the tin (Sn) layer. The structure of the devices is indium-tin oxide (ITO)/copper phthalocyanine (CuPc)(12 nm)/N, N'-diphenyl-N, N'-bis(1-naphthyl)-(1,1'-biphenyl)-4, 4'-diamine (NPB) (60 nm)/tris-(8-hydroxyquinoline)aluminum (Alq3) (60 nm)/Sn/aluminum (Al)(120 nm). It is found that compared to OLEDs with only Al cathode, both the electron injection efficiency and electroluminescence are improved when the thickness of the Sn layer is properly chosen. The maximum efficiency and brightness of the devices with Sn (2.1 nm)/Al and Al cathode are 0.54lm/W and 9800cd/m2, 0.26lm/W and 3000cd/m2, respectively. One possible explanation to this phenomenon is that the enhancement of the electron density of the Sn layer due to the electron transfer from the Al to the Sn layer leads to the improvement of the electron injection efficiency and electroluminescence.
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Photocurrent Property of GaN on the Si Photodetector with a Nearly Polycrystalline α-Al2O3 Buffer Layer
JIANG Ruo-Lian, WANG Jun-Zhuan, CHEN Peng, ZHAO Zuo-Ming, MEI Yong-Feng, SHEN Bo, ZHANG Rong, WU Xing-Long, ZHENG You-Dou
Chin. Phys. Lett. 2002, 19 (10):
1553-1555
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Using nearly polycrystalline α-Al2O3 as the buffer layer, GaN epilayers were grown on Si (111) substrates by low pressure metalorgnic chemical-vapor deposition. The nearly polycrystalline α-Al2O3 was formed by anodic porous alumina annealed at high temperature. Prototype photoconductive detectors were fabricated with these materials. The spectral response of these detectors exhibits a relatively sharp cutoff near the wavelength of 360 nm and a peak at 340 nm with a shoulder near 360 nm. Under 5 V bias, the responsivities at 340 nm and 360 nm were measured to be 3.3 A/W and 2.4 A/W, respectively. The relationship between the responsivity and the bias voltage shows that the responsivity is saturated when the bias voltage reaches 5 V.
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52 articles
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