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High Performance Micro CO Sensors Based on ZnO-SnO2 Composite Nanofibers with Anti-Humidity Characteristics
YUE Xue-Jun, HONG Tian-Sheng, XIANG Wei, CAI Kun, XU Xing
Chin. Phys. Lett. 2012, 29 (12):
120702
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DOI: 10.1088/0256-307X/29/12/120702
ZnO-SnO2 composite nanofibers are synthesized via an electrospinning method and characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Micro sensors are fabricated by spinning the nanofibers on Si substrates with Pt signal and heater electrodes. The sensors with small areas (600 μm×200 μm) can detect CO down to 1 ppm at 360°C. The corresponding sensitivity, response time, and recovery time are 3.2, 6 s, and 11 s, respectively. Importantly, the sensors can operate at high humidity conditions. The sensitivity only decreases to 2.3 when the sensors are exposed to 1 ppm CO at 95% relative humidity. These excellent sensing properties are due to combining the benefits of one-dimensional nanomaterials and the ZnO-SnO2 grain boundary in the nanofibers.
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The Neutrino Energy Loss by Electron Capture of Nuclides 52,53,54,55,56Fe in Core-Collapse Supernova
LIU Jing-Jing
Chin. Phys. Lett. 2012, 29 (12):
122301
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DOI: 10.1088/0256-307X/29/12/122301
Using the shell-model Monte Carlo method and random phase approximation theory, we carry out an estimation on neutrino energy loss (NEL) of 52,53,54,55,56Fe. We find the NEL rates increase greatly at some typical stellar conditions, and even exceed eight orders of magnitude. On the other hand, in order to compare our results of λSMMCLJ (which are calculated by using the SMMC method) with those of λFFNLJ (which are calculated by using the Fuller-Fowler-Newman (FFN) method), the error factor C, between λSMMCLJ and λFFNLJ, is discussed and shows that at higher density and temperature, the fit is fairly good for the two results (λSMMCLJ and λFFNLJ), and the maximum error is ~6.20%. However, the maximum error is ~95.50% (e.g. 53Fe) at lower density and temperature.
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The 1×4 Optical Splitters Based on Silicon Photonic Crystal Self-Collimation Ring Resonators
ZHUANG Dong-Xia, CHEN Xi-Yao, LI Jun-Jun, QIANG Ze-Xuan, JIANG Jun-Zhen, CHEN Zhi-Yong, QIU Yi-Shen, LI Hui
Chin. Phys. Lett. 2012, 29 (12):
124201
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DOI: 10.1088/0256-307X/29/12/124201
We report 1 × 4 optical splitters (OSs) with different splitting ratios based on either rod-type or hole-type silicon photonic crystal self-collimation ring resonators (SCRRs). The four beam splitters of the OSs are formed by changing the radii of silicon rods or air holes. The light beam propagating along the SCRR can be controlled by the self-collimation effect. The transmission spectra at the through and drop ports are investigated by using the finite-difference time-domain (FDTD) method. The simulated results agree well with the theoretical calculation. For 1550-nm dropping wavelength, the free spectral ranges for rod-type and hole-type configurations are 28.8 nm and 32.5 nm, respectively, which almost cover the whole optical communication C-band window. The dimensions of these structures are only about 10 μm × 10 μm .
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A Switchable Multi-wavelength Erbium-Doped Photonic Crystal Fiber Laser with Linear Cavity Configuration
ZHENG Wan-Jun, CHENG Jian-Qun, RUAN Shuang-Chen**, ZHANG Min, LIU Wen-Li, YANG Xi, ZHANG Ying-Ying
Chin. Phys. Lett. 2012, 29 (12):
124204
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DOI: 10.1088/0256-307X/29/12/124204
A switchable multi-wavelength erbium-doped photonic crystal fiber laser with a linear cavity configuration based on a Sagnac loop mirror is proposed and demonstrated experimentally. The laser is based on saturated spectral hole burning and the polarization hole burning effects can be switched among single-wavelength, dual-wavelength, triple-wavelength and quadruple-wavelength outputs at room temperature. The wavelength period of the output spectrum is easily varied by using polarization maintaining fibers of different lengths. The proposed fiber laser has a signal-to-noise ratio of higher than 30 dB and achieves a low threshold power of 37 mW. The power fluctuations of the lasing lines are less than 0.54 dB,1.7 dB and 2.9 dB when the laser operates at single-wavelength, dual-wavelength and triple-wavelength for one hour.
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Temporal, Spectral and Spatial Characterization of High-Energy Laser Pulse with Small Bandwidth Propagating through Long Path
DENG Xue-Wei, WANG Fang, JIA Huai-Ting, XIANG Yong, FENG Bin, LI Ke-Yu, ZHOU Li-Dan
Chin. Phys. Lett. 2012, 29 (12):
124211
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DOI: 10.1088/0256-307X/29/12/124211
Temporal, spectral and spatial characters of 0.3-nm-bandwidth high-energy laser pulse propagating through a long path are studied in detail in one newly constructed beamline of our laser facility. The evolution of propagation, pulse energy and near-field deterioration are analyzed theoretically and experimentally. Substituting argon for air is demonstrated effectively to suppress stimulated rotational Raman scattering and the experimental result provides operating criterion, and engineering parameters for the under-constructed beamlines.
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Monte Carlo Simulation of Scattered Light with Shear Waves Generated by Acoustic Radiation Force for Acousto-Optic Imaging
LU Ming-Zhu, WU Yu-Peng, SHI Yu, GUAN Yu-Bo, GUO Xiao-Li, WAN Ming-Xi
Chin. Phys. Lett. 2012, 29 (12):
124302
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DOI: 10.1088/0256-307X/29/12/124302
A Monte Carlo method of multiple scattered coherent light with the information of shear wave propagation in scattering media is presented. The established Monte-Carlo algorithm is mainly relative to optical phase variations due to the acoustic-radiation-force shear-wave-induced displacements of light scatterers. Both the distributions and temporal behaviors of optical phase increments in probe locations are obtained. Consequently, shear wave speed is evaluated quantitatively. It is noted that the phase increments exactly track the propagations of shear waves induced by focus-ultrasound radiation force. In addition, attenuations of shear waves are demonstrated in simulation results. By using linear regression processing, the shear wave speed, which is set to 2.1 m/s in simulation, is estimated to be 2.18 m/s and 2.35 m/s at time sampling intervals of 0.2 ms and 0.5 ms, respectively.
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Influence of Pressure on the Structural, Electronic and Mechanical Properties of Cubic SrHfO3: A First-Principles Study
FENG Li-Ping, WANG Zhi-Qiang, LIU Qi-Jun, TAN Ting-Ting, LIU Zheng-Tang
Chin. Phys. Lett. 2012, 29 (12):
127103
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DOI: 10.1088/0256-307X/29/12/127103
The structural, electronic and mechanical properties of cubic SrHfO3 under hydrostatic pressure up to 70 GPa are investigated using the first-principles density functional theory (DFT). The calculated lattice parameter, elastic constants and mechanical properties of cubic SrHfO3 at zero pressure are in good agreement with the available experimental data and other calculational values. As pressure increases, cubic SrHfO3 will change from an indirect band gap (Γ –R) compound to a direct band gap (Γ–Γ) compound. Charge densities reveal the coexistence of covalent bonding and ionic bonding in cubic SrHfO3. With the increase of pressure, both the covalent bonding (HfO) and ionic bonding (SrO) are strengthened. Cubic SrHfO3 is mechanically stable when pressure is lower than 55.1 GPa, whereas that is instable when pressure is higher than 55.1 GPa. With the increasing pressure, enthalpy, bulk modulus, shear modulus and Young's modulus increase, whereas the lattice parameter decreases. Moreover, cubic SrHfO3 under pressure has higher hardness and better ductility than that at zero pressure.
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GaSb p-Channel Metal-Oxide-Semiconductor Field-Effect Transistors with Ni/Pt/Au Source/Drain Ohmic Contacts
WU Li-Shu, SUN Bing, CHANG Hu-Dong, ZHAO Wei, XUE Bai-Qing, ZHANG Xiong, LIU Hong-Gang
Chin. Phys. Lett. 2012, 29 (12):
127303
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DOI: 10.1088/0256-307X/29/12/127303
GaSb is an attractive candidate for future high-performance III–V p-channel metal-oxide-semiconductor-field-effect-transistors (pMOSFETs) because of its high hole mobility. The effect of HCl based-chemical cleaning on removing the non-self limiting and instable native oxide layer of GaSb to obtain a clean and smooth surface has been studied. It is observed that the rms roughness of a GaSb surface is significantly reduced from 2.731 nm to 0.693 nm by using HCl:H2O (1:3) solution. The Ni/Pt/Au ohmic contact exhibits an optimal specific contact resistivity of about 6.89×10?7 Ω?cm2 with a 60 s rapid thermal anneal (RTA) at 250°C. Based on the chemical cleaning and ohmic contact experimental results, inversion-channel enhancement GaSb pMOSFETs are demonstrated. For a 6 μm gate length GaSb pMOSFET, a maximum drain current of about 4.0 mA/mm, a drain current on-off (ION/IOFF) ratio of >103, and a subthreshold swing of ~250 mV/decade are achieved. Combined with the split C–V method, a peak hole mobility of about 160 cm2/V?s is obtained for a 24 μm gate length GaSb pMOSFET.
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Ultracompact Refractive Index Sensor Based on Surface-Plasmon-Polariton Interference
WANG Chen, CHEN Jian-Jun, TANG Wei-Hua, XIAO Jing-Hua
Chin. Phys. Lett. 2012, 29 (12):
127304
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DOI: 10.1088/0256-307X/29/12/127304
Using an ultracompact groove-slit-groove (GSG) structure, a refractive index sensor with a broadband response is proposed and experimentally demonstrated. Due to the interference of surface plasmon polaritons (SPPs), the transmission spectra in the GSG structure exhibit oscillation behaviors in a broad bandwidth, and they are quite sensitive to the refractive index of the surroundings. Based on the principle, the characteristics of its refractive index sensing are demonstrated experimentally. In the experiment, the structure is illuminated with a bulk light source (not a tightly focused light source) from the back side. This decreases the difficulty of the experimental measurement and can protect strong light sources from damaging the detection samples. Meanwhile, the whole structure of the sensor can be made more ultracompact without considering the influence of the incident waves.
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Influence of Film Roughness on the Soft Magnetic Properties of Fe/Ni Multilayers
LUO Zhi-Yuan, TANG Jia, MA Bin, ZHANG Zong-Zhi, JIN Qing-Yuan, WANG Jian-Ping
Chin. Phys. Lett. 2012, 29 (12):
127501
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DOI: 10.1088/0256-307X/29/12/127501
The influence of surface/interface roughness on the magnetic properties of Fe/Ni multilayers is investigated. Two methods are employed to tune the film roughness: one varies the substrate temperature, and the other pre-deposits a Ag underlayer on the MgO substrate. For films with higher roughness, a marked rise in coercivity is observed. Three factors are discussed to be mainly responsible for the coercivity rise, involving the formation of pinholes, the reduction of exchange coupling between Fe and Ni layers, and Fe-Ni alloying at interfaces.
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Ultrasonic Energy Transference Based on an MEMS ZnO Film Array
WU Shao-Hua, ZHAO Zhan, ZHAO Jun-Juan, GUO Li-Jun, DU Li-Dong, FANG Zhen, KONG De-Yi, XIAO Li, GAO Zhong-Hua
Chin. Phys. Lett. 2012, 29 (12):
127701
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DOI: 10.1088/0256-307X/29/12/127701
An ultrasonic energy transference system with a ZnO square piezoelectric thin-film array (SPTFA) structure is presented. The design principle of the system is analyzed, and a device with the SPTFA structure is successfully fabricated based on MEMS processes. The characteristics of the energy transference system are investigated in detail. The experimental results reveal that the resonant frequency of the system is 13 MHz, the maximum voltage of the receiving end reaches 10.87 V when the amplitude of excitation voltage is 10 V, at that time the output power of system is 5.377 mW, and power density is 2.581 mW/cm2. The light emitting diode is lit successfully by the system in a distance of 3 mm.
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A Novel Efficient Red Emitting Iridium Complex for Polymer Light Emitting Diodes
HU Zheng-Yong, YANG Jian-Kui, LUO Jing, LIANG Min, WANG Jing
Chin. Phys. Lett. 2012, 29 (12):
127801
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DOI: 10.1088/0256-307X/29/12/127801
Photo-physical properties of iridium complexes bis(1-(2',4'-difluorobiphenyl -4-yl)isoquinoline)iridium(III)(5-(4-(bis(4-methoxyphenyl)amino)phenyl)picolinic acid) used as phosphorescent dopant in polymer light-emitting devices with a blend of poly(9,9-dioctylfluorene) and 2-tert-butyl-phenyl-5-biphenyl-1,3,4-oxadiazole as a host matrix are investigated. The iridium complex exhibits distinct UV-vis absorption bands around 300–450 nm and intense red photoluminescent emissions peaked at around 618 nm in dichloromethane. The devices display a maximum external quantum efficiency of 4.8% and luminous efficiency of 3.1 cd?A?1 at current density of 3.2 mA?cm?2 with a dominant red emission peak around 620 nm and a shoulder around 660 nm. At 100 mA?cm?2, the devices still display a maximum external quantum efficiency as high as 3.9%.
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An Improvement on the Junction Temperature Measurement of Light-Emitting Diodes by using the Peak Shift Method Compared with the Forward Voltage Method
HE Su-Ming, LUO Xiang-Dong, ZHANG Bo, FU Lei, CHENG Li-Wen, WANG Jin-Bin, LU Wei
Chin. Phys. Lett. 2012, 29 (12):
127802
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DOI: 10.1088/0256-307X/29/12/127802
The junction temperature of red, green and blue high power light emitting diodes (LEDs) is measured by using the emission peak shift method and the forward voltage method. Both the emission peak shift and the forward voltage decrease show a linear relationship relative to junction temperature. The linear coefficients of the red, green and blue LEDs for the peak shift method and the forward voltage method range from 0.03 to 0.15 nm/ °C and from 1.33 to 3.59 mV/ °C, respectively. Compared with the forward voltage method, the peak shift method is almost independent of bias current and sample difference. The variation of the slopes is less than 2% for the peak shift method and larger than 30% for the forward voltage method, when the LEDs are driven by different bias currents. It is indicated that the peak shift method gives better stability than the forward voltage method under different LED working conditions.
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The Evolution of Defects in Deformed Cu-Ni-Si Alloys during Isochronal Annealing Studied by Positron Annihilation
QI Ning, JIA Yan-Lin, LIU Hui-Qun, YI Dan-Qing, CHEN Zhi-Quan
Chin. Phys. Lett. 2012, 29 (12):
127803
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DOI: 10.1088/0256-307X/29/12/127803
The effect of isochronal annealing on the deformation-induced defects in pure Cu and Cu-Ni-Si alloys is studied by positron annihilation spectroscopy. For the cold-rolled Cu, annealing up to 900°C causes a gradual recovery of the deformation-induced defects and monotonous decrease of the hardness. This indicates that its hardening is mainly related with defects such as dislocations. However, for the hot-rolled and quenched Cu-Ni-Si alloy, although there is a partial recovery of defects after annealing below 500°C, formation of additional defects is observed after annealing above 500°C. The hardness of Cu-Ni-Si alloy has a maximum value after annealing at 500°C, which suggests that the hardening of Cu-Ni-Si alloy is not due to defects, but primarily due to the precipitation formed during annealing. Further annealing of the Cu-Ni-Si alloy above 500°C results in over-aging effect and the precipitates lose coherence with the host matrix, which leads to positron trapping by vacancy clusters in the incoherent interface region.
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Origin of Ferromagnetism in Zn1?xCoxO Thin Films: Evidences Provided by Hard and Soft X-Ray Absorption Spectroscopy
XI Shi-Bo, CUI Ming-Qi, QIN Xiu-Fang, XU Xiao-Hong, XU Wei, ZHENG Lei, ZHOU Jing, LIU Li-Juan, YANG Dong-Liang, GUO Zhi-Ying
Chin. Phys. Lett. 2012, 29 (12):
127804
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DOI: 10.1088/0256-307X/29/12/127804
Although dilute magnetic semiconductors have promising potentials in spintronics applications, the mechanism of their ferromagnetism remains ambiguous. The extensive theoretical models and exotic experimental evidences provide self-consistent but usually contradictory explanations on its either intrinsic or extrinsic origins. We find room temperature ferromagnetism in a series of Zn1?xCoxO (0.03≤x ≤0.10) thin films prepared using magnetron co-sputtering method and treated with post-annealing at temperatures 350°C and 500°C. The origin of the ferromagnetism is investigated in terms of electronic structure combining hard x-ray absorption spectroscopy (XAS) at Zn and Co K-edge, and soft x-ray XAS at O K-edge and Co L2,3-edge. The full multiple scattering theory is employed to reinforce the interpretation of the XAS spectra, which concludes that full substitution of zinc by cobalt is responsible for the room temperature ferromagnetism due to the d states of cobalt within the framework of bound magnetic polaron. Moreover, the evidence of cobalt nanoclusters is detected at highly doped and annealed samples. The first principles calculation confirms the electronic structural evidences via the formation energy.
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The High Nitrogen Pressure Synthesis of Manganese Nitride
SI Ping-Zhan, JIANG Wei, WANG Hai-Xia, ZHONG Min, GE Hong-Liang, CHOI Chul-Jin, LEE Jung-Goo
Chin. Phys. Lett. 2012, 29 (12):
128101
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DOI: 10.1088/0256-307X/29/12/128101
We report on the structural transformation and unique magnetic properties of manganese nitrides prepared by nitriding Mn under N2 pressures of up to 25 MPa with varying temperatures. High N2 pressure not only makes nitridation more efficient at lower temperatures, but also enhances the N-content in the nitride lattices, which were expanded with increasing N-content. The N-rich nitrides, including ε-Mn4N, ζ-Mn6N2.58 and η-Mn3N2, exhibit unique thermal behaviors. The N-rich ε-phase exhibits much larger coercivity and lower saturation magnetization in comparison with the ε-phase prepared under ambient N2 pressures. The coercivity of the N-rich ζ-phase reaches up to 45054 A/m. A saturation magnetization as large as 31 Am2/kg is observed in the N-rich η-phase. Both are quite different from the conventional antiferromagnetic ζ- and η-phase obtained under ambient N2 pressures. We ascribe the unconventional magnetic properties of the nitrides to the lattice distortion originating from the N-enrichment.
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The Synthesis and Characterization of Peach-Like ZnO
A. Kamalianfar, S. A. Halim, Siamak Pilban Jahromi, M. Navasery, Fasih Ud Din, K. P. Lim, S. K. Chen, J. A. M. Zahedi
Chin. Phys. Lett. 2012, 29 (12):
128102
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DOI: 10.1088/0256-307X/29/12/128102
Peach-like ZnO microstructures are synthesized using vapor phase transport on MgO (001) substrates with a copper oxide (60 nm) buffer layer. The structure and morphology of the product are investigated using an x-ray diffractometer (XRD) and a field-emission scanning electron microscope. The peaches have an average diameter of 3 μm and a wurtzite structure. To study the optical properties, photoluminescence (PL) and Raman spectroscopy are employed. A strong UV emission at 380 nm in the PL spectra is observed, and a sharp and dominant peak at 437 cm?1 in the Raman spectrum can be assigned to the good crystallization of obtained product. In addition, the growth mechanism of the peach-like ZnO structure is tentatively investigated based on the EDX analysis and growth time.
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A 50–60 V Class Ultralow Specific on-Resistance Trench Power MOSFET
HU Sheng-Dong, ZHANG Ling, CHEN Wen-Suo, LUO Jun, TAN Kai-Zhou, GAN Ping, ZHU Zhi, WU Xing-He
Chin. Phys. Lett. 2012, 29 (12):
128502
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DOI: 10.1088/0256-307X/29/12/128502
A 50–60 V class ultralow specific on-resistance (Ron,sp) trench power MOSFET is proposed. The structure is characterized by an n+-layer which is buried on the top surface of the p-substrate and connected to the drain n+-region. The low-resistance n+-layer shortens the motion-path in high-resistance n? drift region for the carriers, and therefore, reduces the Ron,sp in the on-state. Electrical characteristics for the proposed power MOSFET are analyzed and discussed. The 50–60 V class breakdown voltages (VB) with Ron,sp less than 0.35 mΩ?cm2 are obtained. Compared with several power MOSFETs, the proposed power MOSFET has a significantly optimized dependence of Ron,sp on VB.
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Topological and Spectral Perturbations in Complex Networks
YAN Xin, WU Yang
Chin. Phys. Lett. 2012, 29 (12):
128901
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DOI: 10.1088/0256-307X/29/12/128901
Recently many network perturbation techniques, mainly involving topological and spectral perturbations, have been employed to analyze and improve the robustness of complex networks. However, to the best of our knowledge, the relationship between topological perturbation and spectral perturbation has not been studied intensively so far. We introduce a new robustness measure, subgraph centrality defined by eigenvalue spectrum, to investigate the impact of topological perturbation on eigenvalue spectrum. A specific definition of spectral perturbation is given, such that we can examine the impact of spectral perturbation on topological property by a measure of topological performance: global efficiency. Our main finding is that the spectral perturbations we define are equivalent to the conventional topological perturbations, especially for scale-free networks
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Pheromone Static Routing Strategy for Complex Networks
HU Mao-Bin, Henry Y.K. Lau, LING Xiang, JIANG Rui
Chin. Phys. Lett. 2012, 29 (12):
128902
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DOI: 10.1088/0256-307X/29/12/128902
We adopt the concept of using pheromones to generate a set of static paths that can reach the performance of global dynamic routing strategy [ Phys. Rev. E 81 (2010) 016113]. The path generation method consists of two stages. In the first stage, a pheromone is dropped to the nodes by packets forwarded according to the global dynamic routing strategy. In the second stage, pheromone static paths are generated according to the pheromone density. The output paths can greatly improve traffic systems' overall capacity on different network structures, including scale-free networks, small-world networks and random graphs. Because the paths are static, the system needs much less computational resources than the global dynamic routing strategy.
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66 articles
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