In the last 30 days

• Open/close Formation mechanism of anomalous eutectics in highly undercooled Ag–39.9 at%Cu alloys

  Zhao Su et al 2009 Chinese Phys. B 18 1917 Tag this article

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  This paper investigates the solidification behaviour of the Ag–Cu eutectic alloy melt undercooled up to 100 K. It is revealed that lamellar eutectics grow in a dendritic form in the Ag–Cu eutectic melt with undercooling equal to or greater than 76 K. As undercooling increases, the remelted fraction of the primary eutectics during recalescence rises. The severe remelting and the subsequent ripening of the primary eutectic dendrites lead to the formation of anomalous eutectics.

• Open/close Dynamical behaviour of a controlled vibro-impact system

  Wang Liang et al 2008 Chinese Phys. B 17 2446 Tag this article

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  In this paper, we give a controlled two-degree-of-freedom (TDOF) vibro-impact system based on the damping control law, and then investigate the dynamical behaviour of this system. According to numerical simulation, we find that this control scheme can suppress chaos to periodic orbit successfully. Furthermore, the feasibility and the robustness of the controller are confirmed, separately. We also find that this scheme cannot only suppress chaos, but also generate chaos in this system.

• Open/close Bandgap characteristics of 2D plasma photonic crystal with oblique incidence: TM case

  Xie Ying-Tao (谢应涛) and Yang Li-Xia (杨利霞) 2011 Chinese Phys. B 20 060201 Tag this article

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  A novel periodic boundary condition (PBC), that is the constant transverse wavenumber (CTW) method, is introduced to solve the time delay in the transverse plane with oblique incidence. Based on the novel PBC, the FDTD/PBC algorithm is proposed to study periodic structure consisting of plasma and vacuum. Then the reflection coefficient for the plasma slab from the FDTD/PBC algorithm is compared with the analytic results to show the validity of our technique. Finally, the reflection coefficients for the plasma photonic crystals are calculated using the FDTD/PBC algorithm to study the variation of bandgap characteristics with the incident angle and the plasma parameters. Thus it has provided the guiding sense for the actual manufacturing plasma photonic crystal.

• Open/close Negative differential resistance behaviour in N-doped crossed graphene nanoribbons

  Chen Ling-Na et al 2010 Chinese Phys. B 19 097301 Tag this article

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  By using first-principles calculations and nonequilibrium Green's function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.

• Open/close All-dielectric left-handed metamaterial based on dielectric resonator: design, simulation and experiment

  Yang Yi-Ming (杨一鸣) et al 2011 Chinese Phys. B 20 014101 Tag this article

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  Dipoles with Lorentz-type resonant electromagnetic responses can realise negative effective parameters in their negative resonant region. The electric dipole and magnetic dipole can realise, respectively, negative permittivity and negative permeability, so both the field distribution forms of electric and magnetic dipoles are fundamentals in designing left-handed metamaterial. Based on this principle, this paper studies the field distribution in high-permittivity dielectric materials. The field distributions at different resonant modes are analysed based on the dielectric resonator theory. The origination and influence factors of the electric and magnetic dipoles are confirmed. Numerical simulations indicate that by combining dielectric cubes with different sizes, the electric resonance frequency and magnetic resonance frequency can be superposed. Finally, experiments are carried out to verify the feasibility of all-dielectric left-handed metamaterial composed by this means.

• Open/close Design and FPGA Implementation of a new hyperchaotic system

  Wang Guang-Yi et al 2008 Chinese Phys. B 17 3596 Tag this article

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  In this paper, a new four-dimensional autonomous hyperchaotic system is designed for generating complex chaotic signals. In the design, its parameters are selected according to the requirements for chaos and hyperchaos. The hyperchaotic Nature is verified theoretically by using the bifurcation analysis and demonstrated experimentally by the implementation of an analogue electronic circuit. Moreover, the Field Programmable Gate Array (FPGA) technology is applied to implementing a continuous system in a digital form by using a chip of Altera Cyclone II EP2C35F484C8. The digital sequence generated from the FPGA device is observed in our experimental setup.

• Open/close Polymer solar cells based on a PEDOT:PSS layer spin-coated under the action of an electric field

  Feng Zhi-Hui et al 2010 Chinese Phys. B 19 038601 Tag this article

  Article References Full text PDF (1.96 MB)

  In the process of fabrication of polymer photovoltaic (PV) devices, poly (3, 4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) thin film, acting as an anode buffer layer, is spin-coated under the action of an electric field. The PV devices with a PEDOT:PSS layer spin-coated under the action of a static electric field exhibit improved short-circuit current density ( J _sc) and power conversion efficiency (PCE). The investigation of morphology shows that the appropriate intensity of the electric field can increase the roughness of the surface of the PEDOT:PSS layer, which results in improved contact between the anode and hole transport layer and thus enhances the J _sc of the devices. Chemical analysis is also provided by x-ray photoelectron spectroscopy (XPS) spectra.

• Open/close Simultaneous low extinction and high local field enhancement in Ag nanocubes

  Zhou Fei (周 飞) et al 2011 Chinese Phys. B 20 037303 Tag this article

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  We theoretically investigate surface plasmon resonance properties in Au and Ag cubic nanoparticles and find a novel plasmonic mode that exhibits simultaneous low extinction and high local field enhancement properties. We analyse this mode from different aspects by looking at the distribution patterns of local field intensity, energy flux, absorption and charge density. We find that in the mode the polarized charge is highly densified in a very limited volume around the corner of the nanocube and results in very strong local field enhancement. Perturbations of the incident energy flux and light absorption are also strongly localized in this small volume of the corner region, leading to both low absorption and low scattering cross section. As a result, the extinction is low for the mode. Metal nanoparticles involving such peculiar modes may be useful for constructing nonlinear compound materials with low linear absorption and high nonlinearity.

• Open/close Hydrothermal synthesis and chromic properties of hexagonal WO₃ nanowires

  Yuan Hua-Jun (袁华军) et al 2011 Chinese Phys. B 20 036103 Tag this article

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  This paper reports that highly purified hexagonal WO ₃ nanowires are synthesized by a simple hydrothermal method. The as-synthesized WO ₃ nanowires are investigated in detail by ultraviolet—visible—near infrared spectroscopy and electrical transport measurements under different conditions. It finds that the optical band gap and the diffuse reflection coefficient in the wavelength region above 450 nm of WO ₃ nanowires decrease observably upon exposure to ultraviolet light or NH ₃ gas. It is also found that there are electrons being trapped or released in individual WO ₃ nanowires when scanning bias voltage in different directions upon exposure to ultraviolet and NH ₃ gas. The experimental results suggest that the chromic properties might be attributed to the injection/extraction of hydrogen ions induced by ultraviolet light irradiation in air or creation/annihilation of oxygen vacancies induced by NH ₃ gas exposure, which serve as colour centres and trap electrons as polarons. The experimental results also suggest that the hexagonal WO ₃ nanowires will be a good candidate for sensing reduced gas such as NH ₃.

• Open/close Non-Markovian dynamics of a qubit in a reservoir: different solutions of non-Markovian master equation

  Ding Bang-Fu (丁邦福) et al 2011 Chinese Phys. B 20 060304 Tag this article

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  We present a non-Markovian master equation for a qubit interacting with a general reservoir, which is derived according to the Nakajima—Zwanzig and the time convolutionless projection operator technique. The non-Markovian solutions and Markovian solution of dynamical decay of a qubit are compared. The results indicate the validity of non-Markovian approach in different coupling regimes and also show that the Markovian master equation may not precisely describe the dynamics of an open quantum system in some situation. The non-Markovian solutions may be effective for many qubits independently interacting with the heated reservoirs.