| 1. |
- Chen, Shuang, et al.
(författare)
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Quantitative measurement of hydroxyl radical (OH) concentration in premixed flat flame by combining laser-induced fluorescence and direct absorption spectroscopy
- 2016
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Ingår i: Chinese Physics C. - : IOP Publishing. - 1674-1137 .- 1674-1056. ; 25:10
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Tidskriftsartikel (refereegranskat)abstract
- An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence (LIF) methods is developed to quantitatively measure the concentrations of hydroxyl in CH4/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.
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| 2. |
- Bi, Zhaoxia, et al.
(författare)
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Bottom-up approaches to microLEDs emitting red, green and blue light based on GaN nanowires and relaxed InGaN platelets
- 2023
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Miniaturization of light-emitting diodes (LEDs) with sizes down to a few micrometers has become a hot topic in both academia and industry due to their attractive applications on self-emissive displays for high-definition televisions, augmented/mixed realities and head-up displays, and also on optogenetics, high-speed light communication, etc. The conventional top-down technology uses dry etching to define the LED size, leading to damage to the LED side walls. Since sizes of microLEDs approach the carrier diffusion length, the damaged side walls play an important role, reducing microLED performance significantly from that of large area LEDs. In this paper, we review our efforts on realization of microLEDs by direct bottom-up growth, based on selective area metal–organic vapor phase epitaxy. The individual LEDs based on either GaN nanowires or InGaN platelets are smaller than 1 μm in our approach. Such nano-LEDs can be used as building blocks in arrays to assemble microLEDs with different sizes, avoiding the side wall damage by dry etching encountered for the top-down approach. The technology of InGaN platelets is especially interesting since InGaN quantum wells emitting red, green and blue light can be grown on such platelets with a low-level of strain by changing the indium content in the InGaN platelets. This technology is therefore very attractive for highly efficient microLEDs of three primary colors for displays.
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| 3. |
- Hui-Dong, Li, et al.
(författare)
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Simulations of the L-H transition dynamics with different heat and particle sourses
- 2015
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 24:11, s. 115204-
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Tidskriftsartikel (refereegranskat)abstract
- It is crucial to increase the total stored energy by realizing the transition from a low confinement (L-mode) state to a high confinement (H-mode) state in magnetic confinement fusion. The L–H transition process is simulated by using the predictive transport code based on Weiland’s fluid model. Based on the equilibrium parameters obtained from equilibrium fitting (EFIT) in the experiment, the electron density ne, electron temperature Te, ion temperatures Ti, ion poloidal Vp,and toroidal momenta Vt are simulated self-consistently. The L–H transition dynamic behaviors with the formation of the transport barriers of ion and electron temperatures, the electron density, and the ion toroidal momenta are analyzed. During the L–H transition, the strong poloidal flow shear in the edge transport barrier region is observed. The crashes of theelectron and ion temperature pedestals are also observed during the L–H transition. The effects of the heating and particle sources on the L–H transition process are studied systematically, and the critical power threshold of the L–H transition is also found.
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| 4. |
- Liu, Ji-Cai, et al.
(författare)
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Dynamics of cooperative emissions in a cascade three-level molecular system driven by an ultrashort laser pulse
- 2008
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 17:11, s. 4211-4217
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the dynamics of cooperative emissions in a cascade three-level system driven by an ultras short laser pulse by solving numerically the full-wave Maxwell-Bloch equations. The 4, 40-bis(dimethylamino) stilbene molecule is used as the model molecule because of its strong two-photon absorption property. The two-colour cooperative emissions are studied as functions of molecular number density and dephasing rate of the dipole coherence. The propagation effects on the evolution of the cooperative radiations are also taken into account. The cooperative radiations are enhanced for large number density of the molecule, while the fast dephasing of the dipole coherence reduces the intensity of the cooperative radiations and delays the emission times or even inhibits the formation of the emissions. The delay time of the radiation decreases with the increase of the molecular number density and the propagation distance.
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| 5. |
- Zhu, Ri Jia, et al.
(författare)
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Magnetotransport properties of graphene layers decorated with colloid quantum dots
- 2019
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 28:6
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Tidskriftsartikel (refereegranskat)abstract
- The hybrid graphene-quantum dot devices can potentially be used to tailor the electronic, optical, and chemical properties of graphene. Here, the low temperature electronic transport properties of bilayer graphene decorated with PbS colloid quantum dots (CQDs) have been investigated in the weak or strong magnetic fields. The presence of the CQDs introduces additional scattering potentials that alter the magnetotransport properties of the graphene layers, leading to the observation of a new set of magnetoconductance oscillations near zero magnetic field as well as the high-field quantum Hall regime. The results bring about a new strategy for exploring the quantum interference effects in two-dimensional materials which are sensitive to the surrounding electrostatic environment, and open up a new gateway for exploring the graphene sensing with quantum interference effects.
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| 6. |
- Chu, Ming, et al.
(författare)
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Accurate capacitance-voltage characterization of organic thin films with current injection*
- 2021
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Ingår i: Chinese Physics B. - : IOP PUBLISHING LTD. - 1674-1056. ; 30:8
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Tidskriftsartikel (refereegranskat)abstract
- To deal with the invalidation of commonly employed series model and parallel model in capacitance-voltage (C-V) characterization of organic thin films when current injection is significant, a three-element equivalent circuit model is proposed. On this basis, the expression of real capacitance in consideration of current injection is theoretically derived by small-signal analysis method. The validity of the proposed equivalent circuit and theoretical expression are verified by a simulating circuit consisting of a capacitor, a diode, and a resistor. Moreover, the accurate C-V characteristic of an organic thin film device is obtained via theoretical correction of the experimental measuring result, and the real capacitance is 35.7% higher than the directly measured capacitance at 5-V bias in the parallel mode. This work strongly demonstrates the necessity to consider current injection in C-V measurement and provides a strategy for accurate C-V characterization experimentally.
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| 7. |
- Peng, Xu-Biao, et al.
(författare)
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Application of topological soliton in modeling protein folding : Recent progress and perspective
- 2020
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 29:10
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Forskningsöversikt (refereegranskat)abstract
- Proteins are important biological molecules whose structures are closely related to their specific functions. Understanding how the protein folds under physical principles, known as the protein folding problem, is one of the main tasks in modern biophysics. Coarse-grained methods play an increasingly important role in the simulation of protein folding, especially for large proteins. In recent years, we proposed a novel coarse-grained method derived from the topological soliton model, in terms of the backbone C(alpha)chain. In this review, we will first systematically address the theoretical method of topological soliton. Then some successful applications will be displayed, including the thermodynamics simulation of protein folding, the property analysis of dynamic conformations, and the multi-scale simulation scheme. Finally, we will give a perspective on the development and application of topological soliton.
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| 8. |
- Zeng, Hong-Li, et al.
(författare)
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Inverse Ising techniques to infer underlying mechanisms from data
- 2020
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Ingår i: Chinese Physics B. - : IOP Publishing Ltd. - 1674-1056. ; 29:8
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Tidskriftsartikel (refereegranskat)abstract
- As a problem in data science the inverse Ising (or Potts) problem is to infer the parameters of a Gibbs-Boltzmann distributions of an Ising (or Potts) model from samples drawn from that distribution. The algorithmic and computational interest stems from the fact that this inference task cannot be carried out efficiently by the maximum likelihood criterion, since the normalizing constant of the distribution (the partition function) cannot be calculated exactly and efficiently. The practical interest on the other hand flows from several outstanding applications, of which the most well known has been predicting spatial contacts in protein structures from tables of homologous protein sequences. Most applications to date have been to data that has been produced by a dynamical process which, as far as it is known, cannot be expected to satisfy detailed balance. There is therefore no a priori reason to expect the distribution to be of the Gibbs-Boltzmann type, and no a priori reason to expect that inverse Ising (or Potts) techniques should yield useful information. In this review we discuss two types of problems where progress nevertheless can be made. We find that depending on model parameters there are phases where, in fact, the distribution is close to Gibbs-Boltzmann distribution, a non-equilibrium nature of the under-lying dynamics notwithstanding. We also discuss the relation between inferred Ising model parameters and parameters of the underlying dynamics.
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| 9. |
- Zhao, Shuyan, et al.
(författare)
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Stress and strain analysis of Si-based III - V template fabricated by ion-slicing
- 2020
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 29:7
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Tidskriftsartikel (refereegranskat)abstract
- Strain and stress were simulated using finite element method (FEM) for three III-V-on-Insulator (III-VOI) structures, i.e., InP/SiO2/Si, InP/Al2O3/SiO2/Si, and GaAs/Al2O3/SiO2/Si, fabricated by ion-slicing as the substrates for optoelectronic devices on Si. The thermal strain/stress imposes no risk for optoelectronic structures grown on InPOI at a normal growth temperature using molecular beam epitaxy. Structures grown on GaAsOI are more dangerous than those on InPOI due to a limited critical thickness. The intermedia Al2O3 layer was intended to increase the adherence while it brings in the largest risk. The simulated results reveal thermal stress on Al2O3 over 1 GPa, which is much higher than its critical stress for interfacial fracture. InPOI without an Al2O3 layer is more suitable as the substrate for optoelectronic integration on Si.
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| 10. |
- Asghar, M., et al.
(författare)
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Characterization of deep acceptor level in as-grown ZnO thin film by molecular beam epitaxy
- 2014
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 23:9, s. 097101-
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Tidskriftsartikel (refereegranskat)abstract
- We report deep level transient spectroscopy results from ZnO layers grown on silicon by molecular beam epitaxy (MBE). The hot probe measurements reveal mixed conductivity in the as-grown ZnO layers, and the current-voltage (I-V) measurements demonstrate a good quality p-type Schottky device. A new deep acceptor level is observed in the ZnO layer having activation energy of 0.49 +/- 0.03 eV and capture cross-section of 8.57 +/- 10(-18) cm(2). Based on the results from Raman spectroscopy, photoluminescence, and secondary ion mass spectroscopy (SIMS) of the ZnO layer, the observed acceptor trap level is tentatively attributed to a nitrogen-zinc vacancy complex in ZnO.
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| 11. |
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| 12. |
- Fang, Yurui, 1983, et al.
(författare)
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Resonant surface plasmons of a metal nanosphere treated as propagating surface plasmons
- 2018
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 27:6
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Tidskriftsartikel (refereegranskat)abstract
- On the assumption that the resonant surface plasmons on a spherical nanoparticle are formed by standing waves of two counter-propagating surface plasmon waves along the surface, by using Mie theory simulation, we find that the dispersions of surface plasmon resonant modes supported by silver nanospheres match with those of the surface plasmons on a semiinfinite medium-silver interface very well. This suggests that the resonant surface plasmons of a metal nanosphere can be treated as a propagating surface plasmon wave.
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| 13. |
- Feng, Cun-Feng, et al.
(författare)
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Effects of average degree of network on an order-disorder transition in opinion dynamics
- 2010
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Ingår i: Chinese Physics B. - : IOPScience. - 1674-1056. ; 19:6, s. 060203-
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the influence of the average degree (k) of network on the location of an order-disorder transition in opinion dynamics. For this purpose, a variant of majority rule (VMR) model is applied to Watts–Strogatz (WS) small-world networks and Barabási–Albert (BA) scale-free networks which may describe some non-trivial properties of social systems. Using Monte Carlo simulations, we find that the order–disorder transition point of the VMR model is greatly affected by the average degree (k) of the networks; a larger value of (k) results in a more ordered state of the system. Comparing WS networks with BA networks, we find WS networks have better orderliness than BA networks when the average degree (k) is small. With the increase of (k), BA networks have a more ordered state. By implementing finite-size scaling analysis, we also obtain critical exponents β/ν, γ/ν and 1/ν for several values of average degree (k). Our results may be helpful to understand structural effects on order–disorder phase transition in the context of the majority rule model.
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| 14. |
- Gu, Yi, et al.
(författare)
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Optical properties of InGaAsBi/GaAs strained quantum wells studied by temperature-dependent photoluminescence
- 2013
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 22:3, s. 037802-
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Tidskriftsartikel (refereegranskat)abstract
- The effect of bismuth on the optical properties of InGaAsBi/GaAs quantum well structures is investigated using the temperature-dependent photoluminescence from 12 K to 450 K. The incorporation of bismuth in the InGaAsBi quantum well is confirmed and found to result in a red shift of photoluminescence wavelength of 27.3 meV at 300 K. The photoluminescence intensity is significantly enhanced by about 50 times at 12 K with respect to that of the InGaAs quantum well due to the surfactant effect of bismuth. The temperature-dependent integrated photoluminescence intensities of the two samples reveal different behaviors related to various non-radiative recombination processes. The incorporation of bismuth also induces alloy non-uniformity in the quantum well, leading to an increased photoluminescence linewidth.
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| 15. |
- Guan, Jian-Yue, et al.
(författare)
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Cooperation influenced by the correlation degree of two-layered complex networks in evolutionary prisoner's dilemma games
- 2010
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Ingår i: Chinese Physics B. - : Institute of Physics (IOP). - 1674-1056. ; 19:2
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Tidskriftsartikel (refereegranskat)abstract
- An evolutionary prisoner's dilemma game is investigated on two-layered complex networks respectively representing interaction and learning networks in one and two dimensions. A parameter q is introduced to denote the correlation degree between the two-layered networks. Using Monte Carlo simulations we studied the effects of the correlation degree on cooperative behaviour and found that the cooperator density nontrivially changes with q for different payoff parameter values depending on the detailed strategy updating and network dimension. An explanation for the obtained results is provided.
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| 16. |
- Hamzavi, M., et al.
(författare)
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Spinless particles in the field of unequal scalar-vector Yukawa potentials
- 2013
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 22:4, s. 040301-
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Tidskriftsartikel (refereegranskat)abstract
- We present analytical bound state solutions of the spin-zero Klein-Gordon (KG) particles in the field of unequal mixture of scalar and vector Yukawa potentials within the framework of the approximation scheme to the centrifugal potential term for any arbitrary l-state. The approximate energy eigenvalues and unnormalized wave functions are obtained in closed forms using a simple shortcut of the Nikiforov-Uvarov (NU) method. Further, we solve the KG-Yukawa problem for its exact numerical energy eigenvalues via the amplitude phase (AP) method to test the accuracy of the present solutions found by using the NU method. Our numerical tests using energy calculations demonstrate the existence of inter-dimensional degeneracy amongst the energy states of the KG-Yukawa problem. The dependence of the energy on the dimension D is numerically discussed for spatial dimensions D = 2-6.
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| 17. |
- Li, Jia Kai, et al.
(författare)
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Effects of growth conditions on optical quality and surface morphology of InGaAsBi
- 2018
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 27:4
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of Bi flux and pressure of AsH3 on Bi incorporation, surface morphology and optical properties of In-GaAsBi grown by gas source molecular beam epitaxy are studied. It is found that using relatively low pressure of AsH 3 and high Bi flux can strengthen the effect on the incorporation of Bi and increase its content linearly with Bi flux until it nearly reaches a saturation value. The result from Rutherford backscattering spectroscopy (RBS) confirms that the Bi incorporation can increase up to 1.13%. By adjusting Bi and As flux, we could improve the surface morphology of InGaAsBi sample. Room temperature photoluminescence shows strong and broad light emission at energy levels much smaller than the InGaAs bandgap.
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| 18. |
- Na, Zhao, et al.
(författare)
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Liquid-phase and solid-phase microwave irradiations for reduction of graphite oxide
- 2014
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 23:12, s. 128101-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, two microwave irradiation methods: (i) liquid-phase microwave irradiation (MWI) reduction of graphite oxide suspension dissolved in de-ionized water and N, N-dimethylformamide, respectively, and (ii) solid-phase MWI reduction of graphite oxide powder have been successfully carried out to reduce graphite oxide. The reduced graphene oxide products are thoroughly characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectral analysis, Raman spectroscopy, UV-Vis absorption spectral analysis, and four-point probe conductivity measurements. The results show that both methods can efficiently remove the oxygen-containing functional groups attached to the graphite layers, though the solid-phase MWI reduction method can obtain far more efficiently a higher quality-reduced graphene oxide with fewer defects. The I( D)/ I( G) ratio of the solid-phase MWI sample is as low as 0.46, which is only half of that of the liquid-phase MWI samples. The electrical conductivity of the reduced graphene oxide by the solid method reaches 747.9 S/m, which is about 25 times higher than that made by the liquid-phase method.
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| 19. |
- Radziute, Laima, et al.
(författare)
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Weak- and hyperfine-interaction-induced 1s2s 1S0-1s2 1S0 E1 transition rates of He-like ions
- 2015
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Ingår i: Chinese Physics B. - : Institute of Physics Publishing (IOPP). - 1674-1056. ; 24:4
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Tidskriftsartikel (refereegranskat)abstract
- Weak- and hyperfine-interaction-induced 1s2s 1S0 -1s2 1S0 E1 transition rates for the isoelectronic sequence of He-like ions have been calculated using the multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction methods. The results should be helpful for the future experimental investigations of parity non-conservation effects.
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| 20. |
- Sheng-Jun, Wang, et al.
(författare)
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Undetermination of the relation between network synchronizability and betweenness centrality
- 2011
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Ingår i: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 20:4
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Tidskriftsartikel (refereegranskat)abstract
- Betweenness centrality is taken as a sensible indicator of the synchronizability of complex networks. To test whether betweenness centrality is a proper measure of the synchronizability in specific realizations of random networks, this paper adds edges to the networks and then evaluates the changes of betweenness centrality and network synchronizability. It finds that the two quantities vary independently.
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| 21. |
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