Band structures of strained kagome lattices

Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands.We theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin potential.It is found that the Dirac points move with applied strain.Furthermore,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx direction.Our results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.

Generalized projective synchronization of the fractional-order chaotic system using adaptive fuzzy sliding mode control

An adaptive fuzzy sliding mode strategy is developed for the generalized projective synchronization of a fractional- order chaotic system, where the slave system is not necessarily known in advance. Based on the designed adaptive update laws and the linear feedback method, the adaptive fuzzy sliding controllers are proposed via the fuzzy design, and the strength of the designed controllers can he adaptively adjusted according to the external disturbances. Based on the Lya- punov stability theorem, the stability and the robustness of the controlled system are proved theoretically. Numerical simu- lations further support the theoretical results of the paper and demonstrate the efficiency of the proposed method. Moreover, it is revealed that the proposed method allows us to manipulate arbitrarily the response dynamics of the slave system by adjusting the desired scaling factor λi and the desired translating factor ηi, which may be used in a channel-independent chaotic secure communication.

Spectral Property and Stability of Color Centers in Alkali Halide Crystals Induced by He^(+)Ion Implantation at Room Temperature

Thin colored layers with high density defect centers could be produced on alkali halide crystals implanted by 300-400keV He^(+)ions at room temperature.Besides well known absorption bands,several new absorption bands and colloid absorption band are observed in the crystals,such as 520 and 842nm absorption bands in the implanted LiF crystals,840nm absorption band in the implanted NaF:OH^(-)crystals,and 875 nm absorption band in the implanted NaC1:OH^(-)crystals.

Freezing of Soli ton State Between T_(c)^(c) and T_(c)^(h) in K_(2)ZnCl_(4)

The hysteresis effect of commensurate-incommensurate transition has been investigated with the measurement of dielectric constant.The freezing of the soliton state in the hysteresis region was observed.The freezing may be kept for a very long time because of the pinning of impurities.

THEORY OF RESONANT MICROWAVE ABSORPTION OF DNA IN AQUEOUS SOLUTION

The Ostrovskii-Sutin equation of the longitudinal displacement of an elastic rod has been derived for a DNA chain by taking its structure into account.The perturbation solution of this equation shows that the resonant microwave absorption by DNA in solution is possible.In addition to the primary resonance at our theory predicts also a subharmonic resonance at ωn/2,The strength of the latter is proportional to l^(-3),where I is the length of DNA chain.

PREPARATION OF AMORPHOUS Mn-Zn FERRITES AND THEIR MAGNETIC PROPERTIES

This paper describes the preparation of amorphous Mn-Zn ferrites,presents part of the results of the measurements,and the analysis of the samples.

Influence of Bipartite Qubit Coupling on Geometric Phase

The geometric phase of the bipartite Heisenberg spin-1/2 system with one spin driven by rotating magnetic field is investigated. It is found that in the one-site drive case, the intersubsystem coupling can be equivalent to a static quasi-magnetic field in the parameter space. This perspective has satisfactorily explained the irregular asymptote effect of geometric phase. We discuss the property of the two-site magnetic drive spin system and discover that a stationary state with no geometric phase shift is generated.

PHOTOIONIZATION AND TUNABLE LASER OF COLOR CENTERS IN KMgF_(3)

The density of 570nm centers in KMgF_(3) crystals colored by electron beam bombardment at 200K could be increased by irradiating the crystals with 337nm,400nm,and 445nm lasers at room temperature or 200K,respectively.The near infrared laser operation using 570nm centers in KMgF_(3) crystals was realized at room temperature.The tunable range of the laser is from 720nm to 820nm.

RFPRODUCTION OF HIGH DENSITY F_(2)^(+) CENTERS IN UNDOPED AND DOPED SODIUM FLUOWE CRYSTALS

F_(2) centers in colored undoped and doped NaF crystals can be converted nearly completely into F_(2)^(+) centers with the high density of more than 10^(17)cm^(-3) by irradiating the crystals with a 505nm laser at room temperature.A process of conversion from F_(2)^(+) to (F_(2)^(+))^(*) centers in the NaF crystals doped with divalent metal ions such as Mn^(++),Mg^(++) and Ni^(++) after the 505nm laser irradiation was observed in our experiments.

OBSERVATIONS OF COMPLEX NONLINEAR BEHAVIOR IN THE NEURONLIKE OUTPUT OF CRYOGENICALLY COOLED SILICON DEVICES

The experimental observations about the complex nonlinear behavior of spontaneous pulsing of dc biased,p-i-n diodes RC circuits are reported.Time intervals series between successive pulses in spike trains were analyzed.Transitions from quasiperiodicity into chaos via mode-locking were observed.The phase portrait is analyzed to reveal that the system is really characterized by a strange attractor.Finally,the embedding algorithm has applied to determine the fractal dimension of the attractor.

Propagation of Optical Pulses in a Deviated Gaussian Gained Kerr Medium

This paper presents the theoretical studies on the propagation of optical pulses in a deviated Gaussian gained Kerr medium.Our numerical results have shown,for the first time,that the compression of optical pulse widths varies considerably for differently deviated Gaussian gain.

Influence of Thermal Radiation on Hot Cluster Decay Rates and Abundances

The influence of radiative cooling on the unimolecular decay rates of free, hot clusters and molecules with unspecified excitation energies is quantified. Two different regimes, dedined by the magnitude of the energy of the photons emitted, are identified and the boundary between them is given. The boundary is determined in terms of the photon emission rate constants and thermal properties of the particles. Also the abundance spectra are calculated for the continuous cooling case, corresponding to small photon energies. The two regimes correspond to continuous cooling and single photon quenching of the unimolecular decay. The radiative effect can be parametrized by a redefinition of the time each individual cluster has available to undergo evaporation, expressed by an effective radiative time constant.

LASER EMISSION OF F_(3)^(+) COLOR CENTERS IN LiF CRYSTALS AT ROOM TEMPERATURE

Laser emission of F_(3)^(+) color centers in LiF crystal at room temperature(RT)is reported here for the first time.

Multiband Metamaterial Absorber at Terahertz Frequencies

We propose a multi-band metamaterial absorber operating at terahertz frequencies. The design, characteriza- tion, and theoretical calculation of the high performance metamaterial absorber are reported. The multi-band metamaterial absorber consists of two metallic layers separated by a dielectric spacer. Theoretical and simulated results show that the metamaterial absorber has four distinct absorption points at frequenc/es 0.57 THz, 1.03 THz, 1.44 THz and 1.89 THz, with the absorption rates of 99.9%, 90.3%, 83.0%, 96.1%, respectively. Two single band metamaterial absorbers and a dual band metamaterial absorber on the top layer are designed. Some multi-band absorbers can be designed by virtue of combining some single band absorbers. The multiple-reflection theory is used to explain the absorption mechanism of our investigated structures.

Re-excited States in Conjugated Polymers

We investigate the re-exciting process of a soliton, a polaron and a bipolaron in conjugated polymers. For a soliton case, the processes S^0 ＋ hv→ S^± P↓± and S^± ＋ hv→S^0 ＋P± will take place, where S^0 ,S^± and p^± express a neutral soliton, charged solitons and charged polarons, respectively. For a polaron case, the processes P^± ＋ hv→ p^↓± ＋ Bp^±2 will occur, where BP^±2 expresses a charged bipolaron with two electronic units. For a bipolaron case, the processes BP^±2 ＋ hv→ P^± ＋ P^± and BP^±2 ＋ hv→ BP^＋2 ＋ E0 are obtained.

FOURIER TRANSFORM COMBINED WITH HADAMARD TRANSFORM IMAGING SPECTROMETRY

Hadamard mask is utilized as a spatial modulator on Fourier transform spectrometry to provide both spatial and spectral information about the sample.As a re suit,sign alto-noise ratio is improved and the power density at the sample is reduced.

Lyapunov Exponent Spectrum for Two-Mode Model in Spin-Wave Chaos

The results of numerical experiments on the two-mode model for yttrium iron garnet sphere in the parallel-pumping configuration are reported and the complete Lyapunov exponent spectrum is presented.A rather complicated structure of the Lyapunov exponent spectrum can be recognized by the appearance of the associated peak in the Kolmogorov-Sinai entropy and the Lyapunov dimension diagrams.The results confirm an important connexion between the effective number of spin-wave modes involved and the Lyapunov dimension of the attractors.

A PULSE COLOR-CENTER LASER USING F_(3)^(+) CENTER IN LiF CRYSTAL AT ROOM TEMPERATURE

A pulsed LiF:F_(3)^(+) centers laser coaxially pumped by a nitrogenlaser-pumped dye laser operhting at 460nm is reported.The laser output extended from 510nm to 580nm using an LiF crystal and a single pump wavelength.Eight hundred watts peak power with a pulse duration of 4ns is obtained at room temperature.

NONLINEAR OPTICAL PHASE CONJUGATE EFFECT CAUSED BY F^(-)_(2) COLOR CENTER IN LiF CRYSTALS

We report the experimental observation of nonlinear optical phase conjugate(NOPC)effect caused by the resonant saturable absorption of F-2 centers in LiF crystals.The experiment was performed by making use of degenerate four-wave mixing in the laser cavity.We also give the curve of the phase conjugate reflectivity versus the incident energy of the probe light.

NON-PROPAGATING SOLITARY SURFACE WAVE IN AN ANNULAR TROUGH

The nonlinear equation governing the nonpropagating solitary surface wave and its single solitary wave solution were derived by the method of multiple scales.The results obtained were compared with that in rectangular trough.