Possible link of a structurally driven spin flip transition and the insulator-metal transition in the perovskite La(1-x)Ba(x)CoO3

The nature of the magnetic ground state near the insulator-metal transition (IMT) in La(1-x)Ba(x)CoO3 was investigated via neutron scattering. Below the critical concentration, x(c)～0.22, a commensurate antiferromagnetic (AFM) phase appears initially. Upon approaching x(c), the AFM component weakens and a ferromagnetic (FM) ordered phase sets in while in the rhombohedral lattice. At x(c), a spin flip to a new FM structure occurs at the same time as the crystal symmetry transforms to orthorhombic (Pnma). The Pnma phase may be the driving force for the IMT.     

Coherent interference induced transparency in self-coupled optical waveguide-based resonators

We propose a self-coupled optical waveguide (SCOW)-based resonator to generate an optical resonance analogous to electromagnetically induced transparency (EIT). The EIT-like effect is formed by the coherent interference between two resonance paths inherent to the SCOW resonator. For cascaded SCOW resonators, the spectrum they produce is significantly affected by the phase shift between them, with the EIT-like peak flattened or split as the two extreme cases. We also investigate the dispersion characteristics of an infinite array of SCOW resonators and show that the dispersion relation and group index in the EIT subband can be greatly changed by a small phase shift between the SCOW resonators.     

基于异面交会的空中运动目标定位算法及误差分析

介绍了空中运动目标定位测量的经纬定位仪单站定向和双站异面交会定位原理,并对影响定向和定位结果的各个因素进行了误差分析和仿真.结果表明,交会角在[40°,165°]时.测量精度有明显地改善,为组网测量布站提供了依据.黑火药爆炸试验测量结果验证了该方法的可行性和测量精度.     

Bending insensitivity of fiber Bragg gratings in suspended-core optical fibers

This Letter presents simulation and experimental results that explore bending insensitivity of fiber Bragg gratings in suspended-core optical fibers. The implementation of thin silica bridge in the fibers enhances index contrast of the fiber core and reduces bending-induced strain transfer to the fiber core. This fiber design lead to a reduction of over 7 times in strain-induced fiber Bragg grating resonant peak shifts in the suspended-core fiber compared with that in standard telecommunication fiber, and an 0.14 dB bending loss at a bending radius of 6.35 mm.     

Quasi-classical Trajectory Study of Reaction O （^3P）＋HCl （v =2; j=1,6,9） →OH＋Cl

The reaction O（^3P）＋HCl （v=2; j= 1,6,9） → OH＋Cl is theoretically studied with a quasi-classical trajectory method （QCT） on the benchmark potential energy surface of the ground 3A＇＇ state [J. Chem. Phys. 119（2003）9550]. The QCT-calculated state-resolved rotational distributions are in good agreement with the experimental results. The rotational polarization of the product OH molecule becomes weaker as the initial HCl rotation is excited. The calculated results can be explained from the large mass factor cos2 β of the title reaction, the van der Waals well in the potential energy surface and the secondary encounters in the exit channel.     

Multiple-bipolar-tap tunable spectrum sliced microwave photonic filter

A spectrum sliced microwave photonic signal processor structure, which is all-fiber based and features simplicity, together with the ability to realize tunability, reconfigurability, bipolar taps, and multiple-tap rf filtering, is presented. It is based on thermally controlled optical slicing filters induced into two linearly chirped fiber Bragg gratings. Experimental results demonstrate the realization of versatile microwave photonic filters with frequency tunable, reconfiguration, and bipolar-tap generation capabilities.     

Sympathetic cooling of molecular ions in selected rotational and vibrational states produced by threshold photoionization

We present a new method for the generation of rotationally and vibrationally state-selected, translationally cold molecular ions in ion traps. Our technique is based on the state-selective threshold photoionization of neutral molecules followed by sympathetic cooling of the resulting ions with laser-cooled calcium ions. Using N?(+) ions as a test system, we achieve >90% selectivity in the preparation of the ground rovibrational level and state lifetimes on the order of 15 minutes limited by collisions with background-gas molecules. The technique can be employed to produce a wide range of apolar and polar molecular ions in the ground and excited rovibrational states. Our approach opens up new perspectives for cold quantum-controlled ion-molecule-collision studies, frequency-metrology experiments with state-selected molecular ions and molecular-ion qubits.     

Magnetic anisotropy-induced spin-reorientation in spinel FeCr2S4

In this paper, the low-field magnetic behavior of polycrystalline FeCr₂S₄ was investigated by thermal circling the sample from 5 to 200 K at a constant magnetic field. We show that, upon cooling the sample at 50 Oe to a temperature below the Curie temperature then warming back, the magnetization displays irreversibility between cooling and warming sequence. The irreversible behavior was suppressed gradually with increasing magnetic field. By considering spin-reorientation due to the increase of magnetic anisotropy upon cooling, the irreversible behavior has been explained qualitatively.     

Long-range correlations in heart rate variability during computer-mouse work under time pressure

The aim of this study was to investigate the influences of time pressure on long-range correlations in heart rate variability (HRV), the effects of relaxation on the cardiovascular regulation system and the advantages of detrended fluctuation analysis (DFA) over the conventional power spectral analysis in discriminating states of the cardiovascular systems under different levels of time pressure. Volunteer subjects (n=10, male/female=5/5) participated in a computer-mouse task consisting of five sessions, i.e. baseline session (BSS) which was free of time pressure, followed by sessions with 80% (SS80), 100% (SS100), 90% (SS90) and 150% (SS150) of the baseline time. Electrocardiogram (ECG) and task performance were recorded throughout the experiments. Two rest sessions before and after the computer-mouse work, i.e. RS1 and RS2, were also recorded as comparison. HRV series were subsequently analyzed by both conventional power spectral analysis and detrended fluctuation analysis (DFA). The long-term scaling exponent α₂ by DFA was significantly lower in SS80 than that in other sessions. It was also found that short-term release of time pressure had positive influences on the cardiovascular system, i.e. the α₂ in RS2 was significantly higher than that in SS80, SS100 and SS90. No significant differences were found between any two sessions by conventional power spectral analysis. Our results showed that DFA performed better in discriminating the states of cardiovascular autonomic modulation under time pressure than the conventional power spectral analysis.