Fresnel operator, squeezed state and Wigner function for Caldirola-Kanai Hamiltonian

Based on the technique of integration within an ordered product (IWOP) of operators we introduce the Fresnel operator for converting Caldirola-Kanai Hamiltonian into time-independent harmonic oscillator Hamiltonian. The Fresnel operator with the parameters A,B,C,D corresponds to classical optical Fresnel transformation, these parameters are the solution to a set of partial differential equations set up in the above mentioned converting process. In this way the exact wavefunction solution of the Schr\"odinger equation governed by the Caldirola-Kanai Hamiltonian is obtained, which represents a squeezed number state. The corresponding Wigner function is derived by virtue of the Weyl ordered form of the Wigner operator and the order-invariance of Weyl ordered operators under similar transformations. The method used here can be suitable for solving Schr\"odinger equation of other time-dependent oscillators.Comment: 6 pages, 2 figure

The coupling of dynamics in coupled map lattices

We investigate the coupling of dynamics in coupled map lattices (CMLs) which is not only related to coupled parameter, but also the asynchronization among different mean fields in the lattices. Computer simulations show that the optimal coupling among mean fields can be found from the maximum coupling of dynamics in various CMLs. As a consequence, the application areas of coupled systems may be broadened due to the better understanding of their dynamics

Distinct molecular underpinnings of Drosophila olfactory trace conditioning

Trace conditioning is valued as a simple experimental model to assess how the brain associates events that are discrete in time. Here, we adapted an olfactory trace conditioning procedure in Drosophila melanogaster by training fruit flies to avoid an odor that is followed by foot shock many seconds later. The molecular underpinnings of the learning are distinct from the well-characterized simultaneous conditioning, where odor and punishment temporally overlap. First, Rutabaga adenylyl cyclase (Rut-AC), a putative molecular coincidence detector vital for simultaneous conditioning, is dispensable in trace conditioning. Second, dominant-negative Rac expression, thought to sustain early labile memory, significantly enhances learning of trace conditioning, but leaves simultaneous conditioning unaffected. We further show that targeting Rac inhibition to the mushroom body (MB) but not the antennal lobe (AL) suffices to achieve the enhancement effect. Moreover, the absence of trace conditioning learning in D1 dopamine receptor mutants is rescued by restoration of expression specifically in the adult MB. These results suggest the MB as a crucial neuroanatomical locus for trace conditioning, which may harbor a Rac activity-sensitive olfactory "sensory buffer" that later converges with the punishment signal carried by dopamine signaling. The distinct molecular signature of trace conditioning revealed here shall contribute to the understanding of how the brain overcomes a temporal gap in potentially related events

Atomic-level insights into transition mechanism of dominant mixing modes of multi-component fuel droplets: From evaporation to diffusion

For a multi-component hydrocarbon mixture under supercritical conditions, especially for fuels injected into compression ignition engines, the mechanism for the transition of the dominant mixing mode from evaporation to diffusion is not well established. In this paper, evaporation processes of a six-component hydrocarbon fuel (13.16 mol% toluene, 13.81 mol% n-decane, 22.30 mol% n-dodecane, 24.60 mol% n-tetradecane, 14.66 mol% n-hexadecane and 11.47 mol% n-octadecane) droplet in nitrogen environments were studied using molecular dynamics (MD) simulations, in comparison with those of three-component and single-component fuel droplets. The ambient pressure ranged from 2 MPa to 16 MPa and the ambient temperature ranged from 750 K to 1350 K. Results indicated that the transition characteristics of the mixed fuel were not the linearly weighted average of the physical properties of individual components in the mixture based on their mole fractions. The reason why there is a limitation on the maximum transition temperature when diffusion dominates the fuel-ambient gas mixing process under high pressures has been discussed. The average resultant force on a fuel atom of an individual component increases with increasing pressure or decreasing temperature at the supercritical temperature, and diffusion will gradually dominate the mixing process of the fuel. The clustering behavior of fuels under supercritical conditions has also been discussed

Thermal Stress Analysis of Solar Thermochemical Reactor Using Concentrated Solar Radiation

Utilizing solar thermochemical reactor to convert exhaust gas into high-quality clean fuel by concentrated solar radiation is a valuable way to develop renewable energy. Due to the high working temperature, the issue of reactor damage occurs easily as found during the course of the experiment. In order to find out the reasons, some thermal stress simulation and analysis of solar thermochemical reactor were made in this article. The areas where thermal stress is concentrated were investigated in the contour simulation results. Based on the analysis, some suggestions for structural optimization for further research were formulated. Keywords: solar thermochemical, thermal stress, heat transfer and flow, reacto

Intermittent phase synchronization of coupled spatiotemporal chaotic systems

Phase synchronization is studied with a discrete system formed by two coupled map lattices, in which phases are measured in two-dimensional vectors. Simulation results show that by imposing external coupling between the two lattices, phase synchronization can be found in all two-dimensional phase planes between them. When the system is approaching the phase synchronizing state, unstable phase synchronization is observed. This is referred to as intermittent phase synchronization that appears when the trajectories on two interacting phase planes have opposite directions of rotation but with only a small phase difference. The intermittent phase synchronization could also be observed in coupled autonomous systems with diffusive attractors although their phase concepts are inconsistent. Our results show that the intermittent phase synchronization of both discrete and autonomous systems relates to the diffusion or the complexity of the attractors

An improvement of isochronous mass spectrometry: Velocity measurements using two time-of-flight detectors

Isochronous mass spectrometry (IMS) in storage rings is a powerful tool for mass measurements of exotic nuclei with very short half-lives down to several tens of microseconds, using a multicomponent secondary beam separated in-flight without cooling. However, the inevitable momentum spread of secondary ions limits the precision of nuclear masses determined by using IMS. Therefore, the momentum measurement in addition to the revolution period of stored ions is crucial to reduce the influence of the momentum spread on the standard deviation of the revolution period, which would lead to a much improved mass resolving power of IMS. One of the proposals to upgrade IMS is that the velocity of secondary ions could be directly measured by using two time-of-flight (double TOF) detectors installed in a straight section of a storage ring. In this paper, we outline the principle of IMS with double TOF detectors and the method to correct the momentum spread of stored ions.Comment: Accepted by Nuclear Inst. and Methods in Physics Research,

Inelastic X-Ray Scattering Study of Exciton Properties in an Organic Molecular crystal

Excitons in a complex organic molecular crystal were studied by inelastic x-ray scattering (IXS) for the first time. The dynamic dielectric response function is measured over a large momentum transfer region, from which an exciton dispersion of 130 meV is observed. Semiempirical quantum chemical calculations reproduce well the momentum dependence of the measured dynamic dielectric responses, and thus unambiguously indicate that the lowest Frenkel exciton is confined within a fraction of the complex molecule. Our results demonstrate that IXS is a powerful tool for studying excitons in complex organic molecular systems. Besides the energy position, the IXS spectra provide a stringent test on the validity of the theoretically calculated exciton wave functions.Comment: 4 pages, 4 figure