Charge transport properties in microcrystalline KDyFe(CN)6

Microcrystalline solid dysprosium(III) hexacyanoferrate(II) was synthesized by co-precipitation in aqueous solution. The resulting solid has been studied by Fourier transform infrared spectroscopy, X-ray analysis and solid state electrochemistry. The use of a cavity microelectrode was necessary to explore a wide range of time scale and minimize the (undesired) capacitive currents. Cyclic voltametric experiments were very helpful to understand the kinetic of charge transfer in such microstructure. A structure-properties relationship has been established from the crystallographic and the electrochemical properties. A square-scheme is presented to explain the unique electrochemical behavior of hexacyanoferrate containing dysprosium since this compound exhibits a second redox system. The solid presents an open channel-like morphology in which the motion of charged species occurs during the redox processes. Precisely, the electronic transfer is accompanied by a cation diffusion inside the microcrystalline structure. The size of these channels strongly suggests that the kinetic of charge transfer is limited by the cation transport into these structures.     

Near-field optics and control of photonic crystals

We discuss recent progress and the exciting potential of scanning probe microscopy methods for the characterization and control of photonic crystals. We demonstrate that scanning near-field optical microscopy can be used to characterize the performance of photonic crystal device components on the sub-wavelength scale. In addition, we propose scanning probe techniques for realizing local, low-loss tuning of photonic crystal resonances, based on the frequency shifts that high-index nanoscopic probes can induce. Finally, we discuss prospects for on-demand spontaneous emission control. We demonstrate theoretically that photonic crystal membranes induce large variations in spontaneous emission rate over length scales of 50 nm that can be probed by single light sources, or nanoscopic ensembles of light sources attached to the end of a scanning probe.     

A DQ based approach to simulate the vibrations of buckled beams

In this paper, the nonlinear planar response of a hinged–hinged buckled beam to a primary-resonance excitation of its first vibration mode is computed by a new numerical scheme. The beam is subjected to an axial force beyond the critical load of the first buckling mode and to a transverse harmonic excitation. The nonlinear dynamical problem is solved by deducing directly the discretized equations governing the problem thanks to a new approach, here called DQ based approach, since it is based on the application of the quadrature rules of the DQM. As it will be shown, for the problem here considered, the minimum number of degrees of freedom to be retained to limit the numerical errors is four. Computer simulations of the dynamic behaviour of the discretized system are conducted by means of the IDQ method, a method proposed and recently generalized by the author. A sequence of supercritical period-doubling bifurcations leading to chaos, snapthrough motions and quasi-periodic motions can be observed, similarly to some cases existing in literature.     

Alternating sign matrices with one −1 under vertical reflection

We define a bijection that transforms an alternating sign matrix A with one −1 into a pair (N,E) where N is a (so called) neutral alternating sign matrix (with one −1) and E is an integer. The bijection preserves the classical parameters of Mills, Robbins and Rumsey as well as three new parameters (including E). It translates vertical reflection of A into vertical reflection of N. A hidden symmetry allows the interchange of E with one of the remaining two new parameters. A second bijection transforms (N,E) into a configuration of lattice paths called “mixed configuration.”     

某轻客低速轰鸣分析与改进*

某轻客车型在1100-1500rpm加速工况下存在明显车内轰鸣,严重影响乘坐舒适性。本文通过对激励源、悬挂结构传递路径和车身响应详细诊断和分析,分析主要原因为传动系扭振激励过大、激励前悬挂系统模态导致振动传递到车身零件与声腔模态耦合引起轰鸣。最终通过在前风窗下横梁和尾门增加CBS、前围板加强和前转向节增加动力吸振器解决了轰鸣问题。该优化思路为类似问题的优化控制提供重要的参考价值。     

弹性介质中圆柱壳动力响应研究的现状和展望

一、引言在地震动情况下,地下结构与地面结构相比较其动力响应是十分不同的。以桥梁和水堤为例,对这类结构的设计,水平惯性力是一个极为重要的因素。可是,对于地下结构,以埋管为例,惯性荷载主要由其周围的土介质所承受。地下管道系统的地震破坏,     

Sustained photon pulse revivals from inhomogeneously broadened spin ensembles

A very promising recent trend in applied quantum physics is to combine the advantageous features of different quantum systems into what is called “hybrid quantum technology”. One of the key elements in this new field will have to be a quantum memory enabling to store quanta over extended periods of time. Systems that may fulfill the demands of such applications are comb‐shaped spin ensembles coupled to a cavity. Due to the decoherence induced by the inhomogeneous ensemble broadening, the storage time of these quantum memories is, however, still rather limited. Here we demonstrate how to overcome this problem by burning well‐placed holes into the spectral spin density leading to spectacular performance in the multimode regime. Specifically, we show how an initial excitation of the ensemble leads to the emission of more than a hundred well‐separated photon pulses with a decay rate significantly below the fundamental limit of the recently proposed “cavity protection effect”.

     

On the numerical solution of tracked vehicle dynamic equations

In this investigation, the solution of the nonlinear dynamic equations of the multibody tracked vehicle systems are obtained using different procedures. In the first technique, which is based on the augmented formulation that employes the absolute Cartesian coordinates and Lagrange multipliers, the generalized coordinate partitioning of the constraint Jacobian matrix is used to determine the independent coordinates and the associated independent differential equations. An iterative Newton-Raphson algorithm is used to solve the nonlinear constraint equations for the dependent variables. The numerical problems encountered when one set of independent coordinates is used during the simulation of large scale tracked vehicle systems are demonstrated and their relationship to the track dynamics is discussed. The second approach employed in this investigation is the velocity transformation technique. One of the versions of this technique is discussed in this paper and the numerical problems that arise from the use of inconsistent system of kinematic equations are reported. In the velocity transformation technique, the tracked vehicle system is assumed to consist of two kinematically decoupled subsystems; the first subsystem consists of the chassis, the rollers, the sprocket and the idler, while the second subsystem consists of the track which is represented as a closed kinematic chain that consists of rigid links connected by revolute joints. It is demonstrated that the use of one set of recursive equations leads to numerical difficulties because of the change in the track configuration. Singular configurations can be avoided by repeated changes in the recursive equations. The sensitivity of the predictor-corrector multistep numerical integration schemes to the method of formulating the state equations is demonstrated. The numerical results presented in this investigation are obtained using a planner tracked vehicle model that consists of fifty four rigid bodies.     

Seismic behavior of insulated hollow-brick cavity walls using quasi-static experimentation

This paper focuses on an experimental investigation of different types of insulated hollow-brick cavity walls, i.e., walls with a door opening, with a window opening and without any opening, characterized with different tie bar arrangements, subjected to slowly applied cyclic loads. The cracking and damage patterns, strength and stiffness degradation and deterioration, energy dissipation capacity and hysteretic feature are analyzed. Based on the experimental results, the formulae of calculation for the cracking load and the ultimate load of cavity wall are mathematically established. The evaluation equation of strength and stiffness degradation of walls is presented and its parameters are numerically given from regression results. The original characteristic curves of recovery force-displacement of actual specimens under cyclic loads are discussed, and then a standard recovery force-displacement model is suggested with convenient forms for implementation.     

Selective recognition of the ditopic trimethylammonium cations by water-soluble aminocalix[4]arene

In this Letter, the role of the depth of the cavity in the recognition processes of the guests by the hosts has been investigated. The hosts 2, 3 interact with both the cationic function and the aromatic moiety in the guests 5, 6 but with a slight preference for the cationic functions. The host 4 selectively recognizes the trimethylammonium functions of the guests 5 and 6. However, the host 1 selectively recognizes the aromatic moiety of the ditopic trimethylammonium guests 5 and 6. The recognition and orientation of the guest in the cavity of the host are directly dependent on the depth of the hydrophobic cavity of the host.