Electron Transport in Configurational Model of Ferromagnetic Fulleride with Triple Orbital Degeneracy

Abstract

Phenomenon of ferromagnetic ordering was for a long time associated exclusively with transition metal and rare-earth compounds. Nowadays this view is challenged by growing evidence that in molecular carbon-based systems the ferromagnetic alignment of spins can be observed as well. We have developed a microscopical model of a fulleride electronic subsystem taking into account triple orbital degeneracy of energy states within the configurational-operator approach. Using the Green function method the energy spectrum of the model has been calculated. Conditions for the ferromagnetic state stabilization have been determined. Static electrical conductivity and effective masses of current carriers in the system with orbitally degenerated energy band have been obtained. In the ground state and for low temperatures at different forms of unperturbed density of electronic states the concentration dependences of transport characteristics for less-then-half-filled lower quasiparticle subband have been calculated.     

Pole placement controllers for linear time-delay systems with commensurate point delays

This paper investigates the exact and approximate spectrum assignment properties associated with realizable output-feedback pole-placement type controllers for single-input single-output linear time-invariant time-delay systems with commensurate point delays. The controller synthesis problem is discussed through the solvability of a set of coupled diophantine equations of polynomials. An extra complexity is incorporated to the above design to cancel extra unsuitable dynamics being generated when solving the above diophantine equations. Thus, the complete controller tracks any arbitrary prefixed (either finite or delaydependent) closed-loop spectrum. However, if the controller is simplified by deleting the above mentioned extra complexity, then the robust stability and approximated spectrum assignment are still achievable for a certain sufficiently small amount of delayed dynamics. Finally, the approximate spectrum assignment and robust stability problems are revisited under plant disturbances if the nominal controller is maintained. In the current approach, the finite spectrum assignment is only considered as a particular case to the designer‘s choice of a (delay-dependent) arbitrary spectrum assignment objective.     

用自积分式罗氏线圈测量纳秒级高压脉冲电流

介绍了测量纳秒级高压脉冲大电流信号用的自积分式罗氏线圈的优点、用途、基本原理及设计。利用传输理论分析了它的信号响应及干扰。对研制出的罗氏线圈进行了标定。设计的线圈的灵敏度在1.4mV/A,可以采用的上升时间小于2ns,脉宽小于200ns,电流信号10A～40kA。自积分式罗氏线圈广泛用于脉冲功率技术中的快过程大电流测量。     

产电对微生物燃料电池参数的影响

测试了pH值和电导率的变化规律,分析了MFC开路电压的变化情况,为改善MFC的性能提供理论依据.采用驯化培养的菌种,MFC启动时间更短;在恒温、高温和高底物浓度条件下,开路电压更高、更稳.产物在阳极液中的积累会降低开路电压.阴极液和阳极液的pH值的差值与电流正相关.阳极液的电导率会减小,而阴极液的电导率会增大;阳极液中...     

Optimal retirement with borrowing constraints and forced unemployment risk

In this paper, we study optimal retirement in a two-dimensional incomplete market caused by borrowing constraints and forced unemployment risk. We show that the two aspects jointly affect an individual’s optimal consumption, investment, and retirement strategies. In contrast to the complete market case, the endogenously determined wealth threshold for retirement is significantly affected by the two-dimensional market incompleteness, resulting in a lower wealth threshold. We also discuss a possible unemployment insurance scheme for the borrowing-constrained individual to respond to the shocks of forced unemployment.     

Leakage current and sub-bandgap photo-response of oxygen-plasma treated GaN Schottky barrier diodes

The effect of oxygen plasma treatment on the performance of GaN Schottky barrier diodes is studied. The GaN surface is intentionally exposed to oxygen plasma generated in an inductively coupled plasma etching system before Schottky metal deposition. The reverse leakage current of the treated diodes is suppressed in low bias range with enhanced diode ideality factor and series resistance. However, in high bias range the treated diodes exhibit higher reverse leakage current and corresponding lower breakdown voltage. The X-ray photoelectron spectroscopy analysis reveals the growth of a thin GaO_x layer on GaN surface during oxygen plasma treatment. Under sub-bandgap light illumination, the plasma-treated diodes show larger photovoltaic response compared with that of untreated diodes, suggesting that additional defect states at GaN surface are induced by the oxygen plasma treatment.     

Topological structure preserving numerical simulations of dynamical models

This paper brings together two methods producing numerical solutions with a statement of their quality — the nonstandard finite difference method and the method of validated computing. It deals with the construction and the analysis of reliable numerical discretizations of dynamical systems by employing these two techniques. An epidemiological model is used as a model example for their combined application.     

电子初始能量对双向流二极管空间电荷限制流密度的影响

从理论上研究了阴极发射电子初始能量对一维平面非相对论性双向流二极管内空间电荷限制电子、离子流密度的影响,并与阴极发射电子初始能量为0情况下的空间电荷限制电子、离子流密度进行了比较。     

动力飞行体电磁脉冲效应数值分析

 利用时域有限差分方法模拟了在不考虑等离子体高温尾焰情况下,电磁脉冲与动力飞行体的相互作用。计算结果表明：在入射电磁脉冲的作用下, 飞行体蒙皮上将感应很大的皮电流; 感应电流密度的波形为衰减振铃信号波形,振铃周期等于电流波在整个飞行体长度上流动两次的时间;感应皮电流密度分布的特点是飞行体两端电流密度小,中部大。     

Modeling of MIG/MAG welding with experimental validation using an active contour algorithm applied on high speed movies

This paper investigates some issues in physical modeling of metal inert gas/metal active gas (MIG/MAG) welding process in the short arc mode. In this mode, a metal supply is molten in the arc state and then transferred to the weld pool during the short-circuit state. A hybrid model having two distinct continuous states whose switchings are controlled by two guard conditions is proposed. Due to the complexity of the physical phenomena involved in the welding process, simplifications are used to obtain a model accounting for the main physical contributions but simple enough to yield an efficient, fast and numerically tractable simulator which can be used intensively for evaluating different control strategies. In an attempt to validate the proposed model, different measurements have been made including supply voltage and current sampled synchronously with high speed digital video. In order to extract some relevant quantities representative of the metal transfer from image sequences, an active contour algorithm is developed and tested. The effectiveness of the proposed model in the prediction of major tendencies of a welding process, especially in the arc state, is shown using experimental data. Some limitations of the model during the metal transfer are also stressed and possible remedies are then proposed.