Physical modeling of direct current and radio frequency characteristics for In P-based InAlAs/InGaAs HEMTs

Direct current(DC) and radio frequency(RF) performances of InP-based high electron mobility transistors(HEMTs)are investigated by Sentaurus TCAD. The physical models including hydrodynamic transport model, Shockley–Read–Hall recombination, Auger recombination, radiative recombination, density gradient model and high field-dependent mobility are used to characterize the devices. The simulated results and measured results about DC and RF performances are compared, showing that they are well matched. However, the slight differences in channel current and pinch-off voltage may be accounted for by the surface defects resulting from oxidized InAlAs material in the gate-recess region. Moreover,the simulated frequency characteristics can be extrapolated beyond the test equipment limitation of 40 GHz, which gives a more accurate maximum oscillation frequency( f_(max)) of 385 GHz.     

Dynamic instability of collective myosin Ⅱ motors

Some kinds of muscles can oscillate spontaneously,which is related to the dynamic instability of the collective motors.Based on the two-state ratchet model and with consideration of the motor stiffness,the dynamics of collective myosin Ⅱmotors are studied.It is shown that when the motor stiffness is small,the velocity of the collective motors decreases monotonically with load increasing.When the motor stiffness becomes large,dynamic instability appears in the forcevelocity relationship of the collective-motor transport.For a large enough motor stiffness,the zero-velocity point lies in the unstable range of the force-velocity curve,and the motor system becomes unstable before the motion is stopped,so spontaneous oscillations can be generated if the system is elastically coupled to its environment via a spring.The oscillation frequency is related to the motor stiffness,motor binding rate,spring stiffness,and the width of the ATP excitation interval.For a medium motor stiffness,the zero-velocity point lies outside the unstable range of the force-velocity curve,and the motion will be stopped before the instability occurs.     

杂质对量子环上荷负电激子的影响

讨论了在杂质电荷的电场影响下,量子环上荷负电激子X-的能-光谱及其Aharonov-Bohm振荡.当轨道总角动量不守恒的情况下,提出如何按轨道角动量分类构成基矢组并用典型的对角化方法求解体系的本征值和本征矢的方案.该方案计算简单,计算结果令人满意.还讨论了运用等效电荷变换公式和变换图,把位于三维空间的杂质简化为二维平面(或x轴上)的杂质处理,使计算变得更简单,对结果的分析也更明晰.     

Lorentz violation constrained by triplicity of lepton families and neutrino oscillations

In this paper we postulate an algebraic model to relate the triplet characteristic of lepton families to Lorentz violation. Inspired by the two-to-one mapping between the group SL（2, C） and the Lorentz group via the Pauli grading （the elements of SL（2, C） expressed by direct sum of unit matrix and generators of SU（2） group）, we grade the SL（3,C） group with the generators of SU（3）, i. e. the Gell-Mann matrices, then express the SU（3） group in terms of three SU（2） subgroups, each of which stands for a lepton species and is mapped into the proper Lorentz group as in the case of the group SL（2,C）. If the mapping from group SL（3,C） to the Lorentz group is constructed by choosing one SU（2） subgroup as basis, then the other two subgroups display their impact only by one more additional generator to that of the original Lorentz group. Applying the mapping result to the Dirac equation, it is found that only when the kinetic vertex -γμθ^μ is extended to encompass γ5γμθ^μ can the Dirac-equation-form be conserved. The generalized vertex is useful in producing neutrino oscillations and mass differences.     

Results from Super-Kamiokande and K2K

Results from Super-Kamiokande-I’s entire 1496 live days of solar neutrino data are presented, including the absolute flux, energy spectrum, zenith angle (day/night) and seasonal variation. The possibility of MSW and vacuum oscillations is discussed in light of these results. Results from the first 1289 days of Super-K-I’s atmospheric neutrino analysis are also presented, including the evidence for ν_μ →ν _τ oscillations, against ν_μ → ν_sterile oscillations, and the current limits on proton decay. Finally, results based on 56 × 10¹⁹ protons on target are given for the K2K long-baseline neutrino oscillation experiment.     

合肥光源逐束团相位测量及纵向不稳定性诊断

为了研究储存环束流多束团纵向运动特性,在合肥光源（HLS-II）上研制了一套逐束团相位测量系统。该系统利用示波器直接采集BPM和信号,采用过零点检测法、时间差分（Temporal Difference, TD）法相结合的方法从BPM和信号中提取出逐束团相位。介绍了逐束团相位测量系统的系统构架、相位提取方法以及在HLS-II上的一些实验结果。通过对该系统记录的5 ms时间长度的逐束团多圈相位数据的离线分析,得到多束团纵向运动的同步振荡的频率、纵向工作点、束团振荡的模式信息以及振荡模式增长率等特征信息,诊断出HLS-II在top-off恒流运行期间存在2个较强的纵向耦合束团不稳定模式,并提取出了2个振荡模式的增长率。该系统的逐束团相位测量结果及相关纵向不稳定性分析可为机器研究、纵向反馈系统调试评估及高频RF系统的性能评估等提供参考。     

外力驱动下耦合弹簧振子的法诺共振

法诺共振是物理体系中普遍存在的一种非对称共振现象,它最早起源于量子物理,其微观图像是原子谱线中窄的分离态与宽的连续态之间的相干干涉.本文利用经典力学体系中两个弹簧振子的耦合,使其中一个弹簧振子受到周期性外力的驱动,成功类比了量子力学中的法诺共振现象.通过分析每个弹簧振子的动力学方程,严格求解它们的振动公式,从而得到每个...     

受迫振动非线性特性的教学拓展

受迫振动在大学物理和大学物理实验中均是重点教学内容,为了使学生更加深入理解受迫振动的非线性特性,本文基于波耳共振仪所涉及的非线性因素和实验数据,对受迫振动方程进行非线性修正,利用数值分析探讨其非线性特性.通过引入硬弹簧型杜芬方程,探讨系统由周期性运动进入混沌状态的演化,将受迫振动中相对稳定的平衡点与奇异吸引子进行类比,...     

时标上二阶广义Emden-Fowler型动态方程的振荡性

研究了时标上的一类具有阻尼项的二阶广义Emden-Fowler型泛函动态方程的振荡性,利用时标上的微积分理论和广义的Riccati变换及不等式技巧,建立了该方程振荡的若干判别准则, 推广且改进了一些已有的结果,并用具体实例来说明本文的主要结论。     

一类三阶非线性分布时滞动力方程的振动结果

研究一类三阶非线性分布时滞动力方程的振动性,通过构造广义Riccati变换得到一类新的广义Riccati不等式,利用积分平均技巧等方法,建立了保证该方程一切解均振动或收敛于0的若干新的振动结果,推广和改进了近期文献的相关结论,并给出了若干例子。