整体式转向梯形的运动分析及优化设计

提出了更接近于实际的弹性轮胎的理论转向特性 ,用空间梯形模型 ,分析了车辆上常用的整体式转向梯形所确定的实际转向特性。在此基础上 ,又提出了用实际梯形转向特性逼近理论转向特性的优化设计方法 。

Numerical simulation of the multiple reversed shear Alfvén eigenmodes associated with the triangularity Alfvén gap

It was found that there are multiplicity of low shear toroidicity-induced Alfv′en eigenmodes in a zero beta limit if the inverse aspect ratio is larger than the magnetic shear at the mode location(Candy 1996 Phys. Lett. A 215 299). Because the reversed shear Alfv′en eigenmode(RSAE) and even the RSAE associated with the non-circular triangularity-induced Alfv′en eigenmode(NAE) gap(NAE–RSAE) usually reside near the shear-reversal point, the condition that the inverse aspect ratio is larger than the magnetic shear is naturally satisfied. For this reason, we numerically investigate the existence of multiplicity of core-localized NAE–RSAEs and mode characteristics in the present work. We firstly verify the existence of the multiplicity for zero beta plasma by using a D-shaped equilibrium. It is pointed out that, for a given toroidal mode number, the Alfv′en cascade spectrum accommodates down-sweeping and up-sweeping modes above and below the NAE range of frequencies. An analytical model for the existence of multiple RSAE modes is in good agreement with the simulation results. One notices that the triangularity has a greater effect on the odd-type modes than that on the even-type modes: the odd-type modes come into existence because of the plasma triangularity.

The residual zonal flow in tokamak plasmas with a poloidal electric field

In a tokamak plasma with auxiliary heating by cyclotron waves, a poloidal electric field will be produced, and as a consequence influence the residual zonal flow(RZF) level. The poloidal electric field can also be induced through biasing electrodes at the edge region of tokamaks.Numerical evaluation for a large aspect ratio circular cross section tokamak for the electron cyclotron wave heating indicates that the RZF level decreases significantly when the poloidal electric field increases. Qualitatively, the ion cyclotron wave heating is able to increase the RZF level. It is difficult to apply the calculation to the real cyclotron wave heating experiments since we need to know factors such as the plasma profiles, the exact power deposition and the cross section geometry, etc. It is possible to use the cyclotron wave heating to control the zonal flow and then to control the turbulence level in tokamak experiments.

Geodesic acoustic modes in tokamak plasmas with anisotropic distribution and a radial equilibrium electric field

The dispersion relation of standard geodesic acoustic modes in tokamak plasmas with anisotropic distribution and a radial equilibrium electric field is derived and analyzed. Both frequencies and damping rates increase with respect to the poloidal Mach number which indicates the strength of the radial electric field. The strength of anisotropy is denoted by the ratio of the parallel temperature(T_‖) to the perpendicular temperature(T_⊥). It is shown that, when the parallel temperature is lower than the perpendicular temperature, the enhanced anisotropy tends to enlarge the real frequency but reduces the damping rate, and when the parallel temperature is higher than the perpendicular temperature, the effect is opposite. The radial equilibrium electric field has stronger effect on the frequency and damping rate for the case with higher parallel temperature than the case with higher perpendicular temperature.

电商背景下汽车服务企业面临的挑战

随着我国汽车行业迅猛发展,如何快速提升产品销量及项目服务至关重要。目前我国电子商务及直播产业逐渐成熟,将电商直播应用到汽车服务企业营销运营中十分关键。通过近年来大多研究发现,电商直播产业及相关平台日益智能化、多元性发展。本次研究将对电商背景下汽车服务企业面临的挑战进行分析,为下一步工作开展提供依据参考。

SIRT1对阿尔茨海默病氧化应激的调控和机制

SIRT1属于沉默信息调节因子家族成员,具有去乙酰化酶活性,在阿尔茨海默病中发挥重要保护作用。氧化应激是阿尔茨海默病的发病机制之一,当前研究已发现,SIRT1可通过Aβ、PGC1-α、FOXO3a、Nrf2、p53影响ROS产生、抗氧化酶活性、神经元存活状态,从而调节大脑氧化应激损伤,但其机制尚未阐明。该文通过综述国内外最新研究进展,深入探讨SIRT1对阿尔茨海默病氧化应激的调控机制,将为SIRT1作为阿尔茨海默病的治疗标靶提供依据和方向。

星载合成孔径雷达距离模糊度计算方法

本文介绍了星载合成孔径雷达距离模糊产生的原因,以及在系统设计时通过脉冲重复频率选择避开星下点的干扰。在考虑地球曲率的情况下,给出了合成孔径雷达距离模糊度的理论计算模型,以及同一波位不同入射角、不同波位不同入射角下的距离模糊度计算流程,并采用所提计算方法通过仿真试验对某一典型系统参数下的距离模糊度进行了计算。