具有不变锥面族的二次系统

本文研究了以二次锥面不变曲面的空间二次系统,给出了这类二次系统在锥面上极限环的不存在性,存在性,以及唯一性的条件。     

基于Hotelling线性城市模型的国有土地出让配置效率研究

我国国有土地出让过程中,享受土地出让金返还政策的开发商与无返还政策的开发商同时参与竞争的现象普遍存在.采用Hotelling线性城市模型,度量享受返还政策开发商和无返还政策开发商的土地成交概率,研究非对称环境下的国有土地出让配置效率.通过演绎开发商的均衡报价策略和出让结果发现:土地出让金返还政策是我国国有土地出让配置效率低的原因之一;如政府在出让过程中公开返还政策,则可有效提高国有土地配置效率.并提出了增加信息公开度,提高土地市场化配置效率等对策措施.     

Numerical simulation of the magnetoresistance effect controlled by electric field in p–n junction

The magnetoresistance effect of a p–n junction under an electric field which is introduced by the gate voltage at room temperature is investigated by simulation. As auxiliary models, the Lombardi CVT model and carrier generationrecombination model are introduced into a drift-diffusion transport model and carrier continuity equations. All the equations are discretized by the finite-difference method and the box integration method and then solved by Newton iteration.Taking advantage of those models and methods, an abrupt junction with uniform doping is studied systematically, and the magnetoresistance as a function of doping concentration, SiO_2 thickness and geometrical size is also investigated. The simulation results show that the magnetoresistance(MR) can be controlled substantially by the gate and is dependent on the polarity of the magnetic field.     

Numerical simulation study of organic nonvolatile memory with polysilicon floating gate

A polysilicon-based organic nonvolatile floating-gate memory device with a bottom-gate top-contact configuration is investigated,in which polysilicon is sandwiched between oxide layers as a floating gate.Simulations for the electrical characteristics of the polysilicon floating gate-based memory device are performed.The shifted transfer characteristics and corresponding charge trapping mechanisms during programing and erasing(P/E) operations at various P/E voltages are discussed.The simulated results show that present memory exhibits a large memory window of 57.5 V,and a high read current on/off ratio of ≈ 10~3.Compared with the reported experimental results,these simulated results indicate that the polysilicon floating gate based memory device demonstrates remarkable memory effects,which shows great promise in device designing and practical application.