一类投资价值为变量的研究与开发项目的Nash解问题

本文考虑一类完全信息下研究与开发 (R& D)项目中的纯策略问题 .设有一个 R& D项目 ,两位风险中性的投资人竞争 .项目需要的投资量至少是 I,投资较多的一方取胜 .项目成功后的价值是确定的 ,但是其价值大小对这两位投资人不一样 (品牌知名度 ,管理水平 ,营销能力等方面的差异导致的价格和销量不同 ) ,我们使用博弈论方法对此进行研究 ,得到的结果显示 :如果他们所实现的项目价值是常量 ,则不存在均衡解 ;而当项目价值是一个关于投资总量的单增函数时 ,则在两位投资人的价值函数的差异较大时 ,存在一个同时还是社会占优的 Nash均衡解 ,在两位投资人的价值函数差异不太大时 ,不存在均衡解 ,此时的竞争会导致社会效益下降 .从而提示政府应当通过一定的方式 (如招投标法 ,审批法 )对投资活动予以控制 .     

有限时间水平保险债务分析

利用公司金融期权博弈理论,讨论了有限到期日保险债券的价值,分析了公司最优资本结构;在破产首次到达时的概率分布已知时,获得了股东内生破产阈值和担保人最优保险费率的解析表达式,为保险债券的设计提供了理论依据．     

The improvement of Al2O3/AlGaN/GaN MISHEMT performance by N2 plasma pretreatment

This paper discusses the effect of N 2 plasma treatment before dielectric deposition on the electrical performance of a Al2O3 /AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor(MISHEMT),with Al2O3 deposited by atomic layer deposition.The results indicated that the gate leakage was decreased two orders of magnitude after the Al2O3 /AlGaN interface was pretreated by N 2 plasma.Furthermore,effects of N 2 plasma pretreatment on the electrical properties of the AlGaN/Al2O3 interface were investigated by x-ray photoelectron spectroscopy measurements and the interface quality between Al2O3 and AlGaN film was improved.     

几类Lotka-Volterra模型的定性分析

本文考虑几类“捕食者—食饵”型的Lotka—Volterra模型,给出了这些模型全局稳定与所有正解最终有界的充分条件;对这些条件的描述与论证,本文运用了图论的概念与方法。     

场板抑制GaN高电子迁移率晶体管电流崩塌的机理研究

通过实验和数值器件仿真研究了钝化GaN高电子迁移率晶体管(HEMTs)、栅场板GaN HEMTs和栅源双层场板GaN HEMTs电流崩塌现象的物理机理,建立了电流崩塌强度与帽层中载流子浓度、陷阱电离率和电场的内在联系.研究结果表明,场板可以有效调制帽层中横向和纵向电场的强度分布,并可有效调制纵向电场的方向,减弱栅极附近电场强度,增加场板下方电场强度,这会减弱栅极附近自由电子的横向运动,增强场板下方自由电子的纵向运动,进而可以有效调制帽层中自由电子浓度的分布,提高陷阱的电离率,减小器件的电流崩塌. 关键词： 电流崩塌 钝化器件 场板器件 陷阱电离率     

一类含指数函数的不定积分的探讨

通常的微积分教材中,可以计算的不定积分主要包括有理函数、三角函数有理式和某些含根式的函数.受几个具体函数积分方法的启发,证明了一类含有指数函数的积分公式,该结果包含了微积分教材中用常规积分方法较难推演的一类含指数函数的积分.     

临河凹陷QK3钻孔220 ka以来的沉积环境演变记录

临河凹陷是河套盆地的一部分,黄河由西向东流经,其内发育了巨厚的沉积地层,是第四纪环境演变的理想场所。通过分析临河凹陷中QK3钻孔地层的粒度特征,结合年代地层重建了研究区中更新世晚期以来的沉积环境演变过程:189.9 ka.BP～220.26 ka.BP表现为滨湖相沉积;117.47 ka.BP～189.9 ka.BP表现为河流边滩沉积;117.47 ka.BP～189.9 ka.BP表现为河流边滩沉积;38.5 ka.BP～117.47 ka.BP表现为河流边滩和河漫湖泊的交替沉积环境;13.49 ka.BP～38.5 ka.BP表现为河流边滩相沉积环境;13.49 ka.BP以来表现为河漫湖泊相沉积环境。     

创新体系下微积分作业模式多样化的探索与实践

微积分作业是微积分教学过程中的一个重要环节.传统的作业布置方式存在着"一刀切"的弊病,对学生的多样化、个性化的学习需求考虑不足,不利于创新型人才的培养.近几年我们在教学改革中着力开展研究性教学和研究性学习,在保留经过时间检验的传统作业模式的基础上,增加了拓展探索型、总结归纳型、应用实践型和体会反思型等开放式作业,在提高学生数学素质、培养学生自主研究意识和提升创新能力等方面取得了一定成效.     

A study of GaN MOSFETs with atomic-layer-deposited A1203 as the gate dielectric

Accumulation-type GaN metal-oxide-semiconductor field-effect transistors （MOSFETs） with atomic-layerdeposited Al₂O₃ gate dielectrics are fabricated.The device,with atomic-layer-deposited Al₂O₃ as the gate dielectric,presents a drain current of 260 mA/mm and a broad maximum transconductance of 34 mS/mm,which are better than those reported previously with Al₂O₃ as the gate dielectric.Furthermore,the device shows negligible current collapse in a wide range of bias voltages,owing to the effective passivation of the GaN surface by the Al₂O₃ film.The gate drain breakdown voltage is found to be about 59.5 V,and in addition the channel mobility of the n-GaN layer is about 380 cm2 /Vs,which is consistent with the Hall result,and it is not degraded by atomic-layer-deposition Al₂O₃ growth and device fabrication.     

Neutron irradiation effects on A1GaN//GaN high electron mobility transistors

AlGaN/GaN high electron mobility transistors(HEMTs) were exposed to 1 MeV neutron irradiation at a neutron fluence of 1 × 10 15 cm 2.The dc characteristics of the devices,such as the drain saturation current and the maximum transconductance,decreased after neutron irradiation.The gate leakage currents increased obviously after neutron irradiation.However,the rf characteristics,such as the cut-off frequency and the maximum frequency,were hardly affected by neutron irradiation.The AlGaN/GaN heterojunctions have been employed for the better understanding of the degradation mechanism.It is shown in the Hall measurements and capacitance-voltage tests that the mobility and concentration of two-dimensional electron gas(2DEG) decreased after neutron irradiation.There was no evidence of the full-width at half-maximum of X-ray diffraction(XRD) rocking curve changing after irradiation,so the dislocation was not influenced by neutron irradiation.It is concluded that the point defects induced in AlGaN and GaN by neutron irradiation are the dominant mechanisms responsible for performance degradations of AlGaN/GaN HEMT devices.