MOCVD外延Al2O3基AlGaN/GaN超晶格的结构和光学特性

通过X射线衍射分析、透射电镜观察、红外透射光谱分析、紫外-可见吸收光谱分析和光致发光试验,研究了用金属有机物化学汽相沉积（MOCVD）的方法,在带有GaN缓冲层的蓝宝石（Al2O3）衬底上生长的AlGaN/GaN超晶格材料的微观结构、光吸收性质和发光特性.X射线衍射结果表明,GaN基材料均为纤锌矿六方结构,薄膜具有良好的结晶质量,薄膜生长沿c轴择优取向.透射电镜观察表明,超晶格试样的周期结构分布均匀,实际周期为13.3nm，且观察到高密度的位错存在于外延膜中。通过光学试验数据，确定了试样的光学吸收边都是在370nm附近，理论计算显示试样为直接跃迁型半导体，禁带宽度约为3．4eV。试样的折射率随光子能量的增加而增加、随波长的增加而减小，计算表明消光系数的极小值位于370nm处。光致发光测试分析表明，超晶格有很好的发光性能，并发现存在黄带发光。     

焊接接头韧度CTOD评定的适用性与允许值研究

对厚钢板两种焊接工艺焊接接头中的焊缝材料和热影响区材料进行拉伸试验。发现各自的拉伸曲线都可视为理想弹塑性，符合Wells提出裂纹尖端张开位移（crack tip opening displacemem，CTOD）理论的假设条件。因此，证明CTOD试验评定焊接接头韧度的适用性。提出确定钢结构焊接接头CTOD允许值的“母材参考法”和“类比法”，为在钢结构的设计和建造中合理地确定焊接接头韧度指标提供方法。     

Geomagnetic polarity transitions recorded in the Miocene lavas of the Wuyu basin,Tibet

Geomagnetic polarity transitions were the most important phenomena in the study of the geomagnetic field evolution and the earth's deep interior dynamics.The Miocene postcollisional ultrapotassic-potassic rocks are widely distributed in the Lhasa Block of southern Tibet.Paleomagnetic studies on the Wuyu Formation indicated that these volcanic rocks recorded the C5Bn.2n-C5Bn.1r and C5ACr-C5ACn geomagnetic polarity transitions.The virtual geomagnetic poles(VGPs) of these two polarity transitions were located ...     

Memristive neuron model with an adapting synapse and its hardware experiments

Electromagnetic induction effect caused by neuron potential can be mimicked using memristor. This paper considers a fluxcontrolled memristor to imitate the electromagnetic induction effect of adapting feedback synapse and presents a memristive neuron model with the adapting synapse. The memristive neuron model is three-dimensional and non-autonomous. It has the time-varying equilibria with multiple stabilities, which results in the global coexistence of multiple firing patterns. Multiple numerical plots are executed to uncover diverse coexisting firing patterns in the memristive neuron model. Particularly, a nonlinear fitting scheme is raised and a fitting activation function circuit is employed to implement the memristive mono-neuron model. Diverse coexisting firing patterns are observed from the hardware experiment circuit and the measured results verify the numerical simulations well.     

用直流电阻电桥测量导体电阻测量不确定度的评定

本文论述了用双臂电桥测量导体电阻测量不确定度的的评定方法。     

大直径薄壁核电环类铸件焊接防变形技术

测量大直径、薄壁核电环类铸钢件在焊接工序的尺寸变化情况,利用因果图和"FMEA"分析方法,找出了环类铸件焊接变形的成因。从增强铸件的刚度、控制焊接部位的热输入量、合理安排焊接顺序、焊后消应力等方面,采取一系列改进措施,有效防止环类铸件焊接变形。     

Inverse problem for Chaplygin’s nonholonomic systems

Chaplygin’s nonholonomic systems are familiar mechanical systems subject to unintegrable linear constraints, which can be reduced into holonomic nonconservative systems in a subspace of the original state space. The inverse problem of the calculus of variations or Lagrangian inverse problem for such systems is analyzed by making use of a reduction of the systems into new ones with time reparametrization symmetry and a genotopic transformation related with a conformal transformation. It is evident that the L...     

包含共格畸变的立方合金沉淀机制的计算机模拟

利用包含共格畸变能的微观扩散方程对立方合金的沉淀过程进行计算机模拟。结果表明：共格畸变阻碍了过渡区合金沉淀过程的进行，随共格畸变能的增大，沉淀相分布的取向性越来越明显，由原来离散分布的等轴粒子状向椭片状转变。靠近高浓度合金的过渡区合金，随共格畸变能的增大，其沉淀机制由非经典形核长大和大稳分解的混合特征逐渐向非经典形核长大型的沉淀特征转变。     

使用ObjectARX实现自动检查点线矛盾的探讨

提出了不同的点线关系判断方法和使用六点法检查的方法，探讨了另外一种用程序自动检查点线矛盾的准确、高效的方法。     

基于组合代理模型的三角履带轮多工况疲劳优化

应急救援车辆的三角履带轮需要在各种地形和路况条件下具备高机动性和可靠性.针对三角履带支撑架在多工况疲劳优化中的计算时程过长问题,以组合代理模型来加速优化求解,为了保证代理模型的精度,提出新的代理模型评价指标.首先,对可更换三角履带轮的支撑架在四个工况下的疲劳寿命进行分析;然后,以克里金模型和响应面模型为基础对支撑架的质量及四个工况的疲劳寿命进行组合代理模型的构建,其中,为了在寻优过程中更易逼近组合代理模型的全局最优点,使得预测值和观测值具有一致的凹凸性,提出了局部趋势误差作为构建组合代理模型的评价标准;最后,对支撑架的数学模型进行了尺寸优化.结果 表明,组合代理模型不但保证了计算精度,而且具备一定的鲁棒性,减重后的三角履带轮在保证质量的前提下寿命提高了43.59％.