二维产品二维成组更换间隔期优化研究

针对故障受日历时间与使用时间共同影响的二维产品,传统的只按照单一时间变量开展的预防性维修已不能满足二维产品的实际维修保障需求,鉴于此,本文针对二维产品提出了二维预防性维修的策略,以日历时间与使用时间对二维产品进行二维预防性维修决策。本文首先建立二维产品故障率函数表达式,然后对二维预防性维修的过程进行具体的分析,在有限使用条件下分别从经济性的角度与任务性的角度建立二维成组更换的费用模型与可用度模型。根据所建模型,结合实例,采用了费效分析中的费效比准则来优化二维成组更换间隔期,通过对比分析验证了该模型的适用性与有效性,最后对二维预防性维修提出了展望。     

二维核磁共振数据处理与显示系统

详细介绍了我们在386微机上建立的二维NMR数据处理与分析系统,该系统采用菜单驱动方式,具有良好的用户界面,可进行标准的常规二维NMR数据处理与分析,数据处理结果可由标准设备输出或者以文件方式存储以便其它应用软件处理,该系统的建立可使通用微计算机成为有效的核磁共振数据处理站。     

自旋玻璃的二维随机格点模型模拟

本文对自旋玻璃CuMn进行了二维随机格点模型的蒙特卡罗研究。同时提出了一种快速产生二维随几格点的方法。用这个模型对CuMn进行了磁化热,磁化率等物理量的模拟测量,并对模型的有限大小问题进行了探讨。     

二维振镜扫描系统调向误差分析

对比分析现有光束扫描系统的优劣,提出采用二维振镜扫描系统作为多光谱集成靶标的光轴调向装置,光轴调向装置的调向精度影响多光谱集成靶标的校准精度。通过对二维振镜扫描系统调向误差进行分析,建立二维振镜扫描系统调向模型,并进行了二维振镜扫描系统调向误差测量实验。结果表明:二维振镜扫描系统的方位角误差和俯仰角误差小于8″,调向角误差小于9″,调向误差小于10″,能够满足多光谱集成靶标光轴调向精度要求。     

沙漏计时原理二维数值模拟

提出沙漏计时二维数值模型,并用元胞自动机的方法对该模型进行计算机模拟.结果表明由于开口处沙粒的流动而引起的沙堆崩塌行为是一个准周期性振荡过程,开口大小与崩塌总时间近似成线性关系.特殊的开口位置会引起崩塌"拍",且随沙堆高度呈周期性变化.     

二维相关光谱的猪肉TVB-N特征变量优选研究

为了探讨利用二维相关可见/近红外光谱法优选猪肉挥发性盐基氮(TVB-N)特征变量的可行性,以贮藏时间为外扰,研究了不同新鲜程度猪肉样本的二维相关光谱特性。首先,获取56个猪肉样本在贮藏1～14 d的400~1 000 nm范围的可见/近红外反射光谱,经过标准正态变量变换(SNV)处理后,基于全波段光谱建立TVB-N的偏最小二乘回归(PLSR)模型。然后,依据TVB-N实测值,从中挑选出10个具有一定浓度梯度的样本(贮藏时间分别为0,36,72,108,144,180,216,252,288和324 h),利用一阶导数对光谱进行预处理后,根据不同样本之间的光谱差异,选取7个波段用于二维相关光谱解析。分析各个波段的二维相关同步谱和自相关谱,从7个波段范围内共选取23个变量作为不同贮藏时间下与TVB-N相关的敏感波长,并建立简化的PLSR模型。相较于全波段光谱数据所建模型,模型效果有所改善,预测集决定系数R2_p由0.792 1上升至0.865 8,误差从3.658 2 mg·(100 g)-1下降至3.246 0 mg·(100 g)-1。表明基于二维相关光谱对猪肉TVB-N特征变量进行优选的思路是可行的,该方法能够从全光谱数据中筛选出与目标物质相关的敏感变量,这也为近红外光谱特征波长选择提供了一个新的方法。     

亚100 nm应变Si/SiGe nMOSFET阈值电压二维解析模型

本文基于二维泊松方程,建立了适用于亚100 nm应变Si/SiGe nMOSFET的阈值电压理论模型.为了保证该模型的准确性,同时考虑了器件尺寸减小所导致的物理效应,如短沟道效应,量子化效应等.通过将模型的计算结果与二维器件模拟器ISE的仿真结果进行对比分析,证明了本文提出的模型的正确性.最后,还讨论了亚100 nm器件中常规工艺对阈值电压的影响.该模型为亚100 nm小尺寸应变Si器件的分析设计提供了一定的参考. 关键词： 亚100nm 应变Si/SiGe nMOSFET 二维表面势 阈值电压     

基于FFCNN的二维恒星光谱分类

天体光谱处理中的一项基本任务是对大量的恒星光谱进行自动分类。到目前为止,恒星光谱的分类工作多是基于一维光谱数据。该研究打破传统的天体光谱数据处理流程,提出了基于二维恒星光谱分类的方法。在LAMOST(the large sky area multi-object fiber spectroscopic telescope)的数据处理流程中,所有的一维光谱都是由二维光谱抽谱、合并得来。二维光谱是由光谱仪产生的图像,包括蓝端图像和红端图像。基于LAMOST二维光谱数据,提出了特征融合卷积神经网络（FFCNN）分类模型,用于二维恒星光谱的分类。该模型是一个有监督的算法,通过两个CNN模型分别提取蓝端图像和红端图像的特征,然后将二者进行融合得到新的特征,再利用CNN对新特征进行分类。所使用的数据全部来源于LAMOST,我们在LMOST DR7中随机选择了一批源,然后获得了它们的二维光谱。一共有14 840根F,G和K型恒星的二维光谱用于FFCNN模型的训练,其中包括7 420根蓝端光谱和7 420根红端光谱。由于三类恒星光谱的数量并不均衡,在训练的过程中分别为每类恒星光谱设置了不同权重,防止模型出现分类失衡现象。同时,为了加快模型收敛,对二维光谱数据采用Z-score归一化处理。此外,为了充分利用所有样本,提高模型的可靠度,采用五折交叉验证的方法验证模型。3 710根二维光谱用作测试集,使用准确率、精确率、召回率和F1-score来对FFCNN模型的性能进行评价。实验结果显示,F,G和K型恒星的精确率分别达到87.6%,79.2%和88.5%,而且它们超过了一维光谱分类的结果。实验结果证明基于FFCNN的二维恒星光谱分类是一种有效的方法,它也为恒星光谱的处理提供了新的思路和方法。     

应用格子Boltzmann模型模拟一类二维偏微分方程

针对一类含源的二维非线性偏微分方程, 通过Chapman-Enskog展开技术和多尺度分析提出了带修正项的简单格子Boltzmann模型. 用模型模拟了几类二维偏微分方程, 数值模拟结果与精确解相符合. 成功将格子Boltzmann方法应用到二维偏微分方程的数值求解中. 关键词： 二维非线性偏微分方程 格子Boltzmann模型 Chapman-Enskog多尺度展开     

InAlN/GaN异质结二维电子气波函数的变分法研究

使用变分法推导了InAlN/GaN异质结二维电子气波函数和基态能级的解析表达式,并讨论了InAlN/GaN异质结结构参数对二维电子气电学特性的影响.在假设二维电子气来源于表面态的前提下,使用了一个包含两个变分参数的尝试波函数推导电子总能量期望值,并通过寻找能量期望极小值确定变分参数.计算结果显示,二维电子气面密度随InAlN厚度的增大而增大,且理论结果与实验结果一致.二维电子气面密度增大抬高了基态能级与费米能级,并保持二者之差增大以容纳更多电子.InAlN/GaN界面处的极化强度失配随着In组分增大而减弱,二维电子气面密度随之减小,并导致基态能级与费米能级减小.所建立的模型能够解释InAlN/GaN异质结二维电子气的部分电学行为,并为电子输运与光学跃迁的研究提供了解析表达式.     

Two-Dimensional CW-ESR Correlation Spectroscopy

In the present paper, a new method called two-dimensional continuous-wave electron spin resonance (2-D CW-ESR) correlation spectroscopy is introduced. This method is based on mathematical analysis of ESR data obtained from common CW-ESR spectra. It is different from conventional 2-D ESR, which is built on multiple-pulse sequences. Synchronous and asynchronous 2-D CW-ESR correlation spectra defined by two independent magnetic field variable axes are generated by a correlation analysis of dynamic fluctuations of ESR signals induced by an external perturbation. The basic property of 2-D ESR correlation spectra is described. Several examples are investigated and discussed on applications of 2-D ESR correlation spectra in the spin self-trapping of 2-methyl-2-nitrosopropane (MNP), the mixture of spin adducts generated by self-trapping of MNP and 5,5-dimethyl-1-pyrroline N-oxide, and the coordination reaction of benzo-15-crown-5 with cupric ion in boron trifluoride-ether solution. The potential applications of this new 2-D CW-ESR method are discussed. Authors' address: Yong Li, Department of Chemistry, Tsinghua University, Beijing 100084, China     

Two-Dimensional Topological Strings Revisited

The topological string of the type A with a two-dimensional target space is studied, an explicit formula for the string partition function is found and the target space field theory reproducing this partition function is proposed. This field theory has an infinite set of additional deformations overlooked by the standard definition of the topological string. It can be in turn coupled to gravity, thereby realizing the “worldsheets for worldsheets” idea. We also exhibit the wave function nature of the string partition function and suggest a new relation to quantum integrable systems.     

谱-空间2D ESR成像

在Bruker ER 200D ESR 谱仪上安装一套自制的谱-空间2D ESR成像系统,这套系统由一对梯度场线圈、电源、微机及图像重建程序组成. 用滤波反投影图像重建方法,实现了两种自由基样品的谱-空间2D ESR成像,由2D 图像得到样品中自由基的自旋密度空间分布及相应的波谱参数. 讨论了成像参数与图像精度的关系.     

Complexity of Two-Dimensional Patterns

In dynamical systems such as cellular automata and iterated maps, it is often useful to look at a language or set of symbol sequences produced by the system. There are well-established classification schemes, such as the Chomsky hierarchy, with which we can measure the complexity of these sets of sequences, and thus the complexity of the systems which produce them. In this paper, we look at the first few levels of a hierarchy of complexity for two-or-more-dimensional patterns. We show that several definitions of regular language or local rule that are equivalent in d=1 lead to distinct classes in d2. We explore the closure properties and computational complexity of these classes, including undecidability and L, NL, and NP-completeness results. We apply these classes to cellular automata, in particular to their sets of fixed and periodic points, finite-time images, and limit sets. We show that it is undecidable whether a CA in d2 has a periodic point of a given period, and that certain local lattice languages are not finite-time images or limit sets of any CA. We also show that the entropy of a d-dimensional CA's finite-time image cannot decrease faster than t ^–d unless it maps every initial condition to a single homogeneous state.     

On Two-Dimensional Sonic-Subsonic Flow

A compensated compactness framework is established for sonic-subsonic approximate solutions to the two-dimensional Euler equations for steady irrotational flows that may contain stagnation points. Only crude estimates are required for establishing compactness. It follows that the set of subsonic irrotational solutions to the Euler equations is compact; thus flows with sonic points over an obstacle, such as an airfoil, may be realized as limits of sequences of strictly subsonic flows. Furthermore, sonic-subsonic flows may be constructed from approximate solutions. The compactness framework is then extended to self-similar solutions of the Euler equations for unsteady irrotational flows.     

New Two-Dimensional Ice Models

This paper presents a new approach for enumerating all hydrogen bond arrangements of ice-like systems with periodic boundary conditions. It is founded on a topological procedure for the dimensional reduction and a new variant of the transfer matrix method based on small conditional transfer matrices. We consider a couple of new two-dimensional ice models on very unusual lattices. One of them is the twisted square ice model with crossing H-bonds. The other is the digonal-hexagonal model with double H-bonds. In spite of their uncommonness, these models are quite realistic, because from the standpoint of combinatorics and topology they are equivalent to the layers of usual hexagonal ice Ih under periodic boundary conditions in one of the directions. The exact proton configuration statistics for a number of 2D-expanded unit cells of hexagonal ice Ih and the residual entropy of the new ice models in the large system limit are presented.     

Existence and Stability of Two-Dimensional Compact-Like Discrete Breathers in Discrete Two-Dimensional Monatomic Square Lattices

Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generalized discrete two-dimensional monatomic model. It is proven that the two- dimensional compact-like discrete breathers exist not only in two-dimensional soft Φ4 potentials but also in hard two-dimensional Φ4 potentials and pure two-dimensional K4 lattices. The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Φ4 potential are determined by coupling parameter K4, while those in pure two-dimensional K4 lattices have no coupling with parameter K4. The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.