新型衬底晶体LiGaO2的生长和结晶性质研究

氮化物长期以来被看作是在蓝光及紫外波段光电子应用中最有希望的材料[1].但在改进材料质量方面最大的困难是:缺乏一种能和GaN在晶格及热性能方面十分匹配的理想衬底材料[2].Al2O3被普遍认为可以作为GaN的衬底材料.这主要是由于它具有的结构、热性能好,和生长加工容易等特点.     

The monoid of strong endomorphisms of a graph

We explicitly find all the idempotents in eachL(R)-class and all the inverses of each element of the strong endomorphism monoid of a graph. The number of these idempotents and inverses is also obtained. The author is deeply indebted to Professor Dr. T. E. Hall for his stimulating questions about this theme and much improvement made to an earlier version of this paper. The author would like to thank Professor Dr. U. Knauer and Dr. E. Wilkeit for helpful comments.     

Magnetic behavior of 3d dopants in superconducting REBa2Cu3−xFexO7+δ (RE=Dy, Er)

Mössbauer studies on ⁵⁷Fe-doped superconducting REBa₂Cu₃O_7+δ (RE=Er, Dy) were made as a function of temperature for x=0.15 and 0.30. The magnetic behavior of the 3d dopants, which mainly occupy Cu(1) sites, undergoes antiferromagnetic ordering which is coexistent with superconductivity at low temperature. The dimensionality of the magnetic interaction changes from 2D to 3D when the rare earth changes from Er to Dy. the line-widths of the Mössbauer subspectra are characteristic of magnetic fluctuation behavior in the vicinity of a phase transition. Combining these results with those of Fe-doped Y-123 (pseudo 1D) and Gd (3D), the magnitude of the rare earth moments appears to be strongly correlated with the dimensionality of the magnetic interaction of Fe dopants in these compounds. However, the Mössbauer spectrum for ¹⁵⁵Gd in GdBa₂Cu_2.85Fe_0.15O_7+δ (T_{N(Fe) 14 K}) shows no magnetic order at 4.9 K.     

Composite-cavity-based Fabry-Perot interferometric strain sensors

A composite-cavity-based Fabry-Perot interferometric strain sensor system is proposed to gain the minimum cross sensitivity to temperature and a high multiplexing capability at the same time. The interrogation of the sensor system is based on a white-light interferometric technology, and the demodulation is achieved by analyzing the coherence spectra. A demonstration system with two sensors is presented and tested.     

Effect of Intercalated LiF on Interface Contact Characteristics of MoS2 Field Effect Transistor: A First-Principles Study

Based on the first-principles calculation, the effect of intercalated LiF on the contact characteristics of the interface between Au electrode and MoS₂ layer is studied. It is found that adding LiF film can change the contact type between metal electrode Au and MoS₂ layer from Schottky contact to ohmic contact, which is accompanied by interfacial charge transfer from LiF layer to MoS₂ layer and the downward movement of d (d_xy and d_z2) orbital of Mo atom and p (p_x and p_y) orbital of S atom to Fermi level. And the interlayer spacing between LiF layer and Au electrode has a great impact on the interface contact characteristics. The electric field effect and stress effect of interface contact of Au, LiF and MoS₂ (Au/LiF/MoS₂)is more obvious than that of interface contact of Au and MoS₂ (Au/MoS₂). Au/LiF/MoS₂ shows ohmic contact with the interlayer spacing between Au layer and LiF layer less than 3.05 Å and with the electric field less than 0.15 VÅ⁻¹, respectively, while Au/MoS₂ still shows N-type Schottky contact. These findings are helpful to control the contact resistance and have guiding significance for high performance MoS₂ field effect transistor and other electronic components.     

抗扭刚度自动测定仪的研究

本文详细介绍了基于电磁涡流比拟理论运用微电脑和辅助机构，研究制造的抗扭刚度自动测定仪的基本原理，系统的误差分析等。对工程轴类以及几种特殊面杆件的抗扭刚度进行了测试研究。     

填充聚四氟乙烯对尼龙6摩擦磨损性能影响的研究

用Timken试验机考察了热压成形的PTFE填充尼龙6在干摩擦状态下的摩擦磨损性能及PTFE填充量、滑动速度和负荷对摩擦磨损的影响,并用X-光电子能谱仪(XPS)和电子探针(EPMA)研究了金属偶件摩擦表面转移膜的组成与形貌。结果表明,在给定的试验条件下,填充PTFE能够有效地改善尼龙6的摩擦磨损性能,PTFE的填充量在8～20％(vol)之间时的效果较好,8％PTFE填充尼龙6的PV值可比纯尼龙6的高1倍;填充PTFE的效用主要取决于转移膜的特性和PTFE在转移膜中的富集量。     

聚乙烯醇及磷酸酯气相润滑下氮化硅的磨损特性研究

采用球－三盘磨损试验机在３７０℃，聚乙烯醇及磷酸三甲苯基酯气相润滑下研究了Ｓｉ３Ｎ４与Ｍ５０工具钢对磨时的磨损特性．结果表明：在气相润滑下聚乙烯醇可以有效地降低Ｓｉ３Ｎ４的磨损；在聚乙烯醇中添加少量的三甲苯基磷酸酯可以进一步降低Ｓｉ３Ｎ４的磨损．Ｘ射线光电子能谱分析发现，Ｓｉ３Ｎ４的摩擦表面形成了主要由元素碳、氧和磷组成的固体润滑膜，Ｓｉ３Ｎ４发生了氧化并生成了ＳｉＯ２和—ＳｉＮＯ等化合物，而三甲苯基磷酸酯则在摩擦过程中发生了降解．     

一次性分配的力矩分配法

提出以多跨连续梁为单元参与力矩分配法的设想，导出了任意跨连续梁的杆端转动刚度 和结点处弯矩传递系数的递推计算式，使得设想能够实施．改变了传统力矩分配法的渐近解 法，只需一次性分配就可求得精确解．