粗糙表面分维计算的立方体覆盖法

针对三角形棱柱表面积法和投影覆盖法在计算粗糙表面分形维数中存在的问题,提出了计算粗糙表面分维的立方体覆盖法,对计算结果进行了对比分析,并进一步对表面分维计算中的有关理论问题进行了分析,发现立方体覆盖法作为一种几何意义上的覆盖法,并计算结果比三角形棱柱表面积法和投影覆盖法更接近实际。     

聚晶立方氮化硼刀具切削高锰钢的磨损机制

在半精加工试验条件(切削深度ap=0．5mm，进给量f=0．3mm／r，干切)下研究了聚晶立方氮化硼刀具切削奥氏体高锰钢时的磨损机制，用WDH-Ⅱ型光电温度计测量了切削温度，用工具显微镜测量后刀面磨损量，进而考察了切削时间和切削速度对后刀面磨损量的影响，采用S-250MK型扫描电子显微镜观察刀具前、后刀面的磨损形貌和组成变化．结果表明：当切削温度为400～750℃时，聚晶立方氮化硼刀具同高锰钢中的γ相及其析出相(Fe，Mn)3C之间产生严重的机械磨损；当切削温度超过800℃时，聚晶立方氮化硼刀具同高锰钢单一γ相之间产生扩散磨损；聚晶立方氮化硼刀具适合于高速切削.     

单轴拉伸下氧化锆纳米柱相变机理的分子动力学研究

通过分子动力学模拟,观察到[001]取向的四方氧化锆纳米柱在拉伸载荷下具有两个线弹性变形的应力-应变关系.这一现象是四方结构向单斜结构相变的结果 .为了进一步阐明应力-应变曲线,进行了包括晶体结构分析和原子应变计算在内的详细研究.晶格取向强烈影响塑性变形机制,即[001]和[111]取向的纳米柱在拉伸载荷下经历相变,而沿[110]取向的纳米柱导致脆性断裂.观察到显著的温度效应,随着温度从300K升高到1500K,弹性模量从573.45GPa线性降低到482.65GPa.此外,还用轻推弹性带(NEB)理论估算了相变能垒,观察到相变能垒随温度的升高而降低.这一工作将有助于加深对氧化锆的四方相到单斜相转变和纳米尺度力学行为的理解.     

Modelling Spatial Variations of the Speed of Light

We extend a new method to measure possible variation of the speed of light by using Baryon Acoustic Oscillations and the Hubble function onto an inhomogeneous pressure model of the universe. The method relies on the fact that there is a simple relation between the angular diameter distance maximum and the Hubble function (H) evaluated at the same maximum‐condition redshift, which includes the speed of light c. One limit of such a method was the assumption of the vanishing of spatial curvature (though, as it has been shown, a non‐zero curvature has negligible effect). In this paper, apart from taking into account an inhomogeneity, we consider non‐zero spatial curvature and calculate an exact relation between and H. Our main result is the evaluation if current or future missions such as Square Kilometer Array (SKA) can be sensitive enough to detect any spatial variation of c which can in principle be related to the recently observed spatial variation of the fine structure constant (an effect known as α‐dipole).     

基于液晶光调制器的夏克-哈特曼波前探测技术

微透镜阵列是夏克-哈特曼波前探测器的关键器件。利用液晶器件的空间相位调制特性,可实现微透镜阵列功能,且具有孔径和焦距可变的优点。论述了基于液晶光调制的夏克-哈特曼波前探测校正技术的特征、技术进展、及应用前景。     

三代微光和超二代微光夜视技术的研究和开发

介绍三代微光和超二代微光夜视技术的发展概况：阐明了它们各自的原理、技术特点和关键课题；着重指出了两者间的异同和相互联系。     

High-brightness white light-emitting organic electroluminescent devices using poly(N-vinylcarbazole) as a hole-transporter

A white light-emitting organic electroluminescent (EL) device with multilayer thin-film structure, which shows high-brightness and high-efficiency, is demonstrated. The device structure of glass substrate/indium–tin oxide/poly(N-vinylcarbazole) (PVK)/1,1,4,4-tetraphenyl-1,3-butadiene/8-(quinolinolate)-aluminum (Alq) doped with 5,6,11,12-tetraphenylnaphthacene/Alq/Mg/Al was employed. The turn-on voltage is as low as 2.5 V. The white light emission covers a wide range of the visible region, and the Commission Internationale de 1' Eclairage coordinates of the emitted light are (0.319, 0.332) at 10 V. Bright white light, over 20 000 cd/m², was successfully obtained at about 18 V, and the maximum efficiency reaches to 1.24 lm/W at 9 V. The reasons of obtaining high level EL properties of our device have been discussed.     

三次数域的整基和幂元整基

如何有效地找出数域的整基,是人们长期思考的问题.本文给出了求三次数域的整基的一个简单方法.此外,人们还对数域是否存在幂元整基的问题感兴趣.二次域和分圆域均存在幂元整基,而对于三次数域情形,则尚不清楚.本文给出了三次数域存在幂元整基的充要条件,从而对于三次数域情形给出了完整的答案.     

Optimization design of RIS-assisted high-capacity visible light communications based on HDMA

In this paper, a new non-orthogonal multiple access (NOMA) scheme is proposed for the reconfigurable intelligent surface (RIS) assisted high-capacity visible light communication (VLC) system, which is named hybrid domain multiple access (HDMA). HDMA enjoys the benefit of hybrid-domain signals, including the power domain, code domain, and frequency domain, where the message passing algorithm (MPA) and successive interference cancellation (SIC) detectors are jointly used at the HDMA receiver. Furthermore, to achieve a higher communication capacity for the VLC system, we proposed an optimization model by jointly optimizing the power allocation ratio and RIS reflection units. The simulation results verified the proposed scheme. By comparing the system capacity of different RIS allocation schemes and multiple access methods, the VLC system based on HDMA proposed in this paper can significantly improve its communication capacity.