提升现代民营企业管理水平的对策

现代民营企业是最具普遍意义的企业组织形态,其自身的众多特点为企业的建立和初期的发展具有功不可没的作用,但随着社会分工的精细化和经营的国际化,现代民营企业要想永葆青春、不断飞跃,必须做好改革与创新。     

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给出了不同坐标系中介质参数张量的变换,得到了磁化冷等离子体球电场的表达式,得出了任意各向异性目标散射场的表达式,研究了磁化冷等离子体球的微分散射截面、散射截面等的函数关系,仿真结果与有关文献一致,表明了本算法的有效性,从而为各向异性目标识别等提供理论支持。     

等离子体风洞中释放二氧化碳降低电子密度

航天器从近地空间进入大气层过程中,由于激波加热,会在航天器外表面形成等离子体鞘套,导致航天器与地面之间的无线电通信中断,即“黑障”效应.为了缓解“黑障”效应,国内外学者进行了多方面的技术研究,其中化学物质释放被认为是一种有效的方法.以往,主要针对卤族元素和水开展理论和实飞研究.本文基于二氧化碳不易在高温流场中发生裂解的特性,利用电弧和高频风洞产生等离子体流场,主动释放二氧化碳降低等离子体电子密度.结果表明,在风洞等离子体中,释放不同流量的二氧化碳可使电子密度下降1—2个量级,为解决再入过程中黑障问题提供了一种可行方法.     

Gravitational quasinormal modes of static Einstein-Gauss-Bonnet anti-de Sitter black holes

In this paper, we describe quasinormal modes(QNMs) for gravitational perturbations of Einstein-GaussBonnet black holes(BHs) in higher dimensional spacetimes, and derive the corresponding parameters of such black holes in three types of spacetime(flat, de Sitter(d S) and anti-de Sitter(Ad S)). Our attention is concentrated on discussing the(in)stability of Einstein-Gauss-Bonnet Ad S BHs through the temporal evolution of all types of gravitational perturbation fields(tensor, vector and scalar). It is concluded that the potential functions in vector and scalar gravitational perturbations have negative regions, which suppress quasinormal ringing. Furthermore,the influences of the Gauss-Bonnet coupling parameter α, the number of dimensions n and the angular momentum quantum number l on the Einstein-Gauss-Bonnet Ad S BHs quasinormal spectrum are analyzed. The QNM frequencies have greater oscillation and lower damping rate with the growth of α. This indicates that QNM frequencies become increasingly unstable with large α. Meanwhile, the dynamic evolutions of the perturbation field are compliant with the results of computation from the Horowitz and Hubeny method. Because the number of extra dimensions is connected with the string scale, the relationship between α and properties of Einstein-Gauss-Bonnet Ad S BHs might be beneficial for the exploitation of string theory and extra-dimensional brane worlds.     

彩超和造影对输卵管积水的诊断价值

目的比较彩超与子宫输卵管造影(hysterosalpingography,HSG)对输卵管积水的诊断率,为宫腹腔镜联合术前输卵管积水的处理提供准确的评估依据。方法选取2011年10月—2015年1月因不孕症在暨南大学医学院附属宝安妇幼保健院生殖健康科就诊,均行彩超和输卵管造影诊断为输卵管积水,且经宫腹腔镜联合手术后证实为输卵管积水的患者共58例,对其彩超结果及输卵管造影结果进行回顾性分析。结果宫腹腔镜术中发现积水输卵管共82条,轻度积水38条,中度积水44条,重度积水7条,彩超结果:轻度积水19条,中度积水24条,重度积水5条;HSG结果:轻度积水26条,中度积水28条,重度积水5条。结论 HSG诊断输卵管积水的准确率明显高于彩超,特别对输卵管轻度积水诊断阳性率更高,两者比较有统计学意义,对中度、重度输卵管积水,特别是重度输卵管积水,两者诊断阳性率差别不大,差异无统计学意义。     

Noise in a coupling electromagnetic detecting system for high frequency gravitational waves

This paper discusses the basic categories of noise in detecting high frequency gravitational waves in the microwave band (～0.1--10 GHz), which contain shot noise from the laser and the thermal radiation photons, thermal noise from statistical fluctuation of the thermal photons and fluctuation of the temperature, radiation press noise on the fractal membrane, the noise caused by the scattering of the Gaussian Beam (GB) in the detecting tube and noise in the microwave radiometers. The analysis shows that a reasonable signal-to-noise ratio may be achieved for a detecting device with the fixed power of GB (10⁵ W), only when the temperature of the environment is no more than T=1 K, and the optimal length of the microwave radiometers is about 0.3 m.     

Transverse Propagation Characteristics and Coherent Effect of Gaussian Beams

As an important electromagnetic Held in experiment,Gaussian beams have non-vanishing longitudinal electric and magnetic components that generate significant energy fluxes on transverse directions.We focus on the transverse energy flux and derive the theoretical propagation properties.Unlike the longitudinal energy flux,the transverse energy flux has many unique physical behaviors,such as the odd symmetry on propagation,slower decay rate on resonant condition.By means of the characteristics of tr...     

各向异性圆锥体的平面光波散射特性

基于通用的矢量电位和标量电位与介电常数张量无关的原理,由激发的电偶极子与位函数的关系得到了任意各向异性目标散射场的表达式。得到了通用的介电常数张量的变换关系,具体地给出了介电常数张量在球坐标系中的表达式,将目标的内外电场展为级数,得到了各向异性晶体圆锥体一级散射场的解析表达式。理论结果与文献一致,验证了算法的正确性。在光波波长与粒子尺寸相近的情况下,对所得结果进行了仿真,表明各向异性圆锥体的散射具有偶极辐射的特点。所得结果简单、通用,为研究形状更为复杂的各向异性目标、纳米粒子等的光散射研究提供了理论基础。     

离散谱折射率法分析深刻蚀、单模GaAs/GaAlAs脊形光波导

本文采用离散谱折射率法对深蚀刻、GaAs/GaAlAs多层脊形光波导模式特性进行了具体分析和设计,获得了较大截面、低损耗的单模脊形光波导.利用这种横向具有最大折射率差的深蚀刻脊形光波导不但可以提高多模干涉(MMI)型器件的性能,而且在设计和制作弯曲波导、分支结构时,具有结构紧凑、易于集成等优点.     

我在春天等你

春天就要来了,在我们静静期待春天来到的时候,一起动动手,把春天里的一幕幕美景制作出来吧! 材料与工具 相同大小的黑、白长方形卡纸若干,白色珠光纸若干,剪刀,丸棒,毛巾,双面胶,泡棉胶,黑、白色中性笔,彩色铅笔,针和线. 制作步骤 第一步:白色卡纸横放并对折,用黑色中性笔在每页纸中画出你喜欢的图或者记录下故事,在两张卡纸...