住宅小区光纤入户设计

以采用EPON技术为基础,分析了光纤入户的各种解决方案,并详细介绍了光纤入户设计中涉及到的OLT及光分路器设置、光功率预算、小区机房和交接间的设计标准、楼内配纤设计等。     

广州市居民食品安全科普意向调查及探究

为探究广州居民对本市食品科普现状的认知及意向,为开展食品安全科普提供依据,我们随机抽取广州市412名居民作为研究对象,以问卷方式调查食品安全科普意向。调查结果显示,广州居民对食品安全科普兴趣浓厚,但认为广州市目前的科普现状有待提高;广州居民最信任的食品安全科普知识来源是专业机构,最喜欢的食品安全科普形式是电视广播,最关注的食品安全科普内容是优劣食品的辨别;广州居民的年龄、文化程度等对其食品安全科普意向有影响。未来应依据居民科普需求及喜好的科普方式开展有针对性的食品安全科普,提高居民食品安全素质。     

束源杂质引发的MBE HgCdTe表面缺陷

研究了利用GaAs作为衬底的HgCdTe MBE薄膜的表面缺陷，发现其中一类缺陷与Hg源中杂质有关。采用SEM对这类缺陷进行正面和横截面的观察，并采用EDX对其正面和横截面进行成分分析。并设计了两个实验：其一，在CdTe／GaAs衬底上，低温下用Hg源照射20min，再在其上继续高温生长CdTe；其二，在CdTe／GaAs衬底上，一直用Hg源照射下高温生长CdTe。两个实验后CdTe表面都出现与HgCdTe表面相比在形状和分布上类似的表面缺陷，采用光学显微镜和SEM对CdTe表面缺陷进行了观察，通过CdTe表面缺陷和HgCdTe表面缺陷的比较，我们证实了这类表面缺陷的成核起源于Hg源中杂质。     

基于FTP的动态相位展开方法的研究

在采用结构照明的光学三维传感方法中 ,相位展开是被测物体三维面形正确重建的关键步骤之一 ,也是一个难点。本文就动态傅里叶变换轮廓术中相位展开问题进行研究 ,对比分析了直接相位展开算法、基于相邻帧间相位差之间的相位展开算法和基于调制度排序的相位展开算法。解决了基于傅立叶变换轮廓术的动态三维测量中相位展开问题 ,特别是孤立区域的相位展开。为动态傅立叶变换轮廓术的在冲击和爆轰过程中应用 ,提供了理论基础。文中给出了详细的理论分析和计算机模拟     

Overview of electrical processes in fractal geometry: fromelectrodynamic relaxation to superconductivity

The consequences of the parameterization of the fractal set on the electrodynamics of this set are analyzed. The relevance of scaling properties to electrochemical, dielectric, and magnetic relaxations is considered with a special emphasis on the use of noninteger derivative operators in electromagnetism and superconductivity. In electromagnetism, the above analysis includes a brief overview of the main results already obtained, focusing especially on the introduction of dissipative terms in the equation of propagation and on the generalized form of the uncertainty principle in fractal media. The new Laplacian and d'Alembertian operators are evoked as well as the scale relativity on which this new analysis is founded. For superconductivity, the analysis introduces a geometrical interpretation founded on frustration acting not only on topology but on the metric of the space-time in a particular type of fractal geometry. Although this point of view may appear as a breakthrough in the theory of superconductors, the model offers some relations with the theory of fractional statistics and the theory of Anyons     

大气湍流对激光传输的影响

为了研究大气湍流对激光传输的影响,以大气湍流的激光传输效应为基础,建立了激光到达接收面的光强分布模型.模型考虑了折射率结构常数、传输距离、发射面和接收面孔径以及湍流引起的光束展宽等参数,分析这些参数对接收面光强分布的影响,以此研究大气湍流对激光传输的影响,并提出降低湍流影响采取的措施.     

A Test of Rivaling Approaches to Explain News Effects: News on Issue Positions of Parties, Real-World Developments, Support and Criticism, and Success and Failure

Different "paradigmatic" approaches to explain news effects on voting may supplement each other, because their starting points are based on different news types in political campaign news: news on issue positions of parties, news on real-world developments, news on support or criticism for parties, and news on success and failure of parties. Daily content analysis data and a weekly multiwave panel survey from the 2003 election campaign in the Netherlands are used for a simultaneous test. A logistic regression analysis demonstrates that the paradigmatic approaches supplement each other. The data reveal a huge impact of the news from a campaigner's point of view in spite of a huge variety in responses to the news at the level of individual respondents.     

The location of filamentous hemagglutinin and pertussis toxin antigens of Bordetella pertussis by immunoelectron microscopy

Immunoelectron microscopy using colloidal gold-tagged antibodies was used to detect filamentous hemagglutinin (FHA) and pertussis toxin (PT) antigens on the surface and in the cytoplasm of Bordetella pertussis cells. Both gold-tagged antibodies to FHA and PT labeled the aggregates of filamentous material on the surface of sediment-settled phase I cells under static conditions. FHA and PT antigens were detected also on ultrathin sections made after embedding the phase I cells in Lowicryl K4M resin. On the ultrathin sections, intense label of gold-tagged antibodies to FHA and PT was present on the cell surface and also in the cytoplasm, but not in the nucleoid. The aggregates of filamentous material adhering on the surface of phase I cells were most abundant on culture day 3, the end of the logarithmic growth stage, but most of the aggregates were found detached from the cell surface on culture day 5 or 7, the stationary stage. The aggregates were not found on the surface of phase III cells. The present study suggested that FHA and PT antigens were localized on the same cell structure and that both antigens were synthesized in the cytoplasm and secreted across the cell membrane mainly in the logarithmic growth stage of the phase I cells.     

Properties of MODFET's grown on Si substrates at DC and microwave frequencies

We report the first microwave characterization of 1-µm gate GaAs/AlGaAs modulation-doped field-effect transistors (MODFET's) grown on Si substrates by MBE. Maximum transconductances of 170 mS/mm at room temperature were obtained in structures on Si, which compares to values of 200-250 mS/mm for this type of structure on GaAs. At 77 K, no collapse was observed in these structures, and transconductances of 270 mS/mm were obtained. From microwave S-parameter measurements at room temperature, current gain cutoff frequencies of 15 GHz were obtained from these GaAs/AlGaAs MOD FET's on Si, which compares with 12-15 GHz obtained on GaAs substrates. From high-frequency equivalent circuit modeling, very little difference was observed in any of the parameters between growth on Si and on GaAs. This is significant in that it demonstrates the suitability of GaAs on Si for device applications.     

DC-DC转换器中功率沟槽MOSFET的优化设计

利用工艺和器件模拟软件TSUPREM-4和MEDICI,研究了工艺参数对DC-DC转换器中的功率沟槽MOSFET的通态电阻Ron、栅-漏电容Cgd的影响以及栅-漏电荷Qgd在开关过程中的变化,指出了在设计和工艺上减小通态电阻Ron和栅-漏电容Cgd,提高器件综合性能的途径。     

植物内皮层凯氏带及其在抗盐胁迫中的作用

内皮层凯氏带是植物根中水分和离子径向运输的屏障.由于内皮层凯氏带的精细结构及化学性质等方面的研究难度较大,因此多年来进展缓慢.随着显微技术和鉴定方法的不断改进,对凯氏带的结构和功能的研究得以深入,但对其发育、化学成分及与抗盐胁迫的关系方面的报道还不多见.本文就凯氏带的结构发育、化学组成以及其在抗盐胁迫中的作用进行了综述...     

玻璃和聚酰亚胺衬底上磁控溅射沉积的ZnO:Al透明导电膜的结构、电学和光学性能(英文)

利用射频磁控溅射方法在玻璃和聚酰亚胺膜(PI)衬底上沉积了氧化铝质量分数为2%的掺铝氧化锌透明导电薄膜(ZnO∶Al)。系统地研究了不同衬底材料对薄膜的结构、电学以及光学性能的影响。分析表明,衬底材料对薄膜的结晶性和电学性能有较大的影响,对可见光透射率却影响不大。X射线衍射(XRD)分析得出所有的ZnO∶Al具有良好的c轴择优取向性,在可见光区(400～800nm)两种衬底上的薄膜都达到了85%的透射率。玻璃衬底上的薄膜呈现出更强的(002)衍射峰及相对更小的半峰全宽(FWHM),薄膜电阻率达到了2.352×10-4Ω.cm。电镜分析表明,相对于PI上的ZnO∶Al膜,玻璃上ZnO∶Al膜表面有更致密的微观结构及更大的晶粒尺寸。PI衬底上的ZnO∶Al膜也有相对较好的电、光学性能,其中电阻率达到了6.336×10-4Ω.cm,而且由于PI衬底柔性可弯曲,使得它适于在柔性太阳电池和柔性液晶显示中做窗口层材料及透明导电电极。玻璃上的ZnO∶Al膜则可应用在平板显示和太阳电池技术中。     

论顾客关注与关注顾客

论文以ISO 9000标准提出的8项管理原则的第一条-以顾客为关注的焦点为出发点，论述了如何关注顾客和顾客关注的内涵，以及两个关注之间的联系，从而在实践中真正做到以顾客为关注的焦点。     

桌面虚拟化存储备份技术应用研究

桌面虚拟化技术的应用可简化管理,但需要正确规划才能消除存储设备的瓶颈,确保用户感受和满足增长需求。本文结合桌面虚拟化项目的部署经验,探讨桌面虚拟化部署过程中存储、备份的需求、面临的挑战及技术的选择和应用。     

Limitations to and solutions for optical loss in optical backplanes

In this paper, recent literature on the discussion on high-speed backplanes with optical, electrical, and mixed solutions, as well as on polymer-waveguide systems suitable for implementation on printed circuit boards (PCBs), is reviewed from the point of view of their optical losses. The reevaluation of the optical power budget for realistic high-speed optical polymer-waveguide links on backplanes showed that signal amplification is necessary to boost the signal, which resulted in an additional literature review on advances in optical amplifiers based on silicon bench technology available. Finally, a concept study of an active optical waveguide amplifier device, based on planar optical waveguide amplifiers and semiconductor optical amplifiers, was performed. The amplification device can be flip-chip mounted on the backplane to compensate for optical losses due to signal routing, which increases the overall degree of freedom in waveguide routing on high-density interconnects for backplanes. The hybrid concept design guarantees compatibility with the processes of the PCB industry.     

Low-current beam?plasma experiments with a bearing on turbulence

Experiments are described and discussed on the excitation by low-voltage electron beams of plasma electron and ion oscillations in almost the whole acoustic-to-gigahertz frequency range, and on the reaction of these on single and double beams and on one another, which provide examples of the development and nature of turbulence, in the generalised sense in which this is now understood.     

基于用户群的细分挖掘运营商在电子商务上的机会

基于e声网的调研数据,重点讨论了目前网络购物用户群的细分,研究各细分用户群网上购物的行为和动因,分析各用户群在电信运营商网上营业厅的消费现状和评价以及判断他们未来可能的消费态度,最后建议运营商发展电子商务应针对不同用户群,突出重点,构建三位一体的电子渠道,强化自有网上营业厅的用户体验。     

Graphs, tessellations, and perfect codes on flat tori

Quadrature amplitude modulation (QAM)-like signal sets are considered in this paper as coset constellations placed on regular graphs on surfaces known as flat tori. Such signal sets can be related to spherical, block, and trellis codes and may be viewed as geometrically uniform (GU) in the graph metric in a sense that extends the concept introduced by Forney . Homogeneous signal sets of any order can then be labeled by a cyclic group, induced by translations on the Euclidean plane. We construct classes of perfect codes on square graphs including Lee spaces, and on hexagonal and triangular graphs, all on flat tori. Extension of this approach to higher dimensions is also considered.     

External constraints and national resources: Reflections on the Europeanisation of communications policy

The article takes a starting point in theories on the distinctiveness of “small states” and discusses the relevance of this approach in the analysis of the current changes in communication policies in Europe. In order to assess the applicability of these perspectives, external constraints on national policy-making are identified. These constraints, convergence of technologies and markets and the Europeanisation of communications polices work as levelling forces on differences across countries, and should, accordingly, contribute to the removal of national characteristics. In the second part of the article this hypothesis is challenged although not refuted. Drawing on instiutional perspectives on political and social change and data from an on-going research comparative policy analysis-project, the author argues that historical legacies and national characteristics may have a lasting and distinctive effects on the formulation of communication policies also in the future.     

Professional and organizational commitment among engineers:conflicting or complementing?

Organizational commitment and professional commitment have been viewed as both complementary and conflicting in their effects on organizational outcomes. Engineering has many characteristics of a profession, but its practitioners usually have careers in organizational settings. Thus, the effects of these commitments on job satisfaction, job performance and job problems are particularly important in an engineering work environment. Results of this study based on data collected from 114 engineers in a bureaucratic work environment indicate that organizational commitment has a significant and direct effect on job satisfaction and job performance and a significant inverse effect on job problems. Professional commitment was marginally significant in respect to job performance. In addition, the highest levels of satisfaction and performance were reported by individuals high on both forms of commitment, while the lowest levels of satisfaction and performance were reported by individuals with low organizational commitment and high professional commitment. Results were mixed for job problems