Biconical antenna and V-conical antenna with elliptic cross section

The methods of coodinates transfomation and conformal maping are applied to the problem of ra diation from a biconical antenna and V-conical an tenna with elliptic cross section. The infinite el liptic cone geometry can be transformed into two dimentions plane under the assumption of pure TEM spherical wave. The Closed-form solutions for the fields, currents, and characteristic parameters are obtained.     

光通信无源器件的现状和展望

文章介绍了近年来光纤活动连接器,光分、合波器,光开关等光通信无源器件的现状及发展趋势,尤其介绍了光纤用户网系统光纤无源器件的开发情况。     

A quantum amplifier model for predicting temporal variations in theoutput power from a semiconductor laser on a picosecond time scale

A new model for simulating temporal fluctuations in the power emitted by a semiconductor laser is described. Light in the cavity is assumed to circulate in the form of traveling photon packets, in which the photon number fluctuates due to the processes of spontaneous emission, stimulated emission, absorption, scattering, and reflection. The dipole dephasing time T plays a critical role in modeling the interaction of the photon packets and gain medium. The Monte Carlo method is used to simulate the temporal behavior of a continuously pumped Fabry-Perot laser. The laser output power is found to exhibit periodic fluctuations at the cavity transit time frequency (longitudinal mode beat frequency). The amplitude of these fluctuations, as well as the relaxation oscillation, which occurs at a much lower frequency, is strongly influenced by the magnitude of T. The results of these simulations are related to the temporal behavior expected from a conventional FP laser     

Role of interfacial-charge in the growth of GaN on α-SiC

The growth of GaN and A1N films on (0001) substrates of 6H-SiC has produced high-quality opto-electronic films. The SiC surface at the interface with GaN or A1N is either Si-terminated or C-terminated, and the Si-terminated interface is known to be the better substrate, producing higher-quality films. The polarity of the interface is important, as recognized by Sasaki and Matsuoka. We propose that the main relevant parameter for characterizing the interface and its potential for producing high-quality opto-electronic GaN or A1N films is the interfacial charge, which leads to the best films when the charge is positive and relatively large. The positive charge reduces the size of the Nions at the interface and hence improves the local lattice match. (The charges are approximately −0.45 lei and +0.55 lei on the interfacial N and Si atoms, respectively.) Therefore, while the polarity of the interface is important, the polarity's effect on the local lattice mismatch is what leads to a high-quality interface. These ideas are consistent with XPS data and are supported by electronegativity arguments, by calculations for ordinary mono-bonded GaN/SiC superlattices (with N-Si and Ga-C interfaces) and by computations for superlattices with tri-bonded interfaces. We predict that the tri-bonded N-Si interface of GaN/SiC should produce excellent GaN and AIN films.     

油管柱立式自动排架设计

针对目前油田修井作业中油管大都水平放置,手工作业量大,且不易实现自动化等问题,开发了一种油管柱立式自动排架。初步测试表明,该自动排架设计新颖,控制程序简单,制造成本低,能与现有修井设备配合使用,有助于简化油管的运动轨迹,实现油管起下作业的自动化。该装置的推广应用将大大减轻工人的劳动强度,提高修井作业的工作效率,并能减少油管螺纹的损坏,防止修井事故的发生,对油田修井作业整体效益的提高具有十分重要的意义。     

烧结助剂对BiNbO4陶瓷烧结特性及介电性能的影响

研究了ZnO-B2O3、ZnO-B2O3-SiO2、B2O3对BiNbO4陶瓷烧结特性及介电性能的影响。结果表明:ZnO-B2O3、ZnO-B2O3-SiO2、B2O3液相存在于晶粒和晶界上,不同程度地促进烧结,大幅度降低BiNbO4的相变温度;ZnO-B2O3-SiO2、B2O3的加入,对BiNbO4的介电常数、Q值影响较大;而添加1%质量分数的ZnO-B2O3,致密化温度降低到900,达到96%的理论密度,在920保温4h,材料的r为41,Q·f为13500GHz。     

Analysis of UWB Echoes Using Bispectrum Model

According to the features of the echoes of the ultra-wide band radar, this paper analyses the estimating effects of choosing the AR model, MA model and ARMA model based on bispectrum. It shows that ARMA model is much better than others. Simulations verify this result, also demonstrate the estimation precision has been improved. ARMA model parametric bispectrum estimation is very efficient to echoes of ultra-wide band radar.     

Effect of shroud flow on high quality InxGa1−xN deposition in a production scale multi-wafer-rotating-disc reactor

High quality InGaN thin films and InGaN/GaN double heterojunction (DH) structures have been epitaxially grown on c-sapphire substrates by MOCVD in a production scale multi-wafer-rotating-disc reactor between 770 to 840°C. We observed that shroud flow (majority carrier gas in the reaction chamber) is the key to obtaining high quality InGaN thin films. High purity H₂ as the shroud flow results in poor crystal quality and surface morphology but strong photolumines-cence (PL) at room temperature. However, pure N₂ as the shroud flow results in high crystal quality InGaN with an x-ray full width at half maximum (FWHM)_InGaN(0002) of 7.5 min and a strong room temperature PL peaking at 400 nm. In addition, InGaN/GaN single heterojunction (SH) and DH structures both have excellent surface morphology and sharp interfaces. The full width at half maximum of PL at 300K from an InGaN/GaN DH structure is about 100 meV which is the best reported to date. A high indium mole fraction in InGaN of 60% and high quality zinc doped InGaN depositions were also achieved.     

应用井壁取心资料对厚层内夹层遮挡作用的认识

围绕萨北和喇嘛甸油田开发过程中厚层内夹层能否起遮挡作用的热点问题,从油层水淹机理分析入手,利用井壁取心分析样品,应用地化录井分析技术,获得岩石热解、热解气相色谱、荧光显微图像等资料,从录井技术分析方法的角度,通过对比夹层上、下油层被驱替后的变化,间接分析认识夹层遮挡作用.根据萨北和喇嘛甸油田实际资料统计情况,归纳了夹层遮挡作用的界定标准,探讨了厚层内夹层的类型、厚度、位置及注采关系对上、下层遮挡作用的影响,为了解油田开发中高含水后期剩余油的分布规律以及提高对夹层遮挡作用的认识水平提供了新方法.