Surface wave modes of printed circuits on ferrite substrates

Surface waves due to a current source on a grounded ferrite slab are investigated. Electromagnetic fields of the structure are in terms of a continuous plane wave spectrum. The spectrum of each field component is obtained numerically through the exponential-matrix method. The surface waves of the structure are extracted from the continuous spectrum by using the residue theorem and the method of steepest descent. Two types of surface waves are found and their properties are described. The surface wave modes found include dynamic surface wave modes which are closely related to the surface waves of a grounded dielectric slab, and magnetostatic surface wave modes which are related to the solution of Laplace's equation for the magnetic potential     

Reply to comments on “Error rate performance of theprojection code”

The authors reply to the comments by Koppelaar and Tolhuizen (see ibid. vol.46, no.9, p.573, 1998). They state that the optimum choice of the slopes used to perform the encoding process in a projection code always results in maximizing the minimum Hamming distance so that d=2 ^r     

Influence of preparation methods on structure and properties of PA6/PA66 blends: A comparison of melt‐mixing and in situ blending

The blends composed of polyamide 6 (PA6) and polyamide 66 (PA66) were obtained using two different preparation methods, one of which was the melt‐mixing through a twin‐screw extruder and the subsequent injection molding; and the other, the in situ blending through anionic polymerization of ε‐caprolactam in the presence of PA66. For the former, there existed a remarkable improvement in toughness but a drastic drop in strength and modulus; however, for the latter, a reverse but less significant trend of mechanical properties change appeared. Various characterizations were conducted, including the analyses of crystalline morphology, crystallographic form, and crystallization and melting behaviors using polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC), respectively; observation of morphology of fractured surface with scanning electron microscope (SEM); measurement of glass transition through dynamic mechanical analysis (DMA); and the intermolecular interaction as well as the interchange reaction between the two components by Fourier transform infrared spectrometry (FT‐IR) and ¹³C solution NMR. The presence and absence of interchange reaction was verified for the in situ and melt‐mixed blends, respectively. It is believed that the transreaction resulted in a drop in glass transition temperature (T_g) for the in situ blends, contrary to an increase of T_g with increasing PA66 content for the melt‐mixed ones. And the two kinds of fabrication methods led to significant differences in the crystallographic form, spherulite size and crystalline content and perfection as well. Accordingly, it is attempted to explain the reasons for the opposite trends of changes in the mechanical properties for these two blends. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1176–1186, 2007     

Theoretical study of a potential low-noise semimetal-basedavalanche photodetector

The authors present a theoretical analysis of a possible avalanching photodetector (APD)-based on II-VI compound semiconductors. Each unit cell is composed of a HgTe layer, or a similar semimetal, sandwiched between two layers of CdTe and HgCdTe or similar semiconducting materials. The barrier layers are graded so that the leading barrier height is just high enough to eliminate the thermionic emission dark current out of the well. The use of a semimetal within the well has a distinct advantage over a semiconductor, which is that the ionization process is essentially an interband mechanism since the confined carriers within the well lie within the overlapping conduction and valence bands. As a result, the concentration of target carriers is virtually inexhaustible as in a conventional interband device     

面向下一代网络的资源管理与服务开通解决方案

在向下一代网络演进的过程中，网络结构正经历一场深刻的变革。在这一背景下，新的业务种类和丰富多彩的增值服务大量涌现；同时，如何降低成本和改进服务水平也成为服务提供商越来越关注的问题。     

Viscometric properties of dilute polystyrene/dioctyl phthalate solutions

We report viscometric data collected in a Couette rheometry on dilute, single‐solvent polystyrene (PS)/dioctyl phthalate (DOP) solutions over a variety of polymer molecular weights (5.5 × 10⁵ ≤ M_w ≤ 3.0 × 10⁶ Da) and system temperatures (288 K ≤ T ≤ 318 K). In view of the essential viscometric features, the current data may be classified into three categories: The first concerns all the investigated solutions at low shear rates, where the solution properties are found to agree excellently with the Zimm model predictions. The second includes all sample solutions, except for high‐molecular‐weight PS samples (M_w ≥ 2.0 × 10⁶ Da), where excellent time–temperature superposition is observed for the steady‐state polymer viscosity at constant polymer molecular weights. No similar superposition applies at a constant temperature but varied polymer molecular weights, however. The third appears to be characteristic of dilute high‐molecular‐weight polymer solutions, for which the effects of temperature on the viscosity curve are further complicated at high shear rates. The implications concerning the relative importance of hydrodynamic interactions, segmental interactions, and chain extensibility with increasing polymer molecular weight, system temperature, and shear rate are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 787–794, 2006     

中国台湾电信市场现状

台湾电信市场的开放大致分四个阶段,从1995年起,陆续开放了移动通信、卫星通信及固定通信等多种业务。固网市场,2001年新世纪资通、台湾固网和力霸宽频电信的加入打破了中华电信的独家垄断,开始形成四强竞争的新局面。移动领域,1997年底6家运营商8张民营执照的发放开始了该领域史无前例的竞争。在2001年1月,台湾大哥大、远致电信、亚太行动宽频、联邦电信和中华电信获得了3G执照,累计竞标金额达488.99亿元(新台币)。     

回旋管的应用研究

文章论述了推广回旋管应用中所碰到的高功率传输,模式变换和辐射尖锐的波束等技术难点,对现有的准光系统提出了改进措施。     

多功能智能流量计研制

本文详细论述了利用单片微计算机构成的多功能、多用途流量计量与自动控制系统的研制设计，给出了系统硬件原理框图与软件结构框图。该仪器适用范围较广，具有广阔的应用前景。     

激光干涉环圆心位置测定技术及应用

本文利用在平面内绕定轴旋转的线阵ＣＣＤ及微机系统自动测定激光干涉环圆心位置及应用于激光外径千分尺平行度检查仪平行度检查结果的自动数字化输出。