Structural Characterization of the Transient Amorphous Calcium Carbonate Precursor Phase in Sea Urchin Embryos

Sea urchin embryos form their calcitic spicular skeletons via a transient precursor phase composed of amorphous calcium carbonate (ACC). Transition of ACC to calcite in whole larvae and isolated spicules during development has been monitored using X‐ray absorption spectroscopy (XAS). Remarkably, the changing nature of the mineral phase can clearly be monitored in the whole embryo samples. More detailed analyses of isolated spicules at different stages of development using both XAS and infrared spectroscopy demonstrate that the short‐range order of the transient ACC phase resembles calcite, even though infrared spectra show that the spicules are mostly composed of an amorphous mineral phase. The coordination sphere is at first distorted but soon adopts the octahedral symmetry typical of calcite. Long‐range lattice rearrangement follows to form the calcite single crystal of the mature spicule. These studies demonstrate the feasibility of real‐time monitoring of mineralized‐tissue development using XAS, including the structural characterization of transient amorphous phases at the atomic level.     

Managing the simultaneous execution of coupled phases in concurrentproduct development

Concurrent engineering (CE) calls for the simultaneous execution of coupled product development phases. One approach to simultaneous execution involves performing a downstream information absorbing product development phase concurrently with an information supplying upstream phase. However, such simultaneous execution of coupled phases, in the absence of careful management, can lead to substantial deterioration in the product development performance. In this paper, the author presents the managerial implications of a model-based framework to manage the risks involving the simultaneous execution of coupled development phases. He describes how the framework would apply to an automobile instrument panel development process, and discusses the changes in organizational perspective required for successful simultaneous product development     

侧墙技术在相变存储器中的应用

从相变存储器(phase change random access memory,PCRAM)的基本结构和工作原理出发,首先介绍了PCRAM的技术优势、面临的技术挑战、常用的解决策略以及存在的相应问题;接着阐述了在微电子加工中广泛应用的关键工艺——侧墙技术,并将其在PCRAM中的应用成果进行了分类;然后从加热电极的制备、相变材料限制结构的制备、新相变材料的制备与表征和器件间互联等4个方面展开叙述;最后展望了该技术在相变存储领域应用发展的趋势。侧墙技术因其具备自对准的特点,制备工艺可控性好,制备精度不依赖于光刻精度,在纳米技术飞速发展的今天,侧墙技术将会在更高精度上发挥其作用。     

A solid-state instrument for the measurement of frequency and phase angle in power systems

This paper describes the development of an instrument, using electronic switching circuits for the measurement of frequency and phase angles in power systems. The phase angle and frequency are indicated on a meter with linear scale. The instrument responds to changes in system frequency and the phase-angle measurement is inherently lead-lag sensitive.     

预氧化对DBC基板的影响及敷接机理研究

随着绝缘栅双极型晶体管等功率器件的发展,对陶瓷敷铜基板(DBC)的需求越来越大。分别介绍了DBC基板的种类、结构,预氧化工艺对DBC基板的影响和敷接机理。用扫描电镜、X射线衍射等分析手段确定铜箔表面氧化后的物相成份,用X射线扫描确定敷接后界面空洞,并分析产生空洞的原因。用SEM观察界面的形貌并进行断面分析,用XRD和X-RAY分析界面产物的物相成份,从而确定DBC基板的敷接机理。     

三维成像雷达高度计机载原理样机及机载试验

本文介绍了三维成像雷达高度计的工作原理和系统设计,重点介绍机载样机系统及首次机载飞行试验.机载试验在国内首次获得单轨双天线干涉相位图像.对干涉相位进行算法处理后得到了三维地形图.     

相位激光测距技术研究概述

文章简述了相位激光测距技术的原理，就激光测距研究中关键技术研究状况做了详细阐述。介绍了相位式激光测距仪的发展历史和最新进展，并就相位测距技术的研究发展方向做了分析。     

SBS相位共轭技术在激光大气传输中的应用

评述了受激布里渊散射相位共轭技术在激光大气传输中的应用,重点分析了在激光大气传输过程中利用受激布里渊散射阈值效应可以在目标上主动获得小面积信标光斑的方法及利用SBS相位共轭实现激光大气传输的闭环过程,指出其发展前景。     

直接式频率合成器相位噪声限制因素

频率合成器被称为雷达电子系统的"心脏",其相位噪声对设备和系统的性能影响很大,随着现代雷达技术的不断发展,对频率合成器的低相位噪声提出了较高的要求。文中简单介绍了频率合成器相位噪声的基本概念,基于频率合成器的基本实现方法,阐述了直接式频率合成器相位噪声的限制因素。并通过实践论证了这些限制因素对相位噪声的影响程度,以及介绍了未来频率合成器的发展方向,对低相位噪声频率合成器的工程设计和生产调试具有一定的指导意义。     

An analogy between the operational voltage amplifier and the PLL

Fundamental characteristics of phase locked loop (PLL) and delay locked loop (DLL) circuits including their block diagrams and operating principles are briefly presented. The voltage follower constructed with an operational voltage amplifier (OVA) is related to those devices and considered by analogy as a voltage locked loop (VLL). A set of characteristics of this VLL and an analyzed example with a Zener diode in its feedback loop, sounds the proposed analogy. It is pointed out that a current follower built using an operational current amplifier (OCA) is susceptible to an analogous treatment. Therefore, those devices can be considered as a family of locked loops. Afterwards, the importance of phase/delay in electronic systems nowadays is highlighted putting as “laws” their circuital performance. An application example built using a PLL was feedback with a particular phase to phase converter, obtaining through PSPICE simulations, instead of a phase change between the input signal and that of the voltage controlled oscillator (VCO) a change in the duty cycle of the last one. The result could be explained based on the phase laws. The generalization obtained through the proposed analogy is favourable from the didactic standpoint and may lead to the development of new applications of the locked loop family.     

Algorithms for the Clinical Analysis of Nystagmus Eye Movements

Two algorithms used in the clinical analysis of nystagmus are described. Their development was necessitated by the greater complexity of the nystagmus waveforms in response to system identification types of vestibular and optokinetic stimuli as compued to the less complex response to a step input. Practical considerations for clinical application also influenced their development. The first algorithm converts nystagmus data into a regulary sampled estimate of slow phase velocity (SPV), an important feature of the signal. It uses a new set of fast phase detection conditions which allow for automatic processing of reversals in nystagmus direction and for wide variability for clinical data. The second algorithm detects noise induced spikes in this SPV estimate using an adaptive criterion based upon a measure of the overall "noisiness" of the data compared to the stimulus.     

Application of GaAs Discrete p‐HEMTs in Low Cost Phase Shifters and QPSK Modulators

The application of a discrete pseudomorphic high electron mobility transistor (p‐HEMT) as a grounded switch allows for the development of low cost phase shifters and phase modulators operating in a Ku band. This fills the gap in the development of phase control devices comprising p‐i‐n diodes and microwave monolithic integrated circuits (MMICs). This paper describes a discrete p‐HEMT characterization and modeling in switching mode as well as the development of a low‐cost four‐bit phase shifter and direct quadrature phase shift keying (QPSK) modulator. The developed devices operate in a Ku band with parameters comparable to commercially available MMIC counterparts. Both of them are CMOS compatible and have no power consumption. The parameters of the QPSK modulator are very close to the requirements of available standards for satellite earth stations.     

激光大气传输光波相位不连续性问题研究进展

激光在大气中长距离传输时,即使湍流很弱也会产生强湍流效应。在强湍流效应中,一个重要的问题就是光波的相位不再是连续的,相位不连续性问题会引起现有的自适应光学校正能力的降低。介绍了相位不连续点产生的机理和基本性质,阐述了激光大气传输相位不连续性问题近年来的研究进展,为激光大气传输及自适应光学校正技术研究工作的更好开展提供了参考。     

The superhighway in action: the Cambridge trial

UK companies are at the forefront of world efforts to bring the communications revolution to the home. The author describes a comprehensive ATM-based trial currently running in the UK. The first phase of the trial was set up to solve the technical issues involved in setting up and operating a low cost, fully switched ATM-end-to-end infrastructure capable of delivering a wide range of information types, up to and including video. It also explored the basic logistics of service provision, including for example, a regularly updated news-on-demand service. The second phase extends the number of users and implements some cost reductions in the technology employed, but also focuses on the development of services. For this expansion of the trial an environment has been created (the `Service Nursery') for development and trialling of the new generation of multimedia services that will make the superhighway a commercial reality     

A subspace identification extension to the phase correlation method

The phase correlation method (PCM) is known to provide straightforward estimation of rigid translational motion between two images. It is often claimed that the original method is best suited to identify integer pixel displacements, which has prompted the development of numerous subpixel displacement identification methods. However, the fact that the phase correlation matrix is rank one for a noise-free rigid translation model is often overlooked. This property leads to the low complexity subspace identification technique presented here. The combination of non-integer pixel displacement identification without interpolation, robustness to noise, and limited computational complexity make this approach a very attractive extension of the PCM. In addition, this approach is shown to be complementary with other subpixel phase correlation based techniques.     

环境适应性试验若干问题探讨

分析了环境适应性试验的目的与分类，探讨了研制阶段环境适应性试验的工作要点和程序，提出了环境适应性鉴定试验管理与监督的主要工作，总结了例行试验的实施与控制的成熟做法。     

基于灰关联分析法的故障选相新方法的研究

随着电力系统的发展,广泛采用自动重合闸方法来提高电力系统的稳定性,对故障选相的要求也越来越高.微机保护装置不仅要求能够准确判别出单相故障的故障相,还要准确判断出相间故障的相别.因此提出了一种基于模故障分量灰关联分析法的电力系统故障选相新方法,并通过Matlab进行建模仿真,证实了这一方法的具有需要样本少,计算量较小,选相准确度和可靠性高的特点,具有较高的实用价值.     

自适应聚焦下基于强度传输方程的相位恢复

基于强度传输方程的非干涉相位恢复方法是通过对强度图像求解方程来获取相位的一种途径。在图像采集过程中,对聚焦图像的选择是很重要的。但该过程通常是由主观方法来确定,从而导致聚焦定位不准确,进而影响相位恢复结果的精度。首先,提出了一种基于强度传输方程的自适应聚焦相位恢复方法;其次,使用边缘占空比对采集图像进行定位,在求解相位之后进行循环角谱传播,直到边缘占空比定位位置不变,即被认为是定位到了最佳聚焦位置;最后,再使用强度传输方程求解样本的相位。结果证明:该方法不仅提高了相位恢复的准确性而且减少了获取大量图像的次数。在模拟实验中,恢复相位与原始相位的相关系数达到0.9866,均方根误差为0.3050。在实际的微透镜阵列实验中,用所提出的相位恢复方法恢复出的微透镜高度与真实高度误差仅为5.7%,证明了在显微成像领域,所提算法可以定位到最优聚焦位置,有利于自动聚焦技术的发展,进而提高相位恢复的精度。     

干涉仪测向技术现状与发展研究

从解模糊和天线排列形式、鉴相技术、通道幅相不一致校正方法和接收数据处理方式四个方面论述了干涉仪测向技术的现状和发展趋势。对每一方面现存的不同实现方法的主要原理和优劣性做了详细说明和比较,探讨了下一步的发展和改进思路。为干涉仪测向装备在特定条件下应用技术的选择提供理论依据,为新装备的研制提供参考意见。     

物联网浅谈

物联网将是继互联网之后引领IT世界向下一个15年发展的关键领域。本文对物联网的相关概念进行了辨析,对物联网的关键技术、产业链条、发展阶段、商业模式进行了探讨。