Design and some applications of extended bandwidth finite gain amplifiers

A general theory is developed for extended bandwidth operation of actively compensated finite gain amplifiers. Designs for three new circuits are given which implement the theory. These circuits employ only operational amplifiers and resistors and their gains depend only on their resistor ratios. Thus they are suitable for IC fabrication. Further in IC technology, the characteristics of the operational amplifiers as well as the resistor ratios track closely with each other with reference to temperature and aging. Thus the extended bandwidth operation of the amplifiers will be available over a wide temperature range as well as under varying aging conditions. Their characteristics can be tuned easily by trimming only two resistors. Applications of the new amplifiers have been considered in RC active filters as well as in inductance simulation schemes. Experimental results are given which closely agree with theoretical predictions. The results also indicate that substantial improvement in the usable bandwidth of the circuits employing the new amplifiers may be expected over those using the conventional design of finite gain amplifiers.     

盾构隧道纵向结构刚度性状研究

在隧道等效连续化模型基础上,认为环缝影响范围有限,尚未达到整环管片,对隧道纵向等效连续化模型进行深化.考虑环缝的影响范围,根据在轴力和弯矩作用下,等效连续梁模型的轴线变形与相同荷载作用下隧道的轴线变形一致的原则,并且引入横向接头影响系数和土层约束系数,得到隧道"等效弯曲刚度"的计算公式.最后,以上海地铁一号线隧道的几何数据和力学参数为基础,分别探讨了隧道结构本身各主要参数变化对其纵向刚度的影响,通过对计算结果的分析,可以增强对盾构法隧道纵向性能的认识.     

An active-rc biquadratic section with reduced sensitivity to operational amplifier imperfections

A new active RC biquadratic section using three operational amplifiers (op. amps) and capable of realizing high Q at high frequencies is presented. The circuit has low-sensitivity to variations in both the passive components and the op. amp gain-bandwidth products (GB). Compared to some existing circuits which require well-matched op. amps to achieve low sensitivity to GB, the proposed circuit has the important advantage of being insensitive to GB variations even if the op. amps are non-identical. The influence of the finite open loop d.c. gain and finite GB of the op. amps on the proposed design is examined. The new realization is then compared to those available in the literature, such as the circuits due to Kerwin–Huelsman–Newcomb, Akerberg–Mossberg, Mikhael–Bhattacharyya, Tarmy–Ghausi, and Wilson–Bedri–Bowron. Finally, some experimental results are provided to verify the theory.     

基于MOCC的电流模式高通滤波器

在典则 FL F结构的基础上 ,提出了一个利用多端输出电流传送器 ( MOCC)实现的电流模式高通滤波器 .给出了系统的设计公式 .作为例子 ,设计了一个四阶 Butterworth高通滤波器 ,模拟仿真结果与理论分析吻合     

流阻和摩擦对流体流动作功装置性能的影响

研究非线性流阻和作功机械内部摩擦对流体流动作功装置性能的影响,导出输出功率与机械效率以及功率损耗与机械效率间的关系,又由此导出最大输出功率及其相应的一些重要性能参数,并作些有意义的讨论。所得结论可为流体流动作功装置的优化设计提供些新理论依据。     

基于USB接口CT实验仪的数据采集系统设计

介绍一种采用USB（Univer salSerial Bus）接口技术的计算机断层扫描（Computer Tomography,简称CT）教学实验仪的数据采集的硬件系统设计,主要包括闪烁探测器、线性放大器、基于ADC的多道分析器和USB接口电路。     

资产减值准备对盈余管理的影响——基于"东北高速"的剖析

以东北高速为研究对象,通过相关性分析来揭示资产减值准备计提与盈余管理的关系,并得出资产减值准备与企业盈余波动负相关;资产减值准备与现金流量不相关.证明了新会计准则正式实施之前,上市公司确实存在利用资产减值准备进行盈余管理的现象.     

The audio transformer as a selective amplifier

A selective amplifier is developed which is simple, and more flexible than other types. It utilizes an audio transformer with a variable series resistance in the primary circuit, and a variable secondary load capacitance both of which may be adjusted to give broad or narrow peaked amplification at any frequency within a wide range, or flat amplification throughout this range. Theoretical and experimental amplification curves are shown, and a transient solution gives the primary and secondary currents resulting when a voltage is suddenly applied to the amplifier. This analysis shows that the time constants for the circuit are comparable with those for other peaked amplifiers. Oscillograms are shown illustrating the transient behavior of the amplifier.     

某超临界机翼风洞模型转捩方式研究

本文介绍了风洞试验转捩技术的常规方法和应用,通过对某超临界机翼在风洞试验中自由转捩和固定转捩对阻力的影响结果,结合该机翼的压力分布云图进行了分析,提出了超临界机翼在风洞试验中模拟转捩时的方法。     

ReGR: Relation-aware graph reasoning framework for video question answering

As one of the challenging cross-modal tasks, video question answering (VideoQA) aims to fully understand video content and answer relevant questions. The mainstream approach in current work involves extracting appearance and motion features to characterize videos separately, ignoring the interactions between them and with the question. Furthermore, some crucial semantic interaction details between visual objects are overlooked. In this paper, we propose a novel Relation-aware Graph Reasoning (ReGR) framework for video question answering, which first combines appearance–motion and location–semantic multiple interaction relations between visual objects. For the interaction between appearance and motion, we design the Appearance–Motion Block, which is question-guided to capture the interdependence between appearance and motion. For the interaction between location and semantics, we design the Location–Semantic Block, which utilizes the constructed Multi-Relation Graph Attention Network to capture the geometric position and semantic interaction between objects. Finally, the question-driven Multi-Visual Fusion captures more accurate multimodal representations. Extensive experiments on three benchmark datasets, TGIF-QA, MSVD-QA, and MSRVTT-QA, demonstrate the superiority of our proposed ReGR compared to the state-of-the-art methods.     

特征因子与其他文献计量指标关系研究——基于面板数据的估计

为了研究期刊特征因子与其他文献计量指标间的关系,克服简单相关系数和普通回归分析的缺陷,本文基于汤森路透JCR纯数学期刊数据,采用面板数据(Panel Data)研究特征因子分值(Eigenfactor Score)及论文影响分值(Article Influence Score)与其他文献计量指标的关系。研究发现:特征因子分值和论文影响分值互为高度相关。即年指标及影响因子与特征因子分值无关,但和论文影响分值正相关。被引半衰期及5年影响因子与特征因子分值负相关,与论文影响分值正相关。总被引频次及期刊论文数量与特征因子分值正相关,与论文影响分值负相关。研究认为,特征因子的推出有利于期刊重视提高学术质量而不是提高文献计量指标值,对文献计量指标的相关关系的研究方法要重新审视,对于其他学科特征因子与文献计量指标的关系有待进一步研究。     

浅谈齐岳山隧道应急配电设施的配置

文章对齐岳山高风险隧道的供电方式提出了具体作法,特别对应急措施的供电系统双回路和双电源设置自动切换,提出了改善措施,达到了隧道供电的安全效果,对长大风险隧道配电方案设计施工有一定的指导意义。     

基于直接变量法的钢管混凝土结构可靠度分析

将影响抗力及荷载效应不定性的各变量视为直接基本变量,对<钢管混凝土结构设计与施工规程>(CECS)中钢管混凝土纯弯构件的承载力公式进行了可靠度分析,并且研究了不同混凝土标号、钢号、荷载组合、荷载效应比以及含钢率等变异因素对钢管混凝土纯弯构件可靠度的影响.     

姚家2号隧道洞身浅埋段中管棚施工

通过对姚家2号隧道浅埋段分析,在符合施工设计的基础上,进行工序细化,提出了双线隧道浅埋段的中间管棚施工工法,提高隧道施工质量,满足双线隧道洞身浅埋段施工作业安全的要求。     

岳英山水库除险加固工程设计

本文首先介绍了岳英山水库的概况,分析了工程现状。针对水库除险加固的主体工程即坝体工程、溢洪道和输水洞设计,从主坝坝坡整修、副坝迎水坡放缓及护坡、坝基防渗溢洪道和输水洞等方面进行了探讨。     

时速250km高速铁路隧道膨胀岩地层复合式衬砌结构安全性研究

膨胀岩属软岩,它具有显著吸水膨胀和失水收缩的特性。处于这种岩性中的隧道,当膨胀围岩自有的含水量或工程引起的含水量增加时,围岩将产生较大的变形,同时衬砌结构将承受很大的围岩压力。隧道工程穿越膨胀性围岩地段时,围岩的膨胀性将导致支护结构承受额外的附加荷载,降低了支护结构的安全储备,甚至超过了支护结构的承载能力,造成结构破坏。结合国内时速250km高速铁路隧道Ⅳ、Ⅴ级围岩地段加强型衬砌设计,利用数值模拟手段,模拟不同工况下结构的受力状态,分析得到膨胀岩地层隧道处理措施。     

高效节能低噪风扇优化设计

根据扭曲风叶成型原理和叶栅理论,推导出扭曲风叶风扇气动设计计算方法,分析叶轮结构与其气动性能参数的内在关系,编制成风扇优化设计软件。通过该软件得到了用户需要的座舱风扇的扇叶几何图形及气动特性曲线,并与实测的数据相比较,误差在设计范围内。     

砂井地基固结的概率特性

基于砂井地基固结对固结参数的敏感性分析，得出了砂井地基固结概率分析的简化方法；推导了砂井地基固结度概率特征值的计算公式；研究了砂井地基固结的概率设计方法，并探讨了简化方法的精度。     

构架企业公关信息系统的探讨与分析

从企业战略管理角度讲,企业采取积极、成熟的公关战略是适应市场竞争的需要,是在我国加入WTO后,国内企业在激烈的国际市场竞争中实现扬长避短、战胜危机的需要。而构架合理、高效的公关信息系统又是顺利实施企业公关战略的重要一环。为此,本文分析了企业公关信息系统的开发背景、系统设计、总体结构及其意义。     

外部关系能否帮助企业从突破式创新中获利?

突破式创新具有高风险和高价值的特点,然而并非所有的突破式创新都能为企业带来收益。研究在我国转型经济环境下,企业与外部组织的关系能否以及如何影响企业突破式创新与绩效之间的关系。通过对中国279家制造企业的研究发现,政府关系和同行关系会对突破式创新与绩效之间的关系有积极的调节作用,而供应商关系则会带来消极的调节作用,同时没有发现顾客关系存在着显著的调节作用。