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目前,工业锅炉防止结垢,普遍采用炉外软化水处理法。但是软化水处理设备成本高,操作和化验复杂,本文所提出的“离子界而结渣防腐理论”用于工业锅炉处理水质时,不但可以控制水垢的生成,而且,在防止锅炉腐蚀方面也有很大的应用价值。 相似文献
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This paper investigates the feasibility of using a lanthanum oxide thin film (La2O3) with a high dielectric constant as a gate dielectric on GaAs pHEMTs to reduce gate leakage current and improve the gate to drain breakdown voltage relative to the conventional GaAs pHEMT. An E/D mode pHEMT in a single chip was realized by selecting the appropriate La2O3 thickness. The thin La2O3 film was characterized: its chemical composition and crystalline structure were determined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. La2O3 exhibited good thermal stability after post-deposition annealing at 200, 400 and 600℃ because of its high binding-energy (835.6 eV). Experimental results clearly demonstrated that the La2O3 thin film was thermally stable. The DC and RF characteristics of Pt/La2O3/Ti/Au gate and conventional Pt/Ti/Au gate pHEMTs were examined. The measurements indicated that the transistor with the Pt/La2O3/Ti/Au gate had a higher breakdown voltage and lower gate leakage current. Accordingly, the La2O3 thin film is a potential high-k material for use as a gate dielectric to improve electrical performance and the thermal effect in high-power applications. 相似文献
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客户需求重要度的确定是产品族规划的关键环节,对企业产品族开发成功与否起着至关重要的作用。目前地铁产品族的设计大部分仅考虑城市运营商的需求,而缺乏对其终端用户,即普通乘客的需求进行分析。为此,提出一种面向多主体客户的地铁需求重要度确定方法。首先,基于熵值法确定城市运营商的需求重要度;其次,采用模糊Kano模型确定出普通乘客的必备需求、期望需求以及魅力需求;最后,根据普通乘客的需求分类结果,引入重要度调整函数对运营商需求重要度进行调整,从而确定出综合考虑普通乘客与运营商偏好的最终需求重要度。以地铁车辆为例,验证了该方法的有效性和可行性。 相似文献
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针对高性能伺服控制器对复杂的控制算法以及较小延时的需求,研究了一种基于FPGA和DSP的高性能伺服控制器设计方法。FPGA完成电流环、坐标变换、空间脉宽矢量调制、电流位置读取,DSP则负责速度环、位置环和上位机通信,使系统既能实现复杂的控制算法,又能将延时控制到最小,从而保证控制器的最佳性能。此外,详细介绍了两者之间的通信方式以及三环控制器设计。试验数据结果表明,伺服控制器速度环带宽能达到100 Hz,额定转速下稳速精度在1 r/min以内,定位精度能达到0.02°,证实了该控制器结构的实效性。 相似文献
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This investigation explores a low-noise amplifier(LNA) with a coplanar waveguide(CPW) structure,in which a two-stage amplifier is associated with a cascade schematic circuit,implemented in 0.15-μm GaAs pseudomorphic high electron mobility transistor(pHEMT) technology in a Ka-band(26.5-40.0 GHz) microwave monolithic integrated circuit(MMIC).The experimental results demonstrate that the proposed LNA has a peak gain of 12.53 dB at 30 GHz and a minimum noise figure of 3.3 dB at 29.5 GHz,when biased at a V_(d... 相似文献