First Harmonic (2f) Characterisation of Resonant Frequency and Q-Factor of Micromechanical Transducers

In this paper, the response to the first harmonic component (2f) of the electrostatic force in single terminal driven electrostatic comb-drive and parallel-plate drive was used as a signal to extract device parameters, namely, the Q-factor and resonant frequency instead of the fundamental (1f) resonance response. It is shown that the difficulty in motional measurement due to electrical cross-talk (parasitics) using 1f measurement can be overcome with a higher signal-to-noise ratio of the 2f signal. Both atmospheric (low-Q) and reduced pressure environment were investigated using off-chip electronics and lock-in amplifier. The measurements were done on the electrostatic comb-drive and capacitive parallel plate sensing plates that form the two core modules of a yaw rate sensor (dual-axis resonator). The effects of AC and DC bias voltages on the measured response have been investigated. Experimental amplitude and phase response data have been analysed using the Lorentzian curve-fit, Resonance Curve Area (RCA) method, the half-power bandwidth method (3 dB) and the Nyquist plot for data fitting and determination of the Q-factor and resonance frequency.     

Bond strength prediction for deformed steel rebar embedded in recycled coarse aggregate concrete

This paper summarizes the results of an experimental investigation into the bond behavior between recycled aggregate concrete (RAC) and deformed steel rebars, with the main variables being the recycled coarse aggregate replacement ratio (RCAr) and water-to-cement ratio of the concrete mixture. The investigation into splitting cracking strength indicates that the degradation of the bond splitting tensile stress of the cover concrete was affected by not only the roundness of the coarse aggregate particles but also the weak interfacial transition zone (ITZ) between the cement paste and the RCA that has a more porous structure in the ITZ than normal concrete. In this study, a linear relationship between the bond strength and the density of the RCA was found, but the high compressive strength reduced the effects of the parameters. To predict the bond strength of RAC using the main parameters, a multivariable model was developed using nonlinear regression analysis. It can be inferred from this study that the degradation characteristic of the bond strength of RAC can be predicted well, whereas other empirical equations and code provisions are very conservative.     

Fuzzy cognitive maps enabled root cause analysis in complex projects

This paper presents a Fuzzy Cognitive Maps (FCM) enabled Root Cause Analysis (RCA) approach to assessing the TBM performance in tunnel construction. Fuzzy logic is used to capture and utilize construction experience and knowledge from domain experts, and a cause-effect model consisting of nine concepts is established for simulating the TBM performance within the FCM framework. A tunnel case in the Wuhan metro system in China is used to demonstrate the applicability of the developed approach. Results indicate that (i) C₄ (Soil Density) displays a strongest negative correlation with the concept C_T (TBM Advance Rate); while C₈ (Grouting Speed) displays a strongest positive correlation with C_T; (ii) TBM performance is very sensitive to the change of operational conditions, where the values of operational parameters can be adjusted to go up (or down) in case the TBM performance negatively (or positively) reduces; and (iii) we can identify the magnitude of the adjustment scope of operational variables when the TBM operational performance suffers a reduction. The novelty of the proposed approach is that it is verified to be capable of modeling dynamics of system behaviors over time and performing many kinds of what-if scenario analysis, including predictive, diagnostic, and hybrid RCA, which turns out to be a more competitive solution that deals with uncertainty, dynamics, and interactions in the approximate reasoning process, compared to other traditional approximate methods (i.e. Fault Tree Analysis (FTA), Rule-Based Reasoning (RBR), and Case-Based Reasoning (CBR)). The proposed approach can be used as a decision support tool for ensuring the satisfactory performance of TBMs, and thus, increases the efficiency of tunnel construction projects.     

兆声清洗法和离心喷射清洗法的比较

用基于改进的RCA清洗液结合兆声清洗法和离心喷射法清洗抛光的硅片，干燥后用激光扫描法测试抛光硅片表面颗粒．结果表明，改进的RCA清洗液结合兆声的清洗方法对于去除硅片表面的微小颗粒具有更高的效率．     

水胶比和再生粗骨料取代率对再生混凝土强度影响的试验研究

为了更好地掌握再生混凝土强度变化规律,利用废弃混凝土试块作为再生粗骨料原料,依据水胶比和再生粗骨料取代率不同配制了15组共计75个再生混凝土试块进行试验对比分析。试验结果表明：再生混凝土破坏过程和破坏形态与普通混凝土基本一致,但相对于普通混凝土来说,再生混凝土的基本力学性能较差。再生混凝土抗压强度随水胶比增大而降低,再生粗骨料取代率的增加会对再生混凝土的基本力学性能产生不利影响。     

通过添加表面活性剂和螯合剂改进硅片化学清洗工艺的研究

通过在传统RCA清洗法所用的SC-1液中,添加表面活性剂四甲基氢氧化铵(TMAH)和/或螯合剂乙二胺四乙酸(EDTA),实验比较了不同清洗方法对颗粒粘污、金属粘污的去除效率;并测试了其对硅片表面粗糙度的影响。用MOS电容结构的击穿电场强度Weibull分布,评价了不同清洗方法所得氧化层的质量。结果表明,上述改进能够显著提高对颗粒粘污和金属粘污的去除效果,同时能省去RCA的SC-2清洗步骤,具有节省工时、化学试剂消耗量小的优势。     

水质模型在武汉水环境管理中的应用

武汉水质模型项目是在亚行支持下,通过在东湖、长江等试点水体建立水质模型,科学准确地反映武汉市水环境质量实际变化情况和未来发展趋势,指导污水处理厂的建设及运营,从而提高水环境管理的技术水平.简要介绍了武汉水质模型的基本构架及原理,并对武汉水质模型在国内水环境管理中进一步的应用提出了深入构想.     

逆导型快速可控硅高频逆变CO2激光电源

采用逆导型快速可控硅ＲＣＡ Ｓ３９００ＭＦ研制的高频逆变ＣＯ２激光电源，逆变频率高达４０ｋＨｚ，具有效率高、成本低、启动快、稳流精度高等突出优点。     

根本原因分析技术的应用

以美国西屋公司对核质保人员根本原因(Root Cause Analysis简称RCA)分析培训课程教材为基础,详细论述了RCA的基本概念、实施过程分析方法和应用案例。     

历史的结晶:1960年代美国RCA实验室矩阵寻址液晶电视发展历程

液晶电视的普及之路在45年前始于美国新泽西州普林斯顿的RCA实验室.RCA老将Bernard J.Lechner当时在那工作,在此他回顾了LCD的早期研发工作.