Automatic feature selection for unsupervised clustering of cycle-based signals in manufacturing processes

Recent developments in sensing and computer technology have resulted in most manufacturing processes becoming a data-rich environment. A cycle-based signal refers to an analog or digital signal that is obtained during each repetition of an operation cycle in a manufacturing process. It is a very important class of in-process sensing signals for manufacturing processes because it contains extensive information on the process condition and product quality (e.g., the forming force signal in forging processes). In contrast with currently available supervised classification approaches that heavily depend on the training dataset or engineering field knowledge, this paper aims to develop an automatic feature selection method for the unsupervised clustering of cycle-base signals. First, principal component analysis is applied to the raw signals. Then a new method is proposed to select information containing principal components to allow clustering to be performed. The dimension of the problem can be significantly reduced through the use of these two steps. Finally, a model-based clustering method is applied to the selected principal components to find the clusters in the cycle-based signals. A numerical example and a real-world example of a forging process are used to illustrate the effectiveness of the proposed method. The proposed technique is an important data pre-processing technique for the monitoring and diagnostic system development using cycle-based signals for manufacturing processes.     

A flight control system for aerial robots: algorithms and experiments

This paper presents a hierarchical flight control system for unmanned aerial vehicles. The proposed system executes high-level mission objectives by progressively substantiating them into machine-level commands. The acquired information from various sensors is propagated back to the higher layers for reactive decision making. Each vehicle is connected via standardized wireless communication protocol for scalable multi-agent coordination. The proposed system has been successfully implemented on a number of small helicopters and validated in various applications. Results from waypoint navigation, a probabilistic pursuit-evasion game and vision-based target tracking demonstrate the potential of the proposed approach toward intelligent flying robots.     

斜面焊口超声波探伤中的缺陷定位

详细介绍了在斜面焊口超声波探伤中采用声程调节扫描比例进行缺陷定位的计算方法，并给出了计算公式。     

Comments on “Quadratic stabilization of continuous timesystems with state-delay and norm-bounded time-varyinguncertainties”

In the above mentioned paper by Mahmoud-Muthairi (ibid. vol.39 (1994)) a sufficient condition for memoryless stabilization of a class of uncertain linear systems with a variable-state delay and norm-bounded time-varying uncertainties is derived in terms of an algebraic Riccati equation. This Riccati equation depends on several free matrix variables, and a subsequent result in the paper, Theorem 2, states that failure or success of the stabilization algorithm is independent of the selection of these matrix variables. In this paper, we give a counterexample to this Theorem 2 as well as providing a fix     

交流电机软起动

介绍了用ＮＥ５５５控制固态继电器，实现交流电机软起动的装置，以及电流闭环控制设计。实验证明：该方案具有良好的软起动性能，且造价低。     

《建筑结构学报》引文统计与分析

以《建筑结构学报》为调查对象，对１９９１年～１９９６年所刊载的论文，运用引文分析法，对其引文的数量、文献类型、语种及年代分布进行了统计分析，并做出相应的评价．     

嵌入式MCU的SOC设计中的低功耗设计

以Motorola龙珠系列中MXL芯片为例介绍了嵌入式MCU SOC设计中的低功耗设计技术。从加工工艺、硬件设计和软件设计方面来 阐述其中的低功耗设计技术。     

氟化钡晶体质子辐照损伤分布的计算

根据经典辐射理论，描述质子辐照BaF2晶体的能量损失，讨论受照晶体的辐照损伤分布，用Monte Carlo方法模拟碰撞过程，具体用TRIM程序分别计算出能量为1．5Mev和2．0Mev质子辐照BaF2晶体所产生的辐照损伤，对计算结果进行讨论，将这两种能量情况下的BaF2晶体辐照损伤分布进行比较。得到的结论与实验结果基本相符。     

EXPERIMENTAL STUDIES OF NEW TECHNOLOGY ON HIGH GLOSSINESS GRANITE SURFACE

On the basis of analysing thecharacter of granite and its polishingtechnology,the authors have manufactureda kind of polishing disk to polish graniteand good results have been obtained.Through studying the polishing process ofgranite in theory and experiment,theauthors think that the high glossinesssurface is the result of grinding ofabrasives and adhering of soft metal.Moreover,orthogonal test is carried outabout the technical parameters for threeetypical kinds of granites and some usefulresults for production are obtained.     

Academic trajectories of newcomer immigrant youth.

Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve analysis revealed that although some newcomer students performed at high or improving levels over time, others showed diminishing performance. Multinomial logistic regressions identified significant group differences in academic trajectories, particularly between the high-achieving youth and the other groups. In keeping with ecological–developmental and stage–environment fit theories, School Characteristics (school segregation rate, school poverty rate, and student perceptions of school violence), Family Characteristics (maternal education, parental employment, and household structure), and Individual Characteristics (academic English proficiency, academic engagement, psychological symptoms, gender, and 2 age-related risk factors, number of school transitions and being overaged for grade placement) were associated with different trajectories of academic performance. A series of case studies triangulate many of the quantitative findings as well as illuminate patterns that were not detected in the quantitative data. Thus, the mixed-methods approach sheds light on the cumulative developmental challenges that immigrant students face as they adjust to their new educational settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)