Predictive maintenance of abnormal wind turbine events by using machine learning based on condition monitoring for anomaly detection

Journal of Mechanical Science and Technology - The predictive maintenance of wind turbines has become a critical issue with the rapid development of wind power generation. The early detection of...     

基于互相关定位法的干涉仪分析与仿真

首次提出用时域互相关法处理Sagnac/Mach-Zehnder分布式光纤传感系统的干涉输出信号, 对扰动进行检测和定位。首先对Sagnac/Mach-Zehnder分布式光纤传感系统进行了扰动检测和定位的理论分析, 推导出扰动引起的干涉输出信号的表达式, 利用Bessel函数展开, 确定了该系统的两路干涉输出满足时域互相关的特性。在此基础上进一步分析了两路干涉信号的表达式, 提出基频定位法和微分定位法两种时域互相关方法处理干涉信号, 确定扰动位置。对两种扰动定位方法进行了Matlab仿真, 并通过实验在多个扰动位置多次验证了两种方法的正确性。     

Nanoprobe-based affinity mass spectrometry for selected protein profiling in human plasma

In recent decades, magnetic nanoparticles have emerged as a promising new platform in biomedical applications, particularly bioseparations. We have developed an immunoassay using antibody-conjugated magnetic nanoparticles as an efficient affinity probe to simultaneously preconcentrate and isolate targeted antigens from biological media. We combined this probe with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI MS) to profile proteins in diluted human plasma. The nanoparticles were designed to detect several disease-associated proteins and could be used directly in MALDI MS without an elution step, thereby facilitating multiple antigen screening and the characterization of antigen variants. Plasma antigens bound rapidly (approximately 10 min) to the antibody-conjugated nanoparticles, allowing the assay to be performed within 20 min. With sensitivity of detection in the femtomole range, the nanoscale immunoassay is superior to assays using microscale particles. We applied our method to comparative protein profiling of patients with gastric cancer and healthy individuals and found differential protein expression levels associated with the disease as well as individuals. Given the flexibility of manipulating functional groups on the nanoprobes, their low cost, robustness, and simplicity of the assay, our approach shows promise for targeted proteome profiling in clinical settings.     

Influence of grating parameters on the linewidths of external-cavity diode lasers

We investigate experimentally the influence of the grating reflectivity, grating resolution, and diode facet antireflection (AR) coating on the intrinsic linewidth of an external-cavity diode laser built with a diffraction grating in a Littrow configuration. Grating lasers at 399, 780, and 852 nm are determined to have typical linewidths between 250 and 600 kHz from measurements of their frequency noise power spectral densities. The linewidths are little affected by the presence of an AR coating on the diode facet but narrow as the grating reflectivity and grating resolution are increased, with the resolution exerting a greater effect. We also use frequency noise measurements to characterize a laser mount with improved mechanical stability.     

A passive auto-focus camera control system

This paper presents a passive auto-focus camera control system which can easily achieve the function of auto-focus with no necessary of any active component (e.g., infrared or ultrasonic sensor) in comparison with the conventional active focus system. To implement the technique we developed, the hardware system including the adjustable lens with CMOS sensor and servo motor, an 8051 image capture micro-controller, a field programmable gate array (FPGA) sharpness measurement circuit, a pulse width modulation (PWM) controller, and a personal digital assistant (PDA) image displayer was constructed. The discrete wavelet transformation (DWT), the morphology edge enhancement sharpness measurement algorithms, and the self-organizing map (SOM) neural network were used in developing the control mechanism of the system. Compared with other passive auto-focus methods, the method we proposed has the advantages of lower computational complexity and easier hardware implementation.     

Security of lightweight mutual authentication protocols

Sensors and IoT (Internet of Things), which include RFID (Radio-Frequency IDentification) tags, have witnessed widespread adoption across a wide variety of application domains over the last two decades. These sensors and IoT devices are often a part of distributed sensor networks. As with any distributed processing scenario, there is a need to ensure that these devices provide required security and privacy to the tagged object as well as its bearer. Cryptography has been used to address the security and privacy aspects of RFID tags. Unlike a majority of other IoT devices, the commonly used passive RFID tags are extremely resource-constrained and therefore can accommodate only lightweight operations. Security and privacy concerns still need to be addressed as they remain significant regardless of implementation details. We evaluate RFID-based lightweight mutual authentication protocols that have been recently proposed and identify vulnerabilities.

     

Task-irrelevant angry faces capture attention in visual search while modulated by resources.

We investigated the attentional capture effect of emotional faces under sufficient or restricted attentional conditions. In a modified visual search paradigm, three kinds of schematic faces (angry, happy, and neutral) served as stimuli. Participants were instructed to search for a target face indicated by a dot and to respond to the dot's position. In this design, the emotional content of the face is task-irrelevant and does not need to be attended. The results of Experiment 1 demonstrate that having an angry face as the target face elicited a faster response than did the neutral target face, and when the angry face is used as a distractor, the response to the target was delayed compared to the response with no such distractor. Experiment 2 included inverted faces to decrease emotional content; results showed that inversion of the faces reduced the effect of angry faces on the search performance. When attention was cued to a specific area in Experiment 3, the effect of angry faces outside of the cued area became weaker. In conclusion, the results indicate that a task-irrelevant angry face can capture attention beyond top-down control, but this effect is modulated by the availability of attentional resources. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Feasibility of using a rotating packed bed in preparing coupled ZnO/SnO2 photocatalysts

In this work, coupled ZnO/SnO₂ photocatalysts were prepared in a rotating packed bed (RPB) via co-precipitation. The precursors of coupled ZnO/SnO₂ photocatalysts were formed from solutions of zinc sulfate, tin tetrachloride and sodium hydroxide. The calcinations of these precursors yielded coupled ZnO/SnO₂ photocatalysts. The effect of calcination temperature on the characteristics and photocatalytic activity of coupled ZnO/SnO₂ photocatalysts was studied. The photocatalytic activity of coupled ZnO/SnO₂ photocatalysts was evaluated using the photocatalytic decolorization of methylene blue. The experimental results reveal that coupled ZnO/SnO₂ photocatalysts that were obtained by calcination at 600 °C for 10 h were the most efficient in decolorizing methylene blue.