Search results for " Sensor."

Residents’corner June 2014. PhotogRaphic Clues: Best Settings for Dermatologic Photography

2014

Obtaining digital images either for documentation or research purposes is a daily need for the dermatologist. Photography, as the art of capturing light, relies mainly on three modifiable elements: lens aperture (defined as the opening through which light reaches the camera sensor; expressed as “F-stops”, the smaller the number, the broader the aperture), shutter speed (the total time during which light reaches the sensor; it is indicated as fractions of a second) and ISO sensitivity (the light [...]

Sub-Millimeter Displacement Sensing by Passive UHF RFID Antennas

2014

A slotted patch is transformed into a wireless passive UHF-RFID sensor of uni-dimensional displacements by introducing a mechanic-electromagnetic modulation capable to convert sub-millimeter deformations into changes of the antenna's response, remotely detectable. A design methodology allows to obtain the desired sensitivity and dynamic range in a fully controllable way. The sensor and the methodology are discussed through the help of preliminary laboratory experimentations on a concrete brick, showing the possibility to achieve resolutions better than 0.1 mm with low cost readers.

Disabilità complessa: quali risposte alle domande terapeutiche riabilitative, educative e formative nei contesti del territorio e dei centri speciali…

2008

Advanced Ultrasonic Structural Monitoring of Waveguides

2008

Ultrasonic Guided Waves (UGWs) are a useful tool in those structural health monitoring applications that can benefit from built-in transduction, moderately large inspection ranges and high sensitivity to small flaws. This paper describes two methods, based on linear and nonlinear acoustics for structural damage detection based on UGWs. The linear method combine the advantages of UGW inspection with the outcomes of the Discrete Wavelet Transform (DWT) that is used for extracting defect-sensitive features that can be combined to perform a multivariate diagnosis of damage. In particular, the DWT is exploited to generate a set of relevant wavelet coefficients to construct a uni-dimensional or m…

Ultrasonic Guided Waves-Based Monitoring of Rail Head: Laboratory and Field Tests

2010

Recent train accidents have reaffirmed the need for developing a rail defect detection system more effective than that currently used. One of the most promising techniques in rail inspection is the use of ultrasonic guided waves and noncontact probes. A rail inspection prototype based on these concepts and devoted to the automatic damage detection of defects in rail head is the focus of this paper. The prototype includes an algorithm based on wavelet transform and outlier analysis. The discrete wavelet transform is utilized to denoise ultrasonic signals and to generate a set of relevant damage sensitive data. These data are combined into a damage index vector fed to an unsupervised learning…

An unsupervised Learning Algorithm for Fatigue Crack Detection in Waveguides

2009

Ultrasonic guided waves (UGWs) are a useful tool in structural health monitoring (SHM) applications that can benefit from built-in transduction, moderately large inspection ranges, and high sensitivity to small flaws. This paper describes an SHM method based on UGWs and outlier analysis devoted to the detection and quantification of fatigue cracks in structural waveguides. The method combines the advantages of UGWs with the outcomes of the discrete wavelet transform (DWT) to extract defect-sensitive features aimed at performing a multivariate diagnosis of damage. In particular, the DWT is exploited to generate a set of relevant wavelet coefficients to construct a uni-dimensional or multi-di…

Outlier analysis and principal component analysis to detect fatigue cracks in waveguides

2009

Ultrasonic Guided Waves (UGWs) are a useful tool in structural health monitoring (SHM) applications that can benefit from built-in transduction, moderately large inspection ranges and high sensitivity to small flaws. This paper describes a SHM method based on UGWs, discrete wavelet transform (DWT), outlier analysis and principal component analysis (PCA) able to detect and quantify the onset and propagation of fatigue cracks in structural waveguides. The method combines the advantages of guided wave signals processed through the DWT with the outcomes of selecting defectsensitive features to perform a multivariate diagnosis of damage. The framework presented in this paper is applied to the de…

Digital signal processing for rail monitoring by means of ultrasonic guided waves

2007

Recent train accidents have reaffirmed the need for developing rail defect detection systems that are more effective than those used today. One of the recent developments in rail inspection is the use of ultrasonic guided waves (UGWs) and non-contact probing techniques to target transverse-type defects. Besides the obvious advantages of non-contact probing, that include robustness and a potential for large inspection speed, such a system can theoretically detect transverse defects under horizontal shelling or head checks. This paper demonstrates the effectiveness of digital signal processing to enhance the damage detection sensitivity of the non-contact system. The method proposed here comb…

Application of principal component analysis and wavelet transform to fatigue crack detection in waveguides

2010

Ultrasonic Guided Waves (UGWs) are a useful tool in structural health monitoring (SHM) applications that can benefit from built-in transduction, moderately large inspection ranges and high sensitivity to small flaws. This paper describes a SHM method based on UGWs, discrete wavelet transform (DWT), and principal component analysis (PCA) able to detect and quantify the onset and propagation of fatigue cracks in structural waveguides. The method combines the advantages of guided wave signals processed through the DWT with the outcomes of selecting defect-sensitive features to perform a multivariate diagnosis of damage. This diagnosis is based on the PCA. The framework presented in this paper …

HybridS: A Scheme for Secure Distributed Data Storage in WSNs

2008

In unattended wireless sensor networks (WSNs), data is stored locally or at designated nodes upon sensing, and users can access it on demand. This paradigm can improve energy efficiency by making use of the upcoming cheap and large flash memory, as well as system robustness. Nevertheless, the security and dependability of distributed storage are critical for the applicability of such WSNs. In this paper, we propose a secure and dependable data storage scheme by taking advantages of secret sharing and Reed-Solomon code, which has computational security and yet maintains optimal data size. The extensive analysis verifies our scheme can provide secure and dependable data storage in WSNs in the…