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The ability to identify electric shock in the human body is a crucial consideration in the design of touch/leakage protective devices. In this paper, the $\alpha$ -dispersion characteristics of electrical impedance in the human body are investigated based on the Cole–Cole model. An improved electric shock identification method is proposed accordingly. The effects of various factors (e.g., transition resistance and feeder reactance) on the accuracy and reliability are analyzed. Feasibility and effectiveness of the method are verified via numerical simulation. The results indicate that 1) $\alpha$-dispersion is an effective feature for distinguishing living or nonliving organisms; 2) the proposed method is robust and unaffected by transition resistance; and 3) the computational cost is low to satisfy standard leakage current protective device requirements. This paper provides a solution to the dead-zone problem as well as a set of workable guidelines for protective device design. [ABSTRACT FROM AUTHOR]

At present, the UHVDC transmission lines in the Northwest China are inevitably built across sandstorm-prone areas, whereas the influences of strong wind and dust particles have not been paid enough attention in the existing design guidelines and standards. Since the corona characteristics are greatly influenced by environmental factors, to study the effect of sandstorm environment on the corona characteristics, corona tests were carried out on five ?1100 kV fitting models under different experimental conditions of wind speed and dust particle size in artificial sandstorm environment. The results show that the corona inception voltage decreases under the influence of wind and dust particles. Moreover, the voltage increases along with the wind speed rising, whereas the particle size shows little effect on the corona characteristics. Then the test results were verified and analyzed by electric field simulation and flow field simulation using ANSYS and Fluent software. These results could promote future DC corona mechanism study and practical engineering. [ABSTRACT FROM AUTHOR]

The instantaneous vital sign rates, which are related to physiological dynamics, are important indicators of human health condition. This paper presents a noncontact way to measure the human instantaneous vital signs using digital-intermediate frequency (IF) Doppler radar. The synchrosqueezing transform-based algorithm has been proposed to get a concentrated time-frequency (TF) distribution, so that the high-resolution instantaneous heartbeat and respiratory rates and the time-domain signals can be acquired. Moreover, the developed radar with customized radio frequency module employs the direct IF sampling technique to achieve high sensitivity to capture the tiny vital sign variations. Experiments with different human subjects and physiological conditions have been carried out. Compared with the landmark-based method and traditional TF algorithms, the results show that instantaneous vital signs can be acquired more accurately within 3 m at a −13 dBm transmit power by the proposed method. Therefore, the radar can be used for evaluating the physiological dynamics and assessing health condition. [ABSTRACT FROM PUBLISHER]

Long range transmission lines in north-west China are inevitably set up across sandstorm-prone areas. Pollution deposition of insulators working under such rigorous environment is nonuniform due to the influences of flow field and electric field, thus withstand characteristics obtained in traditional artificial pollution test might not be accurate enough. In this paper, sandstorm simulation experiments were carried out to simulate the actual working conditions, and a comparison was made between the withstand characteristics obtained in simulation experiments and artificial pollution tests. The results show that the withstand voltages of insulators went through sandstorm simulation experiment decreased significantly comparing to those prepared by quantitative Brushing Method, which applies the pollution layer uniformly on the insulator surface. Moreover, the withstand voltages of each shed on the insulator string are different at different position and various wind speeds, which reflect the influence of electric field and flow field. In addition, the mechanisms of the influences of flow field and electric field on withstand characteristics of insulators were discussed. [ABSTRACT FROM PUBLISHER]

Shear wave speed can be used to assess tissue elasticity, which is associated with tissue health. Ultrasound shear wave elastography techniques based on measuring the propagation speed of the shear waves induced by acoustic radiation force are becoming promising alternatives to biopsy in liver fibrosis staging. However, shear waves generated by such methods are typically very weak. Therefore, the penetration may become problematic, especially for overweight or obese patients. In this study, we developed a new method called external vibration multi-directional ultrasound shearwave elastography (EVMUSE), in which external vibration from a loudspeaker was used to generate a multi-directional shear wave field. A directional filter was then applied to separate the complex shear wave field into several shear wave fields propagating in different directions. A 2-D shear wave speed map was reconstructed from each individual shear wave field, and a final 2-D shear wave speed map was constructed by compounding these individual wave speed maps. The method was validated using two homogeneous phantoms and one multi-purpose tissue-mimicking phantom. Ten patients undergoing liver magnetic resonance elastography (MRE) were also studied with EVMUSE to compare results between the two methods. Phantom results showed EVMUSE was able to quantify tissue elasticity accurately with good penetration. In vivo EVMUSE results were well correlated with MRE results, indicating the promise of using EVMUSE for liver fibrosis staging. [ABSTRACT FROM AUTHOR]

Ultrasound tissue harmonic imaging is widely used to improve ultrasound B-mode imaging quality thanks to its effectiveness in suppressing imaging artifacts associated with ultrasound reverberation, phase aberration, and clutter noise. In ultrasound shear wave elastography (SWE), because the shear wave motion signal is extracted from the ultrasound signal, these noise sources can significantly deteriorate the shear wave motion tracking process and consequently result in noisy and biased shear wave motion detection. This situation is exacerbated in in vivo SWE applications such as heart, liver, and kidney. This paper, therefore, investigated the possibility of implementing harmonic imaging, specifically pulse-inversion harmonic imaging, in shear wave tracking, with the hypothesis that harmonic imaging can improve shear wave motion detection based on the same principles that apply to general harmonic B-mode imaging. We first designed an experiment with a gelatin phantom covered by an excised piece of pork belly and show that harmonic imaging can significantly improve shear wave motion detection by producing less underestimated shear wave motion and more consistent shear wave speed measurements than fundamental imaging. Then, a transthoracic heart experiment on a freshly sacrificed pig showed that harmonic imaging could robustly track the shear wave motion and give consistent shear wave speed measurements of the left ventricular myocardium while fundamental imaging could not. Finally, an in vivo transthoracic study of seven healthy volunteers showed that the proposed harmonic imaging tracking sequence could provide consistent estimates of the left ventricular myocardium stiffness in end-diastole with a general success rate of 80% and a success rate of 93.3% when excluding the subject with Body Mass Index higher than 25. These promising results indicate that pulse-inversion harmonic imaging can significantly improve shear wave motion tracking and thus potentially facilitate more robust assessment of tissue elasticity by SWE. [ABSTRACT FROM AUTHOR]

Fast and accurate tissue elasticity imaging is essential in studying dynamic tissue mechanical properties. Various ultrasound shear elasticity imaging techniques have been developed in the last two decades. However, to reconstruct a full field-of-view 2-D shear elasticity map, multiple data acquisitions are typically required. In this paper, a novel shear elasticity imaging technique, comb-push ultrasound shear elastography (CUSE), is introduced in which only one rapid data acquisition (less than 35 ms) is needed to reconstruct a full field-of-view 2-D shear wave speed map (40\,\times \,38 mm). Multiple unfocused ultrasound beams arranged in a comb pattern (comb-push) are used to generate shear waves. A directional filter is then applied upon the shear wave field to extract the left-to-right (LR) and right-to-left (RL) propagating shear waves. Local shear wave speed is recovered using a time-of-flight method based on both LR and RL waves. Finally, a 2-D shear wave speed map is reconstructed by combining the LR and RL speed maps. Smooth and accurate shear wave speed maps are reconstructed using the proposed CUSE method in two calibrated homogeneous phantoms with different moduli. Inclusion phantom experiments demonstrate that CUSE is capable of providing good contrast (contrast-to-noise ratio \ge 25 dB) between the inclusion and background without artifacts and is insensitive to inclusion positions. Safety measurements demonstrate that all regulated parameters of the ultrasound output level used in CUSE sequence are well below the FDA limits for diagnostic ultrasound. [ABSTRACT FROM AUTHOR]

Ultrasound images of muscle fascicles have been widely used to investigate muscle properties under static/dynamic and pathologic conditions. Fascicle images are usually detected and measured manually, which is subjective and time consuming, especially when dealing with large number of images. In this study, an automatic linear extraction method based on localized Radon transform and revoting strategy is proposed to detect and track muscle fascicles in ultrasound images. The performance of the proposed method is compared to another automatic linear feature extraction method of revoting Hough transform using both simulated images generated by Field II and clinical images from two human subjects. The proposed tracking method is further validated using experimental data. Both the simulation and experimental results show that the proposed method is robust in the presence of speckle noise, accurate in terms of orientation and position measurement, and feasible for analyzing clinical data. [ABSTRACT FROM AUTHOR]

Cancelable biometrics is a powerful remedy for information leakage caused by the extensive usage of unprotected biometric data. Current measures usually suffer from deteriorated accuracy, which is known as the security–performance tradeoff. Motivated by these concerns, in this article, a novel cancelable fingerprint approach, i.e., Indexing-Min–Max (IMM) hashing, is proposed to securely transform a fixed-length fingerprint feature vector to a discrete index hashed code. IMM hashing is essentially established upon the min–max hash and further strengthened by the integration of the partial Hadamard transform, which alleviates performance deterioration while maintaining a high security level. Extensive experiments on FVC2002 and FVC2004 fingerprint datasets coupled with comprehensive theoretical analyses demonstrate the favorable accuracy and strong anti-attack resilience of the proposed method. Besides, compared to the unprotected counterpart, the matching precision of the protected templates yields little accuracy loss or even improved performance, which means the security–performance tradeoff is well handled. Furthermore, IMM hashing also meets the unlinkability and revocability requisites of cancelable biometrics. [ABSTRACT FROM AUTHOR]

Local energy pattern, a statistical histogram-based representation, is proposed for texture classification. First, we use normalized local-oriented energies to generate local feature vectors, which describe the local structures distinctively and are less sensitive to imaging conditions. Then, each local feature vector is quantized by self-adaptive quantization thresholds determined in the learning stage using histogram specification, and the quantized local feature vector is transformed to a number by N-nary coding, which helps to preserve more structure information during vector quantization. Finally, the frequency histogram is used as the representation feature. The performance is benchmarked by material categorization on KTH-TIPS and KTH-TIPS2-a databases. Our method is compared with typical statistical approaches, such as basic image features, local binary pattern (LBP), local ternary pattern, completed LBP, Weber local descriptor, and VZ algorithms (VZ-MR8 and VZ-Joint). The results show that our method is superior to other methods on the KTH-TIPS2-a database, and achieving competitive performance on the KTH-TIPS database. Furthermore, we extend the representation from static image to dynamic texture, and achieve favorable recognition results on the University of California at Los Angeles (UCLA) dynamic texture database. [ABSTRACT FROM PUBLISHER]

Rotary ultrasonic machining (RUM) is a superior technology to machine hard and brittle materials. Traditionally, the compensation optimization for the RUM system is limited to a single resonant frequency. This article presents a novel double compensation approach for the impedance and frequency regulations of RUM via multiobjective genetic algorithm (MOGA) aiming to achieve the system resonance and monitor the machining process in real time. For this, we first establish the impedance model of the rotary ultrasonic holder (RUH) by adopting the T-type circuit that includes the comprehensive electromagnetic parameters. The obtained impedance model reveals that both frequency mismatch and impedance mismatch exist in the RUM system, causing the low voltage gain and low vibration transmission. To obtain the optimal compensation to match both the frequency and impedance, an optimization model-based MOGA is developed to intelligently search the accurate capacitance values, where the Pareto frontier is employed to visualize the capacitance solution distribution. Moreover, the response feature of the RUH system is attained by using the state-space equation. Detailed comparisons of four compensation topologies show that the series–series (SS) topology offers the optimal performance, which can match both of the frequency and the impedance well, improving the output active power 7.634 times compared to the conventional one. Finally, the validity of the proposed optimization method is confirmed by using both simulations and experiments. Note to Practitioners—This article was motivated by the transmission efficiency and the stability of ultrasonic vibration in the rotary ultrasonic machining (RUM). The matching issue is critical in RUM because the whole system is very complicated with multiple components such as electrical devices, piezoelectric rings, and mechanical horn. In the conventional RUM, the system matching is limited to a single resonant frequency between the piezoelectric transducer and the electrical driver. However, the impedance matching is also important to influence the ultrasonic vibration. The problem of the ultrasonic matching stems from empirical experiences of the engineers’ or simple heuristic rules instead of advanced approaches. On the other hand, optimization-based techniques are viewed as a great success in industrial and engineering applications. With the assistance of our proposed numerical model and the corresponding simulation, we found that the multiobjective genetic algorithm (MOGA) can intelligently search the optimal compensated parameters to achieve the double matching for both the resonant frequency and the impedance in the RUM system. Finally, our experiments prove that the MOGA optimization can attain optimal transmission efficiency for the electrical voltage and current compared with conventional approaches. This significantly benefits the application of the RUM technology in industry, especially for the precision machining of the hard and brittle materials. [ABSTRACT FROM AUTHOR]

Two-dimensional shear-wave elastography presents 2-D quantitative shear elasticity maps of tissue, which are clinically useful for both focal lesion detection and diffuse disease diagnosis. Realization of 2-D shear-wave elastography on conventional ultrasound scanners, however, is challenging because of the low tracking pulse-repetition-frequency (PRF) of these systems. Although some clinical and research platforms support software beamforming and plane-wave imaging with high PRF, the majority of current clinical ultrasound systems do not have the software beamforming capability, which presents a critical challenge for translating the 2-D shear-wave elastography technique from laboratory to clinical scanners. To address this challenge, this paper presents a time-aligned sequential tracking (TAST) method for shear-wave tracking on conventional ultrasound scanners. TAST takes advantage of the parallel beamforming capability of conventional systems and realizes high-PRF shear-wave tracking by sequentially firing tracking vectors and aligning shear wave data in the temporal direction. The comb-push ultrasound shear elastography (CUSE) technique was used to simultaneously produce multiple shear wave sources within the field-of-view (FOV) to enhance shear wave SNR and facilitate robust reconstructions of 2-D elasticity maps. TAST and CUSE were realized on a conventional ultrasound scanner. A phantom study showed that the shear-wave speed measurements from the conventional ultrasound scanner were in good agreement with the values measured from other 2-D shear wave imaging technologies. An inclusion phantom study showed that the conventional ultrasound scanner had comparable performance to a state-of-the-art shear-wave imaging system in terms of bias and precision in measuring different sized inclusions. Finally, in vivo case analysis of a breast with a malignant mass, and a liver from a healthy subject demonstrated the feasibility of using the conventional ultrasound scanner for in vivo 2-D shear-wave elastography. These promising results indicate that the proposed technique can enable the implementation of 2-D shear-wave elastography on conventional ultrasound scanners and potentially facilitate wider clinical applications with shear-wave elastography. [ABSTRACT FROM AUTHOR]

Comb-push ultrasound shear elastography (CUSE) has recently been shown to be a fast and accurate 2-D elasticity imaging technique that can provide a full field-of-view (FOV) shear wave speed map with only one rapid data acquisition. The initial version of CUSE was termed U-CUSE because unfocused ultrasound push beams were used. In this paper, we present two new versions of CUSE—focused CUSE (F-CUSE) and marching CUSE (M-CUSE), which use focused ultrasound push beams to improve acoustic radiation force penetration and produce stronger shear waves in deep tissues (e.g., kidney and liver). F-CUSE divides transducer elements into several subgroups which transmit multiple focused ultrasound beams simultaneously. M-CUSE uses more elements for each focused push beam and laterally marches the push beams. Both F-CUSE and M-CUSE can generate comb-shaped shear wave fields that have shear wave motion at each imaging pixel location so that a full FOV 2-D shear wave speed map can be reconstructed with only one data acquisition. Homogeneous phantom experiments showed that U-CUSE, F-CUSE, and M-CUSE can all produce smooth shear wave speed maps with accurate shear wave speed estimates. An inclusion phantom experiment showed that all CUSE methods could provide good contrast between the inclusion and background with sharp boundaries while F-CUSE and M-CUSE require shorter push durations to achieve shear wave speed maps with comparable SNR to U-CUSE. A more challenging inclusion phantom experiment with a very stiff and deep inclusion shows that better shear wave penetration could be gained by using F-CUSE and M-CUSE. Finally, a shallow inclusion experiment showed that good preservations of inclusion shapes could be achieved by both U-CUSE and F-CUSE in the near field. Safety measurements showed that all safety parameters are below FDA regulatory limits for all CUSE methods. These promising results suggest that, using various push beams, CUSE is capable of reconstructing a 2-D full FOV shear elasticity map using only one push-detection data acquisition in a wide range of depths for soft tissue elasticity imaging. [ABSTRACT FROM AUTHOR]