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The detection of minerals (mines) or rocks would have been extremely difficult without the expansion of the Sound Navigation Ranging methodology, which uses specific parameters to determine if a barrier or a surface is a mine or rock. Hence, this proposed work is concerned with the progression of distinctive among metal cylinder which is named as mines and cylindrical shape material which is named as rocks using deep learning based algorithms. Moreover, this work introduced novel technique as Rock or mine Detection Neural Network for performing rock/mine prediction and classification in underwater acoustics. The proposed RDNN method outperforms the outcomes by attaining high accuracy as 92.85% mean accuracy that makes better model performance.

Modified split-ring resonators (SRR) are used develop a high gain UWB antenna for microwave imaging applications. This paper analyzes two different ground designs for the proposed patch radiator with modified SRR; defected ground structure and the second one is rectangular slotted ground. Two SRRs are placed on the circular radiator patch element, each in the shape of alphabet letters ‘S’ and ‘V’. The results of the first design with DGS demonstrate that the reflection coefficient is well below −10 dB in the frequency range from 1.9 GHZ −11.9 GHz with the fractional bandwidth of 110%. Further modification in the resonant modes of UWB is obtained by introducing single rectangular slot on the ground plane. This helps in eliminating the lower band from 1.9 GHz to 6 GHz. This band rejection helps in alleviating the interferences caused by other unlicensed wireless applications lying in sub 6GHZ band.

The most important variables to consider in the design of antennas for RFED applications and effective communications are low cost, low profile, and reduced size. The dipole antenna, often known as a dipole aerial, is the most basic and widely used type of antenna. Among other antennas, this is one of the most straightforward antenna layouts. It may be achieved by applying a sinusoidal voltage differential between two thin metallic rods. The dipole antenna is a particularly important type of RF antenna that is frequently used for radio transmission and reception. For many types of antennas, this antenna can be employed as a radiating or driving element. This Dipole antenna may be used in the radio frequency spectrum sections HF, VHF and UHF. The major advantage of a dipole antenna is that it can serve as both a broadcast transmitter and receiver. So, to obtain the most crucial factors, we'll design an antenna in COMSOL Multi Physics and display the results as Radiation patterns.

Recently, reconfigurable intelligent surface (RIS) has attracted continuous attention in wireless communications. Because the normal incidence condition of electromagnetic waves cannot always be satisfied in practical applications, the angular insensitivity in RISs has become an important issue. The angular sensitivity in RISs may lead to the failure of RIS-assisted wireless communication networks that rely on the reciprocity of wireless channels. In this work, an angle-insensitive 3-bit RIS meta-atom is proposed. By introducing metallic vias in the substrate of programmable meta-atoms, the interference induced by multiple reflections in the multilayered structure is restrained, and the decoupling between adjacent meta-atoms makes the metasurface insensitive to the incident angle. Hence the angular insensitivity can be achieved. An RIS is fabricated using the proposed angleinsensitive programmable meta-atom with metallic vias, which is capable of maintaining stable phase and amplitude responses at oblique incidences. Both simulated and measured results show stable angle performance. A maximum of 3150 phase range and eight digital coding states with 450 stable interval are obtained for wide incidence angles from 00 to 600. Finally, numerical simulations and experimental results of anomalous reflections are performed to verify the angular reciprocity of the proposed RIS, which is important in wireless communications.

Background: Propagated sensation along channels occurs because of stimulations during acupuncture therapies and tends to transmit the stimulating signals along the meridians. From the Western medicine aspect, researchers consider the phenomena as neurotransmissions initiated by nerves, and various ions regulate the physiological functions of the nervous systems. Objective: This research investigates the critical characteristics of ions at acupoints and the mechanism of propagated sensation along channels, crossing meridians in traditional Chinese medicine (TCM). Methods: This research first conducts experiments by applying intense pulse light beams, which replace the traditional acupuncture treatments, on designated acupoints of studied human subjects, and employs a thermal infrared imager to monitor the temperature responses, which are induced by post sensation, in adjacent regions of the acupoints. Meanwhile, the research applies a synchrotron radiation technique on adult SD (Sprague Dawley) rats. The study analyzes the output responses with an X-ray Absorption Fine Spectroscopy (XAFS) to investigate the ion distributions in the relevant acupoints, which trigger the propagated sensation crossing meridians. Results: Experimental results demonstrate significant temperature increases simultaneously at the stimulated acupoints and specific other acupoints, whether in the same meridians. Moreover, XAFS experimental results indicate significantly high calcium, potassium, and sulfide ions at the stimulated acupoint regions. On the contrary, the measured chloride ions level at the regions is correspondingly lower. Conclusions: The thermal infrared imager monitoring shows significant temperature variations of crossing-meridian acupoints after implementing the intense pulse light beams on designated acupoints, and it implies the occurring of prolonged sensation along channels using acupuncture therapies. The X-ray absorption spectrum demonstrates significant differences in ion amounts and distributions between the acupoints and non-acupoints, and acupuncture therapies result in ion concentrations in the correlated regions inducing propagated sensation crossing meridians in TCM. Hence, the stimulated acupoints operate as ion reservoirs to provide high-concentration of specific ions to trigger the crossing-meridian post sensation.

Modeling the electromagnetic response of carbon nanotube (CNT) reinforced composites is inherently a three dimensional (3D) multi-scale problem that is challenging to solve in real-time for nondestructive evaluation applications. This article presents a fast and accurate full-wave electromagnetic solver based on a multi-layer dyadic Green’s function approach. In this approach, we account for the effects of the dielectric slab, where the CNTs are embedded, without explicitly discretizing its interfaces. Due to their large aspect ratios, the CNTs are modeled as arbitrary thin wires (ATWs), and the method of moment (MoM) formulation with distributed line impedance is used to solve for their coupled currents. The accuracy of the inhouse solver is validated against commercial method of moment (MoM) and finite element method (FEM) solvers over a broad range of frequencies (from 1 GHz to 10 THz) and for a wide range of dielectric slab properties. Examples of 100nm long vertical and horizontal CNTs embedded in a 1 μm thick lossy dielectric substrate are presented. The in-house solver provides more than 50 ✕ speed up while solving the vertical CNT, and more than 570 ✕ speed up while solving the horizontal CNT than a commercial MoM solver over the GHz to THz frequency range.

In order to address the issue of wireless communication signal blocking in the traditional cavity resonance wireless power transfer (CR WPT), a wall-meshed cavity resonator constructed of the meshed metallic walls is proposed together with an analytical design method. This cavity resonator can not only generate and confine the electromagnetic waves of natural resonant modes inside the cavity resonator, but also support wireless communications with outside. The wall-meshed cavity resonator is analytically designed by the known theoretical equations without time-consuming optimizations and verified by electromagnetic simulations and experiments. The results show that the proposed CR WPT system can achieve simultaneous wireless power transfer in the cavity and wireless communications with outside. The maximum power transfer efficiency is higher than 85%. The power transfer efficiency exceeds 60% within about 70% areas inside the wall-meshed cavity. For wireless communication signals passing through the wall-meshed cavity, the attenuation at 2.1 GHz (4G), 2.45 GHz (Wi-Fi), and 3.5 GHz (5G) is about 6.0 dB, 5.1 dB, and 3.8 dB, respectively. Additionally, the safety performance of the proposed CR WPT system is numerically investigated by the specific absorption rate analysis of a human torso model.

As an increasingly recognized optical interferometric technique for nondestructive testing and evaluation, shearography has attracted extensive interest in various industrial applications. However, it suffers from the ignorance of the whole process of dynamic surface deformation and the difficulty in determining the depth-resolved information of inhomogeneities. In this regard, a novel speckle pattern interferometric modality named photothermal radar shearography is proposed. Unlike the differential mode of conventional shearography, the present work focuses on the dynamic surface displacement field channel technique with more comprehensive understanding of the subsurface structural information. With the utilization of frequency modulated photothermal excitation, the depth-distributed information of subsurface structures and inhomogeneities is encoded into the induced dynamic surface deformation. Using Hilbert transform and least-square method solved by discrete cosine transform, the time-domain interference signal of each pixel from the recorded speckle patterns sequence is demodulated and unwrapped to obtain the transient full-field shearographic phase distribution which indicates the dynamic surface deformation. In the meanwhile, incrementally delayed cross-correlation matched filtering allows for the localization of axial energy distribution to generate depth-selective structural display for tomography. This proposed transient-based interferometric methodology thus enables depth-tomographic profiles and three-dimensional visualization of subsurface anomalies for the first time, which significantly improves the superiority and attractiveness of shearography in providing insight into the status, performance and reliability of industry.

Objectives This study aimed to determine the acoustic characteristics of the external auditory canal (EAC) and predict the real-ear aided response (REAR) using an EAC model that includes the standing wave effect. Methods The EAC transfer function equations were derived by summing the incoming and outgoing waves. First, we investigated the real-ear unaided gain (REUG). Second, seven patients (eight ears) wearing hearing aids (HAs) were enrolled as subjects to examine the REAR. We conducted wideband tympanometry (WBT) to measure the absorbance, the frequency response at 65 dB (65dB-FR) of the HAs, and the measured REAR for an international speech test signal (ISTS) at 65 dB. Results The EAC model that includes the standing-wave effect is considered to be valid from examination of the REUG. A significant correlation was found between the measured and calculated REARs at 900 Hz, 1000 Hz, 2000 Hz, and 3000 Hz in an uncorrelated test. A two-way analysis of variance (ANOVA) found significant differences in the 65dB-FR and the measured REARs at 800, 900, 1000, and 2000 Hz, but this difference disappeared after correction of the calculated acoustic characteristics of the EAC. Conclusions By measuring the WBT characteristics and correcting them with an EAC model, the in-situ REAR can be determined from the HA characteristics in the mid-frequency range. There is a risk of insufficient HA amplification in the mid-frequency range when no real-ear measurements are performed.

This work deals with the sensitivity to the plate roughness of Lamb waves. An experimental study is performed involving an air-coupling transducer system. Signal processing allows us to extract the Lamb waves characteristics: phase velocity and attenuation. Plate surface topographies are obtained by means of an optical surface profiler. The acoustic characteristics and the surface topographies are finally linked.

It is challenging to apply deep learning in professional fields that lack big data support, especially in industrial nondestructive testings (NDT). To solve this problem, one feasible solution is to introduce the concept of NDT physics into a deep neural network to compensate for the network's poor predictive abilities when trained on small datasets. Therefore, we propose a physics-informed deep neural network, named GuwNet, using a unidirectional oblique-focusing (UOF) high-frequency, high-order shear horizontal guided wave electromagnetic acoustic transducer (EMAT) to quantify microcrack defects more accurately. We study the quantification principle of microcrack defects suitable for UOF-EMAT, and propose a network using physical knowledge regarding this theory including the network structure and loss functions design. Compared with traditional nonphysics-informed methods, the length, depth, and direction of the quantification errors are reduced to 0.127 mm, 0.279% dt, and 1.843', respectively, and the average quantification error is reduced by more than 80%

The Third Sonic Boom Prediction Workshop was held on January 4–5, 2020, in conjunction with the AIAA SciTech conference. The workshop had 23 participants who represented 6 different countries and 1...

The accuracy of traffic noise prediction models (TNMs) is impaired by affecting factors and system errors. In addition, the traditional traffic noise source cannot be tested as the sound source is generated in the centreline of the road. To address these limitations, a TNM based on the equivalent sound source at the road shoulder was developed. First, the equivalent traffic flow based on the acoustic-equivalent conversion coefficient was calculated and the traffic noise source intensity model was deduced. The shoulder's sound pressure level (SPL) data were then used to formulate a single-vehicle equivalent SPL model and correct the traffic noise source intensity model. The propagation model was fitted according to the attenuation law that traffic noise strength attenuates gradually from the shoulder to the road outside and fluctuates periodically. The results of a case study showed that the absolute percentage error of the proposed model's prediction was 2·3% compared with the measured value, which was better than the performance of the current model suggested in the Chinese specification. The proposed prediction model provides a friendly and less time-consuming approach for city planners and traffic engineers to conduct freeway traffic noise prediction and assessment.

Focused airborne ultrasound provides various noncontact spatiotemporal pressure patterns on the skin. However, the presentation of static force remains an untouched issue because the static radiation force by ultrasound is too weak for the human hand to perceive. Hence, creatable sensations have been limited to vibrations or some dynamically changing feelings. This study demonstrates that a non-vibratory pressure sensation is presented by low-frequency Lateral Modulation (LM) with a fine spatial step width. LM is a pressure modulation method that moves a single ultrasound focus laterally and repetitively along the skin surface. The produced sensation in this study was not perfectly static, but the vibratory perception contained in the stimulus was significantly suppressed under a condition while maintaining its intense perception. We found the condition was 5 to 15 Hz in the LM frequency with a motion step width of less than 1 mm. In a comparison test in the most vibration-suppressed case, the participants reported 0.21 N as an equivalent force to the LM stimulus, significantly higher than the 0.027 N force physically applied by the ultrasound. The statistical analysis also showed that the step width of the LM had a significant effect on its vibratory sensation but not on the intensity of the evoked pressure sensation.

AIM To determine which acoustic parameters may be associated with vocal fatigue among college professors in Bogota-Colombia. METHOD This was a cross-sectional study including 27 voice samples of college professors. RESULTS A gender analysis showed that mean fundamental frequency increased significantly among men and women who reported vocal fatigue compared with the those without fatigue (138.2Hz vs 122.3Hz for males; and 228.7Hz vs 188.9Hz for females; Mann-Whitney U test P value

This paper presents a bidirectional Thermo-resistive Micro Calorimetric Flow (TMCF) sensor implemented by a 0.18 m CMOS-MEMS technology, while the sensor thickness is thinned to 2.7 m through an in-house developed MEMS fabrication process. For the bidirectional airflow of -6 ~ 6 m/s, the TMCF sensor achieves the highest sensitivity of 453 mV/(m/s), and its highest normalized sensitivity with respect to the signal amplification gain (gain = 250) and the input heating power (1.58 ~ 1.72 mW) is 1150 mV/(m/s)/W. By reducing the heating power to the sub-mW of < 220 W, the TMCF sensor can still give a remarkable sensitivity of 87.4 mV/(m/s). In addition, the developed TMCF sensor has an intrinsic minimum detectable flow velocity (MDFV) of 99 m/s and a response time of 4.8 ms. The performance achieved by this flow sensor enables accurate indoor airflow measurements even when dealing with the extremely low-speed flow (< 0.05 m/s). Furthermore, the high-performance TMCF sensor is applied for remote human motion detection, where different walking speeds and moving patterns of the occupants can be captured. Therefore, this developed CMOS-MEMS sensor will not only be a promising flow sensing node in the HVAC system, but also potentially be used for the non-visible and private occupant counting in buildings/rooms.

With the rapid development of vehicle information systems, liquid crystal displays (LCDs) have been widely used to enhance information experience. A linear vibration motor is usually placed behind the LCD to provide sufficient haptic feedback. A linear vibration motor with a large permanent magnet causes massive flux leakage around the display. As a result, it may cause unpredictable harm to people with implanted medical devices. Therefore, in this paper, a novel magnetic circuit design of a slim-width type linear vibration motor is introduced to reduce the static magnetic flux leakage. The haptic performance of the slim-width type linear vibration motor was analyzed using the electromagnetic-mechanical coupling method. Three types of experimental results were obtained to verify the analysis results. In conclusion, compared to the prototype motor, the slim-width type linear vibration motor proposed in this paper exhibits significant flux leakage reduction of 94.01% and 96.34% at the measuring positions. Furthermore, the slim-width type linear vibration motor exhibits an acceleration similar to that of the prototype motor.

The performance of therapeutic ultrasonic (TUS) devices has a high degree of variability because of the fragility of the equipment (its transducer in particular) and its handling. These facts raise doubts about the effectiveness and safety of treatments employing such devices. Currently there is no simple way to adequately verify the performance of these devices. In our first experiments, we used a thermochromatic test body (typically a cylindrical plate 3.7 cm in diameter and 5.8 mm high) irradiated with therapeutic transducers driven by a standard radiofrequency (RF) generator. Results revealed a linear relationship between the thermal image areas, generated by the transducer's irradiation, and their respective effective radiation areas (ERAs), suggesting a good correlation. With five 3-MHz transducers, our group also observed the linear relationship using commercial TUS RF driving devices. In the present work, we used four 1-MHz transducers with their respective TUS RF driving devices and verified that there is a linear relationship between the thermal images and the ERAs at intensities of 1.0 ± 0.1 and 0.5 ± 0.05 W/cm2. The linear relationship obtained at both intensities confirms the suggestion that these thermochromatic test bodies can be used as the first evaluation of the ERAs and can monitor their changes with use. Moreover, if a previous assessment of the ERA and transducer intensities is performed, it is possible to follow the variation in ERA simply by monitoring the test body thermal stain.

Objectives Acoustic noise emission from MRI scanners is considered a major factor of patient discomfort during routine MRI examinations. We prospectively evaluated the impact of acoustic noise reduction using software implementations in routine clinical MRI on subjective patient experience and image quality. Methods Two-hundred consecutive patients undergoing one of four MRI examinations (brain, lumbar spine, shoulder, and knee) at a single center were prospectively randomized into two groups at a 1 to 1 ratio: standard MRI examination and MRI examination with acoustic noise reduction. After the examination, patients were asked to complete a questionnaire aimed at defining their subjective experience (primary endpoint). Two readers assessed subjective image quality of all patient studies in consensus (secondary endpoint). Nonparametric tests and logistic regression models were used for statistical analysis. Results Hundred-seventy-four patients were included in the final study. Patients in the intervention group felt less discomforted by the acoustic noise (p = 0.01) and reported increased audibility of music through the headphones (p = 0.03). No significant difference in subjective image quality was found. Conclusion Our study indicates that the effects of acoustic noise reduction in routine clinical MRI can be translated into reduced patient discomfort from acoustic noise and improved audibility of music. Acoustic noise reduction thus significantly contributes to increased patient comfort during MRI examinations.

We demonstrate the efficacy of periodic corrugations, fabricated as part of the radar cover to serve the dual purpose of protecting the radar circuitry and maximizing transmission in millimeter-wave automotive radars. A 2-dimensional array of square-base pyramids engraved on the plastic radar cover was optimized to achieve minimum reflection for a wide range of incident angles, ± 40° and across the operating frequency band of 76 to 81 GHz. More importantly, we present an alternative radome texture, namely the inverse-pyramid corrugations that results in improved structural integrity as compared to the pyramidal corrugations. This novel inverse-pyramid radome structure is also much easier to manufacture and achieves similar performance as the more conventional pyramid structure. Both designs are shown to significantly reduce radar cover reflections, which is perhaps the most significant bottleneck in modern millimeter-wave automotive radar sensor performance.

Background: The use of virtual noses to predict the outcome of surgery is of increasing interests, particularly, as detailed and objective pre- and postoperative assessments of nasal airway obstruction (NAO) are difficult to perform. The objective of this article is to validate predictions using virtual noses against their experimentally measured counterpart in rigid 3D-printed models. Methods: Virtual nose models, with and without NAO, were reconstructed from patients' cone beam computed tomography scans, and used to evaluate airflow characteristics through computational fluid dynamics simulations. Prototypes of the reconstructed models were 3D printed and instrumented experimentally for pressure measurements. Results: Correlation between the numerical predictions and experimental measurements was shown. Analysis of the flow field indicated that the NAO in the nasal valve increases significantly the wall pressure, shear stress, and incremental nasal resistance behind the obstruction. Conclusions: Airflow predictions in static virtual noses correlate well with detailed experimental measurements on 3D-printed replicas of patient airways.

Satellites that orbit planets with radiation belts are subjected to experience internal electrostatic discharge (IESD) events as they interact with charged particles. When charge accumulation exceeds the threshold of the dielectric material on the spacecraft, large discharges occur. The discharges generate electromagnetic pulses that couple to the antennas and induce high voltages. Protection from these discharges is of paramount concern for instrument fidelity of the spacecraft. Modeling the spacecraft and simulating these IESD events using a Maxwell's equations solver can describe how IESDs couple to the antennas of the spacecraft and thus provide information on how to properly protect the instruments from these high voltages. In particular, the finite-difference time-domain (FDTD) method offers advantages for this application over other electromagnetic numerical solvers because in a straight-forward manner it can simulate wideband transient pulses and also accurately solve near-field effects. A generalized analysis method is proposed and carried out in which an FDTD model is used to obtain transfer functions for IESD's occurring at hundreds of different locations on the spacecraft, which are then linearly combined to represent a wide variety of possible scenarios.

The Focused Ultrasound Foundation has developed a low-cost, validated, open-source hydrophone scanner for the spatial characterization of ultrasound transducers. Assembly instructions and a MATLAB control graphical user interface are provided such that the device can be easily replicated for less than $1000 in roughly 40 person-hours. The low-cost scanning tank's performance was compared with data collected with a commercial automated scanning tank. Pressure measurements of a focused transducer and a planar transducer had less than a 10% difference between the two scanning systems. Two-dimensional automated scans (20 × 20 mm at 0.25-mm resolution) took the low-cost scanning tank 45 min compared with the commercial system's 30 min. A reproducibility study found that the low-cost scanner made consistent peak negative pressure measurements as reflected by the low coefficient of variation for both focused (1.88%) and planar (0.98%) transducers. The low-cost scanner described here is a viable alternative for ultrasound laboratories needing efficient, accurate characterization of ultrasound transducers.

PURPOSE: This study aims to confirm the usefulness of active acoustic emission (Active AE) for reproducible and non-invasive generation of physical external force which is required for conventional AE. METHODS: Experiment 1: A root dentin-resin adhesive interface was observed. The post space was filled with a dual-cure resin composite core material with and without adhesive. The vibration characteristics of the data obtained from the time-frequency analysis were evaluated. Experiment 2: A crown-abutment tooth adhesive interface was observed. Adhesive resin cement was used for luting the crown and adhesion states in the same specimen over time were analyzed with three measurements: at trial-fitting, immediately after luting, and 2 weeks after luting. Data were subjected to time-frequency analysis and relationships between amplitude (indicating loudness) and frequency (indicating the sound component) were analyzed. RESULTS: Experiment 1: Time-frequency analysis confirmed multiple peak frequencies for each specimen without adhesive and monomodal peak frequency in all specimens using adhesive. Experiment 2: Two weeks after luting, all specimens showed a single major peak except one which showed multiple weak peaks. The three-dimensional visualization of time-frequency analysis revealed one specimen with multiple weak peaks while all others displayed a single, low-amplitude band at 2 weeks after luting. CONCLUSION: The state of the adhesive interface can be evaluated using active AE. This basic technique may prove useful to evaluate changes in the adhesive interface of prostheses over time. ispartof: JOURNAL OF PROSTHODONTIC RESEARCH vol:66 issue:2 pages:236-242 ispartof: location:Japan status: published

This paper reports an experimental study on power consumption of PolyJet 3D printing. Controllable variables studied are location of samples on the build platform and volume of printed samples. The measured output is “Power Efficiency”: electrical power consumed per unit volume (cubic millimeter) of printed samples. Power Efficiency values are determined by dividing the product of consumed wattage and total print time by total volume of samples. Samples of different volumes are placed at different locations on the build platform. The results show that Power Efficiency is higher when samples are arranged along the X axis than when they are arranged along the Y axis.

A differentially fed capsule antenna with a complex input impedance is proposed in this paper. The antenna maintains a circular flat shape with a diameter of 10 mm, and operating at the desired band of the RF chip (2.4 - 2.525 GHz). With the utilization of an inductively coupled fed structure and dual meandered radiators, a -10 dB impedance bandwidth of 10.2% is achieved. In the meantime, the high impedance tunability can be realized by adjusting corresponding structural parameters. The operating mechanisms and parametric studies are explored in detail to investigate the characteristic of the proposed structure. The capsule antenna prototype is fabricated, assembled, and measured according to the practical scenario. And the measured results highly agree with the simulation ones, which indicate that the proposed antenna could be a good candidate for wireless capsule endoscopy applications.

Planar mirrored-coil structures are often used in the field of biomedicine as a sensor to measure physiological signals wirelessly. Although there are many studies on interrogation methodologies, research on the sensor itself remains understudied. In this article, we report an analytical formulation and a data-fitted formula to calculate the resonant frequency for a planar mirrored-coil sensor. Compared to the measured results, our analytical formula and data-fitted formula deviate by 13% and 9% median errors, respectively, which is much more accurate than the conventional one, 23%. It shows that both methods provide a way to quickly evaluate and design a planar mirrored-coil structure with high precision.

Interface recombination is one of the factors limiting the performance of Cu(In,Ga)Se_2 (CIGS). Especially in the absence of band grading at the front and rear surface, interface passivation approaches become important to improve device performance. The integration of an oxide layer as passivation layer at the front surface of the CIGS requires meticulous considerations in order not to impact the further steps of the solar cell production. In this article, a novel approach is reported to try to tackle the problem of interface recombination at the front surface of CIGS without affecting further solar cell production steps. In this approach, an Al_2O_3/HfO_2 multi-stack layer with contact openings is applied. NaCl template patterning with preliminarily selected parameters was used to create a homogeneous pattern of contact opening on the CIGS surface and allow the current flow in the device. After the removal of the NaCl islands, the holes in the multi-stack (openings) were visualized by scanning electron microscopy. In addition, energy-dispersive X-ray spectroscopy (EDS) was performed before and after chemical bath deposition of the buffer layer. The EDS result confirmed that the undesired etching of the Al_2O_3 layer during buffer layer deposition was prevented by using a thin HfO_2 layer. Solar cells were produced by using preliminarily selected parameters for the multi-stack design. As a result, without having a significant negative impact on the solar cell parameters, a device design was achieved which is almost comparable with the reference device. In addition, options for future improvement and development are discussed. European Union's H2020 Research and Innovation Program [715027]

In this paper, we propose and experimentally demonstrate a scheme of deep learning enhanced long-range fast Brillouin optical time-domain analysis (BOTDA). The volumetric data from fast BOTDA is denoised and demodulated by using a deep video denoising network and a deep neural network, respectively. Benefitting from the advanced deep learning algorithms, the sensing range of fast BOTDA is extended to 10 km successfully. In experiment, vibration signal is measured with a sampling rate of 23 Hz, 2 m spatial resolution, and 1.19 MHz accuracy over 10 km single-mode fiber with only 4 averages. Due to the low computational complexity and GPU acceleration, the network takes less than 0.04 s to process 100x21800 data, which is much faster than the conventional algorithms. This method provides the potential for real-time vibration measurement in fast BOTDA with long sensing range.

We present a study on beam coupling in radiating structures that support multiple simultaneous beams. The formation of multiple beams is relevant in modern wireless communication applications when diverse data streams can be sent from a single transmitter to users located in different directions. General expressions are provided that relate the coupling between radiated beams to the associated current distributions on the radiating aperture. When expanding the currents in terms of basis functions, the beam coupling can be also written in terms of coupling contributions due to each pair of basis functions. The analysis is applied to antenna arrays with different levels of mutual coupling between the array elements. More specifically, arrays of resonant elements, characterized by very low mutual coupling, are compared with arrays of connected elements, which are strongly coupled. We show that, even for a very high level of mutual coupling between individual array elements, it is possible to obtain orthogonal beams if the total current distributions associated with the beams are uncoupled.

Transcranial focused ultrasound (tFUS) is a promising non-invasive technique for treating neurological and psychiatric disorders. One of the challenges for tFUS is the disruption of wave propagation through the skull. Consequently, despite the risks associated with exposure to ionizing radiation, computed tomography (CT) is required to estimate the acoustic transmission through the skull. This study aims to generate synthetic CT (sCT) from T1-weighted magnetic resonance imaging (MRI) and investigate its applicability to tFUS acoustic simulation. We trained a 3D conditional generative adversarial network (3D-cGAN) with 15 subjects. We then assessed image quality with 15 test subjects: mean absolute error (MAE) = 85.72± 9.50 HU (head) and 280.25±24.02 HU (skull), dice coefficient similarity (DSC) = 0.88±0.02 (skull). In terms of skull density ratio (SDR) and skull thickness (ST), no significant difference was found between sCT and real CT (rCT). When the acoustic simulation results of rCT and sCT were compared, the intracranial peak acoustic pressure ratio was found to be less than 4%, and the distance between focal points less than 1 mm.

Dual-energy X-ray radiography is an important inspection technology in imaging large cargos for finding illegal materials. A useful aspect of dual-energy X-ray radiography is the possibility of discriminating and identifying materials with different atomic numbers which can be obtained by imaging large cargos at two different X-ray energies (normally above 3 MeV). The performance of both single and dual-energy radiography depends on many factors such as beam energy and filtration, radiation dose, scanned object size, the content of the object, etc. One of the parameters that can affect the quality of the material discrimination is the location of the scanned objects (different heights from the ground). It is due to the fact that the generated X-ray beams from the Linac are angle dependent and therefore, energy spectrums vary at different angles. In this work, our main goal was to find equations for material discrimination curves as a function of height for graphite, aluminum, steel, and lead materials. After obtaining simulated and experimental curves for a range of heights, we searched for best-fitting polynomial equations and finally the best equation for each material was obtained. Our results showed that there is a good agreement between the simulated and experimental curves compared to those obtained from the fitted equations. According to obtained results, material discrimination curves can be obtained for a range of heights using the fitted equations without performing any further simulation and experimental processes. This can be very helpful in reducing calibration time and increasing calibration accuracy in inspection systems.

Four-wheeler automotive vehicle is the basic need of people in today’s life all over the world. But the noise coming from the exhaust system is highly affecting the human health. Among all the noise produce in vehicle, exhaust system noise is maximum. Muffler is one such acoustic filter used for reducing this exhaust noise. Hybrid muffler is one type of muffler which combines the properties of both reactive muffler and dissipative muffler and it operates at wide frequency range. In this study an already existing muffler (Reactive type muffler) used in 91bhp, 6000 RPM four-cylinder petrol engine was optimized to hybrid muffler. Aerodynamic and acoustic performance parameters were the main performance parameter and were determined by CFD analysis and acoustic analysis. The existing reactive muffler of the four-cylinder petrol engine could be replaced by the hybrid muffler. Here the mufflers were designed in ANSYS design modular and analyses were performed in ANSYS Fluent and COMSOL software. CFD analysis was performed for the existing muffler and three other newly designed muffler by considering inlet velocity boundary condition at inlet velocity 40 m/s and 80 m/s. It was observed that increase in pressure drop (aerodynamic performance) in model 4, model 3 and model 2 is around 38%, 33.2% and 29% respectively. Again, from acoustic analysis the transmission loss (TL) in model 4 was observed to be 47 dB whereas in other models it was around 20 dB. Further it was observed that the sound pressure level from model 1 at the exit is around 75–78 dB whereas in model 4 it was observed to be around 45–50 dB at the exit. Hence from both the analysis it is concluded that model 4 which is hybrid type muffler is the most optimized muffler.

This article presents a thermal control design method for a surface acoustic wave (SAW) device. We designed a heat-dissipation structure and packaging scheme to solve three key issues observed in SAW devices using anisotropic crystals as piezoelectric substrates in acoustofluidics (e.g., lithium niobate): SAW chip cracking caused by thermal stress, SAW chip cracking caused by mismatched thermal expansion coefficients of the packaging materials, and enhancement of the structural strength and stability of the SAW chip. This study establishes the physical model of the designed structure and the relationship between the steady-state working temperature and the physical properties of the material. By comparing these physical properties and numerical calculations, we identified nanosilver adhesive as the most effective bonding material between the SAW chip and the heat sink. In addition to designing and fabricating, we also evaluated our SAW devices experimentally. The results not only confirmed that the abovementioned three key problems were solved but also demonstrated the significant enhancement of the stability of the SAW device.

Acoustic Bessel beams are commonly used as ideal sources to study the characteristics for acoustic-vortex (AV) beams, exhibiting prosperous perspectives in contactless object manipulations and acoustic communications. However, accurate Bessel beams are difficult to construct using two-dimensional arrays in practical applications. By integrating active phase control and passive phase modulation to a ring-array of sectorial planar transducers, quasi-Bessel acoustic-vortex (QB-AV) beams of arbitrary order are built by the line-focus of AV fields in the current study. Based on the Snell’s refraction law, a circular saw-tooth lens of phase modulation is designed to converge incident waves toward the beam axis at a same deflection angle. QB-AV beams constructed by the main lobes of the sectorial sources are demonstrated by theoretical derivations, numerical simulations and quality evaluations, while those created by the side lobes are neglected to avoid the pressure fluctuations in the near field. Experimental measurements for AV beams of different orders coincide basically with the simulations, demonstrating that line-focused QB-AV beams can be generated along the beam axis across the pressure peak. With the increase of the topological charge, the peak-pressure of the beam decreases accordingly with a reduced effective axial range. The favorable results prove that, as a special kind of diffraction sources, the adjustable QB-AV beams may enable more important biomedical applications where Bessel beams are necessary, especially for the line-focused manipulation of biological and drug particles.

Materials with well-characterized acoustic properties are of great interest for the development of tissue-mimicking phantoms with designed (micro)vasculature networks. These represent a useful means for controlled in-vitro experiments to validate perfusion imaging methods such as Doppler and contrast-enhanced ultrasound (CEUS) imaging. In this work, acoustic properties of seven tissue-mimicking phantom materials at different concentrations of their compounds and five phantom case materials are characterized and compared at room temperature. The goal of this research is to determine the most suitable phantom and case material for ultrasound perfusion imaging experiments. The measurements show a wide range in speed of sound varying from 1057 to 1616 m/s, acoustic impedance varying from 1.09 to 1.71 × 106 kg/m2s, and attenuation coefficients varying from 0.1 to 22.18 dB/cm at frequencies varying from 1 MHz to 6 MHz for different phantom materials. The nonlinearity parameter B/A varies from 6.1 to 12.3 for most phantom materials. This work also reports the speed of sound, acoustic impedance and attenuation coefficient for case materials. According to our results, polyacrylamide (PAA) and polymethylpentene (TPX) are the optimal materials for phantoms and their cases, respectively. To demonstrate the performance of the optimal materials, we performed power Doppler ultrasound imaging of a perfusable phantom, and CEUS imaging of that phantom and a perfusion system. The obtained results can assist researchers in the selection of the most suited materials for in-vitro studies with ultrasound imaging.

High-amplitude noise could interfere with useful seismic signals, affecting our ability in processing and interpreting seismic data. Thus, attenuating seismic noise is an important task in seismic processing. Total variation (TV) has played an important role in many steps of seismic data processing but always neglected the seismic structural information. Directional TV (DTV), however, considers the structural direction of seismic events but tends to cause the staircasing effect on seismic records based on the first-order formulation. Here, we develop a high-order DTV (HDTV) method for seismic denoising. It considers the local structural direction of the seismic data and calculates the higher order derivatives of seismic images to avoid the staircasing effect. We design several synthetic models that are contaminated by various types of random noise to test the denoising ability. The denoising performance of our new method is compared with the first-order DTV, conventional high-order TV, and TV regularization methods from two aspects, i.e., the signal-to-noise ratio and the effective signal leakage degree. Then, the advantages of the proposed method are further validated via several field seismic data sets.

Two-dimensional (2-D) wireless power transfer (WPT) systems can be controlled by either the directional method or the rotational method. The rotational method refers to the use of omnidirectional transmitter generating rotational flux regardless of the load positions, while the directional method refers to the use of omnidirectional transmitter generating magnetic flux directly toward the power-consuming load directions. This article compares the overall efficiency of the two methods for 2-D WPT systems. Theoretical analysis reveals that the directional WPT can be more efficient than the rotational WPT with either single or multiple loads when the magnetic field vector is controlled within the feasible zones; and the efficiency difference between the two methods are more significant when the dimensions of the receiver coils are smaller. Both simulation and experimental results are consistent in validating the two discoveries. They indicate that the averaged efficiency of the directional method is at least 5% higher than that of the rotational one.

Dust impacts on spacecraft are commonly detected by antenna instruments as transient voltage perturbations. The signal waveform is generated by the interaction between the impact-generated plasma cloud and the elements of the antenna-spacecraft system. A general electrostatic model is presented that includes the two key elements of the interaction, namely the charge recollected from the impact plasma by the spacecraft and the fraction electrons and cations that escape to infinity. The clouds of escaping electrons and cations generate induced signals, and their vastly different escape speeds are responsible for the characteristic shape of the waveforms. The induced signals are modeled numerically for the geometry of the system and the location of the impact. The model employs a Maxwell capacitance matrix to keep track of the mutual interaction between the elements of the system. A new reduced-size model spacecraft is constructed for laboratory measurements using the dust accelerator facility. The model spacecraft is equipped with four antennas: two operating in a monopole mode, and one pair configured as a dipole. Submicron-sized iron dust particles accelerated to > 20 km/s are used for test measurements, where the waveforms of each antenna are recorded. The electrostatic model provides a remarkably good fit to the data using only a handful of physical fitting parameters, such as the escape speeds of electrons and cations. The presented general model provides the framework for analyzing antenna waveforms and is applicable for a range of space missions investigating the distribution of dust particles in relevant environments., Manuscript accepted online by JGR: Space Physics on 13 August 2021

Spectral Doppler ultrasound velocimetry involves systematic analysis of the spectrum of frequencies that constitute the Doppler signal. This chapter presents a general perspective on Doppler signal anlyses and describes the spectral Doppler ultrasound devices commercially available for clinical use. They include continuous-wave (CW) Doppler, pulsed-wave (PW) Doppler and duplex Doppler devices. Within the realm of obstetric usage, the application needs are diverse and require various choices of equipment. For example, fetal Doppler echocardiography requires advanced duplex ultrasound instrumentation, which combines the capabilities of high-resolution two-dimensional imaging with the PW Doppler mode and an acoustic power output appropriate for fetal application. For umbilical arterial hemodynamic assessment, simpler, substantially less expensive CW Doppler equipment with a spectral analyzer may be sufficient. It is essential therefore that one develop a basic understanding of the implementation of Doppler ultrasound technology.

Crack orientation is a vital factor in the behavioral study of fractures, especially the study of crack propagation in structures that are under dynamic or fatigue loading. Indeed, many non-destructive testing (NDT) techniques have been developed recently for the detection of cracks such as the eddy current testing (ECT). However, the crack orientation has not been undertaken into consideration. In this paper, a NDT based on eddy current using 3D finite element modeling, is proposed for the determination of the crack orientation. The idea of this proposed technique benefits from the influences of crack orientation, which can be observed on the components of eddy current and the related magnetic flux density following the x, y axes, for the estimation of the crack angle orientation based on an interpolation criteria. The obtained results through the presented simulation prove the validity of the proposed technique for the detection of crack angle orientation.

Introduction Direction-aware mapping algorithms improve the accuracy of voltage mapping by measuring the maximal voltage amplitude recorded in the direction of wavefront propagation. While beneficial for stationary catheters, its utility for roving catheters collecting electrograms at multiple angles is unknown. Objective To compare the directional dependency of bipolar voltage amplitude between stationary and roving catheters. Methods In 10 swine, a transcaval ablation line with gap was created. The gap was mapped using an array catheter (Optrell™, Biosense Webster). In step 1, the array was kept stationary over the gap, and 4 voltage maps were created during activation of the gap from superior, inferior, septal, and lateral directions. In step 2, 4 additional maps were created, however the catheter was allowed to move with points acquired at multiple angles. In step 3, the gap was re-mapped, however bipoles were computed using a direction-aware mapping algorithm. Results In a stationary catheter position, bipolar voltage distribution was influenced by the direction of activation with maximal differences obtained between orthogonal directions 32% (13-53%). However, roving the catheter produced similar bipolar voltage maps irrespective of the direction of activation 11% (5-18%). A direction-aware mapping algorithm was beneficial for reducing the directional dependency of voltage maps created by stationary catheters but not by roving catheters. Conclusions The directional dependency of bipolar voltage amplitude is greatest when the catheter is stationary. However, when the catheter is allowed to rove and collect electrograms at multiple angles as occurs clinically, the directional dependency of bipolar voltage is minimal. This article is protected by copyright. All rights reserved.

Sex, head and neck posture, and cervical muscle preparation are contributing factors in the severity of head and neck injuries. However, it is unknown how these factors modulate the head kinematics. In this study, twenty-four (16 male and 8 female) participants experienced 50 impulsive forces to their heads with and without an acoustic warning. Female participants demonstrated a 71 ms faster (p = 0.002) muscle activation onset compared to males after warning. The magnitude of muscle activation was not significant between sexes. Females exhibited 21% (p < 0.008) greater peak angular velocity in all force directions and 18% (p < 0.04) greater peak angular acceleration in sagittal plane compared to males. Females exhibited 15% (p = 0.03) greater peak linear acceleration compared to males only in sagittal flexion. Preparation attenuated head kinematics significantly (p < 0.03) in 11 out of 18 investigated head kinematics for both sexes. A warning eliciting a startle response 420 ms prior to the impact resulted in significant attenuation of all measured head kinematics in sagittal extension (p < 0.037). In conclusion, both sex and warning type were significant factors in head kinematics. These data provide insight into the complex relationship of muscle activation and sex, and may help identify innovative strategies to reduce head and neck injury risk in sports.