Reflected Wave Reduction Based on Time-Delay Separation for the Plane Array of Multilayer Acoustic Absorbers

This paper presents a control technique for reducing the reflection of acoustic signals for the plane array of multilayer acoustic absorbers underwater. In order to achieve this, a plane array of multilayer acoustic absorbers is proposed to attenuate low-frequency noise, with each unit consisting of a piezoelectric transducer, two layers of polyvinylidene fluorides and three layers of the acoustic window. Time-delay separation is used to find the incident and reflected acoustic signals to achieve reflected sound reduction. Experimental comparison of the attenuation rate of the reflected acoustic signal when performing passive and active controls is considered to verify the effectiveness of the time-delay separation technique applied plane array absorbers. Experiments on the plane array of smart skin absorbers confirmed that the reduction of reflected acoustic signals makes it suitable for a wide range of underwater applications.

Evidential regression-based blood glucose detection using waveform features

<div>As one of the necessary diabetes control and treatment methods, the photoacoustic blood glucose detection technology has great potential due to its deep detection depth and low interference from stray light. Previous research mainly focused on improving the detection capabilities of hardware systems and ignored the exploration of the physical meaning of the signal itself. We analyzed the characteristics of the signal amplitude decay in the photoacoustic signal and employed the forced damping vibration equation to model the signal waveform. A new waveform feature was constructed to describe the amplitude attenuation rate. Moreover, facing low accuracy of blood glucose prediction in the case of small data, we proposed a stable and effective blood glucose detection combining time-frequency feature and waveform features with evidential regression. Finally, in human tissue and glucose solution experiments, the minimum error is achieved 1.02±0.71 mg/dL and 13.28±10.33 mg/dL, respectively.</div><div><br></div>

Evidential regression-based blood glucose detection using waveform features

<div>As one of the necessary diabetes control and treatment methods, the photoacoustic blood glucose detection technology has great potential due to its deep detection depth and low interference from stray light. Previous research mainly focused on improving the detection capabilities of hardware systems and ignored the exploration of the physical meaning of the signal itself. We analyzed the characteristics of the signal amplitude decay in the photoacoustic signal and employed the forced damping vibration equation to model the signal waveform. A new waveform feature was constructed to describe the amplitude attenuation rate. Moreover, facing low accuracy of blood glucose prediction in the case of small data, we proposed a stable and effective blood glucose detection combining time-frequency feature and waveform features with evidential regression. Finally, in human tissue and glucose solution experiments, the minimum error is achieved 1.02±0.71 mg/dL and 13.28±10.33 mg/dL, respectively.</div><div><br></div>

Potential of Optical Frequency Domain Imaging for Differentiation Between Early and Advanced Coronary Atherosclerosis

Purpose Optical frequency domain imaging (OFDI) is widely used to characterize lipidic-atherosclerotic plaques, shown as signal-poor regions with diffuse borders, in clinical setting. Given that lipid components are common to both fibroatheroma (FA) and pathological intimal thickening (PIT), it is unclear whether OFDI can be used to accurately distinguish between FA and PIT. This study evaluated the differences in OFDI findings between FA and PIT in comparison with histopathology. Methods A total of 631 histological cross-sections from 14 autopsy hearts were analyzed for the comparison between OFDI and histological images. Of those, 190 (30%) sections were diagnosed with PIT and 120 (19%) with FA. All OFDI images were matched with histology and the OFDI signal attenuation rate was calculated from an exponential. The lipid length was measured longitudinally, and the lipid arc was measured with a protractor centered in the center of the lumen. Results There was no significant difference in the OFDI signal attenuation rate between FA and PIT (3.09 ± 1.04 versus 2.79 ± 1.20, p = 0.13). However, the lipid length was significantly longer and the maximum lipid arc was significantly larger in FA than in PIT (7.5 [4.3–10.3] mm versus 4.3 [2.7–5.8] mm, p < 0.0001, and 125 [101–174]° versus 96 [74–131]°, p < 0.0001, respectively). Conclusions OFDI may be capable of discriminating advanced lipid plaques from early stage atherosclerosis based on the longitudinal and circumferential extent of signal-poor region.

Nonlinear dynamic analysis of multiple grooved water-lubricated journal bearings using attenuation rate interpolation method

Purpose The stringent requirements for environmental protection have induced the extensive applications of water-lubricated journal bearings in marine propulsion. The nonlinear dynamic analysis of multiple grooved water-lubricated bearings (MGWJBs) has not been fully covered so far in the literature. This study aims to conduct the nonlinear dynamic analysis of the instability for MGWJBs. Design/methodology/approach An attenuation rate interpolation method is proposed for the determination of the critical instability speed. Based on a structured mesh movement algorithm, the transient hydrodynamic force model of MGWJBs is set up. Furthermore, the parameters’ analysis of nonlinear instability for MGWJBs is conducted. The minimum water film thickness, side leakage, friction torque and power loss of friction are fully analyzed. Findings With the increase of speed, the journal orbits come across the steady state equilibrium motion, sub-harmonic motion and limit circle motion successively. At the limit circle motion stage, the orbits are much larger than that of steady state equilibrium and sub-harmonic motion. The critical instability speed increases when the spiral angle decreases or the groove angle increases. The minimum water film thickness peak is at the rotor speed of 4,000 r/min for the MGWJB with Sa = 0°. As rotor speed increases, the side leakage decreases slightly while the friction torque and the power loss of friction increase gradually. Originality/value Present research provides a beneficial reference for the dynamic mechanism analysis and design of MGWJBs.

A Fluorescence Kinetic-Based Aptasensor Employing Stilbene Isomerization for Detection of Thrombin

It is important to detect thrombin due to its physiological and pathological roles, where rapid and simple analytical approaches are needed. In this study, an aptasensor based on fluorescence attenuation kinetics for the detection of thrombin is presented, which incorporates the features of stilbene and aptamer. We designed and synthesized an aptasensor by one-step coupling of stilbene compound and aptamer, which employed the adaptive binding of the aptamer with thrombin to cause a change in stilbene fluorescence attenuation kinetics. The sensor realized detection of thrombin by monitoring the variation in apparent fluorescence attenuation rate constant (kapp), which could be further used for probing of enzyme–aptamer binding. In comprehensive studies, the developed aptasensor presented satisfactory performance on repeatability, specificity, and regeneration capacity, which realized rapid sensing (10 s) with a limit of detection (LOD) of 0.205 μM. The strategy was successful across seven variants of thrombin aptasensors, with tunable kapp depending on the SITS (4-Acetamido-4′-isothiocyanato-2,2′-stilbenedisulfonic acid disodium salt hydrate) grafting site. Analyte detection mode was demonstrated in diluted serum, requiring no separation or washing steps. The new sensing mode for thrombin detection paves a way for high-throughput kinetic-based sensors for exploiting aptamers targeted at clinically relevant proteins.

Soil exploration using ground penetrating radar

Geophysical methods are extensively utilized in the field of geology and in geotechnical engineering such as seismic, gravitational, magnetic and electromagnetic fields. These methods are used to locate or to understand conditions below the ground surface, and the physical properties of subsurface. GPR also known as Radio Detecting and Ranging is based on the electromagnetic waves. It is a specially designed radar unit for transmitting electromagnetic pulses below the ground instead of air. In GPR the medium is soil which is heterogeneous and has higher attenuation rate than air. This method is used to measure the length, depth or to locate the soil layers and its deposits. GPR is one of the most versatile sensors; it provides high resolution profiles for shallow depth. GPR has been used in diverse fields such as archaeology, non-destructive testing, probing underground caves, detecting landmines, mapping pipes and conduits, investigating the reinforcement and conditions of roads, bridges and airport runways, to name a few. Use of this technique/method is being extensively adopted from recent years because of its properties and vast applications. The main applications of GPR in subsurface mapping are: mapping of subsurface utility structures, detection and mapping of unexploded ordnance and mines, extraction of hazardous waste containers or unexploded ammunitions, maintenance or repair of subsurface structures. This paper presents an understanding of the concept or the need of GPR dedicated to civil engineering applications in general and in the field of geotechnical engineering in particular.

Analysis of the LNAPL Migration Process in the Vadose Zone under Two Different Media Conditions

This study focused on the processes of free infiltration, precipitation displacement, and natural attenuation of the LNAPL under the condition of near-surface leakage. Sandbox experiments were performed to explore the migration characteristics of LNAPL in the vadose zone with two media structures and the influences of the soil interface on the migration of LNAPL. The results indicate that the vertical migration velocity of the LNAPL infiltration front in medium and coarse sand was 1 order of magnitude higher than that in fine sand and that the LNAPL accumulated at the coarse–fine interface, which acted as the capillary barrier. Displacement of precipitation for LNAPL had little relationship with rainfall intensity and was obviously affected by medium particle size, where coarse sand (40.78%) > medium sand (20.5%) > fine sand (10%). The natural attenuation rate of the LNAPL in the vadose zone was related to the water content of the media; the natural attenuation rate of fine sand was higher. This study simulated the process of the LNAPL leakage from the near surface into the layered heterogeneous stratum, improved the understanding of the migration of the LNAPL under different stratum conditions, and can provide support for the treatment of LNAPL leakage events in the actual site.

FDTD analysis of ELF radio wave propagation in the spherical Earth-ionosphere waveguide and its validation based on analytical solutions

The FDTD model of electromagnetic wave propagation in the Earth-ionosphere cavity was developed under assumption of axisymmetric system, solving the reduced Maxwell’s equations in a 2D spherical coordinate system. The model was validated on different conductivity profiles for the electric and magnetic field components for various locations on Earth along the meridian. The characteristic electric and magnetic altitudes, the phase velocity and attenuation rate were calculated. We compared the results of numerical and analytical calculations and found good agreement between them. The undertaken FDTD modeling enables us to analyze the Schumann resonances and the propagation of individual lightning discharges occurring at various distances from the receiver. The developed model is particularly useful when analyzing ELF measurements.