Numerical analysis of ultrasonic multiple scattering for fine dust number density estimation

In this study, a method is presented for estimating the number density of fine dust particles (the number of particles per unit area) through numerical simulations of multiply scattered ultrasonic wavefields. The theoretical background of the multiple scattering of ultrasonic waves under different regimes is introduced. A series of numerical simulations were performed to generate multiply scattered ultrasonic wavefield data. The generated datasets are subsequently processed using an ultrasound data processing approach to estimate the number density of fine dust particles in the air based on the independent scattering approximation theory. The data processing results demonstrate that the proposed approach can estimate the number density of fine dust particles with an average error of 43.4% in the frequency band 1-10 MHz (wavenumber × particle radius ≤ 1) at a particle volume fraction of 1%. Several other factors that affect the accuracy of the number density estimation are also presented

Experimental analysis of ultrasonic multiple scattering attenuation through the air with fine dust

In this study, we experimentally evaluated the application of multiple scattering theory for measuring ultrasonic attenuation. Based on the independent approximation theory, the method adopted for calculating the attenuation of coherent waves through air with fine dust is discussed. To obtain a scattering wavefield, a unique ultrasonic scattering hardware was developed, and signal processing schemes were suggested. Four cases of standard particle doses (0, 0.004, 0.008, and 0.012 g) were investigated inside a chamber. The results obtained from the experiments demonstrate that the proposed signal processing approach successfully calculates the scattering attenuation, which correlates well with the applied doses of fine dust. In addition, we discuss the irregular shape and composition of fine dust relative to the scattering cross-section

Concrete delamination depth estimation using a noncontact mems ultrasonic sensor array and an optimization approach

In this study, we present a method to estimate the depth of near-surface shallow delamination in concrete using a noncontact micro-electromechanical system (MEMS) ultrasonic sensor array and an optimization-based data processing approach. The proposed approach updates the bulk wave velocities of the tested concrete element by solving an optimization problem using reference ultrasonic scanning data collected from a full-depth concrete region. Subsequently, the depth of concrete delamination is estimated by solving a separate optimization problem. Numerical simulations and laboratory experiments were conducted to evaluate the performance of the proposed ultrasonic data processing approach. The results demonstrated that the depth of shallow delamination in concrete structures could be accurately estimated

Numerical Computation on the Generation of CH3 and H Radicals by the Thermal Plasma Decomposition of Hydrocarbons

A two-dimensional numerical analysis on the thermal decomposition of methane (CH4) by Ar/H2 thermal plasmas has been carried out using a FLUENT code to nd out the effects of thermal plasma fields on the production rates of CH3 and H radicals during the CH4 decomposition process in a dc arc-jet diamond CVD. In the numerical analysis, the partial di erential equations describing conservations of mass, momentum, and energy as well as mass of individual chemical species are taken into account along with the K-epsilon turbulence model. The numerical calculations are performed in the following consecutive procedure. In the first step, the thermal plasma fields inside a reaction chamber are calculated from the inlet boundary conditions without considering chemical reactions. Uniform profiles of the plasma temperature and velocity at the torch exit are assumed as the inlet boundary conditions in this step. Next in the second calculation step, the chemical kinetic equations, involving 13 species and 25 reactions, are solved in the environment of the calculated two-dimensional plasma fields to give the concentration fields of all chemical species generated in the CH4 decomposition process. The calculated results show that the developed plasma elds inside the reaction chamber strongly depend on the reaction chamber geometry, and significantly affect the concentration fields and generation rates of the decomposed radicals, such as CH3 and H.Supported by the Korea Institute of Science and Technology Evaluation and Planning (KISTEP) in Kore

Bioluminescence-Activated Deep-Tissue Photodynamic Therapy of Cancer

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Experimental Analysis of Ultrasonic Multiple Scattering Attenuation through the Air with Fine Dust

In this study, we experimentally evaluated the application of multiple scattering theory for measuring ultrasonic attenuation. Based on the independent approximation theory, the method adopted for calculating the attenuation of coherent waves through air with fine dust is discussed. To obtain a scattering wavefield, a unique ultrasonic scattering hardware was developed, and signal processing schemes were suggested. Four cases of standard particle doses (0, 0.004, 0.008, and 0.012 g) were investigated inside a chamber. The results obtained from the experiments demonstrate that the proposed signal processing approach successfully calculates the scattering attenuation, which correlates well with the applied doses of fine dust. In addition, we discuss the irregular shape and composition of fine dust relative to the scattering cross-section

Concrete Delamination Depth Estimation Using a Noncontact MEMS Ultrasonic Sensor Array and an Optimization Approach

In this study, we present a method to estimate the depth of near-surface shallow delamination in concrete using a noncontact micro-electromechanical system (MEMS) ultrasonic sensor array and an optimization-based data processing approach. The proposed approach updates the bulk wave velocities of the tested concrete element by solving an optimization problem using reference ultrasonic scanning data collected from a full-depth concrete region. Subsequently, the depth of concrete delamination is estimated by solving a separate optimization problem. Numerical simulations and laboratory experiments were conducted to evaluate the performance of the proposed ultrasonic data processing approach. The results demonstrated that the depth of shallow delamination in concrete structures could be accurately estimated

Application of a Wireless and Contactless Ultrasonic System to Evaluate Optimal Sawcut Time for Concrete Pavements

A recently developed contactless ultrasonic testing scheme is applied to define the optimal saw-cutting time for concrete pavement. The ultrasonic system is improved using wireless data transfer for field applications, and the signal processing and data analysis are proposed to evaluate the modulus of elasticity of early-age concrete. Numerical simulation of leaky Rayleigh wave in joint-half space including air and concrete is performed to demonstrate the proposed data analysis procedure. The hardware and algorithms developed for the ultrasonic system are experimentally validated with a comparison of saw-cutting procedures. In addition, conventional methods for the characterization of early-age concrete, including pin penetration and maturity methods, are applied. The results demonstrated that the developed wireless system presents identical results to the wired system, and the initiation time of leaky Rayleigh wave possibly represents 5% of raveling damage compared to the optimal saw cutting. Further data analysis implies that saw-cutting would be optimally performed at approximately 11.5 GPa elastic modulus of concrete obtained by the wireless and contactless ultrasonic system

Pressure-dependent heat transfer at multilayer graphene and gas interface

We report the pressure dependent heat transfer at a multilayer graphene and gas interface. We find the resistance of a heated graphene device is changed due to convective heat transfer between a multilayer graphene and gas interface in gaseous environments. The pressure dependent convective heat transfer also shows differentiability for the gas species. Our findings suggest that such graphene based electrothermal microelectronics can be used for Pirani gauges and gas sensors. © 2016 Elsevier B.V.1111sciescopuskc

Soft Coulomb gap and asymmetric scaling towards metal-insulator quantum criticality in multilayer MoS2

Quantum localization-delocalization of carriers are well described by either carrier-carrier interaction or disorder. When both effects come into play, however, a comprehensive understanding is not well established mainly due to complexity and sparse experimental data. Recently developed two-dimensional layered materials are ideal in describing such mesoscopic critical phenomena as they have both strong interactions and disorder. The transport in the insulating phase is well described by the soft Coulomb gap picture, which demonstrates the contribution of both interactions and disorder. Using this picture, we demonstrate the critical power law behavior of the localization length, supporting quantum criticality. We observe asymmetric critical exponents around the metal-insulator transition through temperature scaling analysis, which originates from poor screening in insulating regime and conversely strong screening in metallic regime due to free carriers. The effect of asymmetric scaling behavior is weakened in monolayer MoS2 due to a dominating disorder. © 2018 The Author(s