Backscatter Energy Research Articles

Corrigendum to "A Data-Driven Approach for Estimating Temperature Variations Based on B-mode Ultrasound Images and Changes in Backscattered Energy".

Corrigendum to "A Data-Driven Approach for Estimating Temperature Variations Based on B-mode Ultrasound Images and Changes in Backscattered Energy".

A Novel 3-D Printed Dual-Port Rectenna for Simultaneous Energy Harvesting and Backscattering of a Passively Generated UWB Pulse

A Novel 3-D Printed Dual-Port Rectenna for Simultaneous Energy Harvesting and Backscattering of a Passively Generated UWB Pulse

A Data-Driven Approach for Estimating Temperature Variations Based on B-mode Ultrasound Images and Changes in Backscattered Energy.

Thermal treatments that use ultrasound devices as a tool have as a key point the temperature control to be applied in a specific region of the patient's body. This kind of procedure requires caution because the wrong regulation can either limit the treatment or aggravate an existing injury. Therefore, determining the temperature in a region of interest in real-time is a subject of high interest. Although this is still an open problem, in the field of ultrasound analysis, the use of machine learning as a tool for both imaging and automated diagnostics are application trends. In this work, a data-driven approach is proposed to address the problem of estimating the temperature in regions of a B-mode ultrasound image as a supervised learning problem. The proposal consists in presenting a novel data modeling for the problem that includes information retrieved from conventional B-mode ultrasound images and a parametric image built based on changes in backscattered energy (CBE). Then, we compare the performance of classic models in the literature. The computational results presented that, in a simulated scenario, the proposed approach that a Gradient Boosting model would be able to estimate the temperature with a mean absolute error of around 0.5°C, which is acceptable in practical environments both in physiotherapic treatments and high intensity focused ultrasound (HIFU).

Fatigue life evaluation of metastable austenitic stainless steel AISI 347 based on nondestructive testing methods for different environmental conditions

Due to aging nuclear power plants there is an increasing need for methods to evaluate the integrity of components and structures of nuclear engineering. During power plant operation, nuclear materials are exposed to the effects of temperature, corrosion and cyclic loading. These lead to microstructural changes resulting in material degradation, which can be detected by suitable nondestructive testing (NDT) methods. Fatigue testing setups for ambient temperature, distilled water and 300 °C were designed to represent relevant environmental conditions and instrumented with in-situ measurements of temperature, electric, micromagnetic and electrochemical NDT parameters. Constant amplitude and strain increase tests with specimens of metastable austenitic stainless steel AISI 347 (X6CrNiNb18-10, 1.4550) typically used for pipe components were conducted in total strain control. Data obtained were employed in short-time evaluation procedure StrainLife to generate fatigue life data. To establish an understanding between microstructure evolution and NDT data, scanning electron microscopic methods such as electron backscatter diffraction and energy dispersive X-ray spectroscopy were used. Electrochemical data yields fatigue life results as good as conventionally used parameters like stress and strain. These findings could enable usage of presented parameters for mobile or even online testing systems, since accessibility depending on application case can be much improved.

Remote Versus Local Impacts of Energy Backscatter on the North Atlantic SST Biases in a Global Ocean Model

AbstractThe use of coarse resolution and strong grid‐scale dissipation has prevented global ocean models from simulating the correct kinetic energy level. Recently parameterizing energy backscatter has been proposed to energize the model simulations. Parameterizing backscatter reduces long‐standing North Atlantic sea surface temperature (SST) and associated surface current biases, but the underlying mechanism remains unclear. Here, we apply backscatter in different geographic regions to distinguish the different physical processes at play. We show that an improved Gulf Stream path is due to backscatter acting north of the Grand Banks to maintain a strong deep western boundary current. An improved North Atlantic Current path is due to backscatter acting around the Flemish Cap, with likely an improved nearby topography‐flow interactions. These results suggest that the SST improvement with backscatter is partly due to the resulted strengthening of resolved currents, whereas the role of improved eddy physics requires further research.

Subgrid Parameterizations of Ocean Mesoscale Eddies Based on Germano Decomposition

AbstractOcean models at intermediate resolution (1/4°), which partially resolve mesoscale eddies, can be seen as Large eddy simulations of the primitive equations, in which the effect of unresolved eddies must be parameterized. In this work, we propose new subgrid models that are consistent with the physics of two‐dimensional flows. We analyze subgrid fluxes in barotropic decaying turbulence using Germano (1986, https://doi.org/10.1063/1.865568) decomposition. We show that Leonard and Cross stresses are responsible for the enstrophy dissipation, while the Reynolds stress is responsible for additional kinetic energy (KE) backscatter. We utilize these findings to propose a new model, consisting of three parts, that is compared to a baseline dynamic Smagorinsky model. The three‐component model accurately simulates the spectral transfer of energy and enstrophy and improves the representation of KE spectrum, resolved KE and enstrophy decay in a posteriori experiments. The backscattering component of the new model (Reynolds stress) is implemented both in quasi‐geostrophic and primitive equation ocean models and improves statistical characteristics, such as the vertical profile of eddy KE, meridional overturning circulation and cascades of kinetic and potential energy.

Interpreting the Response of Forest Stock Volume with Dual Polarization SAR Images in Boreal Coniferous Planted Forest in the Non-Growing Season

Polarimetric Synthetic Aperture Radar (PolSAR) images with dual polarization modes have great potential to map forest stock volume (FSV) by excellent penetration capabilities and distinct microwave scattering processes. However, the response of these SAR data to FSV is still uncertain in the non-growing season. To further interpret the response of FSV to different dual polarization SAR images, three types of dual polarization SAR images (GF-3, Sentinel-1, and ALOS-2) were initially acquired in coniferous planted forest in the non-growing season. Then, sensitivity between FSV and all alternative features extracted from each type of SAR image was analyzed to express the response of FSV to dual polarization SAR images with bands and polarization modes in the non-growing season in deciduous (Larch) and evergreen (Chinese pine) forests. Finally, mapped FSV using single and combined dual polarization images were derived by optimal feature sets and four machine learning models, respectively. The combined effects were also analyzed to clarify the difference of bands and polarization modes in deciduous and evergreen forests in the non-growing season. The results demonstrated that the backscattering energy from different sensors is significantly different in Chinese pine, and the difference is gradually reduced in Larch forests. It is also implied that the polarization mode is more important than penetration capability in mapping forest FSV in deciduous forest in the non-growing season. By comparing the accuracy of mapped FSV using single and combined images, combined images have more capability to improve the accuracy and reliability of mapped FSV. Meanwhile, it is confirmed that compensation effects with bands and polarization modes not only have great potential to delay the saturation phenomenon, but also have the capability to reduce errors caused by overestimation.

Rotating Shallow Water Equations with Bottom Drag: Bifurcations and Growth Due to Kinetic Energy Backscatter

Rotating Shallow Water Equations with Bottom Drag: Bifurcations and Growth Due to Kinetic Energy Backscatter

Microstructure characteristics and evolution of the bonding interface between SCC and steam-cured concrete

The microstructure of the bonding interface in CRTS III ballastless track structures is critical to the mechanical properties and durability of high-speed railway structures. The microstructure evolution of the bonding interfacial zone between steam-cured concrete and SCC (self-compacting concrete) is widely studied. This paper investigates the pore structure and phase evolution of the bonding interface zone using backscattered electronic and energy dispersive spectroscopy (BSE + EDS). Based on the nanoindentation test, the microstructure characteristics of the bonding interfacial zone were studied. The results show that the microstructure reveals a gradient change at the bonding interface zone, and the gradient characteristics of the microstructure weaken as curing age increases (especially at 7 days and 56 days). The width of the bonding interface zone is about 15 μm, and the width is more about 20 μm at 1 day. The elastic modulus of C-S-H at the bonding interface zone is low and the C-S-H is mostly LD C-S-H. VMA is beneficial to improve the elastic modulus of C-S-H.

Compact Single-Port Harmonic Transponder for Backscattering Communications and Energy Harvesting Applications

This article proposes a novel architecture for the design of a single-port harmonic transponder. The need for a diplexer is eliminated by adding a quarter-wave and a one-eighth-wave transmission line, combined with the two quarter-wave stubs that are usually needed in a conventional harmonic transponder. The proposed architecture provides isolation between the fundamental and the second harmonic signals and sends them to the desired port, while only introducing extremely low insertion loss. Compared with a single-resonator-based diplexer, it has a much wider bandwidth and a much more compact size than the conventional dual-port design. The proposed diplexing structure can also be used in the design of a compact single-port harmonic transponder with dc power supply capability. With such a design, the harmonic transponder can not only generate harmonics for communication purposes, but also provide power for the operation of communication modules, while being small in size and working with a single antenna. A harmonic tag with a simple modulation module based on this architecture is designed to demonstrate its practical value. The proposed design can work at a low input power level and is very suitable for future low-power Internet of Things (IoT) applications.

Exploring the Impact of Fe-Implantation on the Electrical Characteristics of Al/p-Si Schottky Barrier Diodes

The effects of Fe-implantation on the electrical characteristics of Au/p-Si Schottky barrier diodes (SBDs) were studied using current–voltage (I–V) and capacitance–voltage (C–V) techniques. The Rutherford Backscattering Spectrometry (RBS) and Energy Dispersive Spectroscopy (EDS) results showed that Fe ions are well implanted and present in the Fe-implanted Si material. The acquired results from I–V and C–V analysis showed that the diodes were well fabricated, and Fe-implantation changed the normal diode’s I–V behaviour from typical exponential to ohmic. The ohmic behaviour was described in terms of the defect levels induced by Fe in the middle of the band gap of Si. The conduction mechanism for both forward and reverse currents was presented, and the effect of Fe-implantation on the conduction mechanisms was investigated. The C–V results show that Fe generates a high density of minority carriers in p-Si, which agreed with the increase in reverse current observed in the I–V results. The diode parameters in terms of saturation current, ideality factor, Schottky barrier height, doping density, and space charge region (SCR) width were used to investigate the effect of Fe in p-Si based diode. Owing to the observed changes, which were analogous to those induced by dopants that improve the radiation hardness of silicon, it was safe to say that Fe can also assist in the quest to improve the radiation hardness of silicon using the defect-engineering method.

The Study on Heat Treatment Microstructure and Properties of Extruded Al-Mg-Si-Mn-Cr-Zr Alloy

In order to obtain a high-strength Al-Mg-Si aluminum alloy with a tensile strength of more than 400MPa, a trace amount of Zr is added to the 6082 aluminum alloy to obtain an Al-1.0Mg-1.05Si-0.55Mn-0.15Cr-0.045Zr alloy. The mechanical properties and microstructure of the extruded Al-1.0Mg-1.05Si-0.55Mn-0.15Cr-0.045Zr alloy were studied by tensile performance test, metallography, scanning electron microscope (SEM), transmission electron microscope (TEM), electron backscatter diffraction (EBSD) observation and energy spectrum analysis. The results show that, after 545°C×2h+170°C×8h heat treatment, the alloy has the best mechanical properties. The tensile strength, yield strength and elongation at break reached 423MPa, 402MPa and 14%, respectively. The alloy strengthening mechanism is mainly due to the large number of dispersed needle-like β′ phases, sub-micron α-Al(MnCrFe)Si phases, α-Al(MnFe)Si phases and micron-level α-Al(MnCrFe)Si phases precipitated inside the grains and grain boundaries. The alloy precipitates sub-micron α-Al(MnCrFe)Si phase, α-Al(MnFe)Si phase and micron-level α-Al(MnCrFe)Si phase. After the alloy is treated at 545°C×2h+170°C×8h, a large number of dispersed needle-like β″ precipitations are uniformly precipitated in the inside the grains respectively. These precipitations can improve the strength of the material. The average grain size of the alloy is 7.41μm, and a bimodal grain structure composed of low-angle grain boundaries and high-angle grain boundaries is formed.

Modeling Near-Surface Turbulence in Large-Eddy Simulations of a Tornado: An Application of Thin Boundary Layer Equations

Abstract Unsteadiness and horizontal heterogeneities frequently characterize atmospheric motions, especially within convective storms, which are frequently studied using large-eddy simulations (LES). The models of near-surface turbulence employed by atmospheric LES, however, predominantly assume statistically steady and horizontally homogeneous conditions (known as the equilibrium approach). The primary objective of this work is to investigate the potential consequences of such unrealistic assumptions in simulations of tornadoes. Cloud Model 1 (CM1) LES runs are performed using three approaches to model near-surface turbulence: the “semi-slip” boundary condition (which is the most commonly used equilibrium approach), a recently proposed nonequilibrium approach that accounts for some of the effects of turbulence memory, and a nonequilibrium approach based on thin boundary layer equations (TBLE) originally proposed by the engineering community for smooth-wall boundary layer applications. To be adopted for atmospheric applications, the TBLE approach is modified to account for the surface roughness. The implementation of TBLE into CM1 is evaluated using LES results of an idealized, neutral atmospheric boundary layer. LES runs are then performed for an idealized tornado characterized by rapid evolution, strongly curved air parcel trajectories, and substantial horizontal heterogeneities. The semi-slip boundary condition, by design, always yields a surface shear stress opposite the horizontal wind at the lowest LES grid level. The nonequilibrium approaches of modeling near-surface turbulence allow for a range of surface-shear-stress directions and enhance the resolved turbulence and wind gusts. The TBLE approach even occasionally permits kinetic energy backscatter from unresolved to resolved scales. Significance Statement The traditional approach of modeling the near-surface turbulence is not suitable for a tornado characterized by rapid evolution, strongly curved air parcel trajectories, and substantial horizontal heterogeneities. To understand the influence of statistically unsteady and horizontally heterogeneous near-surface conditions on tornadoes, this work adopts a fairly sophisticated approach from the engineering community and implements it into a widely used atmospheric model with necessary modifications. Compared to the traditional approach, the newly implemented approach produces more turbulent near-surface winds, more flexible surface-drag directions, and stronger wind gusts. These findings suggest a simulated tornado is very sensitive to the modeling approach of near-surface turbulence.

Resource allocation of backscatter communication based on reconfigurable intelligent surface

AbstractIn this article, we propose a double reconfigurable intelligent surface (RIS)‐aided ambient backscatter communication (AmBC) network combined with non‐orthogonal multiple access (NOMA) technology, which not only successfully assists the base station (BS) in connecting with the cell edge user, but also enhances backscatter communication rate, energy efficiency, and spectrum efficiency. In an effort to obtain the highest backscatter communication rate, we design a RIS and BS‐based resource allocation problem which is solved by determining the optimal phase shifts of RISs and the optimal power allocation for signals of NOMA users. We break it down into two smaller challenges in order to discover the best solution. For one thing, we iterate the optimal phase shifts between the two RIS combinations using an alternating optimization technique. For another, the bisection method is used to provide the NOMA user with the ideal power allocation. Finally, the results of the simulation substantiate the viability of the proposed scheme.

High-resolution P- and S-wave reflection studies of an intraplate structure: The Azambuja fault, Portugal

The Azambuja fault is a NNE trending structure located 50 km north of Lisbon, the capital and most populous city of Portugal. The fault has been considered as a possible source for the historical, large earthquakes. Understanding this fault is a priority in seismic hazard evaluation of this region. The fault has a clear morphological signature. Miocene and Pliocene sediments are tilted eastward and cut by steeply dipping mesoscale fault segments, presenting reverse and normal offsets with a net downthrow to the east. Neotectonic studies indicate a Quaternary slip on the fault of 0.05–0.06 mm/year. However, no direct evidence of the Azambuja fault affecting the Pleistocene or Holocene sediments was found so far. Here, we present the findings from high-resolution seismic reflection studies using both P- and S-waves over the Holocene deposits. The detection of small-throw faulting in ductile sediments is a challenging task. We show that multiple signatures, like perturbations in the reflection hyperbolae visible in shot and CMP gathers, interruptions of reflectors in stacked sections, lateral seismic velocity variations obtained by horizon velocity analysis, all at coincident locations, strongly suggest that the activity of the Azambuja fault has affected the Holocene sediments in the study area. The lateral velocity variations are corroborated by wavepath eikonal traveltime tomography and velocity analysis supported by seismic modeling. By means of 2D viscoelastic modeling, we explain the absence of fault-related diffractions and negligible back-scattered energy from the fault. Using data from nearby boreholes, we find that the 15 ka old alluvium cover has indeed been disturbed by the presence of shallow fault strands. Considering the estimated vertical throws and the empirical relationships between fault length, co-seismic rupture and magnitude, a slip rate of 0.07 mm/y, slightly larger than previously thought, is expected for this fault.

A Highly Efficient Method for Designing Bisymmetric P‐B Phase Element Patterns of Coding Metasurfaces

AbstractThe conventional trial‐and‐error method employed in the element pattern design of coding metasurfaces lacks theoretical guidance and requires considerable time and computational resources. To overcome this problem, this paper proposes a highly efficient design method for bisymmetric Pancharatnam‐Berry (P‐B) phase element patterns. First, the equivalent impedances of the element patterns are derived from the expected reflectance and frequency range using the transmission matrix method. Subsequently, the optimal geometric parameters of the element patterns are obtained using the equivalent circuit model. For the same element pattern, the time consumption is reduced by more than 25 times compared with that required for a single full‐wave simulation. The simulation results show that metasurfaces adopting various design element patterns and the same coding sequence exhibit excellent backscattering energy homogenization performance, with a radar‐cross‐section reduction (RCSR) of less than −10 dB in the 9.47–17.57 GHz band. Two types of metasurfaces are fabricated using a meshed pattern, a sodium–calcium glass and a metallic mesh. The measured RCSR is less than −10 dB for a broadband of 7.74 GHz, and the normalized optical transmittance is 85% within 380–2500 nm, which is favorable for optical windows used in aerospace, medical, and precision instrumentation.

Experimental investigation of suspension-type abrasive water jet machining of nitrile rubber for positive displacement motor applications

The lightweight elastomers (such as nitrile rubber) frequently used in the Positive Displacement Motor (PDM) stator assembly are subjected to harsh environmental conditions. These elastomeric components are manufactured by primary casting/shaping methods, followed by secondary manufacturing/machining processes. The production of intricate shapes/sizes in single or batch-size elastomeric components using primary casting methods requires a customized mould to fulfil the requirement of sudden breakdown conditions, which is uneconomical. It necessitates an alternate production method that can satisfy the need for the elastomeric component at the stage of failure. The current research focuses on the possibility of producing nitrile rubber components using a non-conventional machining method, Suspension-type Abrasive Water Jet Machining (AWJM), suitable for batch production with better dimensional stability and versatility in shape/size. This work presents the experimental investigation of Suspension-type AWJM of nitrile rubber specimens (15 mm thick) using a custom-designed Tungsten Carbide (WC) nozzle under room-temperature condition. The top surface of the machined slot is analyzed to determine the mineral composition and abrasive particle embedding through Energy Dispersive Spectroscopy (EDX) and Backscatter Electron (BSE) detector. The Taguchi Orthogonal Array (OA) is employed to study the effect of the process parameters (Water Jet Pressure (WJP), Traverse rate (Vf), and Stand-Off Distance (SOD)) on the performance parameters (Kerf Taper Ratio (KTR), and Material Removal Rate (MRR)). The Analysis of Variance (ANOVA) is applied to check the statistical significance and percentage contribution of each process parameter on the performance of Suspension-type AWJM. The uniformity in the geometry of the machined slot is analyzed by the waviness patterns observed in the profile images of the cut specimen. The analysis of the EDX results reveals the presence of Manganese (Mn) and an increased percentage of Silicon (Si) particles near the top surface of the machined slot. The SOD influences KTR the most, whereas Vf highly influences MRR. It is observed that the waviness pattern is minimal at high WJP experimental runs. The outcome of this research work provides a quick and economical method of producing the PDM bushings instead of the casting/moulding method.

Influence of refractory and platinum group metals on the microstructure and thermo-physical properties of Co-Al-W-based superalloys

The influence of various alloying elements on Co-Al-W based superalloys has been investigated in detail since the discovery of the Co3(Al,W) phase. However, a full picture on the role of the refractory and platinum group elements is still lacking. Accordingly, this work covers the microstructural changes and phase stability in Co9Al9W-X superalloys with 2 at% Zr, Ru, Rh, Pd, Hf, Re, Ir, and Pt. The experimental findings are compared with thermodynamic calculations. Generally, alloying with refractory and platinum group elements preserves γ/γ′ microstructures, but causes the formation of additional intermetallic phases. Electron backscatter diffraction and energy dispersive X-ray spectroscopy reveal that Ru, Ir, and Pt cause discontinuous formation of β (B2) and χ (D019) phases whereas in the Re-containing alloy β and µ (D85) precipitates are present along the grain boundaries. Also unidentified Hf- and Zr-rich phases form in the alloys containing these elements. Additionally, differential scanning calorimetry measurements and scanning electron microscopy analysis indicate an increasing γ′ solvus temperature as well as γ′ volume fraction for most of the refractory and platinum group elements. This can be explained by their γ′/γ partitioning behavior, which has been examined by atom probe tomography.

Optimization Design of MK-GGBS Based Geopolymer Repairing Mortar Based on Response Surface Methodology

There are several influencing factors in the preparation of MK (metakaolin)-GGBS (ground granulated blast furnace slag)-based geopolymer repair mortars, including the MK-GGBS ratio, the alkalinity of the alkali activator solution, the modulus of the alkali activator solution, and the water-to-solid ratio. There are interactions between these factors, such as the different alkaline and modulus requirements of MK and GGBS, the interaction between the alkaline and modulus of the alkali activator solution, and the influence of water throughout the process. The effect of these interactions on the geopolymer repair mortar is not fully understood, making optimization of the MK-GGBS repair mortar ratio difficult. Therefore, in this paper, the response surface methodology (RSM) was used to optimize the preparation of the repair mortar, with GGBS content, SiO2/Na2O molar ratio, Na2O/binder ratio, and water/binder ratio as influencing factors and 1 d compressive strength, 1 d flexural strength, and 1 d bond strength as evaluation indices. Additionally, the repair mortar's overall performance was assessed in terms of setting time, long-term compressive and bond strength, shrinkage, water absorption, and efflorescence. The results show that RSM was successful in establishing a relationship between the repair mortar's properties and the factors. The recommended values of the GGBS content, Na2O/binder ratio, SiO2/Na2O molar ratio, and water/binder ratio are 60%, 10.1%, 1.19, and 0.41, respectively. The optimized mortar meets the standard's requirements for set time, water absorption, shrinkage values, and mechanical strength, with minimal visual efflorescence. The back-scattered electron (BSE) images and energy dispersive spectroscopy (EDS) analysis show that the geopolymer and cement have good interfacial adhesion, and a denser interfacial transition zone exists in the optimized proportion.

316L stainless steel repaired layers by weld surfacing and laser cladding on a 27SiMn steel: A comparative study of microstructures, corrosion, hardness and wear performances

In this study, 316L stainless steel repaired layers were fabricated on a 27SiMn steel substrate using weld surfacing and laser cladding, respectively. The microstructures of repaired layers were subjected to dedicated characterizations using X-ray diffraction, electron backscatter diffraction and energy dispersive spectrometry, with their surface properties (corrosion and wear performances) measured and correlated with the revealed microstructure features. Both the weld-surfacing and the laser-cladding repaired layers (RLs) are found to be mainly comprised of columnar-grained γ-Fe phase, with their average grain widths measured as 17.0 ± 20 μm and 15.3 ± 13.7 μm, respectively. Between their RLs and substrates, an unreported transition layer (∼50 μm in thickness) jointly composed of γ-Fe and α-Fe is identified. After surface property tests, the RL fabricated by the laser cladding shows superior corrosion and wear resistance to that of the weld surfacing. Comprehensive analyses based on their microstructure features suggest that the better performance of the laser-cladding RL can be ascribed to the laser-induced ultrafast cooling that allows denser and finer grain structures to be produced.