Metallic Region Research Articles

Investigation of doping effect on structural, magnetic and magnetoresistance properties by Ru doping in the manganite La0.6Ce0.05Ba0.35Mn1-xRuxO3 (0 ≤ x ≤ 0.2)

During this study, we were conducted to analyze the properties of structural, magnetic, magnetocaloric, electrical resistivity and magnetoresistance (by applying magnetic fields of zero, 2 and 5T) of ceramics La0.6Ce0.05Ba0.35Mn1-xRuxO3 (0 ≤ x ≤ 0.2). These samples are prepared by solid-state reaction. The compounds have simple rhombohedral structure R-3c space group. Arrot curves display that all materials exhibit a second-order magnetic transition from ferromagnetic to paramagnetic order. All the manganites synthesized show a maximum variation in magnetic entropy (|ΔSM|) with values between 6.2 J/kg.K for x = 0 and 3.4 J/kg.K for x = 0.2. In addition, the relative cooling power (RCP) values are very important (160 J/kg for x = 0 to 248 J/kg for x = 0.2). Environment-friendly compounds applied in the domestic refrigeration.The samples La0.6Ce0.05Ba0.35Mn1-xRuxO3 (0 ≤ x ≤ 0.1) show a transition from ferromagnetic-metal (FM) to paramagnetic-insulator (MI). Sample La0.6Ce0.05Ba0.35Mn0.8Ru0.2O3 exhibits semiconductor behavior over the entire temperature range. The metallic conduction is due to the diffusion of electrons (by the phonons and the grain boundaries) while the semiconducting behavior is due to the attendance of polarons. The curves of the compounds (0 ≤ x ≤ 0.1) in the metallic region (T < Tp), have been fitted to the equationρ=αT2+βT5+1(γ+δT1/2). For the high temperature, the semiconductor region was fitted by the small polaron hopping model (ASPH) and by the variable hopping range model (VRH). The electrical resistivity behavior indicates that the substitution of Ru3+ ions weakened the double exchange process and improved the Jahn-Teller effect. Studies of magnetoresistance (MR) under 2 and 5 T magnetic field show two kinds of contribution: one is intrinsic MR and the other is extrinsic MR.

Study on stray current corrosion of buried metal in layered soil

In order to study the effect of layered soil structure on the stray current corrosion of buried metal in urban rail transit, a micro experimental platform for stray current corrosion is established. The research results are obtained by observing the corrosion morphology of buried metal, weighing the mass loss and calculating the corrosion rate. Firstly, the magnitude of stray current in layered soil structure is measured according to the FEM experimental model. Then, with a stray current as the experimental group and without a stray current as the control group studying the effects of the burial depth of metal, soil resistivity and layered soil structure on corrosion respectively. The experimental results show that the degree of stray current corrosion on buried metal in the layered soil structure will be slowed down comparing with the single-layer uniform soil structure, and the degree of stray current corrosion on buried metal will be decreased with the increasing of soil resistivity. Stray current corrosion is mainly concentrated in the anode region of buried metal, and the stray current corrosion of buried metal will be exacerbated with the stray current. In the same soil environment, the closer the buried metal is to the rail, the more serious the corrosion is. Finally, a multiphysics simulation model corresponding to the experiment is established using COMSOL simulation software. After comparison and verification, the simulation results are basically consistent with the experimental results, which prove the accuracy of the experimental results. A theoretical basis for the protection and design of stray current corrosion of buried metal can be provided by the research results.

Dissimilar autogenous TIG joint of Alloy 617 and AISI 304H steel for AUSC application

To reduce costs and improve high-temperature performance in Advanced Ultra Super Critical (AUSC) boilers, it is necessary to weld austenitic steel to Inconel alloy. In this study, the autogenous tungsten inert gas (TIG) welding process was used to join Alloy 617 and an austenitic AISI 304H steel plate of thickness 5 mm. Microstructural analysis showed that the microstructure formation was uneven along the weldments, with columnar and cellular dendrites near the interface while the central area of the weld exhibited a combination of columnar, cellular, and equiaxed dendrites. The use of energy dispersive spectroscopy and electron probe micro-analysis unveiled the presence of an unmixed layer at the interface between the weld and AISI 304H steel. Furthermore, a notable variation in the concentration of alloying elements such as Fe, Cr, Ni, Co, and Mo was observed. Within the weld metal, inter-dendritic areas showed the presence of precipitates rich in Cr, Ti, and Mo. Meanwhile, the heat-affected zone (HAZ) of Alloy 617 exhibited the presence of phases like Cr and Mo-rich M23C6 as well as Mo-rich M6C. Hardness tests showed non-uniform hardness along the weldments, with a hardness of 199 ± 6 HV in the weld metal and 225 ± 4 HV in Alloy 617 HAZ, and 207 ± 7 HV in AISI 304H HAZ. The Mo and Cr segregation in the inter-dendritic spaces led to a decline in the tensile properties of the welded parts and resulted in failure from the region of the weld metal.

A dual attention network for automatic metallic corrosion detection in natural environment

Industrial and residential facilities worldwide are exposed to significant costs and hazards due to metallic corrosion in urban systems. It is necessary to develop a method to automatically detect metallic corrosion precisely. However, existing metallic corrosion detection methods cannot detect either from the realistic natural images or from all kinds of metallic erosion with a high accuracy rate. In this work, a Dual Attention Metallic Corrosion Network (DAMCN) is proposed to automatically detect the metallic corrosion regions with various sizes and shapes from digital images, which are collected in natural environment by unmanned aerial vehicles. By embedding the dual attention modules (i.e., the CBAM blocks) into different locations of the backbone network (i.e. Mask-RCNN), important metallic corrosion features are enhanced either in the feature encoding (i.e. DAMCN-V1) or in the multi-scale feature extraction (i.e. DAMCN-V2). Extensive experiments on three benchmark datasets validate the effectiveness of the proposed method on metallic corrosion detection with varying region size and shape. Comparison results among our DAMCN-V1 and DAMCN-V2 to other existing related methods also demonstrate the superiority of our DAMCN-V1, which achieves the best result while its counter-part (DAMCN-V2) comes to the second.

Identifying the influence of transient thermal tensioning treatments on minimizing distortion and improving fatigue behavior of steel welded

Due to the cost efficiency of welding repairs, the use of transient thermal tensioning (TTT) has begun to be applied to minimize distortion and residual stresses, particularly on thin plates. However, it requires a long preheating time especially on large structures, so that the efficiency of welding process cannot be maximized. Application of TTT treatment using flame heater on TTT treatment which require no preheating time so that welding efficiency can be increased. The aims of this study are to investigate the TTT treatment in reducing distortion, investigate the effect of TTT treatment on tensile strength and hardness, investigate the microstructure and its effect on tensile strength and hardness, investigated the effect of TTT treatment on fatigue crack growth rate. In this research, TTT treatment was performed by flame heating on the both side of weld line integrated in welding process. Temperature in both side plates were controlled and measured using thermocouple. The tests on the weld joints were carried out including distortion measurement, microstructure examination, hardness measurement, tensile test and fatigue test. Results showed that the TTT (60) treatment is the most effective in decreasing the longitudinal distortion which placing the flame heating a 60 mm behind welding torch. It tends to increase the tensile strength of weld metal supported by its increasing hardness. The increase in the percentage of the acicular ferrite phase is linearly related to the tensile strength and hardness of the weld joint. The fatigue behavior could be improved by TTT treatment (60) which is associated with the effect of decreasing residual stress in the weld metal region. This treatment is the best parameter in an effort to increase the welding efficiency of the TTT method

Heavy metals distribution in the bottom sediments of Nizampatnam Bay -Lankevanidibba Coast, East Coast of India

This study determined metal concentrations in the bottom sediment of the Nizampatnam Bay-Lankevanidibba Coast, East Coast of India. Also, the heavy metal pollution load index (PLI), enrichment factor (E.F.), and geo-accumulation index (Igeo) were calculated for sediments from the Nizampatnam Bay-Lankevanidibba Coast on the East Coast of India. It was observed that metal concentrations in river entry sediment were lower. Still, those in river entry water were higher than corresponding values on the Nizampatnam Bay-Lankevanidibba Coast, East Coast of India. Heavy metal concentrations (ppm) in the bottom sediments have been studied to establish their concentration in Fe (ppm). The concentration of heavy metals is measured using ICP-OES instruments. It observes that heavy metal concentrations in the sediments meet the criteria of international marine sediment quality. However, the geoaccumulation index (Igeo), enrichment factor (E.F.), and pollution load index (PLI) values suggested the elevation of a few region's metal concentrations. It continuously monitors the Nizampatnam Bay-Lankavanidibba coast and sediment to minimize the risk to population health and the detrimental impacts on the aquatic ecosystem. The pollutant levels for pre-monsoon and post-monsoon studies are compared in this work.

Influence of Interfacial Voids and Grain Boundary Conductivity on Depletion Kinetics of Sodium Metal Anodes in All-Solid-State Batteries

An electrochemical micro-scale phase-field model is developed to simulate the stripping and plating kinetics of a Na-metal anode in all-solid-state Na-ion batteries. In this model, in addition to the metallic anode and ceramic separator regions, a highly conductive but Na-poor region representing the free space is assumed to simulate the shrinking of the Na-anode during electro-stripping and its growth during plating. For a perfect anode/separator interface, we find that the growth and depletion kinetics are linear. However, the presence of multiple interfacial voids at the anode/separator interface causes deviation from this linear behaviour. Finally, we show that depletion kinetics is also proportional to the ratio of the grain boundary conductivity to that of the grain conductivity (σgb/σg) in the separator phase, either with or without interfacial voids.

Designing selective stripping processes for Al-Cr-N hard coatings on WC-Co cemented carbides

Hard coatings like (Al,Cr)N are commonly used to protect cemented carbide cuttings tools from wear and corrosion. While such coatings increase the tool-lifetime, they also hinder the recycling effort of damaged tools. We report a new recycling strategy for coated cemented carbide tools by applying an interlayer between an arc evaporated Al0.7Cr0.3N coating and the WC-Co substrate. By selectively dissolving this interlayer in a concentrated basic solution, the coating spalls off the substrate, which is left intact. Four bases have been tested as saturated solutions: LiOH, NaOH, KOH, and CsOH, of which NaOH showed the highest reactivity. It was therefore used for subsequent investigations. Three different methods have been tested: (1) a metallic Al-doped interlayer region between substrate and coating can be removed in ▪ at ▪. Depositing an (2) Al0.7Cr0.3 or (3) Al0.9Cr0.1N interlayer leads to a significantly faster removal compared to the first method. Hereby a substrate could be fully de-coated in ▪ at only ▪. The reaction time was also decreased by pre-treating the samples in concentrated HCl, HNO3, or H2SO4 solutions at ▪ for ▪ before subjecting the samples to the NaOH bath. Such treated substrates were fully de-coated in ▪ at only ▪. While HNO3 oxidized the substrates significantly, HCl and H2SO4 caused only negligible substrate damage.

High-temperature mechanical properties and microstructure of welded joint in GH4169/IC10 dissimilar nickel-based superalloys by vacuum electron beam welding

Jointing precipitation-reinforced GH4169 and newly-developed IC10 nickel-based superalloy through vacuum electron beam welding (VEBW) has become increasingly attractive for aeroengine's blade and disc. In this study, solution treatments (GH4169 for 980 °C/1.5 h and IC10 for 1180 °C/2 h) was chosen before welding, and different aging treatments (900 °C, 950 °C, 1000 °C, 1050 °C and 1100 °C for 6 h, respectively) were used for eliminating uneven compositions and structures of the GH4169/IC10 welded joint after VEBW method. Through optical microscopy (OM) observations, there are distinct morphological differences between the base metal (BM) and fusion zone (FZ) regions, with the BMs regions mainly being equiaxed and the FZ region mainly being dendritic grains after VEBW. Through scanning electron microscopy (SEM) observations, the carbides are mainly distributed at grain boundaries in BMs, and Ni–Cr–Nb phases are the dominant second phases in the FZs after VEBW. Moreover, the grain orientation is obviously strong in FZs with adjacent {001} orientation by electron backscattered diffraction (EBSD) characterizations. while grain orientation chiefly of BMs presents anisotropy. After heat treatments, the maximum microhardness of the welded joint was obtained after aging at 900 °C (242–258 HV), and the minimum microhardness was obtained after aging at 1050 °C (183–190 HV). Besides, among the aged welded joints, the 900 °C aged welded joint has the best high-temperature mechanical properties (tensile strength for 559 MPa and elongation for 19.3%) through high-temperature tensile tests, owing to the strengthening effect of numerous γ′ and γ′′ precipitates, nevertheless, 1050 °C aged welded joint has lower tensile strength than solution treated welded joint, mainly resulting from the numbers of δ precipitates isolating matrix. Moreover, combined with transmission electron microscopy (TEM) observations, the carbides, γ′, γ′′, and δ precipitates lead to different high-temperature tensile properties of welded joints, the transformation of γ′′ precipitates and coarsening of γ′ precipitate promote fracture crack initiation and propagation along grain boundaries.

A single gate Si1−xGex dopingless TFET functioned as an effective label-free biosensor

This paper examines the sensitivity of a newly presented heterojunction dopingless tunnel field effect transistor (HJ-DLTFET) biosensor for the label-free detection of biomolecules. The etched nanocavity is introduced in the source metal region for better sensing ability. The dielectric constants (k) of five neutral biomolecules are employed in this paper to test the sensitivity of the proposed biosensor. The electrostatic performance is investigated based on transfer characteristics, energy band, tunneling distance (λ) at source/channel (S/C) interface, drain current (ID) variation for different dielectric constant (k), drain to source voltage (VDS) variation and mole fraction (x) variation respectively. Further, the RF performance analysis includes gate/source capacitance (Cgs), total gate capacitance (Cgg), cut-off frequency (ft), and maximum frequency (fm) analysis. Similarly, sensitivity analysis consists of current sensitivity (SID), current ratio sensitivity (Sratio), average SS sensitivity (SSS), Cgs sensitivity, Cgg sensitivity, ft sensitivity, and fm sensitivity. The investigation is carried out with the variation of neutral biomolecules in terms of various k inside the cavity. Similarly, the impact of charged biomolecules on the sensitivity of the proposed biosensor is investigated. The HJ-DLTFET sensor provides the maximum sensitivity SID of 1.56 × 1010, Sratio of 5.95 × 109, and SSS of 0.80 for Gelatin (k = 12.00) at room temperature using the Silvaco TCAD simulation tool. Combining a low band gap Si0.6Ge0.4 source with a high band gap silicon channel and a high-k (HfO2) improves drain current sensitivity without impacting leakage current.

Phase Transition Field Effect Transistor Observed in an α-(BEDT-TTF)2I3 Single Crystal

The metal–insulator transition induced by the gate electric field in the charge order phase of the α-(BEDT-TTF)2I3 single-crystal field-effect transistor (FET) structure was clearly observed near the phase transition temperature. An abrupt increase in the electrical conductance induced by the applied gate electric field was evident, which corresponds to the partial dissolution of the charge order phase triggered by the gate electric field. The estimated nominal dissolved charge order region (i.e., the gate-induced metallic region) was overestimated in 130–150 K, suggesting additional effects such as Joule heating. On the other hand, in the lower temperature region below 120 K, the corresponding dissolved charge order was several monolayers of BEDT-TTF, suggesting that it is possible to dissolve the charge order phase within the bistable temperature region.

Phase-dependent charge and heat current in thermally biased short Josephson junctions formed at helical edge states

We explore the phase-dependent charge and heat current in short Josephson junctions (JJs) with two normal metal regions attached at opposite ends, formed at helical edge states of two-dimensional topological insulators. For all finite phases, an asymmetry appears around the zero energy in the transmission spectra except for , where n is a half-integer and φ 0 () is the flux quantum. The phase-induced asymmetry plays a key role in inducing charge and heat current through the thermally biased junction. However, the current amplitudes are sensitive to the size of the junction. We show that in the short JJ when subject to a temperature gradient, the charge current shows an odd symmetry in phase. It indicates that the phase-tunable asymmetry around the zero energy is not sufficient to induce a dissipative thermoelectric current in the junction. This is in contrast to the behavior of long JJ, as shown in the literature. The phase-tunable heat currents are obtained with amplitudes set by the phase difference, base temperature, and system size.

Design Rules for Resistors, Capacitors and Inductors Fabricated From Single Layer Y-Ba-Cu-O Thin Films With Focused Helium Ion Beam Irradiation

Yttrium barium copper oxide (YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-<inline-formula><tex-math notation="LaTeX">$\delta$</tex-math></inline-formula></sub> or YBCO) Josephson junctions fabricated using focused helium gas field ion sources show great promise for high transition temperature superconducting electronics. A unique feature of this technology is that it can also be utilized for the fabrication of resistors, capacitors and inductors in the same material and process step. The key to this method is that the electrical resistivity of high critical temperature superconductors is very sensitive to ion irradiation. The ions introduce disorder into the material which causes it to undergo a metal-to-insulator transition. By carefully controlling the position of the beam and ion dose delivered to the material, insulating pathways and reduced critical temperature metallic regions can be fabricated to construct the aforementioned passive components. We have prepared this manuscript to serve as a guide for circuit designers utilizing this process. We discuss the capabilities and limitations of helium ion beam lithographic patterning of YBCO and estimate the practical ranges of the values that can be obtained for resistors, capacitors and inductors in single layer thin films. Estimates are provided for two processes: one with the highest resolution with the smallest beam diameter (0.5 nm) and another based on the highest source current (100 pA) for fastest write time.

Dense gas and star formation in the outer Milky Way

We present maps and spectra of the HCN(1−0) and HCO+(1−0) lines in the extreme outer Galaxy, at galactocentric radii between 14 and 22 kpc, with the 13.7 m Delingha telescope. The nine molecular clouds were selected from a CO/13CO survey of the outer quadrants. The goal is to better understand the structure of molecular clouds in these poorly studied subsolar metallicity regions and the relation with star formation. The lines are all narrow, less than 2 km s−1 at half power, enabling the detection of the HCN hyperfine structure in the stronger sources and allowing us to observationally test hyperfine collision rates. The hyperfine line ratios show that the HCN emission is optically thin with column densities estimated at N(HCN) ≈ 3 × 1012 cm−2. The HCO+ emission is approximately twice as strong as the HCN (taken as the sum of all components), in contrast with the inner Galaxy and nearby galaxies where they are similarly strong. For an abundance ratio χHCN/χHCO+ = 3, this requires a relatively low-density solution for the dense gas, with n(H2) ~ 103−104 cm−3. The 12CO/13CO line ratios are similar to solar neighborhood values, which are roughly 7.5, despite the low 13CO abundance expected at such large radii. The HCO+/CO and HCO+/13CO integrated intensity ratios are also standard at about 1/35 and one-fifth, respectively. The HCN is weak compared to the CO emission, with HCN/CO ~ 1 /70 even after summing all hyperfine components. In low-metallicity galaxies, the HCN deficit is attributed to a low [N/O] abundance ratio; however, in the outer disk clouds, it may also be due to a low-volume density. At the parsec scales observed here, the correlation between star formation, as traced by 24 μm emission as is standard in extragalactic work, and dense gas via the HCN or HCO+ emission is poor, perhaps due to the lack of dynamic range. We find that the lowest dense gas fractions are in the sources at high galactic latitude (b &gt; 2°, h ≳ 300 pc above the plane), possibly due to lower pressure.

Degradation of nuclear fuel debris analog by siderophore-releasing microorganisms

ABSTRACT In damaged Fukushima Daiichi NPP reactors, groundwater microorganisms have continuously seeped into contaminated water. We investigated the effect of a siderophore-releasing microorganism (SB) on fuel debris analogs. Fuel debris analog pellet samples (FDAPS) and powder samples containing CeO2 (an alternative to UO2)-ZrO2 solid solution and metallic iron were formed. FDAPSs were contacted with SB on a membrane filter placed on agar medium for 50 days. With the addition of SB, Fe-containing degradation products were detected by SEM-EDX analyses on FDAPSs, on the filter, and on the agar medium, revealing that some fractions of Fe ions were dissolved and precipitated on FDAPSs, and the rest became detached from FDAPSs and migrated through the filter. The SB-derived degradation differed from those by P. fluorescens and Na-citrate solution. The RBS and ERDA spectrometry analyses identified the degradation products as Fe oxyhydroxides. Although Zr was detected in small amounts in the Fe area by SEM-EDX and by SIMS analyses, the dissolution of Zr may be limited. These results clarify that the presence of SB accelerates the degradation of fuel debris in which Fe metal regions are preferentially degraded, and some fraction of Fe were detached and migrated from the fuel debris analog.

Analysis of the Frictional Performance of AW-5251 Aluminium Alloy Sheets Using the Random Forest Machine Learning Algorithm and Multilayer Perceptron.

This paper is devoted to the determination of the coefficient of friction (COF) in the drawbead region in metal forming processes. As the test material, AW-5251 aluminium alloys sheets fabricated under various hardening conditions (AW-5251-O, AW-5251-H14, AW-5251-H16 and AW-5251H22) were used. The sheets were tested using a drawbead simulator with different countersample roughness and different orientations of the specimens in relation to the sheet rolling direction. A drawbead simulator was designed to model the friction conditions when the sheet metal passed through the drawbead in sheet metal forming. The experimental tests were carried out under conditions of dry friction and lubrication of the sheet metal surfaces with three lubricants: machine oil, hydraulic oil, and engine oil. Based on the results of the experimental tests, the value of the COF was determined. The Random Forest (RF) machine learning algorithm and artificial neural networks (ANNs) were used to identify the parameters affecting the COF. The R statistical package software version 4.1.0 was used for running the RF model and neural network. The relative importance of the inputs was analysed using 12 different activation functions in ANNs and nine different loss functions in the RF. Based on the experimental tests, it was concluded that the COF for samples cut along the sheet rolling direction was greater than for samples cut in the transverse direction. However, the COF's most relevant input was oil viscosity (0.59), followed by the average counter sample roughness Ra (0.30) and the yield stress Rp0.2 and strength coefficient K (0.05 and 0.06, respectively). The hard sigmoid activation function had the poorest R2 (0.25) and nRMSE (0.30). The ideal run was found after training and testing the RF model (R2 = 0.90 ± 0.028). Ra values greater than 1.1 and Rp0.2 values between 105 and 190 resulted in a decreased COF. The COF values dropped to 9-35 for viscosity and 105-190 for Rp0.2, with a gap between 110 and 130 when the oil viscosity was added. The COF was low when the oil viscosity was 9-35, and the Ra was 0.95-1.25. The interaction between K and the other inputs, which produces a relatively limited range of reduced COF values, was the least relevant. The COF was reduced by setting the Rp0.2 between 105 and 190, the Ra between 0.95 and 1.25, and the oil viscosity between 9 and 35.

Formation, Microstructure, and Properties of Dissimilar Welded Joint between CrMnFeCoNi and Fe.

This research explores the welding process of a high-entropy CrMnFeCoNi alloy with iron, unraveling the intricate chemical compositions that materialize in distinct regions of the weld joint. A mid-wave infrared thermal camera was deployed to monitor the cooling sequences during welding. A thorough analysis of the metallographic sample from the weld joint, along with measurements taken using a nano-hardness indenter, provided insights into the hardness and Young's modulus. The element distribution across the weld joint was assessed using a scanning electron microscope equipped with an EDS spectrometer. Advanced techniques such as X-ray diffraction and Mössbauer spectroscopy underscored the prevalence of the martensitic phase within the weld joint, accompanied by the presence of bcc (iron) and fcc phases. In contrast, Young's modulus in the base metal areas displayed typical values for a high-entropy alloy (202 GPa) and iron (204 GPa). The weld joint material displayed substantial chemical heterogeneity, leading to noticeable concentration gradients of individual elements. The higher hardness noted in the weld (up to 420 HV), when compared to the base metal regions (up to 290 HV for CrMnFeCoNi alloy and approximately 150 HV for iron), can be ascribed to the dominance of the martensitic phase. These findings provide valuable insights for scenarios involving diverse welded joints containing high-entropy alloys, contributing to our understanding of materials engineering.

Analysis of Effect of Temperature Variation Preheat on SMAW Welding of Microstructures, and ST60 and SS400 Steel Hardness

Welding is a metal joining process by melting some base and filler metals. SMAW welding (Shielded Metal Arc Welding) is one of the industry's most widely used welding methods. SMAW welding requires preheating (preheating) to reduce residual stress, distortion, and cold cracking in the weld metal. Preheat also can affect the microstructure and hardness of the weld metal. This study aims to analyze variations preheating on SS400 and ST60 steel against micro tests by SMAW welding, namely electric arc welding with covered electrodes. Temperature variation preheating used in SS400 steel was 140°C, 170°C, 300°C and 400°C in ST 60 steel. The results showed that the higher the temperature preheat, the larger the grain size of the microstructure in the parent metal region, the heat-affected area, and the weld metal area. The higher temperature preheat also led to a decrease in violence in the three areas. ST60 steel has a larger microstructure grain size and lower hardness than SS400 steel at all temperature variations preheat.

Differentiation and decreased genetic diversity in field contaminated oysters Crassostrea hongkongensis: Identification of selection signatures

The extent to which chemical contamination affects the population structure and genetic diversity of natural populations remains elusive. Here, we used the whole-genome resequencing and transcriptome to diagnose the effects of long-term exposure to multiple elevated chemical pollutants on the population differentiation and genetic diversity in oysters Crassostrea hongkongensis in a typically polluted Pearl River Estuary (PRE) of Southern China. Population structure revealed an obvious differentiation between the PRE oysters and those collected from a nearby clean Beihai (BH) individuals, while no significant differentiation was observed among individuals collected from the three pollution sites within PRE due to the high gene flow. The decreased genetic diversity in the PRE oysters reflected the long-term effects of chemical pollutants. Selective sweeps between BH and PRE oysters revealed that chemical defensome genes, including glutathione S-transferase, zinc transporter, were responsible for their differentiation, sharing common metabolic process of other pollutants. Combined with the genome-wide association analysis, 25 regions containing 77 genes were identified to be responsible for the direct selection regions of metals. Linkage disequilibrium blocks and haplotypes within these regions provided the biomarkers of permanent effects. Our results provide important insights to the genetic mechanisms underlying the rapid evolution under chemical contamination in marine bivalves.

Hybrid model-based and deep learning-based metal artifact reduction method in dental cone-beam computed tomography

ObjectiveTo present a hybrid approach that incorporates a constrained beam-hardening estimator (CBHE) and deep learning (DL)-based post-refinement for metal artifact reduction in dental cone-beam computed tomography (CBCT). MethodsConstrained beam-hardening estimator (CBHE) is derived from a polychromatic X-ray attenuation model with respect to X-ray transmission length, which calculates associated parameters numerically. Deep-learning-based post-refinement with an artifact disentanglement network (ADN) is performed to mitigate the remaining dark shading regions around a metal. Artifact disentanglement network (ADN) supports an unsupervised learning approach, in which no paired CBCT images are required. The network consists of an encoder that separates artifacts and content and a decoder for the content. Additionally, ADN with data normalization replaces metal regions with values from bone or soft tissue regions. Finally, the metal regions obtained from the CBHE are blended into reconstructed images. The proposed approach is systematically assessed using a dental phantom with two types of metal objects for qualitative and quantitative comparisons. ResultsThe proposed hybrid scheme provides improved image quality in areas surrounding the metal while preserving native structures. ConclusionThis study may significantly improve the detection of areas of interest in many dentomaxillofacial applications.