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Propulsion performance produced by laser ablation of polymer made of acrylonitrile butadiene styrene is experimentally investigated using the first, second, and third harmonics of a Nd: YAG laser. A ballistic pendulum is employed to assess the impulse and coupling coefficient for laser propulsion application. Fast photography, target ablation, and optical emission spectroscopy are proposed to analyze the energy coupling characteristic. The impulse and coupling coefficient under different pressures are demonstrated to depend on the target ablation and plasma properties which are relevant to laser wavelength. As the laser wavelength decreases, the crater depth and ablation mass are enhanced. Meanwhile, the plasma plume separates at atmospheric pressure and its length extends continuously in the low-pressure range. As a result, plasma including more ejected particles with higher velocity contributes to obtaining excellent impulse and coupling coefficient. In addition, the decreased electron density and temperature indicate higher collision frequency and photoionization dominate rather than inverse bremsstrahlung absorption at shorter laser wavelengths. This work provides a better understanding of the energy conversion mechanism and a reference for improving propulsion performance. [ABSTRACT FROM AUTHOR]

Ferrohydrodynamic pumps, with their compact design, offer a practical and efficient alternative to traditional pneumatic or mechanical pumps for driving microfluidic channels and fluidic devices, eliminating mechanical vibrations. A novel self‐circulating ferrohydrodynamic system has been developed to remotely control fluid flow within a linear acoustic cavity using a laser‐induced photothermal temperature gradient. This system enables the modulation of fluid flow rates in compact channels through adjustments in a D.C. magnetic field or laser‐induced surface temperature changes. Notably, laser intensity can accelerate, decelerate, or reverse flow rates within the channel, influencing ultrasonic waves propagating through fluidic cavities designed to resonate between 500 kHz and 700 kHz. The dynamic nature of the magnetoactive fluid cavity enhances wave‐matter interactions, particularly in acoustic domains. Laser‐induced flow control allows for precise manipulation of ultrasonic wave characteristics such as frequency, amplitude, mode splitting, phase shifting, and unidirectional transmission. This capability also supports the optical regulation of acoustic energy flow rates by halting or reversing fluid motion within the cavity. These advancements hold significant potential for applications in cavity acoustodynamics and underwater signal processing, promising innovations in remote fluidic control and acoustic modulation technologies. [ABSTRACT FROM AUTHOR]

The principle of the conventional ultrasound test states that the detectable voids cannot be smaller than the acoustic wavelength. However, by using effective medium approximation, the fraction of small voids can be estimated by the variation of the effective density. In this study, a non-contacting ultrasound-based porosity fraction mapping methodology is developed for estimated small voids in coal with long operating wavelength in air. This novel ultrasonic technique based on the mechanical properties of coal offers a rapid scan of the effective density mapping and distribution of void fraction over a large sample area, which overcame the limitation of small voids detection in the conventional ultrasound testing. [ABSTRACT FROM AUTHOR]

In additive manufacturing, modification of the viscosity of softened or molten metal plays a significant role in the development of mechanical properties distribution. Similar to soft polymers, molten or softened metal usually exhibits vastly different viscoelastic properties. During scratching tests, viscoelastic polymers undergo spatiotemporal stress development and relaxation, causing stress ripples to form on their surfaces. It is observed that friction stir-based solid-state manufacturing can yield similar stress ripples on softened aluminum alloys due to the linear motion of the deposition tool. Softened aluminum alloys exhibit viscoelastic and viscoplastic responses similar to polymeric material during the solid-state deposition process. In the final product, residual stress ripples appear on the surface of the metal alloy due to periodic residual stress relaxation, leading to oscillatory behavior from the bulk mechanical properties of the material. The orientation of the in-built stress pattern formed in the bulk of the additively manufactured metal alloy underneath the visually evident onion ring-like surface pattern formation is diametrically in the opposite direction. The experimentally observed results are consistent with analytical calculation and numerical simulations in terms of behaviors. [ABSTRACT FROM AUTHOR]

Due to the multilayer deposition nature of metal additive manufacturing processes, each layer being printed experiences the state of thermokinetic and thermomechanical stress that in turn interfere with the state of thermokinetics and thermomechanical stress of subsequently deposited layers. Especially, this multilayer interference significantly affects the resultant properties of the component fabricated using solid-state additive friction stir deposition due to evolution of asymmetric state of planar stress. Due to the lack of comprehensive and suitable in situ diagnosis technique, the complex interference of inter- and multi-layer stresses during additive friction stir deposition was studied in an integrated approach of numerical simulation of fluidic state and experimental probing of stress influenced ultrasonic elastography. The uni-directional and bi-directional layer deposition configurations adopted during additive friction stir deposition result in the generation of constructive and destructive interference of the interlayer stress and hence, asymmetric and symmetric dynamic elasticity distribution respectively within the subsequent layers. With subsequent deposition of additional layers, the odd and even numbers of deposited layers generate asymmetric and nearly symmetric dynamic elasticity distributions. [ABSTRACT FROM AUTHOR]

An efficient oxygen carrier (OC) is in great demand in the biomass chemical looping gasification (BCLG) process. In the present study, an innovative rare earth oxide doped ferric oxide OC (Fe2O3−REaOb) derived from the Nd‐Fe‐B sintered magnet waste scraps was employed for the BCLG process for hydrogen‐rich syngas production. The critical variables, including the temperature of gasification, the mass ratio of OC/biomass, the mass ratio of steam/biomass, and the cycle performance of the novel OC, were investigated regarding syngas yield and carbon conversion efficiency. Results found that the optimum conditions were achieved at 900°C, with a mass ratio of OC to biomass of 3:1 and a mass ratio of steam to biomass of 0.4, and a syngas yield of 1.19 Nm3/kg with an H2/CO mole ratio of 2.45, and a carbon conversion efficiency of 76.80% was reached. Additionally, a comparison between Fe2O3−REaOb OC, Fe2O3−Al2O3 OC, and Fe2O3−CeO2 OC was also conducted, with Fe2O3−REaOb OC demonstrating a superior performance. The synergistic effects between REaOb and Fe2O3, particularly the generation of perovskite oxide NdFeO3, contributed to the excellent performance of the Fe2O3−REaOb OC during the BCLG process. The outward diffusion of Fe and sintering of the OC reduced the syngas yield and carbon conversion efficiency by about 16.00% and 25.00% over the 20 redox cycles of the BCLG process. In summary, Fe2O3−REaOb can be an efficient and promising OC for hydrogen‐rich syngas production in the BCLG process. [ABSTRACT FROM AUTHOR]

The removal of tar is conducive for improving the energy efficiency of equipment and reducing the damage caused to it. A two-stage continuous feeding apparatus was applied to examine the homogeneous conversion characteristic of biomass pyrolysis tar under the effect of steam. The tar yield could be effectively reduced from 6.68 to 2.30% by increasing steam and feedstock mass ratio (S/F) from 0 to 1.6. Furthermore, given that steam significantly affects phenyl formate (PF) cracking, Gaussian was employed to analyze its reaction mechanism. Rising the temperature from 600 to 1000 °C can improve the pyrolysis rate constant of PF by five to six orders of magnitude, and its primary products are phenol and CO. When PF reacts with H or OH radicals, the most crucial route is these radicals abstract H atom, following by releasing CO from the intermediate products. H radicals can also promote PF craking by combining with C\O atom in oxygen-containing group; among them, H radicals easily bond with the C atom. [ABSTRACT FROM AUTHOR]

Electro-osmotic micromixers (EMMs) are used for manipulating microfluidics because of the advantages on electro-osmosis mechanisms. The intricate interdependence between various fields in the EMM model presents a challenge for traditional numerical methods. In this paper, the flow parameters and electric potential are predicted based on the solute concentration by utilizing the physics-informed neural networks (PINNs) method. The unknown spatiotemporal dependent fields are derived from a deep neural network trained by minimizing the loss function integrating data of scalar field and corresponding governing equations. Moreover, the auto-encoder structure is developed to improve the performance of PINNs in the EMM. The comparisons between the results of auto-encoder PINNs and previous PINNs show a reduction in relative errors for transverse and longitudinal velocities from 83.35% and 84.24% to 9.88% and 12.29%, respectively, in regions with large-gradient velocities. Furthermore, our results demonstrate that the proposed method is robust to noise in the scalar concentration. [ABSTRACT FROM AUTHOR]

Metals are excellent conductors for phonon transportation such as vibration, sound, and heat. Generally, metal sound insulators require multimaterial structure or defects and unimetal sound insulators are challenging. Therefore, a design of a defect‐free sound insulator made by single alloys with multiple friction stir processes (FSPs) is proposed. Periodic friction stir processing can induce superlattice‐like local mechanical properties' modifications. By experimental acoustic characterization, it is observed that FSP can introduce clear acoustic–elastic property contrast on an aluminum plate by the presence of stir zone and heat‐affected zones. In numerical simulations, the signature FSP‐induced property profile is periodically and parallelly arranged on a long aluminum plate. The transmission gap frequencies are present on the frequency spectrum with the sound propagation direction perpendicular to the FSP paths. Disorder offsets on FSP periodicity are further introduced. Anderson localization is found on a resonance frequency, which provides −11 dB sound reduction by an exponential decay. Due to the finite design length, the slight disorder can also enhance sound insulation in the periodic transmission gap frequency. With analysis and comparison with different configurations, the best performance in the models can achieve −30 dB sound insulation in the 350 mm‐long aluminum alloy plate with 14 parallel FSPs. [ABSTRACT FROM AUTHOR]

We have used the OH laser-induced fluorescence (LIF) method to measure the kinetics of the simplest Criegee intermediate (CH2OO) reacting with two abundant amines in the atmosphere: dimethylamine ((CH3)2NH) and trimethylamine ((CH3)3N). Our experiments were conducted under pseudo-first-order approximation conditions. The rate coefficients we report are (2.15 ± 0.28) × 10−11 cm3 molecule−1 s−1 for (CH3)2NH at 298 K and 10 Torr, and (1.56 ± 0.23) × 10−12 cm3 molecule−1 s−1 for (CH3)3N at 298 K and 25 Torr with Ar as the bath gas. Both reactions exhibit a negative temperature dependence. The activation energy and pre-exponential factors derived from the Arrhenius equation were (−2.03 ± 0.26) kcal mol−1 and (6.89 ± 0.90) × 10−13 cm3 molecule−1 s−1 for (CH3)2NH, and (−1.60 ± 0.24) kcal mol−1 and (1.06 ± 0.16) × 10−13 cm3 molecule−1 s−1 for (CH3)3N. We propose that the electronegativity of the atom in the co-reactant attached to the C atom of CH2OO, in addition to the dissociation energy of the fragile covalent bonds with H atoms (H–X bond), plays an important role in the 1,2-insertion reactions. Under certain circumstances, the title reactions can contribute to the sink of amines and Criegee intermediates and to the formation of secondary organic aerosol (SOA). [ABSTRACT FROM AUTHOR]

The dependence of propulsion performance generated by laser ablation of polyvinyl chloride on laser energy and pressure is investigated using Q-switched Nd: YAG laser with the wavelength of 1064 nm. When the pressure is decreased, the impulse and coupling coefficient rise first and then decline. Such a trend is also reflected in the variation of coupling coefficient with laser energy in the whole pressure range. However, the change in impulse with laser energy at atmospheric pressure is not completely consistent with that at low pressure levels. The dynamic behavior and duration of plasma plume are considered to be the factors for the difference in propulsion performance. By capturing the fast exposure images of plume, the separation at atmospheric pressure and severe expansion accompanied by rapid quenching in near vacuum are observed. Moreover, the plasma plume lasts longer time at high pressures. It is ascribed to the higher electron temperature, which promotes background gas to excite and ionize. Since the electron density increases with the improvement of laser energy and pressure, the absorption of electrons to laser energy becomes stronger through the inverse bremsstrahlung mechanism. Accordingly, the shielding effect of plasma is enhanced, causing the weak laser-target interaction. The result is that the crater depth and ablative mass increase with decreasing pressure. This work is important for understanding the energy conversion mechanism and optimizing the laser propulsion performance. [ABSTRACT FROM AUTHOR]

The largemouth bass Micropterus salmoides is a carnivorous fish species that is widely farmed in China using artificial compound feeds. Alterations from its natural diet affect intestinal microbiota structure and growth performance and can reduce disease and stress resistance. In this study, we examined growth performance, immunity, intestinal microflora, and resistance to Aeromonas veronii infections-fed prey fish (PF) and artificial compound feed (ACF). Weight gains in the PF group were 27% significantly (P < 0.05) greater than the ACF group. Antioxidant enzyme activities of superoxide dismutase, catalase, and glutathione peroxidase and mRNA expression of inducible nitric oxide synthase, transforming growth factor β1, and interleukin 10 were also significantly higher than for the ACF group. In contrast, levels of malondialdehyde were lower for the PF group consistent with the antioxidant activities. These results indicated that the commercial artificial compound diet reduced the immunity and anti-stress ability of the fish. Survival in against A. versonii infection were similar although the PF fish resisted the infection to a greater extent and succumbed at a slower rate. The gut microbiomes also differed between the PF and ACF feeding groups and operational taxonomic units were 1105.75 and 971.63, respectively. The high abundance of Verrucomicrobia were associated with weight gain and enhanced immunity for the PF group and were significantly (P < 0.05) higher than that in ACF group. Bacteroidetes abundance was closely related to weight loss in the ACF group. The results of this study suggest that the changes in intestinal microflora structure caused by dietary changes in largemouth bass affected its growth performance and reduce its immune and anti-stress abilities and provide a theoretical basis for the improvement of largemouth bass compound feeds. [ABSTRACT FROM AUTHOR]

Inspired by the electrical insulators made by high‐entropy alloys, this work studies the feasibility of using a 2D high‐entropy phononic crystal (PnC) to achieve Anderson localization within its first transmission band. The entropy of sound increases proportionally with the increase of additional eigenmodes at a certain frequency which decreases the transmitted energy through the structure. 2D disorder in sizes (or) and materials of the scatterers is introduced to achieve that on a perfect periodic PnC designed with metallic scatterers in an ambient water‐based lattice medium. Around the band edge of the first transmission band, Anderson's localization of sound is discovered. At a resonant frequency within a perfect periodic crystal, the introduction of a disorder in the PnC results in an exponential decay of sound wave transmission along the propagation direction due to the entropy generation from acoustic energy. Furthermore, the temperature tunability of the proposed crystal is proposed. A variation of the room temperature to 0 °C leads to the phase transition of water to ice and results in a strong transition of the acoustic localization at resonant frequencies with a 25 dB+ difference. [ABSTRACT FROM AUTHOR]

Dielectric/plasmonic lattice relaxation spectroscopy is theoretically discussed in this work. A lattice relaxation effect generally occurs in nanocrystals, which means that from the bulk phase to the crystal surface, lattice parameters show a gradual shift. Here, lattice relaxation is introduced into finite polarizable point arrays or rod arrays as an adjusting tool, and its effect on lattice resonance extinction spectrum peaks is calculated. DDA (discrete dipole approximation) and FDTD (finite difference time domain) methods are applied. Different from an ideal infinite array, a finite array exhibits a broad, rippled extinction spectral peak. The application of an expanded/contracted lattice relaxation to the finite array can compress the ripple on one shoulder of the peak, as a cost, and the other shoulder of the peak gets more rippled, showing a "ripple transfer" effect. The strategy introduced in this work can contribute to the micro/nano optical measurement, on-chip adjustable optical cavity for OPOs (optical parameter oscillators)/lasers and controlling of fluorescence or hot-electron chemistry. [ABSTRACT FROM AUTHOR]

In this study, the influence of laser energy and pressure on propulsion performance of zinc and acrylonitrile butadiene styrene (ABS) is investigated by impulse measurement, fast exposure images, spectral diagnostics and target ablation. A Q-switched Nd:YAG laser with the wavelength of 1064 nm and pulse width of 6 ns is employed. The impulse and coupling coefficient generated by laser ablation ABS are greater than that of Zn, and they exhibit a similar variation trend with pressure. However, at higher pressure levels, the change in impulse versus laser energy is not completely coincident between Zn and ABS samples. The target property plays a significant role in the generation and propagation of plume related to the plasma parameters such as electron density and temperature. The temporal evolution images indicate that the plasma plume of laser-induced Zn presents a faster decay in comparison with that of ABS, which is ascribed to the fact that the gas temperature of ABS is higher than the electron temperature of Zn plasma in the local thermodynamical equilibrium. Also, the electron density is lower for Zn due to the rapid heat diffusion and higher ablation threshold of metal. It is found that the surface absorption is dominant for metal because the ablated crater of Zn performs larger diameter and shallower depth. On the contrary, the shrinkage in diameter but enhancement in depth of crater is observed from ABS surface, and the ablation mass is larger, suggesting the obvious volume absorption for polymer. The results reveal that the target property can engender an important effect on the energy conversion between laser, target and plasma. [ABSTRACT FROM AUTHOR]

Surface quality of fused silica, particularly surface defect and surface roughness, is a key factor affecting the performance of high‐power laser and short‐wave optical instrument, and so on. Herein, the super smooth surface of fused silica with roughness of sub‐angstrom level and exceedingly few submicron defects was achieved by using ultrafine nano‐CeO2 with primary particle size less than 4 nm, low secondary particle agglomeration strength, and high Ce3+ concentration. Furthermore, CeO2 involve in polishing process in the form of primary particle was certified by experiment. Moreover, the cause for the generation of submicron defects on fused silica surface was investigated for the first time from the perspective of secondary particle agglomeration strength of CeO2. The concentration of Ce3+ in CeO2 was characterized by the redshift of the band‐gap energy, and the analysis of material removal rate (MRR) and contact angle of polished fused silica shows that Ce3+ enhances MRR through increasing the silanol group on fused silica. [ABSTRACT FROM AUTHOR]

Background: Methanol, a promising non-food fermentation substrate, has gained increasing interest as an alternative feedstock to sugars for the bio-based production of value-added chemicals. Butyribacterium methylotrophicum, one of methylotrophic-acetogenic bacterium, is a promising host to assimilate methanol coupled with CO2 fixation for the production of organic acids, such as butyric acid. Although the methanol utilization pathway has been identified in B. methylotrophicum, little knowledge was currently known about its regulatory targets, limiting the rational engineering to improve methanol utilization. Results: In this study, we found that methanol assimilation of B. methylotrophicum could be significantly improved when using corn steep liquor (CSL) as the co-substrate. The further investigation revealed that high level of lysine was responsible for enhanced methanol utilization. Through the transcriptome analysis, we proposed a potential mechanism by which lysine confers improved methylotrophy via modulating NikABCDE and FhuBCD transporters, both of which are involved in the uptake of cofactors essential for enzymes of methanol assimilation. The improved methylotrophy was also confirmed by overexpressing NikABCDE or FhuBCD operon. Finally, the de novo synthetic pathway of lysine was further engineered and the methanol utilization and butyric acid production of B. methylotrophicum were improved by 63.2% and 79.7%, respectively. After an optimization of cultivation medium, 3.69 g/L of butyric acid was finally achieved from methanol with a yield of 76.3%, the highest level reported to date. Conclusion: This study revealed a novel mechanism to regulate methanol assimilation by lysine in B. methylotrophicum and engineered it to improve methanol bioconversion to butyric acid, culminating in the synthesis of the highest butyric acid titer reported so far in B. methylotrophicum. What's more, our work represents a further advancement in the engineering of methylotrophic-acetogenic bacterium to improve C1-compound utilization. [ABSTRACT FROM AUTHOR]

In this work, we report a non-destructive and non-contacting ultrasound system with a novel air-coupled transducer to continuously monitor the drying process of prickly pear (nopal) pads in a lab environment. Compared with conventional imaging and spectroscopic methods or electrical-based approaches, ultrasound-based methods are non-invasive, cost-effective, and suitable for large volume evaluation. The time-dependent elastic modulus of the cactus can be obtained and monitored by using our proposed ultrasonic method. The evaluated elastic modulus behavior shows a good agreement with the destructive testing results in the existing literature. With further development, the proposed method can be used for in vivo plant health monitoring. [ABSTRACT FROM AUTHOR]

Current work explored solid-state additive manufacturing of AZ31B-Mg alloy using additive friction stir deposition. Samples with relative densities ≥ 99.4% were additively produced. Spatial and temporal evolution of temperature during additive friction stir deposition was predicted using multi-layer computational process model. Microstructural evolution in the additively fabricated samples was examined using electron back scatter diffraction and high-resolution transmission electron microscopy. Mechanical properties of the additive samples were evaluated by non-destructive effective bulk modulus elastography and destructive uni-axial tensile testing. Additively produced samples experienced evolution of predominantly basal texture on the top surface and a marginal increase in the grain size compared to feed stock. Transmission electron microscopy shed light on fine scale precipitation of Mg 17 Al 12 within feed stock and additive samples. The fraction of Mg 17 Al 12 reduced in the additively produced samples compared to feed stock. The bulk dynamic modulus of the additive samples was slightly lower than the feed stock. There was a ∼ 30 MPa reduction in 0.2% proof stress and a 10–30 MPa reduction in ultimate tensile strength for the additively produced samples compared to feed stock. The elongation of the additive samples was 4–10% lower than feed stock. Such a property response for additive friction stir deposited AZ31B-Mg alloy was realized through distinct thermokinetics driven multi-scale microstructure evolution. [ABSTRACT FROM AUTHOR]

Largemouth bass is an important commercially farmed fish in China, but the rapid expansion of its breeding has resulted in increased incidence of diseases caused by bacteria, viruses and parasites. In this study, moribund largemouth bass containing ulcer foci on body surfaces indicated the most likely pathogens were iridovirus and rhabdovirus members and this was confirmed using a combination of immunohistochemistry, cell culture, electron microscopy and conserved gene sequence analysis. We identified that these fish had been co-infected with these viruses. We observed bullet-shaped virions (100–140 nm long and 50–100 nm in diameter) along with hexagonal virions with 140 nm diameters in cell culture inoculated with tissue homogenates. The viruses were plaque purified and a comparison of the highly conserved regions of the genome of these viruses indicated that they are most similar to largemouth bass virus (LMBV) and hybrid snakehead rhabdovirus (HSHRV), respectively. Regression infection experiments indicated fish mortalities for LMBV-FS2021 and HSHRV-MS2021 were 86.7 and 11.1%, respectively. While co-infection resulted in 93.3% mortality that was significantly (p < 0.05) higher than the single infections even though the viral loads differed by >100-fold. Overall, we simultaneously isolated and identified LMBV and a HSHRV-like virus from diseased largemouth bass, and our results can provide novel ideas for the prevention and treatment of combined virus infection especially in largemouth bass. [ABSTRACT FROM AUTHOR]

We designed and characterized a 3D printed acoustic shear wave polarization rotator (PR) based on the specific nature of the fused-deposition-modeling printing process. The principle of the PR is based on rotation of the polarization axis of a shear wave due to the gradual change in orientation of the axis of anisotropy along the direction of wave propagation of a printed layered structure. The component of the shear modulus parallel to the infilled lines within each layer is significantly higher than that in the perpendicular direction. As the PR was printing, a small angle between neighboring layers was introduced, resulting in a 3D helicoidal pattern of distribution of the axes of anisotropy. The polarization of the propagating shear wave follows this pattern leading to the rotation of the polarization axis by a desirable angle. The total rotation angle can be tuned by the number of printed layers. The fabricated 90 ° rotators demonstrate high performance that can be improved by changing the infill fraction settings. [ABSTRACT FROM AUTHOR]

Largemouth bass ranavirus disease (LMBVD) caused by largemouth bass ranavirus (LMBV) has resulted in severe economic losses in the largemouth bass (Micropterus salmoides) farming industry in China. Early and accurate diagnosis is the key measure for the prevention and control of LMBVD. In this study, a quantitative polymerase chain reaction (qPCR) and a real‐time recombinase‐aided amplification (real‐time RAA) assay were established for the detection of LMBV. The sensitivity and specificity of these two methods, and the efficacy for detection of LMBV from clinical samples were also evaluated. Results showed that the real‐time RAA reaction was completed in <30 min at 39℃ with a detection limit of 58.3 copies, while qPCR reaction required 60 min with a detection limit of 5.8 copies. Both methods were specific for LMBV, where no cross‐reactions observed with the other tested fish pathogens. Comparing the amplification results of both assays to the results obtained by virus isolation using 53 clinical tissue samples, results showed that the clinical sensitivity of real‐time RAA and qPCR were 93.75% and 100% respectively, and the clinical specificity of both were 100%. Our results showed that qPCR is more suitable for quantitative analysis and accurate detection of LMBV in the laboratory, while real‐time RAA is more suitable as a point‐of‐care diagnostic tool for on‐site detection and screening of LMBV under farm conditions and in poorly equipped laboratories. [ABSTRACT FROM AUTHOR]

Monitoring tool degradation during manufacturing can ensure product accuracy and reliability. However, due to variations in degradation conditions and complexity in signal analysis, effective and broadly applicable monitoring is still challenging to achieve. Herein, a novel monitoring method using ultrasound signals augmented with a numerically trained machine learning technique is reported to monitor the wear condition of friction stir welding and processing tools. Ultrasonic signals travel axially inside the tools, and even minor tool wear will change the time and amplitude of the reflected signal. An artificial intelligence (AI) algorithm is selected as a suitable referee to identify the small variations in the tool conditions based on the reflected ultrasound signals. To properly train the AI referee, a human‐error‐free data bank using numerical simulation is generated. The simulation models the experimental conditions with high fidelity and can provide comparable ultrasound signals. As a result, the trained AI model can recognize the tool wear from real experiments with subwavelength accuracy prediction of the worn amount on the tool pins. [ABSTRACT FROM AUTHOR]

The square lattice phononic crystal (PnC) has been used extensively to demonstrate metamaterial effects. Here, positive and negative refraction and reflection are observed simultaneously due to the presence of Umklapp scattering of sound at the surface of PnC and square-like equifrequency contours (EFCs). It is found that a shift in the EFC of the third transmission band away from the center of the Brillouin zone results in an effectively inverted EFC. The overlap of the EFC of the second and third band produce quasimomentum-matching conditions that lead to multi-refringence phenomena from a single incident beam without the introduction of defects into the lattice. Additionally, the coupling of a near-normal incident wave to a propagating almost perpendicular Bloch mode is shown to lead to strong right-angle redirection and collimation of the incident acoustic beam. Each effect is demonstrated both numerically and experimentally for scattering of ultrasound at a 10-period PnC slab in water environment. [ABSTRACT FROM AUTHOR]

The co-pyrolysis tar formed from microcrystalline cellulose (MCC) and polyethylene (PE) was used to study their further conversion path under the effect of steam. This paper addressed the yield and transformation of tar with different steam/feedstock mass ratios (S/F= 0.8, 1.6) in a two-stage fixed bed when the two stages' furnace temperature was set at 600°C and 800°C, separately. Compared with pyrolysis, steam promoted tar cracking effectively, the tar yield decreased at least 1/3. However, when the S/F ratio increases to 1.6, the cracking effect of tar is not further improved. The tar yield depended more on the PE content in the mixture, which was enhanced with PE increment. Besides, the H/C atom ratio was related to the conversion path of tar. Steam was beneficial to the cracking of compounds, but the generated hydrogen radicals affected the direction of the subsequent reaction. The steam mainly promotes the cracking of long-chain hydrocarbons, accompanied by cyclization and aromatization when the steam was limited. Nevertheless, the chain compounds are hard to crack efficiently when the steam was excessive, and the cyclization and aromatization processes were hindered due to the apparent effect of hydrogenation. [ABSTRACT FROM AUTHOR]

Substrates provide the necessary support for scientific explorations of numerous promising features and exciting potential applications in two-dimensional (2D) transition metal dichalcogenides (TMDs). To utilize substrate engineering to alter the properties of 2D TMDs and avoid introducing unwanted adverse effects, various experimental techniques, such as high-frequency Raman spectroscopy, have been used to understand the interactions between 2D TMDs and substrates. However, sample-substrate interaction in 2D TMDs is not yet fully understood due to the lack of systematic studies by techniques that are sensitive to 2D TMD-substrate interaction. This work systematically investigates the interaction between tungsten disulfide (WS2) monolayers and substrates by low-frequency Raman spectroscopy, which is very sensitive to WS2-substrate interaction. Strong coupling with substrates is clearly revealed in chemical vapor deposition (CVD)-grown monolayer WS2 by its low-wavenumber interface mode. It is demonstrated that the enhanced sample-substrate interaction leads to tensile strain on monolayer WS2, which is induced during the cooling process of CVD growth and could be released for monolayer WS2 sample after transfer or fabricated by an annealing-free method such as mechanical exfoliation. These results not only suggest the effectiveness of low-frequency Raman spectroscopy for probing sample-substrate interactions in 2D TMDs, but also provide guidance for the design of high-performance devices with the desired sample-substrate coupling strength based on 2D TMDs. [ABSTRACT FROM AUTHOR]

The pure P2(8) line radiation of chemical hydrogen fluoride (HF) laser which can be weakly absorbed by atmosphere was generated using an absorbed module in a line-selected cavity. A numerical model of laser gain was investigated to predict and optimize the laser performance. An experimental verification was carried out in a compact continue wave (cw) tunable chemical HF laser device. It is found that P1(11) line can be suppressed by fundamental HF particles generated by combustion reaction, meanwhile the proportion of P2(8) line can be increased close to 100% from original 38%. The absorbance as well as output power of P2(8) line can also be influenced by concentration of absorbing media. [ABSTRACT FROM AUTHOR]

Background: Staphylococcus aureus is the causative agent of chronic mastitis, and can form a biofilm that is difficult to completely remove once formed. Disinfectants are effective against S. aureus, but their activity is easily affected by environmental factors and they are corrosive to equipment and chemically toxic to livestock and humans. Therefore, we investigated the potential utility of a bacteriophage as a narrow-spectrum disinfectant against biofilms formed by S. aureus. In this study, we isolated and characterized bacteriophage vB_SauM_SDQ (abbreviated to SDQ) to determine its efficacy in removing S. aureus biofilms. Results: SDQ belongs to the family Myoviridae and consists of a hexagonal head, long neck, and short tail. This phage can sterilize a 109 CFU/mL culture of S. aureus in 12 h and multiply itself 1000-fold in that time. Biofilms formed on polystyrene, milk, and mammary-gland tissue were significantly reduced after SDQ treatment. Fluorescence microscopy and scanning electron microscopy showed that SDQ destroyed the biofilm structure. Moreover, the titer of SDQ remained relatively high after the lysis of the bacteria and the removal of the biofilm, exerting a continuous bacteriostatic effect. SDQ also retained its full activity under conditions that mimic common environments, i.e., in the presence of nonionic detergents, tap water, or organic materials. A nonionic detergent (Triton X-100) enhanced the removal of biofilm by SDQ. Conclusions: Our results suggest that SDQ, a specific lytic S. aureus phage, can be used to control biofilm infections. SDQ maintains its full activity in the presence of nonionic detergents, tap water, metal chelators, and organic materials, and can be used in combination with detergents. We propose this phage as a narrow-spectrum disinfectant against S. aureus, to augment or supplement the use of broad-spectrum disinfectants in the prevention and control of the mastitis and dairy industry contamination caused by S. aureus. [ABSTRACT FROM AUTHOR]

Rapid thermokinetics associated with laser-based additive manufacturing produces strong bulk crystallographic texture in the printed component. The present study identifies such a bulk texture effect on elastic anisotropy in laser powder bed fused Ti6Al4V by employing an effective bulk modulus elastography technique coupled with ultrasound shear wave velocity measurement at a frequency of 20 MHz inside the material. The combined technique identified significant attenuation of shear velocity from 3322 ± 20.12 to 3240 ± 21.01 m/s at 45 ∘ and 90 ∘ orientations of shear wave plane with respect to the build plane of printed block of Ti6Al4V. Correspondingly, the reduction in shear modulus from 48.46 ± 0.82 to 46.40 ± 0.88 GPa was obtained at these orientations. Such attenuation is rationalized based on the orientations of α ′ crystallographic variants within prior columnar β grains in additively manufactured Ti6Al4V. [ABSTRACT FROM AUTHOR]

In this study, a novel acoustic doublet meta-material lens has been designed and tested to demonstrate both a far-field focal point and ultra-long collimation characteristics past the Fresnel zone. The switching of the two behaviors can be adjusted by a simple linear mechanical translation of one of the lens units. The doublet lens can focus the sound wave beyond 38λ away from the experiment's lens, which is farther than any existing ultrasonic transducer or meta-lenses lenses. In terms of collimating behavior, the doublet lens is a unique metamaterial lens that experimentally demonstrates a long and narrow collimating beam over 70λ. Besides the design and characterization, the meta-lens have been used to detect real objects, including inorganic and organic matter. A subwavelength spatial resolution has been demonstrated. The detection limit was 0.26λ in the monostatic setup and 0.62λ in a bistatic experimental setup. This lens demonstrates super-resolution detection capabilities at distances of 42λ and can enable ultrasonic diagnostics deep within a material or a biological tissue. The experimental performance of the doublet meta-material lens illustrated its potential to apply acoustic metamaterial elements in a practical imaging application, including the detection of biological tissues [ABSTRACT FROM AUTHOR]

In this study, we introduce a novel method using longitudinal sound to detect underground soil voids to inspect underwater bed property in terms of effective bulk modulus and effective density of the material properties. The model was simulated in terms of layered material within a monostatic detection configuration. The numerical model demonstrates the feasibility of detecting an underground air void with a spatial resolution of about 0.5 λ and can differentiate a soil firmness of about 5%. The proposed technique can overcome limitations imposed by conventional techniques that use spacing-consuming sonar devices and suffer from low penetration depth and leakage of the transverse sound wave propagating in an underground fluid environment. [ABSTRACT FROM AUTHOR]

Ultrasound is a continually developing technology that is broadly used for fast, non-destructive mechanical property detection of hard and soft materials in applications ranging from manufacturing to biomedical. In this study, a novel monostatic longitudinal ultrasonic pulsing elastography imaging method is introduced. The existing elastography methods require an acoustic radiational or dynamic compressive externally applied force to determine the effective bulk modulus or density. This new, passive M-mode imaging technique does not require an external stress and can be effectively used for both soft and hard materials. Strain map imaging and shear wave elastography are two current categories of M-mode imaging that show both relative and absolute elasticity information. The new technique is applied to hard materials and soft material tissue phantoms for demonstrating effective bulk modulus and effective density mapping. When compared with standard techniques, the effective parameters fall within 10% of standard characterization methods for both hard and soft materials. As neither the standard A-mode imaging technique nor the presented technique require an external applied force, the techniques are applied to composite heterostructures and the findings presented for comparison. The presented passive M-mode technique is found to have enhanced resolution over standard A-mode modalities. [ABSTRACT FROM AUTHOR]

State-to-state rotational relaxation processes play a critical role in predicting rotational nonequilibrium, which can significantly affect total laser power and spectral distribution. In this paper, the state-to-state rotational relaxation rate coefficients for the pumping reaction of F + H2, the rotational energy transfer processes of HF(υ, j = 0–10) + HF(υ′, j′ = 0–10) and HF(υ, j = 0–10) + H2 are calculated. Subsequently, a detailed state-to-state chemical kinetic mechanism is constructed including 61 species and 124,482 elementary reactions for HF chemical lasers. All of these rotational relaxation rate coefficients have been expressed with Arrhenius-like formulas. A comparison of the Boltzmann distribution model with the detailed state-to-state chemical mechanism has been analysed and discussed. These results show that rotational nonequilibrium processes can significantly affect the distribution of ro-vibrational excited HF molecules. The rotational distributions of HF(υ = 0–2, j) are far from equilibrium distribution. Conversely, the distributions of HF(υ = 3, 4, j) seem to be a Boltzmann distribution. These results indicate that numerical models must include the rotational nonequilibrium processes and numerical models using a Boltzmann distribution for the rotational populations cannot predict performance of real HF chemical lasers. [ABSTRACT FROM AUTHOR]

In this paper, a 2-D beamforming phased array using a novel 2-D Nolen matrix network is presented. The Nolen matrix is a novel antenna feeding network composed of only couplers with dedicated coupling ratios and phase shifters. It does not require crossover and load termination compared to other networks based on Butler and Blass matrix. To be specific, the closed-form equations are derived first for uniplanar single $3 \times 3$ Nolen matrix, which is composed of three couplers and three phase delay lines. Most importantly, it is found that the proposed Nolen matrix can employ couplers with arbitrary phase differences to achieve relatively flexible progressive phase delays across the radiating elements, presenting a high degree of freedom on circuit topology and beamforming performance. Then, a 2-D antenna feeding network is designed by stacking and cascading six $3 \times 3$ Nolen matrices, and a 2-D patch antenna array is integrated with the proposed feeding network to generate nine radiation beams with unique directions on azimuth and elevation planes, realizing the 2-D beamforming function. To verify the proposed design concept, a prototype of 2-D beamforming phased array operating at 5.8 GHz is designed, fabricated, and measured, and the experimental results agree well with simulation and theoretical analysis. [ABSTRACT FROM AUTHOR]

Abstract: Bioferment residue of drugs (BRD) is one kind of harmful and hazardous substance which has complex compositions. Thus, proper treatment of these residues has become an important concern. BRD can be utilized harmlessly and economically by mixing it with coal powder, water, and dispersant to prepare slurry fuel, named as coal‐BRD‐slurry (CBRDS). In this study, the influence of BRD on the slurry ability and combustion behaviour of CBRDS was investigated with coal water slurry (CWS) as reference. Results showed that the dispersant can reduce the slurry viscosity of CBRDS and CWS, and its optimum dosage was 0.6 wt% on the dried coal basis. The fixed‐viscosity concentration of CBRDS decreased with increasing BRD dosage. CBRDS and CWS exhibited shear‐thinning behaviour. The rheological behaviour was fitted by the power law. CBRDS exhibited higher apparent viscosity and stronger shear‐thinning behaviour because of the flocculent structure and well‐developed pores of the BRD. BRD can improve the stability of CWS by decreasing solid‐liquid separation of the slurry. Addition of BRD decreased the ignition temperature and increased the ash residues, suggesting a synergistic effect of CWS and BRD occurred during the combustion of CBRDS. [ABSTRACT FROM AUTHOR]

Organic hazardous waste often contains some salt, owing to the widespread use of alkali salts during industrial manufacturing processes. These salts cause complications during the treatment of this type of waste. Molten salt oxidation is a flameless, robust thermal process, with inherent capability of destroying the organic constituents of wastes, while retaining the inorganic ingredients in the molten salt. In the present study, molten salt oxidation is employed for treating a typical organic hazardous waste with a high content of alkali salts. The hazardous waste derives from the production of thiotriazinone. Molten salt oxidation experiments have been conducted using a lab-scale molten salt oxidation reactor, and the emissions of CO, NO, SO2, HCl and dioxins are studied. Impacts are investigated from the composition of the molten salts, the types of feeding tube, the temperature of molten carbonates and the air factor. Results show that the waste can be oxidised effectively in a molten salt bath. Temperature of molten carbonates plays the most important role. With the temperature rising from 600 °C to 750 °C, the oxidation efficiency increases from 91.1% to 98.3%. Compared with the temperature, air factor has but a minor effect, as well as the composition of the molten salts and the type of feeding tube. The molten carbonates retain chlorine with an efficiency higher than 99.9% and the emissions of dioxins are below 8 pg TEQ g-1 sample. The present study shows that molten salt oxidation is a promising alternative for the disposal of organic hazardous wastes containing a high salt content. [ABSTRACT FROM AUTHOR]

Ultra-high reflectors, working as a critical optical component, has been widely applied as a cavity mirror in fine optical systems such as laser gyro, F-P interferometer, etc. For decades, ion beam sputtering (IBS) technology, which can deposit ultra-low loss and dense layers, has been commonly believed to be the only and irreplaceable method to fabricate ultra-high reflectors. Thus, reports on other methods are rare and a reflectivity above 99.99% obtained by evaporation technology (includingion assisted evaporation) has not been seen yet. In the present study, an energetic radio frequency (RF) ion source was introduced during the electron beam evaporation process, which improved the layer quality dramatically. An ultra-high reflector at 1319 nm with reflectivity of 99.992% (measured by cavity-ring down method) was successfully deposited on a ø 100 mm × 25 mm single crystal silicon substrate whose surface roughness was approximately 0.420 nm. The surface figure of the reflector was accurately controlled superior to 1/6λ (λ = 632.8 nm). The measured absorption was approximately 3-5 ppm and the calculated scatter based on surface roughness measurement was approximately 6.64 ppm. Total loss of the reflector was systematically discussed. This study showed that it is possible to apply electron beam evaporation in ultra-high reflector manufacture and the method is capable of depositing reflectors with an aperture larger than 600 mm which is the maximum capacity of current IBS technology. [ABSTRACT FROM AUTHOR]

Irradiation cross-linked polyethylene (PEX) and irradiation cross-linked polyethylene with carbon black filler (CB-PEX) are two types of scraps, generated in electric cable production. Their pyrolysis is studied in this work using instrumental TG\DSC\FTIR techniques and kinetic analysis. The experiments are performed at a constant heating rate of 10 °C/min in nitrogen flow at atmospheric pressure. It is found that the main pyrolysis stage is in the temperature range of 395-503 °C for PEX, and in range of 408-515 °C for CB-PEX. In the main pyrolysis stage, CB-PEX requires more external heat than PEX does. Olefins are the major products of pyrolysis for both materials, but they are quite different in their composition and molecular weight distribution. PEX can be converted almost quantitatively into volatile compounds. CB-PEX has a stronger coking tendency, as well as a larger residue composed of carbon black. [ABSTRACT FROM AUTHOR]

The waste management of e-wastes is a significant challenge, especially for the disposal of waste printed circuit boards (WPCBs). An effective, economic and environmental-kind recycling technology is in great demand. Molten salt oxidation (MSO) is a robust thermal process, has the inherent capability of destroying organic constituents of wastes while retaining the inorganic constituents in the molten salt. In the present study MSO is employed for the disposal of waste printed circuit boards aimed at describing the treating method of WPCBs using MSO, and evaluating the efficiency of this alternative. Molten salt oxidation experiments of WPCBs have been conducted in a lab-scale molten salt reactor using a ternary carbonate salt (Li, Na, K)CO. The operation parameters investigated are the temperature of molten salts, the excess air factor and the residence time of the reactants in the salt bath. Results show that the retention efficiency of bromine is higher than 99.9%, irrespective of the operating conditions. The emissions of CO and SO decrease with temperature increasing, while the emission of NO first decreases and later increases. And when the residence time is lengthened, the emissions of CO, NO and SO decrease. Compared to the temperature and the residence time's role, the effect of excess air factor on the emissions of CO, NO and SO is relatively small. Over 95% of the copper in WPCBs are recycled. The fibreglass that is the main component of the ash content is dissolved by the molten carbonates and retains in the salt bath. The results of the present study show molten salt oxidation is an environmentally friendly and effective alternative technology for the disposal of WPCBs. [ABSTRACT FROM AUTHOR]

We have established a new method for realizing a typical '2-color' collinear CARS (coherent anti-Stokes Raman scattering) system. The system mainly consists of a laser source, a DO cell, and a spectrometer. The pump/probe beam and the Stokes beam are provided by SBS (stimulated Brillouin scattering) and BSRS (backward stimulated Raman scattering) of DO, respectively. The CARS system is statistically stable, and it is also a broadband and alignment-free system. Measurement of N signal in air with this system is demonstrated. Detection of N in 0.006 bar air is realized with this system. Time-resolved pulse shapes of SBS and BSRS are measured to confirm their generation. Transference of energy from the SBS pulse to the BSRS pulse is realized with a Rhodamine 101 dye cuvette and discussed. This results in a better energy distribution between the pump/probe and Stokes pulses for CARS. [ABSTRACT FROM AUTHOR]

We present the design and investigation of a novel chemosorption vacuum pump (CSVP) for discharging the exhaust gases of a chemical oxygen-iodine laser system diluted with carbon dioxide (CO-COIL). The CSVP comprises two fixed-bed reactors separately filled with CO/HO and O/I/Cl adsorbents, which can efficiently chemically absorb the CO-COIL exhaust gases at room or higher temperature. We consider the effects of the adsorbents in different specifications and fixed beds of various constructions on the adsorption performance of the CSVP. We develop and study the sealed CO-COIL system with the CSVP. We achieve a stable operation with a cumulative duration time of 40 s for four runs and an average output power up to 2.0 kW at a Cl flow rate of ∼158 mmol/s and a CO flow rate of 132 mmol/s. The experimental results indicate that the COIL system with the CSVP performs similarly to a conventional COIL with a vacuum tank. Taking into account that the CSVP is free of vibration and noise, avoids air pollution, is easily operated, and has a short preparation time, we believe that the chemosorption vacuum pump is an excellent alternative pump system for a transportable COIL system. [ABSTRACT FROM AUTHOR]

In this letter, a novel planar branch line balun with transparent port impedance is presented. The balun is designed based on a symmetric four-port network with an open-ended transmission line stub in the middle of the branch at its unbalanced port side. From the even-odd mode analysis, the equivalent network is derived to be a short circuit under even-mode excitation, and the input impedance looking into the unbalanced port satisfies impedance matching under odd-mode excitation. Unlike previous designs, the equivalent cascaded impedance transformer in the proposed structure is independent to the system reference impedance in odd-mode excitation so that the termination at the unbalanced port is transparent to balanced ports. To prove the design concept, the closed-form equations are derived, and multiple prototypes with termination impedances 35, 50, and $75 ~\Omega $ are simulated, fabricated, and characterized. [ABSTRACT FROM AUTHOR]