Efficient Drilling of Amorphous Alloy Foils Using Low-Energy Long Pulses of a Nd:YAG Laser

Laser drilling of amorphous alloy foils was conducted using low-energy long-pulses (LP) generated using a Nd:YAG laser. Results showed that LP can drill an amorphous alloy foil more efficiently than a nanosecond pulse (NSP) can: an LP at 1 mJ can open a through-hole on an amorphous alloy foil with 25 mm thickness although single shot NSP at 20 mJ formed a crater with ca. 3 mm depth. From these findings, we infer that the markedly higher drilling efficiency of a low-energy LP than that of NSP is attributable to 1) lower plasma generation by LP than by NSP, and 2) repeated irradiation of the target material by multiple sub-pulses in an LP. Results also demonstrate that low-energy LP drilling is applicable to various metal foils and that the drilling efficiency depends on the metal species.

A Fungal Modified Material With High Uranium (VI) Absorption Capacity And Strong Anti-Interference Ability

With polydioxyethylene ether as the bridge chain, a new fungal modified material with diamidoxime groups was prepared by a series of uncomplex synthesis reaction. The orthogonal experiment obtained its optimized adsorption conditions as follows: the initial pH value 6.5, the initial uranyl concentration 40 mg L-1, the contact time 130 min, and the solid-liquid ratio 25 mg L-1. The maximum adsorption capacity of target material was 446.20 mg g-1, and it was much greater than that of the similar monoamidoxime material (295.48 mg g−1). The linear Langmuir (R2 = 0.9856) isotherm models and the linear pseudo-second-order kinetic model (R2 = 0.9931) fit the experimental data of uranium (VI) adsorption better, indicating the adsorption mechanism should mainly be the monolayer adsorption and chemical process. In addition, the relevant experiments exhibited the prepared material was of the good reuse and the excellent anti-interference performance, which suggested the new acquisition should also have well-applied prospect in the future.

Study of DC Magnetron Sputtered Nb Films

As Nb films are widely used as superconducting electrodes of Josephson junctions, it is important to investigate the properties of Nb films in order to fabricate high-quality Josephson junctions. In this work, we conducted a comprehensive analysis of the relationships among the properties of DC magnetron sputtered Nb films with a constant power fabricated at the National Institute of Metrology (China). The film properties, including superconductivity, stress, lattice constant, and surface roughness, were investigated. It was found that in the case of constant power and Ar pressure, the stress and other parameters of the Nb films can maintain a relatively stable state during the continuous consumption of the target material.

Characterization of Graphenic Carbon Produced by Pulsed Laser Ablation of Sacrificial Carbon Tapes

This paper reports on the pulsed laser deposition of nanocarbon films on metal and dielectric substrates, using high-purity sacrificial carbon tape as a carbon source on a neutral gas background. The films were characterized by X-ray diffraction (XRD), photoelectron (XPS) and Raman spectroscopy. The XRD and Raman structural analyses revealed that the synthesized films have a graphenic nanocrystalline turbostratic structure, with sp2 clusters about 15–18 nm in size, depending on the laser fluence. A significant decrease in the oxygen and hydrogen contents in the films, in comparison with the target material, was established using XPS, as well as a significant decrease in the sp3 carbon content. The deposited films were found to be similar to reduced graphene oxide (rGO) in composition, with a surprisingly low number of defects in the sp2-matrix. The method proposed in the work may have good prospects of application in the production of energy storage and nonvolatile memory devices.

Optimizing a metabarcoding primer portfolio for species-level detection of taxa in complex mixtures of diverse fishes

DNA metabarcoding is used to enumerate and identify taxa in both environmental samples and tissue mixtures. The composition and resolution of metabarcoding data depend on the primer(s) used. Markers that amplify different genes can mitigate biases in primer affinity, amplification efficiency, and reference database resolution, but few empirical studies have evaluated markers for complementary performance. Here, we assess the individual and joint performance of 22 markers for detecting species in a DNA pool of >100 species of primarily marine and freshwater fishes, but also including representatives of elasmobranchs, cephalopods, and crustaceans. Marker performance includes the integrated effect of primer specificity and reference availability. We find that a portfolio of four markers targeting 12S, 16S, and multiple regions of COI identifies 100% of reference taxa to family and nearly 60% to species. We then use the four markers in this portfolio to evaluate metabarcoding of heterogeneous tissue mixtures, using experimental fishmeal to test: 1) the tissue input threshold to ensure detection; 2) how read depth scales with tissue abundance; and 3) the effect of non-target material in the mixture on recovery of target taxa. We consistently detect taxa that make up >1% of fishmeal mixtures and can detect taxa at the lowest input level of 0.01%, but rare taxa (<1%) were detected inconsistently across markers and replicates. Read counts showed weak correlation with tissue input, suggesting they are not a valid proxy for relative abundance. Despite this limitation, our results demonstrate the value of a primer portfolio approach—tailored to the taxa of interest—for detecting and identifying both rare and abundant species in heterogeneous tissue mixtures.

Determination of plastic deformation rate after solid particle erosion in ductile materials

AA6082-T6 aluminium alloy is a candidate material, specifically in aviation applications, which could be exposed to solid particle erosion. Solid particle erosion occurs due to repetitive high-speed impact of erodent particles on a target material. Every individual impingement of the erodent particle results in elastic/plastic deformations and material removal from the target material. In this study, solid particle erosion investigations were carried out under 1.5 and 3 bar with 60 and 120 mesh alumina particles. Both erosion rates and worn volumes of the samples were calculated and measured. Also, the authors present the plastic deformation rate in this study as a proportion of the actual (measured) worn volume to the equivalent volume of the mass loss. In addition, the average surface roughness of the samples were investigated, which is another parameter for understanding the effect of plastic deformation on surface properties during particle erosion.

Direct comparison of PEN and TPB wavelength shifters in a liquid argon detector

A large number of particle detectors employ liquid argon as their target material owing to its high scintillation yield and its ability to drift ionization charge over large distances. Scintillation light from argon is peaked at 128 nm and a wavelength shifter is required for its efficient detection. In this work, we directly compare the light yield achieved in two identical liquid argon chambers, one of which is equipped with polyethylene naphthalate (PEN) and the other with tetraphenyl butadiene (TPB) wavelength shifter. Both chambers are lined with enhanced specular reflectors and instrumented with SiPMs with a coverage fraction of approximately 1%, which represents a geometry comparable to the future large scale detectors. We measured the light yield of the PEN chamber to be 39.4$$\,\pm \,$$ ± 0.4(stat)$$\,\pm \,$$ ± 1.9(syst)% of the yield of the TPB chamber. Using a Monte Carlo simulation this result is used to extract the wavelength shifting efficiency of PEN relative to TPB equal to 47.2$$\,\pm \,$$ ± 5.7%. This result paves the way for the use of easily available PEN foils as a wavelength shifter, which can substantially simplify the construction of future liquid argon detectors.

High Precision Half‑Life Measurement of the Extinct Radio‑Lanthanide Dysprosium-154

Sixty years after the discovery of 154Dy, the half-life of this pure alpha-emitter was re-measured. 154Dy was radiochemically separated from proton-irradiated tantalum samples. Sector field- and multicollector-inductively coupled plasma mass spectrometry were used to determine the amount of 154Dy retrieved. The disintegration rate of the radio-lanthanide was measured by means of α-spectrometry. The half-life value was determined as (1.33 ± 0.07)∙106 y, with an uncertainty reduced by a factor of ~10 compared to the currently adopted value of (3.0 ± 1.5)∙106 y. This precise half-life value is crucial for the correct estimation of p-process nucleosynthetic reactions in the lanthanide region, as well as for the safe disposal of irradiated target material from spallation facilities. As a first application of the half-life value found in this work, the excitation functions for the production of 154Dy in proton-irradiated Ta, Pb, and W targets were re-evaluated, which found to be in agreement with theoretical calculations.

Multiscale Research on Pore Structure Characteristics and Permeability Prediction of Sandstone

The random existence of many irregular pore structures in geotechnical materials has a decisive influence on its permeability and other macroscopic properties. The analysis and characterization of the micropore structure of the material and its permeability are of great significance for geotechnical engineering. In this study, digital images with different magnifications were used to examine the pore structure and permeability of sandstone samples. The image processing method is used to obtain binary images, and then, the pore size distribution method is used to calculate the pore size distribution. Therefore, based on the Hagen-Poiseuille formula, we get the prediction value of material’s permeability and compare it with the value obtained from mercury intrusion porosimetry (MIP). It is found that different microscopic images with different magnification and various statistical methods of pore size have a specific influence on the characterization of pore structure and permeability prediction. The porosity of different magnifications is not the same, and the results obtained at higher magnifications are more consistent with the results obtained with MIP. With the increase of magnification, we can observe more pores in large sizes. The effect of CPSD (continuous pore size distribution) in pore size statistics is better than that of DPSD (discrete pore size distribution). In permeability prediction, the prediction result of higher magnification images are closer to the instrument test value, and the value of DPSD is more significant than that of CPSD. In future research, an appropriate method should be selected to obtain a reasonable prediction of the permeability of the target material.

Mathematical Modelling and Experimental Investigation of Abrasive Jet Machining for Various Abrasive Particles

Abrasive water-jet machining operates by the impingements of a high velocity abrasive laden water-jet against the work piece. The jet is formed by mixing abrasive particles with high-velocity water in the mixing region and is forced through the orifice. The accelerated jet exiting the nozzle travels at a very high velocity and cuts as it passes through the work piece. It is a difficult task of predicting the values of major cutting performance measures in Abrasive Water Jet (AWJ) cutting. AWJ cutting process involves a large number of process and material parameters, which are related to the water-jet, the abrasive particles, and work-piece material. Those parameters are expected to affect the material removal rates and depth of penetration. In this paper, various models of wear by particle erosion and the most accepted models for predicting the depth of penetration in AWJ cutting are reviewed. However, there has been very little reported study on AWJ machining using various abrasive particles. In this paper, an attempt has been made for the development of the predictive mathematical model for AWJ cutting with various abrasive particles having different geometrical shapes and physical properties. Also, their effect on the target material has also been studied. Afterward, this model is verified with the experimental investigation. Keywords: AWJM, Abrasive, Mathematical-Modelling, Manufacturing, Water-Jet