Pulsed Method Research Articles

A Novel Heat Pulse Method in Determining “Effective” Thermal Properties in Frozen Soil

AbstractAccurate and fast measurements of thermal properties are frequently required for characterizing the heat‐water dynamics in frozen soil. Measuring the thermal properties of frozen soil without inducing ice thaw has proven challenging with conventional heat pulse (HP) methods. In this study, based on an Infinite Line Source (ILS) semi‐analytical model that applies a constant temperature lower than the freezing point at the heat source to prevent the initiation of ice thaw in the frozen soil, we propose a novel HP‐based approach to measure thermal properties, applicable at temperatures below or above 0°C. Laboratory experiments and numerical modeling were utilized to validate the applicability of the approach and optimization strategies of the measurement. We found that the proposed HP‐based approach effectively maintained the maximum spatial temperature below the freezing point and therefore estimated the bulk thermal properties of quartz sand and ice contents. An optimized measurement strategy was proposed to monitor the temperature variations 2–4 cm away from the center of the heat probe after 60 s. This progress can largely facilitate the determination of the thermal properties of multi‐phase and ‐component frozen soil such as thermal conductivity, heat flux, and ice content in cold areas across soil science, hydrology, engineering, and climate science.

Synthesized aluminum gallium nitride/porous-Si thin films at different compositions by pulsed laser deposition method

Synthesized aluminum gallium nitride/porous-Si thin films at different compositions by pulsed laser deposition method

Enhancing NiCoB alloy coatings with hBN nanoparticles: exploring structural, mechanical, and corrosion improvements through pulse electrodeposition

ABSTRACT NiCoB/hBN composite coatings deposited onto a 304 stainless steel substrate by pulsed current electrodeposition method. The morphology, chemical composition, structural, mechanical and corrosion properties of the coatings were investigated. Optimal microhardness, corrosion resistance, and a lower coefficient of friction were achieved when the hBN concentration in the plating bath was 8 g L−1 . Vickers microhardness increased from 610 to 980 HV and the coefficient of friction decreased from 0.53 to 0.4. Grain size decreased as the amount of added hBN increased, affecting the microstructure of the coating. Increasing the concentration of hBN in the plating solution increased the percentage of hBN particles in the film, reducing the percentage of total metal from 95.18% to 89.76%. The magnitude of the Nyquist parabola of the composite film from the bath containing 8 g L−1 hBN increased by an average of 5 times compared to that of the NiCoB metal alloy film.

Preparation and Properties of Thick Tungsten Coating Electrodeposited from Na2WO4-WO3-KCl-NaF Molten Salt System

The pulsed current electrodeposition method was employed for the first time to achieve tungsten coating with a thickness of 433.72 μm on a CuCrZr alloy from Na2WO4-WO3-KCl-NaF molten salt. The microstructure of the coating was observed and the coating density, porosity, hardness, bonding strength, residual stress and oxygen content were tested. The results revealed that the tungsten coating exhibited desirable characteristics such as high density, absence of impurities, excellent adhesion to the matrix (53.16 MPa), residual compressive stress as surface stress, and good stability and durability. Moreover, this thick tungsten coating possesses high density and hardness, low oxygen content and porosity. This offers a novel solution to solve the challenging issue of the connection between tungsten material and heat sink material.

Conceptual study of subcritical assembly with neutron generator for reactor physics experiments and neutron utilization

In Japan, critical assemblies are regulated under the “Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactions” which provides guidelines for the construction and the operation of nuclear facilities: the core configurations of nuclear experiments are constrained accordingly. In addition, the nuclear facilities are required to comply with strict administrations if the nuclear facilities have more than the certain amount of nuclear fuels. On the other hand, subcritical assemblies are not subjected to the nuclear reactor regulation because the subcritical assemblies are not classified as nuclear reactors. We propose the subcritical assembly with a pulsed accelerator neutron source, which uses nuclear fuels below the regulation amount to ease maintenance and to widen experimental capabilities. Conceptual study of such system was carried out to calculate the deviation between reactivity difference in critical state and that in subcritical state by using the MCNP 6.2 code and the JENDL 4 library. Neutron source multiplication method and pulsed neutron source method were performed. The deviation can be estimated around 10 % by setting detectors in appropriate positions. Additionally, neutron radiography was studied as a simple application. The geometrical shapes of sample rods were seen clearly.

Evaluation of the In Vitro Behavior of Electrochemically Deposited Plate-like Crystal Hydroxyapatite Coatings.

The purpose of coatings is to protect or enhance the functionality of the substrate material, irrespective of the field in which the material was designed. The use of coatings in medicine is rapidly expanding with the objective of enhancing the osseointegration ability of metallic materials such as titanium. The aim of this study was to obtain biomimetic hydroxyapatite (HAp)-based coatings on titanium by using the pulsed galvanostatic method. The morphology of the HAp-based coatings revealed the presence of very thin and wide plate-like crystals, grown perpendicular to the Ti substrate, while the chemical composition highlighted a Ca/P ratio of 1.66, which is close to that of stoichiometric HAp (1.67). The main phases and chemical bonds identified confirmed the presence of the HAp phase in the developed coatings. A roughness of 228 nm and a contact angle of approx. 17° were obtained for the HAp coatings, highlighting a hydrophilic character. In terms of biomineralization and electrochemical behavior, it was shown that the HAp coatings have significantly enhanced the titanium properties. Finally, the in vitro cell tests carried out with human mesenchymal stem cells showed that the Ti samples coated with HAp have increased cell viability, extracellular matrix, and Ca intracellular deposition when compared with the uncoated Ti, indicating the beneficial effect.

Non-Destructive Evaluation of Fixation Status of Post-Installed Anchor by Electromagnetic Pulse Method

Non-Destructive Evaluation of Fixation Status of Post-Installed Anchor by Electromagnetic Pulse Method

Characterisation and evaluation of paint-coated marine corrosion in carbon steel based on pulsed eddy current thermography and BEMD noise-reducing method

ABSTRACT Eddy current pulsed thermography (ECPT) technique has been investigated for steel corrosion detection and evaluation. However, the random interference was not considered and disposed adequately, which bedims the original thermal images and reconstructed feature ones. This paper applied bidimensional empirical mode decomposition (BEMD) method which used to denoise the thermal image sequences, and the contrast between corroded and uncorroded regions in the skewness reconstructed images of 6-months and 12-months samples was improved by 19% and 28%, respectively. By this means, the skewness of the temperature response curve of each pixel was extracted to reconstruct the feature image. Furthermore, the differential skewness and the contrast of reconstructed skewness image are utilised for distinguishing the early corrosion and the moderate corrosion. The results demonstrate that the method provides higher sensitivity and accuracy in corrosion detection with ECPT.

Modeling for formation of microdroplets prepared by pulsated orifice ejection method

Abstract This study investigated the preparation of metallic microdroplets by pulsed orifice ejection method. Computational fluid dynamics simulations, combined with volume-of-fluid model, were employed to analyze the jet break-up and droplet formation behaviors of various metallic materials within a certain Weber number (We) range. An energy-based physical model under inlet boundary conditions was established to precisely control the generation of droplets. The results indicate that the break-up state of metal jets is significantly influenced by material properties within the range that We = 12 ∼ 24, which makes the materials exhibiting higher surface tension and density relatively favorable to the production of mono-sized microdroplets. Moreover, the break-up behavior of the jet is closely related to the ratio of volume force to surface tension (Bond number). And the proposed model effectively predicts the properties of droplets. This research provides theoretical guidance and technical support for the precise preparation of metallic microdroplets.

The pulse Sn-assisted growth promotes the preparation of high-quality single-crystal ε-Ga2O3 films using MOCVD technology.

The single crystal ε-Ga2O3 thin films were successfully grown on c-plane sapphire substrates using metal-organic chemical vapor deposition (MOCVD). By employing the pulse method to introduce Sn as a growth adjuvant, the issue of phase mixing between β and ε phases, which commonly occurs when high-purity oxygen is used as the oxygen source in MOCVD, was effectively resolved. The physical phase composition, film surface quality and thickness of the epitaxial films of three sets of samples (not Sn, pulse Sn, direct Sn) were characterized using X-ray diffractometer, atomic force microscope and scanning electron microscope. High-quality ε-Ga2O3 single-crystal thin films were obtained under the conditions of Sn-assisted growth using the pulse method, resulting in a 51% increase in the epitaxial growth rate. Elemental analysis through X-ray photoelectron spectroscopy, combined with Gibbs free energy changes, that insight into the role of elemental Sn in the reaction. Through comparison and analysis, it was found that pulsed Sn is more fully involved in the reaction and plays a more efficient role than the direct Sn. The concentration of elemental Sn in the epitaxial film was analyzed using SIMS tests, from the substrate interface to the surface of the film, the Sn element exhibited a gradual accumulation toward the surface. The microstructures of the different samples were compared by transmission electron microscopy. Additionally, the reason that Sn elements promote the formation of ε-Ga2O3 single crystal was explained from the perspective of structure.

Pulsed EPR Methods in the Angstrom to Nanometre Scale Shed Light on the Conformational Flexibility of a Fluoride Riboswitch.

Riboswitches control gene regulation upon external stimuli such as environmental factors or ligand binding. The fluoride sensing riboswitch from Thermotoga petrophila is a complex regulatory RNA proposed to be involved in resistance to F- cytotoxicity. The details of structure and dynamics underpinning the regulatory mechanism are currently debated. Here we demonstrate that a combination of pulsed electron paramagnetic resonance (ESR/EPR) spectroscopies, detecting distances in the angstrom to nanometre range, can probe distinct regions of conformational flexibility in this riboswitch. PELDOR (pulsed electron-electron double resonance) revealed a similar preorganisation of the sensing domain in three forms, i.e. the free aptamer, the Mg2+-bound apo, and the F--bound holo form. 19F ENDOR (electron-nuclear double resonance) was used to investigate the active site structure of the F--bound holo form. Distance distributions without a priori structural information were compared with in silico modelling of spin label conformations based on the crystal structure. While PELDOR, probing the periphery of the RNA fold, revealed conformational flexibility of the RNA backbone, ENDOR indicated low structural heterogeneity at the ligand binding site. Overall, the combination of PELDOR and ENDOR with sub-angstrom precision gave insight into structural organisation and flexibility of a riboswitch, not easily attainable by other biophysical techniques.

Comparison of microwave and pulsed electric field methods on extracting antioxidant compounds from Arvaneh plant (Hymenocrater platystegius Rech. F)

Improving the quality of extracts derived from medicinal plants is a critical concern due to their extensive use across various industries. The Arvaneh plant (Hymenocrater platystegius Rech. F), a species native to the Khorasan province in Iran and belonging to the mint family, was the focus of this study. We optimized the extraction of Arvaneh plant using both microwave (MW) and pulsed electric field (PEF) techniques. The MW method was tested at different processing times (90, 180, and 270 s) and power levels (180, 540, and 900 W), while the PEF method was evaluated with varying electric field intensities (0.25, 3.25, and 6.25 kV/cm) and pulse numbers (10, 45, and 80) using a central composite design (CCD). The results revealed that extraction efficiency, total phenolic content, and total flavonoid content were significantly higher with the PEF method compared to the MW method (p < 0.05). Moreover, the PEF technique showed superior performance in preserving the antioxidant properties of the extract, as assessed by DPPH and FRAP methods. GC/MS analysis confirmed the presence of 27 bioactive compounds in the Arvaneh extract obtained through PEF-assisted extraction. In conclusion, the PEF method proved to be highly efficient for extracting bioactive compounds from the Arvaneh plant.

Step Pulse-Mediated Low-Triggering Potential Electrochemiluminescence of Polyfluorene Nanoparticles for Bioassay.

When the electrochemiluminescence (ECL) reaction occurs at a triggering potential beyond ±1.0 V, the interference from the adverse oxidation-reduction reaction cannot be ignored. However, currently reported anode ECL usually occurs above +1.0 V. This study innovatively developed a convenient and simple step pulse (SP) method to modulate the low ECL triggering potential of poly [(9,9-dioctyl-fluorenyl-2,7-diacyl)-alt-co-(9-hexyl-3,6-carbazole)] (PFA) nanoparticles (NPs). Compared to cyclic voltammetry with a triggering potential exceeding +1.25 V for PFA NPs, SP scanning enabled PFA NPs to exhibit a strong and stable ECL emission with a triggering potential as low as +0.75 V and tripropylamine (TPrA) as a coreactant. PFA NPs coupled an efficient aptameric recognition-driven cascade nucleic acid amplification strategy to construct a sensitive biosensing platform for measuring phosphorylated Tau (p-Tau) protein as an Alzheimer's disease biomarker. p-Tau could release the secondary target (ST) chain through the aptameric recognition reaction with the aptamer, and the released ST could further trigger cascade catalytic hairpin assembly (CHA) and rolling circle amplification (RCA) at the PFA NP-modified electrode, producing a large number of long chains. The large amount of G-quadruplex/hemin formed by long chains and hemin will consume the ECL quencher H2O2 added in detection solution, thereby restoring the ECL signal and enabling the low potential quantitative analysis of p-Tau with a limit of detection of 4.15 fg/mL. SP technique provides a new way to reduce ECL triggering potential, and PFA NPs create a promising low-triggering potential ECL-sensing platform for bioanalysis.

Confirmation of Solid Phase Extracted Post‐Blast Explosives Residues Analyzed Using Pulsed Split Injection GC/MS

AbstractA pulsed split injection method was developed for the improved detection of explosives using gas chromatography with mass spectrometric detection (GC/MS) with negative chemical ionization for 12 organic explosives (nitramines, nitrate esters, nitroalkanes, nitroaromatics) and electron ionization with selected ion monitoring for triacetone triperoxide (TATP). An order of magnitude increase in signal (average factor of 13) was observed for all organic explosives with the utilization of the pulsed split injection for samples processed by solid phase extraction (SPE). The method was successfully applied to post‐blast explosives residue processed by SPE and syringe filtration as a confirmatory technique following gas chromatography with electron capture detection (GC/ECD) screening. Compared to current methodologies previously reported, a decrease in the false screen rate (the number of compounds that passed the screening criteria, but not confirmed present) was achieved when employing this method. Processing of post‐blast explosives samples using SPE decreased the false screen rate from 60% to 34%, while using syringe filtration decreased the false screen rate from 73% to 51%.

The effect of positive and reverse current cycles on the wettability, morphology, and corrosion behaviour of electrodeposited nickel matrix layer

ABSTRACT In this study, Ni-TiO2 coatings were formed using a multi-step pulse method with positive and, in some cases, reverse current steps. All coatings were produced at a current density of 4 A dm−2 and a frequency and duty cycle of 10 Hz and 10%, respectively with a thickness of 30 µm. The results showed that by applying the reverse current cycle, the codeposition of TiO2 particles in the coating decreased and the morphology of the coating became irregular. It was found that the effect of the wetting angle of the coating is greater than the incorporation of TiO2 particles on the corrosion behaviour of the coating. Thus, a coating was created with a positive 4-step pulse current with the lowest amount of TiO2 particles (7.7 vol.%) having the highest resistance against corrosion. The sample had compact morphology and high wetting angle (82.61o֯).

A novel simulation of space charge decay dynamics after removing the voltage in epoxy resin composites

Abstract Epoxy resin serves as a critical insulating component in ultra-high voltage dry direct current bushings. However, the accumulation of space charges within the epoxy resin, a byproduct of charge mobility, poses a significant risk to the reliability and operational safety of bushings. Conventional space charge attenuation models, especially after voltage removal, have limited use in simulations aimed at understanding this phenomenon. This study introduces an improved model integrating the bipolar charge transport mechanism with space charge decay based on the hopping conduction mechanism and Schottky’s theorem, establishes a theoretical framework for predicting the space charge behavior following voltage removal, and conducts a simulation to investigate the decay process within the internal structure of epoxy resin and measure the residual charges after voltage removal using the pulsed electro-acoustic method. The experimental data validate the accuracy of the proposed model and theoretical assumptions. The findings show that the remaining negative charges after voltage removal are not enhanced by the field enhancement; the anodic positive and cathodic positive charges are distributed in two-segment discontinuous traps, whereas the negative charges are distributed in one-segment traps. The model identifies two distinct trapping sites for anodic and cathodic positive charges, and one trapping site for negative charges. After voltage removal, when the field strength exceeded 40 kV mm−1, positive charges exist near the upper and lower electrodes, and negative charges exist near the center of the specimen. The consistency between the simulated predictions and experimental data proves the effectiveness of the proposed model in accurately simulating the space charge decay in epoxy materials after voltage removal.

Analytical relations for fields and currents in magnetic-pulsed «expansion» of tubular conductors of small diameter

Introduction. This work was initiated by the problems of cardiovascular diseases, which are one of the main causes of mortality of the population of our planet. More than ten years ago, in 2012, approximately 3.7 million people died of acute coronary syndrome worldwide. The fight against such pathologies is carried out with the help of so-called stents, the manufacture of which can be carried out by the method of magnetic pulse «expansion» from hollow metal cylinders. The limited production possibilities of magnetic pulse «expansion» were caused by the minimum cross-sectional size of the inductor-instrument, which can be practically manufactured. Other tools are required to perform this operation. Novelty. A system of magnetic-pulse expansion of thin-walled pipes of small diameter with an inductor that excites an azimuthal electromagnetic field in the case of direct current passing through the processing object and in the absence of its connection in an electric circuit with an inductor is proposed. Purpose. The main analytical dependencies for the characteristics of the electromagnetic processes taking place in the inductor systems for the expansion of cylindrical conductive pipes of small diameter when direct passage of current through the processed object and when it is not connected to an electric circuit with an inductor (insulated billet) is derived. Methods. The solution of the boundary value problem with given boundary conditions was carried out by applying Laplace transforms and integrating Maxwell’s equations. Results. Analytical expressions were obtained for the main characteristics of the processes: the intensities of the excited electromagnetic fields and currents in the system depending on the parameters of the studied systems. The analysis of possible technical schemes for solving the given problem indicated the choice of the optimal variant of an effective system of magnetic-pulse «stretching» of thin-walled cylindrical conductors of small diameter. Practical value. Based on the qualitative analysis of the obtained results, recommendations for the practical implementation of the proposed system were formulated. The obtained dependences allow us to give numerical estimates of the effectiveness of excitation of magnetic pressure forces on the object of processing and to choose directions for further improvement of the magnetic pulse technology for solving such problems. References 23, figures 2.

Rationalising spin relaxation during slice-selective refocusing pulses

Slice-selective refocusing pulses are powerful building blocks in contemporary magnetic resonance experiments, but their use in quantitative applications is complicated by the site-dependent signal loss they introduce. One source of this attenuation is the spin relaxation that occurs during such pulses, which causes losses that depend on the specific longitudinal and transverse relaxation time constants for a given resonance. This dependence is complicated both by any amplitude shaping of the radiofrequency pulse, and by the presence of the spatial encoding pulsed field gradient. The latter causes the net signal measured to be the weighted sum of signal contributions from a continuous range of offsets from resonance. In general, each offset will make a different contribution to the overall signal, and will be attenuated by a different mixture of longitudinal and transverse relaxation that is dictated by the different trajectories that the nuclear magnetisations take during experiments. Despite this complex behaviour, we present evidence from experiments and numerical simulations showing that in practical experimental applications a relatively simple empirical function can be used to accurately predict relaxational attenuation during slice-selective refocusing pulses. This approach may be of practical use in correcting for relaxational losses in quantitative applications of slice-selective pulse methods such as Zangger–Sterk pure shift NMR.

Physical coherent cancellation of optical addressing crosstalk in a trapped-ion experiment

Abstract We present an experimental investigation of coherent crosstalk cancellation methods for light delivered to a linear ion chain cryogenic quantum register. The ions are individually addressed using focused laser beams oriented perpendicular to the crystal axis, which are created by imaging each output of a multi-core photonic-crystal fibre waveguide array onto a single ion. The measured nearest-neighbor native crosstalk intensity of this device for ions spaced by 5 µm is found to be ∼ 10 − 2 . We show that we can suppress this intensity crosstalk from waveguide channel coupling and optical diffraction effects by a factor &gt; 10 3 using cancellation light supplied to neighboring channels which destructively interferes with the crosstalk. We measure a rotation error per gate on the order of ϵ x ∼ 10 − 5 on spectator qubits, demonstrating a suppression of crosstalk error by a factor of &gt; 10 2 . We compare the performance to composite pulse methods for crosstalk cancellation, and describe the appropriate calibration methods and procedures to mitigate phase drifts between these different optical paths, including accounting for problems arising due to pulsing of optical modulators.

Speed of sound measurements of binary n-octane+ ethylcyclohexane mixture at liquid-gas phase transition curve

Bio-jet fuel is a key element in the aviation industry to reduce operating costs and environmental impacts. Bio-jet fuel is a complex mixture of four hydrocarbons (n-alkanes, isoalkanes, cycloalkanes and aromatics). In the present work, the speed of sound in pure n-octane, ethylcyclohexane, and their mixtures with six selected compositions of (0.3004, 0.4191, 0.4999, 0.5538, 0.6991, and 0.7852 mole fraction of ethylcyclohexane) has been measured along the l-G saturation curve in the temperature ranges from (286 to 443) K using the pulse method with a constant (acoustic) sounding base. The combined expanded absolute and relative uncertainties (0.95 level of confidence, k = 2) of the temperature, concentration, and speed of sound measurements are estimated to be 20 mK, 0.0006 mole fraction, and 0.2 %, respectively. The measured speed of sound data together with our previous reported density data for the pure component (ethylcyclohexane) and the mixture were used to calculate derived thermodynamic properties, such as isentropic compressibility kS and heat capacity ratios CPCV as a function of temperature along the l-G saturation curve for the pure components and the mixture for selected concentration of x = 0.8 mole fraction of ethylcyclohexane. The deviation of the measured speed of sound data for the mixture from the linear additive rule has been determined using the pure component data.