Resonance Experiments Research Articles

Correlation between ferroelectricity and torsional motion of acetyl groups in tris(4-acetylphenyl)amine observed by muon spin relaxation

It is demonstrated by muon spin relaxation and resonance experiments that the switchable spontaneous polarization of the organic ferroelectric compound tris(4-acetylphenyl)amine is governed by the local molecular dynamics of the acetyl group. The implanted muon forms paramagnetic states, which exhibit longitudinal spin relaxation due to the fluctuation of hyperfine fields exerted from unpaired electrons. The first-principle density functional theory calculations indicate that these states are muonated radicals localized at the phenyl group and on the carbon/oxygen of the acetyl group, thereby suggesting that the spin relaxation is dominated by the random torsional motion of an acetyl group around the C–C bond to the phenyl group. The stepwise change in the relative yield of radicals at T0≈350 K and the gradual increase in the spin relaxation rate with temperature (T) indicate that the torsional motion is significantly enhanced by thermal excitation above T0. This occurs concomitantly with the strong enhancement in the atomic displacement parameter of oxygen in the acetyl group (which is non-linear in T), indicating that it is the local molecular motion of the acetyl groups that drives the structural transition.

UltraStat: Ultrafast Spectroscopy beyond the Fourier Limit Using Bayesian Inference.

The discrete Fourier transform (dFT) plays a central role in many ultrafast experiments, allowing the recovery of spectroscopic observables from time-domain measurements. In resonant experiments when population relaxation and coherence components of the signal coexist, the dFT is usually preceded by multiexponential fitting to remove the large population term. However, this procedure results in errors in both the recovered decay rates and the line shapes of the coherence spectral components. While other methods such as linear prediction singular value decomposition fit both terms simultaneously, they are limited to specific models that may not represent the true signal. These methods do not allow for systematic noise analysis or error estimation and require a priori knowledge of the signal rank. Here, we describe a general approach to parameter estimation in ultrafast spectroscopy─UltraStat─grounded in Bayesian analysis without the limitations set by Fourier theory. Using simulated, but realistic data, we demonstrate in a statistical sense how UltraStat provides accurate parameter estimation in the presence of many experimental constraints: noise, signal truncation, limited photon budget, and nonuniform sampling. UltraStat provides superior resolution compared to the dFT, up to an order of magnitude in cases where the line shapes are well-approximated. In these cases, we establish that primarily noise, not sampling, limits spectral resolution. Moreover, we show that subsampling may reduce the number of acquired points by 90% compared to the Nyquist-Shannon criteria. UltraStat greatly improves parameter estimation by providing statistically bound spectral and dynamics analysis, pushing the limits of ultrafast science.

Experimental Study on the Skyhook Control of a Magnetorheological Torsional Vibration Damper.

This study proposes a dual-coil magnetorheological torsional vibration damper (MRTVD) and verifies the effectiveness of semi-active damping control to suppress the shaft system's torsional vibration via experimental research. Firstly, the mechanical model of the designed MRTVD and its coupling mechanical model with the rotating shaft system are established. Secondly, the torsional response of the shaft system is obtained via resonance experiments, and the influence of the current on the torsional characteristics of the magnetorheological torsional damper is analyzed. Finally, the MRTVD is controlled using the skyhook control approach. The experimental results demonstrate that when the main shaft passes through the critical speed range at various accelerations, the amplitude of the shaft's torsional vibration decreases by more than 15%, and the amplitude of the shaft's torsional angular acceleration decreases by more than 22%. These conclusions validate the inhibitory effect of MRTVD on the main shaft's torsional vibrations under skyhook control.

Treatment of multiple-beam X-ray diffraction in energy-dependent measurements.

During X-ray diffraction experiments on single crystals, the diffracted beam intensities may be affected by multiple-beam X-ray diffraction (MBD). This effect is particularly frequent at higher X-ray energies and for larger unit cells. The appearance of this so-called Renninger effect often impairs the interpretation of diffracted intensities. This applies in particular to energy spectra analysed in resonant experiments, since during scans of the incident photon energy these conditions are necessarily met for specific X-ray energies. This effect can be addressed by carefully avoiding multiple-beam reflection conditions at a given X-ray energy and a given position in reciprocal space. However, areas which are (nearly) free of MBD are not always available. This article presents a universal concept of data acquisition and post-processing for resonant X-ray diffraction experiments. Our concept facilitates the reliable determination of kinematic (MBD-free) resonant diffraction intensities even at relatively high energies which, in turn, enables the study of higher absorption edges. This way, the applicability of resonant diffraction, e.g. to reveal the local atomic and electronic structure or chemical environment, is extended for a vast majority of crystalline materials. The potential of this approach compared with conventional data reduction is demonstrated by the measurements of the Ta L3 edge of well studied lithium tantalate LiTaO3.

A design method of high-compatibility horn for broad-bandwidth transducer.

Broad-bandwidth transducers are one of the main areas of focus for the development of power ultrasonic systems, which address the issues that the contactless transformer system cannot track transducer frequency and narrowband transducers are not compatible with different tools. This paper aims to investigate the potential capabilities of broad-bandwidth transducers in terms of compatibility with different horns and to propose a design method for highly compatible tools. The frequency equation of horn is nondimensionalized to calculate relative frequency errors δ. The effects of shape, dimensionless size, and order number on δ are investigated based on the equation. A compatibility range is proposed, and the relationship between it and the required relative bandwidth of the transducer is investigated. Various horns were designed, and the corresponding simulations, impedance measurements, and resonance experiments were conducted to explore the effects of these factors on δ, amplitude, and the quality factor Q. These experiments also verified the feasibility of using a broad-bandwidth transducer that is compatible with different tools. Finally, the application scenarios of the three horns are summarized based on a comparison of their matching ability, amplitude, operational stability, and compatibility range.

Effect and mechanism analysis of resonance on physical parameters of unconventional reservoirs

Inducing shale reservoir resonance is an environmentally friendly and efficient unconventional oil/gas production technology. It is necessary to study the effect of resonance on shale physical parameters. This paper clarifies the resonance mechanism of improving shale reservoirs and constructs the natural frequency parameter equation under a single excitation direction using vibration system theory and rock mechanics. The resonance experiment is carried out after the physical parameters of the shale and coal samples are verified by material characterization technology. Meanwhile, CT scanning technology and matrix permeability tests are used to measure the samples’ pore development and permeability changes. Eventually, the coalbed methane field in Qinshui Basin, Shanxi province, was selected as the experimental object for the reservoir resonance test. We analyzed the production data of the test wellhead. The results indicate that the mechanism of resonance improvement of shale physical parameters promotes the redevelopment of primary cracks in the rock mass; the porosity and permeability of rock mass are increased by 2–12 times and 2–8 times, respectively, after the once resonance test. The CBM (coalbed methane) wells whose productivity is in a state of decay have been significantly enhanced after resonance stimulation, and the relative daily gas production is increased by 101.61%.

Electromagnetic Design and Analysis of Permanent Magnet Linear Synchronous Motor

Since permanent magnet linear synchronous motors are widely used in fatigue testing, in this paper, the thrust of a permanent magnet linear synchronous motor (PMLSM) is amplified more than 10 times by the method of resonance. Firstly, the air gap magnetic field is analyzed by the equivalent magnetization current method (EMC), the electromagnetic thrust is calculated, and the expression is given by the Maxwell tensor method. The vibration analysis of the whole machine is used to obtain the conditions under which the motor resonates. The dynamic and static characteristics of the motor are analyzed through finite element simulation, the results of the motor design are judged to be reasonable, and the theoretical calculation results are compared with the simulation results to verify the accuracy of the theoretical calculation. The accuracy of the simulation results is verified by static force experiments. Finally, the rated thrust of the motor was enlarged more than 10 times by resonance experiments.

Quantification of Pore Size and Movable Fluid Distribution in Zhangjiatan Shale of the Ordos Basin, China

The Triassic Zhangjiatan shale in the Ordos basin, recognized as one of most promising shale oil and gas resources in China, is one example of medium-low-maturity lacustrine shale reservoirs wherein the pore network has been proven to be different from those of both conventional and high-maturity marine shale reservoirs. Here, we examine the quantitative characterization of pore size and movable fluid distribution of the Zhangjiatan shale reservoir. Eight shale core plugs were measured in a series of nuclear magnetic resonance (NMR) experiments to determine the pore structure and pore fluid transport during the processes of centrifuging and heating. The complete pore size distribution was obtained from the T 2 spectrum by integrating NMR, high-pressure mercury intrusion, and nitrogen gas adsorption. The results show that the movable fluid saturation of Zhangjiatan shale is 19.47–33.02% and the capillary-bound fluid saturation is 14.53–27.62%, whereas the unrecoverable fluid saturation was 43.51–65.26%. The movable fluids are mainly detected in macropores and mesopores with a minimum pore size of 50.5–121.2 nm, while capillary-bound fluids are mainly found in small pores and some mesopores with a minimum size of 25.8–67.5 nm. Almost all unrecoverable fluids are in micropores and small pores. In contrast to high-maturity shale reservoirs, the Zhangjiatan shale shows a poor correlation between total organic carbon content and unrecoverable fluid saturation but a good correlation between clay minerals and unrecoverable fluid saturation, showing that most micropores are associated with clay minerals and the organic matter pores are less developed. This study provides an accurate determination of the pore size distribution and pore fluid typing of Zhangjiatan shale, which is of great significance for the development of high-quality but medium-low-maturity shale reservoirs in China.

Design, synthesis, and biological evaluation of chalcones for anticancer properties targeting glycogen synthase kinase 3 beta

Chalcones compounds have been investigated to exhibit anticancer activity through various physiological modes of action. In order to develop chalcone compounds with novel anticancer-related modes of action, diverse chalcone compounds were designed and synthesized. Variously substituted poly-methoxy chalcone compounds 1–17 were prepared, and their structures were identified using high-resolution mass spectrometry (HR/MS) and nuclear magnetic resonance (NMR) experiments. Long-term survival clonogenic assay was applied to evaluate their anti-cancer abilities and revealed that their GI50 values ranged between 1.33 and 172.20 μM. When MCF-7SC cells were treated with various concentrations of compound 14, reduced cell viability and induced apoptosis in MCF-7SC cells were observed in a dose-dependent manner. Wound healing assay demonstrated that compound 14 prevented the MCF7-SC migrated cells at non-lethal concentrations after 12 and 24 h of exposure. The efficiency of compound 14 on the levels of Epithelial-mesenchymal transition (EMT) markers was accessed by the western blot analysis. For the concrete understanding of anticancer properties at the molecular level, in vitro kinase assays on 12 cancer related proteins were carried out. Glycogen synthase kinase 3 beta (GSK3β) was most effectively inhibited by compound 14 with 89% inhibitory activity at 10 µM against GSK3β. The binding mode of compound 14 with GSK3β was reinforced through in silico experiments, which demonstrated compound 14 binds with GSK3β at binding affinity ranged between − 7.5 kcal/mol and − 6.8 kcal/mol. SwissADME analysis provided the druggability and leadlikeness of compound 14, which unveiled drug development possibilities of chalcone compound 14.

Heat-activated peracetic acid for degradation of diclofenac: kinetics, influencing factors and mechanism

ABSTRACT Heat-activated peracetic acid (PAA) was used to degrade diclofenac (DCF) in this study. Electron paramagnetic resonance and radical scavenging experiments proved that organic radicals (i.e. CH3C(=O)O• and CH3C(=O)OO•) were the primary active species for DCF removal in the heat/PAA process. The degradation efficiency of DCF increased with the increase of temperature or initial PAA concentration in the heat/PAA process, and the optimal reaction pH for DCF removal was neutral. The presence of NO3 − or SO4 2− insignificantly affected DCF degradation, while Cl− was favourable for DCF removal in this process. In contrast, an obvious inhibition on the removal of DCF was observed with the addition of natural organic matter, which might be responsible for the lower DCF removal in real waters. Finally, dechlorination, formylation, dehydrogenation and hydroxylation were proposed to be four degradation pathways of DCF in the heat/PAA system based on the five detected transformation products.

Mesoscopic structural damage and permeability evolution of Shale subjected to freeze\u2013thaw treatment

To study the mesoscopic damage and permeability evolution characteristics of rock under freeze–thaw (F–T) cycles, freeze–thaw cycle experiments were carried out of shale under different F–T temperatures and numbers of cycles, and nuclear magnetic resonance (NMR) and permeability experiments of shale were conducted thereafter. On the basis of these experiments, the pores and permeability of the F–T shale were analyzed, and the existing permeability model is modified and improved; Therefore, the mesoscopic damage evolution characteristics and permeability evolution law of the F–T shale are obtained. It was found that with increasing number of cycles, the pore structure of the rock samples changed as the pore size expanded and the number of pores increased, and the average porosity also increased correspondingly. The influence of the F–T cycle temperature on the shale permeability was not as notable as that of the number of F–T cycles. Based on the SDR-REV permeability model, the spectral area ratio parameters of large pores and fractures in the T2 spectrum were considered for correction, and a direct relationship between the permeability, F–T temperature and number of cycles was obtained via regression analysis. Compared to the experimental results, it was found that the modified model achieved a good applicability. The damage and permeability characteristics of shale under different F–T conditions were analysed from a microscopic perspective, which could yield an important reference for engineering construction in frozen soil areas.

Valorization of Hesperidin from Citrus Residues: Evaluation of Microwave-As

The aim of the current study was the valorization of hesperidin, the dominant flavonoid in citrus processing waste, by microwave-assisted synthesis of hesperidin-Mg complex, improving its antioxidant activity and insecticidal potential. Here we show, for the first time, that microwaveassisted synthesis of [Mg(hesp)2(phen)]OAc (1) (hesp: hesperidin, phen: phenanthroline) improve the reaction rate and yield. The nuclear magnetic resonance (NMR) experiments proved to be powerful tools for the identification of three isomers in metal complexes. Moreover, we explore the insecticidal potential of 1 and [Mg(phen)2(Isov)]OAc (2) (Isov : isovanillic acid) complexes against three insects. Complex 1 killed 80% of adults whitefly at 0.14 μmol L-1, and 2 76% at 0.36 μmol L-1. There was a total mortality of Spodoptera frugiperda with 2 at 0.39 μmol L-1, and 83% with 1 at 0.14 μmol L-1. Both have similar activity, and represent a novel group of insecticide for Bemisia tabaci and S. frugiperda; nevertheless, the benefits of both as Myzus persicae repellent require further evaluation.

Engineering high-coherence superconducting qubits

Advances in materials science and engineering have played a central role in the development of classical computers and will undoubtedly be critical in propelling the maturation of quantum information technologies. In approaches to quantum computation based on superconducting circuits, as one goes from bulk materials to functional devices, amorphous films and non-equilibrium excitations — electronic and phononic — are introduced, leading to dissipation and fluctuations that limit the computational power of state-of-the-art qubits and processors. In this Review, the major sources of decoherence in superconducting qubits are identified through an exploration of seminal qubit and resonator experiments. The proposed microscopic mechanisms associated with these imperfections are summarized, and directions for future research are discussed. The trade-offs between simple qubit primitives based on a single Josephson tunnel junction and more complex designs that use additional circuit elements, or new junction modalities, to reduce sensitivity to local noise sources are discussed, particularly in the context of materials optimization strategies for each architecture. Superconducting qubits hold great promise for quantum computing, and recently there have been dramatic improvements in both coherence times and the power of quantum processors. This Review explores how the path forward involves balancing circuit complexity and materials perfection, eliminating defects while designing qubits with engineered noise resilience.

Experimental study on response characteristics of coal adsorption and desorption under electric field enhancement

ABSTRACT DC electric field intensified oil and gas production technology is widely used in oil and gas field in China. Aiming at the characteristics of the coal reservoir medium under the electric field, we have the self-made adsorption and desorption experimental system of coal and rock samples under the high-strength electricity. Using the anthracite coal from Jiulishan mine and Zhaogu No.2 mine to carry out gas adsorption and desorption experiments with real-time on-line electricity. And we carried out the nuclear magnetic resonance (NMR) experiment and mercury intrusion experiment of coal samples. Our experiments show that: (i) the high-strength direct current alone to intensify the adsorption process, we found that have a characteristic field strength, which is beneficial to the adsorption of gas by the coal sample. The adsorption capacity and the field strength have a parabolic relationship, and the maximum value under characteristic field strength; The high-strength direct current is applied in the whole process of adsorption and desorption, we found that the desorption volume and desorption rate were obviously enhanced; The high-strength direct current alone to intensify desorption process, the experiment phenomenon is same as the former, but the enhancing result is weaker than the whole process with the electric field; In the experiment of direct current intensifying, the gas absorption volume, desorption volume and desorption rate are the largest at 60 kV/m that we were preliminarily determined to be the advantage field intensity of coal sample; Under this field intensity, the Gibbs free energy reaches the maximum, increased by 23.5% and 3.01%, respectively, the P2 peak area of T2 spectrum increases nearly 9 times, and the peak shifts to the right. At the same time, the proportion of the specific surface area of the micropores in the mercury injection experiment decreased, and the proportion of the pore volume increased. These together indicated that the advantageous field strength has the effect of increasing pores and cracks in the strengthening effect of the coal sample. And it is reflected in the macroscopically to promote adsorption and promoting desorption. In this paper, we explain the relationship among direct current electric field, gas adsorption and desorption from the experimental point of view. The experimental results provide a new perspective for the design of the internal surface of the coal body through a direct current electric field and it can make the internal surface of coal rock has the characteristics of efficient gas extraction.

Fractal characteristics of the microstructure of loaded coal based on NMR and μ-CT

ABSTRACT The change in the fracture microstructure of loaded coal affects the gas seepage characteristics of the coal. Using micron CT scanning (μ-CT) and nuclear magnetic resonance (NMR) experiments, the fractal characteristics of coal fracture structure under triaxial compression are studied from two aspects of theoretical and experimental fractal dimension for the first time. VG Studio MAX software was used to reconstruct the three-dimensional (3D) fracture structure of the coal samples, and the 3D fracture structure was modified by the porosity measured by NMR. Through the analysis of the reconstruction model and the T2 relaxation spectrum, the spatial distribution of internal cracks in coal was obtained. The fractal geometry theory, NMR experimental fractal dimension algorithm and 3D box counting method were used to calculate the theoretical and experimental fractal dimensions and then comprehensively analyze the fractal characteristics of cracks in loaded coal. The results show that an external load promotes the development of pores/cracks in coal. With increasing theoretical fractal dimension, CT porosity increases from 0.0630% to 0.101%, and NMR porosity increases from 0.0655% to 0.105%. The relationship between porosity and theoretical fractal dimension can be expressed by y = ax2+ bx+c (fractal dimension is an independent variable). With increasing porosity, the experimental fractal dimension of NMR decreases linearly from 2.975 to 2.951, and the experimental fractal dimension of μ-CT increases linearly from 2.191 to 2.324. The different changing trends of theoretical and experimental fractal dimensions verify the differences in their representational meanings.

A study on core spontaneous imbibition behavior via nuclear magnetic resonance and displacement experiments

ABSTRACT Spontaneous imbibition is auniversal phenomenon in nature, which plays asignificant role in the two-phase flow of gas reservoirs with water. To quantitatively evaluate the spontaneous imbibition behavior of tight sandstone gas reservoirs, this paper conducts experiments on cores with different imbibition times based on core imbibition experiments, combined with nuclear magnetic resonance (NMR) and displacement experiments. In this paper, some significant findings were obtained by the imbibition experiments and NMR, which mainly included the T2 spectral response of spontaneous imbibition and the relationship between threshold pressure gradient (TPG) and water saturation. Homogenous propulsion of water through the macropores which are about 0.5 μm and the effective permeability has decreased by 70–80%. Displacement experiments proved that the threshold pressure phenomenon existed in the imbibition cores, the longer the imbibition time, the higher the water saturation, and the bigger TPG. After the dimensionless treatment, there is apositive linear correlation between TPG and water saturation. The results of this research play an important role in the study of percolation laws of agas reservoir with water and distribution characteristics of residual gas.

Design optimization analysis of an anti-backlash geared servo system using a mechanical resonance simulation and experiment

Abstract. In many mechatronic systems, gear transmission chains are often used to transmit motion and power between motors and loads, especially for light, small but large torque output systems. Gear transmission chains will inevitably bring backlash as well as elasticity of shafts and meshing teeth. All of these nonlinear factors will affect the performance of mechatronic systems. Anti-backlash gear systems can reduce the transmission error, but elasticity has to be considered too. The aim of this paper is to find the key parameters affecting the resonance and anti-resonance frequencies of anti-backlash gear systems and then to give the design optimization methods of improving performance, both from element parameters and mechanical designing. The anti-backlash geared servo system is modeled using a two-inertia approximate model; a method of computing the equivalent stiffness of anti-backlash gear train is proposed, which comprehensively considers the total backlash of transmission chain, gear mesh stiffness, gear shaft stiffness and torsional spring stiffness. With the s-domain block diagram model of the anti-backlash geared servo system, the influences of four main factors on the resonance and anti-resonance frequencies of system are analyzed by simulation according to the frequency response, and the simulation analysis results dependent on torsional spring stiffness of anti-backlash gear pair and load moment of inertia variation are verified by the experiment. The errors between simulation and experimental results are less than 10 Hz. With these simulation and experiment results, the design optimization methods of improving the resonance and anti-resonance frequencies such as designing the center distance adjusting mechanism to reduce the initial total backlash, increasing the stiffness of torsional spring and lightweight design of load are proposed in engineering applications.

LAB-BASED LEARNING IN UNIVERSITY FOR PRIMARY SCHOOL STUDENTS FOCUSED ON ACOUSTICS

This paper deals with the using of interactive acoustic experiments in teaching from the lowest levels of the education system, motivation and stimulation into science, physics and acoustics from early childhood. Initial playful experimentation is usually a stimulating factor that will later motivate students to analyse and evaluate higher cognitive goals according to Bloom's taxonomy in their studies at the technical universities. Recording of sounds followed by frequency analysis, investigation of oscillate solid, Chladni's pictures, Kund's tube, Helmholtz resonator and other acoustic experiments are very useful and illustrative not only for students at a technical university but they can also help in building basic ideas about the propagation of sound in children attending the primary school. The Children's University of Žilina every year in summer time try to increase the education level of the nation with the emphasis especially on the young people to show the research and development importance for the future improvement of the society.

Molecular beam magnetic resonance coupled with a cryogenically cooled, pulsed laser vaporization source and time-of-flight mass spectrometry

A molecular beam magnetic resonance apparatus designed for the study of polyatomic molecules and small metal clusters is described. In contrast to atoms, vibrational and rotational excitation in clusters and molecules invoke spin relaxation upon a change of magnetic flux density. To prevent this, a pulsed laser vaporization source with a cryogenically cooled nozzle is utilized to minimize thermal excitation and a magnet setup has been designed to diminish magnetic field fluctuations. The apparatus is evaluated by Stern–Gerlach and resonance experiments on an atomic europium beam with the identical pulsed laser vaporization source.

Solid-state NMR spectroscopic studies of 13C,15N,29Si-enriched biosilica from the marine diatom Cyclotella cryptica

Diatoms are algae producing micro- and nano-structured cell walls mainly containing amorphous silica. The shape and patterning of these cell walls is species-specific. Herein, the biosilica of Cyclotella cryptica, a centric marine diatom with a massive organic matrix, is studied. Solid-state NMR spectroscopy is applied to gain deeper insight into the interactions at the organic–inorganic interface of the cell walls. The various organic compounds like polysaccharides as well as proteins and long-chain polyamines (LCPAs) are detected by observation of heteronuclei like 13C and 15N whereas the silica phase is studied using 29Si NMR spectroscopy. The sensitivity of the NMR experiments is strongly enhanced by isotope-labeling of the diatoms during cultivation with 13C, 15N and 29Si. The presence of two different chitin species in the biosilica is demonstrated. This observation is supported by a monosaccharide analysis of the silica-associated organic matrix where a high amount of glucosamine is found. Moreover, the Rotational Echo Double Resonance (REDOR) experiment provides distance information for heteronuclear spins. 13C{29Si} REDOR experiments reveal proximities between different organic compounds and the silica phase. The closest contacts between silica and organic compounds appear for different signals in the 13C-chemical shift range of 40–60 ppm, the typical range for LCPAs.