Tunneling Effect Research Articles

Quantum tunnelling effect in the cis-trans isomerization of uranyl tetrahydroxide.

The role of quantum tunnelling (QT) in the proton transfer kinetics of the uranyl tetrahydroxide (UTH, [UO2(OH)4]2-) cis to trans isomerization was computationally studied under three possible reaction pathways. The first pathway involved a direct proton transfer from the hydroxide ligand to the oxo atom. In the other two pathways, one or two water molecules were added to the second sphere. The first H2O, bound by hydrogen bonds to the ligands, acts as a bridge enabling a proton shuttling, a concerted hopping of a proton from the hydroxide to the oxo atom similar to the Grotthuss mechanism. In the third pathway, the second water molecule does not participate in the H-transfer chain, but works as an anchor for the first water molecule, limiting its movement and therefore enhancing the QT. Since experimentally the reaction occurs in water, the first two pathways (no water or one H2O) serve only as models of the gas phase behaviour, while the third pathway will always be thermodynamically and kinetically preferred. The effects were investigated in the gas phase as well as in a continuum aqueous model, including the H/D Kinetic Isotope Effect (KIE). The results indicate that at very low temperatures, QT is the only mechanism that permits the reaction kinetics, consistent with the large computed KIE. At higher temperatures, thermally activated tunnelling competes with the classical crossing over the potential barrier.

Precise weight tuning in quantum dot-based resistive-switching memory for neuromorphic systems.

In this study, nonvolatile bipolar resistive switching and synaptic emulation behaviors are performed in an InGaP quantum dots (QDs)/HfO2-based memristor device. First, the physical and chemical properties of InGaP QDs are investigated by high-resolution transmission electron microscopy and spectrophotometric analysis. Through comparative experiments, it is proven that the HfO2 layer improves the variations in resistive switching characteristics. Additionally, the Al/QDs/HfO2/ITO device exhibits reversible switching performances with excellent data retention. Fast switching speeds in the order of nanoseconds were confirmed, which could be explained by trapping/detrapping and quantum tunneling effects by the trap provided by nanoscale InGaP QDs. In addition, the operating voltage is decreased when the device is exposed to ultraviolet light for low-power switching. Biological synapse features such as spike-timing-dependent plasticity are emulated for neuromorphic systems. Finally, the incremental step pulse using proven algorithm method enabled the implementation of four-bit states (16 states), markedly enhancing the inference precision of neuromorphic systems.

Theoretical kinetic studies on intramolecular H-migration reactions of peroxy radicals of diethoxymethane.

Diethoxymethane (DEM), a promising carbon-neutral fuel, has high reactivity at low temperatures. The intramolecular hydrogen migration reaction of the DEM peroxy radicals can be viewed as a critical step in the low temperature oxidation mechanism of DEM. In this work, multistructural transition state theory (MS-TST) was utilized to calculate the high-pressure limit rate constants of 1,5, 1,6 and 1,7 H-migration reactions for DEM peroxy radicals. In addition to the tunneling effects and anharmonic effects, the intramolecular effects, including steric hindrance, intramolecular hydrogen bonding and conformational changes in reactants and transition states, are also considered in the rate constant calculations. The calculated energy barriers and rate constants demonstrated the substantial impact of intramolecular effects on the kinetics of H-migration reactions in DEM peroxy radicals. Specifically, the distinct configurations of transition states could potentially influence the reaction kinetics. The pressure-dependent rate constants are computed using system-specific quantum RRK theory. The calculated results show that the falloff effect of 1,5 and 1,6 H-migration reactions is more pronounced than that of the 1,7 H-migration reaction. The thermodynamics and kinetics presented in this study could be instrumental in understanding the low-temperature oxidation mechanism of DEM and might prove crucial for future research on comprehensively analyzing the autoignition behavior.

TABAKALI ZEMİNLERDE TÜNEL AÇMANIN KAZIKLI TEMEL ÜZERİNDEKİ ETKİSİ

It is believed that tunnel construction will have significant and intricate effects on structures supported by piles. One of the most popular approaches to research is numerical modeling. This study looked into how tunnel placement affected piled foundation systems in layered soil. In sixteen models utilizing PLAXIS 2D finite element analysis, a square foundation with dimensions of 26×26×2 meters and a load of 200 kPa was applied to the soil profile representing Istanbul's Avcilar district. In the 11×7 formation, two groups of piles were created, each with a fixed spacing of 2.4 meters and varying diameters of 0.8, 1.2 with 30 meters in length. The piles were placed 4 meters out of the plane and 1 meter from the edges. For every pile group, a 10-meter-diameter tunnel was examined at two various Z⁄D and four various X⁄D from the foundation's center to determine the influence of the tunnel location. According to the results, the surface total settlement values decrease, and the differential settlements increase as the tunnel is positioned farther in the x direction from the foundation center axis. The pile's bending moment slightly decreases as the tunnel's horizontal location gets farther away from it. The tunnel's effect decreases with increasing distance within the influence zone. Tunnel settlement cannot be significantly reduced by deepening the tunnel or increasing the pile's diameter.

여수-남해 해저터널 효과 극대화를 위한 채널 터널사례 분석으로 본 여수 발전전략 고찰

여수-남해 해저터널 효과 극대화를 위한 채널 터널사례 분석으로 본 여수 발전전략 고찰

Impact of nanoparticles on human health and disease.

Nanoparticles (NPs) are small particles with a surface area ranging from 1 to 100 nm in diameter that are rampantly used in different fields, e.g., medicine, engineering, and others. Because of their unique properties, such as their tiny size, magnetic properties, quantum size effects, and macroscopic quantum tunnelling effects, they are crucial for a wide range of potential applications. NPs play a significant role in the treatment of vascular disorders, the production of vaccines, and the development of drug carriers for diverse therapies due to their bioavailability, targeting ability, and efficacy. However, significant risks to the environment and health are also associated with it. NPs cause necrotic plasma membrane rupture or apoptosis, which leads to cell death. NPs interfere with cell signalling, endosomal membranes, and organelles like the nucleus or mitochondria, affecting their function. NPs cause autophagic cell death, which causes a stress response and sterile inflammation. The primary routes for the entry of NPs into the human body are inhalation, ingestion, and skin contact. NPs accumulate in the respiratory system based on their size, shape, and surface properties. NPs can cause lung inflammation and fibrosis, disrupt the endocrine system by attaching to hormone receptors, and produce reactive oxygen species (ROS) associated with DNA damage, oligospermia, and male infertility. Carcinogenic properties of NPs cause mutations, apoptosis, and inflammatory responses. Collaborative research between ecologists and epidemiologists may enlighten ways to reduce the harmful effects of NPs.

Analysis of the Deformation and Dynamics of High-Speed Railway Bridge Under the Coupling Effect of Shield Tunneling and Train Load

In order to study the dynamic response of high-speed railway bridge and its deformation law under the coupling effect of vibration load and shield tunneling, a coupling model of shield tunneling and train load is established based on the actual case of tunneling under an adjacent bridge. The deformation characteristics and dynamic response of the bridge are investigated by analyzing the deformation under different tunneling conditions and train running speeds. The results show that the maximum disturbance of the original stress field around the bridge is caused when the shield penetrates to the near side of the bridge structure, at which time, the damping effect of the ground and bridge system on the vibration load is weakened, thus intensifying the dynamic response of the bridge system, and the additional deformation caused by the vibration load is the largest; the presence of train loads during the shield excavation slightly attenuates the differential settlement of the bridge, but increases the cumulative settlement of the bridge, in addition, the additional deformation of the bridge will increase with the increase of the train running speed; the additional deformation caused by the train load within 2[Formula: see text]m of the shield crossing on both sides of the bridge is large, so the construction should be avoided as much as possible when the train is running in this construction section.

Tunneling induced transparency and slow light in an asymmetric double quantum dot molecule—Metal nanoparticle hybrid

We investigate the optical properties appearing in a nanostructure that is composed of an asymmetric double semiconductor quantum dot (SQD) molecule and a metal nanoparticle (MNP). The profile of the total linear absorption spectrum is proportional to the SQD contribution, while the MNP contribution is important. The profile of the doublet of resonances detected on the total linear absorption spectrum creates a transparency window. The doublet is asymmetric for small SQD-MNP distances and has a narrow peak and a wide peak. The width of the transparency window is increased, either with the enhancement of the rate at which the electron tunneling effect takes place within the double SQD molecule or with the decrease of the distance that separates the SQD molecule from the center of the MNP. The steep slope detected on the linear dispersion spectrum for frequencies laying within the transparency window owes its presence to the tunneling induced transparency and leads to slow light production. The corresponding value of the slow down factor is maximized for low values of the electron tunneling rate as well as for low center-to-center distances between the components of the hybrid nanostructure.

Study on waterproof and drainage technology of mountain tunnel in high-pressure and water-rich region

High-pressure groundwater brings great challenges to the construction of mountain tunnels. Hence, controlling and discharging groundwater are two key problems that must be addressed before constructing tunnels in high-pressure and water-rich region. Fluid–solid coupling seepage analysis method is used to analyze the variation of displacement, stress and pore water pressure of the tunnel. A waterproof and drainage method suitable for tunnels in high-pressure and water-rich region is proposed. Curtain grouting plays a dual role in waterproof and reinforcing surrounding rock. Decompression drainage holes are designed in order to further reduce the pore water pressure acting on the initial lining. The thickness of grouting circle, the permeability coefficient ratio and the decompression drainage holes distribution rate of the initial lining are the main factors that affect the waterproof and drainage effect of tunnels in high-pressure and water-rich region. Suggested parameters on waterproof and drainage measures for tunnels in high-pressure and water-rich region are given after comprehensive analysis, which can provide basis for the technology on high-pressure groundwater treatments and constructions of underground engineering under complex geological conditions.

Structural, dielectric, magnetic, optical, and electrical properties of double‐perovskite Sr1.5Mn0.5Fe0.5Hf1.5O6 oxides

AbstractHalf‐metallic ferromagnets (HMFs) exhibit semiconductor behavior for one spin projection and metal characteristics for the other, which have promising applications in spintronics. It is a great challengeable for HMFs to have wide spin energy gap, large saturation magnetization (MS), and high Curie temperature (TC) simultaneously. Here, we report the Sr1.5Mn0.5Fe0.5Hf1.5O6 (SMFHO) double perovskite compounds synthesized by solid‐state reaction and display a magnetic TC up to 804 K due to the strong Mn3+(↑)Fe3+(↑) spin interactions, which is the reported record in perovskite‐type HMFs so far. The measured MS value at 300 K was 4.87 μB/f.u., and it further increased up to 6.09 μB/f.u. at 2 K. The SMFHO powders exhibited butterfly‐shaped magnetoresistance (MR)–H curve at 2 K, and the MR (2 K, 7 T) value was measured as −3.86% due to the intergranular magnetic tunneling effect. Variation of the resistivity of the SMFHO ceramics versus temperature exhibits a semiconductor behavior, and the electrical transport properties of the SMFHO ceramics are well studied by Mott's range jump model, thermally activated semiconductor conductance model and small polaron jumping model, respectively. The optical absorption spectrum of the SMFHO powders demonstrates an indirect optical bandgap of 3.56 eV. Our present work demonstrates the intriguing properties of the SMFHO oxides where high TC, wide energy gap, and large MS value are preserved at the same time, which open the way to their promising applications in advanced spintronic devices at or beyond room temperature.

Neutron shielding analysis for a gadolinium doped nickel alloy

Rare-earth-nickel (RE-Ni) alloy is a kind of appealing neutron shielding material for advanced reactors and spent fuel storage containers. The incorporation of neutron-absorbing additive RE elements results in a RE-Ni alloy with integrated structural and functional features, which can drastically reduce shielding material weight. Gadolinium (Gd), in comparison to other rare-earth elements, has a much larger thermal neutron absorption cross section, necessitating only a low fraction to achieve the desired shielding capability. Hence, gadolinium is doped into a nickel-based alloy to form a gadolinium-nickel (Gd-Ni) alloy. Due to its extremely low solubility in the nickel phase, gadolinium is commonly manifested as heterogeneously spatially scattered Gd-rich phases in existing preparation procedures of alloys rather than homogeneously distributed gadolinium elements. This would result in a strong neutron tunneling effect, limiting the neutron shielding capability of Gd-Ni alloys. In this work, a superfine layered Gd-Ni alloy doped with Gd-rich phases and arranged in dislocations is proposed to provide an adequate dislocation density of Gd-rich phases to suppress the neutron tunneling effect. With the same Gd content, the thermal neutron shielding ability of a layered Gd-Ni alloy is comparable to the case that Gd is assumed to be an ideally homogeneous distribution in the material. The smaller the particle size of the Gd-rich phase, the weaker the neutron tunneling effect, and the lower the thermal neutron transmission ratio. For a 0.5 cm-thick Gd-Ni alloy, the particle size of Gd-rich phase should be kept within 20μm to achieve a thermal neutron transmission ratio of less than 10−5 for natural gadolinium content of 0.6 at.%. This work provides an important guidance for the design and fabrication of the next-generation neutron shielding materials.

Analysis of tunneling effect in different structures of one-dimensional barriers

Through the construction of mathematical model and the derivation of quantum mechanics formula, transmission coefficients of different one-dimensional barrier are explored. The difference of transmission coefficient and other properties under different materials was studied by controlling the change amount in the experiment. This study focuses on the analysis of one-dimensional barrier transmission coefficients of triangles and trapezoids, and ensures the accuracy of the experimental process through a large number of literature analysis. On this basis, the study of quantum tunneling effect should be easier, and it will be applied to more fields, which will play a crucial role for further research in the future. The special point of this experiment is to analyze and compare the transmission coefficient of different forms of one-dimensional barrier, compare the theoretical value with the actual value, and correct.The purpose of this experiment is to re-examine the original inherent conclusions and add new ones, so as to keep pace with the time.

The quantum tunnelling effect in double barrier structure

The purpose of this paper is to study the quantum tunnelling effect of double barriers. At the beginning, the research background and application of quantum tunnelling effect are described, and then the research purpose is explained. Although the real double barriers are very complex, most of them are composed of double barrier, double triangle barrier and double parabola barrier. The author mainly studies the barrier of double parabola. The reason is that the quantum tunnelling effect proposed by Hund will greatly adjust the internal structure of triangular conical molecules, which has great research significance. In triangular conical molecules, the change of potential energy of a single atom with its position may be very complicated, but the part that can occur with the consequential effect is similar to the potential barrier of a double parabola. In this paper, the wave function, projection and reflection coefficients of the biparabolic barrier tunnelling effect are analysed to determine whether it has a great adjustment effect on triangular conical molecules.

The discussion of the transmission coefficient of one-dimensional double barrier

Quantum theory plays a significant part in the modern physics and makes modern technology rapidly developed. Quantum tunnel effect is one of the most important discoveries. The exact expression of potential barrier is tough to derive, even for the double barrier. Many researchers have analysed the applications of quantum tunnel effect in real electronic devices. However, the exact expression of double barriers transmission coefficient was discussed rarely. In this article, the exact expression of the transmission coefficient will be given and the effect of parameters of barrier such as the width and the height will be discussed. In addition, the difference between symmetric and asymmetric double barrier will be given. This paper has the discussion of the transmission coefficient in order to not only give a clear understanding of the effect of parameters of double barrier to tyro and researchers, but also give a simpler way to consider the periodic barrier.

Transmission coefficient in double barrier quantum tunnelling effect

At the turn of the twentieth century, the establishment of quantum theory propelled rapid advancements, particularly in the understanding of quantum tunnellinga fundamental phenomenon in quantum mechanics crucial for various physical processes. The quantum phenomenon of particle passes through potential barriers is of great importance. In classical physics, when the energy of a particle is less than the height of a double barrier structure, it is impossible for it to pass through. However, quantum mechanics allows a particle to penetrate the barrier and emerge on the other side. This paper explores the quantum tunnelling effect, focusing on the single potential barrier model in one dimension and subsequently extending to the double potential barrier model. The Schrdinger equation provides the foundational framework for elucidating the motion of microscopic particles, emphasizing wave-particle duality inherent in quantum mechanics. The analysis of the single potential barrier model involves solving the Schrdinger equation in different regions, determining wave functions and coefficients through boundary conditions. The transmission coefficient is derived, representing the probability of a particle passing through a barrier. In the case of a thick barrier, an approximate form for transmission coefficient is provided, demonstrating the exponential decrease in transmission probability with increasing barrier thickness.

Tunable Epsilon‐and‐Mu‐Near‐Zero Metacomposites

AbstractEpsilon‐and‐mu‐near‐zero (EMNZ) metamaterials have garnered significant attention in near‐zero‐parameter metamaterial research for their exceptional ability to attain concurrent near‐zero permittivity and permeability. Nowadays achieving EMNZ properties through the use of metacomposites remains a novel endeavor. Presented here is an innovative approach of near‐zero‐parameter metacomposites, illustrating excellent and tunable EMNZ properties in the radio frequency regime. The self‐organization approach is applied to construct the conductive 3D network and the circuits, serving as the underlying framework for achieving EMNZ properties. Near‐zero permeability is effectively maintained while permittivity reaches epsilon‐near‐zero frequency regime. Efficient manipulation of electromagnetic parameters is initially realized via adjusting component content in metacomposites. Significantly, an excellent EMNZ property is observed as carbon content reaches 15 wt.% at 915 MHz. Through both numerical simulations and experimental testing, the PGC metacomposites have exhibited tunneling effects and directional emission characteristics, confirming their EMNZ properties. Besides, the Lego‐like adjustment facilitates the achievement of EMNZ property and advances the EMNZ frequency point to 700 MHz, expanding the EMNZ range. Furthermore, thanks to the remarkable excitation effect of photo‐induced adjustment, the metacomposite with low‐carbon content also achieves extraordinary EMNZ properties. This research offers promising self‐organized EMNZ metacomposites and lays the foundation for future endeavors in precisely adjusting near‐zero parameters.

Statistical Model of Hydrogen Diffusion in BCC Metals

The purpose of this work is developing of the statistical model of hydrogen diffusion in the crystal lattice of BCC metals with an estimate of the contribution of quantum effects and deviations from the Arrhenius equation. The values of the statistical model calculations of H diffusion coefficients in Fe, V, Nb and Ta are in good agreement with the experimental data. The statistical model can also explain deviations from the Arrhenius equation at temperatures 300-500 K in Fe and Nb. The downward deviation of the diffusion coefficient at 300K can be explained by the fact that the statistical model does not consider the tunneling effect at temperatures below 300K. It was suggested that thermally activated fast tunnelling transition of hydrogen atoms through the potential barrier at temperatures below 500 K provides an almost free movement of H atoms in the α-Fe and V. Using the statistical model allows for the prediction of the diffusion coefficient for H in BCC metals at intermediate temperatures.

Hydrogen Tunneling in Stoichiometric and Catalytic Reactions involving Transition Metals

AbstractHydrogen tunneling is a type of quantum tunneling in which a hydrogen atom passes through a potential barrier without reaching the transition state governed by classical mechanics. The participation of hydrogen tunneling in a chemical reaction (stoichiometric or catalytic) can result in the formation of products that without this phenomenon would be impossible to achieve or would be formed in a very slow way. This concept paper aims to review some of the most representative examples of transition‐metal mediated chemical reactions involving hydrogen tunneling. The experimental tools to determine the possibility of the participation of quantum tunneling in a chemical reaction are presented. In addition, the theoretical methods that have been developed to calculate the effect of quantum tunneling on chemical reactions are discussed. Finally, from a personal perspective, the steps to be taken in order to predict and implement this phenomenon are proposed.

Photonic Spin Hall Effect as a Highly Sensitive Refractive Index Sensing Platform for Glucose

AbstractThis study presents an innovative refractive index (RI) sensor that measures glucose concentration by utilizing the photonic spin Hall effect (SHE) in a resonant optical tunneling effect (ROTE) structure. The ROTE structure consists of three InP layers with the high RI and two analyte layers (with a high‐low‐high‐low‐high RI distribution), in which glucose solution samples with the low RI are injected. By subjecting the InP layers to external bias‐assisted light, the photonic SHE can be flexibly manipulated, enabling the modulation of the sensing performance accordingly. It is found that the transverse shift of photonic SHE presents a large variation in response to the tiny change in glucose concentrations. By optimizing the parameters (i.e., intensity or wavelength) of bias light, the sensitivity of this sensor can reach as high as 735.7 µm RIU−1. Compared to traditional glucose sensors, this original work implements the novel photonic SHE with the superior sensing performance. Therefore, the proposed design shows promising potential for biomedical applications, such as medical diagnoses and drug discovery.

Theoretical Kinetic Study on Hydrogen Abstraction Reactions from n-Pentane by NO2.

The interaction of fuel with NOx chemistry is important for the construction of the reaction mechanism and engine application. In this work, the reaction pathways of nC5H12 + NO2 were studied by high-level electronic structure calculations (DLPNO-CCSD(T)-F12/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ). The rate constants were calculated by using the multistructural canonical transition-state theory with the Eckart tunneling method (TST/MS-T/ET). The studied condition is in a wide temperature range of 298-2400 K. The influence of MS-T anharmonicity and tunneling effect will be clarified for these site-specific H-abstraction pathways. The result reflects the large deviation introduced by the treatment of MS-T anharmonicity, especially at a high temperature. For the same type of reactions, the rate constants of H-abstraction both occurring at the secondary carbon are not almost identical. The branching ratios show that abstraction from the secondary site forming cis-HONO (R2c) contributes 36-78% to nC5H12 consumption in the temperature range of 298-2400 K. The current results show that the multistructural torsional anharmonicity has a crucial influence on the accurate estimation of branching ratios.