Field Inside Research Articles

A terahertz signal enhancement implemented by subwavelength metallic grooves

This research analyzes the field enhancement properties of a subwavelength metallic groove working at 0.4 terahertz (THz), which is potentially applicable as a receiver to enhance THz signals in integrated circuits. We derive the analytic formulation of the field magnification by utilizing the distinctive characteristics of the electromagnetic (EM) field inside and above the groove with the EM field continuity on the upper and lower surfaces of the groove. This method, known as the Bruijn theory, has been applied in acoustics and optics to obtain reflection and absorption coefficients. Then, the dependence of these field enhancement properties on both the groove width and depth is examined by theoretical analysis and numerical simulations consistently. Results show that the field enhancement varies periodically with the groove depth in a period of 0.5λ, featuring the typical Fabry–Perot resonance. The field enhancement is inversely proportional to the groove width due to the cavity effect. Besides, the field intensity can be further enhanced by 10% via appropriately rounding the sharp vertices at the inlet of the groove. Moreover, the incident angle effect on the field enhancing property is explored. An enhancement of >32 dB can be realized at any incident angle with a groove of dimensions 158×225μm2. These results are helpful for understanding the field enhancement mechanism and designing novel THz plasmonic devices, such as an easily manufactured antenna receiver or sensor with simple and compact configuration, as well as offering a feasible solution for the high attenuation problem of THz communications.

Temperature Field Measurements In The Cross-Section Of Falling Liquid Films By Laser-Induced Fluorescence

Thin wavy liquid films a reused in many applications as heat a nd mass transfer promoters thanks to their great performances for a small liquid consumption. To further understand the exact mechanisms of coupling between the wavy fluid dynamics and the heat transfer, a laser-induced fluorescence technique has been developed. The technique enables a measurement of the temperature field inside of a wavy film flowing down an inclined plane with a high spatial resolution. This paper reports on the development of the technique. Water liquid films were investigated under two-dimensional waves conditions. The measurements reveal the regions where mixing is enhanced by convective circulation zones and enables the evaluation of the intensification of the heat transfer due to the waves.

Discriminating protein tags on a dsDNA construct using a Dual Nanopore Device

We report Brownian dynamics simulation results with the specific goal to identify key parameters controlling the experimentally measurable characteristics of protein tags on a dsDNA construct translocating through a double nanopore setup. First, we validate the simulation scheme in silico by reproducing and explaining the physical origin of the asymmetric experimental dwell time distributions of the oligonucleotide flap markers on a 48 kbp long dsDNA at the left and the right pore. We study the effect of the electric field inside and beyond the pores, critical to discriminate the protein tags based on their effective charges and masses revealed through a generic power-law dependence of the average dwell time at each pore. The simulation protocols monitor piecewise dynamics at a sub-nanometer length scale and explain the disparate velocity using the concepts of nonequilibrium tension propagation theory. We further justify the model and the chosen simulation parameters by calculating the Péclet number which is in close agreement with the experiment. We demonstrate that our carefully chosen simulation strategies can serve as a powerful tool to discriminate different types of neutral and charged tags of different origins on a dsDNA construct in terms of their physical characteristics and can provide insights to increase both the efficiency and accuracy of an experimental dual-nanopore setup.

Numerical calculation of near-field in vicinity of three-dimensional nano-optical probes using boundary element method

The diffraction limit is one of the main obstacles in the development of microscopes to analyze the morphology and structure of materials. The main idea of near field scanning optical microscopy (NSOM) is to overcome the diffraction limit using sub-wavelength apertures. In this work, the near-field is simulated in the vicinity of three-dimensional nano-optical apertureless probes. For this purpose, the Helmholtz equation is solved using the boundary element method (BEM). The effects of different parameters on the near field generated in the vicinity of the optical probe are studied. These parameters consist of the length and radius of the probe, the size of the aperture, the angle of the tapered tip, and the geometry of the probe tip. The main advantages of the proposed method are the high accuracy, the very short calculation time, and the ability to calculate the near field inside and outside the optical probe without any approximation.

Synaptic Plasticity and Quantized Conductance States in TiN-Nanoparticles-Based Memristor for Neuromorphic System

Controlled conductive filament formation in the resistive random access memory device is an essential requirement for analog resistive switching to develop artificial synapses. In this work, we have studied Au/Ti/HfAlOx/TiN-NP/HfAlOx/ITO RRAM device to demonstrate conductance quantization behavior to achieve the high-density memory application. Stepwise change in conductance under DC and pulse voltage confirms the quantized conductance states with integer and half-integer multiples of G0. Reactive TiN-NPs inside the switching layer helps to form and rupture the atomic scale conductive filaments due to enhancing the local electric field inside. Bipolar resistive switching characteristics at low SET/RESET voltage were obtained with memory window > 10 and stable endurance of 103 cycles. Short-term and long-term plasticities are successfully demonstrated by modulating the pre-spike number, magnitude, and frequency. The quantized conductance behavior with promising synaptic properties obtained in the experiments suggests HfAlOx/TiN-NP/HfAlOx switching layer is suitable for multilevel high-density storage RRAM devices.

Deep Learning in Physics: A Study of Dielectric Quasi-Cubic Particles in a Uniform Electric Field

Solving physics problems for which we know the equations, boundary conditions and symmetries can be done by deep learning. Here, we calculate the induced field inside and outside a dielectric quasi-cube placed in a uniform electric field, wherein the dielectric mismatch at edges and corners of the cube makes accurate calculations challenging. The electric potential is expressed as an ansatz incorporating neural networks with known leading order forms and symmetries, then Laplace's equation with boundary conditions at the dielectric interface is solved by minimizing a loss function inside a large solution domain. We study how the electric potential inside and outside the particle evolves through a sequence of shapes from a sphere to a cube. The neural network being differentiable, it is straightforward to calculate the electric field over the whole domain, the induced surface charge distribution and the polarizability. The neural network being retentive, one can efficiently follow how the field changes upon particle's shape or dielectric constant by iterating from previously converged solution. The present work's objective is two-fold, first to show how can a priori knowledge be incorporated into neural networks to achieve efficient learning and second to apply the method and study how the induced field and polarizability change when a dielectric particle progressively changes its shape from a sphere to a cube.

The qualification of GEM detector and its application to imaging

The Gas Electron Multiplier (GEM) is a new age detector, which can handle the high flux of particles. The GEM foil, which is constructed using 50 μm highly insulating foil (Kapton/Apical) coated with 5 μm layers of copper, on both sides, with a network of specifically shaped holes is the major component of these detectors. The European Center for Nuclear Research (CERN) has been the sole supplier of the GEM foils until recently when a few other companies started manufacturing GEM foils under the transfer of technology (TOT) agrement from CERN. Techtra is one such company in Europe which gained a right to use CERN developed technology in order to produce commercially viable GEM foils. Micropack Pvt. Ltd. is another company in India which has successfully manufactured good quality GEM foils. Due to the microscopic structure of holes and dependence on the electric field inside, it becomes essential to study the defect and uniformity of holes along with the electrical property of foils under ambient conditions. In this work we are reporting the tests condition of Techtra GEM foils. We report on the development of a cost effective and efficient technique to study the GEM foils holes geometry, distribution, and defects. We also report on the electrical properties of these foils like leakage current, stability, and discharges. At the detector level, we describe the high voltage (HV) response, gain, uniformity, and stability. The GEMs have been proposed to have a wider applications, so we performed a feasibility study to utilize these for the imaging. We irrediated various objects of varying density with X-rays and reconstructed the images. The reconstructed image shows a good distinction between materials of different densities, which can be very useful in various applications like medical imaging or cargo imaging.

A hybrid spectral element-infinite element approach for 3D controlled-source electromagnetic modeling

In this study, we developed a novel hybrid approach for 3D controlled-source electromagnetic (CSEM) forward modeling. The hybrid approach combines vector spectral element method (SEM) with scalar infinite element method (IFEM) by using infinite element instead of traditional truncated boundary. Based on Maxwell's equations, the curl-curl control equation satisfied by secondary electric field is derived. The boundary value problem in differential form is transformed into integral weak form by using Galerkin weighted residual method. Then the global problem is discretized by element subdivision and high-order orthogonal basis function interpolation. The computational domain is discretized using hexahedral spectral elements and a single layer of infinite elements is added outside the domain. The SEM with high-order Gauss-Lobatto-Legendre (GLL) vector basis functions is used to represent the interior electric field, and the IFEM with high-order Gauss-Lobatto-Legendre (GLL) scalar basis functions is uesd as a boundary condition. Finally, the global numerical solution is obtained by solving large-scale linear equations. The layered model verifies the accuracy and correctness of the approach, and the 3D model verifies the efficiency and numerical stability of the approach. Numerical experiments show that the hybrid SEM-IFEM approach developed in this study can reach similar accuracy to the conventional spectral element method, but the computational domain required can be much smaller, and the corresponding CPU time and memory requirement are greatly reduced, namely, the high precision three-dimensional electromagnetic response can be obtained with less computational resource consumption.

Magnetic accumulation effect on the inner and outer surfaces of pipeline magnetic penetration in natural environment

In view of the detection requirements of pipeline internal and external surface defects and pipeline special regular structure detection, based on the magnetic shielding effect inside and outside the pipeline, the principle of magnetic field refraction at the interface between the pipe wall and air, and the principle of the magnetic field concentration on the pipe surface and the gap, this article focuses on the natural environment (geomagnetic background). The magnetic field distribution inside and outside the pipeline has been theoretically analyzed. After that, the finite element simulation software is used to model the finite length pipeline, and the internal and external magnetic fields are simulated and researched in combination with the finite element method. Finally, the tunnel magneto resistance (TMR) magnetic sensor is used to collect and process the internal magnetic field of the actual pipeline model, which verifies the correctness of the theoretical analysis. This paper analyzes the magnetic field inside and outside the pipeline by means of principle deduction, finite element simulation, and sensor measurement. The analysis results show that the distribution of the magnetic field in the pipeline under the excitation of the geomagnetic field has a very obvious regularity, which can meet the needs of pipeline defect detection. In addition, because the pipelines of different structures have different magnetic field distribution laws, they can also be used for the detection and analysis of pipelines with special structures.

A spectral target signature for thin surfaces with higher order jump conditions

<p style='text-indent:20px;'>In this paper we consider the inverse problem of determining structural properties of a thin anisotropic and dissipative inhomogeneity in <inline-formula><tex-math id="M1">\begin{document}$ {\mathbb R}^m $\end{document}</tex-math></inline-formula>, <inline-formula><tex-math id="M2">\begin{document}$ m = 2, 3 $\end{document}</tex-math></inline-formula> from scattering data. In the asymptotic limit as the thickness goes to zero, the thin inhomogeneity is modeled by an open <inline-formula><tex-math id="M3">\begin{document}$ m-1 $\end{document}</tex-math></inline-formula> dimensional manifold (here referred to as screen), and the field inside is replaced by jump conditions on the total field involving a second order surface differential operator. We show that all the surface coefficients (possibly matrix valued and complex) are uniquely determined from far field patterns of the scattered fields due to infinitely many incident plane waves at a fixed frequency. Then we introduce a target signature characterized by a novel eigenvalue problem such that the eigenvalues can be determined from measured scattering data, adapting the approach in [<xref ref-type="bibr" rid="b20">20</xref>]. Changes in the measured eigenvalues are used to identified changes in the coefficients without making use of the governing equations that model the healthy screen. In our investigation the shape of the screen is known, since it represents the object being evaluated. We present some preliminary numerical results indicating the validity of our inversion approach</p>

Design and Experiment of an Automatic Temperature Control Device of Composite Shape-Stabilized Phase Change Material for Concrete Box Bridges

To solve the problem of bridge surface cracking caused by an uneven temperature field inside and outside the web of a concrete box structure, an automatic temperature control device applied to the beam surface of a concrete box bridge in the daytime is developed. The device, hanging on the surface of the box girder webs, consists of a radiation cooling coating and a composite shape-stabilized phase change material. With reference to a bridge in Guizhou Province, finite element analysis, short-term temperature monitoring and temperature-drop monitoring are carried out using the device. The result shows that the automatic temperature control device works well continuously. For a box girder without an automatic temperature control device, the inside and outside of the web demonstrate different sensitivities to the temperature of the external environment, with a high temperature fluctuation and a relatively high temperature stress. For a box girder with an automatic temperature control device, as the cooling coating reflects part of the solar radiation and the phase transformation of the composite shape-stabilized phase change material releases or absorbs part of the latent heat to or from the external environment, the temperature fluctuation and temperature stress of the inside and outside of the web are relatively small. When the temperature suddenly drops, the automatic temperature control device works better than under conventional weather conditions because it can reduce the external temperature by approximately 50% on the outer surface of the box girder webs.

The flow topology transition of liquid\u2013liquid Taylor flows in square microchannels

This work investigates the change of the flow topology of Taylor flow and qualitatively relates it to the excess velocity. Ensemble-averaged 3D2C-upmu PIV measurements simultaneously resolve the flow field inside and outside the droplets of a liquid–liquid Taylor flow that moves through a rectangular horizontal microchannel. While maintaining a constant Capillary number Ca = 0.005, the Reynolds number (0.52 le {text{Re}} le 2.14), the viscosity ratio (0.24 le lambda le 2.67) and surfactant concentrations of sodium dodecyl sulfate (0–3 CMC) are varied. We experimentally identified the product of the Reynolds number Re and the viscosity ratio lambda to indicate the momentum transport from the continuous phase (slugs) into the droplets (plugs). The position and size of the droplet’s main vortex core as well as the flow topology in the cross section of this vortex core changed with increased momentum transfer. Further, we found that the relative velocity of the Taylor droplet correlates negatively with the evoked topology change. A correlation is proposed to describe the effect quantitatively.Graphical abstract

Modeling of the Magnetic Field of Current Carrying Conductor with Finite Elements Method

In this paper, we have modeled and simulated the magnetic field of the conductor by using the finite element method, which is incorporated in Ansoft Maxwell software. Modeling and simulation are done for a conductor and two conductors located at a small distance between them. Our study is based on the method of finite elements and Biot-Savart law for calculating the magnetic field depending on the distance from the conductor. We have observed that the calculated values of the magnetic field are in good accordance with Biot-Savart law [1]. We have found that magnetic field normal to the main axis of the conductor falls linearly towards it, whereas outside the conductor magnetic field is inversely proportional to distance. In the case of simultaneous calculation of the field inside and outside the conductor, a small margin has been found. This difference is as a result of the simultaneous calculation of magnetic field in two environments with different magnetic permeability. Finally, we have computed the magnetic field at an equal point between two conductors when the currents have opposite and same direction, whereby a huge difference between the magnetic fields is found. We show that we can amplify or reduce the intensity of the magnetic field, based not only on the distance between the conductors but also on the basis of the directions of the currents flowing through these conductors.

The dangers of the construction of hydroelectric dams upstream of the Mekong River adversely effect on the ecosystems and livelihoods of people in the Mekong Delta, Viet Nam

The main purpose of the article is with the results of scientific and serious research to let the world know the enormous harm of upstream hydroelectric dams, mainly of China, causing huge, multifaceted, and global damage. impact on the downstream area, but especially on the Mekong Delta of Vietnam: "Wetland" will become "dead land" The development of hydro-electric projects of the up-stream Mekong countries has been and will be inevitable and greatly impact on the down-stream areas, in which the Mekong Delta is suffering a lot of losses., especially, for Viet Nam.. The Processes have been happening at the same time: The process of depleting water, for agriculture, for industry, for daily life and people's livelihoods. The processes at the same time, the effects that resonate with the process of climate change cause great harm. The drought has accelerated the acidification process, because the potential drought of acid sulfate soil (1,700,000 ha) will become intense, damaging the ecosystem and human livelihoods..The drought due to the construction of hydroelectric dams upstream (especially Lan Thuong river, China) makes the process of salinization with saline intrusion fierce (seawater 4 gr/L) Many, penetrating into the interior fields more than 100KM, the harm is extremely great. If want to reduce the harm, the Mekong River Commission must ask the upstream countries to share it with the downstream

Hormones Nanofiltration in Carbon Nanotubes and Boron Nitride Nanotubes Using Uniform External Electric Field Through Molecular Dynamics.

Hormones are a dangerous group of molecules that can cause harm to humans. This study based on classical molecular dynamics proposes the nanofiltration of wastewater contaminated by hormones from a computer simulation study, in which the water and the hormone were filtered in two single-walled nanotube compositions. The calculations were carried out by changing the intensities of the electric field that acted as a force exerting pressure on the filtration along the nanotube, in the simulation time of 100 ps. The hormones studied were estrone, estradiol, estriol, progesterone, ethinylestradiol, diethylbestrol, and levonorgestrel in carbon nanotubes (CNTs) and boron nitride (BNNTs). The most efficient nanofiltrations were for fields with low intensities in the order of 10-8 au and 10-7 au. The studied nanotubes can be used in membranes for nanofiltration in water treatment plants due to the evanescent field potential caused by the action of the electric field inside. Our data showed that the action of EF in conjunction with the van der Walls forces of the nanotubes is sufficient to generate the attractive potential. Evaluating the transport of water molecules in CNTs and BNNTs, under the influence of the electric field, a sequence of simulations with the same boundary conditions was carried out, seeking to know the percentage of water molecules filtered in the nanotubes.

3D edge-based and nodal finite element modeling of magnetotelluric in general anisotropic media

Research on the magnetotelluric (MT) forward modeling response in anisotropic media has been important since the discovery of anisotropic electric fields in the Earth's interior. In this study, we presented an edge-based and nodal finite-element method (FEM) for three-dimensional (3D) MT forward modeling problems in general anisotropic media. Partial differential equations are derived using the Coulomb-gauged approach from Maxwell's equation and discretized by the edge-based and nodal FEM. The magnetic vector A was discretized by an edge-based FEM and the electric scalar ψ was discretized by nodal FEM. The computational domain was refined using a hexahedral mesh. The Galerkin variant of the weighted residuals method was used to obtain a sparse linear system for magnetic vector A and electric scalar ψ. Three models were designed to validate and analyze our forward modeling code by comparing it with a one-dimensional analytical solution and with the results from codes developed by other scholars. A direct solver and iterative solvers with preprocessors were used to evaluate the performance of our code. Numerical experiments showed that our forward modeling code is accurate and robust and converges faster. In addition, the stiffness matrix assembled by our algorithm was smaller than that assembled by the nodal FEM, which further demonstrates the advantage of our algorithm in terms of computational memory.

Method for analyzing spatial organization of information for predicting anthropogenic impact on environment

In the emerging ecological crisis, there are no analysis methods enabling to assess the degree of environmental hazard from a unified position. Moreover, when new characteristics are obtained, the idea of the phenomenon under study can radically change. The article considers the method of informological analysis based on the study of the structure of the spatial organization of information in urbanized territories. In the course of the study, it was shown that the information field formed by natural objects and the technosphere interact with each other in such a way that they form their internally organized information space. The information field inside is estimated according to the results of production control over technological parameters of an enterprise. According to its state inside the object, zones of information intensity of the object itself are identified, and external feature fields contribute to describing the impact of an individual enterprise on the environment of territories limited by the size of each feature information field. The latter is the initial element of the mechanism for transforming information of an industrial facility situated at a larger space, which may include interconnected objects of the industry structure, cover zones of characteristic environmental changes not only within the location of an industrial territorial unit but also outside it. In these zones, fields of information interaction being the factors of environmental hazard although often not taken into account by traditional methods of analysis can generate. A probabilistic-theoretical model of the message source for calculating the entropy state of space is proposed, which allows describing the characteristic features of the influence of an object on the environment of the territories. A specific example shows its fundamental applicability to studying information aspects of phenomena of various nature, using entropy to identify important properties of the process under study with an unknown model. Further development of the method can be used in various ways for determining environmental hazard factors, which include spaces that form around objects and have a direct or indirect impact on the environment on a local, regional and global scale.

Casimir densities induced by a sphere in the hyperbolic vacuum of de Sitter spacetime

Complete set of modes and the Hadamard function are constructed for a scalar field inside and outside a sphere in (D+1)-dimensional de Sitter spacetime foliated by negative constant curvature spaces. We assume that the field obeys Robin boundary condition on the sphere. The contributions in the Hadamard function induced by the sphere are explicitly separated and the vacuum expectation values (VEVs) of the field squared and energy-momentum tensor are investigated for the hyperbolic vacuum. In the flat spacetime limit the latter is reduced to the conformal vacuum in the Milne universe and is different from the maximally symmetric Bunch-Davies vacuum state. The vacuum energy-momentum tensor has a nonzero off-diagonal component that describes the energy flux in the radial direction. The latter is a purely sphere-induced effect and is absent in the boundary-free geometry. Depending on the constant in Robin boundary condition and also on the radial coordinate, the energy flux can be directed either from the sphere or towards the sphere. At early stages of the cosmological expansion the effects of the spacetime curvature on the sphere-induced VEVs are weak and the leading terms in the corresponding expansions coincide with those for a sphere in the Milne universe. The influence of the gravitational field is essential at late stages of the expansion. Depending on the field mass and the curvature coupling parameter, the decay of the sphere-induced VEVs, as functions of the time coordinate, is monotonic or damping oscillatory. At large distances from the sphere the fall-off of the sphere-induced VEVs, as functions of the geodesic distance, is exponential for both massless and massive fields.

Fabrication of Microparticles with Front-Back Asymmetric Shapes Using Anisotropic Gelation.

Droplet-based microfluidics is a powerful tool for producing monodispersed micrometer-sized droplets with controlled sizes and shapes; thus, it has been widely applied in diverse fields from fundamental science to industries. Toward a simpler method for fabricating microparticles with front–back asymmetry in their shapes, we studied anisotropic gelation of alginate droplets, which occurs inside a flow-focusing microfluidic device. In the proposed method, sodium alginate (NaAlg) aqueous phase fused with a calcium chloride () emulsion dispersed in the organic phase just before the aqueous phase breaks up into the droplets. The fused droplet with a front–back asymmetric shape was generated, and the asymmetric shape was kept after geometrical confinement by a narrow microchannel was removed. The shape of the fused droplet depended on the size of prefused NaAlg aqueous phase and a emulsion, and the front–back asymmetry appeared in the case of the smaller emulsion size. The analysis of the velocity field inside and around the droplet revealed that the stagnation point at the tip of the aqueous phase also played an important role. The proposed mechanism will be potentially applicable as a novel fabrication technique of microparticles with asymmetric shapes.

Investigation of entrance effects on particle electrophoretic behavior near a nanopore for resistive pulse sensing.

Resistive pulse sensing using solid-state nanopores provides a unique platform for detecting the structure and concentration of molecules of different types of analytes in an electrolyte solution. The capture of an entity into a nanopore is subject not only to the electrostatic force but also the effect of electroosmotic flow originating from the charged nanopore surface. In this study, we theoretically analyze spherical particle electrophoretic behavior near the entrance of a charged nanopore. By investigating the effects of pore size, particle-pore distance, and salt concentration on particle velocity, we summarize dominant mechanisms governing particle behavior for a range of conditions. In the literature, the Helmholtz-Smoluchowski equation is often adopted to evaluate particle translocation by considering the zeta potential difference between the particle and nanopore surfaces. We point out that, due to the difference of the electric field inside and outside the nanopore and the influence from the existence of the particle itself, the zeta potential of the particle, however, needs to be at least 30% higher than that of the nanopore to allow the particle to enter into the nanopore when its velocity is close to zero. Accordingly, we summarize the effective salt concentrations that enable successful particle capture and detection for different pore sizes, offering direct guidance for nanopore applications.