Proper Field Research Articles

Twin formation from a twin boundary in Mg during in-situ nanomechanical testing

An important fundamental question regarding deformation twinning is whether it is possible for twins to nucleate at boundaries or interfaces when specific stress fields are present. A corollary that follows from this question is: if this is indeed possible, what determines the proper stress field and how does it occur at the nanoscale? Here, we demonstrate the application of an in-situ nanoindentation approach to confine and dynamically capture the stages in the formation of a deformation twin at an internal twin boundary in single crystal Mg. We observe the formation of contraction twin embryos at the pre-existing extension twin boundary, and the subsequent propagation of the twin embryos into the crystal. We reveal an intermediate step, involving the coalescence of tiny embryos into a larger embryo before the nucleus emanates into the crystal. De-twinnning of the twin embryos is captured during unloading and shown to leave a remnant nanosized twin (<10 nm) after complete unloading. A 3D full-field, crystal plasticity model identifies that the twin type and variant selection of the stable embryo are governed by the internal local stress state prevailing at the pre-existing twin boundary. The possible role played by <c+a> dislocations and boundary structure (incoherent vs. coherent) in embryo formation, as suggested by the TEM and modeling analyses, are discussed.

Toward an Intermediate Level: Making the Most of Evaluation in Italian Community Archaeology

Over the last decade public and community archaeology have established themselves as essential parts of the Italian contemporary archaeological debate, as a result of work at a series of venues and a growing commitment to public engagement within fieldwork. However, data and evaluation reports about participation are rarely found in academic literature, limiting the development of a critical attitude to the topic. This paper attempts to outline a specific scenario for the development of Italian community archaeology as a proper field of research. This scenario consists of two main stages: the development of a shared attitude to evaluation and the creation of a native theoretical framework. Between them there is the ‘intermediate level’, that may be properly considered as the comparison and interpretation of the data resulting from the multiple evaluation processes conducted in Italian community archaeology projects in the context of the existing international theoretical framework. The brief presentation of an evaluation process conducted for the case study of ‘Uomini e Cose a Vignale’ — a long-term excavation project in Tuscany jointly managed by archaeologists and local stakeholders — fosters a reflection on specific opportunities provided by conceiving evaluation as a first step toward an ‘intermediate level’.

A Delay Learning Algorithm Based on Spike Train Kernels for Spiking Neurons.

Neuroscience research confirms that the synaptic delays are not constant, but can be modulated. This paper proposes a supervised delay learning algorithm for spiking neurons with temporal encoding, in which both the weight and delay of a synaptic connection can be adjusted to enhance the learning performance. The proposed algorithm firstly defines spike train kernels to transform discrete spike trains during the learning phase into continuous analog signals so that common mathematical operations can be performed on them, and then deduces the supervised learning rules of synaptic weights and delays by gradient descent method. The proposed algorithm is successfully applied to various spike train learning tasks, and the effects of parameters of synaptic delays are analyzed in detail. Experimental results show that the network with dynamic delays achieves higher learning accuracy and less learning epochs than the network with static delays. The delay learning algorithm is further validated on a practical example of an image classification problem. The results again show that it can achieve a good classification performance with a proper receptive field. Therefore, the synaptic delay learning is significant for practical applications and theoretical researches of spiking neural networks.

Numerical investigation of a thermosyphon MHD electrical power generator

A conceptual design of a thermosyphonic Magnetohydrodynamic power generator is presented and its performance is numerically investigated. A simplified two-dimensional model of generator is considered. Liquid gallium is selected as working fluid. The left wall and right wall of thermosyphon are at constant temperature Th and Tc, (Th > TC) respectively. Other walls and baffle are insulated. A constant magnetic field is applied horizontally. Separate pairs of electrodes are considered to conduct the generated current. A proper magnetic field reference is introduced to nondimensionalize the governing equations. A numerical code based on the finite volume technique is developed to solve the unsteady governing equations for a laminar natural convection flow. The effects of the Rayleigh number (Ra), Hartmann number (Ha), aspect ratio (Ar) and electric efficiency (K) on the thermo-fluid behaviour throughout the thermosyphon, on the induced electric current density, and on the generated power are investigated. Increasing the aspect ratio and Hartmann number, causes to decrease the natural convection effects, and reduces the Nusselt number. While increasing the Rayleigh number augments the effect of natural convection and consequently the generated power (W*), electric current density (J*), and electric field (E*) increases. It is seen that for a given Rayleigh number, there is a Hartmann number, an aspect ratio, and an electric efficiency, for which the generated power, W*, becomes maximum. For a given Rayleigh number and aspect ratio, it is shown that the generated power does not monotonically varies with Ha. It decreases by increasing Ha from certain values.

Design and implementation of quasi-optical components for the upgrade of the TCV EC-system

The EC-system of the TCV tokamak is progressively being upgraded with the addition of two MW-class dual-frequency gyrotrons (84 and 126 GHz/2s/1MW). In order to connect the two gyrotrons to the existing low field side and top launchers, new waveguide routing from gyrotron hall to TCV tokamak was designed and dedicated Matching Optics Units (MOU) have been developed. The internal optics of the system have been determined aiming at optimal coupling to the HE11 waveguides. The laws of quasi-optics were used to find quadratic surfaces to shape an incoming Gaussian beam representative of the gyrotron output into a beam matching the proper field distribution at the waveguide entrance and with HE11 content compatible with the system requirements. A solution with one flat (movable) mirror and two shaping mirrors was found and characterized with the physical optics code GRASP. The resulting field distribution is then truncated and projected onto the HE11 component to evaluate the design solution (coupled power at the waveguide entrance >98.4% and HE11 content >96.8% for both frequencies). The model and the results of this analysis will be presented and compared to a model based on the Rayleigh–Sommerfeld scalar diffraction integral. GRASP was also used to evaluate preliminary misalignment effects in terms of coupled power to the waveguide and the MOU design moved to the manufacturing phase. In parallel to the gyrotron integration and to extend the level of flexibility of the TCV EC-system, a modular closed divertor chamber is developed, requiring the X3 top-launcher to be redesigned. Preliminary antenna conceptual design studies including new curvature to cope with the requirements of modularity and flexibility will be presented.

Microstructure evolution and magnetic properties of annealed magnetostrictive Fe81Al19 coatings and their ultrasonic guided wave transducing performance

The microstructure, magnetic and magnetostrictive properties as well as ultrasonic guided wave sensing performance of annealed Fe81Al19 coatings prepared on 316L stainless steel by high velocity oxy-fuel spraying were investigated systematically. The maximum magnetostriction reaches 38 ppm with the coating annealed at 400 °C and the saturation magnetic field is <400 Oe. The phase transformation behavior of A2 → A2 + DO3 occurs with the annealing temperature increases above 470 °C. Effects of annealing on texture and structural evolution and magnetic properties of the coating are also discussed. Based on magnetostrictive effect and Villari effect of Fe81Al19 coating, the ultrasonic guided waves are actuated and detected successfully. With proper bias magnetic field, the amplitudes of echo signals can be enhanced in Fe-Al coating annealed at 500 °C. The corresponding (dλ/dH)max under a lower bias magnetic field indicates less eddy current loss and the optimal transduction. The deeper electromagnetic skin depth in the annealed coating results in a higher ultrasonic guided wave amplitude and improves the detection sensitivity in the electromagnetic acoustic transducers. This work exhibits the prospect of the magnetostrictive coatings in a range of potential applications, such as electromagnetic acoustical transducers used for non-destructive testing.

Light cone black holes

When probed with conformally invariant matter fields, light cones in Minkowski spacetime satisfy thermodynamical relations which are the analog of those satisfied by stationary black holes coupled to standard matter fields. These properties stem from the fact that light cones are conformal Killing horizons stationary with respect to observers following the radial conformal Killing fields in flat spacetime. The four laws of light cone thermodynamics relate notions such as (conformal) temperature, (conformal) surface gravity, (conformal) energy and a conformally invariant notion related to area change. These quantities do not admit a direct physical interpretation in flat spacetime. However, they become the usual thermodynamical quantities when Minkowski is mapped, via a Weyl transformation, to a target spacetime where the conformal Killing field becomes a proper Killing field. In this paper we study the properties of such spacetimes. The simplest realisation turns out to be the Bertotti-Robinson solution, which is known to encode the near horizon geometry of near extremal and extremal charged black holes. The analogy between light cones in flat space and black hole horizons is therefore strengthened. The construction works in arbitrary dimensions; in two dimensions one recovers the Jackiv-Teitelboim black hole of dilaton gravity. Other interesting realisations are also presented.

Why the particle-in-cell method captures instability enhanced collisions

While the particle-in-cell (PIC) method has been the subject of years of theoretical study, the common misconception that PIC approximates the collisionless Vlasov-Maxwell system of equations, or the Vlasov-Poisson system for the electrostatic case, is widely cited. In this paper, a PIC-relevant generalization of the instability enhanced Lenard-Balescu collision operator is derived. The analysis of this collision operator demonstrates that while coulomb collisions are truncated by the electric field grid resolution, longer range collisions that arise from imperfect shielding in the presence of instabilities persist. These instability enhanced collisions are completely captured by PIC as long as there is sufficient grid resolution to resolve the wavenumber of the unstable modes of the instability. The inclusion of this behavior is akin to particle wave interactions in the Vlasov based quasilinear theory but with one important difference. Quasilinear theory requires an initial spectral energy density which cannot be supplied self-consistently from within the theory because its initial value is determined by non-Vlasov collisional effects. With the proper electric field grid resolution, the initial spectral energy density is included self-consistently, along with the generation of plasma waves originating from discrete particle motion. Predictions of the grid resolution effect are found to be in agreement with PIC simulations at varying grid resolutions.

On the downward direction of the flat panel display speaker

Information display devices are being advancement by ICT development. Particularly, besides the image quality and appearance design of the information display device, the development of the accompanying elements such as the sound quality is also progressed. Conventional information display devices such as LCD and LED TV have focused on the pixel configuration and color implementation and developed to such an extent that the human eye can not follow it, and the image quality is as good as the actual view in a proper field of view. However, in the case of sound, it has occurred at various alternative positions with the limitation that it cannot penetrate the hard screen. In the case of a flat-screen TV, however, the position of the sound was properly configured by reproducing the sound directly from the left and right sides of the screen. However, focusing on the image quality and design elements, it was hidden above. With several experimental factors, we were able to reproduce a lot of sound from the bottom speaker. This is disadvantageous in that it cannot hear the reproduced sound directly, hears mainly the reflected waves of the space below the space where the information display device is located, and hears different sounds depending on the characteristics of the reflection surface. In this study, we introduce a technique to make a sound with a direct screen that complements these shortcomings.

New Theoretical Insights into the Crystal-Field Splitting and Transition Mechanism for Nd3+-Doped Y3Al5O12.

There has been considerable research interest paid to rare-earth transition-metal-doped Y3Al5O12, which has great potential for application as a laser crystal of new-type laser devices because of its unique optoelectronic and photophysical properties. Here, we present new research conducted on the structural evolution and crystal-field characteristics of a rare-earth Nd-doped Y3Al5O12 laser crystal by using the CALYPSO structure search method and our newly developed WEPMD method. A novel cage-like structure with a Nd3+ concentration of 4.16% is uncovered, which belongs to the standardized C222 space group. Our results indicate that the impurity Nd3+ ions are likely to substitute the Y3+ at the central site of the host Y3Al5O12 crystal lattice. The laser emission 4F3/2 → 4I11/2 occurring at 1077 nm is in accord with that of the experimental data. By introducing the proper correlation crystal field, three transitions, 4G5/2 → 4I9/2, 4F7/2 → 4I9/2, and 4S3/2 → 4I9/2, are predicted to be good candidates for laser action. These findings can provide powerful guidelines for further experiments of rare-earth-metal-doped laser crystals.

Ab initio research of a metal-free C/N van der Waals bilayer heterostructure with graphdiyne and g-C3N4

The structural, electronic, and optical properties of a mono-layered graphdiyne and g-C3N4 van der Waals (vdW) heterostructure are investigated by first-principle calculations. The bandgap of the vdW bilayer directly forms a type-II heterostructure in which spatially separated active states favor the production of photon-generated carriers. Due to carrier transfer at interfaces, a proper internal electric field is formed, which inhibits the recombination of photon-generated electron−hole pairs. This effect is beneficial for solar energy conversion. We also find that graphdiyne could act as an inorganic photosensitizer, and that the optical absorption spectrum under visible light is broadened. The results could reveal mechanisms for improved energy conversion properties.

Energy gaps and half-metallicity in β-graphyne nanoribbons

We investigate the energy gaps and half-metallicity of the zigzag-edged β-graphyne nanoribbons via a tight-binding approach. In the presence of on-site Coulomb repulsion and proper transverse electric field strengths, the nanoribbons are forced into a half-metallic state by the electric field. A phase transition from half-metal to insulator is realized by changing the electric field or Coulomb potential. Both the electric field and Coulomb repulsion can open direct band gaps, resulting in a metal-insulator phase transition. The band gaps oscillate with the electric field, contrary to linear change with the Coulomb potential.

Selective control of molecule charge state on graphene using tip-induced electric field and nitrogen doping

The combination of graphene with molecules offers promising opportunities to achieve new functionalities. In these hybrid structures, interfacial charge transfer plays a key role in the electronic properties and thus has to be understood and mastered. Using scanning tunneling microscopy and ab initio density functional theory calculations, we show that combining nitrogen doping of graphene with an electric field allows for a selective control of the charge state in a molecular layer on graphene. On pristine graphene, the local gating applied by the tip induces a shift of the molecular levels of adsorbed molecules and can be used to control their charge state. Ab initio calculations show that under the application of an electric field, the hybrid molecule/graphene system behaves like an electrostatic dipole with opposite charges in the molecule and graphene sub-units that are found to be proportional to the electric field amplitude, which thereby controls the charge transfer. When local gating is combined with nitrogen doping of graphene, the charging voltage of molecules on nitrogen is greatly lowered. Consequently, applying the proper electric field allows one to obtain a molecular layer with a mixed charge state, where a selective reduction is performed on single molecules at nitrogen sites.

Soliton-Like Spherical Symmetric Solutions of the Nonlinear Spinor Field Equations Depending on the Invariant Function &amp;lt;i&amp;gt;I&amp;lt;sub&amp;gt;P&amp;lt;/sub&amp;gt;&amp;lt;/i&amp;gt;=&amp;lt;i&amp;gt;P&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt; in the General Relativity Theory

The present research work is considered as part II of the previous work entitled [Plane Symmetric Solutions to the Nonlinear Spinor Field Equations in General Relativity Theory, jmp, 2019, 10, 1222-1234]. Here, we opt for the static spherical symmetric metric. In this metric, we have obtained spherical symmetric soliton-like solutions to the spinor field equations with nonlinear terms, which are arbitrary functions of , taking into account the proper gravitational field of elementary particles. Equations with power and polynomial nonlinearities are investigated in detail. It is shown that the initial set of the Einstein and spinor field equations with a power-law nonlinearity possess regular solutions with a localized energy density of the spinor field only if we consider massless particle without losing the generality (m = 0). In this case, a soliton-like configuration has negative energy. In order to define the role of the nonlinearity and the own gravitational field of the elementary particles in this model, we have obtained exact static symmetric solutions to the above spinor field equations in the linear case by considering Dirac’s equations and in flat space-time. It is proved that soliton-like solutions are absent in the linear case. But in flat space-time soliton-like configurations exist and have positive total energy.

Soliton-Like Spherical Symmetric Solutions of the Nonlinear Spinor Field equations in General Relativity

In this research work, we opt for the static spherical symmetric metric. Thus, taking into account the own gravitational field of elementary particles, we have obtained exact static spheric symmetric solutions of the nonlinear spinor and gravitational fields equations. The nonlinear terms in the spinor lagrangian density characterize the self-interaction of a spinor field. We have investigated in detail equations with power and polynomial nonlinearities. In this case, we have obtained exact regular solutions which have a localized energy density and limited total energy (soliton-like solutions) only if the mass parameter in the spinor field equations is equal to zero. In additional to this, the total charge and the total spin are bounded. We have also shown that in the linear case, soliton-like solutions are absent. But in the flat space-time, the obtained solutions are soliton-like configurations. Therefore, the proper gravitational field of elementary particles, the geometrical properties of the metric and the nonlinear terms in the lagrangian density play a crucial role in the purpose to get the regular solutions with localized energy density and limited total energy.

Solving the Complexity Problem in the Electronics Production Process by Reducing the Sensitivity of Transmission Line Characteristics to Their Parameter Variations

In this paper we consider the complexity problem in electronics production process. Particularly, we investigate the ways to reduce sensitivity of transmission line characteristics to their parameter variations. The reduction is shown for the per‐unit‐length delay and characteristic impedance of several modifications of microstrip transmission lines. It can be obtained by means of making an optimal choice of parameter values, enabling proper electric field redistribution in the air and the substrate. To achieve this aim we used an effective simulation technique and software tools. Taken together, for the first time, they have allowed formulating general approach which is relevant to solve a wide range of similar tasks.

Sunflower Moth (Lepidoptera: Pyralidae) Biology, Ecology, and Management

AbstractSunflower moth, Homoeosoma electellum (Hulst) is an important insect pest of cultivated sunflower in North America. In this review, we outline sunflower moth life history and biology and describe direct and indirect crop injury to cultivated sunflower. Pest management strategies for sunflower moth are discussed including proper field scouting, pheromone trapping, use of economic thresholds and biological control, cultural control, host plant resistance and chemical control for incorporation into an integrated pest management (IPM) program.

Determination of Effective Parameters of Gas Injection in Naturally Fractured Reservoirs by Combination of Reservoir Simulation and Design of Experiment Techniques

Screening analysis is a useful guideline which helps us with proper field selection for different enhanced oil recovery processes. In this work, reservoir simulation is combined with experimental design to estimate main effects and possible interactions of reservoir rock and fluid properties on performance of different gas injection processes in naturally fractured reservoirs (NFRs). Studied parameters include reservoir thickness (h), oil viscosity μo), pore size distribution (λ), horizontal permeability (Kh), storage capacity (ω), reservoir dip, critical water saturation (Swc) and threshold capillary pressure (pct). The recovery factors of different simulation designs are analyzed by use of fractional factorial design (FFD) approach. Finally, the statistical significance of results are evaluated by hypothesis testing and ANOVA, and presented by Pareto and tornado plots. Main effect analysis showed that effective parameters are ordered with respect to their importance as follows: For Methane and nitrogen injection: Kh, dip, Swc, ω, h, μo and λ; threshold capillary pressure showed a minor effect on recovery factor. For Carbon dioxide injection: μo, dip, Swc, ω, h and Kh; Pore size distribution (λ) and threshold pressure were not shown to be statistically significant in this process. Likeness of main effects and parameter interactions for methane and nitrogen injection prove the similarity of dominant mechanisms and characteristics of these processes compared to CO2 injection which seems almost different.

A Machine Learning Approach for the Automatic Classification of Schizophrenic Discourse

Schizophrenia is a chronic neurobiological disorder whose early detection has attracted significant attention from the clinical, psychiatric, and also artificial intelligence communities. This latter approach has been mainly focused on the analysis of neuroimaging and genetic data. A less explored strategy consists in exploiting the power of natural language processing (NLP) algorithms applied over narrative texts produced by schizophrenic subjects. In this paper, a novel dataset collected from a proper field study is presented. Also, grammatical traits discovered in narrative documents are used to build computational representations of texts, allowing an automatic classification of discourses generated by schizophrenic and non-schizophrenic subjects. The attained results showed that the use of the proposed computational representations along with machine learning techniques enables a novel and precise strategy to automatically detect texts produced by schizophrenic subjects.

Improvement of microstructure and performance for steel/Al welds produced by magnetic field assisted laser welding

In this paper, we presented joining of galvanized steel/aluminum alloy dissimilar metals using magnetic field assisted laser welding. Influence of magnetic field on weld appearance and microstructural evolution were carefully characterized using an optical microscope, scanning electron microscope and X-Ray Diffraction. The results showed that a joint with good weld quality can be achieved by magnetic field assisted laser welding. The microstructure and element distribution at interface can be effectively improved by the magnetic field effect. The interface layer mainly involved Fe2Al5 phase, FeAl3 phase, Al192.4Fe46.22 phase and a limited amount of FeAl phase and Fe3Al phase. More Fe-rich IMCs (intermetallic compounds) with better ductility and toughness can be formed, which can obviously reduce the susceptibility of hot cracking and improve the shear strength of joints. It was also found that the weld geometric features were closely associated with magnetic field variables. A method was proposed to control formation of IMCs at interface and inhibit the crack growth via adding proper magnetic field during the process of laser welding.