Short Range Research Articles

Chemical short range order and deformation mechanism of a refractory high entropy alloy HfNbTaZr under nanoindentation: An atomistic study

Refractory high entropy alloys (RHEA) are promising potential used as structural materials owing to the remarkable mechanical properties, such as excellent thermal stability and strength. However, the dynamic nanoindentation response of the nanocrystalline RHEA at atomic scale is not fully revealed. Here, the mechanical behaviour of the as-cast and annealed nanocrystalline HfNbTaZr RHEA under nanoindentation is investigated for first time using a large scale molecular dynamics simulation, in the terms of indentation force, microstructural evolution, stress distribution, shear strain distribution, and surface topography. The results show the annealed nanocrystalline HfNbTaZr RHEA has obvious chemical short-range ordered structure (CSRO), including Ta enrichment and Hf–Nb segregation. The elastic modulus of the annealed RHEA is larger than that of random RHEA, agreeing with the previous experiment. CSRO improves the indentation force and work hardening, due to the inhibition of dislocation nucleation and motion. Interestingly, the hardening behavior is found in the unloading stage, which is rarely reported in traditional alloys. The crystal-to-amorphous phase transition takes place under the loading, and the inverse phase transformation occurs under the unloading. The increase rate of high Von Mises stress and hydrostatic stress region is lower than the change rate of the high strain region. Certainly, almost all atoms move to consume stored energy after unloading, leading to the decrease of stress and strain. The current study not only gives an insight into probing the mechanical behavior of the nanocrystalline RHEA, but also provides an avenue to design high performance RHEAs based on the heat treatment process.

Percolative transport and metamagnetic transition in phase separated La0.55Ca0.45Mn1-xAlxO3-δ

The Al3+ doping effects on the ferromagnetic metallic state of La0.55Ca0.45MnO3 have been studied by preparing the La0.55Ca0.45Mn1-xAlxO3-δ (x = 0, 0.05, 0.1, 0.15) ceramics. Various measurements such as ac susceptibility, relaxation, magnetization and resistivity were performed to study the magnetic and magnetotransport properties. The magnetic disorder produced by the Al3+ dopants and the oxygen vacancies suppress the long range ferromagnetic ordering and induce a short range charge ordered antiferromagnetic clusters, leading to a phase separated behavior in the Al3+-doped samples. A Griffith-like behavior is observed due to the occurrence of short range ferromagnetic clusters in the paramagnetic phase. The 15% Al3+ doping sample exhibits a spin-glass state. The 10% Al3+ doping system is blocked in a metastable state upon cooling at zero field, and a sharp metamagnetic transition is induced by applying a high magnetic field, in which the antiferromagnetic phase is transformed into ferromagnetic phase and the ferromagnetic clusters grow in size. The ferromagnetic domains grows rapidly when applying a high magnetic field. Once the conducting ferromagnetic domains are interconnected throughout the sample, a percolative insulating-to-metallic state transition would occur, accompanied by a sharp drop in resistivity.

Absorption properties and mechanisms of metallic moth-eye structures

The antireflection and absorption properties of non-metallic moth-eye structures have been intensively studied, however the research on those of metallic moth-eye structures, especially their absorption mechanisms, is far from enough. In this paper, the absorption properties and mechanisms of a metallic Au moth-eye structure are studied in detail. The results show that broadband perfect absorption covering the entire visible to the near infrared range with polarization independence and in a wide incident angle range can be easily realized using a single-layer single-material Au moth-eye structure. As for the absorption mechanism, in the short wavelength range of 300 nm–550 nm, due to the high loss of the Au material, the antireflection effect plays a main role. While in the long wavelength range of 550 nm–1000 nm, the widely accepted absorption mechanisms (the antireflection effect as well as the cascaded multiple plasmonic resonances, and even the combination of them) cannot completely account for the broadband perfect absorption. We found that the adiabatic nanofocusing effect of the plasmonic resonances enabled by the ultra-sharp air grooves plays a key role in the absorption. It is the nanofocusing effect that effectively increases the absorption to nearly 100% in a broad wavelength band. These findings provide a deeper insight into the absorption mechanisms of metallic moth-eye structures and offer an effective guide to explore demanded excellent absorption performance.

Quantum transports in two-dimensions with long range hopping

We investigate the effects of disorder and shielding on quantum transports in a two dimensional system with all-to-all long range hopping. In the weak disorder, cooperative shielding manifests itself as perfect conducting channels identical to those of the short range model, as if the long range hopping does not exist. With increasing disorder, the average and fluctuation of conductance are larger than those in the short range model, since the shielding is effectively broken and therefore long range hopping starts to take effect. Over several orders of disorder strength (until sim 10^4 times of nearest hopping), although the wavefunctions are not fully extended, they are also robustly prevented from being completely localized into a single site. Each wavefunction has several localization centers around the whole sample, thus leading to a fractal dimension remarkably smaller than 2 and also remarkably larger than 0, exhibiting a hybrid feature of localization and delocalization. The size scaling shows that for sufficiently large size and disorder strength, the conductance tends to saturate to a fixed value with the scaling function beta sim 0, which is also a marginal phase between the typical metal (beta >0) and insulating phase (beta <0). The all-to-all coupling expels one isolated but extended state far out of the band, whose transport is extremely robust against disorder due to absence of backscattering. The bond current picture of this isolated state shows a quantum version of short circuit through long hopping.

Higher Precision Encoder Using Hologram Scale

Semiconductor manufacturing equipment requires improvement of the accuracy by a linear encoder in a short measurement range. The error in the short range involves the interpolation error and other errors. Improvement in the interpolation error had already achieved in existing research. In contrast, this paper describes the development of a grid interferometer-type linear encoder using a hologram scale with excellent accuracy in a short measurement range. The developed encoder can achieve the error excluding interpolation error less than 10-6 magnitude per measurement range of 50 μm. In the development, error factors in the short-range measurement were examined. An equipment to identify the accuracy in this short-range measurement with high resolution and accuracy was then developed. Error analysis by the developed accuracy measurement equipment made it possible to improve a linear encoder accuracy. As a result, the accuracy of grid interferometer type linear encoder was able to reach at ±20 pm in the measurement range of 50 μm.

Short-range magnetic correlation, metamagnetism, and coincident dielectric anomaly in Na5Co15.5Te6O36

Here we explore the structural, magnetic and dielectric properties of Co based compound Na$_5$Co$_{15.5}$Te$_6$O$_{36}$ as a candidate of short-range magnetic correlations driven development of dielectric anomaly above N$\acute{e}$el temperature of ($T_N$=) 50 K. Low temperature neutron powder diffraction (NPD) in zero applied magnetic field clearly indicates that the canted spin structure is responsible for the antiferromagnetic transition and partially occupied Co form short range magnetic correlation with other Co, which further facilitates the structural distortion and consequent development of dielectric anomaly above antiferromagnetic transition. Additionally, the temperature dependent magnetic heat capacity and electron spin resonance measurements reveal the presence of short-range magnetic correlations which coincides with an anomaly in the dielectric constant vs temperature curve. Moreover, significant changes in the lattice parameters are also observed around the same temperature, indicating presence of noticeable spin-lattice coupling. Further, sharp jump in the magnetic field dependent magnetization clearly indicates the presence of metamagnetic transition and magnetic field dependent NPD confirms that rotations of Co spins with applied magnetic field are responsible for this metamagnetic phase transition. As a result, this transition causes the magnetocaloric effect to be developed in the system, which is suitable for the application in low temperature refrigeration.

3-D Positioning Method of Pipeline Robots Based on a Rotating Permanent Magnet Mechanical Antenna

At present, the 3-D positioning of pipeline robots is limited by complex structures, large device sizes, and difficulties in the miniaturization of the sensor array. In this article, a multipoint magnetic field measurement method (MFM) is proposed for the spatial positioning of pipeline robots. The method can effectively obtain the 3-D coordinate positioning of pipeline robots in a short range, without complex sensor arrays, and without knowing the direction of the pipeline in advance. Furthermore, to address the problem in which weak magnetic field value is very susceptible to background noise and ferromagnetic interference in the environment, a dislocation superposition method (DSM) is developed to process the measured signals. In the MFM, a rotating permanent magnet mechanical antenna is used as the transmitter of low-frequency magnetic signals due to its advantages of small size, low energy consumption, and high radiation efficiency. Moreover, a single three-axis fluxgate sensor is used to measure the magnetic signal at multiple points. Finally, to verify the superiority of the proposed MFM and DSM, experiments are carried out in a seabed engineering laboratory. The test results show that the average absolute error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x}$ </tex-math></inline-formula> -axis positioning is 0.04 m, the average absolute error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y}$ </tex-math></inline-formula> -axis positioning is 0.01 m, and the average absolute error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${z}$ </tex-math></inline-formula> -axis positioning is 0.07 m.

Thermodynamic Evaluation and Optimization of the Ag-As-S system

A critical evaluation of all available phase diagram and thermodynamic data has been performed for Ag-As, Ag-S, As-S and Ag-As-S systems, including a detailed review of the gaseous species involved in the As-S system. Thermodynamic assessments over the whole composition range for these four systems are presented using the CALPHAD method. To predict thermodynamic properties and phase equilibria, the Modified Quasichemical Model for short range ordering was used for the liquid phases, and the Compound Energy Formalism was used for the solid solutions. For the As-S binary system, natural logarithm terms for the temperature dependence of the excess Gibbs energy of the liquid solution have been used. This led to a significant improvement compared with the previous assessment of this system. The optimization of Ag-As-S systems is in good agreement with the existing experimental data.

High Speed DMT for 224 Gb/s and Faster Wireline Transmission

This paper presents a high data rate wireline Discrete Multitone (DMT) transceiver capable of operating at 252 Gbps and higher for short range chip-to-chip and chip-to-module applications. The use of DMT allows for higher spectral efficiency than PAM SERDES systems, using similar bandwidth as proposed 224 Gb/s PAM-4 systems but achieves higher data rates. Data rates have improved over other published wireline DMT designs with the use of narrow sub-channels with both adaptive bit- and power-loading along with a combined transmit and receive side equalization. Simulation and measured results show that the transmit side pre-compensation has improved the BER by a factor of 104 at 250 Gb/s. The system is measured over a channel with a loss of 18 dB at 50 GHz, showing a data rate of 252 Gb/s with a BER of 10-6, and a data rate of 400 Gb/s with a BER of 10-2.

Signatures of Non-universal Quantum Dynamics of Ultracold Chemical Reactions of Polar Alkali Dimer Molecules with Alkali Metal Atoms: Li(2S) + NaLi(a3Σ+) → Na(2S) + Li2(a3Σu+).

Ultracold chemical reactions of weakly bound triplet-state alkali metal dimer molecules have recently attracted much experimental interest. We perform rigorous quantum scattering calculations with a new ab initio potential energy surface to explore the chemical reaction of spin-polarized NaLi(a3Σ+) and Li(2S) to form Li2(a3Σu+) and Na(2S). The reaction is exothermic and proceeds readily at ultralow temperatures. Significantly, we observe strong sensitivity of the total reaction rate to small variations of the three-body part of the Li2Na interaction at short range, which we attribute to a relatively small number of open Li2(a3Σu+) product channels populated in the reaction. This provides the first signature of highly non-universal dynamics seen in rigorous quantum reactive scattering calculations of an ultracold exothermic insertion reaction involving a polar alkali dimer molecule, opening up the possibility of probing microscopic interactions in atom+molecule collision complexes via ultracold reactive scattering experiments.

Electric Arc Furnace Stirring: A Review

Thermodynamics and kinetics are affected by the stirring conditions. Higher‐stirring intensities promote conditions closer to equilibrium and increase the mass‐transfer coefficients. A major limitation of the conventional electric arc furnace (EAF) is the low velocities of liquid steel which result in very poor mixing conditions. The practical consequences are lower decarburization rates and lower melting rates. Herein, the forces that operate and promote the motion of liquid steel in a conventional EAF are reviewed in detail; buoyancy forces, momentum transfer by the oxygen jets, drag forces by CO bubbles are produced by decarburization and local electromagnetic forces at the electrode regions. It is shown in the short range and limited intensity of the previous forces. Bottom gas injection and electromagnetic stirring are the main methods that can induce forced convection in the EAF. The information available is summarized and analyzed to describe the results obtained at laboratory level and industrial scale using different stirring mechanisms. Finally, guidelines are provided in this review for further research on the basis of the limitations of the current results.

Effect of down-shifting phosphor particles on crystalline silicon solar cells

Introducing down-shifting phosphor particles onto solar cells can improve their spectral response to short wavelength photons, but it also leads to the rise of reflection in middle and long wavelength range due to the scattering by phosphor particles. In this work, the down-shifting solar cells are fabricated by packaging crystalline silicon solar cells with ethylene vinyl acetate (EVA) films which include different concentration of down-shifting Ce-doped yttrium aluminum garnet (YAG:Ce) phosphor particles. Experimental result shows that the increasing concentration of YAG:Ce phosphors strengthens the down-shifting effect and makes the reflection rise. The competition between the down-shifting effect and the reflection results in the best improvement of the solar cells when the phosphor's concentration is 0.7%. The optical ray-tracing simulations clarify that the packaged solar cell with YAG:Ce absorbs less photons than those without YAG:Ce, but their conversion efficiency is higher than those without YAG:Ce. This indicates that the penetration depth of the short wavelength photons is responsible for the poorer spectral response of the solar cells in the short wavelength range.

REDfold: accurate RNA secondary structure prediction using residual encoder-decoder network

BackgroundAs the RNA secondary structure is highly related to its stability and functions, the structure prediction is of great value to biological research. The traditional computational prediction for RNA secondary prediction is mainly based on the thermodynamic model with dynamic programming to find the optimal structure. However, the prediction performance based on the traditional approach is unsatisfactory for further research. Besides, the computational complexity of the structure prediction using dynamic programming is O(N^3); it becomes O(N^6) for RNA structure with pseudoknots, which is computationally impractical for large-scale analysis.ResultsIn this paper, we propose REDfold, a novel deep learning-based method for RNA secondary prediction. REDfold utilizes an encoder-decoder network based on CNN to learn the short and long range dependencies among the RNA sequence, and the network is further integrated with symmetric skip connections to efficiently propagate activation information across layers. Moreover, the network output is post-processed with constrained optimization to yield favorable predictions even for RNAs with pseudoknots. Experimental results based on the ncRNA database demonstrate that REDfold achieves better performance in terms of efficiency and accuracy, outperforming the contemporary state-of-the-art methods.

Review of animal transmission experiments of respiratory viruses: Implications for transmission risk of SARS-COV-2 in humans via different routes.

Exploring transmission risk of different routes has major implications for epidemic control. However, disciplinary boundaries have impeded the dissemination of epidemic information, have caused public panic about "air transmission," "air-conditioning transmission," and "environment-to-human transmission," and have triggered "hygiene theater." Animal experiments provide experimental evidence for virus transmission, but more attention is paid to whether transmission is driven by droplets or aerosols and using the dichotomy to describe most transmission events. Here, according to characteristics of experiment setups, combined with patterns of human social interactions, we reviewed and grouped animal transmission experiments into four categories-close contact, short-range, fomite, and aerosol exposure experiments-and provided enlightenment, with experimental evidence, on the transmission risk of severe acute respiratory syndrome coronavirus (SARS-COV-2) in humans via different routes. When referring to "air transmission," context should be showed in elaboration results, rather than whether close contact, short or long range is uniformly described as "air transmission." Close contact and short range are the major routes. When face-to-face, unprotected, horizontally directional airflow does promote transmission, due to virus decay and dilution in air, the probability of "air conditioning transmission" is low; the risk of "environment-to-human transmission" highly relies on surface contamination and human behavior based on indirect path of "fomite-hand-mucosa or conjunctiva" and virus decay on surfaces. Thus, when discussing the transmission risk of SARS-CoV-2, we should comprehensively consider the biological basis of virus transmission, environmental conditions, and virus decay. Otherwise, risk of certain transmission routes, such as long-range and fomite transmission, will be overrated, causing public excessive panic, triggering ineffective actions, and wasting epidemic prevention resources.

Multivariable Rheological Models for Commercial Polypropylene with High Molar Masses

AbstractThis work investigates the fitting performance of conventional rheological models and the development of multivariable rheological models to reproduce experimental rheological data of different industrial grades of linear isotactic polypropylene (iPP) having high mass average molar masses, Mm (164–404 kg mol−1), at three temperature values (180–220 °C) over a wide range of shear rates (10−1–104 s−1). A shear thinning behavior is found in all investigated conditions. However, a low shear rate primary Newtonian plateau for a short shear rate range is only identified for the smallest Mm among those investigated, and for higher Mm such primary plateaus are even found at shorter shear rate range. Among the investigated models, only Cross and Carreau–Yasuda models are effective to reproduce the data for a specific PP grade. Two modified models are proposed that incorporate three variables. In the modified Cross Model, it has been shown that the characteristic time (λ) between the Newtonian plateau at the low shear rates and the shear‐rate range with shear‐thinning behavior depends exponentially on the Mm, and it does not depend on the temperature. Both proposed models fit very well with the experimental data with shear thinning behavior for a wide range of Mm.

Drones Do Not Drift between Nests in a Wild Population of Apis cerana.

The modes through which individuals disperse prior to reproduction has important consequences for gene flow in populations. In honey bees (Apis sp.), drones (males) reproduce within a short flight range of their natal nest, leaving and returning each afternoon within a narrow mating window. Drones are assumed to return to their natal nests as they depend on workers to feed them. However, in apiaries, drones are reported to regularly make navigation errors and return to a non-natal nest, where they are accepted and fed by unrelated workers. If such a "drone drift" occurred in wild populations, it could facilitate some further degree of dispersal for males, particularly if drones drift into host nests some distance away from their natal nest. Here, we investigated whether drone drift occurs in an invasive population of the Asian honey bee (Apis cerana). Based on the genotypes of 1462 drones from 19 colonies, we found only a single drone that could be considered a candidate drifter (~0.07%). In three other colonies, drones whose genotypes differed from the inferred queen were best explained by recent queen turnover or worker-laying. We concluded that drone drift in this population is low at best, and A. cerana drones either rarely make navigation errors in wild populations or are not accepted into foreign nests when they do so. We therefore confirm that drone dispersal distance is limited to the distance of daily drone flights from natal nests, a key assumption of both colony density estimates based on sampling of drone congregation areas and population genetic models of gene flow in honey bees.

Comparative study of Lutetium-177 and Phosphorus-32 in radioactive bone cement for the treatment of vertebral body metastasis.

Vertebroplasty is a minimally invasive outpatient procedure to stabilize compression fractures in the spine. This procedure involves injecting bone cement into the vertebrae that have been cracked or broken, typically due to osteoporosis. The cement hardens inside the bones, providing stability to the fractures and supporting the spine. Additionally, radioactive bone cement and brachytherapy sources have been utilized to suppress tumor growth in the vertebral body. We present a novel brachytherapy technique for treating vertebral body metastases using a liquid form of radioactive sources, Phosphorus-32 and Lutetium-177, separately mixed with bone cement and injected into vertebral body bone prostheses. We also investigated the dose distribution of the radioactive bone cement by theoretically calculating it using GEANT4 Monte Carlo and measuring it using TLD dosimeters for Phosphorus-32 and Lutetium-177 loaded in vertebral bodies. CT-scanned images of each vertebral body (L2 and L3) were imported into GEANT4 for simulation purposes. Two simulations were performed to evaluate the possibility of using PLA prostheses in ex vivo measurements, using bone and PLA material as a bone substitute for brachytherapy of Lutetium-177 and Phosphorus-32. The simulations calculated the dose distribution, dose rates, and deposited dose to the spinal cord and aorta. Next, 3D-printed bone prostheses were drilled and separately filled with bone cement, including PMMA-P32 and PMMA-Lu177, in liquid form using the Vertebroplasty technique. The dose to regions of interest was measured using Thermoluminescence dosimeters. When comparing the simulated and measured results of dose rates, it was observed that P32 delivers higher doses to normal organs such as the spinal cord and aorta. At the same time, Lu177 has better sparing in these regions of interest. Therefore, while P32 and Lu177 are suitable for radioactive bone cement treatment, Lu177 delivers relatively lower doses to vital organs such as the spinal cord and aorta. Additionally, Lu177 has characteristics such as a shorter range and lower energies of beta particles in tissue and the presence of gamma rays that make it a better choice for the same treatments. It also provides the possibility of SPECT imaging.

Towards Designing a Planet Walk Simulation in a Controlled Environment

Planet Walk Simulation involves several parametric readings like physical human body conditions, geographic and atmospheric conditions, etc. In this work, we have set goals including system state monitoring, terrain mapping, and user navigation. Specific objectives are displaying the user’s telemetry, elevating their spatial awareness through short range object detection, and displaying their location relative to origin using wi-fi routers. The experimental results showed navigation motion paths for astronauts and identify obstacles in the path with the help of LiDAR and Hololens.

Alkali-oxygen cooking coupled with ultrasonic etching for directly defibrillation of bagasse parenchyma cells into cellulose nanofibrils

A scheme combining alkali‑oxygen cooking and ultrasonic etching cleaning was developed for the short range preparation of CNF from bagasse pith, which has a soft tissue structure and is rich in parenchyma cells. This scheme expands the utilization path of sugar waste sucrose pulp. The effect of NaOH, O2, macromolecular carbohydrates, and lignin on subsequent ultrasonic etching was analyzed, and it was found that the degree of alkali‑oxygen cooking was positively correlated with the difficulty of subsequent ultrasonic etching. The mechanism of ultrasonic nano-crystallization was found to be the bidirectional etching mode from the edge and surface cracks of the cell fragments by ultrasonic microjet in the microtopography of CNF. The optimum preparation scheme was obtained under the condition of 28 % NaOH content and 0.5 MPa O2, which solves the problem of low-value utilization of bagasse pith and environmental pollution, providing a new possibility for the source of CNF.

Underwater Positioning System Based on Drifting Buoys and Acoustic Modems

GNSS (Global Navigation Satellite System) positioning is not available underwater due to the very short range of electromagnetic waves in the sea water medium. In this article a LBL (Long Base Line) acoustic repeater system of the GNSS positioning is presented. The system is hyperbolic, i.e., based on time differences and it does not need very accurate atomic clocks to synchronize repeaters. The system architecture and system calculations that demonstrate the feasibility of the solution are presented. The system uses four buoys that sequentially transmit their position and the time of the instant of transmission, for which they are equipped with GNSS receivers and acoustic modems. The buoys can be fixed or even drifting, but they are inexpensive devices, which pose no hazard to navigation and can be easily and quickly deployed for a specific underwater mission. The multilateration algorithm used in the receiver is presented. To simplify the algorithm, the depth of the receiver, measured by a depth sensor, is used. Results are presented for the position error of an underwater vehicle due to its displacement during the transmission frame of the four buoys.