bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum mechanical investigation of N + N2 collision: state-to-state non-reaction and exchange reaction probabilities and rate constants
Authors: Li Na , Zhang Hong , Cheng Xin-Lu
Published: December 2021

We present a state-to-state dynamical calculation on the exchange reaction N + N2 → N2 + N and the non-reaction N + N2 → N + N2 based on the potential energy surface published by Mankodi et al. The calculation is performed using the time-independent quantum reaction scattering program. The reactivity of both reaction processes is discussed by reaction properties of vibrational quantum numbers v = 0–3 and rotational quantum numbers j = 0–32 (such as cumulative reaction probability, state-to-state reaction probabilities, and cross sections of N exchange, state-to-state rate constants for both reactions). The threshold energy of the exchange reaction can decrease with the decrease of vibrational excitation or the increase of rotational excitation. By using the J-shifting approximation, rate constants are reported for both reactions. The comparison of the presented total rate constant of the N + N2 exchange reaction with the previous results shows that the quantum effect is not negligible at low temperatures. For the exchange reaction, the rate constant at 500 K decreases by about 10 orders of magnitude when the vibrational level of N2 increases from 0 to 7, indicating that the rate constants are sensitive to the initial vibrational level of N2 at low temperatures. For non-reactive collision, the rate constants have little effect on the initial ro-vibrational levels of N2 at low temperatures.
Influence of Rashba spin–orbit and Rabi couplings on the spin-mixing and ground state phases of binary Bose–Einstein condensates
Authors: Ravisankar R , Sriraman T , Kumar R Kishor , Muruganandam P , Mishra P K
Published: December 2021

We study the miscibility properties and ground state phases of two-component spin–orbit (SO) coupled Bose–Einstein condensates (BECs) in a harmonic trap with strong axial confinement. By numerically solving the coupled Gross–Pitaevskii equations in the two-dimensional setting, we analyze the SO-coupled BECs for two possible permutations of the intra- and interspecies interactions, namely (i) weak intra- and weak interspecies interactions (W–W) and (ii) weak intra- and strong interspecies interactions (W–S). Considering the density overlap integral as a miscibility order parameter, we investigate the miscible–immiscible transition by varying the coupling parameters. We obtain various ground state phases, including plane wave, half quantum vortex, elongated plane wave, and different stripe wave patterns for W–W interactions. For finite Rabi coupling, an increase in SO coupling strength leads to the transition from the fully miscible to the partially miscible state. We also characterize different ground states in the coupling parameter space using the root mean square sizes of the condensate. The spin density vector for the ground state phases exhibits density, quadrupole and dipole like spin polarizations. For the W–S interaction, in addition to that observed in the W–W case, we witness semi vortex, mixed mode, and shell-like immiscible phases. We notice a wide variety of spin polarizations, such as density, dipole, quadrupole, symbiotic, necklace, and stripe-like patterns for the W–S case. A detailed investigation in the coupling parameter space indicates immiscible to miscible state phase transition upon varying the Rabi coupling for a fixed Rashba SO coupling. The critical Rabi coupling for the immiscible–miscible phase transition decreases upon increasing the SO coupling strength.
Recent progress in zinc-based redox flow batteries: a review
Authors: Wang Guixiang , Zou Haitao , Zhu Xiaobo , Ding Mei , Jia Chuankun
Published: December 2021

Zinc-based redox flow batteries (ZRFBs) have been considered as ones of the most promising large-scale energy storage technologies owing to their low cost, high safety, and environmental friendliness. However, their commercial application is still hindered by a few key problems. First, the hydrogen evolution and zinc dendrite formation cause poor cycling life, of which needs to ameliorated or overcome by finding suitable anolytes. Second, the stability and energy density of catholytes are unsatisfactory due to oxidation, corrosion, and low electrolyte concentration. Meanwhile, highly catalytic electrode materials remain to be explored and the ion selectivity and cost efficiency of membrane materials demands further improvement. In this review, we summarize different types of ZRFBs according to their electrolyte environments including ZRFBs using neutral, acidic, and alkaline electrolytes, then highlight the advances of key materials including electrode and membrane materials for ZRFBs, and finally discuss the challenges and perspectives for the future development of high-performance ZRFBs.
Depth detection of spar cap defects in large-scale wind turbine blades based on a 3D heat conduction model using step heating infrared thermography
Authors: Zhang X Y , Zhou B , Li H , Xin W
Published: December 2021

The defects dispersed in a spar cap often lead to the failure of large-scale wind turbine blades. To predict the residual service life of the blade and make the repair, it is necessary to detect the depth of spar cap defects. Step-heating thermography (SHT) is a common infrared technique in this domain. However, the existing methods of SHT on defect depth detection are generally based on 1D models, which are unable to accurately detect the depth of spar cap defects due to ignoring material anisotropy and in-plane heat flow. To improve the depth detection accuracy of spar cap defects, a 3D model based on the theory of heat transfer is established by using the equivalent source method (ESM), and a defect depth criterion is proposed based on the analytical solution of the heat conduction equation. The modeling process is as follows. The heat conduction model of SHT was established by ESM. Then, coordinate transformation, variables separation, and Laplace transformation were utilized to solve the 3D heat conduction equation. A defect depth criterion was proposed based on emerging contrast Cr. A glass fiber reinforced plastic composite plate containing 12 square flat-bottom holes with different sizes and depths was manufactured to represent a spar cap with large thermal resistance defects, such as delamination and cracks. The experimental results demonstrate the validity of the 3D model. Then, the model was applied to an on-site SHT test of a 1.5 MW wind turbine blade. The test results prove that the depth detection accuracy of spar cap defects can be significantly improved by using the 3D model. In addition, by using an improved principle component analysis (PCA) method containing a contrast enhancement factor, artifacts can be reduced and the recognition time of defects can be shortened. The 3D model provides a tool for detecting the depth of deep-lying defects in a thick composite structure, and the SHT technology is optimized by improved PCA.
Monte Carlo-Discrete Dislocation Dynamics: a technique for studying the formation and evolution of dislocation structures
Authors: Deka Nipal , Sills Ryan B
Published: December 2021

A novel Monte Carlo (MC) based solver for discrete dislocation dynamics (DDD) has been developed, by which dislocation lines are inserted to the system in succession subject to a user-defined acceptance criterion. Utilizing this solver, dislocation structure evolution can be examined in a controlled fashion that is not possible using conventional DDD methods. The outcomes of the MC-DDD simulations establish for the first time that dislocation wall structures can adopt a characteristic width that naturally arises from elastic interactions within the network. This characteristic width does not alter as additional dislocation lines are inserted and the density in the wall increases, meaning it is independent of the mean dislocation spacing. However, the wall width is influenced by the acceptance criterion used during MC steps; the wall gets thinner as the interactions within the wall become more attractive. Finally, we demonstrate that algorithmic aspects of MC-DDD simulations can provide insights into structure evolution. Overall, this new MC-DDD technique will allow systematic studies of dislocation structures, providing unprecedented insight into the underlying mechanics.
Progressive evaluation in spectroscopic sensors for non-invasive blood haemoglobin analysis—a review
Authors: Kumar Yogesh , Dogra Ayush , Kaushik Ajeet , Kumar Sanjeev
Published: December 2021

Objective. Frequent monitoring of haemoglobin concentration is highly recommended by physicians to diagnose anaemia and polycythemia vera. Moreover, other conditions that also demand assessment of haemoglobin are blood loss, before blood donation, during pregnancy, and preoperative, perioperative and postoperative conditions. The cyanmethemoglobin/haemiglobincyanide method, portable haemoglobinometers and haematology analyzers are some of the standard methods used to diagnose the aforementioned ailments. However, discomfort, delay and risk of infection are typical limitations of traditional measuring solutions. These limitations create the necessity to develop a non-invasive haemoglobin monitoring technique for a better lifestyle. Approach. Various methods and products have already been developed and are popular due to their non-invasiveness; however, invasive solutions are still considered as the reference standard method. Therefore, this review summarizes the attributes of existing non-invasive solutions. These attributes are finalized as brief details, accuracy, optimal benefits and research challenges for exploring potential gaps, advancements and possibilities to consider as futuristic alternative methodologies. Main results. Non-invasive total haemoglobin assessment techniques are mainly based on optical spectroscopy (reflectance/transmittance) or digital photography, or spectroscopic imaging in spot-check/continuous monitoring mode. In all these techniques, we have noticed that there is a need to consider different light conditions, motion artefacts, melanocytes, other blood constituents, smoking and precise fixing of the sensor from the sensing spot for exact formulation. Significance. Moreover, based on careful and critical analysis of outcomes, none of these techniques or products are used independently or intended to replace invasive laboratory testing. Therefore, there is a requirement for a more accurate technique that can eliminate the requirement for blood samples and likely end up as a reference standard method.
Controlling the breakdown delay time in pulsed gas discharge
Authors: Schweigert I V , Hopkins M M , Barnat E , Keidar M
Published: December 2021

In experiment and 2D3V PIC MCC simulations, the breakdown development in a pulsed discharge in helium is studied for U = 3.2 kV and 10 kV and P = 100 Torr. The breakdown process is found to have a stochastic nature, and the electron avalanche develops in different experimental and simulation runs with time delays ranging from 0.3 to 8 μs. Nevertheless our experiments demonstrate that the breakdown delay time distribution can be controlled with a change of the pulse discharge frequency. The simulation results show that the breakdown process can be distinguished in three stages with (a) the ionization by seed electrons, (b) the ions drift to the cathode and (c) the enhanced ionization within the cathode sheath by the electrons emitted from the cathode. The effects of variation of seed electron concentrations, voltage rise times, voltage amplitudes and ion–electron emission coefficients on the breakdown development in the pulsed gas discharge are reported.
STDP implementation using multi-state spin−orbit torque synapse
Authors: Ghanatian Hamdam , Ronchini Margherita , Farkhani Hooman , Moradi Farshad
Published: December 2021

The abundance of data to be processed calls for new computing paradigms, which could accommodate, and directly map artificial neural network architectures at the hardware level. Neuromorphic computing has emerged as a potential solution, proposing the implementation of artificial neurons and synapses on physical substrates. Conventionally, neuromorphic platforms are deployed in complementary metal-oxide-semiconductor technology. However, such implementations still cannot compete with the highly energy-efficient performance of the brain. This calls for novel ultra-low-power nano-scale devices with the possibility of upscaling for the implementation of complex networks. In this paper, a multi-state spin−orbit torque (SOT) synapse based on the three-terminal perpendicular anisotropy magnetic tunnel junction (P-MTJ) is proposed. In this implementation, P-MTJs use common heavy metals but with different cross-section areas, thereby creating multiple states that can be harnessed to implement synapses. The proposed multi-state SOT synapse can solve the state-limited issue of spin-based synapses. Moreover, it is shown that the proposed multi-state SOT synapse can be programmed to reproduce the spike-timing-dependent plasticity learning algorithm.
Utilising angle-dependent critical current data in the electromagnetic modelling of HTS coils
Authors: Wimbush Stuart C , Strickland Nicholas M
Published: December 2021

A detailed methodology is presented for modelling the electromagnetic characteristics of HTS coils using angle-dependent critical current data obtained from experimental measurements of real wire samples. The results of such an analysis are contrasted with those obtained using more prevalent approaches such as a global minimum critical current method or an elliptical field magnitude-dependent functional approximation. Several interesting design consequences of significance to real-world devices that emerge only when the full anisotropy of real wires is taken into account are outlined and discussed. These include the beneficial impact on various performance metrics of the adoption of mixed conductor windings, the importance of coil orientation in optimising device performance, and the potential opportunity to derive a specific design benefit from the targeted use of conductors possessing inclined planarity.
Comparative study of the highly sensitive plasmonic sensor based on a D-Shaped photonic crystal fiber with silver or gold layers
Authors: Meshginqalam Bahar , Barvestani Jamal
Published: December 2021

A highly sensitive D-shaped photonic crystal fiber sensor with circular lattice is proposed for external plasmonic sensing. The proposed design of plasmonic material in a D-shaped form effectively facilitates the excitation of surface plasmons and enhances the sensor performance. As a comparative study, two different plasmonic materials, gold and silver, are applied D-shapely on the fiber and the proposed sensor performance is numerically investigated and evaluated. Moreover, the optimized structural parameters such as air-hole diameters and the thickness of silver and gold layers are selected via simulation results which cause the highest sensitivity of 40000 nm/RIU for the gold coated fiber using the wavelength interrogation method. Furthermore, the maximum figure of merit can reach 621.50

RIU

−
1

.

Analytes with the refractive indices ranging from 1.34 to 1.39 can be detected by double-loss peak that is a more reliable method of simultaneous detection and verification of sensing characteristics. Due to its promising results, the proposed sensor can be widely useful in the area of chemical and biological sensing.
An analysis of axisymmetric Sezawa waves in elastic solids
Authors: Bian Chunlei , Wang Ji , Bin Huang  , Xie Longtao , Yi Lijun , Yuan Lili , Li Honglang , Tian Yahui
Published: December 2021

The wave propagation in elastic solids covered by a thin layer has received significant attention due to the existence of Sezawa waves in many applications such as medical imaging. With a Helmholtz decomposition in cylindrical coordinates and subsequent solutions with Bessel functions, it is found that the velocity of such Sezawa waves is the same as the one in Cartesian coordinates, but the displacement will be decaying along the radius with eventual conversion to plane waves. The decaying with radius exhibits a strong contrast to the uniform displacement in the Cartesian formulation, and the asymptotic approximation is accurate in the range about one wavelength away from the origin. The displacement components in the vicinity of origin are naturally given in Bessel functions which can be singular, making it more suitable to analyze waves excited by a point source with solutions from cylindrical coordinates. This is particularly important in extracting vital wave properties and reconstructing the waveform in the vicinity of source of excitation with measurement data from the outer region.
Investigation of defect levels in Bi12SiO20 single crystals by thermally stimulated current measurements
Authors: Isik M , Delice S , Gasanly N M
Published: December 2021

Bi12SiO20 (BSO) single crystal belongs to the sillenite semiconducting family known as defective compounds. The present paper investigates the defect centers in BSO grown by Czochralski method by means of thermally stimulated current (TSC) measurements performed in the 10–260 K range. The TSC glow curve obtained at heating rate of β = 0.1 K s−1 presented several peaks associated with intrinsic defect centers. The activation energies of defect centers were revealed as 0.09, 0.15, 0.18, 0.22, 0.34, 0.70 and 0.82 eV accomplishing the curve fit analyses method. The peak maximum temperatures and orders of kinetics of each deconvoluted peak were also determined as an outcome of fitting process. TSC experiments were expanded by making the measurements at various heating rates between 0.1 and 0.3 K s−1 to get information about the heating rate dependent peak parameters.
Halo current rotation scaling in post-disruption plasmas
Authors: Saperstein A.R. , Levesque J.P. , Mauel M.E. , Navratil G.A.
Published: December 2021

Halo current (HC) rotation during disruptions can be potentially dangerous if resonant with the structures surrounding a tokamak plasma. We propose a drift-frequency-based scaling law for the rotation frequency of the asymmetric component of the HC as a function of toroidal field strength and plasma minor radius (f
rot ∝ 1/B
T
a
2). This scaling law is consistent with results reported for many tokamaks and is motivated by the faster HC rotation observed in the HBT-EP tokamak. Projection of the rotation frequency to ITER and SPARC parameters suggest the asymmetric HC rotation will be on the order of 10 Hz and 60 Hz, respectively.
Hands-on with OWL: the Oak–Ridge Wang–Landau Monte Carlo software suite
Authors: Wai Li Ying , Chaitanya Pitike Krishna , Eisenbach Markus , Cooper Valentino R.
Published: December 2021

The Oak–Ridge Wang–Landau (OWL) package is an open-source scientific software specialized for large-scale, Monte Carlo simulations for the study of materials properties at finite temperature. In this paper, we discuss the main features and capabilities of OWL, followed by detailed descriptions of building and running the code. The readers will be guided through the usage and functionality of the code with a few hands-on examples. This paper is based on a tutorial on OWL given at the 32nd Center for Simulational Physics Workshop on Recent Developments in Computer Simulation Studies in Condensed Matter Physics.
Edge cloud task scheduling model based on layered excellent gene replication strategy
Authors: Zhu Leilei , Zhao Ke , Lin Huaze , Liu Dan , Li Li
Published: December 2021

With the development of the Internet of Things and 5G. Edge cloud technology has gradually become a research hotspot. When facing the massive and concurrent tasks of terminal users, reasonable resource scheduling strategy is a key technology. Because edge cloud needs to respond quickly to real-time tasks and ensure the stability of nodes at the same time, the optimal task scheduling strategy needs to be selected to meet the low latency requirements of edge users. In view of the above problems in resource allocation of edge cloud, this paper established a layered excellent gene replication strategy (HEGPSO model), in which the optimal replicator is added, and an evolutionary particle swarm optimization algorithm is proposed. In each iteration, the population is divided into three layers based on individual fitness. After that, the optimal replication factor is added to each layer of individuals to enhance the global search ability of the algorithm and ensure the good convergence of the algorithm. Finally, a balanced resource allocation model is established. Experiments show that the HEGPSO model proposed in this paper has high fitness and fast convergence speed, and is suitable for large-scale task access scenarios.
Group recommendation method combining short-term interest and long-term preference
Authors: Zhu Hangyu , Gao Maoting
Published: December 2021

Based on self-attention and outer product-based neural collaborative filtering,this paper proposed a SLAR model.The model uses the recent interaction information of each user in the group and self-attention mechanism to obtain the short-term interest vector of the group.The attention mechanism and self-attention mechanism are used to calculate the influence of each user and the influence between members during the interaction between the target group and item, so as to aggregate them into the long-term preference vector of the group, and then the sum of short-term interest and long-term preference is input into ONCF model as the embedding vector of the group to mine the interaction between the group and the project from the data, and finally complete the group recommendation. Compared with the traditional group fusion strategy on CAMR2011 data set, the experimental results show that SLGR model achieves better results.
Research on Optimization of Fuzzy Network Control System Based on New Smith Predictive Time Delay Compensation
Authors: Lu Cong , Xian Xuehui , Li Changqing
Published: December 2021

Aiming at the problem of network delay when the network control system transmits data, this paper adopts a new type of fuzzy control method of Smith predictor to compensate for the delay. In actual application scenarios, it is difficult to accurately match the Smith prediction model with the actual model. At the same time, the quantization factor and scale factor in the fuzzy PID controller are too dependent on experience, which makes the system’s adaptability to actual working conditions very poor. In this paper, genetic algorithm is used to optimizes fuzzy PID. According to the simulation results, when the Smith predictive model does not match the actual model, the steady-state performance and dynamic performance of the system under the fuzzy PID control optimized by the genetic algorithm are improved.
Optimal Security Protection Selection Strategy Based on Markov Model Attack Graph
Authors: Yang Jinwei , Yang Yu
Published: December 2021

Intrusion intent and path prediction are important for security administrators to gain insight into the possible threat behavior of attackers. Existing research has mainly focused on path prediction in ideal attack scenarios, yet the ideal attack path is not always the real path taken by an intruder. In order to accurately and comprehensively predict the path information of network intrusion, a multi-step attack path prediction method based on absorbing Markov chains is proposed. Firstly, the node state transfer probability normalization algorithm is designed by using the nil posteriority and absorption of state transfer in absorbing Markov chain, and it is proved that the complete attack graph can correspond to absorbing Markov chain, and the economic indexes of protection cost and attack benefit and the index quantification method are constructed, and the optimal security protection policy selection algorithm based on particle swarm algorithm is proposed, and finally the experimental verification of the model in protection Finally, we experimentally verify the feasibility and effectiveness of the model in protection policy decision-making, which can effectively reduce network security risks and provide more security protection guidance for timely response to network attack threats.
Coordinated intelligent manipulator based on exoskeleton
Authors: Wang Xiang , Yang Fan
Published: December 2021

Manipulators have a wide range of applications in telemedicine, deep-sea exploration, remote explosive-removal and prosthesis for the disabled. Based on exoskeleton and voice control, a coordinated intelligent manipulator was proposed in this paper. The main design scheme, attitude angle data acquisition and data processing methods were given, and the final test results were obtained.
STI direct test method based on wavelet transform to extract envelope
Authors: Wang Wenxin , Zhu Ranran , Zhao Hongliang
Published: December 2021

Speech transmission index (STI for short) is an important index to evaluate the quality of speech transmission of the room, it can better reflect the degree of voice signal affected by room reverberation and noise in the transmission process.This paper presents an algorithm for directly measuring STI index, white noise is filtered by Paul Kellet filter to generate pink noise, the signal envelope is extracted by wavelet transform, which improves the extraction accuracy of signal envelope and makes the measurement of STI index more accurate.
Transmission line surface defect detection method based on uav autonomous inspection
Authors: Xie Xu
Published: December 2021

The existing transmission line surface defect detection methods have the problem of incomplete image data set, resulting in a low recognition success rate. A transmission line surface defect detection method based on uav autonomous inspection is designed. The safety of power grid operation is evaluated, the local linearization process is transformed into linear equation expression, the image data set is obtained by uav autonomous inspection, the transmission line state is judged, the corresponding constraint conditions are set, the type of transmission line surface defects are identified, the number of image poles and towers is matched, and the detection mode is optimized by edge detection algorithm. Experimental results: The average recognition success rate of the transmission line surface defect detection method in this paper and the other two detection methods is 59.89%, 51.89% and 52.03%, proving that the transmission line surface defect detection method integrating UAV technology inspection has a wider application space.
Deep attributed network embedding by mutual information maximization
Authors: Tao Wujun , Ye Yu , Feng Bailin
Published: December 2021

There is a growing body of literature that recognizes the importance of network embedding. It intends to encode the graph structure information into a low-dimensional vector for each node in the graph, which benefits the downstream tasks. Most of recent works focus on supervised learning. But they are usually not feasible in real-world datasets owing to the high cost to obtain labels. To address this issue, we design a new unsupervised attributed network embedding method, deep attributed network embedding by mutual information maximization (DMIM). Our method focuses on maximizing mutual information between the hidden representations of the global topological structure and the node attributes, which allows us to obtain the node embedding without manual labeling. To illustrate the effectiveness of our method, we carry out the node classification task using the learned node embeddings. Compared with the state-of-the-art unsupervised methods, our method achieves superior results on various datasets.
A People-Oriented Designing for Pattern Carving Intelligent Control Integrated Device
Authors: Li Yan , Fang Shuguang
Published: December 2021

Aiming at solving the problems of weak human-computer interaction, poor scalability, low system integration, and lack of information management capabilities of the original engraving equipment, a set of pattern engraving intelligence integrated management and control device has been developed. The device flexibly integrates the main processes of engraving machining, detection, sorting, etc, and realizes the automatic machining of multi-mode engraving tasks such as on-site touch screen delivery, remote machine vision collection, network PC communication, and mobile APP sending. It can identify and evaluate the characteristic parameters of engraved final products over non-contact machine vision; and use the SCARA robot for intelligent sorting and palletizing of engraved final products. In addition,its information management platform can realize real-time monitoring of production status and production data storage and statistical analysis. In general, the device realizes the intelligent upgrade and informatization transformation of traditional engraving equipment.
Analysis and Treatment of Electrical Fault of Ship Windlass
Authors: Wang Yanyang , Liu Chongchong , Hu Linxiang , Chen Shuai
Published: December 2021

This paper aims at the electrical failure of the ship anchor machine, the potential causes of the failure are summarized and summarized by analyzing the electrical principle of the anchor machine. After the on-site failure investigation, the cause of the failure is accurately located, so as to put forward a feasible plan for the use and daily maintenance of the ship anchor machine. Because of its simple structure, stable operation and easy maintenance, the anchor machine is used for anchoring and maintenance of ships. Port docking is very important for ship safety and is widely used on ships.
Study on Rheological Properties of Nanofluids
Authors: Bian Yan-qing , Wu Pu-cheng , Hao Jing , Shi Quan , Qin Guo-wei
Published: December 2021

Based on the previous research on the rheological properties of nanofluids by many scholars at home and abroad, to solve the problem that the viscosity of conventional polymer water control agents is large and cannot meet the demand for increasing production capacity in the process of tight gas reservoir exploitation, this paper takes self-made nanofluids as the research object, tests the rheological properties of self-made nanofluids by rheological experiment, and systematically studies the effects of concentration, temperature and shear action on the viscosity of nanofluids, and the dynamic viscoelasticity and thixotropy of nanofluids were discussed. The results show that the rheological type of nanofluid belongs to power-law fluid, but it is related to the shear rate. The viscosity of nanofluids increases with the increase of concentration; when the temperature increases, the viscosity of nanofluids decreases and the fluidity increases; under the shear action, the viscosity of nanofluid changes very little and has good shear resistance; the dynamic viscoelastic test shows that the storage modulus G´ of the nanofluid is larger than the loss modulus G”, showing elastic characteristics; the thixotropy test shows that when the shear rate is accelerated, the viscosity decreases with time, and when the shear rate is slowed down, the viscosity recovers rapidly with time, which has good thixotropy. The research results provide an important theoretical basis for further research on the application of nanomaterials in tight oil and gas reservoirs.
Deep learning classification and regression models for temperature values on a simulated fibre specklegram sensor
Authors: Arango J D , Aristizabal V H , Carrasquilla J F , Gomez J A , Quijano J C , Velez F J , Herrera-Ramirez J
Published: December 2021

Fiber optic specklegram sensors use the modal interference pattern (or specklegram) to determine the magnitude of a disturbance. The most used interrogation methods for these sensors have focused on point measurements of intensity or correlations between specklegrams, with limitations in sensitivity and useful measurement range. To investigate alternative methods of specklegram interrogation that improve the performance of the fiber specklegram sensors, we implemented and compared two deep learning models: a classification model and a regression model. To test and train the models, we use physical-optical models and simulations by the finite element method to create a database of specklegram images, covering the temperature range between 0 °C and 100 °C. With the prediction tests, we showed that both models can cover the entire proposed temperature range and achieve an accuracy of 99.5%, for the classification model, and a mean absolute error of 2.3 °C, in the regression model. We believe that these results show that the strategies implemented can improve the metrological capabilities of this type of sensor.
Box-Jenkins stochastic models for studying air pollutants in a Latin American megacity
Authors: Pinzón-Hassan A D , Tique-Ortiz V , Zafra-Mejía C A
Published: December 2021

The objective of this paper is to show the development of Box-Jenkins stochastic models to study the behavior of air pollutants concentrations in the megacity of Bogotá, Colombia. Information was collected from 10 stations in the city’s air quality monitoring network over a ten-year period. The temporal relationship between air pollutants, their spatial variation, and the occurrence of extreme pollution episodes was studied using Box-Jenkins models. The results showed that the moving average term of the models developed was the main indicator of spatial distribution for the daily pollutant concentrations. In the case of atmospheric particulate matter < 10 μm, the following spatial distribution was identified in the megacity: northwestern, center-southwest, and southeast. For atmospheric particulate matter < 2.5 μm: north, center, and southwest. For ozone: northwest, center, and south. Maximum hourly particulate matter concentrations were observed between 6-10 a.m., and between 11 a.m. - 4 p.m. for ozone. Monthly, the highest particulate matter concentrations were observed in February (14.1%), January (13.5%), and March (12.2%). In the context of atmospheric physics, this study was relevant for the following findings: The usefulness of Box-Jenkins models in simulating the temporal behavior of air pollutants, and for their adequate performance in detecting urban spatial trends.
Numerical simulation to evaluate the influence of geometric parameters on the physical behavior of heat exchangers
Authors: Rojas Suárez J P , Pabón León J A , Orjuela Abril M S
Published: December 2021

In the present investigation, a methodology was developed by means of numerical simulation for the evaluation of the influence of the geometric parameters of the heat exchangers used in thermoelectric generation devices. The validation of the proposed methodology was carried out through experimental tests on a diesel engine test bench under four load conditions (2 Nm, 4 Nm, 6 Nm, and 8 Nm) and a constant speed of 3600 rpm. The results obtained show that the methodology proposed by means of the numerical simulation presents a high concordance with the behavior described experimentally. The deviation between the simulation predictions and the experimental results was less than 4%. Additionally, it was evidenced that the change in the geometry of the heat exchanger has a considerable impact on the parameters of heat flow and surface temperature. It was shown that a 50% reduction in fin distance causes an increase of 2% and 2.4% in the previous parameters. Through geometric modifications, the electrical power generated increased by 7.9%. In general, the methodology developed through numerical simulation allows the analysis of the physical, thermal, and hydraulic phenomena present in heat exchangers focused on use in thermoelectric devices.
Representation of gas metal arc pulsed welding process behavior on bead geometry: a study of leading variables
Authors: Lázaro Plata J L , Sánchez Rincón C S
Published: December 2021

Gas metal arc welding is one of the most influential processes in the production and repair of structures and equipment; therefore, the need to improve the productivity and quality of welded joints has led to the development of techniques for good control of welding parameters. Also, the development of semi-automatic welding processes led to the control of one of the variables such as pulsed current; this technique is characterized by a lower heat input and lower energy expenditure, which directly influences the structural quality of the welded joint and the geometry of the weld bead. This work focused on evaluating the effects of various welding operating parameters using the central composite design tool based on the response surface methodology; next, the experimental development employed an inverter type power source for weld depositions, a commercial grade Stargold clean 96% Ar and 4% CO2 shielding gas at the rate of 15 L/min stationary arc, a 1.2 mm metal cored wire for welding deposit and a carbon steel base plate with a thickness of 6 mm. During the welding process, the torch was kept at a 90° inclination and a 16 mm stroke. To examine the adequacy of the empirical models and the significance of the regression coefficients, the variance analysis was employed. Consequently, the graphs were obtained through the determination of the model; from the statistical results obtained, it was shown that the above models were adequate to predict the weld width, bead height, and penetration within the range of variables studied. Furthermore, it was observed that the wire feed rate it has a very marked effect on weld bead geometry, followed by frequency pulse and peak current; finally, the effectiveness of employing these methodologies for the management of variables attributing to the execution of welding tasks with higher accuracy was demonstrated.
Determination of the physical-mechanical properties of a permeable block
Authors: Jaramillo H Y , Gómez-Camperos J A , Quintero-Quintero N
Published: December 2021

This study aims to analyze the influence of the incorporation of crushed polyethylene terephthalate as a substitute for fine aggregate in percentages of 10%, 15%, and 20% for the elaboration of concrete blocks. The methodology used is experimental quantitative approach, where the influence of the addition of crushed polyethylene terephthalate as a substitute for fine aggregate for the elaboration of concrete blocks was analyzed to identify the variation in the physical and mechanical properties of samples elaborated under different substitutions and in this way compare with the Colombian standard procedures. The results found in this study indicated that the blocks with the different percentages of polyethylene terephthalate presented a good resistance compared to the block without polyethylene terephthalate, which presented a resistance of 8 MPa. The blocks with polyethylene terephthalate at 10%, 15%, and 20% presented an average resistance of 6.36 MPa, 3.58 MPa, and 4.63 MPa, respectively. Finally, it was analyzed that the blocks with 10% aggregate are waterproof with normal density. In comparison, the blocks with 15% and 20% polyethylene terephthalate have high permeability, with the ability to drain 1 liter of water in 105 s and 38 s, respectively.
Design and first result of combined Langmuir-magnetic probe on J-TEXT tokamak
Authors: YANG Qinghu , CHEN Zhipeng , HAO Zhigang , ZHAO Yangming , XU Xin , LI Shuhao , YANG Jie , YAN Wei , JIANG Zhonghe , CHEN Zhongyong , WANG Nengchao , YANG Zhoujun , PAN Yuan , DING Yonghua
Published: December 2021

In order to measure boundary electrostatic and magnetic fluctuations simultaneously, a combined Langmuir-magnetic probe (CLMP) has been designed and built on joint-Texas experimental tokamak. The probe consists of 8 graphite probe pins and a 3D magnetic probe, driven by a mechanical pneumatic device. By means of simulation, the shielding effect of the graphite sleeve on the magnetic fluctuation signal is explored, and the influence of the eddy current was reduced by cutting the graphite sleeve. In the experiment, it has been verified that the mutual inductance of electromagnetic signals can be ignored, and a 70–90 kHz electromagnetic mode is observed around the last closed magnetic surface. The establishment of CLMP provides data for the exploration of the coupling of electrostatic and magnetic fluctuations.
Quantitative analysis of electrically active defects in Au/AlGaN/GaN HEMTs structure using capacitance–frequency and DLTS measurements
Authors: Bano Nargis , Hussain Ijaz , Al-Ghamdi Eman A. , Ahmad M. Saeed
Published: December 2021

Electrical trap states in the AlGaN-based high-electron-mobility transistor (HEMT) structures limit the performances of devices. In this study, we present a comprehensive study of the electrical trap states in AlGaN/GaN HEMT structures and examine their influence on the device performance. We performed capacitance–frequency and conductance–frequency measurements to determine the time constant and the density of the interface states. The density of the interface states was calculated to be 2 × 1010 cm−2 eV−1, and the time constant of the interface states was 1 μs. Deep-level transient spectroscopy showed the presence of one electron trap E1 (negative peak) and three hole-like traps P1, P2, and P3 (positive peaks). The thermal activation energies for E1, P1, P2, and P3 traps were calculated to be 1.19, 0.64, 0.95, and 1.32 eV, respectively. The electron trap E1 and the hole-like traps P1, P2 and P3 were observed to originate from the point defects or their complexes in the material. The hole-like traps reflected the changes created in the population of the surface states owing to the capture of the surface states; these traps originated from the point defects related to the nitrogen vacancy.
Some new multi-cell Ramsey theoretic results
Authors: Bergelson Vitaly , Hindman Neil
Published: December 2021

We extend an old Ramsey Theoretic result which guarantees sums of terms from all partition regular linear systems in one cell of a partition of the set

N

\mathbb {N}

of positive integers. We were motivated by a quite recent result which guarantees a sequence in one set with all of its sums two or more at a time in the complement of that set. A simple instance of our new results is the following. Let

P

f

(

N

)

\mathcal {P}_{f}(\mathbb {N})

be the set of finite nonempty subsets of

N

\mathbb {N}

. Given any finite partition

R

{\mathcal R}

of

N

\mathbb {N}

, there exist

B
1

B_1

,

B
2

B_2

,

A

1
,
2

A_{1,2}

, and

A

2
,
1

A_{2,1}

in

R

{\mathcal R}

and sequences

⟨

x

1
,
n

⟩

n
=
1

∞

\langle x_{1,n}\rangle _{n=1}^\infty

and

⟨

x

2
,
n

⟩

n
=
1

∞

\langle x_{2,n}\rangle _{n=1}^\infty

in

N

\mathbb {N}

such that (1) for each

F
∈

P

f

(

N

)

F\in \mathcal {P}_{f}(\mathbb {N})

,

∑

t
∈
F

x

1
,
t

∈

B
1

\sum _{t\in F}x_{1,t}\in B_1

and

∑

t
∈
F

x

2
,
t

∈

B
2

\sum _{t\in F}x_{2,t}\in B_2

and (2) whenever

F
,
G
∈

P

f

(

N

)

F,G\in \mathcal {P}_{f}(\mathbb {N})

and

max
F
>
min
G

\max F > \min G

, one has

∑

t
∈
F

x

1
,
t

+

∑

t
∈
G

x

2
,
t

∈

A

1
,
2

\sum _{t\in F}x_{1,t}+\sum _{t\in G}x_{2,t}\in A_{1,2}

and

∑

t
∈
F

x

2
,
t

+

∑

t
∈
G

x

1
,
t

∈

A

2
,
1

\sum _{t\in F}x_{2,t}+\sum _{t\in G}x_{1,t}\in A_{2,1}

. The partition

R

{\mathcal R}

can be refined so that the cells

B
1

B_1

,

B
2

B_2

,

A

1
,
2

A_{1,2}

, and

A

2
,
1

A_{2,1}

must be pairwise disjoint.
Spanning the isogeny class of a power of an elliptic curve
Authors: Kirschmer Markus , Narbonne Fabien , Ritzenthaler Christophe , Robert Damien
Published: December 2021

Let

E
E

be an ordinary elliptic curve over a finite field and

g
g

be a positive integer. Under some technical assumptions, we give an algorithm to span the isomorphism classes of principally polarized abelian varieties in the isogeny class of

E
g

E^g

. The varieties are first described as hermitian lattices over (not necessarily maximal) quadratic orders and then geometrically in terms of their algebraic theta null point. We also show how to algebraically compute Siegel modular forms of even weight given as polynomials in the theta constants by a careful choice of an affine lift of the theta null point. We then use these results to give an algebraic computation of Serre’s obstruction for principally polarized abelian threefolds isogenous to

E
3

E^3

and of the Igusa modular form in dimension

4
4

. We illustrate our algorithms with examples of curves with many rational points over finite fields.
5. The plot thickens…and thins
Authors: Kahn Andrew
Published: December 2021

‘The plot thickens…and thins’ describes the changing status of plot in the genre. For much of the 19th century, anecdote and incident inspired short fiction written for a mass market. The incident or anecdote-based short story made a virtue of brevity, and the economy of style and consequential arrangement of causes and effects well suited slice-of-life episodes, whodunits, and ghost stories. What these modes all share is a skill in building up suspense. Yet the genre has been enjoying a long postmodernist reincarnation in which it has adopted almost the opposite approach. Losing the plot has been a source of fictional experimentation and liberation from linearity. Repetition with subtle variation has become a key structure.
1. Beginnings
Authors: Pierrehumbert Raymond T.
Published: December 2021

‘Beginnings’ discusses the general processes that form planetary systems, particularly the Solar System. Most of the Universe is made of a mysterious substance called ‘dark matter’, and an even more mysterious substance called ‘dark energy’. After the birth of the Universe in the Big Bang, the tiny bits of stardust which have accumulated contain the heavier elements (baryonic matter) that make it possible to form beings like ourselves, and the planets on which we live. We mustn't forget the importance of the formation of protostars, as well as gas and ice giant planets, the evolution of the proto-Sun, and the formation of inner rocky planets.
7. How it all ends
Authors: Pierrehumbert Raymond T.
Published: December 2021

‘How it all ends’ reflects on the different ways that the Solar System can end. Some six billion years from now, if anybody is left standing on Earth to witness it, they will see the Sun begin to go through some alarming transformations. Earth will cross the runaway greenhouse threshold in about a half billion years, whereafter the oceans will evaporate away, the surface will be heated to sterilizing temperatures, and water will break up and be irretrievably lost to space. Meanwhile, planets around low mass M stars will not suffer a crisis by fire because such stars evolve very slowly. Such planets end their lives in ice instead.
Justification and being in a position to know
Authors: Waxman Daniel
Published: December 2021

According to an influential recent view, S is propositionally justified in believing p iff S is in no position to know that S is in no position to know p. I argue that this view faces compelling counterexamples.