bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling inductive radio frequency coupling in powerful negative hydrogen ion sources: validating a self-consistent fluid model
Authors: Zielke D , Briefi S , Lishev S , Fantz U 
Published: February 2022

Abstract
Radio frequency (RF) negative hydrogen ion sources utilized in fusion and for accelerators use inductively coupled plasmas, which are operated at a low driving frequency, high power densities and gas pressures in the order of 1 MHz, 10 W cm−3 and 1 Pa, respectively. In this work a numerical fluid model is developed for a self-consistent description of the RF power coupling in these discharges. After validating the RF power coupling mechanism, such a model is a valuable tool for the optimization of RF power coupling and hence can help to increase the efficiency and reliability of RF ion sources. The model validation is achieved using measurements from the ITER RF prototype ion source. Steady state numerical solutions are obtained for the first time, where all modeled trends fit well. Remaining systematic quantitative differences could be caused by 3D effects such as highly non-uniform magnetic fields that cannot be captured in the current model formulation, which is 2D cylindrically symmetric. The coupling between the RF fields and the electrons is realized in the electron momentum transport equation, where approximations consistent with the operating regime of RF ion sources are applied. Here large magnetic RF fields lead to a plasma compression by the nonlinear RF Lorentz force. Using a local approximation for the electron viscosity, it is found that increased diffusion of the RF current density mitigates the compression. Navier–Stokes equations for the neutral atoms and molecules are used to capture neutral depletion. In this way it is shown that at high powers neutral depletion has a large impact on the power coupling via the viscosity of the electrons. The application of the self-consistent model for optimization of the RF power coupling will be described in a forthcoming paper.
The prolonged decay of RKKY interactions by interplay of relativistic and non-relativistic electrons in semi-Dirac semimetals
Authors: Duan Hou-Jian , Wu Yong-Jia , Yang Yan-Yan , Zheng Shi-Han , Zhu Chang-Yong , Deng Ming-Xun , Yang Mou , Wang Rui-Qiang 
Published: February 2022

Abstract
The Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction has been extensively explored in isotropic Dirac systems with linear dispersion, which typically follows an exponent decaying rate with the impurity distance R, i.e., J ∝ 1/R

d
(1/R
2d−1) in d-dimensional systems at finite (zero) Fermi energy. This fast decay makes it rather difficult to be detected and limits its application in spintronics. Here, we theoretically investigate the influence of anisotropic dispersion on the RKKY interaction, and find that the introduction of non-relativistic dispersion in semi-Dirac semimetals (S-DSMs) can significantly prolong the decay of the RKKY interaction and can remarkably enhance the Dzyaloshinskii–Moriya interaction around the relativistic direction. The underlying physics is attributed to the highly increased density of states in the linear-momentum direction as a result of the interplay of relativistic and non-relativistic electrons. Furthermore, we propose a general formula to determine the decaying rate of the RKKY interaction, extending the typical formula for isotropic DSMs. Our results suggest that the S-DSM materials are a powerful platform to detect and control the magnetic exchange interaction, superior to extensively adopted isotropic Dirac systems.
What can CMB observations tell us about the neutrino distribution function?
Authors: Alvey James , Escudero Miguel , Sabti Nashwan 
Published: February 2022

Abstract
Cosmic Microwave Background (CMB) observations have been used extensively to constrain key properties of neutrinos, such as their mass. However, these inferences are typically dependent on assumptions about the cosmological model, and in particular upon the distribution function of neutrinos in the early Universe. In this paper, we aim to assess the full extent to which CMB experiments are sensitive to the shape of the neutrino distribution. We demonstrate that Planck and CMB-S4-like experiments have no prospects for detecting particular features in the distribution function. Consequently, we take a general approach and marginalise completely over the form of the neutrino distribution to derive constraints on the relativistic and non-relativistic neutrino energy densities, characterised by N
eff = 3.0 ± 0.4 and ρν,0
NR < 14 eV cm-3 at 95% CL, respectively. The fact that these are the only neutrino properties that CMB data can constrain has important implications for neutrino mass limits from cosmology. Specifically, in contrast to the ΛCDM case where CMB and BAO data tightly constrain the sum of neutrinos masses to be ∑m
ν < 0.12 eV, we explicitly show that neutrino masses as large as ∑ m
ν∼ 3 eV are perfectly consistent with this data. Importantly, for this to be the case, the neutrino number density should be suitably small such that the bound on ρν,0
NR = ∑ m
ν
n
ν,0 is still satisfied. We conclude by giving an outlook on the opportunities that may arise from other complementary experimental probes, such as galaxy surveys, neutrino mass experiments and facilities designed to directly detect the cosmic neutrino background. GitHub: Parameter files for MCMC analysis and code to reproduce all plots can be found here.
Regulation of optical properties by applied external fields for a quantum well with Hulthen potential
Authors: Turkoglu Aslan 
Published: February 2022

Abstract
In this present study, the effects of electric, magnetic, and non-resonant intense laser field (ILF) on the linear, third-order nonlinear, and total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) of GaAs quantum well, having Hulthen confinement potential, were theoretically investigated. In addition, the dependence of the nonlinear optical properties in the structure on the optical intensity of incident photon and the inverse relaxation time was also calculated. To do this research, firstly the energy eigenvalues and eigenfunctions of the structure were calculated by using the effective mass and envelope function approaches. By using these calculated subband energy levels and wave functions belonging to these levels, the nonlinear optical properties of the system were obtained via the iterative method, within the compact density matrix approach framework. The obtained numerical results show that the optical properties of the considered system depend on the externally applied fields. With the applied external electric and magnetic field, the peak positions of TOACs and RRICs shift to higher energies, and the peak magnitudes increase. The high-frequency ILF applied to the structure shifts the peak positions of TOACs and RRICs initially towards higher energies and then towards lower energies and their peak sizes increase. These results show that the optical properties of the system can be adjusted purposively by changing the magnitude of applied external fields.
Surface oxygen versus native oxide on tungsten: contrasting effects on deuterium retention and release
Authors: Dunand A. , Minissale M. , Faure J.-B. , Gallais L. , Angot T. , Bisson R. 
Published: February 2022

Abstract
We performed a direct comparison of deuterium retention and release from tungsten in presence or in absence of oxygen impurities. A single crystal of W(110) was used to prepare tungsten with four different surface states: with its native oxide, atomically clean, covered with half a monolayer of oxygen atoms, and covered with three fourths of a monolayer of oxygen atoms. For a D ion fluence of 3 × 1021 D+ m−2 implanted at 300 K, deuterium retention was highest with the native oxide, lowest with three fourths of a monolayer of oxygen atoms at the surface and intermediate for the clean surface. This counterintuitive result is explained by a different localization of deuterium retention in these samples. For tungsten with its native oxide, deuterium retention occurs solely in the bulk, i.e. below the first atomic plane of the surface. For clean tungsten, deuterium retention occurs in part at the surface and sputtering should play a role. For tungsten with a sub-monolayer surface coverage of oxygen atoms, a transition from surface to bulk retention is observed above half a monolayer of adsorbed oxygen. Striking differences in desorption peak(s) temperature(s) are observed between D ion-implanted samples and D2 molecules-exposed samples. These results highlight the importance of the (near-) surface localization of oxygen and deuterium on the temperature dependence of deuterium desorption rate i.e. on the fusion fuel recycling coefficient.
A noniterative solution to the inverse Ising problem using a convex upper bound on the partition function
Authors: Sano Takashi 
Published: February 2022

Abstract
The inverse Ising problem, or the learning of Ising models, is notoriously difficult, as evaluating the partition function has a large computational cost. To quickly solve this problem, inverse formulas using approximation methods such as the Bethe approximation have been developed. In this paper, we employ the tree-reweighted (TRW) approximation to construct a new inverse formula. An advantage of using the TRW approximation is that it provides a rigorous upper bound on the partition function, allowing us to optimize a lower bound for the learning objective function. We show that the moment-matching and self-consistency conditions can be solved analytically, and we obtain an analytic form of the approximate interaction matrix as a function of the given data statistics. Using this solution, we can compute the interaction matrix that is optimal to the approximate objective function without iterative computation. To evaluate the accuracy of the derived learning formula, we compared our formula to those obtained by other approximations. From our experiments on reconstructing interaction matrices, we found that the proposed formula gives the best estimates in models with strongly attractive interactions on various graphs.
Approximate-analytical solutions of the quadratic Logistic differential model via SAM
Authors: Edeki S.O. , Fadugba S.E. , Udjor V.O. , Ogundile O.P. , Dosunmu D.A. , Ugbenu O. , Akindele N. , Zelibe S.C. , Kehinde T.O. , Jonah B.A. 
Published: February 2022

Abstract
This paper applies the novel Successive Approximation Method (SAM) for the solution of the quadratic Logistic Differential Model (LDM). To confirm the reliability of the method, illustrative examples are considered, and it is remarked that the approximate-analytical solutions of the considered cases are computed with ease. The proposed technique is used directly, without transformation, discretization, linearization, or any restrictive assumptions.
Analysis of Exponential–Polynomial Single Step Method for Singularly Perturbed Delay Differential Equations
Authors: Fadugba S. E , Vinci Shaalini J. , Ogunmiloro O.M. , Okunlola J.T. , Oyelami F.H. 
Published: February 2022

Abstract
This research presents Exponential – Polynomial Single Step Method (EPSSM), which uses non-linear polynomial interpolating function to solve Singularly Perturbed Delay Differential Equations (SPPDDEs). The stability polynomial of the method is obtained. The Local Grid Search Algorithm termed LGSA is applied in determining the stability region. The efficiency of these methods is compared with the other two numerical methods, namely Runge-Kutta Method (RKM) and Rational Single Step Method (RSM) through two examples of Singularly Perturbed Delay Differential Equations (SPPDDEs).
Homotopy Analysis Method for Fractional Barrier Option PDE
Authors: Fadugba S. E , Edeki S. O. 
Published: February 2022

Abstract
This paper proposes a fractional numerical study on Time-Fractional Barrier Option Model (T-FBOM) via highly convergence solution series method known as Homotopy Analysis Method (HAM). Furthermore, the pricing formula for T-FBOM was obtained. The performance of the method on some illustrative examples has been considered. The results obtained were compared with some existing approaches.
Structural and electronic properties of silver-adsorbed silicene nanoribbons: A first-principles study
Authors: Nguyen Thanh Tung 
Published: February 2022

Abstract
The geometrical and electrical features of Ag adsorption armchair silicene nanoribbons structure have been investigated using first-principles calculations. The findings reveal that the bandgap of doped Ag has changed, as it does for chemical adsorption on the surface of ASiNRs; this material became metallic at the valance band contact fermi level, with a mean bandgap of 0 eV. Furthermore, the survey to discover the best height 6.39 of Ag and 2.26 bond length Si-Si and Si-Si-Si bond angle 115015’ with structural stability near to the pristine situation has shown promising results for developing novel spintronic and optoelectronic materials in the future.
Application of microcontroller and Blynk for cultured cordyceps
Authors: Nguyen Thanh Tung 
Published: February 2022

Abstract
Cordyceps is a precious herb in the world; it was discovered in the Tibetan Plateau of China. It has many good uses for human health as used to replenish the kidney and soothe the lung for the treatment of fatigue, night sweating, homosexualities, hyperglycemia, hyperlipidemia, asthenia after severe illness, respiratory disease, renal dysfunction and renal failure, arrhythmias, and other heart diseases, and liver disease. Due to the production of natural cordyceps exploited each year is increasingly scarce and depleted in recent times. Therefore currently, the cultivation of this herb has been applied to meet the higher demand of the market. Using microcontrollers to monitor and manage environmental parameters such as light, temperature and humidity, and soil moisture, we have produced medicinal substances from cordyceps of similar high quality as natural products.
Research, Design and Manufacturing of a Prototype Tidal Generator
Authors: Phu Huynh Minh , Nguyen Thanh Tung 
Published: February 2022

Abstract
This paper talks about the research, design, and manufacturing of a tidal power generator prototype. This model is built to take advantage of tidal changes in the Southwest region of Vietnam. Here, the Mekong River has a tidal regime with high water and low water level every day. The difference in potential energy between the high tide and the low tide is utilized to generate the kinetic energy of the blades of the tidal generator turbine. The generated electricity will be stored in a lithium battery, combined with a system that transmits information to the phone via Bluetooth.
Design of a Passive Radar based on RTL-SDR technology with coherent dual channel
Authors: Mediavilla Juan Romero , Espinoza Cristian Arias , Espinosa Alex Pachacama , Salazar Franklin 
Published: February 2022

Abstract
In this research, a passive radar aimed at the detection of unmanned aerial vehicles was developed. As a UAV navigates at low altitudes and high speeds, RTL-SDR modules are used that with the help of two antennas, one directional and one reference, the position of the object is detected through bounce and signal discrimination, for which several tests were carried out in based on frequencies that are in the FM range. For this, GNU radio is used and data processing with Python in the Anaconda guide that facilitates obtaining data visually through a video of the frequency of the Doppler effect vs the distance in kilometers. Also, mention is made of the synchronization arrangement that is established between the RTL-SDR modules based on their oscillator.
A Note on Analytical Roots of the Navier-Stokes Equation
Authors: Akinlabi G. O. , Edeki S. O. , Braimah J.A. 
Published: February 2022

AbstractA new approach called the Generalised Picard Iteration Sch eme (GPIS) is used to solve the Navier-Stokes equations in this paper. The solutions are organized in a series with components that are readily computed. Because it delivers the exact solution to the solved issue with minimal computing effort while retaining a high degree of accuracy, this method appears to be extremely adaptable, efficient, effective, and dependable. It is not necessary to identify Lagrange multipliers. As a result, the presented method is recommended for dealing with higher-order linear and non-linear models.
Al doping in germanene nanoribbons in the presence of an external electric field
Authors: Ngoc Hoang Van 
Published: February 2022

Abstract
Germanene by description, is a two-dimensional material with many different properties from graphene. Germanene also has a honeycomb hexagonal form but it is not a planar structure. Germanene nanoribbons (GNRs) are created from germanene with edges that have been changed by other atoms; in this study, two of the GNRs’ edges have been modified by hydrogen. The density of states (DOS), energy formation, and band structure of the system are computed, displayed, and studied using density functional theory (DFT). Due to the presence of hydrogen at the two edges, GNRs have a narrow band gap. This research will look into Al doping in GNRs with the system being immersed in a 0.5V/Angstrom external electric field. Two configurations are examined in this section: the top configuration and the valley configuration. The doped configurations do not break up in the electric field, and both configurations become semi-metals with bands crossing the Fermi level. This research lays the groundwork for future applications in nanochip technology
Application of solar energy and microcontroller for automanagement of road train tracks crossing barriers
Authors: Nguyen Thanh Tung , Azizah  
Published: February 2022

Abstract
Traffic safety is a legitimate and vital necessity in the current life of everyone in the world. For developed countries, the transport infrastructure system is basically invested, the traffic law is also stable due to the process of testing and applying for a long time. For developing countries, by studying the Vietnam database, we assess that the reality of road traffic in general and railways, in particular, is still quite inadequate. Although the Government has actively applied many measures, people are still insecure when traveling on the road because there are still many unfortunate accidents every day. In particular, there are many places where people open new roads to cross the tracks, causing traffic jams and affecting people’s lives and properties. In this project, we use solar panels to power the microcontroller circuit to work. They have the function of alarming, closing, and opening barriers when trains pass by to reduce loss of life and property from accidents, combined with the use of solar energy to make installation easier in mountainous areas, on the other hand, contribute to environmental protection in the future.
On Non-Linear Non-Gaussian Autoregressive Model with Application to Daily Exchange Rate
Authors: Adedotun A. F. , Olatayo T. O. , Odekina G. O. 
Published: February 2022

Abstract
The most often used distribution in statistical modeling follows Gaussian distribution. But many real-life time series data do not follow normal distribution and assumptions; therefore, inference from such a model could be misleading. Thus, a reparameterized non-Gaussian Autoregressive (NGAR) model that has the capabilities of handling non-Gaussian time series was proposed, while Anderson Darling statistics was used to identify the distribution embedded in the time series. In order to determine the performance of the proposed model, the Nigerian monthly exchange rate (Dollar-Naira Selling Rate) was analyzed using proposed and classical autoregressive models. The proposed model was used to determine the joint distribution of the observed series by separating the marginal distribution from the serial dependence. The maximum Likelihood (MLE) estimation method was used to obtain an optimal solution in estimating the generalized gamma distribution of the proposed model. The selection criteria used in this study were Akaike Information Criterion (AIC). The result revealed through the value of the Anderson Darling statistics that the data set were not normally distributed. The best model was selected using the minimum values of AIC value. The study concluded that the proposed model clearly shows that the non-Gaussian Autoregressive model is a very good alternative for analyzing time series data that deviate from the assumptions of normality and, in particular, for the estimation of its parameters.
Stability Analysis of a Nontrivial Solution for Delayed Nicholson Blowflies’ Model with Linear Harvesting Function
Authors: Ezekiel I D , Iyase S A , Anake T A 
Published: February 2022

Abstract
The study investigates stability analysis of Nicholson-blowflies’ equation with a linear harvesting function, where sufficient conditions are obtained for nontrivial equilibrium of a delayed model using the corresponding characteristic equation and Hopf bifurcation analysis. The Hopf bifurcation is studied for the qualitative character of the dynamical system, and conditions for the existence of periodic oscillation are identified. The periodic orbit of the model is equally investigated, from which further chaotic results are obtained using numerical example via MATLAB software. The study supplements theoretical improvement to earlier results obtained in the literature.
Design of Pointing Control Mechanism for Spacecraft Antenna Communication
Authors: Li Qiuyuan , Wang Shuquan , Zhang Long 
Published: February 2022

Abstract
Satellite antennas are widely used in satellite communications and now have become an indispensable part of satellite. It affects and restricts the performance and functions of the entire wireless communication system. Flexible pointing and low power consumption are required for antennas installed on satellites, which makes the design of the pointing mechanism of the satellite antenna more challenging. This paper focuses on the design and analysis of the pointing control mechanism to help improve the flexibility of satellite communication. An optimized structure consisting of spring hinge mechanism, manipulator arm and universal adjustment mechanism is proposed. The material selection and mechanical analysis are also made. Finally, the pointing angle is described based on the mathematical model of the pointing control mechanism.
Development of an Underwater Detection Robot
Authors: Wang Ruilin , Li Zhiqing , Ma Shugen , An Xiaosong 
Published: February 2022

Abstract
The ocean contains huge valuable resources, due to the huge pressure in the deep water and the danger of diving, human development is very little. In this paper, we design a small underwater observation robot, which can replace human beings to dive into deep water, detect the deepwater area and sample the water quality. Following the principle of fish diving, the robot uses the piston bucket to pump water and drain water to change its gravity to achieve floating and diving. The main propeller at the tail provides the main driving force. The robot turns by propellers on both sides working at different speeds and propellers can change the thrust direction to provide assist force in the process of diving and floating. The structure design of the tumbler(the design of anti-roll) ensures the anti-interference ability of the robot to the wind and wave. In addition, the robot can be equipped with cameras, depth sensors, temperature and humidity sensors, and other sensors to achieve efficient underwater data sampling. The depth sensor, propeller, and pumping piston are used to control the hovering depth of the robot. The ROV can record good quality of video if provided with proper video graphic tool. The design of ROV which we have conceptualize, is handy and can be powered by 24V DC power which can be easily available at remote location. The experimental results verify the structural reliability of the underwater detection robot and provide a new mobile mechanism platform and a new idea for deep-sea exploration and scientific research.