bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoparticle-induced control (MWCNTs–TiO2) on grain size and tensile strength response and multi-response optimization on TIG welded joints
Authors: Muzamil Muhammad , Wu Jianjun , Akhtar Maaz , Azher Kashif , Majeed Arfan , Zhang Zengkun , Shazad Atif
Published: April 2022

This study discusses the effectual variable parameters of multi-walled carbon nanotubes and titanium oxide (MWCNT–TiO2) contents and welding current in obtaining a response on mechanical behavior. The experimental work involved three levels of both parameters, which included 1, 1.5, and 2 wt.% of MWCNTs–TiO2 and 160, 180, and 200 A of current by forming a full design that represented a 32 (3 k) factorial model. The results of an analysis of variance (ANOVA) were critically employed to assess the variation between the variables and within their levels for approaching the significant combination of parameters. The joints welded with MWCNT–TiO2-coated fillers tendered a significant reduction in grain size (GS) along with high values of tensile strength (TS). From the ANOVA, it was determined that both the investigated parameters and their combined effect created a significant response for GS reduction and increment in TS. The presented empirical regression quadratic model was validated for the adequacy of the projected results that were shown to be acceptable with the experimental investigated data. In addition, the desirability function approach was applied for a multiple response optimization in yielding the desired responses of GS and TS and simultaneously providing an optimized set of process parameters. Thus, the function declared 1.5 wt.% MWCNT–TiO2 and 180 A as the optimized process set for delivering the maximum TS at the designated range of GS for this system.
Limits on primordial black holes detectability with Isatis: a BlackHawk tool
Authors: Auffinger Jérémy
Published: April 2022

Primordial black holes (PBHs) are convenient candidates to explain the elusive dark matter (DM). However, years of constraints from various astronomical observations have constrained their abundance over a wide range of masses, leaving only a narrow window open at $$10^{17}\,\mathrm{g} \lesssim M \lesssim 10^{22}\,$$

10
17

g
≲
M
≲

10
22

g for all DM in the form of PBHs. We reexamine this disputed window with a critical eye, interrogating the general hypotheses underlying the direct photon constraints. We review 4 levels of assumptions: (i) instrument characteristics, (ii) prediction of the (extra)galactic photon flux, (iii) statistical method of signal-to-data comparison and (iv) computation of the Hawking radiation rate. Thanks to , a new tool designed for the public Hawking radiation code , we first revisit the existing and prospective constraints on the PBH abundance and investigate the impact of assumptions (i)–(iv). We show that the constraints can vary by several orders of magnitude, advocating the necessity of a reduction of the theoretical sources of uncertainties. Second, we consider an “ideal” instrument and we demonstrate that the PBH DM scenario can only be constrained by the direct photon Hawking radiation phenomenon below $$M_{\mathrm{max}} \sim 10^{20}\,$$

M
max

∼

10
20

g. The upper part of the mass window should therefore be closed by other means.
Gravitational field of slightly deformed naked singularities
Authors: Toktarbay Saken , Quevedo Hernando , Abishev Medeu , Muratkhan Aray
Published: April 2022

We derive a particular approximate solution of Einstein equations, describing the gravitational field of a mass distribution that slightly deviates from spherical symmetry. The deviation is described by means of a quadrupole parameter that is responsible for the appearance of a curvature singularity, which is not covered by a horizon. We investigate the motion of test particles in the gravitational field of this naked singularity and show that the quadrupole parameter affects the properties of Schwarzschild trajectories. By investigating radial geodesics, we find that no effects of repulsive gravity are present. We interpreted this result as indicating that repulsive gravity is non-linear effect.
Complexity growth in Gubser–Rocha models with momentum relaxation
Authors: Babaei-Aghbolagh H. , Yekta Davood Mahdavian , Velni Komeil Babaei , Mohammadzadeh H.
Published: April 2022

The Einstein–Maxwell–Axion–Dilaton (EMAD) theories, based on the Gubser–Rocha (GR) model, are very interesting in holographic calculations of strongly correlated systems in condensed matter physics. Due to the presence of spatially dependent massless axionic scalar fields, the momentum is relaxed, and we have no translational invariance at finite charge density. It would be of interest to study some aspects of quantum information theory for such systems in the context of AdS/CFT where EMAD theory is a holographic dual theory. For instance, in this paper we investigate the complexity and its time dependence for charged AdS black holes of EMAD theories in diverse dimensions via the complexity equals action (CA) conjecture. We will show that the growth rate of the holographic complexity violates Lloyd’s bound at finite times. However, as shown at late times, it depends on the strength of the momentum relaxation and saturates the bound for these black holes.
THE SPEED AND QUALITY OF CHINA’S ECONOMIC GROWTH DURING THE COVID-19 PANDEMIC
Authors: ZHAO LINHAI , LIN KAO-JEN
Published: April 2022

The purpose of this study is to understand the speed and quality of China’s economic growth during the COVID-19 pandemic. This study defines high-quality economic growth as a growth rate with a low variance and adopts quarterly time-series data for China’s real GDP growth rate to analyze its regime switches and structural changes by estimating a conditional Markov chain model. The study further utilizes the estimated parameters to predict the smoothed probabilities of each of four joint states for China’s real GDP growth rate from 2021 Q4 to 2025 Q3. The primary finding of this study is that, during the period from 2020 Q1 to 2021 Q3, the outbreak of COVID-19 shocked China’s economy and its economic growth rate fluctuated dramatically, which resulted in its variance being relatively high. However, China’s economic growth rate is very likely to gradually stabilize (as evidenced by a low variance) and to grow at a medium-to-high speed with high quality during the forecast period.
A FREQUENCY-DOMAIN ANALYSIS OF MEDIUM-SCALE DSGE MODELS
Authors: WU JINSHUN , MAITI TAPS
Published: April 2022

This paper employs the local Bayesian likelihood methodology to estimate a medium-scale dynamic stochastic general equilibrium (DSGE) model on different frequencies and uses frequency-domain tools to evaluate the time-varying parameter model and the fixed-parameter model. These techniques yield fresh insights into theoretical and empirical implications conveyed by alternative models beyond what conventional time-domain approaches can offer. We show that parameter estimates are sensitive to frequencies, and goodness-of-fit varies substantially with the frequency bands. Overall, the estimated time-varying parameter model captures the properties of the U.S. data better in the business cycle frequency band, and beyond this band, the fixed-parameter model performs better. Additionally, our study also reveals the importance of structural shocks in improving the fit between models and data. Finally, we utilize the spectral representation of generalized forecast error variance decomposition to investigate the frequency dynamics of volatility connectedness. We find shocks to economic activity have an impact on variables at different frequencies with different strengths, and markets become more connected during crisis periods. Furthermore, this study provides insights into a question policymakers are much concerned with: which shocks are major sources of economic volatilities and which sectors serve as major recipients of shocks?
A fast difference scheme on a graded mesh for time-fractional and space distributed-order diffusion equation with nonsmooth data
Authors: Fardi Mojtaba , Khan Yasir
Published: April 2022

The time-fractional and space distributed-order diffusion equation with a singularity at the initial time is investigated in this paper. For the solution of this equation, we propose a new difference scheme on a graded mesh. The theoretical underpinning for the suggested procedure is presented, which includes the stability and convergence of the difference scheme. Furthermore, the difference strategy proves to be unconditionally stable in this research. Additionally, we demonstrate that the difference technique is convergent and that the temporal convergence rate is faster than when a uniform mesh uses. Finally, a test example is provided to ensure that the theoretical analysis is accurate.
Infinite conservation laws and new solutions of (3+1)-dimensional generalized Konopelchenko–Dubrovsky–Kaup–Kupershmidt equation
Authors: Zhang Shi-Jie , Bao Taogetusang
Published: April 2022

In this paper, a (3+1)-dimensional generalized Konopelchenko–Dubrovsky–Kaup–Kupershmidt equation (gKDKK) is investigated. Based on Bell polynomial theory, the bilinear form, Bilinear Bäcklund transformation, Lax pair and infinite conservation laws of the equation are obtained. Lump solution and half periodic kink solution are obtained by combining the test function with bilinear form. Furthermore, with the help of the variable separation method, we obtain some new compound solutions composed of exponential function, trigonometric function, hyperbolic function, rational function and Jacobi elliptic function in various forms. Using computer software to draw the three-dimensional diagram and profile of the solutions, the dynamic properties of the solutions are analyzed.
Failure of the finitely generated intersection property for ascending HNN extensions of free groups
Authors: Bamberger Jacob , Wise Daniel T.
Published: April 2022

The main result in this paper is the failure of the finitely generated intersection property (FGIP) of ascending HNN extensions of non-cyclic finite rank free groups. This class of groups consists of free-by-cyclic groups and properly ascending HNN extensions of free groups. We also give a sufficient condition for the failure of the FGIP in the context of relative hyperbolicity, we apply this to free-by-cyclic groups of exponential growth.
Shadow and massless particles around regular Bardeen black holes in 4D Einstein Gauss–Bonnet gravity
Authors: Rayimbaev Javlon , Bardiev Dilshodbek , Mirzaev Temurbek , Abdujabbarov Ahmadjon , Khalmirzaev Akram
Published: April 2022

In this paper, we study dynamics of massless (photon and neutrino-like) particles in the spacetime of regular Bardeen black hole (BH) in novel four-dimensional Einstein–Gauss–Bonnet (4D EGB) theory. First, we have analyzed the hor properties of the spacetime of the Bardeen BH with respect to the Gauss–Bonnet (GB) coupling parameter [Formula: see text]. Our detailed analysis has shown that the GB coupling parameter is limited by maximum and minimum values at, [Formula: see text] and the extreme value of magnetic charge of the BH depends on the parameter [Formula: see text]. We have explored motion of neutrino-like particles and photons around the Bardeen BH. We have also explored the possibility of mimicking cases of the spin of Kerr BH and charge of Reissner–Nordström BH by the Bardeen charge, providing the same values of impact parameter for photons corresponding to the BH shadow size. Finally, we have investigated spherically infalling accretion and shadow of the Bardeen BHs in 4D EGB theory.
Off-Line Hybrid Simulation Method on Train–Track–Bridge Coupling Vibration in High-Speed Railway
Authors: Guo Wei , Long Yan , He Chang , Wang Yang , Zeng Yongping , Song Jianping
Published: April 2022

The technology of real-time hybrid simulation (RTHS), which is one of the methods to test the performance of train operation on bridge in recent years, has strict real-time requirements. Combined with the fixed-point iteration (FPI) algorithm, this paper developed an off-line iterative hybrid simulation (OIHS) method, avoiding real-time synchronization between numerical and physical parts in RTHS to reproduce train–track–bridge coupling-vibration (TTBV) of high-speed railway in laboratory. In OIHS, the physical train model was installed on the shake table, while the response of the numerical track–bridge structure was simulated. To improve the test reproduction accuracy of the TTBV in high-speed railway, based on the shake table inherent off-line iterative control which is reproduce the commands issued to the shake table, an outer loop off-line iterative controller was designed to form a double-layer off-line iterative control framework to correct the response error between the subsystems. Compared with traditional finite element analysis, the accuracy and efficiency of the OIHS method were validated by numerical simulation and shake table test. The results demonstrated that the OIHS method can solve the dynamic convergence problem of the train–track–bridge on high-speed railway accurately and efficiently.
Generalized Breathing Functions for Stiffness Model of Transversely Cracked Hollow Shaft
Authors: Yang Hyong-Ju , Hwang Je-Hyon , Kim Tae-Jong , Kim Inchol
Published: April 2022

The exact breathing mechanism of the transverse crack in the hollow shaft that appears due to the shaft weight is important to analyze correctly the dynamic behavior of the rotor system. We discuss a breathing phenomenon which appears only in the hollow shaft rotation and determine the exact time-varying area moments of inertia for the cracked element cross-section. Considering the variation behavior of the area moments of inertia, generalized breathing functions are suggested to formulate the finite-element stiffness matrix of the crack element. The harmonic balance method (HBM) is employed to solve the finite-element model of the rotor-bearing-disk system. We study the influence of ratio of the internal and external diameter of shaft, dimensionless crack depth, location of crack and angle between the crack and imbalance directions. Some significant behaviors of the system are compared with some previously published results, and they can be contributed to detecting the crack in hollow shaft early. Comparison shows the generalized breathing functions are accurate to model the stiffness variation of shaft due to the crack.
Cross-Section Stability and Design of Normal Strength and High Strength Steel I-Sections in Fire
Authors: Kucukler Merih
Published: April 2022

The structural response and design of normal strength and high strength steel I-sections at elevated temperatures are investigated in this paper. The shell finite element models of steel I-section elements capable of replicating their behavior in fire are developed and validated against experimental results from the literature. The validated shell finite element models are then utilized to generate extensive structural performance data for steel I-sections, considering a broad range of plate slenderness values for cross-section elements, elevated temperature levels, cross-section aspect ratios as well as different loading conditions and normal strength and high strength steel grades. The accuracy of the existing methods provided in the European structural steel fire design standard EN 1993-1-2 and its upcoming version prEN 1993-1-2 for the ultimate strength predictions of normal strength and high strength steel cross-sections in fire is assessed. Scope for improvement is observed. Considering this, a new method for the ultimate strength predictions of normal strength and high strength steel sections at elevated temperatures is put forward. It is shown that the proposed method leads to more accurate ultimate strength predictions for normal strength and high strength steel I-sections in fire with a higher level of reliability relative to the existing design methods provided in EN 1993-1-2 and prEN 1993-1-2.
Simultaneous State-Input-Stiffness Estimation for Nonlinear Duffing Oscillators Avoiding Jacobian Linearization
Authors: Shereena O. A. , Krishnanunni C. G. , Rao B. N.
Published: April 2022

This paper presents a simultaneous state-input-stiffness estimation framework for nonlinear systems. The technique combines an unbiased minimum variance estimator (MVE) from the data assimilation context with the Moore–Penrose pseudo-inverse. The investigation employs synthetically generated measurement data with additive Gaussian noise to replicate the field measurements. In the first stage of the algorithm, the MVE estimates a total force component, a function of the unknown system parameters and unknown input excitation. In the second stage, a system of over-determined equations is established by representing the input excitation with a Fourier series (with N coefficients) expansion. A least-squares solution for the unknown stiffness parameters and the Fourier coefficients is then achieved using the Moore–Penrose inverse. A dimensionless transformation handles the scale difference between the Fourier coefficients and unknown parameters. The novelty of the work is that the inputs and the parameters of the nonlinear systems are estimated simultaneously, circumventing any linearization of the system, and the associated computational hassles. The method by construction has a unique solution and an upper bound for stiffness estimation error is derived. The method is demonstrated numerically for Duffing oscillator systems excited by random inputs. The robustness of the technique is assessed by conducting various parametric studies. Numerical results reveal that the developed method accurately estimates the nonlinear cubic stiffness parameter, input force, and state responses.
Symplectic Framework-Based New Analytic Solutions for Thermal Buckling of Temperature-Dependent Moderately Thick Functionally Graded Rectangular Plates
Authors: Xiong Sijun , Zhou Chao , Zhao Liang , Zheng Xinran , Zhao Yan , Wang Bo , Li Rui
Published: April 2022

This paper presents some new analytic thermal buckling solutions of temperature-dependent moderately thick functionally graded (FG) rectangular plates with non-Lévy-type constraints within the symplectic solution framework in the Hamiltonian system. An original problem is reduced to the superposition of two constructed subproblems that are analytically solved via the rigorous symplectic elasticity approach with mathematical techniques such as variable separation in the symplectic space and symplectic eigen expansion. The physical neutral surface is employed to remove the stretching-bending coupling in constitutive equations. The main characteristic of the present symplectic superposition strategy is on the rational derivation without assumption on solution forms, which, however, is hard to achieve by conventional semi-inverse methods. Comprehensive benchmark results are presented, including critical buckling temperatures as well as mode shapes of typical non-Lévy-type FG plates in uniform and nonlinear temperature fields, and are verified by available numerical results. The effects of boundary constraint, aspect ratio, volume fraction exponent, and thickness-to-width ratio on buckling temperatures are quantitatively investigated. The occurrence of thermal buckling is further studied by presenting a failure mode map covering a wide range of geometric parameters.
Influence of Longitudinal Inertia of Sliding Mass on Nonlinear Transverse Vibrations of Hydraulic Cylinder Piston Rod
Authors: Uzny Sebastian , Kutrowski Łukasz , Osadnik Michał
Published: April 2022

In this work, transverse vibrations of the piston rod of a hydraulic cylinder, which is connected with a system characterized by its own high weight, e.g. a tank gate, were considered. The case is considered when the actuator is fully extended and the piston rod is not affected by external static axial forces (the actuator acts in a horizontal position, as a result of which the weight load at its end does not compress the piston rod). To analyze this issue, a beam model was developed taking into account the longitudinal inertia of the mass element associated with one of the ends of the system. The boundary problem of vibrations was formulated using the Bernoulli–Euler theory. Taking into account mass inertia (directed longitudinally) results in the appearance of nonlinear terms in equations describing the behavior of the system during vibrations. The small parameter method was used to finally formulate the problem of nonlinear vibrations. In the description thus adopted, the vibrations of the considered system strictly depend on the dead weight of the gate valve as well as the amplitude of the piston rod oscillations. The results of numerical simulations are presented taking into account the impact of piston rod stiffness and stiffness of mounting to the valve on its vibrations. In the considered range of masses, the effect of amplitude on the value of the natural frequency of the system is presented. Theoretical considerations have been confirmed to some extent by experimental studies.
Simultaneous Identification of Fundamental Frequency, Mode Shape, and Damping of a Bridge by a Passing Vehicle-Trailer System
Authors: Zhang Yao
Published: April 2022

A theoretical framework is proposed to identify fundamental frequency, mode shape, and damping of a bridge simultaneously by a passing vehicle-trailers system with only accelerometers. The framework is the first attempt to use indirect method to identify all fundamental modal properties of a bridge simultaneously without shaker, laser sensors and pre-known information. The vehicle performs as both “tractor” and “excitor” and the trailers perform as “message carriers”. The residual response defined as the response difference of one trailer to another one was usually adopted in the previous studies to remove the adverse effect of road roughness; however, it lacks theoretical support. Instead, the residual response of one trailer–bridge contact point to another one is used in this study, and theoretical analysis proves that it can effectively eliminate the adverse effect of road roughness. Different from previous studies, the residual response of contact point in this study is obtained in the frequency domain rather than the time domain. Frequency and damping can be evaluated by applying single degree-of-freedom (SDOF) model-based curve fitting technique to several discrete values from the Fourier transform of the residual response. Mode shapes can be reconstructed by dividing the Fourier transform of one residual response at the natural frequency by another one without time lag. The proposed framework is validated by independent finite element (FE) analysis and it shows great performance. Parametric study including vehicle speed, measurement noise, calibration error, road surface roughness and boundary condition has also been conducted to check its feasibility in various scenarios.
A Novel Approach to the Integration for Generating Consistent Ground Acceleration, Velocity and Displacement Time Histories
Authors: Yang Lanlan , Ly Binh-Le , Xie Wei-Chau , Mao Chenxi , Qin Xiangnan
Published: April 2022

The velocity and the displacement time history obtained by directly integrating the acceleration time history will drift unrealistically because of the over-determinacy of the integration constants. Applying baseline corrections to resolve drift disturbs the frequency content and renders the corrected processes mutually inconsistent. In this study, eigenfunctions of sixth-order eigenvalue problem are introduced as basis functions for decomposing recorded ground motion time history. Taking advantage of the eigenfunctions and their first two order of differentiations are drift-free and consistent, the decomposed and reconstructed acceleration, velocity, and displacement time histories can be drift-free and mutually consistent without direct integration and baseline correction. Two earthquake ground motions are presented as examples, which show that the decomposed acceleration, velocity, and displacement time histories are drift-free, mutually consistent, and almost the same as the seed motion. The new approach can replace integral in the generation of velocity and displacement time histories.
Blended Learning During Pandemic Through Knowledge Management: An Analytical Study
Authors: Hasan Khandakar Kamrul , Mostofa Sk Mamun , Othman Roslina , Mukherjee Debarshi
Published: April 2022

Blended Learning (BL) essentially fuses high-tech digital learning with traditional ones to involve students in “network learning”, which helps in transcending physical boundaries. Especially during the ongoing COVID-19 pandemic, BL has been embraced as a realistic possibility to ensure seamless knowledge distribution regardless of time and space. Knowledge Management (KM)-based approaches are typically used to collect, coordinate, and control processes that may be utilised efficiently to both recognise and address customer needs. This study aims to explain how to apply KM techniques within the BL environment to increase educational excellence and quality. We used a quantitative approach, specifically by adopting an online questionnaire circulated to about 272 undergraduate students, primarily from the Department of Information Science and Library Management (ISLM) of the University of Dhaka, Bangladesh. We received completed answers from 74 students; the data gathered were analysed using Statistical Package for the Social Sciences (SPSS) version 20. The findings reveal that KM can be used with BL, especially during crisis times like the one we have today, as it includes integrated tasks and online and e-learning. Finally, the study also proposed an intuitive model for applying BL through KM. Importantly, this study seems to be among the first to examine the students’ perceptions about BL and KM integration during a pandemic. Therefore, this research would possibly prompt further research on different aspects of the combined learning process at different universities, especially within Bangladesh.
Network Dynamics of COVID-19 Fake and True News Diffusion Networks
Authors: Zahid Sumaiyah , Shams Malick Rauf Ahmed , Sagri Muhammad Rabeet
Published: April 2022

Social media platforms have become an integral source to spread and consume information. Twitter has emerged as the fastest medium to disseminate any information. This blind trust on social media has raised the concern to quantify the truth or fakeness of what we are consuming. During COVID-19, the usage of social platforms has dramatically increased in everyone’s life. It is high time to distinguish between the type of users involved in spreading fake and true news content. Our study aims to answer two questions. First, what is the complex network structure of users involved in spreading any news? How two types (i.e. Fake and True) of networks are different in terms of network topology. Second, what is the role of influential users in spreading both types of news? To answer these, the fake and true news of COVID-19 are collected which have been classified by fact-checking websites. Diffusion networks have been created to perform the experiments. Network topological analysis revealed that despite having differences, most properties show similar behaviour. Though, it can be stated that during COVID-19, behaviour of users remained the same in spreading fake or true content. Resilience analysis discovered that fake networks were more densely connected than true ones. There were more centric nodes or influential users were present in Fake news networks than True news networks.
A Blockchain-Based Security Model for IoT Systems
Authors: Chen Bing , Liu Ding , Zhang Ting
Published: April 2022

The current Internet of Things (IoT) technology has entered a relatively mature development stage, and more and more IoT devices can readily access the Internet. However, along with this, the IoT system still faces fragile security of device nodes, easy data tampering, and low system stability. To this end, this paper proposes a smart contract-based security model for IoT systems. The proposal is based on the super ledger Fabric blockchain platform having decentralised, tamper-proof, and programmable features. These features achieve credible authentication of IoT device nodes on the one hand and tamper-proof data storage on the other hand. Further, with these features, we gain a trustworthy environment for enhancing the security of the whole IoT system.
Stuttering Disfluency Detection Using Machine Learning Approaches
Authors: Al-Banna Abedal-Kareem , Edirisinghe Eran , Fang Hui , Hadi Wael
Published: April 2022

Stuttering is a neurodevelopmental speech disorder wherein people suffer from disfluency in speech generation. Recent research has applied machine learning and deep learning approaches to stuttering disfluency recognition and classification. However, these studies have focussed on small datasets, generated by a limited number of speakers and within specific tasks, such as reading. This paper rigorously investigates the effective use of eight well-known machine learning classifiers, on two publicly available datasets (FluencyBank and SEP-28k) to automatically detect stuttering disfluency using multiple objective metrics, i.e. prediction accuracy, recall, precision, F1-score, and AUC measures. Our experimental results on the two datasets show that the Random Forest classifier achieves the best performance, with an accuracy of 50.3% and 50.35%, a recall of 50% and 42%, a precision of 42% and 46%, and an F1 score of 42% and 34%, against the FluencyBank and SEP-28K datasets, respectively. Moreover, we show that the machine learning-based approaches may not be effective in accurate stuttering disfluency evaluation, due to diverse variations in speech rate, and differences in vocal tracts between children and adults. We argue that the use of deep learning approaches and Automatic Speech Recognition (ASR) with language models may improve outcomes, specifically for large scale and imbalanced datasets.
Application of Quality Function Deployment as an Integrative Method to Knowledge Management Implementation
Authors: Reis Luciana Paula , Fernandes June Marques , Silva Sérgio Evangelista , Pereira Alana Deusilan Sester
Published: April 2022

Knowledge Management Implementation (KMI) can be analysed from three perspectives: Knowledge Management System (KMS) implementation, Knowledge Management Processes (KMPs) implementation and Organisational Outcomes (OO). Quality Function Deployment (QFD), conceived within the scope of quality, represents a method capable of bringing significant contributions to the knowledge field of KMI. The QFD method stands out as a comprehensive approach to improve the quality of products and services, focussing on customer requirements. The literature presents a scarcity of studies that discuss the KMI implementation process, addressing these three perspectives. Furthermore, studies that address QFD in the context of KM are more focussed on the KMS implementation perspective. In this context, this research proposes an innovative approach adopting QFD in order to structure the KMI, encompassing the three perspectives presented (KMS implementation, KMP implementation and OO). In this context, QFD is seen as a method of integrating and operationalising KMI activities. To validate this approach, we applied the case study in an academic support department at a Brazilian public university. As a result, it was possible to verify that the QFD helps in the operationalisation of the KMS and KMP and also improves OO. Still, it was observed that the approach to knowledge management seems to be easy to apply in the academic setting and has produced good results in the service offered in the department where it was applied.
On integrability of the Nosé–Hoover oscillator and generalized Nosé–Hoover oscillator
Authors: Li Wenlei , Shi Shaoyun , Yang Shuangling
Published: April 2022

The Nosé–Hoover system is a basic primitive model for the molecular dynamics simulations, which describes the equilibrium characterized by canonical distributions at a constant temperature. Its simplest form, called the Nosé–Hoover oscillator (NH), is a three-dimensional quadratic polynomial system that admits both regular invariant tori and chaotic trajectories. Recently, a similar system, called the generalized Nosé–Hoover oscillator (GNH), was constructed to show the coexistence of invariant tori and topological horseshoe for time-reversible systems in [Formula: see text]. This paper aims to study the integrability of both NH and GNH models. We show that (i) in the case of [Formula: see text], both NH and GNH models are integrable by quadratures and the general solutions are given; (ii) in the case of [Formula: see text] the non-existence of either global analytic first integrals or Darboux first integrals of two models are discussed and a complete characterization of Darboux polynomials and exponential factors are given; (iii) both NH and GNH models are not rationally integrable in an extended Liouville sense except for several parameter values by an extended Morales–Ramis theory; (iv) the reduced systems of NH and GNH models at the Poincaré compactification balls are integrable, which yields complete descriptions of dynamics at infinity for NH and GNH models. Interestingly, the topological structure of NH and GNH models at infinity strongly depends on the sign of [Formula: see text]. These results may help us better understand the complex and rich dynamics of nonlinear time-reversible systems.
Infinite families of congruences modulo powers of 2 for some partition functions involving only odd parts
Authors: Baruah Nayandeep Deka , Das Hirakjyoti
Published: April 2022

Let [Formula: see text] and [Formula: see text] count the 8-colored partitions of n into odd parts and the 2k-color partitions of n into odd parts, respectively, where the multiples of r can appear in 2k colors and the others can appear in k colors. In this paper, we find infinite families of congruences modulo powers of 2 for [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].
Computing base extensions of ordinary abelian varieties over finite fields
Authors: Marseglia Stefano
Published: April 2022

We study base field extensions of ordinary abelian varieties defined over finite fields using the module theoretic description introduced by Deligne. As applications we give algorithms to determine the minimal field of definition of such a variety and to determine whether two such varieties are twists.
Nano-Porous Self-Supporting Ta2O5 Thin Film Electrode for Highly Reversible Li Ion Storage
Authors: Wang Lixia , Zhao Taibao , Tan Wenlong , Luo Hewei , Fang Hua , Zhang Linsen , Chen Ruiping , Cao Yang
Published: April 2022

Nano-porous Ta2O5 thin film electrodes are prepared by magnetron sputtering at low pressure in the presence of an oxygen atmosphere with an inert gas. The sputtered Ta2O5 thin film is subsequently annealed at 350∘C for 2[Formula: see text]h in high pure N2 (Ta2O5-350) to introduce oxygen deficiency. The Ta2O5-350 electrode possesses highly reversible lithium ion storage and good rate capability, which has high specific capacities of about 480[Formula: see text]mAh g[Formula: see text] at a rate of 0.1[Formula: see text]C. Furthermore, after 2000 cycles at a rate of 5[Formula: see text]C the Ta2O5-350 electrode shows no obvious capacity decay and retains specific capacity of about 160[Formula: see text]mAh[Formula: see text]g[Formula: see text]. The excellent lithium storage properties of Ta2O5-350 electrode can be correlated to the nano-porous electrode architecture and oxygen deficiency.
Facile Synthesis, Physicochemical Properties, and Photocatalytic Activity ofIn SituGr@WO3⋅H2O Nanoplate Nanocomposite
Authors: Nguyen Cong Tu , Nguyen Tuan Son , Pham Tuan Phong , Nguyen Thi Tuyet Mai , Nguyen Xuan Sang , Luu Thi Lan Anh
Published: April 2022

In situ nanocomposites of graphene (Gr) and tungsten oxide hydrate (WO[Formula: see text]O) nanoplates were synthesized via facile and energy-saving acid precipitation method at room temperature. The effect of the in situ composition on the physicochemical properties of WO[Formula: see text]O platform material in nanocomposites was examined with X-ray diffraction, Raman scattering, UV–Vis reflectance spectra. Gr helped reduce microstrain, reduce the average crystalline size, increase the distance between (111) planes in WO[Formula: see text]O platform nanoplates, and abnormally increase the optical bandgap. All samples showed a moderate photocatalytic activity in methylene blue (MB) removing efficiency under visible light irradiation, which was remarkably enhanced by adding 0.1[Formula: see text]mL H2O2. In comparison with both pristine and nanocomposite samples, the sample having 0.1[Formula: see text]wt.% of Gr in nanocomposite showed the highest MB removing efficiency of 47% and 99% in corresponding to without and with 0.1[Formula: see text]mL H2O2. The photocatalytic activity was assigned to the key role of the photogenerated holes, which was enhanced by compositing with Gr and/or the appearance of H2O2. The results of this work were a contribution to studying the photocatalytic mechanism of tungsten oxide hydrate-based nanocomposite and also proposed a facile method for preparing WO[Formula: see text]O-based nanocomposite.
Mathematical analysis of a model of Ebola disease with control measures
Authors: Tadmon Calvin , Kengne Jacques Ndé
Published: April 2022

The re-emergence of the Ebola virus disease has pushed researchers to investigate more on this highly deadly disease in order to better understand and control the outbreak and recurrence of epidemics. It is in this perspective that we formulate a realistic mathematical model for the dynamic transmission of Ebola virus disease, incorporating relevant control measures and factors such as ban on eating bush-meat, social distancing, observance of hygiene rules and containment, waning of the vaccine-induced, imperfect contact tracing and vaccine efficacy, quarantine, hospitalization and screening to fight against the spread of the disease. First, by considering the constant control parameters case, we thoroughly compute the control reproduction number [Formula: see text] from which the dynamics of the model is analyzed. The existence and stability of steady states are established under appropriate assumptions on [Formula: see text]. Also, the effect of all the control measures is investigated and the global sensitivity analysis of the control reproduction number is performed in order to determine the impact of parameters and their relative importance to disease transmission and prevalence. Second, in the time-dependent control parameters case, an optimal control problem is formulated to design optimal control strategies for eradicating the disease transmission. Using Pontryagin’s Maximum Principle, we derive necessary conditions for optimal control of the disease. The cost-effectiveness analysis of all combinations of the control measures is made by calculating the infection averted ratio and the incremental cost-effectiveness ratio. This reveals that combining the four restrictive measures conveyed through educational campaigns, screening, safe burial and the care of patients in health centers for better isolation is the most cost-effective among the strategies considered. Numerical simulations are performed to illustrate the theoretical results obtained.
Facile synthesis of Ni foam-supported prickly Au nanoparticles by galvanic displacement for electrocatalytic oxidation of glycerol
Authors: Cai Tong , Zhang Pujing , She Guangwei , Zhou Qingli , Mu Lixuan , Liu Yun , Shi Wensheng
Published: April 2022

The development of electrocatalysts with high activity is essential to convbar glycerol into value-added chemicals through electrocatalytic oxidation. Nano-sized metals with prickly structures are expected to possess high electrocatalytic activity due to the strong electric field at the sharp tips. We propose a facile approach to prepare Au nanoparticles with prickly structure by galvanic displacement in this work. The reaction between Au3+ and Ni generates in situ highly dispersed Au nanoparticles with prickly structures on the Ni foam. Owing to appropriate prickly structure, the Au nanoparticles prepared at 25∘C for 30 s exhibited the best electrocatalytic performance. Finite element simulation method simulations show that the high-density of positive charge at the tips forms strong electric field, which enriches OH− ions and promotes glycerol oxidation, thus exhibiting excellent electrocatalytic activity. This study will guide further design/development of electrocatalytic nanostructured Au particles and provide an effective route to electrocatalytically oxidize glycerol.
Reducing future climate impact on rural transport infrastructure in developing countries; the role of engineering geology
Authors: Cook J. R.
Published: April 2022

Hard-won development gains are under real threat due to climate change impacts on rural transport infrastructure (RTI) and it is a major challenge, within normally available budgets, to ensure that rural access is made sustainably climate resilient. The ability of engineers and engineering geologists to identify problems and to devise solutions that provide sustainable cost-effective access for the rural poor is a key factor in overarching aims of poverty reduction and socio-economic development in lower and middle-income countries (LMICs). Engineering geology, through its inherent wide-ranging and inclusive approach to earth science, has an important role to play in providing a holistic and cross-sectorial framework to meet this challenge in a sustainable manner. This paper firstly emphasizes the importance of RTI, then outlines the climate change risks to RTI and hence to socio-economic development in LMICs. The paper then describes the key contribution that engineering geology can make to combatting this challenge through cost-effective climate-strengthening measures aided by the practical application of sound earth-science principles in a budget-constrained environment. Illustrative examples are taken from recent and ongoing LMIC projects funded by the UKAID Department for International Development, the Word Bank, the Asian Development Bank and Kreditanstaltfür Wiederaufbau – the German Development Bank.

Thematic collection:
This article is part of the Climate change and resilience in Engineering Geology and Hydrogeology collection available at:
https://www.lyellcollection.org/cc/climate-change-and-resilience-in-engineering-geology-and-hydrogeology
Temporal and spatial variations in calcium carbonate deposition in a mixed siliciclastic–carbonate deep marine system: the Ediacaran Deeside Limestone Formation, Aboyne, Scotland
Authors: Drake Stephen J. , Gomez-Rivas Enrique , Ickert Ryan B. , Macdonald David I.M.
Published: April 2022

The Deeside Limestone Formation (DLF), outcropping in western Aberdeenshire, comprises the eastern margin of a distinctive Upper Dalradian mixed siliciclastic–carbonate system of Ediacaran age which may be correlated southwestwards for more than 400 km to County Donegal in Ireland. A reconstructed stratigraphic column suggests three broad vertical sequences (S1–S3), each comprising a general upward proportionate increase in calcium carbonate with respect to quartz, locally capped by metalimestones (L1–L3). A simple explanation for this upward change lies in the differing physical response of the two heterolithic components under the same hydrodynamic process, with the heavier quartz grains preferentially enriching the bedload and the finer carbonate mud fraction, the suspended load. The three metalimestone intervals are observed only in central/eastern parts of the field area, suggesting a lateral facies variation. The predominance of calcareous–siliciclastic bed-scale compositional mixing within the DLF suggests sedimentation on the Dalradian shelf comprised contemporaneous mixing of the siliciclastic and carbonate fractions prior to subsequent re-mixing during transportation downslope into the deep water, punctuated by pulses of point-sourced siliciclastic input.
Cognitive Load Theory in Computing Education Research: A Review
Authors: Duran Rodrigo , Zavgorodniaia Albina , Sorva Juha
Published: April 2022

One of the most commonly cited theories in computing education research is cognitive load theory (CLT), which explains how learning is affected by the bottleneck of human working memory and how teaching may work around that limitation. The theory has evolved over a number of decades, addressing shortcomings in earlier versions; other issues remain and are being debated by the CLT community. We conduct a systematic mapping review of how CLT has been used across a number of leading computing education research (CER) forums since 2010. We find that the most common reason to cite CLT is to mention it briefly as a design influence; authors predominantly cite old versions of the theory; hypotheses phrased in terms of cognitive load components are rare; and only a small selection of cognitive load measures have been applied, sparsely. Overall, the theory’s evolution and recent themes in CLT appear to have had limited impact on CER so far. We recommend that studies in CER explain which version of the theory they use and why; clearly distinguish between load components (e.g., intrinsic and extraneous load); phrase hypotheses in terms of load components
a priori
; look further into validating different measures of cognitive load; accompany cognitive load measures with complementary constructs, such as motivation; and explore themes such as collaborative CLT and individual differences in working-memory capacity.
Grand Theories or Design Guidelines? Perspectives on the Role of Theory in Computing Education Research
Authors: Tedre Matti , Pajunen John
Published: April 2022

A rich body of empirically grounded results and a solid theory base have often been viewed as signs of a mature discipline. Many disciplines have frequently debated what they should accept as legitimate kinds of theories, the proper roles of theory, and appropriate reference disciplines. Computing education research (CER) in particular has seen a growing number of calls for the development of domain-specific theories for CER, an adaptation of theories from other fields, and engagement with theory-based experimental and predictive research in CER. Many of those calls share the same concerns and aims, yet they use very different vocabulary and lack a consensus over an essential concept: theory.

This article presents sticking points and trouble spots in CER’s theory debates and presents a number of suggestions and ways forward. Firstly, by slightly shifting towards a model-based view of science, CER can avoid centuries of conceptual baggage related to the concept of theory. Secondly, insofar as fields like design, engineering, and social science are considered to be legitimate parts of CER, the role of theory in many CER studies needs to be judged by the criteria of the philosophy of engineering, technology, and social science, not the philosophy of (natural) science. Thirdly, instead of force-fitting elements of ill-suited research paradigms from other disciplines, the philosophy of CER should focus on building a consensus on CER’s own paradigm and describing the field’s relationship with theory in CER’s own terms.