Theoretical Strengths Research Articles

Factor Structure, Measurement Invariance, and Nomological Network of Teaching Presence in Online Foreign Language Education.

Though online learning has gained popularity in foreign language (FL) education, there is a lack of measurement tools with robust psychometric properties to comprehensively assess the quality of online FL instruction. This study explored the factor structure and measurement invariance of teaching presence in the framework of Community of Inquiry (CoI), a critical construct to understand instructors' responsibilities in precipitating and facilitating successful online learning. Data was collected from 564 college-level online learners of Chinese as a Foreign Language (CFL). Results of exploratory factor analysis and confirmatory factor analysis supported a five-factor structure of teaching presence, including design and organization, facilitating discourse, direct instruction, assessment and feedback, and technological support. Further evidence was also found to support the internal consistency and convergent validity of the derived factor structure of teaching presence. The nomological validity of the developed scale was established with the positive relationships between each subcomponent of teaching presence and online interaction (learner-instructor interaction, learner-learner interaction, learner-content interaction, and learner-technology interaction). Multi-group CFA indicated strict measurement invariance of the 27-item teaching presence scale across gender, age, and prior online experience. The findings extended the theoretical strengths of the teaching presence construct into FL education and highlighted its important role in fostering interactive online FL learning environments. Furthermore, the developed teaching presence scale can serve as an effective tool for future teacher educators and practitioners to evaluate instructional quality from the learners' perspective, thereby ensuring meaningful online FL learning experiences.

Classrooms to Networks: Applying Connectivism Principles in Pedagogy ```

The integration of digital technologies has led to a significant transformation in educational practices, shifting from traditional classroom models to more dynamic, networked learning environments. This paper explores the concept of connectivism, a learning theory developed by Siemens and Downes, which emphasizes the importance of networks, connectivity, and collaboration in acquiring knowledge. Unlike traditional pedagogies that focus on content delivery, connectivism promotes the creation and navigation of networks to facilitate continuous learning. Key principles of connectivism include the diversity of opinions, the distribution of knowledge across networks, and the critical role of digital tools in learning processes. The paper discusses the practical applications of connectivism approaches in contemporary pedagogy, focusing on how educators can transform traditional classrooms into engaging, networked learning spaces. Despite its theoretical strengths, the implementation of connectivism faces challenges, including technological access, information management, and the need for pedagogical adaptation. Through this exploration, the paper aims to provide insights into how connectivism can enhance educational practices and prepare students for the complexities of a rapidly evolving, networked society.

Study on the fabrication and mechanical properties of SiCp/SiC gradient lattice structure based on selective laser sintering technology

ABSTRACT Conventional uniform lattice structures are subject to non-uniform loads or concentrated loads alternating back and forth during service, which can no longer meet the refinement requirements. In this paper, SiCp/SiC gradient lattice structures are prepared by selective laser sintering (SLS) technology and polymer impregnation pyrolysis (PIP) process, and compression standard specimens with different tilt angles are prepared according to the structural model by changing the printing direction, to analyze the influence of the anisotropic properties of the materials due to the SLS molding technology on the load-bearing behaviour of the core rod, and to further study the mechanical properties of the gradient lattice structures and the Failure behaviour. The results show that: with the increase of the angle of printing direction, the compression performance of the densification specimen decreases gradually; the compression strength of the gradient lattice structure is 13.95 MPa. During compression, the core rods with tilt angles of 60° and 75° mainly exhibit shear failure and crushing failure, respectively. The theoretical and simulated compression strengths were 16.08 and 16.32 MPa, respectively. This paper provides a new insight into the research and application of gradient lattice structures.

Improved Astrophysical and Computational Oscillator Strengths for Ultraviolet P ii Lines

Abundance measurements for the volatile element phosphorus are important for measuring the metallicity in interstellar and circumgalactic gas, where their accuracies are limited by uncertainties in the oscillator strengths. We report updated oscillator strength values for two resonant transitions of the dominant ion P II, the transitions at 961.041 and 963.801 Å, which have historically shown large uncertainties. Using a combination of observational measurements and highly accurate quasi-relativistic Hartree–Fock theoretical calculations, we present an updated oscillator strength of f = 0.147 ± 0.021 for the poorly constrained P II resonant transition at 961.401 Å, which arises from the ground electronic state 3s 23p 2 3P0 to the excited level 3s 23p3d 3D 1o . This result utilizes archival optical spectra obtained with the Very Large Telescope for the quasar PKS 0528–250, which has a damped Lyα absorber at z = 2.811. We calculate a theoretical f-value = 0.153 for 961.401 Å consistent with our empirically derived value, and calculate a theoretical f-value = 1.79 for 963.801 Å. We also present theoretical oscillator strengths for the P II resonant transitions at 972.779, 1124.945, 1152.818, 1301.874, and 1532.533 Å, as well as for multiple P II fine-structure and excited-level transitions. The updated f-value for the P II 961 Å transition will be useful in future studies of P abundances, especially in sight lines where the 1152 Å line is saturated.

Struggling Models: An Analysis of Logistic Regression and Random Forest in Predicting Repeat Buyers with Imbalanced Performance Metrics

Predicting repeat buyers is essential for businesses seeking to improve customer retention and maximize profitability. This study examines the effectiveness of logistic regression and random forest algorithms in forecasting repeat buyers, utilizing an e-commerce dataset from Kaggle. Despite the theoretical strengths of these models, our results indicate significant performance challenges. Both models were evaluated on key metrics: accuracy, precision, recall, F1 score, and ROC-AUC. The findings revealed that the models logistic regression and random forest performed poorly, with accuracy hovering around 50%, precision and recall demonstrating imbalanced performance, and ROC-AUC scores barely exceeding random guessing levels. Such metrics highlight the limited discriminative power of these models in identifying repeat buyers. The analysis suggests that issues such as data quality, feature relevance, and class imbalance contribute to these shortcomings. Specifically, the models struggled to effectively learn from the data, leading to suboptimal predictions. These results underscore the need for enhanced feature engineering, better handling of class imbalance, and possibly exploring more advanced algorithms. This study provides a critical assessment of the limitations inherent in using Logistic Regression and Random Forest for predicting repeat buyers, hence implements feature engineering, SMOTE and hyperparameter tuning using RandomSearchCV to get better result.

Addressing immortal time bias in precision medicine: Practical guidance and methods development.

To compare theoretical strengths and limitations of common immortal time adjustment methods, propose a new approach using multiple imputation (MI), and provide practical guidance for using MI in precision medicine evaluations centered on a real-world case study. Methods comparison, guidance, and real-world case study based on previous literature. We compared landmark analysis, time-distribution matching, time-dependent analysis, and our proposed MI application. Guidance for MI spanned (1) selecting the imputation method; (2) specifying and applying the imputation model; and (3) conducting comparative analysis and pooling estimates. Our case study used a matched cohort design to evaluate overall survival benefits of whole-genome and transcriptome analysis, a precision medicine technology, compared to usual care for advanced cancers, and applied both time-distribution matching and MI. Bootstrap simulation characterized imputation sensitivity to varying data missingness and sample sizes. Case study used population-based administrative data and single-arm precision medicine program data from British Columbia, Canada for the study period 2012 to 2015. While each method described can reduce immortal time bias, MI offers theoretical advantages. Compared to alternative approaches, MI minimizes information loss and better characterizes statistical uncertainty about the true length of the immortal time period, avoiding false precision. Additionally, MI explicitly considers the impacts of patient characteristics on immortal time distributions, with inclusion criteria and follow-up period definitions that do not inadvertently risk biasing evaluations. In the real-world case study, survival analysis results did not substantively differ across MI and time distribution matching, but standard errors based on MI were higher for all point estimates. Mean imputed immortal time was stable across simulations. Precision medicine evaluations must employ immortal time adjustment methods for unbiased, decision-grade real-world evidence generation. MI is a promising solution to the challenge of immortal time bias.

Comparative study of kilonova opacities for three elements of the sixth period (hafnium, osmium, and gold) from new atomic structure calculations in Hf I–IV, Os I–IV, and Au I–IV

Aims. It is now well established that a large amount of heavy (trans-iron) elements are produced during neutron star (NS) mergers. These elements can be detected in the spectra of the kilonova emitted from the post-merger ejected materials. Due to the high level densities that characterize the complex configurations belonging to heavy elements, thus giving rise to millions of absorption lines, the kilonova ejecta opacity is of significant importance. The elements that contribute the most to the latter are those with an unfilled nd subshell belonging to the fifth and the sixth rows of the periodic table, and those with an unfilled nf subshell belonging to the lanthanide and actinide groups. The aim of the present work is to make a new contribution to this field by performing large-scale atomic structure calculations in three specific sixth-row 5d elements, namely hafnium, osmium, and gold, in the first four charge stages (I–IV), and by computing the corresponding opacities, while focusing on the importance of the atomic models used. Methods. The pseudo-relativistic Hartree–Fock (HFR) method, including extended sets of interacting configurations, was used for the atomic structure and radiative parameter calculations, while the expansion formalism was used to estimate the opacities. Results. Theoretical energy levels, wavelengths, and oscillator strengths were computed for millions of spectral lines in Hf I–IV, Os I–IV, and Au I–IV ions, the reliability of these parameters being assessed through detailed comparisons with previously published experimental and theoretical results. The newly obtained atomic data were then used to calculate expansion opacities for typical kilonova conditions expected one day after the NS merger; these are a density of ρ = 10−13 g cm−3 and temperatures ranging from T = 5000 K to T = 15 000 K. Some agreements and differences were found when comparing our results with available data, highlighting the importance of using sufficiently complete atomic models for the determination of opacities.

Transition probabilities and suitable coupling scheme for 6p→6s transition array of neutral xenon using hollow cathode discharge lamp technique

In the present work, analyses have been performed to determine spectroscopic parameters, including transition probabilities, and relative line strengths of discharge-produced xenon plasma. We present the transition probabilities of twenty-three emission lines originating from the 5p56p →5p56s transition array of neutral xenon covering the wavelength range from 450 to 1100 nm using a xenon-filled hollow cathode discharge lamp. The experimental absolute transition probabilities have been measured by combining the reported lifetimes of upper levels with the integrated spectral intensities of xenon transitions. The results agree well with the reported data in the NIST database, where available. The theoretical line strengths for all spectral transitions originating from the 5p56p→5p56s transition array have been calculated in the LS, LK, jj, and jck coupling schemes using the 3j, 6j, and 9j symbol relations. Furthermore, the normalized experimental line strengths have also been measured and compared with theoretical line strengths, which confirm that the jj and jck coupling scheme is more appropriate for the level designation of xenon.

Vaccine Impact Bonds: An Alternative Way of Allocating the Economic Risks of Mass Vaccination Programs.

Vaccines can be an appropriate tool for combating pandemics. Accordingly, expectations were high when the first Covid-19 vaccines were administered. However, even though the vaccines have not met these high initial expectations, vaccine manufacturers and their investors were making large profits, while most of the associated economic risks have remained with the taxpaying public. Thus, this paper applies the concept of social impact bonds to mass vaccination programs by conceptualizing vaccine impact bonds (VIBs) as an alternative to the advance purchase agreements (APAs) for Covid-19 vaccines. Rather than rewarding vaccine manufacturers and their investors based on the quantity of doses distributed, VIBs intend to link the real-world vaccine impact to the financial returns of vaccine manufacturers and their investors. This paper indicates that VIBs can theoretically shift the economic risks of mass vaccination programs from the taxpaying public to private investors, thereby aligning commercial and public interests. However, it also identifies several major weaknesses such as the complexity of defining and evaluating the vaccine impact as well as the inherent trade-off between relieving taxpayers (through VIBs) and allowing innovation. As these substantial drawbacks outweigh the theoretical strengths of VIBs, this paper calls for further research in order to identify better alternatives to the Covid-19 vaccine contracts.

On the Remarkable Advancement of Assistive Robotics in Human-Robot Interaction-Based Health-Care Applications: An Exploratory Overview of the Literature

With the rapid advancement of technology, assistive robotic entities have arisen as indispensable instruments within diverse Human-Robot Interaction (HRI)-based health-care applications. By integrating Artificial Intelligence (AI) into these assistive robotic entities, they gain the capacity to autonomously perceive, engage in sophisticated reasoning, and execute actions within highly dynamic and complex environments. In light of these impressive achievements, this paper highlights a three-stage exploratory overview of the literature on the remarkable advancement of assistive robotics in HRI-based health-care applications. The first stage initiates an assessment of assistive robotics spanning historical epochs from ancient to modern times. Following this, the second stage comprehensively explores assistive robotics investigations in the realm of HRI-based health-care with its four sub-fields including rehabilitation, geriatric-care, pediatric-care, and nursing. Finally, the third stage entails a thorough analysis of the common challenges encountered in these pertinent investigations and provides a set of recommendations. This comprehensive paper not only provides an abundance of studies for each concept, method, and application in HRI, but it also presents their theoretical foundations, strengths, gaps, critical challenges, and recommendations. The results of the conducted exploratory overview shed light on the noteworthy prominence of assistive robotic entities within the HRI-based health-care field. The acquired findings emphasize the positive impact of such entities on human health, affirming their pivotal role in contributing to the advancement and effectiveness of health-care interventions. Furthermore, this paper provides an opportunity for scholars and researchers actively engaged in the pertinent field to obtain comprehensive additional insights, serving as a guiding resource for their academic endeavors.

Cerebral autoregulation, spreading depolarization, and implications for targeted therapy in brain injury and ischemia.

Cerebral autoregulation is an intrinsic myogenic response of cerebral vasculature that allows for preservation of stable cerebral blood flow levels in response to changing systemic blood pressure. It is effective across a broad range of blood pressure levels through precapillary vasoconstriction and dilation. Autoregulation is difficult todirectly measure and methods to indirectly ascertain cerebral autoregulation status inherently require certain assumptions. Patients with impaired cerebral autoregulation may be at risk of brain ischemia. One of the central mechanisms of ischemia in patients with metabolically compromised states is likely the triggering of spreading depolarization (SD) events and ultimately, terminal (or anoxic) depolarization. Cerebral autoregulation and SD are therefore linked when considering the risk of ischemia. In this scoping review, we will discuss the range of methods to measure cerebral autoregulation, their theoretical strengths and weaknesses, and the available clinical evidence to support their utility. We will then discuss the emerging link between impaired cerebral autoregulation and the occurrence of SD events. Such an approach offers the opportunity to better understand an individual patient's physiology and provide targeted treatments.

The gig verse: building a sustainable future

PurposeDespite the popularity of gig employment amid the changing business landscape, gig scholarship is somewhat limited and the untold reality about gig is yet to be fully revealed. This study aims to critically address the nature of gig employment, its ambiguities, evolution, theoretical premises and the appropriate future road ahead.Design/methodology/approachThis paper adopts a dual analytical approach – bibliometric and thematic analyses. After incorporating the exclusion–inclusion criteria, the authors identified 2,135 articles for the bibliometric analyses by using VOSviewer. Additionally, for the deep-delving synthesis, the authors conducted thematic analyses following Braun and Clarke (2006), based on 351 papers.FindingsThe findings revealed that gig work, in its different forms, is emerging as an alternative work arrangement with respect to the future of work. This study also identified multilevel perspectives of gig employment along with its holistic nomological network. Finally, this study offers some critical research directions that should help enhance the theoretical and practical strengths of this nascent scholarship in future.Research limitations/implicationsThe review findings are limited in nature owing to the paucity of quality research papers published in the said domain.Practical implicationsThe paper brings more clarity to what gig is and isn’t, along with its critical perspectives from multilevel lenses.Originality/valueThis paper identifies critical perspectives related to gig work and suggests appropriate directions for future gig work related scholarship.

Outcomes of Humble Leadership on Employee Organizational Citizenship Behaviors; Mediating Role of Psychological Safety

The current study model asserts a certain influence concerning humble leadership over employees' outcome (OCB) is treated through psychological safety and draws its assumptions from the social exchange theory. According to the theory, leader humility fosters high levels of employee psychological safety in order to increases employee OCB towards the organization. An analysis of the findings was done utilizing a quantitative research approach. Due to the use of a time-lag research strategy, the sample size for this study is 247. Since data was collected from Pakistan's banking industry. The findings support the idea that humble leadership and employees' OCB are mediated by employees' psychological safety. The current study draws this conclusion based on its theoretical and methodological strengths, implications, and research limitations for the future.

A HITRAN-formatted UV line list of S2-containing transitions involving X3 Σg-, B3 Σu-, and B″ 3 Πu electronic states

ABSTRACT The sulfur dimer (S2) is an important molecular constituent in cometary atmospheres and volcanic plumes on Jupiter’s moon Io. It is also expected to play an important role in the photochemistry of exoplanets. The ultraviolet (UV) spectrum of S2 contains transitions between vibronic levels above and below the dissociation limit, giving rise to a distinctive spectral signature. Using spectroscopic information from the literature, and the spectral simulation program PGOPHER, a UV line list of S2 is provided. This line list includes the primary $B\, ^{3}\Sigma ^{-}_{u}-X\, ^{3}\Sigma ^{-}_{g}$ (v′ = 0–27, v″ = 0–10) electronic transition, where vibrational bands with v′≥10 are pre-dissociated. Intensities have been calculated from existing experimental and theoretical oscillator strengths, and semi-empirical strengths for the pre-dissociated bands of S2 have been derived from comparisons with experimental cross-sections. The S2 line list also includes the $B^{\prime \prime }\, ^{3}\Pi _{u}-X\, ^{3}\Sigma ^{-}_{g}$ (v′ = 0–19, v″ = 0–10) vibronic bands due to the strong interaction with the B state. In summary, we present the new HITRAN-formatted S2 line list and its validation against existing laboratory spectra. The extensive line list covers the spectral range 21 700–41 300 cm−1 (∼242–461 nm) and can be used for modelling both absorption and emission.

Discriminação percebida no local de trabalho por imigrantes sul-americanos no Chile: um estudo quantitativo em uma grande amostra

Abstract South American immigrants in Chile constantly suffer workplace discrimination, which is usually related to different variables that are inherent to their immigration process. The objective of this article was to evaluate perceived workplace discrimination by South American immigrants in Chile. A cross-sectional design with a descriptive scope was used, where the final sample was made up of 612 South American immigrants of legal age who have been living in the country for more than a year. The results indicate that immigrants who perceive more discrimination in the workplace are those who mainly interact with foreigners from a third nationality. Finally, the discussion is presented, contrasting the results with the theoretical framework, weaknesses and strengths of the study are analyzed, and future lines of research are suggested.

M23C6-assisted formation mechanism of grain boundary cellular structure and its role on the brittle fracture in an austenitic Fe-Mn-Al-C lightweight alloy

The austenitic Fe-Mn-Al-C lightweight alloy is limited using its full-hardened state due to its brittleness after long-term aging treatment. This study investigates the formation mechanism of grain boundary precipitates and their effect on crack initiation and propagation. The alloy showed typical age-hardening behavior but exhibited intergranular fracture after a critical aging time. TEM study revealed that the amount of Mn segregation increased and Al decreased at the grain boundary at the early aging stage. M23C6 is first formed at the grain boundary, and α-ferrite is formed at the coherent M23C6/γ interface. Finally, the grain boundary cellular structure of α-ferrite+κ-carbide is formed by the continuous formation of α + κ and growing into their incoherent interfaces with γ. As this cellular structure decorates the grain boundaries, the fracture type changed from ductile to intergranular brittle fracture. The grain boundary cracks initiated at the coarse grain boundary κ-carbide and propagated through the {100} planes of α and κ. The lowest theoretical cohesive strengths in the {100} planes of both phases are suggested as the origin of the crack initiation and propagation.

A Scalar Approach to Vaccination Ethics

Should people get vaccinated for the sake of others? What could ground—and limit—the normative claim that people ought to do so? In this paper, we propose a reasons-based consequentialist account of vaccination for the benefit of others. We outline eight harm-based and probabilistic factors that, we argue, give people moral reasons to get vaccinated. Instead of understanding other-directed vaccination in terms of binary moral duties (i.e., where people either have or do not have a moral duty to get vaccinated), we develop a scalar approach according to which people can have stronger or weaker moral reasons to get vaccinated in view of the moral good of vaccination. One advantage of our approach is that it can capture why a person might have strong moral reasons to get vaccinated with Vaccine A, but only weak moral reasons to get vaccinated with Vaccine B. We discuss theoretical strengths of our approach and provide a case study of vaccination against COVID-19 to demonstrate its practical significance.

First-Principles Computation of Microscopic Mechanical Properties and Atomic Migration Behavior for Al4Si Aluminum Alloy

In this paper, the interfacial behavior and the atom diffusion behavior of an Al4Si alloy were systematically investigated by means of first-principles calculations. The K-points and cutoff energy of the computational system were determined by convergence tests, and the surface energies for five different surfaces of Al4Si alloys were investigated. Among the five surfaces investigated for Al4Si, it was found that the (111) surface was the surface with the lowest surface energy. Subsequently, we investigated the interfacial stability of the (111) surface and found that there were two types of interfaces, the Al/Al interface and the Al/Si interface. The fracture energies and theoretical strengths of the two interfaces were calculated; the results show that the Al/Al interface had the highest interfacial strength, and the calculation of their electronic results explained the above phenomenon. Subsequently, we investigated the diffusion and migration behavior of Si atoms in the alloy system, mainly in the form of vacancies. We considered the diffusion of Si atoms in vacancies of Al and Si atoms, respectively; the results showed that Si atoms are more susceptible to diffusive migration to Al atomic vacancies than to Si atomic vacancies. The results of the calculations on the micromechanics of aluminum alloys, as well as the diffusion migration behavior, provide a theoretical basis for the further development of new aluminum alloys.

The Impact of Aspect Ratio, Characteristic Strength and Compression Rebars on the Shear Capacity of Shallow RC Beams

This paper investigates the impact of the aspect ratio, the characteristics strength of the concrete, and the compression steel ratio on the shear capacity of wide-shallow beams. An experimental program consists of seven specimens, including a control specimen, all tested under a three-point load test. Three specimens were considered for each parameter (the control specimen was included in all three variables). The experimental results were compared to the theoretical values of six different codes of practice; they were also analyzed to determine the ductility, stiffness, and dissipated energy of each specimen. The results indicated that the shear reinforcement was fully functioning until it yielded, with a minimum contribution of 55% of the total shear capacity of the specimens. The aspect ratio and the characteristic strength had a notable impact on the shear capacity of the specimens, while the compression steel ratio had a minor effect on the shear capacity, but it improved the stiffness and the ductility of the beams. Theoretical concrete shear strengths from design codes ranged between 77 and 163% of the experimental values; EN-1992 was the closest code to the experimental results. A comparison between the experimental results and predicted values using GP and EPR methods from previous research showed accuracies of 72% and 81%, respectively. Doi: 10.28991/CEJ-2023-09-09-012 Full Text: PDF

Artificial Intelligence in Predicting Mechanical Properties of Composite Materials

The determination of mechanical properties plays a crucial role in utilizing composite materials across multiple engineering disciplines. Recently, there has been substantial interest in employing artificial intelligence, particularly machine learning and deep learning, to accurately predict the mechanical properties of composite materials. This comprehensive review paper examines the applications of artificial intelligence in forecasting the mechanical properties of different types of composites. The review begins with an overview of artificial intelligence and then outlines the process of predicting material properties. The primary focus of this review lies in exploring various machine learning and deep learning techniques employed in predicting the mechanical properties of composites. Furthermore, the review highlights the theoretical foundations, strengths, and weaknesses of each method used for predicting different mechanical properties of composites. Finally, based on the findings, the review discusses key challenges and suggests future research directions in the field of material properties prediction, offering valuable insights for further exploration. This review is intended to serve as a significant reference for researchers engaging in future studies within this domain.