Past Studies Research Articles

Experimental planning analysis of cement pastes using cement for oil wells, microsilica and superplasticizer

The study and development of cement pastes are essential to determine the properties of matrices with cement for oil wells. Using different mixtures and adaptations requires analysis and verifications for each product generated. Thus, it is observed that additions and additives can contribute to forming cement matrices with predetermined properties. Thus, this work presents the study of the viscosity of pastes through the Marsh Funnel and Mini-Slump tests using mixtures with oil well cement (OWC) with additions of micro silica and superplasticizer in different proportions. In this context, a 3³ factorial experimental design and replications are presented considering the variables of active silica content, water/binder ratio (w/c), and superplasticizer content. The Statistica software obtains the response surface and different significance coefficients for each variable and their interactions in the process, thus optimizing the matrix for the desired cement paste. Finally, the statistical influence of each of the variables analyzed is analyzed, observing that the proportion between cement and silica is mainly relevant to the viscosity of the paste.

A Numerical Study of Flow Past a Wall-Mounted Dolphin Dorsal Fin at Low Reynolds Numbers.

Dolphin swimming has been a captivating subject, yet the dorsal fin's hydrodynamics remain underexplored. In this study, we conducted three-dimensional simulations of flow around a wall-mounted dolphin dorsal fin derived from a real dolphin scan. The NEK5000 (spectral element method) was employed with a second-order hex20 mesh to ensure high simulation accuracy and efficiency. A total of 13 cases were simulated, covering angles of attack (AoAs) ranging from 0° to 60° and Reynolds numbers (Re) between 691 and 2000. Our results show that both drag and lift increase significantly with the AoA. Almost no vortex was observed at AoA=0°, whereas complex vortex structures emerged for AoA≥30°, including half-horseshoe, hairpin, arch, and wake vortices. This study offers insights that can inform the design of next-generation underwater robots, heat exchangers, and submarine sails.

THE THIRD RENAISSANCE MOVEMENT IN UZBEKISTAN

This article examines the periods of rapid development in science and culture in Central Asia, specifically the First and Second Renaissance periods and their essence. It also addresses the activities, exemplary lives, and unique works of the great thinkers who lived and worked during those times. The article provides analytical insights into the glorious history of Mavarannahr, the gradual decline of science in the region, the processes leading to the end of statehood, and their causes and consequences. It offers relevant information on the scientific study of the great past, the lives and spiritual legacy of the scholars of the First and Second Renaissance periods, and the historical foundation for the Third Renaissance, as well as its relevance to real life, along with appropriate conclusions and suggestions.

Archaeology meets environmental genomics: implementing sedaDNA in the study of the human past

Sedimentary ancient DNA (sedaDNA) has become one of the standard applications in the field of paleogenomics in recent years. It has been used for paleoenvironmental reconstructions, detecting the presence of prehistoric species in the absence of macro remains and even investigating the evolutionary history of a few species. However, its application in archaeology has been limited and primarily focused on humans. This article argues that sedaDNA holds significant potential in addressing key archaeological questions concerning the origins, lifestyles, and environments of past human populations. Our aim is to facilitate the integration of sedaDNA into the standard workflows in archaeology as a transformative tool, thereby unleashing its full potential for studying the human past. Ultimately, we not only underscore the challenges inherent in the sedaDNA field but also provide a research agenda for essential enhancements needed for implementing sedaDNA into the archaeological workflow.

Образ Средневековья в трилогии Итало Кальвино «Наши предки»

The article delves into the study of the medieval past in the European historical consciousness and cultural memory after the World War II. Reception and representation of the Middle Ages are considered as constants of the development of European and universal culture. The main subject of analysis is the image of the Middle Ages constructed in the fiction of the period. The focus of the study is the trilogy “Our Ancestors” (1960) by the Italian writer, publicist, literary critic Italo Calvino (1923–1985). The image of the Middle Ages in Calvino’s novels is considered in the context of understanding the European Enlightenment and current historical and philosophical reflection. The ways of constructing the image of the Middle Ages in Calvino’s texts are revealed, also its relationship with history, literature and folklore is examined. The study of the image of the Middle Ages can be useful both for clarifying the peculiarities of historical representations of his time and for understanding the epoch itself, which gave rise to the image.

Preparation of Paste Filling Body and Study on Supported Transportation Laws Using Flac3D Simulation

This paper proposes a new type of gangue filling body (GFB) to address the issues of the low stability, strength, poor shrinkage performance, and inadequate seepage resistance of paste filling materials in overburdened mining conditions, as well as the challenge of fully utilizing solid waste gangue. The coal gangue (CG), U-expanding agent (UEA), and amount of water added were kept constant, and the mass ratio of the various components was adjusted to the design. The standard for filling was assessed using slump tests, uniaxial compression tests, shrinkage tests, and penetration tests. A further microscopic analysis of the pastes with an optimal filling performance was conducted using SEM. The support pressure and overburden migration patterns in the GFBs were evaluated using Flac3D. The results indicate that the GFB with ratio 4 performed best, highlighting the significant role of Portland cement (OPC). The GFB with ratio 3 demonstrated the second-best performance, suggesting that GFBs with a higher early strength should be chosen to fill hollow zones for an effective filling outcome. This study introduced a new type of paste filling material and confirmed the rock transport law of this material under overburdened conditions using Flac3D, offering significant insights for the engineering field.

Ergonomic evaluation of upper extremities muscle activity pattern during 60-min smartphone texting.

Smartphone usage has increased rapidly in the last decade due to rapid technological advancements. This extensive usage of smartphones led to physiological problems and musculoskeletal disorders (MSD) due to inappropriate postures. Past studies have reported the effects/discomfort of smartphone usage for short periods, ranging from 3-20 min, which does not represent the current era of smartphone dependency (approximately 7-hr/day). This study was performed on fifty-four participants aged 20-28 with 1-hr smartphone texting in a sitting posture. Flexion angles, both sides (dominant and non-dominant) muscle activity (maximum voluntary contraction %) at sternocleidomastoid (SCM), upper-trapezius (TRP), extensor digitorum (EDM) and abductor pollicis brevis (APB) muscles, and subjective discomfort were analyzed. After 1-hr smartphone texting, the muscle activity at eight upper extremities: SCM (24.80%), TRP (29.45%), EDM (14.44%) and APB (19.87%) significantly (p < 0.001) increased by 1.5-1.9 times with 27.4±3.18° and 82.94±7.03° head and lower-arm flexion angles, respectively. The mechanical loads on the cervical spine increased by 4.6 times, and subjective discomfort by 3 times. Maintaining the same posture for a long duration causes postural stress, muscular imbalances, and discomfort, leading to MSD with increased cervical intervertebral disc pressure.

СТАНОВЛЕННЯ УКРАЇНСЬКО-РУМУНСЬКИХ ВІДНОСИН КРІЗЬ ПРИЗМУ АРТІЛЬНОЇ КУЛЬТУРИ

The updating of bilateral relations in modern political science is designed to rethink the entire existing system of international relations. Interstate relations are the complex and multi-stage process, where the issue of intercultural com- munication is undeniably important. The author emphasizes that culture primarily serves as a background that helps build bilateral relations and smoothes out the negatives of misunderstandings or disputes that arise over long years of shared history. Common cultural heritage becomes the driving force that stimulates the search for a common solution and an adequate response to the challenges of the time for the sake of maintaining bilateral relations and peace in the world. Culture occupies an important place in relations between Ukraine and Romania, as it accelerates reconciliation and ensures the cohesion of neighbouring peoples. At the moment, there is a spiritual revival and self-affirmation of independent Ukraine. An important component of the regeneration of society is a deep study and comprehension of the historical past, the restoration and preserva- tion of cultural memory, the formation of national patriotism, civic position and awareness of oneʼs own responsibility for the preservation of both the inherited cultural heritage and the Ukrainian culture that is being formed today in times of war. The objective basis for the formation of new approaches in the field of cultural and humanitarian cooperation with Romania is its unconditional support for Ukraine from the first days of the war, the unprecedented solidarity of Ro- manian society with the Ukrainian people in their struggle to defend the na- tional sovereignty, territorial integrity and inviolability of Ukraineʼs borders, Romaniaʼs strong condemnation of moscowʼs criminal actions, Bucharestʼs comprehensive encouragement of the European integration aspirations of our country to the Euro-Atlantic area. The author explored the origin and beginning of the cultural ties’ formation between Ukraine and Romania through the prism of civilizational development and common heritage – the culture of Trypillia-Cucuteni. The author differen- tiates between the concepts of «Old Europe» and «New Europe», reveals the uniqueness of the culture of Trypillia-Cucuteni as an eastern outpost of Europe- an civilization and analyzes it in the context of the modern Russian-Ukrainian war, presents the museum dimension of the culture of Trypillia-Cucuteni, high- lights language and traditions as codes for understanding culture and represents the common culture as the key to successful bilateral intercultural communica- tion.

Mechanical, Rheological, and Microstructural Study of Ternary Alkali-Activated Pastes Using BOF Slag, Metakaolin, and Glass Powder as Precursors

Mechanical, Rheological, and Microstructural Study of Ternary Alkali-Activated Pastes Using BOF Slag, Metakaolin, and Glass Powder as Precursors

Linking formulation feedstock to printability by robocasting: A case study of eco-friendly alumina pastes

Robocasting stands as a pertinent additive manufacturing technique for producing intricate ceramic parts. Amidst stricter environmental regulations, the adoption of natural additives becomes imperative. This study investigates the influence of plant-based additives on the rheology and printability of eco-friendly pastes.Various 50 vol%-alumina pastes were formulated using natural binders, plasticizers and dispersants (e.g., lignosulfonate, polysaccharides, glycerol) and then assessed through oscillation and flow rheological analyses. Paste viscosity and rigidity often deviated from printability maps reported in the literature, showing the complexity of defining universal printability criteria. A comprehensive investigation was conducted on the water retention capabilities of additives, liquid phase migration and paste drying kinetics.This paper highlights the critical importance of constraining liquid phase migration within eco-friendly ceramic pastes and the crucial role of polymer chain reorientation under shear. Consequently, this research lays diversifying formulations, offering sustainable solutions for industrial ceramic applications.

Race, Racism, and Ethnicity

This article examines the debates over historiographical uses of the terms race, racism, and ethnicity in the study of the premodern past. It begins with an analysis of conventional approaches to defining race, which understand the concept to be fundamentally modern and reject uses of the term in the study of the premodern world. Such conventional approaches to historicizing race are predicated on problematically essentialist definitions of the term that preclude comparisons of varying types of racisms that manifest across different historical periods. The article spotlights some of the arguments in favor of formulations of race and racism that allow for comparative analyses of premodern instances of racism, relying on the ideas of scholars working in race theory, philosophy of race, and premodern critical race studies. It also puts forward a working model of racism useful for analyzing examples of race-thinking found in Christian texts of the late antique period, focusing specifically on negative significations of blackness. Broadly, the article aims to outline more dynamic and fruitful approaches to conceptualizing race, racism, and ethnicity in the study of the ancient world.

The Evolution of Entrepreneurship: A Comparative Study of Perspectives Past, Present, and Future

Entrepreneurship has become an important element in the economic and social development of a country. This research aims to analyze the development of entrepreneurship from the past to the present, as well as predict how entrepreneurship will develop in the future. Social, economic, and cultural factors that influence society's views on entrepreneurship will be explored to gain a comprehensive understanding. Through comparative analysis, it is hoped that changes and continuity in entrepreneurship throughout history can be revealed, as well as the opportunities and challenges that will be faced in the future era. The data and information in this research were collected from various sources, including academic literature, industry publications, and statistical reports. It is hoped that the findings of this research will provide valuable insights for academics, practitioners, and policymakers in the field of entrepreneurship

Fly ash-GGBS blended geopolymer mortar for early engineering characteristic at ambient temperature

Geopolymer concept is by using industrial waste materials which is rich in silica and alumina, then activating them with alkaline solution. An appropriate binder combination that achieves high early age strength at ambient temperature using FA is still subject required. Thus, this study has been designed in two stages which involving the paste and mortar studies. The alkaline activator as a blend of sodium hydroxide and sodium silicate solution with SS/SH ratio of 2.5, NaOH molarity of 12 M and L/B ratio of 0.43 are used for geopolymer composite. Compressive strength, water absorption and shrinkage are tested on geopolymer mortar with various level of blended combination. High volume content (60–80 %) gave a promising early age compressive strength at ambient temperature. Metakaolin gave a further strength improvement on geopolymer mortar. Overall, the finding suggested that the geopolymer with high FA content is suitable for cement-based material repair product.

Do you cite what you tweet? Investigating the relationship between tweeting and citing research articles

Abstract The last decade of altmetrics research has demonstrated that altmetrics have a low to moderate correlation with citations, depending on the platform and the discipline, among other factors. Most past studies used academic works as their unit of analysis to determine whether the attention they received on Twitter was a good predictor of academic engagement. Our work revisits the relationship between tweets and citations where the tweet itself is the unit of analysis, and the question is to determine if, at the individual level, the act of tweeting an academic work can shed light on the likelihood of the act of citing that same work. We model this relationship by considering the research activity of the tweeter and its relationship to the tweeted work. The results show that tweeters are more likely to cite works affiliated with their same institution, works published in journals in which they also have published, and works in which they hold authorship. It finds that the older the academic age of a tweeter the less likely they are to cite what they tweet, though there is a positive relationship between citations and the number of works they have published and references they have accumulated over time.

Stability Analysis and Robust Parameter Design of DC-Voltage Loop for Three-Phase Grid-Connected PV Inverter Under Weak Grid Condition

In the grid-connected inverter, both the PLL (phase-locked loop) and DVL (DC-voltage loop) can lead to the frequency coupling in the weak grid. Instabilities caused by PLL frequency coupling have been widely discussed. For DVL, past studies have analyzed the effect of DVL parameters on the degree of frequency coupling, but it is quite unclear how DVL parameters affect the inverter stability and how DVL can be designed under the weak grid. Hence, by fully considering the abovementioned frequency coupling, an accurate admittance model of PV (photovoltaic) grid-connected inverter is established in this study. By deriving the modified admittance matrix, the effects of grid impedance and DVL parameters on the frequency coupling are clearly studied. In addition, by modeling the equivalent inverter output impedance, the impact of DVL on the inverter stability under the weak grid is revealed. As proved, the increase of DVL bandwidth <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vbw</sub> and grid impedance will aggravate the frequency coupling, but the current distortion does not necessarily increase. Meanwhile, the increase of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vbw</sub> helps to improve the inverter stability under the weak grid. Accordingly, a novel design for DVL in the weak grid is proposed. Experiments verify the correctness of the analysis and design.

A systematic review on the formative assessment practice in teaching and learning in secondary school

Formative assessment is an assessment that is conducted throughout the teaching and learning process. Therefore, teachers should play an important role in mastering the appropriate approaches to practicing formative assessment. According to previous studies, some teachers are unable to comprehend the roles of formative assessment practices in teaching and learning, which prevents them from using them effectively in the classroom. Many researchers have conducted research related to the practice of formative assessment in schools due to this issue. Therefore, this article aims to conduct a systematic literature review (SLR) on past studies related to the practice of formative assessment in teaching and learning in secondary schools. This SLR writing process has been referred to as the Preferred Reporting Items for systematic review and meta-analysis (PRISMA) writing standard. To find related articles and resources in this systematic literature review, two main databases, namely Web of Science and Scopus, were used. A total of 19 articles were extracted from 366 from 2017 to 2021, with exceptions and inclusion criteria considered. Based on the theme analysis, this SLR has three main themes: assessment diversity; assessment strategies, and student learning development. Thus, this study suggests that all compulsory levels of education understand formative assessment conceptually and its implementation comprehensively. This can be disseminated through teacher professional development training programs. It is hoped that such programs will develop teachers who are committed to integrating the concept and practice of assessment for the benefit of students in twenty-first century education.

Sport, migration and diaspora: the case of Ivorian track and field athletes

PurposeThis study focused on Ivorian track and field athletes who were current or former members of the Ivorian national team to understand athletes’ experiences with migration, diaspora and sport.Design/methodology/approachParticipatory action research (PAR) methodology was used in this research study (Lenette and Nesvaderani, 2021). According to Schinke and Blodgett (2016), PAR is a type of qualitative research used to engage the researcher and researched. The researcher and researched work together to understand the issues of a situation and communicate a plan to work toward resolving those issues (Kemmis et al., 2014). Using PAR helped to engage multiple people in the study, and as more research studies explore forced migration and sport, more scholars are starting to lean on the methodology to create a more diverse perspective and to include marginalized populations in the world of scholarly research (Stone, 2018; Robinson et al., 2019).FindingsKey findings illustrate Ivorian athletes’ ability to forge a bond that transcended tribal and political differences through geographical proximity and sport opportunity, allowing them to (re)connect with their Ivorian diaspora by representing the national team.Originality/valueThis research paper expands on past studies in sport and migration by showcasing the fluid nature of how diaspora constructs an athlete’s national identity once they are forced to leave their homeland.

Marine lebensspuren: improving the classification of seafloor traces from underwater imagery and observations

Taxonomy is a dynamic and evolving scientific field in biological and paleontological research, which describes and systematises species and other taxa and thus lays the foundation to solve and structure biological questions. The study of past (fossil) and modern (present) seafloor traces holds huge potential for understanding the composition, behavioural ecology, and ecosystem impact of benthic communities, e.g., in terms of bioturbation and carbon cycling. In trace fossil research (paleoichnology), ichnotaxonomical analysis is based on the application of ichnotaxobases, morphology being the most important and useful criterion. However, marine neoichnological analyses (modern traces; lebensspuren) have no standardised ichnotaxobases. In the literature, classification based on morphological descriptions or behavioural assignations can be found, but without consensus. This lack of standardised terminology hinders comparisons among studies and regions. Through this manuscript, we discuss the limitations of marine lebensspuren characterisation through underwater observations and how further classification could be done (i.e., possible ichnotaxobases). Considering that most of the classifications will be based on marine still images, we propose a classification for marine lebensspuren based on a combination of three labels: 1) morphology (e.g., M-ridged trail), 2) behaviour determination (e.g., locomotion and feeding), and 3) tracemaker taxonomy (e.g., Echinocrepis rostrata). Accordingly, the classification will be 1) M-ridged trail 2) Locomotion and feeding 3) Echinocrepsis rostrata. A set of recommendations is given to address all three labels. Also, we describe some of the contrasting positions of paleo- and neoichnology, particularly where a solution presently seems difficult to find, and argue that open nomenclature could be useful as still images contain large amounts of information. Finally, we provide examples of the usage of this classification for input to a marine lebensspuren online repository and how this nomenclature can help to compare worldwide lebensspuren in a consistent way.

DNA metabarcoding reveals ecological patterns and driving mechanisms of archaeal, bacterial, and eukaryotic communities in sediments of the Sansha Yongle Blue Hole

The Sansha Yongle Blue Hole (SYBH) is the world’s deepest marine blue hole with unique physicochemical characteristics. However, our knowledge of the biodiversity and community structure in SYBH sediments remains limited, as past studies have mostly focused on microbial communities in the water column. Here, we collected sediment samples from the aerobic zone (3.1 to 38.6 m) and the deep anaerobic zone (150 m, 300 m) of the SYBH and extracted DNA to characterize the archaeal, bacterial, and eukaryotic communities inhabiting these sediments. Our results showed that the archaeal and bacterial communities were dominated by Thaumarchaeota and Proteobacteria, respectively. The dominant taxa of eukaryotes in different sites varied greatly, mainly including Phaeophyceae, Annelida, Diatomea and Arthropoda. All three examined domains showed clear vertical distributions and significant differences in community composition between the aerobic and anaerobic zones. Sulfide played a prominent role in structuring the three domains, followed by salinity, nitrous oxide, pH, temperature and dissolved oxygen, all of which were positively correlated with the turnover component, the main contributor to beta diversity. Neutral community model revealed that stochastic processes contributed to more than half of the community variations across the three domains. Co-occurrence network showed an equal number of positive and negative interactions in the archaeal network, while positive interactions accounted for ~ 80% in the bacterial and eukaryotic networks. Our findings reveal the ecological features of prokaryotes and eukaryotes in SYBH sediments and shed new light on community dynamics and survival strategies in the special environment of marine blue holes.

Loanwords in Basic Vocabulary as an Indicator of Borrowing Profiles

Abstract Loanwords carry information on linguistic interactions, and can also reveal (pre-)historical population contacts. The contact history of a particular language family is an essential component of historical linguistics, but it is also illuminating for integrative studies of the human past. However, data availability and the time-consuming nature of etymology mean that comprehensive research on loanword layers exists for relatively few languages, forcing us to rely on limited material for others. This paper compares the loanword layers in the basic and total vocabulary of six well-studied Uralic languages, assessing how accurately the borrowing profile in basic vocabulary reflects the full profile of a language. We define “borrowing profile” as the known contact history of a language reflected by its loanword layers. We demonstrate that the loanword layers in basic vocabulary provide an adequate cross-section of the full borrowing profile, although basic vocabulary manifests prehistoric contacts more strongly than more recent contacts.