Search Results (21,296)

In this study, we introduce the generalized Repunit sequence and its hybrid quaternion extension derived from a parametric recurrence relation that preserves the base-10 structure of classical Repunit numbers. Fundamental properties of the proposed sequences, including the characteristic equation, generating function, and Binet-type formula, are systematically investigated. Several algebraic identities, such as bilinear index-reduction formulas, are established to demonstrate the internal structure and consistency of the construction. Numerical experiments and graphical analyses are conducted to examine the structural behavior of the generalized Repunit sequence and its hybrid quaternion counterpart. While the scalar Repunit sequence exhibits regular and predictable growth, the hybrid quaternion extension displays significantly higher structural complexity and variability. Density distributions, contour plots, histogram representations, and discrete variation measures confirm the presence of enhanced diffusion and local irregularity in the quaternion-based structure. These statistical, graphical, and numerical findings indicate that generalized Repunit hybrid quaternion sequences possess properties that are relevant to encoding, masking, and preprocessing mechanisms in applied mathematical and computational frameworks. However, this work does not propose a complete cryptographic algorithm, nor does it claim compliance with established cryptographic security standards such as NIST SP 800-22. The results should therefore be interpreted as pre-cryptographic indicators that motivate further research toward rigorous security evaluation, algorithmic development, and broader applications in areas such as coding theory, signal processing, and nonlinear dynamical systems. Full article

Soil erosion in the purple soil region presents severe challenges with complex driving mechanisms. At the same time, evaluation and prediction of runoff and sediment dynamics are lacking for natural vegetation restoration in bare areas. The Mann–Kendall and Pettitt tests were employed to identify abrupt shift points in runoff and sediment dynamics, utilizing monitoring data from the Suining Soil and Water Conservation Experimental Station over the period from 1984 to 2018. Therefore, the research periods were divided into a baseline period (1984–1992) and an evaluation period (1993–2018). Subsequently, encompassing rainfall, runoff, sediment, topography, soil properties, and vegetation parameters, a Water Erosion Prediction Project (WEPP) model was established to quantify the reduction benefits of runoff and sediment during the period of forest restoration. We found that the calibrated WEPP model demonstrated satisfactory performance based on Nash–Sutcliffe efficiency coefficients (NSE > 0.5) and determination coefficients (R² > 0.5) for runoff and sediment simulations. The WEPP model and double-mass curve analysis method revealed that forest restoration reduced runoff and sediment by more than 80%. It is recommended to implement artificial vegetation restoration before reaching the threshold for natural vegetation restoration to achieve soil and water conservation goals. Full article

The oxidation of sulfide minerals in the presence of oxygen and water, facilitated by microbes, is the principal cause of acid mine drainage (AMD). Static testing for the quantitative assessment of the acidic potential and acid-neutralizing capacity of mineral samples has been thoroughly investigated; the extent of its accuracy remains uncertain. This study involved 329 ore samples from 34 drill holes from abandoned mining sites and conducted laboratory static tests and mineralogical analysis. Static testing and mineralogical characterization identified a significant positive correlation between total sulfur and net acid generation (NAG), confirming that sulfide oxidation is the dominant mechanism for acid production. Furthermore, the strong positive correlation between calcium content and acid-neutralizing capacity (ANC) demonstrates that the buffering capacity stems mainly from carbonate dissolution, with negligible contribution from silicate weathering. The effectiveness of a detailed acid-generating potential discrimination chart was also assessed. Through the examination of acid drainage samples and groundwater from the research area, with their stable isotope and Deuterium excess (D-excess) properties, hydrochemical classifications were established, and sources of acid drainage were evaluated. This comprehensive method pinpoints the main “acid-generating sources” in the abandoned mining sites, elucidating the geochemical origins of acid drainage in the research area. It offers a case study and analytical framework for employing static test findings from abandoned mining sites to evaluate acid-generating potential in those areas. Full article

Wood–polymer composites (WPCs) consistently garner considerable attention owing to their material versatility and sustainability, resulting in numerous review studies across diverse disciplines. Nonetheless, since a comprehensive synthesis that consolidates these disparate reviews is lacking, this study performs a meta-synthesis of review articles focused on WPCs employing a science-mapping approach enhanced by CiteSpace software. A systematic search of the Web of Science Core Collection (last updated in June 2025) was conducted, yielding 51 review-type articles selected using PRISMA screening guidelines. Network-based co-citation, clustering, and keyword analyses reveal that recent WPC research centers on three interconnected areas: (i) reinforcement and interfacial engineering, (ii) processing–structure–property relationships, and (iii) sustainability-focused design involving recycling, fire safety, thermal pretreatment, and PCM-based thermal management. Sixteen author/reference clusters and nine keyword clusters highlight well-defined knowledge communities on durability and fire safety, nano- and bio-based reinforcements, recycled and bioplastic matrices, and advanced manufacturing techniques such as co-extrusion, flat-pressing, 3D printing, and wood–polymer impregnation. Timeline and burst analyses show that mechanical performance remains the primary focus, while emerging areas include recycled/waste-derived polymers, cellulose micro- and nanofibers, moisture-resistant hybrids, and wood-based additive manufacturing for construction applications. Full article

The rapid proliferation of artificial intelligence (AI) systems across high-stakes domains—with global AI adoption accelerating since 2023—has created an urgent need to identify which AI challenges and issues are materializing into real-world harms so that policymakers can develop targeted regulations, organizations can implement effective risk management, and accountability mechanisms can address actual rather than speculative problems. Public concern has risen sharply: 52% of Americans now feel more concerned than excited about AI (up from 38% in 2022), and 80% believe government should maintain AI safety rules even if development slows. Yet existing approaches exhibit critical limitations that impede evidence-based governance. Ethics frameworks, while establishing normative principles across 84+ published guidelines, remain aspirational rather than empirical. Survey-based studies capture perceptions from over 48,000 respondents globally but measure expectations rather than documented harms. Incident databases catalog over 1200 AI failures but depend on media coverage, systematically overrepresenting high-profile cases while underrepresenting routine organizational problems. This study addresses this gap by analyzing 347 AI-related U.S. litigation cases using machine learning text analytics, providing empirical evidence of AI problems that have crossed the threshold from abstract concern into documented legal conflict. Employing Latent Dirichlet Allocation (LDA) and Non-negative Matrix Factorization (NMF) topic modeling with coherence validation (NMF achieving 0.276 NPMI vs. LDA’s 0.164), the analysis identifies nine distinct AI issue areas with specific case distributions: cybersecurity vulnerabilities and data breaches (116 cases, 33.4%), intellectual property and AI ownership (61 cases, 17.6%), AI misrepresentation and inflated claims (59 cases, 17.0%), criminal justice and algorithmic due process (37 cases, 10.7%), employment automation (33 cases, 9.5%), privacy and surveillance (31 cases, 8.9%), platform accountability (21 cases, 6.1%), algorithmic bias (19 cases, 5.5%), and government AI deployment (6 cases, 1.7%). The findings reveal a systematic mismatch between AI ethics discourse—which emphasizes fairness and transparency—and litigation patterns, where data security (33.4%) and intellectual property (17.6%) dominate while algorithmic bias comprises only 5.5% of cases. Most disputes are addressed through existing legal frameworks (First Amendment, Lanham Act, FOIA, Title VII) rather than AI-specific regulation, underscoring the urgent need for governance mechanisms aligned with empirically documented AI challenges. Full article

Background: In recent years, hyaluronic acid filler for the restoration and increase in buttock volume has been a procedure that has seen increasing success, both thanks to the considerable increase in patient demand and thanks to the improvement of implant techniques and device manufacturing technologies. Aims: The primary objective of this pilot study is to demonstrate the validity of an innovative filler inoculation technique in the upper quadrants of the buttocks and in the supra- and subfascial area in order to optically restore the appearance of a pleasant lumbar lordosis and to lift the upper quadrants with reduction in the infragluteal fold. The secondary objective is to evaluate the safety and efficacy of Sofiderm SubSkin^® (Techderm Biological Products Co., Ltd., Hangzhou, China), a highly versatile hyaluronic acid filler, formulated with a rheology suitable for use on the face and body. Patients/Methods: Five female subjects (50–63 years) were subjected to gluteal fillers in the supra- and subfascial areas; the correct positioning of the filler was investigated by means of a 20 Mhz ultrasound probe. Results: All patients obtained a significant improvement in the projection of the upper part of the buttocks. The implantation technique and the optimal rheological properties of the device brought about a natural and well-defined increase in volume, with a projection of the upper part of the buttocks and a consequent lifting of the lower parts and reduction in the length of the infragluteal fold. Conclusions: This study confirmed the efficacy and safety of the cross-linked hyaluronic acid Sofiderm Derm SubSkin^® in increasing the projection of the upper part of the buttocks, using an innovative mixed implantation technique, in a sample of selected patients. Full article

As the global population continues to expand and demand for protein increases, alternative proteins (e.g., edible insect proteins, microalgae proteins, fungal or bacterial proteins) have emerged as a significant area of research interest due to their high nutritional value and sustainability. However, these novel protein sources may contain allergenic components, such as tropomyosin and arginine kinase in insects, phycocyanin in microalgae, and ribosomal proteins in fungi, which may trigger allergic reactions and cross-reactivity with traditional allergens. In this review, we systematically retrieved published studies from databases including PubMed and Web of Science, employing keywords such as microbial proteins, edible insects, and allergenicity. Articles were screened based on their relevance to allergenic properties and processing effects, with selected studies subjected to thematic analysis. The present paper reviews the allergenic properties of edible Insects, microalgae, and microorganisms’ proteins and their molecular mechanisms, and explores the effects of various processing techniques (e.g., heat treatment, enzymatic hydrolysis, high-pressure treatment, and glycosylation) on the reduction of allergenic activity. It was determined that the impact of processing methodologies is contingent on protein structure, with certain techniques having the potential to augment sensitization through epitope exposure. Furthermore, there are still gaps in the current research on the reduction in allergenicity of microbial and algal allergens, and future research should focus on the in-depth characterization of allergenic protein structures and the development of novel sensitization reduction techniques. This review provides a significant reference point for the safe development and rational application of edible insects, microalgae, and microorganisms proteins, which is of great importance for the development of sustainable food systems. Full article

A batch of drill pipe joints in a well cracked and failed due to hardbanding. In this study, various experiments were conducted to analyze the reasons for cracking failure, including data verification, macroscopic morphology analysis, mechanical properties, microstructure analysis, and micro-Vickers hardness of cracked areas, as well as macroscopic, metallographic, and energy spectrum analysis of the fracture surface after opening the cracked area. The results indicated that (1) the chemical composition, tensile strength, Charpy impact test, and Brinell hardness results of the joint met the requirements of the order technical conditions. (2) The hardbanding in the cracked area had multiple pores and cracks on its outer surface and inside. The maximum diameter of the internal porosity was about 3.4 mm, and the length of the internal crack was about 1 mm. (3) The main reason for the cracking of a batch of drill pipe joints due to hardbanding is a quality problem of the secondary repair welding of the hardbanding. The cracks in the failed drill pipe originated from the porosity and cracks in the hardbanding of the drill pipe box joint. Under the influence of alternating stress and high-pressure mud erosion underground, the cracks rapidly extended to the inner wall, and the porosity in the hardbanding accelerated crack propagation, ultimately causing the drill pipe to crack and fail. Full article

The development of dental restorative materials with improved physical and mechanical properties is an important area of research. In this study, hexaallylaminocyclotriphosphazene (HAP) was used to modify dental composites. HAP is a compound with multiple carbon-carbon bonds that can react with methacrylic resins to form a copolymer. HAP was synthesized by reacting allylamine with hexachlorocyclotriphosphazene and characterized it using ¹H and ³¹P NMR spectroscopy and MALDI-TOF mass spectrometry. Molecular dynamics simulations using the MM2 force field showed that HAP has a nanosize (the diameter of a sphere eclosing the molecule is 1.3 nm), making it a suitable nanomodifier for dental composites. Using 3D printing, samples of dental methacrylic composites containing up to 10 wt. % HAP were prepared and their physicomechanical properties and antibacterial activity against gram-positive bacteria S. mutans were studied. As a result, it was established that the maximum flexural strength (115.1 ± 10.2 MPa) is achieved with a modifier content of 5 wt.% in the composite. The maximum value of inhibition of S. mutans growth in a liquid nutrient medium is achieved with a HAP content of 10 wt.% in the sample. Furthermore, with a HAP content of more than 5 wt.% in the composite, inhibition of biofilm on the material surface is observed. The resulting composite is proposed for use as dental crowns in restorative dentistry. Full article

This paper discusses the application of on-chip terahertz (THz) filters attached to waveguides that can act as sensor elements, including for scanned imaging applications. Our work presents a comparative numerical study of several different geometries (comprising five split-ring resonator geometries and a quarter-wavelength stub resonator, the latter being well established as a sensor at THz frequencies and therefore able to act as a benchmark). We designed each structure to have a resonant frequency of 500 GHz, allowing the impact of resonator geometry on sensing performance to be isolated; the performance was quantified by assessing each design using four figures of merit: resonance quality factor, sensitivity (relative frequency shift under dielectric loading), responsivity (sensitivity weighted by resonance sharpness), and the electric field confinement area. Simulations were conducted using Ansys HFSS using the properties of a commercially available photoresist (Shipley 1813) as a dielectric load to assess performance under conditions comparable to previous experimental studies. The analysis showed that while sensitivity remained broadly similar across geometries, responsivity and quality factor differed substantially between resonators. Furthermore, the spatial distribution of the electric field and current density, particularly in rotated configurations, was found to significantly impact coupling efficiency between the resonator and transmission line. Our findings provide guidance for the general design of systems employing THz sensors while establishing a framework with which to benchmark future sensor geometries. Full article

Biochar has emerged as a promising material for carbon storage, exhibiting properties analogous to those of activated carbon. Biochar has a particularly high absorbance due to its high porosity, surface area, and functional groups, although these parameters depend on the feedstock and pyrolysis conditions. The sorbent properties of biochar make it suitable for many applications, including the biological treatment of organic waste. In the context of composting, biochar addition seems to positively impact the process performance and the final compost characteristics. Furthermore, it reduces greenhouse gas and odor emissions, which is a crucial step in preventing the full implementation of composting. The objective of this review is to provide a comprehensive description of the effects of biochar on composting emissions and the reported mechanisms, highlighting the limitations of current research. In summary, the use of biochar in composting is still in its early stages and requires further research and consensus on fundamental issues, such as the optimal biochar dosage and mitigation mechanisms. Moreover, there is a significant lack of full-scale implementation. Accordingly, future work should focus on overcoming these critical challenges to take a step forward towards a consistent and complete picture of the environmental impacts and a rigorous economic analysis of the use of biochar in composting. Full article

In this study, Ni/Mn-doped cobalt–reduced graphene oxide (Co-RGO) composites were successfully synthesized as advanced electrode materials for supercapacitors. The structural and morphological properties of the composites were characterized using FTIR, XRD, SEM, TEM, and UV–Vis spectroscopy. Their electrochemical performance was evaluated through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD). Among the prepared samples, Co-RGO doped with Ni/Mn at a 40:10 ratio exhibited the most outstanding capacitive behavior, achieving a specific capacitance of 7414 F g⁻¹ at a current density of 10 A g⁻¹, along with a high energy density of 565 Wh kg⁻¹ and a power density of 4998 W kg⁻¹. The high capacitance arises from faradaic pseudocapacitive reactions rather than electric double-layer capacitance, eliminating the need for a large surface area. These results confirm that Ni doping significantly enhances pseudocapacitance and conductivity in the Co-RGO matrix, making Ni/Mn (40:10)–Co-RGO a potential material for advanced energy storage systems. Full article

Composite bonded anchors represent an innovative solution in the field of fastening technology, finding wide application in construction and civil engineering. This article presents a comprehensive review of the available scientific literature, a market analysis and a survey of patent databases related to this issue. Key aspects of the design, mechanical properties and durability of composite bonded anchors under various operating conditions are discussed. Special attention was paid to comparing composite solutions with traditional anchoring systems, highlighting their advantages and limitations. The results presented indicate a growing interest in this technology, which is due to both its high strength, corrosion resistance and applicability to lightweight structures. In conclusion, the article identifies key directions for further research and potential areas for the development of composite bonded anchors in the context of modern engineering challenges. Full article

Depending on the factors to which the soils are exposed, many properties and engineering parameters may change. In particular, the temperature parameter affects the strength of the soils, the degree of compressibility, permeability, void ratio, Atterberg limits, and many other parameters. In areas where high temperatures occur, such as heat piles and nuclear waste storage areas, alternative soil mixtures are needed that can stabilize or better optimize the behavior of the soils. For this purpose, additives with high heat transfer capacity and symmetry can be used. In this study, aluminum additive, which is known to have high conductivity, was used together with zeolite–bentonite mixtures. Aluminum-added mixtures were kept at different temperatures, and their thermal conductivity values were measured at the end of different periods. Measurements were first carried out at room temperature for all mixtures. Then, measurements were repeated at the end of 1, 3, and 10 days for 55 °C and 80 °C temperature values. At the end of the heating periods, the samples were left to cool to room temperature, and the thermal conductivity values were examined at the end of the heating–cooling cycle. Experimental results showed that thermal conductivity increased as temperature increased when the same period was taken as a basis, but an increase was observed for 1 and 3 day heating periods, while the thermal conductivity values for the 10th day decreased. The initial increase is attributed to the densification of the material due to the removal of free and weakly bound water or to the improvement of solid–solid contact paths. The subsequent decrease is due to microstructural deterioration, such as increased air-filled porosity, drying shrinkage, and microcracking due to thermal stresses, and material degradation caused by prolonged heating. In addition, thermal conductivity values of the mixtures under high temperature were estimated for days 100 and 365 using the DeepSeek method. The results showed that the thermal conductivity coefficients symmetrically decreased with increasing time. Full article

Human–wildlife conflicts arise from increasing human populations and the growing demand for land for agriculture and urban development. In Saudi Arabia, these dynamics have increased the impact of baboons on human communities, as expanding settlements encroach upon the natural habitats of baboons, while rising baboon populations increasingly invade urban areas in search of food, shelter, and water. We aimed to assess the effects of human–baboon coexistence on residents in the Al-Baha region, Saudi Arabia. From October 2021 to April 2022, we administered a 43-item semi-structured online questionnaire addressing emotional, social, environmental and financial impacts of nearby baboons. A total of 318 residents of the Al-Baha region completed the survey and shared their experiences regarding interactions with hamadryas baboons (Papio hamadryas) near human properties. In addition, three semi-structured life interviews with residents aged over 70 explored historical perceptions. Respondents attributed increased baboon presence to urban expansion, accessible waste, and intentional feeding and strongly supported government-led mitigation plans. Human–baboon interactions in Al Baha produce emotional stress, social disruption, and economic burdens for residents. Findings support integrated management combining public education, improved waste management, non-lethal deterrents, and carefully planned population control measures, developed with community consultation. Limitations of the study include convenience online sampling and reliance on self-reported impacts; future work should quantify baboon abundance and objectively measure economic losses. Full article