16168 research outputs found
Sort by
Modelling and analysis of wind loading effects for heliostat mirrors using computational fluid dynamics /
No full textThis study examines the impact of wind forces on the structural integrity of heliostat assemblies in concentrated solar power systems, specifically tailored to local climatic conditions. The objective is to assess how varying elevation angles influence aerodynamic parameters, thereby informing design optimizations for enhanced operational efficiency. A computational fluid dynamics approach, utilizing the standard k-ε turbulence model, second-order implicit time formulation, and the Green-Gauss cell-based method, was employed to simulate wind interactions with a heliostat model at elevation angles of 0°, 30°, 60°, and 90°. The simulation process encompassed model development, mesh refinement, boundary condition setup, and numerical solution techniques. Post-processing analysis focused on aerodynamic characteristics such as drag and lift forces, static and dynamic pressures, turbulent kinetic energy, and turbulence intensity. Results indicate that drag force increases with elevation angle, peaking at 90°, while lift force is maximized at 30°. Additionally, static and dynamic pressures, skin friction coefficients, and turbulence parameters exhibit strong dependence on the heliostat's elevation angle. The minimum values of the skin friction coefficient, drag coefficient, and turbulence intensity were found to be 0.0111, 0.3580, and 11.42%, respectively, at an elevation angle of 0°. Moreover, the finite element analysis of the heliostat structure to evaluate its resistance under wind loading demonstrated structural integrity with acceptable stress and displacement levels. These findings provide valuable insights for engineers and researchers aiming to optimize heliostat structural dimensions, thereby enhancing the economic and operational performance of concentrated solar power systems
The role of accelerators in enhancing the performance of born-digital healthcare platforms /
No full textPurposeThis study examines the role of accelerators in the performance of born-digital health platform startups. Specifically, we investigate whether accelerators, including both domain-specific and general types, provide measurable performance gains in a complex, regulated and prone to rapid change healthcare environment.Design/methodology/approachDrawing on data from 235 born-digital health platform startups funded between 2010 and 2021, we use a two-step methodology. First, we evaluate performance with the benefit of the doubt composite indicator method. Second, we assess accelerator impact through a quasi-experimental approach employing propensity score matching to examine differences between domain-specific and general accelerator impacts.FindingsContrary to prevailing assumptions, our analysis indicates that non-accelerated startups tend to outperform those that have engaged in accelerator programs. Moreover, domain-specific accelerators do not offer a significant advantage over general ones. These results suggest that startup performance may be more closely linked to inherent capabilities and sector-specific challenges, such as regulatory complexity, rather than to external support from accelerators.Originality/valueThis paper addresses a critical research gap by differentiating the effects of various accelerator types in the digital health sector. The findings challenge traditional views on accelerator effectiveness and offer new insights that can inform more targeted support strategies in healthcare entrepreneurship
In-browser C++ interpreter for lightweight intelligent programming learning environments /
No full textThe paper presents a browser native C++ interpreter integrated into an AI-assisted educational platform designed to enhance programming learning in formal education. The interpreter leverages Parsing Expression Grammars (PEG) to generate Abstract Syntax Trees (AST) and executes C++ code using a TypeScript-based runtime. The system supports key C++ features, including pointer arithmetic, function overloading, and namespace resolution, and emulates memory management via reference-counted JavaScript objects. Integrated within a web-based learning environment, it provides automated feedback, error explanations, and code quality evaluations. The evaluation involved 4582 students in three difficulty levels and feedback from 14 teachers. The results include high system usability scale (SUS) scores (avg. 83.5) and WBLT learning effectiveness scores (avg. 4.58/5). Interpreter performance testing in 65 cases averaged under 10 ms per task, confirming its practical applicability to school curricula. The system supports SCORM and PWA deployment, enabling LMS-independent usage. The work introduces a technical innovation in browser-based C++ execution and a scalable framework for LLM-enhanced programming pedagogy
Searching for 15-minute city in large-scale housing estates: service proximity and diversity in the context of population density /
No full textThe “15-minute city” concept develops a sustainable mobility paradigm in the context of the city’s central neighbourhoods and outlines clear planning parameters. Since in many cities the majority of the population lives outside the city core, a sustainable city needs the adaptation of the “15-minute city” concept to other contexts. Large-scale housing estates (LHE) are home to a significant proportion of the population in many European cities, especially in Eastern and Northern Europe. LHE were planned with the idea that a neighbourhood is a unit that provides both housing and essential daily needs within walking distance. Although the political, social and economic context has changed significantly since the LHE concept was developed in the mid-20th century, the physical environment of LHE has largely retained the principles of the original urban idea. The aim of the paper is to investigate the multifunctionality of modernist estates and assess the correlation between the centers of gravity associated with four travel destinations - public transport stops, groceries, recreation and education. The study analyzed four LHEs in two cities - Riga and Vilnius, assessing the proximity and diversity of their services in the context of population density. The methodology is based on simulative mathematical modeling. The calculation of the gravitational centrality allowed for a spatially functional analysis, revealing movement patterns and better reflecting the functionality of the city in monofunctionally zoned modernist zones. The main results confirm that in all studied LHEs the average population density within 1 km was higher than the average in both cities. The density of other indicators was different in each case. They even exceeded the average values, showing that modernist-era districts could have the critical mass of objects necessary to implement the 15-minute city concept in the neighborhoods of Riga and Vilnius
Nucleosome wrapping energy in CpG islands and the role of epigenetic base modifications /
No full textThe majority of vertebrate promoters have a distinct DNA composition, known as a CpG island. Cytosine methylation in promoter CpG islands is associated with a substantial reduction of transcription initiation. We hypothesise that both atypical sequence composition and epigenetic base modifications may affect the mechanical properties of DNA in CpG islands, influencing the ability of proteins to bind and initiate transcription. In this work, we model two scalar measures of the sequence-dependent propensity of DNA to wrap into nucleosomes: the energy of DNA required to assume a particular nucleosomal configuration and a measure related to the probability of linear DNA spontaneously reaching the nucleosomal configuration. We find that CpG density and modification state can alter DNA mechanics by creating states more or less compatible with nucleosome formation
Development of recommendations for the quality control of magnetic resonance imaging in Lithuanian health care institutions /
No full textThis research is aimed at creating and validating a magnetic resonance imaging (MRI) quality control (QC) protocol which can be used in Lithuanian clinical environments. The investigation relies on the phantom based QC measurements performed evaluating three MRI scanners: Siemens Magnetom Skyra (3T), Siemens Magnetom Altea (1.5T), and Philips Ingenia Prodiva (1.5T). Following phantom based QC tests have been performed: measurements of signal-to-noise ratio (SNR), image uniformity (PIU), geometric distortion, low-contrast detectability and high-contrast spatial resolution. The obtained results matched with American QC standards showing just minor variations among devices and sequences. This allowed prepare the unified recommendations for the creation of national MRI QC protocol. The implementation of such protocol would lead to the uniform requirements for image quality, diagnostic dependability and better patient protection throughout the country
Global Environment Outlook 7: a future we choose – why investing in Earth now can lead to a trillion-dollar benefit for all /
No full textThe Global Environment Outlook, Seventh Edition: A Future We Choose, the product of 287 multi-disciplinary scientists from 82 countries, is the most comprehensive scientific assessment of the global environment ever carried out. The report calls on all actors to acknowledge the urgency of the global environmental crises, build on progress made in recent decades, and collaborate in the co-design and implementation of integrated policies, strategies and actions to deliver a better future for all
Building Digital Twin – digitalisation of the thermo-accumulator used for the building’s heating /
No full textWhen creating a digital twin of a building, all engineering system devices within the building must be digitised and integrated into the numerical model. This research focused on describing the processes occurring in a heat stor-age system, which was designed to accumulate heat during the summer period and utilise it by the building’s heating during the cold period. This is a long-term acting heat storage system with a soil-type filler. Several stages of the thermal energy storage system operation were distinguished: charging, discharging, and heat retention. During all these processes, heat exchange with the environment occurs. Typically, it is heat loss to the environment. Experimental research was per-formed in field conditions to analyse the mentioned processes. After each charge, the heat was dissipated in the soil volume. The output signals of the sensors were recorded and analysed. It was noticed that two temperature measurement sensors are necessary to estimate the type of work regime and charge or discharge inten-sity. More sensors are needed to determine the amount of stored energy more accurately. Creating a validated numerical model and comparing measured temperatures with simulated values at the same points enables a highly accurate assessment of the stored energy in the accumulator, as well as the description and forecast of parameter changes. By integrating the numerical model of the accumulator into the building’s digital twin and combining it with building engineering systems models, it is possible to enhance the efficiency of the building’s engineering systems and reduce energy consumption
P-wave morphological variability exacerbation prior to atrial fibrillation episodes /
No full textThis study analyzes the temporal evolution of the short-term P-wave morphological variability (PWMV) within the one-hour interval immediately preceding the onset of atrial fibrillation (AF) episodes. This PWMV is hypothesized to be an index of vulnerable atrial substrate, allowing to identify instability increases preceding the AF episode onset. We analyzed 32 ambulatory ECG recordings from subjects with paroxysmal AF. For each i-th subject and j-th AF episode, the PWMV was characterized in consecutive 2-min windows (k = 1 . . . 30) within the last 60 min before the AF onset. For each 2-min window, the median absolute deviation (MAD) of the P wave signals pi,j,kMAD(n); and the MAD energy normalized to the median of the P wave energy in each subject Eri,j(k) were measured. Then, for each subject, a normalized median across AF episodes was obtained, Ẽri(k). A two-segment linear function fit of Ẽr(k) temporal evolution, by least squares error (LSE) minimization was used to characterize the cohort dynamics. Analyzing the cohort dynamics of Ẽr(k), a relative stability can be observed up to 8 minutes before the AF episode onset, when Ẽr(k) value starts increasing. In conclusion, PWMV can be monitored by quantifying the P-wave short-time MAD relative energy, which shows an increasing trend within the 8 minutes previous to the AF onset
Impact of textile composition, structure, and treatment on microplastic release during washing: a review /
No full textThis research critically reviewed the influence of textile characteristics, including textile content (fiber composition), yarn construction, material structure, and treatment type, on microplastic release from textile products during washing. To date, the predominant focus of research has been on the washing parameters rather than the intrinsic characteristics of textiles. The findings of this review revealed that natural, man-made, and mixed-composition fabrics tend to release more microfibers compared to pure synthetic fabrics. Divergent results have been observed in studies on the release of microplastics from recycled synthetic fabrics. Woven fabrics release less microplastic compared to knitted fabrics. However, it is evident that yarn construction has more impact on microplastic release than textile composition or structure, and high-twist filament yarns reduce microplastic formation. Mechanical finishes tend to enhance microplastic release, while synthetic and biodegradable reduce it, but their sustainability and durability aspects need further investigation. The impact of different types of dyes on microplastic release remains unclear. All of the textile characteristics specified in this article are of pivotal importance in microplastic research. Overlooking the significance of any of these details can complicate the development of microplastic mitigation strategies