bluuebunny/crossref_metadata_2025 huggingface dataset:
The Impact of tourism activities on the infrastructure of Canggu village settlements reviewed from the perspective of 4a principle
Authors: Bunyamin A. Siti Namirah , Swasto Deva fosterharoldas , Fresiani Anggun , Al Fajar Edy
Published: December 2023

The development of tourism in Bali is rapidly growing, as evidenced by the expansion of tourism activities into settlement areas. This situation has occurred in Canggu Village, one of the villages in the Badung Regency. Although the main tourist destinations are located in coastal areas, many supporting activities have encroached upon the surrounding settlement areas. There are many positive impacts that benefit the community, such as increased local economy, but there are also negative impacts arising from the rapid growth of tourism. The approach used in this research is an overall exploratory qualitative approach with methods such as literature review, secondary data collection, field observations, and interviews. This study focuses on the negative impacts related to settlement infrastructure, especially three fundamental aspects: road networks, drainage, and waste management. Based on field observations, these negative impacts occur because the development of tourism activities within settlement areas is not accompanied by preparedness to accommodate the increased activities associated with high-mobility tourism.
Technological trends in the energy sector: challenges and threats
Authors: Stennikov Valerii , Bayar Bat-Erdene
Published: December 2023

The global trends taking place within the framework of the change of the technological way of life have largely determined the modern transformations taking place in the energy sector. These transformations have become the result of the challenges that have manifested themselves in recent years, and which have already acquired a large-scale character in many ways. They are associated with the rapid development of carbon-free, nature-like energy generation technologies based on renewable energy sources, distributed energy generation, the growth of consumer activity in regulating their demand, intellectualization, digitalization, decarbonization, integration and other processes taking place in the energy sector. These processes are objective and do not depend on conjunctural, political or any other preferences. In these conditions, the most important task of the present and future development and functioning of energy systems and the fuel and energy complex as a whole of the energy sector is to preserve the stability of their functioning and stable operation, ensuring socio-economic growth and energy security of the country.
Qatar's prospects in the global gas market
Authors: Dunaeva Natalia , Kuklina Anna , Darya Yakovleva
Published: December 2023

The article analyzes Qatar's prospects in the global gas market and potential shifts in its export policy. It presents an analysis of the costs of supplying LNG from Qatar to European and Asian markets, examines Qatar's long-term LNG supply contracts, and conducts revenue calculations for export strategies. The article underscores the need for Qatar to diversify its approach to LNG exports, emphasizing the importance of not only securing sales volumes through long-term contracts but also adapting to changing gas market conditions by reserving a portion of volumes for spot sales to more effectively monetize its expanding capacities.
Some factors constraining the development and implementation of power grid voltage harmonics of filter-compensating installations
Authors: Tukshaitov Rafail , Zaripov Rustam , Gibadullin Ramil
Published: December 2023

The factors constraining the development and implementation of filter-compensating installations are considered. The data on the limit values of the parameters of the elements of resonant circuits and the degree of their influence on the quality factor are summarized. It is shown that the main criterion for the efficiency of filter-compensating installations is to ensure the resistance of a sequential resonant circuit significantly less than the impedance of the power grid.
Is Diabetes a Contraindication to Lower Extremity Flap Reconstruction? An Analysis of Threatened Lower Extremities in the NSQIP Database (2010–2020)
Authors: Chen Amy , Garvey Shannon R. , Saxena Nimish , Bustos Valeria P. , Jia Emmeline , Morgenstern Monica , Nanda Asha D. , Dowlatshahi Arriyan S. , Cauley Ryan P.
Published: December 2023

Background The impact of diabetes on complication rates following free flap (FF), pedicled flap (PF), and amputation (AMP) procedures on the lower extremity (LE) is examined.

Methods Patients who underwent LE PF, FF, and AMP procedures were identified from the 2010 to 2020 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP®) database using Current Procedural Terminology and International Classification of Diseases-9/10 codes, excluding cases for non-LE pathologies. The cohort was divided into diabetics and nondiabetics. Univariate and adjusted multivariable logistic regression analyses were performed.

Results Among 38,998 patients undergoing LE procedures, 58% were diabetic. Among diabetics, 95% underwent AMP, 5% underwent PF, and <1% underwent FF. Across all procedure types, noninsulin-dependent (NIDDM) and insulin-dependent diabetes mellitus (IDDM) were associated with significantly greater all-cause complication rates compared with absence of diabetes, and IDDM was generally higher risk than NIDDM. Among diabetics, complication rates were not significantly different across procedure types (IDDM: p = 0.5969; NIDDM: p = 0.1902). On adjusted subgroup analysis by diabetic status, flap procedures were not associated with higher odds of complications compared with amputation for IDDM and NIDDM patients. Length of stay > 30 days was statistically associated with IDDM, particularly those undergoing FF (AMP: 5%, PF: 7%, FF: 14%, p = 0.0004).

Conclusion Our study highlights the importance of preoperative diabetic optimization prior to LE procedures. For diabetic patients, there were few significant differences in complication rates across procedure type, suggesting that diabetic patients are not at higher risk of complications when attempting limb salvage instead of amputation.
Transaneurysmal Access with Suture-Mediated Closure Device to Treat Iatrogenic Common Femoral Artery Pseudoaneurysm under Ultrasound Guidance: A Novel Technique
Authors: Shariq Mohd , Bellam-Premnath Krishna Prasad , Hegab Shady
Published: December 2023

We describe three cases that were complicated by access site-related common femoral artery pseudoaneurysm following therapeutic endovascular procedures. In all the cases, presentation was with painful swelling in the right groin that was tender and pulsatile on palpation; further evaluation with color Doppler ultrasound revealed pseudoaneurysm at the access site in common femoral artery. Ultrasound-guided transaneurysmal access was obtained and ProStyle (Abbott Vascular, Redwood City, California, United States) suture-mediated device was used to treat the pseudoaneurysm safely and successfully.
Globalizing research on global cities and international business
Authors: Fan C. Cindy
Published: December 2023

Living up to the expectations of the JIBS Decade Award, Goerzen, Asmussen, and Nielsen’s 2013 paper not only introduced the literature on global cities to the international business (IB) community but continues to be generative. In their “Retrospective and a Looking Forward” paper 10 years later, the authors highlight megatrends about people, places and things, and new contexts and alternative perspectives, and they encourage further new ways of thinking about global cities and IB. This commentary expands upon their framework of three overlapping circles of global issues, global organizations, and global locations, by drawing especially from recent experiences in the U.S. and research in economic geography and allied fields. Facing global issues of climate change, human rights, health, housing, and the impacts of digital technologies on work, cities offer prospects of responding to these challenges, a context for multinational enterprises (MNEs) to consider. Against the backdrop of large-scale global migrations of unskilled, mostly contract, workers to global cities in developed economies, recruitment agencies and advocacy groups for migrants are global organizations as important as MNEs. Finally, the fluidity of physical boundaries, as illustrated by city-regions, world regions beyond traditional Western-centric perspectives, and intra-national variations, is key to analyzing global locations.
Understanding the paradox of high job quality evaluations among platform workers
Authors: Švagan Barbara
Published: December 2023

This article examines why food delivery platform workers evaluate their job quality as high despite known drawbacks of this type of employment. Using qualitative data obtained from 20 semi-structured interviews conducted with couriers in Slovenia, the study employs a job quality model consisting of four distinct components (psychological well-being, social satisfaction, economic stability, and health and safety) as a conceptual framework used to determine which elements contribute most to the general job quality evaluation. Findings show that couriers often acknowledge the financial challenges and potential health and safety risks associated with their occupation but are willing to overlook some of these drawbacks due to how highly they value the autonomy, freedom and favourable work-life balance platforms offer. This article argues that platform companies, characterised as permissive entities which still hold a significant amount of power over the labour process, take advantage of the workers’ desire for autonomy and the large worker turnover to continue precarious employment practices. This is additionally fuelled by poor management practices and interpersonal relationships in traditional employment, which often push workers into platform work with no human supervisor, where they can “be their own boss”.
IDADA: towards a multimethod methodological framework for PhD by publication underpinned by critical realism
Authors: Adesemowo A. Kayode
Published: December 2023

PhD by publication, a route of attaining a ‘doctorate’, is growing in adoption, yet has not gained universal acceptance. Whilst doctoral students are expected to free range, be independent in their study, and contribute to knowledge, there is a tendency to be schooled or mainly assessed along the lines of positivism and interpretivism. This paper, in part the author’s situational reflexivity and noting Liezel Frick’s “PhD by publication – panacea or paralysis?”, carried out a documentary analysis of academic regulations of 101 universities in the UK, South Africa, Ireland, Australia, and examined the literature for demi-regularities supporting or inhibiting critical realism in doctoral studies. It followed a (multimethod) plural approach. The examination revealed that critical realism is sparse in doctoral studies, and universities do not cohere in nomenclature and ‘form’ of PhD by publication. In filling the ‘free range’ gap, this paper contributes to the ongoing discourse on PhD by publication by introducing the IDADA (‘identify’, ‘define’, ‘analyse’, ‘develop’ and ‘apply’) methodological framework. The framework evolved from the demi-regularities understudied. IDADA is a practical solution-centric, methodological approach to PhD by publication. The paper calls on researchers and practitioners to be open to structured and ‘alternate’ approaches to research whilst ensuring ontological, epistemological, and axiomatic rigour. Researchers need not approach research religiously — as that of a particular paradigm sect; but rather embrace ‘practical adequacy’. Doctoral students should be encouraged to produce research output with more significant impact through interrogation and unearthing phenomena rather than just “observing, outlining and discussing findings” or conforming to ‘writing style’.
Investigation on photonic crystal nanobeam cavity based on mixed diamond–circular holes
Authors: Bin Jingtong , Feng Kerui , Ma Shang , Liu Ke , Cheng Yong , Chen Jing , Liu Qifa
Published: December 2023

A photonic crystal nanobeam cavity (M-PCNC) with a structure incorporating a mixture of diamond-shaped and circular air holes is proposed. The performance of the cavity is simulated and studied theoretically. Using the finite-difference time-domain method, the parameters of the M-PCNC, including cavity thickness and width, lattice constant, and radii and numbers of holes, are optimized, with the quality factor Q and mode volume Vm as performance indicators. Mutual modulation of the lattice constant and hole radius enable the proposed M-PCNC to realize outstanding performance. The optimized cavity possesses a high quality factor Q = 1.45 × 105 and an ultra-small mode volume Vm = 0.01(λ/n) [Zeng et al., Opt Lett 2023:48;3981–3984] in the telecommunications wavelength range. Light can be progressively squeezed in both the propagation direction and the perpendicular in-plane direction by a series of interlocked anti-slots and slots in the diamond-shaped hole structure. Thereby, the energy can be confined within a small mode volume to achieve an ultra-high Q/Vm ratio.
Existence of nontrivial distributional solutions for a class of Schrödinger-Poisson system with Sobolev critical nonlinearity and zero mass
Authors: Li Anran , Wei Chongqing , Zhao Leiga
Published: December 2023

This paper studies a class of Schrödinger-Poisson system in R3 with Sobolev critical nonlinearity and zero mass −Δu+ϕu=λf(u)+u5,x∈R3;−Δϕ=u2,x∈R3, where λ is a positive parameter and f is a continuous function defined on R with some suitable assumptions. One nontrivial distributional solution is obtained by a combination of variational methods and perturbation method.
Flocking and swarming in a multi-agent dynamical system
Authors: Sar Gourab Kumar , Ghosh Dibakar
Published: December 2023

Over the past few decades, the research community has been interested in the study of multi-agent systems and their emerging collective dynamics. These systems are all around us in nature, such as bacterial colonies, fish schools, and bird flocks, as well as in technology, such as microswimmers and robotics, to name a few. Flocking and swarming are two key components of the collective behaviors of multi-agent systems. In flocking, the agents coordinate their direction of motion, but in swarming, they congregate in space to organize their spatial position. We propose a minimal mathematical model of a locally interacting multi-agent system where the agents simultaneously swarm in space and exhibit flocking behavior. Various cluster structures are found depending on the interaction range. When the coupling strength value exceeds a crucial threshold, flocking behavior is observed. We do in-depth simulations and report the findings by changing the other parameters and with the incorporation of noise.
Seizure detection using dynamic memristor-based reservoir computing and leaky integrate-and-fire neuron for post-processing
Authors: Yang Zhiyu , Liu Keqin , Yuan Rui , Wu Xulei , Cai Lei , Zhang Teng , Tao Yaoyu , Jin Yufeng , Yang Yuchao
Published: December 2023

Epilepsy is a prevalent neurological disorder, rendering the development of automated seizure detection systems imperative. While complex machine learning models are powerful, their training and hardware deployment remain challenging. The reservoir computing system offers a low-cost solution in terms of both hardware requirements and training. In this paper, we introduce a compact reservoir computing system for seizure detection, based on the α-In2Se3 dynamic memristors. Leaky integrate-and-fire neurons are used for post-processing the output of the system, and experimental results indicate their effectiveness in suppressing erroneous outputs, where both accuracy and specificity are enhanced by over 2.5%. The optimized compact reservoir system achieves 96.40% accuracy, 86.34% sensitivity, and 96.56% specificity in seizure detection tasks. This work demonstrates the feasibility of using reservoir computing for seizure detection and shows its potential for future application in extreme edge devices.
Lateral polarity controlled quasi-vertical GaN Schottky barrier diode with sidewalls absence of plasma damages
Authors: Dai Yijun , Zhao Zihui , Luo Tian , Yu Zhehan , Guo Wei , Ye Jichun
Published: December 2023

In this Letter, a high-performance quasi-vertical GaN Schottky barrier diode (SBD) with low leakage current and high on/off ratio based on a unique lateral polarity structure (LPS) is presented. The SBD features with the III-polar domain as the active region and the partially wet etched N-polar domain as the current-spreading region, completely eliminating plasma damages. Compared to the SBD fabricated by the conventional plasma etching technique, the leakage current of the LPS-based SBD is two orders of magnitude lower. A high Ion/Ioff of 107, an ideality factor of 1.04, a breakdown voltage of 290 V, and a critical electric field of 2.1 MV/cm were demonstrated for the proposed structure.
Damping effect of surfactants on induced bubble shape deformations
Authors: Vobecká L. , Orvalho S. , Zedníková M. , Vejražka J. , Tihon J.
Published: December 2023

The addition of surfactants suppresses interfacial deformations, and surface elasticity is expected to play a critical role. High-speed imaging is used to study the influence of surfactants on the shape oscillations of air bubbles attached to a capillary and on the rebound of bubbles from a horizontal glass plate. The experiments are conducted in pure water and in aqueous solutions containing five different surfactants: terpineol, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, Triton X-100, and Triton X-45. The frequencies and damping times of the decaying oscillations and the restitution coefficients of the decaying rebounds are evaluated. The damping time and the restitution coefficient both decrease sharply with an increasing surfactant concentration and then reach a minimum before finally stabilizing. The oscillation frequency initially increases due to enhanced surface elasticity but then drops suddenly when the surfactant concentration corresponding to the maximum damping is reached. The suppression of bubble rebounds by surfactants bears a strong resemblance to the damping of quadrupole bubble oscillations. In both cases studied, a surface elasticity of about 4 mN/m is required to achieve the maximum damping of interfacial deformations, regardless of the surfactant used. Moreover, the bubble rebounds are found to be more susceptible to the presence of trace concentrations of surfactants.
Tunable vortex beams generation in visible band via Pr3+:YLF laser with a spot defect
Authors: Zhang Yu , Qi Yaoyao , Sheng Quan , Bai Zhenxu , Wang Yulei , Shi Wei , Lu Zhiwei
Published: December 2023

The generation of optical vortex beams with user-configurable topological charge and spatial profile is a topic of intense research due to the numerous potential applications for these types of laser beams. In this work, we demonstrate the direct generation of vortex laser beams with controllable topological charge and tunable spatial profile from a Pr3+:YLF laser cavity using a spot-defect technique. A theoretical model is established to examine the relationship between the topological charge of the generated vortex beam and how this relates to laser cavity parameters. Experimentally, the selective operation of first- and second-order vortex beams and tunable optical vortex lattices with one to four singularities at 607 nm can be achieved by adjusting the position of the defect spot. This work offers insight into methods for the generation of visible optical vortex beams with controllable topological charge and tunable singularities for a range of applications.
Thermal analysis of magnetized Walter's-B fluid with the application of Prabhakar fractional derivative over an exponentially moving inclined plate
Authors: Ishtiaq Bushra , Nadeem Sohail , Alzabut Jehad , Alzabut Cihad
Published: December 2023

The field of fractional calculus communicates with the conversion of regular derivatives to non-local derivatives with non-integer order. This emerging field has various applications, including population models, electrochemistry, signals processing, and optics. Due to the realistic practices of fractional derivatives, this study focuses on the Walter's-B non-Newtonian fluid flow in terms of fractional-based analysis. Through an exponential movable inclined plate, the magnetized unsteady flow behavior of Walter's-B incompressible fluid is examined. The mass and heat transport mechanisms are scrutinized with the association of chemical reaction and heat absorption/generation, respectively. The conversion of constitutive equations to dimensionless equations is accomplished through the application of dimensionless ansatz. The dimensionless equations are explored through the fractional approach of the Prabhakar derivative with the three-parametric Mittag-Leffler function. Both the Laplace transform and Stehfest methodologies are adopted to address equations based on fractional derivative. The consequence of the physical parameters with distinct time intervals on the concentration, flow field, and temperature distribution is physically visualized through graphics. According to the findings of this study, the velocity distribution decreases as fractional parameter values increase. Moreover, the concentration field exhibits a declining behavior with the improved chemical reaction parameter.
Promoting the uniform propagation of multi-fracture through adjusting the injection rate and perforation parameter: A numerical study
Authors: Wang Bo , Zhang Guchang , Zhang Li , Liu Jinjun , Zhou Fujian
Published: December 2023

The strong stress interference and fluid competitive distribution result in the non-uniform propagation of multiple fractures during horizontal well multi-stage hydraulic fracturing (HWMHF). The uniform stimulation effect can be effectively improved by adjusting the injection rate and perforation scheme. In this work, a two-dimensional fluid–solid fully coupled multi-fracture propagation model is established to investigate the pattern of multi-fracture propagation and the flow distribution. The considering factors include the fluid injection rate, the perforation parameters, and the reservoir heterogeneity. The pipe element is developed to realize the free fluid distribution among multiple fractures. The results show that multiple fractures are more likely to initiate simultaneously and propagate uniformly with a higher fluid injection rate. The stress interference among multiple fractures can be balanced and the equilibrium propagation degree of multiple fractures can be greatly improved by reducing the perforation number. In the homogeneous reservoir, when the fluid injection rate is 12 m3/min and the perforation number per cluster is reduced to 10, the difference coefficient of fluid distribution can be reduced to 3.31%. In the heterogeneous reservoir, multiple perforation clusters with different tensile strengths can generate nearly uniform fractures by increasing the fluid injection rate and reducing the perforation number. When the fluid injection rate is 12 m3/min and the perforation number per cluster is 6, the difference coefficient of fluid distribution can be reduced to 3.26%. This work is of great significance in clarifying the propagation pattern and optimizing the fluid injection rate and the perforation number to improve the uniform propagation degree of multiple fractures.
Closed ecosystems extract energy through self-organized nutrient cycles
Authors: Goyal Akshit , Flamholz Avi I. , Petroff Alexander P. , Murugan Arvind
Published: December 2023

Our planet is a self-sustaining ecosystem powered by light energy from the sun, but roughly closed to matter. Many ecosystems on Earth are also approximately closed to matter and recycle nutrients by self-organizing stable nutrient cycles, e.g., microbial mats, lakes, open ocean gyres. However, existing ecological models do not exhibit the self-organization and dynamical stability widely observed in such planetary-scale ecosystems. Here, we advance a conceptual model that explains the self-organization, stability, and emergent features of closed microbial ecosystems. Our model incorporates the bioenergetics of metabolism into an ecological framework. By studying this model, we uncover a crucial thermodynamic feedback loop that enables metabolically diverse communities to almost always stabilize nutrient cycles. Surprisingly, highly diverse communities self-organize to extract

≈

10

%

of the maximum extractable energy, or

≈

100 fold more than randomized communities. Further, with increasing diversity, distinct ecosystems show strongly correlated fluxes through nutrient cycles. However, as the driving force from light increases, the fluxes of nutrient cycles become more variable and species-dependent. Our results highlight that self-organization promotes the efficiency and stability of complex ecosystems at extracting energy from the environment, even in the absence of any centralized coordination.
Attitudes to language and bilingualism in residential care for older persons in Ireland
Authors: Müller Nicole , Medina Angela M.
Published: December 2023

Language as a primary vehicle for communication and cognition is intimately linked to the construction of identities and social relationships, and to social participation and inclusion. By means of appraisal analysis (a tool grounded in Systemic Functional Linguistics) of interview data, we explored attitudes to language(s), speakers and language use in a nursing home for older people in Ireland, where a large proportion of residents and staff are bilingual in Irish and English. We found that in their interviews, participating residents accord high value to their bilingualism and status of native Irish speakers. Participating staff members emphasize the value of Irish for relationship building and positive interactions among residents and staff. Residents’ strong bilingual identities and language preferences set a standard for deliberately bilingual practices, which affirm the local linguistic and cultural identity, while also actively including non-Irish speaking residents by treating both languages as resources for belonging.
Statistic Study of Gaseous Air Contamination in the City of Svishtov, Bulgaria
Authors: Nikolova Mariana , Zheleva Ivanka , Filipova Margaritka
Published: December 2023

Polluted air has a negative impact on human health and plant and animal life. There are two types of sources of air pollution: human activity (transport, heating, industry and others) and natural phenomena such as natural fires, volcanic activity, deforestation and others. Substances that are the most common air pollutants are dust particles, carbon and nitrogen dioxides, carbon and nitrogen oxides, hydrocarbons; aldehydes; radioactive substances, heavy metals, sulfur dioxide, ozone, etc. Gaseous air pollutants of primary concern in urban environments include sulfur dioxide, nitrogen dioxide, and carbon monoxide. Sulfur dioxide is a colorless gas that is a product of volcanic eruptions and various industrial processes. It’s usually released when coal and oil are burned. Nitrogen oxides, especially nitrogen dioxide, are poisonous gases with a pungent, suffocating odor. There are many regulations aimed at air pollution and pollution monitoring for all European countries. Bulgaria, as part of the EU, must comply with all these regulations. There are still many places and periods of time in Bulgaria over the years with air pollution greater than daily norms. The present study is dedicated to the study of air pollution with gaseous substances in the area of Svishtov, Bulgaria. The town of Svishtov is located in Northern Bulgaria, on the banks of the Danube River, where the southernmost point of the river along its entire length is located. A statistical analysis of the level of air pollution in Svishtov based on official data from the monitoring station in the city is presented. The measurements cover the period 2021 - 2023. All research results are presented graphically and commented.
Improving 3-Junction and 2-Junction solar cell efficiency by down-converting solar UV light to visible
Authors: Fedoseyev Alex , Herasimenka Stan , Sarkisov Sergey , Bogner Brandon , Polly Stephen , Hubbard Seth
Published: December 2023

The approach to efficiency improvement of space 3-Junction and 2-Junction solar cells, that involves a layer of down-converting material on the top of the cell, is presented. The layer consists of a polymer nanocomposite coating impregnated with the nanoparticles of inorganic compounds (fluorides or oxides) doped with rare earth ions down-converting solar UV light to visible matching the spectrum of the responsivity of the cell. Computational model of a solar cell is presented and used for processing the experimental data. Experimental results demonstrate an increase of the generated current and photoelectric efficiency.
Raster image processing using 2D Padé-type approximations
Authors: Olevskyi V I , Olevska Yu B , Olevskyi O V , Hnatushenko V V
Published: December 2023

We have developed a method called the two-dimensional Padé-type approximants method, which can be used to reduce the Gibbs phenomenon in the harmonic two-dimensional Fourier series. This method can be applied to both monochrome and color raster images. To do this, we implement the generalized two-dimensional Padé approximation proposed by Chisholm. In this approach, we select the range of frequency values on the integer grid according to the Vavilov method. We propose a definition of a Padé-type functional and provide examples of its application to simple discontinuous templates represented as raster images. Through this study, we are able to draw conclusions about the practical usage and advantages of the Padé-type approximation. We demonstrate that the Padé-type approximant effectively eliminates distortions associated with the Gibbs phenomenon, and it is visually more appropriate than the Fourier approximant. Additionally, the application of the Padé-type approximation reduces the number of parameters without sacrificing precision.
Reconstruction coefficient analysis of honeybee collapse due to pesticide contamination
Authors: Koleva Miglena N. , Vulkov Lubin G.
Published: December 2023

In this paper we consider the inverse problems of identifying space-dependent coefficients of the mortality rate of the bees and the rate of contamination of the forager bees by pesticides. The model is described by a weakly coupled system of two reaction-diffusion equations for the spatial distribution of uncontaminated and contaminated foraging bees. Final time t = T observations of the density of uncontaminant and contaminant forager bees are used. We propose two approaches for studying the problems. The first one uses the overspecified information to transform the problems into non-linear parabolic equations involving the solution values at the final time. This allows us to prove, using fixed-point arguments, existence of solution to the inverse problems. The second study employs the concept of the quasi-solution to establish existence of solution to the inverse problems as minimizers of least-square cost functionals.
Algebraic Geometry and Elliptic Integrals Approach for Calculation of the Propagation Time of a Signal Between GPS Satellites with Account of General Relativity Theory
Authors: Dimitrov Bogdan G.
Published: December 2023

The approach for calculating the propagation time of a signal between GPS satellites will be summarized, based on the proposed new theoretical approach in several previous publications, as well as the perspectives for future development of the theory. Topics include: 1. Basic notions of inter-satellite communications. 2. Shapiro delay formulae in General Relativity Theory - basic formalism and the necessity to extend the formalism by taking into account the satellite motion on a plane elliptic or space-distributed elliptic orbit. 3. Basic facts about the disturbed motion in celestial mechanics and the necessity to incorporate it in the theory of inter-satellite communications, accounting for General Relativity Effects. 4. Propagation time of a signal, emitted by a satellite on a plane and also space-distributed elliptical orbit in terms of zero-order elliptic integrals and respectively of higher order integrals. Proof of the real-valuedness of the propagation time for all cases as one of the criteria for the correctness of the theoretical approach. 5. New analytical algorithms for calculation of zero-order elliptic integrals in the Legendre form. Relation to two representations in the Weierstrass form. 6. The new formalism of intersecting four-dimensional null cones and the resulting physical notions of the (intersecting)) space-time interval (with the property of being positive, negative or equal to zero) and the (intersecting) geodesic distance (being only positive, because is related to the distance, travelled by light or radio signals). Proof of these properties in the general case and in some partial cases. New numerical estimate E
lim > 45.002510943228 [deg], above which the space-time interval is positive and thus inter-satellite communications between satellites on one plane elliptical orbit are possible. The angular distance of 45[ deg] is typical for the disposition of 8 satellites on one orbit in the Russian satellite constellation GLON ASS, so it might be claimed that such a configuration is favourable from the point of view of inter-satellite communications (with account of GRT effects).
Approaches for improvement of reliability of the Prony’s method computation
Authors: Drobakhin O O , Olevskyi O V
Published: December 2023

Parametric spectral analysis methods such as the Prony’s method can estimate the frequencies and amplitudes of a signal, conforming to their model, with great precision. At the same time, the addition of noise to the signal can lead to a complete model breakdown which leads to erroneous parameter values. This is especially true for the impulse noise. The article explores several possible algorithms which can be applied to the Prony’s method in order to refine the results and make them more noise resistant. Such algorithms include signal segmentation methods where the results of each segment processing influence the final estimate as well as the conceptually related method of point skipping. An approach based on the use of non-Euclidean norms as a measure of the linear algebraic equation system’s solution quality is developed and tested. Initially, the methods are applied to model digital signals, comprised of harmonic components with varying complex frequencies and amplitudes. Additive white Gaussian and impulse noise is added to the model signals. The results are then applied to the noisy results of a real-life synthetic aperture synthesis experiment obtained in the intermediate zone of radiation.
MATT’S PATROL: A Generalized framework to track marine litter path, fare and toll
Authors: Jao J R. , Vallar E A. , Jao J R. , Era M , Lañada M J
Published: December 2023

Attention is given to the mapping of marine litter pathways due to their negative impact on the environment, society, and economy. Many models have been created to examine ocean dynamics and particle tracking systems. This study aims to contribute to these existing models by introducing a framework called “MATT’S PATROLL: MArine liTTer’S PATh, faRe, and tOLL.” This framework examines three pillars needed for the management of marine litter, the computational, socio-ecological, and economic arms. The Lagrangian particle tracking model is used to model the spatio-temporal behavior of litters on the surface of the ocean. The “faRe” component describes the direct and indirect effects of meso-particles on sea and land populations while they wait to accumulate on shorelines and other settlements. The “tOLL” component examines the long-term ecological and socio-economic costs on ecosystems in land and water, as well as the damage and loss in gross revenue from the marine sector when marine litters penetrate habitats and livelihoods. To illustrate the framework, artificially generated litter data around Visayas region is used to simulate path, fare, and toll calculations.
Material characterization of EN AC-Al Si12CuNiMg alloy in stress relaxation and creep conditions
Authors: Sirata G G , Waclawiak K
Published: December 2023

Al–Cu–Mg alloys are widely used in various applications, especially engine components, where it is subjected to elevated temperatures during operation. Prolonged exposure of these components to elevated temperatures gradually leads to creep and relaxation phenomena. This study aims to investigate the effects of temperature on stress relaxation and creep behavior of the aluminum-silicon alloy EN AC-Al Si12CuNiMg. Furthermore, this study evaluates the effect of temperature on the rheological model parameters of this alloy. Experimental tests were conducted to investigate the stress relaxation and creep behavior of this alloy at different temperatures of 150°C, 250°C, and 350°C. The rheological model parameters were then determined from the obtained experimental data. The Standard Linear Solid Model (SLSM) was used to fit the stress relaxation and creep curves obtained from the experiment. Overall, the results indicate that increasing temperature significantly affects the stress relaxation and creep behavior of the investigated alloy, with higher temperatures leading to increased relaxation and creep rates. Additionally, the rheological model parameters of the alloy were found to vary with temperature.
W-beam guardrail crash analysis and evaluation using finite element method
Authors: Lerabo Y S , Habte H S
Published: December 2023

Guardrails are highly recommended to be erected in the median and side corner of a highway road to secure vehicle accidentally loss it track, supports the safety of the vehicle driver and passenger from catastrophic accidents. The design and constructions of different guardrails are done confirming standard to retain their performance that related to energy absorption capacity. Besides, damaged guardrails that compromise their performance are seen in highways due to poor maintenance or repair. This study was conducted to investigate the structural integrity of W-beam guardrail damage. An impact test which leads to non-linear material deformation behavior was simulated using commercially available software, ABAQUS. The geometrical models of the guardrail were modeled adopting AASHTO standard, and a representative Jeep truck used to impact the guardrail at 90o with 42.26km/hr speed. The non-conforming W-beam guardrail was modeled considering a loss connection of supporting leg with the W-beam. Results of the study showed that the structural integrity of the damaged guardrail is affected as the internal and plastic energy was decreased from the W-beam guardrail without damage. More, the damaged W-beam was displaced more, by 14.15%, to the restricted area as compared to the W-beam guardrail without damage.
Impact of and solutions to effects of climate changes for Longyearbyen, Svalbard, Norway
Authors: Winther S N , Gudmestad O T
Published: December 2023

Climate changes forces us to make significant mitigation and adaptation measures. As temperature rises and the environmental conditions changes, a variety of challenges occur. Across the whole globe, harming consequences are already being experienced. The Arctic region is particularly vulnerable to changes in Earth’s climate system, especially because of the albedo effect, and the region is already heavily impacted. Primarily through the melting of ice, both sea ice and glaciers, permafrost thawing and changing precipitation patterns. Longyearbyen, Svalbard, is one examples of a society having to change as a direct result of global warming. This paper focuses on the challenges Longyearbyen will be facing and possible adaption methods and solutions. Because of environmental changes, the risk of natural hazards will increase, infrastructure will get damaged and traditional engineering methods will be impossible to implement. This is threatening to human lives as well as the habitat and survival of mammals, birds, and plants. It will be essential to find ways to predict and limit the effects of climate challenges, by protecting people and infrastructure from them. This will require innovation, adaption and risk-taking. By investigating the climate challenges facing Longyearbyen and possible ways to address them, this paper emphasizes the urgency of tackling the effects of climate changes in the Arctic in order to protect the communities in the Arctic region.
Numerical investigation on pillow plate heat exchangers: Effects of nanofluid and geometry
Authors: Karimi A
Published: December 2023

The current research involves a comprehensive numerical simulation of nanofluid flow within a pillow-plate heat exchanger. Al2O3-water nanofluid and water are used as the working fluids, simulated using a two-phase mixture model. The study explores the influence of geometric properties on the heat exchanger’s hydrodynamic and thermal performance. It also delves into the utilization of nanofluids as the working medium and its impact on dimensionless pressure drop, Nusselt numbers, and dimensionless temperature. An innovative aspect of this research lies in the integration of artificial intelligence (AI) techniques for heat exchanger design optimization. Specifically, a Random Forest Regressor (RFR) AI model is employed to predict crucial parameters, including heat transfer coefficient (HTC) and pressure drop, based on input design variables. Key findings reveal that non-linear hole layouts in heat exchangers significantly improve Nusselt numbers by up to 25 percent. Conversely, larger holes result in higher pressure drops. The use of nanofluids enhances thermal efficiency by up to 10% while increasing pressure drop by around 7%.
Testing the impact energy and determination of the brittleness temperature of the welded joint of steel A516 Gr.70
Authors: Bajramović Ermin , Islamović Fadil
Published: December 2023

Most problems with steel structures occur in the welded joint or its immediate vicinity. For this reason, special attention is paid to testing the properties of the welded joint. Fractures of welded steel structures in operating conditions have led to the need to study the influence of temperature on the behavior of steel and welded joints. For the purpose of these tests, the critical test conditions (temperature) that cause brittle fracture are defined. The paper will present the results of experimental tests of the impact energy of the welded joint of steel A516 Gr.70. Impact energy testing at different temperatures was done with the aim of determining the brittleness transition temperature of the base metal and components of the welded joint. Also, these tests should give an assessment of the influence of temperature on the ratio of the crack formation energy Wiu, and the crack propagation energy Wa in the total fracture energy Wt. This test procedure determines the tendency to brittle fracture, that is, the tendency to increase brittleness during exploitation. The obtained results are most often used for ongoing quality control and evaluation of material homogeneity.
Testing of Mechanical Properties of Polymer PA6 – 30% Glass Fibres
Authors: Ćoralić Amir , Maslo Anel , Manjgo Mirza , Raspudić Vesna , Manjgo Mersida , Vuherer Tomaž
Published: December 2023

Polymers and polymer composite materials, due to their properties, are becoming increasingly important materials in industry. They are used in a wide range of applications in space and aerospace, aviation, marine and automotive industry, as well as in production of sports equipment, household appliances, medical equipment, etc. They are expected to withstand loads during their lifetime, which requires predicting the reliability of structural elements, i.e. knowledge of material properties. To achieve better properties, polymer materials are reinforced with different percentages of fibre-reinforced materials, including glass fibres. The paper presents the results of experimental determination of the mechanical properties of injection moulded PA6 polymer reinforced with 30% glass fibres, determined by tensile and impact tests.
The use of modern 3D technologies for the development of a prototype mountain bike brake lever within the concept of personalized production
Authors: Žibert Sebastijan , Mamić Maša , Hozdić Elvis
Published: December 2023

Mountain biking (MTB) is a popular sport for more and more people. Control over the bike is very important for a successful ride, especially when the rider gets off the mountain bike in rough terrain. Control over the bike is ensured by appropriate braking systems, which differ depending on the type of mountain biking. During a challenging descent, the cyclist consumes energy to overcome obstacles on the trail, so using the right brakes is crucial. The rider performs the braking process with the brake lever of the bicycle. On difficult descents, for example in bad weather (rain), it is important that the finger does not “slip” on the brake lever. Also important is the feeling of contact with the brake lever that the rider has when braking. For this reason, from an ergonomic point of view, the shape of the brake lever is crucial for a safe and controlled mountain bike ride. This paper presents the results of the use of advanced 3D technologies for the development of a prototype mountain bike brake lever within the concept of personalised production. The common thread of the presented research is the process of developing a prototype mountain bike brake lever from an ergonomic point of view, supported by modern 3D technologies such as 3D scanning, 3D modelling and 3D printing.
Calculation of convection coefficient during steel hardening of axisymmetric probes in thermal oils
Authors: Behrem Šefik , Hrnjica Bahrudin
Published: December 2023

The paper presents the results of the convection coefficient during the process of two-dimensional axisymmetric steel hardening of in two different thermal oils used in the area of thermal treatment of steel. One thermal oil was Isorapid 277 HM preheated to the set temperature, and the other one was Marquench 722 also preheated to the set temperature. The experimental work setup consists of six quenches, three dimensionally different axisymmetric probes in two different thermal oils. Steel hardening was done under strictly controlled conditions: heating the sample to the tempering temperature of most steels in a nitrogen atmosphere, vertical slow immersion of the test sample in the opposite flow of thermal oil. The temperature of the thermal oil was kept constant, stopping the test sample in the sample steel hardening area and non-stationary data collection until thermal oil equilibrium temperature with interruption of data collection. The data collection rate was two probes/second in parallel from four points located within the test cylinder. Three measuring points were located directly below the surface of the cylinder distributed along the height of the cylinder, while the fourth one was in the centre of gravity of the cylinder. Time-measured temperature values in the indicated four points of each probe were written in a text file. The set mathematical model describes the non-linear two-dimensional axisymmetric non-stationary heat transfer through the cylinder. The set mathematical model requires the inverse solution of the heat conduction problem, that is, ill-conditioned problems, so the solution of the problem came down to a sufficiently accurate estimation of the unknown convection coefficient imposed on the outer surface of the probe. The chosen solution algorithm was the one from previously published works. The solution algorithm was based on a iterative combination of the finite element method (FEM), while the second part of the solution algorithm is the Levenberg Marquardt method (LMM) from the line of optimization deterministic algorithms, which takes the calculation results of the temperatures at the points of the computational domain from the FEM, and for comparison, that is, error minimization, using the experimental results of temperature measurements at the same place.