VGTU Journals (Vilnius Gediminas Technical University - Vilnius Tech)
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Spline quasi-interpolation numerical methods for integro-differential equations with weakly singular kernels
No full textIn this work, we introduce a numerical approach that utilizes spline quasi-interpolation operators over a bounded interval. This method is designed to provide a numerical solution for a class of Fredholm integro-differential equations with weakly singular kernels. We outline the computational components involved in determining the approximate solution and provide theoretical findings regarding the convergence rate. This convergence rate is analyzed in relation to both the degree of the quasi-interpolant and the grading exponent of the graded grid partition. Finally, we present numerical experiments that validate the theoretical findings
Joint discrete approximation of analytic functions by shifts of Lerch zeta-functions
No full textThe Lerch zeta-function depends on two real parameters λ and and, for σ > 1, is defined by the Dirichlet series , and by analytic continuation elsewhere. In the paper, we consider the joint approximation of collections of analytic functions by discrete shifts with arbitrary 1 and We prove that there exists a non-empty closed set of analytic functions on the critical strip which is approximated by the above shifts. It is proved that the set of shifts approximating a given collection of analytic functions has a positive lower density. The case of positive density also is discussed. A generalization for some compositions is given
Subgrade performance assessment for rigid runway using long-term pavement performance database
No full textMaintaining desired subgrade performance is an effective way to reduce runway pavement deterioration. Due to lack of extensive field test data, life-cycle performance of runway subgrade has not been fully understood. In order to quantitatively estimate subgrade condition, a novel method of evaluating subgrade performance was developed and validated using the 726 sets of Heavy Weight Deflectometer (HWD) test data of ten runway sections. Statistical analysis demonstrates that the structural behaviour of rigid runway subgrade follows normal distribution in different service stages and can be efficiently evaluated by the subgrade performance index (ψ). The results of factor analysis show that Accumulated Air Traffic Volume (ATV) during service life is the major cause of spatial variations in subgrade condition. In the designed service period of runway, it validates that sea-reclaimed subgrade results in faster degradation in the initial stage of service life while thicker pavement exhibits better capability in protecting the subgrade soil in long-term view. Besides, the differences in applied loads and pavement thickness give rise to the subgrade performance variation in longitudinal direction. Meanwhile, the comparison between the main and the less trafficked test lines in transversal direction reveals that the aircraft impacts play a positive role in resisting the natural fatigue process. By the suggested method, subgrade performance of HWD test points can be categorized into 4 levels from “Excellent”, “Good”, “Fair” to “Poor” based on ψ value. It is helpful for airport agency to make scientific decisions on Maintenance and Rehabilitation (M&R) treatment by calculating the effective area of envelope (β) using the ratio of subgrade performance (η)
The impact of R&D efficiency on economic growth in China: non-linear threshold effects
No full textThis study uses a threshold estimation technique to examine whether the effect of R&D efficiency on economic growth in China differs according to the level of financial development. The results broadly confirm a nonlinear relationship between R&D efficiency and economic growth due to the dynamic and static threshold effects of financial development and R&D expenditure. This finding suggests that R&D efficiency does not significantly impact growth in the low and middle-financial development provinces at conventional levels. Hence, the benefit of R&D efficiency in China could stem from the positive effect of R&D in highly financially developed provinces. Though R&D efficiency is poor, R&D investment still enhances economic growth because the amount of R&D investment is enormous. This finding suggests that while it is most important to not unthinkingly expand R&D gross investment, it is also necessary to make full use of R&D investment by improving R&D efficiency.
First published online 29 May 202
Can the green credit policy promote green innovation in enterprises? Empirical evidence from China
No full textThe green credit policy (GCP) is an institutional framework aimed at guiding enterprises towards green transformation and promoting high-quality development, which serves as a crucial tool for supporting the establishment of a green technology innovation system. In this study, utilizing the green credit guidelines as a quasi-natural experiment and constructed a continuous difference-in-difference (DID) model, examines the impact of GCP impact on enterprise green innovation and its internal mechanisms by analyzing data from Chinese A-share listed companies between 2006 and 2021. Our findings indicate that the GCP had a significant impact on enterprise green innovation, inhibiting companies from in-dependently developing green innovation while promoting joint green innovation with other institutions; These results were robust and consistent, even after conducting several sensitiv-ity analyses; This mechanism indicate that the commercial credit plays an important regulatory role in the process of GCP affecting green innovation of enterprises and the financing constraints act as an intermediary factor in the process of GCP affecting green innovation. Based on our research, we offer policy recommendations aimed at improving the GCP and fostering a market-oriented green technology innovation system.
First published online 14 March 202
Malay identity in the exploration of miniature creation as souvenirs: contextual miniature of Malay architecture of North Sumatra, Indonesia
No full textAs a testament to the past Malay glory, there are monumental architectures in Medan (North Sumatra, Indonesia), Langkat (North Sumatra, Indonesia) and Batubara Regencies (North Sumatra, Indonesia) that have become Malay icons. The city of Medan and several areas in North Sumatra are known as tourist destinations since the early 20th century. The tourism has strong potential but it has not been supported by representative souvenir products. This article discusses the preservation of Malay identity through research into the manufacture of miniatures as souvenirs. The aim is to explore the potential of Malay architectural forms to be explored in the production of miniature souvenirs to revitalize North Sumatra’s Malay identity. The replicated research methods are survey, creation (creative experiment), and conservation methods in the socio-cultural approach. Research data was collected from various sources and analyzed using an interactive model. The results of the study explain that the potential identity of Malay architecture can be mapped based on its type (function) and structure. Its exploratory potential, both technically and aesthetically, lies in the dynamic visualization of roof forms and architectural facades. As it is researched based on the iconic Malay architectural figures, the miniature products are exclusive in the form of unique souvenirs with a strong Malay identity
A mathematical model for identifying military training flights
No full textThe main tasks of the Training Air Base concern the practical training of cadets in piloting techniques as well as maintaining and improving the piloting skills of the instructors. It is essential to maintain the infrastructure of the airfield and the Base as a whole ready for operation. This allows for fulfilling the fundamental mission of such military units, which is to provide effective operations for the defence of the state. Therefore, measures to support and improve the operation of such military facilities are extremely important and also became the genesis of this article. It analyses and evaluates the number of flights carried out over seven years (2016–2022) at the studied training base using mathematical modelling, allowing to assess the variability of the studied series. The phase trends method was used for this purpose, preceded by a seasonality study. It allowed the identification of periods in which the number of flights performed varies significantly. Such knowledge enables better regulation of the airport’s operation, adjustment of activities to the needs, and the determination of further directions for airport development and the justification of potential investments. An additional value of the article is the presentation of a mathematical modelling method specifically designed for seasonal time series, along with their diagnostics. It also provides an opportunity for other institutions to carry out tasks while upholding the highest standards
Figurative language effect on consumer engagement: an empirical investigation for Turkish airline industry
No full textIncreasing consumer engagement (CE) on social networks is one of marketing problems that brands face in today’s competitive environment. Although prior studies on this concept suggested that content strategies have essential role in improving CE, little is known about figurative language effect. Thus, a novel model and research design to examine how the use of figurative language influence CE behavior on Facebook were proposed. Drawing on Encoding/Decoding Model and brand-consumer communication studies, the 1687 brand posts of Turkish airline Facebook pages with Multiple Linear Regression (MLR) models were analyzed. The findings indicate that several types of figurative languages (idioms, personifications, and similes) are related to the various CE levels (likes, shares, and comments). The findings of this study give tips for understanding the role of figurative language, reshaping engagement level, and redesigning branded content in marketing communication practices on social networks. The experimental model that provides some clues to reconsider online communication strategies across CE based on figurative language is presented
Enhancing UAS safety through building-induced dangerous zones prediction: concept and simulations
No full textThis study presents a comprehensive approach to operational estimation of the zones of danger for the Unmanned Aerial Systems (UASs) generated at low altitudes in presence of buildings, aimed at ensuring their safer operation. The main tasks are three. The first one is the definition of an inboard measurement methodology appropriate and feasible for UAS that allows Eddy Dissipation Rate (EDR) estimation. An inboard setup with a lightweight and low-cost anemometer operating at a 1 Hz sampling rate, immediately usable on UAS, is proposed. The second one is the definition of empirical equations to estimate the size of dangerous areas for the UAS flights around buildings through numerical simulation. The third one is the validation of the empirical formulas in a real-world case, through the numerical simulation of a group of buildings belonging to a research centre. Results show a good resemblance in the size of the danger zones, highlighting that this multi-faceted approach contributes to enhanced safety protocols for UASs operating in urban environments
Forecasting the real average retirement benefit in the United States using OWA operators
No full textThe issue of pensions has become increasingly topical. This paper presents the ordered weighted averaging real average pension (OWARAP) operator. The OWARAP operator is based on the ordered weighted averaging (OWA) operator and calculates the future average retirement benefit taking into account price changes. Moreover, this work extends the OWARAP operator by using order-inducing variables, generalized means, and probabilities. This paper ends by analyzing the applicability of the OWARAP operator and its extensions in forecasting the real average Social Security benefits for retired workers in each state of the United States (U.S.). The results demonstrate the usefulness of the proposed approach in retirement decision making.
First published online 30 April 202