VGTU Journals (Vilnius Gediminas Technical University - Vilnius Tech)
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Using Chebyshev’s polynomials for solving Fredholm integral equations of the second kind
No full textThe main problem with the Newton method is the computation of the inverse of the first derivative of the operator involved at each iteration step. Thus, when we want to apply the Newton method directly to solve an integral equation, the existence of the inverse of the first derivative is guaranteed, when the kernel is sufficiently differentiable into any of its two components, through its approximation by Taylor’s polynomial. In this paper, we study the case in which the kernel is not differentiable in any of its two components. So, we present a strategy that consists of approximating the kernel of the nonlinear integral equation by a Chebyshev interpolation polynomial, which is separable. This allows us to explicitly calculate the inverse of the first derivative operator in each step of the Newton method and then approximate a solution of the approximate integral equation
Approximation of analytic functions by generalized shifts of the Lerch zeta-function
No full textIn the paper, we approximate analytic functions by generalized shifts of the Lerch zeta-function, where g is a certain increasing to real function having a monotonic derivative. We prove that, for arbitrary parameters λ and α, there exists a closed set of analytic functions defined in the strip 1/2 < σ < 1 which functions are approximated by the above shifts. If the set of logarithms is linearly independent over the field of rational numbers, then the set coincides with the set of all analytic functions in that strip
A class of nonlinear systems with new boundary conditions: existence of solutions, stability and travelling waves
No full textIn this work, we begin by introducing a new notion of coupled closed fractional boundary conditions to study a class of nonlinear sequential systems of Caputo fractional differential equations. The existence and uniqueness of solutions for the class of systems is proved by applying Banach contraction principle. The existence of at least one solution is then accomplished by applying Schauder fixed point theorem. The Ulam Hyers stability, with a limiting-case example, is also discussed. In a second part of our work, we use the tanh method to obtain a new travelling wave solution for the coupled system of Burgers using time and space Khalil derivatives. By bridging these two aspects, we aim to present an understanding of the system’s behaviour
The impact of liquidity constraints on the effectiveness of fiscal policy: evidence from Poland
No full textThe aim of the paper is to estimate the impact of the rapid worsening of households’ access to credit in Poland on the effects of fiscal policy. The novelty of our study is that it extends the analysis of liquidity constrained households’ impact on fiscal multipliers to Central and Eastern European country, where households access to credit is relatively limited and therefore the potential impact of liquidity constrained households on fiscal multipliers is stronger than the existing literature for highly developed economies indicates. The empirical analysis is based on the theoretical model with heterogenous households. We found that the increase in the percentage of liquidity constrained households led to the substantial rise in fiscal multipliers, and thus the increase of effectiveness of Polish fiscal policy. The study indicates that before the worsening of households’ access to loans, the contemporaneous government spending multiplier was relatively low, whereas after a sharp increase in interest rates, contemporaneous government multiplier exceeded one. What is more, our study shows that a sharp increase in interest rates also strengthens medium term fiscal policy impact on GDP in Central and Eastern European economy.
First published online 14 November 202
Evaluating impacts of ICT development on wages of workers
No full textAt the provincial level, there is a research gap in discussing the causality and internal mechanism between ICT development and wages of workers. The study utilizes the province-level balanced panel data over the period 2006–2021 in China, clarifies the impact and internal mechanism of ICT development on wages of workers, and uses the DID method to identify the causality between the two. This study found that there is a positive correlation between ICT development and workers’ wages, and skill level is a mediate transmission channel. Moreover, ICT development has a positive impact on workers’ wages in the central and western regions. Besides, compared to low-wage workers, high-wage workers gain more information dividends. The findings of this study have reference significance for policymakers. First, for the central and western provinces in China, it is necessary to actively develop the ICT industry, cultivate high-tech enterprises, and improve local ICT development levels. Second, we should improve the skill level of workers and enhance their competitive advantage in employment. Third, each province should continue to expand the enrollment scale of higher education institutions, and improve the quality of labor force.
First published online 09 September 202
Can government R&D expenditure promote innovation? New evidence from 37 OECD countries
No full textThis research employs a fixed effect model to empirically estimate panel data from 37 OECD countries spanning 2000 to 2021, revisiting the influence of government R&D expenditure on innovation within the theory of marginal diminishing effect. Results reveal a significant positive effect of government R&D expenditure on national innovation capacity, and this influence remains robust under robustness checks. Then, quantile regression uncovers a nuanced pattern, indicating that as a country’s innovation capacity strengthens, the stimulative effect of government R&D expenditure initially rises and subsequently declines. Additionally, incorporating lags of the independent variable at different periods affirms the time lag effect of government R&D expenditure on national innovation capacity. Deeper scrutiny using two fixed effect models including interaction terms reveals a multifaceted mechanism, where government R&D expenditure fosters innovation by promoting bank credit, yet simultaneously suppresses innovation by hindering non-governmental R&D intensity. Lastly, heterogeneity analysis affirms that government efficiency, democracy, ruling party ideology, political stability, and economic freedom moderate the link between government R&D expenditure and national innovation capacity. These insights offer new references for governments to promote innovation.
First published online 23 October 202
The threshold effect of the Taiwan stock market on ETF under the monetary policy
No full textTaiwan’s central bank produces tightening or easing effects by controlling the rediscount rate, which indirectly affects the stock market. An exchange-traded fund (ETF) is a fund that tracks the stock market index. ETF’s effect on trading involves not only the trading volume brought by ETF trading but also the various ETF trading strategies and the basket trading required by ETF, which makes the trading of other stocks more active. We examine whether there is a threshold effect of Taiwan’s stock market on ETF under monetary policy. The explanatory variable is the price return rate of the stock market’s weighted index; the response variable is the ETF price return rate. The rediscount rate is used as a transition variable. We analyze daily data from September 28, 2011 to September 28, 2020 using a smooth-transition autoregressive model with exogenous variables (STARX). The results reveal a threshold effect between stock market of Taiwan and ETF.
First published online 18 November 202
Can talent allocation drive transformation and upgrading of export trade through technological innovation under low-carbon background
No full textUnder the low-carbon background, regional talent allocation and transformation and upgrading of export trade are all important issues of common concern among academic circles in the stage of sustainable economic and environmental development. This paper explores talent allocation’s impact on the transformation and upgrading of export trade. Based on the results, the improvement in regional talent allocation level has significantly increased the percentage of regional general trade exports. It is conducive to the trans- formation and upgrading of export trade, and such an influence also shows the nonlinear characteristic of increasing “marginal effect”. This conclusion still stands after a series of robustness tests. According to the influencing mechanism test results, the technological innovation brought by the improvement in regional talent allocation level is an important transmission channel for such improvement to facilitate the transformation and upgrading of export trade. Based on the multi-dimensional analysis of the results of transformation and upgrading of export trade, regional talent allocation has significantly enhanced the complexity of exported technologies and actively promoted innovation among exporters. The research provides important inspiration for further promoting the structural reform of regional talent allocation and facilitating the transformation and upgrading of export trade patterns.
First published online 12 February 202
Systemic risk and contagion in the commodity market: identifying volatility transmission during crisis periods
No full textThe commodity market is a key element of the global economy. It is influenced by the political and economic situation of the major participants on the supply and demand side, as exemplified by the geopolitical and economic situation related to the conflict in Ukraine. Another aspect of this influence is the close relationship between commodity markets and financial markets. Both factors contribute to the possibility of the commodity market becoming subject to contagion, resulting in the transfer of supply and demand shocks and volatility. The aim of this article is to identify the commodities that are the source of contagion (volatility) during the transmission of shocks and the increase of systematic risk in selected periods. Combining traditional network theory with vector autoregression (VAR) model, we aim to estimate systemic linkages as a measure of systemic risk and the contagion process underlying it. We used time series of commodity returns from the Refinitiv Eikon database to observe the relationships between commodities during crisis periods, starting from 2006. The results suggest that the commodities with the largest increase in volatility transmission compared to the pre-crisis period acted as a transmission gate for market shocks.
First published online 12 December 202
Robot adoption: evidence from perceived benefits and industry adoption pressure
No full textRecent research suggests that many firms have begun to adopt robots to take over tasks that were previously carried out by humans. However, current study still does not seem to explain the possible reasons and behavioral intentions for this robot adoption preference, and some scholars attribute them only to rising hiring costs, which may lead to a misleading impression, as firms adopting robots do not appear to reduce the wages of their workers. In this paper, we conduct examinations using robot data from the Chinese General Administration of Customs and a range of firm characteristics. The result shows that robot adoption willingness of firms depends more on their perceived benefits from robots and the pressure they feel from their peers than on rising employment costs, and that higher-skilled sectors tend to approach robots proactively, whereas lower-skilled sectors tend to be reactive in the robot adoption process. In addition, firms exhibit different behavioral choices when deciding whether to adopt robots, with those that have advantages in terms of firm size and employee capacity more likely to translate their perceived benefits of robots and industry adoption pressures into robot adoption behavior. This work offers a new explanation for the current phenomenon of robot substitution for human labor in Chinese firms and provide new evidence for technology adoption theory.
First published online 19 February 202