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Firm credit rating changes, capital structure, and the asymmetric moderating role of debt capacity and financial constraints
Get PDFThis study analyzes how debt capacity and financial constraints impact credit rating changes. Using a comprehensive sample of European companies, we analyze rating upgrades and downgrades separately to allow us to uncover whether the effects differ. Our results show that only one of the four commonly used proxies for debt capacity can explain credit rating changes. Specifically, we find that debt capacity can influence both rating upgrades and downgrades, but financial constraints or profitability can only impact rating downgrades. Our results are robust to various model specifications. The Monte Carlo simulation results reveal that uncertainty related to factors causing rating upgrades increases sharply when debt exceeds 30% of total assets. Similarly, when debt exceeds 50% of total assets, uncertainty related to rating downgrades surges
The impact of Search Volume Index on FDI outflow: the moderating role of uncertainty avoidance
Get PDFThis study examines the relationship between the Search Volume Index (SVI) and FDI outflow levels and tests whether the level of national culture, particularly whether the Uncertainty Avoidance Index (UAI), moderates such a relationship. The authors document that SVI is positively associated with FDI outflow in the sample of 69 countries. When we distinguish between low and high-uncertainty avoidance countries, we find that this positive association is significant at the current value of SVI for countries with low uncertainty avoidance. However, the relationship becomes stronger for countries with high uncertainty avoidance at the one-year time lag of SVI. Moreover, the results remain intact after various robustness checks. These results imply that the level of national culture may cause individuals to hesitate to invest through internet search queries. Our empirical findings should be particularly informative for investors from countries whose governments exhibit high levels of uncertainty avoidance, as they spend more time on investment planning than investors from countries whose governments exhibit low uncertainty avoidance
Feasibility study of digitalization possibilities of LEAN solutions in unit and small series production
No full textToday’s digital technology takes manufacturing to the next level. Digitized systems make it possible to identify potential and existing problems in a timely manner and to discover opportunities for improving the company’s operations by customers’ requirements as quickly as possible. In mass production, digital technologies are already widely implemented and used, which allows large companies to gain production flexibility and advantage. At the same time, large manufacturing companies gaining flexibility pose a great threat to small companies, which are creating unit and small series production. This article presents a study that aims to identify the differences between different types of production, examine digitized LEAN solutions and the latest applied technologies, and relate them to each other. This analysis will allow the selection of the most appropriate solutions for small serial and unit production. A twostage empirical study was used for this. In the first part, a questionnaire survey determines the companies’ attitude towards digitization, the LEAN tools applied, and the factors that would promote the digitization of processes. The second study compares the organization of production in a company with a low level of digitalization and in a second company with an extremely high level of digitalization. That was done by visiting companies. In a company with a low digitization level, the identified problem points are solved by applying good practices of a digitized company and by arguing from the analyzed literature sources.
Article in Lithuanian.
LEAN sprendimų skaitmenizacijos galimybių tyrimas vienetinėje ir smulkiaserijinėje gamyboje
Santrauka
Šiandien skaitmeninės technologijos perkelia gamybos procesą į aukštesnį lygmenį. Jos leidžia laiku nustatyti esamas ir potencialias problemas, atrasti įmonės veiklos gerinimo galimybes ir greičiau patenkinti kliento poreikius. Masinėje gamyboje skaitmeninės technologijos jau plačiai diegiamos ir naudojamos – tai suteikia didelėms įmonėms gamybinį lankstumą ir pranašumą. Tokios įmonės kelia didelę grėsmę mažoms organizacijoms, kuriančioms vienetinę ir smulkiaserijinę produkciją. Šiame straipsnyje pristatomas tyrimas, kurio tikslas – nustatyti skirtumus tarp įvairių gamybos tipų, išnagrinėti skaitmenizuotus LEAN sprendimus ir naujausias taikomas technologijas, atskleisti jų tarpusavio sąsajas. Atlikta analizė leidžia parinkti tinkamiausius sprendimus smulkiajai serijinei ir vienetinei gamybai. Tam pasitelktas dviejų etapų empirinis tyrimas. Pirmojoje dalyje atlikta anketinė apklausa, kuria siekta nustatyti įmonių požiūrį į skaitmenizavimą, taikomus LEAN įrankius ir skaitmenizaciją skatinančius veiksnius. Antrojoje dalyje, remiantis vizitų metu surinkta informacija, atliktas žemo ir itin aukšto skaitmenizacijos lygmens įmonių palyginimas.
Reikšminiai žodžiai: daiktų internetas (IoT), debesų kompiuterija, didieji duomenys, dirbtinis intelektas (DI), inovacijos, įrangos tarpusavio sąveika (M2M), kibernetinės fizinės sistemos, LEAN, Pramonė 4.0, skaitmenizacija, trimatis modeliavimas, vienetinė ir smulkiaserijinė gamyba
Evaluation of the quality management systems for aircraft and component manufacturing and maintenance organizations
No full textEnsuring operational efficiency is a critical condition for aviation organizations to maintain high levels of flight safety while remaining competitive. Aircraft and component manufacturing and maintenance organizations are required to comply with European Commission (EC) regulations (EU) No. 1321/2014 and No. 748/2012, which primarily focus on safety rather than broader management aspects. The EN9110:2018 standard based on ISO 9001 principles and of a recommendatory nature, offers an additional opportunity to enhance process efficiency, reduce costs, improve customer satisfaction, and support long-term sustainability. This study aimed to develop a model for assessing the effectiveness of quality management systems specifically adapted to aviation organizations. To achieve this, scientific literature was reviewed, EN9110 requirements were compared with EASA regulations, and expert surveys, interviews, and statistical data analyses were conducted. The resulting model for evaluating the impact of an integrated safety and quality management system enables the identification of relationships between operational efficiency, customer satisfaction, regulatory compliance, and audit outcomes. The findings confirm that the EN9110 standard effectively complements mandatory legal requirements, and its application provides significant benefits when leveraged as a tool for optimizing organizational performance, reducing costs, and enhancing competitive advantage within the aviation sector.
Article in Lithuanian.
Orlaivių ir komponentų gamybinių bei techninės priežiūros organizacijų kokybės valdymo sistemos vertinimas
Santrauka
Aviacijos sektoriaus organizacijoms veiklos efektyvumo užtikrinimas yra būtina sąlyga, siekiant išlaikyti skrydžių saugos lygį ir konkurencingumą. Orlaivių bei jų komponentų gamybos ir techninės priežiūros organizacijos įsipareigoja atitikti EK reglamentus (ES) Nr. 1321/2014 ir Nr. 748/2012, kurie labiau orientuoti į saugą, o ne į vadybinius aspektus. Rekomendacinio pobūdžio EN9110:2018 standartas, paremtas ISO 9001 principais, sudaro galimybę didinti procesų efektyvumą, mažinti sąnaudas, gerinti klientų pasitenkinimą ir užtikrinti ilgalaikį tvarumą. Atlikto tyrimo tikslas – sukurti kokybės valdymo sistemos veiksmingumo vertinimo modelį, pritaikytą aviacijos organizacijoms. Siekiant šio tikslo, analizuota mokslinė literatūra, lyginti EN9110 ir EASA reglamentų reikalavimai, atliktas ekspertinis vertinimas ir statistinė duomenų analizė. Sukurtas integruotos sistemos naudos vertinimo modelis leidžia nustatyti sąsajas tarp organizacijų veiklos efektyvumo, klientų pasitenkinimo, teisinės atitikties ir auditų rezultatų. Tyrimo rezultatai patvirtina, kad EN9110 standartas papildo privalomą teisinį reglamentavimą, jo taikymas suteikia reikšmingų pranašumų. Standartas aviacijos sektoriuje veiksmingai pasitelkiamas kaip priemonė organizacijų veiklai optimizuoti, sąnaudoms mažinti ir konkurenciniam pranašumui didinti.
Reikšminiai žodžiai: kokybė, sauga, valdymas, EN9110 standartas, vertinimas, veiksmingumas, aviacija
Logistics operations management in the Industry 4.0 era: a case study for transition of an automotive company′s operations to fourth-party logistics structure
Get PDFIn recent years, the understanding of minimum inventory and customer satisfaction in the flow of goods and services from manufacturers to end-users is of great importance among the factors that make businesses more interested in outsourcing logistics activities. Additionally, technological transformation and customer requests for complicated technology and services caused the appearance of new circumstances, which is progressively altering the industry. In this regard, choosing, managing and coordinating between multiple vendors become very difficult and time consuming so, companies outsource more functions while supply chain operations getting more complex. Companies generally preferred 3PL providers for their logistics functions including packaging design and management of company-owned assets. On the other hand, with technological transformation in logistic sector, businesses are looking to outsource 4PL more than ever. 4PL system transitions are difficult processes since it requires comprehensive system integration and should be well understood by the company′s supply chain team. Today, although the importance of 4PL systems is more understood and this structure is becoming more widespread, many companies still face similar adaptation problems. From this point of view, it is believed that this study creates important insights into the business world. In this study, the transition process of an automotive company is examined which successfully completed after a 5-month project period. As a detailed case study, the Transportation Management Module (TTM) is selected since the whole transition process was very comprehensive and included many dimensions. Study revealed that adaptation of the new system, developed by the partnership of the automotive company and 4PL company, provided several benefits. In this sense, with the transition of Transportation Management (TM), TTM is reduced by 2 days, almost 10% savings are reported in the whole company and only in the Turkey branch, 243311 € cost saving is achieved in the 1st year. The study proves that focusing on the core business via outsourcing supply chain activities not only increases efficiency in the selected automotive company but also increases supply chain quality as well.
First published online 22 January 202
Tourists′ local buses ridership and pandemic resilience: a smart card data analysis in Southern Catalonia
Get PDFThe COVID-19 pandemic′s harmful effects have varied across economic sectors and been particularly adverse for the transport and tourism sectors. This article analyses the pandemic′s impact on tourists′ use of public transport since 2020, including its patterns of change and general decline, using data from more than 40000 smart card holders considered to be summertime users during the peak tourist season in Camp de Tarragona (Catalonia, Spain). 3 model-based clustering analyses of pre-pandemic data from 2019 were performed and used to classify data generated since the pandemic began in 2020. The 1st model included variables of each smart card′s volume of activity, the 2nd model analysed the concentration or spatial dispersion of validated uses of each card, and the 3rd model examined the temporal dimension of the use of smart cards depending on the defined objective. Among the major findings, the number of journeys plunged by 92% in summer 2020 – that is, by far more than throughout the year (64%), which suggests a higher loss of travellers linked with tourism activities (e.g., tourists, 2nd-residence owners, and workers in the tourism sector). Regarding the spatial dimension, patterns with minor reductions related to trips taken within cities (45%) or between major cities (78%). By contrast, travellers with sprawled patterns fell the use by 93%. Last, profiles obtained from variables of a temporary nature presented similar percentages of losses; the most significant losses were for use distributed throughout the day (91.81%) and throughout the night (90.12%). This article provides valuable insights into the pandemic′s varied effects on the use of public transport during peak season at a tourist destination, insights that could inform policies and actions to ensure a more robust response to future crises
Airport complexity and environmental efficiency metrics for air traffic management evaluation
Get PDFThe aviation industry is experiencing significant growth due to the growing global demand for air travel. The International Civil Aviation Organization predicts that air passenger volumes will quadruple by 2040, putting pressure on airport infrastructure and airspace capacity. This growth is causing environmental challenges, particularly concerning emissions from aircraft operations and airport activities. These emissions contribute to local air pollution and global climate change. Airports are complex operational hubs, requiring sophisticated planning and efficient operations management to mitigate emissions and maximize throughput. This thesis investigates how airport complexity and air traffic management strategies influence inefficiencies in fuel use, time, cost, and environmental impact. Traffic scenarios were generated and analysed using MATLAB code, calculating emissions and fuel consumption across all phases of the landing and take-off (LTO) cycle. The results show significant differences in operational efficiency and environmental impact, offering insights into the effectiveness of modern traffic control methods
Evaluation model of construction quality data uncertainty: a study based on industry park project
Get PDFThis study proposes an evaluation and adjustment model for construction quality data uncertainty based on the research project of the Sichuan Provincial Building Industry Park. The core objective is to address the variability in concrete strength data caused by multiple factors during the construction process through a data-driven approach, which enables the accurate prediction of concrete strength. By analyzing construction quality data across different strength grades and curing ages, this study establishes a dynamic model centered on “data fitting” and “data prediction”. The model defines a reliability range for construction quality specific to the project, which facilitates the cleansing of outlier data and the adjustment of biased data. The results demonstrate that the model significantly enhances the reliability of the construction quality data. Further analysis of data from the same construction site revealed that it is highly applicable, and the date adjustment become more concentrated and stable. The fitting coefficient of this model approaches 1, which significantly improving the representativeness and reliability of the strength data. The findings provide a scientific basis for the dynamic assessment and optimization of construction quality, and robust support for quality control and prediction during the construction process
Investigation of the thermal conductivity of RT58 phase change material during the charging process of a thermal storage tank under natural convection conditions
No full textAs global energy demand grows, more and more attention is being paid to efficient energy storage solutions, among which Phase Change Materials (PCMs) are particularly promising. They allow efficient thermal energy storage by using the latent heat that is absorbed or released during the transformation of the aggregate state. One of the most important properties of PCM for efficient heat transfer is the thermal conductivity. Unfortunately, it is not high for organic materials. This paper presents a study of RT58 PCM, presenting an experimental evaluation of the thermal conductivity of this material and the application of the material in a storage tank. The analytical evaluation focuses on the heat transfer under natural convection conditions, where the aim is to assess the influence of the thermal conductivity of the PCM on the amount of energy stored in the storage tank. In this case, the temperature of the heating surface, the magnitude of the thermal conductivity coefficient and the choice of the other PCM are considered. The experimental results allowed to refine the value of the thermal conductivity coefficient of the RT58 material used (0.188 W/(mK)) and the analytical calculations allowed to trend towards an increase of the heat exchange efficiency of the system with the PCM.
Article in Lithuanian.
RT58 fazinio virsmo medžiagos šilumos laidumo koeficiento tyrimas natūralios konvekcijos sąlygomis akumuliacinės talpos įkrovimo metu
Santrauka
Didėjant pasaulinei energijos paklausai, vis daugiau dėmesio skiriama efektyviems energijos kaupimo sprendimams, tarp kurių itin perspektyvios yra fazinio virsmo medžiagos (FVM). Jos leidžia efektyviai saugoti šiluminę energiją naudojant latentinę šilumą, kuri sugeriama arba išskiriama agregatinės būsenos virsmo metu. Viena iš svarbiausių FVM savybių efektyviems šilumos mainams yra šilumos laidumo koeficientas. Deja, organinių medžiagų atveju jis nėra aukštas. Šiame straipsnyje pateikiama RT58 FVM tyrimas, kuriame pristatomas eksperimentinis šios medžiagos šilumos laidumo įvertinimas ir medžiagos pritaikymas akumuliacinėje talpoje. Atliekant analitinį vertinimą nagrinėjami šilumos mainai natūralios konvekcijos sąlygomis, kai siekiama įvertinti FVM šilumos laidumo įtaką sukauptos energijos kiekiui akumuliacinėje talpoje. Šiuo atveju nagrinėjama šildomojo paviršiaus temperatūra, šilumos laidumo koeficiento dydis ir kitos FVM pasirinkimas. Eksperimentiniai rezultatai leido patikslinti naudojamos RT58 medžiagos šilumos laidumo koeficiento vertę (0,188 W/(mK), o analitiniai skaičiavimai – tendencijas didinti sistemos su FVM šilumos mainų efektyvumą.
Reikšminiai žodžiai: fazinio virsmo medžiaga, natūrali konvekcija, šilumos atidavimas, šilumos laidumo koeficientas
Dependence of cadmium, lead, and copper speciation on soil pH and temperature using VISUAL MINTEQ
No full textSoil contamination by heavy metals poses a significant threat to the environment and human health, primarily due to the toxicity of these metals and their ability to accumulate in organisms. To determine how soil pH and temperature affect the chemical speciation, mobility, and immobilization potential of cadmium (Cd²⁺), lead (Pb²⁺), and copper (Cu²⁺). The main hypothesis posits that as pH increases, the concentration of free heavy metals decreases due to the formation of complexes and precipitation, whereas an increase in temperature accelerates the kinetics of chemical reactions, thereby altering metal activity. Using the Visual MINTEQ modeling tool, simulations were carried out under various pH (4–8) and temperature (15–40 °C) conditions. The results showed that at lower pH, metal activity significantly increases; however, the influence of temperature is more complex–both positive and negative trends were observed depending on the metal. These findings provide a foundation for further research, particularly for optimizing strategies to immobilize contaminated soils. Nonetheless, certain observed trends diverged from initial assumptions and called for additional investigation.
Article in Lithuanian.
Kadmio, švino ir vario specifikacijos priklausomybė nuo dirvožemio pH ir temperatūros naudojant VISUAL MINTEQ
Santrauka
Dirvožemio užterštumas sunkiaisiais metalais kelia reikšmingą grėsmę aplinkai ir žmonių sveikatai, ypač dėl metalų toksiškumo bei jų gebėjimo kauptis organizmuose. Šio tyrimo tikslas – nustatyti, kaip dirvožemio pH ir temperatūra veikia kadmio (Cd²⁺), švino (Pb²⁺) ir vario (Cu²⁺) cheminę specifikaciją, mobilumą bei imobilizacijos potencialą. Didėjant pH laisvųjų sunkiųjų metalų koncentracija mažėja dėl kompleksų susidarymo ir nusėdimo, o temperatūros padidėjimas paspartina cheminių reakcijų kinetiką, keisdamas metalų aktyvumą. Naudojant VISUAL MINTEQ modeliavimą, atlikta simuliacija esant skirtingoms pH (4–8) ir temperatūros (15–40 °C) sąlygoms. Rezultatai parodė, kad esant žemesniam pH metalų aktyvumas reikšmingai padidėja, tačiau temperatūros poveikis yra sudėtingas – priklausomai nuo metalo, pastebimos tiek teigiamos, tiek neigiamos tendencijos. Gauti duomenys suteikia pagrindą tolesniems tyrimams, ypač siekiant optimizuoti užterštų dirvožemių imobilizacijos strategijas, nors kai kurios stebimos tendencijos neatitinka prielaidų ir reikalauja papildomos analizės.
Reikšminiai žodžiai: cheminė specifikacija, metalų mobilumas, sunkieji metalai, užterštas dirvožemis, VISUAL MINTEQ