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Spalování paliv z obnovitelných zdrojů ve dvoupalivových plynových motorech
Nguyen Phu, Dong; Moc Lubomír, doc. Ing. CSc. :55346
Disertační práce zkoumala možnost využití motorových paliv získávaných z obnovitelných zdrojů, biometanu (bioCNG) a hydrogenovaného rostlinného oleje (HVO) k pohonu dvoupalivových plynových vznětových vozidlových motorů. Za tímto účelem jsem navrhl a realizoval dvoupalivovový zkušební motor. Disertační práce se zaměřuje na analýzu, vyhodnocování a porovnávání celkové účinnosti u dvoupalivových motorů při použití bioCNG/HVO a bioCNG/nafta pomocí simulačního softwaru, matematických modelů a experimentálních měření. Z výsledků výzkumu byly vyvozeny důležité body, díky kterým lze optimalizovat provozní parametry pro zlepšení spalovacího procesu, snížení emisí a úsporu paliva. Získané výsledky prokázaly, že vznětové motory mohou provozovány na 100% biologické duální palivo (bioCNG/HVO) funguje stabilně a přesně, a v budoucnu se stane velmi potenciálním duálním palivem, které přispěje ke snížení závislosti nebo odstranění ropného paliva v dopravě.
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A proposal of a relative weighted online 5-star rating system as a way to mitigate online reviews biases
(2025-03-19) Mazurek, Jiri; Perez-Rico, Cristina; Fernandez-Garcia, Carlos
Online ratings and reviews can be considered an electronic word of mouth regarding the quality of goods, products, or services. Reviews provide crucial information for customers, therefore significantly influencing their behavior, and they enable feedback to businesses from their customers, increase visibility, drive sales, help in developing a brand and building trust and reputation among consumers. However, the current 5-star rating system currently used on many Internet platforms such as Amazon or TripAdvisor suffers several drawbacks (biases) such as sentiment bias, polarization bias, non-discrimination bias, or vocal minority-silent majority bias. Therefore, the aim of the paper is to propose a new (weighted) relative 5-star rating system which takes into account reviewers’ history (in the form of the average and variance of the past reviews) and transforms absolute aggregate ratings into relative ones, thus providing less biased information for consumers and businesses. In particular, the proposed system reduces sentiment bias and non-discrimination bias. Moreover, the proposed approach enables to reduce the influence of ratings made by bots or dishonest evaluators-humans. The real-world application of the proposed approach dealing with ratings of selected attractions in Madrid area is provided as well.
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Analysis of circular strategies: A case study of the food processing industry
(2025-03-19) Fernandez-Gonzalez, Raquel; Ricoy-Casas, Rosa Maria; Teixeira Pereira, Zita Graca; Vila Biglieri, Jorge Eduardo
This research investigates the implementation of the circular economy in the Galician canned fish and seafood sector. This sector is crucial, producing 225,000 t annually and representing 75% of Spain’s total production, significantly contributing to the regional economy and employment. Moreover, this industry significantly contributes to the regional economy employing around 12,000 people. Using the PESTLE methodology, the study systematically and holistically examines the most relevant systems and actors in the sector. The analysis is complemented by a SWOT analysis, enriched through brainstorming sessions with 24 industry experts who evaluated and scored each factor’s importance from 0 to 1. From the analysis of the external environment of the circular strategy that the industry is exposed to and does not control, economic uncertainty is identified as the main threat (0.8) and technological innovation as the main opportunity (0.9). The internal environment analysis, influenced by the industry’s current situation, identified the main weakness of the circular strategy as high implementation costs, and the main strength is institutional and regulatory support (0.9). The results highlight significant institutional and regulatory support, availability of public subsidies, and strong technological and research capabilities as major strengths. However, the sector faces challenges such as dependence on public funding, high implementation costs, and a lack of qualified workforce. Opportunities include growing demand for sustainable products and technological innovation, while threats encompass economic uncertainty and global competition. The conclusions emphasize the need for strategic management of these factors to ensure the successful adoption of circular economy practices. Specifically, enhancing collaboration between the public and private sectors, increasing investment in innovation and workforce training, and leveraging favorable legislation are crucial for improving the sector’s sustainability and competitiveness. By strategically managing these elements, the Galician canned fish and seafood sector can not only enhance its environmental sustainability but also achieve greater economic resilience and market competitiveness. This comprehensive approach ensures that the sector can effectively transition to a circular economy, benefiting both the environment and the industry’s long-term viability.
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UNIKNI TUL - Březen 2025
(2025-03-18) Řípová, Jana; Neumannová, Petra
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Profitability determinants of cooperative Islamic insurance companies
(Technická Univerzita v Liberci, ) Savai, Atila; Pjanic, Milos; Mitrasevic, Mirela; Milenkovic, Nada; Ekonomická fakulta
The aim of the paper is to investigate the profitability determinants of cooperative insurance companies in Saudi Arabia. The mentioned insurance companies conduct business activities on the largest Islamic insurance market in the world, which has a growing demand for insurance as an instrument of risk management and a meaningful potential for further growth. A particular motive for conducting this research was the fact that these companies have common characteristics with mutual insurance companies that represent one-third of the European insurance market. Taking into account the characteristics of cooperative insurance companies’ business operations and the special structure of financial reports of these insurers relying on and in accordance with the results of the latest research on this topic as profitability determinants, we use return on assets (ROA), return on equity (ROE) and earnings per share (EPS), while explanatory variables include microeconomic (company size, investment profitability, investment income ratio, operator’s fee, expense ratio, loss ratio, premium growth, risk exposure, capital adequacy, reinsurance dependence, specialization) and macroeconomic (interest rate and equity returns) variables. The data are collected on a quarterly basis for 28 companies from 2012 until the second quarter of 2020. We use first- and second-generation unit-root tests, heteroscedasticity test, cross-sectional dependence test, autocorrelation test, Hausman and Overid tests and multicollinearity test to determine model parameters. Due to the presence of heteroscedasticity and cross-sectional dependence, we analyze the data using Beck and Katz’s panel corrected standard errors (PCSE) method. The results suggest that the financial performance of cooperative insurance companies in Saudi Arabia is determined by expense ratio, loss ratio, specialization (general or life and composite insurer) and the value of the operator’s fee, which depends on the amount of the underwriting surplus. Taking into account the key characteristics of cooperative insurance companies, the results of our research can be used by decision makers of cooperative insurance companies in strategic and operational planning and can provide help for policymakers in other countries that use alternative insurance models.