Prediction of biaxial properties of elastomers and appropriate data processing

An equibiaxial tension test could be necessary to set up hyperelastic material constants for elastomers exactly. Unfortunately, very often, only uniaxial tension experimental data are available. It is possible to use only uniaxial data to compute hyperelastic constants for a hyperelastic model, but the prediction of behavior in different deformation modes (as is equibiaxial or pure shear) will not work correctly with this model. It is quite obvious that there is some relation between uniaxial and equibiaxial behavior for the elastomers. Thus, we could use uniaxial data to predict equibiaxial behavior. If we were able to predict (at least approximately) equibiaxial data, then we could create a hyperelastic model usable for the general prediction of any deformation mode of elastomer. The method of the appropriate processing of experimental data for such prediction is described in the article and is verified by the comparison with the experiment. The presented results include uniaxial and equibiaxial experimental data, the created average curve of both the deformation modes, and the predicted equibiaxial data. Using Student's t-test, a close coincidence of the real and predicted equibiaxial data was confirmed.Tomas Bata University in Zlin [IGA/FT/2024/002]Univerzita Tomáše Bati ve Zlíně, UTB, (IGA/FT/2024/002

Critical Entities Resilience Assessment (CERA) to small-scale disasters

Since 2022, there has been a significant increase in the importance of critical entities in terms of critical infrastructure protection. The adoption of the Critical Entities Resilience Directive must in EU member states ensure not only the protection of critical infrastructure, but also a sufficient resilience level of the entities themselves. This directive obliges critical entities to take measures to increase their resilience but does not provide any methodological support. A necessary starting point for fulfilling this obligation is knowledge of the current state of critical entities resilience to small-scale disasters. The results of the resilience assessment will then enable critical entities to identify vulnerabilities on the basis of which adequate technical, security and organisational measures can be defined. Therefore, this article presents an entirely new semi-quantitative method, CERA, which has been developed for the comprehensive assessment of entity and infrastructure resilience of critical entities. At the core of this method is a procedure that allows critical entities to self-assess their internal resilience through individual factors, which are defined in detail in this article. In order to facilitate the assessment process, the authors of the article have created the CERA Support Tool, which is supplementary material to this article. The Results section of the article also includes a presentation of a practical application example of the proposed procedure.Ministry of the Interior of the Czech Republic [VK01030014]; VSB - Technical University in Ostrava [SP2024/039]Ministerstvo Vnitra České Republiky, (VK01030014, SP2024/039

The "dark side" and negative consequences of cryptocurrencies usage for unethical purposes as barriers to invest in Middle East and African (MEA) countries

Purpose: This paper aims to unveil the darker side of cryptocurrencies by delving into its role as an obstacle to investments in Middle East and African (MEAs) countries, unravelling the challenges involved. Indeed, despite the rise of blockchain-related technologies, specifically cryptocurrencies, having undeniably unlocked new avenues for business and society, crypto for venture funding purposes may exhibit a "dark side" due to their use for unethical purposes, for example, money laundering or terrorism financing, largely diffused in certain areas of MEA countries. Design/methodology/approach: Through an explorative research design, using a mix of techniques based on both qualitative and interpretive methods, we conducted in-depth interviews among 33 European managers of companies engaged in MEA markets or aspiring to invest in such foreign markets, to analyse their thoughts, perceptions and possible strategies concerning the management of the "dark side" of cryptocurrencies in MEAs.FindingsOur investigation unearthed seven pivotal issues, which manifest as significant barriers related to the ambivalent use of crypto for funding projects, encompassing seven important consequential elements: (1) lack of knowledge about the technology's potentialities; (2) perceptions of crypto technology's ambivalence; (3) reputation and image consequences; (4) uncertainty about the destination of the invested funds; (5) decreased attractiveness of MEAs; (6) competition and market; and (7) lack of control and regulation. We grouped these into technology-related, business-related and legal- and policy-related barriers. Such findings underline the probable decrease in attractiveness of MEAs in terms of investments, together with the triggering factors and potential strategic solutions to mitigate such circumstances. Research limitations/implications: Future studies could explore a broader sample of managers since we only considered the perception of European managers operating in companies that invest (or are intending to invest) in MEAs. Moreover, future research may extend the analysis to MEA-native companies or those engaging in reciprocal exchanges with Western countries. Practical implications: Practically, our findings suggest several elements in which to intervene to mitigate managers' negative perception of the unethical use of cryptocurrencies in MEAs and to support CEOs' and CFOs' strategies, together with requirements to ensure the unaltered attractiveness of investments in an otherwise thriving region of the world, without overlooking the protection and safeguarding of investments and the health of the market and competition. Furthermore, a call for future research in this domain, along with at least minimal regulatory mechanisms, clearly emerges. Social implications: Our findings underline the social challenges associated with the perception and acceptance of cryptocurrencies in these contexts, influencing cultural and social dynamics. Moreover, the identification of these barriers could underscore the significance of awareness of and education on blockchain technology and cryptocurrencies within society, including implications for policymakers. Originality/value: Despite prior investigations into the negative effects of cryptocurrencies as a form of venture funding, no studies to date have examined managers' perceptions by focusing on possible barriers to investment in MEA countries due to the unethical usage of crypto. Importantly, this paper unravels the unexplored complexities of crypto's impact on ethical investments in MEAs, showcasing an original perspective

Using tanned leather waste to derive biochars for supercapacitor electrodes in various electrolytes

Chromium-tanned pigskin leather was carbonized in three ways: (1) pyrolysis in an inert atmosphere at 800 °C, (2) pre-carbonization at 500 °C followed by the activation with KOH at 800 °C, and (3) direct activation with excess KOH at 800 °C. The yield of biochars was comparable, 24–28 wt.%. The elemental composition of derived biochars and the content of inorganic elements in ash were determined, and the predominance of chromium and iron was discussed. The changes in the molecular structure after carbonization were assessed with the help of FTIR and Raman spectra. The KOH activation increased specific surface area and porosity but had minimal impact on conductivity. The electric conductivity of powders was determined as a function of applied pressure, achieving a value of approximately 1 S cm−1 at 10 MPa. The electrochemical performance was evaluated using aqueous electrolytes (1 M Na2SO4 and 6 M KOH), as well as an organic electrolyte (1 M tetraethylammonium tetrafluoroborate in acetonitrile, TEABF4/ACN). The highest specific capacitance achieved was 187.7 F g−1 in 6 M KOH using the three-electrode system. Biochar was also tested in a symmetrical supercapacitor, achieving a specific capacitance of 150.9 F g−1 in 6 M KOH, and maintaining 95% capacitance after 5000 charge/discharge cycles. The supercapacitor in 6 M KOH showed the highest power density of 10.5 kW kg−1, whereas the one in 1 M TEABF4/ACN demonstrated the highest energy density of 21.3 Wh kg−1.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (RP/CPS/2024–28/005, RP/2024/UNI/001, ENREGAT LM2023056); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMTMinistry of Education, Youth and Sports of the Czech Republic: DKRVO [RP/CPS/2024-28/005, RP/2024/UNI/001]; Large Research Infrastructure ENREGAT [LM2023056

Analytical approach in designing PID controller for complex fractional order transfer function

The study focuses on the fractional complex order plant model, which has gained popularity in applied mathematics, physics, and control systems. A significant contribution of this research lies in discussing the physical phenomena associated with complex plant models and their impact on system stability and robustness. The main purpose of the method presented in this paper is to tune the controller parameters to ensure the stability and robustness of the system. There are methods presented in the literature for this purpose. One of these methods is to keep the phase curve in the system frequency response flat within a certain range. However, this process is based on equating the derivative of the phase value to zero at a certain frequency and adds great mathematical complexity to the calculations. In this study, reliable analytical formulas are presented for the same purpose using a graphical approach. Since the fractional complex order plant model represents the most general mathematical form, it enables easy creation of other plant models, including integer order and fractional order plant. The reason why this plant is chosen is that this structure can be named as the universal plant, which all other structures can be built by making little variations. For instance, a transfer function having integer, real and/or complex number coefficients and/or orders can be obtained by proper determination of the parameters of the universal plant. A time delay can also be added towards researcher's desire. The main inspiration comes from studying on an inclusive plant. The method in this paper intends to tune the well-known classical Proportional Integral Derivative controller. Thus, effectiveness of the integer order controller on various plants will be shown. This approach provides analytical calculation equations for the physical modifications of plants with integer, fractional, and/or complex coefficients and/or orders. The effectiveness of the method is demonstrated visually with different examples that include these different possible situations. The results observed in the changes of the parameters in the transfer functions were also examined. Thus, pros and cons of the variations of integer, fractional, and complex numbers on system parameters have been shown

Potassium-based emulsifying salts in processed cheese: A rheological, textural, tribological, and thermal approach

The aim of the study was to investigate the effect of potassium-based emulsifying salts (ES; 2% wt/wt concentration) with different phosphate chain lengths (dipotassium hydrogenphosphate [K2HPO4; DKP], tetrapotassium diphosphate [K4P2O7; KTPP], pentapotassium triphosphate [K5P3O10; TKPP]) on the physicochemical, viscoelastic, textural, tribological, thermal, and sensory properties of processed cheese (PC; 40% wt/wt DM, 50% wt/wt fat in DM) during a 60d storage period (6 degrees C +/- 2 degrees C). On the whole, the hardness of all PC samples increased with the increasing chain length of ES (DKP G ''; tan delta < 1). The type of potassium-based ES affected the binding of water into the structure of the PC. Furthermore, the study confirmed that the manufactured PC received optimal sensory scores, without any excessive bitterness. It could be concluded that the type of applied ES and storage length affected the functional properties of PC. Finally, the information provided in this study could serve as a tool for the dairy industry to help appropriately select potassium-based ES for PC manufacture with desired properties.Internal Grant Agency of the Tomas Bata University in Zlin [IGA/FT/2024/005, IGA/CebiaTech/2024/002]Tomas Bata University in Zlín, TBU, (IGA/FT/2024/005, IGA/CebiaTech/2024/002

Do managers trust AI? An exploratory research based on social comparison theory

Purpose: The purpose of this study is to investigate managers' decision-making processes when evaluating suggestions provided by human collaborators or artificial intelligence (AI) systems. We employed the framework of Social Comparison Theory (SCT) in the business context to examine the influence of varying social comparison orientation levels on managers’ willingness to accept advice in their organization. Design/methodology/approach: A survey was conducted on a sample of 192 US managers, in which we carried out an experiment manipulating the source type (human vs AI) and assessing the potential moderating role of social comparison orientation. Results were analyzed using a moderation model by Hayes (2013). Findings: Despite the growing consideration gained by AI systems, results showed a discernible preference for human-generated advice over those originating from Artificial Intelligence (AI) sources. Moreover, the moderation analysis indicated how low levels of social comparison orientation may lead managers to be more willing to accept advice from AI. Research limitations/implications: This study contributes to the current understanding of the interplay between social comparison orientation and managerial decision-making. Based on the results of this preliminary study that used a scenario-based experiment, future research could try to expand these findings by examining managerial behavior in a natural context using field experiments, or multiple case studies. Originality/value: This is among the first studies that examine AI adoption in the organizational context, showing how AI may be used by managers to evade comparison among peers or other experts, thereby illuminating the role of individual factors in affecting managers' decision-making

Changes in the thermal and structural properties of polylactide and its composites during a long-term degradation process

As a polymer degrades, its structure changes, and the course of composting also affects the rate and degree of decomposition. Moreover, the potential exists for the formation of microplastics. This work focuses on the investigation of the long-term hydrolytic degradation of PLA-based composites at different temperatures (50, 55, and 60 °C, respectively). Samples were prepared on semi-industrial equipment, simulating actual production conditions. The effect of the degradation temperature on molecular weight was studied by gel permeation chromatography. Variation in the thermal properties and crystallinity of the PLA and its composites was investigated using differential scanning calorimetry and thermal gravimetric analysis. Mass loss during hydrolytic degradation was assessed using the gravimetric technique, and confirmation of microplastic residues in the hydrolyzed samples was evaluated using Fourier-transform infrared spectroscopy.European Just Transition Fund; Ministerstvo Školství, Mládeže a Tělovýchovy, MSMT; Ministerstvo Životního Prostředí, MoE, (RP/CPS/2024-28/007, CZ.02.01.01/00/23_021/0009004, RP/CPS/2024-28/002, CZ.10.03.01/00/22_003/0000045); Ministerstvo Životního Prostředí, MoE; Technology Agency of the Czech Republic, TACR, (TQ03000235); Technology Agency of the Czech Republic, TACREuropean Just Transition Fund within the Operational Programme: Just Transition under the aegis of the Ministry of the Environment of the Czech Republic; Operational Programme Johannes Amos Comenius OP JAC "Application potential development in the field of polymer materials in the context of circular economy compliance (POCEK)"; Development process of Centre of Polymer Systems, Tomas Bata University in Zlin, program DKRVO [RP/CPS/2024-28/002, RP/CPS/2024-28/007]; Ministry of Education Youth and Sports of the Czech Republic; Technology Agency of the Czech Republic [TQ03000235]; [CZ.10.03.01/00/22_003/0000045]; [CZ.02.01.01/00/23_021/0009004

Test parameter sensitivity of the Lake-Yeoh cutting method for measurement of intrinsic strength of rubber

The intrinsic strength of rubber, T0 is one of the key parameters when describing fracture behaviour of elastomer because it is at this specific value of energy that crack growth initiates within loaded rubber material. The Coesfeld Intrinsic Strength Analyzer (ISA) has been established as the most efficient equipment to directly analyse T0 for various rubber materials. However, to obtain the most reliable and reproducible results it is crucial to understand the influence of boundary conditions of the ISA measuring methodology. Therefore, in this study sets of boundary conditions were chosen to be analysed through mechanical response of reference EPDM material with known T0 value. For the purposes of this study the effects of individual boundary conditions were compared through directly measured value of intrinsic cutting energy, S0 which is proportional to T0. Blade sharpness and geometry showed the greatest impact followed by repetition of blade and specimen milling direction whereas the relaxation time and number of measuring strains showed no significant influence. The results of this study show that the knowledge of blade micro-geometry is at its most importance during the T0 analyses. Moreover, the data clearly indicates possible future modification of boundary conditions to achieve a very efficient testing procedure with significantly reduced time required for the analyses.This project is co-financed from the state budget by the Technology Agency of the Czech Republic under the M-ERA.NET 3 Call 2021 Programme (TH80020008) within the European Union\u2019s Horizon 2020 research an innovation program under grant agreement (No. 958174)\u201D and by the Ministry of Education, Youth and Sports of the Czech Republic\u2014DKRVO (RP_CPS_2024_28_006). The authors are also grateful for the funding of the grant received from The Internal Grant Agency (IGA) of TBU in Zlin\u2014(IGA/CPS/2025/005)CzechELib Transformative Agreemen

Prediction of creep behavior in short fiber reinforced polymer matrix composites using an elementary volume approach

Creep behavior of short glass fiber reinforced poly(butylene terephthalate) (SFRC PBT) composites was analyzed using plates processed by injection molding and push–pull processing, with fiber contents of 0, 20, and 30 wt%. Tensile test bars were extracted parallelly and perpendicularly to the flow direction to assess short-term mechanical properties, fiber length distribution, and orientation. An elementary volume approach was used to predict the longitudinal and transverse creep compliances, showing that the time dependencies were mainly governed by the PBT matrix. Given the minimal fiber orientation in the thickness direction, a transformation based on RM Jones’ mechanics of composite materials was applied to account for fiber misalignment. This led to the introduction of the unknown shear modulus G12, which was addressed by expressing it in terms of the transverse compliance J22 and shear correction factor. Comparison of predicted and measured creep compliances revealed an underestimation of 15–30% parallelly and 5–15% perpendicularly to the flow direction, attributed to imperfect fiber-matrix adhesion. SEM analysis of fracture surfaces indicated different failure behaviors based on the fiber orientation. This suggests that fiber-matrix adhesion is stress-direction dependent. The time range for accurate prediction of composite creep behavior, governed by matrix creep, is defined by the creep time limit, which decreases exponentially with increasing creep stress.CzechELib Transformative Agreemen