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A potential paradigm shift in global mobility? the impact of the COVID-19 pandemic
Get PDFThe COVID-19 pandemic profoundly affected the global mobility (GM) policies of multinational enterprises (MNEs). Through interviews with policy decision-makers in 32 companies, we applied Interpretative Phenomenological Analysis to examine how the pandemic accelerated changes in MNE policies and the management of GM. Our framework builds on contingency theory, traditionally concerned with aligning organizational policies with macro- and meso-level contextual factors. We extend this by integrating micro-level individual variables, such as career aspirations and well-being, as contingent factors influencing GM practices. There is variation in GM responses in relation to the volume of GM activities, GM-related policies, investments in digitalization and technology, and variations in mobility types. We observed a potential paradigm shift that affords employees greater agency in their global mobility paths, thereby greater granularity to contingency theory. This nuanced approach opens new research avenues and equips organizational leaders with a comprehensive set of variables for GM decision-making. Our findings indicate lasting global mobility changes but foresee gradual implementation due to associated risks.This work was supported by the Ministerio de Ciencia e Innovaci´on [Grant number PID2020–115018RB-C31]. This work was supported by the Liikesivistysrahasto (Foundation for Economic Education). [Grant number 22-12559]
Control of flow separation over an aerofoil by external acoustic excitation at a high Reynolds number
Get PDFThe effectiveness of acoustic excitation as a means of flow control at high Reynolds
number turbulent flows is investigated numerically by using Improved Delayed Detached
Eddy Simulations. Previous studies on low Reynolds number laminar flows have shown
that acoustic excitation can substantially suppress flow separation for specific effective
frequency and amplitude ranges. However, the effect of acoustic excitation on higher
Reynolds number turbulent flow separation has not yet been explored due to limitations
on appropriate fidelity computational methods or experimental facility constraints. Therefore,
this paper addresses this research gap. A NACA (National Advisory Committee for
Aeronautics) 0015 aerofoil profile at 1 million Reynolds number based on the aerofoil
chord length is used for the investigations. Acoustic excitation is applied to the baseline
flow field in the form of transient boundary conditions at the computational domain inlet.
A parametric study revealed that the effective sound frequency range shows a Gaussian
distribution around the frequency of the dominant disturbances in the baseline flow. A
maximum of ∼ 43% increase in lift-to-drag ratio is observed for the most effective excitation
frequency F+ = 1.0 at a constant excitation amplitude of Am = 1.8%. The effect
of excitation amplitude follows an asymptotic trend with a maximum effective excitation
amplitude above which the gains are not significant. A fully reattached flow is observed
for the highest excitation level considered (Am = 10%), that results in ∼ 120% rise in
aerofoil lift-to-drag coefficient. Overall, the findings of the current work demonstrate the
higher Reynolds number effectiveness of acoustic excitation on separated turbulent flows,
thereby paving the way for application in realistic flow scenarios observed in aircraft and
gas turbine engine flow fields.Physics of Fluid
Individuals' career perceptions in different institutionalized contexts: a comparative study of career actors in liberal, coordinated, hierarchical and mediterranean market economies
Get PDFLeveraging Weiner's attribution theory of intrapersonal motivation at the micro level and varieties of capitalism theory at the macro level, we conduct a multi-country and cross-level study examining whether individuals' career goals (i.e., perceived importance of learning and development), behaviors (i.e., proactive career behaviors), and outcomes (i.e., perceived employability) as well as the relationships between these variables, differ between different market economies. We challenge extant literature that focuses on the agentic role of individuals and understates the role of context (i.e., market economy influence) in an individual's career development. Using multilevel structural equation modeling, we draw on a survey of 15,201 individuals between 2014 and 2016 from 22 countries representing four different varieties of capitalism. The results showed that workers in hierarchical (HME) and Mediterranean (MME) market economies systematically differed from individuals in coordinated (CME) and liberal (LME) market economies in proactive career behaviors and perceived employability. Moreover, while the positive relationship between perceived importance of learning and development and proactive career behaviors was stronger in CMEs and LMEs compared to HMEs and MMEs, the positive association between proactive career behaviors and perceived employability was weaker. Our study bridges the micro-macro gap in career studies, adding new insights into the ongoing conversation of contextual influence in individuals' career development
Chrysin directing an enhanced solubility through the formation of a supramolecular cyclodextrin–calixarene drug delivery system: a potential strategy in antifibrotic diabetes therapeutics
Get PDFCalixarene 0118 (OTX008) and chrysin (CHR) are promising molecules for the treatment of fibrosis and diabetes complications but require an effective delivery system to overcome their low solubility and bioavailability. Sulfobutylated β-cyclodextrin (SBECD) was evaluated for its ability to increase the solubility of CHR by forming a ternary complex with OTX008. The resulting increase in solubility and the mechanisms of complex formation were identified through phase-solubility studies, while dynamic light-scattering assessed the molecular associations within the CHR-OTX008-SBECD system. Nuclear magnetic resonance, differential scanning calorimetry, and computational studies elucidated the interactions at the molecular level, and cellular assays confirmed the system’s biocompatibility. Combining SBECD with OTX008 enhances CHR solubility more than using SBECD alone by forming water-soluble molecular associates in a ternary complex. This aids in the solubilization and delivery of CHR and OTX008. Structural investigations revealed non-covalent interactions essential to complex formation, which showed no cytotoxicity in hyperglycemic in vitro conditions. A new ternary complex has been formulated to deliver promising antifibrotic agents for diabetic complications, featuring OTX008 as a key structural and pharmacological component.Pharmaceutical
Co-occurrence of PFASs, TPHs, and BTEX in subsurface soils: impacts on native microbial communities and implications for bioremediation
Get PDFThis study investigates the co-occurrence of per- and polyfluoroalkyl substances (PFASs), petroleum hydrocarbons (TPHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) and their effects on the indigenous microbial communities in soils at a contaminated site with a history of petroleum refinery operations. PFASs concentrations were in the range of 5.65–6.73 ng/g, and fluorooctane sulfonate (PFOS) and perfluorobutane sulfonic acid (PFBS) were the dominating compounds. No significant difference was observed in the PFASs concentration profiles between the site and background locations, indicating that PFASs detected in the soil samples were mainly contributed from non-point sources, due to the long-distance transport of PFASs in the region. The concentrations of TPHs and BTEX ranged from 227 to 72,360 mg/kg and 0.06–2109.77 mg/kg, respectively, mainly contributed by the historical refinery activities. The presence of PFASs, TPHs, and BTEX significantly impacted soil microbial community diversity and abundance, altering microbial compositions and enriching bacteria with higher resistance or metabolic capabilities against contamination. Strong correlations were observed between TPHs and its degraders such as Pseudomonas, Azoarcus, and Polaromonas. Significant positive relationship between PFASs and Trichlorobacter implied the potential defluorination capabilities of Trichlorobacter, warranting further investigation. Moreover, the higher energy metabolism including carbon, nitrogen and sulfur metabolisms and higher abundance of metabolic enzymes for alkane, cyclohexane and toluene in the refinery site revealed the potential occurrence of natural biodegradation of contaminants with indigenous microbial community. These findings highlight the complexity of sites contaminated with a mixture of traditional and emerging contaminants, providing valuable insights into the potential for biodegradation of mixed contaminants and underscoring the need for integrated approaches in environmental remediation strategies. This study contributes to understanding the ecological impacts of co-occurring contaminants and emphasizes the importance of considering multiple contaminant types in environmental risk assessments and remediation efforts.National Natural Science Foundation of China, European Commission, Ministry of Science and Technology of the People's Republic of ChinaThis work was funded by the National Natural Science Foundation of China (No. 32061133001; No. 42277029), the National key research and development program of China (No. 2019YFC1805700 and No. 2019YFC1805703), and the CSCEC Eco-Environmental Engineering Research Center (Soil Remediation Technology and Equipment) (CSCEC-PT-009). We acknowledge the cooperation between China and the EU through the EiCLaR project (European Union's Horizon 2020; N◦965945).Environmental Researc
Generalized time-to-go inversion guidance with impact time and angle constraints
Get PDFA major challenge in homing guidance is that accurately predicting the time to go for missiles is generally difficult, which limits the practical application of a certain class of guidance laws with impact-time constraints or cooperative capabilities. To address this issue, a generalized method referred to as the time-to-go inversion guidance is presented, where the time to go is first specified as an explicit function and then the corresponding guidance law is inversely derived. By employing this new method, a variety of guidance laws and their globally accurate time-to-go solutions can be developed, regardless of whether the impact-angle constraint is considered or not. Different from all existing studies, the proposed method addresses the problem of time-to-go estimation without relying on any linearizing approximations or numerical iterations. To enhance the practicality of the proposed method, it is augmented with bias commands to result in either the impact time control guidance law or the impact time and angle control guidance law. Numerical simulation results demonstrate the higher accuracy, larger feasible solution region, and lower computational demand of the proposed guidance laws even for the missiles with nonconstant speeds.Journal of Guidance, Control, and Dynamic
Environmental sustainability performance of US airlines: implications of financial performance and technical efficiency
Get PDFSpecial edition: SI-Operational Research for Sustainability and Sustainable DevelopmentAir transportation significantly contributes to global CO2 emissions. The US Aviation Climate Action Plan introduced in November 2021 aims to decarbonize the aviation sector by 2050. Aligned with this initiative, our study applies Data Envelopment Analysis and fixed-effect panel regression to empirically explore how financial performance and technical efficiency impact Environmental Sustainability Performance (ESP) in the airline industry. We curated panel data of nine US passenger airlines from 2010 to 2019 to examine three key areas: the impact of financial performance on environmental sustainability performance, the influence of efficiency on environmental sustainability performance, and the relationship between flight stage length and environmental sustainability performance. Our findings indicate that improved Financial Performance, higher technical efficiency, and longer stage lengths positively contribute to enhanced environmental sustainability performance. Our study provides valuable insights for managers and policymakers, emphasizing the pivotal role of financial stability in achieving environmental goals within the airline industry. It underscores the intricate connection between economic viability and sustainability, offering guidance for policymakers seeking to balance financial success with environmental goals.Journal of the Operational Research Societ
Sparse online Gaussian process adaptive control of unmanned aerial vehicle with slung payload
Get PDFIn the past decade, Unmanned Aerial Vehicles (UAVs) have garnered significant attention across diverse applications, including surveillance, cargo shipping, and agricultural spraying. Despite their widespread deployment, concerns about maintaining stability and safety, particularly when carrying payloads, persist. The development of such UAV platforms necessitates the implementation of robust control mechanisms to ensure stable and precise maneuvering capabilities. Numerous UAV operations require the integration of payloads, which introduces substantial stability challenges. Notably, operations involving unstable payloads such as liquid or slung payloads pose a considerable challenge in this regard, falling into the category of mismatched uncertain systems. This study focuses on establishing stability for slung payload-carrying systems. Our approach involves a combination of various algorithms: the incremental backstepping control algorithm (IBKS), integrator backstepping (IBS), Proportional–Integral–Derivative (PID), and the Sparse Online Gaussian Process (SOGP), a machine learning technique that identifies and mitigates disturbances. With a comparison of linear and nonlinear methodologies through different scenarios, an investigation for an effective solution has been performed. Implementation of the machine learning component, employing SOGP, effectively detects and counteracts disturbances. Insights are discussed within the remit of rejecting liquid sloshing disturbance.The authors would like to express very great appreciation to the Ministry of National Education of the Republic of Türkiye for funding this project.Drone
The influence of neighbours’ supply network structure on firm’s environmental, social and governance controversies
No full textThis study investigates how the structural characteristics of a firm's supply network and its neighbouring firms affect their environmental, social, and governance (ESG) controversies. A secondary dataset comprising 18,943 firms and 103,632 contractual links from the global automotive industry was employed to test the hypotheses. Publicly available ESG controversies data for 268 firms were gathered from the Thomson Reuters Eikon database. The results indicated a negative relationship between the interconnectedness of neighbours’ networks and their ESG controversies. The results further revealed a positive association between the centrality of a firm’s neighbours and their ESG controversies. Furthermore, the study highlighted that a firm occupying a bridging position positively moderates the relationship between neighbours’ interconnectedness and ESG controversies. Drawing on a real-world large-scale supply network, our study extends the emerging debate on the criticality of broader supply networks in firms’ sustainability by investigating the role of neighbours’ structural properties in firms’ ESG controversies.International Journal of Production Researc
Mechanism-based thermodynamic analysis for one-step and two-step ethanol-to-1,3-butadiene conversion processes
Get PDFRenewable 1,3-butadiene (BD) is essential for sustainability of the synthetic rubber sector. This work presents a comprehensive thermodynamic analysis for one- and two-step ethanol-to-BD conversion processes. The two-step process comprises ethanol dehydrogenation, followed by the condensation of acetaldehyde with another ethanol molecule into BD. The process involves a complex reaction network with a wide range of byproducts depending on the nature of the catalysts and operating conditions, lacking unique consensus on the C-C bond-forming mechanism. This study elucidates the temperature regime for the spontaneity of the reactions proposed in various mechanisms and side reactions based on the standard Gibbs free energy change. The equilibrium conversion and product selectivity were further calculated under a wide temperature and pressure range. The overall reaction in the one-step process is thermodynamically spontaneous above 417 K, while the first and second steps of the two-step process are spontaneous above 550 and 285 K, respectively. Excepting Prins condensation, other mechanisms lack the spontaneity of all reaction steps. The equilibrium BD selectivity is favorable at elevated temperatures and low pressures. The addition of acetaldehyde in the two-step process has a favorable impact with higher BD selectivity, the maximum being at a 1:1 molar ratio of ethanol/acetaldehyde. This study elucidates thermodynamic insights into existing mechanisms and drives the evolution of a feasible mechanism. This effort will eventually help design novel catalysts and optimized processes for sustainable biobased BD production using ethanol derived from renewable feedstocks, aligning with the global commitment to greener and resource-friendly chemical manufacturing.Industrial & Engineering Chemistry Researc