2,316 research outputs found
Linear Amplification in Nonequilibrium Turbulent Boundary Layers
Resolvent analysis is applied to nonequilibrium incompressible adverse pressure gradient (APG) turbulent boundary layers (TBL) and hypersonic boundary layers with high temperature real gas effects, including chemical nonequilibrium. Resolvent analysis is an equation-based, scale-dependent decomposition of the Navier Stokes equations, linearized about a known mean flow field. The decomposition identifies the optimal response and forcing modes, ranked by their linear amplification. To treat the nonequilibrium APG TBL, a biglobal resolvent analysis approach is used to account for the streamwise and wall-normal inhomogeneities in the streamwise developing flow. For the hypersonic boundary layer in chemical nonequilibrium, the resolvent analysis is constructed using a parallel flow assumption, incorporating N₂, O₂, NO, N, and O as a mixture of chemically reacting gases.
Biglobal resolvent analysis is first applied to the zero pressure gradient (ZPG) TBL. Scaling relationships are determined for the spanwise wavenumber and temporal frequency that admit self-similar resolvent modes in the inner layer, mesolayer, and outer layer regions of the ZPG TBL. The APG effects on the inner scaling of the biglobal modes are shown to diminish as their self-similarity improves with increased Reynolds number. An increase in APG strength is shown to increase the linear amplification of the large-scale biglobal modes in the outer region, similar to the energization of large scale modes observed in simulation. The linear amplification of these modes grows linearly with the APG history, measured as the streamwise averaged APG strength, and relates to a novel pressure-based velocity scale.
Resolvent analysis is then used to identify the length scales most affected by the high-temperature gas effects in hypersonic TBLs. It is shown that the high-temperature gas effects primarily affect modes localized near the peak mean temperature. Due to the chemical nonequilibrium effects, the modes can be linearly amplified through changes in chemical concentration, which have non-negligible effects on the higher order modes. Correlations in the components of the small-scale resolvent modes agree qualitatively with similar correlations in simulation data.
Finally, efficient strategies for resolvent analysis are presented. These include an algorithm to autonomously sample the large amplification regions using a Bayesian Optimization-like approach and a projection-based method to approximate resolvent analysis through a reduced eigenvalue problem, derived from calculus of variations.</p
LIPIcs, Volume 251, ITCS 2023, Complete Volume
LIPIcs, Volume 251, ITCS 2023, Complete Volum
Effects of municipal smoke-free ordinances on secondhand smoke exposure in the Republic of Korea
ObjectiveTo reduce premature deaths due to secondhand smoke (SHS) exposure among non-smokers, the Republic of Korea (ROK) adopted changes to the National Health Promotion Act, which allowed local governments to enact municipal ordinances to strengthen their authority to designate smoke-free areas and levy penalty fines. In this study, we examined national trends in SHS exposure after the introduction of these municipal ordinances at the city level in 2010.MethodsWe used interrupted time series analysis to assess whether the trends of SHS exposure in the workplace and at home, and the primary cigarette smoking rate changed following the policy adjustment in the national legislation in ROK. Population-standardized data for selected variables were retrieved from a nationally representative survey dataset and used to study the policy action’s effectiveness.ResultsFollowing the change in the legislation, SHS exposure in the workplace reversed course from an increasing (18% per year) trend prior to the introduction of these smoke-free ordinances to a decreasing (−10% per year) trend after adoption and enforcement of these laws (β2 = 0.18, p-value = 0.07; β3 = −0.10, p-value = 0.02). SHS exposure at home (β2 = 0.10, p-value = 0.09; β3 = −0.03, p-value = 0.14) and the primary cigarette smoking rate (β2 = 0.03, p-value = 0.10; β3 = 0.008, p-value = 0.15) showed no significant changes in the sampled period. Although analyses stratified by sex showed that the allowance of municipal ordinances resulted in reduced SHS exposure in the workplace for both males and females, they did not affect the primary cigarette smoking rate as much, especially among females.ConclusionStrengthening the role of local governments by giving them the authority to enact and enforce penalties on SHS exposure violation helped ROK to reduce SHS exposure in the workplace. However, smoking behaviors and related activities seemed to shift to less restrictive areas such as on the streets and in apartment hallways, negating some of the effects due to these ordinances. Future studies should investigate how smoke-free policies beyond public places can further reduce the SHS exposure in ROK
Current and Future Challenges in Knowledge Representation and Reasoning
Knowledge Representation and Reasoning is a central, longstanding, and active
area of Artificial Intelligence. Over the years it has evolved significantly;
more recently it has been challenged and complemented by research in areas such
as machine learning and reasoning under uncertainty. In July 2022 a Dagstuhl
Perspectives workshop was held on Knowledge Representation and Reasoning. The
goal of the workshop was to describe the state of the art in the field,
including its relation with other areas, its shortcomings and strengths,
together with recommendations for future progress. We developed this manifesto
based on the presentations, panels, working groups, and discussions that took
place at the Dagstuhl Workshop. It is a declaration of our views on Knowledge
Representation: its origins, goals, milestones, and current foci; its relation
to other disciplines, especially to Artificial Intelligence; and on its
challenges, along with key priorities for the next decade
Analytical validation of innovative magneto-inertial outcomes: a controlled environment study.
peer reviewe
Systems Analysis for Sustainable Wellbeing. 50 years of IIASA research, 40 years after the Brundtland Commission, contributing to the post-2030 Global Agenda
This report chronicles the half-century-long history of the International Institute for Applied Systems Analysis (IIASA), established in 1972 in Laxenburg, Austria, to address common social, economic, and environmental challenges at a time when the world was politically dominated by the Cold War.
The report shows IIASA’s transition from its original raison d’être as a cooperative scientific venture between East and West to its position today as a global institute engaged in exploring solutions to some of the world’s most intractable problems—the interconnected problems of population, climate change, biodiversity loss, land, energy, and water use, among others.
It provides a concise overview of IIASA’s key contributions to science over the last 50 years and of the advances it has made not only in analyzing existing and emerging trends but also in developing enhanced scientific tools to address them. The report also shows how IIASA is currently working with distinguished partners worldwide to establish the scientific basis for a successful transition to sustainable development.
The global mandate, to achieve the 2030 Agenda, its 17 Sustainable Development Goals (SDGs), and 169 specific targets, features prominently in the institute’s work and in the report at hand: the pathways needed to achieve the SDGs have been the basis of many scientific studies by IIASA and its partners. The predominantly “bottom-up” nature of tackling the SDGs has required optimal responses to the very diverse and overlapping issues they involve, including judicious tradeoffs among the solutions that can be applied. Now, at the mid-term review point of the 2030 Agenda, this report focuses on the big picture and clarifies why, after years of scientific endeavor, the ultimate goal of this difficult global mandate should be sustainable wellbeing for all.
The report is in six parts that summarize past and current IIASA research highlights and point toward future challenges and solutions: i) Systems analysis for a challenged world; ii) Population and human capital; iii) Food security, ecosystems, and biodiversity; iv) Energy, technology, and climate change; v) Global systems analysis for understanding the drivers of sustainable wellbeing; and vi) Moving into the future: Three critical policy messages.
The three critical policy messages, necessary to trigger discussions about a post-2030 Agenda for Sustainable Development are: (1) Suboptimization is suboptimal: Mainstream a systems-analysis approach into policymaking at all levels. (2) Enhance individual agency: Prioritize women’s empowerment through universal female education; and (3) Strengthen collective action and governance: Global cooperation and representation for the global common
The Application of Simulation to Quantifying the Influence of Bias in Perinatal Epidemiology
Perinatal aetiological associations derived from observational data are susceptible to various types of bias. This thesis demonstrated the application of simulation methodologies to quantify the influence of bias in perinatal epidemiology through a series of simulation studies which quantified the magnitude and direction of bias mechanisms. A framework to guide epidemiologists in the development, implementation and reporting of simulation studies to quantify bias was developed. Simulation is a potent tool to the quantification of bias
Desired sensory branding strategies in-store versus online: the skincare industry
Modern shoppers are inundated with purchasing options in every product category, with thousands of brands competing for their patronage. It has therefore become increasingly important for organisations to differentiate product offerings in the market if they want to be competitive. It has further been highlighted that an individual’s experience of a brand is of paramount importance, as it is directly linked to brand loyalty. A vehicle for creating memorable brand experiences is the utilisation of multi-sensory experiences or sensory branding. Within the context of traditional or in-store shopping, sensory branding encompasses the use of visual, auditory, olfactory, tactile and gustatory stimuli to adjust consumer purchasing behaviour. However, more and more consumers are opting for online shopping, spurred on by the effects of the global COVID-19 pandemic, and are no less demanding of brands online than they would be in-store. The cosmetics and personal care industry is one of the more predominant gainers from e-commerce. The skincare industry exhibited one of the largest growth rates from 2019 – 2025 and had an estimated market value of 788.4 million by 2027 (Statista 2023). With reference to in-store shopping for skincare products, sensory marketing strategies have been known to be heavily relied on. Therefore, with consumers moving towards online shopping, it is essential for skincare businesses to consider how to deliver sensory experiences online as well as in-store. Whilst the importance of the use of sensory branding and marketing in the skincare industry is notable, both in-store and online, it was established that while there is research available on sensory branding, there is very limited academic research on digital sensory branding and the sensory branding of v skincare products. Moreover, to the researcher’s knowledge, no academic literature specifically investigates the digital sensory branding of skincare brands. Therefore, this study will contribute not only by adding academic research to the topic being investigated but also through rreccomendations made based on the outcomes of this study to skincare brands in South Africa. From the comprehensive literature review, a conceptual model was constructed to investigate the relationship between traditional and digital sensory branding strategies (independent variables) and brand loyalty (dependent variable). Two sets of hypotheses were formulated relating to the identified variables of this study and the empirical research conducted was utilised to deduce whether these hypotheses should be rejected or supported. To conduct the empirical research needed for this study, certain research methodology was employed. This study made use of a positivistic paradigm and a quantitative approach. The target population of this study constituted consumers who had purchased skincare products in-store as well as online and, as no true sample frame existed, respondents were selected through the use of non-probability sampling, more specifically, convenience sampling. To collect the data, an online survey was used, with the specific data collection instrument being a web-based self-administered questionnaire, which was distributed via social media platforms, such as Facebook and LinkedIn, as well as via email. Section A of the questionnaire focused on the demographic details of the respondents, while Section B – Section F related to the variables of the study. A total of 372 potential respondents started the questionnaire, however only 321 questionnaires were deemed usable after the data had been coded and cleaned, indicating a response rate of 86.3%. This study made use of both descriptive (measures of central tendency as well as standard deviation and skewness) and inferential (SEM Models, Primary Models, Pearson’s correlation coefficients, Chi-Square test of Association, ANOVAs and Welch Robust test, Tukey test and Games Howell Test as well as Cohen’s d) statistics to interpret the data, which was graphically illustrated. vi The empirical investigation conducted in this study between the variables and sub-variables revealed that significant relationships exist between traditional sensory branding strategies (traditional olfactory and tactile stimuli) and digital sensory branding strategies (digital visual, olfactory and tactile stimuli) and brand loyalty, with refence to the skincare industry. It was further notable that, with specific reference to the skincare industry, the sense of sight, smell and touch are key factors for sensory branding, whereas auditory stimuli were found to only be useful when used in unison with the other senses. Moreover, with reference to in-store shopping, it was deduced that consumers shop for skincare mostly via retail outlets, which could lead to sensory overload. Furthermore, the results of this study suggest that younger consumers are price sensitive. Based on the pertinent empirical results, and corresponding literature findings, of this study, recommendations were provided to businesses operating in the skincare industry. With reference to in-store trading, it was recommended that because skincare is mostly sold via retail outlets, the brand itself does not have control over all sensory stimuli to which the consumer is exposed. As a result, consumers may be subject to sensory overload and skincare brands should keep their sensory branding in-store simple. Moreover, skincare brands could make use of an in-store aesthetician or beautician, which would facilitate consumer-product interaction. With regards to online trading, a recommendation for skincare brands would be to use moving images or GIFs, which will allow the consumer to more easily imagine the feel of the product. Moreover, skincare brands can make use of brand ambassadors to create “unboxing” videos, which will convey more clearly the sensory information of the product and instil confidence in consumers. Reccomendations were also made with reference to the financial state of consumers, as the financial position of the respondents could influence their decision making. The limitations of this study comprised the availability of reliable existing sources to support the study as the concept of digital sensory branding is still relatively new and, due to the study being focused on the skincare industry, taste stimuli were excluded as they were found to have no relevance. Finally, vii based on all the literature findings and empirical results, recommendations for future areas of study were made. This study provides evidence that both traditional and digital sensory branding strategies have an influence on, or relationship with, brand loyalty. Through this study, the importance of sensory branding, with specific reference to the skincare industry, is brought to light. Furthermore, skincare brands can utilise the information provided to improve the experience of their consumers when shopping in-store, as well as online, thereby increasing their base of brand loyal consumers.Thesis (PhD) -- Faculty of Business and Economic Sciences, 202
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Rapid Neutron-Capture Nucleosynthesis from the Births and Deaths of Neutron Stars
The astrophysical origins of the rapid neutron-capture process (r-process), which gives rise to roughly half of the elements heavier than iron, has remained a mystery for almost 70 years. The likely violent events, which seed the r-process abundances in our solar system and galaxy, remain uncertain to this day. This is in part due to nuclear physics uncertainties associated with the r-process itself, but mainly due to uncertainties in astrophysics modeling. The discovery of the radioactively-powered kilonova emission from the neutron star merger event GW170817 confirmed the violent deaths of neutron stars as one key site of the r-process in the universe. However, other evidence appears to favor an additional r-process channel that more promptly follows star formation in the universe, such as core-collapse supernovae (CCSNe), i.e. the brilliant births of neutron stars.
The two viable sites for the r-process are (1) core-collapse supernovae (CCSNe), which are explosions of massive stars at the end of their lives and (2) compact object mergers, which are violent collisions of stellar remnants formed at the endpoints of stellar evolution.
Chapters 2 and 3 of this dissertation present general relativistic magnetohydrodynamic simulations of one potential r-process site associated with CCSNe: the neutrino-driven wind. These outflows are launched from the hot proto-neutron star (PNS) remnant by neutrino-heating above their surfaces, within seconds after the collapse of a massive star. However, previous work has shown that spherically symmetric winds from non-rotating PNS fail to achieve the requisite conditions for a robust r-process. Chapter 2 explores for the first time the combined effects of rapid rotation and strong gravity of the PNS on the wind properties. Chapter 3 explores the impact of a dynamically strong ordered magnetic field on the properties of non-rotating PNS winds. The wind in both cases is simulated in a controlled environment rather than as a part of a self-consistent global CCSNe simulation, to assess the viability of r-process nucleosynthesis as a function of PNS properties (neutrino energies/luminosities, rotation rate, magnetization).
We find that rapid rotation allows for outflows that are ~10% more neutron-rich in the equatorial region, where the mass loss rate is roughly an order of magnitude higher than that of otherwise equivalent non-rotating models. The birth of very rapidly spinning neutron stars may thus be a site for the production of light r-process nuclei (38 < Z < 47). For PNSs with sufficiently strong magnetic fields (such that magnetic pressure exceeds gas pressure above the PNS surface), we find that equatorial outflows are trapped by the magnetic field in a region near the surface, and therefore receive additional neutrino heating relative to a freely-expanding unmagnetized wind. This allows a modest fraction of the wind material to achieves entropies high enough to synthesize 2nd peak r-process elements via an alpha-rich freeze-out mechanism.
The final chapter explores the interplay between the r-process and the dynamics of compact object merger ejecta. Gravitational wave observatories are expected to detect several additional binary neutron star (BNS) and black hole-neutron star (BHNS) mergers in current and future observing runs, some of which may be accompanied by electromagnetic counterparts such as kilonovae. However, distinguishing more distant BNS from BHNS mergers based on their associated gamma-ray bursts (GRB), has proven tricky.
This chapter presents a calculation of the effects of r-process heating on the dynamics of tidal ejecta from BNS and BHNS mergers. In particular we explore whether late-time fall-back of weakly bound debris created during the merger to the central black hole remnant, can explain the temporally extended X-ray emission observed following several merger GRB on timescales of several seconds to minutes. As a result of the different impact that r-process heating has depending on the composition of the ejecta and the mass of the black hole, a method to differentiate BHNS from BNS mergers, based on their extended X-ray emission, is proposed
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