766 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 Nâ‚‚, Oâ‚‚, 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
AI: Limits and Prospects of Artificial Intelligence
The emergence of artificial intelligence has triggered enthusiasm and promise of boundless opportunities as much as uncertainty about its limits. The contributions to this volume explore the limits of AI, describe the necessary conditions for its functionality, reveal its attendant technical and social problems, and present some existing and potential solutions. At the same time, the contributors highlight the societal and attending economic hopes and fears, utopias and dystopias that are associated with the current and future development of artificial intelligence
Pan-cancer analysis of post-translational modifications reveals shared patterns of protein regulation
Post-translational modifications (PTMs) play key roles in regulating cell signaling and physiology in both normal and cancer cells. Advances in mass spectrometry enable high-throughput, accurate, and sensitive measurement of PTM levels to better understand their role, prevalence, and crosstalk. Here, we analyze the largest collection of proteogenomics data from 1,110 patients with PTM profiles across 11 cancer types (10 from the National Cancer Institute\u27s Clinical Proteomic Tumor Analysis Consortium [CPTAC]). Our study reveals pan-cancer patterns of changes in protein acetylation and phosphorylation involved in hallmark cancer processes. These patterns revealed subsets of tumors, from different cancer types, including those with dysregulated DNA repair driven by phosphorylation, altered metabolic regulation associated with immune response driven by acetylation, affected kinase specificity by crosstalk between acetylation and phosphorylation, and modified histone regulation. Overall, this resource highlights the rich biology governed by PTMs and exposes potential new therapeutic avenues
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
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Assembly of polymer colloids at fluid interfaces through external fields and nanoscale surface topography
The superposition of dipolar repulsion and capillary attraction energies between colloidal particles pinned at fluid interfaces dictates their microstructural organization and therefore the macroscopic interfacial material properties of particle-stabilized emulsions and 2D monolayer materials. While isotropic, spherical, particles have been extensively utilized, expanding the possible applications and material property tunability via anisotropic particles has been a challenge due to the propensity of particles to form disordered aggregates at the interface. My thesis presents the synthesis of anisotropic polymer ellipsoids and the development and use of experimental tools to study their interfacial behavior to reveal how dipolar and capillary interactions can be manipulated through external fields and particle topography in order to ultimately create novel 2D monolayer interfacial assemblies.
We first demonstrated a technique to apply an elongation gradient to manufacture multiple batches of lab-scale quantities of colloidal ellipsoids in a single step. A common route to creating anisotropic colloids is the mechanical stretching of spherical polymer colloids into ellipsoids above the glass transition temperature of the polymer. While this general method has been well studied in the production of a single aspect ratio colloidal ellipsoid per batch, we extended the technique to cover the production of multiple monodisperse samples of colloidal ellipsoids. Because these colloidal ellipsoids each underwent the same synthetic procedure, we were able to modulate particle aspect ratio as an independent variable with no sample-to-sample batch variation. Further, we were able to model the elongation of the particles based on the film characteristics to predict their final aspect ratio.
Next, we used these particles to investigate the assembly of ellipsoids under external AC electric fields, both in bulk and at air-water interfaces. We investigated ellipsoidal particle alignment in bulk aqueous solution in order to narrow down the phase space of applied AC electric field strength and frequency, as well as ionic strength to conditions favorable to particle reorientation. We then used these results to inform studies on these same particles at an air-water interface. We developed a first of its kind Mirau interferometer that can measure the relative height profile of the fluid surrounding an interfacially pinned colloid with nanometer precision concurrent with external field application. Under static conditions, increasing the particle aspect ratio decreases the interfacial three-phase contact angle, but increases the relative interfacial deformation and therefore capillary attraction. Applied electric fields change the location of the particle relative to the fluid interface as well as how the fluid interface approaches the three-phase contact line with the particle surface. As the electric field strength increases, the contact angle increases for anisotropic particles. By controlling the contact angle with external fields, the interparticle capillary forces, and thus the final two-dimensional particle assembly, may be controlled in the future.
We also investigated the use of magnetic fields to interfacially assemble spherical polystyrene/iron oxide hybrid colloids. Different combinations of ionic strength and DC magnetic field strengths are applied to monolayers of particles, revealing an intricate state space transitioning between disordered clusters and hexagonal latices. Interfacial assemblies were characterized using 2D finite Fourier transforms to measure the amount of order under different solution-field conditions. The height of the fluid interface surrounding the pinned colloids during magnetic field application was measured using Mirau interferometry, indicating that alteration of capillary interactions via changes to interfacial pinning are occurring simultaneously with induced dipolar forces.
While our previous studies sought to modulate the interparticle potential via induced dipolar and changing capillary forces, we next discovered a way to control interfacial capillary forces through particle engineering. We accomplished this through the introduction of nanoscopic physical heterogeneity to the surface of polymer microellipsoids that alters the interparticle interactions when they are pinned at an aqueous-air interface. Leveraging the experimental tools we developed, we used a combination of Mirau interferometry and video microscopy to show that porous micron-sized ellipsoids at an aqueous-air interface behave in fundamentally different ways than their smooth counterparts. Particles with a nanoscale porous network show no quadrupolar deformation of the fluid interface, a trademark of smooth, homogeneous, colloidal ellipsoids. This causes the capillary interaction energy to be reduced by over an order of magnitude, a result that is confirmed by monitoring the dynamics of pairs of particles as they approach. Our measurements provide direct evidence of a shorter-range attraction with seemingly no orientational specificity between porous ellipsoids, in contrast to homogeneous, smooth ellipsoids. Taken together, these results indicate that incorporating nanoscale surface topography into anisotropic particles is an effective avenue to minimize capillary-driven aggregation and control interparticle interactions. As a result, such particles are promising candidates as building blocks for interfacial assemblies of anisotropic particles with long-range orientational and translational order.
In sum, this thesis presented a combination of novel anisotropic particle synthesis and experimental analysis of interfacial monolayer behavior to inform how the two-dimensional assembly of polymer colloids can be controlled through manipulating dipolar and capillary forces
Proceedings of the 8th Workshop on Detection and Classification of Acoustic Scenes and Events (DCASE 2023)
This volume gathers the papers presented at the Detection and Classification of Acoustic Scenes and Events 2023 Workshop (DCASE2023), Tampere, Finland, during 21–22 September 2023
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