On a Linearized Problem Arising in the Navier-Stokes Flow of a Free Liquid Jet

In this work, we analyze a Stokes problem arising in the study of the Navier-Stokes flow of a liquid jet. The analysis is accomplished by showing that the relevant Stokes operator accounting for a free surface gives rise to a sectorial operator which generates an analytic semigroup of contractions. Estimates on solutions are established using Fourier methods. The result presented is the key ingredient in a local existence and uniqueness proof for solutions of the full nonlinear problem

Ab initio Bogoliubov coupled cluster theory for open-shell nuclei

Ab initio many-body methods address closed-shell nuclei up to mass A ~ 130 on the basis of realistic two- and three-nucleon interactions. Several routes to address open-shell nuclei are currently under investigation, including ideas which exploit spontaneous symmetry breaking. Singly open-shell nuclei can be efficiently described via the sole breaking of $U(1)$ gauge symmetry associated with particle number conservation, to account for their superfluid character. The present work formulates and applies Bogoliubov coupled cluster (BCC) theory, which consists of representing the exact ground-state wavefunction of the system as the exponential of a quasiparticle excitation cluster operator acting on a Bogoliubov reference state. Equations for the ground-state energy and cluster amplitudes are derived at the singles and doubles level (BCCSD) both algebraically and diagrammatically. The formalism includes three-nucleon forces at the normal-ordered two-body level. The first BCC code is implemented in $m$-scheme, which will eventually permit the treatment of doubly open-shell nuclei. Proof-of-principle calculations in an $N_{\text{max}}=6$ spherical harmonic oscillator basis are performed for $^{16,18,20}$O, $^{18}$Ne, $^{20}$Mg in the BCCD approximation with a chiral two-nucleon interaction, comparing to results obtained in standard coupled cluster theory when applicable. The breaking of $U(1)$ symmetry is monitored by computing the variance associated with the particle-number operator. The newly developed many-body formalism increases the potential span of ab initio calculations based on single-reference coupled cluster techniques tremendously, i.e. potentially to reach several hundred additional mid-mass nuclei. The new formalism offers a wealth of potential applications and further extensions dedicated to the description of ground and excited states of open-shell nuclei.Comment: 22 pages, 13 figure

Jeffreys fluids in forced elongation

AbstractIn this paper we study existence, uniqueness and regularity of solutions for the equations governing the forced elongation of fluids with differential constitutive law of Jeffreys type. These equations consist of nonlinear first-order hyperbolic equations in one spatial dimension. Forced elongation is imposed through velocity boundary conditions at the domain entry and exit. The existence result is based on the Schauder fixed point theorem and energy methods in the space of boundary-regular functions

Image Memorability Prediction with Vision Transformers

Behavioral studies have shown that the memorability of images is similar across groups of people, suggesting that memorability is a function of the intrinsic properties of images, and is unrelated to people's individual experiences and traits. Deep learning networks can be trained on such properties and be used to predict memorability in new data sets. Convolutional neural networks (CNN) have pioneered image memorability prediction, but more recently developed vision transformer (ViT) models may have the potential to yield even better predictions. In this paper, we present the ViTMem, a new memorability model based on ViT, and evaluate memorability predictions obtained by it with state-of-the-art CNN-derived models. Results showed that ViTMem performed equal to or better than state-of-the-art models on all data sets. Additional semantic level analyses revealed that ViTMem is particularly sensitive to the semantic content that drives memorability in images. We conclude that ViTMem provides a new step forward, and propose that ViT-derived models can replace CNNs for computational prediction of image memorability. Researchers, educators, advertisers, visual designers and other interested parties can leverage the model to improve the memorability of their image material

Structure and growth of Pacific halibut otoliths: Identifying spatial and temporal variation

Thesis (Ph.D.) University of Alaska Fairbanks, 1997Otoliths are polycrystals of calcium carbonate and protein that grow through the process of biomineralization within the otic capsule of teleost fish. Otoliths of Pacific halibut (Hippoglossus stenolepis) are routinely collected to provide age information, but other information has not been examined in detail. The purpose of this study was to investigate whether otolith structural patterns reveal information about otolith growth, and by inference, about fish growth and habitat during its early life. Variation in the increment widths of the first five annuli of adult halibut otoliths over a 26 year period were partitioned in two ways: the year the growth took place and the year-class to which the fish belonged. The year of growth explained temporal variation in the youngest ages and was attributed to changes in temperature which may influence recruitment success, while the year-class of growth explained temporal variation in older juveniles, but could reflect sampling bias. An analysis of microstructure increments indicated that relative otolith growth rate was an indicator of larval somatic growth. Young halibut from the Gulf of Alaska exhibited similar larval growth histories, though individual and nursery area differences were apparent. Specimens from the Bering Sea had slower larval growth rates than halibut from the Gulf of Alaska. Trace levels of strontium within otoliths were associated with ontogenetic changes of larvae and winter annuli formation of adults. Levels of potassium and sodium varied by nursery area of capture suggesting some utility for stock separation, though there was indication of significant interannual variation. The shape of the larval crystal within the otolith microstructure of young halibut was found not to be associated with nursery area of capture, and thus is not a good candidate as a stock separation tool. The high variation within individuals suggests that the shape of the crystal is not determined by external events. Overall, several patterns preserved in otoliths can provide insight into processes that influence the growth of halibut and distribution of individuals and these patterns can be recovered from adult fish. However careful interpretation is still required to separate meaningful information from spurious data

Framing resistance: How Hamas uses collective action frames to attract and maintain human resources

The purpose of this study is to investigate the use of collective action framing mechanisms and processes by Hamas in order to aquire and maintain potential and existing human resources and to help researchers and scholars of contentious politics and social movement theory to gain a greater understanding of the role frames play in that decision by showing the ways social movement entrepreneurs use them to acquire, maintain, and motivate human resources for the purpose of collective action

The N=4 effective action of type IIA supergravity compactified on SU(2)-structure manifolds

We study compactifications of type IIA supergravity on six-dimensional manifolds with SU(2) structure and compute the low-energy effective action in terms of the non-trivial intrinsic torsion. The consistency with gauged N=4 supergravity is established and the gauge group is determined. Depending on the structure of the intrinsic torsion, antisymmetric tensor fields can become massive.Comment: 29 pages, latex, v2: minor corrections, added references, published versio