Miracle-dz/UniFAR-FTUs huggingface dataset:
VIPeR: Provably Efficient Algorithm for Offline RL with Neural Function Approximation

We propose a novel algorithm for offline reinforcement learning called Value Iteration with Perturbed Rewards (VIPeR), which amalgamates the pessimism principle with random perturbations of the value function. Most current offline RL algorithms explicitly construct statistical confidence regions to obtain pessimism via lower confidence bounds (LCB), which cannot easily scale to complex problems where a neural network is used to estimate the value functions. Instead, VIPeR implicitly obtains pessimism by simply perturbing the offline data multiple times with carefully-designed i.i. d. Gaussian noises to learn an ensemble of estimated state-action {value functions} and acting greedily with respect to the minimum of the ensemble. The estimated state-action values are obtained by fitting a parametric model (e.g., neural networks) to the perturbed datasets using gradient descent. As a result, VIPeR only needs $\mathcal{O}(1)$ time complexity for action selection, while LCB-based algorithms require at least $\Omega(K^2)$, where $K$ is the total number of trajectories in the offline data. We also propose a novel data-splitting technique that helps remove a factor involving the log of the covering number in our bound. We prove that VIPeR yields a provable uncertainty quantifier with overparameterized neural networks and enjoys a bound on sub-optimality of $\tilde{\mathcal{O}}( { \kappa H^{5/2} \tilde{d} }/{\sqrt{K}})$, where $\tilde{d}$ is the effective dimension, $H$ is the horizon length and $\kappa$ measures the distributional shift. We corroborate the statistical and computational efficiency of VIPeR with an empirical evaluation on a wide set of synthetic and real-world datasets. To the best of our knowledge, VIPeR is the first algorithm for offline RL that is provably efficient for general Markov decision processes (MDPs) with neural network function approximation.
A fundamental model of the human thermal system for prediction of thermal comfort

The authors have developed a fundamental model of the human thermal system (AVA model) for the prediction of thermal comfort. The distinguishing feature of this model is a more precise description of heat transfer by blood flow (that is, it includes arteriovenous anastomoses (AVA) of the extremities and a dual vascular network) that conventional models of human thermal systems. The following results were obtained: (1) the experimental verification under three different steady thermal conditions (22, 28 and 34 C) and an unsteady thermal condition (28.1 C {r_arrow} 47.1 {r_arrow} 28.3 C) which suggests that the AVA model can simulate body-temperature profiles well; (2) the visualized results of the model predictions demonstrate that the calculated tissue-temperature and blood-temperature distributions are physiologically plausible.
Discretization of non-uniform rational B-spline (NURBS) models for meshless isogeometric analysis

We present an algorithm for fast generation of quasi-uniform and variable-spacing nodes on domains whose boundaries are represented as computer-aided design (CAD) models, more specifically non-uniform rational B-splines (NURBS). This new algorithm enables the solution of partial differential equations (PDEs) within the volumes enclosed by these CAD models using (collocation-based) meshless numerical discretizations. Our hierarchical algorithm first generates quasi-uniform node sets directly on the NURBS surfaces representing the domain boundary, then uses the NURBS representation in conjunction with the surface nodes to generate nodes within the volume enclosed by the NURBS surface. We provide evidence for the quality of these node sets by analyzing them in terms of local regularity and separation distances. Finally, we demonstrate that these node sets are well-suited (both in terms of accuracy and numerical stability) for meshless radial basis function generated finite differences (RBF-FD) discretizations of the Poisson, Navier-Cauchy, and heat equations. Our algorithm constitutes an important step in bridging the field of node generation for meshless discretizations with isogeometric analysis.
Pressure and temperature dependences of ferroelectricity in liquid crystals

Based on Landau-de-Gennes type free-energy density expansion, we study the influence of pressure and temperature on the spontaneous polarisation, tilt angle and smectic A (Sm A) – chiral smectic C (Sm C*) transition temperature () of ferroelectric mesogen p-(n-decyloxybenzilidene)-p′-amino-(2-methylbutyl) cinnamate (DOBAMBC). The pressure dependence of the ferroic properties is incorporated through the pressure dependent Landau coefficients associated with the order parameters coupling terms of the free-energy density expansion. It is found that the application of pressure reduces the stability of Sm C* phase, while the stability of Sm A phase increases. The order parameter coupling terms play an important role and the ferroelectric properties are in good agreement with the available experimental data of DOBAMBC.
A Slice of the Universe

A preliminary discussion is presented of recent results obtained as part of the extension of the Center of Astrophysics redshift survey. Several features of the results are striking. The distribution of galaxies in the sample, which contains 1100 galaxies in a 6 deg x 117 deg strip going through the Coma cluster, looks like a slice through the suds in the kitchen sink. It appears that the galaxies are on the surfaces of bubble-like structures with diameters of 25-50/h-Mpc. The largest bubble in the survey has a diameter comparable with the most recent estimates of the diameter of the void in Bootes. This topology poses serious challenges for current models for the formation of large-scale structure. The best available model for generating these structures is the explosive galaxy formation theory of Ostriker and Cowie (1981).
Computing robustness of system properties with respect to structured real matrix perturbations

The authors investigate the problem of computing the minimum norm parameter variation that makes some system property fail to hold. They outline an approach which allows several similar system properties to be treated within the same framework. The allowable perturbations are characterized by linear spaces. The system property is characterized by the rank of a matrix pencil, or a collection of matrix pencils. A descent algorithm is formulated based on singular value techniques which converges to a local minimum for a solution of the problem. <<ETX>>
Ion emission from nanodroplets undergoing Coulomb explosions: a continuum numerical study

Abstract A droplet charged above the Rayleigh limit is unstable. In the resulting dynamical process, referred to as a Coulomb explosion, smaller droplets with higher charge-to-mass ratios are ejected, reducing the charge of the parent droplet below the Rayleigh limit. Furthermore, if the droplet is sufficiently small, the electric field on its surface can promote ion field emission. Ion emission can lower the charge of a spherical droplet below its Rayleigh limit, keeping it stable, or reduce the charge of a deforming droplet, changing its dynamics and potentially preventing the Coulomb explosion. This article develops a continuum phase field electrohydrodynamic model to study the interplay between Coulomb explosions and ion emission, using charged nanodroplets of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-Im) as a case study. In small droplets (diameter $D \lesssim 20$ nm for EMI-Im), the electric field is strong enough to emit ions in the early phase of the droplet's evolution, suppressing the Coulomb explosion. For $20 \lesssim D \lesssim 45$ nm, the electric field on the EMI-Im droplet may not promote significant ion emission; however, as the unstable droplet becomes ellipsoidal, ions are emitted from its vertices, ultimately suppressing the Coulomb explosion while shedding $20\unicode{x2013}40\,\%$ of the initial charge. For larger EMI-Im droplets, $45 \lesssim D \lesssim 100$ nm, the evolution typical of a Coulomb explosion is observed, accompanied by ion emission which is however insufficient to prevent the Coulomb explosion. Ion emission and the smaller progeny droplets account for $24\,\%$ and $16\,\%$ of the initial charge, respectively.
SIDE-WEIR FLOW IN CURVED CHANNELS

Side-weirs located on straight channels have attracted considerable interest and research effort. The same, however, is not true for side-weirs on curved channels. The existing studies deal mainly with sediment transport problems and lateral intake structures. The present study focuses on the investigation of the hydraulic behavior of a rectangular sharp crested weir at various locations along a 180° bend. The flow resulting from the effects of the bend and the side-weir was investigated experimentally. Velocity measurements were carried out both for the bend with and without active overflow conditions while surface profiles were determined only for the former case. Velocity measurements were made over the depth at several cross sections along the bend. Observations indicated that a stagnation zone existed at the side-weir section along the inner side of the bend, and that standing waves were present downstream of the side-weir even under subcritical flow conditions. Both phenomena were found to be highly.
Immediate Postpartum Insertion of Copper Intrauterine Device in a Brazilian University Hospital: Expulsion and Continuation Rates

Abstract Objective To evaluate the expulsion and continuation rates of the copper intrauterine device (IUD) inserted in the immediate postpartum period in a Brazilian public university hospital. Materials and Methods In the present cohort study, we included women who received immediate postpartum IUD at vaginal delivery or cesarean s March 2018 to December 2019. Clinical data and the findings of transvaginal ultrasound (US) scans performed 6-weeks postpartum were collected. The expulsion and continuation rates were assessed 6-months postpartum using data from the electronic medical records or by telephone contact. The primary outcome was the proportion of IUDs expelled at 6 months. For the statistical analysis, we used the Student t -test, the Poisson distribution, and the Chi-squared test. Results There were 3,728 births in the period, and 352 IUD insertions were performed, totaling a rate of 9.4%. At 6 weeks postpartum, the IUD was properly positioned in 65.1% of the cases, in 10.8% there was partial expulsion, and in 8.5% it had been completely expelled. At 6 months postpartum, information was obtained from 234 women, 74.4% of whom used IUD, with an overall expulsion rate of 25.6%. The expulsion rate was higher after vaginal delivery when compared with cesarean section (68.4% versus 31.6% respectively; p = 0.031). There were no differences in terms of age, parity, gestational age, final body mass index, and newborn weight. Conclusion Despite the low insertion rate of copper IUDs in the postpartum period and a higher expulsion rate, the rate of long-term continuation of intrauterine contraception was high, indicating that it is a useful intervention to prevent unwanted pregnancies and to reduce short-interval birth.
A new genus for Thalurania ridgwayi (Trochilidae)

Summary. Mexican Woodnymph Thalurania ridgwayi was long included in the genus Thalurania. A previously published molecular phylogenetic study found that this species is in fact sister to the genus Eupherusa. We discuss whether ridgwayi is better lumped with Eupherusa or placed in a different genus, and consider that the latter arrangement best reflects the multiple morphological differences between ridgwayi and Eupherusa. Consequently, we describe a new genus for ridgwayi.
Mode testing via the excess mass estimate

SUMMARY The problem of identifying the number of modal groups manifested in a sample of data is of continuing interest and importance in statistical practice. In this paper, we combine features of two current approaches to the mode-testing problem with some new ideas, to produce a method that provides the data analyst with a powerful and flexible way of exploring modality in univariate data. This approach also provides what appears to be the first satisfactory test of modality for samples of circular data.
Broadening Participation: The Data Science Academy for K-12

The Data Science Academy (DSA) is an extra-curricular program for 7-12th graders that has evolved over the last four years with valuable lessons learned along the way. DSA was created in part because the K-12 curriculum is already packed, so deploying this informal learning environment and outreach program was one way to meet the challenge of the CS4ALL initiative and broaden participation in computing. DSA serves multiple purposes in that regard: it teaches teachers, it gives undergraduates mentoring experience, and it provides a platform for educational research and development. Currently, the DSA comprises five teaching modules, which have been repackaged and delivered as quarter or semester long weekend sessions, or shorter intensive summer programs. That is to say, the DSA accommodates flexible formats, including virtual or in-person ones and soon asynchronous options as well. The DSA provides an opportunity to develop and test lesson modules, including those derived from research projects in partnership with DS-PATH participants (an NSF project to create DS Pathways). Ultimately, the goal is to apply our experience with the DSA in order to expand the K-12 curriculum with new Data Science courses (grades 9-12), modules and pallets (grades 6-8), which is the next phase of our project.
NUMERICAL COMPUTATIONS OF STEADY AND UNSTEADY, SEPARATING, BUOYANT FLOWS - PART II: COMPUTATIONS WITH A LOW-REYNOLDS-NUMBER k -ε MODEL

Numerical computation has been performed to determine the influence of buoyant effects on convective flows with the standard k- k and the low-Reynolds-number k- k models. Results obtained with both turbulent models are compared with the available experimental data. In this work, Kolmogorov velocity, u k = (v k ) 1/4 , is introduced instead of shear velocity, u = ¡ ( w / 𝜌 ), to avoid the singularity that appears at the separating and reattaching point for both turbulence models. Turbulent Prandtl numbers were allowed to vary in the low-Reynolds-number k- k model to mimic the experimental data. Buoyant effects have been investigated with various Richardson numbers for the backward-facing step flow. Various separation patterns as well as vortex shedding were observed beyond a critical Richardson number. In addition, the required grid configration for accurate results for the low-Reynolds-number k- k model has been discussed for the backward-facing step flows.
The infrared diagnostic of a dusty plasma with applications to supernova remnants

IRAS observations of infrared emission from supernova remnants constitute the first observational evidence of shock-heated dust in the interstellar medium. These observations can provide valuable information on the morphology of supernova remnants, and on their interaction with the ambient interstellar medium. In particular, they can be used to study the physical condition and the cooling rate of dusty astrophysical plasmas. In this paper, consideration is given to the possibilities and limitations of using the infrared observations as a diagnostic for the shocked gas, and as a means of determining remnant parameters. The paper presents improved calculations for the cooling rate of a dusty plasma by means of gas-grain collisions, and the equilibrium temperature of the dust for a variety of plasma conditions. These results are then used to define the density-temperature parameter space of the plasma, which, given its infrared spectrum, should be occupied by the observed remnant. This constraint can be used to estimate distances to supernova remnants and to set limits on various parameters that determine their evolution. The analysis is applied to the remnants Cas A and the Cygnus Loop. 39 references.
On the automorphism groups of certain Lie algebras

We fix a ground field k and a finite separable extension K of k. To a Lie algebra L over k is associated the Lie algebra KL = K ⊗kL over K. If we forget the action of K, we can think of KL as a larger Lie algebra over k; in particular we can ask what is the automorphism group Autk KL of KL as a k-algebra. There does not seem to be any simple answer to this question in general; the purpose of this note is to give a simple condition on L which makes Autk KL quite easy to determine. Examples of algebras which satisfy this condition include the free nilpotent Lie algebras and the algebras of all n × n triangular nilpotent matrices.
Doomed to Repeat with IPv6? Characterization of NAT-centric Security in SOHO Routers

With the transition to IPv6, addressing constraints that necessitated a common security architecture under network address translation (NAT) are no longer present. Instead, manufacturers are now able to choose between an open model design, where devices are end-to-end reachable, or a more familiar closed model, where the home gateway may continue to serve as a perimeter security device. The potential for further nuance, such as differences in default access control policies, filtering behaviors, and IPv6 specific requirements, present an environment defined by ambiguity. For the consumer, the potential impact of these changes are unclear. To address this uncertainty, we taxonomize the present NAT-centric model of consumer gateway security through a survey of over 300 common vulnerabilities and exposures surrounding NAT and hole punching protocols. From this survey, we contextualize the limited security NAT has provided while serving as the primary perimeter defense mechanism in home networks. We further define how this baseline security model for consumer gateways is reflected in IPv6 through an assessment of ten commonly deployed consumer gateways. Our conclusion is that familiarity of a NAT-centric design is no longer assured for IPv6, requiring an active involvement by users to limit exposures within their home networks.
Perturbation theory for dual semigroups II. Time-dependent perturbations in the sun-reflexive case

Synopsis We consider time-dependent perturbations of generators of strongly continuous semigroups on a Banach space. The perturbations map the Banach space into a bigger space, which is the second dual of the original space in a specific semigroup sense. Using the theory of dual semigroups we show that the solutions of a generalised variation-of-constants formuladefine an evolutionary system. We investigate continuity and differentiability propertiesof this evolutionary system and its dual system and examine in what sense the perturbed generator and its adjoint generate these evolutionary systems. It is shown that the results apply naturally to retarded functional differential equations and age structured population dynamics.
Graph algorithms for planning and partitioning

In this thesis, we present new approximation algorithms as well as hardness of approximation results for several planning and partitioning problems. In planning problems, one is typically given a set of locations to visit, along with timing constraints, such as deadlines for visiting them; The goal is to visit a large number of locations as efficiently as possible. We give the first approximation algorithms for problems such as ORIENTEERING, DEADLINES-TSP, and TIME-WINDOWS-TSP, as well as results for planning in stochastic graphs (Markov decision processes). The goal in partitioning problems is to partition a set of objects into clusters while satisfying "split" or "combine" constraints on pairs of objects. We consider three kinds of partitioning problems, viz. CORRELATION-C LUSTERING, SPARSEST-CUT, and M ULTICUT. We give approximation algorithms for the first two, and improved hardness of approximation results for SPARSEST-C UT and MULTICUT.
Validation of the gyrokinetic model in ITG and TEM dominated L-mode plasmas

A rigorous validation of the gyrokinetic model was performed in both ion temperature gradient (ITG) and trapped electron mode (TEM) dominated Alcator C-Mod plasmas at (normalized midplane minor radius) r/a = 0.5 and 0.8. Analysis focuses on two L-mode discharges operated with 1.2 and 3.5 MW of ion cyclotron resonance heating. In depth investigation into the experimental uncertainties and simulation sensitivities in these discharges allows for a stringent test of the gyrokinetic model implemented by the GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) in both the centre of the stiff gradient region (r/a = 0.5) and the middle of the region often associated with the transport ‘shortfall’(r/a = 0.8). To identify the nature of the plasma turbulence and to ensure a robust evaluation of the model's ability to reproduce experiment, the sensitivity of the simulation results to experimental uncertainty in turbulence drive and suppression terms were determined at both radial locations. When significant TEM activity is present, nonlinear gyrokinetic simulations are found to reproduce both electron and ion experimental heat fluxes within their diagnosed uncertainties. In contrast, in the absence of TEM, electron heat fluxes are robustly under predicted by low-k, gyrokinetic simulation.
Exploring self-care practices in foster carers: a qualitative study

ABSTRACT This study aimed to explore how foster carers conceptualize and engage in self-care using interviews with 8 participants. Results suggest that self-care practices are an important component of maintaining the physical and mental health of foster carers, preventing burn-out and enhancing therapeutic parenting practices. Several barriers to self-care are identified, including systemic barriers as well a foster carers’ own feelings of guilt for prioritizing their own needs. Results indicate that self-care requires a collaborative approach between foster carers and the broader child welfare system. Improved self-care specific training, resources and coaching from agencies were also identified as important outcomes.
Global epistasis and the emergence of ecological function

The emergence of community functions is the result of a complex web of interactions between organisms and their environment. This complexity poses a significant obstacle in quantitatively predicting ecological function from the species-level composition of a community. In this study, we demonstrate that the collective impact of interspecies interactions leads to the emergence of simple linear models that predict ecological function. These predictive models mirror the patterns of global epistasis reported in genetics, and they can be quantitatively interpreted in terms of pairwise ecological interactions between species. Our results illuminate an unexplored path to quantitatively linking the composition and function of ecological communities, bringing the tasks of predicting biological function at the genetic, organismal, and ecological scales under the same quantitative formalism.