Miracle-dz/UniFAR-FTUs huggingface dataset:
Enhancing Privacy and Fairness in Search Systems

Following a period of expedited progress in the capabilities of digital systems, the society begins to realize that systems designed to assist people in various tasks can also harm individuals and society. Mediating access to information and explicitly or implicitly ranking people in increasingly many applications, search systems have a substantial potential to contribute to such unwanted outcomes. Since they collect vast amounts of data about both searchers and search subjects, they have the potential to violate the privacy of both of these groups of users. Moreover, in applications where rankings influence people’s economic livelihood outside of the platform, such as sharing economy or hiring support websites, search engines have an immense economic power over their users in that they control user exposure in ranked results. This thesis develops new models and methods broadly covering different aspects of privacy and fairness in search systems for both searchers and search subjects. Specifically, it makes the following contributions: • We propose a model for computing individually fair rankings where search subjects get exposure proportional to their relevance. The exposure is amortized over time using constrained optimization to overcome searcher attention biases while preserving ranking utility. • We propose a model for computing sensitive search exposure where each subject gets to know the sensitive queries that lead to her profile in the top-k search results. The problem of finding exposing queries is technically modeled as reverse nearest neighbor search, followed by a weekly-supervised learning to rank model ordering the queries by privacy-sensitivity. • We propose a model for quantifying privacy risks from textual data in online communities. The method builds on a topic model where each topic is annotated by a crowdsourced sensitivity score, and privacy risks are associated with a user’s relevance to sensitive topics. We propose relevance measures capturing different dimensions of user interest in a topic and show how they correlate with human risk perceptions. • We propose a model for privacy-preserving personalized search where search queries of different users are split and merged into synthetic profiles. The model mediates the privacy-utility trade-off by keeping semantically coherent fragments of search histories within individual profiles, while trying to minimize the similarity of any of the synthetic profiles to the original user profiles. The models are evaluated using information retrieval techniques and user studies over a variety of datasets, ranging from query logs, through social media and community question answering postings, to item listings from sharing economy platforms.
Semiconcavity of the value function for exit time problems with nonsmooth target

We prove semiconcavity of the value function of a nonlinear optimal control problem where the cost functional depends on the arrival time of the trajectory on a given target set. We make suitable smoothness assumptions on the dynamics of the system, while the target set can be completely general. As a corollary, we prove differentiability of the value function for a class of linear systems.
A Deterministic Approach To Stochastic Optimal Control With Application To Anticipative Control

Using the decomposition of solution of SDE, we consider the stochastic optimal control problem with anticipative controls as a family of deterministic control problems parametrized by the paths of the driving Wiener process and of a newly introduced Lagrange multiplier stochastic process (nonanticipativity equality constraint). It is shown that the value function of these problems is the unique global solution of a robust equation (random partial differential equation) associated to a linear backward Hamilton-Jacobi-Bellman stochastic partial differential equation (HJB SPDE). This appears as limiting SPDE for a sequence of random HJB PDE's when linear interpolation approximation of the Wiener process is used. Our approach extends the Wong-Zakai type results [20] from SDE to the stochastic dynamic programming equation by showing how this arises as average of the limit of a sequence of deterministic dynamic programming equations. The stochastic characteristics method of Kunita [13] is used to represent the .
An incompressible three-dimensional multiphase particle-in-cell model for dense particle flows

Abstract A three-dimensional, incompressible, multiphase particle-in-cell method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to an Eulerian grid and then mapping back computed stress tensors to particle positions. A subgrid particle, normal stress model for discrete particles which is robust and eliminates the need for an implicit calculation of the particle normal stress on the grid is presented. Interpolation operators and their properties are defined which provide compact support, are conservative, and provide fast solution for a large particle population. The solution scheme allows for distributions of types, sizes, and density of particles, with no numerical diffusion from the Lagrangian particle calculations. Particles are implicitly coupled to the fluid phase, and the fluid momentum and pressure equations are implicitly solved, which gives a robust solution.
The Kinematic Analysis and the Study of Muscle Activities during Backhand Drive in Squash

The purpose of this study was to examine the differences of kinematics and muscle activities depending on the changes of angle approaching balls during backhand drive in squash. The results are as follows. Stride time took the longest at AD2 and step lengths were the biggest at AD1 of left foot contact and right foot contact and AD2 of impact and follow-through. The center of gravity and the speed of racket head were the highest at AD3 and at AD2. Angle of shoulder joint were the biggest at AD1 of left foot contact, right foot contact and impact and AD3 of follow-through. Angle of elbow joint were the biggest at AD3 of left foot contact, right foot contact and follow-through and AD2 of impact. Angle of pelvis joint were the biggest at AD2 of left foot contact, AD1 of right foot contact and AD3 of impact and follow-through. Angle of knee joint were the biggest at AD2 of left foot contact, AD1 of right foot contact and AD3 of impact and follow-through. Angle of ankle joint were the biggest at AD1 of left foot contact and AD3 of right foot contact, impact and follow-through. According to the analysis results of triceps brachii, latissimus dorsi, brachioradialis muscle and flexor carpi ulnaris muscle activities were high at AD1 of all phases. Analysis results of vastus lateralis, vastus medialis, tibialis anterior and gastrocnemius medial muscle activities were high at AD2 of phase1 and phase3. Those of vastus lateralis, vastus medialis and tibialis anterior, gastrocnemius medial were high at AD3 of Phase 2 and AD1 of phase2.
Photorefractive properties of congruent and stoichiometric lithium niobate at high light intensities

In lithium niobate crystals the focused beam of an argon-ion laser induces birefringence changes. We investigate the intensity dependences of the saturation value of these birefringence changes, the photoconductivity, and the photorefractive sensitivity in nominally pure crystals with different lithium contents and in an iron-doped sample. All experimental results can be described assuming Fe2+/3+ centers—of low concentration in the nominally pure samples—and, in addition, intrinsic NbLi polarons as a second photoactive center.
Effects of nonuniform structure on the derived physical parameters of compact synchrotron sources

The time-independent theory of a compact incoherent synchrotron radio source which contains gradients in magnetic field and in relativistic electron distribution is developed and discussed. Analytic expressions for the frequency spectrum are obtained, and we demonstrate the dependence of the spectral index below the synchrotron self-absorption turnover frequency on the gradients in the source and on the source geometry. We show that at high frequencies the existence of a gradient in the magnetic field causes a gradual bend (a steepening) in the spectrum owing to a decrease in effective source radius with increasing frequency. The theoretical interferometric fringe visibility function is computed for a nonuniform source, and it is shown that the characteristic Gaussian angular size derived from this function increases with decreasing frequency below the spectral turnover.We discuss how the important physical parameters of a nonuniform source can be directly derived from observable quantities. The results indicate that the existence of steep gradients in the magnetic field strength and/or the distribution of relativistic electrons can alleviate somewhat the energetic and inverse Compton difficulties of some compact sources, while the presence of moderate gradients only aggravates these problems relative to the homogeneous model.The theory of nonuniform components is applied tomore » the compact radio sources 1633+38 and OQ 172. We find that the radio spectrum of these objects can be interpreted as arising in simple nonuniform sources as opposed to the multiple source models that are necessary when homogeneous components are used. However, the inverse Compton optical and X-ray fluxes in the case of 1633+38 and the predicted minimum angular size in the case of OQ 172 are similar to those obtained via the uniform models. « less
Overestimates of Entrainment From Wetting of Aircraft Temperature Sensors in Cloud.

Abstract Temperature measurements from aircraft, taken with a reverse flow sensor and Rosemount probe, were compared in a penetration through a cloud to determine the effect of sensor wetting on the deduced entrainment. The temperature measured using the Rosemount probe was depressed relative to that measured with the reverse flow probe, leading to an underestimate of the equivalent potential temperature and an overestimate of the deduced entrainment. These results were used to identify possible errors in recent entrainment studies that used temperature as an indicator of entrainment.
Low loss porous terahertz fibers containing multiple subwavelength holes

We propose a porous polymer terahertz fiber with a core composed of a hexagonal array of subwavelength air holes. Numerical simulations show that the larger part of guided power propagates inside the air holes within the fiber core, resulting in suppression of the bulk absorption losses of the core material by a factor of ∼10–20. Confinement of terahertz power in the subwavelength holes greatly reduces effective refractive index of the guided mode but not as much as to considerably increase modal radiation losses due to bending. As a result, tight bends of several centimeter bending radii can be tolerated.
Six Approaches to Calculating Standardized Logistic Regression Coefficients

This article reviews six alternative approaches to constructing standardized logistic regression coefficients. The least attractive of the options is the one currently most readily available in logistic regression software, the unstandardized coefficient divided by its standard error (which is actually the normal distribution version of the Wald statistic). One alternative has the advantage of simplicity, while a slightly more complex alternative most closely parallels the standardized coefficient in ordinary least squares regression, in the sense of being based on variance in the dependent variable and the predictors. The sixth alternative, based on information theory, may be the best from a conceptual standpoint, but unless and until appropriate algorithms are constructed to simplify its calculation, its use is limited to relatively simple logistic regression models in practical application.
Composite control of non-linear singularly perturbed systems: a geometric approach

Using a geometric approach, a composite control—the sum of a slow control and a fast control—is derived for a general class of non-linear singularly perturbed systems. A new and simpler method of composite control design is proposed whereby the fast control is completely designed at the outset. The slow control is then free to be chosen such that the slow integral manifold of the original system approximates a desired design manifold to within any specified order of e accuracy.
Error analysis for general multtvariate kernel estimators

Kernel estimators for d dimensional data are usually parametrized by either a single smoothing parameter, or d smoothing parameters corresponding to each of the coordinate directions. A generalization of each of these parameterizations is to use a d× d matrix which allows smoothing in arbitrary directions. We demonstrate that, at this level of generality, the usual error approximations and their numerical minimization can be done quite simply using matrix algebra. The minimization formulas have the practical importance that they can be applied to data-driven selection of the smoothing parameters using a ”plug-in approach. Particular attention is paid to the special case of kernel estimation of multivariate normal mixture densities where it is shown that the numerical evaluation and minimization of both asymptotic and exact mean integrated squared error can be set up in a matrix algebraic formulation which requires no numerical integration. This provides a flexible family of multivariate smoothing problems.
Speckle effects in target-in-the-loop laser beam projection systems

Abstract In target-in-the-loop laser beam projection scenarios typical of remote sensing, directed energy, and adaptive optics applications, a transmitted laser beam propagates through an optically inhomogeneous medium toward a target, scatters off the target’s rough surface, and returns back to the transceiver plane. Coherent beam scattering off the randomly rough surface results in strong speckle modulation in the transceiver plane. This speckle modulation has been a long-standing challenge that limits performance of remote sensing, active imaging, and adaptive optics techniques. Using physics-based models of laser beam scattering off a randomly rough surface, we show that received speckle-field spatial and temporal characteristics can be used to evaluate the intensity distribution of the beam projected onto the target. We derive analytical expressions that directly couple the measured target-return wave statistical characteristics, or ‘speckle metrics’, with characteristics of the laser beam intensity distribution on the target surface. We also show how measured speckle metrics can be utilized for evaluation of laser beam quality at the target surface and for adaptive compensation of atmospheric turbulence-induced phase aberrations.
Simulating the Sooting Propensity of JP-8 with Surrogate Fuels from Hydrocarbon Fluids

Surrogate fuel mixtures were formulated using hydrocarbon fluids to investigate the ability of different surrogate formulations to match the sooting characteristics of a specific jet fuel (JP-8 POSF 5699). Three different surrogates were studied: two binary mixtures and a ternary mixture. The first surrogate matched the threshold soot index and average molecular weight of the JP-8; the second matched the threshold soot index and hydrogen-to-carbon; and the third matched the threshold soot index, hydrogen-to-carbon, and derived cetane number. For the second and third surrogates, average molecular weight was within 10% of the estimated average molecular weight of the target JP-8. Soot distributions of JP-8 and its surrogates were compared in wick-fed coflow diffusion flames, and net soot production was compared in a model gas turbine combustor. Line-of-sight and local soot volume fraction measurements were obtained using laser extinction on the wick burner for flames at their smoke point. Line-of-sight soot.
On Representation of Densities of Stable Laws by Special Functions

A representation of the density of a one-dimensional strongly stable law via Meijer’s G-functions is obtained. The paper also considers the expressions of integral transforms with Euler kernels of these densities in terms of G-functions which make it possible to obtain representations of distribution functions of strongly stable laws with rational parameters. Some examples are given of representations of densities of multivariate spherically symmetric stable laws in terms of Meijer functions.
Jiving the Four-Step, Waltzing Around Factor Analysis, and Other Serious Fun

It has been proposed that a clear separation of measurement from structural reasons for model failure can be obtained via a procedure testing 4 nested models: (a) a factor model, (b) a confirmatory factor model, (c) the anticipated structural equation model, and (d) possibly, a more constrained model. Advocates of the 4-step procedure contend that these nested models provide a trustworthy way of determining whether one's model is failing as a result of structural (conceptual) inadequacy, or as a result of measurement misspecification. We argue that measurement and structural issues can not be unambiguously separated by the 4 steps, and that the seeming separation is incomplete at best and illusory at worst. The prime difficulty is that the 4-step procedure is incapable of determining whether the proposed model contains the proper number of factors. As long as the number of factors is in doubt, measurement and structural assessments remain dubious and entwined. The assessment of model fit raises additional difficulties because the researcher is implicitly favoring of the null hypothesis, and the logic of the root mean square error of approximation (RMSEA) as a test of "close fit" is inconsistent with the logic of the 4-step. These discussions question whether factor analysis can dependably determine the proper number of factors, and argue against the routine use of. 05 as the probability target for structural equation model chi-square fit.
Estimation across Data Sets: Two-Stage Auxiliary Instrumental Variables Estimation (2SAIV)

Theories demand much of data, often more than a single data collection can provide. For example, many important research questions are set in the past and must rely on data collected at that time and for other purposes. As a result, we often find that the data lack crucial variables. Another common problem arises when we wish to estimate the relationship between variables that are measured in different data sets. A variation of this occurs with a split half sample design in which one or more important variables appear on the “wrong” half. Finally, we may need panel data but have only cross sections available. In each of these cases our ability to estimate the theoretically determined equation is limited by the data that are available.
High external efficiency in a monomode full-photonic-crystal laser under continuous wave electrical injection

We demonstrate continuous wave with an external efficiency over 0.15W∕A and monomode operation of a full photonic crystal (PhC) laser. The optical confinement and a wavelength selectivity better than 25dB are all ensured by a unique PhC. We take advantage of the feedback on the fundamental mode which exists within the photonic gap for some specific designs of the PhC guide. These designs are calculated using the plane wave expansion method.
Positive and real-positive solutions to the equation axa*=c in C*-algebras

We obtain new representations for the general positive and real-positive solutions of the equation axa*=c in a C*-algebra using the characterization of positivity based on a matrix representation of an element and the generalized Schur complement. Applications to the equation AXA*=C for operators between Hilbert spaces and for finite matrices are given.
Small comets: Naked‐eye visibility

We investigate an obvious consequence of the small‐comet hypothesis. We find that the 30‐ton cloud of water‐ice particles formed by a small comet would survive long enough to be an unmistakably bright object. The visual magnitude of such clouds would be between that of a bright star and the full Moon. A whole‐Earth small‐comet flux of 20/min implies the sudden appearance of at least two bright patches of light every five minutes. The two‐hour periods after sunset and before sunrise ought to produce the most spectacular sightings—intermittent punctuations of bright rapidly‐moving points of light. Because such events are not reported, we conclude that this class of object does not exist in detectable numbers.
Intermittent Gas Resonance in Stage Separation Flow Field of Multistage Rocket

Abstract The aerodynamic-dynamic coupled simulation was performed to investigate the interstage flow characteristics of a multistage rocket in the course of stage separation. Results show that the stage separation exhibits five phases, i.e., the initial transient phase, the smooth gas leakage phase, the gas resonance phase, the suspension phase of gas resonance and the resumed gas resonance phase. There is a striking contrast between stage separation flow of a rocket and that of a gas resonance tube, which shows iso-magnitude and iso-period oscillation. The present analysis shows that shock wave structures of the interstage and relative distance between the two stages are the main conditions which lead to this interesting phenomenon.
On the accuracy of fractional step methods for conservation laws in two dimensions

In this paper it is shown that, on the assumption of the initial data belonging to $BV({\bf R}^2 ) \cap L^\infty ({\bf R}^2 )$, the convergence rates in $L^1 ({\bf R}^2 )$ for both Godunov’s spatial splitting method and Strang’s splitting method for scalar conservation laws in two-dimensional spaces are of $O(\Delta t^{1 / 2} )$, where $\Delta t$ is the splitting time step. The author illustrates by numerical experiments that for some two-dimensional Riemann problems the rate is of the order $O(\Delta t)$. It is also shown by counterexamples that if the initial data belongs to $L^\infty ({\bf R}^2 )$, no error estimate of the type $O(\Delta t^\beta )$ for any $\beta > 0$ is valid.
Robust imposition of Dirichlet boundary conditions on embedded surfaces

We develop both stable and stabilized methods for imposing Dirichlet constraints on embedded, three‐dimensional surfaces in finite elements. The stable method makes use of the vital vertex algorithm to develop a stable space for the Lagrange multipliers together with a novel discontinuous set of basis functions for the multiplier field. The stabilized method, on the other hand, follows a Nitsche type variational approach for three‐dimensional surfaces. Algorithmic and implementational details of both methods are provided. Several three‐dimensional benchmark problems are studied to compare and contrast the accuracy of the two approaches. The results indicate that both methods yield optimal rates of convergence in various quantities of interest, with the primary differences being in the surface flux. The utility of the domain integral for extracting accurate surface fluxes is demonstrated for both techniques. Copyright © 2011 John Wiley & Sons, Ltd.