21,308 research outputs found
A Collaborative Approach: Two Perspectives
This article is a story of collaboration between a principal, Baek Chong, and the mathematics coach, Megan Farrelly. This article shows both perspectives: Baek\u27s thoughts are written in regular typeface, whereas Megan\u27s perspective is italicized. Both educators work at Mark Twain Middle School in Fairfax County Public Schools in Virginia which has nearly 900 seventh- and eighth-grade students. Twain Middle School serves a diverse population, of which about 35% of the students arc on free or reduced lunch, 15% receive special education services, 14% receive English language services, and 40% of the students are in the advanced academics program
Variational Inference in Nonconjugate Models
Mean-field variational methods are widely used for approximate posterior
inference in many probabilistic models. In a typical application, mean-field
methods approximately compute the posterior with a coordinate-ascent
optimization algorithm. When the model is conditionally conjugate, the
coordinate updates are easily derived and in closed form. However, many models
of interest---like the correlated topic model and Bayesian logistic
regression---are nonconjuate. In these models, mean-field methods cannot be
directly applied and practitioners have had to develop variational algorithms
on a case-by-case basis. In this paper, we develop two generic methods for
nonconjugate models, Laplace variational inference and delta method variational
inference. Our methods have several advantages: they allow for easily derived
variational algorithms with a wide class of nonconjugate models; they extend
and unify some of the existing algorithms that have been derived for specific
models; and they work well on real-world datasets. We studied our methods on
the correlated topic model, Bayesian logistic regression, and hierarchical
Bayesian logistic regression
Non-Extremal Rotating Black Holes in Five-Dimensional Gauged Supergravity
Supersymmetric black holes in five-dimensional gauged supergravity must
necessarily be rotating, and so in order to study the passage to black holes
away from supersymmetry, it is of great interest to obtain non-extremal black
holes that again have non-zero rotation. In this paper we find a simple
framework for describing non-extremal rotating black holes in five-dimensional
gauged supergravities. Using this framework, we are able to construct a new
solution, describing the general single-charge solution of N=2 gauged
supergravity, with arbitrary values for the two rotation parameters.
Previously-obtained solutions with two or three equal charges also assume a
much simpler form in the new framework, as also does the general solution with
three unequal charges in ungauged N=2 supergravity. We discuss the
thermodynamics and BPS limit of the new single-charge solutions, and we discuss
the separability of the Hamilton-Jacobi and Klein-Gordan equations in these
backgrounds.Comment: Latex, 12 pages. Mis-statement about separability of Hamilton-Jacobi
and Klein-Gordon equations correcte
Calibration of the Pulsed Electroacoustic Technique in the Presence of Trapped Charge
The influence of pulse voltage on the accuracy of charge density distribution in the pulsed electroacoustic technique (PEA) is discussed. It is shown that significant error can be introduced if a low dc voltage and high pulse voltage are used to calibrate charge density. However, our main focus in the present paper is to deal with one of the practical situations where space charge exists in the material prior to any measurements. The conventional calibration method can no longer be used to calibrate charge density due to the interference by the charge on the electrode induced by space charge. A method has been proposed which is based on two measurements. Firstly, the sample containing charge is measured without any applied voltage. The second measurement is carried out with a small external applied voltage. The applied voltage should be small enough so there is no disturbance of the existing charge in the sample. The difference of the two measurements can be used for calibration. An additional advantage of the proposed method avoids the influence of the pulse voltage on calibration and therefore gives a more accurate representation of space charge. The proposed method has been validated
SCR of NO with C3H6 in the presence of excess O2 over Cu/Ag/CeO2-ZrO2 catalyst
The catalytic activity of a series of CeO2-ZrO2 mixed oxides in the selective catalytic reduction (SCR) of NO by C3H6 at 400'C has been investigated. The NO reduction activity of pure CeO2 is enhanced in the presence of Zr, reaching a maximum NO conversion with CeO2(75)-ZrO2(25) catalyst. Then, the catalytic performances of Cu(4)/Ag(1)/CeO2 and Cu(4)/Ag(1)/CeO2(75)-ZrO2(25) catalysts were compared and the latter showed better activity especially in the low temperature region (250-350 C). The stronger metal-support interaction and higher reducibility shown by the Cu(4)/Ag(1)/CeO2(75)-ZrO2(25) catalyst were believed to enhance its performance compared to Cu(4)/Ag(1)/CeO2 catalyst by activating more C3H6 to selectively reduce NO within this temperature region. Central composite response surface design methodology was employed to study the effect of operating variables such as temperature, NO and C3H6 concentrations on the SCR of NO by C3H6 over Cu(4)/Ag(1)/CeO2(75)-ZrO2(25) catalyst and to determine the optimum value of operating variables for maximum NO conversion. Numerical results indicated that the optimum NO conversion of 82.89% is attained at reaction temperature =415.38 C, NO concentration= 1827.16 ppm and C3H6 concentration = 1908.13 ppm. The addition of water vapor to the reactant significantly decreased the NO conversion over Cu(4)/Ag(1)/CeO2 and Cu(4)/Ag(1)/CeO2 (75)-ZrO2(25), but the inhibition was more pronounced over Cu(4)/Ag(1)/CeO2 catalyst
Fairness of performance evaluation procedures and job satisfaction: the role of outcome-based and non-outcome based effects
Prior management accounting studies on fairness perceptions have overlooked two important issues. First, no prior management accounting studies have investigated how procedural fairness, by itself, affects managers' job satisfaction. Second, management accounting researchers have not demonstrated how conflicting theories on procedural fairness can be integrated and explained in a coherent manner. Our model proposes that fairness of procedures for performance evaluation affects job satisfaction through two distinct processes. The first is out-come-based through fairness of outcomes (distributive fairness). The second is non-outcome-based through trust in superior and organisational commitment. Based on a sample of 110 managers, the results indicate that while procedural fairness perceptions affect job satisfaction through both processes, the non-outcome-based process is much stronger than the outcome-based process. These results may be used to develop a unified theory on procedural fairness effects
Fine-Grained Head Pose Estimation Without Keypoints
Estimating the head pose of a person is a crucial problem that has a large
amount of applications such as aiding in gaze estimation, modeling attention,
fitting 3D models to video and performing face alignment. Traditionally head
pose is computed by estimating some keypoints from the target face and solving
the 2D to 3D correspondence problem with a mean human head model. We argue that
this is a fragile method because it relies entirely on landmark detection
performance, the extraneous head model and an ad-hoc fitting step. We present
an elegant and robust way to determine pose by training a multi-loss
convolutional neural network on 300W-LP, a large synthetically expanded
dataset, to predict intrinsic Euler angles (yaw, pitch and roll) directly from
image intensities through joint binned pose classification and regression. We
present empirical tests on common in-the-wild pose benchmark datasets which
show state-of-the-art results. Additionally we test our method on a dataset
usually used for pose estimation using depth and start to close the gap with
state-of-the-art depth pose methods. We open-source our training and testing
code as well as release our pre-trained models.Comment: Accepted to Computer Vision and Pattern Recognition Workshops
(CVPRW), 2018 IEEE Conference on. IEEE, 201
Self-noise produced by an airfoil with nonflat plate trailing-edge serrations
This paper represents the results of an experimental study aimed at reducing the airfoil self-noise by the trailing edge serration of four different sawtooth geometries (defined in the serration angle and length). These serrations have a common feature: all of the sawtooth patterns are cut directly into the trailing edge of a realistic airfoil. This configuration offers better structural strength and integrity. For the sawtooth trailing edges investigated here, the radiation of the extraneous vortex shedding noise in a narrowband frequency due to the partial bluntness at the serration roots is unavoidable. However, this narrowband component tends to be less significant provided that the serration angle is large and the serration length is moderate. Sound power was measured, and some of the sawtooth geometries have been shown to afford significant boundary-layer instability tonal noise and moderate turbulent broadband noise reductions across a fairly large velocity range. This paper demonstrates that a nonflat plate serrated trailing edge can also be effective in the self-noise reduction. Some experimental results are also presented in order to explain the self-noise mechanisms.This work is partly supported by the Brunel Research Initiative and Enterprise fun
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