3,158 research outputs found
Real-time deep hair matting on mobile devices
Augmented reality is an emerging technology in many application domains.
Among them is the beauty industry, where live virtual try-on of beauty products
is of great importance. In this paper, we address the problem of live hair
color augmentation. To achieve this goal, hair needs to be segmented quickly
and accurately. We show how a modified MobileNet CNN architecture can be used
to segment the hair in real-time. Instead of training this network using large
amounts of accurate segmentation data, which is difficult to obtain, we use
crowd sourced hair segmentation data. While such data is much simpler to
obtain, the segmentations there are noisy and coarse. Despite this, we show how
our system can produce accurate and fine-detailed hair mattes, while running at
over 30 fps on an iPad Pro tablet.Comment: 7 pages, 7 figures, submitted to CRV 201
I-V characteristics and differential conductance fluctuations of Au nanowires
Electronic transport properties of Au nano-structure are investigated using
both experimental and theoretical analysis. Experimentally, stable Au nanowires
were created using mechanically controllable break junction in air, and
simultaneous current-voltage (I-V) and differential conductance data were measured. The atomic device scale structures are
mechanically very stable up to bias voltage and have a life time
of a few . Facilitated by a shape function data analysis technique
which finger-prints electronic properties of the atomic device, our data show
clearly differential conductance fluctuations with an amplitude at room
temperature, and a nonlinear I-V characteristics. To understand the transport
features of these atomic scale conductors, we carried out {\it ab initio}
calculations on various Au atomic wires. The theoretical results demonstrate
that transport properties of these systems crucially depend on the electronic
properties of the scattering region, the leads, and most importantly the
interaction of the scattering region with the leads. For ideal, clean Au
contacts, the theoretical results indicate a linear I-V behavior for bias
voltage . When sulfur impurities exist at the contact junction,
nonlinear I-V curves emerge due to a tunnelling barrier established in the
presence of the S atom. The most striking observation is that even a single S
atom can cause a qualitative change of the I-V curve from linear to nonlinear.
A quantitatively favorable comparison between experimental data and theoretical
results is obtained. We also report other results concerning quantum transport
through Au atomic contacts.Comment: 11 pages and 9 figures, submitted to PR
High efficiency resonance-based spectrum filters with tunable transmission bandwidth fabricated using nanoimprint lithography
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98685/1/ApplPhysLett_99_143111.pd
Improved weighting in particle filters applied to precise state estimation in GNSS
In the last decades, the increasing complexity of the fusion of proprioceptive and exteroceptive sensors with Global Navigation Satellite System (GNSS) has motivated the exploration of Artificial Intelligence related strategies for the implementation of the navigation filters. In order to meet the strict requirements of accuracy and precision for Intelligent Transportation Systems (ITS) and Robotics, Bayesian inference algorithms are at the basis of current Positioning, Navigation, and Timing (PNT). Some scientific and technical contributions resort to Sequential Importance Resampling (SIR) Particle Filters (PF) to overcome the theoretical weaknesses of the more popular and efficient Kalman Filters (KFs) when the application relies on non-linear measurements models and non-Gaussian measurements errors. However, due to its higher computational burden, SIR PF is generally discarded. This paper presents a methodology named Multiple Weighting (MW) that reduces the computational burden of PF by considering the mutual information provided by the input measurements about the unknown state. An assessment of the proposed scheme is shown through an application to standalone GNSS estimation as a baseline of more complex multi-sensors, integrated solutions. By relying on the a-priori knowledge of the relationship between states and measurements, a change in the conventional PF routine allows performing a more efficient sampling of the posterior distribution. Results show that the proposed strategy can achieve any desired accuracy with a considerable reduction in the number of particles. Given a fixed and reasonable available computational effort, the proposed scheme allows for an accuracy improvement of the state estimate in the range of 20–40%
MIMIC: Mask Image Pre-training with Mix Contrastive Fine-tuning for Facial Expression Recognition
Cutting-edge research in facial expression recognition (FER) currently favors
the utilization of convolutional neural networks (CNNs) backbone which is
supervisedly pre-trained on face recognition datasets for feature extraction.
However, due to the vast scale of face recognition datasets and the high cost
associated with collecting facial labels, this pre-training paradigm incurs
significant expenses. Towards this end, we propose to pre-train vision
Transformers (ViTs) through a self-supervised approach on a mid-scale general
image dataset. In addition, when compared with the domain disparity existing
between face datasets and FER datasets, the divergence between general datasets
and FER datasets is more pronounced. Therefore, we propose a contrastive
fine-tuning approach to effectively mitigate this domain disparity.
Specifically, we introduce a novel FER training paradigm named Mask Image
pre-training with MIx Contrastive fine-tuning (MIMIC). In the initial phase, we
pre-train the ViT via masked image reconstruction on general images.
Subsequently, in the fine-tuning stage, we introduce a mix-supervised
contrastive learning process, which enhances the model with a more extensive
range of positive samples by the mixing strategy. Through extensive experiments
conducted on three benchmark datasets, we demonstrate that our MIMIC
outperforms the previous training paradigm, showing its capability to learn
better representations. Remarkably, the results indicate that the vanilla ViT
can achieve impressive performance without the need for intricate,
auxiliary-designed modules. Moreover, when scaling up the model size, MIMIC
exhibits no performance saturation and is superior to the current
state-of-the-art methods
High-order stochastic integration schemes for the Rosenbluth-Trubnikov collision operator in particle simulations
In this study, we consider a numerical implementation of the nonlinear Rosenbluth-Trubnikov collision operator for particle simulations in plasma physics in the framework of the finite element method (FEM). The relevant particle evolution equations are formulated as stochastic differential equations, both in the Stratonovich and Itô forms, and are then solved with advanced high-order stochastic numerical schemes. Due to its formulation as a stochastic differential equation, both the drift and diffusion components of the collision operator are treated on an equal footing. Our investigation focuses on assessing the accuracy of these schemes. Previous studies on this subject have used the Euler-Maruyama scheme, which, although popular, is of low order, and requires small time steps to achieve satisfactory accuracy. In this work, we compare the performance of the Euler-Maruyama method to other high-order stochastic methods known in the stochastic differential equations literature. Our study reveals advantageous features of these high-order schemes, such as better accuracy and improved conservation properties of the numerical solution. The main test case used in the numerical experiments is the thermalization of isotropic and anisotropic particle distributions
Optimism Based Exploration in Large-Scale Recommender Systems
Bandit learning algorithms have been an increasingly popular design choice
for recommender systems. Despite the strong interest in bandit learning from
the community, there remains multiple bottlenecks that prevent many bandit
learning approaches from productionalization. Two of the most important
bottlenecks are scaling to multi-task and A/B testing. Classic bandit
algorithms, especially those leveraging contextual information, often requires
reward for uncertainty estimation, which hinders their adoptions in multi-task
recommender systems. Moreover, different from supervised learning algorithms,
bandit learning algorithms emphasize greatly on the data collection process
through their explorative nature. Such explorative behavior induces unfair
evaluation for bandit learning agents in a classic A/B test setting. In this
work, we present a novel design of production bandit learning life-cycle for
recommender systems, along with a novel set of metrics to measure their
efficiency in user exploration. We show through large-scale production
recommender system experiments and in-depth analysis that our bandit agent
design improves personalization for the production recommender system and our
experiment design fairly evaluates the performance of bandit learning
algorithms
How Well Have Practices Followed Guidelines in Prescribing Antihypertensive Drugs: The Role of Health Insurance
BACKGROUND: The US Joint National Committee (JNC) on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure issues guidelines on the optimal first-line drug therapy in treating hypertension. Despite broad dissemination of these guidelines, prescribing practices have long remained discrepant with recommendations. The purpose of this study was to examine the role of insurance type in the selection of drugs for hypertension treatment in light of the JNC guidelines. METHODS: Subjects were derived from the 1996 Medical Expenditures Panel Survey who had a diagnosis of essential hypertension and who were prescribed a diuretic, beta-blocker, calcium channel blocker (CCB), or ACE inhibitor (ACEI) as monotherapy. Using the nationally representative sample, this study presents the first estimates of the impact of insurance policies on the choice of antihypertensive drugs while controlling for predisposing, enabling, and need variables in the context of a logistic health-care utilization model. RESULTS: Nationally in 1996, more than twice as many subjects (7.3 million) were taking ACEIs or CCBs compared to diuretics or beta-blockers (3.1 million) as the first-line drug therapy, a sharp contrast to the JNC guidelines. Patients with health maintenance organization (HMO) insurance were much less likely than fee for service (FFS) patients to follow the JNC guidelines in this respect (odds ratio 0.50, P <.01), controlling for all other factors. Individuals with all other public insurance and no insurance were not statistically different from the FFS group in the use of the study drugs. Other significant factors in the regression model were being of African American descent, being unmarried, having higher out-of-pocket payment, being in excellent physical health, having diabetes, and being diagnosed with essential hypertension after 1988. Each was associated with a decreased likelihood of following the JNC recommendations for the use of diuretics or beta-blockers. CONCLUSIONS: After controlling for other predisposing, enabling, and need variables, patients who had HMO coverage were significantly more likely than FFS patients to receive ACEIs or CCBs. Given a popular public perception of HMOs being most cost conscious in providing health care, further research is needed to understand why prescribing patterns associated with HMOs have poorly followed the JNC recommendations
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