97 research outputs found
HIGH ORDER BOUND-PRESERVING DISCONTINUOUS GALERKIN METHODS AND THEIR APPLICATIONS IN PETROLEUM ENGINEERING
This report contains researches in the theory of high-order bound-preserving (BP) discontinuous Galerkin (DG) method and their applications in petroleum engineering. It contains both theoretical analysis and numerical experiments. The compressible miscible displacements and wormhole propagation problem, arising in petroleum engineering, is used to describe the evolution of the pressure and concentrations of different components of fluid in porous media. The important physical features of concentration and porosity include their boundedness between 0 and 1, as well as the monotone increasing for porosity in wormhole propagation model. How to keep these properties in the simulation is crucial to the robustness of the numerical algorithm. In the first project, we develop high-order bound-preserving discontinuous Galerkin methods for the coupled system of compressible miscible displacements on triangular meshes. We consider the problem with multi-component fluid mixture and the (volumetric) concentration of the jth component,cj, should be between 0 and 1. The main idea is stated as follows. First, we apply the second-order positivity-preserving techniques to all concentrations c′ js and enforce P jcj= 1 simultaneously to obtain physically relevant boundedness for every components. Then, based on the second-order BP schemes, we use the second-order numerical fluxes as the lower order one to combine with high-order numerical fluxes to achieve the high-order accuracy. Finally, since the classical slope limiter cannot be applied to polynomial upper bounds, we introduce a new limiter to our algorithm. Numerical experiments are given to demonstrate the high-order accuracy and good performance of the numerical technique. In our second project, we propose high-order bound-preserving discontinuous Galerkin methods to keep the boundedness for the porosity and concentration of acid, as well as the monotone increasing for porosity. The main technique is to introduce a new variable r to replace the original acid concentration and use a consistent flux pair to deduce a ghost equation such that the positive-preserving technique can be applied on both original and deduced equations. A high-order slope limiter is used to keep a polynomial upper bound which changes over time for r. Moreover, the high-order accuracy is attained by the flux limiter. Numerical examples are given to demonstrate the high-order accuracy and bound-preserving property of the numerical technique
GaitFormer: Revisiting Intrinsic Periodicity for Gait Recognition
Gait recognition aims to distinguish different walking patterns by analyzing
video-level human silhouettes, rather than relying on appearance information.
Previous research on gait recognition has primarily focused on extracting local
or global spatial-temporal representations, while overlooking the intrinsic
periodic features of gait sequences, which, when fully utilized, can
significantly enhance performance. In this work, we propose a plug-and-play
strategy, called Temporal Periodic Alignment (TPA), which leverages the
periodic nature and fine-grained temporal dependencies of gait patterns. The
TPA strategy comprises two key components. The first component is Adaptive
Fourier-transform Position Encoding (AFPE), which adaptively converts features
and discrete-time signals into embeddings that are sensitive to periodic
walking patterns. The second component is the Temporal Aggregation Module
(TAM), which separates embeddings into trend and seasonal components, and
extracts meaningful temporal correlations to identify primary components, while
filtering out random noise. We present a simple and effective baseline method
for gait recognition, based on the TPA strategy. Extensive experiments
conducted on three popular public datasets (CASIA-B, OU-MVLP, and GREW)
demonstrate that our proposed method achieves state-of-the-art performance on
multiple benchmark tests
Redesigning PwC Russia\u27s Careers Website
The purpose of this project was to improve the effectiveness of the careers website for our sponsor, PwC Russia. Using focus groups and interviews with the target population and website design principles we created a demonstration of a new website and developed a set of recommendations for PwC to follow to improve the aesthetics, usability, and ultimately the effectiveness of their careers website in order for them to recruit higher quality applicants to fill their job vacancies
SYENet: A Simple Yet Effective Network for Multiple Low-Level Vision Tasks with Real-time Performance on Mobile Device
With the rapid development of AI hardware accelerators, applying deep
learning-based algorithms to solve various low-level vision tasks on mobile
devices has gradually become possible. However, two main problems still need to
be solved: task-specific algorithms make it difficult to integrate them into a
single neural network architecture, and large amounts of parameters make it
difficult to achieve real-time inference. To tackle these problems, we propose
a novel network, SYENet, with only 6K parameters, to handle multiple
low-level vision tasks on mobile devices in a real-time manner. The SYENet
consists of two asymmetrical branches with simple building blocks. To
effectively connect the results by asymmetrical branches, a Quadratic
Connection Unit(QCU) is proposed. Furthermore, to improve performance, a new
Outlier-Aware Loss is proposed to process the image. The proposed method proves
its superior performance with the best PSNR as compared with other networks in
real-time applications such as Image Signal Processing(ISP), Low-Light
Enhancement(LLE), and Super-Resolution(SR) with 2K60FPS throughput on Qualcomm
8 Gen 1 mobile SoC(System-on-Chip). Particularly, for ISP task, SYENet got the
highest score in MAI 2022 Learned Smartphone ISP challenge
MacFormer: Map-Agent Coupled Transformer for Real-time and Robust Trajectory Prediction
Predicting the future behavior of agents is a fundamental task in autonomous
vehicle domains. Accurate prediction relies on comprehending the surrounding
map, which significantly regularizes agent behaviors. However, existing methods
have limitations in exploiting the map and exhibit a strong dependence on
historical trajectories, which yield unsatisfactory prediction performance and
robustness. Additionally, their heavy network architectures impede real-time
applications. To tackle these problems, we propose Map-Agent Coupled
Transformer (MacFormer) for real-time and robust trajectory prediction. Our
framework explicitly incorporates map constraints into the network via two
carefully designed modules named coupled map and reference extractor. A novel
multi-task optimization strategy (MTOS) is presented to enhance learning of
topology and rule constraints. We also devise bilateral query scheme in context
fusion for a more efficient and lightweight network. We evaluated our approach
on Argoverse 1, Argoverse 2, and nuScenes real-world benchmarks, where it all
achieved state-of-the-art performance with the lowest inference latency and
smallest model size. Experiments also demonstrate that our framework is
resilient to imperfect tracklet inputs. Furthermore, we show that by combining
with our proposed strategies, classical models outperform their baselines,
further validating the versatility of our framework.Comment: Accepted by IEEE Robotics and Automation Letters. 8 Pages, 9 Figures,
9 Tables. Video: https://www.youtube.com/watch?v=XY388iI6sP
Kinetic and thermodynamic investigations of CO2 gasification of coal chars prepared via conventional and microwave pyrolysis
This study examined an isothermal CO2 gasification of four chars prepared via two different methods, i.e., conventional and microwave-assisted pyrolysis, by the approach of thermogravimetric analysis. Physical, chemical, and structural behaviours of chars were examined using ultimate analysis, X-ray diffraction, and scanning electronic microscopy. Kinetic parameters were calculated by applying the shrinking unreacted core (SCM) and random pore (RPM) models. Moreover, char-CO2 gasification was further simulated by using Aspen Plus to investigate thermodynamic performances in terms of syngas composition and cold gas efficiency (CGE). The microwave-induced char has the largest C/H mass ratio and most ordered carbon structure, but the smallest gasification reactivity. Kinetic analysis indicates that the RPM is better for describing both gasification conversion and reaction rates of the studied chars, and the activation energies and pre-exponential factors varied in the range of 78.45–194.72 kJ/mol and 3.15–102,231.99 s−1, respectively. In addition, a compensation effect was noted during gasification. Finally, the microwave-derived char exhibits better thermodynamic performances than the conventional chars, with the highest CGE and CO molar concentration of 1.30% and 86.18%, respectively. Increasing the pyrolysis temperature, gasification temperature, and CO2-to-carbon molar ratio improved the CGE
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