288 research outputs found
Stepwise Design Methodology and Heterogeneous Integration Routine of Air-Cooled SiC Inverter for Electric Vehicle
Carrying on SiC devices, the air-cooled inverter of the electric vehicle (EV) can eliminate the traditional complicated liquid-cooling system in order to obtain a light and compact performance of the powertrain, which is considered as the trend of next-generation EV. However, the air-cooled SiC inverter lacks strategic design methodology and heterogeneous integration routine for critical components. In this article, a stepwise design methodology is proposed for the air-cooled SiC inverter in the power module, dc-link capacitor, and heat sink levels. In the power module level, an electrical-thermal-mechanical multiphysics model is proposed. The multidimension stress distribution principles in a six-in-one SiC power module are demonstrated. An improved power module is presented and confirmed by using the observed multiphysics design principles. In the dc-link capacitor level, ripple modeling of the inverter and capacitor are created. Considering the tradeoffs among ripple voltage, ripple current, and cost, optimal strategies to determine the material and minimize the capacitance of the dc-link capacitor are proposed. In the heat sink level, thermal resistance of air-cooled heat sink is modeled. Structure and material properties of the heat sink are optimally designed by using a comprehensive electro-thermal analysis. Based on the optimal design results, the prototypes of the customized SiC power module and heterogeneously integrated air-cooled inverter are fabricated. Experimental results are presented to demonstrate the feasibility of the designed and manufactured air-cooled SiC inverter.Ministry of Education (MOE)Nanyang Technological UniversityThis work was supported in part by the National Natural Science Foundation of China under Grant 51607016, in part by the National Key Research and Development Program of China under Grant 2017YFB0102303, and in part by the Singapore ACRF Tier 1 Grant RG 85/18. The work of X. Zhang was supported by the NTU Startup Grant (SCOPES)
Dynamics of cold pulses induced by super-sonic molecular beam injection in the EAST tokamak
Evolution of electron temperature, electron density and its fluctuation with
high spatial and temporal resolutions are presented for the cold pulse
propagation induced by super-sonic molecular beam injection (SMBI) in ohmic
plasmas in the EAST tokamak. The non-local heat transport occurs for discharges
with plasma current =450 kA (), and electron density
below a critical value of
. In contrary to the response of
core electron temperature and electron density (roughly 10 ms after SMBI), the
electron density fluctuation in the plasma core increases promptly after SMBI
and reaches its maximum around 15 ms after SMBI. The electron density
fluctuation in the plasma core begins to decrease before the core electron
temperature reaches its maximum (roughly 30 ms). It was also observed that the
turbulence perpendicular velocity close to the inversion point of the
temperature perturbation changes sign after SMBI
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Salmonella produce microRNA-like RNA fragment Sal-1 in the infected cells to facilitate intracellular survival.
Salmonella have developed a sophisticated machinery to evade immune clearance and promote survival in the infected cells. Previous studies were mostly focused on either bacteria itself or host cells, the interaction mechanism of host-pathogen awaits further exploration. In the present study, we show that Salmonella can exploit mammalian cell non-classical microRNA processing machinery to further process bacterial small non-coding RNAs into microRNA-like fragments. Sal-1, one such fragment with the highest copy number in the infected cells, is derived from Salmonella 5-leader of the ribosomal RNA transcript and has a stem structure-containing precursor. Processing of Sal-1 precursors to mature Sal-1 is dependent on host cell Argonaute 2 (AGO2) but not Dicer. Functionally, depleting cellular Sal-1 strongly renders the Salmonella bacteria less resistant to the host defenses both in vitro and in vivo. In conclusion, we demonstrate a novel strategy for Salmonella evading the host immune clearance, in which Salmonella produce microRNA-like functional RNA fragments to establish a microenvironment facilitating bacterial survival
A novel solution for seepage problems using physics-informed neural networks
A Physics-Informed Neural Network (PINN) provides a distinct advantage by
synergizing neural networks' capabilities with the problem's governing physical
laws. In this study, we introduce an innovative approach for solving seepage
problems by utilizing the PINN, harnessing the capabilities of Deep Neural
Networks (DNNs) to approximate hydraulic head distributions in seepage
analysis. To effectively train the PINN model, we introduce a comprehensive
loss function comprising three components: one for evaluating differential
operators, another for assessing boundary conditions, and a third for
appraising initial conditions. The validation of the PINN involves solving four
benchmark seepage problems. The results unequivocally demonstrate the
exceptional accuracy of the PINN in solving seepage problems, surpassing the
accuracy of FEM in addressing both steady-state and free-surface seepage
problems. Hence, the presented approach highlights the robustness of the PINN
and underscores its precision in effectively addressing a spectrum of seepage
challenges. This amalgamation enables the derivation of accurate solutions,
overcoming limitations inherent in conventional methods such as mesh generation
and adaptability to complex geometries
Holistically-Attracted Wireframe Parsing
This paper presents a fast and parsimonious parsing method to accurately and
robustly detect a vectorized wireframe in an input image with a single forward
pass. The proposed method is end-to-end trainable, consisting of three
components: (i) line segment and junction proposal generation, (ii) line
segment and junction matching, and (iii) line segment and junction
verification. For computing line segment proposals, a novel exact dual
representation is proposed which exploits a parsimonious geometric
reparameterization for line segments and forms a holistic 4-dimensional
attraction field map for an input image. Junctions can be treated as the
"basins" in the attraction field. The proposed method is thus called
Holistically-Attracted Wireframe Parser (HAWP). In experiments, the proposed
method is tested on two benchmarks, the Wireframe dataset, and the YorkUrban
dataset. On both benchmarks, it obtains state-of-the-art performance in terms
of accuracy and efficiency. For example, on the Wireframe dataset, compared to
the previous state-of-the-art method L-CNN, it improves the challenging mean
structural average precision (msAP) by a large margin ( absolute
improvements) and achieves 29.5 FPS on single GPU ( relative
improvement). A systematic ablation study is performed to further justify the
proposed method.Comment: Accepted by CVPR 202
Learning Profitable NFT Image Diffusions via Multiple Visual-Policy Guided Reinforcement Learning
We study the task of generating profitable Non-Fungible Token (NFT) images
from user-input texts. Recent advances in diffusion models have shown great
potential for image generation. However, existing works can fall short in
generating visually-pleasing and highly-profitable NFT images, mainly due to
the lack of 1) plentiful and fine-grained visual attribute prompts for an NFT
image, and 2) effective optimization metrics for generating high-quality NFT
images. To solve these challenges, we propose a Diffusion-based generation
framework with Multiple Visual-Policies as rewards (i.e., Diffusion-MVP) for
NFT images. The proposed framework consists of a large language model (LLM), a
diffusion-based image generator, and a series of visual rewards by design.
First, the LLM enhances a basic human input (such as "panda") by generating
more comprehensive NFT-style prompts that include specific visual attributes,
such as "panda with Ninja style and green background." Second, the
diffusion-based image generator is fine-tuned using a large-scale NFT dataset
to capture fine-grained image styles and accessory compositions of popular NFT
elements. Third, we further propose to utilize multiple visual-policies as
optimization goals, including visual rarity levels, visual aesthetic scores,
and CLIP-based text-image relevances. This design ensures that our proposed
Diffusion-MVP is capable of minting NFT images with high visual quality and
market value. To facilitate this research, we have collected the largest
publicly available NFT image dataset to date, consisting of 1.5 million
high-quality images with corresponding texts and market values. Extensive
experiments including objective evaluations and user studies demonstrate that
our framework can generate NFT images showing more visually engaging elements
and higher market value, compared with SOTA approaches
Holistically-Attracted Wireframe Parsing: From Supervised to Self-Supervised Learning
This article presents Holistically-Attracted Wireframe Parsing (HAWP), a
method for geometric analysis of 2D images containing wireframes formed by line
segments and junctions. HAWP utilizes a parsimonious Holistic Attraction (HAT)
field representation that encodes line segments using a closed-form 4D
geometric vector field. The proposed HAWP consists of three sequential
components empowered by end-to-end and HAT-driven designs: (1) generating a
dense set of line segments from HAT fields and endpoint proposals from
heatmaps, (2) binding the dense line segments to sparse endpoint proposals to
produce initial wireframes, and (3) filtering false positive proposals through
a novel endpoint-decoupled line-of-interest aligning (EPD LOIAlign) module that
captures the co-occurrence between endpoint proposals and HAT fields for better
verification. Thanks to our novel designs, HAWPv2 shows strong performance in
fully supervised learning, while HAWPv3 excels in self-supervised learning,
achieving superior repeatability scores and efficient training (24 GPU hours on
a single GPU). Furthermore, HAWPv3 exhibits a promising potential for wireframe
parsing in out-of-distribution images without providing ground truth labels of
wireframes.Comment: Journal extension of arXiv:2003.01663; Accepted by IEEE TPAMI; Code
is available at https://github.com/cherubicxn/haw
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