3,782 research outputs found
LENet: Lightweight And Efficient LiDAR Semantic Segmentation Using Multi-Scale Convolution Attention
LiDAR-based semantic segmentation is critical in the fields of robotics and
autonomous driving as it provides a comprehensive understanding of the scene.
This paper proposes a lightweight and efficient projection-based semantic
segmentation network called LENet with an encoder-decoder structure for
LiDAR-based semantic segmentation. The encoder is composed of a novel
multi-scale convolutional attention (MSCA) module with varying receptive field
sizes to capture features. The decoder employs an Interpolation And Convolution
(IAC) mechanism utilizing bilinear interpolation for upsampling
multi-resolution feature maps and integrating previous and current dimensional
features through a single convolution layer. This approach significantly
reduces the network's complexity while also improving its accuracy.
Additionally, we introduce multiple auxiliary segmentation heads to further
refine the network's accuracy. Extensive evaluations on publicly available
datasets, including SemanticKITTI, SemanticPOSS, and nuScenes, show that our
proposed method is lighter, more efficient, and robust compared to
state-of-the-art semantic segmentation methods. Full implementation is
available at https://github.com/fengluodb/LENet
Prompt-Specific Poisoning Attacks on Text-to-Image Generative Models
Data poisoning attacks manipulate training data to introduce unexpected
behaviors into machine learning models at training time. For text-to-image
generative models with massive training datasets, current understanding of
poisoning attacks suggests that a successful attack would require injecting
millions of poison samples into their training pipeline. In this paper, we show
that poisoning attacks can be successful on generative models. We observe that
training data per concept can be quite limited in these models, making them
vulnerable to prompt-specific poisoning attacks, which target a model's ability
to respond to individual prompts.
We introduce Nightshade, an optimized prompt-specific poisoning attack where
poison samples look visually identical to benign images with matching text
prompts. Nightshade poison samples are also optimized for potency and can
corrupt an Stable Diffusion SDXL prompt in <100 poison samples. Nightshade
poison effects "bleed through" to related concepts, and multiple attacks can
composed together in a single prompt. Surprisingly, we show that a moderate
number of Nightshade attacks can destabilize general features in a
text-to-image generative model, effectively disabling its ability to generate
meaningful images. Finally, we propose the use of Nightshade` and similar tools
as a last defense for content creators against web scrapers that ignore
opt-out/do-not-crawl directives, and discuss possible implications for model
trainers and content creators
Parametric knocking performance investigation of spark ignition natural gas engines and dual fuel engines
Both spark ignition (SI) natural gas engines and compression ignition (CI) dual fuel (DF) engines suffer from knocking when the unburnt mixture ignites spontaneously prior to the flame front arrival. In this study, a parametric investigation is performed on the knocking performance of these two engine types by using the GT-Power software. An SI natural gas engine and a DF engine are modelled by employing a two-zone zero-dimensional combustion model, which uses Wiebe function to determine the combustion rate and provides adequate prediction of the unburnt zone temperature, which is crucial for the knocking prediction. The developed models are validated against experimentally measured parameters and are subsequently used for performing parametric investigations. The derived results are analysed to quantify the effect of the compression ratio, air-fuel equivalence ratio and ignition timing on both engines as well as the effect of pilot fuel energy proportion on the DF engine. The results demonstrate that the compression ratio of the investigated SI and DF engines must be limited to 11 and 16.5, respectively, for avoiding knocking occurrence. The ignition timing for the SI and the DF engines must be controlled after −38 ◦CA and 3 ◦CA, respectively. A higher pilot fuel energy proportion between 5% and 15% results in increasing the knocking tendency and intensity for the DF Engine at high loads. This study results in better insights on the impacts of the investigated engine design and operating settings for natural gas (NG)-fuelled engines, thus it can provide useful support for obtaining the optimal settings targeting a desired combustion behaviour and engine performance while attenuating the knocking tendency
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