1,644 research outputs found
Enhancing Spectrum Sensing via Reconfigurable Intelligent Surfaces: Passive or Active Sensing and How Many Reflecting Elements are Needed?
Cognitive radio has been proposed to alleviate the scarcity of available
spectrum caused by the significant demand for wideband services and the
fragmentation of spectrum resources. However, sensing performance is quite poor
due to the low sensing signal-to-noise ratio, especially in complex
environments with severe channel fading. Fortunately, reconfigurable
intelligent surface (RIS)-aided spectrum sensing can effectively tackle the
above challenge due to its high array gain. Nevertheless, the traditional
passive RIS may suffer from the ``double fading'' effect, which severely limits
the performance of passive RIS-aided spectrum sensing. Thus, a crucial
challenge is how to fully exploit the potential advantages of the RIS and
further improve the sensing performance. To this end, we introduce the active
RIS into spectrum sensing and respectively formulate two optimization problems
for the passive RIS and the active RIS to maximize the detection probability.
In light of the intractability of the formulated problems, we develop a
one-stage optimization algorithm with inner approximation and a two-stage
optimization algorithm with a bisection method to obtain sub-optimal solutions,
and apply the Rayleigh quotient to obtain the upper and lower bounds of the
detection probability. Furthermore, in order to gain more insight into the
impact of the RIS on spectrum sensing, we respectively investigate the number
configuration for passive RIS and active RIS and analyze how many reflecting
elements are needed to achieve the detection probability close to 1. Simulation
results verify that the proposed algorithms outperform existing algorithms
under the same parameter configuration, and achieve a detection probability
close to 1 with even fewer reflecting elements or antennas than existing
schemes
LPT: Long-tailed Prompt Tuning for Image Classification
For long-tailed classification, most works often pretrain a big model on a
large-scale dataset, and then fine-tune the whole model for adapting to
long-tailed data. Though promising, fine-tuning the whole pretrained model
tends to suffer from high cost in computation and deployment of different
models for different tasks, as well as weakened generalization ability for
overfitting to certain features of long-tailed data. To alleviate these issues,
we propose an effective Long-tailed Prompt Tuning method for long-tailed
classification. LPT introduces several trainable prompts into a frozen
pretrained model to adapt it to long-tailed data. For better effectiveness, we
divide prompts into two groups: 1) a shared prompt for the whole long-tailed
dataset to learn general features and to adapt a pretrained model into target
domain; and 2) group-specific prompts to gather group-specific features for the
samples which have similar features and also to empower the pretrained model
with discrimination ability. Then we design a two-phase training paradigm to
learn these prompts. In phase 1, we train the shared prompt via supervised
prompt tuning to adapt a pretrained model to the desired long-tailed domain. In
phase 2, we use the learnt shared prompt as query to select a small best
matched set for a group of similar samples from the group-specific prompt set
to dig the common features of these similar samples, then optimize these
prompts with dual sampling strategy and asymmetric GCL loss. By only
fine-tuning a few prompts while fixing the pretrained model, LPT can reduce
training and deployment cost by storing a few prompts, and enjoys a strong
generalization ability of the pretrained model. Experiments show that on
various long-tailed benchmarks, with only ~1.1% extra parameters, LPT achieves
comparable performance than previous whole model fine-tuning methods, and is
more robust to domain-shift.Comment: ICLR 2023 (poster
Patched Line Segment Learning for Vector Road Mapping
This paper presents a novel approach to computing vector road maps from
satellite remotely sensed images, building upon a well-defined Patched Line
Segment (PaLiS) representation for road graphs that holds geometric
significance. Unlike prevailing methods that derive road vector representations
from satellite images using binary masks or keypoints, our method employs line
segments. These segments not only convey road locations but also capture their
orientations, making them a robust choice for representation. More precisely,
given an input image, we divide it into non-overlapping patches and predict a
suitable line segment within each patch. This strategy enables us to capture
spatial and structural cues from these patch-based line segments, simplifying
the process of constructing the road network graph without the necessity of
additional neural networks for connectivity. In our experiments, we demonstrate
how an effective representation of a road graph significantly enhances the
performance of vector road mapping on established benchmarks, without requiring
extensive modifications to the neural network architecture. Furthermore, our
method achieves state-of-the-art performance with just 6 GPU hours of training,
leading to a substantial 32-fold reduction in training costs in terms of GPU
hours
Rapid flocculation-sedimentation of microalgae with organosilane-functionalized halloysite
Microalgae is a promising feedstock of biofuel for alternating fossil fuels. The major challenge of microalgal biofuels for commercial applications is in designing an efficient harvesting method with high economic feasibility. In this study, a rapid flocculation-sedimentation harvesting method induced by organosilane-functionalized halloysite flocculant was achieved for Scenedesmus dimorphus harvest. The harvesting efficiency was significantly influenced by the pH of microalgal dispersion and the dosage of flocculant. The optimized harvesting condition was pH 3.0 with flocculant dosage of 1.0 g.g(-1) cell dry mass. Under the optimized harvesting condition, microalgae rapidly reached 93% harvesting efficiency within 0.5 min of settling time, and reached 98% harvesting efficiency within 2 min of settling time. The rapid flocculation was attributed to the charge neutralization of the negatively-charged microalgae cells by the positively-charged organosilane-functionalized halloysite flocculant and to the sweep flocculation by organosilane-functionalized halloysite flocculant. The organosilane-functionalized halloysite flocculant did not affect the lipid extraction of microalgae, and not contaminate the extracted residuals. The organosilane-functionalized halloysite flocculant is of high efficient, cost-effective, and eco-friendly, makes it be of promising application for commercial microalgae harvesting.</p
Active screen plasma nitriding enhances cell attachment to polymer surfaces
Active screen plasma nitriding (ASPN) is a well-established technique used for the surface modification of materials, the result of which is often a product with enhanced functional performance. Here we report the modification of the chemical and mechanical properties of ultra-high molecular weight poly(ethylene) (UHMWPE) using 80:20 (v/v) N2/H2 ASPN, followed by growth of 3T3 fibroblasts on the treated and untreated polymer surfaces. ASPN-treated UHMWPE showed extensive fibroblast attachment within 3 h of seeding, whereas fibroblasts did not successfully attach to untreated UHMWPE. Fibroblast coated surfaces were maintained for up to 28 days, monitoring their metabolic activity and morphology throughout. The chemical properties of the ASPN-treated UHMWPE surface were studied using X-ray photoelectron spectroscopy, revealing the presence of C N, C N, and C N chemical bonds. The elastic modulus, surface topography, and adhesion properties of the ASPN-treated UHMWPE surface were studied over 28 days during sample storage under ambient conditions and during immersion in two commonly used cell culture media
AgentTuning: Enabling Generalized Agent Abilities for LLMs
Open large language models (LLMs) with great performance in various tasks
have significantly advanced the development of LLMs. However, they are far
inferior to commercial models such as ChatGPT and GPT-4 when acting as agents
to tackle complex tasks in the real world. These agent tasks employ LLMs as the
central controller responsible for planning, memorization, and tool
utilization, necessitating both fine-grained prompting methods and robust LLMs
to achieve satisfactory performance. Though many prompting methods have been
proposed to complete particular agent tasks, there is lack of research focusing
on improving the agent capabilities of LLMs themselves without compromising
their general abilities. In this work, we present AgentTuning, a simple and
general method to enhance the agent abilities of LLMs while maintaining their
general LLM capabilities. We construct AgentInstruct, a lightweight
instruction-tuning dataset containing high-quality interaction trajectories. We
employ a hybrid instruction-tuning strategy by combining AgentInstruct with
open-source instructions from general domains. AgentTuning is used to
instruction-tune the Llama 2 series, resulting in AgentLM. Our evaluations show
that AgentTuning enables LLMs' agent capabilities without compromising general
abilities. The AgentLM-70B is comparable to GPT-3.5-turbo on unseen agent
tasks, demonstrating generalized agent capabilities. We open source the
AgentInstruct and AgentLM-7B, 13B, and 70B models at
https://github.com/THUDM/AgentTuning, serving open and powerful alternatives to
commercial LLMs for agent tasks.Comment: 31 page
Contrastive Augmented Graph2Graph Memory Interaction for Few Shot Continual Learning
Few-Shot Class-Incremental Learning (FSCIL) has gained considerable attention
in recent years for its pivotal role in addressing continuously arriving
classes. However, it encounters additional challenges. The scarcity of samples
in new sessions intensifies overfitting, causing incompatibility between the
output features of new and old classes, thereby escalating catastrophic
forgetting. A prevalent strategy involves mitigating catastrophic forgetting
through the Explicit Memory (EM), which comprise of class prototypes. However,
current EM-based methods retrieves memory globally by performing
Vector-to-Vector (V2V) interaction between features corresponding to the input
and prototypes stored in EM, neglecting the geometric structure of local
features. This hinders the accurate modeling of their positional relationships.
To incorporate information of local geometric structure, we extend the V2V
interaction to Graph-to-Graph (G2G) interaction. For enhancing local structures
for better G2G alignment and the prevention of local feature collapse, we
propose the Local Graph Preservation (LGP) mechanism. Additionally, to address
sample scarcity in classes from new sessions, the Contrast-Augmented G2G
(CAG2G) is introduced to promote the aggregation of same class features thus
helps few-shot learning. Extensive comparisons on CIFAR100, CUB200, and the
challenging ImageNet-R dataset demonstrate the superiority of our method over
existing methods.Comment: 12 Pages, 5 figure
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