558 research outputs found
Efficient Adaptation of Large Vision Transformer via Adapter Re-Composing
The advent of high-capacity pre-trained models has revolutionized
problem-solving in computer vision, shifting the focus from training
task-specific models to adapting pre-trained models. Consequently, effectively
adapting large pre-trained models to downstream tasks in an efficient manner
has become a prominent research area. Existing solutions primarily concentrate
on designing lightweight adapters and their interaction with pre-trained
models, with the goal of minimizing the number of parameters requiring updates.
In this study, we propose a novel Adapter Re-Composing (ARC) strategy that
addresses efficient pre-trained model adaptation from a fresh perspective. Our
approach considers the reusability of adaptation parameters and introduces a
parameter-sharing scheme. Specifically, we leverage symmetric
down-/up-projections to construct bottleneck operations, which are shared
across layers. By learning low-dimensional re-scaling coefficients, we can
effectively re-compose layer-adaptive adapters. This parameter-sharing strategy
in adapter design allows us to significantly reduce the number of new
parameters while maintaining satisfactory performance, thereby offering a
promising approach to compress the adaptation cost. We conduct experiments on
24 downstream image classification tasks using various Vision Transformer
variants to evaluate our method. The results demonstrate that our approach
achieves compelling transfer learning performance with a reduced parameter
count. Our code is available at
\href{https://github.com/DavidYanAnDe/ARC}{https://github.com/DavidYanAnDe/ARC}.Comment: Paper is accepted to NeurIPS 202
Thermal Properties of Cement-Based Composites for Geothermal Energy Applications
Geothermal energy piles are a quite recent renewable energy technique where geothermal energy in the foundation of a building is used to transport and store geothermal energy. In this paper, a structural–functional integrated cement-based composite, which can be used for energy piles, was developed using expanded graphite and graphite nanoplatelet-based composite phase change materials (CPCMs). Its mechanical properties, thermal-regulatory performance, and heat of hydration were evaluated. Test results showed that the compressive strength of GNP-Paraffin cement-based composites at 28 days was more than 25 MPa. The flexural strength and density of thermal energy storage cement paste composite decreased with increases in the percentage of CPCM in the cement paste. The infrared thermal image analysis results showed superior thermal control capability of cement based materials with CPCMs. Hence, the carbon-based CPCMs are promising thermal energy storage materials and can be used to improve the durability of energy piles
Preparation and Supercooling Modification of Salt Hydrate Phase Change Materials Based on CaCl2 2H2O/CaCl2
Salt hydrates have issues of supercooling when they are utilized as phase change materials
(PCMs). In this research, a new method was adopted to prepare a salt hydrate PCM (based
on a mixture of calcium chloride dihydrate and calcium chloride anhydrous) as a novel PCM
system to reduce the supercooling phenomenon existing in CaCl2 6H2O. Six samples with different
compositions of CaCl2 were prepared. The relationship between the performance and the proportion
of calcium chloride dihydrate (CaCl2 2H2O) and calcium chloride anhydrous (CaCl2) was also
investigated. The supercooling degree of the final PCM reduced with the increase in volume of
CaCl2 2H2O during its preparation. The PCM obtained with 66.21 wt % CaCl2 2H2O reduced the
supercooling degree by about 96.8%. All six samples, whose ratio of CaCl2 2H2O to (CaCl2 plus
CaCl2 2H2O) was 0%, 34.03%, 53.82%, 76.56%, 90.74%, and 100% respectively, showed relatively
higher enthalpy (greater than 155.29 J/g), and have the possibility to be applied in buildings
for thermal energy storage purposes. Hence, CaCl2 2H2O plays an important role in reducing
supercooling and it can be helpful in adjusting the solidification enthalpy. Thereafter, the influence of
adding different percentages of Nano-SiO2 (0.1 wt %, 0.3 wt %, 0.5 wt %) in reducing the supercooling
degree of some PCM samples was investigated. The test results showed that the supercooling of the
salt hydrate PCM in Samples 6 and 5 reduced to 0.2 C and 0.4 C respectively. Finally, the effect of
the different cooling conditions, including frozen storage (20 C) and cold storage (5 C), that were
used to prepare the salt hydrate PCM was considered. It was found that both cooling conditions are
effective in reducing the supercooling degree of the salt hydrate PCM. With the synergistic action of
the two materials, the performance and properties of the newly developed PCM systems were better
especially in terms of reducing the supercooling degree of the PCM. The novel composite PCMs are
promising candidates for thermal energy storage applications
Diatom and silicoflagellate assemblages in modern surface sediments associated with human activity: A case study in Sishili Bay, China
The spatial distribution of diatom and silicoflagellate fossils deposited in modern surface sediments was studied in inshore and offshore zones of Sishili Bay, China, to explore the impact of human activity on the coastal ecosystem. The sediments from 28 sites representing a gradient in intensity of human activity from inshore to offshore were sampled. Although the nutrient parameters inshore showed far higher concentrations than the offshore area, due to sewage discharge and waste dumping in the bay, the average fossil abundance did not differ significantly between the two areas. The diatom fossil Paralia sulcata, supposed to be a eutrophic indicator dominated most sediment samples and displayed a significant and positive correlation with dissolved inorganic nitrogen and phosphorus in the upper water column, but did not show a significant difference in abundance between inshore area and offshore area. Factors such as sediment disturbance (e.g., shipping), grazing pressure (e.g., shellfish aquaculture farm) and sediment characteristics (e.g., grain size) can affect the preservation of fossil debris in the sediment and lower the precision with which human activities can be associated with the fossil abundance.The spatial distribution of diatom and silicoflagellate fossils deposited in modern surface sediments was studied in inshore and offshore zones of Sishili Bay, China, to explore the impact of human activity on the coastal ecosystem. The sediments from 28 sites representing a gradient in intensity of human activity from inshore to offshore were sampled. Although the nutrient parameters inshore showed far higher concentrations than the offshore area, due to sewage discharge and waste dumping in the bay, the average fossil abundance did not differ significantly between the two areas. The diatom fossil Paralia sulcata, supposed to be a eutrophic indicator dominated most sediment samples and displayed a significant and positive correlation with dissolved inorganic nitrogen and phosphorus in the upper water column, but did not show a significant difference in abundance between inshore area and offshore area. Factors such as sediment disturbance (e.g., shipping), grazing pressure (e.g., shellfish aquaculture farm) and sediment characteristics (e.g., grain size) can affect the preservation of fossil debris in the sediment and lower the precision with which human activities can be associated with the fossil abundance. (C) 2012 Elsevier Ltd. All rights reserved
Asymmetric bounded neural control for an uncertain robot by state feedback and output feedback
In this paper, an adaptive neural bounded control scheme is proposed for an n-link rigid robotic manipulator with unknown dynamics. With the combination of the neural approximation and backstepping technique, an adaptive neural network control policy is developed to guarantee the tracking performance of the robot. Different from the existing results, the bounds of the designed controller are known a priori, and they are determined by controller gains, making them applicable within actuator limitations. Furthermore, the designed controller is also able to compensate the effect of unknown robotic dynamics. Via the Lyapunov stability theory, it can be proved that all the signals are uniformly ultimately bounded. Simulations are carried out to verify the effectiveness of the proposed scheme
Species-specific responses to drought, salinity and their interactions in Populus euphratica and P. pruinosa seedlings
Aims Drought and salinity are severe abiotic stress factors, which limit plant growth and productivity, particularly in desert regions. In this study, we employed two desert poplars, Populus euphratica Oliver and Populus pruinosa Schrenk seedlings, to compare their tolerance to drought, salinity and combined stress. Methods We investigated species-specific responses of P. euphratica and P. pruinosa in growth, photosynthetic capacity and pigment contents, nonstructural carbohydrate concentrations, Cl- allocation, osmotic regulation and the accumulation of reactive oxygen species (ROS) under drought, salinity and the combined stress. Important Findings Populus pruinosa exhibited greater growth inhibitory effects, photosynthesis decline, stomata! closure and ROS accumulation, and lower antioxidant enzyme activities and osmotic regulation compared with P. euphratica under drought, salinity and especially under their combined stress. On the other hand, salt-stressed P. euphratica plants restricted salt transportation from roots to leaves, and allocated more Cl- to coarse roots and less to leaves, whereas salt-stressed P. pruinosa allocated more Cl- to leaves. It was shown that there is species-specific variation in these two desert poplars, and P. pruinosa suffers greater negative effects compared with P. euphratica under drought, salinity and especially under the combined stress. Therefore, in ecological restoration and afforestation efforts, species-specific responses and tolerances of these two poplar species to drought and salinity should be considered under climate change with increasing drought and soil salinity developing.Peer reviewe
Efforts to untie the multicollinearity knot and identify factors controlling macropore structures in shale oil reservoirs
Traditional correlation analyses based on whole-rock data have limitations in discerning pore development determinants in shale oil reservoir, given the complex lithology of shale formations and intricate interdependencies (multicollinearity) among geological variables. In this study, mercury injection capillary pressure and digital analysis of scanning electron microscopy were employed to examine the macropore structures of both whole rocks and their constituent lithologies for the Upper Triassic Chang-7 shale of the Ordos Basin. Variations were observed among clay shale (shale primarily consisting of clay-sized mineral grains), massive siltstone and silty laminae within the Chang-7 shale. Through the combination of correlation analysis and scanning electron microscope digital technique, it was demonstrated that total organic carbon content primarily controls the level of macropore development, while lithology primarily governs macropore types and structures. Although quartz and pyrite exhibit correlations with macropore volume, they do not emerge as primary factors; instead, they appear interconnected to total organic carbon. Due to detrital mineral framework preservation during compaction, larger macropores are more developed in massive siltstones and silty laminae than in clay shale. Additionally, silty laminae, situated closer to the source rock and influenced by organic acids, exhibit a higher abundance of larger dissolution pores, potentially favoring shale oil development. This study overcomes traditional method constraints, disentangling multi-correlations, and providing new insights into shale macropore development mechanisms, potentially advancing shale oil exploration and production.Document Type: Original articleCited as: Wang, Z., Dong, L., Jin, Z., Zou, S., Fu, J., Zhu, R. Efforts to untie the multicollinearity knot and identify factors controlling macropore structures in shale oil reservoirs. Advances in Geo-Energy Research, 2024, 11(3): 194-207. https://doi.org/10.46690/ager.2024.03.0
Slag Blended Cement Paste Carbonation under Different CO(2)Concentrations: Controls on Mineralogy and Morphology of Products
To investigate the effect of different CO(2)concentrations on the carbonation results of slag blended cement pastes, carbonation experiments under natural (0.03% CO2) and accelerated conditions (3, 20, and 100% CO2) were investigated with various microscopic testing methods, including X-ray diffraction (XRD),Si-29 magic angle spinning nuclear magnetic resonance (Si-29 MAS NMR) and scanning electron microscopy (SEM). The XRD results indicated that the major polymorphs of CaCO(3)after carbonation were calcite and vaterite. The values of the calcite/(aragonite + vaterite) (c/(a + v)) ratios were almost the same in all carbonation conditions. Additionally, NMR results showed that the decalcification degree of C-S-H gel exposed to 0.03% CO(2)was less than that exposed to accelerated carbonation; under accelerated conditions, it increased from 83.1 to 84.2% when the CO(2)concentration improved from 3% to 100%. In SEM observations, the microstructures after accelerated carbonation were denser than those under natural carbonation but showed minor differences between different CO(2)concentrations. In conclusion, for cement pastes blended with 20% slag, a higher CO(2)concentration (above 3%) led to products different from those produced under natural carbonation. A further increase in CO(2)concentration showed limited variation in generated carbonation products
Research on unbalance vibration signal de-noising of motorized spindle
Using the adaptive redundant lifting wavelet to the vibration signal de-noising has better de-noising effect, but the traditional threshold function of the method has the problems of discontinuous wavelet coefficients or constant deviation. In order to meet the high precision demand of the active balancing of the motorized spindle and improve the extraction accuracy of the unbalance signal, the improved bivariate threshold function was introduced into the method, and then a new de-noising method on unbalance vibration signal of the motorized spindle based on improving adaptive redundant lifting wavelet was put forward. The new method was applied to the engineering unbalance vibration signal. The result showed that the new method can retain the original signal feature of amplitude and phase, as well as eliminate noise more effectively, when the actual vibration signal of motorized spindle is low SNR and non-stationary
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