133 research outputs found
On Unconstrained Quasi-Submodular Function Optimization
With the extensive application of submodularity, its generalizations are
constantly being proposed. However, most of them are tailored for special
problems. In this paper, we focus on quasi-submodularity, a universal
generalization, which satisfies weaker properties than submodularity but still
enjoys favorable performance in optimization. Similar to the diminishing return
property of submodularity, we first define a corresponding property called the
{\em single sub-crossing}, then we propose two algorithms for unconstrained
quasi-submodular function minimization and maximization, respectively. The
proposed algorithms return the reduced lattices in iterations,
and guarantee the objective function values are strictly monotonically
increased or decreased after each iteration. Moreover, any local and global
optima are definitely contained in the reduced lattices. Experimental results
verify the effectiveness and efficiency of the proposed algorithms on lattice
reduction.Comment: 11 page
Microbial community analysis in biocathode microbial fuel cells packed with different materials
Biocathode MFCs using microorganisms as catalysts have important advantages in lowering cost and improving sustainability. Electrode materials and microbial synergy determines biocathode MFCs performance. In this study, four materials, granular activated carbon (GAC), granular semicoke (GS), granular graphite (GG) and carbon felt cube (CFC) were used as packed cathodic materials. The microbial composition on each material and its correlation with the electricity generation performance of MFCs were investigated. Results showed that different biocathode materials had an important effect on the type of microbial species in biocathode MFCs. The microbes belonging to Bacteroidetes and Proteobacteria were the dominant phyla in the four materials packed biocathode MFCs. Comamonas of Betaproteobacteria might play significant roles in electron transfer process of GAC, GS and CFC packed biocathode MFCs, while in GG packed MFC Acidovorax may be correlated with power generation. The biocathode materials also had influence on the microbial diversity and evenness, but the differences in them were not positively related to the power production
A Transferable Intersection Reconstruction Network for Traffic Speed Prediction
Traffic speed prediction is the key to many valuable applications, and it is
also a challenging task because of its various influencing factors. Recent work
attempts to obtain more information through various hybrid models, thereby
improving the prediction accuracy. However, the spatial information acquisition
schemes of these methods have two-level differentiation problems. Either the
modeling is simple but contains little spatial information, or the modeling is
complete but lacks flexibility. In order to introduce more spatial information
on the basis of ensuring flexibility, this paper proposes IRNet (Transferable
Intersection Reconstruction Network). First, this paper reconstructs the
intersection into a virtual intersection with the same structure, which
simplifies the topology of the road network. Then, the spatial information is
subdivided into intersection information and sequence information of traffic
flow direction, and spatiotemporal features are obtained through various
models. Third, a self-attention mechanism is used to fuse spatiotemporal
features for prediction. In the comparison experiment with the baseline, not
only the prediction effect, but also the transfer performance has obvious
advantages.Comment: 14 pages, 12 figure
Spatial-Temporal Feature Extraction and Evaluation Network for Citywide Traffic Condition Prediction
Traffic prediction plays an important role in the realization of traffic
control and scheduling tasks in intelligent transportation systems. With the
diversification of data sources, reasonably using rich traffic data to model
the complex spatial-temporal dependence and nonlinear characteristics in
traffic flow are the key challenge for intelligent transportation system. In
addition, clearly evaluating the importance of spatial-temporal features
extracted from different data becomes a challenge. A Double Layer - Spatial
Temporal Feature Extraction and Evaluation (DL-STFEE) model is proposed. The
lower layer of DL-STFEE is spatial-temporal feature extraction layer. The
spatial and temporal features in traffic data are extracted by multi-graph
graph convolution and attention mechanism, and different combinations of
spatial and temporal features are generated. The upper layer of DL-STFEE is the
spatial-temporal feature evaluation layer. Through the attention score matrix
generated by the high-dimensional self-attention mechanism, the
spatial-temporal features combinations are fused and evaluated, so as to get
the impact of different combinations on prediction effect. Three sets of
experiments are performed on actual traffic datasets to show that DL-STFEE can
effectively capture the spatial-temporal features and evaluate the importance
of different spatial-temporal feature combinations.Comment: 39 pages, 14 figures, 5 table
Progress and summary of reinforcement learning on energy management of MPS-EV
The high emission and low energy efficiency caused by internal combustion
engines (ICE) have become unacceptable under environmental regulations and the
energy crisis. As a promising alternative solution, multi-power source electric
vehicles (MPS-EVs) introduce different clean energy systems to improve
powertrain efficiency. The energy management strategy (EMS) is a critical
technology for MPS-EVs to maximize efficiency, fuel economy, and range.
Reinforcement learning (RL) has become an effective methodology for the
development of EMS. RL has received continuous attention and research, but
there is still a lack of systematic analysis of the design elements of RL-based
EMS. To this end, this paper presents an in-depth analysis of the current
research on RL-based EMS (RL-EMS) and summarizes the design elements of
RL-based EMS. This paper first summarizes the previous applications of RL in
EMS from five aspects: algorithm, perception scheme, decision scheme, reward
function, and innovative training method. The contribution of advanced
algorithms to the training effect is shown, the perception and control schemes
in the literature are analyzed in detail, different reward function settings
are classified, and innovative training methods with their roles are
elaborated. Finally, by comparing the development routes of RL and RL-EMS, this
paper identifies the gap between advanced RL solutions and existing RL-EMS.
Finally, this paper suggests potential development directions for implementing
advanced artificial intelligence (AI) solutions in EMS
Modified Glucose-Insulin-Potassium Regimen Provides Cardioprotection With Improved Tissue Perfusion in Patients Undergoing Cardiopulmonary Bypass Surgery
Background Laboratory studies demonstrate glucose-insulin-potassium (GIK) as a potent cardioprotective intervention, but clinical trials have yielded mixed results, likely because of varying formulas and timing of GIK treatment and different clinical settings. This study sought to evaluate the effects of modified GIK regimen given perioperatively with an insulin-glucose ratio of 1:3 in patients undergoing cardiopulmonary bypass surgery. Methods and Results In this prospective, randomized, double-blinded trial with 930 patients referred for cardiac surgery with cardiopulmonary bypass, GIK (200 g/L glucose, 66.7 U/L insulin, and 80 mmol/L KCl) or placebo treatment was administered intravenously at 1 mL/kg per hour 10 minutes before anesthesia and continuously for 12.5 hours. The primary outcome was the incidence of in-hospital major adverse cardiac events including all-cause death, low cardiac output syndrome, acute myocardial infarction, cardiac arrest with successful resuscitation, congestive heart failure, and arrhythmia. GIK therapy reduced the incidence of major adverse cardiac events and enhanced cardiac function recovery without increasing perioperative blood glucose compared with the control group. Mechanistically, this treatment resulted in increased glucose uptake and less lactate excretion calculated by the differences between arterial and coronary sinus, and increased phosphorylation of insulin receptor substrate-1 and protein kinase B in the hearts of GIK-treated patients. Systemic blood lactate was also reduced in GIK-treated patients during cardiopulmonary bypass surgery. Conclusions A modified GIK regimen administered perioperatively reduces the incidence of in-hospital major adverse cardiac events in patients undergoing cardiopulmonary bypass surgery. These benefits are likely a result of enhanced systemic tissue perfusion and improved myocardial metabolism via activation of insulin signaling by GIK. Clinical Trial Registration URL: clinicaltrials.gov. Identifier: NCT01516138
Wireless Deep Video Semantic Transmission
In this paper, we design a new class of high-efficiency deep joint
source-channel coding methods to achieve end-to-end video transmission over
wireless channels. The proposed methods exploit nonlinear transform and
conditional coding architecture to adaptively extract semantic features across
video frames, and transmit semantic feature domain representations over
wireless channels via deep joint source-channel coding. Our framework is
collected under the name deep video semantic transmission (DVST). In
particular, benefiting from the strong temporal prior provided by the feature
domain context, the learned nonlinear transform function becomes temporally
adaptive, resulting in a richer and more accurate entropy model guiding the
transmission of current frame. Accordingly, a novel rate adaptive transmission
mechanism is developed to customize deep joint source-channel coding for video
sources. It learns to allocate the limited channel bandwidth within and among
video frames to maximize the overall transmission performance. The whole DVST
design is formulated as an optimization problem whose goal is to minimize the
end-to-end transmission rate-distortion performance under perceptual quality
metrics or machine vision task performance metrics. Across standard video
source test sequences and various communication scenarios, experiments show
that our DVST can generally surpass traditional wireless video coded
transmission schemes. The proposed DVST framework can well support future
semantic communications due to its video content-aware and machine vision task
integration abilities.Comment: published in IEEE JSA
Outer-inner Dual Reinforced Micro/Nano Hierarchical Scaffolds for Promoting Osteogenesis
Biomimetic scaffolds have been extensively studied for guiding osteogenesis through structural cues. Inspired by the natural bone growth process, we have employed a hierarchical outer-inner dual reinforcing strategy, which relies on the interfacial ionic bond interaction between amine/calcium and carboxyl group, to build a nanofiber/particle dual strengthened hierarchical silk fibroin scaffold. The scaffold can provide applicable form of osteogenic structural cue and mimic the natural bone forming process. Owing to the active interaction between compositions located in the outer pore space and the inner pore wall, the scaffold has over 4 times improvement on mechanical property, followed by significant alteration on cell-scaffold interaction pattern, demonstrated by over 2 times’ elevation on the spreading area and enhanced osteogenic activity potentially involving activities of integrin, Vinculin and Yes-associated protein (YAP). In vivo performance of the scaffold identified the inherent osteogenic effect of structural cue, which promotes rapid and uniform regeneration. Overall, the hierarchical scaffold is promising in promoting uniform bone regeneration through its specific structural cue endowed by its micro-nano construction.Peer reviewe
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