262 research outputs found
Adaptation response of Pseudomonas fragi on refrigerated solid matrix to a moderate electric field
We have conducted a Raman study of methane (CH4), a major constituent of the outer planets, at pressures up to 165 GPa. We observe splitting of the principal Raman-active vibrational mode above 45 GPa and a nonlinear dependence of Raman peak position on pressure. A discontinuous change in the pressure derivative of the ν3 peak position is observed at approximately 75 GPa, corresponding to the phase change previously observed using X-ray diffraction. The Grüneisen parameters for the principal Raman-active modes of methane in the simple cubic and high-pressure cubic phases are calculated. The predicted dissociation of methane at ultrahigh pressure to form C2H6 and H2 is not observed, but an additional discontinuous change in the pressure-induced shift of the Raman peaks is observed at 110 GPa. We suggest that this may be due to some reorientation or reordering of the methane molecules within the framework of the known cubic lattice
Balance control of grid currents for UPQC under unbalanced loads based on matching-ratio compensation algorithm
Abstract In three-phase four-wire systems, unbalanced loads can cause grid currents to be unbalanced, and this may cause the neutral point potential on the grid side to shift. The neutral point potential shift will worsen the control precision as well as the performance of the three-phase four-wire unified power quality conditioner (UPQC), and it also leads to unbalanced three-phase output voltage, even causing damage to electric equipment. To deal with unbalanced loads, this paper proposes a matching-ratio compensation algorithm (MCA) for the fundamental active component of load currents, and by employing this MCA, balanced three-phase grid currents can be realized under 100% unbalanced loads. The steady-state fluctuation and the transient drop of the DC bus voltage can also be restrained. This paper establishes the mathematical model of the UPQC, analyzes the mechanism of the DC bus voltage fluctuations, and elaborates the interaction between unbalanced grid currents and DC bus voltage fluctuations; two control strategies of UPQC under three-phase stationary coordinate based on the MCA are given, and finally, the feasibility and effectiveness of the proposed control strategy are verified by experiment results
Dynamic Graph Convolutional Network with Attention Fusion for Traffic Flow Prediction
Accurate and real-time traffic state prediction is of great practical
importance for urban traffic control and web mapping services. With the support
of massive data, deep learning methods have shown their powerful capability in
capturing the complex spatialtemporal patterns of traffic networks. However,
existing approaches use pre-defined graphs and a simple set of spatial-temporal
components, making it difficult to model multi-scale spatial-temporal
dependencies. In this paper, we propose a novel dynamic graph convolution
network with attention fusion to tackle this gap. The method first enhances the
interaction of temporal feature dimensions, and then it combines a dynamic
graph learner with GRU to jointly model synchronous spatial-temporal
correlations. We also incorporate spatial-temporal attention modules to
effectively capture longrange, multifaceted domain spatial-temporal patterns.
We conduct extensive experiments in four real-world traffic datasets to
demonstrate that our method surpasses state-of-the-art performance compared to
18 baseline methods.Comment: 8 pages, 5 figure, accepted by ECAI 202
A Grid Synchronization PLL Method Based on Mixed Second- and Third-Order Generalized Integrator for DC-Offset Elimination and Frequency Adaptability
Influence of different sizes of concrete and roller compacted concrete on double-K fracture parameters
Affected by physical properties of various components, characteristics and stress states of junction surface and other multiple factors, concrete, as a kind of multi-phase composite material, has complicated failure mechanism, thus making its fracture mechanism research difficult. But concrete has been widely used in engineering construction, so research on concrete fracture theory is of important realistic significance and construction value. This study discusses influence rule of specimen size and crack-depth ratio (?0/h) on doubleK fracture parameters (initial fracture toughness ini ICK and unstable fracture toughness un ICK ) and its size effects by using fracture test. Different sizes of concretes and roller compacted concrete (RCC) specimens are adopted to explore influence of specimen size on concrete double-K fracture parameters. Results reveal that initial fracture toughness ini ICK and unstable fracture toughness un ICK increase as specimen size enlarges, showing a size effect; besides, subcritical crack extends with the increase of specimen size. With regard to specimens with different crack-depth ratios, its unstable fracture toughness un ICK is unrelated to initial crack-depth ratio when crack-depth ratio is more than or equal to 0.4, while initial fracture toughness ini ICK is correlated with initial crack-depth ratio, which indicate that double-K fracture parameters can be considered as material constants describing concrete initial fracture, stable expansion and whole process of stability failure
New Rotor Position Redundancy Decoding Method Based on Resolver Decoder
In view of the frequent safety problems of electric vehicles, the research on accurately obtaining the rotor position of the motor through the resolver is an important means to improve the functional safety of the system. The commonly used resolver decoding method involves the resolver decoding chip method and software decoding method, but few studies integrate the two decoding methods. A single method of motor rotor position acquisition cannot meet the requirements of system functional safety. To fill this gap, this paper proposes a method to simultaneously integrate hardware decoding and software decoding in the motor control system. The decoding chip and software decoding obtain the angle data at the same time, and they provide redundancy to improve the functional safety of the electronic control system. Finally, the effectiveness of the proposed simultaneous operation of hardware decoding and software decoding is verified by experiments
ENV-607: SURFACTANT-MODIFIED BIOMASS ADSORBENTS FOR ENHANCED REMOVAL OF POLLUTANTS FROM AQUEOUS SOLUTION
From the view of economical efficiency and technology sustainability, considerable attention has been recently given to the use of low-cost biomass residues as adsorbents in pollution control. To achieve a desirable adsorptive efficiency, some efforts have also been made to modify biomass adsorbents through appropriate treatments. There is a particular interest in surfactant-assisted biomass surface modification. Although some findings from previous studies are encouraging, knowledge about the adsorption of pollutants onto surfactant-modified biomass is still limited. A number of issues about the characteristics of involved interface transport are poorly understood. The present study therefore aims to examine the adsorption of anionic azo dyes onto surfactant-modified biomass in the solution. Different surfactants are used for modification. The equilibrium and kinetic studies for the adsorption of anionic azo dyes on modified biomass are conducted and the effects of aqueous chemistry characteristics are also evaluated. The results present the potential of modified biomass as suitable adsorbent for the removal of anionic azo dyes from wastewater. It can help understand the migration patterns of organic pollutants at biomass-water interface
Medical treatment and long-term outcome of chronic atrial fibrillation in the aged with chest distress: a retrospective analysis versus sinus rhythm
Although “chest distress” is the most frequent complication in the aged with chronic atrial frbrillation (AF) in clinical practice, there are few data on the association between chronic AF and coronary artery disease (CAD) in the aged in terms of medical treatment and long-term outcome. We assessed coronary artery lesions in such patients and evaluated the efficacy of medical treatment in long-term follow-ups. Of 315 elderly patients (mean age: 77.39 ± 6.33 years) who had undergone coronary angiography for chest distress, 297 exhibited sinus rhythm (SR), whereas 18 patients exhibited chronic AF. Patients with AF were followed for 4.22 ± 2.21 years. Average diastolic blood pressure (DBP) of AF patients was observed to be markedly less than that of patients with SR (57.33 ± 6.87 mmHg vs 71.08 ± 10.54 mmHg, t-test: P < 0.01). Compared with SR patients, severe stenosis of the coronary artery in AF patients was reduced (73.06% vs 44.44%, Chi-square test: P < 0.01). AF patients with chest distress had high CHADS2 score (3.72 ± 1.27), but only 33.3% patients received oral anticoagulants, and such patients had a significantly lower rate of revascularization (21.43% vs 55.63%, Chi-square test: P < 0.01), and higher rate of all-cause death (22.22% vs 4.38%, Chi-square test: P < 0.01) and thromboembolism (16.67% vs 1.68%, Chi-square test: P < 0.01) in the long-term follow-ups compared with SR patients. Chest distress in the aged with AF was related to insufficient coronary blood supply that was primarily due to a reduced DBP rather than to occult CAD. Adequate and safe medical therapy was difficult to achieve in these patients. Such patients typically have a poor prognosis, and optimal therapeutic strategies to treat them are urgently needed
Analysis of high-speed angular ball bearing lubrication based on bi-directional fluid-solid coupling
The lubrication of angular contact ball bearings under high-speed motion conditions is particularly important to the working performance of rolling bearings. Combining the contact characteristics of fluid domain and solid domain, a lubrication calculation model for angular contact ball bearings is established based on the RNG k-ε method. The pressure and velocity characteristics of the bearing basin under the conditions of rotational speed, number of balls and lubricant parameters are analyzed, and the lubrication conditions and dynamics of the angular contact ball bearings under different working conditions are obtained. The results show that the lubricant film pressure will rise with increasing speed and viscosity of the lubricant. The number of balls affects the pressure and velocity distribution of the flow field inside the bearing but has a small effect on the values of the characteristic parameters of the bearing flow field. The established CFD model provides a new approach to study the effect of fluid flow on bearing performance in angular contact ball bearings
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