We report preparation of carbon-supported Co
3
O
4
electrocatalysts with nano-rods and spherical structures by the solvent-mediated morphological control method. The catalytic properties of the ...prepared catalysts for the oxygen reduction reaction (ORR) in alkaline media are investigated. We show that the ORR catalytic activity of the prepared catalysts is sensitive to the number and activity of surface-exposed Co
3+
ions that can be tailored by the morphology of cobalt oxides. In particular, we demonstrate that the non-precious Co
3
O
4
electrocatalyst with the nano-rod structure (12 nm in length and 5.1 nm in diameter) prepared in the mixed solvent of water to dimethylformamide ratio of 1:1 exhibits a higher current density than a much more expensive palladium-based catalyst does at the low potential region.
We report a promising non-precious carbon-supported Co
3
O
4
nanorod electrocatalyst prepared by the solvent-mediated morphological control method for the oxygen reduction reaction in anion-exchange membrane fuel cells.
Modeling and Simulation of Flow Batteries Esan, Oladapo Christopher; Shi, Xingyi; Pan, Zhefei ...
Advanced energy materials,
08/2020, Letnik:
10, Številka:
31
Journal Article
Recenzirano
Odprti dostop
Flow batteries have received extensive recognition for large‐scale energy storage such as connection to the electricity grid, due to their intriguing features and advantages including their simple ...structure and principles, long operation life, fast response, and inbuilt safety. Market penetration of this technology, however, is still hindered by some critical issues such as electroactive species crossover and its corresponding capacity loss, undesirable side reactions, scale‐up and optimization of structural geometries at different scales, and battery operating conditions. Overcoming these remaining challenges requires a comprehensive understanding of the interrelated structural design parameters and the multivariable operations within the battery system. Numerical modeling and simulation are effective tools not only for gaining an understanding of the underlying mechanisms at different spatial and time scales of flow batteries but also for cost‐effective optimization of reaction interfaces, battery components, and the entire system. Here, the research and development progress in modeling and simulation of flow batteries is presented. In addition to the most studied all‐vanadium redox flow batteries, the modelling and simulation efforts made for other types of flow battery are also discussed. Finally, perspectives for future directions on model development for flow batteries, particularly for the ones with limited model‐based studies are highlighted.
The limited reserves of fossil fuels and environmental concerns have promoted the use of renewable energy sources, notably solar, and wind power. The intermittent, varied nature of such renewable resources makes it difficult to integrate these clean energy sources into electrical supply grids, limiting their applicability. Flow battery technology is an effective approach to improving the reliability, power quality, and economy of these renewable energies.
•Propose a carbon nanoparticle-decorated graphite felt electrode for VRFBs.•The energy efficiency is up to 84.8% at 100mAcm−2.•The new electrode allows the peak power density to reach 508mWcm−2.
...Increasing the performance of vanadium redox flow batteries (VRFBs), especially the energy efficiency and power density, is critically important to reduce the system cost to a level for widespread commercialization. Unlike conventional VRFBs with flow-through structure, in this work we create a VRFB featuring a flow-field structure with a carbon nanoparticle-decorated graphite felt electrode for the battery. This novel structure, exhibiting a significantly reduced ohmic loss through reducing electrode thickness, an increased surface area and improved electrocatalytic activity by coating carbon nanoparticles, allows the energy efficiency up to 84.8% at a current density of as high as 100mAcm−2 and the peak power density to reach a value of 508mWcm−2. In addition, it is demonstrated that the battery with this proposed structure exhibits a substantially improved rate capability and capacity retention as opposed to conventional flow-through structured battery with thick graphite felt electrodes.
Objectives
Sarcopenia, an age-related decrease in muscle mass and function, is associated with several potential adverse health outcomes. Its association with another age-related syndrome, dysphagia ...remains unclear. This systematic review and meta-analysis aims to explore the association between sarcopenia and dysphagia.
Methods
PubMed, Embase, Scopus and CINAHL were searched for cross-sectional, case-control and cohort studies that investigated the association between sarcopenia and dysphagia. First author, publication year, study type, sample size, inclusion and exclusion criteria, participant demographics, definition and measurement for evaluation of sarcopenia and dysphagia, main outcomes were retrieved. The association between sarcopenia and dysphagia were expressed by odds ratio (OR) and 95% confidence interval (CI).
Results
9 studies are eligible in the systematic review, and 5 cross-sectional studies comprising 913 participants which showed dichotomous classification of sarcopenia and dysphagia were included in the meta-analysis. The crude odds ratios (ORs) were extracted from 5 studies, and 4 of them also provide adjusted ORs. The crude ORs between sarcopenia and dysphagia is 6.17 (95% CI, 3.81-10.00), after adjusting for some confounders, such as age, sex, Barthel Index score, nutritional status, sarcopenia is also have an association with dysphagia (adjusted ORs, 4.06; 95% CI, 2.27-7.29). The subgroup analysis showed that there was no significant difference between different sarcopenia diagnostic criteria, assessment tools of skeletal muscle mass and dysphagia.
Conclusion
Sarcopenia was positively associated with dysphagia. Prevention and screening of dysphagia is essential among sarcopenic old patients. The causal relationship requires more prospective cohort study for confirmation.
► The performance of VRFBs with different flow fields is numerically simulated. ► A power-based efficiency is defined and calculated for different flow fields. ► An optimal flow rate exists for each ...type of flow field. ► The serpentine flow field appears to be more suitable for VRFBs.
As a key component of flow batteries, the flow field is to distribute electrolytes and to apply/collect electric current to/from cells. The critical issue of the flow field design is how to minimize the mass transport polarization at a minimum pressure drop. In this work a three-dimensional numerical model is proposed and applied to the study of flow field designs for a vanadium redox flow battery (VRFB). The performance of three VRFBs with no flow field and with serpentine and parallel flow fields is numerically tested. Results show that when a flow field is included a reduction in overpotentials depends not only on whether a flow field can ensure a more even distribution of electrolytes over the electrode surface, but also on whether the flow field can facilitate the transport of electrolytes from the flow field towards the membrane, improving the distribution uniformity in the through-plane direction. It is also shown that the pumping power varies with the selection of flow fields at a given flow rate. To assess the suitability of flow fields, a power-based efficiency, which takes account of both the cell performance and pumping power, is defined and calculated for different flow fields at different electrolyte flow rates. Results indicate that there is an optimal flow rate for each type of flow field at which the maximum efficiency can be achieved. As the cell with the serpentine flow field at the optimal flow rate shows the highest energy-based efficiency and round-trip efficiency (RTE), this type of flow field appears to be more suitable for VRFBs than the parallel flow field does.
Linguistic experience affects speech perception from early infancy, as previously evidenced by behavioral and brain measures. Current research focuses on whether linguistic effects on speech ...perception can be observed at an earlier stage in the neural processing of speech (i.e., auditory brainstem). Brainstem responses reflect rapid, automatic, and preattentive encoding of sounds. Positive experiential effects have been reported by examining the frequency-following response (FFR) component of the complex auditory brainstem response (cABR) in response to sustained high-energy periodic portions of speech sounds (vowels and lexical tones). The current study expands the existing literature by examining the cABR onset component in response to transient and low-energy portions of speech (consonants), employing simultaneous magnetoencephalography (MEG) in addition to electroencephalography (EEG), which provide complementary source information on cABR. Utilizing a cross-cultural design, we behaviorally measured perceptual responses to consonants in native Spanish- and English-speaking adults, in addition to cABR. Brain and behavioral relations were examined. Results replicated previous behavioral differences between language groups and further showed that individual consonant perception is strongly associated with EEG-cABR onset peak latency. MEG-cABR source analysis of the onset peaks complimented the EEG-cABR results by demonstrating subcortical sources for both peaks, with no group differences in peak locations. Current results demonstrate a brainstem–perception relation and show that the effects of linguistic experience on speech perception can be observed at the brainstem level.
Individuals with music training in early childhood show enhanced processing of musical sounds, an effect that generalizes to speech processing. However, the conclusions drawn from previous studies ...are limited due to the possible confounds of predisposition and other factors affecting musicians and nonmusicians. We used a randomized design to test the effects of a laboratory-controlled music intervention on young infants’ neural processing of music and speech. Nine-month-old infants were randomly assigned to music (intervention) or play (control) activities for 12 sessions. The intervention targeted temporal structure learning using triple meter in music (e.g., waltz), which is difficult for infants, and it incorporated key characteristics of typical infant music classes to maximize learning (e.g., multimodal, social, and repetitive experiences). Controls had similar multimodal, social, repetitive play, but without music. Upon completion, infants’ neural processing of temporal structure was tested in both music (tones in triple meter) and speech (foreign syllable structure). Infants’ neural processing was quantified by the mismatch response (MMR) measured with a traditional oddball paradigm using magnetoencephalography (MEG). The intervention group exhibited significantly larger MMRs in response to music temporal structure violations in both auditory and prefrontal cortical regions. Identical results were obtained for temporal structure changes in speech. The intervention thus enhanced temporal structure processing not only in music, but also in speech, at 9 mo of age. We argue that the intervention enhanced infants’ ability to extract temporal structure information and to predict future events in time, a skill affecting both music and speech processing.
The ‘sensitive period’ for phonetic learning (∼6–12 months) is one of the earliest milestones in language acquisition where infants start to become specialized in processing speech sounds in their ...native language. In the last decade, advancements in neuroimaging technologies for infants are starting to shed light on the underlying neural mechanisms supporting this important learning period. The current study reports on a large longitudinal dataset with the aim to replicate and extend on two important questions: 1) what are the developmental changes during the ‘sensitive period’ for native and nonnative speech processing? 2) how does native and nonnative speech processing in infants predict later language outcomes? Fifty-four infants were recruited at 7 months of age and their neural processing of speech was measured using Magnetoencephalography (MEG). Specifically, the neural sensitivity to a native and a nonnative speech contrast was indexed by the mismatch response (MMR). They repeated the measurement again at 11 months of age and their language development was further tracked from 12 months to 30 months of age using the MacArthur-Bates Communicative Development Inventory (CDI). Using an a priori Region-of-Interest (ROI) approach, we observed significant increases for the Native MMR in the left inferior frontal region (IF) and superior temporal region (ST) from 7 to 11 months, but not for the Nonnative MMR. Complementary whole brain comparison revealed more widespread developmental changes for both contrasts. However, only individual differences in the left IF and ST for the Nonnative MMR at 11 months of age were significant predictors of individual vocabulary growth up to 30 months of age. An exploratory machine-learning based analysis further revealed that whole brain time series for both Native and Nonnative contrasts can robustly predict later outcomes, but with very different underlying spatial-temporal patterns. The current study extends our current knowledge and suggests that native and nonnative speech processing may follow different developmental trajectories and utilize different mechanisms that are relevant for later language skills.
This paper presents a numerical investigation of the behaviour of dry granular flows generated by the collapse of prismatic columns via 3D Distinct Element Method (DEM) simulations in plane strain ...conditions. Firstly, by means of dimensional analysis, the governing parameters of the problem are identified, and variables are clustered into dimensionless independent and dependent groups.
Secondly, the results of the DEM simulations are illustrated. Different regimes of granular motion were observed depending on the initial column aspect ratio. The profiles observed at different times for columns of various aspect ratios show to be in good agreement with available experimental results.
Thirdly, a detailed analysis of the way energy is dissipated by the granular flows was performed. It emerges that most of the energy of the columns is dissipated by inter-particle friction, with frictional dissipation increasing with the column aspect ratio. Also, the translational and rotational components of the kinetic energy of the flows, associated to particle rotational and translational motions respectively, were monitored during the run-out process. It is found that the rotational component is negligible in comparison with the translational one; hence in order to calculate the destructive power of a granular flow slide, only the translational contribution of the kinetic energy is relevant.
Finally, a methodology is presented to calculate the flux of kinetic energy over time carried by the granular flow through any vertical section of interest. This can be related to the energy released by landslide induced granular flows impacting against engineering structures under the simplifying assumption of neglecting all structure-flow interactions. This represents the first step towards achieving a computational tool quantitatively predicting the destructive power of a given flow at any location of interest along its path. This can be useful for the design of engineering works for natural hazard mitigation. To this end, also the distribution of the linear momentum of the flow over depth was calculated. It emerges that the distribution is initially bilinear, due to the presence of an uppermost layer of particles in an agitated loose state, but after some time becomes linear.
This type of analysis showcases the potential of the Distinct Element Method to investigate the phenomenology of dry granular flows and to gather unique information currently unachievable by experimentation.
•3D DEM simulations of granular step collapse of various aspect ratios were performed.•A detailed analysis of energy components in the granular flows was carried out.•Profiles over depth of the flux of kinetic energy and of momentum were calculated.
lThe critical thermal issues of lithium-ion batteries are introduced.lThe design principles for batteries thermal management are presented.lThe latest advances on battery thermal management systems ...are summarized.lEmerging technologies for next-generation power batteries are discussed.
Replacing conventional gasoline-powered cars with electric vehicles (EVs) can reduce not only pollution emissions but also the dependence on fossil fuels. As the most widely used power source to propel EVs, lithium-ion batteries are highly sensitive to the operating temperatures, rendering battery thermal management indispensable to ensure their high performance, long cycle life and safe operation. In this review, we summarize the recent advances in thermal management for lithium-ion batteries. The critical thermal issues caused by high temperature, low temperature and temperature non-uniformity are firstly discussed. The design principles and the existing thermal management systems are then presented and elaborated extensively. Emerging technologies such as thermoelectric devices and internal heating methods for future battery thermal management are analyzed. We highlight that the combination of passive and active cooling/heating methods is promising to meet the stringent thermal requirements, particularly under dynamic conditions with drastic power fluctuations. Finally, the remaining challenges and perspectives of thermal management systems with high efficiency and durability are provided. This review offers comprehensive guidance on the design of advanced thermal management system for next-generation power batteries.
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