| 1. |
- Li, Bo, et al.
(author)
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Enhancement of phase change materials by nanoparticles to improve battery thermal management for autonomous underwater vehicles
- 2022
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In: International Communications in Heat and Mass Transfer. - : Elsevier BV. - 0735-1933. ; 137
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Journal article (peer-reviewed)abstract
- Battery thermal management (BTM) plays a significant role in the safety and reliability of autonomous underwater vehicles (AUV) at higher speeds. In this study, a nanoparticle/phase change material (nano-PCM) composite is proposed for the BTM of an AUV. The effects of nanoparticle loading percentage (φ = 5, 10, and 15%) and nanoparticle filling range (α = 30, 60, 90, and 120°) on the battery temperature and PCM melting were investigated numerically. Two criteria for the dimensionless temperature control performance (TCP) factor and dimensionless heat storage performance (HSP) factor were used to evaluate the influence of various variables on the BTM performance. The results show that increasing the nanoparticle loading percentage improves the effective thermal conductivity of the PCM but reduces the overall effective latent heat. An optimal nanoparticle filling range of α = 60° is recommended to accelerate the overall melting rate of the PCM. Compared with those of the pure PCM-based BTM, the TCP rate and TCP density are enhanced by 14.56% and 26.75%, respectively, at α = 60°. The HSP rate increases by 2.84% but the HSP density reduces by 11.85% at α = 60°. These findings can provide a reference for the accurate design of nano-PCM composites for the BTM of AUVs.
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| 2. |
- Mehta, Raghav, et al.
(author)
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QU-BraTS : MICCAI BraTS 2020 Challenge on QuantifyingUncertainty in Brain Tumor Segmentation - Analysis of Ranking Scores and Benchmarking Results
- 2022
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In: Journal of Machine Learning for Biomedical Imaging. - 2766-905X. ; , s. 1-54
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Journal article (peer-reviewed)abstract
- Deep learning (DL) models have provided the state-of-the-art performance in a wide variety of medical imaging benchmarking challenges, including the Brain Tumor Segmentation (BraTS) challenges. However, the task of focal pathology multi-compartment segmentation (e.g., tumor and lesion sub-regions) is particularly challenging, and potential errors hinder the translation of DL models into clinical workflows. Quantifying the reliability of DL model predictions in the form of uncertainties, could enable clinical review of the most uncertain regions, thereby building trust and paving the way towards clinical translation. Recently, a number of uncertainty estimation methods have been introduced for DL medical image segmentation tasks. Developing scores to evaluate and compare the performance of uncertainty measures will assist the end-user in making more informed decisions. In this study, we explore and evaluate a score developed during the BraTS 2019-2020 task on uncertainty quantification (QU-BraTS), and designed to assess and rank uncertainty estimates for brain tumor multi-compartment segmentation. This score (1) rewards uncertainty estimates that produce high confidence in correct assertions, and those that assign low confidence levels at incorrect assertions, and (2) penalizes uncertainty measures that lead to a higher percentages of under-confident correct assertions. We further benchmark the segmentation uncertainties generated by 14 independent participating teams of QU-BraTS 2020, all of which also participated in the main BraTS segmentation task. Overall, our findings confirm the importance and complementary value that uncertainty estimates provide to segmentation algorithms, and hence highlight the need for uncertainty quantification in medical image analyses. Our evaluation code is made publicly available at https://github.com/RagMeh11/QU-BraTS
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| 3. |
- Aristote, Nkongolo Tshamala, et al.
(author)
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Methods of improving the initial Coulombic efficiency and rate performance of both anode and cathode materials for sodium-ion batteries
- 2022
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In: Chinese Chemical Letters. - : Elsevier BV. - 1001-8417 .- 1878-5964. ; 33:2, s. 730-742
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Journal article (peer-reviewed)abstract
- Sodium-ion batteries (SIBs) have gained more scientists’ interest, owing to some facts such as the natural abundance of Na, the similarities of physicochemical characteristics between Li and Na. The irreversible Na+ ions consumption during the first cycle of charge/discharge process (due to the formation of the solid electrolyte interface (SEI) on the electrode surface and other irreversible reactions) is the factor that determines high performance SIBs and largely reduces the capacity of the full cell SIBs. Thus, the initial coulombic efficiency (ICE) of SIBs for both anode and cathode materials, is a key parameter for high performance SIBs, and the point is to increase the transport rate of the Na+ ions. Therefore, developing SIBs with high ICE and rate performance becomes vital to boost the commercialization of SIBs. Here we provide a review on the methods to improve the ICE and the rate performance, by summarizing some methods of improving the ICE and rate performance of the anode and cathode materials for SIBs, and end by a conclusion with some perspectives and recommendations.
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| 4. |
- Chen, Baowei, et al.
(author)
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Methylation mechanism of tin(II) by methylcobalamin in aquatic systems
- 2007
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In: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 68:3, s. 414-419
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Journal article (peer-reviewed)abstract
- The methylation reaction of tin(II) with methylcobalamin (CH(3)B(12)) in aquatic systems was modeled in the laboratory. The products were detected by a sensitive gas chromatography-flame photometric detector (GC-FPD), and further identified by gas chromatography-mass spectrometry (GC-MS). Both monomethyltin (MMT) and dimethyltin (DMT) were found as methylation products. Three important effecting factors during the methylation reaction, salinity, pH and aerobic or anaerobic, were studied. The results showed that methyl group can be transferred from CH(3)B(12) to tin in aquatic solutions as a radical or carbonium, as well as a carbanion. Two explanations for the pH-dependency of the methylation reaction between tin(II) and CH(3)B(12) were proposed: pH-dependency of the equilibrium states of CH(3)B(12), and pH-dependency of inorganic tin(II) species whose reactivity vary with the redox potential in the solution. Salinity can influence the activity of the methyl donor, which cause changes in the methylation efficiency. Kinetic experiments showed that the methylation reaction was pseudo-first-order for CH(3)B(12).
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| 5. |
- Chen, Baowei, et al.
(author)
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Methylation of inorganic mercury by methylcobalamin in aquatic systems
- 2007
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In: Applied organometallic chemistry. - : John Wiley & Sons. - 0268-2605 .- 1099-0739. ; 21:6, s. 462-467
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Journal article (peer-reviewed)abstract
- The methylation of inorganic Hg(II) by methylcobalamin in aquatic systems was studied using high-performance liquid chromatography coupled with UV-digestion cold vapor atomic fluorescence spectrometry (HPLC-UV-CV AFS). Monomethylmercury (MMC) could be positively identified as the reaction product in the aqueous solution. The salinity and pH of the aquatic system have great effects on the formation of MMC, because they could change the species of the reactants in the solution. From an electrophile reaction point of view, salinity and pH alter the electron density of the methyl donor and the electrophilicity of metal ion in the reaction system. This methylation of inorganic Hg(II) is shown to be possible even in highly saline solutions, which indicates its importance in aquatic environments. Kinetic experiments showed that the methylation reaction was fast and first-order for Hg(II). The first-order reaction rate was determined to be 0.00612 and 0.000287 min-1 for pH 5.0 and 1.5, respectively. It is suggested that this methylation could occur in the absence of enzymes, in which Hg(II) acts as an electrophile to attack methylcobalamin with a subsequent transfer of carbanion methyl group to the higher oxidized state of Hg(II).
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| 6. |
- Chen, Baowei, et al.
(author)
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Simulate methylation reaction of arsenic(III) with methyl iodide in an aquatic system
- 2006
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In: Applied organometallic chemistry. - : John Wiley & Sons. - 0268-2605 .- 1099-0739. ; 20:11, s. 747-753
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Journal article (peer-reviewed)abstract
- The methylation reaction of inorganic arsenic occurring in aquatic systems was studied by HPLC-HGAFS as a method to separate and detect soluble methylarsenic species. Transformation from inorganic arsenic to methylarsenic was essential for major changes in toxicity to organisms. Monomethylarsenic [AsOCH(3)(OH)(2)] was the only product in the methylation reaction of inorganic arsenic(III) with methyl iodide (MeI). This process can be described as an oxidative carbonium-ion transfer, with MeI acting as a methyl donor. From a thermodynamic point of view, the activity of the carbonium ion and pH were the two major influencing factors. The pH dependence of redox potential of As(III) was the reason for the effect of pH on methylation of arsenic. The influences of salinity and concentration of the methyl donor may be explained by their effects on the activity of carbonium. Moreover, kinetics experiments demonstrated that the methylation reaction was first-order for both As(III) and methyl iodide. First-order reaction rates were also calculated at different pH, salinity and MeI, and were found to be in the range 0.0026-0.0123 h(-1). The methylation rate varied largely under different reaction conditions.
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| 7. |
- Li, Bing, et al.
(author)
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Diophantine approximation of the orbit of 1 in the dynamical system of beta expansions
- 2014
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In: Mathematische Zeitschrift. - : Springer Science and Business Media LLC. - 0025-5874 .- 1432-1823. ; 276:3-4, s. 799-827
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Journal article (peer-reviewed)abstract
- We consider the distribution of the orbits of the number 1 under the -transformations as varies. Mainly, the size of the set of for which a given point can be well approximated by the orbit of 1 is measured by its Hausdorff dimension. The dimension of the following set is determined, where is a given point in and is a sequence of integers tending to infinity as . For the proof of this result, the notion of the recurrence time of a word in symbolic space is introduced to characterise the lengths and the distribution of cylinders (the set of with a common prefix in the expansion of 1) in the parameter space .
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| 8. |
- Li, Bo, et al.
(author)
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Thermal management performance improvement of phase change material for autonomous underwater vehicles' battery module by optimizing fin design based on quantitative evaluation method
- 2022
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In: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 46:11, s. 15756-15772
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Journal article (peer-reviewed)abstract
- Efficient thermal management of lithium battery modules has become a thorny problem in the development of autonomous underwater vehicles (AUVs), especially under high current discharge. In this article, the fin/phase change material (PCM) composite structure was proposed for AUV's battery thermal management with consideration of natural convection. The temperature behavior of the battery and the melting behavior of PCM were investigated under different key parameters. In addition, the heat transfer mechanism of the melting process of the PCM was revealed. More importantly, the dimensionless temperature control performance (TCP) factor and the dimensionless heat storage performance (HSP) factor were introduced as new criteria to quantitatively evaluate the impact of different design parameters on the battery thermal management performance. The results showed that utilizing fins can significantly accelerate the melting of the PCM. Increasing the number of fins can reduce the temperature of the battery and improve the uniformity of the battery temperature distribution. Compared with the pure PCM, the total time required for PCM melting in the fin/PCM battery thermal management unit with different numbers of fins is reduced by at least 11.5%. The decrease of the time of complete PCM melting is not linearly correlated with the length ratio of fins. The fin number of N = 6, length ratio of R = 0.8, and angle between fins of φ = 36° were identified as the optimal parameters of fin/PCM composite structures. The TCP and HSP were enhanced by 38.1% and 4.54%, respectively. The conclusions of this work can provide reference for the accurate design of fin/PCM composite structures for the thermal management of AUV batteries. Highlights: The fin/phase change material composite structure was introduced for autonomous underwater vehicles' battery thermal management. The temperature and melting behavior were investigated with natural convection. The temperature control performance factor and heat storage performance factor were proposed as new evaluation criteria. Temperature deviation index was used to measure the battery temperature uniformity. The performance was enhanced by optimizing the design parameters of fin.
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| 9. |
- Wang, Yan Feng, et al.
(author)
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Experimental study on immersion phase change cooling of lithium-ion batteries based on R1233ZD(E)/ethanol mixed refrigerant
- 2023
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In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 220
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Journal article (peer-reviewed)abstract
- To improve heat dissipation and temperature uniformity for the lithium-ion battery module of electric vehicle, the immersion phase change cooling characteristics of R1233ZD(E)/Ethanol mixed refrigerant were studied experimentally in a staggered battery module, which is composed of 50 batteries. At 101.3 kPa saturated vapor pressure, coupled wall boiling and forced convection heat transfer was analyzed under different discharge rates (1 C, 2 C, and 3 C), filling volume fractions of R1233ZD(E) (0.463, 0.540, 0.630, 0.735, and 0.857), and inlet volume flow rates (652.0, 1086.0, 1521.0, and 2172.0 mL min- 1). Meanwhile, the outlet vapor quality of the two-phase flow was calculated according to energy conservation. The results show that the heat generation of the battery was dominated by the operating current. With the decrease of the output power of the battery, the heat generation first increases rapidly, then increases gently, and finally decreases sharply. When low boiling point R1233ZD(E) was mixed into ethanol, wall boiling heat transfer was effectively enhanced, and the temperature uniformity of the battery module could be improved by up to 57.0\%. However, the outlet vapor quality of the two-phase flow showed that when the volume fraction of R1233ZD(E) exceeded 0.803, wall boiling departed from the nucleate boiling regime as well as heat transfer and temperature quantities changed accordingly. Forced convection heat transfer of liquid-phase played a leading role in reducing the temperature rise of the battery module, and its contribution increased with the increase of refrigerant inlet flow rate. When the inlet flow rate increased from 652.0 mL min- 1 to 1086.0 mL min- 1, the module temperature rise decreased by 14.8%. Nevertheless, forced convection of liquid-phase weakened battery wall boiling, which adversely affected the temperature uniformity of the battery module.
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| 10. |
- Yin, Yongguang, et al.
(author)
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Possible alkylation of inorganic Hg(II) by photochemical processes in the environment
- 2012
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 88:1, s. 8-16
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Journal article (peer-reviewed)abstract
- The methylation of inorganic Hg by anaerobic bacteria in aquatic environments is considered to be the major pathway for methylmercury (MeHg) production. However, recent research has suggested that abiotic or chemical methylation by humic substances and other low-molecular-weight organic compounds in natural environments is also possible. Here, the aqueous photo-transformation of Hg(2+) to organomercurials was investigated in the presence of ketones, aldehydes and low molecular weight organic acids under UV irradiation. MeHg and/or ethylmercury (EtHg) were identified as the main organomercurial products by multiple analytical techniques, including chromatography-atomic spectrometry and molecular mass spectrometry and further confirmed by stable isotope tracer experiments. The yield of organomercurials was markedly influenced by pH, NaCl concentration, alkylation donor concentration and the presence of chelating ligands in the aqueous solution. Electron paramagnetic resonance spectrometry demonstrated that the radical reaction was not the predominating alkylation pathway, although methyl radicals were detected in the photo-alkylation procedure. A mechanism based on intra-molecular alkyl transfer in the Hg(2+)-low-molecular-weight organic compound complex is proposed. The present work helps us better understand of MeHg and EtHg photo-generation in natural environments.
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