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Статті в журналах з теми "Charge transfers and SEI"
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Qi, Yue. "(Invited) Modeling the Charge Transfer Reactions at Li/SEI/Electrolyte Interfaces in Lithium-Ion Batteries." ECS Meeting Abstracts MA2023-01, no. 45 (August 28, 2023): 2452. http://dx.doi.org/10.1149/ma2023-01452452mtgabs.
Повний текст джерелаАнотація:
Two kinds of charge transfer reactions are critical for the performance and life of lithium battery: the desired ion transfer reaction occurring during each charge/discharge cycle, , and the undesired electron transfer reactions leading to the parasitic chemical decomposition of the electrolyte and solid electrolyte interphase (SEI) formation/growth. The heterogeneous multi-component nature of SEI dominates its ionic and electronic transport properties and controls these two charge transfer reactions. Density Functional Theory (DFT)-informed multiscale modeling has been providing valuable insights under the scarcity of quantitative experiments. For example, the LiF/Li2CO3 interface was demonstrated to increase the ionic conductivity of mixed SEI nanocomposite by forming an ionic space charge region near the interface and promoting more Li-ion interstitials in Li2CO3, although LiF itself has low Li-ion conducting carriers and conductivity. To form a LiF-rich SEI layer, the electrolyte compositions need to be designed. Since the SEI formation occurs on the charged surface, the electric double layer (EDL) structure near the charged surfaces needs to be incorporated into the modeling. Here interactive classical molecular dynamics (MD), DFT, and data statistical analysis were combined to illustrate the effect of EDL on SEI formation in two essential electrolytes, the carbonate-based electrolyte for Li-ion batteries and the ether-based electrolyte for batteries with Li-metal anodes. It was found the effectiveness of adding fluoroethylene carbonate (FEC) to form the beneficial F-containing SEI component (e.g., LiF) varies with the electrolyte and temperature, because of the interplay of ion-solvent interactions with the surface charge. These integrated modeling provided quantitative guidance for electrolyte/SEI/Li-metal interface design.
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Morasch, Robert, Hubert A. Gasteiger, and Bharatkumar Suthar. "Li-Ion Battery Material Impedance Analysis II: Graphite and Solid Electrolyte Interphase Kinetics." Journal of The Electrochemical Society 171, no. 5 (May 1, 2024): 050548. http://dx.doi.org/10.1149/1945-7111/ad48c0.
Повний текст джерелаАнотація:
Li-ion battery graphite electrodes form a solid-electrolyte-interphase (SEI) which is vital in protecting the stability and efficiency of the cell. The SEI properties have been studied extensively in the context of formation and additives, however studying its kinetic features after formation have been neglected. In this study we show the dynamic resistive behavior of the SEI after formation. Via electrochemical impedance spectroscopy measurements on Cu-foil after SEI formation we show how the SEI shows a potential-dependent resistance which can be explained by a change in charge carriers (Li+) in the SEI. Additional measurements on graphite exhibit a similar behavior and allow us to separate the charge transfer kinetics from the SEI resistance, showing that the SEI resistance is the dominating resistance in the graphite kinetics. Measurements on pre-formed electrodes also show how the SEI resistance changes when in contact with electrolyte of different LiPF6 salt concentrations, with the resistance decreasing for increasing salt concentrations. Ultimately, we show that the SEI resistance affects Li-plating by acting as an offset to the plating reaction but does not affect the nucleation overpotential itself.
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Lee, Sangyup, and Soon-Ki Jeong. "Investigation of the electrochemical properties of a propylene carbonate-derived SEI in an ethylene carbonate-based solution." BIO Web of Conferences 62 (2023): 04002. http://dx.doi.org/10.1051/bioconf/20236204002.
Повний текст джерелаАнотація:
Herein, we aim to explore and analyze the influence of electrolytes on the creation of a solid electrolyte interface (SEI) within ethylene carbonate (EC) and propylene carbonate (PC)-based electrolyte solutions. Our investigation reveals that despite variations in the charge consumption during SEI formation, a comparable SEI is generated in a high-concentration PC-based electrolyte as observed in an EC-based electrolyte. However, it is noteworthy that the SEI originating from the PC-based electrolyte exhibits a significantly higher resistance to lithium ion transport when compared to the SEI formed from the EC-based electrolyte. Moreover, an increase in the charge transfer resistance at the graphite/electrolyte interface is observed in the PC-based electrolyte. These significant findings strongly imply that the choice of electrolyte solvent is a critical factor that must be taken into consideration in order to achieve the formation of an effective SEI.
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Jeong, Soon Ki. "Effects of Lithium Salt on Interfacial Reactions between SiC and EC-Based Solutions in Lithium Secondary Batteries." Applied Mechanics and Materials 873 (November 2017): 112–16. http://dx.doi.org/10.4028/www.scientific.net/amm.873.112.
Повний текст джерелаАнотація:
Electrochemical reactions occurring at a SiC electrode were investigated to gain insight into the effects of lithium salts, such as LiPF6, LiClO4, LiCF3SO3, and LiBF4, on the interfacial resistance. Lithium salts were found to exert little effect on the magnitude of the resistance of the solid-electrolyte interphase (SEI). In contrast, the charge-transfer reactions observed in the LiCF3SO3-containing solution exhibited the smallest resistance. Charge-discharge analysis revealed that the nature of the SEI was significantly different from that formed in ethylene carbonate-based solutions containing different lithium salts. The SiC electrode exhibited large discharge capacity and low coulombic efficiency in the LiCF3SO3-containing solution. This might be closely related to the smallest charge-transfer resistance.
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Tsujimoto, Shota, Changhee Lee, Yuto Miyahara, Kohei Miyazaki, and Takeshi Abe. "Effect of Electrolyte on Sodium-Ion Storage Behavior into Non-Graphitizable Carbon Negative Electrode." ECS Meeting Abstracts MA2023-02, no. 4 (December 22, 2023): 806. http://dx.doi.org/10.1149/ma2023-024806mtgabs.
Повний текст джерелаАнотація:
Introduction Sodium-ion batteries (SIBs) are expected to be an alternative power source to lithium-ion batteries (LIBs) because their abundant resources reduce the cost of SIBs. As the negative electrode of SIBs, non-graphitizable carbon recieves a lot of attention because it can store ions not only in the graphene interlayer but also in its internal pores.[1] By controlling the pores, it is possible to achieve larger reversible capacity of more than 400 mAh g−1.[2] While many researchers have studied non-graphitizable carbon from the viewpoint of thermodynamics, there are a few reports that pay attention to kinetic viewpoint. The kinetic viewpoint is a very important factor because it affects the rate performance of the battery. We have focused on the interfacial reactions of non-graphitizable carbon electrodes and found that the charge-transfer resistance and the activation energy of the charge-transfer reaction in SIBs were larger than those in LIBs.[3] This result and the Lewis acidity indicated that the desolvation process was not identified as the rate determining step in the charge-transfer reaction. One of the significant factors responsible for the increased resistance is the effect of the solid electrolyte interphase (SEI). Objective In this work, we used six types of electrolytes and formed SEI on the surface of non-graphitizable carbon. The interfacial reaction of non-graphitizable carbon with SEI derived from these electrolytes was investigated. In this paper, we report about the effects of SEI on the interfacial reaction between electrolyte and non-graphitizable carbon electrode. Experimental Non-graphitizable carbon heat-treated at 2273 K (HC-2000) was used as the negative electrode material. A three-electrode cell was used for electrochemical measurements. HC-2000 composite electrode, natural graphite composite electrode, and sodium metal were used as the working electrode, counter electrode, and reference electrode, respectively. The electrolytes were prepared using sodium bis(trifluoromethanesulfonyl) amide (NaTFSA), sodium bis(fluorosulfonyl) amide (NaFSA), and NaPF6 as sodium salts and ethylene carbonate (EC) + diethyl carbonate (DEC) (1:1 by volume) and fluoroethylene carbonate (FEC) as solvents. Cyclic voltammetry (CV) was performed to form SEI on HC-2000. The scan rate and range were 0.1 mV s−1 and 0–2.5 V, respectively. After CV, electrochemical impedance spectroscopy (EIS) was performed with an electrode potential of 0.2 V and an AC amplitude of 10 mV in the frequency range of 100 kHz–10 mHz. In addition, X-ray photoelectron spectroscopy (XPS) was used to analyze the electrode after CV measurements with respect to SEI. Results and discussion Figure 1 shows the Nyquist plots obtained from the EIS analyses. The semicircles in the low frequency region were attributed to the charge-transfer resistances. Among EC+DEC solvents, the system of NaFSA had the largest charge-transfer resistance. For NaTFSA and NaPF6, the charge-transfer resistances increased in the FEC solvent, while no significant differences in the charge-transfer resistance were observed for the NaFSA system in the EC+DEC and FEC solvents. The SEI components of the HC-2000 composite electrode in each electrolyte were determined by XPS analysis after CV measurements. In NaFSA/EC+DEC system, the amount of NaF was remarkably large, while the amount of NaF was relatively small in NaTFSA/EC+DEC and NaPF6/EC+DEC systems. On the other hand, in FEC solvents, the amount of NaF increased in NaTFSA and NaPF6 systems. The systems with higher NaF contents had the larger charge-transfer resistances. This result indicates that NaF was involved in the charge-transfer resistance. Finally, EIS analyses were performed at different temperatures. The activation energies were calculated using Arrhenius plots and the Arrhenius equation. The values of the activation energies were in the range of 60–70 kJ mol−1. There was a slight variation in the values, but they were within the error range and were not significantly different for all systems. These results showed that NaF affects the frequency factor rather than the activation energy. Conclusion The effects of SEI on the interfacial reaction between electrolyte and non-graphitizable carbon were investigated. The systems with the large charge-transfer resistance had a large amount of NaF. NaF did not affect the activation energy of charge-transfer resistance but did affect the frequency factor. References [1] D. A. Stevens and J. R. Dahn, J. Electrochem. Soc., 147(4), 1271-1273 (2000). [2] A. Kamiyama, K. Kubota, D. Igarashi, Y. Youn, Y. Tateyama, H. Ando, K. Gotoh, and S. Komaba, Angew. Chem. Int. Ed., 60, 5114-5120 (2021). [3] S. Tsujimoto, Y. Kondo, Y. Yokoyama, Y. Miyahara, K. Miyazaki, and T. Abe, J. Electrochem. Soc., 168, 070508 (2021). Figure 1
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Zhou, Xuan, Ping Li, Zhihao Tang, Jialu Liu, Shaowei Zhang, Yingke Zhou, and Xiaohui Tian. "FEC Additive for Improved SEI Film and Electrochemical Performance of the Lithium Primary Battery." Energies 14, no. 22 (November 9, 2021): 7467. http://dx.doi.org/10.3390/en14227467.
Повний текст джерелаАнотація:
The solid electrolyte interphase (SEI) film plays a significant role in the capacity and storage performance of lithium primary batteries. The electrolyte additives are essential in controlling the morphology, composition and structure of the SEI film. Herein, fluoroethylene carbonate (FEC) is chosen as the additive, its effects on the lithium primary battery performance are investigated, and the relevant formation mechanism of SEI film is analyzed. By comparing the electrochemical performance of the Li/AlF3 primary batteries and the microstructure of the Li anode surface under different conditions, the evolution model of the SEI film is established. The FEC additive can decrease the electrolyte decomposition and protect the lithium metal anode effectively. When an optimal 5% FEC is added, the discharge specific capacity of the Li/AlF3 primary battery is 212.8 mAh g−1, and the discharge specific capacities are respectively 205.7 and 122.3 mAh g−1 after storage for 7 days at room temperature and 55 °C. Compared to primary electrolytes, the charge transfer resistance of the Li/AlF3 batteries with FEC additive decreases, indicating that FEC is a promising electrolyte additive to effectively improve the SEI film, increase discharge-specific capacities and promote charge transfer of the lithium primary batteries.
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Li, Galina, Aleksander Rumyantsev, Ekaterina Astrova, and Maxim Maximov. "Growth of the Cycle Life and Rate Capability of LIB Silicon Anodes Based on Macroporous Membranes." Membranes 12, no. 11 (October 25, 2022): 1037. http://dx.doi.org/10.3390/membranes12111037.
Повний текст джерелаАнотація:
This work investigated the possibility of increasing the cycle life and rate capability of silicon anodes, made of macroporous membranes, by adding fluoroethylene carbonate (FEC) to the complex commercial electrolyte. It was found that FEC leads to a decrease in the degradation rate; for a sample without FEC addition, the discharge capacity at the level of Qdch = 1000 mAh/g remained unchanged for 220 cycles and the same sample with 3% FEC added to the electrolyte remained unchanged for over 600 cycles. FEC also improves the power characteristics of the anodes by 5–18%. Studies of impedance hodographs showed that in both electrolytes (with 0% and 3% FEC, respectively) the charge transfer resistance grows with an increasing number of cycles, while Solid Electrolyte Interphase (SEI) parameters, such as its resistance and capacitance, show little change. However, the addition of FEC more than halves the overall system impedance and reduces the resistance of the liquid electrolyte and all current carrying parts as well as the SEI film and charge transfer resistances.
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Housel, Lisa M., Alyson Abraham, Genesis D. Renderos, Kenneth J. Takeuchi, Esther S. Takeuchi, and Amy C. Marschilok. "Surface Electrolyte Interphase Control on Magnetite, Fe3O4, Electrodes: Impact on Electrochemistry." MRS Advances 3, no. 11 (2018): 581–86. http://dx.doi.org/10.1557/adv.2018.294.
Повний текст джерелаАнотація:
ABSTRACTIn battery systems, a solid electrolyte interphase (SEI) is formed through electrolyte reaction on an electrode surface. The formation of SEI can have both positive and negative effects on electrochemistry. The initial formation of the layer protects the electrode from further reactivity, which can improve both shelf and cycle life. However, if the layer continues to form, it can impede charge transfer, which increases cell resistance and limits cycle life. The role of SEI is particularly important when studying conversion electrodes, since phase transformations which unveil new electroactive surfaces during reduction/oxidation can facilitate electrolyte decomposition. This manuscript highlights recent developments in the understanding and control of SEI formation for magnetite (Fe3O4) conversion electrodes through electrolyte and electrode modification.
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Zhuang, Qinqin, Weihuang Yang, Wei Lin, Linxi Dong, and Changjie Zhou. "Gas Sensing of Monolayer GeSe: A First-Principles Study." Nano 14, no. 10 (October 2019): 1950131. http://dx.doi.org/10.1142/s1793292019501315.
Повний текст джерелаАнотація:
The adsorption of various gas molecules (H2, H2O, CO, NH3, NO and NO[Formula: see text] on monolayer GeSe were investigated by first-principles calculations. The most stable configurations, the adsorption energies, and the amounts of charge transfer were determined. Owing to the appropriate adsorption energies and the non-negligible charge transfers, monolayer GeSe could be a promising candidate as a sensor for NH3, CO, NO and NO2. According to the band structures of the H2O, CO, NH3, NO and NO2 adsorbed systems, the reductions of the bandgaps are caused by the orbital hybridizations between the gas molecules and the underlying GeSe. The partial densities of states reveal the degrees of these orbital hybridizations. The mechanisms of charge transfer are discussed in the light of both traditional and orbital mixing charge transfer theories. The charge transfer of the paramagnetic molecules NO and NO2 could be governed by both charge transfer mechanisms, while for the other gas molecules H2, H2O, CO and NH3, it was most likely determined by the mixing of the HOMO or LUMO with the GeSe orbitals.
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Potapenko, Anna V., Oleksandr V. Potapenko, Oleksandr V. Krushevskyi, and Miaomiao Zhou. "EIS Analysis of Sulfur Cathodes with Water-Soluble Binder NV-1A for Lithium-Sulfur Batteries." ECS Transactions 105, no. 1 (November 30, 2021): 225–29. http://dx.doi.org/10.1149/10501.0225ecst.
Повний текст джерелаАнотація:
The paper discusses the electrochemical behavior of a Li-S battery with a new water-soluble binder NV-1A. It is shown that the main contribution is made by the interface, which is formed on the lithium counter electrode. It is noteworthy that the nonlinear growth of the resistance of SEI layer during the discharge process correlates with the change in the resistance of charge transfer through the interface.
Дисертації з теми "Charge transfers and SEI"
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Rabab, Houssam. "Modeling of sodium-ion batteries for on-board diagnosis of their states of charge and health." Electronic Thesis or Diss., Compiègne, 2024. http://www.theses.fr/2024COMP2809.
Повний текст джерелаАнотація:
La thèse présente un modèle basé sur la physique pour les cellules sodium-ion de type NVPF/HC. Le modèle tient compte des complexités de la modélisation de ces cellules, notamment à cause de leurs non-linéarités liées au courant, à la température et à l'état de charge (State of charge : SoC). La structure du modèle est un circuit équivalent amélioré par des concepts utilisés dans les modèles à particules uniques (Single particle model : SPM) pour former une structure ECM-SPe, adaptée aux diagnostics de SoC et d'état de santé (State of health : SoH). La structure ECM-SPe sépare les effets de la diffusion en phase solide et en phase liquide. Il est montré que la modélisation classique des effets de diffusion en phase solide par une impédance entraîne de nombreuses difficultés. En remplacement, une approche novatrice est proposée en utilisant des décalages en SoC de la tension en circuit ouvert (Open circuit voltage : OCV). Ces décalages sont en lien direct avec les phénomènes électrochimiques, ce qui permet la mise en place de modèles de non-linéarités physiques. La structure ECM-SPe caractérise divers phénomènes électrochimiques sous forme de contributions de tension : surtension ohmique ou statique (Vs), surtension de surface (Vsurf) qui comprend les surtensions des transferts de charge et de l'interphase solide-électrolyte (Solid-electrolyte interphase : SEI), surtension de diffusion en phase liquide (Vld) et la tension d'équilibre de surface (Surface equilibrium voltage : SEV). Des modèles analytiques pour les non-linéarités en courant, en température et en SoC sont proposés pour chaque contribution de tension. Ces modèles des non-linéarités sont basés sur des équations théoriques et empiriques pour caractériser les paramètres du modèle sans recours à des tables d'interpolation. Le modèle NVPF/HC est l'ensemble de la structure ECM-SPe avec les modèles des non-linéarités des contributions en tension. La thèse détaille les protocoles expérimentaux pour la détermination des paramètres, ce qui comprend des tests à courant constant, des créneaux de courant, et des spectroscopies d'impédance, réalisés sous divers courants, températures et SoC. La performance du modèle est validée par des comparaisons avec des données expérimentales, démontrant des résultats prometteurs. En plus, le modèle NVPF/HC peut servir comme un outil de diagnostic des transferts de charge et de la SEI en séparant leurs non-linéarités en courant, température et en SoC. Le modèle montre sa fiabilité pour estimer la tension de la cellule dans des applications à courant variable, avec de bonnes performances à des courants allant jusqu'à ±5C et des températures au-dessus de 5 °C. L'étude souligne également la nécessité de développer des tests de caractérisation distincts pour les contributions de diffusion solide et liquideThe thesis presents a physics-based model for sodium-ion cells of the NVPF/HC type. The model takes into account the complexities involved in modeling these cells, notably due to their nonlinearities in current, temperature and state of charge (SoC). The model structure is an equivalent circuit enhanced by concepts used in single particle models (SPM) to form an ECM-SPe structure, suitable for diagnosis of the SoC and the state nof health (SoH) of the cell. The ECM-SPe structure separates the effects of solid-phase and liquid-phase diffusion. It is shown that classical modeling of solid-phase diffusion effects by impedance leads to numerous difficulties. As a replacement, an innovative approach is proposed using shifts in SoC of the open circuit voltage (OCV). These shifts are directly related to electrochemical phenomena, enabling the implementation of physical nonlinearity models. The ECM-SPe structure characterizes various electrochemical phenomena as voltage contributions: ohmic or static overvoltage (Vs), surface overvoltage (Vsurf) which includes charge transfers and the solid electrolyte interphase (SEI) overvoltages, liquid phase diffusion overvoltage (Vld) and the surface equilibrium voltage (SEV). Analytical models for current, temperature and SoC nonlinearities are proposed for each voltage contribution. These nonlinearity models are based on physical and empirical equations to characterize the model parameters without the use of lookup tables. The NVPF/HC model consists of the ECM-SPe structure with the nonlinearity models for the voltage contributions. The PhD details experimental protocols for parameter determination, which include constant current tests, pulse tests, and impedance spectroscopies, performed under various currents, temperatures and SoC. The performance of the model is validated by comparisons with experimental data, demonstrating promising results. In addition, the NVPF/HC model can be used as a diagnostic tool for charge transfers and SEI by separating their nonlinearities in current, temperature and SoC. The NVPF/HC model shows its reliability for estimating the cell voltage in variablecurrent applications, with good performance at currents up to ±5C and temperatures above 5 ◦C. The study also highlights the need to develop distinct characterization tests for solid and liquid diffusion contributions
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Beltran, Carl Antony. "Charge transfers across liquid/liquid interfaces." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333568.
Повний текст джерела
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Sun, Xiao-Jing. "The extent and importance of single electron transfers in organic reactions." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/27981.
Повний текст джерела
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Fortgang, Philippe. "La communication électronique au sein de nano-objets adsorbés." Paris 7, 2010. http://www.theses.fr/2010PA077199.
Повний текст джерелаАнотація:
Le travail présenté porte sur l'utilisation de l’électrochimie ultra-rapide pour caractériser le transfert d'électron dans divers nanoobjets adsorbés sur des électrodes d'or. Un premier chapitre présente et compare les moyens expérimentaux utilisés pour évaluer les performances des systèmes moléculaires. Dans un deuxième chapitre, nous décrivons une technique photolithographique que nous avons mise au point. Celle-ci permet d'effectuer des mesures fiables et reproductibles et représente une amélioration très nette par rapport aux études antérieures. Le troisième chapitre est consacré aux systèmes comportant plusieurs centres redox. La première molécule étudiée est une dyade porphyrine-C6o possédant des performances photovoltaiques importantes. La mesure des constantes de transfert d'électron nous permet d'anticiper une baisse d'efficacité du système adsorbé par rapport au même système en solution, et de donner quelques pistes pour améliorer. Ses performances. La deuxième molécule est un dendrimère comportant dix centres redox ferrocènes. Dans le quatrième, nous avons également voulu tester l'équivalence supposée entre des grandeurs obtenues d'une part via des mesures de jonctions cassées stationnaires formées par STM et celles obtenues par notre méthode transitoire. Cette approche originale démontre un accord qualitatif mais soulève également de nombreuses questions quant à la géométrie réelle de la jonction et au mécanisme de transport d'électrons, le nous avons pu visualiser le rappel effectué par la chaîne dendritique sur les centres redox. Le cinquième et dernier chapitre met en relief l'interdépendance entre mouvements moléculaires et réponse électrochimique pour un composé tetrathiofulvalene vinylogueThe presented work concerns the use of ultra-fast electrochemical technique to characterize the electron transfer in several adsorbed nano-objects on gold electrodes. The first chapter presents and compares the experimental procedures used to estimate the performance of these molecular Systems. In the second chapter, we describe a photolithographic technique which we have used in our System. This technique allows making reliable as well as reproducible measurements and represents a very clear improvement compared to previous studies, The third chapter is dedicated to Systems containing several redox centers. The first studied molecule is a dyade porphyrine-Cso possessing important photovoltaic properties. The measurement of the rate constant of the electron-transfer allows us to anticipate a decline of efficiency of the adsorbed system compared to the same System in solution, and to give some dues in order to improve its performances. The second molecule is a dendrimer containing ten ferrocene redox centers. Here, we were able to visualize the return made by the dendritic chain on the redox centers. In the fourth chapter, we also wanted to verify the assumed equivalence between the values obtained, on one hand, via the mechanical controlled broken junction (STM) technique, and on the other hand, with our passing method This original approach demonstrates in good agreement with theoretical studies but also raises of numerous questions concerning the real geometry of the junction and also the mechanism for the transport of electrons. The fifth and last chapter explores the interdependence between molecular movements and electrochemical answer for a vinylogous tetrathiofulvalene compound
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Raghibi, Mohamed. "Etude des processus limitant la puissance au sein des batteries Li-ion." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI011.
Повний текст джерелаАнотація:
De nos jours, grâce à de nombreux avantages, notamment une haute densité d’énergie, une longue durée de vie, et un rendement élevé, les batteries Li-ion sont prédominantes pour alimenter les appareils électroniques comme les téléphones et ordinateurs portables. De plus, leur utilisation s’est élargie à grande échelle comme système de stockage d’énergie pour les véhicules électrifiés et les applications stationnaires. Néanmoins, pour répondre aux exigences du marché du transport électrique et étendre la pénétration des batteries au Li dans ce secteur, des améliorations sont nécessaires, notamment en termes de densité d’énergie, de sécurité, et de durée de vie. En plus du développement de matériaux actifs, plusieurs approches sont proposées et étudiées en vue d’augmenter l’autonomie des batteries. Parmi elles, une consiste à optimiser le design de l'électrode composite à savoir la porosité, le grammage, la composition et la microstructure. Cela revient à augmenter le ratio des matériaux actifs (épaisseur d’électrode positive et négative) par rapport aux autres composants inactifs à savoir les collecteurs de courant et le séparateur. Cependant, pour les électrodes fortement grammées la capacité de décharge devient limitée par le transport de charges au sein de l’électrode, notamment à fort courant, ce qui implique une forte diminution de la densité de puissance.Ce projet de thèse a pour but d’étudier la capacité restituée dans les batteries au Li en fonction du design de l’électrode, à savoir la formulation (microstructure), la composition chimique (nature des matériaux actifs), le grammage et la porosité, mais aussi la température de travail. Pour cela, deux matériaux d’électrode positive seront étudiés à savoir LiFePO4 (LFP) et LiNi0.8Mn0.1Co0.1O2 (NMC 811), des électrodes à différents grammages (0.4 et 3.4 mAh.cm-2), et compositions, sont formulées et calandrées pour atteindre des porosités variées (20 à 50 %). La morphologie et la surface spécifique des matériaux actifs et des électrodes est investiguée via des analyses MEB, Granulométrique et BET. Ensuite, les performances en puissance de la batterie, capacité vs densité de courant, sont établies en utilisant un protocole de cyclage spécifique, permettant la détermination d’une densité de courant limite (Jlim) qui est relié au coefficient de diffusion effectif (Deff) correspondant au processus de transport limitant. En plus, la résistance de transfère de charge (Rct) en fonction de la stœchiométrie est aussi rapportée en couplant le GITT et l’EIS afin de capturer les processus physico-chimiques mis en jeu lors du fonctionnement de la batterie. Enfin, la corrélation entre le design de l’électrode, la température et les paramètres électrochimiques effectifs tel que le Deff, Jlim, and Rct seront discutésLi-ion batteries have become a necessity in human daily life as the most versatile, efficient and performing energy storage & conversion technology, they power our nomad electronic, cars and buffer the renewable intermittent energy sources. However, improvement of current battery systems is needed to meet the requirements of the transport sector in terms of energy density, safety, and cycle life. Besides the active materials, among the strategies to increase battery autonomy, one consists in optimizing the design parameters of the electrode such as the formulation, loading, microstructure, and porosity. The idea is simply to increase the ratio of active materials (negative and positive electrode thickness) to inactive components (separator, current collector…). However, by doing so, the output power density becomes strongly limited by the charge transport within the composite electrodes, notably at high current densities.In this PhD work, Li-battery capacity is investigated as a function of the current density with respect to electrode design parameters such as porosity, formulation, loading, and microstructure as well as temperature. For this purpose, LiFePO4 (LFP) and LiNi0.8Mn0.1Co0.1O2 (NMC 811) based positive electrodes were formulated at different loadings (from 0.4 to 3.4 mAh.cm-2), compositions (Active material%, Carbon%, PVDF binder %), and calendered to reach different porosities (from 20 to 50 %). The microstructure and specific area of the active materials and the electrodes are fully characterized by SEM, Granulometry and BET. Then, the battery power performance, capacity as a function of discharge current, is fully captured and analyzed using a time-saving methodology which enables the determination of a limiting current density (Jlim) and the extraction of an effective diffusion coefficient (Deff) corresponding to the limiting transport process. In addition, the charge transfer resistance (Rct) as a function of the state of charge (SOC) is also reported by coupling GITT and EIS allowing to capture of the physico-chemical processes at stake during the battery cycling. Afterwards, the correlation between design parameters, the temperature and the effective electrochemical parameters such as Deff, Jlim, and Rct is discussed
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Hoshikawa, Toyohisa. "Evaluation of charge transfers and photoelectrochemical properties of dye-sensitized solar cells by impedance spectroscopy." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144022.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第12336号
工博第2665号
新制||工||1376(附属図書館)
24172
UT51-2006-J328
京都大学大学院工学研究科物質エネルギー化学専攻
(主査)教授 江口 浩一, 教授 垣内 隆, 助教授 井上 正志
学位規則第4条第1項該当
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Delacôte, Cyril Walcarius Alain. "Etudes électroanalytiques de processus de transfert de matière et de charge au sein de silices." [S.l.] : [s.n.], 2005. http://www.scd.uhp-nancy.fr/docnum/SCD_T_2005_0147_DELACOTE.pdf.
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Jaoui, Alexandre. "Charge and Entropy Transport in Dilute metals." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS151.
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Cette thèse traite la dichotomie entre transport électronique de charge et de chaleur ainsi que les propriétés de transport au-delà de la limite quantique dans les métaux dilués. D’abord, nous étudions deux semi-métaux, WP2 et Sb. La loi de Wiedemann-Franz (WF) y est satisfaite à basse température (T≈2K) mais violée à T≈15K. Cette déviation à température finie à la loi de WF résulte de la différence entre les préfacteurs des T2-résistivités. Dans un cadre boltzmannien, cette différence est associée à une abondance de collisions électroniques à petit angle. Cependant, l’exemple de l’3He liquide montre que des collisions fermioniques qui conservent le moment total conduisent à une T2-résistivité thermique. Une interprétation différente est alors possible dans WP2 et Sb : la possible existence d’un régime hydrodynamique des électrons. Pour Sb, le ratio entre les T2-préfacteurs des résistivités thermique et électrique évolue avec la taille du système. Cette découverte appuie le scénario hydrodynamique. Enfin, nous montrons l’existence de corrections hydrodynamiques dans la conductivité thermique due à un autre type de quasiparticules, les phonons. La seconde partie de cette thèse traite du destin de la mer de Fermi au-delà de la limite quantique (QL). Dans le semi-conducteur dopé InAs, nous rapportons l’existence d’un état isolant induit par le champ magnétique selon toutes les géométries de mesure. La comparaison avec la succession d’états induits par le champ dans graphite jusqu’à B=90T révèle que l’état fondamental d’un gaz d’électrons 3D au-delà de la QL n’est pas universel et dépend du système. Nos résultats suggèrent l’existence d’un état de surface conducteur dans InAsThis manuscript focuses on the electronic heat/charge transport dichotomy and the beyond-quantum-limit transport properties of dilute metals.In the first part, we report on a study of two semi-metals, WP2 and Sb. In both cases, we found that the Wiedemann-Franz (WF) law is recovered at low temperature (T ≈ 2 K), but not at T ≈ 15 K. We show that the finite-temperature deviation from the WF law is due to a mismatch between the prefactors of the T 2-resistivities. In the Boltzmann picture of transport, this difference is associated with abundant small-angle scattering among electrons. However, we argue that momentum-conserving fermionic collisions in normal-state liquid 3He also produce a thermal T2-resistivity. This opens the door for an alternative interpretation : the existence of a hydrodynamic regime of electrons in these semi-metals. In this scenario, the larger T2 thermal resistivity is due to momentum-conserving electronic collisions. In the case of Sb, the ratio of the two T2-prefactors evolves with sample size. This observation supports the hydrodynamic scenario. Finally, we find a large hydrodynamic correction in the phononic thermal conductivity. The second part deals with the fate of the Fermi sea in the quantum limit (QL). In the doped semi-conductor InAs, we observe a field-induced insulating state for all geometries of transport. The comparison with the succession of field-induced states in graphite up to B = 90 T reveals that the ground state of a 3D electron gas beyond the QL is system-dependent. The observation of a saturating resistivity accompanied by vanishing thermoelectric coefficients in InAs points to the existence of a conductive surface state
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Vernhet, Laura. "Transfert métallique lors des opérations de toilage à sec des aciers : effet des charges actives." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0016.
Повний текст джерелаАнотація:
Dans les industries automobile et aéronautique, les opérations de finition des pièces métalliques sont souvent réalisées avec des bandes abrasives ; on parle alors de « toilage ». Lors des opérations de toilage à sec des aciers, les conditions à l’interface entre l’outil abrasif et la pièce métallique usinée sont très sévères en termes de pression et de température. Un transfert métallique, communément appelé « chargement métallique » est observé à la surface des grains abrasifs en céramique de la bande abrasive, entrainant une chute de ses performances de coupe. L’objectif de ce travail est de comprendre ce phénomène de chargement métallique et notamment de mettre en évidence les paramètres l’influençant. L’effet de la nature des grains, de la nature des aciers ou encore de la présence de charges actives dans la bande abrasive ont donc été étudié. Une étude a donc été réalisée à différentes échelles : à l’échelle globale du contact bande abrasive / métal sur un dispositif industriel de toilage, puis à l’échelle plus locale du contact entre la céramique (du grain abrasif) et du métal, grâce à un dispositif tribologique adapté. Des caractérisations physico-chimiques par XPS (X-Ray Photoelectron Spectroscopy) et TEM-EDX (Transmission Electron Microscopy couplée avec la spectroscopie Energy Dispersive X-ray) des bandes abrasives ont également été réalisées. L’influence des charges actives, produits fluorés ajoutés à la résine de la bande abrasive, sur l’adhésion du métal sur le grain céramique a ainsi été mise en évidence, notamment dans le cas de l’acier inoxydable 304 où le chargement métallique a été fortement limité. Les mécanismes d’action de ces charges actives sont ensuite discutésIn automotive and aeronautic industries, grinding operations can sometimes be done with abrasive belts. During dry metal grinding, conditions at the interface between the abrasive tool and the metal workpiece are very hard in terms of pressure and temperature. Metal transfer, known as “metal capping”, is observed at the surface of the abrasive ceramic grain inducing a drop in the cutting efficiency. The objective of this work is to understand this metal capping phenomenon and to highlight the parameters which have an influence on it. The effects of abrasive grain nature, metal nature or active filler presence in the abrasive belt are then studied. A study has been done at different scales: at the global scale of the abrasive belt / metal contact thanks to an industrial grinding test, and then at the more local scale of the contact between ceramic (from the abrasive grain) and metal, thanks to a suitable tribological device. Physicochemical characterizations by XPS (X-Ray Photoelectron Spectroscopy) and TEM-EDX (Transmission Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy) were carried out on worn abrasive belts. The influence of the active fillers – fluorinated products added in the resin of the abrasive belt – on metal adhesion on the ceramic grain was then observed, especially in the case of the 304 stainless steel grinding where metal capping was significantly reduced. Action mechanisms of these active fillers were finally discussed
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Abrahams, Dhielnawaaz. "Charge Transfer and Capacitive Properties of Polyaniline/ Polyamide Thin Films." University of the Western Cape, 2018. http://hdl.handle.net/11394/6361.
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Magister Scientiae - MSc (Chemistry)Blending polymers together offers researchers the ability to create novel materials that have a combination of desired properties of the individual polymers for a variety of functions as well as improving specific properties. The behaviour of the resulting blended polymer or blend is determined by the interactions between the two polymers. The resultant synergy from blending an intrinsically conducting polymer like polyaniline (PANI), is that it possesses the electrical, electronic, magnetic and optical properties of a metal while retaining the poor mechanical properties, solubility and processibility commonly associated with a conventional polymer. Aromatic polyamic acid has outstanding thermal, mechanical, electrical, and solvent resistance properties that can overcome the poor mechanical properties and instability of the conventional conducting polymers, such as polyaniline.
Книги з теми "Charge transfers and SEI"
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contributor, Aligică Paul Dragoș, and Institute of Economic Affairs (Great Britain), eds. Sea change: How markets and property rights could transform the fishing industry. London: Institute of Economic Affairs, 2017.
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Górka, Jakub. Transforming payment systems in Europe. Houndmills, Basingstoke, Hampshire: Palgrave Macmillan, 2015.
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Komori, Satoru. Turbulence structure and CO₂ transfer at the air-sea interface and turbulent diffusion in thermally-stratified flows. Tsukuba, Japan: Center for Global Environmental Research, National Institute for Environmental Studies, Environment Agency of Japan, 1996.
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Canada. Bill: An act to change the tenure of the Indian lands in the township of Durham. [Toronto: S. Derbishire & G. Desbarats, 2001.
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Japan. Extension of fishery agreement between the United States and Japan: Message from the President of the United States transmitting an agreement extending the Governing International Fishery Agreement ... pursuant to 16 U.S.C. 1823(a), Public Law 94-265, sec. 203(a). Washington: U.S. G.P.O., 1989.
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Japan. Extension of fishery agreement between the United States and Japan: Message from the President of the United States transmitting an agreement extending the Governing International Fishery Agreement ... pursuant to 16 U.S.C. 1823(a), Public Law 94-265, sec. 203(a). Washington: U.S. G.P.O., 1989.
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Launay, Jean-Pierre, and Michel Verdaguer. The moving electron: electrical properties. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198814597.003.0003.
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The three basic parameters controlling electron transfer are presented: electronic interaction, structural change and interelectronic repulsion. Then electron transfer in discrete molecular systems is considered, with cases of inter- and intramolecular transfers. The semi-classical (Marcus—Hush) and quantum models are developed, and the properties of mixed valence systems are described. Double exchange in magnetic mixed valence entities is introduced. Biological electron transfer in proteins is briefly presented. The conductivity in extended molecular solids (in particular organic conductors) is tackled starting from band theory, with examples such as KCP, polyacetylene and TTF-TCNQ. It is shown that electron–phonon interaction can change the geometrical structure and alter conductivity through Peierls distortion. Another important effect occurs in narrow-band systems where the interelectronic repulsion plays a leading role, for instance in Mott insulators.
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Greene, Stephanie N. Transform the World: 14 Sci-Fi Writers Change the Planet. Other Worlds Ink, 2023.
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Simon, Gleeson, and Guynn Randall. Part III The EU Resolution Regime, 11 Institutional and Cross-Border Issues. Oxford University Press, 2016. http://dx.doi.org/10.1093/law/9780199698011.003.0011.
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This chapter examines how the Bank Recovery and Resolution Directive is implemented in international and cross-border situations, both within the EU and between the EU and third countries. The BRRD requires each member state to recognize in their law the effect of resolution actions taken by other member states. This means that as regards foreign resolution action which purports to transfer assets located in their jurisdiction, or rights or liabilities governed by their law, or write-down or convert liabilities governed by their law or owed to creditors in their jurisdictions, their law must make provision for such transfers or conversions to take effect automatically and cannot be prevented, challenged, or set aside under their law. The chapter covers the scope of the Single Resolution Mechanism, cross-border branching, and the relevant changes to the Credit Institutions (Winding-Up) Directive.
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Marcus, Smith, and Leslie Nico. Part VI Special Regimes for Transfer, 30 Insolvency and Assignment. Oxford University Press, 2018. http://dx.doi.org/10.1093/law/9780198748434.003.0030.
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This chapter discusses insolvency. Insolvency is significant in the law of assignment in a number of respects. In the first place, individual bankruptcy—although not the insolvency of companies—causes the bankrupt to be divested of his property, which automatically becomes vested in his trustee in bankruptcy upon the latter's appointment. So far as choses in action are concerned, this involves what can be termed a statutory assignment. The onset of insolvency—both individual and corporate—also causes the rules regarding assignments generally to change in certain respects. Thus, with the onset of insolvency: the rules regarding the assignability of present rights enforceable in the future change; the rules of champerty and maintenance change; and the rules of set-off change.
Частини книг з теми "Charge transfers and SEI"
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Mager, Humphrey I. X., and Shiao-Chun Tu. "ELECTRON (CHARGE) TRANSFERS IN FLAVIN-MEDIATED LUMINESCENCE." In Flavins and Flavoproteins 1990, edited by B. Curti, S. Ronchi, and G. Zanetti, 277–80. Berlin, Boston: De Gruyter, 1991. http://dx.doi.org/10.1515/9783110855425-054.
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Hsieh, Cheng-Chih, Mei-Lin Ho, and Pi-Tai Chou. "Organic Dyes with Excited-State Transformations (Electron, Charge, and Proton Transfers)." In Springer Series on Fluorescence, 225–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-04702-2_7.
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Park, Hyunwoong. "Interfacial Charge Transfers of Surface-Modified TiO2Nanoparticles in Photocatalytic Water Treatment." In Engineered Nanoparticles and the Environment: Biophysicochemical Processes and Toxicity, 245–60. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119275855.ch13.
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Khoudir, A., J. Maruani, and M. Tronc. "SCF, CI and DFT Charge Transfers and XPS Chemical Shifts in Fluorinated Compounds." In Quantum Systems in Chemistry and Physics Volume 2, 57–89. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/0-306-48145-6_5.
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Yuan, Leqi, Kun Cheng, Haozhi Bian, Yaping Liao, and Chenxi Jiang. "Numerical Simulation of Flow Boiling Heat Transfer in Helical Tubes Under Marine Conditions." In Springer Proceedings in Physics, 1015–30. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_86.
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AbstractLead-based cooled reactors in most countries and some small reactors at sea use helical tube steam generators. Compared with U-tubes, the convection heat transfer coefficient in the spiral tube is higher, the structure is more compact, and the secondary flow is generated under the action of centrifugal force and gravity, which can achieve the effect of wetting the inner wall of the tube. However, due to the importance of the steam generator in the reactor and the complexity of the flow and boiling in the helical tube, the aggregation behavior of bubbles, the distribution of the two-phase interface and the secondary flow in the tube will significantly affect the heat transfer characteristics, so the gas-liquid phase in the tube is studied. Distribution, changes in heat transfer coefficients, and fluid flow characteristics are very important.In order to study the boiling heat transfer characteristics of helical once-through steam generators under static and marine conditions to provide safe and reliable energy supply for offshore facilities such as marine floating, this study uses STAR-CCM+ software, VOF method and Rohsenow boiling model to study the heat transfer capacity and flow characteristics of flow boiling in a helical tube under swaying and tilting conditions. The gas-liquid phase distribution characteristics, secondary flow variation characteristics and convective heat transfer coefficient of the fluid under different swing functions and inclined positions are obtained by numerical calculation, and the law of physical parameters changing with the cycle is found. The research results show that the secondary flow and heat transfer capacity in the tube change with the cycle, and the change is most obvious at the tube length of 0.8m. 5% of the normal condition; when the inclination angle is 45°, the maximum increase of the convection heat transfer coefficient is 16.8%, and the maximum decrease is 6.6%.
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Scagliarini, Andrea, Enrico Calzavarini, Daniela Mansutti, and Federico Toschi. "Modelling Sea Ice and Melt Ponds Evolution: Sensitivity to Microscale Heat Transfer Mechanisms." In Mathematical Approach to Climate Change and its Impacts, 179–98. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-38669-6_6.
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Bönisch-Brednich, Brigitte. "Receiving the Gift of the Master’s Voice: How White Western Academic Paradigms Shape Knowledge and Remittance Economies: A De-Colonial Perspective." In Remittances as Social Practices and Agents of Change, 413–33. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-030-81504-2_18.
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AbstractThis chapter explores the social, political, and cultural agents that drive the engines of gifting academic knowledge. It considers knowledge as a form of social remittance. Viewing knowledge transfers as remittance practices makes processes of (neo)colonial exchange flows visible. It also allows us to see such remittances as what they are: political and social scripts that determine legitimacy, value, and currency of knowledge in a world of economic and social inequalities. We can view knowledge according to Bourdieu as academic capital with skewed exchange rates. This chapter explores the question: How are the positions of sender and receiver linked to neo-colonial inequities? In a world system of university rankings, regionalized hubs of academic influence, money flows, and uneven power relationships, the exchange of knowledge and the definition of what constitutes knowledge is a fraught and fascinating topic when approaching it within a frame of remittance economy.
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Mulsow, Martin. "Positive and Negative Error. A Debate in the Illuminati Order." In Errors, False Opinions and Defective Knowledge in Early Modern Europe, 121–34. Florence: Firenze University Press, 2023. http://dx.doi.org/10.36253/979-12-215-0266-4.09.
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That error could be of interest to Freemasons and Illuminati as a topic becomes evident when one sees it in the context of concepts such as prejudice, ignorance, and gullibility. The perfection of the human being was understood as the detachment from prejudices – from errors –, as overcoming ignorance and as a fight against gullibility. In 1785 there was a discussion among the Illuminati of Gotha about how one should understand error. Prince August of Saxe-Gotha transfers Voltaire’s two types of imagination to two types of errors, using the distinction made by the physicist Charles Du Fay, who distinguished resin electricity (électricité résineuse) with its negative charge from glass electricity (électricité vitreuse) with its positive charge. So August suggests that there are positive and negative errors: the positive errors are attractive, they attract. In this case the cause of error lies on our side, on the side of the subjects: because of certain defects in the knower, facts are not correctly recognized. The negative errors, on the other hand, repel: there it is due to the nature of the representations of the facts themselves, which have pitfalls or are distorted by hallucinations, that we go wrong.
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Takabe, Hideaki. "Non-local Transport of Electrons in Plasmas." In Springer Series in Plasma Science and Technology, 285–323. Cham: Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-45473-8_6.
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AbstractSince plasma is high temperature and the charge particles are running with high temperature, for example, at 1 keV, about the velocity of 109 (electron) and 2 × 107 (ion) [cm/s]. Since Coulomb mean-free-path is proportional to (velocity)4, higher velocity component transfers its energy over a long distance without Coulomb collision. This is usually called as “non-local transport” and the traditional diffusion model in neutral gas cannot be applicable. In laser plasma, the locally heated electron thermal energy is transported into cold over-dense region non-locally. The best way to solve such problem is to solve Fokker-Planck equation, while it is time consuming and some theoretical models have been proposed and studied over the last four decades. The physics of such models are explained here and most recent model SNB is shown and compared to experiments. The difficulty of transport of charges particles such as electrons is how to include the effect of electrostatic field and magnetic field self-consistently.
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Mukherjee, Rila. "The Coast Bouleverses at Kolkata." In Planetary Hinterlands, 81–95. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-24243-4_5.
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AbstractThis chapter argues that “hinterland” is not only a designation related to the economic field, but also a perspective. As the sea is increasingly turned into land for developmental purposes, and as legal strategies transform coastal waters into land-like, developable components of state territory, hinterlands are transforming in nature. This process is markedly visible in Kolkata’s environs, where seemingly passive spaces have changed into active places where people create their own identities and histories.
Тези доповідей конференцій з теми "Charge transfers and SEI"
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Arora, Shashank. "A Novel Technique for Estimation of the Solid Electrolyte Interphase Film Resistance for Li-Ion Batteries." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87311.
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Solid electrolyte interphase (SEI) film resistance is an important parameter in the study of charge transfer kinetics of a Li-ion battery. The passive film affects diffusion process of Li-ions. As such, it becomes essential to include film resistance in battery modelling. However, the traditional method of estimating the SEI film resistance is costly and time consuming. An indirect approach based on Ohm’s law is thus presented in this paper. It relies on determining the interfacial polarisation from the difference of open-circuit voltage measured immediately after switching off the applied current and the equilibrium voltage. The technique is simple, easy to implement and can be used for a quick estimation of SEI film resistance with reasonable accuracy. For instance, average value of SEI film resistance for commercial LFP battery cell is measured as 0.004 Ohm · m2 , which was found to be consistent with the values determined using the impedance spectroscopy techhnique in the published literature for lithium-carbon film electrodes.
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Lu, Gaopeng, and Steven A. Cummer. "Negative sprites produced by consecutive impulse charge transfers in negative strokes." In 2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS). IEEE, 2014. http://dx.doi.org/10.1109/ursigass.2014.6929970.
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Stamatis, A. G., and K. Mathioudakis. "The Influence of Heat Transfer Effects on Turbine Performance Characteristics." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-91039.
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A method allowing the evaluation of the effects related to heat transfer to the turbine blades on its performance characteristics is presented. The effects investigated are the change of passage dimensions, resulting from heat transfer and the change in flow field, exhibited mainly as a different boundary layer development. Change of hot gas temperature combined with cooling air temperature and possibly flow rate, result in a change of the temperature of the blade material, leading to dimension changes, because of the thermal expansion (dilatation). The changes in dimensions have a direct effect on turbine performance. An immediate consequence is a modification of the mass flow characteristic, due to a change of the throat area. Heat transfer also influences the properties of the gas flowing through the passage and in particular the characteristics of the boundary layers developing on the nozzle vanes and hub, tip endwals. Change of the thickness of this layer results in a change of blockage through the passage, a fact that influences directly the turbine flow function. The influence of both effects on turbine performance is studied. The study is performance oriented, aiming to the derivation of simplified models, which can be introduced in engine cycle decks.
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Rutledge, James L., and Jonathan F. McCall. "An Inverse Heat Transfer Approach to Mitigating Sources of Experimental Error in Transient Heat Transfer Experiments." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94583.
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The Inverse Flux Solver for Arbitrary Waveforms (IFSAW) algorithm is a transient, simultaneous solution of time resolved adiabatic effectiveness, η(t), and heat transfer coefficient, h(t). Numerical simulations showed IFSAW maintained its high accuracy despite two experimental sources of error typically found when using a transient heat transfer method. The traditional transient method involves exposing a film cooled wind tunnel model at uniform temperature to a step change in freestream temperature. The experimental design results in nearly one-dimensional heat transfer and allows the surface to be modeled as semi-infinite. Typically, the surface temperature history is correlated to an analytical solution to the governing heat transfer equation (yielding η and h), but the required temperature step change is impossible to achieve in a laboratory. This paper first analyzed the error introduced by imperfect step changes and evaluated an alternative methodology, IFSAW, requiring only an arbitrary change in freestream temperature occurring at any rate. Secondly, severe error in h (found in locations where η is near unity because the surface temperature changes little from the initial temperature) was shown to be mitigated using IFSAW combined with a gradual change in coolant temperature at any point during measurement. With both complications, IFSAW maintains its ability to determine periodic η(t) and h(t) waveforms. In these ways, IFSAW is shown to be superior to the legacy transient method.
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Barbara, Paul F. "Ultrafast studies on intramolecular charge transfer and solvation dynamics." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/up.1990.tub2.
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Much of the recent activity on the study of fast charge (electron) transfer ET reactions stems from the growing appreciation that the rates of ET can be affected by solvent dynamics in contrast to traditional theories of ET which are based on a quasi—equilibrium assumption. Our work has emphasized femtosecond studies of the excited state, S1 small barrier, ultrafast ET reactions of aromatics, including BA, ADMA, derivatives of ADMA, and several other molecules. We have shown theoretically that emission dynamics at the short wavelength edge of the fluorescence band accurately measures the decay of the prepared (reactant’s) concentration. Results on the solvent dependence of <τET> demonstrate that the ET kinetics of the various molecules are controlled by solvation dynamics, see Table 1. However, we have shown that simple continuum models for solvation dynamics (when combined with theories of ET) do not correctly predict ET rates. Rips and Jortner have analyzed our data and shown that the MSA model (combined with ET theory) more accurately agrees with experiments. This emphasizes the importance of molecular interactions in dynamic solvent effects on chemical reactions.
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Bonilla, Joel Lopez, Benoit Fond, Henrik Graichen, Jan Hamann, Frank Beyrau, and Gunar Boye. "Thermal characterization of high-performance battery cells during charging and discharging using optical temperature measurement methods." In FISITA World Congress 2021. FISITA, 2021. http://dx.doi.org/10.46720/f2021-adm-145.
Повний текст джерелаАнотація:
"Lithium-ion batteries currently used in electric vehicles have strong thermal limitations. Thus, both excessively high and low temperatures lead to an accelerated aging process in form of capacity losses through SEI-layer buildup on the one hand and lithium-plating on the other hand. Additionally, temperature gradients within a cell, as well as temperature differences between individual cells have to be minimized in order to increase the system’s durability. With a properly designed battery-thermal-management (BTM), not only the aging process can be minimized but also extreme cases like thermal runaways can be prevented, which otherwise can cause fatal ecological and economical damage or in the worst-case-scenario exposes and harms vehicle occupants to fire, explosion or intoxication due to a damaged battery cell system. For the application of an efficient BTM, a detailed characterization of the battery’s thermal behavior during the charge and discharge cycle with different loads is essential. This paper deals with high-performance pouch cells, as they have a favorable ratio of heat transfer surface area to battery volume for BTM. However, they also present a particular challenge for the acquisition of the surface temperature distribution, as they do not have a solid shell. An external force must be applied to this cell type to prevent it from inflating, when it is under higher loading conditions, because this volume change is expected to change the cell’s thermal behavior. Therefore, the determination of the surface temperature in the present study was carried out while the cell was fixated and forced to stay in its geometric shape. The mechanical fixation has an influence in the thermal behavior and therefore the temperature distribution should be probed in this configuration but this also makes the optical measurement of temperature more difficult as pressure transmission plates must be made transparent. The measured surface temperature distribution can then be used as an input for a FEM-simulation to provide information on the whole cell’s internal temperature field. To the authors´ knowledge, no thermal investigations in this configuration have been reported. Two different optical temperature measurement methods are applied. The first technique is IR-thermography, which is based on the measurement of heat radiation from the surface, and which is restricted to regions on the surface using small IR-transmitting sapphire windows. The second technique, phosphor thermometry, exploits the temperature dependent luminescence properties of thermographic phosphor materials. The phosphors are applied as a thin coating on the surface of the battery and illuminated by a light source. The resulting luminescence emission in the visible range is detected to infer the temperature of the whole surface, since normal glass can be used. The surface temperature distribution obtained by these two techniques are provided and the advantages or disadvantages of each technique are described in terms of precision, accuracy, sensitivity, temporal resolution, spatial resolution and also implementation expenses. The internal temperature field provided by the heat transfer model for a known surface distribution is also presented and the impact of this integral thermal characterization on the BTM is discussed."
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Sobotka, Vincent, Nicolas Boyard, and Didier Delaunay. "Parametric Model for the Analytical Determination of the Solidification and Cooling Times of Semi-Crystalline Polymers." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22663.
Повний текст джерелаАнотація:
This work presents an efficient method to quickly calculate with good accuracy (about 5%) the solidification time of an injected semi-crystalline polymer slab. Under some hypotheses this polymer can be considered as a phase change material with a constant phase change temperature. We use a noteworthy property established on the ratio between the thickness of a solidifying phase change finite medium and the solidified thickness in a semi-infinite medium. The knowledge of this ratio enables to predict analytically the solidification time in a 1D finite medium. This ratio can be parameterized as a function of characteristic numbers in phase change problems: Stefan numbers and the ratio of thermal diffusivities of both phases. The results are compared with those given by a complete model integrating the physics of the coupling between heat transfer and crystallization kinetics. The solidification times computed from both models are very close, demonstrating the relevance of the simplified model. Finally, we also get a very good accuracy in calculating the total cooling time, from injection to ejection.
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Woo, J. H., K. J. Lee, L. Mazur, E. S. Kim, Y. Xiao, F. Mathevet, A. J. Attias, J. W. Wu, and J. C. Ribierre. "Femtosecond transient absorption measurement of energy and charge transfers in donor-acceptor liquid crystalline dyad and triad." In International Conference on Ultrafast Phenomena. Washington, D.C.: OSA, 2014. http://dx.doi.org/10.1364/up.2014.08.tue.p2.29.
Повний текст джерела
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Kumar, Navin, and Debjyoti Banerjee. "Experimental Validation of Numerical Predictions for the Transient Performance of a Simple Latent Heat Storage Unit (LHSU) Utilizing Phase Change Material (PCM) and 3-D Printing." In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-5045.
Повний текст джерелаАнотація:
Experimental validation was performed in this study to verify the efficacy of numerical models for predicting the location of solid-liquid interface in an axi-symmetric configuration during both melting and solidification in a Latent Heat Storage Unit (LHSU). Development of analytical solutions for predicting the location of the solid-liquid interface is often intractable in LHSU due to non-linear temperature distribution in the Phase Change Material (PCM). This is further complicated by the moving boundary problem with free convection within the liquid phase of the PCM. Analytical solutions available in the contemporary literature are based on simplified transient heat conduction models and often fail to reliably predict the charging and discharging time constants for LHSU with complex configurations. This study is designed with the goal of developing more sophisticated numerical models for the estimation of transient thermal performance of an LHSU with a simple configuration involving a shell and tube heat exchanger (HX). The LHSU utilized in this study is realized by integrating various types of Phase Change Materials (PCM) contained in the shell side of a HX. The LHSU is charged or discharged by pumping hot or cold fluids in the tube side of the HX (i.e., by pumping water at a fixed inlet temperature from a commercial chiller apparatus). This study enabled the characterization of the transient response of a LHSU subjected to conduction and forced convection heat transfer. The PCM used in this material was paraffin wax (PURETEMP 29). The HX in the LHSU consisted of a single pass straight tube (½ inch copper pipe) mounted within a single shell configuration. The shell was fabricated from plastic material using additive manufacturing (i.e., “3D Printing”). The temperature variation during melting and solidification of the PCM were measured at different radial and axial locations within the cylindrical shell that was mounted vertically. Temperature measurements were performed at different mass flowrate ranging from 0.004 Kg/sec to 0.007 Kg/sec for the same fluid temperature. The water bath temperatures were maintained at a constant temperature of 40°C for melting and 15°C for solidification. The experiment results show that the transient response of the LHSU for charging and discharging (i.e., time required for melting and solidification of the PCM) vary significantly. Comparison of the experimental data with analytical results (involving quasi-stationary models for phase change) demonstrate that natural convection is the dominant mode during the melting process, while conduction is the dominant mode during the solidification process.
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Duarte, Leonardo José, and Roy Edward Bruns. "Infrared intensities of imaginary frequencies: Gas-Phase SN2 Transition States." In VIII Simpósio de Estrutura Eletrônica e Dinâmica Molecular. Universidade de Brasília, 2020. http://dx.doi.org/10.21826/viiiseedmol202032.
Повний текст джерелаАнотація:
The gas phase SN2 reaction transition state structures for nine [XCZ_3 Y]^- systems, where X,Y=H,F,Cl and Z = H,F were optimized and their normal modes of vibrations were determined at the QCISD/aug-cc-pVTZ level of theory. Using Quantum Theory of Atoms in Molecules (QTAIM), the atomic charges and atomic dipoles were obtained and used to calculate the Charge – Charge Transfer – Dipolar Polarization (CCTDP) contributions to the imaginary normal mode intensity of transition states. The results show that the imaginary bands are strong, ranging from 1217 to 16086 〖km∙mol〗^(-1), much higher than occurs for most bands found in molecules. For all systems, the CT contribution is responsible for 80% of the total intensity on average. The Charge contributions are slightly higher for transitions states with Z = F. Dipolar polarization contributions are always small. The contributions from the Z atoms are negligible, thus only atoms aligned with the reaction axis X-C-Y contribute to total intensity. All charge transfers were evaluated taking the carbon atom as reference, implying that almost all infrared intensity is determined by electron transfers from the nucleophile and carbon and from carbon to the leaving group. The mechanism of charge transfer revealed by the CCTDP model is consistent with the reaction mechanism itself, which points towards the connection between the imaginary normal mode and the reaction coordinate.
Звіти організацій з теми "Charge transfers and SEI"
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Law, Edward, Samuel Gan-Mor, Hazel Wetzstein, and Dan Eisikowitch. Electrostatic Processes Underlying Natural and Mechanized Transfer of Pollen. United States Department of Agriculture, May 1998. http://dx.doi.org/10.32747/1998.7613035.bard.
Повний текст джерелаАнотація:
The project objective was to more fully understand how the motion of pollen grains may be controlled by electrostatic forces, and to develop a reliable mechanized pollination system based upon sound electrostatic and aerodynamic principles. Theoretical and experimental analyses and computer simulation methods which investigated electrostatic aspects of natural pollen transfer by insects found that: a) actively flying honeybees accumulate ~ 23 pC average charge (93 pC max.) which elevates their bodies to ~ 47 V likely by triboelectrification, inducing ~ 10 fC of opposite charge onto nearby pollen grains, and overcoming their typically 0.3-3.9 nN detachment force resulting in non-contact electrostatic pollen transfer across a 5 mm or greater air gap from anther-to-bee, thus providing a theoretical basis for earlier experimental observations and "buzz pollination" events; b) charge-relaxation characteristics measured for flower structural components (viz., 3 ns and 25 ns time constants, respectively, for the stigma-style vs. waxy petal surfaces) ensure them to be electrically appropriate targets for electrodeposition of charged pollen grains but not differing sufficiently to facilitate electrodynamic focusing onto the stigma; c) conventional electrostatic focusing beneficially concentrates pollen-deposition electric fields onto the pistill tip by 3-fold as compared to that onto underlying flower structures; and d) pollen viability is adequately maintained following exposure to particulate charging/management fields exceeding 2 MV/m. Laboratory- and field-scale processes/prototype machines for electrostatic application of pollen were successfully developed to dispense pollen in both a dry-powder phase and in a liquid-carried phase utilizing corona, triboelectric, and induction particulate-charging methods; pollen-charge levels attained (~ 1-10 mC/kg) provide pollen-deposition forces 10-, 77-, and 100-fold greater than gravity, respectively, for such charged pollen grains subjected to a 1 kV/cm electric field. Lab and field evaluations have documented charged vs. ukncharged pollen deposition to be significantly (a = 0.01-0.05) increased by 3.9-5.6 times. Orchard trials showed initial fruit set on branches individually treated with electrostatically applied pollen to typically increase up to ~ 2-fold vs. uncharged pollen applications; however, whole-tree applications have not significantly shown similar levels of benefit and corrective measures continue. Project results thus contribute important basic knowledge and applied electrostatics technology which will provide agriculture with alternative/supplemental mechanized pollination systems as tranditional pollen-transfer vectors are further endangered by natural and man-fade factors.
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Straume, Odd Rune, and Paulo Bastos. Preschool Education in Brazil: Does Public Supply Crowd Out Private Enrollment? Inter-American Development Bank, November 2013. http://dx.doi.org/10.18235/0011518.
Повний текст джерелаАнотація:
This paper examines whether an expansion in the supply of public preschool crowds out private enrollment, using rich data for municipalities in Brazil from 2000-2006, where federal transfers to local governments change discontinuously with given population thresholds. Results from a regression-discontinuity design reveal that larger federal transfers lead to a significant expansion of local public preschool services, but show no effects on the quantity or quality of private provision. These findings are consistent with a theory in which households differ in willingness to pay for preschool services, and private suppliers optimally adjust prices in response to an expansion of lower-quality, free-of-charge public supply.
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Hille, Carsten, Daria Morcinczyk-Meier, Sarah Schneider, and Dana Mietzner. From InnoMix to University–Industry Collaboration: Fostering Exchange at Eye Level. Technische Hochschule Wildau, 2021. http://dx.doi.org/10.15771/innohub_1.
Повний текст джерелаАнотація:
In this paper, we address a specific tool—InnoMix—that is implemented to overcome the lack of university–industry interaction in a selected region facing structural change with its corresponding impact on the economy and society. InnoMix is facilitated and implemented by university-based transfer scouts who act as mediators and translators between the players of the regional innovation system. These transfer scouts are part of the Innovation Hub 13, in which the region’s partners and stakeholders, infrastructures and competencies are systematically networked with each other to set new impulses for knowledge and technology transfer. These new impulses are brought into the region through new transfer approaches ranging from people and tools to infrastructure. InnoMix can be considered to be a highly interactive tool to overcome the weak, direct interaction between researchers and potential corporate partners in the region to foster strong collaboration between academia and industry. InnoMix especially aims to strengthen interdisciplinary exchange to shed light on cross-disciplinary perspectives. For that reason, transfer scouts focusing on transfer activities related to the life sciences, digitalisation and lightweight construction are involved in the implementation of InnoMix. Based on 11 InnoMix running since 2019, we provide insights into the planning and preparation phase of InnoMix and the selection of relevant topics and requirements for matching participants. Furthermore, we clearly indicate which formats of InnoMix work best and in which way university–industry interactions could be curated after InnoMix is implemented.
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Rans, Richard. PR-352-15600-Z01 USM Uncertainty Estimate From Diagnostics. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), March 2020. http://dx.doi.org/10.55274/r0010919.
Повний текст джерелаАнотація:
A method to calculate a common set of Ultrasonic meter Gaussian quadrature �0.809R/�0.309R velocity diagnostics has been developed for multi-path Ultrasonic meters with Gaussian and proprietary path configurations. An uncertainty model has been developed using the changes between the meter's �0.809R/�0.309R calibration velocity diagnostics and the meter's �0.809R/�0.309R first flow/recalibration velocity diagnostics to estimate a Maximum Gaussian Risk/Probable Gaussian Risk calibration transfer uncertainty.
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Баттахов, П. П. Договоры о передаче исключительных прав на объекты промышленной собственности с участием социальных предприятий. DOI CODE, 2021. http://dx.doi.org/10.18411/1818-1538-2021-55669.
Повний текст джерелаАнотація:
The article considers contractual designs aimed at transferring exclusive rights to industrial property. The problem of the contractual process was identified when concluding a contract on the transfer of a set of exclusive rights. Based on the study, a number of changes to Russian laws have been proposed. First of all, this applies to a commercial concession contract. The author proposes to amend the Civil Code of the Russian Federation by supplementing the article on commercial concession with the right of organizations that do not conduct commercial activities to conclude the same contracts on a general basis. The appropriateness of applying the classification of transactions into real and consensual ones in relation to this contract is justified. The peculiarities of transfer of the complex of exclusive rights to objects of industrial property with participation of social enterprises under the legislation of the Russian Federation are studied.
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Sommer, Stefan, Sascha Flögel, Michael Walter, and Frank Wenzhöfer. Autonomous Robotic Network to Resolve Coastal Oxygen Dynamics : Cruise No. AL547, 20.10. – 31.10.2020, Kiel – Kiel, ARCODYN. GEOMAR Helmholtz Centre for Ocean Research Kiel, 2022. http://dx.doi.org/10.3289/cr_al547.
Повний текст джерелаАнотація:
The ALKOR cruise AL547 represents a concluding milestone of the Helmholtz innovation project ARCHES (Autonomous Robotic Networks to Help Modern Societies). The aim was to implement a heterogeneous robotic sensing network to simultaneously monitor changes in the water column and at the seafloor. The network has been developed by a consortium of partners from AWI, DLR, GEOMAR and the University of Kiel. The participating sensing platforms allow for real-time data transfer and the entire network shall be able to autonomously respond to environmental changes in the ocean. The network comprised seven different mobile and stationary platforms. Tests were conducted at the Mittelgrund working area in the entrance of the Eckernförde Bay (western Baltic Sea). During 47 stations the various sensing platforms were deployed and recovered for maintenance. A total of 87853 messages were sent using hydro-acoustics, of which 71734 messages contained O 2 data, 15177 were status messages, 926 messages were commands to trigger a change of the measurement behavior of a platform and 16 messages represented broadcasts about the environmental status. We synoptically recorded short-term O 2 time series on the different platforms, which were placed along a depth gradient in the working area. As the Eckernförde Bay is known for sporadic fish kills by anoxia we hope to contribute to a better understanding of the O 2 dynamics in coastal areas. - (ALKOR-Berichte ; AL547)
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Ptsuty, Norbert, Andrea Habeck, and Christopher Menke. Shoreline position and coastal topographical change monitoring at Gateway National Recreation Area: 2017–2022 and 2007–2022 trend report. National Park Service, August 2023. http://dx.doi.org/10.36967/2299536.
Повний текст джерелаАнотація:
This trend report summarizes the results of shoreline position and coastal topography monitoring conducted at Gateway National Recreation Area (GATE) in 2007 through 2022. The data collection and report were completed by Rutgers University for the National Park Service, Northeast Coastal and Barrier Network, Inventory and Monitoring Program. Gateway National Recreation Area (GATE) is made up of three units: Sandy Hook Unit, Jamaica Bay Unit (Breezy Point, Plumb Beach), and Staten Island Unit (Great Kills, Miller Field, Fort Wadsworth). Shoreline position change results include a spatial depiction and statistical analysis of annual changes and 5-year changes in shoreline position as well as a longer-term trend analysis incorporating the full shoreline analysis of 2007 through 2022, all following the model presented in Psuty et al. (2022a). Coastal topography datasets include profiles of survey data collected annually, annual change metrics, net change metrics, as well as an alongshore depiction of net change, following the model presented in Psuty et al. (2012). This 2007–2022 trend report is the third GATE trend report to incorporate both shoreline position and coastal topographical change data. Due to the variable exposure to incident waves influencing inputs of sediment to the alongshore transport system in the various units from updrift sources, there was no common direction of shoreline displacement or profile change throughout the GATE park units. Engineering structures along the beach and adjacent to inlets altered the shoreline position and coastal topography responses in much of GATE. Generally, the largest vectors of shoreline position change and changes in coastal topography were produced by natural impacts such as storms and by anthropogenic impacts such as dredging or beach nourishment at an updrift location. All of the park units in GATE displayed the impacts of an absence of a source of sediment to counter the erosional impacts of the coastal storms. All of the units had a net inland displacement of shoreline position over the survey period, with some short term recovery associated with local pulses of sediment transfer. Sites with ocean exposure were more heavily eroded (Sandy Hook Oceanside, Breezy Point Oceanside, and Great Kills Oceanside), than sheltered sites (Sandy Hook Bayside, Breezy Point Bayside, Great Kills Bayside, Plumb Beach, Miller Field, Fort Wadsworth). A comparison of the shoreline position and profile data from this survey period with those from the previous trend reports highlights the impacts of Hurricane Sandy and the variety of recovery episodes throughout GATE (Psuty et al. 2018). The trend lines for the sites are often divided into pre-Hurricane Sandy (2012) and post- Hurricane Sandy because of the magnitude of the changes to the shoreline position (1D) and coastal topography (2D) metrics. There was considerable resilience in the system to re-establish the dune-beach system, although not in its original location. The continuing negative sediment budget and the increasing rate of relative sea-level rise will result in episodic inland migration of the dune-beach system and will necessitate a concomitant review of the allocation of space for visitor use and recreation.
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Vélez-Velásquez, Juan Sebastián. Banning Price Discrimination under Imperfect Competition: Evidence from Colombia's Broadband. Banco de la República de Colombia, December 2020. http://dx.doi.org/10.32468/be.1148.
Повний текст джерелаАнотація:
Economic theory is inconclusive regarding the effects of banning third-degree price discrimination under imperfect competition because they depend on how the competing firms rank their market segments. When, relative to uniform pricing, all competitors want higher prices in the same market segments, a ban on price discrimination will reduce profits and benefit some consumers at the expense of others. If, instead, some firms want to charge higher prices in segments where their competitors want to charge lower prices, price discrimination increases competition driving all prices down. In this case, forcing the firms to charge uniform prices can increase their profits and reduce consumer surplus. We use data on Colombian broadband subscriptions to estimate the demand for internet services. Estimated preferences and assumptions about competition are used to simulate a scenario in which firms lose their ability to price discriminate. Our results show large effects on consumer surplus and large effects on firms’ profits. Aggregate profits increase but the effects for individual firms are heterogeneous. The effects on consumer welfare vary by city. In most cities, a uniform price regime causes large welfare transfers from low-income households towards high-income households and in a few cities, prices in all segments rise. Poorer households respond to the increase in prices by subscribing to internet plans with slower download speed.
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Diouf, Awa, Marco Carreras, and Fabrizio Santoro. Taxing Mobile Money in Kenya: Impact on Financial Inclusion. Institute of Development Studies, June 2023. http://dx.doi.org/10.19088/ictd.2023.030.
Повний текст джерелаАнотація:
Many people argue that mobile money has the potential to increase financial inclusion and improve the livelihoods of poor people in Africa. However, while many African governments impose specific taxes on mobile money transactions, very little is known about their effect on the use of mobile money services. This study assesses the short- and long-term impact of the tax on money transfer fees that the Kenyan government introduced in 2013. The tax, more specifically an excise duty, was imposed on fees incurred in all money transactions, including mobile money. It was introduced at 10 per cent and increased to 12 per cent in 2018. Our analysis has two parts. We use country-level data to see if the tax affected the use of mobile money – transaction values and volume – and the number of active mobile money agents. In addition, we use four rounds of nationally representative survey data to estimate changes in the use of mobile money after introduction of the tax. We find that the excise duty did not have a significant impact on different aggregated indicators relating to the use of mobile money. However, survey data shows that the tax may have reduced the rate of increase in use of mobile money services affected by the changes in tax, such as sending and receiving money, compared to services that were not, like savings and paying bills. Importantly, while the amounts transacted may not change, users send and receive money within households less regularly. In addition, the tax seems to have a more detrimental impact on poorer households, which were less likely to be financially included before the tax was introduced. Larger households also show more negative effects after the tax. URI
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Bertoni, Eleonora, Gregory Elacqua, Luana Marotta, Matias Martínez, Humberto Santos, and Sammara Soares. Is School Funding Unequal in Latin America?: A Cross-country Analysis. Inter-American Development Bank, November 2020. http://dx.doi.org/10.18235/0002854.
Повний текст джерелаАнотація:
Public spending on education has increased significantly in Latin America over the last decades. However, less is known whether increased spending has been translated into a more equitable distribution of resources within countries in the region. This study addresses this gap by measuring the inequality in per-pupil spending between regions with different levels of socioeconomic status (SES) within five Latin American countries: Brazil, Chile, Colombia, Ecuador, and Peru. Results show that Brazil, a federal country, has the widest socioeconomic funding gap due to large inequalities in local revenues between high and low SES regions. However, the country's funding gap has narrowed over time. School funding in Colombia has become more regressive over time, but its gap is half the size of the one in Brazil. The distribution of school funding in Peru has changed over time from being regressive-benefiting the richest regions-to being progressive-benefiting the poorest regions. Education spending in Chile and in Ecuador are, on the other hand, consistently progressive. However, while the progressiveness of funding in Ecuador is driven by transfers targeted at disadvantaged rural areas, the funding formulas in Chile addresses socioeconomic inequalities beyond the rural-urban gap.