scholarly journals Fonctionnement hydrologique d'un interfluve sédimentaire de la plaine côtière ancienne de Guyane Française

2005 ◽  
Vol 9 (1) ◽  
pp. 51-74
Author(s):  
P. Andrieux ◽  
M. Voltz ◽  
A. Durbec
Keyword(s):  
Guyane Française ◽  
Conductivité Hydraulique ◽  
Propriétés Physiques ◽  
A Charge

Le fonctionnement hydrologique de la plaine côtière ancienne de Guyane française constitue une des contraintes majeures à sa mise en valeur agricole, du fait de l'existence de périodes d'excès d'eau prolongées. L'objectif de cet article est d'analyser, sur un interfluve caractéristique de la plaine côtière ancienne, la forme et la dynamique de la nappe et ses sources d'alimentation en relation avec la variabilité des propriétés physiques des sols. Sur le plan expérimental, le travail est conduit à partir d'un suivi hydrologique in situ des fluctuations de la nappe observées sur 21 stations et d'une caractérisation de la variabilité spatiale de la conductivité hydraulique des sols par la méthode du trou de tarière à charge variable. Sur le plan de la modélisation, l'identification de la répartition spatiale de la recharge sur l'interfluve est déterminée par une modélisation inverse. Les suivis montrent d'une part la rapidité de réponse de la nappe aux pluies et d'autre part des temps de présence de la nappe en surface variables selon les sols. La modélisation conforte l'hypothèse d'isolement hydraulique de l'interfluve. La dynamique de la nappe est directement reliée aux entrées pluviométriques et dans une moindre mesure aux sols. La variabilité spatiale de la recharge est par ailleurs sous la dépendance de la topographie et de l'hétérogénéité spatiale de la conductivité hydraulique. Enfin, une estimation du ruissellement de surface souligne son importance sur l'interfluve. Les résultats obtenus montrent que l'engorgement des sols de la plaine côtière est sous la dépendance directe des processus hydrologiques observés à l'échelle de chaque interfluve. La prédiction des zones à excès d'eau marqué et des zones où la recharge est homogène peut être envisagée à partir de la connaissance de la topographie et de la distribution des sols. Sur le plan agronomique et pour les sols à forte contrainte hydrique, la mise en place de systèmes de drainage permettant leur mise en valeur agricole est à considérer.

scholarly journals A 1T2C FeCAP-Based In-Situ Bitwise X(N)OR Logic Operation with Two-Step Write-Back Circuit for Accelerating Compute-In-Memory

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 385
Author(s):  
Qiao Wang ◽  
Donglin Zhang ◽  
Yulin Zhao ◽  
Chao Liu ◽  
Qiao Hu ◽  
...  
Keyword(s):  
Nonvolatile Memory ◽  
High Reliability ◽  
Charge Sharing ◽  
Operation Speed ◽  
Sharing Function ◽  
Logic Operations ◽  
A Charge ◽  
Process Compatibility ◽  
Ferroelectric Capacitors

Ferroelectric capacitors (FeCAPs) with high process compatibility, high reliability, ultra-low programming current and fast operation speed are promising candidates to traditional volatile and nonvolatile memory. In addition, they have great potential in the fields of storage, computing, and memory logic. Nevertheless, effective methods to realize logic and memory in FeCAP devices are still lacking. This study proposes a 1T2C FeCAP-based in situ bitwise X(N)OR logic based on a charge-sharing function. First, using the 1T2C structure and a two-step write-back circuit, the nondestructive reading is realized with less complexity than the previous work. Second, a method of two-line activation is used during the operation of X(N)OR. The verification results show that the speed, area and power consumption of the proposed 1T2C FeCAP-based bitwise logic operations are significantly improved.

IONIZATION OF CHARGE-ANTICHARGE PAIRS IN ULTRATHIN PALLADIUM FILMS

1995 ◽  
Vol 09 (15) ◽  
pp. 939-946 ◽  
Author(s):  
YING LIU ◽  
JOHN C. PRICE
Keyword(s):  
Low Temperature ◽  
Electrical Conductance ◽  
Activation Energies ◽  
Arrhenius Behavior ◽  
Low Temperature Deposition ◽  
Temperature Deposition ◽  
A Charge

The electrical conductance and I–V characteristics of ultrathin Pd films prepared by low temperature deposition have been measured in situ. An Arrhenius behavior was found for the electrical conductance. A crossover between regimes with different activation energies was observed at a temperature TK. Below TK, the I–V characteristics of the film were found to be nonlinear. These observations are explained using a charge Kosterlitz-Thouless-Berezinskii transition picture which involves the ionization of charge-anticharge pairs.

Détermination au champ de la conductivité hydraulique saturée à l'aide de l'infiltromètre à charge constante de Côté: théorie et approximations mathématiques

1991 ◽  
Vol 71 (1) ◽  
pp. 119-126 ◽  
Author(s):  
O. Banton ◽  
D. Côté ◽  
M. Trudelle
Keyword(s):  
Hydraulic Conductivity ◽  
Key Words ◽  
Groundwater Table ◽  
Physical Parameters ◽  
Large Area ◽  
Conductivité Hydraulique ◽  
Potential Sources ◽  
Constant Head ◽  
A Charge ◽  
High Level

Saturated hydraulic conductivity is one of the most difficult physical parameters of soil to measure. The most accurate methods are those used in the field in the presence of a groundwater table. However, in many cases, these cannot be used, primarily when no groundwater table is present. The Côté constant head infiltrometer method proves useful in such cases, because the measurement is made on soil which is not necessarily saturated beforehand. The constant head of water used by the infiltrometer is low (3.5 cm), and so representative of precipitation and irrigation conditions. The device (which is 10 cm in diameter) performs the measurement on a large area of soil (roughly 200 cm2), and can therefore integrate varying heterogeneity and macroporosity, rendering the measurement more reliable and representative. The quantity of water needed for a measurement is about 1 L, making operation in the field easier. The Côté constant head infiltrometer is an unsophisticated device which is easy to use. Different mathematical approximations of the saturated flow of water around the infiltometer are described according to the various forms of flow taken into account. The corresponding coefficients may be used to quickly determine this parameter with a high level of confidence. However, one problem and some potential sources of error remain in the evaluation of hydraulic conductivity in the field, due principally to cases in which the soil is not totally saturated, to compaction or smoothing of the hole during digging, and to the variability of the parameter on the site. Key words: Hydraulic conductivity, infiltrometer, permeameter

Insights from Lithium Stripping Dynamics on Fast Charging

2022 ◽  
Author(s):  
Sobana Perumaram Rangarajan ◽  
Partha P Mukherjee ◽  
Yevgen Barsukov ◽  
Conner Fear ◽  
Gayatri Dadheech ◽  
...  
Keyword(s):  
Graphite Electrode ◽  
Lithium Ion ◽  
Visualization Method ◽  
Physical Mechanisms ◽  
S Factor ◽  
Fast Charging ◽  
In Situ Visualization ◽  
Voltage Plateau ◽  
A Charge

Safe and reliable fast charging of lithium-ion batteries is contingent upon the development of facile methods of detection and quantification of lithium plating. Among the leading candidates for online lithium plating detection is analysis of the voltage plateau observed during the rest or discharge phase ensuing a charge. In this work, an operando metric, ‘S-factor,’ is developed from electrochemical data to quantitatively analyze the severity of lithium plating over a range of charge rates and temperatures. An in-situ visualization method is employed to study the physical mechanisms and phase transitions occurring at the graphite electrode during the voltage plateau.

scholarly journals Le pergélisol au Québec nordique : bilan et perspectives

2007 ◽  
Vol 41 (1) ◽  
pp. 141-152 ◽  
Author(s):  
Michel Allard ◽  
Maurice K.-Seguin
Keyword(s):  
Facteurs Climatiques ◽  
Propriétés Physiques ◽  
Changements Climatiques

RÉSUMÉ La compilation de travaux publiés et d'études inédites permet de proposer un bilan des connaissances sur le pergélisol du Québec. Au Québec arctique, quelques études, fondées sur des mesures thermiques dans des trous de forage, ont révélé des épaisseurs de plusieurs centaines de mètres de pergélisol et permis d'en reconstituer l'évolution climatique. Cependant, la morphologie cryogène n'a presque pas été étudiée. Au Québec subarctique, les nombreuses mesures thermiques dans la région de Schefferville et les relevés régionaux, principalement en Hudsonie. mettent en évidence l'étroite relation entre la présence, l'épaisseur et le régime thermique du pergélisol et les facteurs climatiques locaux, en particulier l'enneigement. Ce dernier facteur étant lié de près à la structure du couvert végétal, une nouvelle carte du pergélisol, fondée sur les données les plus récentes de la végétation et des observations personnelles, est proposée. Trois approches ont servi à déterminer l'âge et l'évolution passée du pergélisol : 1) un modèle physico-mathématique développé à partir de mesures thermiques en milieu arctique; 2) l'analyse stratigraphique de tourbières à palses; 3) l'analyse du contexte géologique quaternaire. La dynamique récente du pergélisol a été étudiée par le biais des changements écologiques survenus dans les tourbières. Le pergélisol au Québec subarctique peut dater d'aussi loin que la déglaciation dans les régions jamais boisées; ailleurs, il apparaît être d'âge néoglaciaire. Les feux de forêts ont peut-être eu une influence sur sa dynamique. Les formes cryogènes et les gélisols les plus répandus au Québec subarctique sont brièvement mis en relation avec les différents types de formations superficielles pergélisolées. Les mesures in situ des propriétés physiques et du régime thermique du pergélisol discontinu seront nécessaires pour prévoir l'effet des changements climatiques.

Computational, Electrochemical and 7Li NMR Studies of Lithiated Disordered Carbons Electrodes in Lithium Ion Cells

1997 ◽  
Vol 496 ◽  
Author(s):  
G. Sandί ◽  
R. E. Gerald ◽  
L. G. Scanlon ◽  
K. A. Carrado ◽  
R. E. Winans
Keyword(s):  
Electrochemical Cell ◽  
Lithium Ion ◽  
Reversible Capacity ◽  
Carbon Anode ◽  
Nmr Studies ◽  
Lithium Bonding ◽  
7Li Nmr ◽  
Disordered Carbon ◽  
A Charge

ABSTRACTDisordered carbons that deliver high reversible capacity in electrochemical cells have been synthesized by using inorganic clays as templates to control the pore size and the surface area. The capacities obtained were much higher than those calculated if the resultant carbon had a graphitic-like structure. Computational chemistry was used to investigate the nature of lithium bonding in a carbon lattice unlike graphite. The lithium intercalated fullenere Lin-C60 was used as a model for our (non-graphitic) disordered carbon lattice. A dilithium-C60 system with a charge and multiplicity of (0,1) and a trilithium-C60 system with a charge and multiplicity of (0,4) were investigated. The spatial distribution of lithium ions in an electrochemical cell containing this novel disordered carbon material was investigated in situ by Li-7 NMR using an electrochemical cell that was incorporated into a toroid cavity nuclear magnetic resonance (NMR) imager. The concentration of solvated Li+ ions in the carbon anode appears to be larger than in the bulk electrolyte, is substantially lower near the copper/carbon interface, and does not change with cell charging.

Quantitative in situ hot-stage high-resolution Transmission Electron Microscopy

1994 ◽  
Vol 52 ◽  
pp. 758-759
Author(s):  
J. M. Howe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Interfacial Structure ◽  
Interface Motion ◽  
Charge Coupled Device ◽  
Transmission Electron ◽  
Interface Theory ◽  
A Charge

In situ hot-stage high-resolution transmission electron microscopy (HRTEM) provides unique capabilities for quantifying the dynamics of interfaces at the atomic level. Such information complements detailed static observations and calculations of interfacial structure, and is essential for understanding interface theory and solid-state phase transformations. This paper provides a brief description of particular requirements for performing in situ hot-stage HRTEM and illustrates the use of this technique to obtain quantitative data on the atomic mechanisms and kinetics of interface motion during precipitation of {111} θ phase in an Al-Cu-Mg-Ag alloy.The specimen and microscope requirements for in situ hot-stage HRTEM are not much different from those of static HRTEM, except that one must have a heating holder and equipment for recording and analyzing dynamic images. At present, most HRTEMs are equipped with a TV-rate camera, possibly combined with a charge-coupled device camera. An inexpensive way to record in situ HRTEM images is to send the output from the TV-rate camera directly into a standard VHS format videocassette recorder (VCR).

Cascade charge transfer mediated by in situ interface modulation toward solar hydrogen production

2019 ◽  
Vol 7 (15) ◽  
pp. 8938-8951 ◽  
Author(s):  
Yu-Bing Li ◽  
Tao Li ◽  
Xiao-Cheng Dai ◽  
Ming-Hui Huang ◽  
Yunhui He ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Hydrogen Production ◽  
Hydrogen Generation ◽  
Solar Hydrogen ◽  
Photocatalytic Hydrogen Generation ◽  
Visible Light Driven ◽  
Solar Hydrogen Production ◽  
A Charge ◽  
Interface Modulation

An in situ phase self-transformation combined with an exquisite interface modulation was developed to trigger a charge transfer cascade for visible-light-driven photocatalytic hydrogen generation.

Sign in / Sign up

Export Citation Format

Share Document