1,064 research outputs found
Ăvolution temporelle de lâenvasement des retenues de barrages de Tunisie
La mobilisation et lâexploitation des eaux de surface sont des pratiques anciennes en Tunisie. Les amĂ©nagements rĂ©alisĂ©s au cours du siĂšcle dernier sont exposĂ©s Ă un alluvionnement plus ou moins accĂ©lĂ©rĂ©. La capacitĂ© de stockage des retenues des barrages est sujette Ă une rĂ©duction progressive au cours du temps. Cette perte de capacitĂ©, parfois Ă©levĂ©e, dĂ©passe les prĂ©visions de lâalluvionnement de la retenue. La quantification des sĂ©diments piĂ©gĂ©s se base soit sur les bilans de matiĂšre solide Ă lâĂ©chelle dâune retenue, soit sur des levĂ©s bathymĂ©triques ou topographiques. Les ModĂšles NumĂ©riques de Terrain (MNT) des retenues sont de plus en plus utilisĂ©s. Les diffĂ©rentes Ă©valuations sont entachĂ©es dâune incertitude. Les retenues des barrages tunisiens perdent annuellement 0,5 % Ă 1 % de leur capacitĂ© par alluvionnement. Lâanalyse des rĂ©sultats de mesures montre que lâalluvionnement est liĂ© Ă lâhydrologie du cours dâeau, Ă la gestion de la rĂ©serve dâeau et aux manoeuvres de dĂ©vasement. La comparaison entre les rĂ©sultats de mesures de lâalluvionnement et les prĂ©visions des projets met en Ă©vidence des diffĂ©rences parfois relativement importantes qui sont dues au rĂ©gime hydrologique des cours dâeau. En effet, une crue exceptionnelle peut provoquer un alluvionnement nettement supĂ©rieur Ă la moyenne annuelle en rĂ©gime hydrologique normal. Les retenues mĂ©andriformes sont comblĂ©es rapidement alors que les retenues linĂ©aires offrent la possibilitĂ© de soutirage de quantitĂ©s importantes de sĂ©diments. Les moyennes annuelles des pertes de capacitĂ© des barrages en exploitation et des barrages projetĂ©s jusquâĂ 2010 permettent de quantifier les volumes des sĂ©diments piĂ©gĂ©s Ă 500 Mm3. En 2030, la perte de capacitĂ© de stockage des barrages en exploitation pourrait atteindre 43 % de leur capacitĂ© initiale. Les amĂ©nagements amont et les travaux de conservation des eaux et des sols permettent de rĂ©duire le taux dâalluvionnement et de prolonger la durĂ©e de vie des grands rĂ©servoirs.The mobilization and exploitation of surface water are ancient practices in Tunisia. Installations carried out during last century are exposed to a greater or lesser degree of accelerated silting. The storage capacity of reservoirs is progressively reduced over the course of time. This sometimes accelerated loss of capacity of reserves by silting exceeds the forecasts of hydraulic installation projects. The quantification of trapped sediments is based on the assessment of a reservoirâs retained solid matter, either by bathymetric or topographic rising or by Digital Models of Grounds (DMG) corresponding to different dates. These various evaluations of the sediments trapped in reservoirs are, however, sullied with uncertainty. Tunisian reservoirs lose 0.5% to 1% of their storage capacity to silting annually. The analysis of the results presented in this study shows that silting is related to three factors: river hydrology, water reserve management and dredging operations. The comparison between the silting results and the project forecasts highlights relatively significant differences which may be due to river hydrology. Indeed a significant rising in water level can cause an increase in silting above the annual average found during normal hydrological modes. While meandering reservoirs are quickly filled with sediment, linear reservoirs can undergo dredging to remove a significant quantity of sediment. The annual averages in storage capacity losses of the dam under exploitation and its projections up to the year 2010 enable us to quantify the volumes of the sediment trapped as 500 Mm3. In 2030, the loss of storage capacity of the studied reservoirs may reach 43% of their initial storage capacities. Installations upstream and soil and water conservation efforts may reduce the rate of silting and prolong the lifespan of large dams
Potentialités androgénétiques du palmier dattier Phoenix dactylifera L. et culture in vitro d'anthÚres
Genetic potentialities if five male date palm genotypes, and in vitro culture of anthers. The experimental results derived from the study of five date palm (Phoenix dactylifera L.) genotypes indicate that the ability of microspores to divide varies with genotype and culture medium. The highest frequency of microspore division is obtained with the induction medium [Murashige and Skoog (MS 1962) mineral elements, 2,4-dichlorophenoxyacetique (2,4-D), 2-isopentenylaminopurine (2-IP)] containing activated charcoal. The pollinator T106 was considered as the most efficient genotype in our experimentatio
Room temperature Giant Spin-dependent Photoconductivity in dilute nitride semiconductors
By combining optical spin injection techniques with transport spectroscopy
tools, we demonstrate a spin-photodetector allowing for the electrical
measurement and active filtering of conduction band electron spin at room
temperature in a non-magnetic GaAsN semiconductor structure. By switching the
polarization of the incident light from linear to circular, we observe a Giant
Spin-dependent Photoconductivity (GSP) reaching up to 40 % without the need of
an external magnetic field. We show that the GSP is due to a very efficient
spin filtering effect of conduction band electrons on Nitrogen-induced Ga
self-interstitial deep paramagnetic centers.Comment: 4 pages, 3 figure
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Investigating Trainee Perspectives on Virtual Reality Environments: An In-Depth Examination of Immersive Experiences with Haptic Feedback Vibration
This research investigates trainee reflections on Virithin Reality Environments (VREs) within educational training centers, aiming to understand their experiences, perceptions, and preferences. The study focuses on the impact of haptic feedback vibrations, examining both their general effects during VRE interactions and the specific influence of adaptable vibration configurations triggered by user errors. A convenience sample of 81 participants/trainees, 41 from the computer science and 40 from the aviation engineering departments of a major higher education institution in the U.A.E., was used to run four variations of the same VRE, with two from each field. Results indicate that participants largely embraced the VRE experience, reporting feelings of contentment, joy, and competence. Haptic feedback, particularly in non-adaptable forms, was acknowledged as enhancing the immersive experience. However, the study suggests that further research is needed to explore the nuanced role of adaptable vibration, especially in more complex interactions. Notably, participants expressed a preference for a blended approach, advocating for both VREs and physical labs in their training. The study acknowledges limitations, such as the predominantly single-user focus, and recommends future research extensions into collaborative VRE settings, more intricate interactions, and potential technical issues in multi-user scenarios. Overall, this research sheds light on the evolving landscape of educational training, emphasizing the importance of understanding trainee perspectives to optimize the integration of VREs in learning environment
Building a collaborative culture in cardiothoracic operating rooms: Pre and postintervention study protocol for evaluation of the implementation of teamSTEPPS training and the impact on perceived psychological safety
IntroductionThe importance of effective communication, a key component of teamwork, is well recognised in the healthcare setting. Establishing a culture that encourages and empowers team members to speak openly in the cardiothoracic (CT) operating room (OR) is necessary to improve patient safety in this high-risk environment.Methods and analysisThis study will take place at Barnes-Jewish Hospital, an academic hospital in affiliation with Washington University School of Medicine located in the USA. All team members participating in cardiac and thoracic OR cases during this 17-month study period will be identified by the primary surgical staff attending on the OR schedule.TeamSTEPPS (Team Strategies and Tools to Enhance Performance and Patient Safety) training course will be taught to all CT OR staff. Before TeamSTEPPS training, staff will respond to a 39-item questionnaire that includes constructs from the Agency for Healthcare Research and Quality Hospital Survey on Patient Safety Culture, Edmondsonâs âMeasure of psychological safetyâ questionnaire, and questionnaires on turnover intentions, job satisfaction and âburnoutâ. The questionnaires will be readministered at 6 and 12 months.The primary outcomes to be assessed include the perceived psychological safety of CT OR team members, the overall effect of TeamSTEPPS on burnout and job satisfaction, and observed turnover rate among the OR nurses. As secondary outcomes, we will be assessing self-reported rates of medical error and near misses in the ORs with a questionnaire at the end of each case.Ethics and disseminationEthics approval is not indicated as this project does not meet the federal definitions of research requiring the oversight of the Institutional Review Board (IRB). Patient health information (PHI) will not be generated during the implementation of this project. Results of the trial will be made accessible to the public when published in a peer-reviewed journal following the completion of the study.</jats:sec
Birefringence in nonlinear anisotropic dielectric media
Light propagation is investigated in the context of local anisotropic
nonlinear dielectric media at rest with the dielectric coefficients
and constant ,
in the limit of geometrical optics. Birefringence was examined and the general
conditions for its occurrence were presented. A toy model is exhibited, in
which uniaxial birefringent media with nonlinear dielectric properties could be
driven by external fields in such way that birefringence may be artificially
controlled. The effective geometry interpretation is also addressed.Comment: 5 pages, 1 figur
Simulation of resonant tunneling heterostructures: numerical comparison of a complete Schr{ö}dinger-Poisson system and a reduced nonlinear model
Two different models are compared for the simulation of the transverse electronic transport through an heterostructure: a self-consistent Schr{ö}dinger-Poisson model with a numerically heavy treatment of resonant states and a reduced model derived from an accurate asymptotic nonlinear analysis. After checking the agreement at the qualitative and quantitative level on quite well understood bifurcation diagrams, the reduced model is used to tune double well configurations for which nonlinearly interacting resonant states actually occur in the complete self-consistent model
Second order averaging for the nonlinear Schroedinger equation with strongly anisotropic potential
International audienceWe consider the three dimensional Gross-Pitaevskii equation (GPE) describing a Bose-Einstein Condensate (BEC) which is highly confi ned in vertical z direction. The highly confi ned potential induces high oscillations in time. If the confi nement in the z direction is a harmonic trap (which is widely used in physical experiments), the very special structure of the spectrum of the confi nement operator will imply that the oscillations are periodic in time. Based on this observation, it can be proved that the GPE can be averaged out with an error of order of epsilon, which is the typical period of the oscillations. In this article, we construct a more accurate averaged model, which approximates the GPE up to errors of order epsilon squared. Then, expansions of this model over the eigenfunctions (modes) of the vertical Hamiltonian Hz are given in convenience of numerical application. Effi cient numerical methods are constructed for solving the GPE with cylindrical symmetry in 3D and the approximation model with radial symmetry in 2D, and numerical results are presented for various kinds of initial data
Building an XML document warehouse
International audienceData Warehouses and OLAP (On Line Analytical Processing) technologies are dedicated to analyzing structured data issued from organizations' OLTP (On Line Transaction Processing) systems. Furthermore, in order to enhance their decision support systems, these organizations need to explore XML (eXtensible Markup Language) documents as an additional and important source of unstructured data. In this context, this paper addresses the warehousing of document-centric XML documents. More specifically, we propose a two-method approach to build Document Warehouse conceptual schemas. The first method is for the unification of XML document structures; it aims to elaborate a global and generic view for a set of XML documents belonging to the same domain. The second method is for designing multidimensional galaxy schemas for Document Warehouses
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