Littérature scientifique sur le sujet « Zero mode Laser »
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Articles de revues sur le sujet "Zero mode Laser"
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Yan, Qin, Jian Lu et Xiao Wu Ni. « Measurement of the Transient Velocity of Nanoparticles in Flowing Nanofluids by Using the Method of Dynamic Laser Speckles ». Applied Mechanics and Materials 226-228 (novembre 2012) : 1852–57. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.1852.
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Experimental equipments are designed for the zero-crossing method of dynamic laser speckles to investigate the moving nature of nanoparticles in flowing nanofluids. After the experiments the velocity of nanoparticles in flowing nanofluids is determined according to its relationship with the zero-crossing rate of speckle intensity fluctuation. The results show that the zero-crossing rate is very sensitive to the velocity of nanoparticles when the velocity of nanofluids ranges from 17.6 mm/s to 60.2 mm/s. A TEM10 mode–like laser beam is designed and taken as an incident light to detect the moving direction of nanoparticles in flowing nanofluids. The moving direction of nanoparticles is parallel to the horizontal axis of the TEM10 mode-like laser beam when the zero-crossing rate reaches maximum. Experimental results show that the moving direction of nanoparticles can also be detected by using the zero-crossing method.
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Kolbas, Yu Yu, et M. A. Ivanov. « Improved Algorithm for Mathematical Correction of the Zero Drift of the Zeeman Laser Gyro with Switching Longitudinal Mode of Generation ». Herald of the Bauman Moscow State Technical University. Series Instrument Engineering, no 2 (125) (avril 2019) : 91–103. http://dx.doi.org/10.18698/0236-3933-2019-2-91-103.
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The paper addresses time and temperature zero drifts in Zeeman laser gyroscope (RLG) operating in the mode of periodic adjustment of RLG to the longitudinal mode of generation with the opposite circular polarization of the light wave. In such a gyroscope, the zero drift can be divided into magnetic and non-magnetic components having different nature and making a significantly different contribution to the final error. Algorithmic methods are proposed for mathematical compensation of RLG zero drift, both with and without using initial calibration. It is shown that the simultaneous use of reproducible dependencies of the magnetic and non-magnetic zero drifts due to RLG temperature changes allows solving the problem of RLG zero drift correction in the optimal way. The correction factors are calculated from the temperature of a Zeeman laser gyro at the moment of activation. At the same time, using the difference between the temperatures of the gyroscope and gyro case, where it is installed, it is possible to determine the temperature of the Zeeman laser gyroscope at the moment of switching on, thereby eliminating the problem of calculating the correction factors when the gyroscope is turned off and then on again. Experimental results for several Zeeman laser gyroscopes with typical values of zero drifts are presented
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Zakharyash, V. F., V. M. Klement’ev et E. A. Titov. « Forced mode locking in a semiconductor laser ». Journal of Physics : Conference Series 2067, no 1 (1 novembre 2021) : 012005. http://dx.doi.org/10.1088/1742-6596/2067/1/012005.
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Abstract A brief description of the theory of mode locking of a semiconductor laser when the modulating generator frequency is close to the intermode frequency is given. It is shown that during mode locking there is phase locking, due to which the dispersion of summed intensity in the interpulse interval tends to zero.
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Bourcier, Roy J. « Near-Zero Shift Attachment for Optoelectronic Components ». International Symposium on Microelectronics 2011, no 1 (1 janvier 2011) : 001058–66. http://dx.doi.org/10.4071/isom-2011-tha5-paper3.
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High performance laser-based optoelectronic devices commonly feature the use of free-space optical coupling between the laser diode and optical elements such as filters, secondary harmonic generators and optical fibers. A critical challenge in the assembly of such components is maintaining the required optical alignment precision during attachment of the optical subcomponents to a common platform. In the case of devices based on single mode waveguides, the post-attach shift must often be held to less than a few hundred nanometers to achieve the desired optical coupling efficiency. Historically, these tight tolerances have required the use of costly post-work operations such as laser hammering or re-bend to achieve performance objectives. Over the course of designing several such optoelectronic components, we have used and developed a variety of design concepts and assembly processes which have allowed us to achieve these demanding tolerances, often without the use of post-work. UV-curable structural adhesives and Nd:YAG laser spot welding have been used, individually and in combination, to perform the required sub-micron optomechanical attachments. Several approaches which have been successfully used will be described and their relative merits will be compared. In addition, key design and process elements which can impact post-attach shift will be discussed.
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Clorennec, Dominique, Claire Prada, Daniel Royer et Todd W. Murray. « Laser impulse generation and interferometer detection of zero group velocity Lamb mode resonance ». Applied Physics Letters 89, no 2 (10 juillet 2006) : 024101. http://dx.doi.org/10.1063/1.2220010.
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Lee, Seung Seok, et Sang Whoe Dho. « Suppressing Technique of the Antisymmetric Mode by the Superposition of Lamb Waves Generated by Two Laser Beams in a Thin Plate ». Key Engineering Materials 321-323 (octobre 2006) : 103–7. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.103.
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We present a suppressing technique of the antisymmetric mode by superposition of Lamb waves generated by two laser beams in a thin plate. Two Lamb waves of the same frequency propagating from the opposite direction simultaneously arrive at the point of measurement and are superposed to compose one Lamb wave. The amplitude of the superposed Lamb wave depends on the distance between two laser beams. The suppressing of antisymmetric Lamb wave mode is accomplished by selecting the distance between two beams which simultaneously satisfies the condition of the anti-node(maximum) for the symmetric mode and the minimum for the antisymmetric mode. By this method, the antisymmetric Lamb wave mode is suppressed to the degree of 1.4% of the amplitude measured at zero distance between two beams.
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Cattarusa, Douglas Alan, Xiao Min Jin, Xing Xing Fu, Xiang Ning Kang, Bei Zhang et Guo Yi Zhang. « Optical-Mode Study of Galium Nitrate Based Laser Diodes ». Advanced Materials Research 571 (septembre 2012) : 476–81. http://dx.doi.org/10.4028/www.scientific.net/amr.571.476.
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This paper focuses on the optical mode analysis of laser diodes to improve light emission. Under the mode analysis, we compare the optical confinement factor (OCF) percentage of the emitting light from the LDs. There are two structures which we analyze: a basic GaN waveguide structure and an InGaN waveguide structure. The second structure has additional InGaN waveguides and is analyzed under two additional design variations: the concentration of Indium and the thickness of the top waveguide layer. The results of this study indicate introducing InGaN waveguide layers correlates with lower order modes (zero and first order) and increase the OCF values. The top InGaN waveguide layer, which has a higher concentration of Indium, appears to increase the OCF. However, the increased thickness of the InGaN layer causes the lower modes’ OFC to decrease. Over all, in the best case, InGaN LD has an OCF of 1.8896%, which is about a 312% improvement compared to that of GaN LD ( OCF=0.4535%).
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Hoare, R., R. Mardling et GJ Troup. « Intensity Correlation Functions for 'Thermalised' TEMn0 Laser Beams ». Australian Journal of Physics 39, no 4 (1986) : 505. http://dx.doi.org/10.1071/ph860505.
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A well-stabilised, single mode laser beam will give zero intensity correlation. However, a laser beam may be 'thermalised' by shining it on a rotating ground glass disc, and then intensity correlation experiments will give nonzero results. We present here calculations of the intensity correlation functions of the TEMlO, TEM20, TEM30 and TEM40 Gaussian-Hermite beams. We were led to perform these calculations by the results of intensity correlation measurements on a laser with 'butted-on' mirrors nearing the end of its useful life.
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Debnath, Pulak Chandra, et Dong-Il Yeom. « Ultrafast Fiber Lasers with Low-Dimensional Saturable Absorbers : Status and Prospects ». Sensors 21, no 11 (25 mai 2021) : 3676. http://dx.doi.org/10.3390/s21113676.
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Wide-spectral saturable absorption (SA) in low-dimensional (LD) nanomaterials such as zero-, one-, and two-dimensional materials has been proven experimentally with outstanding results, including low saturation intensity, deep modulation depth, and fast carrier recovery time. LD nanomaterials can therefore be used as SAs for mode-locking or Q-switching to generate ultrafast fiber laser pulses with a high repetition rate and short duration in the visible, near-infrared, and mid-infrared wavelength regions. Here, we review the recent development of emerging LD nanomaterials as SAs for ultrafast mode-locked fiber laser applications in different dispersion regimes such as anomalous and normal dispersion regimes of the laser cavity operating in the near-infrared region, especially at ~1550 nm. The preparation methods, nonlinear optical properties of LD SAs, and various integration schemes for incorporating LD SAs into fiber laser systems are introduced. In addition to these, externally (electrically or optically) controlled pulsed fiber laser behavior and other characteristics of various LD SAs are summarized. Finally, the perspectives and challenges facing LD SA-based mode-locked ultrafast fiber lasers are highlighted.
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Harb, MS, et FG Yuan. « Barely visible impact damage imaging using non-contact air-coupled transducer/laser Doppler vibrometer system ». Structural Health Monitoring 16, no 6 (28 novembre 2016) : 663–73. http://dx.doi.org/10.1177/1475921716678921.
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The aim of this study is to investigate the capability of the zero-lag cross-correlation imaging condition of an A0 Lamb wave mode in imaging a barely visible impact damage in a carbon fiber–reinforced polymer composite using a fully non-contact-guided wave-based non-destructive inspection system. A 16-ply (45/0/-45/90)2s carbon fiber–reinforced polymer laminate was impacted at three different locations with different impact energies using a drop ball at three drop heights causing three barely visible impact damages with different sizes. The A0 Lamb wave mode is generated inside the laminate using a circular air-coupled transducer and detected along the damaged region using a laser Doppler vibrometer. The measured wavefield is then decomposed into a forward and backward propagating wavefields by applying a frequency–wavenumber filtering post-processing technique. The decomposed wavefields are then cross-correlated in the frequency domain using zero-lag cross-correlation imaging condition producing a detailed cumulative damage image. The images obtained in frequency domain highlight the three damaged areas with higher zero-lag cross-correlation values compared to other parts of the inspected areas. The experimental investigation has shown a good correlation between the zero-lag cross-correlation imaging condition and C-scan images, which demonstrate a strong capability of guided wave zero-lag cross-correlation imaging condition technique in approximating the location and size of relatively small barely visible impact damages in thin composite structures.
Thèses sur le sujet "Zero mode Laser"
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Ji, Kaiwen. « Exceptional Points Bifurcations and Zero Mode Lasing in Coupled Nanolaser Arrays ». Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP167.
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La conservation de l'énergie façonne notre compréhension de la réalité. Néanmoins, ce principe peut être violé lorsqu’on considère un sous-système où l'énergie peut être échangée avec l'environnement externe. Un tel scénario physique peut être décrit par un Hamiltonien non-Hermitien présentant un spectre d'énergies complexes. L'étude des systèmes non-Hermitiens a connu des avancées remarquables depuis la découverte de la symétrie Parité-Temps (PT). Dans un tel système PT-symétrique, une singularité, appelée point exceptionnel (EP), a récemment suscité une attention considérable. Dans les systèmes optiques avec des composants gain/pertes, les points exceptionnels sont généralement définis sous le seuil de laser, spécifiquement dans le régime linéaire. En revanche, les dynamiques complexes liées aux points exceptionnels au-dessus du seuil laser n'ont pas encore été explorées. Dans la première partie de cette thèse, nous démontrons, à la fois théoriquement et expérimentalement, que les singularités EP dans des nanolasers couplés à cristal photonique en semi-conducteurs III-V peuvent être approchées au-dessus du seuil de laser, où elles deviennent des points de bifurcation non linéaires. Contrairement à l’idée préconçue selon laquelle le désaccord de cavité empêche la formation des EPs, nous montrons que, dans le contexte des systèmes lasers à semi-conducteurs, un tel désaccord est essentiel pour compenser le décalage de fréquence induit par les porteurs de charge. Le suivi continu du point exceptionnel en régime laser est rendu possible grâce à des expériences de photoluminescence avec une distribution spatiale contrôlable du faisceau de pompe. La deuxième partie de cette thèse aborde la mise en œuvre des mode zéro laser, qui attirent une attention considérable en raison de leur protection par la symétrie ou la topologie des réseaux : il s’agit du domaine des lasers topologiques. Le mode zéro en régime laser est d'abord démontré dans un système à trois nanocavités couplées (trimère) avec un pompage quasi égal sur les deux cavités extrêmes. Néanmoins, les modes zéro photoniques conventionnels, distingués par une émission en opposition de phase une distribution d'intensité confinée aux bords du système (edge modes), limitent considérablement leur applicabilité. Nous pallions à ces deux limitations par la technique d'ingénierie image-barrière d’une part, et la non-Hermiticité d’autre part. La première peut inverser le signe du couplage inter-cavité et générer un mode zéro en accord de phase; la seconde peut réaliser un mode zéro dans le volume (bulk) grâce à la restauration spontanée de la symétrie particule-trou non-Hermitienne. Enfin, nous explorons l'émergence à la fois des EP et du mode zéro dans une structure bidimensionnelle comprenant quatre nanolasers couplés disposés en anneau. La symétrie chirale non-Hermitienne génère un mode zéro à travers la coalescence des modes au niveau du EP, qui est ensuite stabilisée par une saturation non linéaire. De manière surprenante, les modes zéro au EP présentent une singularité de phase, à l’origine d’un vortex optique, observé expérimentalement à l'aide d’un interféromètre de Sagnac. Cette thèse se conclut par la présentation d'une application intrigante du mode zéro : le calcul optique. Nous démontrons, tant théoriquement qu’expérimentalement, que nos nanolasers peuvent exécuter des tâches de classification non triviales, qui s’avèrent difficiles pour une structure de calcul en réseau neuronal à une seule couche. Nous montrons que la couche complexe de nanolasers améliore considérablement la précision de calcul, notamment pour une faible dimensionalité des données d’entréeEnergy conservation shapes our understanding of reality. Nevertheless, this principle is no longer applicable when analyzing a subsystem where energy is exchanged with an external environment. Such a physical scenario can be described by a non-Hermitian Hamiltonian that exhibits a complex-energy spectrum. The investigation of non-Hermitian systems has undergone remarkable advancement since the discovery of Parity Time (PT) symmetry. In a PT symmetric system, a singularity, referred to as an exceptional point (EP), has recently attracted significant attention. In optical systems with gain/loss components, EPs are typically defined below the lasing threshold, specifically in the linear regime. Still, the complex dynamics related to EP above the lasing threshold are yet to be investigated. In the first part of this thesis, we both theoretically and experimentally demonstrate that EP singularities in coupled III-V semiconductor photonic crystal nanolasers can be accessed above the lasing threshold, where they become nonlinear branch points. Contrary to the common belief that the cavity detuning prohibits the formation of EPs, we point out that, in the context of the semiconductor laser system, such detuning is essential for compensating the carrier-induced frequency shift. Continuous tracking of the lasing EP is enabled by unbalanced pumping photoluminescence experiments. The second part of this thesis addresses the implementation of lasing zero modes, which receive considerable attention due to their symmetry or topology protected characteristics: a research domain called topological lasers. The lasing regime of the zero mode is first demonstrated in a photonic trimer system with nearly equal pumping for the two extreme cavities. Nonetheless, the conventional photonic zero modes, distinguished by their out-of-phase emission and the boundary-confined intensity distribution, significantly restrict their applications. We tackle the two aforementioned limitations by the barrier-image engineering technique and the non-Hermiticity. The former can flip the sign of the inter-cavity coupling and generate an in-phase zero mode; the latter can leverage a bulk zero mode through the spontaneous restoration of non-Hermitian particle-hole symmetry. In order to address zero modes in larger coupled-cavity arrays, we investigate the emergence of both EP and zero modes in a two-dimensional structure including four coupled nanolasers arranged in a ring. The non-Hermitian chiral symmetry generates a zero mode through a collision of modes at the EP, which is further stabilized by nonlinear saturation. Interestingly, the modes at EP exhibit a phase singularity, resulting in an optical vortex, which is experimentally observed using near-field interference. This thesis concludes with the presentation of an intriguing application of the zero mode: optical computing capabilities. We demonstrate both theoretically and experimentally that our nanolasers can address non-trivial classification tasks, which prove to be challenging for a single-layer neural network architecture. The complex nanolaser layer markedly enhances computing accuracy, particularly for low dimensional input datasets
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Yan, Guqi. « Zero-group-velocity Lamb modes in laser ultrasonics : fatigue monitoring and material characterization ». Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1026/document.
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Ces dernières années, les modes de Lamb à vitesse de groupe nulle (ZGV) se sont révélés être un outil efficace pour sonder localement et précisément l'épaisseur d'un échantillon ou les propriétés mécaniques de matériaux isotropes ou anisotropes. Ce type particulier d'ondes guidées, telles de fortes résonances locales de la structure, résulte de l'interférence de deux ondes de Lamb ayant une vitesse de phase opposée et coexistant pour un couple fréquence-nombre d'ondes particulier. Les ultrasons laser ont démontré leur capacité à générer et détecter efficacement de telles résonances locales dans la gamme des MHz. En effet, la configuration tout optique, constituée d'une source laser pulsée pour générer les ondes élastiques et d'un interféromètre pour sonder le déplacement normal associé, évite tout contact avec l'échantillon, limitant ainsi l'élargissement ou la suppression de résonances. L'utilisation de modes ZGV pour suivre la fatigue des matériaux et sonder des phénomènes non linéaires reste cependant un défi et constitue le cœur des travaux de recherche présentés ici. La partie théorique porte sur la compréhension de l’effet de la fatigue mécanique sur les modes ZGV à travers l’analyse fréquence-nombre d’ondes des modes de Lamb. La partie expérimentale est consacrée à l’application de cette technique pour l'ECND et le suivi de la fatigue de plaques métalliques minces. Les modes ZGV en ultrasons laser montrent un grand potentiel pour localiser les dommages dus à la fatigue, prédire la vie en fatigue et évaluer qualitativement, voire quantitativement, les différents stades de dommages causés par la fatigueIn recent years, zero-group-velocity (ZGV) Lamb modes have proven to be an efficient tool to probe locally and very accurately the thickness of a sample or the mechanical properties of either isotropic or anisotropic materials. This particular type of guided waves, corresponding to sharp local resonances of the structure, results of the interference of two Lamb waves having opposite phase velocity and coexisting at a couple given frequency-wavenumber. The laser ultrasonic technique has demonstrated its ability to efficiently generate and detect such local resonances within the MHz frequency range. Indeed, the all-optical setup, consisting of a pulsed laser source to generate elastic waves and of an interferometer to probe the associated normal displacement, avoids any contact with the sample, hence limiting the broadening or suppression of the resonances. Yet, the use of ZGV Lamb modes to monitor material fatigue and to probe nonlinear phenomena remains challenging and is the core of the here-reported research. The theoretical part of this PhD research deals with the understanding of the effect of mechanical fatigue on ZGV Lamb modes through the frequency-wavenumber analyzes of the Lamb waves. The experimental part of the PhD research is dedicated to the application of this technique for the nondestructive characterization and for the monitoring of mechanical and thermal fatigue of thin metal plates. Zero-group-velocity Lamb modes in laser ultrasonics shows great promises to locate fatigue damage, to predict the fatigue lifetime, and to qualitatively, and even quantitatively, assess the different stages of fatigue damage in m- to potentially cm-thick solid plates
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Matthews, Desjanelle. « Dimethyl sulfide oxidation in the polluted marine boundary layer : a zero dimensional model study ». Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29455.
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A comprehensive DMS oxidation reaction mechanism was added to a chemical box model (Model of Chemistry Considering Aerosols - MOCCA) to investigate how atmospheric sulfate levels are affected by pollution in the marine boundary layer. The interaction of a remote air mass with a polluted coastal air mass containing elevated NOx, alkane, and alkene levels was simulated for a mid-latitude region of the Northern Hemisphere. Model runs from different settings were compared with respect to species concentrations, branching ratios, and product yields. Results showed moderate decreases in gas phase DMS, DMSO, DMSO2, and MSA concentrations, and increases of approximately 7% and 100% for SO2 and H2SO4 , respectively. A sensitivity analysis was completed to determine how variations in temperature, DMS emission, NO emission, aerosol characterization, accommodation coefficients, PAN reactions, and a background SO2 emission influence the results.
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Meziane, Bilel. « Film thickness build-up in highly loaded lubricated contacts under Zero Entrainment Velocity condition ». Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI005.
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Les contacts lubrifiés sous forte charge sont souvent étudiés dans des conditions de roulement/glissement. Dans ces cas, l’entrainement du lubrifiant dans un coin d’huile explique la présence d’un film séparateur. Cependant, il existe un certain nombre d’applications dans lesquelles les surfaces en contact ont des vitesses égales et opposées. Cela correspond à une vitesse d’entrainement (définie comme la moyenne des vitesses des deux surfaces) nulle. Dans ce cas, les modèles prédictifs de la littérature ne peuvent plus s’appliquer. Dans ce mémoire de thèse, les phénomènes physiques conduisant à une génération de film séparateur à vitesse d’entrainement nulle sont étudiés. Un modèle éléments finis prenant en compte les aspects thermiques et transitoires est mis en œuvre pour mesurer les quantités locales. En régime stationnaire, les résultats numériques sont comparés avec un très bon accord à un jeu de données issu d’une campagne d’expérimentations dédiée. Cette approche duale permet de quantifier l’influence de la charge, de la vitesse des surfaces et de la température externe sur l’épaisseur de film à vitesse d’entrainement nulle. Les contacts sont ensuite étudiés sous une charge variable, ce qui montre l’influence relative des phénomènes thermiques et transitoires pouvant générer une épaisseur de film. En fonction du ratio entre le temps caractéristique de chargement et le temps caractéristique d’échauffement, ces effets peuvent montrer une synergie bénéfique pour le contactHighly loaded lubricated contacts are often studied in rolling/sliding conditions. In those cases, the entrainment of lubricant in a so-called “oil wedge” explains the existence of a separating film thickness. However, in a number of industrial applications, the contact is subjected to opposite surface velocities. In such cases, there is a Zero Entrainment Velocity (defined as the average velocity of the two surfaces) of the fluid. The film thickness prediction formulae developed in the literature for rolling contacts are unusable. In this thesis, the physical phenomena leading to a film build-up under Zero Entrainment Velocity condition are elucidated. A finite element model is used in order to facilitate in-situ measurements. It aims to describe the behaviour of the contact in thermal and transient conditions. In the stationary regime, the numerical values are compared with a very good agreement to a set of results obtained via a tailored experimental campaign. This dual approach enables a quantitative description of the influence of the contact load, surface velocities and external temperature on the film thickness under ZEV condition. Then, the relative influence of the thermal and squeeze effects is studied. Depending on the ratio between the characteristic loading time and the characteristic thermal time, these two effects can show a beneficial synergy for the contact
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von, Stillfried Florian. « Computational fluid-dynamics investigations of vortex generators for flow-separation control ». Doctoral thesis, KTH, Turbulens, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94879.
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Many flow cases in fluid dynamics face undesirable flow separation due to ad-verse pressure gradients on wall boundaries. This occurs, for example, due togeometrical reasons as in a highly curved turbine-inlet duct or on flow-controlsurfaces such as wing trailing-edge flaps within a certain angle-of-attack range.Here, flow-control devices are often used in order to enhance the flow and delayor even totally eliminate flow separation. Flow control can e.g. be achieved byusing passive or active vortex generators (VGs) for momentum mixing in theboundary layer of such flows. This thesis focusses on such passive and activeVGs and their modelling for computational fluid dynamics investigations. First, a statistical VG model approach for passive vane vortex genera-tors (VVGs), developed at the Royal Institute of Technology Stockholm andthe Swedish Defence Research Agency, was evaluated and further improvedby means of experimental data and three-dimensional fully-resolved computa-tions. This statistical VVG model approach models those statistical vortexstresses that are generated at the VG by the detaching streamwise vortices.This is established by means of the Lamb-Oseen vortex model and the Prandtllifting-line theory for the determination of the vortex strength. Moreover, thisansatz adds the additional vortex stresses to the turbulence of a Reynolds-stresstransport model. Therefore, it removes the need to build fully-resolved three-dimensional geometries of VVGs in a computational fluid dynamics mesh. Usu-ally, the generation of these fully-resolved geometries is rather costly in termsof preprocessing and computations. By applying VVG models, the costs arereduced to that of computations without VVGs. The original and an improvedcalibrated passive VVG model show sensitivity for parameter variations suchas the modelled VVG geometry and the VVG model location on a flat plate inzero- and adverse-pressure-gradient flows, in a diffuser, and on an airfoil withits high-lift system extracted. It could be shown that the passive VG modelqualitatively and partly quantitatively describes correct trends and tendenciesfor these different applications. In a second step, active vortex-generator jets (VGJs) are considered. They were experimentally investigated in a zero-pressure-gradient flat-plate flow atTechnische Universitä̈t Braunschweig, Germany, and have been re-evaluated for our purposes and a parameterization of the generated vortices was conducted. Dependencies of the generated vortices and their characteristics on the VGJsetup parameters could be identified and quantified. These dependencies wereused as a basis for the development of a new statistical VGJ model. This modeluses the ansatz of the passive VVG model in terms of the vortex model, theadditional vortex-stress tensor, and its summation to the Reynolds stress ten-sor. Yet, it does not use the Prandtl lifting-line theory for the determinationof the circulation but an ansatz for the balance of the momentum impact thatthe VGJ has on the mean flow. This model is currently under developmentand first results have been evaluated against experimental and fully-resolvedcomputational results of a flat plate without pressure gradient.QC 20120511
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Kaprielian, Leslie. « Modélisation 0D pour la combustion dans les moteurs à allumage commandé : développements en proche paroi et dans le front de flamme ». Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0012/document.
Texte intégralRésumé :
Depuis quelques années, les modèles 0D trouvent un regain d'intérêt auprès des motoristes. En effet, ces modèles, fournissant aisément un comportement thermodynamique du moteur, peuvent être couplés avec des outils de contrôle moteur. Néanmoins, leur précision doit être augmentée, pour répondre aux enjeux technologiques actuels. Dans les moteurs à allumage commandé, la flamme turbulente prémélangée est modélisée comme un ensemble de flammelettes cohérentes entre elles. Cette approche généraliste nécessite un traitement particulier en proche paroi, motivé par une modification de la structure de flamme due aux couches limites thermique et cinématique. Ce présent travail propose des approches de modélisations 0D de la combustion, en proche paroi et dans la zone réactionnelle de la flamme. Pour modéliser la combustion en proche paroi, la flamme est scindée en une contribution en propagation libre, et une contribution en interaction avec les parois. Chaque contribution est divisée en une zone de transport, dans laquelle l'entraînement des gaz frais est décrit, et une zone de réaction, dans laquelle la réaction de combustion est modélisée. L'ajout d'une zone de réaction en interaction avec les parois permet de modéliser un gradient de température et une réaction de combustion ralentie en proche paroi. Pour modéliser la zone réactionnelle, une discrétisation de la flamme en N zones de réaction indépendantes est proposée. Une plage de fonctionnement moteur a été simulée avec nos approches de modélisation, afin de quantifier la variabilité des paramètres de calibration. Pour ce faire, les modèles sont calibrés sur chaque point de fonctionnement, par une méthode de minimisation de l'erreur quadratique moyenne sur la loi de dégagement d'énergie. Des corrélations aisées de paramètres de calibration peuvent être établies, en fonction de paramètres moteurs. Les résultats de simulations, obtenus à partir de ces corrélations, sont satisfaisantsRecently, the interest for zero-dimensional models has increased. Indeed, these models provide easily the engines thermodynamic behavior and can be coupled with control tools. However, their accuracy must be improved to meet the current technological challenges. In the spark ignition engines, the premixed turbulent flame is modeled as a set of coherent flamelets. This approach requires special treatment near the walls, motivated by the modifications of the flame structure due to boundary layers. The present work proposes 0D modeling of combustion near the walls and in the reaction zone of the flame. To combustion model near the walls, the flame is divided into a free propagation contribution, and an interacting contribution with the walls. Each contribution is divided into a convective zone, wherein the entrainment of fresh gas is described, and a reaction zone, wherein the combustion reaction is modeled. Adding a reaction zone near the walls allows modeling a thermal gradient and a slower combustion reaction near the walls. To model the reaction zone, a flame discretization is made into several reaction zones. An engine operating range is simulated with our models, for quantifying the calibration parameters variability. To do this, models are calibrated on each operating point, by a method of minimization of the quadratic error on the heat released rate. Linear correlations can be found, depending on engines parameters. A good agreement between experimental data and simulation results is obtained with these parameters correlations
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Prudík, Jiří. « Model metropolitní optické sítě ». Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217666.
Texte intégralRésumé :
The purpose of this master’s thesis is foremost to provide a simple guide how to build elements of optical metropolitan area network. The basic model consists to sequence of construction, network topology, passive and active parts. The collection contains examples of alternative technology such as Wireless LAN with different frequency. The optical network construction based on optical cable, fibres, splices, trays, adapters, connectors and active parts for example a lot of media convertor models. After that there are demonstrating type of wavelength division multiplexer used in metropolitan area network – passive planar PCL splitter. One of the passive planar splitter are used to increase optical fibre channel. At the end of the collection a simplified examples of used measurements – optical time domain reflectometry and optical fibre transmission. Contains standard protocols or reflectogram. The conclusion of this thesis summarizes costs of FTTb (Fibre To The Building) model of optical metropolitan area network in Czech republic and future contribution for society.
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Pešl, Jiří. « Spínaný zdroj se spínáním při nulovém napětí ». Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242009.
Texte intégralRésumé :
Diploma thesis describes the design of an switched mode power supply with switching at zero voltage for driving the anode of Anode-layer type ion source. First aim of thesis is ion sources and specialy Anode-layer type of ion source in detail. Main aim of thesis are important aspects of the design of switching mode power supply, which comes later the detailed construction of an switched mode power supply with output voltage 2800 V at output power 2800 W.
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Che, Choi-hong, et 謝彩虹. « Preparation of Nanoscale Zero-Valent Iron Suspension and Its Transport Model in Saturated Soil Layer ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/52570937793649047962.
Texte intégralRésumé :
碩士國立臺灣大學
環境工程學研究所
96
Direct injection zero valent iron method has been widely used for treating chlorinated hydrocarbon contaminated groundwater aquifers. However, the efficiency decreases and the cost rises due to the poor spreading ability of iron particles in the subsurface environment. Therefore, if we can enhance the spreading ability of iron in porous media by adding surface modifier we may increase the applicability of iron particles. We used different stabilizing to produce nanoscale iron suspension by means of batch experiments. Also we evaluated the performance of the stabilizing dispersants. It was found that PAA can get the most stable suspension when the final concentration of PAA and total iron were both 5000 ppm. About 90% of the nano-particles remained in suspension for 28 days. The average particle sizes was 87 nm determined by ZetaSizer. Particle sizes were all found to be around 200 nm and the particles seemed to be wrapped in high oxide-containing stabilizing dispersants under the examination with SEM-EDS. Percolation rates of nanoscale iron particles through the soil was tested using column experiments. The percolation results for soil columns with depth of 10 cm, 20 cm and 30 cm were 75.6%, 61%, and 41%, respectively; and the decay coefficient (κ) of the suspended nanoscale iron particles per unit distance was 0.01 cm-1 A transport model of NZVI in saturated soil layer was constructed. The pore structure in soil layer was characterized by the constructed tube model. The absorbing situation of particle of soil surface was determined by trajectory analysis in the constricted tube. The modeling analyses and experimental results indicate that the prediction has over estimated the breakthrough concentration . Simulation value relatively conforms the experimental value when adjusting the diameter of the particles and considering Brownian forces.
Livres sur le sujet "Zero mode Laser"
1
P, Leonard B., et United States. National Aeronautics and Space Administration., dir. A modified mixing length turbulence model for zero and adverse pressure gradients. [Washington, DC] : National Aeronautics and Space Administration, 1994.
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Conley, J. M. A modified mixing length turbulence model for zero and adverse pressure gradients. [Washington, DC] : National Aeronautics and Space Administration, 1994.
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3
Ndaona, Chokani, et Langley Research Center, dir. Hypersonic boundary-layer stability experiments on a flared-cone model at angle of attack in a quiet wind tunnel. Hampton, Va : National Aeronautics and Space Administration, Langley Research Center, 1996.
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4
Ndaona, Chokani, et Langley Research Center, dir. Hypersonic boundary-layer stability experiments on a flared-cone model at angle of attack in a quiet wind tunnel. Hampton, Va : National Aeronautics and Space Administration, Langley Research Center, 1996.
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5
Ndaona, Chokani, et Langley Research Center, dir. Hypersonic boundary-layer stability experiments on a flared-cone model at angle of attack in a quiet wind tunnel. Hampton, Va : National Aeronautics and Space Administration, Langley Research Center, 1996.
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6
Ndaona, Chokani, et Langley Research Center, dir. Hypersonic boundary-layer stability experiments on a flared-cone model at angle of attack in a quiet wind tunnel. Hampton, Va : National Aeronautics and Space Administration, Langley Research Center, 1996.
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Horneff, Vanya, Raimond Maurer et Olivia S. Mitchell. How Persistent Low Expected Returns Alter Optimal Life Cycle Saving, Investment, and Retirement Behavior. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198827443.003.0008.
Texte intégralRésumé :
This chapter explores how an environment of persistent low returns influences saving, investing, and retirement behaviors, compared to what in the past had been conceived of as ‘normal’ financial conditions. Using a calibrated life cycle dynamic model with realistic tax, minimum distribution, and social security benefit rules, we can mimic the large peak at the earliest claiming age at 62 that is seen in the data. Also in line with the evidence, our baseline results show a smaller second peak at the (system-defined) Full Retirement Age of 66. In the context of a zero-return environment, we show that workers will optimally devote more of their savings to non-retirement accounts and less to 401(k) accounts, since the relative appeal of investing in taxable versus tax-qualified retirement accounts is lower in a low return setting. Finally, we show that people claim social security benefits later in a low interest rate environment.
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Kolluri, Surya, et Cynthia Hutchins. Seven Life Priorities in Retirement. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198808039.003.0007.
Texte intégralRésumé :
Using a theoretical life cycle model, this chapter evaluates how much workers benefit from having the option to hire a financial advisor when it is costly for employees to rebalance their own financial portfolios. Results indicate that having access to a financial advisor at the start of one’s career can be quite beneficial. If delegation to an advisor is available only a decade after entering the labor market, the benefit of delegation is cut by half, and it falls further if delegation is available only later in life (at age 60). The chapter also examines whether simpler target date funds (TDF) and fixed weight portfolios benefit consumers, compared to the outcomes with customized financial advice. The authors show that the simpler portfolio products would need to be provided at zero cost, in order to benefit consumers as much as having access to a financial advisor.
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Bunik, Maya. Breastfeeding Telephone Triage and Advice. 2e éd. American Academy of Pediatrics, 2015. http://dx.doi.org/10.1542/9781581109528.
Texte intégralRésumé :
Created by a leading breastfeeding and phone care practitioner, this newly revised problem-solver helps nurses, lactation professionals, and other medical staff confidently advise breastfeeding mothers. It is ideal for use with the acclaimed AAP Pediatric Telephone Protocols. For quick and convenient access, 65 practice-tested protocols are grouped by topic area including: Mother Milk Expression Baby--Early and Later Special Circumstances. More than 50 illuminating photos help triagers zero-in on caller problems. NEW in the 2nd Edition! New protocols -- breast pain chronic >1 week... low milk supply with older baby >6 months... marijuana use....MRSA...sleepy newborn New content throughout -- all sections and references thoroughly updated Essential new information on medications -- including responses to key questions triagers receive from nursing moms NEW quick-reference tables: Pain in breastfeeding Touchpoints for overcoming obstacles to exclusivity NOTE: 1st Edition ebook format of Brestfeeding Telephone Triage and Advice (MA0636) is available for sale for customers interested in purchasing a copy, through October 2015 by contacting AAP Customer Service at csc@aap.org or by calling (847) 434-4000, or toll free (866) 843-2271.
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Milonni, Peter W. An Introduction to Quantum Optics and Quantum Fluctuations. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780199215614.001.0001.
Texte intégralRésumé :
This book is an introduction to quantum optics for students who have studied electromagnetism and quantum mechanics at an advanced undergraduate or graduate level. It provides detailed expositions of theory with emphasis on general physical principles. Foundational topics in classical and quantum electrodynamics, including the semiclassical theory of atom-field interactions, the quantization of the electromagnetic field in dispersive and dissipative media, uncertainty relations, and spontaneous emission, are addressed in the first half of the book. The second half begins with a chapter on the Jaynes-Cummings model, dressed states, and some distinctly quantum-mechanical features of atom-field interactions, and includes discussion of entanglement, the no-cloning theorem, von Neumann’s proof concerning hidden variable theories, Bell’s theorem, and tests of Bell inequalities. The last two chapters focus on quantum fluctuations and fluctuation-dissipation relations, beginning with Brownian motion, the Fokker-Planck equation, and classical and quantum Langevin equations. Detailed calculations are presented for the laser linewidth, spontaneous emission noise, photon statistics of linear amplifiers and attenuators, and other phenomena. Van der Waals interactions, Casimir forces, the Lifshitz theory of molecular forces between macroscopic media, and the many-body theory of such forces based on dyadic Green functions are analyzed from the perspective of Langevin noise, vacuum field fluctuations, and zero-point energy. There are numerous historical sidelights throughout the book, and approximately seventy exercises.
Chapitres de livres sur le sujet "Zero mode Laser"
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Wu, Tong, Yiqiang Chen, Yang Gu, Jiwei Wang, Siyu Zhang et Zhanghu Zhechen. « Multi-Layer Cross Loss Model for Zero-Shot Human Activity Recognition ». Dans Advances in Knowledge Discovery and Data Mining, 210–21. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-47426-3_17.
Texte intégral
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Rosenberg, Mark, Emaline Laney et Claes Tingvall. « Vision Zero in Disease Eradication ». Dans The Vision Zero Handbook, 1165–93. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-76505-7_45.
Texte intégralRésumé :
AbstractThe eradication of smallpox – the first and so far only human disease to be eradicated – generated a tremendous amount of excitement and attention to the idea of disease eradication and elimination. In the twentieth century alone, smallpox had claimed the lives of more than 300,000,000 people (Sneed A, Scientific American, https://www.scientificamerican.com/article/who-remember-smallpox/, 2014). The last natural case occurred in 1977, almost 200 years after the smallpox vaccine was discovered, and in 1979 the World Health Organization declared that the disease had been eradicated (WHO, Smallpox, World Health Organization. World Health Organization. https://www.who.int/csr/disease/smallpox/en/, 2019c). Most importantly, it demonstrated that eradication was possible; that through the use of science, we could change our future for the better in ways that we had not even dared to think about previously. This achievement also helped to focus attention on clear definitions of disease eradication and elimination. Since then, these definitions have been continuously evolving. In 1993, the International Task Force for Disease Eradication (ITFDE I) defined disease control, elimination, and eradication. With that, they evaluated over 90 potential infectious disease candidates and concluded that six were eradicable. Subsequently in 1997, the Dahlem Workshop focused on the science of eradication and defined a range of public health approaches to infectious diseases from control, to elimination of disease, elimination of infections, eradication, and extinction. Three years later, the second International Task Force for Disease Eradication (ITFDE II) convened in 2000 to review the progress over the past decade.Inspired by these efforts, we reviewed our own experience and interviewed leaders of several disease eradication and elimination campaigns to identify lessons learned from a variety of disease elimination campaigns including smallpox, polio, Guinea worm, and onchocerciasis. Our aim was to identify lessons that might be applied to road traffic injuries. We identified 12 lessons from these infectious disease campaigns: (1) this is a cause and effect world; (2) know the truth; (3) coalitions are absolutely essential and absolutely hard; (4) avoid certainty (the Achilles heel of science); (5) measure frequently and build in continuous improvement; (6) respect the culture and work with the people you are trying to help; (7) the best decisions are based on the best science, but the best results, on the best management; (8) the best solutions move us closer to global health equity; (9) do not underestimate the time, resources, or tenacity it will take succeed; (10) eradication does not always require a vaccine or a cure; (11) start in the most difficult places first; and (12) you don’t begin at the end. These concepts from infectious disease campaigns have broader public health applications, and we discuss some of the implications for reducing road traffic injuries.
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Rosenberg, Mark, Emaline Laney et Claes Tingvall. « Vision Zero in Disease Eradication ». Dans The Vision Zero Handbook, 1–29. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-23176-7_45-1.
Texte intégralRésumé :
AbstractThe eradication of smallpox – the first and so far only human disease to be eradicated – generated a tremendous amount of excitement and attention to the idea of disease eradication and elimination. In the twentieth century alone, smallpox had claimed the lives of more than 300,000,000 people (Sneed A, Scientific American, https://www.scientificamerican.com/article/who-remember-smallpox/, 2014). The last natural case occurred in 1977, almost 200 years after the smallpox vaccine was discovered, and in 1979 the World Health Organization declared that the disease had been eradicated (WHO, Smallpox, World Health Organization. World Health Organization. https://www.who.int/csr/disease/smallpox/en/, 2019c). Most importantly, it demonstrated that eradication was possible; that through the use of science, we could change our future for the better in ways that we had not even dared to think about previously. This achievement also helped to focus attention on clear definitions of disease eradication and elimination. Since then, these definitions have been continuously evolving. In 1993, the International Task Force for Disease Eradication (ITFDE I) defined disease control, elimination, and eradication. With that, they evaluated over 90 potential infectious disease candidates and concluded that six were eradicable. Subsequently in 1997, the Dahlem Workshop focused on the science of eradication and defined a range of public health approaches to infectious diseases from control, to elimination of disease, elimination of infections, eradication, and extinction. Three years later, the second International Task Force for Disease Eradication (ITFDE II) convened in 2000 to review the progress over the past decade.Inspired by these efforts, we reviewed our own experience and interviewed leaders of several disease eradication and elimination campaigns to identify lessons learned from a variety of disease elimination campaigns including smallpox, polio, Guinea worm, and onchocerciasis. Our aim was to identify lessons that might be applied to road traffic injuries. We identified 12 lessons from these infectious disease campaigns: (1) this is a cause and effect world; (2) know the truth; (3) coalitions are absolutely essential and absolutely hard; (4) avoid certainty (the Achilles heel of science); (5) measure frequently and build in continuous improvement; (6) respect the culture and work with the people you are trying to help; (7) the best decisions are based on the best science, but the best results, on the best management; (8) the best solutions move us closer to global health equity; (9) do not underestimate the time, resources, or tenacity it will take succeed; (10) eradication does not always require a vaccine or a cure; (11) start in the most difficult places first; and (12) you don’t begin at the end. These concepts from infectious disease campaigns have broader public health applications, and we discuss some of the implications for reducing road traffic injuries.
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Andersson, Ragnar, et Thomas Gell. « Vision Zero on Fire Safety ». Dans The Vision Zero Handbook, 1143–64. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-76505-7_44.
Texte intégralRésumé :
AbstractSince 2010, Sweden has a Vision Zero policy on fire safety: no one should die or be seriously injured as a result of fire. Compared to the traffic safety model, however, the preconditions for successful implementation appear more immature and less convincing in the fire area. The purpose of this chapter is to illustrate, using the Vision Zero policy on fire safety as an example, how a Vision Zero initiative in a new area, where the conditions for governance may differ significantly from the area of inspiration, can be dealt with as a dynamic process to gradually establish credibility and effectiveness.Globally, fire is a significant cause of death and injury. The general trend is toward a slow decline, especially among middle-income and high-income countries. The decline may be due to successful fire safety efforts, but also to other conditions affecting it indirectly. Both risk-increasing and risk-reducing factors determine fire safety. Risk increasing factors include an ageing population, an increasing diversity of possible ignition sources, and a change in the composition and amount of combustible materials present in our homes. The risk-reducing factors include generally favorable socioeconomic and technological developments, including concrete societal actions directed against fire risks such as the promotion of smoke detectors and sprinkler systems.Fire safety is one of the oldest documented examples of societal risk management. City planning and construction were early influenced by fire safety considerations, while in contrast, the legal responsibility for residential fire safety has largely remained a private and individual matter. The situation is similar to the one that for long prevailed in the traffic sector, that is, the primary responsibility rests with the system’s users, not with its designers.The launch of the Vision Zero on fire safety in 2010 represented a clear boost in ambition. Along with the vision, a strategy intended to guide the work toward the visionary goal was also presented. The strategy included four items: information, technical solutions, local collaboration, and evaluation/research. Several actions were taken in line with the strategy, including a significant research effort and the development of a set of indicators to monitor progress.Ten years later, the research effort has brought new knowledge that puts previous perceptions into partly new light. The notion that survival depends on the individual’s personal capacities is strengthened. Adverse outcomes such as death and serious injury appear mainly linked to specific vulnerabilities of certain groups for medical and social reasons. Most fires are handled by the residents themselves without injuries and without assistance from Rescue Services; on the other hand, even minor fires can be fatal for vulnerable residents. This turns the problem framing toward social aspects rather than technical, since broad groups of residents lack the capacities needed, conflicting with the prevailing view that the individual should bear the primary responsibility.Other findings relate to the proven inefficiency of certain measures for groups at elevated risk and the need for re-thinking and innovations to meet the challenges ahead. This includes extended inter-sectoral collaboration on a broader spectrum of residential risks besides fire, threatening the same groups for similar social and medical reasons.This updated state of knowledge is now being used as a basis for renewing current national fire safety strategies. With reference to general principles of systems control, this chapter will discuss obstacles and challenges to establish a more robust and systematic national control of the fire problem in line with the Vision Zero policy. The appropriateness of launching Vision Zero policies in fields that are not yet ripe for systematic governance is also discussed. It is concluded that a Vision Zero initiative can still be meaningful and successfully pursued, provided that limitations in the ability to influence crucial elements in the system are openly identified and systematically addressed in a process in which strategical and policy developments interact with research and innovation.
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Andersson, Ragnar, et Thomas Gell. « Vision Zero on Fire Safety ». Dans The Vision Zero Handbook, 1–22. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-23176-7_44-1.
Texte intégralRésumé :
AbstractSince 2010, Sweden has a Vision Zero policy on fire safety: no one should die or be seriously injured as a result of fire. Compared to the traffic safety model, however, the preconditions for successful implementation appear more immature and less convincing in the fire area. The purpose of this chapter is to illustrate, using the Vision Zero policy on fire safety as an example, how a Vision Zero initiative in a new area, where the conditions for governance may differ significantly from the area of inspiration, can be dealt with as a dynamic process to gradually establish credibility and effectiveness.Globally, fire is a significant cause of death and injury. The general trend is toward a slow decline, especially among middle-income and high-income countries. The decline may be due to successful fire safety efforts, but also to other conditions affecting it indirectly. Both risk-increasing and risk-reducing factors determine fire safety. Risk increasing factors include an ageing population, an increasing diversity of possible ignition sources, and a change in the composition and amount of combustible materials present in our homes. The risk-reducing factors include generally favorable socioeconomic and technological developments, including concrete societal actions directed against fire risks such as the promotion of smoke detectors and sprinkler systems.Fire safety is one of the oldest documented examples of societal risk management. City planning and construction were early influenced by fire safety considerations, while in contrast, the legal responsibility for residential fire safety has largely remained a private and individual matter. The situation is similar to the one that for long prevailed in the traffic sector, that is, the primary responsibility rests with the system’s users, not with its designers.The launch of the Vision Zero on fire safety in 2010 represented a clear boost in ambition. Along with the vision, a strategy intended to guide the work toward the visionary goal was also presented. The strategy included four items: information, technical solutions, local collaboration, and evaluation/research. Several actions were taken in line with the strategy, including a significant research effort and the development of a set of indicators to monitor progress.Ten years later, the research effort has brought new knowledge that puts previous perceptions into partly new light. The notion that survival depends on the individual’s personal capacities is strengthened. Adverse outcomes such as death and serious injury appear mainly linked to specific vulnerabilities of certain groups for medical and social reasons. Most fires are handled by the residents themselves without injuries and without assistance from Rescue Services; on the other hand, even minor fires can be fatal for vulnerable residents. This turns the problem framing toward social aspects rather than technical, since broad groups of residents lack the capacities needed, conflicting with the prevailing view that the individual should bear the primary responsibility.Other findings relate to the proven inefficiency of certain measures for groups at elevated risk and the need for re-thinking and innovations to meet the challenges ahead. This includes extended inter-sectoral collaboration on a broader spectrum of residential risks besides fire, threatening the same groups for similar social and medical reasons.This updated state of knowledge is now being used as a basis for renewing current national fire safety strategies. With reference to general principles of systems control, this chapter will discuss obstacles and challenges to establish a more robust and systematic national control of the fire problem in line with the Vision Zero policy. The appropriateness of launching Vision Zero policies in fields that are not yet ripe for systematic governance is also discussed. It is concluded that a Vision Zero initiative can still be meaningful and successfully pursued, provided that limitations in the ability to influence crucial elements in the system are openly identified and systematically addressed in a process in which strategical and policy developments interact with research and innovation.
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Hell, Wolfram, Kurt Bodewig, Ute Hammer, Christian Kellner, Clemens Klinke, Matthias Mück, Martin Schreiner, Felix Walz et Guido Zielke. « Vision Zero in Germany ». Dans The Vision Zero Handbook, 337–57. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-76505-7_13.
Texte intégralRésumé :
AbstractVision Zero has a central role in traffic safety in Germany. Finally, it was even a relevant point in the coalition treaty from the Federal Governing Parties in the year 2018.It is a unifying theme for safety measures taken on the federal, state, and local levels and in private, nonprofit traffic safety organizations. In later years, cooperation between these different agents has been intensified. Evaluation and measurability are essential in the German approach to Vision Zero. One example of this is the statistical work performed every year to identify “zero cities,” i.e., cities that had zero road fatalities the previous year. A yearly award puts focus on cities that have a particularly long string of zero years, in relation to their size. This is performed on an international level, and cities around the world are incentivized by these recognitions. Munich is used as an example of a city that has recently stepped up its traffic safety work. The city has adopted Vision Zero and followed up this with intensified traffic safety work, including improved data collection, the identification of accident black spots, targeted measures to improve safety in these black spots, safety audits of new infrastructure plans, etc. Before the introduction of new traffic technologies which may have an impact on safety, in-depth technology assessment has to be performed. This is illustrated by an example in which sufficient prior technology assessment did not take place, namely the introduction of e-scooters in Germany. After their introduction, they have turned out to be significantly more dangerous than bicycles, as can be seen from the statistics of fatalities and severe injuries. Proposals are made for measures are needed to reverse this trend, including obligatory use of helmets. The dialogue with neighbor states is also essential. Here the Traffic Expert Society of Medical and Technical Biomechanics, gmttb (Germany, Austria, and Switzerland= D A CH), has initiated to discuss and bundle basic principles of the Vision Zero in three neighbor countries. To promote Vision Zero, gmttb also organizes interdisciplinary yearly conferences with experts from Austria (Vision Zero is a state philosophy) and Switzerland (here named Via Sicura) to bundle strength and adopt ideas together with Swedish and multinational experts. As well as a yearly gmttb Vision Zero Safety Award is granted to motivate people, organizations, and manufacturers to promote good ideas for better traffic safety.
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Hell, Wolfram, Kurt Bodewig, Ute Hammer, Christian Kellner, Clemens Klinke, Matthias Mück, Martin Schreiner, Felix Walz et Guido Zielke. « Vision Zero in Germany ». Dans The Vision Zero Handbook, 1–21. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-23176-7_13-1.
Texte intégralRésumé :
AbstractVision Zero has a central role in traffic safety in Germany. Finally, it was even a relevant point in the coalition treaty from the Federal Governing Parties in the year 2018.It is a unifying theme for safety measures taken on the federal, state, and local levels and in private, nonprofit traffic safety organizations. In later years, cooperation between these different agents has been intensified. Evaluation and measurability are essential in the German approach to Vision Zero. One example of this is the statistical work performed every year to identify “zero cities,” i.e., cities that had zero road fatalities the previous year. A yearly award puts focus on cities that have a particularly long string of zero years, in relation to their size. This is performed on an international level, and cities around the world are incentivized by these recognitions. Munich is used as an example of a city that has recently stepped up its traffic safety work. The city has adopted Vision Zero and followed up this with intensified traffic safety work, including improved data collection, the identification of accident black spots, targeted measures to improve safety in these black spots, safety audits of new infrastructure plans, etc. Before the introduction of new traffic technologies which may have an impact on safety, in-depth technology assessment has to be performed. This is illustrated by an example in which sufficient prior technology assessment did not take place, namely the introduction of e-scooters in Germany. After their introduction, they have turned out to be significantly more dangerous than bicycles, as can be seen from the statistics of fatalities and severe injuries. Proposals are made for measures are needed to reverse this trend, including obligatory use of helmets. The dialogue with neighbor states is also essential. Here the Traffic Expert Society of Medical and Technical Biomechanics, gmttb (Germany, Austria, and Switzerland= D A CH), has initiated to discuss and bundle basic principles of the Vision Zero in three neighbor countries. To promote Vision Zero, gmttb also organizes interdisciplinary yearly conferences with experts from Austria (Vision Zero is a state philosophy) and Switzerland (here named Via Sicura) to bundle strength and adopt ideas together with Swedish and multinational experts. As well as a yearly gmttb Vision Zero Safety Award is granted to motivate people, organizations, and manufacturers to promote good ideas for better traffic safety.
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Panagiotopoulou, Vasiliki C., Alexios Papacharalampopoulos et Panagiotis Stavropoulos. « Developing a Manufacturing Process Level Framework for Green Strategies KPIs Handling ». Dans Lecture Notes in Mechanical Engineering, 1008–15. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-28839-5_112.
Texte intégralRésumé :
AbstractGreen strategies in manufacturing have multifold perspectives implying that are highly diversified in terms of resources management. Popular green strategies are Zero Defect, Circularity and Sustainability. The challenges regarding resources efficiency result from different concepts addressed by each strategy; Zero Defect focuses on defect prevention via quality planning, control, and improvement, while Circularity addresses resources optimisation via resources management, material production, usage and disposal. Sustainability is a different approach, to include economic growth and social impact, besides resources management, waste management and environmental impact. Until now, key performance indicators (KPIs) have been used for individual strategy, while literature shows a lack of frameworks towards transforming KPIs when adopting more than one strategy. The current work is a step towards defining an approach describing the relationship between the KPIs of different green strategies and elaborating the repercussions of this transformation on workflows and specifically on manufacturing processes. Two different approaches could be used (monetary and qualitative) with thermoforming used as a case, and the results are indicative of the method efficiency, where KPIs for Zero Defect, Circularity and Sustainability are compared. The framework is developed to be later generalised and applied to other manufacturing processes.
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Kleinfeller, Nikolai, Christopher M. Gehb, Maximilian Schaeffner, Christian Adams et Tobias Melz. « Assessment of Model Uncertainty in the Prediction of the Vibroacoustic Behavior of a Rectangular Plate by Means of Bayesian Inference ». Dans Lecture Notes in Mechanical Engineering, 264–77. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-77256-7_21.
Texte intégralRésumé :
AbstractDesigning the vibroacoustic properties of thin-walled structures is of particularly high practical relevance in the design of vehicle structures. The vibroacoustic properties of thin-walled structures, e.g., vehicle bodies, are usually designed using finite element models. Additional development effort, e.g., experimental tests, arises if the quality of the model predictions are limited due to inherent model uncertainty. Model uncertainty of finite element models usually occurs in the modeling process due to simplifications of the geometry or boundary conditions. The latter highly affect the vibroacoustic properties of a thin-walled structure. The stiffness of the boundary condition is often assumed to be infinite or zero in the finite element model, which can lead to a discrepancy between the measured and the calculated vibroacoustic behavior. This paper compares two different boundary condition assumptions for the finite element (FE) model of a simply supported rectangular plate in their capability to predict the vibroacoustic behavior. The two different boundary conditions are of increasing complexity in assuming the stiffness. In a first step, a probabilistic model parameter calibration via Bayesian inference for the boundary conditions related parameters for the two FE models is performed. For this purpose, a test stand for simply supported rectangular plates is set up and the experimental data is obtained by measuring the vibrations of the test specimen by means of scanning laser Doppler vibrometry. In a second step, the model uncertainty of the two finite element models is identified. For this purpose, the prediction error of the vibroacoustic behavior is calculated. The prediction error describes the discrepancy between the experimental and the numerical data. Based on the distribution of the prediction error, which is determined from the results of the probabilistic model calibration, the model uncertainty is assessed and the model, which most adequately predicts the vibroacoustic behavior, is identified.
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Becking, Daniel, Maximilian Dreyer, Wojciech Samek, Karsten Müller et Sebastian Lapuschkin. « ECQ$$^{\text {x}}$$ : Explainability-Driven Quantization for Low-Bit and Sparse DNNs ». Dans xxAI - Beyond Explainable AI, 271–96. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-04083-2_14.
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AbstractThe remarkable success of deep neural networks (DNNs) in various applications is accompanied by a significant increase in network parameters and arithmetic operations. Such increases in memory and computational demands make deep learning prohibitive for resource-constrained hardware platforms such as mobile devices. Recent efforts aim to reduce these overheads, while preserving model performance as much as possible, and include parameter reduction techniques, parameter quantization, and lossless compression techniques.In this chapter, we develop and describe a novel quantization paradigm for DNNs: Our method leverages concepts of explainable AI (XAI) and concepts of information theory: Instead of assigning weight values based on their distances to the quantization clusters, the assignment function additionally considers weight relevances obtained from Layer-wise Relevance Propagation (LRP) and the information content of the clusters (entropy optimization). The ultimate goal is to preserve the most relevant weights in quantization clusters of highest information content.Experimental results show that this novel Entropy-Constrained and XAI-adjusted Quantization (ECQ$$^{\text {x}}$$ x ) method generates ultra low-precision (2–5 bit) and simultaneously sparse neural networks while maintaining or even improving model performance. Due to reduced parameter precision and high number of zero-elements, the rendered networks are highly compressible in terms of file size, up to 103$$\times $$ × compared to the full-precision unquantized DNN model. Our approach was evaluated on different types of models and datasets (including Google Speech Commands, CIFAR-10 and Pascal VOC) and compared with previous work.
Actes de conférences sur le sujet "Zero mode Laser"
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Broslavets, Yu Yu, A. A. Fomichev, E. A. Polukeev, V. G. Semenov, D. S. Redichkina et A. R. Pokrovskaya. « Physical factors causing zero drift and noise in a solid-state laser gyroscope based on YAG : Cr4+ at mode locking ». Dans 2024 International Conference Laser Optics (ICLO), 466. IEEE, 2024. http://dx.doi.org/10.1109/iclo59702.2024.10624143.
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Ye, Feng, Xuanyi Liu, H. Y. Fu et Qian Li. « Enhanced Supercontinuum generation by a dispersion-managed L-band ultrafast fiber laser pump ». Dans CLEO : Applications and Technology, JW2A.77. Washington, D.C. : Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_at.2024.jw2a.77.
Texte intégralRésumé :
We propose the scheme using the dispersion-managed L-band mode-locked pulse (near-zero normal net-cavity dispersion) to subtly enable a distinct enhancement of octave-spanning supercontinuum with a broader bandwidth and flatter spectra.
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Lu, Heng, Xinxu Duan, Zhengxin Gao, Hongbo Jiang et Lei Jin. « Impact of dispersion and saturation energy on the mode-locking states in an Yb-doped fiber laser with near-zero net dispersion ». Dans Conference on Spectral Technology and Applications (CSTA 2024), sous la direction de Zhe Wang et Hongbin Ding, 269. SPIE, 2024. https://doi.org/10.1117/12.3037264.
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Troyanosky, Ellen K., Jianyu Liang et Thomas L. Christiansen. « Sub-Zero Treatment of 17-4PH Stainless Steel Manufactured by Laser Powder Bed Fusion ». Dans IFHTSE 2024, 167–72. ASM International, 2024. http://dx.doi.org/10.31399/asm.cp.ifhtse2024p0167.
Texte intégralRésumé :
Abstract Additively manufactured (AM) metals require a modified heat treatment to accommodate for slight differences in composition caused by powder atomization and cover gas used in the manufacturing process. 17-4PH stainless steel (17-4PH) is a precipitation hardening steel which hardens through the formation of Cu precipitates in a martensitic matrix during aging treatment. The powders used in Laser Powder Bed Fusion (LPBF) fabrication of 17-4PH are typically spray atomized using N2 cover gas, which is associated with a certain amount of nitrogen uptake. Nitrogen is a potent austenite stabilizer and will lower the martensite start temperature of the steel. To counteract the effect of nitrogen, a sub-zero heat treatment can be introduced to promote a more complete transformation into martensite. In this work, the effect of nitrogen on the heat treatment response of 17-4PH is investigated through comparing standard wrought, nitrogen loaded wrought, and LPBF 17-4PH. In particular, the effect of introducing a subzero treatment is addressed. After quenching from the solutionizing step (austenitization) LPBF fabricated 17-4PH was cold-treated in different combinations of dry ice (-78 °C) and boiling nitrogen (-196 °C). Subsequently, these conditions were aged in the conventional way. The sub-zero treatments were compared with the conventional heat treatment procedure, which does not entail a sub-zero step. In addition, phase transformations (above room temperature) were monitored in-situ using dilatometry. Finally, hardness tests and XRD analysis were performed to characterize the final microstructure. It is demonstrated that sub-zero treatment can be an effective route to address the problems associated with the additional nitrogen present in LPBF 17-4PH fabricated parts.
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Jia, Wenhe, Chenxin Gao, Yongmin Zhao, Liu Li, Shun Wen, Shuai Wang, Chengying Bao, Chunping Jiang, Changxi Yang et Yuanmu Yang. « Intracavity spatiotemporal laser mode control using metasurfaces strongly coupled to an epsilon-near-zero material ». Dans Nonlinear Optics. Washington, D.C. : Optica Publishing Group, 2023. http://dx.doi.org/10.1364/nlo.2023.th2a.8.
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Murray, T. W., O. Balogun, C. Prada, D. Clorennec, D. Royer, Donald O. Thompson et Dale E. Chimenti. « THEORY AND APPLICATIONS OF LASER GENERATED ZERO-GROUP VELOCITY LAMB MODE RESONANCE ». Dans REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION : 34th Annual Review of Progress in Quantitative Nondestructive Evaluation. AIP, 2008. http://dx.doi.org/10.1063/1.2902667.
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Bale, Brandon G., et J. Nathan Kutz. « Parabolic pulse propagation in mean-zero dispersion-managed transmission systems and mode-locked laser cavities ». Dans SPIE Europe Optics + Optoelectronics, sous la direction de Mario Bertolotti. SPIE, 2009. http://dx.doi.org/10.1117/12.823522.
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Niculae, Anne, et William L. Kath. « Timing jitter reduction in a fiber laser mode-locked by an input bit stream ». Dans Nonlinear Guided Waves and Their Applications. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/nlgw.1996.sad.1.
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It has been demonstrated experimentally that an input data stream can be used to mode-lock a fiber laser, thus providing an efficient all-optical method for clock recovery.1-3 In the experiments, the incoming data pulses passed along a length of dispersion shifted fiber (DSF) that formed part of the ring laser cavity. The laser and signal wavelengths were chosen such that they straddled the zero dispersion point of the DSF, so that little walk-off occurred during propagation. In this manner, the two signals interacted through cross-phase modulation, producing sufficient phase modulation to mode-lock the ring laser cavity.
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Liu, Yusong, Bowen Liu, Yang Xiang, Tao Liu, Yiyang Luo, Zhijun Yan, Perry Ping Shum, Qizhen Sun et Xiahui Tang. « Dispersion-Managed Soliton Molecules in An All-Fiber Mode-Locked Fiber Laser With Near Zero Dispersion ». Dans 2019 18th International Conference on Optical Communications and Networks (ICOCN). IEEE, 2019. http://dx.doi.org/10.1109/icocn.2019.8934326.
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Langlois, Patrick, et Michel Piché. « Self-mode-locked semiconductor laser in a ring cavity ». Dans The European Conference on Lasers and Electro-Optics. Washington, D.C. : Optica Publishing Group, 1998. http://dx.doi.org/10.1364/cleo_europe.1998.cpd1.3.
Texte intégralRésumé :
We report on the generation of short (2 ps) pulses directly from a self-mode-locked semiconductor amplifier inserted in a ring cavity. The amplifier is in fact a superluminescent diode consisting of a 500 mm long double quantum-well InGaAlAs ridge waveguide with strained InGaAs active layers ; an angled stripe geometry provides a low coherence emission with a broad spectrum centered near 855 nm. The amplifier is placed in a ring cavity with three gold minors and a 83% transmission output coupler. Collimation of the laser output and careful alignment of the cavity mirrors allows laser emission with a threshold bias current Ith near 46 mA. Self-mode locking is achieved when the dc bias current is set at ~1.2 Ith, and when the cavity is slightly misaligned. Figures 1 and 2 show typical non-colinear autocorrelation traces and optical spectra of the pulses circulating in the clockwise (cw) and counterclockwise (ccw) directions. The counterpropagating pulses have similar temporal profiles with durations from 2 to 6 ps (after deconvolution) and characterized by a weak pedestal that falls to zero. Remarkably, the pulse respective optical spectra are different, as the spectrum of the ccw pulse has a 2.9 nm bandwidth peaked at 864 nm, whereas that of the cw pulse is peaked near 867 nm with a bandwidth of 0.9 nm. Both circulating pulses have a time-bandwidth product exceeding several times the Fourier-transformed limit, which suggests that they can be compressed to subpicosecond durations.
Rapports d'organisations sur le sujet "Zero mode Laser"
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Liu, Z., et K. Le. Zero-byte Support for Bidirectional Reliable Mode (R-mode) in Extended Link-Layer Assisted RObust Header Compression (ROHC) Profile. RFC Editor, décembre 2002. http://dx.doi.org/10.17487/rfc3408.
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Saltus, Christina, Todd Swannack et S. McKay. Geospatial Suitability Indices Toolbox (GSI Toolbox). Engineer Research and Development Center (U.S.), septembre 2021. http://dx.doi.org/10.21079/11681/41881.
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Habitat suitability models are widely adopted in ecosystem management and restoration, where these index models are used to assess environmental impacts and benefits based on the quantity and quality of a given habitat. Many spatially distributed ecological processes require application of suitability models within a geographic information system (GIS). Here, we present a geospatial toolbox for assessing habitat suitability. The Geospatial Suitability Indices (GSI) toolbox was developed in ArcGIS Pro 2.7 using the Python® 3.7 programming language and is available for use on the local desktop in the Windows 10 environment. Two main tools comprise the GSI toolbox. First, the Suitability Index Calculator tool uses thematic or continuous geospatial raster layers to calculate parameter suitability indices based on user-specified habitat relationships. Second, the Overall Suitability Index Calculator combines multiple parameter suitability indices into one overarching index using one or more options, including: arithmetic mean, weighted arithmetic mean, geometric mean, and minimum limiting factor. The resultant output is a raster layer representing habitat suitability values from 0.0 to 1.0, where zero is unsuitable habitat and one is ideal suitability. This report documents the model purpose and development as well as provides a user’s guide for the GSI toolbox.
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Saltus, Christina, S. McKay et Todd Swannack. Geospatial suitability indices (GSI) toolbox : user's guide. Engineer Research and Development Center (U.S.), août 2022. http://dx.doi.org/10.21079/11681/45128.
Texte intégralRésumé :
Habitat suitability models have been widely adopted in ecosystem management and restoration to assess environmental impacts and benefits according to the quantity and quality of a given habitat. Many spatially distributed ecological processes require application of suitability models within a geographic information system (GIS). This technical report presents a geospatial toolbox for assessing habitat suitability. The geospatial suitability indices (GSI) toolbox was developed in ArcGIS Pro 2.7 using the Python 3.7 programming language and is available for use on the local desktop in the Windows 10 environment. Two main tools comprise the GSI toolbox. First, the suitability index (SIC) calculator tool uses thematic or continuous geospatial raster layers to calculate parameter suitability indices using user-specified habitat relationships. Second, the overall suitability index calculator (OSIC) combines multiple parameter suitability indices into one overarching index using one or more options, including arithmetic mean, weighted arithmetic mean, geometric mean, and minimum limiting factor. The result is a raster layer representing habitat suitability values from 0.0–1.0, where zero (0) is unsuitable habitat and one (1) is ideal suitability. This report documents the model purpose and development and provides a user’s guide for the GSI toolbox.
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Felix, Meier, Wilfried Rickels, Christian Traeger et Martin Quaas. Working paper published on NETs in strategically interacting regions based on simulation and analysis in an extended ACE model. OceanNets, 2022. http://dx.doi.org/10.3289/oceannets_d1.5.
Texte intégralRésumé :
Net-zero climate policies foresee deployment of atmospheric carbon dioxide removal wit geological, terrestrial, or marine carbon storage. While terrestrial and geological storage would be governed under the framework of national property rights, marine storage implies that carbon is transferred from one global common, the atmosphere, to another global common, the ocean, in particular if storage exceeds beyond coastal applications. This paper investigates the option of carbon dioxide removal (CDR) and storage in different (marine) reservoir types in an analytic climate-economy model, and derives implications for optimal mitigation efforts and CDR deployment. We show that the introduction of CDR lowers net energy input and net emissions over the entire time path. Furthermore, CDR affects the Social Cost of Carbon (SCC) via changes in total economic output but leaves the analytic structure of the SCC unchanged. In the first years after CDR becomes available the SCC is lower and in later years it is higher compared to a standard climate-economy model. Carbon dioxide emissions are first higher and then lower relative to a world without CDR. The paper provides the basis for the analysis of decentralized and potentially non-cooperative CDR policies.
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Meier, Felix, Wilfried Rickels, Christian Traeger et Martin Quaas. Working paper published on NETs in strategically interacting regions based on simulation and analysis in an extended ACE model. OceanNets, septembre 2023. http://dx.doi.org/10.3289/oceannets_d1.5_v2.
Texte intégralRésumé :
Net-zero climate policies foresee deployment of atmospheric carbon dioxide removal wit geological, terrestrial, or marine carbon storage. While terrestrial and geological storage would be governed under the framework of national property rights, marine storage implies that carbon is transferred from one global common, the atmosphere, to another global common, the ocean, in particular if storage exceeds beyond coastal applications. This paper investigates the option of carbon dioxide removal (CDR) and storage in different (marine) reservoir types in an analytic climate-economy model, and derives implications for optimal mitigation efforts and CDR deployment. We show that the introduction of CDR lowers net energy input and net emissions over the entire time path. Furthermore, CDR affects the Social Cost of Carbon (SCC) via changes in total economic output but leaves the analytic structure of the SCC unchanged. In the first years after CDR becomes available the SCC is lower and in later years it is higher compared to a standard climate-economy model. Carbon dioxide emissions are first higher and then lower relative to a world without CDR. The paper provides the basis for the analysis of decentralized and potentially non-cooperative CDR policies.