Thèses sur le sujet « Neuron counts »
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1
Rooney, Brian Douglas 1957. « MEASUREMENT OF SUBCRITICALITY IN NEUTRON MULTIPLYING SYSTEMS USING TIME INTERVAL STATISTICS ». Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275556.
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Toyokawa, H., A. Uritani, C. Mori, N. Takeda et K. Kudo. « A Multipurpose Spherical Neutron Counter ». IEEE, 1995. http://hdl.handle.net/2237/6942.
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Burgett, Eric Anthony. « Novel neutron detectors ». Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39622.
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A new set of thermal neutron detectors has been developed as a near term 3He tube replacement. The zinc oxide scintillator is an ultrafast scintillator which can be doped to have performance equal to or superior to 3He tubes. Originally investigated in the early 1950s, this room temperature semiconductor has been evaluated as a thermal neutron scintillator. Zinc oxide can be doped with different nuclei to tune the band gap, improve optical clarity, and improve the thermal neutron detection efficiency. The effects of various dopant effects on the scintillation properties, materials properties, and crystal growth parameters have been analyzed. Two different growth modalities were investigated: bulk melt grown materials as well as thin film scintillators grown by metalorganic chemical vapor deposition (MOCVD). MOCVD has shown significant advantages including precise thickness control, high dopant incorporation, and epitaxial coatings of neutron target nuclei.
Detector designs were modeled and simulated to design an improved thermal neutron detector using doped ZnO layers, conformal coatings and light collection improvements including Bragg reflectors and photonic crystal structures. The detectors have been tested for crystalline quality by XRD and FTIR spectroscopy, for scintillation efficiency by photo-luminescence spectroscopy, and for neutron detection efficiency by alpha and neutron radiation tests. Lastly, a novel method for improving light collection efficiency has been investigated, the creation of a photonic crystal scintillator. Here, the flow of optical light photons is controlled through an engineered structure created with the scintillator materials. This work has resulted in a novel radiation detection material for the near term replacement of 3He tubes with performance characteristics equal to or superior to that of 3He.
4
Khorsandi, Behrooz. « Modeling of displacement damage in silicon carbide detectors resulting from neutron irradiation ». Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1173103438.
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Melton, Andrew Geier. « Development of wide bandgap solid-state neutron detectors ». Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44752.
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In this work novel solid-state neutron detectors based on Gallium Nitride (GaN) have been produced and characterized. GaN is a radiation hard semiconductor which is commonly used in commercial optoelectronic devices. The important design consideration for producing GaN-based neutron detectors have been examined, and device simulations performed. Scintillators and p-i-n diode-type neutron detectors have been grown by metalorganic chemical vapor deposition (MOCVD) and characterized. GaN was found to be intrinsically neutron sensitive through the Nitrogen-14 (n, p) reaction. Neutron conversion layers which produce secondary ionizing radiation were also produced and evaluated. GaN scintillator response was found to scale highly linearly with nuclear reactor power, indicating that GaN-based detectors are suitable for use in the nuclear power industry.
This work is the first demonstration of using GaN for neutron detection. This is a novel application for a mature semiconductor material. The results presented here provide a proof-of-concept for solid-state GaN-based neutron detectors which offer many potential advantages over the current state-of-the-art, including lower cost, lower power operation, and mechanical robustness. At present Helium-3 proportional counters are the preferred technology for neutron detection, however this isotope is extremely rare, and there is a global shortage. Meanwhile demand for neutron detectors from the nuclear power, particle physics, and homeland security sectors requires development of novel neutron detectors which are which are functional, cost-effective, and deployable.
6
Stonehill, Laura C. « Deployment and background characterization of the Sudbury Neutrino Observatory neutral current detectors / ». Thesis, Connect to this title online ; UW restricted, 2005. http://hdl.handle.net/1773/9665.
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Pfeuty, Benjamin. « Rôles des synapses électriques dans la synchronisation neuronale : Une étude théorique ». Phd thesis, Université Pierre et Marie Curie - Paris VI, 2004. http://tel.archives-ouvertes.fr/tel-00007936.
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Il existe deux modes principaux d'interaction entre neurones : les synapses chimiques et les synapses électriques qui, bien que minoritaires par rapport aux premières, sont présentes dans de nombreuses régions du cerveau où elles sont impliquées dans la synchronisation de l'activité neuronale. Notre étude théorique, qui combine calculs analytiques et simulations numériques, montre que l'impact des synapses électriques sur la synchronisation neuronale dépend des propriétés d'excitabilité des neurones déterminées par leurs courants ioniques. Ainsi, associées à des synapses inhibitrices, les synapses électriques peuvent donc amplifier ou réduire la synchronisation de manière linéaire. Toutefois, lorsque le couplage inhibiteur est suffisamment fort, des effets non-linéaires apparaissent tels que les synapses électriques renforcent la précision et la robustesse de la synchronisation. Ce travail de thèse révèle ainsi le caractère flexible de la synchronisation par les synapses électriques.
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Wong, Hon-chi Heymans, et 黃瀚之. « Studies of the optical properties and the calibration of neutron detectors in underground laboratories ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40203530.
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Diochot, Sylvie. « Caractérisation fonctionnelle des courants calciques dépendants du voltage au cours du développement des neurones embryonnaires de souris ». Montpellier 1, 1995. http://www.theses.fr/1995MON1T006.
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Toyokawa, H., M. Yoshizawa, A. Uritani, C. Mori, N. Takeda et K. Kudo. « Performance of a Spherical Neutron Counter for Spectroscopy and Dosimetry ». IEEE, 1997. http://hdl.handle.net/2237/6943.
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Osborne, Mark David. « Simulation of neutron radiation effects in silicon avalanche photodiodes ». Thesis, Brunel University, 2000. http://bura.brunel.ac.uk/handle/2438/7398.
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A new one-dimensional device simulation package developed for the simulation of neutron radiatiol! effects in silicon avalanche photodiodes is described. The software uses a finite difference technique to solve the time-independent semiconductor equations across a user specified structure. Impact ionisation and illumination are included, allowing accurate simulation with minimal assumptions about the device under investigation. The effect of neutron radiation damage is incorporated via the introduction of deep acceptor levels subject to Shockley-Read-Hall statistics. Two models are presented. A reverse reach through model, based on the EG&G C30626E reverse reach through avalanche photo diode originally proposed for use in the CMS electromagnetic calorimeter, and a reach through model, based on widely available commerical devices. A short experimental study on two commercial silicon avalanche photodiodes, a C30719F reverse reach through APD and a C30916E reach through APD, is presented for comparison with the simulation data. To allow full comparison with the simulated predictions, the commercial devices were irradiated at the Rutherford Appleton Laboratory's ISIS facility. The simulated data shows good qualitative agreement with the measurements performed on the commercial devices, quantitative predictions would require exact information about the doping profile. The characteristic behaviour of the devices is predicted over a wide range of conditions both before and after neutron irradiation. The effect of ionised deep acceptors in the bulk of the devices is investigated. The simulation package provides a useful tool for the analysis of semiconductor devices, particularly in areas where a non-ionising radiation damage is prevelent e.g. high energy physics, and provides a good basis for further development.
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Esteves, Alessandra. « Análise comparativa do número de corpos de neurônios em áreas do córtex cerebral de diferentes raças de cães ». Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/10/10132/tde-08082007-131549/.
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Foram enfocadas neste presente estudo, 3 raças de cães, ou seja, Boxer, Dobermann e Rottweiler, com tipos constitucionais e aptidões funcionais característicos e distintos entre si, sendo coletados 4 encéfalos de cada raça. Dos encéfalos foram retirados fragmentos das diferentes áreas do córtex cerebral, que foram preparados segundo técnica histológica convencional e corados por violeta cresil modificada. Através de contagem visual-manual, foram buscados dados comparativos, entre áreas cerebrais versus raça associando tipos constitucionais versus aptidão funcional. As lâminas foram analisadas com auxílio do Axióscopio Zeiss®, acoplado ao programa de análise de imagens KS-400 versão 2.0 Kontron - Zeiss®. Os fatores raças, áreas e hemisférios cerebrais podem ser variáveis dependentes entre si, pois foram encontradas diferenças estatisticamente significativas em valores correspondentes à média de corpos de neurônios das áreas estudadas nas diferentes raças, bem como entre os hemisférios cerebrais.They had been focused in this present study three dog breeds: Boxer, Dobermann e Rottweiler, with types constitutional and aptitudes functional characteristic and between itself, being collected 4 brains of each race. Of the brians they had been removed slices of the different areas of the brain cortex, that they had been prepared second conventional histological technique and stained by modified violet cresil. Through counting appearance-manual, comparative data were reached, mainly between brain areas versus breed associating types constitutional and aptitudes functional. The slices were analyzed with aid of Axióscopio Zeiss® connected to the program of analysis of images KS-400 version 2.0 Kontron - Zeiss®. The factors races, areas and brain hemispheres can be changeable dependents between itself, therefore estatisticament significant differences in corresponding values to the average of bodies of neurons of the areas studied in the different races had been found, as well as between the brain hemispheres.
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Skeen, James Andrew. « Estimating Impervious Surface Cover in Flathead County, Montana ». Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/86416.
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Northwest Montana has seen a significant increase in its population in the past twenty years. The increase in population, and associated development, is thought to be associated with "amenity migration"; people moving to an area to exploit the recreational opportunities that are unique to that area. Impervious surfaces can serve as a suitable proxy for tracking the spread of various anthropogenic influences on an ecosystem; it impacts groundwater recharge, increases overall surface runoff as well as pollution and sediment load, and fragments landscapes. In this study, an Artificial Neural Network model was developed to update NLCD impervious surface product (2011) in Flathead County, Montana. Four Landsat 8 images from 2015 and 2016 were used to characterize imperviousness. This multi-temporal analytical method was designed to reduce the spectral confusion between impervious surface and soil/agricultural lands. We compared the neural network-predicted impervious surface maps with 2011 NLCD. When all four neural network prediction images agreed with a change of 50% or more from the 2011 NLCD map, the average of those four images replaced that pixel from the 2011 imperviousness map. Compared to the ground truth, the method used showed significant promise, with an R2 of 0.73 and RMSE of 0.123. A comparison of the artificial neural network model results and the 2011 NLCD data showed a continuation of urbanization trends; the urban cores of towns in the study remain static while the majority of impervious surface development takes place along the perimeter of urban areas.Master of Science
14
Saal, Hannes. « Information theoretic approach to tactile encoding and discrimination ». Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5737.
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The human sense of touch integrates feedback from a multitude of touch receptors, but how this information is represented in the neural responses such that it can be extracted quickly and reliably is still largely an open question. At the same time, dexterous robots equipped with touch sensors are becoming more common, necessitating better methods for representing sequentially updated information and new control strategies that aid in extracting relevant features for object manipulation from the data. This thesis uses information theoretic methods for two main aims: First, the neural code for tactile processing in humans is analyzed with respect to how much information is transmitted about tactile features. Second, machine learning approaches are used in order to influence both what data is gathered by a robot and how it is represented by maximizing information theoretic quantities. The first part of this thesis contains an information theoretic analysis of data recorded from primary tactile neurons in the human peripheral somatosensory system. We examine the differences in information content of two coding schemes, namely spike timing and spike counts, along with their spatial and temporal characteristics. It is found that estimates of the neurons’ information content based on the precise timing of spikes are considerably larger than for spikes counts. Moreover, the information estimated based on the timing of the very first elicited spike is at least as high as that provided by spike counts, but in many cases considerably higher. This suggests that first spike latencies can serve as a powerful mechanism to transmit information quickly. However, in natural object manipulation tasks, different tactile impressions follow each other quickly, so we asked whether the hysteretic properties of the human fingertip affect neural responses and information transmission. We find that past stimuli affect both the precise timing of spikes and spike counts of peripheral tactile neurons, resulting in increased neural noise and decreased information about ongoing stimuli. Interestingly, the first spike latencies of a subset of afferents convey information primarily about past stimulation, hinting at a mechanism to resolve ambiguity resulting from mechanical skin properties. The second part of this thesis focuses on using machine learning approaches in a robotics context in order to influence both what data is gathered and how it is represented by maximizing information theoretic quantities. During robotic object manipulation, often not all relevant object features are known, but have to be acquired from sensor data. Touch is an inherently active process and the question arises of how to best control the robot’s movements so as to maximize incoming information about the features of interest. To this end, we develop a framework that uses active learning to help with the sequential gathering of data samples by finding highly informative actions. The viability of this approach is demonstrated on a robotic hand-arm setup, where the task involves shaking bottles of different liquids in order to determine the liquid’s viscosity from tactile feedback only. The shaking frequency and the rotation angle of shaking are optimized online. Additionally, we consider the problem of how to better represent complex probability distributions that are sequentially updated, as approaches for minimizing uncertainty depend on an accurate representation of that uncertainty. A mixture of Gaussians representation is proposed and optimized using a deterministic sampling approach. We show how our method improves on similar approaches and demonstrate its usefulness in active learning scenarios. The results presented in this thesis highlight how information theory can provide a principled approach for both investigating how much information is contained in sensory data and suggesting ways for optimization, either by using better representations or actively influencing the environment.
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Sullivan, Daniel D. « Neutron activation analysis and chemical inference for the identification of Buena Vista ceramics ». PDXScholar, 1986. https://pdxscholar.library.pdx.edu/open_access_etds/3699.
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Instrumental Neutron Activation Analysis was used for this study of stonewares collected from the site of the Buena Vista/Oregon Pottery Company (1866-1890).
The results show significant chemical signatures in the samples tested. Thorium/ytterbium and thorium/chromium ratios within their respective ranges of variation demonstrate a relative conformity among all samples of Buena Vista ceramics.
16
Wong, Hon-chi Heymans. « Studies of the optical properties and the calibration of neutron detectors in underground laboratories ». Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/b40203530.
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Mongkolnavin, Rattachat. « CVD polycrystalline diamond a novel neutron detector and applications / ». Thesis, Online version, 1998. http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.481509.
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Thekkudan, Travis Francis. « Calibration of an Artificial Neural Network for Predicting Development in Montgomery County, Virginia : 1992-2001 ». Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33732.
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This study evaluates the effectiveness of an artificial neural network (ANN) to predict locations of urban change at a countywide level by testing various calibrations of the Land Transformation Model (LTM). It utilizes the Stuttgart Neural Network Simulator (SNNS), a common medium through which ANNs run a back-propagation algorithm, to execute neural net training.
This research explores the dynamics of socioeconomic and biophysical variables (derived from the 1990 Comprehensive Plan) and how they affect model calibration for Montgomery County, Virginia. Using NLCD Retrofit Land Use data for 1992 and 2001 as base layers for urban change, we assess the sensitivity of the model with policy-influenced variables from data layers representing road accessibility, proximity to urban lands, distance from urban expansion areas, slopes, and soils. Aerial imagery from 1991 and 2002 was used to visually assess changes at site-specific locations.
Results show a percent correct metric (PCM) of 32.843% and a Kappa value of 0.319. A relative operating characteristic (ROC) value of 0.660 showed that the model predicted locations of change better than chance (0.50). It performs consistently when compared to PCMs from a logistic regression model, 31.752%, and LTMs run in the absence of each driving variable ranging 27.971% â 33.494%. These figures are similar to results from other land use and land cover change (LUCC) studies sharing comparable landscape characteristics. Prediction maps resulting from LTM forecasts driven by the six variables tested provide a satisfactory means for forecasting change inside of dense urban areas and urban fringes for countywide urban planning.Master of Science
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Brandenburg, Kristyn H. « Development of a Neutron Long Counter for (alpha,n) Cross Section Measurements at Ohio University ». Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1512730722722763.
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Nelson, Kyle. « An investigation of aerogels, foams, and foils for multi-wire proportional counter neutron detectors ». Diss., Kansas State University, 2013. http://hdl.handle.net/2097/35278.
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Doctor of PhilosophyDepartment of Mechanical and Nuclear Engineering
Douglas S. McGregor
The 3He gas shortage for neutron detection has caused an increase in research efforts to develop viable alternative technologies. 3He neutron detectors cover areas ranging from 10–1000 cm2 in cylindrical form factors and are ideal for many nuclear applications due to their high intrinsic thermal neutron detection efficiency (> 80%) and gamma-ray discrimination (GRR ≤ 1 x 10-6) capabilities. Neutron monitoring systems for nuclear security applications include Radiation Portal Monitors (RPM’s), backpack, briefcase, and hand-held sensors. A viable replacement technology is presented here and compares three neutron detectors, each with different neutron absorber materials, to current 3He standards. These materials include Li and/or B silica aerogels, LiF impregnated foams, and metallic Li foils. Additionally, other neutron absorbing materials were investigated in this work and include LiF coated Mylar, B foils, BN coated carbon foam, and BN coated plastic honeycomb. From theoretical calculations, the Li foil material showed the greatest promise as a viable 3He alternative, thus a majority of the research efforts were focused on this material. The new neutron detector was a multi-wire proportional counter (MWPC) constructed using alternating banks of anode wires and 95% enriched 6Li foils sheets spaced 1.63 cm apart. In total, six anode banks and five layers of foil were used, thus an anode wire bank was positioned on each side of a suspended foils. Reaction products from the 6Li(n,α)3H reaction were able to escape both side of a foil sheet simultaneously and be measured in the surrounding gas volume concurrently. This new concept of measuring both reaction products from a single neutron absorption in a solid-form absorber material increased the intrinsic thermal neutron detection efficiency and gamma-ray discrimination compared to coated gas-filled detectors. Three different sizes of Li foil MWPC neutron detectors were constructed ranging from 25–1250 cm2 and included detectors for RPM’s, backpacks, and hand-held systems. The measured intrinsic thermal neutron detection efficiency of these devices was approximately 54%, but it is possible to exceed 80% efficiency with additional foils. The gamma-ray discrimination abilities of the detector exceeded 3He tubes by almost three orders of magnitude (GRR = 7.6 x 10-9).
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Wilcox, Eva. « Novel Neutron Detector for n-n Scattering Length Measurement ». Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd900.pdf.
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Giacomelli, Luca. « Development of Neutron Emission Spectroscopy Instrumentation for Deuterium and Deuterium-Tritium Fusion Plasmas at JET ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8199.
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Onken, Arno [Verfasser], et Klaus [Akademischer Betreuer] Obermayer. « Stochastic Analysis of Neural Spike Count Dependencies / Arno Onken. Betreuer : Klaus Obermayer ». Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2011. http://d-nb.info/1014971896/34.
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Molinar, Matthew P. « SNM neutron detection using a time-gated synthetic aperture hybrid approach ». Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50212.
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This work focuses on using forward and adjoint transport in a hybrid application of 3-D deterministic (PENTRAN) and Monte Carlo (MCNP5) codes to model a series of neutron detector blocks. These blocks, or “channels,” contain a unique set of moderators with 4 atm He-3 proportional detectors tuned to detect and profile a gross energy spectrum of a passing neutron (SNM) source. Ganging the units together as a large area system enables one to apply time gating the source-detector response to maximize signal to noise responses from a passing source with minimal background; multiple units may be positioned as a collective synthetic aperture detector array to be used as a way of performing real time neutron spectroscopy for detecting special nuclear materials in moving vehicles.
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Reisi, Fard Mehdi. « The development of a high count rate neutron flux monitoring channel using silicon carbide semiconductor radiation detectors ». Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149088480.
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Wu, Ing-Chyuan. « Neural networks for financial markets analyses and options valuation / ». free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3074457.
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Mickum, George Spencer. « Development and testing of an organic scintillator detector for fast neutron spectrometry ». Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47653.
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The use of organic scintillators is an established method for the measurement of neutron spectra above several hundred keV. Fast neutrons are detected largely by proton recoils in the scintillator resulting from neutron elastic scattering with hydrogen. This leads to a smeared rectangular pulse-height distribution for monoenergetic neutrons. The recoil proton distribution ranges in energy from zero to the incident neutron energy. In addition, the pulse-height distribution is further complicated by structure due to energy deposition from alpha particle recoils from interactions with carbon as well as carbon recoils themselves. In order to reconstruct the incident neutron spectrum, the pulse-height spectrum has to be deconvoluted (unfolded) using the computed or measured response of the scintillator to monoenergetic neutrons. In addition gamma rays, which are always present when neutrons are present, lead to Compton electron recoils in the scintillator. Fortunately, for certain organic scintillators, the electron recoil events can be separated from the heavier particle recoil events in turn to distinguish gamma-ray induced events from neutron-induced events. This is accomplished by using the risetime of the pulse from the organic scintillator seen in the photomultiplier tube as a decay of light.
In this work, an organic scintillator detection system was assembled which includes neutron-gamma separation capabilities to store the neutron-induced and gamma-induced recoil spectra separately. An unfolding code was implemented to deconvolute the spectra into neutron and gamma energy spectra. In order to verify the performance of the system, a measurement of two reference neutron fields will be performed with the system, unmoderated Cf-252 and heavy-water moderated Cf-252. After the detection system has been verified, measurements will be made with an AmBe neutron source.
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Gentry, Matthew David. « Applications of artificial neural networks in the identification of flow units, Happy Spraberry Field, Garza County, Texas ». Texas A&M University, 2003. http://hdl.handle.net/1969.1/1604.
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The use of neural networks in the field of development geology is in its infancy. In this study, a neural network will be used to identify flow units in Happy Spraberry Field, Garza County, Texas. A flow unit is the mappable portion of the total reservoir within which geological and petrophysical properties that affect the flow of fluids are consistent and predictably different from the properties of other reservoir rock volumes (Ebanks, 1987). Ahr and Hammel (1999) further state a highly "ranked" flow unit (i.e. a good flow unit) would have the highest combined values of porosity and permeability with the least resistance to fluid flow. A flow unit may also include nonreservoir features such as shales and cemented layers where combined porosity-permeability values are lower and resistance to fluid flow much higher (i.e. a poor flow unit) (Ebanks, 1987).
Production from Happy Spraberry Field primarily comes from a 100 foot interval of grainstones and packstones, Leonardian in age, at an average depth of 4,900 feet. Happy Spraberry Field is unlike most fields in that the majority of the wells have been cored in the zone of interest. This fact more easily lends the Happy Spraberry Field to a study involving neural networks.
A neural network model was developed using a data set of 409 points where X and Y location, depth, gamma ray, deep resistivity, density porosity, neutron porosity, lab porosity, lab permeability and electrofacies were known throughout Happy Spraberry Field. The model contained a training data set of 205 cases, a verification data set of 102 cases and a testing data set of 102 cases. Ultimately two neural network models were created to identify electrofacies and reservoir quality (i.e. flow units). The neural networks were able to outperform linear methods and have a correct classification rate of 0.87 for electrofacies identification and 0.75 for reservoir quality identification.
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Clayton, Jacob. « Examining Bindley Field, Hodgeman County Kansas and surrounding areas for productive lithofacies using an artificial neural network model ». Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38547.
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Master of ScienceDepartment of Geology
Matthew W. Totten
The Meramec member of Mississippian age is a proficient oil and gas producing formation within the midcontinent region of the United States. It is produced in Kansas, Oklahoma, and Texas. In Kansas, 12% of the state’s petroleum production comes from Mississippian-aged rocks. Bindley Field, located in central west Kansas, has produced 3,669,283 barrels of oil from one facies within the M2 interval of the Meramec formation. This facies is a grain-supported echinoderm/bryozoan dolostone, of variable thickness. Its sporadic occurrence in the subsurface has made exploring Bindley Field and the surrounding area difficult. The challenge in finding oil in this area is in locating a producible zone of this productive facies. Previously, Bindley Field has been the subject of detailed reservoir characterization studies (Ebanks et al., 1977; Johnson, 1990; Johnson, 1994). These studies helped to contribute to a better understanding of Meramecian stratigraphy in Kansas. The Meramec was divided into four major depositional sequences, with some of those sequences nonexistent in the subsurface, due to aerial exposure and erosion post-deposition. The Meramecian units were further separated into parasequence-scale chronostratigraphic units based on marine flooding events. The primary producing interval in Bindley Field is the Meramec 2 interval which consists of seven lithotypes, and is recognized to have six, meter-scale depositional cycles (Johnson, 1990). As production from this interval increased, more information became available about controls on reservoir quality. There are still areas, however, where core data do not exist, and predicting the productive facies remains challenging. The aim of this study is to create a workflow for evaluating the subsurface using regional core and log data from Bindley Field to create a model of the subsurface distribution of the reservoir facies, which could be extended to data poor areas. Geophysical logs (neutron, gamma ray, guard) along with an artificial neural network (ANN), was used to create an accurate prediction of producing intervals within the subsurface. Values are derived from wire line log data and used to develop the ANN definition of facies distribution within Bindley Field. The ANN model was examined for accuracy and precision using core description and well cuttings from wells within Bindley Field and the surrounding area. Correlations were found between the subsurface geometry of the study area, and the production of oil and gas within the study area. An ANN model with an accuracy of 72% was achieved and applied to wells surrounding the Bindley Field, where reservoir intervals have not been as extensively studied. A total of 87 wells in Bindley Field and the surrounding 50 square mile area where applied to the ANN model. The model predicted that the productive facies thickens gradually to the northwest of Bindley Field. Cross sections as well as an isopach map were created using the prediction data from the ANN. Finally, an analysis for the accuracy of the ANN and the predicted facies was created. The productive facies yielded an accuracy value of 77%.
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Lazrak, Amine. « Caractérisation des performances énergétiques des systèmes thermiques innovants pour le bâtiment au travers d'essais de courte durée en régime dynamique ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAA031/document.
Texte intégralRésumé :
Les systèmes solaires thermiques combinés à un système d’appoint tel que une chaudière, une pompe à chaleur ou intégrant une machine à absorption, peuvent jouer un rôle important dans la réduction des consommations des bâtiments pour les besoins de chauffage, de climatisation et de production d’eau chaude sanitaire. Dans ce sens, la caractérisation des performances énergétiques des systèmes thermiques est un enjeu crucial.Les méthodes de caractérisation actuellement disponibles sont soit basées sur plusieurs essais physiques séparés des composants du système à évaluer, chose qui ne prend pas en compte les vraies interactions entre ces derniers, soit sur des modèles physiques qui peuvent être complexes et difficilement identifiables notamment du fait que les systèmes actuels sont compacts et préfabriqués en usine. En l’absence de méthode fiable pour estimer les performances des systèmes solaires thermiques avant leur intégration au bâtiment, le marché de ses derniers subit de fortes contraintes pour son développement.Dans ce contexte il devient indispensable de développer une méthodologie générique qui peut être appliquée à différentes typologies de systèmes et qui pallie les difficultés rencontrées par les méthodes actuelles.L’approche d’évaluation proposée dans ce mémoire est constituée de quatre étapes principales : la détermination d’une séquence de test, l’essai du système dans un banc d’essai semi-virtuel selon la séquence déterminée, l’acquisition des données et l’identification d’un réseau de neurones artificiels (RNA) du système et enfin la simulation du modèle en vue de l’estimation de la consommation du système dans l’environnement désiré. L’avantage d’utiliser un modèle complètement « boîte noire » du système complet à l’aide des RNA la rend totalement « non intrusive ». La connaissance des paramètres internes aux systèmes (rendements, conductivités thermiques, régulation etc.) n’est en conséquence pas nécessaire pour l’application de la méthodologie.La validation de la méthodologie a été réalisée à travers plusieurs expérimentations numériques, pour 7 systèmes issus de 3 typologies différentes, durant lesquelles les estimations des RNA ont été comparées aux calculs des modèles physiques dans plusieurs conditions différentes (qualité du bâtiment, climat et surface du capteur). Une application de l’approche développée dans le cas de 5 systèmes réels a permis la confirmation de la pertinence de la méthodologieSolar thermal systems combined with a backup system such as a boiler, a heat pump or incorporating an absorption chiller, can play an important role in reducing buildings energy consumption for heating, cooling and hot water production needs. In this sense, characterizing the energy performance of thermal systems is crucial.Currently available methods of system characterization are either based on several separate physical tests of system components to be evaluated, which do not take into account the real interactions between them, or on physical models that can be complex and difficult to identify especially because systems nowadays are compact and prefabricated in the factory. Due to the lack of a reliable method to estimate the performance of solar thermal systems before their integration into buildings, their market faces a lot of impediment to be developed.In this context, it becomes essential to develop a generic methodology that can be applied to different types of systems which overcomes the difficulties encountered by the current ones.The proposed evaluation approach in this manuscript is composed of four main steps: determining a test sequence, testing the system in a semi-virtual test bench according to predetermined sequence, data acquisition and identifying an artificial neural network (ANN) of the system and finally the model simulation in order to estimate the system consumption in the desired boundary condition. Using a completely "black box" model of the whole system using the ANN makes the methodology totally "non-intrusive". No prior knowledge about the systems internal parameters (yields, thermal conductivities, regulation etc.) is necessary to apply the proposed approach.The methodology validation was performed through several numerical experiments for seven systems coming from three different typologies. During the validation process, ANN estimates were compared with calculations of physical models in several different conditions (quality of building, climate and collector area). The developed approach was applied to five real systems as well. The application results allowed the confirmation of the methodology relevance
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Seydaliev, Marat Radikovich. « Development and Test of a GEM-Based TEPC for Neutron Protection Dosimetry ». Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14607.
Texte intégralRésumé :
The effective dose equivalent, H (or the effective dose, E ) to an individual is the primary limiting quantity in radiation protection. However, techniques for measuring H for neutrons have not been fully developed. In this regard a new tissue equivalent proportional counter (TEPC) based on a gas electron multiplier (GEM) for measuring H*(10), which is a conservative estimate of H, for neutrons was designed and constructed.
The deposited energy distribution for two different neutron sources (a Cf-252 source and a AmBe source) was measured using the new TEPC. The measurements were performed using two different proportional gases: P-10 gas and a propane-based tissue equivalent gas at various pressures. A computer simulation of the new TEPC, based on the Monte Carlo method, was performed in order to obtain the pulse height distributions for the two neutron sources. The simulated results and the measured results were compared. Results show that the experimental results agree with the computational results within 20% of accuracy for both Cf-252 and AmBe neutron sources.
A new model GEM-based TEPC was developed for use in obtaining H*(10). The value of H*(10) for the Cf-252 source and for the AmBe source using experimental measurements was obtained. These results are presented in this study. The study shows that the GEM-based TEPC can successfully estimate H*(10). With these results and some refinements, this GEM-based TEPC can directly be used as a neutron rem meter.
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Ko, Naonori. « Establishment of quality assurance and quality control measures for Boron Neutron Capture Therapy using microdosimetry ». Kyoto University, 2020. http://hdl.handle.net/2433/253277.
Texte intégral
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Dix, Annika. « Count on the brain ». Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17411.
Texte intégralRésumé :
Wir können Mathematikleistungen über fluide Intelligenz (FI) vorhersagen. Der Einfluss von FI auf kognitive Prozesse und neuronale Mechanismen, die mathematischen Fähigkeiten in verschiedenen Teildisziplinen zugrunde liegen, ist jedoch wenig verstanden. Vorliegende Arbeit spezifiziert FI-bezogene Unterschiede in diesen Prozessen und Mechanismen beim Lösen von Geometrie-, Arithmetik- und Algebra-Aufgaben. Mithilfe eines multimethodalen Ansatzes beleuchtet sie das Zusammenspiel zwischen FI, Leistung und Faktoren wie Aufgabenkomplexität, Lernen und Strategiewahl, die kognitive Prozesse und Anforderungen beim Problemlösen beeinflussen. Leistungsunterschiede wurden durch Messung von Reaktionszeiten und Fehlerraten, Strategien durch Augenbewegungsanalyse erfasst. Als Indikator kortikaler Aktivität diente die ereigniskorrelierte (De-)Synchronisation (ERD/ERS) im Alpha-Band. Um kognitive Prozesse zu unterscheiden, haben wir die ERD/ERS im Theta-Band und den Alpha-Unterbändern einbezogen. Beim Lösen unvertrauter geometrischer Analogien zeichnete sich hohe FI durch verstärkte Verarbeitung visuell-räumlicher Informationen zum Repräsentieren von Merkmalszusammenhängen aus. Schüler mit hoher FI passten ihre Strategiewahl den Anforderungen flexibler an. Erstmals konnten wir durch trialweise Identifikation von Strategien FI-bezogene Unterschiede in der neuronalen Effizienz der Strategieausführung feststellen. Beim Lösen vertrauter arithmetischer und algebraischer Terme zeigten sich bei Schülern mit hoher im Vergleich zu Schülern mit durchschnittlicher FI geringere Anforderungen zur Aktualisierung numerischer Repräsentationen und eine bessere Leistung in komplexen Aufgaben. Weitere Analysen legen nahe, dass Schüler mit hoher FI Zusammenhänge in der Aufgabenstruktur besser erkennen und passende Routinen abrufen können. Die Fähigkeit Zusammenhangsrepräsentationen zu bilden könnte demnach ein Schlüsselaspekt zur Erklärung FI-abhängiger Unterschiede in mathematischen Fähigkeiten sein.Fluid intelligence (FI) is a strong predictor of mathematical performance. However, the impact of FI on cognitive processes and neural mechanisms underlying differences in mathematical abilities across different subdivisions is not well understood. The present work specifies FI-related differences in these processes and mechanisms for students solving geometric, arithmetic, and algebraic problems. We chose a multi-methodological approach to shed light on the interplay between FI, performance, and factors such as task complexity, learning, and strategy selection that influence cognitive processes and task demands in problem-solving. We measured response times and error rates to evaluate performance, eye movements to identify solution strategies, and the event-related (de-)synchronization (ERD/ERS) in the broad alpha band as indicator of general cortical activity. Further, we considered the ERD/ERS in the theta band and the alpha sub-bands to distinguish between associated cognitive processes. For unfamiliar geometric analogy tasks, students with high FI built relational representations based on a more intense processing of spatial information. Strategy analyses revealed a more adaptive strategy choice in response to increasing task demands compared to students with average FI. Further, we conducted the first study identifying strategies and related cortical activity trial-wise and thereby identified FI-related differences in the neural efficiency of strategy execution. For solving familiar arithmetic and algebraic problems, high compared to average FI was associated with lower demands on the updating of numbers leading to a better performance in complex tasks. Further analyses suggest that students with high FI had an advantage to identify the relational structure of the problems and to retrieve routines that match this structure. Thus, the ability to build relational representations might be one key aspect explaining FI-related difference in mathematical abilities.
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Thornton, Angela Lynn. « Development of a portable neutron coincidence counter for field measurements of nuclear materials using the advanced multiplicity capabilities of MCNPX 2.5.F and the neutron coincidence point model ». Thesis, Texas A&M University, 2007. http://hdl.handle.net/1969.1/85859.
Texte intégralRésumé :
Neutron coincidence counting is an important passive Nondestructive Assay (NDA) technique widely used for qualitative and quantitative analysis of nuclear material in bulk samples. During the fission process, multiple neutrons are simultaneously emitted from the splitting nucleus. These neutron groups are often referred to as coincident neutrons. Because different isotopes possess different coincident neutron characteristics, the coincident neutron signature can be used to identify and quantify a given material. In an effort to identify unknown nuclear samples in field inspections, the Portable Neutron Coincidence Counter (PNCC) has been developed. This detector makes use of the coincident neutrons being emitted from a bulk sample. An in-depth analysis has been performed to establish whether the nuclear material in an unknown sample could be quantified with the accuracy and precision needed for safeguards measurements. The analysis was performed by comparing experimental measurements of PuO2 samples to the calculated output produced using MCNPX and the Neutron Coincidence Point Model. Based on the analysis, it is evident that this new portable system can play a useful role in identifying nuclear material for verification purposes.
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Shakshak, Bashir I. O. « The measurements of neutron and gamma dose rates in mixed radiation fields, using a liquid scintillation counter ». Thesis, Aston University, 1989. http://publications.aston.ac.uk/8071/.
Texte intégralRésumé :
Measurements of neutron and gamma dose rates in mixed radiation fields, and gamma dose rates from calibrated gamma sources, were performed using a liquid scintillation counter NE213 with a pulse shape discrimination technique based on the charge comparison method. A computer program was used to analyse the experimental data. The radiation field was obtained from a 241Am-9Be source. There was general agreement between measured and calculated neutron and gamma dose rates in the mixed radiation field, but some disagreement in the measurements of gamma dose rates for gamma sources, due to the dark current of the photomultiplier and the effect of the perturbation of the radiation field by the detector. An optical fibre bundle was used to couple an NE213 scintillator to a photomultiplier, in an attempt to minimise these effects. This produced an improvement in the results for gamma sources. However, the optically coupled detector system could not be used for neutron and gamma dose rate measurements in mixed radiation fields. The pulse shape discrimination system became ineffective as a consequence of the slower time response of the detector system.
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Turck-Chièze, Sylvaine. « Étude de l'électrodésintégration du deutérium ²H(ee'p)n dans un large domaine d'inélasticité et pour des impulsions de recul du neutron allant de 0 à 500 MeV/c ». Paris 11, 1985. http://www.theses.fr/1985PA112170.
Texte intégralRésumé :
Cette thèse présente trois expériences de diffusion exclusive d’électrons ee’p sur le noyau de deutérium. Ces mesures permettent d’extraire la distribution d’impulsion du neutron de recul de 0 à 500 Mev/c. La première expérience concerne les faibles impulsions de recul du neutron de lnl = 0 à 175 Mev/c étudiées dans la région du pic quasi élastique. La deuxième expérience est sensible à la région intermédiaire de lnl = 155 à 355 MeV/c. Les hautes impulsions lnl de 300 à 500 MeV/c sont atteintes dans la troisième cinématique dans une région plus inélastique sensible aux courants d’échange isobariques. L’onde S de la fonction d’onde du deutérium est minimale autour de 450 MeV/c, la troisième mesure est donc principalement sensible à l’état D du deutérium et constitue un test du potentiel nucléon nucléon choisi. La difficulté de ces expériences provient de la faiblesse des sections efficaces (≥ 15 pb/sr²MeV) et de l’emploi d’une cible cryogénique liquide dont il faut maîtriser la densité et l’extension. La détermination de la valeur absolue de ces expériences est discutée en détail. Elle est ici définie à 6 ou 7% prêt. Ces expériences sont comparées aux calculs non relativistes de H. Arenhövel et J. M. Laget, incluant l’interaction de l’électron avec les deux nucléons, les états d’excitation du nucléon, les interactions finales proton neutron et les courants d’échange à dominance pionique. Ces calculs sont en bon accord avec les deux premières expériences pour le potentiel RSC. L’accord du calcul d’Arenhövel avec la troisième expérience est également bon, par contre, un défaut d’invariance de jauge du calcul de Laget lié sans doute au traitement de l’interaction finale existe pour cette troisième cinématique. Les données semblent favoriser les potentiels nucléon nucléon tels que le potentiel RSC ou le potentiel de Paris, des différences allant jusqu’à 30% peuvent être envisagées entre ceux-ci et les potentiels de Bonn. Toutefois, l’étude de l’influence des potentiels nucléon nucléon ne pourra se faire que dans le cadre d’un calcul relativiste completIn this thesis, we present three exclusive electron scattering experiments on deuterium. Recoil neutron momenta from lnl= 0 to 500 MeV/c have been extracted from these measurements. In the first experiment, we studied the law recoil neutron momenta from lnl= 0 to 175 MeV/c in the quasi-elastic region. The second one is sensitive to the intermediate region from lnl = 155 to 335 MeV/c. The high momenta lnl = 300 to 500 MeV/c were covered in the third kinematic condition range, in a more inelastic region influenced by pion exchange currents and isobar configuration. The S-wave component of the deuterium wave function has a minimum near 450 MeV/c, so the third measurement is mainly sensitive to the deuterium D-state and can provide a test of the nucleon-nucleon potential. The difficulty of these experiments comes from the small cross sections (≥ 15pb/sr²/MeV) and the use of cryogenic liquid target whose density and dimension must be known accurately. The determination of the absolute values of the cross section is discussed in detail. The accuracy obtained was about 6 or 7%. The data from these experiments are compared to non-relativistic calculations of H. Arenhövel and J. M. Laget which include electron interaction with the two nucleons, excitation states of the nucleon, proton neutron final state interaction and pionic exchange currents. These calculations are in good agreement with the first experiments for RSC potential. The agreement with Arenhövel calculation is also good in the third one, but for this last experiment, a jauge invariance problem, coming certainly from the final state treatment, still remains in Laget's calculation. Data seem to favor the RSC or Paris nucleon nucleon potentials; 30% differences could be observed between their predictions and those given by the Bonn potentials. Nevertheless the study of the influence of the nucleon nucleon potential can only be done in a complete relativistic calculation
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Kane, Andrew. « An instruction systolic array architecture for multiple neural network types ». Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/16031.
Texte intégralRésumé :
Modern electronic systems, especially sensor and imaging systems, are beginning to incorporate their own neural network subsystems. In order for these neural systems to learn in real-time they must be implemented using VLSI technology, with as much of the learning processes incorporated on-chip as is possible. The majority of current VLSI implementations literally implement a series of neural processing cells, which can be connected together in an arbitrary fashion. Many do not perform the entire neural learning process on-chip, instead relying on other external systems to carry out part of the computation requirements of the algorithm. The work presented here utilises two dimensional instruction systolic arrays in an attempt to define a general neural architecture which is closer to the biological basis of neural networks - it is the synapses themselves, rather than the neurons, that have dedicated processing units. A unified architecture is described which can be programmed at the microcode level in order to facilitate the processing of multiple neural network types. An essential part of neural network processing is the neuron activation function, which can range from a sequential algorithm to a discrete mathematical expression. The architecture presented can easily carry out the sequential functions, and introduces a fast method of mathematical approximation for the more complex functions. This can be evaluated on-chip, thus implementing the entire neural process within a single system. VHDL circuit descriptions for the chip have been generated, and the systolic processing algorithms and associated microcode instruction set for three different neural paradigms have been designed. A software simulator of the architecture has been written, giving results for several common applications in the field.
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Bensetti, Mohamed. « Etude et modélisation de capteurs destinés au contrôle non destructif par courants de Foucault : mise en oeuvre de méthodes d'inversion ». Paris 11, 2004. http://www.theses.fr/2004PA112291.
Texte intégralRésumé :
Ce traval de these aborde des problematiques liees au controle non destructif (cnd) par courants de foucault, il est decompose en trois grandes parties. La premiere a ete consacree a lamise en Œuvre de methodes d'inversion pour l'estimation des parametres physiques et geometriques de cibles. Pour ce fait, nous nous sommes interesses aux modeles inverses a base de reseaux de neurones. Dans ce contexte deux applications ont ete etudiees. Les micro-bobines sont dediees a plusieurs appucations telles que radio frequence (rf), resonance magnetique nucleaire (rmn), controle non destructif (cnd). Selon l'application, ces micro-bobines peuvent ëtre utilisees en haute frequence (hf). Effectivement, la reponse en hf est differente de celle en bf a cause des effets de peau et de proximite qui influent sur les parametres electriques de la micro-bobine. La resistance et l'inductance dependent de la frequence et la capacite de parasite ne peut etre negligee. La seconde partie est consacree a la mise en Œuvre d'une methode original en combinant entre une analyse magnetodynamique et une analyse electrostatique pour la determination des parametres electriques du schema equivalent. Le dernier aspect aborde a ete consacre a l'elaboration d'une approche hybride assosiant la methode des elements finis et la methode des integrales de frontieres (mif) pour calculer la reponse du capteur en presence de fissures. Deux types de validations ont ete realises dans ce travail, une comparaison des resultats obtenus par la methode des elments finis avec des resultats fournis par le cea (logiciel civa) et une validation de la methode hybride en utilisant un dispositif de mesure au laboratoireThis thesis work approaches the problematic related ones to the non destructif testing (ndt) by eddy current, it's divided into three great parts. The first parts is consecrated to implement of the inverse model for the estimate of the physical and geometrical paramters of the tested spicemen. For this fact, we were interested in the inverse models based by neural networks. In this context two application were studied. The micro-coil are dedicated for different applications : radio frequency (rf), nuclear magnetic resonance (nmr), non destructive testing (ndt). . . Depending on the applications, these micro-coils can be used in high frequency. Acctually, the response of the micro-coil at high frequency is significanly different from their low frequency response because of the skin and proximity effects have an influence on the electrical parameters of the micro-coils. The resistance and the inductance of the winding depend on the frequency. The parasitic capacitance of the winding cannot neglected. In the second part of this work, an original method combining by 3d magnetodynamic alalysis and electrostatic analysis is presented to determine the elements of an electric equivalent circuit. The last aspect studied was devoted to developpement of an hybrid approch associating the finite element method (fem) and the boundary integral method (bim) to calculate the response of the coil in the presence of the cracks. Two types of validations were carried out in this work, a comparison of the results obtained by fem with results provided by the cea ( software civa) and a validation of the hybrid method by measurement results
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Heidaripak, Samrend. « PREDICTION OF PUBLIC BUS TRANSPORTATION PLANNING BASED ON PASSENGER COUNT AND TRAFFIC CONDITIONS ». Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-53408.
Texte intégralRésumé :
Artificial intelligence has become a hot topic in the past couple of years because of its potential of solving problems. The most used subset of artificial intelligence today is machine learning, which is essentially the way a machine can learn to do tasks without getting any explicit instructions. A problem that has historically been solved by common knowledge and experience is the planning of bus transportation, which has been prone to mistakes. This thesis investigates how to extract the key features of a raw dataset and if a couple of machine learning algorithms can be applied to predict and plan the public bus transportation, while also considering the weather conditions. By using a pre-processing method to extract the features before creating and evaluating an k-nearest neighbors model as well as an artificial neural network model, predicting the passenger count on a given route could help planning of the bus transportation. The outcome of the thesis was that the feature extraction was successful, and both models could successfully predict the passenger count based on normal conditions. However, in extreme conditions such as the pandemic during 2020, the models could not be proven to successfully predict the passenger count nor being used to plan the bus transportation.
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Jeevarathnam, Nanda Gopal. « Grid-Based RFID Indoor Localization Using Tag Read Count and Received Signal Strength Measurements ». Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/7039.
Texte intégralRésumé :
Passive ultra-high frequency (UHF) radio frequency identification (RFID) systems have gained immense popularity in recent years for their wide-scale industrial applications in inventory tracking and management. In this study, we explore the potential of passive RFID systems for indoor localization by developing a grid-based experimental framework using two standard and easily measurable performance metrics: received signal strength indicator (RSSI) and tag read count (TRC). We create scenarios imitating real life challenges such as placing metal objects and other RFID tags in two different read fields (symmetric and asymmetric) to analyze their impacts on location accuracy. We study the prediction potential of RSSI and TRC both independently and collaboratively. In the end, we demonstrate that both signal metrics can be used for localization with sufficient accuracy whereas the best performance is obtained when both metrics are used together for prediction on an artificial neural network especially for more challenging scenarios. Experimental results show an average error of as low as 0.286 (where consecutive grid distance is defined as unity) which satisfies the grid-based localization benchmark of less than 0.5.
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Trabelsi, Senda. « Étude numérique et expérimentale de coulis de glace à base de propylène- ou d’éthylène-glycol ». Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10534.
Texte intégralRésumé :
Les coulis de glace sont des réfrigérants secondaires considérés comme propres. Ils sont notamment utilisés dans la climatisation, la conservation d’aliments ou certaines applications médicales. Ils se composent de particules de glace et d'un mélange d'eau liquide et d'un additif (ici le propylène-glycol ou l’éthylène-glycol) utilisé pour abaisser le point de congélation de l'eau. Les caractéristiques rhéologiques des coulis de glace ont été mesurées à l'aide d’un rhéomètre de type Discovery HR2 équipé d'une géométrie de type "vane". On considère trois concentrations initiales de soluté (5%, 14% et 24%) pour les deux additifs et les fractions massiques de glace varient entre 5% et 65%. Les résultats expérimentaux révèlent que les coulis de glace sont généralement des fluides non Newtoniens présentant un comportement rhéofluidifiant ou rhéoépaississant en fonction des conditions expérimentales. Les indices d’écoulement et de consistance impliqués dans le modèle de Herschel-Bulkley ont été évalués selon la méthode des moindres carrés. Les résultats sont finalement validés à partir d’une base de données expérimentales issues de la littérature et les prédictions d'un modèle de réseau de neurones artificiels.
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Walker, Scottie. « Spectrally-matched neutron detectors designed using computational adjoint SN for plug-in replacement of Helium-3 ». Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49093.
Texte intégralRésumé :
Neutron radiation detectors are an integral part of the Department of Homeland Security (DHS) efforts to detect the illicit trafficking of radioactive or special nuclear materials into the U.S. In the past decade, the DHS has deployed a vast network of radiation detection systems at various key positions to prevent or to minimize the risk associated with the malevolent use of these materials. The greatest portion of this detection burden has been borne by systems equipped with 3He because of its highly desirable physical and nuclear properties. However, a dramatic increase in demand and dwindling supply, combined with a lack of oversight for the existing 3He stockpile has produced a critical shortage of this gas which has virtually eliminated its viability for detector applications. A number of research efforts have been undertaken to develop suitable 3He replacements; however, these studies have been solely targeted toward simple detection cases where the overall detection efficiency is the only concern. For these cases, an insertion of additional detectors or materials can produce reaction rates that are sufficient, because the neutron spectral response is essentially irrelevant. However, in applications such as safeguards, non-proliferation efforts, and material control and accountability programs (MC&A), a failure to use detectors that are spectrally matched to 3He can potentially produce dire consequences. This is because these more difficult detection scenarios are associated with fissile material assessments for 239Pu and other actinides and these analyses have almost universally been calibrated to an equivalent 3He response. In these instances, a “simple” detector or material addition approach is neither appropriate nor possible, due to influences resulting from the complex nature of neutron scattering in moderators, cross sections, gas pressure variations, geometries, and surrounding structural interference. These more challenging detection cases require a detailed computational transport analysis be performed for each specific application.
A leveraged approach using adjoint transport computations that are validated by forward transport and Monte Carlo computations and laboratory measurements can address these more complex detection cases and this methodology was utilized in the execution of the research. The initial task was to establish the fidelity of a computational approach by executing radiation transport models for existing BF3 and 3He tubes and then comparing the modeling results to laboratory measurements made using these identical devices. Both tubes were 19.6 cm in height, 1-inch in diameter, and operated at 1 and 4 atm pressure respectively. The models were processed using a combination of forward Monte Carlo and forward and adjoint 3-D discrete ordinates (SN) transport methods. The computer codes MCNP5 and PENTRAN were used for all calculations of a nickel-shielded plutonium-beryllium (PuBe) source term that provided a neutron output spectra equivalent to that of weapons-grade plutonium (WGPu).
Once the computational design approach was validated, the adjoint SN method was used to iteratively identify six distinct plug-in models that matched the neutron spectral response and reaction rate of a 1-inch diameter 3He tube with a length of 10 cm and operating at 4 atm pressure. The equivalent designs consist of large singular tubes and dual tubes containing BF3 gas, 10B linings, and/or 10B-loaded polyvinyl toluene (PVT). The reaction rate for each plug-in design was also verified using forward PENTRAN and MCNP5 calculations. In addition to the equivalent designs, the adjoint method also yielded various insights into neutron detector design that can lead to additional designs using a combination of different detector materials such as BF3/10B-loaded PVT, 10B-lined tubes/10B-loaded PVT, etc.
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SAMPA, MARIA H. de O. « Desenvolvimento do processo de deposicao eletroforetica de boro em substratos de aluminio destinados a construcao de detectores de neutrons ». reponame:Repositório Institucional do IPEN, 1988. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9892.
Texte intégralRésumé :
Made available in DSpace on 2014-10-09T12:32:32Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:09Z (GMT). No. of bitstreams: 1 03259.pdf: 2834364 bytes, checksum: fcbdf9e370a39ffdb27be573e65f253c (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Spelta, Michele. « Commissioning of the third n_TOF spallation target : characterization of the neutron flux and beam profile using PPACs ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25126/.
Texte intégralRésumé :
Beyond their application in fundamental nuclear physics and nuclear astrophysics research, neutron-induced reactions play an increasingly important role in emerging nuclear technologies. For instance, in the fields of sustainable low-carbon power production (ADS, generation four fission and fusion reactors), medicine and industry, neutron data are required with high accuracy in a wide energy range. The measurement of neutron-induced reaction cross sections is therefore crucial and it is indeed the main objective of the n_TOF facility, a pulsed white neutron spallation source at CERN.
Recently the facility has been upgraded with the installation of its new third-generation spallation target and a subsequent commissioning was carried out in order to characterize the performances of the experimental areas in terms of neutron flux, energy resolution and background in view of the future experimental campaigns.
I was involved in the first phase of the commissioning at CERN, testing the DAQ system and taking care in particular of one of the employed detectors: a fission chamber based on Parallel Plate Avalanche Counters (PPACs). The data collected in the first experimental area (EAR1) were analyzed to obtain the neutron flux from near thermal energy (0.025 eV) to 1 GeV and the spatial beam profile. The flux from the present analysis is compared to the Monte Carlo simulations and to the preliminary results of another flux detector, while the spatial beam profile is compared to the one obtained with a Timepix Quad detector. In addition, a preliminary analysis of the data collected in the second experimental area (EAR2) was also carried out.
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Boumaaza, Bouharket. « 3D seismic attributes analysis and inversions for prospect evaluation and characterization of Cherokee sandstone reservoir in the Wierman field, Ness County, Kansas ». Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35510.
Texte intégralRésumé :
Master of ScienceDepartment of Geology
Abdelmoneam Raef
Matthew W. Totten
This work focuses on the use of advanced seismically driven technologies to estimate the distribution of key reservoir properties which mainly includes porosity and hydrocarbon reservoir pay. These reservoir properties were estimated by using a multitude of seismic attributes derived from post-stack high resolution inversions, spectral imaging and volumetric curvature. A pay model of the reservoir in the Wierman field in Ness County, Kansas is proposed. The proposed geological model is validated based on comparison with findings of one blind well. The model will be useful in determining future drilling prospects, which should improve the drilling success over previous efforts, which resulted in only few of the 14 wells in the area being productive. The rock properties that were modeled were porosity and Gamma ray. Water saturation and permeability were considered, but the data needed were not available. Sequential geological modeling approach uses multiple seismic attributes as a building block to estimate in a sequential manner dependent petrophysical properties such as gamma ray, and porosity. The sequential modelling first determines the reservoir property that has the ability to be the primary property controlling most of the other subsequent reservoir properties. In this study, the gamma ray was chosen as the primary reservoir property. Hence, the first geologic model built using neural networks was a volume of gamma ray constrained by all the available seismic attributes. The geological modeling included post-stack seismic data and the five wells with available well logs. The post-stack seismic data was enhanced by spectral whitening to gain as much resolution as possible. Volumetric curvature was then calculated to determine where major faults were located. Several inversions for acoustic impedance were then applied to the post-stack seismic data to gain as much information as possible about the acoustic impedance. Spectral attributes were also extracted from the post-stack seismic data. After the most appropriate gamma ray and porosity models were chosen, pay zone maps were constructed, which were based on the overlap of a certain range of gamma ray values with a certain range of porosity values. These pay zone maps coupled with the porosity and gamma ray models explain the performance of previously drilled wells.
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Bobin-Bègue, Anne. « Capacité de traitement temporel des durées courtes chez l'enfant entre 1 & ; 4 ans ». Phd thesis, Ecole pratique des hautes études - EPHE PARIS, 2002. http://tel.archives-ouvertes.fr/tel-00111689.
Texte intégralRésumé :
La dimension temporelle est fondamentale pour la vie des organismes vivants. En l'absence d'organe dédié à la perception de cette grandeur physique, comment ces organismes parviennent à extraire cette information de leur milieu. Les connaissances actuelles permettent de catégoriser différents modes de traitement temporel en fonction de l'échelle de temps à évaluer. Les durées les plus communément traitées sont les durées dites courtes (inférieures à l'heure). Il existe au sein de ces durées courtes une distinction relative au mode de traitement : perception et estimation de la durée. La perception de la durée concerne les durées inférieures à la seconde et consiste à extraire des informations perçues de l'environnement pendant ce présent subjectif une représentation mentale de cette durée qui pourra être exploitée par l'individu. Les données de la littérature convergent en faveur d'un mécanisme central de traitement possédant à sa source une base de temps. De nombreuses expériences ont permis de déterminer les caractéristiques psychophysiques et neurobiologiques du fonctionnement de cette horloge interne. Ces informations ont permis l'élaboration de modèles théoriques plus ou moins aboutis. Les connaissances actuelles sont synthétisées dans une première partie de ce document. Elles permettent notamment de mettre en évidence des lacunes et des contradictions quant à la mise en place de ce système de traitement au cours de la petite enfance.Selon un modèle développemental, le traitement temporel repose sur une période de référence. La sensibilité du système de traitement temporel serait meilleure pour des durées proches de cette période endogène particulière. Compte-tenu des ambiguïtés soulevées par les données de la littérature, nous nous sommes attachés à étudier ces paramètres du traitement temporel (période de référence et seuil de sensibilité) chez les enfants entre 1 et 4 ans par des tâches de perception et de production. Nos résultats ont permis de déterminer les étapes développementales de la mise en place du système de traitement et d'énoncer de nouvelles hypothèses, valables pour cette période critique du développement psychomoteur, cognitif et neurobiologique, quant à ces paramètres fondamentaux. Ainsi, la période de référence, reflet de la base de temps de l'horloge, reste constante pendant la petite enfance mais gagnerait en stabilité. Parallèlement, un seuil de sensibilité deviendrait effectif. Il a été retrouvé à la fois lors de tâches de production et de perception et il ne permet pas de vérifier que le traitement est meilleur à proximité de la période de référence. Par contre, nos résultats suggèrent que ce seuil de sensibilité doive être considéré en valeur absolue et non en valeur relative.
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HOCEINI, SAID. « Techniques d'Apprentissage par Renforcement pour le Routage Adaptatif dans les Réseaux de Télécommunication à Trafic Irrégulie ». Phd thesis, Université Paris XII Val de Marne, 2004. http://tel.archives-ouvertes.fr/tel-00010430.
Texte intégralRésumé :
L'objectif de ce travail de thèse est de proposer des approches algorithmiques permettant de traiter la problématique du routage adaptatif (RA) dans un réseau de communication à trafic irrégulier. L'analyse des algorithmes existants nous a conduit à retenir comme base de travail l'algorithme Q-Routing (QR); celui-ci s'appuie sur la technique d'apprentissage par renforcement basée sur les modèles de Markov. L'efficacité de ce type de routage dépend fortement des informations sur la charge et la nature du trafic sur le réseau. Ces dernières doivent être à la fois, suffisantes, pertinentes et reflétant la charge réelle du réseau lors de la phase de prise de décision. Pour remédier aux inconvénients des techniques utilisant le QR, nous avons proposé deux algorithmes de RA. Le premier, appelé Q-Neural Routing, s'appuie sur un modèle neuronal stochastique pour estimer et mettre à jour les paramètres nécessaires au RA. Afin d'accélérer le temps de convergence, une deuxième approche est proposée : K-Shortest path Q-Routing. Elle est basée sur la technique de routage multi chemin combiné avec l'algorithme QR, l'espace d'exploration étant réduit aux k meilleurs chemins. Les deux algorithmes proposés sont validés et comparés aux approches traditionnelles en utilisant la plateforme de simulation OPNET, leur efficacité au niveau du RA est mise particulièrement en évidence. En effet, ceux-ci permettent une meilleure prise en compte de l'état du réseau contrairement aux approches classiques.
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Reece, Chance. « Investigating the variations in depositional facies by investigating the accuracy of the neural network model within the St. Louis limestone, Kearny County, Kansas ». Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/32588.
Texte intégralRésumé :
Master of ScienceDepartment of Geology
Matt Totten
The Mississippian-aged St. Louis Limestone has been a major producer of oil, and natural gas for years in Kearny County, Kansas. Since 1966 two major fields in the County, the Lakin, and Lakin South fields, have produced over 4,405,800 bbls of oil. The St. Louis can be subdivided into six different depositional facies, all with varying lithologies and porosities. Only one of these facies is productive, and the challenge of exploration in this area is the prediction of the productive facies distribution. A previous study by Martin (2015) used a neural network model using well log data, calibrated with established facies distributed within a cored well, to predict the presence of these facies in adjacent wells without core. It was assumed that the model’s prediction accuracy would be strongest near the cored wells, with increasing inaccuracy as you move further from the cored wells used for the neural network model. The aim of this study was to investigate the accuracy of the neural network model predictions. Additionally, is the greater accuracy closest to the cored wells used to calibrate the model, with a corresponding decrease in predictive accuracy as you move further away? Most importantly, how well did the model predict the primary producing unit (porous ooid grainstone) within the St. Louis Limestone? The results showed that the neural network was not completely reliable in predicting total facies distribution. This can be attributed to many different inefficiencies in the data, including different resolutions between cuttings data and well logs, limited well cuttings available, and missing cuttings from the wells that were observed. Relating the neural network predictions to actual well productivity validates the neural network’s ability to predict the producing facies. There are also instances of the productive facies being present when not predicted. This is likely a function of different facies thickness in these wells from the cored wells used to calibrate the model, rather than distance from the cored well.
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Oates, Sean Benjamin. « Structure of the nucleus ¹¹⁴Sn using gamma-ray coincidence data ». Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1019870.
Texte intégral
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Platel, Jean-Claude. « Activité calcique et communication paracrine avant synaptogenèse dans le développement du néocortex murin ». Phd thesis, Université Joseph Fourier (Grenoble), 2005. http://tel.archives-ouvertes.fr/tel-00011566.
Texte intégralRésumé :
Dans le néocortex murin, la division des cellules précurseurs a lieu dès le stade E11 et donne naissance aux premiers neurones pionniers dont les cellules de Cajal-Retzius. L'activité électrique spontanée, portée par les canaux ioniques, joue un rôle prépondérant dans le développement du système nerveux central. Comprendre la place des canaux ioniques et de la signalisation calcique dans les phases précoces de le neurogenèse était l'objectif principal de mon projet. Nous avons montré l'apparition précoce de canaux sodiques dépendants du voltage dans 55% des cellules neuronales à E13, dont les cellules de Cajal-Retzius. En parallèle, nous avons observé des activités calciques spontanées dans les cellules proliférantes et neuronales au même stade. La conception d'un logiciel d'imagerie nous a permis d'analyser statistiquement ces activités et d'identifier les canaux ioniques impliqués. Alors que les synapses ne sont pas encore formées, nous avons observé la mise en place d'activités synchrones au sein du néocortex et démontré l'existence de communications paracrines entre les cellules. De plus, nous avons identifié l'existence d'une cascade de signalisation où la dépolarisation des récepteurs glycinergiques active les canaux sodiques présents sur les neurones pionniers. Dans ces neurones, l'influx sodique entraîne une augmentation de calcium cytoplasmique via un échangeur Na+/Ca2+ puis une exocytose glutamatergique dont le libération paracrine induit l'activation d'autres cellules néocorticales. L'utilisation de la culture organotypique de cerveau nous a laissé entrevoir une implication physiologique majeure de cette cascade de signalisation dans la corticogenèse.