Efectos de mareas en cúmulos globulares
NASA Astrophysics Data System (ADS)
Ramos, F.; Coenda, V.; Muriel, H.; Abadi, M.
Using an N-body numerical simulation in the framework of the CDM cosmological model we study the globular cluster population in a simulated galaxy cluster. We select particles that trace the bimodal (red and blue) globular cluster system of each individual dark matter halo prior to their incorporation to the cluster virial radius. We found that the blue population is more prone to be removed from the halo than the red one. This result suggests that globular clusters are tidally disrupted; being the blue (more extended) population easily removed. FULL TEXT IN SPANISH
Estudio de los Efectos Gravitomagnéticos en Cuerpos Masivos Rotantes
NASA Astrophysics Data System (ADS)
Velandia Heredia, N.; Tejeiro, J. M.
2008-03-01
A partir del estudio de los Efectos Gravitomagnéticos en cuerpos masivos rotantes, planteamos la expresión para medir el desfase en el tiempo, para diferentes observadores, que se dan cuando viajan dos rayos de luz por una guía de onda o de manera libre (geodésicas), en el plano azimutal y en el plano polar. Con lo anterior queremos abordar el experimento tipo Michelson y Morley, de forma que podamos involucrar el valor de la densidad del momento angular (a) en el retraso temporal para los dos haces de luz que viajan por los brazos del interferómetro, cuando este último es ubicado en el plano ecuatorial.
El efecto de los neutrinos degenerados en la transición de materia nuclear a materia de quarks
NASA Astrophysics Data System (ADS)
Lugones, G.; Benvenuto, O. G.
Se estudia la transicion de materia nuclear a materia de quarks en presencia de un gas degenerado de neutrinos electrónicos y muónicos. Se muestra que la presencia de los neutrinos hace que las densidades de desconfinamiento de quarks sean notablemente mayores que las encontradas en el caso en que no haya neutrinos presentes. Se discuten las posibles consecuencias de este efecto en explosiones de supernova y evolución de proto estrellas de neutrones.
Modelo analítico del efecto de PRS sobre satélites GPS
NASA Astrophysics Data System (ADS)
Meza, A.; Brunini, C.; Usandivaras, J. C.
El sistema GPS (Global Position System) es, hoy en día, la herramienta de navegación y posicionamiento más potente y lo será sin duda en la próxima década. Gran parte de su valiosa utilidad se debe a la alta precisión que permite lograr y ésta, a su vez, depende, entre otras causas, de la precisión con que se conocen las órbitas de los satélites. La presión de radiación solar (PRS) fija el límite de la precisión con que pueden calcularse en la actualidad las efemérides satelitarias. El objetivo de este trabajo es proponer una mejor resolución de este fenómeno. El modelo analítico aquí presentado, se basa en el análisis del comportamiento de los residuos de un ajuste por mínimos cuadrados en el que se utiliza el modelo de PRS propuesto por Beutler. El mismo consiste en un modelo determinista del fenómeno con dos parámetros libres. Los resultados obtenidos ponen de manifiesto que, aún después de aplicar dichos parámetros, prevalecen en los residuos efectos semidiurnos en las componentes radial,tangencial y normal. Estos resultados obtenidos se comparan con los de un trabajo desarrollado por el Instituto de Berne (Beutler et al., 1994), en el que se utilizaron como pseudo-observaciones las órbitas precisas del IGS (CODE). El intervalo de integración escogido por este centro fueron las semanas 680 y 681. En resumen se tienen arcos de 14 días para todos los satélites, donde las efemérides precisas de los mismos para los 14 días fueron utilizados como pseudo-observaciones. El modelo de fuerza que empleó dicho centro fue básicamente el tradicional en lo que respecta al modelo de las fuerzas gravitacionales, y para la PRS utilizo el modelo standard de Beutler. Los parámetros de este modelo junto con las 6 condiciones iniciales (posición y velocidad) fueron ajustados por el método general de mínimos cuadrados. Los residuos en la componente radial, tangencial y normal, para los satélites con un buen comportamiento, presentan una
Extensión del Formalismo de Orbitales de Defecto Cuántico al tratamiento del efecto Stark (SQDO).
NASA Astrophysics Data System (ADS)
Menéndez, J. M.; Martín, I.; Velasco, A. M.
El estudio experimental de las interacciones de átomos Rydberg altamente excitados con campos eléctricos ha experimentado un creciente interés durante las dos últimas décadas debido, en gran medida, al desarrollo de nuevas técnicas para crear y estudiar átomos Rydberg en el laboratorio. Acompañando a estas nuevas técnicas experimentales, es necesario el desarrollo de modelos teóricos que nos permitan contrastar sus medidas y conocer mejor los fundamentos de los mismos. Desde el punto de vista teórico el conocimiento del desdoblamiento de los niveles energéticos de un átomo en función de la magnitud del campo eléctrico aplicado (lo que se conoce como mapa Stark) es el mejor punto de partida para la descripción del sistema y un prerrequisito fundamental para el cálculo de distintas propiedades atómicas en presencia del campo eléctrico tales como intensidades de transición, umbrales de ionización de campo eléctrico, tiempos de vida, posición y anchura de cruces evitados, etc. En este trabajo presentamos la adaptación del método de orbitales de defecto cuántico [1,2,3] al tratamiento del efecto Stark (SQDO) [4] y su aplicación al cálculo de los desdoblamientos energéticos y fuerzas de oscilador de estados Rydberg en los átomos de Li, Na y K. El propósito de este estudio es, por un lado, desarrollar métodos fiables para la determinación de propiedades atómicas en presencia de campos eléctricos y, por otro, mostrar la fiabilidad de las funciones de onda QDO en la descripción del efecto Stark en sistemas atómicos.
Efectos de la irradiación iónica en hielos de moléculas carbonadas
NASA Astrophysics Data System (ADS)
Satorre, M. A.
En Astrofísica podemos encontrar numerosos contextos en los cuales se observan moléculas en estado sólido que, en condiciones estándar de presión y temperatura, se encontrarían como gases o líquidos. Dichas moléculas se denominan hielos y han sido observadas en nubes densas del medio interestelar, en envolturas circumestelares, en satélites del Sistema Solar, en cometas, etc. Los hielos pueden ser alterados en su composición química debido a diversos factores como por ejemplo variaciones de temperatura o aportes energéticos por parte de la irradiación, ya sea tanto de fotones ultravioleta como de iones. Dependiendo del escenario astrofísico que analicemos, unos factores cobran más importancia que otros. Los experimentos de laboratorio muestran el efecto que produce sobre la composición de los hielos la irradiación iónica, en particular sobre los que contenían alguna molécula con átomos de carbono. Dicha composición se analiza con espectroscopía IR en el rango de 2 a ˜ 25μ m. La aplicabilidad de los resultados de los experimentos es distinta dependiendo de la composición química inicial de los hielos, del tipo de ion utilizado y de la dosis total de irradiación. Existen efectos generales de la irradiación sobre la materia en los experimentos de relevancia astrofísica como son: - la formación de nuevas moléculas, que pueden incluir o no el ion incidente; - la progresiva pérdida de hidrógeno (carbonización) cuando irradiamos muestras que originalmente contienen una determinada relación carbono/hidrógeno; - la variación de la temperatura de sublimación que presentan algunos hielos. Esto puede suceder tanto en hielos que estaban presentes antes de la irradiación como en hielos formados por ésta. Se presentará el papel del ion en la formación de nuevas moléculas a partir de las que originalmente se encontraban en el hielo. Al penetrar en él, el ion provoca distintos procesos como rotura de enlaces y excitaciones electr
Loth, E.; Tryggvason, G.; Tsuji, Y.; Elghobashi, S. E.; Crowe, Clayton T.; Berlemont, A.; Reeks, M.; Simonin, O.; Frank, Th; Onishi, Yasuo; Van Wachem, B.
2005-09-01
Slurry flows occur in many circumstances, including chemical manufacturing processes, pipeline transfer of coal, sand, and minerals; mud flows; and disposal of dredged materials. In this section we discuss slurry flow applications related to radioactive waste management. The Hanford tank waste solids and interstitial liquids will be mixed to form a slurry so it can be pumped out for retrieval and treatment. The waste is very complex chemically and physically. The ARIEL code is used to model the chemical interactions and fluid dynamics of the waste.
NASA Technical Reports Server (NTRS)
Zook, H. A.
1985-01-01
A prediction of the future population of satellites, satellite fragments, and assorted spacecraft debris in Earth orbit can be reliably made only after three conditions are satisfied: (1) the size and spatial distributions of these Earth-orbiting objects are established at some present-day time; (2) the processes of orbital evolution, explosions, hypervelocity impact fragmentation, and atmospheric drag are understood; and (3) a reasonable traffic model for the future launch rate of Earth-orbiting objects is assumed. The theoretician will then take these three quantities as input data and will carry through the necessary mathematica and numerical analyses to project the present-day orbital population into the future.
NASA Astrophysics Data System (ADS)
Biscione, Marilisa; Danese, Maria; Masini, Nicola; Sabia, Canio
2016-04-01
(August 5, 2013); doi:10.1117/12.2027954 Danese M., Masini N., Biscione M., Lasaponara R. 2014. Predictive modeling for preventive Archaeology: Overview and case study. Central European Journal of Geosciences. March 2014,Volume 6, Issue 1, 42-55, doi: 10.2478/s13533-012-0160-5 G. Demians d'Archimbaud - Rougiers, Castrum médiéval déserté. In : Pays Sainte-Baume 9 (2001) 6-8 Lasaponara R., Masini N. 2009, Full-waveform Airborne Laser Scanning for the detection of medieval archaeological microtopographic relief, Journal of Cultural Heritage, 10S, pp. e78-e82, doi:10.1016/j.culher.2009.10.004. Lasaponara R., Leucci G., Masini N., Persico R., Scardozzi G., 2016, Towards an operative use of remote sensing for exploring the past using satellite data: The case study of Hierapolis (Turkey), Remote sensing of Environment, vol. 174: 148-164, doi:10.1016/j.rse.2015.12.016 Masini N. 1998, La fotointerpretazione aerea finalizzata allo studio morfologico dei siti urbani e fortificati medioevali della Basilicata, in "Castra ipsa possunt et debent reparari." Indagini conoscitive e metodologie di restauro delle strutture castellane normanno-sveve, a cura C. D. Fonseca, Roma, Edizioni De Luca, tomo I, pp. 205-250, ISBN: 8880162888 Podobnikar, T., Veljanovski, T., Stanèiè, Z., Oštir, K. (2001) Archaeological Predictive Modelling in Cultural Resource Management. In: Konečný, M. (ed): GI in EUROPE: integrative - interoperable - interactive. Proceedings of 4th Agile Conference on Geographic Information Science, April 19-21 2001, Brno, pp. 535-544.
Efectos de la presión magnética en estrellas B peculiares en helio
NASA Astrophysics Data System (ADS)
Vallverdú, R.; Cidale, L.; Rohrmann, R.
Helium--peculiar stars display periodic variations in their helium line spectrum, being the variations of the forbidden components larger than the permitted ones. We model the atmosphere of helium--peculiar stars considering the presence of a magnetic field. For this, we introduce the Lorentz force term into the equation of hydrostatic equilibrium. This model enables us to explain partially the observed intensity variations of helium lines. In this work we improve our model by including the helium forbidden components and analyze the effect of the magnetic pressure on the line profiles. FULL TEXT IN SPANISH
Thrasher, James F; Pérez-Hernández, Rosaura; Arillo-Santillán, Edna; Barrientos-Gutiérrez, Inti
2015-01-01
Resumen Objetivo Evaluar el efecto de las advertencias sanitarias (AS) con pictogramas en las cajetillas de tabaco en adultos fumadores. Material y métodos Cohorte de fumadores con representatividad poblacional de siete ciudades mexi canas, antes (2010) y después (2011) de la implementación de AS con pictogramas (ASP). Para determinar el cambio en las variables sobre el impacto cognitivo y conductual de las advertencias, se estimaron modelos bivariados y ajustados de ecuaciones de estimación generalizada. En el Segundo levantamiento (2011), se estimaron modelos para determiner los factores que se asocian con el reporte de recordar cada advertencia que había entrado al mercado, además de los factores asociados con el autorreporte del impacto de cada advertencia vigente. Resultados Se observaron incrementos importantes de 2010 a 2011 en los conocimientos sobre los riesgos de fumar, los componentes tóxicos del tabaco y el número telefónico para recibir consejos sobre dejar de fumar. La recordación e impacto de las primeras advertencias con pictogramas parecen ser amplios y equitativos a través de la población fumadora. En comparación con 2010, un mayor nivel de ex fumadores entrevistados en 2011 reportaron que las advertencias habían influido mucho en dejar de fumar (RM=2.44, 95% IC 1.27–4.72). Conclusiones Las AS con pictogramas han logrado un impacto importante en el conocimiento y conducta, información relevante para la población y en tomadores de decisiones. PMID:22689162
Guanais, Frederico C.
2015-01-01
Objetivos. Examiné los efectos combinados del acceso a la atención primaria mediante el Programa de Salud Familiar (PSF) y las transferencias condicionadas de dinero en efectivo del Programa Bolsa Familia (PBF) sobre la mortalidad infantil posneonatal (MIPN) en Brasil. Métodos. Empleé un análisis ecológico longitudinal usando datos en panel de 4 583 municipios brasileños de 1998 al 2010, con 54 253 observaciones en total. Estimé modelos de regresión de efectos fijos por mínimos cuadrados ordinarios, con la tasa de MIPN como la variable dependiente y el PSF, el PBF y sus interacciones como las principales variables independientes de interés. Resultados. La asociación de una mayor cobertura del PSF con una menor tasa de MIPN se volvió más fuerte conforme aumentaba la cobertura del PBF. En los promedios de todas las demás variables, cuando la cobertura de PBF era 25%, la MIPN predicha fue 5,24 (intervalo de confianza [IC] de 95% = 4,95, 5,53) para una cobertura del PSF de 0%, y de 3,54 (IC de 95% = 2,77, 4,31) para una cobertura del PSF de 100%. Cuando la cobertura del PBF era de 60%, la MIPN predicha fue 4,65 (IC de 95% = 4,36, 4,94) para una cobertura del PSF de 0%, y de 1,38 (IC de 95% = 0,88, 1,89) para una cobertura del PSF de 100%. Conclusiones. El efecto del PSF depende de la ampliación del PBF. Para las poblaciones empobrecidas y subatendidas, la combinación de intervenciones tanto del lado de la oferta como del lado de la demanda podría ser necesaria para mejorar los resultados en salud.
El efecto de la difusión del Ne en las propiedades evolutivas y pulsacionales de las enanas blancas
NASA Astrophysics Data System (ADS)
Camisassa, M. E.; Miller Bertolami, M. M.; Althaus, L. G.; Córsico, A. H.
2016-08-01
Due the large neutron excess of Ne, this isotope rapidly sediments in the interior of the white dwarfs. This process releases an extra amount of energy, thus delaying the cooling times of the white dwarf. Furthermore, the overabundance of Ne in the inner regions of the star, modifies the Brunt-Vaisala frequency, thus, altering its pulsational properties. In this work, we discuss the impact of Ne sedimentation in white dwarfs derived from solar metallicity progenitors (). We performed evolutionary calculations of white dwarfs of, , and . These models are the result of the full evolutionary calculations of their progenitor stars, starting at the zero age main sequence. Our computations show that Ne sedimentation delays the cooling times of white dwarfs in about 1 Gyr at low luminosities (), affecting the techniques that use white dwarfs to date stellar populations. Neglecting Ne sedimentation when calculating the theoretical white dwarf luminosity function, implies to underestimate the age of the stellar population. Additionally, we studied the consequences of Ne sedimentation on the pulsational properties of ZZ Ceti white dwarfs.
Influencia de efectos cinéticos en la inestabilidad magneto-rotacional en discos de acreción
NASA Astrophysics Data System (ADS)
Montero, M. F.; Platzeck, A. M.; Gómez, D.
The potential role of kinetic effects in the development of instabilities in accretion disks has been recently discussed in various papers. Theoretical models of different types of accretion disks (protostellar, disks associated to binary systems, AGNs), propose mechanisms able to increase the effective viscosity of the flow in order to explain the estimated accretion rates in these objects. The magneto-rotational instability (Chandrasekhar 1960, also Balbus and Hawley 1991) provides a promising mechanism to produce a turbulent regime able to increase the effective viscosity. The relevance of the Hall effect in the linear stage of this instability has been pointed out by Wardle and Ng 1999 (also Balbus and Terquem 2001). We extend this analysis including also the effect of the electronic pressure in the generalized Ohm's law. Considering both the effects of Hall and electronic pressure, we find that a sensible increase of the unstable region in Fourier space is produced whenever the external magnetic field is anti-parallel to the vector describing the angular velocity of the disk. We studied the characteristics of this instability for sub-Keplerian, Keplerian and super-Keplerian disks.
NASA Astrophysics Data System (ADS)
Gonzalez Rivera, Maria M.
Se investigo el efecto de los mapas conceptuales sobre el dominio del proceso de fotosintesis en estudiantes universitarios. La investigacion utilizo dos estrategias: mapas conceptuales individuales y mapas conceptuales colaborativos, con el fin de investigar si existen diferencias significativas en el dominio del proceso de fotosintesis. El analisis de los datos incluyo aspectos cualitativos y cuantitativos. Se desprende del estudio que el 80% de los estudiantes describen la utilizacion de los mapas conceptuales como una experiencia beneficiosa. El 70% de los estudiantes expreso que los mapas conceptuales son utiles en el aprendizaje del proceso de fotosintesis y el 61% indico que facilitan la comprension de los conceptos. Los hallazgos mas importantes del analisis cuantitativo indican que los estudiantes que utilizaron los mapas conceptuales mejoraron significativamente su desempeno en la posprueba global. Se utilizo la prueba Mann-Whitney para investigar si existian diferencias significativas en la posprueba y preprueba global, el valor de W = 1945.0, para un valor p de 0.00, lo cual establece diferencias significativas. Para determinar si existian diferencias significativas entre la posprueba y preprueba del grupo individual, se realizo la prueba nuevamente. El valor de W correspondio a 490.5, que es significativo, con un valor p de 0.00. Se concluye que existen diferencias significativas entre la ejecucion de la posprueba y preprueba del grupo individual. Los datos proveen suficiente evidencia para sostener que los estudiantes que utilizaron la estrategia de mapas conceptuales individuales mejoraron el dominio del proceso de fotosintesis significativamente. Se realizo nuevamente la prueba para los resultados de posprueba y preprueba del grupo colaborativo. El valor de W correspondio a 446 con un valor p de 0.00. Se concluyo que existen diferencias significativas entre la ejecucion de la posprueba y preprueba del grupo colaborativo. Finalmente, se efectuo una
Mahgoub, Mohamed M; Macky, Tamer A
2017-07-11
Objetivo: El objetivo de este estudio fue comparar el efecto de la panfotocoagulación (PFC) en el edema macular diabético (EMD) en pacientes con retinopatía diabética proliferativa (RDP) con el fotocoagulador Pascal® (FP) vs. un fotocoagulador con láser de argón convencional (FLAC). Métodos: Se aleatorizó el uso de FP o FLAC en ochenta ojos con RDP y EMD con afectación central de la mácula. Ambos grupos tuvieron una evaluación de base de mejor agudeza visual corregida y fueron examinados con tomografía de coherencia óptica y angiografía con fluoresceína. Resultados: El número medio de disparos de láser en los grupos de FP y FLAC fue 1.726,10 y 752,00 en la sesión 1 y 1.589,00 y 830,00 (p < 0,001) en la sesión 2, respectivamente. El grosor foveal central (GFC) medio antes de comenzar el estudio fue 306 ± 100 y 314 ± 98 en los grupos de FP y FLAC, respectivamente. A las 8 semanas, el GFC medio fue 332 ± 116 y 347 ± 111 en los grupos de FP y FLAC, respectivamente (p > 0,05). La MAVC media fue similar durante el periodo de estudio y no hubo ninguna diferencia significativa entre los grupos (p > 0,05). Conclusiones: El FP y el FLAC mostraron efectos similares en el EMD en ojos con RDP y fueron igualmente seguros sin un aumento significativo del GFC. © 2017 S. Karger AG, Basel.
Efecto de la difusión y la velocidad en la ionización del átomo de Carbono
NASA Astrophysics Data System (ADS)
Rovira, M. G.; Fontenla, J. M.
The equations of statistical equilibrium for all ionization states of the atom are solved. The effects of diffusion and center of mass velocity are included. In order to estimate the modifications of the ionization curves, they were applied to the Carbon atom. To solve these equations, solar prominences' models obtained in a previous paper were adopted. They were extended to reach a temperature of 1.5 × 106 K and the complete model of the prominence was calculated. Ionization curves for different values of velocity, diffusion and medium models were obtained. The different models represent structures with different densities. Considerable modifications due to these effects are found.
Rol del efecto Hall en la reconexión magnética: aplicación a la magnetopausa terreste
NASA Astrophysics Data System (ADS)
Morales, L. F.; Dasso, S.; Gómez, D. O.
The Earth's magnetosphere is generated by the interaction of the solar wind with the Earth's magnetic field. The structure that separates the solar wind from the magnetosphere is called magnetopause. Magnetic reconnection is believed to be the dominant process by which solar wind particles penetrate into the magnetosphere. These events give rise to a variety of different fenomena such as Geomagnetic storms and aurorae. There are several theorical models of magnetic reconnection within the magnetohydrodynamic framework. Nevertheless, in collisionless fluids like magnetospheric plasma, the Hall effect may be important and may sensibly change the reconnection rate. The present work is focused on the study of Hall magnetic reconnection using a two-and-a-half configuration. Analytical solutions are obtained for steady state and the unsteady ones are studied by means of Hall magnetohydrodynamic simulations.
ten Cate, Jacob M
2015-01-01
Developing experimental models to understand dental caries has been the theme in our research group. Our first, the pH-cycling model, was developed to investigate the chemical reactions in enamel or dentine, which lead to dental caries. It aimed to leverage our understanding of the fluoride mode of action and was also utilized for the formulation of oral care products. In addition, we made use of intra-oral (in situ) models to study other features of the oral environment that drive the de/remineralization balance in individual patients. This model addressed basic questions, such as how enamel and dentine are affected by challenges in the oral cavity, as well as practical issues related to fluoride toothpaste efficacy. The observation that perhaps fluoride is not sufficiently potent to reduce dental caries in the present-day society triggered us to expand our knowledge in the bacterial aetiology of dental caries. For this we developed the Amsterdam Active Attachment biofilm model. Different from studies on planktonic ('single') bacteria, this biofilm model captures bacteria in a habitat similar to dental plaque. With data from the combination of these models, it should be possible to study separate processes which together may lead to dental caries. Also products and novel agents could be evaluated that interfere with either of the processes. Having these separate models in place, a suggestion is made to design computer models to encompass the available information. Models but also role models are of the utmost importance in bringing and guiding research and researchers.
ERIC Educational Resources Information Center
Freeman, Thomas J.
This paper discusses six different models of organizational structure and leadership, including the scalar chain or pyramid model, the continuum model, the grid model, the linking pin model, the contingency model, and the circle or democratic model. Each model is examined in a separate section that describes the model and its development, lists…
Models, Fiction, and Fictional Models
NASA Astrophysics Data System (ADS)
Liu, Chuang
2014-03-01
The following sections are included: * Introduction * Why Most Models in Science Are Not Fictional * Typically Fictional Models in Science * Modeling the Unobservable * Fictional Models for the Unobservable? * References
Mental Models, Conceptual Models, and Modelling.
ERIC Educational Resources Information Center
Greca, Ileana Maria; Moreira, Marco Antonio
2000-01-01
Reviews science education research into representations constructed by students in their interactions with the world, its phenomena, and artefacts. Features discussions of mental models, conceptual models, and the activity of modeling. (Contains 30 references.) (Author/WRM)
NASA Astrophysics Data System (ADS)
Li, Qin; Zhao, Yongxin; Wu, Xiaofeng; Liu, Si
There can be multitudinous models specifying aspects of the same system. Each model has a bias towards one aspect. These models often override in specific aspects though they have different expressions. A specification written in one model can be refined by introducing additional information from other models. The paper proposes a concept of promoting models which is a methodology to obtain refinements with support from cooperating models. It refines a primary model by integrating the information from a secondary model. The promotion principle is not merely an academic point, but also a reliable and robust engineering technique which can be used to develop software and hardware systems. It can also check the consistency between two specifications from different models. A case of modeling a simple online shopping system with the cooperation of the guarded design model and CSP model illustrates the practicability of the promotion principle.
Healy, Richard W.; Scanlon, Bridget R.
2010-01-01
Simulation models are widely used in all types of hydrologic studies, and many of these models can be used to estimate recharge. Models can provide important insight into the functioning of hydrologic systems by identifying factors that influence recharge. The predictive capability of models can be used to evaluate how changes in climate, water use, land use, and other factors may affect recharge rates. Most hydrological simulation models, including watershed models and groundwater-flow models, are based on some form of water-budget equation, so the material in this chapter is closely linked to that in Chapter 2. Empirical models that are not based on a water-budget equation have also been used for estimating recharge; these models generally take the form of simple estimation equations that define annual recharge as a function of precipitation and possibly other climatic data or watershed characteristics.Model complexity varies greatly. Some models are simple accounting models; others attempt to accurately represent the physics of water movement through each compartment of the hydrologic system. Some models provide estimates of recharge explicitly; for example, a model based on the Richards equation can simulate water movement from the soil surface through the unsaturated zone to the water table. Recharge estimates can be obtained indirectly from other models. For example, recharge is a parameter in groundwater-flow models that solve for hydraulic head (i.e. groundwater level). Recharge estimates can be obtained through a model calibration process in which recharge and other model parameter values are adjusted so that simulated water levels agree with measured water levels. The simulation that provides the closest agreement is called the best fit, and the recharge value used in that simulation is the model-generated estimate of recharge.
Yost, S.A.
1991-05-01
Radom matrix models based on an integral over supermatrices are proposed as a natural extension of bosonic matrix models. The subtle nature of superspace integration allows these models to have very different properties from the analogous bosonic models. Two choices of integration slice are investigated. One leads to a perturbative structure which is reminiscent of, and perhaps identical to, the usual Hermitian matrix models. Another leads to an eigenvalue reduction which can be described by a two component plasma in one dimension. A stationary point of the model is described.
This presentation presented information on entrainment models. Entrainment models use entrainment hypotheses to express the continuity equation. The advantage is that plume boundaries are known. A major disadvantage is that the problems that can be solved are rather simple. The ...
This presentation presented information on entrainment models. Entrainment models use entrainment hypotheses to express the continuity equation. The advantage is that plume boundaries are known. A major disadvantage is that the problems that can be solved are rather simple. The ...
ERIC Educational Resources Information Center
James, W. G. G.
1970-01-01
Discusses the historical development of both the wave and the corpuscular photon model of light. Suggests that students should be informed that the two models are complementary and that each model successfully describes a wide range of radiation phenomena. Cites 19 references which might be of interest to physics teachers and students. (LC)
ERIC Educational Resources Information Center
James, W. G. G.
1970-01-01
Discusses the historical development of both the wave and the corpuscular photon model of light. Suggests that students should be informed that the two models are complementary and that each model successfully describes a wide range of radiation phenomena. Cites 19 references which might be of interest to physics teachers and students. (LC)
Nonspherical Radiation Driven Wind Models Applied to Be Stars
NASA Astrophysics Data System (ADS)
Arauxo, F. X.
1990-11-01
ABSTRACT. In this work we present a model for the structure of a radiatively driven wind in the meridional plane of a hot star. Rotation effects and simulation of viscous forces were included in the motion equations. The line radiation force is considered with the inclusion of the finite disk correction in self-consistent computations which also contain gravity darkening as well as distortion of the star by rotation. An application to a typical BlV star leads to mass-flux ratios between equator and pole of the order of 10 and mass loss rates in the range 5.l0 to Mo/yr. Our envelope models are flattened towards the equator and the wind terminal velocities in that region are rather high (1000 Km/s). However, in the region near the star the equatorial velocity field is dominated by rotation. RESUMEN. Se presenta un modelo de la estructura de un viento empujado radiativamente en el plano meridional de una estrella caliente. Se incluyeron en las ecuaciones de movimiento los efectos de rotaci6n y la simulaci6n de fuerzas viscosas. Se consider6 la fuerza de las lineas de radiaci6n incluyendo la correcci6n de disco finito en calculos autoconsistentes los cuales incluyen oscurecimiento gravitacional asi como distorsi6n de la estrella por rotaci6n. La aplicaci6n a una estrella tipica BlV lleva a cocientes de flujo de masa entre el ecuador y el polo del orden de 10 de perdida de masa en el intervalo 5.l0 a 10 Mo/ano. Nuestros modelos de envolvente estan achatados hacia el ecuador y las velocidads terminales del viento en esa regi6n son bastante altas (1000 Km/s). Sin embargo, en la regi6n cercana a la estrella el campo de velocidad ecuatorial esta dominado por la rotaci6n. Key words: STARS-BE -- STARS-WINDS
Hydrological models are mediating models
NASA Astrophysics Data System (ADS)
Babel, L. V.; Karssenberg, D.
2013-08-01
Despite the increasing role of models in hydrological research and decision-making processes, only few accounts of the nature and function of models exist in hydrology. Earlier considerations have traditionally been conducted while making a clear distinction between physically-based and conceptual models. A new philosophical account, primarily based on the fields of physics and economics, transcends classes of models and scientific disciplines by considering models as "mediators" between theory and observations. The core of this approach lies in identifying models as (1) being only partially dependent on theory and observations, (2) integrating non-deductive elements in their construction, and (3) carrying the role of instruments of scientific enquiry about both theory and the world. The applicability of this approach to hydrology is evaluated in the present article. Three widely used hydrological models, each showing a different degree of apparent physicality, are confronted to the main characteristics of the "mediating models" concept. We argue that irrespective of their kind, hydrological models depend on both theory and observations, rather than merely on one of these two domains. Their construction is additionally involving a large number of miscellaneous, external ingredients, such as past experiences, model objectives, knowledge and preferences of the modeller, as well as hardware and software resources. We show that hydrological models convey the role of instruments in scientific practice by mediating between theory and the world. It results from these considerations that the traditional distinction between physically-based and conceptual models is necessarily too simplistic and refers at best to the stage at which theory and observations are steering model construction. The large variety of ingredients involved in model construction would deserve closer attention, for being rarely explicitly presented in peer-reviewed literature. We believe that devoting
Model Experiments and Model Descriptions
NASA Technical Reports Server (NTRS)
Jackman, Charles H.; Ko, Malcolm K. W.; Weisenstein, Debra; Scott, Courtney J.; Shia, Run-Lie; Rodriguez, Jose; Sze, N. D.; Vohralik, Peter; Randeniya, Lakshman; Plumb, Ian
1999-01-01
The Second Workshop on Stratospheric Models and Measurements Workshop (M&M II) is the continuation of the effort previously started in the first Workshop (M&M I, Prather and Remsberg [1993]) held in 1992. As originally stated, the aim of M&M is to provide a foundation for establishing the credibility of stratospheric models used in environmental assessments of the ozone response to chlorofluorocarbons, aircraft emissions, and other climate-chemistry interactions. To accomplish this, a set of measurements of the present day atmosphere was selected. The intent was that successful simulations of the set of measurements should become the prerequisite for the acceptance of these models as having a reliable prediction for future ozone behavior. This section is divided into two: model experiment and model descriptions. In the model experiment, participant were given the charge to design a number of experiments that would use observations to test whether models are using the correct mechanisms to simulate the distributions of ozone and other trace gases in the atmosphere. The purpose is closely tied to the needs to reduce the uncertainties in the model predicted responses of stratospheric ozone to perturbations. The specifications for the experiments were sent out to the modeling community in June 1997. Twenty eight modeling groups responded to the requests for input. The first part of this section discusses the different modeling group, along with the experiments performed. Part two of this section, gives brief descriptions of each model as provided by the individual modeling groups.
Model Experiments and Model Descriptions
NASA Technical Reports Server (NTRS)
Jackman, Charles H.; Ko, Malcolm K. W.; Weisenstein, Debra; Scott, Courtney J.; Shia, Run-Lie; Rodriguez, Jose; Sze, N. D.; Vohralik, Peter; Randeniya, Lakshman; Plumb, Ian
1999-01-01
The Second Workshop on Stratospheric Models and Measurements Workshop (M&M II) is the continuation of the effort previously started in the first Workshop (M&M I, Prather and Remsberg [1993]) held in 1992. As originally stated, the aim of M&M is to provide a foundation for establishing the credibility of stratospheric models used in environmental assessments of the ozone response to chlorofluorocarbons, aircraft emissions, and other climate-chemistry interactions. To accomplish this, a set of measurements of the present day atmosphere was selected. The intent was that successful simulations of the set of measurements should become the prerequisite for the acceptance of these models as having a reliable prediction for future ozone behavior. This section is divided into two: model experiment and model descriptions. In the model experiment, participant were given the charge to design a number of experiments that would use observations to test whether models are using the correct mechanisms to simulate the distributions of ozone and other trace gases in the atmosphere. The purpose is closely tied to the needs to reduce the uncertainties in the model predicted responses of stratospheric ozone to perturbations. The specifications for the experiments were sent out to the modeling community in June 1997. Twenty eight modeling groups responded to the requests for input. The first part of this section discusses the different modeling group, along with the experiments performed. Part two of this section, gives brief descriptions of each model as provided by the individual modeling groups.
Phillips, C.K.
1985-12-01
This lecture provides a survey of the methods used to model fast magnetosonic wave coupling, propagation, and absorption in tokamaks. The validity and limitations of three distinct types of modelling codes, which will be contrasted, include discrete models which utilize ray tracing techniques, approximate continuous field models based on a parabolic approximation of the wave equation, and full field models derived using finite difference techniques. Inclusion of mode conversion effects in these models and modification of the minority distribution function will also be discussed. The lecture will conclude with a presentation of time-dependent global transport simulations of ICRF-heated tokamak discharges obtained in conjunction with the ICRF modelling codes. 52 refs., 15 figs.
NASA Technical Reports Server (NTRS)
Druyan, Leonard M.
2012-01-01
Climate models is a very broad topic, so a single volume can only offer a small sampling of relevant research activities. This volume of 14 chapters includes descriptions of a variety of modeling studies for a variety of geographic regions by an international roster of authors. The climate research community generally uses the rubric climate models to refer to organized sets of computer instructions that produce simulations of climate evolution. The code is based on physical relationships that describe the shared variability of meteorological parameters such as temperature, humidity, precipitation rate, circulation, radiation fluxes, etc. Three-dimensional climate models are integrated over time in order to compute the temporal and spatial variations of these parameters. Model domains can be global or regional and the horizontal and vertical resolutions of the computational grid vary from model to model. Considering the entire climate system requires accounting for interactions between solar insolation, atmospheric, oceanic and continental processes, the latter including land hydrology and vegetation. Model simulations may concentrate on one or more of these components, but the most sophisticated models will estimate the mutual interactions of all of these environments. Advances in computer technology have prompted investments in more complex model configurations that consider more phenomena interactions than were possible with yesterday s computers. However, not every attempt to add to the computational layers is rewarded by better model performance. Extensive research is required to test and document any advantages gained by greater sophistication in model formulation. One purpose for publishing climate model research results is to present purported advances for evaluation by the scientific community.
Braby, L.A.
1990-09-01
The biological effects of ionizing radiation exposure are the result of a complex sequence of physical, chemical, biochemical, and physiological interactions. One way to begin a search for an understanding of health effects of radiation is through the development of phenomenological models of the response. Many models have been presented and tested in the slowly evolving process of characterizing cellular response. A range of models covering different endpoints and phenomena has developed in parallel. Many of these models employ similar assumptions about some underlying processes while differing about the nature of others. An attempt is made to organize many of the models into groups with similar features and to compare the consequences of those features with the actual experimental observations. It is assumed that by showing that some assumptions are inconsistent with experimental observations, the job of devising and testing mechanistic models can be simplified. 43 refs., 13 figs.
NASA Technical Reports Server (NTRS)
Tao, Wei-Kuo; Moncrieff, Mitchell; Einaud, Franco (Technical Monitor)
2001-01-01
Numerical cloud models have been developed and applied extensively to study cloud-scale and mesoscale processes during the past four decades. The distinctive aspect of these cloud models is their ability to treat explicitly (or resolve) cloud-scale dynamics. This requires the cloud models to be formulated from the non-hydrostatic equations of motion that explicitly include the vertical acceleration terms since the vertical and horizontal scales of convection are similar. Such models are also necessary in order to allow gravity waves, such as those triggered by clouds, to be resolved explicitly. In contrast, the hydrostatic approximation, usually applied in global or regional models, does allow the presence of gravity waves. In addition, the availability of exponentially increasing computer capabilities has resulted in time integrations increasing from hours to days, domain grids boxes (points) increasing from less than 2000 to more than 2,500,000 grid points with 500 to 1000 m resolution, and 3-D models becoming increasingly prevalent. The cloud resolving model is now at a stage where it can provide reasonably accurate statistical information of the sub-grid, cloud-resolving processes poorly parameterized in climate models and numerical prediction models.
V. Chipman
2002-10-05
The purpose of the Ventilation Model is to simulate the heat transfer processes in and around waste emplacement drifts during periods of forced ventilation. The model evaluates the effects of emplacement drift ventilation on the thermal conditions in the emplacement drifts and surrounding rock mass, and calculates the heat removal by ventilation as a measure of the viability of ventilation to delay the onset of peak repository temperature and reduce its magnitude. The heat removal by ventilation is temporally and spatially dependent, and is expressed as the fraction of heat carried away by the ventilation air compared to the fraction of heat produced by radionuclide decay. One minus the heat removal is called the wall heat fraction, or the remaining amount of heat that is transferred via conduction to the surrounding rock mass. Downstream models, such as the ''Multiscale Thermohydrologic Model'' (BSC 2001), use the wall heat fractions as outputted from the Ventilation Model to initialize their post-closure analyses. The Ventilation Model report was initially developed to analyze the effects of preclosure continuous ventilation in the Engineered Barrier System (EBS) emplacement drifts, and to provide heat removal data to support EBS design. Revision 00 of the Ventilation Model included documentation of the modeling results from the ANSYS-based heat transfer model. The purposes of Revision 01 of the Ventilation Model are: (1) To validate the conceptual model for preclosure ventilation of emplacement drifts and verify its numerical application in accordance with new procedural requirements as outlined in AP-SIII-10Q, Models (Section 7.0). (2) To satisfy technical issues posed in KTI agreement RDTME 3.14 (Reamer and Williams 2001a). Specifically to demonstrate, with respect to the ANSYS ventilation model, the adequacy of the discretization (Section 6.2.3.1), and the downstream applicability of the model results (i.e. wall heat fractions) to initialize post
Model Selection for Geostatistical Models
Hoeting, Jennifer A.; Davis, Richard A.; Merton, Andrew A.; Thompson, Sandra E.
2006-02-01
We consider the problem of model selection for geospatial data. Spatial correlation is typically ignored in the selection of explanatory variables and this can influence model selection results. For example, the inclusion or exclusion of particular explanatory variables may not be apparent when spatial correlation is ignored. To address this problem, we consider the Akaike Information Criterion (AIC) as applied to a geostatistical model. We offer a heuristic derivation of the AIC in this context and provide simulation results that show that using AIC for a geostatistical model is superior to the often used approach of ignoring spatial correlation in the selection of explanatory variables. These ideas are further demonstrated via a model for lizard abundance. We also employ the principle of minimum description length (MDL) to variable selection for the geostatistical model. The effect of sampling design on the selection of explanatory covariates is also explored.
ERIC Educational Resources Information Center
Oh, Phil Seok; Oh, Sung Jin
2013-01-01
Modeling in science has been studied by education researchers for decades and is now being applied broadly in school. It is among the scientific practices featured in the "Next Generation Science Standards" ("NGSS") (Achieve Inc. 2013). This article describes modeling activities in an extracurricular science club in a high…
NASA Technical Reports Server (NTRS)
Bardina, Jorge E.
1995-01-01
The objective of this work is to develop, verify, and incorporate the baseline two-equation turbulence models which account for the effects of compressibility into the three-dimensional Reynolds averaged Navier-Stokes (RANS) code and to provide documented descriptions of the models and their numerical procedures so that they can be implemented into 3-D CFD codes for engineering applications.
ERIC Educational Resources Information Center
Budiansky, Stephen
1980-01-01
This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)
Forbus, Kenneth D
2011-07-01
Qualitative modeling concerns the representations and reasoning that people use to understand continuous aspects of the world. Qualitative models formalize everyday notions of causality and provide accounts of how to ground symbolic, relational representations in perceptual processes. This article surveys the basic ideas of qualitative modeling and their applications from a cognitive science perspective. It describes the basic principles of qualitative modeling, and a variety of qualitative representations that have been developed for quantities and for relationships between them, providing a kind of qualitative mathematics. Three ontological frameworks for organizing modeling knowledge (processes, components, and field) are summarized, along with research on automatically assembling models for particular tasks from such knowledge. Qualitative simulation and how it carves up time into meaningful units is discussed. We discuss several accounts of causal reasoning about dynamical systems, based on different choices of qualitative mathematics and ontology. Qualitative spatial reasoning is explored, both in terms of relational systems and visual reasoning. Applications of qualitative models of particular interest to cognitive scientists are described, including how they have been used to capture the expertise of scientists and engineers and how they have been used in education. Open questions and frontiers are also discussed, focusing on relationships between ideas developed in the qualitative modeling community and other areas of cognitive science. WIREs Cogni Sci 2011 2 374-391 DOI: 10.1002/wcs.115 For further resources related to this article, please visit the WIREs website.
ERIC Educational Resources Information Center
Oh, Phil Seok; Oh, Sung Jin
2013-01-01
Modeling in science has been studied by education researchers for decades and is now being applied broadly in school. It is among the scientific practices featured in the "Next Generation Science Standards" ("NGSS") (Achieve Inc. 2013). This article describes modeling activities in an extracurricular science club in a high…
ERIC Educational Resources Information Center
Budiansky, Stephen
1980-01-01
This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)
Climate models and model evaluation
Gates, W.L.
1994-12-31
This brief overview addresses aspects of the nature, uses, evaluation and limitations of climate models. A comprehensive global modeling capability has been achieved only for the physical climate system, which is characterized by processes that serve to transport and exchange momentum, heat and moisture within and between the atmosphere, ocean and land surface. The fundamental aim of climate modeling, and the justification for the use of climate models, is the need to achieve a quantitative understanding of the operation of the climate system and to exploit any potential predictability that may exist.
Veronica J. Rutledge
2013-01-01
The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed within Multi-physics Object Oriented Simulation Environment (MOOSE) developed at the Idaho National Laboratory (INL). Off-gas Separation and REcoverY (OSPREY) models the adsorption of off-gas constituents for dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions. Inputs to the model include gas, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. The simulation outputs component concentrations along the column length as a function of time from which breakthrough data is obtained. The breakthrough data can be used to determine bed capacity, which in turn can be used to size columns. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data and parameters were input into the adsorption model to develop models specific for krypton adsorption. The same can be done for iodine, xenon, and tritium. The model will be validated with experimental breakthrough curves. Customers will be given access to
Mitchell, W.D.
1972-01-01
Model hydrographs are composed of pairs of dimensionless ratios, arrayed in tabular form, which, when modified by the appropriate values of rainfall exceed and by the time and areal characteristics of the drainage basin, satisfactorily represent the flood hydrograph for the basin. Model bydrographs are developed from a dimensionless translation hydrograph, having a time base of T hours and appropriately modified for storm duration by routing through reservoir storage, S=kOx. Models fall into two distinct classes: (1) those for which the value of x is unity and which have all the characteristics of true unit hydrographs and (2) those for which the value of x is other than unity and to which the unit-hydrograph principles of proportionality and superposition do not apply. Twenty-six families of linear models and eight families of nonlinear models in tabular form from the principal subject of this report. Supplemental discussions describe the development of the models and illustrate their application. Other sections of the report, supplemental to the tables, describe methods of determining the hydrograph characteristics, T, k, and x, both from observed hydrograph and from the physical characteristics of the drainage basin. Five illustrative examples of use show that the models, when properly converted to incorporate actual rainfall excess and the time and areal characteristics of the drainage basins, do indeed satisfactorily represent the observed flood hydrographs for the basins.
NASA Astrophysics Data System (ADS)
Grimaldi, P.
2012-07-01
These mandatory guidelines are provided for preparation of papers accepted for publication in the series of Volumes of The The stereometric modelling means modelling achieved with : - the use of a pair of virtual cameras, with parallel axes and positioned at a mutual distance average of 1/10 of the distance camera-object (in practice the realization and use of a stereometric camera in the modeling program); - the shot visualization in two distinct windows - the stereoscopic viewing of the shot while modelling. Since the definition of "3D vision" is inaccurately referred to as the simple perspective of an object, it is required to add the word stereo so that "3D stereo vision " shall stand for "three-dimensional view" and ,therefore, measure the width, height and depth of the surveyed image. Thanks to the development of a stereo metric model , either real or virtual, through the "materialization", either real or virtual, of the optical-stereo metric model made visible with a stereoscope. It is feasible a continuous on line updating of the cultural heritage with the help of photogrammetry and stereometric modelling. The catalogue of the Architectonic Photogrammetry Laboratory of Politecnico di Bari is available on line at: http://rappresentazione.stereofot.it:591/StereoFot/FMPro?-db=StereoFot.fp5&-lay=Scheda&-format=cerca.htm&-view
ERIC Educational Resources Information Center
Lin, Tony; Erfan, Sasan
2016-01-01
Mathematical modeling is an open-ended research subject where no definite answers exist for any problem. Math modeling enables thinking outside the box to connect different fields of studies together including statistics, algebra, calculus, matrices, programming and scientific writing. As an integral part of society, it is the foundation for many…
ERIC Educational Resources Information Center
Lin, Tony; Erfan, Sasan
2016-01-01
Mathematical modeling is an open-ended research subject where no definite answers exist for any problem. Math modeling enables thinking outside the box to connect different fields of studies together including statistics, algebra, calculus, matrices, programming and scientific writing. As an integral part of society, it is the foundation for many…
Modeling complexes of modeled proteins.
Anishchenko, Ivan; Kundrotas, Petras J; Vakser, Ilya A
2017-03-01
Structural characterization of proteins is essential for understanding life processes at the molecular level. However, only a fraction of known proteins have experimentally determined structures. This fraction is even smaller for protein-protein complexes. Thus, structural modeling of protein-protein interactions (docking) primarily has to rely on modeled structures of the individual proteins, which typically are less accurate than the experimentally determined ones. Such "double" modeling is the Grand Challenge of structural reconstruction of the interactome. Yet it remains so far largely untested in a systematic way. We present a comprehensive validation of template-based and free docking on a set of 165 complexes, where each protein model has six levels of structural accuracy, from 1 to 6 Å C(α) RMSD. Many template-based docking predictions fall into acceptable quality category, according to the CAPRI criteria, even for highly inaccurate proteins (5-6 Å RMSD), although the number of such models (and, consequently, the docking success rate) drops significantly for models with RMSD > 4 Å. The results show that the existing docking methodologies can be successfully applied to protein models with a broad range of structural accuracy, and the template-based docking is much less sensitive to inaccuracies of protein models than the free docking. Proteins 2017; 85:470-478. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
EPA's modeling community is working to gain insights into certain parts of a physical, biological, economic, or social system by conducting environmental assessments for Agency decision making to complex environmental issues.
NASA Astrophysics Data System (ADS)
Regardt, Olle; Rönnbäck, Lars; Bergholtz, Maria; Johannesson, Paul; Wohed, Petia
Maintaining and evolving data warehouses is a complex, error prone, and time consuming activity. The main reason for this state of affairs is that the environment of a data warehouse is in constant change, while the warehouse itself needs to provide a stable and consistent interface to information spanning extended periods of time. In this paper, we propose a modeling technique for data warehousing, called anchor modeling, that offers non-destructive extensibility mechanisms, thereby enabling robust and flexible management of changes in source systems. A key benefit of anchor modeling is that changes in a data warehouse environment only require extensions, not modifications, to the data warehouse. This ensures that existing data warehouse applications will remain unaffected by the evolution of the data warehouse, i.e. existing views and functions will not have to be modified as a result of changes in the warehouse model.
ERIC Educational Resources Information Center
Taylor, Emma
1991-01-01
A cheap and simple model that can be made and used by pupils to study the human breathing mechanism is presented. A list of needed materials, procedures for construction, possible refinements, and method of use are included. (KR)
NASA Technical Reports Server (NTRS)
Guillet, J. E.
1984-01-01
A reaction kinetics based model of the photodegradation process, which measures all important rate constants, and a computerized model capable of predicting the photodegradation rate and failure modes of a 30 year period, were developed. It is shown that the computerized photodegradation model for polyethylene correctly predicts failure of ELVAX 15 and cross linked ELVAX 150 on outdoor exposure. It is indicated that cross linking ethylene vinyl acetate (EVA) does not significantly change its degradation rate. It is shown that the effect of the stabilizer package is approximately equivalent on both polymers. The computerized model indicates that peroxide decomposers and UV absorbers are the most effective stabilizers. It is found that a combination of UV absorbers and a hindered amine light stabilizer (HALS) is the most effective stabilizer system.
Daniel, David J; Mc Pherson, Allen; Thorp, John R; Barrett, Richard; Clay, Robert; De Supinski, Bronis; Dube, Evi; Heroux, Mike; Janssen, Curtis; Langer, Steve; Laros, Jim
2011-01-14
A programming model is a set of software technologies that support the expression of algorithms and provide applications with an abstract representation of the capabilities of the underlying hardware architecture. The primary goals are productivity, portability and performance.
Energy models characterize the energy system, its evolution, and its interactions with the broader economy. The energy system consists of primary resources, including both fossil fuels and renewables; power plants, refineries, and other technologies to process and convert these r...
Energy models characterize the energy system, its evolution, and its interactions with the broader economy. The energy system consists of primary resources, including both fossil fuels and renewables; power plants, refineries, and other technologies to process and convert these r...
Ray, R.M. )
1986-12-01
PREDICTIVE MODELS is a collection of five models - CFPM, CO2PM, ICPM, PFPM, and SFPM - used in the 1982-1984 National Petroleum Council study of enhanced oil recovery (EOR) potential. Each pertains to a specific EOR process designed to squeeze additional oil from aging or spent oil fields. The processes are: 1) chemical flooding, where soap-like surfactants are injected into the reservoir to wash out the oil; 2) carbon dioxide miscible flooding, where carbon dioxide mixes with the lighter hydrocarbons making the oil easier to displace; 3) in-situ combustion, which uses the heat from burning some of the underground oil to thin the product; 4) polymer flooding, where thick, cohesive material is pumped into a reservoir to push the oil through the underground rock; and 5) steamflood, where pressurized steam is injected underground to thin the oil. CFPM, the Chemical Flood Predictive Model, models micellar (surfactant)-polymer floods in reservoirs, which have been previously waterflooded to residual oil saturation. Thus, only true tertiary floods are considered. An option allows a rough estimate of oil recovery by caustic or caustic-polymer processes. CO2PM, the Carbon Dioxide miscible flooding Predictive Model, is applicable to both secondary (mobile oil) and tertiary (residual oil) floods, and to either continuous CO2 injection or water-alternating gas processes. ICPM, the In-situ Combustion Predictive Model, computes the recovery and profitability of an in-situ combustion project from generalized performance predictive algorithms. PFPM, the Polymer Flood Predictive Model, is switch-selectable for either polymer or waterflooding, and an option allows the calculation of the incremental oil recovery and economics of polymer relative to waterflooding. SFPM, the Steamflood Predictive Model, is applicable to the steam drive process, but not to cyclic steam injection (steam soak) processes.
Model selection for geostatistical models.
Hoeting, Jennifer A; Davis, Richard A; Merton, Andrew A; Thompson, Sandra E
2006-02-01
We consider the problem of model selection for geospatial data. Spatial correlation is often ignored in the selection of explanatory variables, and this can influence model selection results. For example, the importance of particular explanatory variables may not be apparent when spatial correlation is ignored. To address this problem, we consider the Akaike Information Criterion (AIC) as applied to a geostatistical model. We offer a heuristic derivation of the AIC in this context and provide simulation results that show that using AIC for a geostatistical model is superior to the often-used traditional approach of ignoring spatial correlation in the selection of explanatory variables. These ideas are further demonstrated via a model for lizard abundance. We also apply the principle of minimum description length (MDL) to variable selection for the geostatistical model. The effect of sampling design on the selection of explanatory covariates is also explored. R software to implement the geostatistical model selection methods described in this paper is available in the Supplement.
Scalable Models Using Model Transformation
2008-07-13
huge number of web documents. We have created a simplified demo using 5 worker machines in the Ptolemy II modeling and simulation environment [3], as...the pattern of the transformation rule matches any subgraph of the input model. When the TransformationRule actor is opened in the Ptolemy II GUI...tool developed in the Ptolemy II frame- work, existing tools include AGG [14], PROGRES [15], AToM3 [16], FUJABA [17], VIATRA2 [18], and GReAT [19
Curtis, S.B.
1990-09-01
Several models and theories are reviewed that incorporate the idea of radiation-induced lesions (repairable and/or irreparable) that can be related to molecular lesions in the DNA molecule. Usually the DNA double-strand or chromatin break is suggested as the critical lesion. In the models, the shoulder on the low-LET survival curve is hypothesized as being due to one (or more) of the following three mechanisms: (1) interaction'' of lesions produced by statistically independent particle tracks; (2) nonlinear (i.e., linear-quadratic) increase in the yield of initial lesions, and (3) saturation of repair processes at high dose. Comparisons are made between the various approaches. Several significant advances in model development are discussed; in particular, a description of the matrix formulation of the Markov versions of the RMR and LPL models is given. The more advanced theories have incorporated statistical fluctuations in various aspects of the energy-loss and lesion-formation process. An important direction is the inclusion of physical and chemical processes into the formulations by incorporating relevant track structure theory (Monte Carlo track simulations) and chemical reactions of radiation-induced radicals. At the biological end, identification of repair genes and how they operate as well as a better understanding of how DNA misjoinings lead to lethal chromosome aberrations are needed for appropriate inclusion into the theories. More effort is necessary to model the complex end point of radiation-induced carcinogenesis.
Curtis, S.B.
1990-09-01
Several models and theories are reviewed that incorporate the idea of radiation-induced lesions (repairable and/or irreparable) that can be related to molecular lesions in the DNA molecule. Usually the DNA double-strand or chromatin break is suggested as the critical lesion. In the models, the shoulder on the low-LET survival curve is hypothesized as being due to one (or more) of the following three mechanisms: (1) ``interaction`` of lesions produced by statistically independent particle tracks; (2) nonlinear (i.e., linear-quadratic) increase in the yield of initial lesions, and (3) saturation of repair processes at high dose. Comparisons are made between the various approaches. Several significant advances in model development are discussed; in particular, a description of the matrix formulation of the Markov versions of the RMR and LPL models is given. The more advanced theories have incorporated statistical fluctuations in various aspects of the energy-loss and lesion-formation process. An important direction is the inclusion of physical and chemical processes into the formulations by incorporating relevant track structure theory (Monte Carlo track simulations) and chemical reactions of radiation-induced radicals. At the biological end, identification of repair genes and how they operate as well as a better understanding of how DNA misjoinings lead to lethal chromosome aberrations are needed for appropriate inclusion into the theories. More effort is necessary to model the complex end point of radiation-induced carcinogenesis.
Do stroke models model stroke?
Mergenthaler, Philipp; Meisel, Andreas
2012-01-01
Stroke is one of the leading causes of death worldwide and the biggest reason for long-term disability. Basic research has formed the modern understanding of stroke pathophysiology, and has revealed important molecular, cellular and systemic mechanisms. However, despite decades of research, most translational stroke trials that aim to introduce basic research findings into clinical treatment strategies – most notably in the field of neuroprotection – have failed. Among other obstacles, poor methodological and statistical standards, negative publication bias, and incomplete preclinical testing have been proposed as ‘translational roadblocks’. In this article, we introduce the models commonly used in preclinical stroke research, discuss some of the causes of failed translational success and review potential remedies. We further introduce the concept of modeling ‘care’ of stroke patients, because current preclinical research models the disorder but does not model care or state-of-the-art clinical testing. Stringent statistical methods and controlled preclinical trials have been suggested to counteract weaknesses in preclinical research. We conclude that preclinical stroke research requires (1) appropriate modeling of the disorder, (2) appropriate modeling of the care of stroke patients and (3) an approach to preclinical testing that is similar to clinical testing, including Phase 3 randomized controlled preclinical trials as necessary additional steps before new therapies enter clinical testing. PMID:23115201
NASA Technical Reports Server (NTRS)
Denning, Peter J.
1990-01-01
Although powerful computers have allowed complex physical and manmade hardware systems to be modeled successfully, we have encountered persistent problems with the reliability of computer models for systems involving human learning, human action, and human organizations. This is not a misfortune; unlike physical and manmade systems, human systems do not operate under a fixed set of laws. The rules governing the actions allowable in the system can be changed without warning at any moment, and can evolve over time. That the governing laws are inherently unpredictable raises serious questions about the reliability of models when applied to human situations. In these domains, computers are better used, not for prediction and planning, but for aiding humans. Examples are systems that help humans speculate about possible futures, offer advice about possible actions in a domain, systems that gather information from the networks, and systems that track and support work flows in organizations.
NASA Astrophysics Data System (ADS)
Harvey, Alex
1993-10-01
Two of the most common terms employed in discussing cosmological models are open and closed. They are occasionally misused either by not recognizing or by not making it clear that each term may be used to characterize, independently and simultaneously, both the dynamic behavior and spatial geometric structure of the model under discussion. In addition, the spatial geometric structure implied by the terms open and closed is itself often either misunderstood or misused. Lastly, the role played by the cosmological constant is often improperly slighted. This paper is intended to give several examples of the abuse of terminology and clarify the distinction by means of a brief, elementary overview of Friedmann-Robertson-Walker cosmological models.
NASA Technical Reports Server (NTRS)
Sturgess, G. J.
1982-01-01
The objectives, approach, and status of a program to develop the computational fluid dynamics tools needed to improve combustor design and analysis are outlined. The calculation procedure selected consists of a finite difference solution of the time averaged, steady state, primitive variable, elliptic form of the Reynolds equations. Standard TEACH type numerics are used to solve the resulting equations. These include hybrid differencing, SIMPLE algorithm for the pressure field, line by line iterative solution using the ADI method and the tridiagonal matrix algorithm (TDMA). Convergence is facilitated by using under relaxation. The physical processes are modeled by a two equation eddy viscosity model for turbulence; combustion is represented by a simple, irreversible, one step chemical reaction whose rate is influenced only by the time scale of the turbulence. The model evaluation procedure is also described.
Woosley, S.E.; Weaver, T.A.
1980-01-01
Recent progress in understanding the observed properties of Type I supernovae as a consequence of the thermonuclear detonation of white dwarf stars and the ensuing decay of the /sup 56/Ni produced therein is reviewed. Within the context of this model for Type I explosions and the 1978 model for Type II explosions, the expected nucleosynthesis and gamma-line spectra from both kinds of supernovae are presented. Finally, a qualitatively new approach to the problem of massive star death and Type II supernovae based upon a combination of rotation and thermonuclear burning is discussed.
NASA Technical Reports Server (NTRS)
Smith, J. A. (Principal Investigator)
1985-01-01
The overall goal of this work has been to develop a set of computational tools and media abstractions for the terrain bidirectional reflectance problem. The modeling of soil and vegetation surfaces has been emphasized with a gradual increase in the complexity of the media geometries treated. Pragmatic problems involved in the combined modeling of soil, vegetation, and atmospheric effects have been of interest and one of the objectives has been to describe the canopy reflectance problem in a classical radiative transfer sense permitting easier inclusion of our work by other workers in the radiative transfer field.
Although air quality models have been applied historically to address issues specific to ambient air quality standards (i.e., one criteria pollutant at a time) or welfare (e.g.. acid deposition or visibility impairment). they are inherently multipollutant based. Therefore. in pri...
NASA Astrophysics Data System (ADS)
Baart, F.; Donchyts, G.; van Dam, A.; Plieger, M.
2015-12-01
The emergence of interactive art has blurred the line between electronic, computer graphics and art. Here we apply this art form to numerical models. Here we show how the transformation of a numerical model into an interactive painting can both provide insights and solve real world problems. The cases that are used as an example include forensic reconstructions, dredging optimization, barrier design. The system can be fed using any source of time varying vector fields, such as hydrodynamic models. The cases used here, the Indian Ocean (HYCOM), the Wadden Sea (Delft3D Curvilinear), San Francisco Bay (3Di subgrid and Delft3D Flexible Mesh), show that the method used is suitable for different time and spatial scales. High resolution numerical models become interactive paintings by exchanging their velocity fields with a high resolution (>=1M cells) image based flow visualization that runs in a html5 compatible web browser. The image based flow visualization combines three images into a new image: the current image, a drawing, and a uv + mask field. The advection scheme that computes the resultant image is executed in the graphics card using WebGL, allowing for 1M grid cells at 60Hz performance on mediocre graphic cards. The software is provided as open source software. By using different sources for a drawing one can gain insight into several aspects of the velocity fields. These aspects include not only the commonly represented magnitude and direction, but also divergence, topology and turbulence .
ERIC Educational Resources Information Center
Finger Lakes Regional Education Center for Economic Development, Mount Morris, NY.
This guide describes seven model programs that were developed by the Finger Lakes Regional Center for Economic Development (New York) to meet the training needs of female and minority entrepreneurs to help their businesses survive and grow and to assist disabled and dislocated workers and youth in beginning small businesses. The first three models…
Wolkenhauer, Olaf
2014-01-01
Next generation sequencing technologies are bringing about a renaissance of mining approaches. A comprehensive picture of the genetic landscape of an individual patient will be useful, for example, to identify groups of patients that do or do not respond to certain therapies. The high expectations may however not be satisfied if the number of patient groups with similar characteristics is going to be very large. I therefore doubt that mining sequence data will give us an understanding of why and when therapies work. For understanding the mechanisms underlying diseases, an alternative approach is to model small networks in quantitative mechanistic detail, to elucidate the role of gene and proteins in dynamically changing the functioning of cells. Here an obvious critique is that these models consider too few components, compared to what might be relevant for any particular cell function. I show here that mining approaches and dynamical systems theory are two ends of a spectrum of methodologies to choose from. Drawing upon personal experience in numerous interdisciplinary collaborations, I provide guidance on how to model by discussing the question "Why model?"
ERIC Educational Resources Information Center
Goodwyn, Lauren; Salm, Sarah
2007-01-01
Teaching the anatomy of the muscle system to high school students can be challenging. Students often learn about muscle anatomy by memorizing information from textbooks or by observing plastic, inflexible models. Although these mediums help students learn about muscle placement, the mediums do not facilitate understanding regarding integration of…
ERIC Educational Resources Information Center
Finger Lakes Regional Education Center for Economic Development, Mount Morris, NY.
This guide describes seven model programs that were developed by the Finger Lakes Regional Center for Economic Development (New York) to meet the training needs of female and minority entrepreneurs to help their businesses survive and grow and to assist disabled and dislocated workers and youth in beginning small businesses. The first three models…
ERIC Educational Resources Information Center
Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda
2004-01-01
Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…
Ensemble forecasting has been used for operational numerical weather prediction in the United States and Europe since the early 1990s. An ensemble of weather or climate forecasts is used to characterize the two main sources of uncertainty in computer models of physical systems: ...
ERIC Educational Resources Information Center
Goodwyn, Lauren; Salm, Sarah
2007-01-01
Teaching the anatomy of the muscle system to high school students can be challenging. Students often learn about muscle anatomy by memorizing information from textbooks or by observing plastic, inflexible models. Although these mediums help students learn about muscle placement, the mediums do not facilitate understanding regarding integration of…
Although air quality models have been applied historically to address issues specific to ambient air quality standards (i.e., one criteria pollutant at a time) or welfare (e.g.. acid deposition or visibility impairment). they are inherently multipollutant based. Therefore. in pri...
ERIC Educational Resources Information Center
Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda
2004-01-01
Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…
Ensemble forecasting has been used for operational numerical weather prediction in the United States and Europe since the early 1990s. An ensemble of weather or climate forecasts is used to characterize the two main sources of uncertainty in computer models of physical systems: ...
A. Alsaed
2004-09-14
The ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003) presents the methodology for evaluating potential criticality situations in the monitored geologic repository. As stated in the referenced Topical Report, the detailed methodology for performing the disposal criticality analyses will be documented in model reports. Many of the models developed in support of the Topical Report differ from the definition of models as given in the Office of Civilian Radioactive Waste Management procedure AP-SIII.10Q, ''Models'', in that they are procedural, rather than mathematical. These model reports document the detailed methodology necessary to implement the approach presented in the Disposal Criticality Analysis Methodology Topical Report and provide calculations utilizing the methodology. Thus, the governing procedure for this type of report is AP-3.12Q, ''Design Calculations and Analyses''. The ''Criticality Model'' is of this latter type, providing a process evaluating the criticality potential of in-package and external configurations. The purpose of this analysis is to layout the process for calculating the criticality potential for various in-package and external configurations and to calculate lower-bound tolerance limit (LBTL) values and determine range of applicability (ROA) parameters. The LBTL calculations and the ROA determinations are performed using selected benchmark experiments that are applicable to various waste forms and various in-package and external configurations. The waste forms considered in this calculation are pressurized water reactor (PWR), boiling water reactor (BWR), Fast Flux Test Facility (FFTF), Training Research Isotope General Atomic (TRIGA), Enrico Fermi, Shippingport pressurized water reactor, Shippingport light water breeder reactor (LWBR), N-Reactor, Melt and Dilute, and Fort Saint Vrain Reactor spent nuclear fuel (SNF). The scope of this analysis is to document the criticality computational method. The criticality
NASA Astrophysics Data System (ADS)
Lovos, F. V.; Gómez, M.; Ahumada, J. A.; Petrucci, R.; Jofré, J. E.
2016-08-01
Weak Emission T Tauri stars (WTTS) are pre-main sequence stars with ages of 10 10 yr, stage at which circumstellar disk material is being used to form planets. This class of young stars shows photometric variations that correlate with the rotational period and are attributed to magnetic cold spots. To model the planet-spot-star system we use the soap-t code, that allows the construction of light curves including planetary transits and spots at the same time. We focus on the deformations that the spot introduces to the transit profile for the case of a proto-planet with 2 Jupiter radii. We consider spotted areas typical for WTTS covering from to of the visible stellar disk, with temperatures of 500 and 1400 K less than that of the stellar surface. The results show the modulation of the stellar brightness caused by the spot. In particular, this modulation increases the depth of the transit. Furthermore, when the spot is eclipsed by the proto-planet, a rebrightening is observed as the planet blocks a zone cooler than the rest of the stellar surface.
Models, Part V: Composition Models.
ERIC Educational Resources Information Center
Callison, Daniel
2003-01-01
Describes four models: The Authoring Cycle, a whole language approach that reflects the inquiry process; I-Search, an approach to research that uses the power of student interests; Cultural Celebration, using local heritage topics; and Science Lab Report, for the composition of a lab report. (LRW)
NASA Astrophysics Data System (ADS)
Herrmann, H. J.; Kun, F.
2007-12-01
Fibre models have been introduced as simple models to describe failure. They are based on the probability distribution of broken fibres. The load redistribution after a fibre yields can be global or local and the first case can often be solved analytically. We will present an interpolation between these the local and the global case and apply it to experimental situations like the compression of granular packings. Introducing viscoelastic fibres allows to describe the creep of wood. It is even possible to deal analytically with a gradual degradation of fibres and consider damage as well as healing. In this way Basquin's law of fatigue can be reproduced and new universalities concerning the histograms of bursts and waiting times can be uncovered.
NASA Technical Reports Server (NTRS)
2000-01-01
The molecule modeling method known as Multibody Order (N) Dynamics, or MBO(N)D, was developed by Moldyn, Inc. at Goddard Space Flight Center through funding provided by the SBIR program. The software can model the dynamics of molecules through technology which stimulates low-frequency molecular motions and properties, such as movements among a molecule's constituent parts. With MBO(N)D, a molecule is substructured into a set of interconnected rigid and flexible bodies. These bodies replace the computation burden of mapping individual atoms. Moldyn's technology cuts computation time while increasing accuracy. The MBO(N)D technology is available as Insight II 97.0 from Molecular Simulations, Inc. Currently the technology is used to account for forces on spacecraft parts and to perform molecular analyses for pharmaceutical purposes. It permits the solution of molecular dynamics problems on a moderate workstation, as opposed to on a supercomputer.
NASA Astrophysics Data System (ADS)
Fossión, Rubén
2010-09-01
The atomic nucleus is a typical example of a many-body problem. On the one hand, the number of nucleons (protons and neutrons) that constitute the nucleus is too large to allow for exact calculations. On the other hand, the number of constituent particles is too small for the individual nuclear excitation states to be explained by statistical methods. Another problem, particular for the atomic nucleus, is that the nucleon-nucleon (n-n) interaction is not one of the fundamental forces of Nature, and is hard to put in a single closed equation. The nucleon-nucleon interaction also behaves differently between two free nucleons (bare interaction) and between two nucleons in the nuclear medium (dressed interaction). Because of the above reasons, specific nuclear many-body models have been devised of which each one sheds light on some selected aspects of nuclear structure. Only combining the viewpoints of different models, a global insight of the atomic nucleus can be gained. In this chapter, we revise the the Nuclear Shell Model as an example of the microscopic approach, and the Collective Model as an example of the geometric approach. Finally, we study the statistical properties of nuclear spectra, basing on symmetry principles, to find out whether there is quantum chaos in the atomic nucleus. All three major approaches have been rewarded with the Nobel Prize of Physics. In the text, we will stress how each approach introduces its own series of approximations to reduce the prohibitingly large number of degrees of freedom of the full many-body problem to a smaller manageable number of effective degrees of freedom.
Fossion, Ruben
2010-09-10
The atomic nucleus is a typical example of a many-body problem. On the one hand, the number of nucleons (protons and neutrons) that constitute the nucleus is too large to allow for exact calculations. On the other hand, the number of constituent particles is too small for the individual nuclear excitation states to be explained by statistical methods. Another problem, particular for the atomic nucleus, is that the nucleon-nucleon (n-n) interaction is not one of the fundamental forces of Nature, and is hard to put in a single closed equation. The nucleon-nucleon interaction also behaves differently between two free nucleons (bare interaction) and between two nucleons in the nuclear medium (dressed interaction).Because of the above reasons, specific nuclear many-body models have been devised of which each one sheds light on some selected aspects of nuclear structure. Only combining the viewpoints of different models, a global insight of the atomic nucleus can be gained. In this chapter, we revise the the Nuclear Shell Model as an example of the microscopic approach, and the Collective Model as an example of the geometric approach. Finally, we study the statistical properties of nuclear spectra, basing on symmetry principles, to find out whether there is quantum chaos in the atomic nucleus. All three major approaches have been rewarded with the Nobel Prize of Physics. In the text, we will stress how each approach introduces its own series of approximations to reduce the prohibitingly large number of degrees of freedom of the full many-body problem to a smaller manageable number of effective degrees of freedom.
Plimpton, Steven James; Heffernan, Julieanne; Sasaki, Darryl Yoshio; Frischknecht, Amalie Lucile; Stevens, Mark Jackson; Frink, Laura J. Douglas
2005-11-01
Understanding the properties and behavior of biomembranes is fundamental to many biological processes and technologies. Microdomains in biomembranes or ''lipid rafts'' are now known to be an integral part of cell signaling, vesicle formation, fusion processes, protein trafficking, and viral and toxin infection processes. Understanding how microdomains form, how they depend on membrane constituents, and how they act not only has biological implications, but also will impact Sandia's effort in development of membranes that structurally adapt to their environment in a controlled manner. To provide such understanding, we created physically-based models of biomembranes. Molecular dynamics (MD) simulations and classical density functional theory (DFT) calculations using these models were applied to phenomena such as microdomain formation, membrane fusion, pattern formation, and protein insertion. Because lipid dynamics and self-organization in membranes occur on length and time scales beyond atomistic MD, we used coarse-grained models of double tail lipid molecules that spontaneously self-assemble into bilayers. DFT provided equilibrium information on membrane structure. Experimental work was performed to further help elucidate the fundamental membrane organization principles.
NASA Technical Reports Server (NTRS)
Dill, David L.
1995-01-01
Automatic formal verification methods for finite-state systems, also known as model-checking, successfully reduce labor costs since they are mostly automatic. Model checkers explicitly or implicitly enumerate the reachable state space of a system, whose behavior is described implicitly, perhaps by a program or a collection of finite automata. Simple properties, such as mutual exclusion or absence of deadlock, can be checked by inspecting individual states. More complex properties, such as lack of starvation, require search for cycles in the state graph with particular properties. Specifications to be checked may consist of built-in properties, such as deadlock or 'unspecified receptions' of messages, another program or implicit description, to be compared with a simulation, bisimulation, or language inclusion relation, or an assertion in one of several temporal logics. Finite-state verification tools are beginning to have a significant impact in commercial designs. There are many success stories of verification tools finding bugs in protocols or hardware controllers. In some cases, these tools have been incorporated into design methodology. Research in finite-state verification has been advancing rapidly, and is showing no signs of slowing down. Recent results include probabilistic algorithms for verification, exploitation of symmetry and independent events, and the use symbolic representations for Boolean functions and systems of linear inequalities. One of the most exciting areas for further research is the combination of model-checking with theorem-proving methods.
NASA Astrophysics Data System (ADS)
Holmes, Jon L.
1999-06-01
Molecular modeling has trickled down from the realm of pharmaceutical and research laboratories into the realm of undergraduate chemistry instruction. It has opened avenues for the visualization of chemical concepts that previously were difficult or impossible to convey. I am sure that many of you have developed exercises using the various molecular modeling tools. It is the desire of this Journal to become an avenue for you to share these exercises among your colleagues. It is to this end that Ron Starkey has agreed to edit such a column and to publish not only the description of such exercises, but also the software documents they use. The WWW is the obvious medium to distribute this combination and so accepted submissions will appear online as a feature of JCE Internet. Typical molecular modeling exercise: finding conformation energies. Molecular Modeling Exercises and Experiments is the latest feature column of JCE Internet, joining Conceptual Questions and Challenge Problems, Hal's Picks, and Mathcad in the Chemistry Curriculum. JCE Internet continues to seek submissions in these areas of interest and submissions of general interest. If you have developed materials and would like to submit them, please see our Guide to Submissions for more information. The Chemical Education Resource Shelf, Equipment Buyers Guide, and WWW Site Review would also like to hear about chemistry textbooks and software, equipment, and WWW sites, respectively. Please consult JCE Internet Features to learn more about these resources at JCE Online. Email Announcements Would you like to be informed by email when the latest issue of the Journal is available online? when a new JCE Software title is shipping? when a new JCE Internet article has been published or is available for Open Review? when your subscription is about to expire? A new feature of JCE Online makes this possible. Visit our Guestbook to learn how. When
Students' Models of Curve Fitting: A Models and Modeling Perspective
ERIC Educational Resources Information Center
Gupta, Shweta
2010-01-01
The Models and Modeling Perspectives (MMP) has evolved out of research that began 26 years ago. MMP researchers use Model Eliciting Activities (MEAs) to elicit students' mental models. In this study MMP was used as the conceptual framework to investigate the nature of students' models of curve fitting in a problem-solving environment consisting of…
10. MOVABLE BED SEDIMENTATION MODELS. DOGTOOTH BEND MODEL (MODEL SCALE: ...
10. MOVABLE BED SEDIMENTATION MODELS. DOGTOOTH BEND MODEL (MODEL SCALE: 1' = 400' HORIZONTAL, 1' = 100' VERTICAL), AND GREENVILLE BRIDGE MODEL (MODEL SCALE: 1' = 360' HORIZONTAL, 1' = 100' VERTICAL). - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS
Vincent, Julian F V
2003-01-01
Biomimetics is seen as a path from biology to engineering. The only path from engineering to biology in current use is the application of engineering concepts and models to biological systems. However, there is another pathway: the verification of biological mechanisms by manufacture, leading to an iterative process between biology and engineering in which the new understanding that the engineering implementation of a biological system can bring is fed back into biology, allowing a more complete and certain understanding and the possibility of further revelations for application in engineering. This is a pathway as yet unformalized, and one that offers the possibility that engineers can also be scientists. PMID:14561351
Comparative Protein Structure Modeling Using MODELLER
Webb, Benjamin; Sali, Andrej
2016-01-01
Comparative protein structure modeling predicts the three-dimensional structure of a given protein sequence (target) based primarily on its alignment to one or more proteins of known structure (templates). The prediction process consists of fold assignment, target-template alignment, model building, and model evaluation. This unit describes how to calculate comparative models using the program MODELLER and how to use the ModBase database of such models, and discusses all four steps of comparative modeling, frequently observed errors, and some applications. Modeling lactate dehydrogenase from Trichomonas vaginalis (TvLDH) is described as an example. The download and installation of the MODELLER software is also described. PMID:27322406
Pre-Modeling Ensures Accurate Solid Models
ERIC Educational Resources Information Center
Gow, George
2010-01-01
Successful solid modeling requires a well-organized design tree. The design tree is a list of all the object's features and the sequential order in which they are modeled. The solid-modeling process is faster and less prone to modeling errors when the design tree is a simple and geometrically logical definition of the modeled object. Few high…
Pre-Modeling Ensures Accurate Solid Models
ERIC Educational Resources Information Center
Gow, George
2010-01-01
Successful solid modeling requires a well-organized design tree. The design tree is a list of all the object's features and the sequential order in which they are modeled. The solid-modeling process is faster and less prone to modeling errors when the design tree is a simple and geometrically logical definition of the modeled object. Few high…
Modeling metrology for calibration of OPC models
NASA Astrophysics Data System (ADS)
Mack, Chris A.; Raghunathan, Ananthan; Sturtevant, John; Deng, Yunfei; Zuniga, Christian; Adam, Kostas
2016-03-01
Optical Proximity Correction (OPC) has continually improved in accuracy over the years by adding more physically based models. Here, we further extend OPC modeling by adding the Analytical Linescan Model (ALM) to account for systematic biases in CD-SEM metrology. The ALM was added to a conventional OPC model calibration flow and the accuracy of the calibrated model with the ALM was compared to the standard model without the ALM using validation data. Without using any adjustable parameters in the ALM, OPC validation accuracy was improved by 5%. While very preliminary, these results give hope that modeling metrology could be an important next step in OPC model improvement.
Vector models and generalized SYK models
NASA Astrophysics Data System (ADS)
Peng, Cheng
2017-05-01
We consider the relation between SYK-like models and vector models by studying a toy model where a tensor field is coupled with a vector field. By integrating out the tensor field, the toy model reduces to the Gross-Neveu model in 1 dimension. On the other hand, a certain perturbation can be turned on and the toy model flows to an SYK-like model at low energy. A chaotic-nonchaotic phase transition occurs as the sign of the perturbation is altered. We further study similar models that possess chaos and enhanced reparameterization symmetries.
Vector models and generalized SYK models
Peng, Cheng
2017-05-23
Here, we consider the relation between SYK-like models and vector models by studying a toy model where a tensor field is coupled with a vector field. By integrating out the tensor field, the toy model reduces to the Gross-Neveu model in 1 dimension. On the other hand, a certain perturbation can be turned on and the toy model flows to an SYK-like model at low energy. Furthermore, a chaotic-nonchaotic phase transition occurs as the sign of the perturbation is altered. We further study similar models that possess chaos and enhanced reparameterization symmetries.
Building Mental Models by Dissecting Physical Models
ERIC Educational Resources Information Center
Srivastava, Anveshna
2016-01-01
When students build physical models from prefabricated components to learn about model systems, there is an implicit trade-off between the physical degrees of freedom in building the model and the intensity of instructor supervision needed. Models that are too flexible, permitting multiple possible constructions require greater supervision to…
Building Mental Models by Dissecting Physical Models
ERIC Educational Resources Information Center
Srivastava, Anveshna
2016-01-01
When students build physical models from prefabricated components to learn about model systems, there is an implicit trade-off between the physical degrees of freedom in building the model and the intensity of instructor supervision needed. Models that are too flexible, permitting multiple possible constructions require greater supervision to…
John A. Schroeder
2012-06-01
The Standardized Plant Analysis Risk (SPAR) models for the U.S. commercial nuclear power plants currently have very limited instrumentation and control (I&C) modeling [1]. Most of the I&C components in the operating plant SPAR models are related to the reactor protection system. This was identified as a finding during the industry peer review of SPAR models. While the Emergency Safeguard Features (ESF) actuation and control system was incorporated into the Peach Bottom Unit 2 SPAR model in a recent effort [2], various approaches to expend resources for detailed I&C modeling in other SPAR models are investigated.
Forward model nonlinearity versus inverse model nonlinearity
Mehl, S.
2007-01-01
The issue of concern is the impact of forward model nonlinearity on the nonlinearity of the inverse model. The question posed is, "Does increased nonlinearity in the head solution (forward model) always result in increased nonlinearity in the inverse solution (estimation of hydraulic conductivity)?" It is shown that the two nonlinearities are separate, and it is not universally true that increased forward model nonlinearity increases inverse model nonlinearity. ?? 2007 National Ground Water Association.
Modeling natural gas reservoirs: A simple model
Collier, Richard S.; Monash, E.A.
1981-01-01
A mathematical model is developed and tested for the production of natural gas with water encroachment and gas entrapment. The model is built on the material and volumetric balance relations, the Schilthuis water drive model, and a gas entrapment mechanism which assumes that the rate of gas entrapment is proportional to the volumetric rate of water influx. This model represents an alternative to the large grid models because of its low computer, maintenance, and manpower costs.
Engineering Structurally Configurable Models with Model Transformation
2008-12-15
model in the case of Simulink, and a dataflow model in the case of LabVIEW). Research modeling tools such as Ptolemy II [14], ForSyDe [21], SPEX [30...functionality of our model transformation tool built in the Ptolemy II framework, and its application to large models of distributed and parallel embedded...in Ptolemy II, the same idea can be applied to other modeling tools such as Simulink, LabVIEW, ForSyDe, SPEX and ModHel’X. Moreover, the recent OMG
Chao, Dennis L; Longini, Ira M; Morris, J Glenn
2014-01-01
Mathematical modeling can be a valuable tool for studying infectious disease outbreak dynamics and simulating the effects of possible interventions. Here, we describe approaches to modeling cholera outbreaks and how models have been applied to explore intervention strategies, particularly in Haiti. Mathematical models can play an important role in formulating and evaluating complex cholera outbreak response options. Major challenges to cholera modeling are insufficient data for calibrating models and the need to tailor models for different outbreak scenarios.
Longini, Ira M.; Morris, J. Glenn
2014-01-01
Mathematical modeling can be a valuable tool for studying infectious disease outbreak dynamics and simulating the effects of possible interventions. Here, we describe approaches to modeling cholera outbreaks and how models have been applied to explore intervention strategies, particularly in Haiti. Mathematical models can play an important role in formulating and evaluating complex cholera outbreak response options. Major challenges to cholera modeling are insufficient data for calibrating models and the need to tailor models for different outbreak scenarios. PMID:23412687
Uncertainty Modeling Via Frequency Domain Model Validation
NASA Technical Reports Server (NTRS)
Waszak, Martin R.; Andrisani, Dominick, II
1999-01-01
Abstract The majority of literature on robust control assumes that a design model is available and that the uncertainty model bounds the actual variations about the nominal model. However, methods for generating accurate design models have not received as much attention in the literature. The influence of the level of accuracy of the uncertainty model on closed loop performance has received even less attention. The research reported herein is an initial step in applying and extending the concept of model validation to the problem of obtaining practical uncertainty models for robust control analysis and design applications. An extension of model validation called 'sequential validation' is presented and applied to a simple spring-mass-damper system to establish the feasibility of the approach and demonstrate the benefits of the new developments.
Air Quality Dispersion Modeling - Alternative Models
Models, not listed in Appendix W, that can be used in regulatory applications with case-by-case justification to the Reviewing Authority as noted in Section 3.2, Use of Alternative Models, in Appendix W.
Model selection for logistic regression models
NASA Astrophysics Data System (ADS)
Duller, Christine
2012-09-01
Model selection for logistic regression models decides which of some given potential regressors have an effect and hence should be included in the final model. The second interesting question is whether a certain factor is heterogeneous among some subsets, i.e. whether the model should include a random intercept or not. In this paper these questions will be answered with classical as well as with Bayesian methods. The application show some results of recent research projects in medicine and business administration.
China model: Energy modeling the modern dynasty
Shaw, Jason
1996-05-01
In this paper a node-based microeconomic analysis is used to model the Chinese energy system. This model is run across multiple periods employing Lagrangian Relaxation techniques to achieve general equilibrium. Later, carbon dioxide emissions are added and the model is run to answer the question, {open_quotes}How can greenhouse gas emissions be reduced{close_quotes}?
ERIC Educational Resources Information Center
Willden, Jeff
2001-01-01
"Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…
ERIC Educational Resources Information Center
Willden, Jeff
2001-01-01
"Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…
Haiganoush Preisler; Alan Ager
2013-01-01
For applied mathematicians forest fire models refer mainly to a non-linear dynamic system often used to simulate spread of fire. For forest managers forest fire models may pertain to any of the three phases of fire management: prefire planning (fire risk models), fire suppression (fire behavior models), and postfire evaluation (fire effects and economic models). In...
Cloud Scene Simulation Modeling the Enhanced Model
1992-04-01
AD-A265 958 PL-TR-92-2106 CLOUD SCENE SIMULATION MODELING THE ENHANCED MODEL Maureen E. Cianciolo R. Gary Rasmussen TASC 55 Walkers Brook Drive...SUBTITLE 5. FUNDING NUMBERS Cloud Scene Simulation Modeling PF 62101,F The Enhanced Model PR 6670 TA 09 WU BE 6,AUTHOR(S) Contracl Fl1 9628-90-C-0022 7...the cloud field. 37 REFERENCES 1. Cianciolo, M.E., Hersh, J.S., and M.P. Ramos-Johnson, Cloud scene simulation modeling interim technical report, TASC
Bohr model as an algebraic collective model
Rowe, D. J.; Welsh, T. A.; Caprio, M. A.
2009-05-15
Developments and applications are presented of an algebraic version of Bohr's collective model. Illustrative examples show that fully converged calculations can be performed quickly and easily for a large range of Hamiltonians. As a result, the Bohr model becomes an effective tool in the analysis of experimental data. The examples are chosen both to confirm the reliability of the algebraic collective model and to show the diversity of results that can be obtained by its use. The focus of the paper is to facilitate identification of the limitations of the Bohr model with a view to developing more realistic, computationally tractable models.
Building mental models by dissecting physical models.
Srivastava, Anveshna
2016-01-01
When students build physical models from prefabricated components to learn about model systems, there is an implicit trade-off between the physical degrees of freedom in building the model and the intensity of instructor supervision needed. Models that are too flexible, permitting multiple possible constructions require greater supervision to ensure focused learning; models that are too constrained require less supervision, but can be constructed mechanically, with little to no conceptual engagement. We propose "model-dissection" as an alternative to "model-building," whereby instructors could make efficient use of supervisory resources, while simultaneously promoting focused learning. We report empirical results from a study conducted with biology undergraduate students, where we demonstrate that asking them to "dissect" out specific conceptual structures from an already built 3D physical model leads to a significant improvement in performance than asking them to build the 3D model from simpler components. Using questionnaires to measure understanding both before and after model-based interventions for two cohorts of students, we find that both the "builders" and the "dissectors" improve in the post-test, but it is the latter group who show statistically significant improvement. These results, in addition to the intrinsic time-efficiency of "model dissection," suggest that it could be a valuable pedagogical tool. © 2015 The International Union of Biochemistry and Molecular Biology.
Modeling regional wind erosion using different model
NASA Astrophysics Data System (ADS)
Guo, Zhongling; Chang, Chunping; Wang, Rende; Li, Jifeng; Li, Qing
2017-04-01
Wind erosion is an important factor causing soil degradation in arid and semi-arid regions. The need to quantitatively evaluate wind induced soil erosion yields many wind erosion models. These models include Wind Erosion Equation (WEQ), Revised Wind Erosion Equation (RWEQ),Wind Erosion Predicted System (WEPS) etc. at a field scale and Wind Erosion Assessment Model (WEAM), Integrated Wind Erosion Modeling System (IWEMS), AUStralian Land Erodibility Model (AUSLEM) etc. at a regional scale. The challenge of precisely estimating wind erosion at a regional scale still remain to date. To assess regional wind erosion, WEQ, RWEQ and WEPS have been scaled up to regional versions. However, no attempt is performed to compare these models for regional wind erosion modeling. In this study, the regional versions of WEQ, RWEQ, WEPS and WEAM, IWEMS, AUSLEM will be selected to model regional wind erosion of farmlands in the Kangbao County of northern China with annual soil loss by wind erosion based on 137 Cs analysis. Remote sensing image is used to determine the size and shape of local farmlands. Weather data of 2000-2010, China Soil Survey and published soil data, crops rotations etc. are compiled to generate raster layers of inputs for selected models using ArcGIS 10.2. These models were rebuilt based on ArcGIS Model-builder Module. Spatial distribution of annual soil loss by wind erosion determined from different model will be tested using annual soil loss data by 137 Cs analysis. Performances of these models will be investigated, and restrictions of these models will be further ascertained.
Geologic Framework Model Analysis Model Report
R. Clayton
2000-12-19
The purpose of this report is to document the Geologic Framework Model (GFM), Version 3.1 (GFM3.1) with regard to data input, modeling methods, assumptions, uncertainties, limitations, and validation of the model results, qualification status of the model, and the differences between Version 3.1 and previous versions. The GFM represents a three-dimensional interpretation of the stratigraphy and structural features of the location of the potential Yucca Mountain radioactive waste repository. The GFM encompasses an area of 65 square miles (170 square kilometers) and a volume of 185 cubic miles (771 cubic kilometers). The boundaries of the GFM were chosen to encompass the most widely distributed set of exploratory boreholes (the Water Table or WT series) and to provide a geologic framework over the area of interest for hydrologic flow and radionuclide transport modeling through the unsaturated zone (UZ). The depth of the model is constrained by the inferred depth of the Tertiary-Paleozoic unconformity. The GFM was constructed from geologic map and borehole data. Additional information from measured stratigraphy sections, gravity profiles, and seismic profiles was also considered. This interim change notice (ICN) was prepared in accordance with the Technical Work Plan for the Integrated Site Model Process Model Report Revision 01 (CRWMS M&O 2000). The constraints, caveats, and limitations associated with this model are discussed in the appropriate text sections that follow. The GFM is one component of the Integrated Site Model (ISM) (Figure l), which has been developed to provide a consistent volumetric portrayal of the rock layers, rock properties, and mineralogy of the Yucca Mountain site. The ISM consists of three components: (1) Geologic Framework Model (GFM); (2) Rock Properties Model (RPM); and (3) Mineralogic Model (MM). The ISM merges the detailed project stratigraphy into model stratigraphic units that are most useful for the primary downstream models and the
Educating with Aircraft Models
ERIC Educational Resources Information Center
Steele, Hobie
1976-01-01
Described is utilization of aircraft models, model aircraft clubs, and model aircraft magazines to promote student interest in aerospace education. The addresses for clubs and magazines are included. (SL)
NASA Astrophysics Data System (ADS)
Brimicombe, N. W.
1991-07-01
Hot air balloons can be modelled in a number of different ways. The most satisfactory, but least useful model is at a microscopic level. Macroscopic models are easier to use but can be very misleading.
Photochemical Modeling Applications
Provides access to modeling applications involving photochemical models, including modeling of ozone, particulate matter (PM), and mercury for national and regional EPA regulations such as the Clean Air Interstate Rule (CAIR) and the Clean Air Mercury Rule
Educating with Aircraft Models
ERIC Educational Resources Information Center
Steele, Hobie
1976-01-01
Described is utilization of aircraft models, model aircraft clubs, and model aircraft magazines to promote student interest in aerospace education. The addresses for clubs and magazines are included. (SL)
NASA Technical Reports Server (NTRS)
Liou, J. C.
2012-01-01
Presentation outlne: (1) The NASA Orbital Debris (OD) Engineering Model -- A mathematical model capable of predicting OD impact risks for the ISS and other critical space assets (2) The NASA OD Evolutionary Model -- A physical model capable of predicting future debris environment based on user-specified scenarios (3) The NASA Standard Satellite Breakup Model -- A model describing the outcome of a satellite breakup (explosion or collision)
Modeling of geothermal systems
Bodvarsson, G.S.; Pruess, K.; Lippmann, M.J.
1985-03-01
During the last decade the use of numerical modeling for geothermal resource evaluation has grown significantly, and new modeling approaches have been developed. In this paper we present a summary of the present status in numerical modeling of geothermal systems, emphasizing recent developments. Different modeling approaches are described and their applicability discussed. The various modeling tasks, including natural-state, exploitation, injection, multi-component and subsidence modeling, are illustrated with geothermal field examples. 99 refs., 14 figs.
NASA Technical Reports Server (NTRS)
Cellier, Francois E.
1991-01-01
A comprehensive and systematic introduction is presented for the concepts associated with 'modeling', involving the transition from a physical system down to an abstract description of that system in the form of a set of differential and/or difference equations, and basing its treatment of modeling on the mathematics of dynamical systems. Attention is given to the principles of passive electrical circuit modeling, planar mechanical systems modeling, hierarchical modular modeling of continuous systems, and bond-graph modeling. Also discussed are modeling in equilibrium thermodynamics, population dynamics, and system dynamics, inductive reasoning, artificial neural networks, and automated model synthesis.
Interfacing materials models with fire field models
Nicolette, V.F.; Tieszen, S.R.; Moya, J.L.
1995-12-01
For flame spread over solid materials, there has traditionally been a large technology gap between fundamental combustion research and the somewhat simplistic approaches used for practical, real-world applications. Recent advances in computational hardware and computational fluid dynamics (CFD)-based software have led to the development of fire field models. These models, when used in conjunction with material burning models, have the potential to bridge the gap between research and application by implementing physics-based engineering models in a transient, multi-dimensional tool. This paper discusses the coupling that is necessary between fire field models and burning material models for the simulation of solid material fires. Fire field models are capable of providing detailed information about the local fire environment. This information serves as an input to the solid material combustion submodel, which subsequently calculates the impact of the fire environment on the material. The response of the solid material (in terms of thermal response, decomposition, charring, and off-gassing) is then fed back into the field model as a source of mass, momentum and energy. The critical parameters which must be passed between the field model and the material burning model have been identified. Many computational issues must be addressed when developing such an interface. Some examples include the ability to track multiple fuels and species, local ignition criteria, and the need to use local grid refinement over the burning material of interest.
Comparative protein structure modeling using MODELLER.
Eswar, Narayanan; Webb, Ben; Marti-Renom, Marc A; Madhusudhan, M S; Eramian, David; Shen, Min-Yi; Pieper, Ursula; Sali, Andrej
2007-11-01
Functional characterization of a protein sequence is a common goal in biology, and is usually facilitated by having an accurate three-dimensional (3-D) structure of the studied protein. In the absence of an experimentally determined structure, comparative or homology modeling can sometimes provide a useful 3-D model for a protein that is related to at least one known protein structure. Comparative modeling predicts the 3-D structure of a given protein sequence (target) based primarily on its alignment to one or more proteins of known structure (templates). The prediction process consists of fold assignment, target-template alignment, model building, and model evaluation. This unit describes how to calculate comparative models using the program MODELLER and discusses all four steps of comparative modeling, frequently observed errors, and some applications. Modeling lactate dehydrogenase from Trichomonas vaginalis (TvLDH) is described as an example. The download and installation of the MODELLER software is also described. (c) 2007 by John Wiley & Sons, Inc.
Regularized Structural Equation Modeling.
Jacobucci, Ross; Grimm, Kevin J; McArdle, John J
A new method is proposed that extends the use of regularization in both lasso and ridge regression to structural equation models. The method is termed regularized structural equation modeling (RegSEM). RegSEM penalizes specific parameters in structural equation models, with the goal of creating easier to understand and simpler models. Although regularization has gained wide adoption in regression, very little has transferred to models with latent variables. By adding penalties to specific parameters in a structural equation model, researchers have a high level of flexibility in reducing model complexity, overcoming poor fitting models, and the creation of models that are more likely to generalize to new samples. The proposed method was evaluated through a simulation study, two illustrative examples involving a measurement model, and one empirical example involving the structural part of the model to demonstrate RegSEM's utility.
Model Reduction of Viscoelastic Finite Element Models
NASA Astrophysics Data System (ADS)
Park, C. H.; Inman, D. J.; Lam, M. J.
1999-01-01
This paper examines a method of adding viscoelastic properties to finite element models by using additional co-ordinates to account for the frequency dependence usually associated with such damping materials. Several such methods exist and all suffer from an increase in order of the final finite model which is undesirable in many applications. Here we propose to combine one of these methods, the GHM (Golla-Hughes-McTavish) method, with model reduction techniques to remove the objection of increased model order. The result of combining several methods is an ability to add the effects of visoelastic components to finite element or other analytical models without increasing the order of the system. The procedure is illustrated by a numerical example. The method proposed here results in a viscoelastic finite element of a structure without increasing the order of the original model.
ROCK PROPERTIES MODEL ANALYSIS MODEL REPORT
Clinton Lum
2002-02-04
The purpose of this Analysis and Model Report (AMR) is to document Rock Properties Model (RPM) 3.1 with regard to input data, model methods, assumptions, uncertainties and limitations of model results, and qualification status of the model. The report also documents the differences between the current and previous versions and validation of the model. The rock properties models are intended principally for use as input to numerical physical-process modeling, such as of ground-water flow and/or radionuclide transport. The constraints, caveats, and limitations associated with this model are discussed in the appropriate text sections that follow. This work was conducted in accordance with the following planning documents: WA-0344, ''3-D Rock Properties Modeling for FY 1998'' (SNL 1997, WA-0358), ''3-D Rock Properties Modeling for FY 1999'' (SNL 1999), and the technical development plan, Rock Properties Model Version 3.1, (CRWMS M&O 1999c). The Interim Change Notice (ICNs), ICN 02 and ICN 03, of this AMR were prepared as part of activities being conducted under the Technical Work Plan, TWP-NBS-GS-000003, ''Technical Work Plan for the Integrated Site Model, Process Model Report, Revision 01'' (CRWMS M&O 2000b). The purpose of ICN 03 is to record changes in data input status due to data qualification and verification activities. These work plans describe the scope, objectives, tasks, methodology, and implementing procedures for model construction. The constraints, caveats, and limitations associated with this model are discussed in the appropriate text sections that follow. The work scope for this activity consists of the following: (1) Conversion of the input data (laboratory measured porosity data, x-ray diffraction mineralogy, petrophysical calculations of bound water, and petrophysical calculations of porosity) for each borehole into stratigraphic coordinates; (2) Re-sampling and merging of data sets; (3) Development of geostatistical simulations of porosity; (4
Neurometric Modeling: Computational Modeling of Individual Brains
2011-05-16
Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS Neural networks, computational neuroscience, fMRI ...obtained using functional MRI. Algorithmic processing of these measurements can exploit a variety of statistical machine learning methods to... statistical machine learning methods to synthesize a new kind of neuro-cognitive model, which we call neurometric models. These executable models could be
Better models are more effectively connected models
NASA Astrophysics Data System (ADS)
Nunes, João Pedro; Bielders, Charles; Darboux, Frederic; Fiener, Peter; Finger, David; Turnbull-Lloyd, Laura; Wainwright, John
2016-04-01
The concept of hydrologic and geomorphologic connectivity describes the processes and pathways which link sources (e.g. rainfall, snow and ice melt, springs, eroded areas and barren lands) to accumulation areas (e.g. foot slopes, streams, aquifers, reservoirs), and the spatial variations thereof. There are many examples of hydrological and sediment connectivity on a watershed scale; in consequence, a process-based understanding of connectivity is crucial to help managers understand their systems and adopt adequate measures for flood prevention, pollution mitigation and soil protection, among others. Modelling is often used as a tool to understand and predict fluxes within a catchment by complementing observations with model results. Catchment models should therefore be able to reproduce the linkages, and thus the connectivity of water and sediment fluxes within the systems under simulation. In modelling, a high level of spatial and temporal detail is desirable to ensure taking into account a maximum number of components, which then enables connectivity to emerge from the simulated structures and functions. However, computational constraints and, in many cases, lack of data prevent the representation of all relevant processes and spatial/temporal variability in most models. In most cases, therefore, the level of detail selected for modelling is too coarse to represent the system in a way in which connectivity can emerge; a problem which can be circumvented by representing fine-scale structures and processes within coarser scale models using a variety of approaches. This poster focuses on the results of ongoing discussions on modelling connectivity held during several workshops within COST Action Connecteur. It assesses the current state of the art of incorporating the concept of connectivity in hydrological and sediment models, as well as the attitudes of modellers towards this issue. The discussion will focus on the different approaches through which connectivity
Integrity modelling of tropospheric delay models
NASA Astrophysics Data System (ADS)
Rózsa, Szabolcs; Bastiaan Ober, Pieter; Mile, Máté; Ambrus, Bence; Juni, Ildikó
2017-04-01
The effect of the neutral atmosphere on signal propagation is routinely estimated by various tropospheric delay models in satellite navigation. Although numerous studies can be found in the literature investigating the accuracy of these models, for safety-of-life applications it is crucial to study and model the worst case performance of these models using very low recurrence frequencies. The main objective of the INTegrity of TROpospheric models (INTRO) project funded by the ESA PECS programme is to establish a model (or models) of the residual error of existing tropospheric delay models for safety-of-life applications. Such models are required to overbound rare tropospheric delays and should thus include the tails of the error distributions. Their use should lead to safe error bounds on the user position and should allow computation of protection levels for the horizontal and vertical position errors. The current tropospheric model from the RTCA SBAS Minimal Operational Standards has an associated residual error that equals 0.12 meters in the vertical direction. This value is derived by simply extrapolating the observed distribution of the residuals into the tail (where no data is present) and then taking the point where the cumulative distribution has an exceedance level would be 10-7.While the resulting standard deviation is much higher than the estimated standard variance that best fits the data (0.05 meters), it surely is conservative for most applications. In the context of the INTRO project some widely used and newly developed tropospheric delay models (e.g. RTCA MOPS, ESA GALTROPO and GPT2W) were tested using 16 years of daily ERA-INTERIM Reanalysis numerical weather model data and the raytracing technique. The results showed that the performance of some of the widely applied models have a clear seasonal dependency and it is also affected by a geographical position. In order to provide a more realistic, but still conservative estimation of the residual
M. A. Wasiolek
2003-10-27
The purpose of this report is to document the biosphere model, the Environmental Radiation Model for Yucca Mountain, Nevada (ERMYN), which describes radionuclide transport processes in the biosphere and associated human exposure that may arise as the result of radionuclide release from the geologic repository at Yucca Mountain. The biosphere model is one of the process models that support the Yucca Mountain Project (YMP) Total System Performance Assessment (TSPA) for the license application (LA), the TSPA-LA. The ERMYN model provides the capability of performing human radiation dose assessments. This report documents the biosphere model, which includes: (1) Describing the reference biosphere, human receptor, exposure scenarios, and primary radionuclides for each exposure scenario (Section 6.1); (2) Developing a biosphere conceptual model using site-specific features, events, and processes (FEPs), the reference biosphere, the human receptor, and assumptions (Section 6.2 and Section 6.3); (3) Building a mathematical model using the biosphere conceptual model and published biosphere models (Sections 6.4 and 6.5); (4) Summarizing input parameters for the mathematical model, including the uncertainty associated with input values (Section 6.6); (5) Identifying improvements in the ERMYN model compared with the model used in previous biosphere modeling (Section 6.7); (6) Constructing an ERMYN implementation tool (model) based on the biosphere mathematical model using GoldSim stochastic simulation software (Sections 6.8 and 6.9); (7) Verifying the ERMYN model by comparing output from the software with hand calculations to ensure that the GoldSim implementation is correct (Section 6.10); and (8) Validating the ERMYN model by corroborating it with published biosphere models; comparing conceptual models, mathematical models, and numerical results (Section 7).
D. W. Wu
2003-07-16
The purpose of this report is to document the biosphere model, the Environmental Radiation Model for Yucca Mountain, Nevada (ERMYN), which describes radionuclide transport processes in the biosphere and associated human exposure that may arise as the result of radionuclide release from the geologic repository at Yucca Mountain. The biosphere model is one of the process models that support the Yucca Mountain Project (YMP) Total System Performance Assessment (TSPA) for the license application (LA), the TSPA-LA. The ERMYN model provides the capability of performing human radiation dose assessments. This report documents the biosphere model, which includes: (1) Describing the reference biosphere, human receptor, exposure scenarios, and primary radionuclides for each exposure scenario (Section 6.1); (2) Developing a biosphere conceptual model using site-specific features, events, and processes (FEPs), the reference biosphere, the human receptor, and assumptions (Section 6.2 and Section 6.3); (3) Building a mathematical model using the biosphere conceptual model and published biosphere models (Sections 6.4 and 6.5); (4) Summarizing input parameters for the mathematical model, including the uncertainty associated with input values (Section 6.6); (5) Identifying improvements in the ERMYN model compared with the model used in previous biosphere modeling (Section 6.7); (6) Constructing an ERMYN implementation tool (model) based on the biosphere mathematical model using GoldSim stochastic simulation software (Sections 6.8 and 6.9); (7) Verifying the ERMYN model by comparing output from the software with hand calculations to ensure that the GoldSim implementation is correct (Section 6.10); and (8) Validating the ERMYN model by corroborating it with published biosphere models; comparing conceptual models, mathematical models, and numerical results (Section 7).
NASA Astrophysics Data System (ADS)
Dziembowski, W. A.; Goode, Philip R.; Pamyatnykh, A. A.; Sienkiewicz, R.
1995-05-01
Recently released low-l solar oscillation data from the BISON network are combined with BBSO data to obtain an updated solar seismic model of the Sun's interior. For the core, the solar seismic model from the new data is more consistent with the current standard solar models than our earlier seismic model. An astrophysical solution to the solar neutrino problem fades away.
ERIC Educational Resources Information Center
Yeates, Devin Rodney
2011-01-01
The goal of this dissertation is to enable better predictive models by engaging raw experimental data through the Instrumental Model. The Instrumental Model captures the protocols and procedures of experimental data analysis. The approach is formalized by encoding the Instrumental Model in an XML record. Decoupling the raw experimental data from…
2015-09-01
The Biomass Scenario Model (BSM) is a unique, carefully validated, state-of-the-art dynamic model of the domestic biofuels supply chain which explicitly focuses on policy issues, their feasibility, and potential side effects. It integrates resource availability, physical/technological/economic constraints, behavior, and policy. The model uses a system dynamics simulation (not optimization) to model dynamic interactions across the supply chain.
Models for Ammunition Management
1977-08-01
Analysis Operations Research Management Models Mobilization Planning Computer Programming Ammunition Management Economic Analysis Production Planning...ammunition managers on a unique set of nine modern computer models specifically developed to support the conventional ammunition management decision...DECISION MODELS DIRECTORATE ROCK ISLAND, ILLINOIS 61201 r ABSTRACT This special management report presents a unique set of nine computer models
ERIC Educational Resources Information Center
Clancey, William J.
The concept of a qualitative model is used as the focus of this review of qualitative student models in order to compare alternative computational models and to contrast domain requirements. The report is divided into eight sections: (1) Origins and Goals (adaptive instruction, qualitative models of processes, components of an artificial…
Generative Models of Disfluency
ERIC Educational Resources Information Center
Miller, Timothy A.
2010-01-01
This thesis describes a generative model for representing disfluent phenomena in human speech. This model makes use of observed syntactic structure present in disfluent speech, and uses a right-corner transform on syntax trees to model this structure in a very natural way. Specifically, the phenomenon of speech repair is modeled by explicitly…
Models of Counselling Centres.
ERIC Educational Resources Information Center
Calgary Univ. (Alberta).
University counseling centers usually follow one of a variety of themes or "models," although not in pure form. Perhaps the oldest is the vocational counseling model, which concentrates on helping students find suitable careers. In the psychotherapy model, most student concerns are seen for their personal content. Another model, student affairs…
Multimodeling and Model Abstraction
USDA-ARS?s Scientific Manuscript database
The multiplicity of models of the same process or phenomenon is the commonplace in environmental modeling. Last 10 years brought marked interest to making use of the variety of conceptual approaches instead of attempting to find the best model or using a single preferred model. Two systematic approa...
ERIC Educational Resources Information Center
Yeates, Devin Rodney
2011-01-01
The goal of this dissertation is to enable better predictive models by engaging raw experimental data through the Instrumental Model. The Instrumental Model captures the protocols and procedures of experimental data analysis. The approach is formalized by encoding the Instrumental Model in an XML record. Decoupling the raw experimental data from…
ERIC Educational Resources Information Center
Clancey, William J.
The concept of a qualitative model is used as the focus of this review of qualitative student models in order to compare alternative computational models and to contrast domain requirements. The report is divided into eight sections: (1) Origins and Goals (adaptive instruction, qualitative models of processes, components of an artificial…
NASA Astrophysics Data System (ADS)
Rahmani, Fouad Lazhar
2010-11-01
The aim of this paper is to present mathematical modelling of the spread of infection in the context of the transmission of the human immunodeficiency virus (HIV) and the acquired immune deficiency syndrome (AIDS). These models are based in part on the models suggested in the field of th AIDS mathematical modelling as reported by ISHAM [6].
NASA Astrophysics Data System (ADS)
Wenger, Trey V.; Kepley, Amanda K.; Balser, Dana S.
2017-07-01
HII Region Models fits HII region models to observed radio recombination line and radio continuum data. The algorithm includes the calculations of departure coefficients to correct for non-LTE effects. HII Region Models has been used to model star formation in the nucleus of IC 342.
NASA Astrophysics Data System (ADS)
Luczak, Joshua
2017-02-01
Scientific models are frequently discussed in philosophy of science. A great deal of the discussion is centred on approximation, idealisation, and on how these models achieve their representational function. Despite the importance, distinct nature, and high presence of toy models, they have received little attention from philosophers. This paper hopes to remedy this situation. It aims to elevate the status of toy models: by distinguishing them from approximations and idealisations, by highlighting and elaborating on several ways the Kac ring, a simple statistical mechanical model, is used as a toy model, and by explaining why toy models can be used to successfully carry out important work without performing a representational function.
C. Ahlers; H. Liu
2000-03-12
The purpose of this Analysis/Model Report (AMR) is to document the Calibrated Properties Model that provides calibrated parameter sets for unsaturated zone (UZ) flow and transport process models for the Yucca Mountain Site Characterization Project (YMP). This work was performed in accordance with the ''AMR Development Plan for U0035 Calibrated Properties Model REV00. These calibrated property sets include matrix and fracture parameters for the UZ Flow and Transport Model (UZ Model), drift seepage models, drift-scale and mountain-scale coupled-processes models, and Total System Performance Assessment (TSPA) models as well as Performance Assessment (PA) and other participating national laboratories and government agencies. These process models provide the necessary framework to test conceptual hypotheses of flow and transport at different scales and predict flow and transport behavior under a variety of climatic and thermal-loading conditions.
Molenaar, Peter C M
2017-02-16
Equivalences of two classes of dynamic models for weakly stationary multivariate time series are discussed: dynamic factor models and autoregressive models. It is shown that exploratory dynamic factor models can be rotated, yielding an infinite set of equivalent solutions for any observed series. It also is shown that dynamic factor models with lagged factor loadings are not equivalent to the currently popular state-space models, and that restriction of attention to the latter type of models may yield invalid results. The known equivalent vector autoregressive model types, standard and structural, are given a new interpretation in which they are conceived of as the extremes of an innovating type of hybrid vector autoregressive models. It is shown that consideration of hybrid models solves many problems, in particular with Granger causality testing.
Knowledge and information modeling.
Madsen, Maria
2010-01-01
This chapter gives an educational overview of: * commonly used modelling methods what they represent * the importance of selecting the tools and methods suited to the health information system being designed * how the quality of the information or knowledge model is determined by the quality of the system requirements specification * differentiating between the purpose of information models and knowledge models * the benefits of the openEHR approach for health care data modeling.
Introduction to Adjoint Models
NASA Technical Reports Server (NTRS)
Errico, Ronald M.
2015-01-01
In this lecture, some fundamentals of adjoint models will be described. This includes a basic derivation of tangent linear and corresponding adjoint models from a parent nonlinear model, the interpretation of adjoint-derived sensitivity fields, a description of methods of automatic differentiation, and the use of adjoint models to solve various optimization problems, including singular vectors. Concluding remarks will attempt to correct common misconceptions about adjoint models and their utilization.
Stable models of superacceleration
Kaplinghat, Manoj; Rajaraman, Arvind
2007-05-15
We discuss an instability in a large class of models where dark energy is coupled to matter. In these models the mass of the scalar field is much larger than the expansion rate of the Universe. We find models in which this instability is absent, and show that these models generically predict an apparent equation of state for dark energy smaller than -1, i.e., superacceleration. These models have no acausal behavior or ghosts.
WASP TRANSPORT MODELING AND WASP ECOLOGICAL MODELING
A combination of lectures, demonstrations, and hands-on excercises will be used to introduce pollutant transport modeling with the U.S. EPA's general water quality model, WASP (Water Quality Analysis Simulation Program). WASP features include a user-friendly Windows-based interfa...
Model Shrinkage for Discriminative Language Models
NASA Astrophysics Data System (ADS)
Oba, Takanobu; Hori, Takaaki; Nakamura, Atsushi; Ito, Akinori
This paper describes a technique for overcoming the model shrinkage problem in automatic speech recognition (ASR), which allows application developers and users to control the model size with less degradation of accuracy. Recently, models for ASR systems tend to be large and this can constitute a bottleneck for developers and users without special knowledge of ASR with respect to introducing the ASR function. Specifically, discriminative language models (DLMs) are usually designed in a high-dimensional parameter space, although DLMs have gained increasing attention as an approach for improving recognition accuracy. Our proposed method can be applied to linear models including DLMs, in which the score of an input sample is given by the inner product of its features and the model parameters, but our proposed method can shrink models in an easy computation by obtaining simple statistics, which are square sums of feature values appearing in a data set. Our experimental results show that our proposed method can shrink a DLM with little degradation in accuracy and perform properly whether or not the data for obtaining the statistics are the same as the data for training the model.
WASP TRANSPORT MODELING AND WASP ECOLOGICAL MODELING
A combination of lectures, demonstrations, and hands-on excercises will be used to introduce pollutant transport modeling with the U.S. EPA's general water quality model, WASP (Water Quality Analysis Simulation Program). WASP features include a user-friendly Windows-based interfa...
Geochemistry Model Validation Report: External Accumulation Model
K. Zarrabi
2001-09-27
The purpose of this Analysis and Modeling Report (AMR) is to validate the External Accumulation Model that predicts accumulation of fissile materials in fractures and lithophysae in the rock beneath a degrading waste package (WP) in the potential monitored geologic repository at Yucca Mountain. (Lithophysae are voids in the rock having concentric shells of finely crystalline alkali feldspar, quartz, and other materials that were formed due to entrapped gas that later escaped, DOE 1998, p. A-25.) The intended use of this model is to estimate the quantities of external accumulation of fissile material for use in external criticality risk assessments for different types of degrading WPs: U.S. Department of Energy (DOE) Spent Nuclear Fuel (SNF) codisposed with High Level Waste (HLW) glass, commercial SNF, and Immobilized Plutonium Ceramic (Pu-ceramic) codisposed with HLW glass. The scope of the model validation is to (1) describe the model and the parameters used to develop the model, (2) provide rationale for selection of the parameters by comparisons with measured values, and (3) demonstrate that the parameters chosen are the most conservative selection for external criticality risk calculations. To demonstrate the applicability of the model, a Pu-ceramic WP is used as an example. The model begins with a source term from separately documented EQ6 calculations; where the source term is defined as the composition versus time of the water flowing out of a breached waste package (WP). Next, PHREEQC, is used to simulate the transport and interaction of the source term with the resident water and fractured tuff below the repository. In these simulations the primary mechanism for accumulation is mixing of the high pH, actinide-laden source term with resident water; thus lowering the pH values sufficiently for fissile minerals to become insoluble and precipitate. In the final section of the model, the outputs from PHREEQC, are processed to produce mass of accumulation
Model Validation Status Review
E.L. Hardin
2001-11-28
The primary objective for the Model Validation Status Review was to perform a one-time evaluation of model validation associated with the analysis/model reports (AMRs) containing model input to total-system performance assessment (TSPA) for the Yucca Mountain site recommendation (SR). This review was performed in response to Corrective Action Request BSC-01-C-01 (Clark 2001, Krisha 2001) pursuant to Quality Assurance review findings of an adverse trend in model validation deficiency. The review findings in this report provide the following information which defines the extent of model validation deficiency and the corrective action needed: (1) AMRs that contain or support models are identified, and conversely, for each model the supporting documentation is identified. (2) The use for each model is determined based on whether the output is used directly for TSPA-SR, or for screening (exclusion) of features, events, and processes (FEPs), and the nature of the model output. (3) Two approaches are used to evaluate the extent to which the validation for each model is compliant with AP-3.10Q (Analyses and Models). The approaches differ in regard to whether model validation is achieved within individual AMRs as originally intended, or whether model validation could be readily achieved by incorporating information from other sources. (4) Recommendations are presented for changes to the AMRs, and additional model development activities or data collection, that will remedy model validation review findings, in support of licensing activities. The Model Validation Status Review emphasized those AMRs that support TSPA-SR (CRWMS M&O 2000bl and 2000bm). A series of workshops and teleconferences was held to discuss and integrate the review findings. The review encompassed 125 AMRs (Table 1) plus certain other supporting documents and data needed to assess model validity. The AMRs were grouped in 21 model areas representing the modeling of processes affecting the natural and
Practical Marginalized Multilevel Models
Griswold, Michael E.; Swihart, Bruce J.; Caffo, Brian S.; Zeger, Scott L.
2013-01-01
Clustered data analysis is characterized by the need to describe both systematic variation in a mean model and cluster-dependent random variation in an association model. Marginalized multilevel models embrace the robustness and interpretations of a marginal mean model, while retaining the likelihood inference capabilities and flexible dependence structures of a conditional association model. Although there has been increasing recognition of the attractiveness of marginalized multilevel models, there has been a gap in their practical application arising from a lack of readily available estimation procedures. We extend the marginalized multilevel model to allow for nonlinear functions in both the mean and association aspects. We then formulate marginal models through conditional specifications to facilitate estimation with mixed model computational solutions already in place. We illustrate the MMM and approximate MMM approaches on a cerebrovascular deficiency crossover trial using SAS and an epidemiological study on race and visual impairment using R. Datasets, SAS and R code are included as supplemental materials. PMID:24357884
Trapped Radiation Model Uncertainties: Model-Data and Model-Model Comparisons
NASA Technical Reports Server (NTRS)
Armstrong, T. W.; Colborn, B. L.
2000-01-01
The standard AP8 and AE8 models for predicting trapped proton and electron environments have been compared with several sets of flight data to evaluate model uncertainties. Model comparisons are made with flux and dose measurements made on various U.S. low-Earth orbit satellites (APEX, CRRES, DMSP. LDEF, NOAA) and Space Shuttle flights, on Russian satellites (Photon-8, Cosmos-1887, Cosmos-2044), and on the Russian Mir space station. This report gives the details of the model-data comparisons -- summary results in terms of empirical model uncertainty factors that can be applied for spacecraft design applications are given in a companion report. The results of model-model comparisons are also presented from standard AP8 and AE8 model predictions compared with the European Space Agency versions of AP8 and AE8 and with Russian trapped radiation models.
Trapped Radiation Model Uncertainties: Model-Data and Model-Model Comparisons
NASA Technical Reports Server (NTRS)
Armstrong, T. W.; Colborn, B. L.
2000-01-01
The standard AP8 and AE8 models for predicting trapped proton and electron environments have been compared with several sets of flight data to evaluate model uncertainties. Model comparisons are made with flux and dose measurements made on various U.S. low-Earth orbit satellites (APEX, CRRES, DMSP, LDEF, NOAA) and Space Shuttle flights, on Russian satellites (Photon-8, Cosmos-1887, Cosmos-2044), and on the Russian Mir Space Station. This report gives the details of the model-data comparisons-summary results in terms of empirical model uncertainty factors that can be applied for spacecraft design applications are given in a combination report. The results of model-model comparisons are also presented from standard AP8 and AE8 model predictions compared with the European Space Agency versions of AP8 and AE8 and with Russian-trapped radiation models.
Swiler, Laura Painton; Urbina, Angel
2010-07-01
This paper compares three approaches for model selection: classical least squares methods, information theoretic criteria, and Bayesian approaches. Least squares methods are not model selection methods although one can select the model that yields the smallest sum-of-squared error function. Information theoretic approaches balance overfitting with model accuracy by incorporating terms that penalize more parameters with a log-likelihood term to reflect goodness of fit. Bayesian model selection involves calculating the posterior probability that each model is correct, given experimental data and prior probabilities that each model is correct. As part of this calculation, one often calibrates the parameters of each model and this is included in the Bayesian calculations. Our approach is demonstrated on a structural dynamics example with models for energy dissipation and peak force across a bolted joint. The three approaches are compared and the influence of the log-likelihood term in all approaches is discussed.
Modeling nonstationary longitudinal data.
Núñez-Antón, V; Zimmerman, D L
2000-09-01
An important theme of longitudinal data analysis in the past two decades has been the development and use of explicit parametric models for the data's variance-covariance structure. A variety of these models have been proposed, of which most are second-order stationary. A few are flexible enough to accommodate nonstationarity, i.e., nonconstant variances and/or correlations that are not a function solely of elapsed time between measurements. We review five nonstationary models that we regard as most useful: (1) the unstructured covariance model, (2) unstructured antedependence models, (3) structured antedependence models, (4) autoregressive integrated moving average and similar models, and (5) random coefficients models. We evaluate the relative strengths and limitations of each model, emphasizing when it is inappropriate or unlikely to be useful. We present three examples to illustrate the fitting and comparison of the models and to demonstrate that nonstationary longitudinal data can be modeled effectively and, in some cases, quite parsimoniously. In these examples, the antedependence models generally prove to be superior and the random coefficients models prove to be inferior. We conclude that antedependence models should be given much greater consideration than they have historically received.
Modeling volatility using state space models.
Timmer, J; Weigend, A S
1997-08-01
In time series problems, noise can be divided into two categories: dynamic noise which drives the process, and observational noise which is added in the measurement process, but does not influence future values of the system. In this framework, we show that empirical volatilities (the squared relative returns of prices) exhibit a significant amount of observational noise. To model and predict their time evolution adequately, we estimate state space models that explicitly include observational noise. We obtain relaxation times for shocks in the logarithm of volatility ranging from three weeks (for foreign exchange) to three to five months (for stock indices). In most cases, a two-dimensional hidden state is required to yield residuals that are consistent with white noise. We compare these results with ordinary autoregressive models (without a hidden state) and find that autoregressive models underestimate the relaxation times by about two orders of magnitude since they do not distinguish between observational and dynamic noise. This new interpretation of the dynamics of volatility in terms of relaxators in a state space model carries over to stochastic volatility models and to GARCH models, and is useful for several problems in finance, including risk management and the pricing of derivative securities. Data sets used: Olsen & Associates high frequency DEM/USD foreign exchange rates (8 years). Nikkei 225 index (40 years). Dow Jones Industrial Average (25 years).
Reiter, E.R.
1980-01-01
A highly sophisticated and accurate approach is described to compute on an hourly or daily basis the energy consumption for space heating by individual buildings, urban sectors, and whole cities. The need for models and specifically weather-sensitive models, composite models, and space-heating models are discussed. Development of the Colorado State University Model, based on heat-transfer equations and on a heuristic, adaptive, self-organizing computation learning approach, is described. Results of modeling energy consumption by the city of Minneapolis and Cheyenne are given. Some data on energy consumption in individual buildings are included.
Stochastic modeling of rainfall
Guttorp, P.
1996-12-31
We review several approaches in the literature for stochastic modeling of rainfall, and discuss some of their advantages and disadvantages. While stochastic precipitation models have been around at least since the 1850`s, the last two decades have seen an increased development of models based (more or less) on the physical processes involved in precipitation. There are interesting questions of scale and measurement that pertain to these modeling efforts. Recent modeling efforts aim at including meteorological variables, and may be useful for regional down-scaling of general circulation models.
NASA Technical Reports Server (NTRS)
Patel, Umesh D.; Torre, Edward Della; Day, John H. (Technical Monitor)
2002-01-01
A new vector Preisach model, called the Reduced Vector Preisach model (RVPM), was developed for fast computations. This model, derived from the Simplified Vector Preisach model (SVPM), has individual components that like the SVPM are calculated independently using coupled selection rules for the state vector computation. However, the RVPM does not require the rotational correction. Therefore, it provides a practical alternative for computing the magnetic susceptibility using a differential approach. A vector version, using the framework of the DOK model, is implemented. Simulation results for the reduced vector Preisach model are also presented.
NASA Technical Reports Server (NTRS)
McMann, Catherine M. (Inventor); Cohen, Gerald C. (Inventor)
1991-01-01
An improved method and system for automatically generating reliability models for use with a reliability evaluation tool is described. The reliability model generator of the present invention includes means for storing a plurality of low level reliability models which represent the reliability characteristics for low level system components. In addition, the present invention includes means for defining the interconnection of the low level reliability models via a system architecture description. In accordance with the principles of the present invention, a reliability model for the entire system is automatically generated by aggregating the low level reliability models based on the system architecture description.
NASA Astrophysics Data System (ADS)
Marstal, Kasper; Klein, Stefan
2017-02-01
We present the Active Registration Model (ARM) that couples medical image registration with regularization using a statistical model of intensity. Inspired by Active Appearance Models (AAMs), the statistical model is embedded in the registration procedure as a regularization term that penalize differences between a target image and a synthesized model reconstruction of that image. We demonstrate that the method generalizes AAMs to 3D images, many different transformation models, and many different gradient descent optimization methods. The method is validated on magnetic resonance images of human brains.
Program management model study
NASA Technical Reports Server (NTRS)
Connelly, J. J.; Russell, J. E.; Seline, J. R.; Sumner, N. R., Jr.
1972-01-01
Two models, a system performance model and a program assessment model, have been developed to assist NASA management in the evaluation of development alternatives for the Earth Observations Program. Two computer models were developed and demonstrated on the Goddard Space Flight Center Computer Facility. Procedures have been outlined to guide the user of the models through specific evaluation processes, and the preparation of inputs describing earth observation needs and earth observation technology. These models are intended to assist NASA in increasing the effectiveness of the overall Earth Observation Program by providing a broader view of system and program development alternatives.
A future of the model organism model.
Rine, Jasper
2014-03-01
Changes in technology are fundamentally reframing our concept of what constitutes a model organism. Nevertheless, research advances in the more traditional model organisms have enabled fresh and exciting opportunities for young scientists to establish new careers and offer the hope of comprehensive understanding of fundamental processes in life. New advances in translational research can be expected to heighten the importance of basic research in model organisms and expand opportunities. However, researchers must take special care and implement new resources to enable the newest members of the community to engage fully with the remarkable legacy of information in these fields.
Modeling Guru: Knowledge Base for NASA Modelers
NASA Astrophysics Data System (ADS)
Seablom, M. S.; Wojcik, G. S.; van Aartsen, B. H.
2009-05-01
Modeling Guru is an on-line knowledge-sharing resource for anyone involved with or interested in NASA's scientific models or High End Computing (HEC) systems. Developed and maintained by the NASA's Software Integration and Visualization Office (SIVO) and the NASA Center for Computational Sciences (NCCS), Modeling Guru's combined forums and knowledge base for research and collaboration is becoming a repository for the accumulated expertise of NASA's scientific modeling and HEC communities. All NASA modelers and associates are encouraged to participate and provide knowledge about the models and systems so that other users may benefit from their experience. Modeling Guru is divided into a hierarchy of communities, each with its own set forums and knowledge base documents. Current modeling communities include those for space science, land and atmospheric dynamics, atmospheric chemistry, and oceanography. In addition, there are communities focused on NCCS systems, HEC tools and libraries, and programming and scripting languages. Anyone may view most of the content on Modeling Guru (available at http://modelingguru.nasa.gov/), but you must log in to post messages and subscribe to community postings. The site offers a full range of "Web 2.0" features, including discussion forums, "wiki" document generation, document uploading, RSS feeds, search tools, blogs, email notification, and "breadcrumb" links. A discussion (a.k.a. forum "thread") is used to post comments, solicit feedback, or ask questions. If marked as a question, SIVO will monitor the thread, and normally respond within a day. Discussions can include embedded images, tables, and formatting through the use of the Rich Text Editor. Also, the user can add "Tags" to their thread to facilitate later searches. The "knowledge base" is comprised of documents that are used to capture and share expertise with others. The default "wiki" document lets users edit within the browser so others can easily collaborate on the
A future of the model organism model
Rine, Jasper
2014-01-01
Changes in technology are fundamentally reframing our concept of what constitutes a model organism. Nevertheless, research advances in the more traditional model organisms have enabled fresh and exciting opportunities for young scientists to establish new careers and offer the hope of comprehensive understanding of fundamental processes in life. New advances in translational research can be expected to heighten the importance of basic research in model organisms and expand opportunities. However, researchers must take special care and implement new resources to enable the newest members of the community to engage fully with the remarkable legacy of information in these fields. PMID:24577733
D.W. Wu; A.J. Smith
2004-11-08
The purpose of this report is to document the biosphere model, the Environmental Radiation Model for Yucca Mountain, Nevada (ERMYN), which describes radionuclide transport processes in the biosphere and associated human exposure that may arise as the result of radionuclide release from the geologic repository at Yucca Mountain. The biosphere model is one of the process models that support the Yucca Mountain Project (YMP) Total System Performance Assessment (TSPA) for the license application (LA), TSPA-LA. The ERMYN provides the capability of performing human radiation dose assessments. This report documents the biosphere model, which includes: (1) Describing the reference biosphere, human receptor, exposure scenarios, and primary radionuclides for each exposure scenario (Section 6.1); (2) Developing a biosphere conceptual model using site-specific features, events, and processes (FEPs) (Section 6.2), the reference biosphere (Section 6.1.1), the human receptor (Section 6.1.2), and approximations (Sections 6.3.1.4 and 6.3.2.4); (3) Building a mathematical model using the biosphere conceptual model (Section 6.3) and published biosphere models (Sections 6.4 and 6.5); (4) Summarizing input parameters for the mathematical model, including the uncertainty associated with input values (Section 6.6); (5) Identifying improvements in the ERMYN compared with the model used in previous biosphere modeling (Section 6.7); (6) Constructing an ERMYN implementation tool (model) based on the biosphere mathematical model using GoldSim stochastic simulation software (Sections 6.8 and 6.9); (7) Verifying the ERMYN by comparing output from the software with hand calculations to ensure that the GoldSim implementation is correct (Section 6.10); (8) Validating the ERMYN by corroborating it with published biosphere models; comparing conceptual models, mathematical models, and numerical results (Section 7).
NASA Technical Reports Server (NTRS)
Ensey, Tyler S.
2013-01-01
During my internship at NASA, I was a model developer for Ground Support Equipment (GSE). The purpose of a model developer is to develop and unit test model component libraries (fluid, electrical, gas, etc.). The models are designed to simulate software for GSE (Ground Special Power, Crew Access Arm, Cryo, Fire and Leak Detection System, Environmental Control System (ECS), etc. .) before they are implemented into hardware. These models support verifying local control and remote software for End-Item Software Under Test (SUT). The model simulates the physical behavior (function, state, limits and 110) of each end-item and it's dependencies as defined in the Subsystem Interface Table, Software Requirements & Design Specification (SRDS), Ground Integrated Schematic (GIS), and System Mechanical Schematic.(SMS). The software of each specific model component is simulated through MATLAB's Simulink program. The intensiv model development life cycle is a.s follows: Identify source documents; identify model scope; update schedule; preliminary design review; develop model requirements; update model.. scope; update schedule; detailed design review; create/modify library component; implement library components reference; implement subsystem components; develop a test script; run the test script; develop users guide; send model out for peer review; the model is sent out for verifictionlvalidation; if there is empirical data, a validation data package is generated; if there is not empirical data, a verification package is generated; the test results are then reviewed; and finally, the user. requests accreditation, and a statement of accreditation is prepared. Once each component model is reviewed and approved, they are intertwined together into one integrated model. This integrated model is then tested itself, through a test script and autotest, so that it can be concluded that all models work conjointly, for a single purpose. The component I was assigned, specifically, was a
Sumner, J G; Fernández-Sánchez, J; Jarvis, P D
2012-04-07
Recent work has discussed the importance of multiplicative closure for the Markov models used in phylogenetics. For continuous-time Markov chains, a sufficient condition for multiplicative closure of a model class is ensured by demanding that the set of rate-matrices belonging to the model class form a Lie algebra. It is the case that some well-known Markov models do form Lie algebras and we refer to such models as "Lie Markov models". However it is also the case that some other well-known Markov models unequivocally do not form Lie algebras (GTR being the most conspicuous example). In this paper, we will discuss how to generate Lie Markov models by demanding that the models have certain symmetries under nucleotide permutations. We show that the Lie Markov models include, and hence provide a unifying concept for, "group-based" and "equivariant" models. For each of two and four character states, the full list of Lie Markov models with maximal symmetry is presented and shown to include interesting examples that are neither group-based nor equivariant. We also argue that our scheme is pleasing in the context of applied phylogenetics, as, for a given symmetry of nucleotide substitution, it provides a natural hierarchy of models with increasing number of parameters. We also note that our methods are applicable to any application of continuous-time Markov chains beyond the initial motivations we take from phylogenetics. Crown Copyright Â© 2011. Published by Elsevier Ltd. All rights reserved.
Aggregation in ecosystem models and model stability
NASA Astrophysics Data System (ADS)
Giricheva, Evgeniya
2015-05-01
Using a multimodal approach to research ecosystems improves usage of available information on an object. This study presents several models of the Bering Sea ecosystem. The ecosystem is considered as a closed object, that is, the influence of the environment is not provided. We then add the links with the external medium in the models. The models differ in terms of the degree and method of grouping components. Our method is based on the differences in habitat and food source of groups, which allows us to determine the grouping of species with a greater effect on system dynamics. In particular, we determine whether benthic fish aggregation or pelagic fish aggregation can change the consumption structure of some groups of species, and consequently, the behavior of the entire model system.
Nonlinear Modeling by Assembling Piecewise Linear Models
NASA Technical Reports Server (NTRS)
Yao, Weigang; Liou, Meng-Sing
2013-01-01
To preserve nonlinearity of a full order system over a parameters range of interest, we propose a simple modeling approach by assembling a set of piecewise local solutions, including the first-order Taylor series terms expanded about some sampling states. The work by Rewienski and White inspired our use of piecewise linear local solutions. The assembly of these local approximations is accomplished by assigning nonlinear weights, through radial basis functions in this study. The efficacy of the proposed procedure is validated for a two-dimensional airfoil moving at different Mach numbers and pitching motions, under which the flow exhibits prominent nonlinear behaviors. All results confirm that our nonlinear model is accurate and stable for predicting not only aerodynamic forces but also detailed flowfields. Moreover, the model is robustness-accurate for inputs considerably different from the base trajectory in form and magnitude. This modeling preserves nonlinearity of the problems considered in a rather simple and accurate manner.
Aerosol Modeling for the Global Model Initiative
NASA Technical Reports Server (NTRS)
Weisenstein, Debra K.; Ko, Malcolm K. W.
2001-01-01
The goal of this project is to develop an aerosol module to be used within the framework of the Global Modeling Initiative (GMI). The model development work will be preformed jointly by the University of Michigan and AER, using existing aerosol models at the two institutions as starting points. The GMI aerosol model will be tested, evaluated against observations, and then applied to assessment of the effects of aircraft sulfur emissions as needed by the NASA Subsonic Assessment in 2001. The work includes the following tasks: 1. Implementation of the sulfur cycle within GMI, including sources, sinks, and aqueous conversion of sulfur. Aerosol modules will be added as they are developed and the GMI schedule permits. 2. Addition of aerosol types other than sulfate particles, including dust, soot, organic carbon, and black carbon. 3. Development of new and more efficient parameterizations for treating sulfate aerosol nucleation, condensation, and coagulation among different particle sizes and types.
PREDICTIVE MODELS. Enhanced Oil Recovery Model
Ray, R.M.
1992-02-26
PREDICTIVE MODELS is a collection of five models - CFPM, CO2PM, ICPM, PFPM, and SFPM - used in the 1982-1984 National Petroleum Council study of enhanced oil recovery (EOR) potential. Each pertains to a specific EOR process designed to squeeze additional oil from aging or spent oil fields. The processes are: 1 chemical flooding, where soap-like surfactants are injected into the reservoir to wash out the oil; 2 carbon dioxide miscible flooding, where carbon dioxide mixes with the lighter hydrocarbons making the oil easier to displace; 3 in-situ combustion, which uses the heat from burning some of the underground oil to thin the product; 4 polymer flooding, where thick, cohesive material is pumped into a reservoir to push the oil through the underground rock; and 5 steamflood, where pressurized steam is injected underground to thin the oil. CFPM, the Chemical Flood Predictive Model, models micellar (surfactant)-polymer floods in reservoirs, which have been previously waterflooded to residual oil saturation. Thus, only true tertiary floods are considered. An option allows a rough estimate of oil recovery by caustic or caustic-polymer processes. CO2PM, the Carbon Dioxide miscible flooding Predictive Model, is applicable to both secondary (mobile oil) and tertiary (residual oil) floods, and to either continuous CO2 injection or water-alternating gas processes. ICPM, the In-situ Combustion Predictive Model, computes the recovery and profitability of an in-situ combustion project from generalized performance predictive algorithms. PFPM, the Polymer Flood Predictive Model, is switch-selectable for either polymer or waterflooding, and an option allows the calculation of the incremental oil recovery and economics of polymer relative to waterflooding. SFPM, the Steamflood Predictive Model, is applicable to the steam drive process, but not to cyclic steam injection (steam soak) processes.
Solid Waste Projection Model: Model user's guide
Stiles, D.L.; Crow, V.L.
1990-08-01
The Solid Waste Projection Model (SWPM) system is an analytical tool developed by Pacific Northwest Laboratory (PNL) for Westinghouse Hanford company (WHC) specifically to address solid waste management issues at the Hanford Central Waste Complex (HCWC). This document, one of six documents supporting the SWPM system, contains a description of the system and instructions for preparing to use SWPM and operating Version 1 of the model. 4 figs., 1 tab.
Bounding Species Distribution Models
NASA Technical Reports Server (NTRS)
Stohlgren, Thomas J.; Jarnevich, Cahterine S.; Morisette, Jeffrey T.; Esaias, Wayne E.
2011-01-01
Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 (5): 642-647, 2011].
NASA Astrophysics Data System (ADS)
Okai, Tadashi; Otsuka, Takaharu; Arima, Akito
1992-02-01
We study the sp(8) subgroup of the isospin-invariant Ginnocchio model. The allowed quantum numbers are determined in terms of Young's diagrams. Using this result, we discuss the excitation energy of a model hamiltonian.
Bounding species distribution models
Stohlgren, T.J.; Jarnevich, C.S.; Esaias, W.E.; Morisette, J.T.
2011-01-01
Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used. ?? 2011 Current Zoology.
Until recently, sediment geochemical models (diagenetic models) have been only able to explain sedimentary flux and concentration profiles for a few simplified geochemical cycles (e.g., nitrogen, carbon and sulfur). However with advances in numerical methods, increased accuracy ...
Consistent model driven architecture
NASA Astrophysics Data System (ADS)
Niepostyn, Stanisław J.
2015-09-01
The goal of the MDA is to produce software systems from abstract models in a way where human interaction is restricted to a minimum. These abstract models are based on the UML language. However, the semantics of UML models is defined in a natural language. Subsequently the verification of consistency of these diagrams is needed in order to identify errors in requirements at the early stage of the development process. The verification of consistency is difficult due to a semi-formal nature of UML diagrams. We propose automatic verification of consistency of the series of UML diagrams originating from abstract models implemented with our consistency rules. This Consistent Model Driven Architecture approach enables us to generate automatically complete workflow applications from consistent and complete models developed from abstract models (e.g. Business Context Diagram). Therefore, our method can be used to check practicability (feasibility) of software architecture models.
ERIC Educational Resources Information Center
Bennett, Joan
1998-01-01
Recommends the use of a model of DNA made out of Velcro to help students visualize the steps of DNA replication. Includes a materials list, construction directions, and details of the demonstration using the model parts. (DDR)
Rouder, Jeffrey N; Engelhardt, Christopher R; McCabe, Simon; Morey, Richard D
2016-12-01
Analysis of variance (ANOVA), the workhorse analysis of experimental designs, consists of F-tests of main effects and interactions. Yet, testing, including traditional ANOVA, has been recently critiqued on a number of theoretical and practical grounds. In light of these critiques, model comparison and model selection serve as an attractive alternative. Model comparison differs from testing in that one can support a null or nested model vis-a-vis a more general alternative by penalizing more flexible models. We argue this ability to support more simple models allows for more nuanced theoretical conclusions than provided by traditional ANOVA F-tests. We provide a model comparison strategy and show how ANOVA models may be reparameterized to better address substantive questions in data analysis.
Bounding Species Distribution Models
NASA Technical Reports Server (NTRS)
Stohlgren, Thomas J.; Jarnevich, Cahterine S.; Morisette, Jeffrey T.; Esaias, Wayne E.
2011-01-01
Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 (5): 642-647, 2011].
ERIC Educational Resources Information Center
Brinner, Bonnie
1992-01-01
Presents an activity in which models help students visualize both the DNA process and transcription. After constructing DNA, RNA messenger, and RNA transfer molecules; students model cells, protein synthesis, codons, and RNA movement. (MDH)
Kiperman, S.L.
1995-01-01
The problems associated with the accuracy of kinetic models in heterogeneous catalysis and their adequacy to experimental data and reaction mechanisms are considered. The prospects for the further improvement and use of these models is also explored.
ERIC Educational Resources Information Center
Callison, Daniel
2002-01-01
Defines models and describes information search models that can be helpful to instructional media specialists in meeting users' abilities and information needs. Explains pathfinders and Kuhlthau's information search process, including the pre-writing information search process. (LRW)
ERIC Educational Resources Information Center
Bennett, Joan
1998-01-01
Recommends the use of a model of DNA made out of Velcro to help students visualize the steps of DNA replication. Includes a materials list, construction directions, and details of the demonstration using the model parts. (DDR)
NASA Technical Reports Server (NTRS)
Holland, L. D.; Walsh, J. R., Jr.; Wetherington, R. D.
1971-01-01
This report presents the results of work on communications systems modeling and covers three different areas of modeling. The first of these deals with the modeling of signals in communication systems in the frequency domain and the calculation of spectra for various modulations. These techniques are applied in determining the frequency spectra produced by a unified carrier system, the down-link portion of the Command and Communications System (CCS). The second modeling area covers the modeling of portions of a communication system on a block basis. A detailed analysis and modeling effort based on control theory is presented along with its application to modeling of the automatic frequency control system of an FM transmitter. A third topic discussed is a method for approximate modeling of stiff systems using state variable techniques.
ERIC Educational Resources Information Center
Brinner, Bonnie
1992-01-01
Presents an activity in which models help students visualize both the DNA process and transcription. After constructing DNA, RNA messenger, and RNA transfer molecules; students model cells, protein synthesis, codons, and RNA movement. (MDH)
Modeling EERE deployment programs
Cort, K. A.; Hostick, D. J.; Belzer, D. B.; Livingston, O. V.
2007-11-01
The purpose of the project was to identify and characterize the modeling of deployment programs within the EERE Technology Development (TD) programs, address possible improvements to the modeling process, and note gaps in knowledge for future research.
Until recently, sediment geochemical models (diagenetic models) have been only able to explain sedimentary flux and concentration profiles for a few simplified geochemical cycles (e.g., nitrogen, carbon and sulfur). However with advances in numerical methods, increased accuracy ...
Green Infrastructure Modeling Toolkit
EPA's Green Infrastructure Modeling Toolkit is a toolkit of 5 EPA green infrastructure models and tools, along with communication materials, that can be used as a teaching tool and a quick reference resource when making GI implementation decisions.
NASA Technical Reports Server (NTRS)
Agena, S. M.; Pusey, M. L.; Bogle, I. D.
1999-01-01
A thermodynamic framework (UNIQUAC model with temperature dependent parameters) is applied to model the salt-induced protein crystallization equilibrium, i.e., protein solubility. The framework introduces a term for the solubility product describing protein transfer between the liquid and solid phase and a term for the solution behavior describing deviation from ideal solution. Protein solubility is modeled as a function of salt concentration and temperature for a four-component system consisting of a protein, pseudo solvent (water and buffer), cation, and anion (salt). Two different systems, lysozyme with sodium chloride and concanavalin A with ammonium sulfate, are investigated. Comparison of the modeled and experimental protein solubility data results in an average root mean square deviation of 5.8%, demonstrating that the model closely follows the experimental behavior. Model calculations and model parameters are reviewed to examine the model and protein crystallization process. Copyright 1999 John Wiley & Sons, Inc.
NASA Technical Reports Server (NTRS)
Butler, Thomas G.
1987-01-01
Methods of modeling mass for bars are surveyed. A method for extending John Archer's concept of consistent mass beyond just translational inertia effects is included. Recommendations are given for various types of modeling situations.
Modelling pelagic biogeography
NASA Astrophysics Data System (ADS)
Olson, Donald B.; Hood, Raleigh R.
Various combinations of physical and biological models are used to explore factors that determine the distribution of organisms in the world's oceans. The physical models examined include simple box models with parameterized inter-box exchanges that take into account variable box geometries, and specified continuous flows either in the Eulerian frame as stream-functions or as Lagrangian trajectories. A 1-dimensional mixed-layer model and a primitive equation channel model are introduced as examples of dynamical models depicting ocean physics. Biological models are discussed starting with a simple nitrogen (N), phytoplankton (P), zooplankton (Z) and detritus (D), NPZD formulation. The equilibria of this model is explored analytically as an example of computing steady state solutions, and then considering where in parameter space extinction occurs. Nonlinearities and expansion of NPZD to multi-species models are also treated. This is followed by the introduction of a nonlinear three-component food chain model, multi-species Lotka-Voltera competition models, and finally a discussion of structured population models including a derivation of a genetics model written in terms of genotypes. The physical models are then coupled with the biological ones in a series of examples. Both the box model with Lotka-Voltera multi-species population dynamics, and the 1-dimensional mixed-layer model with NPZD are used to demonstrate how the existence of spatial and temporal niches can allow a large number of species to coexist within biogeographic domains even though conditions at most sites and times are not conducive to supporting such diversity. These models recreate the basic diversity patterns observed in the pelagic ecosystem at various latitudes. The box model simulations also demonstrate the tendency for diffusive models to overestimate the dispersion of a species. In order to explore the dynamics of the edges of biogeographic domains a three species food chain model is
Inverse modeling of groundwater flow in the semiarid evaporitic closed basin of Los Monegros, Spain
NASA Astrophysics Data System (ADS)
Samper-Calvete, F. J.; García-Vera, M. A.
Only minor attention has been given in the past to the study of closed-basin hydrogeology in evaporitic environments, because these basins usually contain poor-quality groundwater. The motivation for hydrogeological research in the Los Monegros area in northeastern Spain was the approval in 1986 of a large irrigation project in the Ebre River basin. The irrigation of 60,000 ha is planned, partly in an evaporitic closed basin containing playa lakes. The project has given rise to environmental concerns. The evaluation of the hydrologic impacts of irrigation requires quantifying properly the hydrogeology of the area. With the available information, a conceptual hydrogeological model was formulated that identifies two main aquifers connected through a leaky aquitard. On the basis of the conceptual model, a numerical model was calibrated under steady-state conditions using the method of maximum-likelihood automatic parameter estimation (Carrera and Neuman, 1986a). The calibrated model reproduces the measured hydraulic heads fairly well and is consistent with independent information on groundwater discharge. By the solution of the inverse problem, reliable parameter estimates were obtained. It is concluded that anisotropy plays a major role in some parts of the lower aquifer. The geometric average of model conductivity is almost two orders of magnitude larger than the average conductivity derived from small-scale field tests. This scale effect in hydraulic conductivity is consistent with the findings of Neuman (1994) and Sánchez-Vila et al. (1996). Résumé Dans le passé, on s'est peu intéresséà l'hydrogéologie des bassins fermés en milieu évaporitique, parce que ces bassins possèdent en général de l'eau souterraine de qualité médiocre. L'intérêt porté aux recherches hydrogéologiques dans la région de Los Monegros, dans le nord-est de l'Espagne est dûà l'approbation en 1986 d'un vaste projet d'irrigation dans le bassin de l'Ebre. L'irrigation de 60000
NASA Technical Reports Server (NTRS)
Hildreth, W. W.
1978-01-01
A determination of the state of the art in soil moisture transport modeling based on physical or physiological principles was made. It was found that soil moisture models based on physical principles have been under development for more than 10 years. However, these models were shown to represent infiltration and redistribution of soil moisture quite well. Evapotranspiration has not been as adequately incorporated into the models.
Future of groundwater modeling
Langevin, Christian D.; Panday, Sorab
2012-01-01
With an increasing need to better manage water resources, the future of groundwater modeling is bright and exciting. However, while the past can be described and the present is known, the future of groundwater modeling, just like a groundwater model result, is highly uncertain and any prediction is probably not going to be entirely representative. Thus we acknowledge this as we present our vision of where groundwater modeling may be headed.
NASA Technical Reports Server (NTRS)
Mueller, A. C.
1977-01-01
An atmospheric model developed by Jacchia, quite accurate but requiring a large amount of computer storage and execution time, was found to be ill-suited for the space shuttle onboard program. The development of a simple atmospheric density model to simulate the Jacchia model was studied. Required characteristics including variation with solar activity, diurnal variation, variation with geomagnetic activity, semiannual variation, and variation with height were met by the new atmospheric density model.
Mathematical circulatory system model
NASA Technical Reports Server (NTRS)
Lakin, William D. (Inventor); Stevens, Scott A. (Inventor)
2010-01-01
A system and method of modeling a circulatory system including a regulatory mechanism parameter. In one embodiment, a regulatory mechanism parameter in a lumped parameter model is represented as a logistic function. In another embodiment, the circulatory system model includes a compliant vessel, the model having a parameter representing a change in pressure due to contraction of smooth muscles of a wall of the vessel.
1982-07-01
AFWL-TR-82-9 AFWL-TR-82-9 REINFORCED CONCRETE MODELING H. L. Schreyer J. W. Jeter, Jr. New Mexico Engineering Reseprch Institute University of New...Subtitle) S. TYPE OF REPORT & PERIOD COVERED REINFORCED CONCRETE MODELING Final Report 6. PERFORMING OtG. REPORT NUMBER NMERI TA8-9 7. AUTHORg) S...loading were identified and used to evaluate current concrete models . Since the endochronic and viscoplastic models provide satisfactory descriptions
Methodology for Stochastic Modeling.
1985-01-01
AD-AISS 851 METHODOLOGY FOR STOCHASTIC MODELING(U) ARMY MATERIEL 11 SYSTEMS ANALYSIS ACTIYITY ABERDEEN PROVING GROUND MD H E COHEN JAN 95 RNSAA-TR-41...FORM T REPORT NUMBER 2. GOVT ACCESSION NO. 3. RECIPIENT’$ CATALOG NUMBER 4. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED Methodology for...autoregression models, moving average models, ARMA, adaptive modeling, covariance methods , singular value decom- position, order determination rational
Model Engineering using Multimodeling
2008-04-16
given as a Statecharts model, and interprets it as a hierarchical multimodel. We then show an equivalent model constructed with Ptolemy II [13] that...That work followed on Ptolemy Classic [9], which provided a software architecture supporting a general form of hierarchical multimodeling. In [9...Colif [10]. This approach does not segregate distinct models of computation hierarchically. Ptolemy Classic [9] also illustrated multi-view modeling
2015-11-04
and Hydrology - Coastal Community of Practice (CoP) as a Preferred model for Coastal Engineering and Coastal Navigation studies. The work unit...Coastal Inlets Research Program Coastal Modeling System The work unit develops the Coastal Modeling System (CMS) and conducts basic research to... models for simulations of waves, hydrodynamics, salinity and sediment transport, and morphology change. The CMS was identified by the USACE Hydraulics
Modeling individual tree survial
Quang V. Cao
2016-01-01
Information provided by growth and yield models is the basis for forest managers to makeÂ decisions on how to manage their forests. Among different types of growth models, whole-stand models offerÂ predictions at stand level, whereas individual-tree models give detailed information at tree level. The well-knownÂ logistic regression is commonly used to predict tree...
NASA Astrophysics Data System (ADS)
Tashiro, Tohru
2014-03-01
We propose a new model about diffusion of a product which includes a memory of how many adopters or advertisements a non-adopter met, where (non-)adopters mean people (not) possessing the product. This effect is lacking in the Bass model. As an application, we utilize the model to fit the iPod sales data, and so the better agreement is obtained than the Bass model.
Sharlemann, E.T.
1994-07-01
We are developing a DIAL performance model for CALIOPE at LLNL. The intent of the model is to provide quick and interactive parameter sensitivity calculations with immediate graphical output. A brief overview of the features of the performance model is given, along with an example of performance calculations for a non-CALIOPE application.
ERIC Educational Resources Information Center
Speiser, Bob; Walter, Chuck
2011-01-01
This paper explores how models can support productive thinking. For us a model is a "thing", a tool to help make sense of something. We restrict attention to specific models for whole-number multiplication, hence the wording of the title. They support evolving thinking in large measure through the ways their users redesign them. They assume new…
ERIC Educational Resources Information Center
Bogiages, Christopher A.; Lotter, Christine
2011-01-01
In their research, scientists generate, test, and modify scientific models. These models can be shared with others and demonstrate a scientist's understanding of how the natural world works. Similarly, students can generate and modify models to gain a better understanding of the content, process, and nature of science (Kenyon, Schwarz, and Hug…
ERIC Educational Resources Information Center
Land, Kenneth C.
2001-01-01
Examines the definition, construction, and interpretation of social indicators. Shows how standard classes of formalisms used to construct models in contemporary sociology are derived from the general theory of models. Reviews recent model building and evaluation related to active life expectancy among the elderly, fertility rates, and indicators…
Model Breaking Points Conceptualized
ERIC Educational Resources Information Center
Vig, Rozy; Murray, Eileen; Star, Jon R.
2014-01-01
Current curriculum initiatives (e.g., National Governors Association Center for Best Practices and Council of Chief State School Officers 2010) advocate that models be used in the mathematics classroom. However, despite their apparent promise, there comes a point when models break, a point in the mathematical problem space where the model cannot,…
Crushed Salt Constitutive Model
Callahan, G.D.
1999-02-01
The constitutive model used to describe the deformation of crushed salt is presented in this report. Two mechanisms -- dislocation creep and grain boundary diffusional pressure solution -- are combined to form the basis for the constitutive model governing the deformation of crushed salt. The constitutive model is generalized to represent three-dimensional states of stress. Upon complete consolidation, the crushed-salt model reproduces the Multimechanism Deformation (M-D) model typically used for the Waste Isolation Pilot Plant (WIPP) host geological formation salt. New shear consolidation tests are combined with an existing database that includes hydrostatic consolidation and shear consolidation tests conducted on WIPP and southeastern New Mexico salt. Nonlinear least-squares model fitting to the database produced two sets of material parameter values for the model -- one for the shear consolidation tests and one for a combination of the shear and hydrostatic consolidation tests. Using the parameter values determined from the fitted database, the constitutive model is validated against constant strain-rate tests. Shaft seal problems are analyzed to demonstrate model-predicted consolidation of the shaft seal crushed-salt component. Based on the fitting statistics, the ability of the model to predict the test data, and the ability of the model to predict load paths and test data outside of the fitted database, the model appears to capture the creep consolidation behavior of crushed salt reasonably well.
ERIC Educational Resources Information Center
Fitzsimmons, Charles P.
1986-01-01
Points out the instructional applications and program possibilities of a unit on model rocketry. Describes the ways that microcomputers can assist in model rocket design and in problem calculations. Provides a descriptive listing of model rocket software for the Apple II microcomputer. (ML)
Modeling Applications and Tools
The U.S. EPA's Air Quality Modeling Group (AQMG) conducts modeling analyses to support policy and regulatory decisions in OAR and provides leadership and direction on the full range of air quality models and other mathematical simulation techniques used in
E. Gregory McPherson; Paula J. Peper
2012-01-01
This paper describes three long-term tree growth studies conducted to evaluate tree performance because repeated measurements of the same trees produce critical data for growth model calibration and validation. Several empirical and process-based approaches to modeling tree growth are reviewed. Modeling is more advanced in the fields of forestry and...
Model Breaking Points Conceptualized
ERIC Educational Resources Information Center
Vig, Rozy; Murray, Eileen; Star, Jon R.
2014-01-01
Current curriculum initiatives (e.g., National Governors Association Center for Best Practices and Council of Chief State School Officers 2010) advocate that models be used in the mathematics classroom. However, despite their apparent promise, there comes a point when models break, a point in the mathematical problem space where the model cannot,…
ERIC Educational Resources Information Center
Thornton, Bradley D.; Smalley, Robert A.
2008-01-01
Building information modeling (BIM) uses three-dimensional modeling concepts, information technology and interoperable software to design, construct and operate a facility. However, BIM can be more than a tool for virtual modeling--it can provide schools with a 3-D walkthrough of a project while it still is on the electronic drawing board. BIM can…
ERIC Educational Resources Information Center
Fedorov, Alexander
2011-01-01
The author supposed that media education models can be divided into the following groups: (1) educational-information models (the study of the theory, history, language of media culture, etc.), based on the cultural, aesthetic, semiotic, socio-cultural theories of media education; (2) educational-ethical models (the study of moral, religions,…
ERIC Educational Resources Information Center
Land, Kenneth C.
2001-01-01
Examines the definition, construction, and interpretation of social indicators. Shows how standard classes of formalisms used to construct models in contemporary sociology are derived from the general theory of models. Reviews recent model building and evaluation related to active life expectancy among the elderly, fertility rates, and indicators…
ERIC Educational Resources Information Center
Summerlin, Lee; Borgford, Christie
1989-01-01
Described is an activity which uses a 96-well reaction plate and soda straws to construct a model of the periodic table of the elements. The model illustrates the ionization energies of the various elements. Construction of the model and related concepts are discussed. (CW)
ERIC Educational Resources Information Center
Thornton, Bradley D.; Smalley, Robert A.
2008-01-01
Building information modeling (BIM) uses three-dimensional modeling concepts, information technology and interoperable software to design, construct and operate a facility. However, BIM can be more than a tool for virtual modeling--it can provide schools with a 3-D walkthrough of a project while it still is on the electronic drawing board. BIM can…
ERIC Educational Resources Information Center
Bogiages, Christopher A.; Lotter, Christine
2011-01-01
In their research, scientists generate, test, and modify scientific models. These models can be shared with others and demonstrate a scientist's understanding of how the natural world works. Similarly, students can generate and modify models to gain a better understanding of the content, process, and nature of science (Kenyon, Schwarz, and Hug…
General Graded Response Model.
ERIC Educational Resources Information Center
Samejima, Fumiko
This paper describes the graded response model. The graded response model represents a family of mathematical models that deal with ordered polytomous categories, such as: (1) letter grading; (2) an attitude survey with "strongly disagree, disagree, agree, and strongly agree" choices; (3) partial credit given in accord with an…
2007-03-22
IMPACT-GMI is an atmospheric chemical transport model designed to run on massively parallel computers. It is designed to model trace pollutants in the atmosphere. It includes models for emission, chemistry and deposition of pollutants. It can be used to assess air quality and its impact on future climate change.
Campus Energy Modeling Platform
Sides, Scott; Kemper, Travis; Larsen, Ross; Graf, Peter
2014-09-19
NREL's Campus Energy Modeling project provides a suite of simulation tools for integrated, data driven energy modeling of commercial buildings and campuses using Simulink. The tools enable development of fully interconnected models for commercial campus energy infrastructure, including electrical distribution systems, district heating and cooling, onsite generation (both conventional and renewable), building loads, energy storage, and control systems.
ERIC Educational Resources Information Center
Goodman, Richard E.
1970-01-01
Describes types of molecular models (ball-and-stick, framework, and space-filling) and evaluates commercially available kits. Gives instructions for constructive models from polystyrene balls and pipe-cleaners. Models are useful for class demonstrations although not sufficiently accurate for research use. Illustrations show biologically important…
Designing cyclic universe models.
Khoury, Justin; Steinhardt, Paul J; Turok, Neil
2004-01-23
The phenomenological constraints on the scalar field potential in cyclic models of the Universe are presented. We show that cyclic models require a comparable degree of tuning to that needed for inflationary models. The constraints are reduced to a set of simple design rules including "fast-roll" parameters analogous to the "slow-roll" parameters in inflation.
ERIC Educational Resources Information Center
Speiser, Bob; Walter, Chuck
2011-01-01
This paper explores how models can support productive thinking. For us a model is a "thing", a tool to help make sense of something. We restrict attention to specific models for whole-number multiplication, hence the wording of the title. They support evolving thinking in large measure through the ways their users redesign them. They assume new…
C. Lum
2004-09-16
The purpose of this model report is to document the Rock Properties Model version 3.1 with regard to input data, model methods, assumptions, uncertainties and limitations of model results, and qualification status of the model. The report also documents the differences between the current and previous versions and validation of the model. The rock properties model provides mean matrix and lithophysae porosity, and the cross-correlated mean bulk density as direct input to the ''Saturated Zone Flow and Transport Model Abstraction'', MDL-NBS-HS-000021, REV 02 (BSC 2004 [DIRS 170042]). The constraints, caveats, and limitations associated with this model are discussed in Section 6.6 and 8.2. Model validation accomplished by corroboration with data not cited as direct input is discussed in Section 7. The revision of this model report was performed as part of activities being conducted under the ''Technical Work Plan for: The Integrated Site Model, Revision 05'' (BSC 2004 [DIRS 169635]). The purpose of this revision is to bring the report up to current procedural requirements and address the Regulatory Integration Team evaluation comments. The work plan describes the scope, objectives, tasks, methodology, and procedures for this process.
ERIC Educational Resources Information Center
Harris, Mary B.
To investigate the effect of modeling on altruism, 156 third and fifth grade children were exposed to a model who either shared with them, gave to a charity, or refused to share. The test apparatus, identified as a game, consisted of a box with signal lights and a chute through which marbles were dispensed. Subjects and the model played the game…
ERIC Educational Resources Information Center
Ayers, Jerry B.; And Others
1988-01-01
The Accreditation Plus model developed by the Center for Teacher Education Evaluation of Tennessee Technological University (Cookeville) for evaluation of teacher education programs is described. An amalgamation of the accreditation model and use-tailored evaluation plans, the model calls for informed eclecticism in the assembly of evaluation…
NASA Astrophysics Data System (ADS)
Peterson, Matthew C.
1991-08-01
The United States Air Force Environmental Technical Applications Center (USAFETAC) was tasked to review the scientific literature for studies of the Groves Neutral Density Climatology Model and compare the Groves Model with others in the 30-60 km range. The tasking included a request to investigate the merits of comparing accuracy of the Groves Model to rocketsonde data. USAFETAC analysts found the Groves Model to be state of the art for middle-atmospheric climatological models. In reviewing previous comparisons with other models and with space shuttle-derived atmospheric densities, good density vs altitude agreement was found in almost all cases. A simple technique involving comparison of the model with range reference atmospheres was found to be the most economical way to compare the Groves Model with rocketsonde data; an example of this type is provided. The Groves 85 Model is used routinely in USAFETAC's Improved Point Analysis Model (IPAM). To create this model, Dr. Gerald Vann Groves produced tabulations of atmospheric density based on data derived from satellite observations and modified by rocketsonde observations. Neutral Density as presented here refers to the monthly mean density in 10-degree latitude bands as a function of altitude. The Groves 85 Model zonal mean density tabulations are given in their entirety.
Improved analytic nutation model
NASA Technical Reports Server (NTRS)
Yoder, C. F.; Ivins, E. R.
1988-01-01
Models describing the earth's nutations are discussed. It is found that the simple model of Sasao et al., (1981) differs from Wahr's (1981) theory term by term by less than 0.3 marcsec if a modern earth structure model is used to evaluate the nutation structure constants. In addition, the effect of oceans is estimated.
ERIC Educational Resources Information Center
Goodman, Richard E.
1970-01-01
Describes types of molecular models (ball-and-stick, framework, and space-filling) and evaluates commercially available kits. Gives instructions for constructive models from polystyrene balls and pipe-cleaners. Models are useful for class demonstrations although not sufficiently accurate for research use. Illustrations show biologically important…
Biophysical and spectral modeling
NASA Technical Reports Server (NTRS)
Goel, N. S. (Principal Investigator)
1982-01-01
Activities and results of a project to develop strategies for modeling vegetative canopy reflectance are reported. Specific tasks included the inversion of canopy reflectance models to estimate agronomic variables (particularly leaf area index) from in-situ reflectance measurements, and a study of possible uses of ecological models in analyzing temporal profiles of greenness.
Generalized Latent Trait Models.
ERIC Educational Resources Information Center
Moustaki, Irini; Knott, Martin
2000-01-01
Discusses a general model framework within which manifest variables with different distributions in the exponential family can be analyzed with a latent trait model. Presents a unified maximum likelihood method for estimating the parameters of the generalized latent trait model and discusses the scoring of individuals on the latent dimensions.…
Gaussian Process Morphable Models.
Luthi, Marcel; Gerig, Thomas; Jud, Christoph; Vetter, Thomas
2017-08-14
Models of shape variations have become a central component for the automated analysis of images. An important class of shape models are point distribution models (PDMs). These models represent a class of shapes as a normal distribution of point variations, whose parameters are estimated from example shapes. Principal component analysis (PCA) is applied to obtain a low-dimensional representation of the shape variation in terms of the leading principal components. In this paper, we propose a generalization of PDMs, which we refer to as Gaussian Process Morphable Models (GPMMs). We model the shape variations with a Gaussian process, which we represent using the leading components of its Karhunen-Loève expansion. To compute the expansion, we make use of an approximation scheme based on the Nyström method. The resulting model can be seen as a continuous analog of a standard PDM. However, while for PDMs the shape variation is restricted to the linear span of the example data, with GPMMs we can define the shape variation using any Gaussian process. For example, we can build shape models that correspond to classical spline models and thus do not require any example data. Furthermore, Gaussian processes make it possible to combine different models. For example, a PDM can be extended with a spline model, to obtain a model that incorporates learned shape characteristics but is flexible enough to explain shapes that cannot be represented by the PDM.
Modeling and Remodeling Writing
ERIC Educational Resources Information Center
Hayes, John R.
2012-01-01
In Section 1 of this article, the author discusses the succession of models of adult writing that he and his colleagues have proposed from 1980 to the present. He notes the most important changes that differentiate earlier and later models and discusses reasons for the changes. In Section 2, he describes his recent efforts to model young…
ERIC Educational Resources Information Center
Meara, Paul
2004-01-01
This paper describes some simple simulation models of vocabulary attrition. The attrition process is modelled using a random autonomous Boolean network model, and some parallels with real attrition data are drawn. The paper argues that applying a complex systems approach to attrition can provide some important insights, which suggest that real…
ERIC Educational Resources Information Center
Fitzsimmons, Charles P.
1986-01-01
Points out the instructional applications and program possibilities of a unit on model rocketry. Describes the ways that microcomputers can assist in model rocket design and in problem calculations. Provides a descriptive listing of model rocket software for the Apple II microcomputer. (ML)
ERIC Educational Resources Information Center
Walsh, Jim; McGehee, Richard
2013-01-01
A dynamical systems approach to energy balance models of climate is presented, focusing on low order, or conceptual, models. Included are global average and latitude-dependent, surface temperature models. The development and analysis of the differential equations and corresponding bifurcation diagrams provides a host of appropriate material for…
Richard Haynes; Darius Adams; Peter Ince; John Mills; Ralph Alig
2006-01-01
The United States has a century of experience with the development of models that describe markets for forest products and trends in resource conditions. In the last four decades, increasing rigor in policy debates has stimulated the development of models to support policy analysis. Increasingly, research has evolved (often relying on computer-based models) to increase...
This presentation provides a general overview of SHEDS model features, describes algorithms in the SHEDS-Air Toxics model that focus on mobile source exposures and multipathway exposures, and presents examples of results from application of the SHEDS-Air Toxics model to benzene i...
ERIC Educational Resources Information Center
Summerlin, Lee; Borgford, Christie
1989-01-01
Described is an activity which uses a 96-well reaction plate and soda straws to construct a model of the periodic table of the elements. The model illustrates the ionization energies of the various elements. Construction of the model and related concepts are discussed. (CW)
ERIC Educational Resources Information Center
Walsh, Jim; McGehee, Richard
2013-01-01
A dynamical systems approach to energy balance models of climate is presented, focusing on low order, or conceptual, models. Included are global average and latitude-dependent, surface temperature models. The development and analysis of the differential equations and corresponding bifurcation diagrams provides a host of appropriate material for…
Modeling rapidly rotating stars
NASA Astrophysics Data System (ADS)
Rieutord, M.
2006-06-01
We review the quest of modeling rapidly rotating stars during the past 40 years and detail the challenges to be taken up by models facing new data from interferometry, seismology, spectroscopy... We then present the progress of the ESTER project aimed at giving a physically self-consistent model for the structure and evolution of rapidly rotating stars.
Open Source Molecular Modeling
Pirhadi, Somayeh; Sunseri, Jocelyn; Koes, David Ryan
2016-01-01
The success of molecular modeling and computational chemistry efforts are, by definition, dependent on quality software applications. Open source software development provides many advantages to users of modeling applications, not the least of which is that the software is free and completely extendable. In this review we categorize, enumerate, and describe available open source software packages for molecular modeling and computational chemistry. PMID:27631126
ERIC Educational Resources Information Center
Kim, ChanMin
2013-01-01
The purpose of this paper is to introduce a design model for supporting student volition. First, the construct of volition is explained and the importance of volition is further described in the context of goal attainment. Next, the theoretical basis of the model is described. Last, implications of the model are discussed for the design of…
USDA-ARS?s Scientific Manuscript database
Adsorption-desorption reactions are important processes that affect the transport of contaminants in the environment. Surface complexation models are chemical models that can account for the effects of variable chemical conditions, such as pH, on adsorption reactions. These models define specific ...
Modeling EERE Deployment Programs
Cort, K. A.; Hostick, D. J.; Belzer, D. B.; Livingston, O. V.
2007-11-01
This report compiles information and conclusions gathered as part of the “Modeling EERE Deployment Programs” project. The purpose of the project was to identify and characterize the modeling of deployment programs within the EERE Technology Development (TD) programs, address possible improvements to the modeling process, and note gaps in knowledge in which future research is needed.
Advances in Watershed Models and Modeling
NASA Astrophysics Data System (ADS)
Yeh, G. T.; Zhang, F.
2015-12-01
The development of watershed models and their applications to real-world problems has evolved significantly since 1960's. Watershed models can be classified based on what media are included, what processes are dealt with, and what approaches are taken. In term of media, a watershed may include segregated overland regime, river-canal-open channel networks, ponds-reservoirs-small lakes, and subsurface media. It may also include integrated media of all these or a partial set of these as well as man-made control structures. In term of processes, a watershed model may deal with coupled or decoupled hydrological and biogeochemical cycles. These processes include fluid flow, thermal transport, salinity transport, sediment transport, reactive transport, and biota and microbe kinetics. In terms of approaches, either parametric or physics-based approach can be taken. This talk discusses the evolution of watershed models in the past sixty years. The advances of watershed models center around their increasing design capability to foster these segregated or integrated media and coupled or decoupled processes. Widely used models developed by academia, research institutes, government agencies, and private industries will be reviewed in terms of the media and processes included as well as approaches taken. Many types of potential benchmark problems in general can be proposed and will be discussed. This presentation will focus on three benchmark problems of biogeochemical cycles. These three problems, dealing with water quality transport, will be formulated in terms of reactive transport. Simulation results will be illustrated using WASH123D, a watershed model developed and continuously updated by the author and his PhD graduates. Keywords: Hydrological Cycles, Biogeochemical Cycles, Biota Kinetics, Parametric Approach, Physics-based Approach, Reactive Transport.
Modeling agriculture in the Community Land Model
NASA Astrophysics Data System (ADS)
Drewniak, B.; Song, J.; Prell, J.; Kotamarthi, V. R.; Jacob, R.
2013-04-01
The potential impact of climate change on agriculture is uncertain. In addition, agriculture could influence above- and below-ground carbon storage. Development of models that represent agriculture is necessary to address these impacts. We have developed an approach to integrate agriculture representations for three crop types - maize, soybean, and spring wheat - into the coupled carbon-nitrogen version of the Community Land Model (CLM), to help address these questions. Here we present the new model, CLM-Crop, validated against observations from two AmeriFlux sites in the United States, planted with maize and soybean. Seasonal carbon fluxes compared well with field measurements for soybean, but not as well for maize. CLM-Crop yields were comparable with observations in countries such as the United States, Argentina, and China, although the generality of the crop model and its lack of technology and irrigation made direct comparison difficult. CLM-Crop was compared against the standard CLM3.5, which simulates crops as grass. The comparison showed improvement in gross primary productivity in regions where crops are the dominant vegetation cover. Crop yields and productivity were negatively correlated with temperature and positively correlated with precipitation, in agreement with other modeling studies. In case studies with the new crop model looking at impacts of residue management and planting date on crop yield, we found that increased residue returned to the litter pool increased crop yield, while reduced residue returns resulted in yield decreases. Using climate controls to signal planting date caused different responses in different crops. Maize and soybean had opposite reactions: when low temperature threshold resulted in early planting, maize responded with a loss of yield, but soybean yields increased. Our improvements in CLM demonstrate a new capability in the model - simulating agriculture in a realistic way, complete with fertilizer and residue management
Ritchie, L.T.; Alpert, D.J.; Burke, R.P.; Johnson, J.D.; Ostmeyer, R.M.; Aldrich, D.C.; Blond, R.M.
1984-03-01
The CRAC2 computer code is a revised version of CRAC (Calculation of Reactor Accident Consequences) which was developed for the Reactor Safety Study. This document provides an overview of the CRAC2 code and a description of each of the models used. Significant improvements incorporated into CRAC2 include an improved weather sequence sampling technique, a new evacuation model, and new output capabilities. In addition, refinements have been made to the atmospheric transport and deposition model. Details of the modeling differences between CRAC2 and CRAC are emphasized in the model descriptions.
Mathematical modeling in neuroendocrinology.
Bertram, Richard
2015-04-01
Mathematical models are commonly used in neuroscience, both as tools for integrating data and as devices for designing new experiments that test model predictions. The wide range of relevant spatial and temporal scales in the neuroendocrine system makes neuroendocrinology a branch of neuroscience with great potential for modeling. This article provides an overview of concepts that are useful for understanding mathematical models of the neuroendocrine system, as well as design principles that have been illuminated through the use of mathematical models. These principles are found over and over again in cellular dynamics, and serve as building blocks for understanding some of the complex temporal dynamics that are exhibited throughout the neuroendocrine system.
NASA Astrophysics Data System (ADS)
Alves, Daniele S. M.; Galloway, Jamison; McCullough, Matthew; Weiner, Neal
2016-04-01
Models with Dirac gauginos are appealing scenarios for physics beyond the Standard Model. They have smaller radiative corrections to scalar soft masses, a suppression of certain supersymmetry (SUSY) production processes at the LHC, and ameliorated flavor constraints. Unfortunately, they are generically plagued by tachyons charged under the Standard Model, and attempts to eliminate such states typically spoil the positive features. The recently proposed "Goldstone gaugino" mechanism provides a simple realization of Dirac gauginos that is automatically free of dangerous tachyonic states. We provide details on this mechanism and explore models for its origin. In particular, we find SUSY QCD models that realize this idea simply and discuss scenarios for unification.
NASA Technical Reports Server (NTRS)
Meister, Jeffrey P.
1987-01-01
The Mechanics of Materials Model (MOMM) is a three-dimensional inelastic structural analysis code for use as an early design stage tool for hot section components. MOMM is a stiffness method finite element code that uses a network of beams to characterize component behavior. The MOMM contains three material models to account for inelastic material behavior. These include the simplified material model, which assumes a bilinear stress-strain response; the state-of-the-art model, which utilizes the classical elastic-plastic-creep strain decomposition; and Walker's viscoplastic model, which accounts for the interaction between creep and plasticity that occurs under cyclic loading conditions.
M. McGraw
2000-04-13
The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations.
Storjohann, K.
1990-01-01
This paper describes an imaging model that was derived for use with a laser range camera (LRC) developed by the Advanced Intelligent Machines Division of Odetics. However, this model could be applied to any comparable imaging system. Both the derivation of the model and the determination of the LRC's intrinsic parameters are explained. For the purpose of evaluating the LRC's extrinsic parameters, i.e., its external orientation, a transformation of the LRC's imaging model into a standard camera's (SC) pinhole model is derived. By virtue of this transformation, the evaluation of the LRC's external orientation can be found by applying any SC calibration technique.
NASA Astrophysics Data System (ADS)
Marion, Giles M.; Kargel, Jeffrey S.
Implementation of the Pitzer approach is through the FREZCHEM (FREEZING CHEMISTRY) model, which is at the core of this work. This model was originally designed to simulate salt chemistries and freezing processes at low temperatures (-54 to 25°C) and 1 atm pressure. Over the years, this model has been broadened to include more chemistries (from 16 to 58 solid phases), a broader temperature range for some chemistries (to 113°C), and incorporation of a pressure dependence (1 to 1000 bars) into the model. Implementation, parameterization, validation, and limitations of the FREZCHEM model are extensively discussed in Chapter 3.
T. Ghezzehej
2004-10-04
The purpose of this model report is to document the calibrated properties model that provides calibrated property sets for unsaturated zone (UZ) flow and transport process models (UZ models). The calibration of the property sets is performed through inverse modeling. This work followed, and was planned in, ''Technical Work Plan (TWP) for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654], Sections 1.2.6 and 2.1.1.6). Direct inputs to this model report were derived from the following upstream analysis and model reports: ''Analysis of Hydrologic Properties Data'' (BSC 2004 [DIRS 170038]); ''Development of Numerical Grids for UZ Flow and Transport Modeling'' (BSC 2004 [DIRS 169855]); ''Simulation of Net Infiltration for Present-Day and Potential Future Climates'' (BSC 2004 [DIRS 170007]); ''Geologic Framework Model'' (GFM2000) (BSC 2004 [DIRS 170029]). Additionally, this model report incorporates errata of the previous version and closure of the Key Technical Issue agreement TSPAI 3.26 (Section 6.2.2 and Appendix B), and it is revised for improved transparency.
Collins, Lisa M.; Part, Chérie E.
2013-01-01
Simple Summary In this review paper we discuss the different modeling techniques that have been used in animal welfare research to date. We look at what questions they have been used to answer, the advantages and pitfalls of the methods, and how future research can best use these approaches to answer some of the most important upcoming questions in farm animal welfare. Abstract The use of models in the life sciences has greatly expanded in scope and advanced in technique in recent decades. However, the range, type and complexity of models used in farm animal welfare is comparatively poor, despite the great scope for use of modeling in this field of research. In this paper, we review the different modeling approaches used in farm animal welfare science to date, discussing the types of questions they have been used to answer, the merits and problems associated with the method, and possible future applications of each technique. We find that the most frequently published types of model used in farm animal welfare are conceptual and assessment models; two types of model that are frequently (though not exclusively) based on expert opinion. Simulation, optimization, scenario, and systems modeling approaches are rarer in animal welfare, despite being commonly used in other related fields. Finally, common issues such as a lack of quantitative data to parameterize models, and model selection and validation are discussed throughout the review, with possible solutions and alternative approaches suggested. PMID:26487411
Horizontal model fusion paradigm
NASA Astrophysics Data System (ADS)
Julier, Simon J.; Durrant-Whyte, Hugh F.
1996-05-01
In navigation and tracking problems, the identification of an appropriate model of vehicular or target motion is vital to most practical data fusion algorithms. The true system dynamics are rarely known, and approximations are usually employed. Since systems can exhibit strikingly different behaviors, multiple models may be needed to describe each of these behaviors. Current methods either use model switching (a single process model is chosen from the set using a decision rule) or consider the models as a set of competing hypothesis, only one of which is 'correct'. However, these methods fail to exploit the fact that all models are of the same system and that all of them are, to some degree, 'correct'. In this paper we present a new paradigm for fusing information from a set of multiple process models. The predictions from each process model are regarded as observations which are corrupted by correlated noise. By employing the standard Kalman filter equations we combine data from multiple sensors and multiple process models optimally. There are a number of significant practical advantages to this technique. First, the performance of the system always equals or betters that of the best estimator in the set of models being used. Second, the same decision theoretic machinery can be used to select the process models as well as the sensor suites.
Distributed fuzzy system modeling
Pedrycz, W.; Chi Fung Lam, P.; Rocha, A.F.
1995-05-01
The paper introduces and studies an idea of distributed modeling treating it as a new paradigm of fuzzy system modeling and analysis. This form of modeling is oriented towards developing individual (local) fuzzy models for specific modeling landmarks (expressed as fuzzy sets) and determining the essential logical relationships between these local models. The models themselves are implemented in the form of logic processors being regarded as specialized fuzzy neural networks. The interaction between the processors is developed either in an inhibitory or excitatory way. In more descriptive way, the distributed model can be sought as a collection of fuzzy finite state machines with their individual local first or higher order memories. It is also clarified how the concept of distributed modeling narrows down a gap between purely numerical (quantitative) models and the qualitative ones originated within the realm of Artificial Intelligence. The overall architecture of distributed modeling is discussed along with the detailed learning schemes. The results of extensive simulation experiments are provided as well. 17 refs.
NASA Astrophysics Data System (ADS)
Fischer, Arthur E.
1996-01-01
In this paper a theory of models of the universe is proposed. We refer to such models ascosmological models, where a cosmological model is defined as an Einstein-inextendible Einstein spacetime. A cosmological model isabsolute if it is a Lorentz-inextendible Einstein spacetime,predictive if it is globally hyperbolic, andnon-predictive if it is nonglobally-hyperbolic. We discuss several features of these models in the study of cosmology. As an example, any compact Einstein spacetime is always a non-predictive absolute cosmological model, whereas a noncompact complete Einstein spacetime is an absolute cosmological model which may be either predictive or non-predictive. We discuss the important role played by maximal Einstein spacetimes. In particular, we examine the possible proper Lorentz-extensions of such spacetimes, and show that a spatially compact maximal Einstein spacetime is exclusively either a predictive cosmological model or a proper sub-spacetime of a non-predictive cosmological model. Provided that the Strong Cosmic Censorship conjecture is true, a generic spatially compact maximal Einstein spacetime must be a predictive cosmological model. It isconjectured that the Strong Cosmic Censorship conjecture isnot true, and converting a vice to a virtue it is argued that the failure of the Strong Cosmic Censorship conjecture would point to what may be general relativity's greatest prediction of all, namely,that general relativity predicts that general relativity cannot predict the entire history of the universe.
Johnson, Douglas H.; Cook, R.D.
2013-01-01
In her AAAS News & Notes piece "Can the Southwest manage its thirst?" (26 July, p. 362), K. Wren quotes Ajay Kalra, who advocates a particular method for predicting Colorado River streamflow "because it eschews complex physical climate models for a statistical data-driven modeling approach." A preference for data-driven models may be appropriate in this individual situation, but it is not so generally, Data-driven models often come with a warning against extrapolating beyond the range of the data used to develop the models. When the future is like the past, data-driven models can work well for prediction, but it is easy to over-model local or transient phenomena, often leading to predictive inaccuracy (1). Mechanistic models are built on established knowledge of the process that connects the response variables with the predictors, using information obtained outside of an extant data set. One may shy away from a mechanistic approach when the underlying process is judged to be too complicated, but good predictive models can be constructed with statistical components that account for ingredients missing in the mechanistic analysis. Models with sound mechanistic components are more generally applicable and robust than data-driven models.
NASA Technical Reports Server (NTRS)
Tijidjian, Raffi P.
2010-01-01
The TEAMS model analyzer is a supporting tool developed to work with models created with TEAMS (Testability, Engineering, and Maintenance System), which was developed by QSI. In an effort to reduce the time spent in the manual process that each TEAMS modeler must perform in the preparation of reporting for model reviews, a new tool has been developed as an aid to models developed in TEAMS. The software allows for the viewing, reporting, and checking of TEAMS models that are checked into the TEAMS model database. The software allows the user to selectively model in a hierarchical tree outline view that displays the components, failure modes, and ports. The reporting features allow the user to quickly gather statistics about the model, and generate an input/output report pertaining to all of the components. Rules can be automatically validated against the model, with a report generated containing resulting inconsistencies. In addition to reducing manual effort, this software also provides an automated process framework for the Verification and Validation (V&V) effort that will follow development of these models. The aid of such an automated tool would have a significant impact on the V&V process.
Modelling structured data with Probabilistic Graphical Models
NASA Astrophysics Data System (ADS)
Forbes, F.
2016-05-01
Most clustering and classification methods are based on the assumption that the objects to be clustered are independent. However, in more and more modern applications, data are structured in a way that makes this assumption not realistic and potentially misleading. A typical example that can be viewed as a clustering task is image segmentation where the objects are the pixels on a regular grid and depend on neighbouring pixels on this grid. Also, when data are geographically located, it is of interest to cluster data with an underlying dependence structure accounting for some spatial localisation. These spatial interactions can be naturally encoded via a graph not necessarily regular as a grid. Data sets can then be modelled via Markov random fields and mixture models (e.g. the so-called MRF and Hidden MRF). More generally, probabilistic graphical models are tools that can be used to represent and manipulate data in a structured way while modeling uncertainty. This chapter introduces the basic concepts. The two main classes of probabilistic graphical models are considered: Bayesian networks and Markov networks. The key concept of conditional independence and its link to Markov properties is presented. The main problems that can be solved with such tools are described. Some illustrations are given associated with some practical work.
Toward Scientific Numerical Modeling
NASA Technical Reports Server (NTRS)
Kleb, Bil
2007-01-01
Ultimately, scientific numerical models need quantified output uncertainties so that modeling can evolve to better match reality. Documenting model input uncertainties and verifying that numerical models are translated into code correctly, however, are necessary first steps toward that goal. Without known input parameter uncertainties, model sensitivities are all one can determine, and without code verification, output uncertainties are simply not reliable. To address these two shortcomings, two proposals are offered: (1) an unobtrusive mechanism to document input parameter uncertainties in situ and (2) an adaptation of the Scientific Method to numerical model development and deployment. Because these two steps require changes in the computational simulation community to bear fruit, they are presented in terms of the Beckhard-Harris-Gleicher change model.
Physical modelling in biomechanics.
Koehl, M A R
2003-01-01
Physical models, like mathematical models, are useful tools in biomechanical research. Physical models enable investigators to explore parameter space in a way that is not possible using a comparative approach with living organisms: parameters can be varied one at a time to measure the performance consequences of each, while values and combinations not found in nature can be tested. Experiments using physical models in the laboratory or field can circumvent problems posed by uncooperative or endangered organisms. Physical models also permit some aspects of the biomechanical performance of extinct organisms to be measured. Use of properly scaled physical models allows detailed physical measurements to be made for organisms that are too small or fast to be easily studied directly. The process of physical modelling and the advantages and limitations of this approach are illustrated using examples from our research on hydrodynamic forces on sessile organisms, mechanics of hydraulic skeletons, food capture by zooplankton and odour interception by olfactory antennules. PMID:14561350
Toward Scientific Numerical Modeling
NASA Technical Reports Server (NTRS)
Kleb, Bil
2007-01-01
Ultimately, scientific numerical models need quantified output uncertainties so that modeling can evolve to better match reality. Documenting model input uncertainties and verifying that numerical models are translated into code correctly, however, are necessary first steps toward that goal. Without known input parameter uncertainties, model sensitivities are all one can determine, and without code verification, output uncertainties are simply not reliable. To address these two shortcomings, two proposals are offered: (1) an unobtrusive mechanism to document input parameter uncertainties in situ and (2) an adaptation of the Scientific Method to numerical model development and deployment. Because these two steps require changes in the computational simulation community to bear fruit, they are presented in terms of the Beckhard-Harris-Gleicher change model.
Moffat, Harry K.; Noble, David R.; Baer, Thomas A.; Adolf, Douglas Brian; Rao, Rekha Ranjana; Mondy, Lisa Ann
2008-09-01
In this report, we summarize our work on developing a production level foam processing computational model suitable for predicting the self-expansion of foam in complex geometries. The model is based on a finite element representation of the equations of motion, with the movement of the free surface represented using the level set method, and has been implemented in SIERRA/ARIA. An empirically based time- and temperature-dependent density model is used to encapsulate the complex physics of foam nucleation and growth in a numerically tractable model. The change in density with time is at the heart of the foam self-expansion as it creates the motion of the foam. This continuum-level model uses an homogenized description of foam, which does not include the gas explicitly. Results from the model are compared to temperature-instrumented flow visualization experiments giving the location of the foam front as a function of time for our EFAR model system.
NASA Astrophysics Data System (ADS)
Sobehart, Jorge
2003-03-01
The conventional method for developing credit risk models is to determine the probability of occurrence of credit events that can contribute to business failure. Unfortunately, most of the quantitative approaches to credit risk modeling found in the literature do not accurately portray the situation when the model inputs contain a significant degree of subjectivity or the relationships between inputs are inexact. In practice, data are often sparse, unreliable or nonexistent and the relationships between the model variables are often based on expert judgment. This means that credit risk models often depend on significant subjective expertise as opposed to models derived from first principles. Because of the continuous development of complex derivatives structures and debt instruments, and also because investors are becoming increasingly sophisticated and more reluctant to accept overly simplistic credit risk analysis, it is important to understand the basic limitations of the available credit risk models.
Shipman, Galen M.
2016-06-13
These are the slides for a presentation on programming models in HPC, at the Los Alamos National Laboratory's Parallel Computing Summer School. The following topics are covered: Flynn's Taxonomy of computer architectures; single instruction single data; single instruction multiple data; multiple instruction multiple data; address space organization; definition of Trinity (Intel Xeon-Phi is a MIMD architecture); single program multiple data; multiple program multiple data; ExMatEx workflow overview; definition of a programming model, programming languages, runtime systems; programming model and environments; MPI (Message Passing Interface); OpenMP; Kokkos (Performance Portable Thread-Parallel Programming Model); Kokkos abstractions, patterns, policies, and spaces; RAJA, a systematic approach to node-level portability and tuning; overview of the Legion Programming Model; mapping tasks and data to hardware resources; interoperability: supporting task-level models; Legion S3D execution and performance details; workflow, integration of external resources into the programming model.
V. Chipman; J. Case
2002-12-20
The purpose of the Ventilation Model is to simulate the heat transfer processes in and around waste emplacement drifts during periods of forced ventilation. The model evaluates the effects of emplacement drift ventilation on the thermal conditions in the emplacement drifts and surrounding rock mass, and calculates the heat removal by ventilation as a measure of the viability of ventilation to delay the onset of peak repository temperature and reduce its magnitude. The heat removal by ventilation is temporally and spatially dependent, and is expressed as the fraction of heat carried away by the ventilation air compared to the fraction of heat produced by radionuclide decay. One minus the heat removal is called the wall heat fraction, or the remaining amount of heat that is transferred via conduction to the surrounding rock mass. Downstream models, such as the ''Multiscale Thermohydrologic Model'' (BSC 2001), use the wall heat fractions as outputted from the Ventilation Model to initialize their post-closure analyses. The Ventilation Model report was initially developed to analyze the effects of preclosure continuous ventilation in the Engineered Barrier System (EBS) emplacement drifts, and to provide heat removal data to support EBS design. Revision 00 of the Ventilation Model included documentation of the modeling results from the ANSYS-based heat transfer model. Revision 01 ICN 01 included the results of the unqualified software code MULTIFLUX to assess the influence of moisture on the ventilation efficiency. The purposes of Revision 02 of the Ventilation Model are: (1) To validate the conceptual model for preclosure ventilation of emplacement drifts and verify its numerical application in accordance with new procedural requirements as outlined in AP-SIII-10Q, Models (Section 7.0). (2) To satisfy technical issues posed in KTI agreement RDTME 3.14 (Reamer and Williams 2001a). Specifically to demonstrate, with respect to the ANSYS ventilation model, the adequacy of
Phyloclimatic modeling: combining phylogenetics and bioclimatic modeling.
Yesson, C; Culham, A
2006-10-01
We investigate the impact of past climates on plant diversification by tracking the "footprint" of climate change on a phylogenetic tree. Diversity within the cosmopolitan carnivorous plant genus Drosera (Droseraceae) is focused within Mediterranean climate regions. We explore whether this diversity is temporally linked to Mediterranean-type climatic shifts of the mid-Miocene and whether climate preferences are conservative over phylogenetic timescales. Phyloclimatic modeling combines environmental niche (bioclimatic) modeling with phylogenetics in order to study evolutionary patterns in relation to climate change. We present the largest and most complete such example to date using Drosera. The bioclimatic models of extant species demonstrate clear phylogenetic patterns; this is particularly evident for the tuberous sundews from southwestern Australia (subgenus Ergaleium). We employ a method for establishing confidence intervals of node ages on a phylogeny using replicates from a Bayesian phylogenetic analysis. This chronogram shows that many clades, including subgenus Ergaleium and section Bryastrum, diversified during the establishment of the Mediterranean-type climate. Ancestral reconstructions of bioclimatic models demonstrate a pattern of preference for this climate type within these groups. Ancestral bioclimatic models are projected into palaeo-climate reconstructions for the time periods indicated by the chronogram. We present two such examples that each generate plausible estimates of ancestral lineage distribution, which are similar to their current distributions. This is the first study to attempt bioclimatic projections on evolutionary time scales. The sundews appear to have diversified in response to local climate development. Some groups are specialized for Mediterranean climates, others show wide-ranging generalism. This demonstrates that Phyloclimatic modeling could be repeated for other plant groups and is fundamental to the understanding of
Hammerand, Daniel Carl; Scherzinger, William Mark
2007-09-01
The Library of Advanced Materials for Engineering (LAME) provides a common repository for constitutive models that can be used in computational solid mechanics codes. A number of models including both hypoelastic (rate) and hyperelastic (total strain) constitutive forms have been implemented in LAME. The structure and testing of LAME is described in Scherzinger and Hammerand ([3] and [4]). The purpose of the present report is to describe the material models which have already been implemented into LAME. The descriptions are designed to give useful information to both analysts and code developers. Thus far, 33 non-ITAR/non-CRADA protected material models have been incorporated. These include everything from the simple isotropic linear elastic models to a number of elastic-plastic models for metals to models for honeycomb, foams, potting epoxies and rubber. A complete description of each model is outside the scope of the current report. Rather, the aim here is to delineate the properties, state variables, functions, and methods for each model. However, a brief description of some of the constitutive details is provided for a number of the material models. Where appropriate, the SAND reports available for each model have been cited. Many models have state variable aliases for some or all of their state variables. These alias names can be used for outputting desired quantities. The state variable aliases available for results output have been listed in this report. However, not all models use these aliases. For those models, no state variable names are listed. Nevertheless, the number of state variables employed by each model is always given. Currently, there are four possible functions for a material model. This report lists which of these four methods are employed in each material model. As far as analysts are concerned, this information is included only for the awareness purposes. The analyst can take confidence in the fact that model has been properly implemented
Modeling and Prediction Overview
Ermak, D L
2002-10-18
Effective preparation for and response to the release of toxic materials into the atmosphere hinges on accurate predictions of the dispersion pathway, concentration, and ultimate fate of the chemical or biological agent. Of particular interest is the threat to civilian populations within major urban areas, which are likely targets for potential attacks. The goals of the CBNP Modeling and Prediction area are: (1) Development of a suite of validated, multi-scale, atmospheric transport and fate modeling capabilities for chemical and biological agent releases within the complex urban environment; (2) Integration of these models and related user tools into operational emergency response systems. Existing transport and fate models are being adapted to treat the complex atmospheric flows within and around structures (e.g., buildings, subway systems, urban areas) and over terrain. Relevant source terms and the chemical and physical behavior of gas- and particle-phase species (e.g., losses due to deposition, bio-agent viability, degradation) are also being developed and incorporated into the models. Model validation is performed using both laboratory and field data. CBNP is producing and testing a suite of models with differing levels of complexity and fidelity to address the full range of user needs and applications. Lumped-parameter transport models are being developed for subway systems and building interiors, supplemented by the use of computational fluid dynamics (CFD) models to describe the circulation within large, open spaces such as auditoriums. Both sophisticated CFD transport models and simpler fast-response models are under development to treat the complex flow around individual structures and arrays of buildings. Urban parameterizations are being incorporated into regional-scale weather forecast, meteorological data assimilation, and dispersion models for problems involving larger-scale urban and suburban areas. Source term and dose response models are being
2010-01-01
SUMMARY Interest in targeted disease prevention has stimulated development of models that assign risks to individuals, using their personal covariates. We need to evaluate these models and quantify the gains achieved by expanding a model to include additional covariates. This paper reviews several performance measures and shows how they are related. Examples are used to show that appropriate performance criteria for a risk model depend upon how the model is used. Application of the performance measures to risk models for hypothetical populations and for US women at risk of breast cancer illustrate two additional points. First, model performance is constrained by the distribution of risk-determining covariates in the population. This complicates the comparison of two models when applied to populations with different covariate distributions. Second, all summary performance measures obscure model features of relevance to its utility for the application at hand, such as performance in specific subgroups of the population. In particular, the precision gained by adding covariates to a model can be small overall, but large in certain subgroups. We propose new ways to identify these subgroups and to quantify how much they gain by measuring the additional covariates. Those with largest gains could be targeted for cost-efficient covariate assessment. PMID:20623821
Geochemical modeling: a review
Jenne, E.A.
1981-06-01
Two general families of geochemical models presently exist. The ion speciation-solubility group of geochemical models contain submodels to first calculate a distribution of aqueous species and to secondly test the hypothesis that the water is near equilibrium with particular solid phases. These models may or may not calculate the adsorption of dissolved constituents and simulate the dissolution and precipitation (mass transfer) of solid phases. Another family of geochemical models, the reaction path models, simulates the stepwise precipitation of solid phases as a result of reacting specified amounts of water and rock. Reaction path models first perform an aqueous speciation of the dissolved constituents of the water, test solubility hypotheses, then perform the reaction path modeling. Certain improvements in the present versions of these models would enhance their value and usefulness to applications in nuclear-waste isolation, etc. Mass-transfer calculations of limited extent are certainly within the capabilities of state-of-the-art models. However, the reaction path models require an expansion of their thermodynamic data bases and systematic validation before they are generally accepted.
NASA Astrophysics Data System (ADS)
Mishra, Ashok K.; Singh, Vijay P.
2011-06-01
SummaryIn recent years droughts have been occurring frequently, and their impacts are being aggravated by the rise in water demand and the variability in hydro-meteorological variables due to climate change. As a result, drought hydrology has been receiving much attention. A variety of concepts have been applied to modeling droughts, ranging from simplistic approaches to more complex models. It is important to understand different modeling approaches as well as their advantages and limitations. This paper, supplementing the previous paper ( Mishra and Singh, 2010) where different concepts of droughts were highlighted, reviews different methodologies used for drought modeling, which include drought forecasting, probability based modeling, spatio-temporal analysis, use of Global Climate Models (GCMs) for drought scenarios, land data assimilation systems for drought modeling, and drought planning. It is found that there have been significant improvements in modeling droughts over the past three decades. Hybrid models, incorporating large scale climate indices, seem to be promising for long lead-time drought forecasting. Further research is needed to understand the spatio-temporal complexity of droughts under climate change due to changes in spatio-temporal variability of precipitation. Applications of copula based models for multivariate drought characterization seem to be promising for better drought characterization. Research on decision support systems should be advanced for issuing warnings, assessing risk, and taking precautionary measures, and the effective ways for the flow of information from decision makers to users need to be developed. Finally, some remarks are made regarding the future outlook for drought research.
NASA Technical Reports Server (NTRS)
Schoeberl, Mark; Rood, Richard B.; Hildebrand, Peter; Raymond, Carol
2003-01-01
The Earth System Model is the natural evolution of current climate models and will be the ultimate embodiment of our geophysical understanding of the planet. These models are constructed from components - atmosphere, ocean, ice, land, chemistry, solid earth, etc. models and merged together through a coupling program which is responsible for the exchange of data from the components. Climate models and future earth system models will have standardized modules, and these standards are now being developed by the ESMF project funded by NASA. The Earth System Model will have a variety of uses beyond climate prediction. The model can be used to build climate data records making it the core of an assimilation system, and it can be used in OSSE experiments to evaluate. The computing and storage requirements for the ESM appear to be daunting. However, the Japanese ES theoretical computing capability is already within 20% of the minimum requirements needed for some 2010 climate model applications. Thus it seems very possible that a focused effort to build an Earth System Model will achieve succcss.
Improved Screened Hydrogenic Model
Nishikawa, T.
1996-05-01
Screened Hydrogenic Model is widely used for energy level calculation in hydrodynamic code of inertial confinement fusion because Screened Hydrogenic Model is simple algebraic calculation. More{close_quote}s Screened Hydrogenic Model and his screening constants are usually used to calculate opacity and equation of state. By the use of his model, energy level can be consistently calculated with ion{close_quote}s total energy. But his model take into account the principal quantum number dependence only and cannot reproduce hydrogenic energy levels. As the precise experiment about opacity measurement is performed, it becomes clear that his model is not enough to use for opacity calculation. In this paper, his model is improved in the framework of Screened Hydrogenic Model. The improved model can reproduce the hydrogenic energy levels and include azimuthal quantum number dependence and the effect from another quantum state (a kind of inner quantum number). Screening constants are fitted by spectroscopic data and sophisticate calculations. By the use of improved model, energy levels are calculated more accurately for low-{ital z} ions. {copyright} {ital 1996 American Institute of Physics.}
Quantitative Rheological Model Selection
NASA Astrophysics Data System (ADS)
Freund, Jonathan; Ewoldt, Randy
2014-11-01
The more parameters in a rheological the better it will reproduce available data, though this does not mean that it is necessarily a better justified model. Good fits are only part of model selection. We employ a Bayesian inference approach that quantifies model suitability by balancing closeness to data against both the number of model parameters and their a priori uncertainty. The penalty depends upon prior-to-calibration expectation of the viable range of values that model parameters might take, which we discuss as an essential aspect of the selection criterion. Models that are physically grounded are usually accompanied by tighter physical constraints on their respective parameters. The analysis reflects a basic principle: models grounded in physics can be expected to enjoy greater generality and perform better away from where they are calibrated. In contrast, purely empirical models can provide comparable fits, but the model selection framework penalizes their a priori uncertainty. We demonstrate the approach by selecting the best-justified number of modes in a Multi-mode Maxwell description of PVA-Borax. We also quantify relative merits of the Maxwell model relative to powerlaw fits and purely empirical fits for PVA-Borax, a viscoelastic liquid, and gluten.
Turbulence modeling and experiments
NASA Technical Reports Server (NTRS)
Shabbir, Aamir
1992-01-01
The best way of verifying turbulence is to do a direct comparison between the various terms and their models. The success of this approach depends upon the availability of the data for the exact correlations (both experimental and DNS). The other approach involves numerically solving the differential equations and then comparing the results with the data. The results of such a computation will depend upon the accuracy of all the modeled terms and constants. Because of this it is sometimes difficult to find the cause of a poor performance by a model. However, such a calculation is still meaningful in other ways as it shows how a complete Reynolds stress model performs. Thirteen homogeneous flows are numerically computed using the second order closure models. We concentrate only on those models which use a linear (or quasi-linear) model for the rapid term. This, therefore, includes the Launder, Reece and Rodi (LRR) model; the isotropization of production (IP) model; and the Speziale, Sarkar, and Gatski (SSG) model. Which of the three models performs better is examined along with what are their weaknesses, if any. The other work reported deal with the experimental balances of the second moment equations for a buoyant plume. Despite the tremendous amount of activity toward the second order closure modeling of turbulence, very little experimental information is available about the budgets of the second moment equations. Part of the problem stems from our inability to measure the pressure correlations. However, if everything else appearing in these equations is known from the experiment, pressure correlations can be obtained as the closing terms. This is the closest we can come to in obtaining these terms from experiment, and despite the measurement errors which might be present in such balances, the resulting information will be extremely useful for the turbulence modelers. The purpose of this part of the work was to provide such balances of the Reynolds stress and heat
Ray, T.R.
1993-01-01
Mathematical models are used to elucidate properties of the monomer-monomer and monomer-dimer type chemical reactions on a two-dimensional surface. The authors use mean-field and lattice gas models, detailing similarities and differences due to correlations in the lattice gas model. The monomer-monomer, or AB surface reaction model, with no diffusion, is investigated for various reaction rates k. Study of the exact rate equations reveals that poisoning always occurs if the adsorption rates of the reactants are unequal. If the adsorption rates of the reactants are equal, simulations show slow poisoning, associated with clustering of reactants. This behavior is also shown for the two-dimensional voter model. The authors analyze precisely the slow poisoning kinetics by an analytic treatment for the AB reaction with infinitesimal reaction rate, and by direct comparison with the voter model. They extend the results to incorporate the effects of place-exchange diffusion, and they compare the AB reaction with infinitesimal reaction rate and no diffusion to the voter model with diffusion at rate 1/2. They also consider the relationship of the voter model to the monomer-dimer model, and investigate the latter model for small reaction rates. The monomer-dimer, or AB[sub 2] surface reaction model is also investigated. Specifically, they consider the ZGB-model for CO-oxidation, and in generalizations of this model which include adspecies diffusion. A theory of nucleation to describe properties of non-equilibrium first-order transitions, specifically the evolution between [open quote]reactive[close quote] steady states and trivial adsorbing states, is derived. The behavior of the [open quote]epidemic[close quote] survival probability, P[sub s], for a non-poisoned patch surrounded by a poisoned background is determined below the poisoning transition.
[Mathematical models of hysteresis
Mayergoyz, I.D.
1991-01-01
The research described in this proposal is currently being supported by the US Department of Energy under the contract Mathematical Models of Hysteresis''. Thus, before discussing the proposed research in detail, it is worthwhile to describe and summarize the main results achieved in the course of our work under the above contract. Our ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with nonlocal memories''. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. Our research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. Our study has by and large been centered around the following topics: various generalizations and extensions of the classical Preisach model, finding of necessary and sufficient conditions for the representation of actual hysteretic nonlinearities by various Preisach type models, solution of identification problems for these models, numerical implementation and experimental testing of Preisach type models. Although the study of Preisach type models has constituted the main direction of the research, some effort has also been made to establish some interesting connections between these models and such topics as: the critical state model for superconducting hysteresis, the classical Stoner-Wohlfarth model of vector magnetic hysteresis, thermal activation type models for viscosity, magnetostrictive hysteresis and neural networks.
A Rasch Hierarchical Measurement Model.
ERIC Educational Resources Information Center
Maier, Kimberly S.
This paper describes a model that integrates an item response theory (IRT) Rasch model and a hierarchical linear model and presents a method of estimating model parameter values that does not rely on large-sample theory and normal approximations. The model resulting from the integration of a hierarchical linear model and the Rasch model allows one…
Generalized Multilevel Structural Equation Modeling
ERIC Educational Resources Information Center
Rabe-Hesketh, Sophia; Skrondal, Anders; Pickles, Andrew
2004-01-01
A unifying framework for generalized multilevel structural equation modeling is introduced. The models in the framework, called generalized linear latent and mixed models (GLLAMM), combine features of generalized linear mixed models (GLMM) and structural equation models (SEM) and consist of a response model and a structural model for the latent…
Modeling Imports in a Keynesian Expenditure Model
ERIC Educational Resources Information Center
Findlay, David W.
2010-01-01
The author discusses several issues that instructors of introductory macroeconomics courses should consider when introducing imports in the Keynesian expenditure model. The analysis suggests that the specification of the import function should partially, if not completely, be the result of a simple discussion about the spending and import…
Modeling Imports in a Keynesian Expenditure Model
ERIC Educational Resources Information Center
Findlay, David W.
2010-01-01
The author discusses several issues that instructors of introductory macroeconomics courses should consider when introducing imports in the Keynesian expenditure model. The analysis suggests that the specification of the import function should partially, if not completely, be the result of a simple discussion about the spending and import…
NASA Technical Reports Server (NTRS)
1985-01-01
The outside users payload model which is a continuation of documents and replaces and supersedes the July 1984 edition is presented. The time period covered by this model is 1985 through 2000. The following sections are included: (1) definition of the scope of the model; (2) discussion of the methodology used; (3) overview of total demand; (4) summary of the estimated market segmentation by launch vehicle; (5) summary of the estimated market segmentation by user type; (6) details of the STS market forecast; (7) summary of transponder trends; (8) model overview by mission category; and (9) detailed mission models. All known non-NASA, non-DOD reimbursable payloads forecast to be flown by non-Soviet-block countries are included in this model with the exception of Spacelab payloads and small self contained payloads. Certain DOD-sponsored or cosponsored payloads are included if they are reimbursable launches.
NASA Technical Reports Server (NTRS)
Avrett, E. H.; Kurucz, R. L.; Machado, M. E.
1985-01-01
Further calculated results based on the F1 and F2 chromospheric models of Machado et al. (1980) are presented in addition to results from a model with enhanced temperatures relative to the weak-flare model F1 in the upper photosphere and low chromosphere, and from a model with enhanced temperatures relative to the strong flare model F2 in the upper chromosphere. The coupled equations of statistical equilibrium and radiative transfer for H, H(-), He I-II, C I-IV, Si I-II, Mg I-II, Fe, Al, O I-II, Na, and Ca II are solved, and the overall absorption and emission of radiation by lines throughout the spectrum are determined by means of a reduced set of opacities taken from a compilation of over 10 million lines. Semiempirical models show that the white light flare continuum may arise by extreme chromospheric overheating, as well as by an enhancement of the minimum temperature region.
NASA Astrophysics Data System (ADS)
Avrett, E. H.; Kurucz, R. L.; Machado, M. E.
1985-08-01
Further calculated results based on the F1 and F2 chromospheric models of Machado et al. (1980) are presented in addition to results from a model with enhanced temperatures relative to the weak-flare model F1 in the upper photosphere and low chromosphere, and from a model with enhanced temperatures relative to the strong flare model F2 in the upper chromosphere. The coupled equations of statistical equilibrium and radiative transfer for H, H(-), He I-II, C I-IV, Si I-II, Mg I-II, Fe, Al, O I-II, Na, and Ca II are solved, and the overall absorption and emission of radiation by lines throughout the spectrum are determined by means of a reduced set of opacities taken from a compilation of over 10 million lines. Semiempirical models show that the white light flare continuum may arise by extreme chromospheric overheating, as well as by an enhancement of the minimum temperature region.
NASA Technical Reports Server (NTRS)
North, G. R.; Cahalan, R. F.; Coakley, J. A., Jr.
1981-01-01
An introductory survey of the global energy balance climate models is presented with an emphasis on analytical results. A sequence of increasingly complicated models involving ice cap and radiative feedback processes are solved, and the solutions and parameter sensitivities are studied. The model parameterizations are examined critically in light of many current uncertainties. A simple seasonal model is used to study the effects of changes in orbital elements on the temperature field. A linear stability theorem and a complete nonlinear stability analysis for the models are developed. Analytical solutions are also obtained for the linearized models driven by stochastic forcing elements. In this context the relation between natural fluctuation statistics and climate sensitivity is stressed.
Extended frequency turbofan model
NASA Technical Reports Server (NTRS)
Mason, J. R.; Park, J. W.; Jaekel, R. F.
1980-01-01
The fan model was developed using two dimensional modeling techniques to add dynamic radial coupling between the core stream and the bypass stream of the fan. When incorporated into a complete TF-30 engine simulation, the fan model greatly improved compression system frequency response to planar inlet pressure disturbances up to 100 Hz. The improved simulation also matched engine stability limits at 15 Hz, whereas the one dimensional fan model required twice the inlet pressure amplitude to stall the simulation. With verification of the two dimensional fan model, this program formulated a high frequency F-100(3) engine simulation using row by row compression system characteristics. In addition to the F-100(3) remote splitter fan, the program modified the model fan characteristics to simulate a proximate splitter version of the F-100(3) engine.
David Chassin, Pavel Etingov
2013-04-30
The LMDT software automates the process of the load composite model data preparation in the format supported by the major power system software vendors (GE and Siemens). Proper representation of the load composite model in power system dynamic analysis is very important. Software tools for power system simulation like GE PSLF and Siemens PSSE already include algorithms for the load composite modeling. However, these tools require that the input information on composite load to be provided in custom formats. Preparation of this data is time consuming and requires multiple manual operations. The LMDT software enables to automate this process. Software is designed to generate composite load model data. It uses the default load composition data, motor information, and bus information as an input. Software processes the input information and produces load composition model. Generated model can be stored in .dyd format supported by GE PSLF package or .dyr format supported by Siemens PSSE package.
NASA Astrophysics Data System (ADS)
Tan, A.; Lyatskaya, I.
2009-01-01
The interesting papers by Margaritondo (2005 Eur. J. Phys. 26 401) and by Helene and Yamashita (2006 Eur. J. Phys. 27 855) analysed the great Indian Ocean tsunami of 2004 using a simple one-dimensional canal wave model, which was appropriate for undergraduate students in physics and related fields of discipline. In this paper, two additional, easily understandable models, suitable for the same level of readership, are proposed: one, a two-dimensional model in flat space, and two, the same on a spherical surface. The models are used to study the tsunami produced by the central Kuril earthquake of November 2006. It is shown that the two alternative models, especially the latter one, give better representations of the wave amplitude, especially at far-flung locations. The latter model further demonstrates the enhancing effect on the amplitude due to the curvature of the Earth for far-reaching tsunami propagation.
Bobyn, Justin D; Little, David G; Gray, Randolph; Schindeler, Aaron
2015-04-01
Multiple techniques designed to induce scoliotic deformity have been applied across many animal species. We have undertaken a review of the literature regarding experimental models of scoliosis in animals to discuss their utility in comprehending disease aetiology and treatment. Models of scoliosis in animals can be broadly divided into quadrupedal and bipedal experiments. Quadrupedal models, in the absence of axial gravitation force, depend upon development of a mechanical asymmetry along the spine to initiate a scoliotic deformity. Bipedal models more accurately mimic human posture and consequently are subject to similar forces due to gravity, which have been long appreciated to be a contributing factor to the development of scoliosis. Many effective models of scoliosis in smaller animals have not been successfully translated to primates and humans. Though these models may not clarify the aetiology of human scoliosis, by providing a reliable and reproducible deformity in the spine they are a useful means with which to test interventions designed to correct and prevent deformity.
Probabilistic Mesomechanical Fatigue Model
NASA Technical Reports Server (NTRS)
Tryon, Robert G.
1997-01-01
A probabilistic mesomechanical fatigue life model is proposed to link the microstructural material heterogeneities to the statistical scatter in the macrostructural response. The macrostructure is modeled as an ensemble of microelements. Cracks nucleation within the microelements and grow from the microelements to final fracture. Variations of the microelement properties are defined using statistical parameters. A micromechanical slip band decohesion model is used to determine the crack nucleation life and size. A crack tip opening displacement model is used to determine the small crack growth life and size. Paris law is used to determine the long crack growth life. The models are combined in a Monte Carlo simulation to determine the statistical distribution of total fatigue life for the macrostructure. The modeled response is compared to trends in experimental observations from the literature.
Bergen, Benjamin Karl
2016-07-07
This is the PDF of a powerpoint presentation from a teleconference on Los Alamos programming models. It starts by listing their assumptions for the programming models and then details a hierarchical programming model at the System Level and Node Level. Then it details how to map this to their internal nomenclature. Finally, a list is given of what they are currently doing in this regard.
NASA Astrophysics Data System (ADS)
Arnaoudova, Kristina; Stanchev, Peter
2015-11-01
The business processes are the key asset for every organization. The design of the business process models is the foremost concern and target among an organization's functions. Business processes and their proper management are intensely dependent on the performance of software applications and technology solutions. The paper is attempt for definition of new Conceptual model of IT service provider, it could be examined as IT focused Enterprise model, part of Enterprise Architecture (EA) school.
Young, Michael F.
2015-07-01
Aerosol particles that deposit on surfaces may be subsequently resuspended by air flowing over the surface. A review of models for this liftoff process is presented and compared to available data. Based on this review, a model that agrees with existing data and is readily computed is presented for incorporation into a system level code such as MELCOR. Liftoff Model for MELCOR July 2015 4 This page is intentionally blank
Kim, Hyung Do
2006-11-28
We consider gauge messenger models in which X and Y gauge bosons and gauginos are messengers of supersymmetry breaking. In simple gauge messenger models, all the soft parameters except {mu} and B{mu} are calculated in terms of a single scale parameter MSUSY which is proportional to F / MGUT. Unique prediction on dark matter in gauge messenger models is discussed. (Based on hep-ph/0601036 and hep-ph/0607169)
Numerical Modeling Experiments
1974-09-01
presence of clouds is associated with the occurvence of condensation in the atmospheric models. Cloudiness 3t a particulat grid point is introduced -4...when saturation is predicted as a result of either large-scale moisture flux convergence or vertical convective adjustment. In most models such clouds ... cloud top, cloud thickness, and liquid-water content. In some general circulation models the local fractional convective cloud amountv tre taken
Atmospheric prediction model survey
NASA Technical Reports Server (NTRS)
Wellck, R. E.
1976-01-01
As part of the SEASAT Satellite program of NASA, a survey of representative primitive equation atmospheric prediction models that exist in the world today was written for the Jet Propulsion Laboratory. Seventeen models developed by eleven different operational and research centers throughout the world are included in the survey. The surveys are tutorial in nature describing the features of the various models in a systematic manner.
Overuse Injury Assessment Model
2005-03-01
2.1 Model Framework It is well established that training is needed to increase performance, but overtraining is detrimental and can cause injury ...DAMD17-02-C-0073 TITLE: Overuse Injury Assessment Model PRINCIPAL INVESTIGATOR: James H. Stuhmiller, Ph.D...2005 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER DAMD17-02-C-0073 Overuse Injury Assessment Model 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER
NASA Technical Reports Server (NTRS)
Hsu, H. M.
1980-01-01
A mesoscale numerical model of the Florida peninsula was formulated and applied to a dry, neutral atmosphere. The prospective use of the STAR-100 computer for the submesoscale model is discussed. The numerical model presented is tested under synoptically undisturbed conditions. Two cases, differing only in the direction of the prevailing geostrophic wind, are examined: a prevailing southwest wind and a prevailing southeast wind, both 6 m/sec at all levels initially.
NASA Technical Reports Server (NTRS)
2000-01-01
Dr. Marc Pusey (seated) and Dr. Craig Kundrot use computers to analyze x-ray maps and generate three-dimensional models of protein structures. With this information, scientists at Marshall Space Flight Center can learn how proteins are made and how they work. The computer screen depicts a proten structure as a ball-and-stick model. Other models depict the actual volume occupied by the atoms, or the ribbon-like structures that are crucial to a protein's function.
Engel, D.W.; McGrail, B.P.
1993-11-01
The Office of Civilian Radioactive Waste Management and the Power Reactor and Nuclear Fuel Development Corporation of Japan (PNC) have supported the development of the Analytical Repository Source-Term (AREST) at Pacific Northwest Laboratory. AREST is a computer model developed to evaluate radionuclide release from an underground geologic repository. The AREST code can be used to calculate/estimate the amount and rate of each radionuclide that is released from the engineered barrier system (EBS) of the repository. The EBS is the man-made or disrupted area of the repository. AREST was designed as a system-level models to simulate the behavior of the total repository by combining process-level models for the release from an individual waste package or container. AREST contains primarily analytical models for calculating the release/transport of radionuclides to the lost rock that surrounds each waste package. Analytical models were used because of the small computational overhead that allows all the input parameters to be derived from a statistical distribution. Recently, a one-dimensional numerical model was also incorporated into AREST, to allow for more detailed modeling of the transport process with arbitrary length decay chains. The next step in modeling the EBS, is to develop a model that couples the probabilistic capabilities of AREST with a more detailed process model. This model will need to look at the reactive coupling of the processes that are involved with the release process. Such coupling would include: (1) the dissolution of the waste form, (2) the geochemical modeling of the groundwater, (3) the corrosion of the container overpacking, and (4) the backfill material, just to name a few. Several of these coupled processes are already incorporated in the current version of AREST.
HOMER® Micropower Optimization Model
Lilienthal, P.
2005-01-01
NREL has developed the HOMER micropower optimization model. The model can analyze all of the available small power technologies individually and in hybrid configurations to identify least-cost solutions to energy requirements. This capability is valuable to a diverse set of energy professionals and applications. NREL has actively supported its growing user base and developed training programs around the model. These activities are helping to grow the global market for solar technologies.
Solid model design simplification
Ames, A.L.; Rivera, J.J.; Webb, A.J.; Hensinger, D.M.
1997-12-01
This paper documents an investigation of approaches to improving the quality of Pro/Engineer-created solid model data for use by downstream applications. The investigation identified a number of sources of problems caused by deficiencies in Pro/Engineer`s geometric engine, and developed prototype software capable of detecting many of these problems and guiding users towards simplified, useable models. The prototype software was tested using Sandia production solid models, and provided significant leverage in attacking the simplification problem.
Macklin, R.L.
1989-11-01
A model for gamma-ray cascade de-excitation of a nucleus derived from the Maxwellian energy distribution function but imposing energy conservation was investigated. Energy distributions and multiplicities and their averages were found over a range of nuclear temperatures and excitation energies appropriate to neutron capture. The model was compared to existing measurements for tantalum, a case where the level density was high and thus a good approximation to the model. 7 refs., 13 figs.
2014-09-04
Coastal Inlets Research Program Coastal Modeling System The work unit develops the Coastal Modeling System ( CMS ) and conducts basic research to...further understanding of sediment transport under mixed forcing from waves and currents. The CMS is a suite of coupled two- dimensional numerical...models for simulating waves, hydrodynamics, salinity and sediment transport, and morphology change. The CMS was identified by the USACE Hydraulics and
NASA Technical Reports Server (NTRS)
Levison, W. H.; Baron, S.
1984-01-01
Preliminary results in the application of a closed loop pilot/simulator model to the analysis of some simulator fidelity issues are discussed in the context of an air to air target tracking task. The closed loop model is described briefly. Then, problem simplifications that are employed to reduce computational costs are discussed. Finally, model results showing sensitivity of performance to various assumptions concerning the simulator and/or the pilot are presented.
Rat Endovascular Perforation Model
Sehba, Fatima A.
2014-01-01
Experimental animal models of aneurysmal subarachnoid hemorrhage (SAH) have provided a wealth of information on the mechanisms of brain injury. The Rat endovascular perforation model (EVP) replicates the early pathophysiology of SAH and hence is frequently used to study early brain injury following SAH. This paper presents a brief review of historical development of the EVP model, details the technique used to create SAH and considerations necessary to overcome technical challenges. PMID:25213427
Guidelines for Model Evaluation.
1979-01-01
by a decisionmaker. The full-scale evaluation of a complex model can be an expensive, time- consuming effort requiring diverse talents and skills...relative to PIES, were documented in a report to the Congress. 2/ An important side- effect of that document was that a foundation was laid for model...while for model evaluation there are no generally accepted standards or methods. Hence, GAO perceives the need to expand upon the lessons learned in
1985-09-01
Continue an reer@e side it neceary and Identify by block tmobr) )The concept of the conventional Airy/ Heiskanen isostatic model is investi- gated from...shaped type, and a depth of compensation of about 24 km. A proof of equivalence of using a standard Airy/ Heiskanen model with a larger compensation...postulated. Although in some limited areas the Pratt/Hayford system seemed to prevail, the Airy/ Heiskanen system is now generally believed to model the
NASA Technical Reports Server (NTRS)
Kerstman, Eric; Minard, Charles; Saile, Lynn; Freiere deCarvalho, Mary; Myers, Jerry; Walton, Marlei; Butler, Douglas; Iyengar, Sriram; Johnson-Throop, Kathy; Baumann, David
2010-01-01
The goals of the Integrated Medical Model (IMM) are to develop an integrated, quantified, evidence-based decision support tool useful to crew health and mission planners and to help align science, technology, and operational activities intended to optimize crew health, safety, and mission success. Presentation slides address scope and approach, beneficiaries of IMM capabilities, history, risk components, conceptual models, development steps, and the evidence base. Space adaptation syndrome is used to demonstrate the model's capabilities.
Introduction to Biological Models
2011-05-11
three steady states if NT > (dZ/αg) + (dP /µ), with a P,Z non-zero point being a stable attractor. NPZD The NPZ model assumes all dead organisms or...excreted material is immediately rem- ineralized to usable nutrient. In contrast, the NPZD model assumes that dead organisms and unassimilated...phytoplankton would contribute to a detrital pool that eventually be- 17 Figure 3: Schematic representation of NPZD model showing the fluxes of biomass and the
Global Atmospheric Aerosol Modeling
NASA Technical Reports Server (NTRS)
Hendricks, Johannes; Aquila, Valentina; Righi, Mattia
2012-01-01
Global aerosol models are used to study the distribution and properties of atmospheric aerosol particles as well as their effects on clouds, atmospheric chemistry, radiation, and climate. The present article provides an overview of the basic concepts of global atmospheric aerosol modeling and shows some examples from a global aerosol simulation. Particular emphasis is placed on the simulation of aerosol particles and their effects within global climate models.
Lightning return stroke models
NASA Technical Reports Server (NTRS)
Lin, Y. T.; Uman, M. A.; Standler, R. B.
1980-01-01
We test the two most commonly used lightning return stroke models, Bruce-Golde and transmission line, against subsequent stroke electric and magnetic field wave forms measured simultaneously at near and distant stations and show that these models are inadequate to describe the experimental data. We then propose a new return stroke model that is physically plausible and that yields good approximations to the measured two-station fields. Using the new model, we derive return stroke charge and current statistics for about 100 subsequent strokes.
NASA Technical Reports Server (NTRS)
Briggs, Hugh C.
2008-01-01
An error budget is a commonly used tool in design of complex aerospace systems. It represents system performance requirements in terms of allowable errors and flows these down through a hierarchical structure to lower assemblies and components. The requirements may simply be 'allocated' based upon heuristics or experience, or they may be designed through use of physics-based models. This paper presents a basis for developing an error budget for models of the system, as opposed to the system itself. The need for model error budgets arises when system models are a principle design agent as is increasingly more common for poorly testable high performance space systems.
Multifamily Envelope Leakage Model
Faakye, O.; Griffiths, D.
2015-05-01
The objective of the 2013 research project was to develop the model for predicting fully guarded test results (FGT), using unguarded test data and specific building features of apartment units. The model developed has a coefficient of determination R2 value of 0.53 with a root mean square error (RMSE) of 0.13. Both statistical metrics indicate that the model is relatively strong. When tested against data that was not included in the development of the model, prediction accuracy was within 19%, which is reasonable given that seasonal differences in blower door measurements can vary by as much as 25%.
NASA Technical Reports Server (NTRS)
Sapyta, Joe; Reid, Hank; Walton, Lew
1993-01-01
The topics are presented in viewgraph form and include the following: particle bed reactor (PBR) core cross section; PBR bleed cycle; fuel and moderator flow paths; PBR modeling requirements; characteristics of PBR and nuclear thermal propulsion (NTP) modeling; challenges for PBR and NTP modeling; thermal hydraulic computer codes; capabilities for PBR/reactor application; thermal/hydralic codes; limitations; physical correlations; comparison of predicted friction factor and experimental data; frit pressure drop testing; cold frit mask factor; decay heat flow rate; startup transient simulation; and philosophy of systems modeling.
Simulation modeling of carcinogenesis.
Ellwein, L B; Cohen, S M
1992-03-01
A discrete-time simulation model of carcinogenesis is described mathematically using recursive relationships between time-varying model variables. The dynamics of cellular behavior is represented within a biological framework that encompasses two irreversible and heritable genetic changes. Empirical data and biological supposition dealing with both control and experimental animal groups are used together to establish values for model input variables. The estimation of these variables is integral to the simulation process as described in step-by-step detail. Hepatocarcinogenesis in male F344 rats provides the basis for seven modeling scenarios which illustrate the complexity of relationships among cell proliferation, genotoxicity, and tumor risk.
Brown-VanHoozer, S. A.
1999-06-02
Conscious awareness of our environment is based on a feedback loop comprised of sensory input transmitted to the central nervous system leading to construction of our ''model of the world,'' (Lewis et al, 1982). We then assimilate the neurological model at the unconscious level into information we can later consciously consider useful in identifying belief systems and behaviors for designing diverse systems. Thus, we can avoid potential problems based on our open-to-error perceived reality of the world. By understanding how our model of reality is organized, we allow ourselves to transcend content and develop insight into how effective choices and belief systems are generated through sensory derived processes. These are the processes which provide the designer the ability to meta model (build a model of a model) the user; consequently, matching the mental model of the user with that of the designer's and, coincidentally, forming rapport between the two participants. The information shared between the participants is neither assumed nor generalized, it is closer to equivocal; thus minimizing error through a sharing of each other's model of reality. How to identify individual mental mechanisms or processes, how to organize the individual strategies of these mechanisms into useful patterns, and to formulate these into models for success and knowledge based outcomes is the subject of the discussion that follows.
NASA Technical Reports Server (NTRS)
Wallerstein, D. V.; Lahey, R. S.; Haggenmacher, G. W.
1977-01-01
Many of the practical aspects and problems of ensuring the integrity of a structural model are discussed, as well as the steps which have been taken in the NASTRAN system to assure that these checks can be routinely performed. Model integrity as used applies not only to the structural model but also to the loads applied to the model. Emphasis is also placed on the fact that when dealing with substructure analysis, all of the checking procedures discussed should be applied at the lowest level of substructure prior to any coupling.
NASA Technical Reports Server (NTRS)
Briggs, Hugh C.
2008-01-01
An error budget is a commonly used tool in design of complex aerospace systems. It represents system performance requirements in terms of allowable errors and flows these down through a hierarchical structure to lower assemblies and components. The requirements may simply be 'allocated' based upon heuristics or experience, or they may be designed through use of physics-based models. This paper presents a basis for developing an error budget for models of the system, as opposed to the system itself. The need for model error budgets arises when system models are a principle design agent as is increasingly more common for poorly testable high performance space systems.
Gillespie, Ronald J; Robinson, Edward A
2005-05-01
Although the structure of almost any molecule can now be obtained by ab initio calculations chemists still look for simple answers to the question "What determines the geometry of a given molecule?" For this purpose they make use of various models such as the VSEPR model and qualitative quantum mechanical models such as those based on the valence bond theory. The present state of such models, and the support for them provided by recently developed methods for analyzing calculated electron densities, are reviewed and discussed in this tutorial review.
NASA Astrophysics Data System (ADS)
Wiegelmann, Thomas; Petrie, Gordon J. D.; Riley, Pete
2017-09-01
Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes more restrictive assumptions by neglecting physical effects. The magnetohydrostatic approach neglects time-dependent phenomena and plasma flows, the force-free approach neglects additionally the gradient of the plasma pressure and the gravity force. This leads to the assumption of a vanishing Lorentz force and electric currents are parallel (or anti-parallel) to the magnetic field lines. Finally, the potential field approach neglects also these currents. We outline the main assumptions, benefits and limitations of these models both from a theoretical (how realistic are the models?) and a practical viewpoint (which computer resources to we need?). Finally we address the important problem of noisy and inconsistent photospheric boundary conditions and the possibility of using chromospheric and coronal observations to improve the models.
NASA Astrophysics Data System (ADS)
Schmidt-Eisenlohr, F.; Puñal, O.; Klagges, K.; Kirsche, M.
Apart from the general issue of modeling the channel, the PHY and the MAC of wireless networks, there are specific modeling assumptions that are considered for different systems. In this chapter we consider three specific wireless standards and highlight modeling options for them. These are IEEE 802.11 (as example for wireless local area networks), IEEE 802.16 (as example for wireless metropolitan networks) and IEEE 802.15 (as example for body area networks). Each section on these three systems discusses also at the end a set of model implementations that are available today.
Photovoltaic array performance model.
Kratochvil, Jay A.; Boyson, William Earl; King, David L.
2004-08-01
This document summarizes the equations and applications associated with the photovoltaic array performance model developed at Sandia National Laboratories over the last twelve years. Electrical, thermal, and optical characteristics for photovoltaic modules are included in the model, and the model is designed to use hourly solar resource and meteorological data. The versatility and accuracy of the model has been validated for flat-plate modules (all technologies) and for concentrator modules, as well as for large arrays of modules. Applications include system design and sizing, 'translation' of field performance measurements to standard reporting conditions, system performance optimization, and real-time comparison of measured versus expected system performance.
Railway switch transport model.
Horvat, Martin; Prosen, Tomaž; Benenti, Giuliano; Casati, Giulio
2012-11-01
We propose a simple model of coupled heat and particle transport based on zero-dimensional classical deterministic dynamics, which is reminiscent of a railway switch whose action is a function only of the particle's energy. It is shown that already in the minimal three-terminal model, where the second terminal is considered as a probe with zero net particle and heat currents, one can find extremely asymmetric Onsager matrices as a consequence of time-reversal symmetry breaking of the model. This minimalistic transport model provides a better understanding of thermoelectric heat engines in the presence of time-reversal symmetry breaking.
NASA Technical Reports Server (NTRS)
Wallerstein, D. V.; Lahey, R. S.; Haggenmacher, G. W.
1977-01-01
Many of the practical aspects and problems of ensuring the integrity of a structural model are discussed, as well as the steps which have been taken in the NASTRAN system to assure that these checks can be routinely performed. Model integrity as used applies not only to the structural model but also to the loads applied to the model. Emphasis is also placed on the fact that when dealing with substructure analysis, all of the checking procedures discussed should be applied at the lowest level of substructure prior to any coupling.
Outdoor ground impedance models.
Attenborough, Keith; Bashir, Imran; Taherzadeh, Shahram
2011-05-01
Many models for the acoustical properties of rigid-porous media require knowledge of parameter values that are not available for outdoor ground surfaces. The relationship used between tortuosity and porosity for stacked spheres results in five characteristic impedance models that require not more than two adjustable parameters. These models and hard-backed-layer versions are considered further through numerical fitting of 42 short range level difference spectra measured over various ground surfaces. For all but eight sites, slit-pore, phenomenological and variable porosity models yield lower fitting errors than those given by the widely used one-parameter semi-empirical model. Data for 12 of 26 grassland sites and for three beech wood sites are fitted better by hard-backed-layer models. Parameter values obtained by fitting slit-pore and phenomenological models to data for relatively low flow resistivity grounds, such as forest floors, porous asphalt, and gravel, are consistent with values that have been obtained non-acoustically. Three impedance models yield reasonable fits to a narrow band excess attenuation spectrum measured at short range over railway ballast but, if extended reaction is taken into account, the hard-backed-layer version of the slit-pore model gives the most reasonable parameter values.
Computer Modeling and Simulation
Pronskikh, V. S.
2014-05-09
Verification and validation of computer codes and models used in simulation are two aspects of the scientific practice of high importance and have recently been discussed by philosophers of science. While verification is predominantly associated with the correctness of the way a model is represented by a computer code or algorithm, validation more often refers to model’s relation to the real world and its intended use. It has been argued that because complex simulations are generally not transparent to a practitioner, the Duhem problem can arise for verification and validation due to their entanglement; such an entanglement makes it impossible to distinguish whether a coding error or model’s general inadequacy to its target should be blamed in the case of the model failure. I argue that in order to disentangle verification and validation, a clear distinction between computer modeling (construction of mathematical computer models of elementary processes) and simulation (construction of models of composite objects and processes by means of numerical experimenting with them) needs to be made. Holding on to that distinction, I propose to relate verification (based on theoretical strategies such as inferences) to modeling and validation, which shares the common epistemology with experimentation, to simulation. To explain reasons of their intermittent entanglement I propose a weberian ideal-typical model of modeling and simulation as roles in practice. I suggest an approach to alleviate the Duhem problem for verification and validation generally applicable in practice and based on differences in epistemic strategies and scopes
NASA Technical Reports Server (NTRS)
Levy, R.; Mcginness, H.
1976-01-01
Investigations were performed to predict the power available from the wind at the Goldstone, California, antenna site complex. The background for power prediction was derived from a statistical evaluation of available wind speed data records at this location and at nearby locations similarly situated within the Mojave desert. In addition to a model for power prediction over relatively long periods of time, an interim simulation model that produces sample wind speeds is described. The interim model furnishes uncorrelated sample speeds at hourly intervals that reproduce the statistical wind distribution at Goldstone. A stochastic simulation model to provide speed samples representative of both the statistical speed distributions and correlations is also discussed.
Modelling urban snowmelt runoff
NASA Astrophysics Data System (ADS)
Valeo, C.; Ho, C. L. I.
2004-12-01
Few investigations have been made into modelling snowmelt in urban areas; hence, current urban snowmelt routines have adopted parameters and approaches intended for rural areas that are not appropriate in an urban environment. This paper examines problems with current urban snowmelt models and proposes a model that uses parameters developed from field studies focusing exclusively on urban snow. The Urban Snow Model (USM) uses an energy balance scheme at an hourly time step, changes in urban snow albedo, and incorporates eight different types of redistributed snow cover. USM is tested against observed flow data from a small residential community located in Calgary, Alberta. The degree-day method for snowmelt, the SWMM model, and a modified version of USM that incorporates a partial energy budget scheme relying only on net radiation, are also tested against the observed flow data. The full energy budget version of USM outperformed all other models in terms of time to peak, peak flowrate and model efficiency; however, the modified version of USM fared quite well and is recommended when a lack of data exists. The degree-day method and the SWMM models fared poorly and were unable to simulate peak flowrates in most cases. The tests also demonstrated the need to distribute snow into appropriate snow covers in order to simulate peak flowrates accurately and provide good model efficiency.
Evolutionary financial market models
NASA Astrophysics Data System (ADS)
Ponzi, A.; Aizawa, Y.
2000-12-01
We study computer simulations of two financial market models, the second a simplified model of the first. The first is a model of the self-organized formation and breakup of crowds of traders, motivated by the dynamics of competitive evolving systems which shows interesting self-organized critical (SOC)-type behaviour without any fine tuning of control parameters. This SOC-type avalanching and stasis appear as realistic volatility clustering in the price returns time series. The market becomes highly ordered at ‘crashes’ but gradually loses this order through randomization during the intervening stasis periods. The second model is a model of stocks interacting through a competitive evolutionary dynamic in a common stock exchange. This model shows a self-organized ‘market-confidence’. When this is high the market is stable but when it gets low the market may become highly volatile. Volatile bursts rapidly increase the market confidence again. This model shows a phase transition as temperature parameter is varied. The price returns time series in the transition region is very realistic power-law truncated Levy distribution with clustered volatility and volatility superdiffusion. This model also shows generally positive stock cross-correlations as is observed in real markets. This model may shed some light on why such phenomena are observed.
Convergence of a Moran model to Eigen's quasispecies model.
Dalmau, Joseba
2017-03-02
We prove that a Moran model converges in probability to Eigen's quasispecies model in the infinite population limit. We show further that the invariant probability measure of the Moran model converges to the unique stationary solution of Eigen's quasispecies model.
Radiation Environment Modeling for Spacecraft Design: New Model Developments
NASA Technical Reports Server (NTRS)
Barth, Janet; Xapsos, Mike; Lauenstein, Jean-Marie; Ladbury, Ray
2006-01-01
A viewgraph presentation on various new space radiation environment models for spacecraft design is described. The topics include: 1) The Space Radiatio Environment; 2) Effects of Space Environments on Systems; 3) Space Radiatio Environment Model Use During Space Mission Development and Operations; 4) Space Radiation Hazards for Humans; 5) "Standard" Space Radiation Environment Models; 6) Concerns about Standard Models; 7) Inadequacies of Current Models; 8) Development of New Models; 9) New Model Developments: Proton Belt Models; 10) Coverage of New Proton Models; 11) Comparison of TPM-1, PSB97, AP-8; 12) New Model Developments: Electron Belt Models; 13) Coverage of New Electron Models; 14) Comparison of "Worst Case" POLE, CRESELE, and FLUMIC Models with the AE-8 Model; 15) New Model Developments: Galactic Cosmic Ray Model; 16) Comparison of NASA, MSU, CIT Models with ACE Instrument Data; 17) New Model Developmemts: Solar Proton Model; 18) Comparison of ESP, JPL91, KIng/Stassinopoulos, and PSYCHIC Models; 19) New Model Developments: Solar Heavy Ion Model; 20) Comparison of CREME96 to CREDO Measurements During 2000 and 2002; 21) PSYCHIC Heavy ion Model; 22) Model Standardization; 23) Working Group Meeting on New Standard Radiation Belt and Space Plasma Models; and 24) Summary.
Anisotropic exchange-interaction model: From the Potts model to the exchange-interaction model
NASA Astrophysics Data System (ADS)
King, T. C.; Chen, H. H.
1995-04-01
A spin model called the anisotropic exchange-interaction model is proposed. The Potts model, the exchange-interaction model, and the spin-1/2 anisotropic Heisenberg model are special cases of the proposed model. Thermodynamic properties of the model on the bcc and the fcc lattices are determined by the constant-coupling approximation.
NASA Astrophysics Data System (ADS)
Bahr, Benjamin; Hellmann, Frank; Kamiński, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy
2011-05-01
The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as our main tool. A set of moves we define in the set of the operator spin foams (among other operations) allows us to split the faces and the edges of the foams. We assign to each operator spin foam a contracted operator, by using the contractions at the vertices and suitably adjusted face amplitudes. The emergence of the face amplitudes is the consequence of assuming the invariance of the contracted operator with respect to the moves. Next, we define spin foam models and consider the class of models assumed to be symmetric with respect to the moves we have introduced, and assuming their partition functions (state sums) are defined by the contracted operators. Briefly speaking, those operator spin foam models are invariant with respect to the cellular decomposition, and are sensitive only to the topology and colouring of the foam. Imposing an extra symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with assumed invariance with respect to the edge splitting move, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on a spin(4) BF spin foam model is exactly the way we tend to view 4D quantum gravity, starting with the BC model and continuing with the Engle-Pereira-Rovelli-Livine (EPRL) or Freidel-Krasnov (FK) models. That makes our framework directly applicable to those models. Specifically, our operator spin foam framework can be translated into the language of spin foams and partition functions. Among our natural spin foam models there are the BF spin foam model, the BC model, and a model corresponding to the EPRL intertwiners. Our operator spin foam framework can also be used for more general spin
Ahmed E. Hassan
2006-01-24
Models have an inherent uncertainty. The difficulty in fully characterizing the subsurface environment makes uncertainty an integral component of groundwater flow and transport models, which dictates the need for continuous monitoring and improvement. Building and sustaining confidence in closure decisions and monitoring networks based on models of subsurface conditions require developing confidence in the models through an iterative process. The definition of model validation is postulated as a confidence building and long-term iterative process (Hassan, 2004a). Model validation should be viewed as a process not an end result. Following Hassan (2004b), an approach is proposed for the validation process of stochastic groundwater models. The approach is briefly summarized herein and detailed analyses of acceptance criteria for stochastic realizations and of using validation data to reduce input parameter uncertainty are presented and applied to two case studies. During the validation process for stochastic models, a question arises as to the sufficiency of the number of acceptable model realizations (in terms of conformity with validation data). Using a hierarchical approach to make this determination is proposed. This approach is based on computing five measures or metrics and following a decision tree to determine if a sufficient number of realizations attain satisfactory scores regarding how they represent the field data used for calibration (old) and used for validation (new). The first two of these measures are applied to hypothetical scenarios using the first case study and assuming field data consistent with the model or significantly different from the model results. In both cases it is shown how the two measures would lead to the appropriate decision about the model performance. Standard statistical tests are used to evaluate these measures with the results indicating they are appropriate measures for evaluating model realizations. The use of validation
Biosphere Process Model Report
J. Schmitt
2000-05-25
To evaluate the postclosure performance of a potential monitored geologic repository at Yucca Mountain, a Total System Performance Assessment (TSPA) will be conducted. Nine Process Model Reports (PMRs), including this document, are being developed to summarize the technical basis for each of the process models supporting the TSPA model. These reports cover the following areas: (1) Integrated Site Model; (2) Unsaturated Zone Flow and Transport; (3) Near Field Environment; (4) Engineered Barrier System Degradation, Flow, and Transport; (5) Waste Package Degradation; (6) Waste Form Degradation; (7) Saturated Zone Flow and Transport; (8) Biosphere; and (9) Disruptive Events. Analysis/Model Reports (AMRs) contain the more detailed technical information used to support TSPA and the PMRs. The AMRs consists of data, analyses, models, software, and supporting documentation that will be used to defend the applicability of each process model for evaluating the postclosure performance of the potential Yucca Mountain repository system. This documentation will ensure the traceability of information from its source through its ultimate use in the TSPA-Site Recommendation (SR) and in the National Environmental Policy Act (NEPA) analysis processes. The objective of the Biosphere PMR is to summarize (1) the development of the biosphere model, and (2) the Biosphere Dose Conversion Factors (BDCFs) developed for use in TSPA. The Biosphere PMR does not present or summarize estimates of potential radiation doses to human receptors. Dose calculations are performed as part of TSPA and will be presented in the TSPA documentation. The biosphere model is a component of the process to evaluate postclosure repository performance and regulatory compliance for a potential monitored geologic repository at Yucca Mountain, Nevada. The biosphere model describes those exposure pathways in the biosphere by which radionuclides released from a potential repository could reach a human receptor
Magretta, Joan
2002-05-01
"Business model" was one of the great buzz-words of the Internet boom. A company didn't need a strategy, a special competence, or even any customers--all it needed was a Web-based business model that promised wild profits in some distant, ill-defined future. Many people--investors, entrepreneurs, and executives alike--fell for the fantasy and got burned. And as the inevitable counterreaction played out, the concept of the business model fell out of fashion nearly as quickly as the .com appendage itself. That's a shame. As Joan Magretta explains, a good business model remains essential to every successful organization, whether it's a new venture or an established player. To help managers apply the concept successfully, she defines what a business model is and how it complements a smart competitive strategy. Business models are, at heart, stories that explain how enterprises work. Like a good story, a robust business model contains precisely delineated characters, plausible motivations, and a plot that turns on an insight about value. It answers certain questions: Who is the customer? How do we make money? What underlying economic logic explains how we can deliver value to customers at an appropriate cost? Every viable organization is built on a sound business model, but a business model isn't a strategy, even though many people use the terms interchangeably. Business models describe, as a system, how the pieces of a business fit together. But they don't factor in one critical dimension of performance: competition. That's the job of strategy. Illustrated with examples from companies like American Express, EuroDisney, WalMart, and Dell Computer, this article clarifies the concepts of business models and strategy, which are fundamental to every company's performance.
Comparing root architectural models
NASA Astrophysics Data System (ADS)
Schnepf, Andrea; Javaux, Mathieu; Vanderborght, Jan
2017-04-01
Plant roots play an important role in several soil processes (Gregory 2006). Root architecture development determines the sites in soil where roots provide input of carbon and energy and take up water and solutes. However, root architecture is difficult to determine experimentally when grown in opaque soil. Thus, root architectural models have been widely used and been further developed into functional-structural models that are able to simulate the fate of water and solutes in the soil-root system (Dunbabin et al. 2013). Still, a systematic comparison of the different root architectural models is missing. In this work, we focus on discrete root architecture models where roots are described by connected line segments. These models differ (a) in their model concepts, such as the description of distance between branches based on a prescribed distance (inter-nodal distance) or based on a prescribed time interval. Furthermore, these models differ (b) in the implementation of the same concept, such as the time step size, the spatial discretization along the root axes or the way stochasticity of parameters such as root growth direction, growth rate, branch spacing, branching angles are treated. Based on the example of two such different root models, the root growth module of R-SWMS and RootBox, we show the impact of these differences on simulated root architecture and aggregated information computed from this detailed simulation results, taking into account the stochastic nature of those models. References Dunbabin, V.M., Postma, J.A., Schnepf, A., Pagès, L., Javaux, M., Wu, L., Leitner, D., Chen, Y.L., Rengel, Z., Diggle, A.J. Modelling root-soil interactions using three-dimensional models of root growth, architecture and function (2013) Plant and Soil, 372 (1-2), pp. 93 - 124. Gregory (2006) Roots, rhizosphere and soil: the route to a better understanding of soil science? European Journal of Soil Science 57: 2-12.
Spiral model pilot project information model
NASA Technical Reports Server (NTRS)
1991-01-01
The objective was an evaluation of the Spiral Model (SM) development approach to allow NASA Marshall to develop an experience base of that software management methodology. A discussion is presented of the Information Model (IM) that was used as part of the SM methodology. A key concept of the SM is the establishment of an IM to be used by management to track the progress of a project. The IM is the set of metrics that is to be measured and reported throughout the life of the project. These metrics measure both the product and the process to ensure the quality of the final delivery item and to ensure the project met programmatic guidelines. The beauty of the SM, along with the IM, is the ability to measure not only the correctness of the specification and implementation of the requirements but to also obtain a measure of customer satisfaction.
Bayesian Data-Model Fit Assessment for Structural Equation Modeling
ERIC Educational Resources Information Center
Levy, Roy
2011-01-01
Bayesian approaches to modeling are receiving an increasing amount of attention in the areas of model construction and estimation in factor analysis, structural equation modeling (SEM), and related latent variable models. However, model diagnostics and model criticism remain relatively understudied aspects of Bayesian SEM. This article describes…
Bayesian Data-Model Fit Assessment for Structural Equation Modeling
ERIC Educational Resources Information Center
Levy, Roy
2011-01-01
Bayesian approaches to modeling are receiving an increasing amount of attention in the areas of model construction and estimation in factor analysis, structural equation modeling (SEM), and related latent variable models. However, model diagnostics and model criticism remain relatively understudied aspects of Bayesian SEM. This article describes…
NASA Astrophysics Data System (ADS)
Billings, S. A.
1988-03-01
Time and frequency domain identification methods for nonlinear systems are reviewed. Parametric methods, prediction error methods, structure detection, model validation, and experiment design are discussed. Identification of a liquid level system, a heat exchanger, and a turbocharge automotive diesel engine are illustrated. Rational models are introduced. Spectral analysis for nonlinear systems is treated. Recursive estimation is mentioned.
ERIC Educational Resources Information Center
Flannery, Maura C.
1997-01-01
Addresses the most popular models currently being chosen for biological research and the reasons behind those choices. Among the current favorites are zebra fish, fruit flies, mice, monkeys, and yeast. Concludes with a brief examination of the ethical issues involved, and why some animals may need to be replaced in research with model systems.…
This lecture will present AQUATOX, an aquatic ecosystem simulation model developed by Dr. Dick Park and supported by the U.S. EPA. The AQUATOX model predicts the fate of various pollutants, such as nutrients and organic chemicals, and their effects on the ecosystem, including fi...
USDA-ARS?s Scientific Manuscript database
Models of wind erosion are used to investigate fundamental processes and guide resource management. Many models are similar in that - temporal variables control soil wind erodibility; erosion begins when friction velocity exceeds a threshold; and transport capacity for saltation/creep is proportion...
Examples of Mathematical Modeling
Johnston, Matthew D.; Edwards, Carina M.; Bodmer, Walter F.; Maini, Philip K.; Chapman, S. Jonathan
2008-01-01
Mathematical modeling is being increasingly recognized within the biomedical sciences as an important tool that can aid the understanding of biological systems. The heavily regulated cell renewal cycle in the colonic crypt provides a good example of how modeling can be used to find out key features of the system kinetics, and help to explain both the breakdown of homeostasis and the initiation of tumorigenesis. We use the cell population model by Johnston et al.5 to illustrate the power of mathematical modeling by considering two key questions about the cell population dynamics in the colonic crypt. We ask: how can a model describe both homeostasis and unregulated growth in tumorigenesis; and to which parameters in the system is the model most sensitive? In order to address these questions, we discuss what type of modeling approach is most appropriate in the crypt. We use the model to argue why tumorigenesis is observed to occur in stages with long lag phases between periods of rapid growth, and we identify the key parameters. PMID:17873520
Structural Equation Model Trees
ERIC Educational Resources Information Center
Brandmaier, Andreas M.; von Oertzen, Timo; McArdle, John J.; Lindenberger, Ulman
2013-01-01
In the behavioral and social sciences, structural equation models (SEMs) have become widely accepted as a modeling tool for the relation between latent and observed variables. SEMs can be seen as a unification of several multivariate analysis techniques. SEM Trees combine the strengths of SEMs and the decision tree paradigm by building tree…
ERIC Educational Resources Information Center
Flannery, Maura C.
1997-01-01
Addresses the most popular models currently being chosen for biological research and the reasons behind those choices. Among the current favorites are zebra fish, fruit flies, mice, monkeys, and yeast. Concludes with a brief examination of the ethical issues involved, and why some animals may need to be replaced in research with model systems.…
NASA Technical Reports Server (NTRS)
Sellers, Piers
2012-01-01
Model results will be reviewed to assess different methods for bounding the terrestrial role in the global carbon cycle. It is proposed that a series of climate model runs could be scoped that would tighten the limits on the "missing sink" of terrestrial carbon and could also direct future satellite image analyses to search for its geographical location and understand its seasonal dynamics.
Computational Modeling of Tires
NASA Technical Reports Server (NTRS)
Noor, Ahmed K. (Compiler); Tanner, John A. (Compiler)
1995-01-01
This document contains presentations and discussions from the joint UVA/NASA Workshop on Computational Modeling of Tires. The workshop attendees represented NASA, the Army and Air force, tire companies, commercial software developers, and academia. The workshop objectives were to assess the state of technology in the computational modeling of tires and to provide guidelines for future research.
SWMM is a model for urban hydrology. It has a long history and is relied upon by professional engineers in the US and around the world. SWMM provides both gray and green Infrastructure modeling capabilities. As such, it is a convenient tool for understanding the tradeoff between ...
ERIC Educational Resources Information Center
Wang, Wen-Chung; Wilson, Mark
2005-01-01
The Rasch testlet model for both dichotomous and polytomous items in testlet-based tests is proposed. It can be viewed as a special case of the multidimensional random coefficients multinomial logit model (MRCMLM). Therefore, the estimation procedures for the MRCMLM can be directly applied. Simulations were conducted to examine parameter recovery…
Raby, Stuart
2008-11-23
In this talk I discuss the evolution of SUSY GUT model building as I see it. Starting with 4 dimensional model building, I then consider orbifold GUTs in 5 dimensions and finally orbifold GUTs embedded into the E{sub 8}xE{sub 8} heterotic string.
SWMM is a model for urban hydrology. It has a long history and is relied upon by professional engineers in the US and around the world. SWMM provides both gray and green Infrastructure modeling capabilities. As such, it is a convenient tool for understanding the tradeoff between ...
Introduction to Population Modeling.
ERIC Educational Resources Information Center
Frauenthal, James C.
The focus is on the formulation and solution of mathematical models with the idea of a population employed mainly as a pedogogical tool. If the biological setting is stripped away, the material can be interpreted as topics or the qualitative behavior of differential and difference equations. The first group of models investigate the dynamics of a…
Acid rain: Microphysical model
NASA Technical Reports Server (NTRS)
Dingle, A. N.
1980-01-01
A microphysical model was used to simulate the case of a ground cloud without dilution by entrainment and without precipitation. The numerical integration techniques of the model are presented. The droplet size spectra versus time and the droplet molalities for each value of time are discussed.
ERIC Educational Resources Information Center
Journal of Science and Mathematics Education in Southeast Asia, 1981
1981-01-01
Instructions (with diagrams and parts list) are provided for constructing an eye model with a pliable lens made from a plastic bottle which can vary its convexity to accommodate changing positions of an object being viewed. Also discusses concepts which the model can assist in developing. (Author/SK)
Cloud Scene Simulation Modeling
1991-11-20
PL-M-91-2295 AD-A256 689 CLOUD SCENE SIMULATION MODELING M.E. Cianciolo J.S. Hersh M.R Ramos-Johnson TASC 55 Walkers Brook Drive Reading...1991 Scientific No. 1 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Cloud Scene Simulation Modeling PE 62101F PR 6670 TA 09 WU BE 6. AUTHOR(S) Contract
ERIC Educational Resources Information Center
Buggey, Tom; Ogle, Lindsey
2012-01-01
Video self-modeling (VSM) first appeared on the psychology and education stage in the early 1970s. The practical applications of VSM were limited by lack of access to tools for editing video, which is necessary for almost all self-modeling videos. Thus, VSM remained in the research domain until the advent of camcorders and VCR/DVD players and,…
ERIC Educational Resources Information Center
Zwaan, Rolf A.; Madden, Carol J.
2004-01-01
The authors examined how situation models are updated during text comprehension. If comprehenders keep track of the evolving situation, they should update their models such that the most current information, the here and now, is more available than outdated information. Contrary to this updating hypothesis, E. J. O'Brien, M. L. Rizzella, J. E.…
ERIC Educational Resources Information Center
Fischbein, Efraim
2001-01-01
Analyses several examples of tacit influences exerted by mental models on the interpretation of various mathematical concepts in the domain of actual infinity. Specifically addresses the unconscious effect of the figural-pictorial models of statements related to the infinite sets of geometrical points related to the concepts of function and…
ERIC Educational Resources Information Center
Ivie, Stanley D.
2007-01-01
Humanity delights in spinning conceptual models of the world. These models, in turn, mirror their respective root metaphors. Three root metaphors--spiritual, organic, and mechanical--have dominated western thought. The spiritual metaphor runs from Plato, through Hegel, and connects with Montessori. The organic metaphor extends from Aristotle,…
NASA Astrophysics Data System (ADS)
Perelson, Alan; Conway, Jessica; Cao, Youfang
A large effort is being made to find a means to cure HIV infection. I will present a dynamical model of post-treatment control (PTC) or ``functional cure'' of HIV-infection. Some patients treated with suppressive antiviral therapy have been taken off of therapy and then spontaneously control HIV infection such that the amount of virus in the circulation is maintained undetectable by clinical assays for years. The model explains PTC occurring in some patients by having a parameter regime in which the model exhibits bistability, with both a low and high steady state viral load being stable. The model makes a number of predictions about how to attain the low PTC steady state. Bistability in this model depends upon the immune response becoming exhausted when over stimulated. I will also present a generalization of the model in which immunotherapy can be used to reverse immune exhaustion and compare model predictions with experiments in SIV infected macaques given immunotherapy and then taken off of antiretroviral therapy. Lastly, if time permits, I will discuss one of the hurdles to true HIV eradication, latently infected cells, and present clinical trial data and a new model addressing pharmacological means of flushing out the latent reservoir. Supported by NIH Grants AI028433 and OD011095.
Animal models for osteoporosis
NASA Technical Reports Server (NTRS)
Turner, R. T.; Maran, A.; Lotinun, S.; Hefferan, T.; Evans, G. L.; Zhang, M.; Sibonga, J. D.
2001-01-01
Animal models will continue to be important tools in the quest to understand the contribution of specific genes to establishment of peak bone mass and optimal bone architecture, as well as the genetic basis for a predisposition toward accelerated bone loss in the presence of co-morbidity factors such as estrogen deficiency. Existing animal models will continue to be useful for modeling changes in bone metabolism and architecture induced by well-defined local and systemic factors. However, there is a critical unfulfilled need to develop and validate better animal models to allow fruitful investigation of the interaction of the multitude of factors which precipitate senile osteoporosis. Well characterized and validated animal models that can be recommended for investigation of the etiology, prevention and treatment of several forms of osteoporosis have been listed in Table 1. Also listed are models which are provisionally recommended. These latter models have potential but are inadequately characterized, deviate significantly from the human response, require careful choice of strain or age, or are not practical for most investigators to adopt. It cannot be stressed strongly enough that the enormous potential of laboratory animals as models for osteoporosis can only be realized if great care is taken in the choice of an appropriate species, age, experimental design, and measurements. Poor choices will results in misinterpretation of results which ultimately can bring harm to patients who suffer from osteoporosis by delaying advancement of knowledge.
Generalized simplicial chiral models
NASA Astrophysics Data System (ADS)
Alimohammadi, Masoud
2000-02-01
Using the auxiliary field representation of the simplicial chiral models on a ( d-1)-dimensional simplex, the simplicial chiral models are generalized through replacing the term Tr (AA †) in the Lagrangian of these models by an arbitrary class function of AA †; V(AA †) . This is the same method used in defining the generalized two-dimensional Yang-Mills theories (gYM 2) from ordinary YM 2. We call these models the "generalized simplicial chiral models". Using the results of the one-link integral over a U( N) matrix, the large- N saddle-point equations for eigenvalue density function ρ( z) in the weak ( β> βc) and strong ( β< βc) regions are computed. In d=2, where the model is in some sense related to the gYM 2 theory, the saddle-point equations are solved for ρ( z) in the two regions, and the explicit value of critical point βc is calculated for V(B)= Tr B n(B=AA †) . For V(B)= Tr B 2, Tr B 3, and Tr B4, the critical behaviour of the model at d=2 is studied, and by calculating the internal energy, it is shown that these models have a third order phase transition.
ERIC Educational Resources Information Center
Dworkin, Nancy; Dworkin, Yehoash
The 1978 Summer Reading Institute, which served 58 Washington, D.C., elementary school children, is described in this paper. Major characteristics of the program model are first identified, along with elements that were added to the model in the preplanning stage. Numerous aspects of the program are then described, including the make-up of the…
ERIC Educational Resources Information Center
Watt, James H., Jr.
Pointing out that linear causal models can organize the interrelationships of a large number of variables, this paper contends that such models are particularly useful to mass communication research, which must by necessity deal with complex systems of variables. The paper first outlines briefly the philosophical requirements for establishing a…
Jacob J. Jacobson; Gretchen Matthern
2007-04-01
System Dynamics is a computer-aided approach to evaluating the interrelationships of different components and activities within complex systems. Recently, System Dynamics models have been developed in areas such as policy design, biological and medical modeling, energy and the environmental analysis, and in various other areas in the natural and social sciences. The real power of System Dynamic modeling is gaining insights into total system behavior as time, and system parameters are adjusted and the effects are visualized in real time. System Dynamic models allow decision makers and stakeholders to explore long-term behavior and performance of complex systems, especially in the context of dynamic processes and changing scenarios without having to wait decades to obtain field data or risk failure if a poor management or design approach is used. The Idaho National Laboratory recently has been developing a System Dynamic model of the US Nuclear Fuel Cycle. The model is intended to be used to identify and understand interactions throughout the entire nuclear fuel cycle and suggest sustainable development strategies. This paper describes the basic framework of the current model and presents examples of useful insights gained from the model thus far with respect to sustainable development of nuclear power.
ERIC Educational Resources Information Center
Eichinger, John
2005-01-01
Models are crucial to science teaching and learning, yet they can create unforeseen and overlooked challenges for students and teachers. For example, consider the time-tested clay volcano that relies on a vinegar and-baking-soda mixture for its "eruption." Based on a classroom demonstration of that geologic model, elementary students may interpret…
Barchet, W.R. ); Dennis, R.L. ); Seilkop, S.K. ); Banic, C.M.; Davies, D.; Hoff, R.M.; Macdonald, A.M.; Mickle, R.E.; Padro, J.; Puckett, K. ); Byun, D.; McHenry, J.N.
1991-12-01
The binational Eulerian Model Evaluation Field Study (EMEFS) consisted of several coordinated data gathering and model evaluation activities. In the EMEFS, data were collected by five air and precipitation monitoring networks between June 1988 and June 1990. Model evaluation is continuing. This interim report summarizes the progress made in the evaluation of the Regional Acid Deposition Model (RADM) and the Acid Deposition and Oxidant Model (ADOM) through the December 1990 completion of a State of Science and Technology report on model evaluation for the National Acid Precipitation Assessment Program (NAPAP). Because various assessment applications of RADM had to be evaluated for NAPAP, the report emphasizes the RADM component of the evaluation. A protocol for the evaluation was developed by the model evaluation team and defined the observed and predicted values to be used and the methods by which the observed and predicted values were to be compared. Scatter plots and time series of predicted and observed values were used to present the comparisons graphically. Difference statistics and correlations were used to quantify model performance. 64 refs., 34 figs., 6 tabs.
ERIC Educational Resources Information Center
Gabel, Dorothy; And Others
1992-01-01
Chemistry can be described on three levels: sensory, molecular, and symbolic. Proposes a particle approach to teaching chemistry that uses magnets to aid students construct molecular models and solve particle problems. Includes examples of Johnstone's model of chemistry phenomena, a problem worksheet, and a student concept mastery sheet. (MDH)
Teaching Mathematical Modelling.
ERIC Educational Resources Information Center
Jones, Mark S.
1997-01-01
Outlines a course at the University of Glamorgan in the United Kingdom in which a computer algebra system (CAS) teaches mathematical modeling. The format is based on continual assessment of group and individual work stating the problem, a feature list, and formulation of the models. No additional mathematical word processing package is necessary.…
Computer Model Documentation Guide.
ERIC Educational Resources Information Center
National Bureau of Standards (DOC), Washington, DC. Inst. for Computer Sciences and Technology.
These guidelines for communicating effectively the details of computer model design and operation to persons with varying interests in a model recommend the development of four different types of manuals to meet the needs of managers, users, analysts and programmers. The guidelines for preparing a management summary manual suggest a broad spectrum…
Legal Policy Optimizing Models
ERIC Educational Resources Information Center
Nagel, Stuart; Neef, Marian
1977-01-01
The use of mathematical models originally developed by economists and operations researchers is described for legal process research. Situations involving plea bargaining, arraignment, and civil liberties illustrate the applicability of decision theory, inventory modeling, and linear programming in operations research. (LBH)
Validation of mesoscale models
NASA Technical Reports Server (NTRS)
Kuo, Bill; Warner, Tom; Benjamin, Stan; Koch, Steve; Staniforth, Andrew
1993-01-01
The topics discussed include the following: verification of cloud prediction from the PSU/NCAR mesoscale model; results form MAPS/NGM verification comparisons and MAPS observation sensitivity tests to ACARS and profiler data; systematic errors and mesoscale verification for a mesoscale model; and the COMPARE Project and the CME.
pylightcurve: Exoplanet lightcurve model
NASA Astrophysics Data System (ADS)
Tsiaras, A.; Waldmann, I. P.; Rocchetto, M.; Varley, R.; Morello, G.; Damiano, M.; Tinetti, G.
2016-12-01
pylightcurve is a model for light-curves of transiting planets. It uses the four coefficients law for the stellar limb darkening and returns the relative flux, F(t), as a function of the limb darkening coefficients, an, the Rp/R* ratio and all the orbital parameters based on the nonlinear limb darkening model (Claret 2000).
ERIC Educational Resources Information Center
Morgan, Gwen
Models of state involvement in training child care providers are briefly discussed and the employers' role in training is explored. Six criteria for states that are taken as models are identified, and four are described. Various state activities are described for each criterion. It is noted that little is known about employer and other private…
ERIC Educational Resources Information Center
New Mexico Univ., Albuquerque. American Indian Law Center.
The Model Children's Code was developed to provide a legally correct model code that American Indian tribes can use to enact children's codes that fulfill their legal, cultural and economic needs. Code sections cover the court system, jurisdiction, juvenile offender procedures, minor-in-need-of-care, and termination. Almost every Code section is…
Animal models for osteoporosis
NASA Technical Reports Server (NTRS)
Turner, R. T.; Maran, A.; Lotinun, S.; Hefferan, T.; Evans, G. L.; Zhang, M.; Sibonga, J. D.
2001-01-01
Animal models will continue to be important tools in the quest to understand the contribution of specific genes to establishment of peak bone mass and optimal bone architecture, as well as the genetic basis for a predisposition toward accelerated bone loss in the presence of co-morbidity factors such as estrogen deficiency. Existing animal models will continue to be useful for modeling changes in bone metabolism and architecture induced by well-defined local and systemic factors. However, there is a critical unfulfilled need to develop and validate better animal models to allow fruitful investigation of the interaction of the multitude of factors which precipitate senile osteoporosis. Well characterized and validated animal models that can be recommended for investigation of the etiology, prevention and treatment of several forms of osteoporosis have been listed in Table 1. Also listed are models which are provisionally recommended. These latter models have potential but are inadequately characterized, deviate significantly from the human response, require careful choice of strain or age, or are not practical for most investigators to adopt. It cannot be stressed strongly enough that the enormous potential of laboratory animals as models for osteoporosis can only be realized if great care is taken in the choice of an appropriate species, age, experimental design, and measurements. Poor choices will results in misinterpretation of results which ultimately can bring harm to patients who suffer from osteoporosis by delaying advancement of knowledge.
Modelling University Governance
ERIC Educational Resources Information Center
Trakman, Leon
2008-01-01
Twentieth century governance models used in public universities are subject to increasing doubt across the English-speaking world. Governments question if public universities are being efficiently governed; if their boards of trustees are adequately fulfilling their trust obligations towards multiple stakeholders; and if collegial models of…
ERIC Educational Resources Information Center
Ivie, Stanley D.
2007-01-01
Humanity delights in spinning conceptual models of the world. These models, in turn, mirror their respective root metaphors. Three root metaphors--spiritual, organic, and mechanical--have dominated western thought. The spiritual metaphor runs from Plato, through Hegel, and connects with Montessori. The organic metaphor extends from Aristotle,…
ERIC Educational Resources Information Center
Parks, Melissa
2014-01-01
Model-eliciting activities (MEAs) are not new to those in engineering or mathematics, but they were new to Melissa Parks. Model-eliciting activities are simulated real-world problems that integrate engineering, mathematical, and scientific thinking as students find solutions for specific scenarios. During this process, students generate solutions…
Anticipatory model of cavitation
NASA Astrophysics Data System (ADS)
Kercel, Stephen W.; Allgood, Glenn O.; Dress, William B.; Hylton, James O.
1999-03-01
The Anticipatory System (AS) formalism developed by Robert Rosen provides some insight into the problem of embedding intelligent behavior in machines. AS emulates the anticipatory behavior of biological systems. AS bases its behavior on its expectations about the near future and those expectations are modified as the system gains experience. The expectation is based on an internal model that is drawn from an appeal to physical reality. To be adaptive, the model must be able to update itself. To be practical, the model must run faster than real-time. The need for a physical model and the requirement that the model execute at extreme speeds, has held back the application of AS to practical problems. Two recent advances make it possible to consider the use of AS for practical intelligent sensors. First, advances in transducer technology make it possible to obtain previously unavailable data from which a model can be derived. For example, acoustic emissions (AE) can be fed into a Bayesian system identifier that enables the separation of a weak characterizing signal, such as the signature of pump cavitation precursors, from a strong masking signal, such as a pump vibration feature. The second advance is the development of extremely fast, but inexpensive, digital signal processing hardware on which it is possible to run an adaptive Bayesian-derived model faster than real-time. This paper reports the investigation of an AS using a model of cavitation based on hydrodynamic principles and Bayesian analysis of data from high-performance AE sensors.
Writing Models, Versatile Writers.
ERIC Educational Resources Information Center
VanDeWeghe, Richard
1983-01-01
Presents five research-based writing models to help student writers analyze their composition processes: (1) discovery, (2) direct writing process, (3) five-stage process, (4) write-talk-write, and (5) four key questions. Discusses advantages and disadvantages of each model. (PD)
ERIC Educational Resources Information Center
Gabel, Dorothy; And Others
1992-01-01
Chemistry can be described on three levels: sensory, molecular, and symbolic. Proposes a particle approach to teaching chemistry that uses magnets to aid students construct molecular models and solve particle problems. Includes examples of Johnstone's model of chemistry phenomena, a problem worksheet, and a student concept mastery sheet. (MDH)
Canister Model, Systems Analysis
Pincock, K. D.; Hamelin, R. D.
1993-09-29
This packges provides a computer simulation of a systems model for packaging nuclear waste and spent nuclear fuel in canisters. The canister model calculates overall programmatic cost, number of canisters, and fuel and waste inventories for the Idaho Chemical Processing Plant (other initial conditions can be entered).
ERIC Educational Resources Information Center
Buggey, Tom; Ogle, Lindsey
2012-01-01
Video self-modeling (VSM) first appeared on the psychology and education stage in the early 1970s. The practical applications of VSM were limited by lack of access to tools for editing video, which is necessary for almost all self-modeling videos. Thus, VSM remained in the research domain until the advent of camcorders and VCR/DVD players and,…
Composite Load Model Evaluation
Lu, Ning; Qiao, Hong
2007-09-30
The WECC load modeling task force has dedicated its effort in the past few years to develop a composite load model that can represent behaviors of different end-user components. The modeling structure of the composite load model is recommended by the WECC load modeling task force. GE Energy has implemented this composite load model with a new function CMPLDW in its power system simulation software package, PSLF. For the last several years, Bonneville Power Administration (BPA) has taken the lead and collaborated with GE Energy to develop the new composite load model. Pacific Northwest National Laboratory (PNNL) and BPA joint force and conducted the evaluation of the CMPLDW and test its parameter settings to make sure that: • the model initializes properly, • all the parameter settings are functioning, and • the simulation results are as expected. The PNNL effort focused on testing the CMPLDW in a 4-bus system. An exhaustive testing on each parameter setting has been performed to guarantee each setting works. This report is a summary of the PNNL testing results and conclusions.
Reliability model generator specification
NASA Technical Reports Server (NTRS)
Cohen, Gerald C.; Mccann, Catherine
1990-01-01
The Reliability Model Generator (RMG), a program which produces reliability models from block diagrams for ASSIST, the interface for the reliability evaluation tool SURE is described. An account is given of motivation for RMG and the implemented algorithms are discussed. The appendices contain the algorithms and two detailed traces of examples.
Modelling University Governance
ERIC Educational Resources Information Center
Trakman, Leon
2008-01-01
Twentieth century governance models used in public universities are subject to increasing doubt across the English-speaking world. Governments question if public universities are being efficiently governed; if their boards of trustees are adequately fulfilling their trust obligations towards multiple stakeholders; and if collegial models of…
Structural Equation Model Trees
ERIC Educational Resources Information Center
Brandmaier, Andreas M.; von Oertzen, Timo; McArdle, John J.; Lindenberger, Ulman
2013-01-01
In the behavioral and social sciences, structural equation models (SEMs) have become widely accepted as a modeling tool for the relation between latent and observed variables. SEMs can be seen as a unification of several multivariate analysis techniques. SEM Trees combine the strengths of SEMs and the decision tree paradigm by building tree…
This lecture will present AQUATOX, an aquatic ecosystem simulation model developed by Dr. Dick Park and supported by the U.S. EPA. The AQUATOX model predicts the fate of various pollutants, such as nutrients and organic chemicals, and their effects on the ecosystem, including fi...
Multilevel Mixture Factor Models
ERIC Educational Resources Information Center
Varriale, Roberta; Vermunt, Jeroen K.
2012-01-01
Factor analysis is a statistical method for describing the associations among sets of observed variables in terms of a small number of underlying continuous latent variables. Various authors have proposed multilevel extensions of the factor model for the analysis of data sets with a hierarchical structure. These Multilevel Factor Models (MFMs)…
Modeling Biomimetic Mineralization
2010-03-02
combination of computational methods including Molecular Dynamics, Langevin Dynamics, and Monte Carlo, and theories including statistical mechanics and...treated by a combination of computational methods including Molecular Dynamics, Langevin Dynamics, and Monte Carlo, and theories including...at the interfaces are neglected in our computer modeling so far. Force-field Molecular model Molecular dynamics Langevin dynamics Brownian
Model for Contingency Contracting.
ERIC Educational Resources Information Center
Prince George's Community Coll., Largo, MD. Dept. of Human Development.
The Department of Human Development at Prince George's Community College has developed a contingency contracting model for the department's counseling and student services which presents planning and evaluation as interrelated parts of the same process of self-imposed accountability. The implementation of the model consisted of: (1) planning…
ERIC Educational Resources Information Center
Ifenthaler, Dirk; Seel, Norbert M.
2013-01-01
In this paper, there will be a particular focus on mental models and their application to inductive reasoning within the realm of instruction. A basic assumption of this study is the observation that the construction of mental models and related reasoning is a slowly developing capability of cognitive systems that emerges effectively with proper…
Connectionist Modelling and Education.
ERIC Educational Resources Information Center
Evers, Colin W.
2000-01-01
Provides a detailed, technical introduction to the state of cognitive science research, in particular the rise of the "new cognitive science," especially artificial neural net (ANN) models. Explains one influential ANN model and describes diverse applications and their implications for education. (EV)
The Teacher Improvement Model.
ERIC Educational Resources Information Center
Pokalo, Mariann
The Teacher Improvement Model was begun as an Organizational Development Project using the parallel systems approach in a school for emotionally disturbed junior high school students. Teachers volunteered for committee work and requested observations and evaluations in an effort to define and establish a discipline model best suited to them. Such…
Foundations of Biomolecular Modeling
Jorgensen, William L.
2014-01-01
The 2013 Nobel Prize in Chemistry has been awarded to Martin Kaplus, Michael Levitt, and Arieh Warshel for “Development of Multiscale Models for Complex Chemical Systems”. The honored work from the 1970s has provided a foundation for the widespread activities today in modeling organic and biomolecular systems. PMID:24315087
ERIC Educational Resources Information Center
Baker, William P.; Moore, Cathy Ronstadt
1998-01-01
Understanding antibody structure and function is difficult for many students. The rearrangement of constant and variable regions during antibody differentiation can be effectively simulated using a paper model. Describes a hands-on laboratory exercise which allows students to model antibody diversity using readily available resources. (PVD)
NASA Technical Reports Server (NTRS)
Zhu, Zhifan
2016-01-01
Under the NASA-KAIA-KARI ATM research collaboration agreement, SOSS ICN Model has been developed for Incheon International Airport. This presentation describes the model validation work in the project. The presentation will show the results and analysis of the validation.
Automated Student Model Improvement
ERIC Educational Resources Information Center
Koedinger, Kenneth R.; McLaughlin, Elizabeth A.; Stamper, John C.
2012-01-01
Student modeling plays a critical role in developing and improving instruction and instructional technologies. We present a technique for automated improvement of student models that leverages the DataShop repository, crowd sourcing, and a version of the Learning Factors Analysis algorithm. We demonstrate this method on eleven educational…
ERIC Educational Resources Information Center
Baker, William P.; Moore, Cathy Ronstadt
1998-01-01
Understanding antibody structure and function is difficult for many students. The rearrangement of constant and variable regions during antibody differentiation can be effectively simulated using a paper model. Describes a hands-on laboratory exercise which allows students to model antibody diversity using readily available resources. (PVD)
ERIC Educational Resources Information Center
Mahalik, James R.
1990-01-01
Presents and evaluates four systematic eclectic models of psychotherapy: Beutler's eclectic psychotherapy; Howard, Nance, and Myers' adaptive counseling and therapy; Lazarus' multimodal therapy; and Prochaska and DiClemente's transtheoretical approach. Examines support for these models and makes conceptual and empirical recommendations.…
ERIC Educational Resources Information Center
Miles, David T.; Robinson, Roger E.
The General Teaching Model is a procedural guide for the design, implementation, evaluation, and improvement of instruction. The Model is considered applicable to all levels of education, all subject matters, and any length of instructional unit. It consists of four components: 1) instructional objectives, 2) pre-assessment, 3) instructional…
NASA Astrophysics Data System (ADS)
Morrison, Margaret
2014-02-01
When James Clerk Maxwell set out his famous equations 150 years ago, his model of electromagnetism included a piece of pure fiction: an invisible, all-pervasive "aether" made up of elastic vortices separated by electric charges. Margaret Morrison explores how this and other "fictional" models shape science.
PROSTATE REGULATION: MODELING ENDOGENOUS ...
Prostate function is an important indicator of androgen status in toxicological studies making predictive modeling of the relevant pharmacokinetics and pharmacodynamics desirable. Prostate function is an important indicator of androgen status in toxicological studies making predictive modeling of the relevant pharmacokinetics and pharmacodynamics desirable.
Tsyganenko Geomagnetic Field Models
NASA Astrophysics Data System (ADS)
Tsyganenko, Nikolai
2014-09-01
The Tsyganenko models are semi-empirical best-fit representations for the magnetic field, based on a large number of satellite observations (IMP, HEOS, ISEE, POLAR, Geotail, GOES, etc). The models include the contributions from major external magnetospheric sources: ring current, magnetotail current system, magnetopause currents, and large-scale system of field-aligned currents.
ERIC Educational Resources Information Center
Thornburgh, William R.; Tretter, Thomas R.
2017-01-01
This article describes a unit in which students investigate total solar eclipses, such as the one coming August 21, from several perspectives. It incorporates mathematical thinking and aligns with the "Next Generation Science Standard." This article refers to physical, virtual, and mathematical modeling. Various models and perspectives…
ERIC Educational Resources Information Center
Eichinger, John
2005-01-01
Models are crucial to science teaching and learning, yet they can create unforeseen and overlooked challenges for students and teachers. For example, consider the time-tested clay volcano that relies on a vinegar and-baking-soda mixture for its "eruption." Based on a classroom demonstration of that geologic model, elementary students may interpret…
Unitary Response Regression Models
ERIC Educational Resources Information Center
Lipovetsky, S.
2007-01-01
The dependent variable in a regular linear regression is a numerical variable, and in a logistic regression it is a binary or categorical variable. In these models the dependent variable has varying values. However, there are problems yielding an identity output of a constant value which can also be modelled in a linear or logistic regression with…
Modeling the Teaching Consultant.
ERIC Educational Resources Information Center
Johnson, Brian L.; And Others
1990-01-01
Discusses the teaching consultant process in computer programing courses, describes a teaching consultant model from both the teachers' and students' perspectives, and shows how this model can be used to develop an intelligent teaching consultant (ITC). Differences between this collection of expert systems and conventional intelligent tutoring…
NASA Astrophysics Data System (ADS)
Taniguchi, Tadahiro; Sawaragi, Tetsuo
In this paper, a new machine-learning method, called Dual-Schemata model, is presented. Dual-Schemata model is a kind of self-organizational machine learning methods for an autonomous robot interacting with an unknown dynamical environment. This is based on Piaget's Schema model, that is a classical psychological model to explain memory and cognitive development of human beings. Our Dual-Schemata model is developed as a computational model of Piaget's Schema model, especially focusing on sensori-motor developing period. This developmental process is characterized by a couple of two mutually-interacting dynamics; one is a dynamics formed by assimilation and accommodation, and the other dynamics is formed by equilibration and differentiation. By these dynamics schema system enables an agent to act well in a real world. This schema's differentiation process corresponds to a symbol formation process occurring within an autonomous agent when it interacts with an unknown, dynamically changing environment. Experiment results obtained from an autonomous facial robot in which our model is embedded are presented; an autonomous facial robot becomes able to chase a ball moving in various ways without any rewards nor teaching signals from outside. Moreover, emergence of concepts on the target movements within a robot is shown and discussed in terms of fuzzy logics on set-subset inclusive relationships.
NASA Astrophysics Data System (ADS)
Erpylev, N. P.; Smirnov, M. A.; Bagrov, A. V.
A night sky model is proposed. It includes different components of light polution, such as solar twilight, moon scattered light, zodiacal light, Milky Way, air glow and artificial light pollution. The model is designed for calculating the efficiency of astronomical installations.
NASA Technical Reports Server (NTRS)
Knezovich, F. M.
1976-01-01
A modular structured system of computer programs is presented utilizing earth and ocean dynamical data keyed to finitely defined parameters. The model is an assemblage of mathematical algorithms with an inherent capability of maturation with progressive improvements in observational data frequencies, accuracies and scopes. The Eom in its present state is a first-order approach to a geophysical model of the earth's dynamics.
ERIC Educational Resources Information Center
Fischbein, Efraim
2001-01-01
Analyses several examples of tacit influences exerted by mental models on the interpretation of various mathematical concepts in the domain of actual infinity. Specifically addresses the unconscious effect of the figural-pictorial models of statements related to the infinite sets of geometrical points related to the concepts of function and…
On Some Electroconvection Models
NASA Astrophysics Data System (ADS)
Constantin, Peter; Elgindi, Tarek; Ignatova, Mihaela; Vicol, Vlad
2017-02-01
We consider a model of electroconvection motivated by studies of the motion of a two-dimensional annular suspended smectic film under the influence of an electric potential maintained at the boundary by two electrodes. We prove that this electroconvection model has global in time unique smooth solutions.
ERIC Educational Resources Information Center
Ifenthaler, Dirk; Seel, Norbert M.
2013-01-01
In this paper, there will be a particular focus on mental models and their application to inductive reasoning within the realm of instruction. A basic assumption of this study is the observation that the construction of mental models and related reasoning is a slowly developing capability of cognitive systems that emerges effectively with proper…
NASA Astrophysics Data System (ADS)
Davies, A. D.
1985-07-01
The NBS Center for Fire Research (CFR) conducts scientific research bearing on the fire safety of buildings, vehicles, tunnels and other inhabited structures. Data from controlled fire experiments are collected, analyzed and reduced to the analytical formulas that appear to underly the observed phenomena. These results and more general physical principles are then combined into models to predict the development of environments that may be hostile to humans. This is a progress report of an applied model validation case study. The subject model is Transport of Fire, Smoke and Gases (FAST). Products from a fire in a burn room exit through a connected corridor to outdoors. Cooler counterflow air in a lower layer feeds the fire. The model predicts corridor layer temperatures and thicknesses vs. time, given enclosure, fire and ambient specifications. Data have been collected from 38 tests using several fire sizes, but have not been reduced. Corresponding model results, and model and test documentation are yet to come. Considerable modeling and calculation is needed to convert instrument readings to test results comparable with model outputs so that residual differences may be determined.
Thom, Ronald M.; Judd, Chaeli
2007-07-27
Successful restoration of wetland habitats depends on both our understanding of our system and our ability to characterize it. By developing a conceptual model, looking at different spatial scales and integrating diverse data streams: GIS datasets and NASA products, we were able to develop a dynamic model for site prioritization based on both qualitative and quantitative relationships found in the coastal environment.
Unitary Response Regression Models
ERIC Educational Resources Information Center
Lipovetsky, S.
2007-01-01
The dependent variable in a regular linear regression is a numerical variable, and in a logistic regression it is a binary or categorical variable. In these models the dependent variable has varying values. However, there are problems yielding an identity output of a constant value which can also be modelled in a linear or logistic regression with…
ERIC Educational Resources Information Center
Parks, Melissa
2014-01-01
Model-eliciting activities (MEAs) are not new to those in engineering or mathematics, but they were new to Melissa Parks. Model-eliciting activities are simulated real-world problems that integrate engineering, mathematical, and scientific thinking as students find solutions for specific scenarios. During this process, students generate solutions…
Modelling by Teacher Educators.
ERIC Educational Resources Information Center
Loughran, John; Berry, Amanda
This paper explains one university's approach to explicit modeling of practice. It briefly outlines the university's conception of episteme and phronesis, then explores the university's views of explicit modeling, which is seen as operating concurrently at two levels. At one level, it is about teacher educators "doing" in their practice…
ERIC Educational Resources Information Center
Morgan, Gwen
Models of state involvement in training child care providers are briefly discussed and the employers' role in training is explored. Six criteria for states that are taken as models are identified, and four are described. Various state activities are described for each criterion. It is noted that little is known about employer and other private…
Simplified Models for Dark Matter Model Building
NASA Astrophysics Data System (ADS)
DiFranzo, Anthony Paul
The largest mass component of the universe is a longstanding mystery to the physics community. As a glaring source of new physics beyond the Standard Model, there is a large effort to uncover the quantum nature of dark matter. Many probes have been formed to search for this elusive matter; cultivating a rich environment for a phenomenologist. In addition to the primary probes---colliders, direct detection, and indirect detection---each with their own complexities, there is a plethora of prospects to illuminate our unanswered questions. In this work, phenomenological techniques for studying dark matter and other possible hints of new physics will be discussed. This work primarily focuses on the use of Simplified Models, which are intended to be a compromise between generality and validity of the theoretical description. They are often used to parameterize a particular search, develop a well-defined sense of complementarity between searches, or motivate new search strategies. Explicit examples of such models and how they may be used will be the highlight of each chapter.
Brozoski, Thomas J; Bauer, Carol A
2016-08-01
Presented is a thematic review of animal tinnitus models from a functional perspective. Chronic tinnitus is a persistent subjective sound sensation, emergent typically after hearing loss. Although the sensation is experientially simple, it appears to have central a nervous system substrate of unexpected complexity that includes areas outside of those classically defined as auditory. Over the past 27 years animal models have significantly contributed to understanding tinnitus' complex neurophysiology. In that time, a diversity of models have been developed, each with its own strengths and limitations. None has clearly become a standard. Animal models trace their origin to the 1988 experiments of Jastreboff and colleagues. All subsequent models derive some of their features from those experiments. Common features include behavior-dependent psychophysical determination, acoustic conditions that contrast objective sound and silence, and inclusion of at least one normal-hearing control group. In the present review, animal models have been categorized as either interrogative or reflexive. Interrogative models use emitted behavior under voluntary control to indicate hearing. An example would be pressing a lever to obtain food in the presence of a particular sound. In this type of model animals are interrogated about their auditory sensations, analogous to asking a patient, "What do you hear?" These models require at least some training and motivation management, and reflect the perception of tinnitus. Reflexive models, in contrast, employ acoustic modulation of an auditory reflex, such as the acoustic startle response. An unexpected loud sound will elicit a reflexive motor response from many species, including humans. Although involuntary, acoustic startle can be modified by a lower-level preceding event, including a silent sound gap. Sound-gap modulation of acoustic startle appears to discriminate tinnitus in animals as well as humans, and requires no training or
NASA Technical Reports Server (NTRS)
Brown, R. G.
1984-01-01
The formulation of appropriate state-space models for Kalman filtering applications is studied. The so-called model is completely specified by four matrix parameters and the initial conditions of the recursive equations. Once these are determined, the die is cast, and the way in which the measurements are weighted is determined foreverafter. Thus, finding a model that fits the physical situation at hand is all important. Also, it is often the most difficult aspect of designing a Kalman filter. Formulation of discrete state models from the spectral density and ARMA random process descriptions is discussed. Finally, it is pointed out that many common processes encountered in applied work (such as band-limited white noise) simply do not lend themselves very well to Kalman filter modeling.
Hubbard, W. B.; Militzer, B.
2016-03-20
In anticipation of new observational results for Jupiter's axial moment of inertia and gravitational zonal harmonic coefficients from the forthcoming Juno orbiter, we present a number of preliminary Jupiter interior models. We combine results from ab initio computer simulations of hydrogen–helium mixtures, including immiscibility calculations, with a new nonperturbative calculation of Jupiter's zonal harmonic coefficients, to derive a self-consistent model for the planet's external gravity and moment of inertia. We assume helium rain modified the interior temperature and composition profiles. Our calculation predicts zonal harmonic values to which measurements can be compared. Although some models fit the observed (pre-Juno) second- and fourth-order zonal harmonics to within their error bars, our preferred reference model predicts a fourth-order zonal harmonic whose absolute value lies above the pre-Juno error bars. This model has a dense core of about 12 Earth masses and a hydrogen–helium-rich envelope with approximately three times solar metallicity.
Cardiovascular modeling and diagnostics
Kangas, L.J.; Keller, P.E.; Hashem, S.; Kouzes, R.T.
1995-12-31
In this paper, a novel approach to modeling and diagnosing the cardiovascular system is introduced. A model exhibits a subset of the dynamics of the cardiovascular behavior of an individual by using a recurrent artificial neural network. Potentially, a model will be incorporated into a cardiovascular diagnostic system. This approach is unique in that each cardiovascular model is developed from physiological measurements of an individual. Any differences between the modeled variables and the variables of an individual at a given time are used for diagnosis. This approach also exploits sensor fusion to optimize the utilization of biomedical sensors. The advantage of sensor fusion has been demonstrated in applications including control and diagnostics of mechanical and chemical processes.
Hughes, T.J.; Fastook, J.L.
1994-05-01
The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed.
Jones, Katherine A.; Finley, Patrick D.; Moore, Thomas W.; Nozick, Linda Karen; Martin, Nathaniel; Bandlow, Alisa; Detry, Richard Joseph; Evans, Leland B.; Berger, Taylor Eugen
2013-09-01
Infectious diseases can spread rapidly through healthcare facilities, resulting in widespread illness among vulnerable patients. Computational models of disease spread are useful for evaluating mitigation strategies under different scenarios. This report describes two infectious disease models built for the US Department of Veteran Affairs (VA) motivated by a Varicella outbreak in a VA facility. The first model simulates disease spread within a notional contact network representing staff and patients. Several interventions, along with initial infection counts and intervention delay, were evaluated for effectiveness at preventing disease spread. The second model adds staff categories, location, scheduling, and variable contact rates to improve resolution. This model achieved more accurate infection counts and enabled a more rigorous evaluation of comparative effectiveness of interventions.
NASA Astrophysics Data System (ADS)
Watanabe, Shigeto; Kumamoto, Atsushi; Kakinami, Yoshihiro
2016-07-01
begin{center} {bf Modeling of Plasmasphere} end{center} Electron density at altitudes below 10,000km is estimated from upper-hybrid resonance (UHR) emission observed by the plasma wave and sounder experiments (PWS) on Akebono satellite from February 22, 1989 to April 23, 2015. The electron density of plasmasphere is investigated statistically and compared with International Reference Ionosphere model. We have made an empirical model of electron density of plasmasphere at altitudes between 1000 km and 10000 km. The electron density distribution is also compared with a physical model (Plasmasphere Thermosphere model: PTM) developed in Japan. The electron densities by the Akebono satellite and the PTM show clearly density gradient change at altitude of 1500 km and plasmapause. The density gradient change at 1500 km altitude is corresponding to transition height from O+ to H+. The electron density distribution of plasmasphere shows clearly local time, latitude, season, solar activity and magnetic activity dependences.
Animal models of hepatotoxicity.
Bhakuni, Ganesh Singh; Bedi, Onkar; Bariwal, Jitender; Deshmukh, Rahul; Kumar, Puneet
2016-01-01
Liver is the largest and important organ in the body, involved in the metabolism of food and drugs. Liver diseases are potentially life threatening for humans. The etiology of liver disorder varied due to different reasons like autoimmune disorder, viral infection, toxic chemical, and due to changing diet style. Liver injury produces pathological changes like increase level of SGOT, SGPT, TB and generation of free radical radicals. A better understanding of primary mechanisms is mandatory for designing of new therapeutic drugs. Therefore, animal models are being developed to mimic human liver diseases. Animal models are being used for several decades to study the pathogenesis of liver disorders and related toxicities. In this review, we revealed various animal models with their merits and demerits. Our main focus is to explore all new and traditional animal models under broad classification like non-invasive, invasive and genetic models which directly or indirectly produce hepatotoxicity.
Integrated Workforce Modeling System
NASA Technical Reports Server (NTRS)
Moynihan, Gary P.
2000-01-01
There are several computer-based systems, currently in various phases of development at KSC, which encompass some component, aspect, or function of workforce modeling. These systems may offer redundant capabilities and/or incompatible interfaces. A systems approach to workforce modeling is necessary in order to identify and better address user requirements. This research has consisted of two primary tasks. Task 1 provided an assessment of existing and proposed KSC workforce modeling systems for their functionality and applicability to the workforce planning function. Task 2 resulted in the development of a proof-of-concept design for a systems approach to workforce modeling. The model incorporates critical aspects of workforce planning, including hires, attrition, and employee development.
J.M. Scaglione
2003-03-12
The purpose of the ''Criticality Model Report'' is to validate the MCNP (CRWMS M&O 1998h) code's ability to accurately predict the effective neutron multiplication factor (k{sub eff}) for a range of conditions spanned by various critical configurations representative of the potential configurations commercial reactor assemblies stored in a waste package may take. Results of this work are an indication of the accuracy of MCNP for calculating eigenvalues, which will be used as input for criticality analyses for spent nuclear fuel (SNF) storage at the proposed Monitored Geologic Repository. The scope of this report is to document the development and validation of the criticality model. The scope of the criticality model is only applicable to commercial pressurized water reactor fuel. Valid ranges are established as part of the validation of the criticality model. This model activity follows the description in BSC (2002a).
NASA Technical Reports Server (NTRS)
Badler, N. I.; Lee, P.; Wong, S.
1985-01-01
Strength modeling is a complex and multi-dimensional issue. There are numerous parameters to the problem of characterizing human strength, most notably: (1) position and orientation of body joints; (2) isometric versus dynamic strength; (3) effector force versus joint torque; (4) instantaneous versus steady force; (5) active force versus reactive force; (6) presence or absence of gravity; (7) body somatotype and composition; (8) body (segment) masses; (9) muscle group envolvement; (10) muscle size; (11) fatigue; and (12) practice (training) or familiarity. In surveying the available literature on strength measurement and modeling an attempt was made to examine as many of these parameters as possible. The conclusions reached at this point toward the feasibility of implementing computationally reasonable human strength models. The assessment of accuracy of any model against a specific individual, however, will probably not be possible on any realistic scale. Taken statistically, strength modeling may be an effective tool for general questions of task feasibility and strength requirements.
NASA Astrophysics Data System (ADS)
Alber, Mark S.; Kiskowski, Maria; Jiang, Yi; Newman, Stuart
Modelling pattern formation and morphogenesis are fundamental problems in biology. One useful approach is lattice gas cellular automata (LGCA) model. This paper reviews several stochastic lattice gas models for pattern formation in myxobacteria fruiting body morphogenesis and vertebrate limb skeletogenesis. The fruiting body formation in myxobacteria is a complex morphological process that requires the organized, collective effort of tens of thousands of cells. It provides new insight into collective microbial behavior since myxobacteria morphogenic pattern formation is governed by cell-cell interactions rather than chemotaxis. We describe LGCA models for the aggregation stage of the fruiting body formation. Limb bud precartilage mesenchymal cells in micromass culture undergo chondrogenic pattern formation, which results in the formation of regularly-spaced "islands" of cartilage analogous to the cartilage primordia of the developing limb skeleton. An LGCA model, based on reaction-diffusion coupling and cell-matrix adhesion, is described for this process.
NASA Technical Reports Server (NTRS)
Parke, M. E.
1978-01-01
Two trends evident in global tidal modelling since the first GEOP conference in 1972 are described. The first centers on the incorporation of terms for ocean loading and gravitational self attraction into Laplace's tidal equations. The second centers on a better understanding of the problem of near resonant modelling and the need for realistic maps of tidal elevation for use by geodesists and geophysicists. Although new models still show significant differences, especially in the South Atlantic, there are significant similarities in many of the world's oceans. This allows suggestions to be made for future locations for bottom pressure gauge measurements. Where available, estimates of M2 tidal dissipation from the new models are significantly lower than estimates from previous models.
Bird, R.; Hulstrom, R.L.
1980-01-01
Several recently published models of the direct component of the broadband insolation are compared for clear sky conditions. The comparison includes seven simple models and one rigorous model that is used as a basis for determining accuracy. Where possible, the comparison is made between the results of each model for each atmospheric constituent (H/sub 2/O, CO/sub 2/, O/sub 3/, O/sub 2/, aerosol and molecular scattering) separately as well as for the combined effect of all of the constituents. Two optimum simple models of varying degrees of complexity are developed as a result of this comparison. The study indicates: aerosols dominate the attenuation of the direct beam for reasonable atmospheric conditions; molecular scattering is next in importance; water vapor is an important absorber; and carbon dioxide and oxygen are relatively unimportant as attenuators of the broadband solar energy.
Palliative care delivery models.
Wiencek, Clareen; Coyne, Patrick
2014-11-01
To provide an overview of the four major palliative care delivery models: ambulatory clinics, home-based programs, inpatient palliative care units, and inpatient consultation services. The advantages and disadvantages of each model and the generalist and specialist roles in palliative care will be discussed. Literature review. The discipline of palliative care continues to experience growth in the number of programs and in types of delivery models. Ambulatory- and home-based models are the newest on the scene. Nurses caring for oncology patients with life-limiting disease should be informed about these models for optimal impact on patient care outcomes. Oncology nurses should demonstrate generalist skills in the care of the seriously ill and access specialist palliative care providers as warranted by the patient's condition.
Economic communication model set
NASA Astrophysics Data System (ADS)
Zvereva, Olga M.; Berg, Dmitry B.
2017-06-01
This paper details findings from the research work targeted at economic communications investigation with agent-based models usage. The agent-based model set was engineered to simulate economic communications. Money in the form of internal and external currencies was introduced into the models to support exchanges in communications. Every model, being based on the general concept, has its own peculiarities in algorithm and input data set since it was engineered to solve the specific problem. Several and different origin data sets were used in experiments: theoretic sets were estimated on the basis of static Leontief's equilibrium equation and the real set was constructed on the basis of statistical data. While simulation experiments, communication process was observed in dynamics, and system macroparameters were estimated. This research approved that combination of an agent-based and mathematical model can cause a synergetic effect.
NASA Technical Reports Server (NTRS)
North, G. R.; Crowley, T. J.
1984-01-01
Mathematical climate modelling has matured as a discipline to the point that it is useful in paleoclimatology. As an example a new two dimensional energy balance model is described and applied to several problems of current interest. The model includes the seasonal cycle and the detailed land-sea geographical distribution. By examining the changes in the seasonal cycle when external perturbations are forced upon the climate system it is possible to construct hypotheses about the origin of midlatitude ice sheets and polar ice caps. In particular the model predicts a rather sudden potential for glaciation over large areas when the Earth's orbital elements are only slightly altered. Similarly, the drift of continents or the change of atmospheric carbon dioxide over geological time induces radical changes in continental ice cover. With the advance of computer technology and improved understanding of the individual components of the climate system, these ideas will be tested in far more realistic models in the near future.
Stratiform chromite deposit model
Schulte, Ruth F.; Taylor, Ryan D.; Piatak, Nadine M.; Seal, Robert R., II
2010-01-01
Stratiform chromite deposits are of great economic importance, yet their origin and evolution remain highly debated. Layered igneous intrusions such as the Bushveld, Great Dyke, Kemi, and Stillwater Complexes, provide opportunities for studying magmatic differentiation processes and assimilation within the crust, as well as related ore-deposit formation. Chromite-rich seams within layered intrusions host the majority of the world's chromium reserves and may contain significant platinum-group-element (PGE) mineralization. This model of stratiform chromite deposits is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. The model focuses on features that may be common to all stratiform chromite deposits as a way to gain insight into the processes that gave rise to their emplacement and to the significant economic resources contained in them.
Conditional statistical model building
NASA Astrophysics Data System (ADS)
Hansen, Mads Fogtmann; Hansen, Michael Sass; Larsen, Rasmus
2008-03-01
We present a new statistical deformation model suited for parameterized grids with different resolutions. Our method models the covariances between multiple grid levels explicitly, and allows for very efficient fitting of the model to data on multiple scales. The model is validated on a data set consisting of 62 annotated MR images of Corpus Callosum. One fifth of the data set was used as a training set, which was non-rigidly registered to each other without a shape prior. From the non-rigidly registered training set a shape prior was constructed by performing principal component analysis on each grid level and using the results to construct a conditional shape model, conditioning the finer parameters with the coarser grid levels. The remaining shapes were registered with the constructed shape prior. The dice measures for the registration without prior and the registration with a prior were 0.875 +/- 0.042 and 0.8615 +/- 0.051, respectively.
LDEF environment modeling updates
NASA Technical Reports Server (NTRS)
Gordon, Tim; Rantanen, Ray; Whitaker, Ann F.
1995-01-01
An updated gas dynamics model for gas interactions around the LDEF is presented that includes improved scattering algorithms. The primary improvement is more accurate predictions of surface fluxes in the wake region. The code used is the Integrated Spacecraft Environments Model (ISEM). Additionally, initial results of a detailed ISEM prediction model of the Solar Array Passive LDEF Experiment (SAMPLE), A0171, is presented. This model includes details of the A0171 geometry and outgassing characteristics of the many surfaces on the experiment. The detailed model includes the multiple scattering that exists between the ambient atmosphere, LDEF outgassing, and atomic oxygen erosion products. Predictions are made for gas densities, surface fluxes and deposition at three different time periods of the LDEF mission.
Fidelis, K; Adzhubej, A; Kryshtafovych, A; Daniluk, P
2005-02-23
The phenomenal success of the genome sequencing projects reveals the power of completeness in revolutionizing biological science. Currently it is possible to sequence entire organisms at a time, allowing for a systemic rather than fractional view of their organization and the various genome-encoded functions. There is an international plan to move towards a similar goal in the area of protein structure. This will not be achieved by experiment alone, but rather by a combination of efforts in crystallography, NMR spectroscopy, and computational modeling. Only a small fraction of structures are expected to be identified experimentally, the remainder to be modeled. Presently there is no organized infrastructure to critically evaluate and present these data to the biological community. The goal of the Protein Model Database project is to create such infrastructure, including (1) public database of theoretically derived protein structures; (2) reliable annotation of protein model quality, (3) novel structure analysis tools, and (4) access to the highest quality modeling techniques available.
Newville, Matthew
The XAFS Model Compound Library contains XAFS data on model compounds. The term "model" compounds refers to compounds of homogeneous and well-known crystallographic or molecular structure. Each data file in this library has an associated atoms.inp file that can be converted to a feff.inp file using the program ATOMS. (See the related Searchable Atoms.inp Archive at http://cars9.uchicago.edu/~newville/adb/) This Library exists because XAFS data on model compounds is useful for several reasons, including comparing to unknown data for "fingerprinting" and testing calculations and analysis methods. The collection here is currently limited, but is growing. The focus to date has been on inorganic compounds and minerals of interest to the geochemical community. [Copied, with editing, from http://cars9.uchicago.edu/~newville/ModelLib/
Molecular modeling of peptides.
Kuczera, Krzysztof
2015-01-01
This article presents a review of the field of molecular modeling of peptides. The main focus is on atomistic modeling with molecular mechanics potentials. The description of peptide conformations and solvation through potentials is discussed. Several important computer simulation methods are briefly introduced, including molecular dynamics, accelerated sampling approaches such as replica-exchange and metadynamics, free energy simulations and kinetic network models like Milestoning. Examples of recent applications for predictions of structure, kinetics, and interactions of peptides with complex environments are described. The reliability of current simulation methods is analyzed by comparison of computational predictions obtained using different models with each other and with experimental data. A brief discussion of coarse-grained modeling and future directions is also presented.
V. Chipman
2002-10-31
The purpose of the Ventilation Model is to simulate the heat transfer processes in and around waste emplacement drifts during periods of forced ventilation. The model evaluates the effects of emplacement drift ventilation on the thermal conditions in the emplacement drifts and surrounding rock mass, and calculates the heat removal by ventilation as a measure of the viability of ventilation to delay the onset of peak repository temperature and reduce its magnitude. The heat removal by ventilation is temporally and spatially dependent, and is expressed as the fraction of heat carried away by the ventilation air compared to the fraction of heat produced by radionuclide decay. One minus the heat removal is called the wall heat fraction, or the remaining amount of heat that is transferred via conduction to the surrounding rock mass. Downstream models, such as the ''Multiscale Thermohydrologic Model'' (BSC 2001), use the wall heat fractions as outputted from the Ventilation Model to initialize their postclosure analyses.
Pupo, Amaury; Baez-Nieto, David; Martínez, Agustín; Latorre, Ramón; González, Carlos
2014-01-01
Voltage-gated proton channels are integral membrane proteins with the capacity to permeate elementary particles in a voltage and pH dependent manner. These proteins have been found in several species and are involved in various physiological processes. Although their primary topology is known, lack of details regarding their structures in the open conformation has limited analyses toward a deeper understanding of the molecular determinants of their function and regulation. Consequently, the function-structure relationships have been inferred based on homology models. In the present work, we review the existing proton channel models, their assumptions, predictions and the experimental facts that support them. Modeling proton channels is not a trivial task due to the lack of a close homolog template. Hence, there are important differences between published models. This work attempts to critically review existing proton channel models toward the aim of contributing to a better understanding of the structural features of these proteins. PMID:24755912
Peskin, M.E.
1997-05-01
These lectures constitute a short course in ``Beyond the Standard Model`` for students of experimental particle physics. The author discusses the general ideas which guide the construction of models of physics beyond the Standard model. The central principle, the one which most directly motivates the search for new physics, is the search for the mechanism of the spontaneous symmetry breaking observed in the theory of weak interactions. To illustrate models of weak-interaction symmetry breaking, the author gives a detailed discussion of the idea of supersymmetry and that of new strong interactions at the TeV energy scale. He discusses experiments that will probe the details of these models at future pp and e{sup +}e{sup {minus}} colliders.
Surface electromyogram signal modelling.
McGill, K C
2004-07-01
The paper reviews the fundamental components of stochastic and motor-unit-based models of the surface electromyogram (SEMG). Stochastic models used in ergonomics and kinesiology consider the SEMG to be a stochastic process whose amplitude is related to the level of muscle activation and whose power spectral density reflects muscle conduction velocity. Motor-unit-based models for describing the spatio-temporal distribution of individual motor-unit action potentials throughout the limb are quite robust, making it possible to extract precise information about motor-unit architecture from SEMG signals recorded by multi-electrode arrays. Motor-unit-based models have not yet been proven as successful, however, for extracting information about recruitment and firing rates throughout the full range of contraction. The relationship between SEMG and force during natural dynamic movements is much too complex to model in terms of single motor units.
Linear models: permutation methods
Cade, B.S.; Everitt, B.S.; Howell, D.C.
2005-01-01
Permutation tests (see Permutation Based Inference) for the linear model have applications in behavioral studies when traditional parametric assumptions about the error term in a linear model are not tenable. Improved validity of Type I error rates can be achieved with properly constructed permutation tests. Perhaps more importantly, increased statistical power, improved robustness to effects of outliers, and detection of alternative distributional differences can be achieved by coupling permutation inference with alternative linear model estimators. For example, it is well-known that estimates of the mean in linear model are extremely sensitive to even a single outlying value of the dependent variable compared to estimates of the median [7, 19]. Traditionally, linear modeling focused on estimating changes in the center of distributions (means or medians). However, quantile regression allows distributional changes to be estimated in all or any selected part of a distribution or responses, providing a more complete statistical picture that has relevance to many biological questions [6]...
General background on modeling and specifics of modeling vapor intrusion are given. Three classical model applications are described and related to the problem of petroleum vapor intrusion. These indicate the need for model calibration and uncertainty analysis. Evaluation of Bi...
Australia's Next Top Fraction Model
ERIC Educational Resources Information Center
Gould, Peter
2013-01-01
Peter Gould suggests Australia's next top fraction model should be a linear model rather than an area model. He provides a convincing argument and gives examples of ways to introduce a linear model in primary classrooms.
General background on modeling and specifics of modeling vapor intrusion are given. Three classical model applications are described and related to the problem of petroleum vapor intrusion. These indicate the need for model calibration and uncertainty analysis. Evaluation of Bi...
Saturn Radiation (SATRAD) Model
NASA Technical Reports Server (NTRS)
Garrett, H. B.; Ratliff, J. M.; Evans, R. W.
2005-01-01
The Saturnian radiation belts have not received as much attention as the Jovian radiation belts because they are not nearly as intense-the famous Saturnian particle rings tend to deplete the belts near where their peak would occur. As a result, there has not been a systematic development of engineering models of the Saturnian radiation environment for mission design. A primary exception is that of Divine (1990). That study used published data from several charged particle experiments aboard the Pioneer 1 1, Voyager 1, and Voyager 2 spacecraft during their flybys at Saturn to generate numerical models for the electron and proton radiation belts between 2.3 and 13 Saturn radii. The Divine Saturn radiation model described the electron distributions at energies between 0.04 and 10 MeV and the proton distributions at energies between 0.14 and 80 MeV. The model was intended to predict particle intensity, flux, and fluence for the Cassini orbiter. Divine carried out hand calculations using the model but never formally developed a computer program that could be used for general mission analyses. This report seeks to fill that void by formally developing a FORTRAN version of the model that can be used as a computer design tool for missions to Saturn that require estimates of the radiation environment around the planet. The results of that effort and the program listings are presented here along with comparisons with the original estimates carried out by Divine. In addition, Pioneer and Voyager data were scanned in from the original references and compared with the FORTRAN model s predictions. The results were statistically analyzed in a manner consistent with Divine s approach to provide estimates of the ability of the model to reproduce the original data. Results of a formal review of the model by a panel of experts are also presented. Their recommendations for further tests, analyses, and extensions to the model are discussed.
Maximally Expressive Task Modeling
NASA Technical Reports Server (NTRS)
Japp, John; Davis, Elizabeth; Maxwell, Theresa G. (Technical Monitor)
2002-01-01
Planning and scheduling systems organize "tasks" into a timeline or schedule. The tasks are defined within the scheduling system in logical containers called models. The dictionary might define a model of this type as "a system of things and relations satisfying a set of rules that, when applied to the things and relations, produce certainty about the tasks that are being modeled." One challenging domain for a planning and scheduling system is the operation of on-board experiment activities for the Space Station. The equipment used in these experiments is some of the most complex hardware ever developed by mankind, the information sought by these experiments is at the cutting edge of scientific endeavor, and the procedures for executing the experiments are intricate and exacting. Scheduling is made more difficult by a scarcity of space station resources. The models to be fed into the scheduler must describe both the complexity of the experiments and procedures (to ensure a valid schedule) and the flexibilities of the procedures and the equipment (to effectively utilize available resources). Clearly, scheduling space station experiment operations calls for a "maximally expressive" modeling schema. Modeling even the simplest of activities cannot be automated; no sensor can be attached to a piece of equipment that can discern how to use that piece of equipment; no camera can quantify how to operate a piece of equipment. Modeling is a human enterprise-both an art and a science. The modeling schema should allow the models to flow from the keyboard of the user as easily as works of literature flowed from the pen of Shakespeare. The Ground Systems Department at the Marshall Space Flight Center has embarked on an effort to develop a new scheduling engine that is highlighted by a maximally expressive modeling schema. This schema, presented in this paper, is a synergy of technological advances and domain-specific innovations.
Slim Battery Modelling Features
NASA Astrophysics Data System (ADS)
Borthomieu, Y.; Prevot, D.
2011-10-01
Saft has developed a life prediction model for VES and MPS cells and batteries. The Saft Li-ion Model (SLIM) is a macroscopic electrochemical model based on energy (global at cell level). The main purpose is to predict the battery performances during the life for GEO, MEO and LEO missions. This model is based on electrochemical characteristics such as Energy, Capacity, EMF, Internal resistance, end of charge voltage. It uses fading and calendar law effects on energy and internal impedance vs. time, temperature, End of Charge voltage. Based on the mission profile, satellite power system characteristics, the model proposes the various battery configurations. For each configuration, the model gives the battery performances using mission figures and profiles: power, duration, DOD, end of charge voltages, temperatures during eclipses and solstices, thermal dissipations and cell failures. For the GEO/MEO missions, eclipse and solstice periods can include specific profile such as plasmic propulsion fires and specific balancing operations. For LEO missions, the model is able to simulate high power peaks to predict radar pulses. Saft's main customers have been using the SLIM model available in house for two years. The purpose is to have the satellite builder power engineers able to perform by themselves in the battery pre-dimensioning activities their own battery simulations. The simulations can be shared with Saft engineers to refine the power system designs. This model has been correlated with existing life and calendar tests performed on all the VES and MPS cells. In comparing with more than 10 year lasting life tests, the accuracy of the model from a voltage point of view is less than 10 mV at end Of Life. In addition, thethe comparison with in-orbit data has been also done. b This paper will present the main features of the SLIM software and outputs comparison with real life tests. b0
Maximally Expressive Task Modeling
NASA Technical Reports Server (NTRS)
Japp, John; Davis, Elizabeth; Maxwell, Theresa G. (Technical Monitor)
2002-01-01
Planning and scheduling systems organize "tasks" into a timeline or schedule. The tasks are defined within the scheduling system in logical containers called models. The dictionary might define a model of this type as "a system of things and relations satisfying a set of rules that, when applied to the things and relations, produce certainty about the tasks that are being modeled." One challenging domain for a planning and scheduling system is the operation of on-board experiment activities for the Space Station. The equipment used in these experiments is some of the most complex hardware ever developed by mankind, the information sought by these experiments is at the cutting edge of scientific endeavor, and the procedures for executing the experiments are intricate and exacting. Scheduling is made more difficult by a scarcity of space station resources. The models to be fed into the scheduler must describe both the complexity of the experiments and procedures (to ensure a valid schedule) and the flexibilities of the procedures and the equipment (to effectively utilize available resources). Clearly, scheduling space station experiment operations calls for a "maximally expressive" modeling schema. Modeling even the simplest of activities cannot be automated; no sensor can be attached to a piece of equipment that can discern how to use that piece of equipment; no camera can quantify how to operate a piece of equipment. Modeling is a human enterprise-both an art and a science. The modeling schema should allow the models to flow from the keyboard of the user as easily as works of literature flowed from the pen of Shakespeare. The Ground Systems Department at the Marshall Space Flight Center has embarked on an effort to develop a new scheduling engine that is highlighted by a maximally expressive modeling schema. This schema, presented in this paper, is a synergy of technological advances and domain-specific innovations.
Tsunami Modeling: Development of Benchmarked Models
NASA Astrophysics Data System (ADS)
Kanoglu, U.; Synolakis, C. E.
2008-12-01
We discuss the progress towards the development of benchmarked models for forecasting tsunami inundation. Tsunami hydrodynamics has progressed slower than research in other natural hazards, because for several decades only the largest tsunamis were being reported. With the exception of the 1960 and 1964 events, there had been only qualitative information on inundation. While the basic equations for analysis have been known for decades, the existing synthesis leading to real time forecasts as currently available had to await the development of sophisticated modeling tools, the large-scale laboratory experiments in the 1980s-1990s and the tsunameter recordings of 2003 and since. The field survey results in the 1990s (Synolakis and Okal, 2005) served as crude proxies to free-field tsunami recordings and allowed for the validation and verification of numerical procedures. State-of-the-art inundation and forecasting codes have evolved through a painstaking process of careful validation and verification which can be traced back to the 1990 NSF Catalina workshop on Long-Wave Runup Models (Liu et al., 1991). Operational tsunami forecasting was only made possible through the availability of deep ocean measurements. We will describe this journey from development of the basic field equations to forecasts, through the scientific milestones that served as benchmarks and reality checks. In summary, as research in live networks -where problems and solution ideas arise spontaneously- tsunami hydrodynamic modeling was driven by milestone scientific meetings, and post tsunami surveys that kept identifying novel problem geometries and previously unrecognized phenomena. We discuss necessary validation and verification steps for numerical codes to be used for inundation mapping, design and operations (Synolakis et al., 2007). Liu, P. L.-F., C. E. Synolakis and H. H. Yeh, 1991. Report on the International Workshop on Long-Wave Run- up. J. Fluid Mech., 229, 675-688. Synolakis, C. E. and
Selected Logistics Models and Techniques.
1984-09-01
Programmable Calculator LCC...Program 27 TI-59 Programmable Calculator LCC Model 30 Unmanned Spacecraft Cost Model 31 iv I: TABLE OF CONTENTS (CONT’D) (Subject Index) LOGISTICS...34"" - % - "° > - " ° .° - " .’ > -% > ]*° - LOGISTICS ANALYSIS MODEL/TECHNIQUE DATA MODEL/TECHNIQUE NAME: TI-59 Programmable Calculator LCC Model TYPE MODEL: Cost Estimating DEVELOPED BY:
Modeling mitochondrial function.
Balaban, Robert S
2006-12-01
The mitochondrion represents a unique opportunity to apply mathematical modeling to a complex biological system. Understanding mitochondrial function and control is important since this organelle is critical in energy metabolism as well as playing key roles in biochemical synthesis, redox control/signaling, and apoptosis. A mathematical model, or hypothesis, provides several useful insights including a rigorous test of the consensus view of the operation of a biological process as well as providing methods of testing and creating new hypotheses. The advantages of the mitochondrial system for applying a mathematical model include the relative simplicity and understanding of the matrix reactions, the ability to study the mitochondria as a independent contained organelle, and, most importantly, one can dynamically measure many of the internal reaction intermediates, on line. The developing ability to internally monitor events within the metabolic network, rather than just the inflow and outflow, is extremely useful in creating critical bounds on complex mathematical models using the individual reaction mechanisms available. However, many serious problems remain in creating a working model of mitochondrial function including the incomplete definition of metabolic pathways, the uncertainty of using in vitro enzyme kinetics, as well as regulatory data in the intact system and the unknown chemical activities of relevant molecules in the matrix. Despite these formidable limitations, the advantages of the mitochondrial system make it one of the best defined mammalian metabolic networks that can be used as a model system for understanding the application and use of mathematical models to study biological systems.
NASA Technical Reports Server (NTRS)
Mccutcheon, Kimble D.; Gordon, Stephen S.; Thompson, Paul A.
1992-01-01
NASA uses the Variable Polarity Plasma Arc Welding (VPPAW) process extensively for fabrication of Space Shuttle External Tanks. This welding process has been in use at NASA since the late 1970's but the physics of the process have never been satisfactorily modeled and understood. In an attempt to advance the level of understanding of VPPAW, Dr. Arthur C. Nunes, Jr., (NASA) has developed a mathematical model of the process. The work described in this report evaluated and used two versions (level-0 and level-1) of Dr. Nunes' model, and a model derived by the University of Alabama at Huntsville (UAH) from Dr. Nunes' level-1 model. Two series of VPPAW experiments were done, using over 400 different combinations of welding parameters. Observations were made of VPPAW process behavior as a function of specific welding parameter changes. Data from these weld experiments was used to evaluate and suggest improvements to Dr. Nunes' model. Experimental data and correlations with the model were used to develop a multi-variable control algorithm for use with a future VPPAW controller. This algorithm is designed to control weld widths (both on the crown and root of the weld) based upon the weld parameters, base metal properties, and real-time observation of the crown width. The algorithm exhibited accuracy comparable to that of the weld width measurements for both aluminum and mild steel welds.
NASA Astrophysics Data System (ADS)
Smirnova, Olga
Biologically motivated mathematical models, which describe the dynamics of the major hematopoietic lineages (the thrombocytopoietic, lymphocytopoietic, granulocytopoietic, and erythropoietic systems) in acutely/chronically irradiated humans are developed. These models are implemented as systems of nonlinear differential equations, which variables and constant parameters have clear biological meaning. It is shown that the developed models are capable of reproducing clinical data on the dynamics of these systems in humans exposed to acute radiation in the result of incidents and accidents, as well as in humans exposed to low-level chronic radiation. Moreover, the averaged value of the "lethal" dose rates of chronic irradiation evaluated within models of these four major hematopoietic lineages coincides with the real minimal dose rate of lethal chronic irradiation. The demonstrated ability of the models of the human thrombocytopoietic, lymphocytopoietic, granulocytopoietic, and erythropoietic systems to predict the dynamical response of these systems to acute/chronic irradiation in wide ranges of doses and dose rates implies that these mathematical models form an universal tool for the investigation and prediction of the dynamics of the major human hematopoietic lineages for a vast pattern of irradiation scenarios. In particular, these models could be applied for the radiation risk assessment for health of astronauts exposed to space radiation during long-term space missions, such as voyages to Mars or Lunar colonies, as well as for health of people exposed to acute/chronic irradiation due to environmental radiological events.
Johnson, Jason K.; Oyen, Diane Adele; Chertkov, Michael; ...
2016-12-01
Inference and learning of graphical models are both well-studied problems in statistics and machine learning that have found many applications in science and engineering. However, exact inference is intractable in general graphical models, which suggests the problem of seeking the best approximation to a collection of random variables within some tractable family of graphical models. In this paper, we focus on the class of planar Ising models, for which exact inference is tractable using techniques of statistical physics. Based on these techniques and recent methods for planarity testing and planar embedding, we propose a greedy algorithm for learning the bestmore » planar Ising model to approximate an arbitrary collection of binary random variables (possibly from sample data). Given the set of all pairwise correlations among variables, we select a planar graph and optimal planar Ising model defined on this graph to best approximate that set of correlations. Finally, we demonstrate our method in simulations and for two applications: modeling senate voting records and identifying geo-chemical depth trends from Mars rover data.« less
Computationally modeling interpersonal trust.
Lee, Jin Joo; Knox, W Bradley; Wormwood, Jolie B; Breazeal, Cynthia; Desteno, David
2013-01-01
We present a computational model capable of predicting-above human accuracy-the degree of trust a person has toward their novel partner by observing the trust-related nonverbal cues expressed in their social interaction. We summarize our prior work, in which we identify nonverbal cues that signal untrustworthy behavior and also demonstrate the human mind's readiness to interpret those cues to assess the trustworthiness of a social robot. We demonstrate that domain knowledge gained from our prior work using human-subjects experiments, when incorporated into the feature engineering process, permits a computational model to outperform both human predictions and a baseline model built in naiveté of this domain knowledge. We then present the construction of hidden Markov models to investigate temporal relationships among the trust-related nonverbal cues. By interpreting the resulting learned structure, we observe that models built to emulate different levels of trust exhibit different sequences of nonverbal cues. From this observation, we derived sequence-based temporal features that further improve the accuracy of our computational model. Our multi-step research process presented in this paper combines the strength of experimental manipulation and machine learning to not only design a computational trust model but also to further our understanding of the dynamics of interpersonal trust.
Biophysical models in hadrontherapy
NASA Astrophysics Data System (ADS)
Scholz, M.; Elsaesser, T.
One major rationale for the application of ion beams in tumor therapy is their increased relative biological effectiveness RBE in the Bragg peak region For dose prescription the increased effectiveness has to be taken into account in treatment planning Hence the complex dependencies of RBE on the dose level biological endpoint position in the field etc require biophysical models which have to fulfill two important criteria simplicity and quantitative precision Simplicity means that the number of free parameters should be kept at a minimum Due to the lack of precise quantitative data at least at present this requirement is incompatible with approaches aiming at the molecular modeling of the whole chain of production processing and repair of biological damages Quantitative precision is required since steep gradients in the dose response curves are observed for most tumor and normal tissues thus even small uncertainties in the estimation of the biologically effective dose can transform into large uncertainties in the clinical outcome The paper will give a general introduction into the field followed by a brief description of a specific model the so called Local Effect Model LEM This model has been successfully applied within treatment planning in the GSI pilot project for carbon ion tumor therapy over almost 10 years now The model is based on the knowledge of charged particle track structure in combination with the response of the biological objects to conventional photon radiation The model will be critically discussed with respect to other
Modeling the transition region
NASA Astrophysics Data System (ADS)
Singer, Bart A.
1994-04-01
The calculation of engineering flows undergoing laminar-turbulent transition presents special problems. Mean-flow quantities obey neither the fully laminar nor the fully turbulent correlations. In addition, local maxima in skin friction, wall temperature, and heat transfer often occur near the end of the transition region. Traditionally, modeling this region has been important for the design of turbine blades, where the transition region is long in relation to the chord length of the blade. More recently, the need for better transition-region models has been recognized by designers of hypersonic vehicles where the high Mach number, the low Reynolds number, and the low-disturbance flight environment emphasize the importance of the transition region. Needless to say, a model that might work well for the transitional flows typically found in gas turbines will not necessarily work well for the external surface of a hypersonic vehicle. In Section 2 of this report, some of the important flow features that control the transition region will be discussed. In Section 3, different approaches to the modeling problem will be summarized and cataloged. Fully turbulent flow models will be discussed in detail in Section 4; models specifically designed for transitional flow, in Section 5; and the evaluation of models, in Section 6.
Modelling urban growth patterns
NASA Astrophysics Data System (ADS)
Makse, Hernán A.; Havlin, Shlomo; Stanley, H. Eugene
1995-10-01
CITIES grow in a way that might be expected to resemble the growth of two-dimensional aggregates of particles, and this has led to recent attempts1á¤-3 to model urban growth using ideas from the statistical physics of clusters. In particular, the model of diffusion-limited aggregation4,5 (DLA) has been invoked to rationalize the apparently fractal nature of urban morphologies1. The DLA model predicts that there should exist only one large fractal cluster, which is almost perfectly screened from incoming á¤~development unitsá¤™ (representing, for example, people, capital or resources), so that almost all of the cluster growth takes place at the tips of the clusterá¤™s branches. Here we show that an alternative model, in which development units are correlated rather than being added to the cluster at random, is better able to reproduce the observed morphology of cities and the area distribution of sub-clusters (á¤~towns') in an urban system, and can also describe urban growth dynamics. Our physical model, which corresponds to the correlated percolation model6á¤-8 in the presence of a density gradient9, is motivated by the fact that in urban areas development attracts further development. The model offers the possibility of predicting the global properties (such as scaling behaviour) of urban morphologies.
Johnson, Jason K.; Oyen, Diane Adele; Chertkov, Michael; Netrapalli, Praneeth
2016-12-01
Inference and learning of graphical models are both well-studied problems in statistics and machine learning that have found many applications in science and engineering. However, exact inference is intractable in general graphical models, which suggests the problem of seeking the best approximation to a collection of random variables within some tractable family of graphical models. In this paper, we focus on the class of planar Ising models, for which exact inference is tractable using techniques of statistical physics. Based on these techniques and recent methods for planarity testing and planar embedding, we propose a greedy algorithm for learning the best planar Ising model to approximate an arbitrary collection of binary random variables (possibly from sample data). Given the set of all pairwise correlations among variables, we select a planar graph and optimal planar Ising model defined on this graph to best approximate that set of correlations. Finally, we demonstrate our method in simulations and for two applications: modeling senate voting records and identifying geo-chemical depth trends from Mars rover data.
NASA Astrophysics Data System (ADS)
Jensen, Kristoffer
2002-11-01
A timbre model is proposed for use in multiple applications. This model, which encompasses all voiced isolated musical instruments, has an intuitive parameter set, fixed size, and separates the sounds in dimensions akin to the timbre dimensions as proposed in timbre research. The analysis of the model parameters is fully documented, and it proposes, in particular, a method for the estimation of the difficult decay/release split-point. The main parameters of the model are the spectral envelope, the attack/release durations and relative amplitudes, and the inharmonicity and the shimmer and jitter (which provide both for the slow random variations of the frequencies and amplitudes, and also for additive noises). Some of the applications include synthesis, where a real-time application is being developed with an intuitive gui, classification, and search of sounds based on the content of the sounds, and a further understanding of acoustic musical instrument behavior. In order to present the background of the model, this presentation will start with sinusoidal A/S, some timbre perception research, then present the timbre model, show the validity for individual music instrument sounds, and finally introduce some expression additions to the model.
Animal Models of Atherosclerosis
Getz, Godfrey S.; Reardon, Catherine A.
2012-01-01
Atherosclerosis is a chronic inflammatory disorder that is the underlying cause of most cardiovascular disease. Both cells of the vessel wall and cells of the immune system participate in atherogenesis. This process is heavily influenced by plasma lipoproteins, genetics and the hemodynamics of the blood flow in the artery. A variety of small and large animal models have been used to study the atherogenic process. No model is ideal as each has its own advantages and limitations with respect to manipulation of the atherogenic process and modeling human atherosclerosis or lipoprotein profile. Useful large animal models include pigs, rabbits and non-human primates. Due in large part to the relative ease of genetic manipulation and the relatively short time frame for the development of atherosclerosis, murine models are currently the most extensively used. While not all aspects of murine atherosclerosis are identical to humans, studies using murine models have suggested potential biological processes and interactions that underlie this process. As it becomes clear that different factors may influence different stages of lesion development, the use of mouse models with the ability to turn on or delete proteins or cells in tissue specific and temporal manner will be very valuable. PMID:22383700
Model molecules mimicking asphaltenes.
Sjöblom, Johan; Simon, Sébastien; Xu, Zhenghe
2015-04-01
Asphalthenes are typically defined as the fraction of petroleum insoluble in n-alkanes (typically heptane, but also hexane or pentane) but soluble in toluene. This fraction causes problems of emulsion formation and deposition/precipitation during crude oil production, processing and transport. From the definition it follows that asphaltenes are not a homogeneous fraction but is composed of molecules polydisperse in molecular weight, structure and functionalities. Their complexity makes the understanding of their properties difficult. Proper model molecules with well-defined structures which can resemble the properties of real asphaltenes can help to improve this understanding. Over the last ten years different research groups have proposed different asphaltene model molecules and studied them to determine how well they can mimic the properties of asphaltenes and determine the mechanisms behind the properties of asphaltenes. This article reviews the properties of the different classes of model compounds proposed and present their properties by comparison with fractionated asphaltenes. After presenting the interest of developing model asphaltenes, the composition and properties of asphaltenes are presented, followed by the presentation of approaches and accomplishments of different schools working on asphaltene model compounds. The presentation of bulk and interfacial properties of perylene-based model asphaltene compounds developed by Sjöblom et al. is the subject of the next part. Finally the emulsion-stabilization properties of fractionated asphaltenes and model asphaltene compounds is presented and discussed.
Aydoğdu, A; Frasca, P; D'Apice, C; Manzo, R; Thornton, J M; Gachomo, B; Wilson, T; Cheung, B; Tariq, U; Saidel, W; Piccoli, B
2017-02-21
In this paper we introduce a mathematical model to study the group dynamics of birds resting on wires. The model is agent-based and postulates attraction-repulsion forces between the interacting birds: the interactions are "topological", in the sense that they involve a given number of neighbors irrespective of their distance. The model is first mathematically analyzed and then simulated to study its main properties: we observe that the model predicts birds to be more widely spaced near the borders of each group. We compare the results from the model with experimental data, derived from the analysis of pictures of pigeons and starlings taken in New Jersey: two different image elaboration protocols allow us to establish a good agreement with the model and to quantify its main parameters. We also discuss the potential handedness of the birds, by analyzing the group organization features and the group dynamics at the arrival of new birds. Finally, we propose a more refined mathematical model that describes landing and departing birds by suitable stochastic processes.
Cestari, Andrea
2013-01-01
Predictive modeling is emerging as an important knowledge-based technology in healthcare. The interest in the use of predictive modeling reflects advances on different fronts such as the availability of health information from increasingly complex databases and electronic health records, a better understanding of causal or statistical predictors of health, disease processes and multifactorial models of ill-health and developments in nonlinear computer models using artificial intelligence or neural networks. These new computer-based forms of modeling are increasingly able to establish technical credibility in clinical contexts. The current state of knowledge is still quite young in understanding the likely future direction of how this so-called 'machine intelligence' will evolve and therefore how current relatively sophisticated predictive models will evolve in response to improvements in technology, which is advancing along a wide front. Predictive models in urology are gaining progressive popularity not only for academic and scientific purposes but also into the clinical practice with the introduction of several nomograms dealing with the main fields of onco-urology.
Atmospheric Models for Aerocapture
NASA Technical Reports Server (NTRS)
Justus, C. G.; Duvall, Aleta L.; Keller, Vernon W.
2004-01-01
There are eight destinations in the solar System with sufficient atmosphere for aerocapture to be a viable aeroassist option - Venus, Earth, Mars, Jupiter, Saturn and its moon Titan, Uranus, and Neptune. Engineering-level atmospheric models for four of these targets (Earth, Mars, Titan, and Neptune) have been developed for NASA to support systems analysis studies of potential future aerocapture missions. Development of a similar atmospheric model for Venus has recently commenced. An important capability of all of these models is their ability to simulate quasi-random density perturbations for Monte Carlo analyses in developing guidance, navigation and control algorithm, and for thermal systems design. Similarities and differences among these atmospheric models are presented, with emphasis on the recently developed Neptune model and on planned characteristics of the Venus model. Example applications for aerocapture are also presented and illustrated. Recent updates to the Titan atmospheric model are discussed, in anticipation of applications for trajectory and atmospheric reconstruct of Huygens Probe entry at Titan.
Computationally modeling interpersonal trust
Lee, Jin Joo; Knox, W. Bradley; Wormwood, Jolie B.; Breazeal, Cynthia; DeSteno, David
2013-01-01
We present a computational model capable of predicting—above human accuracy—the degree of trust a person has toward their novel partner by observing the trust-related nonverbal cues expressed in their social interaction. We summarize our prior work, in which we identify nonverbal cues that signal untrustworthy behavior and also demonstrate the human mind's readiness to interpret those cues to assess the trustworthiness of a social robot. We demonstrate that domain knowledge gained from our prior work using human-subjects experiments, when incorporated into the feature engineering process, permits a computational model to outperform both human predictions and a baseline model built in naiveté of this domain knowledge. We then present the construction of hidden Markov models to investigate temporal relationships among the trust-related nonverbal cues. By interpreting the resulting learned structure, we observe that models built to emulate different levels of trust exhibit different sequences of nonverbal cues. From this observation, we derived sequence-based temporal features that further improve the accuracy of our computational model. Our multi-step research process presented in this paper combines the strength of experimental manipulation and machine learning to not only design a computational trust model but also to further our understanding of the dynamics of interpersonal trust. PMID:24363649
Multiscale Cloud System Modeling
NASA Technical Reports Server (NTRS)
Tao, Wei-Kuo; Moncrieff, Mitchell W.
2009-01-01
The central theme of this paper is to describe how cloud system resolving models (CRMs) of grid spacing approximately 1 km have been applied to various important problems in atmospheric science across a wide range of spatial and temporal scales and how these applications relate to other modeling approaches. A long-standing problem concerns the representation of organized precipitating convective cloud systems in weather and climate models. Since CRMs resolve the mesoscale to large scales of motion (i.e., 10 km to global) they explicitly address the cloud system problem. By explicitly representing organized convection, CRMs bypass restrictive assumptions associated with convective parameterization such as the scale gap between cumulus and large-scale motion. Dynamical models provide insight into the physical mechanisms involved with scale interaction and convective organization. Multiscale CRMs simulate convective cloud systems in computational domains up to global and have been applied in place of contemporary convective parameterizations in global models. Multiscale CRMs pose a new challenge for model validation, which is met in an integrated approach involving CRMs, operational prediction systems, observational measurements, and dynamical models in a new international project: the Year of Tropical Convection, which has an emphasis on organized tropical convection and its global effects.
Probabilistic modeling of earthquakes
NASA Astrophysics Data System (ADS)
Duputel, Z.; Jolivet, R.; Jiang, J.; Simons, M.; Rivera, L. A.; Ampuero, J. P.; Gombert, B.; Minson, S. E.
2015-12-01
By exploiting increasing amounts of geophysical data we are able to produce increasingly sophisticated fault slip models. Such detailed models, while they are essential ingredients towards better understanding fault mechanical behavior, can only inform us in a meaningful way if we can assign uncertainties to the inferred slip parameters. This talk will present our recent efforts to infer fault slip models with realistic error estimates. Bayesian analysis is a useful tool for this purpose as it handles uncertainty in a natural way. One of the biggest obstacles to significant progress in observational earthquake source modeling arises from imperfect predictions of geodetic and seismic data due to uncertainties in the material parameters and fault geometries used in our forward models - the impact of which are generally overlooked. We recently developed physically based statistics for the model prediction error and showed how to account for inaccuracies in the Earth model elastic parameters. We will present applications of this formalism to recent large earthquakes such as the 2014 Pisagua earthquake. We will also discuss novel approaches to integrate the large amount of information available from GPS, InSAR, tide-gauge, tsunami and seismic data.
Multiscale Cloud System Modeling
NASA Technical Reports Server (NTRS)
Tao, Wei-Kuo; Moncrieff, Mitchell W.
2009-01-01
The central theme of this paper is to describe how cloud system resolving models (CRMs) of grid spacing approximately 1 km have been applied to various important problems in atmospheric science across a wide range of spatial and temporal scales and how these applications relate to other modeling approaches. A long-standing problem concerns the representation of organized precipitating convective cloud systems in weather and climate models. Since CRMs resolve the mesoscale to large scales of motion (i.e., 10 km to global) they explicitly address the cloud system problem. By explicitly representing organized convection, CRMs bypass restrictive assumptions associated with convective parameterization such as the scale gap between cumulus and large-scale motion. Dynamical models provide insight into the physical mechanisms involved with scale interaction and convective organization. Multiscale CRMs simulate convective cloud systems in computational domains up to global and have been applied in place of contemporary convective parameterizations in global models. Multiscale CRMs pose a new challenge for model validation, which is met in an integrated approach involving CRMs, operational prediction systems, observational measurements, and dynamical models in a new international project: the Year of Tropical Convection, which has an emphasis on organized tropical convection and its global effects.
Spatiochromatic model of vision
NASA Astrophysics Data System (ADS)
Moorhead, Ian R.
1996-04-01
A computer model of human spatiochromatic vision, based on the scheme proposed by De Valois and De Valois has been developed. The implementation of the model enables true color 2-D images to be processed. The input consists of cone signals at each pixel. Subsequent levels of the model are represented by arrays of activity corresponding to the equivalent neural activity. The implementation allows the behavior of different stages of the model -- retinal and cortical -- to be studied with different varieties of spatial and chromatic stimuli of any complexity. In addition the model is extensible to allow different types of neural mechanisms and cortical demultiplexing processes to be incorporated. As well as providing qualitative insight into the operation of the different stages of the model the implementation also permits quantitative predictions to be made. Both increment threshold and hue naming results are predicted by the model, but the accuracy of these predictions is contingent upon an appropriate choice of adaptation state at the retinal cone and ganglion cell level.