State-space size considerations for disease-progression models.
Regnier, Eva D; Shechter, Steven M
2013-09-30
Markov models of disease progression are widely used to model transitions in patients' health state over time. Usually, patients' health status may be classified according to a set of ordered health states. Modelers lump together similar health states into a finite and usually small, number of health states that form the basis of a Markov chain disease-progression model. This increases the number of observations used to estimate each parameter in the transition probability matrix. However, lumping together observably distinct health states also obscures distinctions among them and may reduce the predictive power of the model. Moreover, as we demonstrate, precision in estimating the model parameters does not necessarily improve as the number of states in the model declines. This paper explores the tradeoff between lumping error introduced by grouping distinct health states and sampling error that arises when there are insufficient patient data to precisely estimate the transition probability matrix. Copyright © 2013 John Wiley & Sons, Ltd.
State-space modeling of population sizes and trends in Nihoa Finch and Millerbird
Gorresen, P. Marcos; Brinck, Kevin W.; Camp, Richard J.; Farmer, Chris; Plentovich, Sheldon M.; Banko, Paul C.
2016-01-01
Both of the 2 passerines endemic to Nihoa Island, Hawai‘i, USA—the Nihoa Millerbird (Acrocephalus familiaris kingi) and Nihoa Finch (Telespiza ultima)—are listed as endangered by federal and state agencies. Their abundances have been estimated by irregularly implemented fixed-width strip-transect sampling from 1967 to 2012, from which area-based extrapolation of the raw counts produced highly variable abundance estimates for both species. To evaluate an alternative survey method and improve abundance estimates, we conducted variable-distance point-transect sampling between 2010 and 2014. We compared our results to those obtained from strip-transect samples. In addition, we applied state-space models to derive improved estimates of population size and trends from the legacy time series of strip-transect counts. Both species were fairly evenly distributed across Nihoa and occurred in all or nearly all available habitat. Population trends for Nihoa Millerbird were inconclusive because of high within-year variance. Trends for Nihoa Finch were positive, particularly since the early 1990s. Distance-based analysis of point-transect counts produced mean estimates of abundance similar to those from strip-transects but was generally more precise. However, both survey methods produced biologically unrealistic variability between years. State-space modeling of the long-term time series of abundances obtained from strip-transect counts effectively reduced uncertainty in both within- and between-year estimates of population size, and allowed short-term changes in abundance trajectories to be smoothed into a long-term trend.
Large size space construction for space exploitation
Kondyurin, Alexey
2016-07-01
Space exploitation is impossible without large space structures. We need to make sufficient large volume of pressurized protecting frames for crew, passengers, space processing equipment, & etc. We have to be unlimited in space. Now the size and mass of space constructions are limited by possibility of a launch vehicle. It limits our future in exploitation of space by humans and in development of space industry. Large-size space construction can be made with using of the curing technology of the fibers-filled composites and a reactionable matrix applied directly in free space. For curing the fabric impregnated with a liquid matrix (prepreg) is prepared in terrestrial conditions and shipped in a container to orbit. In due time the prepreg is unfolded by inflating. After polymerization reaction, the durable construction can be fitted out with air, apparatus and life support systems. Our experimental studies of the curing processes in the simulated free space environment showed that the curing of composite in free space is possible. The large-size space construction can be developed. A project of space station, Moon base, Mars base, mining station, interplanet space ship, telecommunication station, space observatory, space factory, antenna dish, radiation shield, solar sail is proposed and overviewed. The study was supported by Humboldt Foundation, ESA (contract 17083/03/NL/SFe), NASA program of the stratospheric balloons and RFBR grants (05-08-18277, 12-08-00970 and 14-08-96011).
White, J Wilson; Nickols, Kerry J; Malone, Daniel; Carr, Mark H; Starr, Richard M; Cordoleani, Flora; Baskett, Marissa L; Hastings, Alan; Botsford, Louis W
2016-12-01
Integral projection models (IPMs) have a number of advantages over matrix-model approaches for analyzing size-structured population dynamics, because the latter require parameter estimates for each age or stage transition. However, IPMs still require appropriate data. Typically they are parameterized using individual-scale relationships between body size and demographic rates, but these are not always available. We present an alternative approach for estimating demographic parameters from time series of size-structured survey data using a Bayesian state-space IPM (SSIPM). By fitting an IPM in a state-space framework, we estimate unknown parameters and explicitly account for process and measurement error in a dataset to estimate the underlying process model dynamics. We tested our method by fitting SSIPMs to simulated data; the model fit the simulated size distributions well and estimated unknown demographic parameters accurately. We then illustrated our method using nine years of annual surveys of the density and size distribution of two fish species (blue rockfish, Sebastes mystinus, and gopher rockfish, S. carnatus) at seven kelp forest sites in California. The SSIPM produced reasonable fits to the data, and estimated fishing rates for both species that were higher than our Bayesian prior estimates based on coast-wide stock assessment estimates of harvest. That improvement reinforces the value of being able to estimate demographic parameters from local-scale monitoring data. We highlight a number of key decision points in SSIPM development (e.g., open vs. closed demography, number of particles in the state-space filter) so that users can apply the method to their own datasets. © 2016 by the Ecological Society of America.
Curreri, Peter A.; Detweiler, Michael
2010-01-01
Creating large space habitats by launching all materials from Earth is prohibitively expensive. Using space resources and space based labor to build space solar power satellites can yield extraordinary profits after a few decades. The economic viability of this program depends on the use of space resources and space labor. To maximize the return on the investment, the early use of high density bolo habitats is required. Other shapes do not allow for the small initial scale required for a quick population increase in space. This study found that 5 Man Year, or 384 person bolo high density habitats will be the most economically feasible for a program started at year 2010 and will cause a profit by year 24 of the program, put over 45,000 people into space, and create a large system of space infrastructure for the further exploration and development of space.
Kassemi, Mohammad; Thompson, David
2016-09-01
An analytic Population Balance Equation model is used to assess the efficacy of citrate, pyrophosphate, and augmented fluid intake as dietary countermeasures aimed at reducing the risk of renal stone formation for astronauts. The model uses the measured biochemical profile of the astronauts as input and predicts the steady-state size distribution of the nucleating, growing, and agglomerating renal calculi subject to biochemical changes brought about by administration of these dietary countermeasures. Numerical predictions indicate that an increase in citrate levels beyond its average normal ground-based urinary values is beneficial but only to a limited extent. Unfortunately, results also indicate that any decline in the citrate levels during space travel below its normal urinary values on Earth can easily move the astronaut into the stone-forming risk category. Pyrophosphate is found to be an effective inhibitor since numerical predictions indicate that even at quite small urinary concentrations, it has the potential of shifting the maximum crystal aggregate size to a much smaller and plausibly safer range. Finally, our numerical results predict a decline in urinary volume below 1.5 liters/day can act as a dangerous promoter of renal stone development in microgravity while urinary volume levels of 2.5-3 liters/day can serve as effective space countermeasures.
Directory of Open Access Journals (Sweden)
J Rasmus Nielsen
Full Text Available Trawl survey data with high spatial and seasonal coverage were analysed using a variant of the Log Gaussian Cox Process (LGCP statistical model to estimate unbiased relative fish densities. The model estimates correlations between observations according to time, space, and fish size and includes zero observations and over-dispersion. The model utilises the fact the correlation between numbers of fish caught increases when the distance in space and time between the fish decreases, and the correlation between size groups in a haul increases when the difference in size decreases. Here the model is extended in two ways. Instead of assuming a natural scale size correlation, the model is further developed to allow for a transformed length scale. Furthermore, in the present application, the spatial- and size-dependent correlation between species was included. For cod (Gadus morhua and whiting (Merlangius merlangus, a common structured size correlation was fitted, and a separable structure between the time and space-size correlation was found for each species, whereas more complex structures were required to describe the correlation between species (and space-size. The within-species time correlation is strong, whereas the correlations between the species are weaker over time but strong within the year.
DEFF Research Database (Denmark)
Nielsen, J. Rasmus; Kristensen, Kasper; Lewy, Peter
2014-01-01
Trawl survey data with high spatial and seasonal coverage were analysed using a variant of the Log Gaussian Cox Process (LGCP) statistical model to estimate unbiased relative fish densities. The model estimates correlations between observations according to time, space, and fish size and includes...
Sizing-tube-fin space radiators
Peoples, J. A.
1978-01-01
Temperature and size considerations of the tube fin space radiator were characterized by charts and equations. An approach of accurately assessing rejection capability commensurate with a phase A/B level output is reviewed. A computer program, based on Mackey's equations, is also presented which sizes the rejection area for a given thermal load. The program also handles the flow and thermal considerations of the film coefficient.
Kassemi, Mohammad; Thompson, David
2016-09-01
An analytical Population Balance Equation model is developed and used to assess the risk of critical renal stone formation for astronauts during future space missions. The model uses the renal biochemical profile of the subject as input and predicts the steady-state size distribution of the nucleating, growing, and agglomerating calcium oxalate crystals during their transit through the kidney. The model is verified through comparison with published results of several crystallization experiments. Numerical results indicate that the model is successful in clearly distinguishing between 1-G normal and 1-G recurrent stone-former subjects based solely on their published 24-h urine biochemical profiles. Numerical case studies further show that the predicted renal calculi size distribution for a microgravity astronaut is closer to that of a recurrent stone former on Earth rather than to a normal subject in 1 G. This interestingly implies that the increase in renal stone risk level in microgravity is relatively more significant for a normal person than a stone former. However, numerical predictions still underscore that the stone-former subject carries by far the highest absolute risk of critical stone formation during space travel.
Controls of eolian dune size and spacing
Lancaster, N.
1988-11-01
Data for the Namib and Gran Desierto sand seas suggest that the controls of dune size and spacing are complex. The relation between dune height and spacing varies with dune type and location and reflects both dune dynamics (vertical accretion vs. migration or extension) and availability of sand. There is no general relation between dune spacing and grain size. In the Namib sand sea the height of compound and complex dunes (draas) is inversely proportional to potential sand-transport rates, whereas the height of dunes superimposed on their flanks varies directly with potential sand-transport rates. These observations can be combined with data on dune spacing to demonstrate the existence of a hierarchy of eolian dunes, each element of which responds to variations in sand-transport rates at different temporal and spatial scales. Whereas the morphology of individual simple dunes and superimposed dunes on draas is related to contemporary rates and directions of sand transport, the morphology and development of draas reflects long-term and regional patterns of sand transport and deposition.
National Oceanic and Atmospheric Administration, Department of Commerce — Collection includes presentation materials and outputs from operational space environment models produced by the NOAA Space Weather Prediction Center (SWPC) and...
Space debris: modeling and detectability
Wiedemann, C.; Lorenz, J.; Radtke, J.; Kebschull, C.; Horstmann, A.; Stoll, E.
2017-01-01
High precision orbit determination is required for the detection and removal of space debris. Knowledge of the distribution of debris objects in orbit is necessary for orbit determination by active or passive sensors. The results can be used to investigate the orbits on which objects of a certain size at a certain frequency can be found. The knowledge of the orbital distribution of the objects as well as their properties in accordance with sensor performance models provide the basis for estimating the expected detection rates. Comprehensive modeling of the space debris environment is required for this. This paper provides an overview of the current state of knowledge about the space debris environment. In particular non-cataloged small objects are evaluated. Furthermore, improvements concerning the update of the current space debris model are addressed. The model of the space debris environment is based on the simulation of historical events, such as fragmentations due to explosions and collisions that actually occurred in Earth orbits. The orbital distribution of debris is simulated by propagating the orbits considering all perturbing forces up to a reference epoch. The modeled object population is compared with measured data and validated. The model provides a statistical distribution of space objects, according to their size and number. This distribution is based on the correct consideration of orbital mechanics. This allows for a realistic description of the space debris environment. Subsequently, a realistic prediction can be provided concerning the question, how many pieces of debris can be expected on certain orbits. To validate the model, a software tool has been developed which allows the simulation of the observation behavior of ground-based or space-based sensors. Thus, it is possible to compare the results of published measurement data with simulated detections. This tool can also be used for the simulation of sensor measurement campaigns. It is
Size Effect in Continuum Modeling
Energy Technology Data Exchange (ETDEWEB)
Lu, Wei-Yang [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Foulk, James W. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Huestis, Edwin M. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Connelly, Kevin [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Song, Bo [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Yang, Nancy Y. C. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Engineered Materials
2008-09-01
The mechanical properties of some materials (Cu, Ni, Ag, etc.) have been shown to develop strong dependence on the geometric dimensions, resulting in a size effect. Several theories have been proposed to model size effects, but have been based on very few experiments conducted at appropriate scales. Some experimental results implied that size effects are caused by increasing strain gradients and have been used to confirm many strain gradient theories. On the other hand, some recent experiments show that a size effect exists in the absence of strain gradients. This report describes a brief analytical and experimental study trying to clarify the material and experimental issues surrounding the most influential size-effect experiments by Fleck et al (1994). This effort is to understand size effects intended to further develop predictive models.
Modeling Size Polydisperse Granular Flows
Lueptow, Richard M.; Schlick, Conor P.; Isner, Austin B.; Umbanhowar, Paul B.; Ottino, Julio M.
2014-11-01
Modeling size segregation of granular materials has important applications in many industrial processes and geophysical phenomena. We have developed a continuum model for granular multi- and polydisperse size segregation based on flow kinematics, which we obtain from discrete element method (DEM) simulations. The segregation depends on dimensionless control parameters that are functions of flow rate, particle sizes, collisional diffusion coefficient, shear rate, and flowing layer depth. To test the theoretical approach, we model segregation in tri-disperse quasi-2D heap flow and log-normally distributed polydisperse quasi-2D chute flow. In both cases, the segregated particle size distributions match results from full-scale DEM simulations and experiments. While the theory was applied to size segregation in steady quasi-2D flows here, the approach can be readily generalized to include additional drivers of segregation such as density and shape as well as other geometries where the flow field can be characterized including rotating tumbler flow and three-dimensional bounded heap flow. Funded by The Dow Chemical Company and NSF Grant CMMI-1000469.
Modeling and Sizing of Supercapacitors
Directory of Open Access Journals (Sweden)
PETREUS, D.
2008-06-01
Full Text Available Faced with numerous challenges raised by the requirements of the modern industries for higher power and higher energy, supercapacitors study started playing an important role in offering viable solutions for some of these requirements. This paper presents the surface redox reactions based modeling in order to study the origin of high capacity of EDLC (electrical double-layer capacitor for better understanding the working principles of supercapacitors. Some application-dependent sizing methods are also presented since proper sizing can increase the efficiency and the life cycle of the supercapacitor based systems.
Space market model space industry input-output model
Hodgin, Robert F.; Marchesini, Roberto
1987-01-01
The goal of the Space Market Model (SMM) is to develop an information resource for the space industry. The SMM is intended to contain information appropriate for decision making in the space industry. The objectives of the SMM are to: (1) assemble information related to the development of the space business; (2) construct an adequate description of the emerging space market; (3) disseminate the information on the space market to forecasts and planners in government agencies and private corporations; and (4) provide timely analyses and forecasts of critical elements of the space market. An Input-Output model of market activity is proposed which are capable of transforming raw data into useful information for decision makers and policy makers dealing with the space sector.
Modelling of Size Effect with Regularised Continua
Directory of Open Access Journals (Sweden)
H. Askes
2004-01-01
Full Text Available A nonlocal damage continuum and a viscoplastic damage continuum are used to model size effects. Three-point bending specimens are analysed, whereby a distinction is made between unnotched specimens, specimens with a constant notch and specimens with a proportionally scaled notch. Numerical finite element simulations have been performed for specimen sizes in a range of 1:64. Size effects are established in terms of nominal strength and compared to existing size effect models from the literature.
Simplicial models for trace spaces
DEFF Research Database (Denmark)
Raussen, Martin
motivation stems from certain models for concurrent computation. So far, spaces of d-paths and their topological invariants have only been determined in cases that were elementary to overlook. In this paper, we develop a systematic approach describing spaces of directed paths - up to homotopy equivalence...... - as prodsimplicial complexes (with products of simplices as building blocks). This method makes use of certain poset categories of binary matrices and applies to a class of directed spaces that arise from a class of models of computation; still restricted but with a fair amount of generality. In the final section......, we outline a generalization to model spaces known as Higher Dimensional Automata. In particular, we describe algorithms that allow to determine not only the fundamental category of such amodel space, but all homological invariants of spaces of directed paths within it. The prodsimplical complexes...
Weinreich, Daniel M; Knies, Jennifer L
2013-10-01
The functional synthesis uses experimental methods from molecular biology, biochemistry and structural biology to decompose evolutionarily important mutations into their more proximal mechanistic determinants. However these methods are technically challenging and expensive. Noting strong formal parallels between R.A. Fisher's geometric model of adaptation and a recent model for the phenotypic basis of protein evolution, we sought to use the former to make inferences into the latter using data on pairwise fitness epistasis between mutations. We present an analytic framework for classifying pairs of mutations with respect to similarity of underlying mechanism on this basis, and also show that these data can yield an estimate of the number of mutationally labile phenotypes underlying fitness effects. We use computer simulations to explore the robustness of our approach to violations of analytic assumptions and analyze several recently published datasets. This work provides a theoretical complement to the functional synthesis as well as a novel test of Fisher's geometric model.
Space Flight Cable Model Development
Spak, Kaitlin
2013-01-01
This work concentrates the modeling efforts presented in last year's VSGC conference paper, "Model Development for Cable-Harnessed Beams." The focus is narrowed to modeling of space-flight cables only, as a reliable damped cable model is not yet readily available and is necessary to continue modeling cable-harnessed space structures. New experimental data is presented, eliminating the low-frequency noise that plagued the first year's efforts. The distributed transfer function method is applied to a single section of space flight cable for Euler-Bernoulli and shear beams. The work presented here will be developed into a damped cable model that can be incorporated into an interconnected beam-cable system. The overall goal of this work is to accurately predict natural frequencies and modal damping ratios for cabled space structures.
Estimating Functions of Distributions Defined over Spaces of Unknown Size
Directory of Open Access Journals (Sweden)
David H. Wolpert
2013-10-01
Full Text Available We consider Bayesian estimation of information-theoretic quantities from data, using a Dirichlet prior. Acknowledging the uncertainty of the event space size m and the Dirichlet prior’s concentration parameter c, we treat both as random variables set by a hyperprior. We show that the associated hyperprior, P(c, m, obeys a simple “Irrelevance of Unseen Variables” (IUV desideratum iff P(c, m = P(cP(m. Thus, requiring IUV greatly reduces the number of degrees of freedom of the hyperprior. Some information-theoretic quantities can be expressed multiple ways, in terms of different event spaces, e.g., mutual information. With all hyperpriors (implicitly used in earlier work, different choices of this event space lead to different posterior expected values of these information-theoretic quantities. We show that there is no such dependence on the choice of event space for a hyperprior that obeys IUV. We also derive a result that allows us to exploit IUV to greatly simplify calculations, like the posterior expected mutual information or posterior expected multi-information. We also use computer experiments to favorably compare an IUV-based estimator of entropy to three alternative methods in common use. We end by discussing how seemingly innocuous changes to the formalization of an estimation problem can substantially affect the resultant estimates of posterior expectations.
Two-level method with coarse space size independent convergence
Energy Technology Data Exchange (ETDEWEB)
Vanek, P.; Brezina, M. [Univ. of Colorado, Denver, CO (United States); Tezaur, R.; Krizkova, J. [UWB, Plzen (Czech Republic)
1996-12-31
The basic disadvantage of the standard two-level method is the strong dependence of its convergence rate on the size of the coarse-level problem. In order to obtain the optimal convergence result, one is limited to using a coarse space which is only a few times smaller than the size of the fine-level one. Consequently, the asymptotic cost of the resulting method is the same as in the case of using a coarse-level solver for the original problem. Today`s two-level domain decomposition methods typically offer an improvement by yielding a rate of convergence which depends on the ratio of fine and coarse level only polylogarithmically. However, these methods require the use of local subdomain solvers for which straightforward application of iterative methods is problematic, while the usual application of direct solvers is expensive. We suggest a method diminishing significantly these difficulties.
Noncommutative spaces from matrix models
Lu, Lei
Noncommutative (NC) spaces commonly arise as solutions to matrix model equations of motion. They are natural generalizations of the ordinary commutative spacetime. Such spaces may provide insights into physics close to the Planck scale, where quantum gravity becomes relevant. Although there has been much research in the literature, aspects of these NC spaces need further investigation. In this dissertation, we focus on properties of NC spaces in several different contexts. In particular, we study exact NC spaces which result from solutions to matrix model equations of motion. These spaces are associated with finite-dimensional Lie-algebras. More specifically, they are two-dimensional fuzzy spaces that arise from a three-dimensional Yang-Mills type matrix model, four-dimensional tensor-product fuzzy spaces from a tensorial matrix model, and Snyder algebra from a five-dimensional tensorial matrix model. In the first part of this dissertation, we study two-dimensional NC solutions to matrix equations of motion of extended IKKT-type matrix models in three-space-time dimensions. Perturbations around the NC solutions lead to NC field theories living on a two-dimensional space-time. The commutative limit of the solutions are smooth manifolds which can be associated with closed, open and static two-dimensional cosmologies. One particular solution is a Lorentzian fuzzy sphere, which leads to essentially a fuzzy sphere in the Minkowski space-time. In the commutative limit, this solution leads to an induced metric that does not have a fixed signature, and have a non-constant negative scalar curvature, along with singularities at two fixed latitudes. The singularities are absent in the matrix solution which provides a toy model for resolving the singularities of General relativity. We also discussed the two-dimensional fuzzy de Sitter space-time, which has irreducible representations of su(1,1) Lie-algebra in terms of principal, complementary and discrete series. Field
Space market model development project
Bishop, Peter C.
1987-01-01
The objectives of the research program, Space Market Model Development Project, (Phase 1) were: (1) to study the need for business information in the commercial development of space; and (2) to propose a design for an information system to meet the identified needs. Three simultaneous research strategies were used in proceeding toward this goal: (1) to describe the space business information which currently exists; (2) to survey government and business representatives on the information they would like to have; and (3) to investigate the feasibility of generating new economical information about the space industry.
Model space of economic events
Romanovsky, M. Yu.
A method for constructing the model or virtual space of economic events when economic objects can be considered as material ones is suggested. We describe change of share rates in time at stock markets as the potential difference of attracted bodies in time in this virtual space. Each share of each enterprise is displayed by a single particle with a unit “charge”. It is shown that the random value of potential difference at the origin of coordinates measured at a definite time interval has the probability density coinciding with the known distribution of “Levy flights” or “Levy walks”. A distribution of alteration in time of the “Standard and Poor” index value obtained by Mantegna and Stanley (they shown that it is the “Levy walks” distribution too) (Mantegna and Stanley, Nature 376 (1995) 46) is used for determination of the introduced potential dependence on coordinates in the model space. A simple phenomenological model of interaction potential is introduced. The potential law of each particle turns out to be closed to r-2.14 in the minimum possible three-dimensional model space. This model permits calculation of time of random potential correlations at a certain point of the model space. These correlations could characterize the time period of making a decision by an investor at stock exchange. It is shown that this time is notably shorter in unstable periods (1987). A “microscopical” model of interaction in the virtual space is also discussed.
Jones, Thomas C.; Dorsey, John T.; Doggett, William R.
2015-01-01
The Tendon-Actuated Lightweight In-Space MANipulator (TALISMAN) is a versatile long-reach robotic manipulator that is currently being tested at NASA Langley Research Center. TALISMAN is designed to be highly mass-efficient and multi-mission capable, with applications including asteroid retrieval and manipulation, in-space servicing, and astronaut and payload positioning. The manipulator uses a modular, periodic, tension-compression design that lends itself well to analytical modeling. Given the versatility of application for TALISMAN, a structural sizing methodology was developed that could rapidly assess mass and configuration sensitivities for any specified operating work space, applied loads and mission requirements. This methodology allows the systematic sizing of the key structural members of TALISMAN, which include the truss arm links, the spreaders and the tension elements. This paper summarizes the detailed analytical derivations and methodology that support the structural sizing approach and provides results from some recent TALISMAN designs developed for current and proposed mission architectures.
Effect of crack size on gas leakage characteristics in a confined space
Energy Technology Data Exchange (ETDEWEB)
Sung, Kun Hyuk; Ryou, Hong Sun; Yoon, Kee Bong; Lee, Hy Uk; Bang, Joo Won [Chung-Ang University, Seoul (Korea, Republic of); Li, Longnan; Choi, Jin Wook; Kim, Dae Joong [Sogang University, Seoul (Korea, Republic of)
2016-07-15
We numerically investigated the influence of crack size on gas leakage characteristics in a confined space. The real scale model of underground Combined cycle power plant (CCPP) was taken for simulating gas leakage characteristics for different crack sizes such as 10 mm, 15 mm and 20 mm. The commercial code of Fluent (v.16.1) was used for three-dimensional simulation. In particular, a risk region showing such a probability of ignition was newly suggested with the concept of Lower flammable limit (LFL) of methane gas used in the present study to characterize the gas propagation and the damage area in space. From the results, the longitudinal and transverse leakage distances were estimated and analyzed for quantitative evaluation of risk area. The crack size was found to have a great impact on the longitudinal leakage distance, showing an increasing tendency with the crack size. In case of a crack size of 20 mm, the longitudinal leakage distance suddenly increased after 180 s, whereas it remained constant after 2 s in the other cases. This is because a confinement effect, which is caused by circulation flows in the whole space, increased the gas concentration near the gas flow released from the crack. The confinement effect is thus closely associated with the released mass flow rate changing with the crack size. This result would be useful in designing the gas detector system for preventing accidents in the confined space as like CCPP.
Probabilistic Sizing and Verification of Space Ceramic Structures
Denaux, David; Ballhause, Dirk; Logut, Daniel; Lucarelli, Stefano; Coe, Graham; Laine, Benoit
2012-07-01
Sizing of ceramic parts is best optimised using a probabilistic approach which takes into account the preexisting flaw distribution in the ceramic part to compute a probability of failure of the part depending on the applied load, instead of a maximum allowable load as for a metallic part. This requires extensive knowledge of the material itself but also an accurate control of the manufacturing process. In the end, risk reduction approaches such as proof testing may be used to lower the final probability of failure of the part. Sizing and verification of ceramic space structures have been performed by Astrium for more than 15 years, both with Zerodur and SiC: Silex telescope structure, Seviri primary mirror, Herschel telescope, Formosat-2 instrument, and other ceramic structures flying today. Throughout this period of time, Astrium has investigated and developed experimental ceramic analysis tools based on the Weibull probabilistic approach. In the scope of the ESA/ESTEC study: “Mechanical Design and Verification Methodologies for Ceramic Structures”, which is to be concluded in the beginning of 2012, existing theories, technical state-of-the-art from international experts, and Astrium experience with probabilistic analysis tools have been synthesized into a comprehensive sizing and verification method for ceramics. Both classical deterministic and more optimised probabilistic methods are available, depending on the criticality of the item and on optimisation needs. The methodology, based on proven theory, has been successfully applied to demonstration cases and has shown its practical feasibility.
Estimating the size of the solution space of metabolic networks
Directory of Open Access Journals (Sweden)
Mulet Roberto
2008-05-01
Full Text Available Abstract Background Cellular metabolism is one of the most investigated system of biological interactions. While the topological nature of individual reactions and pathways in the network is quite well understood there is still a lack of comprehension regarding the global functional behavior of the system. In the last few years flux-balance analysis (FBA has been the most successful and widely used technique for studying metabolism at system level. This method strongly relies on the hypothesis that the organism maximizes an objective function. However only under very specific biological conditions (e.g. maximization of biomass for E. coli in reach nutrient medium the cell seems to obey such optimization law. A more refined analysis not assuming extremization remains an elusive task for large metabolic systems due to algorithmic limitations. Results In this work we propose a novel algorithmic strategy that provides an efficient characterization of the whole set of stable fluxes compatible with the metabolic constraints. Using a technique derived from the fields of statistical physics and information theory we designed a message-passing algorithm to estimate the size of the affine space containing all possible steady-state flux distributions of metabolic networks. The algorithm, based on the well known Bethe approximation, can be used to approximately compute the volume of a non full-dimensional convex polytope in high dimensions. We first compare the accuracy of the predictions with an exact algorithm on small random metabolic networks. We also verify that the predictions of the algorithm match closely those of Monte Carlo based methods in the case of the Red Blood Cell metabolic network. Then we test the effect of gene knock-outs on the size of the solution space in the case of E. coli central metabolism. Finally we analyze the statistical properties of the average fluxes of the reactions in the E. coli metabolic network. Conclusion We propose a
Summary statistics for size over space and time.
Gorea, Andrei; Belkoura, Seddik; Solomon, Joshua A
2014-08-25
A number of studies have investigated how the visual system extracts the average feature-value of an ensemble of simultaneously or sequentially delivered stimuli. In this study we model these two processes within the unitary framework of linear systems theory. The specific feature value used in this investigation is size, which we define as the logarithm of a circle's diameter. Within each ensemble, sizes were drawn from a normal distribution. Average size discrimination was measured using ensembles of one and eight circles. These circles were presented simultaneously (display times: 13-427 ms), one at a time, or eight at a time (temporal-frequencies: 1.2-38 Hz). Thresholds for eight-item ensembles were lower than thresholds for one-item ensembles. Thresholds decreased by a factor of 1.3 for a 3,200% increase in display time, and decreased by the same factor for a 3,200% decrease in temporal frequency. Modeling and simulations show that the data are consistent with one readout of three to four items every 210 ms.
DEFF Research Database (Denmark)
Ravn-Jonsen, Lars
Ecosystem Management requires models that can link the ecosystem level to the operation level. This link can be created by an ecosystem production model. Because the function of the individual fish in the marine ecosystem, seen in trophic context, is closely related to its size, the model groups...... fish according to size. The model summarises individual predation events into ecosystem level properties, and thereby uses the law of conversation of mass as a framework. This paper provides the background, the conceptual model, basic assumptions, integration of fishing activities, mathematical...... completion, and a numeric implementation. Using two experiments, the model's ability to act as tool for economic production analysis and regulation design testing is demonstrated. The presented model is the simplest possible and is built on the principles of (i) size, as the attribute that determines...
Toups, Larry; Simon, Matthew; Smitherman, David; Spexarth, Gary
2012-01-01
NASA's Human Space Flight Architecture Team (HAT) is a multi-disciplinary, cross-agency study team that conducts strategic analysis of integrated development approaches for human and robotic space exploration architectures. During each analysis cycle, HAT iterates and refines the definition of design reference missions (DRMs), which inform the definition of a set of integrated capabilities required to explore multiple destinations. An important capability identified in this capability-driven approach is habitation, which is necessary for crewmembers to live and work effectively during long duration transits to and operations at exploration destinations beyond Low Earth Orbit (LEO). This capability is captured by an element referred to as the Deep Space Habitat (DSH), which provides all equipment and resources for the functions required to support crew safety, health, and work including: life support, food preparation, waste management, sleep quarters, and housekeeping.The purpose of this paper is to describe the design of the DSH capable of supporting crew during exploration missions. First, the paper describes the functionality required in a DSH to support the HAT defined exploration missions, the parameters affecting its design, and the assumptions used in the sizing of the habitat. Then, the process used for arriving at parametric sizing estimates to support additional HAT analyses is detailed. Finally, results from the HAT Cycle C DSH sizing are presented followed by a brief description of the remaining design trades and technological advancements necessary to enable the exploration habitation capability.
Autonomous shooting at middle size space debris objects from space-based APT laser systems
Gambi, J. M.; García del Pino, M. L.
2017-02-01
This paper is motivated by the need of removing middle size space debris objects. It deals with the problem of increasing the pointing accuracy while shooting at these objects by means of autonomous space-based APT systems endowed with very narrow laser beams. It is shown that shooting at these objects with these systems is the one single ballistic problem that becomes singular in space. This means that the shooting direction that is to be implemented by any of these systems to reach an object at a given instant can only be hopefully implemented after the object has been previously reached. Thus, the problem becomes backwards recurrent with no end for any object-system configuration, except when the LOS direction remains constant for some period of time. It is also shown that the implementation of the point-ahead angles from the data acquired prior to the respective shootings is essential to keep accuracy. In fact, one single omission during the action may cause errors larger than the size of the objects. As a consequence, we find that there is only one way for an autonomous system to minimize the pointing errors: any shooting sequence to any of these objects must be started when the transverse component of the relative velocity of the object with respect to the system is zero (actually, as close to zero as possible).
Sample size planning for classification models.
Beleites, Claudia; Neugebauer, Ute; Bocklitz, Thomas; Krafft, Christoph; Popp, Jürgen
2013-01-14
In biospectroscopy, suitably annotated and statistically independent samples (e.g. patients, batches, etc.) for classifier training and testing are scarce and costly. Learning curves show the model performance as function of the training sample size and can help to determine the sample size needed to train good classifiers. However, building a good model is actually not enough: the performance must also be proven. We discuss learning curves for typical small sample size situations with 5-25 independent samples per class. Although the classification models achieve acceptable performance, the learning curve can be completely masked by the random testing uncertainty due to the equally limited test sample size. In consequence, we determine test sample sizes necessary to achieve reasonable precision in the validation and find that 75-100 samples will usually be needed to test a good but not perfect classifier. Such a data set will then allow refined sample size planning on the basis of the achieved performance. We also demonstrate how to calculate necessary sample sizes in order to show the superiority of one classifier over another: this often requires hundreds of statistically independent test samples or is even theoretically impossible. We demonstrate our findings with a data set of ca. 2550 Raman spectra of single cells (five classes: erythrocytes, leukocytes and three tumour cell lines BT-20, MCF-7 and OCI-AML3) as well as by an extensive simulation that allows precise determination of the actual performance of the models in question. Copyright © 2012 Elsevier B.V. All rights reserved.
SpaceNet: Modeling and Simulating Space Logistics
Lee, Gene; Jordan, Elizabeth; Shishko, Robert; de Weck, Olivier; Armar, Nii; Siddiqi, Afreen
2008-01-01
This paper summarizes the current state of the art in interplanetary supply chain modeling and discusses SpaceNet as one particular method and tool to address space logistics modeling and simulation challenges. Fundamental upgrades to the interplanetary supply chain framework such as process groups, nested elements, and cargo sharing, enabled SpaceNet to model an integrated set of missions as a campaign. The capabilities and uses of SpaceNet are demonstrated by a step-by-step modeling and simulation of a lunar campaign.
SpaceNet: Modeling and Simulating Space Logistics
Lee, Gene; Jordan, Elizabeth; Shishko, Robert; de Weck, Olivier; Armar, Nii; Siddiqi, Afreen
2008-01-01
This paper summarizes the current state of the art in interplanetary supply chain modeling and discusses SpaceNet as one particular method and tool to address space logistics modeling and simulation challenges. Fundamental upgrades to the interplanetary supply chain framework such as process groups, nested elements, and cargo sharing, enabled SpaceNet to model an integrated set of missions as a campaign. The capabilities and uses of SpaceNet are demonstrated by a step-by-step modeling and simulation of a lunar campaign.
Benchmarking Ionizing Space Environment Models
Bourdarie, S.; Inguimbert, C.; Standarovski, D.; Vaillé, J.-R.; Sicard-Piet, A.; Falguere, D.; Ecoffet, R.; Poivey, C.; Lorfèvre, E.
2017-08-01
In-flight feedback data are collected, such as displacement damage doses, ionizing doses, and cumulated Single Event upset (SEU) on board various space vehicles and are compared to predictions performed with: 1) proton measurements performed with spectrometers data on board the same spacecraft if any and 2) protons spectrum predicted by the legacy AP8min model and the AP9 and Onera Proton Altitude Low models. When an accurate representation of the 3-D spacecraft shielding as well as appropriate ground calibrations are considered in the calculations, such comparisons provide powerful metrics to investigate engineering model accuracy. To describe >30 MeV trapped protons fluxes, the AP8 min model is found to provide closer predictions to observations than AP9 V1.30.001 (mean and perturbed mean).
Measurement of joint space width and erosion size
Sharp, JI; van der Heijde, D; Angwin, J; Duryea, J; Moens, HJB; Jacobs, JWG; Maillefert, JF; Strand, CV
2005-01-01
Measurement of radiographic abnormalities in metric units has been reported by several investigators during the last 15 years. Measurement of joint space in large joints has been employed in a few trials to evaluate therapy in osteoarthritis. Measurement of joint space width in small joints has been
Measurement of joint space width and erosion size
Sharp, JI; van der Heijde, D; Angwin, J; Duryea, J; Moens, HJB; Jacobs, JWG; Maillefert, JF; Strand, CV
2005-01-01
Measurement of radiographic abnormalities in metric units has been reported by several investigators during the last 15 years. Measurement of joint space in large joints has been employed in a few trials to evaluate therapy in osteoarthritis. Measurement of joint space width in small joints has been
THE USE OF MODELS IN URBAN SPACE PATTERN ANALYSIS ...
African Journals Online (AJOL)
spaces of a modest size is the Figure - Ground relationship or ... (Note the dominance of unstructured open spaces in the City Centre) ordering of ..... their rank. This settlement typology is the formative model of most towns founded by emperors ...
Mathematical model of a cell size checkpoint.
Directory of Open Access Journals (Sweden)
Marco Vilela
Full Text Available How cells regulate their size from one generation to the next has remained an enigma for decades. Recently, a molecular mechanism that links cell size and cell cycle was proposed in fission yeast. This mechanism involves changes in the spatial cellular distribution of two proteins, Pom1 and Cdr2, as the cell grows. Pom1 inhibits Cdr2 while Cdr2 promotes the G2 → M transition. Cdr2 is localized in the middle cell region (midcell whereas the concentration of Pom1 is highest at the cell tips and declines towards the midcell. In short cells, Pom1 efficiently inhibits Cdr2. However, as cells grow, the Pom1 concentration at midcell decreases such that Cdr2 becomes activated at some critical size. In this study, the chemistry of Pom1 and Cdr2 was modeled using a deterministic reaction-diffusion-convection system interacting with a deterministic model describing microtubule dynamics. Simulations mimicked experimental data from wild-type (WT fission yeast growing at normal and reduced rates; they also mimicked the behavior of a Pom1 overexpression mutant and WT yeast exposed to a microtubule depolymerizing drug. A mechanism linking cell size and cell cycle, involving the downstream action of Cdr2 on Wee1 phosphorylation, is proposed.
The Space Laser Business Model
2005-01-01
Creating long-duration, high-powered lasers, for satellites, that can withstand the type of optical misalignment and damage dished out by the unforgiving environment of space, is work that is unique to NASA. It is complicated, specific work, where each step forward is into uncharted territory. In the 1990s, as this technology was first being created, NASA gave free reign to a group of "laser jocks" to develop their own business model and supply the Space Agency with the technology it needed. It was still to be a part of NASA as a division of Goddard Space Flight Center, but would operate independently out of a remote office. The idea for this satellite laboratory was based on the Skunk Works concept at Lockheed Martin Corporation. Formerly known as the Lockheed Corporation, in 1943, the aerospace firm, realizing that the type of advanced research it needed done could not be performed within the confines of a larger company, allowed a group of researchers and engineers to essentially run their own microbusiness without the corporate oversight. The Skunk Works project, in Burbank, California, produced America s first jet fighter, the world s most successful spy plane (U-2), the first 3-times-the-speed-of-sound surveillance aircraft, and the F-117A Nighthawk Stealth Fighter. Boeing followed suit with its Phantom Works, an advanced research and development branch of the company that operates independent of the larger unit and is responsible for a great deal of its most cutting-edge research. NASA s version of this advanced business model was the Space Lidar Technology Center (SLTC), just south of Goddard, in College Park, Maryland. Established in 1998 under a Cooperative Agreement between Goddard and the University of Maryland s A. James Clark School of Engineering, it was a high-tech laser shop where a small group of specialists, never more than 20 employees, worked all hours of the day and night to create the cutting- edge technology the Agency required of them. Drs
My Life with State Space Models
DEFF Research Database (Denmark)
Lundbye-Christensen, Søren
2007-01-01
. The conceptual idea behind the state space model is that the evolution over time in the object we are observing and the measurement process itself are modelled separately. My very first serious analysis of a data set was done using a state space model, and since then I seem to have been "haunted" by state space...
Dynamic models in space and time
Elhorst, J.P.
2001-01-01
This paper presents a first-order autoregressive distributed lag model in both space and time. It is shown that this model encompasses a wide series of simpler models frequently used in the analysis of space-time data as well as models that better fit the data and have never been used before. A fram
Size of the lower third molar space in relation to age in Serbian population
Directory of Open Access Journals (Sweden)
Zelić Ksenija
2013-01-01
Full Text Available Background/Aim. It is considered that the shortage of space is the major cause of the third molar impaction. The aim of this study was to establish the frequency of insufficient lower third molar eruption space in Serbian population, to question the differences in this frequency in the subjects of different age, to determine the influence of the lower third molar space (retromolar space size on third molar eruption, and to investigate a possible correlation between the size of gonial angle and the space/third molar width ratio. Methods. Digital orthopantomograms were taken from 93 patients divided into two groups: early adult (16-18 years of age and adult (18-26 patients. Retromolar space, mesiodistal third molar crown width, gonial angle and eruption levels were measured. Results. The space/third molar width in early adult subjects was smaller (p < 0.0001 and insufficient space was significantly more frequent (p = 0.0003 than in adult patients. Considerably more third molars erupted in case of enough space in both age groups (p < 0.0001. There was no difference between the means of gonial angle size in relations to the available space. Conclusions. The retromolar space/third molar width ratio is more favorable in adult subjects. Gonial angle is not in correlation with the retromolar space/third molar width ratio. [Projekat Ministarstva nauke Republike Srbije, br. 45005
Estimating payload internal temperatures and radiator size for multimegawatt space platforms
Energy Technology Data Exchange (ETDEWEB)
Dobranich, D.
1987-08-01
A conceptual space platform consists of a payload, a power conditioning unit (PCU), and two radiators: the main radiator and a secondary radiator. A computer program was written to determine the required size of the two radiators and the temperatures of the PCU and payload for a given platform power level. An iterative approach is necessary because the required size of the main radiator depends on the size of the secondary radiator and vice versa. Also, the temperatures of the payload and PCU depend on the size of the radiators. The program user can subdivide the two radiators into any number of nodes to increase the accuracy of the radiant heat transfer solution. The use of more nodes also allows better prediction of the nonlinear temperature drop that occurs across the radiators as the working fluid deposits the platform's waste heat in the radiator. View factor expressions are automatically calculated for different choices of the number of nodes. The user can also select different separation distances between the various platform structures. A model is included to couple the radiant and conduction heat transfer that occurs between the payload and its meteoroid shell and between the PCU and its shell. Also, the program allows the use of a refrigerator to cool the payload. If a refrigerator is used, the program determines the amount of additional thermal power needed to run the refrigerator. The results of parametric calculations are included to demonstrate the use of the program.
Zador, Zsolt; Magzoub, Mazin; Jin, Songwan; Manley, Geoffrey T; Papadopoulos, Marios C; Verkman, A S
2008-03-01
Diffusion in brain extracellular space (ECS) is important for nonsynaptic intercellular communication, extracellular ionic buffering, and delivery of drugs and metabolites. We measured macromolecular diffusion in normally light-inaccessible regions of mouse brain by microfiberoptic epifluorescence photobleaching, in which a fiberoptic with a micron-size tip is introduced deep in brain tissue. In brain cortex, the diffusion of a noninteracting molecule [fluorescein isothiocyanate (FITC)-dextran, 70 kDa] was slowed 4.5 +/- 0.5-fold compared with its diffusion in water (D(o)/D), and was depth-independent down to 800 microm from the brain surface. Diffusion was significantly accelerated (D(o)/D of 2.9+/-0.3) in mice lacking the glial water channel aquaporin-4. FITC-dextran diffusion varied greatly in different regions of brain, with D(o)/D of 3.5 +/- 0.3 in hippocampus and 7.4 +/- 0.3 in thalamus. Remarkably, D(o)/D in deep brain was strongly dependent on solute size, whereas diffusion in cortex changed little with solute size. Mathematical modeling of ECS diffusion required nonuniform ECS dimensions in deep brain, which we call "heterometricity," to account for the size-dependent diffusion. Our results provide the first data on molecular diffusion in ECS deep in brain in vivo and demonstrate previously unrecognized hindrance and heterometricity for diffusion of large macromolecules in deep brain.
5-Dimensional Extended Space Model
Tsipenyuk, D. Yu.; Andreev, V. A.
2006-01-01
We put forward an idea that physical phenomena have to be treated in 5-dimensional space where the fifth coordinate is the interval S. Thus, we considered the (1+4) extended space G(T;X,Y,Z,S). In addition to Lorentz transformations (T;X), (T;Y), (T;Z) which are in (1+3)-dimensional Minkowski space, in the proposed (1+4)d extended space two other types of transformations exist in planes (T,S); (X,S), (Y,S), (Z,S) that converts massive particles into massless and vice versa. We also consider e...
Space Heating Load Estimation Procedure for CHP Systems sizing
Vocale, P.; Pagliarini, G.; Rainieri, S.
2015-11-01
Due to its environmental and energy benefits, the Combined Heat and Power (CHP) represents certainly an important measure to improve energy efficiency of buildings. Since the energy performance of the CHP systems strongly depends on the fraction of the useful cogenerated heat (i.e. the cogenerated heat that is actually used to meet building thermal demand), in building applications of CHP, it is necessary to know the space heating and cooling loads profile to optimise the system efficiency. When the heating load profile is unknown or difficult to calculate with a sufficient accuracy, as may occur for existing buildings, it can be estimated from the cumulated energy uses by adopting the loads estimation procedure (h-LEP). With the aim to evaluate the useful fraction of the cogenerated heat for different operating conditions in terms of buildings characteristics, weather data and system capacity, the h-LEP is here implemented with a single climate variable: the hourly average dry- bulb temperature. The proposed procedure have been validated resorting to the TRNSYS simulation tool. The results, obtained by considering a building for hospital use, reveal that the useful fraction of the cogenerated heat can be estimated with an average accuracy of ± 3%, within the range of operative conditions considered in the present study.
Simplicial models of trace spaces
DEFF Research Database (Denmark)
Raussen, Martin
2010-01-01
Directed algebraic topology studies topological spaces in which certain directed paths (d-paths) are singled out; in most cases of interest, the reverse path of a d-path is no longer a d-path. We are mainly concerned with spaces of directed paths between given end points, and how those vary under...
Weirich, Melanie; Simpson, Adrian
2013-10-01
The purpose of this study is to investigate the potential relationship between speaking fundamental frequency and acoustic vowel space size, thus testing a possible perceptual source of sex-specific differences in acoustic vowel space size based on the greater inter-harmonic spacing and a poorer definition of the spectral envelope of higher pitched voices. Average fundamental frequencies and acoustic vowel spaces of 56 female German speakers are analyzed. Several parameters are used to quantify the size and shape of the vowel space defined by /iː ε aː [symbol: see text] uː/ such as the area of the polygon spanned by the five vowels, the absolute difference in F1 or F2 between /iː/ and /uː/ or /aː/, and the Euclidian distance between /iː/ and /aː/. In addition, the potential impact of nasality on the vowel space size is examined. Results reveal no significant correlation between fundamental frequency and vowel space size suggesting other factors must be responsible for the larger female acoustic vowel space.
Mean Shift Detection for State Space Models
Kuhn, J.; Mandjes, M.; Taimre, T.; Weber, T.; McPhee, M.J.; Anderssen, R.S.
2015-01-01
In this paper we develop and validate a procedure for testing against a shift in mean in the observations and hidden state sequence of state space models with Gaussian noise. State space models are popular for modelling stochastic networks as they allow to take into account that observations of the
A Hybrid 3D Indoor Space Model
Jamali, Ali; Rahman, Alias Abdul; Boguslawski, Pawel
2016-10-01
GIS integrates spatial information and spatial analysis. An important example of such integration is for emergency response which requires route planning inside and outside of a building. Route planning requires detailed information related to indoor and outdoor environment. Indoor navigation network models including Geometric Network Model (GNM), Navigable Space Model, sub-division model and regular-grid model lack indoor data sources and abstraction methods. In this paper, a hybrid indoor space model is proposed. In the proposed method, 3D modeling of indoor navigation network is based on surveying control points and it is less dependent on the 3D geometrical building model. This research proposes a method of indoor space modeling for the buildings which do not have proper 2D/3D geometrical models or they lack semantic or topological information. The proposed hybrid model consists of topological, geometrical and semantical space.
A Hybrid 3D Indoor Space Model
Directory of Open Access Journals (Sweden)
A. Jamali
2016-10-01
Full Text Available GIS integrates spatial information and spatial analysis. An important example of such integration is for emergency response which requires route planning inside and outside of a building. Route planning requires detailed information related to indoor and outdoor environment. Indoor navigation network models including Geometric Network Model (GNM, Navigable Space Model, sub-division model and regular-grid model lack indoor data sources and abstraction methods. In this paper, a hybrid indoor space model is proposed. In the proposed method, 3D modeling of indoor navigation network is based on surveying control points and it is less dependent on the 3D geometrical building model. This research proposes a method of indoor space modeling for the buildings which do not have proper 2D/3D geometrical models or they lack semantic or topological information. The proposed hybrid model consists of topological, geometrical and semantical space.
Public space patterns: Modelling the language of urban space
Montenegro, N.; Beirao, J.N.; Duarte, J.P.
2011-01-01
This paper describes the “Public Space Patterns” ontology including its related rule-based model, used as a basic structure of a “City Information Modelling” (CIM). This model was developed within a larger research project aimed at developing a tool for urban planning and design. The main purpose is
Ultrastructural model for size selectivity in glomerular filtration.
Edwards, A; Daniels, B S; Deen, W M
1999-06-01
A theoretical model was developed to relate the size selectivity of the glomerular barrier to the structural characteristics of the individual layers of the capillary wall. Thicknesses and other linear dimensions were evaluated, where possible, from previous electron microscopic studies. The glomerular basement membrane (GBM) was represented as a homogeneous material characterized by a Darcy permeability and by size-dependent hindrance coefficients for diffusion and convection, respectively; those coefficients were estimated from recent data obtained with isolated rat GBM. The filtration slit diaphragm was modeled as a single row of cylindrical fibers of equal radius but nonuniform spacing. The resistances of the remainder of the slit channel, and of the endothelial fenestrae, to macromolecule movement were calculated to be negligible. The slit diaphragm was found to be the most restrictive part of the barrier. Because of that, macromolecule concentrations in the GBM increased, rather than decreased, in the direction of flow. Thus the overall sieving coefficient (ratio of Bowman's space concentration to that in plasma) was predicted to be larger for the intact capillary wall than for a hypothetical structure with no GBM. In other words, because the slit diaphragm and GBM do not act independently, the overall sieving coefficient is not simply the product of those for GBM alone and the slit diaphragm alone. Whereas the calculated sieving coefficients were sensitive to the structural features of the slit diaphragm and to the GBM hindrance coefficients, variations in GBM thickness or filtration slit frequency were predicted to have little effect. The ability of the ultrastructural model to represent fractional clearance data in vivo was at least equal to that of conventional pore models with the same number of adjustable parameters. The main strength of the present approach, however, is that it provides a framework for relating structural findings to the size
Combining search space partition and search Space partition and abstraction for LTL model checking
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The state space explosion problem is still the key obstacle for applying model checking to systems of industrial size.Abstraction-based methods have been particularly successful in this regard.This paper presents an approach based on refinement of search space partition and abstraction which combines these two techniques for reducing the complexity of model checking.The refinement depends on the representation of each portion of search space. Especially, search space can be refined stepwise to get a better reduction. As reported in the case study, the Integration of search space partition and abstraction improves the efficiencyof verification with respect to the requirement of memory and obtains significant advantage over the use of each of them in isolation.
An Evolution Model of Space Debris Environment
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Various types of models including engineering models andevolution models have been developed to understand space debris environment since 1960s. Evolution model, consisting of a set of supporting models such as Launch Model, Breakup Model and Atmosphere Model, can reliably predicts the evolution of space debris environment. Of these supporting models, Breakup Model is employed to describe the distribution of debris and debris cloud during a explosion or collision case which is one of the main factors affecting the amount of total space debris. An analytical orbit debris environment model referred to as the “Particles-In-Boxes" model has been introduced. By regarding the orbit debris as the freedom particles running in the huge volume, the sources and sinks mechanism is established. Then the PIB model is expanded to the case of multiple-species in multiple-tier system. Combined with breakup model, the evolution of orbit debris environment is predicted.
Green space system design in Luoyang using Huff model
Wang, Shengnan; Li, Meng
2008-10-01
Green space system, as part of the urban ecological environment and urban landscape, plays a significant role in the protection of biological diversity of the urban eco-systems. During the process of rapid modernization in China, it is evident that in order to satisfy the residents' needs of entertainment and communication effectively; there should be abundant types and adequate arrangement of green space. And at the same time a comprehensive and stable hierarchical structure of green space system ought to be established. Huff Model is widely used in facility location planning and service area segmentation in business geography, and has potentials in urban facility planning and design. This paper aims to evaluate, design and optimize the urban green space in Luoyang City, Henan Province, using GIS and Huff Model. Considering the existing location, size and shape of the green space supply, the spatial distribution of residence and the urban transportation systems, the attractiveness between residence and green space is estimated. The spatial pattern and service capability of the green space system are also evaluated critically. Based on the findings, the possible optimization design of the green space system in Luoyang is discussed innovatively. Huff model test shows that the design improves the overall spatial accessibility observably. The case study shows that GIS technology and Huff Model have great potential in urban green space evaluation, planning and design.
Size and complexity in model financial systems.
Arinaminpathy, Nimalan; Kapadia, Sujit; May, Robert M
2012-11-06
The global financial crisis has precipitated an increasing appreciation of the need for a systemic perspective toward financial stability. For example: What role do large banks play in systemic risk? How should capital adequacy standards recognize this role? How is stability shaped by concentration and diversification in the financial system? We explore these questions using a deliberately simplified, dynamic model of a banking system that combines three different channels for direct transmission of contagion from one bank to another: liquidity hoarding, asset price contagion, and the propagation of defaults via counterparty credit risk. Importantly, we also introduce a mechanism for capturing how swings in "confidence" in the system may contribute to instability. Our results highlight that the importance of relatively large, well-connected banks in system stability scales more than proportionately with their size: the impact of their collapse arises not only from their connectivity, but also from their effect on confidence in the system. Imposing tougher capital requirements on larger banks than smaller ones can thus enhance the resilience of the system. Moreover, these effects are more pronounced in more concentrated systems, and continue to apply, even when allowing for potential diversification benefits that may be realized by larger banks. We discuss some tentative implications for policy, as well as conceptual analogies in ecosystem stability and in the control of infectious diseases.
Size and complexity in model financial systems
Arinaminpathy, Nimalan; Kapadia, Sujit; May, Robert M.
2012-01-01
The global financial crisis has precipitated an increasing appreciation of the need for a systemic perspective toward financial stability. For example: What role do large banks play in systemic risk? How should capital adequacy standards recognize this role? How is stability shaped by concentration and diversification in the financial system? We explore these questions using a deliberately simplified, dynamic model of a banking system that combines three different channels for direct transmission of contagion from one bank to another: liquidity hoarding, asset price contagion, and the propagation of defaults via counterparty credit risk. Importantly, we also introduce a mechanism for capturing how swings in “confidence” in the system may contribute to instability. Our results highlight that the importance of relatively large, well-connected banks in system stability scales more than proportionately with their size: the impact of their collapse arises not only from their connectivity, but also from their effect on confidence in the system. Imposing tougher capital requirements on larger banks than smaller ones can thus enhance the resilience of the system. Moreover, these effects are more pronounced in more concentrated systems, and continue to apply, even when allowing for potential diversification benefits that may be realized by larger banks. We discuss some tentative implications for policy, as well as conceptual analogies in ecosystem stability and in the control of infectious diseases. PMID:23091020
Control of asperities size and spacing on seismic behavior of subduction megathrusts
Corbi, Fabio; Funiciello, Francesca; Brizzi, Silvia; Lallemand, Serge; Rosenau, Matthias
2017-08-01
The majority of the largest subduction megathrust earthquakes share the common characteristic of rupturing more than one asperity along strike of the margin. Understanding the factors that control coseismic failure of multiple asperities, and thus maximum magnitude, is central for seismic hazard assessment. To investigate the role of asperities size and spacing on maximum magnitude, seismicity rate, and percentage of synchronized ruptures, we use analog models simulating along-strike rupture behavior of megathrust earthquakes. We found negative correlations between the barrier-to-asperity length ratio Db/Da and maximum magnitude and seismicity rate. Db/Da also controls the process of asperities synchronization along the megathrust. A permanent barrier behavior is observed for Db/Da > 0.5. Comparing our experimental results to the Nankai Trough historical seismicity, we propose that the distribution of megathrust frictional heterogeneities likely explains the diversity of earthquakes which occurred there.
Size Evolution and Stochastic Models: Explaining Ostracod Size through Probabilistic Distributions
Krawczyk, M.; Decker, S.; Heim, N. A.; Payne, J.
2014-12-01
The biovolume of animals has functioned as an important benchmark for measuring evolution throughout geologic time. In our project, we examined the observed average body size of ostracods over time in order to understand the mechanism of size evolution in these marine organisms. The body size of ostracods has varied since the beginning of the Ordovician, where the first true ostracods appeared. We created a stochastic branching model to create possible evolutionary trees of ostracod size. Using stratigraphic ranges for ostracods compiled from over 750 genera in the Treatise on Invertebrate Paleontology, we calculated overall speciation and extinction rates for our model. At each timestep in our model, new lineages can evolve or existing lineages can become extinct. Newly evolved lineages are assigned sizes based on their parent genera. We parameterized our model to generate neutral and directional changes in ostracod size to compare with the observed data. New sizes were chosen via a normal distribution, and the neutral model selected new sizes differentials centered on zero, allowing for an equal chance of larger or smaller ostracods at each speciation. Conversely, the directional model centered the distribution on a negative value, giving a larger chance of smaller ostracods. Our data strongly suggests that the overall direction of ostracod evolution has been following a model that directionally pushes mean ostracod size down, shying away from a neutral model. Our model was able to match the magnitude of size decrease. Our models had a constant linear decrease while the actual data had a much more rapid initial rate followed by a constant size. The nuance of the observed trends ultimately suggests a more complex method of size evolution. In conclusion, probabilistic methods can provide valuable insight into possible evolutionary mechanisms determining size evolution in ostracods.
Genome size diversity in angiosperms and its influence on gene space.
Dodsworth, Steven; Leitch, Andrew R; Leitch, Ilia J
2015-12-01
Genome size varies c. 2400-fold in angiosperms (flowering plants), although the range of genome size is skewed towards small genomes, with a mean genome size of 1C=5.7Gb. One of the most crucial factors governing genome size in angiosperms is the relative amount and activity of repetitive elements. Recently, there have been new insights into how these repeats, previously discarded as 'junk' DNA, can have a significant impact on gene space (i.e. the part of the genome comprising all the genes and gene-related DNA). Here we review these new findings and explore in what ways genome size itself plays a role in influencing how repeats impact genome dynamics and gene space, including gene expression. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
Modelling the effect of size-asymmetric competition on size inequality
DEFF Research Database (Denmark)
Rasmussen, Camilla Ruø; Weiner, Jacob
2017-01-01
Abstract The concept of size asymmetry in resource competition among plants, in which larger individuals obtain a disproportionate share of contested resources, appears to be very straightforward, but the effects of size asymmetry on growth and size variation among individuals have proved...... to be controversial. It has often been assumed that competition among individual plants in a population has to be size-asymmetric to result in higher size inequality than in the absence of competition, but here we question this inference. Using very simple, individual-based models, we investigate how size symmetry...... irrespective of their sizes, can, under some assumptions, result in higher size inequality than when competition is absent. We demonstrate our approach by applying it to data from a greenhouse experiment investigating the size symmetry of belowground competition between pairs of Triticum aestivum (wheat...
Space Vehicle Reliability Modeling in DIORAMA
Energy Technology Data Exchange (ETDEWEB)
Tornga, Shawn Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-07-12
When modeling system performance of space based detection systems it is important to consider spacecraft reliability. As space vehicles age the components become prone to failure for a variety of reasons such as radiation damage. Additionally, some vehicles may lose the ability to maneuver once they exhaust fuel supplies. Typically failure is divided into two categories: engineering mistakes and technology surprise. This document will report on a method of simulating space vehicle reliability in the DIORAMA framework.
Momentum-space Harper-Hofstadter model
Ozawa, Tomoki; Price, Hannah M.; Carusotto, Iacopo
2015-08-01
We show how the weakly trapped Harper-Hofstadter model can be mapped onto a Harper-Hofstadter model in momentum space. In this momentum-space model, the band dispersion plays the role of the periodic potential, the Berry curvature plays the role of an effective magnetic field, the real-space harmonic trap provides the momentum-space kinetic energy responsible for the hopping, and the trap position sets the boundary conditions around the magnetic Brillouin zone. Spatially local interactions translate into nonlocal interactions in momentum space: within a mean-field approximation, we show that increasing interparticle interactions leads to a structural change of the ground state, from a single rotationally symmetric ground state to degenerate ground states that spontaneously break rotational symmetry.
3D space analysis of dental models
Chuah, Joon H.; Ong, Sim Heng; Kondo, Toshiaki; Foong, Kelvin W. C.; Yong, Than F.
2001-05-01
Space analysis is an important procedure by orthodontists to determine the amount of space available and required for teeth alignment during treatment planning. Traditional manual methods of space analysis are tedious and often inaccurate. Computer-based space analysis methods that work on 2D images have been reported. However, as the space problems in the dental arch exist in all three planes of space, a full 3D analysis of the problems is necessary. This paper describes a visualization and measurement system that analyses 3D images of dental plaster models. Algorithms were developed to determine dental arches. The system is able to record the depths of the Curve of Spee, and quantify space liabilities arising from a non-planar Curve of Spee, malalignment and overjet. Furthermore, the difference between total arch space available and the space required to arrange the teeth in ideal occlusion can be accurately computed. The system for 3D space analysis of the dental arch is an accurate, comprehensive, rapid and repeatable method of space analysis to facilitate proper orthodontic diagnosis and treatment planning.
Lag space estimation in time series modelling
DEFF Research Database (Denmark)
Goutte, Cyril
1997-01-01
The purpose of this article is to investigate some techniques for finding the relevant lag-space, i.e. input information, for time series modelling. This is an important aspect of time series modelling, as it conditions the design of the model through the regressor vector a.k.a. the input layer...
NP has log-space verifiers with fixed-size public quantum registers
Yakaryilmaz, Abuzer
2011-01-01
In classical Arthur-Merlin games (AM), the class of languages whose membership proofs can be verified by Arthur using logarithmic space coincides with the class P \\cite{Co89}. In this note, we show that if Arthur has a fixed-size quantum register (the size of the register does not depend on the length of the input) instead of another source of random bits, membership in any language in NP can be verified with any desired error bound.
46 CFR 160.002-2 - Size and models.
2010-10-01
...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Life Preservers, Kapok, Adult and Child (Jacket Type), Models 3 and 5 § 160.002-2 Size and models. Each life preserver specified in this subpart is to be a: (a) Model...
Outdoor-indoor Space: Unified Modeling and Shortest Path Search
DEFF Research Database (Denmark)
Jensen, Søren Kejser; Nielsen, Jens Thomas Vejlby; Lu, Hua;
2016-01-01
Graph models are widely used for representing the topology of outdoor space (O-Space) and indoor space (I-Space). However, existing models neglect the intersection between O-Space and I-Space, only allowing for computations such as shortest path and nearest neighbor queries in either O-Space or I...
The State Space Models Toolbox for MATLAB
Directory of Open Access Journals (Sweden)
Jyh-Ying Peng
2011-05-01
Full Text Available State Space Models (SSM is a MATLAB toolbox for time series analysis by state space methods. The software features fully interactive construction and combination of models, with support for univariate and multivariate models, complex time-varying (dy- namic models, non-Gaussian models, and various standard models such as ARIMA and structural time-series models. The software includes standard functions for Kalman fil- tering and smoothing, simulation smoothing, likelihood evaluation, parameter estimation, signal extraction and forecasting, with incorporation of exact initialization for filters and smoothers, and support for missing observations and multiple time series input with com- mon analysis structure. The software also includes implementations of TRAMO model selection and Hillmer-Tiao decomposition for ARIMA models. The software will provide a general toolbox for time series analysis on the MATLAB platform, allowing users to take advantage of its readily available graph plotting and general matrix computation capabilities.
Observational modeling of topological spaces
Energy Technology Data Exchange (ETDEWEB)
Molaei, M.R. [Department of Mathematics, Shahid Bahonar University of Kerman, Kerman 76169-14111 (Iran, Islamic Republic of)], E-mail: mrmolaei@mail.uk.ac.ir
2009-10-15
In this paper a model for a multi-dimensional observer by using of the fuzzy theory is presented. Relative form of Tychonoff theorem is proved. The notion of topological entropy is extended. The persistence of relative topological entropy under relative conjugate relation is proved.
AX-5 space suit reliability model
Reinhardt, AL; Magistad, John
1990-01-01
The AX-5 is an all metal Extra-vehicular (EVA) space suit currently under consideration for use on Space Station Freedom. A reliability model was developed based on the suit's unique design and on projected joint cycle requirements. Three AX-5 space suit component joints were cycled under simulated load conditions in accordance with NASA's advanced space suit evaluation plan. This paper will describe the reliability model developed, the results of the cycle testing, and an interpretation of the model and test results in terms of projected Mean Time Between Failure for the AX-5. A discussion of the maintenance implications and life cycle for the AX-5 based on this projection is also included.
An introduction to Space Weather Integrated Modeling
Zhong, D.; Feng, X.
2012-12-01
The need for a software toolkit that integrates space weather models and data is one of many challenges we are facing with when applying the models to space weather forecasting. To meet this challenge, we have developed Space Weather Integrated Modeling (SWIM) that is capable of analysis and visualizations of the results from a diverse set of space weather models. SWIM has a modular design and is written in Python, by using NumPy, matplotlib, and the Visualization ToolKit (VTK). SWIM provides data management module to read a variety of spacecraft data products and a specific data format of Solar-Interplanetary Conservation Element/Solution Element MHD model (SIP-CESE MHD model) for the study of solar-terrestrial phenomena. Data analysis, visualization and graphic user interface modules are also presented in a user-friendly way to run the integrated models and visualize the 2-D and 3-D data sets interactively. With these tools we can locally or remotely analysis the model result rapidly, such as extraction of data on specific location in time-sequence data sets, plotting interplanetary magnetic field lines, multi-slicing of solar wind speed, volume rendering of solar wind density, animation of time-sequence data sets, comparing between model result and observational data. To speed-up the analysis, an in-situ visualization interface is used to support visualizing the data 'on-the-fly'. We also modified some critical time-consuming analysis and visualization methods with the aid of GPU and multi-core CPU. We have used this tool to visualize the data of SIP-CESE MHD model in real time, and integrated the Database Model of shock arrival, Shock Propagation Model, Dst forecasting model and SIP-CESE MHD model developed by SIGMA Weather Group at State Key Laboratory of Space Weather/CAS.
The STAMP Software for State Space Models
Directory of Open Access Journals (Sweden)
Roy Mendelssohn
2011-05-01
Full Text Available This paper reviews the use of STAMP (Structural Time Series Analyser, Modeler and Predictor for modeling time series data using state-space methods with unobserved components. STAMP is a commercial, GUI-based program that runs on Windows, Linux and Macintosh computers as part of the larger OxMetrics System. STAMP can estimate a wide-variety of both univariate and multivariate state-space models, provides a wide array of diagnostics, and has a batch mode capability. The use of STAMP is illustrated for the Nile river data which is analyzed throughout this issue, as well as by modeling a variety of oceanographic and climate related data sets. The analyses of the oceanographic and climate data illustrate the breadth of models available in STAMP, and that state-space methods produce results that provide new insights into important scientific problems.
Modeling of space environment impact on nanostructured materials. General principles
Voronina, Ekaterina; Novikov, Lev
2016-07-01
In accordance with the resolution of ISO TC20/SC14 WG4/WG6 joint meeting, Technical Specification (TS) 'Modeling of space environment impact on nanostructured materials. General principles' which describes computer simulation methods of space environment impact on nanostructured materials is being prepared. Nanomaterials surpass traditional materials for space applications in many aspects due to their unique properties associated with nanoscale size of their constituents. This superiority in mechanical, thermal, electrical and optical properties will evidently inspire a wide range of applications in the next generation spacecraft intended for the long-term (~15-20 years) operation in near-Earth orbits and the automatic and manned interplanetary missions. Currently, ISO activity on developing standards concerning different issues of nanomaterials manufacturing and applications is high enough. Most such standards are related to production and characterization of nanostructures, however there is no ISO documents concerning nanomaterials behavior in different environmental conditions, including the space environment. The given TS deals with the peculiarities of the space environment impact on nanostructured materials (i.e. materials with structured objects which size in at least one dimension lies within 1-100 nm). The basic purpose of the document is the general description of the methodology of applying computer simulation methods which relate to different space and time scale to modeling processes occurring in nanostructured materials under the space environment impact. This document will emphasize the necessity of applying multiscale simulation approach and present the recommendations for the choice of the most appropriate methods (or a group of methods) for computer modeling of various processes that can occur in nanostructured materials under the influence of different space environment components. In addition, TS includes the description of possible
de Vries, WH; O'Dea, CP; Barthel, PD; Fanti, C; Fanti, R; Lehnert, MD
2000-01-01
We present near-infrared J- and K-band imaging of a sample of powerful radio source host galaxies with the Hubble Space Telescope NICMOS2 camera. These sources have been selected on their double-lobed radio structure and include a wide range of projected radio source sizes. The largest projected
Automated thinning increases uniformity of in-row spacing and plant size in romaine lettuce
Low availability and high cost of farm hand labor make automated thinners a faster and cheaper alternative to hand thinning in lettuce (Lactuca sativa L.). However, the effects of this new technology on uniformity of plant spacing and size as well as crop yield are not proven. Three experiments wer...
Optimum condition of spot size and spacing in particle scanning irradiation
Energy Technology Data Exchange (ETDEWEB)
Yang, Hye Jeong [Dept. of Particle Accelerator and Medical Physics, Dong A University, Busan (Korea, Republic of); Yoo, Seung Hoon; Cho, Il Sung; Song, Yong eun; Shin, Jae Ik; Kim, Eun Ho; Jung, Won Gyun [Div. of Heavy Ion Clinical Research, Korea Institute of Radiological and Medical Science, Seoul (Korea, Republic of)
2015-10-15
In our study, spot size, lateral spot spacing and longitudinal layer intervals were investigated to find optimum conditions for planning quality. Broad beam irradiation was used for the treatment, however, IMPT using scanning irradiation is very important for the reducing OAR dose. In the case of the scanning irradiation, there are many scanning parameters. Spot size, lateral spot spacing and longitudinal layer spacing (layer interval) are very important scanning conditions which affect the planning quality and treatment time. In most of treatment sites using proton scanning irradiation system, the spot size depends on the beam energy and spot spacing was used in 2-4 mm fixed. These conditions are applied all kinds of patients. However, optimized scanning conditions are very important for more efficient treatment of the patients which have individual specific features including PTV volume, irregularity of the target. As spot size decreases, the planning quality of the PTV and OAR became significantly better for skull base compared to the prostate case.
Preliminary Multivariable Cost Model for Space Telescopes
Stahl, H. Philip
2010-01-01
Parametric cost models are routinely used to plan missions, compare concepts and justify technology investments. Previously, the authors published two single variable cost models based on 19 flight missions. The current paper presents the development of a multi-variable space telescopes cost model. The validity of previously published models are tested. Cost estimating relationships which are and are not significant cost drivers are identified. And, interrelationships between variables are explored
Rejoinder: Sifting through model space
Heisey, Dennis M.; Osnas, Erik E.; Cross, Paul C.; Joly, Damien O.; Langenberg, Julia A.; Miller, Michael W.
2010-01-01
Observational data sets generated by complex processes are common in ecology. Traditionally these have been very challenging to analyze because of the limitations of available statistical tools. This seems to be changing, and these are exciting times to be involved with ecological statistics, not just because of the neo-Bayesian revival but also because of the proliferation of computationally intensive methods in general. It is now possible to fit much richer models to observational data than in the relatively recent past, which in turn has stimulated much interest in how to evaluate and compare such models. In such an immature, vibrant, and rapidly growing field, not everyone is going to agree on the best way to do things. This is reflected in the contrast of opinions offered by the discussants. Each offers a thoughtful and thought-provoking critique of our work that reflects the current thinking in a non-negligible segment of the ecological data analysis community. We want to thank them for their insights.
Modelling complete particle-size distributions from operator estimates of particle-size
Roberson, Sam; Weltje, Gert Jan
2014-05-01
Estimates of particle-size made by operators in the field and laboratory represent a vast and relatively untapped data archive. The wide spatial distribution of particle-size estimates makes them ideal for constructing geological models and soil maps. This study uses a large data set from the Netherlands (n = 4837) containing both operator estimates of particle size and complete particle-size distributions measured by laser granulometry. This study introduces a logit-based constrained-cubic-spline (CCS) algorithm to interpolate complete particle-size distributions from operator estimates. The CCS model is compared to four other models: (i) a linear interpolation; (ii) a log-hyperbolic interpolation; (iii) an empirical logistic function; and (iv) an empirical arctan function. Operator estimates were found to be both inaccurate and imprecise; only 14% of samples were successfully classified using the Dutch classification scheme for fine sediment. Operator estimates of sediment particle-size encompass the same range of values as particle-size distributions measured by laser analysis. However, the distributions measured by laser analysis show that most of the sand percentage values lie between zero and one, so the majority of the variability in the data is lost because operator estimates are made to the nearest 1% at best, and more frequently to the nearest 5%. A method for constructing complete particle-size distributions from operator estimates of sediment texture using a logit constrained cubit spline (CCS) interpolation algorithm is presented. This model and four other previously published methods are compared to establish the best approach to modelling particle-size distributions. The logit-CCS model is the most accurate method, although both logit-linear and log-linear interpolation models provide reasonable alternatives. Models based on empirical distribution functions are less accurate than interpolation algorithms for modelling particle-size distributions in
Royal London space analysis: plaster versus digital model assessment.
Grewal, Balpreet; Lee, Robert T; Zou, Lifong; Johal, Ama
2016-08-10
With the advent of digital study models, the importance of being able to evaluate space requirements becomes valuable to treatment planning and the justification for any required extraction pattern. This study was undertaken to compare the validity and reliability of the Royal London space analysis (RLSA) undertaken on plaster as compared with digital models. A pilot study (n = 5) was undertaken on plaster and digital models to evaluate the feasibility of digital space planning. This also helped to determine the sample size calculation and as a result, 30 sets of study models with specified inclusion criteria were selected. All five components of the RLSA, namely: crowding; depth of occlusal curve; arch expansion/contraction; incisor antero-posterior advancement and inclination (assessed from the pre-treatment lateral cephalogram) were accounted for in relation to both model types. The plaster models served as the gold standard. Intra-operator measurement error (reliability) was evaluated along with a direct comparison of the measured digital values (validity) with the plaster models. The measurement error or coefficient of repeatability was comparable for plaster and digital space analyses and ranged from 0.66 to 0.95mm. No difference was found between the space analysis performed in either the upper or lower dental arch. Hence, the null hypothesis was accepted. The digital model measurements were consistently larger, albeit by a relatively small amount, than the plaster models (0.35mm upper arch and 0.32mm lower arch). No difference was detected in the RLSA when performed using either plaster or digital models. Thus, digital space analysis provides a valid and reproducible alternative method in the new era of digital records.
Developing Viable Financing Models for Space Tourism
Eilingsfeld, F.; Schaetzler, D.
2002-01-01
Increasing commercialization of space services and the impending release of government's control of space access promise to make space ventures more attractive. Still, many investors shy away from going into the space tourism market as long as they do not feel secure that their return expectations will be met. First and foremost, attracting investors from the capital markets requires qualifying financing models. Based on earlier research on the cost of capital for space tourism, this paper gives a brief run-through of commercial, technical and financial due diligence aspects. After that, a closer look is taken at different valuation techniques as well as alternative ways of streamlining financials. Experience from earlier ventures has shown that the high cost of capital represents a significant challenge. Thus, the sophistication and professionalism of business plans and financial models needs to be very high. Special emphasis is given to the optimization of the debt-to-equity ratio over time. The different roles of equity and debt over a venture's life cycle are explained. Based on the latter, guidelines for the design of an optimized loan structure are given. These are then applied to simulating the financial performance of a typical space tourism venture over time, including the calculation of Weighted Average Cost of Capital (WACC) and Net Present Value (NPV). Based on a concluding sensitivity analysis, the lessons learned are presented. If applied properly, these will help to make space tourism economically viable.
Sigma-Model Solitons on Noncommutative Spaces
Dabrowski, Ludwik; Landi, Giovanni; Luef, Franz
2015-12-01
We use results from time-frequency analysis and Gabor analysis to construct new classes of sigma-model solitons over the Moyal plane and over noncommutative tori, taken as source spaces, with a target space made of two points. A natural action functional leads to self-duality equations for projections in the source algebra. Solutions, having nontrivial topological content, are constructed via suitable Morita duality bimodules.
Preliminary Analysis on the Relative Solution Space Sizes for MTSP with Genetic Algorithm
Hao, Junling
It is well known that the chromosome design is pivotal to solve the multiple traveling salesman problems with genetic algorithm. A well-designed chromosome coding can eliminate or reduce the redundant solutions. One chromosome and two chromosome design methods and a recently proposed two-part chromosome design are firstly introduced in this paper. Then the preliminary quantitative comparison analysis of the solution spaces of three different chromosome design methods is presented when the number of cities is linear with the travelers. The concept of relative solution space is proposed in order to compare the relative size of the solution spaces. The solution space of two-part chromosome design is much smaller than those of the traditional chromosome design. The result given in this paper provides a good guideline for the possible algorithmic design and engineering applications.
46 CFR 160.005-2 - Size and model.
2010-10-01
...: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Life Preservers, Fibrous Glass, Adult and Child (Jacket Type), Models 52 and 56 § 160.005-2 Size and model. Each life preserver specified in this subpart is a: (a...
Sample Size Determination for Rasch Model Tests
Draxler, Clemens
2010-01-01
This paper is concerned with supplementing statistical tests for the Rasch model so that additionally to the probability of the error of the first kind (Type I probability) the probability of the error of the second kind (Type II probability) can be controlled at a predetermined level by basing the test on the appropriate number of observations.…
A random energy model for size dependence : recurrence vs. transience
Külske, Christof
1998-01-01
We investigate the size dependence of disordered spin models having an infinite number of Gibbs measures in the framework of a simplified 'random energy model for size dependence'. We introduce two versions (involving either independent random walks or branching processes), that can be seen as gener
Hierarchical modeling of cluster size in wildlife surveys
Royle, J. Andrew
2008-01-01
Clusters or groups of individuals are the fundamental unit of observation in many wildlife sampling problems, including aerial surveys of waterfowl, marine mammals, and ungulates. Explicit accounting of cluster size in models for estimating abundance is necessary because detection of individuals within clusters is not independent and detectability of clusters is likely to increase with cluster size. This induces a cluster size bias in which the average cluster size in the sample is larger than in the population at large. Thus, failure to account for the relationship between delectability and cluster size will tend to yield a positive bias in estimates of abundance or density. I describe a hierarchical modeling framework for accounting for cluster-size bias in animal sampling. The hierarchical model consists of models for the observation process conditional on the cluster size distribution and the cluster size distribution conditional on the total number of clusters. Optionally, a spatial model can be specified that describes variation in the total number of clusters per sample unit. Parameter estimation, model selection, and criticism may be carried out using conventional likelihood-based methods. An extension of the model is described for the situation where measurable covariates at the level of the sample unit are available. Several candidate models within the proposed class are evaluated for aerial survey data on mallard ducks (Anas platyrhynchos).
Directory of Open Access Journals (Sweden)
Abdeldjallil eNaceri
2015-09-01
Full Text Available In our daily life experience, the angular size of an object correlates with its distance from the observer, provided that the physical size of the object remains constant. In this work, we investigated depth perception in action space (i.e., beyond the arm reach, while keeping the angular size of the target object constant. This was achieved by increasing the physical size of the target object as its distance to the observer increased. To the best of our knowledge, this is the first time that a similar protocol has been tested in action space, for distances to the observer ranging from 1.4 to 2.4m. We replicated the task in virtual and real environments and we found that the performance was significantly different between the two environments. In the real environment, all participants perceived the depth of the target object precisely. Whereas, in virtual reality the responses were significantly less precise, although, still above chance level in 16 of the 20 observers. The difference in the discriminability of the stimuli was likely due to different contributions of the convergence and the accommodation cues in the two environments. The values of Weber fractions estimated in our study were compared to those reported in previous studies in peripersonal and action space.
Naceri, Abdeldjallil; Moscatelli, Alessandro; Chellali, Ryad
2015-01-01
In our daily life experience, the angular size of an object correlates with its distance from the observer, provided that the physical size of the object remains constant. In this work, we investigated depth perception in action space (i.e., beyond the arm reach), while keeping the angular size of the target object constant. This was achieved by increasing the physical size of the target object as its distance to the observer increased. To the best of our knowledge, this is the first time that a similar protocol has been tested in action space, for distances to the observer ranging from 1.4–2.4 m. We replicated the task in virtual and real environments and we found that the performance was significantly different between the two environments. In the real environment, all participants perceived the depth of the target object precisely. Whereas, in virtual reality (VR) the responses were significantly less precise, although, still above chance level in 16 of the 20 observers. The difference in the discriminability of the stimuli was likely due to different contributions of the convergence and the accommodation cues in the two environments. The values of Weber fractions estimated in our study were compared to those reported in previous studies in peripersonal and action space. PMID:26441608
Cities in Space: Three Simple Models
Paul Krugman
1991-01-01
Urban agglomerations arise at least in part out of the interaction between economies of scale in production and market size effects. This paper develops a simple spatial framework to develop illustrative models of the determinants of urban location, of the number and size of cities, and of the degree of urbanization. A Central theme is the probable existence of multiple equilibria, and the dependence of the range of potential outcomes on a few key parameters.
Multimedia Mapping using Continuous State Space Models
DEFF Research Database (Denmark)
Lehn-Schiøler, Tue
2004-01-01
In this paper a system that transforms speech waveforms to animated faces are proposed. The system relies on continuous state space models to perform the mapping, this makes it possible to ensure video with no sudden jumps and allows continuous control of the parameters in 'face space'. Simulations...... are performed on recordings of 3-5 sec. video sequences with sentences from the Timit database. The model is able to construct an image sequence from an unknown noisy speech sequence fairly well even though the number of training examples are limited....
Hauschildt, Verena; Gerken, Martina
2016-03-01
This study aims to assess plot size related changes in spacing and behavioural synchronization in a herd of 14 German Blackface ewes kept on three different pasture sizes: S (126m(2)), M (1100m(2)), and L (11,200m(2)). In direct field observations, behaviour and nearest neighbour distance were recorded individually. Additionally, interindividual and nearest neighbour distances were derived from aerial photographs of the herd taken on plot sizes S and M. Nearest neighbour distances Synchronization tended to increase with plot size (K(S)=0.42; K(M)=0.52; K(L)=0.66), but was not accompanied by a concomitant increase in dispersion. Aerial photography proved a valuable tool in the analysis of spacing behaviour as intraindividual repeatability of the derived distances was highly significant (Kendall's W between 0.32 and 0.58; psheep kept small distances on all plot sizes, thus the high degree of behavioural synchronization might be mainly attributed to the motivation for close proximity to any conspecific.
Energy Technology Data Exchange (ETDEWEB)
Kumar, N.K.; Roy, B.; Das, J., E-mail: j.das@metal.iitkgp.ernet.in
2015-01-05
Highlights: • Nanotwinned α-brass with varying lamellae thickness (28–170 nm), has been produced by cryorolling. • Equal thickness and uniform distribution of nanotwins increase the hardness homogeneity. • Formation of ∼10 nm subgrains within preexisting twin lamellae causes the refinement. • Flow stress has been predicted considering dislocation density, twin spacing and crystallite size. - Abstract: Nanotwinned α-brass (Cu–30 wt.% Zn) with varying lamellae thickness in the range of 28–170 nm, has been produced by cryorolling (CR). The effect of CR strain (ε{sub CR} = 0.2–0.95) on the evolution of homogeneity and refinement in terms of twin lamellae thickness, twin spacing, and their distribution, have been studied using high-resolution transmission electron microscopy (HRTEM) and microhardness measurements. Analysis of X-ray peak broadening has shown that the crystallite size reduces down to 20 nm at ε{sub CR} = 0.95, which scales with the subgrain size in preexisting twin lamellae, as revealed under HRTEM. The effect of dislocation density and crystallite size on the strength of nanotwinned brass has been correlated using an analytical model.
A model for configuration spaces of points
Campos, Ricardo; Willwacher, Thomas
2016-01-01
The configuration space of points on a $D$-dimensional smooth framed manifold may be compactified so as to admit a right action over the framed little $D$-disks operad. We construct a real combinatorial model for these modules, for compact smooth manifolds without boundary.
Modelling Complex Relevance Spaces with Copulas
C. Eickhoff (Carsten); A.P. de Vries (Arjen)
2014-01-01
htmlabstractModern relevance models consider a wide range of criteria in order to identify those documents that are expected to satisfy the user's information need. With growing dimensionality of the underlying relevance spaces the need for sophisticated score combination and estimation schemes
EFFECT OF SPACING SIZE AND SHAPE ON OIL PUMPKIN YIELD (Cucurbita pepo L. var. oleifera
Directory of Open Access Journals (Sweden)
Zvjezdana Augustinović
2006-12-01
Full Text Available Effect of spacing size and shape on oil pumpkin yield (Cucurbita pepo L. var. oleifera was investigated in two – year field experiments during 2004 and 2005 on The College of Agriculture at Križevci experimental fields. The investigated planting distances were: 100x100, 140x70, 140 x 50, 80 x 80 and 140x30 cm. The experiment was set out by to the Latin square method with five replications, and data was analyzed using analysis of variance. Austrian cultivar Gleissdorf was tested. Number of fruits per plant, average fruit weight, number of fruits per hectare, yield of fruits per hectare, average seed weight per fruit and seed yield per hectare were established. Highly significant large number of fruits per plant in both years was established at greater spacing size (100x100 cm – 1.43 fruit/plant in 2004; 140x70 cm – 1.1 fruit/plant in 2005. Average fruit weight regularly was higher at greater spacing size (140x70 cm – 4239 g in 2004; and 100x100 cm – 4183 g in 2005 but not significant. Even though the differences were not significant between treatmants in both years the greatest number of fruits per hectare (16 167- 2004; 13 917 – 2005 and fruit yield per hectare (60.1 t/ha – 2004; 54.2 t/ha – 2005 was obtained at spacing 140x30 cm. The highest seed yield per hectare in both years (1397.2 kg/ha – 2004; 1167.6 kg/ha – 2005 was obtained at the same spacing (140x30 cm but high significant only in 2004 year.
Habitability Concept Models for Living in Space
Ferrino, M.
2002-01-01
As growing trends show, living in "space" has acquired new meanings, especially considering the utilization of the International Space Station (ISS) with regard to group interaction as well as individual needs in terms of time, space and crew accommodations. In fact, for the crew, the Spaced Station is a combined Laboratory-Office/Home and embodies ethical, social, and cultural aspects as additional parameters to be assessed to achieve a user centered architectural design of crew workspace. Habitability Concept Models can improve the methods and techniques used to support the interior design and layout of space architectures and at the same time guarantee a human focused approach. This paper discusses and illustrates some of the results obtained for the interior design of a Habitation Module for the ISS. In this work, two different but complementary approaches are followed. The first is "object oriented" and based on Video Data (American and Russian) supported by Proxemic methods (Edward T. Hall, 1963 and Francesca Pregnolato, 1998). This approach offers flexible and adaptive design solutions. The second is "subject oriented" and based on a Virtual Reality environment. With this approach human perception and cognitive aspects related to a specific crew task are considered. Data obtained from these two approaches are used to verify requirements and advance the design of the Habitation Module for aspects related to man machine interfaces (MMI), ergonomics, work and free-time. It is expected that the results achieved can be applied to future space related projects.
Concepts of disability: the Activity Space Model.
Kopec, J A
1995-03-01
This paper describes a new conceptual framework for functional assessment, the Activity Space Model (ASM). According to this model, functional impairments may lead to restrictions in an individual's activity space, a multidimensional space that represents human potential for activity. For each elementary ability, restrictions in the corresponding dimension of the activity space can be evaluated by deriving a difficulty curve that depicts the relationship between the level of performance and the psychophysical cost of activity. The effect of disease on daily functioning is explained in terms of a tradeoff between the psychophysical cost and the value of each act of behavior to the disabled individual. These two constructs are measured on the same scale and expressed in units of difficulty. The location of each task within the activity space in relation to the difficulty curve determines whether it will be performed or avoided at a given point in time. The ASM has both theoretical and practical implications. It offers a new, integrated perspective on disability and suggests new strategies for developing and evaluating functional assessment measures.
Cluster-size dependent randomization traffic flow model
Institute of Scientific and Technical Information of China (English)
Gao Kun; Wang Bing-Hong; Fu Chuan-Ji; Lu Yu-Feng
2007-01-01
In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic,the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters'size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speeddependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters.
Mapping mobility patterns to public spaces in a medium-sized city using geolocated tweets
Salas-Olmedo, María Henar
2016-01-01
This research evidences the usefulness of open big data to map mobility patterns in a medium-sized city. Motivated by the novel analysis that big data allow worldwide and in large metropolitan areas, we developed a methodology aiming to complement origin-destination surveys with \\`a la carte spatial boundaries and updated data at a minimum cost. This paper validates the use of Twitter data to map the impact of public spaces on the different parts of the metropolitan area of Concepci\\'on, Chile. Results have been validated by local experts and evidence the main mobility patterns towards spaces of social interaction like malls, leisure areas, parks and so on. The map represents the mobility patterns from census districts to different categories of public spaces with schematic lines at the metropolitan scale and it is centred in the city of Concepci\\'on (Chile) and its surroundings (~10 kilometres).
Chow, V. W.; Mendis, D. A.; Rosenberg, M.
1993-01-01
By virtue of being generally immersed in a plasma environment, cosmic dust is necessarily electrically charged. The fact that secondary emission plays an important role in determining the equilibrium grain potential has long been recognized, but the fact that the grain size plays a crucial role in this equilibrium potential, when secondary emission is important, has not been widely appreciated. Using both conducting and insulating spherical grains of various sizes and also both Maxwellian and generalized Lorentzian plasmas (which are believed to represent certain space plasmas), we have made a detailed study of this problem. In general, we find that the secondary emission yield delta increases with decreasing size and becomes very large for grains whose dimensions are comparable to the primary electron penetration depth, such as in the case of the very small grains observed at comet Halley and inferred in the interstellar medium. Moreover, we observed that delta is larger for insulators and equilibrium potentials are generally more positive when the plasma has a broad non-Maxwellian tail. Interestingly, we find that for thermal energies that are expected in several cosmic regions, grains of different sizes can have opposite charge, the smaller ones being positive while the larger ones are negative. This may have important consequences for grain accretion in polydisperse dusty space plasmas.
QUANTUM SIZE EFFECTS IN THE ATTRACTIVE HUBBARD-MODEL
BORMANN, D; SCHNEIDER, T; FRICK, M
1992-01-01
We investigate superconducting pair correlations in the attractive Hubbard model on a finite square lattice. Our aim is to understand the pronounced size dependence which they display in the weak and intermediate coupling regimes. These size effects originate from the electronic shell structure of f
Approximate Methods for State-Space Models
Koyama, Shinsuke; Shalizi, Cosma Rohilla; Kass, Robert E; 10.1198/jasa.2009.tm08326
2010-01-01
State-space models provide an important body of techniques for analyzing time-series, but their use requires estimating unobserved states. The optimal estimate of the state is its conditional expectation given the observation histories, and computing this expectation is hard when there are nonlinearities. Existing filtering methods, including sequential Monte Carlo, tend to be either inaccurate or slow. In this paper, we study a nonlinear filter for nonlinear/non-Gaussian state-space models, which uses Laplace's method, an asymptotic series expansion, to approximate the state's conditional mean and variance, together with a Gaussian conditional distribution. This {\\em Laplace-Gaussian filter} (LGF) gives fast, recursive, deterministic state estimates, with an error which is set by the stochastic characteristics of the model and is, we show, stable over time. We illustrate the estimation ability of the LGF by applying it to the problem of neural decoding and compare it to sequential Monte Carlo both in simulat...
The theoretical foundations for size spectrum models of fish communities
DEFF Research Database (Denmark)
Andersen, Ken Haste; Jacobsen, Nis Sand; Farnsworth, K.D.
2016-01-01
assessment of fisheries. We describe the fundamental concepts in size-based models about food encounter and the bioenergetics budget of individuals. Within the general framework three model types have emerged that differs in their degree of complexity: the food-web, the trait-based and the community model....... We demonstrate the differences between the models through examples of their response to fishing and their dynamic behavior. We review implementations of size spectrum models and describe important variations concerning the functional response, whether growth is food-dependent or fixed...
Impact of variable body size on pedestrian dynamics by heuristics-based model
Guo, Ning; Hu, Mao-Bin; Jiang, Rui
2017-01-01
In the real world, pedestrians can arch the shoulders or rotate their bodies actively to across the narrow space. The method is helpful to reduce the effective size of the body. In this paper, the impact of variable body size on the direction choice has been investigated by an improved heuristic-based model. In the model, it is assumed that the cost of adjusting body size is a factor in the process to evaluate the optimal direction. In a typical simulation scenario, the pedestrian reluctant to adjust body size will pass by the blocks. On the contrary, the pedestrian caring little about body size will traverse through the exit. There is a direction-choice change behavior between bypass and traverse considering block width and the initial location of the pedestrian.
Modeling Space Radiation with Radiomimetic Agent Bleomycin
Lu, Tao
2017-01-01
Space radiation consists of proton and helium from solar particle events (SPE) and high energy heavy ions from galactic cosmic ray (GCR). This mixture of radiation with particles at different energy levels has different effects on biological systems. Currently, majority studies of radiation effects on human were based on single-source radiation due to the limitation of available method to model effects of space radiation on living organisms. While NASA Space Radiation Laboratory is working on advanced switches to make it possible to have a mixed field radiation with particles of different energies, the radiation source will be limited. Development of an easily available experimental model for studying effects of mixed field radiation could greatly speed up our progress in our understanding the molecular mechanisms of damage and responses from exposure to space radiation, and facilitate the discovery of protection and countermeasures against space radiation, which is critical for the mission to Mars. Bleomycin, a radiomimetic agent, has been widely used to study radiation induced DNA damage and cellular responses. Previously, bleomycin was often compared to low low Linear Energy Transfer (LET) gamma radiation without defined characteristics. Our recent work demonstrated that bleomycin could induce complex clustered DNA damage in human fibroblasts that is similar to DNA damage induced by high LET radiation. These type of DNA damage is difficult to repair and can be visualized by gamma-H2Ax staining weeks after the initial insult. The survival ratio between early and late plating of human fibroblasts after bleomycin treatment is between low LET and high LET radiation. Our results suggest that bleomycin induces DNA damage and other cellular stresses resembling those resulted from mixed field radiation with both low and high LET particles. We hypothesize that bleomycin could be used to mimic space radiation in biological systems. Potential advantages and limitations of
Multipartite geometric entanglement in finite size XY model
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Giampaolo, Salvatore Marco; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2009-06-01
We investigate the behavior of the multipartite entanglement in the finite size XY model by means of the hierarchical geometric measure of entanglement. By selecting specific components of the hierarchy, we study both global entanglement and genuinely multipartite entanglement.
Adaptive Numerical Algorithms in Space Weather Modeling
Toth, Gabor; vanderHolst, Bart; Sokolov, Igor V.; DeZeeuw, Darren; Gombosi, Tamas I.; Fang, Fang; Manchester, Ward B.; Meng, Xing; Nakib, Dalal; Powell, Kenneth G.; Stout, Quentin F.; Glocer, Alex; Ma, Ying-Juan; Opher, Merav
2010-01-01
Space weather describes the various processes in the Sun-Earth system that present danger to human health and technology. The goal of space weather forecasting is to provide an opportunity to mitigate these negative effects. Physics-based space weather modeling is characterized by disparate temporal and spatial scales as well as by different physics in different domains. A multi-physics system can be modeled by a software framework comprising of several components. Each component corresponds to a physics domain, and each component is represented by one or more numerical models. The publicly available Space Weather Modeling Framework (SWMF) can execute and couple together several components distributed over a parallel machine in a flexible and efficient manner. The framework also allows resolving disparate spatial and temporal scales with independent spatial and temporal discretizations in the various models. Several of the computationally most expensive domains of the framework are modeled by the Block-Adaptive Tree Solar wind Roe Upwind Scheme (BATS-R-US) code that can solve various forms of the magnetohydrodynamics (MHD) equations, including Hall, semi-relativistic, multi-species and multi-fluid MHD, anisotropic pressure, radiative transport and heat conduction. Modeling disparate scales within BATS-R-US is achieved by a block-adaptive mesh both in Cartesian and generalized coordinates. Most recently we have created a new core for BATS-R-US: the Block-Adaptive Tree Library (BATL) that provides a general toolkit for creating, load balancing and message passing in a 1, 2 or 3 dimensional block-adaptive grid. We describe the algorithms of BATL and demonstrate its efficiency and scaling properties for various problems. BATS-R-US uses several time-integration schemes to address multiple time-scales: explicit time stepping with fixed or local time steps, partially steady-state evolution, point-implicit, semi-implicit, explicit/implicit, and fully implicit numerical
Holographic Space-time Models of Anti-deSitter Space-times
Banks, Tom
2016-01-01
We study the constraints on HST models of AdS space-time. The causal diamonds of HST along time-like geodesics of AdS space-time, fit nicely into the FRW patch of AdS space. The coordinate singularity of the FRW patch is identified with the proper time at which the Hilbert space of the causal diamond becomes infinite dimensional. For diamonds much smaller than the AdS radius, RAdS, the time dependent Hamiltonians of HST are the same as those used to describe similar diamonds in Minkowski space. In particular, they are invariant under the fuzzy analog of volume preserving diffeomorphisms of the holographic screen, which leads to fast scrambling of perturbations on the horizon of a black hole of size smaller than RAdS. We argue that, in order to take a limit of this system which converges to a CFT, one must choose Hamiltonians, in a range of proper times of order RAdS, which break this invariance, and become local in a particular choice of basis for the variables. We show that, beginning with flat, sub-RAdS, pa...
Study on Strand Space Model Theory
Institute of Scientific and Technical Information of China (English)
JI QingGuang(季庆光); QING SiHan(卿斯汉); ZHOU YongBin(周永彬); FENG DengGuo(冯登国)
2003-01-01
The growing interest in the application of formal methods of cryptographic pro-tocol analysis has led to the development of a number of different ways for analyzing protocol. Inthis paper, it is strictly proved that if for any strand, there exists at least one bundle containingit, then an entity authentication protocol is secure in strand space model (SSM) with some smallextensions. Unfortunately, the results of attack scenario demonstrate that this protocol and the Yahalom protocol and its modification are de facto insecure. By analyzing the reasons of failure offormal inference in strand space model, some deficiencies in original SSM are pointed out. In orderto break through these limitations of analytic capability of SSM, the generalized strand space model(GSSM) induced by some protocol is proposed. In this model, some new classes of strands, oraclestrands, high order oracle strands etc., are developed, and some notions are formalized strictly in GSSM, such as protocol attacks, valid protocol run and successful protocol run. GSSM can thenbe used to further analyze the entity authentication protocol. This analysis sheds light on why thisprotocol would be vulnerable while it illustrates that GSSM not only can prove security protocolcorrect, but also can be efficiently used to construct protocol attacks. It is also pointed out thatusing other protocol to attack some given protocol is essentially the same as the case of using themost of protocol itself.
A simple model for sizing stand alone photovoltaic systems
Energy Technology Data Exchange (ETDEWEB)
Sidrach-de-Cardona, M. [Departamento Fisica Aplicada II, ETSI Informatica, Universidad de Malaga, 29071 Malaga (Spain); Mora Lopez, Ll. [Departamento Lenguajes y C. Computacion, ETSI Informatica, Universidad de Malaga, 29071 Malaga (Spain)
1998-08-24
We consider a general model for sizing a stand-alone photovoltaic system, using as energy input data the information available in any radiation atlas. The parameters of the model are estimated by multivariate linear regression. The results obtained from a numerical sizing method were used as initial input data to fit the model. The expression proposed allows us to determine the photovoltaic array size, with a coefficient of determination ranging from 0.94 to 0.98. System parameters and mean monthly values for daily global radiation on the solar modules surface are taken as independent variables in the model. It is also shown that the proposed model can be used with the same accuracy for other locations not considered in the estimation of the model
Heckmann, Tobias; Gegg, Katharina; Becht, Michael
2013-04-01
Statistical approaches to landslide susceptibility modelling on the catchment and regional scale are used very frequently compared to heuristic and physically based approaches. In the present study, we deal with the problem of the optimal sample size for a logistic regression model. More specifically, a stepwise approach has been chosen in order to select those independent variables (from a number of derivatives of a digital elevation model and landcover data) that explain best the spatial distribution of debris flow initiation zones in two neighbouring central alpine catchments in Austria (used mutually for model calculation and validation). In order to minimise problems arising from spatial autocorrelation, we sample a single raster cell from each debris flow initiation zone within an inventory. In addition, as suggested by previous work using the "rare events logistic regression" approach, we take a sample of the remaining "non-event" raster cells. The recommendations given in the literature on the size of this sample appear to be motivated by practical considerations, e.g. the time and cost of acquiring data for non-event cases, which do not apply to the case of spatial data. In our study, we aim at finding empirically an "optimal" sample size in order to avoid two problems: First, a sample too large will violate the independent sample assumption as the independent variables are spatially autocorrelated; hence, a variogram analysis leads to a sample size threshold above which the average distance between sampled cells falls below the autocorrelation range of the independent variables. Second, if the sample is too small, repeated sampling will lead to very different results, i.e. the independent variables and hence the result of a single model calculation will be extremely dependent on the choice of non-event cells. Using a Monte-Carlo analysis with stepwise logistic regression, 1000 models are calculated for a wide range of sample sizes. For each sample size
Modeling particle size distributions by the Weibull distribution function
Energy Technology Data Exchange (ETDEWEB)
Fang, Zhigang (Rogers Tool Works, Rogers, AR (United States)); Patterson, B.R.; Turner, M.E. Jr (Univ. of Alabama, Birmingham, AL (United States))
1993-10-01
A method is proposed for modeling two- and three-dimensional particle size distributions using the Weibull distribution function. Experimental results show that, for tungsten particles in liquid phase sintered W-14Ni-6Fe, the experimental cumulative section size distributions were well fit by the Weibull probability function, which can also be used to compute the corresponding relative frequency distributions. Modeling the two-dimensional section size distributions facilitates the use of the Saltykov or other methods for unfolding three-dimensional (3-D) size distributions with minimal irregularities. Fitting the unfolded cumulative 3-D particle size distribution with the Weibull function enables computation of the statistical distribution parameters from the parameters of the fit Weibull function.
Size-specific sensitivity: Applying a new structured population model
Energy Technology Data Exchange (ETDEWEB)
Easterling, M.R.; Ellner, S.P.; Dixon, P.M.
2000-03-01
Matrix population models require the population to be divided into discrete stage classes. In many cases, especially when classes are defined by a continuous variable, such as length or mass, there are no natural breakpoints, and the division is artificial. The authors introduce the integral projection model, which eliminates the need for division into discrete classes, without requiring any additional biological assumptions. Like a traditional matrix model, the integral projection model provides estimates of the asymptotic growth rate, stable size distribution, reproductive values, and sensitivities of the growth rate to changes in vital rates. However, where the matrix model represents the size distributions, reproductive value, and sensitivities as step functions (constant within a stage class), the integral projection model yields smooth curves for each of these as a function of individual size. The authors describe a method for fitting the model to data, and they apply this method to data on an endangered plant species, northern monkshood (Aconitum noveboracense), with individuals classified by stem diameter. The matrix and integral models yield similar estimates of the asymptotic growth rate, but the reproductive values and sensitivities in the matrix model are sensitive to the choice of stage classes. The integral projection model avoids this problem and yields size-specific sensitivities that are not affected by stage duration. These general properties of the integral projection model will make it advantageous for other populations where there is no natural division of individuals into stage classes.
Modelling of Patterns in Space and Time
Murray, James
1984-01-01
This volume contains a selection of papers presented at the work shop "Modelling of Patterns in Space and Time", organized by the 80nderforschungsbereich 123, "8tochastische Mathematische Modelle", in Heidelberg, July 4-8, 1983. The main aim of this workshop was to bring together physicists, chemists, biologists and mathematicians for an exchange of ideas and results in modelling patterns. Since the mathe matical problems arising depend only partially on the particular field of applications the interdisciplinary cooperation proved very useful. The workshop mainly treated phenomena showing spatial structures. The special areas covered were morphogenesis, growth in cell cultures, competition systems, structured populations, chemotaxis, chemical precipitation, space-time oscillations in chemical reactors, patterns in flames and fluids and mathematical methods. The discussions between experimentalists and theoreticians were especially interesting and effective. The editors hope that these proceedings reflect ...
Access Nets: Modeling Access to Physical Spaces
Frohardt, Robert; Chang, Bor-Yuh Evan; Sankaranarayanan, Sriram
Electronic, software-managed mechanisms using, for example, radio-frequency identification (RFID) cards, enable great flexibility in specifying access control policies to physical spaces. For example, access rights may vary based on time of day or could differ in normal versus emergency situations. With such fine-grained control, understanding and reasoning about what a policy permits becomes surprisingly difficult requiring knowledge of permission levels, spatial layout, and time. In this paper, we present a formal modeling framework, called AccessNets, suitable for describing a combination of access permissions, physical spaces, and temporal constraints. Furthermore, we provide evidence that model checking techniques are effective in reasoning about physical access control policies. We describe our results from a tool that uses reachability analysis to validate security policies.
Data Model Management for Space Information Systems
Hughes, J. Steven; Crichton, Daniel J.; Ramirez, Paul; Mattmann, chris
2006-01-01
The Reference Architecture for Space Information Management (RASIM) suggests the separation of the data model from software components to promote the development of flexible information management systems. RASIM allows the data model to evolve independently from the software components and results in a robust implementation that remains viable as the domain changes. However, the development and management of data models within RASIM are difficult and time consuming tasks involving the choice of a notation, the capture of the model, its validation for consistency, and the export of the model for implementation. Current limitations to this approach include the lack of ability to capture comprehensive domain knowledge, the loss of significant modeling information during implementation, the lack of model visualization and documentation capabilities, and exports being limited to one or two schema types. The advent of the Semantic Web and its demand for sophisticated data models has addressed this situation by providing a new level of data model management in the form of ontology tools. In this paper we describe the use of a representative ontology tool to capture and manage a data model for a space information system. The resulting ontology is implementation independent. Novel on-line visualization and documentation capabilities are available automatically, and the ability to export to various schemas can be added through tool plug-ins. In addition, the ingestion of data instances into the ontology allows validation of the ontology and results in a domain knowledge base. Semantic browsers are easily configured for the knowledge base. For example the export of the knowledge base to RDF/XML and RDFS/XML and the use of open source metadata browsers provide ready-made user interfaces that support both text- and facet-based search. This paper will present the Planetary Data System (PDS) data model as a use case and describe the import of the data model into an ontology tool
Data Model Management for Space Information Systems
Hughes, J. Steven; Crichton, Daniel J.; Ramirez, Paul; Mattmann, chris
2006-01-01
The Reference Architecture for Space Information Management (RASIM) suggests the separation of the data model from software components to promote the development of flexible information management systems. RASIM allows the data model to evolve independently from the software components and results in a robust implementation that remains viable as the domain changes. However, the development and management of data models within RASIM are difficult and time consuming tasks involving the choice of a notation, the capture of the model, its validation for consistency, and the export of the model for implementation. Current limitations to this approach include the lack of ability to capture comprehensive domain knowledge, the loss of significant modeling information during implementation, the lack of model visualization and documentation capabilities, and exports being limited to one or two schema types. The advent of the Semantic Web and its demand for sophisticated data models has addressed this situation by providing a new level of data model management in the form of ontology tools. In this paper we describe the use of a representative ontology tool to capture and manage a data model for a space information system. The resulting ontology is implementation independent. Novel on-line visualization and documentation capabilities are available automatically, and the ability to export to various schemas can be added through tool plug-ins. In addition, the ingestion of data instances into the ontology allows validation of the ontology and results in a domain knowledge base. Semantic browsers are easily configured for the knowledge base. For example the export of the knowledge base to RDF/XML and RDFS/XML and the use of open source metadata browsers provide ready-made user interfaces that support both text- and facet-based search. This paper will present the Planetary Data System (PDS) data model as a use case and describe the import of the data model into an ontology tool
Spreading Models in Banach Space Theory
Argyros, S A; Tyros, K
2010-01-01
We extend the classical Brunel-Sucheston definition of the spreading model by introducing the $\\mathcal{F}$-sequences $(x_s)_{s\\in\\mathcal{F}}$ in a Banach space and the plegma families in $\\mathcal{F}$ where $\\mathcal{F}$ is a regular thin family. The new concept yields a transfinite increasing hierarchy of classes of 1-subsymmetric sequences. We explore the corresponding theory and we present examples establishing this hierarchy and illustrating the limitation of the theory.
Holonic Business Process Modeling in Small to Medium Sized Enterprises
Directory of Open Access Journals (Sweden)
Nur Budi Mulyono
2012-01-01
Full Text Available Holonic modeling analysis which is the application of system thinking in design, manage, and improvement, is used in a novel context for business process modeling. An approach and techniques of holon and holarchies is presented specifically for small and medium sized enterprise process modeling development. The fitness of the approach is compared with well known reductionist or task breakdown approach. The strength and weaknesses of the holonic modeling is discussed with illustrating case example in term of its suitability for an Indonesia’s small and medium sized industry. The novel ideas in this paper have great impact on the way analyst should perceive business process. Future research is applying the approach in supply chain context.Key words: Business process, holonic modeling, operations management, small to medium sized enterprise
A Hubble space telescope search for a sub-Earth-sized exoplanet in the GJ 436 system
Energy Technology Data Exchange (ETDEWEB)
Stevenson, Kevin B. [NASA Sagan Fellow. (United States); Bean, Jacob L.; Fabrycky, Daniel; Kreidberg, Laura, E-mail: kbs@uchicago.edu [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
2014-11-20
The detection of small planets orbiting nearby stars is an important step toward the identification of Earth twins. In previous work using the Spitzer Space Telescope, we found evidence to support at least one sub-Earth-sized exoplanet orbiting the nearby mid-M dwarf star GJ 436. As a follow up, here we used the Hubble Space Telescope (HST) to investigate the existence of one of these candidate planets, UCF-1.01, by searching for two transit signals as it passed in front of its host star. Interpretation of the data hinges critically on correctly modeling and removing the Wide Field Camera 3 (WFC3) instrument systematics from the light curves. Building on previous HST work, we demonstrate that WFC3 analyses need to explore the use of a quadratic function to fit a visit-long time-dependent systematic. This is important for establishing absolute transit and eclipse depths in the white light curves of all transiting systems. The work presented here exemplifies this point by putatively detecting the primary transit of UCF-1.01 with the use of a linear trend. However, using a quadratic trend, we achieve a better fit to the white light curves and a reduced transit depth that is inconsistent with previous Spitzer measurements. Furthermore, quadratic trends with or without a transit model component produce comparable fits to the available data. Using extant WFC3 transit light curves for GJ 436b, we further validate the quadratic model component by achieving photon-limited model fit residuals and consistent transit depths over multiple epochs. We conclude that, when we fit for a quadratic trend, our new data contradict the prediction of a sub-Earth-sized planet orbiting GJ 436 with the size, period, and ephemeris posited from the Spitzer data by a margin of 3.1σ.
Body size mediated coexistence of consumers competing for resources in space
Basset, A.; Angelis, D.L.
2007-01-01
Body size is a major phenotypic trait of individuals that commonly differentiates co-occurring species. We analyzed inter-specific competitive interactions between a large consumer and smaller competitors, whose energetics, selection and giving-up behaviour on identical resource patches scaled with individual body size. The aim was to investigate whether pure metabolic constraints on patch behaviour of vagile species can determine coexistence conditions consistent with existing theoretical and experimental evidence. We used an individual-based spatially explicit simulation model at a spatial scale defined by the home range of the large consumer, which was assumed to be parthenogenic and semelparous. Under exploitative conditions, competitive coexistence occurred in a range of body size ratios between 2 and 10. Asymmetrical competition and the mechanism underlying asymmetry, determined by the scaling of energetics and patch behaviour with consumer body size, were the proximate determinant of inter-specific coexistence. The small consumer exploited patches more efficiently, but searched for profitable patches less effectively than the larger competitor. Therefore, body-size related constraints induced niche partitioning, allowing competitive coexistence within a set of conditions where the large consumer maintained control over the small consumer and resource dynamics. The model summarises and extends the existing evidence of species coexistence on a limiting resource, and provides a mechanistic explanation for decoding the size-abundance distribution patterns commonly observed at guild and community levels. ?? Oikos.
Numerical modelling of elastic space tethers
DEFF Research Database (Denmark)
Kristiansen, Kristian Uldall; Palmer, P. L.; Roberts, R. M.
2012-01-01
In this paper the importance of the ill-posedness of the classical, non-dissipative massive tether model on an orbiting tether system is studied numerically. The computations document that via the regularisation of bending resistance a more reliable numerical integrator can be produced. Furthermore......, the numerical experiments of an orbiting tether system show that bending may introduce significant forces in some regions of phase space. Finally, numerical evidence for the existence of an almost invariant slow manifold of the singularly perturbed, regularised, non-dissipative massive tether model is provided...
Ruiz-Navarro, Ana; Gillingham, Phillipa K; Britton, J Robert
2016-09-01
Predictions of species responses to climate change often focus on distribution shifts, although responses can also include shifts in body sizes and population demographics. Here, shifts in the distributional ranges ('climate space'), body sizes (as maximum theoretical body sizes, L∞) and growth rates (as rate at which L∞ is reached, K) were predicted for five fishes of the Cyprinidae family in a temperate region over eight climate change projections. Great Britain was the model area, and the model species were Rutilus rutilus, Leuciscus leuciscus, Squalius cephalus, Gobio gobio and Abramis brama. Ensemble models predicted that the species' climate spaces would shift in all modelled projections, with the most drastic changes occurring under high emissions; all range centroids shifted in a north-westerly direction. Predicted climate space expanded for R. rutilus and A. brama, contracted for S. cephalus, and for L. leuciscus and G. gobio, expanded under low-emission scenarios but contracted under high emissions, suggesting the presence of some climate-distribution thresholds. For R. rutilus, A. brama, S. cephalus and G. gobio, shifts in their climate space were coupled with predicted shifts to significantly smaller maximum body sizes and/or faster growth rates, aligning strongly to aspects of temperature-body size theory. These predicted shifts in L∞ and K had considerable consequences for size-at-age per species, suggesting substantial alterations in population age structures and abundances. Thus, when predicting climate change outcomes for species, outputs that couple shifts in climate space with altered body sizes and growth rates provide considerable insights into the population and community consequences, especially for species that cannot easily track their thermal niches.
Holonic Business Process Modeling in Small to Medium Sized Enterprises
Nur Budi Mulyono; Tezar Yuliansyah Saputra; Nur Arief Rahmatsyah
2012-01-01
Holonic modeling analysis which is the application of system thinking in design, manage, and improvement, is used in a novel context for business process modeling. An approach and techniques of holon and holarchies is presented specifically for small and medium sized enterprise process modeling development. The fitness of the approach is compared with well known reductionist or task breakdown approach. The strength and weaknesses of the holonic modeling is discussed with illustrating case exa...
Directory of Open Access Journals (Sweden)
Sandra Elena Gómez
2011-01-01
Full Text Available At present the reconfiguration and re-signification of traditional eating habits are not only connected to the food production process but also to its adaptation to certain globalized consumption and socialization forms [fast food], which are typical of urban life. This proposal was developed together with the students of a UNICEN-dependant secondary school, Colegio Nacional Ernesto Sabato. This paper is about the social consumption space, and it makes use of Human Sciences qualitative perspective to perform an analysis and interpretation in school geography. The film "Super Size Me" was shown and used as a didactic strategy. The complex relation between consumption, territory and society were explored within the current context of local and global growing social consumption practices. This paper is a qualitative approach, from moving visual images, to consumers'behavior, to their motivations and to their consuming habits within urban recreation and food consumption spaces
Directory of Open Access Journals (Sweden)
D. F. AL RIZA
2015-07-01
Full Text Available This paper presents a sizing optimization methodology of panel and battery capacity in a standalone photovoltaic system with lighting load. Performance of the system is identified by performing Loss of Power Supply Probability (LPSP calculation. Input data used for the calculation is the daily weather data and system components parameters. Capital Cost and Life Cycle Cost (LCC is calculated as optimization parameters. Design space for optimum system configuration is identified based on a given LPSP value, Capital Cost and Life Cycle Cost. Excess energy value is used as an over-design indicator in the design space. An economic analysis, including cost of the energy and payback period, for selected configurations are also studied.
Sakurai, Masahiro; Souto-Casares, Jaime; Chelikowsky, James R.
2016-07-01
We examine the structural stability and magnetization for nickel clusters containing up to 500 atoms by performing first-principles calculations based on pseudopotential in real space computed within density-functional theory. After structural relaxation, Ni clusters in this size range favor either an fcc structure, which is a crystal structure in bulk, or an icosahedral structure, which is expected for small clusters. The calculated total magnetic moments per atom of energetically stable clusters agree well with experiment, wherein the moments decrease nonmonotonically toward the bulk value as the cluster size increases. We analyze the spatial distribution of the local magnetic moment, which explains why the magnetic moments of Ni clusters are enhanced compared to their bulk value.
Use of swivel desks and aisle space to promote interaction in mid-sized college classrooms.
Directory of Open Access Journals (Sweden)
Robert G. Henshaw
2011-12-01
Full Text Available Traditional designs for most mid-sized college classrooms discourage 1 face-to-face interaction among students, 2 instructor movement in the classroom, and 3 efficient transitions between different kinds of learning activities. An experimental classroom piloted during Spring Semester 2011 at the University of North Carolina at Chapel Hill uses clusters of stationary desks that swivel 360-degrees and aisle space to address these challenges. The findings from a study involving ten courses taught in the room suggest that there is a need for designs that not only promote quality interactions but also facilitate movement between small group work, class discussion, and lecture.
Space use of wintering waterbirds in India: Influence of trophic ecology on home-range size
Namgail, Tsewang; Takekawa, John Y.; Balachandran, Sivananinthaperumal; Sathiyaselvam, Ponnusamy; Mundkur, Taej; Newman, Scott H.
2014-01-01
Relationship between species' home range and their other biological traits remains poorly understood, especially in migratory birds due to the difficulty associated with tracking them. Advances in satellite telemetry and remote sensing techniques have proved instrumental in overcoming such challenges. We studied the space use of migratory ducks through satellite telemetry with an objective of understanding the influence of body mass and feeding habits on their home-range sizes. We marked 26 individuals, representing five species of migratory ducks, with satellite transmitters during two consecutive winters in three Indian states. We used kernel methods to estimate home ranges and core use areas of these waterfowl, and assessed the influence of body mass and feeding habits on home-range size. Feeding habits influenced the home-range size of the migratory ducks. Carnivorous ducks had the largest home ranges, herbivorous ducks the smallest, while omnivorous species had intermediate home-ranges. Body mass did not explain variation in home-range size. To our knowledge, this is the first study of its kind on migratory ducks, and it has important implications for their conservation and management.
Response Surface Modelling of Electrosprayed Polyacrylonitrile Nanoparticle Size
Directory of Open Access Journals (Sweden)
Sanaz Khademolqorani
2014-01-01
Full Text Available Electrospraying (electrohydrodynamic spraying is a method of liquid atomization by electrical forces. Spraying solutions or suspensions allow production of fine particles, down to nanometer size. These particles are interesting for a wide variety of applications, thanks to their unprecedented chemical and physical behaviour in comparison to their bulk form. Knowledge of the particle size in powders is important in many studies employing nanoparticles. In this paper, the effect of some process parameters on the size of electrosprayed polyacrylonitrile particles is presented in the form of response surface model. The model is achieved by employing a factorial design to evaluate the influence of parameters on the polyacrylonitrile nanoparticle size and response surface methodology. Four electrospraying parameters, namely, applied voltage, electrospraying solution concentration, flow rate, and syringe needle diameter were considered.
Geant4 models for space radiation environment.
Ivantchenko, Anton; Nieminen, Petteri; Incerti, Sebastien; Santin, Giovanni; Ivantchenko, Vladimir; Grichine, Vladimir; Allison, John
The space radiation environment includes wide varieties of particles from electrons to heavy ions. In order to correctly predict the dose received by astronauts and devices the simulation models must have good applicability and produce accurate results from 10 MeV/u up to 10 GeV/u, where the most radioactive hazardous particles are present in the spectra. Appropriate models should also provide a good description of electromagnetic interactions down to very low energies (10 eV/u - 10 MeV/u) for understanding the damage mechanisms due to long-term low doses. Predictions of biological dose during long interplanetary journeys also need models for hadronic interactions of energetic heavy ions extending higher energies (10 GeV/u - 100 GeV/u, but possibly up to 1 TeV/u). Geant4 is a powerful toolkit, which in some areas well surpasses the needs from space radiation studies, while in other areas is being developed and/or validated to properly cover the modelling requirements outlined above. Our activities in ESA projects deal with the research and development of both Geant4 hadronic and electromagnetic physics. Recently the scope of verification tests and benchmarks has been extended. Hadronic tests and benchmarks run proton, pion, and ion interactions with matter at various energies. In the Geant4 hadronic sub-libraries, the most accurate cross sections have been identified and selected as a default for all particle types relevant to space applications. Significant developments were carried out for ion/ion interaction models. These now allow one to perform Geant4 simulations for all particle types and energies relevant to space applications. For the validation of ion models the hadronic testing suite for ion interactions was significantly extended. In this work the results of benchmarking versus data in a wide energy range for projectile protons and ions will be shown and discussed. Here we show results of the tests runs and their precision. Recommendations for Geant4
Model reduction for Space Station Freedom
Williams, Trevor
1992-01-01
Model reduction is an important practical problem in the control of flexible spacecraft, and a considerable amount of work has been carried out on this topic. Two of the best known methods developed are modal truncation and internal balancing. Modal truncation is simple to implement but can give poor results when the structure possesses clustered natural frequencies, as often occurs in practice. Balancing avoids this problem but has the disadvantages of high computational cost, possible numerical sensitivity problems, and no physical interpretation for the resulting balanced 'modes'. The purpose of this work is to examine the performance of the subsystem balancing technique developed by the investigator when tested on a realistic flexible space structure, in this case a model of the Permanently Manned Configuration (PMC) of Space Station Freedom. This method retains the desirable properties of standard balancing while overcoming the three difficulties listed above. It achieves this by first decomposing the structural model into subsystems of highly correlated modes. Each subsystem is approximately uncorrelated from all others, so balancing them separately and then combining yields comparable results to balancing the entire structure directly. The operation count reduction obtained by the new technique is considerable: a factor of roughly r(exp 2) if the system decomposes into r equal subsystems. Numerical accuracy is also improved significantly, as the matrices being operated on are of reduced dimension, and the modes of the reduced-order model now have a clear physical interpretation; they are, to first order, linear combinations of repeated-frequency modes.
Edgeworth streaming model for redshift space distortions
Uhlemann, Cora
2015-01-01
We derive the Edgeworth streaming model (ESM) for the redshift space correlation function starting from an arbitrary distribution function for biased tracers of dark matter by considering its two-point statistics and show that it reduces to the Gaussian streaming model (GSM) when neglecting non-Gaussianities. We test the accuracy of the GSM and ESM independent of perturbation theory using the Horizon Run 2 N-body halo catalog. While the monopole of the redshift space halo correlation function is well described by the GSM, higher multipoles improve upon including the leading order non-Gaussian correction in the ESM: the GSM quadrupole breaks down on scales below 30 Mpc/h whereas the ESM stays accurate to 2% within statistical errors down to 10 Mpc/h. To predict the scale dependent functions entering the streaming model we employ Convolution Lagrangian perturbation theory (CLPT) based on the dust model and local Lagrangian bias. Since dark matter halos carry an intrinsic length scale given by their Lagrangian r...
Modeling utilization distributions in space and time.
Keating, Kim A; Cherry, Steve
2009-07-01
W. Van Winkle defined the utilization distribution (UD) as a probability density that gives an animal's relative frequency of occurrence in a two-dimensional (x, y) plane. We extend Van Winkle's work by redefining the UD as the relative frequency distribution of an animal's occurrence in all four dimensions of space and time. We then describe a product kernel model estimation method, devising a novel kernel from the wrapped Cauchy distribution to handle circularly distributed temporal covariates, such as day of year. Using Monte Carlo simulations of animal movements in space and time, we assess estimator performance. Although not unbiased, the product kernel method yields models highly correlated (Pearson's r = 0.975) with true probabilities of occurrence and successfully captures temporal variations in density of occurrence. In an empirical example, we estimate the expected UD in three dimensions (x, y, and t) for animals belonging to each of two distinct bighorn sheep (Ovis canadensis) social groups in Glacier National Park, Montana, USA. Results show the method can yield ecologically informative models that successfully depict temporal variations in density of occurrence for a seasonally migratory species. Some implications of this new approach to UD modeling are discussed.
Correlators of Matrix Models on Homogeneous Spaces
Kitazawa, Y; Tomino, D; Kitazawa, Yoshihisa; Takayama, Yastoshi; Tomino, Dan
2004-01-01
We investigate the correlators of TrA_{mu}A_{nu} in matrix models on homogeneous spaces: S^2 and S^2 x S^2. Their expectation value is a good order parameter to measure the geometry of the space on which non-commutative gauge theory is realized. They also serve as the Wilson lines which carry the minimum momentum. We develop an efficient procedure to calculate them through 1PI diagrams. We determine the large N scaling behavior of the correlators. The order parameter shows that fuzzy S^2 x S^2 acquires a 4 dimensional fractal structure in contrast to fuzzy S^2. We also find that the two point functions exhibit logarithmic scaling violations.
Cognitive engineering models in space systems
Mitchell, Christine M.
1993-01-01
NASA space systems, including mission operations on the ground and in space, are complex, dynamic, predominantly automated systems in which the human operator is a supervisory controller. Models of cognitive functions in complex systems are needed to describe human performance and form the theoretical basis of operator workstation design, including displays, controls, and decision aids. Currently, there several candidate modeling methodologies. They include the Rasmussen abstraction/aggregation hierarchy and decision ladder, the goal-means network, the problem behavior graph, and the operator function model. The research conducted under the sponsorship of this grant focuses on the extension of the theoretical structure of the operator function model and its application to NASA Johnson mission operations and space station applications. The initial portion of this research consists of two parts. The first is a series of technical exchanges between NASA Johnson and Georgia Tech researchers. The purpose is to identify candidate applications for the current operator function model; prospects include mission operations and the Data Management System Testbed. The second portion will address extensions of the operator function model to tailor it to the specific needs of Johnson applications. At this point, we have accomplished two things. During a series of conversations with JSC researchers, we have defined the technical goal of the research supported by this grant to be the structural definition of the operator function model and its computer implementation, OFMspert. Both the OFM and OFMspert have matured to the point that they require infrastructure to facilitate use by researchers not involved in the evolution of the tools. The second accomplishment this year was the identification of the Payload Deployment and Retrieval System (PDRS) as a candidate system for the case study. In conjunction with government and contractor personnel in the Human-Computer Interaction Lab
Exploring Explanations of Subglacial Bedform Sizes Using Statistical Models.
Directory of Open Access Journals (Sweden)
John K Hillier
Full Text Available Sediments beneath modern ice sheets exert a key control on their flow, but are largely inaccessible except through geophysics or boreholes. In contrast, palaeo-ice sheet beds are accessible, and typically characterised by numerous bedforms. However, the interaction between bedforms and ice flow is poorly constrained and it is not clear how bedform sizes might reflect ice flow conditions. To better understand this link we present a first exploration of a variety of statistical models to explain the size distribution of some common subglacial bedforms (i.e., drumlins, ribbed moraine, MSGL. By considering a range of models, constructed to reflect key aspects of the physical processes, it is possible to infer that the size distributions are most effectively explained when the dynamics of ice-water-sediment interaction associated with bedform growth is fundamentally random. A 'stochastic instability' (SI model, which integrates random bedform growth and shrinking through time with exponential growth, is preferred and is consistent with other observations of palaeo-bedforms and geophysical surveys of active ice sheets. Furthermore, we give a proof-of-concept demonstration that our statistical approach can bridge the gap between geomorphological observations and physical models, directly linking measurable size-frequency parameters to properties of ice sheet flow (e.g., ice velocity. Moreover, statistically developing existing models as proposed allows quantitative predictions to be made about sizes, making the models testable; a first illustration of this is given for a hypothesised repeat geophysical survey of bedforms under active ice. Thus, we further demonstrate the potential of size-frequency distributions of subglacial bedforms to assist the elucidation of subglacial processes and better constrain ice sheet models.
A discrete-space urban model with environmental amenities
Liaila Tajibaeva; Robert G. Haight; Stephen Polasky
2008-01-01
This paper analyzes the effects of providing environmental amenities associated with open space in a discrete-space urban model and characterizes optimal provision of open space across a metropolitan area. The discrete-space model assumes distinct neighborhoods in which developable land is homogeneous within a neighborhood but heterogeneous across neighborhoods. Open...
Modeling size effect in the SMA response: a gradient theory
Tabesh, Majid; Boyd, James G.; Lagoudas, Dimitris C.
2014-03-01
Shape memory alloys (SMAs) show size effect in their response. The critical stresses, for instance, for the start of martensite and austenite transformations are reported to increase in some SMA wires for diameters below 100 μm. Simulation of such a behavior cannot be achieved using conventional theories that lack an intrinsic length scale in their constitutive modeling. To enable the size effect, a thermodynamically consistent constitutive model is developed, that in addition to conventional internal variables of martensitic volume fraction and transformation strain, contains the spatial gradient of martensitic volume fraction as an internal variable. The developed theory is simplified for 1D cases and analytical solutions for pure bending of SMA beams are presented. The gradient model captures the size effect in the response of the studied SMA structures.
Approximate Methods for State-Space Models.
Koyama, Shinsuke; Pérez-Bolde, Lucia Castellanos; Shalizi, Cosma Rohilla; Kass, Robert E
2010-03-01
State-space models provide an important body of techniques for analyzing time-series, but their use requires estimating unobserved states. The optimal estimate of the state is its conditional expectation given the observation histories, and computing this expectation is hard when there are nonlinearities. Existing filtering methods, including sequential Monte Carlo, tend to be either inaccurate or slow. In this paper, we study a nonlinear filter for nonlinear/non-Gaussian state-space models, which uses Laplace's method, an asymptotic series expansion, to approximate the state's conditional mean and variance, together with a Gaussian conditional distribution. This Laplace-Gaussian filter (LGF) gives fast, recursive, deterministic state estimates, with an error which is set by the stochastic characteristics of the model and is, we show, stable over time. We illustrate the estimation ability of the LGF by applying it to the problem of neural decoding and compare it to sequential Monte Carlo both in simulations and with real data. We find that the LGF can deliver superior results in a small fraction of the computing time.
Microblog Sentiment Analysis with Emoticon Space Model
Institute of Scientific and Technical Information of China (English)
姜飞; 刘奕群; 孙甲申; 朱璇; 张敏; 马少平
2015-01-01
Emoticons have been widely employed to express different types of moods, emotions, and feelings in microblog environments. They are therefore regarded as one of the most important signals for microblog sentiment analysis. Most existing studies use several emoticons that convey clear emotional meanings as noisy sentiment labels or similar sentiment indicators. However, in practical microblog environments, tens or even hundreds of emoticons are frequently adopted and all emoticons have their own unique emotional meanings. Besides, a considerable number of emoticons do not have clear emotional meanings. An improved sentiment analysis model should not overlook these phenomena. Instead of manually assigning sentiment labels to several emoticons that convey relatively clear meanings, we propose the emoticon space model (ESM) that leverages more emoticons to construct word representations from a massive amount of unlabeled data. By projecting words and microblog posts into an emoticon space, the proposed model helps identify subjectivity, polarity, and emotion in microblog environments. The experimental results for a public microblog benchmark corpus (NLP&CC 2013) indicate that ESM effectively leverages emoticon signals and outperforms previous state-of-the-art strategies and benchmark best runs.
Size, Albedo, and Taxonomy of the Don Quijote Space Mission Target
Harris, Alan; Mueller, Michael; Fitzsimmons, Alan
2006-03-01
Rendezvous and lander missions are a very effective but very expensive way of investigating Solar-System bodies. The planning, optimization and success of space missions depends crucially on prior remotely-sensed knowledge of target bodies. Near-Earth asteroids (NEAs), which are mainly fragments of main-belt asteroids, are seen as important goals for investigation by space missions, mainly due to the role their forebears played in planet formation and the evolution of the Solar System, but also for the pragmatic reason that these objects can collide with the Earth with potentially devastating consequences. The European Space Agency is currently planning the Don Quijote mission to a NEA, which includes a rendezvous (and perhaps a lander) spacecraft and an impactor vehicle. The aim is to study the physical properties of the target asteroid and the effects of the impact on its dynamical state, as a first step in considering realistic mitigation measures against an eventual hazardous NEA. Two potential targets have been selected for the mission, the preferred one being (10302) 1989 ML, which is energetically easier to reach and is possibly a scientifically interesting primitive asteroid. However, due to the ambiguity of available spectral data, it is currently not possible to confidently determine the taxonomic type and mineralogy of this object. Crucially, the albedo is uncertain by a factor of 10, which leads to large uncertainties in the size and mass and hence the planned near-surface operations of Don Quijote. Thermal-infrared observations are urgently required for accurate size and albedo determination. These observations, which can only be carried out by Spitzer and would require only a modest amount of observing time, would enable an accurate diameter to be derived for the first time and the resulting albedo would remove the taxonomic ambiguity. The proposed Spitzer observations are critical for effective mission planning and would greatly increase our
Cuffed Endotracheal Tube Size and Leakage in Pediatric Tracheal Models
Directory of Open Access Journals (Sweden)
Jun Hyun Kim
2014-04-01
Full Text Available Object: Cuffed endotracheal tubes are increasingly used in pediatric patients in the hope that they can reduce air leakage and tube size mismatch by just inflating the cuff. Authors compared influence of various tube sizes and different levels of cuff pressures to air leakage around the cuff, in artificial tracheal models. Methods: Six PVC cylinders of different internal diameters (ID: 8.15, 8.50, 9.70, 12.05, 14.50, and 20.00 mm were prepared. An artificial lung connected with cylinder was ventilated with an anesthesia machine. Cuffed endotracheal tubes of different sizes (ID 3.0~8.0 were located in the cylinders and the cuff was inflated with various pressures (15, 20, 25, 30 and 35 cm H2O. Expiratory tidal volume was measured with more than 25% loss of baseline expiratory tidal volume was considered significant air leakage. Results: Tube sizes same as, or larger than ID 5.0 didn’t show significant air leakage for any trachea model, only if the inflated cuff size is larger than the cylinder ID, except ID 5.5 tube at cuff pressure 15 cm H2O and 20 cm H2O, in 12.05 mm cylinder. Tubes sizes same as or smaller than ID 4.5, which have short cuff lengths and sizes than tubes larger than, or same as ID 5.0, leaked significantly at any tracheal models, except ID 4.5 tube at cuff pressure 35 cm H2O, in 8.50 mm cylinder. Conclusion: In PVC pediatric tracheal models, tubes same as, or smaller than ID 4.5 are inferior to tubes same as, or larger than ID 5.0 in preventing air leakage, and may need a higher cuff pressure to reduce air leakage. Further clinical studies could be designed based on our results.
Assumptions behind size-based ecosystem models are realistic
DEFF Research Database (Denmark)
Andersen, Ken Haste; Blanchard, Julia L.; Fulton, Elizabeth A.;
2016-01-01
A recent publication about balanced harvesting (Froese et al., ICES Journal of Marine Science; doi:10.1093/icesjms/fsv122) contains several erroneous statements about size-spectrum models. We refute the statements by showing that the assumptions pertaining to size-spectrum models discussed...... by Froese et al. are realistic and consistent. We further show that the assumption about density-dependence being described by a stock recruitment relationship is responsible for determining whether a peak in the cohort biomass of a population occurs late or early in life. Finally, we argue...
Selection of MOSFET Sizes by Fuzzy Sets Intersection in the Feasible Solutions Space
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S. Polanco-Martagón
2012-06-01
Full Text Available A fuzzy sets intersection procedure to select the optimum sizes of analog circuits composed of metal-oxidesemiconductorfield-effect-transistors (MOSFETs, is presented. The cases of study are voltage followers (VFs and acurrent-feedback operational amplifier (CFOA, where the width (W and length (L of the MOSFETs are selected fromthe space of feasible solutions computed by swarm or evolutionary algorithms. The evaluation of three objectives,namely: gain, bandwidth and power consumption; is performed using HSPICETM with standard integrated circuit (ICtechnology of 0.35μm for the VFs and 180nm for the CFOA. Therefore, the intersection procedure among three fuzzysets representing “gain close to unity”, ”high bandwidth” and “minimum power consumption”, is presented. The mainadvantage relies on its usefulness to select feasible W/L sizes automatically but by considering deviation percentagesfrom the desired target specifications. Basically, assigning a threshold to each fuzzy set does it. As a result, theproposed approach selects the best feasible sizes solutions to guarantee and to enhance the performances of the ICsin analog signal processing applications.
Integrated Space Asset Management Database and Modeling
Gagliano, L.; MacLeod, T.; Mason, S.; Percy, T.; Prescott, J.
The Space Asset Management Database (SAM-D) was implemented in order to effectively track known objects in space by ingesting information from a variety of databases and performing calculations to determine the expected position of the object at a specified time. While SAM-D performs this task very well, it is limited by technology and is not available outside of the local user base. Modeling and simulation can be powerful tools to exploit the information contained in SAM-D. However, the current system does not allow proper integration options for combining the data with both legacy and new M&S tools. A more capable data management infrastructure would extend SAM-D to support the larger data sets to be generated by the COI. A service-oriented architecture model will allow it to easily expand to incorporate new capabilities, including advanced analytics, M&S tools, fusion techniques and user interface for visualizations. Based on a web-centric approach, the entire COI will be able to access the data and related analytics. In addition, tight control of information sharing policy will increase confidence in the system, which would encourage industry partners to provide commercial data. SIMON is a Government off the Shelf information sharing platform in use throughout DoD and DHS information sharing and situation awareness communities. SIMON providing fine grained control to data owners allowing them to determine exactly how and when their data is shared. SIMON supports a micro-service approach to system development, meaning M&S and analytic services can be easily built or adapted. It is uniquely positioned to fill this need as an information-sharing platform with a proven track record of successful situational awareness system deployments. Combined with the integration of new and legacy M&S tools, a SIMON-based architecture will provide a robust SA environment for the NASA SA COI that can be extended and expanded indefinitely. First Results of Coherent Uplink from a
Model catalysis by size-selected cluster deposition
Energy Technology Data Exchange (ETDEWEB)
Anderson, Scott [Univ. of Utah, Salt Lake City, UT (United States)
2015-11-20
This report summarizes the accomplishments during the last four years of the subject grant. Results are presented for experiments in which size-selected model catalysts were studied under surface science and aqueous electrochemical conditions. Strong effects of cluster size were found, and by correlating the size effects with size-dependent physical properties of the samples measured by surface science methods, it was possible to deduce mechanistic insights, such as the factors that control the rate-limiting step in the reactions. Results are presented for CO oxidation, CO binding energetics and geometries, and electronic effects under surface science conditions, and for the electrochemical oxygen reduction reaction, ethanol oxidation reaction, and for oxidation of carbon by water.
Brisset, Julie; Kothe, Stefan; Weidling, René; Blum, Jürgen
2013-01-01
The Suborbital Particle Aggregation and Collision Experiment (SPACE) is a novel approach to study the collision properties of submillimeter-sized, highly porous dust aggregates. The experiment was designed, built and carried out to increase our knowledge about the processes dominating the first phase of planet formation. During this phase, the growth of planetary precursors occurs by agglomeration of micrometer-sized dust grains into aggregates of at least millimeters to centimeters in size. However, the formation of larger bodies from the so-formed building blocks is not yet fully understood. Recent numerical models on dust growth lack a particular support by experimental studies in the size range of submillimeters, because these particles are predicted to collide at very gentle relative velocities of below 1 cm/s that can only be achieved in a reduced-gravity environment. The SPACE experiment investigates the collision behavior of an ensemble of silicate-dust aggregates inside several evacuated glass contai...
Modeling Bivariate Longitudinal Hormone Profiles by Hierarchical State Space Models.
Liu, Ziyue; Cappola, Anne R; Crofford, Leslie J; Guo, Wensheng
2014-01-01
The hypothalamic-pituitary-adrenal (HPA) axis is crucial in coping with stress and maintaining homeostasis. Hormones produced by the HPA axis exhibit both complex univariate longitudinal profiles and complex relationships among different hormones. Consequently, modeling these multivariate longitudinal hormone profiles is a challenging task. In this paper, we propose a bivariate hierarchical state space model, in which each hormone profile is modeled by a hierarchical state space model, with both population-average and subject-specific components. The bivariate model is constructed by concatenating the univariate models based on the hypothesized relationship. Because of the flexible framework of state space form, the resultant models not only can handle complex individual profiles, but also can incorporate complex relationships between two hormones, including both concurrent and feedback relationship. Estimation and inference are based on marginal likelihood and posterior means and variances. Computationally efficient Kalman filtering and smoothing algorithms are used for implementation. Application of the proposed method to a study of chronic fatigue syndrome and fibromyalgia reveals that the relationships between adrenocorticotropic hormone and cortisol in the patient group are weaker than in healthy controls.
Multivariable Wind Modeling in State Space
DEFF Research Database (Denmark)
Sichani, Mahdi Teimouri; Pedersen, B. J.
2011-01-01
Turbulence of the incoming wind field is of paramount importance to the dynamic response of wind turbines. Hence reliable stochastic models of the turbulence should be available from which time series can be generated for dynamic response and structural safety analysis. In the paper an empirical...... cross-spectral density function for the along-wind turbulence component over the rotor plane is taken as the starting point. The spectrum is spatially discretized in terms of a Hermitian cross-spectral density matrix for the turbulence state vector which turns out not to be positive definite. Since...... the succeeding state space and ARMA modeling of the turbulence rely on the positive definiteness of the cross-spectral density matrix, the problem with the non-positive definiteness of such matrices is at first addressed and suitable treatments regarding it are proposed. From the adjusted positive definite cross...
Modeling Physarum space exploration using memristors
Ntinas, V.; Vourkas, I.; Sirakoulis, G. Ch; Adamatzky, A. I.
2017-05-01
Slime mold Physarum polycephalum optimizes its foraging behaviour by minimizing the distances between the sources of nutrients it spans. When two sources of nutrients are present, the slime mold connects the sources, with its protoplasmic tubes, along the shortest path. We present a two-dimensional mesh grid memristor based model as an approach to emulate Physarum’s foraging strategy, which includes space exploration and reinforcement of the optimally formed interconnection network in the presence of multiple aliment sources. The proposed algorithmic approach utilizes memristors and LC contours and is tested in two of the most popular computational challenges for Physarum, namely maze and transportation networks. Furthermore, the presented model is enriched with the notion of noise presence, which positively contributes to a collective behavior and enables us to move from deterministic to robust results. Consequently, the corresponding simulation results manage to reproduce, in a much better qualitative way, the expected transportation networks.
A probabilistic model of RNA conformational space
DEFF Research Database (Denmark)
Frellsen, Jes; Moltke, Ida; Thiim, Martin
2009-01-01
The increasing importance of non-coding RNA in biology and medicine has led to a growing interest in the problem of RNA 3-D structure prediction. As is the case for proteins, RNA 3-D structure prediction methods require two key ingredients: an accurate energy function and a conformational sampling...... procedure. Both are only partly solved problems. Here, we focus on the problem of conformational sampling. The current state of the art solution is based on fragment assembly methods, which construct plausible conformations by stringing together short fragments obtained from experimental structures. However...... efficient sampling of RNA conformations in continuous space, and with associated probabilities. We show that the model captures several key features of RNA structure, such as its rotameric nature and the distribution of the helix lengths. Furthermore, the model readily generates native-like 3-D...
Space Weathering in the Fine Size Fractions of Lunar Soils: Soil Maturity Effects
Keller, L. P.; Wentworth, S. J.; McKay, D. S.; Taylor, L. A.; Pieters, C.; Morris, R. V.
1999-01-01
The effects of space weathering on the optical properties of lunar materials have been well documented. These effects include a reddened continuum slope, lowered albedo, and attenuated absorption features in reflectance spectra of lunar soils as compared to finely comminuted rocks from the same Apollo sites. However, the regolith processes that cause these effects are not well known, nor is the petrographic setting of the products of these processes fully understood. A Lunar Soil Characterization Consortium has been formed with the purpose of systematically integrating chemical and mineralogical data with the optical properties of lunar soils. Understanding space-weathering effects is critical in order to fully integrate the lunar sample collection with remotely-sensed data from recent robotic missions (e.g., Lunar Prospector, Clementine, and Galileo) We have shown that depositional processes (condensation of impact-derived vapors, sputter deposits, accreted impact material, e.g., splash glass, spherules, etc.) are a major factor in the modification of the optical surfaces of lunar regolith materials. In mature soils, it is the size and distribution of the nanophase metal in the soil grains that has the major effect on optical properties. In this report, we compare and contrast the space-weathering effects in an immature and a mature soil with similar elemental compositions. For this study, we analyzed effects). The nanophase Fe in these rims probably accounts for a significant fraction of the increase in Is/FeO measured in these size fractions. In addition to the rims, the majority of particles also show abundant accreted material in the form of glass splashes and spherules that also contain nanophase Fe. In stark contrast, the surfaces of the mineral grains in the 71061 sample are relatively prisitine, as only about 14% of the mineral grains in the sample exhibited amorphous rims. Furthermore, the mineral particles are more angular and show greater surface
Granger causality for state-space models.
Barnett, Lionel; Seth, Anil K
2015-04-01
Granger causality has long been a prominent method for inferring causal interactions between stochastic variables for a broad range of complex physical systems. However, it has been recognized that a moving average (MA) component in the data presents a serious confound to Granger causal analysis, as routinely performed via autoregressive (AR) modeling. We solve this problem by demonstrating that Granger causality may be calculated simply and efficiently from the parameters of a state-space (SS) model. Since SS models are equivalent to autoregressive moving average models, Granger causality estimated in this fashion is not degraded by the presence of a MA component. This is of particular significance when the data has been filtered, downsampled, observed with noise, or is a subprocess of a higher dimensional process, since all of these operations-commonplace in application domains as diverse as climate science, econometrics, and the neurosciences-induce a MA component. We show how Granger causality, conditional and unconditional, in both time and frequency domains, may be calculated directly from SS model parameters via solution of a discrete algebraic Riccati equation. Numerical simulations demonstrate that Granger causality estimators thus derived have greater statistical power and smaller bias than AR estimators. We also discuss how the SS approach facilitates relaxation of the assumptions of linearity, stationarity, and homoscedasticity underlying current AR methods, thus opening up potentially significant new areas of research in Granger causal analysis.
Finite size scaling in the planar Lebwohl-Lasher model
Mondal, Enakshi; Roy, Soumen Kumar
2003-06-01
The standard finite size scaling method for second order phase transition has been applied to Monte Carlo data obtained for a planar Lebwohl-Lasher lattice model using the Wolff cluster algorithm. We obtain Tc and the exponents γ, ν, and z and the results are different from those obtained by other investigators.
A Dynamic Lot-Sizing Model with Demand Time Windows
C.Y. Lee (Chung-Yee); S. Çetinkaya; A.P.M. Wagelmans (Albert)
1999-01-01
textabstractOne of the basic assumptions of the classical dynamic lot-sizing model is that the aggregate demand of a given period must be satisfied in that period. Under this assumption, if backlogging is not allowed then the demand of a given period cannot be delivered earlier or later than the
A dynamic lot-sizing model with demand time windows
C.Y. Lee (Chung-Yee); S. Cetinkaya; A.P.M. Wagelmans (Albert)
1999-01-01
textabstractOne of the basic assumptions of the classical dynamic lot-sizing model is that the aggregate demand of a given period must be satisfied in that period. Under this assumption, if backlogging is not allowed then the demand of a given period cannot be delivered earlier or later than the
Resilience and Critical Stock Size in a Stochastic Recruitment Model
Grasman, J.; Huiskes, M.J.
2001-01-01
A stochastic model for fish recruitment is fitted to data after performing an age-structured stock assessment. The main aim is to investigate the relation between safe levels of spawning stock size and fish stock resilience. Resilience indicators, such as stock recovery time and the frequency that a
A dynamic lot-sizing model with demand time windows
C.Y. Lee (Chung-Yee); S. Cetinkaya; A.P.M. Wagelmans (Albert)
1999-01-01
textabstractOne of the basic assumptions of the classical dynamic lot-sizing model is that the aggregate demand of a given period must be satisfied in that period. Under this assumption, if backlogging is not allowed then the demand of a given period cannot be delivered earlier or later than the pe
A Dynamic Lot-Sizing Model with Demand Time Windows
C.Y. Lee (Chung-Yee); S. Çetinkaya; A.P.M. Wagelmans (Albert)
1999-01-01
textabstractOne of the basic assumptions of the classical dynamic lot-sizing model is that the aggregate demand of a given period must be satisfied in that period. Under this assumption, if backlogging is not allowed then the demand of a given period cannot be delivered earlier or later than the per
Parabolic Free Boundary Price Formation Models Under Market Size Fluctuations
Markowich, Peter A.
2016-10-04
In this paper we propose an extension of the Lasry-Lions price formation model which includes uctuations of the numbers of buyers and vendors. We analyze the model in the case of deterministic and stochastic market size uctuations and present results on the long time asymptotic behavior and numerical evidence and conjectures on periodic, almost periodic, and stochastic uctuations. The numerical simulations extend the theoretical statements and give further insights into price formation dynamics.
Boundary states and finite size effects in sine-Gordon model with Neumann boundary condition
Bajnok, Z; Takács, G
2001-01-01
The sine-Gordon model with Neumann boundary condition is investigated. Using the bootstrap principle the spectrum of boundary bound states is established. Somewhat surprisingly it is found that Coleman-Thun diagrams and bound state creation may coexist. A framework to describe finite size effects in boundary integrable theories is developed and used together with the truncated conformal space approach to confirm the bound states and reflection factors derived by bootstrap.
Cascades in the Threshold Model for varying system sizes
Karampourniotis, Panagiotis; Sreenivasan, Sameet; Szymanski, Boleslaw; Korniss, Gyorgy
2015-03-01
A classical model in opinion dynamics is the Threshold Model (TM) aiming to model the spread of a new opinion based on the social drive of peer pressure. Under the TM a node adopts a new opinion only when the fraction of its first neighbors possessing that opinion exceeds a pre-assigned threshold. Cascades in the TM depend on multiple parameters, such as the number and selection strategy of the initially active nodes (initiators), and the threshold distribution of the nodes. For a uniform threshold in the network there is a critical fraction of initiators for which a transition from small to large cascades occurs, which for ER graphs is largerly independent of the system size. Here, we study the spread contribution of each newly assigned initiator under the TM for different initiator selection strategies for synthetic graphs of various sizes. We observe that for ER graphs when large cascades occur, the spread contribution of the added initiator on the transition point is independent of the system size, while the contribution of the rest of the initiators converges to zero at infinite system size. This property is used for the identification of large transitions for various threshold distributions. Supported in part by ARL NS-CTA, ARO, ONR, and DARPA.
Modeling of Microporosity Size Distribution in Aluminum Alloy A356
Yao, Lu; Cockcroft, Steve; Zhu, Jindong; Reilly, Carl
2011-12-01
Porosity is one of the most common defects to degrade the mechanical properties of aluminum alloys. Prediction of pore size, therefore, is critical to optimize the quality of castings. Moreover, to the design engineer, knowledge of the inherent pore population in a casting is essential to avoid potential fatigue failure of the component. In this work, the size distribution of the porosity was modeled based on the assumptions that the hydrogen pores are nucleated heterogeneously and that the nucleation site distribution is a Gaussian function of hydrogen supersaturation in the melt. The pore growth is simulated as a hydrogen-diffusion-controlled process, which is driven by the hydrogen concentration gradient at the pore liquid interface. Directionally solidified A356 (Al-7Si-0.3Mg) alloy castings were used to evaluate the predictive capability of the proposed model. The cast pore volume fraction and size distributions were measured using X-ray microtomography (XMT). Comparison of the experimental and simulation results showed that good agreement could be obtained in terms of both porosity fraction and size distribution. The model can effectively evaluate the effect of hydrogen content, heterogeneous pore nucleation population, cooling conditions, and degassing time on microporosity formation.
An introduction to state space modeling (in Russian)
Alexander Tsyplakov
2011-01-01
Many time series models, primarily various models with unobservable components, can be represented in a so called state space form. A state space model is a powerful tool that allows one to apply to the original model a wide range of standard procedures including estimation and forecasting. This essay provides a survey of this universal class of models and related procedures.
Investigation of FE model size definition for surface coating application
Chen, Yanhong; Zhuang, Weimin; Wang, Shiwen; Lin, Jianguo; Balint, Daniel; Shan, Debin
2012-09-01
An efficient prediction mechanical performance of coating structures has been a constant concern since the dawn of surface engineering. However, predictive models presented by initial research are normally based on traditional solid mechanics, and thus cannot predict coating performance accurately. Also, the high computational costs that originate from the exclusive structure of surface coating systems (a big difference in the order of coating and substrate) are not well addressed by these models. To fill the needs for accurate prediction and low computational costs, a multi-axial continuum damage mechanics (CDM)-based constitutive model is introduced for the investigation of the load bearing capacity and fracture properties of coatings. Material parameters within the proposed constitutive model are determined for a typical coating (TiN) and substrate (Cu) system. An efficient numerical subroutine is developed to implement the determined constitutive model into the commercial FE solver, ABAQUS, through the user-defined subroutine, VUMAT. By changing the geometrical sizes of FE models, a series of computations are carried out to investigate (1) loading features, (2) stress distributions, and (3) failure features of the coating system. The results show that there is a critical displacement corresponding to each FE model size, and only if the applied normal loading displacement is smaller than the critical displacement, a reasonable prediction can be achieved. Finally, a 3D map of the critical displacement is generated to provide guidance for users to determine an FE model with suitable geometrical size for surface coating simulations. This paper presents an effective modelling approach for the prediction of mechanical performance of surface coatings.
Verdian, J. P.; Sklar, L. S.; Moore, J. R.; Rosenberg, D. J.
2016-12-01
What controls the size of sediments produced on hillslopes and supplied to river channels? This is an important but unanswered question in geomorphology and sedimentology. One hypothesis is that the initial size distribution of rock fragments eroded from bedrock is related to the distribution of spacing between pre-existing fractures in the bedrock. Slopes of talus that accumulate below eroding cliffs provide a simple natural experiment to test this hypothesis. We studied talus slopes and cliff faces at more than 20 locations in California, USA, where cliff retreat rates were previously measured by Moore et al., 2009. Rock types included andesite, basalt, granodiorite and meta-sediment. To quantify fracture spacing we measured fracture frequency and orientation along scan lines at the base of the cliff. We also used scaled photographs of the cliff face to characterize the shape, size and surface area of discrete blocks. We measured talus particle size distributions using surface point counts along transects oriented downslope from the cliff face, and mapped facies of distinct size distributions. To explore the effect of chemical weathering on talus size we sampled cliff faces and talus particles for x-ray fluorescence analysis to test for depletion of labile cations relative to source rock. Preliminary results suggest that talus size distributions are strongly correlated with bedrock fracture spacing, although systematic differences do occur. In some cases, talus sizes are larger than the spacing between fractures because the detached particles still retain truncated fractures. In other cases, talus is smaller than cliff fracture spacing, presumably because particle size is reduced by fragmentation on impact and weathering during transport down the talus slope. Further analysis will explore whether cliff retreat rate and extent of chemical weathering, as well as rock type and local climate, can explain between-site differences in the size of particles produced.
Size reduction techniques for vital compliant VHDL simulation models
Rich, Marvin J.; Misra, Ashutosh
2006-08-01
A method and system select delay values from a VHDL standard delay file that correspond to an instance of a logic gate in a logic model. Then the system collects all the delay values of the selected instance and builds super generics for the rise-time and the fall-time of the selected instance. Then, the system repeats this process for every delay value in the standard delay file (310) that correspond to every instance of every logic gate in the logic model. The system then outputs a reduced size standard delay file (314) containing the super generics for every instance of every logic gate in the logic model.
Modeling the reconstructed BAO in Fourier space
Seo, Hee-Jong; Beutler, Florian; Ross, Ashley J.; Saito, Shun
2016-08-01
The density field reconstruction technique, which partially reverses the non-linear degradation of the Baryon acoustic oscillation (BAO) feature in the galaxy redshift surveys, has been successful in substantially improving the cosmology constraints from recent surveys such as Baryon Oscillation Spectroscopic Survey (BOSS). We estimate the efficiency of the method as a function of various reconstruction details. To directly quantify the BAO information in non-linear density fields before and after reconstruction, we calculate the cross-correlations (i.e. propagators) of the pre(post)-reconstructed density field with the initial linear field using a mock sample that mimics the clustering of the BOSS galaxies. The results directly provide the BAO damping as a function of wavenumber that can be implemented into the Fisher matrix analysis. We focus on investigating the dependence of the propagator on a choice of smoothing filters and on two major different conventions of the redshift-space density field reconstruction that have been used in literature. By estimating the BAO signal to noise for each case, we predict constraints on the angular diameter distance and Hubble parameter using the Fisher matrix analysis. We thus determine an optimal Gaussian smoothing filter scale for the signal-to-noise level of the BOSS CMASS. We also present appropriate BAO fitting models for different reconstruction methods based on the first- and second-order Lagrangian perturbation theory in Fourier space. Using the mock data, we show that the modified BAO fitting model can substantially improve the accuracy of the BAO position in the best fits as well as the goodness of the fits.
Modeling missing data in knowledge space theory.
de Chiusole, Debora; Stefanutti, Luca; Anselmi, Pasquale; Robusto, Egidio
2015-12-01
Missing data are a well known issue in statistical inference, because some responses may be missing, even when data are collected carefully. The problem that arises in these cases is how to deal with missing data. In this article, the missingness is analyzed in knowledge space theory, and in particular when the basic local independence model (BLIM) is applied to the data. Two extensions of the BLIM to missing data are proposed: The former, called ignorable missing BLIM (IMBLIM), assumes that missing data are missing completely at random; the latter, called missing BLIM (MissBLIM), introduces specific dependencies of the missing data on the knowledge states, thus assuming that the missing data are missing not at random. The IMBLIM and the MissBLIM modeled the missingness in a satisfactory way, in both a simulation study and an empirical application, depending on the process that generates the missingness: If the missing data-generating process is of type missing completely at random, then either IMBLIM or MissBLIM provide adequate fit to the data. However, if the pattern of missingness is functionally dependent upon unobservable features of the data (e.g., missing answers are more likely to be wrong), then only a correctly specified model of the missingness distribution provides an adequate fit to the data.
Space Station crew safety - Human factors model
Cohen, M. M.; Junge, M. K.
1984-01-01
A model of the various human factors issues and interactions that might affect crew safety is developed. The first step addressed systematically the central question: How is this Space Station different from all other spacecraft? A wide range of possible issue was identified and researched. Five major topics of human factors issues that interacted with crew safety resulted: Protocols, Critical Habitability, Work Related Issues, Crew Incapacitation and Personal Choice. Second, an interaction model was developed that would show some degree of cause and effect between objective environmental or operational conditions and the creation of potential safety hazards. The intermediary steps between these two extremes of causality were the effects on human performance and the results of degraded performance. The model contains three milestones: stressor, human performance (degraded) and safety hazard threshold. Between these milestones are two countermeasure intervention points. The first opportunity for intervention is the countermeasure against stress. If this countermeasure fails, performance degrades. The second opportunity for intervention is the countermeasure against error. If this second countermeasure fails, the threshold of a potential safety hazard may be crossed.
Coagulation-Fragmentation Model for Animal Group-Size Statistics
Degond, Pierre; Liu, Jian-Guo; Pego, Robert L.
2017-04-01
We study coagulation-fragmentation equations inspired by a simple model proposed in fisheries science to explain data for the size distribution of schools of pelagic fish. Although the equations lack detailed balance and admit no H-theorem, we are able to develop a rather complete description of equilibrium profiles and large-time behavior, based on recent developments in complex function theory for Bernstein and Pick functions. In the large-population continuum limit, a scaling-invariant regime is reached in which all equilibria are determined by a single scaling profile. This universal profile exhibits power-law behavior crossing over from exponent -2/3 for small size to -3/2 for large size, with an exponential cutoff.
Coagulation-Fragmentation Model for Animal Group-Size Statistics
Degond, Pierre; Liu, Jian-Guo; Pego, Robert L.
2016-10-01
We study coagulation-fragmentation equations inspired by a simple model proposed in fisheries science to explain data for the size distribution of schools of pelagic fish. Although the equations lack detailed balance and admit no H-theorem, we are able to develop a rather complete description of equilibrium profiles and large-time behavior, based on recent developments in complex function theory for Bernstein and Pick functions. In the large-population continuum limit, a scaling-invariant regime is reached in which all equilibria are determined by a single scaling profile. This universal profile exhibits power-law behavior crossing over from exponent -2/3 for small size to -3/2 for large size, with an exponential cutoff.
Trap configuration and spacing influences parameter estimates in spatial capture-recapture models.
Directory of Open Access Journals (Sweden)
Catherine C Sun
Full Text Available An increasing number of studies employ spatial capture-recapture models to estimate population size, but there has been limited research on how different spatial sampling designs and trap configurations influence parameter estimators. Spatial capture-recapture models provide an advantage over non-spatial models by explicitly accounting for heterogeneous detection probabilities among individuals that arise due to the spatial organization of individuals relative to sampling devices. We simulated black bear (Ursus americanus populations and spatial capture-recapture data to evaluate the influence of trap configuration and trap spacing on estimates of population size and a spatial scale parameter, sigma, that relates to home range size. We varied detection probability and home range size, and considered three trap configurations common to large-mammal mark-recapture studies: regular spacing, clustered, and a temporal sequence of different cluster configurations (i.e., trap relocation. We explored trap spacing and number of traps per cluster by varying the number of traps. The clustered arrangement performed well when detection rates were low, and provides for easier field implementation than the sequential trap arrangement. However, performance differences between trap configurations diminished as home range size increased. Our simulations suggest it is important to consider trap spacing relative to home range sizes, with traps ideally spaced no more than twice the spatial scale parameter. While spatial capture-recapture models can accommodate different sampling designs and still estimate parameters with accuracy and precision, our simulations demonstrate that aspects of sampling design, namely trap configuration and spacing, must consider study area size, ranges of individual movement, and home range sizes in the study population.
Trap configuration and spacing influences parameter estimates in spatial capture-recapture models.
Sun, Catherine C; Fuller, Angela K; Royle, J Andrew
2014-01-01
An increasing number of studies employ spatial capture-recapture models to estimate population size, but there has been limited research on how different spatial sampling designs and trap configurations influence parameter estimators. Spatial capture-recapture models provide an advantage over non-spatial models by explicitly accounting for heterogeneous detection probabilities among individuals that arise due to the spatial organization of individuals relative to sampling devices. We simulated black bear (Ursus americanus) populations and spatial capture-recapture data to evaluate the influence of trap configuration and trap spacing on estimates of population size and a spatial scale parameter, sigma, that relates to home range size. We varied detection probability and home range size, and considered three trap configurations common to large-mammal mark-recapture studies: regular spacing, clustered, and a temporal sequence of different cluster configurations (i.e., trap relocation). We explored trap spacing and number of traps per cluster by varying the number of traps. The clustered arrangement performed well when detection rates were low, and provides for easier field implementation than the sequential trap arrangement. However, performance differences between trap configurations diminished as home range size increased. Our simulations suggest it is important to consider trap spacing relative to home range sizes, with traps ideally spaced no more than twice the spatial scale parameter. While spatial capture-recapture models can accommodate different sampling designs and still estimate parameters with accuracy and precision, our simulations demonstrate that aspects of sampling design, namely trap configuration and spacing, must consider study area size, ranges of individual movement, and home range sizes in the study population.
Bilayer Thickness Mismatch Controls Domain Size in Model Membranes
Energy Technology Data Exchange (ETDEWEB)
Heberle, Frederick A [ORNL; Petruzielo, Robin S [ORNL; Pan, Jianjun [ORNL; Drazba, Paul [ORNL; Kucerka, Norbert [Canadian Neutron Beam Centre and Comelius University (Slovakia); Feigenson, Gerald [Cornell University; Katsaras, John [ORNL
2013-01-01
The observation of lateral phase separation in lipid bilayers has received considerable attention, especially in connection to lipid raft phenomena in cells. It is widely accepted that rafts play a central role in cellular processes, notably signal transduction. While micrometer-sized domains are observed with some model membrane mixtures, rafts much smaller than 100 nm beyond the reach of optical microscopy are now thought to exist, both in vitro and in vivo. We have used small-angle neutron scattering, a probe free technique, to measure the size of nanoscopic membrane domains in unilamellar vesicles with unprecedented accuracy. These experiments were performed using a four-component model system containing fixed proportions of cholesterol and the saturated phospholipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), mixed with varying amounts of the unsaturated phospholipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoylsn- glycero-3-phosphocholine (DOPC). We find that liquid domain size increases with the extent of acyl chain unsaturation (DOPC:POPC ratio). Furthermore, we find a direct correlation between domain size and the mismatch in bilayer thickness of the coexisting liquid-ordered and liquid-disordered phases, suggesting a dominant role for line tension in controlling domain size. While this result is expected from line tension theories, we provide the first experimental verification in free-floating bilayers. Importantly, we also find that changes in bilayer thickness, which accompany changes in the degree of lipid chain unsaturation, are entirely confined to the disordered phase. Together, these results suggest how the size of functional domains in homeothermic cells may be regulated through changes in lipid composition.
EMPIRICAL MODEL FOR HYDROCYCLONES CORRECTED CUT SIZE CALCULATION
Directory of Open Access Journals (Sweden)
André Carlos Silva
2012-12-01
Full Text Available Hydrocyclones are devices worldwide used in mineral processing for desliming, classification, selective classification, thickening and pre-concentration. A hydrocyclone is composed by one cylindrical and one conical section joint together, without any moving parts and it is capable of perform granular material separation in pulp. The mineral particles separation mechanism acting in a hydrocyclone is complex and its mathematical modelling is usually empirical. The most used model for hydrocyclone corrected cut size is proposed by Plitt. Over the years many revisions and corrections to Plitt´s model were proposed. The present paper shows a modification in the Plitt´s model constant, obtained by exponential regression of simulated data for three different hydrocyclones geometry: Rietema, Bradley and Krebs. To validate the proposed model literature data obtained from phosphate ore using fifteen different hydrocyclones geometry are used. The proposed model shows a correlation equals to 88.2% between experimental and calculated corrected cut size, while the correlation obtained using Plitt´s model is 11.5%.
Modeling the Floe-Size Distribution to Improve the Prediction of Sea Ice in the Marginal Seas
2002-09-30
in basin-scale, rheology-type sea ice models. Lateral ablation and sea ice mechanics depend on the size of floes and yet their distribution in present-day models is assumed to be homogeneous in space and constant in time .
International Space Station Radiation Shielding Model Development
Qualls, G. D.; Wilson, J. W.; Sandridge, C.; Cucinotta, F. A.; Nealy, J. E.; Heinbockel, J. H.; Hugger, C. P.; Verhage, J.; Anderson, B. M.; Atwell, W.
2001-01-01
The projected radiation levels within the International Space Station (ISS) have been criticized by the Aerospace Safety Advisory Panel in their report to the NASA Administrator. Methods for optimal reconfiguration and augmentation of the ISS shielding are now being developed. The initial steps are to develop reconfigurable and realistic radiation shield models of the ISS modules, develop computational procedures for the highly anisotropic radiation environment, and implement parametric and organizational optimization procedures. The targets of the redesign process are the crew quarters where the astronauts sleep and determining the effects of ISS shadow shielding of an astronaut in a spacesuit. The ISS model as developed will be reconfigurable to follow the ISS. Swapping internal equipment rack assemblies via location mapping tables will be one option for shield optimization. Lightweight shield augmentation materials will be optimally fit to crew quarter areas using parametric optimization procedures to minimize the augmentation shield mass. The optimization process is being integrated into the Intelligence Synthesis Environment s (ISE s) immersive simulation facility at the Langley Research Center and will rely on High Performance Computing and Communication (HPCC) for rapid evaluation of shield parameter gradients.
Raindrop size distribution: Fitting performance of common theoretical models
Adirosi, E.; Volpi, E.; Lombardo, F.; Baldini, L.
2016-10-01
Modelling raindrop size distribution (DSD) is a fundamental issue to connect remote sensing observations with reliable precipitation products for hydrological applications. To date, various standard probability distributions have been proposed to build DSD models. Relevant questions to ask indeed are how often and how good such models fit empirical data, given that the advances in both data availability and technology used to estimate DSDs have allowed many of the deficiencies of early analyses to be mitigated. Therefore, we present a comprehensive follow-up of a previous study on the comparison of statistical fitting of three common DSD models against 2D-Video Distrometer (2DVD) data, which are unique in that the size of individual drops is determined accurately. By maximum likelihood method, we fit models based on lognormal, gamma and Weibull distributions to more than 42.000 1-minute drop-by-drop data taken from the field campaigns of the NASA Ground Validation program of the Global Precipitation Measurement (GPM) mission. In order to check the adequacy between the models and the measured data, we investigate the goodness of fit of each distribution using the Kolmogorov-Smirnov test. Then, we apply a specific model selection technique to evaluate the relative quality of each model. Results show that the gamma distribution has the lowest KS rejection rate, while the Weibull distribution is the most frequently rejected. Ranking for each minute the statistical models that pass the KS test, it can be argued that the probability distributions whose tails are exponentially bounded, i.e. light-tailed distributions, seem to be adequate to model the natural variability of DSDs. However, in line with our previous study, we also found that frequency distributions of empirical DSDs could be heavy-tailed in a number of cases, which may result in severe uncertainty in estimating statistical moments and bulk variables.
Ports: Definition and study of types, sizes and business models
Directory of Open Access Journals (Sweden)
Ivan Roa
2013-09-01
Full Text Available Purpose: In the world today there are thousands of port facilities of different types and sizes, competing to capture some market share of freight by sea, mainly. This article aims to determine the type of port and the most common size, in order to find out which business model is applied in that segment and what is the legal status of the companies of such infrastructure.Design/methodology/approach: To achieve this goal, we develop a research on a representative sample of 800 ports worldwide, which manage 90% of the containerized port loading. Then you can find out the legal status of the companies that manage them.Findings: The results indicate a port type and a dominant size, which are mostly managed by companies subject to a concession model.Research limitations/implications: In this research, we study only those ports that handle freight (basically containerized, ignoring other activities such as fishing, military, tourism or recreational.Originality/value: This is an investigation to show that the vast majority of the studied segment port facilities are governed by a similar corporate model and subject to pressure from the markets, which increasingly demand efficiency and service. Consequently, we tend to concession terminals to private operators in a process that might be called privatization, but in the strictest sense of the term, is not entirely realistic because the ownership of the land never ceases to be public
Chulaki, A.; Kuznetsova, M. M.; Rastaetter, L.; MacNeice, P. J.; Shim, J. S.; Pulkkinen, A. A.; Taktakishvili, A.; Mays, M. L.; Mendoza, A. M. M.; Zheng, Y.; Mullinix, R.; Collado-Vega, Y. M.; Maddox, M. M.; Pembroke, A. D.; Wiegand, C.
2015-12-01
Community Coordinated Modeling Center (CCMC) is a NASA affiliated interagency partnership with the primary goal of aiding the transition of modern space science models into space weather forecasting while supporting space science research. Additionally, over the past ten years it has established itself as a global space science education resource supporting undergraduate and graduate education and research, and spreading space weather awareness worldwide. A unique combination of assets, capabilities and close ties to the scientific and educational communities enable this small group to serve as a hub for raising generations of young space scientists and engineers. CCMC resources are publicly available online, providing unprecedented global access to the largest collection of modern space science models (developed by the international research community). CCMC has revolutionized the way simulations are utilized in classrooms settings, student projects, and scientific labs and serves hundreds of educators, students and researchers every year. Another major CCMC asset is an expert space weather prototyping team primarily serving NASA's interplanetary space weather needs. Capitalizing on its unrivaled capabilities and experiences, the team provides in-depth space weather training to students and professionals worldwide, and offers an amazing opportunity for undergraduates to engage in real-time space weather monitoring, analysis, forecasting and research. In-house development of state-of-the-art space weather tools and applications provides exciting opportunities to students majoring in computer science and computer engineering fields to intern with the software engineers at the CCMC while also learning about the space weather from the NASA scientists.
A Maximum Entropy Modelling of the Rain Drop Size Distribution
Directory of Open Access Journals (Sweden)
Francisco J. Tapiador
2011-01-01
Full Text Available This paper presents a maximum entropy approach to Rain Drop Size Distribution (RDSD modelling. It is shown that this approach allows (1 to use a physically consistent rationale to select a particular probability density function (pdf (2 to provide an alternative method for parameter estimation based on expectations of the population instead of sample moments and (3 to develop a progressive method of modelling by updating the pdf as new empirical information becomes available. The method is illustrated with both synthetic and real RDSD data, the latest coming from a laser disdrometer network specifically designed to measure the spatial variability of the RDSD.
RESULTS OF INTERBANK EXCHANGE RATES FORECASTING USING STATE SPACE MODEL
Directory of Open Access Journals (Sweden)
Muhammad Kashif
2008-07-01
Full Text Available This study evaluates the performance of three alternative models for forecasting daily interbank exchange rate of U.S. dollar measured in Pak rupees. The simple ARIMA models and complex models such as GARCH-type models and a state space model are discussed and compared. Four different measures are used to evaluate the forecasting accuracy. The main result is the state space model provides the best performance among all the models.
Wegener, Veronika; Jorysz, Gabriele; Arnoldi, Andreas; Utzschneider, Sandra; Wegener, Bernd; Jansson, Volkmar; Heimkes, Bernhard
2017-03-01
Evaluation of hip joint space width during child growth is important to aid in the early diagnosis of hip pathology in children. We established reference values for hip joint space and femoral head size for each age. Hip joint space development during growth was retrospectively investigated medial and cranial in 1350 hip joints of children using standard anteroposterior supine plain pelvic radiographs. Maximum capital femoral epiphysis diameter and femoral radii were further more investigated. Hip joint space values show a slow decline during growth. Joint space was statistically significantly (p < 0.006) larger in boys than girls. Our hip joint space measurements on supine subjects seem slightly larger than those reported by Hughes on standing subjects. Evaluation of the femoral head diameter and the radii showed a size curve quite parallel to the known body growth charts. Radii medial and perpendicular to the physis are not statistically significantly different. We recommend to compare measurements of hip joint space at two locations to age dependent charts using the same imaging technique. During growth, a divergence in femoral head size from the expected values or loss of the spherical shape should raise the question of hip disorder. Clin. Anat. 30:267-275, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
A Hubble Space Telescope Search for a Sub-Earth-Sized Exoplanet in the GJ 436 System
Stevenson, Kevin B; Fabrycky, Daniel; Kreidberg, Laura
2014-01-01
The detection of small planets orbiting nearby stars is an important step towards the identification of Earth twins. In previous work using the Spitzer Space Telescope, we found evidence to support at least one sub-Earth-sized exoplanet orbiting the nearby mid-M dwarf star GJ 436. As a follow up, here we used the Hubble Space Telescope to investigate the existence of one of these candidate planets, UCF-1.01, by searching for two transit signals as it passed in front of its host star. Interpretation of the data hinges critically on correctly modeling and removing the WFC3 instrument systematics from the light curves. Building on previous HST work, we demonstrate that WFC3 analyses need to explore the use of a quadratic function to fit a visit-long time-dependent systematic. This is important for establishing absolute transit and eclipse depths in the white light curves of all transiting systems. The work presented here exemplifies this point by putatively detecting the primary transit of UCF-1.01 with the use ...
Optimization using surrogate models - by the space mapping technique
DEFF Research Database (Denmark)
Søndergaard, Jacob
2003-01-01
mapping surrogate has a lower approximation error for long steps. For short steps, however, the Taylor model of the expensive model is best, due to exact interpolation at the model origin. Five algorithms for space mapping optimization are presented and the numerical performance is evaluated. Three...... conditions are satisfied. So hybrid methods, combining the space mapping technique with classical optimization methods, should be used if convergence to high accuracy is wanted. Approximation abilities of the space mapping surrogate are compared with those of a Taylor model of the expensive model. The space...
Optimization using surrogate models - by the space mapping technique
DEFF Research Database (Denmark)
Søndergaard, Jacob
2003-01-01
mapping surrogate has a lower approximation error for long steps. For short steps, however, the Taylor model of the expensive model is best, due to exact interpolation at the model origin. Five algorithms for space mapping optimization are presented and the numerical performance is evaluated. Three...... conditions are satisfied. So hybrid methods, combining the space mapping technique with classical optimization methods, should be used if convergence to high accuracy is wanted. Approximation abilities of the space mapping surrogate are compared with those of a Taylor model of the expensive model. The space...
Equivariance on Discrete Space and Yang-Mills-Higgs Model
Ikemori, Hitoshi; Matsui, Yoshimitsu; Otsu, Hideharu; Sato, Toshiro
2015-01-01
We introduce the basic equivariant quantity $Q$ in the gauge theory on the noncommutative descrete $Z_{2}$ space, which plays an important role for the equivariant dimensional reduction. If the gauge configuration of the ground state on the extra dimensional space is described by the equivariant $Q$, then the extra dimensional space is invisible. Especially, using the equivariance principle, we show that the Yang-Mills theory on $R^{2}\\times Z_{2}$ space is equivalent to the Yang-Mills-Higgs model on $R^{2}$ space. It can be said that this model is the simplest model of this type.
Space Particle Hazard Measurement and Modeling
2016-09-01
launch in 2012. Key Publication: • [54] ISO Standard 11221 Space Systems – Space Solar Panels – Spacecraft Charging Induced - Electrostatic...plasma [71]. Completed charge testing on 3 solar panel cover glass replacement candidates developed by the Advanced Space Power program in AFRL/RVS...of Lifetimes Against Pitch Angle Diffusion, J. Atmos. Solar -Terr. Phys., 71, 1647, doi:10.1016/j.jastp.2008.07.004, 2009. [18] Meredith, N. P., et
Ringe, Stefan; Oberhofer, Harald; Hille, Christoph; Matera, Sebastian; Reuter, Karsten
2016-08-01
The size-modified Poisson-Boltzmann (MPB) equation is an efficient implicit solvation model which also captures electrolytic solvent effects. It combines an account of the dielectric solvent response with a mean-field description of solvated finite-sized ions. We present a general solution scheme for the MPB equation based on a fast function-space-oriented Newton method and a Green's function preconditioned iterative linear solver. In contrast to popular multigrid solvers, this approach allows us to fully exploit specialized integration grids and optimized integration schemes. We describe a corresponding numerically efficient implementation for the full-potential density-functional theory (DFT) code FHI-aims. We show that together with an additional Stern layer correction the DFT+MPB approach can describe the mean activity coefficient of a KCl aqueous solution over a wide range of concentrations. The high sensitivity of the calculated activity coefficient on the employed ionic parameters thereby suggests to use extensively tabulated experimental activity coefficients of salt solutions for a systematic parametrization protocol.
Building predictive models of soil particle-size distribution
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Alessandro Samuel-Rosa
2013-04-01
Full Text Available Is it possible to build predictive models (PMs of soil particle-size distribution (psd in a region with complex geology and a young and unstable land-surface? The main objective of this study was to answer this question. A set of 339 soil samples from a small slope catchment in Southern Brazil was used to build PMs of psd in the surface soil layer. Multiple linear regression models were constructed using terrain attributes (elevation, slope, catchment area, convergence index, and topographic wetness index. The PMs explained more than half of the data variance. This performance is similar to (or even better than that of the conventional soil mapping approach. For some size fractions, the PM performance can reach 70 %. Largest uncertainties were observed in geologically more complex areas. Therefore, significant improvements in the predictions can only be achieved if accurate geological data is made available. Meanwhile, PMs built on terrain attributes are efficient in predicting the particle-size distribution (psd of soils in regions of complex geology.
Distribution of human waste samples in relation to sizing waste processing in space
Parker, Dick; Gallagher, S. K.
1992-01-01
Human waste processing for closed ecological life support systems (CELSS) in space requires that there be an accurate knowledge of the quantity of wastes produced. Because initial CELSS will be handling relatively few individuals, it is important to know the variation that exists in the production of wastes rather than relying upon mean values that could result in undersizing equipment for a specific crew. On the other hand, because of the costs of orbiting equipment, it is important to design the equipment with a minimum of excess capacity because of the weight that extra capacity represents. A considerable quantity of information that had been independently gathered on waste production was examined in order to obtain estimates of equipment sizing requirements for handling waste loads from crews of 2 to 20 individuals. The recommended design for a crew of 8 should hold 34.5 liters per day (4315 ml/person/day) for urine and stool water and a little more than 1.25 kg per day (154 g/person/day) of human waste solids and sanitary supplies.
Enhanced surrogate models for statistical design exploiting space mapping technology
DEFF Research Database (Denmark)
Koziel, Slawek; Bandler, John W.; Mohamed, Achmed S.;
2005-01-01
We present advances in microwave and RF device modeling exploiting Space Mapping (SM) technology. We propose new SM modeling formulations utilizing input mappings, output mappings, frequency scaling and quadratic approximations. Our aim is to enhance circuit models for statistical analysis...
Macro Level Simulation Model Of Space Shuttle Processing
2000-01-01
The contents include: 1) Space Shuttle Processing Simulation Model; 2) Knowledge Acquisition; 3) Simulation Input Analysis; 4) Model Applications in Current Shuttle Environment; and 5) Model Applications for Future Reusable Launch Vehicles (RLV's). This paper is presented in viewgraph form.
Modeling the impact of soil aggregate size on selenium immobilization
Directory of Open Access Journals (Sweden)
M. F. Kausch
2012-09-01
Full Text Available Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate-scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI, and selenite, Se(IV, can be microbially reduced to solid, elemental Se, Se(0, and anoxic microzones within soil aggregates are thought to promote this process in otherwise well aerated soils.
To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI via Se(IV to Se(0. Aggregates were surrounded by a constant flow providing Se(VI and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O_{2}, and Se-species. The spatial and temporal dynamics of the model were validated with data from experiments and predictive simulations were performed covering aggregate sizes between 1 and 2.5 cm diameter.
Simulations predict that selenium retention scales with aggregate size. Depending on O_{2}, Se(VI, and pyruvate concentrations, selenium retention was 4–23 times higher in 2.5-cm-aggregates compared to 1-cm-aggregates. Under oxic conditions, aggregate size and pyruvate-concentrations were found to have a positive synergistic
Modeling the impact of soil aggregate size on selenium immobilization
Kausch, M. F.; Pallud, C. E.
2013-03-01
Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se) mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI), and selenite, Se(IV), can be microbially reduced to solid, elemental Se, Se(0), and anoxic microzones within soil aggregates are thought to promote this process in otherwise well-aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm) made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI) via Se(IV) to Se(0). Aggregates were surrounded by a constant flow providing Se(VI) and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se species. The spatial and temporal dynamics of the model were validated with data from experiments, and predictive simulations were performed covering aggregate sizes 1-2.5 cm in diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI), and pyruvate concentrations, selenium retention was 4-23 times higher in 2.5 cm aggregates compared to 1 cm aggregates. Under oxic conditions, aggregate size and pyruvate concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil aggregation on
Modeling the impact of soil aggregate size on selenium immobilization
Directory of Open Access Journals (Sweden)
M. F. Kausch
2013-03-01
Full Text Available Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI, and selenite, Se(IV, can be microbially reduced to solid, elemental Se, Se(0, and anoxic microzones within soil aggregates are thought to promote this process in otherwise well-aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI via Se(IV to Se(0. Aggregates were surrounded by a constant flow providing Se(VI and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se species. The spatial and temporal dynamics of the model were validated with data from experiments, and predictive simulations were performed covering aggregate sizes 1–2.5 cm in diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI, and pyruvate concentrations, selenium retention was 4–23 times higher in 2.5 cm aggregates compared to 1 cm aggregates. Under oxic conditions, aggregate size and pyruvate concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil
Space-time modeling of electricity spot prices
DEFF Research Database (Denmark)
Abate, Girum Dagnachew; Haldrup, Niels
In this paper we derive a space-time model for electricity spot prices. A general spatial Durbin model that incorporates the temporal as well as spatial lags of spot prices is presented. Joint modeling of space-time effects is necessarily important when prices and loads are determined in a network...
Embedding a State Space Model Into a Markov Decision Process
DEFF Research Database (Denmark)
Nielsen, Lars Relund; Jørgensen, Erik; Højsgaard, Søren
2011-01-01
estimated from data collected from the animal or herd. State space models (SSMs) are a general tool for modeling repeated measurements over time where the model parameters can evolve dynamically. In this paper we consider methods for embedding an SSM into an MDP with finite state and action space. Different...
Modelling Parsing Constraints with High-Dimensional Context Space.
Burgess, Curt; Lund, Kevin
1997-01-01
Presents a model of high-dimensional context space, the Hyperspace Analogue to Language (HAL), with a series of simulations modelling human empirical results. Proposes that HAL's context space can be used to provide a basic categorization of semantic and grammatical concepts; model certain aspects of morphological ambiguity in verbs; and provide…
Sesto, Mary E; Irwin, Curtis B; Chen, Karen B; Chourasia, Amrish O; Wiegmann, Douglas A
2012-06-01
The aim of this study was to investigate the effect of button size and spacing on touch characteristics (forces, impulses, and dwell times) during a digit entry touch screen task. A secondary objective was to investigate the effect of disability on touch characteristics. Touch screens are common in public settings and workplaces. Although research has examined the effect of button size and spacing on performance, the effect on touch characteristics is unknown. A total of 52 participants (n = 23, fine motor control disability; n = 14, gross motor control disability; n = 15, no disability) completed a digit entry task. Button sizes varied from 10 mm to 30 mm, and button spacing was 1 mm or 3 mm. Touch characteristics were significantly affected by button size. The exerted peak forces increased 17% between the largest and the smallest buttons, whereas impulses decreased 28%. Compared with the fine motor and nondisabled groups, the gross motor group had greater impulses (98% and 167%, respectively) and dwell times (60% and 129%, respectively). Peak forces were similar for all groups. Button size but not spacing influenced touch characteristics during a digit entry task. The gross motor group had significantly greater dwell times and impulses than did the fine motor and nondisabled groups. Research on touch characteristics, in conjunction with that on user performance, can be used to guide human computer interface design strategies to improve accessibility of touch screen interfaces. Further research is needed to evaluate the effect of the exerted peak forces and impulses on user performance and fatigue.
Process Model for Defining Space Sensing and Situational Awareness Requirements
2006-04-01
process model for defining systems for space sensing and space situational awareness is presented. The paper concentrates on eight steps for determining the requirements to include: decision maker needs, system requirements, exploitation methods and vulnerabilities, critical capabilities, and identify attack scenarios. Utilization of the USAF anti-tamper (AT) implementation process as a process model departure point for the space sensing and situational awareness (SSSA...is presented. The AT implementation process model , as an
Statistical traffic modeling of MPEG frame size: Experiments and Analysis
Directory of Open Access Journals (Sweden)
Haniph A. Latchman
2009-12-01
Full Text Available For guaranteed quality of service (QoS and sufficient bandwidth in a communication network which provides an integrated multimedia service, it is important to obtain an analytical and tractable model of the compressed MPEG data. This paper presents a statistical approach to a group of picture (GOP MPEG frame size model to increase network traffic performance in a communication network. We extract MPEG frame data from commercial DVD movies and make probability histograms to analyze the statistical characteristics of MPEG frame data. Six candidates of probability distributions are considered here and their parameters are obtained from the empirical data using the maximum likelihood estimation (MLE. This paper shows that the lognormal distribution is the best fitting model of MPEG-2 total frame data.
Energy Technology Data Exchange (ETDEWEB)
Correa, E.B.S. [Universidade Federal do Sul e Sudeste do Para, Instituto de Ciencias Exatas, Maraba (Brazil); Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Linhares, C.A. [Universidade do Estado do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro (Brazil); Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Malbouisson, J.M.C. [Universidade Federal da Bahia, Instituto de Fisica, Salvador (Brazil); Santana, A.E. [Universidade de Brasilia, Instituto de Fisica, Brasilia, DF (Brazil)
2017-04-15
We study effects coming from finite size, chemical potential and from a magnetic background on a massive version of a four-fermion interacting model. This is performed in four dimensions as an application of recent developments for dealing with field theories defined on toroidal spaces. We study effects of the magnetic field and chemical potential on the size-dependent phase structure of the model, in particular, how the applied magnetic field affects the size-dependent critical temperature. A connection with some aspects of the hadronic phase transition is established. (orig.)
The economic production lot size model with several production rates
DEFF Research Database (Denmark)
Larsen, Christian
should be chosen in the interval between the demand rate and the production rate, which minimize unit production costs, and should be used in an increasing order. Then, given the production rates, we derive closed form solutions for the optimal runtimes as well as the minimum average cost. Finally we......We study an extension of the economic production lot size model, where more than one production rate can be used during a cycle. The production rates and their corresponding runtimes are decision variables. We decompose the problem into two subproblems. First, we show that all production rates...
Determining state-space models from sequential output data
Lin, Jiguan Gene
1988-01-01
This talk focuses on the determination of state-space models for large space systems using only the output data. The output data could be generated by the unknown or deliberate initial conditions of the space structure in question. We shall review some relevant fundamental work on the state-space modeling of sequential output data that is potentially applicable to large space structures. If formulated in terms of some generalized Markov parameters, this approach is in some sense similar to, but much simpler than, the Juang-Pappa Eigensystem Realization Algorithm (ERA) and the Ho-Kalman construction procedure.
Ion size effect on colloidal forces within the primitive model
Directory of Open Access Journals (Sweden)
J.Wu
2005-01-01
Full Text Available The effect of ion size on the mean force between a pair of isolated charged particles in an electrolyte solution is investigated using Monte Carlo simulations within the framework of the primitive model where both colloidal particles and small ions are represented by charged hard spheres and the solvent is treated as a dielectric continuum. It is found that the short-ranged attraction between like-charged macroions diminishes as the diameter of the intermediating divalent counterions and coions increases and the maximum attractive force is approximately a linear function of the counterion diameter. This size effect contradicts the prediction of the Asakura-Oosawa theory suggesting that an increase in the excluded volume of small ions would lead to a stronger depletion between colloidal particles. Interestingly, the simulation results indicate that both the hard-sphere collision and the electrostatic contributions to the mean force are insensitive to the size disparity of colloidal particles with the same average diameter.
Gori, Simone; Spillmann, Lothar
2010-06-11
Three experiments were performed to compare thresholds for the detection of non-uniformity in spacing, size and luminance with thresholds for grouping. In the first experiment a row of 12 black equi-spaced dots was used and the spacing after the 3rd, 6th, and 9th dot increased in random steps to determine the threshold at which the observer detected an irregularity in the size of the gaps. Thereafter, spacing in the same locations was increased further to find the threshold at which the observer perceived four groups of three dots each (triplets). In the second experiment, empty circles were used instead of dots and the diameter of the circles in the first and second triplet increased until the difference in size gave rise either to a detection or grouping response. In the third experiment, the dots in the second and fourth triplet were increased in luminance. The aim again was to compare the difference in brightness required for detection or grouping, respectively. Results demonstrate that the threshold for perceiving stimuli as irregularly spaced or dissimilar in size or brightness is much smaller than the threshold for grouping. In order to perceive stimuli as grouped, stimulus differences had to be 5.2 times (for dot spacing), 7.4 times (for size) and 6.6 times (for luminance) larger than for detection. Two control experiments demonstrated that the difference between the two kinds of thresholds persisted even when only two gaps were used instead of three and when gap position was randomized. Copyright 2010 Elsevier Ltd. All rights reserved.
Space Size and Accuracy of Second and Third Grade Students' Cursive Handwriting.
Trap-Porter, Jennifer; And Others
1983-01-01
A study of the accuracy of letter strokes made on wide- and normal-spaced paper by students during the transition to cursive writing confirms the advantages of wide-spaced paper. Both second- and third-grade students made more accurate strokes on wide-spaced paper. (Authors/PP)
Non-commutative Complex Projective Spaces and the Standard Model
Dolan, Brian P
2003-01-01
The standard model fermion spectrum, including a right handed neutrino, can be obtained as a zero-mode of the Dirac operator on a space which is the product of complex projective spaces of complex dimension two and three. The construction requires the introduction of topologically non-trivial background gauge fields. By borrowing from ideas in Connes' non-commutative geometry and making the complex spaces `fuzzy' a matrix approximation to the fuzzy space allows for three generations to emerge...
Ko, William L.; Olona, Timothy
1987-01-01
The effect of element size on the solution accuracies of finite-element heat transfer and thermal stress analyses of space shuttle orbiter was investigated. Several structural performance and resizing (SPAR) thermal models and NASA structural analysis (NASTRAN) structural models were set up for the orbiter wing midspan bay 3. The thermal model was found to be the one that determines the limit of finite-element fineness because of the limitation of computational core space required for the radiation view factor calculations. The thermal stresses were found to be extremely sensitive to a slight variation of structural temperature distributions. The minimum degree of element fineness required for the thermal model to yield reasonably accurate solutions was established. The radiation view factor computation time was found to be insignificant compared with the total computer time required for the SPAR transient heat transfer analysis.
Modeling photoacoustic spectral features of micron-sized particles.
Strohm, Eric M; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael C
2014-10-07
The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Biocompatible perfluorocarbon droplets, 3-5 μm in diameter containing optically absorbing nanoparticles were used as the representative ideal particles, as they are spherical, homogeneous, optically translucent, and have known physical properties. The photoacoustic spectrum of micron-sized single droplets in suspension and on a reflecting boundary were measured over the frequency range of 100-500 MHz and compared directly to analytical models and the FEM. Good agreement between the analytical model, FEM and measured values were observed for a droplet in suspension, where the spectral minima agreed to within a 3.3 MHz standard deviation. For a droplet on a reflecting boundary, spectral features were correctly reproduced using the FEM but not the analytical model. The photoacoustic spectra from other common particle configurations such as particle with an absorbing shell and a
Modeling photoacoustic spectral features of micron-sized particles
Strohm, Eric M.; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael C.
2014-10-01
The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Biocompatible perfluorocarbon droplets, 3-5 μm in diameter containing optically absorbing nanoparticles were used as the representative ideal particles, as they are spherical, homogeneous, optically translucent, and have known physical properties. The photoacoustic spectrum of micron-sized single droplets in suspension and on a reflecting boundary were measured over the frequency range of 100-500 MHz and compared directly to analytical models and the FEM. Good agreement between the analytical model, FEM and measured values were observed for a droplet in suspension, where the spectral minima agreed to within a 3.3 MHz standard deviation. For a droplet on a reflecting boundary, spectral features were correctly reproduced using the FEM but not the analytical model. The photoacoustic spectra from other common particle configurations such as particle with an absorbing shell and a
A Simulation and Modeling Framework for Space Situational Awareness
Olivier, S.
This paper describes the development and initial demonstration of a new, integrated modeling and simulation framework, encompassing the space situational awareness enterprise, for quantitatively assessing the benefit of specific sensor systems, technologies and data analysis techniques. This framework includes detailed models for threat scenarios, signatures, sensors, observables and knowledge extraction algorithms. The framework is based on a flexible, scalable architecture to enable efficient simulation of the current SSA enterprise, and to accommodate future advancements in SSA systems. In particular, the code is designed to take advantage of massively parallel computer systems available, for example, at Lawrence Livermore National Laboratory. We will describe the details of the modeling and simulation framework, including hydrodynamic models of satellite intercept and debris generation, orbital propagation algorithms, radar cross section calculations, optical and infra-red brightness calculations, generic radar system models, generic optical and infra-red system models, specific Space Surveillance Network models, object detection algorithms, orbit determination algorithms, and visualization tools. The specific modeling of the Space Surveillance Network is performed in collaboration with the Air Force Space Command Space Control Group. We will demonstrate the use of this integrated simulation and modeling framework on specific threat scenarios, including space debris and satellite maneuvers, and we will examine the results of case studies involving the addition of new sensor systems, used in conjunction with the Space Surveillance Network, for improving space situational awareness.
Cheboyina, Sreekhar; O'Haver, John; Wyandt, Christy M
2006-01-01
A mathematical model was developed based on the theory of drop formation to predict the size of the pellets formed in the freeze pelletization process. Further the model was validated by studying the effect of various parameters on the pellet size such as viscosity of the pellet forming and column liquids, surface/interfacial tension, density difference between pellet forming and column liquids; size, shape, and material of construction of the needle tips and temperatures maintained in the columns. In this study, pellets were prepared from different matrices including polyethylene glycols and waxes. The column liquids studied were silicone oils and aqueous glycerol solutions. The surface/interfacial tension, density difference between pellet forming and column liquids and needle tip size were found to be the most important factors affecting pellet size. The viscosity of the column liquid was not found to significantly affect the size of the pellets. The size of the pellets was also not affected by the pellet forming liquids of low viscosities. An increase in the initial column temperature slightly decreased the pellet size. The mathematical model developed was found to successfully predict the size of the pellets with an average error of 3.32% for different matrices that were studied.
Primordial gravitational waves from the space-condensate inflation model
Koh, Seoktae; Tumurtushaa, Gansukh
2015-01-01
We consider the space-condensate inflation model to study the primordial gravitational waves generated in the early Universe. We calculate the energy spectrum of gravitational waves induced by the space-condensate inflation model for full frequency range with assumption that the phase transition between two consecutive regimes to be abrupt during evolution of the Universe. The suppression of energy spectrum is found in our model for the decreasing frequency of gravitational waves depending on the model parameter. To realize the suppression of energy spectrum of the primordial gravitational waves, we study an existence of the early phase transition during inflation for the space-condensate inflation model.
Vector space model for document representation in information retrieval
Directory of Open Access Journals (Sweden)
Dan MUNTEANU
2007-12-01
Full Text Available This paper presents the basics of information retrieval: the vector space model for document representation with Boolean and term weighted models, ranking methods based on the cosine factor and evaluation measures: recall, precision and combined measure.
Space Station Freedom electrical performance model
Hojnicki, Jeffrey S.; Green, Robert D.; Kerslake, Thomas W.; Mckissock, David B.; Trudell, Jeffrey J.
1993-01-01
The baseline Space Station Freedom electric power system (EPS) employs photovoltaic (PV) arrays and nickel hydrogen (NiH2) batteries to supply power to housekeeping and user electrical loads via a direct current (dc) distribution system. The EPS was originally designed for an operating life of 30 years through orbital replacement of components. As the design and development of the EPS continues, accurate EPS performance predictions are needed to assess design options, operating scenarios, and resource allocations. To meet these needs, NASA Lewis Research Center (LeRC) has, over a 10 year period, developed SPACE (Station Power Analysis for Capability Evaluation), a computer code designed to predict EPS performance. This paper describes SPACE, its functionality, and its capabilities.
Investigation and modeling of the avalanche effect in MOSFETs with non-uniform finger spacing
Institute of Scientific and Technical Information of China (English)
Liu Jun; Sun Lingling; Marissa Condon
2011-01-01
This paper investigates the effect of a non-uniform gate-finger spacing layout structure on the avalanche breakdown performance of RF CMOS technology.Compared with a standard multi-finger device with uniform gate-finger spacing,a device with non-uniform gate-finger spacing represents an improvement of 8.5% for the drain-source breakdown voltage(BVds)and of 20% for the thermally-related drain conductance.A novel compact model is proposed to accurately predict the variation of BVds with the total area of devices,which is dependent on the different finger spacing sizes.The model is verified and validated by the excellent match between the measured and simulated avalanche breakdown characteristics for a set of uniform and non-uniform gate-finger spacing arranged nMOSFETs.
Standardization Process for Space Radiation Models Used for Space System Design
Barth, Janet; Daly, Eamonn; Brautigam, Donald
2005-01-01
The space system design community has three concerns related to models of the radiation belts and plasma: 1) AP-8 and AE-8 models are not adequate for modern applications; 2) Data that have become available since the creation of AP-8 and AE-8 are not being fully exploited for modeling purposes; 3) When new models are produced, there is no authorizing organization identified to evaluate the models or their datasets for accuracy and robustness. This viewgraph presentation provided an overview of the roadmap adopted by the Working Group Meeting on New Standard Radiation Belt and Space Plasma Models.
HEISHI: A fuel performance model for space nuclear applications
Energy Technology Data Exchange (ETDEWEB)
Young, M.F.
1994-08-01
HEISHI is a Fortran computer model designed to aid in analysis, prediction, and optimization of fuel characteristics for use in Space Nuclear Thermal Propulsion (SNTP). Calculational results include fission product release rate, fuel failure fraction, mode of fuel failure, stress-strain state, and fuel material morphology. HEISHI contains models for decay chain calculations of retained and released fission products, based on an input power history and release coefficients. Decay chain parameters such as direct fission yield, decay rates, and branching fractions are obtained from a database. HEISHI also contains models for stress-strain behavior of multilayered fuel particles with creep and differential thermal expansion effects, transient particle temperature profile, grain growth, and fuel particle failure fraction. Grain growth is treated as a function of temperature; the failure fraction depends on the coating tensile strength, which in turn is a function of grain size. The HEISHI code is intended for use in analysis of coated fuel particles for use in particle bed reactors; however, much of the code is geometry-independent and applicable to fuel geometries other than spherical.
A Spatial Expansion of a Pocket Size Homeland: Heinrich Heine’s Construction of Jewish Space
DEFF Research Database (Denmark)
Simonsen, Cecilie Speggers Schrøder
2016-01-01
This article explores Heinrich Heine’s two texts about Jews and Jewish life, ÜberPolen and Der Rabbi von Bacherach, to show how the foundations for a Jewish homeland were laid in Jewish literature of early 19th-century Western and Central Europe. The article demonstrates how a common Jewish space...... literature. The article explores the potential of Jewish cultural space and shows how Heine constructed a modern Jewish cultural space with room for both traditional and modern Jews....
Modeling diurnal hormone profiles by hierarchical state space models.
Liu, Ziyue; Guo, Wensheng
2015-10-30
Adrenocorticotropic hormone (ACTH) diurnal patterns contain both smooth circadian rhythms and pulsatile activities. How to evaluate and compare them between different groups is a challenging statistical task. In particular, we are interested in testing (1) whether the smooth ACTH circadian rhythms in chronic fatigue syndrome and fibromyalgia patients differ from those in healthy controls and (2) whether the patterns of pulsatile activities are different. In this paper, a hierarchical state space model is proposed to extract these signals from noisy observations. The smooth circadian rhythms shared by a group of subjects are modeled by periodic smoothing splines. The subject level pulsatile activities are modeled by autoregressive processes. A functional random effect is adopted at the pair level to account for the matched pair design. Parameters are estimated by maximizing the marginal likelihood. Signals are extracted as posterior means. Computationally efficient Kalman filter algorithms are adopted for implementation. Application of the proposed model reveals that the smooth circadian rhythms are similar in the two groups but the pulsatile activities in patients are weaker than those in the healthy controls. Copyright © 2015 John Wiley & Sons, Ltd.
Influence of sex and ethnic tooth-size differences on mixed-dentition space analysis
Altherr, Edward R.; Koroluk, Lorne D.; Phillips, Ceib
2013-01-01
Introduction Most mixed-dentition space analyses were developed by using subjects of northwestern European descent and unspecified sex. The purpose of this study was to determine the predictive accuracy of the Tanaka-Johnston analysis in white and black subjects in North Carolina. Methods A total of 120 subjects (30 males and 30 females in each ethnic group) were recruited from clinics at the University of North Carolina School of Dentistry. Ethnicity was verified to 2 previous generations. All subjects were less than 21 years of age and had a full complement of permanent teeth. Digital calipers were used to measure the mesiodistal widths of all teeth on study models fabricated from alginate impressions. The predicted widths of the canines and the premolars in both arches were compared with the actual measured widths. Results In the maxillary arch, there was a significant interaction of ethnicity and sex on the predictive accuracy of the Tanaka-Johnston analysis (P = .03, factorial ANOVA). The predictive accuracy was significantly overestimated in the white female group (P <.001, least square means). In the mandibular arch, there was no significant interaction between ethnicity and sex (P = .49). Conclusions The Tanaka-Johnston analysis significantly overestimated in females (P <.0001) and underestimated in blacks (P <.0001) (factorial ANOVA). Regression equations were developed to increase the predictive accuracy in both arches. (Am J Orthod Dentofacial Orthop 2007;132:332-9) PMID:17826601
Brisset, Julie; Heißelmann, Daniel; Kothe, Stefan; Weidling, René; Blum, Jürgen
2013-09-01
The Suborbital Particle Aggregation and Collision Experiment (SPACE) is a novel approach to study the collision properties of submillimeter-sized, highly porous dust aggregates. The experiment was designed, built, and carried out to increase our knowledge about the processes dominating the first phase of planet formation. During this phase, the growth of planetary precursors occurs by agglomeration of micrometer-sized dust grains into aggregates of at least millimeters to centimeters in size. However, the formation of larger bodies from the so-formed building blocks is not yet fully understood. Recent numerical models on dust growth lack a particular support by experimental studies in the size range of submillimeters, because these particles are predicted to collide at very gentle relative velocities of below 1 cm/s that can only be achieved in a reduced-gravity environment. The SPACE experiment investigates the collision behavior of an ensemble of silicate-dust aggregates inside several evacuated glass containers which are being agitated by a shaker to induce the desired collisions at chosen velocities. The dust aggregates are being observed by a high-speed camera, allowing for the determination of the collision properties of the protoplanetary dust analog material. The data obtained from the suborbital flight with the REXUS (Rocket Experiments for University Students) 12 rocket will be directly implemented into a state-of-the-art dust growth and collision model.
Brisset, Julie; Heißelmann, Daniel; Kothe, Stefan; Weidling, René; Blum, Jürgen
2013-09-01
The Suborbital Particle Aggregation and Collision Experiment (SPACE) is a novel approach to study the collision properties of submillimeter-sized, highly porous dust aggregates. The experiment was designed, built, and carried out to increase our knowledge about the processes dominating the first phase of planet formation. During this phase, the growth of planetary precursors occurs by agglomeration of micrometer-sized dust grains into aggregates of at least millimeters to centimeters in size. However, the formation of larger bodies from the so-formed building blocks is not yet fully understood. Recent numerical models on dust growth lack a particular support by experimental studies in the size range of submillimeters, because these particles are predicted to collide at very gentle relative velocities of below 1 cm/s that can only be achieved in a reduced-gravity environment. The SPACE experiment investigates the collision behavior of an ensemble of silicate-dust aggregates inside several evacuated glass containers which are being agitated by a shaker to induce the desired collisions at chosen velocities. The dust aggregates are being observed by a high-speed camera, allowing for the determination of the collision properties of the protoplanetary dust analog material. The data obtained from the suborbital flight with the REXUS (Rocket Experiments for University Students) 12 rocket will be directly implemented into a state-of-the-art dust growth and collision model.
Queuing theory models used for port equipment sizing
Dragu, V.; Dinu, O.; Ruscă, A.; Burciu, Ş.; Roman, E. A.
2017-08-01
The significant growth of volumes and distances on road transportation led to the necessity of finding solutions to increase water transportation market share together with the handling and transfer technologies within its terminals. It is widely known that the biggest times are consumed within the transport terminals (loading/unloading/transfer) and so the necessity of constantly developing handling techniques and technologies in concordance with the goods flows size so that the total waiting time of ships within ports is reduced. Port development should be achieved by harmonizing the contradictory interests of port administration and users. Port administrators aim profit increase opposite to users that want savings by increasing consumers’ surplus. The difficulty consists in the fact that the transport demand - supply equilibrium must be realised at costs and goods quantities transiting the port in order to satisfy the interests of both parties involved. This paper presents a port equipment sizing model by using queueing theory so that the sum of costs for ships waiting operations and equipment usage would be minimum. Ship operation within the port is assimilated to a mass service waiting system in which parameters are later used to determine the main costs for ships and port equipment.
Numerical modelling of riverbed grain size stratigraphic evolution
Institute of Scientific and Technical Information of China (English)
Peng HU; Zhi-xian CAO; Gareth PENDER; Huai-han LIU
2014-01-01
For several decades, quantification of riverbed grain size stratigraphic evolution has been based upon the active layer formulation (ALF), which unfortunately involves considerable uncertainty. While it is the sediment exchange across the bed surface that directly affects the riverbed stratigraphy, it has been assumed in the ALF that the sediment fraction at the lower interface of the active layer is a linear function of the sediment fraction in the flow. Here it is proposed that the sediment fraction of the sediment exchange flux is used directly in estimating the sediment fraction at the lower surface of the active layer. Together with the size-specific mass conservation for riverbed sediment, the modified approach is referred to as the surface-based formulation (SBF). When incorporated into a coupled non-capacity modelling framework for fluvial processes, the SBF leads to results that agree as well or better than those using ALF with laboratory and field observations. This is illustrated for typical cases featuring bed aggradation and degradation due to graded bed-load sediment transport. Systematic experiments on graded sediment transport by unsteady flows are warranted for further testing the modified formulation.
de Boer, Hugo Jan; Price, Charles A.; Wagner-Cremer, Friederike; Dekker, Stefan C.; Franks, Peter J.; Veneklaas, Erik J.
2015-04-01
Stomata on plant leaves are key traits in the regulation of terrestrial fluxes of water and carbon. The basic morphology of stomata consists of a diffusion pore and two guard cells that regulate the exchange of CO2 and water vapour between the leaf interior and the atmosphere. This morphology is common to nearly all land plants, yet stomatal size (defined as the area of the guard cell pair) and stomatal density (the number of stomata per unit area) range over three orders of magnitude across species. Evolution of stomatal sizes and densities is driven by selection pressure on the anatomical maximum stomatal conductance (gsmax), which determines the operational range of leaf gas exchange. Despite the importance of stomata traits for regulating leaf gas exchange, a quantitative understanding of the relation between adaptation of gsmax and the underlying co-evolution of stomatal sizes and densities is still lacking. Here we develop a theoretical framework for a scaling relationship between stomatal sizes and densities within the constraints set by the allocation of epidermal space and stomatal gas exchange. Our theory predicts an optimal scaling relationship that maximizes gsmax and minimizes epidermal space allocation to stomata. We test whether stomatal sizes and densities reflect this optimal scaling with a global compilation of stomatal trait data on 923 species reflecting most major clades. Our results show optimal scaling between stomatal sizes and densities across all species in the compiled data set. Our results also show optimal stomatal scaling across angiosperm species, but not across gymnosperm and fern species. We propose that the evolutionary flexibility of angiosperms to adjust stomatal sizes underlies their optimal allocation of leaf epidermal space to gas exchange.
Smooth spaces versus continuous spaces in models for synthetic differential geometry
Reyes, G.E.; Moerdijk, I.
1984-01-01
In topos models for synthetic differential geometry we study connections between smooth spaces (which interpret synthetic calculus) and continuous spaces (which interpret intuitionistic analysis). Our main tools are adjoint retractions of toposes and the standard map from the smooth reals to the con
SIMPLIFIED MATHEMATICAL MODEL OF SMALL SIZED UNMANNED AIRCRAFT VEHICLE LAYOUT
Directory of Open Access Journals (Sweden)
2016-01-01
Full Text Available Strong reduction of new aircraft design period using new technology based on artificial intelligence is the key problem mentioned in forecasts of leading aerospace industry research centers. This article covers the approach to devel- opment of quick aerodynamic design methods based on artificial intelligence neural system. The problem is being solved for the classical scheme of small sized unmanned aircraft vehicle (UAV. The principal parts of the method are the mathe- matical model of layout, layout generator of this type of aircraft is built on aircraft neural networks, automatic selection module for cleaning variety of layouts generated in automatic mode, robust direct computational fluid dynamics method, aerodynamic characteristics approximators on artificial neural networks.Methods based on artificial neural networks have intermediate position between computational fluid dynamics methods or experiments and simplified engineering approaches. The use of ANN for estimating aerodynamic characteris-tics put limitations on input data. For this task the layout must be presented as a vector with dimension not exceeding sev-eral hundred. Vector components must include all main parameters conventionally used for layouts description and com- pletely replicate the most important aerodynamics and structural properties.The first stage of the work is presented in the paper. Simplified mathematical model of small sized UAV was developed. To estimate the range of geometrical parameters of layouts the review of existing vehicle was done. The result of the work is the algorithm and computer software for generating the layouts based on ANN technolo-gy. 10000 samples were generated and the dataset containig geometrical and aerodynamic characteristics of layoutwas created.
Lee, Nolan C.; Voss, Christine; Frazer, Amanda D.; Hirsch, Jana A.; McKay, Heather A.; Winters, Meghan
2015-01-01
Background Physical activity (PA) is closely linked with child and youth health, and active travel may be a solution to enhancing PA levels. Activity spaces depict the geographic coverage of one's travel. Little is known about activity spaces and PA in adolescents. Objective To explore the relation between adolescent travel (using a spatial measure of activity space size) and daily moderate-to-vigorous PA (MVPA), with a focus on school days. Methods We used Global Positioning Systems to manually identify trips and generate activity spaces for each person-day; quantified by area for 39 students (13.8 ± 0.6 years, 38% female) attending high school in urban Downtown Vancouver, Canada. We assessed the association between activity space area and MVPA using multi-level regression. We calculated total, school-day and trip-based MVPA for each valid person-day (accelerometry; ≥ 600 min wear time). Results On school days, students accrued 68.2 min/day (95% CI 60.4–76.0) of MVPA. Daily activity spaces averaged 2.2 km2 (95% CI 1.3–3.0). There was no association between activity space size and school-day MVPA. Students accrued 21.8 min/day (95% CI 19.2–24.4) of MVPA during school hours, 19.4 min/day (95% CI 15.1–23.7) during travel, and 28.3 min/day (95% CI 22.3–34.3) elsewhere. Conclusion School and school travel are important sources of PA in Vancouver adolescents, irrespective of activity space area covered. PMID:26807349
Lee, Nolan C; Voss, Christine; Frazer, Amanda D; Hirsch, Jana A; McKay, Heather A; Winters, Meghan
2016-06-01
Physical activity (PA) is closely linked with child and youth health, and active travel may be a solution to enhancing PA levels. Activity spaces depict the geographic coverage of one's travel. Little is known about activity spaces and PA in adolescents. To explore the relation between adolescent travel (using a spatial measure of activity space size) and daily moderate-to-vigorous PA (MVPA), with a focus on school days. In Fall 2012, we used Global Positioning Systems to manually identify trips and generate activity spaces for each person-day; quantified by area for 39 students (13.8±0.6 years, 38% female) attending high school in urban Downtown Vancouver, Canada. We assessed the association between activity space area and MVPA using multi-level regression. We calculated total, school-day and trip-based MVPA for each valid person-day (accelerometry; ≥ 600 min wear time). On school days, students accrued 68.2 min/day (95% CI 60.4-76.0) of MVPA. Daily activity spaces averaged 2.2 km(2) (95% CI 1.3-3.0). There was no association between activity space size and school-day MVPA. Students accrued 21.8 min/day (95% CI 19.2-24.4) of MVPA during school hours, 19.4 min/day (95% CI 15.1-23.7) during travel, and 28.3 min/day (95% CI 22.3-34.3) elsewhere. School and school travel are important sources of PA in Vancouver adolescents, irrespective of activity space area covered.
A Quotient Space Approximation Model of Multiresolution Signal Analysis
Institute of Scientific and Technical Information of China (English)
Ling Zhang; Bo Zhang
2005-01-01
In this paper, we present a quotient space approximation model of multiresolution signal analysis and discuss the properties and characteristics of the model. Then the comparison between wavelet transform and the quotient space approximation is made. First, when wavelet transform is viewed from the new quotient space approximation perspective, it may help us to gain an insight into the essence of multiresolution signal analysis. Second, from the similarity between wavelet and quotient space approximations, it is possible to transfer the rich wavelet techniques into the latter so that a new way for multiresolution analysis may be found.
Fan, Xitao; Wang, Lin; Thompson, Bruce
1999-01-01
A Monte Carlo simulation study investigated the effects on 10 structural equation modeling fit indexes of sample size, estimation method, and model specification. Some fit indexes did not appear to be comparable, and it was apparent that estimation method strongly influenced almost all fit indexes examined, especially for misspecified models. (SLD)
Manifestations of Isospin in Nearest Neighbor Spacing Distributions for the f-p Model Space
Quinonez, Michael; Zamick, Larry
2016-01-01
The strong interactions are charge independent. If we limit ourselves to the strong interactions, we have the isospin $T$ as a good quantum number. Here we consider the lack of level repulsion of states of different isospin and how this effect manifests in nearest neighbor spacing (NNS) histograms, which provide a visual and statistical context in which to study distributions of energy level spacings. In particular, we study nucleons in the f-p model space for the nucleus $^{44}$Ti. We also study the effect of the Coulomb interaction on the level spacing distribution.
Kalu, A. E.
A model for Space Weather (SW) Circulation with Plasma Clouds as background radiation medium of Space Environment has been proposed and discussed. Major characteristics of the model are outlined and the model assumes a baroclinic Space Environment in view of observed pronounced horizontal electron temperature gradient with prevailing weak vertical temperature gradient. The primary objective of the study is to be able to monitor and realistically predict on real- or near real-time SW and Space Storms (SWS) affecting human economic systems on Earth as well as the safety and Physiologic comfort of human payload in Space Environment in relation to planned increase in human space flights especially with reference to the ISS Space Shuttle Taxi (ISST) Programme and other prolonged deep Space Missions. Although considerable discussions are now available in the literature on SW issues, routine Meteorological operational applications of SW forecast data and information for Space Environment are still yet to receive adequate attention. The paper attempts to fill this gap in the literature of SW. The paper examines the sensitivity and variability in 3-D continuum of Plasmas in response to solar radiation inputs into the magnetosphere under disturbed Sun condition. Specifically, the presence of plasma clouds in the form of Coronal Mass Ejections (CMEs) is stressed as a major source of danger to Space crews, spacecraft instrumentation and architecture charging problems as well as impacts on numerous radiation - sensitive human economic systems on Earth. Finally, the paper considers the application of model results in the form of effective monitoring of each of the two major phases of manned Spaceflights - take-off and re-entry phases where all-time assessment of spacecraft transient ambient micro-incabin and outside Space Environment is vital for all manned Spaceflights as recently evidenced by the loss of vital information during take-off of the February 1, 2003 US Columbia
Development, validation and application of numerical space environment models
Honkonen, Ilja
2013-10-01
Currently the majority of space-based assets are located inside the Earth's magnetosphere where they must endure the effects of the near-Earth space environment, i.e. space weather, which is driven by the supersonic flow of plasma from the Sun. Space weather refers to the day-to-day changes in the temperature, magnetic field and other parameters of the near-Earth space, similarly to ordinary weather which refers to changes in the atmosphere above ground level. Space weather can also cause adverse effects on the ground, for example, by inducing large direct currents in power transmission systems. The performance of computers has been growing exponentially for many decades and as a result the importance of numerical modeling in science has also increased rapidly. Numerical modeling is especially important in space plasma physics because there are no in-situ observations of space plasmas outside of the heliosphere and it is not feasible to study all aspects of space plasmas in a terrestrial laboratory. With the increasing number of computational cores in supercomputers, the parallel performance of numerical models on distributed memory hardware is also becoming crucial. This thesis consists of an introduction, four peer reviewed articles and describes the process of developing numerical space environment/weather models and the use of such models to study the near-Earth space. A complete model development chain is presented starting from initial planning and design to distributed memory parallelization and optimization, and finally testing, verification and validation of numerical models. A grid library that provides good parallel scalability on distributed memory hardware and several novel features, the distributed cartesian cell-refinable grid (DCCRG), is designed and developed. DCCRG is presently used in two numerical space weather models being developed at the Finnish Meteorological Institute. The first global magnetospheric test particle simulation based on the
Energy Spectrum Symmetry of Heisenberg Model in Fock Space
Institute of Scientific and Technical Information of China (English)
WANG An-Min; ZHU Ren-Gui
2006-01-01
@@ We extend the BCS paring model with equally spaced energy levels to a general one-dimensional spin-l/2 Heisenberg model. The two well-known symmetries of the Heisenberg model, i.e. permutational and spin-inversion symmetries, no longer exist. However, when jointing these two operations together, we find a new symmetry of energy spectrum between its subspace n and subspace L - n of the Fock space. A rigorous proof is presented.
A FORMAL SPECIFICATION LANGUAGE FOR DYNAMIC STRAND SPACE MODEL
Institute of Scientific and Technical Information of China (English)
刘东喜; 李晓勇; 白英彩
2002-01-01
Specification language is used to provide enough information for the model of the cryptographic protocol. This paper first extends strand space model to dynamic strand model, and then a formal specification language for this model is defined by using BNF grammar. Compared with those in literatures, it is simpler because of only concerning the algebraic properties of cryptographic protocols.
Space Mapping Optimization of Microwave Circuits Exploiting Surrogate Models
DEFF Research Database (Denmark)
Bakr, M. H.; Bandler, J. W.; Madsen, Kaj
2000-01-01
A powerful new space-mapping (SM) optimization algorithm is presented in this paper. It draws upon recent developments in both surrogate model-based optimization and modeling of microwave devices, SM optimization is formulated as a general optimization problem of a surrogate model. This model...
Numerical modeling of space-time wave extremes using WAVEWATCH III
Barbariol, Francesco; Alves, Jose-Henrique G. M.; Benetazzo, Alvise; Bergamasco, Filippo; Bertotti, Luciana; Carniel, Sandro; Cavaleri, Luigi; Chao, Yung Y.; Chawla, Arun; Ricchi, Antonio; Sclavo, Mauro; Tolman, Hendrik
2017-01-01
A novel implementation of parameters estimating the space-time wave extremes within the spectral wave model WAVEWATCH III (WW3) is presented. The new output parameters, available in WW3 version 5.16, rely on the theoretical model of Fedele (J Phys Oceanogr 42(9):1601-1615, 2012) extended by Benetazzo et al. (J Phys Oceanogr 45(9):2261-2275, 2015) to estimate the maximum second-order nonlinear crest height over a given space-time region. In order to assess the wave height associated to the maximum crest height and the maximum wave height (generally different in a broad-band stormy sea state), the linear quasi-determinism theory of Boccotti (2000) is considered. The new WW3 implementation is tested by simulating sea states and space-time extremes over the Mediterranean Sea (forced by the wind fields produced by the COSMO-ME atmospheric model). Model simulations are compared to space-time wave maxima observed on March 10th, 2014, in the northern Adriatic Sea (Italy), by a stereo camera system installed on-board the "Acqua Alta" oceanographic tower. Results show that modeled space-time extremes are in general agreement with observations. Differences are mostly ascribed to the accuracy of the wind forcing and, to a lesser extent, to the approximations introduced in the space-time extremes parameterizations. Model estimates are expected to be even more accurate over areas larger than the mean wavelength (for instance, the model grid size).
Relationship of fuel size and spacing to combustion characteristics of laboratory fuel cribs
Hal E. Anderson
1990-01-01
Flaming combustion in cribs of large woody fuels, thickness 5 cm or greater, is not sustained when fuel spacing ratio, fuel edge-to-edge separation distance to fuel thickness, is greater than 3:1. The flame length associated with the large-fuel burning rate was found to drop rapidly when the large-fuel spacing ratio increases beyond 2.23:1. This supports the critical...
Kuznetsova, Maria
The Community Coordinated Modeling Center (CCMC, http://ccmc.gsfc.nasa.gov) was established at the dawn of the new millennium as a long-term flexible solution to the problem of transition of progress in space environment modeling to operational space weather forecasting. CCMC hosts an expanding collection of state-of-the-art space weather models developed by the international space science community. Over the years the CCMC acquired the unique experience in preparing complex models and model chains for operational environment and developing and maintaining custom displays and powerful web-based systems and tools ready to be used by researchers, space weather service providers and decision makers. In support of space weather needs of NASA users CCMC is developing highly-tailored applications and services that target specific orbits or locations in space and partnering with NASA mission specialists on linking CCMC space environment modeling with impacts on biological and technological systems in space. Confidence assessment of model predictions is an essential element of space environment modeling. CCMC facilitates interaction between model owners and users in defining physical parameters and metrics formats relevant to specific applications and leads community efforts to quantify models ability to simulate and predict space environment events. Interactive on-line model validation systems developed at CCMC make validation a seamless part of model development circle. The talk will showcase innovative solutions for space weather research, validation, anomaly analysis and forecasting and review on-going community-wide model validation initiatives enabled by CCMC applications.
Modeling the long-term evolution of space debris
Nikolaev, Sergei; De Vries, Willem H.; Henderson, John R.; Horsley, Matthew A.; Jiang, Ming; Levatin, Joanne L.; Olivier, Scot S.; Pertica, Alexander J.; Phillion, Donald W.; Springer, Harry K.
2017-03-07
A space object modeling system that models the evolution of space debris is provided. The modeling system simulates interaction of space objects at simulation times throughout a simulation period. The modeling system includes a propagator that calculates the position of each object at each simulation time based on orbital parameters. The modeling system also includes a collision detector that, for each pair of objects at each simulation time, performs a collision analysis. When the distance between objects satisfies a conjunction criterion, the modeling system calculates a local minimum distance between the pair of objects based on a curve fitting to identify a time of closest approach at the simulation times and calculating the position of the objects at the identified time. When the local minimum distance satisfies a collision criterion, the modeling system models the debris created by the collision of the pair of objects.
Modeling the long-term evolution of space debris
Energy Technology Data Exchange (ETDEWEB)
Nikolaev, Sergei; De Vries, Willem H.; Henderson, John R.; Horsley, Matthew A.; Jiang, Ming; Levatin, Joanne L.; Olivier, Scot S.; Pertica, Alexander J.; Phillion, Donald W.; Springer, Harry K.
2017-03-07
A space object modeling system that models the evolution of space debris is provided. The modeling system simulates interaction of space objects at simulation times throughout a simulation period. The modeling system includes a propagator that calculates the position of each object at each simulation time based on orbital parameters. The modeling system also includes a collision detector that, for each pair of objects at each simulation time, performs a collision analysis. When the distance between objects satisfies a conjunction criterion, the modeling system calculates a local minimum distance between the pair of objects based on a curve fitting to identify a time of closest approach at the simulation times and calculating the position of the objects at the identified time. When the local minimum distance satisfies a collision criterion, the modeling system models the debris created by the collision of the pair of objects.
Space-Time Structures from IIB Matrix Model
Aoki, H; Kawai, H; Kitazawa, Y; Tada, T
1998-01-01
We derive a long distance effective action for space-time coordinates from a IIB matrix model. It provides us an effective tool to study the structures of space-time. We prove the finiteness of the theory for finite $N$ to all orders of the perturbation theory. Space-time is shown to be inseparable and its dimensionality is dynamically determined. The IIB matrix model contains a mechanism to ensure the vanishing cosmological constant which does not rely on the manifest supersymmetry. We discuss possible mechanisms to obtain realistic dimensionality and gauge groups from the IIB matrix model.
A Learning State-Space Model for Image Retrieval
Directory of Open Access Journals (Sweden)
Lee Greg C
2007-01-01
Full Text Available This paper proposes an approach based on a state-space model for learning the user concepts in image retrieval. We first design a scheme of region-based image representation based on concept units, which are integrated with different types of feature spaces and with different region scales of image segmentation. The design of the concept units aims at describing similar characteristics at a certain perspective among relevant images. We present the details of our proposed approach based on a state-space model for interactive image retrieval, including likelihood and transition models, and we also describe some experiments that show the efficacy of our proposed model. This work demonstrates the feasibility of using a state-space model to estimate the user intuition in image retrieval.
Properties of Brownian Image Models in Scale-Space
DEFF Research Database (Denmark)
Pedersen, Kim Steenstrup
2003-01-01
In this paper it is argued that the Brownian image model is the least committed, scale invariant, statistical image model which describes the second order statistics of natural images. Various properties of three different types of Gaussian image models (white noise, Brownian and fractional...... Brownian images) will be discussed in relation to linear scale-space theory, and it will be shown empirically that the second order statistics of natural images mapped into jet space may, within some scale interval, be modeled by the Brownian image model. This is consistent with the 1/f 2 power spectrum...... law that apparently governs natural images. Furthermore, the distribution of Brownian images mapped into jet space is Gaussian and an analytical expression can be derived for the covariance matrix of Brownian images in jet space. This matrix is also a good approximation of the covariance matrix...
Simulation Modeling of Space Missions Using the High Level Architecture
Directory of Open Access Journals (Sweden)
Luis Rabelo
2013-01-01
Full Text Available This paper discusses an environment being developed to model a mission of the Space Launch System (SLS and the Multipurpose Crew Vehicle (MPCV being launched from Kennedy Space Center (KSC to the International Space Station (ISS. Several models representing different phases of the mission such as the ground operations processes, engineered systems, and range components such as failure tree, blast, gas dispersion, and debris modeling are explained. These models are built using different simulation paradigms such as continuous, system dynamics, discrete-event, and agent-based simulation modeling. The High Level Architecture (HLA is the backbone of this distributed simulation. The different design decisions and the information fusion scheme of this unique environment are explained in detail for decision-making. This can also help in the development of exploration missions beyond the International Space Station.
Quantum-Dot Semiconductor Optical Amplifiers: State Space Model versus Rate Equation Model
Directory of Open Access Journals (Sweden)
Hussein Taleb
2013-01-01
Full Text Available A simple and accurate dynamic model for QD-SOAs is proposed. The proposed model is based on the state space theory, where by eliminating the distance dependence of the rate equation model of the QD-SOA; we derive a state space model for the device. A comparison is made between the rate equation model and the state space model under both steady state and transient regimes. Simulation results demonstrate that the derived state space model not only is much simpler and faster than the rate equation model, but also it is as accurate as the rate equation model.
Margetan, Frank J.; Leckey, Cara A.; Barnard, Dan
2012-01-01
The size and shape of a delamination in a multi-layered structure can be estimated in various ways from an ultrasonic pulse/echo image. For example the -6dB contours of measured response provide one simple estimate of the boundary. More sophisticated approaches can be imagined where one adjusts the proposed boundary to bring measured and predicted UT images into optimal agreement. Such approaches require suitable models of the inspection process. In this paper we explore issues pertaining to model-based size estimation for delaminations in carbon fiber reinforced laminates. In particular we consider the influence on sizing when the delamination is non-planar or partially transmitting in certain regions. Two models for predicting broadband sonic time-domain responses are considered: (1) a fast "simple" model using paraxial beam expansions and Kirchhoff and phase-screen approximations; and (2) the more exact (but computationally intensive) 3D elastodynamic finite integration technique (EFIT). Model-to-model and model-to experiment comparisons are made for delaminations in uniaxial composite plates, and the simple model is then used to critique the -6dB rule for delamination sizing.
Modeling Spaces for Self-Directed Learning at University Courses
Pata, Kai
2009-01-01
This paper conceptualizes the theoretical framework of modeling learning spaces for self-directed learning at university courses. It binds together two ideas: (a) self-directed learners' common learning spaces may be characterized as abstract niches, (b) niche characteristics are collectively determined through individually perceived affordances.…
A Simulation and Modeling Framework for Space Situational Awareness
Energy Technology Data Exchange (ETDEWEB)
Olivier, S S
2008-09-15
This paper describes the development and initial demonstration of a new, integrated modeling and simulation framework, encompassing the space situational awareness enterprise, for quantitatively assessing the benefit of specific sensor systems, technologies and data analysis techniques. The framework is based on a flexible, scalable architecture to enable efficient, physics-based simulation of the current SSA enterprise, and to accommodate future advancements in SSA systems. In particular, the code is designed to take advantage of massively parallel computer systems available, for example, at Lawrence Livermore National Laboratory. The details of the modeling and simulation framework are described, including hydrodynamic models of satellite intercept and debris generation, orbital propagation algorithms, radar cross section calculations, optical brightness calculations, generic radar system models, generic optical system models, specific Space Surveillance Network models, object detection algorithms, orbit determination algorithms, and visualization tools. The use of this integrated simulation and modeling framework on a specific scenario involving space debris is demonstrated.
Space ecoliteracy- five informal education models for community empowerment
Venkataramaiah, Jagannatha; Jagannath, Sahana; J, Spandana; J, Sadhana; Jagannath, Shobha
Space ecoliteracy is a historical necessity and vital aspect of space age.Space Situational Awareness has taught lessons for mankind to look inward while stretching beyond cradle in human endeavours. Quality of life for every one on the only home of mankind-TERRA shall be a feasibility only after realizing Space ecoliteracy amongst all stakeholders in space quest. Objectives of Informal Environmental Education(UNESCO/UNEP/IEEP,1977) mandates awareness, attitude, knowledge, skill and participation at Individual and Community domains. Application of Space Technology at both Telecommunications and Remote Sensing domain have started making the fact that mankind has a challenge to learn and affirm earthmanship. Community empowerment focus after Earth Summit 1992 mandate of Sustainable Development has demonstrated a deluge of best practices in Agriculture,Urban, Industries and service sectors all over the globe. Further, deployment of Space technologies have proved the immense potential only after pre-empting the participatory approach at individual and community levels.Indian Space Programme with its 44th year of space service to national development has demonstrated self reliance in space technology for human development. Space technology for the most underdeveloped is a success story both in communication and information tools for quality of life. In this presentation Five Space Ecoliteracy models designed and validated since 1985 till date on informal environmental education namely 1) Ecological Environmental Studies by Students-EESS (1988): cited as one of the 20 best eco -education models by Earth Day Network,2)Community Eco Literacy Campaign-CEL,(2000): cited as a partner under Clean Up the World Campaign,UN, 3) Space Eco Literacy(2011)-an informa 8 week space eco literacy training reported at 39th COSPAR 12 assembly and 4) Space Eco Literacy by Practice(2014)- interface with formal education at institutions and 5) Space Ecoliteracy Mission as a space out reach in
Directory of Open Access Journals (Sweden)
Benjamin D Charlton
Full Text Available Examining how increasing distance affects the information content of vocal signals is fundamental for determining the active space of a given species' vocal communication system. In the current study we played back male koala bellows in a Eucalyptus forest to determine the extent that individual classification of male koala bellows becomes less accurate over distance, and also to quantify how individually distinctive acoustic features of bellows and size-related information degrade over distance. Our results show that the formant frequencies of bellows derived from Linear Predictive Coding can be used to classify calls to male koalas over distances of 1-50 m. Further analysis revealed that the upper formant frequencies and formant frequency spacing were the most stable acoustic features of male bellows as they propagated through the Eucalyptus canopy. Taken together these findings suggest that koalas could recognise known individuals at distances of up to 50 m and indicate that they should attend to variation in the upper formant frequencies and formant frequency spacing when assessing the identity of callers. Furthermore, since the formant frequency spacing is also a cue to male body size in this species and its variation over distance remained very low compared to documented inter-individual variation, we suggest that male koalas would still be reliably classified as small, medium or large by receivers at distances of up to 150 m.
Nonlinear Sigma Models with Compact Hyperbolic Target Spaces
Gubser, Steven; Schoenholz, Samuel S; Stoica, Bogdan; Stokes, James
2015-01-01
We explore the phase structure of nonlinear sigma models with target spaces corresponding to compact quotients of hyperbolic space, focusing on the case of a hyperbolic genus-2 Riemann surface. The continuum theory of these models can be approximated by a lattice spin system which we simulate using Monte Carlo methods. The target space possesses interesting geometric and topological properties which are reflected in novel features of the sigma model. In particular, we observe a topological phase transition at a critical temperature, above which vortices proliferate, reminiscent of the Kosterlitz-Thouless phase transition in the $O(2)$ model. Unlike in the $O(2)$ case, there are many different types of vortices, suggesting a possible analogy to the Hagedorn treatment of statistical mechanics of a proliferating number of hadron species. Below the critical temperature the spins cluster around six special points in the target space known as Weierstrass points. The diversity of compact hyperbolic manifolds suggest...
mathematical model for direct evaporative space cooling systems
African Journals Online (AJOL)
eobe
MATHEMATICAL MODEL FOR DIRECT EVAPORATIVE SPACE COOLING. SYSTEMS ... Water is the working fluid in evaporative cooling thus it is ..... co o lin g efficien cy (%. ) Time (hrs) predicted experimental. 0. 10. 20. 30. 40. 50. 60. 70. 80.
Lagrangian formulation of symmetric space sine-Gordon models
Bakas, Ioannis; Shin, H J; Park, Q Han
1996-01-01
The symmetric space sine-Gordon models arise by conformal reduction of ordinary 2-dim \\sigma-models, and they are integrable exhibiting a black-hole type metric in target space. We provide a Lagrangian formulation of these systems by considering a triplet of Lie groups F \\supset G \\supset H. We show that for every symmetric space F/G, the generalized sine-Gordon models can be derived from the G/H WZW action, plus a potential term that is algebraically specified. Thus, the symmetric space sine-Gordon models describe certain integrable perturbations of coset conformal field theories at the classical level. We also briefly discuss their vacuum structure, Backlund transformations, and soliton solutions.
Statistical modeling of space shuttle environmental data
Tubbs, J. D.; Brewer, D. W.
1983-01-01
Statistical models which use a class of bivariate gamma distribution are examined. Topics discussed include: (1) the ratio of positively correlated gamma varieties; (2) a method to determine if unequal shape parameters are necessary in bivariate gamma distribution; (3) differential equations for modal location of a family of bivariate gamma distribution; and (4) analysis of some wind gust data using the analytical results developed for modeling application.
A Situative Space Model for Mobile Mixed-Reality Computing
DEFF Research Database (Denmark)
Pederson, Thomas; Janlert, Lars-Erik; Surie, Dipak
2011-01-01
This article proposes a situative space model that links the physical and virtual realms and sets the stage for complex human-computer interaction defined by what a human agent can see, hear, and touch, at any given point in time.......This article proposes a situative space model that links the physical and virtual realms and sets the stage for complex human-computer interaction defined by what a human agent can see, hear, and touch, at any given point in time....
Space engineering modeling and optimization with case studies
Pintér, János
2016-01-01
This book presents a selection of advanced case studies that cover a substantial range of issues and real-world challenges and applications in space engineering. Vital mathematical modeling, optimization methodologies and numerical solution aspects of each application case study are presented in detail, with discussions of a range of advanced model development and solution techniques and tools. Space engineering challenges are discussed in the following contexts: •Advanced Space Vehicle Design •Computation of Optimal Low Thrust Transfers •Indirect Optimization of Spacecraft Trajectories •Resource-Constrained Scheduling, •Packing Problems in Space •Design of Complex Interplanetary Trajectories •Satellite Constellation Image Acquisition •Re-entry Test Vehicle Configuration Selection •Collision Risk Assessment on Perturbed Orbits •Optimal Robust Design of Hybrid Rocket Engines •Nonlinear Regression Analysis in Space Engineering< •Regression-Based Sensitivity Analysis and Robust Design ...
Hypersurface-deformation algebroids and effective space-time models
Bojowald, Martin; Buyukcam, Umut; D'Ambrosio, Fabio
2016-01-01
In canonical gravity, covariance is implemented by brackets of hypersurface-deformation generators forming a Lie algebroid. Lie algebroid morphisms therefore allow one to relate different versions of the brackets that correspond to the same space-time structure. An application to examples of modified brackets found mainly in models of loop quantum gravity can in some cases map the space-time structure back to the classical Riemannian form after a field redefinition. For one type of quantum corrections (holonomies), signature change appears to be a generic feature of effective space-time, and is shown here to be a new quantum space-time phenomenon which cannot be mapped to an equivalent classical structure. In low-curvature regimes, our constructions prove the existence of classical space-time structures assumed elsewhere in models of loop quantum cosmology, but also shows the existence of additional quantum corrections that have not always been included.
mizer: an R package for multispecies, trait-based and community size spectrum ecological modelling
DEFF Research Database (Denmark)
Scott, Finlay; Blanchard, Julia L.; Andersen, Ken Haste
2014-01-01
1. Size spectrum ecological models are representations of a community of individuals which grow and change trophic level. A key emergent feature of these models is the size spectrum; the total abundance of all individuals that scales negatively with size. The models we focus on are designed...
Modeling thermally active building components using space mapping
DEFF Research Database (Denmark)
Pedersen, Frank; Weitzmann, Peter; Svendsen, Svend
2005-01-01
simplified models of the components do not always provide useful solutions, since they are not always able to reproduce the correct thermal behavior. The space mapping technique transforms a simplified, but computationally inexpensive model, in order to align it with a detailed model or measurements....... This paper describes the principle of the space mapping technique, and introduces a simple space mapping technique. The technique is applied to a lumped parameter model of a thermo active component, which provides a model of the thermal performance of the component as a function of two design parameters......In order to efficiently implement thermally active building components in new buildings, it is necessary to evaluate the thermal interaction between them and other building components. Applying parameter investigation or numerical optimization methods to a differential-algebraic (DAE) model...
McArdle, C B; Richardson, C J; Nicholas, D A; Mirfakhraee, M; Hayden, C K; Amparo, E G
1987-01-01
Magnetic resonance (MR) imaging with a 0.6-T magnet was performed on 51 neonates, aged 29-42 weeks postconception. In 45 neonates, the ventricular/brain ratio (V/B) at the level of the frontal horns and midbody of the lateral ventricles ranged from 0.26 to 0.34. In six other infants a V/B of 0.36 or greater was associated with either cerebral atrophy or obstructive hydrocephalus. The width of the extracerebral space measured along specified points varied little in the neonatal period and ranged from 0 to 4 mm in 48 infants. Extracerebral space widths of 5-6 mm were seen in three other infants with severe asphyxia. Prominence of the subarachnoid space overlying the posterior parietal lobes is normal in neonates and should not be confused with cerebral atrophy. The authors conclude that V/B ratios of 0.26-0.34 and extracerebral space widths of 0-4 mm represent the normal range, and that neonates whose measurements exceed these values should be followed up.
Calculation and measurement of space charge in MV-size xxtruded cables systems under load conditions
Morshuis, P.H.F.; Bodega, R.; Fabiani, D.; Montanari, G.C.; Dissado, L.A; Smit, J.J.
2007-01-01
A load current in dc high voltage cables results in a temperature drop across the insulation and hence a radial distribution of the insulation conductivity is found. Direct consequence is an accumulation of space charge in the bulk of the nsulation, that may significantly affect its reliability. Thi
IBAR: Interacting boson model calculations for large system sizes
Casperson, R. J.
2012-04-01
Scaling the system size of the interacting boson model-1 (IBM-1) into the realm of hundreds of bosons has many interesting applications in the field of nuclear structure, most notably quantum phase transitions in nuclei. We introduce IBAR, a new software package for calculating the eigenvalues and eigenvectors of the IBM-1 Hamiltonian, for large numbers of bosons. Energies and wavefunctions of the nuclear states, as well as transition strengths between them, are calculated using these values. Numerical errors in the recursive calculation of reduced matrix elements of the d-boson creation operator are reduced by using an arbitrary precision mathematical library. This software has been tested for up to 1000 bosons using comparisons to analytic expressions. Comparisons have also been made to the code PHINT for smaller system sizes. Catalogue identifier: AELI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELI_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 28 734 No. of bytes in distributed program, including test data, etc.: 4 104 467 Distribution format: tar.gz Programming language: C++ Computer: Any computer system with a C++ compiler Operating system: Tested under Linux RAM: 150 MB for 1000 boson calculations with angular momenta of up to L=4 Classification: 17.18, 17.20 External routines: ARPACK (http://www.caam.rice.edu/software/ARPACK/) Nature of problem: Construction and diagonalization of large Hamiltonian matrices, using reduced matrix elements of the d-boson creation operator. Solution method: Reduced matrix elements of the d-boson creation operator have been stored in data files at machine precision, after being recursively calculated with higher than machine precision. The Hamiltonian matrix is calculated and diagonalized, and the requested transition strengths are calculated
The Hierarchy Model of the Size Distribution of Centres
J. Tinbergen (Jan)
1968-01-01
textabstractWe know that human beings live in centres, that is, cities, towns and villages of different size. Both large and small centres have a number of advantages and disadvantages, different for different people and this is why we have a whole range of sizes. Statistically, we even find that th
Electron Emitter for small-size Electrodynamic Space Tether using MEMS Technology
DEFF Research Database (Denmark)
Fleron, René A. W.; Blanke, Mogens
2004-01-01
system with focus on electron emitter design and manufacture using micro-electro-mechanical- system (MEMS) technology. The paper addresses the system concepts of a small size electrodynamic tether mission and shows a novel electron emitter for the 1-2 mA range where altitude can be effectively affected...
Validation of ecological state space models using the Laplace approximation
DEFF Research Database (Denmark)
Thygesen, Uffe Høgsbro; Albertsen, Christoffer Moesgaard; Berg, Casper Willestofte
2017-01-01
Many statistical models in ecology follow the state space paradigm. For such models, the important step of model validation rarely receives as much attention as estimation or hypothesis testing, perhaps due to lack of available algorithms and software. Model validation is often based on a naive...... for estimation in general mixed effects models. Implementing one-step predictions in the R package Template Model Builder, we demonstrate that it is possible to perform model validation with little effort, even if the ecological model is multivariate, has non-linear dynamics, and whether observations...... are continuous or discrete. With both simulated data, and a real data set related to geolocation of seals, we demonstrate both the potential and the limitations of the techniques. Our results fill a need for convenient methods for validating a state space model, or alternatively, rejecting it while indicating...
Space Weather: Measurements, Models and Predictions
2014-03-21
and record high levels of cosmic ray flux. There were broad-ranging terrestrial responses to this inactivity of the Sun. BC was involved in the...techniques for converting from one coordinate system (e.g., the invariant coordinate system used for the model) to another (e.g., the latitude- radius
Parton model in Lorentz invariant noncommutative space
Haghighat, M.; Ettefaghi, M. M.
2004-08-01
We consider the Lorentz invariant noncommutative QED and complete the Feynman rules for the theory up to the order θ2. In the Lorentz invariant version of the noncommutative QED the particles with fractional charges can be also considered. We show that in the parton model, even at the lowest order, the Bjorken scaling violates as ˜θ2Q4.
Interactions In Space For Archaeological Models
Evans, T S; Knappett, C
2011-01-01
In this article we examine a variety of quantitative models for describing archaeological networks, with particular emphasis on the maritime networks of the Aegean Middle Bronze Age. In particular, we discriminate between those gravitational networks that are most likely (maximum entropy) and most efficient (best cost/benefit outcomes).
Solvable Models on Noncommutative Spaces with Minimal Length Uncertainty Relations
Dey, Sanjib
2014-01-01
Our main focus is to explore different models in noncommutative spaces in higher dimensions. We provide a procedure to relate a three dimensional q-deformed oscillator algebra to the corresponding algebra satisfied by canonical variables describing non-commutative spaces. The representations for the corresponding operators obey algebras whose uncertainty relations lead to minimal length, areas and volumes in phase space, which are in principle natural candidates of many different approaches of quantum gravity. We study some explicit models on these types of noncommutative spaces, first by utilising the perturbation theory, later in an exact manner. In many cases the operators are not Hermitian, therefore we use PT -symmetry and pseudo-Hermiticity property, wherever applicable, to make them self-consistent. Apart from building mathematical models, we focus on the physical implications of noncommutative theories too. We construct Klauder coherent states for the perturbative and nonperturbative noncommutative ha...
Parameter redundancy in discrete state‐space and integrated models
McCrea, Rachel S.
2016-01-01
Discrete state‐space models are used in ecology to describe the dynamics of wild animal populations, with parameters, such as the probability of survival, being of ecological interest. For a particular parametrization of a model it is not always clear which parameters can be estimated. This inability to estimate all parameters is known as parameter redundancy or a model is described as nonidentifiable. In this paper we develop methods that can be used to detect parameter redundancy in discrete state‐space models. An exhaustive summary is a combination of parameters that fully specify a model. To use general methods for detecting parameter redundancy a suitable exhaustive summary is required. This paper proposes two methods for the derivation of an exhaustive summary for discrete state‐space models using discrete analogues of methods for continuous state‐space models. We also demonstrate that combining multiple data sets, through the use of an integrated population model, may result in a model in which all parameters are estimable, even though models fitted to the separate data sets may be parameter redundant. PMID:27362826
Parameter redundancy in discrete state-space and integrated models.
Cole, Diana J; McCrea, Rachel S
2016-09-01
Discrete state-space models are used in ecology to describe the dynamics of wild animal populations, with parameters, such as the probability of survival, being of ecological interest. For a particular parametrization of a model it is not always clear which parameters can be estimated. This inability to estimate all parameters is known as parameter redundancy or a model is described as nonidentifiable. In this paper we develop methods that can be used to detect parameter redundancy in discrete state-space models. An exhaustive summary is a combination of parameters that fully specify a model. To use general methods for detecting parameter redundancy a suitable exhaustive summary is required. This paper proposes two methods for the derivation of an exhaustive summary for discrete state-space models using discrete analogues of methods for continuous state-space models. We also demonstrate that combining multiple data sets, through the use of an integrated population model, may result in a model in which all parameters are estimable, even though models fitted to the separate data sets may be parameter redundant. © 2016 The Author. Biometrical Journal published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
A Modeler's Perspective on Space Weather Forecasting (Invited)
Wiltberger, M. J.
2010-12-01
Space physics is moving into a new era where numerical models originally developed for answering science questions are used as the basis for making operational space weather forecasts. Answering this challenge requires developments on multiple fronts requiring collaborations across space physics disciplines and between the research and operations communities. Since space weather in geospace is driven by the solar wind conditions a natural solution to improving the forecast lead time is to couple geospace models to heliospheric models. The quality of these forecast is dependent upon the ability of the heliospheric models to accurately model IMF Bz. Another challenge presented by moving into the forecasting arena is preparing the models for real-time operation which includes both computational performance and data redundancy issues. Moving into operations also presents modelers with an opportunity to assess their models performance over calculation intervals unprecedented duration. A key collaboration in the transition of models to operation is the discussion between forecasters and developers on what forecast parameters can accurately be predicted by the current generation of numerical models. This collaboration naturally includes a discussion of the definition of the best metrics to be used in quantitatively assessing performance.
Callahan, S R; Cross, A J; DeDecker, A E; Lindemann, M D; Estienne, M J
2017-01-01
The objective was to determine effects of nursery group-size-floor space allowance on growth, physiology, and hematology of replacement gilts. A 3 × 3 factorial arrangement of treatments was used wherein gilts classified as large, medium, or small ( = 2537; BW = 5.6 ± 0.6 kg) from 13 groups of weaned pigs were placed in pens of 14, 11, or 8 pigs resulting in floor space allowances of 0.15, 0.19, or 0.27 m/pig, respectively. Pigs were weighed on d 0 (weaning) and d 46 (exit from nursery). The ADG was affected by group-size-floor space allowance × pig size ( = 0.04). Large- and medium-size gilts allowed the most floor space had greater ( floor space but for small size gilts there was no effect ( > 0.05) of group size-floor space allowance. Mortality in the nursery was not affected ( > 0.05) by treatment, size, or treatment × size and overall was approximately 2.1%. Complete blood counts and blood chemistry analyses were performed on samples collected at d 6 and 43 from a subsample of gilts ( = 18/group-size-floor space allowance) within a single group. The concentration ( blood cell distribution width the greatest ( floor space (effects of treatment). Blood calcium was affected by treatment ( = 0.02) and concentrations for gilts allowed the greatest and intermediate amounts of floor space were greater ( floor space. Serum concentrations of cortisol were not affected by treatment × day ( = 0.27). Cortisol concentrations increased from d 6 to d 43 in all groups and were affected by day ( blood parameters and resulted in large- and medium-size replacement gilts displaying increased ADG. Further study will determine if these effects influence lifetime reproductive capacity and sow longevity.
Duane, Gregory S; Wang, Yanwei; Walters, Blake R; Kim, Jae K
2014-01-01
To adjust pulse sequences that produce diffusion-weighted MRI signals for increased sensitivity to nucleus size, the impulse-propagator method in q-space is applied to a spherical geometry that would describe each member of a collection of cells and their nuclei, with several possible representations of the extracellular space. The method is extended to allow propagation between nucleus, cytoplasm, and extracellular space through semi-permeable membranes, using an approximate adjustment of intra-compartment propagators. Diffraction patterns are first calculated for the three compartments separately, for PGSE and OGSE pulse sequences, and verified by comparison with Monte Carlo simulations. The detailed patterns from the separate compartments determine the q value for maximum contrast in the total signal between large and small nuclei, an optimization that is not accurate in a Gaussian Phase Distribution (GPD) approximation. Then diffraction patterns are calculated for the case of linked compartments with semi-permeable membranes. The treatment of permeability adequately estimates pulse-sequence parameters for maximum contrast in calculated signal as nucleus size varies. Copyright © 2013 Elsevier Inc. All rights reserved.
A Space Radiation Test Model Study
1989-02-17
approxiniationis fi iso - the course of the ssork. tit, other criterion was applied to the latirig the dominant contributions to the right-hand side of...these Iso end gics (t 17, ; .i rli rlc population ire assUrnd sufficietitv issues, at discussion oif eachi is necessary at the outset high rhir i7...Lopez, J. Geophys. Res., 92, 13485 , 1987. B-16 GEOPHYSICAL RESEARCH LETTERS, VOL. 14, NO. 11, PACES 1166-1169, NDVEM13ER 1981 A NONLINEAR MODEL OF WAVE
Formulating state space models in R with focus on longitudinal regression models
DEFF Research Database (Denmark)
Dethlefsen, Claus; Lundbye-Christensen, Søren
We provide a language for formulating a range of state space models. The described methodology is implemented in the R -package sspir available from cran.r-project.org . A state space model is specified similarly to a generalized linear model in R , by marking the time-varying terms in the form...... We provide a language for formulating a range of state space models. The described methodology is implemented in the R -package sspir available from cran.r-project.org . A state space model is specified similarly to a generalized linear model in R , by marking the time-varying terms...
Cancer screening: a mathematical model relating secreted blood biomarker levels to tumor sizes.
Directory of Open Access Journals (Sweden)
Amelie M Lutz
2008-08-01
Full Text Available BACKGROUND: Increasing efforts and financial resources are being invested in early cancer detection research. Blood assays detecting tumor biomarkers promise noninvasive and financially reasonable screening for early cancer with high potential of positive impact on patients' survival and quality of life. For novel tumor biomarkers, the actual tumor detection limits are usually unknown and there have been no studies exploring the tumor burden detection limits of blood tumor biomarkers using mathematical models. Therefore, the purpose of this study was to develop a mathematical model relating blood biomarker levels to tumor burden. METHODS AND FINDINGS: Using a linear one-compartment model, the steady state between tumor biomarker secretion into and removal out of the intravascular space was calculated. Two conditions were assumed: (1 the compartment (plasma is well-mixed and kinetically homogenous; (2 the tumor biomarker consists of a protein that is secreted by tumor cells into the extracellular fluid compartment, and a certain percentage of the secreted protein enters the intravascular space at a continuous rate. The model was applied to two pathophysiologic conditions: tumor biomarker is secreted (1 exclusively by the tumor cells or (2 by both tumor cells and healthy normal cells. To test the model, a sensitivity analysis was performed assuming variable conditions of the model parameters. The model parameters were primed on the basis of literature data for two established and well-studied tumor biomarkers (CA125 and prostate-specific antigen [PSA]. Assuming biomarker secretion by tumor cells only and 10% of the secreted tumor biomarker reaching the plasma, the calculated minimally detectable tumor sizes ranged between 0.11 mm(3 and 3,610.14 mm(3 for CA125 and between 0.21 mm(3 and 131.51 mm(3 for PSA. When biomarker secretion by healthy cells and tumor cells was assumed, the calculated tumor sizes leading to positive test results ranged
A probabilistic model of RNA conformational space
DEFF Research Database (Denmark)
Frellsen, Jes; Moltke, Ida; Thiim, Martin;
2009-01-01
The increasing importance of non-coding RNA in biology and medicine has led to a growing interest in the problem of RNA 3-D structure prediction. As is the case for proteins, RNA 3-D structure prediction methods require two key ingredients: an accurate energy function and a conformational sampling......, the discrete nature of the fragments necessitates the use of carefully tuned, unphysical energy functions, and their non-probabilistic nature impairs unbiased sampling. We offer a solution to the sampling problem that removes these important limitations: a probabilistic model of RNA structure that allows...... conformations for 9 out of 10 test structures, solely using coarse-grained base-pairing information. In conclusion, the method provides a theoretical and practical solution for a major bottleneck on the way to routine prediction and simulation of RNA structure and dynamics in atomic detail....
State-Space Modelling of Loudspeakers using Fractional Derivatives
DEFF Research Database (Denmark)
King, Alexander Weider; Agerkvist, Finn T.
2015-01-01
This work investigates the use of fractional order derivatives in modeling moving-coil loudspeakers. A fractional order state-space solution is developed, leading the way towards incorporating nonlinearities into a fractional order system. The method is used to calculate the response....... It is shown that the identified parameters can be used in a linear fractional order state-space model to simulate the loudspeakers’ time domain response...... of a fractional harmonic oscillator, representing the mechanical part of a loudspeaker, showing the effect of the fractional derivative and its relationship to viscoelasticity. Finally, a loudspeaker model with a fractional order viscoelastic suspension and fractional order voice coil is fit to measurement data...
Dynamic State Space Partitioning for External Memory Model Checking
DEFF Research Database (Denmark)
Evangelista, Sami; Kristensen, Lars Michael
2009-01-01
We describe a dynamic partitioning scheme usable by model checking techniques that divide the state space into partitions, such as most external memory and distributed model checking algorithms. The goal of the scheme is to reduce the number of transitions that link states belonging to different...
Applying reliability models to the maintenance of Space Shuttle software
Schneidewind, Norman F.
1992-01-01
Software reliability models provide the software manager with a powerful tool for predicting, controlling, and assessing the reliability of software during maintenance. We show how a reliability model can be effectively employed for reliability prediction and the development of maintenance strategies using the Space Shuttle Primary Avionics Software Subsystem as an example.
CAD-model-based vision for space applications
Shapiro, Linda G.
1988-01-01
A pose acquisition system operating in space must be able to perform well in a variety of different applications including automated guidance and inspections tasks with many different, but known objects. Since the space station is being designed with automation in mind, there will be CAD models of all the objects, including the station itself. The construction of vision models and procedures directly from the CAD models is the goal of this project. The system that is being designed and implementing must convert CAD models to vision models, predict visible features from a given view point from the vision models, construct view classes representing views of the objects, and use the view class model thus derived to rapidly determine the pose of the object from single images and/or stereo pairs.
A grain size distribution model for non-catalytic gas-solid reactions
Heesink, Albertus B.M.; Prins, W.; van Swaaij, Willibrordus Petrus Maria
1993-01-01
A new model to describe the non-catalytic conversion of a solid by a reactant gas is proposed. This so-called grain size distribution (GSD) model presumes the porous particle to be a collection of grains of various sizes. The size distribution of the grains is derived from mercury porosimetry measur
Sample Size Determination for Regression Models Using Monte Carlo Methods in R
Beaujean, A. Alexander
2014-01-01
A common question asked by researchers using regression models is, What sample size is needed for my study? While there are formulae to estimate sample sizes, their assumptions are often not met in the collected data. A more realistic approach to sample size determination requires more information such as the model of interest, strength of the…
solar magnetic fiber and space solar telescope in engineering model
Ai, G.
The solar magnetic fiber and the magnetic element are the most important factor in the solar activity and solar atmosphere. Because the space resolution of measurement of solar magnetic field is much lower than that of the size of the nature solar magnetic fiber and element from the earth atmospheric turbulence. The estimate of the magnetic element nature from various indirect researches shows great difference with several orders. The research results about magnetic elements have been reviewed in the paper.Because the size of the magnetic element has been estimated for 0.1T-0.2T, the space solar magnetic field telescope with big diameter is the most basic choice. For the exploration of solar magnetic fiber and element, a Space Solar Telescope is under development in the phase C and D, there are five payloads which are: 1) MOT, 1 diameter telescope with 8 channels real time 2-D spectrograph and 8 sets CCD with 2K`2K; 2) EUV, 4 tubes of soft X-ray Telescope with 0.252 space resolution; 3) WBS, the wide Band Spectrometer with 256 channel from soft X-ray to Gamma-ray. 4) HAT, Ha and white light telescope; 5) SIRA, Solar and interplanetary Radio Spectrometer, with 100 KHZ-60 MHZ. The assembly and test will be introduced.
Modeling of space-time focusing of localized nondiffracting pulses
Zamboni-Rached, Michel; Besieris, Ioannis M.
2016-10-01
In this paper we develop a method capable of modeling the space-time focusing of nondiffracting pulses. These pulses can possess arbitrary peak velocities and, in addition to being resistant to diffraction, can have their peak intensities and focusing positions chosen a priori. More specifically, we can choose multiple locations (spatial ranges) of space and time focalization; also, the pulse intensities can be chosen in advance. The pulsed wave solutions presented here can have very interesting applications in many different fields, such as free-space optical communications, remote sensing, medical apparatus, etc.
Modeling of Space-Time Focusing of Localized Nondiffracting Pulses
Zamboni-Rached, Michel
2015-01-01
In this paper we develop a method capable of modeling the space-time focusing of nondiffracting pulses. The new pulses can possess arbitrary peak velocities and, in addition to being resistant to diffraction, can have their peak intensities and focusing positions chosen a priori. More specifically, we can choose multiple locations (spatial ranges) of space/time focalization; also, the pulse intensities can be chosen in advance. The pulsed wave solutions presented here can have very interesting applications in many different fields, such as free-space optical communications, remote sensing, medical apparatus, etc.
Institute of Scientific and Technical Information of China (English)
Daisuke Tashima; Masahisa Otsubo
2011-01-01
The space-charge distributions of electric double-layer capacitors (EDLCs),which are energy storage devices,were examined with the pulsed electroacoustic (PEA) method. It was found that the experimental results could be influenced by the reflection and penetration of sound waves when the space-charge distributions of EDLCs were measured with the PEA method. This is because EDLCs have a five-layer structure consisting of three materials (aluminum,cellulose,and activated carbon). We calculated the reflection wave components that influenced the charge density through the acoustic impedance and the relative permittivity of the materials. In this way,we found that the changes in the space-charge distributions of EDLCs and their charge characteristics corresponded closely. We determined that measuring the spacecharge distributions with the PEA method was effective for evaluating the charge accumulation of EDLCs.In this study,a polarized electrode was prepared for use in EDLCs. The ratio of the surface area to the average pore diameter of the polarized electrode was measured with the nitrogen adsorption method at 77 K. The relationship between the ratio of the surface area to the average pore size and the space-charge distributions of EDLCs is also discussed in this paper.
Hoyle, Rick H; Gottfredson, Nisha C
2015-10-01
When the goal of prevention research is to capture in statistical models some measure of the dynamic complexity in structures and processes implicated in problem behavior and its prevention, approaches such as multilevel modeling (MLM) and structural equation modeling (SEM) are indicated. Yet the assumptions that must be satisfied if these approaches are to be used responsibly raise concerns regarding their use in prevention research involving smaller samples. In this article, we discuss in nontechnical terms the role of sample size in MLM and SEM and present findings from the latest simulation work on the performance of each approach at sample sizes typical of prevention research. For each statistical approach, we draw from extant simulation studies to establish lower bounds for sample size (e.g., MLM can be applied with as few as ten groups comprising ten members with normally distributed data, restricted maximum likelihood estimation, and a focus on fixed effects; sample sizes as small as N = 50 can produce reliable SEM results with normally distributed data and at least three reliable indicators per factor) and suggest strategies for making the best use of the modeling approach when N is near the lower bound.
Modeling electron fractionalization with unconventional Fock spaces
Cobanera, Emilio
2017-08-01
It is shown that certain fractionally-charged quasiparticles can be modeled on D-dimensional lattices in terms of unconventional yet simple Fock algebras of creation and annihilation operators. These unconventional Fock algebras are derived from the usual fermionic algebra by taking roots (the square root, cubic root, etc) of the usual fermionic creation and annihilation operators. If the fermions carry non-Abelian charges, then this approach fractionalizes the Abelian charges only. In particular, the mth-root of a spinful fermion carries charge e/m and spin 1/2. Just like taking a root of a complex number, taking a root of a fermion yields a mildly non-unique result. As a consequence, there are several possible choices of quantum exchange statistics for fermion-root quasiparticles. These choices are tied to the dimensionality D=1,2,3,\\ldots of the lattice by basic physical considerations. One particular family of fermion-root quasiparticles is directly connected to the parafermion zero-energy modes expected to emerge in certain mesoscopic devices involving fractional quantum Hall states. Hence, as an application of potential mesoscopic interest, I investigate numerically the hybridization of Majorana and parafermion zero-energy edge modes caused by fractionalizing but charge-conserving tunneling.
Mirror contamination in space I: mirror modelling
Krijger, J. M.; Snel, R.; van Harten, G.; Rietjens, J. H. H.; Aben, I.
2014-10-01
We present a comprehensive model that can be employed to describe and correct for degradation of (scan) mirrors and diffusers in satellite instruments that suffer from changing optical Ultraviolet to visible (UV-VIS) properties during their operational lifetime. As trend studies become more important, so does the importance of understanding and correcting for this degradation. This is the case not only with respect to the transmission of the optical components, but also with respect to wavelength, polarisation, or scan-angle effects. Our hypothesis is that mirrors in flight suffer from the deposition of a thin absorbing layer of contaminant, which slowly builds up over time. We describe this with the Mueller matrix formalism and Fresnel equations for thin multi-layer contamination films. Special care is taken to avoid the confusion often present in earlier publications concerning the Mueller matrix calculus with out-of-plane reflections. The method can be applied to any UV-VIS satellite instrument. We illustrate and verify our approach to the optical behaviour of the multiple scan mirrors of SCIAMACHY (onboard ENVISAT).
Modeling the seasonal evolution of the Arctic sea ice floe size distribution
Directory of Open Access Journals (Sweden)
Jinlun Zhang
2016-09-01
Full Text Available Abstract To better simulate the seasonal evolution of sea ice in the Arctic, with particular attention to the marginal ice zone, a sea ice model of the distribution of ice thickness, floe size, and enthalpy was implemented into the Pan-arctic Ice–Ocean Modeling and Assimilation System (PIOMAS. Theories on floe size distribution (FSD and ice thickness distribution (ITD were coupled in order to explicitly simulate multicategory FSD and ITD distributions simultaneously. The expanded PIOMAS was then used to estimate the seasonal evolution of the Arctic FSD in 2014 when FSD observations are available for model calibration and validation. Results indicate that the simulated FSD, commonly described equivalently as cumulative floe number distribution (CFND, generally follows a power law across space and time and agrees with the CFND observations derived from TerraSAR-X satellite images. The simulated power-law exponents also correlate with those derived using MODIS images, with a low mean bias of –2%. In the marginal ice zone, the modeled CFND shows a large number of small floes in winter because of stronger winds acting on thin, weak first-year ice in the ice edge region. In mid-spring and summer, the CFND resembles an upper truncated power law, with the largest floes mostly broken into smaller ones; however, the number of small floes is lower than in winter because floes of small sizes or first-year ice are easily melted away. In the ice pack interior there are fewer floes in late fall and winter than in summer because many of the floes are “welded” together into larger floes in freezing conditions, leading to a relatively flat CFND with low power-law exponents. The simulated mean floe size averaged over all ice-covered areas shows a clear annual cycle, large in winter and smaller in summer. However, there is no obvious annual cycle of mean floe size averaged over the marginal ice zone. The incorporation of FSD into PIOMAS results in reduced
Virus-sized colloid transport in a single pore: Model development and sensitivity analysis
Seetha, N.; Mohan Kumar, M. S.; Majid Hassanizadeh, S.; Raoof, Amir
2014-08-01
A mathematical model is developed to simulate the transport and deposition of virus-sized colloids in a cylindrical pore throat considering various processes such as advection, diffusion, colloid-collector surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-collector interaction forces dominate the transport in the potential region where colloid deposition occurs. The governing equations are non-dimensionalized and solved numerically. A sensitivity analysis indicates that the virus-sized colloid transport and deposition is significantly affected by various pore-scale parameters such as the surface potentials on colloid and collector, ionic strength of the solution, flow velocity, pore size and colloid size. The adsorbed concentration and hence, the favorability of the surface for adsorption increases with: (i) decreasing magnitude and ratio of surface potentials on colloid and collector, (ii) increasing ionic strength and (iii) increasing pore radius. The adsorbed concentration increases with increasing Pe, reaching a maximum value at Pe = 0.1 and then decreases thereafter. Also, the colloid size significantly affects particle deposition with the adsorbed concentration increasing with increasing particle radius, reaching a maximum value at a particle radius of 100 nm and then decreasing with increasing radius. System hydrodynamics is found to have a greater effect on larger particles than on smaller ones. The secondary minimum contribution to particle deposition has been found to increase as the favorability of the surface for adsorption decreases. The sensitivity of the model to a given parameter will be high
Finite size scaling analysis on Nagel-Schreckenberg model for traffic flow
Balouchi, Ashkan; Browne, Dana
2015-03-01
The traffic flow problem as a many-particle non-equilibrium system has caught the interest of physicists for decades. Understanding the traffic flow properties and though obtaining the ability to control the transition from the free-flow phase to the jammed phase plays a critical role in the future world of urging self-driven cars technology. We have studied phase transitions in one-lane traffic flow through the mean velocity, distributions of car spacing, dynamic susceptibility and jam persistence -as candidates for an order parameter- using the Nagel-Schreckenberg model to simulate traffic flow. The length dependent transition has been observed for a range of maximum velocities greater than a certain value. Finite size scaling analysis indicates power-law scaling of these quantities at the onset of the jammed phase.
Development and application of an aerosol screening model for size-resolved urban aerosols.
Stanier, Charles O; Lee, Sang-Rin
2014-06-01
Predictive models of vehicular ultrafine particles less than 0.1 microm in diameter (UFPs*) and other urban pollutants with high spatial and temporal variation are useful and important in applications such as (1) decision support for infrastructure projects, emissions controls, and transportation-mode shifts; (2) the interpretation and enhancement of observations (e.g., source apportionment, extrapolation, interpolation, and gap-filling in space and time); and (3) the generation of spatially and temporally resolved exposure estimates where monitoring is unfeasible. The objective of the current study was to develop, test, and apply the Aerosol Screening Model (ASM), a new physically based vehicular UFP model for use in near-road environments. The ASM simulates hourly average outdoor concentrations of roadway-derived aerosols and gases. Its distinguishing features include user-specified spatial resolution; use of the Weather Research and Forecasting (WRF) meteorologic model for winds estimates; use of a database of more than 100,000 road segments in the Los Angeles, California, region, including freeway ramps and local streets; and extensive testing against more than 9000 hours of observed particle concentrations at 11 sites. After initialization of air parcels at an upwind boundary, the model solves for vehicle emissions, dispersion, coagulation, and deposition using a Lagrangian modeling framework. The Lagrangian parcel of air is subdivided vertically (into 11 levels) and in the crosswind direction (into 3 parcels). It has overall dimensions of 10 m (downwind), 300 m (vertically), and 2.1 km (crosswind). The simulation is typically started 4 km upwind from the receptor, that is, the location at which the exposure is to be estimated. As parcels approach the receptor, depending on the user-specified resolution, step size is decreased, and crosswind resolution is enhanced through subdivision of parcels in the crosswind direction. Hourly concentrations and size
A stochastic space-time model for intermittent precipitation occurrences
Sun, Ying
2016-01-28
Modeling a precipitation field is challenging due to its intermittent and highly scale-dependent nature. Motivated by the features of high-frequency precipitation data from a network of rain gauges, we propose a threshold space-time t random field (tRF) model for 15-minute precipitation occurrences. This model is constructed through a space-time Gaussian random field (GRF) with random scaling varying along time or space and time. It can be viewed as a generalization of the purely spatial tRF, and has a hierarchical representation that allows for Bayesian interpretation. Developing appropriate tools for evaluating precipitation models is a crucial part of the model-building process, and we focus on evaluating whether models can produce the observed conditional dry and rain probabilities given that some set of neighboring sites all have rain or all have no rain. These conditional probabilities show that the proposed space-time model has noticeable improvements in some characteristics of joint rainfall occurrences for the data we have considered.
NASA Space Radiation Program Integrative Risk Model Toolkit
Kim, Myung-Hee Y.; Hu, Shaowen; Plante, Ianik; Ponomarev, Artem L.; Sandridge, Chris
2015-01-01
NASA Space Radiation Program Element scientists have been actively involved in development of an integrative risk models toolkit that includes models for acute radiation risk and organ dose projection (ARRBOD), NASA space radiation cancer risk projection (NSCR), hemocyte dose estimation (HemoDose), GCR event-based risk model code (GERMcode), and relativistic ion tracks (RITRACKS), NASA radiation track image (NASARTI), and the On-Line Tool for the Assessment of Radiation in Space (OLTARIS). This session will introduce the components of the risk toolkit with opportunity for hands on demonstrations. The brief descriptions of each tools are: ARRBOD for Organ dose projection and acute radiation risk calculation from exposure to solar particle event; NSCR for Projection of cancer risk from exposure to space radiation; HemoDose for retrospective dose estimation by using multi-type blood cell counts; GERMcode for basic physical and biophysical properties for an ion beam, and biophysical and radiobiological properties for a beam transport to the target in the NASA Space Radiation Laboratory beam line; RITRACKS for simulation of heavy ion and delta-ray track structure, radiation chemistry, DNA structure and DNA damage at the molecular scale; NASARTI for modeling of the effects of space radiation on human cells and tissue by incorporating a physical model of tracks, cell nucleus, and DNA damage foci with image segmentation for the automated count; and OLTARIS, an integrated tool set utilizing HZETRN (High Charge and Energy Transport) intended to help scientists and engineers study the effects of space radiation on shielding materials, electronics, and biological systems.
Estimation methods for nonlinear state-space models in ecology
DEFF Research Database (Denmark)
Pedersen, Martin Wæver; Berg, Casper Willestofte; Thygesen, Uffe Høgsbro
2011-01-01
The use of nonlinear state-space models for analyzing ecological systems is increasing. A wide range of estimation methods for such models are available to ecologists, however it is not always clear, which is the appropriate method to choose. To this end, three approaches to estimation in the theta...... logistic model for population dynamics were benchmarked by Wang (2007). Similarly, we examine and compare the estimation performance of three alternative methods using simulated data. The first approach is to partition the state-space into a finite number of states and formulate the problem as a hidden...... Markov model (HMM). The second method uses the mixed effects modeling and fast numerical integration framework of the AD Model Builder (ADMB) open-source software. The third alternative is to use the popular Bayesian framework of BUGS. The study showed that state and parameter estimation performance...
Continuous-time discrete-space models for animal movement
Hanks, Ephraim M.; Hooten, Mevin B.; Alldredge, Mat W.
2015-01-01
The processes influencing animal movement and resource selection are complex and varied. Past efforts to model behavioral changes over time used Bayesian statistical models with variable parameter space, such as reversible-jump Markov chain Monte Carlo approaches, which are computationally demanding and inaccessible to many practitioners. We present a continuous-time discrete-space (CTDS) model of animal movement that can be fit using standard generalized linear modeling (GLM) methods. This CTDS approach allows for the joint modeling of location-based as well as directional drivers of movement. Changing behavior over time is modeled using a varying-coefficient framework which maintains the computational simplicity of a GLM approach, and variable selection is accomplished using a group lasso penalty. We apply our approach to a study of two mountain lions (Puma concolor) in Colorado, USA.
Hyperstate matrix models : extending demographic state spaces to higher dimensions
Roth, G.; Caswell, H.
2016-01-01
1. Demographic models describe population dynamics in terms of the movement of individuals among states (e.g. size, age, developmental stage, parity, frailty, physiological condition). Matrix population models originally classified individuals by a single characteristic. This was enlarged to two cha
Geodetic Space Weather Monitoring by means of Ionosphere Modelling
Schmidt, Michael
2017-04-01
The term space weather indicates physical processes and phenomena in space caused by radiation of energy mainly from the Sun. Manifestations of space weather are (1) variations of the Earth's magnetic field, (2) the polar lights in the northern and southern hemisphere, (3) variations within the ionosphere as part of the upper atmosphere characterized by the existence of free electrons and ions, (4) the solar wind, i.e. the permanent emission of electrons and photons, (5) the interplanetary magnetic field, and (6) electric currents, e.g. the van Allen radiation belt. It can be stated that ionosphere disturbances are often caused by so-called solar storms. A solar storm comprises solar events such as solar flares and coronal mass ejections (CMEs) which have different effects on the Earth. Solar flares may cause disturbances in positioning, navigation and communication. CMEs can effect severe disturbances and in extreme cases damages or even destructions of modern infrastructure. Examples are interruptions to satellite services including the global navigation satellite systems (GNSS), communication systems, Earth observation and imaging systems or a potential failure of power networks. Currently the measurements of solar satellite missions such as STEREO and SOHO are used to forecast solar events. Besides these measurements the Earth's ionosphere plays another key role in monitoring the space weather, because it responses to solar storms with an increase of the electron density. Space-geodetic observation techniques, such as terrestrial GNSS, satellite altimetry, space-borne GPS (radio occultation), DORIS and VLBI provide valuable global information about the state of the ionosphere. Additionally geodesy has a long history and large experience in developing and using sophisticated analysis and combination techniques as well as empirical and physical modelling approaches. Consequently, geodesy is predestinated for strongly supporting space weather monitoring via
The application of expanded rank-size model in Turkish urban settlements
Dokmeci, Vedia; Turk, Sevkiye Sence
2001-01-01
The objective of this paper is to analyze the structure of urban system in Turkey from 1980 to 1997 by using expanded rank-size model. The former studies related to rank-size model in Turkey have illustrated important hierarchical regularities in rank-size relationships. In these studies changes in city- size distributions over time examined noting differences in slope and intercept at the different points in time. Then, these results are interpreted to indicate growth (decline) in entire sys...
Directory of Open Access Journals (Sweden)
Valerie A O'Brien
Full Text Available The transmission of parasites and pathogens among vertebrates often depends on host population size, host species diversity, and the extent of crowding among potential hosts, but little is known about how these variables apply to most vector-borne pathogens such as the arboviruses (arthropod-borne viruses. Buggy Creek virus (BCRV; Togaviridae: Alphavirus is an RNA arbovirus transmitted by the swallow bug (Oeciacus vicarius to the cliff swallow (Petrochelidon pyrrhonota and the introduced house sparrow (Passer domesticus that has recently invaded swallow nesting colonies. The virus has little impact on cliff swallows, but house sparrows are seriously affected by BCRV. For house sparrows occupying swallow nesting colonies in western Nebraska, USA, the prevalence of BCRV in nestling sparrows increased with sparrow colony size at a site but decreased with the number of cliff swallows present. If one nestling in a nest was infected with the virus, there was a greater likelihood that one or more of its nest-mates would also be infected than nestlings chosen at random. The closer a nest was to another nest containing infected nestlings, the greater the likelihood that some of the nestlings in the focal nest would be BCRV-positive. These results illustrate that BCRV represents a cost of coloniality for a vertebrate host (the house sparrow, perhaps the first such demonstration for an arbovirus, and that virus infection is spatially clustered within nests and within colonies. The decreased incidence of BCRV in sparrows as cliff swallows at a site increased reflects the "dilution effect," in which virus transmission is reduced when a vector switches to feeding on a less competent vertebrate host.
O'Brien, Valerie A; Brown, Charles R
2011-01-01
The transmission of parasites and pathogens among vertebrates often depends on host population size, host species diversity, and the extent of crowding among potential hosts, but little is known about how these variables apply to most vector-borne pathogens such as the arboviruses (arthropod-borne viruses). Buggy Creek virus (BCRV; Togaviridae: Alphavirus) is an RNA arbovirus transmitted by the swallow bug (Oeciacus vicarius) to the cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that has recently invaded swallow nesting colonies. The virus has little impact on cliff swallows, but house sparrows are seriously affected by BCRV. For house sparrows occupying swallow nesting colonies in western Nebraska, USA, the prevalence of BCRV in nestling sparrows increased with sparrow colony size at a site but decreased with the number of cliff swallows present. If one nestling in a nest was infected with the virus, there was a greater likelihood that one or more of its nest-mates would also be infected than nestlings chosen at random. The closer a nest was to another nest containing infected nestlings, the greater the likelihood that some of the nestlings in the focal nest would be BCRV-positive. These results illustrate that BCRV represents a cost of coloniality for a vertebrate host (the house sparrow), perhaps the first such demonstration for an arbovirus, and that virus infection is spatially clustered within nests and within colonies. The decreased incidence of BCRV in sparrows as cliff swallows at a site increased reflects the "dilution effect," in which virus transmission is reduced when a vector switches to feeding on a less competent vertebrate host.
Orbital Optimization in the Active Space Decomposition Model
Kim, Inkoo; Shiozaki, Toru
2015-01-01
We report the derivation and implementation of orbital optimization algorithms for the active space decomposition (ASD) model, which are extensions of complete active space self-consistent field (CASSCF) and its occupation-restricted variants in the conventional multiconfiguration electronic-structure theory. Orbital rotations between active subspaces are included in the optimization, which allows us to unambiguously partition the active space into subspaces, enabling application of ASD to electron and exciton dynamics in covalently linked chromophores. One- and two-particle reduced density matrices, which are required for evaluation of orbital gradient and approximate Hessian elements, are computed from the intermediate tensors in the ASD energy evaluation. Numerical results on 4-(2-naphthylmethyl)-benzaldehyde and [3$_6$]cyclophane and model Hamiltonian analyses of triplet energy transfer processes in the Closs systems are presented. Furthermore model Hamiltonians for hole and electron transfer processes in...
Semi-Automated Design Space Exploration for Formal Modelling
Grov, Gudmund; Ireland, Andrew; Llano, Maria Teresa; Kovacs, Peter; Colton, Simon; Gow, Jeremy
2016-01-01
Refinement based formal methods allow the modelling of systems through incremental steps via abstraction. Discovering the right levels of abstraction, formulating correct and meaningful invariants, and analysing faulty models are some of the challenges faced when using this technique. Here, we propose Design Space Exploration, an approach that aims to assist a designer by automatically providing high-level modelling guidance in real-time. More specifically, through the combination of common p...
Space and Time Ontology: New Models for New Physics
Directory of Open Access Journals (Sweden)
Sara Lumbreras Sancho
2015-02-01
Full Text Available Nickel proposes a model for movement – and in general, for change – in which each instant in time (characterized as the set of real numbers is assigned to one point in a configuration space. As much as this model seems to intuitively fit to our experience, it implies a number of assumptions about the nature of space and time that are interesting to explore. Different perspectives have been developed across History, and it could well be that the next scientific revolution is set in motion by an innovative conception of space and time. One of this alternative perspectives was proposed by Julian Barbour, who has developed a new model of Physics where time does not exist [Barbour, 1999]. This paper reviews not only this concept but also other similarly provocative ideas that might prove useful for improving our understanding of the universe. Prior to this, the relevance of the philosophy of space and time will be briefly outlined and its history reviewed to provide some background for the discussed models. Finally, an approach where space and time are only defined by convention will be considered.
Space Surveillance Network Scheduling Under Uncertainty: Models and Benefits
Valicka, C.; Garcia, D.; Staid, A.; Watson, J.; Rintoul, M.; Hackebeil, G.; Ntaimo, L.
2016-09-01
Advances in space technologies continue to reduce the cost of placing satellites in orbit. With more entities operating space vehicles, the number of orbiting vehicles and debris has reached unprecedented levels and the number continues to grow. Sensor operators responsible for maintaining the space catalog and providing space situational awareness face an increasingly complex and demanding scheduling requirements. Despite these trends, a lack of advanced tools continues to prevent sensor planners and operators from fully utilizing space surveillance resources. One key challenge involves optimally selecting sensors from a network of varying capabilities for missions with differing requirements. Another open challenge, the primary focus of our work, is building robust schedules that effectively plan for uncertainties associated with weather, ad hoc collections, and other target uncertainties. Existing tools and techniques are not amenable to rigorous analysis of schedule optimality and do not adequately address the presented challenges. Building on prior research, we have developed stochastic mixed-integer linear optimization models to address uncertainty due to weather's effect on collection quality. By making use of the open source Pyomo optimization modeling software, we have posed and solved sensor network scheduling models addressing both forms of uncertainty. We present herein models that allow for concurrent scheduling of collections with the same sensor configuration and for proactively scheduling against uncertain ad hoc collections. The suitability of stochastic mixed-integer linear optimization for building sensor network schedules under different run-time constraints will be discussed.
Modeling size-dependent photosynthesis: light absorption and the allometric rule.
Finkel, Z V; Irwin, A J
2000-06-07
Microalgal photosynthesis can be predicted using empirical allometric or mechanistic bio-optic models. These two descriptions are usually considered independently. We compare the size scaling of photosynthesis predicted by these two models. Size scaling exponents for phytoplankton often deviate from the allometric 3/4 rule. This may be because the allometric model does not account for the size dependence of light absorption and its effect on the size scaling of photosynthesis. In contrast to the allometric model and experimental data, the bio-optic model predicts photosynthesis should be independent of cell size when intracellular pigment concentrations are low or inversely related to cell diameter. A composite of the allometric and bio-optic models is described and compared to laboratory data of light-limited nutrient-saturated diatom photosynthesis. The allo-bio-optic model provides a mechanistic explanation for the anomalous size scaling found in laboratory and field studies of microalgal photosynthesis and growth.
Nonlinear sigma models with compact hyperbolic target spaces
Gubser, Steven; Saleem, Zain H.; Schoenholz, Samuel S.; Stoica, Bogdan; Stokes, James
2016-06-01
We explore the phase structure of nonlinear sigma models with target spaces corresponding to compact quotients of hyperbolic space, focusing on the case of a hyperbolic genus-2 Riemann surface. The continuum theory of these models can be approximated by a lattice spin system which we simulate using Monte Carlo methods. The target space possesses interesting geometric and topological properties which are reflected in novel features of the sigma model. In particular, we observe a topological phase transition at a critical temperature, above which vortices proliferate, reminiscent of the Kosterlitz-Thouless phase transition in the O(2) model [1, 2]. Unlike in the O(2) case, there are many different types of vortices, suggesting a possible analogy to the Hagedorn treatment of statistical mechanics of a proliferating number of hadron species. Below the critical temperature the spins cluster around six special points in the target space known as Weierstrass points. The diversity of compact hyperbolic manifolds suggests that our model is only the simplest example of a broad class of statistical mechanical models whose main features can be understood essentially in geometric terms.
Marriage of Electromagnetism and Gravity in an Extended Space Model and Astrophysical Phenomena
Andreev, V. A.; Tsipenyuk, D. Yu.
2013-09-01
The generalization of Einstein's special theory of relativity (SRT) is proposed. In this model the possibility of unification of scalar gravity and electromagnetism into a single unified field is considered. Formally, the generalization of the SRT is that instead of (1+3)-dimensional Minkowski space the (1+4)-dimensional extension G is considered. As a fifth additional coordinate the interval S is used. This value is saved under the usual Lorentz transformations in Minkowski space M, but it changes when the transformations in the extended space G are used. We call this model the extended space model (ESM). From a physical point of view our expansion means that processes in which the rest mass of the particles changes are acceptable now. If the rest mass of a particle does not change and the physical quantities do not depend on an additional variable S, then the electromagnetic and gravitational fields exist independently of each other. But if the rest mass is variable and there is a dependence on S, then these two fields are combined into a single unified field. In the extended space model a photon can have a nonzero mass and this mass can be either positive or negative. The gravitational effects such as the speed of escape, gravitational red shift and detection of light can be analyzed in the frame of the extended space model. In this model all these gravitational effects can be found algebraically by the rotations in the (1+4) dimensional space. Now it becomes possible to predict some future results of visible size of supermassive objects in our Universe due to new stage of experimental astronomy development in the RadioAstron Project and analyze phenomena is an explosion of the star V838 Mon.
Transformation of Neural State Space Models into LFT Models for Robust Control Design
DEFF Research Database (Denmark)
Bendtsen, Jan Dimon; Trangbæk, Klaus
2000-01-01
This paper considers the extraction of linear state space models and uncertainty models from neural networks trained as state estimators with direct application to robust control. A new method for writing a neural state space model in a linear fractional transformation form in a non...
Formulating state space models in R with focus on longitudinal regression models
DEFF Research Database (Denmark)
Dethlefsen, Claus; Lundbye-Christensen, Søren
2006-01-01
We provide a language for formulating a range of state space models with response densities within the exponential family. The described methodology is implemented in the R-package sspir. A state space model is specified similarly to a generalized linear model in R, and then the time-varying terms...
Effective Actions of Matrix Models on Homogeneous Spaces
Imai, T; Takayama, Y; Tomino, D
2002-01-01
We evaluate the effective actions of supersymmetric matrix models on fuzzy S^2times S^2 up to the two loop level. Remarkably it turns out to be a consistent solution of IIB matrix model. Based on the power counting and SUSY cancellation arguments, we can identify the 't Hooft coupling and large N scaling behavior of the effective actions to all orders. In the large N limit, the quantum corrections survive except in 2 dimensional limits. They are O(N) and O(N^{4over 3}) for 4 and 6 dimensional spaces respectively. We argue that quantum effects single out 4 dimensionality of space-time.
A Right Coprime Factorization of Neural State Space Models
DEFF Research Database (Denmark)
Bendtsen, Jan Dimon
2007-01-01
In recent years, various methods for identification of nonlinear systems in closed loop using open-loop approaches have received considerable attention. However, these methods rely on differentially coprime factorizations of the nonlinear plants, which can be difficult to compute in practice....... To address this issue, this paper presents various technical results leading up to explicit formulae for right coprime factorizations of neural state space models, i.e., nonlinear system models represented in state space using neural networks, which satisfy a Bezout identity. ...
SpaceWire model development technology for satellite architecture.
Energy Technology Data Exchange (ETDEWEB)
Eldridge, John M.; Leemaster, Jacob Edward; Van Leeuwen, Brian P.
2011-09-01
Packet switched data communications networks that use distributed processing architectures have the potential to simplify the design and development of new, increasingly more sophisticated satellite payloads. In addition, the use of reconfigurable logic may reduce the amount of redundant hardware required in space-based applications without sacrificing reliability. These concepts were studied using software modeling and simulation, and the results are presented in this report. Models of the commercially available, packet switched data interconnect SpaceWire protocol were developed and used to create network simulations of data networks containing reconfigurable logic with traffic flows for timing system distribution.
Energy Technology Data Exchange (ETDEWEB)
Sipola, Petri [Kuopio University Hospital, Department of Clinical Radiology, Kuopio (Finland); University of Eastern Finland, Institute of Clinical Medicine, Faculty of Health Sciences, Kuopio (Finland); Niemitukia, Lea H. [Kuopio University Hospital, Department of Clinical Radiology, Kuopio (Finland); Hyttinen, Mika M. [University of Eastern Finland, Institute of Biomedicine, Anatomy, Kuopio (Finland); Arokoski, Jari P.A. [Kuopio University Hospital, Department of Physical and Rehabilitation Medicine, Kuopio (Finland)
2011-04-15
To determine the number of participants required in controlled clinical trials investigating the progression of osteoarthritis (OA) of the hip as evaluated by the joint space width (JSW) on radiographs and to evaluate the reproducibility of the JSW measurement methods. Anteroposterior radiographs of hip were taken from 13 healthy volunteers and from 18 subjects with radiographic hip OA. The reproducibility of the JSW was determined from four segments using digital caliper measurements performed on film radiographs and using semiautomatic computerized image analysis of digitized images. Pearson correlation coefficient, coefficient of variability [CV (%)], and sample size values were calculated. It was found that 20 was a typical number of patients for a sufficiently powered study. The highest sample size was found in subjects with OA in the lateral segment. The reproducibility of the semiautomatic computerized method was not significantly better than the digital caliper method. The number of study subjects required to detect a significant joint space narrowing in follow-up studies is influenced by the baseline hip joint OA severity. The JSW measurements with computerized image analysis did not improve the reproducibility and thus performing JSW measurements with a digital caliper is acceptable. (orig.)
Nishimura, T; Doi, K; Fujimoto, H
2015-08-01
Touch-sensitive screen terminals enabling intuitive operation are used as input interfaces in a wide range of fields. Tablet terminals are one of the most common devices with a touch-sensitive screen. They have a feature of good portability, enabling use under various conditions. On the other hand, they require a GUI designed to prevent decrease of usability under various conditions. For example, the angle of fingertip contact with the display changes according to finger posture during operation and how the case is held. When a human fingertip makes contact with an object, the contact area between the fingertip and contact object increases or decreases as the contact angle changes. A touch-sensitive screen detects positions using the change in capacitance of the area touched by the fingertip; hence, differences in contact area between the touch-sensitive screen and fingertip resulting from different forefinger angles during operation could possibly affect operability. However, this effect has never been studied. We therefore conducted an experiment to investigate the relationship between size/spacing and operability, while taking the effect of fingertip contact angle into account. As a result, we have been able to specify the button size and spacing conditions that enable accurate and fast operation regardless of the forefinger contact angle.
Increase of larger-sized islets in C57/black mice during the long-term space flight.
Proshchina, Alexandra; Krivova, Yulia
Alteration of metabolism has been suggested as a major limiting factor to long-term space flight. Metabolic studies during simulated microgravity and true microgravity in flight have shown changes in blood glucose and in insulin and glucagon concentrations. It was suggested that endocrine pancreas undergoes subclinical diabetogenic changes such as alterations in insulin secretion, insulin sensitivity, glucose tolerance in microgravity conditions. In this study, we analyzed pancreata of the C57 black mice in order to estimate the effects of the long-term space flight. 5 mice, which were flown on the “Bion-M1” satellite for 30 days, were served for this study (flight group). Five animals were used as the vivarium ground control and five mice as the delayed synchronous ground control. The mice from synchronous control were put into container, similar to that one of the flight group for 30 days. Interestingly, the mean body weight of researched animals was higher in the flight group than in two control groups. Body weight in synchronous ground control group was higher than in vivarium control. From each mouse, the splenic part of the pancreas was removed and immediately fixed in 4% formaldehyde. Samples were embedded in paraffin, and 10 mcm serial sections were prepared. Double immunohistochemical staining with anti-insulin(Sigma,USA) and anti-glucagon (Thermo Fisher Scientific, USA) antibodies were performed. Signals were visualized using the MultiVision Polymer Detection System (Thermo Fisher Scientific, USA). Stained sections were photographed, using a 10 x objective and morphometrical parameters were examined. The size of each islet in ten non-overlapping observation fields in pancreatic sections of each mouse was measured using Image J software and analyzed. A software statistical package was used (Statistica 6.0, Statsoft Inc., Tusla, USA). A nonparametric tests (Kruskal -Wallis and Mann-Whitney tests) were used, because the islets number in the examined
Kane Method Based Dynamics Modeling and Control Study for Space Manipulator Capturing a Space Target
Directory of Open Access Journals (Sweden)
Yanhua Han
2016-01-01
Full Text Available Dynamics modeling and control problem of a two-link manipulator mounted on a spacecraft (so-called carrier freely flying around a space target on earth’s circular orbit is studied in the paper. The influence of the carrier’s relative movement on its manipulator is considered in dynamics modeling; nevertheless, that of the manipulator on its carrier is neglected with the assumption that the mass and inertia moment of the manipulator is far less than that of the carrier. Meanwhile, we suppose that the attitude control system of the carrier guarantees its side on which the manipulator is mounted points accurately always the space target during approaching operation. The ideal constraint forces can be out of consideration in dynamics modeling as Kane method is used. The path functions of the manipulator’s end-effector approaching the space target as well as the manipulator’s joints control torque functions are programmed to meet the soft touch requirement that the end-effector’s relative velocity to the space target is zero at touch moment. Numerical simulation validation is conducted finally.
Man in space - The use of animal models
Ballard, Rodney W.; Souza, Kenneth A.
1991-01-01
The use of animal surrogates as experimental subjects in order to provide essential missing information on the effects of long-term spaceflights, to validate countermeasures, and to test medical treatment techniques is discussed. Research needs also include the definition of biomedical adaptations to flight, and the developments of standards for safe space missions to assure human health and productivity during and following flight. NASA research plans in this area are outlined. Over the next 40 years, NASA plans to concentrate on the use of rodents and nonhuman primates as the models of choice for various physiological responses observed in humans during extended stays in space. This research will include flights on the Space Shuttle, unmanned biosatellites, and the Space Station Freedom.
A hypocentral version of the space-time ETAS model
Guo, Yicun; Zhuang, Jiancang; Zhou, Shiyong
2015-10-01
The space-time Epidemic-Type Aftershock Sequence (ETAS) model is extended by incorporating the depth component of earthquake hypocentres. The depths of the direct offspring produced by an earthquake are assumed to be independent of the epicentre locations and to follow a beta distribution, whose shape parameter is determined by the depth of the parent event. This new model is verified by applying it to the Southern California earthquake catalogue. The results show that the new model fits data better than the original epicentre ETAS model and that it provides the potential for modelling and forecasting seismicity with higher resolutions.
Paul, Heather L.; Waguespack, Glenn M.; Paul, Thomas H.; Conger, Bruce C.
2008-01-01
As part of NASA s initiative to develop an advanced portable life support system (PLSS), a baseline schematic has been chosen that includes gaseous oxygen in a closed circuit ventilation configuration. Supply oxygen enters the suit at the back of the helmet and return gases pass over the astronaut s body to be extracted at the astronaut s wrists and ankles through the liquid cooling and ventilation garment (LCVG). The extracted gases are then treated using a rapid cycling amine (RCA) system for carbon dioxide and water removal and activated carbon for trace gas removal before being mixed with makeup oxygen and reintroduced into the helmet. Thermal control is provided by a suit water membrane evaporator (SWME). As an extension of the original schematic development, NASA evaluated several Helmet Exhalation Capture System (HECS) configurations as alternatives to the baseline. The HECS configurations incorporate the use of full contact masks or non-contact masks to reduce flow requirements within the PLSS ventilation subsystem. The primary scope of this study was to compare the alternatives based on mass and volume considerations; however other design issues were also briefly investigated. This paper summarizes the results of this sizing analysis task.
Methodology of problem space modeling in industrial enterprise management system
Directory of Open Access Journals (Sweden)
V.V. Glushchevsky
2015-03-01
Full Text Available The aim of the article. The aim of the article is to develop methodological principles for building a problem space model which can be integrated into industrial enterprise management system. The results of the analysis. The author developed methodological principles for constructing the problem space of an industrial enterprise as a structural and functional model. These problems appear on enterprise business process network topology and can be solved by its management system. The centerpiece of the article is description of the main stages of implementation of modeling methodology of industrial enterprise typical management problems. These stages help to solve several units of organizational management system structure of enterprise within their functional competence. Author formulated an axiom system of structural and characteristic properties of modeling space problems elements, and interconnections between them. This system of axioms is actually a justification for the correctness and adequacy of the proposed modeling methodology and comes as theoretical basis in the construction of the structural and functional model of the management problems space. This model generalizes three basic structural components of the enterprise management system with the help of axioms system: a three-dimensional model of the management problem space (the first dimension is the enterprise business process network, the second dimension is a set of management problems, the third dimension is four vectors of measurable and qualitative characteristics of management problems, which can be analyzed and managed during enterprise functioning; a two-dimensional model of the cybernetic space of analytical problems, which are formalized form of management problems (multivariate model experiments can be implemented with the help of this model to solve wide range of problem situations and determine the most effective or optimal management solutions; a two-dimensional model
Nonlinear regime-switching state-space (RSSS) models.
Chow, Sy-Miin; Zhang, Guangjian
2013-10-01
Nonlinear dynamic factor analysis models extend standard linear dynamic factor analysis models by allowing time series processes to be nonlinear at the latent level (e.g., involving interaction between two latent processes). In practice, it is often of interest to identify the phases--namely, latent "regimes" or classes--during which a system is characterized by distinctly different dynamics. We propose a new class of models, termed nonlinear regime-switching state-space (RSSS) models, which subsumes regime-switching nonlinear dynamic factor analysis models as a special case. In nonlinear RSSS models, the change processes within regimes, represented using a state-space model, are allowed to be nonlinear. An estimation procedure obtained by combining the extended Kalman filter and the Kim filter is proposed as a way to estimate nonlinear RSSS models. We illustrate the utility of nonlinear RSSS models by fitting a nonlinear dynamic factor analysis model with regime-specific cross-regression parameters to a set of experience sampling affect data. The parallels between nonlinear RSSS models and other well-known discrete change models in the literature are discussed briefly.
Modeling of particle size segregation: calibration using the discrete particle method
Thornton, Anthony; Weinhart, Thomas; Luding, Stefan; Bokhove, Onno
2012-01-01
Over the last 25 years a lot of work has been undertaken on constructing continuum models for segregation of particles of different sizes. We focus on one model that is designed to predict segregation and remixing of two differently sized particle species. This model contains two dimensionless param
Nguyen, Sao Mai; Oudeyer, Pierre-Yves
2011-01-01
This paper presents an algorithm for learning a highly redundant inverse model in continuous and non-preset environments. Our Socially Guided Intrinsic Motivation by Demonstrations (SGIM-D) algorithm combines the advantages of both social learning and intrinsic motivation, to specialise in a wide range of skills, while lessening its dependence on the teacher. SGIM-D is evaluated on a fishing skill learning experiment.
Chicoli, A.; Bak-Coleman, J.; Coombs, S.; Paley, D. A.
2015-12-01
Many fish exhibit rheotaxis, a behavior in which fish orient themselves relative to flow. Rheotaxis confers many benefits, including energetic cost savings and interception of drifting prey. Despite the fact that most species of fish school during at least some portion of their life, little is known about the importance of rheotactic behavior to schooling fish and, conversely, how the presence of nearby conspecifics affects rheotactic behavior. Understanding how rheotaxis is modified by social factors is thus of ecological importance. Here we present a mathematical model in the form of an all-to-all, coupled-oscillator framework over the non-Euclidean space of fish orientations to model group rheotactic behavior. Individuals in the model measure the orientation of their neighbors and the flow direction relative to their own orientation. These measures are corrupted by sensory noise. We study the effect of sensory noise and group size on internal (i.e., within the school) and external (i.e., with the flow) disagreement in orientation. We find that under noisy environmental conditions, increased group size improves rheotaxis. Results of this study have implications for understanding animal behavior, as well as for potential applications in bio-inspired engineering.
Processing Approach of Non-linear Adjustment Models in the Space of Non-linear Models
Institute of Scientific and Technical Information of China (English)
LI Chaokui; ZHU Qing; SONG Chengfang
2003-01-01
This paper investigates the mathematic features of non-linear models and discusses the processing way of non-linear factors which contributes to the non-linearity of a nonlinear model. On the basis of the error definition, this paper puts forward a new adjustment criterion, SGPE.Last, this paper investigates the solution of a non-linear regression model in the non-linear model space and makes the comparison between the estimated values in non-linear model space and those in linear model space.
The Cosmological Constant for the Crystalline Vacuum Cosmic Space Model
Montemayor-Aldrete, J A; Morales-Mori, A; Mendoza-Allende, A; Montemayor-Varela, A; Castillo-Mussot, M; Vazquez, G J
2005-01-01
The value of the cosmological constant arising from a crystalline model for vacuum cosmic space with lattice parameter of the order of the neutron radius [1] has been calculated. The model allows to solve, in an easy way, the problem of the cosmological constant giving the right order of magnitude, which corresponds very well with the mean value of matter density in the universe. The obtained value is about 10-48 Km-2. Diffraction experiments with non-thermal neutron beam in cosmic space are proposed to search for the possibility of crystalline structure of vacuum space and to measure the lattice parameter. PACS numbers: 98.80.Es, 04.20.-q, 03.65.-w, 61.50.-f, 98.80.Ft
Multi-scale gravity field modeling in space and time
Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric
2016-04-01
The Earth constantly deforms as it undergoes dynamic phenomena, such as earthquakes, post-glacial rebound and water displacement in its fluid envelopes. These processes have different spatial and temporal scales and are accompanied by mass displacements, which create temporal variations of the gravity field. Since 2002, the GRACE satellite missions provide an unprecedented view of the gravity field spatial and temporal variations. Gravity models built from these satellite data are essential to study the Earth's dynamic processes (Tapley et al., 2004). Up to present, time variations of the gravity field are often modelled using spatial spherical harmonics functions averaged over a fixed period, as 10 days or 1 month. This approach is well suited for modeling global phenomena. To better estimate gravity related to local and/or transient processes, such as earthquakes or floods, and adapt the temporal resolution of the model to its spatial resolution, we propose to model the gravity field using localized functions in space and time. For that, we build a model of the gravity field in space and time with a four-dimensional wavelet basis, well localized in space and time. First we design the 4D basis, then, we study the inverse problem to model the gravity field from the potential differences between the twin GRACE satellites, and its regularization using prior knowledge on the water cycle. Our demonstration of surface water mass signals decomposition in time and space is based on the use of synthetic along-track gravitational potential data. We test the developed approach on one year of 4D gravity modeling and compare the reconstructed water heights to those of the input hydrological model. Perspectives of this work is to apply the approach on real GRACE data, addressing the challenge of a realistic noise, to better describe and understand physical processus with high temporal resolution/low spatial resolution or the contrary.
Applying Model Checking to Industrial-Sized PLC Programs
AUTHOR|(CDS)2079190; Darvas, Daniel; Blanco Vinuela, Enrique; Tournier, Jean-Charles; Bliudze, Simon; Blech, Jan Olaf; Gonzalez Suarez, Victor M
2015-01-01
Programmable logic controllers (PLCs) are embedded computers widely used in industrial control systems. Ensuring that a PLC software complies with its specification is a challenging task. Formal verification has become a recommended practice to ensure the correctness of safety-critical software but is still underused in industry due to the complexity of building and managing formal models of real applications. In this paper, we propose a general methodology to perform automated model checking of complex properties expressed in temporal logics (\\eg CTL, LTL) on PLC programs. This methodology is based on an intermediate model (IM), meant to transform PLC programs written in various standard languages (ST, SFC, etc.) to different modeling languages of verification tools. We present the syntax and semantics of the IM and the transformation rules of the ST and SFC languages to the nuXmv model checker passing through the intermediate model. Finally, two real cases studies of \\CERN PLC programs, written mainly in th...
Interfacial and Wall Transport Models for SPACE-CAP Code
Energy Technology Data Exchange (ETDEWEB)
Hong, Soon Joon; Choo, Yeon Joon; Han, Tae Young; Hwang, Su Hyun; Lee, Byung Chul [FNC Tech., Seoul (Korea, Republic of); Choi, Hoon; Ha, Sang Jun [Korea Electric Power Research Institute, Daejeon (Korea, Republic of)
2009-10-15
The development project for the domestic design code was launched to be used for the safety and performance analysis of pressurized light water reactors. And CAP (Containment Analysis Package) code has been also developed for the containment safety and performance analysis side by side with SPACE. The CAP code treats three fields (gas, continuous liquid, and dispersed drop) for the assessment of containment specific phenomena, and is featured by its multidimensional assessment capabilities. Thermal hydraulics solver was already developed and now under testing of its stability and soundness. As a next step, interfacial and wall transport models was setup. In order to develop the best model and correlation package for the CAP code, various models currently used in major containment analysis codes, which are GOTHIC, CONTAIN2.0, and CONTEMPT-LT, have been reviewed. The origins of the selected models used in these codes have also been examined to find out if the models have not conflict with a proprietary right. In addition, a literature survey of the recent studies has been performed in order to incorporate the better models for the CAP code. The models and correlations of SPACE were also reviewed. CAP models and correlations are composed of interfacial heat/mass, and momentum transport models, and wall heat/mass, and momentum transport models. This paper discusses on those transport models in the CAP code.
Stability patterns for a size-structured population model and its stage-structured counterpart
DEFF Research Database (Denmark)
Zhang, Lai; Pedersen, Michael; Lin, Zhigui
2015-01-01
In this paper we compare a general size-structured population model, where a size-structured consumer feeds upon an unstructured resource, to its simplified stage-structured counterpart in terms of equilibrium stability. Stability of the size-structured model is understood in terms of an equivalent...... delayed system consisting of a renewal equation for the consumer population birth rate and a delayed differential equation for the resource. Results show that the size- and stage-structured models differ considerably with respect to equilibrium stability, although the two models have completely identical...
Joint space-time geostatistical model for air quality surveillance
Russo, A.; Soares, A.; Pereira, M. J.
2009-04-01
Air pollution and peoples' generalized concern about air quality are, nowadays, considered to be a global problem. Although the introduction of rigid air pollution regulations has reduced pollution from industry and power stations, the growing number of cars on the road poses a new pollution problem. Considering the characteristics of the atmospheric circulation and also the residence times of certain pollutants in the atmosphere, a generalized and growing interest on air quality issues led to research intensification and publication of several articles with quite different levels of scientific depth. As most natural phenomena, air quality can be seen as a space-time process, where space-time relationships have usually quite different characteristics and levels of uncertainty. As a result, the simultaneous integration of space and time is not an easy task to perform. This problem is overcome by a variety of methodologies. The use of stochastic models and neural networks to characterize space-time dispersion of air quality is becoming a common practice. The main objective of this work is to produce an air quality model which allows forecasting critical concentration episodes of a certain pollutant by means of a hybrid approach, based on the combined use of neural network models and stochastic simulations. A stochastic simulation of the spatial component with a space-time trend model is proposed to characterize critical situations, taking into account data from the past and a space-time trend from the recent past. To identify near future critical episodes, predicted values from neural networks are used at each monitoring station. In this paper, we describe the design of a hybrid forecasting tool for ambient NO2 concentrations in Lisbon, Portugal.
The neural code for auditory space depends on sound frequency and head size in an optimal manner.
Directory of Open Access Journals (Sweden)
Nicol S Harper
Full Text Available A major cue to the location of a sound source is the interaural time difference (ITD-the difference in sound arrival time at the two ears. The neural representation of this auditory cue is unresolved. The classic model of ITD coding, dominant for a half-century, posits that the distribution of best ITDs (the ITD evoking a neuron's maximal response is unimodal and largely within the range of ITDs permitted by head-size. This is often interpreted as a place code for source location. An alternative model, based on neurophysiology in small mammals, posits a bimodal distribution of best ITDs with exquisite sensitivity to ITDs generated by means of relative firing rates between the distributions. Recently, an optimal-coding model was proposed, unifying the disparate features of these two models under the framework of efficient coding by neural populations. The optimal-coding model predicts that distributions of best ITDs depend on head size and sound frequency: for high frequencies and large heads it resembles the classic model, for low frequencies and small head sizes it resembles the bimodal model. The optimal-coding model makes key, yet unobserved, predictions: for many species, including humans, both forms of neural representation are employed, depending on sound frequency. Furthermore, novel representations are predicted for intermediate frequencies. Here, we examine these predictions in neurophysiological data from five mammalian species: macaque, guinea pig, cat, gerbil and kangaroo rat. We present the first evidence supporting these untested predictions, and demonstrate that different representations appear to be employed at different sound frequencies in the same species.
The neural code for auditory space depends on sound frequency and head size in an optimal manner.
Harper, Nicol S; Scott, Brian H; Semple, Malcolm N; McAlpine, David
2014-01-01
A major cue to the location of a sound source is the interaural time difference (ITD)-the difference in sound arrival time at the two ears. The neural representation of this auditory cue is unresolved. The classic model of ITD coding, dominant for a half-century, posits that the distribution of best ITDs (the ITD evoking a neuron's maximal response) is unimodal and largely within the range of ITDs permitted by head-size. This is often interpreted as a place code for source location. An alternative model, based on neurophysiology in small mammals, posits a bimodal distribution of best ITDs with exquisite sensitivity to ITDs generated by means of relative firing rates between the distributions. Recently, an optimal-coding model was proposed, unifying the disparate features of these two models under the framework of efficient coding by neural populations. The optimal-coding model predicts that distributions of best ITDs depend on head size and sound frequency: for high frequencies and large heads it resembles the classic model, for low frequencies and small head sizes it resembles the bimodal model. The optimal-coding model makes key, yet unobserved, predictions: for many species, including humans, both forms of neural representation are employed, depending on sound frequency. Furthermore, novel representations are predicted for intermediate frequencies. Here, we examine these predictions in neurophysiological data from five mammalian species: macaque, guinea pig, cat, gerbil and kangaroo rat. We present the first evidence supporting these untested predictions, and demonstrate that different representations appear to be employed at different sound frequencies in the same species.
Lyons, James E.; Kendall, William; Royle, J. Andrew; Converse, Sarah J.; Andres, Brad A.; Buchanan, Joseph B.
2016-01-01
We present a novel formulation of a mark–recapture–resight model that allows estimation of population size, stopover duration, and arrival and departure schedules at migration areas. Estimation is based on encounter histories of uniquely marked individuals and relative counts of marked and unmarked animals. We use a Bayesian analysis of a state–space formulation of the Jolly–Seber mark–recapture model, integrated with a binomial model for counts of unmarked animals, to derive estimates of population size and arrival and departure probabilities. We also provide a novel estimator for stopover duration that is derived from the latent state variable representing the interim between arrival and departure in the state–space model. We conduct a simulation study of field sampling protocols to understand the impact of superpopulation size, proportion marked, and number of animals sampled on bias and precision of estimates. Simulation results indicate that relative bias of estimates of the proportion of the population with marks was low for all sampling scenarios and never exceeded 2%. Our approach does not require enumeration of all unmarked animals detected or direct knowledge of the number of marked animals in the population at the time of the study. This provides flexibility and potential application in a variety of sampling situations (e.g., migratory birds, breeding seabirds, sea turtles, fish, pinnipeds, etc.). Application of the methods is demonstrated with data from a study of migratory sandpipers.
Radiation Belt Environment Model: Application to Space Weather and Beyond
Fok, Mei-Ching H.
2011-01-01
Understanding the dynamics and variability of the radiation belts are of great scientific and space weather significance. A physics-based Radiation Belt Environment (RBE) model has been developed to simulate and predict the radiation particle intensities. The RBE model considers the influences from the solar wind, ring current and plasmasphere. It takes into account the particle drift in realistic, time-varying magnetic and electric field, and includes diffusive effects of wave-particle interactions with various wave modes in the magnetosphere. The RBE model has been used to perform event studies and real-time prediction of energetic electron fluxes. In this talk, we will describe the RBE model equation, inputs and capabilities. Recent advancement in space weather application and artificial radiation belt study will be discussed as well.
Modeling thermally active building components using space mapping
DEFF Research Database (Denmark)
Pedersen, Frank; Weitzmann, Peter; Svendsen, Svend
2005-01-01
In order to efficiently implement thermally active building components in new buildings, it is necessary to evaluate the thermal interaction between them and other building components. Applying parameter investigation or numerical optimization methods to a differential-algebraic (DAE) model....... This paper describes the principle of the space mapping technique, and introduces a simple space mapping technique. The technique is applied to a lumped parameter model of a thermo active component, which provides a model of the thermal performance of the component as a function of two design parameters...... of a building provides a systematic way of estimating efficient building designs. However, using detailed numerical calculations of the components in the building is a time consuming process, which may become prohibitive if the DAE model is to be used for parameter variation or optimization. Unfortunately...
Fast Filtering and Smoothing for Multivariate State Space Models
Koopman, S.J.M.; Durbin, J.
1998-01-01
This paper gives a new approach to diffuse filtering and smoothing for multivariate state space models. The standard approach treats the observations as vectors while our approach treats each element of the observational vector individually. This strategy leads to computationally efficient methods f
Magnetic Testing, and Modeling, Simulation and Analysis for Space Applications
Boghosian, Mary; Narvaez, Pablo; Herman, Ray
2012-01-01
The Aerospace Corporation (Aerospace) and Lockheed Martin Space Systems (LMSS) participated with Jet Propulsion Laboratory (JPL) in the implementation of a magnetic cleanliness program of the NASA/JPL JUNO mission. The magnetic cleanliness program was applied from early flight system development up through system level environmental testing. The JUNO magnetic cleanliness program required setting-up a specialized magnetic test facility at Lockheed Martin Space Systems for testing the flight system and a testing program with facility for testing system parts and subsystems at JPL. The magnetic modeling, simulation and analysis capability was set up and performed by Aerospace to provide qualitative and quantitative magnetic assessments of the magnetic parts, components, and subsystems prior to or in lieu of magnetic tests. Because of the sensitive nature of the fields and particles scientific measurements being conducted by the JUNO space mission to Jupiter, the imposition of stringent magnetic control specifications required a magnetic control program to ensure that the spacecraft's science magnetometers and plasma wave search coil were not magnetically contaminated by flight system magnetic interferences. With Aerospace's magnetic modeling, simulation and analysis and JPL's system modeling and testing approach, and LMSS's test support, the project achieved a cost effective approach to achieving a magnetically clean spacecraft. This paper presents lessons learned from the JUNO magnetic testing approach and Aerospace's modeling, simulation and analysis activities used to solve problems such as remnant magnetization, performance of hard and soft magnetic materials within the targeted space system in applied external magnetic fields.
Swales' Cars Model and the Metaphor of Research Space: An ...
African Journals Online (AJOL)
ANDCORPgh changing the world
following academics for reading through drafts of the paper and offering valuable ... The CARS (Create a Research Space) model for writing academic introductions ..... metaphysical and sometimes mystical or psychological experience of the poet, .... 'COVERT' STEP 3: [A lot has been written about the traditional music of.
Modeling irregularly spaced residual series as a continuous stochastic process
Von Asmuth, J.R.; Bierkens, M.F.P.
2005-01-01
In this paper, the background and functioning of a simple but effective continuous time approach for modeling irregularly spaced residual series is presented. The basic equations were published earlier by von Asmuth et al. (2002), who used them as part of a continuous time transfer function noise mo
The System of Occupations: Modeling Occupations in Sociodemographic Space.
Rotolo, Thomas; McPherson, J. Miller
2001-01-01
Analysis of the age and education composition of occupations in Current Population Survey Annual Demographic Files, 1972-82, supports an ecological model in which occupations compete for members in a shifting niche space defined by members' sociodemographic characteristics. In contrast, the movement of professions in the education dimension…
International Space Station Alpha (ISSA) Integrated Traffic Model
Gates, R. E.
1995-01-01
The paper discusses the development process of the International Space Station Alpha (ISSA) Integrated Traffic Model which is a subsystem analyses tool utilized in the ISSA design analysis cycles. Fast-track prototyping of the detailed relationships between daily crew and station consumables, propellant needs, maintenance requirements and crew rotation via spread sheets provide adequate benchmarks to assess cargo vehicle design and performance characteristics.
improved mathematical models for particle-size distribution data ...
African Journals Online (AJOL)
BirukEdimon
bimodal curve fitting models are shown to give an extremely ... property for assessing the likely behavior of granular ... a need to investigate alternative better models for fitting the .... other in a similar way to the shape parameters used for the ...
Virtual Construction of Space Habitats: Connecting Building Information Models (BIM) and SysML
Polit-Casillas, Raul; Howe, A. Scott
2013-01-01
Current trends in design, construction and management of complex projects make use of Building Information Models (BIM) connecting different types of data to geometrical models. This information model allow different types of analysis beyond pure graphical representations. Space habitats, regardless their size, are also complex systems that require the synchronization of many types of information and disciplines beyond mass, volume, power or other basic volumetric parameters. For this, the state-of-the-art model based systems engineering languages and processes - for instance SysML - represent a solid way to tackle this problem from a programmatic point of view. Nevertheless integrating this with a powerful geometrical architectural design tool with BIM capabilities could represent a change in the workflow and paradigm of space habitats design applicable to other aerospace complex systems. This paper shows some general findings and overall conclusions based on the ongoing research to create a design protocol and method that practically connects a systems engineering approach with a BIM architectural and engineering design as a complete Model Based Engineering approach. Therefore, one hypothetical example is created and followed during the design process. In order to make it possible this research also tackles the application of IFC categories and parameters in the aerospace field starting with the application upon the space habitats design as way to understand the information flow between disciplines and tools. By building virtual space habitats we can potentially improve in the near future the way more complex designs are developed from very little detail from concept to manufacturing.
Virtual Construction of Space Habitats: Connecting Building Information Models (BIM) and SysML
Polit-Casillas, Raul; Howe, A. Scott
2013-01-01
Current trends in design, construction and management of complex projects make use of Building Information Models (BIM) connecting different types of data to geometrical models. This information model allow different types of analysis beyond pure graphical representations. Space habitats, regardless their size, are also complex systems that require the synchronization of many types of information and disciplines beyond mass, volume, power or other basic volumetric parameters. For this, the state-of-the-art model based systems engineering languages and processes - for instance SysML - represent a solid way to tackle this problem from a programmatic point of view. Nevertheless integrating this with a powerful geometrical architectural design tool with BIM capabilities could represent a change in the workflow and paradigm of space habitats design applicable to other aerospace complex systems. This paper shows some general findings and overall conclusions based on the ongoing research to create a design protocol and method that practically connects a systems engineering approach with a BIM architectural and engineering design as a complete Model Based Engineering approach. Therefore, one hypothetical example is created and followed during the design process. In order to make it possible this research also tackles the application of IFC categories and parameters in the aerospace field starting with the application upon the space habitats design as way to understand the information flow between disciplines and tools. By building virtual space habitats we can potentially improve in the near future the way more complex designs are developed from very little detail from concept to manufacturing.
Reduced-size kernel models for nonlinear hybrid system identification.
Le, Van Luong; Bloch, Grard; Lauer, Fabien
2011-12-01
This brief paper focuses on the identification of nonlinear hybrid dynamical systems, i.e., systems switching between multiple nonlinear dynamical behaviors. Thus the aim is to learn an ensemble of submodels from a single set of input-output data in a regression setting with no prior knowledge on the grouping of the data points into similar behaviors. To be able to approximate arbitrary nonlinearities, kernel submodels are considered. However, in order to maintain efficiency when applying the method to large data sets, a preprocessing step is required in order to fix the submodel sizes and limit the number of optimization variables. This brief paper proposes four approaches, respectively inspired by the fixed-size least-squares support vector machines, the feature vector selection method, the kernel principal component regression and a modification of the latter, in order to deal with this issue and build sparse kernel submodels. These are compared in numerical experiments, which show that the proposed approach achieves the simultaneous classification of data points and approximation of the nonlinear behaviors in an efficient and accurate manner.
A Management Model for International Participation in Space Exploration Missions
George, Patrick J.; Pease, Gary M.; Tyburski, Timothy E.
2005-01-01
This paper proposes an engineering management model for NASA's future space exploration missions based on past experiences working with the International Partners of the International Space Station. The authors have over 25 years of combined experience working with the European Space Agency, Japan Aerospace Exploration Agency, Canadian Space Agency, Italian Space Agency, Russian Space Agency, and their respective contractors in the design, manufacturing, verification, and integration of their elements electric power system into the United States on-orbit segment. The perspective presented is one from a specific sub-system integration role and is offered so that the lessons learned from solving issues of technical and cultural nature may be taken into account during the formulation of international partnerships. Descriptions of the types of unique problems encountered relative to interactions between international partnerships are reviewed. Solutions to the problems are offered, taking into consideration the technical implications. Through the process of investigating each solution, the important and significant issues associated with working with international engineers and managers are outlined. Potential solutions are then characterized by proposing a set of specific methodologies to jointly develop spacecraft configurations that benefits all international participants, maximizes mission success and vehicle interoperability while minimizing cost.
A generalized statistical model for the size distribution of wealth
Clementi, F.; Gallegati, M.; Kaniadakis, G.
2012-12-01
In a recent paper in this journal (Clementi et al 2009 J. Stat. Mech. P02037), we proposed a new, physically motivated, distribution function for modeling individual incomes, having its roots in the framework of the κ-generalized statistical mechanics. The performance of the κ-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabilistic functions and inequality measures of this generalized model for wealth distribution are obtained in closed form. In order to check the validity of the proposed model, we analyze the US household wealth distributions from 1984 to 2009 and conclude an excellent agreement with the data that is superior to any other model already known in the literature.
Applying Model Based Systems Engineering to NASA's Space Communications Networks
Bhasin, Kul; Barnes, Patrick; Reinert, Jessica; Golden, Bert
2013-01-01
System engineering practices for complex systems and networks now require that requirement, architecture, and concept of operations product development teams, simultaneously harmonize their activities to provide timely, useful and cost-effective products. When dealing with complex systems of systems, traditional systems engineering methodology quickly falls short of achieving project objectives. This approach is encumbered by the use of a number of disparate hardware and software tools, spreadsheets and documents to grasp the concept of the network design and operation. In case of NASA's space communication networks, since the networks are geographically distributed, and so are its subject matter experts, the team is challenged to create a common language and tools to produce its products. Using Model Based Systems Engineering methods and tools allows for a unified representation of the system in a model that enables a highly related level of detail. To date, Program System Engineering (PSE) team has been able to model each network from their top-level operational activities and system functions down to the atomic level through relational modeling decomposition. These models allow for a better understanding of the relationships between NASA's stakeholders, internal organizations, and impacts to all related entities due to integration and sustainment of existing systems. Understanding the existing systems is essential to accurate and detailed study of integration options being considered. In this paper, we identify the challenges the PSE team faced in its quest to unify complex legacy space communications networks and their operational processes. We describe the initial approaches undertaken and the evolution toward model based system engineering applied to produce Space Communication and Navigation (SCaN) PSE products. We will demonstrate the practice of Model Based System Engineering applied to integrating space communication networks and the summary of its
Model Experiments for the Determination of Airflow in Large Spaces
DEFF Research Database (Denmark)
Nielsen, Peter V.
Model experiments are one of the methods used for the determination of airflow in large spaces. This paper will discuss the formation of the governing dimensionless numbers. It is shown that experiments with a reduced scale often will necessitate a fully developed turbulence level of the flow....... Details of the flow from supply openings are very important for the determination of room air distribution. It is in some cases possible to make a simplified supply opening for the model experiment....
Phase space analysis of some interacting Chaplygin gas models
Energy Technology Data Exchange (ETDEWEB)
Khurshudyan, M. [Academy of Sciences of Armenia, Institute for Physical Research, Ashtarak (Armenia); Tomsk State University of Control Systems and Radioelectronics, Laboratory for Theoretical Cosmology, Tomsk (Russian Federation); Tomsk State Pedagogical University, Department of Theoretical Physics, Tomsk (Russian Federation); Myrzakulov, R. [Eurasian National University, Eurasian International Center for Theoretical Physics, Astana (Kazakhstan)
2017-02-15
In this paper we discuss a phase space analysis of various interacting Chaplygin gas models in general relativity. Linear and nonlinear sign changeable interactions are considered. For each case appropriate late time attractors of field equations are found. The Chaplygin gas is one of the dark fluids actively considered in modern cosmology due to the fact that it is a joint model of dark energy and dark matter. (orig.)
Gu, Fei; Preacher, Kristopher J; Wu, Wei; Yung, Yiu-Fai
2014-01-01
Although the state space approach for estimating multilevel regression models has been well established for decades in the time series literature, it does not receive much attention from educational and psychological researchers. In this article, we (a) introduce the state space approach for estimating multilevel regression models and (b) extend the state space approach for estimating multilevel factor models. A brief outline of the state space formulation is provided and then state space forms for univariate and multivariate multilevel regression models, and a multilevel confirmatory factor model, are illustrated. The utility of the state space approach is demonstrated with either a simulated or real example for each multilevel model. It is concluded that the results from the state space approach are essentially identical to those from specialized multilevel regression modeling and structural equation modeling software. More importantly, the state space approach offers researchers a computationally more efficient alternative to fit multilevel regression models with a large number of Level 1 units within each Level 2 unit or a large number of observations on each subject in a longitudinal study.
Nonlinear state space model identification of synchronous generators
Energy Technology Data Exchange (ETDEWEB)
Dehghani, M.; Nikravesh, S.K.Y. [Electrical Engineering Department, Amirkabir University of Technology, Tehran (Iran)
2008-05-15
A method for identification of a synchronous generator is suggested in this paper. The method uses the theoretical relations of machine parameters and the Prony method to find the state space model of the system. Such models are useful for controller design and stability tests. The proposed identification method is applied to a third order model of a synchronous generator. In this study, the field voltage is considered as the input and the active output power and the rotor angle are considered as the outputs of the synchronous generator. Simulation results show good accuracy of the identified model. (author)
Space in multi-agent systems modelling spatial processes
Directory of Open Access Journals (Sweden)
Petr Rapant
2007-06-01
Full Text Available Need for modelling of spatial processes arise in the spehere of geoinformation systems in the last time. Some processes (espetially natural ones can be modeled by means of using external tools, e. g. for modelling of contaminant transport in the environment. But in the case of socio-economic processes suitable tools interconnected with GIS are still in quest of reserch and development. One of the candidate technologies are so called multi-agent systems. Their theory is developed quite well, but they lack suitable means for dealing with space. This article deals with this problem and proposes solution for the field of a road transport modelling.
Neuro-Space Mapping for Modeling Heterojunction Bipolar Transistor
Institute of Scientific and Technical Information of China (English)
Yan Shuxia; Cheng Qianfu; Wu Haifeng; Zhang Qijun
2015-01-01
A neuro-space mapping(Neuro-SM) for modeling heterojunction bipolar transistor(HBT) is presented, which can automatically modify the input signals of the given model by neural network. The novel Neuro-SM formu-lations for DC and small-signal simulation are proposed to obtain the mapping network. Simulation results show that the errors between Neuro-SM models and the accurate data are less than 1%, demonstrating that the accurcy of the proposed method is higher than those of the existing models.
Dynamical real space renormalization group applied to sandpile models.
Ivashkevich, E V; Povolotsky, A M; Vespignani, A; Zapperi, S
1999-08-01
A general framework for the renormalization group analysis of self-organized critical sandpile models is formulated. The usual real space renormalization scheme for lattice models when applied to nonequilibrium dynamical models must be supplemented by feedback relations coming from the stationarity conditions. On the basis of these ideas the dynamically driven renormalization group is applied to describe the boundary and bulk critical behavior of sandpile models. A detailed description of the branching nature of sandpile avalanches is given in terms of the generating functions of the underlying branching process.
Discrete state space modeling and control of nonlinear unknown systems.
Savran, Aydogan
2013-11-01
A novel procedure for integrating neural networks (NNs) with conventional techniques is proposed to design industrial modeling and control systems for nonlinear unknown systems. In the proposed approach, a new recurrent NN with a special architecture is constructed to obtain discrete-time state-space representations of nonlinear dynamical systems. It is referred as the discrete state-space neural network (DSSNN). In the DSSNN, the outputs of the hidden layer neurons of the DSSNN represent the system's (pseudo) state. The inputs are fed to output neurons and the delayed outputs of the hidden layer neurons are fed to their inputs via adjustable weights. The discrete state space model of the actual system is directly obtained by training the DSSNN with the input-output data. A training procedure based on the back-propagation through time (BPTT) algorithm is developed. The Levenberg-Marquardt (LM) method with a trust region approach is used to update the DSSNN weights. Linear state space models enable to use well developed conventional analysis and design techniques. Thus, building a linear model of a system has primary importance in industrial applications. Thus, a suitable linearization procedure is proposed to derive the linear state space model from the nonlinear DSSNN representation. The controllability, observability and stability properties are examined. The state feedback controllers are designed with both the linear quadratic regulator (LQR) and the pole placement techniques. The regulator and servo control problems are both addressed. A full order observer is also designed to estimate the state variables. The performance of the proposed procedure is demonstrated by applying for both single-input single-output (SISO) and multiple-input multiple-output (MIMO) nonlinear control problems. © 2013 ISA. Published by Elsevier Ltd. All rights reserved.
Modelling studies to proper size a hydrogen generator for fuel cells
Energy Technology Data Exchange (ETDEWEB)
Maggio, G.; Recupero, V.; Di Leonardo, R.; Lagana, M. [Istituto CNR-TAE, Lucia, Messina (Italy)
1996-12-31
Based upon an extensive survey of literature a mathematical model has been developed to study the temperature profile along the catalytic bed of a reactor for the methane partial oxidation. The model allowed a preliminary design of a 5 Nm{sup 3} syngas/h prototype to be integrated with second generation fuel cells as hydrogen generator (in the framework of the EC-JOU2 contract). This design was based on some target features, including the choice of a GHSV (gas hour space velocity) equal to 80000 h{sup -1}, a catalyst particle size of 1/8inches, a molar air/methane ratio of 2.7 (i.e. O{sub 2}/CH{sub 4}=0.53), a linear velocity in the catalytic bed of about 2 m/sec, and an inert/catalyst ratio 3:1. Starting from this data, the work has been concerned with the identification of the controlling regime (kinetic or diffusional), and then with the estimation of the gas composition and temperature profiles along the reactor. A comparison between experimental and model results has also been accomplished.
Henderson, Laura S.; Subbarao, Kamesh
2016-12-01
This work presents a case wherein the selection of models when producing synthetic light curves affects the estimation of the size of unresolved space objects. Through this case, "inverse crime" (using the same model for the generation of synthetic data and data inversion), is illustrated. This is done by using two models to produce the synthetic light curve and later invert it. It is shown here that the choice of model indeed affects the estimation of the shape/size parameters. When a higher fidelity model (henceforth the one that results in the smallest error residuals after the crime is committed) is used to both create, and invert the light curve model the estimates of the shape/size parameters are significantly better than those obtained when a lower fidelity model (in comparison) is implemented for the estimation. It is therefore of utmost importance to consider the choice of models when producing synthetic data, which later will be inverted, as the results might be misleadingly optimistic.
Space modeling with SolidWorks and NX
Duhovnik, Jože; Drešar, Primož
2015-01-01
Through a series of step-by-step tutorials and numerous hands-on exercises, this book aims to equip the reader with both a good understanding of the importance of space in the abstract world of engineers and the ability to create a model of a product in virtual space – a skill essential for any designer or engineer who needs to present ideas concerning a particular product within a professional environment. The exercises progress logically from the simple to the more complex; while SolidWorks or NX is the software used, the underlying philosophy is applicable to all modeling software. In each case, the explanation covers the entire procedure from the basic idea and production capabilities through to the real model; the conversion from 3D model to 2D manufacturing drawing is also clearly explained. Topics covered include modeling of prism, axisymmetric, symmetric, and sophisticated shapes; digitization of physical models using modeling software; creation of a CAD model starting from a physical model; free fo...
State space modeling of Memristor-based Wien oscillator
Talukdar, Abdul Hafiz Ibne
2011-12-01
State space modeling of Memristor based Wien \\'A\\' oscillator has been demonstrated for the first time considering nonlinear ion drift in Memristor. Time dependant oscillating resistance of Memristor is reported in both state space solution and SPICE simulation which plausibly provide the basis of realizing parametric oscillation by Memristor based Wien oscillator. In addition to this part Memristor is shown to stabilize the final oscillation amplitude by means of its nonlinear dynamic resistance which hints for eliminating diode in the feedback network of conventional Wien oscillator. © 2011 IEEE.
Life sciences research in space: The requirement for animal models
Fuller, C. A.; Philips, R. W.; Ballard, R. W.
1987-01-01
Use of animals in NASA space programs is reviewed. Animals are needed because life science experimentation frequently requires long-term controlled exposure to environments, statistical validation, invasive instrumentation or biological tissue sampling, tissue destruction, exposure to dangerous or unknown agents, or sacrifice of the subject. The availability and use of human subjects inflight is complicated by the multiple needs and demands upon crew time. Because only living organisms can sense, integrate and respond to the environment around them, the sole use of tissue culture and computer models is insufficient for understanding the influence of the space environment on intact organisms. Equipment for spaceborne experiments with animals is described.
Space Object Tracking Method Based on a Snake Model
Zhan-wei, Xu; Xin, Wang
2016-04-01
In this paper, aiming at the problem of unstable tracking of low-orbit variable and bright space objects, adopting an active contour model, a kind of improved GVF (Gradient Vector Flow) - Snake algorithm is proposed to realize the real-time search of the real object contour on the CCD image. Combined with the Kalman filter for prediction, a new adaptive tracking method is proposed for space objects. Experiments show that this method can overcome the tracking error caused by the fixed window, and improve the tracking robustness.
A Model of Emergent Universe in Inhomogeneous Space-Time
Bhattacharya, Subhra
2016-01-01
A scenario of an emergent universe is constructed in the background of an inhomogeneous space-time model which is asymptotically (at spatial infinity) FRW space-time. The cosmic substratum consists of non-interacting two components, namely {\\bf a)} homogeneous and isotropic fluid but dissipative in nature and {\\bf b)} an inhomogeneous and anisotropic barotropic fluid. In non-equilibrium thermodynamic prescription (second order deviations), particle creation mechanism is considered the cause for the dissipative phenomena. It is found that for constant value of the particle creation rate parameter there exists a scenario of emergent universe.
Improving active space telescope wavefront control using predictive thermal modeling
Gersh-Range, Jessica; Perrin, Marshall D.
2015-01-01
Active control algorithms for space telescopes are less mature than those for large ground telescopes due to differences in the wavefront control problems. Active wavefront control for space telescopes at L2, such as the James Webb Space Telescope (JWST), requires weighing control costs against the benefits of correcting wavefront perturbations that are a predictable byproduct of the observing schedule, which is known and determined in advance. To improve the control algorithms for these telescopes, we have developed a model that calculates the temperature and wavefront evolution during a hypothetical mission, assuming the dominant wavefront perturbations are due to changes in the spacecraft attitude with respect to the sun. Using this model, we show that the wavefront can be controlled passively by introducing scheduling constraints that limit the allowable attitudes for an observation based on the observation duration and the mean telescope temperature. We also describe the implementation of a predictive controller designed to prevent the wavefront error (WFE) from exceeding a desired threshold. This controller outperforms simpler algorithms even with substantial model error, achieving a lower WFE without requiring significantly more corrections. Consequently, predictive wavefront control based on known spacecraft attitude plans is a promising approach for JWST and other future active space observatories.
1D-3D Hybrid Modelling - From Multi-Compartment Models to Full Resolution Models in Space and Time
Directory of Open Access Journals (Sweden)
Stephan eGrein
2014-07-01
Full Text Available Investigation of cellular and network dynamics in the brain by means of modeling & simulation has evolved into a highly interdisciplinary field, that uses sophisticated modeling & simulation approaches to understand distinct areas of brain function. Depending on the underlying complexity, these models vary in level of detail to cope with the attached computational cost. Hence for large network simulations, single neurons are typically reduced to time-dependent signal processors, dismissing spatial aspects of the cells. For single cell or small-world networks, general purpose simulators allow for space and time-dependent simulations of electrical signal processing, based on the cable equation theory. An emerging field in Computational Neuroscience encompasses a new level of detail by incorporating the 3D morphology of cells and organelles into 3D space and time-dependent simulations. Every approach has its advantages and limitations, such as computational cost, integrated and methods-spanning simulation approaches, depending on the network size could establish new ways to investigate the brain. We present a hybrid simulation approach, that makes use of reduced 1D-models using e.g. the NEURON which couples to fully resolved models for simulating cellular and sub-cellular dynamics, including the detailed 3D-morphology of neurons and organelles. To couple 1D- & 3D-simulations, we present a geometry and membrane potential mapping framework, with which graph-based morphologies, e.g. in swc-/hoc-format, are mapped to full surface and volume representations of the neuron; membrane potential data from 1D-simulations are used as boundary conditions for full 3D simulations. Thus, established models and data, based on general purpose 1D-simulators, can be directly coupled to the emerging field of fully resolved highly detailed 3D-modeling approaches. The new framework is applied to investigate electrically active neurons and their intracellular spatio
Self-similarity of phase-space networks of frustrated spin models and lattice gas models
Peng, Yi; Wang, Feng; Han, Yilong
2013-03-01
We studied the self-similar properties of the phase-spaces of two frustrated spin models and two lattice gas models. The frustrated spin models included (1) the anti-ferromagnetic Ising model on a two-dimensional triangular lattice (1a) at the ground states and (1b) above the ground states and (2) the six-vertex model. The two lattice gas models were (3) the one-dimensional lattice gas model and (4) the two-dimensional lattice gas model. The phase spaces were mapped to networks so that the fractal analysis of complex networks could be applied, i.e. the box-covering method and the cluster-growth method. These phase spaces, in turn, establish new classes of networks with unique self-similar properties. Models 1a, 2, and 3 with long-range power-law correlations in real space exhibit fractal phase spaces, while models 1b and 4 with short-range exponential correlations in real space exhibit nonfractal phase spaces. This behavior agrees with one of untested assumptions in Tsallis nonextensive statistics. Hong Kong GRC grants 601208 and 601911
The attention-weighted sample-size model of visual short-term memory
DEFF Research Database (Denmark)
Smith, Philip L.; Lilburn, Simon D.; Corbett, Elaine A.
2016-01-01
exceeded that predicted by the sample-size model for both simultaneously and sequentially presented stimuli. Instead, the set-size effect and the serial position curves with sequential presentation were predicted by an attention-weighted version of the sample-size model, which assumes that one of the items......We investigated the capacity of visual short-term memory (VSTM) in a phase discrimination task that required judgments about the configural relations between pairs of black and white features. Sewell et al. (2014) previously showed that VSTM capacity in an orientation discrimination task was well...... described by a sample-size model, which views VSTM as a resource comprised of a finite number of noisy stimulus samples. The model predicts the invariance of ∑i(di ′)2, the sum of squared sensitivities across items, for displays of different sizes. For phase discrimination, the set-size effect significantly...
From Bacteria to Whales: Using Functional Size Spectra to Model Marine Ecosystems.
Blanchard, Julia L; Heneghan, Ryan F; Everett, Jason D; Trebilco, Rowan; Richardson, Anthony J
2017-03-01
Size-based ecosystem modeling is emerging as a powerful way to assess ecosystem-level impacts of human- and environment-driven changes from individual-level processes. These models have evolved as mechanistic explanations for observed regular patterns of abundance across the marine size spectrum hypothesized to hold from bacteria to whales. Fifty years since the first size spectrum measurements, we ask how far have we come? Although recent modeling studies capture an impressive range of sizes, complexity, and real-world applications, ecosystem coverage is still only partial. We describe how this can be overcome by unifying functional traits with size spectra (which we call functional size spectra) and highlight the key knowledge gaps that need to be filled to model ecosystems from bacteria to whales. Copyright © 2017 Elsevier Ltd. All rights reserved.
Mapping from Speech to Images Using Continuous State Space Models
DEFF Research Database (Denmark)
Lehn-Schiøler, Tue; Hansen, Lars Kai; Larsen, Jan
2005-01-01
In this paper a system that transforms speech waveforms to animated faces are proposed. The system relies on continuous state space models to perform the mapping, this makes it possible to ensure video with no sudden jumps and allows continuous control of the parameters in 'face space......'. The performance of the system is critically dependent on the number of hidden variables, with too few variables the model cannot represent data, and with too many overfitting is noticed. Simulations are performed on recordings of 3-5 sec.\\$\\backslash\\$ video sequences with sentences from the Timit database. From...... a subjective point of view the model is able to construct an image sequence from an unknown noisy speech sequence even though the number of training examples are limited....
A growing social network model in geographical space
Antonioni, Alberto; Tomassini, Marco
2017-09-01
In this work we propose a new model for the generation of social networks that includes their often ignored spatial aspects. The model is a growing one and links are created either taking space into account, or disregarding space and only considering the degree of target nodes. These two effects can be mixed linearly in arbitrary proportions through a parameter. We numerically show that for a given range of the combination parameter, and for given mean degree, the generated network class shares many important statistical features with those observed in actual social networks, including the spatial dependence of connections. Moreover, we show that the model provides a good qualitative fit to some measured social networks.
Stochastic modelling of dissolved inorganic nitrogen in space and time
DEFF Research Database (Denmark)
Lophaven, Søren Nymand; Carstensen, Niels Jacob; Rootzen, Helle
2006-01-01
Environmental monitoring datasets often contain a large amount of missing values, and are characterized as being sampled over time on a distinct number of locations in the area of interest. This paper proposes a stochastic approach for modelling such data in space and time, by taking the spatial...... and temporal correlations in data into account. It has been applied to observations of dissolved inorganic nitrogen in the Kattegat during the period 1993-1997. Modelling results are shown as maps of the spatial distribution of dissolved inorganic nitrogen (DIN) in 4 weeks, representing the four seasons......, and as time series of DIN at three different locations. However, the model approach could be applied to any space-time point given by a location in the Kattegat area and a week in the 5-year period 1993-1997. The results can be interpreted from a biological and physical point of view. Thus for the specific...
The importance of understanding: Model space moderates goal specificity effects.
Kistner, Saskia; Burns, Bruce D; Vollmeyer, Regina; Kortenkamp, Ulrich
2016-01-01
The three-space theory of problem solving predicts that the quality of a learner's model and the goal specificity of a task interact on knowledge acquisition. In Experiment 1 participants used a computer simulation of a lever system to learn about torques. They either had to test hypotheses (nonspecific goal), or to produce given values for variables (specific goal). In the good- but not in the poor-model condition they saw torque depicted as an area. Results revealed the predicted interaction. A nonspecific goal only resulted in better learning when a good model of torques was provided. In Experiment 2 participants learned to manipulate the inputs of a system to control its outputs. A nonspecific goal to explore the system helped performance when compared to a specific goal to reach certain values when participants were given a good model, but not when given a poor model that suggested the wrong hypothesis space. Our findings support the three-space theory. They emphasize the importance of understanding for problem solving and stress the need to study underlying processes.
Institute of Scientific and Technical Information of China (English)
Guoquan Liu; Haibo Yu; Xiaoyan Song; Xiangge Qin; Chao Wang
2004-01-01
A Hillert-type three-dimensional grain growth rate model was derived through the grain topology-size correlation model,combined with a topology-dependent grain growth rate equation in three dimensions. It shows clearly that the Hillert-type 3D grain growth rate model may also be described with topology considerations of microstructure. The size parameter bearing in the model is further discussed both according to the derived model and in another approach with the aid of quantitative relationship between the grain size and the integral mean curvature over grain surface. Both approaches successfully demonstrate that, if the concerned grains can be well approximated by a space-filling convex polyhedra in shape, the grain size parameter bearing in the Hillert-type 3D grain growth model should be a parameter proportional to the mean grain tangent radius.
Space physiology IV: mathematical modeling of the cardiovascular system in space exploration.
Keith Sharp, M; Batzel, Jerry Joseph; Montani, Jean-Pierre
2013-08-01
Mathematical modeling represents an important tool for analyzing cardiovascular function during spaceflight. This review describes how modeling of the cardiovascular system can contribute to space life science research and illustrates this process via modeling efforts to study postflight orthostatic intolerance (POI), a key issue for spaceflight. Examining this application also provides a context for considering broader applications of modeling techniques to the challenges of bioastronautics. POI, which affects a large fraction of astronauts in stand tests upon return to Earth, presents as dizziness, fainting and other symptoms, which can diminish crew performance and cause safety hazards. POI on the Moon or Mars could be more critical. In the field of bioastronautics, POI has been the dominant application of cardiovascular modeling for more than a decade, and a number of mechanisms for POI have been investigated. Modeling approaches include computational models with a range of incorporated factors and hemodynamic sophistication, and also physical models tested in parabolic and orbital flight. Mathematical methods such as parameter sensitivity analysis can help identify key system mechanisms. In the case of POI, this could lead to more effective countermeasures. Validation is a persistent issue in modeling efforts, and key considerations and needs for experimental data to synergistically improve understanding of cardiovascular responses are outlined. Future directions in cardiovascular modeling include subject-specific assessment of system status, as well as research on integrated physiological responses, leading, for instance, to assessment of subject-specific susceptibility to POI or effects of cardiovascular alterations on muscular, vision and cognitive function.
Nonlinear sigma models with compact hyperbolic target spaces
Energy Technology Data Exchange (ETDEWEB)
Gubser, Steven [Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States); Saleem, Zain H. [Department of Physics and Astronomy, University of Pennsylvania,Philadelphia, PA 19104 (United States); National Center for Physics, Quaid-e-Azam University Campus,Islamabad 4400 (Pakistan); Schoenholz, Samuel S. [Department of Physics and Astronomy, University of Pennsylvania,Philadelphia, PA 19104 (United States); Stoica, Bogdan [Walter Burke Institute for Theoretical Physics, California Institute of Technology,452-48, Pasadena, CA 91125 (United States); Stokes, James [Department of Physics and Astronomy, University of Pennsylvania,Philadelphia, PA 19104 (United States)
2016-06-23
We explore the phase structure of nonlinear sigma models with target spaces corresponding to compact quotients of hyperbolic space, focusing on the case of a hyperbolic genus-2 Riemann surface. The continuum theory of these models can be approximated by a lattice spin system which we simulate using Monte Carlo methods. The target space possesses interesting geometric and topological properties which are reflected in novel features of the sigma model. In particular, we observe a topological phase transition at a critical temperature, above which vortices proliferate, reminiscent of the Kosterlitz-Thouless phase transition in the O(2) model V.L. Berezinskii, Destruction of long-range order in one-dimensional and two-dimensional systems having a continuous symmetry group II. Quantum systems, Sov. Phys. JETP 34 (1972) 610. J.M. Kosterlitz and D.J. Thouless, Ordering, metastability and phase transitions in two-dimensional systems, J. Phys. C 6 (1973) 1181 [http://inspirehep.net/search?p=find+J+%22J.Phys.,C6,1181%22]. . Unlike in the O(2) case, there are many different types of vortices, suggesting a possible analogy to the Hagedorn treatment of statistical mechanics of a proliferating number of hadron species. Below the critical temperature the spins cluster around six special points in the target space known as Weierstrass points. The diversity of compact hyperbolic manifolds suggests that our model is only the simplest example of a broad class of statistical mechanical models whose main features can be understood essentially in geometric terms.
National Oceanic and Atmospheric Administration, Department of Commerce — This dataset represents sediment size predictions from a sediment spatial model developed for the New York offshore spatial planning area. The model also includes...
Asteroid age distributions determined by space weathering and collisional evolution models
Willman, Mark; 10.1016/j.icarus.2010.02.017
2010-01-01
We provide evidence of consistency between the dynamical evolution of main belt asteroids and their color evolution due to space weathering. The dynamical age of an asteroid's surface \\citep{bib.bot05a,bib.nes05} is the time since its last catastrophic disruption event which is a function of the object's diameter. The age of an S-complex asteroid's surface may also be determined from its color using a space weathering model \\citep[e.g.][]{bib.wil10,bib.jed04,bib.wil08,bib.mar06}. We used a sample of 95 S-complex asteroids from SMASS and obtained their absolute magnitudes and $u,g,r,i,z$ filter magnitudes from SDSS. The absolute magnitudes yield a size-derived age distribution. The $u,g,r,i,z$ filter magnitudes lead to the principal component color which yields a color-derived age distribution by inverting our color-age relationship, an enhanced version of the `dual $\\tau$' space weathering model of \\citet{bib.wil10}. We fit the size-age distribution to the enhanced dual $\\tau$ model and found characteristic w...
Waif goodbye! Average-size female models promote positive body image and appeal to consumers.
Diedrichs, Phillippa C; Lee, Christina
2011-10-01
Despite consensus that exposure to media images of thin fashion models is associated with poor body image and disordered eating behaviours, few attempts have been made to enact change in the media. This study sought to investigate an effective alternative to current media imagery, by exploring the advertising effectiveness of average-size female fashion models, and their impact on the body image of both women and men. A sample of 171 women and 120 men were assigned to one of three advertisement conditions: no models, thin models and average-size models. Women and men rated average-size models as equally effective in advertisements as thin and no models. For women with average and high levels of internalisation of cultural beauty ideals, exposure to average-size female models was associated with a significantly more positive body image state in comparison to exposure to thin models and no models. For men reporting high levels of internalisation, exposure to average-size models was also associated with a more positive body image state in comparison to viewing thin models. These findings suggest that average-size female models can promote positive body image and appeal to consumers.
Foresight Model of Turkey's Defense Industries' Space Studies until 2040
Yuksel, Nurdan; Cifci, Hasan; Cakir, Serhat
2016-07-01
Being advanced in science and technology is inevitable reality in order to be able to have a voice in the globalized world. Therefore, for the countries, making policies in consistent with their societies' intellectual, economic and political infrastructure and attributing them to the vision having been embraced by all parties of the society is quite crucial for the success. The generated policies are supposed to ensure the usage of countries' resources in the most effective and fastest way, determine the priorities and needs of society and set their goals and related roadmaps. In this sense, technology foresight studies based on justified forecasting in science and technology have critical roles in the process of developing policies. In this article, Foresight Model of Turkey's Defense Industries' Space Studies, which is turned out to be the important part of community life and fundamental background of most technologies, up to 2040 is presented. Turkey got late in space technology studies. Hence, for being fast and efficient to use its national resources in a cost effective way and within national and international collaboration, it should be directed to its pre-set goals. By taking all these factors into consideration, the technology foresight model of Turkey's Defense Industry's Space Studies was presented in the study. In the model, the present condition of space studies in the World and Turkey was analyzed; literature survey and PEST analysis were made. PEST analysis will be the inputs of SWOT analysis and Delphi questionnaire will be used in the study. A two-round Delphi survey will be applied to the participants from universities, public and private organizations operating in space studies at Defense Industry. Critical space technologies will be distinguished according to critical technology measures determined by expert survey; space technology fields and goals will be established according to their importance and feasibility indexes. Finally, for the
Influence of horizontal resolution and ensemble size on model performance
CSIR Research Space (South Africa)
Dalton, A
2014-10-01
Full Text Available southern Africa. Furthermore a comparison is made between forecast skill of the 850 hPa geopotential heights and raw model rainfall outputs. The determination of skill was done by way of empirical post-processing procedures in order to project ensemble mean...
Portfolio size as funktion of the premium: modeling and optimization
DEFF Research Database (Denmark)
Asmussen, Søren; Christensen, Bent Jesper; Taksar, Michael I
An insurance company has a large number N of potential customers characterized by i.i.d. r.v.'s A1,…,AN giving the arrival rates of claims. Customers are risk averse, and a customer accepts an offered premium p according to his A-value. The modeling further involves a discount rate d>r of customers...
A Note on Sample Size and Solution Propriety for Confirmatory Factor Analytic Models
Jackson, Dennis L.; Voth, Jennifer; Frey, Marc P.
2013-01-01
Determining an appropriate sample size for use in latent variable modeling techniques has presented ongoing challenges to researchers. In particular, small sample sizes are known to present concerns over sampling error for the variances and covariances on which model estimation is based, as well as for fit indexes and convergence failures. The…
Constraining the Size of the Dark Region Around the M87 Black Hole by Space-VLBI Observations
Takahashi, Rohta; Mineshige, Shin
2011-03-01
In order to examine if the next-generation space very long baseline interferometer (VLBI), such as VSOP-2 (VLBI Space Observatory Programme-2), will make it possible to obtain direct images of the accretion flow around the M87 black hole, we calculate the expected observed images by relativistic ray-tracing simulations under considerations of possible observational errors. We consider various cases of electron temperature profiles, as well various values for the distance, mass, and spin of the M87 black hole. We find it feasible to detect an asymmetric intensity profile around the black hole caused by rapid disk rotation, as long as the electron temperature does not rise steeply toward the black hole, as was predicted by the accretion disk theory and three-dimensional magnetohydrodynamic simulations. Further, we can detect a deficit in the observed intensity around the black hole when the apparent size of the gravitational radius is larger than gsim1.5 μas. In the cases that the inner edge of the disk is located at the radius of the innermost stable circular orbit (ISCO), moreover, even the black hole spin will be measured. We also estimate the required signal-to-noise ratio {R}_SN for achieving the scientific goals mentioned above, finding that it should be at least 10 at 22 GHz. To conclude, direct mapping observations by the next-generation space VLBI will provide us a unique opportunity to provide the best evidence for the presence of a black hole and to test the accretion disk theory.
A phase-space model for Pleistocene ice volume
Imbrie, John Z; Lisiecki, Lorraine E
2011-01-01
We present a phase-space model that simulates Pleistocene ice volume changes based on Earth's orbital parameters. Terminations in the model are triggered by a combination of ice volume and orbital forcing and agree well with age estimates for Late Pleistocene terminations. The average phase at which model terminations begin is approximately 90 +/- 90 degrees before the maxima in all three orbital cycles. The large variability in phase is likely caused by interactions between the three cycles and ice volume. Unlike previous ice volume models, this model produces an orbitally driven increase in 100-kyr power during the mid-Pleistocene transition without any change in model parameters. This supports the hypothesis that Pleistocene variations in the 100-kyr power of glacial cycles could be caused, at least in part, by changes in Earth's orbital parameters, such as amplitude modulation of the 100-kyr eccentricity cycle, rather than changes within the climate system.
A Full-Size Mockup of the Cabin for the Crew Return Vehicle (CRV) for the International Space Statio
1999-01-01
This photo, taken at NASA's Johnson Space Center, Houston, Texas, shows a full-size mockup of the cabin for the Crew Return Vehicle (CRV) for the International Space Station The X-38 Crew Return Vehicle (CRV) research project is designed to develop the technology for a prototype emergency crew return vehicle, or lifeboat, for the International Space Station. The project is also intended to develop a crew return vehicle design that could be modified for other uses, such as a joint U.S. and international human spacecraft that could be launched on the French Ariane-5 Booster. The X-38 project is using available technology and off-the-shelf equipment to significantly decrease development costs. Original estimates to develop a capsule-type crew return vehicle were estimated at more than $2 billion. X-38 project officials have estimated that development costs for the X-38 concept will be approximately one quarter of the original estimate. Off-the-shelf technology is not necessarily 'old' technology. Many of the technologies being used in the X-38 project have never before been applied to a human-flight spacecraft. For example, the X-38 flight computer is commercial equipment currently used in aircraft and the flight software operating system is a commercial system already in use in many aerospace applications. The video equipment for the X-38 is existing equipment, some of which has already flown on the space shuttle for previous NASA experiments. The X-38's primary navigational equipment, the Inertial Navigation System/Global Positioning System, is a unit already in use on Navy fighters. The X-38 electromechanical actuators come from previous joint NASA, U.S. Air Force, and U.S. Navy research and development projects. Finally, an existing special coating developed by NASA will be used on the X-38 thermal tiles to make them more durable than those used on the space shuttles. The X-38 itself was an unpiloted lifting body designed at 80 percent of the size of a projected
Acoustic Predictions in Industrial Spaces Using a Diffusion Model
Directory of Open Access Journals (Sweden)
Alexis Billon
2012-01-01
Full Text Available Industrial spaces are known to be very noisy working environment. This noise exposure can be uncomfortable, tiring, or even harmful, at worst. Industrial spaces have several characteristics: they are often huge flat volumes fitted with many obstacles and sound sources. Moreover, they are usually surrounded by rooms where low noise levels are required. The existing prediction tools can seldom model all these phenomena accurately. In this paper, a prediction model based on a diffusion equation is presented. The successive developments carried out to deal with the various propagating phenomena met in industrial spaces are shown. For each phenomenon, numerical or experimental examples are given to highlight the validity of this model. It is also shown that its computation load is very little in comparison to ray-tracing-based methods. In addition, this model can be used as a reliable and flexible tool to study the physics of the coupling between rooms. Finally, an application to a virtual factory is presented.
Directory of Open Access Journals (Sweden)
Parvaneh Shabanzadeh
2013-01-01
Full Text Available Artificial neural network (ANN models have the capacity to eliminate the need for expensive experimental investigation in various areas of manufacturing processes, including the casting methods. An understanding of the interrelationships between input variables is essential for interpreting the sensitivity data and optimizing the design parameters. Silver nanoparticles (Ag-NPs have attracted considerable attention for chemical, physical, and medical applications due to their exceptional properties. The nanocrystal silver was synthesized into an interlamellar space of montmorillonite by using the chemical reduction technique. The method has an advantage of size control which is essential in nanometals synthesis. Silver nanoparticles with nanosize and devoid of aggregation are favorable for several properties. In this investigation, the accuracy of artificial neural network training algorithm was applied in studying the effects of different parameters on the particles, including the AgNO3 concentration, reaction temperature, UV-visible wavelength, and montmorillonite (MMT d-spacing on the prediction of size of silver nanoparticles. Analysis of the variance showed that the AgNO3 concentration and temperature were the most significant factors affecting the size of silver nanoparticles. Using the best performing artificial neural network, the optimum conditions predicted were a concentration of AgNO3 of 1.0 (M, MMT d-spacing of 1.27 nm, reaction temperature of 27°C, and wavelength of 397.50 nm.
Medical Modeling of Particle Size Effects for CB Inhalation Hazards
2015-09-01
of body orientation ( posture ) on deposition, and availability of 30 stochastic lung geometry for more realistic assessment of variation of dose in... hygiene community, with their role of monitoring and protecting workers in the workplace, has had a key role in developing standard models of...M.G., Miller, F.J. and Raabe, O.G. (1995). Particle Inhalability Curves for Humans and Small Laboratory Animals. Annals of Occupational Hygiene 39
Insights into plant size-density relationships from models and agricultural crops.
Deng, Jianming; Zuo, Wenyun; Wang, Zhiqiang; Fan, Zhexuan; Ji, Mingfei; Wang, Genxuan; Ran, Jinzhi; Zhao, Changming; Liu, Jianquan; Niklas, Karl J; Hammond, Sean T; Brown, James H
2012-05-29
There is general agreement that competition for resources results in a tradeoff between plant mass, M, and density, but the mathematical form of the resulting thinning relationship and the mechanisms that generate it are debated. Here, we evaluate two complementary models, one based on the space-filling properties of canopy geometry and the other on the metabolic basis of resource use. For densely packed stands, both models predict that density scales as M(-3/4), energy use as M(0), and total biomass as M(1/4). Compilation and analysis of data from 183 populations of herbaceous crop species, 473 stands of managed tree plantations, and 13 populations of bamboo gave four major results: (i) At low initial planting densities, crops grew at similar rates, did not come into contact, and attained similar mature sizes; (ii) at higher initial densities, crops grew until neighboring plants came into contact, growth ceased as a result of competition for limited resources, and a tradeoff between density and size resulted in critical density scaling as M(-0.78), total resource use as M(-0.02), and total biomass as M(0.22); (iii) these scaling exponents are very close to the predicted values of M(-3/4), M(0), and M(1/4), respectively, and significantly different from the exponents suggested by some earlier studies; and (iv) our data extend previously documented scaling relationships for trees in natural forests to small herbaceous annual crops. These results provide a quantitative, predictive framework with important implications for the basic and applied plant sciences.
Energy Technology Data Exchange (ETDEWEB)
Gamez-Mendoza, Liliana; Terban, Maxwell W.; Billinge, Simon J. L.; Martinez-Inesta, Maria
2017-04-13
The particle size of supported catalysts is a key characteristic for determining structure–property relationships. It is a challenge to obtain this information accurately and
Discrete random walk models for space-time fractional diffusion
Energy Technology Data Exchange (ETDEWEB)
Gorenflo, Rudolf; Mainardi, Francesco; Moretti, Daniele; Pagnini, Gianni; Paradisi, Paolo
2002-11-01
A physical-mathematical approach to anomalous diffusion may be based on generalized diffusion equations (containing derivatives of fractional order in space or/and time) and related random walk models. By space-time fractional diffusion equation we mean an evolution equation obtained from the standard linear diffusion equation by replacing the second-order space derivative with a Riesz-Feller derivative of order {alpha} is part of (0,2] and skewness {theta} (module{theta}{<=}{l_brace}{alpha},2-{alpha}{r_brace}), and the first-order time derivative with a Caputo derivative of order {beta} is part of (0,1]. Such evolution equation implies for the flux a fractional Fick's law which accounts for spatial and temporal non-locality. The fundamental solution (for the Cauchy problem) of the fractional diffusion equation can be interpreted as a probability density evolving in time of a peculiar self-similar stochastic process that we view as a generalized diffusion process. By adopting appropriate finite-difference schemes of solution, we generate models of random walk discrete in space and time suitable for simulating random variables whose spatial probability density evolves in time according to this fractional diffusion equation.
Nuclear model calculations and their role in space radiation research
Townsend, L. W.; Cucinotta, F. A.; Heilbronn, L. H.
2002-01-01
Proper assessments of spacecraft shielding requirements and concomitant estimates of risk to spacecraft crews from energetic space radiation requires accurate, quantitative methods of characterizing the compositional changes in these radiation fields as they pass through thick absorbers. These quantitative methods are also needed for characterizing accelerator beams used in space radiobiology studies. Because of the impracticality/impossibility of measuring these altered radiation fields inside critical internal body organs of biological test specimens and humans, computational methods rather than direct measurements must be used. Since composition changes in the fields arise from nuclear interaction processes (elastic, inelastic and breakup), knowledge of the appropriate cross sections and spectra must be available. Experiments alone cannot provide the necessary cross section and secondary particle (neutron and charged particle) spectral data because of the large number of nuclear species and wide range of energies involved in space radiation research. Hence, nuclear models are needed. In this paper current methods of predicting total and absorption cross sections and secondary particle (neutrons and ions) yields and spectra for space radiation protection analyses are reviewed. Model shortcomings are discussed and future needs presented. c2002 COSPAR. Published by Elsevier Science Ltd. All right reserved.
Dispersion modeling of thermal power plant emissions on stochastic space
Gorle, J. M. R.; Sambana, N. R.
2016-05-01
This study aims to couple a deterministic atmospheric dispersion solver based on Gaussian model with a nonintrusive stochastic model to quantify the propagation of multiple uncertainties. The nonintrusive model is based on probabilistic collocation framework. The advantage of nonintrusive nature is to retain the existing deterministic plume dispersion model without missing the accuracy in extracting the statistics of stochastic solution. The developed model is applied to analyze the SO2 emission released from coal firing unit in the second stage of the National Thermal Power Corporation (NTPC) in Dadri, India using "urban" conditions. The entire application is split into two cases, depending on the source of uncertainty. In case 1, the uncertainties in stack gas exit conditions are used to construct the stochastic space while in case 2, meteorological conditions are considered as the sources of uncertainty. Both cases develop 2D uncertain random space in which the uncertainty propagation is quantified in terms of plume rise and pollutant concentration distribution under slightly unstable atmospheric stability conditions. Starting with deterministic Gaussian plume model demonstration and its application, development of stochastic collocation model, convergence study, error analysis, and uncertainty quantification are presented in this paper.
Budic, Lara; Didenko, Gregor; Dormann, Carsten F
2016-01-01
In species distribution analyses, environmental predictors and distribution data for large spatial extents are often available in long-lat format, such as degree raster grids. Long-lat projections suffer from unequal cell sizes, as a degree of longitude decreases in length from approximately 110 km at the equator to 0 km at the poles. Here we investigate whether long-lat and equal-area projections yield similar model parameter estimates, or result in a consistent bias. We analyzed the environmental effects on the distribution of 12 ungulate species with a northern distribution, as models for these species should display the strongest effect of projectional distortion. Additionally we choose four species with entirely continental distributions to investigate the effect of incomplete cell coverage at the coast. We expected that including model weights proportional to the actual cell area should compensate for the observed bias in model coefficients, and similarly that using land coverage of a cell should decrease bias in species with coastal distribution. As anticipated, model coefficients were different between long-lat and equal-area projections. Having progressively smaller and a higher number of cells with increasing latitude influenced the importance of parameters in models, increased the sample size for the northernmost parts of species ranges, and reduced the subcell variability of those areas. However, this bias could be largely removed by weighting long-lat cells by the area they cover, and marginally by correcting for land coverage. Overall we found little effect of using long-lat rather than equal-area projections in our analysis. The fitted relationship between environmental parameters and occurrence probability differed only very little between the two projection types. We still recommend using equal-area projections to avoid possible bias. More importantly, our results suggest that the cell area and the proportion of a cell covered by land should be
Vitorge, Elsa; Szenknect, Stéphanie; Martins, Jean M F; Gaudet, Jean-Paul
2013-08-01
This study investigates the size and concentration effects on the transport of silica colloids in columns of sandy aquifer material. Colloid transport experiments were performed with specifically developed fluorescent labeled silica colloids in columns of a repacked natural porous medium under hydro-geochemical conditions representative of sandy aquifers. Breakthrough curves and vertical deposition profiles of colloids were measured for various colloid concentrations and sizes. The results showed that for a given colloid concentration injected, deposition increased when increasing the size of the colloids. For a given colloid size, retention was also shown to be highly concentration-dependent with a non-monotonous pattern presenting low and high concentration specificities. Deposition increases when increasing both size and injected concentration, until a threshold concentration is reached, above which retention decreases, thus increasing colloid mobility. Results observed above the threshold concentration agree with a classical blocking mechanism typical of a high concentration regime. Results observed at lower colloid concentrations were not modeled with a classical blocking model and a depth- and time-dependent model with a second order kinetic law was necessary to correctly fit the experimental data in the entire range of colloid concentrations with a single set of parameters for each colloidal size. The colloid deposition mechanisms occuring at low concentrations were investigated through a pore structure analysis carried out with Mercury Intrusion Porosimetry and image analysis. The determined pore size distribution permitted estimation of the maximal retention capacity of the natural sand as well as some low flow zones. Altogether, these results stress the key role of the pore space geometry of the sand in controlling silica colloids deposition under hydro-geochemical conditions typical of sandy aquifers. Our results also showed originally that colloid
Transformation of Neural State Space Models into LFT Models for Robust Control Design
DEFF Research Database (Denmark)
Bendtsen, Jan Dimon; Trangbæk, Klaus
2000-01-01
This paper considers the extraction of linear state space models and uncertainty models from neural networks trained as state estimators with direct application to robust control. A new method for writing a neural state space model in a linear fractional transformation form in a non-conservative ......This paper considers the extraction of linear state space models and uncertainty models from neural networks trained as state estimators with direct application to robust control. A new method for writing a neural state space model in a linear fractional transformation form in a non......-conservative way is proposed, and it is demonstrated how a standard robust control law can be designed for a system described by means of a multi layer perceptron....
Zhao, Jinsong; Chen, Boyu
2016-03-01
Species sensitivity distribution (SSD) is a widely used model that extrapolates the ecological risk to ecosystem levels from the ecotoxicity of a chemical to individual organisms. However, model choice and sample size significantly affect the development of the SSD model and the estimation of hazardous concentrations at the 5th centile (HC5). To interpret their effects, the SSD model for chlorpyrifos, a widely used organophosphate pesticide, to aquatic organisms is presented with emphases on model choice and sample size. Three subsets of median effective concentration (EC50) with different sample sizes were obtained from ECOTOX and used to build SSD models based on parametric distribution (normal, logistic, and triangle distribution) and nonparametric bootstrap. The SSD models based on the triangle distribution are superior to the normal and logistic distributions according to several goodness-of-fit techniques. Among all parametric SSD models, the one with the largest sample size based on the triangle distribution gives the most strict HC5 with 0.141μmolL(-1). The HC5 derived from the nonparametric bootstrap is 0.159μmol L(-1). The minimum sample size required to build a stable SSD model is 11 based on parametric distribution and 23 based on nonparametric bootstrap. The study suggests that model choice and sample size are important sources of uncertainty for application of the SSD model. Copyright © 2015 Elsevier Inc. All rights reserved.
Latent state-space models for neural decoding.
Aghagolzadeh, Mehdi; Truccolo, Wilson
2014-01-01
Ensembles of single-neurons in motor cortex can show strong low-dimensional collective dynamics. In this study, we explore an approach where neural decoding is applied to estimated low-dimensional dynamics instead of to the full recorded neuronal population. A latent state-space model (SSM) approach is used to estimate the low-dimensional neural dynamics from the measured spiking activity in population of neurons. A second state-space model representation is then used to decode kinematics, via a Kalman filter, from the estimated low-dimensional dynamics. The latent SSM-based decoding approach is illustrated on neuronal activity recorded from primary motor cortex in a monkey performing naturalistic 3-D reach and grasp movements. Our analysis show that 3-D reach decoding performance based on estimated low-dimensional dynamics is comparable to the decoding performance based on the full recorded neuronal population.
Joint Dynamics Modeling and Parameter Identification for Space Robot Applications
Directory of Open Access Journals (Sweden)
Adenilson R. da Silva
2007-01-01
Full Text Available Long-term mission identification and model validation for in-flight manipulator control system in almost zero gravity with hostile space environment are extremely important for robotic applications. In this paper, a robot joint mathematical model is developed where several nonlinearities have been taken into account. In order to identify all the required system parameters, an integrated identification strategy is derived. This strategy makes use of a robust version of least-squares procedure (LS for getting the initial conditions and a general nonlinear optimization method (MCS—multilevel coordinate search—algorithm to estimate the nonlinear parameters. The approach is applied to the intelligent robot joint (IRJ experiment that was developed at DLR for utilization opportunity on the International Space Station (ISS. The results using real and simulated measurements have shown that the developed algorithm and strategy have remarkable features in identifying all the parameters with good accuracy.
State Space Modelling and Data Analysis Exercises in LISA Pathfinder
Nofrarias, M.; Antonucci, F.; Armano, M.; Audley, H.; Auger, G.; Benedetti, M.; Binetruy, P.; Bogenstahl, J.; Bortoluzzi, D.; Brandt, N.; Caleno, M.; Cavalleri, A.; Congedo, G.; Cruise, M.; Danzmann, K.; De Marchi, F.; Diaz-Aguilo, M.; Diepholz, I.; Dixon, G.; Dolesi, R.; Dunbar, N.; Fauste, J.; Ferraioli, L.; Ferroni, V.; Fichter, W.; Fitzsimons, E.; Freschi, M.; García Marirrodriga, C.; Gerndt, R.; Gesa, L.; Gibert, F.; Giardini, D.; Grimani, C.; Grynagier, A.; Guzmán, F.; Harrison, I.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Huesler, J.; Jennrich, O.; Jetzer, P.; Johlander, B.; Karnesis, N.; Korsakova, N.; Killow, C.; Llamas, X.; Lloro, I.; Lobo, A.; Maarschalkerweerd, R.; Madden, S.; Mance, D.; Martin, V.; Mateos, I.; McNamara, P.; Mendes, J.; Mitchell, E.; Nicolodi, D.; Perreur-Lloyd, M.; Plagnol, E.; Prat, P.; Ramos-Castro, J.; Reiche, J.; Romera Perez, J. A.; Robertson, D.; Rozemeijer, H.; Russano, G.; Schleicher, A.; Shaul, D.; Sopuerta, C. F.; Sumner, T. J.; Taylor, A.; Texier, D.; Trenkel, C.; Tu, H. B.; Vitale, S.; Wanner, G.; Ward, H.; Waschke, S.; Wass, P.; Wealthy, D.; Wen, S.; Weber, W.; Ziegler, T.; Zweifel, P.
2013-01-01
LISA Pathfinder is a mission planned by the European Space Agency (ESA) to test the key technologies that will allow the detection of gravitational waves in space. The instrument on-board, the LISA Technology package, will undergo an exhaustive campaign of calibrations and noise characterisation campaigns in order to fully describe the noise model. Data analysis plays an important role in the mission and for that reason the data analysis team has been developing a toolbox which contains all the functionality required during operations. In this contribution we give an overview of recent activities, focusing on the improvements in the modelling of the instrument and in the data analysis campaigns performed both with real and simulated data.
State space modelling and data analysis exercises in LISA Pathfinder
Nofrarias, M; Armano, M; Audley, H; Auger, G; Benedetti, M; Binetruy, P; Bogenstahl, J; Bortoluzzi, D; Bosetti, P; Brandt, N; Caleno, M; Cañizares, P; Cavalleri, A; Cesa, M; Chmeissani, M; Conchillo, A; Congedo, G; Cristofolin, I; Cruise, M; Danzmann, K; De Marchi, F; Diaz-Aguilo, M; Diepholz, I; Dixon, G; Dolesi, R; Dunbar, N; Fauste, J; Ferraioli, L; Fichter, V Ferroni W; Fitzsimons, E; Freschi, M; Marin, A García; Marirrodriga, C García; Gesa, R Gerndt L; Gibert, F; Giardini, D; Grimani, C; Grynagier, A; Guillaume, B; Guzmán, F; Harrison, I; Heinzel, G; Hernández, V; Hewitson, M; Hollington, D; Hough, J; Hoyland, D; Hueller, M; Huesler, J; Jennrich, O; Jetzer, P; Johlander, B; Killow, C; Llamas, X; Lloro, I; Lobo, A; Maarschalkerweerd, R; Madden, S; Mance, D; Mateos, I; McNamara, P W; Mendes, J; Mitchell, E; Monsky, A; Nicolini, D; Nicolodi, D; Pedersen, F; Perreur-Lloyd, M; Plagnol, E; Prat, P; Racca, G D; Ramos-Castro, J; Reiche, J; Perez, J A Romera; Robertson, D; Rozemeijer, H; Sanjuan, J; Schleicher, A; Schulte, M; Shaul, D; Stagnaro, L; Strandmoe, S; Steier, F; Sumner, T J; Taylor, A; Texier, D; Trenkel, C; Vitale, H-B Tu S; Wanner, G; Ward, H; Waschke, S; Wass, P; Weber, W J; Ziegler, T; Zweifel, P
2013-01-01
LISA Pathfinder is a mission planned by the European Space Agency to test the key technologies that will allow the detection of gravitational waves in space. The instrument on-board, the LISA Technology package, will undergo an exhaustive campaign of calibrations and noise characterisation campaigns in order to fully describe the noise model. Data analysis plays an important role in the mission and for that reason the data analysis team has been developing a toolbox which contains all the functionalities required during operations. In this contribution we give an overview of recent activities, focusing on the improvements in the modelling of the instrument and in the data analysis campaigns performed both with real and simulated data.
Dynamical 3-Space Gravity Theory: Effects on Polytropic Solar Models
Directory of Open Access Journals (Sweden)
Cahill R. T.
2011-01-01
Full Text Available Numerous experiments and observations have confirmed the existence of a dynamical 3-space, detectable directly by light-speed anisotropy experiments, and indirectly by means of novel gravitational effects, such as bore hole g-anomalies, predictable black hole masses, flat spiral-galaxy rotation curves, and the expansion of the universe, all without dark matter and dark energy. The dynamics for this 3-space follows from a unique generalisation of Newtonian gravity, once that is cast into a velocity formalism. This new theory of gravity is applied to the solar model of the sun to compute new density, pressure and temperature profiles, using polytrope modelling of the equation of state for the matter. These results should be applied to a re-analysis of solar neutrino production, and to stellar evolution in general.
Dynamical 3-Space Gravity Theory: Effects on Polytropic Solar Models
Directory of Open Access Journals (Sweden)
May R. D.
2011-01-01
Full Text Available Numerous experiments and observations have confirmed the existence of a dynamical 3-space, detectable directly by light-speed anisotropy experiments, and indirectly by means of novel gravitational effects, such as bore hole g anomalies, predictable black hole masses, flat spiral-galaxy rotation curves, and the expansion of the universe, all without dark matter and dark energy. The dynamics for this 3-space follows from a unique generalisation of Newtonian gravity, once that is cast into a velocity formalism. This new theory of gravity is applied to the solar model of the sun to compute new density, pressure and temperature profiles, using polytrope modelling of the equation of state for the matter. These results should be applied to a re-analysis of solar neutrino production, and to stellar evolution in general.
Energy Technology Data Exchange (ETDEWEB)
Pogosov, W.V., E-mail: walter.pogosov@gmail.com [N.L. Dukhov All-Russia Research Institute of Automatics, Moscow (Russian Federation); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny (Russian Federation); Shapiro, D.S. [N.L. Dukhov All-Russia Research Institute of Automatics, Moscow (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny (Russian Federation); V.A. Kotel' nikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Moscow (Russian Federation); National University of Science and Technology MISIS, Moscow (Russian Federation); Bork, L.V. [N.L. Dukhov All-Russia Research Institute of Automatics, Moscow (Russian Federation); Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Onishchenko, A.I. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny (Russian Federation); Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow (Russian Federation)
2017-06-15
We consider an exactly solvable inhomogeneous Dicke model which describes an interaction between a disordered ensemble of two-level systems with single mode boson field. The existing method for evaluation of Richardson–Gaudin equations in the thermodynamical limit is extended to the case of Bethe equations in Dicke model. Using this extension, we present expressions both for the ground state and lowest excited states energies as well as leading-order finite-size corrections to these quantities for an arbitrary distribution of individual spin energies. We then evaluate these quantities for an equally-spaced distribution (constant density of states). In particular, we study evolution of the spectral gap and other related quantities. We also reveal regions on the phase diagram, where finite-size corrections are of particular importance.
Directory of Open Access Journals (Sweden)
W.V. Pogosov
2017-06-01
Full Text Available We consider an exactly solvable inhomogeneous Dicke model which describes an interaction between a disordered ensemble of two-level systems with single mode boson field. The existing method for evaluation of Richardson–Gaudin equations in the thermodynamical limit is extended to the case of Bethe equations in Dicke model. Using this extension, we present expressions both for the ground state and lowest excited states energies as well as leading-order finite-size corrections to these quantities for an arbitrary distribution of individual spin energies. We then evaluate these quantities for an equally-spaced distribution (constant density of states. In particular, we study evolution of the spectral gap and other related quantities. We also reveal regions on the phase diagram, where finite-size corrections are of particular importance.
Small Fish Species as Powerful Model Systems to Study Vertebrate Physiology in Space
Muller, M.; Aceto, J.; Dalcq, J.; Alestrom, P.; Nourizadeh-Lillabadi, R.; Goerlich, R.; Schiller, V.; Winkler, C.; Renn, J.; Eberius, M.; Slenzka, K.
2008-06-01
Small fish models, mainly zebrafish (Danio rerio) and medaka (Oryzias latipes), have been used for many years as powerful model systems for vertebrate developmental biology. Moreover, these species are increasingly recognized as valuable systems to study vertebrate physiology, pathology, pharmacology and toxicology, including in particular bone physiology. The biology of small fishes presents many advantages, such as transparency of the embryos, external and rapid development, small size and easy reproduction. Further characteristics are particularly useful for space research or for large scale screening approaches. Finally, many technologies for easily characterizing bones are available. Our objective is to investigate the changes induced by microgravity in small fish. By combining whole genome analysis (microarray, DNA methylation, chromatin modification) with live imaging of selected genes in transgenic animals, a comprehensive and integrated characterization of physiological changes in space could be gained, especially concerning bone physiology.
Mathematical analysis techniques for modeling the space network activities
Foster, Lisa M.
1992-01-01
The objective of the present work was to explore and identify mathematical analysis techniques, and in particular, the use of linear programming. This topic was then applied to the Tracking and Data Relay Satellite System (TDRSS) in order to understand the space network better. Finally, a small scale version of the system was modeled, variables were identified, data was gathered, and comparisons were made between actual and theoretical data.
Quantum-dot Semiconductor Optical Amplifiers in State Space Model
Institute of Scientific and Technical Information of China (English)
Hussein Taleb; Kambiz Abedi; Saeed Golmohammadi
2013-01-01
A state space model (SSM) is derived for quantum-dot semiconductor optical amplifiers (QD-SOAs).Rate equations of QD-SOA are formulated in the form of state update equations,where average occupation probabilities along QD-SOA cavity are considered as state variables of the system.Simulations show that SSM calculates QD-SOA's static and dynamic characteristics with high accuracy.
Recent improvements in atmospheric environment models for Space Station applications
Anderson, B. Jeffrey; Suggs, Ronnie J.; Smith, Robert E.; Hickey, Michael; Catlett, Karen
1991-01-01
The capability of empirical models of the earth's thermosphere must continually be updated if they are to keep pace with their many applications in the aerospace industry. This paper briefly summarizes the progress of several such efforts in support of the Space Station Program. The efforts consists of the development of data bases, analytical studies of the data, and evaluation and intercomparison of thermosphere models. A geomagnetic storm model of Slowey does not compare as well to the MSIS-86 model as does the Marshall Engineering Thermosphere (MET). LDEF orbit decay data is used to evaluate the performance of the MET and MSIS-86 during a period of high solar activity; equal to or exceeding the highest levels that existed during the time of the original data sets upon which these models are based.
Holographic Space-time Models in $1 + 1$ Dimensions
Banks, T
2015-01-01
We construct Holographic Space-time models that reproduce the dynamics of $1 + 1$ dimensional string theory. The necessity for a dilaton field in the $1 + 1$ effective Lagrangian for classical geometry, the appearance of fermions, and even the form of the universal potential in the canonical $1$ matrix model, follow from general HST considerations. We note that 't Hooft's ansatz for the leading contribution to the black hole S-matrix, accounts for the entire S-matrix in these models in the limit that the string scale coincides with the Planck scale, up to transformations between near horizon and asymptotic coordinates. These $1 + 1$ dimensional models are describable as decoupling limits of the near horizon geometry of higher dimensional extremal black holes or black branes, and this suggests that deformations of the simplest model are equally physical. After proposing a notion of "relevant deformations", we describe deformations, which contain excitations corresponding to linear dilaton black holes, some of ...
A semantic space for modeling children's semantic memory
Denhière, Guy; Bellissens, Cédrick; Jhean, Sandra
2008-01-01
The goal of this paper is to present a model of children's semantic memory, which is based on a corpus reproducing the kinds of texts children are exposed to. After presenting the literature in the development of the semantic memory, a preliminary French corpus of 3.2 million words is described. Similarities in the resulting semantic space are compared to human data on four tests: association norms, vocabulary test, semantic judgments and memory tasks. A second corpus is described, which is composed of subcorpora corresponding to various ages. This stratified corpus is intended as a basis for developmental studies. Finally, two applications of these models of semantic memory are presented: the first one aims at tracing the development of semantic similarities paragraph by paragraph; the second one describes an implementation of a model of text comprehension derived from the Construction-integration model (Kintsch, 1988, 1998) and based on such models of semantic memory.
Multivariable parametric cost model for space and ground telescopes
Stahl, H. Philip; Henrichs, Todd
2016-09-01
Parametric cost models can be used by designers and project managers to perform relative cost comparisons between major architectural cost drivers and allow high-level design trades; enable cost-benefit analysis for technology development investment; and, provide a basis for estimating total project cost between related concepts. This paper hypothesizes a single model, based on published models and engineering intuition, for both ground and space telescopes: OTA Cost (X) D (1.75 +/- 0.05) λ (-0.5 +/- 0.25) T-0.25 e (-0.04) Y Specific findings include: space telescopes cost 50X to 100X more ground telescopes; diameter is the most important CER; cost is reduced by approximately 50% every 20 years (presumably because of technology advance and process improvements); and, for space telescopes, cost associated with wavelength performance is balanced by cost associated with operating temperature. Finally, duplication only reduces cost for the manufacture of identical systems (i.e. multiple aperture sparse arrays or interferometers). And, while duplication does reduce the cost of manufacturing the mirrors of segmented primary mirror, this cost savings does not appear to manifest itself in the final primary mirror assembly (presumably because the structure for a segmented mirror is more complicated than for a monolithic mirror).
Noise-Induced Transitions in a Population Growth Model Based on Size-Dependent Carrying Capacity
Directory of Open Access Journals (Sweden)
Neeme Lumi
2014-01-01
Full Text Available The stochastic dynamics of a population growth model with size-dependent carrying capacity is considered. The effect of a fluctuating environment on population growth is modeled as a multiplicative dichotomous noise. At intermediate values of population size the deterministic counterpart of the model behaves similarly to the Von Foerster model for human population, but at small and very large values of population size substantial differences occur. In the stochastic case, an exact analytical solution for the stationary probability distribution is found. It is established that variation of noise correlation time can cause noise-induced transitions between three different states of the system characterized by qualitatively different behaviors of the probability distributions of the population size. Also, it is shown that, in some regions of the system parameters, variation of the amplitude of environmental fluctuations can induce single unidirectional abrupt transitions of the mean population size.
Directory of Open Access Journals (Sweden)
Leopoldo Eduardo Cárdenas-Barrón
2015-01-01
Full Text Available The determination of production-shipment policies for a vendor-buyer system is dealt within this paper. The main objective is to derive the optimal replenishment lot size and shipment policy for an EPQ inventory model with multiple deliveries and rework. This inventory model contains two decision variables: the replenishment lot size and the number of deliveries. Previous researches solve this inventory model considering both variables to be continuous. However, the number of deliveries must be considered as a discrete variable. In this direction, this paper solves the inventory model considering two cases: Case 1: the replenishment lot size as a continuous variable and the number of shipments as a discrete variable and Case 2: the replenishment lot size and the number of shipments as discrete variables. The final results are two simple and easy-to-apply solution procedures to find the optimal values for the replenishment lot size and the number of deliveries for each case.
Analysis of traffic accident size for Korean highway using structural equation models.
Lee, Ju-Yeon; Chung, Jin-Hyuk; Son, Bongsoo
2008-11-01
Accident size can be expressed as the number of involved vehicles, the number of damaged vehicles, the number of deaths and/or the number of injured. Accident size is the one of the important indices to measure the level of safety of transportation facilities. Factors such as road geometric condition, driver characteristic and vehicle type may be related to traffic accident size. However, all these factors interact in complicate ways so that the interrelationships among the variables are not easily identified. A structural equation model is adopted to capture the complex relationships among variables because the model can handle complex relationships among endogenous and exogenous variables simultaneously and furthermore it can include latent variables in the model. In this study, we use 2649 accident data occurred on highways in Korea and estimate relationship among exogenous factors and traffic accident size. The model suggests that road factors, driver factors and environment factors are strongly related to the accident size.
Inference and Decoding of Motor Cortex Low-Dimensional Dynamics via Latent State-Space Models.
Aghagolzadeh, Mehdi; Truccolo, Wilson
2016-02-01
Motor cortex neuronal ensemble spiking activity exhibits strong low-dimensional collective dynamics (i.e., coordinated modes of activity) during behavior. Here, we demonstrate that these low-dimensional dynamics, revealed by unsupervised latent state-space models, can provide as accurate or better reconstruction of movement kinematics as direct decoding from the entire recorded ensemble. Ensembles of single neurons were recorded with triple microelectrode arrays (MEAs) implanted in ventral and dorsal premotor (PMv, PMd) and primary motor (M1) cortices while nonhuman primates performed 3-D reach-to-grasp actions. Low-dimensional dynamics were estimated via various types of latent state-space models including, for example, Poisson linear dynamic system (PLDS) models. Decoding from low-dimensional dynamics was implemented via point process and Kalman filters coupled in series. We also examined decoding based on a predictive subsampling of the recorded population. In this case, a supervised greedy procedure selected neuronal subsets that optimized decoding performance. When comparing decoding based on predictive subsampling and latent state-space models, the size of the neuronal subset was set to the same number of latent state dimensions. Overall, our findings suggest that information about naturalistic reach kinematics present in the recorded population is preserved in the inferred low-dimensional motor cortex dynamics. Furthermore, decoding based on unsupervised PLDS models may also outperform previous approaches based on direct decoding from the recorded population or on predictive subsampling.
Ribeiro, Flavio F; Qin, Jian G
2013-01-01
This study quantified size-dependent cannibalism in barramundi Lates calcarifer through coupling a range of prey-predator pairs in a different range of fish sizes. Predictive models were developed using morphological traits with the alterative assumption of cannibalistic polyphenism. Predictive models were validated with the data from trials where cannibals were challenged with progressing increments of prey sizes. The experimental observations showed that cannibals of 25-131 mm total length could ingest the conspecific prey of 78-72% cannibal length. In the validation test, all predictive models underestimate the maximum ingestible prey size for cannibals of a similar size range. However, the model based on the maximal mouth width at opening closely matched the empirical observations, suggesting a certain degree of phenotypic plasticity of mouth size among cannibalistic individuals. Mouth size showed allometric growth comparing with body depth, resulting in a decreasing trend on the maximum size of ingestible prey as cannibals grow larger, which in parts explains why cannibalism in barramundi is frequently observed in the early developmental stage. Any barramundi has the potential to become a cannibal when the initial prey size was cannibal body length, but fish could never become a cannibal when prey were >58% of their size, suggesting that 50% of size difference can be the threshold to initiate intracohort cannibalism in a barramundi population. Cannibalistic polyphenism was likely to occur in barramundi that had a cannibalistic history. An experienced cannibal would have a greater ability to stretch its mouth size to capture a much larger prey than the models predict. The awareness of cannibalistic polyphenism has important application in fish farming management to reduce cannibalism.
Directory of Open Access Journals (Sweden)
Flavio F Ribeiro
Full Text Available This study quantified size-dependent cannibalism in barramundi Lates calcarifer through coupling a range of prey-predator pairs in a different range of fish sizes. Predictive models were developed using morphological traits with the alterative assumption of cannibalistic polyphenism. Predictive models were validated with the data from trials where cannibals were challenged with progressing increments of prey sizes. The experimental observations showed that cannibals of 25-131 mm total length could ingest the conspecific prey of 78-72% cannibal length. In the validation test, all predictive models underestimate the maximum ingestible prey size for cannibals of a similar size range. However, the model based on the maximal mouth width at opening closely matched the empirical observations, suggesting a certain degree of phenotypic plasticity of mouth size among cannibalistic individuals. Mouth size showed allometric growth comparing with body depth, resulting in a decreasing trend on the maximum size of ingestible prey as cannibals grow larger, which in parts explains why cannibalism in barramundi is frequently observed in the early developmental stage. Any barramundi has the potential to become a cannibal when the initial prey size was 58% of their size, suggesting that 50% of size difference can be the threshold to initiate intracohort cannibalism in a barramundi population. Cannibalistic polyphenism was likely to occur in barramundi that had a cannibalistic history. An experienced cannibal would have a greater ability to stretch its mouth size to capture a much larger prey than the models predict. The awareness of cannibalistic polyphenism has important application in fish farming management to reduce cannibalism.
A model to estimate the size of nanoparticle agglomerates in gas−solid fluidized beds
Energy Technology Data Exchange (ETDEWEB)
Martín, Lilian de, E-mail: L.DeMartinMonton@tudelft.nl; Ommen, J. Ruud van [Delft University of Technology, Department of Chemical Engineering (Netherlands)
2013-11-15
The estimation of nanoparticle agglomerates’ size in fluidized beds remains an open challenge, mainly due to the difficulty of characterizing the inter-agglomerate van der Waals force. The current approach is to describe micron-sized nanoparticle agglomerates as micron-sized particles with 0.1–0.2-μm asperities. This simplification does not capture the influence of the particle size on the van der Waals attraction between agglomerates. In this paper, we propose a new description where the agglomerates are micron-sized particles with nanoparticles on the surface, acting as asperities. As opposed to previous models, here the van der Waals force between agglomerates decreases with an increase in the particle size. We have also included an additional force due to the hydrogen bond formation between the surfaces of hydrophilic and dry nanoparticles. The average size of the fluidized agglomerates has been estimated equating the attractive force obtained from this method to the weight of the individual agglomerates. The results have been compared to 54 experimental values, most of them collected from the literature. Our model approximates without a systematic error the size of most of the nanopowders, both in conventional and centrifugal fluidized beds, outperforming current models. Although simple, the model is able to capture the influence of the nanoparticle size, particle density, and Hamaker coefficient on the inter-agglomerate forces.
Economic analysis of open space box model utilization in spacecraft
Mohammad, Atif F.; Straub, Jeremy
2015-05-01
It is a known fact that the amount of data about space that is stored is getting larger on an everyday basis. However, the utilization of Big Data and related tools to perform ETL (Extract, Transform and Load) applications will soon be pervasive in the space sciences. We have entered in a crucial time where using Big Data can be the difference (for terrestrial applications) between organizations underperforming and outperforming their peers. The same is true for NASA and other space agencies, as well as for individual missions and the highly-competitive process of mission data analysis and publication. In most industries, conventional opponents and new candidates alike will influence data-driven approaches to revolutionize and capture the value of Big Data archives. The Open Space Box Model is poised to take the proverbial "giant leap", as it provides autonomic data processing and communications for spacecraft. We can find economic value generated from such use of data processing in our earthly organizations in every sector, such as healthcare, retail. We also can easily find retailers, performing research on Big Data, by utilizing sensors driven embedded data in products within their stores and warehouses to determine how these products are actually used in the real world.
Optimal State-Space Reduction for Pedigree Hidden Markov Models
Kirkpatrick, Bonnie
2012-01-01
To analyze whole-genome genetic data inherited in families, the likelihood is typically obtained from a Hidden Markov Model (HMM) having a state space of 2^n hidden states where n is the number of meioses or edges in the pedigree. There have been several attempts to speed up this calculation by reducing the state-space of the HMM. One of these methods has been automated in a calculation that is more efficient than the naive HMM calculation; however, that method treats a special case and the efficiency gain is available for only those rare pedigrees containing long chains of single-child lineages. The other existing state-space reduction method treats the general case, but the existing algorithm has super-exponential running time. We present three formulations of the state-space reduction problem, two dealing with groups and one with partitions. One of these problems, the maximum isometry group problem was discussed in detail by Browning and Browning. We show that for pedigrees, all three of these problems hav...
A logistics model for large space power systems
Koelle, H. H.
Space Power Systems (SPS) have to overcome two hurdles: (1) to find an attractive design, manufacturing and assembly concept and (2) to have available a space transportation system that can provide economical logistic support during the construction and operational phases. An initial system feasibility study, some five years ago, was based on a reference system that used terrestrial resources only and was based partially on electric propulsion systems. The conclusion was: it is feasible but not yet economically competitive with other options. This study is based on terrestrial and extraterrestrial resources and on chemical (LH 2/LOX) propulsion systems. These engines are available from the Space Shuttle production line and require small changes only. Other so-called advanced propulsion systems investigated did not prove economically superior if lunar LOX is available! We assume that a Shuttle derived Heavy Lift Launch Vehicle (HLLV) will become available around the turn of the century and that this will be used to establish a research base on the lunar surface. This lunar base has the potential to grow into a lunar factory producing LOX and construction materials for supporting among other projects also the construction of space power systems in geostationary orbit. A model was developed to simulate the logistics support of such an operation for a 50-year life cycle. After 50 years 111 SPS units with 5 GW each and an availability of 90% will produce 100 × 5 = 500 GW. The model comprises 60 equations and requires 29 assumptions of the parameter involved. 60-state variables calculated with the 60 equations mentioned above are given on an annual basis and as averages for the 50-year life cycle. Recycling of defective parts in geostationary orbit is one of the features of the model. The state-of-the-art with respect to SPS technology is introduced as a variable Mg mass/MW electric power delivered. If the space manufacturing facility, a maintenance and repair facility
Modeling the effects of size on patch dynamics of an inert tracer
Directory of Open Access Journals (Sweden)
P. Xiu
2009-08-01
Full Text Available Mesoscale iron enrichment experiments have revealed that additional iron affects the phytoplankton productivity and carbon cycle. However, the role of initial size of fertilized patch in determining the patch evolution is poorly quantified due to the limited time of research vessels at sea. Using a three-dimensional ocean circulation model, we simulated different sizes of inert tracer patches that were only regulated by physical circulation and diffusion. Model results showed that during the first few days since release of inert tracer, the calculated dilution rate was found to be a linear function with time, which was sensitive to the initial patch size with steeper slope for smaller size patch. After the initial phase of rapid decay, the relationship between dilution rate and time became an exponential function, which was also size dependent. Therefore, larger initial size patches can usually last longer and ultimately affect biogeochemical processes much stronger than smaller patches.
On bimodal size distribution of spin clusters in the one dimensional Ising model
Ivanytskyi, A. I.; Chelnokov, V. O.
2015-01-01
The size distribution of geometrical spin clusters is exactly found for the one dimensional Ising model of finite extent. For the values of lattice constant $\\beta$ above some "critical value" $\\beta_c$ the found size distribution demonstrates the non-monotonic behavior with the peak corresponding to the size of largest available cluster. In other words, at high values of lattice constant there are two ways to fill the lattice: either to form a single largest cluster or to create many cluster...
Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies
Suh, Peter M.; Conyers, Howard Jason; Mavris, Dimitri N.
2015-01-01
This report introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this report is on tool presentation, verification, and validation. These processes are carried out in stages throughout the report. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust.
Modelling the size effect on the melting temperature of nanoparticles, nanowires and nanofilms
Energy Technology Data Exchange (ETDEWEB)
Safaei, A [Department of Materials Science and Engineering, Tarbiat Modares University, PO Box 14115-143, Tehran (Iran, Islamic Republic of); Shandiz, M Attarian [Department of Materials Science and Engineering, Tarbiat Modares University, PO Box 14115-143, Tehran (Iran, Islamic Republic of); Sanjabi, S [Department of Materials Science and Engineering, Tarbiat Modares University, PO Box 14115-143, Tehran (Iran, Islamic Republic of); Barber, Z H [Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)
2007-05-30
A model has been developed to account for the dependence of melting temperature on the size of nanosolids (nanoparticles, nanowires and nanofilms). In this model the effect of particle size and shape, lattice and surface packing factor, and the coordination number of the lattice and of the surface crystalline planes are considered. A general equation is proposed, having nonlinear form as a function of the reciprocal of nanosolid size. This model is consistent with reported experimental data for nanoparticles of In and Au, nanowires of Pb and In, and nanofilms of In.
Space Partitioning for Privacy Enabled 3D City Models
Filippovska, Y.; Wichmann, A.; Kada, M.
2016-10-01
Due to recent technological progress, data capturing and processing of highly detailed (3D) data has become extensive. And despite all prospects of potential uses, data that includes personal living spaces and public buildings can also be considered as a serious intrusion into people's privacy and a threat to security. It becomes especially critical if data is visible by the general public. Thus, a compromise is needed between open access to data and privacy requirements which can be very different for each application. As privacy is a complex and versatile topic, the focus of this work particularly lies on the visualization of 3D urban data sets. For the purpose of privacy enabled visualizations of 3D city models, we propose to partition the (living) spaces into privacy regions, each featuring its own level of anonymity. Within each region, the depicted 2D and 3D geometry and imagery is anonymized with cartographic generalization techniques. The underlying spatial partitioning is realized as a 2D map generated as a straight skeleton of the open space between buildings. The resulting privacy cells are then merged according to the privacy requirements associated with each building to form larger regions, their borderlines smoothed, and transition zones established between privacy regions to have a harmonious visual appearance. It is exemplarily demonstrated how the proposed method generates privacy enabled 3D city models.
On vector autoregressive modeling in space and time
di Giacinto, Valter
2010-06-01
Despite the fact that it provides a potentially useful analytical tool, allowing for the joint modeling of dynamic interdependencies within a group of connected areas, until lately the VAR approach had received little attention in regional science and spatial economic analysis. This paper aims to contribute in this field by dealing with the issues of parameter identification and estimation and of structural impulse response analysis. In particular, there is a discussion of the adaptation of the recursive identification scheme (which represents one of the more common approaches in the time series VAR literature) to a space-time environment. Parameter estimation is subsequently based on the Full Information Maximum Likelihood (FIML) method, a standard approach in structural VAR analysis. As a convenient tool to summarize the information conveyed by regional dynamic multipliers with a specific emphasis on the scope of spatial spillover effects, a synthetic space-time impulse response function (STIR) is introduced, portraying average effects as a function of displacement in time and space. Asymptotic confidence bands for the STIR estimates are also derived from bootstrap estimates of the standard errors. Finally, to provide a basic illustration of the methodology, the paper presents an application of a simple bivariate fiscal model fitted to data for Italian NUTS 2 regions.
A Bayesian state-space formulation of dynamic occupancy models.
Royle, J Andrew; Kéry, Marc
2007-07-01
Species occurrence and its dynamic components, extinction and colonization probabilities, are focal quantities in biogeography and metapopulation biology, and for species conservation assessments. It has been increasingly appreciated that these parameters must be estimated separately from detection probability to avoid the biases induced by non-detection error. Hence, there is now considerable theoretical and practical interest in dynamic occupancy models that contain explicit representations of metapopulation dynamics such as extinction, colonization, and turnover as well as growth rates. We describe a hierarchical parameterization of these models that is analogous to the state-space formulation of models in time series, where the model is represented by two components, one for the partially observable occupancy process and another for the observations conditional on that process. This parameterization naturally allows estimation of all parameters of the conventional approach to occupancy models, but in addition, yields great flexibility and extensibility, e.g., to modeling heterogeneity or latent structure in model parameters. We also highlight the important distinction between population and finite sample inference; the latter yields much more precise estimates for the particular sample at hand. Finite sample estimates can easily be obtained using the state-space representation of the model but are difficult to obtain under the conventional approach of likelihood-based estimation. We use R and WinBUGS to apply the model to two examples. In a standard analysis for the European Crossbill in a large Swiss monitoring program, we fit a model with year-specific parameters. Estimates of the dynamic parameters varied greatly among years, highlighting the irruptive population dynamics of that species. In the second example, we analyze route occupancy of Cerulean Warblers in the North American Breeding Bird Survey (BBS) using a model allowing for site
A Bayesian state-space formulation of dynamic occupancy models
Royle, J. Andrew; Kery, M.
2007-01-01
Species occurrence and its dynamic components, extinction and colonization probabilities, are focal quantities in biogeography and metapopulation biology, and for species conservation assessments. It has been increasingly appreciated that these parameters must be estimated separately from detection probability to avoid the biases induced by nondetection error. Hence, there is now considerable theoretical and practical interest in dynamic occupancy models that contain explicit representations of metapopulation dynamics such as extinction, colonization, and turnover as well as growth rates. We describe a hierarchical parameterization of these models that is analogous to the state-space formulation of models in time series, where the model is represented by two components, one for the partially observable occupancy process and another for the observations conditional on that process. This parameterization naturally allows estimation of all parameters of the conventional approach to occupancy models, but in addition, yields great flexibility and extensibility, e.g., to modeling heterogeneity or latent structure in model parameters. We also highlight the important distinction between population and finite sample inference; the latter yields much more precise estimates for the particular sample at hand. Finite sample estimates can easily be obtained using the state-space representation of the model but are difficult to obtain under the conventional approach of likelihood-based estimation. We use R and Win BUGS to apply the model to two examples. In a standard analysis for the European Crossbill in a large Swiss monitoring program, we fit a model with year-specific parameters. Estimates of the dynamic parameters varied greatly among years, highlighting the irruptive population dynamics of that species. In the second example, we analyze route occupancy of Cerulean Warblers in the North American Breeding Bird Survey (BBS) using a model allowing for site
Kempe, Marius; Lycett, Stephen; Mesoudi, Alex
2012-01-01
Archaeologists interested in explaining changes in artifact morphology over long time periods have found it useful to create models in which the only source of change is random and unintentional copying error, or 'cultural mutation'. These models can be used as null hypotheses against which to detect non-random processes such as cultural selection or biased transmission. One proposed cultural mutation model is the accumulated copying error model, where individuals attempt to copy the size of another individual's artifact exactly but make small random errors due to physiological limits on the accuracy of their perception. Here, we first derive the model within an explicit mathematical framework, generating the predictions that multiple independently-evolving artifact chains should diverge over time such that their between-chain variance increases while the mean artifact size remains constant. We then present the first experimental test of this model in which 200 participants, split into 20 transmission chains, were asked to faithfully copy the size of the previous participant's handaxe image on an iPad. The experimental findings supported the model's prediction that between-chain variance should increase over time and did so in a manner quantitatively in line with the model. However, when the initial size of the image that the participants resized was larger than the size of the image they were copying, subjects tended to increase the size of the image, resulting in the mean size increasing rather than staying constant. This suggests that items of material culture formed by reductive vs. additive processes may mutate differently when individuals attempt to replicate faithfully the size of previously-produced artifacts. Finally, we show that a dataset of 2601 Acheulean handaxes shows less variation than predicted given our empirically measured copying error variance, suggesting that other processes counteracted the variation in handaxe size generated by perceptual
Validation of elastic cross section models for space radiation applications
Werneth, C. M.; Xu, X.; Norman, R. B.; Ford, W. P.; Maung, K. M.
2017-02-01
The space radiation field is composed of energetic particles that pose both acute and long-term risks for astronauts in low earth orbit and beyond. In order to estimate radiation risk to crew members, the fluence of particles and biological response to the radiation must be known at tissue sites. Given that the spectral fluence at the boundary of the shielding material is characterized, radiation transport algorithms may be used to find the fluence of particles inside the shield and body, and the radio-biological response is estimated from experiments and models. The fidelity of the radiation spectrum inside the shield and body depends on radiation transport algorithms and the accuracy of the nuclear cross sections. In a recent study, self-consistent nuclear models based on multiple scattering theory that include the option to study relativistic kinematics were developed for the prediction of nuclear cross sections for space radiation applications. The aim of the current work is to use uncertainty quantification to ascertain the validity of the models as compared to a nuclear reaction database and to identify components of the models that can be improved in future efforts.
Theories and models on the biological of cells in space
Todd, P.; Klaus, D. M.
1996-01-01
A wide variety of observations on cells in space, admittedly made under constraining and unnatural conditions in may cases, have led to experimental results that were surprising or unexpected. Reproducibility, freedom from artifacts, and plausibility must be considered in all cases, even when results are not surprising. The papers in symposium on 'Theories and Models on the Biology of Cells in Space' are dedicated to the subject of the plausibility of cellular responses to gravity -- inertial accelerations between 0 and 9.8 m/sq s and higher. The mechanical phenomena inside the cell, the gravitactic locomotion of single eukaryotic and prokaryotic cells, and the effects of inertial unloading on cellular physiology are addressed in theoretical and experimental studies.
Theories and models on the Biology of Cells in Space
Todd, P.; Klaus, D. M.
A wide variety of observations on cells in space, admittedly made under constraining and unnatural conditions in many cases, have led to experimental results that were surprising or unexpected. Reproducibility, freedom from artifacts, and plausibility must be considered in all cases, even when results are not surprising. The papers in the symposium on ``Theories and Models on the Biology of Cells in Space'' are dedicated to the subject of theplausibility of cellular responses to gravity -- inertial accelerations between 0 and 9.8 m/s^2 and higher. The mechanical phenomena inside the cell, the gravitactic locomotion of single eukaryotic and prokaryotic cells, and the effects of inertial unloading on cellular physiology are addressed in theoretical and experimental studies.
Monitoring Murder Crime in Namibia Using Bayesian Space-Time Models
Directory of Open Access Journals (Sweden)
Isak Neema
2012-01-01
Full Text Available This paper focuses on the analysis of murder in Namibia using Bayesian spatial smoothing approach with temporal trends. The analysis was based on the reported cases from 13 regions of Namibia for the period 2002–2006 complemented with regional population sizes. The evaluated random effects include space-time structured heterogeneity measuring the effect of regional clustering, unstructured heterogeneity, time, space and time interaction and population density. The model consists of carefully chosen prior and hyper-prior distributions for parameters and hyper-parameters, with inference conducted using Gibbs sampling algorithm and sensitivity test for model validation. The posterior mean estimate of the parameters from the model using DIC as model selection criteria show that most of the variation in the relative risk of murder is due to regional clustering, while the effect of population density and time was insignificant. The sensitivity analysis indicates that both intrinsic and Laplace CAR prior can be adopted as prior distribution for the space-time heterogeneity. In addition, the relative risk map show risk structure of increasing north-south gradient, pointing to low risk in northern regions of Namibia, while Karas and Khomas region experience long-term increase in murder risk.
A model study of the size and composition distribution of aerosols in an aircraft exhaust
Energy Technology Data Exchange (ETDEWEB)
Sorokin, A.A. [SRC `ECOLEN`, Moscow (Russian Federation)
1997-12-31
A two-dimensional, axisymmetric flow field model which includes water and sulphate aerosol formation represented by moments of the size and composition distribution function is used to calculate the effect of radial turbulent jet mixing on the aerosol size distribution and mean modal composition. (author) 6 refs.
Molecular Dynamics Modeling of Tethered Organics in Confined Spaces
Energy Technology Data Exchange (ETDEWEB)
Waksburg, Avi [Monash University, Australia; Nguyen, M [Monash University, Australia; Chaffe, Alan [Monash University, Australia; Kidder, Michelle [ORNL; Buchanan III, A C [ORNL; Britt, Phillip F [ORNL
2011-01-01
A computational method for constructing and evaluating the dynamic behaviour of functionalised hexagonal mesoporous silica (HMS) MCM-41 models is reported. HMS with three pore diameters (1.7, 2.2 and 2.9 nm) were prepared, and, from these, two series of derivative structures were constructed - one with 1,3-diphenylpropyl (DPP) tethers and the other with smaller dimethylsilyl (DMS) tethers attached to the mesopores internal surfaces. Comparison with experimental data shows that simulation results correctly predict the maximum tether density that can be achieved for each tether and each pore diameter. For the smaller pore models, the extent of DPP functionalisation that can be achieved is limited by the available pore volume. However, for the larger pore model, the extent of functionalisation is limited by access to potentially reactive sites on the pore surface. The dynamic behaviour of the models was investigated over a range of temperatures (240-648 K). At lower temperatures (< 400 K), the mobility of DPP tethers in the 2.9 nm model is actually less than that observed in either the 2.2 nm model or the 1.7 nm model due to the extensive non-bonded interactions that are able to develop between tethers and the silica surface at this diameter. At higher temperatures, the free ends of these tethers break away from the surface, extend further into the pore space and the DPP mobility in the 2.9 nm model is higher than in the smaller pore systems.
Nonlinear State Space Modeling and System Identification for Electrohydraulic Control
Directory of Open Access Journals (Sweden)
Jun Yan
2013-01-01
Full Text Available The paper deals with nonlinear modeling and identification of an electrohydraulic control system for improving its tracking performance. We build the nonlinear state space model for analyzing the highly nonlinear system and then develop a Hammerstein-Wiener (H-W model which consists of a static input nonlinear block with two-segment polynomial nonlinearities, a linear time-invariant dynamic block, and a static output nonlinear block with single polynomial nonlinearity to describe it. We simplify the H-W model into a linear-in-parameters structure by using the key term separation principle and then use a modified recursive least square method with iterative estimation of internal variables to identify all the unknown parameters simultaneously. It is found that the proposed H-W model approximates the actual system better than the independent Hammerstein, Wiener, and ARX models. The prediction error of the H-W model is about 13%, 54%, and 58% less than the Hammerstein, Wiener, and ARX models, respectively.
Implementing a multispecies size-spectrum model in a data-poor ecosystem
Institute of Scientific and Technical Information of China (English)
ZHANG Chongliang; CHEN Yong; THOMPSON Katherine; REN Yiping
2016-01-01
Multispecies ecological models have been used for predicting the effects of fishing activity and evaluating the performance of management strategies. Size-spectrum models are one type of physiologically-structured ecological model that provide a feasible approach to describing fish communities in terms of individual dietary variation and ontogenetic niche shift. Despite the potential of ecological models in improving our understanding of ecosystems, their application is usually limited for data-poor fisheries. As a first step in implementing ecosystem-based fisheries management (EBFM), this study built a size-spectrum model for the fish community in the Haizhou Bay, China. We describe data collection procedures and model parameterization to facilitate the implementation of such size-spectrum models for future studies of data-poor ecosystems. The effects of fishing on the ecosystem were exemplified with a range of fishing effort and were monitored with a set of ecological indicators. Total community biomass, biodiversity index, W-statistic, LFI (Large fish index), MeanW (mean body weight) and Slope (slope of community size spectra) showed a strong non-linear pattern in response to fishing pressure, and largest fishing effort did not generate the most drastic responses in certain scenarios. We emphasize the value and feasibility of developing size-spectrum models to capture ecological dynamics and suggest limitations as well as potential for model improvement. This study aims to promote a wide use of this type of model in support of EBFM.
Extension of the gurson model accounting for the void size effect
Institute of Scientific and Technical Information of China (English)
Jie Wen; Keh-Chih Hwang; Yonggang Huang
2005-01-01
A continuum model of solids with cylindrical microvoids is proposed based on the Taylor dislocation model.The model is an extension of Gurson model in the sense that the void size effect is accounted for. Beside the void volume fraction f, the intrinsic material length l becomes a parameter representing voids since the void size comes into play in the Gurson model. Approximate yield functions in analytic forms are suggested for both solids with cylindrical microvoids and with spherical microvoids. The application to uniaxial tension curves shows a precise agreement between the approximate analytic yield function and the "exact" parametric form of integrals.
Haveman, Steven; Bonnema, Gerrit Maarten
2013-01-01
Most formal models are used in detailed design and focus on a single domain. Few effective approaches exist that can effectively tie these lower level models to a high level system model during design space exploration. This complicates the validation of high level system requirements during
Space shuttle’s liftoff: a didactical model
Borghi, Riccardo; Spinozzi, Turi Maria
2017-07-01
The pedagogical aim of the present paper, thought for an undergraduate audience, is to help students to appreciate how the development of elementary models based on physics first principles is a fundamental and necessary preliminary step for the behaviour of complex real systems to be grasped with minimal amounts of math. In some particularly fortunate cases, such models also show reasonably good results when are compared to reality. The speed behaviour of the Space Shuttle during its first two minutes of flight from liftoff is here analysed from such a didactical point of view. Only the momentum conservation law is employed to develop the model, which is eventually applied to quantitatively interpret the telemetry of the 2011 last launches of Shuttle Discovery and Shuttle Endeavour. To the STS-51-L and STS-107 astronauts, in memoriam.
Real space renormalization group theory of disordered models of glasses.
Angelini, Maria Chiara; Biroli, Giulio
2017-03-28
We develop a real space renormalization group analysis of disordered models of glasses, in particular of the spin models at the origin of the random first-order transition theory. We find three fixed points, respectively, associated with the liquid state, with the critical behavior, and with the glass state. The latter two are zero-temperature ones; this provides a natural explanation of the growth of effective activation energy scale and the concomitant huge increase of relaxation time approaching the glass transition. The lower critical dimension depends on the nature of the interacting degrees of freedom and is higher than three for all models. This does not prevent 3D systems from being glassy. Indeed, we find that their renormalization group flow is affected by the fixed points existing in higher dimension and in consequence is nontrivial. Within our theoretical framework, the glass transition results in an avoided phase transition.
[Prognostic model of the space station contamination stage].
Zlotovol'skiĭ, V M; Smolenskaia, G S
1998-01-01
Forty two non-metallic materials, 8 human metabolites and a process liquid (ethylene glycol) were selected for development of a prognostic model of space station contamination by harmful trace admixtures (HTAs). Removal technologies made allowance for absorption by atmospheric condensate (AC) and filter adsorption. Calculations took in 18 HTAs representative of 8 classes of compounds. Simulation modeling allowed to determine HTA migration rates and percent ratio (1), calculate concentrations of contaminants in the atmosphere and atmospheric condensate (2), and to assess filter efficiency by comparison of loads on the filter and a refrigeration/drying set (3). Comparison of empirical and measured data permitted conclusions about adequacy of the model and its potentiality for predicting ramifications of nominal and contingency situations.
Energy Technology Data Exchange (ETDEWEB)
Tonks, Michael R [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bai, Xianming [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2014-06-01
This report summarizes development work funded by the Nuclear Energy Advanced Modeling Simulation program's Fuels Product Line (FPL) to develop a mechanistic model for the average grain size in UO₂ fuel. The model is developed using a multiscale modeling and simulation approach involving atomistic simulations, as well as mesoscale simulations using INL's MARMOT code.
Modeling size segregation of granular materials: the roles of segregation, advection and diffusion
Fan, Yi; Umbanhowar, Paul B; Ottino, Julio M; Lueptow, Richard M
2014-01-01
Predicting segregation of granular materials composed of different-sized particles is a challenging problem. In this paper, we develop and implement a theoretical model that captures the interplay between advection, segregation, and diffusion in size bidisperse granular materials. The fluxes associated with these three driving factors depend on the underlying kinematics, whose characteristics play key roles in determining particle segregation configurations. Unlike previous models for segregation, our model uses parameters based on kinematic measures from discrete element method simulations instead of arbitrarily adjustable fitting parameters, and it achieves excellent quantitative agreement with both experimental and simulation results when applied to quasi-two-dimensional bounded heaps. The model yields two dimensionless control parameters, both of which are only functions of physically control parameters (feed rate, particle sizes, and system size) and kinematic parameters (diffusion coefficient, flowing l...
Operational Space Weather Models: Trials, Tribulations and Rewards
Schunk, R. W.; Scherliess, L.; Sojka, J. J.; Thompson, D. C.; Zhu, L.
2009-12-01
There are many empirical, physics-based, and data assimilation models that can probably be used for space weather applications and the models cover the entire domain from the surface of the Sun to the Earth’s surface. At Utah State University we developed two physics-based data assimilation models of the terrestrial ionosphere as part of a program called Global Assimilation of Ionospheric Measurements (GAIM). One of the data assimilation models is now in operational use at the Air Force Weather Agency (AFWA) in Omaha, Nebraska. This model is a Gauss-Markov Kalman Filter (GAIM-GM) model, and it uses a physics-based model of the ionosphere and a Kalman filter as a basis for assimilating a diverse set of real-time (or near real-time) measurements. The physics-based model is the Ionosphere Forecast Model (IFM), which is global and covers the E-region, F-region, and topside ionosphere from 90 to 1400 km. It takes account of five ion species (NO+, O2+, N2+, O+, H+), but the main output of the model is a 3-dimensional electron density distribution at user specified times. The second data assimilation model uses a physics-based Ionosphere-Plasmasphere Model (IPM) and an ensemble Kalman filter technique as a basis for assimilating a diverse set of real-time (or near real-time) measurements. This Full Physics model (GAIM-FP) is global, covers the altitude range from 90 to 30,000 km, includes six ions (NO+, O2+, N2+, O+, H+, He+), and calculates the self-consistent ionospheric drivers (electric fields and neutral winds). The GAIM-FP model is scheduled for delivery in 2012. Both of these GAIM models assimilate bottom-side Ne profiles from a variable number of ionosondes, slant TEC from a variable number of ground GPS/TEC stations, in situ Ne from four DMSP satellites, line-of-sight UV emissions measured by satellites, and occultation data. Quality control algorithms for all of the data types are provided as an integral part of the GAIM models and these models take account of
A Knowledge Discovery from POS Data using State Space Models
Sato, Tadahiko; Higuchi, Tomoyuki
The number of competing-brands changes by new product's entry. The new product introduction is endemic among consumer packaged goods firm and is an integral component of their marketing strategy. As a new product's entry affects markets, there is a pressing need to develop market response model that can adapt to such changes. In this paper, we develop a dynamic model that capture the underlying evolution of the buying behavior associated with the new product. This extends an application of a dynamic linear model, which is used by a number of time series analyses, by allowing the observed dimension to change at some point in time. Our model copes with a problem that dynamic environments entail: changes in parameter over time and changes in the observed dimension. We formulate the model with framework of a state space model. We realize an estimation of the model using modified Kalman filter/fixed interval smoother. We find that new product's entry (1) decreases brand differentiation for existing brands, as indicated by decreasing difference between cross-price elasticities; (2) decreases commodity power for existing brands, as indicated by decreasing trend; and (3) decreases the effect of discount for existing brands, as indicated by a decrease in the magnitude of own-brand price elasticities. The proposed framework is directly applicable to other fields in which the observed dimension might be change, such as economic, bioinformatics, and so forth.
Reliability models applicable to space telescope solar array assembly system
Patil, S. A.
1986-01-01
A complex system may consist of a number of subsystems with several components in series, parallel, or combination of both series and parallel. In order to predict how well the system will perform, it is necessary to know the reliabilities of the subsystems and the reliability of the whole system. The objective of the present study is to develop mathematical models of the reliability which are applicable to complex systems. The models are determined by assuming k failures out of n components in a subsystem. By taking k = 1 and k = n, these models reduce to parallel and series models; hence, the models can be specialized to parallel, series combination systems. The models are developed by assuming the failure rates of the components as functions of time and as such, can be applied to processes with or without aging effects. The reliability models are further specialized to Space Telescope Solar Arrray (STSA) System. The STSA consists of 20 identical solar panel assemblies (SPA's). The reliabilities of the SPA's are determined by the reliabilities of solar cell strings, interconnects, and diodes. The estimates of the reliability of the system for one to five years are calculated by using the reliability estimates of solar cells and interconnects given n ESA documents. Aging effects in relation to breaks in interconnects are discussed.
Finite Size Corrected Relativistic Mean-Field Model and QCD Critical End Point
Uddin, Saeed; Ahmad, Jan Shabir
2012-01-01
The effect of finite size of hadrons on the QCD phase diagram is analyzed using relativistic mean field model for the hadronic phase and the Bag model for the QGP phase. The corrections to the EOS for hadronic phase are incorporated in a thermodynamic consistent manner for Van der Waals like interaction. It is found that the effect of finite size of baryons is to shift CEP to higher chemical potential values.
Differential geometry of the space of Ising models
Machta, Benjamin; Chachra, Ricky; Transtrum, Mark; Sethna, James
2012-02-01
We use information geometry to understand the emergence of simple effective theories, using an Ising model perturbed with terms coupling non-nearest-neighbor spins as an example. The Fisher information is a natural metric of distinguishability for a parameterized space of probability distributions, applicable to models in statistical physics. Near critical points both the metric components (four-point susceptibilities) and the scalar curvature diverge with corresponding critical exponents. However, connections to Renormalization Group (RG) ideas have remained elusive. Here, rather than looking at RG flows of parameters, we consider the reparameterization-invariant flow of the manifold itself. To do this we numerically calculate the metric in the original parameters, taking care to use only information available after coarse-graining. We show that under coarse-graining the metric contracts very anisotropically, leading to a ``sloppy'' spectrum with the metric's Eigenvalues spanning many orders of magnitude. Our results give a qualitative explanation for the success of simple models: most directions in parameter space become fundamentally indistinguishable after coarse-graining.
Simulation Modeling and Performance Evaluation of Space Networks
Jennings, Esther H.; Segui, John
2006-01-01
In space exploration missions, the coordinated use of spacecraft as communication relays increases the efficiency of the endeavors. To conduct trade-off studies of the performance and resource usage of different communication protocols and network designs, JPL designed a comprehensive extendable tool, the Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE). The design and development of MACHETE began in 2000 and is constantly evolving. Currently, MACHETE contains Consultative Committee for Space Data Systems (CCSDS) protocol standards such as Proximity-1, Advanced Orbiting Systems (AOS), Packet Telemetry/Telecommand, Space Communications Protocol Specification (SCPS), and the CCSDS File Delivery Protocol (CFDP). MACHETE uses the Aerospace Corporation s Satellite Orbital Analysis Program (SOAP) to generate the orbital geometry information and contact opportunities. Matlab scripts provide the link characteristics. At the core of MACHETE is a discrete event simulator, QualNet. Delay Tolerant Networking (DTN) is an end-to-end architecture providing communication in and/or through highly stressed networking environments. Stressed networking environments include those with intermittent connectivity, large and/or variable delays, and high bit error rates. To provide its services, the DTN protocols reside at the application layer of the constituent internets, forming a store-and-forward overlay network. The key capabilities of the bundling protocols include custody-based reliability, ability to cope with intermittent connectivity, ability to take advantage of scheduled and opportunistic connectivity, and late binding of names to addresses. In this presentation, we report on the addition of MACHETE models needed to support DTN, namely: the Bundle Protocol (BP) model. To illustrate the use of MACHETE with the additional DTN model, we provide an example simulation to benchmark its performance. We demonstrate the use of the DTN protocol
Insular dwarfism in hippos and a model for brain size reduction in Homo floresiensis.
Weston, Eleanor M; Lister, Adrian M
2009-05-07
Body size reduction in mammals is usually associated with only moderate brain size reduction, because the brain and sensory organs complete their growth before the rest of the body during ontogeny. On this basis, 'phyletic dwarfs' are predicted to have a greater relative brain size than 'phyletic giants'. However, this trend has been questioned in the special case of dwarfism of mammals on islands. Here we show that the endocranial capacities of extinct dwarf species of hippopotamus from Madagascar are up to 30% smaller than those of a mainland African ancestor scaled to equivalent body mass. These results show that brain size reduction is much greater than predicted from an intraspecific 'late ontogenetic' model of dwarfism in which brain size scales to body size with an exponent of 0.35. The nature of the proportional change or grade shift observed here indicates that selective pressures on brain size are potentially independent of those on body size. This study demonstrates empirically that it is mechanistically possible for dwarf mammals on islands to evolve significantly smaller brains than would be predicted from a model of dwarfing based on the intraspecific scaling of the mainland ancestor. Our findings challenge current understanding of brain-body allometric relationships in mammals and suggest that the process of dwarfism could in principle explain small brain size, a factor relevant to the interpretation of the small-brained hominin found on the Island of Flores, Indonesia.
Institute of Scientific and Technical Information of China (English)
SUN Zai; HUANG Zhen; WANG JiaSong
2007-01-01
A size-specific aerosol dynamic model is set up to predict the evolution of particle number concentration within a chamber. Particle aggregation is based on the theory of Brownian coagulation, and the model not only comprises particle loss due to coagulation, but also considers the formation of large particles by collision. To validate the model, three different groups of chamber experiments with SMPS (Scanning Mobility Particle Sizer) are conducted. The results indicate that the advantage of the model over the past simple size bin model is its provision of detailed information of size spectrum evolution,and the results can be used to analyze the variations of number concentration and CMD (Count Median Diameter). Furthermore, some aerosol dynamic mechanisms that cannot be measured by instrument can be analyzed by the model simulation, which is significant for better understanding the removal and control mechanisms of ultrafine particles.
A Model for Predicting Thermomechanical Response of Large Space Structures.
1984-06-01
Dr. Tony Amos (202)767-4937 u.DD FORM 1473, 83 APR EDITION OF I JAN 73 IS OBSOLETE. SECURITY CLASSIFICATION CF THIS PAGE .. ’o 1 v A MODEL FOR...SYMBOL Dr. Tony Amos (202)767-4937 SDD FORM 1473, 83 APR E c , TION OF 1 JAN 73 ,S OBSOLETE. SECLUHITY (CLASSI. ICATION Oi) THI PAGE -i LARGE SPACE...94] for predicting the buckling loads associated with general instability of beam-like lattice trusses. Bazant and Christensen [95] present a
A Coarse Estimation of Cell Size Region from a Mesoscopic Stochastic Cell Cycle Model
Yi, Ming; Jia, Ya; Liu, Quan; Zhu, Chun-Lian; Yang, Li-Jian
2007-07-01
Based on a deterministic cell cycle model of fission yeast, the effects of the finite cell size on the cell cycle regulation in wee1- cdc25Δ double mutant type are numerically studied by using of the chemical Langevin equations. It is found that at a certain region of cell size, our numerical results from the chemical Langevin equations are in good qualitative agreement with the experimental observations. The two resettings to the G2 phase from early stages of mitosis can be induced under the moderate cell size. The quantized cycle times can be observed during such a cell size region. Therefore, a coarse estimation of cell size is obtained from the mesoscopic stochastic cell cycle model.
Modelling the impact of intrinsic size and luminosity correlations on magnification estimation
Ciarlariello, Sandro
2016-01-01
Spatial correlations of the observed sizes and luminosities of galaxies can be used to estimate the magnification that arises through weak gravitational lensing. However, the intrinsic prop- erties of galaxies can be similarly correlated through local physical effects, and these present a possible contamination to the weak lensing estimation. In an earlier paper (Ciarlariello et al. 2015) we modelled the intrinsic size correlations using the halo model, assuming the galaxy sizes reflect the mass in the associated halo. Here we extend this work to consider galaxy magnitudes and show that these may be even more affected by intrinsic correlations than galaxy sizes, making this a bigger systematic for measurements of the weak lensing signal. We also quantify how these intrinsic correlations are affected by sample selection criteria based on sizes and magnitudes.
A Coarse Estimation of Cell Size Region from a Mesoscopic Stochastic Cell Cycle Model
Institute of Scientific and Technical Information of China (English)
YI Ming; JIA Ya; LIU Quan; ZHU Chun-Lian; YANG Li-Jian
2007-01-01
Based on a deterministic cell cycle model of fission yeast, the effects of the finite cell size on the cell cycle regulation in wee1- cdc25△ double mutant type are numerically studied by using of the chemical Langevin equations. It is found that at a certain region of cell size, our numerical results from the chemical Langevin equations are in good qualitative agreement with the experimental observations. The two resettings to the G2 phase from early stages of mitosis can be induced under the moderate cell size. The quantized cycle times can be observed during such a cell size region. Therefore, a coarse estimation of cell size is obtained from the mesoscopic stochastic cell cycle model.
A Bounding Surface Plasticity Model for Intact Rock Exhibiting Size-Dependent Behaviour
Masoumi, Hossein; Douglas, Kurt J.; Russell, Adrian R.
2016-01-01
A new constitutive model for intact rock is presented recognising that rock strength, stiffness and stress-strain behaviour are affected by the size of the rock being subjected to loading. The model is formulated using bounding surface plasticity theory. It is validated against a new and extensive set of unconfined compression and triaxial compression test results for Gosford sandstone. The samples tested had diameters ranging from 19 to 145 mm and length-to-diameter ratios of 2. The model captures the continuous nonlinear stress-strain behaviour from initial loading, through peak strength to large shear strains, including transition from brittle to ductile behaviour. The size dependency was accounted for through a unified size effect law applied to the unconfined compressive strength—a key model input parameter. The unconfined compressive strength increases with sample size before peaking and then decreasing with further increasing sample size. Inside the constitutive model two hardening laws act simultaneously, each driven by plastic shear strains. The elasticity is stress level dependent. Simple linear loading and bounding surfaces are adopted, defined using the Mohr-Coulomb criterion, along with a non-associated flow rule. The model simulates well the stress-strain behaviour of Gosford sandstone at confining pressures ranging from 0 to 30 MPa for the variety of sample sizes considered.
Analysis of litter size and average litter weight in pigs using a recursive model
DEFF Research Database (Denmark)
Varona, Luis; Sorensen, Daniel; Thompson, Robin
2007-01-01
An analysis of litter size and average piglet weight at birth in Landrace and Yorkshire using a standard two-trait mixed model (SMM) and a recursive mixed model (RMM) is presented. The RMM establishes a one-way link from litter size to average piglet weight. It is shown that there is a one......-to-one correspondence between the parameters of SMM and RMM and that they generate equivalent likelihoods. As parameterized in this work, the RMM tests for the presence of a recursive relationship between additive genetic values, permanent environmental effects, and specific environmental effects of litter size...
Influence of Li-ion Battery Models in the Sizing of Hybrid Storage Systems with Supercapacitors
DEFF Research Database (Denmark)
Pinto, Claudio; Barreras, Jorge Varela; de Castro, Ricardo
2014-01-01
This paper presents a comparative study of the influence of different aggregated electrical circuit battery models in the sizing process of a hybrid energy storage system (ESS), composed by Li-ion batteries and supercapacitors (SCs). The aim is to find the number of cells required to propel......-order dynamics of the battery. Simulation results demonstrate that the adoption of a more accurate battery model in the sizing of hybrid ESSs prevents over-sizing, leading to a reduction in the number of cells of up to 29%, and a cost decrease of up to 10%....
Modeling loggerhead turtle movement in the Mediterranean: importance of body size and oceanography.
Eckert, Scott A; Moore, Jeffrey E; Dunn, Daniel C; van Buiten, Ricardo Sagarminaga; Eckert, Karen L; Halpin, Patrick N
2008-03-01
Adapting state-space models (SSMs) to telemetry data has been helpful for dealing with location error and for modeling animal movements. We used a combination of two hierarchical Bayesian SSMs to estimate movement pathways from Argos satellite-tag data for 15 juvenile loggerhead turtles (Caretta caretta) in the western Mediterranean Sea, and to probabilistically assign locations to one of two behavioral movement types and relate those behaviors to environmental features. A Monte Carlo procedure helped propagate location uncertainty from the first SSM into the estimation of behavioral states and environment--behavior relationships in the second SSM. Turtles using oceanic habitats of the Balearic Sea (n = 9 turtles) within the western Mediterranean were more likely to exhibit "intensive search" behavior as might occur during foraging, but only larger turtles responded to variations in sea-surface height. This suggests that they were better able than smaller turtles to cue on environmental features that concentrate prey resources or were more dependent on high-quality feeding areas. These findings stress the importance of individual heterogeneity in the analysis of movement behavior and, taken in concert with descriptive studies of Pacific loggerheads, suggest that directed movements toward patchy ephemeral resources may be a general property of larger juvenile loggerheads in different populations. We discovered size-based variation in loggerhead distribution and documented use of the western Mediterranean Sea by turtles larger than previously thought to occur there. With one exception, only individuals > 57 cm curved carapace length used the most westerly basin in the Mediterranean (western Alborán Sea). These observations shed new light on loggerhead migration phenology.
Flyby of Large-Size Space Debris Objects Situated at Leo with Their Successive De-Orbiting
Directory of Open Access Journals (Sweden)
A. A. Baranov
2016-01-01
Full Text Available Regarding the large-size space debris objects with a cross-section more than 5 m2 situated at LEO, it is possible to mark out 5 non-structured groups of such objects according to their spatial distribution. The orbits of objects in a group have approximately the same inclinations whereas the deviations in the Right Ascension of the Ascending node (RAAN may be arbitrary. The features of changing orbital planes’ mutual orientation in a group are seen from the RAAN deviations’ evolution portrait. The flights between the objects are being executed by a single active space vehicle (SV which captures a LSSD object and takes it away to the especially calculated circular or elliptical low disposal orbit (DO, and then returns back for the next object.The calculation of flyby maneuvers, in fact, breaks up into two independent tasks. At first, one can determine the parameters of the DO for each LSSD object using special software, so the coplanar maneuvers can be calculated ensuring the object’s transition to this orbit. Secondly, the flight to attain a new object is carried out from the DO of the previous object at the moment when their orbital planes will become equal. So it is possible to calculate the maneuvers, which help to return back for the next object, using numerical-analytical algorithm developed for noncoplanar rendez-vous of middle duration.The time interval for an active SV to stay at the DO is defined by difference of precession velocities of orbital planes of the de-orbited object and of the next object. The usage of a circular DO allows an LSSD object to leave promptly from the region (over 700 km where active SVs and other debris exist for a long time, whereas the apogee of the elliptical DO remains in the mentioned belt for 10 years. While forming elliptical DO one will need approximately 30% less of required summary characteristic velocity as compared with circular DO. The collision risk for an object staying at the elliptical DO
Directory of Open Access Journals (Sweden)
E.E. Uzgiris
2008-01-01
Full Text Available Tumor endothelial leakiness is quantified in a rat mammary adenocarcinoma model using dynamic contrast enhancement MRI and contrast agents of widely varying sizes. The contrast agents were constructed to be of globular configuration and have their uptake rate into tumor interstitium be driven by the same diffusion process and limited only by the availability of endothelial pores of passable size. It was observed that the endothelial pore distribution has a steep power law dependence on size, r−β, with an exponent of −4.1. The model of large pore dominance in tumor leakiness as reported in some earlier investigation with fluorescent probes and optical chamber methods is rejected for this tumor model and a number of other tumor types including chemically induced tumors. This steep power law dependence on size is also consistent with observations on human breast cancer.
Space Weathering of Olivine: Samples, Experiments and Modeling
Keller, L. P.; Berger, E. L.; Christoffersen, R.
2016-01-01
Olivine is a major constituent of chondritic bodies and its response to space weathering processes likely dominates the optical properties of asteroid regoliths (e.g. S- and many C-type asteroids). Analyses of olivine in returned samples and laboratory experiments provide details and insights regarding the mechanisms and rates of space weathering. Analyses of olivine grains from lunar soils and asteroid Itokawa reveal that they display solar wind damaged rims that are typically not amorphized despite long surface exposure ages, which are inferred from solar flare track densities (up to 10 (sup 7 y)). The olivine damaged rim width rapidly approaches approximately 120 nm in approximately 10 (sup 6 y) and then reaches steady-state with longer exposure times. The damaged rims are nanocrystalline with high dislocation densities, but crystalline order exists up to the outermost exposed surface. Sparse nanophase Fe metal inclusions occur in the damaged rims and are believed to be produced during irradiation through preferential sputtering of oxygen from the rims. The observed space weathering effects in lunar and Itokawa olivine grains are difficult to reconcile with laboratory irradiation studies and our numerical models that indicate that olivine surfaces should readily blister and amorphize on relatively short time scales (less than 10 (sup 3 y)). These results suggest that it is not just the ion fluence alone, but other variable, the ion flux that controls the type and extent of irradiation damage that develops in olivine. This flux dependence argues for caution in extrapolating between high flux laboratory experiments and the natural case. Additional measurements, experiments, and modeling are required to resolve the discrepancies among the observations and calculations involving solar wind processing of olivine.
Model of strong stationary vortex turbulence in space plasmas
Directory of Open Access Journals (Sweden)
G. D. Aburjania
2009-01-01
Full Text Available This paper investigates the macroscopic consequences of nonlinear solitary vortex structures in magnetized space plasmas by developing theoretical model of plasma turbulence. Strongly localized vortex patterns contain trapped particles and, propagating in a medium, excite substantial density fluctuations and thus, intensify the energy, heat and mass transport processes, i.e., such vortices can form strong vortex turbulence. Turbulence is represented as an ensemble of strongly localized (and therefore weakly interacting vortices. Vortices with various amplitudes are randomly distributed in space (due to collisions. For their description, a statistical approach is applied. It is supposed that a stationary turbulent state is formed by balancing competing effects: spontaneous development of vortices due to nonlinear twisting of the perturbations' fronts, cascading of perturbations into short scales (direct spectral cascade and collisional or collisionless damping of the perturbations in the short-wave domain. In the inertial range, direct spectral cascade occurs through merging structures via collisions. It is shown that in the magneto-active plasmas, strong turbulence is generally anisotropic Turbulent modes mainly develop in the direction perpendicular to the local magnetic field. It is found that it is the compressibility of the local medium which primarily determines the character of the turbulent spectra: the strong vortex turbulence forms a power spectrum in wave number space. For example, a new spectrum of turbulent fluctuations in k^{−8/3} is derived which agrees with available experimental data. Within the framework of the developed model particle diffusion processes are also investigated. It is found that the interaction of structures with each other and particles causes anomalous diffusion in the medium. The effective coefficient of diffusion has a square root dependence on the stationary level of noise.
Confronting AeroCom models with particle size distribution data from surface in situ stations
Platt, Stephen; Fiebig, Markus; Mann, Graham; Schulz, Michael
2016-04-01
The size distribution is the most important property for describing any interaction of an aerosol particle population with its surroundings. In first order, it determines both, the aerosol optical properties quantifying the direct aerosol climate effect, and the fraction of aerosol particles acting as cloud condensation nuclei quantifying the indirect aerosol climate effect. Aerosol schemes of modern climate models resolve the aerosol particle size distribution (APSD) explicitly. In improving the skill of climate models, it is therefore highly useful to confront these models with precision APSD data observed at surface stations. Corresponding previous work focussed on comparing size integrated, seasonal particle concentrations at selected sites with ensemble model averages to assess overall model skill. Building on this work, this project intends to refine the approach by comparing median particle size and integral concentration of fitted modal size distributions. It will also look at skill differences between models in order to find reasons for matches and discrepancies. The presentation will outline the project, and will elaborate on input requested from modelling groups to participate in the exercise.
The Harari Shupe preon model and nonrelativistic quantum phase space
Żenczykowski, P.
2008-03-01
We propose that the whole algebraic structure of the Harari-Shupe rishon model originates via a Dirac-like linearization of quadratic form x2 +p2, with position and momentum satisfying standard commutation relations. The scheme does not invoke the concept of preons as spin-1/2 subparticles, thus evading the problem of preon confinement, while fully explaining all symmetries emboded in the Harari-Shupe model. Furthermore, the concept of quark colour is naturally linked to the ordering of rishons. Our scheme leads to group U (1) ⊗ SU (3) combined with SU (2), with two of the SU (2) generators not commuting with reflections. An interpretation of intra-generation quark-lepton transformations in terms of genuine rotations and reflections in phase space is proposed.
Automated photogrammetry for three-dimensional models of urban spaces
Leberl, Franz; Meixner, Philipp; Wendel, Andreas; Irschara, Arnold
2012-02-01
The location-aware Internet is inspiring intensive work addressing the automated assembly of three-dimensional models of urban spaces with their buildings, circulation spaces, vegetation, signs, even their above-ground and underground utility lines. Two-dimensional geographic information systems (GISs) and municipal utility information exist and can serve to guide the creation of models being built with aerial, sometimes satellite imagery, streetside images, indoor imaging, and alternatively with light detection and ranging systems (LiDARs) carried on airplanes, cars, or mounted on tripods. We review the results of current research to automate the information extraction from sensor data. We show that aerial photography at ground sampling distances (GSD) of 1 to 10 cm is well suited to provide geometry data about building facades and roofs, that streetside imagery at 0.5 to 2 cm is particularly interesting when it is collected within community photo collections (CPCs) by the general public, and that the transition to digital imaging has opened the no-cost option of highly overlapping images in support of a more complete and thus more economical automation. LiDAR-systems are a widely used source of three-dimensional data, but they deliver information not really superior to digital photography.
MODEL JOINT ECONOMIC LOT SIZE PADA KASUS PEMASOK-PEMBELI DENGAN PERMINTAAN PROBABILISTIK
Directory of Open Access Journals (Sweden)
Wakhid Ahmad Jauhari
2009-01-01
Full Text Available In this paper we consider single vendor single buyer integrated inventory model with probabilistic demand and equal delivery lot size. The model contributes to the current literature by relaxing the deterministic demand assumption which has been used for almost all integrated inventory models. The objective is to minimize expected total costs incurred by the vendor and the buyer. We develop effective iterative procedures for finding the optimal solution. Numerical examples are used to illustrate the benefit of integration. A sensitivity analysis is performed to explore the effect of key parameters on delivery lot size, safety factor, production lot size factor and the expected total cost. The results of the numerical examples indicate that our models can achieve a significant amount of savings. Finally, we compare the results of our proposed model with a simulation model. Abstract in Bahasa Indonesia: Pada penelitian ini akan dikembangkan model gabungan pemasok-pembeli dengan permintaan probabilistik dan ukuran pengiriman sama. Pada model setiap lot pemesanan akan dikirim dalam beberapa lot pengiriman dan pemasok akan memproduksi barang dalam ukuran batch produksi yang merupakan kelipatan integer dari lot pengiriman. Dikembangkan pula suatu algoritma untuk menyelesaikan model matematis yang telah dibuat. Selain itu, pengaruh perubahan parameter terhadap perilaku model diteliti dengan analisis sensitivitas terhadap beberapa parameter kunci, seperti ukuran lot, stok pengaman dan total biaya persediaan. Pada penelitian ini juga dibuat model simulasi untuk melihat performansi model matematis pada kondisi nyata. Kata kunci: model gabungan, permintaan probabilistik, lot pengiriman, supply chain
Assembly interruptability robustness model with applications to Space Station Freedom
Wade, James William
1991-02-01
Interruptability robustness of a construction project together with its assembly sequence may be measured by calculating the probability of its survival and successful completion in the face of unplanned interruptions of the assembly process. Such an interruption may jeopardize the survival of the structure being assembled, the survival of the support equipment, and/or the safety of the members of the construction crew, depending upon the stage in the assembly sequence when the interruption occurs. The interruption may be due to a number of actors such as: machinery break-downs, environmental damage, worker emergency illness or injury, etc. Each source of interruption has a probability of occurring, and adds an associated probability of loss, schedule delay, and cost to the project. Several options may exist for reducing the consequences of an interruption at a given point in the assembly sequence, including altering the assembly sequence, adding extra components or equipment as interruptability 'insurance', increasing the capability of support facilities, etc. Each option may provide a different overall performance of the project as it relates to success, assembly time, and project cost. The Interruptability Robustness Model was devised and provides a method which allows the overall interruptability robustness of construction of a project design and its assembly sequence to be quantified. In addition, it identifies the susceptibility to interruptions for the assembly sequence at all points within the assembly sequence. The model is applied to the present problem of quantifying and improving interruptability robustness during the construction of Space Station Freedom. This application was used as a touchstone for devising the Interruptability Robustness Model. However, the model may be utilized to assist in the analysis of interruptability robustness for other space-related construction projects such as the lunar base and orbital assembly of the manned Mars
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Adrien Fredj Baranes
2014-10-01
Full Text Available Devising efficient strategies for exploration in large open-ended spaces is one of the most difficult computational problems of intelligent organisms. Because the available rewards are ambiguous or unknown during the exploratory phase, subjects must act in intrinsically motivated fashion. However, a vast majority of behavioral and neural studies to date have focused on decision making in reward-based tasks, and the rules guiding intrinsically motivated exploration remain largely unknown. To examine this question we developed a paradigm for systematically testing the choices of human observers in a free play context. Adult subjects played a series of short computer games of variable difficulty, and freely choose which game they wished to sample without external guidance or physical rewards. Subjects performed the task in three distinct conditions where they sampled from a small or a large choice set (7 vs 64 possible levels of difficulty, and where they did or did not have the possibility to sample new games at a constant level of difficulty. We show that despite the absence of external constraints, the subjects spontaneously adopted a structured exploration strategy whereby they (1 started with easier games and progressed to more difficult games, (2 sampled the entire choice set including extremely difficult games that could not be learnt, (3 repeated moderately and high difficulty games much more frequently than was predicted by chance, and (4 had higher repetition rates and chose higher speeds if they could generate new sequences at a constant level of difficulty. The results suggest that intrinsically motivated exploration is shaped by several factors including task difficulty, novelty and the size of the choice set, and these come into play to serve two internal goals - maximize the subjects’ knowledge of the available tasks (exploring the limits of the task set, and maximize their competence (performance and skills across the task set.
Baranes, Adrien F; Oudeyer, Pierre-Yves; Gottlieb, Jacqueline
2014-01-01
Devising efficient strategies for exploration in large open-ended spaces is one of the most difficult computational problems of intelligent organisms. Because the available rewards are ambiguous or unknown during the exploratory phase, subjects must act in intrinsically motivated fashion. However, a vast majority of behavioral and neural studies to date have focused on decision making in reward-based tasks, and the rules guiding intrinsically motivated exploration remain largely unknown. To examine this question we developed a paradigm for systematically testing the choices of human observers in a free play context. Adult subjects played a series of short computer games of variable difficulty, and freely choose which game they wished to sample without external guidance or physical rewards. Subjects performed the task in three distinct conditions where they sampled from a small or a large choice set (7 vs. 64 possible levels of difficulty), and where they did or did not have the possibility to sample new games at a constant level of difficulty. We show that despite the absence of external constraints, the subjects spontaneously adopted a structured exploration strategy whereby they (1) started with easier games and progressed to more difficult games, (2) sampled the entire choice set including extremely difficult games that could not be learnt, (3) repeated moderately and high difficulty games much more frequently than was predicted by chance, and (4) had higher repetition rates and chose higher speeds if they could generate new sequences at a constant level of difficulty. The results suggest that intrinsically motivated exploration is shaped by several factors including task difficulty, novelty and the size of the choice set, and these come into play to serve two internal goals-maximize the subjects' knowledge of the available tasks (exploring the limits of the task set), and maximize their competence (performance and skills) across the task set.
Cross-Compiler for Modeling Space-Flight Systems
James, Mark
2007-01-01
Ripples is a computer program that makes it possible to specify arbitrarily complex space-flight systems in an easy-to-learn, high-level programming language and to have the specification automatically translated into LibSim, which is a text-based computing language in which such simulations are implemented. LibSim is a very powerful simulation language, but learning it takes considerable time, and it requires that models of systems and their components be described at a very low level of abstraction. To construct a model in LibSim, it is necessary to go through a time-consuming process that includes modeling each subsystem, including defining its fault-injection states, input and output conditions, and the topology of its connections to other subsystems. Ripples makes it possible to describe the same models at a much higher level of abstraction, thereby enabling the user to build models faster and with fewer errors. Ripples can be executed in a variety of computers and operating systems, and can be supplied in either source code or binary form. It must be run in conjunction with a Lisp compiler.
Women's Preferences for Penis Size: A New Research Method Using Selection among 3D Models.
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Nicole Prause
Full Text Available Women's preferences for penis size may affect men's comfort with their own bodies and may have implications for sexual health. Studies of women's penis size preferences typically have relied on their abstract ratings or selecting amongst 2D, flaccid images. This study used haptic stimuli to allow assessment of women's size recall accuracy for the first time, as well as examine their preferences for erect penis sizes in different relationship contexts. Women (N = 75 selected amongst 33, 3D models. Women recalled model size accurately using this method, although they made more errors with respect to penis length than circumference. Women preferred a penis of slightly larger circumference and length for one-time (length = 6.4 inches/16.3 cm, circumference = 5.0 inches/12.7 cm versus long-term (length = 6.3 inches/16.0 cm, circumference = 4.8 inches/12.2 cm sexual partners. These first estimates of erect penis size preferences using 3D models suggest women accurately recall size and prefer penises only slightly larger than average.
Women's Preferences for Penis Size: A New Research Method Using Selection among 3D Models.
Prause, Nicole; Park, Jaymie; Leung, Shannon; Miller, Geoffrey
2015-01-01
Women's preferences for penis size may affect men's comfort with their own bodies and may have implications for sexual health. Studies of women's penis size preferences typically have relied on their abstract ratings or selecting amongst 2D, flaccid images. This study used haptic stimuli to allow assessment of women's size recall accuracy for the first time, as well as examine their preferences for erect penis sizes in different relationship contexts. Women (N = 75) selected amongst 33, 3D models. Women recalled model size accurately using this method, although they made more errors with respect to penis length than circumference. Women preferred a penis of slightly larger circumference and length for one-time (length = 6.4 inches/16.3 cm, circumference = 5.0 inches/12.7 cm) versus long-term (length = 6.3 inches/16.0 cm, circumference = 4.8 inches/12.2 cm) sexual partners. These first estimates of erect penis size preferences using 3D models suggest women accurately recall size and prefer penises only slightly larger than average.
Modeling Size-number Distributions of Seeds for Use in Soil Bank Studies
Institute of Scientific and Technical Information of China (English)
Hugo Casco; Alexandra Soveral Dias; Luís Silva Dias
2008-01-01
Knowledge of soil seed banks is essential to understand the dynamics of plant populations and communities and would greatly benefit from the integration of existing knowledge on ecological correlations of seed size and shape. The present study aims to establish a feasible and meaningful method to describe size-number distributions of seeds in multi-species situations. For that purpose, size-number distributions of seeds with known length, width and thickness were determined by sequential sieving. The most appropriate combination of sieves and seeds dimensions was established, and the adequacy of the power function and the Weibull model to describe size-number distributions of spherical, non.spherical, and all seeds was investigated. We found that the geometric mean of seed length, width and thickness was the most adequate size estimator, providing shape-independent measures of seeds volume directly related to sieves mesh side, and that both the power function and the Weibuli model provide high quality descriptions of size-number distributions of spherical,non-spherical, and all seeds. We also found that, in spite of its slightly lower accuracy, the power function is, at this stage, a more trustworthy model to characterize size-number distributions of seeds in soil banks because in some Weibull equations the estimates of the scale parameter were not acceptable.
Battery Sizing for Plug-in Hybrid Electric Vehicles in Beijing: A TCO Model Based Analysis
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Cong Hou
2014-08-01
Full Text Available This paper proposes a total cost of ownership (TCO model for battery sizing of plug-in hybrid electric vehicles (PHEVs. The proposed systematic TCO model innovatively integrates the Beijing driving database and optimal PHEV energy management strategies developed earlier. The TCO, including battery, fuel, electricity, and salvage costs, is calculated in yearly cash flows. The salvage cost, based on battery degradation model, is proposed for the first time. The results show that the optimal battery size for PHEVs in Beijing is 6–8 kWh. Several additional scenarios are also analyzed: (1 10% increase in battery price or discount rate leads to an optimal battery size of 6 kWh, and 10% increase in fuel price shifts the optimal battery size to 8 kWh; (2 the longer and more dispersive daily range distribution in the U.S. increases the optimal battery size to 14 kWh; (3 the subsidy in China results in an optimal battery size of 13 kWh, while that in the U.S. results in 17 kWh, and a fuel savings rate based subsidy policy is innovatively proposed; (4 the optimal battery size with Li4Ti5O12 batteries is 2 kWh, but the TCO of Li4Ti5O12 batteries is higher than that of LiFePO4 batteries.
Geospatial modeling of fire-size distributions in historical low-severity fire regimes
McKenzie, D.; Kellogg, L. B.; Larkin, N. K.
2006-12-01
Low-severity fires are recorded by fire-scarred trees. These records can provide temporal depth for reconstructing fire history because one tree may record dozens of separate fires over time, thereby providing adequate sample size for estimating fire frequency. Estimates of actual fire perimeters from these point-based records are uncertain, however, because fire boundaries can only be located approximately. We indirectly estimate fire-size distributions without attempting to establish individual fire perimeters. The slope and intercept of the interval-area function, a power-law relationship between sample area and mean fire-free intervals for that area, provide surrogates for the moments of a fire-size distribution, given a distribution of fire- free intervals. Analogously, by deconstructing variograms that use a binary distance measure (Sorensen's index) for the similarity of the time-series of fires recorded by pairs of recorder trees, we provide estimates of modal fire size. We link both variograms and interval-area functions to fire size distributions by simulating fire size distributions on neutral landscapes with and without right- censoring to represent topographic controls on maximum fire size. From parameters of the two functions produced by simulations we can back-estimate means and variances of fire sizes on real landscapes. This scale-based modeling provides a robust alternative to empirical and heuristic methods and a means to extrapolate estimates of fire-size distributions to unsampled landscapes.
Equivalence and Differences between Structural Equation Modeling and State-Space Modeling Techniques
Chow, Sy-Miin; Ho, Moon-ho R.; Hamaker, Ellen L.; Dolan, Conor V.
2010-01-01
State-space modeling techniques have been compared to structural equation modeling (SEM) techniques in various contexts but their unique strengths have often been overshadowed by their similarities to SEM. In this article, we provide a comprehensive discussion of these 2 approaches' similarities and differences through analytic comparisons and…
Equivalence and differences between structural equation modeling and state-space modeling techniques
Chow, Sy-Miin; Ho, Moon-ho R.; Hamaker, E.L.; Dolan, C.V.
2010-01-01
State-space modeling techniques have been compared to structural equation modeling (SEM) techniques in various contexts but their unique strengths have often been overshadowed by their similarities to SEM. In this article, we provide a comprehensive discussion of these 2 approaches' similarities and