Existence conditions for unknown input functional observers
Fernando, T.; MacDougall, S.; Sreeram, V.; Trinh, H.
2013-01-01
This article presents necessary and sufficient conditions for the existence and design of an unknown input Functional observer. The existence of the observer can be verified by computing a nullspace of a known matrix and testing some matrix rank conditions. The existence of the observer does not require the satisfaction of the observer matching condition (i.e. Equation (16) in Hou and Muller 1992, 'Design of Observers for Linear Systems with Unknown Inputs', IEEE Transactions on Automatic Control, 37, 871-875), is not limited to estimating scalar functionals and allows for arbitrary pole placement. The proposed observer always exists when a state observer exists for the unknown input system, and furthermore, the proposed observer can exist even in some instances when an unknown input state observer does not exist.
OBSERVATIONS REGARDING EXISTING INVERTEBRATES FROM PLUM ORCHARDS
Directory of Open Access Journals (Sweden)
Mihai Tălmaciu
2016-07-01
Full Text Available The observations were made during the two years, 2013 and 2014 in a plantation belonging plum fruit growing from Teaching Station Vasile Adamachi of USAMV Iasi, Iasi County Rivers Early variety.Collecting the material was done with traps type Barber from May until August at intervals between 10 and 20 days. Collection of 2013 was made on the following dates: 20.05, 30.05, 15.06, 5.07, 25.07, 10.08 and 23.08.In total 2013 were collected 265 samples belonging to 22 species (taxa. Species (taxa with the largest number of samples collected were Dermestes laniarius L. 42 samples Heteroptera. (bedbugs with 38 samples, and Polydrosus sericeus Schall. 26 samples. In 2014 collection of the biological material was made on the following dates: 07.05, 21.05, 19.06, 08.07, 27.07, 15.08, 04.09. In total in 2014 were collected 744 samples belonging to 41 species (taxa with the highest number of samples were colected: Hymenoptera (bees with 92 saples, Orthoptera (locusts with 87 samples, Lepidoptera (larvae with 37samplres, and Homoptera (cycads with 31samples.
Modeling Truth Existence in Truth Discovery.
Zhi, Shi; Zhao, Bo; Tong, Wenzhu; Gao, Jing; Yu, Dian; Ji, Heng; Han, Jiawei
2015-08-01
When integrating information from multiple sources, it is common to encounter conflicting answers to the same question. Truth discovery is to infer the most accurate and complete integrated answers from conflicting sources. In some cases, there exist questions for which the true answers are excluded from the candidate answers provided by all sources. Without any prior knowledge, these questions, named no-truth questions, are difficult to be distinguished from the questions that have true answers, named has-truth questions. In particular, these no-truth questions degrade the precision of the answer integration system. We address such a challenge by introducing source quality, which is made up of three fine-grained measures: silent rate, false spoken rate and true spoken rate. By incorporating these three measures, we propose a probabilistic graphical model, which simultaneously infers truth as well as source quality without any a priori training involving ground truth answers. Moreover, since inferring this graphical model requires parameter tuning of the prior of truth, we propose an initialization scheme based upon a quantity named truth existence score, which synthesizes two indicators, namely, participation rate and consistency rate. Compared with existing methods, our method can effectively filter out no-truth questions, which results in more accurate source quality estimation. Consequently, our method provides more accurate and complete answers to both has-truth and no-truth questions. Experiments on three real-world datasets illustrate the notable advantage of our method over existing state-of-the-art truth discovery methods.
The pastor as model for peaceful existence
Directory of Open Access Journals (Sweden)
Terence Cooke
2011-06-01
Full Text Available Many people are disillusioned in the democratic South Africa. That is because they went out from the assumption that with the dawn of democracy, violence would disappear. Unfortunately this did not happen. As with most things in life it is not an either � or, but a both � and scenario. In fact, violence is part of the democratic system. Real peace between men and powers can only be the peace of God, the peace which alone heals all disorder. The peace of the world is at best peaceful coexistence, not peace.In South Africa we have a negotiated agreement to peaceful coexistence, and sometimes, for example, after the miracle of the 1994 election and the euphoria of the World Cups of 1995, 2007 and 2010, we may even think we have achieved real peace. It is indeed in these times of euphoria that the people of South Africa may be tempted to lower our aim and settle for second best thinking that we have arrived.Model is used not in the sense of the pastor being an example of a peaceful existence to be followed. It is rather used in the sense that a pastor in his or her professional capacity has the knowledge of the meaning of the term �peaceful existence� and also the hermeneutic competency to apply that knowledge in concrete situations. This opens the exiting possibility that pastors can become travel companions on the road to real peace.The different aspects of being a pastor, office bearer, professional and person, each contribute to the pastor being a model for peace. It must be emphasised that the different aspects always work together as a unity and the strength of the pastor as a model for a peaceful existence is in the simultaneous application of these aspects in the context in which the pastor lives.
Generating navigation models from existing building data
Liu, L.; Zlatanova, S.
2013-01-01
Research on indoor navigation models mainly focuses on geometric and logical models .The models are enriched with specific semantic information which supports localisation, navigation and guidance. Geometric models provide information about the structural (physical) distribution of spaces in a build
Generating navigation models from existing building data
Liu, L.; Zlatanova, S.
2013-01-01
Research on indoor navigation models mainly focuses on geometric and logical models .The models are enriched with specific semantic information which supports localisation, navigation and guidance. Geometric models provide information about the structural (physical) distribution of spaces in a
THE EXISTENCE THEOREM OF OPTIMAL GROWTH MODEL
Institute of Scientific and Technical Information of China (English)
Gong Liutang; Peng Xianze
2005-01-01
This paper proves a general existence theorem of optimal growth theory. This theorem is neither restricted to the case of a constant technology progress, nor stated in terms of mathematical conditions which have no direct economic interpretation and moreover, are difficult to apply.
Local Existence of Smooth Solutions to the FENE Dumbbell Model
Institute of Scientific and Technical Information of China (English)
Ge YANG
2012-01-01
The author proves the local existence of smooth solutions to the finite extensible nonlinear elasticity (FENE) dumbbell model of polymeric flows in some weighted spaces if the non-dimensional parameter b ＞ 2.
Individual Colorimetric Observer Model.
Directory of Open Access Journals (Sweden)
Yuta Asano
Full Text Available This study proposes a vision model for individual colorimetric observers. The proposed model can be beneficial in many color-critical applications such as color grading and soft proofing to assess ranges of color matches instead of a single average match. We extended the CIE 2006 physiological observer by adding eight additional physiological parameters to model individual color-normal observers. These eight parameters control lens pigment density, macular pigment density, optical densities of L-, M-, and S-cone photopigments, and λmax shifts of L-, M-, and S-cone photopigments. By identifying the variability of each physiological parameter, the model can simulate color matching functions among color-normal populations using Monte Carlo simulation. The variabilities of the eight parameters were identified through two steps. In the first step, extensive reviews of past studies were performed for each of the eight physiological parameters. In the second step, the obtained variabilities were scaled to fit a color matching dataset. The model was validated using three different datasets: traditional color matching, applied color matching, and Rayleigh matches.
Geomagnetic Observations and Models
Mandea, Mioara
2011-01-01
This volume provides comprehensive and authoritative coverage of all the main areas linked to geomagnetic field observation, from instrumentation to methodology, on ground or near-Earth. Efforts are also focused on a 21st century e-Science approach to open access to all geomagnetic data, but also to the data preservation, data discovery, data rescue, and capacity building. Finally, modeling magnetic fields with different internal origins, with their variation in space and time, is an attempt to draw together into one place the traditional work in producing models as IGRF or describing the magn
Global existence for a degenerate haptotaxis model of cancer invasion
Zhigun, Anna; Surulescu, Christina; Uatay, Aydar
2016-12-01
We propose and study a strongly coupled PDE-ODE system with tissue-dependent degenerate diffusion and haptotaxis that can serve as a model prototype for cancer cell invasion through the extracellular matrix. We prove the global existence of weak solutions and illustrate the model behavior by numerical simulations for a two-dimensional setting.
A coupled chemotaxis-fluid model: Global existence
Liu, Jian-Guo
2011-09-01
We consider a model arising from biology, consisting of chemotaxis equations coupled to viscous incompressible fluid equations through transport and external forcing. Global existence of solutions to the Cauchy problem is investigated under certain conditions. Precisely, for the chemotaxis-Navier- Stokes system in two space dimensions, we obtain global existence for large data. In three space dimensions, we prove global existence of weak solutions for the chemotaxis-Stokes system with nonlinear diffusion for the cell density.© 2011 Elsevier Masson SAS. All rights reserved.
Small data global existence for a fluid-structure model
Ignatova, Mihaela; Kukavica, Igor; Lasiecka, Irena; Tuffaha, Amjad
2017-02-01
We address the system of partial differential equations modeling motion of an elastic body inside an incompressible fluid. The fluid is modeled by the incompressible Navier-Stokes equations while the structure is represented by the damped wave equation with interior damping. The additional boundary stabilization γ, considered in our previous paper, is no longer necessary. We prove the global existence and exponential decay of solutions for small initial data in a suitable Sobolev space.
van der Wijk, Lars; Proost, Johannes H.; Sinha, Bhanu; Touw, Daan J.
2017-01-01
Gentamicin shows large variations in half-life and volume of distribution (Vd) within and between individuals. Thus, monitoring and accurately predicting serum levels are required to optimize effectiveness and minimize toxicity. Currently, two population pharmacokinetic models are applied for predicting gentamicin doses in adults. For endocarditis patients the optimal model is unknown. We aimed at: 1) creating an optimal model for endocarditis patients; and 2) assessing whether the endocarditis and existing models can accurately predict serum levels. We performed a retrospective observational two-cohort study: one cohort to parameterize the endocarditis model by iterative two-stage Bayesian analysis, and a second cohort to validate and compare all three models. The Akaike Information Criterion and the weighted sum of squares of the residuals divided by the degrees of freedom were used to select the endocarditis model. Median Prediction Error (MDPE) and Median Absolute Prediction Error (MDAPE) were used to test all models with the validation dataset. We built the endocarditis model based on data from the modeling cohort (65 patients) with a fixed 0.277 L/h/70kg metabolic clearance, 0.698 (±0.358) renal clearance as fraction of creatinine clearance, and Vd 0.312 (±0.076) L/kg corrected lean body mass. External validation with data from 14 validation cohort patients showed a similar predictive power of the endocarditis model (MDPE -1.77%, MDAPE 4.68%) as compared to the intensive-care (MDPE -1.33%, MDAPE 4.37%) and standard (MDPE -0.90%, MDAPE 4.82%) models. All models acceptably predicted pharmacokinetic parameters for gentamicin in endocarditis patients. However, these patients appear to have an increased Vd, similar to intensive care patients. Vd mainly determines the height of peak serum levels, which in turn correlate with bactericidal activity. In order to maintain simplicity, we advise to use the existing intensive-care model in clinical practice to avoid
A Dissipative Model for Hydrogen Storage: Existence and Regularity Results
Chiodaroli, Elisabetta
2010-01-01
We prove global existence of a solution to an initial and boundary value problem for a highly nonlinear PDE system. The problem arises from a termomechanical dissipative model describing hydrogen storage by use of metal hydrides. In order to treat the model from an analytical point of view, we formulate it as a phase transition phenomenon thanks to the introduction of a suitable phase variable. Continuum mechanics laws lead to an evolutionary problem involving three state variables: the temperature, the phase parameter and the pressure. The problem thus consists of three coupled partial differential equations combined with initial and boundary conditions. Existence and regularity of the solutions are here investigated by means of a time discretization-a priori estimate-passage to the limit procedure joined with compactness and monotonicity arguments.
Percolation Model for the Existence of a Mitochondrial Eve
Neves, A G M
2005-01-01
We look at the process of inheritance of mitochondrial DNA as a percolation model on trees equivalent to the Galton-Watson process. The model is exactly solvable for its percolation threshold $p_c$ and percolation probability critical exponent. In the approximation of small percolation probability, and assuming limited progeny number, we are also able to find the maximum and minimum percolation probabilities over all probability distributions for the progeny number constrained to a given $p_c$. As a consequence, we can relate existence of a mitochondrial Eve to quantitative knowledge about demographic evolution of early mankind. In particular, we show that a mitochondrial Eve may exist even in an exponentially growing population, provided that the average number of children per individual is constrained to a small range depending on the probability $p$ that a newborn child is a female.
Existence of needle crystals in local models of solidification
Langer, J. S.
1986-01-01
The way in which surface tension acts as a singular perturbation to destroy the continuous family of needle-crystal solutions of the steady-state growth equations is analyzed in detail for two local models of solidification. All calculations are performed in the limit of small surface tension or, equivalently, small velocity. The basic mathematical ideas are introduced in connection with a quasilinear, isotropic version of the geometrical model of Brower et al., in which case the continuous family of solutions dissappears completely. The formalism is then applied to a simplified boundary-layer model with an anisotropic kinetic attachment coefficient. In the latter case, the solvability condition for the existence of needle crystals can be satisfied whenever the coefficient of anisotropy is arbitrarily small but nonzero.
Modeling and optimization of existing beam port facility of PSBR
Energy Technology Data Exchange (ETDEWEB)
Alim, Fatih [Department of Mechanical and Nuclear Engineering, Penn State University, Reber Building, University Park, State College, PA 16802 (United States); Bekar, Kursat [Department of Mechanical and Nuclear Engineering, Penn State University, Reber Building, University Park, State College, PA 16802 (United States); Ivanov, Kostadin [Department of Mechanical and Nuclear Engineering, Penn State University, Reber Building, University Park, State College, PA 16802 (United States)]. E-mail: kni1@psu.edu; Unlu, Kenan [Department of Mechanical and Nuclear Engineering, Penn State University, Reber Building, University Park, State College, PA 16802 (United States); Brenizer, Jack [Department of Mechanical and Nuclear Engineering, Penn State University, Reber Building, University Park, State College, PA 16802 (United States); Azmy, Yousry [Department of Mechanical and Nuclear Engineering, Penn State University, Reber Building, University Park, State College, PA 16802 (United States)
2006-11-15
Due to inherited design issues with the current arrangement of beam ports (BPs) and reactor core-moderator assembly in The Perm State Breazeale Reactor (PSBR), the development of innovative experimental facilities utilizing neutron beams is extremely limited. Therefore, a study has started to examine the existing BPs for neutron and gamma outputs and develop a new core-moderator location and BP geometry in PSBR. Although 7 BPs are placed in PSBR, 2 of them are using currently. In this study BP 4, one of the currently being used BP, is examined. With changing the location of the BP 4 and structure of the core assembly, some artificial models are developed and compared with the original model.
THE FLAT TAX - A COMPARATIVE STUDY OF THE EXISTING MODELS
Directory of Open Access Journals (Sweden)
Schiau (Macavei Laura - Liana
2011-07-01
Full Text Available In the two last decades the flat tax systems have spread all around the globe from East and Central Europe to Asia and Central America. Many specialists consider this phenomenon a real fiscal revolution, but others see it as a mistake as long as the new systems are just a feint of the true flat tax designed by the famous Stanford University professors Robert Hall and Alvin Rabushka. In this context this paper tries to determine which of the existing flat tax systems resemble the true flat tax model by comparing and contrasting their main characteristics with the features of the model proposed by Hall and Rabushka. The research also underlines the common features and the differences between the existing models. The idea of this kind of study is not really new, others have done it but the comparison was limited to one country. For example Emil Kalchev from New Bulgarian University has asses the Bulgarian income system, by comparing it with the flat tax and concluding that taxation in Bulgaria is not simple, neutral and non-distortive. Our research is based on several case studies and on compare and contrast qualitative and quantitative methods. The study starts form the fiscal design drawn by the two American professors in the book The Flat Tax. Four main characteristics of the flat tax system were chosen in order to build the comparison: fiscal design, simplicity, avoidance of double taxation and uniformity of the tax rates. The jurisdictions chosen for the case study are countries all around the globe with fiscal systems which are considered flat tax systems. The results obtained show that the fiscal design of Hong Kong is the only flat tax model which is built following an economic logic and not a legal sense, being in the same time a simple and transparent system. Others countries as Slovakia, Albania, Macedonia in Central and Eastern Europe fulfill the requirement regarding the uniformity of taxation. Other jurisdictions avoid the double
Shelter models and observations
DEFF Research Database (Denmark)
Peña, Alfredo; Bechmann, Andreas; Conti, Davide;
This report documents part of the work performed by work package (WP) 3 of the ‘Online WAsP’ project funded by the Danish Energy Technology and Demonstration Program (EUDP). WP3 initially identified the shortcomings of the current WAsP engine for small and medium wind turbines (Peña et al., 2014b...... in the wake of a fence. The experiment is the basis of the study of the error and uncertainty of the obstacle models....
Using the EXIST Active Shields for Earth Occultation Observations of X-ray Sources
Wilson, C A; Hong, J S; Grindlay, J E; Krawczynski, H; Wilson, Colleen A.
2005-01-01
The EXIST active shields, planned for the main detectors of the coded aperture telescope, will have approximately 15 times the area of the BATSE detectors, and they will have a good geometry on the spacecraft for viewing both the leading and trailing Earth's limb for occultation observations. These occultation observations will complement the imaging observations of EXIST and can extend them to higher energies. Earth occultation observations of the hard X-ray sky with BATSE on the Compton Gamma Ray Observatory developed and demonstrated the capabilities of large, flat, uncollimated detectors for applying this observation method. With BATSE, a catalog of 179 X-ray sources was monitored twice every spacecraft orbit for 9 years at energies above about 25 keV, resulting in 83 definite detections and 36 possible detections with 5 sigma detection sensitivities of 3.5-20 mcrab (20-430 keV) depending on the sky location. This catalog included four transients discovered with this technique and many variable objects (g...
Does thyroid stunning exist? A model with benign thyroid disease
Energy Technology Data Exchange (ETDEWEB)
Sabri, O.; Zimny, M.; Schreckenberger, M.; Meyer-Oelmann, A.; Reinartz, P.; Buell, U. [Clinic of Nuclear Medicine, Aachen Univ. of Technology (Germany)
2000-11-01
<0.00005), the latter correlation fitting a logarithmic model best. Multivariate factor analysis also revealed first absorbed energy dose to be the only decisive stunning factor. In conclusion, our study confirms that stunning exists in benign thyroid conditions and that it is a purely radiobiological inhibitory phenomenon related to absorbed dose. (orig.)
Fox, Michael H
2010-01-01
Jahiel and Scherer point out very astutely that time can be a baffling confounder in viewing disability, taxing our ability to meaningfully apply the International Classification of Function, Disability and Health (ICF) model to outcomes analysis. Their approach to segmenting person and environment is constructive. But distilling factors based upon an a priori self-determination of disability as part of the model may also undercut the validity of the larger construct. While the authors are to be applauded for their efforts to extend existing models of disability to address their current shortcomings, attention must also be given to important socio- or geo-political factors that may deserve more than a contextual discussion and their own place in this developing theory.
Protocols for terrestrial bioaccumulation assessments are far less-developed than for aquatic systems. This manuscript reviews modeling approaches that can be used to assess the terrestrial bioaccumulation potential of commercial organic chemicals. Models exist for plant, inver...
Personnel shift assignment: Existence conditions and network models
Berg, van den Jeroen P.; Panton, David M.
1994-01-01
The personnel scheduling problem is known to be a five-stage process in which the final stage involves the assignment of shifts to the days worked in the schedule. This paper discusses the existence conditions for both continuous and forward rotating shift assignments and heuristic network algorithm
Mathematical Existence Results for the Doi-Edwards Polymer Model
Chupin, Laurent
2017-01-01
In this paper, we present some mathematical results on the Doi-Edwards model describing the dynamics of flexible polymers in melts and concentrated solutions. This model, developed in the late 1970s, has been used and extensively tested in modeling and simulation of polymer flows. From a mathematical point of view, the Doi-Edwards model consists in a strong coupling between the Navier-Stokes equations and a highly nonlinear constitutive law. The aim of this article is to provide a rigorous proof of the well-posedness of the Doi-Edwards model, namely that it has a unique regular solution. We also prove, which is generally much more difficult for flows of viscoelastic type, that the solution is global in time in the two dimensional case, without any restriction on the smallness of the data.
A study about the existence of the leverage effect in stochastic volatility models
Florescu, Ionuţ; Pãsãricã, Cristian Gabriel
2009-02-01
The empirical relationship between the return of an asset and the volatility of the asset has been well documented in the financial literature. Named the leverage effect or sometimes risk-premium effect, it is observed in real data that, when the return of the asset decreases, the volatility increases and vice versa. Consequently, it is important to demonstrate that any formulated model for the asset price is capable of generating this effect observed in practice. Furthermore, we need to understand the conditions on the parameters present in the model that guarantee the apparition of the leverage effect. In this paper we analyze two general specifications of stochastic volatility models and their capability of generating the perceived leverage effect. We derive conditions for the apparition of leverage effect in both of these stochastic volatility models. We exemplify using stochastic volatility models used in practice and we explicitly state the conditions for the existence of the leverage effect in these examples.
Observations involving broadband impedance modelling
Energy Technology Data Exchange (ETDEWEB)
Berg, J.S. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)
1996-08-01
Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)
Observations involving broadband impedance modelling
Energy Technology Data Exchange (ETDEWEB)
Berg, J.S.
1995-08-01
Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impendance. This paper discusses three aspects of broadband impendance modeling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f cavity. The last is a discussion of requirements for the mathematical form of an impendance which follow from the general properties of impendances.
Nazmul, Mohammad Ahsan
2017-01-01
The study was undertaken to investigate the restaurant switching intention among existing customers of ethnic Indian restaurants in Helsinki and to explore implications of the existing consumers’ switching intention on new ethnic Indian restaurants. It has practical significance for both existing and to-be-opened new ethnic Indian restaurants in Helsinki in understanding consumers’ restaurant switching behaviour and in formulating strategies to retain/attract consumers and overall marketing s...
Are there consistent models giving observable NSI ?
Martinez, Enrique Fernandez
2013-01-01
While the existing direct bounds on neutrino NSI are rather weak, order 10(−)(1) for propagation and 10(−)(2) for production and detection, the close connection between these interactions and new NSI affecting the better-constrained charged letpon sector through gauge invariance make these bounds hard to saturate in realistic models. Indeed, Standard Model extensions leading to neutrino NSI typically imply constraints at the 10(−)(3) level. The question of whether consistent models leading to observable neutrino NSI naturally arises and was discussed in a dedicated session at NUFACT 11. Here we summarize that discussion.
Hyperbolic Plykin attractor can exist in neuron models
DEFF Research Database (Denmark)
Belykh, V.; Belykh, I.; Mosekilde, Erik
2005-01-01
Strange hyperbolic attractors are hard to find in real physical systems. This paper provides the first example of a realistic system, a canonical three-dimensional (3D) model of bursting neurons, that is likely to have a strange hyperbolic attractor. Using a geometrical approach to the study...... of the neuron model, we derive a flow-defined Poincare map giving ail accurate account of the system's dynamics. In a parameter region where the neuron system undergoes bifurcations causing transitions between tonic spiking and bursting, this two-dimensional map becomes a map of a disk with several periodic...... holes. A particular case is the map of a disk with three holes, matching the Plykin example of a planar hyperbolic attractor. The corresponding attractor of the 3D neuron model appears to be hyperbolic (this property is not verified in the present paper) and arises as a result of a two-loop (secondary...
Comparative analysis of existing models for power-grid synchronization
Nishikawa, Takashi
2015-01-01
The dynamics of power-grid networks is becoming an increasingly active area of research within the physics and network science communities. The results from such studies are typically insightful and illustrative, but are often based on simplifying assumptions that can be either difficult to assess or not fully justified for realistic applications. Here we perform a comprehensive comparative analysis of three leading models recently used to study synchronization dynamics in power-grid networks -- a fundamental problem of practical significance given that frequency synchronization of all power generators in the same interconnection is a necessary condition for a power grid to operate. We show that each of these models can be derived from first principles within a common framework based on the classical model of a generator, thereby clarifying all assumptions involved. This framework allows us to view power grids as complex networks of coupled second-order phase oscillators with both forcing and damping terms. U...
Comparative analysis of existing models for power-grid synchronization
Nishikawa, Takashi; Motter, Adilson E.
2015-01-01
The dynamics of power-grid networks is becoming an increasingly active area of research within the physics and network science communities. The results from such studies are typically insightful and illustrative, but are often based on simplifying assumptions that can be either difficult to assess or not fully justified for realistic applications. Here we perform a comprehensive comparative analysis of three leading models recently used to study synchronization dynamics in power-grid networks—a fundamental problem of practical significance given that frequency synchronization of all power generators in the same interconnection is a necessary condition for a power grid to operate. We show that each of these models can be derived from first principles within a common framework based on the classical model of a generator, thereby clarifying all assumptions involved. This framework allows us to view power grids as complex networks of coupled second-order phase oscillators with both forcing and damping terms. Using simple illustrative examples, test systems, and real power-grid datasets, we study the inherent frequencies of the oscillators as well as their coupling structure, comparing across the different models. We demonstrate, in particular, that if the network structure is not homogeneous, generators with identical parameters need to be modeled as non-identical oscillators in general. We also discuss an approach to estimate the required (dynamical) system parameters that are unavailable in typical power-grid datasets, their use for computing the constants of each of the three models, and an open-source MATLAB toolbox that we provide for these computations.
Exploring Higher Education Business Models ("If Such a Thing Exists")
Harney, John O.
2013-01-01
The global economic recession has caused students, parents, and policymakers to reevaluate personal and societal investments in higher education--and has prompted the realization that traditional higher ed "business models" may be unsustainable. Predicting a shakeout, most presidents expressed confidence for their own school's ability to…
Modelling the feasibility of retrofitting hydropower to existing South ...
African Journals Online (AJOL)
water pressure into mechanical shaft rotation which is then. Hydro power (14%) ... hydropower retrofitting model (HRM) applies, a water-to-wire system will most ..... A set amount of flow is drawn off constantly to produce a constant amount of ...
Exploring Higher Education Business Models ("If Such a Thing Exists")
Harney, John O.
2013-01-01
The global economic recession has caused students, parents, and policymakers to reevaluate personal and societal investments in higher education--and has prompted the realization that traditional higher ed "business models" may be unsustainable. Predicting a shakeout, most presidents expressed confidence for their own school's ability to…
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.
INTERVAL OBSERVER FOR A BIOLOGICAL REACTOR MODEL
Directory of Open Access Journals (Sweden)
T. A. Kharkovskaia
2014-05-01
Full Text Available The method of an interval observer design for nonlinear systems with parametric uncertainties is considered. The interval observer synthesis problem for systems with varying parameters consists in the following. If there is the uncertainty restraint for the state values of the system, limiting the initial conditions of the system and the set of admissible values for the vector of unknown parameters and inputs, the interval existence condition for the estimations of the system state variables, containing the actual state at a given time, needs to be held valid over the whole considered time segment as well. Conditions of the interval observers design for the considered class of systems are shown. They are: limitation of the input and state, the existence of a majorizing function defining the uncertainty vector for the system, Lipschitz continuity or finiteness of this function, the existence of an observer gain with the suitable Lyapunov matrix. The main condition for design of such a device is cooperativity of the interval estimation error dynamics. An individual observer gain matrix selection problem is considered. In order to ensure the property of cooperativity for interval estimation error dynamics, a static transformation of coordinates is proposed. The proposed algorithm is demonstrated by computer modeling of the biological reactor. Possible applications of these interval estimation systems are the spheres of robust control, where the presence of various types of uncertainties in the system dynamics is assumed, biotechnology and environmental systems and processes, mechatronics and robotics, etc.
Advancing an Information Model for Environmental Observations
Horsburgh, J. S.; Aufdenkampe, A. K.; Hooper, R. P.; Lehnert, K. A.; Schreuders, K.; Tarboton, D. G.; Valentine, D. W.; Zaslavsky, I.
2011-12-01
have been modified to support data management for the Critical Zone Observatories (CZOs). This paper will present limitations of the existing information model used by the CUAHSI HIS that have been uncovered through its deployment and use, as well as new advances to the information model, including: better representation of both in situ observations from field sensors and observations derived from environmental samples, extensibility in attributes used to describe observations, and observation provenance. These advances have been developed by the HIS team and the broader scientific community and will enable the information model to accommodate and better describe wider classes of environmental observations and to better meet the needs of the hydrologic science and CZO communities.
Multi-criteria decision model for retrofitting existing buildings
Directory of Open Access Journals (Sweden)
M. D. Bostenaru Dan
2004-01-01
Full Text Available Decision is an element in the risk management process. In this paper the way how science can help in decision making and implementation for retrofitting buildings in earthquake prone urban areas is investigated. In such interventions actors from various spheres are involved. Their interests range among minimising the intervention for maximal preservation or increasing it for seismic safety. Research was conducted to see how to facilitate collaboration between these actors. A particular attention was given to the role of time in actors' preferences. For this reason, on decision level, both the processural and the personal dimension of risk management, the later seen as a task, were considered. A systematic approach was employed to determine the functional structure of a participative decision model. Three layers on which actors implied in this multi-criteria decision problem interact were identified: town, building and element. So-called 'retrofit elements' are characteristic bearers in the architectural survey, engineering simulations, costs estimation and define the realms perceived by the inhabitants. This way they represent an interaction basis for the interest groups considered in a deeper study. Such orientation means for actors' interaction were designed on other levels of intervention as well. Finally, an 'experiment' for the implementation of the decision model is presented: a strategic plan for an urban intervention towards reduction of earthquake hazard impact through retrofitting. A systematic approach proves thus to be a very good communication basis among the participants in the seismic risk management process. Nevertheless, it can only be applied in later phases (decision, implementation, control only, since it serves verifying and improving solution and not developing the concept. The 'retrofit elements' are a typical example of the detailing degree reached in the retrofit design plans in these phases.
Chan, Man Ho
2010-01-01
We show that the existence of a degenerate halo of sterile neutrinos with rest mass of 17.4 keV near the Galactic Center can account for both the excess 8.7 keV emission observed by the $Suzaku$ mission and the power needed ($10^{40}$ erg s$^{-1}$) to maintain the high temperature of the hot gas (8 keV) near the Galactic Center. The required decay rate and mixing angle of the sterile neutrinos are $\\Gamma \\ge 5 \\times 10^{-20}$ s$^{-1}$ and $\\sin^22 \\theta \\sim 10^{-3}-10^{-4}$ respectively. These values are consistent with a low reheating temperature in the inflation model, and suggest the exciting possibility that the sterile - active neutrino oscillation can be visible in near future experiments.
A simplified dynamic model for existing buildings using CTF and thermal network models
Energy Technology Data Exchange (ETDEWEB)
Xu, Xinhua; Wang, Shengwei [Department of Building Services Engineering, The Hong Kong Polytechnic University (China)
2008-09-15
An alternative simplified building model is developed to describe existing building system aiming at providing performance benchmark for performance evaluation and diagnosis at building level and performance prediction for air-conditioning system optimal control. This model combines detailed physical models of building envelopes and a thermal network model of building internal mass. The detailed physical models are the CTF (Conduction Transfer Function) models of building envelopes based on the easily available detailed physical properties of exterior walls and roof. The thermal network model is the 2R2C model, and its parameters are estimated and optimized using genetic algorithm with short-term monitored operation data. The parameter optimization of the simplified building internal mass model (2R2C) and the simplified dynamic building model (i.e., CTF+2R2C model) are validated in a high-rising commercial office building under various weather conditions. This CTF+2R2C model is an alternative modeling approach for simulating the overall building dynamic thermal performance when CTF model is chosen to model the building envelope. (author)
Gobas, Frank A P C; Burkhard, Lawrence P; Doucette, William J; Sappington, Keith G; Verbruggen, Eric M J; Hope, Bruce K; Bonnell, Mark A; Arnot, Jon A; Tarazona, Jose V
2016-01-01
Protocols for terrestrial bioaccumulation assessments are far less-developed than for aquatic systems. This article reviews modeling approaches that can be used to assess the terrestrial bioaccumulation potential of commercial organic chemicals. Models exist for plant, invertebrate, mammal, and avian species and for entire terrestrial food webs, including some that consider spatial factors. Limitations and gaps in terrestrial bioaccumulation modeling include the lack of QSARs for biotransformation and dietary assimilation efficiencies for terrestrial species; the lack of models and QSARs for important terrestrial species such as insects, amphibians and reptiles; the lack of standardized testing protocols for plants with limited development of plant models; and the limited chemical domain of existing bioaccumulation models and QSARs (e.g., primarily applicable to nonionic organic chemicals). There is an urgent need for high-quality field data sets for validating models and assessing their performance. There is a need to improve coordination among laboratory, field, and modeling efforts on bioaccumulative substances in order to improve the state of the science for challenging substances.
A Note on the Existence of the Posteriors for One-way Random Effect Probit Models.
Lin, Xiaoyan; Sun, Dongchu
2010-01-01
The existence of the posterior distribution for one-way random effect probit models has been investigated when the uniform prior is applied to the overall mean and a class of noninformative priors are applied to the variance parameter. The sufficient conditions to ensure the propriety of the posterior are given for the cases with replicates at some factor levels. It is shown that the posterior distribution is never proper if there is only one observation at each factor level. For this case, however, a class of proper priors for the variance parameter can provide the necessary and sufficient conditions for the propriety of the posterior.
Effects of Injected Fluids on Pre-existing Faults observed from Surface and Downhole Seismic Arrays
Tang, Y.; Niu, F.; Chen, H.; Zuo, Q.
2016-12-01
Hydraulic fracturing is the key stimulation technology to improve unconventional hydrocarbon recovery. It involves pumping high-pressure fluid into reservoir rocks to force the opening of cracks, which could allow oil and gas to flow freely. The effects of injected fluids and associated stress changes on pre-existing faults must be monitored carefully to avoid undesirable ruptures. We deployed a small-scale seismic array consisting of 22 broadband seismographs at the surface and 20 downhole seismographs to study the dynamic processes involved in hydraulic fracturing. The simultaneous monitoring of surface and downhole seismic array could increase the detectability of microseismic events and enhance location accuracy. The downhole seismic array detected a total of 7270 microseismic events and 961 events were recorded by surface seismic array with high signal-to-noise ratios (SNRs). We found that induced seismicity occurred during and after the fluid injection with large spatial variations. This is also true to the inverted focal mechanisms. We noticed that several clusters of events are located >1 km away from the perforation shots such that their occurrence seems to have no direct involvement of the inject fluid. More likely they seem to be triggered slips on pre-existing faults. The pre-existing faults were reactivated by the injection of the early stages, and the triggered seismicity continued during the later operation regardless whether there is inflow of the fluid injected by the later stages. Overall, the "dry" triggered remote seismicity seems to have a higher average magnitude and a lower b-value in comparison with the "wet" inducted seismicity around the perforation shots.
Primary observations of the existence of Fas-like cytoplasmic death factor in plant cells
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The main activity of Fas is to trigger cytoplasm death program in animal cells. In G2 pea, vacuole plays a pivotal role in inducing cell death in the cytoplasm of longday (LD) grown apical meristem cells. Expression patterns of the Fas in G2 pea cells revealed that the Fas is mainly localized in the vacuole of cells undergoing programmed cell death (PCD). The Fas expression is corresponding to the initiation of menadione-induced PCD in tobacco protoplasts.The results suggest the existence of the Fas-like mediated cytoplasmic death pathway in plant cells.``
Pinkerton, John E.; Blosser, Russell O.
Particulate matter emission sources at a kraft pulp mill include kraft recovery furnaces, lime kilns, smelt dissolving tanks and power boilers. Chemical and physical characteristics of these paniculate emissions are reviewed. Measurements of particle size distributions for these sources made with cascade impactors and microscopic counting techniques both before and after paniculate control devices such as multiple cyclones, wet scrubbers, and electrostatic precipitalors are discussed. In general, particles with equivalent diameters less than 3 jim comprise the bulk of the controlled paniculate emissions from all sources. Sodium sulfate is the dominant paniculate emission from kraft recovery furnaces, smelt dissolving tanks and lime kilns. Results from a field investigation of the relationship between human observations of near-stack plume opacity and measured in-stack paniculate concentrations and opacities are summarized. Trained cenified panels of observers were used in the investigation to estimate plume opacities from two kraft recovery furnaces, a combination wood/coal-fired boiler, and a combination wood/oil-fired boiler at four different pulp mill locations. Plume opacities were varied from near-zero to 45 % by adjustment of the paniculate control equipment operation. The effects of different background viewing conditions, observer positions, observer experience levels, and plume characteristics are enumerated. It is concluded that there can be substantial variations between measured in-stack opacities and human perceptions of near-stack plume opacities. The degree of agreement between the human judgements and measured in-stack opacities is significantly affected by the background viewing conditions. It is further shown that even with a panel of six or seven trained observers with similar visual acuity, there can be significant departures of individual opacity readings from the panel mean opacity. Although this investigation deals with questions of human
On the existence of oscillations in solar filaments observed in H alpha and C IV lines
Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E.
1986-01-01
Time sequence observations of filaments in both the H alpha line and the 1548 A C IV line were analyzed with the Fourier transform technique in the frequency range (1 - 10 mHz). No oscillation is detected in filaments except at the footpoints where a steady velocity gradient is large. The energy is probably due to convective motions rather than pressure oscillations.
Dark energy observational evidence and theoretical models
Novosyadlyj, B; Shtanov, Yu; Zhuk, A
2013-01-01
The book elucidates the current state of the dark energy problem and presents the results of the authors, who work in this area. It describes the observational evidence for the existence of dark energy, the methods and results of constraining of its parameters, modeling of dark energy by scalar fields, the space-times with extra spatial dimensions, especially Kaluza---Klein models, the braneworld models with a single extra dimension as well as the problems of positive definition of gravitational energy in General Relativity, energy conditions and consequences of their violation in the presence of dark energy. This monograph is intended for science professionals, educators and graduate students, specializing in general relativity, cosmology, field theory and particle physics.
Directory of Open Access Journals (Sweden)
Weller Iris
2003-02-01
Full Text Available Abstract Background Unlike other cardiovascular diseases the incidence and prevalence of congestive heart failure (CHF continues to increase. While gender differences in coronary artery disease have been well described, to date, there has been a relative paucity of similar data in patients with CHF. We conducted a pilot study to evaluate the profile and management of patients with CHF at a tertiary care centre to determine if a gender difference exists. Methods A chart review was performed at a tertiary care centre on consecutive patients admitted with a primary diagnosis of CHF between June 1997 and 1998. Co-morbidity, diagnostic investigations, and management of CHF were recorded. Comparisons between male and female patients were conducted. Results One hundred and forty five patients were reviewed. There were 80 male (M and 65 female (F patients of similar age [71.6 vs. 71.3 (M vs. F, p = NS]. Male patients were more likely to have had a previous myocardial infarction (66% vs. 35%, p Conclusions This pilot study demonstrated that there seem to be important gender differences in the profile and management of patients with CHF. Importantly women were less likely to have an evaluation of LV function. As assessment of LV function has significant implications on patient management, this data justifies the need for larger studies to assess gender differences in CHF profile and treatment.
Steady-state existence of passive vector fields under the Kraichnan model.
Arponen, Heikki
2010-03-01
The steady-state existence problem for Kraichnan advected passive vector models is considered for isotropic and anisotropic initial values in arbitrary dimension. The models include the magnetohydrodynamic (MHD) equations, linear pressure model, and linearized Navier-Stokes (LNS) equations. In addition to reproducing the previously known results for the MHD model, we obtain the values of the Kraichnan model roughness parameter xi for which the LNS steady state exists.
Olson, Daniel W; Ou, Jia; Tian, Mingwei; Dorfman, Kevin D
2011-02-01
Several continuous-time random walk (CTRW) models exist to predict the dynamics of DNA in micropost arrays, but none of them quantitatively describes the separation seen in experiments or simulations. In Part I of this series, we examine the assumptions underlying these models by observing single molecules of λ DNA during electrophoresis in a regular, hexagonal array of oxidized silicon posts. Our analysis takes advantage of a combination of single-molecule videomicroscopy and previous Brownian dynamics simulations. Using a custom-tracking program, we automatically identify DNA-post collisions and thus study a large ensemble of events. Our results show that the hold-up time and the distance between collisions for consecutive collisions are uncorrelated. The distance between collisions is a random variable, but it can be smaller than the minimum value predicted by existing models of DNA transport in post arrays. The current CTRW models correctly predict the exponential decay in the probability density of the collision hold-up times, but they fail to account for the influence of finite-sized posts on short hold-up times. The shortcomings of the existing models identified here motivate the development of a new CTRW approach, which is presented in Part II of this series.
Could the real (not virtual) static observer exist outside a Schwarzschild black hole?
Berezin, Victor
2011-01-01
The aim of this Letter is rather pedagogical. We considered the static spherically symmetric ensemble of observers, having finite bare mass and trying to measure geometrical and physical properties of the environmental static (Schwarzschild) space-time. It is shown that, using the photon rockets (which the mass together with the mass of their fuel is also taken into account) they can managed to keep themselves on the fixed value of radius. The process of diminishing the total bare mass up to zero lasts infinitely long time. It is important that the problem is solved self-consistently, i.e., with full account for the back reaction of both bare mass and radiation from rockets on the space-time geometry.
Existence of almost periodic solution of a model of phytoplankton allelopathy with delay
Abbas, Syed; Mahto, Lakshman
2012-09-01
In this paper we discuss a non-autonomous two species competitive allelopathic phytoplankton model in which both species are producing chemical which stimulate the growth of each other. We have studied the existence and uniqueness of an almost periodic solution for the concerned model system. Sufficient conditions are derived for the existence of a unique almost periodic solution.
Observational evidence for various models of Moving Magnetic Features
Lee, Jeongwoo W.
1992-01-01
New measurements of Moving Magnetic Features (MMFs) based on the observations of the active region NOAA 5612 made at Big Bear Solar Observatory (BBSO) on August 2, 1989 are presented. The existing theoretical models are checked against the new observations, and the origin of MMFs conjectured from the deduced observational constraints is discussed.
Model Observers in Medical Imaging Research
He, Xin; Park, Subok
2013-01-01
Model observers play an important role in the optimization and assessment of imaging devices. In this review paper, we first discuss the basic concepts of model observers, which include the mathematical foundations and psychophysical considerations in designing both optimal observers for optimizing imaging systems and anthropomorphic observers for modeling human observers. Second, we survey a few state-of-the-art computational techniques for estimating model observers and the principles of im...
Platt, Thomas L; Reeves, Valerie L; Murphy, M Paul
2013-09-01
Animal models have been used for decades in the Alzheimer's disease (AD) research field and have been crucial for the advancement of our understanding of the disease. Most models are based on familial AD mutations of genes involved in the amyloidogenic process, such as the amyloid precursor protein (APP) and presenilin 1 (PS1). Some models also incorporate mutations in tau (MAPT) known to cause frontotemporal dementia, a neurodegenerative disease that shares some elements of neuropathology with AD. While these models are complex, they fail to display pathology that perfectly recapitulates that of the human disease. Unfortunately, this level of pre-existing complexity creates a barrier to the further modification and improvement of these models. However, as the efficacy and safety of viral vectors improves, their use as an alternative to germline genetic modification is becoming a widely used research tool. In this review we discuss how this approach can be used to better utilize common mouse models in AD research. This article is part of a Special Issue entitled: Animal Models of Disease.
Model observers in medical imaging research.
He, Xin; Park, Subok
2013-10-04
Model observers play an important role in the optimization and assessment of imaging devices. In this review paper, we first discuss the basic concepts of model observers, which include the mathematical foundations and psychophysical considerations in designing both optimal observers for optimizing imaging systems and anthropomorphic observers for modeling human observers. Second, we survey a few state-of-the-art computational techniques for estimating model observers and the principles of implementing these techniques. Finally, we review a few applications of model observers in medical imaging research.
Reconstruction of Existing Reservoir Model for Its Calibration to Dynamic Data
Le Ravalec-Dupin, M.; Hu, L. Y.; Roggero, F.
The increase in computer power and the recent developments in history-matching can motivate the reexamination of previously built reservoir models. To save the time of engineers and the CPU time, four distinct algorithms, which allow for rebuilding an existing reservoir model without restarting the reservoir study from scratch, were formulated. The algorithms involve techniques such as optimization, relaxation, Wiener filtering, or sequential reconstruction. They are used to identify a stochastic function and a set of random numbers. Given the stochastic function, the random numbers yield a realization that is close to the existing reservoir model. Once the random numbers are known, the existing reservoir model can be submitted to a new history-matching process to improve the data fit or to account for newly collected data. A practical implementation is presented within the context of facies reservoirs. This article focuses on a previously built facies reservoir model. Although the simulation procedure is unknown to the authors, a set of random numbers are identified so that when provided to a multiple-point statistics simulator, a realization very close to the existing reservoir model is obtained. A new history-matching procedure is then run to update the existing reservoir model and to integrate the fractional flow rates measured in two producing wells drilled after the building of the existing reservoir model.
Existence and Uniqueness of Endemic States for the Age-structured MSEIR Epidemic Model
Institute of Scientific and Technical Information of China (English)
Xue-zhi Li; Geni Gupur; Guang-tian Zhu
2002-01-01
The existence and uniqueness of positive steady states for the age-structured MSEIR epidemic model with age-dependent transmission coefficient is considered. Threshold results for the existence of endemic states are established; under certain conditions, uniqueness is also shown.
Comparison between observations and model
Claußnitzer, Antje
2010-01-01
In recent years the development of numerical weather prediction models has shown great progress in the short-term and medium-range forecast of temperature, wind speed or direction and cloud coverage, but only little success in the quantitative precipitation forecast. Rainfall is one of the most difficult forecasting meteorological variable. To improve the numerical models, it is necessary to understand the rainfall processes. This thesis contributes towards an understanding since the precipit...
Global existence and asymptotic behavior for a nonlinear degenerate SIS model
Directory of Open Access Journals (Sweden)
Tarik Ali Ziane
2013-01-01
Full Text Available In this paper we investigate the global existence and asymptotic behavior of a reaction diffusion system with degenerate diffusion arising in the modeling and the spatial spread of an epidemic disease.
Kai Zhou; Qi-Ru Wang
2014-01-01
This paper is concerned with the existence of traveling waves for a delayed SIRS epidemic diffusion model with saturation incidence rate. By using the cross-iteration method and Schauder’s fixed point theorem, we reduce the existence of traveling waves to the existence of a pair of upper-lower solutions. By careful analyzsis, we derive the existence of traveling waves connecting the disease-free steady state and the endemic steady state through the establishment of the suitable upper-lower...
Existence and Convergence of the Positive Solutions of a Discrete Epidemic Model
Directory of Open Access Journals (Sweden)
Zhijian Wei
2015-01-01
Full Text Available We consider a class of system of nonlinear difference equations arising from mathematical models describing a discrete epidemic model. Sufficient conditions are established that guarantee the existence of positive solutions, the existence of a unique nonnegative equilibrium, and the convergence of the positive solutions to the nonnegative equilibrium of the system of difference equations. The obtained results are new and they complement previously known results.
Global Existence of Weak Solutions to a Fractional Model in Magnetoelastic Interactions
Directory of Open Access Journals (Sweden)
Idriss Ellahiani
2016-01-01
Full Text Available The paper deals with global existence of weak solutions to a one-dimensional mathematical model describing magnetoelastic interactions. The model is described by a fractional Landau-Lifshitz-Gilbert equation for the magnetization field coupled to an evolution equation for the displacement. We prove global existence by using Faedo-Galerkin/penalty method. Some commutator estimates are used to prove the convergence of nonlinear terms.
Modelling a New Product Model on the Basis of an Existing STEP Application Protocol
Directory of Open Access Journals (Sweden)
B.-R. Hoehn
2005-01-01
Full Text Available During the last years a great range of computer aided tools has been generated to support the development process of various products. The goal of a continuous data flow, needed for high efficiency, requires powerful standards for the data exchange. At the FZG (Gear Research Centre of the Technical University of Munich there was a need for a common gear data format for data exchange between gear calculation programs. The STEP standard ISO 10303 was developed for this type of purpose, but a suitable definition of gear data was still missing, even in the Application Protocol AP 214, developed for the design process in the automotive industry. The creation of a new STEP Application Protocol or the extension of existing protocol would be a very time consumpting normative process. So a new method was introduced by FZG. Some very general definitions of an Application Protocol (here AP 214 were used to determine rules for an exact specification of the required kind of data. In this case a product model for gear units was defined based on elements of the AP 214. Therefore no change of the Application Protocol is necessary. Meanwhile the product model for gear units has been published as a VDMA paper and successfully introduced for data exchange within the German gear industry associated with FVA (German Research Organisation for Gears and Transmissions. This method can also be adopted for other applications not yet sufficiently defined by STEP.
Incorporation of Electrical Systems Models Into an Existing Thermodynamic Cycle Code
Freeh, Josh
2003-01-01
Integration of entire system includes: Fuel cells, motors, propulsors, thermal/power management, compressors, etc. Use of existing, pre-developed NPSS capabilities includes: 1) Optimization tools; 2) Gas turbine models for hybrid systems; 3) Increased interplay between subsystems; 4) Off-design modeling capabilities; 5) Altitude effects; and 6) Existing transient modeling architecture. Other factors inclde: 1) Easier transfer between users and groups of users; 2) General aerospace industry acceptance and familiarity; and 3) Flexible analysis tool that can also be used for ground power applications.
EXISTENCE OF PERIODIC SOLUTIONS FOR A DISCRETE-TIME MODEL OF TWO-CELL CNNS
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
We investigate a class of discrete-time model of two-cell cellular neural networks with symmetric template. By using the Lyapunov direct method, La-Salle's invariance principle, we discuss the existence and the stability of periodic solutions. The model considered has attractive 2-periodic and unstable 2-periodic solutions.
On the Existence and Uniqueness of Maximum-Likelihood Estimates in the Rasch Model.
Fischer, Gerhard H.
1981-01-01
Necessary and sufficient conditions for the existence and uniqueness of a solution of the so-called "unconditional" and the "conditional" maximum-likelihood estimation equations in the dichotomous Rasch model are given. It is shown how to apply the results in practical uses of the Rasch model. (Author/JKS)
Existence and linear stability of planar waves in the Oregonator model
Institute of Scientific and Technical Information of China (English)
周天寿; 何小兰
2002-01-01
In this paper, various waves in the Oregonator model are investigated in detail. The existence of planar waves (in particular, spiral waves) is rigorously proven and their linear stability is analysed. In addition, some non-planar waves in the model are also presented.
EXISTENCE AND UNIQUENESS OF ENDEMIC STATES FOR THE AGE-STRUCTURED SEIR EPIDEMIC MODEL
Institute of Scientific and Technical Information of China (English)
Xuezhi LI; Jing CHEN
2006-01-01
An age-structured SEIR epidemic model of a vertically as well as horizontally transmitted disease is investigated. Threshold results for the existence of endemic states are established for most cases. Under certain conditions, uniqueness is also shown. Threshold used are explicitly computable in term of demographic and epidemiological parameters of the model.
Directory of Open Access Journals (Sweden)
Cosimo Bambi
2013-01-01
Full Text Available Black holes have the peculiar and intriguing property of having an event horizon, a one-way membrane causally separating their internal region from the rest of the Universe. Today, astrophysical observations provide some evidence for the existence of event horizons in astrophysical black hole candidates. In this short paper, I compare the constraint we can infer from the nonobservation of electromagnetic radiation from the putative surface of these objects with the bound coming from the ergoregion instability, pointing out the respective assumptions and limitations.
Static Universe model existing due to the Matter-Dark Energy coupling
Bizet, Alejandro Cabo
2007-01-01
The work investigate a static, isotropic and almost homogeneous Universe containing a real scalar field modeling the Dark-Energy (quintaessence) interacting with pressureless matter. It is argued that the interaction between matter and the Dark Energy, is essential for the very existence of the considered solution. Assuming the possibility that Dark-Energy can be furnished by the Dilaton (a scalar field reflecting the condensation of string states with zero angular momentum) we fix the value of scalar field at the origin to the Planck scale. It became possible to fix the ratio of the amount of Dark Energy to matter energy, in the currently estimated value 0.7/0.3, and also the observed magnitude of the Hubble constant. The value of the mass for the scalar field chosen for fixing the above ratio and Hubble effect strength, results to be of the order of 10^{-29}cm^{-1}, a small mass which seems to be compatible with the zero mass of the Dilaton in the lowest approximations.
Discrete modeling of hydraulic fracturing processes in a complex pre-existing fracture network
Kim, K.; Rutqvist, J.; Nakagawa, S.; Houseworth, J. E.; Birkholzer, J. T.
2015-12-01
Hydraulic fracturing and stimulation of fracture networks are widely used by the energy industry (e.g., shale gas extraction, enhanced geothermal systems) to increase permeability of geological formations. Numerous analytical and numerical models have been developed to help understand and predict the behavior of hydraulically induced fractures. However, many existing models assume simple fracturing scenarios with highly idealized fracture geometries (e.g., propagation of a single fracture with assumed shapes in a homogeneous medium). Modeling hydraulic fracture propagation in the presence of natural fractures and homogeneities can be very challenging because of the complex interactions between fluid, rock matrix, and rock interfaces, as well as the interactions between propagating fractures and pre-existing natural fractures. In this study, the TOUGH-RBSN code for coupled hydro-mechanical modeling is utilized to simulate hydraulic fracture propagation and its interaction with pre-existing fracture networks. The simulation tool combines TOUGH2, a simulator of subsurface multiphase flow and mass transport based on the finite volume approach, with the implementation of a lattice modeling approach for geomechanical and fracture-damage behavior, named Rigid-Body-Spring Network (RBSN). The discrete fracture network (DFN) approach is facilitated in the Voronoi discretization via a fully automated modeling procedure. The numerical program is verified through a simple simulation for single fracture propagation, in which the resulting fracture geometry is compared to an analytical solution for given fracture length and aperture. Subsequently, predictive simulations are conducted for planned laboratory experiments using rock-analogue (soda-lime glass) samples containing a designed, pre-existing fracture network. The results of a preliminary simulation demonstrate selective fracturing and fluid infiltration along the pre-existing fractures, with additional fracturing in part
Constraining Cosmological Models with Different Observations
Wei, J. J.
2016-07-01
With the observations of Type Ia supernovae (SNe Ia), scientists discovered that the Universe is experiencing an accelerated expansion, and then revealed the existence of dark energy in 1998. Since the amazing discovery, cosmology has became a hot topic in the physical research field. Cosmology is a subject that strongly depends on the astronomical observations. Therefore, constraining different cosmological models with all kinds of observations is one of the most important research works in the modern cosmology. The goal of this thesis is to investigate cosmology using the latest observations. The observations include SNe Ia, Type Ic Super Luminous supernovae (SLSN Ic), Gamma-ray bursts (GRBs), angular diameter distance of galaxy cluster, strong gravitational lensing, and age measurements of old passive galaxies, etc. In Chapter 1, we briefly review the research background of cosmology, and introduce some cosmological models. Then we summarize the progress on cosmology from all kinds of observations in more details. In Chapter 2, we present the results of our studies on the supernova cosmology. The main difficulty with the use of SNe Ia as standard candles is that one must optimize three or four nuisance parameters characterizing SN luminosities simultaneously with the parameters of an expansion model of the Universe. We have confirmed that one should optimize all of the parameters by carrying out the method of maximum likelihood estimation in any situation where the parameters include an unknown intrinsic dispersion. The commonly used method, which estimates the dispersion by requiring the reduced χ^{2} to equal unity, does not take into account all possible variances among the parameters. We carry out such a comparison of the standard ΛCDM cosmology and the R_{h}=ct Universe using the SN Legacy Survey sample of 252 SN events, and show that each model fits its individually reduced data very well. Moreover, it is quite evident that SLSNe Ic may be useful
Existence of Global Weak Solutions to a Hybrid Vlasov-MHD Model for Magnetized Plasmas
Cheng, Bin; Tronci, Cesare
2016-01-01
We prove the global-in-time existence of large-data finite-energy weak solutions to an incompressible hybrid Vlasov-magnetohydrodynamic model in three space dimensions. The model couples three essential ingredients of magnetized plasmas: a transport equation for the probability density function, which models energetic rarefied particles of one species; the incompressible Navier--Stokes system for the bulk fluid; and a parabolic evolution equation, involving magnetic diffusivity, for the magnetic field. The physical derivation of our model is given. It is also shown that the weak solution, whose existence is established, has nonincreasing total energy, and that it satisfies a number of physically relevant properties, including conservation of the total momentum, conservation of the total mass, and nonnegativity of the probability density function for the energetic particles. The proof is based on a one-level approximation scheme, which is carefully devised to avoid increase of the total energy for the sequence...
On the Existence and Uniqueness of JML Estimates for the Partial Credit Model
Bertoli-Barsotti, Lucio
2005-01-01
A necessary and sufficient condition is given in this paper for the existence and uniqueness of the maximum likelihood (the so-called joint maximum likelihood) estimate of the parameters of the Partial Credit Model. This condition is stated in terms of a structural property of the pattern of the data matrix that can be easily verified on the basis…
Existence of global weak solution for a reduced gravity two and a half layer model
Energy Technology Data Exchange (ETDEWEB)
Guo, Zhenhua, E-mail: zhenhua.guo.math@gmail.com; Li, Zilai, E-mail: lizilai0917@163.com; Yao, Lei, E-mail: yaolei1056@hotmail.com [Department of Mathematics and CNS, Northwest University, Xi' an 710127 (China)
2013-12-15
We investigate the existence of global weak solution to a reduced gravity two and a half layer model in one-dimensional bounded spatial domain or periodic domain. Also, we show that any possible vacuum state has to vanish within finite time, then the weak solution becomes a unique strong one.
Necessary and sufficient conditions for the existence of the UMRE estimator in growth curve models
Institute of Scientific and Technical Information of China (English)
吴启光
1995-01-01
The necessary and sufficient conditions are derived for the existence of the uniformly minimum risk equivariant (UMRE) estimator of regression coefficient matrix in normal growth carve models with arbitrary covariance matrix or uniform oovananoe structure or serial covariance structure under an affine group and a transitive group of transformations for quadratic losses and matrix losses, respectively.
Existence of limit cycles in the Solow model with delayed-logistic population growth.
Bianca, Carlo; Guerrini, Luca
2014-01-01
This paper is devoted to the existence and stability analysis of limit cycles in a delayed mathematical model for the economy growth. Specifically the Solow model is further improved by inserting the time delay into the logistic population growth rate. Moreover, by choosing the time delay as a bifurcation parameter, we prove that the system loses its stability and a Hopf bifurcation occurs when time delay passes through critical values. Finally, numerical simulations are carried out for supporting the analytical results.
Mentoring for junior medical faculty: Existing models and suggestions for low-resource settings.
Menon, Vikas; Muraleedharan, Aparna; Bhat, Ballambhattu Vishnu
2016-02-01
Globally, there is increasing recognition about the positive benefits and impact of mentoring on faculty retention rates, career satisfaction and scholarly output. However, emphasis on research and practice of mentoring is comparatively meagre in low and middle income countries. In this commentary, we critically examine two existing models of mentorship for medical faculty and offer few suggestions for an integrated hybrid model that can be adapted for use in low resource settings.
Borlawsky, Tara; LaFountain, Jeanne; Petty, Lynda; Saltz, Joel H; Payne, Philip R O
2008-11-06
Workflow analysis is frequently performed in the context of operations research and process optimization. In order to develop a data-driven workflow model that can be employed to assess opportunities to improve the efficiency of perioperative care teams at The Ohio State University Medical Center (OSUMC), we have developed a method for integrating standard workflow modeling formalisms, such as UML activity diagrams with data-centric annotations derived from our existing data warehouse.
Existing and Required Modeling Capabilities for Evaluating ATM Systems and Concepts
Odoni, Amedeo R.; Bowman, Jeremy; Delahaye, Daniel; Deyst, John J.; Feron, Eric; Hansman, R. John; Khan, Kashif; Kuchar, James K.; Pujet, Nicolas; Simpson, Robert W.
1997-01-01
ATM systems throughout the world are entering a period of major transition and change. The combination of important technological developments and of the globalization of the air transportation industry has necessitated a reexamination of some of the fundamental premises of existing Air Traffic Management (ATM) concepts. New ATM concepts have to be examined, concepts that may place more emphasis on: strategic traffic management; planning and control; partial decentralization of decision-making; and added reliance on the aircraft to carry out strategic ATM plans, with ground controllers confined primarily to a monitoring and supervisory role. 'Free Flight' is a case in point. In order to study, evaluate and validate such new concepts, the ATM community will have to rely heavily on models and computer-based tools/utilities, covering a wide range of issues and metrics related to safety, capacity and efficiency. The state of the art in such modeling support is adequate in some respects, but clearly deficient in others. It is the objective of this study to assist in: (1) assessing the strengths and weaknesses of existing fast-time models and tools for the study of ATM systems and concepts and (2) identifying and prioritizing the requirements for the development of additional modeling capabilities in the near future. A three-stage process has been followed to this purpose: 1. Through the analysis of two case studies involving future ATM system scenarios, as well as through expert assessment, modeling capabilities and supporting tools needed for testing and validating future ATM systems and concepts were identified and described. 2. Existing fast-time ATM models and support tools were reviewed and assessed with regard to the degree to which they offer the capabilities identified under Step 1. 3 . The findings of 1 and 2 were combined to draw conclusions about (1) the best capabilities currently existing, (2) the types of concept testing and validation that can be carried
Global existence and blowup of solutions to a free boundary problem for mutualistic model
Institute of Scientific and Technical Information of China (English)
KIM; KwangIk
2010-01-01
This article is concerned with a system of semilinear parabolic equations with a free boundary,which arises in a mutualistic ecological model.The local existence and uniqueness of a classical solution are obtained.The asymptotic behavior of the free boundary problem is studied.Our results show that the free problem admits a global slow solution if the inter-specific competitions are strong,while if the inter-specific competitions are weak there exist the blowup solution and global fast solution.
3D mapping of existing observing capabilities in the frame of GAIA-CLIM H2020 project
Emanuele, Tramutola; Madonna, Fabio; Marco, Rosoldi; Francesco, Amato
2017-04-01
The aim of the Gap Analysis for Integrated Atmospheric ECV CLImate Monitoring (GAIA-CLIM) project is to improve our ability to use ground-based and sub-orbital observations to characterise satellite observations for a number of atmospheric Essential Climate Variables (ECVs). The key outcomes will be a "Virtual Observatory" (VO) facility of co-locations and their uncertainties and a report on gaps in capabilities or understanding, which shall be used to inform subsequent Horizon 2020 activities. In particular, Work Package 1 (WP1) of the GAIA-CLIM project is devoted to the geographical mapping of existing non-satellite measurement capabilities for a number of ECVs in the atmospheric, oceanic and terrestrial domains. The work carried out within WP1 has allowed to provide the users with an up-to-date geographical identification, at the European and global scales, of current surface-based, balloon-based and oceanic (floats) observing capabilities on an ECV by ECV basis for several parameters which can be obtained using space-based observations from past, present and planned satellite missions. Having alighted on a set of metadata schema to follow, a consistent collection of discovery metadata has been provided into a common structure and will be made available to users through the GAIA-CLIM VO in 2018. Metadata can be interactively visualized through a 3D Graphical User Interface. The metadataset includes 54 plausible networks and 2 aircraft permanent infrastructures for EO Characterisation in the context of GAIA-CLIM currently operating on different spatial domains and measuring different ECVs using one or more measurement techniques. Each classified network has in addition been assessed for suitability against metrological criteria to identifyy those with a level of maturity which enables closure on a comparison with satellite measurements. The metadata GUI is based on Cesium, a virtual globe freeware and open source written in Javascript. It allows users to apply
Existence and regularity of weak solutions to a model for coarsening in molecular beam epitaxy
Zhang, Jun
2011-01-01
Taking into account the occurrence of a zero of the surface diffusion current and the requirement of the Ehrlich-Schwoebel effect, Siegert et al \\cite{Siegert94} formulate a model of Langevin type that describes the growth of pyramidlike structures on a surface under conditions of molecular beam epitaxy, and that the slope of these pyramids is selected by the crystalline symmetries of the growing film. In this article, the existence and uniqueness of weak solution to an initial boundary value problem for this model is proved, in the case that the noise is neglected. The regularity of the weak solution to models, with/without slope selection, is also investigated.
Observing and Modeling Earth's Energy Flows
Stevens, Bjorn; Schwartz, Stephen E.
2012-07-01
This article reviews, from the authors' perspective, progress in observing and modeling energy flows in Earth's climate system. Emphasis is placed on the state of understanding of Earth's energy flows and their susceptibility to perturbations, with particular emphasis on the roles of clouds and aerosols. More accurate measurements of the total solar irradiance and the rate of change of ocean enthalpy help constrain individual components of the energy budget at the top of the atmosphere to within ±2 W m-2. The measurements demonstrate that Earth reflects substantially less solar radiation and emits more terrestrial radiation than was believed even a decade ago. Active remote sensing is helping to constrain the surface energy budget, but new estimates of downwelling surface irradiance that benefit from such methods are proving difficult to reconcile with existing precipitation climatologies. Overall, the energy budget at the surface is much more uncertain than at the top of the atmosphere. A decade of high-precision measurements of the energy budget at the top of the atmosphere is providing new opportunities to track Earth's energy flows on timescales ranging from days to years, and at very high spatial resolution. The measurements show that the principal limitation in the estimate of secular trends now lies in the natural variability of the Earth system itself. The forcing-feedback-response framework, which has developed to understand how changes in Earth's energy flows affect surface temperature, is reviewed in light of recent work that shows fast responses (adjustments) of the system are central to the definition of the effective forcing that results from a change in atmospheric composition. In many cases, the adjustment, rather than the characterization of the compositional perturbation (associated, for instance, with changing greenhouse gas concentrations, or aerosol burdens), limits accurate determination of the radiative forcing. Changes in clouds contribute
EXISTENCE OF GLOBAL SMOOTH SOLUTION TO JIN-XIN MODEL WITH LARGE INITIAL DATA
Institute of Scientific and Technical Information of China (English)
Ruan Lizhi; Zhang Zhiyong
2004-01-01
In this paper, Under the assumption that the relaxation time e is suf-ficiently small, we prove the existence of the global smooth solution to the Cauchyproblem for the Jin-Xin model without any smallness assumption for the initial data.The analysis is based on some a priori estimates which are obtained by the method ofcharacteristic and the maximum principle of first-order quasilinear hyperbolic system.
Existence theory for a Poisson-Nernst-Planck model of electrophoresis
Bedin, Luciano
2011-01-01
A system modeling the electrophoretic motion of a charged rigid macromolecule immersed in a incompressible ionized fluid is considered. The ionic concentration is governing by the Nernst-Planck equation coupled with the Poisson equation for the electrostatic potential, Navier-Stokes and Newtonian equations for the fluid and the macromolecule dynamics, respectively. A local in time existence result for suitable weak solutions is established, following the approach of Desjardins and Esteban [Comm. Partial Diff. Eq., 25 (2000), 1399--1414].
Observational constraints on the LLTB model
Marra, Valerio
2010-01-01
We directly compare the concordance LCDM model to the inhomogeneous matter-only alternative represented by LTB void models. To achieve a "democratic" confrontation we explore LLTB models with non-vanishing cosmological constant and perform a global likelihood analysis in the parameter space of cosmological constant and void radius. In our analysis we carefully consider SNe, Hubble constant, CMB and BAO measurements, marginalizing over the age of the universe and the background curvature. We find that the LCDM model is not the only possibility compatible with the observations, and that a matter-only void model is a viable alternative to the concordance model only if the BAO constraints are relaxed. Moreover, we will show that the areas of the parameter space which give a good fit to the observations are always disconnected with the result that a small local void does not significantly affect the parameter extraction for LCDM models.
Had the Planet Mars Not Existed: Kepler's Equant Model and Its Physical Consequences
Bracco, C.; Provost, J.P.
2009-01-01
We examine the equant model for the motion of planets, which was the starting point of Kepler's investigations before he modified it because of Mars observations. We show that, up to first order in eccentricity, this model implies for each orbit a velocity, which satisfies Kepler's second law and Hamilton's hodograph, and a centripetal…
Hardison, David; Medina, Johnny; Dell, Greg
2016-01-01
The Earth Observer System (EOS) was officially established in 1990 and went operational in December 1999 with the launch of its flagship spacecraft Terra. Aqua followed in 2002 and Aura in 2004. All three spacecraft are still operational and producing valuable scientific data. While all are beyond their original design lifetime, they are expected to remain viable well into the 2020s. The EOS Ground System is a multi-mission system based at NASA Goddard Space Flight Center that supports science and spacecraft operations for these three missions. Over its operational lifetime to date, the EOS Ground System has evolved as needed to accommodate mission requirements. With an eye towards the future, several updates are currently being deployed. Subsystem interconnects are being upgraded to reduce data latency and improve system performance. End-of-life hardware and operating systems are being replaced to mitigate security concerns and eliminate vendor support gaps. Subsystem hardware is being consolidated through the migration to Virtual Machine based platforms. While mission operations autonomy was not a design goal of the original system concept, there is an active effort to apply state-of-the-art products from the Goddard Mission Services Evolution Center (GMSEC) to facilitate automation where possible within the existing heritage architecture. This presentation will provide background information on the EOS ground system architecture and evolution, discuss latest improvements, and conclude with the results of a recent effort that investigated how the current system could accommodate a proposed new earth science mission.
Observational Challenges for the Standard FLRW Model
Buchert, Thomas; Kleinert, Hagen; Roukema, Boudewijn F; Wiltshire, David L
2015-01-01
In the context of the "Fourteenth Marcel Grossman Meeting on General Relativity" parallel session DE3, "Large--scale Structure and Statistics", concerning observational issues in cosmology, we summarise some of the main observational challenges for the standard FLRW model and describe how the results presented in the session are related to these challenges.
Delle Monache, M. L.; Goatin, P.
2014-12-01
We consider a strongly coupled PDE-ODE system that describes the influence of a slow and large vehicle on road traffic. The model consists of a scalar conservation law accounting for the main traffic evolution, while the trajectory of the slower vehicle is given by an ODE depending on the downstream traffic density. The moving constraint is expressed by an inequality on the flux, which models the bottleneck created in the road by the presence of the slower vehicle. We prove the existence of solutions to the Cauchy problem for initial data of bounded variation.
EXISTENCE AND REGULARITY OF SOLUTIONS TO MODEL FOR LIQUID MIXTURE OF 3HE-4HE
Institute of Scientific and Technical Information of China (English)
Luo Hong; Pu Zhilin
2012-01-01
Existence and regularity of solutions to model for liquid mixture of 3He-4He is considered in this paper.First,it is proved that this system possesses a unique global weak solution in H1(Ω,C × R) by using Galerkin method.Secondly,by using an iteration procedure,regularity estimates for the linear semigroups,it is proved that the model for liquid mixture of 3He-4He has a unique solution in Hk(Ω,C × R) for all k ≥ 1.
Isbell, James M; Deppen, Stephen; Putnam, Joe B; Nesbitt, Jonathan C; Lambright, Eric S; Dawes, Aaron; Massion, Pierre P; Speroff, Theodore; Jones, David R; Grogan, Eric L
2011-01-01
Patients undergoing resections for suspicious pulmonary lesions have a 9% to 55% benign rate. Validated prediction models exist to estimate the probability of malignancy in a general population and current practice guidelines recommend their use. We evaluated these models in a surgical population to determine the accuracy of existing models to predict benign or malignant disease. We conducted a retrospective review of our thoracic surgery quality improvement database (2005 to 2008) to identify patients who underwent resection of a pulmonary lesion. Patients were stratified into subgroups based on age, smoking status, and fluorodeoxyglucose positron emission tomography (PET) results. The probability of malignancy was calculated for each patient using the Mayo and solitary pulmonary nodules prediction models. Receiver operating characteristic and calibration curves were used to measure model performance. A total of 189 patients met selection criteria; 73% were malignant. Patients with preoperative PET scans were divided into four subgroups based on age, smoking history, and nodule PET avidity. Older smokers with PET-avid lesions had a 90% malignancy rate. Patients with PET-nonavid lesions, PET-avid lesions with age less than 50 years, or never smokers of any age had a 62% malignancy rate. The area under the receiver operating characteristic curve for the Mayo and solitary pulmonary nodules models was 0.79 and 0.80, respectively; however, the models were poorly calibrated (p<0.001). Despite improvements in diagnostic and imaging techniques, current general population models do not accurately predict lung cancer among patients referred for surgical evaluation. Prediction models with greater accuracy are needed to identify patients with benign disease to reduce nontherapeutic resections. Copyright © 2011 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.
Rajaraman, Prathish K; Manteuffel, T A; Belohlavek, M; Heys, Jeffrey J
2017-01-01
A new approach has been developed for combining and enhancing the results from an existing computational fluid dynamics model with experimental data using the weighted least-squares finite element method (WLSFEM). Development of the approach was motivated by the existence of both limited experimental blood velocity in the left ventricle and inexact numerical models of the same flow. Limitations of the experimental data include measurement noise and having data only along a two-dimensional plane. Most numerical modeling approaches do not provide the flexibility to assimilate noisy experimental data. We previously developed an approach that could assimilate experimental data into the process of numerically solving the Navier-Stokes equations, but the approach was limited because it required the use of specific finite element methods for solving all model equations and did not support alternative numerical approximation methods. The new approach presented here allows virtually any numerical method to be used for approximately solving the Navier-Stokes equations, and then the WLSFEM is used to combine the experimental data with the numerical solution of the model equations in a final step. The approach dynamically adjusts the influence of the experimental data on the numerical solution so that more accurate data are more closely matched by the final solution and less accurate data are not closely matched. The new approach is demonstrated on different test problems and provides significantly reduced computational costs compared with many previous methods for data assimilation. Copyright © 2016 John Wiley & Sons, Ltd.
A review of existing models and methods to estimate employment effects of pollution control policies
Energy Technology Data Exchange (ETDEWEB)
Darwin, R.F.; Nesse, R.J.
1988-02-01
The purpose of this paper is to provide information about existing models and methods used to estimate coal mining employment impacts of pollution control policies. The EPA is currently assessing the consequences of various alternative policies to reduce air pollution. One important potential consequence of these policies is that coal mining employment may decline or shift from low-sulfur to high-sulfur coal producing regions. The EPA requires models that can estimate the magnitude and cost of these employment changes at the local level. This paper contains descriptions and evaluations of three models and methods currently used to estimate the size and cost of coal mining employment changes. The first model reviewed is the Coal and Electric Utilities Model (CEUM), a well established, general purpose model that has been used by the EPA and other groups to simulate air pollution control policies. The second model reviewed is the Advanced Utility Simulation Model (AUSM), which was developed for the EPA specifically to analyze the impacts of air pollution control policies. Finally, the methodology used by Arthur D. Little, Inc. to estimate the costs of alternative air pollution control policies for the Consolidated Coal Company is discussed. These descriptions and evaluations are based on information obtained from published reports and from draft documentation of the models provided by the EPA. 12 refs., 1 fig.
Global existence of solutions to a tear film model with locally elevated evaporation rates
Gao, Yuan; Ji, Hangjie; Liu, Jian-Guo; Witelski, Thomas P.
2017-07-01
Motivated by a model proposed by Peng et al. (2014) for break-up of tear films on human eyes, we study the dynamics of a generalized thin film model. The governing equations form a fourth-order coupled system of nonlinear parabolic PDEs for the film thickness and salt concentration subject to non-conservative effects representing evaporation. We analytically prove the global existence of solutions to this model with mobility exponents in several different ranges and present numerical simulations that are in agreement with the analytic results. We also numerically capture other interesting dynamics of the model, including finite-time rupture-shock phenomenon due to the instabilities caused by locally elevated evaporation rates, convergence to equilibrium and infinite-time thinning.
Evaluation Between Existing and Improved CCF Modeling Using the NRC SPAR Models
Energy Technology Data Exchange (ETDEWEB)
James K. Knudsen
2010-06-01
Abstract: The NRC SPAR models currently employ the alpha factor common cause failure (CCF) methodology and model CCF for a group of redundant components as a single “rolled-up” basic event. These SPAR models will be updated to employ a more computationally intensive and accurate approach by expanding the CCF basic events for all active components to include all terms that appear in the Basic Parameter Model (BPM). A discussion is provided to detail the differences between the rolled-up common cause group (CCG) and expanded BPM adjustment concepts based on differences in core damage frequency and individual component importance measures. Lastly, a hypothetical condition is evaluated with a SPAR model to show the difference in results between the current adjustment method (rolled-up CCF events) and the newer method employing all of the expanded terms in the BPM. The event evaluation on the SPAR model employing the expanded terms will be solved using the graphical evaluation module (GEM) and the proposed method discussed in Reference 1.
Observations and Modelling of DQ White Dwarfs
Vornanen, Tommi; Berdyugin, Andrei
2012-01-01
We present spectropolarimetric observations and modelling of 12 DQ white dwarfs. Modelling is based on the method presented in Berdyugina et al. (2005). We use the model to fit the C_2 absorption bands to get atmospheric parameters in different configurations, including stellar spots and stratified atmospheres, searching for the best possible fit. We still have problem to solve before we can give temperature estimates based on the Swan bands alone.
Models and observations of sunspot penumbrae
Institute of Scientific and Technical Information of China (English)
BORRERO; Juan; Manuel
2009-01-01
The mysteries of sunspot penumbrae have been under an intense scrutiny for the past 10 years. During this time, some models have been proposed and refuted, while the surviving ones had to be modified, adapted and evolved to explain the ever-increasing array of observational constraints. In this contribution I will review two of the present models, emphasizing their contributions to this field, but also pinpointing some of their inadequacies to explain a number of recent observations at very high spatial resolution (0.32 ). To help explaining these new observations I propose some modifications to each of those models. These modifications bring those two seemingly opposite models closer together into a general picture that agrees well with recent 3D magneto-hydrodynamic simulations.
Towards real-time change detection in videos based on existing 3D models
Ruf, Boitumelo; Schuchert, Tobias
2016-10-01
Image based change detection is of great importance for security applications, such as surveillance and reconnaissance, in order to find new, modified or removed objects. Such change detection can generally be performed by co-registration and comparison of two or more images. However, existing 3d objects, such as buildings, may lead to parallax artifacts in case of inaccurate or missing 3d information, which may distort the results in the image comparison process, especially when the images are acquired from aerial platforms like small unmanned aerial vehicles (UAVs). Furthermore, considering only intensity information may lead to failures in detection of changes in the 3d structure of objects. To overcome this problem, we present an approach that uses Structure-from-Motion (SfM) to compute depth information, with which a 3d change detection can be performed against an existing 3d model. Our approach is capable of the change detection in real-time. We use the input frames with the corresponding camera poses to compute dense depth maps by an image-based depth estimation algorithm. Additionally we synthesize a second set of depth maps, by rendering the existing 3d model from the same camera poses as those of the image-based depth map. The actual change detection is performed by comparing the two sets of depth maps with each other. Our method is evaluated on synthetic test data with corresponding ground truth as well as on real image test data.
Numerical Modelling of Extended Leak-Off Test with a Pre-Existing Fracture
Lavrov, A.; Larsen, I.; Bauer, A.
2016-04-01
Extended leak-off test (XLOT) is one of the few techniques available for stress measurements in oil and gas wells. Interpretation of the test is often difficult since the results depend on a multitude of factors, including the presence of natural or drilling-induced fractures in the near-well area. Coupled numerical modelling of XLOT has been performed to investigate the pressure behaviour during the flowback phase as well as the effect of a pre-existing fracture on the test results in a low-permeability formation. Essential features of XLOT known from field measurements are captured by the model, including the saw-tooth shape of the pressure vs injected volume curve, and the change of slope in the pressure vs time curve during flowback used by operators as an indicator of the bottomhole pressure reaching the minimum in situ stress. Simulations with a pre-existing fracture running from the borehole wall in the radial direction have revealed that the results of XLOT are quite sensitive to the orientation of the pre-existing fracture. In particular, the fracture initiation pressure and the formation breakdown pressure increase steadily with decreasing angle between the fracture and the minimum in situ stress. Our findings seem to invalidate the use of the fracture initiation pressure and the formation breakdown pressure for stress measurements or rock strength evaluation purposes.
Sathnur, Ashwini
2017-04-01
" positives. Cost - free data made available. Minimum band - width problem. Rapid communication system. Validation and Requirements of the New products of the Remote Sensing instruments The qualities of the existing products would be present in the new products also. Along with these qualities, newly devised additional qualities are also required in order to build an advanced remote sensing instrument. The new additional requirements are mentioned below:- Review Comment Number 1 Enlarging the spatial resolution so that the volcanic plumes erupting from the early volcanic eruption is captured by the remote sensing instrument. This spatial resolution data capture would involve better video and camera facilities on the remote sensing instrument. Review Comment Number 2 Capturing the traces of carbon, carbonic acid and water vapour, along with the existing product's capture of sulphur dioxide and volcanic Ash. Review Comment Number 3 Creating an additional module in the instrument to derive the functionality of forecasting a volcanic eruption. This new forecast model should be able to predict the occurrences of volcanic eruption several months in advance. This is basically to create mechanisms for providing early solutions to the problems of mitigation of volcanic hazards. Review Comment Number 4 Creating additional features in the remote sensing instrument to enable the automatic transfer of forecasted eruptions of volcanoes, to the disaster relief operations team. This transfer of information is to be performed automatically, without any request raised from the relief operations team, for the predicted forecast information. This is for the purpose of receiving the information at the right - time, thus eliminating any possibility of occurrences of errors during hazard management.
Analytic proof of the existence of the Lorenz attractor in the extended Lorenz model
Ovsyannikov, I. I.; Turaev, D. V.
2017-01-01
We give an analytic (free of computer assistance) proof of the existence of a classical Lorenz attractor for an open set of parameter values of the Lorenz model in the form of Yudovich-Morioka-Shimizu. The proof is based on detection of a homoclinic butterfly with a zero saddle value and rigorous verification of one of the Shilnikov criteria for the birth of the Lorenz attractor; we also supply a proof for this criterion. The results are applied in order to give an analytic proof for the existence of a robust, pseudohyperbolic strange attractor (the so-called discrete Lorenz attractor) for an open set of parameter values in a 4-parameter family of 3D Henon-like diffeomorphisms.
Measuring and Managing Value Co-Creation Process: Overview of Existing Theoretical Models
Directory of Open Access Journals (Sweden)
Monika Skaržauskaitė
2013-08-01
Full Text Available Purpose — the article is to provide a holistic view on concept of value co-creation and existing models for measuring and managing it by conducting theoretical analysis of scientific literature sources targeting the integration of various approaches. Most important and relevant results of the literature study are presented with a focus on changed roles of organizations and consumers. This article aims at contributing theoretically to the research stream of measuring co-creation of value in order to gain knowledge for improvement of organizational performance and enabling new and innovative means of value creation. Design/methodology/approach. The nature of this research is exploratory – theoretical analysis and synthesis of scientific literature sources targeting the integration of various approaches was performed. This approach was chosen due to the absence of established theory on models of co-creation, possible uses in organizations and systematic overview of tools measuring/suggesting how to measure co-creation. Findings. While the principles of managing and measuring co-creation in regards of consumer motivation and involvement are widely researched, little attempt has been made to identify critical factors and create models dealing with organizational capabilities and managerial implications of value co-creation. Systematic analysis of literature revealed a gap not only in empirical research concerning organization’s role in co-creation process, but in theoretical and conceptual levels, too. Research limitations/implications. The limitations of this work as a literature review lies in its nature – the complete reliance on previously published research papers and the availability of these studies. For a deeper understanding of co-creation management and for developing models that can be used in real-life organizations, a broader theoretical, as well as empirical, research is necessary. Practical implications. Analysis of the
Identifying best existing practice for characterization modeling in life cycle impact assessment
DEFF Research Database (Denmark)
Hauschild, Michael Zwicky; Goedkoop, Mark; Guinée, Jeroen
2013-01-01
Purpose: Life cycle impact assessment (LCIA) is a field of active development. The last decade has seen prolific publication of new impact assessment methods covering many different impact categories and providing characterization factors that often deviate from each other for the same substance...... continents and still support aggregation of impact scores over the whole life cycle. For the impact categories human toxicity and ecotoxicity, we are now able to recommend a model, but the number of chemical substances in common use is so high that there is a need to address the substance data shortage...... was performed for the Joint Research Centre of the European Commission (JRC). Methods Existing LCIA methods were collected and their individual characterization models identified at both midpoint and endpoint levels and supplemented with other environmental models of potential use for LCIA. No new developments...
Models and Observations of Sunspot Penumbrae
Borrero, J M
2008-01-01
The mysteries of sunspot penumbrae have been under an intense scrutiny for the past 10 years. During this time, some models have been proposed and refuted, while the surviving ones had to be modified, adapted and evolved to explain the ever-increasing array of observational constraints. In this contribution I will review two of the present models, emphasizing their contributions to this field, but also pinpointing some of their inadequacies to explain a number of recent observations at very high spatial resolution. To help explaining these new observations I propose some modifications to each of them. These modifications bring those two seemingly opposite models closer together into a general picture that agrees well with recent 3D magneto-hydrodynamic simulations.
THE EXISTENCE OF POSITIVE PERIODIC SOLUTIONS IN A LOGISTIC DIFFERENCE MODEL WITH A FEEDBACK CONTROL
Institute of Scientific and Technical Information of China (English)
刘智钢; 陈安平
2004-01-01
Consider the following nonautonomous delayed periodic logistic difference model with feedback control term N(k+1)=N(k)exp[r(k)-a1(k)N(k)-a2(k)N(k-τ(k))-c(k)u(k)],Δu(k)=-a(k)u(k)+b(k)N(k-τ(k)), which describes the evolution of a single species. The existence of a positive periodic solution is established by using the method of Mawhin's coincidence degree. This work has important significance in both theory and applications.
Existence and qualitative properties of travelling waves for an epidemiological model with mutations
Griette, Quentin; Raoul, Gaël
2016-05-01
In this article, we are interested in a non-monotonic system of logistic reaction-diffusion equations. This system of equations models an epidemic where two types of pathogens are competing, and a mutation can change one type into the other with a certain rate. We show the existence of travelling waves with minimal speed, which are usually non-monotonic. Then we provide a description of the shape of those constructed travelling waves, and relate them to some Fisher-KPP fronts with non-minimal speed.
Existence of a line of critical points in a two-dimensional Lebwohl Lasher model
Energy Technology Data Exchange (ETDEWEB)
Shabnam, Sabana [Department of Physics, Lady Brabourne College, Kolkata 700017 (India); DasGupta, Sudeshna, E-mail: sudeshna.dasgupta10@gmail.com [Department of Physics, Lady Brabourne College, Kolkata 700017 (India); Roy, Soumen Kumar [Department of Physics, Jadavpur University, Kolkata 700032 (India)
2016-02-15
Controversy regarding transitions in systems with global symmetry group O(3) has attracted the attention of researchers and the detailed nature of this transition is still not well understood. As an example of such a system in this paper we have studied a two-dimensional Lebwohl Lasher model, using the Wolff cluster algorithm. Though we have not been able to reach any definitive conclusions regarding the order present in the system, from finite size scaling analysis, hyperscaling relations and the behavior of the correlation function we have obtained strong indications regarding the presence of quasi-long range order and the existence of a line of critical points in our system.
Existence of a line of critical points in a two-dimensional Lebwohl Lasher model
Shabnam, Sabana; DasGupta, Sudeshna; Roy, Soumen Kumar
2016-02-01
Controversy regarding transitions in systems with global symmetry group O(3) has attracted the attention of researchers and the detailed nature of this transition is still not well understood. As an example of such a system in this paper we have studied a two-dimensional Lebwohl Lasher model, using the Wolff cluster algorithm. Though we have not been able to reach any definitive conclusions regarding the order present in the system, from finite size scaling analysis, hyperscaling relations and the behavior of the correlation function we have obtained strong indications regarding the presence of quasi-long range order and the existence of a line of critical points in our system.
Local existence and stability for a hyperbolic-elliptic system modeling two-phase reservoir flow
Directory of Open Access Journals (Sweden)
H. J. Schroll
2000-01-01
Full Text Available A system arising in the modeling of oil-recovery processes is analyzed. It consists of a hyperbolic conservation law governing the saturation and an elliptic equation for the pressure. By an operator splitting approach, an approximate solution is constructed. For this approximation appropriate a-priori bounds are derived. Applying the Arzela-Ascoli theorem, local existence and uniqueness of a classical solution for the original hyperbolic-elliptic system is proved. Furthermore, convergence of the approximation generated by operator splitting towards the unique solution follows. It is also proved that the unique solution is stable with respect to perturbations of the initial data.
Directory of Open Access Journals (Sweden)
Emile Franc Doungmo Goufo
2014-01-01
Full Text Available Until now, classical models of clusters’ fission remain unable to fully explain strange phenomena like the phenomenon of shattering (Ziff and McGrady, 1987 and the sudden appearance of infinitely many particles in some systems having initial finite number of particles. That is why there is a need to extend classical models to models with fractional derivative order and use new and various techniques to analyze them. In this paper, we prove the existence of strongly continuous solution operators for nonlocal fragmentation models with Michaud time derivative of fractional order (Samko et al., 1993. We focus on the case where the splitting rate is dependent on size and position and where new particles generating from fragmentation are distributed in space randomly according to some probability density. In the analysis, we make use of the substochastic semigroup theory, the subordination principle for differential equations of fractional order (Prüss, 1993, Bazhlekova, 2000, the analogy of Hille-Yosida theorem for fractional model (Prüss, 1993, and useful properties of Mittag-Leffler relaxation function (Berberan-Santos, 2005. We are then able to show that the solution operator to the full model is positive and contractive.
An existence result for a model of complete damage in elastic materials with reversible evolution
Bonetti, Elena; Freddi, Francesco; Segatti, Antonio
2016-07-01
In this paper, we consider a model describing evolution of damage in elastic materials, in which stiffness completely degenerates once the material is fully damaged. The model is written by using a phase transition approach, with respect to the damage parameter. In particular, a source of damage is represented by a quadratic form involving deformations, which vanishes in the case of complete damage. Hence, an internal constraint is ensured by a maximal monotone operator. The evolution of damage is considered "reversible", in the sense that the material may repair itself. We can prove an existence result for a suitable weak formulation of the problem, rewritten in terms of a new variable (an internal stress). Some numerical simulations are presented in agreement with the mathematical analysis of the system.
An existence result for a model of complete damage in elastic materials with reversible evolution
Bonetti, Elena; Freddi, Francesco; Segatti, Antonio
2017-01-01
In this paper, we consider a model describing evolution of damage in elastic materials, in which stiffness completely degenerates once the material is fully damaged. The model is written by using a phase transition approach, with respect to the damage parameter. In particular, a source of damage is represented by a quadratic form involving deformations, which vanishes in the case of complete damage. Hence, an internal constraint is ensured by a maximal monotone operator. The evolution of damage is considered "reversible", in the sense that the material may repair itself. We can prove an existence result for a suitable weak formulation of the problem, rewritten in terms of a new variable (an internal stress). Some numerical simulations are presented in agreement with the mathematical analysis of the system.
Uniform existence of the integrated density of states for models on Z^d
Gruber, Michael J; VeseliÄ, Ivan
2007-01-01
We give an overview and extension of recent results on ergodic random Schr\\"odinger operators for models on $\\mathbb{Z}^d$. The operators we consider are defined on combinatorial or metric graphs, with random potentials, random boundary conditions and random metrics taking values in a finite set. We show that normalized finite volume eigenvalue counting functions converge to a limit uniformly in the energy variable, at least locally. This limit, the integrated density of states (IDS), can be expressed by a closed Shubin-Pastur type trace formula. The set of points of increase of the IDS supports the spectrum and its points of discontinuity are characterized by existence of compactly supported eigenfunctions. This applies to several examples, including various periodic operators and percolation models.
Prevaba: a Bayesian Model to Predict the Existence of Victims in car accidents
Directory of Open Access Journals (Sweden)
TELLES, M.J.
2015-12-01
Full Text Available Road safety is an area which is concerned with both the reduction of accidents as with the care provided to the victims. Several initiatives are proposed to assist with reducing the number of accidents, such as surveillance, awareness campaigns and support equipment to drivers. Other initiatives for prevention and protection are proposed by vehicle manufacturers in terms of requirements of governament entities. As a final resort, that is, in the event of the accident and the victim needs medical attention, this should be done as quickly as possible. To assist in identifying the existence of the victim and the need for medical care, we propose a Bayesian model, called Prevaba, which uses Bayesian Networks (BN, which aims to predict the existence of victims in traffic accidents. In order to validate the model, we developed a prototype that performed the actual data classification in Porto Alegre - RS for the year 2013. The prototype made the classification based on the previous year's data (2012, showing an index above 90% accuracy, taking into account the incorrect classications are only classified as victimless, but actually was has a victim.
Stratospheric dryness: model simulations and satellite observations
Directory of Open Access Journals (Sweden)
J. Lelieveld
2007-01-01
Full Text Available The mechanisms responsible for the extreme dryness of the stratosphere have been debated for decades. A key difficulty has been the lack of comprehensive models which are able to reproduce the observations. Here we examine results from the coupled lower-middle atmosphere chemistry general circulation model ECHAM5/MESSy1 together with satellite observations. Our model results match observed temperatures in the tropical lower stratosphere and realistically represent the seasonal and inter-annual variability of water vapor. The model reproduces the very low water vapor mixing ratios (below 2 ppmv periodically observed at the tropical tropopause near 100 hPa, as well as the characteristic tape recorder signal up to about 10 hPa, providing evidence that the dehydration mechanism is well-captured. Our results confirm that the entry of tropospheric air into the tropical stratosphere is forced by large-scale wave dynamics, whereas radiative cooling regionally decelerates upwelling and can even cause downwelling. Thin cirrus forms in the cold air above cumulonimbus clouds, and the associated sedimentation of ice particles between 100 and 200 hPa reduces water mass fluxes by nearly two orders of magnitude compared to air mass fluxes. Transport into the stratosphere is supported by regional net radiative heating, to a large extent in the outer tropics. During summer very deep monsoon convection over Southeast Asia, centered over Tibet, moistens the stratosphere.
Observations and NLTE modeling of Ellerman bombs
Berlicki, Arkadiusz
2014-01-01
Ellerman bombs (EBs) are short-lived and compact structures that are observed well in the wings of the hydrogen H-alpha line. EBs are also observed in the chromospheric CaII lines and in UV continua. H-alpha line profiles of EBs show a deep absorption at the line center and enhanced emission in the line wings. Similar shapes of the line profiles are observed for the CaII IR line at 8542 ang. It is generally accepted that EBs may be considered as compact microflares located in lower solar atmosphere. However, it is still not clear where exactly the emission of EBs is formed in the solar atmosphere. High-resolution spectrophotometric observations of EBs were used for determining of their physical parameters and construction of semi-empirical models. In our analysis we used observations of EBs obtained in the H-alpha and CaII H lines. We also used NLTE numerical codes for the construction of grids of 243 semi-empirical models simulating EBs structures. In this way, the observed emission could be compared with th...
Supporting observation campaigns with high resolution modeling
Klocke, Daniel; Brueck, Matthias; Voigt, Aiko
2017-04-01
High resolution simulation in support of measurement campaigns offers a promising and emerging way to create large-scale context for small-scale observations of clouds and precipitation processes. As these simulation include the coupling of measured small-scale processes with the circulation, they also help to integrate the research communities from modeling and observations and allow for detailed model evaluations against dedicated observations. In connection with the measurement campaign NARVAL (August 2016 and December 2013) simulations with a grid-spacing of 2.5 km for the tropical Atlantic region (9000x3300 km), with local refinement to 1.2 km for the western part of the domain, were performed using the icosahedral non-hydrostatic (ICON) general circulation model. These simulations are again used to drive large eddy resolving simulations with the same model for selected days in the high definition clouds and precipitation for advancing climate prediction (HD(CP)2) project. The simulations are presented with the focus on selected results showing the benefit for the scientific communities doing atmospheric measurements and numerical modeling of climate and weather. Additionally, an outlook will be given on how similar simulations will support the NAWDEX measurement campaign in the North Atlantic and AC3 measurement campaign in the Arctic.
Endoscopic skull base training using 3D printed models with pre-existing pathology.
Narayanan, Vairavan; Narayanan, Prepageran; Rajagopalan, Raman; Karuppiah, Ravindran; Rahman, Zainal Ariff Abdul; Wormald, Peter-John; Van Hasselt, Charles Andrew; Waran, Vicknes
2015-03-01
Endoscopic base of skull surgery has been growing in acceptance in the recent past due to improvements in visualisation and micro instrumentation as well as the surgical maturing of early endoscopic skull base practitioners. Unfortunately, these demanding procedures have a steep learning curve. A physical simulation that is able to reproduce the complex anatomy of the anterior skull base provides very useful means of learning the necessary skills in a safe and effective environment. This paper aims to assess the ease of learning endoscopic skull base exposure and drilling techniques using an anatomically accurate physical model with a pre-existing pathology (i.e., basilar invagination) created from actual patient data. Five models of a patient with platy-basia and basilar invagination were created from the original MRI and CT imaging data of a patient. The models were used as part of a training workshop for ENT surgeons with varying degrees of experience in endoscopic base of skull surgery, from trainees to experienced consultants. The surgeons were given a list of key steps to achieve in exposing and drilling the skull base using the simulation model. They were then asked to list the level of difficulty of learning these steps using the model. The participants found the models suitable for learning registration, navigation and skull base drilling techniques. All participants also found the deep structures to be accurately represented spatially as confirmed by the navigation system. These models allow structured simulation to be conducted in a workshop environment where surgeons and trainees can practice to perform complex procedures in a controlled fashion under the supervision of experts.
Non-existence of Steady State Equilibrium in the Neoclassical Growth Model with a Longevity Trend
DEFF Research Database (Denmark)
Hermansen, Mikkel Nørlem
of steady state equilibrium when considering the empirically observed trend in longevity. We extend a standard continuous time overlapping generations model by a longevity trend and are thereby able to study the properties of mortality-driven population growth. This turns out to be exceedingly complicated......Longevity has been increasing in the developed countries for almost two centuries and further increases are expected in the future. In the neoclassical growth models the case of population growth driven by fertility is well-known, whereas the properties of population growth caused by persistently...
Placing Observational Constraints on Massive Star Models
Rosenfield, Philip
2011-10-01
The lives and deaths of massive stars are intricately linked to the evolution of galaxies. Yet, despite their integral importance to understanding galaxy evolution, models of massive stars are inconsistent with observations. These uncertainties can be traced to limited observational constraints available for improving massive star models. A sensitive test of the underlying physics of massive stars, e.g., convection, rotation, and mass loss is to measure the ratio of blue core helium burning stars {BHeB} to red core helium burning stars {RHeB}, 5-20Msun stars in the stage evolution immediately following the main sequence. Even the most sophisticated models cannot accurately predict the observed ratio over a range of metallicities, suggesting an insufficient understanding of the underlying physics. However, observational measurements of this ratio over a wide range of environments would provide substantial constraints on the physical parameters governing the evolution of all stars >5 Msun.We propose to place stringent observational constraints on the physics of massive star evolution by uniformly measuring the B/R HeB ratio in a wide range of galaxies. The HST archive contains high quality optical imaging of resolved stellar populations of dozens of nearby galaxies. From the ANGST program, we identified 38 galaxies, spanning 2 dex in metallicity that have significant BHeB and RHeB populations. Using this sample, we will empirically characterize the colors of the BHeB and RHeB sequences as a function of luminosity and metallicity, measure the B/R ratio, and constrain the lifetimes of the BHeB and RHeBs in the Padova stellar evolution models and the Cambridge STARS code.
Constraining Numerical Geodynamo Modeling with Surface Observations
Kuang, Weijia; Tangborn, Andrew
2006-01-01
Numerical dynamo solutions have traditionally been generated entirely by a set of self-consistent differential equations that govern the spatial-temporal variation of the magnetic field, velocity field and other fields related to dynamo processes. In particular, those solutions are obtained with parameters very different from those appropriate for the Earth s core. Geophysical application of the numerical results therefore depends on correct understanding of the differences (errors) between the model outputs and the true states (truth) in the outer core. Part of the truth can be observed at the surface in the form of poloidal magnetic field. To understand these differences, or errors, we generate new initial model state (analysis) by assimilating sequentially the model outputs with the surface geomagnetic observations using an optimal interpolation scheme. The time evolution of the core state is then controlled by our MoSST core dynamics model. The final outputs (forecasts) are then compared with the surface observations as a means to test the success of the assimilation. We use the surface geomagnetic data back to year 1900 for our studies, with 5-year forecast and 20-year analysis periods. We intend to use the result; to understand time variation of the errors with the assimilation sequences, and the impact of the assimilation on other unobservable quantities, such as the toroidal field and the fluid velocity in the core.
Hamilton, George S.; Williams, Jermaine C.
1998-01-01
This paper describes the methods, rationale, and comparative results of the conversion of an intravehicular (IVA) 3D human computer model (HCM) to extravehicular (EVA) use and compares the converted model to an existing model on another computer platform. The task of accurately modeling a spacesuited human figure in software is daunting: the suit restricts the human's joint range of motion (ROM) and does not have joints collocated with human joints. The modeling of the variety of materials needed to construct a space suit (e. g. metal bearings, rigid fiberglass torso, flexible cloth limbs and rubber coated gloves) attached to a human figure is currently out of reach of desktop computer hardware and software. Therefore a simplified approach was taken. The HCM's body parts were enlarged and the joint ROM was restricted to match the existing spacesuit model. This basic approach could be used to model other restrictive environments in industry such as chemical or fire protective clothing. In summary, the approach provides a moderate fidelity, usable tool which will run on current notebook computers.
Existence of complex patterns in the Beddington-DeAngelis predator-prey model.
Haque, Mainul
2012-10-01
The study of reaction-diffusion system constitutes some of the most fascinating developments of late twentieth century mathematics and biology. This article investigates complexity and chaos in the complex patterns dynamics of the original Beddington-DeAngelis predator-prey model which concerns the influence of intra species competition among predators. We investigate the emergence of complex patterns through reaction-diffusion equations in this system. We derive the conditions for the codimension-2 Turing-Hopf, Turing-Saddle-node, and Turing-Transcritical bifurcation, and the codimension-3 Turing-Takens-Bogdanov bifurcation. These bifurcations give rise to very complex patterns that have not been observed in previous predator-prey models. A large variety of different types of long-term behavior, including homogenous distributions and stationary spatial patterns are observed through extensive numerical simulations with experimentally-based parameter values. Finally, a discussion of the ecological implications of the analytical and numerical results concludes the paper.
ON THE SPECIFIC AREA OF INHOMOGENEOUS BOOLEAN MODELS. EXISTENCE RESULTS AND APPLICATIONS
Directory of Open Access Journals (Sweden)
Elena Villa
2011-05-01
Full Text Available The problem of the evaluation of the so-called specific area of a random closed set, in connection with its mean boundary measure, is mentioned in the classical book by Matheron on random closed sets (Matheron, 1975, p. 50; it is still an open problem, in general. We offer here an overview of some recent results concerning the existence of the specific area of inhomogeneous Boolean models, unifying results from geometric measure theory and from stochastic geometry. A discussion of possible applications to image analysis concerning the estimation of the mean surface density of random closed sets, and, in particular, to material science concerning birth-and-growth processes, is also provided.
Existence of Dyons in Minimally Gauged Skyrme Model via Constrained Minimization
Gao, Zhifeng
2011-01-01
We prove the existence of electrically and magnetically charged particlelike static solutions, known as dyons, in the minimally gauged Skyrme model developed by Brihaye, Hartmann, and Tchrakian. The solutions are spherically symmetric, depend on two continuous parameters, and carry unit monopole and magnetic charges but continuous Skyrme charge and non-quantized electric charge induced from the 't Hooft electromagnetism. The problem amounts to obtaining a finite-energy critical point of an indefinite action functional, arising from the presence of electricity and the Minkowski spacetime signature. The difficulty with the absence of the Higgs field is overcome by achieving suitable strong convergence and obtaining uniform decay estimates at singular boundary points so that the negative sector of the action functional becomes tractable.
Heinz, Sebastian; Mielke, Alexander
2016-04-28
We revisit the model for a two-well phase transformation in a linearly elastic body that was introduced and studied in Mielke et al. (2002 Arch. Ration. Mech. Anal. 162: , 137-177). This energetic rate-independent system is posed in terms of the elastic displacement and an internal variable that gives the phase portion of the second phase. We use a new approach based on mutual recovery sequences, which are adjusted to a suitable energy increment plus the associated dissipated energy and, thus, enable us to pass to the limit in the construction of energetic solutions. We give three distinct constructions of mutual recovery sequences which allow us (i) to generalize the existence result in Mielke et al. (2002), (ii) to establish the convergence of suitable numerical approximations via space-time discretization and (iii) to perform the evolutionary relaxation from the pure-state model to the relaxed-mixture model. All these results rely on weak converge and involve the H-measure as an essential tool.
Frequency domain modeling and dynamic characteristics evaluation of existing wind turbine systems
Chiang, Chih-Hung; Yu, Chih-Peng
2016-04-01
It is quite well accepted that frequency domain procedures are suitable for the design and dynamic analysis of wind turbine structures, especially for floating offshore wind turbines, since random wind loads and wave induced motions are most likely simulated in the frequency domain. This paper presents specific applications of an effective frequency domain scheme to the linear analysis of wind turbine structures in which a 1-D spectral element was developed based on the axially-loaded member. The solution schemes are summarized for the spectral analyses of the tower, the blades, and the combined system with selected frequency-dependent coupling effect from foundation-structure interactions. Numerical examples demonstrate that the modal frequencies obtained using spectral-element models are in good agreement with those found in the literature. A 5-element mono-pile model results in less than 0.3% deviation from an existing 160-element model. It is preliminarily concluded that the proposed scheme is relatively efficient in performing quick verification for test data obtained from the on-site vibration measurement using the microwave interferometer.
Existence of the critical endpoint in the vector meson extended linear sigma model
Kovács, Peter; Wolf, György
2016-01-01
The chiral phase transition of the strongly interacting matter is investigated at nonzero temperature and baryon chemical potential mu_B within an extended (2+1) flavor Polyakov constituent quark-meson model which incorporates the effect of the vector and axial vector mesons. The effect of the fermionic vacuum and thermal fluctuations computed from the grand potential of the model is taken into account in the curvature masses of the scalar and pseudoscalar mesons. The parameters of the model are determined by comparing masses and tree-level decay widths with experimental values in a chi^2-minimization procedure which selects between various possible assignments of scalar nonet states to physical particles. We examine the restoration of the chiral symmetry by monitoring the temperature evolution of condensates and the chiral partners' masses and of the mixing angles for the pseudoscalar eta-eta' and the corresponding scalar complex. We calculate the pressure and various thermodynamical observables derived from...
Had the planet mars not existed: Kepler's equant model and its physical consequences
Bracco, Christian
2009-01-01
We examine the equant model for the motion of planets, which has been the starting point of Kepler's investigations before he modified it because of Mars observations. We show that, up to first order in eccentricity, this model implies for each orbit a velocity which satisfies Kepler's second law and Hamilton's hodograph, and a centripetal acceleration with an inverse square dependence on the distance to the sun. If this dependence is assumed to be universal, Kepler's third law follows immediately. This elementary execice in kinematics for undergraduates emphasizes the proximity of the equant model coming from Ancient Greece with our present knowledge. It adds to its historical interest a didactical relevance concerning, in particular, the discussion of the Aristotelian or Newtonian conception of motion.
Controllability, Observability, and Stability of Mathematical Models
Iggidr, Abderrahman
2004-01-01
International audience; This article presents an overview of three fundamental concepts in Mathematical System Theory: controllability, stability and observability. These properties play a prominent role in the study of mathematical models and in the understanding of their behavior. They constitute the main research subject in Control Theory. Historically the tools and techniques of Automatic Control have been developed for artificial engineering systems but nowadays they are more and more ap...
Evaluation of CNN as anthropomorphic model observer
Massanes, Francesc; Brankov, Jovan G.
2017-03-01
Model observers (MO) are widely used in medical imaging to act as surrogates of human observers in task-based image quality evaluation, frequently towards optimization of reconstruction algorithms. In this paper, we explore the use of convolutional neural networks (CNN) to be used as MO. We will compare CNN MO to alternative MO currently being proposed and used such as the relevance vector machine based MO and channelized Hotelling observer (CHO). As the success of the CNN, and other deep learning approaches, is rooted in large data sets availability, which is rarely the case in medical imaging systems task-performance evaluation, we will evaluate CNN performance on both large and small training data sets.
Energy Technology Data Exchange (ETDEWEB)
Combescure, D.; Sollogoub, P.; Jeanvoine, E.; Politopoulos, I
2000-07-01
Models for the sizing of new structures are more and more reliable. Meanwhile the seismic prediction of an old building is a more complex problem. The non-linear displacements have to be take into account in the sizing codes. The CEA developed assessment methods of these non-linear deformations. This paper presents the different non-linear models, their particularities and two examples of structure analysis. (A.L.B.)
Observation and modelling of urban dew
Richards, Katrina
Despite its relevance to many aspects of urban climate and to several practical questions, urban dew has largely been ignored. Here, simple observations an out-of-doors scale model, and numerical simulation are used to investigate patterns of dewfall and surface moisture (dew + guttation) in urban environments. Observations and modelling were undertaken in Vancouver, B.C., primarily during the summers of 1993 and 1996. Surveys at several scales (0.02-25 km) show that the main controls on dew are weather, location and site configuration (geometry and surface materials). Weather effects are discussed using an empirical factor, FW . Maximum dew accumulation (up to ~ 0.2 mm per night) is seen on nights with moist air and high FW , i.e., cloudless conditions with light winds. Favoured sites are those with high Ysky and surfaces which cool rapidly after sunset, e.g., grass and well insulated roofs. A 1/8-scale model is designed, constructed, and run at an out-of-doors site to study dew patterns in an urban residential landscape which consists of house lots, a street and an open grassed park. The Internal Thermal Mass (ITM) approach is used to scale the thermal inertia of buildings. The model is validated using data from full-scale sites in Vancouver. Patterns in the model agree with those seen at the full-scale, i.e., dew distribution is governed by weather, site geometry and substrate conditions. Correlation is shown between Ysky and surface moisture accumulation. The feasibility of using a numerical model to simulate urban dew is investigated using a modified version of a rural dew model. Results for simple isolated surfaces-a deciduous tree leaf and an asphalt shingle roof-show promise, especially for built surfaces.
Existence and uniqueness of endemic states for the age-structured S-I-R epidemic model.
Cha, Y; Iannelli, M; Milner, F A
1998-06-15
The existence and uniqueness of positive steady states for the age structured S-I-R epidemic model with intercohort transmission is considered. Threshold results for the existence of endemic states are established for most cases. Uniqueness is shown in each case. Threshold used are explicitly computable in terms of demographic and epidemiological parameters of the model.
Existence of solutions of a nonlinear system modelling fluid flow in porous media
Directory of Open Access Journals (Sweden)
dam Besenyei
2006-12-01
Full Text Available We investigate the existence of weak solutions for nonlinear differential equations that describe fluid flow through a porous medium. Existence is proved using the theory of monotone operators, and some examples are given.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The authors prove the local existence and uniqueness of weak solution of a hyperbolic-parabolic system and establish the global existence of the weak solution for this system for the spatial dimension n = 1.
Observational signatures of anisotropic inflationary models
Ohashi, Junko; Tsujikawa, Shinji
2013-01-01
We study observational signatures of two classes of anisotropic inflationary models in which an inflaton field couples to (i) a vector kinetic term F_{mu nu}F^{mu nu} and (ii) a two-form kinetic term H_{mu nu lambda}H^{mu nu lambda}. We compute the corrections from the anisotropic sources to the power spectrum of gravitational waves as well as the two-point cross correlation between scalar and tensor perturbations. The signs of the anisotropic parameter g_* are different depending on the vector and the two-form models, but the statistical anisotropies generally lead to a suppressed tensor-to-scalar ratio r and a smaller scalar spectral index n_s in both models. In the light of the recent Planck bounds of n_s and r, we place observational constraints on several different inflaton potentials such as those in chaotic and natural inflation in the presence of anisotropic interactions. In the two-form model we also find that there is no cross correlation between scalar and tensor perturbations, while in the vector ...
Observations and Modeling of Geospace Energetic Particles
Li, Xinlin
2016-07-01
Comprehensive measurements of energetic particles and electric and magnetic fields from state-of-art instruments onboard Van Allen Probes, in a geo-transfer-like orbit, revealed new features of the energetic particles and the fields in the inner magnetosphere and impose new challenges to any quantitative modeling of the physical processes responsible for these observations. Concurrent measurements of energetic particles by satellites in highly inclined low Earth orbits and plasma and fields by satellites in farther distances in the magnetospheres and in the up stream solar wind are the critically needed information for quantitative modeling and for leading to eventual accurate forecast of the variations of the energetic particles in the magnetosphere. In this presentation, emphasis will be on the most recent advance in our understanding of the energetic particles in the magnetosphere and the missing links for significantly advance in our modeling and forecasting capabilities.
Global existence for a hydrogen storage model with full energy balance
Bonetti, Elena; Laurençot, Philippe
2011-01-01
A thermo-mechanical model describing hydrogen storage by use of metal hydrides has been recently proposed in a paper by Bonetti, Fr\\'emond and Lexcellent. It describes the formation of hydrides using the phase transition approach. By virtue of the laws of continuum thermo-mechanics, the model leads to a phase transition problem in terms of three state variables: the temperature, the phase parameter representing the fraction of one solid phase, and the pressure, and is derived within a generalization of the principle of virtual powers proposed by Fr\\'emond accounting for micro-forces, responsible for the phase transition, in the whole energy balance of the system. Three coupled nonlinear partial differential equations combined with initial and boundary conditions have to be solved. The main difficulty in investigating the resulting system of partial differential equations relies on the presence of the squared time derivative of the order parameter in the energy balance equation. Here, the global existence of a...
Arndt, Sandra
2016-04-01
Marine sediments are key components in the Earth System. They host the largest carbon reservoir on Earth, provide the only long term sink for atmospheric CO2, recycle nutrients and represent the most important climate archive. Biogeochemical processes in marine sediments are thus essential for our understanding of the global biogeochemical cycles and climate. They are first and foremost, donor controlled and, thus, driven by the rain of particulate material from the euphotic zone and influenced by the overlying bottom water. Geochemical species may undergo several recycling loops (e.g. authigenic mineral precipitation/dissolution) before they are either buried or diffuse back to the water column. The tightly coupled and complex pelagic and benthic process interplay thus delays recycling flux, significantly modifies the depositional signal and controls the long-term removal of carbon from the ocean-atmosphere system. Despite the importance of this mutual interaction, coupled regional/global biogeochemical models and (paleo)climate models, which are designed to assess and quantify the transformations and fluxes of carbon and nutrients and evaluate their response to past and future perturbations of the climate system either completely neglect marine sediments or incorporate a highly simplified representation of benthic processes. On the other end of the spectrum, coupled, multi-component state-of-the-art early diagenetic models have been successfully developed and applied over the past decades to reproduce observations and quantify sediment-water exchange fluxes, but cannot easily be coupled to pelagic models. The primary constraint here is the high computation cost of simulating all of the essential redox and equilibrium reactions within marine sediments that control carbon burial and benthic recycling fluxes: a barrier that is easily exacerbated if a variety of benthic environments are to be spatially resolved. This presentation provides an integrative overview of
Applying direct observation to model workflow and assess adoption.
Unertl, Kim M; Weinger, Matthew B; Johnson, Kevin B
2006-01-01
Lack of understanding about workflow can impair health IT system adoption. Observational techniques can provide valuable information about clinical workflow. A pilot study using direct observation was conducted in an outpatient chronic disease clinic. The goals of the study were to assess workflow and information flow and to develop a general model of workflow and information behavior. Over 55 hours of direct observation showed that the pilot site utilized many of the features of the informatics systems available to them, but also employed multiple non-electronic artifacts and workarounds. Gaps existed between clinic workflow and informatics tool workflow, as well as between institutional expectations of informatics tool use and actual use. Concurrent use of both paper-based and electronic systems resulted in duplication of effort and inefficiencies. A relatively short period of direct observation revealed important information about workflow and informatics tool adoption.
Tidal Movement of Nioghalvfjerdsfjorden Glacier, Northeast Greenland: Observations and Modelling
DEFF Research Database (Denmark)
Reeh, Niels; Mayer, C.; Olesen, O. B.
2000-01-01
, 1997 and 1998. As part of this work, tidal-movement observations were carried out by simultaneous differential global positioning system (GPS) measurements at several locations distributed on the glacier surface. The GPS observations were performed continuously over several tidal cycles. At the same....... The observations show that the main part of the glacier tongue responds as a freely floating plate to the phase and amplitude of the local tide in the sea. However, kilometre-wide flexure zones exist along the marginal and upstream grounding lines. Attempts to model the observed tidal deflection and tilt patterns...... in the flexure zone by elastic-beam theory are unsuccessful, in contrast to previous findings by other investigators. The strongest disagreement between our measurements and results derived from elastic-beam theory is a significant variation of the phase of the tidal records with distance from the grounding line...
Boutillier, J.; Ehrhardt, L.; De Mezzo, S.; Deck, C.; Magnan, P.; Naz, P.; Willinger, R.
2017-08-01
With the increasing use of improvised explosive devices (IEDs), the need for better mitigation, either for building integrity or for personal security, increases in importance. Before focusing on the interaction of the shock wave with a target and the potential associated damage, knowledge must be acquired regarding the nature of the blast threat, i.e., the pressure-time history. This requirement motivates gaining further insight into the triple point (TP) path, in order to know precisely which regime the target will encounter (simple reflection or Mach reflection). Within this context, the purpose of this study is to evaluate three existing TP path empirical models, which in turn are used in other empirical models for the determination of the pressure profile. These three TP models are the empirical function of Kinney, the Unified Facilities Criteria (UFC) curves, and the model of the Natural Resources Defense Council (NRDC). As discrepancies are observed between these models, new experimental data were obtained to test their reliability and a new promising formulation is proposed for scaled heights of burst ranging from 24.6-172.9 cm/kg^{1/3}.
Observational Equivalence of Discrete String Models and Market Models
Kerkhof, F.L.J.; Pelsser, A.
2002-01-01
In this paper we show that, contrary to the claim made in Longsta, Santa-Clara, and Schwartz (2001a) and Longsta, Santa-Clara, and Schwartz (2001b), discrete string models are not more parsimonious than market models.In fact, they are found to be observationally equivalent.We derive that, for the es
Nimmo, J.R.; Herkelrath, W.N.; Laguna, Luna A.M.
2007-01-01
Numerous models are in widespread use for the estimation of soil water retention from more easily measured textural data. Improved models are needed for better prediction and wider applicability. We developed a basic framework from which new and existing models can be derived to facilitate improvements. Starting from the assumption that every particle has a characteristic dimension R associated uniquely with a matric pressure ?? and that the form of the ??-R relation is the defining characteristic of each model, this framework leads to particular models by specification of geometric relationships between pores and particles. Typical assumptions are that particles are spheres, pores are cylinders with volume equal to the associated particle volume times the void ratio, and that the capillary inverse proportionality between radius and matric pressure is valid. Examples include fixed-pore-shape and fixed-pore-length models. We also developed alternative versions of the model of Arya and Paris that eliminate its interval-size dependence and other problems. The alternative models are calculable by direct application of algebraic formulas rather than manipulation of data tables and intermediate results, and they easily combine with other models (e.g., incorporating structural effects) that are formulated on a continuous basis. Additionally, we developed a family of models based on the same pore geometry as the widely used unsaturated hydraulic conductivity model of Mualem. Predictions of measurements for different suitable media show that some of the models provide consistently good results and can be chosen based on ease of calculations and other factors. ?? Soil Science Society of America. All rights reserved.
Moores, P P; Issitt, P D; Pavone, B G; McKeever, B G
1975-01-01
Bloods from three individuals, one each of the phenotypes Oh-A, Oh-B and Oh-O have been studied. The work of Dzierzkowa-Borodej, et al.-10 was confirmed when it was shown that all three samples of Oh red blood cells had increased I antigen strength. The i, Sd-a, Le-a and Le-x antigens were not found to be increased. Attempts were made to adsorb and elute anti-A, anti-B and anti-A,B with the Oh red blood cells, using sera that contained high titered anti-I antibodies. This was done in the belief that previously reported positive results in such tests might be due to the high level of I on the Oh red blood cells, anti-I in the sera containing the ABO antibodies, and the Matuhasi-Ogata phenomenon. However, in no instance were we able to adsorb an ABO antibody onto the Oh red blood cells. Contrary to the report of others-10 the titers of anti-A, anti-B and anti-H in the sera of the three Oh individuals studied did not differ significantly. We suggest that the evidence from our findings and the work of others is sufficient to show that at least two forms of the Oh phenotype exist: one representing total suppression of H, A, and B antigens, and the other marked but not total suppression, with partial inhibition of antibody production.
Observations and Models of Galaxy Assembly Bias
Campbell, Duncan A.
2017-01-01
The assembly history of dark matter haloes imparts various correlations between a halo’s physical properties and its large scale environment, i.e. assembly bias. It is common for models of the galaxy-halo connection to assume that galaxy properties are only a function of halo mass, implicitly ignoring how assembly bias may affect galaxies. Recently, programs to model and constrain the degree to which galaxy properties are influenced by assembly bias have been undertaken; however, the extent and character of galaxy assembly bias remains a mystery. Nevertheless, characterizing and modeling galaxy assembly bias is an important step in understanding galaxy evolution and limiting any systematic effects assembly bias may pose in cosmological measurements using galaxy surveys.I will present work on modeling and constraining the effect of assembly bias in two galaxy properties: stellar mass and star-formation rate. Conditional abundance matching allows for these galaxy properties to be tied to halo formation history to a variable degree, making studies of the relative strength of assembly bias possible. Galaxy-galaxy clustering and galactic conformity, the degree to which galaxy color is correlated between neighbors, are sensitive observational measures of galaxy assembly bias. I will show how these measurements can be used to constrain galaxy assembly bias and the peril of ignoring it.
On the redistribution of existing inputs using the spherical frontier dea model
Directory of Open Access Journals (Sweden)
José Virgilio Guedes de Avellar
2010-04-01
Full Text Available The Spherical Frontier DEA Model (SFM (Avellar et al., 2007 was developed to be used when one wants to fairly distribute a new and fixed input to a group of Decision Making Units (DMU's. SFM's basic idea is to distribute this new and fixed input in such a way that every DMU will be placed on an efficiency frontier with a spherical shape. We use SFM to analyze the problems that appear when one wants to redistribute an already existing input to a group of DMU's such that the total sum of this input will remain constant. We also analyze the case in which this total sum may vary.O Modelo de Fronteira Esférica (MFE (Avellar et al., 2007 foi desenvolvido para ser usado quando se deseja distribuir de maneira justa um novo insumo a um conjunto de unidades tomadoras de decisão (DMU's, da sigla em inglês, Decision Making Units. A ideia básica do MFE é a de distribuir esse novo insumo de maneira que todas as DMU's sejam colocadas numa fronteira de eficiência com um formato esférico. Neste artigo, usamos MFE para analisar o problema que surge quando se deseja redistribuir um insumo já existente para um grupo de DMU's de tal forma que a soma desse insumo para todas as DMU's se mantenha constante. Também analisamos o caso em que essa soma possa variar.
Meystre, Stéphane M; Lee, Sanghoon; Jung, Chai Young; Chevrier, Raphaël D
2012-08-01
An increasing need for collaboration and resources sharing in the Natural Language Processing (NLP) research and development community motivates efforts to create and share a common data model and a common terminology for all information annotated and extracted from clinical text. We have combined two existing standards: the HL7 Clinical Document Architecture (CDA), and the ISO Graph Annotation Format (GrAF; in development), to develop such a data model entitled "CDA+GrAF". We experimented with several methods to combine these existing standards, and eventually selected a method wrapping separate CDA and GrAF parts in a common standoff annotation (i.e., separate from the annotated text) XML document. Two use cases, clinical document sections, and the 2010 i2b2/VA NLP Challenge (i.e., problems, tests, and treatments, with their assertions and relations), were used to create examples of such standoff annotation documents, and were successfully validated with the XML schemata provided with both standards. We developed a tool to automatically translate annotation documents from the 2010 i2b2/VA NLP Challenge format to GrAF, and automatically generated 50 annotation documents using this tool, all successfully validated. Finally, we adapted the XSL stylesheet provided with HL7 CDA to allow viewing annotation XML documents in a web browser, and plan to adapt existing tools for translating annotation documents between CDA+GrAF and the UIMA and GATE frameworks. This common data model may ease directly comparing NLP tools and applications, combining their output, transforming and "translating" annotations between different NLP applications, and eventually "plug-and-play" of different modules in NLP applications.
Lagrangian Observations and Modeling of Marine Larvae
Paris, Claire B.; Irisson, Jean-Olivier
2017-04-01
Just within the past two decades, studies on the early-life history stages of marine organisms have led to new paradigms in population dynamics. Unlike passive plant seeds that are transported by the wind or by animals, marine larvae have motor and sensory capabilities. As a result, marine larvae have a tremendous capacity to actively influence their dispersal. This is continuously revealed as we develop new techniques to observe larvae in their natural environment and begin to understand their ability to detect cues throughout ontogeny, process the information, and use it to ride ocean currents and navigate their way back home, or to a place like home. We present innovative in situ and numerical modeling approaches developed to understand the underlying mechanisms of larval transport in the ocean. We describe a novel concept of a Lagrangian platform, the Drifting In Situ Chamber (DISC), designed to observe and quantify complex larval behaviors and their interactions with the pelagic environment. We give a brief history of larval ecology research with the DISC, showing that swimming is directional in most species, guided by cues as diverse as the position of the sun or the underwater soundscape, and even that (unlike humans!) larvae orient better and swim faster when moving as a group. The observed Lagrangian behavior of individual larvae are directly implemented in the Connectivity Modeling System (CMS), an open source Lagrangian tracking application. Simulations help demonstrate the impact that larval behavior has compared to passive Lagrangian trajectories. These methodologies are already the base of exciting findings and are promising tools for documenting and simulating the behavior of other small pelagic organisms, forecasting their migration in a changing ocean.
Existence and Attractiveness of Order One Periodic Solution of a Holling I Predator-Prey Model
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Huidong Cheng
2012-01-01
Full Text Available According to the integrated pest management strategies, a Holling type I functional response predator-prey system concerning state-dependent impulsive control is investigated. By using differential equation geometry theory and the method of successor functions, we prove the existence of order one periodic solution, and the attractivity of the order one periodic solution by sequence convergence rules and qualitative analysis. Numerical simulations are carried out to illustrate the feasibility of our main results which show that our method used in this paper is more efficient than the existing ones for proving the existence and attractiveness of order one periodic solution.
Modern observations and models of Solar flares
Gritsyk, Pavel; Somov, Boris
As well known, that fast particles propagating along flare loop generate bremsstrahlung hard x-ray emission and gyro-synchrotron microwave emission. We present the self-consistent kinetic description of propagation accelerated particles. The key point of this approach is taking into account the effect of reverse current. In our two-dimensional model the electric field of reverse current has the strong influence to the beam of accelerated particles. It decelerates part of the electrons in the beam and turns back other part of them without significant energy loss. The exact analytical solution for the appropriate kinetic equation with Landau collision integral was found. Using derived distribution function of electrons we’ve calculated evolution of their energy spectrum and plasma heating, coronal microwave emission and characteristics of hard x-ray emission in the corona and in the chromosphere. All results were compared with modern high precision space observations.
Institute of Scientific and Technical Information of China (English)
Syed ABBAS; Yonghui XIA
2013-01-01
In this paper we discuss the existence and global attractivity of k-almost automorphic sequence solution of a model of cellular neural networks.We consider the corresponding difference equation analogue of the model system using suitable discretization method and obtain certain conditions for the existence of solution.Almost automorphic function is a good generalization of almost periodic function.This is the first paper considering such solutions of the neural networks.
The Whisper of Deep Basins: Observation & Modelling
Burjanek, J.; Ermert, L. A.; Poggi, V.; Michel, C.; Fäh, D.
2013-12-01
Free oscillations of Earth have been used for a long time to retrieve information about the deep Earth's interior. On a much smaller scale, standing waves develop in deep sedimentary basins and can possibly be used in a similar way. The sensitivity of these waves to subsurface properties makes them a potential source of information about the deep basin characteristics. We investigated the sequence of two-dimensional resonance modes occurring in Rhône Valley, a strongly over-deepened, glacially carved basin with a sediment fill reaching up to 900 m thickness. We obtained two synchronous linear-array recordings of ambient vibrations and analysed them with two different processing techniques. First, both 2D resonance frequencies and their corresponding modal shapes were identified by frequency-domain decomposition of the signal cross-spectral density matrix. Second, time-frequency polarization analysis was applied to support the addressing of the modes and to determine the relative contributions of the vertical and horizontal components of the fundamental in-plane mode. Simplified 2-D finite element models were then used to support the interpretation of the observations. We were able to identify several resonance modes including previously unmeasured higher modes at all investigated locations in the valley. Good agreement was found between results of our study and previous studies, between the two processing techniques and between observed and modelled results. Finally, a parametric study was performed to qualitatively assess the sensitivity of the mode's order, shape and frequency to subsurface properties like bedrock geometry, Poisson's ratio and shear wave velocity of the sediments. We concluded that the sequence of modes as they appear by frequency depends strongly on subsurface properties. Therefore addressing of the higher modes can be done reliably only with prior information on the sediment structure.
Global Existence of Classical Solutions for Some Oldroyd-B Model via the Incompressible Limit
Institute of Scientific and Technical Information of China (English)
Zhen LEI
2006-01-01
In this paper, we prove local and global existence of classical solutions for a system of equations concerning an incompressible viscoelastic fluid of Oldroyd-B type via the incompressible limit when the initial data are sufficiently small.
De Rijcke, Sven; Boelens, Thomas
2014-01-01
We show that the general relativistic theory of the dynamics of isotropic stellar clusters can be developed essentially along the same lines as the Newtonian theory. We prove that the distribution function can be derived from any isotropic momentum moment and that every higher-order moment of the distribution can be written as an integral over a zeroth-order moment. We propose a mathematically simple expression for the distribution function of a family of isotropic general relativistic cluster models and investigate their dynamical properties. In the Newtonian limit, these models obtain a distribution function of the form F(E) ~ (E-E_0)^alpha, with E binding energy and E_0 a constant that determines the model's outer radius. The slope alpha sets the steepness of the distribution function and the corresponding radial density and pressure profiles. We show that the field equations only yield solutions with finite mass for alpha3.5, only Newtonian models exist. In other words: within the context of this family o...
Institute of Scientific and Technical Information of China (English)
吴启光; 杨国庆
2002-01-01
In this paper, we study the existence of the uniformly minimum risk equivariant (UMRE) estimators of parameters in a class of normal linear models, which include the normal variance components model,the growth curve model, the extended growth curve model, and the seemingly unrelated regression equations model, and so on. The necessary and sufficient conditions are given for the existence of UMRE estimators of the estimable linear functions of regression coefficients, the covariance matrix V and (trV)a, where a＞ 0is known, in the models under an affine group of transformations for quadratic losses and matrix losses, respectively. Under the (extended) growth curve model and the seemingly unrelated regression equations model,the conclusions given in literature for estimating regression coefficients can be derived by applying the general results in this paper, and the sufficient conditions for non-existence of UMRE estimators of V and tr(V) are expanded to be necessary and sufficient conditions. In addition, the necessary and sufficient conditions that there exist UMRE estimators of parameters in the variance components model are obtained for the first time.
Canards existence in FitzHugh-Nagumo and Hodgkin-Huxley neuronal models
Ginoux, Jean-Marc
2015-01-01
In a previous paper we have proposed a new method for proving the existence of "canard solutions" for three and four-dimensional singularly perturbed systems with only one fast variable. The aim of this work is to extend this method to the case of four-dimensional singularly perturbed systems with two slow and two fast variables. This method enables to state a unique generic condition for the existence of "canard solutions" for such four-dimensional singularly perturbed systems which is based...
Canards Existence in FitzHugh-Nagumo and Hodgkin-Huxley Neuronal Models
Jean-Marc Ginoux; Jaume Llibre
2015-01-01
In a previous paper we have proposed a new method for proving the existence of “canard solutions” for three- and four-dimensional singularly perturbed systems with only one fast variable which improves the methods used until now. The aim of this work is to extend this method to the case of four-dimensional singularly perturbed systems with two slow and two fast variables. This method enables stating a unique generic condition for the existence of “canard solutions” for such four-dimensional s...
Existence and uniqueness of positive solutions for a nonlocal dispersal population model
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Jian-Wen Sun
2014-06-01
Full Text Available In this article, we study the solutions of a nonlocal dispersal equation with a spatial weight representing competitions and aggregation. To overcome the limitations of comparison principles, we introduce new definitions of upper-lower solutions. The proof of existence and uniqueness of positive solutions is based on the method of monotone iteration sequences.
A Key Challenge in Global HRM: Adding New Insights to Existing Expatriate Spouse Adjustment Models
Gupta, Ritu; Banerjee, Pratyush; Gaur, Jighyasu
2012-01-01
This study is an attempt to strengthen the existing knowledge about factors affecting the adjustment process of the trailing expatriate spouse and the subsequent impact of any maladjustment or expatriate failure. We conducted a qualitative enquiry using grounded theory methodology with 26 Indian spouses who had to deal with their partner's…
Data on dose-volume effects in the rat spinal cord do not support existing NTCP models
Van Luijk, P; Bijl, HP; Konings, AWT; Van Der Kogel, AJ; Schippers, JM
2005-01-01
Purpose: To evaluate several existing dose-volume effect models for their ability to describe the occurrence of white matter necrosis in rat spinal cord after irradiation with small proton beams. Methods and Materials: A large number of dose-volume effect models has been fitted to data on the occurr
Institute of Scientific and Technical Information of China (English)
无
2012-01-01
The positive periodic solutions to a three-species delayed Lotka-Volterra model with dispersion and harvesting terms are studied in this paper. By the coincidence degree theory, the sufficient conditions for existence of eight positive periodic solutions to the model are obtained.
Wu, Sainan; Shi, Junping; Wu, Boying
2016-04-01
This paper proves the global existence and boundedness of solutions to a general reaction-diffusion predator-prey system with prey-taxis defined on a smooth bounded domain with no-flux boundary condition. The result holds for domains in arbitrary spatial dimension and small prey-taxis sensitivity coefficient. This paper also proves the existence of a global attractor and the uniform persistence of the system under some additional conditions. Applications to models from ecology and chemotaxis are discussed.
Institute of Scientific and Technical Information of China (English)
Yidong Wang; Jingrui Pan; Yu Qiu; Xiangpen Li; Mei Li; Ying Peng
2009-01-01
BACKGROUND: Hypoxic tissue surrounding the ischemic core may represent the ischemic penumbra following cerebral infarction. However, some studies have shown that the duration of ischemic tissue is longer than previously believed.OBJECTIVE: To clarify whether cerebral hypoxic tissue could survive long-term and whether it is altered in rats following cerebral infarction; to establish an ischemia/reperfusion model in which hypoxic tissue exists for extended periods of time.DESIGN, TIME AND SETTING: A completely randomized grouping and controlled experiment was performed at the Experimental Animal Center of Sun Yat-sen University and Medical Research Center, the Second Affiliated Hospital of Sun Yat-sen University between June and December 2008. MATERIALS: 4,9-diaza-3,3,10,10-tetramethyldodecan-2, 11-dione dioxime (BnAO) (HL91), used as the hypoxic marker for autoradiography, was supplied by the Beijing Syncor Star Medicinal, China, and the flesh eluent Na99TcmO4 to mark HL91 was supplied by Guangzhou Medical Isotope Center of the China Institute of Atomic Energy. 2-(2-nitro-1H-imidazole-1-yl)-N-(2,2,3,3,3-pentafluoropropyl) acetamide (EF5) and its antibody ELK3-51, used as a hypoxic marker for immunofluorescence, were supplied by the University of Pennsylvania, USA.METHODS: Male Sprague Dawley rats were randomly divided into four groups: 1.5-hour ischemia/reperfusion group (1.5 h IR), 2-hour ischemia/reperfusion group (2 h IR), 3-hour ischemia/reperfusion group (3 h IR), and permanent ischemia (PI) group, with 21 rats in each group. The middle cerebral artery occlusion model was established using the intraluminal suture method, while reperfusion was performed by removing the suture at each observation time point. However, in the PI group, the suture was left in the artery.MAIN OUTCOME MEASURES: Area and average absorbance of fluorescence, representing hypoxic tissue, were measured by image-analysis.RESULTS: Autoradiography revealed positive hypoxia at days 1 and 14
Wen, Zijuan; Fan, Meng; Asiri, Asim M; Alzahrani, Ebraheem O; El-Dessoky, Mohamed M; Kuang, Yang
2017-04-01
This paper studies the global existence and uniqueness of classical solutions for a generalized quasilinear parabolic equation with appropriate initial and mixed boundary conditions. Under some practicable regularity criteria on diffusion item and nonlinearity, we establish the local existence and uniqueness of classical solutions based on a contraction mapping. This local solution can be continued for all positive time by employing the methods of energy estimates, Lp-theory, and Schauder estimate of linear parabolic equations. A straightforward application of global existence result of classical solutions to a density-dependent diffusion model of in vitro glioblastoma growth is also presented.
Existence Theorems for Vortices in the Aharony-Bergman-Jaferis-Maldacena Model
Han, Xiaosen; Yang, Yisong
2015-01-01
A series of sharp existence and uniqueness theorems are established for the multiple vortex solutions in the supersymmetric Chern-Simons-Higgs theory formalism of Aharony, Bergman, Jaferis, and Maldacena, for which the Higgs bosons and Dirac fermions lie in the bifundamental representation of the general gauge symmetry group . The governing equations are of the BPS type and derived by Kim, Kim, Kwon, and Nakajima in the mass-deformed framework labeled by a continuous parameter.
Finite element model updating of existing steel bridge based on structural health monitoring
Institute of Scientific and Technical Information of China (English)
HE Xu-hui; YU zhi-wu; CHEN Zheng-qing
2008-01-01
Based on the physical meaning of sensitivity, a new finite element (FE) model updating method was proposed. In this method, a three-dimensional FE model of the Nanjing Yangtze River Bridge (NYRB) with ANSYS program was established and updated by modifying some design parameters. To further validate the updated FE model, the analytical stress-time histories responses of main members induced by a moving train were compared with the measured ones. The results show that the relative error of maximum stress is 2.49% and the minimum relative coefficient of analytical stress-time histories responses is 0.793. The updated model has a good agreement between the calculated data and the tested data, and provides a current baseline FE model for long-term health monitoring and condition assessment of the NYRB. At the same time, the model is validated by stress-time histories responses to be feasible and practical for railway steel bridge model updating.
A Scoping Review on Models of Integrative Medicine: What Is Known from the Existing Literature?
Lim, Eun Jin; Vardy, Janette L; Oh, Byeong Sang; Dhillon, Haryana M
2017-01-01
Integrative medicine (IM) has been recognized and introduced into Western healthcare systems over the past two decades. Limited information on IM models is available to guide development of an optimal healthcare service. A scoping review was carried out to evaluate IM models in the extant literature, including the distinctive features of each model, to gain an understanding of the core requirements needed to develop models of IM that best meet the needs of patients. Directed content analysis was used to classify the IM models into systems based on coding schema developed from theoretical models and to identify the key concepts of each system. From 1374 articles identified, 45 studies were included. Models were categorized as theoretical and practical and were subdivided into five main models: coexistence, cooptative, cooperative, collaborative, and patient-centered care. They were then divided into three systems-independent, dependent, and integrative-on the basis of the level of involvement of general practitioners and complementary and alternative medicine (CAM) practitioners. The theoretical coexistence and cooptative models have distinct roles for different health care professionals, whereas practical models tend to be ad hoc market-driven services, dependent on patient demand. The cooperative and collaborative models were team-based, with formalized interaction between the two medical paradigms of conventional medicine and CAM, with the practical models focusing on facilitating communication, behaviors, and relationships. The patient-centered care model recognized the philosophy of CAM and required collaboration between disciplines based around patient needs. The focus of IM models has transferred from providers to patients with the independent and integrative systems. This may require a philosophical shift for IM. Further research is required to best understand how to practice patient-centered care in IM services.
Observations and Modeling of Solar Flare Atmospheric Dynamics
Li, Y.
2015-09-01
spectral lines at the first point are mostly blueshifted, with the hotter lines showing a dominant blueshifted component over the stationary one. At the second point, however, only weak upflows are detected; instead, notable downflows appear at high temperatures (up to 2.5-5.0 MK). The third point is similar to the second one except that it shows evidence of multi-component downflows. While the evaporated plasma falling back down as warm rain is a possible cause of the redshifts at the second and third points, the different patterns of chromospheric evaporation at the three points imply the existence of different heating mechanisms in the flaring region. Then, we study the flare heating and dynamics using the ``enthalpy-based thermal evolution of loops'' (EBTEL) model. We analyze an M1.0 flare on 2011 February 16. This flare is composed of two distinctive loop systems observed in EUV images. The UV 1600 Å emission at the feet of these loops exhibits a rapid rise, followed by enhanced emission in different EUV channels observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). Such a behavior is indicative of impulsive energy deposit, and the subsequent response of overlying coronal loops. Using the method recently developed, we infer empirical heating functions from the rapid rise of the UV light curves for the two loop systems, respectively, treated as two big loops with cross-sectional area of 5'' by 5'', and compute the plasma evolution in the loops using the EBTEL model. We further compute the synthetic EUV light curves, which, with the limitation of the model, agree reasonably with the observed light curves obtained in multiple AIA channels and EIS lines: they show the same evolution trend, and their magnitudes are comparable within a factor of two. We also compare the computed mean enthalpy flow velocity with the Doppler shifts of EIS lines during the decay phase of the two loops. Our results suggest that the two different
Comparison of existing models to simulate anaerobic digestion of lipid-rich waste.
Béline, F; Rodriguez-Mendez, R; Girault, R; Bihan, Y Le; Lessard, P
2017-02-01
Models for anaerobic digestion of lipid-rich waste taking inhibition into account were reviewed and, if necessary, adjusted to the ADM1 model framework in order to compare them. Experimental data from anaerobic digestion of slaughterhouse waste at an organic loading rate (OLR) ranging from 0.3 to 1.9kgVSm(-3)d(-1) were used to compare and evaluate models. Experimental data obtained at low OLRs were accurately modeled whatever the model thereby validating the stoichiometric parameters used and influent fractionation. However, at higher OLRs, although inhibition parameters were optimized to reduce differences between experimental and simulated data, no model was able to accurately simulate accumulation of substrates and intermediates, mainly due to the wrong simulation of pH. A simulation using pH based on experimental data showed that acetogenesis and methanogenesis were the most sensitive steps to LCFA inhibition and enabled identification of the inhibition parameters of both steps.
The Existence and Long-Time Behavior of Weak Solution to Bipolar Quantum Drift-Diffusion Model
Institute of Scientific and Technical Information of China (English)
Xiuqing CHEN; Li CHEN; Huaiyu JIAN
2007-01-01
The authors study the existence and long-time behavior of weak solutions to the bipolar transient quantum drift-diffusion model, a fourth order parabolic system. Using semi-discretization in time and entropy estimate, the authors get the global existence of nonnegative weak solutions to the one-dimensional model with nonnegative initial and homogenous Neumann (or periodic) boundary conditions. Furthermore, by a logarithmic Sobolev inequality, it is proved that the periodic weak solution exponentially approaches its mean value as time increases to infinity.
Directory of Open Access Journals (Sweden)
Shiqian Nie
2017-01-01
Full Text Available The fractional advection-diffusion equation (fADE model is a new approach to describe the vertical distribution of suspended sediment concentration in steady turbulent flow. However, the advantages and parameter definition of the fADE model in describing the sediment suspension distribution are still unclear. To address this knowledge gap, this study first reviews seven models, including the fADE model, for the vertical distribution of suspended sediment concentration in steady turbulent flow. The fADE model, among others, describes both Fickian and non-Fickian diffusive characteristics of suspended sediment, while the other six models assume that the vertical diffusion of suspended sediment follows Fick’s first law. Second, this study explores the sensitivity of the fractional index of the fADE model to the variation of particle sizes and sediment settling velocities, based on experimental data collected from the literatures. Finally, empirical formulas are developed to relate the fractional derivative order to particle size and sediment settling velocity. These formulas offer river engineers a substitutive way to estimate the fractional derivative order in the fADE model.
Refsgaard, J.C.; Henriksen, H.; Harrar, B.; Scholten, H.; Kassahun, A.
2005-01-01
Quality assurance (QA) is defined as protocols and guidelines to support the proper application of models. In the water management context we classify QA guidelines according to how much focus is put on the dialogue between the modeller and the water manager as: (Type 1) Internal technical guideline
Embodied Agents, E-SQ and Stickiness: Improving Existing Cognitive and Affective Models
de Diesbach, Pablo Brice
This paper synthesizes results from two previous studies of embodied virtual agents on commercial websites. We analyze and criticize the proposed models and discuss the limits of the experimental findings. Results from other important research in the literature are integrated. We also integrate concepts from profound, more business-related, analysis that deepens on the mechanisms of rhetoric in marketing and communication, and the possible role of E-SQ in man-agent interaction. We finally suggest a refined model for the impacts of these agents on web site users, and limits of the improved model are commented.
Directory of Open Access Journals (Sweden)
J. E. Macías-Díaz
2017-01-01
Full Text Available We depart from the well-known one-dimensional Fisher’s equation from population dynamics and consider an extension of this model using Riesz fractional derivatives in space. Positive and bounded initial-boundary data are imposed on a closed and bounded domain, and a fully discrete form of this fractional initial-boundary-value problem is provided next using fractional centered differences. The fully discrete population model is implicit and linear, so a convenient vector representation is readily derived. Under suitable conditions, the matrix representing the implicit problem is an inverse-positive matrix. Using this fact, we establish that the discrete population model is capable of preserving the positivity and the boundedness of the discrete initial-boundary conditions. Moreover, the computational solubility of the discrete model is tackled in the closing remarks.
Observational signatures of holographic models of inflation
P. McFadden; K. Skenderis
2009-01-01
We discuss the phenomenology of recently proposed holographic models of inflation, in which the very early universe is non-geometric and is described by a dual three-dimensional quantum field theory (QFT). We analyze models determined by a specific class of dual QFTs and show that they have the foll
Observations and modelling of snow avalanche entrainment
Directory of Open Access Journals (Sweden)
B. Sovilla
2002-01-01
Full Text Available In this paper full scale avalanche dynamics measurements from the Italian Pizzac and Swiss Vallée de la Sionne test sites are used to develop a snowcover entrainment model. A detailed analysis of three avalanche events shows that snowcover entrainment at the avalanche front appears to dominate over bed erosion at the basal sliding surface. Furthermore, the distribution of mass within the avalanche body is primarily a function of basal friction. We show that the mass distribution in the avalanche changes the flow dynamics significantly. Two different dynamical models, the Swiss Voellmy-fluid model and the Norwegian NIS model, are used to back calculate the events. Various entrainment methods are investigated and compared to measurements. We demon-strate that the Norwegian NIS model is clearly better able to simulate the events once snow entrainment has been included in the simulations.
A robust circle criterion observer with application to neural mass models
2012-01-01
International audience; A robust circle criterion observer is designed and applied to neural mass models. At present, no existing circle criterion observers apply to the considered models, i.e. the required linear matrix inequality is infeasible. Therefore, we generalise available results to derive a suitable estimation algorithm. Additionally, the design also takes into account input uncertainty and measurement noise. We show how to apply the observer to estimate the mean membrane potential ...
Grunsven, van R.H.A.; Donners, M.; Boekee, K.; Tichelaar, I.; Geffen, van K.G.; Groenendijk, D.; Berendse, F.; Veenendaal, E.M.
2014-01-01
Artificial illumination attracts insects, but to what extent light attracts insects, depends on the spectral composition of the light. Response models have been developed to predict the attractiveness of artificial light sources. In this study we compared attraction of insects by existing light sour
Escher, Joachim; Matioc, Bogdan-Vasile
2011-01-01
We prove global existence of nonnegative weak solutions to a degenerate parabolic system which models the interaction of two thin fluid films in a porous medium. Furthermore, we show that these weak solutions converge at an exponential rate towards flat equilibria.
Global Existence of Classical Solutions to a Three-Species Predator-Prey Model with Two Prey-Taxes
Directory of Open Access Journals (Sweden)
Chenglin Li
2012-01-01
Full Text Available We are concerned with three-species predator-prey model including two prey-taxes and Holling type II functional response under no flux boundary condition. By applying the contraction mapping principle, the parabolic Schauder estimates, and parabolic Lp estimates, we prove that there exists a unique global classical solution of this system.
Post-Hoc Pattern-Oriented Testing and Tuning of an Existing Large Model: Lessons from the Field Vole
DEFF Research Database (Denmark)
Topping, Christopher John; Dalkvist, Trine; Grimm, Volker
2012-01-01
develop an existing agent-based model of the field vole (Microtus agrestis), which was developed and tested within the ALMaSS framework. This framework is complex because it includes a high-resolution representation of the landscape and its dynamics, of the individual’s behavior, and of the interaction...
Qin, Yuming; Zhang, Jianlin
2016-12-01
In this paper, we establish the global existence, uniqueness and asymptotic behavior of cylindrically symmetric solutions for the 3D infrarelativistic model with radiation in H^i× (H^i)^3× H^i× H^{i+1}(i=1,2,4) . The key point is that the smallness of initial data is not needed.
Moore, C. W.; Dastoor, A.; Steffen, A.; Nghiem, S. V.; Agnan, Y.; Obrist, D.
2015-12-01
Northern hemisphere background atmospheric concentrations of gaseous elemental mercury (GEM) have been declining by up to 25% over the last ten years at some lower latitude sites. However, this decline has ranged from no decline to 9% over 10 years at Arctic long-term measurement sites. Measurements also show a highly dynamic nature of mercury (Hg) species in Arctic air and snow from early spring to the end of summer when biogeochemical transformations peak. Currently, models are unable to reproduce this variability accurately. Estimates of Hg accumulation in the Arctic and Arctic Ocean by models require a full mechanistic understanding of the multi-phase redox chemistry of Hg in air and snow as well as the role of meteorology in the physicochemical processes of Hg. We will show how findings from ground-based atmospheric Hg measurements like those made in spring 2012 during the Bromine, Ozone and Mercury Experiment (BROMEX) near Barrow, Alaska can be used to reduce the discrepancy between measurements and model output in the Canadian GEM-MACH-Hg model. The model is able to reproduce and to explain some of the variability in Arctic Hg measurements but discrepancies still remain. One improvement involves incorporation of new physical mechanisms such as the one we were able to identify during BROMEX. This mechanism, by which atmospheric mercury depletion events are abruptly ended via sea ice leads opening and inducing shallow convective mixing that replenishes GEM (and ozone) in the near surface atmospheric layer, causing an immediate recovery from the depletion event, is currently lacking in models. Future implementation of this physical mechanism will have to incorporate current remote sensing sea ice products but also rely on the development of products that can identify sea ice leads quantitatively. In this way, we can advance the knowledge of the dynamic nature of GEM in the Arctic and the impact of climate change along with new regulations on the overall
Observational Tests of Planet Formation Models
Sozzetti, A; Latham, D W; Carney, B W; Laird, J B; Stefanik, R P; Boss, A P; Charbonneau, D; O'Donovan, F T; Holman, M J; Winn, J N
2007-01-01
We summarize the results of two experiments to address important issues related to the correlation between planet frequencies and properties and the metallicity of the hosts. Our results can usefully inform formation, structural, and evolutionary models of gas giant planets.
Fatigue assessment of an existing steel bridge by finite element modelling and field measurements
Kwad, J.; Alencar, G.; Correia, J.; Jesus, A.; Calçada, R.; Kripakaran, P.
2017-05-01
The evaluation of fatigue life of structural details in metallic bridges is a major challenge for bridge engineers. A reliable and cost-effective approach is essential to ensure appropriate maintenance and management of these structures. Typically, local stresses predicted by a finite element model of the bridge are employed to assess the fatigue life of fatigue-prone details. This paper illustrates an approach for fatigue assessment based on measured data for a connection in an old bascule steel bridge located in Exeter (UK). A finite element model is first developed from the design information. The finite element model of the bridge is calibrated using measured responses from an ambient vibration test. The stress time histories are calculated through dynamic analysis of the updated finite element model. Stress cycles are computed through the rainflow counting algorithm, and the fatigue prone details are evaluated using the standard SN curves approach and the Miner’s rule. Results show that the proposed approach can estimate the fatigue damage of a fatigue prone detail in a structure using measured strain data.
Three-Dimensional Model Test Study on the Existing Caisson Breakwater at Port of Castellon, Spain
DEFF Research Database (Denmark)
Nørgaard, Jørgen Harck; Andersen, Thomas Lykke
This report present the results of 3-D physical model tests (length scale 1:60) carried out in a wave basin at Department of Civil Engineering, Aalborg University (AAU) on behalf of the client; BP OIL ESPAÑA. Associate Prof. Thomas Lykke Andersen and M.Sc. Jørgen Quvang Harck Nørgaard were in cha...
Institute of Scientific and Technical Information of China (English)
黎勇; 陈丽
2002-01-01
In this paper, we study the asymptotic behavior of global smooth solution to the initial boundary problem for the 1-D energy transport model in semiconductor science. We prove that the smooth solution of the problem converges to a stationary solution exponentially fast as t - ∞ when the initial data is a small perturbation of the stationary solution.
Numerical Acoustic Models Including Viscous and Thermal losses: Review of Existing and New Methods
DEFF Research Database (Denmark)
Andersen, Peter Risby; Cutanda Henriquez, Vicente; Aage, Niels
2017-01-01
This work presents an updated overview of numerical methods including acoustic viscous and thermal losses. Numerical modelling of viscothermal losses has gradually become more important due to the general trend of making acoustic devices smaller. Not including viscothermal acoustic losses in such...
Bayesian Network Models for Local Dependence among Observable Outcome Variables
Almond, Russell G.; Mulder, Joris; Hemat, Lisa A.; Yan, Duanli
2009-01-01
Bayesian network models offer a large degree of flexibility for modeling dependence among observables (item outcome variables) from the same task, which may be dependent. This article explores four design patterns for modeling locally dependent observations: (a) no context--ignores dependence among observables; (b) compensatory context--introduces…
Energy Technology Data Exchange (ETDEWEB)
G.J. Kramer; S.E. Sharapov; R. Nazikian; N.N. Gorelenkov; R. Budny; JET-EFDA contributors
2003-01-15
Experimental evidence is presented for the existence of the theoretically predicted odd Torodicity-induced Alfven Eigenmode (TAEs) from the simultaneous appearance of odd and even TAEs in a normal shear discharge. The modes are observed in low central magnetic shear plasmas created by injecting lower hybrid current drive. A fast ion population was created by applying ion cyclotron heating at the high field side to excite the TAEs in the weak magnetic shear region. The odd TAEs were identified from their frequency, mode number, and timing relative to the even TAEs.
2010-08-01
units Generators Boilers Chillers Fire alarm display panels Sprinkler valves Fire hose connections Exhaust fans Telephone panels Switchgear...captured for each component. Once all data is captured for the space, the system would automatically move on to the next space. Furthermore, all...Information Modeling (BIM) systems . The Army Corps of Engineers requires the use of BIM on all new construction projects associated with the Army
On the existence of anisotropic cosmological models in higher order theories of gravity
Middleton, Jonathan
2010-01-01
Abstract We investigate the behaviour on approach to the initial singularity in higher-order extensions of general relativity by finding exact cosmological solutions for a wide class of models in which the Lagrangian is allowed to depend nonlinearly upon the three possible linear and quadratic scalars built from the Riemann tensor ; R, R ab R ab and R abcd R abcd. We present new anisotropic vacuum solutions analagous to the Kasner solutions of general relativity and extend previous results...
Sereda, Valentin; Sawaya, Michael R; Lednev, Igor K
2015-09-01
Many different proteins undergo misfolding and self-assemble into amyloid fibrils, resulting in a range of neurodegenerative diseases. The limitations of conventional methods of structural biology for fibril characterization have led to the use of polarized Raman spectroscopy for obtaining quantitative structural information regarding the organization of amyloid fibrils. Herein, we report the orientation of selected chemical groups and secondary structure elements in aligned insulin fibrils, including β-sheets, which possess a high level of orientation in the cross-β core, and α-helices in the disordered portions of the fibrils. Strong orientation of disulfide bonds in amyloid fibrils was also revealed, indicating their association with the fibril core. The determined orientation of chemical groups provides strong constraints for modeling the overall structure of amyloid fibrils, including the core and disordered parts. The developed methodology allows for the validation of structural models proposed in the literature for amyloid fibrils. Specifically, the polarized Raman data obtained herein strongly agreed with two insulin fibril models (Jiménez et al., Proc. Natl. Acad. Sci. U. S. A. 2002, 99, 9196-9201 and Ivanova et al., Proc. Natl. Acad. Sci. U. S. A. 2009, 106, 18990-18995) yet revealed significant qualitative and quantitative differences. This work demonstrates the great potential of polarized Raman spectroscopy for structural characterization of anisotropic biological species.
Energy Technology Data Exchange (ETDEWEB)
Deodhar, Aniruddha; Stewart, Emma; Young, Rahul; Khan, Haider
2010-09-15
Retrofits of existing buildings represent a huge, growing market and an opportunity to achieve some of the most sizable and cost-effective carbon reductions in any sector of the economy. More 'zero energy' and 'carbon neutral' buildings are being conceived daily by combining energy efficiency measures with renewable energy technologies. However, for all the progress, the building industry faces technical and cost challenges in identifying the highest potential retrofit candidates. This presentation investigates one potential solution, a technology driven workflow called rapid energy modeling, to accelerate and scale the process of analyzing performance for existing buildings in prioritizing improvements.
Can a regional climate model reproduce observed extreme temperatures?
Directory of Open Access Journals (Sweden)
Peter F. Craigmile
2013-10-01
Full Text Available Using output from a regional Swedish climate model and observations from the Swedish synoptic observational network, we compare seasonal minimum temperatures from model output and observations using marginal extreme value modeling techniques. We make seasonal comparisons using generalized extreme value models and empirically estimate the shift in the distribution as a function of the regional climate model values, using the Doksum shift function. Spatial and temporal comparisons over south central Sweden are made by building hierarchical Bayesian generalized extreme value models for the observed minima and regional climate model output. Generally speaking the regional model is surprisingly well calibrated for minimum temperatures. We do detect a problem in the regional model to produce minimum temperatures close to 0◦C. The seasonal spatial effects are quite similar between data and regional model. The observations indicate relatively strong warming, especially in the northern region. This signal is present in the regional model, but is not as strong.
Directory of Open Access Journals (Sweden)
Magnolia Tilca
2014-10-01
Full Text Available The aim of this paper is to study the existence of the solution for the overlapping generations model, using fixed point theorems in metric spaces endowed with a graph. The overlapping generations model has been introduced and developed by Maurice Allais (1947, Paul Samuelson (1958, Peter Diamond (1965 and so on. The present paper treats the case presented by Edmond (2008 in (Edmond, 2008 for a continuous time. The theorem of existence of the solution for the prices fixed point problem derived from the overlapping generations model gives an approximation of the solution via the graph theory. The tools employed in this study are based on applications of the Jachymski fixed point theorem on metric spaces endowed with a graph (Jachymski, 2008
Television Advertising and Children's Observational Modeling.
Atkin, Charles K.
This paper assesses advertising effects on children and adolescents from a social learning theory perspective, emphasizing imitative performance of vicariously reinforced consumption stimuli. The basic elements of social psychologist Albert Bandura's modeling theory are outlined. Then specific derivations from the theory are applied to the problem…
Bicycle Rider Control: Observations, Modeling & Experiments
Kooijman, J.D.G.
2012-01-01
Bicycle designers traditionally develop bicycles based on experience and trial and error. Adopting modern engineering tools to model bicycle and rider dynamics and control is another method for developing bicycles. This method has the potential to evaluate the complete design space, and thereby dev
Global Existence for a Parabolic-hyperbolic Free Boundary Problem Modelling Tumor Growth
Institute of Scientific and Technical Information of China (English)
Shang-bin Cui; Xue-mei Wei
2005-01-01
In this paper we study a free boundary problem modelling tumor growth, proposed by A. Friedman in 2004. This free boundary problem involves a nonlinear second-order parabolic equation describing the diffusion of nutrient in the tumor, and three nonlinear first-order hyperbolic equations describing the evolution of proliferative cells, quiescent cells and dead cells, respectively. By applying Lp theory of parabolic equations, the characteristic theory of hyperbolic equations, and the Banach fixed point theorem, we prove that this problem has a unique global classical solution.
Comparing Blast Effects on Human Torso Finite Element Model against Existing Lethality Curves
2010-07-15
Torso FEM Development Geometry The anatomical geometry for the finite element model originated from the geometry supplied by the 4D NURBS -based...by the WORLDSID project (Moss 2000). The geometry was imported as NURBS surfaces and manipulated to contain distinct organs and bones. The Human...Volume 40, Issue 1, 2007, Pages 125‐ 136. Segars, W.P. Development of a new dynamic NURBS ‐based cardiac‐torso (NCAT) phantom. The University of North
A New Hybrid Model Rotor Flux Observer and Its Application
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A new hybrid model rotor flux observer, based on a new voltage model, is presented. In the first place, the voltage model of an induction machine was constructed by using the modeling method discussed in this paper and then the current model using a flux feedback was adopted in this flux observer. Secondly, the two models were combined via a filter and then the rotor flux observer was established. In the M-T synchronous coordinate, the observer was analyzed theoretically and several important functions were derived. A comparison between the observer and the traditional models was made using Matlab software. The simulation results show that the observer model had a better performance than the traditional model.
Does a General Temperature-Dependent Q10 Model of Soil Respiration Exist at Biome and Global Scale?
Institute of Scientific and Technical Information of China (English)
Hua CHEN; Han-Qin TIAN
2005-01-01
Soil respiration (SR) is commonly modeled by a Q10 (an indicator of temperature sensitivity)function in ecosystem models. Q10is usually treated as a constant of 2 in these models, although Q10 value of SR often decreases with increasing temperatures. It remains unclear whether a general temperaturedependent Q10 model of SR exists at biome and global scale. In this paper, we have compiled the long-term Q10 data of 38 SR studies ranging from the Boreal, Temperate, to Tropical/Subtropical biome on four continents.Our analysis indicated that the general temperature-dependent biome Q10 models of SR existed, especially in the Boreal and Temperate biomes. A single-exponential model was better than a simple linear model in fitting the average Q10 values at the biome scale. Average soil temperature is a better predictor of Q10 value than average air temperature in these models, especially in the Boreal biome. Soil temperature alone could explain about 50% of the Q10 variations in both the Boreal and Temperate biome single-exponential Q10 model. Q10 value of SR decreased with increasing soil temperature but at quite different rates among the three biome Q10 models. The k values (Q10 decay rate constants) were 0.09, 0.07, and 0.02/℃ in the Boreal, Temperate, and Tropical/Subtropical biome, respectively, suggesting that Q10 value is the most sensitive to soil temperature change in the Boreal biome, the second in the Temperate biome, and the least sensitive in the Tropical/Subtropical biome. This also indirectly confirms that acclimation of SR in many soil warming experiments probably occurs. The k value in the "global" single-exponential Q10 model which combined both the Boreal and Temperate biome data set was 0.08/℃. However, the global general temperature-dependent Q10model developed using the data sets of the three biomes is not adequate for predicting Q10 values of SR globally.The existence of the general temperature-dependent Q10 models of SR in the Boreal and
On the Existence of a Weak Solution of a Half-Cell Model for PEM Fuel Cells
Directory of Open Access Journals (Sweden)
Shuh-Jye Chern
2010-01-01
Full Text Available A nonlinear boundary value problem (BVP from the modelling of the transport phenomena in the cathode catalyst layer of a one-dimensional half-cell single-phase model for proton exchange membrane (PEM fuel cells, derived from the 3D model of Zhou and Liu (2000, 2001, is studied. It is a BVP for a system of three coupled ordinary differential equations of second order. Schauder's fixed point theorem is applied to show the existence of a solution in the Sobolev space 1.
Schild, R E; Robertson, S L; Schild, Rudolph E.; Leiter, Darryl J.; Robertson, Stanley L.
2005-01-01
Recent auto-correlation and fluctuation analysis of time series data in the brightness curves and micro-lensing size scales seen in Q0957+561 A,B has produced important information about the existence and characteristic physical dimensions of a new non-standard internal structure contained within this quasar. We find that the new internal quasar structure, which we shall call the Schild-Vakulik Structure, can be consistently explained in terms of a new calss of gravitationally collapsing solutions to the Einstein field equations which describe highly redshifted, Eddington limited, Magnetospheric Eternally Collapsing Objects (MECO) that contain intrinsic magnetic moments. Since observation of the Schild-Vakulik structure within Q0957+561 implies that this quasar contains an observable intrinsic magnetic moment, this represents strong evidence that this quasar does not have an event horizon
Design of a Representative Low Earth Orbit Satellite to Improve Existing Debris Models
Clark, S.; Dietrich, A.; Werremeyer, M.; Fitz-Coy, N.; Liou, J.-C.
2012-01-01
This paper summarizes the process and methodologies used in the design of a small-satellite, DebriSat, that represents materials and construction methods used in modern day Low Earth Orbit (LEO) satellites. This satellite will be used in a future hypervelocity impact test with the overall purpose to investigate the physical characteristics of modern LEO satellites after an on-orbit collision. The major ground-based satellite impact experiment used by DoD and NASA in their development of satellite breakup models was conducted in 1992. The target used for that experiment was a Navy Transit satellite (40 cm, 35 kg) fabricated in the 1960 s. Modern satellites are very different in materials and construction techniques from a satellite built 40 years ago. Therefore, there is a need to conduct a similar experiment using a modern target satellite to improve the fidelity of the satellite breakup models. The design of DebriSat will focus on designing and building a next-generation satellite to more accurately portray modern satellites. The design of DebriSat included a comprehensive study of historical LEO satellite designs and missions within the past 15 years for satellites ranging from 10 kg to 5000 kg. This study identified modern trends in hardware, material, and construction practices utilized in recent LEO missions, and helped direct the design of DebriSat.
Barlow, J. R.; Clark, B. R.
2010-12-01
The alluvial plain in northwestern Mississippi, locally referred to as the Delta, is a major agricultural area, which contributes significantly to the economy of Mississippi. Land use in this area can be greater than 90 percent agriculture, primarily for growing catfish, corn, cotton, rice, and soybean. Irrigation is needed to smooth out the vagaries of climate and is necessary for the cultivation of rice and for the optimization of corn and soybean. The Mississippi River Valley alluvial (MRVA) aquifer, which underlies the Delta, is the sole source of water for irrigation, and over use of the aquifer has led to water-level declines, particularly in the central region. The Yazoo-Mississippi-Delta Joint Water Management District (YMD), which is responsible for water issues in the 17-county area that makes up the Delta, is directing resources to reduce the use of water through conservation efforts. The U.S. Geological Survey (USGS) recently completed a regional groundwater flow model of the entire Mississippi embayment, including the Mississippi Delta region, to further our understanding of water availability within the embayment system. This model is being used by the USGS to assist YMD in optimizing their conservation efforts by applying various water-use reduction scenarios, either uniformly throughout the Delta, or in focused areas where there have been large groundwater declines in the MRVA aquifer.
Holmes, Philip; Cohen, Jonathan D
2014-04-01
We review how leaky competing accumulators (LCAs) can be used to model decision making in two-alternative, forced-choice tasks, and we show how they reduce to drift diffusion (DD) processes in special cases. As continuum limits of the sequential probability ratio test, DD processes are optimal in producing decisions of specified accuracy in the shortest possible time. Furthermore, the DD model can be used to derive a speed-accuracy trade-off that optimizes reward rate for a restricted class of two alternative forced-choice decision tasks. We review findings that compare human performance with this benchmark, and we reveal both approximations to and deviations from optimality. We then discuss three potential sources of deviations from optimality at the psychological level--avoidance of errors, poor time estimation, and minimization of the cost of control--and review recent theoretical and empirical findings that address these possibilities. We also discuss the role of cognitive control in changing environments and in modulating exploitation and exploration. Finally, we consider physiological factors in which nonlinear dynamics may also contribute to deviations from optimality.
Observation Constraints on the Simplified GCG Model
Institute of Scientific and Technical Information of China (English)
DONG Su-Mei; WU Pu-Xun
2007-01-01
A simplified version of generalized Chaplygin gas (GCG) as a dark energy model is studied. By using the latest 162 ESSENCE type la supernovae (Sne la) data, 30 high redshift Sne la data, the baryonk acoustic oscillation peak from SDSS and the CMB data from WMAP3, a strong constraint on this simplified GCG model is obtained. At the 95.4% confidence level we obtain 0.21 ≤ Ωm ≤ 0.31 and 0.994 ≤ a ≤ 1.0 with the best fit fim = 0.25 and a = 1. This best fit scenario corresponds to an accelerating universe with qo ～_0.65 and z ～- 0.81 (a redshift of cosmic phase transition from deceleration to acceleration).
Observations and modelling of snow avalanche entrainment
2002-01-01
In this paper full scale avalanche dynamics measurements from the Italian Pizzac and Swiss Vallée de la Sionne test sites are used to develop a snowcover entrainment model. A detailed analysis of three avalanche events shows that snowcover entrainment at the avalanche front appears to dominate over bed erosion at the basal sliding surface. Furthermore, the distribution of mass within the avalanche body is primarily a function of basal fric...
Structural equation modeling for observational studies
Grace, J.B.
2008-01-01
Structural equation modeling (SEM) represents a framework for developing and evaluating complex hypotheses about systems. This method of data analysis differs from conventional univariate and multivariate approaches familiar to most biologists in several ways. First, SEMs are multiequational and capable of representing a wide array of complex hypotheses about how system components interrelate. Second, models are typically developed based on theoretical knowledge and designed to represent competing hypotheses about the processes responsible for data structure. Third, SEM is conceptually based on the analysis of covariance relations. Most commonly, solutions are obtained using maximum-likelihood solution procedures, although a variety of solution procedures are used, including Bayesian estimation. Numerous extensions give SEM a very high degree of flexibility in dealing with nonnormal data, categorical responses, latent variables, hierarchical structure, multigroup comparisons, nonlinearities, and other complicating factors. Structural equation modeling allows researchers to address a variety of questions about systems, such as how different processes work in concert, how the influences of perturbations cascade through systems, and about the relative importance of different influences. I present 2 example applications of SEM, one involving interactions among lynx (Lynx pardinus), mongooses (Herpestes ichneumon), and rabbits (Oryctolagus cuniculus), and the second involving anuran species richness. Many wildlife ecologists may find SEM useful for understanding how populations function within their environments. Along with the capability of the methodology comes a need for care in the proper application of SEM.
The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible un...
Elements of attention in HIV-infected adults: Evaluation of an existing model
Levine, Andrew J.; Hardy, David J.; Barclay, Terry R.; Reinhard, Matthew J.; Cole, Michael M.; Hinkin, Charles H.
2010-01-01
Because of the multifactorial nature of neuropsychological tests, attention remains poorly defined from a neuropsychological perspective, and conclusions made regarding attention across studies may be limited due to the different nature of the measures used. Thus, a more definitive schema for this neurocognitive domain is needed. We assessed the applicability of Mirsky and Duncan's (2001) neuropsychological model of attention to a cohort of 104 HIV+ adults. Our analysis resulted in a five-factor structure similar to that of previous studies, which explained 74.5% of the variance. However, based on the psychometric characteristics of the measures comprising each factor, we offer an alternative interpretation of the factors. Findings also indicate that one factor, which is generally not assessed in clinical neuropsychology settings, may be more predictive of real-world behaviors (such as medication adherence) than those composed of traditional measures. Suggestions for further research in this important area are discussed. PMID:17852595
Directory of Open Access Journals (Sweden)
Dan Scott
2012-11-01
Full Text Available Scholarly publishing has gone through turbulent times. Enormous growth in supply and expenditure has been followed – dramatically and unexpectedly – by severe contraction of budgets. The ‘creative destruction’ of the 2008 global financial crisis has produced new opportunities and forced legislators, administrators, academics and librarians to consider alternatives to traditional subscription models. This article presents a case study of one UK-based ‘gold’ publisher's attempts to create a viable, sustainable alternative, which aims to bring the same benefits of open access publishing to the social sciences and arts & humanities as have been proven to work in STM – so, providing insights into the strategic choices of product, scope and aims, pricing, marketing, etc. By the time of publication, 'Social Sciences Directory' will have published its first issue, and 'Humanities Directory' will be close to following suit.
Interacting Dark Energy Models and Observations
Shojaei, Hamed; Urioste, Jazmin
2017-01-01
Dark energy is one of the mysteries of the twenty first century. Although there are candidates resembling some features of dark energy, there is no single model describing all the properties of dark energy. Dark energy is believed to be the most dominant component of the cosmic inventory, but a lot of models do not consider any interaction between dark energy and other constituents of the cosmic inventory. Introducing an interaction will change the equation governing the behavior of dark energy and matter and creates new ways to explain cosmic coincidence problem. In this work we studied how the Hubble parameter and density parameters evolve with time in the presence of certain types of interaction. The interaction serves as a way to convert dark energy into matter to avoid a dark energy-dominated universe by creating new equilibrium points for the differential equations. Then we will use numerical analysis to predict the values of distance moduli at different redshifts and compare them to the values for the distance moduli obtained by WMAP (Wilkinson Microwave Anisotropy Probe). Undergraduate Student
Lingsma, Hester F; Yue, John K; Maas, Andrew I R; Steyerberg, Ewout W; Manley, Geoffrey T
2015-01-15
Although the majority of patients with mild traumatic brain injury (mTBI) recover completely, some still suffer from disabling ailments at 3 or 6 months. We validated existing prognostic models for mTBI and explored predictors of poor outcome after mTBI. We selected patients with mTBI from TRACK-TBI Pilot, an unselected observational cohort of TBI patients from three centers in the United States. We validated two prognostic models for the Glasgow Outcome Scale Extended (GOS-E) at 6 months after injury. One model was based on the CRASH study data and another from Nijmegen, The Netherlands. Possible predictors of 3- and 6-month GOS-E were analyzed with univariate and multi-variable proportional odds regression models. Of the 386 of 485 patients included in the study (median age, 44 years; interquartile range, 27-58), 75% (n=290) presented with a Glasgow Coma Score (GCS) of 15. In this mTBI population, both previously developed models had a poor performance (area under the receiver operating characteristic curve, 0.49-0.56). In multivariable analyses, the strongest predictors of lower 3- and 6-month GOS-E were older age, pre-existing psychiatric conditions, and lower education. Injury caused by assault, extracranial injuries, and lower GCS were also predictive of lower GOS-E. Existing models for mTBI performed unsatisfactorily. Our study shows that, for mTBI, different predictors are relevant as for moderate and severe TBI. These include age, pre-existing psychiatric conditions, and lower education. Development of a valid prediction model for mTBI patients requires further research efforts.
Lingsma, Hester F.; Yue, John K.; Maas, Andrew I.R.; Steyerberg, Ewout W.; Cooper, Shelly R.; Dams-O'Connor, Kristen; Gordon, Wayne A.; Menon, David K.; Mukherjee, Pratik; Okonkwo, David O.; Puccio, Ava M.; Schnyer, David M.; Valadka, Alex B.; Vassar, Mary J.; Yuh, Esther L.
2015-01-01
Abstract Although the majority of patients with mild traumatic brain injury (mTBI) recover completely, some still suffer from disabling ailments at 3 or 6 months. We validated existing prognostic models for mTBI and explored predictors of poor outcome after mTBI. We selected patients with mTBI from TRACK-TBI Pilot, an unselected observational cohort of TBI patients from three centers in the United States. We validated two prognostic models for the Glasgow Outcome Scale Extended (GOS-E) at 6 months after injury. One model was based on the CRASH study data and another from Nijmegen, The Netherlands. Possible predictors of 3- and 6-month GOS-E were analyzed with univariate and multi-variable proportional odds regression models. Of the 386 of 485 patients included in the study (median age, 44 years; interquartile range, 27–58), 75% (n=290) presented with a Glasgow Coma Score (GCS) of 15. In this mTBI population, both previously developed models had a poor performance (area under the receiver operating characteristic curve, 0.49–0.56). In multivariable analyses, the strongest predictors of lower 3- and 6-month GOS-E were older age, pre-existing psychiatric conditions, and lower education. Injury caused by assault, extracranial injuries, and lower GCS were also predictive of lower GOS-E. Existing models for mTBI performed unsatisfactorily. Our study shows that, for mTBI, different predictors are relevant as for moderate and severe TBI. These include age, pre-existing psychiatric conditions, and lower education. Development of a valid prediction model for mTBI patients requires further research efforts. PMID:25025611
Markowich, Peter
2010-06-01
We study the system ct + u · ∇c = ∇c -nf(c) nt + u · ∇n = ∇n m - ∇ · (n×(c) ∇c) ut + u·∇u + ∇P - η∇u + n∇φ/ = 0 ∇·u = 0. arising in the modelling of the motion of swimming bacteria under the effect of diffusion, oxygen-taxis and transport through an incompressible fluid. The novelty with respect to previous papers in the literature lies in the presence of nonlinear porous-medium-like diffusion in the equation for the density n of the bacteria, motivated by a finite size effect. We prove that, under the constraint m ε (3/2, 2] for the adiabatic exponent, such system features global in time solutions in two space dimensions for large data. Moreover, in the case m = 2 we prove that solutions converge to constant states in the large-time limit. The proofs rely on standard energy methods and on a basic entropy estimate which cannot be achieved in the case m = 1. The case m = 2 is very special as we can provide a Lyapounov functional. We generalize our results to the three-dimensional case and obtain a smaller range of exponents m ε (m*, 2] with m* > 3/2, due to the use of classical Sobolev inequalities.
Yasui, Yuzuru; Hashimoto, Yuichi; Noguchi, Tatsuya; Kagawa, Takao
In order to reduce discrepancies between ground models based on the microtremor array observation in Fukui Plain and models by the H/V survey method and gravity analysis, the existing array ground models were reevaluated. The representative of the dispersion curves was selected so as to fit a theoretical fundamental mode dispersion curve of the H/V ground model. By using the method of selection, a reasonable reevaluation became possible. As a result the correspondences among the three models were much improved as a whole, but in the edge site of the Plain the differences against the gravity model are not reduced.
Observations, Modeling and Theory of Debris Disks
Matthews, Brenda C; Wyatt, Mark C; Bryden, Geoff; Eiroa, Carlos
2014-01-01
Main sequence stars, like the Sun, are often found to be orbited by circumstellar material that can be categorized into two groups, planets and debris. The latter is made up of asteroids and comets, as well as the dust and gas derived from them, which makes debris disks observable in thermal emission or scattered light. These disks may persist over Gyrs through steady-state evolution and/or may also experience sporadic stirring and major collisional breakups, rendering them atypically bright for brief periods of time. Most interestingly, they provide direct evidence that the physical processes (whatever they may be) that act to build large oligarchs from micron-sized dust grains in protoplanetary disks have been successful in a given system, at least to the extent of building up a significant planetesimal population comparable to that seen in the Solar System's asteroid and Kuiper belts. Such systems are prime candidates to host even larger planetary bodies as well. The recent growth in interest in debris dis...
Europlanet/IDIS: Combining Diverse Planetary Observations and Models
Schmidt, Walter; Capria, Maria Teresa; Chanteur, Gerard
2013-04-01
Planetary research involves a diversity of research fields from astrophysics and plasma physics to atmospheric physics, climatology, spectroscopy and surface imaging. Data from all these disciplines are collected from various space-borne platforms or telescopes, supported by modelling teams and laboratory work. In order to interpret one set of data often supporting data from different disciplines and other missions are needed while the scientist does not always have the detailed expertise to access and utilize these observations. The Integrated and Distributed Information System (IDIS) [1], developed in the framework of the Europlanet-RI project, implements a Virtual Observatory approach ([2] and [3]), where different data sets, stored in archives around the world and in different formats, are accessed, re-formatted and combined to meet the user's requirements without the need of familiarizing oneself with the different technical details. While observational astrophysical data from different observatories could already earlier be accessed via Virtual Observatories, this concept is now extended to diverse planetary data and related model data sets, spectral data bases etc. A dedicated XML-based Europlanet Data Model (EPN-DM) [4] was developed based on data models from the planetary science community and the Virtual Observatory approach. A dedicated editor simplifies the registration of new resources. As the EPN-DM is a super-set of existing data models existing archives as well as new spectroscopic or chemical data bases for the interpretation of atmospheric or surface observations, or even modeling facilities at research institutes in Europe or Russia can be easily integrated and accessed via a Table Access Protocol (EPN-TAP) [5] adapted from the corresponding protocol of the International Virtual Observatory Alliance [6] (IVOA-TAP). EPN-TAP allows to search catalogues, retrieve data and make them available through standard IVOA tools if the access to the archive
Directory of Open Access Journals (Sweden)
Natasa M Milic
Full Text Available Although recent studies report on the benefits of blended learning in improving medical student education, there is still no empirical evidence on the relative effectiveness of blended over traditional learning approaches in medical statistics. We implemented blended along with on-site (i.e. face-to-face learning to further assess the potential value of web-based learning in medical statistics.This was a prospective study conducted with third year medical undergraduate students attending the Faculty of Medicine, University of Belgrade, who passed (440 of 545 the final exam of the obligatory introductory statistics course during 2013-14. Student statistics achievements were stratified based on the two methods of education delivery: blended learning and on-site learning. Blended learning included a combination of face-to-face and distance learning methodologies integrated into a single course.Mean exam scores for the blended learning student group were higher than for the on-site student group for both final statistics score (89.36±6.60 vs. 86.06±8.48; p = 0.001 and knowledge test score (7.88±1.30 vs. 7.51±1.36; p = 0.023 with a medium effect size. There were no differences in sex or study duration between the groups. Current grade point average (GPA was higher in the blended group. In a multivariable regression model, current GPA and knowledge test scores were associated with the final statistics score after adjusting for study duration and learning modality (p<0.001.This study provides empirical evidence to support educator decisions to implement different learning environments for teaching medical statistics to undergraduate medical students. Blended and on-site training formats led to similar knowledge acquisition; however, students with higher GPA preferred the technology assisted learning format. Implementation of blended learning approaches can be considered an attractive, cost-effective, and efficient alternative to traditional
Energy Technology Data Exchange (ETDEWEB)
Gordon, Andrew [Building America Partnership for Improved Residential Construction (BA-PIRC), Cocoa, FL (United States); Lubliner, Michael [Building America Partnership for Improved Residential Construction (BA-PIRC), Cocoa, FL (United States); Howard, Luke [Building America Partnership for Improved Residential Construction (BA-PIRC), Cocoa, FL (United States); Kunkle, Rick [Building America Partnership for Improved Residential Construction (BA-PIRC), Cocoa, FL (United States); Salzberg, Emily [Building America Partnership for Improved Residential Construction (BA-PIRC), Cocoa, FL (United States)
2014-04-01
This project analyzes the cost effectiveness of energy savings measures installed by a large public housing authority in Salishan, a community in Tacoma Washington. Research focuses on the modeled and measured energy usage of the first six phases of construction, and compares the energy usage of those phases to phase 7. Market-ready energy solutions were also evaluated to improve the efficiency of affordable housing for new and existing (built since 2001) affordable housing in the marine climate of Washington State.
Energy Technology Data Exchange (ETDEWEB)
Gordon, A.; Lubliner, M.; Howard, L.; Kunkle, R.; Salzberg, E.
2014-04-01
This project analyzes the cost effectiveness of energy savings measures installed by a large public housing authority in Salishan, a community in Tacoma Washington. Research focuses on the modeled and measured energy usage of the first six phases of construction, and compares the energy usage of those phases to phase 7. Market-ready energy solutions were also evaluated to improve the efficiency of affordable housing for new and existing (built since 2001) affordable housing in the marine climate of Washington State.
Regional gravity field modelling from GOCE observables
Pitoňák, Martin; Šprlák, Michal; Novák, Pavel; Tenzer, Robert
2017-01-01
In this article we discuss a regional recovery of gravity disturbances at the mean geocentric sphere approximating the Earth over the area of Central Europe from satellite gravitational gradients. For this purpose, we derive integral formulas which allow converting the gravity disturbances onto the disturbing gravitational gradients in the local north-oriented frame (LNOF). The derived formulas are free of singularities in case of r ≠ R . We then investigate three numerical approaches for solving their inverses. In the initial approach, the integral formulas are firstly modified for solving individually the near- and distant-zone contributions. While the effect of the near-zone gravitational gradients is solved as an inverse problem, the effect of the distant-zone gravitational gradients is computed by numerical integration from the global gravitational model (GGM) TIM-r4. In the second approach, we further elaborate the first scenario by reducing measured gravitational gradients for gravitational effects of topographic masses. In the third approach, we apply additional modification by reducing gravitational gradients for the reference GGM. In all approaches we determine the gravity disturbances from each of the four accurately measured gravitational gradients separately as well as from their combination. Our regional gravitational field solutions are based on the GOCE EGG_TRF_2 gravitational gradients collected within the period from November 1 2009 until January 11 2010. Obtained results are compared with EGM2008, DIR-r1, TIM-r1 and SPW-r1. The best fit, in terms of RMS (2.9 mGal), is achieved for EGM2008 while using the third approach which combine all four well-measured gravitational gradients. This is explained by the fact that a-priori information about the Earth's gravitational field up to the degree and order 180 was used.
Understanding atmospheric peroxyformic acid chemistry: observation, modeling and implication
Directory of Open Access Journals (Sweden)
H. Liang
2015-01-01
Full Text Available The existence and importance of peroxyformic acid (PFA in the atmosphere has been under controversy. We present here, for the first time, the observation data for PFA from four field measurements carried out in China. These data provided powerful evidence that PFA can stay in the atmosphere, typically in dozens of pptv level. The relationship between PFA and other detected peroxides was examined. The results showed that PFA had a strong positive correlation with its homolog, peroxyacetic acid, due to their similar sources and sinks. Through an evaluation of PFA production and removal rates, we proposed that the reactions between peroxyformyl radical (HC(OO2 and formaldehyde or the hydroperoxyl radical (HO2 were likely to be the major source and degradation into formic acid (FA was likely to be the major sink for PFA. Based on a box model evaluation, we proposed that the HC(OO2 and PFA chemistry was a major source for FA under low NOx conditions. Furthermore, it is found that the impact of the HC(OO2 and PFA chemistry on radical cycling was dependent on the yield of HC(OO2 radical from HC(O + O2 reaction. When this yield exceeded 50%, the HC(OO2 and PFA chemistry should not be neglected for calculating the radical budget. To make clear the exact importance of HC(OO2 and PFA chemistry in the atmosphere, further kinetic, field and modeling studies are required.
The near-global mesospheric potassium layer: Observations and modeling
Dawkins, E. C. M.; Plane, J. M. C.; Chipperfield, M. P.; Feng, W.
2015-08-01
The meteoric metal layers act as unique tracers of chemistry and dynamics in the upper atmosphere. Existing lidar studies from a few locations show that K exhibits a semiannual seasonality (winter and summer maxima), quite unlike the annual seasonality (winter maximum and summer minimum) seen with Na and Fe. This work uses spaceborne observations made with the Optical Spectrograph and InfraRed Imager System instrument on the Odin satellite to retrieve the near-global K layer for the first time. The satellite data (2004 to mid-2013) are used to validate the implementation of a recently proposed potassium chemistry scheme in a whole atmosphere chemistry climate model, which provides a chemical basis for this semiannual seasonal behavior. The satellite and model data show that this semiannual seasonality is near global in extent, with the strongest variation at middle and high latitudes. The column abundance, centroid layer height, and root-mean-square width of the K layer are consistent with the limited available lidar record. The K data set is then used to investigate the impact of polar mesospheric clouds on the metal layers at high latitudes during summer. Finally, the occurrence frequency of sporadic K layers and their possible link to sporadic E layers are examined.
The near‐global mesospheric potassium layer: Observations and modeling
Dawkins, E. C. M.; Chipperfield, M. P.; Feng, W.
2015-01-01
Abstract The meteoric metal layers act as unique tracers of chemistry and dynamics in the upper atmosphere. Existing lidar studies from a few locations show that K exhibits a semiannual seasonality (winter and summer maxima), quite unlike the annual seasonality (winter maximum and summer minimum) seen with Na and Fe. This work uses spaceborne observations made with the Optical Spectrograph and InfraRed Imager System instrument on the Odin satellite to retrieve the near‐global K layer for the first time. The satellite data (2004 to mid‐2013) are used to validate the implementation of a recently proposed potassium chemistry scheme in a whole atmosphere chemistry climate model, which provides a chemical basis for this semiannual seasonal behavior. The satellite and model data show that this semiannual seasonality is near global in extent, with the strongest variation at middle and high latitudes. The column abundance, centroid layer height, and root‐mean‐square width of the K layer are consistent with the limited available lidar record. The K data set is then used to investigate the impact of polar mesospheric clouds on the metal layers at high latitudes during summer. Finally, the occurrence frequency of sporadic K layers and their possible link to sporadic E layers are examined. PMID:27478716
Directory of Open Access Journals (Sweden)
Jose Luiz Boldrini
2003-11-01
Full Text Available We study the existence and regularity of weak solutions of a phase field type model for pure material solidification in presence of natural convection. We assume that the non-stationary solidification process occurs in a two dimensional bounded domain. The governing equations of the model are the phase field equation coupled with a nonlinear heat equation and a modified Navier-Stokes equation. These equations include buoyancy forces modelled by Boussinesq approximation and a Carman-Koseny term to model the flow in mushy regions. Since these modified Navier-Stokes equations only hold in the non-solid regions, which are not known a priori, we have a free boundary-value problem.
Impact of Model and Observation Error on Assimilating Snow Cover Fraction Observations
Arsenault, Kristi R.
Accurately modeling or observing snow cover fraction (SCF) estimates, which represent fractional snow cover area within a gridcell, can help with better understanding earth system dynamics, improving weather and climate prediction, and providing end-use water solutions. Seeking to obtain more accurate snowpack estimates, high resolution snow cover fraction observations are assimilated with different data assimilation (DA) methods within a land surface model (LSM). The LSM simulates snowpack states, snow water equivalent and snow depth, to obtain improved snowpack estimates known as the analysis. Data assimilation experiments are conducted for two mountainous areas where high spatial snow variability occurs, which can impact realistic snowpack representation for different hydrological and meteorological applications. Consequently, the experiments are conducted at higher model resolutions to better capture this variability. This study focuses on four key aspects of how assimilating SCF observations may improve snowpack estimates and impact the LSM overall. These include investigating the role of data assimilation method complexity, evaluating the impact of model and observational errors on snow state analysis estimates, improving the model's SCF representation for assimilation using observation operators, and examining subsequent model state and flux impacts when SCF observations are assimilated. A simpler direct insertion (DI) and a more complex ensemble Kalman filter (EnKF) data assimilation method were applied. The more complex method proved to be superior to the simpler one; however, this method required accounting for more realistic observational and model errors. Also, the EnKF method required an ensemble of model forecasts, in which bias in the ensemble generation was found and removed. Reducing this bias improved the model snowpack estimates. Detection and geolocation errors in the satellite-based snow cover fraction observations also contributed to degrading
Constraining snow model choices in a transitional snow environment with intensive observations
Wayand, N. E.; Massmann, A.; Clark, M. P.; Lundquist, J. D.
2014-12-01
The performance of existing energy balance snow models exhibits a large spread in the simulated snow water equivalent, snow depth, albedo, and surface temperature. Indentifying poor model representations of physical processes within intercomparison studies is difficult due to multiple differences between models as well as non-orthogonal metrics used. Efforts to overcome these obstacles for model development have focused on a modeling framework that allows multiple representations of each physical process within one structure. However, there still exists a need for snow study sites within complex terrain that observe enough model states and fluxes to constrain model choices. In this study we focus on an intensive snow observational site located in the maritime-transitional snow climate of Snoqualmie Pass WA (Figure 1). The transitional zone has been previously identified as a difficult climate to simulate snow processes; therefore, it represents an ideal model-vetting site. From two water years of intensive observational data, we have learned that a more honest comparison with observations requires that the modeled states or fluxes be as similar to the spatial and temporal domain of the instrument, even if it means changing the model to match what is being observed. For example, 24-hour snow board observations do not capture compaction of the underlying snow; therefore, a modeled "snow board" was created that only includes new snow accumulation and new snow compaction. We extend this method of selective model validation to all available Snoqualmie observations to constrain model choices within the Structure for Understanding Multiple Modeling Alternatives (SUMMA) framework. Our end goal is to provide a more rigorous and systematic method for diagnosing problems within snow models at a site given numerous snow observations.
Bundhun, Pravesh Kumar; Li, Nuo; Chen, Meng-Hua
2015-11-01
Several studies have shown the existence of an obesity paradox after Percutaneous Coronary Intervention (PCI). However, other studies have shown its absence. This study sought to perform a systematic review and meta-analysis of studies comparing the mortality risk between high body mass index patients and normal weight patients after PCI.We have searched PubMed, Embase, and Chinese medical journal for randomized controlled trials (RCTs) and observational studies published between the year 2000 and 2015 by typing the keywords "percutaneous coronary intervention" and "obesity paradox." The main outcome was "all-cause mortality". RevMan 5.3 software was used to calculate the risk ratio (RR) with 95% confidence interval (CI) to express the pooled effect on discontinuous variables.Twenty-two studies have been included in this meta-analysis consisting of a total of 242,377 patients with 73,143 normal weight patients, 103,608 overweight, and 65,626 obese patients. Younger age, higher cardiovascular risk factors and the intensive use of medications have mainly been observed among obese patients followed by overweight and normal weight patients respectively. In-hospital, 12 months and ≥ 1 year (long-term) mortality risks were significantly lower in the overweight and obese groups with (RR: 0.67; 95% CI: 0.63-0.72, P obesity paradox" does exist after PCI. The mortality in overweight and obese patients is really significantly lower compared to the normal weight patients. However, the exact reasons for this phenomenon need further exploration and research in the future.
Fireball and cannonball models of gamma ray bursts confront observations
Dar, Arnon
2005-01-01
The two leading contenders for the theory of gamma-ray bursts (GRBs) and their afterglows, the Fireball and Cannonball models, are compared and their predictions are confronted, within space limitations, with key GRB observations, including recent observations with SWIFT
Model-independent inference on compact-binary observations
Mandel, Ilya; Farr, Will M.; Colonna, Andrea; Stevenson, Simon; Tiňo, Peter; Veitch, John
2016-01-01
The recent advanced LIGO detections of gravitational waves from merging binary black holes enhance the prospect of exploring binary evolution via gravitational-wave observations of a population of compact-object binaries. In the face of uncertainty about binary formation models, model-independent inference provides an appealing alternative to comparisons between observed and modelled populations. We describe a procedure for clustering in the multi-dimensional parameter space of observations t...
Directory of Open Access Journals (Sweden)
Marie Savina
Full Text Available We have used an end-to-end ecosystem model to explore responses over 30 years to coastal no-take reserves covering up to 6% of the fifty thousand square kilometres of continental shelf and slope off the coast of New South Wales (Australia. The model is based on the Atlantis framework, which includes a deterministic, spatially resolved three-dimensional biophysical model that tracks nutrient flows through key biological groups, as well as extraction by a range of fisheries. The model results support previous empirical studies in finding clear benefits of reserves to top predators such as sharks and rays throughout the region, while also showing how many of their major prey groups (including commercial species experienced significant declines. It was found that the net impact of marine reserves was dependent on the pre-existing levels of disturbance (i.e. fishing pressure, and to a lesser extent on the size of the marine reserves. The high fishing scenario resulted in a strongly perturbed system, where the introduction of marine reserves had clear and mostly direct effects on biomass and functional biodiversity. However, under the lower fishing pressure scenario, the introduction of marine reserves caused both direct positive effects, mainly on shark groups, and indirect negative effects through trophic cascades. Our study illustrates the need to carefully align the design and implementation of marine reserves with policy and management objectives. Trade-offs may exist not only between fisheries and conservation objectives, but also among conservation objectives.
Savina, Marie; Condie, Scott A; Fulton, Elizabeth A
2013-01-01
We have used an end-to-end ecosystem model to explore responses over 30 years to coastal no-take reserves covering up to 6% of the fifty thousand square kilometres of continental shelf and slope off the coast of New South Wales (Australia). The model is based on the Atlantis framework, which includes a deterministic, spatially resolved three-dimensional biophysical model that tracks nutrient flows through key biological groups, as well as extraction by a range of fisheries. The model results support previous empirical studies in finding clear benefits of reserves to top predators such as sharks and rays throughout the region, while also showing how many of their major prey groups (including commercial species) experienced significant declines. It was found that the net impact of marine reserves was dependent on the pre-existing levels of disturbance (i.e. fishing pressure), and to a lesser extent on the size of the marine reserves. The high fishing scenario resulted in a strongly perturbed system, where the introduction of marine reserves had clear and mostly direct effects on biomass and functional biodiversity. However, under the lower fishing pressure scenario, the introduction of marine reserves caused both direct positive effects, mainly on shark groups, and indirect negative effects through trophic cascades. Our study illustrates the need to carefully align the design and implementation of marine reserves with policy and management objectives. Trade-offs may exist not only between fisheries and conservation objectives, but also among conservation objectives.
Directory of Open Access Journals (Sweden)
Pieter W. G. Bots
2011-06-01
Full Text Available When hydrological models are used in support of water management decisions, stakeholders often contest these models because they perceive certain aspects to be inadequately addressed. A strongly contested model may be abandoned completely, even when stakeholders could potentially agree on the validity of part of the information it can produce. The development of a new model is costly, and the results may be contested again. We consider how existing hydrological models can be used in a policy process so as to benefit from both hydrological knowledge and the perspectives and local knowledge of stakeholders. We define a code of conduct as a set of "rules of the game" that we base on a case study of developing a water management plan for a Natura 2000 site in the Netherlands. We propose general rules for agenda management and information sharing, and more specific rules for model use and option development. These rules structure the interactions among actors, help them to explicitly acknowledge uncertainties, and prevent expertise from being neglected or overlooked. We designed the rules to favor openness, protection of core stakeholder values, the use of relevant substantive knowledge, and the momentum of the process. We expect that these rules, although developed on the basis of a water-management issue, can also be applied to support the use of existing computer models in other policy domains. As rules will shape actions only when they are constantly affirmed by actors, we expect that the rules will become less useful in an "unruly" social environment where stakeholders constantly challenge the proceedings.
Directory of Open Access Journals (Sweden)
D. Bachmann
2004-01-01
Full Text Available Using a new 3-D physical modelling technique we investigated the initiation and evolution of large scale landslides in presence of pre-existing large scale fractures and taking into account the slope material weakening due to the alteration/weathering. The modelling technique is based on the specially developed properly scaled analogue materials, as well as on the original vertical accelerator device enabling increases in the 'gravity acceleration' up to a factor 50. The weathering primarily affects the uppermost layers through the water circulation. We simulated the effect of this process by making models of two parts. The shallower one represents the zone subject to homogeneous weathering and is made of low strength material of compressive strength σl. The deeper (core part of the model is stronger and simulates intact rocks. Deformation of such a model subjected to the gravity force occurred only in its upper (low strength layer. In another set of experiments, low strength (σw narrow planar zones sub-parallel to the slope surface (σwl were introduced into the model's superficial low strength layer to simulate localized highly weathered zones. In this configuration landslides were initiated much easier (at lower 'gravity force', were shallower and had smaller horizontal size largely defined by the weak zone size. Pre-existing fractures were introduced into the model by cutting it along a given plan. They have proved to be of small influence on the slope stability, except when they were associated to highly weathered zones. In this latter case the fractures laterally limited the slides. Deep seated rockslides initiation is thus directly defined by the mechanical structure of the hillslope's uppermost levels and especially by the presence of the weak zones due to the weathering. The large scale fractures play a more passive role and can only influence the shape and the volume of the sliding units.
Energy Technology Data Exchange (ETDEWEB)
Li, Ke; Garrett, John [Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, Wisconsin 53705 (United States); Chen, Guang-Hong [Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, Wisconsin 53705 and Department of Radiology, University of Wisconsin-Madison, 600 Highland Avenue, Madison, Wisconsin 53792 (United States)
2013-11-15
Purpose: With the recently expanding interest and developments in x-ray differential phase contrast CT (DPC-CT), the evaluation of its task-specific detection performance and comparison with the corresponding absorption CT under a given radiation dose constraint become increasingly important. Mathematical model observers are often used to quantify the performance of imaging systems, but their correlations with actual human observers need to be confirmed for each new imaging method. This work is an investigation of the effects of stochastic DPC-CT noise on the correlation of detection performance between model and human observers with signal-known-exactly (SKE) detection tasks.Methods: The detectabilities of different objects (five disks with different diameters and two breast lesion masses) embedded in an experimental DPC-CT noise background were assessed using both model and human observers. The detectability of the disk and lesion signals was then measured using five types of model observers including the prewhitening ideal observer, the nonprewhitening (NPW) observer, the nonprewhitening observer with eye filter and internal noise (NPWEi), the prewhitening observer with eye filter and internal noise (PWEi), and the channelized Hotelling observer (CHO). The same objects were also evaluated by four human observers using the two-alternative forced choice method. The results from the model observer experiment were quantitatively compared to the human observer results to assess the correlation between the two techniques.Results: The contrast-to-detail (CD) curve generated by the human observers for the disk-detection experiments shows that the required contrast to detect a disk is inversely proportional to the square root of the disk size. Based on the CD curves, the ideal and NPW observers tend to systematically overestimate the performance of the human observers. The NPWEi and PWEi observers did not predict human performance well either, as the slopes of their CD
2 types of spicules "observed" in 3D realistic models
Martínez-Sykora, Juan
2010-01-01
Realistic numerical 3D models of the outer solar atmosphere show two different kind of spicule-like phenomena, as also observed on the solar limb. The numerical models are calculated using the 2 types of spicules "observed" in 3D realistic models Oslo Staggered Code (OSC) to solve the full MHD equations with non-grey and NLTE radiative transfer and thermal conduction along the magnetic field lines. The two types of spicules arise as a natural result of the dynamical evolution in the models. We discuss the different properties of these two types of spicules, their differences from observed spicules and what needs to be improved in the models.
DEFF Research Database (Denmark)
Nielsen, Kenneth Hagde Mandrup; Ottesen, Johnny T.; Pociot, Flemming
2014-01-01
Type 1 diabetes is a disease with serious personal and socioeconomic consequences that has attracted the attention of modellers recently. But as models of this disease tend to be complicated, there has been only limited mathematical analysis to date. Here we address this problem by providing...... a bifurcation analysis of a previously published mathematical model for the early stages of type 1 diabetes in diabetes-prone NOD mice, which is based on the data available in the literature. We also show positivity and the existence of a family of attracting trapping regions in the positive 5D cone, converging...... towards a smaller trapping region, which is the intersection over the family. All these trapping regions are compact sets, and thus, practical weak persistence is guaranteed. We conclude our analysis by proposing 4 novel treatment strategies: increasing the phagocytic ability of resting macrophages...
Observation-Based Modeling for Model-Based Testing
Kanstrén, T.; Piel, E.; Gross, H.-G.
2009-01-01
One of the single most important reasons that modeling and modelbased testing are not yet common practice in industry is the perceived difficulty of making the models up to the level of detail and quality required for their automated processing. Models unleash their full potential only through suffi
Observation-Based Modeling for Model-Based Testing
Kanstrén, T.; Piel, E.; Gross, H.-G.
2009-01-01
One of the single most important reasons that modeling and modelbased testing are not yet common practice in industry is the perceived difficulty of making the models up to the level of detail and quality required for their automated processing. Models unleash their full potential only through
Tests of scanning model observers for myocardial SPECT imaging
Gifford, H. C.; Pretorius, P. H.; Brankov, J. G.
2009-02-01
Many researchers have tested and applied human-model observers as part of their evaluations of reconstruction methods for SPECT perfusion imaging. However, these model observers have generally been limited to signal-known- exactly (SKE) detection tasks. Our objective is to formulate and test scanning model observers that emulate humans in detection-localization tasks involving perfusion defects. Herein, we compare several models based on the channelized nonprewhitening (CNPW) observer. Simulated Tc-99m images of the heart with and without defects were created using a mathematical anthropomorphic phantom. Reconstructions were performed with an iterative algorithm and postsmoothed with a 3D Gaussian filter. Human and model-observer studies were conducted to assess the optimal number of iterations and the smoothing level of the filter. The human-observer study was a multiple-alternative forced-choice (MAFC) study with five defects. The CNPW observer performed the MAFC study, but also performed an SKE-but-variable (SKEV) study and a localization ROC (LROC) study. A separate LROC study applied an observer based on models of human search in mammograms. The amount of prior knowledge about the possible defects differed for these four model-observer studies. The trend was towards improved agreement with the human observers as prior knowledge decreased.
Broderick, Avery E; Johnson, Michael D; Rosenfeld, Katherine; Wang, Carlos; Doeleman, Sheperd S; Akiyama, Kazunori; Johannsen, Tim; Roy, Alan L
2016-01-01
An initial three-station version of the Event Horizon Telescope, a millimeter-wavelength very-long baseline interferometer, has observed Sagittarius A* (Sgr A*) repeatedly from 2007 to 2013, resulting in the measurement of a variety of interferometric quantities. Of particular importance, there is now a large set of closure phases, measured over a number of independent observing epochs. We analyze these observations within the context of a realization of semi-analytic radiatively inefficient disk models, implicated by the low luminosity of Sgr A*. We find a broad consistency among the various observing epochs and between different interferometric data types, with the latter providing significant support for this class of models of Sgr A*. The new data significantly tighten existing constraints on the spin magnitude and its orientation within this model context, finding a spin magnitude of $a=0.10^{+0.30+0.56}_{-0.10-0.10}$, an inclination with respect to the line of sight of $\\theta={60^\\circ}^{+5^\\circ+10^\\c...
Neotectonic stresses in Fennoscandia: field observations and modelling
Pascal, Christophe
2013-04-01
The present-day stress state of Fennoscandia is traditionally viewed as the combination of far field sources and residual glacial loading stresses. Investigations were conducted in different regions of Norway with the purpose of detecting and measuring stress-relief features and to derive from them valuable information on the crustal stress state. Stress-relief features are induced by blasting and sudden rock unloading in road construction and quarrying operations and are common in Norway and very likely in other regions of Fennoscandia. Stress relief at the Earth's surface is diagnostic of anomalously high stress levels at shallow depths in the crust and appears to be a characteristic of the formerly glaciated Baltic and Canadian Precambrian shields. The studied stress-relief features are, in general, indicative of NW-SE compression, suggesting ridge-push as the main source of stress. Our derived stress directions are also in excellent agreement with the ones derived from other kinds of stress indicators, including focal mechanisms from deep earthquakes, demonstrating that stress-relief features are valuable for neotectonic research. As a second step we applied numerical modelling techniques to simulate the neotectonic stress field in Fennoscandia with particular emphasis to southern Norway. A numerical method was used to reconstruct the structure of the Fennoscandian lithosphere. The numerical method involves classical steady-state heat equations to derive lithosphere thickness, geotherm and density distribution and, in addition, requires the studied lithosphere to be isostatically compensated at its base. The a priori crustal structure was derived from previous geophysical studies. Undulations of the geoid were used to calibrate the models. Once the density structure of the Fennoscandian lithosphere is reconstructed it is straightforward to quantify its stress state and compare modelling results with existing stress indicators. The modelling suggests that
Existence, multiplicity and stability of endemic states for an age-structured S-I epidemic model.
Breda, D; Visetti, D
2012-01-01
We study an S-I type epidemic model in an age-structured population, with mortality due to the disease. A threshold quantity is found that controls the stability of the disease-free equilibrium and guarantees the existence of an endemic equilibrium. We obtain conditions on the age-dependence of the susceptibility to infection that imply the uniqueness of the endemic equilibrium. An example with two endemic equilibria is shown. Finally, we analyse numerically how the stability of the endemic equilibrium is affected by the extra-mortality and by the possible periodicities induced by the demographic age-structure.
Directory of Open Access Journals (Sweden)
Zhenguo Luo
2013-01-01
Full Text Available Suffiicient and realistic conditions are established in this paper for the existence and global attractivity of a positive periodic solution to the neutral multidelay logarithmic population model with impulse by using the theory of abstract continuous theorem of k-set contractive operator and some inequality techniques. The results improve and generalize the known ones in Li 1999, Lu and Ge 2004, Y. Luo and Z. G. Luo 2010, and Wang et al. 2009. As an application, we also give an example to illustrate the feasibility of our main results.
Institute of Scientific and Technical Information of China (English)
应阳君; 黄祖洽
2001-01-01
Frequency catastrophe is found in a cell Ca2+ nonlinear oscillation model with time delay. The relation of the frequency transition to the time delay is studied by numerical simulations and theoretical analysis. There is a range of parameters in which two kinds of attractors with great frequency differences co-exist in the system. Along with parameter changes, a critical phenomenon occurs and the oscillation frequency changes greatly. This mechanism helps us to deepen the understanding of the complex dynamics of delay systems, and might be of some meaning in cell signalling.
Observing and modelling phytoplankton community structure in the North Sea
Ford, David A.; van der Molen, Johan; Hyder, Kieran; Bacon, John; Barciela, Rosa; Creach, Veronique; McEwan, Robert; Ruardij, Piet; Forster, Rodney
2017-03-01
Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical-biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled
Is the island universe model consistent with observations?
Piao, Yun-Song
2005-01-01
We study the island universe model, in which initially the universe is in a cosmological constant sea, then the local quantum fluctuations violating the null energy condition create the islands of matter, some of which might corresponds to our observable universe. We examine the possibility that the island universe model is regarded as an alternative scenario of the origin of observable universe.
Energy Technology Data Exchange (ETDEWEB)
Ho, C.K.; Webb, S.W.
1996-05-01
A review of mechanisms, models, and data relevant to the postulated phenomenon of enhanced vapor-phase diffusion in porous media is presented. Information is obtained from literature spanning two different disciplines (soil science and engineering) to gain a diverse perspective on this topic. Findings indicate that while enhanced vapor diffusion tends to correct the discrepancies observed between past theory and experiments, no direct evidence exists to support the postulated processes causing enhanced vapor diffusion. Numerical modeling analyses of experiments representative of the two disciplines are presented in this paper to assess the sensitivity of different systems to enhanced vapor diffusion. Pore-scale modeling is also performed to evaluate the relative significance of enhanced vapor diffusion mechanisms when compared to Fickian diffusion. The results demonstrate the need for additional experiments so that more discerning analyses can be performed.
Testing models of triggered star formation: theory and observation
Haworth, Thomas J; Acreman, David M
2012-01-01
One of the main reasons that triggered star formation is contentious is the failure to accurately link the observations with models in a detailed, quantitative, way. It is therefore critical to continuously test and improve the model details and methods with which comparisons to observations are made. We use a Monte Carlo radiation transport and hydrodynamics code TORUS to show that the diffuse radiation field has a significant impact on the outcome of radiatively driven implosion (RDI) models. We also calculate SEDs and synthetic images from the models to test observational diagnostics that are used to determine bright rimmed cloud conditions and search for signs of RDI.
Holonomy observables in Ponzano-Regge type state sum models
Barrett, John W
2011-01-01
We study observables on group elements in the Ponzano-Regge model. We show that these observables have a natural interpretation in terms of Feynman diagrams on a sphere and contrast them to the well studied observables on the spin labels. We elucidate this interpretation by showing how they arise from the no-gravity limit of the Turaev-Viro model and Chern-Simons theory.
Directory of Open Access Journals (Sweden)
Zhenguo Luo
2014-01-01
Full Text Available An impulsive Lotka-Volterra type predator-prey model with prey dispersal in two-patch environments and time delays is investigated, where we assume the model of patches with a barrier only as far as the prey population is concerned, whereas the predator population has no barriers between patches. By applying the continuation theorem of coincidence degree theory and by means of a suitable Lyapunov functional, a set of easily verifiable sufficient conditions are obtained to guarantee the existence, uniqueness, and global stability of positive periodic solutions of the system. Some known results subject to the underlying systems without impulses are improved and generalized. As an application, we also give two examples to illustrate the feasibility of our main results.
Topping, David; Alibay, Irfan; Ruske, Simon; Hindriksen, Vincent; Noisternig, Michael
2016-04-01
To predict the evolving concentration, chemical composition and ability of aerosol particles to act as cloud droplets, we rely on numerical modeling. Mechanistic models attempt to account for the movement of compounds between the gaseous and condensed phases at a molecular level. This 'bottom up' approach is designed to increase our fundamental understanding. However, such models rely on predicting the properties of molecules and subsequent mixtures. For partitioning between the gaseous and condensed phases this includes: saturation vapour pressures; Henrys law coefficients; activity coefficients; diffusion coefficients and reaction rates. Current gas phase chemical mechanisms predict the existence of potentially millions of individual species. Within a dynamic ensemble model, this can often be used as justification for neglecting computationally expensive process descriptions. Indeed, on whether we can quantify the true sensitivity to uncertainties in molecular properties, even at the single aerosol particle level it has been impossible to embed fully coupled representations of process level knowledge with all possible compounds, typically relying on heavily parameterised descriptions. Relying on emerging numerical frameworks, and designed for the changing landscape of high-performance computing (HPC), in this study we show that comprehensive microphysical models from single particle to larger scales can be developed to encompass a complete state-of-the-art knowledge of aerosol chemical and process diversity. We focus specifically on the ability to capture activity coefficients in liquid solutions using the UNIFAC method, profiling traditional coding strategies and those that exploit emerging hardware.
Parshad, Rana
2013-01-01
The purpose of this manuscript is to propose a model for the biological control of invasive species, via introduction of phenotypically modified organisms into a target population. We are inspired by the earlier Trojan Y Chromosome model [J.B. Gutierrez, J.L. Teem, J. Theo. Bio., 241(22), 333-341, 2006]. However, in the current work, we remove the assumption of logisticgrowth rate, and do not consider the addition of sex-reversed supermales. Also the constant birth and death coefficients, considered earlier, are replaced by functionally dependent ones. In this case the nonlinearities present serious difficulties since they change sign, and the components of the solution are not a priori bounded, in some Lp-space for p large, to permit theapplication of the well known regularizing effect principle. Thus functional methods to deducethe global existence in time, for the system in question, are not applicable. Our techniques are based on the Lyapunov functional method. We prove global existence of solutions, as well asexistence of a finite dimensional global attractor, that supports states of extinction. Our analytical finding are in accordance with numerical simulations, which we also present. © 2013 International Press.
Fuzzy model-based observers for fault detection in CSTR.
Ballesteros-Moncada, Hazael; Herrera-López, Enrique J; Anzurez-Marín, Juan
2015-11-01
Under the vast variety of fuzzy model-based observers reported in the literature, what would be the properone to be used for fault detection in a class of chemical reactor? In this study four fuzzy model-based observers for sensor fault detection of a Continuous Stirred Tank Reactor were designed and compared. The designs include (i) a Luenberger fuzzy observer, (ii) a Luenberger fuzzy observer with sliding modes, (iii) a Walcott-Zak fuzzy observer, and (iv) an Utkin fuzzy observer. A negative, an oscillating fault signal, and a bounded random noise signal with a maximum value of ±0.4 were used to evaluate and compare the performance of the fuzzy observers. The Utkin fuzzy observer showed the best performance under the tested conditions.
WDAC Task Team on Observations for Model Evaluation: Facilitating the use of observations for CMIP
Waliser, D. E.; Gleckler, P. J.; Ferraro, R.; Eyring, V.; Bosilovich, M. G.; Schulz, J.; Thepaut, J. N.; Taylor, K. E.; Chepfer, H.; Bony, S.; Lee, T. J.; Joseph, R.; Mathieu, P. P.; Saunders, R.
2015-12-01
Observations are essential for the development and evaluation of climate models. Satellite and in-situ measurements as well as reanalysis products provide crucial resources for these purposes. Over the last two decades, the climate modeling community has become adept at developing model intercomparison projects (MIPs) that provide the basis for more systematic comparisons of climate models under common experimental conditions. A prominent example among these is the coupled MIP (CMIP). Due to its growing importance in providing input to the IPCC, the framework for CMIP, now planning CMIP6, has expanded to include a very comprehensive and precise set of experimental protocols, with an advanced data archive and dissemination system. While the number, types and sophistication of observations over the same time period have kept pace, their systematic application to the evaluation of climate models has yet to be fully exploited due to a lack of coordinated protocols for identifying, archiving, documenting and applying observational resources. This presentation will discuss activities and plans of the World Climate Research Program (WCRP) Data Advisory Council's (WDAC) Task Team on Observations for Model Evaluation for facilitating the use of observations for model evaluation. The presentation will include an update on the status of the obs4MIPs and ana4MIPs projects, whose purpose is to provide a limited collection of well-established and documented observation and reanalysis datasets for comparison with Earth system models, targeting CMIP in particular. The presentation will also describe the role these activities and datasets play in the development of a set of community standard observation-based climate model performance metrics by the Working Group on Numerical Experimentation (WGNE)'s Performance Metrics Panel, as well as which CMIP6 experiments these activities are targeting, and where additional community input and contributions to these activities are needed.
Directory of Open Access Journals (Sweden)
Svetlana Strbac Savic
2015-01-01
Full Text Available Forecasting the operational efficiency of an existing underground mine plays an important role in strategic planning of production. Degree of Operating Leverage (DOL is used to express the operational efficiency of production. The forecasting model should be able to involve common time horizon, taking the characteristics of the input variables that directly affect the value of DOL. Changes in the magnitude of any input variable change the value of DOL. To establish the relationship describing the way of changing we applied multivariable grey modeling. Established time sequence multivariable response formula is also used to forecast the future values of operating leverage. Operational efficiency of production is often associated with diverse sources of uncertainties. Incorporation of these uncertainties into multivariable forecasting model enables mining company to survive in today’s competitive environment. Simulation of mean reversion process and geometric Brownian motion is used to describe the stochastic diffusion nature of metal price, as a key element of revenues, and production costs, respectively. By simulating a forecasting model, we imitate its action in order to measure its response to different inputs. The final result of simulation process is the expected value of DOL for every year of defined time horizon.
Predicting the future completing models of observed complex systems
Abarbanel, Henry
2013-01-01
Predicting the Future: Completing Models of Observed Complex Systems provides a general framework for the discussion of model building and validation across a broad spectrum of disciplines. This is accomplished through the development of an exact path integral for use in transferring information from observations to a model of the observed system. Through many illustrative examples drawn from models in neuroscience, fluid dynamics, geosciences, and nonlinear electrical circuits, the concepts are exemplified in detail. Practical numerical methods for approximate evaluations of the path integral are explored, and their use in designing experiments and determining a model's consistency with observations is investigated. Using highly instructive examples, the problems of data assimilation and the means to treat them are clearly illustrated. This book will be useful for students and practitioners of physics, neuroscience, regulatory networks, meteorology and climate science, network dynamics, fluid dynamics, and o...
Correcting biased observation model error in data assimilation
Harlim, John
2016-01-01
While the formulation of most data assimilation schemes assumes an unbiased observation model error, in real applications, model error with nontrivial biases is unavoidable. A practical example is the error in the radiative transfer model (which is used to assimilate satellite measurements) in the presence of clouds. As a consequence, many (in fact 99\\%) of the cloudy observed measurements are not being used although they may contain useful information. This paper presents a novel nonparametric Bayesian scheme which is able to learn the observation model error distribution and correct the bias in incoming observations. This scheme can be used in tandem with any data assimilation forecasting system. The proposed model error estimator uses nonparametric likelihood functions constructed with data-driven basis functions based on the theory of kernel embeddings of conditional distributions developed in the machine learning community. Numerically, we show positive results with two examples. The first example is des...
Prosser-Loose, Erin J; Smith, Shari E; Paterson, Phyllis G
2011-05-01
Protein-energy malnutrition (PEM) affects ~16% of patients at admission for stroke. We previously modeled this in a gerbil global cerebral ischemia model and found that PEM impairs functional outcome and influences mechanisms of ischemic brain injury and recovery. Since this model is no longer reliable, we investigated the utility of the rat 2-vessel occlusion (2-VO) with hypotension model of global ischemia for further study of this clinical problem. Male, Sprague-Dawley rats were exposed to either control diet (18% protein) or PEM induced by feeding a low protein diet (2% protein) for 7d prior to either global ischemia or sham surgery. PEM did not significantly alter the hippocampal CA1 neuron death (p = 0.195 by 2-factor ANOVA) or the increase in dendritic injury caused by exposure to global ischemia. Unexpectedly, however, a strong trend was evident for PEM to decrease the consistency of hippocampal damage, as shown by an increased incidence of unilateral or no hippocampal damage (p=0.069 by chi-square analysis). Although PEM caused significant changes to baseline arterial blood pH, pO(2), pCO(2), and fasting glucose (p0.269). Intra-ischemic tympanic temperature and blood pressure were strictly and equally controlled between ischemic groups. We conclude that co-existing PEM confounded the consistency of hippocampal injury in the 2-VO model. Although the mechanisms responsible were not identified, this model of brain ischemia should not be used for studying this co-morbidity factor. © 2011 Bentham Science Publishers Ltd.
What sea-ice biogeochemical modellers need from observers
Directory of Open Access Journals (Sweden)
Nadja Steiner
2016-02-01
Full Text Available Abstract Numerical models can be a powerful tool helping to understand the role biogeochemical processes play in local and global systems and how this role may be altered in a changing climate. With respect to sea-ice biogeochemical models, our knowledge is severely limited by our poor confidence in numerical model parameterisations representing those processes. Improving model parameterisations requires communication between observers and modellers to guide model development and improve the acquisition and presentation of observations. In addition to more observations, modellers need conceptual and quantitative descriptions of the processes controlling, for example: primary production and diversity of algal functional types in sea ice, ice algal growth, release from sea ice, heterotrophic remineralisation, transfer and emission of gases (e.g., DMS, CH4, BrO, incorporation of seawater components in growing sea ice (including Fe, organic and inorganic carbon, and major salts and subsequent release; CO2 dynamics (including CaCO3 precipitation, flushing and supply of nutrients to sea-ice ecosystems; and radiative transfer through sea ice. These issues can be addressed by focused observations, as well as controlled laboratory and field experiments that target specific processes. The guidelines provided here should help modellers and observers improve the integration of measurements and modelling efforts and advance toward the common goal of understanding biogeochemical processes in sea ice and their current and future impacts on environmental systems.
Thermal Infrared Observations and Thermophysical Modeling of Phobos
Smith, Nathan Michael; Edwards, Christopher Scott; Mommert, Michael; Trilling, David E.; Glotch, Timothy
2016-10-01
Mars-observing spacecraft have the opportunity to study Phobos from Mars orbit, and have produced a sizeable record of observations using the same instruments that study the surface of the planet below. However, these observations are generally infrequent, acquired only rarely over each mission.Using observations gathered by Mars Global Surveyor's (MGS) Thermal Emission Spectrometer (TES), we can investigate the fine layer of regolith that blankets Phobos' surface, and characterize its thermal properties. The mapping of TES observations to footprints on the Phobos surface has not previously been undertaken, and must consider the orientation and position of both MGS and Phobos, and TES's pointing mirror angle. Approximately 300 fully resolved observations are available covering a significant subset of Phobos' surface at a variety of scales.The properties of the surface regolith, such as grain size, density, and conductivity, determine how heat is absorbed, transferred, and reradiated to space. Thermophysical modeling allows us to simulate these processes and predict, for a given set of assumed parameters, how the observed thermal infrared spectra will appear. By comparing models to observations, we can constrain the properties of the regolith, and see how these properties vary with depth, as well as regionally across the Phobos surface. These constraints are key to understanding how Phobos formed and evolved over time, which in turn will help inform the environment and processes that shaped the solar system as a whole.We have developed a thermophysical model of Phobos adapted from a model used for unresolved observations of asteroids. The model has been modified to integrate thermal infrared flux across each observed portion of Phobos. It will include the effects of surface roughness, temperature-dependent conductivity, as well as radiation scattered, reflected, and thermally emitted from the Martian surface. Combining this model with the newly-mapped TES
Valentine, D. W., Jr.; Aufdenkampe, A. K.; Horsburgh, J. S.; Hsu, L.; Lehnert, K. A.; Mayorga, E.; Song, L.; Zaslavsky, I.; Whitenack, T.
2014-12-01
The Observations Data Model v1 (ODMv1) schema has been utilized of the basis hydrologic cyberinfrastructures include the CUAHSI HIS. The first version of ODM focused on timeseries, and ultimately led the development of OGC "WaterML2 Part 1: Timeseries", which is being proposed to be developed into OGC TimeseriesML.Our team has developed an ODMv2 model to address ODMv1 shortcomings, and to encompass a wider community of spatially discrete, feature-based earth observations. The development process included collecting requirements from several existing Earth Observations data systems: HIS,CZOData, IEDA and EarthChem system, and IOOS. We developed ODM2 as a set of core entities with additional extensioncomponents that can be utilized. These extensions include for shared functionality (e.g. data quality, provenance), as well as specific use cases (e.g. laboratory analysis, equipment). Initially, we closely followed the Observations and Measures (ISO19156) concept model. After prototyping and reviewing the requirements, we extended the ODMv2 conceptual model to include entities to document ancillary acts that do not always produce a result. Differing from O&M where acts are expected to produce a result. ODMv2 includes the core concept of an "Action" which encapsulates activities or actions associated that are performed in the process of making an observation, but may not produce a result. Actions, such as a sample analysis, that observe a property and produce a result are equivalent to O&M observation. But in many use cases, many actions have no resulting observation. Examples of such actions are a site visit or sample preparation (splitting of a sample). These actions are part of a chain of actions, iwhich produce the final observation. Overall the ODMv2 generally follows the O&M conceptual model. The nearly final ODMv2 includes a core and extensions. The core entities include actions, feature actions (observations), datasets (groupings), methods (procedures), sampling
Observational semantics of the Prolog Resolution Box Model
Deransart, Pierre; Ferrand, Gérard
2007-01-01
This paper specifies an observational semantics and gives an original presentation of the Byrd box model. The approach accounts for the semantics of Prolog tracers independently of a particular Prolog implementation. Prolog traces are, in general, considered as rather obscure and difficult to use. The proposed formal presentation of its trace constitutes a simple and pedagogical approach for teaching Prolog or for implementing Prolog tracers. It is a form of declarative specification for the tracers. The trace model introduced here is only one example to illustrate general problems relating to tracers and observing processes. Observing processes know, from observed processes, only their traces. The issue is then to be able to reconstitute, by the sole analysis of the trace, part of the behaviour of the observed process, and if possible, without any loss of information. As a matter of fact, our approach highlights qualities of the Prolog resolution box model which made its success, but also its insufficiencies...
Akers, David
1990-10-01
A status report is presented on the existence of quarks carrying the Dirac unit of magnetic charge g = (137/2) e. The Paschen-Back effect in dyonium is discussed. From the dyonium model, Akers predicted the existence of a new η meson at 1814 MeV with I G(JPC) = 0+(0-+). Experimental evidence now confirms the existence of the meson resonance.
Directory of Open Access Journals (Sweden)
Yan Cai
Full Text Available We propose a coupled mathematical modelling system to investigate glioblastoma growth in response to dynamic changes in chemical and haemodynamic microenvironments caused by pre-existing vessel co-option, remodelling, collapse and angiogenesis. A typical tree-like architecture network with different orders for vessel diameter is designed to model pre-existing vasculature in host tissue. The chemical substances including oxygen, vascular endothelial growth factor, extra-cellular matrix and matrix degradation enzymes are calculated based on the haemodynamic environment which is obtained by coupled modelling of intravascular blood flow with interstitial fluid flow. The haemodynamic changes, including vessel diameter and permeability, are introduced to reflect a series of pathological characteristics of abnormal tumour vessels including vessel dilation, leakage, angiogenesis, regression and collapse. Migrating cells are included as a new phenotype to describe the migration behaviour of malignant tumour cells. The simulation focuses on the avascular phase of tumour development and stops at an early phase of angiogenesis. The model is able to demonstrate the main features of glioblastoma growth in this phase such as the formation of pseudopalisades, cell migration along the host vessels, the pre-existing vasculature co-option, angiogenesis and remodelling. The model also enables us to examine the influence of initial conditions and local environment on the early phase of glioblastoma growth.
Cai, Yan; Wu, Jie; Li, Zhiyong; Long, Quan
2016-01-01
We propose a coupled mathematical modelling system to investigate glioblastoma growth in response to dynamic changes in chemical and haemodynamic microenvironments caused by pre-existing vessel co-option, remodelling, collapse and angiogenesis. A typical tree-like architecture network with different orders for vessel diameter is designed to model pre-existing vasculature in host tissue. The chemical substances including oxygen, vascular endothelial growth factor, extra-cellular matrix and matrix degradation enzymes are calculated based on the haemodynamic environment which is obtained by coupled modelling of intravascular blood flow with interstitial fluid flow. The haemodynamic changes, including vessel diameter and permeability, are introduced to reflect a series of pathological characteristics of abnormal tumour vessels including vessel dilation, leakage, angiogenesis, regression and collapse. Migrating cells are included as a new phenotype to describe the migration behaviour of malignant tumour cells. The simulation focuses on the avascular phase of tumour development and stops at an early phase of angiogenesis. The model is able to demonstrate the main features of glioblastoma growth in this phase such as the formation of pseudopalisades, cell migration along the host vessels, the pre-existing vasculature co-option, angiogenesis and remodelling. The model also enables us to examine the influence of initial conditions and local environment on the early phase of glioblastoma growth.
Technical Note: Calibration and validation of geophysical observation models
Salama, M.S.; van der Velde, R.; van der Woerd, H.J.; Kromkamp, J.C.; Philippart, C.J.M.; Joseph, A.T.; O'Neill, P.E.; Lang, R.H.; Gish, T.; Werdell, P.J.; Su, Z.
2012-01-01
We present a method to calibrate and validate observational models that interrelate remotely sensed energy fluxes to geophysical variables of land and water surfaces. Coincident sets of remote sensing observation of visible and microwave radiations and geophysical data are assembled and subdivided i
Time-symmetric universe model and its observational implication
Energy Technology Data Exchange (ETDEWEB)
Futamase, T.; Matsuda, T.
1987-08-01
A time-symmetric closed-universe model is discussed in terms of the radiation arrow of time. The time symmetry requires the occurrence of advanced waves in the recontracting phase of the Universe. We consider the observational consequences of such advanced waves, and it is shown that a test observer in the expanding phase can observe a time-reversed image of a source of radiation in the future recontracting phase.
Use of an Existing Airborne Radon Data Base in the Verification of the NASA/AEAP Core Model
Kritz, Mark A.
1998-01-01
The primary objective of this project was to apply the tropospheric atmospheric radon (Rn222) measurements to the development and verification of the global 3-D atmospheric chemical transport model under development by NASA's Atmospheric Effects of Aviation Project (AEAP). The AEAP project had two principal components: (1) a modeling effort, whose goal was to create, test and apply an elaborate three-dimensional atmospheric chemical transport model (the NASA/AEAP Core model to an evaluation of the possible short and long-term effects of aircraft emissions on atmospheric chemistry and climate--and (2) a measurement effort, whose goal was to obtain a focused set of atmospheric measurements that would provide some of the observational data used in the modeling effort. My activity in this project was confined to the first of these components. Both atmospheric transport and atmospheric chemical reactions (as well the input and removal of chemical species) are accounted for in the NASA/AEAP Core model. Thus, for example, in assessing the effect of aircraft effluents on the chemistry of a given region of the upper troposphere, the model must keep track not only of the chemical reactions of the effluent species emitted by aircraft flying in this region, but also of the transport into the region of these (and other) species from other, remote sources--for example, via the vertical convection of boundary layer air to the upper troposphere. Radon, because of its known surface source and known radioactive half-life, and freedom from chemical production or loss, and from removal from the atmosphere by physical scavenging, is a recognized and valuable tool for testing the transport components of global transport and circulation models.
Bonini, Lorenzo; Basili, Roberto; Toscani, Giovanni; Burrato, Pierfrancesco; Seno, Silvio; Valensise, Gianluca
2016-08-01
We use wet-clay analog models to investigate how pre-existing discontinuities (i.e. structures inherited from previous tectonic phases) affect the evolution of a normal fault at the Earth's surface. To this end we first perform a series of three reference experiments driven by a 45° dipping master fault unaffected by pre-existing discontinuities to generate a mechanically isotropic learning set of models. We then replicate the experiment six times introducing a 60°-dipping precut in the clay cake, each time with a different attitude and orientation with respect to an initially-blind, 45°-dipping, master normal fault. In all experiments the precut intersects the vertical projection of the master fault halfway between the center and the right-hand lateral tip. All other conditions are identical for all seven models. By comparing the results obtained from the mechanically isotropic experiments with results from experiments with precuts we find that the surface evolution of the normal fault varies depending on the precut orientation. In most cases the parameters of newly-forming faults are strongly influenced. The largest influence is exerted by synthetic and antithetic discontinuities trending respectively at 30° and 45° from the strike of the master fault, whereas a synthetic discontinuity at 60° and an antithetic discontinuity at 30° show moderate influence. Little influence is exerted by a synthetic discontinuity at 45° and an antithetic discontinuity at 60° from the strike of the master fault. We provide a ranking chart to assess fault-to-discontinuity interactions with respect to essential surface fault descriptors, such as segmentation, vertical-displacement profile, maximum displacement, and length, often used as proxies to infer fault properties at depth. Considering a single descriptor, the amount of deviation induced by different precuts varies from case to case in a rather unpredictable fashion. Multiple observables should be taken into
Broderick, Avery E.; Fish, Vincent L.; Johnson, Michael D.; Rosenfeld, Katherine; Wang, Carlos; Doeleman, Sheperd S.; Akiyama, Kazunori; Johannsen, Tim; Roy, Alan L.
2016-04-01
An initial three-station version of the Event Horizon Telescope, a millimeter-wavelength very-long baseline interferometer, has observed Sagittarius A* (Sgr A*) repeatedly from 2007 to 2013, resulting in the measurement of a variety of interferometric quantities. Of particular importance is that there is now a large set of closure phases measured over a number of independent observing epochs. We analyze these observations within the context of a realization of semi-analytic radiatively inefficient disk models, implicated by the low luminosity of Sgr A*. We find a broad consistency among the various observing epochs and between different interferometric data types, with the latter providing significant support for this class of model of Sgr A*. The new data significantly tighten existing constraints on the spin magnitude and its orientation within this model context, finding a spin magnitude of a={0.10}-0.10-0.10+0.30+0.56, an inclination with respect to the line of sight of θ ={60^\\circ }-{8^\\circ -{13}^\\circ }+{5^\\circ +{10}^\\circ }, and a position angle of ξ ={156^\\circ }-{17^\\circ -{27}^\\circ }+{10^\\circ +{14}^\\circ } east of north. These are in good agreement with previous analyses. Notably, the previous 180° degeneracy in the position angle has now been conclusively broken by the inclusion of the closure-phase measurements. A reflection degeneracy in the inclination remains, permitting two localizations of the spin vector orientation, one of which is in agreement with the orbital angular momentum of the infrared gas cloud G2 and the clockwise disk of young stars. This may support a relationship between Sgr A*'s accretion flow and these larger-scale features.
The detection of observations possibly influential for model selection
Ph.H.B.F. Franses (Philip Hans)
1991-01-01
textabstractModel selection can involve several variables and selection criteria. A simple method to detect observations possibly influential for model selection is proposed. The potentials of this method are illustrated with three examples, each of which is taken from related studies.
Bedrossian, Jacob
2011-01-01
The $L^1$-critical parabolic-elliptic Patlak-Keller-Segel system is a classical model of chemotactic aggregation in micro-organisms well-known to have critical mass phenomena. In this paper we study this critical mass phenomenon in the context of Patlak-Keller-Segel models with spatially varying diffusivity and decay rate of the chemo-attractant. The primary tool for the proof of global existence below the critical mass is the use of pseudo-differential operators to precisely evaluate the leading order quadratic portion of the potential energy (interaction energy). Under the assumption of radial symmetry, blow-up is proved above critical mass using a maximum-principle type argument based on comparing the mass distribution of solutions to a barrier consisting of the unique stationary solutions of the scale-invariant PKS. Although effective where standard Virial methods do not apply, this method seems to be dependent on the assumption of radial symmetry. For technical reasons we work in dimensions three and hig...
Directory of Open Access Journals (Sweden)
Veronika I Zarnitsyna
2016-06-01
Full Text Available The development of next-generation influenza vaccines that elicit strain-transcendent immunity against both seasonal and pandemic viruses is a key public health goal. Targeting the evolutionarily conserved epitopes on the stem of influenza's major surface molecule, hemagglutinin, is an appealing prospect, and novel vaccine formulations show promising results in animal model systems. However, studies in humans indicate that natural infection and vaccination result in limited boosting of antibodies to the stem of HA, and the level of stem-specific antibody elicited is insufficient to provide broad strain-transcendent immunity. Here, we use mathematical models of the humoral immune response to explore how pre-existing immunity affects the ability of vaccines to boost antibodies to the head and stem of HA in humans, and, in particular, how it leads to the apparent lack of boosting of broadly cross-reactive antibodies to the stem epitopes. We consider hypotheses where binding of antibody to an epitope: (i results in more rapid clearance of the antigen; (ii leads to the formation of antigen-antibody complexes which inhibit B cell activation through Fcγ receptor-mediated mechanism; and (iii masks the epitope and prevents the stimulation and proliferation of specific B cells. We find that only epitope masking but not the former two mechanisms to be key in recapitulating patterns in data. We discuss the ramifications of our findings for the development of vaccines against both seasonal and pandemic influenza.
Model-independent inference on compact-binary observations
Mandel, Ilya; Farr, Will M.; Colonna, Andrea; Stevenson, Simon; Tiňo, Peter; Veitch, John
2017-03-01
The recent advanced LIGO detections of gravitational waves from merging binary black holes enhance the prospect of exploring binary evolution via gravitational-wave observations of a population of compact-object binaries. In the face of uncertainty about binary formation models, model-independent inference provides an appealing alternative to comparisons between observed and modelled populations. We describe a procedure for clustering in the multidimensional parameter space of observations that are subject to significant measurement errors. We apply this procedure to a mock data set of population-synthesis predictions for the masses of merging compact binaries convolved with realistic measurement uncertainties, and demonstrate that we can accurately distinguish subpopulations of binary neutron stars, binary black holes, and mixed neutron star-black hole binaries with tens of observations.
Numedahl, Paul Joseph
The purpose of this study was to gain an understanding of the effects an interactive-constructive teaching and learning approach, the use of children's literature in science teaching and parental involvement in elementary school science had on student achievement in and attitudes toward science. The study was done in the context of Science PALS, a professional development program for inservice teachers. An existing model for interactive-constructive elementary science was modified to include five model variables; student achievement, student attitudes, teacher perceptions, teacher performance, and student perceptions. Data were collected from a sample of 12 teachers and 260 third and fourth grade students. Data analysis included two components, (1) the examination of relationships between teacher performance, teacher perceptions, student achievement and attitudes, and (2) the verification of a model using path analysis. Results showed a significant correlation between teacher perceptions and student attitude. However, only one model path was significant; thus, the model could not be verified. Further examination of the significant model path was completed. Study findings included: (1) Constructivist notions of teaching and learning may cause changes in the traditional role relationship between teachers and students leading to negative student attitudes. (2) Children who perceive parental interest toward science education are likely to have a positive attitude toward science learning, increased self-confidence in science and possess accurate ideas concerning the nature of science. (3) Students who perceive science instruction as relevant are likely to possess a positive attitude toward science learning, increased self-confidence in science, and possess accurate ideas concerning the nature of science. (4) Students who perceive their classroom as aligning with constructivist principles are likely to possess a positive attitude toward science, an increased self
Hints on halo evolution in SFDM models with galaxy observations
Gonzalez-Morales, Alma X; Urena-Lopez, L Arturo; Valenzuela, Octavio
2012-01-01
A massive, self-interacting scalar field has been considered as a possible candidate for the dark matter in the universe. We present an observational constraint to the model arising from strong lensing observations in galaxies. The result points to a discrepancy in the properties of scalar field dark matter halos for dwarf and lens galaxies, mainly because halo parameters are directly related to physical quantities in the model. This is an important indication that it becomes necessary to have a better understanding of halo evolution in scalar field dark matter models, where the presence of baryons can play an important role.
Observational Constraints on a Variable Dark Energy Model
Movahed, M S; Movahed, Mohammad Sadegh; Rahvar, Sohrab
2006-01-01
We present cosmological tests for a phenomenological parametrization of quintessence model with time-varying equation of state on low, intermediate and high redshift observations \\cite{w04}. We study the sensitivity of the comoving distance and volume element with the Alcock-Paczynski test to the time varying model of dark energy. At the intermediate redshifts, Gold supernova Type Ia data is used to fit the quintessence model to the observed distance modulus. The value of the observed acoustic angular scale by WMAP experiment also is compared with the model. The combined result of CMB and SNIa data confines $w=p/\\rho$ to be more than -1.3 which can violate the dominant energy condition.
Modelling of an explosive event observed by SUMER & TRACE
Price, Daniel; Taroyan, Youra; Ishak, Bebe
2016-07-01
To fully understand coronal heating, we must first understand the different solar processes that move energy throughout the solar atmosphere. TRACE observations have revealed a short cold loop evolving over a small timescale, seemingly with multiple explosive events occurring along its length. An adaptive hydrodynamic radiation code was used to simulate the loop under non-equilibrium ionization. Footpoint heating and cold plasma injection were considered as possible scenarios to reproduce the observations. The simulation results were converted into synthetic observations through forward modelling, for comparison to SOHO/SUMER spectral observations of the loop.
How useful are stream level observations for model calibration?
Seibert, Jan; Vis, Marc; Pool, Sandra
2014-05-01
Streamflow estimation in ungauged basins is especially challenging in data-scarce regions and it might be reasonable to take at least a few measurements. Recent studies demonstrated that few streamflow measurements, representing data that could be measured with limited efforts in an ungauged basin, might be needed to constrain runoff models for simulations in ungauged basins. While in these previous studies we assumed that few streamflow measurements were taken during different points in time over one year, obviously it would be reasonable to (also) measure stream levels. Several approaches could be used in practice for such stream level observations: water level loggers have become less expensive and easier to install and can be used to obtain continuous stream level time series; stream levels will in the near future be increasingly available from satellite remote sensing resulting in evenly space time series; community-based approaches (e.g., crowdhydrology.org), finally, can offer level observations at irregular time intervals. Here we present a study where a catchment runoff model (the HBV model) was calibrated for gauged basins in Switzerland assuming that only a subset of the data was available. We pretended that only stream level observations at different time intervals, representing the temporal resolution of the different observation approaches mentioned before, and a small number of streamflow observations were available. The model, which was calibrated based on these data subsets, was then evaluated on the full observed streamflow record. Our results indicate that streamlevel data alone already can provide surprisingly good model simulation results, which can be further improved by the combination with one streamflow observation. The surprisingly good results with only streamlevel time series can be explained by the relatively high precipitation in the studied catchments. Constructing a hypothetical catchment with reduced precipitation resulted in poorer
Used of observed snow in the Snomod model
Sorteberg, H. K.
2009-04-01
For the hydroelectric industry in Norway, it is important to know exactly what resources are available at all times. The correct volume of snow reserves and the accurate forecasting of the spring flood volume can provide the best basis for maximising production values. The forward market can fluctuate considerably, and it is therefore important to know what is available at the right time. For many years, the Snomod model has been used to calculate snow reserves and to forecast the spring flood volume. Snomod is based on a regression equation between the annual observations of inflow and one or more precipitation series. Manual snow measurements are used in both Snomod and the HBV model and other models to estimate the correct snow reserves. In operational use, Snomod is updated manually with the snow estimate that is considered to be correct. Following the winter of 2007-2008, analyses were carried out to determine how accurate the forecasting was. The analyses were based on comparing the spring flood volume forecast with the observed spring flood volume using the ‘observed precipitation' precipitation scenario. Such analyses can tell us something about the quality of the model results for this winter. Analyses have been carried out for 18 models using Snomod. When the results from the analyses are compared with the spring floods, the spring flood volume has been forecast accurately for most of the models with observed precipitation when observed snow has been used in the forecasting process. The results indicate that nine of the models are very good, five are good and two are reasonable. Only one model produced a poor forecast of the spring flood volume. If a corresponding analysis without correction for observed snow is carried out, and the observed spring flood is compared with the forecast spring flood, the results are not as good. This may stem from the fact that during the spring of 2008 there were higher levels of evaporation during the melting season than
The role of observational uncertainties in testing model hypotheses
Westerberg, I. K.; Birkel, C.
2012-12-01
Knowledge about hydrological processes and the spatial and temporal distribution of water resources is needed as a basis for managing water for hydropower, agriculture and flood-protection. Conceptual hydrological models may be used to infer knowledge on catchment functioning but are affected by uncertainties in the model representation of reality as well as in the observational data used to drive the model and to evaluate model performance. Therefore, meaningful hypothesis testing of the hydrological functioning of a catchment requires such uncertainties to be carefully estimated and accounted for in model calibration and evaluation. The aim of this study was to investigate the role of observational uncertainties in hypothesis testing, in particular whether it was possible to detect model-structural representations that were wrong in an important way given the uncertainties in the observational data. We studied the relatively data-scarce tropical Sarapiqui catchment in Costa Rica, Central America, where water resources play a vital part for hydropower production and livelihood. We tested several model structures of varying complexity as hypotheses about catchment functioning, but also hypotheses about the nature of the modelling errors. The tests were made within a learning framework for uncertainty estimation which enabled insights into data uncertainties, suitable model-structural representations and appropriate likelihoods. The observational uncertainty in discharge data was estimated from a rating-curve analysis and precipitation measurement errors through scenarios relating the error to, for example, canopy interception, wind-driven rain and the elevation gradient. The hypotheses were evaluated in a posterior analysis of the simulations where the performance of each simulation was analysed relative to the observational uncertainties for the entire hydrograph as well as for different aspects of the hydrograph (e.g. peak flows, recession periods, and base flow
Testing ocean tide models using GGP superconducting gravimeter observations
Baker, T.; Bos, M.
2003-04-01
Observations from the global network of superconducting gravimeters in the Global Geodynamics Project (GGP) are used to test 10 ocean tide models (SCHW; FES94.1, 95.2, 98, 99; CSR3.0, 4.0; TPXO.5; GOT99.2b; and NAO.99b). In addition, observations are used from selected sites with LaCoste and Romberg gravimeters with electrostatic feedback, where special attention has been given to achieving a calibration accuracy of 0.1%. In Europe, there are several superconducting gravimeter stations in a relatively small area and this can be used to advantage in testing the ocean (and body) tide models and in identifying sites with anomalous observations. At some of the superconducting gravimeter sites there are anomalies in the in-phase components of the main tidal harmonics, which are due to calibration errors of up to 0.3%. It is shown that the recent ocean tide models are in better agreement with the tidal gravity observations than were the earlier models of Schwiderski and FES94.1. However, no single ocean tide model gives completely satisfactory results in all areas of the world. For example, for M2 the TPXO.5 and NAO99b models give anomalous results in Europe, whereas the FES95.2, FES98 and FES99 models give anomalous results in China and Japan. It is shown that the observations from this improved set of tidal gravity stations will provide an important test of the new ocean tide models that will be developed in the next few years. For further details see Baker, T.F. and Bos, M.S. (2003). "Validating Earth and ocean tide models using tidal gravity measurements", Geophysical Journal International, 152.
Total cloud cover from satellite observations and climate models
Directory of Open Access Journals (Sweden)
P. Probst
2010-09-01
Full Text Available Global and zonal monthly means of cloud cover fraction for total cloudiness (CF from the ISCCP D2 dataset are compared to same quantity produced by the 20th century simulations of 21 climate models from the World Climate Research Programme's (WCRP's Coupled Model Intercomparison Project phase 3 (CMIP3 multi-model dataset archived by the Program for Climate Model Diagnosis and Intercomparison (PCMDI. The comparison spans the time frame from January 1984 to December 1999 and the global and zonal average of CF are studied. The restriction to total cloudiness depends on the output of some models that does not include the 3D cloud structure. It is shown that the global mean of CF for the PCMDI/CMIP3 models, averaged over the whole period, exhibits a considerable variance and generally underestimates the ISCCP value. Very large discrepancies among models, and between models and observations, are found in the polar areas, where both models and satellite observations are less reliable, and especially near Antarctica. For this reason the zonal analysis is focused over the 60° S–60° N latitudinal belt, which includes the tropical area and mid latitudes. The two hemispheres are analyzed separately to show the variation of the amplitude of the seasonal cycle. Most models overestimate the yearly averaged values of CF over all of the analysed areas, while differences emerge in their ability to capture the amplitude of the seasonal cycle. The models represent, in a qualitatively correct way, the magnitude and the weak sign of the seasonal cycle over the whole geographical domain, but overestimate the strength of the signal in the tropical areas and at mid-latitudes, when taken separately. The interannual variability of the two yearly averages and of the amplitude of the seasonal cycle is greatly underestimated by all models in each area analysed. This work shows that the climate models have an heterogeneous behaviour in simulating the CF over
The Szekeres Swiss Cheese model and the CMB observations
Bolejko, Krzysztof
2008-01-01
This paper presents the application of the Szekeres Swiss Cheese model to observations of the cosmic microwave background (CMB) radiation. It aims to study the CMB temperature fluctuations by the means of the exact inhomogeneous Szekeres model. So far the impact of inhomogeneous matter distribution on the CMB observations has been almost exclusively studied within the linear perturbations of the Friedmann model. However, since the density contrast of cosmic structures is larger than 1 this issue is worth studying using another approach. The Szekeres model is an inhomogeneous, non-symmetrical and exact solution of the Einstein equations. In this model, light propagation and matter evolution can be exactly calculated, without approximations such as small amplitude of the density contrast. This will allow us to examine the impact of light propagation effects on the CMB temperature fluctuations. The results of such analysis show that small-scale, non-linear inhomogeneities introduce - via light propagation effect...
Obs4MIPS: Satellite Observations for Model Evaluation
Ferraro, R.; Waliser, D. E.; Gleckler, P. J.
2015-12-01
This poster will review the current status of the obs4MIPs project, whose purpose is to provide a limited collection of well-established and documented datasets for comparison with Earth system models (https://www.earthsystemcog.org/projects/obs4mips/). These datasets have been reformatted to correspond with the CMIP5 model output requirements, and include technical documentation specifically targeted for their use in model output evaluation. There are currently over 50 datasets containing observations that directly correspond to CMIP5 model output variables. We will review recent additions to the obs4MIPs collection, and provide updated download statistics. We will also provide an update on changes to submission and documentation guidelines, the work of the WCRP Data Advisory Council (WDAC) Observations for Model Evaluation Task Team, and engagement with the CMIP6 MIP experiments.
Modeling of diffuse molecular gas applied to HD 102065 observations
Nehme, Cyrine; Boulanger, Francois; Forets, Guillaume Pineau des; Gry, Cecile
2008-01-01
Aims. We model a diffuse molecular cloud present along the line of sight to the star HD 102065. We compare our modeling with observations to test our understanding of physical conditions and chemistry in diffuse molecular clouds. Methods. We analyze an extensive set of spectroscopic observations which characterize the diffuse molecular cloud observed toward HD 102065. Absorption observations provide the extinction curve, H2, C I, CO, CH, and CH+ column densities and excitation. These data are complemented by observations of CII, CO and dust emission. Physical conditions are determined using the Meudon PDR model of UV illuminated gas. Results. We find that all observational results, except column densities of CH, CH+ and H2 in its excited (J > 2) levels, are consistent with a cloud model implying a Galactic radiation field (G~0.4 in Draine's unit), a density of 80 cm-3 and a temperature (60-80 K) set by the equilibrium between heating and cooling processes. To account for excited (J >2) H2 levels column densit...
Observations that polar climate modelers use and want
Kay, J. E.; de Boer, G.; Hunke, E. C.; Bailey, D. A.; Schneider, D. P.
2012-12-01
Observations are essential for motivating and establishing improvement in the representation of polar processes within climate models. We believe that explicitly documenting the current methods used to develop and evaluate climate models with observations will help inform and improve collaborations between the observational and climate modeling communities. As such, we will present the current strategy of the Polar Climate Working Group (PCWG) to evaluate polar processes within Community Earth System Model (CESM) using observations. Our presentation will focus primarily on PCWG evaluation of atmospheric, sea ice, and surface oceanic processes. In the future, we hope to expand to include land surface, deep ocean, and biogeochemical observations. We hope our presentation, and a related working document developed by the PCWG (https://docs.google.com/document/d/1zt0xParsFeMYhlihfxVJhS3D5nEcKb8A41JH0G1Ic-E/edit) inspires new and useful interactions that lead to improved climate model representation of polar processes relevant to polar climate.
Tests of Quantum Gravity and Large Extra Dimensions Models Using High Energy Gamma Ray Observations
Stecker, F W
2004-01-01
Observations of the multi-TeV spectra of the nearby BL Lac objects Mkn 421 and Mkn 501 exhibit the high energy cutoffs predicted to be the result of intergalactic annihilation interactions, primarily with IR photons having a flux level as determined by various astronomical observations. After correcting for such intergalactic absorption, these spectra can be explained within the framework of synchrotron self-Compton emission models. Stecker & Glashow have shown that the existence of this annihilation via electron-positron pair production puts strong constraints on Lorentz violation. Such constraints have important implications for quantum gravity models and large extra dimension models. We also discuss the implications of observations of high energy gamma-rays from the Crab Nebula on constraining quantum gravity models.
MHD models compared with Artemis observations at -60 Re
Gencturk Akay, Iklim; Sibeck, David; Angelopoulos, Vassilis; Kaymaz, Zerefsan; Kuznetsova, Maria
2016-07-01
The distant magnetotail has been one of the least studied magnetic regions of the Earth's magnetosphere compared to the other near Earth both dayside and nightside magnetospheric regions owing to the limited number of spacecraft observations. Since 2011, ARTEMIS spacecraft give an excellent opportunity to study the magnetotail at lunar distances in terms of data quality and parameter space. This also gives opportunities to improve the magnetotail models at -60 Re and encourages the modelling studies of the distant magnetotail. Using ARTEMIS data in distant magnetotail, we create magnetic field and plasma flow vector maps in different planes and separated with IMF orientation to understand the magnetotail dynamics at this distance. For this study, we use CCMC's Run-on-Request resources of the MHD models; specifically SWMF-BATS-R-US, OpenGGCM, and LFM and perform the similar analysis with the models. Our main purpose in this study is to measure the performance of the MHD models at -60 Re distant magnetotail by comparing the model results with Artemis observations. In the literature, such a comprehensive comparative study is lacking in the distant tail. Preliminary results show that in general all three models underestimate the magnetic field structure while overestimating the flow speed. In the cross-sectional view, LFM seems to produce the better agreement with the observations. A clear dipolar magnetic field structure is seen with dawn-dusk asymmetry in all models owing to slight positive IMF By but the effect was found to be exaggerated. All models show tailward flows at this distance of the magnetotail, most possibly owing to the magnetic reconnection at the near Earth tail distances. A detailed comparison of several tail characteristics from the models will be presented and discussions will be given with respect to the observations from Artemis at this distance.
Influence of rainfall observation network on model calibration and application
Directory of Open Access Journals (Sweden)
A. Bárdossy
2008-01-01
Full Text Available The objective in this study is to investigate the influence of the spatial resolution of the rainfall input on the model calibration and application. The analysis is carried out by varying the distribution of the raingauge network. A meso-scale catchment located in southwest Germany has been selected for this study. First, the semi-distributed HBV model is calibrated with the precipitation interpolated from the available observed rainfall of the different raingauge networks. An automatic calibration method based on the combinatorial optimization algorithm simulated annealing is applied. The performance of the hydrological model is analyzed as a function of the raingauge density. Secondly, the calibrated model is validated using interpolated precipitation from the same raingauge density used for the calibration as well as interpolated precipitation based on networks of reduced and increased raingauge density. Lastly, the effect of missing rainfall data is investigated by using a multiple linear regression approach for filling in the missing measurements. The model, calibrated with the complete set of observed data, is then run in the validation period using the above described precipitation field. The simulated hydrographs obtained in the above described three sets of experiments are analyzed through the comparisons of the computed Nash-Sutcliffe coefficient and several goodness-of-fit indexes. The results show that the model using different raingauge networks might need re-calibration of the model parameters, specifically model calibrated on relatively sparse precipitation information might perform well on dense precipitation information while model calibrated on dense precipitation information fails on sparse precipitation information. Also, the model calibrated with the complete set of observed precipitation and run with incomplete observed data associated with the data estimated using multiple linear regressions, at the locations treated as
Foundation observation of teaching project--a developmental model of peer observation of teaching.
Pattison, Andrew Timothy; Sherwood, Morgan; Lumsden, Colin James; Gale, Alison; Markides, Maria
2012-01-01
Peer observation of teaching is important in the development of educators. The foundation curriculum specifies teaching competencies that must be attained. We created a developmental model of peer observation of teaching to help our foundation doctors achieve these competencies and develop as educators. A process for peer observation was created based on key features of faculty development. The project consisted of a pre-observation meeting, the observation, a post-observation debrief, writing of reflective reports and group feedback sessions. The project was evaluated by completion of questionnaires and focus groups held with both foundation doctors and the students they taught to achieve triangulation. Twenty-one foundation doctors took part. All completed reflective reports on their teaching. Participants described the process as useful in their development as educators, citing specific examples of changes to their teaching practice. Medical students rated the sessions as better or much better quality as their usual teaching. The study highlights the benefits of the project to individual foundation doctors, undergraduate medical students and faculty. It acknowledges potential anxieties involved in having teaching observed. A structured programme of observation of teaching can deliver specific teaching competencies required by foundation doctors and provides additional benefits.
A Generalized Ideal Observer Model for Decoding Sensory Neural Responses
Directory of Open Access Journals (Sweden)
Gopathy ePurushothaman
2013-09-01
Full Text Available We show that many ideal observer models used to decode neural activity can be generalizedto a conceptually and analytically simple form. This enables us to study the statisticalproperties of this class of ideal observer models in a unified manner. We consider in detailthe problem of estimating the performance of this class of models. We formulate the problemde novo by deriving two equivalent expressions for the performance and introducing the correspondingestimators. We obtain a lower bound on the number of observations (N requiredfor the estimate of the model performance to lie within a specified confidence interval at aspecified confidence level. We show that these estimators are unbiased and consistent, withvariance approaching zero at the rate of 1/N. We find that the maximum likelihood estimatorfor the model performance is not guaranteed to be the minimum variance estimator even forsome simple parametric forms (e.g., exponential of the underlying probability distributions.We discuss the application of these results for designing and interpreting neurophysiologicalexperiments that employ specific instances of this ideal observer model.
A hybrid double-observer sightability model for aerial surveys
Griffin, Paul C.; Lubow, Bruce C.; Jenkins, Kurt J.; Vales, David J.; Moeller, Barbara J.; Reid, Mason; Happe, Patricia J.; Mccorquodale, Scott M.; Tirhi, Michelle J.; Schaberi, Jim P.; Beirne, Katherine
2013-01-01
Raw counts from aerial surveys make no correction for undetected animals and provide no estimate of precision with which to judge the utility of the counts. Sightability modeling and double-observer (DO) modeling are 2 commonly used approaches to account for detection bias and to estimate precision in aerial surveys. We developed a hybrid DO sightability model (model MH) that uses the strength of each approach to overcome the weakness in the other, for aerial surveys of elk (Cervus elaphus). The hybrid approach uses detection patterns of 2 independent observer pairs in a helicopter and telemetry-based detections of collared elk groups. Candidate MH models reflected hypotheses about effects of recorded covariates and unmodeled heterogeneity on the separate front-seat observer pair and back-seat observer pair detection probabilities. Group size and concealing vegetation cover strongly influenced detection probabilities. The pilot's previous experience participating in aerial surveys influenced detection by the front pair of observers if the elk group was on the pilot's side of the helicopter flight path. In 9 surveys in Mount Rainier National Park, the raw number of elk counted was approximately 80–93% of the abundance estimated by model MH. Uncorrected ratios of bulls per 100 cows generally were low compared to estimates adjusted for detection bias, but ratios of calves per 100 cows were comparable whether based on raw survey counts or adjusted estimates. The hybrid method was an improvement over commonly used alternatives, with improved precision compared to sightability modeling and reduced bias compared to DO modeling.
Observational constraints on the generalized $\\alpha$ attractor model
Shahalam, M; Myrzakul, Shynaray; Wang, Anzhong
2016-01-01
We study the generalized $\\alpha$ attractor model in context of late time cosmic acceleration; the model interpolates between freezing and thawing dark energy models. In the slow roll regime, the originally potential is modified whereas the modification ceases in the asymptotic regime and the effective potential behaves as quadratic. In our setting, field rolls slowly around the present epoch and mimics dark matter in future. We put observational constraints on the model parameters for which we use an integrated data base (SN+Hubble+BAO+CMB) for carrying out the data analysis.
Spires-Jones, Tara L; Friedman, Taylor; Pitstick, Rose; Polydoro, Manuela; Roe, Allyson; Carlson, George A; Hyman, Bradley T
2014-03-06
Alzheimer's disease is characterized pathologically by aggregation of amyloid beta into senile plaques and aggregation of pathologically modified tau into neurofibrillary tangles. While changes in amyloid processing are strongly implicated in disease initiation, the recent failure of amyloid-based therapies has highlighted the importance of tau as a therapeutic target. "Tangle busting" compounds including methylene blue and analogous molecules are currently being evaluated as therapeutics in Alzheimer's disease. Previous studies indicated that methylene blue can reverse tau aggregation in vitro after 10 min, and subsequent studies suggested that high levels of drug reduce tau protein levels (assessed biochemically) in vivo. Here, we tested whether methylene blue could remove established neurofibrillary tangles in the rTg4510 model of tauopathy, which develops robust tangle pathology. We find that 6 weeks of methylene blue dosing in the water from 16 months to 17.5 months of age decreases soluble tau but does not remove sarkosyl insoluble tau, or histologically defined PHF1 or Gallyas positive tangle pathology. These data indicate that methylene blue treatment will likely not rapidly reverse existing tangle pathology. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
Kim, Jongchan; Archer, Rosalind
2017-04-01
In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).
Redmond, Anthony K; Pettinello, Rita; Dooley, Helen
2017-03-01
The molecular machinery required for lymphocyte development and differentiation appears to have emerged concomitantly with distinct B- and T-like lymphocyte subsets in the ancestor of all vertebrates. The TNFSF superfamily (TNFSF) members BAFF (TNFSF13/Blys) and APRIL (TNFSF13) are key regulators of B cell development survival, and activation in mammals, but the temporal emergence of these molecules, and their precise relationship to the newly identified TNFSF gene BALM (BAFF and APRIL-like molecule), have not yet been elucidated. Here, to resolve the early evolutionary history of this family, we improved outgroup sampling and alignment quality, and applied better fitting substitution models compared to past studies. Our analyses reveal that BALM is a definitive TNFSF13 family member, which split from BAFF in the gnathostome (jawed vertebrate) ancestor. Most importantly, however, we show that both the APRIL and BAFF lineages existed in the ancestors of all extant vertebrates. This implies that APRIL has been lost, or is yet to be found, in cyclostomes (jawless vertebrates). Our results suggest that lineage-specific gene duplication and loss events have caused lymphocyte regulation, despite shared origins, to become secondarily distinct between gnathostomes and cyclostomes. Finally, the structure of lamprey BAFF-like, and its phylogenetic placement as sister to BAFF and BALM, but not the more slowly evolving APRIL, indicates that the primordial lymphocyte regulator was more APRIL-like than BAFF-like.
Testing protostellar disk formation models with ALMA observations
Harsono, Daniel; Bruderer, Simon; Li, Zhi-Yun; Jorgensen, Jes
2015-01-01
Abridged: Recent simulations have explored different ways to form accretion disks around low-mass stars. We aim to present observables to differentiate a rotationally supported disk from an infalling rotating envelope toward deeply embedded young stellar objects and infer their masses and sizes. Two 3D magnetohydrodynamics (MHD) formation simulations and 2D semi-analytical model are studied. The dust temperature structure is determined through continuum radiative transfer RADMC3D modelling. A simple temperature dependent CO abundance structure is adopted and synthetic spectrally resolved submm rotational molecular lines up to $J_{\\rm u} = 10$ are simulated. All models predict similar compact components in continuum if observed at the spatial resolutions of 0.5-1$"$ (70-140 AU) typical of the observations to date. A spatial resolution of $\\sim$14 AU and high dynamic range ($> 1000$) are required to differentiate between RSD and pseudo-disk in the continuum. The peak-position velocity diagrams indicate that the...
Modeling the Compton Hump Reverberation Observed in Active Galactic Nuclei
Hoormann, Janie; Beheshtipour, Banafsheh; Krawczynski, Henric
2016-04-01
In recent years, observations of the Iron K alpha reverberation in supermassive black holes have provided a new way to probe the inner accretion flow. Furthermore, a time lag between the direct coronal emission and the reprocessed emission forming the Compton Hump in AGN has been observed. In order to model this Compton Hump reverberation we performed general relativistic ray tracing studies of the accretion disk surrounding supermassive black holes, taking into account both the radial and angular dependence of the ionization parameter. We are able to model emission not only from a lamp-post corona but also implementing 3D corona geometries. Using these results we are able to model the observed data to gain additional insight into the geometry of the corona and the structure of the inner accretion disk.
Model-independent inference on compact-binary observations
Mandel, Ilya; Colonna, Andrea; Stevenson, Simon; Tiňo, Peter; Veitch, John
2016-01-01
The recent advanced LIGO detections of gravitational waves from merging binary black holes enhance the prospect of exploring binary evolution via gravitational-wave observations of a population of compact-object binaries. In the face of uncertainty about binary formation models, model-independent inference provides an appealing alternative to comparisons between observed and modelled populations. We describe a procedure for clustering in the multi-dimensional parameter space of observations that are subject to significant measurement errors. We apply this procedure to a mock data set of population-synthesis predictions for the masses of merging compact binaries convolved with realistic measurement uncertainties, and demonstrate that we can accurately distinguish subpopulations of binary neutron stars, binary black holes, and mixed black hole -- neutron star binaries.
Solar Spectral Irradiance Variability in Cycle 24: Observations and Models
Marchenko, S V; Lean, J L
2016-01-01
Utilizing the excellent stability of the Ozone Monitoring Instrument (OMI), we characterize both short-term (solar rotation) and long-term (solar cycle) changes of the solar spectral irradiance (SSI) between 265-500 nm during the on-going Cycle 24. We supplement the OMI data with concurrent observations from the GOME-2 and SORCE instruments and find fair-to-excellent, depending on wavelength, agreement among the observations and predictions of the NRLSSI2 and SATIRE-S models.
Diagnostic Modeling of PAMS VOC Observation on Regional Scale Environment
Chen, S.; Liu, T.; Chen, T.; Ou Yang, C.; Wang, J.; Chang, J. S.
2008-12-01
While a number of gas-phase chemical mechanisms, such as CBM-Z, RADM2, SAPRC-07 had been successful in studying gas-phase atmospheric chemical processes they all used some lumped organic species to varying degrees. Photochemical Assessment Monitoring Stations (PAMS) has been in use for over ten years and yet it is not clear how the detailed organic species measured by PAMS compare to the lumped model species under regional-scale transport and chemistry interactions. By developing a detailed mechanism specifically for the PAMS organics and embedding this diagnostic model within a regional-scale transport and chemistry model we can then directly compare PAMS observation with regional-scale model simulations. We modify one regional-scale chemical transport model (Taiwan Air Quality Model, TAQM) by adding a submodel with chemical mechanism for interactions of the 56 species observed by PAMS. This submodel then calculates the time evolution of these 56 PAMS species within the environment established by TAQM. It is assumed that TAQM can simulate the overall regional-scale environment including impact of regional-scale transport and time evolution of oxidants and radicals. Therefore we can scale these influences to the PAMS organic species and study their time evolution with their species-specific source functions, meteorological transport, and chemical interactions. Model simulations of each species are compared with PAMS hourly surface measurements. A case study located in a metropolitan area in central Taiwan showed that with wind speeds lower than 3 m/s, when meteorological simulation is comparable with observation, the diurnal pattern of each species performs well with PAMS data. It is found that for many observations meteorological transport is an influence and that local emissions of specific species must be represented correctly. At this time there are still species that cannot be modeled properly. We suspect this is mostly due to lack of information on local
Optimal designs for the Michaelis Menten model with correlated observations
Dette, Holger; Kunert, Joachim
2012-01-01
In this paper we investigate the problem of designing experiments for weighted least squares analysis in the Michaelis Menten model. We study the structure of exact D-optimal designs in a model with an autoregressive error structure. Explicit results for locally D-optimal are derived for the case where 2 observations can be taken per subject. Additionally standardized maximin D-optimal designs are obtained in this case. The results illustrate the enormous difficulties to find e...
The Martian Plasma Environment: Model Calculations and Observations
Lichtenegger, H. I. M.; Dubinin, E.; Schwingenschuh, K.; Riedler, W.
Based on a modified version of the model of an induced martian magnetosphere developed by Luhmann (1990), the dynamics and spatial distribution of different planetary ion species is examined. Three main regions are identified: A cloud of ions travelling along cycloidal trajectories, a plasma mantle and a plasma sheet. The latter predominantly consists of oxygen ions of ionospheric origin with minor portions of light particles. Comparison of model results with Phobos-2 observations shows reasonable agreement.
Scale invariant cosmology III: dynamical models and comparisons with observations
Maeder, Andre
2016-01-01
We examine the properties of the scale invariant cosmological models, also making the specific hypothesis of the scale invariance of the empty space at large scales. Numerical integrations of the cosmological equations for different values of the curvature parameter k and of the density parameter Omega_m are performed. We compare the dynamical properties of the models to the observations at different epochs. The main numerical data and graphical representations are given for models computed with different curvatures and density parameters. The models with non-zero density start explosively with first a braking phase followed by a continuously accelerating expansion. The comparison of the models with the recent observations from supernovae SN Ia, BAO and CMB data from Planck 2015 shows that the scale invariant model with k=0 and Omega_m=0.30 very well fits the observations in the usual Omega_m vs. Omega_Lambda plane and consistently accounts for the accelerating expansion or dark energy. The expansion history ...
Linking Geomechanical Models with Observations of Microseismicity during CCS Operations
Verdon, J.; Kendall, J.; White, D.
2012-12-01
During CO2 injection for the purposes of carbon capture and storage (CCS), injection-induced fracturing of the overburden represents a key risk to storage integrity. Fractures in a caprock provide a pathway along which buoyant CO2 can rise and escape the storage zone. Therefore the ability to link field-scale geomechanical models with field geophysical observations is of paramount importance to guarantee secure CO2 storage. Accurate location of microseismic events identifies where brittle failure has occurred on fracture planes. This is a manifestation of the deformation induced by CO2 injection. As the pore pressure is increased during injection, effective stress is decreased, leading to inflation of the reservoir and deformation of surrounding rocks, which creates microseismicity. The deformation induced by injection can be simulated using finite-element mechanical models. Such a model can be used to predict when and where microseismicity is expected to occur. However, typical elements in a field scale mechanical models have decameter scales, while the rupture size for microseismic events are typically of the order of 1 square meter. This means that mapping modeled stress changes to predictions of microseismic activity can be challenging. Where larger scale faults have been identified, they can be included explicitly in the geomechanical model. Where movement is simulated along these discrete features, it can be assumed that microseismicity will occur. However, microseismic events typically occur on fracture networks that are too small to be simulated explicitly in a field-scale model. Therefore, the likelihood of microseismicity occurring must be estimated within a finite element that does not contain explicitly modeled discontinuities. This can be done in a number of ways, including the utilization of measures such as closeness on the stress state to predetermined failure criteria, either for planes with a defined orientation (the Mohr-Coulomb criteria) for
The effects of numerical-model complexity and observation type on estimated porosity values
Starn, J. Jeffrey; Bagtzoglou, Amvrossios C.; Green, Christopher T.
2015-09-01
The relative merits of model complexity and types of observations employed in model calibration are compared. An existing groundwater flow model coupled with an advective transport simulation of the Salt Lake Valley, Utah (USA), is adapted for advective transport, and effective porosity is adjusted until simulated tritium concentrations match concentrations in samples from wells. Two calibration approaches are used: a "complex" highly parameterized porosity field and a "simple" parsimonious model of porosity distribution. The use of an atmospheric tracer (tritium in this case) and apparent ages (from tritium/helium) in model calibration also are discussed. Of the models tested, the complex model (with tritium concentrations and tritium/helium apparent ages) performs best. Although tritium breakthrough curves simulated by complex and simple models are very generally similar, and there is value in the simple model, the complex model is supported by a more realistic porosity distribution and a greater number of estimable parameters. Culling the best quality data did not lead to better calibration, possibly because of processes and aquifer characteristics that are not simulated. Despite many factors that contribute to shortcomings of both the models and the data, useful information is obtained from all the models evaluated. Although any particular prediction of tritium breakthrough may have large errors, overall, the models mimic observed trends.
Utilization of remote sensing observations in hydrologic models
Ragan, R. M.
1977-01-01
Most of the remote sensing related work in hydrologic modeling has centered on modifying existing models to take advantage of the capabilities of new sensor techniques. There has been enough success with this approach to insure that remote sensing is a powerful tool in modeling the watershed processes. Unfortunately, many of the models in use were designed without recognizing the growth of remote sensing technology. Thus, their parameters were selected to be map or field crew definable. It is believed that the real benefits will come through the evolution of new models having new parameters that are developed specifically to take advantage of our capabilities in remote sensing. The ability to define hydrologically active areas could have a significant impact. The ability to define soil moisture and the evolution of new techniques to estimate evoportransportation could significantly modify our approach to hydrologic modeling. Still, without a major educational effort to develop an understanding of the techniques used to extract parameter estimates from remote sensing data, the potential offered by this new technology will not be achieved.
Paterson, S. R.; Okaya, D. A.; Memeti, V.; Mundil, R.; Lackey, J.; Clemens-Knott, D.
2009-12-01
,00-500,000 years, (2) the outer margins of the main chamber solidified prior to emplacement of inner magma batches, but that (3) large parts of the main chamber stayed above the solidus for 1-2 million years resulting in large magma chambers. Our thermochronology (U-Pb zircon and titanite, 40Ar/39Ar of hornblende and large and small biotite populations) in general agree with the above conclusions but do show some intriguing differences from the thermal modeling predictions particularly in locations where we think parts of the chamber were removed by or recycled into younger pulses. Finally the conclusion that large magma chambers existed matches our geochemical studies, which indicate that in situ fractionation dominated in the rapidly crystallized magma lobes whereas additional mixing processes obscured fractionation patterns in the more slowly crystallized main chambers explaining the more complex compositional patterns and mineral histories in this part of the batholith.
Calibration of a numerical ionospheric model with EISCAT observations
Directory of Open Access Journals (Sweden)
P.-L. Blelly
Full Text Available A set of EISCAT UHF and VHF observations is used for calibrating a coupled fluid-kinetic model of the ionosphere. The data gathered in the period 1200- 2400 UT on 24 March 1995 had various intervals of interest for such a calibration. The magnetospheric activity was very low during the afternoon, allowing for a proper examination of a case of quiet ionospheric conditions. The radars entered the auroral oval just after 1900 UT: a series of dynamic events probably associated with rapidly moving auroral arcs was observed until after 2200 UT. No attempts were made to model the dynamical behaviour during the 1900–2200 UT period. In contrast, the period 2200–2400 UT was characterised by quite steady precipitation: this latter period was then chosen for calibrating the model during precipitation events. The adjustment of the model on the four primary parameters observed by the radars (namely the electron concentration and temperature and the ion temperature and velocity needed external inputs (solar fluxes and magnetic activity index and the adjustments of a neutral atmospheric model in order to reach a good agreement. It is shown that for the quiet ionosphere, only slight adjustments of the neutral atmosphere models are needed. In contrast, adjusting the observations during the precipitation event requires strong departures from the model, both for the atomic oxygen and hydrogen. However, it is argued that this could well be the result of inadequately representing the vibrational states of N_{2} during precipitation events, and that these factors have to be considered only as ad hoc corrections.
Observation-based correction of dynamical models using thermostats
Frank, Jason; Leimkuhler, Benedict
2017-01-01
Models used in simulation may give accurate short-term trajectories but distort long-term (statistical) properties. In this work, we augment a given approximate model with a control law (a ‘thermostat’) that gently perturbs the dynamical system to target a thermodynamic state consistent with a set of prescribed (possibly evolving) observations. As proof of concept, we provide an example involving a point vortex fluid model on the sphere, for which we show convergence of equilibrium quantities (in the stationary case) and the ability of the thermostat to dynamically track a transient state. PMID:28265197
Unsteady aerodynamic modeling based on POD-observer method
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
A new hybrid approach to constructing reduced-order models(ROM)of unsteady aerodynamics applicable to aeroelastic analysis is presented by using proper orthogonal decomposition(POD)in combination with observer techniques.Fluid modes are generated through POD by sampling observations of solutions derived from the full-order model.The response in the POD training is projected onto the fluid modes to determine the time history of the modal amplitudes.The resulting data are used to extract the Markov parameters of the low-dimensional model for modal amplitudes using a related deadbeat observer.The state-space realization is synthesized from the system’s Markov parameters that are processed with the eigensystem realization algorithm.The POD-observer method is applied to a two-dimensional airfoil system in subsonic flow field.The results predicted by the ROM are in general agreement with those from the full-order system.The ROM obtained by the hybrid approach captures the essence of a fluid system and produces vast reduction in both degrees of freedom and computational time relative to the full-order model.
Sixth International Workshop on the Mars Atmosphere: Modelling and Observations
Forget, F.; Millour, M.
2017-01-01
The scope of this workshop is to bring together experts in observations and modelling of the present and past Mars climate systems and discuss the nature of the atmospheric circulation and the photochemistry (up to the thermosphere), the dust cycle, the water cycle (vapor, clouds and frost) and the carbon dioxide cycle (polar caps).
Observations and models for needle-tissue interactions
Misra, Sarthak; Reed, Kyle B.; Schafer, Benjamin W.; Ramesh, K.T.; Okamura, Allison M.
2009-01-01
The asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. In this study we present a mechanics-based model that calculates the deflection of the needle embedded in an elastic medium. Microscopic observations for several needle- gel interactions
S-AMP for non-linear observation models
DEFF Research Database (Denmark)
Cakmak, Burak; Winther, Ole; Fleury, Bernard H.
2015-01-01
Recently we presented the S-AMP approach, an extension of approximate message passing (AMP), to be able to handle general invariant matrix ensembles. In this contribution we extend S-AMP to non-linear observation models. We obtain generalized AMP (GAMP) as the special case when the measurement...
Cortis, Clorinda; Sarigu, Alessio; Montaldo, Nicola; Saba, Andrea
2013-04-01
The recent floods observed in 2004 and 2008 in Sardinia (Italy) showed a significant flood increase in magnitude and frequency and put the attention on the problem of the hydraulic safety of existing dams. Thirty dams built for both electric production and water supply for irrigation and civil uses during the 1920-1960 are present in Sardinia (Italy). The distributed hydrologic model is an event model (FEST) which assesses runoff through a simplified approach based on Soil Conservation Service equations and runoff propagation through the Muskingum-Cunge approach. The FEST needs the calibration of different parameters: 1) the critical support area that defines the minimum drainage area required to initiate a channel, 2) the ratio between cross-section width and flood flow depth for hillslope, 3) the hillslope values of the Gaulckler-Stickler roughness coefficient, and 4) the Curve Number obtained/extracted from the landscape characteristics of each basin. The data collection of numerous historical flood observations of the Sardinian basins allow for the first time to accurately calibrate an hydrologic model for the Sardinian basins, characterized by hortonian runoff mechanisms typically, steep hillslopes and thin soils. Areas of the catchments are between 4 and 3147 Km2 and the basins are characterized by an high variability of the landscape characteristics such as geology, topography, soil, land use and vegetation. Using the calibrated hydrologic model and the synthetic design hyetograph the design floods of the dams are estimated. The comparison between peak flows of the generated design floods and those estimated using typical regionalized statistical methods (based for Sardinian studies on two components extreme value (TCEV) and logarithmic probabilistic distributions) shows contradiction and interesting results. For large scale basin (> 200 km2) the two contrasting methods agree, while for small basins the proposed method underestimates the peak respect to the
Some observational tests of a minimal galaxy formation model
Cohn, J D
2016-01-01
Dark matter simulations can serve as a basis for creating galaxy histories via the galaxy-dark matter connection. Here, one such model by Becker (2015) is implemented with several variations on three different dark matter simulations. Stellar mass and star formation rates are assigned to all simulation subhalos at all times, using subhalo mass gain to determine stellar mass gain. The observational properties of the resulting galaxy distributions are compared to each other and observations for a range of redshifts from 0-2. Although many of the galaxy distributions seem reasonable, there are noticeable differences as simulations, subhalo mass gain definitions, or subhalo mass definitions are altered, suggesting that the model should change as these properties are varied. Agreement with observations may improve by including redshift dependence in the added-by-hand random contribution to star formation rate. There appears to be an excess of faint quiescent galaxies as well (perhaps due in part to differing defin...
Energy Technology Data Exchange (ETDEWEB)
McJunkin, Timothy; Epiney, Aaron; Rabiti, Cristian
2017-06-01
This report provides a summary of the effort in the Nuclear-Renewable Hybrid Energy System (N-R HES) project on the level 4 milestone to consider integration of existing grid models into the factors for optimization on shorter time intervals than the existing electric grid models with the Risk Analysis Virtual Environment (RAVEN) and Modelica [1] optimizations and economic analysis that are the focus of the project to date.
ENLIL Global Heliospheric Modeling as a Context For Multipoint Observations
Mays, M. Leila; Odstrcil, Dusan; Luhmann, Janet; Bain, Hazel; Li, Yan; Schwadron, Nathan; Gorby, Matt; Thompson, Barbara; Jian, Lan; Möstl, Christian; Rouillard, Alexis; Davies, Jackie; Temmer, Manuela; Rastaetter, Lutz; Taktakishvili, Aleksandre; MacNeice, Peter; Kuznetsova, Maria
2016-04-01
We present heliospheric simulation case studies using recent enhancements to WSA--ENLIL+Cone (version 2.8) at the Community Coordinated Modeling Center (CCMC). The global 3D MHD ENLIL model provides a time-dependent description of the background solar wind plasma and magnetic field using a sequence of WSA coronal model maps as input at the inner boundary of 21.5 Rs. A homogeneous, over-pressured hydrodynamic plasma cloud is launched through the inner boundary of the heliospheric computational domain and into the background solar wind. Multipoint observations help constrain simulations and this modeling system provides global context and arrival times of the solar wind streams and CMEs at Earth, planets, and spacecraft. Additionally, one can extract the magnetic topologies of observer-connected magnetic field lines and all plasma and shock properties along those field lines. ENLIL "likelihood/all-clear" forecasting maps provide expected intensity, timing/duration of events at locations throughout the heliosphere with "possible SEP affected areas" color-coded based on shock strength. ENLIL simulations are also useful to drive SEP models such as the Solar Energetic Particle Model (SEPMOD) (Luhmann et al. 2007, 2010) and Energetic Particle Radiation Environment Module (EPREM) (Schwadron et al., 2010). SEPMOD injects protons onto a sequence observer field lines at intensities dependent on the connected shock source strength which are then integrated at the observer to approximate the proton flux. EPREM couples with MHD models such as ENLIL and computes energetic particle distributions based on the focused transport equation along a Lagrangian grid of nodes that propagate out with the solar wind. Studies have shown that accurate descriptions of the heliosphere, and hence modeled CME arrival times and SEPs, are achieved by ENLIL only when the background solar wind is well-reproduced and CME parameters are accurate. It is essential to include all of the relevant CMEs and
Testing the Empirical Shock Arrival Model using Quadrature Observations
Gopalswamy, N; Xie, H; Yashiro, S
2013-01-01
The empirical shock arrival (ESA) model was developed based on quadrature data from Helios (in-situ) and P-78 (remote-sensing) to predict the Sun-Earth travel time of coronal mass ejections (CMEs) [Gopalswamy et al. 2005a]. The ESA model requires earthward CME speed as input, which is not directly measurable from coronagraphs along the Sun-Earth line. The Solar Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory (SOHO) were in quadrature during 2010 - 2012, so the speeds of Earth-directed CMEs were observed with minimal projection effects. We identified a set of 20 full halo CMEs in the field of view of SOHO that were also observed in quadrature by STEREO. We used the earthward speed from STEREO measurements as input to the ESA model and compared the resulting travel times with the observed ones from L1 monitors. We find that the model predicts the CME travel time within about 7.3 hours, which is similar to the predictions by the ENLIL model. We also find that CME-CME and CME...
SuperLFV: An SLHA tool for lepton flavor violating observables in supersymmetric models
Murakami, Brandon
2013-01-01
We introduce SuperLFV, a numerical tool for calculating low-energy LFV observables in the context of the minimal supersymmetric standard model (MSSM). As the Large Hadron Collider and MEG, a dedicated mu -> e gamma experiment, are presently acquiring data, there is need for tools that provide rapid discrimination of models that exhibit lepton flavor violation (LFV). SuperLFV accepts an SLHA-compliant spectrum file that contains the MSSM couplings and masses with complex phases at the supersymmetry breaking scale. In this manner, SuperLFV is compatible with but divorced from existing SLHA spectrum calculators that provides the low energy spectrum. Hence, input spectra are not confined to the LFV sources provided by established SLHA spectrum calculators. Input spectra may be generated by personal code or by hand, allowing for arbitrary models not supported by existing spectrum calculators.
Linear system identification via backward-time observer models
Juang, Jer-Nan; Phan, Minh
1993-01-01
This paper presents an algorithm to identify a state-space model of a linear system using a backward-time approach. The procedure consists of three basic steps. First, the Markov parameters of a backward-time observer are computed from experimental input-output data. Second, the backward-time observer Markov parameters are decomposed to obtain the backward-time system Markov parameters (backward-time pulse response samples) from which a backward-time state-space model is realized using the Eigensystem Realization Algorithm. Third, the obtained backward-time state space model is converted to the usual forward-time representation. Stochastic properties of this approach will be discussed. Experimental results are given to illustrate when and to what extent this concept works.
Modelling multimodal photometric redshift regression with noisy observations
Kügler, S D
2016-01-01
In this work, we are trying to extent the existing photometric redshift regression models from modeling pure photometric data back to the spectra themselves. To that end, we developed a PCA that is capable of describing the input uncertainty (including missing values) in a dimensionality reduction framework. With this "spectrum generator" at hand, we are capable of treating the redshift regression problem in a fully Bayesian framework, returning a posterior distribution over the redshift. This approach allows therefore to approach the multimodal regression problem in an adequate fashion. In addition, input uncertainty on the magnitudes can be included quite naturally and lastly, the proposed algorithm allows in principle to make predictions outside the training values which makes it a fascinating opportunity for the detection of high-redshifted quasars.
Comparing models of star formation simulating observed interacting galaxies
Quiroga, L. F.; Muñoz-Cuartas, J. C.; Rodrigues, I.
2017-07-01
In this work, we make a comparison between different models of star formation to reproduce observed interacting galaxies. We use observational data to model the evolution of a pair of galaxies undergoing a minor merger. Minor mergers represent situations weakly deviated from the equilibrium configuration but significant changes in star fomation (SF) efficiency can take place, then, minor mergers provide an unique scene to study SF in galaxies in a realistic but yet simple way. Reproducing observed systems also give us the opportunity to compare the results of the simulations with observations, which at the end can be used as probes to characterize the models of SF implemented in the comparison. In this work we compare two different star formation recipes implemented in Gadget3 and GIZMO codes. Both codes share the same numerical background, and differences arise mainly in the star formation recipe they use. We use observations from Pico dos Días and GEMINI telescopes and show how we use observational data of the interacting pair in AM2229-735 to characterize the interacting pair. Later we use this information to simulate the evolution of the system to finally reproduce the observations: Mass distribution, morphology and main features of the merger-induced star formation burst. We show that both methods manage to reproduce roughly the star formation activity. We show, through a careful study, that resolution plays a major role in the reproducibility of the system. In that sense, star formation recipe implemented in GIZMO code has shown a more robust performance. Acknowledgements: This work is supported by Colciencias, Doctorado Nacional - 617 program.
Inferring effective field observables from a discrete model
Bény, Cédric
2017-01-01
A spin system on a lattice can usually be modeled at large scales by an effective quantum field theory. A key mathematical result relating the two descriptions is the quantum central limit theorem, which shows that certain spin observables satisfy an algebra of bosonic fields under certain conditions. Here, we show that these particular observables and conditions are the relevant ones for an observer with certain limited abilities to resolve spatial locations as well as spin values. This is shown by computing the asymptotic behaviour of a quantum Fisher information metric as function of the resolution parameters. The relevant observables characterise the state perturbations whose distinguishability does not decay too fast as a function of spatial or spin resolution.
Tectonic stressing in California modeled from GPS observations
Parsons, T.
2006-01-01
What happens in the crust as a result of geodetically observed secular motions? In this paper we find out by distorting a finite element model of California using GPS-derived displacements. A complex model was constructed using spatially varying crustal thickness, geothermal gradient, topography, and creeping faults. GPS velocity observations were interpolated and extrapolated across the model and boundary condition areas, and the model was loaded according to 5-year displacements. Results map highest differential stressing rates in a 200-km-wide band along the Pacific-North American plate boundary, coinciding with regions of greatest seismic energy release. Away from the plate boundary, GPS-derived crustal strain reduces modeled differential stress in some places, suggesting that some crustal motions are related to topographic collapse. Calculated stressing rates can be resolved onto fault planes: useful for addressing fault interactions and necessary for calculating earthquake advances or delays. As an example, I examine seismic quiescence on the Garlock fault despite a calculated minimum 0.1-0.4 MPa static stress increase from the 1857 M???7.8 Fort Tejon earthquake. Results from finite element modeling show very low to negative secular Coulomb stress growth on the Garlock fault, suggesting that the stress state may have been too low for large earthquake triggering. Thus the Garlock fault may only be stressed by San Andreas fault slip, a loading pattern that could explain its erratic rupture history.
Siberian Arctic black carbon sources constrained by model and observation
Winiger, Patrik; Andersson, August; Eckhardt, Sabine; Stohl, Andreas; Semiletov, Igor P.; Dudarev, Oleg V.; Charkin, Alexander; Shakhova, Natalia; Klimont, Zbigniew; Heyes, Chris; Gustafsson, Örjan
2017-02-01
Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ngṡm-3 to 302 ngṡm-3) and dual-isotope-constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth.
An observer model for quantifying panning artifacts in digital pathology
Avanaki, Ali R. N.; Espig, Kathryn S.; Xthona, Albert; Lanciault, Christian; Kimpe, Tom R. L.
2017-03-01
Typically, pathologists pan from one region of a slide to another, choosing areas of interest for closer inspection. Due to finite frame rate and imperfect zero-order hold reconstruction (i.e., the non-zero time to reach the target brightness after a change in pixel drive), panning in whole slide images (WSI) cause visual artifacts. It is important to study the impact of such artifacts since research suggests that 49% of navigation is conducted in low-power/overview with digital pathology (Molin et al., Histopathology 2015). In this paper, we explain what types of medical information may be harmed by panning artifacts, propose a method to simulate panning artifacts, and design an observer model to predict the impact of panning artifacts on typical human observers' performance in basic diagnostically relevant visual tasks. The proposed observer model is based on derivation of perceived object border maps from luminance and chrominance information and may be tuned to account for visual acuity of the human observer to be modeled. Our results suggest that increasing the contrast (e.g., using a wide gamut display) with a slow response panel may not mitigate the panning artifacts which mostly affect visual tasks involving spatial discrimination of objects (e.g., normal vs abnormal structure, cell type and spatial relationships between them, and low-power nuclear morphology), and that the panning artifacts worsen with increasing panning speed. The proposed methods may be used as building blocks in an automatic WSI quality assessment framework.
Observing the observer (I): meta-bayesian models of learning and decision-making.
Daunizeau, Jean; den Ouden, Hanneke E M; Pessiglione, Matthias; Kiebel, Stefan J; Stephan, Klaas E; Friston, Karl J
2010-12-14
In this paper, we present a generic approach that can be used to infer how subjects make optimal decisions under uncertainty. This approach induces a distinction between a subject's perceptual model, which underlies the representation of a hidden "state of affairs" and a response model, which predicts the ensuing behavioural (or neurophysiological) responses to those inputs. We start with the premise that subjects continuously update a probabilistic representation of the causes of their sensory inputs to optimise their behaviour. In addition, subjects have preferences or goals that guide decisions about actions given the above uncertain representation of these hidden causes or state of affairs. From a Bayesian decision theoretic perspective, uncertain representations are so-called "posterior" beliefs, which are influenced by subjective "prior" beliefs. Preferences and goals are encoded through a "loss" (or "utility") function, which measures the cost incurred by making any admissible decision for any given (hidden) state of affair. By assuming that subjects make optimal decisions on the basis of updated (posterior) beliefs and utility (loss) functions, one can evaluate the likelihood of observed behaviour. Critically, this enables one to "observe the observer", i.e. identify (context- or subject-dependent) prior beliefs and utility-functions using psychophysical or neurophysiological measures. In this paper, we describe the main theoretical components of this meta-Bayesian approach (i.e. a Bayesian treatment of Bayesian decision theoretic predictions). In a companion paper ('Observing the observer (II): deciding when to decide'), we describe a concrete implementation of it and demonstrate its utility by applying it to simulated and real reaction time data from an associative learning task.
Observing the observer (I: meta-bayesian models of learning and decision-making.
Directory of Open Access Journals (Sweden)
Jean Daunizeau
Full Text Available In this paper, we present a generic approach that can be used to infer how subjects make optimal decisions under uncertainty. This approach induces a distinction between a subject's perceptual model, which underlies the representation of a hidden "state of affairs" and a response model, which predicts the ensuing behavioural (or neurophysiological responses to those inputs. We start with the premise that subjects continuously update a probabilistic representation of the causes of their sensory inputs to optimise their behaviour. In addition, subjects have preferences or goals that guide decisions about actions given the above uncertain representation of these hidden causes or state of affairs. From a Bayesian decision theoretic perspective, uncertain representations are so-called "posterior" beliefs, which are influenced by subjective "prior" beliefs. Preferences and goals are encoded through a "loss" (or "utility" function, which measures the cost incurred by making any admissible decision for any given (hidden state of affair. By assuming that subjects make optimal decisions on the basis of updated (posterior beliefs and utility (loss functions, one can evaluate the likelihood of observed behaviour. Critically, this enables one to "observe the observer", i.e. identify (context- or subject-dependent prior beliefs and utility-functions using psychophysical or neurophysiological measures. In this paper, we describe the main theoretical components of this meta-Bayesian approach (i.e. a Bayesian treatment of Bayesian decision theoretic predictions. In a companion paper ('Observing the observer (II: deciding when to decide', we describe a concrete implementation of it and demonstrate its utility by applying it to simulated and real reaction time data from an associative learning task.
The Szekeres Swiss Cheese model and the CMB observations
Bolejko, Krzysztof
2009-08-01
This paper presents the application of the Szekeres Swiss Cheese model to the analysis of observations of the cosmic microwave background (CMB) radiation. The impact of inhomogeneous matter distribution on the CMB observations is in most cases studied within the linear perturbations of the Friedmann model. However, since the density contrast and the Weyl curvature within the cosmic structures are large, this issue is worth studying using another approach. The Szekeres model is an inhomogeneous, non-symmetrical and exact solution of the Einstein equations. In this model, light propagation and matter evolution can be exactly calculated, without such approximations as small amplitude of the density contrast. This allows to examine in more realistic manner the contribution of the light propagation effect to the measured CMB temperature fluctuations. The results of such analysis show that small-scale, non-linear inhomogeneities induce, via Rees-Sciama effect, temperature fluctuations of amplitude 10-7-10-5 on angular scale ϑ 750). This is still much smaller than the measured temperature fluctuations on this angular scale. However, local and uncompensated inhomogeneities can induce temperature fluctuations of amplitude as large as 10-3, and thus can be responsible the low multipoles anomalies observed in the angular CMB power spectrum.
Observational constraints on new generalized Chaplygin gas model
Liao, Kai; Zhu, Zong-Hong
2012-01-01
We use the latest data to investigate observational constraints on the new generalized Chaplygin gas (NGCG) model. Using the Markov Chain Monte Carlo (MCMC) method, we constrain the NGCG model with the type Ia supernovae (SNe Ia) from Union2 set (557 data), the usual baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey (SDSS) data release 7 (DR7) galaxy sample, the cosmic microwave background (CMB) observation from the 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) results, the newly revised $H(z)$ data, as well as a value of $\\theta_{BAO} (z=0.55) = (3.90 \\pm 0.38)^{\\circ}$ for the angular BAO scale. The constraint results for NGCG model are $\\omega_X = -1.0510_{-0.1685}^{+0.1563}(1\\sigma)_{-0.2398}^{+0.2226}(2\\sigma)$, $\\eta = 1.0117_{-0.0502}^{+0.0469}(1\\sigma)_{-0.0716}^{+0.0693}(2\\sigma)$, and $\\Omega_X = 0.7297_{-0.0276}^{+0.0229}(1\\sigma)_{-0.0402}^{+0.0329}(2\\sigma)$, which give a rather stringent constraint. From the results, we can see a phantom model ...
Comparing theoretical models of our galaxy with observations
Directory of Open Access Journals (Sweden)
Johnston K.V.
2012-02-01
Full Text Available With the advent of large scale observational surveys to map out the stars in our galaxy, there is a need for an efficient tool to compare theoretical models of our galaxy with observations. To this end, we describe here the code Galaxia, which uses efficient and fast algorithms for creating a synthetic survey of the Milky Way, and discuss its uses. Given one or more observational constraints like the color-magnitude bounds, a survey size and geometry, Galaxia returns a catalog of stars in accordance with a given theoretical model of the Milky Way. Both analytic and N-body models can be sampled by Galaxia. For N-body models, we present a scheme that disperses the stars spawned by an N-body particle, in such a way that the phase space density of the spawned stars is consistent with that of the N-body particles. The code is ideally suited to generating synthetic data sets that mimic near future wide area surveys such as GAIA, LSST and HERMES. In future, we plan to release the code publicly at http://galaxia.sourceforge.net. As an application of the code, we study the prospect of identifying structures in the stellar halo with future surveys that will have velocity information about the stars.
Observational constraints on the new generalized Chaplygin gas model
Institute of Scientific and Technical Information of China (English)
Kai Liao; Yu Pan; Zong-Hong Zhu
2013-01-01
We use the latest data to investigate observational constraints on the new generalized Chaplygin gas (NGCG) model.Using the Markov Chain Monte Carlo method,we constrain the NGCG model with type Ⅰa supernovae from the Union2 set (557 data),the usual baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey data release 7 galaxy sample,the cosmic microwave background observation from the 7-year Wilkinson Microwave Anisotropy Probe results,newly revised data on H(z),as well as a value of θBAO (z =0.55) =(3.90° ± 0.38°) for the angular BAO scale.The constraint results for the NGCG model are ωx=-1.0510(-0.1685)(+0.1563)(1σ)(-0.2398)(+0.2226)(2σ),η=1.0117(-0.0502)(+0.0469)(1σ)(-0.0716)(+0.0693)(2σ) and Ωx=0.7297(-0.0276)(+0.0229)(1σ)(-0.0402)(+0.0329)(2σ),which give a rather stringent constraint.From the results,we can see that a phantom model is slightly favored and the proba-bility that energy transfers from dark matter to dark energy is a little larger than the inverse.
Observations of CMEs and Models of the Eruptive Corona
Gopalswamy, Nat
2012-01-01
It is now realized that coronal mass ejections (CMEs) are the most energetic phenomenon in the heliosphere. Although early observations (in the 1970s and 19805) revealed most of the properties of CMEs, it is the extended and uniform data set from the Solar and Heliospheric Observatory (SOHO) mission that helped us consolidate our knowledge on CMEs. The Solar Terrestrial Relations Observatory (STEREO) mission has provided direct confirmation of the three-dimensional structure of CMEs. The broadside view provided by the STEREO coronagraphs helped us estimate the width of the halo CMEs and hence validate CME cone models. Current theoretical ideas on the internal structure of CMEs suggest that a flux rope is central to the CME structure, which has considerable observational support both from remote-sensing and in-situ observations. The flux-rope nature is also consistent with the post-eruption arcades with high-temperature plasma and the charge states observed within CMEs arriving at Earth. The quadrature observations also helped us understand the relation between the radial and expansion speeds of CMEs, which were only known from empirical relations in the past. This paper highlights some of these results obtained during solar cycle 23 and 24 and discusses implications for CME models.
Solanki, Jayesh Dalpatbhai; Basida, Sanket D; Mehta, Hemant B; Panjwani, Sunil J; Gadhavi, Bhakti P; Patel, Pathik
2016-01-01
Type 2 diabetes mellitus (T2DM) is a proven threat of cardiac dysautonomia with paucity of studies from India. Poor disease control makes it further worse with co-existence of hypertension in majority. Heart rate variability (HRV) is a validated noninvasive tool to assess cardiac autonomic status. We studied HRV parameters of type 2 diabetics looking for effects of disease control and other co-existing risk factors. Ninety-eight hypertensive and forty normotensive under-treatment, Gujarati type 2 diabetics were evaluated for disease control and risk stratification. Five minutes resting, HRV was measured by Variowin HR, software-based instrument, using standard protocols to record time domain, frequency domain, and Poincare plot HRV parameters. They were compared between subgroups for the difference with P < 0.05 defining statistical significance. All HRV parameters were reduced in type 2 diabetics, having mean age 56 years, mean duration 6 years with poor glycemic but comparatively better pressure control. HRV parameters were significantly not different in good compared to poor glycemics or in subjects with optimum pressure control than those without it. Results did not differ significantly, by the presence of individual cardiovascular risk factor in diabetics except resting heart rate. Our findings of HRV suggest that type 2 diabetics with poor glycemic control do not have a significant difference of cardiac dysautonomia by pressure control, glycemic control, and absence of risk cardiovascular factor. It suggests diabetes as a major cause for cardiac dysautonomia, residual risk despite treatment and need for HRV screening, strict glycemic control, and further studies.
Directory of Open Access Journals (Sweden)
Jayesh Dalpatbhai Solanki
2016-01-01
Full Text Available Background: Type 2 diabetes mellitus (T2DM is a proven threat of cardiac dysautonomia with paucity of studies from India. Poor disease control makes it further worse with co-existence of hypertension in majority. Heart rate variability (HRV is a validated noninvasive tool to assess cardiac autonomic status. Aim: We studied HRV parameters of type 2 diabetics looking for effects of disease control and other co-existing risk factors. Materials and Methods: Ninety-eight hypertensive and forty normotensive under–treatment, Gujarati type 2 diabetics were evaluated for disease control and risk stratification. Five minutes resting, HRV was measured by Variowin HR, software-based instrument, using standard protocols to record time domain, frequency domain, and Poincare plot HRV parameters. They were compared between subgroups for the difference with P< 0.05 defining statistical significance. Results: All HRV parameters were reduced in type 2 diabetics, having mean age 56 years, mean duration 6 years with poor glycemic but comparatively better pressure control. HRV parameters were significantly not different in good compared to poor glycemics or in subjects with optimum pressure control than those without it. Results did not differ significantly, by the presence of individual cardiovascular risk factor in diabetics except resting heart rate. Conclusion: Our findings of HRV suggest that type 2 diabetics with poor glycemic control do not have a significant difference of cardiac dysautonomia by pressure control, glycemic control, and absence of risk cardiovascular factor. It suggests diabetes as a major cause for cardiac dysautonomia, residual risk despite treatment and need for HRV screening, strict glycemic control, and further studies.
Networking Sensor Observations, Forecast Models & Data Analysis Tools
Falke, S. R.; Roberts, G.; Sullivan, D.; Dibner, P. C.; Husar, R. B.
2009-12-01
This presentation explores the interaction between sensor webs and forecast models and data analysis processes within service oriented architectures (SOA). Earth observation data from surface monitors and satellite sensors and output from earth science models are increasingly available through open interfaces that adhere to web standards, such as the OGC Web Coverage Service (WCS), OGC Sensor Observation Service (SOS), OGC Web Processing Service (WPS), SOAP-Web Services Description Language (WSDL), or RESTful web services. We examine the implementation of these standards from the perspective of forecast models and analysis tools. Interoperable interfaces for model inputs, outputs, and settings are defined with the purpose of connecting them with data access services in service oriented frameworks. We review current best practices in modular modeling, such as OpenMI and ESMF/Mapl, and examine the applicability of those practices to service oriented sensor webs. In particular, we apply sensor-model-analysis interfaces within the context of wildfire smoke analysis and forecasting scenario used in the recent GEOSS Architecture Implementation Pilot. Fire locations derived from satellites and surface observations and reconciled through a US Forest Service SOAP web service are used to initialize a CALPUFF smoke forecast model. The results of the smoke forecast model are served through an OGC WCS interface that is accessed from an analysis tool that extract areas of high particulate matter concentrations and a data comparison tool that compares the forecasted smoke with Unattended Aerial System (UAS) collected imagery and satellite-derived aerosol indices. An OGC WPS that calculates population statistics based on polygon areas is used with the extract area of high particulate matter to derive information on the population expected to be impacted by smoke from the wildfires. We described the process for enabling the fire location, smoke forecast, smoke observation, and
Some observational tests of a minimal galaxy formation model
Cohn, J. D.
2017-04-01
Dark matter simulations can serve as a basis for creating galaxy histories via the galaxy-dark matter connection. Here, one such model by Becker is implemented with several variations on three different dark matter simulations. Stellar mass and star formation rates are assigned to all simulation subhaloes at all times, using subhalo mass gain to determine stellar mass gain. The observational properties of the resulting galaxy distributions are compared to each other and observations for a range of redshifts from 0 to 2. Although many of the galaxy distributions seem reasonable, there are noticeable differences as simulations, subhalo mass gain definitions or subhalo mass definitions are altered, suggesting that the model should change as these properties are varied. Agreement with observations may improve by including redshift dependence in the added-by-hand random contribution to star formation rate. There appears to be an excess of faint quiescent galaxies as well (perhaps due in part to differing definitions of quiescence). The ensemble of galaxy formation histories for these models tend to have more scatter around their average histories (for a fixed final stellar mass) than the two more predictive and elaborate semi-analytic models of Guo et al. and Henriques et al., and require more basis fluctuations (using principal component analysis) to capture 90 per cent of the scatter around their average histories. The codes to plot model predictions (in some cases alongside observational data) are publicly available to test other mock catalogues at https://github.com/jdcphysics/validation/. Information on how to use these codes is in Appendix A.
Quantitative comparisons of satellite observations and cloud models
Wang, Fang
Microwave radiation interacts directly with precipitating particles and can therefore be used to compare microphysical properties found in models with those found in nature. Lower frequencies (minimization procedures but produce different CWP and RWP. The similarity in Tb can be attributed to comparable Total Water Path (TWP) between the two retrievals while the disagreement in the microphysics is caused by their different degrees of constraint of the cloud/rain ratio by the observations. This situation occurs frequently and takes up 46.9% in the one month 1D-Var retrievals examined. To attain better constrained cloud/rain ratios and improved retrieval quality, this study suggests the implementation of higher microwave frequency channels in the 1D-Var algorithm. Cloud Resolving Models (CRMs) offer an important pathway to interpret satellite observations of microphysical properties of storms. High frequency microwave brightness temperatures (Tbs) respond to precipitating-sized ice particles and can, therefore, be compared with simulated Tbs at the same frequencies. By clustering the Tb vectors at these frequencies, the scene can be classified into distinct microphysical regimes, in other words, cloud types. The properties for each cloud type in the simulated scene are compared to those in the observation scene to identify the discrepancies in microphysics within that cloud type. A convective storm over the Amazon observed by the Tropical Rainfall Measuring Mission (TRMM) is simulated using the Regional Atmospheric Modeling System (RAMS) in a semi-ideal setting, and four regimes are defined within the scene using cluster analysis: the 'clear sky/thin cirrus' cluster, the 'cloudy' cluster, the 'stratiform anvil' cluster and the 'convective' cluster. The relationship between Tb difference of 37 and 85 GHz and Tb at 85 GHz is found to contain important information of microphysical properties such as hydrometeor species and size distributions. Cluster
Adjoint inversion modeling of Asian dust emission using lidar observations
Directory of Open Access Journals (Sweden)
K. Yumimoto
2008-06-01
Full Text Available A four-dimensional variational (4D-Var data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4 is applied to an adjoint inversion of a heavy dust event over eastern Asia during 20 March–4 April 2007. The vertical profiles of the dust extinction coefficients derived from NIES Lidar network are directly assimilated, with validation using observation data. Two experiments assess impacts of observation site selection: Experiment A uses five Japanese observation sites located downwind of dust source regions; Experiment B uses these and two other sites near source regions. Assimilation improves the modeled dust extinction coefficients. Experiment A and Experiment B assimilation results are mutually consistent, indicating that observations of Experiment A distributed over Japan can provide comprehensive information related to dust emission inversion. Time series data of dust AOT calculated using modeled and Lidar dust extinction coefficients improve the model results. At Seoul, Matsue, and Toyama, assimilation reduces the root mean square differences of dust AOT by 35–40%. However, at Beijing and Tsukuba, the RMS differences degrade because of fewer observations during the heavy dust event. Vertical profiles of the dust layer observed by CALIPSO are compared with assimilation results. The dense dust layer was trapped at potential temperatures (θ of 280–300 K and was higher toward the north; the model reproduces those characteristics well. Latitudinal distributions of modeled dust AOT along the CALIPSO orbit paths agree well with those of CALIPSO dust AOT, OMI AI, and MODIS coarse-mode AOT, capturing the latitude at which AOTs and AI have high values. Assimilation results show increased dust emissions over the Gobi Desert and Mongolia; especially for 29–30 March, emission flux is about 10 times greater. Strong dust uplift fluxes over the Gobi Desert and Mongolia cause the heavy dust event. Total optimized dust emissions are 57
A Theoretic Model for the Shock Observed in Geo-space
Institute of Scientific and Technical Information of China (English)
SHI Jian-Kui; WANG Xiao; ZHANG Tie-Long; Torkar Klaus; LIU Zhen-Xing
2005-01-01
An electrostatic model for the shock observed in the earth's polar region is established by deriving the "Sagdeev potential" from the magnetohydrodynamic equations in a cylindrical coordinate system. The results show that the shock can develop from the ion acoustic wave or ion cyclotron wave. in the polar region, and can exist when the Mach number M and the initial electric field E0 satisfy the condition of |(a/M2 - 1) E0| = 1. Also, some features of the shock wave are discussed. The result can interpret the electrostatic shock observed in the earth's polar region.
Solar spectral irradiance variability in cycle 24: observations and models
Directory of Open Access Journals (Sweden)
Marchenko Sergey V.
2016-01-01
Full Text Available Utilizing the excellent stability of the Ozone Monitoring Instrument (OMI, we characterize both short-term (solar rotation and long-term (solar cycle changes of the solar spectral irradiance (SSI between 265 and 500 nm during the ongoing cycle 24. We supplement the OMI data with concurrent observations from the Global Ozone Monitoring Experiment-2 (GOME-2 and Solar Radiation and Climate Experiment (SORCE instruments and find fair-to-excellent, depending on wavelength, agreement among the observations, and predictions of the Naval Research Laboratory Solar Spectral Irradiance (NRLSSI2 and Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE-S models.
Observations and modeling of a tidal inlet dye tracer plume
Feddersen, Falk; Olabarrieta, Maitane; Guza, R. T.; Winters, D.; Raubenheimer, Britt; Elgar, Steve
2016-10-01
A 9 km long tracer plume was created by continuously releasing Rhodamine WT dye for 2.2 h during ebb tide within the southern edge of the main tidal channel at New River Inlet, NC on 7 May 2012, with highly obliquely incident waves and alongshore winds. Over 6 h from release, COAWST (coupled ROMS and SWAN, including wave, wind, and tidal forcing) modeled dye compares well with (aerial hyperspectral and in situ) observed dye concentration. Dye first was transported rapidly seaward along the main channel and partially advected across the ebb-tidal shoal until reaching the offshore edge of the shoal. Dye did not eject offshore in an ebb-tidal jet because the obliquely incident breaking waves retarded the inlet-mouth ebb-tidal flow and forced currents along the ebb shoal. The dye plume largely was confined to <4 m depth. Dye was then transported downcoast in the narrow (few 100 m wide) surfzone of the beach bordering the inlet at 0.3 m s-1 driven by wave breaking. Over 6 h, the dye plume is not significantly affected by buoyancy. Observed dye mass balances close indicating all released dye is accounted for. Modeled and observed dye behaviors are qualitatively similar. The model simulates well the evolution of the dye center of mass, lateral spreading, surface area, and maximum concentration, as well as regional ("inlet" and "ocean") dye mass balances. This indicates that the model represents well the dynamics of the ebb-tidal dye plume. Details of the dye transport pathways across the ebb shoal are modeled poorly perhaps owing to low-resolution and smoothed model bathymetry. Wave forcing effects have a large impact on the dye transport.
New Cosmological Model and Its Implications on Observational Data Interpretation
Directory of Open Access Journals (Sweden)
Vlahovic Branislav
2013-09-01
Full Text Available The paradigm of ΛCDM cosmology works impressively well and with the concept of inflation it explains the universe after the time of decoupling. However there are still a few concerns; after much effort there is no detection of dark matter and there are significant problems in the theoretical description of dark energy. We will consider a variant of the cosmological spherical shell model, within FRW formalism and will compare it with the standard ΛCDM model. We will show that our new topological model satisfies cosmological principles and is consistent with all observable data, but that it may require new interpretation for some data. Considered will be constraints imposed on the model, as for instance the range for the size and allowed thickness of the shell, by the supernovae luminosity distance and CMB data. In this model propagation of the light is confined along the shell, which has as a consequence that observed CMB originated from one point or a limited space region. It allows to interpret the uniformity of the CMB without inflation scenario. In addition this removes any constraints on the uniformity of the universe at the early stage and opens a possibility that the universe was not uniform and that creation of galaxies and large structures is due to the inhomogeneities that originated in the Big Bang.
A sliding mode observer for hemodynamic characterization under modeling uncertainties
Zayane, Chadia
2014-06-01
This paper addresses the case of physiological states reconstruction in a small region of the brain under modeling uncertainties. The misunderstood coupling between the cerebral blood volume and the oxygen extraction fraction has lead to a partial knowledge of the so-called balloon model describing the hemodynamic behavior of the brain. To overcome this difficulty, a High Order Sliding Mode observer is applied to the balloon system, where the unknown coupling is considered as an internal perturbation. The effectiveness of the proposed method is illustrated through a set of synthetic data that mimic fMRI experiments.
Constraining interacting dark energy models with latest cosmological observations
Xia, Dong-Mei; Wang, Sai
2016-11-01
The local measurement of H0 is in tension with the prediction of Λ cold dark matter model based on the Planck data. This tension may imply that dark energy is strengthened in the late-time Universe. We employ the latest cosmological observations on cosmic microwave background, the baryon acoustic oscillation, large-scale structure, supernovae, H(z) and H0 to constrain several interacting dark energy models. Our results show no significant indications for the interaction between dark energy and dark matter. The H0 tension can be moderately alleviated, but not totally released.
Constraining interacting dark energy models with latest cosmological observations
Xia, Dong-Mei
2016-01-01
The local measurement of $H_0$ is in tension with the prediction of $\\Lambda$CDM model based on the Planck data. This tension may imply that dark energy is strengthened in the late-time Universe. We employ the latest cosmological observations on CMB, BAO, LSS, SNe, $H(z)$ and $H_0$ to constrain several interacting dark energy models. Our results show no significant indications for the interaction between dark energy and dark matter. The $H_0$ tension can be moderately alleviated, but not totally released.
Altitude dependence of atmospheric temperature trends: Climate models versus observation
Douglass, D H; Singer, F
2004-01-01
As a consequence of greenhouse forcing, all state of the art general circulation models predict a positive temperature trend that is greater for the troposphere than the surface. This predicted positive trend increases in value with altitude until it reaches a maximum ratio with respect to the surface of as much as 1.5 to 2.0 at about 200 to 400 hPa. However, the temperature trends from several independent observational data sets show decreasing as well as mostly negative values. This disparity indicates that the three models examined here fail to account for the effects of greenhouse forcings.
The s Process: Nuclear Physics, Stellar Models, Observations
Kaeppeler, Franz; Bisterzo, Sara; Aoki, Wako
2010-01-01
Nucleosynthesis in the s process takes place in the He burning layers of low mass AGB stars and during the He and C burning phases of massive stars. The s process contributes about half of the element abundances between Cu and Bi in solar system material. Depending on stellar mass and metallicity the resulting s-abundance patterns exhibit characteristic features, which provide comprehensive information for our understanding of the stellar life cycle and for the chemical evolution of galaxies. The rapidly growing body of detailed abundance observations, in particular for AGB and post-AGB stars, for objects in binary systems, and for the very faint metal-poor population represents exciting challenges and constraints for stellar model calculations. Based on updated and improved nuclear physics data for the s-process reaction network, current models are aiming at ab initio solution for the stellar physics related to convection and mixing processes. Progress in the intimately related areas of observations, nuclear...
The solar dynamo: inferences from observations and modeling
Kitchatinov, L L
2014-01-01
It can be shown on observational grounds that two basic effects of dynamo theory for solar activity - production of the toroidal field from the poloidal one by differential rotation and reverse conversion of the toroidal field to the poloidal configuration by helical motions - are operating in the Sun. These two effects, however, do not suffice for constructing a realistic model for the solar dynamo. Only when a non-local version of the alpha-effect is applied, is downward diamagnetic pumping included and field advection by the equatorward meridional flow near the base of the convection zone allowed for, can the observed activity cycles be closely reproduced. Fluctuations in the alpha-effect can be estimated from sunspot data. Dynamo models with fluctuating parameters reproduce irregularities of solar cycles including the grand activity minima. The physics of parametric excitation of irregularities remains, however, to be understood.
Modeling Earth Albedo Currents on Sun Sensors for Improved Vector Observations
DEFF Research Database (Denmark)
Bhanderi, Dan
2006-01-01
Earth albedo influences vector measurements of the solar line of sight vector, due to the induced current on in the photo voltaics of Sun sensors. Although advanced digital Sun sensors exist, these are typically expensive and may not be suited for satellites in the nano or pico-class. Previously...... data, showing significant improvement in the Earth albedo induced current estimates. Additionally an algorithm for utilizing the Earth albedo model in obtaining a vector observation pair which is superior to the solar line of sight vector pair. It is concluded that the Earth albedo model is valid...
Distribution of [sup 32]Si in the world ocean: Model compared to observation
Energy Technology Data Exchange (ETDEWEB)
Peng, T.H. (Oak Ridge National Lab., TN (United States)); Maier-Reimer, E. (Max-Planck Institut fuer Meteorologie, Hamburg (Germany)); Broecker, W.S. (Columbia Univ., Palisades, NY (United States))
1993-06-01
The most difficult measurement of the GEOSECS survey was that of silicon 32. This paper compares the observed distribution from the survey with the distributions predicted from two global ocean models. Existing measurements show little surface to bottom or ocean to ocean variations where as the models predict three to five fold greater ratios in the deep Atlantic Ocean than in the deep Pacific and Indian oceans. A flaw in the measurements is one possibility for the discrepancy. 9 refs., 8 figs., 5 tabs.
Jiang, Fayu; Yang, Shuhong
2015-01-01
We present multi-wavelength observations of a fan-spine dome in the active region NOAA 11996 with the \\textit{Interface Region Imaging Spectrograph} (\\emph{IRIS}) and the Atmospheric Imaging Assembly on board the \\textit{Solar Dynamics Observatory} (\\emph{SDO}) on March 9, 2014. The destruction of the fan-spine topology owing to the interaction between its magnetic fields and an nearby emerging flux region (EFR) is firstly observed. The line-of-sight magnetograms from the Helioseismic and Magnetic Imager on board the \\emph{SDO} reveal that the dome is located on the mixed magnetic fields, with its rim rooted in the redundant positive polarity surrounding the minority parasitic negative fields. The fan surface of the dome consists of a filament system and recurring jets are observed along its spine. The jet occurring around 13:54 UT is accompanied with a quasi-circular ribbon that brightens in the clockwise direction along the bottom rim of the dome, which may indicate an occurrence of slipping reconnection in...
Observations, Thermochemical Calculations, and Modeling of Exoplanetary Atmospheres
Blecic, Jasmina
2016-01-01
This dissertation as a whole aims to provide means to better understand hot-Jupiter planets through observing, performing thermochemical calculations, and modeling their atmospheres. We used Spitzer multi-wavelength secondary-eclipse observations and targets with high signal-to-noise ratios, as their deep eclipses allow us to detect signatures of spectral features and assess planetary atmospheric structure and composition with greater certainty. Chapter 1 gives a short introduction. Chapter 2 presents the Spitzer secondary-eclipse analysis and atmospheric characterization of WASP-14b. WASP-14b is a highly irradiated, transiting hot Jupiter. By applying a Bayesian approach in the atmospheric analysis, we found an absence of thermal inversion contrary to theoretical predictions. Chapter 3 describes the infrared observations of WASP-43b Spitzer secondary eclipses, data analysis, and atmospheric characterization. WASP-43b is one of the closest-orbiting hot Jupiters, orbiting one of the coolest stars with a hot Ju...
Mock Observations of Blue Stragglers in Globular Cluster Models
Sills, Alison; Chatterjee, Sourav; Rasio, Frederic A
2013-01-01
We created artificial color-magnitude diagrams of Monte Carlo dynamical models of globular clusters, and then used observational methods to determine the number of blue stragglers in those clusters. We compared these blue stragglers to various cluster properties, mimicking work that has been done for blue stragglers in Milky Way globular clusters to determine the dominant formation mechanism(s) of this unusual stellar population. We find that a mass-based prescription for selecting blue stragglers will choose approximately twice as many blue stragglers than a selection criterion that was developed for observations of real clusters. However, the two numbers of blue stragglers are well-correlated, so either selection criterion can be used to characterize the blue straggler population of a cluster. We confirm previous results that the simplified prescription for the evolution of a collision or merger product in the BSE code overestimates the lifetime of collision products. Because our observationally-motivated s...
Observational & modeling analysis of surface heat and moisture fluxes
Energy Technology Data Exchange (ETDEWEB)
Smith, E. [Florida State Univ., Tallahassee, FL (United States)
1995-09-01
An observational and modeling study was conducted to help assess how well current GCMs are predicting surface fluxes under the highly variable cloudiness and flow conditions characteristic of the real atmosphere. The observational data base for the study was obtained from a network of surface flux stations operated during the First ISLSCP Field Experiment (FIFE). The study included examination of a surface-driven secondary circulation in the boundary layer resulting from a persistent cross-site gradient in soil moisture, to demonstrate the sensitivity of boundary layer dynamics to heterogeneous surface fluxes, The performance of a biosphere model in reproducing the measured surface fluxes was evaluated with and without the use of satellite retrieval of three key canopy variables with RMS uncertainties commensurate with those of the measurements themselves. Four sensible heat flux closure schemes currently being used in GCMs were then evaluated against the FIFE observations. Results indicate that the methods by which closure models are calibrated lead to exceedingly large errors when the schemes are applied to variable boundary layer conditions. 4 refs., 2 figs.
Flare-CME Models: An Observational Perspective (Invited Review)
Schmieder, B.; Aulanier, G.; Vršnak, B.
2015-12-01
Eruptions, flares, and coronal mass ejection (CMEs) are due to physical phenomena mainly driven by an initially force-free current-carrying magnetic field. We review some key observations relevant to the current theoretical trigger mechanisms of the eruption and to the energy release via reconnection. Sigmoids observed in X-rays and UV, as well as the pattern (double J-shaped) of electric currents in the photosphere show clear evidence of the existence of currents parallel to the magnetic field and can be the signature of a flux rope that is detectable in CMEs. The magnetic helicity of filaments and active regions is an interesting indirectly measurable parameter because it can quantify the twist of the flux rope. On the other hand, the magnetic helicity of the solar structures allows us to associate solar eruptions and magnetic clouds in the heliosphere. The magnetic topology analysis based on the 3D magnetic field extrapolated from vector magnetograms is a good tool for identifying the reconnection locations (null points and/or the 3D large volumes - hyperbolic flux tube, HFT). Flares are associated more with quasi-separatrix layers (QSLs) and HFTs than with a single null point, which is a relatively rare case. We review various mechanisms that have been proposed to trigger CMEs and their observable signatures: by "breaking" the field lines overlying the flux rope or by reconnection below the flux rope to reduce the magnetic tension, or by letting the flux rope to expand until it reaches a minimum threshold height (loss of equilibrium or torus instability). Additional mechanisms are commonly operating in the solar atmosphere. Examples of observations are presented throughout the article and are discussed in this framework.
Coronal Loops: Observations and Modeling of Confined Plasma
Directory of Open Access Journals (Sweden)
Fabio Reale
2014-07-01
Full Text Available Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered and, therefore, topics such as loop oscillations and flaring loops (except for non-solar ones, which provide information on stellar loops are not specifically addressed here. The observational section discusses the classification, populations, and the morphology of coronal loops, its relationship with the magnetic field, and the loop stranded structure. The section continues with the thermal properties and diagnostics of the loop plasma, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics, hot and cool flows, and waves are illustrated. In the modeling section, some basics of loop physics are provided, supplying fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are divided into those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. More specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC and impulsive (DC heating. Large-scale models including atmosphere boxes and the magnetic field are also discussed. Finally, a brief discussion about stellar coronal loops is followed by highlights and open questions.
Directory of Open Access Journals (Sweden)
Rebecca B Hoyle
Full Text Available Phenotypic differences of genetically identical cells under the same environmental conditions have been attributed to the inherent stochasticity of biochemical processes. Various mechanisms have been suggested, including the existence of alternative steady states in regulatory networks that are reached by means of stochastic fluctuations, long transient excursions from a stable state to an unstable excited state, and the switching on and off of a reaction network according to the availability of a constituent chemical species. Here we analyse a detailed stochastic kinetic model of two-component system signalling in bacteria, and show that alternative phenotypes emerge in the absence of these features. We perform a bifurcation analysis of deterministic reaction rate equations derived from the model, and find that they cannot reproduce the whole range of qualitative responses to external signals demonstrated by direct stochastic simulations. In particular, the mixed mode, where stochastic switching and a graded response are seen simultaneously, is absent. However, probabilistic and equation-free analyses of the stochastic model that calculate stationary states for the mean of an ensemble of stochastic trajectories reveal that slow transcription of either response regulator or histidine kinase leads to the coexistence of an approximate basal solution and a graded response that combine to produce the mixed mode, thus establishing its essential stochastic nature. The same techniques also show that stochasticity results in the observation of an all-or-none bistable response over a much wider range of external signals than would be expected on deterministic grounds. Thus we demonstrate the application of numerical equation-free methods to a detailed biochemical reaction network model, and show that it can provide new insight into the role of stochasticity in the emergence of phenotypic diversity.
Can brane dark energy model be probed observationally by distant supernovae?
Szydlowski, M; Szydlowski, Marek; Godlowski, Wlodzimierz
2006-01-01
The recent astronomical measurements of distant supernovae as well as other observations indicate that our universe is presently accelerating. There are different proposals for the explanation of this acceleration. Most of these proposals require the existence of exotic matter with negative pressure violating the strong energy condition. On the other hand, there have appeared many models which offer dramatically different mechanism for the current acceleration, in which dark energy emerges from the gravity sector rather than from the matter sector. In this paper, we compare the concordance $\\Lambda$CDM model with the braneworld models of dark energy by using Akaike and Bayesian informative critera. We show that, although this model has extra parameters (the fundamental constants of the bulk space) resulting in an improved fit to the SNIa data, these new parameters are actually not important for description of present acceleration epoch. With the example of the Sahni--Shtanov braneworld model \\cite{Shtanov03},...
An observational model for biomechanical assessment of sprint kayaking technique.
McDonnell, Lisa K; Hume, Patria A; Nolte, Volker
2012-11-01
Sprint kayaking stroke phase descriptions for biomechanical analysis of technique vary among kayaking literature, with inconsistencies not conducive for the advancement of biomechanics applied service or research. We aimed to provide a consistent basis for the categorisation and analysis of sprint kayak technique by proposing a clear observational model. Electronic databases were searched using key words kayak, sprint, technique, and biomechanics, with 20 sources reviewed. Nine phase-defining positions were identified within the kayak literature and were divided into three distinct types based on how positions were defined: water-contact-defined positions, paddle-shaft-defined positions, and body-defined positions. Videos of elite paddlers from multiple camera views were reviewed to determine the visibility of positions used to define phases. The water-contact-defined positions of catch, immersion, extraction, and release were visible from multiple camera views, therefore were suitable for practical use by coaches and researchers. Using these positions, phases and sub-phases were created for a new observational model. We recommend that kayaking data should be reported using single strokes and described using two phases: water and aerial. For more detailed analysis without disrupting the basic two-phase model, a four-sub-phase model consisting of entry, pull, exit, and aerial sub-phases should be used.
Observer analysis and its impact on task performance modeling
Jacobs, Eddie L.; Brown, Jeremy B.
2014-05-01
Fire fighters use relatively low cost thermal imaging cameras to locate hot spots and fire hazards in buildings. This research describes the analyses performed to study the impact of thermal image quality on fire fighter fire hazard detection task performance. Using human perception data collected by the National Institute of Standards and Technology (NIST) for fire fighters detecting hazards in a thermal image, an observer analysis was performed to quantify the sensitivity and bias of each observer. Using this analysis, the subjects were divided into three groups representing three different levels of performance. The top-performing group was used for the remainder of the modeling. Models were developed which related image quality factors such as contrast, brightness, spatial resolution, and noise to task performance probabilities. The models were fitted to the human perception data using logistic regression, as well as probit regression. Probit regression was found to yield superior fits and showed that models with not only 2nd order parameter interactions, but also 3rd order parameter interactions performed the best.
Observational constraints on non-minimally coupled Galileon model
Jamil, Mubasher; Myrzakulov, Ratbay; 10.1140/epjc/s10052-013-2300-6
2013-01-01
As an extension of Dvali-Gabadadze-Porrati (DGP) model, the Galileon theory has been proposed to explain the "self-accelerating problem" and "ghost instability problem". In this Paper, we extend the Galileon theory by considering a non-minimally coupled Galileon scalar with gravity. We find that crossing of phantom divide line is possible for such model. Moreover we perform the statefinder analysis and $Om(z)$ diagnostic and constraint the model parameters from the latest Union 2 type Ia Supernova (SNe Ia) set and the baryonic acoustic oscillation (BAO). Using these data sets, we obtain the constraints $\\Omega_\\text{m0}=0.263_{-0.031}^{+0.031}$, $n=1.53_{-0.37}^{+0.21}$ (at the 95% confidence level) with $\\chi^2_{\\text{min}}=473.376$. Further we study the evolution of the equation of state parameter for the effective dark energy and observe that SNe Ia + BAO prefers a phantom-like dark energy.
Shen, Chung-Wei; Chen, Yi-Hau
2015-10-01
Missing observations and covariate measurement error commonly arise in longitudinal data. However, existing methods for model selection in marginal regression analysis of longitudinal data fail to address the potential bias resulting from these issues. To tackle this problem, we propose a new model selection criterion, the Generalized Longitudinal Information Criterion, which is based on an approximately unbiased estimator for the expected quadratic error of a considered marginal model accounting for both data missingness and covariate measurement error. The simulation results reveal that the proposed method performs quite well in the presence of missing data and covariate measurement error. On the contrary, the naive procedures without taking care of such complexity in data may perform quite poorly. The proposed method is applied to data from the Taiwan Longitudinal Study on Aging to assess the relationship of depression with health and social status in the elderly, accommodating measurement error in the covariate as well as missing observations.
Meteor layers in the Martian ionosphere: Observations and Modelling
Peter, Kerstin; Molina Cuberos, Gregorio J.; Witasse, Olivier; Paetzold, Martin
Observations by the radio science experiments MaRS on Mars Express and VeRa on Venus Express revealed the appearance of additional electron density layers in the Martian and Venu-sian ionosphere below the common secondary layers in some of the ionospheric profiles. This may be an indicator for the signature of meteoric particles in the Martian atmosphere. There are two main sources of meteoric flux into planetary atmospheres: the meteoroid stream com-ponent whose origin is related to comets, and the sporadic meteoroid component which has its source in body collisions i.e. in the Kuiper belt or the asteoroid belt. This paper will present the detection status for the Martian meteor layers in MaRS electron density profiles and the first steps towards modelling this feature. The presented meteor layer model will show the influence of the sporadic meteoric component on the Martian ionosphere. Input param-eters to this model are the ablation profiles of atomic Magnesium and Iron in the Martian atmosphere caused by sporadic meteoric influx, the neutral atmosphere which is taken from the Mars Climate Database and electron density profiles for an undisturbed ionosphere from a simple photochemical model. The meteor layer model includes the effects of molecular and eddy diffusion processes of metallic species and contains chemical reaction schemes for atomic Magnesium and Iron. It calculates the altitude-density-profiles for several metallic species on the basis of Mg and Fe in chemical equilibrium by analytical solution of the reaction equations. A first comparison of model and observed meteoric structures in the Martian ionosphere will be presented.
Recent space shuttle observations of the South Atlantic anomaly and the radiation belt models
Konradi, A.; Badhwar, G. D.; Braby, L. A.
1994-01-01
Active ingredients consisting of Tissue Equivalent Proportional Counter (TEPC) and a Proton and Heavy Ion Detector (PHIDE) have been carried on a number of Space Shuttle flights. These instruments have allowed us to map out parts of the South Atlantic Particle Anomaly (SAA) and to compare some of it's features with predictions of the AP-8 energetic proton flux models. We have observed that consistent with the generally observed westward drift of the surface features of the terrestial magnetic field of the SAA has moved west by about 6.9 degrees longitude between the epoch year 1970 of the AP-8 solar maximum model and the Space Shuttle observations made twenty years later. However, calculations indicate that except for relatively brief periods following very large magnetic storms the SAA seems to occupy the same position in L-space as in 1970. After the great storm of 24 March 1991 reconfiguration of the inner radiation belt and/or proton injection into the inner belt, a second energetic proton belt was observed to form at approximately equal to 2. As confirmed by a subsequent flight observations, this belt was shown to persist at least for six months. Our measurements also indicate an upward shift in the L location of the primary belt from L = 1.4 to L = 1.5. In addition we confirm through direct real time observations the existence and the approximate magnitude of the East-West effect. If the need exists for improved and updated radiation belt models in the Space Station era, these observations point out the specific features that should be considered and incorporated when this task is undertaken.
Sarkar, Abhijit; Blondé, Laurent; Le Callet, Patrick; Autrusseau, Florent; Stauder, Jürgen; Morvan, Patrick
2009-01-01
International audience; This paper compares CIE 2006 model predictions and the 1964 10° standard colorimetric observer with the average observer data from three distinct subgroups of 47 Stiles-Burch observers formed on the basis of observer ages. For two of these subgroups, the long-wave sensitive (x-) color matching functions obtained from the CIE06 model did not accurately predict the intra-group average observer functions. In terms of display color perception, the prediction error is refle...
Tchapnda, S B; Tchapnda, Sophonie Blaise; Noutchegueme, Norbert
2003-01-01
The Einstein-Vlasov system describes a self-gravitating, collisionless gas within the framework of general relativity. We investigate the initial value problem in a cosmological setting with surface symmetry and a non-zero cosmological constant and prove local existence and continuation criteria in both time directions. The continuation criterion says that as long as the maximum velocity remains bounded and the lapse function remains bounded then the solution can be continued. This applies to either time direction.
Directory of Open Access Journals (Sweden)
Rohit Mittal
Full Text Available While much of cancer immunology research has focused on anti-tumor immunity both systemically and within the tumor microenvironment, little is known about the impact of pre-existing malignancy on pathogen-specific immune responses. Here, we sought to characterize the antigen-specific CD8+ T cell response following a bacterial infection in the setting of pre-existing pancreatic adenocarcinoma. Mice with established subcutaneous pancreatic adenocarcinomas were infected with Listeria monocytogenes, and antigen-specific CD8+ T cell responses were compared to those in control mice without cancer. While the kinetics and magnitude of antigen-specific CD8+ T cell expansion and accumulation was comparable between the cancer and non-cancer groups, bacterial antigen-specific CD8+ T cells and total CD4+ and CD8+ T cells in cancer mice exhibited increased expression of the coinhibitory receptors BTLA, PD-1, and 2B4. Furthermore, increased inhibitory receptor expression was associated with reduced IFN-γ and increased IL-2 production by bacterial antigen-specific CD8+ T cells in the cancer group. Taken together, these data suggest that cancer's immune suppressive effects are not limited to the tumor microenvironment, but that pre-existing malignancy induces phenotypic exhaustion in T cells by increasing expression of coinhibitory receptors and may impair pathogen-specific CD8+ T cell functionality and differentiation.
Dust properties inside molecular clouds from coreshine modeling and observations
Lefèvre, Charlène; Juvela, Mika; Paladini, Roberta; Lallement, Rosine; Marshall, D J; Andersen, Morten; Bacmann, Aurore; Mcgee, Peregrine M; Montier, Ludovic; Noriega-Crespo, Alberto; Pelkonen, V -M; Ristorcelli, Isabelle; Steinacker, Jürgen
2014-01-01
Context. Using observations to deduce dust properties, grain size distribution, and physical conditions in molecular clouds is a highly degenerate problem. Aims. The coreshine phenomenon, a scattering process at 3.6 and 4.5 $\\mu$m that dominates absorption, has revealed its ability to explore the densest parts of clouds. We want to use this effect to constrain the dust parameters. The goal is to investigate to what extent grain growth (at constant dust mass) inside molecular clouds is able to explain the coreshine observations. We aim to find dust models that can explain a sample of Spitzer coreshine data. We also look at the consistency with near-infrared data we obtained for a few clouds. Methods. We selected four regions with a very high occurrence of coreshine cases: Taurus-Perseus, Cepheus, Chameleon and L183/L134. We built a grid of dust models and investigated the key parameters to reproduce the general trend of surface bright- nesses and intensity ratios of both coreshine and near-infrared observation...
Coronal loops above an Active Region - observation versus model
Bourdin, Philippe-A; Peter, Hardi
2014-01-01
We conducted a high-resolution numerical simulation of the solar corona above a stable active region. The aim is to test the field-line braiding mechanism for a sufficient coronal energy input. We also check the applicability of scaling laws for coronal loop properties like the temperature and density. Our 3D-MHD model is driven from below by Hinode observations of the photosphere, in particular a high-cadence time series of line-of-sight magnetograms and horizontal velocities derived from the magnetograms. This driving applies stress to the magnetic field and thereby delivers magnetic energy into the corona, where currents are induced that heat the coronal plasma by Ohmic dissipation. We compute synthetic coronal emission that we directly compare to coronal observations of the same active region taken by Hinode. In the model, coronal loops form at the same places as they are found in coronal observations. Even the shapes of the synthetic loops in 3D space match those found from a stereoscopic reconstruction ...
Land Surface Microwave Emissivity Dynamics: Observations, Analysis and Modeling
Tian, Yudong; Peters-Lidard, Christa D.; Harrison, Kenneth W.; Kumar, Sujay; Ringerud, Sarah
2014-01-01
Land surface microwave emissivity affects remote sensing of both the atmosphere and the land surface. The dynamical behavior of microwave emissivity over a very diverse sample of land surface types is studied. With seven years of satellite measurements from AMSR-E, we identified various dynamical regimes of the land surface emission. In addition, we used two radiative transfer models (RTMs), the Community Radiative Transfer Model (CRTM) and the Community Microwave Emission Modeling Platform (CMEM), to simulate land surface emissivity dynamics. With both CRTM and CMEM coupled to NASA's Land Information System, global-scale land surface microwave emissivities were simulated for five years, and evaluated against AMSR-E observations. It is found that both models have successes and failures over various types of land surfaces. Among them, the desert shows the most consistent underestimates (by approx. 70-80%), due to limitations of the physical models used, and requires a revision in both systems. Other snow-free surface types exhibit various degrees of success and it is expected that parameter tuning can improve their performances.
Atmospheric Circulation on Hot Jupiters: Modeling and Observable Signatures
Rauscher, Emily Christine
2010-12-01
Hot Jupiters are unlike any planets in our Solar System and yet one of the most common types of extrasolar planet discovered. These gas giants orbit their parent stars with periods of a few days. Expected to be tidally locked into synchronous rotation, hot Jupiters experience intense, asymmetric heating from stellar irradiation, such that day-night temperature contrasts could reach hundreds of degrees Kelvin. This unique state of radiative forcing, as well as the slow rotation rates of these planets, places hot Jupiters within a new regime of atmospheric circulation. Hot Jupiters have also been the first type of extrasolar planet with direct detections of their atmospheres, through measurements of emitted, reflected, and transmitted light. This thesis investigates observational methods to distinguish between various atmospheric models, observational signatures of potential atmospheric variability, and presents a three dimensional model with which to study hot Jupiter circulation patterns. First, we find that eclipse mapping is a technique that can be used to image the day sides of these planets and although this is beyond the ability of current instruments, it will be achievable with future missions, such as the James Webb Space Telescope. Second, we consider the signatures of large-scale atmospheric variability in measurements of secondary eclipses and thermal orbital phase curves. For various models we predict the amount of variation in eclipse depth, and the amplitudes and detailed shapes of phase curves. Lastly, we develop a three-dimensional model of hot Jupiter atmospheric dynamics with simplified forcing and adopt a set-up nearly identical to work by another group to facilitate code inter-comparison. Our results are broadly consistent with theirs, with a transonic flow and the hottest region of the atmosphere advected eastward of the substellar point. However, we note important differences and identify areas of concern for future modeling efforts.
Polar F-layer model-observation comparisons: a neutral wind surprise
Directory of Open Access Journals (Sweden)
J. J. Sojka
2005-01-01
Full Text Available The existence of a month-long continuous database of incoherent scatter radar observations of the ionosphere from the EISCAT Savlbard Radar (ESR at Longyearbyen, Norway, provides an unprecedented opportunity for model/data comparisons. Physics-based ionospheric models, such as the Utah State University Time Dependent Ionospheric Model (TDIM, are usually only compared with observations over restricted one or two day events or against climatological averages. In this study, using the ESR observations, the daily weather, day-to-day variability, and month-long climatology can be simultaneously addressed to identify modeling shortcomings and successes. Since for this study the TDIM is driven by climatological representations of the magnetospheric convection, auroral oval, neutral atmosphere, and neutral winds, whose inputs are solar and geomagnetic indices, it is not surprising that the daily weather cannot be reproduced. What is unexpected is that the horizontal neutral wind has come to the forefront as a decisive model input parameter in matching the diurnal morphology of density structuring seen in the observations.
Chemistry-transport modeling of the satellite observed distribution of tropical troposheric ozone
Directory of Open Access Journals (Sweden)
W. Peters
2002-01-01
Full Text Available We have compared the 14-year record of satellite derived tropical tropospheric ozone columns (TTOC from the NIMBUS--7 Total Ozone Mapping Spectrometer (TOMS to TTOC calculated by achemistry-transport model (CTM. An objective measure of error, based on the zonal distribution of TTOC in the tropics, is applied to perform this comparison systematically. In addition, the sensitivity of the model to several key processes in the tropics is quantified to select directions for future improvements. The comparisons indicate a widespread, systematic (20% discrepancy over the tropical Atlantic Ocean, which maximizes during austral Spring. Although independent evidence from ozonesondes shows that some of the disagreement is due to satellite overestimate of TTOC, the Atlantic mismatch is largely due to a misrepresentation of seasonally recurring processes in the model. Only minor differences between the model and observations over the Pacific occur, mostly due to interannual variability not captured by the model. Although chemical processes determine the TTOC extent, dynamical processes dominate the TTOC distribution, as the use of actual meteorology pertaining to the year of observations always leads to a better agreement with TTOC observations than using a random year or a climatology. The modeled TTOC is remarkably insensitive to many model parameters due to efficient feedbacks in the ozone budget. Nevertheless, the simulations would profit from an improved biomass burning calendar, as well as from an increase in NOx abundances in free tropospheric biomass burning plumes. The model showed the largest response to lightning NOx emissions, but systematic improvements could not be found. The use of multi-year satellite derived tropospheric data to systematically test and improve a CTM is a promising new addition to existing methods of model validation, and is a first step to integrating tropospheric satellite observations into global ozone modeling studies
This elusive objective existence
Mohrhoff, U
2004-01-01
Zurek's existential interpretation of quantum mechanics suffers from three classical prejudices, including the belief that space and time are intrinsically and infinitely differentiated. They compel him to relativize the concept of objective existence in two ways. The elimination of these prejudices makes it possible to recognize the quantum formalism's ontological implications - the relative and contingent reality of spatiotemporal distinctions and the extrinsic and finite spatiotemporal differentiation of the physical world - which in turn makes it possible to arrive at an unqualified objective existence. Contrary to a widespread misconception, viewing the quantum formalism as being fundamentally a probability algorithm does not imply that quantum mechanics is concerned with states of knowledge rather than states of Nature. On the contrary, it makes possible a complete and strongly objective description of the physical world that requires no reference to observers. What objectively exists, in a sense that r...
Further ALMA observations and detailed modeling of the Red Rectangle
Bujarrabal, V; Alcolea, J; Santander-Garcia, M; Van Winckel, H; Contreras, C Sanchez
2016-01-01
We present new high-quality ALMA observations of the Red Rectangle (a well known post-AGB object) in C17O J=6-5 and H13CN J=4-3 line emission and results from a new reduction of already published 13CO J=3-2 data. A detailed model fitting of all the molecular line data, including previous maps and single-dish spectra, was performed using a sophisticated code. These observations and the corresponding modeling allowed us to deepen the analysis of the nebular properties. We also stress the uncertainties in the model fitting. We confirm the presence of a rotating equatorial disk and an outflow, which is mainly formed of gas leaving the disk. The mass of the disk is ~ 0.01 Mo, and that of the CO-rich outflow is ~ 10 times smaller. High temperatures of ~ 100 K are derived for most components. From comparison of the mass values, we roughly estimate the lifetime of the rotating disk, which is found to be of about 10000 yr. Taking data of a few other post-AGB composite nebulae into account, we find that the lifetimes o...
Anisotropy in Fracking: A Percolation Model for Observed Microseismicity
Norris, J. Quinn; Turcotte, Donald L.; Rundle, John B.
2015-01-01
Hydraulic fracturing (fracking), using high pressures and a low viscosity fluid, allow the extraction of large quantiles of oil and gas from very low permeability shale formations. The initial production of oil and gas at depth leads to high pressures and an extensive distribution of natural fractures which reduce the pressures. With time these fractures heal, sealing the remaining oil and gas in place. High volume fracking opens the healed fractures allowing the oil and gas to flow to horizontal production wells. We model the injection process using invasion percolation. We use a 2D square lattice of bonds to model the sealed natural fractures. The bonds are assigned random strengths and the fluid, injected at a point, opens the weakest bond adjacent to the growing cluster of opened bonds. Our model exhibits burst dynamics in which the clusters extend rapidly into regions with weak bonds. We associate these bursts with the microseismic activity generated by fracking injections. A principal object of this paper is to study the role of anisotropic stress distributions. Bonds in the y-direction are assigned higher random strengths than bonds in the x-direction. We illustrate the spatial distribution of clusters and the spatial distribution of bursts (small earthquakes) for several degrees of anisotropy. The results are compared with observed distributions of microseismicity in a fracking injection. Both our bursts and the observed microseismicity satisfy Gutenberg-Richter frequency-size statistics.
Model and observed seismicity represented in a two dimensional space
Directory of Open Access Journals (Sweden)
M. Caputo
1976-06-01
Full Text Available In recent years theoretical seismology lias introduced
some formulae relating the magnitude and the seismic moment of earthquakes
to the size of the fault and the stress drop which generated the
earthquake.
In the present paper we introduce a model for the statistics of the
earthquakes based on these formulae. The model gives formulae which
show internal consistency and are also confirmed by observations.
For intermediate magnitudes the formulae reproduce also the trend
of linearity of the statistics of magnitude and moment observed in all the
seismic regions of the world. This linear trend changes into a curve with
increasing slope for large magnitudes and moment.
When a catalogue of the magnitudes and/or the seismic moment of
the earthquakes of a seismic region is available, the model allows to estimate
the maximum magnitude possible in the region.
Schlupp, A.; Sira, C.; Schmitt, K.; Schaming, M.
2013-12-01
In charge of intensity estimations in France, BCSF has collected and manually analyzed more than 47000 online individual macroseismic questionnaires since 2000 up to intensity VI. These macroseismic data allow us to estimate one SQI value (Single Questionnaire Intensity) for each form following the EMS98 scale. The reliability of the automatic intensity estimation is important as they are today used for automatic shakemaps communications and crisis management. Today, the automatic intensity estimation at BCSF is based on the direct use of thumbnails selected on a menu by the witnesses. Each thumbnail corresponds to an EMS-98 intensity value, allowing us to quickly issue an intensity map of the communal intensity by averaging the SQIs at each city. Afterwards an expert, to determine a definitive SQI, manually analyzes each form. This work is time consuming and not anymore suitable considering the increasing number of testimonies at BCSF. Nevertheless, it can take into account incoherent answers. We tested several automatic methods (USGS algorithm, Correlation coefficient, Thumbnails) (Sira et al. 2013, IASPEI) and compared them with 'expert' SQIs. These methods gave us medium score (between 50 to 60% of well SQI determined and 35 to 40% with plus one or minus one intensity degree). The best fit was observed with the thumbnails. Here, we present new approaches based on 3 statistical ranking methods as 1) Multinomial logistic regression model, 2) Discriminant analysis DISQUAL and 3) Support vector machines (SVMs). The two first methods are standard methods, while the third one is more recent. Theses methods could be applied because the BCSF has already in his database more then 47000 forms and because their questions and answers are well adapted for a statistical analysis. The ranking models could then be used as automatic method constrained on expert analysis. The performance of the automatic methods and the reliability of the estimated SQI can be evaluated thanks to
Probability distribution analysis of observational extreme events and model evaluation
Yu, Q.; Lau, A. K. H.; Fung, J. C. H.; Tsang, K. T.
2016-12-01
Earth's surface temperatures were the warmest in 2015 since modern record-keeping began in 1880, according to the latest study. In contrast, a cold weather occurred in many regions of China in January 2016, and brought the first snowfall to Guangzhou, the capital city of Guangdong province in 67 years. To understand the changes of extreme weather events as well as project its future scenarios, this study use statistical models to analyze on multiple climate data. We first use Granger-causality test to identify the attribution of global mean temperature rise and extreme temperature events with CO2 concentration. The four statistical moments (mean, variance, skewness, kurtosis) of daily maximum temperature distribution is investigated on global climate observational, reanalysis (1961-2010) and model data (1961-2100). Furthermore, we introduce a new tail index based on the four moments, which is a more robust index to measure extreme temperatures. Our results show that the CO2 concentration can provide information to the time series of mean and extreme temperature, but not vice versa. Based on our new tail index, we find that other than mean and variance, skewness is an important indicator should be considered to estimate extreme temperature changes and model evaluation. Among the 12 climate model data we investigate, the fourth version of Community Climate System Model (CCSM4) from National Center for Atmospheric Research performs well on the new index we introduce, which indicate the model have a substantial capability to project the future changes of extreme temperature in the 21st century. The method also shows its ability to measure extreme precipitation/ drought events. In the future we will introduce a new diagram to systematically evaluate the performance of the four statistical moments in climate model output, moreover, the human and economic impacts of extreme weather events will also be conducted.
Economic model of observation versus immediate resection of hepatic adenomas.
Vanounou, Tsafrir; Groeschl, Ryan T; Geller, David A; Marsh, J Wallis; Gamblin, T Clark
2012-09-15
For small asymptomatic hepatic adenomas (HA), available data are insufficient to establish the superiority of either observation or surgery. We sought to investigate the cost-effectiveness of two initial management strategies. We performed a comparative analysis of two theoretical cohorts of 100 patients with small (cash flow (DCF) models compared the net present value (NPV) of both treatment options at year 10 under three distinct progression rate scenarios. A break-even (BE) analysis was used to determine the BE point at which the NPV for observation and immediate surgery intersect. The NPV for immediate surgery was $1,733,955. The NPV for observation varied between $2,065,315-$2,745,631 for computed tomography (CT), $2,264,575-$2,929,541 for magnetic resonance imaging (MRI), and $802,837-$1,580,413 for ultrasound (US). The BE point was between 6 and 8 years for CT and 5-7 years for MRI. The BE point for US was not reached except in the highest progression rate scenario (12 years). This study highlights the importance of the underlying progression rate and the cost of imaging when following patients with asymptomatic HA. Overall, US surveillance is the most cost-efficient approach to observing small asymptomatic HA. If cross-sectional imaging is utilized, then immediate surgery is the most cost-effective decision at 5-8 years. Copyright © 2012 Wiley Periodicals, Inc.
Implications of RHESSI Flare Observations for Magnetic Reconnection Models
Holman, Gordon D.; Sui, Linhui; Dennis, Brian R.
2004-01-01
The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations of the 2002 April 15 solar flare and related flares provide compelling evidence for the formation of a large-scale, reconnecting current sheet in at least some flares. We describe the observed evolution of the April 15 flare in terms of magnetic reconnection models. We argue that the flare most likely evolved through magnetic geometries associated with super-slow reconnection (early rise phase), fast reconnection (impulsive phase), and slow reconnection (gradual phase). We also provide evidence for X-ray brightenings within the evolving current sheet, possibly induced by the tearing mode instability. This work was supported in part by the RHESSI Program and NASA's Sun-Earth Connection Program. This work would not have been possible without the dedicated efforts of the entire RHESSI team.
Structures and components in galaxy clusters: observations and models
Bykov, A M; Ferrari, C; Forman, W R; Kaastra, J S; Klein, U; Markevitch, M; de Plaa, J
2015-01-01
Clusters of galaxies are the largest gravitationally bounded structures in the Universe dominated by dark matter. We review the observational appearance and physical models of plasma structures in clusters of galaxies. Bubbles of relativistic plasma which are inflated by supermassive black holes of AGNs, cooling and heating of the gas, large scale plasma shocks, cold fronts, non-thermal halos and relics are observed in clusters. These constituents are reflecting both the formation history and the dynamical properties of clusters of galaxies. We discuss X-ray spectroscopy as a tool to study the metal enrichment in clusters and fine spectroscopy of Fe X-ray lines as a powerful diagnostics of both the turbulent plasma motions and the energetics of the non-thermal electron populations. The knowledge of the complex dynamical and feedback processes is necessary to understand the energy and matter balance as well as to constrain the role of the non-thermal components of clusters.
Philbin, R.
2015-05-22
This study validates the near-surface temperature and precipitation output from decadal runs of eight atmospheric ocean general circulation models (AOGCMs) against observational proxy data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis temperatures and Global Precipitation Climatology Project (GPCP) precipitation data. We model the joint distribution of these two fields with a parsimonious bivariate Matérn spatial covariance model, accounting for the two fields\\' spatial cross-correlation as well as their own smoothnesses. We fit output from each AOGCM (30-year seasonal averages from 1981 to 2010) to a statistical model on each of 21 land regions. Both variance and smoothness values agree for both fields over all latitude bands except southern mid-latitudes. Our results imply that temperature fields have smaller smoothness coefficients than precipitation fields, while both have decreasing smoothness coefficients with increasing latitude. Models predict fields with smaller smoothness coefficients than observational proxy data for the tropics. The estimated spatial cross-correlations of these two fields, however, are quite different for most GCMs in mid-latitudes. Model correlation estimates agree well with those for observational proxy data for Australia, at high northern latitudes across North America, Europe and Asia, as well as across the Sahara, India, and Southeast Asia, but elsewhere, little consistent agreement exists.
Modelling 1-minute directional observations of the global irradiance.
Thejll, Peter; Pagh Nielsen, Kristian; Andersen, Elsa; Furbo, Simon
2016-04-01
Direct and diffuse irradiances from the sky has been collected at 1-minute intervals for about a year from the experimental station at the Technical University of Denmark for the IEA project "Solar Resource Assessment and Forecasting". These data were gathered by pyrheliometers tracking the Sun, as well as with apertured pyranometers gathering 1/8th and 1/16th of the light from the sky in 45 degree azimuthal ranges pointed around the compass. The data are gathered in order to develop detailed models of the potentially available solar energy and its variations at high temporal resolution in order to gain a more detailed understanding of the solar resource. This is important for a better understanding of the sub-grid scale cloud variation that cannot be resolved with climate and weather models. It is also important for optimizing the operation of active solar energy systems such as photovoltaic plants and thermal solar collector arrays, and for passive solar energy and lighting to buildings. We present regression-based modelling of the observed data, and focus, here, on the statistical properties of the model fits. Using models based on the one hand on what is found in the literature and on physical expectations, and on the other hand on purely statistical models, we find solutions that can explain up to 90% of the variance in global radiation. The models leaning on physical insights include terms for the direct solar radiation, a term for the circum-solar radiation, a diffuse term and a term for the horizon brightening/darkening. The purely statistical model is found using data- and formula-validation approaches picking model expressions from a general catalogue of possible formulae. The method allows nesting of expressions, and the results found are dependent on and heavily constrained by the cross-validation carried out on statistically independent testing and training data-sets. Slightly better fits -- in terms of variance explained -- is found using the purely
Precision Electroweak Observables in the Minimal Moose Little Higgs Model
Kilic, C; Kilic, Can; Mahbubani, Rakhi
2004-01-01
Little Higgs theories, in which the Higgs particle is realized as the pseudo-Goldstone boson of an approximate global chiral symmetry have generated much interest as possible alternatives to weak scale supersymmetry. In this paper we place constraints on the parameters of two such models by comparing their contributions to precision electroweak observables with current experimental bounds. This is done in the effective field theory framework by matching coefficients of operators in the low and high energy theories at around 1 TeV.
On the Ungerboeck and Forney Observation Models for Offset QPSK
2012-03-12
ANSI Std. Z39.18 On the Ungerboeck and Forney Observation Models for Offset QPSK Michael Rice Brigham Young University Provo, UT 84602 Email: mdr ... Tb is the bit time (sec/bit), and the binary symbols x(n) are defined by x(n) = { a(n) n even ja(n) n odd . (5) Here, OQPSK is thought of as a binary...3] (see also [9]) and an equivalent CPM representation [8, Chapter 3] (see also [10]). 2Because both Tb and Ts = 2Tb spaced pulse trains are
Palfreyman, Zoe; Haycraft, Emma; Meyer, Caroline
2015-03-01
Parents are important role models for their children's eating behaviours. This study aimed to further validate the recently developed Parental Modelling of Eating Behaviours Scale (PARM) by examining the relationships between maternal self-reports on the PARM with the modelling practices exhibited by these mothers during three family mealtime observations. Relationships between observed maternal modelling and maternal reports of children's eating behaviours were also explored. Seventeen mothers with children aged between 2 and 6 years were video recorded at home on three separate occasions whilst eating a meal with their child. Mothers also completed the PARM, the Children's Eating Behaviour Questionnaire and provided demographic information about themselves and their child. Findings provided validation for all three PARM subscales, which were positively associated with their observed counterparts on the observational coding scheme (PARM-O). The results also indicate that habituation to observations did not change the feeding behaviours displayed by mothers. In addition, observed maternal modelling was significantly related to children's food responsiveness (i.e., their interest in and desire for foods), enjoyment of food, and food fussiness. This study makes three important contributions to the literature. It provides construct validation for the PARM measure and provides further observational support for maternal modelling being related to lower levels of food fussiness and higher levels of food enjoyment in their children. These findings also suggest that maternal feeding behaviours remain consistent across repeated observations of family mealtimes, providing validation for previous research which has used single observations. Copyright © 2014 Elsevier Ltd. All rights reserved.
Observable Algebra in Field Algebra of G-spin Models
Institute of Scientific and Technical Information of China (English)
蒋立宁
2003-01-01
Field algebra of G-spin models can provide the simplest examples of lattice field theory exhibiting quantum symmetry. Let D(G) be the double algebra of a finite group G and D(H), a sub-algebra of D(G) determined by subgroup H of G. This paper gives concrete generators and the structure of the observable algebra AH, which is a D(H)-invariant sub-algebra in the field algebra of G-spin models F, and shows that AH is a C*-algebra. The correspondence between H and AH is strictly monotonic. Finally, a duality between D(H) and AH is given via an irreducible vacuum C*-representation of F.
Analysis of rainfall seasonality from observations and climate models
Pascale, Salvatore; Feng, Xue; Porporato, Amilcare; Hasson, Shabeh-ul
2014-01-01
Precipitation seasonality of observational datasets and CMIP5 historical simulations are analyzed using novel quantitative measures based on information theory. Two new indicators, the relative entropy (RE) and the dimensionless seasonality index (DSI), together with the mean annual rainfall, are evaluated on a global scale for recently updated precipitation gridded datasets and for historical simulations from coupled atmosphere-ocean general circulation models. The RE provides a measure of how peaked the shape of the annual rainfall curve is whereas the DSI quantifies the intensity of the rainfall during the wet season. The global monsoon regions feature the largest values of the DSI. For precipitation regimes featuring one maximum in the monthly rain distribution the RE is related to the duration of the wet season. We show that the RE and the DSI are measures of rainfall seasonality fairly independent of the time resolution of the precipitation data, thereby allowing objective metrics for model intercompari...
Dispersion Relations for Electroweak Observables in Composite Higgs Models
Contino, Roberto
2015-01-01
We derive dispersion relations for the electroweak oblique observables measured at LEP in the context of $SO(5)/SO(4)$ composite Higgs models. It is shown how these relations can be used and must be modified when modeling the spectral functions through a low-energy effective description of the strong dynamics. The dispersion relation for the parameter $\\epsilon_3$ is then used to estimate the contribution from spin-1 resonances at the 1-loop level. Finally, it is shown that the sign of the contribution to the $\\hat S$ parameter from the lowest-lying spin-1 states is not necessarily positive definite, but depends on the energy scale at which the asymptotic behavior of current correlators is attained.
Models for Near-Ridge Seamounts Constrained by Gravity Observations
Kostlan, M.; McClain, J. S.
2009-12-01
In an analysis of the seamount chain centered at 105°20’W, 9°05’N, west of the East Pacific Rise and south of the Clipperton transform fault, we compared measured free air gravity anomaly values with modeled gravity anomaly values. The seamount chain contains approximately ten seamounts trending roughly east-west, perpendicular to the mid-ocean ridge axis. They lie on lithosphere between 1.5 and 2.7 Ma in age. Based on its position and age, the seamount chain appears to be associated with the 9°03’N overlapping spreading center (OSC). This OSC includes several associated seamount chains, aligned generally east-west, and of varying ages. The observed data include both free air gravity anomalies and bathymetry of the seamount chain, provided by the National Geophysical Data Center (NGDC), and was selected because the gravity measurements are relatively well covered. We used a series of different structural models of the oceanic crust and mantle to generate gravity anomalies associated with the sea mounts. The models utilize Parker’s algorithm to generate these free air gravity anomalies. We compute a gravity residual by subtracting the calculated anomalies from the observed anomalies. The models include one with a crust of a constant thickness (6 km), while another introduces a constant-thickness Layer 2A. In contrast, a third model included a variable thickness crust, where the thickness is governed by Airy compensation. The calculations show that the seamounts must be partly compensated, because the constant-thickness models predict a high negative residual (or they produce an anomaly which is too high). In contrast, the Airy compensation model produces an anomaly that is too low at the longer wavelengths, indicating that the lithosphere must have some strength, and that flexure must be supporting part of the load of the seamount chain. This contrasts with earlier studies that indicate young, near-ridge seamounts do not result in flexure of the thin
Modeling Earth Albedo Currents on Sun Sensors for Improved Vector Observations
DEFF Research Database (Denmark)
Bhanderi, Dan
2006-01-01
Earth albedo influences vector measurements of the solar line of sight vector, due to the induced current on in the photo voltaics of Sun sensors. Although advanced digital Sun sensors exist, these are typically expensive and may not be suited for satellites in the nano or pico-class. Previously...... for modeling Sun sensor output by incorporating the Earth albedo model is presented. This model utilizes the directional information of in the Earth albedo model, which is achieved by Earth surface partitioning. This allows accurate simulation of the Sun sensor output and the results are consistent with Ørsted...... and useful for space environment simulations, and may be utilized to improve attitude estimation algorithms applying Sun sensor vector observations....
Constraints on Disks Models of The Big Blue Bump from UV/Optical/IR Observations
Antonucci, R
1998-01-01
Optical/UV observations provide many constraints on accretion disk models of AGN which aren't always appreciated by modelers of the X-ray emission (or sometimes even of the optical/UV emission). The spectral behavior at the Ly edge, the polarization, the continuum slopes and breaks, and the variability timescales and phasing all conflict with simple models and strongly constrain the more Baroque ones. Partial-covering absorbers and microlensing data suggest that the radiation is not released simply according to where the potential drop (modified by standard viscous transport) takes place. On the other hand, the orientation-based unified model is in accord with the K-\\alpha inclination distributions for the AGN spectral classes, basing the latter on the limited existing data and theoretical understanding.
Microbial Life in Soil - Linking Biophysical Models with Observations
Or, Dani; Tecon, Robin; Ebrahimi, Ali; Kleyer, Hannah; Ilie, Olga; Wang, Gang
2015-04-01
Microbial life in soil occurs within fragmented aquatic habitats formed in complex pore spaces where motility is restricted to short hydration windows (e.g., following rainfall). The limited range of self-dispersion and physical confinement promote spatial association among trophically interdepended microbial species. Competition and preferences for different nutrient resources and byproducts and their diffusion require high level of spatial organization to sustain the functioning of multispecies communities. We report mechanistic modeling studies of competing multispecies microbial communities grown on hydrated surfaces and within artificial soil aggregates (represented by 3-D pore network). Results show how trophic dependencies and cell-level interactions within patchy diffusion fields promote spatial self-organization of motile microbial cells. The spontaneously forming patterns of segregated, yet coexisting species were robust to spatial heterogeneities and to temporal perturbations (hydration dynamics), and respond primarily to the type of trophic dependencies. Such spatially self-organized consortia may reflect ecological templates that optimize substrate utilization and could form the basic architecture for more permanent surface-attached microbial colonies. Hydration dynamics affect structure and spatial arrangement of aerobic and anaerobic microbial communities and their biogeochemical functions. Experiments with well-characterized artificial soil microbial assemblies grown on porous surfaces provide access to community dynamics during wetting and drying cycles detected through genetic fingerprinting. Experiments for visual observations of spatial associations of tagged bacterial species with known trophic dependencies on model porous surfaces are underway. Biophysical modeling provide a means for predicting hydration-mediated critical separation distances for activation of spatial self-organization. The study provides new modeling and observational tools
Using observations to evaluate biosphere-atmosphere interactions in models
Green, Julia; Konings, Alexandra G.; Alemohammad, Seyed H.; Gentine, Pierre
2017-04-01
Biosphere-atmosphere interactions influence the hydrologic cycle by altering climate and weather patterns (Charney, 1975; Koster et al., 2006; Seneviratne et al., 2006), contributing up to 30% of precipitation and radiation variability in certain regions (Green et al., 2017). They have been shown to contribute to the persistence of drought in Europe (Seneviratne et al., 2006), as well as to increase rainfall in the Amazon (Spracklen et al., 2012). Thus, a true representation of these feedbacks in Earth System Models (ESMs) is crucial for accurate forecasting and planning. However, it has been difficult to validate the performance of ESMs since often-times surface and atmospheric flux data are scarce and/or difficult to observe. In this study, we use the results of a new global observational study (using remotely sensed solar-induced fluorescence to represent the biosphere flux) (Green et al., 2017) to determine how well a suite of 13 ESMs capture biosphere-atmosphere feedbacks. We perform a Conditional Multivariate Granger Causality analysis in the frequency domain with radiation, precipitation and temperature as atmospheric inputs and GPP as the biospheric input. Performing the analysis in the frequency domain allows for separation of feedbacks at different time-scales (subseasonal, seasonal or interannual). Our findings can be used to determine whether there is agreement between models, as well as, to pinpoint regions or time-scales of model bias or inaccuracy, which will provide insight on potential improvement. We demonstrate that in addition to the well-known problem of convective parameterization over land in models, the main issue in representing feedbacks between the land and the atmosphere is due to the misrepresentation of water stress. These results provide a direct quantitative assessment of feedbacks in models and how to improve them. References: Charney, J.G. Dynamics of deserts and drought in the Sahel. Quarterly Journal of the Royal Meteorological
Gounaris, Alexandros Frantzis; Poulakis, Pantelis; Chautems, Christophe; Raffaela, Carloni; Stramigioli, Stefano
2011-01-01
The Automation & Robotics Section of the European Space Agency (ESA) is developing a platform for investigation of different levels of autonomy of planetary rovers. Within this scope a physical flight model is required and the Lunar Rover Model (LRM) is chosen. The LRM is a 4 wheel, medium-scale (12
Gounaris, Alexandros Frantzis; Poulakis, Pantelis; Chautems, Christophe; Raffaela, Carloni; Stramigioli, Stefano
2011-01-01
The Automation & Robotics Section of the European Space Agency (ESA) is developing a platform for investigation of different levels of autonomy of planetary rovers. Within this scope a physical flight model is required and the Lunar Rover Model (LRM) is chosen. The LRM is a 4 wheel, medium-scale
On the viability of quintessential inflationary models from observational data
de Haro, Jaume
2016-01-01
Assuming that primordial density fluctuationas are nearly Gaussian, from a frequentist viewpoint, the two-dimensional marginalized joint coincidence contour in the plane $(n_s,r)$ (being $n_s$ the spectral index and $r$ the ratio of tensor to scalar perturbations), without the presence of running is usually used to test the viability of the inflationary models. The models that provide, between $50$ and $60$ e-folds, a curve in that plane, which lies outside the $95.5 \\%$ C.L are ruled out. I will basically argue that the this low number of e-folds is unjustified, and that models leading to a theoretical value of the running different from zero must be checked with observational data allowing the running. When both prescriptions are taken into account, dealing in the context of quintessential inflation, i.e. when the potential is a combination of an inflationary with a quintessential one that leads to a deflationary regime, inflationary models such as the quartic or the Higgs potential are allowed.
On the viability of quintessential inflation models from observational data
de Haro, Jaume
2017-01-01
Assuming that primordial density fluctuations are nearly Gaussian, from a frequentist viewpoint, the two-dimensional marginalized joint coincidence contour in the plane (n_s,r) (being n_s the spectral index and r the ratio of tensor to scalar perturbations), without the presence of running is often used to test the viability of the inflationary models. The models that provide, between 50 and 60 e-folds, a curve in that plane lying outside the 95.5% C.L are ruled out. I will basically argue that, in quintessential inflation, this low number of e-folds is unjustified, and that models leading to a theoretical value of the running different from zero must be checked with observational data allowing the running. When both prescriptions are taken into account, dealing in the context of quintessential inflation, i.e. when the potential is a combination of an inflationary with a quintessential one that leads to a kination (also called deflation) regime, inflationary models such as the quartic or the Higgs potential are allowed.
Spectral Models for Early Time SN 2011fe Observations
Baron, E; Sullivan, M; Hsiao, E; Ellis, R S; Gal-Yam, A; Howell, D A; Nugent, P E; Dominguez, I; Krisciunas, K; Phillips, M M; Suntzeff, N; Wang, L; Thomas, R C
2015-01-01
We use observed UV through near IR spectra to examine whether SN 2011fe can be understood in the framework of Branch-normal SNe Ia and to examine its individual peculiarities. As a benchmark, we use a delayed-detonation model with a progenitor metallicity of Z_solar/20. We study the sensitivity of features to variations in progenitor metallicity, the outer density profile, and the distribution of radioactive nickel. The effect of metallicity variations in the progenitor have a relatively small effect on the synthetic spectra. We also find that the abundance stratification of SN 2011fe resembles closely that of a delayed detonation model with a transition density that has been fit to other Branch-normal Type Ia supernovae. At early times, the model photosphere is formed in material with velocities that are too high, indicating that the photosphere recedes too slowly or that SN 2011fe has a lower specific energy in the outer ~0.1 M_sun than does the model. We discuss several explanations for the discrepancies. ...
Constraints on surface evapotranspiration: implications for modeling and observations
Gentine, P.
2015-12-01
The continental hydrological cycle and especially evapotranspiration are constrained by additional factors such as the energy availability and the carbon cycle. As a results trying to understand and predict the surface hydrologic cycle in isolation might be highly unreliable. We present two examples were constraints induced by 1) radiation control through cloud albedo feedback and 2) carbon control on the surface water use efficiency are essential to correctly predict the seasonal hydrologic cycle. In the first example we show that correctly modeling diurnal and seasonal convection and the associated cloud-albedo feedback (through land-atmosphere and convection-large-scale circulation feedbacks) is essential to correctly model the surface hydrologic cycle in the Amazon, and to correct biases observed in all general circulation models. This calls for improved modeling of convection to correctly predict the tropical continental hydrologic cycle.In the second example we show that typical drought index based only on energy want water availability misses vegetation physiological and carbon feedback and cannot correctly represent the seasonal cycle of soil moisture stress. The typical Palmer Drought Stress Index is shown to be incapable of rejecting water stress in the future. This calls for new drought assessment metrics that may include vegetation and carbon feedback.
Observationally-Based Data/Model Metrics from the Southern Ocean Climate Model Atlas
Abell, J.; Russell, J. L.; Goodman, P. J.
2015-12-01
The Southern Ocean Climate Model Atlas makes available observationally-based standardized data/model metrics of the latest simulations of climate and projections of climate change from available climate models. Global climate model simulations differ greatly in the Southern Ocean, so the development of consistent, observationally-based metrics, by which to assess the fidelity of model simulations is essential. We will present metrics showing and quantifying the results of the modern day climate simulations over the Southern Ocean from models submitted as part of the CMIP5/IPCC-AR5 process. Our analysis will focus on the simulations of the temperature, salinity and carbon at various depths and along significant hydrographic sections. The models exhibit different skill levels with various metrics between models and also within individual models.
Energy Technology Data Exchange (ETDEWEB)
Schoenfelder, Martin; Esser-Frey, Anke; Fichtner, Wolf [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Chair of Energy Economics; Schick, Michael; Heuveline, Vincent [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Engineering Mathematics and Computing Lab.; Leibfried, Thomas [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. of Electric Energy Systems and High-Voltage Technology
2012-03-15
This paper is based on Groschke et al. (Z. Energiewirtsch. 33(1):14-22 2009) and continues the description of new developments in modeling network constraints in techno-economic energy system models with a focus on capacity expansion planning and a long-term time horizon. Based on the presentation of recent and future developments in the German energy system, current challenges in energy system modeling are derived. The following analysis of the state of research reveals a lack of high-precision load flow calculation in current energy system models with a long-term time horizon. Hence, this paper presents an outlook on a new mathematical approach, which already proved as a promising method to meet the challenges identified. (orig.)
Assimilation of gridded terrestrial water storage observations from GRACE into a land surface model
Girotto, Manuela; De Lannoy, Gabriëlle J. M.; Reichle, Rolf H.; Rodell, Matthew
2016-05-01
Observations of terrestrial water storage (TWS) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have a coarse resolution in time (monthly) and space (roughly 150,000 km2 at midlatitudes) and vertically integrate all water storage components over land, including soil moisture and groundwater. Data assimilation can be used to horizontally downscale and vertically partition GRACE-TWS observations. This work proposes a variant of existing ensemble-based GRACE-TWS data assimilation schemes. The new algorithm differs in how the analysis increments are computed and applied. Existing schemes correlate the uncertainty in the modeled monthly TWS estimates with errors in the soil moisture profile state variables at a single instant in the month and then apply the increment either at the end of the month or gradually throughout the month. The proposed new scheme first computes increments for each day of the month and then applies the average of those increments at the beginning of the month. The new scheme therefore better reflects submonthly variations in TWS errors. The new and existing schemes are investigated here using gridded GRACE-TWS observations. The assimilation results are validated at the monthly time scale, using in situ measurements of groundwater depth and soil moisture across the U.S. The new assimilation scheme yields improved (although not in a statistically significant sense) skill metrics for groundwater compared to the open-loop (no assimilation) simulations and compared to the existing assimilation schemes. A smaller impact is seen for surface and root-zone soil moisture, which have a shorter memory and receive smaller increments from TWS assimilation than groundwater. These results motivate future efforts to combine GRACE-TWS observations with observations that are more sensitive to surface soil moisture, such as L-band brightness temperature observations from Soil Moisture Ocean Salinity (SMOS) or Soil Moisture Active Passive
Post-Hoc Pattern-Oriented Testing and Tuning of an Existing Large Model: Lessons from the Field Vole
DEFF Research Database (Denmark)
Topping, Christopher John; Dalkvist, Trine; Grimm, Volker
2012-01-01
between landscape and individual behavior. Results of fitting to the range of patterns chosen were generally very good, but the procedure required to achieve this was long and complicated. To obtain good correspondence between model and the real world it was often necessary to model the real world...... environment closely. We therefore conclude that post-hoc POM is a useful and viable way to test a highly complex simulation model, but also warn against the dangers of over-fitting to real world patterns that lack details in their explanatory driving factors. To overcome some of these obstacles we suggest...
CORAL: model for no observed adverse effect level (NOAEL).
Toropov, Andrey A; Toropova, Alla P; Pizzo, Fabiola; Lombardo, Anna; Gadaleta, Domenico; Benfenati, Emilio
2015-08-01
The in vivo repeated dose toxicity (RDT) test is intended to provide information on the possible risk caused by repeated exposure to a substance over a limited period of time. The measure of the RDT is the no observed adverse effect level (NOAEL) that is the dose at which no effects are observed, i.e., this endpoint indicates the safety level for a substance. The need to replace in vivo tests, as required by some European Regulations (registration, evaluation authorization and restriction of chemicals) is leading to the searching for reliable alternative methods such as quantitative structure-activity relationships (QSAR). Considering the complexity of the RDT endpoint, for which data quality is limited and depends anyway on the study design, the development of QSAR for this endpoint is an attractive task. Starting from a dataset of 140 organic compounds with NOAEL values related to oral short term toxicity in rats, we developed a QSAR model based on optimal descriptors calculated with simplified molecular input-line entry systems and the graph of atomic orbitals by the Monte Carlo method, using CORAL software. Three different splits into the training, calibration, and validation sets are studied. The mechanistic interpretation of these models in terms of molecular fragment with positive or negative contributions to the endpoint is discussed. The probabilistic definition for the domain of applicability is suggested.
Reconciling Glyoxal Observations Over Oceans with Model Simulations: A 3D sensitivity study
Myriokefalitakis, S.; Daskalakis, N.; Tsigaridis, K.; Baidar, S.; Dix, B. K.; Coburn, S.; Sinreich, R.; Volkamer, R. M.; Kanakidou, M.
2012-12-01
Glyoxal, the smallest dicarbonyl can be observed from space, is expected to provide indications on volatile organic compounds (VOC) oxidation and secondary aerosol formation in the troposphere. Glyoxal (CHOCHO) is known to be both of natural origin as a by-product of biogenic VOC oxidation and also produced during anthropogenically emitted hydrocarbon tropospheric chemical transformations, like acetylene and aromatics. CHOCHO's short chemical lifetime in the boundary layer and the lower troposphere makes it an excellent indicator of photochemical hotspots and rapidly changing atmospheric conditions around the globe. Although over land CHOCHO atmospheric load is well established, concentrations over ocean deserts observed by satellite instruments and in-situ measurements remain a challenge for all state of the art chemistry transport models (CTM). High column amounts and concentrations of CHOCHO above oceans are observed close to upwelling areas and above regions with large concentrations of phytoplankton that suggest strong maritime biological activity. In addition, the short lifetime of CHOCHO limits long range transport from continental regions. The observed enhancement of CHOCHO load over the tropical ocean during the TORERO campaign corroborate with satellite retrieval points to the existence of primary and/or secondary tropical oceanic sources of CHOCHO; currently neglected or underestimated these chemical pathways by current knowledge. This hypothesis is investigated based on simulations using global TM4-ECPL CTM. The modeling focuses in the TORERO region and reconciles TORERO ship and aircraft observations with the model results.
Patell, Hilla
2016-01-01
In order to achieve the goal of observation, preparation of the adult, the observer, is necessary. This preparation, says Hilla Patell, requires us to "have an appreciation of the significance of the child's spontaneous activities and a more thorough understanding of the child's needs." She discusses the growth of both the desire to…
Kripalani, Lakshmi A.
2016-01-01
The adult who is inexperienced in the art of observation may, even with the best intentions, react to a child's behavior in a way that hinders instead of helping the child's development. Kripalani outlines the need for training and practice in observation in order to "understand the needs of the children and...to understand how to remove…
Sokół, Justyna M; Bzowski, Maciej; Swaczyna, Paweł
2015-01-01
We have developed a refined and optimized version of the Warsaw Test Particle Model of interstellar neutral gas in the heliosphere, specially tailored for analysis of IBEX-Lo observations. The former version of the model was used in the analysis of neutral He observed by IBEX that resulted in an unexpected conclusion that the interstellar neutral He flow vector was different than previously thought and that a new population of neutral He, dubbed the Warm Breeze, exists in the heliosphere. It was also used in the reanalysis of Ulysses observations that confirmed the original findings on the flow vector, but suggested a significantly higher temperature. The present version model has two strains targeted for different applications, based on an identical paradigm, but differing in the implementation and in the treatment of ionization losses. We present the model in detail and discuss numerous effects related to the measurement process that potentially modify the resulting flux of ISN~He observed by IBEX, and iden...
Reconciling the observed and modeled Southern Hemisphere circulation response to volcanic eruptions
McGraw, Marie C.; Barnes, Elizabeth A.; Deser, Clara
2016-07-01
Confusion exists regarding the tropospheric circulation response to volcanic eruptions, with models and observations seeming to disagree on the sign of the response. The forced Southern Hemisphere circulation response to the eruptions of Pinatubo and El Chichón is shown to be a robust positive annular mode, using over 200 ensemble members from 38 climate models. It is demonstrated that the models and observations are not at odds, but rather, internal climate variability is large and can overwhelm the forced response. It is further argued that the state of the El Niño-Southern Oscillation can at least partially explain the sign of the observed anomalies and may account for the perceived discrepancy between model and observational studies. The eruptions of both El Chichón and Pinatubo occurred during El Niño events, and it is demonstrated that the Southern Annular Mode anomalies following volcanic eruptions are weaker during El Niño events compared to La Niña events.
Cheung, M C M; Tarbell, T D; Title, A M
2008-01-01
We present results from numerical modeling of emerging flux regions on the solar surface. The modeling was carried out by means of 3D radiative MHD simulations of the rise of buoyant magnetic flux tubes through the convection zone and into the photosphere. Due to the strong stratification of the convection zone, the rise results in a lateral expansion of the tube into a magnetic sheet, which acts as a reservoir for small-scale flux emergence events at the scale of granulation. The interaction of the convective downflows and the rising magnetic flux undulates it to form serpentine field lines emerging into the photosphere. Observational characteristics including the pattern of emerging flux regions, the cancellation of surface flux and associated high speed downflows, the convective collapse of photospheric flux tubes, the appearance of anomalous darkenings, the formation of bright points and the possible existence of transient kilogauss horizontal fields are discussed in the context of new observations from t...
On radial heliospheric magnetic fields: Voyager 2 observation and model
Wang, C.; Richardson, J. D.; Burlaga, L. F.; Ness, N. F.
2003-05-01
The heliospheric magnetic field (HMF) direction, on average, conforms well to the Parker spiral. However, numerous examples of events where the HMF is oriented in near-radial directions for many hours have been reported on the basis of observations inside 5 AU from spacecraft such as ISEE-3 and Ulysses. The magnetic field data observed by Voyager 2 from launch in 1977 through the end of 1982 (i.e., between 1 and ˜10 AU) were searched for all instances of radial fields with durations of 6 hours or more. Radial fields of significant durations at large distances are unusual as the Parker spiral is very tightly wound. The radial HMF events in the inner heliosphere typically occur at times when the solar wind speed is declining gradually, while they tend to be associated with steady wind speeds at distances beyond ˜6 AU. The durations of these events appear to be independent of distance and solar cycle, with an average duration of ˜11 hours. They generally are not associated with interplanetary coronal mass ejections (ICMEs). Possible generation mechanisms of the radial field events related to speed variations near the Sun are investigated by use of a MHD model. We find that a noticeable low-speed plateau of limited duration in solar wind speed near the Sun can produce radial field events having durations of the order of 10 hours in the heliosphere as observed by Voyager 2.
Directory of Open Access Journals (Sweden)
Paladi Lela Naga Ramesh,
2010-05-01
Full Text Available This paper examines the suitability of various drag models for predicting the hydrodynamics of the turbulent fluidization of FCC particles on the Fluent V6.2 platform. The drag models reviewed are Syamlal–O’Brien, Gidaspow, Arastoopour and Syamlal–O’Brien, . Comparison between experimental data and simulated results showed that the Syamlal–O’Brien, Arastoopour and Gidaspow models highly overestimated gas–solid momentum exchange and could not predict the formation of dense phase in the fluidized bed. The standard Syamlal–O’Brien drag model was then modified based on the minimum luidization condition. This has proved applicable for FCC particles in turbulent fluidization for the high dense phase, density solid-up phase and low density phases under fast fluidization conditions. This was finally proposed to calculate the gas–solid exchange coefficient in the turbulent fluidization of FCC particles and was validated by satisfactory agreement between prediction and experiment.
Whistler emissions in the magnetosphere - satellite observations and numerical modeling
Chum, J.; Jiricek, F.; Shklyar, D. R.
The investigation of ionospheric and magnetospheric wave phenomena related to lightning strokes began from classical research by Eckersley (Nature, Lond., 135, 104, 1935) and Storey (Phil. Trans. Roy. Soc. Lond., A246, 908, 113-141, 1953) among others, and it has continued up to the present. VLF spectrograms from the MAGION 4 and MAGION 5 satellites contain most of the known types of VLF emissions, as well as some new ones not discussed previously. A partial list of the observed emissions involving nonducted propagation includes: magnetospherically reflected (MR) whistlers (and their subclass, Nu whistlers) predicted by Kimura (Radio Sci., 1, 3, 269-283, 1966) and then found by Smith and Angerami in the spectrograms of wave data from OGO 1 and 3 (J. Geophys. Res., 73, 1, 1-20, 1968); lower hybrid resonance (LHR) noise bands; LHR whistlers and LHR spherics; and oblique noise bands above the local LHR frequency. Recently, a new line of investigation was initiated by numerical modeling of VLF spectrograms of nonducted emissions caused by lightning. For such emissions, as observed by a satellite in the magnetosphere, the spectrograms depend on several factors: the properties of the source, the geomagnetic field structure and the cold plasma distribution which jointly influence the wave propagation, and the resonant interactions of the waves with energetic particles. Therefore, numerical modeling of spectrograms and comparing them with real ones may serve as an indirect tool for investigating the factors mentioned above and any other processes that affect the spectrograms. This tool is especially effective when the source of the emission is known, in particular with lightning-induced emissions. The main features of our numerical method for modeling spectrograms include: a) representation of the wave field as the sum of wave packets treatable by geometrical optics; b) construction of a frequency-time plot based on the notion of a group front; c) calculation of the
Models of Warm Jupiter Atmospheres: Observable Signatures of Obliquity
Rauscher, Emily
2017-09-01
We present three-dimensional atmospheric circulation models of a hypothetical “warm Jupiter” planet, for a range of possible obliquities from 0° to 90°. We model a Jupiter-mass planet on a 10 day orbit around a Sun-like star, since this hypothetical planet sits at the boundary between planets for which we expect that tidal forces should have aligned their rotation axes with their orbital axes (i.e., ones with zero obliquity) and planets whose timescale for tidal alignment is longer than the typical age of an exoplanet system. In line with observational progress, which is pushing atmospheric characterization for planets on longer orbital periods, we calculate the observable signatures of obliquity for a transiting warm Jupiter: in orbital phase curves of thermal emission and in the hemispheric flux gradients that could be measured by eclipse mapping. For both of these predicted measurements, the signal that we would see depends strongly on our viewing geometry relative to the orientation of the planet’s rotation axis, and we thoroughly identify the degeneracies that result. We compare these signals to the predicted sensitivities of current and future instruments and determine that the James Webb Space Telescope should be able to constrain the obliquities of nearby warm Jupiters to be small (if ≤slant 10^\\circ ) or to directly measure them if significantly non-zero (≥slant 30^\\circ ) using the technique of eclipse mapping. For a bright target and assuming photon-limited precision, this could be done with a single secondary eclipse observation.
Fanouriakis, Antonis; Pamfil, Cristina; Rednic, Simona; Sidiropoulos, Prodromos; Bertsias, George; Boumpas, Dimitrios T
2016-01-01
Models for the attribution of neuropsychiatric manifestations to systemic lupus erythematosus (NPSLE) that incorporate timing and type of manifestation, exclusion/confounding or favouring factors have been proposed. We tested their diagnostic performance against expert physician judgment. SLE patients with neuropsychiatric manifestations were identified through retrospective chart review. Manifestations were classified according to physician judgment as attributed to SLE, not attributed or uncertain. Results were compared against the Systemic Lupus International Collaborating Clinics (SLICC) attribution models A and B, and one introduced by the Italian Study Group on NPSLE. 191 patients experienced a total 242 neuropsychiatric manifestations, 136 of which were attributed to SLE according to physician. Both SLICC models showed high specificity (96.2% and 79.2% for model A and B, respectively) but low sensitivity (22.8% and 34.6%, respectively) against physician judgment. Exclusion of cases of headache, anxiety disorders, mild mood and cognitive disorders and polyneuropathy without electrophysiologic confirmation led to modest increases in sensitivity (27.7% and 42.0% for SLICC models A and B, respectively) and reductions in specificity (94.8% and 65.5%, respectively). The Italian Group model showed good accuracy in NPSLE attribution with an area under the curve of the receiver operating characteristics analysis of 0.862; values ≥7 showed the best combination of sensitivity and specificity (82.4% and 82.9%, respectively). Attribution models can be useful in NPSLE diagnosis in routine clinical practice and their performance is superior in major neuropsychiatric manifestations. The Italian Study Group model is accurate, with values ≥7 showing the best combination of sensitivity and specificity.
Comiskey, D; Api, A M; Barrett, C; Ellis, G; McNamara, C; O'Mahony, C; Robison, S H; Rose, J; Safford, B; Smith, B; Tozer, S
2017-08-01
In order to accurately assess aggregate exposure to a fragrance material in consumers, data are needed on consumer habits and practices, as well as the concentration of the fragrance material in those products. The present study describes the development of Phase 2 Creme RIFM model by expanding the previously developed Phase 1 model to include an additional six product types. Using subject-matching algorithms, the subjects in the Phase 1 Creme RIFM database were paired with subjects in the SUPERB and BodyCare surveys based on age and gender. Consumption of the additional products was simulated to create a seven day diary allowing full data integration in a consistent format. The inhalation route was also included for air care and other products where a fraction of product used is inhaled, derived from the RIFM 2-box model. The expansion of the Phase 1 Creme RIFM model has resulted in a more extensive and refined model, which covers a broader range of product categories and now, includes all relevant routes of exposure. An evaluation of the performance of the model has been carried out in an accompanying publication to this one. Copyright © 2017 Elsevier Inc. All rights reserved.
General Description of Fission Observables: GEF Model Code
Energy Technology Data Exchange (ETDEWEB)
Schmidt, K.-H. [CENBG, CNRS/IN2 P3, Chemin du Solarium, B.P. 120, F-33175 Gradignan (France); Jurado, B., E-mail: jurado@cenbg.in2p3.fr [CENBG, CNRS/IN2 P3, Chemin du Solarium, B.P. 120, F-33175 Gradignan (France); Amouroux, C. [CEA, DSM-Saclay (France); Schmitt, C., E-mail: schmitt@ganil.fr [GANIL, Bd. Henri Becquerel, B.P. 55027, F-14076 Caen Cedex 05 (France)
2016-01-15
The GEF (“GEneral description of Fission observables”) model code is documented. It describes the observables for spontaneous fission, neutron-induced fission and, more generally, for fission of a compound nucleus from any other entrance channel, with given excitation energy and angular momentum. The GEF model is applicable for a wide range of isotopes from Z = 80 to Z = 112 and beyond, up to excitation energies of about 100 MeV. The results of the GEF model are compared with fission barriers, fission probabilities, fission-fragment mass- and nuclide distributions, isomeric ratios, total kinetic energies, and prompt-neutron and prompt-gamma yields and energy spectra from neutron-induced and spontaneous fission. Derived properties of delayed neutrons and decay heat are also considered. The GEF model is based on a general approach to nuclear fission that explains a great part of the complex appearance of fission observables on the basis of fundamental laws of physics and general properties of microscopic systems and mathematical objects. The topographic theorem is used to estimate the fission-barrier heights from theoretical macroscopic saddle-point and ground-state masses and experimental ground-state masses. Motivated by the theoretically predicted early localisation of nucleonic wave functions in a necked-in shape, the properties of the relevant fragment shells are extracted. These are used to determine the depths and the widths of the fission valleys corresponding to the different fission channels and to describe the fission-fragment distributions and deformations at scission by a statistical approach. A modified composite nuclear-level-density formula is proposed. It respects some features in the superfluid regime that are in accordance with new experimental findings and with theoretical expectations. These are a constant-temperature behaviour that is consistent with a considerably increased heat capacity and an increased pairing condensation energy that is
The 2010 Saturn's Great White Spot: Observations and models
Sanchez-Lavega, A.
2011-12-01
On December 5, 2010, a major storm erupted in Saturn's northern hemisphere at a planetographic latitude of 37.7 deg [1]. These phenomena are known as "Great White Spots" (GWS) and they have been observed once per Saturn year since the first case confidently reported in 1876. The last event occurred at Saturn's Equator in 1990 [2]. A GWS differs from similar smaller-scale storms in that it generates a planetary-scale disturbance that spreads zonally spanning the whole latitude band. We report on the evolution and motions of the 2010 GWS and its associated disturbance during the months following the outbreak, based mainly on high quality images obtained in the visual range submitted to the International Outer Planet Watch PVOL database [3], with the 1m telescope at Pic-du-Midi Observatory and the 2.2 m telescope at Calar Alto Observatory. The GWS "head source" extinguished by June 2011 implying that it survived about 6 months. Since this source is assumed to be produced by water moist convection, a reservoir of water vapor must exist at a depth of 10 bar and at the same time a disturbance producing the necessary convergence to trigger the ascending motions. The high temporal sampling and coverage allowed us to study the dynamics of the GWS in detail and the multi-wavelength observations provide information on its cloud top structure. We present non-linear simulations using the EPIC code of the evolution of the potential vorticity generated by a continuous Gaussian heat source extending from 10 bar to about 1 bar, that compare extraordinary well to the observed cloud field evolution. Acknowledgements: This work has been funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. The presentation is done on behalf of the team listed in Reference [1]. [1]Sánchez-Lavega A., et al., Nature, 475, 71-74 (2011) [2]Sánchez-Lavega A., et al., Nature, 353, 397-401 (1991) [3]Hueso R., et al., Planet. Space Sci., 58, 1152-1159 (2010).
Glider observations and modeling of sediment transport in Hurricane Sandy
Miles, Travis; Seroka, Greg; Kohut, Josh; Schofield, Oscar; Glenn, Scott
2015-03-01
Regional sediment resuspension and transport are examined as Hurricane Sandy made landfall on the Mid-Atlantic Bight (MAB) in October 2012. A Teledyne-Webb Slocum glider, equipped with a Nortek Aquadopp current profiler, was deployed on the continental shelf ahead of the storm, and is used to validate sediment transport routines coupled to the Regional Ocean Modeling System (ROMS). The glider was deployed on 25 October, 5 days before Sandy made landfall in southern New Jersey (NJ) and flew along the 40 m isobath south of the Hudson Shelf Valley. We used optical and acoustic backscatter to compare with two modeled size classes along the glider track, 0.1 and 0.4 mm sand, respectively. Observations and modeling revealed full water column resuspension for both size classes for over 24 h during peak waves and currents, with transport oriented along-shelf toward the southwest. Regional model predictions showed over 3 cm of sediment eroded on the northern portion of the NJ shelf where waves and currents were the highest. As the storm passed and winds reversed from onshore to offshore on the southern portion of the domain waves and subsequently orbital velocities necessary for resuspension were reduced leading to over 3 cm of deposition across the entire shelf, just north of Delaware Bay. This study highlights the utility of gliders as a new asset in support of the development and verification of regional sediment resuspension and transport models, particularly during large tropical and extratropical cyclones when in situ data sets are not readily available.
Che, Chenggang
1992-09-01
In recent years, the manufacturing of parts with compound surfaces relies more and more on computer integrated manufacturing (CIM) because of the ever increasing complexity of surface features. For a standard CIM cycle, it starts from a computer aided design (CAD) model which was designed previously be experienced mechanical drafters. The CAD model is then interpreted as numerical controlled (NC) machining codes according to which the part is finally manufactured, this is usually referred to as the normal manufacturing process in Figure 1. However, in many cases, a CAD model of a part is not always readily available to begin the CIM cycle. For instance, in automobile industry, the development of new car models takes a long time from concept to model because of the tedious manual digitization process. Also, in some other cases, the mechanical design of a product may need frequent modification, such as ship hulls, aeroplane fuselages, wings and turbine blades, etc. This was traditionally done by copymilling of a master model. In a computer aided manufacturing (CAM) environment, a mathematical model or representation of a part is required to begin a CIM cycle. The automation of the whole manufacturing system requires a rapid part modeling tool. Fortunately, this becomes possible with the advent of recent development in optical sensing devices and many non-contact sensing techniques. Before a part model is established, surface digitization should first be implemented so that enough measurement points can be fitted later, and this is the most important step of the reverse engineering process as in Figure 1. And also, it is obvious that the efficiency and accuracy of the surface modeling relies heavily on the efficiency and accuracy of the surface digitization. The present paper aims at achieving surface digitization accurately and rapidly with a coordinate measurement machine (CMM) and an inexpensive laser range-finding probe. By making full use of the control system of
Rabadi, Ghaith
2005-01-01
A significant portion of lifecycle costs for launch vehicles are generated during the operations phase. Research indicates that operations costs can account for a large percentage of the total life-cycle costs of reusable space transportation systems. These costs are largely determined by decisions made early during conceptual design. Therefore, operational considerations are an important part of vehicle design and concept analysis process that needs to be modeled and studied early in the design phase. However, this is a difficult and challenging task due to uncertainties of operations definitions, the dynamic and combinatorial nature of the processes, and lack of analytical models and the scarcity of historical data during the conceptual design phase. Ultimately, NASA would like to know the best mix of launch vehicle concepts that would meet the missions launch dates at the minimum cost. To answer this question, we first need to develop a model to estimate the total cost, including the operational cost, to accomplish this set of missions. In this project, we have developed and implemented a discrete-event simulation model using ARENA (a simulation modeling environment) to determine this cost assessment. Discrete-event simulation is widely used in modeling complex systems, including transportation systems, due to its flexibility, and ability to capture the dynamics of the system. The simulation model accepts manifest inputs including the set of missions that need to be accomplished over a period of time, the clients (e.g., NASA or DoD) who wish to transport the payload to space, the payload weights, and their destinations (e.g., International Space Station, LEO, or GEO). A user of the simulation model can define an architecture of reusable or expendable launch vehicles to achieve these missions. Launch vehicles may belong to different families where each family may have it own set of resources, processing times, and cost factors. The goal is to capture the required
Avanaki, Ali R. N.; Espig, Kathryn; Knippel, Eddie; Kimpe, Tom R. L.; Xthona, Albert; Maidment, Andrew D. A.
2016-03-01
In this paper, we specify a notion of background tissue complexity (BTC) as perceived by a human observer that is suited for use with model observers. This notion of BTC is a function of image location and lesion shape and size. We propose four unsupervised BTC estimators based on: (i) perceived pre- and post-lesion similarity of images, (ii) lesion border analysis (LBA; conspicuous lesion should be brighter than its surround), (iii) tissue anomaly detection, and (iv) mammogram density measurement. The latter two are existing methods we adapt for location- and lesion-dependent BTC estimation. To validate the BTC estimators, we ask human observers to measure BTC as the visibility threshold amplitude of an inserted lesion at specified locations in a mammogram. Both human-measured and computationally estimated BTC varied with lesion shape (from circular to oval), size (from small circular to larger circular), and location (different points across a mammogram). BTCs measured by different human observers are correlated (ρ=0.67). BTC estimators are highly correlated to each other (0.84cine mode is outlined. The proposed estimators, as-is or customized to a specific human observer, may be used to construct a BTC-aware model observer, with applications such as optimization of contrast-enhanced medical imaging systems, and creation of a diversified image dataset with characteristics of a desired population.
Directory of Open Access Journals (Sweden)
M. V. Nezlin
1999-01-01
Full Text Available Three kinds of results have been described in this paper. Firstly, an experimental study of the Rossby vortex meridional drift on the rotating shallow water has been carried out. Owing to the stringent physical analogy between the Rossby vortices and drift vortices in the magnetized plasma, the results obtained have allowed one to make a conclusion that the transport rate of the plasma, trapped by the drift vortices, across the magnetic field is equivalent to the “gyro-Bohm” diffusion coefficient. Secondly, a model of big vortices of the type of the Great Red Spot of Jupiter, dominating in the atmospheres of the outer planets, has been produced. Thirdly, the rotating shallow water modeling has been carried out of the hydrodynamical generation mechanism of spiral structures in galaxies. Trailing spiral waves of various azimuthal modes, generated by a shear flow between fast rotating “nucleus” and slow rotating periphery, were produced. The spirals are similar to those existing in the real galaxies. The hydrodynamical concept of the spiral structure formation in galaxies has been substantiated. Strong anticyclonic vortices between the spiral arms of the structures under study have been discovered for the first time. The existence of analogous vortices in real galaxies has been predicted. (This prediction has been reliably confirmed recently in special astronomical observations, carried out on the basis of the mentioned laboratory modeling and the prediction made – see the paper by A. Fridman et al. (Astrophysics and Space Science, 1997, 252, 115.
A Multiagent Robotic System for In-Situ Modeling and Observation of Icebergs
Coogle, R. A.; Howard, A.
2013-12-01
Ships that operate in polar regions continue to face the threat of floating ice sheets and icebergs generated from ice ablation processes. Systems have been implemented to track these threats, with varying degrees of success. We propose a definition of this tracking problem that re-casts it within a class of robotic, multiagent target observation problems. The focus in this new definition is on minimization of the time an initial contact for newly generated targets is obtained, as opposed to obtaining target contacts long after a target has been generated from a source. Focusing on the initial contact time provides for the ability to enact early countermeasures. A probabilistic model that can be computed in-situ by the robotic agents is presented for the target sources (e.g, iceberg calving regions), and methods of extracting information from that model are provided. Algorithms for computing costs associated with the model for reallocating robotic agents during an observation task and determining the behavior of the targets within the model are presented. The effectiveness of these solutions is demonstrated by comparison with an existing observation technique using simulation, and an implementation is provided for a real hardware system that models the type of system that would be required.
Green, Christopher T.; Zhang, Yong; Jurgens, Bryant C.; Starn, J. Jeffrey; Landon, Matthew K.
2014-01-01
Analytical models of the travel time distribution (TTD) from a source area to a sample location are often used to estimate groundwater ages and solute concentration trends. The accuracies of these models are not well known for geologically complex aquifers. In this study, synthetic datasets were used to quantify the accuracy of four analytical TTD models as affected by TTD complexity, observation errors, model selection, and tracer selection. Synthetic TTDs and tracer data were generated from existing numerical models with complex hydrofacies distributions for one public-supply well and 14 monitoring wells in the Central Valley, California. Analytical TTD models were calibrated to synthetic tracer data, and prediction errors were determined for estimates of TTDs and conservative tracer (NO3−) concentrations. Analytical models included a new, scale-dependent dispersivity model (SDM) for two-dimensional transport from the watertable to a well, and three other established analytical models. The relative influence of the error sources (TTD complexity, observation error, model selection, and tracer selection) depended on the type of prediction. Geological complexity gave rise to complex TTDs in monitoring wells that strongly affected errors of the estimated TTDs. However, prediction errors for NO3− and median age depended more on tracer concentration errors. The SDM tended to give the most accurate estimates of the vertical velocity and other predictions, although TTD model selection had minor effects overall. Adding tracers improved predictions if the new tracers had different input histories. Studies using TTD models should focus on the factors that most strongly affect the desired predictions.
MILES FORMULAE FOR BOOLEAN MODELS OBSERVED ON LATTICES
Directory of Open Access Journals (Sweden)
Joachim Ohser
2011-05-01
Full Text Available The densities of the intrinsic volumes – in 3D the volume density, surface density, the density of the integral of the mean curvature and the density of the Euler number – are a very useful collection of geometric characteristics of random sets. Combining integral and digital geometry we develop a method for efficient and simultaneous calculation of the intrinsic volumes of random sets observed in binary images in arbitrary dimensions. We consider isotropic and reflection invariant Boolean models sampled on homogeneous lattices and compute the expectations of the estimators of the intrinsic volumes. It turns out that the estimator for the surface density is proved to be asymptotically unbiased and thusmultigrid convergent for Boolean models with convex grains. The asymptotic bias of the estimators for the densities of the integral of the mean curvature and of the Euler number is assessed for Boolean models of balls of random diameters. Miles formulae with corresponding correction terms are derived for the 3D case.
Suppressing Electroweak Precision Observables in 5D Warped Models
Cabrer, Joan A; Quiros, Mariano
2011-01-01
We elaborate on a recently proposed mechanism to suppress large contributions to the electroweak precision observables in five dimensional (5D) warped models, without the need for an extended 5D gauge sector. The main ingredient is a modification of the AdS metric in the vicinity of the infrared (IR) brane corresponding to a strong deviation from conformality in the IR of the 4D holographic dual. We compute the general low energy effective theory of the 5D warped Standard Model, emphasizing additional IR contributions to the wave function renormalization of the light Higgs mode. We also derive expressions for the S and T parameters as a function of a generic 5D metric and zero-mode wave functions. We give an approximate formula for the mass of the radion that works even for strong deviation from the AdS background. We proceed to work out the details of an explicit model and derive bounds for the first KK masses of the various bulk fields. The radion is the lightest new particle although its mass is already at...
K-Pg Wildfires: modeling, experiments and observations
Morgan, J.; Artemieva, N.; Belcher, C.; Hadden, R.; Rein, G.; Goldin, T.
2013-09-01
The discovery of soot in K-Pg boundary clays [1] started a long debate about whether the asteroid impact ignited global wildfires. The K-Pg layer is formed from material ejected from the Chicxulub site, which travelled at hypervelocities around the world. When such ejecta re-enters the Earth's atmosphere it decelerates and heats up, and delivers a pulse of radiation to the Earth's surface. Recent estimates of the radiation associated with ejecta re-entry [2] are argued to be large enough to have ignited fires globally [3]. Here, we present new 3D models of the thermal pulse that takes in to account the asymmetric distribution of ejecta, which depends on the angle and direction of the Chicxulub impact [4]. We have replicated some of the modeled thermal pulses with a Fire propagation Apparatus (FPA), to investigate their effect on both dry and living plant matter. The models, experiments and observational data are consistent with some wildfires being ignited as a direct result of the impact, but the mass flux of ejecta at sites uprange of Chicxulub is too low to ignite even the most susceptible of plant matter.
Modelling variability in black hole binaries: linking simulations to observations
Ingram, Adam
2011-01-01
Black hole accretion flows show rapid X-ray variability. The Power Spectral Density (PSD) of this is typically fit by a phenomenological model of multiple Lorentzians for both the broad band noise and Quasi-Periodic Oscillations (QPOs). Our previous paper (Ingram & Done 2011) developed the first physical model for the PSD and fit this to observational data. This was based on the same truncated disc/hot inner flow geometry which can explain the correlated properties of the energy spectra. This assumes that the broad band noise is from propagating fluctuations in mass accretion rate within the hot flow, while the QPO is produced by global Lense-Thirring precession of the same hot flow. Here we develop this model, making some significant improvements. Firstly we specify that the viscous frequency (equivalently, surface density) in the hot flow has the same form as that measured from numerical simulations of precessing, tilted accretion flows. Secondly, we refine the statistical techniques which we use to fit...
Institute of Scientific and Technical Information of China (English)
Li Xiao-Jing
2008-01-01
This paper studies a time delay equation for sea-air oscillator model. The existence and asymptotic estimates of periodic solutions of corresponding problem are obtained by employing the technique of upper and lower solution, and by using the continuation theorem of coincidence degree theory.
Dobbs-Dixon, Ian
The explosion in the number of exoplanets detected to date has revealed a surprising diversity. When attempting to model this diversity, it is crucial to account for the uncertainties resulting from our limited knowledge of chemical, dynamical, and cloud formation processes in their atmospheres. Combining a retrieval technique with theorydriven models is a particularly promising way to address these processes and constrain a physically plausible atmospheric structure. In particular, a detailed micro-physical treatment of clouds and the longitudinal and latitudinal assessments of temperature and chemical profiles, have yet to be addressed in the field. Our team members are experts in radiative-hydrodynamic modeling (Dr. Ian DobbsDixon), cloud kinetics (Dr. Christiana Helling), retrievals and thermo-equilibrium chemistry (Dr. Jasmina Blecic), and observational diagnostics and predictions (Dr. Thomas Greene). The key goals of this proposal are to extend our understanding of the 3D atmospheric structure of gas-giant exoplanets by coupling state-of-the-art selfconsistent models together with a retrieval framework to 1) address cloud kinetics in retrievals, 2) assess 3D temperature and chemical structures in retrievals, 3) model a suite of well-observed planets within the framework of our models, and 4) make observational predictions for current and future NASA missions. To address these goals we have developed a number of tools: Drift-RHD, TEA, BART, and OBS. Drift-RHD solves both the 3D radiative-hydrodynamic equations and a time dependent kinetic cloud model. TEA, Thermochemical Equilibrium Abundances, calculates abundances of chemical species present in the atmosphere. BART, a Bayesian Atmospheric Radiative Transfer code, is a statistical retrieval framework to explore the parameter space of atmospheric chemical abundances and thermal profiles. OBS is a suite of tools developed to simulate observations. Though these tools exist and have been utilized independently in
Model observer design for detecting multiple abnormalities in anatomical background images
Wen, Gezheng; Markey, Mia K.; Park, Subok
2016-03-01
As psychophysical studies are resource-intensive to conduct, model observers are commonly used to assess and optimize medical imaging quality. Existing model observers were typically designed to detect at most one signal. However, in clinical practice, there may be multiple abnormalities in a single image set (e.g., multifocal and multicentric breast cancers (MMBC)), which can impact treatment planning. Prevalence of signals can be different across anatomical regions, and human observers do not know the number or location of signals a priori. As new imaging techniques have the potential to improve multiple-signal detection (e.g., digital breast tomosynthesis may be more effective for diagnosis of MMBC than planar mammography), image quality assessment approaches addressing such tasks are needed. In this study, we present a model-observer mechanism to detect multiple signals in the same image dataset. To handle the high dimensionality of images, a novel implementation of partial least squares (PLS) was developed to estimate different sets of efficient channels directly from the images. Without any prior knowledge of the background or the signals, the PLS channels capture interactions between signals and the background which provide discriminant image information. Corresponding linear decision templates are employed to generate both image-level and location-specific scores on the presence of signals. Our preliminary results show that the model observer using PLS channels, compared to our first attempts with Laguerre-Gauss channels, can achieve high performance with a reasonably small number of channels, and the optimal design of the model observer may vary as the tasks of clinical interest change.
Energy Technology Data Exchange (ETDEWEB)
Lakhin, V. P.; Sorokina, E. A., E-mail: sorokina.ekaterina@gmail.com, E-mail: vilkiae@gmail.com; Ilgisonis, V. I. [National Research Centre Kurchatov Institute (Russian Federation); Konovaltseva, L. V. [Peoples’ Friendship University of Russia (Russian Federation)
2015-12-15
A set of reduced linear equations for the description of low-frequency perturbations in toroidally rotating plasma in axisymmetric tokamak is derived in the framework of ideal magnetohydrodynamics. The model suitable for the study of global geodesic acoustic modes (GGAMs) is designed. An example of the use of the developed model for derivation of the integral conditions for GGAM existence and of the corresponding dispersion relation is presented. The paper is dedicated to the memory of academician V.D. Shafranov.
Starkey, Eleanor; Parkin, Geoff; Birkinshaw, Stephen; Large, Andy; Quinn, Paul; Gibson, Ceri
2017-05-01
Despite there being well-established meteorological and hydrometric monitoring networks in the UK, many smaller catchments remain ungauged. This leaves a challenge for characterisation, modelling, forecasting and management activities. Here we demonstrate the value of community-based ('citizen science') observations for modelling and understanding catchment response as a contribution to catchment science. The scheme implemented within the 42 km2 Haltwhistle Burn catchment, a tributary of the River Tyne in northeast England, has harvested and used quantitative and qualitative observations from the public in a novel way to effectively capture spatial and temporal river response. Community-based rainfall, river level and flood observations have been successfully collected and quality-checked, and used to build and run a physically-based, spatially-distributed catchment model, SHETRAN. Model performance using different combinations of observations is tested against traditionally-derived hydrographs. Our results show how the local network of community-based observations alongside traditional sources of hydro-information supports characterisation of catchment response more accurately than using traditional observations alone over both spatial and temporal scales. We demonstrate that these community-derived datasets are most valuable during local flash flood events, particularly towards peak discharge. This information is often missed or poorly represented by ground-based gauges, or significantly underestimated by rainfall radar, as this study clearly demonstrates. While community-based observations are less valuable during prolonged and widespread floods, or over longer hydrological periods of interest, they can still ground-truth existing traditional sources of catchment data to increase confidence during characterisation and management activities. Involvement of the public in data collection activities also encourages wider community engagement, and provides important
Existence of Néel Order in the S=1 Bilinear-Biquadratic Heisenberg Model via Random Loops
Lees, Benjamin
2016-10-01
We consider the general spin-1 SU(2) invariant Heisenberg model with a two-body interaction. A random loop model is introduced and relation to quantum spin systems is proved. Using this relation it is shown that for dimensions 3 and above Néel order occurs for a large range of values of the relative strength of the bilinear (- J 1) and biquadratic (- J 2) interaction terms. The proof uses the method of reflection positivity and infrared bounds. Links between spin correlations and loop correlations are proved.
Further ALMA observations and detailed modeling of the Red Rectangle
Bujarrabal, V.; Castro-Carrizo, A.; Alcolea, J.; Santander-García, M.; Van Winckel, H.; Sánchez Contreras, C.
2016-01-01
Aims We aim to study the rotating and expanding gas in the Red Rectangle, which is a well known object that recently left the asymptotic giant branch (AGB) phase. We analyze the properties of both components and the relation between them. Rotating disks have been very elusive in post-AGB nebulae, in which gas is almost always found to be in expansion. Methods We present new high-quality ALMA observations of C17O J=6−5 and H13CN J=4−3 line emission and results from a new reduction of already published 13CO J=3−2 data. A detailed model fitting of all the molecular line data, including previous maps and single-dish observations of lines of CO, CII, and CI, was performed using a sophisticated code that includes an accurate nonlocal treatment of radiative transfer in 2D. These observations (of low- and high-opacity lines requiring various degrees of excitation) and the corresponding modeling allowed us to deepen the analysis of the nebular properties. We also stress the uncertainties, particularly in the determination of the boundaries of the CO-rich gas and some properties of the outflow. Results We confirm the presence of a rotating equatorial disk and an outflow, which is mainly formed of gas leaving the disk. The mass of the disk is ~ 0.01 M⊙, and that of the CO-rich outflow is around ten times smaller. High temperatures of ≳ 100 K are derived for most components. From comparison of the mass values, we roughly estimate the lifetime of the rotating disk, which is found to be of about 10000 yr. Taking data of a few other post-AGB composite nebulae into account, we find that the lifetimes of disks around post-AGB stars typically range between 5000 and more than 20000 yr. The angular momentum of the disk is found to be high, ~ 9 M⊙ AU km s−1, which is comparable to that of the stellar system at present. Our observations of H13CN show a particularly wide velocity dispersion and indicate that this molecule is only abundant in the inner Keplerian disk, at
Observation and modelling of HOx radicals in a boreal forest
Directory of Open Access Journals (Sweden)
K. Hens
2014-08-01
Full Text Available Measurements of OH and HO2 radicals were conducted in a pine-dominated forest in southern Finland during the HUMPPA-COPEC-2010 (Hyytiälä United Measurements of Photochemistry and Particles in Air – Comprehensive Organic Precursor Emission and Concentration study field campaign in summer 2010. Simultaneous side-by-side measurements of hydroxyl radicals were conducted with two instruments using chemical ionization mass spectrometry (CIMS and laser-induced fluorescence (LIF, indicating small systematic disagreement, OHLIF / OHCIMS = (1.31 ± 0.14. Subsequently, the LIF instrument was moved to the top of a 20 m tower, just above the canopy, to investigate the radical chemistry at the ecosystem–atmosphere interface. Comprehensive measurements including observations of many volatile organic compounds (VOCs and the total OH reactivity were conducted and analysed using steady-state calculations as well as an observationally constrained box model. Production rates of OH calculated from measured OH precursors are consistent with those derived from the steady-state assumption and measured total OH loss under conditions of moderate OH reactivity. The primary photolytic sources of OH contribute up to one-third to the total OH production. OH recycling, which occurs mainly by HO2 reacting with NO and O3, dominates the total hydroxyl radical production in this boreal forest. Box model simulations agree with measurements for hydroxyl radicals (OHmod. / OHobs. = 1.00 ± 0.16, while HO2 mixing ratios are significantly under-predicted (HO2mod. / HO2obs. = 0.3 ± 0.2, and simulated OH reactivity does not match the observed OH reactivity. The simultaneous under-prediction of HO2 and OH reactivity in periods in which OH concentrations were simulated realistically suggests that the missing OH reactivity is an unaccounted-for source of HO2. Detailed analysis of the HOx production, loss, and recycling pathways suggests that in periods of high total OH reactivity
Radar observations and shape model of asteroid 16 Psyche
Shepard, Michael K.; Richardson, James; Taylor, Patrick A.; Rodriguez-Ford, Linda A.; Conrad, Al; de Pater, Imke; Adamkovics, Mate; de Kleer, Katherine; Males, Jared R.; Morzinski, Katie M.; Close, Laird M.; Kaasalainen, Mikko; Viikinkoski, Matti; Timerson, Bradley; Reddy, Vishnu; Magri, Christopher; Nolan, Michael C.; Howell, Ellen S.; Benner, Lance A. M.; Giorgini, Jon D.; Warner, Brian D.; Harris, Alan W.
2017-01-01
Using the S-band radar at Arecibo Observatory, we observed 16 Psyche, the largest M-class asteroid in the main belt. We obtained 18 radar imaging and 6 continuous wave runs in November and December 2015, and combined these with 16 continuous wave runs from 2005 and 6 recent adaptive-optics (AO) images (Drummond et al., 2016) to generate a three-dimensional shape model of Psyche. Our model is consistent with a previously published AO image (Hanus et al., 2013) and three multi-chord occultations. Our shape model has dimensions 279 × 232 × 189 km (± 10%), Deff = 226 ± 23 km, and is 6% larger than, but within the uncertainties of, the most recently published size and shape model generated from the inversion of lightcurves (Hanus et al., 2013). Psyche is roughly ellipsoidal but displays a mass-deficit over a region spanning 90° of longitude. There is also evidence for two ∼50-70 km wide depressions near its south pole. Our size and published masses lead to an overall bulk density estimate of 4500 ± 1400 kgm-3. Psyche's mean radar albedo of 0.37 ± 0.09 is consistent with a near-surface regolith composed largely of iron-nickel and ∼40% porosity. Its radar reflectivity varies by a factor of 1.6 as the asteroid rotates, suggesting global variations in metal abundance or bulk density in the near surface. The variations in radar albedo appear to correlate with large and small-scale shape features. Our size and Psyche's published absolute magnitude lead to an optical albedo of pv = 0.15 ± 0.03, and there is evidence for albedo variegations that correlate with shape features.
Asteroid 16 Psyche: Radar Observations and Shape Model
Shepard, Michael K.; Richardson, James E.; Taylor, Patrick A.; Rodriguez-Ford, Linda A.; Conrad, Al; de Pater, Imke; Adamkovics, Mate; de Kleer, Katherine R.; Males, Jared; Morzinski, Kathleen M.; Miller Close, Laird; Kaasalainen, Mikko; Viikinkoski, Matti; Timerson, Bradley; Reddy, Vishnu; Magri, Christopher; Nolan, Michael C.; Howell, Ellen S.; Warner, Brian D.; Harris, Alan W.
2016-10-01
We observed 16 Psyche, the largest M-class asteroid in the main belt, using the S-band radar at Arecibo Observatory. We obtained 18 radar imaging and 6 continuous wave runs in November and December 2015, and combined these with 16 continuous wave runs from 2005 and 6 recent adaptive-optics (AO) images to generate a three-dimensional shape model of Psyche. Our model is consistent with a previously published AO image [Hanus et al. Icarus 226, 1045-1057, 2013] and three multi-chord occultations. Our shape model has dimensions 279 x 232 x 189 km (±10%), Deff = 226 ± 23 km, and is 6% larger than, but within the uncertainties of, the most recently published size and shape model generated from the inversion of lightcurves [Hanus et al., 2013]. Psyche is roughly ellipsoidal but displays a mass-deficit over a region spanning 90° of longitude. There is also evidence for two ~50-70 km wide depressions near its south pole. Our size and published masses lead to an overall bulk density estimate of 4500 ± 1400 kg m-3. Psyche's mean radar albedo of 0.37 ± 0.09 is consistent with a near-surface regolith composed largely of iron-nickel and ~40% porosity. Its radar reflectivity varies by a factor of 1.6 as the asteroid rotates, suggesting global variations in metal abundance or bulk density in the near surface. The variations in radar albedo appear to correlate with large and small-scale shape features. Our size and Psyche's published absolute magnitude lead to an optical albedo of pv = 0.15 ± 0.03, and there is evidence for albedo variegations that correlate with shape features.
Energy Technology Data Exchange (ETDEWEB)
NONE
1995-08-01
The objectives of this Report are two-fold: (1) to provide overviews of the state-of-the-art and state-of-the-practice with respect to air sparging technology, air sparging models and related or augmentation technologies (e.g., soil vapor extraction); and (2) to provide the basis for the development of the conceptual Decision Tool. The Project Team conducted an exhaustive review of available literature. The complete listing of the documents, numbering several hundred and reviewed as a part of this task, is included in Appendix A. Even with the large amount of material written regarding the development and application of air sparging, there still are significant gaps in the technical community`s understanding of the remediation technology. The results of the literature review are provided in Section 2. In Section 3, an overview of seventeen conceptual, theoretical, mathematical and empirical models is presented. Detailed descriptions of each of the models reviewed is provided in Appendix B. Included in Appendix D is a copy of the questionnaire used to compile information about the models. The remaining sections of the document reflect the analysis and synthesis of the information gleaned during the literature and model reviews. The results of these efforts provide the basis for development of the decision tree and conceptual decision tool for determining applicability and optimization of air sparging. The preliminary decision tree and accompanying information provided in Section 6 describe a three-tiered approach for determining air sparging applicability: comparison with established scenarios; calculation of conceptual design parameters; and the conducting of pilot-scale studies to confirm applicability. The final two sections of this document provide listings of the key success factors which will be used for evaluating the utility of the Decision Tool and descriptions of potential applications for Decision Tool use.
Chavarie, Louise; Muir, Andrew M.; Zimmerman, Mara S.; Baillie, Shauna M.; Hansen, Michael J.; Nate, Nancy A.; Yule, Daniel L.; Middel, Trevor; Bentzen, Paul; Krueger, Charles C.
2016-01-01
All examples of lake charr (Salvelinus namaycush) diversity occur within the largest, deepest lakes of North America (i.e. > 2000 km2). We report here Rush Lake (1.3 km2) as the first example of a small lake with two lake charr morphs (lean and huronicus). Morphology, diet, life history, and genetics were examined to demonstrate the existence of morphs and determine the potential influence of evolutionary processes that led to their formation or maintenance. Results showed that the huronicus morph, caught in deep-water, had a deeper body, smaller head and jaws, higher eye position, greater buoyancy, and deeper peduncle than the shallow-water lean morph. Huronicus grew slower to a smaller adult size, and had an older mean age than the lean morph. Genetic comparisons showed low genetic divergence between morphs, indicating incomplete reproductive isolation. Phenotypic plasticity and differences in habitat use between deep and shallow waters associated with variation in foraging opportunities seems to have been sufficient to maintain the two morphs, demonstrating their important roles in resource polymorphism. Rush Lake expands previous explanations for lake charr intraspecific diversity, from large to small lakes and from reproductive isolation to the presence of gene flow associated with strong ecological drivers.
Halliwell, G. R.; Srinivasan, A.; Kourafalou, V. H.; Yang, H.; Le Henaff, M.; Atlas, R. M.
2012-12-01
The accuracy of hurricane intensity forecasts produced by coupled forecast models is influenced by errors and biases in SST forecasts produced by the ocean model component and the resulting impact on the enthalpy flux from ocean to atmosphere that powers the storm. Errors and biases in fields used to initialize the ocean model seriously degrade SST forecast accuracy. One strategy for improving ocean model initialization is to design a targeted observing program using airplanes and in-situ devices such as floats and drifters so that assimilation of the additional data substantially reduces errors in the ocean analysis system that provides the initial fields. Given the complexity and expense of obtaining these additional observations, observing system design methods such as OSSEs are attractive for designing efficient observing strategies. A new fraternal-twin ocean OSSE system based on the HYbrid Coordinate Ocean Model (HYCOM) is used to assess the impact of targeted ocean profiles observed by hurricane research aircraft, and also by in-situ float and drifter deployments, on reducing errors in initial ocean fields. A 0.04-degree HYCOM simulation of the Gulf of Mexico is evaluated as the nature run by determining that important ocean circulation features such as the Loop Current and synoptic cyclones and anticyclones are realistically simulated. The data-assimilation system is run on a 0.08-degree HYCOM mesh with substantially different model configuration than the nature run, and it uses a new ENsemble Kalman Filter (ENKF) algorithm optimized for the ocean model's hybrid vertical coordinates. The OSSE system is evaluated and calibrated by first running Observing System Experiments (OSEs) to evaluate existing observing systems, specifically quantifying the impact of assimilating more than one satellite altimeter, and also the impact of assimilating targeted ocean profiles taken by the NOAA WP-3D hurricane research aircraft in the Gulf of Mexico during the Deepwater
Adaptive mixture observation models for multiple object tracking
Institute of Scientific and Technical Information of China (English)
CUI Peng; SUN LiFeng; YANG ShiQiang
2009-01-01
Multiple object tracking (MOT) poses many difficulties to conventional well-studied single object track-ing (SOT) algorithms, such as severe expansion of configuration space, high complexity of motion con-ditions, and visual ambiguities among nearby targets, among which the visual ambiguity problem is the central challenge. In this paper, we address this problem by embedding adaptive mixture observation models (AMOM) into a mixture tracker which is implemented in Particle Filter framework. In AMOM, the extracted multiple features for appearance description are combined according to their discriminative power between ambiguity prone objects, where the discriminability of features are evaluated by online entropy-based feature selection techniques. The induction of AMOM can help to surmount the Incapa-bility of conventional mixture tracker in handling object occlusions, and meanwhile retain its merits of flexibility and high efficiency. The final experiments show significant improvement in MOT scenarios compared with other methods.
Gaussian estimation for discretely observed Cox-Ingersoll-Ross model
Wei, Chao; Shu, Huisheng; Liu, Yurong
2016-07-01
This paper is concerned with the parameter estimation problem for Cox-Ingersoll-Ross model based on discrete observation. First, a new discretized process is built based on the Euler-Maruyama scheme. Then, the parameter estimators are obtained by employing the maximum likelihood method and the explicit expressions of the error of estimation are given. Subsequently, the consistency property of all parameter estimators are proved by applying the law of large numbers for martingales, Holder's inequality, B-D-G inequality and Cauchy-Schwarz inequality. Finally, a numerical simulation example for estimators and the absolute error between estimators and true values is presented to demonstrate the effectiveness of the estimation approach used in this paper.
ARMA模型平稳解存在性问题的一些研究%Some Results on the Existence of Stationary Solutions to ARMA Models
Institute of Scientific and Technical Information of China (English)
马新生; 胡文玉; 翁瑾; 刘县明
2009-01-01
ARMA模型是现代时间序列分析中最为常用的模型之一,在科学研究和工程系统中具有广泛的运用.ARMA 模型使用的前提条件是,建立的时间序列是由一个零均值的平稳随机过程所产生的,即其存在性能够得到保证.基于此,详细讨论了所有情形下AR模型及ARMA模型平稳解的存在性条件,然后将一维ARMA模型的渐进平稳性转化为向量AR模型的平稳性,从而给出了ARMA模型存在渐进平稳解的充分条件.%ARMA model is one of the most common models in the modern time series analysis which is widely used in scientific researches and engineering systems.However,the precondition of applying ARMA model is that the established time-series model must be generated from a zero-mean and stationary stochastic process,say,the existence of the solution to the ARMA model.Based on this,the existence of the stationary solutions to ARMA model and AR model is studied in detail firstly,and then the sufficient conditions for the existence of asymptotic stationary solutions to the ARMA model are given,which is obtained by transforming the case of one dimensional ARMA model to the case of vector AR model.
Photometric Observation and Modeling Study of the Asteroid (26) Proserpina
Bin, Li; Hai-bin, Zhao; Xin, Wang
2016-07-01
We present the new CCD observations on the asteroid (26) Proserpina performed between 2011 December and 2012 February. Based upon the new observations, a synodic rotation period of (13.107 ± 0.002) h is obtained. Using all the light curves available sofar, the rotation vector, rotation period, and the shape model of the asteroid are determined with the convex-hull inversion method. Further more, a bootstrap method is applied to estimating the uncertainties of the rotation parameters. We derive a pair of possible rotation poles for (26) Proserpina, and believe that it has a retrograde rotation. The rotation poles are determined to be λ1 = 90.8° ± 1.4°, β1 = -53.1° ± 3.2°, and λ2 = 259.3° ± 2.2°, β2 = -62.0° ± 2.0°. The sidereal rotation periods corresponding to the two poles are almost the same as (13.109777 ± 3.8 × 10-6) h. And corresponding to this pair of rotation poles, the convex-hull shapes of the asteroid are the mirror images of each other.
Modelling Agro-Met Station Observations Using Genetic Algorithm
Directory of Open Access Journals (Sweden)
Prashant Kumar
2014-01-01
Full Text Available The present work discusses the development of a nonlinear data-fitting technique based on genetic algorithm (GA for the prediction of routine weather parameters using observations from Agro-Met Stations (AMS. The algorithm produces the equations that best describe the temporal evolutions of daily minimum and maximum near-surface (at 2.5-meter height air temperature and relative humidity and daily averaged wind speed (at 10-meter height at selected AMS locations. These enable the forecasts of these weather parameters, which could have possible use in crop forecast models. The forecast equations developed in the present study use only the past observations of the above-mentioned parameters. This approach, unlike other prediction methods, provides explicit analytical forecast equation for each parameter. The predictions up to 3 days in advance have been validated using independent datasets, unknown to the training algorithm, with impressive results. The power of the algorithm has also been demonstrated by its superiority over persistence forecast used as a benchmark.
ENSO Amplitude Change in Observation and Coupled Models
Institute of Scientific and Technical Information of China (English)
ZHANG Qiong; GUAN Yue; YANG Haijun
2008-01-01
Observations show that the tropical El Nino-Southern Oscillation (ENSO) variability, after removing both the long term trend and decadal change of the background climate, has been enhanced by as much as 60% during the past 50 years. This shift in ENSO amplitude can be related to mean state changes in global climate. Past global warming has caused a weakening of the Walker circulation over the equatorial Indo-Pacific oceans, as well as a weakening of the trade winds and a reduction in the equatorial upwelling. These changes in tropical climatology play as stabilizing factors of the tropical coupling system. However, the shallower and strengthening thermocline in the equatorial Pacific increases the SST sensitivity to thermocline and wind stress variabilities and tend to destabilize the tropical coupling system. Observations suggest that the destabilizing factors, such as the strengthening thermocline, may have overwhelmed the stabilizing effects of the atmosphere, and played a deterministic role in the enhanced ENSO variability, at least during the past half century. This is different from the recent assessment of IPCC-AR4 coupled models.
Joossen, Cedric; Lanckacker, Ellen; Zakaria, Nadia; Koppen, Carina; Joossens, Jurgen; Cools, Nathalie; De Meester, Ingrid; Lambeir, Anne-Marie; Delputte, Peter; Maes, Louis; Cos, Paul
2016-05-01
The aim of this research was to optimize and validate an animal model for dry eye, adopting clinically relevant evaluation parameters. Dry eye was induced in female Wistar rats by surgical removal of the exorbital lacrimal gland. The clinical manifestations of dry eye were evaluated by tear volume measurements, corneal fluorescein staining, cytokine measurements in tear fluid, MMP-9 mRNA expression and CD3(+) cell infiltration in the conjunctiva. The animal model was validated by treatment with Restasis(®) (4 weeks) and commercial dexamethasone eye drops (2 weeks). Removal of the exorbital lacrimal gland resulted in 50% decrease in tear volume and a gradual increase in corneal fluorescein staining. Elevated levels of TNF-α and IL-1α have been registered in tear fluid together with an increase in CD3(+) cells in the palpebral conjunctiva when compared to control animals. Additionally, an increase in MMP-9 mRNA expression was recorded in conjunctival tissue. Reference treatment with Restasis(®) and dexamethasone eye drops had a positive effect on all evaluation parameters, except on tear volume. This rat dry eye model was validated extensively and judged appropriate for the evaluation of novel compounds and therapeutic preparations for dry eye disease.
TIME-IGGCAS model validation:Comparisons with empirical models and observations
Institute of Scientific and Technical Information of China (English)
2008-01-01
The TIME-IGGCAS (Theoretical Ionospheric Model of the Earth in Institute of Ge- ology and Geophysics, Chinese Academy of Sciences) has been developed re- cently on the basis of previous works. To test its validity, we have made compari- sons of model results with other typical empirical ionospheric models (IRI, NeQuick-ITUR, and TItheridge temperature models) and multi-observations (GPS, Ionosondes, Topex, DMSP, FORMOSAT, and CHAMP) in this paper. Several conclu- sions are obtained from our comparisons. The modeled electron density and elec- tron and ion temperatures are quantitatively in good agreement with those of em- pirical models and observations. TIME-IGGCAS can model the electron density variations versus several factors such as local time, latitude, and season very well and can reproduce most anomalistic features of ionosphere including equatorial anomaly, winter anomaly, and semiannual anomaly. These results imply a good base for the development of ionospheric data assimilation model in the future. TIME-IGGCAS underestimates electron temperature and overestimates ion tem- perature in comparison with either empirical models or observations. The model results have relatively large deviations near sunrise time and sunset time and at the low altitudes. These results give us a reference to improve the model and enhance its performance in the future.
Jones, Ant
2015-01-01
The construction of viable and physically-realistic interstellar dust models is only possible if the constraints imposed by laboratory data on interstellar dust analogue materials are respected and used within a meaningful theoretical framework. These physical dust models can then be directly compared to observations without the need for any tuning to fit the observations. Such models will generally fail to achieve the excellent fits to observations that empirical models are able to achieve. However, the physically-realistic approach will necessarily lead to a deeper insight and a fuller understanding of the nature and evolution of interstellar dust. The THEMIS modelling approach, based on (hydrogenated) amorphous carbons and amorphous silicates with metallic Fe and/or FeS nano-inclusions appears to be a promising move in this direction.
Model of load distribution for earth observation satellite
Tu, Shumin; Du, Min; Li, Wei
2017-03-01
For the system of multiple types of EOS (Earth Observing Satellites), it is a vital issue to assure that each type of payloads carried by the group of EOS can be used efficiently and reasonably for in astronautics fields. Currently, most of researches on configuration of satellite and payloads focus on the scheduling for launched satellites. However, the assignments of payloads for un-launched satellites are bit researched, which are the same crucial as the scheduling of tasks. Moreover, the current models of satellite resources scheduling lack of more general characteristics. Referring the idea about roles-based access control (RBAC) of information system, this paper brings forward a model based on role-mining of RBAC to improve the generality and foresight of the method of assignments of satellite-payload. By this way, the assignment of satellite-payload can be mapped onto the problem of role-mining. A novel method will be introduced, based on the idea of biclique-combination in graph theory and evolutionary algorithm in intelligence computing, to address the role-mining problem of satellite-payload assignments. The simulation experiments are performed to verify the novel method. Finally, the work of this paper is concluded.
Tropical widening in models, reanalyses, and satellite observations
Davis, S. M.; Rosenlof, K. H.; Young, P. J.
2012-12-01
Poleward migration of the latitudinal edge of the tropics of ~0.25 - 3° decade-1 has been reported in several recent studies based on satellite, radiosonde, and reanalysis data covering the past ~30 years. Disagreements between models and observations have been noted, and to date, it has been unclear to what extent this large range of trends can be explained by the use of different data sources, time periods, and edge definitions. In this presentation, we address these issues by applying a suite of tropical edge latitude diagnostics based on tropopause height, winds, precipitation/evaporation, and outgoing longwave radiation (OLR) to six reanalyses and four satellite data sets. These diagnostics include both previously used definitions and new definitions designed for more robust detection. The wide range of widening trends is shown to be primarily due to the use of different data sets and edge definitions, and only secondarily due to varying start/end dates. We also show that the large trends (> ~ 1° decade-1) previously reported in tropopause and OLR diagnostics are partially due to the use of subjective definitions based on absolute thresholds. Statistically significant Hadley cell expansion based on the mean meridional streamfunction of ~1.0° decade-1 is present in all but one reanalysis, whereas other diagnostics yield trends of -0.5 - 0.8° decade-1 that are mostly insignificant. These results are compared to coupled model trends calculated over both the 20th and 21st centuries.
Infrared Observations Of Saturn's Rings : Azimuthal Variations And Thermal Modeling
Leyrat, C.; Spilker, L. J.; Altobelli, N.; Pilorz, S.; Ferrari, C.; Edgington, S. G.; Wallis, B. D.; Nugent, C.; Flasar, M.
2007-12-01
Saturn's rings represent a collection of icy centimeter to meter size particles with their local dynamic dictated by self gravity, mutual collisions, surface roughness and thickness of the rings themselves. The infrared observations obtained by the CIRS infrared spectrometer on board Cassini over the last 3.5 year contain informations on the local dynamic, as the thermal signature of planetary rings is influenced both by the ring structure and the particle properties. The ring temperature is very dependent on the solar phase angle (Spilker et al., this issue), and on the local hour angle around Saturn, depending on whether or not particles' visible hemispheres are heated by the Sun. The geometric filling factor, which can be estimated from CIRS spectra, is less dependent on the local hour angle, suggesting that the non isothermal behavior of particles' surfaces have low impact, but it is very dependent on the spacecraft elevation for the A and C rings. The ring small scale structure can be explored using CIRS data. Variations of the filling factor with the local hour angle relative to the spacecraft azimuth reveals self-gravity wakes. We derive morphological parameters of such wakes in both A and B rings assuming that wakes can be modeled either by regularly spaced bars with infinite or finite optical depth. Our results indicates that wakes in the A ring are almost flat, with a ratio height/width ≈ 0.44 ± 0.16 and with a pitch angle relative to the orbital motion direction of ≍ 27deg. This is consistent with UVIS (Colwell et al., 2006) and VIMS data (Hedman et al., 2007). Such models are more difficult to constrain in the B ring, but small variations of the filling factor indicate that the pitch angle decreases drastically in this ring. We also present a new thermal bar model to explain azimuthal variations of temperatures in the A ring. We compare results with previous ring thermal models of spherical particles. The Cassini/CIRS azimuthal scans data set is
Directory of Open Access Journals (Sweden)
Larin S. N.
2016-04-01
Full Text Available Studying the problems of the development of Russian business education today seems urgent in view of the serious impact of globalization factors on world markets, as well as taking into account the factors of global economic recession and to the undeclared war sanctions restrictions against the Russian economy and not having under itself no justification other than political. The article presents the results of the analysis of positive and negative factors in the development of the Russian business education, because of which it was concluded, that for the further development of the Russian system of business education needs a new approach. It should be based on the formation of the conceptual model, taking into account the current realities in the Russian economy. The authors set out to become the key provisions of the new approach, namely to ensure the growth of professional and specialist competencies required functionality; the study of «effective practical techniques», a reasonable reduction of the duration of the MBA program of study; distribution of specialists trained in powers depending on their positions. The above provisions allowed forming a conceptual model of business education, which is based on four practical degree professional training laid. In addition, the article justified criteria for evaluating the quality and composition requirements for modern business education program. The proposed in the article new approach and the conceptual model of the development of Russian business education are targeted at practitioners who want to gain more knowledge in a limited period and very reasonable cost of education. The further development of the Russian business education system in the very near future will show the validity of this approach
Atmospheric Nitrogen Deposition to the Oceans: Observation- and Model-Based Estimates
Baker, Alex
2016-04-01
The reactive nitrogen (Nr) burden of the atmosphere has been increased by a factor of 3-4 by anthropogenic activity since the Industrial Revolution. This has led to large increases in the deposition of nitrate and ammonium to the surface waters of the open ocean, particularly downwind of major human population centres, such as those in North America, Europe and Southeast Asia. In oligotrophic waters, this deposition has the potential to significantly impact marine productivity and the global carbon cycle. Global-scale understanding of N deposition to the oceans is reliant on our ability to produce effective models of reactive nitrogen emission, atmospheric chemistry, transport and deposition (including deposition to the land surface). Over land, N deposition models can be assessed using comparisons to regional monitoring networks of precipitation chemistry (notably those located in North America, Europe and Southeast Asia). No similar datasets exist which would allow observation - model comparisons of wet deposition for the open oceans, because long-term wet deposition records are available for only a handful of remote island sites and rain collection over the open ocean itself is logistically very difficult. In this work we attempt instead to use ~2800 observations of aerosol nitrate and ammonium concentrations, acquired from sampling aboard ships in the period 1995 - 2012, to assess the performance of modelled N deposition fields over the remote ocean. This database is non-uniformly distributed in time and space. We selected three ocean regions (the eastern tropical North Atlantic, the northern Indian Ocean and northwest Pacific) where we considered the density and distribution of observational data is sufficient to provide effective comparison to the model ensemble. Our presentation will focus on the eastern tropical North Atlantic region, which has the best data coverage of the three. We will compare dry deposition fluxes calculated from the observed nitrate
Directory of Open Access Journals (Sweden)
Seyyed Aqil Hoseiny
2013-08-01
Full Text Available In the Bewley models, the endowment is faced to idiosyncratic risks. But contingent claims markets is restricted or completely excluded by assumption and so households couldn’t insure themselves against these risks. Consequently, households will have strong motive to precautionary saving for self-insurance. Households’ only option is to “self-insure” by managing a stock of a single asset to buffer their consumption against adverse shocks. The bewley models differ mainly with respect to the particular asset that is the instrument for self-insurance: fiat currency, credit (such as IOU's, bank deposits, government bonds and so on or capital. In these models if the interest rate would be equal to the rate of the time preference then asset and consumption diverge to infinity and so monetary equilibrium doesn't exist. Therefore these models conclude that the use of Friedman rule can be misleading in an incomplete market setup. Therefore these models reduce the interest rate so that asset and consumption converge and consequently the monetary equilibrium exists.In this paper we extend the bewley models and construct a heterogeneous model with idiosyncratic risks and borrowing constraint where agents hold money and bearing interest assets as government bonds for precautionary motives and self-insurance. We show that the consequences of bewley models in this condition are still true: There should be the interest rate lower than time preference to insure the existence of monetary equilibrium. With sufficient uncertainty in the income and interest rate sequences, consumption will grow without bound even if the rate of interest is equal to or greater than the discount rate.
Brown, Patrick T; Li, Wenhong; Cordero, Eugene C; Mauget, Steven A
2015-04-21
The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much public and scientific attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible unforced states of the climate system (the Envelope of Unforced Noise; EUN). Typically, the EUN is derived from climate models themselves, but climate models might not accurately simulate the correct characteristics of unforced GMT variability. Here, we simulate a new, empirical, EUN that is based on instrumental and reconstructed surface temperature records. We compare the forced GMT signal produced by climate models to observations while noting the range of GMT values provided by the empirical EUN. We find that the empirical EUN is wide enough so that the interdecadal variability in the rate of global warming over the 20(th) century does not necessarily require corresponding variability in the rate-of-increase of the forced signal. The empirical EUN also indicates that the reduced GMT warming over the past decade or so is still consistent with a middle emission scenario's forced signal, but is likely inconsistent with the steepest emission scenario's forced signal.
Air-Sea interactions:Observations and models
Clayson, C. A.
2014-12-01
these analyses between satellite data sets, reanalysis products, and CMIP5 models. By focusing to a large extent on distributional characteristics, and particularly to extremes, comparisons of in situ observations and satellite data sets with distributions from coupled models (e.g. CMIP5) can be made directly.
Tidally modulated eruptions on Enceladus: Cassini ISS observations and models
Energy Technology Data Exchange (ETDEWEB)
Nimmo, Francis [Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064 (United States); Porco, Carolyn; Mitchell, Colin, E-mail: carolyn@ciclops.org [CICLOPS, Space Science Institute, Boulder, CO 80304 (United States)
2014-09-01
We use images acquired by the Cassini Imaging Science Subsystem (ISS) to investigate the temporal variation of the brightness and height of the south polar plume of Enceladus. The plume's brightness peaks around the moon's apoapse, but with no systematic variation in scale height with either plume brightness or Enceladus' orbital position. We compare our results, both alone and supplemented with Cassini near-infrared observations, with predictions obtained from models in which tidal stresses are the principal control of the eruptive behavior. There are three main ways of explaining the observations: (1) the activity is controlled by right-lateral strike slip motion; (2) the activity is driven by eccentricity tides with an apparent time delay of about 5 hr; (3) the activity is driven by eccentricity tides plus a 1:1 physical libration with an amplitude of about 0.°8 (3.5 km). The second hypothesis might imply either a delayed eruptive response, or a dissipative, viscoelastic interior. The third hypothesis requires a libration amplitude an order of magnitude larger than predicted for a solid Enceladus. While we cannot currently exclude any of these hypotheses, the third, which is plausible for an Enceladus with a subsurface ocean, is testable by using repeat imaging of the moon's surface. A dissipative interior suggests that a regional background heat source should be detectable. The lack of a systematic variation in plume scale height, despite the large variations in plume brightness, is plausibly the result of supersonic flow; the details of the eruption process are yet to be understood.
Image quality in CT: From physical measurements to model observers.
Verdun, F R; Racine, D; Ott, J G; Tapiovaara, M J; Toroi, P; Bochud, F O; Veldkamp, W J H; Schegerer, A; Bouwman, R W; Giron, I Hernandez; Marshall, N W; Edyvean, S
2015-12-01
Evaluation of image quality (IQ) in Computed Tomography (CT) is important to ensure that diagnostic questions are correctly answered, whilst keeping radiation dose to the patient as low as is reasonably possible. The assessment of individual aspects of IQ is already a key component of routine quality control of medical x-ray devices. These values together with standard dose indicators can be used to give rise to 'figures of merit' (FOM) to characterise the dose efficiency of the CT scanners operating in certain modes. The demand for clinically relevant IQ characterisation has naturally increased with the development of CT technology (detectors efficiency, image reconstruction and processing), resulting in the adaptation and evolution of assessment methods. The purpose of this review is to present the spectrum of various methods that have been used to characterise image quality in CT: from objective measurements of physical parameters to clinically task-based approaches (i.e. model observer (MO) approach) including pure human observer approach. When combined together with a dose indicator, a generalised dose efficiency index can be explored in a framework of system and patient dose optimisation. We will focus on the IQ methodologies that are required for dealing with standard reconstruction, but also for iterative reconstruction algorithms. With this concept the previously used FOM will be presented with a proposal to update them in order to make them relevant and up to date with technological progress. The MO that objectively assesses IQ for clinically relevant tasks represents the most promising method in terms of radiologist sensitivity performance and therefore of most relevance in the clinical environment.
Radiation Observations from CREAM & CREDO and Comparison with Standard Models
Dyer, C.; Watson, C.; Truscott, P.; Peerless, C.
1996-12-01
The Cosmic Radiation Environment and Activation Monitor (CREAM) has flown on six Shuttle flights between September 1991 and February 1995, covering the full range of inclinations as well as altitudes between 210 and 550 km. Meanwhile the Cosmic Radiation Environment and Dosimetry experiment (CREDO) has operated continuously on UOSAT-3 in 800 km, 98.7 degree orbit since April 1990. Similar detectors were launched on KITSAT-1 (1330 km, 66 degree inclination) in August 1992 and POSAT-l (790 km, 98.7 degree inclination) in September 1993. Since the summer of 1994, CREDO-II versions have been operating on APEX in an eccentric orbit (350x2486 km) at 70 degree inclination, and on STRV in geostationary transfer orbit (298x35953 km, 7 degree inclination). These experiments are designed to measure protons, cosmic rays and accumulated dose. Through the variety of missions employed they have now achieved wide coverage of the magnetosphere as well as a significant portion of a solar cycle. The LEO observations have shown the Westward drift of the South Atlantic Anomaly, new regimes of trapped protons in the region of L=2.6 following solar flare events in March 1991 and October 1992, and an altitude dependence of trapped protons which is at variance with AP8. On STRV the background channel of the Cold Ion Detector serves as a complementary electron detector and shows the extreme time variability of the outer radiation belt, while the total dose is significantly less than AE8 predictions. In addition to the data on trapped radiation, important results are being obtained on the linear energy transfer spectra from cosmic rays. Detailed shielding models of the APEX and STRV spacecraft have been constructed and used to compare the observations of dose and LET spectra with predictions from AE8, AP8 and CREME for a variety of shielding depths. Consistent results on the LET spectra are obtained from APEX and STRV when data are selected by cut-off rigidity. The influence of spacecraft
Bunn, Emory F; Zheng, Haoxuan
2016-01-01
We examine the degree to which observations of large-scale cosmic microwave background (CMB) polarization can shed light on the puzzling large-scale power modulation in maps of CMB anisotropy. We consider a phenomenological model in which the observed anomaly is caused by modulation of large-scale primordial curvature perturbations, and calculate Fisher information and error forecasts for future polarization data, constrained by the existing CMB anisotropy data. Because a significant fraction of the available information is contained in correlations with the anomalous temperature data, it is essential to account for these constraints. We also present a systematic approach to finding a set of normal modes that maximize the available information, generalizing the well-known Karhunen-Loeve transformation to take account of the constraints from the temperature data. A polarization map covering at least $\\sim 60\\%$ of the sky should be able to provide a $3\\sigma$ detection of modulation at the level favored by the...
Eight Year Climatologies from Observational (AIRS) and Model (MERRA) Data
Hearty, Thomas; Savtchenko, Andrey; Won, Young-In; Theobalk, Mike; Vollmer, Bruce; Manning, Evan; Smith, Peter; Ostrenga, Dana; Leptoukh, Greg
2010-01-01
We examine climatologies derived from eight years of temperature, water vapor, cloud, and trace gas observations made by the Atmospheric Infrared Sounder (AIRS) instrument flying on the Aqua satellite and compare them to similar climatologies constructed with data from a global assimilation model, the Modern Era Retrospective-Analysis for Research and Applications (MERRA). We use the AIRS climatologies to examine anomalies and trends in the AIRS data record. Since sampling can be an issue for infrared satellites in low earth orbit, we also use the MERRA data to examine the AIRS sampling biases. By sampling the MERRA data at the AIRS space-time locations both with and without the AIRS quality control we estimate the sampling bias of the AIRS climatology and the atmospheric conditions where AIRS has a lower sampling rate. While the AIRS temperature and water vapor sampling biases are small at low latitudes, they can be more than a few degrees in temperature or 10 percent in water vapor at higher latitudes. The largest sampling biases are over desert. The AIRS and MERRA data are available from the Goddard Earth Sciences Data and Information Services Center (GES DISC). The AIRS climatologies we used are available for analysis with the GIOVANNI data exploration tool. (see, http://disc.gsfc.nasa.gov).
Tolkach, Yuri; Eminaga, Okyaz; Wötzel, Fabian; Huss, Sebastian; Bettendorf, Olaf; Eltze, Elke; Abbas, Mahmoud; Imkamp, Florian; Semjonow, Axel
2017-03-01
Fresh tissue is mandatory to perform high-quality translation studies. Several models for tissue extraction from prostatectomy specimens without guidance by frozen sections are already introduced. However, little is known about the sampling efficacy of these models, which should provide representative tissue in adequate volumes, account for multifocality and heterogeneity of tumor, not violate the routine final pathological examination, and perform quickly without frozen section-based histological control. The aim of the study was to evaluate the sampling efficacy of the existing tissue extraction models without guidance by frozen sections ("blind") and to develop an optimized model for tissue extraction. Five hundred thirty-three electronic maps of the tumor distribution in prostates from a single-center cohort of the patients subjected to radical prostatectomy were used for analysis. Six available models were evaluated in silico for their sampling efficacy. Additionally, a novel model achieving the best sampling efficacy was developed. The available models showed high efficacies for sampling "any part" from the tumor (up to 100%), but were uniformly low in efficacy to sample all tumor foci from the specimens (with the best technique sampling only 51.6% of the all tumor foci). The novel 4-level extraction model achieved a sampling efficacy of 93.1% for all tumor foci. The existing "blind" tissue extraction models from prostatectomy specimens without frozen sections control are suitable to target tumor tissues but these tissues do not represent the whole tumor. The novel 4-level model provides the highest sampling efficacy and a promising potential for integration into routine. Prostate 77: 396-405, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
Winder, Joshua S; Lyn-Sue, Jerome; Kunselman, Allen R; Pauli, Eric M
2017-02-01
Posterior component separation herniorrhaphy via transversus abdominis release (TAR) permits midline reapproximation of large fascial defects. To date, no report delineates the reduction in tensile force to reapproximate midline fascia following TAR. We hypothesized that open and laparoscopic TAR would provide similar reductions in midline reapproximation forces in a porcine model. Under general anesthesia, a 20-cm midline laparotomy was created and bilateral lipocutaneous flaps were raised to expose the anterior rectus sheath. Five stainless steel hooks were placed at 1-cm intervals lateral to the midline at three locations: 5 cm above, at, and 5 cm below the umbilicus bilaterally. Baseline force measurements were taken by pulling each lateral point to midline. Laparoscopic TAR was performed unilaterally by incising the parietal peritoneum and transversus muscle lateral to the linea semilunaris. Open TAR was performed contralaterally, and force measurements were repeated. Comparisons were made to baseline and between the groups. Following laparoscopic TAR, 87 % (13/15) of points showed significant reduction compared to baseline forces, whereas only 20 % (3/15) of open TAR points had significant force reductions. Compared to open TAR, three locations favored the laparoscopic approach [1 cm lateral to midline, 5 cm above the umbilicus (p = 0.04; 95 % CI 0.78-1.00), 2 cm lateral to midline at the umbilicus (p = 0.04; 95 % CI 0.80-1.00), and 1 cm lateral to midline 5 cm below the umbilicus (p = 0.05; 95 % CI 0.79-1.00)]. The mean length of TAR was longer for laparoscopic than open at 27.29 versus 19.55 cm (p force at few locations, suggesting that the mechanism by which TAR facilitates herniorraphy may not solely be through reductions in linea alba tensile forces. At specific locations, laparoscopic TAR provides superior reduction in midline closure force compared to open TAR, likely as a result of a longer muscle release.
Institute of Scientific and Technical Information of China (English)
Zhen WANG; Hui ZHANG
2014-01-01
In this work, we obtain the global existence and uniqueness of classical solu-tions to a viscous liquid-gas two-phase model with mass-dependent viscosity and vacuum in one dimension, where the initial vacuum is allowed. We get the upper and lower bounds of gas and liquid masses n and m by the continuity methods which we use to study the compressible Navier-Stokes equations.
Model-observer similarity, error modeling and social learning in rhesus macaques.
Monfardini, Elisabetta; Hadj-Bouziane, Fadila; Meunier, Martine
2014-01-01
Monkeys readily learn to discriminate between rewarded and unrewarded items or actions by observing their conspecifics. However, they do not systematically learn from humans. Understanding what makes human-to-monkey transmission of knowledge work or fail could help identify mediators and moderators of social learning that operate regardless of language or culture, and transcend inter-species differences. Do monkeys fail to learn when human models show a behavior too dissimilar from the animals' own, or when they show a faultless performance devoid of error? To address this question, six rhesus macaques trained to find which object within a pair concealed a food reward were successively tested with three models: a familiar conspecific, a 'stimulus-enhancing' human actively drawing the animal's attention to one object of the pair without actually performing the task, and a 'monkey-like' human performing the task in the same way as the monkey model did. Reward was manipulated to ensure that all models showed equal proportions of errors and successes. The 'monkey-like' human model improved the animals' subsequent object discrimination learning as much as a conspecific did, whereas the 'stimulus-enhancing' human model tended on the contrary to retard learning. Modeling errors rather than successes optimized learning from the monkey and 'monkey-like' models, while exacerbating the adverse effect of the 'stimulus-enhancing' model. These findings identify error modeling as a moderator of social learning in monkeys that amplifies the models' influence, whether beneficial or detrimental. By contrast, model-observer similarity in behavior emerged as a mediator of social learning, that is, a prerequisite for a model to work in the first place. The latter finding suggests that, as preverbal infants, macaques need to perceive the model as 'like-me' and that, once this condition is fulfilled, any agent can become an effective model.
Interacting dark energy models in Cosmology and large-scale structure observational tests
Marcondes, Rafael J F
2016-01-01
Modern Cosmology offers us a great understanding of the universe with striking precision, made possible by the modern technologies of the newest generations of telescopes. The standard cosmological model, however, is not absent of theoretical problems and open questions. One possibility that has been put forward is the existence of a coupling between dark sectors. The idea of an interaction between the dark components could help physicists understand why we live in an epoch of the universe where dark matter and dark energy are comparable in terms of energy density, which can be regarded as a coincidence given that their time evolutions are completely different. We introduce the interaction phenomenologically and proceed to test models of interaction with observations of redshift-space distortions. In a flat universe composed only of those two fluids, we consider separately two forms of interaction, through terms proportional to the densities of both dark energy and dark matter. An analytic expression for the ...
Meloni, Davide; Riad, Stella
2014-01-01
In the context of non-supersymmetric SO(10) models, we analyze the renormalization group equations for the fermions (including neutrinos) from the GUT energy scale down to the electroweak energy scale, explicitly taking into account the effects of an intermediate energy scale induced by a Pati--Salam gauge group. To determine the renormalization group running, we use a numerical minimization procedure based on a nested sampling algorithm that randomly generates the values of 19 model parameters at the GUT scale, evolves them, and finally constructs the values of the physical observables and compares them to the existing experimental data at the electroweak scale. We show that the evolved fermion masses and mixings present sizable deviations from the values obtained without including the effects of the intermediate scale.
Meloni, Davide; Ohlsson, Tommy; Riad, Stella
2014-12-01
In the context of non-supersymmetric SO(10) models, we analyze the renormalization group equations for the fermions (including neutrinos) from the GUT energy scale down to the electroweak energy scale, explicitly taking into account the effects of an intermediate energy scale induced by a Pati-Salam gauge group. To determine the renormalization group running, we use a numerical minimization procedure based on a nested sampling algorithm that randomly generates the values of 19 model parameters at the GUT scale, evolves them, and finally constructs the values of the physical observables and compares them to the existing experimental data at the electroweak scale. We show that the evolved fermion masses and mixings present sizable deviations from the values obtained without including the effects of the intermediate scale.
DEFF Research Database (Denmark)
Rossiter, John R.; Percy, Larry
2013-01-01
as requiring a new model of how advertising communicates and persuades, which, as the authors' textbooks explain, is sheer nonsense and contrary to the goal of integrated marketing. We provide in this article a translation of practitioners' jargon into more scientifically acceptable terminology as well...... product or service or to achieve a higher price that consumers are willing to pay than would obtain in the absence of advertising. What has changed in recent years is the notable worsening of the academic-practitioner divide, which has seen academic advertising researchers pursuing increasingly...... unrealistic laboratory studies, textbook writers continuing to ignore practitioners' research appearing in trade publications and practitioner-oriented journals, and practitioners peeling off into high-sounding but meaningless jargon. also evident is the tendency to regard the new electronic media...
Earth Observations, Models and Geo-Design in Support of SDG Implementation and Monitoring
Plag, H. P.; Jules-Plag, S.
2016-12-01
Implementation and Monitoring of the United Nations' Sustainable Development Goals (SDGs) requires support from Earth observation and scientific communities. Applying a goal-based approach to determine the data needs to the Targets and Indicators associated with the SDGs demonstrates that integration of environmental with socio-economic and statistical data is required. Large data gaps exist for the built environment. A Geo-Design platform can provide the infrastructure and conceptual model for the data integration. The development of policies and actions to foster the implementation of SDGs in many cases requires research and the development of tools to answer "what if" questions. Here, agent-based models and model webs combined with a Geo-Design platform are promising avenues. This advanced combined infrastructure can also play a crucial role in the necessary capacity building. We will use the example of SDG 5 (Gender equality) to illustrate these approaches. SDG 11 (Sustainable Cities and Communities) is used to underline the cross-goal linkages and the joint benefits of Earth observations, data integration, and modeling tools for multiple SDGs.
Anthropogenic desertification by high-albedo pollution Observations and modeling
Otterman, J.; Rosenberg, N. W.; Rosenberg, E.
1974-01-01
ERTS-1 MSS albedo data of Western Negev, Sinai and the Gaza strip are presented. A sharp contrast in albedo exists across the Negev-Sinai and Negev-Gaza strip borders. Anthropogenic desertification has occurred on the Arab side due to overgrazing and Bedouin agriculture, whereas natural vegetation grows much more abundantly on the Israeli side.
Observing the observer (I): meta-bayesian models of learning and decision-making.
Daunizeau, J.; Ouden, H.E.M. den; Pessiglione, M.; Kiebel, S.J.; Stephan, K.E.; Friston, K.J.
2010-01-01
In this paper, we present a generic approach that can be used to infer how subjects make optimal decisions under uncertainty. This approach induces a distinction between a subject's perceptual model, which underlies the representation of a hidden "state of affairs" and a response model, which predic
Khan, Iftekhar; Morris, Stephen
2014-11-12
The performance of the Beta Binomial (BB) model is compared with several existing models for mapping the EORTC QLQ-C30 (QLQ-C30) on to the EQ-5D-3L using data from lung cancer trials. Data from 2 separate non small cell lung cancer clinical trials (TOPICAL and SOCCAR) are used to develop and validate the BB model. Comparisons with Linear, TOBIT, Quantile, Quadratic and CLAD models are carried out. The mean prediction error, R(2), proportion predicted outside the valid range, clinical interpretation of coefficients, model fit and estimation of Quality Adjusted Life Years (QALY) are reported and compared. Monte-Carlo simulation is also used. The Beta-Binomial regression model performed 'best' among all models. For TOPICAL and SOCCAR trials, respectively, residual mean square error (RMSE) was 0.09 and 0.11; R(2) was 0.75 and 0.71; observed vs. predicted means were 0.612 vs. 0.608 and 0.750 vs. 0.749. Mean difference in QALY's (observed vs. predicted) were 0.051 vs. 0.053 and 0.164 vs. 0.162 for TOPICAL and SOCCAR respectively. Models tested on independent data show simulated 95% confidence from the BB model containing the observed mean more often (77% and 59% for TOPICAL and SOCCAR respectively) compared to the other models. All algorithms over-predict at poorer health states but the BB model was relatively better, particularly for the SOCCAR data. The BB model may offer superior predictive properties amongst mapping algorithms considered and may be more useful when predicting EQ-5D-3L at poorer health states. We recommend the algorithm derived from the TOPICAL data due to better predictive properties and less uncertainty.
A diagnostic model to estimate winds and small-scale drag from Mars Observer PMIRR data
Barnes, J. R.
1993-01-01
Theoretical and modeling studies indicate that small-scale drag due to breaking gravity waves is likely to be of considerable importance for the circulation in the middle atmospheric region (approximately 40-100 km altitude) on Mars. Recent earth-based spectroscopic observations have provided evidence for the existence of circulation features, in particular, a warm winter polar region, associated with gravity wave drag. Since the Mars Observer PMIRR experiment will obtain temperature profiles extending from the surface up to about 80 km altitude, it will be extensively sampling middle atmospheric regions in which gravity wave drag may play a dominant role. Estimating the drag then becomes crucial to the estimation of the atmospheric winds from the PMIRR-observed temperatures. An interative diagnostic model based upon one previously developed and tested with earth satellite temperature data will be applied to the PMIRR measurements to produce estimates of the small-scale zonal drag and three-dimensional wind fields in the Mars middle atmosphere. This model is based on the primitive equations, and can allow for time dependence (the time tendencies used may be based upon those computed in a Fast Fourier Mapping procedure). The small-scale zonal drag is estimated as the residual in the zonal momentum equation; the horizontal winds having first been estimated from the meridional momentum equation and the continuity equation. The scheme estimates the vertical motions from the thermodynamic equation, and thus needs estimates of the diabatic heating based upon the observed temperatures. The latter will be generated using a radiative model. It is hoped that the diagnostic scheme will be able to produce good estimates of the zonal gravity wave drag in the Mars middle atmosphere, estimates that can then be used in other diagnostic or assimilation efforts, as well as more theoretical studies.
Chen, Xingyuan; Rubin, Yoram; Ma, Siyan; Baldocchi, Dennis
2008-08-01
The study of water exchange between soil, plants, and the atmosphere in response to seasonal or periodic droughts is critical to modeling the hydrologic cycle and biogeochemical processes in water-controlled ecosystems. An essential step in such studies is to characterize changes in evaporation and transpiration under water stress. The objectives of this study are to investigate how soil moisture controls the evapotranspiration in a Californian oak savanna that experiences seasonal droughts, using multiyear field observations at the daily and stand scale, and to model these controls stochastically. The influence of soil moisture on evapotranspiration at the stand scale is studied using correlations between tower-based evapotranspiration measurements and representative soil moisture obtained by aggregating point measurements. The observed pattern of this effect is found in agreement with an existing model that features a linear reduction of the evapotranspiration when soil moisture falls below a critical value. The model parameters are inferred using a Bayesian framework, and they are found to vary from year to year because of climate variability. The comparison between various aggregations of soil moisture at the stand scale from point measurements demonstrates that the spatial variability of the soil moisture and the water uptake capacity limited by the root biomass need be taken into account to produce a model that is most resistant to interannual variability. Finally, the parameterized model is used to predict the actual evapotranspiration with uncertainty estimates determined using the joint distribution of the parameters derived from the Bayesian framework. The satisfactory agreement between the predicted and measured evapotranspiration suggests that the calibrated model can be incorporated into water balance studies in the future.
Directory of Open Access Journals (Sweden)
Zhenwei Huang
2013-01-01
Full Text Available Arctic Ocean sea-level change is an important indicator of climate change. Contemporary geodetic observations, including data from tide gages, satellite altimetry and Gravity Recovery and Climate Experiment (GRACE, are sensitive to the effect of the ongoing glacial isostatic adjustment (GIA process. To fully exploit these geodetic observations to study climate related sea-level change, this GIA effect has to be removed. However, significant uncertainty exists with regard to the GIA model, and using different GIA models could lead to different results. In this study we use an ensemble of 14 contemporary GIA models to investigate their differences when they are applied to the above-mentioned geodetic observations to estimate sea-level change in the Arctic Ocean. We find that over the Arctic Ocean a large range of differences exists in GIA models when they are used to remove GIA effect from tide gage and GRACE observations, but with a relatively smaller range for satellite altimetry observations. In addition, we compare the derived sea-level trend from observations after applying different GIA models in the study regions, sea-level trend estimated from long-term tide gage data shows good agreement with altimetry result over the same data span. However the mass component of sea-level change obtained from GRACE data does not agree well with the result derived from steric-corrected altimeter observation due primarily to the large uncertainty of GIA models, errors in the Arctic Ocean altimetry or steric measurements, inadequate data span, or all of the above. We conclude that GIA correction is critical for studying sea-level change over the Arctic Ocean and further improvement in GIA modelling is needed to reduce the current discrepancies among models.
Zhu, Wei; Lin, Che-Jen; Wang, Xun; Sommar, Jonas; Fu, Xuewu; Feng, Xinbin
2016-04-01
Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East
Towards real-time assimilation of crowdsourced observations in hydrological modeling
Mazzoleni, Maurizio; Verlaan, Martin; Alfonso, Leonardo; Norbiato, Daniele; Monego, Martina; Ferri, Michele; Solomatine, Dimitri
2016-04-01
The continued technological advances have stimulated the spread of low-cost sensors that can be used by citizens to provide crowdsourced observations (CO) of different hydrological variables. An example of such low-cost sensors is a staff gauge connected to a QR code on which people can read the water level indication and send the measurement via a mobile phone application. The goal of this study is to assess the combined effect of the assimilation of CO coming from a distributed network of low-cost sensors, and the existing streamflow observations from physical sensors, on the performance of a semi-distributed hydrological model. The methodology is applied to the Bacchiglione catchment, North East of Italy, where an early warning system is used by the Alto Adriatico Water Authority to issue forecasted water level along the river network which cross important cities such as Vicenza and Padua. In this study, forecasted precipitation values are used as input in the hydrological model to estimate the simulated streamflow hydrograph used as boundary condition for the hydraulic model. Observed precipitation values are used to generate realistic synthetic streamflow values with various characteristics of arrival frequency and accuracy, to simulate CO coming at irregular time steps. These observations are assimilated into the semi-distributed model using a Kalman filter based method. The results of this study show that CO, asynchronous in time and with variable accuracy, can still improve flood prediction when integrated in hydrological models. When both physical and low-cost sensors are located at the same places, the assimilation of CO gives the same model improvement than the assimilation of physical observations only for high number of non-intermittent sensors. However, the integration of observations from low-cost sensors and single physical sensors can improve the flood prediction even when small a number of intermittent CO are available. This study is part of the
Kim, Kue Bum; Kwon, Hyun-Han; Han, Dawei
2015-11-01
In this paper, we present a comparative study of bias correction methods for regional climate model simulations considering the distributional parametric uncertainty underlying the observations/models. In traditional bias correction schemes, the statistics of the simulated model outputs are adjusted to those of the observation data. However, the model output and the observation data are only one case (i.e., realization) out of many possibilities, rather than being sampled from the entire population of a certain distribution due to internal climate variability. This issue has not been considered in the bias correction schemes of the existing climate change studies. Here, three approaches are employed to explore this issue, with the intention of providing a practical tool for bias correction of daily rainfall for use in hydrologic models ((1) conventional method, (2) non-informative Bayesian method, and (3) informative Bayesian method using a Weather Generator (WG) data). The results show some plausible uncertainty ranges of precipitation after correcting for the bias of RCM precipitation. The informative Bayesian approach shows a narrower uncertainty range by approximately 25-45% than the non-informative Bayesian method after bias correction for the baseline period. This indicates that the prior distribution derived from WG may assist in reducing the uncertainty associated with parameters. The implications of our results are of great importance in hydrological impact assessments of climate change because they are related to actions for mitigation and adaptation to climate change. Since this is a proof of concept study that mainly illustrates the logic of the analysis for uncertainty-based bias correction, future research exploring the impacts of uncertainty on climate impact assessments and how to utilize uncertainty while planning mitigation and adaptation strategies is still needed.
Meierbachtol, Toby W.; Harper, Joel T.; Johnson, Jesse V.; Humphrey, Neil F.; Brinkerhoff, Douglas J.
2015-03-01
The surface and basal boundary conditions exert an important control on the thermodynamic state of the Greenland Ice Sheet, but their representation in numerical ice sheet models is poorly constrained due to the lack of observations. Here we investigate a land-terminating sector of western Greenland and (1) quantify differences between new observations and commonly used boundary condition data sets and (2) demonstrate the impact of improved boundary conditions on simulated thermodynamics in a higher-order numerical flow model. We constrain near-surface temperature with measurements from two 20 m boreholes in the ablation zone and 10 m firn temperature from the percolation zone. We constrain basal heat flux using in situ measurement in a deep bedrock hole at the study area margin and other existing assessments. To assess boundary condition influences on simulated thermal-mechanical processes, we compare model output to multiple full-thickness temperature profiles collected in the ablation zone. Our observation-constrained basal heat flux is 30 mW m-2 less than commonly used representations. In contrast, measured near-surface temperatures are warmer than common surface temperature data sets by up to 15°C. Application of lower basal heat flux increases a model cold bias compared to the measured temperature profiles and causes frozen basal conditions across the ablation zone. Temperate basal conditions are reestablished by our warmer surface boundary. Warmer surface ice and firn can introduce several times more energy to the modeled ice mass than what is lost at the bed from reduced basal heat flux, indicating that the thermomechanical state of the ice sheet is highly sensitive to near-surface effects.