Jurgens, Bryant; Bohlke, John Karl; Kauffman, Leon J.; Belitz, Kenneth; Esser, Bradley K.
2016-01-01
A partial exponential lumped parameter model (PEM) was derived to determine age distributions and nitrate trends in long-screened production wells. The PEM can simulate age distributions for wells screened over any finite interval of an aquifer that has an exponential distribution of age with depth. The PEM has 3 parameters – the ratio of saturated thickness to the top and bottom of the screen and mean age, but these can be reduced to 1 parameter (mean age) by using well construction information and estimates of the saturated thickness. The PEM was tested with data from 30 production wells in a heterogeneous alluvial fan aquifer in California, USA. Well construction data were used to guide parameterization of a PEM for each well and mean age was calibrated to measured environmental tracer data (3H, 3He, CFC-113, and 14C). Results were compared to age distributions generated for individual wells using advective particle tracking models (PTMs). Age distributions from PTMs were more complex than PEM distributions, but PEMs provided better fits to tracer data, partly because the PTMs did not simulate 14C accurately in wells that captured varying amounts of old groundwater recharged at lower rates prior to groundwater development and irrigation. Nitrate trends were simulated independently of the calibration process and the PEM provided good fits for at least 11 of 24 wells. This work shows that the PEM, and lumped parameter models (LPMs) in general, can often identify critical features of the age distributions in wells that are needed to explain observed tracer data and nonpoint source contaminant trends, even in systems where aquifer heterogeneity and water-use complicate distributions of age. While accurate PTMs are preferable for understanding and predicting aquifer-scale responses to water use and contaminant transport, LPMs can be sensitive to local conditions near individual wells that may be inaccurately represented or missing in an aquifer-scale flow model.
Engdahl, Nicholas B.; Ginn, Timothy R.; Fogg, Graham E.
2015-01-01
Groundwater age distributions are used to estimate the parameters of Fickian, and non-Fickian, effective models of solute transport. Based on the similarities between the transport and age equations, we develop a deconvolution based approach that describes transport between two monitoring wells. We show that the proposed method gives exact estimates of the travel time distribution between two wells when the domain is stationary and that the method still provides useful information on transport when the domain is non-stationary. The method is demonstrated using idealized uniform and layered 2-D aquifers. Homogeneous transport is determined exactly and non-Fickian transport in a layered aquifer was also approximated very well, even though this example problem is shown to be scale-dependent. This work introduces a method that addresses a significant limitation of tracer tests and non-Fickian transport modeling which is the difficulty in determining the effective parameters of the transport model. PMID:25821342
NASA Astrophysics Data System (ADS)
Filippazzo, Joseph C.; Rice, Emily L.; Faherty, Jacqueline; Cruz, Kelle L.; Van Gordon, Mollie M.; Looper, Dagny L.
2015-09-01
We combine optical, near-infrared, and mid-infrared spectra and photometry to construct expanded spectral energy distributions for 145 field age (>500 Myr) and 53 young (lower age estimate <500 Myr) ultracool dwarfs (M6-T9). This range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. A subsample of 29 objects have well constrained ages as probable members of a nearby young moving group. We use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities (Lbol) and radius estimates from evolutionary models give semi-empirical effective temperatures (Teff) for the full range of young and field age late-M, L, and T dwarfs. We construct age-sensitive relationships of luminosity, temperature, and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as Teff, surface gravity, and clouds on spectral morphology. We report bolometric corrections in J for both field age and young objects and find differences of up to a magnitude for late-L dwarfs. Our correction in Ks shows a larger dispersion but not necessarily a different relationship for young and field age sequences. We also characterize the NIR-MIR reddening of low gravity L dwarfs and identify a systematically cooler Teff of up to 300 K from field age objects of the same spectral type and 400 K cooler from field age objects of the same MH magnitude.
Age Distribution of Groundwater
NASA Astrophysics Data System (ADS)
Morgenstern, U.; Daughney, C. J.
2012-04-01
Groundwater at the discharge point comprises a mixture of water from different flow lines with different travel time and therefore has no discrete age but an age distribution. The age distribution can be assessed by measuring how a pulse shaped tracer moves through the groundwater system. Detection of the time delay and the dispersion of the peak in the groundwater compared to the tracer input reveals the mean residence time and the mixing parameter. Tritium from nuclear weapons testing in the early 1960s resulted in a peak-shaped tritium input to the whole hydrologic system on earth. Tritium is the ideal tracer for groundwater because it is an isotope of hydrogen and therefore is part of the water molecule. Tritium time series data that encompass the passage of the bomb tritium pulse through the groundwater system in all common hydrogeologic situations in New Zealand demonstrate a semi-systematic pattern between age distribution parameters and hydrologic situation. The data in general indicate high fraction of mixing, but in some cases also indicate high piston flow. We will show that still, 45 years after the peak of the bomb tritium, it is possible to assess accurately the parameters of age distributions by measuring the tail of the bomb tritium.
NASA Astrophysics Data System (ADS)
Filippazzo, Joe; Rice, Emily L.; Faherty, Jacqueline K.; Cruz, Kelle L.; Godfrey, Paige A.; BDNYC
2016-01-01
The physical and atmospheric properties of ultracool dwarfs are deeply entangled due to the degenerate effects of mass, age, metallicity, clouds and dust, activity, rotation, and possibly even formation mechanism on observed spectra. Accurate determination of fundamental parameters for a wide diversity of objects at the low end of the IMF is thus crucial to testing stellar and planetary formation theories. To determine these quantities, we constructed and flux calibrated nearly-complete spectral energy distributions (SEDs) for 221 M, L, T, and Y dwarfs using published parallaxes and 0.3-40 μm spectra and photometry. From these homogeneous SEDs, we calculated bolometric luminosity (Lbol), effective temperature (Teff), mass, surface gravity, radius, spectral indexes, synthetic photometry, and bolometric corrections (BCs) for each object. We used these results to derive Lbol, Teff, and BC polynomial relations across the entire very-low-mass star/brown dwarf/planetary mass regime. We use a subsample of objects with age constraints based on nearby young moving group membership, companionship with a young star, or spectral signatures of low surface gravity to define new age-sensitive diagnostics and characterize the reddening of young substellar atmospheres as a redistribution of flux from the near-infrared into the mid-infrared. Consequently we find the SED flux pivots at Ks band, making BCKs as a function of spectral type a tight and age independent relationship. We find that young L dwarfs are systematically 300 K cooler than field age objects of the same spectral type and up to 600 K cooler than field age objects of the same absolute H magnitude. Finally, we present preliminary comparisons of these empirical results to best fit parameters from four different model atmosphere grids via Markov-Chain Monte Carlo analysis in order to create prescriptions for the reliable and efficient characterization of new ultracool dwarfs.
Topological aspects of age parameter
NASA Technical Reports Server (NTRS)
Capdevielle, J. N.; Gawin, J.
1985-01-01
The well known NKG function is a very useful tool to describe the lateral extension of the electromagnetic component in Extensive Air Showers (EAS); however, in spite of non-negligible qualities (simplicity, normalization by beta function), it doesn't correspond exactly to the natural shape of the lateral electron distribution. Several bias may occur in size estimation if NKG is used without correction. It is shown that the longitudinal age parameter s sub t can be correlated with the information obtained from the lateral electron densities according to the conditions of use of the NKG function.
Eberts, S.M.; Böhlke, J.K.; Kauffman, L.J.; Jurgens, B.C.
2012-01-01
Environmental age tracers have been used in various ways to help assess vulnerability of drinking-water production wells to contamination. The most appropriate approach will depend on the information that is available and that which is desired. To understand how the well will respond to changing nonpoint-source contaminant inputs at the water table, some representation of the distribution of groundwater ages in the well is needed. Such information for production wells is sparse and difficult to obtain, especially in areas lacking detailed field studies. In this study, age distributions derived from detailed groundwater-flow models with advective particle tracking were compared with those generated from lumped-parameter models to examine conditions in which estimates from simpler, less resource-intensive lumped-parameter models could be used in place of estimates from particle-tracking models. In each of four contrasting hydrogeologic settings in the USA, particle-tracking and lumped-parameter models yielded roughly similar age distributions and largely indistinguishable contaminant trends when based on similar conceptual models and calibrated to similar tracer data. Although model calibrations and predictions were variably affected by tracer limitations and conceptual ambiguities, results illustrated the importance of full age distributions, rather than apparent tracer ages or model mean ages, for trend analysis and forecasting.
NASA Astrophysics Data System (ADS)
Jurgens, B. C.; Bohlke, J. K.; Voss, S.; Fram, M. S.; Esser, B.
2015-12-01
Tracer-based, lumped parameter models (LPMs) are an appealing way to estimate the distribution of age for groundwater because the cost of sampling wells is often less than building numerical groundwater flow models sufficiently complex to provide groundwater age distributions. In practice, however, tracer datasets are often incomplete because of anthropogenic or terrigenic contamination of tracers, or analytical limitations. While age interpretations using such datsets can have large uncertainties, it may still be possible to identify key parts of the age distribution if LPMs are carefully chosen to match hydrogeologic conceptualization and the degree of age mixing is reasonably estimated. We developed a systematic approach for evaluating groundwater age distributions using LPMs with a large but incomplete set of tracer data (3H, 3Hetrit, 14C, and CFCs) from 535 wells, mostly used for public supply, in the Central Valley, California, USA that were sampled by the USGS for the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment or the USGS National Water Quality Assessment Programs. In addition to mean ages, LPMs gave estimates of unsaturated zone travel times, recharge rates for pre- and post-development groundwater, the degree of age mixing in wells, proportion of young water (<60 yrs), and the depth of the boundary between post-development and predevelopment groundwater throughout the Central Valley. Age interpretations were evaluated by comparing past nitrate trends with LPM predicted trends, and whether the presence or absence of anthropogenic organic compounds was consistent with model results. This study illustrates a practical approach for assessing groundwater age information at a large scale to reveal important characteristics about the age structure of a major aquifer, and of the water supplies being derived from it.
NASA Astrophysics Data System (ADS)
Jurgens, B. C.; Bohlke, J. K.; Kauffman, L. J.; Belitz, K.
2013-12-01
Age distributions for 30 production wells (mostly public-supply) were determined using two methods: 1) calibration of age tracer data with lumped parameter models (LPMs) and 2) by advective particle tracking (PT) simulations using MODPATH and a regional steady-state groundwater flow model. The LPMs were calibrated with measurements of 3H, 3He(trit), and 14C by minimizing the Chi-square test statistic using a non-linear solver. A partial exponential model (PEM) was the primary LPM used in this study and a combination of two PEMs were used in cases where binary age mixtures were identified. The PEM is a reformulated version of the exponential model that is parameterized to simulate the age distribution in a well that is screened over any finite interval within the aquifer. The regional numerical model was calibrated to water-levels and gradients, and simulated PT age tracer concentrations were calibrated to the MODPATH porosity value. Age distributions were then used to predict nitrate concentrations in wells using agricultural application rates of nitrate in the central eastside of the San Joaquin Valley, California. Both methods showed that wells in the study area captured groundwater with a broad range of ages, spanning decades to millennia. Age distributions from the LPMs predicted age tracer and nitrate concentrations more accurately than the regional PT simulation; whereas PT simulations incorporating more detailed information about water-levels and hydraulic gradients near wells also provided good fits. 14C concentrations were not simulated well by the regional steady-state model, especially for wells with a significant fraction of old groundwater, because the model simulates the current, perturbed system and does not simulate recharge rates and velocities of the predevelopment system. Results from the LPMs yielded an average recharge rate of 0.55 m/yr, which was similar to the average recharge rate of 0.54 m/yr determined from a water budget analysis for the
The Age Parameter in Giant EAS
NASA Astrophysics Data System (ADS)
Capdevielle, J. N.; Cohen, F.; Sanosyan, K.
The age parameter from the longitudinal development can be used to describe the lateral distribution in giant EAS up to 5 km from the axis, even if the scaling properties of Approximation B in cascade theory fail after 3.5 Moliere radii. A set of analytic descriptions is proposed under the gaussian hypergeometric formalism replacing the Eulerian formalism of the classical NKG distribution, valid for electrons, muons and vertical equivalent muons (v.e.m.).
Distributed transit compartments for arbitrary lifespan distributions in aging populations.
Koch, Gilbert; Schropp, Johannes
2015-09-01
Transit compartment models (TCM) are often used to describe aging populations where every individual has its own lifespan. However, in the TCM approach these lifespans are gamma-distributed which is a serious limitation because often the Weibull or more complex distributions are realistic. Therefore, we extend the TCM concept to approximately describe any lifespan distribution and call this generalized concept distributed transit compartment models (DTCMs). The validity of DTCMs is obtained by convergence investigations. From the mechanistic perspective the transit rates are directly controlled by the lifespan distribution. Further, DTCMs could be used to approximate the convolution of a signal with a probability density function. As example a stimulatory effect of a drug in an aging population with a Weibull-distributed lifespan is presented where distribution and model parameters are estimated based on simulated data. PMID:26100181
Five-Parameter Bivariate Probability Distribution
NASA Technical Reports Server (NTRS)
Tubbs, J.; Brewer, D.; Smith, O. W.
1986-01-01
NASA technical memorandum presents four papers about five-parameter bivariate gamma class of probability distributions. With some overlap of subject matter, papers address different aspects of theories of these distributions and use in forming statistical models of such phenomena as wind gusts. Provides acceptable results for defining constraints in problems designing aircraft and spacecraft to withstand large wind-gust loads.
Parameter estimation for distributed parameter models of complex, flexible structures
NASA Technical Reports Server (NTRS)
Taylor, Lawrence W., Jr.
1991-01-01
Distributed parameter modeling of structural dynamics has been limited to simple spacecraft configurations because of the difficulty of handling several distributed parameter systems linked at their boundaries. Although there is other computer software able to generate such models or complex, flexible spacecraft, unfortunately, neither is suitable for parameter estimation. Because of this limitation the computer software PDEMOD is being developed for the express purposes of modeling, control system analysis, parameter estimation and structure optimization. PDEMOD is capable of modeling complex, flexible spacecraft which consist of a three-dimensional network of flexible beams and rigid bodies. Each beam has bending (Bernoulli-Euler or Timoshenko) in two directions, torsion, and elongation degrees of freedom. The rigid bodies can be attached to the beam ends at any angle or body location. PDEMOD is also capable of performing parameter estimation based on matching experimental modal frequencies and static deflection test data. The underlying formulation and the results of using this approach for test data of the Mini-MAST truss will be discussed. The resulting accuracy of the parameter estimates when using such limited data can impact significantly the instrumentation requirements for on-orbit tests.
Multivariate distributions of soil hydraulic parameters
NASA Astrophysics Data System (ADS)
Qu, Wei; Pachepsky, Yakov; Huisman, Johan Alexander; Martinez, Gonzalo; Bogena, Heye; Vereecken, Harry
2014-05-01
Statistical distributions of soil hydraulic parameters have to be known when synthetic fields of soil hydraulic properties need to be generated in ensemble modeling of soil water dynamics and soil water content data assimilation. Pedotransfer functions that provide statistical distributions of water retention and hydraulic conductivity parameters for textural classes are most often used in the parameter field generation. Presence of strong correlations can substantially influence the parameter generation results. The objective of this work was to review and evaluate available data on correlations between van Genuchten-Mualem (VGM) model parameters. So far, two different approaches were developed to estimate these correlations. The first approach uses pedotransfer functions to generate VGM parameters for a large number of soil compositions within a textural class, and then computes parameter correlations for each of the textural classes. The second approach computes the VGM parameter correlations directly from parameter values obtained by fitting VGM model to measured water retention and hydraulic conductivity data for soil samples belonging to a textural class. Carsel and Parish (1988) used the Rawls et al. (1982) pedotransfer functions, and Meyer et al. (1997) used the Rosetta pedotransfer algorithms (Schaap, 2002) to develop correlations according to the first approach. We used the UNSODA database (Nemes et al. 2001), the US Southern Plains database (Timlin et al., 1999), and the Belgian database (Vereecken et al., 1989, 1990) to apply the second approach. A substantial number of considerable (>0.7) correlation coefficients were found. Large differences were encountered between parameter correlations obtained with different approaches and different databases for the same textural classes. The first of the two approaches resulted in generally higher values of correlation coefficients between VGM parameters. However, results of the first approach application depend
Parton Distributions in the Impact Parameter Space
Matthias Burkardt
2009-08-01
Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark is transversely polarized. In combination with the final state interactions, this transverse deformation provides a natural mechanism for naive-T odd transverse single-spin asymmetries in semi-inclusive DIS. The deformation can also be related to the transverse force acting on the active quark in polarized DIS at higher twist.
Distributed parameter statics of magnetic catheters.
Tunay, Ilker
2011-01-01
We discuss how to use special Cosserat rod theory for deriving distributed-parameter static equilibrium equations of magnetic catheters. These medical devices are used for minimally-invasive diagnostic and therapeutic procedures and can be operated remotely or controlled by automated algorithms. The magnetic material can be lumped in rigid segments or distributed in flexible segments. The position vector of the cross-section centroid and quaternion representation of an orthonormal triad are selected as DOF. The strain energy for transversely isotropic, hyperelastic rods is augmented with the mechanical potential energy of the magnetic field and a penalty term to enforce the quaternion unity constraint. Numerical solution is found by 1D finite elements. Material properties of polymer tubes in extension, bending and twist are determined by mechanical and magnetic experiments. Software experiments with commercial FEM software indicate that the computational effort with the proposed method is at least one order of magnitude less than standard 3D FEM. PMID:22256282
The global age distribution of granitic pegmatites
McCauley, Andrew; Bradley, Dwight C.
2014-01-01
An updated global compilation of 377 new and previously published ages indicates that granitic pegmatites range in age from Mesoarchean to Neogene and have a semi-periodic age distribution. Undivided granitic pegmatites show twelve age maxima: 2913, 2687, 2501, 1853, 1379, 1174, 988, 525, 483, 391, 319, and 72 Ma. These peaks correspond broadly with various proxy records of supercontinent assembly, including the age distributions of granites, detrital zircon grains, and passive margins. Lithium-cesium-tantalum (LCT) pegmatites have a similar age distribution to the undivided granitic pegmatites, with maxima at 2638, 1800, 962, 529, 485, 371, 309, and 274 Ma. Lithium and Ta resources in LCT pegmatites are concentrated in the Archean and Phanerozoic. While there are some Li resources from the Proterozoic, the dominantly bimodal distribution of resources is particularly evident for Ta. This distribution is similar to that of orogenic gold deposits, and has been interpreted to reflect the preservation potential of the orogenic belts where these deposits are formed. Niobium-yttrium-fluorine (NYF) pegmatites show similar age distributions to LCT pegmatites, but with a strong maximum at ca. 1000 Ma.
Determination of dose distributions and parameter sensitivity
Napier, B.A.; Farris, W.T.; Simpson, J.C.
1992-12-01
A series of scoping calculations has been undertaken to evaluate the absolute and relative contribution of different radionuclides and exposure pathways to doses that may have been received by individuals living in the vicinity of the Hanford site. This scoping calculation (Calculation 005) examined the contributions of numerous parameters to the uncertainty distribution of doses calculated for environmental exposures and accumulation in foods. This study builds on the work initiated in the first scoping study of iodine in cow's milk and the third scoping study, which added additional pathways. Addressed in this calculation were the contributions to thyroid dose of infants from (1) air submersion and groundshine external dose, (2) inhalation, (3) ingestion of soil by humans, (4) ingestion of leafy vegetables, (5) ingestion of other vegetables and fruits, (6) ingestion of meat, (7) ingestion of eggs, and (8) ingestion of cows' milk from Feeding Regime 1 as described in Calculation 001.
Linking age, survival, and transit time distributions
NASA Astrophysics Data System (ADS)
Calabrese, Salvatore; Porporato, Amilcare
2015-10-01
Although the concepts of age, survival, and transit time have been widely used in many fields, including population dynamics, chemical engineering, and hydrology, a comprehensive mathematical framework is still missing. Here we discuss several relationships among these quantities by starting from the evolution equation for the joint distribution of age and survival, from which the equations for age and survival time readily follow. It also becomes apparent how the statistical dependence between age and survival is directly related to either the age dependence of the loss function or the survival-time dependence of the input function. The solution of the joint distribution equation also allows us to obtain the relationships between the age at exit (or death) and the survival time at input (or birth), as well as to stress the symmetries of the various distributions under time reversal. The transit time is then obtained as a sum of the age and survival time, and its properties are discussed along with the general relationships between their mean values. The special case of steady state case is analyzed in detail. Some examples, inspired by hydrologic applications, are presented to illustrate the theory with the specific results. This article was corrected on 11 Nov 2015. See the end of the full text for details.
Some properties of a 5-parameter bivariate probability distribution
NASA Technical Reports Server (NTRS)
Tubbs, J. D.; Brewer, D. W.; Smith, O. E.
1983-01-01
A five-parameter bivariate gamma distribution having two shape parameters, two location parameters and a correlation parameter was developed. This more general bivariate gamma distribution reduces to the known four-parameter distribution. The five-parameter distribution gives a better fit to the gust data. The statistical properties of this general bivariate gamma distribution and a hypothesis test were investigated. Although these developments have come too late in the Shuttle program to be used directly as design criteria for ascent wind gust loads, the new wind gust model has helped to explain the wind profile conditions which cause large dynamic loads. Other potential applications of the newly developed five-parameter bivariate gamma distribution are in the areas of reliability theory, signal noise, and vibration mechanics.
Theoretical foundation for measuring the groundwater age distribution.
Gardner, William Payton; Arnold, Bill Walter
2014-01-01
In this study, we use PFLOTRAN, a highly scalable, parallel, flow and reactive transport code to simulate the concentrations of 3H, 3He, CFC-11, CFC-12, CFC-113, SF6, 39Ar, 81Kr, 4He and themean groundwater age in heterogeneous fields on grids with an excess of 10 million nodes. We utilize this computational platform to simulate the concentration of multiple tracers in high-resolution, heterogeneous 2-D and 3-D domains, and calculate tracer-derived ages. Tracer-derived ages show systematic biases toward younger ages when the groundwater age distribution contains water older than the maximum tracer age. The deviation of the tracer-derived age distribution from the true groundwater age distribution increases with increasing heterogeneity of the system. However, the effect of heterogeneity is diminished as the mean travel time gets closer the tracer age limit. Age distributions in 3-D domains differ significantly from 2-D domains. 3D simulations show decreased mean age, and less variance in age distribution for identical heterogeneity statistics. High-performance computing allows for investigation of tracer and groundwater age systematics in high-resolution domains, providing a platform for understanding and utilizing environmental tracer and groundwater age information in heterogeneous 3-D systems. Groundwater environmental tracers can provide important constraints for the calibration of groundwater flow models. Direct simulation of environmental tracer concentrations in models has the additional advantage of avoiding assumptions associated with using calculated groundwater age values. This study quantifies model uncertainty reduction resulting from the addition of environmental tracer concentration data. The analysis uses a synthetic heterogeneous aquifer and the calibration of a flow and transport model using the pilot point method. Results indicate a significant reduction in the uncertainty in permeability with the addition of environmental tracer data, relative
Age-dependency of posture parameters in children and adolescents
Ludwig, Oliver; Mazet, Carola; Mazet, Dirk; Hammes, Annette; Schmitt, Eduard
2016-01-01
[Purpose] Poor posture in children and adolescents is a well-known problem. Therefore, early detection of incorrect posture is important. Photometric posture analysis is a cost-efficient and easy method, but needs reliable reference values. As children’s posture changes as they grow, the assessment needs to be age-specific. This study aimed to investigate the development of both one-dimensional posture parameter (body inclination angle) and complex parameter (posture index) in different age groups (childhood to adolescence). [Subjects and Methods] The participants were 372 symptom-free children and adolescents (140 girls and 232 boys aged 6–17). Images of their habitual posture were obtained in the sagittal plane. High-contrast marker points and marker spheres were placed on anatomical landmarks. Based on the marker points, the body inclination angle (INC) and posture index (PI) were calculated using the Corpus concepts software. [Results] The INC angle significantly increased with age. The PI did not change significantly among the age groups. No significant differences between the corresponding age groups were found for PI and INC for both sexes. [Conclusion] When evaluating posture using the body inclination angle, the age of the subject needs to be considered. Posture assessment with an age-independent parameter may be more suitable. PMID:27313382
Spatial distribution of intracortical porosity varies across age and sex
Nirody, Jasmine A.; Cheng, Karen P.; Parrish, Robin M.; Burghardt, Andrew J.; Majumdar, Sharmila; Link, Thomas M.; Kazakia, Galateia J.
2015-01-01
Cortical bone porosity is a major determinant of strength, stiffness, and fracture toughness of cortical tissue. The goal of this work was to investigate changes in spatial distribution and microstructure of cortical porosity associated with aging in men and women. The specific aims were to: 1) develop an automated technique for spatial analysis of cortical microstructure based on HR-pQCT data, and; 2) apply this technique to explore sex- and age-specific spatial distribution and microstructure of porosity within the cortex. We evaluated HR-pQCT images of the distal tibia from a cross-sectional cohort of 145 individuals, characterizing detectable pores as being in the endosteal, midcortical, or periosteal layers of the cortex. Metrics describing porosity, pore number, and pore size were quantifiedwithin each layer and compared across sexes, age groups, and cortical layers. The elderly cohort (65–78 years, n=22) displayed higher values than the young cohort (20–29 years, n=29) for all parameters both globally and within each layer. While all three layers displayed significant age-related porosity increases, the greatest difference in porosity between the young and elderly cohort was in the midcortical layer (+344%, p < 0.001). Similarly, the midcortical layer reflected the greatest differences between young and elderly cohorts in both pore number (+243%, p < 0.001) and size (+28%, p < 0.001). Females displayed greater age-related changes in porosity and pore number than males. Females and males displayed comparable small to non-significant changes with age in pore size. In summary, considerable variability exists in the spatial distribution of detectable cortical porosity at the distal tibia, and this variability is dependent on age and sex. Intracortical pore distribution analysis may ultimately provide insight into both mechanisms of pore network expansion and biomechanical consequences of pore distribution. PMID:25701139
Computational methods for the control of distributed parameter systems
NASA Technical Reports Server (NTRS)
Burns, J. A.; Cliff, E. M.; Powers, R. K.
1986-01-01
Finite dimensional approximation schemes that work well for distributed parameter systems are often not suitable for the analysis and implementation of feedback control systems. The relationship between approximation schemes for distributed parameter systems and their application to optimal control problems is discussed. A numerical example is given.
Eakin, T; Shouman, R; Qi, Y; Liu, G; Witten, M
1995-05-01
Studies of the biology of aging (both experimental and evolutionary) frequently involve the estimation of parameters arising in various multi-parameter survival models such as the Gompertz or Weibull distribution. Standard parameter estimation methodologies, such as maximum likelihood estimation (MLE) or nonlinear regression (NLR), require knowledge of the actual life spans or their explicit algebraic equivalents in order to provide reliable parameter estimates. Many fundamental biological discussions and conclusions are highly dependent upon accurate estimates of these survival parameters (this has historically been the case in the study of genetic and environmental effects on longevity and the evolutionary biology of aging). In this article, we examine some of the issues arising in the estimation of gerontologic survival model parameters. We not only address issues of accuracy when the original life-span data are unknown, we consider the accuracy of the estimates even when the exact life spans are known. We examine these issues as applied to known experimental data on diet restriction and we fit the frequently used, two-parameter Gompertzian survival distribution to these experimental data. Consequences of methodological misuse are demonstrated and subsequently related to the values of the final parameter estimates and their associated errors. These results generalize to other multiparametric distributions such as the Weibull, Makeham, and logistic survival distributions. PMID:7743396
Distributed activation energy model parameters of some Turkish coals
Gunes, M.; Gunes, S.K.
2008-07-01
A multi-reaction model based on distributed activation energy has been applied to some Turkish coals. The kinetic parameters of distributed activation energy model were calculated via computer program developed for this purpose. It was observed that the values of mean of activation energy distribution vary between 218 and 248 kJ/mol, and the values of standard deviation of activation energy distribution vary between 32 and 70 kJ/mol. The correlations between kinetic parameters of the distributed activation energy model and certain properties of coal have been investigated.
Age-dependent pupillary light reflex parameters in children.
Daluwatte, Chathuri; Miles, Judith H; Christ, Shawn E; Beversdorf, David Q; Lofgreen, Andrew; Berliner, Nathan; Yao, Gang
2012-01-01
Pupillary light reflex (PLR) refers to the phenomenon where pupil size changes in response to stimulation with a flash of light. It is a simple functional test that can reveal dysfunctions associated with the PLR pathway. Although abnormal PLR responses have been reported in many neurological disorders, few studies investigated neurodevelopmental effects on PLR parameters. We studied the effect of age on PLR in a group of 6 to 17 year old children with typical development. A significant and consistent age effect was found on PLR latency in children younger than 10 years old. Age effects were also observed in resting pupil diameter and constriction amplitude. However such age related trends were not observed in children with neurodevelopment disorders. These results suggest that PLR has the potential to be used as a simple noninvasive tool for monitoring neurodevelopment in children. PMID:23366750
Efficient Calibration of Categorical Parameter Distributions using Subspace Methods
NASA Astrophysics Data System (ADS)
Khambhammettu, P.; Renard, P.; Doherty, J.
2014-12-01
Categorical parameter distributions are common-place in hydrogeological systems consisting of rock-types / aquifer materials with distinct properties, eg: sand channels in a clay matrix. Model calibration is difficult in such systems because the inverse problem is hindered by the discontinuities in the parameter space. In this paper, we present two approaches based on sub-space methods to generate categorical parameter distributions of aquifer parameters that meet calibration constraints (eg:- measured water level data, gradients) while honoring prior geological constraints. In the first approach, the prior geological information and acceptable parameter distributions are encapsulated in a simple object-based model. In the second approach, a Multiple-Point Statistics simulator is used to represent the prior geological information. Sub-space methods in conjunction with dynamic pilot points are then employed to explore the parameter space and determine the parameter combinations that optimally honor geologic and calibration constraints. Using a simple aquifer system, we demonstrate that the new approach is capable of quickly generating multiple multiple parameter distributions that honor both geological and calibration constraints. We also explore the underlying parameter and predictive uncertainty using Null Space Monte Carlo techniques.
Large capacitor performs as a distributed parameter pulse line
NASA Technical Reports Server (NTRS)
Gooding, T. J.
1966-01-01
Capacitor of extended foil construction performs as a distributed parameter pulse line in which current, amplitude, and period are readily controlled. The capacitor is used as the energy storage element in a pulsed plasma accelerator.
Distributed parameter modeling for the control of flexible spacecraft
NASA Technical Reports Server (NTRS)
Taylor, Lawrence W., Jr.
1990-01-01
The use of FEMs of spacecraft structural dynamics is a common practice, but it has a number of shortcomings. Distributed-parameter models offer an alternative, but present both advantages and difficulties. First, the model order does not have to be reduced prior to the inclusion of control system dynamics. This advantage eliminates the risk involved with model 'order reduction'. Second, distributed parameter models inherently involve fewer parameters, thereby enabling more accurate parameter estimation using experimental data. Third, it is possible to include the damping in the basic model, thereby increasing the accuracy of the structural damping. The difficulty in generating distributed parameter models of complex spacecraft configurations has been greatly alleviated by the use of PDEMOD, BUNVIS-RG, or DISTEL. PDEMOD is being developed for simultaneously modeling structural dynamics and control system dynamics.
Vortex age as a wake turbulence scaling parameter
NASA Technical Reports Server (NTRS)
Marshall, J. R.; Marchman, J. F., III
1973-01-01
Research which was conducted to determine the significance of vortex age as a scaling parameter in wake turbulence development and dissipation is reported. Tests were conducted at three angles of attack, three free stream speeds, and seven downstream positions from 2 to 30 chordlengths using an NACA 0012 wing and a five hole yawhead pitot probe. The end surface of the wing tip was flat. Speeds were selected to give a predetermined range of vortex ages. The complete velocity structure of the vortex was measured at each station and speed. The resulting plots of maximum tangential velocity and vortex core diameter versus downstream distance and vortex age indicate that vortex age is not a self sufficient scaling parameter. In addition to the expected effect of lift coefficient there is also a definite free stream speed influence at high wing angles of attack. The exact cause and nature of this effect is not fully understood, but it does not appear to be explainable in terms of Mach number or Reynolds number; however, the influence of tip edge shape on spanwise flow separation appears to be an important factor.
Estimation of modal parameters using bilinear joint time frequency distributions
NASA Astrophysics Data System (ADS)
Roshan-Ghias, A.; Shamsollahi, M. B.; Mobed, M.; Behzad, M.
2007-07-01
In this paper, a new method is proposed for modal parameter estimation using time-frequency representations. Smoothed Pseudo Wigner-Ville distribution which is a member of the Cohen's class distributions is used to decouple vibration modes completely in order to study each mode separately. This distribution reduces cross-terms which are troublesome in Wigner-Ville distribution and retains the resolution as well. The method was applied to highly damped systems, and results were superior to those obtained via other conventional methods.
Distributional Phonetic Learning at 10 Months of Age
ERIC Educational Resources Information Center
Yoshida, Katherine A.; Pons, Ferran; Maye, Jessica; Werker, Janet F.
2010-01-01
Infant phonetic perception reorganizes in accordance with the native language by 10 months of age. One mechanism that may underlie this perceptual change is distributional learning, a statistical analysis of the distributional frequency of speech sounds. Previous distributional learning studies have tested infants of 6-8 months, an age at which…
The Power of Heterogeneity: Parameter Relationships from Distributions
Röding, Magnus; Bradley, Siobhan J.; Williamson, Nathan H.; Dewi, Melissa R.; Nann, Thomas; Nydén, Magnus
2016-01-01
Complex scientific data is becoming the norm, many disciplines are growing immensely data-rich, and higher-dimensional measurements are performed to resolve complex relationships between parameters. Inherently multi-dimensional measurements can directly provide information on both the distributions of individual parameters and the relationships between them, such as in nuclear magnetic resonance and optical spectroscopy. However, when data originates from different measurements and comes in different forms, resolving parameter relationships is a matter of data analysis rather than experiment. We present a method for resolving relationships between parameters that are distributed individually and also correlated. In two case studies, we model the relationships between diameter and luminescence properties of quantum dots and the relationship between molecular weight and diffusion coefficient for polymers. Although it is expected that resolving complicated correlated relationships require inherently multi-dimensional measurements, our method constitutes a useful contribution to the modelling of quantitative relationships between correlated parameters and measurements. We emphasise the general applicability of the method in fields where heterogeneity and complex distributions of parameters are obstacles to scientific insight. PMID:27182701
Distribution of coal quality parameters in lignites of northeast Texas
Crowley, S.S.; Warwick, P.D.; Thomas, R.E.; Mason, W.H.
1996-12-31
The distribution of coal quality characteristics was examined in lignites (Wilcox Group, Paleocene-Eocene) near Mt. Pleasant, Texas. Coal quality parameters including ash yield, sulfur forms, moisture, calorific value, and selected potentially hazardous trace elements were plotted on cross sections of lignite beds to determine their stratigraphic distribution. This study has been undertaken as a part of the US Geological Survey`s National Coal Resource Assessment (NCRA) program in the Gulf Coast Lignite Region. The distribution in coal of Hazardous Air Pollutant elements (HAPs), as defined in the Clean Air Act Amendments of 1990, are an important focus of the NCRA program.
Development of a distribution system for measuring nozzle integrative parameters
Technology Transfer Automated Retrieval System (TEKTRAN)
The experimental system used in this study was equipped with sensors and computer-controlled processing technology. This system was used in the measurement of major performance parameters such as pressure, flux, spray angle, spray distribution character of the nozzle and its integrative performance...
Distributed parameter modelling of flexible spacecraft: Where's the beef?
NASA Technical Reports Server (NTRS)
Hyland, D. C.
1994-01-01
This presentation discusses various misgivings concerning the directions and productivity of Distributed Parameter System (DPS) theory as applied to spacecraft vibration control. We try to show the need for greater cross-fertilization between DPS theorists and spacecraft control designers. We recommend a shift in research directions toward exploration of asymptotic frequency response characteristics of critical importance to control designers.
Chandrasekhar equations and computational algorithms for distributed parameter systems
NASA Technical Reports Server (NTRS)
Burns, J. A.; Ito, K.; Powers, R. K.
1984-01-01
The Chandrasekhar equations arising in optimal control problems for linear distributed parameter systems are considered. The equations are derived via approximation theory. This approach is used to obtain existence, uniqueness, and strong differentiability of the solutions and provides the basis for a convergent computation scheme for approximating feedback gain operators. A numerical example is presented to illustrate these ideas.
Iterative methods for distributed parameter estimation in parabolic PDE
Vogel, C.R.; Wade, J.G.
1994-12-31
The goal of the work presented is the development of effective iterative techniques for large-scale inverse or parameter estimation problems. In this extended abstract, a detailed description of the mathematical framework in which the authors view these problem is presented, followed by an outline of the ideas and algorithms developed. Distributed parameter estimation problems often arise in mathematical modeling with partial differential equations. They can be viewed as inverse problems; the `forward problem` is that of using the fully specified model to predict the behavior of the system. The inverse or parameter estimation problem is: given the form of the model and some observed data from the system being modeled, determine the unknown parameters of the model. These problems are of great practical and mathematical interest, and the development of efficient computational algorithms is an active area of study.
Campesi, Ilaria; Occhioni, Stefano; Tonolo, Giancarlo; Cherchi, Sara; Basili, Stefania; Carru, Ciriaco; Zinellu, Angelo; Franconi, Flavia
2016-01-01
Background: Gender medicine requires a global analysis of an individual's life. Menopause and ageing induce variations of some cardiometabolic parameters, but, it is unknown if this occurs in a sex-specific manner. Here, some markers of oxidative stress, systemic inflammation, and endothelial dysfunction are analysed in men younger and older than 45 years and in pre- and postmenopausal women. Methods: Serum and plasma sample were assayed for TNF-α and IL-6, malondialdehyde and protein carbonyls and for methylated arginines using ELISA kits, colorimetric methods and capillary electrophoresis. Results: Before body weight correction, men overall had higher creatinine, red blood cells and haemoglobin and lower triglycerides than women. Men younger than 45 years had lower levels of TNF-α and malondialdehyde and higher levels of arginine than age-matched women, while postmenopausal women had higher IL-6 concentrations than men, and higher total cholesterol, triglycerides, creatinine and IL-6 levels than younger women. Men younger than 45 years had lower total cholesterol and malondialdehyde than older men. After correction, some differences remained, others were amplified, others disappeared and some new differences emerged. Moreover, some parameters showed a correlation with age, and some of them correlated with each other as functions of ageing and ageing/menopausal status. Conclusions: Ageing/menopausal status increased many more cardiovascular risk factors in women than ageing in men, confirming that postmenopausal women had increased vascular vulnerability and indicating the need of early cardiovascular prevention in women. Sex-gender differences are also influenced by body weight, indicating as a matter of debate whether body weight should be seen as a true confounder or as part of the causal pathway. PMID:26941571
Age distribution among NASA scientists and engineers
NASA Technical Reports Server (NTRS)
Ciancone, Michael L.
1989-01-01
The loss of technical expertise through attrition in NASA and the aerospace industry is discussed. This report documents historical age-related information for scientific and engineering personnel in general and the NASA Lewis Research Center in particular, for 1968 through 1987. Recommendations are made to promote discussion and to establish the groundwork for action.
Control of Groundwater Remediation Process as Distributed Parameter System
NASA Astrophysics Data System (ADS)
Mendel, M.; Kovács, T.; Hulkó, G.
2014-12-01
Pollution of groundwater requires the implementation of appropriate solutions which can be deployed for several years. The case of local groundwater contamination and its subsequent spread may result in contamination of drinking water sources or other disasters. This publication aims to design and demonstrate control of pumping wells for a model task of groundwater remediation. The task consists of appropriately spaced soil with input parameters, pumping wells and control system. Model of controlled system is made in the program MODFLOW using the finitedifference method as distributed parameter system. Control problem is solved by DPS Blockset for MATLAB & Simulink.
Maximum likelihood estimation for distributed parameter models of flexible spacecraft
NASA Technical Reports Server (NTRS)
Taylor, L. W., Jr.; Williams, J. L.
1989-01-01
A distributed-parameter model of the NASA Solar Array Flight Experiment spacecraft structure is constructed on the basis of measurement data and analyzed to generate a priori estimates of modal frequencies and mode shapes. A Newton-Raphson maximum-likelihood algorithm is applied to determine the unknown parameters, using a truncated model for the estimation and the full model for the computation of the higher modes. Numerical results are presented in a series of graphs and briefly discussed, and the significant improvement in computation speed obtained by parallel implementation of the method on a supercomputer is noted.
Huang, Dan; Chen, Xuejuan; Gong, Qi; Yuan, Chaoqun; Ding, Hui; Bai, Jing; Zhu, Hui; Fu, Zhujun; Yu, Rongbin; Liu, Hu
2016-01-01
This survey was conducted to determine the testability, distribution and associations of ocular biometric parameters in Chinese preschool children. Ocular biometric examinations, including the axial length (AL) and corneal radius of curvature (CR), were conducted on 1,688 3-year-old subjects by using an IOLMaster in August 2015. Anthropometric parameters, including height and weight, were measured according to a standardized protocol, and body mass index (BMI) was calculated. The testability was 93.7% for the AL and 78.6% for the CR overall, and both measures improved with age. Girls performed slightly better in AL measurements (P = 0.08), and the difference in CR was statistically significant (P < 0.05). The AL distribution was normal in girls (P = 0.12), whereas it was not in boys (P < 0.05). For CR1, all subgroups presented normal distributions (P = 0.16 for boys; P = 0.20 for girls), but the distribution varied when the subgroups were combined (P < 0.05). CR2 presented a normal distribution (P = 0.11), whereas the AL/CR ratio was abnormal (P < 0.001). Boys exhibited a significantly longer AL, a greater CR and a greater AL/CR ratio than girls (all P < 0.001). PMID:27384307
Huang, Dan; Chen, Xuejuan; Gong, Qi; Yuan, Chaoqun; Ding, Hui; Bai, Jing; Zhu, Hui; Fu, Zhujun; Yu, Rongbin; Liu, Hu
2016-01-01
This survey was conducted to determine the testability, distribution and associations of ocular biometric parameters in Chinese preschool children. Ocular biometric examinations, including the axial length (AL) and corneal radius of curvature (CR), were conducted on 1,688 3-year-old subjects by using an IOLMaster in August 2015. Anthropometric parameters, including height and weight, were measured according to a standardized protocol, and body mass index (BMI) was calculated. The testability was 93.7% for the AL and 78.6% for the CR overall, and both measures improved with age. Girls performed slightly better in AL measurements (P = 0.08), and the difference in CR was statistically significant (P < 0.05). The AL distribution was normal in girls (P = 0.12), whereas it was not in boys (P < 0.05). For CR1, all subgroups presented normal distributions (P = 0.16 for boys; P = 0.20 for girls), but the distribution varied when the subgroups were combined (P < 0.05). CR2 presented a normal distribution (P = 0.11), whereas the AL/CR ratio was abnormal (P < 0.001). Boys exhibited a significantly longer AL, a greater CR and a greater AL/CR ratio than girls (all P < 0.001). PMID:27384307
Control of the SCOLE configuration using distributed parameter models
NASA Technical Reports Server (NTRS)
Hsiao, Min-Hung; Huang, Jen-Kuang
1994-01-01
A continuum model for the SCOLE configuration has been derived using transfer matrices. Controller designs for distributed parameter systems have been analyzed. Pole-assignment controller design is considered easy to implement but stability is not guaranteed. An explicit transfer function of dynamic controllers has been obtained and no model reduction is required before the controller is realized. One specific LQG controller for continuum models had been derived, but other optimal controllers for more general performances need to be studied.
Computational methods for the control of distributed parameter systems
NASA Technical Reports Server (NTRS)
Burns, J. A.; Cliff, E. M.; Powers, R. K.
1985-01-01
It is shown that care must be taken to ensure that finite dimensional approximations of distributed parameter systems preserve important system properties (i.e., controllability, observability, stabilizability, detectability, etc.). It is noted that, if the particular scheme used to construct the finite dimensional model does not take into account these system properties, the model may not be suitable for control design and analysis. These ideas are illustrated by a simple example, i.e., a cable-spring-mass system.
Flaw strength distributions and statistical parameters for ceramic fibers: the normal distribution.
R'mili, M; Godin, N; Lamon, J
2012-05-01
The present paper investigates large sets of ceramic fibre failure strengths (500 to 1000 data) produced using tensile tests on tows that contained either 500 or 1000 filaments. The probability density function was determined through acoustic emission monitoring which allowed detection and counting of filament fractures. The statistical distribution of filament strengths was described using the normal distribution. The Weibull equation was then fitted to this normal distribution for estimation of statistical parameters. A perfect agreement between both distributions was obtained, and a quite negligible scatter in statistical parameters was observed, as opposed to the wide variability that is reported in the literature. Thus it was concluded that flaw strengths are distributed normally and that the statistical parameters that were derived are the true ones. In a second step, the conventional method of estimation of Weibull parameters was applied to these sets of data and, then, to subsets selected randomly. The influence of other factors involved in the conventional method of determination of statistical parameters is discussed. It is demonstrated that selection of specimens, sample size, and method of construction of so-called Weibull plots are responsible for statistical parameters variability. PMID:23004702
Flaw strength distributions and statistical parameters for ceramic fibers: The normal distribution
NASA Astrophysics Data System (ADS)
R'Mili, M.; Godin, N.; Lamon, J.
2012-05-01
The present paper investigates large sets of ceramic fibre failure strengths (500 to 1000 data) produced using tensile tests on tows that contained either 500 or 1000 filaments. The probability density function was determined through acoustic emission monitoring which allowed detection and counting of filament fractures. The statistical distribution of filament strengths was described using the normal distribution. The Weibull equation was then fitted to this normal distribution for estimation of statistical parameters. A perfect agreement between both distributions was obtained, and a quite negligible scatter in statistical parameters was observed, as opposed to the wide variability that is reported in the literature. Thus it was concluded that flaw strengths are distributed normally and that the statistical parameters that were derived are the true ones. In a second step, the conventional method of estimation of Weibull parameters was applied to these sets of data and, then, to subsets selected randomly. The influence of other factors involved in the conventional method of determination of statistical parameters is discussed. It is demonstrated that selection of specimens, sample size, and method of construction of so-called Weibull plots are responsible for statistical parameters variability.
Skeletal distribution and biochemical parameters of Paget's disease
Meunier, P.J.; Salson, C.; Mathieu, L.; Chapuy, M.C.; Delmas, P.; Alexandre, C.; Charhon, S.
1987-04-01
Quantitative bone scans were performed with /sup 99m/Tc-EHDP in 170 untreated pagetic patients (93 men, 77 women; mean age, 65.4 years). The distribution of 863 pagetic skeletal locations was analyzed. Bone scans demonstrated 8.3% more pagetic sites than roentgenograms. The extent of Paget's disease was evaluated in each patient by a scintigraphic skeletal index. This index correlated with serum alkaline phosphatase (SAP) and urinary hydroxyproline (HyPro) levels, and also with hypocalcemic acute response to calcitonin. The correlation of SAP with an index of activity (extent index adjusted by uptake ratios) was better than with the nonadjusted index. Only 30.6% of pagetic sites were responsible for clinical symptoms. No correlation was found between age and skeletal index of the disease.
Control of complex dynamics and chaos in distributed parameter systems
Chakravarti, S.; Marek, M.; Ray, W.H.
1995-12-31
This paper discusses a methodology for controlling complex dynamics and chaos in distributed parameter systems. The reaction-diffusion system with Brusselator kinetics, where the torus-doubling or quasi-periodic (two characteristic incommensurate frequencies) route to chaos exists in a defined range of parameter values, is used as an example. Poincare maps are used for characterization of quasi-periodic and chaotic attractors. The dominant modes or topos, which are inherent properties of the system, are identified by means of the Singular Value Decomposition. Tested modal feedback control schemas based on identified dominant spatial modes confirm the possibility of stabilization of simple quasi-periodic trajectories in the complex quasi-periodic or chaotic spatiotemporal patterns.
Sediment load estimation using statistical distributions with streamflow dependent parameters
NASA Astrophysics Data System (ADS)
Mailhot, A.; Rousseau, A. N.; Talbot, G.; Quilbé, R.
2005-12-01
The classical approaches to estimate sediment and chemical loads are all deterministic: averaging methods, ratio estimators, regression methods (rating curves) and planning level load estimation methods. However, none of these methods is satisfactory since they are often inaccurate and do not take into account nor quantify uncertainty. To fill this gap, statistical methods have to be investigated. This presentation proposes a new statistical method in which sediment concentration is assimilated to a random variable and is described by distribution functions. Three types of distributions are considered: Log-Normal, Gamma and Weibull distributions. Correlation between sediment concentrations and streamflows is integrated to the model by assuming that distribution parameters (mean and coefficient of variation) are related to streamflow using several different functional forms: exponential, quadratic and power law forms for the mean, constant and linear for the coefficient of variation. Parameter estimation is realized through maximization of the likelihood function. This approach is applied on a data set (1989 to 2004) from the Beaurivage River (Quebec, Canada) with weekly to monthly sampling for sediment concentration. A comparison of different models (selection of a distribution function with functional forms relating the mean and the coefficient of variation to streamflow) shows that the Log-Normal distribution with power law mean and coefficient of variation independent of streamflow provides the best result. When comparing annual load results with those obtained using deterministic methods, we observe that ratio estimators values are rarely within the [0.1, 0.9] quantile interval. For the 1997-2004 period, ratio estimator values are almost systematically smaller than the 0.1 quantile. This could presumably be due to the small number of sediment concentration samples for these years. This study suggests that, if deterministic methods such as the ratio estimator
Transfer function modeling of damping mechanisms in distributed parameter models
NASA Technical Reports Server (NTRS)
Slater, J. C.; Inman, D. J.
1994-01-01
This work formulates a method for the modeling of material damping characteristics in distributed parameter models which may be easily applied to models such as rod, plate, and beam equations. The general linear boundary value vibration equation is modified to incorporate hysteresis effects represented by complex stiffness using the transfer function approach proposed by Golla and Hughes. The governing characteristic equations are decoupled through separation of variables yielding solutions similar to those of undamped classical theory, allowing solution of the steady state as well as transient response. Example problems and solutions are provided demonstrating the similarity of the solutions to those of the classical theories and transient responses of nonviscous systems.
Radial Distributions of Dusty Plasma Parameters in a Glow Discharge
Fedoseev, A. V.; Sukhinin, G. I.
2011-11-29
A self-consistent model for radial distributions of dusty plasma parameters in a DC glow discharge based on the non-local Boltzmann equation for EEDF, the drift-diffusion equation for ions, and the Poisson equation for self-consistent electric field is presented. The results show that for the case of high dust particles density when the recombination of electrons and ions exceeds the ionization near the tube axis, radial electron and ion fluxes change their direction toward the center of the tube, and the radial electric field is reversed.
Tensile strength of randomly perforated aluminum plates: Weibull distribution parameters
NASA Astrophysics Data System (ADS)
Klein, Claude A.
2008-07-01
Recently, Yanay and collaborators [J. Appl. Phys. 101, 104911 (2007)] addressed issues regarding the fracture strength of randomly perforated aluminum plates subjected to tensile loads. Based on comprehensive measurements and computational simulations, they formulate statistical predictions for the tensile strength dependence on the hole density but conclude that their data are inadequate for the purpose of deriving the strength distribution function. The primary purpose of this contribution is to demonstrate that, on dividing the totality of applicable data into seven "bins" of comparable population, the strength distribution of perforated plates of similar hole density obeys a conventional two-parameter Weibull model. Furthermore, on examining the fracture stresses as recorded in the vicinity of the percolation threshold, we find that the strength obeys the expression σo(P -Pth)β with Pth≃0.64 and β ≃0.4. In this light, and taking advantage of percolation theory, we formulate equations that specify how the two Weibull parameters (characteristic strength and shape factor) depend on the hole density. This enables us to express the failure probability as a function of the tensile stress, over the entire range of hole densities, i.e., P =0.02 up to the percolation threshold.
C -parameter distribution at N 3 LL ' including power corrections
Hoang, André H.; Kolodrubetz, Daniel W.; Mateu, Vicent; Stewart, Iain W.
2015-05-15
We compute the e⁺e⁻ C-parameter distribution using the soft-collinear effective theory with a resummation to next-to-next-to-next-to-leading-log prime accuracy of the most singular partonic terms. This includes the known fixed-order QCD results up to O(α3s), a numerical determination of the two-loop nonlogarithmic term of the soft function, and all logarithmic terms in the jet and soft functions up to three loops. Our result holds for C in the peak, tail, and far tail regions. Additionally, we treat hadronization effects using a field theoretic nonperturbative soft function, with moments Ωn. To eliminate an O(ΛQCD) renormalon ambiguity in the soft function, we switchmore » from the MS¯ to a short distance “Rgap” scheme to define the leading power correction parameter Ω1. We show how to simultaneously account for running effects in Ω1 due to renormalon subtractions and hadron-mass effects, enabling power correction universality between C-parameter and thrust to be tested in our setup. We discuss in detail the impact of resummation and renormalon subtractions on the convergence. In the relevant fit region for αs(mZ) and Ω1, the perturbative uncertainty in our cross section is ≅ 2.5% at Q=mZ.« less
C -parameter distribution at N3LL' including power corrections
NASA Astrophysics Data System (ADS)
Hoang, André H.; Kolodrubetz, Daniel W.; Mateu, Vicent; Stewart, Iain W.
2015-05-01
We compute the e+e- C -parameter distribution using the soft-collinear effective theory with a resummation to next-to-next-to-next-to-leading-log prime accuracy of the most singular partonic terms. This includes the known fixed-order QCD results up to O (αs3), a numerical determination of the two-loop nonlogarithmic term of the soft function, and all logarithmic terms in the jet and soft functions up to three loops. Our result holds for C in the peak, tail, and far tail regions. Additionally, we treat hadronization effects using a field theoretic nonperturbative soft function, with moments Ωn. To eliminate an O (ΛQCD) renormalon ambiguity in the soft function, we switch from the MS ¯ to a short distance "Rgap" scheme to define the leading power correction parameter Ω1. We show how to simultaneously account for running effects in Ω1 due to renormalon subtractions and hadron-mass effects, enabling power correction universality between C -parameter and thrust to be tested in our setup. We discuss in detail the impact of resummation and renormalon subtractions on the convergence. In the relevant fit region for αs(mZ) and Ω1, the perturbative uncertainty in our cross section is ≃ 2.5 % at Q =mZ.
The response of aggregate production to fertility-induced changes in population age distribution.
Denton, F T; Mountain, D C; Spencer, B G
1996-01-01
With a particular focus upon long-term supply effects, the authors explored the implications of different population age distributions for the productive capacity of an economy. A multilevel aggregate production process was specified, plausible values assigned to its parameters, and steady-state solutions obtained under a range of alternative fertility assumptions. The theoretical model was calibrated to conform with Canadian data and published estimates of age-sex substitution elasticities. The study found productive capacity to be related to age distribution, although the output effects exceed 8%, regardless of the structure of the economy, only when total fertility rate is less than 1.6 or well above 3.0; within the range of variation, productive capacity and output per capita are lower for both younger and older populations; altering the elasticity of substitution between different tasks has negligible effects upon the sensitivity of the economy to changes in age distribution; altering the elasticity of substitution between different age-sex groups for a given task has a markedly greater effect; introducing either increasing or decreasing returns to scale has only a minor effect upon the sensitivity of the economy to changes in age distribution; and marginal products are quite sensitive to changes in age distribution for both younger and older workers, but far less sensitive for middle-aged workers. PMID:12320140
Inversion of generalized relaxation time distributions with optimized damping parameter
NASA Astrophysics Data System (ADS)
Florsch, Nicolas; Revil, André; Camerlynck, Christian
2014-10-01
Retrieving the Relaxation Time Distribution (RDT), the Grains Size Distribution (GSD) or the Pore Size Distribution (PSD) from low-frequency impedance spectra is a major goal in geophysics. The “Generalized RTD” generalizes parametric models like Cole-Cole and many others, but remains tricky to invert since this inverse problem is ill-posed. We propose to use generalized relaxation basis function (for instance by decomposing the spectra on basis of generalized Cole-Cole relaxation elements instead of the classical Debye basis) and to use the L-curve approach to optimize the damping parameter required to get smooth and realistic inverse solutions. We apply our algorithm to three examples, one synthetic and two real data sets, and the program includes the possibility of converting the RTD into GSD or PSD by choosing the value of the constant connecting the relaxation time to the characteristic polarization size of interest. A high frequencies (typically above 1 kHz), a dielectric term in taken into account in the model. The code is provided as an open Matlab source as a supplementary file associated with this paper.
Vayá, Amparo; Sarnago, Ana; Fuster, Oscar; Alis, Rafael; Romagnoli, Marco
2015-01-01
Red blood cell distribution width (RDW) is a routine red blood cell count parameter which has been shown to be associated with inflammatory parameters. Recently, some authors proposed that RDW seems to be a marker of an adverse lipidic profile. In order to clarify whether RDW is related to inflammation, plasma lipids, or both, we determined anthropometric, hematimetric, inflammatory and lipidic parameters in 1111 healthy subjects. RDW correlated directly with age, body mass index (BMI), inflammatory parameters (plasma viscosity, erythrocyte sedimentation rate (ESR), fibrinogen, leukocyte and neutrophil count), and inversely with iron and hematimetric parameters (P < 0.05). When subjects were divided according to gender, RDW correlated inversely with triglycerides only in women (P < 0.05). When subjects were classified into RDW-quartiles, increased RDW values were accompanied by decreased serum iron levels and hematimetric indices (P < 0.01), whereas age and inflammatory markers increased according to RDW-quartiles (P < 0.001 and P < 0.05, respectively). However, plasma lipids did not change with increasing RDW-quartiles (P > 0.05). In the linear regression analysis, age, hemoglobin, MCV (beta coefficient: 0.202, -0.234, -0.316, P < 0.001) and fibrinogen (beta coefficient: 0.059, P = 0.048) were the only independent predictors of RDW. The present study indicates that RDW is associated with inflammatory markers and hematimetric indices, but not with plasma lipid levels in a healthy population. PMID:25159489
Distributed parameter approach to the dynamics of complex biological processes
Lee, T.T.; Wang, F.Y.; Newell, R.B.
1999-10-01
Modeling and simulation of a complex biological process for the removal of nutrients (nitrogen and phosphorus) from municipal wastewater are addressed. The model developed in this work employs a distributed-parameter approach to describe the behavior of components within three different bioreaction zones and the behavior of sludge in the anaerobic zone and soluble phosphate in the aerobic zone in two experiments. Good results are achieved despite the apparent plant-model mismatch, such as uncertainties with the behavior of phosphorus-accumulating organisms. Validation of the proposed secondary-settler model shows that it is superior to two state-of-the-art models in terms of the sum of the square relative errors.
Sound propagation and absorption in foam - A distributed parameter model.
NASA Technical Reports Server (NTRS)
Manson, L.; Lieberman, S.
1971-01-01
Liquid-base foams are highly effective sound absorbers. A better understanding of the mechanisms of sound absorption in foams was sought by exploration of a mathematical model of bubble pulsation and coupling and the development of a distributed-parameter mechanical analog. A solution by electric-circuit analogy was thus obtained and transmission-line theory was used to relate the physical properties of the foams to the characteristic impedance and propagation constants of the analog transmission line. Comparison of measured physical properties of the foam with values obtained from measured acoustic impedance and propagation constants and the transmission-line theory showed good agreement. We may therefore conclude that the sound propagation and absorption mechanisms in foam are accurately described by the resonant response of individual bubbles coupled to neighboring bubbles.
Numerical studies of identification in nonlinear distributed parameter systems
NASA Technical Reports Server (NTRS)
Banks, H. T.; Lo, C. K.; Reich, Simeon; Rosen, I. G.
1989-01-01
An abstract approximation framework and convergence theory for the identification of first and second order nonlinear distributed parameter systems developed previously by the authors and reported on in detail elsewhere are summarized and discussed. The theory is based upon results for systems whose dynamics can be described by monotone operators in Hilbert space and an abstract approximation theorem for the resulting nonlinear evolution system. The application of the theory together with numerical evidence demonstrating the feasibility of the general approach are discussed in the context of the identification of a first order quasi-linear parabolic model for one dimensional heat conduction/mass transport and the identification of a nonlinear dissipation mechanism (i.e., damping) in a second order one dimensional wave equation. Computational and implementational considerations, in particular, with regard to supercomputing, are addressed.
NASA Astrophysics Data System (ADS)
Zurfluh, Florian J.; Hofmann, Beda A.; Gnos, Edwin; Eggenberger, Urs; Jull, A. J. Timothy
2016-07-01
We have investigated 128 14C-dated ordinary chondrites from Oman for macroscopically visible weathering parameters, for thin section-based weathering degrees, and for chemical weathering parameters as analyzed with handheld X-ray fluorescence. These 128 14C-dated meteorites show an abundance maximum of terrestrial age at 19.9 ka, with a mean of 21.0 ka and a pronounced lack of samples between 0 and 10 ka. The weathering degree is evaluated in thin section using a refined weathering scale based on the current W0 to W6 classification of Wlotzka (1993), with five newly included intermediate steps resulting in a total of nine (formerly six) steps. We find significant correlations between terrestrial ages and several macroscopic weathering parameters. The correlation of various chemical parameters including Sr and Ba with terrestrial age is not very pronounced. The microscopic weathering degree of metal and sulfides with newly added intermediate steps shows the best correlation with 14C terrestrial ages, demonstrating the significance of the newly defined weathering steps. We demonstrate that the observed 14C terrestrial age distribution can be modeled from the abundance of meteorites with different weathering degrees, allowing the evaluation of an age-frequency distribution for the whole meteorite population.
NASA Astrophysics Data System (ADS)
Zurfluh, Florian J.; Hofmann, Beda A.; Gnos, Edwin; Eggenberger, Urs; Jull, A. J. Timothy
2016-09-01
We have investigated 128 14C-dated ordinary chondrites from Oman for macroscopically visible weathering parameters, for thin section-based weathering degrees, and for chemical weathering parameters as analyzed with handheld X-ray fluorescence. These 128 14C-dated meteorites show an abundance maximum of terrestrial age at 19.9 ka, with a mean of 21.0 ka and a pronounced lack of samples between 0 and 10 ka. The weathering degree is evaluated in thin section using a refined weathering scale based on the current W0 to W6 classification of Wlotzka (1993), with five newly included intermediate steps resulting in a total of nine (formerly six) steps. We find significant correlations between terrestrial ages and several macroscopic weathering parameters. The correlation of various chemical parameters including Sr and Ba with terrestrial age is not very pronounced. The microscopic weathering degree of metal and sulfides with newly added intermediate steps shows the best correlation with 14C terrestrial ages, demonstrating the significance of the newly defined weathering steps. We demonstrate that the observed 14C terrestrial age distribution can be modeled from the abundance of meteorites with different weathering degrees, allowing the evaluation of an age-frequency distribution for the whole meteorite population.
Estimating the Age Distribution of Oceanic Dissolved Organic Carbon
NASA Astrophysics Data System (ADS)
Follett, C. L.; Forney, D. C.; Repeta, D.; Rothman, D.
2010-12-01
Dissolved organic carbon (DOC) is a large, ubiquitous component of open ocean water at all depths and impacts atmospheric carbon dioxide levels at both short and long timescales. It is currently believed that oceanic DOC contains a multi-thousand-year-old refractory deep-water component which is mixed with a young labile component in surface waters. Unfortunately, the only evidence for this comes from a few isolated depth profiles of both DOC concentration and bulk radiocarbon. Although the profile data is consistent with a two-component mixing model, directly separating the two components has proven to be a challenge. We explore the validity of the two component mixing model by directly estimating the age distribution of oceanic DOC. The two-component model suggests that the age distribution is composed of two distinct peaks. In order to obtain an estimate of the age distribution we first record changes in both concentration and percent radiocarbon as a sample is oxidized under ultra-violet radiation [1]. We formulate a mathematical model relating the age distribution to these changes, assuming that they result from components of different radiocarbon age and UV-reactivity. This allows us to numerically invert the data and estimate the age distribution. We apply our procedure to DOC samples collected from three distinct depths (50, 500, and 2000 meters) in the north-central Pacific Ocean. [1] S.R. Beaupre, E.R.M. Druffel, and S. Griffin. A low-blank photochemical extraction system for concentration and isotopic analyses of marine dissolved organic carbon. Limnol. Oceanogr. Methods, 5:174-184, 2007.
Effects of intraborehole flow on groundwater age distribution
Zinn, B.A.; Konikow, L.F.
2007-01-01
Environmental tracers are used to estimate groundwater ages and travel times, but the strongly heterogeneous nature of many subsurface environments can cause mixing between waters of highly disparate ages, adding additional complexity to the age-estimation process. Mixing may be exacerbated by the presence of wells because long open intervals or long screens with openings at multiple depths can transport water and solutes rapidly over a large vertical distance. The effect of intraborehole flow on groundwater age was examined numerically using direct age transport simulation coupled with the Multi-Node Well Package of MODFLOW. Ages in a homogeneous, anisotropic aquifer reached a predevelopment steady state possessing strong depth dependence. A nonpumping multi-node well was then introduced in one of three locations within the system. In all three cases, vertical transport along the well resulted in substantial changes in age distributions within the system. After a pumping well was added near the nonpumping multi-node well, ages were further perturbed by a flow reversal in the nonpumping multi-node well. Results indicated that intraborehole flow can substantially alter groundwater ages, but the effects are highly dependent on local or regional flow conditions and may change with time. ?? Springer-Verlag 2007.
THE AGE AND STELLAR PARAMETERS OF THE PROCYON BINARY SYSTEM
Liebert, James; Arnett, David; Fontaine, Gilles; Young, Patrick A.; Williams, Kurtis A. E-mail: darnett@as.arizona.edu E-mail: pyoung.3@asu.edu
2013-05-20
The Procyon AB binary system (orbital period 40.838 yr, a newly refined determination) is near and bright enough that the component radii, effective temperatures, and luminosities are very well determined, although more than one possible solution to the masses has limited the claimed accuracy. Preliminary mass determinations for each component are available from Hubble Space Telescope imaging, supported by ground-based astrometry and an excellent Hipparcos parallax; we use these for our preferred solution for the binary system. Other values for the masses are also considered. We have employed the TYCHO stellar evolution code to match the radius and luminosity of the F5 IV-V primary star to determine the system's most likely age as 1.87 {+-} 0.13 Gyr. Since prior studies of Procyon A found its abundance indistinguishable from solar, the solar composition of Asplund, Grevesse, and Sauval (Z = 0.014) is assumed for the Hertzsprung-Russell diagram fitting. An unsuccessful attempt to fit using the older solar abundance scale of Grevesse and Sauval (Z = 0.019) is also reported. For Procyon B, 11 new sequences for the cooling of non-DA white dwarfs have been calculated to investigate the dependences of the cooling age on (1) the mass, (2) core composition, (3) helium layer mass, and (4) heavy-element opacities in the helium envelope. Our calculations indicate a cooling age of 1.19 {+-} 0.11 Gyr, which implies that the progenitor mass of Procyon B was 2.59{sub -0.26}{sup +0.44} M{sub Sun }. In a plot of initial versus final mass of white dwarfs in astrometric binaries or star clusters (all with age determinations), the Procyon B final mass lies several {sigma} below a straight line fit.
Data-Driven H∞ Control for Nonlinear Distributed Parameter Systems.
Luo, Biao; Huang, Tingwen; Wu, Huai-Ning; Yang, Xiong
2015-11-01
The data-driven H∞ control problem of nonlinear distributed parameter systems is considered in this paper. An off-policy learning method is developed to learn the H∞ control policy from real system data rather than the mathematical model. First, Karhunen-Loève decomposition is used to compute the empirical eigenfunctions, which are then employed to derive a reduced-order model (ROM) of slow subsystem based on the singular perturbation theory. The H∞ control problem is reformulated based on the ROM, which can be transformed to solve the Hamilton-Jacobi-Isaacs (HJI) equation, theoretically. To learn the solution of the HJI equation from real system data, a data-driven off-policy learning approach is proposed based on the simultaneous policy update algorithm and its convergence is proved. For implementation purpose, a neural network (NN)- based action-critic structure is developed, where a critic NN and two action NNs are employed to approximate the value function, control, and disturbance policies, respectively. Subsequently, a least-square NN weight-tuning rule is derived with the method of weighted residuals. Finally, the developed data-driven off-policy learning approach is applied to a nonlinear diffusion-reaction process, and the obtained results demonstrate its effectiveness. PMID:26277007
Modeling the brain morphology distribution in the general aging population
NASA Astrophysics Data System (ADS)
Huizinga, W.; Poot, D. H. J.; Roshchupkin, G.; Bron, E. E.; Ikram, M. A.; Vernooij, M. W.; Rueckert, D.; Niessen, W. J.; Klein, S.
2016-03-01
Both normal aging and neurodegenerative diseases such as Alzheimer's disease cause morphological changes of the brain. To better distinguish between normal and abnormal cases, it is necessary to model changes in brain morphology owing to normal aging. To this end, we developed a method for analyzing and visualizing these changes for the entire brain morphology distribution in the general aging population. The method is applied to 1000 subjects from a large population imaging study in the elderly, from which 900 were used to train the model and 100 were used for testing. The results of the 100 test subjects show that the model generalizes to subjects outside the model population. Smooth percentile curves showing the brain morphology changes as a function of age and spatiotemporal atlases derived from the model population are publicly available via an interactive web application at agingbrain.bigr.nl.
The relation between the lateral profile of giant extensive air showers and the age parameter
NASA Astrophysics Data System (ADS)
Capdevielle, Jean-Noël; Cohen, Fabrice
2005-05-01
After performing extensive simulations with the code CoRSiKa, we have obtained an analytical description fitting with surprising accuracy the numerical densities up to distances larger than 5 km from the shower axis. This was achieved by using the hypergeometric formalism in place of the traditional NKG approach. The difficulty of cascade theory (validity limited to 3.5 Moliere radii), underlined with reason by the particle data group, is solved here, after overcoming the constraints of approximation B, to show that the distribution of lateral profiles at large distances is also correlated with the age parameter. This is an important step for a coherent interpretation of hybrid events recorded with both surface array and fluorescence telescopes, even with other information coming from Cerenkov or radio emission. A set of hypergeometric Gaussian functions, with a consistent relation between age parameter and total size, is proposed in the ultra-high-energy range (above 1 EeV) for electrons, muons and vertical equivalent muons.
Hematopoiesis and aging. IV. Mass and distribution of erythroid marrow in aged mice
Boggs, D.R.
1985-11-01
Aged mice are ''anemic,'' i.e., they have a lower hematocrit than young adult mice, but this appears to be a ''dilutional'' anemia; the red cell mass is normal. Other observations have supported the hypothesis that basal erythropoiesis does not change as mice grow old. In the present study, the percentage of injected VZFe found in the skeleton and spleen, VZFe distribution between various bones and bone groups, and the number of nucleated erythroid cells per humerus were studied and the total mass of erythroid precursors was calculated. There was no significant difference in any of these values between mice aged 3-27 months. The variability of VZFe distribution within various skeletal parts was no greater in aged than in young mice. Thus, these data further strengthen the case for normal basal rates of erythropoiesis in aged mice.
Aged boreal biomass burning aerosol size distributions from BORTAS 2011
NASA Astrophysics Data System (ADS)
Sakamoto, K. M.; Allan, J. D.; Coe, H.; Taylor, J. W.; Duck, T. J.; Pierce, J. R.
2014-09-01
Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number size-distributions in climate model inventories lead to uncertainties in the CCN concentrations and forcing estimates derived from these models. The BORTAS-B measurement campaign was designed to sample boreal biomass-burning outflow over Eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size-distribution of aged biomass-burning emissions (aged ∼1-2 days) from boreal wildfires in Northwestern Ontario. The composite median size-distribution yields a single dominant accumulation mode with Dpm = 230 nm (number-median diameter), σ = 1.7, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (ΔOA / ΔCO) along the path of Flight b622 show values of 0.05-0.18 μg m-3 ppbv-1 with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA production/evaporation within the aged plume over the sampling period. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size-distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the ΔOA / ΔCO enhancement ratios. We estimate that the fresh-plume median diameter was in the range of 59-94 nm with modal widths in the range of 1.7-2.8 (the ranges are due to uncertainty in the entrainment rate). Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in
Aged Boreal Biomass Burning Size Distributions from Bortas 2011
NASA Astrophysics Data System (ADS)
Pierce, J. R.; Sakamoto, K.; Allan, J. D.; Coe, H.; Taylor, J.; Duck, T.
2014-12-01
Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are strong functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number size-distributions in climate model inventories lead to uncertainties in the CCN concentrations and forcing estimates derived from these models. The BORTAS-B measurement campaign was designed to sample boreal biomass-burning outflow over Eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size-distribution of aged biomass-burning emissions (aged ~ 1.5 - 2 days) from boreal wildfires in Northwestern Ontario. The composite median size-distribution yields a single dominant accumulation mode with Dpm = 232 nm, σ = 1.7, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (ΔOA/ΔCO) along the path of Flight b622 show values of 0.08-0.18 μg m-3 ppbv-1 with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA production/evaporation within the aged plume over the sampling period. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution and flux corresponding to the BORTAS-B aged size-distributions. The model was restricted to coagulation and dilution processes only based on the insignificant net OA production/evaporation derived from the ΔOA/ΔCO enhancement ratios. Depending on the, we estimate that the fresh-plume median diameter was in the range of 59-94 nm with modal widths in the range of 1.7-2.8. Thus, the size of the freshly emitted particles is somewhat unconstrained due to the uncertainties in the plume dilution rates.
Distribution system water age can create premise plumbing corrosion hotspots.
Masters, Sheldon; Parks, Jeffrey; Atassi, Amrou; Edwards, Marc A
2015-09-01
Cumulative changes in chemical and biological properties associated with higher "water age" in distribution systems may impact water corrosivity and regulatory compliance with lead and copper action levels. The purpose of this study was to examine the effects of water age and chemistry on corrosivity of various downstream premise plumbing pipe materials and configurations using a combination of controlled laboratory studies and a field survey. Examination of lead pipe, copper pipe with lead solder, and leaded brass materials in a replicated lab rig simulating premise plumbing stagnation events indicated that lead or copper release could increase as much as ∼440 % or decrease as much as 98 % relative to water treatment plant effluent. In field studies at five utilities, trends in lead and copper release were highly dependent on circumstance; for example, lead release increased with water age in 13 % of cases and decreased with water age in 33 % of conditions tested. Levels of copper in the distribution system were up to 50 % lower and as much as 30 % higher relative to levels at the treatment plant. In many cases, high-risks of elevated lead and copper did not co-occur, demonstrating that these contaminants will have to be sampled separately to identify "worst case" conditions for human exposure and monitoring. PMID:26251058
Fundamental Parameters of Nearby Red Dwarfs: Stellar Radius as an Indicator of Age
NASA Astrophysics Data System (ADS)
Silverstein, Michele L.; Henry, Todd J.; Winters, Jennifer G.; Jao, Wei-Chun; Riedel, Adric R.; Dieterich, Sergio; RECONS Team
2016-01-01
Red dwarfs dominate the Galactic population, yet determining one of their most fundamental characteristics --- age --- has proven difficult. The characterization of red dwarfs in terms of their age is fundamental to mapping the history of star and, ultimately, planet formation in the Milky Way. Here we report on a compelling technique to evaluate the radii of red dwarfs, which can be used to provide leverage in estimating their ages. These radii are also particularly valuable in the cases of transiting exoplanet hosts because accurate stellar radii are required to determine accurate planetary radii.In this work, we use the BT-Settl models in combination with Johnson-Kron-Cousins VRI, 2MASS JHK, and WISE All-Sky Release photometry to produce spectral energy distributions (SEDs) to determine the temperatures and bolometric fluxes for 500 red dwarfs, most of which are in the southern sky. The full suites of our photometric and astrometric data (including hundreds of accurate new parallaxes from the RECONS team at the CTIO/SMARTS 0.9m) allow us to also determine the bolometric luminosities and radii. This method of radius determination is validated by a comparison of our measurements to those found using the CHARA Array (Boyajian et al. 2012), which match within a few percent.In addition to a compilation of red dwarf fundamental parameters, our findings provide a snapshot of relative stellar ages in the solar neighborhood. Of particular interest are the cohorts of very young and very old stars identified within 50 pc. These outliers exemplify the demographic extremes of the nearest stars.This effort has been supported by the NSF through grants AST-0908402, AST-1109445, and AST-1412026, and via observations made possible by the SMARTS Consortium.
NASA Astrophysics Data System (ADS)
Åkesson, Maria; Suckow, Axel; Visser, Ate; Sültenfuβ, Jürgen; Laier, Troels; Purtschert, Roland; Sparrenbom, Charlotte J.
2015-09-01
Twenty-five public supply wells throughout the hydrogeologically diverse region of Scania, southern Sweden are subjected to environmental tracer analysis (3H-3He, 4He, CFCs, SF6 and for one well only also 85Kr and 39Ar) to study well and aquifer vulnerability and evaluate possibilities of groundwater age distribution assessment. We find CFC and SF6 concentrations well above solubility equilibrium with modern atmosphere, indicating local contamination, as well as indications of CFC degradation. The tracer-specific complications considerably constrain possibilities for sound quantitative regional groundwater age distribution assessments and demonstrate the importance of initial qualitative assessment of tracer-specific reliability, as well a need for additional, complementary tracers (e.g. 85Kr, 39Ar and potentially also 14C). Lumped parameter modelling yields credible age distribution assessments for representative wells in four type aquifers. Pollution vulnerability of the aquifer types was based on the selected LPM models and qualitative age characterisation. Most vulnerable are unconfined dual porosity and fractured bedrock aquifers, due to a large component of very young groundwater. Unconfined sedimentary aquifers are vulnerable due to young groundwater and a small pre-modern component. Less vulnerable are semi-confined sedimentary or dual-porosity aquifers, due to older age of the modern component and a larger pre-modern component. Confined aquifers appear least vulnerable, due an entirely pre-modern groundwater age distribution (recharged before 1963). Tracer complications aside, environmental tracer analyses and lumped parameter modelling aid in vulnerability assessment and protection of regional groundwater resources.
Asquith, William H.
2014-01-01
The implementation characteristics of two method of L-moments (MLM) algorithms for parameter estimation of the 4-parameter Asymmetric Exponential Power (AEP4) distribution are studied using the R environment for statistical computing. The objective is to validate the algorithms for general application of the AEP4 using R. An algorithm was introduced in the original study of the L-moments for the AEP4. A second or alternative algorithm is shown to have a larger L-moment-parameter domain than the original. The alternative algorithm is shown to provide reliable parameter production and recovery of L-moments from fitted parameters. A proposal is made for AEP4 implementation in conjunction with the 4-parameter Kappa distribution to create a mixed-distribution framework encompassing the joint L-skew and L-kurtosis domains. The example application provides a demonstration of pertinent algorithms with L-moment statistics and two 4-parameter distributions (AEP4 and the Generalized Lambda) for MLM fitting to a modestly asymmetric and heavy-tailed dataset using R.
Estimation of Heterogeneity in Diagnostic Parameters of Age-related Diseases.
Blokh, David; Stambler, Ilia
2014-08-01
The heterogeneity of parameters is a ubiquitous biological phenomenon, with critical implications for biological systems functioning in normal and diseased states. We developed a method to estimate the level of objects set heterogeneity with reference to particular parameters and applied it to type II diabetes and heart disease, as examples of age-related systemic dysfunctions. The Friedman test was used to establish the existence of heterogeneity. The Newman-Keuls multiple comparison method was used to determine clusters. The normalized Shannon entropy was used to provide the quantitative evaluation of heterogeneity. There was obtained an estimate for the heterogeneity of the diagnostic parameters in healthy subjects, as well as in heart disease and type II diabetes patients, which was strongly related to their age. With aging, as with the diseases, the level of heterogeneity (entropy) was reduced, indicating a formal analogy between these phenomena. The similarity of the patterns in aging and disease suggested a kind of "early aging" of the diseased subjects, or alternatively a "disease-like" aging process, with reference to these particular parameters. The proposed method and its validation on the chronic age-related disease samples may support a way toward a formal mathematical relation between aging and chronic diseases and a formal definition of aging and disease, as determined by particular heterogeneity (entropy) changes. PMID:25110613
Yin, F J; Kang, J; Han, N N; Ma, H T
2015-01-01
The aim of the current study was to evaluate the effect of chronic dehydroepiandrosterone (DHEA) administration on steroid hormones and antioxidant parameters in aged rats. To this end, three groups of Sprague-Dawley rats were compared: young (3 months of age) untreated; aged (19 months old) untreated; and aged rats treated with 20 mg/kg DHEA for 8 weeks. Major organs of aged rats in the untreated group demonstrated physiological atrophy, compared to those of young rats; this effect appeared to have been partially reversed by DHEA treatment. Testosterone and estradiol contents were significantly decreased and aldosterone significantly increased in aged untreated, compared to young untreated rats. Steroid hormone levels were obviously reversed, however, in aged rats treated with DHEA. Additionally, superoxide dismutase activity in serum, brain, heart, and liver was decreased, and maleic dialdehyde content in heart was markedly increased in untreated aged, compared to young, rats. Importantly, these changes in brain and heart of aged rats were reversed by DHEA treatment. Heme oxygenase mRNA levels were increased and inducible nitric oxide synthase mRNA levels decreased in aged, compared to young, rats; DHEA treatment appeared to reverse these changes. These results indicate that chronic DHEA administration may have effects on steroid hormone levels and antioxidant parameters in aged rats and result in postponement of the aging process. PMID:26400361
Scale Shrinkage and the Estimation of Latent Distribution Parameters.
ERIC Educational Resources Information Center
Camilli, Gregory
1988-01-01
The phenomenon of scale shrinkage is examined. Focus is on the pattern of decreasing variances in item response theory scale scores from fall to spring within a grade. It is demonstrated that questions concerning population distributions of true ability can be addressed with empirical Bayes techniques. (TJH)
Methods of computing vocabulary size for the two-parameter rank distribution
NASA Technical Reports Server (NTRS)
Edmundson, H. P.; Fostel, G.; Tung, I.; Underwood, W.
1972-01-01
A summation method is described for computing the vocabulary size for given parameter values in the 1- and 2-parameter rank distributions. Two methods of determining the asymptotes for the family of 2-parameter rank-distribution curves are also described. Tables are computed and graphs are drawn relating paris of parameter values to the vocabulary size. The partial product formula for the Riemann zeta function is investigated as an approximation to the partial sum formula for the Riemann zeta function. An error bound is established that indicates that the partial product should not be used to approximate the partial sum in calculating the vocabulary size for the 2-parameter rank distribution.
A distributed parameter wire model for transient electrical discharges
NASA Astrophysics Data System (ADS)
Maier, William B., II; Kadish, A.; Sutherland, C. D.; Robiscoe, R. T.
1990-06-01
This paper presents a three-dimensional model developed for freely propagating electrical discharges, such as lightning and punch-through arcs. In this model, charge transport is described by a nonlinear differential equation containing two phenomenological parameters characteristic of the medium and the arc; the electromagnetic field is described by Maxwell's equations. Using this model, a cylindrically symmetric small-diameter discharge is analyzed. It is shown that the model predicts discharge properties consistent with experimentally known phenomena.
OTDR and OFDR for distributed multi-parameter sensing
NASA Astrophysics Data System (ADS)
Bao, Xiaoyi; Li, Wenhai; Qin, Zengguang; Chen, Liang
2014-03-01
The drive for high spatial resolution (millimeters) distributed fiber sensors has renewed the interest in optical frequency domain reflectrometry (OFDR) systems. Because millimeters equivalent spatial resolution in optical time domain reflectrometry (OTDR) systems would require a data acquisition card with a bandwidth of 10 GHz and a sampling rate of tens of G Samples/s, such a digitizer or data acquisition card plus the pulse generator and detection system will make a distributed sensors very expensive, while a tunable laser with a wide tuning range can provide millimeters resolution with short sensing range (<100m). We developed a high precision temperature (0.1°C) and strain (1μ strain) resolution and 2.5mm spatial resolution over 180m range by auto and cross-correlation of OFDR in PMF. The dual modes of PMF allow the discrimination of the temperature and strain with distinct dependency. The application of this sensor for internal crack detection of concrete beam has been demonstrated. For distributed dynamic measurement, the upper frequency is limited by the repetition rate of the laser pulse in sensing fiber; in addition the weak Rayleigh scattering signal demands many averaging to improve SNR. The continuous wavelet transform approach has been introduced in phase OTDR sensor system to suppress random noise, and multiple vibration disturbances have been measured simultaneously for power generator monitoring. For the high frequency vibration detection, the coherent detection combined with polarization diversity scheme is implemented.
NASA Astrophysics Data System (ADS)
Rajkumar, K. V.; Vaidyanathan, S.; Kumar, Anish; Jayakumar, T.; Raj, Baldev; Ray, K. K.
2007-05-01
The best combinations of mechanical properties (yield stress and fracture toughness) of M250 maraging steel is obtained through short-term thermal aging (3-10 h) at 755 K. This is attributed to the microstructure containing precipitation of intermetallic phases in austenite-free low-carbon martensite matrix. Over-aged microstructure, containing reverted austenite degrades the mechanical properties drastically. Hence, it necessitates identification of a suitable non-destructive evaluation (NDE) technique for detecting any reverted austenite unambiguously during aging. The influence of aging on microstructure, room temperature hardness and non-destructive magnetic parameters such as coercivity ( Hc), saturation magnetization ( Ms) and magnetic Barkhausen emission (MBE) RMS peak voltage is studied in order to derive correlations between these parameters in aged M250 maraging steel. Hardness was found to increase with precipitation of intermetallics during initial aging and decrease at longer durations due to austenite reversion. Among the different magnetic parameters studied, MBE RMS peak voltage was found to be very sensitive to austenite reversion (non-magnetic phase) as they decreased drastically up on initiation of austenite reversion. Hence, this parameter can be effectively utilized to detect and quantify the reverted austenite in maraging steel specimen. The present study clearly indicates that the combination of MBE RMS peak voltage and hardness can be used for unambiguous characterization of microstructural features of technological and practical importance (3-10 h of aging duration at 755 K) in M250 grade maraging steel.
Jurgens, Bryant C.; Böhlke, J.K.; Eberts, Sandra M.
2012-01-01
TracerLPM is an interactive Excel® (2007 or later) workbook program for evaluating groundwater age distributions from environmental tracer data by using lumped parameter models (LPMs). Lumped parameter models are mathematical models of transport based on simplified aquifer geometry and flow configurations that account for effects of hydrodynamic dispersion or mixing within the aquifer, well bore, or discharge area. Five primary LPMs are included in the workbook: piston-flow model (PFM), exponential mixing model (EMM), exponential piston-flow model (EPM), partial exponential model (PEM), and dispersion model (DM). Binary mixing models (BMM) can be created by combining primary LPMs in various combinations. Travel time through the unsaturated zone can be included as an additional parameter. TracerLPM also allows users to enter age distributions determined from other methods, such as particle tracking results from numerical groundwater-flow models or from other LPMs not included in this program. Tracers of both young groundwater (anthropogenic atmospheric gases and isotopic substances indicating post-1940s recharge) and much older groundwater (carbon-14 and helium-4) can be interpreted simultaneously so that estimates of the groundwater age distribution for samples with a wide range of ages can be constrained. TracerLPM is organized to permit a comprehensive interpretive approach consisting of hydrogeologic conceptualization, visual examination of data and models, and best-fit parameter estimation. Groundwater age distributions can be evaluated by comparing measured and modeled tracer concentrations in two ways: (1) multiple tracers analyzed simultaneously can be evaluated against each other for concordance with modeled concentrations (tracer-tracer application) or (2) tracer time-series data can be evaluated for concordance with modeled trends (tracer-time application). Groundwater-age estimates can also be obtained for samples with a single tracer measurement at one
Miller, G; Melo, D; Martz, H; Bertelli, L
2008-01-01
A simplified biokinetic model for (137)Cs has six parameters representing transfer of material to and from various compartments. Using a Bayesian analysis, the joint probability distribution of these six parameters is determined empirically for two cases with quite a lot of bioassay data. The distribution is found to be a multivariate log-normal. Correlations between different parameters are obtained. The method utilises a fairly large number of pre-determined forward biokinetic calculations, whose results are stored in interpolation tables. Four different methods to sample the multidimensional parameter space with a limited number of samples are investigated: random, stratified, Latin Hypercube sampling with a uniform distribution of parameters and importance sampling using a lognormal distribution that approximates the posterior distribution. The importance sampling method gives much smaller sampling uncertainty. No sampling method-dependent differences are perceptible for the uniform distribution methods. PMID:18420573
Automated CFD Parameter Studies on Distributed Parallel Computers
NASA Technical Reports Server (NTRS)
Rogers, Stuart E.; Aftosmis, Michael; Pandya, Shishir; Tejnil, Edward; Ahmad, Jasim; Kwak, Dochan (Technical Monitor)
2002-01-01
The objective of the current work is to build a prototype software system which will automated the process of running CFD jobs on Information Power Grid (IPG) resources. This system should remove the need for user monitoring and intervention of every single CFD job. It should enable the use of many different computers to populate a massive run matrix in the shortest time possible. Such a software system has been developed, and is known as the AeroDB script system. The approach taken for the development of AeroDB was to build several discrete modules. These include a database, a job-launcher module, a run-manager module to monitor each individual job, and a web-based user portal for monitoring of the progress of the parameter study. The details of the design of AeroDB are presented in the following section. The following section provides the results of a parameter study which was performed using AeroDB for the analysis of a reusable launch vehicle (RLV). The paper concludes with a section on the lessons learned in this effort, and ideas for future work in this area.
Applications of computer algebra to distributed parameter systems
NASA Technical Reports Server (NTRS)
Storch, Joel A.
1993-01-01
In the analysis of vibrations of continuous elastic systems, one often encounters complicated transcendental equations with roots directly related to the system's natural frequencies. Typically, these equations contain system parameters whose values must be specified before a numerical solution can be obtained. The present paper presents a method whereby the fundamental frequency can be obtained in analytical form to any desired degree of accuracy. The method is based upon truncation of rapidly converging series involving inverse powers of the system natural frequencies. A straightforward method to developing these series and summing them in closed form is presented. It is demonstrated how Computer Algebra can be exploited to perform the intricate analytical procedures which otherwise would render the technique difficult to apply in practice. We illustrate the method by developing two analytical approximations to the fundamental frequency of a vibrating cantilever carrying a rigid tip body. The results are compared to the numerical solution of the exact (transcendental) frequency equation over a range of system parameters.
Parameter sensitivity study of Arctic aerosol vertical distribution in CAM5
NASA Astrophysics Data System (ADS)
Jiao, C.; Flanner, M.
2015-12-01
Arctic surface temperature response to light-absorbing aerosols (black carbon, brown carbon and dust) depends strongly on their vertical distributions. Improving model simulations of three dimensional aerosol fields in the remote Arctic region will therefore lead to improved projections of the climate change caused by aerosol emissions. In this study, we investigate how different physical parameterizations in the Community Atmosphere Model version 5 (CAM5) influence the simulated vertical distribution of Arctic aerosols. We design experiments to test the sensitivity of the simulated aerosol fields to perturbations of selected aerosol process-related parameters in the Modal Aerosol Module with seven lognormal modes (MAM7), such as those govern aerosol aging, in-cloud and below-cloud scavenging, aerosol hygroscopicity and so on. The simulations are compared with observed aerosol vertical distributions and total optical depth to assess model performance and quantify uncertainties associated with these model parameterizations. Observations applied here include Arctic aircraft measurements of black carbon and sulfate vertical profiles, along with Aerosol Robotic Network (AERONET) optical depth measurements. We also assess the utility of using High Spectral Resolution Lidar (HSRL) measurements from the ARM Barrow site to infer vertical profiles of aerosol extinction. The sensitivity study explored here will provide guidance for optimizing global aerosol simulations.
Greenwood, J.A.; Landwehr, J.M.; Matalas, N.C.; Wallis, J.R.
1979-01-01
Distributions whose inverse forms are explicitly defined, such as Tukey's lambda, may present problems in deriving their parameters by more conventional means. Probability weighted moments are introduced and shown to be potentially useful in expressing the parameters of these distributions. -Authors
Probabilistic approach to identify sensitive parameter distributions in multimedia pathway analysis.
Kamboj, S.; Gnanapragasam, E.; LePoire, D.; Biwer, B. M.; Cheng, J.; Arnish, J.; Yu, C.; Chen, S. Y.; Mo, T.; Abu-Eid, R.; Thaggard, M.; Environmental Assessment; NRC
2002-01-01
Sensitive parameter distributions were identified with the use of probabilistic analysis in the RESRAD computer code. RESRAD is a multimedia pathway analysis code designed to evaluate radiological exposures resulting from radiological contamination in soil. The dose distribution was obtained by using a set of default parameter distribution/values. Most of the variations in the output dose distribution could be attributed to uncertainty in a small set of input parameters that could be considered as sensitive parameter distributions. The identification of the sensitive parameters is a first step in the prioritization of future research and information gathering. When site-specific parameter distribution/values are available for an actual site, the same process should be used with these site-specific data. Regression analysis used to identify sensitive parameters indicated that the dominant pathways depended on the radionuclide and source configurations. However, two parameter distributions were sensitive for many radionuclides: the external shielding factor when external exposure was the dominant pathway and the plant transfer factor when plant ingestion was the dominant pathway. No single correlation or regression coefficient can be used alone to identify sensitive parameters in all the cases. The coefficients are useful guides, but they have to be used in conjunction with other aids, such as scatter plots, and should undergo further analysis.
Reliability analysis of structural ceramic components using a three-parameter Weibull distribution
NASA Technical Reports Server (NTRS)
Duffy, Stephen F.; Powers, Lynn M.; Starlinger, Alois
1992-01-01
Described here are nonlinear regression estimators for the three-parameter Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data.
NASA Astrophysics Data System (ADS)
Milham, Merrill E.
1994-10-01
In this report, relevant parts of the scattering theory for magnetic spheres are presented. Mass extinction coefficients, and the lognormal size distribution are defined. The theory and algorithms for integrating scattering parameters over size distributions are developed. The integrations are carried out in terms of dimensionless scattering, and size distribution parameters, which are simply related to the usual mass scattering coefficients. Fortran codes, which implement the algorithmic design, are presented, and examples of code use are given. Code listings are included.
SAMDIST: A Computer Code for Calculating Statistical Distributions for R-Matrix Resonance Parameters
Leal, L.C.
1995-01-01
The: SAMDIST computer code has been developed to calculate distribution of resonance parameters of the Reich-Moore R-matrix type. The program assumes the parameters are in the format compatible with that of the multilevel R-matrix code SAMMY. SAMDIST calculates the energy-level spacing distribution, the resonance width distribution, and the long-range correlation of the energy levels. Results of these calculations are presented in both graphic and tabular forms.
SAMDIST: A computer code for calculating statistical distributions for R-matrix resonance parameters
Leal, L.C.; Larson, N.M.
1995-09-01
The SAMDIST computer code has been developed to calculate distribution of resonance parameters of the Reich-Moore R-matrix type. The program assumes the parameters are in the format compatible with that of the multilevel R-matrix code SAMMY. SAMDIST calculates the energy-level spacing distribution, the resonance width distribution, and the long-range correlation of the energy levels. Results of these calculations are presented in both graphic and tabular forms.
Fast Airborne Size Distribution Measurements of an Aerosol Processes and Aging
NASA Astrophysics Data System (ADS)
Kapustin, V.; Clarke, A. D.; Zhou, J.; Brekhovskikh, V.; McNaughton, C. S.; Howell, S.
2009-12-01
During MILAGRO/INTEX experiment the Hawaii Group for Environmental Aerosol Research (HIGEAR) deployed a wide range of aerosol instrumentation aboard NSF C-130 and NASA DC-8. These were designed to provide rapid information on aerosol composition, state of mixing (internal or external), spectral optical properties (scattering and absorption), the humidity dependence of light scattering - f(RH), and the role of condensed species in changing the absorption properties of black carbon (BC) and inferred properties of organic carbon (OC). We also flew the Fast Mobility Particle Spectrometer (FMPS, TSI Inc.) to measure aerosol size distributions in a range 5.6 - 560 nm. For all our flights around Mexico City, an aerosol number concentration usually was well above the nominal FMPS sensitivity (from ~100 particles/cc @ Dp = 5.6 nm to 1 part/cc @ 560nm), providing us with reliable size distributions even at 1 sec resolution. FMPS measurements revealed small scale structure of an aerosol and allowed us to examine size distributions varying over space and time associated with mixing processes previously unresolved. These 1-Hz measurements during aircraft profiles captured variations in size distributions within shallow layers. Other dynamic processes observed included orography induced aerosol layers and evolution of the nanoparticles formed by nucleation. We put FMPS high resolution size distribution data in a context of aerosol evolution and aging, using a range of established (for MIRAGE/INTEX) chemical, aerosol and transport aging parameters.
A comparative study of ballpoint ink ageing parameters using GC/MS.
Koenig, Agnès; Magnolon, Sophie; Weyermann, Céline
2015-07-01
For more than a decade scientists tried to develop methods capable of dating ink by monitoring the loss of phenoxyethanol (PE) over time. While many methods were proposed in the literature, few were really used to solve practical cases and they still raise much concern within the scientific community. In fact, due to the complexity of ink drying processes it is particularly difficult to find a reliable ageing parameter to reproducibly follow ink ageing. Moreover, systematic experiments are required in order to evaluate how different factors actually influence the results over time. Therefore, this work aimed at evaluating the capacity of four different ageing parameters to reliably follow ink ageing over time: (1) the quantity of solvent PE in an ink line, (2) the relative peak area (RPA) normalising the PE results using stable volatile compounds present in the ink formulation, (3) the solvent loss ratio (R%) calculated from PE results obtained by the analyses of naturally and artificially aged samples, (4) a modified solvent loss ratio version (R%*) calculated from RPA results. After the determination of the limits of reliable measurements of the analytical method, the repeatability of the different ageing parameters was evaluated over time, as well as the influence of ink composition, writing pressure and storage conditions on the results. Surprisingly, our results showed that R% was not the most reliable parameter, as it showed the highest standard deviation. Discussion of the results in an ink dating perspective suggests that other proposed parameters, such as RPA values, may be more adequate to follow ink ageing over time. PMID:25989257
NASA Astrophysics Data System (ADS)
Edouard, C.; Petit, M.; Forgez, C.; Bernard, J.; Revel, R.
2016-09-01
In this work, a simplified electrochemical and thermal model that can predict both physicochemical and aging behavior of Li-ion batteries is studied. A sensitivity analysis of all its physical parameters is performed in order to find out their influence on the model output based on simulations under various conditions. The results gave hints on whether a parameter needs particular attention when measured or identified and on the conditions (e.g. temperature, discharge rate) under which it is the most sensitive. A specific simulation profile is designed for parameters involved in aging equations in order to determine their sensitivity. Finally, a step-wise method is followed to limit the influence of parameter values when identifying some of them, according to their relative sensitivity from the study. This sensitivity analysis and the subsequent step-wise identification method show very good results, such as a better fitting of the simulated cell voltage with experimental data.
NASA Astrophysics Data System (ADS)
Zhao, Zhiwen
Our purpose is to deal with the parameter estimation and hypothesis testing on the equality of two negative binomial distribution populations with missing data. The consistency and asymptotic normality of the estimations are proved. In addition statistic on testing equality of two negative distributions and its limiting distribution are obtained.
Distribution parameters of Dendroctonus frontalis in a Georgia landscape
NASA Astrophysics Data System (ADS)
Christel, Lynne Marie
model output to infestation sites resulted in Chi-squared and Cramer's V values of 55.4 and 0.16, respectively, indicating that infestation risk distributions strongly paralleled site infestation. Comparison of model output and low, medium and high infestation density clusters resulted in Chi-squared and Cramer's V values of 241.24 and 0.66, respectively, indicating a more substantive relationship between infestation density and risk classes.
Shabani, Farzin; Kumar, Lalit
2014-01-01
Using CLIMEX and the Taguchi Method, a process-based niche model was developed to estimate potential distributions of Phoenix dactylifera L. (date palm), an economically important crop in many counties. Development of the model was based on both its native and invasive distribution and validation was carried out in terms of its extensive distribution in Iran. To identify model parameters having greatest influence on distribution of date palm, a sensitivity analysis was carried out. Changes in suitability were established by mapping of regions where the estimated distribution changed with parameter alterations. This facilitated the assessment of certain areas in Iran where parameter modifications impacted the most, particularly in relation to suitable and highly suitable locations. Parameter sensitivities were also evaluated by the calculation of area changes within the suitable and highly suitable categories. The low temperature limit (DV2), high temperature limit (DV3), upper optimal temperature (SM2) and high soil moisture limit (SM3) had the greatest impact on sensitivity, while other parameters showed relatively less sensitivity or were insensitive to change. For an accurate fit in species distribution models, highly sensitive parameters require more extensive research and data collection methods. Results of this study demonstrate a more cost effective method for developing date palm distribution models, an integral element in species management, and may prove useful for streamlining requirements for data collection in potential distribution modeling for other species as well. PMID:24722140
Age-related alterations to immune parameters in Labrador retriever dogs.
Blount, Daniel G; Pritchard, David I; Heaton, Paul R
2005-12-15
In order to assess age-related changes in the immune status of Labrador retriever dogs, leukocyte phenotypes, lymphocyte proliferative capacity, and serum antibody levels were measured in four cohorts of dogs, ranging from 2 to 10 years of age. Absolute numbers of white blood cells, lymphocytes, monocytes, granulocytes, and CD3+, CD4+, CD8+ and CD21+ lymphocytes significantly decreased with increasing age. Relative percentages of lymphocytes and CD4 cells were significantly decreased, and relative percentages of granulocytes and CD8 cells significantly increased, with age. The CD4:CD8 ratio showed a significant age-related decrease. Proliferative responses of T-cells to mitogens in whole-blood cultures either increased (Concanavalin A) or remained the same (phytohemagglutinin) with age when data was normalised to allow for differences in responding cell number. Similarly, normalised data of proliferative response to anti-CD3 stimulation together with phorbol 12-myristate 13-acetate showed an age-related increase. Serum levels of total IgA significantly increased with age whereas total IgG levels remained unchanged. These observations illustrate a significant change to a number of immune parameters with age. However, further work is required to determine whether the differences reported here are sufficient to cause overt or functional immune senescence in Labrador retriever dogs. PMID:16105688
ERIC Educational Resources Information Center
Kumari, Neeraj
2014-01-01
The objective of the study is to examine the students' perspective (age wise, gender wise and year wise) of parameters affecting the undergraduate engineering education system present in a private technical institution in NCR [National Capital Region], Haryana. It is a descriptive type of research in nature. The data has been collected with the…
Genetic parameters for weaning weight by age of dam for Brazilian Nellore
Technology Transfer Automated Retrieval System (TEKTRAN)
The objective was to estimate genetic parameters by age of dam subclass for weaning weight of Nellore cattle raised on pasture in two regions of São Paulo State, Brazil, between 1975 and 2001. The data were from ABCZ / EMBRAPA and included 51,664 weights at 205 d (W205) from progeny of 24,996 cows....
[The motor activity as an age parameter of the rat (authors transl)].
Hofecker, G; Kment, A; Niedermüller, H
1978-05-01
The motor activity as an behavioural parameter provides information about the functional state of the organism as a whole. Therefore it is an important age parameter. The results of activity measurements, however, depend strongly on the method of registration. Using 3 groups of male Sprague-Dawley rats aged 9, 15 and 29 months two methods have been tested: 1) An electronic recording: the rats were registrated in their normal cages on the Animex-Activity-Meter during the dark-phase in complete darkness. The activity measured by this method has been regarded as spontaneous activity. 2) A kinematographic method: the rats were registrated in a changed environment at constant light during the dark-phase. The activity assessed by this method has been regarded as reactive activity. Spontaneous and reactive activity show a different age dependence. For the use of the motor activity as an age parameter, both, spontaneous and reactive activity, should be assessed to get a better information about the ageing of the different functional levels of the systems governing the animal's behaviour. PMID:26274
Variations of immune parameters in terrestrial isopods: a matter of gender, aging and Wolbachia.
Sicard, Mathieu; Chevalier, Frédéric; De Vlechouver, Mickaël; Bouchon, Didier; Grève, Pierre; Braquart-Varnier, Christine
2010-09-01
Ecological factors modulate animal immunocompetence and potentially shape the evolution of their immune systems. Not only environmental parameters impact on immunocompetence: Aging is one major cause of variability of immunocompetence between individuals, and sex-specific levels of immunocompetence have also been frequently described. Moreover, a growing core of data put in light that vertically transmitted symbionts can dramatically modulate the immunocompetence of their hosts. In this study, we addressed the influence of gender, age and the feminising endosymbiont Wolbachia (wVulC) on variations in haemocyte density, total PO activity and bacterial load in the haemolymph of the terrestrial isopod Armadillidium vulgare. This host-symbiont system is of particular interest to address this question since: (1) wVulC was previously shown as immunosuppressive in middle-aged females and (2) wVulC influences sex determination. We show that age, gender and Wolbachia modulate together immune parameters in A. vulgare. However, wVulC, which interacts with aging, appears to be the prominent factor interfering with both PO activity and haemocyte density. This interference with immune parameters is not the only aspect of wVulC virulence on its host, as reproduction and survival are also altered. PMID:20676599
Variations of immune parameters in terrestrial isopods: a matter of gender, aging and Wolbachia
NASA Astrophysics Data System (ADS)
Sicard, Mathieu; Chevalier, Frédéric; de Vlechouver, Mickaël; Bouchon, Didier; Grève, Pierre; Braquart-Varnier, Christine
2010-09-01
Ecological factors modulate animal immunocompetence and potentially shape the evolution of their immune systems. Not only environmental parameters impact on immunocompetence: Aging is one major cause of variability of immunocompetence between individuals, and sex-specific levels of immunocompetence have also been frequently described. Moreover, a growing core of data put in light that vertically transmitted symbionts can dramatically modulate the immunocompetence of their hosts. In this study, we addressed the influence of gender, age and the feminising endosymbiont Wolbachia ( wVulC) on variations in haemocyte density, total PO activity and bacterial load in the haemolymph of the terrestrial isopod Armadillidium vulgare. This host-symbiont system is of particular interest to address this question since: (1) wVulC was previously shown as immunosuppressive in middle-aged females and (2) wVulC influences sex determination. We show that age, gender and Wolbachia modulate together immune parameters in A. vulgare. However, wVulC, which interacts with aging, appears to be the prominent factor interfering with both PO activity and haemocyte density. This interference with immune parameters is not the only aspect of wVulC virulence on its host, as reproduction and survival are also altered.
Age-dependence of lipid parameters in the general population and vegetarians.
Richter, V; Rassoul, F; Hentschel, B; Kothe, K; Krobara, M; Unger, R; Purschwitz, K; Rotzsch, W; Thiery, J; Muradian, K
2004-06-01
Age-dependent changes of lipid metabolism may arise both as a result of mechanisms of biological ageing and factors influencing age-dependent changes. To study possible influences of nutrition and life-style of vegetarians on age-dependence of lipid parameters, subjects of general population were compared with vegetarians. In the frame of population-based lipid screening projects in the city of Leipzig/Germany (Lipid Study Leipzig, LSL) 10 550 subjects (3,816 men and 6,734 women, age 18-99 years) of general population were compared with 417 vegetarians (vegans, lacto-vegetarians, lacto-ovo-vegetarians, 148 men and 269 women, age 18-93 years). Most of the vegetarians included in the study were members of the German Society of Vegetarians. The study program included capillary blood cholesterol measurements and the determination of high-density lipoprotein (HDL)-cholesterol, the measurement of other cardiovascular risk factors and the evaluation of dietary and life-style factors. Evaluation of cardiovascular risk profile within LSL was connected with individual consultation. The mean total cholesterol and non-HDL-cholesterol level and the total: HDL-cholesterol ratio showed the expected age-dependence, with maximum values within the decade 60-70 years. Vegetarians showed lower total and non-HDL-cholesterol levels in comparison with the general population. Furthermore, the age-dependent increase of these parameters is less pronounced under the conditions of vegetarian nutrition and life-style. Especially in young adulthood a significant difference is observed. Thus, the results of the present study reveal the role of nutritional and life-style factors that determine the lipid profile on a population basis and suggest that the known age-dependent rise of the level of atherogenic plasma lipoproteins is partly preventable. PMID:15224241
Climatic influence on demographic parameters of a tropical seabird varies with age and sex.
Oro, Daniel; Torres, Roxana; Rodríguez, Cristina; Drummond, Hugh
2010-04-01
In marine ecosystems climatic fluctuation and other physical variables greatly influence population dynamics, but differential effects of physical variables on the demographic parameters of the two sexes and different age classes are largely unexplored. We analyzed the effects of climate on the survival and recruitment of both sexes and several age classes of a long-lived tropical seabird, the Blue-footed Booby (Sula nebouxii), using long-term observations on marked individuals. Results demonstrated a complex interaction between yearly fluctuations in climate (both local and global indexes, during both winter and breeding season) and the sex and age of individuals. Youngest birds' survival and recruitment were commonly affected by local climate, whereas oldest birds' parameters tended to be constant and less influenced by environmental variables. These results confirm the theoretical prediction that sex- and age-related variation in life-history demographic traits is greater under poor environmental conditions, and they highlight the importance of including variability in fitness components in demographic and evolutionary models. Males and females showed similar variation in survival but different recruitment patterns, in relation to both age and the spatial scale of climatic influence (local or global). Results indicate different life-history tactics for each sex and different ages, with birds likely trying to maximize their fitness by responding to the environmental contingencies of each year. PMID:20462134
Influence of emphysema distribution on pulmonary function parameters in COPD patients
Bastos, Helder Novais e; Neves, Inês; Redondo, Margarida; Cunha, Rui; Pereira, José Miguel; Magalhães, Adriana; Fernandes, Gabriela
2015-01-01
ABSTRACT OBJECTIVE: To evaluate the impact that the distribution of emphysema has on clinical and functional severity in patients with COPD. METHODS: The distribution of the emphysema was analyzed in COPD patients, who were classified according to a 5-point visual classification system of lung CT findings. We assessed the influence of emphysema distribution type on the clinical and functional presentation of COPD. We also evaluated hypoxemia after the six-minute walk test (6MWT) and determined the six-minute walk distance (6MWD). RESULTS: Eighty-six patients were included. The mean age was 65.2 ± 12.2 years, 91.9% were male, and all but one were smokers (mean smoking history, 62.7 ± 38.4 pack-years). The emphysema distribution was categorized as obviously upper lung-predominant (type 1), in 36.0% of the patients; slightly upper lung-predominant (type 2), in 25.6%; homogeneous between the upper and lower lung (type 3), in 16.3%; and slightly lower lung-predominant (type 4), in 22.1%. Type 2 emphysema distribution was associated with lower FEV1, FVC, FEV1/FVC ratio, and DLCO. In comparison with the type 1 patients, the type 4 patients were more likely to have an FEV1 < 65% of the predicted value (OR = 6.91, 95% CI: 1.43-33.45; p = 0.016), a 6MWD < 350 m (OR = 6.36, 95% CI: 1.26-32.18; p = 0.025), and post-6MWT hypoxemia (OR = 32.66, 95% CI: 3.26-326.84; p = 0.003). The type 3 patients had a higher RV/TLC ratio, although the difference was not significant. CONCLUSIONS: The severity of COPD appears to be greater in type 4 patients, and type 3 patients tend to have greater hyperinflation. The distribution of emphysema could have a major impact on functional parameters and should be considered in the evaluation of COPD patients. PMID:26785956
Model reference control of distributed parameter systems: Application to the SCOLE problem
NASA Technical Reports Server (NTRS)
Kaufman, H.; Minnick, D.; Balas, M.; Musalem, A.
1987-01-01
The model reference control of lumped linear systems and the model reference control of the distributed parameter system (DPS) are presented with their theory and Spacecraft Control Laboratory Experiment (SCOLE) applications.
Frequency distributions and correlations of solar X-ray flare parameters
NASA Technical Reports Server (NTRS)
Crosby, Norma B.; Aschwanden, Markus J.; Dennis, Brian R.
1993-01-01
Frequency distributions of flare parameters are determined from over 12,000 solar flares. The flare duration, the peak counting rate, the peak hard X-ray flux, the total energy in electrons, and the peak energy flux in electrons are among the parameters studied. Linear regression fits, as well as the slopes of the frequency distributions, are used to determine the correlations between these parameters. The relationship between the variations of the frequency distributions and the solar activity cycle is also investigated. Theoretical models for the frequency distribution of flare parameters are dependent on the probability of flaring and the temporal evolution of the flare energy build-up. The results of this study are consistent with stochastic flaring and exponential energy build-up. The average build-up time constant is found to be 0.5 times the mean time between flares.
Reliability analysis of structural ceramic components using a three-parameter Weibull distribution
NASA Technical Reports Server (NTRS)
Duffy, Stephen F.; Powers, Lynn M.; Starlinger, Alois
1992-01-01
Described here are nonlinear regression estimators for the three-Weibull distribution. Issues relating to the bias and invariance associated with these estimators are examined numerically using Monte Carlo simulation methods. The estimators were used to extract parameters from sintered silicon nitride failure data. A reliability analysis was performed on a turbopump blade utilizing the three-parameter Weibull distribution and the estimates from the sintered silicon nitride data.
NASA Astrophysics Data System (ADS)
Miyasato, Yoshihiko
The problem of constructing model reference adaptive H∞ control for distributed parameters systems of hyperbolic type is considered in this paper. Distributed parameters systems are infinite dimensional processes, but the proposed control scheme is constructed from finite dimensional controllers. The stabilizing control signal is added to regulate the effect of spill-over terms, and it is derived as a solution of certain H∞ control problem where spill-overs are considered as external disturbances to the process.
A Hierarchical Approach to Distributed Parameter Estimation in Rainfall-Runoff Modeling
NASA Astrophysics Data System (ADS)
Chu, W.; Gao, X.; Sorooshian, S.
2007-12-01
Distributed rainfall-runoff models intend to account for the heterogeneous characteristics of rainfall distributions and runoff generations thereby, improve the river forecast. In this study, a distributed river forecast model is built on the hierarchy of sub-basins connected through a river-routing system. These hydrologic units (sub-basins) possess a no-flux boundary and traditionally can be simulated by conceptual models with a limited number of parameters. However, calibration is needed to make such a model perform well. In the case of distributed modeling, the lack of streamflow observations inside a river system poses a challenge to estimate the model parameters at sub-basin scales. A hierarchical approach is proposed as follows: First, the study basin (a parent basin) is modeled in lumped mode and calibrated to obtain the optimized parameters. In the next step, the parent basin is divided into three sub-basins (children basins). The same model (with tripled parameters) is applied to the sub-basins driven by the rainfalls over the sub-basins and the model parameters for each sun-basin are calibrated using the parent parameters as their prior values. After obtaining the optimal parameters for the sub-basins, the hydrograph at the outlet of each sub-basin can be generated. Finally, by repeating the similar procedure, each sub-basin can be taken as a parent basin and obtaining the parameters for its children sub-basins. Applying this method to one of the DIMP-2 test basins: the Illinois River basin at south of Siloam Spring, the results show that (1) the streamflow results are improved by using the distributed rainfall and distributed parameters in comparing with the lumped simulation results, and (2) taking the parent basin's parameters as the priors can help to determine reasonable searching ranges when optimizing the parameters of children basins and also reduce the chance of resulting in an optimum which is not physically plausible. Applying this method to
Age-density relation of Main galaxies at fixed parameters or for different galaxy families
NASA Astrophysics Data System (ADS)
Deng, Xin-Fa; Song, Jun; Chen, Yi-Qing; Jiang, Peng; Ding, Ying-Ping
2015-09-01
Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 10 (SDSS DR10), we examine the environmental dependence of galaxy age at fixed parameters or for different galaxy families. Statistical results show that the environmental dependence of galaxy age is stronger for late type galaxies, but can be still observed for the early types: the age of galaxies in the densest regime is preferentially older than that in the lowest density regime with the same morphological type. We also find that the environmental dependence of galaxy age for red galaxies and Low Stellar Mass (LSM) galaxies is stronger, while the one for blue galaxies and High Stellar Mass ( HSM ) galaxies is very weak.
The role of a roughness scaling parameter in describing alpine snow distribution (Invited)
NASA Astrophysics Data System (ADS)
Lehning, M.; Grünewald, T.; Schirmer, M.
2010-12-01
The mountain snow distribution affects not only the storage of snow water and avalanche danger but also the local conditions for plant and animal life. The snow distribution in the alpine zone is shaped by a general altitudinal gradient of precipitation, the locally varying deposition of snow and subsequent redistribution processes due to wind but also to snow slides. While progress has been made in understanding of processes involved in snow distribution, it has not been possible to satisfactorily predict snow distribution on the basis of local terrain parameters. We use a unique data set of high resolution snow depth measurements from an airborne laser scanner in two small mountain catchments to predict mean snow depth in topographic control units as a function of two terrain parameters: the conventional altitudinal gradient plus a new fractal roughness parameter. The analysis showed that heterogeneous snow distribution can be captured by merely analysing the terrain and the mean precipitation.
NASA Astrophysics Data System (ADS)
Takeda, Y.; Tajitsu, A.; Sato, B.; Liu, Y.-J.; Chen, Y.-Q.; Zhao, G.
2016-04-01
Spectroscopic parameters (effective temperature, metallicity, etc) were determined for a large sample of ˜100 red giants in the Kepler field, for which mass, radius, and evolutionary status had already been asteroseismologically established. These two kinds of spectroscopic and seismic information suffice to define the position on the `luminosity versus effective temperature' diagram and to assign an appropriate theoretical evolutionary track to each star. Making use of this advantage, we examined whether the stellar location on this diagram really matches the assigned track, which would make an interesting consistency check between theory and observation. It turned out that satisfactory agreement was confirmed in most cases (˜90 per cent, though appreciable discrepancies were seen for some stars such as higher mass red-clump giants), suggesting that recent stellar evolution calculations are practically reliable. Since the relevant stellar age could also be obtained by this comparison, we derived the age-metallicity relation for these Kepler giants and found the following characteristics: (1) the resulting distribution is quite similar to what was previously concluded for F-, G-, and K-type stars dwarfs; (2) the dispersion of metallicity progressively increases as the age becomes older; (3) nevertheless, the maximum metallicity at any stellar age remains almost flat, which means the existence of super/near-solar metallicity stars in a considerably wide age range from ˜(2-3) × 108 to ˜1010 yr.
Park, Yoon Soo; Lee, Young-Sun; Xing, Kuan
2016-01-01
This study investigates the impact of item parameter drift (IPD) on parameter and ability estimation when the underlying measurement model fits a mixture distribution, thereby violating the item invariance property of unidimensional item response theory (IRT) models. An empirical study was conducted to demonstrate the occurrence of both IPD and an underlying mixture distribution using real-world data. Twenty-one trended anchor items from the 1999, 2003, and 2007 administrations of Trends in International Mathematics and Science Study (TIMSS) were analyzed using unidimensional and mixture IRT models. TIMSS treats trended anchor items as invariant over testing administrations and uses pre-calibrated item parameters based on unidimensional IRT. However, empirical results showed evidence of two latent subgroups with IPD. Results also showed changes in the distribution of examinee ability between latent classes over the three administrations. A simulation study was conducted to examine the impact of IPD on the estimation of ability and item parameters, when data have underlying mixture distributions. Simulations used data generated from a mixture IRT model and estimated using unidimensional IRT. Results showed that data reflecting IPD using mixture IRT model led to IPD in the unidimensional IRT model. Changes in the distribution of examinee ability also affected item parameters. Moreover, drift with respect to item discrimination and distribution of examinee ability affected estimates of examinee ability. These findings demonstrate the need to caution and evaluate IPD using a mixture IRT framework to understand its effects on item parameters and examinee ability. PMID:26941699
Park, Yoon Soo; Lee, Young-Sun; Xing, Kuan
2016-01-01
This study investigates the impact of item parameter drift (IPD) on parameter and ability estimation when the underlying measurement model fits a mixture distribution, thereby violating the item invariance property of unidimensional item response theory (IRT) models. An empirical study was conducted to demonstrate the occurrence of both IPD and an underlying mixture distribution using real-world data. Twenty-one trended anchor items from the 1999, 2003, and 2007 administrations of Trends in International Mathematics and Science Study (TIMSS) were analyzed using unidimensional and mixture IRT models. TIMSS treats trended anchor items as invariant over testing administrations and uses pre-calibrated item parameters based on unidimensional IRT. However, empirical results showed evidence of two latent subgroups with IPD. Results also showed changes in the distribution of examinee ability between latent classes over the three administrations. A simulation study was conducted to examine the impact of IPD on the estimation of ability and item parameters, when data have underlying mixture distributions. Simulations used data generated from a mixture IRT model and estimated using unidimensional IRT. Results showed that data reflecting IPD using mixture IRT model led to IPD in the unidimensional IRT model. Changes in the distribution of examinee ability also affected item parameters. Moreover, drift with respect to item discrimination and distribution of examinee ability affected estimates of examinee ability. These findings demonstrate the need to caution and evaluate IPD using a mixture IRT framework to understand its effects on item parameters and examinee ability. PMID:26941699
Spatial variability of the parameters of a semi-distributed hydrological model
NASA Astrophysics Data System (ADS)
de Lavenne, Alban; Thirel, Guillaume; Andréassian, Vazken; Perrin, Charles; Ramos, Maria-Helena
2016-05-01
Ideally, semi-distributed hydrologic models should provide better streamflow simulations than lumped models, along with spatially-relevant water resources management solutions. However, the spatial distribution of model parameters raises issues related to the calibration strategy and to the identifiability of the parameters. To analyse these issues, we propose to base the evaluation of a semi-distributed model not only on its performance at streamflow gauging stations, but also on the spatial and temporal pattern of the optimised value of its parameters. We implemented calibration over 21 rolling periods and 64 catchments, and we analysed how well each parameter is identified in time and space. Performance and parameter identifiability are analysed comparatively to the calibration of the lumped version of the same model. We show that the semi-distributed model faces more difficulties to identify stable optimal parameter sets. The main difficulty lies in the identification of the parameters responsible for the closure of the water balance (i.e. for the particular model investigated, the intercatchment groundwater flow parameter).
The effect of age on pressure flow parameters in women with lower urinary tract symptoms.
Basu, M; Postlethwaite, C; Cheema, K; Duckett, J
2013-11-01
This study aimed to evaluate changes in voiding with age in women with different urodynamic diagnoses. Correlation was used to analyse the association between age and voiding parameters (maximum flow rate, voided volume, flow rate centile and maximum detrusor pressure - PdetMax) in 896 datasets. Multivariate analysis was used to analyse the data further by age group and diagnosis - urodynamic stress incontinence (USI); detrusor overactivity (DO); mixed USI and DO; no urodynamic abnormality. Results showed that diagnosis accounts for a significant amount of variation in all four of the dependent variables Age group shows a significant effect on voiding volume but does not show significant effects on any other variable studied. There is no significant interaction term in any of the analyses, meaning that age and diagnosis do not appear to function together, e.g. age does not relate to flow rate centile, maximum flow rate or PdetQMax. It was concluded that the data suggest that there is no significant change in voiding function related to age. In the elderly, the main alteration in voiding is due to a higher prevalence of DO. PMID:24219733
Fetal kidney length as a useful adjunct parameter for better determination of gestational age
Ugur, Mete G.; Mustafa, Aynur; Ozcan, Huseyin C.; Tepe, Neslihan B.; Kurt, Huseyin; Akcil, Emre; Gunduz, Reyhan
2016-01-01
Objectives: To determine the validity of fetal kidney length and amniotic fluid index (AFI) in labor dating. Methods: This prospective study included 180 pregnant women followed up in the outpatient clinic at the Department of Obstetrics and Gynecology, Gaziantep University, Turkey, between January 2014 and January 2015. The gestational age (GA) was estimated by early fetal ultrasound measures and last menstrual period. Routine fetal biometric parameters, fetal kidney length, and amniotic fluid index were measured. We studied the correlation between fetal kidney length, amniotic fluid index, and gestational age. Result: The mean gestational age depending on last menstrual period and early ultrasound was 31.98±4.29 (24-39 weeks). The mean kidney length was 35.66±6.61 (19-49 mm). There was a significant correlation between gestational age and fetal kidney length (r=0.947, p=0.001). However, there was a moderate negative correlation between GA and AFI. Adding fetal kidney length to the routine biometrics improved the effectiveness of the model used to estimate GA (R2=0.965 to R2=0.987). Conclusion: Gestational age can be better predicted by adding fetal kidney length to other routine parameters. PMID:27146616
NASA Technical Reports Server (NTRS)
Park, Won J.; Crampton, George H.
1988-01-01
The suitability of the two-parameter Weibull distribution for describing highly censored cat motion sickness latency data was evaluated by estimating the parameters with the maximum likelihood method and testing for goodness of fit with the Kolmogorov-Smirnov statistic. A procedure for determining confidence levels and testing for significance of the difference between Weibull parameters is described. Computer programs for these procedures may be obtained from an archival source.
A Method for Determining If Unequal Shape Parameters are Necessary in a Bivariate Gamma Distribution
NASA Technical Reports Server (NTRS)
Tubbs, J. D.
1983-01-01
A procedure to aid in the deciding between four and five parameters in a Jensen's type bivariate gamma distribution is presented. It is based upon the CDF of the ratio of correlated gamma distributed variates. The criteria are posed in a test of hypothesis setting and results are presented.
NASA Astrophysics Data System (ADS)
Leavesley, G.; Hay, L.; Viger, R.; de Jong, C.
The use of distributed-parameter models in mountainous terrain requires the ability to define the spatial and temporal distributions of input meteorological variables and the physical basin characteristics that affect the processes being simulated. Application of these models to complex problems, such as assessing the impacts of land-use and climate change, limits one's ability to calibrate model parameters and necessitates the use of parameter-estimation methods that rely on measurable climate and basin char- acteristics. The increasing availability of high-resolution spatial and temporal data sets now enables the development and evaluation of a variety of parameter-estimation methods over a wide range of climatic and physiographic regions. For example, pa- rameters related to basin characteristics can be estimated from digital soils, vegetation, and topographic databases. Parameters related to the temporal and spatial distribution of meteorological variables, such as precipitation and temperature, can be estimated from multiple linear regression relations using latitude, longitude, and elevation of measurement stations and basin subareas. This approach also supports the use of sta- tistical and dynamical downscaling of atmospheric model output for use in distributed hydrological model applications. A set of tools to objectively apply and evaluate distributed meteorological and hydro- logical parameter-estimation methods, and process models, is being developed using the U.S. Geological Survey's Modular Modeling System (MMS). Tools include meth- ods to analyze model parameters and evaluate the extent to which uncertainty in model parameters affects uncertainty in simulation results. Methodologies that integrate re- motely sensed information with the distributed-model results are being incorporated in the tool set to facilitate the assessment of the spatial and temporal accuracy of model results. An application of selected models and parameter-estimation methods is
Distribution and titres of rotavirus antibodies in different age groups.
Elias, M. M.
1977-01-01
Three hundred and fifty-seven sera selected at random from hospital patients of all ages were examined for rotavirus antibodies using indirect immunofluorescence (FA) and complement fixation levels (CFT). Three hundred and fourteen of these were also tested for neutralizing antibodies to human rotavirus. Sera from patients admitted with a diagnosis of acute gastroenteritis were excluded from this survey. FA antibodies were found in newborn infants but fell to undetectable titres at 3 months. The highest titres were found in children between the ages of one and three years. In older age groups, the model titre fell gradually with increasing age until, in sera from those above 70 years of age, FA antibodies were almost undetectable. The same pattern was observed with neutralizing antibodies. A high model titre of CF antibodies was only found in sera from those aged one to three years. PMID:200676
Effects of Age and Oral Disease on Systemic Inflammatory and Immune Parameters in Nonhuman Primates▿
Ebersole, J. L.; Steffen, M. J.; Gonzalez-Martinez, J.; Novak, M. J.
2008-01-01
This report evaluated systemic inflammatory and immune biomarkers in a cohort of Macaca mulatta (rhesus monkeys) maintained as a large family social unit, including an age range from <1 year to >24 years. We hypothesized that the systemic host responses would be affected by the age, gender, and clinical oral presentation of the population, each contributing to inflammatory and immune responses that would reflect chronic oral infections. The results demonstrated that the prevalence and severity of periodontitis, including missing teeth, increased significantly with age. Generally, minimal differences in clinical parameters were noted between the genders. Systemic inflammatory mediators, including acute-phase reactants, prostaglandin E2 (PGE2), cytokines/chemokines, and selected matrix metalloproteinases (MMP), demonstrated significant differences among the various age groups of animals. Levels of many of these were increased with age, although PGE2, RANTES, bactericidal permeability-inducing factor (BPI), MMP-1, and MMP-9 levels were significantly increased in the young group (∼1 to 3 years old) relative to those for the older animals. We observed that in the adult and aged animals, levels of the systemic inflammatory mediators related to gingival inflammation and periodontal tissue destruction were significantly elevated. Serum antibody levels in response to a battery of periodontal pathogens were generally lower in the young animals, <50% of those in the adults, and were significantly related to aging in the cohort. The levels of antibodies, particularly those to Porphorymonas gingivalis, Fusobacterium nucleatum, and Tannerella forsythia, were most significantly elevated in animals with periodontal disease, irrespective of the age of the animal. These results provide a broad description of oral health and host responses in a large cohort of nonhuman primates from very young animals to the aged of this species. The findings afford a base of data with which to
The eye lens: age-related trends and individual variations in refractive index and shape parameters.
Pierscionek, Barbara; Bahrami, Mehdi; Hoshino, Masato; Uesugi, Kentaro; Regini, Justyn; Yagi, Naoto
2015-10-13
The eye lens grows throughout life by cell accrual on its surface and can change shape to adjust the focussing power of the eye. Varying concentrations of proteins in successive cell layers create a refractive index gradient. The continued growth of the lens and age-related changes in proteins render it less able to alter shape with loss of capacity by the end of the sixth decade of life. Growth and protein ageing alter the refractive index but as accurate measurement of this parameter is difficult, the nature of such alterations remains uncertain. The most accurate method to date for measuring refractive index in intact lenses has been developed at the SPring-8 synchrotron. The technique, based on Talbot interferometry, has an X-ray source and was used to measure refractive index in sixty-six human lenses, aged from 16 to 91 years. Height and width were measured for forty-five lenses. Refractive index contours show decentration in some older lenses but individual variations mask age-related trends. Refractive index profiles along the optic axis have relatively flat central sections with distinct micro-fluctuations and a steep gradient in the cortex but do not exhibit an age-related trend. The refractive index profiles in the equatorial aspect show statistical significance with age, particularly for lenses below the age of sixty that had capacity to alter shape in vivo. The maximum refractive index in the lens centre decreases slightly with age with considerable scatter in the data and there are age-related variations in sagittal thickness and equatorial height. PMID:26416418
The eye lens: age-related trends and individual variations in refractive index and shape parameters
Pierscionek, Barbara; Bahrami, Mehdi; Hoshino, Masato; Uesugi, Kentaro; Regini, Justyn; Yagi, Naoto
2015-01-01
The eye lens grows throughout life by cell accrual on its surface and can change shape to adjust the focussing power of the eye. Varying concentrations of proteins in successive cell layers create a refractive index gradient. The continued growth of the lens and age-related changes in proteins render it less able to alter shape with loss of capacity by the end of the sixth decade of life. Growth and protein ageing alter the refractive index but as accurate measurement of this parameter is difficult, the nature of such alterations remains uncertain. The most accurate method to date for measuring refractive index in intact lenses has been developed at the SPring-8 synchrotron. The technique, based on Talbot interferometry, has an X-ray source and was used to measure refractive index in sixty-six human lenses, aged from 16 to 91 years. Height and width were measured for forty-five lenses. Refractive index contours show decentration in some older lenses but individual variations mask age-related trends. Refractive index profiles along the optic axis have relatively flat central sections with distinct micro-fluctuations and a steep gradient in the cortex but do not exhibit an age-related trend. The refractive index profiles in the equatorial aspect show statistical significance with age, particularly for lenses below the age of sixty that had capacity to alter shape in vivo. The maximum refractive index in the lens centre decreases slightly with age with considerable scatter in the data and there are age-related variations in sagittal thickness and equatorial height. PMID:26416418
Myrhaug, D. . Dept. of Marine Hydrodynamics); Rue, H. . Division of Industrial Mathematics)
1993-08-01
In this paper, a joint distribution of wave steepness parameters for two successive waves is presented. The wave steepness parameters considered herein are the crest front steepness and the total wave steepness. The joint distribution of wave steepness parameters for two successive waves is represented by a two-dimensional Weibull distribution with the parameters [alpha]=0.84 and [beta]=1.40. The application of the results is illustrated by an example. Overall these results seem to be physically sound, although they are valid for the particular sea state chosen. The present approach has some basis in measured wave data, but comparison with data on the joint distribution of steepness parameters for two successive waves are needed before any conclusion can be drawn on the ability of this approach to describe measured wave data. Such a data base should be established from carefully designed field measurements in order to have the possibility to measure nonlinear properties of the waves. However, at present this joint distribution of steepness parameters for two successive waves should represent a useful tool for engineering applications.
Pye, Stephen R.; Vanderschueren, Dirk; Boonen, Steven; Gielen, Evelien; Adams, Judith E.; Ward, Kate A.; Lee, David M.; Bartfai, György; Casanueva, Felipe F.; Finn, Joseph D.; Forti, Gianni; Giwercman, Aleksander; Han, Thang S.; Huhtaniemi, Ilpo T.; Kula, Krzysztof; Lean, Michael E.; Pendleton, Neil; Punab, Margus; Wu, Frederick C.; O'Neill, Terence W.
2015-01-01
Background: low bone mineral density measured by dual-energy x-ray absorptiometry is associated with increased mortality. The relationship between other skeletal phenotypes and mortality is unclear. The aim of this study was to determine the relationship between quantitative heel ultrasound parameters and mortality in a cohort of European men. Methods: men aged 40–79 years were recruited for participation in a prospective study of male ageing: the European Male Ageing Study (EMAS). At baseline, subjects attended for quantitative ultrasound (QUS) of the heel (Hologic—SAHARA) and completed questionnaires on lifestyle factors and co-morbidities. Height and weight were measured. After a median of 4.3 years, subjects were invited to attend a follow-up assessment, and reasons for non-participation, including death, were recorded. The relationship between QUS parameters (broadband ultrasound attenuation [BUA] and speed of sound [SOS]) and mortality was assessed using Cox proportional hazards model. Results: from a total of 3,244 men (mean age 59.8, standard deviation [SD] 10.8 years), 185 (5.7%) died during the follow-up period. After adjusting for age, centre, body mass index, physical activity, current smoking, number of co-morbidities and general health, each SD decrease in BUA was associated with a 20% higher risk of mortality (hazard ratio [HR] per SD = 1.2; 95% confidence interval [CI] = 1.0–1.4). Compared with those in higher quintiles (2nd–5th), those in the lowest quintile of BUA and SOS had a greater mortality risk (BUA: HR = 1.6; 95% CI = 1.1–2.3 and SOS: HR = 1.6; 95% CI = 1.2–2.2). Conclusion: lower heel ultrasound parameters are associated with increased mortality in European men. PMID:26162912
Investigation of the Gamma Distribution Shape Parameter in Shallow Cumulus Clouds
NASA Astrophysics Data System (ADS)
Igel, A. L.; van den Heever, S. C.
2014-12-01
Many bulk microphysics parameterizations assume that the droplet size distribution (DSD) of hydrometeor species such as cloud water and rain water conform to a gamma probability distribution function (PDF). Such an assumption is necessary in order to simplify the description of microphysical processes in such bulk parameterizations. The gamma PDF has a parameter that influences the width of the distribution that is commonly referred to as the shape parameter. In one- and two-moment bulk microphysics schemes, this parameter is often arbitrarily set to a fixed value throughout the simulation. This is in part due to limited observations of the shape parameter. While many studies have sought to understand this parameter for rain, few studies examine this parameter for cloud droplets. In this study, we use high-resolution simulations of shallow cumulus clouds with a spectral bin representation of the hydrometeor species to find best-fit parameters of the gamma PDF to the predicted cloud DSDs. These simulations reveal that the cloud shape parameter is high in the supersaturated regions of the cloud and low in regions where the cloud water is evaporating. Values many times higher than the standard values of 1-4 are not uncommon in the bin simulations. The results of this analysis are used to suggest appropriate values of the cloud shape parameter in simulations employing a bulk microphysics scheme. The sensitivity of cloud properties, dynamics, and rainfall to the cloud shape parameter are investigated in simulations in which the parameter is fixed. Conclusions about the importance of choosing an appropriate cloud shape parameter for simulating cumulus clouds in climate or weather models are drawn.
Begum, K; Ahmed, M U; Rahman, M M; Hossain, M M; Begum, M; Sarkar, S K; Reza, M T; Hoshneara, M; Beg, A; Sultana, F; Begum, F; Akter, F A
2016-04-01
The objective of the study was to find out correlation between umbilical cord diameter, cross sectional area with gestational age and foetal anthropometric parameters. This cross sectional study was conducted among healthy women between the 24th and 40th completed weeks of a normal pregnancy in the Department of Radiology & Imaging, Mymensingh Medical College Hospital, Mymensingh during the study period, from July 2009 to June 2011. A total of 230 consecutive normal pregnancy patients were included in the study. The diameter & cross-sectional area of the umbilical cord were measured on a plane adjacent to the junction of the umbilical cord and the fetal abdomen, in cross-section, with maximum magnification of the image. The cord was manually circled, and it's cross sectional areas was automatically calculated by the ultrasonograph. The mean±SD age was 24.3±4.7 years with range from 19 to 36 years. The mean gestational age was 32.1±4.5 weeks and more than a half (56.4%) of the pregnant women were nulliparas. A positive significant (p<0.001) correlation were found between umbilical cord diameter with bi-parietal diameter (r=0.548); head circumference (r=0.411); abdominal circumference (r=0.444); femur length (r=0.366) and gestational age gestation age (r=0.643). Similarly, a significant (p<0.001) positive week correlation were found between umbilical cross sectional area with bi-parietal diameter (r=0.3303); head circumference (r=0.3202); abdominal circumference (r=0.2651); femur length (r=0.3307) and gestation age (r=0.4051). A positive significant better correlation was found with umbilical cord diameter than cross sectional area with foetal anthropometric parameters. PMID:27277346
NASA Astrophysics Data System (ADS)
Ligi, R.; Creevey, O.; Mourard, D.; Crida, A.; Lagrange, A.-M.; Nardetto, N.; Perraut, K.; Schultheis, M.; Tallon-Bosc, I.; ten Brummelaar, T.
2016-02-01
Context. Accurate stellar parameters are needed in numerous domains of astrophysics. The position of stars on the Hertzsprung-Russell diagram is an important indication of their structure and evolution, and it helps improve stellar models. Furthermore, the age and mass of stars hosting planets are required elements for studying exoplanetary systems. Aims: We aim at determining accurate parameters of a set of 18 bright exoplanet host and potential host stars from interferometric measurements, photometry, and stellar models. Methods: Using the VEGA/CHARA interferometer operating in the visible domain, we measured the angular diameters of 18 stars, ten of which host exoplanets. We combined them with their distances to estimate their radii. We used photometry to derive their bolometric flux and, then, their effective temperature and luminosity to place them on the H-R diagram. We then used the PARSEC models to derive their best fit ages and masses, with error bars derived from Monte Carlo calculations. Results: Our interferometric measurements lead to an average of 1.9% uncertainty on angular diameters and 3% on stellar radii. There is good agreement between measured and indirect estimations of angular diameters (either from SED fitting or from surface brightness relations) for main sequence (MS) stars, but not as good for more evolved stars. For each star, we provide a likelihood map in the mass-age plane; typically, two distinct sets of solutions appear (an old and a young age). The errors on the ages and masses that we provide account for the metallicity uncertainties, which are often neglected by other works. From measurements of its radius and density, we also provide the mass of 55 Cnc independently of models. From the stellar masses, we provide new estimates of semi-major axes and minimum masses of exoplanets with reliable uncertainties. We also derive the radius, density, and mass of 55 Cnc e, a super-Earth that transits its stellar host. Our exoplanetary
Chlorine decay in drinking-water transmission and distribution systems: pipe service age effect.
Al-Jasser, A O
2007-01-01
Water quality can deteriorate in the transmission and distribution system beyond the treatment plant. Minimizing the potential for biological regrowth can be attained by chlorinating the finished water. While flowing through pipes, the chlorine concentration decreases for different reasons. Reaction with the pipe material itself and the reaction with both the biofilm and tubercles formed on the pipe wall are known as pipe wall demand, which may vary with pipe parameters. The aim of this paper was to assess the impact of the service age of pipes on the effective chlorine wall decay constant. Three hundred and two pipe sections of different sizes and eight different pipe materials were collected and tested for their chlorine first-order wall decay constants. The results showed that pipe service age was an important factor that must not be ignored in some pipes such as cast iron, steel, cement-lined ductile iron (CLDI), and cement-lined cast iron (CLCI) pipes especially when the bulk decay is not significant relative to the wall decay. For the range of the 55 years of pipe service age used in this study, effective wall decay constants ranged from a decrease by -92% to an increase by +431% from the corresponding values in the recently installed pipes. The effect of service age on the effective wall decay constants was most evident in cast iron pipes, whereas steel pipes were less affected. Effective chlorine wall decay for CLCI and CLDI pipes was less affected by service age as compared to steel and cast iron pipes. Chlorine wall decay constants for PVC, uPVC, and polyethylene pipes were affected negatively by pipe service age and such effect was relatively small. PMID:17140619
NASA Astrophysics Data System (ADS)
1994-04-01
This practice covers the evaluation and subsequent reporting of uniaxial strength data and the estimation of probability distribution parameters for advanced ceramics that fail in a brittle fashion. The failure strength of advanced ceramics is treated as a continuous random variable. Typically, a number of test specimens with well-defined geometry are failed under well-defined isothermal loading conditions. The load at which each specimen fails is recorded. The resulting failure stresses are used to obtain parameter estimates associated with the underlying population distribution. This practice is restricted to the assumption that the distribution underlying the failure strengths is the two parameter Weibull distribution with size scaling. Furthermore, this practice is restricted to test specimens (tensile, flexural, pressurized ring, etc.) that are primarily subjected to uniaxial stress states. Section 8 outlines methods to correct for bias errors in the estimated Weibull parameters and to calculate confidence bounds on those estimates from data sets where all failures originate from a single flaw population (that is, a single failure mode). In samples where failures originate from multiple independent flaw populations (for example, competing failure modes), the methods outlined in Section 8 for bias correction and confidence bounds are not applicable. Measurements of the strength at failure are taken for one of two reasons: either for a comparison of the relative quality of two materials, or the prediction of the probability of failure (or, alternatively, the fracture strength) for a structure of interest. This practice will permit estimates of the distribution parameters that are needed for either.
Data-free inference of the joint distribution of uncertain model parameters.
Marzouk, Youssef M.; Adalsteinsson, Helgi; Berry, Robert Dan; Debusschere, Bert J.; Najm, Habib N.
2010-05-01
It is known that, in general, the correlation structure in the joint distribution of model parameters is critical to the uncertainty analysis of that model. Very often, however, studies in the literature only report nominal values for parameters inferred from data, along with confidence intervals for these parameters, but no details on the correlation or full joint distribution of these parameters. When neither posterior nor data are available, but only summary statistics such as nominal values and confidence intervals, a joint PDF must be chosen. Given the summary statistics it may not be reasonable nor necessary to assume the parameters are independent random variables. We demonstrate, using a Bayesian inference procedure, how to construct a posterior density for the parameters exhibiting self consistent correlations, in the absence of data, given (1) the fit-model, (2) nominal parameter values, (3) bounds on the parameters, and (4) a postulated statistical model, around the fit-model, for the missing data. Our approach ensures external Bayesian updating while marginalizing over possible data realizations. We then address the matching of given parameter bounds through the choice of hyperparameters, which are introduced in postulating the statistical model, but are not given nominal values. We discuss some possible approaches, including (1) inferring them in a separate Bayesian inference loop and (2) optimization. We also perform an empirical evaluation of the algorithm showing the posterior obtained with this data free inference compares well with the true posterior obtained from inference against the full data set.
NASA Astrophysics Data System (ADS)
Pasari, S.; Kundu, D.; Dikshit, O.
2012-12-01
Earthquake recurrence interval is one of the important ingredients towards probabilistic seismic hazard assessment (PSHA) for any location. Exponential, gamma, Weibull and lognormal distributions are quite established probability models in this recurrence interval estimation. However, they have certain shortcomings too. Thus, it is imperative to search for some alternative sophisticated distributions. In this paper, we introduce a three-parameter (location, scale and shape) exponentiated exponential distribution and investigate the scope of this distribution as an alternative of the afore-mentioned distributions in earthquake recurrence studies. This distribution is a particular member of the exponentiated Weibull distribution. Despite of its complicated form, it is widely accepted in medical and biological applications. Furthermore, it shares many physical properties with gamma and Weibull family. Unlike gamma distribution, the hazard function of generalized exponential distribution can be easily computed even if the shape parameter is not an integer. To contemplate the plausibility of this model, a complete and homogeneous earthquake catalogue of 20 events (M ≥ 7.0) spanning for the period 1846 to 1995 from North-East Himalayan region (20-32 deg N and 87-100 deg E) has been used. The model parameters are estimated using maximum likelihood estimator (MLE) and method of moment estimator (MOME). No geological or geophysical evidences have been considered in this calculation. The estimated conditional probability reaches quite high after about a decade for an elapsed time of 17 years (i.e. 2012). Moreover, this study shows that the generalized exponential distribution fits the above data events more closely compared to the conventional models and hence it is tentatively concluded that generalized exponential distribution can be effectively considered in earthquake recurrence studies.
Distributed and decentralized state estimation in gas networks as distributed parameter systems.
Ahmadian Behrooz, Hesam; Boozarjomehry, R Bozorgmehry
2015-09-01
In this paper, a framework for distributed and decentralized state estimation in high-pressure and long-distance gas transmission networks (GTNs) is proposed. The non-isothermal model of the plant including mass, momentum and energy balance equations are used to simulate the dynamic behavior. Due to several disadvantages of implementing a centralized Kalman filter for large-scale systems, the continuous/discrete form of extended Kalman filter for distributed and decentralized estimation (DDE) has been extended for these systems. Accordingly, the global model is decomposed into several subsystems, called local models. Some heuristic rules are suggested for system decomposition in gas pipeline networks. In the construction of local models, due to the existence of common states and interconnections among the subsystems, the assimilation and prediction steps of the Kalman filter are modified to take the overlapping and external states into account. However, dynamic Riccati equation for each subsystem is constructed based on the local model, which introduces a maximum error of 5% in the estimated standard deviation of the states in the benchmarks studied in this paper. The performance of the proposed methodology has been shown based on the comparison of its accuracy and computational demands against their counterparts in centralized Kalman filter for two viable benchmarks. In a real life network, it is shown that while the accuracy is not significantly decreased, the real-time factor of the state estimation is increased by a factor of 10. PMID:26138354
NASA Astrophysics Data System (ADS)
Ulbrich, Carlton W.
1985-06-01
A description is given of a method of estimating the effects of truncating the raindrop size distribution (DSD) at lower and upper drop diameters Dmin and Dmax which assumes that the DSD can be approximated by a gamma distribution (including the exponential distribution). The method is used to investigate the effects of DSD truncation on rainfall integral parameters (e.g., reflectivity factor, liquid water content etc.) and on empirical relations between pairs of these integral parameters. Tests of the theoretical predictions are performed using a set of drop size data collected with a Joss disdrometer. A brief description is also given of the use of the method to determine DSD truncation effects on precipitation parameters deduced from dual-measurement techniques.
Heidari, M.; Ranjithan, S.R.
1998-01-01
In using non-linear optimization techniques for estimation of parameters in a distributed ground water model, the initial values of the parameters and prior information about them play important roles. In this paper, the genetic algorithm (GA) is combined with the truncated-Newton search technique to estimate groundwater parameters for a confined steady-state ground water model. Use of prior information about the parameters is shown to be important in estimating correct or near-correct values of parameters on a regional scale. The amount of prior information needed for an accurate solution is estimated by evaluation of the sensitivity of the performance function to the parameters. For the example presented here, it is experimentally demonstrated that only one piece of prior information of the least sensitive parameter is sufficient to arrive at the global or near-global optimum solution. For hydraulic head data with measurement errors, the error in the estimation of parameters increases as the standard deviation of the errors increases. Results from our experiments show that, in general, the accuracy of the estimated parameters depends on the level of noise in the hydraulic head data and the initial values used in the truncated-Newton search technique.In using non-linear optimization techniques for estimation of parameters in a distributed ground water model, the initial values of the parameters and prior information about them play important roles. In this paper, the genetic algorithm (GA) is combined with the truncated-Newton search technique to estimate groundwater parameters for a confined steady-state ground water model. Use of prior information about the parameters is shown to be important in estimating correct or near-correct values of parameters on a regional scale. The amount of prior information needed for an accurate solution is estimated by evaluation of the sensitivity of the performance function to the parameters. For the example presented here, it is
Strategic Decision-Making Learning from Label Distributions: An Approach for Facial Age Estimation
Zhao, Wei; Wang, Han
2016-01-01
Nowadays, label distribution learning is among the state-of-the-art methodologies in facial age estimation. It takes the age of each facial image instance as a label distribution with a series of age labels rather than the single chronological age label that is commonly used. However, this methodology is deficient in its simple decision-making criterion: the final predicted age is only selected at the one with maximum description degree. In many cases, different age labels may have very similar description degrees. Consequently, blindly deciding the estimated age by virtue of the highest description degree would miss or neglect other valuable age labels that may contribute a lot to the final predicted age. In this paper, we propose a strategic decision-making label distribution learning algorithm (SDM-LDL) with a series of strategies specialized for different types of age label distribution. Experimental results from the most popular aging face database, FG-NET, show the superiority and validity of all the proposed strategic decision-making learning algorithms over the existing label distribution learning and other single-label learning algorithms for facial age estimation. The inner properties of SDM-LDL are further explored with more advantages. PMID:27367691
Distributed parameter estimation for NASA Mini-Mast truss through displacement measurements
NASA Technical Reports Server (NTRS)
Huang, Jen-Kuang; Shen, Ji-Yao; Taylor, Lawrence W., Jr.
1991-01-01
Most methods of system identification of large flexible structures by far are based on the lumped parameter approach. Because of the considerable computational burden due to the large number of unknown parameters, distributed parameter approach, which greatly decreases the number of unknowns, has being investigated. In this paper a distributed parameter model for the estimation of modal characteristics of NASA Mini-Mast truss has been formulated. Both Bernoulli-Euler beam and Timoshenko beam equations are used to characterize the lateral bending vibrations of the truss. The measurement of the lateral displacement at the tip of the truss is provided to the maximum likelihood estimator. Closed-form solutions of the partial differential equations and closed-form expressions of the sensitivity functions are derived so that the estimation algorithm is highly efficient. The resulting estimates from test data by using Timoshenko beam model are found to be comparable to those derived from finite element analysis.
Parameter estimation in nonlinear distributed systems - Approximation theory and convergence results
NASA Technical Reports Server (NTRS)
Banks, H. T.; Reich, Simeon; Rosen, I. G.
1988-01-01
An abstract approximation framework and convergence theory is described for Galerkin approximations applied to inverse problems involving nonlinear distributed parameter systems. Parameter estimation problems are considered and formulated as the minimization of a least-squares-like performance index over a compact admissible parameter set subject to state constraints given by an inhomogeneous nonlinear distributed system. The theory applies to systems whose dynamics can be described by either time-independent or nonstationary strongly maximal monotonic operators defined on a reflexive Banach space which is densely and continuously embedded in a Hilbert space. It is demonstrated that if readily verifiable conditions on the system's dependence on the unknown parameters are satisfied, and the usual Galerkin approximation assumption holds, then solutions to the approximating problems exist and approximate a solution to the original infinite-dimensional identification problem.
NASA Technical Reports Server (NTRS)
Kemmerer, A. J.; Benigno, J. A.
1973-01-01
A feasibility study to demonstrate the potential of satellites for providing fisheries significant information was conducted in the Mississippi Sound and adjacent offshore waters. Attempts were made to relate satellite acquired imagery to selected oceanographic parameters and then to relate these parameters to aircraft remotely sensed distribution patterns of resident surface schooling fishes. Initial results suggest that this approach is valid and that the satellite acquired imagery may have important fisheries resource assessment implications.
NASA Technical Reports Server (NTRS)
Kemmerer, A. J.; Benigno, J. A.
1973-01-01
The author has identified the following significant results. A feasibility study to demonstrate the potential of satellites for providing fisheries significant information was conducted in the Mississippi Sound and adjacent offshore waters. Attempts were made to relate satellite acquired imagery to selected oceanographic parameters and then to relate these parameters to aircraft remotely sensed distribution patterns of resident surface schooling fishes. Initial results suggest that this approach is valid and that the satellite acquired imagery may have important fisheries resource assessment implications.
Factorization and reduction methods for optimal control of distributed parameter systems
NASA Technical Reports Server (NTRS)
Burns, J. A.; Powers, R. K.
1985-01-01
A Chandrasekhar-type factorization method is applied to the linear-quadratic optimal control problem for distributed parameter systems. An aeroelastic control problem is used as a model example to demonstrate that if computationally efficient algorithms, such as those of Chandrasekhar-type, are combined with the special structure often available to a particular problem, then an abstract approximation theory developed for distributed parameter control theory becomes a viable method of solution. A numerical scheme based on averaging approximations is applied to hereditary control problems. Numerical examples are given.
Probability distribution of the order parameter in the directed percolation universality class.
Martins, P H L
2012-04-01
The probability distributions of the order parameter for two models in the directed percolation universality class were evaluated. Monte Carlo simulations have been performed for the one-dimensional generalized contact process and the Domany-Kinzel cellular automaton. In both cases, the density of active sites was chosen as the order parameter. The criticality of those models was obtained by solely using the corresponding probability distribution function. It has been shown that the present method, which has been successfully employed in treating equilibrium systems, is indeed also useful in the study of nonequilibrium phase transitions. PMID:22680423
Comparison of Two New Robust Parameter Estimation Methods for the Power Function Distribution
Shakeel, Muhammad; Haq, Muhammad Ahsan ul; Abdulhamid, Alaa Mohamd; Faisal, Muhammad
2016-01-01
Estimation of any probability distribution parameters is vital because imprecise and biased estimates can be misleading. In this study, we investigate a flexible power function distribution and introduced new two methods such as, probability weighted moments, and generalized probability weighted methods for its parameters. We compare their results with L-moments, trimmed L-moments by a simulation study and a real data example based on performance measures such as, mean square error and total deviation. We concluded that all the methods perform well in the case of large sample size (n>30), however, the generalized probability weighted moment method performs better for small sample size. PMID:27500404
The radial distributions of galactic molecular clouds and their physical parameters.
NASA Astrophysics Data System (ADS)
Xiang, D.-L.; Lou, G.-F.
In this paper, the data of 391 J = 1-0 spectra of 13CO surveys, which were made with the NRAO 11-m telescope and along the galactic plane from l = 20.50° to 40.00° with 3arcmin spacings, and 665 molecular clouds synthesized by the above-mentioned data are used to derive the galactic radial distributions of several physical parameters of molecular clouds. Comparative analyses are made between the galactic radial distributions of physical parameters of molecular clouds and the molecular counterparts of 21 cm H I spiral arms identified by Cohen et al. (1980) in their CO surveys.
Comparison of Two New Robust Parameter Estimation Methods for the Power Function Distribution.
Shakeel, Muhammad; Haq, Muhammad Ahsan Ul; Hussain, Ijaz; Abdulhamid, Alaa Mohamd; Faisal, Muhammad
2016-01-01
Estimation of any probability distribution parameters is vital because imprecise and biased estimates can be misleading. In this study, we investigate a flexible power function distribution and introduced new two methods such as, probability weighted moments, and generalized probability weighted methods for its parameters. We compare their results with L-moments, trimmed L-moments by a simulation study and a real data example based on performance measures such as, mean square error and total deviation. We concluded that all the methods perform well in the case of large sample size (n>30), however, the generalized probability weighted moment method performs better for small sample size. PMID:27500404
NASA Astrophysics Data System (ADS)
Chen, Y.; Li, J.; Xu, H.
2015-10-01
Physically based distributed hydrological models discrete the terrain of the whole catchment into a number of grid cells at fine resolution, and assimilate different terrain data and precipitation to different cells, and are regarded to have the potential to improve the catchment hydrological processes simulation and prediction capability. In the early stage, physically based distributed hydrological models are assumed to derive model parameters from the terrain properties directly, so there is no need to calibrate model parameters, but unfortunately, the uncertanties associated with this model parameter deriving is very high, which impacted their application in flood forecasting, so parameter optimization may also be necessary. There are two main purposes for this study, the first is to propose a parameter optimization method for physically based distributed hydrological models in catchment flood forecasting by using PSO algorithm and to test its competence and to improve its performances, the second is to explore the possibility of improving physically based distributed hydrological models capability in cathcment flood forecasting by parameter optimization. In this paper, based on the scalar concept, a general framework for parameter optimization of the PBDHMs for catchment flood forecasting is first proposed that could be used for all PBDHMs. Then, with Liuxihe model as the study model, which is a physically based distributed hydrological model proposed for catchment flood forecasting, the improverd Particle Swarm Optimization (PSO) algorithm is developed for the parameter optimization of Liuxihe model in catchment flood forecasting, the improvements include to adopt the linear decreasing inertia weight strategy to change the inertia weight, and the arccosine function strategy to adjust the acceleration coefficients. This method has been tested in two catchments in southern China with different sizes, and the results show that the improved PSO algorithm could be
Massoudieh, Arash; Visser, Ate; Sharifi, Soroosh; Broers, Hans Peter
2013-10-15
The mixing of groundwaters with different ages in aquifers, groundwater age is more appropriately represented by a distribution rather than a scalar number. To infer a groundwater age distribution from environmental tracers, a mathematical form is often assumed for the shape of the distribution and the parameters of the mathematical distribution are estimated using deterministic or stochastic inverse methods. We found that the prescription of the mathematical form limits the exploration of the age distribution to the shapes that can be described by the selected distribution. In this paper, the use of freeform histograms as groundwater age distributions is evaluated. A Bayesian Markov Chain Monte Carlo approach is used to estimate the fraction of groundwater in each histogram bin. This method was able to capture the shape of a hypothetical gamma distribution from the concentrations of four age tracers. The number of bins that can be considered in this approach is limited based on the number of tracers available. The histogram method was also tested on tracer data sets from Holten (The Netherlands; ^{3}H, ^{3}He, ^{85}Kr, ^{39}Ar) and the La Selva Biological Station (Costa-Rica; SF_{ 6}, CFCs, ^{3}H, ^{4}He and ^{14}C), and compared to a number of mathematical forms. According to standard Bayesian measures of model goodness, the best mathematical distribution performs better than the histogram distributions in terms of the ability to capture the observed tracer data relative to their complexity. Among the histogram distributions, the four bin histogram performs better in most of the cases. The Monte Carlo simulations showed strong correlations in the posterior estimates of bin contributions, indicating that these bins cannot be well constrained using the available age tracers. The fact that mathematical forms overall perform better than the freeform histogram does not undermine the benefit of the
Massoudieh, Arash; Visser, Ate; Sharifi, Soroosh; Broers, Hans Peter
2013-10-15
The mixing of groundwaters with different ages in aquifers, groundwater age is more appropriately represented by a distribution rather than a scalar number. To infer a groundwater age distribution from environmental tracers, a mathematical form is often assumed for the shape of the distribution and the parameters of the mathematical distribution are estimated using deterministic or stochastic inverse methods. We found that the prescription of the mathematical form limits the exploration of the age distribution to the shapes that can be described by the selected distribution. In this paper, the use of freeform histograms as groundwater age distributions is evaluated.more » A Bayesian Markov Chain Monte Carlo approach is used to estimate the fraction of groundwater in each histogram bin. This method was able to capture the shape of a hypothetical gamma distribution from the concentrations of four age tracers. The number of bins that can be considered in this approach is limited based on the number of tracers available. The histogram method was also tested on tracer data sets from Holten (The Netherlands; 3H, 3He, 85Kr, 39Ar) and the La Selva Biological Station (Costa-Rica; SF 6, CFCs, 3H, 4He and 14C), and compared to a number of mathematical forms. According to standard Bayesian measures of model goodness, the best mathematical distribution performs better than the histogram distributions in terms of the ability to capture the observed tracer data relative to their complexity. Among the histogram distributions, the four bin histogram performs better in most of the cases. The Monte Carlo simulations showed strong correlations in the posterior estimates of bin contributions, indicating that these bins cannot be well constrained using the available age tracers. The fact that mathematical forms overall perform better than the freeform histogram does not undermine the benefit of the freeform approach, especially for the cases where a larger amount of observed data is
Clusters and cycles in the cosmic ray age distributions of meteorites
NASA Technical Reports Server (NTRS)
Woodard, M. F.; Marti, K.
1985-01-01
Statistically significant clusters in the cosmic ray exposure age distributions of some groups of iron and stone meteorites were observed, suggesting epochs of enhanced collision and breakups. Fourier analyses of the age distributions of chondrites reveal no significant periods, nor does the same analysis when applied to iron meteorite clusters.
Effects of Exendin-4 on Male Reproductive Parameters of D-Galactose Induced Aging Mouse Model
Ahangarpour, Akram; Heidari, Hamid
2014-01-01
Purpose The purpose of this study was to evaluate the role of exendin-4 on reproductive alteration in a D-galactose-induced aging mouse model. Materials and Methods In this experimental study, 72 male Naval Medical Research Institute mice (20~25 g) were randomly divided into six groups: control, exendin-4 (1 nmol/kg), exendin-4 (10 nmol/kg), D-galactose (500 mg/kg), D-galactose+exendin-4 (1 nmol/kg), and D-galactose+exendin-4 (10 nmol/kg). The aging model animals were gavaged with D-galactose for six weeks, and exendin-4 was injected intraperitoneally in the last 10 days. At the end of treatment serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone levels were evaluated and the cauda epididymis and testis were removed to analyze the sperm count and testis morphology. Results The testis weight and volume decreased in the D-galactose group (p<0.01 and p<0.05) respectively. Exendin-4 (1, 10 nmol/kg) increased these parameters in the normal and aging mouse models. Serum LH and FSH levels increased and the sperm count decreased in the D-galactose group (p<0.05). Further, exendin-4 (1 nmol/kg) decreased LH and FSH levels and increased the serum testosterone level and sperm count in both normal and aging animals. Conclusions D-galactose can induce aging alternations in the male reproductive system such as decreased sperm count and increased serum LH and FSH levels through reactive oxygen species over production and reduced antioxidant enzyme activity. Further, co-administration of exendin-4 reduced reproductive complications of D-galactose in an aging mouse model. PMID:25606567
Variation of Biophysical Parameters of the Skin with Age, Gender, and Body Region
Firooz, Alireza; Sadr, Bardia; Babakoohi, Shahab; Sarraf-Yazdy, Maryam; Fanian, Ferial; Kazerouni-Timsar, Ali; Nassiri-Kashani, Mansour; Naghizadeh, Mohammad Mehdi; Dowlati, Yahya
2012-01-01
Background. Understanding the physiological, chemical, and biophysical characteristics of the skin helps us to arrange a proper approach to the management of skin diseases. Objective. The aim of this study was to measure 6 biophysical characteristics of normal skin (sebum content, hydration, transepidermal water loss (TEWL), erythema index, melanin index, and elasticity) in a normal population and assess the effect of sex, age, and body location on them. Methods. Fifty healthy volunteers in 5 age groups (5 males and females in each) were enrolled in this study. A multifunctional skin physiology monitor (Courage & Khazaka electronic GmbH, Germany) was used to measure skin sebum content, hydration, TEWL, erythema index, melanin index, and elasticity in 8 different locations of the body. Results. There were significant differences between the hydration, melanin index, and elasticity of different age groups. Regarding the locations, forehead had the highest melanin index, where as palm had the lowest value. The mean values of erythema index and melanin index and TEWL were significantly higher in males and anatomic location was a significant independent factor for all of 6 measured parameters. Conclusion. Several biophysical properties of the skin vary among different gender, age groups, and body locations. PMID:22536139
Evaluation of Experimental Parameters in the Accelerated Aging of Closed-Cell Foam Insulation
Stovall, Therese K; Vanderlan, Michael; Atchley, Jerald Allen
2012-12-01
The thermal conductivity of many closed-cell foam insulation products changes over time as production gases diffuse out of the cell matrix and atmospheric gases diffuse into the cells. Thin slicing has been shown to be an effective means of accelerating this process in such a way as to produce meaningful results. Efforts to produce a more prescriptive version of the ASTM C1303 standard test method led to the ruggedness test described here. This test program included the aging of full size insulation specimens for time periods of five years for direct comparison to the predicted results. Experimental parameters under investigation include: slice thickness, slice origin (at the surface or from the core of the slab), thin slice stack composition, product facings, original product thickness, product density, and product type. The test protocol has been completed and this report provides a detailed evaluation of the impact of the test parameters on the accuracy of the 5-year thermal conductivity prediction.
Quantification of Parameter Uncertainty of a Distributed Hydraulic Model Using Ensemble Smoother
NASA Astrophysics Data System (ADS)
Li, Ning; McLaughlin, Dennis; Kinzelbach, Wolfgang; Li, Wenpeng; Dong, Xinguang
2014-05-01
Yanqi basin is an important agricultural region in Xinjiang, in Northwest China. The irrigated agricultural land has been increasing in the past decades and made the basin suffer from many environmental problems such as soil salinization, decreased lake level, deteriorated lake water quality, decreased surface water flow to the downstream and damaged riverine forests. A 3-dimensional distributed numerical flow and transport model is built using MIKESHE/MIKE11 which contains saturated and unsaturated zones, rivers and lakes. It allows to better understand the impacts of individual hydrological units and their interactions. Before using the model for quantifying solutions for the environmental problems, the parameter uncertainties of the complex distributed model are assessed using an Ensemble Smoother (ES). ES is a data assimilation method to improve an ensemble of prior parameters by assimilating time series of observations over the whole time period available. It is basically a stochastic calibration method. In this case study, an iterative ES is applied, called Ensemble Smoother with Multiple Data Assimilation (ESMDA) (Emerick and Reynolds, 2012). Two alternatives are considered to update parameters in each iteration. One is the Ensemble Kalman Filter with perturbed observations and the other is an Unbiased Square root filter which updates parameter means and perturbations separately. Seventeen parameters are chosen from the distributed flow and transport model to quantify their uncertainty. Fifty prior replicates of each parameter are generated using the Latin Hypercube Sampling method. The distribution of posterior parameters and outputs obtained from the alternative methods are similar. The results indicate that the uncertainty of the parameters is narrowed during the smoother updating process, reflecting the information obtained from the observations. The most sensitive parameters are the dispersion coefficient of the lakes and the hydraulic conductivity of
A unified framework for approximation in inverse problems for distributed parameter systems
NASA Technical Reports Server (NTRS)
Banks, H. T.; Ito, K.
1988-01-01
A theoretical framework is presented that can be used to treat approximation techniques for very general classes of parameter estimation problems involving distributed systems that are either first or second order in time. Using the approach developed, one can obtain both convergence and stability (continuous dependence of parameter estimates with respect to the observations) under very weak regularity and compactness assumptions on the set of admissible parameters. This unified theory can be used for many problems found in the recent literature and in many cases offers significant improvements to existing results.
Pobrotyn, Piotr; Susło, Robert; Milczanowski, Piotr; Drobnik, Jarosław
2016-01-01
Introduction Rheumatic diseases are becoming more and more common in Poland with the ageing of the population. Nearly 18% of the total hospital admissions in Poland result from rheumatic diseases, which was equivalent to 350 thousand cases in the year 2008. These diseases tend to last for many decades, decreasing both the quality of life and income of the patients as well as increasing the medical institutions’ workload and society's financial burden. The aim of the study was to determine whether the medical care parameters in a rheumatic disease hospital ward show any significant differences among different patient age groups – especially such that would support taking them into account as a basis for adjusting the financial coverage level of medical services. Material and methods Data on hospitalizations at the Rheumatic Diseases Ward of Wroclaw University Hospital in Wroclaw in the years 2009–2015 were analyzed, taking into account the age groups, number of hospital admissions, their duration and causes. Relevant statistical data analysis was performed. Discussion The study revealed that the number of old patients hospitalized at the rheumatic diseases ward increased over the last 6 years and that such statistically significant differences do exist: on average the old patients not only tend to stay much longer at the hospital, but also suffer from a different and more diverse spectrum of diseases in comparison to their younger counterparts. Conclusions The detected differences in medical care parameters support the need for more individualized medical care and increased cost of the hospital stay in the case of older patients. Consequently, those factors justify the necessity to increase the value of medical services in the case of old patients, possibly also taking into account the variation between age subgroups. PMID:27407280
SU-E-T-113: Dose Distribution Using Respiratory Signals and Machine Parameters During Treatment
Imae, T; Haga, A; Saotome, N; Kida, S; Nakano, M; Takeuchi, Y; Shiraki, T; Yano, K; Yamashita, H; Nakagawa, K; Ohtomo, K
2014-06-01
Purpose: Volumetric modulated arc therapy (VMAT) is a rotational intensity-modulated radiotherapy (IMRT) technique capable of acquiring projection images during treatment. Treatment plans for lung tumors using stereotactic body radiotherapy (SBRT) are calculated with planning computed tomography (CT) images only exhale phase. Purpose of this study is to evaluate dose distribution by reconstructing from only the data such as respiratory signals and machine parameters acquired during treatment. Methods: Phantom and three patients with lung tumor underwent CT scans for treatment planning. They were treated by VMAT while acquiring projection images to derive their respiratory signals and machine parameters including positions of multi leaf collimators, dose rates and integrated monitor units. The respiratory signals were divided into 4 and 10 phases and machine parameters were correlated with the divided respiratory signals based on the gantry angle. Dose distributions of each respiratory phase were calculated from plans which were reconstructed from the respiratory signals and the machine parameters during treatment. The doses at isocenter, maximum point and the centroid of target were evaluated. Results and Discussion: Dose distributions during treatment were calculated using the machine parameters and the respiratory signals detected from projection images. Maximum dose difference between plan and in treatment distribution was −1.8±0.4% at centroid of target and dose differences of evaluated points between 4 and 10 phases were no significant. Conclusion: The present method successfully evaluated dose distribution using respiratory signals and machine parameters during treatment. This method is feasible to verify the actual dose for moving target.
NASA Astrophysics Data System (ADS)
Chen, Y.; Li, J.; Xu, H.
2016-01-01
Physically based distributed hydrological models (hereafter referred to as PBDHMs) divide the terrain of the whole catchment into a number of grid cells at fine resolution and assimilate different terrain data and precipitation to different cells. They are regarded to have the potential to improve the catchment hydrological process simulation and prediction capability. In the early stage, physically based distributed hydrological models are assumed to derive model parameters from the terrain properties directly, so there is no need to calibrate model parameters. However, unfortunately the uncertainties associated with this model derivation are very high, which impacted their application in flood forecasting, so parameter optimization may also be necessary. There are two main purposes for this study: the first is to propose a parameter optimization method for physically based distributed hydrological models in catchment flood forecasting by using particle swarm optimization (PSO) algorithm and to test its competence and to improve its performances; the second is to explore the possibility of improving physically based distributed hydrological model capability in catchment flood forecasting by parameter optimization. In this paper, based on the scalar concept, a general framework for parameter optimization of the PBDHMs for catchment flood forecasting is first proposed that could be used for all PBDHMs. Then, with the Liuxihe model as the study model, which is a physically based distributed hydrological model proposed for catchment flood forecasting, the improved PSO algorithm is developed for the parameter optimization of the Liuxihe model in catchment flood forecasting. The improvements include adoption of the linearly decreasing inertia weight strategy to change the inertia weight and the arccosine function strategy to adjust the acceleration coefficients. This method has been tested in two catchments in southern China with different sizes, and the results show
NASA Astrophysics Data System (ADS)
Dai, Mi; Wang, Yun
2016-06-01
In order to obtain robust cosmological constraints from Type Ia supernova (SN Ia) data, we have applied Markov Chain Monte Carlo (MCMC) to SN Ia lightcurve fitting. We develop a method for sampling the resultant probability density distributions (pdf) of the SN Ia lightcuve parameters in the MCMC likelihood analysis to constrain cosmological parameters, and validate it using simulated data sets. Applying this method to the `joint lightcurve analysis (JLA)' data set of SNe Ia, we find that sampling the SN Ia lightcurve parameter pdf's leads to cosmological parameters closer to that of a flat Universe with a cosmological constant, compared to the usual practice of using only the best-fitting values of the SN Ia lightcurve parameters. Our method will be useful in the use of SN Ia data for precision cosmology.
Dana L. Kelly; Albert Malkhasyan
2010-06-01
There is a nearly ubiquitous assumption in PSA that parameter values are at least piecewise-constant in time. As a result, Bayesian inference tends to incorporate many years of plant operation, over which there have been significant changes in plant operational and maintenance practices, plant management, etc. These changes can cause significant changes in parameter values over time; however, failure to perform Bayesian inference in the proper time-dependent framework can mask these changes. Failure to question the assumption of constant parameter values, and failure to perform Bayesian inference in the proper time-dependent framework were noted as important issues in NUREG/CR-6813, performed for the U. S. Nuclear Regulatory Commission’s Advisory Committee on Reactor Safeguards in 2003. That report noted that “industry lacks tools to perform time-trend analysis with Bayesian updating.” This paper describes an application of time-dependent Bayesian inference methods developed for the European Commission Ageing PSA Network. These methods utilize open-source software, implementing Markov chain Monte Carlo sampling. The paper also illustrates the development of a generic prior distribution, which incorporates multiple sources of generic data via weighting factors that address differences in key influences, such as vendor, component boundaries, conditions of the operating environment, etc.
Thompson, Robert S.; Anderson, Katherine H.; Bartlein, Patrick J.
1999-01-01
This atlas explores the continental-scale relations between the geographic ranges of woody plant species and climate in North America. A 25-km equal-area grid of modern climatic and bioclimatic parameters was constructed from instrumental weather records. The geographic distributions of selected tree and shrub species were digitized, and the presence or absence of each species was determined for each cell on the 25-km grid, thus providing a basis for comparing climatic data and species distributions. The relations between climate and plant distributions are explored in graphical and tabular form. The results of this effort are primarily intended for use in biogeographic, paleoclimatic, and global-change research.
Aging of distribution and other lifeline systems due to corrosion
Isenberg, J. )
1993-05-01
Statistics derived from public works maintenance records for buried steel and cast iron pipelines indicate that aging may be seen in increasing rates of repairs. Maintenance increases with age due to cumulative traffic loads, ground settlement and, among the most important causes, corrosion. The tendency for repair rates gradually to increase and the opposing effects of corrosion control and planned replacement are punctuated by the rapid rise in leakage and required maintenance in the aftermath of an earthquake. These data were uncovered as a byproduct of studying five western US earthquakes in which performance of steel pipelines under seismic conditions and under normal operating conditions appear to be correlated. Evidence also points to temporary and, sometimes, to permanent increase in the rate of leakage and failure in the aftermath of an earthquake. The underlying cause of this correlation is thinning of pipe walls due to corrosion, which is facilitated by stray current and conductive soil. 6 refs., 4 figs., 1 tab.
An EOQ Model with Two-Parameter Weibull Distribution Deterioration and Price-Dependent Demand
ERIC Educational Resources Information Center
Mukhopadhyay, Sushanta; Mukherjee, R. N.; Chaudhuri, K. S.
2005-01-01
An inventory replenishment policy is developed for a deteriorating item and price-dependent demand. The rate of deterioration is taken to be time-proportional and the time to deterioration is assumed to follow a two-parameter Weibull distribution. A power law form of the price dependence of demand is considered. The model is solved analytically…
The reduced order model problem in distributed parameter systems adaptive identification and control
NASA Technical Reports Server (NTRS)
Johnson, C. R., Jr.
1980-01-01
The research concerning the reduced order model problem in distributed parameter systems is reported. The adaptive control strategy was chosen for investigation in the annular momentum control device. It is noted, that if there is no observation spill over, and no model errors, an indirect adaptive control strategy can be globally stable. Recent publications concerning adaptive control are included.
In this article, we consider the least-squares approach for estimating parameters of a spatial variogram and establish consistency and asymptotic normality of these estimators under general conditions. Large-sample distributions are also established under a sp...
The values of the parameters of some multilayer distributed RC null networks
NASA Technical Reports Server (NTRS)
Huelsman, L. P.; Raghunath, S.
1974-01-01
In this correspondence, the values of the parameters of some multilayer distributed RC notch networks are determined, and the usually accepted values are shown to be in error. The magnitude of the error is illustrated by graphs of the frequency response of the networks.
Methods for the identification of material parameters in distributed models for flexible structures
NASA Technical Reports Server (NTRS)
Banks, H. T.; Crowley, J. M.; Rosen, I. G.
1986-01-01
Theoretical and numerical results are presented for inverse problems involving estimation of spatially varying parameters such as stiffness and damping in distributed models for elastic structures such as Euler-Bernoulli beams. An outline of algorithms used and a summary of computational experiences are presented.
NASA Astrophysics Data System (ADS)
Kuleshova, E. O.; Plyusnin, A. A.; Shandarova, E. B.; Tikhomirova, O. V.
2016-04-01
This paper considers the simulation capability of nonuniform distributed-parameter circuit transients by using MatLab Simulink. This approach is capable of determining currents and voltages of nodes for power networks of any configurations and modes. The paper contains results of nonuniform line simulations in idle, short-circuit and load modes.
Study of Parameters And Methods of LL-Ⅳ Distributed Hydrological Model in DMIP2
NASA Astrophysics Data System (ADS)
Li, L.; Wu, J.; Wang, X.; Yang, C.; Zhao, Y.; Zhou, H.
2008-05-01
: The Physics-based distributed hydrological model is considered as an important developing period from the traditional experience-hydrology to the physical hydrology. The Hydrology Laboratory of the NOAA National Weather Service proposes the first and second phase of the Distributed Model Intercomparison Project (DMIP)，that it is a great epoch-making work. LL distributed hydrological model has been developed to the fourth generation since it was established in 1997 on the Fengman-I district reservoir area (11000 km2).The LL-I distributed hydrological model was born with the applications of flood control system in the Fengman-I in China. LL-II was developed under the DMIP-I support, it is combined with GIS, RS, GPS, radar rainfall measurement.LL-III was established along with Applications of LL Distributed Model on Water Resources which was supported by the 973-projects of The Ministry of Science and Technology of the People's Republic of China. LL-Ⅳ was developed to face China's water problem. Combined with Blue River and the Baron Fork River basin of DMIP-II, the convection-diffusion equation of non-saturated and saturated seepage was derived from the soil water dynamics and continuous equation. In view of the technical characteristics of the model, the advantage of using convection-diffusion equation to compute confluence overall is longer period of predictable, saving memory space, fast budgeting, clear physical concepts, etc. The determination of parameters of hydrological model is the key, including experience coefficients and parameters of physical parameters. There are methods of experience, inversion, and the optimization to determine the model parameters, and each has advantages and disadvantages. This paper briefly introduces the LL-Ⅳ distribution hydrological model equations, and particularly introduces methods of parameters determination and simulation results on Blue River and Baron Fork River basin for DMIP-II. The soil moisture diffusion
Fitting Three- and Four-Parameter Probability Distributions to Daily Streamflow
NASA Astrophysics Data System (ADS)
Archfield, S. A.; Vogel, R. M.
2014-12-01
Daily streamflow information is critical for solving any number of hydrologic problems. One promising approach to estimate a time series of daily streamflow at an ungauged location is to estimate a continuous, daily, period-of-record flow-duration curve (FDC) at the ungauged location and use the timing of observed streamflows from a donor streamgauge to transform the FDC at the ungauged location into a time series of streamflow. Ideally, if one were to find a suitable probability density function (pdf) to represent daily streamflow, only the parameters of the distribution would need to be estimated at the ungauged location. Determining the pdf of daily streamflow could also provide functional linkages between the pdfs of daily precipitation and other catchment processes toward a probabilistic framework which explains how catchments filter the precipitation signal. Three- and four parameter distributions were fit to daily streamflow observations from streamgauges located in the north- and southeastern United States. No suitable three or four-parameter probability distribution were found to adequately represent the distribution of daily streamflow, particularly at streamflow quantiles greater than 0.9 and less than 0.01 exceedence probabilities. Furthermore, the properties of these distributions caused estimated streamflows to be bounded at both the highest and lowest streamflow quantiles, creating a severe bias in the estimation of the FDC. Traditional goodness-of-fit statistics were also unable to revealing this lack of fit; only examination of the individual probability plots showed this inadequacy.
Visser, A; Moran, J E; Hillegonds, Darren; Singleton, M J; Kulongoski, Justin T; Belitz, Kenneth; Esser, B K
2016-03-15
Key characteristics of California groundwater systems related to aquifer vulnerability, sustainability, recharge locations and mechanisms, and anthropogenic impact on recharge are revealed in a spatial geostatistical analysis of a unique data set of tritium, noble gases and other isotopic analyses unprecedented in size at nearly 4000 samples. The correlation length of key groundwater residence time parameters varies between tens of kilometers ((3)H; age) to the order of a hundred kilometers ((4)Heter; (14)C; (3)Hetrit). The correlation length of parameters related to climate, topography and atmospheric processes is on the order of several hundred kilometers (recharge temperature; δ(18)O). Young groundwater ages that highlight regional recharge areas are located in the eastern San Joaquin Valley, in the southern Santa Clara Valley Basin, in the upper LA basin and along unlined canals carrying Colorado River water, showing that much of the recent recharge in central and southern California is dominated by river recharge and managed aquifer recharge. Modern groundwater is found in wells with the top open intervals below 60 m depth in the southeastern San Joaquin Valley, Santa Clara Valley and Los Angeles basin, as the result of intensive pumping and/or managed aquifer recharge operations. PMID:26803267
Radar meteors range distribution model. III. Ablation, shape-density and self-similarity parameters
NASA Astrophysics Data System (ADS)
Pecinová, D.; Pecina, P.
2007-10-01
The theoretical radar meteors Range Distribution of the overdense echoes developed by Pecinová and Pecina (2007 a) is applied here to observed range distributions of meteors belonging to the Quadrantid, Perseid, Leonid, Geminid, γ Draconid (Giacobinid), ζ Perseid and β Taurid streams to study the variability of the shape-density, ablation, and self-similarity parameters of meteoroids of these streams. We have found in accordance with results of photographical observations that ablation parameter σ is higher for members of showers of clearly cometary origin, and is lower for Geminid and daytime shower meteoroids. Levin's self-similarity parameter μ was found to be much greater than the classical value 2/3 for all investigated streams with the exception of Geminids, for which the value found is almost classical, i.e. 0.66 ± 0.01. The method of getting μ by means of fitting the light curve of faint TV meteors is also suggested.
Comparison of Two Methods Used to Model Shape Parameters of Pareto Distributions
Liu, C.; Charpentier, R.R.; Su, J.
2011-01-01
Two methods are compared for estimating the shape parameters of Pareto field-size (or pool-size) distributions for petroleum resource assessment. Both methods assume mature exploration in which most of the larger fields have been discovered. Both methods use the sizes of larger discovered fields to estimate the numbers and sizes of smaller fields: (1) the tail-truncated method uses a plot of field size versus size rank, and (2) the log-geometric method uses data binned in field-size classes and the ratios of adjacent bin counts. Simulation experiments were conducted using discovered oil and gas pool-size distributions from four petroleum systems in Alberta, Canada and using Pareto distributions generated by Monte Carlo simulation. The estimates of the shape parameters of the Pareto distributions, calculated by both the tail-truncated and log-geometric methods, generally stabilize where discovered pool numbers are greater than 100. However, with fewer than 100 discoveries, these estimates can vary greatly with each new discovery. The estimated shape parameters of the tail-truncated method are more stable and larger than those of the log-geometric method where the number of discovered pools is more than 100. Both methods, however, tend to underestimate the shape parameter. Monte Carlo simulation was also used to create sequences of discovered pool sizes by sampling from a Pareto distribution with a discovery process model using a defined exploration efficiency (in order to show how biased the sampling was in favor of larger fields being discovered first). A higher (more biased) exploration efficiency gives better estimates of the Pareto shape parameters. ?? 2011 International Association for Mathematical Geosciences.
STRUCTURAL PARAMETERS OF SEVEN SMALL MAGELLANIC CLOUD INTERMEDIATE-AGE AND OLD STAR CLUSTERS
Glatt, Katharina; Grebel, Eva K.; Kayser, Andrea; Gallagher, John S.; Harbeck, Daniel; Nota, Antonella; Sabbi, Elena; Sirianni, Marco; Clementini, Gisella; Tosi, Monica; Da Costa, Gary; Koch, Andreas
2009-11-15
We present structural parameters for the seven intermediate-age and old star clusters NGC 121, Lindsay 1, Kron 3, NGC 339, NGC 416, Lindsay 38, and NGC 419 in the Small Magellanic Cloud (SMC). We fit King profiles and Elson, Fall, and Freeman profiles to both surface-brightness and star-count data taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope. Clusters older than {approx}1 Gyr show a spread in cluster core radii that increases with age, while the youngest clusters have relatively compact cores. No evidence for post-core-collapse clusters was found. We find no correlation between core radius and distance from the SMC center, although consistent with other studies of dwarf galaxies, some relatively old and massive clusters have low densities. The oldest SMC star cluster, the only globular NGC121, is the most elliptical object of the studied clusters. No correlation is seen between ellipticity and distance from the SMC center. The structures of these massive intermediate-age (1-8 Gyr) SMC star clusters thus appear to primarily result from internal evolutionary processes.
NASA Astrophysics Data System (ADS)
Mat Jan, Nur Amalina; Shabri, Ani
2015-09-01
TL-moments approach has been used in an analysis to identify the best-fitting distributions to represent the annual series of maximum streamflow data over seven stations in Johor, Malaysia. The TL-moments with different trimming values are used to estimate the parameter of the selected distributions namely: Three-parameter lognormal (LN3) and Pearson Type III (P3) distribution. The main objective of this study is to derive the TL-moments (t 1,0), t 1 = 1,2,3,4 methods for LN3 and P3 distributions. The performance of TL-moments (t 1,0), t 1 = 1,2,3,4 was compared with L-moments through Monte Carlo simulation and streamflow data over a station in Johor, Malaysia. The absolute error is used to test the influence of TL-moments methods on estimated probability distribution functions. From the cases in this study, the results show that TL-moments with four trimmed smallest values from the conceptual sample (TL-moments [4, 0]) of LN3 distribution was the most appropriate in most of the stations of the annual maximum streamflow series in Johor, Malaysia.
Budic, Lara; Didenko, Gregor; Dormann, Carsten F
2016-01-01
In species distribution analyses, environmental predictors and distribution data for large spatial extents are often available in long-lat format, such as degree raster grids. Long-lat projections suffer from unequal cell sizes, as a degree of longitude decreases in length from approximately 110 km at the equator to 0 km at the poles. Here we investigate whether long-lat and equal-area projections yield similar model parameter estimates, or result in a consistent bias. We analyzed the environmental effects on the distribution of 12 ungulate species with a northern distribution, as models for these species should display the strongest effect of projectional distortion. Additionally we choose four species with entirely continental distributions to investigate the effect of incomplete cell coverage at the coast. We expected that including model weights proportional to the actual cell area should compensate for the observed bias in model coefficients, and similarly that using land coverage of a cell should decrease bias in species with coastal distribution. As anticipated, model coefficients were different between long-lat and equal-area projections. Having progressively smaller and a higher number of cells with increasing latitude influenced the importance of parameters in models, increased the sample size for the northernmost parts of species ranges, and reduced the subcell variability of those areas. However, this bias could be largely removed by weighting long-lat cells by the area they cover, and marginally by correcting for land coverage. Overall we found little effect of using long-lat rather than equal-area projections in our analysis. The fitted relationship between environmental parameters and occurrence probability differed only very little between the two projection types. We still recommend using equal-area projections to avoid possible bias. More importantly, our results suggest that the cell area and the proportion of a cell covered by land should be
ERIC Educational Resources Information Center
Xu, Xueli; Jia, Yue
2011-01-01
Estimation of item response model parameters and ability distribution parameters has been, and will remain, an important topic in the educational testing field. Much research has been dedicated to addressing this task. Some studies have focused on item parameter estimation when the latent ability was assumed to follow a normal distribution,…
NASA Workshop on Distributed Parameter Modeling and Control of Flexible Aerospace Systems
NASA Technical Reports Server (NTRS)
Marks, Virginia B. (Compiler); Keckler, Claude R. (Compiler)
1994-01-01
Although significant advances have been made in modeling and controlling flexible systems, there remains a need for improvements in model accuracy and in control performance. The finite element models of flexible systems are unduly complex and are almost intractable to optimum parameter estimation for refinement using experimental data. Distributed parameter or continuum modeling offers some advantages and some challenges in both modeling and control. Continuum models often result in a significantly reduced number of model parameters, thereby enabling optimum parameter estimation. The dynamic equations of motion of continuum models provide the advantage of allowing the embedding of the control system dynamics, thus forming a complete set of system dynamics. There is also increased insight provided by the continuum model approach.
Distributions of electric parameters in MOS structures on 3C-SiC substrate
NASA Astrophysics Data System (ADS)
Piskorski, Krzysztof; Przewlocki, Henryk M.; Esteve, Romain; Bakowski, Mietek
2013-02-01
In this work studies of some electrical parameters of the MOS structure based on 3C-SiC substrate are presented. The effective contact potential difference ϕ MS , the barrier height at the gate-dielectric interface E BG and the flat-band in semiconductor voltage V FB were measured using several electric and photoelectric techniques. Values of these parameters obtained on structures with different gate areas decrease monotonically with increasing parameter R, defined as the ratio of the gate perimeter to the gate area. Such behavior confirmed results obtained on MOS structures on silicon substrate and also supported our hypothesis that the mechanical stress in the dielectric layer under the metal gate causes non uniform distribution of some parameters over the gate area of MOS structure.
Distributions of electric parameters in MOS structures on 3C-SiC substrate
NASA Astrophysics Data System (ADS)
Piskorski, Krzysztof; Przewlocki, Henryk; Esteve, Romain; Bakowski, Mietek
2013-02-01
In this work studies of some electrical parameters of the MOS structure based on 3C-SiC substrate are presented. The effective contact potential difference ϕMS, the barrier height at the gate-dielectric interface E BG and the flat-band in semiconductor voltage V FB were measured using several electric and photoelectric techniques. Values of these parameters obtained on structures with different gate areas decrease monotonically with increasing parameter R, defined as the ratio of the gate perimeter to the gate area. Such behavior confirmed results obtained on MOS structures on silicon substrate and also supported our hypothesis that the mechanical stress in the dielectric layer under the metal gate causes non uniform distribution of some parameters over the gate area of MOS structure.
Kawasaki, Yohei; Ide, Kazuki; Yamada, Hiroshi; Furukawa, Toshiaki A.; Ono, Yutaka
2016-01-01
Background. Previous research has reported inconsistent evidence of the trajectory of depressive symptoms across the adult lifespan. We investigated how the distributions of each item score change with age and determined whether the trajectory of depressive symptoms varied with the scoring methods of the questionnaire. Methods. We analyzed data collected from 21,040 subjects who participated in the national survey in Japan. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). The CES-D has 20 items, each of which is scored in four grades of “rarely,” “some,” “much,” and “most of the time.” We used the exponential distribution model which fits the distributions of 16 negative symptom items of CES-D, with the probabilities of “some,” “much,” “most,” and “rarely” expressed as P, Pr, Pr2, and 1 − P × (r2 + r + 1). Results. The distributions of the responses to 16 negative symptom items followed the common exponential model across all age groups. The mean of the estimated parameter r of 16 negative items showed a U-shape pattern, being high during 12–29 years, remaining low during 30–50 years, and then increasing again over 60 years. The trajectory of depressive symptom scores simulating the binary method was different from that of the empirical scores using the Likert method. Conclusions. Our findings show that the increase in the depressive symptoms score during older age is based on the increase of the parameter r. The differences in the scoring method may contribute to the different age-related patterns across the adult lifespan. PMID:26788427
Tomitaka, Shinichiro; Kawasaki, Yohei; Ide, Kazuki; Yamada, Hiroshi; Furukawa, Toshiaki A; Ono, Yutaka
2016-01-01
Background. Previous research has reported inconsistent evidence of the trajectory of depressive symptoms across the adult lifespan. We investigated how the distributions of each item score change with age and determined whether the trajectory of depressive symptoms varied with the scoring methods of the questionnaire. Methods. We analyzed data collected from 21,040 subjects who participated in the national survey in Japan. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). The CES-D has 20 items, each of which is scored in four grades of "rarely," "some," "much," and "most of the time." We used the exponential distribution model which fits the distributions of 16 negative symptom items of CES-D, with the probabilities of "some," "much," "most," and "rarely" expressed as P, Pr, Pr (2), and 1 - P × (r (2) + r + 1). Results. The distributions of the responses to 16 negative symptom items followed the common exponential model across all age groups. The mean of the estimated parameter r of 16 negative items showed a U-shape pattern, being high during 12-29 years, remaining low during 30-50 years, and then increasing again over 60 years. The trajectory of depressive symptom scores simulating the binary method was different from that of the empirical scores using the Likert method. Conclusions. Our findings show that the increase in the depressive symptoms score during older age is based on the increase of the parameter r. The differences in the scoring method may contribute to the different age-related patterns across the adult lifespan. PMID:26788427
Mathematical results new and revisited on the distribution of groundwater age
NASA Astrophysics Data System (ADS)
Ginn, T. R.; Massoudieh, A.; Foglia, L.
2009-12-01
The equation governing the distribution of groundwater age under transient, 3D flow conditions is analyzed under several simplifying cases to illustrate some relations among groundwater age equations and some results about steady-state and transient age distributions. First linkages are made among the various groundwater age equations recently published, showing them all to be different simplifications of the same equation. The most basic analysis in 1D shows that groundwater age is at lease inverse-Gaussian distributed. More generally, steady state age moments, when they exist, are given by breakthrough curve moments and this allows us to use the temporal moment results from the solute transport literature as steady state age moments. In particular, age moment equations with arbitrary diffusive mass transfer (two-domain, radial microscopic, powerlaw) at steady state are already available as the temporal flux moment equations for solute transport under analogous boundary conditions. Lastly transient simulations of age in 1D are calculated to illustrate several aspects of the evolution of groundwater age distributions in time in the presences of multidomain diffusive transport.
Stochastic parameter estimation in nonlinear time-delayed vibratory systems with distributed delay
NASA Astrophysics Data System (ADS)
Torkamani, Shahab; Butcher, Eric A.
2013-07-01
The stochastic estimation of parameters and states in linear and nonlinear time-delayed vibratory systems with distributed delay is explored. The approach consists of first employing a continuous time approximation to approximate the delayed integro-differential system with a large set of ordinary differential equations having stochastic excitations. Then the problem of state and parameter estimation in the resulting stochastic ordinary differential system is represented as an optimal filtering problem using a state augmentation technique. By adapting the extended Kalman-Bucy filter to the augmented filtering problem, the unknown parameters of the time-delayed system are estimated from noise-corrupted, possibly incomplete measurements of the states. Similarly, the upper bound of the distributed delay can also be estimated by the proposed technique. As an illustrative example to a practical problem in vibrations, the parameter, delay upper bound, and state estimation from noise-corrupted measurements in a distributed force model widely used for modeling machine tool vibrations in the turning operation is investigated.
Precipitation classification at mid-latitudes in terms of drop size distribution parameters
NASA Astrophysics Data System (ADS)
Caracciolo, C.; Porcã¹, F.; Prodi, F.
2008-04-01
The drop size distribution (DSD) is a fundamental property of rainfall because the shape of the distribution reflects the physics of rain formation processes. Given the lack of studies on the DSD at mid-latitudes, the present work focuses on the microphysical characterization of precipitation events occurring in Italy, using two different types of disdrometer. A large number of different rain events was collected: they underwent microphysical analysis by computing the Z-R relationships, observing the average DSDs and DSD parameters, fitting the real distribution for different rainfall rate categories and applying convective (C) - stratiform (S) discrimination algorithms. A general agreement with past works at mid-latitudes is found both in the Z-R relationship and in DSD parameters. The rain distribution is well described by a gamma DSD and only in some cases (especially the light rain events) by an exponential DSD. Marked differences are observed in DSD parameters and Z-R relationships between C and S episodes. The use of disdrometers for areas covered by multiparametric radar is suggested and will be performed in the near future.
NASA Astrophysics Data System (ADS)
Castaings, W.; Dartus, D.; Le Dimet, F.-X.; Saulnier, G.-M.
2009-04-01
Variational methods are widely used for the analysis and control of computationally intensive spatially distributed systems. In particular, the adjoint state method enables a very efficient calculation of the derivatives of an objective function (response function to be analysed or cost function to be optimised) with respect to model inputs. In this contribution, it is shown that the potential of variational methods for distributed catchment scale hydrology should be considered. A distributed flash flood model, coupling kinematic wave overland flow and Green Ampt infiltration, is applied to a small catchment of the Thoré basin and used as a relatively simple (synthetic observations) but didactic application case. It is shown that forward and adjoint sensitivity analysis provide a local but extensive insight on the relation between the assigned model parameters and the simulated hydrological response. Spatially distributed parameter sensitivities can be obtained for a very modest calculation effort (~6 times the computing time of a single model run) and the singular value decomposition (SVD) of the Jacobian matrix provides an interesting perspective for the analysis of the rainfall-runoff relation. For the estimation of model parameters, adjoint-based derivatives were found exceedingly efficient in driving a bound-constrained quasi-Newton algorithm. The reference parameter set is retrieved independently from the optimization initial condition when the very common dimension reduction strategy (i.e. scalar multipliers) is adopted. Furthermore, the sensitivity analysis results suggest that most of the variability in this high-dimensional parameter space can be captured with a few orthogonal directions. A parametrization based on the SVD leading singular vectors was found very promising but should be combined with another regularization strategy in order to prevent overfitting.
NASA Astrophysics Data System (ADS)
Gao, Li-Na; Liu, Fu-Hu; Lacey, Roy A.
2016-05-01
Experimental results of the transverse-momentum distributions of φ mesons and Ω hyperons produced in gold-gold (Au-Au) collisions with different centrality intervals, measured by the STAR Collaboration at different energies (7.7, 11.5, 19.6, 27, and 39 GeV) in the beam energy scan (BES) program at the relativistic heavy-ion collider (RHIC), are approximately described by the single Erlang distribution and the two-component Schwinger mechanism. Moreover, the STAR experimental transverse-momentum distributions of negatively charged particles, produced in Au-Au collisions at RHIC BES energies, are approximately described by the two-component Erlang distribution and the single Tsallis statistics. The excitation functions of free parameters are obtained from the fit to the experimental data. A weak softest point in the string tension in Ω hyperon spectra is observed at 7.7 GeV.
Numerical approach for the evaluation of Weibull distribution parameters for hydrologic purposes
NASA Astrophysics Data System (ADS)
Pierleoni, A.; Di Francesco, S.; Biscarini, C.; Manciola, P.
2016-06-01
In hydrology, the statistical description of low flow phenomena is very important in order to evaluate the available water resource especially in a river and the related values can be obviously considered as random variables, therefore probability distributions dealing with extreme values (maximum and/or minimum) of the variable play a fundamental role. Computational procedures for the estimation of the parameters featuring these distributions are actually very useful especially when embedded into analysis software [1][2] or as standalone applications. In this paper a computational procedure for the evaluation of the Weibull[3] distribution is presented focusing on the case when the lower limit of the distribution is not known or not set to a specific value a priori. The procedure takes advantage of the Gumbel[4] moment approach to the problem.
Optimization of hydrological parameters of a distributed runoff model based on multiple flood events
NASA Astrophysics Data System (ADS)
Miyamoto, Mamoru; Matsumoto, Kazuhiro; Tsuda, Morimasa; Yamakage, Yuzuru; Iwami, Yoichi; Anai, Hirokazu
2015-04-01
The error sources of flood forecasting by a runoff model commonly include input data, model structures, and parameter settings. This study focused on a calibration procedure to minimize errors due to parameter settings. Although many studies have been done on hydrological parameter optimization, they are mostly about individual optimization cases applying a specific optimization technique to a specific flood. Consequently, it is difficult to determine the most appropriate parameter set to make forecasts on future floods, because optimized parameter sets vary by flood type. Thus, this study aimed to develop a comprehensive method for optimizing hydrological parameters of a distributed runoff model for future flood forecasting. A distributed runoff model, PWRI-DHM, was applied to the Gokase River basin of 1,820km2 in Japan in this study. The model with gridded two-layer tanks for the entire target river basin includes hydrological parameters, such as hydraulic conductivity, surface roughness and runoff coefficient, which are set according to land-use and soil-type distributions. Global data sets, e.g., Global Map and DSMW (Digital Soil Map of the World), were employed as input data such as elevation, land use and soil type. Thirteen optimization algorithms such as GA, PSO and DEA were carefully selected from seventy-four open-source algorithms available for public use. These algorithms were used with three error assessment functions to calibrate the parameters of the model to each of fifteen past floods in the predetermined search range. Fifteen optimized parameter sets corresponding to the fifteen past floods were determined by selecting the best sets from the calibration results in terms of reproducible accuracy. This process helped eliminate bias due to type of optimization algorithms. Although the calibration results of each parameter were widely distributed in the search range, statistical significance was found in comparisons between the optimized parameters
Angular distribution of cosmological parameters as a probe of space-time inhomogeneities
NASA Astrophysics Data System (ADS)
Carvalho, C. Sofia; Marques, Katrine
2016-08-01
We develop a method based on the angular distribution on the sky of cosmological parameters to probe the inhomogeneity of large-scale structure and cosmic acceleration. We demonstrate this method on the largest type Ia supernova (SN) data set available to date, as compiled by the Joint Light-curve Analysis (JLA) collaboration and, hence, consider the cosmological parameters that affect the luminosity distance. We divide the SN sample into equal surface area pixels and estimate the cosmological parameters that minimize the chi-square of the fit to the distance modulus in each pixel, hence producing maps of the cosmological parameters {ΩM,ΩΛ,H0} . In poorly sampled pixels, the measured fluctuations are mostly due to an inhomogeneous coverage of the sky by the SN surveys; in contrast, in well-sampled pixels, the measurements are robust enough to suggest a real fluctuation. We also measure the anisotropy of the parameters by computing the power spectrum of the corresponding maps of the parameters up to ℓ = 3. For an analytical toy model of an inhomogeneous ensemble of homogeneous pixels, we derive the backreaction term in the deceleration parameter due to the fluctuations of H0 across the sky and measure it to be of order 10-3 times the corresponding average over the pixels in the absence of backreaction. We conclude that, for the toy model considered, backreaction is not a viable dynamical mechanism to emulate cosmic acceleration.
Tsunami source parameters estimated from slip distribution and their relation to tsunami intensity
NASA Astrophysics Data System (ADS)
Bolshakova, Anna; Nosov, Mikhail; Kolesov, Sergey
2015-04-01
Estimation of the level of tsunami hazard on the basis of earthquake moment magnitude often fails. The most important reason for this is that tsunamis are related to earthquakes in a complex and ambiguous way. In order to reveal a measure of tsunamigenic potential of an earthquake that would be better than moment magnitude of earthquake we introduce a set of tsunami source parameters that can be calculated from co-seismic ocean-bottom deformation and bathymetry. We consider more than two hundred ocean-bottom earthquakes (1923-2014) those for which detailed slip distribution data (Finite Fault Model) are available on USGS, UCSB, Caltech, and eQuake-RC sites. Making use of the Okada formulae the vector fields of co-seismic deformation of ocean bottom are estimated from the slip distribution data. Taking into account bathymetry (GEBCO_08) we determine tsunami source parameters such as double amplitude of bottom deformation, displaced water volume, potential energy of initial elevation, etc. The tsunami source parameters are examined as a function of earthquake moment magnitude. The contribution of horisontal component of ocean bottom deformation to tsunami generation is investigated. We analyse the Soloviev-Imamura tsunami intensity as a function of tsunami source parameters. The possibility of usage of tsunami source parameters instead of moment magnitude in tsunami warning is discussed. This work was supported by the Russian Foundation for Basic Research, project 14-05-31295
[Distribution of the different patterns of aging over the system of animal world].
Popov, I Iu
2011-01-01
Since the system of animal world reflects evolutionary trends, an analysis of distribution of patterns of aging over this system provides information on the causes of the formation of differences among them. In this paper the system of the main animal groups in form of a table is presented, and the distribution of patterns demonstrating minimum and maximum of aging is discussed. Meanwhile the colonial animals are considered as a "minimum of aging", the animals demonstrating drastic self-liquidation after reproduction are considered as a "maximum of aging" (the most well-known example is the pink salmon). It is shown, that as far as the degree of difference from the simplest ancestor increases in process of evolution, the increase of the manifestations of aging takes place. Slow aging of relatively simple organisms cannot be a direct source of measures to prevent aging of complex ones. PMID:21957572
Huang, Feng; Jiang, Xiangqian; Yuan, Haiming; Yang, Hanning; Li, Siren; Sun, Xiudong
2016-04-01
A method to detect the full Stokes parameters utilizing a double-ring and Archimedes-curves distributed nanoslits plasmonic lenses is proposed. We demonstrate theoretically and numerically that both of these two plasmonic lenses can focus surface plasmon polaritons to centrally symmetric fields with subwavelength-sized focal spots under linear, elliptical, and circular polarization incidence. The intensity at the focal spots is modulated by the polarization state of incident light. Utilizing this intensity polarization sensitivity, the full Stokes parameters of incident light are detected by recoding only four intensities at the focal spots of these two plasmonic lenses. PMID:27192318
SAC-SMA a priori parameter differences and their impact on distributed hydrologic model simulations
NASA Astrophysics Data System (ADS)
Zhang, Ziya; Koren, Victor; Reed, Seann; Smith, Michael; Zhang, Yu; Moreda, Fekadu; Cosgrove, Brian
2012-02-01
SummaryDeriving a priori gridded parameters is an important step in the development and deployment of an operational distributed hydrologic model. Accurate a priori parameters can reduce the manual calibration effort and/or speed up the automatic calibration process, reduce calibration uncertainty, and provide valuable information at ungauged locations. Underpinned by reasonable parameter data sets, distributed hydrologic modeling can help improve water resource and flood and flash flood forecasting capabilities. Initial efforts at the National Weather Service Office of Hydrologic Development (NWS OHD) to derive a priori gridded Sacramento Soil Moisture Accounting (SAC-SMA) model parameters for the conterminous United States (CONUS) were based on a relatively coarse resolution soils property database, the State Soil Geographic Database (STATSGO) (Soil Survey Staff, 2011) and on the assumption of uniform land use and land cover. In an effort to improve the parameters, subsequent work was performed to fully incorporate spatially variable land cover information into the parameter derivation process. Following that, finer-scale soils data (the county-level Soil Survey Geographic Database (SSURGO) ( Soil Survey Staff, 2011a,b), together with the use of variable land cover data, were used to derive a third set of CONUS, a priori gridded parameters. It is anticipated that the second and third parameter sets, which incorporate more physical data, will be more realistic and consistent. Here, we evaluate whether this is actually the case by intercomparing these three sets of a priori parameters along with their associated hydrologic simulations which were generated by applying the National Weather Service Hydrology Laboratory's Research Distributed Hydrologic Model (HL-RDHM) ( Koren et al., 2004) in a continuous fashion with an hourly time step. This model adopts a well-tested conceptual water balance model, SAC-SMA, applied on a regular spatial grid, and links to physically
Olsen, Anya
2012-01-01
Policymakers have proposed increases to the early eligibility age (EEA) and/or full retirement age (FRA) to address increasing life expectancy and Social Security solvency issues. This analysis uses the Social Security Administration's Modeling Income in the Near Term, version 6 (MINT6) model to compare three retirement-age increases suggested by the Social Security Advisory Board: increase the gap between the EEA and FRA by raising only the FRA, increase both the EEA and FRA to maintain a 4-year gap between them, and increase both the EEA and FRA to maintain a 5-year gap between them. Although all three options would improve system solvency by similar proportions, their effect on individual beneficiaries in the future would vary. Benefit reductions are greater under the proposals with more months between the EEA and FRA, while the option that maintains a 4-year gap results in benefit increases for some beneficiaries compared with current law. PMID:23397744
NASA Astrophysics Data System (ADS)
Gedalin, M.
2015-12-01
> Upon crossing the shock front, ions begin to gyrate. The ion distribution just behind the ramp is manifestly non-gyrotropic. The gyration of the ion distribution as a whole results in spatially periodic oscillations of the ion pressure. The magnetic pressure must oscillate in the opposite phase to ensure the maintenance of the pressure balance throughout the shock front. The ion non-gyrotropy and the pressure oscillations gradually damp due to the collisionless gyrophase mixing. The rate of this relaxation depends on the basic shock parameters. The most influential are the angle between the shock normal and the magnetic field, the upstream ion temperature and the magnetic compression.
Kim, Young-Do; Lee, Young-Kwang; Lee, Hyo-Chang; Chung, Chin-Wook
2013-02-15
Spatial characteristics of plasma parameters such as electron temperature, plasma density, plasma potential, and electron energy distribution (EED) were studied in inductively coupled plasma with an axial dc magnetic field. With dc magnetic field, the measured EEDs in the total electron energy scale are spatially coincided except cutting of the low electron energy part indicating the conserved non-local electron kinetics in an axial direction, even though the dc magnetic field is applied. Spatial distributions of the plasma densities at axial positions have almost same trends with various magnetic field strengths. We also discuss the reduction of the ambipolar potential along the axial direction as the applied magnetic field increased.
NASA Astrophysics Data System (ADS)
Aryan, Homayon; Yearby, Keith; Balikhin, Michael; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Boynton, Richard
2014-08-01
Energetic electrons within the Earth's radiation belts represent a serious hazard to geostationary satellites. The interactions of electrons with chorus waves play an important role in both the acceleration and loss of radiation belt electrons. The common approach is to present model wave distributions in the inner magnetosphere under different values of geomagnetic activity as expressed by the geomagnetic indices. However, it has been shown that only around 50% of geomagnetic storms increase flux of relativistic electrons at geostationary orbit while 20% causes a decrease and the remaining 30% has relatively no effect. This emphasizes the importance of including solar wind parameters such as bulk velocity (V), density (n), flow pressure (P), and the vertical interplanetary magnetic field component (Bz) that are known to be predominately effective in the control of high energy fluxes at the geostationary orbit. Therefore, in the present study the set of parameters of the wave distributions is expanded to include the solar wind parameters in addition to the geomagnetic activity. The present study examines almost 4 years (1 January 2004 to 29 September 2007) of Spatio-Temporal Analysis of Field Fluctuation data from Double Star TC1 combined with geomagnetic indices and solar wind parameters from OMNI database in order to present a comprehensive model of wave magnetic field intensities for the chorus waves as a function of magnetic local time, L shell (L), magnetic latitude (λm), geomagnetic activity, and solar wind parameters. Generally, the results indicate that the intensity of chorus emission is not only dependent upon geomagnetic activity but also dependent on solar wind parameters with velocity and southward interplanetary magnetic field Bs (Bz < 0), evidently the most influential solar wind parameters. The largest peak chorus intensities in the order of 50 pT are observed during active conditions, high solar wind velocities, low solar wind densities, high
NASA Astrophysics Data System (ADS)
Long, Andrew J.; Putnam, Larry D.
2009-10-01
SummaryConvolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers. The framework of a quasi-transient convolution model that is applicable to two-domain flow in karst aquifers is presented. The model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon (CFC) and tritium ( 3H) data are available. We show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined. As an example, the model was applied to water from a pumped well open to the Madison aquifer in central USA with input functions of CFC-11, CFC-12, CFC-113, and 3H, and was calibrated to several samples collected during a 16-year period. A bimodal age distribution was modeled to represent quick and slow flow less than 50 years old. The effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow. Quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0-2 and 26-41 years, respectively. The fraction of long-term flow (>50 years) was estimated but was not dateable. The different tracers had different degrees of influence on parameter estimation and uncertainty assessments, where 3H was the most critical, and CFC-113 was least influential.
Long, A.J.; Putnam, L.D.
2009-01-01
Convolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers. The framework of a quasi-transient convolution model that is applicable to two-domain flow in karst aquifers is presented. The model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon (CFC) and tritium (3H) data are available. We show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined. As an example, the model was applied to water from a pumped well open to the Madison aquifer in central USA with input functions of CFC-11, CFC-12, CFC-113, and 3H, and was calibrated to several samples collected during a 16-year period. A bimodal age distribution was modeled to represent quick and slow flow less than 50 years old. The effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow. Quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0-2 and 26-41 years, respectively. The fraction of long-term flow (>50 years) was estimated but was not dateable. The different tracers had different degrees of influence on parameter estimation and uncertainty assessments, where 3H was the most critical, and CFC-113 was least influential.
Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately
NASA Technical Reports Server (NTRS)
Huang, Zhaofeng; Porter, Albert A.
1991-01-01
The mathematical relationships between the shape parameter Beta and estimates of reliability and a life limit lower bound for the two parameter Weibull distribution are investigated. It is shown that under rather general conditions, both the reliability lower bound and the allowable life limit lower bound (often called a tolerance limit) have unique global minimums over a range of Beta. Hence lower bound solutions can be obtained without assuming or estimating Beta. The existence and uniqueness of these lower bounds are proven. Some real data examples are given to show how these lower bounds can be easily established and to demonstrate their practicality. The method developed here has proven to be extremely useful when using the Weibull distribution in analysis of no-failure or few-failures data. The results are applicable not only in the aerospace industry but anywhere that system reliabilities are high.
Lower bound on reliability for Weibull distribution when shape parameter is not estimated accurately
NASA Technical Reports Server (NTRS)
Huang, Zhaofeng; Porter, Albert A.
1990-01-01
The mathematical relationships between the shape parameter Beta and estimates of reliability and a life limit lower bound for the two parameter Weibull distribution are investigated. It is shown that under rather general conditions, both the reliability lower bound and the allowable life limit lower bound (often called a tolerance limit) have unique global minimums over a range of Beta. Hence lower bound solutions can be obtained without assuming or estimating Beta. The existence and uniqueness of these lower bounds are proven. Some real data examples are given to show how these lower bounds can be easily established and to demonstrate their practicality. The method developed here has proven to be extremely useful when using the Weibull distribution in analysis of no-failure or few-failures data. The results are applicable not only in the aerospace industry but anywhere that system reliabilities are high.
Effects of Forest Bathing on Cardiovascular and Metabolic Parameters in Middle-Aged Males
Kobayashi, Maiko; Kumeda, Shigeyoshi; Ochiai, Toshiya; Miura, Takashi; Imai, Michiko; Wang, Zhiyu; Otsuka, Toshiaki; Kawada, Tomoyuki
2016-01-01
In the present study, we investigated the effects of a forest bathing on cardiovascular and metabolic parameters. Nineteen middle-aged male subjects were selected after they provided informed consent. These subjects took day trips to a forest park in Agematsu, Nagano Prefecture, and to an urban area of Nagano Prefecture as control in August 2015. On both trips, they walked 2.6 km for 80 min each in the morning and afternoon on Saturdays. Blood and urine were sampled before and after each trip. Cardiovascular and metabolic parameters were measured. Blood pressure and pulse rate were measured during the trips. The Japanese version of the profile of mood states (POMS) test was conducted before, during, and after the trips. Ambient temperature and humidity were monitored during the trips. The forest bathing program significantly reduced pulse rate and significantly increased the score for vigor and decreased the scores for depression, fatigue, anxiety, and confusion. Urinary adrenaline after forest bathing showed a tendency toward decrease. Urinary dopamine after forest bathing was significantly lower than that after urban area walking, suggesting the relaxing effect of the forest bathing. Serum adiponectin after the forest bathing was significantly greater than that after urban area walking. PMID:27493670
Effects of Forest Bathing on Cardiovascular and Metabolic Parameters in Middle-Aged Males.
Li, Qing; Kobayashi, Maiko; Kumeda, Shigeyoshi; Ochiai, Toshiya; Miura, Takashi; Kagawa, Takahide; Imai, Michiko; Wang, Zhiyu; Otsuka, Toshiaki; Kawada, Tomoyuki
2016-01-01
In the present study, we investigated the effects of a forest bathing on cardiovascular and metabolic parameters. Nineteen middle-aged male subjects were selected after they provided informed consent. These subjects took day trips to a forest park in Agematsu, Nagano Prefecture, and to an urban area of Nagano Prefecture as control in August 2015. On both trips, they walked 2.6 km for 80 min each in the morning and afternoon on Saturdays. Blood and urine were sampled before and after each trip. Cardiovascular and metabolic parameters were measured. Blood pressure and pulse rate were measured during the trips. The Japanese version of the profile of mood states (POMS) test was conducted before, during, and after the trips. Ambient temperature and humidity were monitored during the trips. The forest bathing program significantly reduced pulse rate and significantly increased the score for vigor and decreased the scores for depression, fatigue, anxiety, and confusion. Urinary adrenaline after forest bathing showed a tendency toward decrease. Urinary dopamine after forest bathing was significantly lower than that after urban area walking, suggesting the relaxing effect of the forest bathing. Serum adiponectin after the forest bathing was significantly greater than that after urban area walking. PMID:27493670
On the design derivatives of eigenvalues and eigenvectors for distributed parameter systems
NASA Technical Reports Server (NTRS)
Reiss, R.
1985-01-01
In this paper, analytic expressions are obtained for the design derivatives of eigenvalues and eigenfunctions of self-adjoint linear distributed parameter systems. Explicit treatment of boundary conditions is avoided by casting the eigenvalue equation into integral form. Results are expressed in terms of the linear operators defining the eigenvalue problem, and are therefore quite general. Sufficiency conditions appropriate to structural optimization of eigenvalues are obtained.
Pseudorational Impulse Responses — Algebraic System Theory for Distributed Parameter Systems
NASA Astrophysics Data System (ADS)
Yamamoto, Yutaka
This paper gives a comprehensive account on a class of distributed parameter systems, whose impulse response is called pseudorational. This notion was introduced by the author in 1980's, and is particularly amenable for the study of systems with bounded-time memory. We emphasize algebraic structures induced by this class of systems. Some recent results on coprimeness issues and H∞ control are discussed and illustrated.
NASA Astrophysics Data System (ADS)
Kostunin, D.; Bezyazeekov, P. A.; Hiller, R.; Schröder, F. G.; Lenok, V.; Levinson, E.
2016-02-01
We investigate features of the lateral distribution function (LDF) of the radio signal emitted by cosmic ray air-showers with primary energies Epr > 0.1 EeV and its connection to air-shower parameters such as energy and shower maximum using CoREAS simulations made for the configuration of the Tunka-Rex antenna array. Taking into account all significant contributions to the total radio emission, such as by the geomagnetic effect, the charge excess, and the atmospheric refraction we parameterize the radio LDF. This parameterization is two-dimensional and has several free parameters. The large number of free parameters is not suitable for experiments of sparse arrays operating at low SNR (signal-to-noise ratios). Thus, exploiting symmetries, we decrease the number of free parameters based on the shower geometry and reduce the LDF to a simple one-dimensional function. The remaining parameters can be fit with a small number of points, i.e. as few as the signal from three antennas above detection threshold. Finally, we present a method for the reconstruction of air-shower parameters, in particular, energy and Xmax (shower maximum), which can be reached with a theoretical accuracy of better than 15% and 30 g/cm2, respectively.
Paleoclimate signals and age distributions from 41 public water works in the Netherlands
NASA Astrophysics Data System (ADS)
Broers, Hans Peter; de Weert, Jasperien; Sueltenfuss, Juergen; Aeschbach-Hertig, Werner; Vonhof, Hubert; Casteleijns, Jeroen
2015-04-01
Knowing the age distribution of water abstracted from public water supply wells is of prime importance to ensure customer trust and to underpin predictions of water quality evolution in time. Especially, age distributions enable the assessment of the vulnerability of well fields, both in relation to surface sources of contamination as in relation to subsurface sources, such as possibly related to shale gas extraction. We sampled the raw water of 41 large public supply well fields which represents a mixture of groundwaters and used the a discrete travel time distribution model (DTTDM, Visser et al. 2013, WRR) in order to quantify the age distribution of the mixture. Measurements included major ion chemistry, 3H, 3He, 4He, 18O, 2H, 14C, 13CDIC and 13CCH4 and the full range of noble gases. The heavier noble gases enable the calculation of the Noble Gas Temperature (NGT) which characterizes the temperature of past recharge conditions. The 14C apparent age of each mixture was derived correcting for dead carbon sources and included carbonate dissolution and methanogenesis as the defining processes. The DTTDM used the 3H and 4He concentrations, the 14C apparent age and the NGT as the four distinctive tracers to estimate the age distributions. The use of 18O was less effective because the processes that led to more enriched values are too uncertain . Especially 4He and NGT provide extra information on the older part of the age distributions and showed that the 14C apparent ages are often the result of mixing of waters ranging between 2.000 and 35.000 years old, instead of being discrete ages with a limited .variance as sometimes assumed. The results show a large range of age distributions, comprising vulnerable well fields with >60% young water (< 100 yrs) and well-protected well fields with >85% very old groundwater (> 25 kyrs) and all forms of TTD's in between. The age distributions are well in correspondence with the hydrogeological setting of the well fields; all well
Paleoclimate Signals and Age Distributions from 41 Public Water Works in the Netherlands
NASA Astrophysics Data System (ADS)
Broers, H. P.; Weert, J. D.; Sültenfuß, J.; Aeschbach, W.; Vonhof, H.; Casteleijns, J.
2015-12-01
Knowing the age distribution of water abstracted from public water supply wells is of prime importance to ensure customer trust and to underpin predictions of water quality evolution in time. Especially, age distributions enable the assessment of the vulnerability of well fields, both in relation to surface sources of contamination as in relation to subsurface sources, such as possibly related to shale gas extraction. We sampled the raw water of 41 large public supply well fields which represents a mixture of groundwaters and used the a discrete travel time distribution model (DTTDM, Visser et al. 2013, WRR) in order to quantify the age distribution of the mixture. Measurements included major ion chemistry, 3H, 3He, 4He, 18O, 2H, 14C, 13CDIC and 13CCH4 and the full range of noble gases. The heavier noble gases enable the calculation of the Noble Gas Temperature (NGT) which characterizes the temperature of past recharge conditions. The 14C apparent age of each mixture was derived correcting for dead carbon sources. The DTTDM used the 3H and 4He concentrations, the 14C apparent age and the NGT as the four distinctive tracers to estimate the age distributions. Especially 4He and NGT provide extra information on the older part of the age distributions and showed that the 14C apparent ages are often the result of mixing of waters ranging between 2.000 and 35.000 years old, instead of being discrete ages with a limited .variance as sometimes assumed.The results show a large range of age distributions, comprising vulnerable well fields with >60% young water (< 100 yrs) and well-protected well fields with >85% very old groundwater (> 25 kyrs) and all forms of TTD's in between. The age distributions are well in correspondence with the hydrogeological setting of the well fields; all well fields with an age distribution skewed towards older ages are in the Roer Valley Graben structure, where fluvial and marine aquitards provide protection from recent recharge. Especially
Louzada, Francisco; Ramos, Pedro L; Perdoná, Gleici S C
2016-01-01
We have considered different estimation procedures for the unknown parameters of the extended exponential geometric distribution. We introduce different types of estimators such as the maximum likelihood, method of moments, modified moments, L-moments, ordinary and weighted least squares, percentile, maximum product of spacings, and minimum distance estimators. The different estimators are compared by using extensive numerical simulations. We discovered that the maximum product of spacings estimator has the smallest mean square errors and mean relative estimates, nearest to one, for both parameters, proving to be the most efficient method compared to other methods. Combining these results with the good properties of the method such as consistency, asymptotic efficiency, normality, and invariance we conclude that the maximum product of spacings estimator is the best one for estimating the parameters of the extended exponential geometric distribution in comparison with its competitors. For the sake of illustration, we apply our proposed methodology in two important data sets, demonstrating that the EEG distribution is a simple alternative to be used for lifetime data. PMID:27579052
Shape parameters and distribution of macroborings: St. Croix, US Virgin Islands
Jacobs, E.B.
1983-03-01
Many marine invertebrates that inhabit coral reefs excavate the coral substrate in order to create protective domiciles. In turn, the organisms comprising the coral-reef community display a pronounced biotic zonation that can be closely correlated to bathymetry. This study considers the distribution of these endolithic organisms covering a variety of reef habitats. Vast differences in the major environmental parameters have a profound effect upon the distribution patterns of macroboring organisms and govern the boring morphologies. Of these parameters, hydraulic energy has the strongest influences on the morphotypes and distributions of the macroborings. An equivalent macroboring assemblage dominated by sponges and bivalves prevails in both the shallow back-reef zone and the deep fore-reef zone, both of which are low-energy settings. Boring assemblages in more turbulent zones within the reef consist of polychaete and sipunculid worms, sea urchins, and barnacles, with sponges and bivalves less dominant and less abundant. Other environmental factors which may be important locally include: nutrient availability, photic energy, sediment size and sedimentation rate, competition for substrate, and predation pressure upon the live coral tissue. Shape parameters for different boring types are provided as a means of identification and as an indication of the environmental control upon boring shape. An understanding of the variability of boring types with respect to the ambient environment within modern reefs facilitates the use of borings as paleoenvironmental indicators within Cenozoic carbonate systems.
An alternating direction algorithm for total variation reconstruction of distributed parameters.
Brás, Nuno B; Bioucas-Dias, J; Martins, Raul C; Serra, A C
2012-06-01
Augmented Lagrangian variational formulations and alternating optimization have been adopted to solve distributed parameter estimation problems. The alternating direction method of multipliers (ADMM) is one of such formulations/optimization methods. Very recently, the number of applications of the ADMM, or variants of it, to solve inverse problems in image and signal processing has increased at an exponential rate. The reason for this interest is that ADMM decomposes a difficult optimization problem into a sequence of much simpler problems. In this paper, we use the ADMM to reconstruct piecewise-smooth distributed parameters of elliptical partial differential equations from noisy and linear (blurred) observations of the underlying field. The distributed parameters are estimated by solving an inverse problem with total variation (TV) regularization. The proposed instance of the ADMM solves, in each iteration, an l(2) and a decoupled l(2) - l(1) optimization problems. An operator splitting is used to simplify the treatment of the TV regularizer, avoiding its smooth approximation and yielding a simple yet effective ADMM reconstruction method compared with previously proposed approaches. The competitiveness of the proposed method, with respect to the state-of-the-art, is illustrated in simulated 1-D and 2-D elliptical equation problems, which are representative of many real applications. PMID:22345538
Ramos, Pedro L.; Perdoná, Gleici S. C.
2016-01-01
We have considered different estimation procedures for the unknown parameters of the extended exponential geometric distribution. We introduce different types of estimators such as the maximum likelihood, method of moments, modified moments, L-moments, ordinary and weighted least squares, percentile, maximum product of spacings, and minimum distance estimators. The different estimators are compared by using extensive numerical simulations. We discovered that the maximum product of spacings estimator has the smallest mean square errors and mean relative estimates, nearest to one, for both parameters, proving to be the most efficient method compared to other methods. Combining these results with the good properties of the method such as consistency, asymptotic efficiency, normality, and invariance we conclude that the maximum product of spacings estimator is the best one for estimating the parameters of the extended exponential geometric distribution in comparison with its competitors. For the sake of illustration, we apply our proposed methodology in two important data sets, demonstrating that the EEG distribution is a simple alternative to be used for lifetime data.
Improving flash flood forecasting with distributed hydrological model by parameter optimization
NASA Astrophysics Data System (ADS)
Chen, Yangbo
2016-04-01
In China, flash food is usually regarded as flood occured in small and medium sized watersheds with drainage area less than 200 km2, and is mainly induced by heavy rains, and occurs in where hydrological observation is lacked. Flash flood is widely observed in China, and is the flood causing the most casualties nowadays in China. Due to hydrological data scarcity, lumped hydrological model is difficult to be employed for flash flood forecasting which requires lots of observed hydrological data to calibrate model parameters. Physically based distributed hydrological model discrete the terrain of the whole watershed into a number of grid cells at fine resolution, assimilate different terrain data and precipitation to different cells, and derive model parameteris from the terrain properties, thus having the potential to be used in flash flood forecasting and improving flash flood prediction capability. In this study, the Liuxihe Model, a physically based distributed hydrological model mainly proposed for watershed flood forecasting is employed to simulate flash floods in the Ganzhou area in southeast China, and models have been set up in 5 watersheds. Model parameters have been derived from the terrain properties including the DEM, the soil type and land use type, but the result shows that the flood simulation uncertainty is high, which may be caused by parameter uncertainty, and some kind of uncertainty control is needed before the model could be used in real-time flash flood forecastin. Considering currently many Chinese small and medium sized watersheds has set up hydrological observation network, and a few flood events could be collected, it may be used for model parameter optimization. For this reason, an automatic model parameter optimization algorithm using Particle Swam Optimization(PSO) is developed to optimize the model parameters, and it has been found that model parameters optimized even only with one observed flood events could largely reduce the flood
Development of a distributed-parameter mathematical model for simulation of cryogenic wind tunnels
NASA Technical Reports Server (NTRS)
Tripp, J. S.
1983-01-01
A one-dimensional distributed-parameter dynamic model of a cryogenic wind tunnel was developed which accounts for internal and external heat transfer, viscous momentum losses, and slotted-test-section dynamics. Boundary conditions imposed by liquid-nitrogen injection, gas venting, and the tunnel fan were included. A time-dependent numerical solution to the resultant set of partial differential equations was obtained on a CDC CYBER 203 vector-processing digital computer at a usable computational rate. Preliminary computational studies were performed by using parameters of the Langley 0.3-Meter Transonic Cryogenic Tunnel. Studies were performed by using parameters from the National Transonic Facility (NTF). The NTF wind-tunnel model was used in the design of control loops for Mach number, total temperature, and total pressure and for determining interactions between the control loops. It was employed in the application of optimal linear-regulator theory and eigenvalue-placement techniques to develop Mach number control laws.
EFFECTS OF MIXING AND AGING ON WATER QUALITY IN DISTRIBUTION SYSTEM STORAGE FACILITIES
Aging of water in distribution system storage facilities can lead to deterioration of the water quality due to loss of disinfectant residual and bacterial regrowth. Facilities should be operated to insure that the age of the water is not excessive taking into account the quality...
NASA Astrophysics Data System (ADS)
Gautheron, Cécile; Balout, Hilal; Roques, Jérôme; Allard, Thierry; Morin, Guillaume; Tassan-Got, Laurent
2016-04-01
At the Earth's surface, hematite and goethite are common minerals occurring in soils and sediments, including ores. The understanding of the corresponding alteration and weathering processes relies on our ability to perform the dating of formation of these minerals. Two relevant and recent dating methods have been developed, which are related to (U-Th)/He and (U-Th)/Ne geochronometers. They are based on accumulation of 4He and 21Ne associated with the alpha decay of U and Th. Both methods are of particular interest because of possible He and Ne retention over geological ages at surface temperature. However, because of different atomic radius between He and Ne, retention behavior of these two species can be quite different. Moreover, the dating procedure is particularly challenging because of the small crystals size and frequent polycrystalline structure of hematite and goethite. As a matter of fact, some uncertainty exists about He and Ne diffusion parameters, due to the nanometric to micrometric crystal size of natural iron oxide mineral. Accordingly, the determination of (U-Th)/He and (U-Th)/Ne ages requires the understanding of He and Ne production and retention (which may be partial) in iron oxide crystals. In this study, we theoretically investigate and discuss for the first time the age evolution for pure goethite and hematite crystals with different thermal histories, including reheating to simulate burial. The aim is to quantify the He and/or Ne loss by ejection and diffusion for crystals of different morphology and polycrystalline structures. This will allow one to provide some correction factor for the age. For this purpose, we used new He and Ne diffusion coefficients obtained by multi-scale theoretical approach using Density Functional Theory (DFT) (Balout et al., submitted, a,b), associated with 3D production and diffusion code (Gautheron and Tassan-Got, 2010). The impact of Multi Diffusion Domains simulating polycrystalline structure has been
An analysis of the size distribution of Italian firms by age
NASA Astrophysics Data System (ADS)
Cirillo, Pasquale
2010-02-01
In this paper we analyze the size distribution of Italian firms by age. In other words, we want to establish whether the way that the size of firms is distributed varies as firms become old. As a proxy of size we use capital. In [L.M.B. Cabral, J. Mata, On the evolution of the firm size distribution: Facts and theory, American Economic Review 93 (2003) 1075-1090], the authors study the distribution of Portuguese firms and they find out that, while the size distribution of all firms is fairly stable over time, the distributions of firms by age groups are appreciably different. In particular, as the age of the firms increases, their size distribution on the log scale shifts to the right, the left tails becomes thinner and the right tail thicker, with a clear decrease of the skewness. In this paper, we perform a similar analysis with Italian firms using the CEBI database, also considering firms’ growth rates. Although there are several papers dealing with Italian firms and their size distribution, to our knowledge a similar study concerning size and age has not been performed yet for Italy, especially with such a big panel.
PATTERNS OF ROOT GROWTH, TURNOVER, AND DISTRIBUTION IN DIFFERENT AGED PONDEROSA PINE STANDS
The objectives of this study are to examine the spatial distribution of roots in relation to canopy size and tree distribution, and to determine if rates of fine root production and turnover are similar in the different aged stands. During the fall of 1998, 54 clear plexiglass t...
NASA Astrophysics Data System (ADS)
Becker, Thorsten W.; Conrad, Clinton P.; Buffett, Bruce; Müller, R. Dietmar
2009-02-01
Variations in Earth's rates of seafloor generation and recycling have far-reaching consequences for sea level, ocean chemistry, and climate. However, there is little agreement on the correct parameterization for the time-dependent evolution of plate motions. A strong constraint is given by seafloor age distributions, which are affected by variations in average spreading rate, ridge length, and the age distribution of seafloor being removed by subduction. Using a simplified evolution model, we explore which physical parameterizations of these quantities are compatible with broad trends in the area per seafloor age statistics for the present-day and back to 140 Ma from paleo-age reconstructions. We show that a probability of subduction based on plate buoyancy (slab-pull, or "sqrt(age)") and a time-varying spreading rate fits the observed age distributions as well as, or better than, a subduction probability consistent with an unvarying "triangular" age distribution and age-independent destruction of ocean floor. Instead, we interpret the present near-triangular distribution of ages as a snapshot of a transient state of the evolving oceanic plate system. Current seafloor ages still contain hints of a ˜ 60 Myr periodicity in seafloor production, and using paleoages, we find that a ˜ 250 Myr period variation is consistent with geologically-based reconstructions of production rate variations. These long-period variations also imply a decrease of oceanic heat flow by ˜ - 0.25%/Ma during the last 140 Ma, caused by a 25-50% decrease in the rate of seafloor production. Our study offers an improved understanding of the non-uniformitarian evolution of plate tectonics and the interplay between continental cycles and the self-organization of the oceanic plates.
A theory of the cancer age-specific incidence data based on extreme value distributions
NASA Astrophysics Data System (ADS)
Soto-Ortiz, Luis; Brody, James P.
2012-03-01
The incidence of cancers varies with age, if normalized this is called the age-specific incidence. A mathematical model that describes this variation should provide a better understanding of how cancers develop. We suggest that the age-specific incidence should follow an extreme value distribution, based on three widely accepted assumptions: (1) a tumor develops from a single cell, (2) many potential tumor progenitor cells exist in a tissue, and (3) cancer is diagnosed when the first of these many potential tumor cells develops into a tumor. We tested this by comparing the predicted distribution to the age-specific incidence data for colon and prostate carcinomas collected by the Surveillance, Epidemiology and End Results network of 17 cancer registries. We found that colon carcinoma age-specific incidence data is consistent with an extreme value distribution, while prostate carcinomas age-specific incidence data generally follows the distribution. This model indicates that both colon and prostate carcinomas only occur in a subset of the population (22% for prostate and 13.5% for colon.) Because of their very general nature, extreme value distributions might be applicable to understanding other chronic human diseases.
Uranium distribution and 'excessive' U-He ages in iron meteoritic troilite
NASA Astrophysics Data System (ADS)
Fisher, D. E.
1985-03-01
Fission tracking techniques were used to measure the uranium distribution in meteoritic troilite and graphite. The obtained fission tracking data showed a heterogeneous distribution of tracks with a significant portion of track density present in the form of uranium clusters at least 10 microns in size. The matrix containing the clusters was also heterogeneous in composition with U concentrations of about 0.2-4.7 ppb. U/He ages could not be estimated on the basis of the heterogeneous U distributions, so previously reported estimates of U/He ages in the presolar range are probably invalid.
Uranium distribution and 'excessive' U-He ages in iron meteoritic troilite
NASA Technical Reports Server (NTRS)
Fisher, D. E.
1985-01-01
Fission tracking techniques were used to measure the uranium distribution in meteoritic troilite and graphite. The obtained fission tracking data showed a heterogeneous distribution of tracks with a significant portion of track density present in the form of uranium clusters at least 10 microns in size. The matrix containing the clusters was also heterogeneous in composition with U concentrations of about 0.2-4.7 ppb. U/He ages could not be estimated on the basis of the heterogeneous U distributions, so previously reported estimates of U/He ages in the presolar range are probably invalid.
Nonlinear and distributed parameter models of the mini-mast truss
NASA Technical Reports Server (NTRS)
Taylor, Lawrence W., Jr.
1989-01-01
Large spacecraft such as Space Station Freedom employ large trusses in their construction. The structural dynamics of such trusses often exhibit nonlinear behavior and little damping which can impact significantly the performance of control systems. The Mini-MAST truss was constructed to research such structural dynamics and control systems. The Mini-MAST truss is an object of study for the guest investigator program as part of NASA's controls-structures interaction program. The Mini-MAST truss is deployable and about 65 ft long. Although the bending characteristics of the Mini-MAST truss are essentially linear, the angular deflection under torsional loading has exhibited significant hysteresis and nonlinear stiffness. It is the purpose to develop nonlinear and distributed parameter models of the truss and to compare the model dynamics with actual measurements. Distributed parameter models have the advantage of requiring fewer model parameters. A tangent function is used to describe the nonlinear stiffness in torsion, partly because of the convenience of its easily expressed inverse. Hysteretic slip elements are introduced and extended to a continuum to account for the observed hysteresis in torsion. The contribution of slipping to the structural damping is analyzed and found to be strongly dependent on the applied loads. Because of the many factors which affect the damping and stiffness in a truss, it is risky to assume linearity.
NASA Astrophysics Data System (ADS)
Mohammadi, Hiwa; Bayrak, Yusuf
2016-04-01
The Gumbel's third asymptotic distribution (GIII) of the extreme value method is employed to evaluate the earthquake hazard parameters in the Iranian Plateau. This research quantifies spatial mapping of earthquake hazard parameters like annual and 100-year mode beside their 90 % probability of not being exceeded (NBE) in the Iranian Plateau. Therefore, we used a homogeneous and complete earthquake catalogue during the period 1900-2013 with magnitude M w ≥ 4.0, and the Iranian Plateau is separated into equal area mesh of 1° late × 1° long. The estimated result of annual mode with 90 % probability of NBE is expected to exceed the values of M w 6.0 in the Eastern part of Makran, most parts of Central and East Iran, Kopeh Dagh, Alborz, Azerbaijan, and SE Zagros. The 100-year mode with 90 % probability of NBE is expected to overpass the value of M w 7.0 in the Eastern part of Makran, Central and East Iran, Alborz, Kopeh Dagh, and Azerbaijan. The spatial distribution of 100-year mode with 90 % probability of NBE uncovers the high values of earthquake hazard parameters which are frequently connected with the main tectonic regimes of the studied area. It appears that there is a close communication among the seismicity and the tectonics of the region.
NASA Astrophysics Data System (ADS)
Madsen, Henrik
A consistent framework for parameter estimation in distributed hydrological catchment modelling using automatic calibration is formulated. The framework focuses on the different steps in the estimation process from model parameterisation and selection of calibration parameters, formulation of calibration criteria, and choice of optimisation algorithm. The calibration problem is formulated in a general multi-objective context in which different objective functions that measure individual process descriptions can be optimised simultaneously. Within this framework it is possible to tailor the model calibration to the specific objectives of the model application being considered. A test example is presented that illustrates the use of the calibration framework for parameter estimation in the MIKE SHE integrated and distributed hydrological modelling system. A significant trade-off between the performance of the groundwater level simulations and the catchment runoff is observed in this case, defining a Pareto front with a very sharp structure. The Pareto optimum solution corresponding to a proposed balanced aggregated objective function is seen to provide a proper balance between the two objectives. Compared to a manual expert calibration, the balanced Pareto optimum solution provides generally better simulation of the runoff, whereas virtually similar performance is obtained for the groundwater level simulations.
Temple, W D; Skowrońska, M; Bomke, A A
2014-06-15
A spin-type centrifugal spreader was evaluated using fresh and aged poultry litter upon dry mass, product nitrogen (N), phosphorus (P) and potassium (K), incubation study soil available N and particle size distribution patterns. Relative to the aged litter (37% moisture content), the fresh litter (17% moisture content) had greater <1.00 mm particle size fraction weights and atmospheric particulate was launched, which posed as a potential fallout to adjacent fields, waterways and residences. Relative to the aged litter, the broadcast fresh litter resulted in higher coefficients of variation (CV) over its transverse distance, a narrower calculated space distance between passes for uniform spread and lower soil available N concentrations. For nitrogen application over the broadcast transverse distance the fresh litter displayed a high R(2) best fit 4th order polynomial distribution pattern, while the aged litter showed high R(2) best fit 6th order polynomial distribution pattern. A soil incubation study of the fresh and aged broadcast litter resulted in a more variable or lower R(2) best fit 2nd order polynomial distribution pattern. For both the fresh and aged litter, the calculated distance between passes to achieve a uniform mass distribution was greater than that required for the broadcast of soil available N. For the fresh litter, the soil available N and litter P concentration levels strongly correlated (relatively high p and R(2) values) with the <1.00 mm fraction weight, while for the aged litter this relationship was not as significant. In addition to reducing the health risk (i.e. pathogens, antibiotic residues and resistant bacteria) and/or environment issues (particulate fallout onto waterways, adjacent fields and/or residences) our study mass, particulate and N distribution patterns results suggest that poultry litter should be allowed to age before broadcast application is attempted. PMID:24705099
Jevtić, Aleksandar; Gutiérrez, Álvaro
2011-01-01
Swarms of robots can use their sensing abilities to explore unknown environments and deploy on sites of interest. In this task, a large number of robots is more effective than a single unit because of their ability to quickly cover the area. However, the coordination of large teams of robots is not an easy problem, especially when the resources for the deployment are limited. In this paper, the Distributed Bees Algorithm (DBA), previously proposed by the authors, is optimized and applied to distributed target allocation in swarms of robots. Improved target allocation in terms of deployment cost efficiency is achieved through optimization of the DBA’s control parameters by means of a Genetic Algorithm. Experimental results show that with the optimized set of parameters, the deployment cost measured as the average distance traveled by the robots is reduced. The cost-efficient deployment is in some cases achieved at the expense of increased robots’ distribution error. Nevertheless, the proposed approach allows the swarm to adapt to the operating conditions when available resources are scarce. PMID:22346677
Jevtić, Aleksandar; Gutiérrez, Alvaro
2011-01-01
Swarms of robots can use their sensing abilities to explore unknown environments and deploy on sites of interest. In this task, a large number of robots is more effective than a single unit because of their ability to quickly cover the area. However, the coordination of large teams of robots is not an easy problem, especially when the resources for the deployment are limited. In this paper, the distributed bees algorithm (DBA), previously proposed by the authors, is optimized and applied to distributed target allocation in swarms of robots. Improved target allocation in terms of deployment cost efficiency is achieved through optimization of the DBA's control parameters by means of a genetic algorithm. Experimental results show that with the optimized set of parameters, the deployment cost measured as the average distance traveled by the robots is reduced. The cost-efficient deployment is in some cases achieved at the expense of increased robots' distribution error. Nevertheless, the proposed approach allows the swarm to adapt to the operating conditions when available resources are scarce. PMID:22346677
Determination of the age distribution of sea ice from Lagrangian observations of ice motion
Kwok, R.; Cunningham, G.F.; Rothrock, D.A.; Stern, H.L.
1995-03-01
A procedure for monitoring the local age distribution of the Arctic sea ice cover is presented. The age distribution specifies the area covered by ice in different age classes. In the authors` approach, a regular array of grid points is defined initially on the first image of a long time series, and an ice tracker finds the positions of those points in all subsequent images of the series. These Lagrangian points mark the corners of a set of cells that move and deform with the ice cover. The area of each cell changes with each new image or time step. A positive change indicates that ice in a new age class was formed in the cell. A negative change is assumed to have ridged the youngest ice in the cell, reducing its area. The ice in each cell ages as it progresses through the time series. The area of multiyear ice in each cell is computed using an ice classification algorithm. Any area that is not accounted for by the young ice or multiyear ice is assigned to a category of older first-year ice. They thus have a fine age resolution in the young end of the age distribution, and coarse resolution for older ice. The age distribution of the young ice can be converted to a thickness distribution using a simple empirical relation between accumulated freezing-degree days and ice thickness, or using a more complicated thermodynamic model. They describe a general scheme for implementing this procedure for the Arctic Ocean from fall freeze-up until the onset of melt in the spring. The concept is illustrated with a time series of five ERS-1 SAR images spanning a period of 12 days. Such a scheme could be implemented with RADARSAT SAR imagery to provide basin-wide ice age and thickness information.
An approximation theory for the identification of nonlinear distributed parameter systems
NASA Technical Reports Server (NTRS)
Banks, H. T.; Reich, Simeon; Rosen, I. G.
1990-01-01
An abstract approximation framework for the identification of nonlinear distributed parameter systems is developed. Inverse problems for nonlinear systems governed by strongly maximal monotone operators (satisfying a mild continuous dependence condition with respect to the unknown parameters to be identified) are treated. Convergence of Galerkin approximations and the corresponding solutions of finite dimensional approximating identification problems to a solution of the original finite dimensional identification problem is demonstrated using the theory of nonlinear evolution systems and a nonlinear analog of the Trotter-Kato appproximation result for semigroups of bounded linear operators. The nonlinear theory developed here is shown to subsume an existing linear theory as a special case. It is also shown to be applicable to a broad class of nonlinear elliptic operators and the corresponding nonlinear parabolic partial differential equations to which they lead. An application of the theory to a quasilinear model for heat conduction or mass transfer is discussed.
An approximation theory for the identification of nonlinear distributed parameter systems
NASA Technical Reports Server (NTRS)
Banks, H. T.; Reich, Simeon; Rosen, I. G.
1988-01-01
An abstract approximation framework for the identification of nonlinear distributed parameter systems is developed. Inverse problems for nonlinear systems governed by strongly maximal monotone operators (satisfying a mild continuous dependence condition with respect to the unknown parameters to be identified) are treated. Convergence of Galerkin approximations and the corresponding solutions of finite dimensional approximating identification problems to a solution of the original finite dimensional identification problem is demonstrated using the theory of nonlinear evolution systems and a nonlinear analog of the Trotter-Kato approximation result for semigroups of bounded linear operators. The nonlinear theory developed here is shown to subsume an existing linear theory as a special case. It is also shown to be applicable to a broad class of nonlinear elliptic operators and the corresponding nonlinear parabolic partial differential equations to which they lead. An application of the theory to a quasilinear model for heat conduction or mass transfer is discussed.
Costabel, Stephan; Yaramanci, Ugur
2013-04-01
[1] For characterizing water flow in the vadose zone, the water retention curve (WRC) of the soil must be known. Because conventional WRC measurements demand much time and effort in the laboratory, alternative methods with shortened measurement duration are desired. The WRC can be estimated, for instance, from the cumulative pore size distribution (PSD) of the investigated material. Geophysical applications of nuclear magnetic resonance (NMR) relaxometry have successfully been applied to recover PSDs of sandstones and limestones. It is therefore expected that the multiexponential analysis of the NMR signal from water-saturated loose sediments leads to a reliable estimation of the WRC. We propose an approach to estimate the WRC using the cumulative NMR relaxation time distribution and approximate it with the well-known van-Genuchten (VG) model. Thereby, the VG parameter n, which controls the curvature of the WRC, is of particular interest, because it is the essential parameter to predict the relative hydraulic conductivity. The NMR curves are calibrated with only two conventional WRC measurements, first, to determine the residual water content and, second, to define a fixed point that relates the relaxation time to a corresponding capillary pressure. We test our approach with natural and artificial soil samples and compare the NMR-based results to WRC measurements using a pressure plate apparatus and to WRC predictions from the software ROSETTA. We found that for sandy soils n can reliably be estimated with NMR, whereas for samples with clay and silt contents higher than 10% the estimation fails. This is the case when the hydraulic properties of the soil are mainly controlled by the pore constrictions. For such samples, the sensitivity of the NMR method for the pore bodies hampers a plausible WRC estimation. Citation: Costabel, S., and U. Yaramanci (2013), Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions, Water
NASA Astrophysics Data System (ADS)
Engdahl, N. B.; Maxwell, R. M.
2013-12-01
Descriptions of age in hydrologic systems are often limited to the residence time in the surface water system or the subsurface with little consideration of the interaction between the two, or the different ways geochemical tracers are altered in each domain. Understanding the way tracer concentrations change in each domain is essential to accurate estimation of age, but few models have explicitly modeled the fully coupled system or considered distributions of age. This work presents a numerical laboratory that is specifically designed to investigate composite age distributions (CADs) and their connections to tracer concentrations. The CAD is defined here as the combination of the residence time distributions for surface flows, vadose zone, and groundwater systems, providing an accounting for the total time a discrete fluid parcel has spent within the integrated hydrologic system. CADs are generated by particle tracking through a fully integrated flow model and it is straight forward to realistically simulate the transport of environmental tracers such as 85-Krypton and 39-Argon that can be used for estimating water ages. This framework allows explicit modeling of the different processes in each domain that affect tracer concentrations including the mixing of different source waters, partial equilibrium with the atmosphere through the vadose zone, evaporative enrichment in surface flows, and diffusive fractionation in the subsurface. Transient forcings, such as seasonal or daily variations in precipitation, can also be simulated and the effects of this transience on concentrations and age distributions can easily be investigated. The model domain used to demonstrate these tools is based on a well-defined watershed within Rocky Mountain National Park. The mountain pine beetle has devastated the park's forests and the massive tree-kill has begun to affect the quality and distribution of the water resources. Accurate modeling of the CADs in the park is a crucial step
Synoptic thermal and oceanographic parameter distributions in the New York Bight Apex
NASA Technical Reports Server (NTRS)
Johnson, R. W.; Bahn, G. S.; Thomas, J. P.
1981-01-01
Concurrent surface water measurements made from a moving oceanographic research vessel were used to calibrate and interpret remotely sensed data collected over a plume in the New York Bight Apex on 23 June 1977. Multiple regression techniques were used to develop equations to map synoptic distributions of chlorophyll a and total suspended matter in the remotely sensed scene. Thermal (which did not have surface calibration values) and water quality parameter distributions indicated a cold mass of water in the Bight Apex with an overflowing nutrient-rich warm water plume that originated in the Sandy Hook Bay and flowed south near the New Jersey shoreline. Data analysis indicates that remotely sensed data may be particularly useful for studying physical and biological processes in the top several metres of surface water at plume boundaries.
Universal scaling of the order-parameter distribution in strongly disordered superconductors
NASA Astrophysics Data System (ADS)
Lemarié, G.; Kamlapure, A.; Bucheli, D.; Benfatto, L.; Lorenzana, J.; Seibold, G.; Ganguli, S. C.; Raychaudhuri, P.; Castellani, C.
2013-05-01
We investigate theoretically and experimentally the statistical properties of the inhomogeneous order-parameter distribution (OPD) at the verge of the superconductor-insulator transition (SIT). We find within two prototype fermionic and bosonic models for disordered superconductors that one can identify a universal rescaling of the OPD. By performing scanning-tunneling microscopy experiments in three samples of NbN with increasing disorder we show that such a rescaling also describes the experimental data with excellent accuracy. These results can provide a breakthrough in our understanding of the SIT.
Factorization and the synthesis of optimal feedback gains for distributed parameter systems
NASA Technical Reports Server (NTRS)
Milman, Mark H.; Scheid, Robert E.
1990-01-01
An approach based on Volterra factorization leads to a new methodology for the analysis and synthesis of the optimal feedback gain in the finite-time linear quadratic control problem for distributed parameter systems. The approach circumvents the need for solving and analyzing Riccati equations and provides a more transparent connection between the system dynamics and the optimal gain. The general results are further extended and specialized for the case where the underlying state is characterized by autonomous differential-delay dynamics. Numerical examples are given to illustrate the second-order convergence rate that is derived for an approximation scheme for the optimal feedback gain in the differential-delay problem.
OPTIMAL SHRINKAGE ESTIMATION OF MEAN PARAMETERS IN FAMILY OF DISTRIBUTIONS WITH QUADRATIC VARIANCE
Xie, Xianchao; Kou, S. C.; Brown, Lawrence
2015-01-01
This paper discusses the simultaneous inference of mean parameters in a family of distributions with quadratic variance function. We first introduce a class of semi-parametric/parametric shrinkage estimators and establish their asymptotic optimality properties. Two specific cases, the location-scale family and the natural exponential family with quadratic variance function, are then studied in detail. We conduct a comprehensive simulation study to compare the performance of the proposed methods with existing shrinkage estimators. We also apply the method to real data and obtain encouraging results. PMID:27041778
NASA Astrophysics Data System (ADS)
Wang, C.; Rubin, Y.
2014-12-01
Spatial distribution of important geotechnical parameter named compression modulus Es contributes considerably to the understanding of the underlying geological processes and the adequate assessment of the Es mechanics effects for differential settlement of large continuous structure foundation. These analyses should be derived using an assimilating approach that combines in-situ static cone penetration test (CPT) with borehole experiments. To achieve such a task, the Es distribution of stratum of silty clay in region A of China Expo Center (Shanghai) is studied using the Bayesian-maximum entropy method. This method integrates rigorously and efficiently multi-precision of different geotechnical investigations and sources of uncertainty. Single CPT samplings were modeled as a rational probability density curve by maximum entropy theory. Spatial prior multivariate probability density function (PDF) and likelihood PDF of the CPT positions were built by borehole experiments and the potential value of the prediction point, then, preceding numerical integration on the CPT probability density curves, the posterior probability density curve of the prediction point would be calculated by the Bayesian reverse interpolation framework. The results were compared between Gaussian Sequential Stochastic Simulation and Bayesian methods. The differences were also discussed between single CPT samplings of normal distribution and simulated probability density curve based on maximum entropy theory. It is shown that the study of Es spatial distributions can be improved by properly incorporating CPT sampling variation into interpolation process, whereas more informative estimations are generated by considering CPT Uncertainty for the estimation points. Calculation illustrates the significance of stochastic Es characterization in a stratum, and identifies limitations associated with inadequate geostatistical interpolation techniques. This characterization results will provide a multi
NASA Astrophysics Data System (ADS)
van Dijk, A. I. J. M.; Meesters, A. G. C. A.; Schellekens, J.; Bruijnzeel, L. A.
2005-01-01
Most runoff and erosion models require rainfall intensity data of high temporal resolution, which restricts their application and predictive potential. In this paper, a simple exponential rainfall depth-intensity distribution (ERDID) was tested, involving only two storm characteristics that are easily calculated from rainfall intensity measurements: rainfall depth ( P) and depth-averaged rainfall intensity ( Ř). This distribution fitted well to tipping bucket rainfall intensity measurements during 30 storms of 33-81 mm in West Java, Indonesia. The ERDID was used to derive analytical expressions for the hydrological model variables of two commonly used erosion models, i.e. the 'R' factor in RUSLE and normalised soil loss in GUEST. The ERDID-based expressions reproduced hydrological variables for the 30 storms with high accuracy for both models (mean difference of ±4-17% for individual storms and between -2 and 14% on aggregate). A comparison of results obtained with the original (high temporal resolution) measurements and data resampled into 5-min intervals shows that resampling had a significant effect on calculations with the original models (cumulative values were decreased by 2-26%). In some cases the use of ERDID-based expressions with distribution parameters calculated from resampled data partially corrected this underestimation. The proposed rainfall depth-intensity distribution combines physically meaningful, clearly defined variables with theoretical simplicity and high descriptive accuracy and so provides a good scope for further application in runoff and erosion modelling.
NASA Technical Reports Server (NTRS)
Armand, J. P.
1972-01-01
An extension of classical methods of optimal control theory for systems described by ordinary differential equations to distributed-parameter systems described by partial differential equations is presented. An application is given involving the minimum-mass design of a simply-supported shear plate with a fixed fundamental frequency of vibration. An optimal plate thickness distribution in analytical form is found. The case of a minimum-mass design of an elastic sandwich plate whose fundamental frequency of free vibration is fixed. Under the most general conditions, the optimization problem reduces to the solution of two simultaneous partial differential equations involving the optimal thickness distribution and the modal displacement. One equation is the uniform energy distribution expression which was found by Ashley and McIntosh for the optimal design of one-dimensional structures with frequency constraints, and by Prager and Taylor for various design criteria in one and two dimensions. The second equation requires dynamic equilibrium at the preassigned vibration frequency.
Baverel, Paul G; Savic, Radojka M; Karlsson, Mats O
2011-02-01
When parameter estimates are used in predictions or decisions, it is important to consider the magnitude of imprecision associated with the estimation. Such imprecision estimates are, however, presently lacking for nonparametric algorithms intended for nonlinear mixed effects models. The objective of this study was to develop resampling-based methods for estimating imprecision in nonparametric distribution (NPD) estimates obtained in NONMEM. A one-compartment PK model was used to simulate datasets for which the random effect of clearance conformed to a (i) normal (ii) bimodal and (iii) heavy-tailed underlying distributional shapes. Re-estimation was conducted assuming normality under FOCE, and NPDs were estimated sequential to this step. Imprecision in the NPD was then estimated by means of two different resampling procedures. The first (full) method relies on bootstrap sampling from the raw data and a re-estimation of both the preceding parametric (FOCE) and the nonparametric step. The second (simplified) method relies on bootstrap sampling of individual nonparametric probability distributions. Nonparametric 95% confidence intervals (95% CIs) were obtained and mean errors (MEs) of the 95% CI width were computed. Standard errors (SEs) of nonparametric population estimates were obtained using the simplified method and evaluated through 100 stochastic simulations followed by estimations (SSEs). Both methods were successfully implemented to provide imprecision estimates for NPDs. The imprecision estimates adequately reflected the reference imprecision in all distributional cases and regardless of the numbers of individuals in the original data. Relative MEs of the 95% CI width of CL marginal density when original data contained 200 individuals were equal to: (i) -22 and -12%, (ii) -22 and -9%, (iii) -13 and -5% for the full and simplified (n = 100), respectively. SEs derived from the simplified method were consistent with the ones obtained from 100 SSEs. In conclusion
NASA Astrophysics Data System (ADS)
Müller, Markus; Meztler, Holger; Glatt, Anna; Sierra, Carlos
2016-04-01
We present theoretical methods to compute dynamic residence and transit time distributions for non-autonomous systems of pools governed by coupled nonlinear differential equations. Although transit time and age distributions have been used to describe reservoir models for a long time, a closer look to their assumptions reveals two major restrictions of generality in previous studies. First, the systems are assumed to be in equilibrium; and second, the equations under consideration are assumed to be linear. While both these assumptions greatly ease the computation and interpretation of transit time and age distributions they are not applicable to a wide range of problems. Moreover, the transfer of previous results learned from linear systems in steady state to the more complex nonlinear non-autonomous systems that do not even need to have equilibria, can be dangerously misleading. Fortunately the topic of time dependent age and transit time distributions has received some attention recently in hydrology, we aim to compute these distributions for systems of multiple reservoirs. We will discuss how storage selection functions can augment the information represented in an ODE system describing a system of reservoirs. We will present analytical and numerical algorithms and a Monte Carlo simulator to compute solutions for system transit time and age distributions for system-wide storage selection functions including the most simple, but important case of well mixed pools.