Inference in high-dimensional parameter space.
O'Hare, Anthony
2015-11-01
Model parameter inference has become increasingly popular in recent years in the field of computational epidemiology, especially for models with a large number of parameters. Techniques such as Approximate Bayesian Computation (ABC) or maximum/partial likelihoods are commonly used to infer parameters in phenomenological models that best describe some set of data. These techniques rely on efficient exploration of the underlying parameter space, which is difficult in high dimensions, especially if there are correlations between the parameters in the model that may not be known a priori. The aim of this article is to demonstrate the use of the recently invented Adaptive Metropolis algorithm for exploring parameter space in a practical way through the use of a simple epidemiological model. PMID:26176624
Physiological parameters in space settlement design
NASA Technical Reports Server (NTRS)
Billingham, J.
1977-01-01
One of the major goals of space settlement design is the provision of an environment which will allow full health and effective performance for all members of the population. Attention is given to questions concerning an alternation of 1 G-0 G environment, the physiology of weightlessness, the transit between earth and settlement, research on physiological parameters, and the need for a sensitivity analysis.
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.
A Tool for Parameter-space Explorations
NASA Astrophysics Data System (ADS)
Murase, Yohsuke; Uchitane, Takeshi; Ito, Nobuyasu
A software for managing simulation jobs and results, named "OACIS", is presented. It controls a large number of simulation jobs executed in various remote servers, keeps these results in an organized way, and manages the analyses on these results. The software has a web browser front end, and users can submit various jobs to appropriate remote hosts from a web browser easily. After these jobs are finished, all the result files are automatically downloaded from the computational hosts and stored in a traceable way together with the logs of the date, host, and elapsed time of the jobs. Some visualization functions are also provided so that users can easily grasp the overview of the results distributed in a high-dimensional parameter space. Thus, OACIS is especially beneficial for the complex simulation models having many parameters for which a lot of parameter searches are required. By using API of OACIS, it is easy to write a code that automates parameter selection depending on the previous simulation results. A few examples of the automated parameter selection are also demonstrated.
Parameter space for successful soccer kicks
NASA Astrophysics Data System (ADS)
Cook, Brandon G.; Goff, John Eric
2006-07-01
A computational model of two important types of soccer kicks, the free kick and the corner kick, is developed with the goal of determining the success rate for each type of kick. What is meant by 'success rate' is the probability of getting an unassisted goal via a free kick and the probability of having a corner kick reach an optimum location so that a teammate's chance of scoring a goal is increased. Success rates are determined through the use of four-dimensional parameter space volumes. A one-in-ten success rate is found for the free kick while the corner-kick success rate is found to be one in four.
Physical parameters affecting living cells in space.
Langbein, D
1986-01-01
The question is posed: Why does a living cell react to the absence of gravity? What sensors may it have? Does it note pressure, sedimentation, convection, or other parameters? If somewhere in a liquid volume sodium ions are replaced by potassium ions, the density of the liquid changes locally: the heavier regions sink, the lighter regions rise. This may contribute to species transport, to the metabolism. Under microgravity this mechanism is strongly reduced. On the other hand, other reasons for convection like thermal and solutal interface convection are left. Do they affect species transport? Another important effect of gravity is the hydrostatic pressure. On the macroscopic side, the pressure between our head and feet changes by 0.35 atmospheres. On the microscopic level the hydrostatic pressure on the upper half of a cell membrane is lower than on the lower half. This, by affecting the ion transport through the membrane, may change the surrounding electric potential. It has been suggested to be one of the reasons for graviperception. Following the discussion of these and other effects possibly important in life sciences in space, an order of magnitude analysis of the residual accelerations tolerable during experiments in materials sciences is outlined. In the field of life sciences only rough estimates are available at present. PMID:11537842
Global Model Analysis by Parameter Space Partitioning
ERIC Educational Resources Information Center
Pitt, Mark A.; Kim, Woojae; Navarro, Daniel J.; Myung, Jay I.
2006-01-01
To model behavior, scientists need to know how models behave. This means learning what other behaviors a model can produce besides the one generated by participants in an experiment. This is a difficult problem because of the complexity of psychological models (e.g., their many parameters) and because the behavioral precision of models (e.g.,…
Supersymmetric parameter space of family symmetries
Velasco-Sevilla, L.
2008-11-23
In this talk I have emphasized the effects of considering departures from the minimal flavour violation conditions, in the context of CMSSM-like theories, introduced by boundary conditions at GUT scale from Family Symmetries. In [1] we have shown the results of running these conditions down to EW, where constraints from fermion masses and CKM matrix elements have been used. Only when the expansion parameter in the sdown-squark sector is relatively large it is possible to relax the lower limit from b{yields}s{gamma} on the universal gaugino mass. The expansion parameter associated with the slepton sector needs to be smaller than the analogous in the sdown-squark sector in order to satisfy the bound imposed by the decay of {tau}{yields}{mu}{mu}.
Atlas performance and imploding liner parameter space
Reinovsky, R.; Lindemuth, I. R.; Atchison, W. L.; Cochrane, J. C. , Jr.; Faehl, R. J.
2002-01-01
Ultra-high magnetic fields have many applications in the confining and controlling plasmas and in exploring electron physics as manifested in the magnetic properties of materials. Another application of high fields is the acceleration of metal conductors to velocities higher than that achievable with conventional high explosive drive or gas guns. The Atlas pulse power system is the world's first pulse power system specifically designed to implode solid and near-solid density metal liners for use in pulse power hydrodynamic experiments. This paper describes the Atlas system during the first year of its operational life at Los Alamos, (comprising 10-15 implosion experiments); describes circuit models that adequately predicted the bulk kinematic behavior of liner implosions; and shows how those (now validated) models can be used to describe the range of parameters accessible through Atlas implosions.
Mission planning parameters for the Space Shuttle large format camera
NASA Technical Reports Server (NTRS)
Wood, G. A.
1979-01-01
The paper discusses the impact of various Space Shuttle mission parameters on the efficient and meaningful utilization of the large format camera (LFC) as a photographic acquisition system. Some of the LFC's vital statistics and its mounting within the Orbiter payload are described. LFC characteristics and mounting dictate certain mission parameters. The controlling parameters are orbit inclinations, launch time of year, launch time of day, orbital altitude, mission duration, overlap selection, film capacity, and climatological prediction. A mission case is evaluated relative to controlling parameters and geographical area(s) of interest.
Phase-space rotations and orbital Stokes parameters.
Alieva, Tatiana; Bastiaans, Martin J
2009-02-15
We introduce the orbital Stokes parameters as a linear combination of a beam's second-order moments. Similar to the ones describing the field polarization and associated with beam energy and its spin angular momentum, the orbital Stokes parameters are related to the total beam width and its orbital angular momentum. We derive the transformation laws for these parameters during beam propagation through first-order optical systems associated with phase-space rotations. The values of the orbital Stokes parameters for Gaussian modes and arbitrary fields expressed as their linear superposition are obtained. PMID:19373324
Determining frequentist confidence limits using a directed parameter space search
Daniel, Scott F.; Connolly, Andrew J.; Schneider, Jeff
2014-10-10
We consider the problem of inferring constraints on a high-dimensional parameter space with a computationally expensive likelihood function. We propose a machine learning algorithm that maps out the Frequentist confidence limit on parameter space by intelligently targeting likelihood evaluations so as to quickly and accurately characterize the likelihood surface in both low- and high-likelihood regions. We compare our algorithm to Bayesian credible limits derived by the well-tested Markov Chain Monte Carlo (MCMC) algorithm using both multi-modal toy likelihood functions and the seven yr Wilkinson Microwave Anisotropy Probe cosmic microwave background likelihood function. We find that our algorithm correctly identifies the location, general size, and general shape of high-likelihood regions in parameter space while being more robust against multi-modality than MCMC.
Estimability of geodetic parameters from space VLBI observables
NASA Technical Reports Server (NTRS)
Adam, Jozsef
1990-01-01
The feasibility of space very long base interferometry (VLBI) observables for geodesy and geodynamics is investigated. A brief review of space VLBI systems from the point of view of potential geodetic application is given. A selected notational convention is used to jointly treat the VLBI observables of different types of baselines within a combined ground/space VLBI network. The basic equations of the space VLBI observables appropriate for convariance analysis are derived and included. The corresponding equations for the ground-to-ground baseline VLBI observables are also given for a comparison. The simplified expression of the mathematical models for both space VLBI observables (time delay and delay rate) include the ground station coordinates, the satellite orbital elements, the earth rotation parameters, the radio source coordinates, and clock parameters. The observation equations with these parameters were examined in order to determine which of them are separable or nonseparable. Singularity problems arising from coordinate system definition and critical configuration are studied. Linear dependencies between partials are analytically derived. The mathematical models for ground-space baseline VLBI observables were tested with simulation data in the frame of some numerical experiments. Singularity due to datum defect is confirmed.
Extreme Meteorological Parameters During Space Shuttle Pad Exposure Periods
NASA Technical Reports Server (NTRS)
Roberts, Barry C.; Overbey, B. Glenn
2004-01-01
During the 113 missions of the Space Transportation System (STS), the Space Shuttle fleet has been exposed to the elements on the launch pad for a total of 4195 days. This paper provides a summary of the historical record of the meteorological extremes encountered by the Space Shuttle fleet during the pad exposure period. Parameters included are temperature, dew point, relative humidity, wind speed, sea level pressure and precipitation. All the data presented are archived by the Marshall Space Flight Center Environments Group, and were obtained from a combination of surface observations and meteorological towers at Kennedy Space Center (KSC), Florida. Data are provided from the first launch of the STS in 1981 through the launch of STS-107 in 2003.
Held, Christian; Nattkemper, Tim; Palmisano, Ralf; Wittenberg, Thomas
2013-01-01
Introduction: Research and diagnosis in medicine and biology often require the assessment of a large amount of microscopy image data. Although on the one hand, digital pathology and new bioimaging technologies find their way into clinical practice and pharmaceutical research, some general methodological issues in automated image analysis are still open. Methods: In this study, we address the problem of fitting the parameters in a microscopy image segmentation pipeline. We propose to fit the parameters of the pipeline's modules with optimization algorithms, such as, genetic algorithms or coordinate descents, and show how visual exploration of the parameter space can help to identify sub-optimal parameter settings that need to be avoided. Results: This is of significant help in the design of our automatic parameter fitting framework, which enables us to tune the pipeline for large sets of micrographs. Conclusion: The underlying parameter spaces pose a challenge for manual as well as automated parameter optimization, as the parameter spaces can show several local performance maxima. Hence, optimization strategies that are not able to jump out of local performance maxima, like the hill climbing algorithm, often result in a local maximum. PMID:23766941
Mutagenesis by outer space parameters other than cosmic rays
NASA Astrophysics Data System (ADS)
Horneck, Gerda; Rabbow, Elke
We have studied the ability of microorganisms to cope with the complex interplay of the parameters of space in experiments in low Earth orbit and using space simulation facilities on ground. Emphasis was laid on space parameters other than cosmic rays. The studies are directed towards understanding prebiotic chemical evolution and biological evolution processes, and interplanetary transfer of life. Effects of space vacuum: Space experiments have shown that up to 70% of bacterial and fungal spores survived short-term exposure to space vacuum. The chances of survival in space were increased when spores were embedded in chemical protectants such as sugars, or salt crystals, or when they were exposed in multilayer. During the six years lasting LDEF mission up to 80% of bacterial spores survived exposure to space vacuum. A 10-fold increased mutation rate over the spontaneous rate has been observed in spores of Bacillus subtilis after exposure to space vacuum, which is probably based on a unique molecular signature of tandem-double base change at restricted sites in the DNA. In addition, DNA strand breaks have been observed to be induced by vacuum treatment. Effects of extraterrestrial solar UV radiation: Solar UV radiation has been found to be the most deleterious factor of space. The reason for this is the highly energetic UV-C and vacuum UV radiation that is directly absorbed by the DNA and which induces specific photoproducts in the DNA that are highly mutagenic and lethal. The damaging effect of extraterrestrial solar UV radiation was even aggravated, when the spores were simultaneously exposed to both, solar UV radiation and space vacuum. In order to investigate the mutagenic potential of solar UV radiation, DNA of the Escherichia coli plasmid pUC19 was exposed to selected wavebands of UV radiation (from vacuum UV to UV-A) by use of a solar simulator and space simulation facilities. Action spectra revealed that for vacuum UV different kinds of photochemical damage
Parameter space of the Rulkov chaotic neuron model
NASA Astrophysics Data System (ADS)
Wang, Caixia; Cao, Hongjun
2014-06-01
The parameter space of the two dimensional Rulkov chaotic neuron model is taken into account by using the qualitative analysis, the co-dimension 2 bifurcation, the center manifold theorem, and the normal form. The goal is intended to clarify analytically different dynamics and firing regimes of a single neuron in a two dimensional parameter space. Our research demonstrates the origin that there exist very rich nonlinear dynamics and complex biological firing regimes lies in different domains and their boundary curves in the two dimensional parameter plane. We present the parameter domains of fixed points, the saddle-node bifurcation, the supercritical/subcritical Neimark-Sacker bifurcation, stability conditions of non hyperbolic fixed points and quasiperiodic solutions. Based on these parameter domains, it is easy to know that the Rulkov chaotic neuron model can produce what kinds of firing regimes as well as their transition mechanisms. These results are very useful for building-up a large-scale neuron network with different biological functional roles and cognitive activities, especially in establishing some specific neuron network models of neurological diseases.
A new parameter space study of cosmological microlensing
NASA Astrophysics Data System (ADS)
Vernardos, G.; Fluke, C. J.
2013-09-01
Cosmological gravitational microlensing is a useful technique for understanding the structure of the inner parts of a quasar, especially the accretion disc and the central supermassive black hole. So far, most of the cosmological microlensing studies have focused on single objects from ˜90 currently known lensed quasars. However, present and planned all-sky surveys are expected to discover thousands of new lensed systems. Using a graphics processing unit (GPU) accelerated ray-shooting code, we have generated 2550 magnification maps uniformly across the convergence (κ) and shear (γ) parameter space of interest to microlensing. We examine the effect of random realizations of the microlens positions on map properties such as the magnification probability distribution (MPD). It is shown that for most of the parameter space a single map is representative of an average behaviour. All of the simulations have been carried out on the GPU Supercomputer for Theoretical Astrophysics Research.
Space geodetic techniques for global modeling of ionospheric peak parameters
NASA Astrophysics Data System (ADS)
Alizadeh, M. Mahdi; Schuh, Harald; Schmidt, Michael
The rapid development of new technological systems for navigation, telecommunication, and space missions which transmit signals through the Earth’s upper atmosphere - the ionosphere - makes the necessity of precise, reliable and near real-time models of the ionospheric parameters more crucial. In the last decades space geodetic techniques have turned into a capable tool for measuring ionospheric parameters in terms of Total Electron Content (TEC) or the electron density. Among these systems, the current space geodetic techniques, such as Global Navigation Satellite Systems (GNSS), Low Earth Orbiting (LEO) satellites, satellite altimetry missions, and others have found several applications in a broad range of commercial and scientific fields. This paper aims at the development of a three-dimensional integrated model of the ionosphere, by using various space geodetic techniques and applying a combination procedure for computation of the global model of electron density. In order to model ionosphere in 3D, electron density is represented as a function of maximum electron density (NmF2), and its corresponding height (hmF2). NmF2 and hmF2 are then modeled in longitude, latitude, and height using two sets of spherical harmonic expansions with degree and order 15. To perform the estimation, GNSS input data are simulated in such a way that the true position of the satellites are detected and used, but the STEC values are obtained through a simulation procedure, using the IGS VTEC maps. After simulating the input data, the a priori values required for the estimation procedure are calculated using the IRI-2012 model and also by applying the ray-tracing technique. The estimated results are compared with F2-peak parameters derived from the IRI model to assess the least-square estimation procedure and moreover, to validate the developed maps, the results are compared with the raw F2-peak parameters derived from the Formosat-3/Cosmic data.
Pseudohyphal variations of yeasts exposed to specific space flight parameters.
Volz, P A; Hunter, R L
1998-01-01
Phenotypes of Saccharomyces cerevisiae and Rhodotorula rubra exposed to specific parameters of space flight, which were measured both quantitatively and qualitatively, produced variations in pseudohyphal formation. Both the length of the parent and branch psuedohyphal filaments varied according to specific wavelengths and energy levels of UV light exposures when phenotypic isolates were compared with the parent or ground control isolate of each yeast species. PMID:9881461
Global Characterization of Model Parameter Space Using Information Topology
NASA Astrophysics Data System (ADS)
Transtrum, Mark
A generic parameterized model is a mapping between parameters and data and is naturally interpreted as a prediction manifold embedded in data space. In this interpretation, known as Information Geometry, the Fisher Information Matrix (FIM) is a Riemannian metric that measures the identifiability of the model parameters. Varying the experimental conditions (e.g., times at which measurements are made) alters both the FIM and the geometric properties of the model. However, several global features of the model manifold (e.g., edges and corners) are invariant to changes in experimental conditions as long as the FIM is not singular. Invariance of these features to changing experimental conditions generates an ''Information Topology'' that globally characterizes a model's parameter space and reflects the underlying physical principles from which the model was derived. Understanding a model's information topology can give insights into the emergent physics that controls a system's collective behavior, identify reduced models and describe the relationship among them, and determine which parameter combinations will be difficult to identify for various experimental conditions.
The Space Weather Effect of Interplanetary Shock Parameters
NASA Astrophysics Data System (ADS)
Li, Changxing; Wang, Chi
The ring current is the key element in the magnetic storms in the near-Earth space which absorbs and stores geomagnetic storm energy and then releases it slowly over subsequent days and weeks Understanding the structure and property of the ring current can lead to more accurate predictions of the space environment of the inner magnetosphere for the ongoing rapid development of human activities When a sudden increase in the solar wind dynamic pressure following an interplanetary shock IPS compresses the Earth magnetosphere the inner magnetospheric currents significantly intensify especially the ring current However how the interplanetary shock triggers the magnetic storm and how it affects the intensification and the decay of the ring current are not fully understood For this purpose we statistically study how critical parameters of an IPS such as the orientation and the strength of the IPS correlate with the geomagnetic indices such as Dst SYM and ASY which relate to the disturbances in the ring current In order to investigate the effectiveness of an IPS on the near Earth space environment we apply Gaussian wavelet transform method to the solar wind plasma and the interplanetary magnetic field data from WIND and ACE satellites to determine the critical parameters of the IPS We have successfully identified more than 300 IPSs from the archives of WIND and ACE measurements The initial results have shows that 1 Gaussian wavelet transform method has good responses to the changing features of interplanetary shocks 2 The lag time
Describing variations of the Fisher-matrix across parameter space
NASA Astrophysics Data System (ADS)
Schäfer, Björn Malte; Reischke, Robert
2016-08-01
Forecasts in cosmology, both with Monte Carlo Markov-chain methods and with the Fisher-matrix formalism, depend on the choice of the fiducial model because both the signal strength of any observable and the model non-linearities linking observables to cosmological parameters vary in the general case. In this paper we propose a method for extrapolating Fisher-forecasts across the space of cosmological parameters by constructing a suitable basis. We demonstrate the validity of our method with constraints on a standard dark energy model extrapolated from a ΛCDM-model, as can be expected from two-bin weak lensing tomography with an Euclid-like survey, in the parameter pairs (Ωm, σ8), (Ωm, w0) and (w0, wa). Our numerical results include very accurate extrapolations across a wide range of cosmological parameters in terms of shape, size and orientation of the parameter likelihood, and a decomposition of the change of the likelihood contours into modes, which are straightforward to interpret in a geometrical way. We find that in particular the variation of the dark energy figure of merit is well captured by our formalism.
Order parameter aided phase space exploration under extreme conditions
NASA Astrophysics Data System (ADS)
Samanta, Amit; Hamel, Sebastian; Schwegler, Eric
Efficient exploration of configuration space and identification of metastable structures in condensed phase systems are challenging from both computational as well as algorithmic perspectives. In this talk I will illustrate how we can extend the recently proposed order-parameter aided temperature accelerated sampling schemes to efficiently and systematically explore free energy surfaces, and search for metastable states and reaction pathways within the framework of density functional theory based molecular dynamics. I will illustrate how this sampling scheme can be used to explore the relevant parts of configuration space in prototypical materials, like SiO2 and identify the different metastable structures, transition pathways and phase boundaries. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Parameter space of experimental chaotic circuits with high-precision control parameters.
de Sousa, Francisco F G; Rubinger, Rero M; Sartorelli, José C; Albuquerque, Holokx A; Baptista, Murilo S
2016-08-01
We report high-resolution measurements that experimentally confirm a spiral cascade structure and a scaling relationship of shrimps in the Chua's circuit. Circuits constructed using this component allow for a comprehensive characterization of the circuit behaviors through high resolution parameter spaces. To illustrate the power of our technological development for the creation and the study of chaotic circuits, we constructed a Chua circuit and study its high resolution parameter space. The reliability and stability of the designed component allowed us to obtain data for long periods of time (∼21 weeks), a data set from which an accurate estimation of Lyapunov exponents for the circuit characterization was possible. Moreover, this data, rigorously characterized by the Lyapunov exponents, allows us to reassure experimentally that the shrimps, stable islands embedded in a domain of chaos in the parameter spaces, can be observed in the laboratory. Finally, we confirm that their sizes decay exponentially with the period of the attractor, a result expected to be found in maps of the quadratic family. PMID:27586603
Parameter space of experimental chaotic circuits with high-precision control parameters
NASA Astrophysics Data System (ADS)
de Sousa, Francisco F. G.; Rubinger, Rero M.; Sartorelli, José C.; Albuquerque, Holokx A.; Baptista, Murilo S.
2016-08-01
We report high-resolution measurements that experimentally confirm a spiral cascade structure and a scaling relationship of shrimps in the Chua's circuit. Circuits constructed using this component allow for a comprehensive characterization of the circuit behaviors through high resolution parameter spaces. To illustrate the power of our technological development for the creation and the study of chaotic circuits, we constructed a Chua circuit and study its high resolution parameter space. The reliability and stability of the designed component allowed us to obtain data for long periods of time (˜21 weeks), a data set from which an accurate estimation of Lyapunov exponents for the circuit characterization was possible. Moreover, this data, rigorously characterized by the Lyapunov exponents, allows us to reassure experimentally that the shrimps, stable islands embedded in a domain of chaos in the parameter spaces, can be observed in the laboratory. Finally, we confirm that their sizes decay exponentially with the period of the attractor, a result expected to be found in maps of the quadratic family.
Flavor Data Constraints on the SUSY Parameter Space
Mahmoudi, Farvah
2008-11-23
We present an overview of the indirect constraints from flavor physics on supersymmetric models. During the past few years flavor data, and in particular b{yields}s{gamma} transitions, have been extensively used in order to constrain supersymmetric parameter spaces. We will briefly illustrate here the constraints obtained by a collection of low energy observables including FCNC transitions, rare decays, leptonic and semileptonic decays of B mesons, as well as leptonic decays of K mesons. The theoretical predictions can be obtained using the computer program SuperIso.
Multidimensional Optimization of Signal Space Distance Parameters in WLAN Positioning
Brković, Milenko; Simić, Mirjana
2014-01-01
Accurate indoor localization of mobile users is one of the challenging problems of the last decade. Besides delivering high speed Internet, Wireless Local Area Network (WLAN) can be used as an effective indoor positioning system, being competitive both in terms of accuracy and cost. Among the localization algorithms, nearest neighbor fingerprinting algorithms based on Received Signal Strength (RSS) parameter have been extensively studied as an inexpensive solution for delivering indoor Location Based Services (LBS). In this paper, we propose the optimization of the signal space distance parameters in order to improve precision of WLAN indoor positioning, based on nearest neighbor fingerprinting algorithms. Experiments in a real WLAN environment indicate that proposed optimization leads to substantial improvements of the localization accuracy. Our approach is conceptually simple, is easy to implement, and does not require any additional hardware. PMID:24757443
No-reference image sharpness assessment in autoregressive parameter space.
Gu, Ke; Zhai, Guangtao; Lin, Weisi; Yang, Xiaokang; Zhang, Wenjun
2015-10-01
In this paper, we propose a new no-reference (NR)/blind sharpness metric in the autoregressive (AR) parameter space. Our model is established via the analysis of AR model parameters, first calculating the energy- and contrast-differences in the locally estimated AR coefficients in a pointwise way, and then quantifying the image sharpness with percentile pooling to predict the overall score. In addition to the luminance domain, we further consider the inevitable effect of color information on visual perception to sharpness and thereby extend the above model to the widely used YIQ color space. Validation of our technique is conducted on the subsets with blurring artifacts from four large-scale image databases (LIVE, TID2008, CSIQ, and TID2013). Experimental results confirm the superiority and efficiency of our method over existing NR algorithms, the stateof-the-art blind sharpness/blurriness estimators, and classical full-reference quality evaluators. Furthermore, the proposed metric can be also extended to stereoscopic images based on binocular rivalry, and attains remarkably high performance on LIVE3D-I and LIVE3D-II databases. PMID:26054063
Entropy considerations in constraining the mSUGRA parameter space
Nunez, Dario; Sussman, Roberto A.; Zavala, Jesus; Nellen, Lukas; Cabral-Rosetti, Luis G.; Mondragon, Myriam
2006-09-25
We explore the use of two criteria to constraint the allowed parameter space in mSUGRA models. Both criteria are based in the calculation of the present density of neutralinos as dark matter in the Universe. The first one is the usual ''abundance'' criterion which is used to calculate the relic density after the ''freeze-out'' era. To compute the relic density we used the numerical public code micrOMEGAs. The second criterion applies the microcanonical definition of entropy to a weakly interacting and self-gravitating gas evaluating then the change in the entropy per particle of this gas between the ''freeze-out'' era and present day virialized structures (i.e systems in virial equilibrium). An ''entropy-consistency'' criterion emerges by comparing theoretical and empirical estimates of this entropy. The main objective of our work is to determine for which regions of the parameter space in the mSUGRA model are both criteria consistent with the 2{sigma} bounds according to WMAP for the relic density: 0.0945 < {omega}CDMh2 < 0.1287. As a first result, we found that for A0 = 0, sgn{mu} +, small values of tan{beta} are not favored; only for tan{beta} {approx_equal} 50 are both criteria significantly consistent.
Emergence and spread of antibiotic resistance: setting a parameter space
Baquero, Fernando
2014-01-01
The emergence and spread of antibiotic resistance among human pathogens is a relevant problem for human health and one of the few evolution processes amenable to experimental studies. In the present review, we discuss some basic aspects of antibiotic resistance, including mechanisms of resistance, origin of resistance genes, and bottlenecks that modulate the acquisition and spread of antibiotic resistance among human pathogens. In addition, we analyse several parameters that modulate the evolution landscape of antibiotic resistance. Learning why some resistance mechanisms emerge but do not evolve after a first burst, whereas others can spread over the entire world very rapidly, mimicking a chain reaction, is important for predicting the evolution, and relevance for human health, of a given mechanism of resistance. Because of this, we propose that the emergence and spread of antibiotic resistance can only be understood in a multi-parameter space. Measuring the effect on antibiotic resistance of parameters such as contact rates, transfer rates, integration rates, replication rates, diversification rates, and selection rates, for different genes and organisms, growing under different conditions in distinct ecosystems, will allow for a better prediction of antibiotic resistance and possibilities of focused interventions. PMID:24678768
Parameter Estimation for a Model of Space-Time Rainfall
NASA Astrophysics Data System (ADS)
Smith, James A.; Karr, Alan F.
1985-08-01
In this paper, parameter estimation procedures, based on data from a network of rainfall gages, are developed for a class of space-time rainfall models. The models, which are designed to represent the spatial distribution of daily rainfall, have three components, one that governs the temporal occurrence of storms, a second that distributes rain cells spatially for a given storm, and a third that determines the rainfall pattern within a rain cell. Maximum likelihood and method of moments procedures are developed. We illustrate that limitations on model structure are imposed by restricting data sources to rain gage networks. The estimation procedures are applied to a 240-mi2 (621 km2) catchment in the Potomac River basin.
Parallel axes gear set optimization in two-parameter space
NASA Astrophysics Data System (ADS)
Theberge, Y.; Cardou, A.; Cloutier, L.
1991-05-01
This paper presents a method for optimal spur and helical gear transmission design that may be used in a computer aided design (CAD) approach. The design objective is generally taken as obtaining the most compact set for a given power input and gear ratio. A mixed design procedure is employed which relies both on heuristic considerations and computer capabilities. Strength and kinematic constraints are considered in order to define the domain of feasible designs. Constraints allowed include: pinion tooth bending strength, gear tooth bending strength, surface stress (resistance to pitting), scoring resistance, pinion involute interference, gear involute interference, minimum pinion tooth thickness, minimum gear tooth thickness, and profile or transverse contact ratio. A computer program was developed which allows the user to input the problem parameters, to select the calculation procedure, to see constraint curves in graphic display, to have an objective function level curve drawn through the design space, to point at a feasible design point and to have constraint values calculated at that point. The user can also modify some of the parameters during the design process.
Dynamical quantum Hall effect in the parameter space
Gritsev, V.; Polkovnikov, A.
2012-01-01
Geometric phases in quantum mechanics play an extraordinary role in broadening our understanding of fundamental significance of geometry in nature. One of the best known examples is the Berry phase [M.V. Berry (1984), Proc. Royal. Soc. London A, 392:45], which naturally emerges in quantum adiabatic evolution. So far the applicability and measurements of the Berry phase were mostly limited to systems of weakly interacting quasi-particles, where interference experiments are feasible. Here we show how one can go beyond this limitation and observe the Berry curvature, and hence the Berry phase, in generic systems as a nonadiabatic response of physical observables to the rate of change of an external parameter. These results can be interpreted as a dynamical quantum Hall effect in a parameter space. The conventional quantum Hall effect is a particular example of the general relation if one views the electric field as a rate of change of the vector potential. We illustrate our findings by analyzing the response of interacting spin chains to a rotating magnetic field. We observe the quantization of this response, which we term the rotational quantum Hall effect. PMID:22493228
Space-to-Space Based Relative Motion Estimation Using Direct Relative Orbit Parameters
NASA Astrophysics Data System (ADS)
Bennett, T.; Schaub, H.
There has been an increasing interest in space-based space situational awareness around satellite assets and the tracking of orbital debris. Of particular interest is the space-based tracking of objects near critical circular orbit regimes, for example near the Geostationary belt or the International Space Station. Relative orbit descriptions such as the Clohessy-Wiltshire equations describe the motion using time-varying Cartesian or curvilinear coordinates. Orbit element differences describe the unperturbed motion using constant variations of inertial orbit elements. With perturbations these only vary slowly, but can be challenging to estimate. Linearized Relative Orbit Elements (LROEs) employ invariants of the linearized relative motion, are thus constant for the unperturbed linear case, and share the benefit of the CW equations in that they directly related to space-based relative motion measurements. The variational LROE equations enable the relative orbit to be directly propagated including perturbation forces. Utilization of the invariant-inspired relative motion parameters exhibits exciting applications in relative motion sensing and control. Many methods of relative motion estimation involve the direct estimation of time-evolving position and velocity variables. Developed is an angles-only relative orbit Extended Kalman filter (EKF) navigation approach that directly estimates these nominally constant LROEs. The proposed variational equations and filtering scheme enables direct estimation of geometric parameters with clear geometric insight. Preliminary numerical simulation results demonstrate the relative orbit insight gained and speed of convergence. EKF implementations often exhibit significant sensitivity to initial conditions, however, initial results show that the LROE filter converges within fractions of an orbit with initialization errors that exceed 100 percent. The manuscript presents the invariants of motion, develops the variational equations for
Variation in the modal parameters of space structures
NASA Technical Reports Server (NTRS)
Crawley, Edward F.; Barlow, Mark S.; Van Schoor, Marthinus C.; Bicos, Andrew S.
1992-01-01
An analytic and experimental study of gravity and suspension influences on space structural test articles is presented. A modular test article including deployable, erectable, and rotary modules was assembled in three one- and two-dimensional structures. The two deployable modules utilized cable diagonal bracing rather than rigid cross members; within a bay of one of the deployable modules, the cable preload was adjustable. A friction lock was used on the alpha joint to either allow or prohibit rotary motion. Suspension systems with plunge fundamentals of 1, 2, and 5 Hz were used for ground testing to evaluate the influences of suspension stiffness. Assembly and reassembly testing was performed, as was testing on two separate shipsets at two test sites. Trends and statistical variances in modal parameters are presented as a function of force amplitude, joint preload, reassembly, shipset and suspension. Linear finite element modeling of each structure provided analytical results for 0-g unsuspended and 1-g suspended models, which are correlated with the analytical model.
Derivation of Delaware Bay tidal parameters from space shuttle photography
Zheng, Quanan; Yan, Xiaohai; Klemas, V. )
1993-06-01
The tide-related parameters of the Delaware Bay are derived from space shuttle time-series photographs. The water areas in the bay are measured from interpretation maps of the photographs with a CALCOMP 9100 digitizer and ERDAS Image Processing System. The corresponding tidal levels are calculated using the exposure time annotated on the photographs. From these data, an approximate function relating the water area to the tidal level at a reference point is determined. Based on the function, the water areas of the Delaware Bay at mean high water (MHW) and mean low water (MLW), below 0 m, and for the tidal zone are inferred. With MHW and MLW areas and the mean tidal range, the authors calculate the tidal influx of the Delaware Bay, which is 2.76 x 1O[sup 9] m[sup 3]. Furthermore, the velocity of flood tide at the bay mouth is determined using the tidal flux and an integral of the velocity distribution function at the cross section between Cape Henlopen and Cape May. The result is 132 cm/s, which compares well with the data on tidal current charts.
Temperature characteristics of silicon space solar cells and underlying parameters
NASA Technical Reports Server (NTRS)
Anspaugh, B. E.; Kachare, Ram; Garlick, G. F. J.
1987-01-01
Silicon space cells, 2 cm x 2 cm, with 10 ohm-cm p-base resistivity, 8-mil base thickness, and no back-surface fields have been investigated over the temperature range from 301 to 223 K by measurements of dark forward and reverse current-voltage characteristics and current-voltage relations under illumination. From dark forward bias data, the first and second diode saturation currents, I01 and I02, are determined and hence the base diffusion length and lifetime of minority carriers as functions of temperature. Lifetime increases exponentially with temperature and is explained by a Shockley-Read-Hall model with deep recombination levels 0.245 eV above the valence band. The I02 variation with temperature follows the Sah-Noyce-Shockley-Choo model except at low temperature where extra transitions raise the value above the predicted level. Reverse bias current at low voltage is a thermally assisted tunneling process via deep levels which are observed in base recombination at higher temperatures. The tunneling effects tend to become independent of temperature in the low-temperature region. These results demonstrate the ability to deduce basic parameters such as lifetime from simple measurements and show that back-surface fields offer no advantage at temperatures below 230 K. The analysis also explains the fall in lifetimes observed as the base conductivity increases, attributing it to native defects (perhaps carbon-oxygen-vacancy complexes) rather than the concentration of base dopant.
Two space scatterer formalism calculation of bulk parameters of thunderclouds
NASA Technical Reports Server (NTRS)
Phanord, Dieudonne D.
1994-01-01
In a previous study, we used a modified two-space scatterer formalism of Twersky to establish for a cloud modeled as a statistically homogeneous distribution of spherical water droplets, the dispersion relations that determine its bulk propagation numbers and bulk indexes of refraction in terms of the vector equivalent scattering amplitude and the dyadic scattering amplitude of the single water droplet in isolation. The results were specialized to the forward direction of scattering while demanding that the scatterers preserve the incident polarization. We apply this approach to obtain specific numerical values for the macroscopic parameters of the cloud. We work with a cloud of density rho = 100 cm(exp -3), a wavelength lambda = 0.7774 microns, and with spherical water droplets of common radius alpha = 10 microns. In addition, the scattering medium is divided into three parts, the medium outside the cloud, moist air (the medium inside the cloud but outside the droplets), and the medium inside the spherical water droplets. The results of this report are applicable to a cloud of any geometry since the boundary does not interfere with the calculations. Also, it is important to notice the plane wave nature of the incidence wave in the moist atmosphere.
NASA Astrophysics Data System (ADS)
Dumedah, G.; Berg, A. A.; Wineberg, M.
2009-12-01
Hydrological models are increasingly been calibrated using multi-objective genetic algorithms (GAs). Multi-objective GAs facilitate the evaluation of several model evaluation objectives and the examination of massive combinations of parameter sets. Usually, the outcome is a set of several equally-accurate parameter sets which make-up a trade-off surface between the objective functions often referred to as Pareto set. The Pareto set describes a decision-front in a way that each solution has unique values in parameter space with competing accuracy in objective space. An automated framework of choosing a single from such a trade-off surface has not been thoroughly investigated in the model calibration literature. As a result, this presentation will demonstrate an automated selection of robust solutions from a trade-off surface using the distribution of solutions in both objective space and parameter space. The trade-off surface was generated using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) to calibrate the Soil and Water Assessment Tool (SWAT) for streamflow simulation based on model bias and root mean square error. Our selection method generates solutions with unique properties including a representative pathway in parameter space, a basin of attraction or the center of mass in objective space, and a proximity to the origin in objective space. Additionally, our framework determines a robust solution as a balanced compromise for the distribution of solutions in objective space and parameter space. That is, the robust solution emphasizes stability in model parameter values and in objective function values in a way that similarity in parameter space implies similarity in objective space.
Searching the Force Field Electrostatic Multipole Parameter Space.
Jakobsen, Sofie; Jensen, Frank
2016-04-12
We show by tensor decomposition analyses that the molecular electrostatic potential for amino acid peptide models has an effective rank less than twice the number of atoms. This rank indicates the number of parameters that can be derived from the electrostatic potential in a statistically significant way. Using this as a guideline, we investigate different strategies for deriving a reduced set of atomic charges, dipoles, and quadrupoles capable of reproducing the reference electrostatic potential with a low error. A full combinatorial search of selected parameter subspaces for N-methylacetamide and a cysteine peptide model indicates that there are many different parameter sets capable of providing errors close to that of the global minimum. Among the different reduced multipole parameter sets that have low errors, there is consensus that atoms involved in π-bonding require higher order multipole moments. The possible correlation between multipole parameters is investigated by exhaustive searches of combinations of up to four parameters distributed in all possible ways on all possible atomic sites. These analyses show that there is no advantage in considering combinations of multipoles compared to a simple approach where the importance of each multipole moment is evaluated sequentially. When combined with possible weighting factors related to the computational efficiency of each type of multipole moment, this may provide a systematic strategy for determining a computational efficient representation of the electrostatic component in force field calculations. PMID:26925529
A note on deep space optical communication link parameters
NASA Technical Reports Server (NTRS)
Dolinar, S. J.; Yuen, J. H.
1982-01-01
Topical communication in the context of a deep space communication link. Communication link analysis at the optical frequencies differs significantly from that at microwave frequencies such as the traditional S and X-bands used in deep space applications, due to the different technology of transmitter, antenna, modulators, and receivers. In addition, the important role of quantum noise in limiting system performance is quite different than that of thermal noise. The optical link design is put in a design control table format similar to a microwave telecom link design. Key considerations unique to the optical link are discussed.
GRID-BASED EXPLORATION OF COSMOLOGICAL PARAMETER SPACE WITH SNAKE
Mikkelsen, K.; Næss, S. K.; Eriksen, H. K.
2013-11-10
We present a fully parallelized grid-based parameter estimation algorithm for investigating multidimensional likelihoods called Snake, and apply it to cosmological parameter estimation. The basic idea is to map out the likelihood grid-cell by grid-cell according to decreasing likelihood, and stop when a certain threshold has been reached. This approach improves vastly on the 'curse of dimensionality' problem plaguing standard grid-based parameter estimation simply by disregarding grid cells with negligible likelihood. The main advantages of this method compared to standard Metropolis-Hastings Markov Chain Monte Carlo methods include (1) trivial extraction of arbitrary conditional distributions; (2) direct access to Bayesian evidences; (3) better sampling of the tails of the distribution; and (4) nearly perfect parallelization scaling. The main disadvantage is, as in the case of brute-force grid-based evaluation, a dependency on the number of parameters, N{sub par}. One of the main goals of the present paper is to determine how large N{sub par} can be, while still maintaining reasonable computational efficiency; we find that N{sub par} = 12 is well within the capabilities of the method. The performance of the code is tested by comparing cosmological parameters estimated using Snake and the WMAP-7 data with those obtained using CosmoMC, the current standard code in the field. We find fully consistent results, with similar computational expenses, but shorter wall time due to the perfect parallelization scheme.
Grid-based Exploration of Cosmological Parameter Space with Snake
NASA Astrophysics Data System (ADS)
Mikkelsen, K.; Næss, S. K.; Eriksen, H. K.
2013-11-01
We present a fully parallelized grid-based parameter estimation algorithm for investigating multidimensional likelihoods called Snake, and apply it to cosmological parameter estimation. The basic idea is to map out the likelihood grid-cell by grid-cell according to decreasing likelihood, and stop when a certain threshold has been reached. This approach improves vastly on the "curse of dimensionality" problem plaguing standard grid-based parameter estimation simply by disregarding grid cells with negligible likelihood. The main advantages of this method compared to standard Metropolis-Hastings Markov Chain Monte Carlo methods include (1) trivial extraction of arbitrary conditional distributions; (2) direct access to Bayesian evidences; (3) better sampling of the tails of the distribution; and (4) nearly perfect parallelization scaling. The main disadvantage is, as in the case of brute-force grid-based evaluation, a dependency on the number of parameters, N par. One of the main goals of the present paper is to determine how large N par can be, while still maintaining reasonable computational efficiency; we find that N par = 12 is well within the capabilities of the method. The performance of the code is tested by comparing cosmological parameters estimated using Snake and the WMAP-7 data with those obtained using CosmoMC, the current standard code in the field. We find fully consistent results, with similar computational expenses, but shorter wall time due to the perfect parallelization scheme.
A six-parameter space to describe galaxy diversification
NASA Astrophysics Data System (ADS)
Fraix-Burnet, D.; Chattopadhyay, T.; Chattopadhyay, A. K.; Davoust, E.; Thuillard, M.
2012-09-01
Context. The diversification of galaxies is caused by transforming events such as accretion, interaction, or mergers. These explain the formation and evolution of galaxies, which can now be described by many observables. Multivariate analyses are the obvious tools to tackle the available datasets and understand the differences between different kinds of objects. However, depending on the method used, redundancies, incompatibilities, or subjective choices of the parameters can diminish the usefulness of these analyses. The behaviour of the available parameters should be analysed before any objective reduction in the dimensionality and any subsequent clustering analyses can be undertaken, especially in an evolutionary context. Aims: We study a sample of 424 early-type galaxies described by 25 parameters, 10 of which are Lick indices, to identify the most discriminant parameters and construct an evolutionary classification of these objects. Methods: Four independent statistical methods are used to investigate the discriminant properties of the observables and the partitioning of the 424 galaxies: principal component analysis, K-means cluster analysis, minimum contradiction analysis, and Cladistics. Results: The methods agree in terms of six parameters: central velocity dispersion, disc-to-bulge ratio, effective surface brightness, metallicity, and the line indices NaD and OIII. The partitioning found using these six parameters, when projected onto the fundamental plane, looks very similar to the partitioning obtained previously for a totally different sample and based only on the parameters of the fundamental plane. Two additional groups are identified here, and we are able to provide some more constraints on the assembly history of galaxies within each group thanks to the larger number of parameters. We also identify another "fundamental plane" with the absolute K magnitude, the linear diameter, and the Lick index Hβ. We confirm that the Mg b vs. velocity dispersion
Parameter spaces for linear and nonlinear whistler-mode waves
Summers, Danny; Tang, Rongxin; Omura, Yoshiharu; Lee, Dong-Hun
2013-07-15
We examine the growth of magnetospheric whistler-mode waves which comprises a linear growth phase followed by a nonlinear growth phase. We construct time-profiles for the wave amplitude that smoothly match at the transition between linear and nonlinear wave growth. This matching procedure can only take place over a limited “matching region” in (N{sub h}/N{sub 0},A{sub T})-space, where A{sub T} is the electron thermal anisotropy, N{sub h} is the hot (energetic) electron number density, and N{sub 0} is the cold (background) electron number density. We construct this matching region and determine how the matching wave amplitude varies throughout the region. Further, we specify a boundary in (N{sub h}/N{sub 0},A{sub T})-space that separates a region where only linear chorus wave growth can occur from the region in which fully nonlinear chorus growth is possible. We expect that this boundary should prove of practical use in performing computationally expensive full-scale particle simulations, and in interpreting experimental wave data.
Space shuttle propulsion parameter estimation using optimal estimation techniques
NASA Technical Reports Server (NTRS)
1983-01-01
The first twelve system state variables are presented with the necessary mathematical developments for incorporating them into the filter/smoother algorithm. Other state variables, i.e., aerodynamic coefficients can be easily incorporated into the estimation algorithm, representing uncertain parameters, but for initial checkout purposes are treated as known quantities. An approach for incorporating the NASA propulsion predictive model results into the optimal estimation algorithm was identified. This approach utilizes numerical derivatives and nominal predictions within the algorithm with global iterations of the algorithm. The iterative process is terminated when the quality of the estimates provided no longer significantly improves.
Internal wave parameters retrieval from space-borne SAR image
NASA Astrophysics Data System (ADS)
Fan, Kaiguo; Fu, Bin; Gu, Yanzhen; Yu, Xingxiu; Liu, Tingting; Shi, Aiqin; Xu, Ke; Gan, Xilin
2015-12-01
Based on oceanic internal wave SAR imaging mechanism and the microwave scattering imaging model for oceanic surface features, we developed a new method to extract internal wave parameters from SAR imagery. Firstly, the initial wind fields are derived from NCEP reanalysis data, the sea water density and oceanic internal wave pycnocline depth are estimated from the Levites data, the surface currents induced by the internal wave are calculated according to the KDV equation. The NRCS profile is then simulated by solving the action balance equation and using the sea surface radar backscatter model. Both the winds and internal wave pycnocline depth are adjusted by using the dichotomy method step by step to make the simulated data approach the SAR image. Then, the wind speed, pycnocline depth, the phase speed, the group velocity and the amplitude of internal wave can be retrieved from SAR imagery when a best fit between simulated signals and the SAR image appears. The method is tested on one scene SAR image near Dongsha Island, in the South China Sea, results show that the simulated oceanic internal wave NRCS profile is in good agreement with that on the SAR image with the correlation coefficient as high as 90%, and the amplitude of oceanic internal wave retrieved from the SAR imagery is comparable with the SODA data. Besides, the phase speeds retrieved from other 16 scene SAR images in the South China Sea are in good agreement with the empirical formula which describes the relations between internal wave phase speed and water depths, both the root mean square and relative error are less than 0.11 m•s-1 and 7%, respectively, indicating that SAR images are useful for internal wave parameters retrieval and the method developed in this paper is convergent and applicable.
Space motion sickness medications: interference with biomedical parameters
NASA Technical Reports Server (NTRS)
Vernikos-Danellis, J.; Winget, C. M.; Leach, C. S.; Rosenblatt, L. S.; Lyman, J.; Beljan, J. R.
1977-01-01
The possibility that drugs administered to Skylab 3 (SL-3) and 4 (SL-4) crewmen for space motion sickness may have interfered with their biomedical evaluation in space was investigated. Healthy volunteers received combinations of Scopolamine/Dexedrine for four days in regimens similar to those used in these missions. Urine samples, heart rate, body temperature, mood and performance were analyzed for drug-related changes. Twenty-four hour urine samples were analyzed by the same procedures as those used to analyze the flight samples. Hormone concentrations determined included cortisol, epinephrine, norepinephrine, aldosterone and antidiuretic hormone (ADH). In addition, volume, specific gravity, osmolarity, sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chloride (Cl), inorganic phosphate, uric acid and creatinine were measured. Performance was not affected by the Scopolamine/Dexedrine. The drug combination increased daily mean heart rate (HR) significantly in all the subjects and daily mean rectal temperature (RT) in some of the subjects. A 2-4 hr phase shift in the HR circadian rhythm was also observed which indicates that internal circadian synchrony was disturbed by the drugs. Psychological and subjective evaluation indicated that the subjects could usually identify which days they were given the drugs by an increase in tension and anxiety, decreased patience, restlessness, decreased appetite, difficulty in sleeping and feelings of increased heart rate and body temperature. Urinary electrolytes were not changed significantly by the drug, but marked and significant changes occurred in urine volume and hormone excretion patterns. Scopolamine/Dexedrine caused consistent elevations in urinary cortisol and epinephrine and a transient elevation in ADH. Norepinephrine excretion was decreased, but there was no significant change in aldosterone excretion or in 24 hr urine volume. A comparison of these findings with the first four days of inflight data from the
Automated Image Registration Using Geometrically Invariant Parameter Space Clustering (GIPSC)
Seedahmed, Gamal H.; Martucci, Louis M.
2002-09-01
Accurate, robust, and automatic image registration is a critical task in many typical applications, which employ multi-sensor and/or multi-date imagery information. In this paper we present a new approach to automatic image registration, which obviates the need for feature matching and solves for the registration parameters in a Hough-like approach. The basic idea underpinning, GIPSC methodology is to pair each data element belonging to two overlapping images, with all other data in each image, through a mathematical transformation. The results of pairing are encoded and exploited in histogram-like arrays as clusters of votes. Geometrically invariant features are adopted in this approach to reduce the computational complexity generated by the high dimensionality of the mathematical transformation. In this way, the problem of image registration is characterized, not by spatial or radiometric properties, but by the mathematical transformation that describes the geometrical relationship between the two images or more. While this approach does not require feature matching, it does permit recovery of matched features (e.g., points) as a useful by-product. The developed methodology incorporates uncertainty modeling using a least squares solution. Successful and promising experimental results of multi-date automatic image registration are reported in this paper.
Quantum-classical transition and quantum activation of ratchet currents in the parameter space.
Beims, M W; Schlesinger, M; Manchein, C; Celestino, A; Pernice, A; Strunz, W T
2015-05-01
The quantum ratchet current is studied in the parameter space of the dissipative kicked rotor model coupled to a zero-temperature quantum environment. We show that vacuum fluctuations blur the generic isoperiodic stable structures found in the classical case. Such structures tend to survive when a measure of statistical dependence between the quantum and classical currents are displayed in the parameter space. In addition, we show that quantum fluctuations can be used to overcome transport barriers in the phase space. Related quantum ratchet current activation regions are spotted in the parameter space. Results are discussed based on quantum, semiclassical, and classical calculations. While the semiclassical dynamics involves vacuum fluctuations, the classical map is driven by thermal noise. PMID:26066230
Space Shuttle Pad Exposure Period Meteorological Parameters STS-1 Through STS-107
NASA Technical Reports Server (NTRS)
Overbey, B. G.; Roberts, B. C.
2005-01-01
During the 113 missions of the Space Transportation System (STS) to date, the Space Shuttle fleet has been exposed to the elements on the launch pad for approx. 4,195 days. The Natural Environments Branch at Marshall Space Flight Center archives atmospheric environments to which the Space Shuttle vehicles are exposed. This Technical Memorandum (TM) provides a summary of the historical record of the meteorological conditions encountered by the Space Shuttle fleet during the pad exposure period. Parameters included in this TM are temperature, relative humidity, wind speed, wind direction, sea level pressure, and precipitation. Extremes for each of these parameters for each mission are also summarized. Sources for the data include meteorological towers and hourly surface observations. Data are provided from the first launch of the STS in 1981 through the launch of STS-107 in 2003.
NASA Astrophysics Data System (ADS)
Aslanov, Vladimir S.; Yudintsev, Vadim V.
2015-01-01
Active debris removal is one of the promising techniques that will decrease the population of large, non-functional spacecraft (space debris) on orbit. Properties of space debris should be taken into account during planning an active debris removal mission. In this paper the thrusting phase of tethered deorbit of large space debris with flexible appendages is considered. The goal of the work is to investigate the mutual influence of the tether vibrations and the vibrations of flexible appendages during thrusting phase. A mathematical model of the space tug and the towed space debris with flexible appendages is developed. Parameters of the system are determined with assumptions that the system is moving in straight line, avoiding high amplitude vibrations of flexible appendages. The expression of the discriminant indicates that the vibrations of the tether and flexible appendages influence each other. A critical tether stiffness exists for the given space tug mass that should be avoided.
The Application of Parameter Space Design Method for Generator Excitation Control
NASA Astrophysics Data System (ADS)
Iki, Hiroyuki; Yoshimura, Shyuta; Uriu, Yosihisa
Recently, control engineering changes from classical control theory to modern control theory, and analogue to digital. However, as a matter of fact, the sensitivity adjustment of the parameters using Bode diagram require many time and works. In this paper, the tool of Matlab/Simulink that adjusted the AVR control parameter of the PI control type brushless and Thyristor excitation method by using the technique for based on the parameter space planning method by QE was made. Moreover, the adjustment of the sensitivity parameter of the excitation control method intended for the dynamic stability level area in Single Machine Infinite Bus is examined with the tool.
NASA Astrophysics Data System (ADS)
Zhang, Teng; Yue, Xiaokui; Ning, Xin; Yuan, Jianping
2016-06-01
This paper presents a new control scheme for the problem of a space robot after capturing an unknown tumbling target, such as space debris. Robotic capturing the target may destabilize the base of spacecraft and control torque is bounded which would affect the performance of attitude control system. To stabilize the base with bounded torque in postcapture scenario, a new control scheme which utilizes the control torque to balance angular momentum and motion of the manipulator to compensate limitation of the torque, is proposed. Considering uncertainties of the target, parameter identification technique for tumbling target with linear momentum is utilized to correct parameters of the controller. To verify validity and feasibility of the proposed concept, a planar space robot capturing small, medium and large target with or without linear momentum is studied. The results show that the whole system is stabilized finally and all the inertial parameters of the target converge to their real values.
Chaves, Madalena; Sengupta, Anirvan; Sontag, Eduardo D.
2010-01-01
The concept of robustness of regulatory networks has been closely related to the nature of the interactions among genes, and the capability of pattern maintenance or reproducibility. Defining this robustness property is a challenging task, but mathematical models have often associated it to the volume of the space of admissible parameters. Not only the volume of the space but also its topology and geometry contain information on essential aspects of the network, including feasible pathways, switching between two parallel pathways or distinct/disconnected active regions of parameters. A method is presented here to characterize the space of admissible parameters, by writing it as a semi-algebraic set, and then theoretically analyzing its topology and geometry, as well as volume. This method provides a more objective and complete measure of the robustness of a developmental module. As a detailed case study, the segment polarity gene network is analyzed. PMID:18987858
Efficient estimation of decay parameters in acoustically coupled-spaces using slice sampling.
Jasa, Tomislav; Xiang, Ning
2009-09-01
Room-acoustic energy decay analysis of acoustically coupled-spaces within the Bayesian framework has proven valuable for architectural acoustics applications. This paper describes an efficient algorithm termed slice sampling Monte Carlo (SSMC) for room-acoustic decay parameter estimation within the Bayesian framework. This work combines the SSMC algorithm and a fast search algorithm in order to efficiently determine decay parameters, their uncertainties, and inter-relationships with a minimum amount of required user tuning and interaction. The large variations in the posterior probability density functions over multidimensional parameter spaces imply that an adaptive exploration algorithm such as SSMC can have advantages over the exiting importance sampling Monte Carlo and Metropolis-Hastings Markov Chain Monte Carlo algorithms. This paper discusses implementation of the SSMC algorithm, its initialization, and convergence using experimental data measured from acoustically coupled-spaces. PMID:19739741
Naden, Levi N; Shirts, Michael R
2016-04-12
We show how thermodynamic properties of molecular models can be computed over a large, multidimensional parameter space by combining multistate reweighting analysis with a linear basis function approach. This approach reduces the computational cost to estimate thermodynamic properties from molecular simulations for over 130,000 tested parameter combinations from over 1000 CPU years to tens of CPU days. This speed increase is achieved primarily by computing the potential energy as a linear combination of basis functions, computed from either modified simulation code or as the difference of energy between two reference states, which can be done without any simulation code modification. The thermodynamic properties are then estimated with the Multistate Bennett Acceptance Ratio (MBAR) as a function of multiple model parameters without the need to define a priori how the states are connected by a pathway. Instead, we adaptively sample a set of points in parameter space to create mutual configuration space overlap. The existence of regions of poor configuration space overlap are detected by analyzing the eigenvalues of the sampled states' overlap matrix. The configuration space overlap to sampled states is monitored alongside the mean and maximum uncertainty to determine convergence, as neither the uncertainty or the configuration space overlap alone is a sufficient metric of convergence. This adaptive sampling scheme is demonstrated by estimating with high precision the solvation free energies of charged particles of Lennard-Jones plus Coulomb functional form with charges between -2 and +2 and generally physical values of σij and ϵij in TIP3P water. We also compute entropy, enthalpy, and radial distribution functions of arbitrary unsampled parameter combinations using only the data from these sampled states and use the estimates of free energies over the entire space to examine the deviation of atomistic simulations from the Born approximation to the solvation free
Dual-parameter radar rainfall measurement from space - A test result from an aircraft experiment
NASA Technical Reports Server (NTRS)
Kozu, Toshiaki; Nakamura, Kenji; Meneghini, Robert; Boncyk, Wayne C.
1991-01-01
An aircraft experiment has been conducted with a dual-frequency (X/Ka-bands) radar to test various rainfall retrieval methods from space. The authors test a method to derive raindrop size distribution (DSD) parameters from the combination of a radar reflectivity profile and a path-integrated attenuation derived from surface return, which may be available from most spaceborne radars. The estimated DSD parameters are reasonable in that the values generally fall within the range of commonly measured ones and that shifts in DSD parameters appear to be correlated with changes in storm type. The validity of the estimation result is also demonstrated by a consistency check using the Ka-band reflectivity profile which is independent of the DSD estimation process. Although errors may occur in the cases of nonuniform beam filling, these test results indicate the feasibility of the dual-parameter radar measurement from space in achieving a better accuracy in quantitative rainfall remote measurements.
A new parameter of geomagnetic storms for the severity of space weather
NASA Astrophysics Data System (ADS)
Balan, N.; Batista, I. S.; Tulasi Ram, S.; Rajesh, P. K.
2016-12-01
Using the continuous Dst data available since 1957 and H component data for the Carrington space weather event of 1859, the paper shows that the mean value of Dst during the main phase of geomagnetic storms, called mean DstMP, is a unique parameter that can indicate the severity of space weather. All storms having high mean DstMP (≤-250 nT), which corresponds to high amount of energy input in the magnetosphere-ionosphere system in short duration, are found associated with severe space weather events that caused all known electric power outages and telegraph system failures.
A Summary of Meteorological Parameters During Space Shuttle Pad Exposure Periods
NASA Technical Reports Server (NTRS)
Overbey, Glenn; Roberts, Barry C.
2005-01-01
During the 113 missions of the Space Transportation System (STS), the Space Shuffle fleet has been exposed to the elements on the launch pad for a total of 4195 days. The Natural Environments Branch at Marshall Space Flight Center archives atmospheric environments to which the Space Shuttle vehicles are exposed. This paper provides a summary of the historical record of the meteorological conditions encountered by the Space Shuttle fleet during the pad exposure period. Sources of the surface parameters, including temperature, dew point temperature, relative humidity, wind speed, wind direction, sea level pressure and precipitation are presented. Data is provided from the first launch of the STS in 1981 through the launch of STS-107 in 2003.
New coordinates for the amplitude parameter space of continuous gravitational waves
NASA Astrophysics Data System (ADS)
Whelan, John T.; Prix, Reinhard; Cutler, Curt J.; Willis, Joshua L.
2014-03-01
The parameter space for continuous gravitational waves (GWs) can be divided into amplitude parameters (signal amplitude, inclination and polarization angles describing the orientation of the source, and an initial phase) and phase-evolution parameters (signal frequency and frequency derivatives, and parameters such as sky position which determine the Doppler modulation of the signal). The division is useful in part because of the existence of a set of functions known as the Jaranowski-Królak-Schutz (JKS) coordinates, which are a set of four coordinates on the amplitude parameter space such that the GW signal can be written as a linear combination of four template waveforms (which depend on the phase-evolution parameters) with the JKS coordinates as coefficients. We define a new set of coordinates on the amplitude parameter space, with the same properties, which can be more closely connected to the physical amplitude parameters. These naturally divide into two pairs of Cartesian-like coordinates on two-dimensional subspaces, one corresponding to left- and the other to right-circular polarization. We thus refer to these as circular polarization factored (CPF) coordinates. The corresponding two sets of polar coordinates (known as CPF-polar) can be related in a simple way to the physical parameters. A further coordinate transformation can be made, within each subspace, between CPF and so-called root-radius coordinates, whose radial coordinate is the fourth root of the radial coordinate in CPF-polar coordinates. We illustrate some simplifying applications for these various coordinate systems, such as a calculation of the Jacobian for the transformation between JKS or CPF coordinates and the physical amplitude parameters (amplitude, inclination, polarization and initial phase); a demonstration that the Jacobian between root-radius coordinates and the physical parameters is a constant; an illustration of the signal coordinate singularities associated with left- and right
Flat parameter-space metric for all-sky searches for gravitational-wave pulsars
NASA Astrophysics Data System (ADS)
Wette, Karl; Prix, Reinhard
2013-12-01
All-sky, broadband, coherent searches for gravitational-wave pulsars are computationally limited. It is therefore important to make efficient use of available computational resources, notably by minimizing the number of templates used to cover the signal parameter space of sky position and frequency evolution. For searches over the sky, however, the required template density (determined by the parameter-space metric) is different at each sky position, which makes it difficult in practice to achieve an efficient covering. Previous work on this problem has found various choices of sky and frequency coordinates that render the parameter-space metric approximately constant but that are limited to coherent integration times of either less than a few days or greater than several months. These limitations restrict the sensitivity achievable by hierarchical all-sky searches and hinder the development of follow-up pipelines for interesting gravitational-wave pulsar candidates. We present a new flat parameter-space metric approximation and associated sky and frequency coordinates, which do not suffer from these limitations. Furthermore, the new metric is numerically well conditioned, which facilitates its practical use.
On-line estimation of inertia parameters of space debris for its tether-assisted removal
NASA Astrophysics Data System (ADS)
Zhang, Fan; Sharf, Inna; Misra, Arun; Huang, Panfeng
2015-02-01
This paper presents a new methodology for on-line inertia parameters estimation for a rigid space debris captured by a tethered system, based on a new dynamics model of the system where the base satellite (chaser) and the space debris (target) are modeled as rigid bodies and the attachment points of the tether are offset from the centers of mass of the two bodies. Parameters estimation of unknown debris is critical for subsequent tasks in the space debris remediation mission, in particular, for debris retrieval and de-orbiting. In the proposed algorithm, the chaser and target are modeled as rigid bodies, the latter with unknown inertia parameters. Then, the parameters identification problem is formulated and solved in three phases. First, a coarse estimate of the target mass is obtained during the post-capture phase, while the length of tether is much longer than the offsets of base and target satellite, and the rigid body model is degenerated to a mass point model. Then, with a proper tension control scheme and the coarse estimate used as an initial guess, the debris is retrieved smoothly and a precise mass estimate is achieved during the first half of the retrieval. Finally, when the tether is retrieved relatively short and the rigid body model is used, moments of inertia and the offsets of the space debris will be estimated with a proper tension control scheme for rigid body model.
Variation ranges of motion parameters for space debris in the geosynchronous ring
NASA Astrophysics Data System (ADS)
Zhao, Chang-Yin; Zhang, Ming-Jiang; Yu, Sheng-Xian; Xiong, Jian-Ning; Zhang, Wei; Zhu, Ting-Lei
2016-06-01
We propose a method that uses only one set of known orbital elements to directly determine the motion state and variation ranges of motion parameters, including the inclination, right ascension of the ascending node (RAAN), evolution period of the orbital plane, maximum libration amplitude of the semi-major axis, commensurable angle, libration period and drift period, for space debris in the geosynchronous ring. These variation ranges of motion parameters characterize the evolution of debris quantitatively and illustrate the three-dimensional (3D) variations. Employing the proposed method, we study the motion state and variation ranges of motion parameters for catalogued and uncontrolled space debris with existing two-line element (TLE) data in the geosynchronous ring, and present specific results. We also compare our results with actual observational results derived from long-term TLE historical data, and find that, in the vast majority of cases, our proposed method of determining the motion state and variation ranges of motion parameters via only one set of known orbital elements is effective. In addition, before the elaboration of the variation ranges of motion parameters stated above, we obtain the statistical distribution of space debris in the orbital plane and the daily motion from the TLE historical data. We then derive two mathematical formulae that explain the statistical distribution and daily motion on the basis of the essence of dynamics, which contributes to the characterization of the evolution of debris.
Trap configuration and spacing influences parameter estimates in spatial capture-recapture models
Sun, Catherine C.; Fuller, Angela K.; Royle, J. Andrew
2014-01-01
An increasing number of studies employ spatial capture-recapture models to estimate population size, but there has been limited research on how different spatial sampling designs and trap configurations influence parameter estimators. Spatial capture-recapture models provide an advantage over non-spatial models by explicitly accounting for heterogeneous detection probabilities among individuals that arise due to the spatial organization of individuals relative to sampling devices. We simulated black bear (Ursus americanus) populations and spatial capture-recapture data to evaluate the influence of trap configuration and trap spacing on estimates of population size and a spatial scale parameter, sigma, that relates to home range size. We varied detection probability and home range size, and considered three trap configurations common to large-mammal mark-recapture studies: regular spacing, clustered, and a temporal sequence of different cluster configurations (i.e., trap relocation). We explored trap spacing and number of traps per cluster by varying the number of traps. The clustered arrangement performed well when detection rates were low, and provides for easier field implementation than the sequential trap arrangement. However, performance differences between trap configurations diminished as home range size increased. Our simulations suggest it is important to consider trap spacing relative to home range sizes, with traps ideally spaced no more than twice the spatial scale parameter. While spatial capture-recapture models can accommodate different sampling designs and still estimate parameters with accuracy and precision, our simulations demonstrate that aspects of sampling design, namely trap configuration and spacing, must consider study area size, ranges of individual movement, and home range sizes in the study population.
Trap Configuration and Spacing Influences Parameter Estimates in Spatial Capture-Recapture Models
Sun, Catherine C.; Fuller, Angela K.; Royle, J. Andrew
2014-01-01
An increasing number of studies employ spatial capture-recapture models to estimate population size, but there has been limited research on how different spatial sampling designs and trap configurations influence parameter estimators. Spatial capture-recapture models provide an advantage over non-spatial models by explicitly accounting for heterogeneous detection probabilities among individuals that arise due to the spatial organization of individuals relative to sampling devices. We simulated black bear (Ursus americanus) populations and spatial capture-recapture data to evaluate the influence of trap configuration and trap spacing on estimates of population size and a spatial scale parameter, sigma, that relates to home range size. We varied detection probability and home range size, and considered three trap configurations common to large-mammal mark-recapture studies: regular spacing, clustered, and a temporal sequence of different cluster configurations (i.e., trap relocation). We explored trap spacing and number of traps per cluster by varying the number of traps. The clustered arrangement performed well when detection rates were low, and provides for easier field implementation than the sequential trap arrangement. However, performance differences between trap configurations diminished as home range size increased. Our simulations suggest it is important to consider trap spacing relative to home range sizes, with traps ideally spaced no more than twice the spatial scale parameter. While spatial capture-recapture models can accommodate different sampling designs and still estimate parameters with accuracy and precision, our simulations demonstrate that aspects of sampling design, namely trap configuration and spacing, must consider study area size, ranges of individual movement, and home range sizes in the study population. PMID:24505361
Lee, B C; Schulz, M; de Supinski, B R
2006-09-28
Increasing system and algorithmic complexity, combined with a growing number of tunable application parameters, pose significant challenges for analytical performance modeling. This report outlines a series of robust techniques that enable efficient parameter space exploration based on empirical statistical modeling. In particular, this report applies statistical techniques such as clustering, association, correlation analyses to understand the parameter space better. Results from these statistical techniques guide the construction of piecewise polynomial regression models. Residual and significance tests ensure the resulting model is unbiased and efficient. We demonstrate these techniques in R, a statistical computing environment, for predicting the performance of semicoarsening multigrid. 50 and 75 percent of predictions achieve error rates of 5.5 and 10.0 percent or less, respectively.
Parameter-space correlations of the optimal statistic for continuous gravitational-wave detection
Pletsch, Holger J.
2008-11-15
The phase parameters of matched-filtering searches for continuous gravitational-wave signals are sky position, frequency, and frequency time-derivatives. The space of these parameters features strong global correlations in the optimal detection statistic. For observation times smaller than 1 yr, the orbital motion of the Earth leads to a family of global-correlation equations which describes the 'global maximum structure' of the detection statistic. The solution to each of these equations is a different hypersurface in parameter space. The expected detection statistic is maximal at the intersection of these hypersurfaces. The global maximum structure of the detection statistic from stationary instrumental-noise artifacts is also described by the global-correlation equations. This permits the construction of a veto method which excludes false candidate events.
Modified Brans-Dicke theory with space-time anisotropic parameters
Moon, Taeyoon; Oh, Phillial E-mail: ploh@skku.edu
2014-03-01
We consider the ADM formalism of the Brans-Dicke theory and propose a space-time anisotropic extension of the theory by introducing five free parameters. We find that the resulting theory reveals many interesting aspects which are not present in the original BD theory. We first discuss the ghost instability and strong coupling problems which are present in the gravity theory without the full diffeomorphism symmetry and show that they can be avoided in a region of the parameter space. We also perform the post-Newtonian approximation and show that the constraint of the Brans-Dicke parameter ω{sub BD} being large to be consistent with the solar system observations could be evaded in the extended theory. We also discuss that accelerating Universe can be achieved without the need of the potential for the Brans-Dicke scalar.
Robust H infinity control design for the space station with structured parameter uncertainty
NASA Technical Reports Server (NTRS)
Byun, Kuk-Whan; Wie, Bong; Geller, David; Sunkel, John
1992-01-01
A robust H-infinity control design methodology and its application to a Space Station attitude and momentum control problem are presented. This new approach incorporates nonlinear multi-parameter variations in the state-space formulation of H-infinity control theory. An application of this robust H-infinity control synthesis technique to the Space Station control problem yields a remarkable result in stability robustness with respect to the moments-of-inertia variation of about 73% in one of the structured uncertainty directions. The performance and stability of this new robust H-infinity controller for the Space Station are compared to those of other controllers designed using a standard linear-quadratic-regulator synthesis technique.
Exploring Replica-Exchange Wang-Landau sampling in higher-dimensional parameter space
Valentim, Alexandra; Rocha, Julio C. S.; Tsai, Shan-Ho; Li, Ying Wai; Eisenbach, Markus; Fiore, Carlos E; Landau, David P
2015-01-01
We considered a higher-dimensional extension for the replica-exchange Wang-Landau algorithm to perform a random walk in the energy and magnetization space of the two-dimensional Ising model. This hybrid scheme combines the advantages of Wang-Landau and Replica-Exchange algorithms, and the one-dimensional version of this approach has been shown to be very efficient and to scale well, up to several thousands of computing cores. This approach allows us to split the parameter space of the system to be simulated into several pieces and still perform a random walk over the entire parameter range, ensuring the ergodicity of the simulation. Previous work, in which a similar scheme of parallel simulation was implemented without using replica exchange and with a different way to combine the result from the pieces, led to discontinuities in the final density of states over the entire range of parameters. From our simulations, it appears that the replica-exchange Wang-Landau algorithm is able to overcome this diculty, allowing exploration of higher parameter phase space by keeping track of the joint density of states.
On standard conjugate families for natural exponential families with bounded natural parameter space
Hornik, Kurt; Grün, Bettina
2014-01-01
Diaconis and Ylvisaker (1979) give necessary conditions for conjugate priors for distributions from the natural exponential family to be proper as well as to have the property of linear posterior expectation of the mean parameter of the family. Their conditions for propriety and linear posterior expectation are also sufficient if the natural parameter space is equal to the set of all d-dimensional real numbers. In this paper their results are extended to characterize when conjugate priors are proper if the natural parameter space is bounded. For the special case where the natural exponential family is through a spherical probability distribution η, we show that the proper conjugate priors can be characterized by the behavior of the moment generating function of η at the boundary of the natural parameter space, or the second-order tail behavior of η. In addition, we show that if these families are non-regular, then linear posterior expectation never holds. The results for this special case are also extended to natural exponential families through elliptical probability distributions. PMID:24748693
SP_Ace: a new code to derive stellar parameters and elemental abundances
NASA Astrophysics Data System (ADS)
Boeche, C.; Grebel, E. K.
2016-03-01
Context. Ongoing and future massive spectroscopic surveys will collect large numbers (106-107) of stellar spectra that need to be analyzed. Highly automated software is needed to derive stellar parameters and chemical abundances from these spectra. Aims: We developed a new method of estimating the stellar parameters Teff, log g, [M/H], and elemental abundances. This method was implemented in a new code, SP_Ace (Stellar Parameters And Chemical abundances Estimator). This is a highly automated code suitable for analyzing the spectra of large spectroscopic surveys with low or medium spectral resolution (R = 2000-20 000). Methods: After the astrophysical calibration of the oscillator strengths of 4643 absorption lines covering the wavelength ranges 5212-6860 Å and 8400-8924 Å, we constructed a library that contains the equivalent widths (EW) of these lines for a grid of stellar parameters. The EWs of each line are fit by a polynomial function that describes the EW of the line as a function of the stellar parameters. The coefficients of these polynomial functions are stored in a library called the "GCOG library". SP_Ace, a code written in FORTRAN95, uses the GCOG library to compute the EWs of the lines, constructs models of spectra as a function of the stellar parameters and abundances, and searches for the model that minimizes the χ2 deviation when compared to the observed spectrum. The code has been tested on synthetic and real spectra for a wide range of signal-to-noise and spectral resolutions. Results: SP_Ace derives stellar parameters such as Teff, log g, [M/H], and chemical abundances of up to ten elements for low to medium resolution spectra of FGK-type stars with precision comparable to the one usually obtained with spectra of higher resolution. Systematic errors in stellar parameters and chemical abundances are presented and identified with tests on synthetic and real spectra. Stochastic errors are automatically estimated by the code for all the parameters
Moving to continuous facial expression space using the MPEG-4 facial definition parameter (FDP) set
NASA Astrophysics Data System (ADS)
Karpouzis, Kostas; Tsapatsoulis, Nicolas; Kollias, Stefanos D.
2000-06-01
Research in facial expression has concluded that at least six emotions, conveyed by human faces, are universally associated with distinct expressions. Sadness, anger, joy, fear, disgust and surprise are categories of expressions that are recognizable across cultures. In this work we form a relation between the description of the universal expressions and the MPEG-4 Facial Definition Parameter Set (FDP). We also investigate the relation between the movement of basic FDPs and the parameters that describe emotion-related words according to some classical psychological studies. In particular Whissel suggested that emotions are points in a space, which seem to occupy two dimensions: activation and evaluation. We show that some of the MPEG-4 Facial Animation Parameters (FAPs), approximated by the motion of the corresponding FDPs, can be combined by means of a fuzzy rule system to estimate the activation parameter. In this way variations of the six archetypal emotions can be achieved. Moreover, Plutchik concluded that emotion terms are unevenly distributed through the space defined by dimensions like Whissel's; instead they tend to form an approximately circular pattern, called 'emotion wheel,' modeled using an angular measure. The 'emotion wheel' can be defined as a reference for creating intermediate expressions from the universal ones, by interpolating the movement of dominant FDP points between neighboring basic expressions. By exploiting the relation between the movement of the basic FDP point and the activation and angular parameters we can model more emotions than the primary ones and achieve efficient recognition in video sequences.
Mazinan, A H; Shakhesi, S
2016-05-01
The research attempts to deal with the autonomous space systems incorporating new automated maneuvers strategies in the presence of parameters uncertainties. The main subject behind the investigation is to realize the high-resolution small amplitude orbital maneuvers via the first control strategy. And subsequently to realize the large amplitude orbital maneuvers via the second control strategy, as well. There is a trajectory optimization to provide the three-axis referenced commends for the aforementioned overactuated autonomous space system to be able to transfer from the initial orbit to its final ones, in finite burn, as long as the uncertainties of key parameters of the system such as the thrust vector, the center of the gravity, the moments of the inertia and so on are taken into real consideration. The strategies performances are finally considered through a series of experiments and a number of benchmarks to be tangibly verified. PMID:26895709
Efficiently enclosing the compact binary parameter space by singular-value decomposition
Cannon, Kipp; Hanna, Chad; Keppel, Drew
2011-10-15
Gravitational-wave searches for the merger of compact binaries use matched filtering as the method of detecting signals and estimating parameters. Such searches construct a fine mesh of filters covering a signal parameter space at high density. Previously it has been shown that singular-value decomposition can reduce the effective number of filters required to search the data. Here we study how the basis provided by the singular-value decomposition changes dimension as a function of template-bank density. We will demonstrate that it is sufficient to use the basis provided by the singular-value decomposition of a low-density bank to accurately reconstruct arbitrary points within the boundaries of the template bank. Since this technique is purely numerical, it may have applications to interpolating the space of numerical relativity waveforms.
A Parameter Space as an Improved Tool for Investigating Extraterrestrial Intelligence
NASA Astrophysics Data System (ADS)
Ashworth, S.
2014-06-01
For the past half century the Drake Equation and the Fermi Paradox have provided the intellectual foundation for investigating the possible existence of extraterrestrial intelligence. But both the Equation and the Paradox are flawed and of questionable scientific utility. A replacement needs to be found, based on a different principle, and a parameter space for extraterrestrial intelligence is proposed as an improved tool of thought. This generates six distinct scenarios, whose implications for SETI are discussed.
On equivalent parameter learning in simplified feature space based on Bayesian asymptotic analysis.
Yamazaki, Keisuke
2012-07-01
Parametric models for sequential data, such as hidden Markov models, stochastic context-free grammars, and linear dynamical systems, are widely used in time-series analysis and structural data analysis. Computation of the likelihood function is one of primary considerations in many learning methods. Iterative calculation of the likelihood such as the model selection is still time-consuming though there are effective algorithms based on dynamic programming. The present paper studies parameter learning in a simplified feature space to reduce the computational cost. Simplifying data is a common technique seen in feature selection and dimension reduction though an oversimplified space causes adverse learning results. Therefore, we mathematically investigate a condition of the feature map to have an asymptotically equivalent convergence point of estimated parameters, referred to as the vicarious map. As a demonstration to find vicarious maps, we consider the feature space, which limits the length of data, and derive a necessary length for parameter learning in hidden Markov models. PMID:22503779
NASA Technical Reports Server (NTRS)
Suit, William T.
1989-01-01
Estimates of longitudinal stability and control parameters for the space shuttle were determined by applying a maximum likelihood parameter estimation technique to Challenger flight test data. The parameters for pitching moment coefficient, C(m sub alpha), (at different angles of attack), pitching moment coefficient, C(m sub delta e), (at different elevator deflections) and the normal force coefficient, C(z sub alpha), (at different angles of attack) describe 90 percent of the response to longitudinal inputs during Space Shuttle Challenger flights with C(m sub delta e) being the dominant parameter. The values of C(z sub alpha) were found to be input dependent for these tests. However, when C(z sub alpha) was set at preflight predictions, the values determined for C(m sub delta e) changed less than 10 percent from the values obtained when C(z sub alpha) was estimated as well. The preflight predictions for C(z sub alpha) and C(m sub alpha) are acceptable values, while the values of C(z sub delta e) should be about 30 percent less negative than the preflight predictions near Mach 1, and 10 percent less negative, otherwise.
Corticothalamic dynamics: Structure of parameter space, spectra, instabilities, and reduced model
NASA Astrophysics Data System (ADS)
Roberts, J. A.; Robinson, P. A.
2012-01-01
Linear instabilities are analyzed in a physiologically based mean-field corticothalamic model and a reduced-parameter model derived from it. In both models, the stable zone corresponding to normal arousal states is bounded by a series of surfaces demarcating the onsets of instabilities. The stable zone is found to depend on delay and rate parameters, whose values have a simple relationship to the number of instabilities and dominant frequencies on the stable zone's boundary. The dominant frequencies of linear activity inside the stable zone are found to lie in clearly delineated regions, each corresponding to an instability surface on its boundary and having approximately the same dominant frequency. These regions are ordered in parameter space according to their dominant frequencies, and an instability associated with the intrathalamic loop is shown to have the highest frequency that can become unstable. This reveals an important role for the thalamus in controlling the stability and bandwidth of dynamics in the corticothalamic system as a whole. The reduced model is found to agree well with the full model in a wide region of parameter space and, thus, is a useful guide to the full model's dynamics.
Modal parameters of space structures in 1 G and 0 G
NASA Technical Reports Server (NTRS)
Bicos, Andrew S.; Crawley, Edward F.; Barlow, Mark S.; Van Schoor, Marthinus C.; Masters, Brett
1993-01-01
Analytic and experimental results are presented from a study of the changes in the modal parameters of space structural test articles from one- to zero-gravity. Deployable, erectable, and rotary modules was assembled to form three one- and two-dimensional structures, in which variations in bracing wire and rotary joint preload could be introduced. The structures were modeled as if hanging from a suspension system in one gravity, and unconstrained, as if free floating in zero-gravity. The analysis is compared with ground experimental measurements, which were made on a spring-wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, reassembly, shipset, suspension, and ambient gravity level.
Predicting engine parameters using the optic spectrum of the space shuttle main engine exhaust plume
NASA Astrophysics Data System (ADS)
Srivastava, Ashok N.; Buntine, Wray
The Optical Plume Anomaly Detection (OPAD) system is under development to predict engine anomalies and engine parameters of the Space Shuttle's Main Engine (SSME). The anomaly detection is based on abnormal metal concentrations in the optical spectrum of the rocket plume. Such abnormalities could be indicative of engine corrosion or other malfunctions. Here, we focus on the second task of the OPAD system, namely the prediction of engine parameters such as rated power level (RPL) and mixture ratio (MR). Because of the high dimensionality of the spectrum, we developed a linear algorithm to resolve the optical spectrum of the exhaust plume into a number of separate components, each with a different physical interpretation. These components are used to predict the metal concentrations and engine parameters for online support of ground-level testing of the SSME. Currently, these predictions are labor intensive and cannot be done online. We predict RPL using neural networks and give preliminary results.
Controller design and parameter identifiability studies for a large space antenna
NASA Technical Reports Server (NTRS)
Joshi, S. M.
1985-01-01
The problem of control systems synthesis and parameter identifiability are considered for a large, space-based antenna. Two methods are considered for control system synthesis, the first of which uses torque actuators and collocated attitude and rate sensors, and the second method is based on the linear-quadratic-Gaussian (LQG) control theory. The predicted performance obtained by computing variances of pointing, surface and feed misalignment errors in the presence of sensor noise indicates that the LQG-based controller yields superior results. Since controller design requires the knowledge of the system parameters, the identifiability of the structural parameters is investigated by obtaining Cramer-Rao lower bounds. The modal frequencies are found to have the best identifiability, followed by damping ratios, and mode-slopes.
The dynamics of blood biochemical parameters in cosmonauts during long-term space flights
NASA Astrophysics Data System (ADS)
Markin, Andrei; Strogonova, Lubov; Balashov, Oleg; Polyakov, Valery; Tigner, Timoty
Most of the previously obtained data on cosmonauts' metabolic state concerned certain stages of the postflight period. In this connection, all conclusions, as to metabolism peculiarities during the space flight, were to a large extent probabilistic. The purpose of this work was study of metabolism characteristics in cosmonauts directly during long-term space flights. In the capillary blood samples taken from a finger, by "Reflotron IV" biochemical analyzer, "Boehringer Mannheim" GmbH, Germany, adapted to weightlessness environments, the activity of GOT, GPT, CK, gamma-GT, total and pancreatic amylase, as well as concentration of hemoglobin, glucose, total bilirubin, uric acid, urea, creatinine, total, HDL- and LDL cholesterol, triglycerides had been determined. HDL/LDL-cholesterol ratio also was computed. The crewmembers of 6 main missions to the "Mir" orbital station, a total of 17 cosmonauts, were examined. Biochemical tests were carryed out 30-60 days before lounch, and in the flights different stages between the 25-th and the 423-rd days of flights. In cosmonauts during space flight had been found tendency to increase, in compare with basal level, GOT, GPT, total amylase activity, glucose and total cholesterol concentration, and tendency to decrease of CK activity, hemoglobin, HDL-cholesterol concentration, and HDL/LDL — cholesterol ratio. Some definite trends in variations of other determined biochemical parameters had not been found. The same trends of mentioned biochemical parameters alterations observed in majority of tested cosmonauts, allows to suppose existence of connection between noted metabolic alterations with influence of space flight conditions upon cosmonaut's body. Variations of other studied blood biochemical parameters depends on, probably, pure individual causes.
Virchow-Robin Spaces: Correlations with Polysomnography-Derived Sleep Parameters
Berezuk, Courtney; Ramirez, Joel; Gao, Fuqiang; Scott, Christopher J.M.; Huroy, Menal; Swartz, Richard H.; Murray, Brian J.; Black, Sandra E.; Boulos, Mark I.
2015-01-01
Study Objectives: To test the hypothesis that enlarged Virchow-Robin space volumes (VRS) are associated with objective measures of poor quality sleep. Design: Retrospective cross-sectional study. Setting: Sunnybrook Health Sciences Centre. Patients: Twenty-six patients being evaluated for cerebrovascular disease were assessed using polysomnography and high-resolution structural magnetic resonance imaging. Measurements and Results: Regionalized VRS were quantified from three-dimensional high-resolution magnetic resonance imaging and correlated with measures of polysomnography-derived sleep parameters while controlling for age, stroke volume, body mass index, systolic blood pressure, and ventricular cerebrospinal fluid volume. Sleep efficiency was negatively correlated with total VRS (rho = −0.47, P = 0.03) and basal ganglia VRS (rho = −0.54, P = 0.01), whereas wake after sleep onset was positively correlated with basal ganglia VRS (rho = 0.52, P = 0.02). Furthermore, VRS in the basal ganglia were negatively correlated with duration of N3 (rho = −0.53, P = 0.01). Conclusions: These preliminary results suggest that sleep may play a role in perivascular clearance in ischemic brain disease, and invite future research into the potential relevance of Virchow-Robin spaces as an imaging biomarker for nocturnal metabolite clearance. Citation: Berezuk C, Ramirez J, Gao F, Scott CJ, Huroy M, Swartz RH, Murray BJ, Black SE, Boulos MI. Virchow-Robin spaces: correlations with polysomnography-derived sleep parameters. SLEEP 2015;38(6):853–858. PMID:26163465
Space radiation parameters for EUI and the Sun Sensor of Solar Orbiter, ESIO, and JUDE instruments
NASA Astrophysics Data System (ADS)
Rossi, Laurence; Jacques, Lionel; Halain, Jean-Philippe; Renotte, Etienne; Thibert, Tanguy; Grodent, Denis
2014-08-01
This paper presents predictions of space radiation parameters for four space instruments performed by the Centre Spatial de Liège (ULg - Belgium); EUI, the Extreme Ultra-violet Instrument, on-board the Solar Orbiter platform; ESIO, Extreme-UV solar Imager for Operations, and JUDE, the Jupiter system Ultraviolet Dynamics Experiment, which was proposed for the JUICE platform. For Solar Orbiter platform, the radiation environment is defined by ESA environmental specification and the determination of the parameters is done through ray-trace analyses inside the EUI instrument. For ESIO instrument, the radiation environment of the geostationary orbit is defined through simulations of the trapped particles flux, the energetic solar protons flux and the galactic cosmic rays flux, taking the ECSS standard for space environment as a guideline. Then ray-trace analyses inside the instrument are performed to predict the particles fluxes at the level of the most radiation-sensitive elements of the instrument. For JUICE, the spacecraft trajectory is built from ephemeris files provided by ESA and the radiation environment is modeled through simulations by JOSE (Jovian Specification Environment model) then ray-trace analyses inside the instrument are performed to predict the particles fluxes at the level of the most radiation-sensitive elements of the instrument.
Space Shuttle propulsion parameter estimation using optimal estimation techniques, volume 1
NASA Technical Reports Server (NTRS)
1983-01-01
The mathematical developments and their computer program implementation for the Space Shuttle propulsion parameter estimation project are summarized. The estimation approach chosen is the extended Kalman filtering with a modified Bryson-Frazier smoother. Its use here is motivated by the objective of obtaining better estimates than those available from filtering and to eliminate the lag associated with filtering. The estimation technique uses as the dynamical process the six degree equations-of-motion resulting in twelve state vector elements. In addition to these are mass and solid propellant burn depth as the ""system'' state elements. The ""parameter'' state elements can include aerodynamic coefficient, inertia, center-of-gravity, atmospheric wind, etc. deviations from referenced values. Propulsion parameter state elements have been included not as options just discussed but as the main parameter states to be estimated. The mathematical developments were completed for all these parameters. Since the systems dynamics and measurement processes are non-linear functions of the states, the mathematical developments are taken up almost entirely by the linearization of these equations as required by the estimation algorithms.
A parameter database for large scientific projects: application to the Gaia space astrometry mission
NASA Astrophysics Data System (ADS)
Perryman, Michael; de Bruijne, Jos; Lammers, Uwe
2008-10-01
The parallel development of many aspects of a complex space science mission like Gaia, which includes numerous participants in ESA, industrial companies, and a large and active scientific collaboration throughout Europe, makes keeping track of the many design changes, instrument and operational parameters, and numerical values for the data analysis and simulations, a challenging but crucially important problem. A comprehensive, easily-accessible, up-to-date, and definitive compilation of a large range of numerical quantities is required, and the Gaia parameter database has been established to satisfy these needs. The database is a centralised repository containing, besides mathematical, physical, and astronomical constants, many satellite and subsystem design parameters. Version control provides both a ‘live’ version with the most recent parameters, as well as previous ‘reference’ versions of the full database contents. Query results are formatted by default in HTML, while an important feature is that data can also be retrieved as Java, ANSI-C, C++, Ruby, or XML structures for direct inclusion into software codes, such that all collaborating scientists can use the retrieved database parameters and values directly linked to computational routines.
Parameter-space screening: a powerful tool for high-throughput crystal structure determination.
Liu, Zhi-Jie; Lin, Dawei; Tempel, Wolfram; Praissman, Jeremy L; Rose, John P; Wang, Bi-Cheng
2005-05-01
The determination of protein structures on a genomic scale requires both computing capacity and efficiency increases at many stages along the complex process. By combining bioinformatics workflow-management techniques, cluster-based computing and popular crystallographic structure-determination software packages, an efficient and powerful new tool for structural biology/genomics has been developed. Using the workflow manager and a simple web interface, the researcher can, in a few easy steps, set up hundreds of structure-determination jobs, each using a slightly different set of program input parameters, thus efficiently screening parameter space for the optimal input-parameter combination, i.e. a set of parameters that leads to a successful structure determination. Upon completion, results from the programs are harvested, analyzed, sorted based on success and presented to the user via the web interface. This approach has been applied with success in more than 30 cases. Examples of successful structure determinations based on single-wavelength scattering (SAS) are described and include cases where the 'rational' crystallographer-based selection of input parameters values had failed. PMID:15858261
Nunez, Dario; Zavala, Jesus; Nellen, Lukas; Sussman, Roberto A; Cabral-Rosetti, Luis G; Mondragon, Myriam E-mail: jzavala@nucleares.unam.mx E-mail: lukas@nucleares.unam.mx E-mail: lgcabral@ciidet.edu.mx; Collaboration: For the Instituto Avanzado de Cosmologia, IAC
2008-05-15
We derive an expression for the entropy of a dark matter halo described using a Navarro-Frenk-White model with a core. The comparison of this entropy with that of dark matter in the freeze-out era allows us to constrain the parameter space in mSUGRA models. Moreover, combining these constraints with the ones obtained from the usual abundance criterion and demanding that these criteria be consistent with the 2{sigma} bounds for the abundance of dark matter: 0.112{<=}{Omega}{sub DM}h{sup 2}{<=}0.122, we are able to clearly identify validity regions among the values of tan{beta}, which is one of the parameters of the mSUGRA model. We found that for the regions of the parameter space explored, small values of tan{beta} are not favored; only for tan {beta} Asymptotically-Equal-To 50 are the two criteria significantly consistent. In the region where the two criteria are consistent we also found a lower bound for the neutralino mass, m{sub {chi}}{>=}141 GeV.
Effects of Space Weather on Biomedical Parameters during the Solar Activity Cycles 23-24.
Ragul'skaya, M V; Rudenchik, E A; Chibisov, S M; Gromozova, E N
2015-06-01
The results of long-term (1998-2012) biomedical monitoring of the biotropic effects of space weather are discussed. A drastic change in statistical distribution parameters in the middle of 2005 was revealed that did not conform to usual sinusoidal distribution of the biomedical data reflecting changes in the number of solar spots over a solar activity cycle. The dynamics of space weather of 2001-2012 is analyzed. The authors hypothesize that the actual change in statistical distributions corresponds to the adaptation reaction of the biosphere to nonstandard geophysical characteristics of the 24th solar activity cycle and the probable long-term decrease in solar activity up to 2067. PMID:26085362
Near minimum-time maneuvers of large space structures using parameter optimization
NASA Technical Reports Server (NTRS)
Carter, M. T.; Vadali, S. R.; Singh, T.
1993-01-01
Near minimum-time attitude maneuvers for large, inherently-flexible space structures with finite fuel supplies are investigated. The open loop maneuver is determined with the Sequential Quadratic Programming (SQP) algorithm, which optimizes a bang-off-bang control parameter set for the given maneuver. Torque smoothing is used to prevent discontinuities in the control which would excite the flexible structure. Additional system dynamics such as thruster inefficiency, spring forces and pressure leaks are identified from preliminary experiments on the ASTREX test article.
Introduction of a valence space in QRPA: Impact on vibrational mass parameters and spectroscopy
Lechaftois, F. Péru, S.; Deloncle, I.
2015-10-15
For the first time, using a unique finite range interaction (D1M Gogny force), a fully coherent and time-feasible calculation of the Bohr Hamiltonian vibrational mass is envisioned in a Hartree-Fock-Bogoliubov + Quasiparticle Random Phase Approximation (QRPA) framework. In order to reach handable computation time, we evaluate the feasibility of this method by considering the insertion of a valence space for QRPA. We validate our approach in the even-even tin isotopes comparing the convergence scheme of the mass parameter with those of built-in QRPA outputs: excited state energy and reduced transition probability. The seeming convergence of these intrinsic quantities is shown to be misleading and the difference with the theoretical expected value is quantified. This work is a primary step towards the systematic calculation of mass parameters.
Effect of alloy deformation on the average spacing parameters of non-deforming particles
Fisher, J; Gurland, J
1980-02-01
It is shown on the basis of stereological definitions and a few simple experiments that the commonly used average dispersion parameters, area fraction (A/sub A/)/sub ..beta../, areal particle density N/sub A..beta../ and mean free path lambda/sub ..cap alpha../, remain invariant during plastic deformation in the case of non-deforming equiaxed particles. Directional effects on the spacing parameters N/sub A..beta../ and lambda/sub ..cap alpha../ arise during uniaxial deformation by rotation and preferred orientation of nonequiaxed particles. Particle arrangement in stringered or layered structures and the effect of deformation on nearest neighbor distances of particles and voids are briefly discussed in relation to strength and fracture theories.
Effects of space environment on composites: An analytical study of critical experimental parameters
NASA Technical Reports Server (NTRS)
Gupta, A.; Carroll, W. F.; Moacanin, J.
1979-01-01
A generalized methodology currently employed at JPL, was used to develop an analytical model for effects of high-energy electrons and interactions between electron and ultraviolet effects. Chemical kinetic concepts were applied in defining quantifiable parameters; the need for determining short-lived transient species and their concentration was demonstrated. The results demonstrates a systematic and cost-effective means of addressing the issues and show qualitative and quantitative, applicable relationships between space radiation and simulation parameters. An equally important result is identification of critical initial experiments necessary to further clarify the relationships. Topics discussed include facility and test design; rastered vs. diffuse continuous e-beam; valid acceleration level; simultaneous vs. sequential exposure to different types of radiation; and interruption of test continuity.
Density dependent B parameter of relativistic stars with anisotropy in pseudo-spheroidal space-time
NASA Astrophysics Data System (ADS)
Chattopadhyay, P. K.; Paul, B. C.
2016-04-01
We present a class of relativistic solutions for compact cold stars with strange matter in a pseudo-spheroidal space-time. Considering strange matter equation of state namely, p = 1/3(ρ -4B), where ρ , p and B are energy density, pressure and MIT Bag parameter respectively, stellar models are obtained. In the presence of anisotropy with a pseudo-spheroidal geometry described by Vaidya-Tikekar, metric stellar models are explored where the Bag parameter varies with the energy density (ρ ) inside the compact object. We determine the density dependence of B at different anisotropy. It is noted that although B varies with anisotropy inside the star, finally at the surface it attains a value which is independent of the anisotropy. The Bag parameter B is found to increase with an increase in anisotropy for a given compactness factor (M/b) and spheroidicity λ . It is also noted that for a star with given mass and radius, the parameter B increases with the increase in λ and finally at large λ , it attains a constant. The equation of state (EoS) obtained here from geometrical consideration with allowed `B' value is found same to that one obtains from micro-physics. The stability of the stellar models for compact stars with anisotropy in hydrostatic equilibrium obtained here is also studied.
Dimension of model parameter space and operating characteristics in adaptive dose-finding studies.
Iasonos, Alexia; Wages, Nolan A; Conaway, Mark R; Cheung, Ken; Yuan, Ying; O'Quigley, John
2016-09-20
Adaptive, model-based, dose-finding methods, such as the continual reassessment method, have been shown to have good operating characteristics. One school of thought argues in favor of the use of parsimonious models, not modeling all aspects of the problem, and using a strict minimum number of parameters. In particular, for the standard situation of a single homogeneous group, it is common to appeal to a one-parameter model. Other authors argue for a more classical approach that models all aspects of the problem. Here, we show that increasing the dimension of the parameter space, in the context of adaptive dose-finding studies, is usually counter productive and, rather than leading to improvements in operating characteristics, the added dimensionality is likely to result in difficulties. Among these are inconsistency of parameter estimates, lack of coherence in escalation or de-escalation, erratic behavior, getting stuck at the wrong level, and, in almost all cases, poorer performance in terms of correct identification of the targeted dose. Our conclusions are based on both theoretical results and simulations. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27090197
A new parameter space study of the fermionic cold dark matter model
NASA Astrophysics Data System (ADS)
Bagherian, Z.; Ettefaghi, M. M.; Haghgouyan, Z.; Moazzemi, R.
2014-10-01
We consider the standard model (SM) extended by a gauge singlet fermion as cold dark matter (SFCDM) and a gauge singlet scalar (singlet Higgs) as a mediator. The parameter space of the SM is enlarged by seven new ones. We obtain the total annihilation cross section of singlet fermions to the SM particles and singlet Higgs at tree level. Regarding the relic abundance constraint obtained by WMAP observations, we study the dependency on each parameter separately, for dark matter masses up to 1 TeV. In particular, the coupling of SFCDM to singlet Higgs gs, the SFCDM mass mψ, the second Higgs mass mh2, and the Higgs bosons mixing angel θ are investigated accurately. Three other parameters play no significant role. For a maximal mixing of Higgs bosons or at resonances, gs is applicable for the perturbation theory at tree level. We also obtain the scattering cross section of SFCDM off nucleons and compare our results with experiments which have already reported data in this mass range; XENON100, LUX, COUPP and PICASSO collaborations. Our results show that the SFCDM is excluded by these experiments for choosing parameters which are consistent with perturbation theory and relic abundance constraints.
A new parameter space study of the fermionic cold dark matter model
Bagherian, Z.; Ettefaghi, M.M.; Haghgouyan, Z.; Moazzemi, R. E-mail: mettefaghi@qom.ac.ir E-mail: r.moazzemi@qom.ac.ir
2014-10-01
We consider the standard model (SM) extended by a gauge singlet fermion as cold dark matter (SFCDM) and a gauge singlet scalar (singlet Higgs) as a mediator. The parameter space of the SM is enlarged by seven new ones. We obtain the total annihilation cross section of singlet fermions to the SM particles and singlet Higgs at tree level. Regarding the relic abundance constraint obtained by WMAP observations, we study the dependency on each parameter separately, for dark matter masses up to 1 TeV. In particular, the coupling of SFCDM to singlet Higgs g{sub s}, the SFCDM mass m{sub ψ}, the second Higgs mass m{sub h{sub 2}}, and the Higgs bosons mixing angel θ are investigated accurately. Three other parameters play no significant role. For a maximal mixing of Higgs bosons or at resonances, g{sub s} is applicable for the perturbation theory at tree level. We also obtain the scattering cross section of SFCDM off nucleons and compare our results with experiments which have already reported data in this mass range; XENON100, LUX, COUPP and PICASSO collaborations. Our results show that the SFCDM is excluded by these experiments for choosing parameters which are consistent with perturbation theory and relic abundance constraints.
Parameter-space metric for all-sky semicoherent searches for gravitational-wave pulsars
NASA Astrophysics Data System (ADS)
Wette, Karl
2015-10-01
The sensitivity of all-sky searches for gravitational-wave pulsars is primarily limited by the finite availability of computing resources. Semicoherent searches are a widely used method of maximizing sensitivity to gravitational-wave pulsars at fixed computing cost: the data from a gravitational-wave detector are partitioned into a number of segments, each segment is coherently analyzed, and the analysis results from each segment are summed together. The generation of template banks for the coherent analysis of each segment, and for the summation, requires knowledge of the metrics associated with the coherent and semicoherent parameter spaces respectively. We present a useful approximation to the semicoherent parameter-space metric, analogous to that presented in Wette and Prix [Phys. Rev. D 88, 123005 (2013)] for the coherent metric. The new semicoherent metric is compared to previous work in Pletsch [Phys. Rev. D 82, 042002 (2010)], and Brady and Creighton [Phys. Rev. D 61, 082001 (2000)]. We find that semicoherent all-sky searches require orders of magnitude more templates than previously predicted.
Application of separable parameter space techniques to multi-tracer PET compartment modeling
Zhang, Jeff L; Morey, A Michael; Kadrmas, Dan J
2016-01-01
Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg–Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models. PMID:26788888
Application of separable parameter space techniques to multi-tracer PET compartment modeling
NASA Astrophysics Data System (ADS)
Zhang, Jeff L.; Morey, A. Michael; Kadrmas, Dan J.
2016-02-01
Multi-tracer positron emission tomography (PET) can image two or more tracers in a single scan, characterizing multiple aspects of biological functions to provide new insights into many diseases. The technique uses dynamic imaging, resulting in time-activity curves that contain contributions from each tracer present. The process of separating and recovering separate images and/or imaging measures for each tracer requires the application of kinetic constraints, which are most commonly applied by fitting parallel compartment models for all tracers. Such multi-tracer compartment modeling presents challenging nonlinear fits in multiple dimensions. This work extends separable parameter space kinetic modeling techniques, previously developed for fitting single-tracer compartment models, to fitting multi-tracer compartment models. The multi-tracer compartment model solution equations were reformulated to maximally separate the linear and nonlinear aspects of the fitting problem, and separable least-squares techniques were applied to effectively reduce the dimensionality of the nonlinear fit. The benefits of the approach are then explored through a number of illustrative examples, including characterization of separable parameter space multi-tracer objective functions and demonstration of exhaustive search fits which guarantee the true global minimum to within arbitrary search precision. Iterative gradient-descent algorithms using Levenberg-Marquardt were also tested, demonstrating improved fitting speed and robustness as compared to corresponding fits using conventional model formulations. The proposed technique overcomes many of the challenges in fitting simultaneous multi-tracer PET compartment models.
Constraining the mSUGRA parameter space through entropy and abundance criteria
Cabral-Rosetti, Luis G.; Mondragon, Myriam; Nunez, Dario; Sussman, Roberto A.; Zavala, Jesus; Nellen, Lukas
2007-06-19
We explore the use of two criteria to constrain the allowed parameter space in mSUGRA models; both criteria are based in the calculation of the present density of neutralinos {chi}0 as Dark Matter in the Universe. The first one is the usual ''abundance'' criterion that requieres that present neutralino relic density complies with 0.0945 < {omega}CDMh2 < 0.1287, which are the 2{sigma} bounds according to WMAP. To calculate the relic density we use the public numerical code micrOMEGAS. The second criterion is the original idea presented in [3] that basically applies the microcanonical definition of entropy to a weakly interacting and self-gravitating gas, and then evaluate the change in entropy per particle of this gas between the freeze-out era and present day virialized structures. An 'entropy consistency' criterion emerges by comparing theoretical and empirical estimates of this entropy. One of the objetives of the work is to analyze the joint application of both criteria, already done in [3], to see if their results, using approximations for the calculations of the relic density, agree with the results coming from the exact numerical results of micrOMEGAS. The main objetive of the work is to use this method to constrain the parameter space in mSUGRA models that are inputs for the calculations of micrOMEGAS, and thus to get some bounds on the predictions for the SUSY spectra.
NASA Astrophysics Data System (ADS)
Mazoyer, Johan; Pueyo, Laurent; Norman, Colin; N'Diaye, Mamadou; Mawet, Dimitri; Soummer, Rémi; Perrin, Marshall; Choquet, Élodie; Carlotti, Alexis
2015-09-01
As the performance of coronagraphs improves, the achievable contrast is more and more dependent of the shape of the pupil. The future generation of space and ground based coronagraphic instruments will have to achieve high contrast levels on on-axis and/or segmented telescopes. To correct for the high amplitude aberrations introduced by secondary mirror structures and segmentation of the primary mirror, we explore a two deformable mirror (DM) method. The major difficulty of several DM methods is the non-linear relation linking actuator strokes to the point spread function in the coronagraph focal plane. The Active Compensation of Aperture Discontinuities (ACAD) method is achieving this minimization by solving a non linear differential Monge Ampere equation. Once this open loop method have reached the minimum, a close-loop stroke minimization method can be applied to correct for phase and amplitude aberrations to achieve the ultimate contrast. In this paper, I describe the results of the parametric analysis that that I have undertaken on this method. After recalling the principle of the method, I will described the explored parameter space (deformable mirror set-up, shape of the pupil, bandwidth, coronagraph designs). I will precisely described the way I simulated the Vortex coronagraph for this numerical simulation. Finally I will present the preliminary results of this parametric analysis for space telescope pupils only.
NASA Astrophysics Data System (ADS)
Zhao, Jieliang; Yan, Shaoze; Wu, Jianing
2014-05-01
Space manipulator is an important tool for spacecraft to complete a variety of tasks in space. Nowadays the harmonic drive is widely used as the reducer in the space manipulator, which may influence the dynamical properties of flexible space manipulator. The analysis of dynamic reliability and parameter sensitivity of space manipulator with harmonic drive is of significant importance for space manipulator designers in the early stage of design. The trajectory precision of the manipulator determines whether the mechanism performs normally. However, it is difficult to use the existing methods to resolve reliability apportionment issues because of the data insufficiency and the uncertainty of the relations among the components in the mechanical system. This paper establishes the dynamical models of space manipulator considering the harmonic hysteresis phenomenon derived from the harmonic reducer. A new method is proposed to analyze the dynamic reliability and parameter sensitivity of space manipulator with harmonic drive. The proposed method extends the previous response surface method (RSM) and focuses on the characteristics of the output dynamical property of the space manipulator. With the result of parameter sensitivity analysis, we can prolong the fine arm or shorten the main arm to improve the motion precision reliability of space manipulator. Therefore, our revised response surface method (RRSM) is suitable for reliability apportionment of the space manipulator when the design information has not been clearly identified, particularly in early design phrase.
Cosmogenic neutrinos: parameter space and detectabilty from PeV to ZeV
Kotera, K.; Olinto, A.V.; Allard, D. E-mail: allard@apc.univ-paris7.fr
2010-10-01
While propagating from their source to the observer, ultrahigh energy cosmic rays interact with cosmological photon backgrounds and generate to the so-called ''cosmogenic neutrinos''. Here we study the parameter space of the cosmogenic neutrino flux given recent cosmic ray data and updates on plausible source evolution models. The shape and normalization of the cosmogenic neutrino flux are very sensitive to some of the current unknowns of ultrahigh energy cosmic ray sources and composition. We investigate various chemical compositions and maximum proton acceleration energies E{sub p,max} which are allowed by current observations. We consider different models of source evolution in redshift and three possible scenarios for the Galactic to extragalactic transition. We summarize the parameter space for cosmogenic neutrinos into three regions: an optimistic scenario that is currently being constrained by observations, a plausible range of models in which we base many of our rate estimates, and a pessimistic scenario that will postpone detection for decades to come. We present the implications of these three scenarios for the detection of cosmogenic neutrinos from PeV to ZeV (10{sup 14−21} eV) with the existing and upcoming instruments. In the plausible range of parameters, the narrow flux variability in the EeV energy region assures low but detectable rates for IceCube (0.06–0.2 neutrino per year) and the Pierre Auger Observatory (0.03–0.06 neutrino per year), and detection should happen in the next decade. If EeV neutrinos are detected, PeV information can help select between competing models of cosmic ray composition at the highest energy and the Galactic to extragalactic transition at ankle energies. With improved sensitivity, ZeV neutrino observatories, such as ANITA and JEM-EUSO could explore and place limits on the maximum acceleration energy.
Domain Decomposition PN Solutions to the 3D Transport Benchmark over a Range in Parameter Space
NASA Astrophysics Data System (ADS)
Van Criekingen, S.
2014-06-01
The objectives of this contribution are twofold. First, the Domain Decomposition (DD) method used in the parafish parallel transport solver is re-interpreted as a Generalized Schwarz Splitting as defined by Tang [SIAM J Sci Stat Comput, vol.13 (2), pp. 573-595, 1992]. Second, parafish provides spherical harmonic (i.e., PN) solutions to the NEA benchmark suite for 3D transport methods and codes over a range in parameter space. To the best of the author's knowledge, these are the first spherical harmonic solutions provided for this demanding benchmark suite. They have been obtained using 512 CPU cores of the JuRoPa machine installed at the Jülich Computing Center (Germany).
NASA Astrophysics Data System (ADS)
Suriza, A. Z.; Md Rafiqul, Islam; Wajdi, A. K.; Naji, A. W.
2013-03-01
As the demand for higher and unlimited bandwidth for communication channel is increased, Free Space Optics (FSO) is a good alternative solution. As it is protocol transparent, easy to install, cost effective and have capabilities like fiber optics, its demand rises very fast. Weather condition, however is the limiting factor for FSO link. In the temperate region the major blockage for FSO link feasibility is fog. In the tropical region high rainfall rate is expected to be the major drawback of FSO link availability. Rain attenuation is the most significant to influence FSO link availability in tropical region. As for now the available k and α values are developed using data from temperate regions. Therefore, the objective of this paper is to propose new parameters for specific rain attenuation prediction model that represents tropical weather condition. The proposed values are derived from data measured in Malaysia and using methods recommended by ITU-R.
A variational approach for dissipative quantum transport in a wide parameter space
Zhang, Yu Kwok, YanHo; Chen, GuanHua; Yam, ChiYung
2015-09-14
Recent development of theoretical method for dissipative quantum transport has achieved notable progresses in the weak or strong electron-phonon coupling regime. However, a generalized theory for dissipative quantum transport in a wide parameter space had not been established. In this work, a variational polaron theory for dissipative quantum transport in a wide range of electron-phonon coupling is developed. The optimal polaron transformation is determined by the optimization of the Feynman-Bogoliubov upper bound of free energy. The free energy minimization ends up with an optimal mean-field Hamiltonian and a minimal interaction Hamiltonian. Hence, second-order perturbation can be applied to the transformed system, resulting in an accurate and efficient method for the treatment of dissipative quantum transport with different electron-phonon coupling strength. Numerical benchmark calculation on a single site model coupled to one phonon mode is presented.
A variational approach for dissipative quantum transport in a wide parameter space
NASA Astrophysics Data System (ADS)
Zhang, Yu; Yam, ChiYung; Kwok, YanHo; Chen, GuanHua
2015-09-01
Recent development of theoretical method for dissipative quantum transport has achieved notable progresses in the weak or strong electron-phonon coupling regime. However, a generalized theory for dissipative quantum transport in a wide parameter space had not been established. In this work, a variational polaron theory for dissipative quantum transport in a wide range of electron-phonon coupling is developed. The optimal polaron transformation is determined by the optimization of the Feynman-Bogoliubov upper bound of free energy. The free energy minimization ends up with an optimal mean-field Hamiltonian and a minimal interaction Hamiltonian. Hence, second-order perturbation can be applied to the transformed system, resulting in an accurate and efficient method for the treatment of dissipative quantum transport with different electron-phonon coupling strength. Numerical benchmark calculation on a single site model coupled to one phonon mode is presented.
NASA Technical Reports Server (NTRS)
Hirasaki, P. N.
1971-01-01
Shielding a spacecraft from the severe thermal environment of an atmospheric entry requires a sophisticated thermal protection system (TPS). Thermal computer program models were developed for two such TPS designs proposed for the space shuttle orbiter. The multilayer systems, a reusable surface insulation TPS, and a re-radiative metallic skin TPS, were sized for a cross-section of trajectories in the entry corridor. This analysis indicates the relative influence of the entry parameters on the weight of each TPS concept. The results are summarized graphically. The trajectory variables considered were down-range, cross-range, orbit inclination, entry interface velocity and flight path angle, maximum heating rate level, angle of attack, and ballistic coefficient. Variations in cross-range and flight path angle over the ranges considered had virtually no effect on the required entry TPS weight. The TPS weight was significantly more sensitive to variations in angle of attack than to dispersions in the other trajectory considered.
Drummond, Alexei J; Nicholls, Geoff K; Rodrigo, Allen G; Solomon, Wiremu
2002-01-01
Molecular sequences obtained at different sampling times from populations of rapidly evolving pathogens and from ancient subfossil and fossil sources are increasingly available with modern sequencing technology. Here, we present a Bayesian statistical inference approach to the joint estimation of mutation rate and population size that incorporates the uncertainty in the genealogy of such temporally spaced sequences by using Markov chain Monte Carlo (MCMC) integration. The Kingman coalescent model is used to describe the time structure of the ancestral tree. We recover information about the unknown true ancestral coalescent tree, population size, and the overall mutation rate from temporally spaced data, that is, from nucleotide sequences gathered at different times, from different individuals, in an evolving haploid population. We briefly discuss the methodological implications and show what can be inferred, in various practically relevant states of prior knowledge. We develop extensions for exponentially growing population size and joint estimation of substitution model parameters. We illustrate some of the important features of this approach on a genealogy of HIV-1 envelope (env) partial sequences. PMID:12136032
Plesko, Catherine S; Clement, R Ryan; Weaver, Robert P; Bradley, Paul A; Huebner, Walter F
2009-01-01
The mitigation of impact hazards resulting from Earth-approaching asteroids and comets has received much attention in the popular press. However, many questions remain about the near-term and long-term, feasibility and appropriate application of all proposed methods. Recent and ongoing ground- and space-based observations of small solar-system body composition and dynamics have revolutionized our understanding of these bodies (e.g., Ryan (2000), Fujiwara et al. (2006), and Jedicke et al. (2006)). Ongoing increases in computing power and algorithm sophistication make it possible to calculate the response of these inhomogeneous objects to proposed mitigation techniques. Here we present the first phase of a comprehensive hazard mitigation planning effort undertaken by Southwest Research Institute and Los Alamos National Laboratory. We begin by reviewing the parameter space of the object's physical and chemical composition and trajectory. We then use the radiation hydrocode RAGE (Gittings et al. 2008), Monte Carlo N-Particle (MCNP) radiation transport (see Clement et al., this conference), and N-body dynamics codes to explore the effects these variations in object properties have on the coupling of energy into the object from a variety of mitigation techniques, including deflection and disruption by nuclear and conventional munitions, and a kinetic impactor.
Technology Transfer Automated Retrieval System (TEKTRAN)
Retrieving soil moisture from space-borne microwave radiometer observations often requires ancillary parameters such as surface vegetation opacity or vegetation water content. The conventional approach for deriving representative footprint-scale values of these parameters is to simply average the co...
Accuracy of q-space related parameters in MRI: simulations and phantom measurements.
Lätt, Jimmy; Nilsson, Markus; Malmborg, Carin; Rosquist, Hannah; Wirestam, Ronnie; Ståhlberg, Freddy; Topgaard, Daniel; Brockstedt, Sara
2007-11-01
The accuracy of q-space measurements was evaluated at a 3.0-T clinical magnetic resonance imaging (MRI) scanner, as compared with a 4.7-T nuclear magnetic resonance (NMR) spectrometer. Measurements were performed using a stimulated-echo pulse-sequence on n-decane as well as on polyethylene glycol (PEG) mixed with different concentrations of water, in order to obtain bi-exponential signal decay curves. The diffusion coefficients as well as the modelled diffusional kurtosis K(fit) were obtained from the signal decay curve, while the full-width at half-maximum (FWHM) and the diffusional kurtosis K were obtained from the displacement distribution. Simulations of restricted diffusion, under conditions similar to those obtainable with a clinical MRI scanner, were carried out assuming various degrees of violation of the short gradient pulse (SGP) condition and of the long diffusion time limit. The results indicated that an MRI system can not be used for quantification of structural sizes less than about 10 microm by means of FWHM since the parameter underestimates the confinements due to violation of the SGP condition. However, FWHM can still be used as an important contrast parameter. The obtained kurtosis values were lower than expected from theory and the results showed that care must be taken when interpreting a kurtosis estimate deviating from zero. PMID:18041259
NASA Astrophysics Data System (ADS)
Huang, Yiqing; Sun, Changyin; Qian, Chengshan; Wang, Li
2015-12-01
This paper deals with the problem of linear parameter varying (LPV) switching attitude control for a near space hypersonic vehicle (NSHV) with parametric uncertainties. First, due to the enormous complexity of the NSHV nonlinear attitude dynamics, a slow-fast loop polytopic LPV attitude model is developed by using Jacobian linearisation and the tensor product model transformation approach. Second, for the purpose of less conservative attitude controller design, the flight envelope is divided into four subregions. For each parameter subregion, slow-loop and fast-loop LPV controllers are designed. By the defined switching character function, these slow-fast loop LPV controllers are then switched in order to guarantee the closed-loop NSHV system to be asymptotically stable and satisfy a specified tracking performance criterion. The condition of LPV switching attitude controller synthesis is given in terms of linear matrix inequalities, which can be readily solved via standard numerical software, and the robust stability analysis of the closed-loop NSHV system is verified based on multiple Lypapunov functions. Finally, numerical simulations have demonstrated the effectiveness of the proposed approach.
NASA Astrophysics Data System (ADS)
Smith, David; Schuldt, Carsten; Lorenz, Jessica; Tschirner, Teresa; Moebius-Winkler, Maximilian; Kaes, Josef; Glaser, Martin; Haendler, Tina; Schnauss, Joerg
2015-03-01
Biologically evolved materials are often used as inspiration in the development of new materials as well as examinations into the underlying physical principles governing their behavior. For instance, the biopolymer constituents of the highly dynamic cellular cytoskeleton such as actin have inspired a deep understanding of soft polymer-based materials. However, the molecular toolbox provided by biological systems has been evolutionarily optimized to carry out the necessary functions of cells, and the inability modify basic properties such as biopolymer stiffness hinders a meticulous examination of parameter space. Using actin as inspiration, we circumvent these limitations using model systems assembled from programmable materials such as DNA. Nanorods with comparable, but controllable dimensions and mechanical properties as actin can be constructed from small sets of specially designed DNA strands. In entangled gels, these allow us to systematically determine the dependence of network mechanical properties on parameters such as persistence length and crosslink strength. At higher concentrations in the presence of local attractive forces, we see a transition to highly-ordered bundled and ``aster'' phases similar to those previously characterized in systems of actin or microtubules.
Estimating the modal parameters from multiple measurement setups using a joint state space model
NASA Astrophysics Data System (ADS)
Cara, F. Javier; Juan, Jesús; Alarcón, Enrique
2014-02-01
Computing the modal parameters of structural systems often requires processing data from multiple non-simultaneously recorded setups of sensors. These setups share some sensors in common, the so-called reference sensors, which are fixed for all measurements, while the other sensors change their position from one setup to the next. One possibility is to process the setups separately resulting in different modal parameter estimates for each setup. Then, the reference sensors are used to merge or glue the different parts of the mode shapes to obtain global mode shapes, while the natural frequencies and damping ratios are usually averaged. In this paper we present a new state space model that processes all setups at once. The result is that the global mode shapes are obtained automatically, and only a value for the natural frequency and damping ratio of each mode is estimated. We also investigate the estimation of this model using maximum likelihood and the Expectation Maximization algorithm, and apply this technique to simulated and measured data corresponding to different structures.
A modal test of a space-truss for structural parameter identification
Carne, T.G.; Mayes, R.L.; Levine-West, M.B.
1992-12-01
The Jet Propulsion Laboratory is developing a large space-truss to support a micro-precision interferometer. A finite element model will be used to design and place passive and active elements in the truss to suppress vibration. To improve the model`s predictive capability, it is desirable to identify uncertain structural parameters in the model by utilizing experimental modal data. Testing of both the components and the system was performed to obtain the data necessary to identify the structural parameters. Extracting a modal model, absent of bias errors, from measured data requires great care in test design and implementation. Testing procedures that are discussed include: verification of non-constraining shaker attachment, quantification of the non-linear structural response, and the design and effects of suspension systems used to simulate a free structure. In addition to these procedures, the accuracy of the measured frequency response functions are evaluated by comparing functions measured with random excitation, using various frequency resolutions, and with step sine excitation.
A modal test of a space-truss for structural parameter identification
Carne, T.G.; Mayes, R.L. ); Levine-West, M.B. )
1992-01-01
The Jet Propulsion Laboratory is developing a large space-truss to support a micro-precision interferometer. A finite element model will be used to design and place passive and active elements in the truss to suppress vibration. To improve the model's predictive capability, it is desirable to identify uncertain structural parameters in the model by utilizing experimental modal data. Testing of both the components and the system was performed to obtain the data necessary to identify the structural parameters. Extracting a modal model, absent of bias errors, from measured data requires great care in test design and implementation. Testing procedures that are discussed include: verification of non-constraining shaker attachment, quantification of the non-linear structural response, and the design and effects of suspension systems used to simulate a free structure. In addition to these procedures, the accuracy of the measured frequency response functions are evaluated by comparing functions measured with random excitation, using various frequency resolutions, and with step sine excitation.
NASA Astrophysics Data System (ADS)
Eo, Yun Suk; Wolgast, Steven; Kurdak, Cagliyan; Sun, Kai; Kim, Dae-Jeong; Fisk, Zachary; Hatnean, Monica Ciomaga; Balakrishnan, Geetha
There is growing interest in studying the conducting surface of SmB6, which is believed to originate from its nontrivial band topology. Up to date, different measurement techniques, including ARPES, dHvA, and Hall bar transport still disagree on important parameters such as the carrier density. In order to find the carrier density (n) and mobility (μ) for the Dirac pockets participating in transport, we measure magnetotransport on Corbino devices fabricated on (100), (110), and (111) surfaces grown by floating zone and flux methods. Our samples do not exhibit Shubnikov-de Haas oscillations at high field pulsed measurements up to 90 Tesla, which provides an upper bound of μ of each channels. Also, angle-dependent magnetotransport up to 35 T allows us to extract an effective n and μ of the combined channels. Together, a parameter space that confines the possible n and μ of each channel is constructed, and appears to be in agreement with ARPES reports. Additionally, the effective n and μ change up to 20 percent when applying magnetic field up to 35 T. We will discuss how the Landau fan diagram can be nonlinear by this effect. This project was funded by NSF Grant #DMR-1006500. This project was performed at the National High Magnetic Field Laboratory, and in the Lurie Nanofabrication Facility.
NASA Astrophysics Data System (ADS)
Williamson, Daniel; Goldstein, Michael; Allison, Lesley; Blaker, Adam; Challenor, Peter; Jackson, Laura; Yamazaki, Kuniko
2013-10-01
We apply an established statistical methodology called history matching to constrain the parameter space of a coupled non-flux-adjusted climate model (the third Hadley Centre Climate Model; HadCM3) by using a 10,000-member perturbed physics ensemble and observational metrics. History matching uses emulators (fast statistical representations of climate models that include a measure of uncertainty in the prediction of climate model output) to rule out regions of the parameter space of the climate model that are inconsistent with physical observations given the relevant uncertainties. Our methods rule out about half of the parameter space of the climate model even though we only use a small number of historical observations. We explore 2 dimensional projections of the remaining space and observe a region whose shape mainly depends on parameters controlling cloud processes and one ocean mixing parameter. We find that global mean surface air temperature (SAT) is the dominant constraint of those used, and that the others provide little further constraint after matching to SAT. The Atlantic meridional overturning circulation (AMOC) has a non linear relationship with SAT and is not a good proxy for the meridional heat transport in the unconstrained parameter space, but these relationships are linear in our reduced space. We find that the transient response of the AMOC to idealised CO2 forcing at 1 and 2 % per year shows a greater average reduction in strength in the constrained parameter space than in the unconstrained space. We test extended ranges of a number of parameters of HadCM3 and discover that no part of the extended ranges can by ruled out using any of our constraints. Constraining parameter space using easy to emulate observational metrics prior to analysis of more complex processes is an important and powerful tool. It can remove complex and irrelevant behaviour in unrealistic parts of parameter space, allowing the processes in question to be more easily
NASA Astrophysics Data System (ADS)
Briseño, Jessica; Herrera, Graciela S.
2010-05-01
Herrera (1998) proposed a method for the optimal design of groundwater quality monitoring networks that involves space and time in a combined form. The method was applied later by Herrera et al (2001) and by Herrera and Pinder (2005). To get the estimates of the contaminant concentration being analyzed, this method uses a space-time ensemble Kalman filter, based on a stochastic flow and transport model. When the method is applied, it is important that the characteristics of the stochastic model be congruent with field data, but, in general, it is laborious to manually achieve a good match between them. For this reason, the main objective of this work is to extend the space-time ensemble Kalman filter proposed by Herrera, to estimate the hydraulic conductivity, together with hydraulic head and contaminant concentration, and its application in a synthetic example. The method has three steps: 1) Given the mean and the semivariogram of the natural logarithm of hydraulic conductivity (ln K), random realizations of this parameter are obtained through two alternatives: Gaussian simulation (SGSim) and Latin Hypercube Sampling method (LHC). 2) The stochastic model is used to produce hydraulic head (h) and contaminant (C) realizations, for each one of the conductivity realizations. With these realization the mean of ln K, h and C are obtained, for h and C, the mean is calculated in space and time, and also the cross covariance matrix h-ln K-C in space and time. The covariance matrix is obtained averaging products of the ln K, h and C realizations on the estimation points and times, and the positions and times with data of the analyzed variables. The estimation points are the positions at which estimates of ln K, h or C are gathered. In an analogous way, the estimation times are those at which estimates of any of the three variables are gathered. 3) Finally the ln K, h and C estimate are obtained using the space-time ensemble Kalman filter. The realization mean for each one
NASA Technical Reports Server (NTRS)
Riddick, Stephen E.; Hinton, David A.
2000-01-01
A study has been performed on a computer code modeling an aircraft wake vortex spacing system during final approach. This code represents an initial engineering model of a system to calculate reduced approach separation criteria needed to increase airport productivity. This report evaluates model sensitivity toward various weather conditions (crosswind, crosswind variance, turbulent kinetic energy, and thermal gradient), code configurations (approach corridor option, and wake demise definition), and post-processing techniques (rounding of provided spacing values, and controller time variance).
NASA Astrophysics Data System (ADS)
Hillman, Y.; Prialnik, D.; Kovetz, A.; Shara, M. M.
2016-03-01
Can a white dwarf (WD), accreting hydrogen-rich matter from a non-degenerate companion star, ever exceed the Chandrasekhar mass and explode as a SN Ia? We explore the range of accretion rates that allow a WD to secularly grow in mass, and derive limits on the accretion rate and on the initial mass that will allow it to reach 1.4M⊙—the Chandrasekhar mass. We follow the evolution through a long series of hydrogen flashes, during which a thick helium shell accumulates. This determines the effective helium mass accretion rate for long-term, self-consistent evolutionary runs with helium flashes. We find that net mass accumulation always occurs despite helium flashes. Although the amount of mass lost during the first few helium shell flashes is a significant fraction of that accumulated prior to the flash, that fraction decreases with repeated helium shell flashes. Eventually no mass is ejected at all during subsequent flashes. This unexpected result occurs because of continual heating of the WD interior by the helium shell flashes near its surface. The effect of heating is to lower the electron degeneracy throughout the WD, especially in the outer layers. This key result yields helium burning that is quasi-steady state, instead of explosive. We thus find a remarkably large parameter space within which long-term, self-consistent simulations show that a WD can grow in mass and reach the Chandrasekhar limit, despite its helium flashes.
The derivation of constraints on the msugra parameter space from the entropy of dark matter halos
Cabral-Rosetti, L. G.; Mondragon, M.; Nellen, L.; Nunez, D.; Sussmann, R.; Zavala, J.
2009-04-20
We derive an expression for the entropy of a present dark matter halo described by a Navarro-Frenk-White modified model with a central core. We obtain an expression for the relic abundance of neutralinos by comparing this entropy of the halo with the value it had during the freeze-out era. Using WMAP observations, we constrain the parameter space for mSUGRA models. Combining our results with the usual abundance criteria, we are able to discriminate clearly among different validity regions for tan {beta} values. For this, we require both criteria to be consistent within a 2{sigma} bound of the WMAP observations for the relic density: 0.112<{omega}h{sup 2}<0.122. We find that for sgn {mu} = +1, small values of tan {beta} are not favored; only for tan {beta}{approx}50 are both criteria significantly consistent. Both criteria allow us to put a lower bound on the neutralino mass, m{sub {chi}}{>=}141 GeV.
NASA Technical Reports Server (NTRS)
Funk, Joan G.; Sykes, George F., Jr.
1989-01-01
The effects of simulated space environmental parameters on microdamage induced by the environment in a series of commercially available graphite-fiber-reinforced composite materials were determined. Composites with both thermoset and thermoplastic resin systems were studied. Low-Earth-Orbit (LEO) exposures were simulated by thermal cycling; geosynchronous-orbit (GEO) exposures were simulated by electron irradiation plus thermal cycling. The thermal cycling temperature range was -250 F to either 200 F or 150 F. The upper limits of the thermal cycles were different to ensure that an individual composite material was not cycled above its glass transition temperature. Material response was characterized through assessment of the induced microcracking and its influence on mechanical property changes at both room temperature and -250 F. Microdamage was induced in both thermoset and thermoplastic advanced composite materials exposed to the simulated LEO environment. However, a 350 F cure single-phase toughened epoxy composite was not damaged during exposure to the LEO environment. The simuated GEO environment produced microdamage in all materials tested.
NASA Technical Reports Server (NTRS)
Long, S. A. T.
1975-01-01
The effects of various experimental parameters on the displacement errors in the triangulation solution of an elongated object in space due to pointing uncertainties in the lines of sight have been determined. These parameters were the number and location of observation stations, the object's location in latitude and longitude, and the spacing of the input data points on the azimuth-elevation image traces. The displacement errors due to uncertainties in the coordinates of a moving station have been determined as functions of the number and location of the stations. The effects of incorporating the input data from additional cameras at one of the stations were also investigated.
NASA Astrophysics Data System (ADS)
Jones-Selden, Felicia L.
Costs of aerospace missions have increased over the last twenty years, placing the future of the space program in jeopardy. A potential source for such growth can be attributed to the complex multidisciplinary and challenging nature of earth and space science instrument development. Design margins are additional resources carried in technical performance parameters to mitigate uncertainties throughout the product lifecycle. Margins are traditionally derived and allocated based upon historical experience intrinsic to organizations, as opposed to quantitative methods, jeopardizing the development of low-cost space-based instruments. This dissertation utilizes a methodology to evaluate the interrelationships between pre-launch and actual launch margins for the key technical performance parameters of mass, power, and data-rate to identify the extent to which excessive or insufficient margins are used in the design of space-based instruments in an effort to control instrument cost growth. The research examined 62 space-based instruments from the National Aeronautics and Space Administration, Federally Funded Research and Development Centers, and universities. Statistical analysis consisting of paired t-tests and multiple linear regression were utilized to determine the degree to which space-based instruments are over or under designed by the use of excessive or insufficient design margins and to determine the effect of design margins for the technical performance parameters of mass, power, and data-rate on the percentage instrument cost growth from the preliminary design phase to launch. Findings confirm, that in the implementation of space-based instruments, design margins are allocated to technical performance parameters above suggested government/industry standards, impacting the development of low-cost space-based instruments. The findings provide senior leadership, systems engineers, project managers, and resource managers with the ability to determine where
NASA Astrophysics Data System (ADS)
da Costa, Diogo Ricardo; Hansen, Matheus; Guarise, Gustavo; Medrano-T, Rene O.; Leonel, Edson D.
2016-04-01
We show that extreme orbits, trajectories that connect local maximum and minimum values of one dimensional maps, play a major role in the parameter space of dissipative systems dictating the organization for the windows of periodicity, hence producing sets of shrimp-like structures. Here we solve three fundamental problems regarding the distribution of these sets and give: (i) their precise localization in the parameter space, even for sets of very high periods; (ii) their local and global distributions along cascades; and (iii) the association of these cascades to complicate sets of periodicity. The extreme orbits are proved to be a powerful indicator to investigate the organization of windows of periodicity in parameter planes. As applications of the theory, we obtain some results for the circle map and perturbed logistic map. The formalism presented here can be extended to many other different nonlinear and dissipative systems.
Sloan Digital Sky Survey QSO's in the context of the 4D Eigenvector 1 Parameter Space
NASA Astrophysics Data System (ADS)
Zamfir, Nicolae Sebastian
We explore spectroscopic properties of N ~ 470 quasars with redshift z within 0.7. It is a large and homogeneous sample of Sloan Digital Sky Survey (SDSS) "QSO" sources brighter than either 17.5 psf g- or i-band magnitude. The research is developed in the framework of the 4D Eigenvector 1 (4DE1) Parameter Space. We exploit and also test the concept of two quasar populations (labeled A and B) nominally separated at FWHM(Hb) = 4000 km s -1 . The project comprises three chapters: (1) a search for a dichotomy/bimodality between radio-loud (RL) and radio-quiet (RQ) quasars, (2) an analysis of the Hb profile diversity and (3) an investigation of the luminosity effects on the 4DE1 measures. The second part is a dual approach: constructing composite/median spectra and (complementary) defining a set of diagnostic measures (asymmetry, kurtosis, centroid shift) in individual sources profiles. The third section incorporates a sample of N = 53 quasars at z [approximate] 0.9-3.0 with VLT/ISAAC spectra of the Hb region. This addition allows us to cover six decades of luminosity. We find that the RL quasars occupy a much more restricted domain in the optical plane of the 4DE1 compared to the RQ sources, which supports the notion of bimodality. FRII and CD RL sources show significant 4DE1 domain differences that likely reflect differences in line of sight orientation (inclined versus face-on, respectively) for these two classes. Quasars do not distribute randomly about an average optical spectrum. Our results support the conceptof two populations A and B. Population A composite Hb profiles are best described by a Lorentzian, but Population B spectra require a double Gaussian. High and low accretion sources (another version of the Population A/B concept) show significant differences in terms of Black Hole (BH) mass and Eddington ratio L bol /L Edd . Moreover, they show distinct properties in terms of line asymmetry, shift and shapes. The minimum detectable FWHM (Hb) increases with
Parameter Trade Studies For Coherent Lidar Wind Measurements of Wind from Space
NASA Technical Reports Server (NTRS)
Kavaya, Michael J.; Frehlich, Rod G.
2007-01-01
The design of an orbiting wind profiling lidar requires selection of dozens of lidar, measurement scenario, and mission geometry parameters; in addition to prediction of atmospheric parameters. Typical mission designs do not include a thorough trade optimization of all of these parameters. We report here the integration of a recently published parameterization of coherent lidar wind velocity measurement performance with an orbiting coherent wind lidar computer simulation; and the use of these combined tools to perform some preliminary parameter trades. We use the 2006 NASA Global Wind Observing Sounder mission design as the starting point for the trades.
NASA Astrophysics Data System (ADS)
Nair, Remya; Jhingan, Sanjay; Tanaka, Takahiro
2016-05-01
We study the advantages of the coexistence of future ground- and space-based gravitational-wave detectors in estimating the parameters of a binary coalescence. Space measurements will act as a precursor to ground measurements. Also, since space measurements will provide much better localization information on the source, they will aid electromagnetic follow-up of the source and hence increase the probability of finding an electromagnetic counterpart of the gravitational-wave event. Using the post-Newtonian waveform for the inspiral of nonspinning neutron star-black hole binaries in circular orbits, we analyze how estimates for the chirp mass, the symmetric mass ratio, and the time and phase at coalescence are improved by combining the data from different space-ground detector pairs. Since the gravitational waves produced by binary coalescence also provide a suitable domain where we can investigate strong field gravity, we also study the deviations from general relativity using the parameterized post-Einsteinian framework. As an example, focusing on the Einstein telescope and DECIGO pair, we demonstrate that there exists a sweet-spot range of sensitivity in the pre-DECIGO period where the best enhancement due to the synergy effect can be obtained for estimates of the post-Newtonian waveform parameters. Similar results are obtained for the parameter that characterizes deviation from general relativity.
Robust H(infinity) control design for the Space Station with structured parameter uncertainty
NASA Technical Reports Server (NTRS)
Byun, Kuk-Whan; Wie, Bong; Geller, David; Sunkel, John
1990-01-01
A robust H(infinity) control design methodology and its application to a Space Station attitude and momentum control problem are presented. This new approach incorporates nonlinear multiparameter variations in the state-space formulation of H(infinity) control theory. An application of this robust control synthesis technique tothe Space Station control problem yields a remarkable result in stability robustness with respect to the moments-of-inertia variation of about 73 percent in one of the structured uncertainty directions. The performance and stability of this new robust H(infinity) controller for the Space Station are compared to those of other controllers designed using a standard linear-quadratic-regulator synthesis technique.
An adaptive threshold detector and channel parameter estimator for deep space optical communications
NASA Technical Reports Server (NTRS)
Arabshahi, P.; Mukai, R.; Yan, T. -Y.
2001-01-01
This paper presents a method for optimal adaptive setting of ulse-position-modulation pulse detection thresholds, which minimizes the total probability of error for the dynamically fading optical fee space channel.
Electrode performance parameters for a radioisotope-powered AMTEC for space power applications
NASA Technical Reports Server (NTRS)
Underwood, M. L.; O'Connor, D.; Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Bankston, C. P.
1992-01-01
The alkali metal thermoelastic converter (AMTEC) is a device for the direct conversion of heat to electricity. Recently a design of an AMTEC using a radioisotope heat source was described, but the optimum condenser temperature was hotter than the temperatures used in the laboratory to develop the electrode performance model. Now laboratory experiments have confirmed the dependence of two model parameters over a broader range of condenser and electrode temperatures for two candidate electrode compositions. One parameter, the electrochemical exchange current density at the reaction interface, is independent of the condenser temperature, and depends only upon the collision rate of sodium at the reaction zone. The second parameter, a morphological parameter, which measures the mass transport resistance through the electrode, is independent of condenser and electrode temperatures for molybdenum electrodes. For rhodium-tungsten electrodes, however, this parameter increases for decreasing electrode temperature, indicating an activated mass transport mechanism such as surface diffusion.
Mastroleo, Felice; Van Houdt, Rob; Leroy, Baptiste; Benotmane, M Abderrafi; Janssen, Ann; Mergeay, Max; Vanhavere, Filip; Hendrickx, Larissa; Wattiez, Ruddy; Leys, Natalie
2009-12-01
In view of long-haul space exploration missions, the European Space Agency initiated the Micro-Ecological Life Support System Alternative (MELiSSA) project targeting the total recycling of organic waste produced by the astronauts into oxygen, water and food using a loop of bacterial and higher plant bioreactors. In that purpose, the alpha-proteobacterium, Rhodospirillum rubrum S1H, was sent twice to the International Space Station and was analyzed post-flight using a newly developed R. rubrum whole genome oligonucleotide microarray and high throughput gel-free proteomics with Isotope-Coded Protein Label technology. Moreover, in an effort to identify a specific response of R. rubrum S1H to space flight, simulation of microgravity and space-ionizing radiation were performed on Earth under identical culture set-up and growth conditions as encountered during the actual space journeys. Transcriptomic and proteomic data were integrated and permitted to put forward the importance of medium composition and culture set-up on the response of the bacterium to space flight-related environmental conditions. In addition, we showed for the first time that a low dose of ionizing radiation (2 mGy) can induce a significant response at the transcriptomic level, although no change in cell viability and only a few significant differentially expressed proteins were observed. From the MELiSSA perspective, we could argue the effect of microgravity to be minimized, whereas R. rubrum S1H could be more sensitive to ionizing radiation during long-term space exploration mission. PMID:19571896
Lika, Konstadia; Augustine, Starrlight; Pecquerie, Laure; Kooijman, Sebastiaan A L M
2014-08-01
The standard Dynamic Energy Budget (DEB) model assumes that food is converted to reserve and a fraction κ of mobilised reserve of an individual is allocated to somatic maintenance plus growth, while the rest is allocated to maturity maintenance plus maturation (in embryos and juveniles) or reproduction (in adults). The add_my_pet collection of over 300 animal species from most larger phyla, and all chordate classes, shows that this model fits energy data very well. Nine parameters determine nine data points at abundant food: dry/wet weight ratio, age at birth, puberty, death, weight at birth, metamorphosis, puberty, ultimate weight and ultimate reproduction rate. We demonstrate that, given a few other parameters, these nine data points also determine the nine parameters uniquely that are independent of food availability: maturity at birth, metamorphosis and puberty, specific assimilation, somatic maintenance and costs for structure, allocation fraction of mobilised reserve to soma, energy conductance, and ageing acceleration. We provide an efficient algorithm for mapping between data and parameter space in both directions and found expressions for the boundaries of the parameter and data spaces. One of them quantifies the position of species in the supply-demand spectrum, which reflects the internalisation of energetic control. We link eco-physiological properties of species to their position in this spectrum and discuss it in the context of homeostasis. Invertebrates and ray-finned fish turn out to be close to the supply end of the spectrum, while other vertebrates, including cartilaginous fish, have stronger demand tendencies. We explain why birds and mammals up-regulate metabolism during reproduction. We study some properties of the bijection using elasticity coefficients. The properties have applications in parameter estimation and in the analysis of evolutionary constraints on parameter values; the relationship between DEB parameters and data has similarities
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.
Effect of space flight on cytokine production and other immunologic parameters of rhesus monkeys
NASA Technical Reports Server (NTRS)
Sonnenfeld, G.; Davis, S.; Taylor, G. R.; Mandel, A. D.; Konstantinova, I. V.; Lesnyak, A.; Fuchs, B. B.; Peres, C.; Tkackzuk, J.; Schmitt, D. A.
1996-01-01
During a recent flight of a Russian satellite (Cosmos #2229), initial experiments examining the effects of space flight on immunologic responses of rhesus monkeys were performed to gain insight into the effect of space flight on resistance to infection. Experiments were performed on tissue samples taken from the monkeys before and immediately after flight. Additional samples were obtained approximately 1 month after flight for a postflight restraint study. Two types of experiments were carried out throughout this study. The first experiment determined the ability of leukocytes to produce interleukin-1 and to express interleukin-2 receptors. The second experiment examined the responsiveness of rhesus bone marrow cells to recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF). Human reagents that cross-reacted with monkey tissue were utilized for the bulk of the studies. Results from both studies indicated that there were changes in immunologic function attributable to space flight. Interleukin-1 production and the expression of interleukin-2 receptors was decreased after space flight. Bone marrow cells from flight monkeys showed a significant decrease in their response to GM-CSF compared with the response of bone marrow cells from nonflight control monkeys. These results suggest that the rhesus monkey may be a useful surrogate for humans in future studies that examine the effect of space flight on immune response, particularly when conditions do not readily permit human study.
NASA Technical Reports Server (NTRS)
Barnes, G. D.
1982-01-01
The feasibility of a polygeneration plant at Kennedy Space Center was studied. Liquid hydrogen and gaseous nitrogen are the two principal products in consideration. Environmental parameters (air quality, water quality, biological diversity and hazardous waste disposal) necessary for the feasibility study were investigated. A National Environmental Policy Act (NEPA) project flow sheet was to be formulated for the environmental impact statement. Water quality criteria for Florida waters were to be established.
High Resolution Parameter-Space from a Two-Level Model on Semi-Insulating GaAs
NASA Astrophysics Data System (ADS)
da Silva, S. L.; Viana, E. R.; de Oliveira, A. G.; Ribeiro, G. M.; da Silva, R. L.
Semi-insulating Gallium Arsenide (SI-GaAs) samples experimentally show, under high electric fields and even at room temperature, negative differential conductivity in N-shaped form (NNDC). Since the most consolidated model for n-GaAs, namely, "the model", proposed by E. Schöll was not capable to generate the NNDC curve for SI-GaAs, in this work we have proposed an alternative model. The model proposed, "the two-valley model" is based on the minimal set of generation-recombination equations for two valleys inside of the conduction band, and an equation for the drift velocity as a function of the applied electric field, that covers the physical properties of the nonlinear electrical conduction of the SI-GaAs system. The "two-valley model" was capable to generate theoretically the NNDC region for the first time, and with that, we were able to build a high resolution parameter-space of the periodicity (PSP) using a Periodicity-Detection (PD) routine. In the parameter-space were observed self-organized periodic structures immersed in chaotic regions. The complex regions are presented in a "shrimp" shape rotated around a focal point, which forms in large-scale a "snail shell" shape, with intricate connections between different "shrimps". The knowledge of detailed information on parameter spaces is crucial to localize wide regions of smooth and continuous chaos.
NASA Astrophysics Data System (ADS)
Alekseev, V.; Sychev, V.
Dormancy is a widespread adaptation protected many species of animals and plants in harsh environmental conditions within months or even hundred years This can be perspective for long-term transportation of ecosystem elements in space missions when renewable source of food and an efficient method to recycle oxygen are required Effect of space station conditions such as space radiation strong magnetic electric fields and microgravity on resting stages has not been studies yet We examined life cycle parameters in a cladoceran D magna after one month exposition as resting eggs at the Russian segment of International Space Station ISS The reference group were kept in laboratory at the same temperature 20 o C moister 50 and packed in the same material polyethylene zipped bags The samples from orbit in 10 days after delivering to the Earth were transported to laboratory for detailed analyses of their reactivation patterns life span parameters and productive reproductive potential We found statistically significant differences between D magna from orbit and control in reactivation maturation time and the first clutch size Animals exposed at orbit demonstrated lower level of reactivation and less fitness to high productive conditions they were cultivated than in reference group In offspring of ISS treated female about 50 of males appeared and no one in control Embryos of D magna from orbit showed significantly higher sensitiveness to the fungal parasite Pitium daphniarum than
NASA Technical Reports Server (NTRS)
Sulyma, P. R.; Penny, M. M.
1978-01-01
A base pressure data correlation study was conducted to define exhaust plume similarity parameters for use in Space Shuttle power-on launch vehicle aerodynamic test programs. Data correlations were performed for single bodies having, respectively, single and triple nozzle configurations and for a triple body configuration with single nozzles on each of the outside bodies. Base pressure similarity parameters were found to differ for the single nozzle and triple nozzle configurations. However, the correlation parameter for each was found to be a strong function of the nozzle exit momentum. Results of the data base evaluation are presented indicating an assessment of all data points. Analytical/experimental data comparisons were made for nozzle calibrations and correction factors derived, where indicated for use in nozzle exit plane data calculations.
Fine-structure constant constraints on dark energy. II. Extending the parameter space
NASA Astrophysics Data System (ADS)
Martins, C. J. A. P.; Pinho, A. M. M.; Carreira, P.; Gusart, A.; López, J.; Rocha, C. I. S. A.
2016-01-01
Astrophysical tests of the stability of fundamental couplings, such as the fine-structure constant α , are a powerful probe of new physics. Recently these measurements, combined with local atomic clock tests and Type Ia supernova and Hubble parameter data, were used to constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, ζ , to the electromagnetic sector) the α variation. One caveat of these analyses was that it was based on fiducial models where the dark energy equation of state was described by a single parameter (effectively its present day value, w0). Here we relax this assumption and study broader dark energy model classes, including the Chevallier-Polarski-Linder and early dark energy parametrizations. Even in these extended cases we find that the current data constrains the coupling ζ at the 1 0-6 level and w0 to a few percent (marginalizing over other parameters), thus confirming the robustness of earlier analyses. On the other hand, the additional parameters are typically not well constrained. We also highlight the implications of our results for constraints on violations of the weak equivalence principle and improvements to be expected from forthcoming measurements with high-resolution ultrastable spectrographs.
Reducing the parameter space for unparticle-inspired models using white dwarf masses
NASA Astrophysics Data System (ADS)
de Souza, Rodrigo Alvares; Horvath, J. E.
2012-07-01
Based on astrophysical constraints derived from Chandrasekhar’s mass limit for white dwarfs, we study the effects of the model on the parameters of unparticle-inspired gravity, on scales ΛU>1TeV and dU≈1.
Chiral-odd generalized parton distributions in transverse and longitudinal impact parameter spaces
Chakrabarti, D.; Manohar, R.; Mukherjee, A.
2009-02-01
We investigate the chiral-odd generalized parton distributions for nonzero skewness {zeta} in transverse and longitudinal position spaces by taking Fourier transform with respect to the transverse and longitudinal momentum transfer, respectively. We present overlap formulas for the chiral-odd generalized parton distributions in terms of light-front wave functions (LFWFs) of the proton both in the Efremov-Radyushkin-Brodsky-Lepage and Dokshitzer-Gribov-Lipatov-Altarelli-Parisi regions. We calculate them in a field theory inspired model of a relativistic spin-1/2 composite state with the correct correlation between the different LFWFs in Fock space, namely, that of the quantum fluctuations of an electron in a generalized form of QED. We show the spin-orbit correlation effect of the two-particle LFWF as well as the correlation between the constituent spin and the transverse spin of the target.
Chiral-odd generalized parton distributions in transverse and longitudinal impact parameter spaces
NASA Astrophysics Data System (ADS)
Chakrabarti, D.; Manohar, R.; Mukherjee, A.
2009-02-01
We investigate the chiral-odd generalized parton distributions for nonzero skewness ζ in transverse and longitudinal position spaces by taking Fourier transform with respect to the transverse and longitudinal momentum transfer, respectively. We present overlap formulas for the chiral-odd generalized parton distributions in terms of light-front wave functions (LFWFs) of the proton both in the Efremov-Radyushkin-Brodsky-Lepage and Dokshitzer-Gribov-Lipatov-Altarelli-Parisi regions. We calculate them in a field theory inspired model of a relativistic spin-1/2 composite state with the correct correlation between the different LFWFs in Fock space, namely, that of the quantum fluctuations of an electron in a generalized form of QED. We show the spin-orbit correlation effect of the two-particle LFWF as well as the correlation between the constituent spin and the transverse spin of the target.
NASA Astrophysics Data System (ADS)
Kuznetsova, T. V.; Laptukhov, A. I.
As we become a space culture, we are more and more in need of a predictive understanding of the key processes that constitute the interaction of the solar wind plasma and the IMF with the terrestrial magnetic field. The paper presents results of our analysis of geoeffective parameters of the solar wind calculated from measurements of the solar wind and interplanetary magnetic field (IMF) for the period from 1964-1999 of space measurements at 1 a.u. at ecliptic plane and Kp, Dst indexes (planetary geomagnetic activity). We attract for calculation of geoeffective parameters a reconnection model that describes a reconnection between terrestrial magnetic field and an IMF of arbitrary orientation taking into account annual and daily rotations of the Earth's dipole (Kuznetsova and Laptukhov, 2001). As result we introduce two new geoeffective invariant parameters (independent from a choice of a coordinate system) that have clear physical sense of components of electric field of the solar wind along special directions of the geomagnetic moment (M): vector of electric field of the solar wind E are presented by its projections along and across the M vector (Em and Emv). For calculations of the electric field we used measured components of the IMF and solar wind velocity V. To project vector E along the directions we calculated orientation of geomagnetic moment at each moment of the Universal Time during its orbital motion (in GSE coordinate system). In terms of our approach mutual orientation of vectors of E and M is important. We obtained two functional dependencies: Kp=F1(Emv), Kp=F2(Em) on the basis of measurements for 35 years. Remarkable feature of derived functions Kp=F1(Emv), Kp=F2(Em) is that standard error is nearly the same both for high and low values of Kp (including extreme values). Results demonstrate that Emv electric field is one the main contributor to the Kp variations. Results of our detailed analysis showed that Emv can explain 94.5 % variations in Kp, Em
Measurement of the PPN parameter γ by testing the geometry of near-Earth space
NASA Astrophysics Data System (ADS)
Luo, Jie; Tian, Yuan; Wang, Dian-Hong; Qin, Cheng-Gang; Shao, Cheng-Gang
2016-06-01
The Beyond Einstein Advanced Coherent Optical Network (BEACON) mission was designed to achieve an accuracy of 10^{-9} in measuring the Eddington parameter γ , which is perhaps the most fundamental Parameterized Post-Newtonian parameter. However, this ideal accuracy was just estimated as a ratio of the measurement accuracy of the inter-spacecraft distances to the magnitude of the departure from Euclidean geometry. Based on the BEACON concept, we construct a measurement model to estimate the parameter γ with the least squares method. Influences of the measurement noise and the out-of-plane error on the estimation accuracy are evaluated based on the white noise model. Though the BEACON mission does not require expensive drag-free systems and avoids physical dynamical models of spacecraft, the relatively low accuracy of initial inter-spacecraft distances poses a great challenge, which reduces the estimation accuracy in about two orders of magnitude. Thus the noise requirements may need to be more stringent in the design in order to achieve the target accuracy, which is demonstrated in the work. Considering that, we have given the limits on the power spectral density of both noise sources for the accuracy of 10^{-9}.
Generalized parity relations for large space structures with uncertain parameters. M.S. Thesis
NASA Technical Reports Server (NTRS)
Dutilloy, J. R.
1986-01-01
The generalized parity relations method is a technique that can be used to detect sensor and actuator failures on a large space structure. A model of a grid structure was used to evaluate the performance of these relations. It shows their relative sensitivity to modeling errors. A method using sensor outputs and actuator inputs is required for the design of the generalized parity relations. Three different estimators are studied. The last estimator can generate relations optimized for the detection of a particular failure which are interesting when the level of sensor noise is high.
NASA Technical Reports Server (NTRS)
Brewer, Dana A.; Hall, John B., Jr.
1986-01-01
An evaluation is made of the NASA Space Station Reference Configuration trace contaminant production and depletion level effects of CO2, O2, humidity, temperature, and pressure variations, on the basis of a computer model of the Reference Configuration's chemical reactions and physical processes as functions of time. The effects of changes in the initial concentrations of such contaminants as nonmethane hydrocarbons and nitrogen oxides are also examined, and these are found to result in more significant changes in the concentration levels of trace contaminants than pressure and humidity variations. O2 and CO2 changes are found to have negligible effects on trace contaminant concentrations.
Experimental Determination of The Space and Flow Rate Dependency of The Subsoil Transport Parameters
NASA Astrophysics Data System (ADS)
Javaux, M.; Vanclooster, M.
Within this presentation, the influence of the flow rate and scale on the transport of a non-reactive saline tracer in a large undisturbed sandy subsoil monolith is stud- ied. The monolithique sample was extracted in a quarry at 10 m depth from the sur- face and equipped in the laboratory with tensiometers, temperature probes and time- domain-reflectometry probes. Eight solute breakthrough experiments were conducted at different flow rates allowing to elucidate the solute transport parameters in terms of a variable flow rate. The latter was controlled by means of a high precision irri- gation system in a range between 1 and 100 cm/d. Solute resident concentrations of a saline tracer was continuously monitored through 10 TDR probes of 0.4 m length, inserted in 3 vertical transects. Time series were used to estimate apparent dispersiv- ities and velocities at different locations by inversion of the analytical solution of the convection-dispersion equation for solute resident concentrations. The evolution of the apparent dispersivity with depth is studied in order to characterize the transport pro- cesses. Horizontal heterogeneity of the effective parameters is related to a mesoscale effective dispersivity factor. Furthermore, influence of the flow rate on the estimated dispersivity is also investigated.
NASA Astrophysics Data System (ADS)
Dittmore, Andrew; Trail, Collin; Olsen, Thomas; Wiener, Richard J.
2003-11-01
We have previously demonstrated the experimental control of chaos in a Modified Taylor-Couette system with hourglass geometry( Richard J. Wiener et al), Phys. Rev. Lett. 83, 2340 (1999).. Identifying fixed points susceptible to algorithms for the control of chaos is key. We seek to learn about this process in the accessible numerical model of the damped, driven pendulum. Following Baker(Gregory L. Baker, Am. J. Phys. 63), 832 (1995)., we seek points susceptible to the OGY(E. Ott, C. Grebogi, and J. A. Yorke, Phys. Rev. Lett. 64), 1196 (1990). algorithm. We automate the search for fixed points that are candidates for control. We present comparisons of the space of candidate fixed points with the bifurcation diagrams and Poincare sections of the system. We demonstrate control at fixed points which do not appear on the attractor. We also show that the control algorithm may be employed to shift the system between non-communicating branches of the attractor.
NASA Technical Reports Server (NTRS)
Rodriguez, G.
1979-01-01
In-flight estimation of large structure model errors in order to detect inevitable deficiencies in large structure controller/estimator models is discussed. Such an estimation process is particularly applicable in the area of shape control system design required to maintain a prescribed static structural shape and, in addition, suppress dynamic disturbances due to the vehicle vibrational modes. The paper outlines a solution to the problem of static shape estimation where the vehicle shape must be reconstructed from a set of measurements discretely located throughout the structure. The estimation process is based on the principle of least-squares that inherently contains the definition and explicit computation of model error estimates that are optimal in some sense. Consequently, a solution is provided for the problem of estimation of static model errors (e.g., external loads). A generalized formulation applicable to distributed parameters systems is first worked out and then applied to a one-dimensional beam-like structural configuration.
XMM Observations of Intermediate-Luminosity BLRGs: Expanding the parameter space
NASA Astrophysics Data System (ADS)
Sambruna, R.
2005-10-01
From the SDSS radio-loud AGN sample of Best et al. (2005) we extracted a volume-limited (z<0.1) sample of 11 Broad Line Radio Galaxies, with X-ray luminosities in the range 10^41-10^43 erg/s, 3 orders of magnitude lower than classical BLRGs, and matching most Seyferts. The XMM observations of this new sample will allow us to: 1) measure the X-ray continua; 2) test multiwavelength correlations valid for bright BLRGs; and 3) constrain the optical-to-X-ray SEDs. We will constrain the nature of the accretion flow and relative importance of the jet in these sources,and compare to luminous radio-loud and radio-quiet AGNs to uncover the fundamental parameters that determine the properties of radio-loud AGN.
Mapping magnetized geologic structures from space: The effect of orbital and body parameters
NASA Technical Reports Server (NTRS)
Schnetzler, C. C.; Taylor, P. T.; Langel, R. A.
1984-01-01
When comparing previous satellite magnetometer missions (such as MAGSAT) with proposed new programs (for example, Geopotential Research Mission, GRM) it is important to quantify the difference in scientific information obtained. The ability to resolve separate magnetic blocks (simulating geological units) is used as a parameter for evaluating the expected geologic information from each mission. The effect of satellite orbital altitude on the ability to resolve two magnetic blocks with varying separations is evaluated and quantified. A systematic, nonlinear, relationship exists between resolution and distance between magnetic blocks as a function of orbital altitude. The proposed GRM would provide an order-of-magnitude greater anomaly resolution than the earlier MAGSAT mission for widely separated bodies. The resolution achieved at any particular altitude varies depending on the location of the bodies and orientation.
NASA Astrophysics Data System (ADS)
Simard, Luc; Willmer, Christopher N. A.; Vogt, Nicole P.; Sarajedini, Vicki L.; Phillips, Andrew C.; Weiner, Benjamin J.; Koo, David C.; Im, Myungshin; Illingworth, Garth D.; Faber, S. M.
2002-09-01
The quantitative morphological classification of distant galaxies is essential to the understanding of the evolution of galaxies over the history of the universe. This paper presents Hubble Space Telescope WFPC2 F606W and F814W photometric structural parameters for 7450 galaxies in the ``Groth Strip.'' These parameters are based on a two-dimensional bulge+disk surface brightness model and were obtained using an automated reduction and analysis pipeline described in detail here. A first set of fits was performed separately in each bandpass, and a second set of fits was performed simultaneously on both bandpasses. The information produced by these two types of fits can be used to explore different science goals. Systematic and random fitting errors in all structural parameters as well as bulge and disk colors are carefully characterized through extensive sets of simulations. The results of these simulations are given in catalogs similar to the real science catalogs so that both real and simulated measurements can be sampled according to the same selection criteria to show biases and errors in the science data subset of interest. The effects of asymmetric structures on the recovered bulge+disk fitting parameters are also explored through simulations. The full multidimensional photometric survey selection function of the Groth Strip is also computed. This selection function, coupled to bias maps from simulations, provides a complete and objective reproduction of the observational limits, and these limits can be applied to theoretical predictions from galaxy evolution models for direct comparisons with the data. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by AURA, Inc., under contract with NASA.
Optimization of space borne imaging ladar sensor for asteroid studies using parameter design
NASA Astrophysics Data System (ADS)
Wheel, Peter J.; Dobbs, Michael E.; Sharp, William E.
2002-10-01
Imaging LADAR is a hybrid technology that offers the ability to measure basic physical and morphological characteristics (topography, rotational state, and density) of a small body from a single fast flyby, without requiring months in orbit. In addition, the imaging LADAR provides key flight navigation information including range, altitude, hazard/target avoidance, and closed-loop landing/fly-by navigation information. The Near Laser Ranger demonstrated many of these capabilities as part of the NEAR mission. The imaging LADAR scales the concept of a laser ranger into a full 3D imager. Imaging LADAR systems combine laser illumination of the target (which means that imaging is independent of solar illumination and the image SNR is controlled by the observer), with laser ranging and imaging (producing high resolution 3D images in a fraction of the time necessary for a passive imager). The technical concept described below alters the traditional design space (dominated by pulsed LADAR systems) with the introduction of a pseudo-noise (PN) coded continuous wave (CW) laser system which allows for variable range resolution mapping and leverages enormous commercial investments in high power, long-life lasers for telecommunications.
NASA Technical Reports Server (NTRS)
Bjorkman, W. S.; Uphoff, C. W.
1973-01-01
This Parameter Estimation Supplement describes the PEST computer program and gives instructions for its use in determination of lunar gravitation field coefficients. PEST was developed for use in the RAE-B lunar orbiting mission as a means of lunar field recovery. The observations processed by PEST are short-arc osculating orbital elements. These observations are the end product of an orbit determination process obtained with another program. PEST's end product it a set of harmonic coefficients to be used in long-term prediction of the lunar orbit. PEST employs some novel techniques in its estimation process, notably a square batch estimator and linear variational equations in the orbital elements (both osculating and mean) for measurement sensitivities. The program's capabilities are described, and operating instructions and input/output examples are given. PEST utilizes MAESTRO routines for its trajectory propagation. PEST's program structure and subroutines which are not common to MAESTRO are described. Some of the theoretical background information for the estimation process, and a derivation of linear variational equations for the Method 7 elements are included.
Computer code for space-time diagnostics of nuclear safety parameters
Solovyev, D. A.; Semenov, A. A.; Gruzdov, F. V.; Druzhaev, A. A.; Shchukin, N. V.; Dolgenko, S. G.; Solovyeva, I. V.; Ovchinnikova, E. A.
2012-07-01
The computer code ECRAN 3D (Experimental and Calculation Reactor Analysis) is designed for continuous monitoring and diagnostics of reactor cores and databases for RBMK-1000 on the basis of analytical methods for the interrelation parameters of nuclear safety. The code algorithms are based on the analysis of deviations between the physically obtained figures and the results of neutron-physical and thermal-hydraulic calculations. Discrepancies between the measured and calculated signals are equivalent to obtaining inadequacy between performance of the physical device and its simulator. The diagnostics system can solve the following problems: identification of facts and time for inconsistent results, localization of failures, identification and quantification of the causes for inconsistencies. These problems can be effectively solved only when the computer code is working in a real-time mode. This leads to increasing requirements for a higher code performance. As false operations can lead to significant economic losses, the diagnostics system must be based on the certified software tools. POLARIS, version 4.2.1 is used for the neutron-physical calculation in the computer code ECRAN 3D. (authors)
Macroscopicity of quantum superpositions on a one-parameter unitary path in Hilbert space
NASA Astrophysics Data System (ADS)
Volkoff, T. J.; Whaley, K. B.
2014-12-01
We analyze quantum states formed as superpositions of an initial pure product state and its image under local unitary evolution, using two measurement-based measures of superposition size: one based on the optimal quantum binary distinguishability of the branches of the superposition and another based on the ratio of the maximal quantum Fisher information of the superposition to that of its branches, i.e., the relative metrological usefulness of the superposition. A general formula for the effective sizes of these states according to the branch-distinguishability measure is obtained and applied to superposition states of N quantum harmonic oscillators composed of Gaussian branches. Considering optimal distinguishability of pure states on a time-evolution path leads naturally to a notion of distinguishability time that generalizes the well-known orthogonalization times of Mandelstam and Tamm and Margolus and Levitin. We further show that the distinguishability time provides a compact operational expression for the superposition size measure based on the relative quantum Fisher information. By restricting the maximization procedure in the definition of this measure to an appropriate algebra of observables, we show that the superposition size of, e.g., NOON states and hierarchical cat states, can scale linearly with the number of elementary particles comprising the superposition state, implying precision scaling inversely with the total number of photons when these states are employed as probes in quantum parameter estimation of a 1-local Hamiltonian in this algebra.
NASA Astrophysics Data System (ADS)
Zhurkin, I. G.; Kuzminykh, V. A.
1985-03-01
Selection of the optimum conditions and formulation of a program for a survey of planets from a space vehicle requires the knowledge of the probability of entry of planets into the star camera field of view (SCFV) and the time of presence of a planet in the SCFV. It is assumed that the optical axis of the star camera has a random orientation at a fixed moment in time and that the point of intersection of the optical axis of the star camera and the celestial sphere at a given moment in time t is uniformly distributed in the region L of possible values of the angular coordinates alfa, delta (right ascension, declination). By integration of a system of equations of motion for the large planets it is possible to determine the geocentric radius-vector corresponding to the moment in time t and it is possible to ascertain the probability of at least one planet falling in the SCFV. The P (probability) values, are given in five tables. The data make it easy to select the optimum regimes for star camera operation for the registry of at least one planet. A solution of the second problem is presented. It is assumed that: (1) during the considered time interval the planetary motion is Keplerian; (2) the SCFV is a right circular cone whose apex coincides with the center of the Earth's mass; (3) the rotation of the optical axis of the star camera occurs with a period equal to the period of revolution of the satellite carrying the star camera. An expression is derived for the presence of a planet within or at the boundary of the cone at a stipulated time.
NASA Astrophysics Data System (ADS)
Ala-Luhtala, Juha; Whiteley, Nick; Heine, Kari; Piche, Robert
2016-09-01
Twisted particle filters are a class of sequential Monte Carlo methods recently introduced by Whiteley and Lee to improve the efficiency of marginal likelihood estimation in state-space models. The purpose of this article is to extend the twisted particle filtering methodology, establish accessible theoretical results which convey its rationale, and provide a demonstration of its practical performance within particle Markov chain Monte Carlo for estimating static model parameters. We derive twisted particle filters that incorporate systematic or multinomial resampling and information from historical particle states, and a transparent proof which identifies the optimal algorithm for marginal likelihood estimation. We demonstrate how to approximate the optimal algorithm for nonlinear state-space models with Gaussian noise and we apply such approximations to two examples: a range and bearing tracking problem and an indoor positioning problem with Bluetooth signal strength measurements. We demonstrate improvements over standard algorithms in terms of variance of marginal likelihood estimates and Markov chain autocorrelation for given CPU time, and improved tracking performance using estimated parameters.
NASA Astrophysics Data System (ADS)
Wehrer, Markus; Totsche, Kai Uwe
2010-05-01
Only the combination of physical models and experiments can elucidate the processes of reactive transport in porous media. Column scale percolation experiments offer a great opportunity to identify and quantify processes of reactive transport. In contrast to batch experiments, approximately natural flow dynamics can be realized. However, due to the complexity of interactions and wide range of parameters the experiment can be insensitive to the wanted process and misinterpretation of the results is likely. In the proposed talk we want to show how numerical tools can be applied for thorough planning and evaluation of experiments. The central tool are maps of regions of equifinality, which are gained by a thorough sensitivity analysis of the parameter space. This tool can help on the one hand to plan the experimental boundary conditions such that the results are sensitive to the wanted process. On the other hand, they provide information on the reliability of inversely gained parameters of flow and transport. In the proposed talk we want to show from all three phases of the method. In the first phase the equifinality maps are used to choose an appropriate boundary condition for the experiment. In the second phase, the according column experiments are conducted and simulated inversely. We show break-through curves from such experiments with materials from different soils, sites and materials (Coke oven sites, abandoned industrial sites, destruction debris, municipal waste incineration ash). The columns were subjected to multiple flow interruptions and different flow velocities and parameters of reactive transport were gained in inverse simulations. The third phase consisted of an evaluation of the reliability of the parameters applying again maps of equifinality. Some drawbacks of the model could be identified and gave valuable hints on the actual processes.
NASA Technical Reports Server (NTRS)
Salem, Jonathan A.
2003-01-01
To characterize the stress corrosion parameters and predict the life of a sapphire window being considered for use in the International Space Station's Fluids and Combustion Facility, researchers at the NASA Glenn Research Center conducted stress corrosion tests, fracture toughness tests, and reliability analyses, as shown in the figures. Standardized test methods, developed and updated by the author under the auspices of American Society for Testing and Materials, were employed. One interesting finding is that sapphire exhibits a susceptibility to stress corrosion in water similar to that of glass. In addition to generating the stress corrosion parameters and fracture toughness data, closed-form expressions for the variances of the crack growth parameters were derived. The expressions allow confidence bands to be easily placed on life predictions of ceramic components. Brittle materials such as sapphire and quartz are required for windows in a variety of applications such as the Fluids and Combustion Facility. To minimize the launch weight of such facilities, researchers must design the windows to be as lightweight as possible. The safe use of lightweight, brittle windows in structural applications is limited by two factors: low fracture toughness and slow crack growth, or stress corrosion. Stress corrosion of these and other optical materials can occur in relatively common environments, such as humid air. Access to the data has been requested by designers for use in the life prediction of a Northrop Grumman F16 instrument window and a Jet Propulsion Laboratory instrument window. One Space Act Agreement has been formed. Future work includes the measurement of the life of subscale windows.
Grigorév, A I; Larina, I M; Noskov, V B; Menshtkin, V V; Natochkin, I V
1996-01-01
The purpose of the present investigation was to look for original approaches to the analysis of physical-chemical (osmolality, sodium, potassium, and calcium concentrations) and hormonal (cortisol, aldosterone, vasopressin, parathormone, calcitonin) parameters of cosmonauts' serum. To this event, we investigated 35 cosmonauts who had made either short- (up to 8 days) or long-term (up to 366 days) space flights. The dispersion factor of these parameters was found to be a criterion for assessment of the reaction of human regulatory systems to extreme impacts. No evident correlative link between the preflight and postflight concentrations of inorganic serum components was established; however, there was a high correlation of parathormone and cortisol concentrations inferring the participation of these hormones in readaptation. Integral analysis of all the mineral and hormonal parameters of blood serum shapes them into something unique apt to change after flight. Our data alludes to the fact that the approaches used for evaluation of the data resulting from conventional techniques open up new possibilities for prediction of changes in and identification of the character of individual reaction of humans to the spaceflight factors. PMID:8963264
NASA Astrophysics Data System (ADS)
Li, Yi-Chao; Wu, Feng-Quan; Lu, You-Jun; Chen, Xue-Lei
2014-11-01
A large inflationary tensor-to-scalar ratio r0.002 =0.20-0.05+0.07 is reported by the BICEP2 team based on their B-mode polarization detection, which is outside of the 95% confidence level of the Planck best fit model. We explore several possible ways to reduce the tension between the two by considering a model in which αs, nt, ns and the neutrino parameters Neff and Σmν are set as free parameters. Using the Markov Chain Monte Carlo (MCMC) technique to survey the complete parameter space with and without the BICEP2 data, we find that the resulting constraints on r0.002 are consistent with each other and the apparent tension seems to be relaxed. Further detailed investigations on those fittings suggest that Neff probably plays the most important role in reducing the tension. We also find that the results obtained from fitting without adopting the consistency relation do not deviate much from the consistency relation. With available Planck, WMAP, BICEP2 and BAO data sets altogether, we obtain r0.002 =0.14-0.11+0.05, nt =0.35-0.47+0.28, ns =0.98-0.02+0.02, and αs = -0.0086-0.0189+0.0148; if the consistency relation is adopted, we get r0.002 =0.22-0.06+0.05.
NASA Astrophysics Data System (ADS)
Mognard, N. M.; Cazenave, A.; Alsdorf, D. E.; Rodriguez, E.
2006-12-01
Different instruments on board Earth observing satellite missions that were designed either for ocean missions or land surface classification have been used to retrieve continental surface hydrology parameters. Conventional altimeter profilers that have been designed for measuring the ocean surface topography provide limited use for surface hydrology. Analysis of conventional altimeter time series over lakes and rivers clearly indicates superimposed seasonal and interannual variabilities while the synergy of altimeter water height estimate with the water extent provided by radiometers is a means of estimating water volume variations. The synergy with the GRACE gravimetry mission, which estimates the variations of the integrated water mass, can provide estimates of the underground water mass variability. However, profiling altimetric methods of measuring water surface elevations and their changes are incapable of capturing the inherent dynamics of all continental surface waters. For example, using a profiling altimeter and a 16-day orbital repeat cycle, like that of Terra, misses about 30 percent of the rivers and 70 percent of the lakes in the global data bases. An international team is proposing the Water Elevation Recovery mission (WatER), a high-resolution, image- based approach with two-dimensional acquisitions of water surface elevations h, dh/dt, and dh/dx required to answer important hydrologic questions. A key technology of the WatER mission is a Ka-band Radar INterferometer (KaRIN) which is a near-nadir viewing, 120 km wideswath based instrument that uses interferometric SAR processing of the returned pulses to yield single-look 5m azimuth and 10m to 70m range resolution, with an elevation accuracy of approximately 50 cm. Polynomial based averaging of heights along the water body increases the height accuracy to about 3 cm. The entire globe is covered twice every 16 days and orbit subcycles allow the average visit to be about half this time at low to mid
NASA Astrophysics Data System (ADS)
Roberts, Arthur; Lhuillier, Andrew; Liu, Yi; Ruggiu, Alessandra; Shi, Yufang
Elucidation of the effects of space flight on the immune system of astronauts and other animal species is important for the survival and success of manned space flight, especially long-term missions. Space flight exposes astronauts to microgravity, galactic cosmic radiation (GCR), and various psycho-social stressors. Blood samples from astronauts returning from space flight have shown changes in the numbers and types of circulating leukocytes. Similarly, normal lym-phocyte homeostasis has been shown to be severely affected in mice using ground-based models of microgravity and GCR exposure, as demonstrated by profound effects on several immuno-logical parameters examined by other investigators and ourselves. In particular, lymphocyte numbers are significantly reduced and subpopulation distribution is altered in the spleen, thy-mus, and peripheral blood following hindlimb unloading (HU) in mice. Lymphocyte depletion was found to be mediated through corticosteroid-induced apoptosis, although the molecular mechanism of apoptosis induction is still under investigation. The proliferative capacity of TCR-stimulated lymphocytes was also inhibited after HU. We have similarly shown that mice exposed to high-energy 56Fe ion radiation have decreased lymphocyte numbers and perturba-tions in proportions of various subpopulations, including CD4+ and CD8+ T cells, and B cells in the spleen, and maturation stages of immature T cells in the thymus. To compare these ground-based results to the effects of actual space-flight, fresh spleen and thymus samples were recently obtained from normal and transgenic mice immediately after 90 d. space-flight in the MDS, and identically-housed ground control mice. Total leukocyte numbers in each organ were enumerated, and subpopulation distribution was examined by flow cytometric analysis of CD3, CD4, CD8, CD19, CD25, DX-5, and CD11b. Splenic T cells were stimulated with anti-CD3 and assessed for proliferation after 2-4 d., and production of
Effect of quantum parameter – H on space-charge wave spectra in n-type semiconductor plasmas
Ghosh, S. Muley, Apurva
2015-07-31
The present paper deals with the propagation characteristics of very fundamental wave i.e. space – charge wave while propagating through quantum semiconductor plasma. We have used quantum hydrodynamic model to derive the most general dispersion relation in terms of quantum parameter – H. We have found that in presence of an external electrostatic field, the wave spectra (dispersion as well as gain characteristics) not only modified due to presence of quantum effect but also two novel modes of propagation are introduced due to this effect. Hence it may be concluded that to miniaturize the opto-electronic devices, one should use highly doped semiconductor medium at comparatively lower temperature so that the quantum effects predominate.
Stability Analysis and Mapping of Multiple Dynamics of Chua’s Circuit in Full Four-Parameter Spaces
NASA Astrophysics Data System (ADS)
Rocha, Ronilson; Medrano-T., Rene Orlando
2015-12-01
The stability analysis is used in order to identify and to map different dynamics of Chua’s circuit in full four-parameter spaces. The study is performed using describing functions that allow to identify fixed point, periodic orbit, and unstable states with relative accuracy, as well as to predict route to chaos and hidden dynamics that conventional computational methods do not detect. Numerical investigations based on the computation of eigenvalues and Lyapunov exponents partially support the predictions obtained from the theoretical analysis since they do not capture the multiple dynamics that can coexist in the operation of Chua’s circuit. Attractors obtained from initial conditions outside of neighborhoods of the equilibrium points confirm the multiplicity of dynamics in the operation of Chua’s circuit and corroborate the theoretical analysis.
Murphy, W A; Lumsden, R D
1984-08-01
Using nonpermeating, radiolabeled solutes to estimate the magnitude of the "unstirred water layer" (="mucosal epithelial space") of the surface of Hymenolepis diminuta, a value approximating 1% of the worm's fluid volume (0.011-0.022 ml/g wet tissue) was obtained. This value was compared with those previously reported by other workers which were greater by an order of magnitude. The difference between these results appears to be related to the use in previous studies of a permeating marker (mannitol), and a failure to divest the surface of nonspecifically adherent bathing fluid in excess of the actual "unstirred layer". These parameters must be considered in future studies on this useful model for the study of transport. PMID:6438294
NASA Astrophysics Data System (ADS)
Parshina, S. S.; Samsonov, S. N.; Manykina, V. I.; Afanasyeva, T. N.; Vishnevsky, V. V.; Petrova, P. G.; Petrova, V. D.; Strekalovskaya, A. A.; Tokayeva, L. K.; Kaplanova, T. I.; Potapova, M. V.
A simultaneous monitoring in evaluating of the response of a cardiovascular system of healthy volunteers was performed. The research was oriented to changes of a space weather parameters in aurural (Tixie), subauroral (Yakutsk) and medium (Saratov) areas. In each of the experimental groups there was revealed an effect of synchronization between repolarization processes of ventrical myocard responding (according to a T-wave symmetry coefficient of a cardiogram) and geomagnetic activity (according Kp-index). At rest the group effect of synchronization (GES) of myocard in geomagnetic activity change was noticed in 33,3%-61,3% of the respondents. The origin of GES has features depending on the area of habitation and an age of the volunteers. The study is performed with the partial financial support in partnership with Russian-Ukrainian grant RFFI №14-02-90424 ukr_a.
Huang, Zhihua; Lin, Honghuan; Xu, Dangpeng; Li, Mingzhong; Wang, Jianjun; Deng, Ying; Zhang, Rui; Zhang, Yongliang; Tian, Xiaocheng; Wei, Xiaofeng
2013-07-15
Collective laser coupling of the fiber array in the inertial confinement fusion (ICF) laser driver based on the concept of fiber amplification network (FAN) is researched. The feasible parameter space is given for laser coupling of the fundamental, second and third harmonic waves by neglecting the influence of the frequency conversion on the beam quality under the assumption of beam quality factor conservation. Third harmonic laser coupling is preferred due to its lower output energy requirement from a single fiber amplifier. For coplanar fiber array, the energy requirement is around 0.4 J with an effective mode field diameter of around 500 μm while maintaining the fundamental mode operation which is more than one order of magnitude higher than what can be achieved with state-of-the-art technology. Novel waveguide structure needs to be developed to enlarge the fundamental mode size while mitigating the catastrophic self-focusing effect. PMID:23938500
Volz, P A; Long, J D; Veselenak, J M
1995-01-01
Keratinophilic Trichophyton terrestre conidia were exposed to selected parameters of space flight including 254, 280 and 300 nm UV light, full light and total darkness of space. Phenotypic isolates were grown on human hair collected from one source at years 1 and 23 after splashdown. The patterns of fungal growth on the hair, and the hair deterioration rates, were noted according to the space exposure. Growth and deterioration were consistent but slightly reduced at year 23. PMID:7476563
NASA Astrophysics Data System (ADS)
Ouzounov, D. P.; Pulinets, S. A.; Liu, J. G.; Hattori, K.; Kalenda, P.; Shen, W.; Bobrovskiy, V. S.; Windsor, C.; Kafatos, M.; Taylor, P. T.
2011-12-01
We present for the first time new data for joint observations of pre-earthquake signals of atmospheric-thermal, ionospheric, Global Positioning System/Total Electron Content, gravitational, telluric currents and stress related signals in relation to major earthquakes. Our results and the work of others have shown that there were some electromagnetic effects in the atmosphere/ionosphere caused by strong earthquakes. We are studying the Earth's atmospheric electromagnetic environment by developing a multi-sensor model for monitoring the signals related to active tectonic faulting and earthquake processes. Two of the most recent earthquakes in Asia, M7.9 Wenchuan earthquake (China, 2008) and the latest M9.0 Tohoku earthquake/tsunami (Japan, 2011) caused great devastation and significant loss of life, which is another indication that development of an earthquake risk management scheme requires diverse interdisciplinary efforts. In this paper we address what is currently lacking in the studies of pre-earthquake signals: the synergy in the multi-disciplinary observation needed to understand the earthquake process and systematic and abnormal trends within multi-parameters simultaneously, utilizing the integration of ground and space observations. We discuss the lessons learned from both Wenchuan earthquake and Tohoku earthquakes in relation to pre-earthquake signals and how new methodologies could help for the future space- and ground-based observation of earthquake related precursor phenomena.
NASA Astrophysics Data System (ADS)
Li, Yun-He; Zhang, Jing-Fei; Zhang, Xin
2014-12-01
Dark energy can modify the dynamics of dark matter if there exists a direct interaction between them. Thus, a measurement of the structure growth, e.g., redshift-space distortions (RSDs), can provide a powerful tool to constrain the interacting dark energy (IDE) models. For the widely studied Q =3 β H ρde model, previous works showed that only a very small coupling [β ˜O (10-3) ] can survive in current RSD data. However, all of these analyses had to assume w >-1 and β >0 due to the existence of the large-scale instability in the IDE scenario. In our recent work [Phys. Rev. D 90, 063005 (2014)], we successfully solved this large-scale instability problem by establishing a parametrized post-Friedmann framework for the IDE scenario. So we, for the first time, have the ability to explore the full parameter space of the IDE models. In this work, we re-examine the observational constraints on the Q =3 β H ρde model within the parametrized post-Friedmann framework. By using the Planck data, the baryon acoustic oscillation data, the JLA sample of supernovae, and the Hubble constant measurement, we get β =-0.01 0-0.033+0.037 (1 σ ). The fit result becomes β =-0.014 8-0.0089+0.0100 (1 σ ) once we further incorporate the RSD data in the analysis. The error of β is substantially reduced with the help of the RSD data. Compared with the previous results, our results show that a negative β is favored by current observations, and a relatively larger interaction rate is permitted by current RSD data.
NASA Astrophysics Data System (ADS)
Jia, Ying-Hong; Hu, Quan; Xu, Shi-Jie
2014-02-01
A dynamics-based adaptive control approach is proposed for a planar dual-arm space robot in the presence of closed-loop constraints and uncertain inertial parameters of the payload. The controller is capable of controlling the position and attitude of both the satellite base and the payload grasped by the manipulator end effectors. The equations of motion in reduced-order form for the constrained system are derived by incorporating the constraint equations in terms of accelerations into Kane's equations of the unconstrained system. Model analysis shows that the resulting equations perfectly meet the requirement of adaptive controller design. Consequently, by using an indirect approach, an adaptive control scheme is proposed to accomplish position/attitude trajectory tracking control with the uncertain parameters being estimated on-line. The actuator redundancy due to the closed-loop constraints is utilized to minimize a weighted norm of the joint torques. Global asymptotic stability is proven by using Lyapunov's method, and simulation results are also presented to demonstrate the effectiveness of the proposed approach. [Figure not available: see fulltext.
NASA Astrophysics Data System (ADS)
Avercheva, Olga; Berkovich, Yuliy A.; Smolyanina, Svetlana; Bassarskaya, Elizaveta; Pogosyan, Sergey; Ptushenko, Vasiliy; Erokhin, Alexei; Zhigalova, Tatiana
2014-06-01
Currently light emitting diodes (LEDs) are considered to be most preferable source for space plant growth facilities. We performed a complex study of growth and photosynthesis in Chinese cabbage plants (Brassica chinensis L.) grown with continuous LED lighting based on red (650 nm) and blue (470 nm) LEDs with a red to blue photon ratio of 7:1. Plants grown with high-pressure sodium (HPS) lamps were used as a control. PPF levels used were about 100 μmol/(m2 s) (PPF 100) and nearly 400 μmol/(m2 s) (PPF 400). One group of plants was grown with PPF 100 and transferred to PPF 400 at the age of 12 days. Plants were studied at the age of 15 and 28 days (harvest age); some plants were left to naturally end their life cycle. We studied a number of parameters reflecting different stages of photosynthesis: photosynthetic pigment content; chlorophyll fluorescence parameters (photosystem II quantum yield, photochemical and non-photochemical chlorophyll fluorescence quenching); electron transport rate, proton gradient on thylakoid membranes (ΔpH), and photophosphorylation rate in isolated chloroplasts. We also tested parameters reflecting plant growth and productivity: shoot and root fresh and dry weight, sugar content and ascorbic acid content in shoots. Our results had shown that at PPF 100, plants grown with LEDs did not differ from control plants in shoot fresh weight, but showed substantial differences in photophosphorylation rate and sugar content. Differences observed in plants grown with PPF 100 become more pronounced in plants grown with PPF 400. Most parameters characterizing the plant photosynthetic performance, such as photosynthetic pigment content, electron transport rate, and ΔpH did not react strongly to light spectrum. Photophosphorylation rate differed strongly in plants grown with different spectrum and PPF level, but did not always reflect final plant yield. Results of the present work suggest that narrow-band LED lighting caused changes in Chinese
NASA Astrophysics Data System (ADS)
Ray Pitambar Mohapatra, Satyanarayan
This is an exciting time for Gravitational Wave (GW) theory and observations. From a theoretical standpoint, the grand-challenge problem of the full evolution of a Binary Black Hole (BBH) system has been solved numerically, and a variety of source simulations are made available steadfastly. On the observational side, the first generation of state-of-the-art GW detectors, LIGO and Virgo, have achieved their design goal, collected data and provided astrophysically meaningful limits. The second generation of detectors are expected to start running by 2015. Inspired by this zeitgeist, this thesis focuses on the detection of potential GW signatures from the coalescence of BBH in ground-based laser interferometers. The LIGO Scientific Collaboration has implemented different algorithms to search for transient GW signatures, targeting different portions of the BBH coalescence waveform. This thesis has used the existing algorithms to study the detection potential of GW from colliding BBH in LIGO in a wide range of source parameters, such as mass and spin of the black holes, using a sample of data from the last two months of the S5 LIGO science run (14 Aug 2007 to 30 Sept 2007). This thesis also uses numerical relativity waveforms made available via the Numerical INJection Analysis project (NINJA). Methods such as the Chirplet based analysis and the use of multivariate classifiers to optimize burst search algorithms have been introduced in this thesis. These performance studies over a wide parameter space were designed to optimize the discovery potential of ground-based GW detectors and defining strategies for the search of BBH signatures in advanced LIGO data, as a step towards the realization of GW astronomy.
Vitale, Salvatore
2016-07-29
With the discovery of the binary-black-hole (BBH) coalescence GW150914 the era of gravitational-wave (GW) astronomy has started. It has recently been shown that BBH with masses comparable to or higher than GW150914 would be visible in the Evolved Laser Interferometer Space Antenna (eLISA) band a few years before they finally merge in the band of ground-based detectors. This would allow for premerger electromagnetic alerts, dramatically increasing the chances of a joint detection, if BBHs are indeed luminous in the electromagnetic band. In this Letter we explore a quite different aspect of multiband GW astronomy, and verify if, and to what extent, measurement of masses and sky position with eLISA could improve parameter estimation and tests of general relativity with ground-based detectors. We generate a catalog of 200 BBHs and find that having prior information from eLISA can reduce the uncertainty in the measurement of source distance and primary black hole spin by up to factor of 2 in ground-based GW detectors. The component masses estimate from eLISA will not be refined by the ground based detectors, whereas joint analysis will yield precise characterization of the newly formed black hole and improve consistency tests of general relativity. PMID:27517762
NASA Astrophysics Data System (ADS)
Vitale, Salvatore
2016-07-01
With the discovery of the binary-black-hole (BBH) coalescence GW150914 the era of gravitational-wave (GW) astronomy has started. It has recently been shown that BBH with masses comparable to or higher than GW150914 would be visible in the Evolved Laser Interferometer Space Antenna (eLISA) band a few years before they finally merge in the band of ground-based detectors. This would allow for premerger electromagnetic alerts, dramatically increasing the chances of a joint detection, if BBHs are indeed luminous in the electromagnetic band. In this Letter we explore a quite different aspect of multiband GW astronomy, and verify if, and to what extent, measurement of masses and sky position with eLISA could improve parameter estimation and tests of general relativity with ground-based detectors. We generate a catalog of 200 BBHs and find that having prior information from eLISA can reduce the uncertainty in the measurement of source distance and primary black hole spin by up to factor of 2 in ground-based GW detectors. The component masses estimate from eLISA will not be refined by the ground based detectors, whereas joint analysis will yield precise characterization of the newly formed black hole and improve consistency tests of general relativity.
Pooley, C M; Bishop, S C; Marion, G
2015-06-01
Bayesian statistics provides a framework for the integration of dynamic models with incomplete data to enable inference of model parameters and unobserved aspects of the system under study. An important class of dynamic models is discrete state space, continuous-time Markov processes (DCTMPs). Simulated via the Doob-Gillespie algorithm, these have been used to model systems ranging from chemistry to ecology to epidemiology. A new type of proposal, termed 'model-based proposal' (MBP), is developed for the efficient implementation of Bayesian inference in DCTMPs using Markov chain Monte Carlo (MCMC). This new method, which in principle can be applied to any DCTMP, is compared (using simple epidemiological SIS and SIR models as easy to follow exemplars) to a standard MCMC approach and a recently proposed particle MCMC (PMCMC) technique. When measurements are made on a single-state variable (e.g. the number of infected individuals in a population during an epidemic), model-based proposal MCMC (MBP-MCMC) is marginally faster than PMCMC (by a factor of 2-8 for the tests performed), and significantly faster than the standard MCMC scheme (by a factor of 400 at least). However, when model complexity increases and measurements are made on more than one state variable (e.g. simultaneously on the number of infected individuals in spatially separated subpopulations), MBP-MCMC is significantly faster than PMCMC (more than 100-fold for just four subpopulations) and this difference becomes increasingly large. PMID:25994297
Pooley, C. M.; Bishop, S. C.; Marion, G.
2015-01-01
Bayesian statistics provides a framework for the integration of dynamic models with incomplete data to enable inference of model parameters and unobserved aspects of the system under study. An important class of dynamic models is discrete state space, continuous-time Markov processes (DCTMPs). Simulated via the Doob–Gillespie algorithm, these have been used to model systems ranging from chemistry to ecology to epidemiology. A new type of proposal, termed ‘model-based proposal’ (MBP), is developed for the efficient implementation of Bayesian inference in DCTMPs using Markov chain Monte Carlo (MCMC). This new method, which in principle can be applied to any DCTMP, is compared (using simple epidemiological SIS and SIR models as easy to follow exemplars) to a standard MCMC approach and a recently proposed particle MCMC (PMCMC) technique. When measurements are made on a single-state variable (e.g. the number of infected individuals in a population during an epidemic), model-based proposal MCMC (MBP-MCMC) is marginally faster than PMCMC (by a factor of 2–8 for the tests performed), and significantly faster than the standard MCMC scheme (by a factor of 400 at least). However, when model complexity increases and measurements are made on more than one state variable (e.g. simultaneously on the number of infected individuals in spatially separated subpopulations), MBP-MCMC is significantly faster than PMCMC (more than 100-fold for just four subpopulations) and this difference becomes increasingly large. PMID:25994297
NASA Astrophysics Data System (ADS)
Savcheva, Antonia; Tassev, Svetlin; DeLuca, Edward E.; Gibson, Sarah; Fan, Yuhong
2016-05-01
Knowledge of the 3D magnetic filed structure at the time of major solar eruptions is vital to the understanding of the space weather effects of these eruptions. Multiple data-constrained techniques that reconstruct the 3D coronal field based on photospheric magnetograms have been used to achieve this goal. In particular, we have used the flux rope insertion method to obtain the coronal magnetic field of multiple regions containing flux ropes or sheared arcades based on line-of-sight magnetograms and X-ray and EUV observations of coronal loops. For the purpose of developing statistical measures of the goodness of fit of these models to the observations, here we present our modeling of flux ropes based on synthetic magnetograms obtained from aFan & Gibson emerging flux rope simulation. The goal is to study the effect of of different input flux rope parameters on the geometry of currents, field line connectivity, and topology, in a controled setting. For this purpose we create a large grid of models with the flux rope insertion method with different combinations of axial and poloidal flux, which give us different morphology of the flux rope. We create synthetic images of these flux ropes in AIA passbands with the FORWARD forward-fitting code. The present parametric study will later be used to get a better handle on the initial condition for magnetofrictional and MHD simulations of observed regions containing flux ropes, such as sigmoids and polar-crown filaments.
Regulation of NF-κB oscillation by spatial parameters in true intracellular space (TiCS)
NASA Astrophysics Data System (ADS)
Ohshima, Daisuke; Sagara, Hiroshi; Ichikawa, Kazuhisa
2013-10-01
Transcription factor NF-κB is activated by cytokine stimulation, viral infection, or hypoxic environment leading to its translocation to the nucleus. The nuclear NF-κB is exported from the nucleus to the cytoplasm again, and by repetitive import and export, NF-κB shows damped oscillation with the period of 1.5-2.0 h. Oscillation pattern of NF-κB is thought to determine the gene expression profile. We published a report on a computational simulation for the oscillation of nuclear NF-κB in a 3D spherical cell, and showed the importance of spatial parameters such as diffusion coefficient and locus of translation for determining the oscillation pattern. Although the value of diffusion coefficient is inherent to protein species, its effective value can be modified by organelle crowding in intracellular space. Here we tested this possibility by computer simulation. The results indicate that the effective value of diffusion coefficient is significantly changed by the organelle crowding, and this alters the oscillation pattern of nuclear NF-κB.
NASA Technical Reports Server (NTRS)
Tatnall, Chistopher R.
1998-01-01
The counter-rotating pair of wake vortices shed by flying aircraft can pose a threat to ensuing aircraft, particularly on landing approach. To allow adequate time for the vortices to disperse/decay, landing aircraft are required to maintain certain fixed separation distances. The Aircraft Vortex Spacing System (AVOSS), under development at NASA, is designed to prescribe safe aircraft landing approach separation distances appropriate to the ambient weather conditions. A key component of the AVOSS is a ground sensor, to ensure, safety by making wake observations to verify predicted behavior. This task requires knowledge of a flowfield strength metric which gauges the severity of disturbance an encountering aircraft could potentially experience. Several proposed strength metric concepts are defined and evaluated for various combinations of metric parameters and sensor line-of-sight elevation angles. Representative populations of generating and following aircraft types are selected, and their associated wake flowfields are modeled using various wake geometry definitions. Strength metric candidates are then rated and compared based on the correspondence of their computed values to associated aircraft response values, using basic statistical analyses.
NASA Astrophysics Data System (ADS)
Zwenzner, H.; Voigt, S.
2009-05-01
Severe flood events turned out to be the most devastating catastrophes for Europe's population, economy and environment during the past decades. The total loss caused by the August 2002 flood is estimated to be 10 billion Euros for Germany alone. Due to their capability to present a synoptic view of the spatial extent of floods, remote sensing technology, and especially synthetic aperture radar (SAR) systems, have been successfully applied for flood mapping and monitoring applications. However, the quality and accuracy of the flood masks and derived flood parameters always depends on the scale and the geometric precision of the original data as well as on the classification accuracy of the derived data products. The incorporation of auxiliary information such as elevation data can help to improve the plausibility and reliability of the derived flood masks as well as higher level products. This paper presents methods to improve the matching of flood masks with very high resolution digital elevation models as derived from LiDAR measurements for example. In the following, a cross section approach is presented that allows the dynamic fitting of the position of flood mask profiles according to the underlying terrain information from the DEM. This approach is tested in two study areas, using different input data sets. The first test area is part of the Elbe River (Germany) where flood masks derived from Radarsat-1 and IKONOS during the 2002 flood are used in combination with a LiDAR DEM of 1 m spatial resolution. The other test data set is located on the River Severn (UK) and flood masks derived from the TerraSAR-X satellite and aerial photos acquired during the 2007 flood are used in combination with a LiDAR DEM of 2 m pixel spacing. By means of these two examples the performance of the matching technique and the scaling effects are analysed and discussed. Furthermore, the systematic flood mapping capability of the different imaging systems are examined. It could be
NASA Astrophysics Data System (ADS)
Zwenzner, H.; Voigt, S.
2008-10-01
Severe flood events turned out to be the most devastating catastrophes for Europe's population, economy and environment during the past decades. The total loss caused by the August 2002 flood is estimated to be 10 billion Euros for Germany alone. Due to their capability to present a synoptic view of the spatial extent of floods, remote sensing technology, and especially synthetic aperture radar (SAR) systems, have been successfully applied for flood mapping and monitoring applications. However, the quality and accuracy of the flood masks and derived flood parameters always depends on the scale and the geometric precision of the original data as well as on the classification accuracy of the derived data products. The incorporation of auxiliary information such as elevation data can help to improve the plausibility and reliability of the derived flood masks as well as higher level products. This paper presents methods to improve the matching of flood masks with very high resolution digital elevation models as derived from LiDAR measurements for example. In the following, a cross section approach is presented that allows the dynamic fitting of the position of flood mask profiles according to the underlying terrain information from the DEM. This approach is tested in two study areas, using different input data sets. The first test area is part of the Elbe River (Germany) where flood masks derived from Radarsat-1 and IKONOS during the 2002 flood are used in combination with a LiDAR DEM of 1 m spatial resolution. The other test data set is located on the River Severn (UK) and flood masks derived from the TerraSAR-X satellite and aerial photos acquired during the 2007 flood are used in combination with a LiDAR DEM of 2 m pixel spacing. By means of these two examples the performance of the matching technique and the scaling effects are analysed and discussed. Furthermore, the systematic flood mapping capability of the different imaging systems are examined. It could be
NASA Astrophysics Data System (ADS)
Churyumov, Klim; Kleshchonok, Valery; Mozgova, Alyona
Rosetta, a European space vehicle was head to the icy nucleus of the short period comet 67P/Churyumov-Gerasimenko on 2 March, 2004 from cosmodrome Kouru. On 20 Jan. 2014, Rosetta after 10 years of flight and 31-month sleep has been woke up succesfully and now will approche to the icy nucleus of comet Churyumov-Gerasimenko and pass away into orbit around the cometary nucleus. In November 2014 the Philae probe will be sent from Rosetta on the nucleus of comet 67P to study the relict matter of the Solar system. Comet 67P was discovered by the Kyiv astronomers Klim Churyumov and Svitlana Gerasimenko on 22 October 1969 on the five photographic plates exponed with the help of 50-cm Maksutov’s reflector of the Alma-Ata Astrophysical Institute on 9, 11 and 21 Sept. 1969. First 5 exact positions of comet were sent to Dr Brian Marsden. Dr B.Marsden showed it was new comet. The comet had an apparent magnitude of 13 and a faint tail about 1 arcmin in length at position angle 280 degrees. The astronomer Nikolay Belyaev from Saint-Petersbourg calculated that the comet followed an elliptical orbit. In 1982 it had the close encounter with the Earth at 0.3910 A.U. On the basis of the observations of comet 67P obtained in Nizhny Arkhyz with the help of the 6- BTA reflector of SAO of RAS some physical parameters of its comet plasma tail (coefficients of diffusion Dp(parallel) , Ds(perpendicular) and induction of magnetic field B) were determined. Other results of exploration of comet 67P (its polarisation, spectral observations, the light curve and morphology) in different apparitions are discussed.
SU-D-19A-04: Parameter Characterization of Electron Beam Monte Carlo Phase Space of TrueBeam Linacs
Rodrigues, A; Yin, F; Wu, Q; Sawkey, D
2014-06-01
Purpose: For TrueBeam Monte Carlo simulations, Varian does not distribute linac head geometry and material compositions, instead providing a phase space file (PSF) for the users. The PSF has a finite number of particle histories and can have very large file size, yet still contains inherent statistical noises. The purpose of this study is to characterize the electron beam PSF with parameters. Methods: The PSF is a snapshot of all particles' information at a given plane above jaws including type, energy, position, and directions. This study utilized a preliminary TrueBeam PSF, of which validation against measurement is presented in another study. To characterize the PSF, distributions of energy, position, and direction of all particles are analyzed as piece-wise parameterized functions of radius and polar angle. Subsequently, a pseudo PSF was generated based on this characterization. Validation was assessed by directly comparing the true and pseudo PSFs, and by using both PSFs in the down-stream MC simulations (BEAMnrc/DOSXYZnrc) and comparing dose distributions for 3 applicators at 15 MeV. Statistical uncertainty of 4% was limited by the number of histories in the original PSF. Percent depth dose (PDD) and orthogonal (PRF) profiles at various depths were evaluated. Results: Preliminary results showed that this PSF parameterization was accurate, with no visible differences between original and pseudo PSFs except at the edge (6 cm off axis), which did not impact dose distributions in phantom. PDD differences were within 1 mm for R{sub 7} {sub 0}, R{sub 5} {sub 0}, R{sub 3} {sub 0}, and R{sub 1} {sub 0}, and PRF field size and penumbras were within 2 mm. Conclusion: A PSF can be successfully characterized by distributions for energy, position, and direction as parameterized functions of radius and polar angles; this facilitates generating sufficient particles at any statistical precision. Analyses for all other electron energies are under way and results will be
Zhang, Yunpeng; Li, En Guo, Gaofeng; Xu, Jiadi; Wang, Chao
2014-09-15
A pair of spot-focusing horn lens antenna is the key component in a free-space measurement system. The electromagnetic constitutive parameters of a planar sample are determined using transmitted and reflected electromagnetic beams. These parameters are obtained from the measured scattering parameters by the microwave network analyzer, thickness of the sample, and wavelength of a focused beam on the sample. Free-space techniques introduced by most papers consider the focused wavelength as the free-space wavelength. But in fact, the incident wave projected by a lens into the sample approximates a Gaussian beam, thus, there has an elongation of the wavelength in the focused beam and this elongation should be taken into consideration in dielectric and magnetic measurement. In this paper, elongation of the wavelength has been analyzed and measured. Measurement results show that the focused wavelength in the vicinity of the focus has an elongation of 1%–5% relative to the free-space wavelength. Elongation's influence on the measurement result of the permittivity and permeability has been investigated. Numerical analyses show that the elongation of the focused wavelength can cause the increase of the measured value of the permeability relative to traditionally measured value, but for the permittivity, it is affected by several parameters and may increase or decrease relative to traditionally measured value.
ERIC Educational Resources Information Center
Web Feet K-8, 2001
2001-01-01
This annotated subject guide to Web sites and additional resources focuses on space and astronomy. Specifies age levels for resources that include Web sites, CD-ROMS and software, videos, books, audios, and magazines; offers professional resources; and presents a relevant class activity. (LRW)
NASA Technical Reports Server (NTRS)
Sepehry-Fard, F.; Coulthard, Maurice H.
1995-01-01
The objective of this publication is to introduce the enhancement methods for the overall reliability and maintainability methods of assessment on the International Space Station. It is essential that the process to predict the values of the maintenance time dependent variable parameters such as mean time between failure (MTBF) over time do not in themselves generate uncontrolled deviation in the results of the ILS analysis such as life cycle costs, spares calculation, etc. Furthermore, the very acute problems of micrometeorite, Cosmic rays, flares, atomic oxygen, ionization effects, orbital plumes and all the other factors that differentiate maintainable space operations from non-maintainable space operations and/or ground operations must be accounted for. Therefore, these parameters need be subjected to a special and complex process. Since reliability and maintainability strongly depend on the operating conditions that are encountered during the entire life of the International Space Station, it is important that such conditions are accurately identified at the beginning of the logistics support requirements process. Environmental conditions which exert a strong influence on International Space Station will be discussed in this report. Concurrent (combined) space environments may be more detrimental to the reliability and maintainability of the International Space Station than the effects of a single environment. In characterizing the logistics support requirements process, the developed design/test criteria must consider both the single and/or combined environments in anticipation of providing hardware capability to withstand the hazards of the International Space Station profile. The effects of the combined environments (typical) in a matrix relationship on the International Space Station will be shown. The combinations of the environments where the total effect is more damaging than the cumulative effects of the environments acting singly, may include a
NASA Astrophysics Data System (ADS)
Reynerson, Charles Martin
This research has been performed to create concept design and economic feasibility data for space business parks. A space business park is a commercially run multi-use space station facility designed for use by a wide variety of customers. Both space hardware and crew are considered as revenue producing payloads. Examples of commercial markets may include biological and materials research, processing, and production, space tourism habitats, and satellite maintenance and resupply depots. This research develops a design methodology and an analytical tool to create feasible preliminary design information for space business parks. The design tool is validated against a number of real facility designs. Appropriate model variables are adjusted to ensure that statistical approximations are valid for subsequent analyses. The tool is used to analyze the effect of various payload requirements on the size, weight and power of the facility. The approach for the analytical tool was to input potential payloads as simple requirements, such as volume, weight, power, crew size, and endurance. In creating the theory, basic principles are used and combined with parametric estimation of data when necessary. Key system parameters are identified for overall system design. Typical ranges for these key parameters are identified based on real human spaceflight systems. To connect the economics to design, a life-cycle cost model is created based upon facility mass. This rough cost model estimates potential return on investments, initial investment requirements and number of years to return on the initial investment. Example cases are analyzed for both performance and cost driven requirements for space hotels, microgravity processing facilities, and multi-use facilities. In combining both engineering and economic models, a design-to-cost methodology is created for more accurately estimating the commercial viability for multiple space business park markets.
NASA Technical Reports Server (NTRS)
Kavaya, Michael J.; Frehlich, Rod G.
2007-01-01
The global measurement of vertical profiles of horizontal vector winds has been highly desired for many years by NASA, NOAA and the Integrated Program Office (IPO) implementing the National Polar-orbiting Operational Environmental Satellite Systems (NPOESS). Recently the global wind mission was one of 15 missions recommended to NASA by the first ever NRC Earth Sciences Decadal Survey. Since before 1978, the most promising method to make this space-based measurement has been pulsed Doppler lidar. The favored technology and technique has evolved over the years from obtaining line-of-sight (LOS) wind profiles from a single laser shot using pulsed CO2 gas laser technology to the current plans to use both a coherent-detection and direct-detection pulsed Doppler wind lidar systems with each lidar employing multiple shot accumulation to produce an LOS wind profile. The idea of using two lidars (hybrid concept) entails coherent detection using the NASA LaRC-developed pulsed 2-micron solid state laser technology, and direct detection using pulsed Nd:YAG laser technology tripled in frequency to 355 nm wavelength.
NASA Astrophysics Data System (ADS)
Kumar, Ranjeet; Chandra, Navin; Tomar, Surekha
2016-02-01
This paper deals with the role of triple encounters with low initial velocities and equal masses in the framework of statistical escape theory in two-dimensional space. This system is described by allowing for both energy and angular momentum conservation in the phase space. The complete statistical solutions (i.e. the semi-major axis `a', the distributions of eccentricity `e', and energy Eb of the final binary, escape energy Es of escaper and its escape velocity vs) of the system are calculated. These are in good agreement with the numerical results of Chandra and Bhatnagar (1999) in the range of perturbing velocities vi (10^{-1} ≤ vi ≤ 10^{-10}) in two-dimensional space. The double limit process has been applied to the system. It is observed that when vi to 0^{ +}, a vs2 to 2 / 3 for all directions in two-dimensional space.
Chaudhry, S.R.; Ahmed-Zaid, S.; Demerdash, N.A.
1995-12-01
An artificial neural network (ANN) is used in the identification of saturated synchronous machine parameters under diverse operating conditions. The training data base for the ANN is generated by a time-stepping coupled finite-element/state-space (CFE-SS) modeling technique which is used in the computation of the saturated parameters of a 20-kV, 733-MVA, 0.85 pf (lagging) turbogenerator at discrete load points in the P-Q capability plane for three different levels of terminal voltage. These computed parameters constitute a learning data base for a multilayer ANN structure which is successfully trained using the back-propagation algorithm. Results indicate that the trained ANN can identify saturated machine reactances for arbitrary load points in the P-Q plane with an error less than 2% of those values obtained directly from the CFE-SS algorithm. Thus, significant savings in computational time are obtained in such parameter computation tasks.
NASA Astrophysics Data System (ADS)
Jang, Seok-Myeong; You, Dae-Joon; Jang, Won-Bum; Park, Ji-Hoon
2005-05-01
This paper presents the practical parameter estimation for a slotless air-cored permanent magnet linear synchronous motor (PMLSM) using an analytical method and experiment. In the analytical method, the linkage flux is calculated through the generalized magnetic vector potential obtained by the space harmonics and transfer relation with each region of permanent magnet (PM) mover, air gap, and winding stator. This linkage flux is used to estimate the dynamic parameters such as magnetization inductance, backemf, and thrust constant. Also, the resistance and self-inductance with one phase are obtained by the experiment. Therefore, dynamic simulation of a linear synchronous motor composed of dynamic parameters is performed by the nonrotating (d-q) voltage equation. In good agreement with the estimated parameter values, the experimental results confirm the validity of the analysis method and simulation.
NASA Technical Reports Server (NTRS)
Crucian, Brian; Chouker, Alexander; Pierson, Duane; Simpson, Richard; Basner, Mathias; Otto, Christian; Goodwin, Thomas
2015-01-01
Spaceflight has been established to profoundly dysregulate immunity. In various Terrestrial situations hypoxia has also been demonstrated to negatively influence immunity. NASA has selected 8.2 PSI, 34% Oxygen as the proposed atmosphere for exploration-class deep space missions. It is unknown how the proposed hypoxic atmosphere will further influence crew physiology and possibly enhance crew clinical risk during exploration class deep space missions. The primary purpose of the study is to determine both acute and chronic alterations in crewmember hematologic, immunologic (both innate + adaptive) and oxidative stress parameters, with cognition and VIIP, during exposure to the proposed exploration atmosphere during spaceflight.
NASA Astrophysics Data System (ADS)
Sato, T.; Mizoguchi, A.; Kasai, Y.; Kanamori, H.
2009-12-01
A new generation of sub-millimeter-wave receivers employing sensitive SIS (Superconductor Insulator Superconductor) detector technology will provide new opportunities for precise remote sensing measurements of minor constituents in the earth and planetary atmosphere.Superconducting Sub-Millimeter-Wave Limb-Emission Sounder (SMILES) was designed to be onboard the Japanese Experiment Module (JEM) on the International Space Station (ISS) as a collaboration project of National Institute of Information and Communications Technology (NICT) and Japan Aerospace Exploration Agency (JAXA).SMILES in Transfer Vehicle (HTV) plan to launch in September 11 2009 by Japanese H-IIB rocket. JEM/SMILES will allow to observe the atmospheric species such as O3, H35Cl, H37Cl, ClO, BrO, HOCl, HO2, H2O2, HNO3 and CH3CN, Ozone isotope species, and water vapor with the precisions in a few to several tens percents [1] in the altitude region upper troposphere (about 8km in mid-latitude) and the mesosphere (about 90km in mid-latitude). In this paper, laboratory measurement of the pressure broadening parameter (γ) of Hydrogen peroxide (H2O2) at JKa,Kc = 201,19 - 192,17 rotational transition (625.044 GHz) will be presented. This is one of the target transitions of JEM/SMILES observation. γ of H2O2 in sub-millimeter-wave region was measured for the first time. The measurement was carried out using a sub-millimeter-wave absorption spectrometric system in Tokyo Institute of Technology.The radiation source from a backward wave oscillator (BWO) was phase-locked to the harmonics of a synthesized sweeper with two-step phase lock loop. The BWO source frequency was modulated with the modulation frequency of 51 kHz. H2O2 sample was prerpared by distillation of commercial available 30% solution. The pressures of sample and buffer gas (N2 and O2) were controlled by a mass flow meter and monitored by two Baratron monitors in the cell. From the observed profiles of the spectrum, the pressure broadening line
NASA Technical Reports Server (NTRS)
Haines, R. F.
1985-01-01
The question of the merits of placing windows on proposed future space stations is addressed. The use of windows for human visual capabilities is compared to using closed circuit television. Placement and field of view, as well as the number of windows is discussed.
NASA Technical Reports Server (NTRS)
Sepehry-Fard, F.; Coulthard, Maurice H.
1995-01-01
The process of predicting the values of maintenance time dependent variable parameters such as mean time between failures (MTBF) over time must be one that will not in turn introduce uncontrolled deviation in the results of the ILS analysis such as life cycle costs, spares calculation, etc. A minor deviation in the values of the maintenance time dependent variable parameters such as MTBF over time will have a significant impact on the logistics resources demands, International Space Station availability and maintenance support costs. There are two types of parameters in the logistics and maintenance world: a. Fixed; b. Variable Fixed parameters, such as cost per man hour, are relatively easy to predict and forecast. These parameters normally follow a linear path and they do not change randomly. However, the variable parameters subject to the study in this report such as MTBF do not follow a linear path and they normally fall within the distribution curves which are discussed in this publication. The very challenging task then becomes the utilization of statistical techniques to accurately forecast the future non-linear time dependent variable arisings and events with a high confidence level. This, in turn, shall translate in tremendous cost savings and improved availability all around.
NASA Technical Reports Server (NTRS)
Hagan, Ronald Donald; Norcross, Jason; DeWitt, John; Lee, Stuart M.; McCleary, Frank; Edwards, W. Brent
2006-01-01
Both motorized (T-M) and non-motorized (T-NM) treadmill locomotion are used on the International Space Station (ISS) as countermeasures to the deleterious effects of prolonged weightlessness. However, the ground reaction forces (GRF) and gait parameters of these exercise modes have not been examined. The purpose of this study was to determine if differences in GRF and gait parameters exist while walking (1.34 m/s) and running (3.13 m/s) on T-M and T-NM. Dissimilar GRF and gait parameters suggest that T-M and T-NM locomotion may elicit different physiologic effects. T-NM may result in a reduced stimulus to bone formation due to a lower LR, but an increased energy cost as a result of shorter, more frequent strides. Therefore, the usage of each mode should depend upon the desired training stimulus.
Vavoulis, Dimitrios V.; Straub, Volko A.; Aston, John A. D.; Feng, Jianfeng
2012-01-01
Traditional approaches to the problem of parameter estimation in biophysical models of neurons and neural networks usually adopt a global search algorithm (for example, an evolutionary algorithm), often in combination with a local search method (such as gradient descent) in order to minimize the value of a cost function, which measures the discrepancy between various features of the available experimental data and model output. In this study, we approach the problem of parameter estimation in conductance-based models of single neurons from a different perspective. By adopting a hidden-dynamical-systems formalism, we expressed parameter estimation as an inference problem in these systems, which can then be tackled using a range of well-established statistical inference methods. The particular method we used was Kitagawa's self-organizing state-space model, which was applied on a number of Hodgkin-Huxley-type models using simulated or actual electrophysiological data. We showed that the algorithm can be used to estimate a large number of parameters, including maximal conductances, reversal potentials, kinetics of ionic currents, measurement and intrinsic noise, based on low-dimensional experimental data and sufficiently informative priors in the form of pre-defined constraints imposed on model parameters. The algorithm remained operational even when very noisy experimental data were used. Importantly, by combining the self-organizing state-space model with an adaptive sampling algorithm akin to the Covariance Matrix Adaptation Evolution Strategy, we achieved a significant reduction in the variance of parameter estimates. The algorithm did not require the explicit formulation of a cost function and it was straightforward to apply on compartmental models and multiple data sets. Overall, the proposed methodology is particularly suitable for resolving high-dimensional inference problems based on noisy electrophysiological data and, therefore, a potentially useful tool in
NASA Astrophysics Data System (ADS)
Khawli, Toufik Al; Gebhardt, Sascha; Eppelt, Urs; Hermanns, Torsten; Kuhlen, Torsten; Schulz, Wolfgang
2016-06-01
In production industries, parameter identification, sensitivity analysis and multi-dimensional visualization are vital steps in the planning process for achieving optimal designs and gaining valuable information. Sensitivity analysis and visualization can help in identifying the most-influential parameters and quantify their contribution to the model output, reduce the model complexity, and enhance the understanding of the model behavior. Typically, this requires a large number of simulations, which can be both very expensive and time consuming when the simulation models are numerically complex and the number of parameter inputs increases. There are three main constituent parts in this work. The first part is to substitute the numerical, physical model by an accurate surrogate model, the so-called metamodel. The second part includes a multi-dimensional visualization approach for the visual exploration of metamodels. In the third part, the metamodel is used to provide the two global sensitivity measures: i) the Elementary Effect for screening the parameters, and ii) the variance decomposition method for calculating the Sobol indices that quantify both the main and interaction effects. The application of the proposed approach is illustrated with an industrial application with the goal of optimizing a drilling process using a Gaussian laser beam.
NASA Technical Reports Server (NTRS)
Papadopoulos, Michael; Tolson, Robert H.
1993-01-01
The Modal Identification Experiment (MIE) is a proposed experiment to define the dynamic characteristics of Space Station Freedom. Previous studies emphasized free-decay modal identification. The feasibility of using a forced response method (Observer/Kalman Filter Identification (OKID)) is addressed. The interest in using OKID is to determine the input mode shape matrix which can be used for controller design or control-structure interaction analysis, and investigate if forced response methods may aid in separating closely spaced modes. A model of the SC-7 configuration of Space Station Freedom was excited using simulated control system thrusters to obtain acceleration output. It is shown that an 'optimum' number of outputs exists for OKID. To recover global mode shapes, a modified method called Global-Local OKID was developed. This study shows that using data from a long forced response followed by free-decay leads to the 'best' modal identification. Twelve out of the thirteen target modes were identified for such an output.
A Hubble Space Telescope/WFPC2 Survey of Bright Young Clusters in M31. III. Structural Parameters
NASA Astrophysics Data System (ADS)
Barmby, P.; Perina, S.; Bellazzini, M.; Cohen, J. G.; Hodge, P. W.; Huchra, J. P.; Kissler-Patig, M.; Puzia, T. H.; Strader, J.
2009-12-01
Surface brightness profiles for 23 M31 star clusters were measured using images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope, and fitted to two types of models to determine the clusters' structural properties. The clusters are primarily young (~108 yr) and massive (~104.5 M sun), with median half-light radius 7 pc and dissolution times of a few Gyr. The properties of the M31 clusters are comparable to those of clusters of similar age in the Magellanic Clouds. Simulated star clusters are used to derive a conversion from statistical measures of cluster size to half-light radius so that the extragalactic clusters can be compared to young massive clusters in the Milky Way. All three sets of star clusters fall approximately on the same age-size relation. The young M31 clusters are expected to dissolve within a few Gyr and will not survive to become old, globular clusters. However, they do appear to follow the same fundamental plane (FP) relations as old clusters; if confirmed with velocity dispersion measurements, this would be a strong indication that the star cluster FP reflects universal cluster formation conditions. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-10818 (PI: J. Cohen) and GO-8296 (PI: P. Hodge).
NASA Astrophysics Data System (ADS)
Cykhotsky, V. M.; Sementsov, A. N.; Grigoriev, Y. I.; Prokhorov, Y. M.; Gorbenko, G. A.; Malukhin, C. A.; Ganja, E. P.
1999-01-01
Central Two-Phase Thermal Control System (TPS) of the International Space Station ``ALPHA'' Russian Segment (ISSA RS) is a complex thermalhydraulic system aimed to collect heat from the station modules and transport it to Central Heat Exchanger-Radiator (RAD). The TPS is based on a two-phase ammonia heat transfer loop. Proper work of the TPS Parameters Control System is an important factor for ISSA reliability to be maintained. The Control System is mainly intended to provide the following characteristics of the Station: rated values of the Station thermal condition parameters, high tolerance of the Station thermal condition to instabilities caused by selfspontained deviations of the parameters, ability of the system to regain its rated operation parameters in case of failures or accidents. In particular, the Control System should provide stable ammonia evaporative temperature and pressure in Evaporative Heat Exchanger (EHEX), stable liquid coolant (antifreeze) temperature, high vapor quality and prevent the TPS elements from low temperatures. Heat Controlled Accumulator (HCA) maintains nearly constant pressure in vapor line. To control the TPS elements functioning some control methods have been suggested. Namely, how to control HCA electric heater operation, FCV operation, RAD panel rotation, turning on/off Electric Heater and bypass valves operation. Results of mathematical modeling of the TPS operation during ISSA orbital flight and experimental investigations carried out in the Center of Technical Physics of Kharkov Aviation Institute (CEP KhAI) (Ukraine) are presented. It is proved the TPS Parameters Control System designed to be reliable.
HE, YI; XIAO, YI; LIWO, ADAM; SCHERAGA, HAROLD A.
2009-01-01
We explored the energy-parameter space of our coarse-grained UNRES force field for large-scale ab initio simulations of protein folding, to obtain good initial approximations for hierarchical optimization of the force field with new virtual-bond-angle bending and side-chain-rotamer potentials which we recently introduced to replace the statistical potentials. 100 sets of energy-term weights were generated randomly, and good sets were selected by carrying out replica-exchange molecular dynamics simulations of two peptides with a minimal α-helical and a minimal β-hairpin fold, respectively: the tryptophan cage (PDB code: 1L2Y) and tryptophan zipper (PDB code: 1LE1). Eight sets of parameters produced native-like structures of these two peptides. These eight sets were tested on two larger proteins: the engrailed homeodomain (PDB code: 1ENH) and FBP WW domain (PDB code: 1E0L); two sets were found to produce native-like conformations of these proteins. These two sets were tested further on a larger set of nine proteins with α or α + β structure and found to locate native-like structures of most of them. These results demonstrate that, in addition to finding reasonable initial starting points for optimization, an extensive search of parameter space is a powerful method to produce a transferable force field. PMID:19242966
NASA Technical Reports Server (NTRS)
Sullins, W. R., Jr.; Rogers, J. G.
1974-01-01
The kinds of activities that are attractive to man in long duration isolation are delineated considering meaningful work as major activity and a choice of leisure/living provisions. The dependent variables are the relative distribution between various work, leisure, and living activities where external constraints on the subject's freedom of choice are minimized. Results indicate that an average of at least five hours per day of significant meaningful work is required for satisfactory enjoyment of the situation; most other parameters of the situation have less effects on overall performance and satisfaction
NASA Astrophysics Data System (ADS)
Bezruchko, K. V.; Davidov, A. O.; Katorgina, J. G.; Logvin, V. M.; Kharchenko, A. A.
2013-11-01
The review and analysis of several mathematical methods for prediction of electrochemical accumulator parameters are provided in the article: according to the mathematical expectation, the latest entry, a statistical prediction, Box-Jenkins model, decomposition Volta, ARMA, ARIMA and Kalman filter. The results of these methods for prediction of the electrochemical battery 22НКГ-4CK characteristics which is a part of spacecraft power plant of the “Mikrosputnik” type are given. Possible usage of these methods for long prediction of electrochemical accumulator characteristics on space-rocket objects power plants is showed.
Cotta, R.C.; Gainer, J.S.; Hewett, J.L.; Rizzo, T.G.; /SLAC
2010-08-26
We present a summary of recent results obtained from a scan of the 19-dimensional parameter space of the pMSSM and its implications for dark matter searches. We have generated a large set of points in parameter space (which we call 'models') for the 19-parameter CP-conserving pMSSM, where MFV has been assumed. We subjected these models to numerous experimental and theoretical constraints to obtain a set of {approx}68 K models which are consistent with existing data. We attempted to be somewhat conservative in our implementation of these constraints; in particular we only demanded that the relic density of the LSP not be greater than the measured value of {Omega}H{sup 2} for non-baryonic dark matter, rather than assuming that the LSP must account for the entire observed relic density. Examining the properties of the neutralinos in these models, we find that many are relatively pure gauge eigenstates with Higgsinos being the most common, followed by Winos. The relative prevalence of Higgsino and Wino LSPs leads many of our models to have a chargino as nLSP, often with a relatively small mass splitting between this nLSP and the LSP; this has important consequences in both collider and astroparticle phenomenology. We find that, in general, the LSP in our models provides a relatively small ({approx} 4%) contribution to the dark matter, however there is a long tail to this distribution and a substantial number of models for which the LSP makes up all or most of the dark matter. Typically these neutralinos are mostly Binos. Examining the signatures of our models in direct and indirect dark matter detection experiments, we find a wide range of signatures for both cases. In particular, we find a much larger range of WIMP-nucleon cross sections than is found in any particular model of SUSY-breaking. As these cross sections also enter the regions of parameter space suggested by non-SUSY models, it appears that the discovery of WIMPs in direct detection experiments might not
Newton, W. G.; Gearheart, M.; Li Baoan
2013-01-15
We present a systematic survey of the range of predictions of the neutron star inner crust composition, crust-core transition densities and pressures, and density range of the nuclear 'pasta' phases at the bottom of the crust provided by the compressible liquid drop model in light of the current experimental and theoretical constraints on model parameters. Using a Skyrme-like model for nuclear matter, we construct baseline sequences of crust models by consistently varying the density dependence of the bulk symmetry energy at nuclear saturation density, L, under two conditions: (1) that the magnitude of the symmetry energy at saturation density J is held constant, and (2) J correlates with L under the constraint that the pure neutron matter (PNM) equation of state (EoS) satisfies the results of ab initio calculations at low densities. Such baseline crust models facilitate consistent exploration of the L dependence of crustal properties. The remaining surface energy and symmetric nuclear matter parameters are systematically varied around the baseline, and different functional forms of the PNM EoS at sub-saturation densities implemented, to estimate theoretical 'error bars' for the baseline predictions. Inner crust composition and transition densities are shown to be most sensitive to the surface energy at very low proton fractions and to the behavior of the sub-saturation PNM EoS. Recent calculations of the energies of neutron drops suggest that the low-proton-fraction surface energy might be higher than predicted in Skyrme-like models, which our study suggests may result in a greatly reduced volume of pasta in the crust than conventionally predicted.
NASA Astrophysics Data System (ADS)
Namysłowska-Wilczyńska, Barbara
2016-04-01
. These data were subjected to spatial analyses using statistical and geostatistical methods. The evaluation of basic statistics of the investigated quality parameters, including their histograms of distributions, scatter diagrams between these parameters and also correlation coefficients r were presented in this article. The directional semivariogram function and the ordinary (block) kriging procedure were used to build the 3D geostatistical model. The geostatistical parameters of the theoretical models of directional semivariograms of the studied water quality parameters, calculated along the time interval and along the wells depth (taking into account the terrain elevation), were used in the ordinary (block) kriging estimation. The obtained results of estimation, i.e. block diagrams allowed to determine the levels of increased values Z* of studied underground water quality parameters. Analysis of the variability in the selected quality parameters of underground water for an analyzed area in Klodzko water intake was enriched by referring to the results of geostatistical studies carried out for underground water quality parameters and also for a treated water and in Klodzko water supply system (iron Fe, manganese Mn, ammonium ion NH4+ contents), discussed in earlier works. Spatial and time variation in the latter-mentioned parameters was analysed on the basis of the data (2007÷2011, 2008÷2011). Generally, the behaviour of the underground water quality parameters has been found to vary in space and time. Thanks to the spatial analyses of the variation in the quality parameters in the Kłodzko underground water intake area some regularities (trends) in the variation in water quality have been identified.
Tian, Yuan; Higgs, Jessica; Li, Ailin; Barney, Brandon; Austin, Daniel E
2014-03-01
A broad effort is underway to make radiofrequency (RF) ion trap mass spectrometers small enough for portable chemical analysis. A variety of trap geometries and fabrication approaches are under development from several research groups. A common issue is the reduced trapping capacity in smaller traps, with the associated reduction in sensitivity. This article explores the key variables that scale with trap size including RF voltage, frequency, electrical capacitance, power and pseudopotential well depth. High-field electric breakdown constrains the maximum RF voltages used in smaller ion traps. Simulations show the effects of space charge and the limits of trapping capacity as a function of trap dimensions for cylindrical ion traps down to the micrometer level. RF amplitudes that scale as the 1/3, 1/2 and 2/3 power of trap radius, r0, were studied. At a fixed level of performance, the number of analyzable ions scales as r0(n), with n ranging from 1.55 to 1.75 depending on the choice of voltage scaling. The implications for miniaturized ion trap mass spectrometry are discussed. PMID:24619549
Andrade, Henrique; Alcoforado, Maria-João; Oliveira, Sandra
2011-09-01
We aim to understand the relationship between people's declared bioclimatic comfort, their personal characteristics (age, origin, clothing, activity and motivation, etc.) and the atmospheric conditions. To attain this goal, questionnaire surveys were made concurrently with weather measurements (air temperature, relative humidity, solar and long-wave radiation and wind speed) in two open leisure areas of Lisbon (Portugal), during the years 2006 and 2007. We analysed the desire expressed by the interviewees to decrease, maintain or increase the values of air temperature and wind speed, in order to improve their level of comfort. Multiple logistic regression was used to analyse the quantitative relation between preference votes and environmental and personal parameters. The preference for a different temperature depends on the season and is strongly associated with wind speed. Furthermore, a general decrease of discomfort with increasing age was also found. Most people declared a preference for lower wind speed in all seasons; the perception of wind shows significant differences depending on gender, with women declaring a lower level of comfort with higher wind speed. It was also found that the tolerance of warmer conditions is higher than of cooler conditions, and that adaptive strategies are undertaken by people to improve their level of comfort outdoors. PMID:21053024
NASA Astrophysics Data System (ADS)
Andrade, Henrique; Alcoforado, Maria-João; Oliveira, Sandra
2011-09-01
We aim to understand the relationship between people's declared bioclimatic comfort, their personal characteristics (age, origin, clothing, activity and motivation, etc.) and the atmospheric conditions. To attain this goal, questionnaire surveys were made concurrently with weather measurements (air temperature, relative humidity, solar and long-wave radiation and wind speed) in two open leisure areas of Lisbon (Portugal), during the years 2006 and 2007. We analysed the desire expressed by the interviewees to decrease, maintain or increase the values of air temperature and wind speed, in order to improve their level of comfort. Multiple logistic regression was used to analyse the quantitative relation between preference votes and environmental and personal parameters. The preference for a different temperature depends on the season and is strongly associated with wind speed. Furthermore, a general decrease of discomfort with increasing age was also found. Most people declared a preference for lower wind speed in all seasons; the perception of wind shows significant differences depending on gender, with women declaring a lower level of comfort with higher wind speed. It was also found that the tolerance of warmer conditions is higher than of cooler conditions, and that adaptive strategies are undertaken by people to improve their level of comfort outdoors.
NASA Astrophysics Data System (ADS)
Leaci, Paola; Prix, Reinhard
2015-05-01
We derive simple analytic expressions for the (coherent and semicoherent) phase metrics of continuous-wave sources in low-eccentricity binary systems for the two regimes of long and short segments compared to the orbital period. The resulting expressions correct and extend previous results found in the literature. We present results of extensive Monte Carlo studies comparing metric mismatch predictions against the measured loss of detection statistics for binary parameter offsets. The agreement is generally found to be within ˜10 %- 30 % . For an application of the metric template expressions, we estimate the optimal achievable sensitivity of an Einstein@Home directed search for Scorpius X-1, under the assumption of sufficiently small spin wandering. We find that such a search, using data from the upcoming advanced detectors, would be able to beat the torque-balance level [R. V. Wagoner, Astrophys. J. 278, 345 (1984); L. Bildsten, Astrophys. J. 501, L89 (1998).] up to a frequency of ˜500 - 600 Hz , if orbital eccentricity is well constrained, and up to a frequency of ˜160 - 200 Hz for more conservative assumptions about the uncertainty on orbital eccentricity.
Chaudhry, S.R.; Ahmed-Zaid, S.; Demerdash, N.A.
1995-03-01
In this paper, a coupled finite-element/state-space modeling technique is applied in the determination of the steady-state parameters of a 733-MVA turbogenerator in the abc frame of reference. In this modeling environment, the forward rotor stepping-finite element procedure described in a companion paper is used to obtain the various machine self and mutual inductances under short-circuit and load conditions. A fourth-order state-space model of the armature and field winding flux linkages in the ABC frame of reference is then used to obtain the next set of flux linkages and forcing function currents for the finite-element model. In this process, one iterates between the finite-element and state-space techniques until the terminal conditions converge to specified values. This method is applied to the determination of the short-circuit, and reduced and rated-voltage load characteristics, and the corresponding machine inductances. The spatial harmonics of these inductances are analyzed via Fourier analysis to reveal the impact of machine geometry and stator-to-rotor relative motion, winding layout, magnetic saturation, and other effects. In the full-load infinite-bus case, it is found that, while the three-phase terminal voltages are pure sinusoidal waveforms, the steady-state armature phase currents are non-sinusoidal and contain a substantial amount of odd harmonics which cannot be obtained using the traditional two-axis analysis.
NASA Technical Reports Server (NTRS)
Wingard, Charles Doug; Munafo, Paul M. (Technical Monitor)
2002-01-01
Protein crystals are grown in microgravity experiments inside the Space Shuttle during orbit. Such crystals are basically grown in a five-component system containing a salt, buffer, polymer, organic and water. During these experiments, a number of different polymeric containment materials must be compatible with up to hundreds of different PCG solutions in various concentrations for durations up to 180 days. When such compatibility experiments are performed at NASA/MSFC (Marshall Space Flight Center) simultaneously on containment material samples immersed in various solutions in vials, the samples are rather small out of necessity. DMA4 modulus was often used as the primary screening parameter for such small samples as a pass/fail criterion for incompatibility issues. In particular, the TA Instruments DMA 2980 film tension clamp was used to test rubber O-rings as small in I.D. as 0.091 in. by cutting through the cross-section at one place, then clamping the stretched linear cord stock at each end. The film tension clamp was also used to successfully test short length samples of medical/surgical grade tubing with an O.D. of 0.125 in.
NASA Technical Reports Server (NTRS)
Rhee, Ihnseok; Speyer, Jason L.
1990-01-01
A game theoretic controller is developed for a linear time-invariant system with parameter uncertainties in system and input matrices. The input-output decomposition modeling for the plant uncertainty is adopted. The uncertain dynamic system is represented as an internal feedback loop in which the system is assumed forced by fictitious disturbance caused by the parameter uncertainty. By considering the input and the fictitious disturbance as two noncooperative players, a differential game problem is constructed. It is shown that the resulting time invariant controller stabilizes the uncertain system for a prescribed uncertainty bound. This game theoretic controller is applied to the momentum management and attitude control of the Space Station in the presence of uncertainties in the moments of inertia. Inclusion of the external disturbance torque to the design procedure results in a dynamical feedback controller which consists of conventional PID control and cyclic disturbance rejection filter. It is shown that the game theoretic design, comparing to the LQR design or pole placement design, improves the stability robustness with respect to inertia variations.
NASA Technical Reports Server (NTRS)
Deal, Don E.
1991-01-01
The chief goals of the summer project have been twofold - first, for my host group and myself to learn as much of the working details of Taguchi analysis as possible in the time allotted, and, secondly, to apply the methodology to a design problem with the intention of establishing a preliminary set of near-optimal (in the sense of producing a desired response) design parameter values from among a large number of candidate factor combinations. The selected problem is concerned with determining design factor settings for an automated approach program which is to have the capability of guiding the Shuttle into the docking port of the Space Station under controlled conditions so as to meet and/or optimize certain target criteria. The candidate design parameters under study were glide path (i.e., approach) angle, path intercept and approach gains, and minimum impulse bit mode (a parameter which defines how Shuttle jets shall be fired). Several performance criteria were of concern: terminal relative velocity at the instant the two spacecraft are mated; docking offset; number of Shuttle jet firings in certain specified directions (of interest due to possible plume impingement on the Station's solar arrays), and total RCS (a measure of the energy expended in performing the approach/docking maneuver). In the material discussed here, we have focused on single performance criteria - total RCS. An analysis of the possibility of employing a multiobjective function composed of a weighted sum of the various individual criteria has been undertaken, but is, at this writing, incomplete. Results from the Taguchi statistical analysis indicate that only three of the original four posited factors are significant in affecting RCS response. A comparison of model simulation output (via Monte Carlo) with predictions based on estimated factor effects inferred through the Taguchi experiment array data suggested acceptable or close agreement between the two except at the predicted optimum
NASA Technical Reports Server (NTRS)
Berman, A. L.
1976-01-01
In the last two decades, increasingly sophisticated deep space missions have placed correspondingly stringent requirements on navigational accuracy. As part of the effort to increase navigational accuracy, and hence the quality of radiometric data, much effort has been expended in an attempt to understand and compute the tropospheric effect on range (and hence range rate) data. The general approach adopted has been that of computing a zenith range refraction, and then mapping this refraction to any arbitrary elevation angle via an empirically derived function of elevation. The prediction of zenith range refraction derived from surface measurements of meteorological parameters is presented. Refractivity is separated into wet (water vapor pressure) and dry (atmospheric pressure) components. The integration of dry refractivity is shown to be exact. Attempts to integrate wet refractivity directly prove ineffective; however, several empirical models developed by the author and other researchers at JPL are discussed. The best current wet refraction model is here considered to be a separate day/night model, which is proportional to surface water vapor pressure and inversely proportional to surface temperature. Methods are suggested that might improve the accuracy of the wet range refraction model.
Pini, Núbia Inocencya Pavesi; Marchi, Luciana Manzotti De; Pascotto, Renata Corrêa
2015-01-01
Maxillary lateral incisor agenesis (MLIA) is a condition that affects both dental esthetics and function in young patients, and represents an important challenge for clinicians. Although several treatment options are available, the mesial repositioning of the canines followed by teeth recontouring into lateral incisors; or space opening/maintenance followed by implant placement have recently emerged as two important treatment approaches. In this article, the current and latest literature has been reviewed in order to summarize the functional and esthetic outcomes obtained with these two forms of treatment of MLIA patients in recent years. Indications, clinical limitations and the most important parameters to achieve the best possible results with each treatment modality are also discussed. Within the limitations of this review, it is not possible to assert at this point in time that one treatment approach is more advantageous than the other. Long-term followup studies comparing the existing treatment options are still lacking in the literature, and they are necessary to shed some light on the issue. It is possible, however, to state that adequate multidisciplinary diagnosis and planning are imperative to define the treatment option that will provide the best individual results for patients with MLIA. PMID:25646137
Grimes, Morad; Bouhadjera, Abdelmalek; Haddad, Sofiane; Benkedidah, Toufik
2012-07-01
In testing cancellous bone using ultrasound, two types of longitudinal Biot's waves are observed in the received signal. These are known as fast and slow waves and their appearance depend on the alignment of bone trabeculae in the propagation path and the thickness of the specimen under test (SUT). They can be used as an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. However, the identification of these waves in the received signal can be difficult to achieve. In this study, ultrasonic wave propagation in a 4mm thick bovine cancellous bone in the direction parallel to the trabecular alignment is considered. The observed Biot's fast and slow longitudinal waves are superimposed; which makes it difficult to extract any information from the received signal. These two waves can be separated using the space alternating generalized expectation maximization (SAGE) algorithm. The latter has been used mainly in speech processing. In this new approach, parameters such as, arrival time, center frequency, bandwidth, amplitude, phase and velocity of each wave are estimated. The B-Scan images and its associated A-scans obtained through simulations using Biot's finite-difference time-domain (FDTD) method are validated experimentally using a thin bone sample obtained from the femoral-head of a 30 months old bovine. PMID:22284937
Sun, Yipeng; Raubenheimer, Tor; Wu, Juhao; /SLAC
2011-08-19
Hard x-ray Free electron lasers (FEL) are being built or proposed at many accelerator laboratories as it supports wide range of applications in many aspects. Most of the hard x-ray FEL design is similar with the SLAC Linac Coherent Light Source (LCLS), which features a two (or multiple) stage bunch compression. For the first stage of the bunch compression, usually the beam is accelerated in a lower-frequency RF section (such as S-band for LCLS), and then the longitudinal phase space is linearized by a higher-frequency RF section (harmonic RF, such as X-band for LCLS). In this paper, a compact hard x-ray FEL design is proposed, which is based on X-band RF acceleration and eliminating the need of a harmonic RF. The parameter selection and relation is discussed, and the longitudinal phase space simulation is presented. The FEL coherence condition of the electron beam in the undulators requires a large charge density, a small emittance and small energy spread. The RMS electron bunch length from the injector is in the ps scale, with a bunch charge in the range of hundreds pC to several nC, which means that the current is roughly 0.1 kA. According to the requirement from soft x-ray lasing and hard x-ray lasing, a peak current of 1 kA and 3 kA is needed respectively. Thus the bunch has to be compressed. Usually a two stage bunch compression or multipole stage bunch compression is adopted. The z-correlated energy chirp is normally established by letting the beam pass through a section of RF cavities, with a RF phase off crest. As stated above, S-band RF (3 GHz) acceleration could be applied in this section. Due to the nature of RF acceleration wave, the chirp on the bunch is not linear, but has the RF curvature on it. In order to linearize the energy chirp, a harmonic RF section with higher frequency is needed. For LCLS a short X-band RF section (12 GHz) is used which is a fourth order harmonic. The linearized bunch is then passing by a dispersive region, in which the
NASA Technical Reports Server (NTRS)
Roth, E. A.
1971-01-01
Motion in the general gravity field is described mathematically. A covariance analysis, based on two simple models, is presented. Two drag-free space probes were considered, for which the orbital elements are given.
NASA Astrophysics Data System (ADS)
Semiletov, I. P.; Shakhova, N. E.; Pipko, I. I.; Pugach, S. P.; Charkin, A. N.; Dudarev, O. V.; Kosmach, D. A.; Nishino, S.
2013-09-01
This study aims to improve understanding of carbon cycling in the Buor-Khaya Bay (BKB) and adjacent part of the Laptev Sea by studying the inter-annual, seasonal, and meso-scale variability of carbon and related hydrological and biogeochemical parameters in the water, as well as factors controlling carbon dioxide (CO2) emission. Here we present data sets obtained on summer cruises and winter expeditions during 12 yr of investigation. Based on data analysis, we suggest that in the heterotrophic BKB area, input of terrestrially borne organic carbon (OC) varies seasonally and inter-annually and is largely determined by rates of coastal erosion and river discharge. Two different BKB sedimentation regimes were revealed: Type 1 (erosion accumulation) and Type 2 (accumulation). A Type 1 sedimentation regime occurs more often and is believed to be the quantitatively most important mechanism for suspended particular matter (SPM) and particulate organic carbon (POC) delivery to the BKB. The mean SPM concentration observed in the BKB under a Type 1 regime was one order of magnitude greater than the mean concentration of SPM (~ 20 mg L-1) observed along the Lena River stream in summer 2003. Loadings of the BKB water column with particulate material vary by more than a factor of two between the two regimes. Higher partial pressure of CO2 (pCO2), higher concentrations of nutrients, and lower levels of oxygen saturation were observed in the bottom water near the eroded coasts, implying that coastal erosion and subsequent oxidation of eroded organic matter (OM) rather than the Lena River serves as the predominant source of nutrients to the BKB. Atmospheric CO2 fluxes from the sea surface in the BKB vary from 1 to 95 mmol m-2 day-1 and are determined by specific features of hydrology and wind conditions, which change spatially, seasonally, and inter-annually. Mean values of CO2 emission from the shallow Laptev Sea were similar in September 1999 and 2005 (7.2 and 7.8 mmol m-2 day-1
NASA Astrophysics Data System (ADS)
Espindola, Aquino L.; Girardi, Daniel; Penna, Thadeu J. P.; Bauch, Chris T.; Martinez, Alexandre S.; Cabella, Brenno C. T.
2012-06-01
In this work we present an agent-based model for the spread of tuberculosis where the individuals can be infected with either drug-susceptible or drug-resistant strains and can also receive a treatment. The dynamics of the model and the role of each one of the parameters are explained. The whole set of parameters is explored to check their importance in the numerical simulation results. The model captures the beneficial impact of the adequate treatment on the prevalence of tuberculosis. Nevertheless, depending on the treatment parameters range, it also captures the emergence of drug resistance. Drug resistance emergence is particularly likely to occur for parameter values corresponding to less efficacious treatment, as usually found in developing countries.
NASA Technical Reports Server (NTRS)
Glasser, M. E.; Rundel, R. D.
1978-01-01
A method for formulating these changes into the model input parameters using a preprocessor program run on a programed data processor was implemented. The results indicate that any changes in the input parameters are small enough to be negligible in comparison to meteorological inputs and the limitations of the model and that such changes will not substantially increase the number of meteorological cases for which the model will predict surface hydrogen chloride concentrations exceeding public safety levels.
NASA Astrophysics Data System (ADS)
Shayganpour, A.; Idris, M. H.; Izman, S.; Jafari, H.
2012-09-01
Lost foam casting as a relatively new manufacturing process is extensively employed to produce sound complicated castings. In this study, an experimental investigation on lost foam casting of an Al-Si-Cu aluminium cast alloy was conducted. The research was aimed in evaluating the effect of different pouring temperatures, slurry viscosities, vibration durations and sand grain sizes on eutectic silicon spacing of thin-wall castings. A stepped-pattern was used in the study and the focus of the investigations was at the thinnest 3 mm section. A full two-level factorial design experimental technique was used to plan the experiments and afterwards identify the significant factors affecting casting silicon spacing. The results showed that pouring temperature and its interaction with vibration time have pronounced effect on eutectic silicon phase size. Increasing pouring temperature coarsened the eutectic silicon spacing while the higher vibration time diminished coarsening effect. Moreover, no significant effects on silicon spacing were found with variation of sand size and slurry viscosity.
NASA Astrophysics Data System (ADS)
Baevsky, Roman M.; Chernikova, Anna G.; Funtova, Irina I.; Tank, Jens
2011-12-01
Optimization of the cardiovascular system under conditions of long term space flight is provided by individual changes of autonomic cardiovascular control. Heart rate variability (HRV) analysis is an easy to use method under these extreme conditions. We tested the hypothesis that individual HRV analysis provides important information for crew health monitoring. HRV data from 14 Russian cosmonauts measured during long term space flights are presented (two times before and after flight, monthly in flight). HRV characteristics in the time and in the frequency domain were calculated. Predefined discriminant function equations obtained in reference groups (L1=-0.112*HR-1.006*SI-0.047*pNN50-0.086*HF; L2=0.140*HR-0.165*SI-1.293*pNN50+0.623*HF) were used to define four functional states. (1) Physiological normal, (2) prenosological, (3) premorbid and (4) pathological. Geometric mean values for the ISS cosmonauts based on L1 and L2 remained within normal ranges. A shift from the physiological normal state to the prenosological functional state during space flight was detected. The functional state assessed by HRV improved during space flight if compared to pre-flight and early post-flight functional states. Analysis of individual cosmonauts showed distinct patterns depending on the pre-flight functional state. Using the developed classification a transition process from the state of physiological normal into a prenosological state or premorbid state during different stages of space flight can be detected for individual Russian cosmonauts. Our approach to an estimation of HR regulatory pattern can be useful for prognostic purposes.
NASA Technical Reports Server (NTRS)
Sulyma, P. R.
1980-01-01
Fundamental equations and similarity definition and application are described as well as the computational steps of a computer program developed to design model nozzles for wind tunnel tests conducted to define power-on aerodynamic characteristics of the space shuttle over a range of ascent trajectory conditions. The computer code capabilities, a user's guide for the model nozzle design program, and the output format are examined. A program listing is included.
PARAMETERS FOR QUANTIFYING BEAM HALO
C.K. ALLEN; T.P. WANGLER
2001-06-01
Two different parameters for the quantitative description of beam halo are introduced, both based on moments of the particle distribution. One parameter is a measure of spatial halo formation and has been defined previously by Wangler and Crandall [3], termed the profile parameter. The second parameter relies on kinematic invariants to quantify halo formation in phase space; we call it the halo parameter. The profile parameter can be computed from experimental beam profile data. The halo parameter provides a theoretically more complete description of halo in phase space, but is difficult to obtain experimentally.
NASA Astrophysics Data System (ADS)
Tan, Ivy; Storelvmo, Trude
2015-04-01
Substantial improvements have been made to the cloud microphysical schemes used in the latest generation of global climate models (GCMs), however, an outstanding weakness of these schemes lies in the arbitrariness of their tuning parameters, which are also notoriously fraught with uncertainties. Despite the growing effort in improving the cloud microphysical schemes in GCMs, most of this effort has neglected to focus on improving the ability of GCMs to accurately simulate the present-day global distribution of thermodynamic phase partitioning in mixed-phase clouds. Liquid droplets and ice crystals not only influence the Earth's radiative budget and hence climate sensitivity via their contrasting optical properties, but also through the effects of their lifetimes in the atmosphere. The current study employs NCAR's CAM5.1, and uses observations of cloud phase obtained by NASA's CALIOP lidar over a 79-month period (November 2007 to June 2014) guide the accurate simulation of the global distribution of mixed-phase clouds in 20∘ latitudinal bands at the -10∘ C, -20∘C and -30∘C isotherms, by adjusting six relevant cloud microphysical tuning parameters in the CAM5.1 via Quasi-Monte Carlo sampling. Among the parameters include those that control the Wegener-Bergeron-Findeisen (WBF) timescale for the conversion of supercooled liquid droplets to ice and snow in mixed-phase clouds, the fraction of ice nuclei that nucleate ice in the atmosphere, ice crystal sedimentation speed, and wet scavenging in stratiform and convective clouds. Using a Generalized Linear Model as a variance-based sensitivity analysis, the relative contributions of each of the six parameters are quantified to gain a better understanding of the importance of their individual and two-way interaction effects on the liquid to ice proportion in mixed-phase clouds. Thus, the methodology implemented in the current study aims to search for the combination of cloud microphysical parameters in a GCM that
NASA Astrophysics Data System (ADS)
Zamfir, S.; Sulentic, J. W.; Marziani, P.
2008-06-01
We search for a dichotomy/bimodality between radio-loud (RL) and radio-quiet (RQ) type 1 active galactic nuclei (AGN). We examine several samples of Slogan Digital Sky Survey (SDSS) quasi-stellar objects (QSOs) with high signal-to-noise ratio optical spectra and matching Faint Images of the Radio Sky at Twenty-cm/NRAO VLA Sky Survey (FIRST/NVSS) radio observations. We use the radio data to identify the weakest RL sources with a Fanaroff-Riley type II (FRII) structure to define a RL/RQ boundary which corresponds to log L1.4GHz = 31.6 ergs-1 Hz-1. We measure the properties of broad-line Hβ and FeII emission to define the optical plane of a 4DE1 spectroscopic diagnostic space. The RL quasars occupy a much more restricted domain in this optical plane compared to the RQ sources, which a 2D Kolmogorov-Smirnov test finds to be highly significant. This tells us that the range of broad-line region kinematics and structure for RL sources is more restricted than for the RQ QSOs, which supports the notion of dichotomy. FRII and CD RL sources also show significant 4DE1 domain differences that likely reflect differences in line-of-sight orientation (inclined versus face-on, respectively) for these two classes. The possibility of a distinct radio-intermediate (RI) population between RQ and RL source is disfavoured because a 4DE1 diagnostic space comparison shows no difference between RI and RQ sources. We show that searches for dichotomy in radio versus bolometric luminosity diagrams will yield ambiguous results mainly because in a reasonably complete sample, the radio brightest RQ sources will be numerous enough to blur the gap between RQ and RL sources. Within resolution constraints of NVSS and FIRST, we find no FRI sources among the broad-line quasar population.
NASA Astrophysics Data System (ADS)
Mineev, Iu. V.; Spirkova, E. S.; Shestopalov, I. P.
From November 1973 to February 1974, the distance between the Mars-7 space probe and the Prognoz-3 satellite varied from 0.3 AU to 1 AU, and the angle between Mars-7, the sun, and the earth changed from 6 deg to 50 deg. The proton and electron data observed during the four solar rotations of this period are compared with intensity variations of galactic cosmic rays (GCR), with changes of the solar wind velocity and with their effect on the interplanetary magnetic field (IMF) parameters. It was found that in each of the four recurrent solar events, the electron (greater than or equal to 40 MeV) and the proton (greater than or equal to 1 MeV) increase was accompanied by a GCR intensity decrease, by an increase in the solar wind velocity, and by changes in the IMF parameters (magnitude and sign).
NASA Astrophysics Data System (ADS)
Ireland, Gareth; North, Matthew R.; Petropoulos, George P.; Srivastava, Prashant K.; Hodges, Crona
2015-04-01
Acquiring accurate information on the spatio-temporal variability of soil moisture content (SM) and evapotranspiration (ET) is of key importance to extend our understanding of the Earth system's physical processes, and is also required in a wide range of multi-disciplinary research studies and applications. The utility and applicability of Earth Observation (EO) technology provides an economically feasible solution to derive continuous spatio-temporal estimates of key parameters characterising land surface interactions, including ET as well as SM. Such information is of key value to practitioners, decision makers and scientists alike. The PREMIER-EO project recently funded by High Performance Computing Wales (HPCW) is a research initiative directed towards the development of a better understanding of EO technology's present ability to derive operational estimations of surface fluxes and SM. Moreover, the project aims at addressing knowledge gaps related to the operational estimation of such parameters, and thus contribute towards current ongoing global efforts towards enhancing the accuracy of those products. In this presentation we introduce the PREMIER-EO project, providing a detailed overview of the research aims and objectives for the 1 year duration of the project's implementation. Subsequently, we make available the initial results of the work carried out herein, in particular, related to an all-inclusive and robust evaluation of the accuracy of existing operational products of ET and SM from different ecosystems globally. The research outcomes of this project, once completed, will provide an important contribution towards addressing the knowledge gaps related to the operational estimation of ET and SM. This project results will also support efforts ongoing globally towards the operational development of related products using technologically advanced EO instruments which were launched recently or planned be launched in the next 1-2 years. Key Words: PREMIER
Aschwanden, Markus J.; Zhang, Jie; Liu, Kai E-mail: jzhang7@gmu.edu
2013-09-20
We extend a previous statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO to all seven coronal wavelengths (94, 131, 171, 193, 211, 304, and 335 Å) to test the wavelength dependence of scaling laws and statistical distributions. Except for the 171 and 193 Å wavelengths, which are affected by EUV dimming caused by coronal mass ejections (CMEs), we find near-identical size distributions of geometric (lengths L, flare areas A, volumes V, and fractal dimension D{sub 2}), temporal (flare durations T), and spatio-temporal parameters (diffusion coefficient κ, spreading exponent β, and maximum expansion velocities v{sub max}) in different wavelengths, which are consistent with the universal predictions of the fractal-diffusive avalanche model of a slowly driven, self-organized criticality (FD-SOC) system, i.e., N(L)∝L {sup –3}, N(A)∝A {sup –2}, N(V)∝V {sup –5/3}, N(T)∝T {sup –2}, and D{sub 2} = 3/2, for a Euclidean dimension d = 3. Empirically, we find also a new strong correlation κ∝L {sup 0.94±0.01} and the three-parameter scaling law L∝κ T {sup 0.1}, which is more consistent with the logistic-growth model than with classical diffusion. The findings suggest long-range correlation lengths in the FD-SOC system that operate in the vicinity of a critical state, which could be used for predictions of individual extreme events. We find also that eruptive flares (with accompanying CMEs) have larger volumes V, longer flare durations T, higher EUV and soft X-ray fluxes, and somewhat larger diffusion coefficients κ than confined flares (without CMEs)
NASA Technical Reports Server (NTRS)
Hsia, Wei Shen
1989-01-01
A validated technology data base is being developed in the areas of control/structures interaction, deployment dynamics, and system performance for Large Space Structures (LSS). A Ground Facility (GF), in which the dynamics and control systems being considered for LSS applications can be verified, was designed and built. One of the important aspects of the GF is to verify the analytical model for the control system design. The procedure is to describe the control system mathematically as well as possible, then to perform tests on the control system, and finally to factor those results into the mathematical model. The reduction of the order of a higher order control plant was addressed. The computer program was improved for the maximum entropy principle adopted in Hyland's MEOP method. The program was tested against the testing problem. It resulted in a very close match. Two methods of model reduction were examined: Wilson's model reduction method and Hyland's optimal projection (OP) method. Design of a computer program for Hyland's OP method was attempted. Due to the difficulty encountered at the stage where a special matrix factorization technique is needed in order to obtain the required projection matrix, the program was successful up to the finding of the Linear Quadratic Gaussian solution but not beyond. Numerical results along with computer programs which employed ORACLS are presented.
Lung, Chi-Wen; Yang, Tim D.; Crane, Barbara A.; Elliott, Jeannette; Dicianno, Brad E.; Jan, Yih-Kuen
2014-01-01
The purpose of this study was to determine the effect of the sensel window's location and size when calculating the peak pressure index (PPI) of pressure mapping with varying degrees of wheelchair tilt-in-space (tilt) and recline in people with spinal cord injury (SCI). Thirteen power wheelchair users were recruited into this study. Six combinations of wheelchair tilt (15°, 25°, and 35°) and recline (10° and 30°) were used by the participants in random order. Displacements of peak pressure and center of pressure were extracted from the left side of the mapping system. Normalized PPI was computed for three sensel window dimensions (3 sensels × 3 sensels, 5 × 5, and 7 × 7). At least 3.33 cm of Euclidean displacement of peak pressures was observed in the tilt and recline. For every tilt angle, peak pressure displacement was not significantly different between 10° and 30° recline, while center of pressure displacement was significantly different (P < .05). For each recline angle, peak pressure displacement was not significantly different between pairs of 15°, 25°, and 35° tilt, while center of pressure displacement was significantly different between 15° versus 35° and 25° versus 35°. Our study showed that peak pressure displacement occurs in response to wheelchair tilt and recline, suggesting that the selected sensel window locations used to calculate PPI should be adjusted during changes in wheelchair configuration. PMID:25057491
NASA Astrophysics Data System (ADS)
Latyshev, L. A.; Semashko, N. N.
The possibility of meeting future global energy demands by producing energy in space is addressed. Comparisons are made between the parameters of space plants producing solar electric power, nuclear electric power, and thermonuclear electric power.
Horneck, Gerda; Klaus, David M.; Mancinelli, Rocco L.
2010-01-01
Summary: The responses of microorganisms (viruses, bacterial cells, bacterial and fungal spores, and lichens) to selected factors of space (microgravity, galactic cosmic radiation, solar UV radiation, and space vacuum) were determined in space and laboratory simulation experiments. In general, microorganisms tend to thrive in the space flight environment in terms of enhanced growth parameters and a demonstrated ability to proliferate in the presence of normally inhibitory levels of antibiotics. The mechanisms responsible for the observed biological responses, however, are not yet fully understood. A hypothesized interaction of microgravity with radiation-induced DNA repair processes was experimentally refuted. The survival of microorganisms in outer space was investigated to tackle questions on the upper boundary of the biosphere and on the likelihood of interplanetary transport of microorganisms. It was found that extraterrestrial solar UV radiation was the most deleterious factor of space. Among all organisms tested, only lichens (Rhizocarpon geographicum and Xanthoria elegans) maintained full viability after 2 weeks in outer space, whereas all other test systems were inactivated by orders of magnitude. Using optical filters and spores of Bacillus subtilis as a biological UV dosimeter, it was found that the current ozone layer reduces the biological effectiveness of solar UV by 3 orders of magnitude. If shielded against solar UV, spores of B. subtilis were capable of surviving in space for up to 6 years, especially if embedded in clay or meteorite powder (artificial meteorites). The data support the likelihood of interplanetary transfer of microorganisms within meteorites, the so-called lithopanspermia hypothesis. PMID:20197502
Parameter estimating state reconstruction
NASA Technical Reports Server (NTRS)
George, E. B.
1976-01-01
Parameter estimation is considered for systems whose entire state cannot be measured. Linear observers are designed to recover the unmeasured states to a sufficient accuracy to permit the estimation process. There are three distinct dynamics that must be accommodated in the system design: the dynamics of the plant, the dynamics of the observer, and the system updating of the parameter estimation. The latter two are designed to minimize interaction of the involved systems. These techniques are extended to weakly nonlinear systems. The application to a simulation of a space shuttle POGO system test is of particular interest. A nonlinear simulation of the system is developed, observers designed, and the parameters estimated.
Achieving agility through parameter space qualification
Diegert, K.V.; Easterling, R.G.; Ashby, M.R.; Benavides, G.L.; Forsythe, C.; Jones, R.E.; Longcope, D.B.; Parratt, S.W.
1995-02-01
The A-primed (Agile Product Realization of Innovative electro-Mechanical Devices) project is defining and proving processes for agile product realization for the Department of Energy complex. Like other agile production efforts reported in the literature, A-primed uses concurrent engineering and information automation technologies to enhance information transfer. A unique aspect of our approach to agility is the qualification during development of a family of related product designs and their production processes, rather than a single design and its attendant processes. Applying engineering principles and statistical design of experiments, economies of test and analytic effort are realized for the qualification of the device family as a whole. Thus the need is minimized for test and analysis to qualify future devices from this family, thereby further reducing the design-to-production cycle time. As a measure of the success of the A-primed approach, the first design took 24 days to produce, and operated correctly on the first attempt. A flow diagram for the qualification process is presented. Guidelines are given for implementation, based on the authors experiences as members of the A-primed qualification team.
NASA Astrophysics Data System (ADS)
Xu, Peiliang
2015-04-01
Satellite orbits have been routinely used to produce models of the Earth's gravity field. The numerical integration method is most widely used by almost all major institutions to determine standard gravity models from space geodetic measurements. As a basic component of the method, the partial derivatives of a satellite orbit with respect to the force parameters to be determined, namely, the unknown harmonic coefficients of the gravitational model, have been first computed by setting the initial values of partial derivatives to zero. In this talk, we first design some simple mathematical examples to show that setting the initial values of partial derivatives to zero is generally erroneous mathematically. We then prove that it is prohibited physically. In other words, setting the initial values of partial derivatives to zero violates the physics of motion of celestial bodies. To conclude, the numerical integration method, as is widely used today by major institutions to produce standard satellite gravity models, is simply incorrect mathematically. As a direct consequence, further work is required to confirm whether the numerical integration method can still be used as a mathematical foundation to produce standard satellite gravity models. More details can be found in Xu (2009, Sci China Ser D-Earth Sci, 52, 562-566).
NASA Technical Reports Server (NTRS)
Iliff, Kenneth W.
1987-01-01
The aircraft parameter estimation problem is used to illustrate the utility of parameter estimation, which applies to many engineering and scientific fields. Maximum likelihood estimation has been used to extract stability and control derivatives from flight data for many years. This paper presents some of the basic concepts of aircraft parameter estimation and briefly surveys the literature in the field. The maximum likelihood estimator is discussed, and the basic concepts of minimization and estimation are examined for a simple simulated aircraft example. The cost functions that are to be minimized during estimation are defined and discussed. Graphic representations of the cost functions are given to illustrate the minimization process. Finally, the basic concepts are generalized, and estimation from flight data is discussed. Some of the major conclusions for the simulated example are also developed for the analysis of flight data from the F-14, highly maneuverable aircraft technology (HiMAT), and space shuttle vehicles.