NASA Astrophysics Data System (ADS)
Gersch, W.; Brotherton, T.; Braun, S.
1980-04-01
A multiple input/scalar output stationary time series identification problem is considered from a parametric model time domain point of view. Particular emphasis is on the source identification problem. Closed form formula estimates of the individual source power contributions are expressed in terms of sample correlations that are obtained from the observed input and output time series and from parametric models fitted to that data. The estimates of the noise power contributions are asymptotically jointly normally distributed. The mean values and covariance matrix of those estimates yield confidence interval estimates of the individual and joint power contributions. The motivation for developing a rational polynomial transfer function or ARMA model of the multi-input scalar output plus additive noise situation is given. A two correlated input/single output version of this model is considered for a Monte Carlo simulation study. Parametric ARMA and approximate AR models are fitted to the simulated data. The asymptotic normality, and the distribution of the mean and covariances of the source power contribution computed from the ARMA and AR models are appraised. Several facets of the relative performance of windowed periodogram and AR model spectral analysis are examined for the multiple input/scalar output identification problem. The points that are emphasized are that conventional windowed periodogram spectral analysis is subjective, not particularly satisfactory for the sharp spectral peak situation that is commonly encountered in vibration data analysis and very likely not as good as "objective" Akaike criterion order AR modelled spectral analysis.
Parametric time-series analysis of daily air pollutants of city of Shumen, Bulgaria
NASA Astrophysics Data System (ADS)
Ivanov, A.; Voynikova, D.; Gocheva-Ilieva, S.; Boyadzhiev, D.
2012-10-01
The urban air pollution is one of the main factors determining the ambient air quality, which affects on the human health and the environment. In this paper parametric time series models are obtained for studying the distribution over time of primary pollutants as sulphur and nitrogen oxides, particulate matter and a secondary pollutant ground level ozon in the town of Shumen, Bulgaria. The methods of factor analysis and ARIMA are used to carry out the time series analysis based on hourly average data in 2011 and first quarter of 2012. The constructed models are applied for a short-term air pollution forecasting. The results are estimated on the basis of national and European regulation indices. The sources of pollutants in the region and their harmful effects on human health are also discussed.
One-stage parametric meta-analysis of time-to-event outcomes
Siannis, F; Barrett, J K; Farewell, V T; Tierney, J F
2010-01-01
Methodology for the meta-analysis of individual patient data with survival end-points is proposed. Motivated by questions about the reliance on hazard ratios as summary measures of treatment effects, a parametric approach is considered and percentile ratios are introduced as an alternative to hazard ratios. The generalized log-gamma model, which includes many common time-to-event distributions as special cases, is discussed in detail. Likelihood inference for percentile ratios is outlined. The proposed methodology is used for a meta-analysis of glioma data that was one of the studies which motivated this work. A simulation study exploring the validity of the proposed methodology is available electronically. Copyright © 2010 John Wiley & Sons, Ltd. PMID:20963770
NASA Astrophysics Data System (ADS)
Jiang, Shifeng; Treps, Nicolas; Fabre, Claude
2012-04-01
We present in this paper a general model for determining the quantum properties of the light generated by a synchronously pumped optical parametric oscillator (SPOPO) operating below threshold. This model considers time and frequency on an equal footing, which allows us to find new quantum properties, related for example to the carrier envelope offset (CEO) phase, and to consider situations that are close to real experiments. We show that, in addition to multimode squeezing in the so-called ‘supermodes’, the system exhibits quadrature entanglement between frequency combs of opposite CEO phases. We have also determined the quantum properties of the individual pulses and their quantum correlations with the neighboring pulses. Finally, we determine the quantum Cramer-Rao limit for an ultra-short time delay measurement using a given number of pulses generated by the SPOPO.
NASA Astrophysics Data System (ADS)
Choi, Jongseong
The performance of a hypersonic flight vehicle will depend on existing materials and fuels; this work presents the performance of the ideal scramjet engine for three different combustion chamber materials and three different candidate fuels. Engine performance is explored by parametric cycle analysis for the ideal scramjet as a function of material maximum service temperature and the lower heating value of jet engine fuels. The thermodynamic analysis is based on the Brayton cycle as similarly employed in describing the performance of the ramjet, turbojet, and fanjet ideal engines. The objective of this work is to explore material operating temperatures and fuel possibilities for the combustion chamber of a scramjet propulsion system to show how they relate to scramjet performance and the seven scramjet engine parameters: specific thrust, fuel-to-air ratio, thrust-specific fuel consumption, thermal efficiency, propulsive efficiency, overall efficiency, and thrust flux. The information presented in this work has not been done by others in the scientific literature. This work yields simple algebraic equations for scramjet performance which are similar to that of the ideal ramjet, ideal turbojet and ideal turbofan engines.
Parametric analysis of ATT configurations.
NASA Technical Reports Server (NTRS)
Lange, R. H.
1972-01-01
This paper describes the results of a Lockheed parametric analysis of the performance, environmental factors, and economics of an advanced commercial transport envisioned for operation in the post-1985 time period. The design parameters investigated include cruise speeds from Mach 0.85 to Mach 1.0, passenger capacities from 200 to 500, ranges of 2800 to 5500 nautical miles, and noise level criteria. NASA high performance configurations and alternate configurations are operated over domestic and international route structures. Indirect and direct costs and return on investment are determined for approximately 40 candidate aircraft configurations. The candidate configurations are input to an aircraft sizing and performance program which includes a subroutine for noise criteria. Comparisons are made between preferred configurations on the basis of maximum return on investment as a function of payload, range, and design cruise speed.
Ford, Eric B.; Fabrycky, Daniel C.; Steffen, Jason H.; Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Lissauer, Jack J.; Moorhead, Althea V.; Morehead, Robert C.; Ragozzine, Darin; Rowe, Jason F.; /NASA, Ames /SETI Inst., Mtn. View /San Diego State U., Astron. Dept.
2012-01-01
We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies are in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the transit timing variations of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.
Ford, Eric B.; Moorhead, Althea V.; Morehead, Robert C.; Fabrycky, Daniel C.; Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Ragozzine, Darin; Charbonneau, David; Lissauer, Jack J.; Rowe, Jason F.; Borucki, William J.; Bryson, Stephen T.; Burke, Christopher J.; Caldwell, Douglas A.; Welsh, William F.; Allen, Christopher; Buchhave, Lars A.; Collaboration: Kepler Science Team; and others
2012-05-10
We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.
Robustness analysis for real parametric uncertainty
NASA Technical Reports Server (NTRS)
Sideris, Athanasios
1989-01-01
Some key results in the literature in the area of robustness analysis for linear feedback systems with structured model uncertainty are reviewed. Some new results are given. Model uncertainty is described as a combination of real uncertain parameters and norm bounded unmodeled dynamics. Here the focus is on the case of parametric uncertainty. An elementary and unified derivation of the celebrated theorem of Kharitonov and the Edge Theorem is presented. Next, an algorithmic approach for robustness analysis in the cases of multilinear and polynomic parametric uncertainty (i.e., the closed loop characteristic polynomial depends multilinearly and polynomially respectively on the parameters) is given. The latter cases are most important from practical considerations. Some novel modifications in this algorithm which result in a procedure of polynomial time behavior in the number of uncertain parameters is outlined. Finally, it is shown how the more general problem of robustness analysis for combined parametric and dynamic (i.e., unmodeled dynamics) uncertainty can be reduced to the case of polynomic parametric uncertainty, and thus be solved by means of the algorithm.
Quantum finite time availability for parametric oscillators
NASA Astrophysics Data System (ADS)
Hoffmann, Karl Heinz; Schmidt, Kim; Salamon, Peter
2015-06-01
The availability of a thermodynamic system out of equilibrium with its environment describes its ability to perform work in a reversible process which brings it to equilibrium with this environment. Processes in finite time can usually not be performed reversibly thus leading to unavoidable losses. In order to account for these losses the concept of finite time availability was introduced. We here add a new feature through the introduction of quantum finite time availability for an ensemble of parametric oscillators. For such systems there exists a certain critical time, the FEAT time. Quantum finite time availability quantifies the available work from processes which are shorter than the FEAT time of the oscillator ensemble.
Parametric instabilities in picosecond time scales
Baldis, H.A.; Rozmus, W.; Labaune, C.; Mounaix, Ph.; Pesme, D.; Baton, S.; Tikhonchuk, V.T.
1993-03-01
The coupling of intense laser light with plasmas is a rich field of plasma physics, with many applications. Among these are inertial confinement fusion (ICF), x-ray lasers, particle acceleration, and x-ray sources. Parametric instabilities have been studied for many years because of their importance to ICF; with laser pulses with duration of approximately a nanosecond, and laser intensities in the range 10{sup 14}--10{sup 15}W/cm{sup 2} these instabilities are of crucial concern because of a number of detrimental effects. Although the laser pulse duration of interest for these studies are relatively long, it has been evident in the past years that to reach an understanding of these instabilities requires their characterization and analysis in picosecond time scales. At the laser intensities of interest, the growth rate for stimulated Brillouin scattering (SBS) is of the order of picoseconds, and of an order of magnitude shorter for stimulated Raman scattering (SRS). In this paper the authors discuss SBS and SRS in the context of their evolution in picosecond time scales. They describe the fundamental concepts associated with their growth and saturation, and recent work on the nonlinear treatment required for the modeling of these instabilities at high laser intensities.
A Cartesian parametrization for the numerical analysis of material instability
Mota, Alejandro; Chen, Qiushi; Foulk, III, James W.; Ostien, Jakob T.; Lai, Zhengshou
2016-02-25
We examine four parametrizations of the unit sphere in the context of material stability analysis by means of the singularity of the acoustic tensor. We then propose a Cartesian parametrization for vectors that lie a cube of side length two and use these vectors in lieu of unit normals to test for the loss of the ellipticity condition. This parametrization is then used to construct a tensor akin to the acoustic tensor. It is shown that both of these tensors become singular at the same time and in the same planes in the presence of a material instability. Furthermore, themore » performance of the Cartesian parametrization is compared against the other parametrizations, with the results of these comparisons showing that in general, the Cartesian parametrization is more robust and more numerically efficient than the others.« less
Analysis of parametric transformer with rectifier load
Ichinokura, O.; Jinzenji, T. ); Tajima, K. )
1993-03-01
This paper describes a push-pull parametric transformer constructed using a pair of orthogonal-cores. The operating characteristics of the parametric transformer with a rectifier load were analyzed based on SPICE simulations. The analysis results show good agreement with experiment. It was found that the input surge current of the full-wave rectifier circuit with a smoothing capacitor can be compensated by the parametric transformer. Use of the parametric transformer as a power stabilizer is anticipated owing to its various functions such as for voltage regulation and overload protection.
Parametric phase diffusion analysis of irregular oscillations
NASA Astrophysics Data System (ADS)
Schwabedal, Justus T. C.
2014-09-01
Parametric phase diffusion analysis (ΦDA), a method to determine variability of irregular oscillations, is presented. ΦDA is formulated as an analysis technique for sequences of Poincaré return times found in numerous applications. The method is unbiased by the arbitrary choice of Poincaré section, i.e. isophase, which causes a spurious component in the Poincaré return times. Other return-time variability measures can be biased drastically by these spurious return times, as shown for the Fano factor of chaotic oscillations in the Rössler system. The empirical use of ΦDA is demonstrated in an application to heart rate data from the Fantasia Database, for which ΦDA parameters successfully classify heart rate variability into groups of age and gender.
Macchiato, M. ); Serio, C. ); Lapenna, V. ); Rotonda, L.La. )
1993-07-01
The statistical analysis of cold air temperatures (cold spells) and hot air temperatures (hot spells) is discussed. Air temperature time series observed at 50 stations in southern Italy are investigated. The deterministic and stochastic components of the time series are identified and described by a dynamic-stochastic model that is periodic in the deterministic part (the annual cycle) and Markovian (first-order autoregressive) in the stochastic part. The annual cycle is described by only a few Fourier coefficients. Based on the model fitted to the data, the theoretical probability of cold (hot) spells is computed and compared to that estimated from the observed data. Spatial patterns of identified that make it possible to extrapolate the probability of cold (hot) spells at locations where no direct observations are available. 19 refs., 13 figs., 2 tabs.
Meadows, Cheyney; Rajala-Schultz, Päivi J; Frazer, Grant S; Phillips, Gary; Meiring, Richard W; Hoblet, Kent H
2007-07-16
The effect of a contract breeding program offered by a breeding co-operative was assessed using parametric frailty models with event-time analysis technique in a field study of Ohio dairies. The program featured tail chalking and daily evaluation of cows for insemination by co-operative technicians; dairy employees no longer handled estrus detection activities. Test day records were obtained between early 2002 and mid-2004 for 16,453 lactations representing 11,398 cows in 31 herds identified as well-managed client herds by the breeding co-operative. Various parametric distributions for event times available in a commercial software (Stata 9.1, College Station, TX) were tested to assess which distribution fit the calving-to-conception data best. After identifying the distribution with the best fit, a full model with potential confounders and other significant predictors of time to pregnancy was developed and then frailty terms were included in the model. Generalized gamma and log-normal distributions fit the data best, but since gamma distribution does not allow the use of frailty effects, log-normal distribution was used in further modeling. Separate accelerated failure time models with frailty terms to account for latent effects at the herd, cow, or lactation level were developed, testing both gamma and inverse Gaussian frailty distributions. In these models, potential confounders and statistically significant predictors were also controlled for, and the association between the contract breeding program and the mean time to pregnancy was characterized using time ratios. The log-normal model identified that interval to pregnancy was associated with breed, herd size, use of ovulation synchronization protocols, parity, calving season and somatic cell score (above or below 4.5) and maximum milk yield prior to pregnancy or censoring. While controlling for these factors, there was a reduction in average time to pregnancy among cows managed under the contract breeding
Parametric analysis of ATM solar array.
NASA Technical Reports Server (NTRS)
Singh, B. K.; Adkisson, W. B.
1973-01-01
The paper discusses the methods used for the calculation of ATM solar array performance characteristics and provides the parametric analysis of solar panels used in SKYLAB. To predict the solar array performance under conditions other than test conditions, a mathematical model has been developed. Four computer programs have been used to convert the solar simulator test data to the parametric curves. The first performs module summations, the second determines average solar cell characteristics which will cause a mathematical model to generate a curve matching the test data, the third is a polynomial fit program which determines the polynomial equations for the solar cell characteristics versus temperature, and the fourth program uses the polynomial coefficients generated by the polynomial curve fit program to generate the parametric data.
Adaptive time-frequency parametrization of epileptic spikes
NASA Astrophysics Data System (ADS)
Durka, Piotr J.
2004-05-01
Adaptive time-frequency approximations of signals have proven to be a valuable tool in electroencephalogram (EEG) analysis and research, where it is believed that oscillatory phenomena play a crucial role in the brain’s information processing. This paper extends this paradigm to the nonoscillating structures such as the epileptic EEG spikes, and presents the advantages of their parametrization in general terms such as amplitude and half-width. A simple detector of epileptic spikes in the space of these parameters, tested on a limited data set, gives very promising results. It also provides a direct distinction between randomly occurring spikes or spike/wave complexes and rhythmic discharges.
Parametric Cost Analysis: A Design Function
NASA Technical Reports Server (NTRS)
Dean, Edwin B.
1989-01-01
Parametric cost analysis uses equations to map measurable system attributes into cost. The measures of the system attributes are called metrics. The equations are called cost estimating relationships (CER's), and are obtained by the analysis of cost and technical metric data of products analogous to those to be estimated. Examples of system metrics include mass, power, failure_rate, mean_time_to_repair, energy _consumed, payload_to_orbit, pointing_accuracy, manufacturing_complexity, number_of_fasteners, and percent_of_electronics_weight. The basic assumption is that a measurable relationship exists between system attributes and the cost of the system. If a function exists, the attributes are cost drivers. Candidates for metrics include system requirement metrics and engineering process metrics. Requirements are constraints on the engineering process. From optimization theory we know that any active constraint generates cost by not permitting full optimization of the objective. Thus, requirements are cost drivers. Engineering processes reflect a projection of the requirements onto the corporate culture, engineering technology, and system technology. Engineering processes are an indirect measure of the requirements and, hence, are cost drivers.
Parametric cost analysis for advanced energy concepts
Not Available
1983-10-01
This report presents results of an exploratory study to develop parametric cost estimating relationships for advanced fossil-fuel energy systems. The first of two tasks was to develop a standard Cost Chart of Accounts to serve as a basic organizing framework for energy systems cost analysis. The second task included development of selected parametric cost estimating relationships (CERs) for individual elements (or subsystems) of a fossil fuel plant, nominally for the Solvent-Refined Coal (SRC) process. Parametric CERs are presented for the following elements: coal preparation, coal slurry preparation, dissolver (reactor); gasification; oxygen production; acid gas/CO/sub 2/ removal; shift conversion; cryogenic hydrogen recovery; and sulfur removal. While the nominal focus of the study was on the SRC process, each of these elements is found in other fossil fuel processes. Thus, the results of this effort have broader potential application. However, it should also be noted that the CERs presented in this report are based upon a limited data base. Thus, they are applicable over a limited range of values (of the independent variables) and for a limited set of specific technologies (e.g., the gasifier CER is for the multi-train, Koppers-Totzek process). Additional work is required to extend the range of these CERs. 16 figures, 13 tables.
Parametric systems analysis for tandem mirror hybrids
Lee, J.D.; Chapin, D.L.; Chi, J.W.H.
1980-09-01
Fusion fission systems, consisting of fissile producing fusion hybrids combining a tandem mirror fusion driver with various blanket types and net fissile consuming LWR's, have been modeled and analyzed parametrically. Analysis to date indicates that hybrids can be competitive with mined uranium when U/sub 3/O/sub 8/ cost is about 100 $/lb., adding less than 25% to present day cost of power from LWR's. Of the three blanket types considered, uranium fast fission (UFF), thorium fast fission (ThFF), and thorium fission supressed (ThFS), the ThFS blanket has a modest economic advantage under most conditions but has higher support ratios and potential safety advantages under all conditions.
Model reduction for parametric instability analysis in shells conveying fluid
NASA Astrophysics Data System (ADS)
Kochupillai, Jayaraj; Ganesan, N.; Padmanabhan, Chandramouli
2003-05-01
Flexible pipes conveying fluid are often subjected to parametric excitation due to time-periodic flow fluctuations. Such systems are known to exhibit complex instability phenomena such as divergence and coupled-mode flutter. Investigators have typically used weighted residual techniques, to reduce the continuous system model into a discrete model, based on approximation functions with global support, for carrying out stability analysis. While this approach is useful for straight pipes, modelling based on FEM is needed for the study of complicated piping systems, where the approximation functions used are local in support. However, the size of the problem is now significantly larger and for computationally efficient stability analysis, model reduction is necessary. In this paper, model reduction techniques are developed for the analysis of parametric instability in flexible pipes conveying fluids under a mean pressure. It is shown that only those linear transformations which leave the original eigenvalues of the linear time invariant system unchanged are admissible. The numerical technique developed by Friedmann and Hammond (Int. J. Numer. Methods Eng. Efficient 11 (1997) 1117) is used for the stability analysis. One of the key research issues is to establish criteria for deciding the basis vectors essential for an accurate stability analysis. This paper examines this issue in detail and proposes new guidelines for their selection.
Threshold Analysis of a THz-Wave Parametric Oscillator
NASA Astrophysics Data System (ADS)
Li, Zhong-Yang; Yao, Jian-Quan; Zhu, Neng-Nian; Wang, Yu-Ye; Xu, De-Gang
2010-06-01
The parametric gain of a terahertz wave parametric oscillator (TPO) is analyzed. Meanwhile the expression of TPO threshold pump intensity is derived and theoretically analyzed with different factors. The effective interaction length between the pump wave and Stokes wave is calculated, and particular attention is paid to the coupling efficiency of the pump wave and Stokes wave. Such an analysis is useful for the experiments of TPO.
Lottery Spending: A Non-Parametric Analysis
Garibaldi, Skip; Frisoli, Kayla; Ke, Li; Lim, Melody
2015-01-01
We analyze the spending of individuals in the United States on lottery tickets in an average month, as reported in surveys. We view these surveys as sampling from an unknown distribution, and we use non-parametric methods to compare properties of this distribution for various demographic groups, as well as claims that some properties of this distribution are constant across surveys. We find that the observed higher spending by Hispanic lottery players can be attributed to differences in education levels, and we dispute previous claims that the top 10% of lottery players consistently account for 50% of lottery sales. PMID:25642699
Lottery spending: a non-parametric analysis.
Garibaldi, Skip; Frisoli, Kayla; Ke, Li; Lim, Melody
2015-01-01
We analyze the spending of individuals in the United States on lottery tickets in an average month, as reported in surveys. We view these surveys as sampling from an unknown distribution, and we use non-parametric methods to compare properties of this distribution for various demographic groups, as well as claims that some properties of this distribution are constant across surveys. We find that the observed higher spending by Hispanic lottery players can be attributed to differences in education levels, and we dispute previous claims that the top 10% of lottery players consistently account for 50% of lottery sales. PMID:25642699
NASA Astrophysics Data System (ADS)
Donnelly, Aoife; Misstear, Bruce; Broderick, Brian
2015-02-01
This paper presents a model for producing real time air quality forecasts with both high accuracy and high computational efficiency. Temporal variations in nitrogen dioxide (NO2) levels and historical correlations between meteorology and NO2 levels are used to estimate air quality 48 h in advance. Non-parametric kernel regression is used to produce linearized factors describing variations in concentrations with wind speed and direction and, furthermore, to produce seasonal and diurnal factors. The basis for the model is a multiple linear regression which uses these factors together with meteorological parameters and persistence as predictors. The model was calibrated at three urban sites and one rural site and the final fitted model achieved R values of between 0.62 and 0.79 for hourly forecasts and between 0.67 and 0.84 for daily maximum forecasts. Model validation using four model evaluation parameters, an index of agreement (IA), the correlation coefficient (R), the fraction of values within a factor of 2 (FAC2) and the fractional bias (FB), yielded good results. The IA for 24 hr forecasts of hourly NO2 was between 0.77 and 0.90 at urban sites and 0.74 at the rural site, while for daily maximum forecasts it was between 0.89 and 0.94 for urban sites and 0.78 for the rural site. R values of up to 0.79 and 0.81 and FAC2 values of 0.84 and 0.96 were observed for hourly and daily maximum predictions, respectively. The model requires only simple input data and very low computational resources. It found to be an accurate and efficient means of producing real time air quality forecasts.
Soil Analysis using the semi-parametric NAA technique
Zamboni, C. B.; Silveira, M. A. G.; Medina, N. H.
2007-10-26
The semi-parametric Neutron Activation Analysis technique, using Au as a flux monitor, was applied to measure element concentrations of Br, Ca, Cl, K, Mn and Na for soil characterization. The results were compared with those using the Instrumental Neutron Activation Analysis technique and they found to be compatible. The viability, advantages, and limitations of using these two analytic methodologies are discussed.
Parametric analysis of cryogenic carbon dioxide cooling of shell eggs.
Sabliov, C M; Farkas, B E; Keener, K M; Curtis, P A
2002-11-01
Parametric analysis of cryogenic cooling of shell eggs was performed using finite element analysis. Two cooling temperatures (-50 and -70 C), three cooling convective heat transfer coefficients (20, 50, and 100 W/ m2K), two equilibration temperatures (7 and 25 C), and two equilibration heat transfer coefficients (0 and 20 W/ m2K) were considered in the analysis. Lower temperatures and higher cooling convective heat transfer coefficients resulted in higher cooling rates and lower final egg temperatures. A chart and equation were developed to identify combinations of processing parameters to yield the desired egg temperature (7 C) at the end of adiabatic equilibration. Results show that a cooling time of 8.2 min was required to reach a final egg temperature of 7 C for a cooling temperature of -50 C and a convective heat transfer coefficient of 20 W/m2K. The cooling time decreased to 2 min when the convective heat transfer coefficient increased to 100 W/m2K, at a cooling temperature of -50 C. Processing at -70 C and 20 W/m2K, required 5.3 min to reach a final temperature of 7 C. At a higher convective heat transfer coefficient (100 W/m2K) and -70 C, a processing time of 1.3 min was sufficient to reach the target temperature of 7 C. The results may be used as a reference in process or equipment design for shell egg cooling in cryogenic CO2. PMID:12455606
Bayesian parametric estimation of stop-signal reaction time distributions.
Matzke, Dora; Dolan, Conor V; Logan, Gordon D; Brown, Scott D; Wagenmakers, Eric-Jan
2013-11-01
The cognitive concept of response inhibition can be measured with the stop-signal paradigm. In this paradigm, participants perform a 2-choice response time (RT) task where, on some of the trials, the primary task is interrupted by a stop signal that prompts participants to withhold their response. The dependent variable of interest is the latency of the unobservable stop response (stop-signal reaction time, or SSRT). Based on the horse race model (Logan & Cowan, 1984), several methods have been developed to estimate SSRTs. None of these approaches allow for the accurate estimation of the entire distribution of SSRTs. Here we introduce a Bayesian parametric approach that addresses this limitation. Our method is based on the assumptions of the horse race model and rests on the concept of censored distributions. We treat response inhibition as a censoring mechanism, where the distribution of RTs on the primary task (go RTs) is censored by the distribution of SSRTs. The method assumes that go RTs and SSRTs are ex-Gaussian distributed and uses Markov chain Monte Carlo sampling to obtain posterior distributions for the model parameters. The method can be applied to individual as well as hierarchical data structures. We present the results of a number of parameter recovery and robustness studies and apply our approach to published data from a stop-signal experiment. PMID:23163766
Parametric analysis of a magnetized cylindrical plasma
Ahedo, Eduardo
2009-11-15
The relevant macroscopic model, the spatial structure, and the parametric regimes of a low-pressure plasma confined by a cylinder and an axial magnetic field is discussed for the small-Debye length limit, making use of asymptotic techniques. The plasma response is fully characterized by three-dimensionless parameters, related to the electron gyroradius, and the electron and ion collision mean-free-paths. There are the unmagnetized regime, the main magnetized regime, and, for a low electron-collisionality plasma, an intermediate-magnetization regime. In the magnetized regimes, electron azimuthal inertia is shown to be a dominant phenomenon in part of the quasineutral plasma region and to set up before ion radial inertia. In the main magnetized regime, the plasma structure consists of a bulk diffusive region, a thin layer governed by electron inertia, a thinner sublayer controlled by ion inertia, and the non-neutral Debye sheath. The solution of the main inertial layer yields that the electron azimuthal energy near the wall is larger than the electron thermal energy, making electron resistivity effects non-negligible. The electron Boltzmann relation is satisfied only in the very vicinity of the Debye sheath edge. Ion collisionality effects are irrelevant in the magnetized regime. Simple scaling laws for plasma production and particle and energy fluxes to the wall are derived.
Incorporating parametric uncertainty into population viability analysis models
McGowan, Conor P.; Runge, Michael C.; Larson, Michael A.
2011-01-01
Uncertainty in parameter estimates from sampling variation or expert judgment can introduce substantial uncertainty into ecological predictions based on those estimates. However, in standard population viability analyses, one of the most widely used tools for managing plant, fish and wildlife populations, parametric uncertainty is often ignored in or discarded from model projections. We present a method for explicitly incorporating this source of uncertainty into population models to fully account for risk in management and decision contexts. Our method involves a two-step simulation process where parametric uncertainty is incorporated into the replication loop of the model and temporal variance is incorporated into the loop for time steps in the model. Using the piping plover, a federally threatened shorebird in the USA and Canada, as an example, we compare abundance projections and extinction probabilities from simulations that exclude and include parametric uncertainty. Although final abundance was very low for all sets of simulations, estimated extinction risk was much greater for the simulation that incorporated parametric uncertainty in the replication loop. Decisions about species conservation (e.g., listing, delisting, and jeopardy) might differ greatly depending on the treatment of parametric uncertainty in population models.
Multi-level approach for parametric roll analysis
NASA Astrophysics Data System (ADS)
Kim, Taeyoung; Kim, Yonghwan
2011-03-01
The present study considers multi-level approach for the analysis of parametric roll phenomena. Three kinds of computation method, GM variation, impulse response function (IRF), and Rankine panel method, are applied for the multi-level approach. IRF and Rankine panel method are based on the weakly nonlinear formulation which includes nonlinear Froude- Krylov and restoring forces. In the computation result of parametric roll occurrence test in regular waves, IRF and Rankine panel method show similar tendency. Although the GM variation approach predicts the occurrence of parametric roll at twice roll natural frequency, its frequency criteria shows a little difference. Nonlinear roll motion in bichromatic wave is also considered in this study. To prove the unstable roll motion in bichromatic waves, theoretical and numerical approaches are applied. The occurrence of parametric roll is theoretically examined by introducing the quasi-periodic Mathieu equation. Instability criteria are well predicted from stability analysis in theoretical approach. From the Fourier analysis, it has been verified that difference-frequency effects create the unstable roll motion. The occurrence of unstable roll motion in bichromatic wave is also observed in the experiment.
Parametric identification of a servo-hydraulic actuator for real-time hybrid simulation
NASA Astrophysics Data System (ADS)
Qian, Yili; Ou, Ge; Maghareh, Amin; Dyke, Shirley J.
2014-10-01
In a typical Real-time Hybrid Simulation (RTHS) setup, servo-hydraulic actuators serve as interfaces between the computational and physical substructures. Time delay introduced by actuator dynamics and complex interaction between the actuators and the specimen has detrimental effects on the stability and accuracy of RTHS. Therefore, a good understanding of servo-hydraulic actuator dynamics is a prerequisite for controller design and computational simulation of RTHS. This paper presents an easy-to-use parametric identification procedure for RTHS users to obtain re-useable actuator parameters for a range of payloads. The critical parameters in a linearized servo-hydraulic actuator model are optimally obtained from genetic algorithms (GA) based on experimental data collected from various specimen mass/stiffness combinations loaded to the target actuator. The actuator parameters demonstrate convincing convergence trend in GA. A key feature of this parametric modeling procedure is its re-usability under different testing scenarios, including different specimen mechanical properties and actuator inner-loop control gains. The models match well with experimental results. The benefit of the proposed parametric identification procedure has been demonstrated by (1) designing an H∞ controller with the identified system parameters that significantly improves RTHS performance; and (2) establishing an analysis and computational simulation of a servo-hydraulic system that help researchers interpret system instability and improve design of experiments.
Parametric investigation of Radome analysis methods. Volume 4: Experimental results
NASA Astrophysics Data System (ADS)
Bassett, H. L.; Newton, J. M.; Adams, W.; Ussailis, J. S.; Hadsell, M. J.; Huddleston, G. K.
1981-02-01
This Volume 4 of four volumes presents 140 measured far-field patterns and boresight error data for eight combinations of three monopulse antennas and five tangent ogive Rexolite radomes at 35 GHz. The antennas and radomes, all of different sizes, were selected to provide a range of parameters as found in the applications. The measured data serve as true data in the parametric investigation of radome analysis methods to determine the accuracies and ranges of validity of selected methods of analysis.
Enhanced optical squeezing from a degenerate parametric amplifier via time-delayed coherent feedback
NASA Astrophysics Data System (ADS)
Német, Nikolett; Parkins, Scott
2016-08-01
A particularly simple setup is introduced to study the influence of time-delayed coherent feedback on the optical squeezing properties of the degenerate parametric amplifier. The possibility for significantly enhanced squeezing is demonstrated both on resonance and in sidebands, at a reduced pump power compared to the case without feedback. We study a broad range of operating parameters and their influence on the characteristic squeezing of the system. A classical analysis of the system dynamics reveals the connection between the feedback-modified landscape of stability and enhanced squeezing.
Parametric analysis of transient skin heating induced by terahertz radiation.
Zilberti, Luca; Arduino, Alessandro; Bottauscio, Oriano; Chiampi, Mario
2014-07-01
This paper investigates the effect of relevant physical parameters on transient temperature elevation induced in human tissues by electromagnetic waves in the terahertz (THz) band. The problem is defined by assuming a plane wave, which, during a limited time interval, normally impinges on the surface of a 3-layer model of the human body, causing a thermal transient. The electromagnetic equations are solved analytically, while the thermal ones are handled according to the finite element method. A parametric analysis is performed with the aim of identifying the contribution of each parameter, showing that the properties of the first skin layer (except blood flow) play a major role in the computation of the maximum temperature rise for the considered exposure situation. Final results, obtained by combining all relevant parameters together, show that the deviation from the reference solution of the maximum temperature elevation in skin is included in the coverage intervals from -30% to +10% at 0.1 THz and from -33% to +18% at 1 THz (with 95% confidence level). These data allow bounding the possible temperature increase against the spread of tissue properties that could be reasonably used for dosimetric simulations. PMID:24510310
From wavelets to adaptive approximations: time-frequency parametrization of EEG.
Durka, Piotr J
2003-01-01
This paper presents a summary of time-frequency analysis of the electrical activity of the brain (EEG). It covers in details two major steps: introduction of wavelets and adaptive approximations. Presented studies include time-frequency solutions to several standard research and clinical problems, encountered in analysis of evoked potentials, sleep EEG, epileptic activities, ERD/ERS and pharmaco-EEG. Based upon these results we conclude that the matching pursuit algorithm provides a unified parametrization of EEG, applicable in a variety of experimental and clinical setups. This conclusion is followed by a brief discussion of the current state of the mathematical and algorithmical aspects of adaptive time-frequency approximations of signals. PMID:12605721
Scaramuzzino, F.
2009-09-09
This paper considers a qualitative analysis of the solution of a pure exchange general economic equilibrium problem according to two independent parameters. Some recently results obtained by the author in the static and the dynamic case have been collected. Such results have been applied in a particular parametric case: it has been focused the attention on a numerical application for which the existence of the solution of time-depending parametric variational inequality that describes the equilibrium conditions has been proved by means of the direct method. By using MatLab computation after a linear interpolation, the curves of equilibrium have been visualized.
Parametric analysis of closed cycle magnetohydrodynamic (MHD) power plants
NASA Technical Reports Server (NTRS)
Owens, W.; Berg, R.; Murthy, R.; Patten, J.
1981-01-01
A parametric analysis of closed cycle MHD power plants was performed which studied the technical feasibility, associated capital cost, and cost of electricity for the direct combustion of coal or coal derived fuel. Three reference plants, differing primarily in the method of coal conversion utilized, were defined. Reference Plant 1 used direct coal fired combustion while Reference Plants 2 and 3 employed on site integrated gasifiers. Reference Plant 2 used a pressurized gasifier while Reference Plant 3 used a ""state of the art' atmospheric gasifier. Thirty plant configurations were considered by using parametric variations from the Reference Plants. Parametric variations include the type of coal (Montana Rosebud or Illinois No. 6), clean up systems (hot or cold gas clean up), on or two stage atmospheric or pressurized direct fired coal combustors, and six different gasifier systems. Plant sizes ranged from 100 to 1000 MWe. Overall plant performance was calculated using two methodologies. In one task, the channel performance was assumed and the MHD topping cycle efficiencies were based on the assumed values. A second task involved rigorous calculations of channel performance (enthalpy extraction, isentropic efficiency and generator output) that verified the original (task one) assumptions. Closed cycle MHD capital costs were estimated for the task one plants; task two cost estimates were made for the channel and magnet only.
Deriving the Coronal Magnetic Field Using Parametric Transformation Analysis
NASA Technical Reports Server (NTRS)
Gary, G. Allen; Rose, M. Franklin (Technical Monitor)
2001-01-01
When plasma-beta greater than 1 then the gas pressure dominates over the magnetic pressure. This ratio as a function along the coronal magnetic field lines varies from beta greater than 1 in the photosphere at the base of the field lines, to beta much less than 1 in the mid-corona, to beta greater than 1 in the upper corona. Almost all magnetic field extrapolations do not or cannot take into account the full range of beta. They essentially assume beta much less than 1, since the full boundary conditions do not exist in the beta greater than 1 regions. We use a basic parametric representation of the magnetic field lines such that the field lines can be manipulated to match linear features in the EUV and SXR coronal images in a least squares sense. This research employs free-form deformation mathematics to generate the associated coronal magnetic field. In our research program, the complex magnetic field topology uses Parametric Transformation Analysis (PTA) which is a new and innovative method to describe the coronal fields that we are developing. In this technique the field lines can be viewed as being embedded in a plastic medium, the frozen-in-field-line concept. As the medium is deformed the field lines are similarly deformed. However the advantage of the PTA method is that the field line movement represents a transformation of one magnetic field solution into another magnetic field solution. When fully implemented, this method will allow the resulting magnetic field solution to fully match the magnetic field lines with EUV/SXR coronal loops by minimizing the differences in direction and dispersion of a collection of PTA magnetic field lines and observed field lines. The derived magnetic field will then allow beta greater than 1 regions to be included, the electric currents to be calculated, and the Lorentz force to be determined. The advantage of this technique is that the solution is: (1) independent of the upper and side boundary conditions, (2) allows non
Parametric and experimental analysis using a power flow approach
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.
1990-01-01
A structural power flow approach for the analysis of structure-borne transmission of vibrations is used to analyze the influence of structural parameters on transmitted power. The parametric analysis is also performed using the Statistical Energy Analysis approach and the results are compared with those obtained using the power flow approach. The advantages of structural power flow analysis are demonstrated by comparing the type of results that are obtained by the two analytical methods. Also, to demonstrate that the power flow results represent a direct physical parameter that can be measured on a typical structure, an experimental study of structural power flow is presented. This experimental study presents results for an L shaped beam for which an available solution was already obtained. Various methods to measure vibrational power flow are compared to study their advantages and disadvantages.
NASA Astrophysics Data System (ADS)
Zaghari, Bahareh; Rustighi, Emiliano; Ghandchi Tehrani, Maryam
2015-03-01
Vibration energy harvesting is the transformation of vibration energy to electrical energy. The motivation of this work is to use vibration energy harvesting to power wireless sensors that could be used in inaccessible or hostile environments to transmit information for condition health monitoring. Although considerable work has been done in the area of energy harvesting, there is still a demand for making a robust and small vibration energy harvesters from random excitations in a real environment that can produce a reliable amount of energy. Parametrically excited harvesters can have time-varying stiffness. Parametric amplification is used to tune vibration energy harvesters to maximize energy gains at system superharmonics, often at twice the first natural frequency. In this paper the parametrically excited harvester with cubic and cubic parametric nonlinearity is introduced as a novel work. The advantages of having cubic and cubic nonlinearity are explained theoretically and experimentally.
Containment Sump Neutralization Using Trisodium Phosphate: Parametric Analysis
Zaki, Tarek G.
2002-07-01
For post-LOCA conditions, the pH of the aqueous solution collected in the containment sump after completion of injection of containment spray and ECC water, and all additives for reactivity control, fission product removal, and other purposes, should be maintained at a level sufficiently high to provide assurance that significant long-term iodine re-evolution does not occur. Long-term iodine retention may be assumed only when the equilibrium sump solution pH is above 7. This pH value should be achieved by the onset of the spray recirculation mode. A trisodium phosphate (TSP)-based, passive system can be used to achieve this pH value. This is a proven technology that is already in use in nuclear power plants. This system consists of several wire mesh baskets, filled with TSP and strategically located in the sump in order to insure timely dissolution of TSP and rapid pH rise under LOCA conditions. Accurate determination of the total quantity of TSP required to raise the pH of borated water in the sump to within the acceptable range is the key element to a proper design of this system. However, this type of analysis is quite involved and highly iterative, which requires the use of a computer program. This paper describes the basis for a computer program that determines the required quantity of TSP as a function of the quantity of borated water in the sump, the boron concentration, the sump temperature, and the specified pH value. The equilibrium quantities of boric acid species are calculated iteratively based on its molal equilibrium quotients. The equilibrium quantities of phosphoric acid species are calculated iteratively based on its dissociation constants. The charge balance error (CBE) is the sum of ionic charges for all species and ions in the solution, including sodium. All species are in equilibrium when the CBE reduces to zero. The paper also presents the results of a parametric analysis that is performed using this computer program. Ranges of borated water
NASA Astrophysics Data System (ADS)
Murray, E. M.; Cobourn, K.; Flores, A. N.; Pierce, J. L.
2014-12-01
As climate changes, the final date of spring snowmelt is projected to occur earlier in the year within the western United States. This earlier snowmelt timing may impact crop yield in snow-dominated watersheds by changing the timing of water delivery to agricultural fields. There is considerable uncertainty about how agricultural impacts of snowmelt timing may vary by region, crop-type, and practices like irrigation vs. dryland farming. Establishing the relationship between snowmelt timing and agricultural yield is important for understanding how changes in large-scale climatic indices (like snowmelt date) may be associated with changes in agricultural yield. A better understanding of the influence of changes in snowmelt on non-irrigated crop yield may additionally be extrapolated to better understand how climate change may alter biomass production in non-managed ecosystems. We utilized parametric regression techniques to isolate the magnitude of impact snowmelt timing has had on historical crop yield independently of climate and spatial variables that also impact yield. To do this, we examined the historical relationship between snowmelt timing and non-irrigated wheat and barley yield using a multiple linear regression model to predict yield in several Idaho counties as a function of snowmelt date, climate variables (precipitation and growing degree-days), and spatial differences between counties. We utilized non-parametric techniques to determine where snowmelt timing has positively versus negatively impacted yield. To do this, we developed classification and regression trees to identify spatial controls (e.g. latitude, elevation) on the relationship between snowmelt timing and yield. Most trends suggest a decrease in crop yield with earlier snowmelt, but a significant opposite relationship is observed in some regions of Idaho. An earlier snowmelt date occurring at high latitudes corresponds with higher than average wheat yield. Therefore, Northern Idaho may
Desiccant Enhanced Evaporative Air Conditioning: Parametric Analysis and Design; Preprint
Woods, J.; Kozubal, E.
2012-10-01
This paper presents a parametric analysis using a numerical model of a new concept in desiccant and evaporative air conditioning. The concept consists of two stages: a liquid desiccant dehumidifier and a dew-point evaporative cooler. Each stage consists of stacked air channel pairs separated by a plastic sheet. In the first stage, a liquid desiccant film removes moisture from the process (supply-side) air through a membrane. An evaporatively-cooled exhaust airstream on the other side of the plastic sheet cools the desiccant. The second-stage indirect evaporative cooler sensibly cools the dried process air. We analyze the tradeoff between device size and energy efficiency. This tradeoff depends strongly on process air channel thicknesses, the ratio of first-stage to second-stage area, and the second-stage exhaust air flow rate. A sensitivity analysis reiterates the importance of the process air boundary layers and suggests a need for increasing airside heat and mass transfer enhancements.
Nonlinear parametric model for Granger causality of time series
NASA Astrophysics Data System (ADS)
Marinazzo, Daniele; Pellicoro, Mario; Stramaglia, Sebastiano
2006-06-01
The notion of Granger causality between two time series examines if the prediction of one series could be improved by incorporating information of the other. In particular, if the prediction error of the first time series is reduced by including measurements from the second time series, then the second time series is said to have a causal influence on the first one. We propose a radial basis function approach to nonlinear Granger causality. The proposed model is not constrained to be additive in variables from the two time series and can approximate any function of these variables, still being suitable to evaluate causality. Usefulness of this measure of causality is shown in two applications. In the first application, a physiological one, we consider time series of heart rate and blood pressure in congestive heart failure patients and patients affected by sepsis: we find that sepsis patients, unlike congestive heart failure patients, show symmetric causal relationships between the two time series. In the second application, we consider the feedback loop in a model of excitatory and inhibitory neurons: we find that in this system causality measures the combined influence of couplings and membrane time constants.
Syndrome Surveillance Using Parametric Space-Time Clustering
KOCH, MARK W.; MCKENNA, SEAN A.; BILISOLY, ROGER L.
2002-11-01
As demonstrated by the anthrax attack through the United States mail, people infected by the biological agent itself will give the first indication of a bioterror attack. Thus, a distributed information system that can rapidly and efficiently gather and analyze public health data would aid epidemiologists in detecting and characterizing emerging diseases, including bioterror attacks. We propose using clusters of adverse health events in space and time to detect possible bioterror attacks. Space-time clusters can indicate exposure to infectious diseases or localized exposure to toxins. Most space-time clustering approaches require individual patient data. To protect the patient's privacy, we have extended these approaches to aggregated data and have embedded this extension in a sequential probability ratio test (SPRT) framework. The real-time and sequential nature of health data makes the SPRT an ideal candidate. The result of space-time clustering gives the statistical significance of a cluster at every location in the surveillance area and can be thought of as a ''health-index'' of the people living in this area. As a surrogate to bioterrorism data, we have experimented with two flu data sets. For both databases, we show that space-time clustering can detect a flu epidemic up to 21 to 28 days earlier than a conventional periodic regression technique. We have also tested using simulated anthrax attack data on top of a respiratory illness diagnostic category. Results show we do very well at detecting an attack as early as the second or third day after infected people start becoming severely symptomatic.
Towards the generation of a parametric foot model using principal component analysis: A pilot study.
Scarton, Alessandra; Sawacha, Zimi; Cobelli, Claudio; Li, Xinshan
2016-06-01
There have been many recent developments in patient-specific models with their potential to provide more information on the human pathophysiology and the increase in computational power. However they are not yet successfully applied in a clinical setting. One of the main challenges is the time required for mesh creation, which is difficult to automate. The development of parametric models by means of the Principle Component Analysis (PCA) represents an appealing solution. In this study PCA has been applied to the feet of a small cohort of diabetic and healthy subjects, in order to evaluate the possibility of developing parametric foot models, and to use them to identify variations and similarities between the two populations. Both the skin and the first metatarsal bones have been examined. Besides the reduced sample of subjects considered in the analysis, results demonstrated that the method adopted herein constitutes a first step towards the realization of a parametric foot models for biomechanical analysis. Furthermore the study showed that the methodology can successfully describe features in the foot, and evaluate differences in the shape of healthy and diabetic subjects. PMID:27068864
Parametric and experimental analysis using a power flow approach
NASA Technical Reports Server (NTRS)
Cuschieri, J. M.
1988-01-01
Having defined and developed a structural power flow approach for the analysis of structure-borne transmission of structural vibrations, the technique is used to perform an analysis of the influence of structural parameters on the transmitted energy. As a base for comparison, the parametric analysis is first performed using a Statistical Energy Analysis approach and the results compared with those obtained using the power flow approach. The advantages of using structural power flow are thus demonstrated by comparing the type of results obtained by the two methods. Additionally, to demonstrate the advantages of using the power flow method and to show that the power flow results represent a direct physical parameter that can be measured on a typical structure, an experimental investigation of structural power flow is also presented. Results are presented for an L-shaped beam for which an analytical solution has already been obtained. Furthermore, the various methods available to measure vibrational power flow are compared to investigate the advantages and disadvantages of each method.
2014-01-01
Background Early methods for estimating divergence times from gene sequence data relied on the assumption of a molecular clock. More sophisticated methods were created to model rate variation and used auto-correlation of rates, local clocks, or the so called “uncorrelated relaxed clock” where substitution rates are assumed to be drawn from a parametric distribution. In the case of Bayesian inference methods the impact of the prior on branching times is not clearly understood, and if the amount of data is limited the posterior could be strongly influenced by the prior. Results We develop a maximum likelihood method – Physher – that uses local or discrete clocks to estimate evolutionary rates and divergence times from heterochronous sequence data. Using two empirical data sets we show that our discrete clock estimates are similar to those obtained by other methods, and that Physher outperformed some methods in the estimation of the root age of an influenza virus data set. A simulation analysis suggests that Physher can outperform a Bayesian method when the real topology contains two long branches below the root node, even when evolution is strongly clock-like. Conclusions These results suggest it is advisable to use a variety of methods to estimate evolutionary rates and divergence times from heterochronous sequence data. Physher and the associated data sets used here are available online at http://code.google.com/p/physher/. PMID:25055743
Interactive flutter analysis and parametric study for conceptual wing design
NASA Technical Reports Server (NTRS)
Mukhopadhyay, Vivek
1995-01-01
An interactive computer program was developed for wing flutter analysis in the conceptual design stage. The objective was to estimate the flutter instability boundary of a flexible cantilever wing, when well defined structural and aerodynamic data are not available, and then study the effect of change in Mach number, dynamic pressure, torsional frequency, sweep, mass ratio, aspect ratio, taper ratio, center of gravity, and pitch inertia, to guide the development of the concept. The software was developed on MathCad (trademark) platform for Macintosh, with integrated documentation, graphics, database and symbolic mathematics. The analysis method was based on nondimensional parametric plots of two primary flutter parameters, namely Regier number and Flutter number, with normalization factors based on torsional stiffness, sweep, mass ratio, aspect ratio, center of gravity location and pitch inertia radius of gyration. The plots were compiled in a Vaught Corporation report from a vast database of past experiments and wind tunnel tests. The computer program was utilized for flutter analysis of the outer wing of a Blended Wing Body concept, proposed by McDonnell Douglas Corporation. Using a set of assumed data, preliminary flutter boundary and flutter dynamic pressure variation with altitude, Mach number and torsional stiffness were determined.
NASA Astrophysics Data System (ADS)
Wei, Sha; Han, Qinkai; Peng, Zhike; Chu, Fulei
2016-05-01
Some system parameters in mechanical systems are always uncertain due to uncertainties in geometric and material properties, lubrication condition and wear. For a more reasonable estimation of dynamic analysis of the parametrically excited system, the effect of uncertain parameters should be taken into account. This paper presents a new non-probabilistic analysis method for solving the dynamic responses of parametrically excited systems under uncertainties and multi-frequency excitations. By using the multi-dimensional harmonic balance method (MHBM) and the Chebyshev inclusion function (CIF), an interval multi-dimensional harmonic balance method (IMHBM) is obtained. To illustrate the accuracy of the proposed method, a time-varying geared system of wind turbine with different kinds of uncertainties is demonstrated. By comparing with the results of the scanning method, it is shown that the presented method is valid and effective for the parametrically excited system with uncertainties and multi-frequency excitations. The effects of some uncertain system parameters including uncertain mesh stiffnesses and uncertain bearing stiffnesses on the frequency responses of the system are also discussed in detail. It is shown that the dynamic responses of the system are insensitive to the uncertain mesh stiffness and bearing stiffnesses of the planetary gear stage. The uncertain bearing stiffnesses of the intermediate and high-speed stages will lead to relatively large uncertainties in the dynamic responses around resonant regions. It will provide valuable guidance for the optimal design and condition monitoring of wind turbine gearboxes.
Parametric analysis of orthopedic screws in relation to bone density.
Zanetti, Elisabetta M; Salaorno, Massimiliano; Grasso, Giovanni; Audenino, Alberto L
2009-01-01
A global study of geometry and material properties of orthopedic screws was performed, considering not only the effect of each single factor (screw pitch, number of threads, fillet angle, etc.) but also their interactions with respect to bone density.The stress patterns resulting from different screw geometries and bone densities were analyzed using finite element techniques, taking into account different levels of osseointegration between the screw and the bone. These numerical models where validated through experimental pull-out tests, where a pull out force of 120 N produced localized failure of the last thread (stresses above 0.42 MPa). The results of the numerical simulations were then summarised using a multi-factorial parametric analysis. This demonstrated the great relevance of the interaction between bone density and screw pitch, showing that the optimal screw pitch can vary by more than 25% for different densities (0.35 g/cm(3) and 0.47 g/cm(3), respectively).The parameters calculated by means of the multi-factorial analysis allow the pull out force to be estimated for different osseointegration levels, different screw geometries and material properties, and for different bone densities. The final objective is to determine the best choice of implant for each individual patient. PMID:19587807
NASA Astrophysics Data System (ADS)
Andronov, I. L.; Chinarova, L. L.
Numerical comparison of the methods for periodogram analysis is carried out for the parametric modifications of the Fourier transform by Deeming T.J. (1975, Ap. Space Sci., 36, 137); Lomb N.R. (1976, Ap. Space Sci., 39, 447); Andronov I.L. (1994, Odessa Astron. Publ., 7, 49); parametric modifications based on the spline approximations of different order k and defect k by Jurkevich I. (1971, Ap. Space Sci., 13, 154; n = 0, k = 1); Marraco H.G., Muzzio J.C. (1980, P.A.S.P., 92, 700; n = 1, k = 2); Andronov I.L. (1987, Contrib. Astron. Inst. Czechoslovak. 20, 161; n = 3, k = 1); non-parametric modifications by Lafler J. and Kinman T.D. (1965, Ap.J.Suppl., 11, 216), Burke E.W., Rolland W.W. and Boy W.R. (1970, J.R.A.S.Canada, 64, 353), Deeming T.J. (1970, M.N.R.A.S., 147, 365), Renson P. (1978, As. Ap., 63, 125) and Dworetsky M.M. (1983, M.N.R.A.S., 203, 917). For some numerical models the values of the mean, variance, asymmetry and excess of the test-functions are determined, the correlations between them are discussed. Analytic estimates of the mathematical expectation of the test function for different methods and of the dispersion of the test function by Lafler and Kinman (1965) and of the parametric functions are determined. The statistical distribution of the test functions computed for fixed data and various frequencies is significantly different from that computed for various data realizations. The histogram for the non-parametric test functions is nearly symmetric for normally distributed uncorrelated data and is characterized by a distinctly negative asymmetry for noisy data with periodic components. The non-parametric test-functions may be subdivided into two groups - similar to that by Lafler and Kinman (1965) and to that by Deeming (1970). The correlation coefficients for the test-functions within each group are close to unity for large number of data. Conditions for significant influence of the phase difference between the data onto the test functions are
Parametric analysis of a passive cyclic control device for helicopters
NASA Technical Reports Server (NTRS)
Kumagai, H.
1984-01-01
A parametric study of a passive device which provides a cyclic longitudinal control moment for a helicopter rotor was performed. It utilizes a rotor blade tip which is structurally decoupled from the blade inboard section. This rotor configuration is generally called the Free-Tip Rotor. A two dimensional numerical model was used to review the Constant Lift Tip Rotor, a predecessor of the current configuration, and then the same model was applied to the Passive Cyclic Control Device. The Constant Lift Tip was proven to have the ability to suppress the vibratory lift loading on the tip around the azimuth and to eliminate a significant negative lift peak on the advancing tip. The Passive Cyclic Control Device showed a once-per-revolution lift oscillation with a large amplitude, while minimizing the higher harmonic terms of the lift oscillation. This once-per-revolution oscillation results in the cyclic moment to trim the rotor longitudinally. A rotor performance analysis was performed by a three dimensional numerical model. It indicated that the vortices shed from the junction between the tip and the inboard section has a strong influence on the tip, and it may severely limit the tip performance. It was also shown that the Free-Tip allows the inboard section to have a larger twist, which results in a better performance.
Numerical model of solar dynamic radiator for parametric analysis
NASA Technical Reports Server (NTRS)
Rhatigan, Jennifer L.
1989-01-01
Growth power requirements for Space Station Freedom will be met through addition of 25 kW solar dynamic (SD) power modules. The SD module rejects waste heat from the power conversion cycle to space through a pumped-loop, multi-panel, deployable radiator. The baseline radiator configuration was defined during the Space Station conceptual design phase and is a function of the state point and heat rejection requirements of the power conversion unit. Requirements determined by the overall station design such as mass, system redundancy, micrometeoroid and space debris impact survivability, launch packaging, costs, and thermal and structural interaction with other station components have also been design drivers for the radiator configuration. Extensive thermal and power cycle modeling capabilities have been developed which are powerful tools in Station design and analysis, but which prove cumbersome and costly for simple component preliminary design studies. In order to aid in refining the SD radiator to the mature design stage, a simple and flexible numerical model was developed. The model simulates heat transfer and fluid flow performance of the radiator and calculates area mass and impact survivability for many combinations of flow tube and panel configurations, fluid and material properties, and environmental and cycle variations. A brief description and discussion of the numerical model, it's capabilities and limitations, and results of the parametric studies performed is presented.
Parametric sensitivity analysis of an agro-economic model of management of irrigation water
NASA Astrophysics Data System (ADS)
El Ouadi, Ihssan; Ouazar, Driss; El Menyari, Younesse
2015-04-01
The current work aims to build an analysis and decision support tool for policy options concerning the optimal allocation of water resources, while allowing a better reflection on the issue of valuation of water by the agricultural sector in particular. Thus, a model disaggregated by farm type was developed for the rural town of Ait Ben Yacoub located in the east Morocco. This model integrates economic, agronomic and hydraulic data and simulates agricultural gross margin across in this area taking into consideration changes in public policy and climatic conditions, taking into account the competition for collective resources. To identify the model input parameters that influence over the results of the model, a parametric sensitivity analysis is performed by the "One-Factor-At-A-Time" approach within the "Screening Designs" method. Preliminary results of this analysis show that among the 10 parameters analyzed, 6 parameters affect significantly the objective function of the model, it is in order of influence: i) Coefficient of crop yield response to water, ii) Average daily gain in weight of livestock, iii) Exchange of livestock reproduction, iv) maximum yield of crops, v) Supply of irrigation water and vi) precipitation. These 6 parameters register sensitivity indexes ranging between 0.22 and 1.28. Those results show high uncertainties on these parameters that can dramatically skew the results of the model or the need to pay particular attention to their estimates. Keywords: water, agriculture, modeling, optimal allocation, parametric sensitivity analysis, Screening Designs, One-Factor-At-A-Time, agricultural policy, climate change.
Second-order contributions to relativistic time delay in the parametrized post-Newtonian formalism
Richter, G.W.; Matzner, R.A.
1983-12-15
Using a parametrized expansion of the solar metric to second order in the Newtonian potential, we calculate the relativistic delay in the round-trip travel time of a radar signal reflected from a nearby planet. We find that one second-order contribution to the delay is on the order of ten nanoseconds, which is comparable to the uncertainties in present-day experiments involving the Viking spacecraft.
NASA Astrophysics Data System (ADS)
Kraft, Manuel; Hein, Sven M.; Lehnert, Judith; Schöll, Eckehard; Hughes, Stephen; Knorr, Andreas
2016-08-01
Quantum coherent feedback control is a measurement-free control method fully preserving quantum coherence. In this paper we show how time-delayed quantum coherent feedback can be used to control the degree of squeezing in the output field of a cavity containing a degenerate parametric oscillator. We focus on the specific situation of Pyragas-type feedback control where time-delayed signals are fed back directly into the quantum system. Our results show how time-delayed feedback can enhance or decrease the degree of squeezing as a function of time delay and feedback strength.
SAT-Based (Parametric) Reachability for a Class of Distributed Time Petri Nets
NASA Astrophysics Data System (ADS)
Penczek, Wojciech; Pòłrola, Agata; Zbrzezny, Andrzej
Formal methods - among them the model checking techniques - play an important role in the design and production of both systems and software. In this paper we deal with an adaptation of the bounded model checking methods for timed systems, developed for timed automata, to the case of time Petri nets. We consider distributed time Petri nets and parametric reachability checking, but the approach can be easily adapted to verification of other kinds of properties for which the bounded model checking methods exist. A theoretical description is supported by some experimental results, generated using an extension of the model checker verICS.
ERIC Educational Resources Information Center
Osler, James Edward
2014-01-01
This monograph provides an epistemological rational for the design of a novel post hoc statistical measure called "Tri-Center Analysis". This new statistic is designed to analyze the post hoc outcomes of the Tri-Squared Test. In Tri-Center Analysis trichotomous parametric inferential parametric statistical measures are calculated from…
Fuel cell on-site integrated energy system parametric analysis of a residential complex
NASA Technical Reports Server (NTRS)
Simons, S. N.
1977-01-01
A parametric energy-use analysis was performed for a large apartment complex served by a fuel cell on-site integrated energy system (OS/IES). The variables parameterized include operating characteristics for four phosphoric acid fuel cells, eight OS/IES energy recovery systems, and four climatic locations. The annual fuel consumption for selected parametric combinations are presented and a breakeven economic analysis is presented for one parametric combination. The results show fuel cell electrical efficiency and system component choice have the greatest effect on annual fuel consumption; fuel cell thermal efficiency and geographic location have less of an effect.
Rosenberg, D; Marino, R; Herbert, C; Pouquet, A
2016-01-01
We study rotating stratified turbulence (RST) making use of numerical data stemming from a large parametric study varying the Reynolds, Froude and Rossby numbers, Re, Fr and Ro in a broad range of values. The computations are performed using periodic boundary conditions on grids of 1024(3) points, with no modeling of the small scales, no forcing and with large-scale random initial conditions for the velocity field only, and there are altogether 65 runs analyzed in this paper. The buoyancy Reynolds number defined as R(B) = ReFr2 varies from negligible values to ≈ 10(5), approaching atmospheric or oceanic regimes. This preliminary analysis deals with the variation of characteristic time scales of RST with dimensionless parameters, focusing on the role played by the partition of energy between the kinetic and potential modes, as a key ingredient for modeling the dynamics of such flows. We find that neither rotation nor the ratio of the Brunt-Väisälä frequency to the inertial frequency seem to play a major role in the absence of forcing in the global dynamics of the small-scale kinetic and potential modes. Specifically, in these computations, mostly in regimes of wave turbulence, characteristic times based on the ratio of energy to dissipation of the velocity and temperature fluctuations, T(V) and T(P), vary substantially with parameters. Their ratio γ=T(V)/T(P) follows roughly a bell-shaped curve in terms of Richardson number Ri. It reaches a plateau - on which time scales become comparable, γ≈0.6 - when the turbulence has significantly strengthened, leading to numerous destabilization events together with a tendency towards an isotropization of the flow. PMID:26830757
NASA Astrophysics Data System (ADS)
Wu, Zhishen; Xu, Bin
2003-07-01
A structural parametric identification strategy based on neural networks algorithms using dynamic macro-strain measurements in time domain from a long-gage strain sensor by fiber optic sensing technique such as Fiber Bragg Grating (FBG) sensor is developed. An array of long-gage sensors is bounded on the structure to measure reliably and accurately macro-strains. By the proposed methodology, the structural parameter of stiffness can be identified. A beam model with known mass distribution is considered as an object structure. Without any eigenvalue analysis or optimization computation, the structural parameter of stiffness can be identified. First an emulator neural network is presented to identify the beam structure in current state. Free vibration macro-strain responses of the beam structure are used to train the emulator neural network. The trained emulator neural network can be used to forecast the free vibration macro-strain response of the beam structure with enough precision and decide the difference between the free vibration macro-strain responses of other assumed structure with different structural parameters and those of the original beam structure. The root mean square (RMS) error vector is presented to evaluate the difference. Subsequently, corresponding to each assumed structure with different structural parameters, the RMS error vector can be calculated. By using the training data set composed of the structural parameters and RMS error vector, a parametric evaluation neural network is trained. A beam structure is considered as an existing structure, based on the trained parametric evaluation neural network, the stiffness of the beam structure can be forecast. It is shown that the parametric identification strategy using macro-strain measurement from long-gage sensors has the potential of being a practical tool for a health monitoring methodology applied to civil engineering structures.
Ressler, Johann; Dirscherl, Andreas; Grothe, Helmut; Wolf, Bernhard
2007-02-01
In many cases of bioanalytical measurement, calculation of large amounts of data, analysis of complex signal waveforms or signal speed can overwhelm the performance of microcontrollers, analog electronic circuits or even PCs. One method to obtain results in real time is to apply a digital signal processor (DSP) for the analysis or processing of measurement data. In this paper we show how DSP-supported multiplying and accumulating (MAC) operations, such as time/frequency transformation, pattern recognition by correlation, convolution or filter algorithms, can optimize the processing of bioanalytical data. Discrete integral calculations are applied to the acquisition of impedance values as part of multi-parametric sensor chips, to pH monitoring using light-addressable potentiometric sensors (LAPS) and to the analysis of rapidly changing signal shapes, such as action potentials of cultured neuronal networks, as examples of DSP capability. PMID:17313351
Theoretical analysis of terahertz parametric oscillator using KTiOPO4 crystal
NASA Astrophysics Data System (ADS)
Li, Zhongyang; Bing, Pibin; Yuan, Sheng
2016-08-01
Terahertz parametric oscillator (TPO) using KTiOPO4 (KTP) crystal with a noncollinear phase-matching scheme is investigated. Frequency tuning characteristics of terahertz wave (THz-wave) by varying the phase-matching angle and pump wavelength are analyzed. The expression of the effective parametric gain length under the noncollinear phase matching condition is deduced. Parametric gain and absorption characteristics of THz-wave in KTP are theoretically simulated for the first time. The characteristics of KTP for TPO are compared with MgO:LiNbO3. The analyses indicate that KTP is more suitable than MgO:LiNbO3 for TPO.
NASA Technical Reports Server (NTRS)
Pandya, Shishir; Chaderjian, Neal; Ahmad, Jasim; Kwak, Dochan (Technical Monitor)
2002-01-01
A process is described which enables the generation of 35 time-dependent viscous solutions for a YAV-8B Harrier in ground effect in one week. Overset grids are used to model the complex geometry of the Harrier aircraft and the interaction of its jets with the ground plane and low-speed ambient flow. The time required to complete this parametric study is drastically reduced through the use of process automation, modern computational platforms, and parallel computing. Moreover, a dual-time-stepping algorithm is described which improves solution robustness. Unsteady flow visualization and a frequency domain analysis are also used to identify and correlated key flow structures with the time variation of lift.
a Model for the Parametric Analysis and Optimization of Inertance Tube Pulse Tube Refrigerators
NASA Astrophysics Data System (ADS)
Dodson, C.; Lopez, A.; Roberts, T.; Razani, A.
2008-03-01
A first order model developed for the design analysis and optimization of Inertance Tube Pulse Tube Refrigerators (ITPTRs) is integrated with the code NIST REGEN 3.2 capable of modeling the regenerative heat exchangers used in ITPTRs. The model is based on the solution of simultaneous non-linear differential equations representing the inertance tube, an irreversibility parameter model for the pulse tube, and REGEN 3.2 to simulate the regenerator. The integration of REGEN 3.2 is accomplished by assuming a sinusoidal pressure wave at the cold side of the regenerator. In this manner, the computational power of REGEN 3.2 is conveniently used to reduce computational time required for parametric analysis and optimization of ITPTRs. The exergy flow and exergy destruction (irreversibility) of each component of ITPTRs is calculated and the effect of important system parameters on the second law efficiency of the refrigerators is presented.
Cole, B F; Gelber, R D; Anderson, K M
1994-09-01
We present a parametric methodology for performing quality-of-life-adjusted survival analysis using multivariate censored survival data. It represents a generalization of the nonparametric Q-TWiST method (Quality-adjusted Time without Symptoms and Toxicity). The event times correspond to transitions between states of health that differ in terms of quality of life. Each transition is governed by a competing risks model where the health states are the competing risks. Overall survival is the sum of the amount of time spent in each health state. The first step of the proposed methodology consists of defining a quality function that assigns a "score" to a life having given health state transitions. It is a composite measure of both quantity and quality of life. In general, the quality function assigns a small value to a short life with poor quality and a high value to a long life with good quality. In the second step, parametric survival models are fit to the data. This is done by repeatedly modeling the conditional cause-specific hazard functions given the previous transitions. Covariates are incorporated by accelerated failure time regression, and the model parameters are estimated by maximum likelihood. Lastly, the modeling results are used to estimate the expectation of quality functions. Standard errors and confidence intervals are computed using the bootstrap and delta methods. The results are useful for simultaneously evaluating treatments in terms of quantity and quality of life. To demonstrate the proposed methods, we perform an analysis of data from the International Breast Cancer Study Group Trial V, which compared short-duration chemotherapy versus long-duration chemotherapy in the treatment of node-positive breast cancer. The events studied are: (1) the end of treatment toxicity, (2) disease recurrence, and (3) overall survival. PMID:7981389
Parametric analysis of a thermionic space nuclear power system
NASA Technical Reports Server (NTRS)
Strohmayer, W. H.; Van Hagan, T. H.
1987-01-01
Key parameters in the design of a thermionic space nuclear power system are identified and analysed in various system tradeoffs. The results are referenced to the thermionic system currently being studied for the SP-100 program. The SP-100 requirements provide definitive guidelines with respect to system optimization, the primary ones being the system mass limit of 3000 kg, the system volume constrraint of one-third of the Space Shuttle cargo bay, and the system lifetime of seven years. Many parametric influences are described and the methods used to optimize system design, in the context of the requirements, are indicated. Considerable design flexiblity is demonstrated.
Pataky, Todd C; Vanrenterghem, Jos; Robinson, Mark A
2015-05-01
Biomechanical processes are often manifested as one-dimensional (1D) trajectories. It has been shown that 1D confidence intervals (CIs) are biased when based on 0D statistical procedures, and the non-parametric 1D bootstrap CI has emerged in the Biomechanics literature as a viable solution. The primary purpose of this paper was to clarify that, for 1D biomechanics datasets, the distinction between 0D and 1D methods is much more important than the distinction between parametric and non-parametric procedures. A secondary purpose was to demonstrate that a parametric equivalent to the 1D bootstrap exists in the form of a random field theory (RFT) correction for multiple comparisons. To emphasize these points we analyzed six datasets consisting of force and kinematic trajectories in one-sample, paired, two-sample and regression designs. Results showed, first, that the 1D bootstrap and other 1D non-parametric CIs were qualitatively identical to RFT CIs, and all were very different from 0D CIs. Second, 1D parametric and 1D non-parametric hypothesis testing results were qualitatively identical for all six datasets. Last, we highlight the limitations of 1D CIs by demonstrating that they are complex, design-dependent, and thus non-generalizable. These results suggest that (i) analyses of 1D data based on 0D models of randomness are generally biased unless one explicitly identifies 0D variables before the experiment, and (ii) parametric and non-parametric 1D hypothesis testing provide an unambiguous framework for analysis when one׳s hypothesis explicitly or implicitly pertains to whole 1D trajectories. PMID:25817475
NASA Astrophysics Data System (ADS)
Cunningham, Robert K.; Waxman, Allen M.
1991-06-01
This is the first Annual Technical Summary of the MIT Lincoln Laboratory effort into the parametric study of diffusion-enhancement networks for spatiotemporal grouping in real-time artificial vision. Spatiotemporal grouping phenomena are examined in the context of static and time-varying imagery. Dynamics that exhibit static feature grouping on multiple scales as a function of time and long-range apparent motion between time-varying inputs are developed for a biologically plausible diffusion-enhancement bilayer. The architecture consists of a diffusion and a contrast-enhancement layer coupled by feedforward and feedback connections: input is provided by a separate feature extracting layer. The model is cast as an analog circuit that is realizable in VLSI, the parameters of which are selected to satisfy a psychophysical database on apparent motion. Specific topics include: neural networks, astrocyte glial networks, diffusion enhancement, long-range apparent motion, spatiotemporal grouping dynamics, and interference suppression.
Parametric Studies of Square Solar Sails Using Finite Element Analysis
NASA Technical Reports Server (NTRS)
Sleight, David W.; Muheim, Danniella M.
2004-01-01
Parametric studies are performed on two generic square solar sail designs to identify parameters of interest. The studies are performed on systems-level models of full-scale solar sails, and include geometric nonlinearity and inertia relief, and use a Newton-Raphson scheme to apply sail pre-tensioning and solar pressure. Computational strategies and difficulties encountered during the analyses are also addressed. The purpose of this paper is not to compare the benefits of one sail design over the other. Instead, the results of the parametric studies may be used to identify general response trends, and areas of potential nonlinear structural interactions for future studies. The effects of sail size, sail membrane pre-stress, sail membrane thickness, and boom stiffness on the sail membrane and boom deformations, boom loads, and vibration frequencies are studied. Over the range of parameters studied, the maximum sail deflection and boom deformations are a nonlinear function of the sail properties. In general, the vibration frequencies and modes are closely spaced. For some vibration mode shapes, local deformation patterns that dominate the response are identified. These localized patterns are attributed to the presence of negative stresses in the sail membrane that are artifacts of the assumption of ignoring the effects of wrinkling in the modeling process, and are not believed to be physically meaningful. Over the range of parameters studied, several regions of potential nonlinear modal interaction are identified.
Inverse synthetic aperture radar processing using parametric time-frequency estimators Phase I
Candy, J.V., LLNL
1997-12-31
This report summarizes the work performed for the Office of the Chief of Naval Research (ONR) during the period of 1 September 1997 through 31 December 1997. The primary objective of this research was aimed at developing an alternative time-frequency approach which is recursive-in-time to be applied to the Inverse Synthethic Aperture Radar (ISAR) imaging problem discussed subsequently. Our short term (Phase I) goals were to: 1. Develop an ISAR stepped-frequency waveform (SFWF) radar simulator based on a point scatterer vehicular target model incorporating both translational and rotational motion; 2. Develop a parametric, recursive-in-time approach to the ISAR target imaging problem; 3. Apply the standard time-frequency short-term Fourier transform (STFT) estimator, initially to a synthesized data set; and 4. Initiate the development of the recursive algorithm. We have achieved all of these goals during the Phase I of the project and plan to complete the overall development, application and comparison of the parametric approach to other time-frequency estimators (STFT, etc.) on our synthesized vehicular data sets during the next phase of funding. It should also be noted that we developed a batch minimum variance translational motion compensation (TMC) algorithm to estimate the radial components of target motion (see Section IV). This algorithm is easily extended to recursive solution and will probably become part of the overall recursive processing approach to solve the ISAR imaging problem. Our goals for the continued effort are to: 1. Develop and extend a complex, recursive-in-time, time- frequency parameter estimator based on the recursive prediction error method (RPEM) using the underlying Gauss- Newton algorithms. 2. Apply the complex RPEM algorithm to synthesized ISAR data using the above simulator. 3. Compare the performance of the proposed algorithm to standard time-frequency estimators applied to the same data sets.
Time resolved imaging using non-collinear parametric down-conversion
NASA Astrophysics Data System (ADS)
Park, Jung-Rae
In this thesis I present a method for measuring the time resolved spatial profile of a single laser pulse and its application to the semiconductor devices. In OMEGA laser system, spatial profile of a laser beam can change as a function of time due to spontaneous effects such as the B-integral or imposed effects such as smoothing by spectral dispersion. The method presented here uses a non-collinear parametric down-conversion process to multiply sample a single laser pulse. In the non-collinear parametric down-conversion process, an infrared laser beam at 1064 nm is mixed with an intense ultraviolet beam at 351 nm to generate the green signal beam at 524 nm. Calculations have been carried out to determine the threshold power of the infrared probe beam for generating a detectable signal beam. The generated green beam is captured by a cooled optical multichannel analyzer camera and the image of signal beam is analyzed. This temporal spatial measurement can also be applied to the dynamic image detection schemes of semiconductor devices.
NASA Technical Reports Server (NTRS)
Shishir, Pandya; Chaderjian, Neal; Ahmad, Jsaim; Kwak, Dochan (Technical Monitor)
2001-01-01
Flow simulations using the time-dependent Navier-Stokes equations remain a challenge for several reasons. Principal among them are the difficulty to accurately model complex flows, and the time needed to perform the computations. A parametric study of such complex problems is not considered practical due to the large cost associated with computing many time-dependent solutions. The computation time for each solution must be reduced in order to make a parametric study possible. With successful reduction of computation time, the issue of accuracy, and appropriateness of turbulence models will become more tractable.
Non-parametric estimation of seasonal variations in GNSS-derived time series
NASA Astrophysics Data System (ADS)
Gruszczynska, Marta; Bogusz, Janusz; Klos, Anna
2015-04-01
The seasonal variations in GNSS station's position may arise from geophysical excitations, thermal changes combined together with hydrodynamics or various errors which, when superimposed, cause the seasonal oscillations not exactly of real geodynamical origin, but still have to be included in time series modelling. These variations with different periods included in frequency band from Chandler up to quarter-annual ones will all affect the reliability of permanent station's velocity, which in turn, strictly influences the quality of kinematic reference frames. As shown before by a number of authors, the annual (dominant) sine curve, has the amplitude and phase that both change in time due to the different reasons. In this research we focused on the determination of annual changes in GNSS-derived time series of North, East and Up components. We used here the daily position changes from PPP (Precise Point Positioning) solution obtained by JPL (Jet Propulsion Laboratory) processed in the GIPSY-OASIS software. We analyzed here more than 140 globally distributed IGS stations with the minimum data length of 3 years. The longest time series were even 17 years long (1996-2014). Each of the topocentric time series (North, East and Up) was divided into years (from January to December), then the observations gathered in the same days of year were stacked and the weighted medians obtained for all of them such that each of time series was represented by matrix of size 365xn where n is the data length. In this way we obtained the median annual signal for each of analyzed stations that was then decomposed into different frequency bands using wavelet decomposition with Meyer wavelet. We assumed here 7 levels of decomposition, with annual curve as the last approximation of it. The signal approximations made us to obtain the seasonal peaks that prevail in North, East and Up data for globally distributed stations. The analysis of annual curves, by means of non-parametric estimation
Real-time tuning of a double quantum dot using a Josephson parametric amplifier
NASA Astrophysics Data System (ADS)
Stehlik, J.; Liu, Y.-Y.; Quintana, C. M.; Eichler, C.; Hartke, T. R.; Petta, J. R.
Josephson parametric amplifiers (JPAs) have enabled advances in readout of quantum systems. Here we demonstrate JPA-assisted readout of a cavity-coupled double quantum dot (DQD). Utilizing a JPA we improve the signal-to-noise ratio (SNR) by a factor of 2000 compared to the situation with the parametric amplifier turned off. At an interdot charge transition we achieve a SNR of 76 (19 dB) with an integration time τ = 400 ns, which is limited by the linewidth of our cavity. By measuring the SNR as a function of τ we extract an equivalent charge sensitivity of 8 ×10-5 e /√{ Hz} . We develop a dual-gate-voltage rastering scheme that allows us to acquire a DQD charge stability diagram in just 20 ms. Such rapid data acquisition rates enable device tuning in live ``video-mode,'' where the results of parameter changes are immediately displayed. Live tuning allows the DQD confinement potential to be rapidly tuned, a capability that will become increasingly important as semiconductor spin qubits are scaled to a larger number of dots. Research is supported by the Packard Foundation, ARO Grant No. W911NF-15-1-0149, DARPA QuEST Grant No. HR0011-09-1-0007, and the NSF (Grants No. DMR-1409556 and DMR-1420541).
Real-time gas density measurement using a ring cavity terahertz parametric oscillator
NASA Astrophysics Data System (ADS)
Ohno, S.; Guo, R.; Minamide, H.; Ito, H.
2007-05-01
We carried out real-time measurement of gas density using monochromatic terahertz waves. The THz-wave absorbance is useful to measure the density of a gas having a characteristic spectrum in the THz region. We used the ring cavity THz-wave parametric oscillator (ring-TPO) as a monochromatic tunable THz-wave source. One can change the oscillation frequency of ring-TPO with a rotating galvano mirror forming the ring cavity. The frequency can be changed by synchronization with a repeating pump-pulse of 500 Hz. We demonstrated real-time measurement of the gas density in R-22, which had some spectral structure in THz frequency region. The gas density in the sample cell was changed by controlling the pressure to lower than 1 atm. When the gas density in the cell was the most tenuous, the maximum sensitivity was about 5%, which was limited by the fluctuation of THz-wave intensity.
Tool Support for Parametric Analysis of Large Software Simulation Systems
NASA Technical Reports Server (NTRS)
Schumann, Johann; Gundy-Burlet, Karen; Pasareanu, Corina; Menzies, Tim; Barrett, Tony
2008-01-01
The analysis of large and complex parameterized software systems, e.g., systems simulation in aerospace, is very complicated and time-consuming due to the large parameter space, and the complex, highly coupled nonlinear nature of the different system components. Thus, such systems are generally validated only in regions local to anticipated operating points rather than through characterization of the entire feasible operational envelope of the system. We have addressed the factors deterring such an analysis with a tool to support envelope assessment: we utilize a combination of advanced Monte Carlo generation with n-factor combinatorial parameter variations to limit the number of cases, but still explore important interactions in the parameter space in a systematic fashion. Additional test-cases, automatically generated from models (e.g., UML, Simulink, Stateflow) improve the coverage. The distributed test runs of the software system produce vast amounts of data, making manual analysis impossible. Our tool automatically analyzes the generated data through a combination of unsupervised Bayesian clustering techniques (AutoBayes) and supervised learning of critical parameter ranges using the treatment learner TAR3. The tool has been developed around the Trick simulation environment, which is widely used within NASA. We will present this tool with a GN&C (Guidance, Navigation and Control) simulation of a small satellite system.
Parametric Rietveld refinement
Stinton, Graham W.; Evans, John S. O.
2007-01-01
In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model. Parametric refinement offers a number of potential benefits over independent or sequential analysis. It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of ‘non-crystallographic’ quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima. PMID:19461841
NASA Astrophysics Data System (ADS)
Ruiz Dominguez, C.; Kachenoura, N.; DeCesare, A.; Delouche, A.; Lim, P.; Gérard, O.; Herment, A.; Diebold, B.; Frouin, F.
2005-07-01
The computerized study of the regional contraction of the left ventricle has undergone numerous developments, particularly in relation to echocardiography. A new method, parametric analysis of main motion (PAMM), is proposed in order to synthesize the information contained in a cine loop of images in parametric images. PAMM determines, for the intensity variation time curves (IVTC) observed in each pixel, two amplitude coefficients characterizing the continuous component and the alternating component; the variable component is generated from a mother curve by introducing a time shift coefficient and a scale coefficient. Two approaches, a PAMM data driven and a PAMM model driven (simpler and faster), are proposed. On the basis of the four coefficients, an amplitude image and an image of mean contraction time are synthesized and interpreted by a cardiologist. In all cases, both PAMM methods allow better IVTC adjustment than the other methods of parametric imaging used in echocardiography. A preliminary database comprising 70 segments is scored and compared with the visual analysis, taken from a consensus of two expert interpreters. The levels of absolute and relative concordance are 79% and 97%. PAMM model driven is a promising method for the rapid detection of abnormalities in left ventricle contraction.
Parametric systems analysis of the Modular Stellarator Reactor (MSR)
NASA Astrophysics Data System (ADS)
Miller, R. L.; Krakowski, R. A.; Bathke, C. G.
1982-05-01
The close coupling in the stellarator/torsatron/heliotron (S/T/H) between coil design, magnetics topology, and plasma performance complicates the reactor assessment more so than for most magnetic confinement systems. To provide an additional degree of resolution of this problem for the Modular Stellarator Reactor (MSR), a parametric systems model was applied. This model reduces key issues associated with plasma performance, first wall/blanket/shield (FW/B/S), and coil design to a simple relationship between beta, system geometry, and a number of indicators of overall plant performance. The results are used to guide more detailed, multidimensional plasma, magnetics, and coil design efforts towards technically and economically viable operating regimes. It is shown that beta values 0.08 may be needed if the MSR approach is to be substantially competitive with other approaches to magnetic fusion in terms of system power density, mass utilization, and cost for total power output around 4.0 GWt; lower powers will require even higher betas.
Lunar lander configuration study and parametric performance analysis
NASA Astrophysics Data System (ADS)
Donahue, Benjamin B.; Fowler, C. R.
1993-06-01
Future Lunar exploration plans will call for delivery of significant mounts or cargo to provide for crew habitation, surface tansportation, and scientific exploration activities. Minimization of costly surface based infrastructure is in large part directly related to the design of the cargo delivery/landing craft. This study focused on evaluating Lunar lander concepts from a logistics oriented perspective, and outlines the approach used in the development of a preferred configuration, sets forth the benefits derived from its utilization and describes the missions and system considered. Results indicate that only direct-to-surface downloading of payloads provides for unassisted cargo removal operations imperative to efficient and low risk site buildup, including the emplacement of Space Station derivative surface habitat modules, immediate cargo jettison for both descent abort and emergency surface ascent essential to piloted missions carrying cargo, and short habitat egress/ingress paths necessary to productive surface work tours for crew members carrying hand held experiments, tools and other bulky articles. Accommodating cargo in a position underneath the vehicles structural frame, landing craft described herein eliminate altogether the necessity for dedicated surface based off-loading vehicles, the operations and maintenance associated with their operation, and the precipitous ladder climbs to and from the surface that are inherent to traditional designs. Parametric evaluations illustrate performance and mass variation with respect to mission requirements.
Lunar lander configuration study and parametric performance analysis
NASA Technical Reports Server (NTRS)
Donahue, Benjamin B.; Fowler, C. R.
1993-01-01
Future Lunar exploration plans will call for delivery of significant mounts or cargo to provide for crew habitation, surface tansportation, and scientific exploration activities. Minimization of costly surface based infrastructure is in large part directly related to the design of the cargo delivery/landing craft. This study focused on evaluating Lunar lander concepts from a logistics oriented perspective, and outlines the approach used in the development of a preferred configuration, sets forth the benefits derived from its utilization and describes the missions and system considered. Results indicate that only direct-to-surface downloading of payloads provides for unassisted cargo removal operations imperative to efficient and low risk site buildup, including the emplacement of Space Station derivative surface habitat modules, immediate cargo jettison for both descent abort and emergency surface ascent essential to piloted missions carrying cargo, and short habitat egress/ingress paths necessary to productive surface work tours for crew members carrying hand held experiments, tools and other bulky articles. Accommodating cargo in a position underneath the vehicles structural frame, landing craft described herein eliminate altogether the necessity for dedicated surface based off-loading vehicles, the operations and maintenance associated with their operation, and the precipitous ladder climbs to and from the surface that are inherent to traditional designs. Parametric evaluations illustrate performance and mass variation with respect to mission requirements.
Network of time-multiplexed optical parametric oscillators as a coherent Ising machine
NASA Astrophysics Data System (ADS)
Marandi, Alireza; Wang, Zhe; Takata, Kenta; Byer, Robert L.; Yamamoto, Yoshihisa
2014-12-01
Finding the ground states of the Ising Hamiltonian maps to various combinatorial optimization problems in biology, medicine, wireless communications, artificial intelligence and social network. So far, no efficient classical and quantum algorithm is known for these problems and intensive research is focused on creating physical systems—Ising machines—capable of finding the absolute or approximate ground states of the Ising Hamiltonian. Here, we report an Ising machine using a network of degenerate optical parametric oscillators (OPOs). Spins are represented with above-threshold binary phases of the OPOs and the Ising couplings are realized by mutual injections. The network is implemented in a single OPO ring cavity with multiple trains of femtosecond pulses and configurable mutual couplings, and operates at room temperature. We programmed a small non-deterministic polynomial time-hard problem on a 4-OPO Ising machine and in 1,000 runs no computational error was detected.
NASA Technical Reports Server (NTRS)
Marston, C. H.; Alyea, F. N.; Bender, D. J.; Davis, L. K.; Dellinger, T. C.; Hnat, J. G.; Komito, E. H.; Peterson, C. A.; Rogers, D. A.; Roman, A. J.
1980-01-01
The performance and cost of moderate technology coal-fired open cycle MHD/steam power plant designs which can be expected to require a shorter development time and have a lower development cost than previously considered mature OCMHD/steam plants were determined. Three base cases were considered: an indirectly-fired high temperature air heater (HTAH) subsystem delivering air at 2700 F, fired by a state of the art atmospheric pressure gasifier, and the HTAH subsystem was deleted and oxygen enrichment was used to obtain requisite MHD combustion temperature. Coal pile to bus bar efficiencies in ease case 1 ranged from 41.4% to 42.9%, and cost of electricity (COE) was highest of the three base cases. For base case 2 the efficiency range was 42.0% to 45.6%, and COE was lowest. For base case 3 the efficiency range was 42.9% to 44.4%, and COE was intermediate. The best parametric cases in bases cases 2 and 3 are recommended for conceptual design. Eventual choice between these approaches is dependent on further evaluation of the tradeoffs among HTAH development risk, O2 plant integration, and further refinements of comparative costs.
NASA Technical Reports Server (NTRS)
Dean, Edwin B.
1995-01-01
Parametric cost analysis is a mathematical approach to estimating cost. Parametric cost analysis uses non-cost parameters, such as quality characteristics, to estimate the cost to bring forth, sustain, and retire a product. This paper reviews parametric cost analysis and shows how it can be used within the cost deployment process.
Reluctance network analysis of an orthogonal-core type parametric induction motor
Tajima, Katsubumi; Sato, Kohei; Komukai, Toshihiko; Ichinokura, Osamu
1999-09-01
In this paper, an analytical method of an orthogonal-core type parametric induction motor is proposed, based on a reluctance network model of the stator. The model is derived by a similar technique applied to an orthogonal-core transformer. Using this model the parametric oscillation characteristic of the motor, without a rotor, is computed. The simulation results agree well with the experiments. It is obvious that the analytical model of the stator presented here is proper for analysis of the motor and that, by use of this model and suitable analytical model of the rotor, the motor characteristics can be analyzed.
Analysis of 808nm centered optical parametric chirped pulse amplifier based on DKDP crystals
NASA Astrophysics Data System (ADS)
Sun, Meizhi; Cui, Zijian; Kang, Jun; Zhang, Yanli; Zhang, Junyong; Cui, Ying; Xie, Xinglong; Liu, Cheng; Liu, Dean; Zhu, Jianqiang; Lin, Zunqi
2015-08-01
The non-collinear phase-matching in Potassium Dideuterium Phosphate (DKDP) crystal is analyzed in detail with signal pulse of center wavelength at 808 nm and pump pulse of wavelength at 526.5 nm. By numerical analysis, parametric bandwidths for various DKDP crystals of different deuteration level are presented. In particularly for DKDP crystals of 95% deuteration level, the optimal non-collinear angles, phase-matching angles, parametric bandwidths, walk-off angles, acceptance angles, efficiency coefficients, gain and gain bandwidths are provided based on the parameter concepts. Optical parametric chirped pulse amplifier based on DKDP crystal is designed and the output characteristics are simulated by OPA coupled wave equations for further discuss. It is concluded that DKDP crystals higher than 90% deuteration level can be utilized in ultra-short high power laser systems with compressed pulses broader than 30fs. The disadvantage is that the acceptance angles are small, increasing the difficulty of engineering regulation.
Parametric Mass Modeling for Mars Entry, Descent and Landing System Analysis Study
NASA Technical Reports Server (NTRS)
Samareh, Jamshid A.; Komar, D. R.
2011-01-01
This paper provides an overview of the parametric mass models used for the Entry, Descent, and Landing Systems Analysis study conducted by NASA in FY2009-2010. The study examined eight unique exploration class architectures that included elements such as a rigid mid-L/D aeroshell, a lifting hypersonic inflatable decelerator, a drag supersonic inflatable decelerator, a lifting supersonic inflatable decelerator implemented with a skirt, and subsonic/supersonic retro-propulsion. Parametric models used in this study relate the component mass to vehicle dimensions and mission key environmental parameters such as maximum deceleration and total heat load. The use of a parametric mass model allows the simultaneous optimization of trajectory and mass sizing parameters.
A Conceptual Wing Flutter Analysis Tool for Systems Analysis and Parametric Design Study
NASA Technical Reports Server (NTRS)
Mukhopadhyay, Vivek
2003-01-01
An interactive computer program was developed for wing flutter analysis in the conceptual design stage. The objective was to estimate flutt er instability boundaries of a typical wing, when detailed structural and aerodynamic data are not available. Effects of change in key flu tter parameters can also be estimated in order to guide the conceptual design. This userfriendly software was developed using MathCad and M atlab codes. The analysis method was based on non-dimensional paramet ric plots of two primary flutter parameters, namely Regier number and Flutter number, with normalization factors based on wing torsion stiffness, sweep, mass ratio, taper ratio, aspect ratio, center of gravit y location and pitch-inertia radius of gyration. These parametric plo ts were compiled in a Chance-Vought Corporation report from database of past experiments and wind tunnel test results. An example was prese nted for conceptual flutter analysis of outer-wing of a Blended-Wing- Body aircraft.
Augustine, C.
2013-10-01
Parametric analysis of the factors controlling the costs of sedimentary geothermal systems was carried out using a modified version of the Geothermal Electricity Technology Evaluation Model (GETEM). The sedimentary system modeled assumed production from and injection into a single sedimentary formation.
Bernasconi, Davide Paolo; Rebora, Paola; Iacobelli, Simona; Valsecchi, Maria Grazia; Antolini, Laura
2016-03-30
The 'landmark' and 'Simon and Makuch' non-parametric estimators of the survival function are commonly used to contrast the survival experience of time-dependent treatment groups in applications such as stem cell transplant versus chemotherapy in leukemia. However, the theoretical survival functions corresponding to the second approach were not clearly defined in the literature, and the use of the 'Simon and Makuch' estimator was criticized in the biostatistical community. Here, we review the 'landmark' approach, showing that it focuses on the average survival of patients conditional on being failure free and on the treatment status assessed at the landmark time. We argue that the 'Simon and Makuch' approach represents counterfactual survival probabilities where treatment status is forced to be fixed: the patient is thought as under chemotherapy without possibility to switch treatment or as under transplant since the beginning of the follow-up. We argue that the 'Simon and Makuch' estimator leads to valid estimates only under the Markov assumption, which is however less likely to occur in practical applications. This motivates the development of a novel approach based on time rescaling, which leads to suitable estimates of the counterfactual probabilities in a semi-Markov process. The method is also extended to deal with a fixed landmark time of interest. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26503800
Mounaix, P.; Pesme, D. ); Rozmus, W. ); Casanova, M. )
1993-09-01
The space and time behavior of the decay waves is computed analytically in the regime of standard parametric decay. The plasma is assumed to be homogeneous and bounded. The pump wave has a finite pulse duration. The propagation of the pump wave is taken into account, its depletion is ignored. The parametric growth is solved in terms of fluctuating initial and boundary conditions corresponding to thermal noise at equilibrium. Fluctuating source terms, representing noise emission, are accordingly retained in the coupled mode equations. The initial stage of parametric growth is investigated in detail; the time from which the asymptotic concept of absolute or convective instability applies is computed. The connection between the Manley--Rowe and flux conservation relations is discussed.
AWclust: point-and-click software for non-parametric population structure analysis
Gao, Xiaoyi; Starmer, Joshua D
2008-01-01
Background Population structure analysis is important to genetic association studies and evolutionary investigations. Parametric approaches, e.g. STRUCTURE and L-POP, usually assume Hardy-Weinberg equilibrium (HWE) and linkage equilibrium among loci in sample population individuals. However, the assumptions may not hold and allele frequency estimation may not be accurate in some data sets. The improved version of STRUCTURE (version 2.1) can incorporate linkage information among loci but is still sensitive to high background linkage disequilibrium. Nowadays, large-scale single nucleotide polymorphisms (SNPs) are becoming popular in genetic studies. Therefore, it is imperative to have software that makes full use of these genetic data to generate inference even when model assumptions do not hold or allele frequency estimation suffers from high variation. Results We have developed point-and-click software for non-parametric population structure analysis distributed as an R package. The software takes advantage of the large number of SNPs available to categorize individuals into ethnically similar clusters and it does not require assumptions about population models. Nor does it estimate allele frequencies. Moreover, this software can also infer the optimal number of populations. Conclusion Our software tool employs non-parametric approaches to assign individuals to clusters using SNPs. It provides efficient computation and an intuitive way for researchers to explore ethnic relationships among individuals. It can be complementary to parametric approaches in population structure analysis. PMID:18237431
A Parametric Study of Nonlinear Seismic Response Analysis of Transmission Line Structures
Wang, Yanming; Yi, Zhenhua
2014-01-01
A parametric study of nonlinear seismic response analysis of transmission line structures subjected to earthquake loading is studied in this paper. The transmission lines are modeled by cable element which accounts for the nonlinearity of the cable based on a real project. Nonuniform ground motions are generated using a stochastic approach based on random vibration analysis. The effects of multicomponent ground motions, correlations among multicomponent ground motions, wave travel, coherency loss, and local site on the responses of the cables are investigated using nonlinear time history analysis method, respectively. The results show the multicomponent seismic excitations should be considered, but the correlations among multicomponent ground motions could be neglected. The wave passage effect has a significant influence on the responses of the cables. The change of the degree of coherency loss has little influence on the response of the cables, but the responses of the cables are affected significantly by the effect of coherency loss. The responses of the cables change little with the degree of the difference of site condition changing. The effect of multicomponent ground motions, wave passage, coherency loss, and local site should be considered for the seismic design of the transmission line structures. PMID:25133215
A parametric study of nonlinear seismic response analysis of transmission line structures.
Tian, Li; Wang, Yanming; Yi, Zhenhua; Qian, Hui
2014-01-01
A parametric study of nonlinear seismic response analysis of transmission line structures subjected to earthquake loading is studied in this paper. The transmission lines are modeled by cable element which accounts for the nonlinearity of the cable based on a real project. Nonuniform ground motions are generated using a stochastic approach based on random vibration analysis. The effects of multicomponent ground motions, correlations among multicomponent ground motions, wave travel, coherency loss, and local site on the responses of the cables are investigated using nonlinear time history analysis method, respectively. The results show the multicomponent seismic excitations should be considered, but the correlations among multicomponent ground motions could be neglected. The wave passage effect has a significant influence on the responses of the cables. The change of the degree of coherency loss has little influence on the response of the cables, but the responses of the cables are affected significantly by the effect of coherency loss. The responses of the cables change little with the degree of the difference of site condition changing. The effect of multicomponent ground motions, wave passage, coherency loss, and local site should be considered for the seismic design of the transmission line structures. PMID:25133215
NASA Astrophysics Data System (ADS)
Cicirello, Alice; Langley, Robin S.
2013-04-01
An existing hybrid finite element (FE)/statistical energy analysis (SEA) approach to the analysis of the mid- and high frequency vibrations of a complex built-up system is extended here to a wider class of uncertainty modeling. In the original approach, the constituent parts of the system are considered to be either deterministic, and modeled using FE, or highly random, and modeled using SEA. A non-parametric model of randomness is employed in the SEA components, based on diffuse wave theory and the Gaussian Orthogonal Ensemble (GOE), and this enables the mean and variance of second order quantities such as vibrational energy and response cross-spectra to be predicted. In the present work the assumption that the FE components are deterministic is relaxed by the introduction of a parametric model of uncertainty in these components. The parametric uncertainty may be modeled either probabilistically, or by using a non-probabilistic approach such as interval analysis, and it is shown how these descriptions can be combined with the non-parametric uncertainty in the SEA subsystems to yield an overall assessment of the performance of the system. The method is illustrated by application to an example built-up plate system which has random properties, and benchmark comparisons are made with full Monte Carlo simulations.
Haque, Md Mazharul; Washington, Simon
2014-01-01
The use of mobile phones while driving is more prevalent among young drivers-a less experienced cohort with elevated crash risk. The objective of this study was to examine and better understand the reaction times of young drivers to a traffic event originating in their peripheral vision whilst engaged in a mobile phone conversation. The CARRS-Q advanced driving simulator was used to test a sample of young drivers on various simulated driving tasks, including an event that originated within the driver's peripheral vision, whereby a pedestrian enters a zebra crossing from a sidewalk. Thirty-two licensed drivers drove the simulator in three phone conditions: baseline (no phone conversation), hands-free and handheld. In addition to driving the simulator each participant completed questionnaires related to driver demographics, driving history, usage of mobile phones while driving, and general mobile phone usage history. The participants were 21-26 years old and split evenly by gender. Drivers' reaction times to a pedestrian in the zebra crossing were modelled using a parametric accelerated failure time (AFT) duration model with a Weibull distribution. Also tested where two different model specifications to account for the structured heterogeneity arising from the repeated measures experimental design. The Weibull AFT model with gamma heterogeneity was found to be the best fitting model and identified four significant variables influencing the reaction times, including phone condition, driver's age, license type (provisional license holder or not), and self-reported frequency of usage of handheld phones while driving. The reaction times of drivers were more than 40% longer in the distracted condition compared to baseline (not distracted). Moreover, the impairment of reaction times due to mobile phone conversations was almost double for provisional compared to open license holders. A reduction in the ability to detect traffic events in the periphery whilst distracted
Crash risk analysis for Shanghai urban expressways: A Bayesian semi-parametric modeling approach.
Yu, Rongjie; Wang, Xuesong; Yang, Kui; Abdel-Aty, Mohamed
2016-10-01
Urban expressway systems have been developed rapidly in recent years in China; it has become one key part of the city roadway networks as carrying large traffic volume and providing high traveling speed. Along with the increase of traffic volume, traffic safety has become a major issue for Chinese urban expressways due to the frequent crash occurrence and the non-recurrent congestions caused by them. For the purpose of unveiling crash occurrence mechanisms and further developing Active Traffic Management (ATM) control strategies to improve traffic safety, this study developed disaggregate crash risk analysis models with loop detector traffic data and historical crash data. Bayesian random effects logistic regression models were utilized as it can account for the unobserved heterogeneity among crashes. However, previous crash risk analysis studies formulated random effects distributions in a parametric approach, which assigned them to follow normal distributions. Due to the limited information known about random effects distributions, subjective parametric setting may be incorrect. In order to construct more flexible and robust random effects to capture the unobserved heterogeneity, Bayesian semi-parametric inference technique was introduced to crash risk analysis in this study. Models with both inference techniques were developed for total crashes; semi-parametric models were proved to provide substantial better model goodness-of-fit, while the two models shared consistent coefficient estimations. Later on, Bayesian semi-parametric random effects logistic regression models were developed for weekday peak hour crashes, weekday non-peak hour crashes, and weekend non-peak hour crashes to investigate different crash occurrence scenarios. Significant factors that affect crash risk have been revealed and crash mechanisms have been concluded. PMID:26847949
Parametric analysis of synthetic aperture radar data for the study of forest stand characteristics
NASA Technical Reports Server (NTRS)
Wu, Shih-Tseng
1988-01-01
A parametric analysis of a Gulf Coast forest stand was performed using multipolarization, multipath airborne SAR data, and forest plot properties. Allometric equations were used to compute the biomass and basal area for the test plots. A multiple regression analysis with stepwise selection of independent variables was performed. It is found that forest stand characteristics such as biomass, basal area, and average tree height are correlated with SAR data.
Recent results on parametric analysis of differential Omega error
NASA Technical Reports Server (NTRS)
Baxa, E. G., Jr.; Piserchia, P. V.
1974-01-01
Previous tests of the differential Omega concept and an analysis of the characteristics of VLF propagation make it possible to delineate various factors which might contribute to the variation of errors in phase measurements at an Omega receiver site. An experimental investigation is conducted to determine the effect of each of a number of parameters on differential Omega accuracy and to develop prediction equations. The differential Omega error form is considered and preliminary results are presented of the regression analysis used to study differential error.
Multilevel Latent Class Analysis: Parametric and Nonparametric Models
ERIC Educational Resources Information Center
Finch, W. Holmes; French, Brian F.
2014-01-01
Latent class analysis is an analytic technique often used in educational and psychological research to identify meaningful groups of individuals within a larger heterogeneous population based on a set of variables. This technique is flexible, encompassing not only a static set of variables but also longitudinal data in the form of growth mixture…
Parametric analysis of lunar resources for space energy systems
NASA Astrophysics Data System (ADS)
Woodcock, Gordon R.
The possible use of lunar resource in the construction of solar power satellites (SPS) to provide energy for use on earth is discussed. The space transportation and operational aspects of the SPS program are compared to other energy concepts. Cost/benefit analysis are used to study the advantages of using lunar oxygen for the SPS program and producing helium-3 on the moon. Options for lunar surface power are considered and the economic benefits of using lunar resources are examined.
Bifurcation analysis of parametrically excited bipolar disorder model
NASA Astrophysics Data System (ADS)
Nana, Laurent
2009-02-01
Bipolar II disorder is characterized by alternating hypomanic and major depressive episode. We model the periodic mood variations of a bipolar II patient with a negatively damped harmonic oscillator. The medications administrated to the patient are modeled via a forcing function that is capable of stabilizing the mood variations and of varying their amplitude. We analyze analytically, using perturbation method, the amplitude and stability of limit cycles and check this analysis with numerical simulations.
Pouthier, Vincent
2010-09-29
A detailed analysis is performed to show that the second order time-convolutionless master equation fails to describe the exciton-phonon dynamics in a finite size lattice. To proceed, special attention is paid to characterizing the coherences of the exciton reduced density matrix. These specific elements measure the ability of the exciton to develop superimpositions involving the vacuum and the one-exciton states. It is shown that the coherences behave as wavefunctions whose dynamics is governed by a time-dependent effective Hamiltonian defined in terms of the so-called time-dependent relaxation operator. Due to the confinement, quantum recurrences provide to the relaxation operator an almost periodic nature, so the master equation reduces to a linear system of differential equations with almost periodic coefficients. We show that, in accordance with the Floquet theory, unstable solutions emerge due to parametric resonances involving specific frequencies of the relaxation operator and specific excitonic eigenfrequencies. These resonances give rise to an unphysical exponential growth of the coherences, indicating the breakdown of the second order master equation. PMID:21386551
A parametric analysis of the growing CFHB (Wistar) rat.
Pullen, A H
1976-01-01
Measurements of body weight and body, tail and hindlimb lengths were made at various times during the postnatal development of the CFHB-Wistar rat using simple techniques which avoided unnecessary stress being applied to the animal. All the graphical relationships studied using these measurements indicated that growth was divided into two phases which meet at 16 days. This was particularly noticeable when either body length or hindlimb length was plotted against either age or body weight. Body weight appeared to be a better indication of maturity than time; and linear relationships were found when measurements of body lengths were plotted against the square root of body weight. Curvilinear graphs were obtained when body weight was plotted on alternative scales. Results suggest that prior to 16 days metabolism is probably directed more towards attaining sufficient maturity to enable the animal to survive independently, than to increasing its stature; but after 16 days this situation is reversed. PMID:931783
NASA Astrophysics Data System (ADS)
Wei, Dang; Qing, Liao; Peng-Cheng, Mao; Hong-Bing, Fu; Yu-Xiang, Weng
2016-05-01
Femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) is a versatile technique with advantages of high sensitivity, broad detection bandwidth, and intrinsic spectrum correction function. These advantages should benefit the study of coherent emission, such as measurement of lasing dynamics. In this letter, the FNOPAS was used to trace the lasing process in Rhodamine 6G (R6G) solution and organic semiconductor nano-wires. High-quality transient emission spectra and lasing dynamic traces were acquired, which demonstrates the applicability of FNOPAS in the study of lasing dynamics. Our work extends the application scope of the FNOPAS technique. Project supported by the National Natural Science Foundation of China (Grant Nos. 20925313 and 21503066), the Innovation Program of Chinese Academy of Sciences (Grant No. KJCX2-YW-W25), the Postdoctoral Project of Hebei University, China, and the Project of Science and Technology Bureau of Baoding City, China (Grant No. 15ZG029).
Parametric analysis and testing of an electrorheological fluid damper
NASA Astrophysics Data System (ADS)
Lindler, Jason E.; Wereley, Norman M.
1999-06-01
This study seeks to validate a predictive damper analysis, based on an idealized Bingham plastic shear flow mechanism, which incorporates leakage effects in an electrorheological (ER) damper. The ER bypass damper operates by a piston head pushing ER fluid out of a hydraulic cylinder and through an ER fluid bypass. The pressure to force ER fluid through the bypass produces the majority of the device's damping. The ER bypass is composed of an annulus formed from two concentric aluminum tubes. The application of a voltage potential between the aluminum tubes creates an electric field in the annulus that increases the yield stress of the ER fluid. The yield stress modifies the velocity profile of the fluid in the annulus and augments the damping coefficient of the device. The ER fluid damper contains a controlled amount of leakage around the piston head. The leakage allows ER fluid to flow from one side of the piston head to the opposite side without passing through the ER bypass. In this analysis, the leakage damping coefficient with incorporated leakage effects, predict the amount of energy dissipated for a complete cycle of the piston rod. Measured force verses displacement cycles for multiple frequencies and electric fields validate the ability of the non-dimensional groups and the leakage damping coefficient to predict the damping levels for an ER bypass damper with leakage.
Aerodynamic canard/wing parametric analysis for general aviation applications
NASA Technical Reports Server (NTRS)
Keith, M. W.; Selberg, B. P.
1984-01-01
Vortex panel and vortex lattice methods have been utilized in an analytic study to determine the two- and three-dimensional aerodynamic behavior of canard and wing configurations. The purpose was to generate data useful for the design of general aviation canard aircraft. Essentially no two-dimensional coupling was encountered and the vertical distance between the lifting surfaces was found to be the main contributor to interference effects of the three-dimensional analysis. All canard configurations were less efficient than a forward wing with an aft horizontal tail, but were less sensitive to off-optimum division of total lift between the two surfaces, such that trim drag could be less for canard configurations. For designing a general aviation canard aircraft, results point toward large horizontal and vertical distance between the canard and wing, a large wing-to-canard area ratio, and with the canard at a low incidence angle relative to the wing.
Complexity in parametric Bose-Hubbard Hamiltonians and structural analysis of eigenstates
Hiller, Moritz; Kottos, Tsampikos; Geisel, T.
2006-06-15
We consider a family of chaotic Bose-Hubbard Hamiltonians parametrized by the coupling strength k between neighboring sites. As k increases the eigenstates undergo changes, reflected in the structure of the local density of states. We analyze these changes, both numerically and analytically, using perturbative and semiclassical methods. Although our focus is on the quantum trimer, the presented methodology is applicable for the analysis of longer lattices as well.
Parametric analysis of performance and design characteristics for advanced earth-to-orbit shuttles
NASA Technical Reports Server (NTRS)
Willis, E. A., Jr.; Strack, W. C.; Padrutt, J. A.
1972-01-01
Performance, trajectory, and design characteristics are presented for (1) a single-stage shuttle with a single advanced rocket engine, (2) a single-stage shuttle with an initial parallel chemical engine and advanced engine burn followed by an advanced engine sustainer burn, (3) a single-stage shuttle with an initial chemical engine burn followed by an advanced engine burn, and (4) a two-stage shuttle with a chemical propulsion booster stage and an advanced propulsion upper stage. The ascent trajectory profile includes a brief initial vertical rise; zero-lift flight through the sensible atmosphere; variational steering into an 83-kilometer by 185-kilometer intermediate orbit; and a fixed, 460-meter per second allowance for subsequent maneuvers. Results are given in terms of burnout mass fractions (including structure and payload), trajectory profiles, propellant loadings, and burn times. These results are generated with a trajectory analysis that includes a parametric variation of the specific impulse from 800 to 3000 seconds and the specific engine weight from 0 to 1.0.
Parametric sensitivity analysis for stochastic molecular systems using information theoretic metrics
Tsourtis, Anastasios; Pantazis, Yannis Katsoulakis, Markos A.; Harmandaris, Vagelis
2015-07-07
In this paper, we present a parametric sensitivity analysis (SA) methodology for continuous time and continuous space Markov processes represented by stochastic differential equations. Particularly, we focus on stochastic molecular dynamics as described by the Langevin equation. The utilized SA method is based on the computation of the information-theoretic (and thermodynamic) quantity of relative entropy rate (RER) and the associated Fisher information matrix (FIM) between path distributions, and it is an extension of the work proposed by Y. Pantazis and M. A. Katsoulakis [J. Chem. Phys. 138, 054115 (2013)]. A major advantage of the pathwise SA method is that both RER and pathwise FIM depend only on averages of the force field; therefore, they are tractable and computable as ergodic averages from a single run of the molecular dynamics simulation both in equilibrium and in non-equilibrium steady state regimes. We validate the performance of the extended SA method to two different molecular stochastic systems, a standard Lennard-Jones fluid and an all-atom methane liquid, and compare the obtained parameter sensitivities with parameter sensitivities on three popular and well-studied observable functions, namely, the radial distribution function, the mean squared displacement, and the pressure. Results show that the RER-based sensitivities are highly correlated with the observable-based sensitivities.
Parametric analysis of thermal stratification during the Monju turbine trip test
Sofu, T.
2012-07-01
CFD-based simulation techniques are evaluated using a simplified symmetric Monju model to study multi-dimensional mixing and heat transfer in the upper plenum during a turbine trip test. When the test starts and core outlet temperatures drop due to reactor shutdown, the cooler sodium is trapped near the bottom of the vessel and the hotter (less dense) primary sodium at the higher elevations stays largely stagnant for an extended period of time inhibiting natural circulation. However, the secondary flow through a set of holes on the inner barrel bypasses the thermally stratified region as a shorter path to the intermediate heat exchanger and improves the natural circulation flow rate to cool the core. The calculations with strict adherence to benchmark specifications predict a much shorter duration for thermal stratification in the upper plenum than the experimental data indicates. In this paper, the results of a parametric analysis are presented to address this discrepancy. Specifically, the role of the holes on the inner barrel is reassessed in terms of their ability to provide larger by-pass flow. Assuming inner barrel holes with rounded edge produces results more consistent with the experiments. (authors)
Parametric analysis of the end face engagement worm gear
NASA Astrophysics Data System (ADS)
Deng, Xingqiao; Wang, Jueling; Wang, Jinge; Chen, Shouan; Yang, Jie
2015-11-01
A novel specific type of worm drive, so-called end face engagement worm gear(EFEWD), is originally presented to minimize or overcome the gear backlash. Different factors, including the three different types, contact curves, tooth profile, lubrication angle and the induced normal curvature are taken into account to investigate the meshing characteristics and create the profile of a novel specific type of worm drive through mathematical models and theoretical analysis. The tooth of the worm wheel is very specific with the sine-shaped tooth which is located at the alveolus of the worm and the tooth profile of a worm is generated by the meshing movement of the worm wheel with the sine-shaped tooth, but just the end face of the worm(with three different typical meshing types) is adapted to meshing, and therefore an extraordinary manufacturing methods is used to generate the profile of the end face engagement worm. The research results indicates that the bearing contacts of the generated conjugate hourglass worm gear set are in line contacts, with certain advantages of no-backlash, high precision and high operating efficiency over other gears and gear systems besides the end face engagement worm gear drive may improve bearing contact, reduce the level of transmission errors and lessen the sensitivity to errors of alignment. Also, the end face engagement worm can be easily made with superior meshing and lubrication performance compared with the conventional techniques. In particular, the meshing and lubrication performance of the end face engagement worm gear by using the end face to meshing can be increased over 10% and 7%, respectively. This investigate is expect to provide a new insight on the design of the future no-backlash worm drive for industry.
Parametric cost analysis of a HYLIFE-II power plant
Bieri, R.L. Massachusetts Inst. of Tech., Cambridge, MA )
1990-10-04
The SAFIRE (Systems Analysis for ICF Reactor Economics) code was adapted to model a power plant using a HYLIFE-II reactor chamber. The code was then used to examine the dependence of the plant capital costs and busbar cost of electricity (COE) on a variety of design parameters (type of driver, chamber repetition rate, and net electric power). The results show the most attractive operating space for each set of driver/target assumptions and quantify the benefits of improvements in key design parameters. The base case plant was a 1,000 MWe plant containing a reactor vessel driven by an induction linac heavy ion accelerator run at 7.3 Hz with a driver energy of 5 MJ and a target yield of 370 MJ. The total direct cost for this plant was 2,800 M$ (where all $ in this paper are 1988$s), and the COE was 9 {cents}/KW*hour. The COE and total capital costs for the base plant assumptions for a 1,000 MWe plant are approximately independent of chosen repetition rate for all repetition rates between 4 and 10 Hz. For comparison, the COE for a coal or future fission plant would be 4.5--5.5 {cents}/KW*hour. The COE for a 1,000 MWe plant could be reduced to 7.6 {cents}/KW*hour by using advanced targets and could be cut to 6.8 {cents}/KW*hour with conventional targets if the driver cost could be cut in half. There is a large economy of scale with heavy ion driven ICF plants; a 5,000 MWe plant with one heavy ion driver and either one or two HYLIFE-II chambers would have a COE of only 4.4 {cents}/KW*hour.
Performance prediction and parametric analysis of two stage stirling cycle cryocooler
NASA Astrophysics Data System (ADS)
Natu, P. V.; Narayankhedkar, K. G.
The lowest temperature that can be achieved inStirling cycle cryocooler is governed by various losses. This paper presents performance prediction of Two Stage Stirling Cryocooler(for 20K as the second stage temperature) by using second order analysis which calculates the ideal refrigerating effect at intermediate and final stage temperatures and the ideal power input. The losses are found out for both the stages to determine the actual refrigerating effects and power input. The results obtained are in good agreement with reported values. The performance of the cryocooler is governed by various operating and geometric parameters. Parametric analysis is carried.
Biological Parametric Mapping: A Statistical Toolbox for Multi-Modality Brain Image Analysis
Casanova, Ramon; Ryali, Srikanth; Baer, Aaron; Laurienti, Paul J.; Burdette, Jonathan H.; Hayasaka, Satoru; Flowers, Lynn; Wood, Frank; Maldjian, Joseph A.
2006-01-01
In recent years multiple brain MR imaging modalities have emerged; however, analysis methodologies have mainly remained modality specific. In addition, when comparing across imaging modalities, most researchers have been forced to rely on simple region-of-interest type analyses, which do not allow the voxel-by-voxel comparisons necessary to answer more sophisticated neuroscience questions. To overcome these limitations, we developed a toolbox for multimodal image analysis called biological parametric mapping (BPM), based on a voxel-wise use of the general linear model. The BPM toolbox incorporates information obtained from other modalities as regressors in a voxel-wise analysis, thereby permitting investigation of more sophisticated hypotheses. The BPM toolbox has been developed in MATLAB with a user friendly interface for performing analyses, including voxel-wise multimodal correlation, ANCOVA, and multiple regression. It has a high degree of integration with the SPM (statistical parametric mapping) software relying on it for visualization and statistical inference. Furthermore, statistical inference for a correlation field, rather than a widely-used T-field, has been implemented in the correlation analysis for more accurate results. An example with in-vivo data is presented demonstrating the potential of the BPM methodology as a tool for multimodal image analysis. PMID:17070709
NASA Astrophysics Data System (ADS)
Takara, K. T.
2015-12-01
This paper describes a non-parametric frequency analysis method for hydrological extreme-value samples with a size larger than 100, verifying the estimation accuracy with a computer intensive statistics (CIS) resampling such as the bootstrap. Probable maximum values are also incorporated into the analysis for extreme events larger than a design level of flood control. Traditional parametric frequency analysis methods of extreme values include the following steps: Step 1: Collecting and checking extreme-value data; Step 2: Enumerating probability distributions that would be fitted well to the data; Step 3: Parameter estimation; Step 4: Testing goodness of fit; Step 5: Checking the variability of quantile (T-year event) estimates by the jackknife resampling method; and Step_6: Selection of the best distribution (final model). The non-parametric method (NPM) proposed here can skip Steps 2, 3, 4 and 6. Comparing traditional parameter methods (PM) with the NPM, this paper shows that PM often underestimates 100-year quantiles for annual maximum rainfall samples with records of more than 100 years. Overestimation examples are also demonstrated. The bootstrap resampling can do bias correction for the NPM and can also give the estimation accuracy as the bootstrap standard error. This NPM has advantages to avoid various difficulties in above-mentioned steps in the traditional PM. Probable maximum events are also incorporated into the NPM as an upper bound of the hydrological variable. Probable maximum precipitation (PMP) and probable maximum flood (PMF) can be a new parameter value combined with the NPM. An idea how to incorporate these values into frequency analysis is proposed for better management of disasters that exceed the design level. The idea stimulates more integrated approach by geoscientists and statisticians as well as encourages practitioners to consider the worst cases of disasters in their disaster management planning and practices.
Semi-parametric time-domain quantification of HR-MAS data from prostate tissue
Ratiney, Helene; Albers, Mark J.; Rabeson, Herald; Kurhanewicz, John
2011-01-01
High Resolution – Magic Angle Spinning (HR-MAS) spectroscopy provides rich biochemical profiles that require accurate quantification to permit biomarker identification and to understand the underlying pathological mechanisms. Meanwhile, quantification of HR-MAS data from prostate tissue samples is challenging due to significant overlap between the resonant peaks, the presence of short T2∗ metabolites such as citrate or polyamines (T2 from 25 to 100 msec) and macromolecules, and variations in chemical shifts and T2∗s within a metabolite’s spin systems. Since existing methods do not address these challenges completely, a new quantification method was developed and optimized for HR-MAS data acquired with an ultra short TE and over 30,000 data points. The proposed method, named HR-QUEST (High Resolution – QUEST), iteratively employs the QUEST time-domain semi-parametric strategy with a new model function that incorporates prior knowledge from whole and subdivided metabolite signals. With these features, HR-QUEST is able to independently fit the chemical shifts and T2∗s of a metabolite’s spin systems, a necessity for HR-MAS data. By using the iterative fitting approach, it is able to account for significant contributions from macromolecules and to handle shorter T2 metabolites, such as citrate and polyamines. After subdividing the necessary metabolite basis signals, the root mean square (RMS) of the residual was reduced by 52% for measured HR-MAS data from prostate tissue. Monte Carlo studies on simulated spectra with varied macromolecular contributions showed that the iterative fitting approach (6 iterations) coupled with inclusion of long T2 macromolecule components in the basis set improve the quality of the fit, as assessed by the reduction of the RMS of the residual and of the RMS error of the metabolite signal estimate, by 27% and 71% respectively. With this optimized configuration, HR-QUEST was applied to measured HR-MAS prostate data and reliably
Axenovich, Tatiana I; Zorkoltseva, Irina V
2012-02-01
Often the quantitative data coming from proteomics and metabolomics studies have irregular distribution with a spike. None of the wide used methods for human QTL mapping are applicable to such traits. Researchers have to reduce the sample, excluding the spike, and analyze only continuous measurements. In this study, we propose a method for the parametric linkage analysis of traits with a spike in the distribution, and a software GADS, which implements this method. Our software includes not only the programs for parametric linkage analysis, but also the program for complex segregation analysis, which allows the estimation of the model parameters used in linkage. We tested our method on the real data about vertical cup-to-disc ratio, the important characteristic of the optic disc associated with glaucoma, in a large pedigree from a Dutch isolated population. Significant linkage signal was identified on chromosome 6 with the help of GADS, whereas the analysis of the normal distributed part of the sample demonstrated only a suggestive linkage peak on this chromosome. The software GADS is freely available at http://mga.bionet.nsc.ru/soft/index.html. PMID:22340440
Lau, Bryan; Cole, Stephen R.; Gange, Stephen J.
2010-01-01
In the analysis of survival data, there are often competing events that preclude an event of interest from occurring. Regression analysis with competing risks is typically undertaken using a cause-specific proportional hazards model. However, modern alternative methods exist for the analysis of the subdistribution hazard with a corresponding subdistribution proportional hazards model. In this paper, we introduce a flexible parametric mixture model as a unifying method to obtain estimates of the cause-specific and subdistribution hazards and hazard ratio functions. We describe how these estimates can be summarized over time to give a single number that is comparable to the hazard ratio that is obtained from a corresponding cause-specific or subdistribution proportional hazards model. An application to the Women’s Interagency HIV Study is provided to investigate injection drug use and the time to either the initiation of effective antiretroviral therapy, or clinical disease progression as a competing event. PMID:21337360
NASA Astrophysics Data System (ADS)
Lobach, I.; Benediktovitch, A.
2016-07-01
The possibility of quantitative texture analysis by means of parametric x-ray radiation (PXR) from relativistic electrons with Lorentz factor γ > 50MeV in a polycrystal is considered theoretically. In the case of rather smooth orientation distribution function (ODF) and large detector (θD >> 1/γ) the universal relation between ODF and intensity distribution is presented. It is shown that if ODF is independent on one from Euler angles, then the texture is fully determined by angular intensity distribution. Application of the method to the simulated data shows the stability of the proposed algorithm.
Parametric analysis of 2D guided-wave photonic band gap structures
NASA Astrophysics Data System (ADS)
Ciminelli, C.; Peluso, F.; Armenise, M. N.
2005-11-01
The parametric analysis of the electromagnetic properties of 2D guided wave photonic band gap structures is reported with the aim of providing a valid tool for the optimal design. The modelling approach is based on the Bloch-Floquet method. Different lattice configurations and geometrical parameters are considered. An optimum value for the ratio between the hole (or rod) radius and the lattice constant does exist and the calculation demonstrated that it is almost independent from the etching depth, only depending on the lattice type. The results are suitable for the design optimisation of photonic crystal reflectors to be used in integrated optical devices.
Parametric analysis of 2D guided-wave photonic band gap structures.
Ciminelli, C; Peluso, F; Armenise, M
2005-11-28
The parametric analysis of the electromagnetic properties of 2D guided wave photonic band gap structures is reported with the aim of providing a valid tool for the optimal design. The modelling approach is based on the Bloch-Floquet method. Different lattice configurations and geometrical parameters are considered. An optimum value for the ratio between the hole (or rod) radius and the lattice constant does exist and the calculation demonstrated that it is almost independent from the etching depth, only depending on the lattice type. The results are suitable for the design optimisation of photonic crystal reflectors to be used in integrated optical devices. PMID:19503180
NASA Astrophysics Data System (ADS)
Brahim, S.; Bodnar et, J. L.; Grossel, P.
2010-03-01
The aim of this work is to approach in an experimental way, the possibilities of diffusivity thermal measurement, under less energy constraints, offered by front face random photothermal radiometry associated to a parametric analysis. First, we present the principle of the random method. Then, we present the experimental device SAMMIR used in our study. In a third stage, we present the studied sample, the experimental conditions selected and the model developed for the study. We show finally, using the experimental study of a sample of nylon 6.6 that the photothermal method allows, in a particular case, a good approximation of the thermal diffusivity parameter.
A Parametric Analysis of Solidification in Y(Fe,Ni,Cr)-Nb-C Alloys
DuPont, J.N.; Robino, C.V.
1999-02-22
A parametric analysis is presented which summarizes the amount of total ({gamma}/NbC + {gamma}/Laves) and individual {gamma}/NbC and {gamma}/Laves constituents which form during solidification of {gamma}{sub (Fe,Ni,Cr)} alloys with variations in nominal Nb and C contents. Calculated results are presented for Fe base alloys and Ni base alloys. The results provide a quantitative rationale for understanding the relation between alloy composition and solidification microstructures and should provide useful insight into commercial alloys of similar composition.
An Interactive Software for Conceptual Wing Flutter Analysis and Parametric Study
NASA Technical Reports Server (NTRS)
Mukhopadhyay, Vivek
1996-01-01
An interactive computer program was developed for wing flutter analysis in the conceptual design stage. The objective was to estimate the flutter instability boundary of a flexible cantilever wing, when well-defined structural and aerodynamic data are not available, and then study the effect of change in Mach number, dynamic pressure, torsional frequency, sweep, mass ratio, aspect ratio, taper ratio, center of gravity, and pitch inertia, to guide the development of the concept. The software was developed for Macintosh or IBM compatible personal computers, on MathCad application software with integrated documentation, graphics, data base and symbolic mathematics. The analysis method was based on non-dimensional parametric plots of two primary flutter parameters, namely Regier number and Flutter number, with normalization factors based on torsional stiffness, sweep, mass ratio, taper ratio, aspect ratio, center of gravity location and pitch inertia radius of gyration. The parametric plots were compiled in a Vought Corporation report from a vast data base of past experiments and wind-tunnel tests. The computer program was utilized for flutter analysis of the outer wing of a Blended-Wing-Body concept, proposed by McDonnell Douglas Corp. Using a set of assumed data, preliminary flutter boundary and flutter dynamic pressure variation with altitude, Mach number and torsional stiffness were determined.
Performance evaluation and parametric analysis on cantilevered ramp injector in supersonic flows
NASA Astrophysics Data System (ADS)
Huang, Wei; Li, Shi-bin; Yan, Li; Wang, Zhen-guo
2013-03-01
The cantilevered ramp injector is one of the most promising candidates for the mixing enhancement between the fuel and the supersonic air, and its parametric analysis has drawn an increasing attention of researchers. The flow field characteristics and the drag force of the cantilevered ramp injector in the supersonic flow with the freestream Mach number 2.0 have been investigated numerically, and the predicted injectant mole fraction and static pressure profiles have been compared with the available experimental data in the open literature. At the same time, the grid independency analysis has been performed by using the coarse, the moderate and the refined grid scales, and the influence of the turbulence model on the flow field of the cantilevered ramp injector has been carried on as well. Further, the effects of the swept angle, the ramp angle and the length of the step on the performance of the cantilevered ramp injector have been discussed subsequently. The obtained results show that the grid scale has only a slight impact on the flow field of the cantilevered ramp injector except in the region near the fuel injector, and the predicted results show reasonable agreement with the experimental data. Additionally, the turbulence model makes a slight difference to the numerical results, and the results obtained by the RNG k-ɛ and SST k-ω turbulence models are almost the same. The swept angle and the ramp angle have the same impact on the performance of the cantilevered ramp injector, and the kidney-shaped plume is formed with shorter distance with the increase of the swept and ramp angles. At the same time, the shape of the injectant mole fraction contour at X/H=6 goes through a transition from a peach-shaped plume to a kidney-shaped plume, and the cantilevered ramp injector with larger swept and ramp angles has the higher mixing efficiency and the larger drag force. The length of the step has only a slight impact on the drag force performance of the cantilevered
Generative pulsar timing analysis
NASA Astrophysics Data System (ADS)
Lentati, L.; Alexander, P.; Hobson, M. P.
2015-03-01
A new Bayesian method for the analysis of folded pulsar timing data is presented that allows for the simultaneous evaluation of evolution in the pulse profile in either frequency or time, along with the timing model and additional stochastic processes such as red spin noise, or dispersion measure variations. We model the pulse profiles using `shapelets' - a complete orthonormal set of basis functions that allow us to recreate any physical profile shape. Any evolution in the profiles can then be described as either an arbitrary number of independent profiles, or using some functional form. We perform simulations to compare this approach with established methods for pulsar timing analysis, and to demonstrate model selection between different evolutionary scenarios using the Bayesian evidence. The simplicity of our method allows for many possible extensions, such as including models for correlated noise in the pulse profile, or broadening of the pulse profiles due to scattering. As such, while it is a marked departure from standard pulsar timing analysis methods, it has clear applications for both new and current data sets, such as those from the European Pulsar Timing Array and International Pulsar Timing Array.
Time evolution of parametric instability in large-scale gravitational-wave interferometers
NASA Astrophysics Data System (ADS)
Danilishin, Stefan L.; Vyatchanin, Sergey P.; Blair, David G.; Li, Ju; Zhao, Chunnong
2014-12-01
We present a study of three-mode parametric instability in large-scale gravitational-wave detectors. Previous work used a linearized model to study the onset of instability. This paper presents a nonlinear study of this phenomenon, which shows that the initial stage of an exponential rise of the amplitudes of a higher-order optical mode and the mechanical internal mode of the mirror is followed by a saturation phase, in which all three participating modes reach a new equilibrium state with constant oscillation amplitudes. Results suggest that stable operation of interferometers may be possible in the presence of such instabilities, thereby simplifying the task of suppression.
Pouillot, Régis; Lubran, Meryl B; Cates, Sheryl C; Dennis, Sherri
2010-02-01
Home refrigeration temperatures and product storage times are important factors for controlling the growth of Listeria monocytogenes in refrigerated ready-to-eat foods. In 2005, RTI International, in collaboration with Tennessee State University and Kansas State University, conducted a national survey of U.S. adults to characterize consumers' home storage and refrigeration practices for 10 different categories of refrigerated ready-to-eat foods. No distributions of storage time or refrigeration temperature were presented in any of the resulting publications. This study used classical parametric survival modeling to derive parametric distributions from the RTI International storage practices data set. Depending on the food category, variability in product storage times was best modeled using either exponential or Weibull distributions. The shape and scale of the distributions varied greatly depending on the food category. Moreover, the results indicated that consumers tend to keep a product that is packaged by a manufacturer for a longer period of time than a product that is packaged at retail. Refrigeration temperatures were comparable to those previously reported, with the variability in temperatures best fit using a Laplace distribution, as an alternative to the empirical distribution. In contrast to previous research, limited support was found for a correlation between storage time and temperature. The distributions provided in this study can be used to better model consumer behavior in future risk assessments. PMID:20132677
A bifurcation analysis of boiling water reactor on large domain of parametric spaces
NASA Astrophysics Data System (ADS)
Pandey, Vikas; Singh, Suneet
2016-09-01
The boiling water reactors (BWRs) are inherently nonlinear physical system, as any other physical system. The reactivity feedback, which is caused by both moderator density and temperature, allows several effects reflecting the nonlinear behavior of the system. Stability analyses of BWR is done with a simplified, reduced order model, which couples point reactor kinetics with thermal hydraulics of the reactor core. The linear stability analysis of the BWR for steady states shows that at a critical value of bifurcation parameter (i.e. feedback gain), Hopf bifurcation occurs. These stable and unstable domains of parametric spaces cannot be predicted by linear stability analysis because the stability of system does not include only stability of the steady states. The stability of other dynamics of the system such as limit cycles must be included in study of stability. The nonlinear stability analysis (i.e. bifurcation analysis) becomes an indispensable component of stability analysis in this scenario. Hopf bifurcation, which occur with one free parameter, is studied here and it formulates birth of limit cycles. The excitation of these limit cycles makes the system bistable in the case of subcritical bifurcation whereas stable limit cycles continues in an unstable region for supercritical bifurcation. The distinction between subcritical and supercritical Hopf is done by two parameter analysis (i.e. codimension-2 bifurcation). In this scenario, Generalized Hopf bifurcation (GH) takes place, which separates sub and supercritical Hopf bifurcation. The various types of bifurcation such as limit point bifurcation of limit cycle (LPC), period doubling bifurcation of limit cycles (PD) and Neimark-Sacker bifurcation of limit cycles (NS) have been identified with the Floquet multipliers. The LPC manifests itself as the region of bistability whereas chaotic region exist because of cascading of PD. This region of bistability and chaotic solutions are drawn on the various
Babalola, Omotunde M; Bonassar, Lawrence J
2009-06-01
While mechanical stimulation of cells seeded within scaffolds is widely thought to be beneficial, the amount of benefit observed is highly variable between experimental systems. Although studies have investigated specific experimental loading protocols thought to be advantageous for cartilage growth, less is known about the physical stimuli (e.g., pressures, velocities, and local strains) cells experience during these experiments. This study used results of a literature survey, which looked for patterns in the efficacy of mechanical stimulation of chondrocyte seeded scaffolds, to inform the modeling of spatial patterns of physical stimuli present in mechanically stimulated constructs. The literature survey revealed a large variation in conditions used in mechanical loading studies, with a peak to peak strain of 10% (i.e., the maximum amount of deformation experienced by the scaffold) at 1 Hz on agarose scaffolds being the most frequently studied parameters and scaffold. This loading frequency was then used as the basis for simulation in the finite element analyses. 2D axisymmetric finite element models of 2x4 mm2 scaffolds with 360 modulus/permeability combinations were constructed using COMSOL MULTIPHYSICS software. A time dependent coupled pore pressure/effective stress analysis was used to model fluid/solid interactions in the scaffolds upon loading. Loading was simulated using an impermeable frictionless loader on the top boundary with fluid and solid displacement confined to the radial axis. As expected, all scaffold materials exhibited classic poro-elastic behavior having pressurized cores with low fluid flow and edges with high radial fluid velocities. Under the simulation parameters of this study, PEG scaffolds had the highest pressure and radial fluid velocity but also the lowest shear stress and radial strain. Chitosan and KLD-12 simulated scaffold materials had the lowest radial strains and fluid velocities, with collagen scaffolds having the lowest
NASA Astrophysics Data System (ADS)
Dodonov, V. V.; Valverde, C.; Souza, L. S.; Baseia, B.
2011-10-01
The exact Wigner function of a parametrically excited quantum oscillator in a phase-sensitive amplifying/attenuating reservoir is found for initial even/odd coherent states. Studying the evolution of negativity of the Wigner function we show the difference between the “initial positivization time” (IPT), which is inversely proportional to the square of the initial size of the superposition, and the “final positivization time” (FPT), which does not depend on this size. Both these times can be made arbitrarily long in maximally squeezed high-temperature reservoirs. Besides, we find the conditions when some (small) squeezing can exist even after the Wigner function becomes totally positive.
NASA Technical Reports Server (NTRS)
Jeffries, K. S.; Renz, D. D.
1984-01-01
A parametric analysis was performed of transmission cables for transmitting electrical power at high voltage (up to 1000 V) and high frequency (10 to 30 kHz) for high power (100 kW or more) space missions. Large diameter (5 to 30 mm) hollow conductors were considered in closely spaced coaxial configurations and in parallel lines. Formulas were derived to calculate inductance and resistance for these conductors. Curves of cable conductance, mass, inductance, capacitance, resistance, power loss, and temperature were plotted for various conductor diameters, conductor thickness, and alternating current frequencies. An example 5 mm diameter coaxial cable with 0.5 mm conductor thickness was calculated to transmit 100 kW at 1000 Vac, 50 m with a power loss of 1900 W, an inductance of 1.45 micron and a capacitance of 0.07 micron-F. The computer programs written for this analysis are listed in the appendix.
A parametric analysis of performance characteristics of satellite-borne multiple-beam antennas
NASA Technical Reports Server (NTRS)
Salmasi, A. B.
1980-01-01
An analytical and empirical model is presented for parametric study of multiple beam antenna frequency reuse capacity and interbeam isolation. Two types of reflector antennas, the axisymmetric parabolic and the offset-parabolic reflectors, are utilized to demonstrate the model. The parameters of the model are introduced and their limitations are discussed in the context of parabolic reflector antennas. The model, however, is not restricted to analysis of reflector antenna performance. Results of the analyses are covered in two tables. The model parameters, objectives, and descriptions are given, multiple-beam antenna frequency reuse capacity and interbeam isolation analysis of the two types of reflectors are discussed as well as future developments of the program model.
Parametric analysis of a cylindrical negative Poisson’s ratio structure
NASA Astrophysics Data System (ADS)
Wang, Yuanlong; Wang, Liangmo; Ma, Zheng-dong; Wang, Tao
2016-03-01
Much research related to negative Poisson’s ratio (NPR), or auxetic, structures is emerging these days. Several types of 3D NPR structure have been proposed and studied, but almost all of them had cuboid shapes, which were not suitable for certain engineering applications. In this paper, a cylindrical NPR structure was developed and researched. It was expected to be utilized in springs, bumpers, dampers and other similar applications. For the purpose of parametric analysis, a method of parametric modeling of cylindrical NPR structures was developed using MATLAB scripts. The scripts can automatically establish finite element models, invoke ABAQUS, read results etc. Subsequently the influences of structural parameters, including number of cells, number of layers and layer heights, on the uniaxial compression behavior of cylinder NPR structures were researched. This led to the conclusion that the stiffness of the cylindrical NPR structure was enhanced on increasing the number of cells and reducing the effective layer height. Moreover, small numbers of layers resulted in a late transition area of the load-displacement curve from low stiffness to high stiffness. Moreover, the middle contraction regions were more apparent with larger numbers of cells, smaller numbers of layers and smaller effective layer heights. The results indicate that the structural parameters had significant effects on the load-displacement curves and deformed shapes of cylindrical NPR structures. This paper is conducive to the further engineering applications of cylindrical NPR structures.
Borri, Marco; Schmidt, Maria A.; Powell, Ceri; Koh, Dow-Mu; Riddell, Angela M.; Partridge, Mike; Bhide, Shreerang A.; Nutting, Christopher M.; Harrington, Kevin J.; Newbold, Katie L.; Leach, Martin O.
2015-01-01
Purpose To describe a methodology, based on cluster analysis, to partition multi-parametric functional imaging data into groups (or clusters) of similar functional characteristics, with the aim of characterizing functional heterogeneity within head and neck tumour volumes. To evaluate the performance of the proposed approach on a set of longitudinal MRI data, analysing the evolution of the obtained sub-sets with treatment. Material and Methods The cluster analysis workflow was applied to a combination of dynamic contrast-enhanced and diffusion-weighted imaging MRI data from a cohort of squamous cell carcinoma of the head and neck patients. Cumulative distributions of voxels, containing pre and post-treatment data and including both primary tumours and lymph nodes, were partitioned into k clusters (k = 2, 3 or 4). Principal component analysis and cluster validation were employed to investigate data composition and to independently determine the optimal number of clusters. The evolution of the resulting sub-regions with induction chemotherapy treatment was assessed relative to the number of clusters. Results The clustering algorithm was able to separate clusters which significantly reduced in voxel number following induction chemotherapy from clusters with a non-significant reduction. Partitioning with the optimal number of clusters (k = 4), determined with cluster validation, produced the best separation between reducing and non-reducing clusters. Conclusion The proposed methodology was able to identify tumour sub-regions with distinct functional properties, independently separating clusters which were affected differently by treatment. This work demonstrates that unsupervised cluster analysis, with no prior knowledge of the data, can be employed to provide a multi-parametric characterization of functional heterogeneity within tumour volumes. PMID:26398888
NASA Astrophysics Data System (ADS)
Dai, Xiaoqian; Tian, Jie; Chen, Zhe
2010-03-01
Parametric images can represent both spatial distribution and quantification of the biological and physiological parameters of tracer kinetics. The linear least square (LLS) method is a well-estimated linear regression method for generating parametric images by fitting compartment models with good computational efficiency. However, bias exists in LLS-based parameter estimates, owing to the noise present in tissue time activity curves (TTACs) that propagates as correlated error in the LLS linearized equations. To address this problem, a volume-wise principal component analysis (PCA) based method is proposed. In this method, firstly dynamic PET data are properly pre-transformed to standardize noise variance as PCA is a data driven technique and can not itself separate signals from noise. Secondly, the volume-wise PCA is applied on PET data. The signals can be mostly represented by the first few principle components (PC) and the noise is left in the subsequent PCs. Then the noise-reduced data are obtained using the first few PCs by applying 'inverse PCA'. It should also be transformed back according to the pre-transformation method used in the first step to maintain the scale of the original data set. Finally, the obtained new data set is used to generate parametric images using the linear least squares (LLS) estimation method. Compared with other noise-removal method, the proposed method can achieve high statistical reliability in the generated parametric images. The effectiveness of the method is demonstrated both with computer simulation and with clinical dynamic FDG PET study.
Examining deterrence of adult sex crimes: A semi-parametric intervention time series approach
Park, Jin-Hong; Bandyopadhyay, Dipankar; Letourneau, Elizabeth
2013-01-01
Motivated by recent developments on dimension reduction (DR) techniques for time series data, the association of a general deterrent effect towards South Carolina (SC)’s registration and notification (SORN) policy for preventing sex crimes was examined. Using adult sex crime arrestee data from 1990 to 2005, the the idea of Central Mean Subspace (CMS) is extended to intervention time series analysis (CMS-ITS) to model the sequential intervention effects of 1995 (the year SC’s SORN policy was initially implemented) and 1999 (the year the policy was revised to include online notification) on the time series spectrum. The CMS-ITS model estimation was achieved via kernel smoothing techniques, and compared to interrupted auto-regressive integrated time series (ARIMA) models. Simulation studies and application to the real data underscores our model’s ability towards achieving parsimony, and to detect intervention effects not earlier determined via traditional ARIMA models. From a public health perspective, findings from this study draw attention to the potential general deterrent effects of SC’s SORN policy. These findings are considered in light of the overall body of research on sex crime arrestee registration and notification policies, which remain controversial. PMID:24795489
Broadband fiber-optical parametric amplification for ultrafast time-stretch imaging at 1.0 μm.
Wei, Xiaoming; Lau, Andy K S; Xu, Yiqing; Zhang, Chi; Mussot, Arnaud; Kudlinski, Alexandre; Tsia, Kevin K; Wong, Kenneth K Y
2014-10-15
We demonstrate a broadband all-fiber-optical parametric amplifier for ultrafast time-stretch imaging at 1.0 μm, featured by its compact design, alignment-free, high efficiency, and flexible gain spectrum through fiber nonlinearity- and dispersion-engineering: specifically on a dispersion-stabilized photonic-crystal fiber (PCF) to achieve a net gain over 20 THz (75 nm) and a highest gain of ~6000 (37.5 dB). Another unique feature of the parametric amplifier, over other optical amplifiers, is the coherent generation of a synchronized signal replica (called idler) that can be exploited to offer an extra 3-dB gain by optically superposing the signal and idler. It further enhances signal contrast and temporal stability. For proof-of-concept purpose, ultrahigh speed and diffraction-limited time-stretch microscopy is demonstrated with a single-shot line-scan rate of 13 MHz based on the dual-band (signal and idler) detection. Our scheme can be extended to other established bioimaging modalities, such as optical coherence tomography, near infrared fluorescence, and photoacoustic imaging, where weak signal detection at high speed is required. PMID:25361137
Takeuchi, E.S.; Size, P.J.
1994-12-31
The Taguchi Method of Experimental Design was utilized to parametrically assess the effects of four variables in cell configuration on performance of spirally wound lithium oxyhalide D cells. This approach utilizes fractional factorial designs requiring a fraction of the number of experiments required of full factorial experiments. The Taguchi approach utilizes ANOVA analysis for calculating the percent contribution of each factor to battery performance as well as main effects of each factor. The four factors investigated in this study were the electrolyte type, the electrolyte concentration, the depolarizer type, and the mechanical cell design. The effects of these four factors on 1A constant current discharge, low temperature discharge, start-up, and shelf-life were evaluated. The factor having the most significant effect on cell performance was the electrolyte type.
Ethanol production by enzymatic hydrolysis: parametric analysis of a base-case process
Isaacs, S.H.
1984-05-01
A base-case flowsheet for an enzymatic hydrolysis process is presented. Included is a parametric sensitivity analysis to identify key research issues and an assessment of this technology. The plant discussed is a large-scale facility, producing 50 million gallons of ethanol per year. The plant design is based on the process originally conceived by the US National Army Command and consists of these process steps: pretreatment; enzyme production; enzyme hydrolysis; fermentation; and distillation. The base-case design parameters are based on recent laboratory data from Lawrence Berkeley Laboratories and the University of California at Berkeley. The selling price of ethanol is used to compare variations in the base-case operating parameters, which include hydrolysis efficiencies, capital costs, enzyme production efficiencies, and enzyme recycle. 28 references, 38 figures, 8 tables.
NASA Astrophysics Data System (ADS)
Kumar, Deepak; Kumar, Vivek; Singh, V. P.
2009-07-01
In the present paper, the effects of cake thickness and time on the efficiency of brown stock washer of the paper mill are studied by using mathematical model of pulp washing for the species of sodium and lignin ions. The mechanism of the diffusion- dispersion washing of the bed of the pulp fibers is mathematically modeled by the basic material balance and adsorption isotherm is used to describe the equilibrium between the concentration of the solute in the liquor and concentration of the solute on the fibers. To study the parametric effect, numerical solutions of the axial domain of the system governed by partial differential equations (transport and isotherm equations) for different boundary conditions are obtained by the "pdepe" solver in MATLAB source code. The effects of both the parameters are shown by three dimensional graphical representation as well as concentration profiles.
Parametric analysis of the thermal effects on the divertor in tokamaks during plasma disruptions
Bruhn, M.L.
1988-04-01
Plasma disruptions are an ever present danger to the plasma-facing components in today's tokamak fusion reactors. This threat results from our lack of understanding and limited ability to control this complex phenomenon. In particular, severe energy deposition occurs on the divertor component of the double-null configured tokamak reactor during such disruptions. A hybrid computational model developed to estimate and graphically illustrate global thermal effects of disruptions on the divertor plates is described in detail. The quasi-two-dimensional computer code, TADDPAK (Thermal Analysis Divertor during Disruptions PAcKage), is used to conduct parametric analysis for the TIBER II Tokamak Engineering Test Reactor Design. The dependence of these thermal effects on divertor material choice, disruption pulse length, disruption pulse shape, and the characteristic thickness of the plasma scrape-off layer is investigated for this reactor design. Results and conclusions from this analysis are presented. Improvements to this model and issues that require further investigation are discussed. Cursory analysis for ITER (International Thermonuclear Experimental Reactor) is also presented in the appendix. 75 refs., 49 figs., 10 tabs.
Global analysis and parametric dependencies for potential unintended hydrogen-fuel releases
Harstad, Kenneth; Bellan, Josette
2006-01-01
Global, simplified analyses of gaseous-hydrogen releases from a high-pressure vessel and liquid-hydrogen pools are conducted for two purposes: (1) establishing order-of-magnitude values of characteristic times and (2) determining parametric dependencies of these characteristic times on the physical properties of the configuration and on the thermophysical properties of hydrogen. According to the ratio of the characteristic release time to the characteristic mixing time, two limiting configurations are identified: (1) a rich cloud exists when this ratio is much smaller than unity, and (2) a jet exists when this ratio is much larger than unity. In all cases, it is found that the characteristic release time is proportional to the total released mass and inversely proportional to a characteristic area. The approximate size, convection velocity, and circulation time of unconfined burning-cloud releases scale with the cloud mass at powers 1/3, 1/6, and 1/6, respectively, multiplied by an appropriately dimensional constant; the influence of cross flow can only be important if its velocity exceeds that of internal convection. It is found that the fireball lifetime is approximately the maximum of the release time and thrice the convection-associated characteristic time. Transition from deflagration to detonation can occur only if the size of unconfined clouds exceeds by a factor of O(10) that of a characteristic detonation cell, which ranges from 0.015 m under stoichiometric conditions to approximately 1 m under extreme rich/lean conditions. For confined vapor pockets, transition occurs only for pocket sizes larger than the cell size. In jets, the release time is inversely proportional to the initial vessel pressure and has a square root dependence on the vessel temperature. Jet velocities are a factor of 10 larger than convective velocities in fireballs and combustion is possible only in the subsonic, downstream region where entrainment may occur.
A Bayesian Semi-parametric Approach for the Differential Analysis of Sequence Counts Data.
Guindani, Michele; Sepúlveda, Nuno; Paulino, Carlos Daniel; Müller, Peter
2014-04-01
Data obtained using modern sequencing technologies are often summarized by recording the frequencies of observed sequences. Examples include the analysis of T cell counts in immunological research and studies of gene expression based on counts of RNA fragments. In both cases the items being counted are sequences, of proteins and base pairs, respectively. The resulting sequence-abundance distribution is usually characterized by overdispersion. We propose a Bayesian semi-parametric approach to implement inference for such data. Besides modeling the overdispersion, the approach takes also into account two related sources of bias that are usually associated with sequence counts data: some sequence types may not be recorded during the experiment and the total count may differ from one experiment to another. We illustrate our methodology with two data sets, one regarding the analysis of CD4+ T cell counts in healthy and diabetic mice and another data set concerning the comparison of mRNA fragments recorded in a Serial Analysis of Gene Expression (SAGE) experiment with gastrointestinal tissue of healthy and cancer patients. PMID:24833809
NASA Astrophysics Data System (ADS)
Lee, Jae-Seung; Im, In-Chul; Kang, Su-Man; Goo, Eun-Hoe; Kwak, Byung-Joon
2013-07-01
This study aimed to quantitatively analyze data from diffusion tensor imaging (DTI) using statistical parametric mapping (SPM) in patients with brain disorders and to assess its potential utility for analyzing brain function. DTI was obtained by performing 3.0-T magnetic resonance imaging for patients with Alzheimer's disease (AD) and vascular dementia (VD), and the data were analyzed using Matlab-based SPM software. The two-sample t-test was used for error analysis of the location of the activated pixels. We compared regions of white matter where the fractional anisotropy (FA) values were low and the apparent diffusion coefficients (ADCs) were increased. In the AD group, the FA values were low in the right superior temporal gyrus, right inferior temporal gyrus, right sub-lobar insula, and right occipital lingual gyrus whereas the ADCs were significantly increased in the right inferior frontal gyrus and right middle frontal gyrus. In the VD group, the FA values were low in the right superior temporal gyrus, right inferior temporal gyrus, right limbic cingulate gyrus, and right sub-lobar caudate tail whereas the ADCs were significantly increased in the left lateral globus pallidus and left medial globus pallidus. In conclusion by using DTI and SPM analysis, we were able to not only determine the structural state of the regions affected by brain disorders but also quantitatively analyze and assess brain function.
Infinitesimal-area 2D radiative analysis using parametric surface representation, through NURBS
Daun, K.J.; Hollands, K.G.T.
1999-07-01
The use of form factors in the treatment of radiant enclosures requires that the radiosity and surface properties be treated as uniform over finite areas. This restriction can be relaxed by applying an infinitesimal-area analysis, where the radiant exchange is taken to be between infinitesimal areas, rather than finite areas. This paper presents a generic infinitesimal-area formulation that can be applied to two-dimensional enclosure problems. (Previous infinitesimal-area analyses have largely been restricted to specific, one-dimensional problems.) Specifically, the paper shows how the analytical expression for the kernel of the integral equation can be obtained without human intervention, once the enclosure surface has been defined parametrically. This can be accomplished by using a computer algebra package or by using NURBS algorithms, which are the industry standard for the geometrical representations used in CAD-CAM codes. Once the kernel has been obtained by this formalism, the 2D integral equation can be set up and solved numerically. The result is a single general-purpose infinitesimal-area analysis code that can proceed from surface specification to solution. The authors have implemented this 2D code and tested it on 1D problems, whose solutions have been given in the literature, obtaining agreement commensurate with the accuracy of the published solutions.
NASA Astrophysics Data System (ADS)
Lee, Liming; Kou, Kit Ian; Zhang, Wentao; Liang, Jinling; Liu, Yang
2016-07-01
In this paper, we consider finite-time control problems for linear multi-agent systems subject to exogenous constant disturbances and impulses. Some sufficient conditions are obtained to ensure the finite-time boundedness of the multi-agent systems, which could be then reduced to a feasibility problem involving linear matrix inequalities. Numerical examples are given to illustrate the results.
Non-parametric seismic hazard analysis in the presence of incomplete data
NASA Astrophysics Data System (ADS)
Yazdani, Azad; Mirzaei, Sajjad; Dadkhah, Koroush
2016-07-01
The distribution of earthquake magnitudes plays a crucial role in the estimation of seismic hazard parameters. Due to the complexity of earthquake magnitude distribution, non-parametric approaches are recommended over classical parametric methods. The main deficiency of the non-parametric approach is the lack of complete magnitude data in almost all cases. This study aims to introduce an imputation procedure for completing earthquake catalog data that will allow the catalog to be used for non-parametric density estimation. Using a Monte Carlo simulation, the efficiency of introduced approach is investigated. This study indicates that when a magnitude catalog is incomplete, the imputation procedure can provide an appropriate tool for seismic hazard assessment. As an illustration, the imputation procedure was applied to estimate earthquake magnitude distribution in Tehran, the capital city of Iran.
NASA Technical Reports Server (NTRS)
Mizukami, M.; Saunders, J. D.
1995-01-01
The supersonic diffuser of a Mach 2.68 bifurcated, rectangular, mixed-compression inlet was analyzed using a two-dimensional (2D) Navier-Stokes flow solver. Parametric studies were performed on turbulence models, computational grids and bleed models. The computer flowfield was substantially different from the original inviscid design, due to interactions of shocks, boundary layers, and bleed. Good agreement with experimental data was obtained in many aspects. Many of the discrepancies were thought to originate primarily from 3D effects. Therefore, a balance should be struck between expending resources on a high fidelity 2D simulation, and the inherent limitations of 2D analysis. The solutions were fairly insensitive to turbulence models, grids and bleed models. Overall, the k-e turbulence model, and the bleed models based on unchoked bleed hole discharge coefficients or uniform velocity are recommended. The 2D Navier-Stokes methods appear to be a useful tool for the design and analysis of supersonic inlets, by providing a higher fidelity simulation of the inlet flowfield than inviscid methods, in a reasonable turnaround time.
NASA Astrophysics Data System (ADS)
Moradian, Zabihallah; Einstein, Herbert H.; Ballivy, Gerard
2016-03-01
Determination of the cracking levels during the crack propagation is one of the key challenges in the field of fracture mechanics of rocks. Acoustic emission (AE) is a technique that has been used to detect cracks as they occur across the specimen. Parametric analysis of AE signals and correlating these parameters (e.g., hits and energy) to stress-strain plots of rocks let us detect cracking levels properly. The number of AE hits is related to the number of cracks, and the AE energy is related to magnitude of the cracking event. For a full understanding of the fracture process in brittle rocks, prismatic specimens of granite containing pre-existing flaws have been tested in uniaxial compression tests, and their cracking process was monitored with both AE and high-speed video imaging. In this paper, the characteristics of the AE parameters and the evolution of cracking sequences are analyzed for every cracking level. Based on micro- and macro-crack damage, a classification of cracking levels is introduced. This classification contains eight stages (1) crack closure, (2) linear elastic deformation, (3) micro-crack initiation (white patch initiation), (4) micro-crack growth (stable crack growth), (5) micro-crack coalescence (macro-crack initiation), (6) macro-crack growth (unstable crack growth), (7) macro-crack coalescence and (8) failure.
A Parametric Cycle Analysis of a Separate-Flow Turbofan with Interstage Turbine Burner
NASA Technical Reports Server (NTRS)
Marek, C. J. (Technical Monitor); Liew, K. H.; Urip, E.; Yang, S. L.
2005-01-01
Today's modern aircraft is based on air-breathing jet propulsion systems, which use moving fluids as substances to transform energy carried by the fluids into power. Throughout aero-vehicle evolution, improvements have been made to the engine efficiency and pollutants reduction. This study focuses on a parametric cycle analysis of a dual-spool, separate-flow turbofan engine with an Interstage Turbine Burner (ITB). The ITB considered in this paper is a relatively new concept in modern jet engine propulsion. The JTB serves as a secondary combustor and is located between the high- and the low-pressure turbine, i.e., the transition duct. The objective of this study is to use design parameters, such as flight Mach number, compressor pressure ratio, fan pressure ratio, fan bypass ratio, linear relation between high- and low-pressure turbines, and high-pressure turbine inlet temperature to obtain engine performance parameters, such as specific thrust and thrust specific fuel consumption. Results of this study can provide guidance in identifying the performance characteristics of various engine components, which can then be used to develop, analyze, integrate, and optimize the system performance of turbofan engines with an ITB.
NASA Astrophysics Data System (ADS)
Abot, Jandro L.; Kiyono, César Y.; Thomas, Gilles P.; Silva, Emílio C. N.
2015-07-01
Carbon nanotube (CNT) yarns are micron-size fibers that contain thousands of intertwined CNTs in their cross sections and exhibit piezoresistance characteristics that can be tapped for sensing purposes. Sensor yarns can be integrated into polymeric and composite materials to measure strain through resistance measurements without adding weight or altering the integrity of the host material. This paper includes the details of novel strain gauge sensor configurations comprised of CNT yarn, the numerical modeling of their piezoresistive response, and the parametric analysis schemes that determines the highest sensor sensitivity to mechanical loading. The effect of several sensor configuration parameters are discussed including the inclination and separation of the CNT yarns within the sensor, the mechanical properties of the CNT yarn, the direction and magnitude of the applied mechanical load, and the dimensions and shape of the sensor. The sensor configurations that yield the highest sensitivity are presented and discussed in terms of the mechanical and electrical properties of the CNT yarn. It is shown that strain gauge sensors consisting of CNT yarn are sensitive enough to measure strain, and could exhibit even higher gauge factors than those of metallic foil strain gauges.
NASA Astrophysics Data System (ADS)
Sayadi, Taraneh; Schmid, Peter; Richecoeur, Franck; Durox, Daniel
2014-11-01
Thermo-acoustic systems belong to a class of dynamical systems that are governed by multiple parameters. Changing these parameters alters the response of the dynamical system and causes it to bifurcate. Due to their many applications and potential impact on a variety of combustion systems, there is great interest in devising control strategies to weaken or suppress thermo-acoustic instabilities. However, the system dynamics have to be available in reduced-order form to allow the design of such controllers and their operation in real-time. As the dominant modes and their respective frequencies change with varying the system parameters, the dynamical system needs to be analyzed separately for a set of fixed parameter values, before the dynamics can be linked in parameter-space. This two-step process is not only cumbersome, but also ambiguous when applied to systems operating close to a bifurcation point. Here we propose a parametrized decomposition algorithm which is capable of analyzing dynamical systems as they go through a bifurcation, extracting the dominant modes of the pre- and post-bifurcation regime. The algorithm is applied to a thermo-acoustically oscillating flame and to pressure signals from experiments. A few selected mode are capable of reproducing the dynamics.
NASA Astrophysics Data System (ADS)
Ozden, Ender; Tari, Ilker
2016-02-01
A Polymer Electrolyte Membrane (PEM) fuel cell is numerically investigated both as fresh and as degraded with the help of observed degradation patterns reported in the literature. The fresh fuel cell model is validated and verified with the data from the literature. Modifying the model by varying the parameters affected by degradation, a degraded PEM fuel cell model is created. The degraded fuel cell is parametrically analyzed by using a commercial Computational Fluid Dynamics (CFD) software. The investigated parameters are the membrane equivalent weight, the Catalyst Layer (CL) porosity and viscous resistance, the Gas Diffusion Layer (GDL) porosity and viscous resistance, and the bipolar plate contact resistance. It is shown for the first time that PEM fuel cell overall degradation can be numerically estimated by combining experimental data from degraded individual components. By comparing the simulation results for the fresh and the degraded PEM fuel cells for two years of operation, it is concluded that the effects of overall degradation on cell potential is significant - estimated to be 17% around the operating point of the fuel cell at 0.95 V open circuit voltage and 70 °C operating temperature.
Marmarelis, Vasilis Z.; Shin, Dae C.; Zhang, Yaping; Kautzky-Willer, Alexandra; Pacini, Giovanni; D’Argenio, David Z.
2013-01-01
Background: Modeling studies of the insulin–glucose relationship have mainly utilized parametric models, most notably the minimal model (MM) of glucose disappearance. This article presents results from the comparative analysis of the parametric MM and a nonparametric Laguerre based Volterra Model (LVM) applied to the analysis of insulin modified (IM) intravenous glucose tolerance test (IVGTT) data from a clinical study of gestational diabetes mellitus (GDM). Methods: An IM IVGTT study was performed 8 to 10 weeks postpartum in 125 women who were diagnosed with GDM during their pregnancy [population at risk of developing diabetes (PRD)] and in 39 control women with normal pregnancies (control subjects). The measured plasma glucose and insulin from the IM IVGTT in each group were analyzed via a population analysis approach to estimate the insulin sensitivity parameter of the parametric MM. In the nonparametric LVM analysis, the glucose and insulin data were used to calculate the first-order kernel, from which a diagnostic scalar index representing the integrated effect of insulin on glucose was derived. Results: Both the parametric MM and nonparametric LVM describe the glucose concentration data in each group with good fidelity, with an improved measured versus predicted r2 value for the LVM of 0.99 versus 0.97 for the MM analysis in the PRD. However, application of the respective diagnostic indices of the two methods does result in a different classification of 20% of the individuals in the PRD. Conclusions: It was found that the data based nonparametric LVM revealed additional insights about the manner in which infused insulin affects blood glucose concentration. PMID:23911176
Dismuke, C E; Sena, V
1999-05-01
The use of Diagnosis Related Groups (DRG) as a mechanism for hospital financing is a currently debated topic in Portugal. The DRG system was scheduled to be initiated by the Health Ministry of Portugal on January 1, 1990 as an instrument for the allocation of public hospital budgets funded by the National Health Service (NHS), and as a method of payment for other third party payers (e.g., Public Employees (ADSE), private insurers, etc.). Based on experience from other countries such as the United States, it was expected that implementation of this system would result in more efficient hospital resource utilisation and a more equitable distribution of hospital budgets. However, in order to minimise the potentially adverse financial impact on hospitals, the Portuguese Health Ministry decided to gradually phase in the use of the DRG system for budget allocation by using blended hospital-specific and national DRG case-mix rates. Since implementation in 1990, the percentage of each hospital's budget based on hospital specific costs was to decrease, while the percentage based on DRG case-mix was to increase. This was scheduled to continue until 1995 when the plan called for allocating yearly budgets on a 50% national and 50% hospital-specific cost basis. While all other non-NHS third party payers are currently paying based on DRGs, the adoption of DRG case-mix as a National Health Service budget setting tool has been slower than anticipated. There is now some argument in both the political and academic communities as to the appropriateness of DRGs as a budget setting criterion as well as to their impact on hospital efficiency in Portugal. This paper uses a two-stage procedure to assess the impact of actual DRG payment on the productivity (through its components, i.e., technological change and technical efficiency change) of diagnostic technology in Portuguese hospitals during the years 1992-1994, using both parametric and non-parametric frontier models. We find evidence
NASA Astrophysics Data System (ADS)
Zha, N.; Capaldi, D. P. I.; Pike, D.; McCormack, D. G.; Cunningham, I. A.; Parraga, G.
2015-03-01
Pulmonary x-ray computed tomography (CT) may be used to characterize emphysema and airways disease in patients with chronic obstructive pulmonary disease (COPD). One analysis approach - parametric response mapping (PMR) utilizes registered inspiratory and expiratory CT image volumes and CT-density-histogram thresholds, but there is no consensus regarding the threshold values used, or their clinical meaning. Principal-component-analysis (PCA) of the CT density histogram can be exploited to quantify emphysema using data-driven CT-density-histogram thresholds. Thus, the objective of this proof-of-concept demonstration was to develop a PRM approach using PCA-derived thresholds in COPD patients and ex-smokers without airflow limitation. Methods: Fifteen COPD ex-smokers and 5 normal ex-smokers were evaluated. Thoracic CT images were also acquired at full inspiration and full expiration and these images were non-rigidly co-registered. PCA was performed for the CT density histograms, from which the components with the highest eigenvalues greater than one were summed. Since the values of the principal component curve correlate directly with the variability in the sample, the maximum and minimum points on the curve were used as threshold values for the PCA-adjusted PRM technique. Results: A significant correlation was determined between conventional and PCA-adjusted PRM with 3He MRI apparent diffusion coefficient (p<0.001), with CT RA950 (p<0.0001), as well as with 3He MRI ventilation defect percent, a measurement of both small airways disease (p=0.049 and p=0.06, respectively) and emphysema (p=0.02). Conclusions: PRM generated using PCA thresholds of the CT density histogram showed significant correlations with CT and 3He MRI measurements of emphysema, but not airways disease.
A parametric analysis of lithospheric imaging by Full-Waveform Inversion of teleseismic body-waves
NASA Astrophysics Data System (ADS)
Beller, Stephen; Monteiller, Vadim; Operto, Stéphane; Nolet, Guust; Virieux, Jean
2015-04-01
With the deployment of dense seismic arrays and the continuous growth of computing facilities, full-waveform inversion (FWI) of teleseismic data has become a method of choice for 3D high-resolution lithospheric imaging. FWI is a local optimization problem that seeks to estimate Earth's elastic properties by iteratively minimizing the misfit function between observed and modeled seismograms. Recent investigations have shown the feasibility of such local inversions by injecting a pre-computed global wavefield at the edges of the lithospheric target. In this study, we present all the methodological ingredients needed for the application of FWI to lithospheric data. The global wavefield, which is computed in an axisymmetric global earth with AxiSEM, is injected in the lithospheric target by the so-called total-field/scattered-field method. The inversion, which is implemented with an adjoint formalism, is performed following a multiscale approach, proceeding hierarchically from low to high frequencies. We further perform a parametric analysis in a realistic model representative of the Western Alps. This analysis mainly focus on the FWI sensitivity to the source characteristics. One key issue is the estimation of the temporal source excitation, as there might be some trade-off between the source estimation and the subsurface update. We also investigate the imprint of the sources repartition on the spatial resolution of the imaging, the FWI sensitivity to the accuracy of the starting model and the effects of considering a complex topography. Seismic modeling in the FWI models allows us to assess which parts of the teleseismic wavefield significantly contribute to the imaging.
NASA Astrophysics Data System (ADS)
Kosmidis, Kosmas; Kalampokis, Alkiviadis; Argyrakis, Panos
2006-10-01
We use the detrended fluctuation analysis (DFA) and the Grassberger-Proccacia analysis (GP) methods in order to study language characteristics. Despite that we construct our signals using only word lengths or word frequencies, excluding in this way huge amount of information from language, the application of GP analysis indicates that linguistic signals may be considered as the manifestation of a complex system of high dimensionality, different from random signals or systems of low dimensionality such as the Earth climate. The DFA method is additionally able to distinguish a natural language signal from a computer code signal. This last result may be useful in the field of cryptography.
NASA Astrophysics Data System (ADS)
Soumia, Sid Ahmed; Messali, Zoubeida; Ouahabi, Abdeldjalil; Trepout, Sylvain; Messaoudi, Cedric; Marco, Sergio
2015-01-01
The 3D reconstruction of the Cryo-Transmission Electron Microscopy (Cryo-TEM) and Energy Filtering TEM images (EFTEM) hampered by the noisy nature of these images, so that their alignment becomes so difficult. This noise refers to the collision between the frozen hydrated biological samples and the electrons beam, where the specimen is exposed to the radiation with a high exposure time. This sensitivity to the electrons beam led specialists to obtain the specimen projection images at very low exposure time, which resulting the emergence of a new problem, an extremely low signal-to-noise ratio (SNR). This paper investigates the problem of TEM images denoising when they are acquired at very low exposure time. So, our main objective is to enhance the quality of TEM images to improve the alignment process which will in turn improve the three dimensional tomography reconstructions. We have done multiple tests on special TEM images acquired at different exposure time 0.5s, 0.2s, 0.1s and 1s (i.e. with different values of SNR)) and equipped by Golding beads for helping us in the assessment step. We herein, propose a structure to combine multiple noisy copies of the TEM images. The structure is based on four different denoising methods, to combine the multiple noisy TEM images copies. Namely, the four different methods are Soft, the Hard as Wavelet-Thresholding methods, Bilateral Filter as a non-linear technique able to maintain the edges neatly, and the Bayesian approach in the wavelet domain, in which context modeling is used to estimate the parameter for each coefficient. To ensure getting a high signal-to-noise ratio, we have guaranteed that we are using the appropriate wavelet family at the appropriate level. So we have chosen âĂIJsym8âĂİ wavelet at level 3 as the most appropriate parameter. Whereas, for the bilateral filtering many tests are done in order to determine the proper filter parameters represented by the size of the filter, the range parameter and the
Soumia, Sid Ahmed; Messali, Zoubeida; Ouahabi, Abdeldjalil; Trepout, Sylvain E-mail: cedric.messaoudi@curie.fr Messaoudi, Cedric E-mail: cedric.messaoudi@curie.fr Marco, Sergio E-mail: cedric.messaoudi@curie.fr
2015-01-13
The 3D reconstruction of the Cryo-Transmission Electron Microscopy (Cryo-TEM) and Energy Filtering TEM images (EFTEM) hampered by the noisy nature of these images, so that their alignment becomes so difficult. This noise refers to the collision between the frozen hydrated biological samples and the electrons beam, where the specimen is exposed to the radiation with a high exposure time. This sensitivity to the electrons beam led specialists to obtain the specimen projection images at very low exposure time, which resulting the emergence of a new problem, an extremely low signal-to-noise ratio (SNR). This paper investigates the problem of TEM images denoising when they are acquired at very low exposure time. So, our main objective is to enhance the quality of TEM images to improve the alignment process which will in turn improve the three dimensional tomography reconstructions. We have done multiple tests on special TEM images acquired at different exposure time 0.5s, 0.2s, 0.1s and 1s (i.e. with different values of SNR)) and equipped by Golding beads for helping us in the assessment step. We herein, propose a structure to combine multiple noisy copies of the TEM images. The structure is based on four different denoising methods, to combine the multiple noisy TEM images copies. Namely, the four different methods are Soft, the Hard as Wavelet-Thresholding methods, Bilateral Filter as a non-linear technique able to maintain the edges neatly, and the Bayesian approach in the wavelet domain, in which context modeling is used to estimate the parameter for each coefficient. To ensure getting a high signal-to-noise ratio, we have guaranteed that we are using the appropriate wavelet family at the appropriate level. So we have chosen âĂIJsym8âĂİ wavelet at level 3 as the most appropriate parameter. Whereas, for the bilateral filtering many tests are done in order to determine the proper filter parameters represented by the size of the filter, the range parameter and the
NASA Astrophysics Data System (ADS)
Nguyen, C.; Chandra, C. V.
2014-12-01
The separation of radar signatures depicting cloud and drizzle within a pulse radar volume is a fundamental problem whose solution is required to decouple the microphysical and dynamical processes introduced by turbulence. Such a solution would lead to the development of new meteorological products.In this presentation, a method to detect, separate and estimate multiple radar echoes from cloud and drizzle obtained from vertically pointing cloud Doppler spectra is described. In the case when only clouds are present, the Doppler spectrum is symmetrical and is well approximated by a Gaussian. To extract cloud echoes, a parametric maximum likelihood estimator in the time domain is employed using the recorded radar Doppler spectra data. To detect skewness in the radar spectrum, goodness of fit parameters are defined. It is shown that these new detection parameters exhibit a low level sensitivity to poor signal-to-noise ratios and large signal spectrum widths. The proposed method can consequently be applied to signals with shorter integration time; this significantly reduces the impact of small-scale dynamics present in the Doppler spectrum. Additionally, signals near the cloud top and cloud base are used as constraints to optimize the detection and estimation algorithm's performance.The applications of the technique include inference of the vertical air motion and the particle size distribution of the drizzle. The method will be tested on datasets that have been collected by the ARM cloud radars.
Non-parametric causal assessment in deep-time geological records
NASA Astrophysics Data System (ADS)
Agasøster Haaga, Kristian; Diego, David; Brendryen, Jo; Hannisdal, Bjarte
2016-04-01
The interplay between climate variables and the timing of their feedback mechanisms are typically investigated using fully coupled climate system models. However, as we delve deeper into the geological past, mechanistic process models become increasingly uncertain, making nonparametric approaches more attractive. Here we explore the use of two conceptually different methods for nonparametric causal assessment in palaeoenvironmental archives of the deep past: convergent cross mapping (CCM) and information transfer (IT). These methods have the potential to capture interactions in complex systems even when data are sparse and noisy, which typically characterises geological proxy records. We apply these methods to proxy time series that capture interlinked components of the Earth system at different temporal scales, and quantify both the interaction strengths and the feedback lags between the variables. Our examples include the linkage between the ecological prominence of common planktonic species to oceanographic changes over the last ~65 million years, and global interactions and teleconnections within the climate system during the last ~800,000 years.
NASA Astrophysics Data System (ADS)
Sayadi, Taraneh; Schmid, Peter J.; Richecoeur, Franck; Durox, Daniel
2015-03-01
Dynamic mode decomposition (DMD) belongs to a class of data-driven decomposition techniques, which extracts spatial modes of a constant frequency from a given set of numerical or experimental data. Although the modal shapes and frequencies are a direct product of the decomposition technique, the determination of the respective modal amplitudes is non-unique. In this study, we introduce a new algorithm for defining these amplitudes, which is capable of capturing physical growth/decay rates of the modes within a transient signal and is otherwise not straightforward using the standard DMD algorithm. In addition, a parametric DMD algorithm is introduced for studying dynamical systems going through a bifurcation. The parametric DMD alleviates multiple applications of the DMD decomposition to the system with fixed parametric values by including the bifurcation parameter in the decomposition process. The parametric DMD with amplitude correction is applied to a numerical and experimental data sequence taken from thermo-acoustically unstable systems. Using DMD with amplitude correction, we are able to identify the dominant modes of the transient regime and their respective growth/decay rates leading to the final limit-cycle. In addition, by applying parametrized DMD to images of an oscillating flame, we are able to identify the dominant modes of the bifurcation diagram.
Time- and power-dependent operation of a parametric spin-wave amplifier
Brächer, T.; Heussner, F.; Pirro, P.; Fischer, T.; Geilen, M.; Heinz, B.; Lägel, B.; Serga, A. A.; Hillebrands, B.
2014-12-08
We present the experimental observation of the localized amplification of externally excited, propagating spin waves in a transversely in-plane magnetized Ni{sub 81}Fe{sub 19} magnonic waveguide by means of parallel pumping. By employing microfocussed Brillouin light scattering spectroscopy, we analyze the dependency of the amplification on the applied pumping power and on the delay between the input spin-wave packet and the pumping pulse. We show that there are two different operation regimes: At large pumping powers, the spin-wave packet needs to enter the amplifier before the pumping is switched on in order to be amplified while at low powers the spin-wave packet can arrive at any time during the pumping pulse.
Lucero-Acuña, Armando; Guzmán, Roberto
2015-10-15
A mathematical model of drug release that incorporates the simultaneous contributions of initial burst, nanoparticle degradation-relaxation and diffusion was developed and used to effectively describe the release of a kinase inhibitor and anticancer drug, PHT-427. The encapsulation of this drug into PLGA nanoparticles was performed by following the single emulsion-solvent evaporation technique and the release was determined in phosphate buffer pH 7.4 at 37 °C. The size of nanoparticles was obtained in a range of 162-254 nm. The experimental release profiles showed three well defined phases: an initial fast drug release, followed by a nanoparticle degradation-relaxation slower release and then a diffusion release phase. The effects of the controlled release most relevant parameters such as drug diffusivity, initial burst constant, nanoparticle degradation-relaxation constant, and the time to achieve a maximum rate of drug release were evaluated by a parametrical analysis. The theoretical release studies were corroborated experimentally by evaluating the cytotoxicity effectiveness of the inhibitor AKT/PDK1 loaded nanoparticles over BxPC-3 pancreatic cancer cells in vitro. These studies show that the encapsulated inhibitor AKT/PDK1 in the nanoparticles is more accessible and thus more effective when compared with the drug alone, indicating their potential use in chemotherapeutic applications. PMID:26216413
Freitez, Juan A.; Sanchez, Morella; Ruette, Fernando
2009-08-13
Application of simulated annealing (SA) and simplified GSA (SGSA) techniques for parameter optimization of parametric quantum chemistry method (CATIVIC) was performed. A set of organic molecules were selected for test these techniques. Comparison of the algorithms was carried out for error function minimization with respect to experimental values. Results show that SGSA is more efficient than SA with respect to computer time. Accuracy is similar in both methods; however, there are important differences in the final set of parameters.
Analysis and Parametric Investigation of Active Open Cross Section Thin Wall Beams
NASA Astrophysics Data System (ADS)
Griffiths, James
The static behaviour of active Open Cross Section Thin Wall Beams (OCSTWB) with embedded Active/Macro Fibre Composites (AFCs/MFCs) has been investigated for the purpose of advancing the fundamental theory needed in the development of advanced smart structures. An efficient code that can analyze active OCSTWB using analytical equations has been studied. Various beam examples have been investigated in order to verify this recently developed analytical active OCSTWB analysis tool. The cross sectional stiffness constants and induced force, moments and bimoment predicted by this analytical code have been compared with those predicted by the 2-D finite element beam cross section analysis codes called the Variational Asymptotic Beam Sectional (VABS) analysis and the University of Michigan VABS (UM/VABS). Good agreement was observed between the results obtained from the analytical tool and VABS. The calculated cross sectional stiffness constants and induced force/moments, the constitutive relation and the six intrinstic static equilibrium equations for OCSTWB were all used together in a first-order accurate forward difference scheme in order to determine the average twist and deflections along the beam span. In order to further verify the analytical code, the static behaviour of a number of beam examples was investigated using 3-D Finite Element Analysis (FEA). For a particular cross section, the rigid body twist and displacements were minimized with the displacements of all the nodes in the 3-D FEA model that compose the cross section. This was done for a number of cross sections along the beam span in order to recover the global beam twist and displacement profiles from the 3-D FEA results. The global twist and deflections predicted by the analytical code agreed closely with those predicted by UM/VABS and 3-D FEA. The study was completed by a parametric investigation to determine the boundary conditions and the composite ply lay-ups of the active and passive plies that
Quantum analysis of the nondegenerate optical parametric oscillator with injected signal
Coutinho dos Santos, B.; Dechoum, K.; Khoury, A.Z.; Silva, L.F. da; Olsen, M.K.
2005-09-15
In this paper we study the nondegenerate optical parametric oscillator with injected signal, both analytically and numerically. We develop a perturbation approach which allows us to find approximate analytical solutions, starting from the full equations of motion in the positive-P representation. We demonstrate the regimes of validity of our approximations via comparison with the full stochastic results. We find that, with reasonably low levels of injected signal, the system allows for demonstrations of quantum entanglement and the Einstein-Podolsky-Rosen paradox. In contrast to the normal optical parametric oscillator operating below threshold, these features are demonstrated with relatively intense fields.
NASA Technical Reports Server (NTRS)
Prudhomme, C.; Rovas, D. V.; Veroy, K.; Machiels, L.; Maday, Y.; Patera, A. T.; Turinici, G.; Zang, Thomas A., Jr. (Technical Monitor)
2002-01-01
We present a technique for the rapid and reliable prediction of linear-functional outputs of elliptic (and parabolic) partial differential equations with affine parameter dependence. The essential components are (i) (provably) rapidly convergent global reduced basis approximations, Galerkin projection onto a space W(sub N) spanned by solutions of the governing partial differential equation at N selected points in parameter space; (ii) a posteriori error estimation, relaxations of the error-residual equation that provide inexpensive yet sharp and rigorous bounds for the error in the outputs of interest; and (iii) off-line/on-line computational procedures, methods which decouple the generation and projection stages of the approximation process. The operation count for the on-line stage, in which, given a new parameter value, we calculate the output of interest and associated error bound, depends only on N (typically very small) and the parametric complexity of the problem; the method is thus ideally suited for the repeated and rapid evaluations required in the context of parameter estimation, design, optimization, and real-time control.
NASA Astrophysics Data System (ADS)
McKenna, C.; Berx, B.; Austin, W. E. N.
2016-01-01
The Faroe-Shetland Channel (FSC) is an important conduit for the poleward flow of Atlantic water towards the Nordic Seas and, as such, it plays an integral part in the Atlantic's thermohaline circulation. Mixing processes in the FSC are thought to result in an exchange of properties between the channel's inflow and outflow, with wider implications for this circulation; the nature of this mixing in the FSC is, however, uncertain. To constrain this uncertainty, we used a novel empirical method known as Parametric Optimum Multi-Parameter (POMP) analysis to objectively quantify the distribution of water masses in the channel in May 2013. This was achieved by using a combination of temperature and salinity measurements, as well as recently available nutrient and δ18O measurements. The outcomes of POMP analysis are in good agreement with established literature and demonstrate the benefits of representing all five water masses in the FSC. In particular, our results show the recirculation of Modified North Atlantic Water in the surface layers, and the pathways of Norwegian Sea Arctic Intermediate Water and Norwegian Sea Deep Water from north to south for the first time. In a final step, we apply the mixing fractions from POMP analysis to decompose the volume transport through the FSC by water mass. Despite a number of caveats, our study suggests that improved estimates of the volume transport of Atlantic inflow towards the Arctic and, thus, the associated poleward fluxes of salt and heat are possible. A new prospect to more accurately monitor the strength of the FSC branch of the thermohaline circulation emerges from this study.
[Non-Parametric Analysis of Radiation Risks of Mortality among Chernobyl Clean-Up Workers].
Gorsky, A I; Maksioutov, M A; Tumanov, K A; Shchukina, N V; Chekin, S Yu; Ivanov, V K
2016-01-01
Analysis of the relationship between dose and mortality from cancer and circulation diseases in the cohort of Chernobyl clean-up workers based on the data from the National Radiation and Epidemiological Registry was performed. Medical and dosimetry information on the clean-up workers, males, who got radiation doses from April 26, 1986 to April 26, 1987, which was accumulated from 1992 to 2012, was used for the analysis. The total size of the cohort was 42929 people, 12731 deaths were registered in the cohort, among them 1893 deaths from solid cancers and 5230 deaths were from circulation diseases. An average age of the workers was 39 years in 1992 and the mean dose was 164 mGy. The dose-effect relationship was estimated with the use of non-parametric analysis of survival with regard to concurrence of risks of mortality. The risks were estimated in 6 dose groups of similar size (1-70, 70-130, 130-190, 190-210, 210-230 and.230-1000 mGy). The group "1-70 mGy" was used as control. Estimated dose-effect relationship related to cancers and circulation diseases is described approximately with a linear model, coefficient of determination (the proportion of variability explained by the linear model) for cancers was 23-25% and for circulation diseases - 2-13%. The slope coefficient of the dose-effect relationship normalized to 1 Gy for the ratio of risks for cancers in the linear model was 0.47 (95% CI: -0.77, 1.71), and for circulation diseases it was 0.22 (95% CI: -0.58, 1.02). Risks coefficient (slope coefficient of excess mortality at a dose of 1 Gy) for solid cancers was 1.94 (95% CI: - 3.10, 7.00) x 10(-2) and for circulation diseases it was 0.67 (95% CI: -9.61, 11.00) x 10(-2). 137 deaths from radiation-induced cancers and 47 deaths from circulation diseases were registered during a follow up period. PMID:27534064
ERIC Educational Resources Information Center
Olejnik, Stephen F.; Algina, James
The present investigation developed power curves for two parametric and two nonparametric procedures for testing the equality of population variances. Both normal and non-normal distributions were considered for the two group design with equal and unequal sample frequencies. The results indicated that when population distributions differed only in…
Rasch analysis for the evaluation of rank of student response time in multiple choice examinations.
Thompson, James J; Yang, Tong; Chauvin, Sheila W
2013-01-01
The availability of computerized testing has broadened the scope of person assessment beyond the usual accuracy-ability domain to include response time analyses. Because there are contexts in which speed is important, e.g. medical practice, it is important to develop tools by which individuals can be evaluated for speed. In this paper, the ability of Rasch measurement to convert ordinal nonparametric rankings of speed to measures is examined and compared to similar measures derived from parametric analysis of response times (pace) and semi-parametric logarithmic time-scaling procedures. Assuming that similar spans of the measures were used, non-parametric methods of raw ranking or percentile-ranking of persons by questions gave statistically acceptable person estimates of speed virtually identical to the parametric or semi-parametric methods. Because no assumptions were made about the underlying time distributions with ranking, generality of conclusions was enhanced. The main drawbacks of the non-parametric ranking procedures were the lack of information on question duration and the overall assignment by the model of variance to the person by question interaction. PMID:24064578
Sava, H; Durand, L G; Cloutier, G
1999-05-01
To achieve an accurate estimation of the instantaneous turbulent velocity fluctuations downstream of prosthetic heart valves in vivo, the variability of the spectral method used to measure the mean frequency shift of the Doppler signal (i.e. the Doppler velocity) should be minimised. This paper investigates the performance of various short-time spectral parametric methods such as the short-time Fourier transform, autoregressive modelling based on two different approaches, autoregressive moving average modelling based on the Steiglitz-McBride method, and Prony's spectral method. A simulated Doppler signal was used to evaluate the performance of the above mentioned spectral methods and Gaussian noise was added to obtain a set of signals with various signal-to-noise ratios. Two different parameters were used to evaluate the performance of each method in terms of variability and accurate matching of the theoretical Doppler mean instantaneous frequency variation within the cardiac cycle. Results show that autoregressive modelling outperforms the other investigated spectral techniques for window lengths varying between 1 and 10 ms. Among the autoregressive algorithms implemented, it is shown that the maximum entropy method based on a block data processing technique gives the best results for a signal-to-noise ratio of 20 dB. However, at 10 and 0 dB, the Levinson-Durbin algorithm surpasses the performance of the maximum entropy method. It is expected that the intrinsic variance of the spectral methods can be an important source of error for the estimation of the turbulence intensity. The range of this error varies from 0.38% to 24% depending on the parameters of the spectral method and the signal-to-noise ratio. PMID:10505377
Parametric number covariance in quantum chaotic spectra
NASA Astrophysics Data System (ADS)
Vinayak, Kumar, Sandeep; Pandey, Akhilesh
2016-03-01
We study spectral parametric correlations in quantum chaotic systems and introduce the number covariance as a measure of such correlations. We derive analytic results for the classical random matrix ensembles using the binary correlation method and obtain compact expressions for the covariance. We illustrate the universality of this measure by presenting the spectral analysis of the quantum kicked rotors for the time-reversal invariant and time-reversal noninvariant cases. A local version of the parametric number variance introduced earlier is also investigated.
Parametric number covariance in quantum chaotic spectra.
Vinayak; Kumar, Sandeep; Pandey, Akhilesh
2016-03-01
We study spectral parametric correlations in quantum chaotic systems and introduce the number covariance as a measure of such correlations. We derive analytic results for the classical random matrix ensembles using the binary correlation method and obtain compact expressions for the covariance. We illustrate the universality of this measure by presenting the spectral analysis of the quantum kicked rotors for the time-reversal invariant and time-reversal noninvariant cases. A local version of the parametric number variance introduced earlier is also investigated. PMID:27078354
NASA Astrophysics Data System (ADS)
Dang, Wei; Mao, Pengcheng; Weng, Yuxiang
2013-07-01
We report an improved setup of femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS) with a 210 fs temporal response. The system employs a Cassegrain objective to collect and focus fluorescence photons, which eliminates the interference from the coherent photons in the fluorescence amplification by temporal separation of the coherent photons and the fluorescence photons. The gain factor of the Cassegrain objective-assisted FNOPAS is characterized as 1.24 × 105 for Rhodamine 6G. Spectral corrections have been performed on the transient fluorescence spectra of Rhodamine 6G and Rhodamine 640 in ethanol by using an intrinsic calibration curve derived from the spectrum of superfluorescence, which is generated from the amplification of the vacuum quantum noise. The validity of spectral correction is illustrated by comparisons of spectral shape and peak wavelength between the corrected transient fluorescence spectra of these two dyes acquired by FNOPAS and their corresponding standard reference spectra collected by the commercial streak camera. The transient fluorescence spectra of the Rhodamine 6G were acquired in an optimized phase match condition, which gives a deviation in the peak wavelength between the retrieved spectrum and the reference spectrum of 1.0 nm, while those of Rhodamine 640 were collected in a non-optimized phase match condition, leading to a deviation in a range of 1.0-3.0 nm. Our results indicate that the improved FNOPAS can be a reliable tool in the measurement of transient fluorescence spectrum for its high temporal resolution and faithfully corrected spectrum.
Parametric Analysis of a Hover Test Vehicle using Advanced Test Generation and Data Analysis
NASA Technical Reports Server (NTRS)
Gundy-Burlet, Karen; Schumann, Johann; Menzies, Tim; Barrett, Tony
2009-01-01
Large complex aerospace systems are generally validated in regions local to anticipated operating points rather than through characterization of the entire feasible operational envelope of the system. This is due to the large parameter space, and complex, highly coupled nonlinear nature of the different systems that contribute to the performance of the aerospace system. We have addressed the factors deterring such an analysis by applying a combination of technologies to the area of flight envelop assessment. We utilize n-factor (2,3) combinatorial parameter variations to limit the number of cases, but still explore important interactions in the parameter space in a systematic fashion. The data generated is automatically analyzed through a combination of unsupervised learning using a Bayesian multivariate clustering technique (AutoBayes) and supervised learning of critical parameter ranges using the machine-learning tool TAR3, a treatment learner. Covariance analysis with scatter plots and likelihood contours are used to visualize correlations between simulation parameters and simulation results, a task that requires tool support, especially for large and complex models. We present results of simulation experiments for a cold-gas-powered hover test vehicle.
Robust biological parametric mapping: an improved technique for multimodal brain image analysis
NASA Astrophysics Data System (ADS)
Yang, Xue; Beason-Held, Lori; Resnick, Susan M.; Landman, Bennett A.
2011-03-01
Mapping the quantitative relationship between structure and function in the human brain is an important and challenging problem. Numerous volumetric, surface, region of interest and voxelwise image processing techniques have been developed to statistically assess potential correlations between imaging and non-imaging metrics. Recently, biological parametric mapping has extended the widely popular statistical parametric approach to enable application of the general linear model to multiple image modalities (both for regressors and regressands) along with scalar valued observations. This approach offers great promise for direct, voxelwise assessment of structural and functional relationships with multiple imaging modalities. However, as presented, the biological parametric mapping approach is not robust to outliers and may lead to invalid inferences (e.g., artifactual low p-values) due to slight mis-registration or variation in anatomy between subjects. To enable widespread application of this approach, we introduce robust regression and robust inference in the neuroimaging context of application of the general linear model. Through simulation and empirical studies, we demonstrate that our robust approach reduces sensitivity to outliers without substantial degradation in power. The robust approach and associated software package provides a reliable way to quantitatively assess voxelwise correlations between structural and functional neuroimaging modalities.
Yu, Jintao; Liang, Yi; Thompson, Simon; Cull, Grant; Wang, Lin
2014-01-01
The aim of the study was to establish a parametric transfer function to describe the relationship between ocular perfusion pressure (OPP) and blood flow (BF) in the optic nerve head (ONH). A third-order parametric theoretical model was proposed to describe the ONH OPP-BF relationship within the lower OPP range of the autoregulation curve (< 80 mmHg) based on experimentally induced BF response to a rapid intraocular pressure (IOP) increase in 6 rhesus monkeys. The theoretical and actual data fitted well and suggest that this parametric third-order transfer function can effectively describe both the linear and nonlinear feature in dynamic and static autoregulation in the ONH within the OPP range studied. It shows that the BF autoregulation fully functions when the OPP was > 40 mmHg and becomes incomplete when the OPP was < 40 mmHg. This model may be used to help investigating the features of autoregulation in the ONH under different experimental conditions. PMID:24665355
Brace, Christopher L.
2011-01-01
Purpose: Design and validate an efficient dual-slot coaxial microwave ablation antenna that produces an approximately spherical heating pattern to match the shape of most abdominal and pulmonary tumor targets.Methods: A dual-slot antenna geometry was utilized for this study. Permutations of the antenna geometry using proximal and distal slot widths from 1 to 10 mm separated by 1–20 mm were analyzed using finite-element electromagnetic simulations. From this series, the most optimal antenna geometry was selected using a two-term sigmoidal objective function to minimize antenna reflection coefficient and maximize the diameter-to-length aspect ratio of heat generation. Sensitivities to variations in tissue properties and insertion depth were also evaluated in numerical models. The most optimal dual-slot geometry of the parametric analysis was then fabricated from semirigid coaxial cable. Antenna reflection coefficients at various insertion depths were recorded in ex vivo bovine livers and compared to numerical results. Ablation zones were then created by applying 50 W for 2–10 min in simulations and ex vivo livers. Mean zone diameter, length, aspect ratio, and reflection coefficients before and after heating were then compared to a conventional monopole antenna using ANOVA with post-hoc t-tests. Statistical significance was indicated for P < 0.05.Results: Antenna performance was highly sensitive to dual-slot geometry. The best-performing designs utilized a proximal slot width of 1 mm, distal slot width of 4 mm ± 1 mm and separation of 8 mm ± 1 mm. These designs were characterized by an active choking mechanism that focused heating to the distal tip of the antenna. A dual-band resonance was observed in the most optimal design, with a minimum reflection coefficient of −20.9 dB at 2.45 and 1.25 GHz. Total operating bandwidth was greater than 1 GHz, but the desired heating pattern was achieved only near 2.45 GHz. As a result, antenna performance was
NASA Technical Reports Server (NTRS)
Halt, D. W.; Harris, W. L.
1982-01-01
The results reported here are based on applying the method of parametric differentiation (MPD) to transform the nonlinear differential equation governing small-disturbance transonic flow to a linear equation. Implicit approximate factorization and monotone methods were used to accelerate convergence of the linear problem by an order of magnitude over successive line over-relaxation. The relative merits of using MPD are discussed in comparison to conventional small-disturbance applications. Several MPD analyses are performed on an array of airfoils. A design procedure utilizing MPD is discussed and demonstrated for two nonlifting cases.
Non-parametric trend analysis of water quality data of rivers in Kansas
NASA Astrophysics Data System (ADS)
Yu, Yun-Sheng; Zou, Shimin; Whittemore, Donald
1993-09-01
Surface water quality data for 15 sampling stations in the Arkansas, Verdigris, Neosho, and Walnut river basins inside the state of Kansas were analyzed to detect trends (or lack of trends) in 17 major constituents by using four different non-parametric methods. The results show that concentrations of specific conductance, total dissolved solids, calcium, total hardness, sodium, potassium, alkalinity, sulfate, chloride, total phosphorus, ammonia plus organic nitrogen, and suspended sediment generally have downward trends. Some of the downward trends are related to increases in discharge, while others could be caused by decreases in pollution sources. Homogeneity tests show that both station-wide trends and basinwide trends are non-homogeneous.
Parametric thermodynamic analysis of closed-cycle gas-laser operation in space
NASA Technical Reports Server (NTRS)
Burns, R. K.
1974-01-01
Cycle efficiency and radiator area required were calculated for thermally and electrically pumped lasers operating in closed cycles with a compressor and the required heat exchangers. A thermally pumped laser included within a Brayton cycle was also analyzed. Performance of all components, including the laser, was parametrically varied. For the thermally pumped laser the cycle efficiencies range below 10 percent and are very sensitive to the high-pressure losses associated with the supersonic diffuser required at the laser cavity exit. The efficiencies predicted for the electrically pumped laser cycles range slightly higher, but radiator area also tends to be larger.
Permutations and time series analysis.
Cánovas, Jose S; Guillamón, Antonio
2009-12-01
The main aim of this paper is to show how the use of permutations can be useful in the study of time series analysis. In particular, we introduce a test for checking the independence of a time series which is based on the number of admissible permutations on it. The main improvement in our tests is that we are able to give a theoretical distribution for independent time series. PMID:20059199
Parametric Analysis of Cyclic Phase Change and Energy Storage in Solar Heat Receivers
NASA Technical Reports Server (NTRS)
Hall, Carsie A., III; Glakpe, Emmanuel K.; Cannon, Joseph N.; Kerslake, Thomas W.
1997-01-01
A parametric study on cyclic melting and freezing of an encapsulated phase change material (PCM), integrated into a solar heat receiver, has been performed. The cyclic nature of the present melt/freeze problem is relevant to latent heat thermal energy storage (LHTES) systems used to power solar Brayton engines in microgravity environments. Specifically, a physical and numerical model of the solar heat receiver component of NASA Lewis Research Center's Ground Test Demonstration (GTD) project was developed. Multi-conjugate effects such as the convective fluid flow of a low-Prandtl-number fluid, coupled with thermal conduction in the phase change material, containment tube and working fluid conduit were accounted for in the model. A single-band thermal radiation model was also included to quantify reradiative energy exchange inside the receiver and losses through the aperture. The eutectic LiF-CaF2 was used as the phase change material (PCM) and a mixture of He/Xe was used as the working fluid coolant. A modified version of the computer code HOTTube was used to generate results in the two-phase regime. Results indicate that parametric changes in receiver gas inlet temperature and receiver heat input effects higher sensitivity to changes in receiver gas exit temperatures.
A parametric shell analysis of the shuttle 51-L SRB AFT field joint
NASA Technical Reports Server (NTRS)
Davis, Randall C.; Bowman, Lynn M.; Hughes, Robert M., IV; Jackson, Brian J.
1990-01-01
Following the Shuttle 51-L accident, an investigation was conducted to determine the cause of the failure. Investigators at the Langley Research Center focused attention on the structural behavior of the field joints with O-ring seals in the steel solid rocket booster (SRB) cases. The shell-of-revolution computer program BOSOR4 was used to model the aft field joint of the solid rocket booster case. The shell model consisted of the SRB wall and joint geometry present during the Shuttle 51-L flight. A parametric study of the joint was performed on the geometry, including joint clearances, contact between the joint components, and on the loads, induced and applied. In addition combinations of geometry and loads were evaluated. The analytical results from the parametric study showed that contact between the joint components was a primary contributor to allowing hot gases to blow by the O-rings. Based upon understanding the original joint behavior, various proposed joint modifications are shown and analyzed in order to provide additional insight and information. Finally, experimental results from a hydro-static pressurization of a test rocket booster case to study joint motion are presented and verified analytically.
Robust non-parametric one-sample tests for the analysis of recurrent events.
Rebora, Paola; Galimberti, Stefania; Valsecchi, Maria Grazia
2010-12-30
One-sample non-parametric tests are proposed here for inference on recurring events. The focus is on the marginal mean function of events and the basis for inference is the standardized distance between the observed and the expected number of events under a specified reference rate. Different weights are considered in order to account for various types of alternative hypotheses on the mean function of the recurrent events process. A robust version and a stratified version of the test are also proposed. The performance of these tests was investigated through simulation studies under various underlying event generation processes, such as homogeneous and nonhomogeneous Poisson processes, autoregressive and renewal processes, with and without frailty effects. The robust versions of the test have been shown to be suitable in a wide variety of event generating processes. The motivating context is a study on gene therapy in a very rare immunodeficiency in children, where a major end-point is the recurrence of severe infections. Robust non-parametric one-sample tests for recurrent events can be useful to assess efficacy and especially safety in non-randomized studies or in epidemiological studies for comparison with a standard population. PMID:21170908
Modeling personnel turnover in the parametric organization
NASA Technical Reports Server (NTRS)
Dean, Edwin B.
1991-01-01
A model is developed for simulating the dynamics of a newly formed organization, credible during all phases of organizational development. The model development process is broken down into the activities of determining the tasks required for parametric cost analysis (PCA), determining the skills required for each PCA task, determining the skills available in the applicant marketplace, determining the structure of the model, implementing the model, and testing it. The model, parameterized by the likelihood of job function transition, has demonstrated by the capability to represent the transition of personnel across functional boundaries within a parametric organization using a linear dynamical system, and the ability to predict required staffing profiles to meet functional needs at the desired time. The model can be extended by revisions of the state and transition structure to provide refinements in functional definition for the parametric and extended organization.
NASA Astrophysics Data System (ADS)
Cosmidis, J.; Heggy, E.; Clifford, S. M.
2007-12-01
Laboratory dielectric characterizations of Ice-dust mixtures are crucial for the quantitative analysis of radar sounding data as for the case of the MARSIS and SHARAD experiments. Understanding the range of the dielectric properties of the Martian northmen Polar layer deposits as well as their geographical an vertical distribution result in a better topographical mapping of the basement material below the northern polar cap and help constrain the ambiguities on the identification of layering and any potential subglaciar melting. In order to achieve this task, we constructed first order modeled maps of the surface dielectric properties oh the NPLD. We first used the recent Mars Global Surveyor Thermal Emission Spectrometer (TES) thermal inertia observations in order to derive a map of the dust mass fraction in the ice at the top of the permanent cap. Then we used parametric laboratory measurements of the dielectric properties of Martian polar ice analogs with various temperatures, radar frequencies and mass fractions and compositions of dust in order to obtain the parametric dielectric maps. Thermal inertia maps have been derived from recent TES observations of the surface temperatures of Mars taken over three Mars-years from orbit 1583 to 24346. Laboratory dielectric characterization of ice-dust mixtures has been performed using TES dust calibration samples provided by the ARES group at NASA JSC. Our Maps suggest that surface dielectric properties of the northern Polar cap ranges from 2.72 to 3.23 in the 2-20 MHz band for a dust inclusion typical of Martian basalt. Parametric maps of loss tangent, penetration depth for several dust types will be presented at the conference.
Eberhard, B.J.; Harbour, J.R.; Plodinec, M.J.
1994-06-01
As part of the DWPF Startup Test Program, a parametric study has been performed to determine a range of welder operating parameters which will produce acceptable final welds for canistered waste forms. The parametric window of acceptable welds defined by this study is 90,000 {plus_minus} 15,000 lb of force, 248,000 {plus_minus} 22,000 amps of current, and 95 {plus_minus} 15 cycles (@ 60 cops) for the time of application of the current.
Plodinec, M.J.
1998-11-20
After being filled with glass, DWPF canistered waste forms will be welded closed using an upset resistance welding process. This final closure weld must be leaktight, and must remain so during extended storage at SRS. As part of the DWPF Startup Test Program, a parametric study (DWPF-WP-24) has been performed to determine a range of welder operating parameters which will produce acceptable welds. The parametric window of acceptable welds defined by this study is 90,000 + 15,000 lb of force, 248,000 + 22,000 amps of current, and 95 + 15 cycles* for the time of application of the current.
NASA Astrophysics Data System (ADS)
Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang
2015-12-01
Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300-1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10-5M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.
Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang
2015-12-15
Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300–1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10{sup −5}M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.
Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang
2015-12-01
Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300-1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10(-5)M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process. PMID:26724012
Zhang, W.; Casademunt, J.; Vinals, J. )
1993-12-01
A stochastic formulation is introduced to study the large amplitude and high-frequency components of residual accelerations found in a typical microgravity environment (or [ital g]-jitter). The linear response of a fluid surface to such residual accelerations is discussed in detail. The analysis of the stability of a free fluid surface can be reduced in the underdamped limit to studying the equation of the parametric harmonic oscillator for each of the Fourier components of the surface displacement. A narrow-band noise is introduced to describe a realistic spectrum of accelerations, that interpolates between white noise and monochromatic noise. Analytic results for the stability of the second moments of the stochastic parametric oscillator are presented in the limits of low-frequency oscillations, and near the region of subharmonic parametric resonance. Based upon simple physical considerations, an explicit form of the stability boundary valid for arbitrary frequencies is proposed, which interpolates smoothly between the low frequency and the near resonance limits with no adjustable parameter, and extrapolates to higher frequencies. A second-order numerical algorithm has also been implemented to simulate the parametric stochastic oscillator driven with narrow-band noise. The simulations are in excellent agreement with our theoretical predictions for a very wide range of noise parameters. The validity of previous approximate theories for the particular case of Ornstein--Uhlenbeck noise is also checked numerically. Finally, the results obtained are applied to typical microgravity conditions to determine the characteristic wavelength for instability of a fluid surface as a function of the intensity of residual acceleration and its spectral width.
NASA Astrophysics Data System (ADS)
Allan, Alasdair
2014-06-01
FROG performs time series analysis and display. It provides a simple user interface for astronomers wanting to do time-domain astrophysics but still offers the powerful features found in packages such as PERIOD (ascl:1406.005). FROG includes a number of tools for manipulation of time series. Among other things, the user can combine individual time series, detrend series (multiple methods) and perform basic arithmetic functions. The data can also be exported directly into the TOPCAT (ascl:1101.010) application for further manipulation if needed.
Open cycle OTEC thermal-hydraulic systems analysis and parametric studies
NASA Astrophysics Data System (ADS)
Patsons, B.; Bharathan, D.; Althof, J.
1984-06-01
An analytic thermohydraulic systems model of the power cycle an seawater supply systems for an open cycle ocean thermal energy conversion (OTEC) plant has been developed that allows ready examination of the effects of system and component operating points on plant size and parasitic power requirements. This paper presents the results of three parametric studies on the effects of system temperature distribution, plant gross electric capacity, and the allowable seawater velocity in the supply and discharge pipes. The paper also briefly discusses the assumptions and equations used in the model and the state-of-the-art component limitations. The model provides a useful tool for an OTEC plant designer to evaluate system trade-offs and define component interactions and performance.
NASA Technical Reports Server (NTRS)
To, Wing H.
2005-01-01
Quantum optical experiments require all the components involved to be extremely stable relative to each other. The stability can be "measured" by using an interferometric experiment. A pair of coherent photons produced by parametric down-conversion could be chosen to be orthogonally polarized initially. By rotating the polarization of one of the wave packets, they can be recombined at a beam splitter such that interference will occur. Theoretically, the interference will create four terms in the wave function. Two terms with both photons going to the same detector, and two terms will have the photons each going to different detectors. However, the latter will cancel each other out, thus no photons will arrive at the two detectors simultaneously under ideal conditions. The stability Of the test-bed can then be inferred by the dependence of coincidence count on the rotation angle.
A parametric study of supersonic laminar flow for swept wings using linear stability analysis
NASA Technical Reports Server (NTRS)
Cummings, Russell M.; Garcia, Joseph A.; Tu, Eugene L.
1995-01-01
A parametric study to predict the extent of laminar flow on the upper surface of a generic swept-back wing (NACA 64A010 airfoil section) at supersonic speeds was conducted. The results were obtained by using surface pressure predictions from an Euler/Navier-Stokes computational fluid dynamics code coupled with a boundary layer code, which predicts detailed boundary layer profiles, and finally with a linear stability code to determine the extent of laminar flow. The parameters addressed are Reynolds number, angle of attack, and leading-edge wing sweep. The results of this study show that an increase in angle of attack, for specific Reynolds numbers, can actually delay transition. Therefore, higher lift capability, caused by the increased angle of attack, as well as a reduction in viscous drag due to the delay in transition is possible for certain flight conditions.
Parametric modeling for quantitative analysis of pulmonary structure to function relationships
NASA Astrophysics Data System (ADS)
Haider, Clifton R.; Bartholmai, Brian J.; Holmes, David R., III; Camp, Jon J.; Robb, Richard A.
2005-04-01
While lung anatomy is well understood, pulmonary structure-to-function relationships such as the complex elastic deformation of the lung during respiration are less well documented. Current methods for studying lung anatomy include conventional chest radiography, high-resolution computed tomography (CT scan) and magnetic resonance imaging with polarized gases (MRI scan). Pulmonary physiology can be studied using spirometry or V/Q nuclear medicine tests (V/Q scan). V/Q scanning and MRI scans may demonstrate global and regional function. However, each of these individual imaging methods lacks the ability to provide high-resolution anatomic detail, associated pulmonary mechanics and functional variability of the entire respiratory cycle. Specifically, spirometry provides only a one-dimensional gross estimate of pulmonary function, and V/Q scans have poor spatial resolution, reducing its potential for regional assessment of structure-to-function relationships. We have developed a method which utilizes standard clinical CT scanning to provide data for computation of dynamic anatomic parametric models of the lung during respiration which correlates high-resolution anatomy to underlying physiology. The lungs are segmented from both inspiration and expiration three-dimensional (3D) data sets and transformed into a geometric description of the surface of the lung. Parametric mapping of lung surface deformation then provides a visual and quantitative description of the mechanical properties of the lung. Any alteration in lung mechanics is manifest by alterations in normal deformation of the lung wall. The method produces a high-resolution anatomic and functional composite picture from sparse temporal-spatial methods which quantitatively illustrates detailed anatomic structure to pulmonary function relationships impossible for translational methods to provide.
Accelerating pulsar timing data analysis
NASA Astrophysics Data System (ADS)
van Haasteren, Rutger
2013-02-01
The analysis of pulsar timing data, especially in pulsar timing array (PTA) projects, has encountered practical difficulties: evaluating the likelihood and/or correlation-based statistics can become prohibitively computationally expensive for large data sets. In situations where a stochastic signal of interest has a power spectral density that dominates the noise in a limited bandwidth of the total frequency domain (e.g. the isotropic background of gravitational waves), a linear transformation exists that transforms the timing residuals to a basis in which virtually all the information about the stochastic signal of interest is contained in a small fraction of basis vectors. By only considering such a small subset of these `generalized residuals', the dimensionality of the data analysis problem is greatly reduced, which can cause a large speedup in the evaluation of the likelihood: the ABC-method (Acceleration By Compression). The compression fidelity, calculable with crude estimates of the signal and noise, can be used to determine how far a data set can be compressed without significant loss of information. Both direct tests on the likelihood, and Bayesian analysis of mock data, show that the signal can be recovered as well as with an analysis of uncompressed data. In the analysis of International PTA Mock Data Challenge data sets, speedups of a factor of 3 orders of magnitude are demonstrated. For realistic PTA data sets the acceleration may become greater than six orders of magnitude due to the low signal-to-noise ratio.
Hu, Leland S.; Ning, Shuluo; Eschbacher, Jennifer M.; Gaw, Nathan; Dueck, Amylou C.; Smith, Kris A.; Nakaji, Peter; Plasencia, Jonathan; Ranjbar, Sara; Price, Stephen J.; Tran, Nhan; Loftus, Joseph; Jenkins, Robert; O’Neill, Brian P.; Elmquist, William; Baxter, Leslie C.; Gao, Fei; Frakes, David; Karis, John P.; Zwart, Christine; Swanson, Kristin R.; Sarkaria, Jann; Wu, Teresa
2015-01-01
Background Genetic profiling represents the future of neuro-oncology but suffers from inadequate biopsies in heterogeneous tumors like Glioblastoma (GBM). Contrast-enhanced MRI (CE-MRI) targets enhancing core (ENH) but yields adequate tumor in only ~60% of cases. Further, CE-MRI poorly localizes infiltrative tumor within surrounding non-enhancing parenchyma, or brain-around-tumor (BAT), despite the importance of characterizing this tumor segment, which universally recurs. In this study, we use multiple texture analysis and machine learning (ML) algorithms to analyze multi-parametric MRI, and produce new images indicating tumor-rich targets in GBM. Methods We recruited primary GBM patients undergoing image-guided biopsies and acquired pre-operative MRI: CE-MRI, Dynamic-Susceptibility-weighted-Contrast-enhanced-MRI, and Diffusion Tensor Imaging. Following image coregistration and region of interest placement at biopsy locations, we compared MRI metrics and regional texture with histologic diagnoses of high- vs low-tumor content (≥80% vs <80% tumor nuclei) for corresponding samples. In a training set, we used three texture analysis algorithms and three ML methods to identify MRI-texture features that optimized model accuracy to distinguish tumor content. We confirmed model accuracy in a separate validation set. Results We collected 82 biopsies from 18 GBMs throughout ENH and BAT. The MRI-based model achieved 85% cross-validated accuracy to diagnose high- vs low-tumor in the training set (60 biopsies, 11 patients). The model achieved 81.8% accuracy in the validation set (22 biopsies, 7 patients). Conclusion Multi-parametric MRI and texture analysis can help characterize and visualize GBM’s spatial histologic heterogeneity to identify regional tumor-rich biopsy targets. PMID:26599106
2013-01-01
Background Stochastic modeling and simulation provide powerful predictive methods for the intrinsic understanding of fundamental mechanisms in complex biochemical networks. Typically, such mathematical models involve networks of coupled jump stochastic processes with a large number of parameters that need to be suitably calibrated against experimental data. In this direction, the parameter sensitivity analysis of reaction networks is an essential mathematical and computational tool, yielding information regarding the robustness and the identifiability of model parameters. However, existing sensitivity analysis approaches such as variants of the finite difference method can have an overwhelming computational cost in models with a high-dimensional parameter space. Results We develop a sensitivity analysis methodology suitable for complex stochastic reaction networks with a large number of parameters. The proposed approach is based on Information Theory methods and relies on the quantification of information loss due to parameter perturbations between time-series distributions. For this reason, we need to work on path-space, i.e., the set consisting of all stochastic trajectories, hence the proposed approach is referred to as “pathwise”. The pathwise sensitivity analysis method is realized by employing the rigorously-derived Relative Entropy Rate, which is directly computable from the propensity functions. A key aspect of the method is that an associated pathwise Fisher Information Matrix (FIM) is defined, which in turn constitutes a gradient-free approach to quantifying parameter sensitivities. The structure of the FIM turns out to be block-diagonal, revealing hidden parameter dependencies and sensitivities in reaction networks. Conclusions As a gradient-free method, the proposed sensitivity analysis provides a significant advantage when dealing with complex stochastic systems with a large number of parameters. In addition, the knowledge of the structure of the
NASA Technical Reports Server (NTRS)
Housner, J. M.; Stein, M.
1975-01-01
A computer program is presented which was developed for the combined compression and shear of stiffened variable thickness orthotropic composite panels on discrete springs: boundary conditions are general and include elastic boundary restraints. Buckling solutions are obtained by using a newly developed trigonometric finite difference procedure which improves the solution convergence rate over conventional finite difference methods. The classical general shear buckling results which exist only for simply supported panels over a limited range of orthotropic properties, were extended to the complete range of these properties for simply supported panels and, in addition, to the complete range of orthotropic properties for clamped panels. The program was also applied to parametric studies which examine the effect of filament orientation upon the buckling of graphite-epoxy panels. These studies included an examination of the filament orientations which yield maximum shear or compressive buckling strength for panels having all four edges simply supported or clamped over a wide range of aspect ratios. Panels with such orientations had higher buckling loads than comparable, equal weight, thin skinned aluminum panels. Also included among the parameter studies were examinations of combined axial compression and shear buckling and examinations of panels with rotational elastic edge restraints.
NASA Technical Reports Server (NTRS)
Masunaga, Hirohiko; Kummerow, Christian D.
2005-01-01
A methodology to analyze precipitation profiles using the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and precipitation radar (PR) is proposed. Rainfall profiles are retrieved from PR measurements, defined as the best-fit solution selected from precalculated profiles by cloud-resolving models (CRMs), under explicitly defined assumptions of drop size distribution (DSD) and ice hydrometeor models. The PR path-integrated attenuation (PIA), where available, is further used to adjust DSD in a manner that is similar to the PR operational algorithm. Combined with the TMI-retrieved nonraining geophysical parameters, the three-dimensional structure of the geophysical parameters is obtained across the satellite-observed domains. Microwave brightness temperatures are then computed for a comparison with TMI observations to examine if the radar-retrieved rainfall is consistent in the radiometric measurement space. The inconsistency in microwave brightness temperatures is reduced by iterating the retrieval procedure with updated assumptions of the DSD and ice-density models. The proposed methodology is expected to refine the a priori rain profile database and error models for use by parametric passive microwave algorithms, aimed at the Global Precipitation Measurement (GPM) mission, as well as a future TRMM algorithms.
NASA Astrophysics Data System (ADS)
Hartwig, Jason; Adin Mann, Jay; Darr, Samuel R.
2014-09-01
This paper presents the parametric investigation of the factors which govern screen channel liquid acquisition device bubble point pressure in a low pressure propellant tank. The five test parameters that were varied included the screen mesh, liquid cryogen, liquid temperature and pressure, and type of pressurant gas. Bubble point data was collected using three fine mesh 304 stainless steel screens in two different liquids (hydrogen and nitrogen), over a broad range of liquid temperatures and pressures in subcooled and saturated liquid states, using both a noncondensible (helium) and autogenous (hydrogen or nitrogen) gas pressurization scheme. Bubble point pressure scales linearly with surface tension, but does not scale inversely with the fineness of the mesh. Bubble point pressure increases proportional to the degree of subcooling. Higher bubble points are obtained using noncondensible pressurant gases over the condensable vapor. The bubble point model is refined using a temperature dependent pore diameter of the screen to account for screen shrinkage at reduced liquid temperatures and to account for relative differences in performance between the two pressurization schemes. The updated bubble point model can be used to accurately predict performance of LADs operating in future cryogenic propellant engines and cryogenic fuel depots.
NASA Astrophysics Data System (ADS)
Silveri, M.; Zalys-Geller, E.; Hatridge, M.; Leghtas, Z.; Devoret, M. H.; Girvin, S. M.
2015-03-01
In the remote entanglement process, two distant stationary qubits are entangled with separate flying qubits and the which-path information is erased from the flying qubits by interference effects. As a result, an observer cannot tell from which of the two sources a signal came and the probabilistic measurement process generates perfect heralded entanglement between the two signal sources. Notably, the two stationary qubits are spatially separated and there is no direct interaction between them. We study two transmon qubits in superconducting cavities connected to a Josephson Parametric Converter (JPC). The qubit information is encoded in the traveling wave leaking out from each cavity. Remarkably, the quantum-limited phase-preserving amplification of two traveling waves provided by the JPC can work as a which-path information eraser. By using a stochastic master approach we demonstrate the probabilistic production of heralded entangled states and that unequal qubit-cavity pairs can be made indistinguishable by simple engineering of driving fields. Additionally, we will derive measurement rates, measurement optimization strategies and discuss the effects of finite amplification gain, cavity losses, and qubit relaxations and dephasing. Work supported by IARPA, ARO and NSF.
Introduction to Time Series Analysis
NASA Technical Reports Server (NTRS)
Hardin, J. C.
1986-01-01
The field of time series analysis is explored from its logical foundations to the most modern data analysis techniques. The presentation is developed, as far as possible, for continuous data, so that the inevitable use of discrete mathematics is postponed until the reader has gained some familiarity with the concepts. The monograph seeks to provide the reader with both the theoretical overview and the practical details necessary to correctly apply the full range of these powerful techniques. In addition, the last chapter introduces many specialized areas where research is currently in progress.
Martinez Manzanera, Octavio; Elting, Jan Willem; van der Hoeven, Johannes H.; Maurits, Natasha M.
2016-01-01
In the clinic, tremor is diagnosed during a time-limited process in which patients are observed and the characteristics of tremor are visually assessed. For some tremor disorders, a more detailed analysis of these characteristics is needed. Accelerometry and electromyography can be used to obtain a better insight into tremor. Typically, routine clinical assessment of accelerometry and electromyography data involves visual inspection by clinicians and occasionally computational analysis to obtain objective characteristics of tremor. However, for some tremor disorders these characteristics may be different during daily activity. This variability in presentation between the clinic and daily life makes a differential diagnosis more difficult. A long-term recording of tremor by accelerometry and/or electromyography in the home environment could help to give a better insight into the tremor disorder. However, an evaluation of such recordings using routine clinical standards would take too much time. We evaluated a range of techniques that automatically detect tremor segments in accelerometer data, as accelerometer data is more easily obtained in the home environment than electromyography data. Time can be saved if clinicians only have to evaluate the tremor characteristics of segments that have been automatically detected in longer daily activity recordings. We tested four non-parametric methods and five parametric methods on clinical accelerometer data from 14 patients with different tremor disorders. The consensus between two clinicians regarding the presence or absence of tremor on 3943 segments of accelerometer data was employed as reference. The nine methods were tested against this reference to identify their optimal parameters. Non-parametric methods generally performed better than parametric methods on our dataset when optimal parameters were used. However, one parametric method, employing the high frequency content of the tremor bandwidth under consideration
NASA Astrophysics Data System (ADS)
Branch, Allan C.
1998-01-01
Parametric mapping (PM) lies midway between older and proven artificial landmark based guidance systems and yet to be realized vision based guidance systems. It is a simple yet effective natural landmark recognition system offering freedom from the need for enhancements to the environment. Development of PM systems can be inexpensive and rapid and they are starting to appear in commercial and industrial applications. Together with a description of the structural framework developed to generically describe robot mobility, this paper illustrates clearly the parts of any mobile robot navigation and guidance system and their interrelationships. Among other things, the importance of the richness of the reference map, and not necessarily the sensor map, is introduced, the benefits of dynamic path planners to alleviate the need for separate object avoidance, and the independence of the PM system to the type of sensor input is shown.
NASA Astrophysics Data System (ADS)
Lemerle, P.; Höppner, O.; Rebelle, J.
2011-10-01
This paper describes the examination of the vehicle dynamics and stability of four-wheeled forklift trucks (FLTs) in cornering situations. Cornering at excessive speed is one major reason for fatal accidents with forklifts caused by lateral tipover. In order to increase the lateral stability of this kind of working machinery, the influence of certain important design properties has been studied using an appropriate vehicle simulation model and a driving simulator. The simulation model is based on a multi-body system approach and includes submodels for the propulsion system and the tyres. The driving behaviour of the operator has not been modelled. Instead, a driving simulator has been built up and a real human driver was employed for ensuring adequate and realistic model input. As there have not been any suitable standardised test manoeuvres available for FLTs, a new driving test has been developed to assess the lateral stability. This test resembles the well-known J turn/Fishhook turn, but includes a more dynamic counter-steering action. Furthermore, the dimensions of the test track are defined. Therefore, the test is better adapted to the driving dynamics of forklifts and reflects the real driver behaviour more closely. Finally, a parametrical study has been performed, examining the influence of certain important technical properties of the truck such as the maximum speed, the position of centre of gravity, rear axle design features and tyre properties. The results of this study may lead to a better understanding of the vehicle dynamics of forklifts and facilitate goal-oriented design improvements.
NASA Astrophysics Data System (ADS)
Li, Jiang-Fan; Fang, Jia-Yuan; Xiao, Fu-Liang; Liu, Xin-Hai; Wang, Cheng-Zhi
2009-03-01
By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the degenerate and non-degenerate coupled parametric down-conversion system with driving term. By means of this invariant and the Lewis-Riesenfeld quantum invariant theory, we obtain closed formulae of the quantum state and the evolution operator of the system. We show that the time evolution of the quantum system directly leads to production of various generalized one- and two-mode combination squeezed states, and the squeezed effect is independent of the driving term of the Hamiltonian. In some special cases, the current solution can reduce to the results of the previous works.
Jansen, Jacobus FA; Lu, Yonggang; Gupta, Gaorav; Lee, Nancy Y; Stambuk, Hilda E; Mazaheri, Yousef; Deasy, Joseph O; Shukla-Dave, Amita
2016-01-01
AIM: To investigate the merits of texture analysis on parametric maps derived from pharmacokinetic modeling with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as imaging biomarkers for the prediction of treatment response in patients with head and neck squamous cell carcinoma (HNSCC). METHODS: In this retrospective study, 19 HNSCC patients underwent pre- and intra-treatment DCE-MRI scans at a 1.5T MRI scanner. All patients had chemo-radiation treatment. Pharmacokinetic modeling was performed on the acquired DCE-MRI images, generating maps of volume transfer rate (Ktrans) and volume fraction of the extravascular extracellular space (ve). Image texture analysis was then employed on maps of Ktrans and ve, generating two texture measures: Energy (E) and homogeneity. RESULTS: No significant changes were found for the mean and standard deviation for Ktrans and ve between pre- and intra-treatment (P > 0.09). Texture analysis revealed that the imaging biomarker E of ve was significantly higher in intra-treatment scans, relative to pretreatment scans (P < 0.04). CONCLUSION: Chemo-radiation treatment in HNSCC significantly reduces the heterogeneity of tumors. PMID:26834947
Parametric Analysis of a Turbine Trip Event in a BWR Using a 3D Nodal Code
Gorzel, A.
2006-07-01
Two essential thermal hydraulics safety criteria concerning the reactor core are that even during operational transients there is no fuel melting and not-permissible cladding temperatures are avoided. A common concept for boiling water reactors is to establish a minimum critical power ratio (MCPR) for steady state operation. For this MCPR it is shown that only a very small number of fuel rods suffers a short-term dryout during the transient. It is known from experience that the limiting transient for the determination of the MCPR is the turbine trip with blocked bypass system. This fast transient was simulated for a German BWR by use of the three-dimensional reactor analysis transient code SIMULATE-3K. The transient behaviour of the hot channels was used as input for the dryout calculation with the transient thermal hydraulics code FRANCESCA. By this way the maximum reduction of the CPR during the transient could be calculated. The fast increase in reactor power due to the pressure increase and to an increased core inlet flow is limited mainly by the Doppler effect, but automatically triggered operational measures also can contribute to the mitigation of the turbine trip. One very important method is the short-term fast reduction of the recirculation pump speed which is initiated e. g. by a pressure increase in front of the turbine. The large impacts of the starting time and of the rate of the pump speed reduction on the power progression and hence on the deterioration of CPR is presented. Another important procedure to limit the effects of the transient is the fast shutdown of the reactor that is caused when the reactor power reaches the limit value. It is shown that the SCRAM is not fast enough to reduce the first power maximum, but is able to prevent the appearance of a second - much smaller - maximum that would occur around one second after the first one in the absence of a SCRAM. (author)
Hydrodynamic analysis of time series
NASA Astrophysics Data System (ADS)
Suciu, N.; Vamos, C.; Vereecken, H.; Vanderborght, J.
2003-04-01
It was proved that balance equations for systems with corpuscular structure can be derived if a kinematic description by piece-wise analytic functions is available [1]. For example, the hydrodynamic equations for one-dimensional systems of inelastic particles, derived in [2], were used to prove the inconsistency of the Fourier law of heat with the microscopic structure of the system. The hydrodynamic description is also possible for single particle systems. In this case, averages of physical quantities associated with the particle, over a space-time window, generalizing the usual ``moving averages'' which are performed on time intervals only, were shown to be almost everywhere continuous space-time functions. Moreover, they obey balance partial differential equations (continuity equation for the 'concentration', Navier-Stokes equation, a. s. o.) [3]. Time series can be interpreted as trajectories in the space of the recorded parameter. Their hydrodynamic interpretation is expected to enable deterministic predictions, when closure relations can be obtained for the balance equations. For the time being, a first result is the estimation of the probability density for the occurrence of a given parameter value, by the normalized concentration field from the hydrodynamic description. The method is illustrated by hydrodynamic analysis of three types of time series: white noise, stock prices from financial markets and groundwater levels recorded at Krauthausen experimental field of Forschungszentrum Jülich (Germany). [1] C. Vamoş, A. Georgescu, N. Suciu, I. Turcu, Physica A 227, 81-92, 1996. [2] C. Vamoş, N. Suciu, A. Georgescu, Phys. Rev E 55, 5, 6277-6280, 1997. [3] C. Vamoş, N. Suciu, W. Blaj, Physica A, 287, 461-467, 2000.
Saunders, Marnie M; Schwentker, Edwards P; Kay, David B; Bennett, Gordon; Jacobs, Christopher R; Verstraete, Mary C; Njus, Glen O
2003-02-01
In this study, we developed an approach for prosthetic foot design incorporating motion analysis, mechanical testing and computer analysis. Using computer modeling and finite element analysis, a three-dimensional (3D), numerical foot model of the solid ankle cushioned heel (SACH) foot was constructed and analyzed based upon loading conditions obtained from the gait analysis of an amputee and validated experimentally using mechanical testing. The model was then used to address effects of viscoelastic heel performance numerically. This is just one example of the type of parametric analysis and design enabled by this approach. More importantly, by incorporating the unique gait characteristics of the amputee, these parametric analyses may lead to prosthetic feet more appropriately representing a particular user's needs, comfort and activity level. PMID:12623440
Real-time analysis keratometer
NASA Technical Reports Server (NTRS)
Adachi, Iwao P. (Inventor); Adachi, Yoshifumi (Inventor); Frazer, Robert E. (Inventor)
1987-01-01
A computer assisted keratometer in which a fiducial line pattern reticle illuminated by CW or pulsed laser light is projected on a corneal surface through lenses, a prismoidal beamsplitter quarterwave plate, and objective optics. The reticle surface is curved as a conjugate of an ideal corneal curvature. The fiducial image reflected from the cornea undergoes a polarization shift through the quarterwave plate and beamsplitter whereby the projected and reflected beams are separated and directed orthogonally. The reflected beam fiducial pattern forms a moire pattern with a replica of the first recticle. This moire pattern contains transverse aberration due to differences in curvature between the cornea and the ideal corneal curvature. The moire pattern is analyzed in real time by computer which displays either the CW moire pattern or a pulsed mode analysis of the transverse aberration of the cornea under observation, in real time. With the eye focused on a plurality of fixation points in succession, a survey of the entire corneal topography is made and a contour map or three dimensional plot of the cornea can be made as a computer readout in addition to corneal radius and refractive power analysis.
Timing analysis by model checking
NASA Technical Reports Server (NTRS)
Naydich, Dimitri; Guaspari, David
2000-01-01
The safety of modern avionics relies on high integrity software that can be verified to meet hard real-time requirements. The limits of verification technology therefore determine acceptable engineering practice. To simplify verification problems, safety-critical systems are commonly implemented under the severe constraints of a cyclic executive, which make design an expensive trial-and-error process highly intolerant of change. Important advances in analysis techniques, such as rate monotonic analysis (RMA), have provided a theoretical and practical basis for easing these onerous restrictions. But RMA and its kindred have two limitations: they apply only to verifying the requirement of schedulability (that tasks meet their deadlines) and they cannot be applied to many common programming paradigms. We address both these limitations by applying model checking, a technique with successful industrial applications in hardware design. Model checking algorithms analyze finite state machines, either by explicit state enumeration or by symbolic manipulation. Since quantitative timing properties involve a potentially unbounded state variable (a clock), our first problem is to construct a finite approximation that is conservative for the properties being analyzed-if the approximation satisfies the properties of interest, so does the infinite model. To reduce the potential for state space explosion we must further optimize this finite model. Experiments with some simple optimizations have yielded a hundred-fold efficiency improvement over published techniques.
NASA Astrophysics Data System (ADS)
Lausch, A.; Jensen, N. K. G.; Chen, J.; Lee, T. Y.; Lock, M.; Wong, E.
2014-03-01
Purpose: To investigate the effects of registration error (RE) on parametric response map (PRM) analysis of pre and post-radiotherapy (RT) functional images. Methods: Arterial blood flow maps (ABF) were generated from the CT-perfusion scans of 5 patients with hepatocellular carcinoma. ABF values within each patient map were modified to produce seven new ABF maps simulating 7 distinct post-RT functional change scenarios. Ground truth PRMs were generated for each patient by comparing the simulated and original ABF maps. Each simulated ABF map was then deformed by different magnitudes of realistic respiratory motion in order to simulate RE. PRMs were generated for each of the deformed maps and then compared to the ground truth PRMs to produce estimates of RE-induced misclassification. Main findings: The percentage of voxels misclassified as decreasing, no change, and increasing, increased with RE For all patients, increasing RE was observed to increase the number of high post-RT ABF voxels associated with low pre-RT ABF voxels and vice versa. 3 mm of average tumour RE resulted in 18-45% tumour voxel misclassification rates. Conclusions: RE induced misclassification posed challenges for PRM analysis in the liver where registration accuracy tends to be lower. Quantitative understanding of the sensitivity of the PRM method to registration error is required if PRMs are to be used to guide radiation therapy dose painting techniques.
Christopoulou, Maria; Karabetsos, Efthymios
2015-04-01
From 2008 through 2013, more than 6,000 in situ frequency selective audits, in the proximity of base stations, were conducted throughout Greece by the Greek Atomic Energy Commission (EEAE), in order to verify exposure limit compliance. EEAE is the competent national authority for protection of the general public against artificially produced non-ionizing radiation. This paper presents the first post processing and multi-parametric year statistical analysis of in situ measurement data corresponding to 4,705 audits in the whole country, compared to general public exposure levels, according to Greek legislation. The aim is to derive nationwide conclusions for the characterization of general public exposure to radiofrequency electromagnetic fields, during the last 6 years. The results' presentation includes electric field exposure ratios referring to broadband and frequency selective measurements at the highest exposure measurement point. Statistical analysis is applied to assist the data presentation and evaluation, based on selected criteria and classification parameters, including: (i) year (2008-2013); (ii) environment (urban/suburban/rural); (iii) frequency bands of selected common telecommunication services (e.g., TV, FM, GSM, DCS, UMTS); and (iv) number of service providers installed at the same site. In general, measurement results revealed that the vast majority of exposure values were below reference levels for general public exposure, as defined by Greek legislation. Data are constantly updated with the latest measurements, including emerging wireless technologies. PMID:25726724
Askin, Amanda Christine; Barter, Garrett; West, Todd H.; Manley, Dawn Kataoka
2015-02-14
Here, we present a parametric analysis of factors that can influence advanced fuel and technology deployments in U.S. Class 7–8 trucks through 2050. The analysis focuses on the competition between traditional diesel trucks, natural gas vehicles (NGVs), and ultra-efficient powertrains. Underlying the study is a vehicle choice and stock model of the U.S. heavy-duty vehicle market. Moreover, the model is segmented by vehicle class, body type, powertrain, fleet size, and operational type. We find that conventional diesel trucks will dominate the market through 2050, but NGVs could have significant market penetration depending on key technological and economic uncertainties. Compressed naturalmore » gas trucks conducting urban trips in fleets that can support private infrastructure are economically viable now and will continue to gain market share. Ultra-efficient diesel trucks, exemplified by the U.S. Department of Energy's SuperTruck program, are the preferred alternative in the long haul segment, but could compete with liquefied natural gas (LNG) trucks if the fuel price differential between LNG and diesel increases. However, the greatest impact in reducing petroleum consumption and pollutant emissions is had by investing in efficiency technologies that benefit all powertrains, especially the conventional diesels that comprise the majority of the stock, instead of incentivizing specific alternatives.« less
NASA Technical Reports Server (NTRS)
Guerreiro, Nelson M.; Butler, Ricky W.; Hagen, George E.; Maddalon, Jeffrey M.; Lewis, Timothy A.
2016-01-01
A loss-of-separation (LOS) is said to occur when two aircraft are spatially too close to one another. A LOS is the fundamental unsafe event to be avoided in air traffic management and conflict detection (CD) is the function that attempts to predict these LOS events. In general, the effectiveness of conflict detection relates to the overall safety and performance of an air traffic management concept. An abstract, parametric analysis was conducted to investigate the impact of surveillance quality, level of intent information, and quality of intent information on conflict detection performance. The data collected in this analysis can be used to estimate the conflict detection performance under alternative future scenarios or alternative allocations of the conflict detection function, based on the quality of the surveillance and intent information under those conditions.Alternatively, this data could also be used to estimate the surveillance and intent information quality required to achieve some desired CD performance as part of the design of a new separation assurance system.
Askin, Amanda Christine; Barter, Garrett; West, Todd H.; Manley, Dawn Kataoka
2015-02-14
Here, we present a parametric analysis of factors that can influence advanced fuel and technology deployments in U.S. Class 7–8 trucks through 2050. The analysis focuses on the competition between traditional diesel trucks, natural gas vehicles (NGVs), and ultra-efficient powertrains. Underlying the study is a vehicle choice and stock model of the U.S. heavy-duty vehicle market. Moreover, the model is segmented by vehicle class, body type, powertrain, fleet size, and operational type. We find that conventional diesel trucks will dominate the market through 2050, but NGVs could have significant market penetration depending on key technological and economic uncertainties. Compressed natural gas trucks conducting urban trips in fleets that can support private infrastructure are economically viable now and will continue to gain market share. Ultra-efficient diesel trucks, exemplified by the U.S. Department of Energy's SuperTruck program, are the preferred alternative in the long haul segment, but could compete with liquefied natural gas (LNG) trucks if the fuel price differential between LNG and diesel increases. However, the greatest impact in reducing petroleum consumption and pollutant emissions is had by investing in efficiency technologies that benefit all powertrains, especially the conventional diesels that comprise the majority of the stock, instead of incentivizing specific alternatives.
A multiscale approach to InSAR time series analysis
NASA Astrophysics Data System (ADS)
Simons, M.; Hetland, E. A.; Muse, P.; Lin, Y. N.; Dicaprio, C.; Rickerby, A.
2008-12-01
We describe a new technique to constrain time-dependent deformation from repeated satellite-based InSAR observations of a given region. This approach, which we call MInTS (Multiscale analysis of InSAR Time Series), relies on a spatial wavelet decomposition to permit the inclusion of distance based spatial correlations in the observations while maintaining computational tractability. This approach also permits a consistent treatment of all data independent of the presence of localized holes in any given interferogram. In essence, MInTS allows one to considers all data at the same time (as opposed to one pixel at a time), thereby taking advantage of both spatial and temporal characteristics of the deformation field. In terms of the temporal representation, we have the flexibility to explicitly parametrize known processes that are expected to contribute to a given set of observations (e.g., co-seismic steps and post-seismic transients, secular variations, seasonal oscillations, etc.). Our approach also allows for the temporal parametrization to includes a set of general functions (e.g., splines) in order to account for unexpected processes. We allow for various forms of model regularization using a cross-validation approach to select penalty parameters. The multiscale analysis allows us to consider various contributions (e.g., orbit errors) that may affect specific scales but not others. The methods described here are all embarrassingly parallel and suitable for implementation on a cluster computer. We demonstrate the use of MInTS using a large suite of ERS-1/2 and Envisat interferograms for Long Valley Caldera, and validate our results by comparing with ground-based observations.
Park, Taeyoung; Krafty, Robert T.; Sánchez, Alvaro I.
2012-01-01
A Poisson regression model with an offset assumes a constant baseline rate after accounting for measured covariates, which may lead to biased estimates of coefficients in an inhomogeneous Poisson process. To correctly estimate the effect of time-dependent covariates, we propose a Poisson change-point regression model with an offset that allows a time-varying baseline rate. When the nonconstant pattern of a log baseline rate is modeled with a nonparametric step function, the resulting semi-parametric model involves a model component of varying dimension and thus requires a sophisticated varying-dimensional inference to obtain correct estimates of model parameters of fixed dimension. To fit the proposed varying-dimensional model, we devise a state-of-the-art MCMC-type algorithm based on partial collapse. The proposed model and methods are used to investigate an association between daily homicide rates in Cali, Colombia and policies that restrict the hours during which the legal sale of alcoholic beverages is permitted. While simultaneously identifying the latent changes in the baseline homicide rate which correspond to the incidence of sociopolitical events, we explore the effect of policies governing the sale of alcohol on homicide rates and seek a policy that balances the economic and cultural dependencies on alcohol sales to the health of the public. PMID:23393408
Ruiz-Sanchez, Eduardo
2015-12-01
The Neotropical woody bamboo genus Otatea is one of five genera in the subtribe Guaduinae. Of the eight described Otatea species, seven are endemic to Mexico and one is also distributed in Central and South America. Otatea acuminata has the widest geographical distribution of the eight species, and two of its recently collected populations do not match the known species morphologically. Parametric and non-parametric methods were used to delimit the species in Otatea using five chloroplast markers, one nuclear marker, and morphological characters. The parametric coalescent method and the non-parametric analysis supported the recognition of two distinct evolutionary lineages. Molecular clock estimates were used to estimate divergence times in Otatea. The results for divergence time in Otatea estimated the origin of the speciation events from the Late Miocene to Late Pleistocene. The species delimitation analyses (parametric and non-parametric) identified that the two populations of O. acuminata from Chiapas and Hidalgo are from two separate evolutionary lineages and these new species have morphological characters that separate them from O. acuminata s.s. The geological activity of the Trans-Mexican Volcanic Belt and the Isthmus of Tehuantepec may have isolated populations and limited the gene flow between Otatea species, driving speciation. Based on the results found here, I describe Otatea rzedowskiorum and Otatea victoriae as two new species, morphologically different from O. acuminata. PMID:26265258
NASA Astrophysics Data System (ADS)
Nguyen, Frédéric; Hermans, Thomas
2015-04-01
Inversion of time-lapse resistivity data allows obtaining 'snapshots' of changes occurring in monitored systems for applications such as aquifer storage, geothermal heat exchange, site remediation or tracer tests. Based on these snapshots, one can infer qualitative information on the location and morphology of changes occurring in the subsurface but also quantitative estimates on the degree of changes in certain property such as temperature or total dissolved solid content. Analysis of these changes can provide direct insight into flow and transport and associated processes and controlling parameters. However, the reliability of the analysis is dependent on survey geometry, measurement schemes, data error, and regularization. Survey design parameters may be optimized prior to the monitoring survey. Regularization, on the other hand, may be chosen depending on available information collected during the monitoring. Common approaches consider smoothing model changes both in space and time but it is often needed to obtain a sharp temporal anomaly, for example in fractured aquifers. We here propose to use the alternative regularization approach based on minimum gradient support (MGS) (Zhdanov, 2002) for time-lapse surveys which will focus the changes in tomograms snapshots. MGS will limit the occurrences of changes in electrical resistivity but will also restrict the variations of these changes inside the different zones. A commonly encountered difficulty by practitioners in this type of regularization is the choice of an additional parameter, the so-called β, required to define the MGS functional. To the best of our knowledge, there is no commonly accepted or standard methodology to optimize the MGS parameter β. The inversion algorithm used in this study is CRTomo (Kemna 2000). It uses a Gauss-Newton scheme to iteratively minimize an objective function which consists of a data misfit functional and a model constraint functional. A univariate line search is performed
Moran, John L; Solomon, Patricia J
2007-06-01
In Part I, we reviewed graphical display and data summary, followed by a consideration of linear regression models. Generalised linear models, structured in terms of an exponential response distribution and link function, are now introduced, subsuming logistic and Poisson regression. Time-to-event ("survival") analysis is developed from basic principles of hazard rate, and survival, cumulative distribution and density functions. Semi-parametric (Cox) and parametric (accelerated failure time) regression models are contrasted. Time-series analysis is explicated in terms of trend, seasonal, and other cyclical and irregular components, and further illustrated by development of a classical Box-Jenkins ARMA (autoregressive moving average) model for monthly ICU-patient hospital mortality rates recorded over 11 years. Multilevel (random-effects) models and principles of meta-analysis are outlined, and the review concludes with a brief consideration of important statistical aspects of clinical trials: sample size determination, interim analysis and "early stopping". PMID:17536991
Parametric study of turbine blade platform friction damping using the lumped parameter analysis
NASA Technical Reports Server (NTRS)
Dominic, R. J.
1984-01-01
The hardware configuration used in the present study of turbine blade planform friction damping, by means of the lumped parameter analysis, is the first turbine stage of the Space Shuttle Main Engine's High Pressure Fuel Turbopump. The analysis procedure solves the nonlinear equations of motion for a turbine blade that is acted on by a platform friction damper, using an iterative matrix method. Attention is given to the effects on blade deflection response of variations in friction coefficient, the normal force on the friction surface interface, blade hysteretic damping, the blade-to-blade phase angle of the harmonic forcing function, and the amplitude of the forcing function.
Deng, Xingqiao; Potula, S; Grewal, H; Solanki, K N; Tschopp, M A; Horstemeyer, M F
2013-06-01
In this study, we investigated and assessed the dependence of dummy head injury mitigation on the side curtain airbag and occupant distance under a side impact of a Dodge Neon. Full-scale finite element vehicle simulations of a Dodge Neon with a side curtain airbag were performed to simulate the side impact. Owing to the wide range of parameters, an optimal matrix of finite element calculations was generated using the design method of experiments (DOE); the DOE method was performed to independently screen the finite element results and yield the desired parametric influences as outputs. Also, analysis of variance (ANOVA) techniques were used to analyze the finite element results data. The results clearly show that the influence of moving deformable barrier (MDB) strike velocity was the strongest influence parameter on both cases for the head injury criteria (HIC36) and the peak head acceleration, followed by the initial airbag inlet temperature. Interestingly, the initial airbag inlet temperature was only a ~30% smaller influence than the MDB velocity; also, the trigger time was a ~54% smaller influence than the MDB velocity when considering the peak head accelerations. Considering the wide range in MDB velocities used in this study, results of the study present an opportunity for design optimization using the different parameters to help mitigate occupant injury. As such, the initial airbag inlet temperature, the trigger time, and the airbag pressure should be incorporated into vehicular design process when optimizing for the head injury criteria. PMID:23567214
Arahira, Shin; Murai, Hitoshi; Sasaki, Hironori
2016-08-22
In this paper we report the generation of wavelength-division-multiplexed, time-bin entangled photon pairs by using cascaded optical second nonlinearities (sum-frequency generation and subsequent spontaneous parametric downconversion) in a periodically poled LiNbO_{3} device. Visibilities of approximately 94% were clearly observed in two-photon interference experiments for all the wavelength-multiplexed channels under investigation (five pairs), with insensitivity to the polarization states of the photon pairs. We also evaluated the performances in terms of quantum-key-distribution (QKD) applications by using four single-photon detectors, which enables to evaluate the QKD performance properly. The results showed long-term stability over 70 hours, maintaining approximately 3% of the quantum error rate and 110 bit/s of the sifted key rate. PMID:27557236
A Semi-Parametric Bayesian Mixture Modeling Approach for the Analysis of Judge Mediated Data
ERIC Educational Resources Information Center
Muckle, Timothy Joseph
2010-01-01
Existing methods for the analysis of ordinal-level data arising from judge ratings, such as the Multi-Facet Rasch model (MFRM, or the so-called Facets model) have been widely used in assessment in order to render fair examinee ability estimates in situations where the judges vary in their behavior or severity. However, this model makes certain…
Papapanagiotou, Vasileios; Diou, Christos; Langlet, Billy; Ioakimidis, Ioannis; Delopoulos, Anastasios
2015-08-01
Monitoring and modification of eating behaviour through continuous meal weight measurements has been successfully applied in clinical practice to treat obesity and eating disorders. For this purpose, the Mandometer, a plate scale, along with video recordings of subjects during the course of single meals, has been used to assist clinicians in measuring relevant food intake parameters. In this work, we present a novel algorithm for automatically constructing a subject's food intake curve using only the Mandometer weight measurements. This eliminates the need for direct clinical observation or video recordings, thus significantly reducing the manual effort required for analysis. The proposed algorithm aims at identifying specific meal related events (e.g. bites, food additions, artifacts), by applying an adaptive pre-processing stage using Delta coefficients, followed by event detection based on a parametric Probabilistic Context-Free Grammar on the derivative of the recorded sequence. Experimental results on a dataset of 114 meals from individuals suffering from obesity or eating disorders, as well as from individuals with normal BMI, demonstrate the effectiveness of the proposed approach. PMID:26738112
Koohbor, Behrad; Kidane, Addis; Lu, Wei -Yang; Sutton, Michael A.
2016-01-25
Dynamic stress–strain response of rigid closed-cell polymeric foams is investigated in this work by subjecting high toughness polyurethane foam specimens to direct impact with different projectile velocities and quantifying their deformation response with high speed stereo-photography together with 3D digital image correlation. The measured transient displacement field developed in the specimens during high stain rate loading is used to calculate the transient axial acceleration field throughout the specimen. A simple mathematical formulation based on conservation of mass is also proposed to determine the local change of density in the specimen during deformation. By obtaining the full-field acceleration and density distributions,more » the inertia stresses at each point in the specimen are determined through a non-parametric analysis and superimposed on the stress magnitudes measured at specimen ends to obtain the full-field stress distribution. Furthermore, the process outlined above overcomes a major challenge in high strain rate experiments with low impedance polymeric foam specimens, i.e. the delayed equilibrium conditions can be quantified.« less
Applications of non-parametric statistics and analysis of variance on sample variances
NASA Technical Reports Server (NTRS)
Myers, R. H.
1981-01-01
Nonparametric methods that are available for NASA-type applications are discussed. An attempt will be made here to survey what can be used, to attempt recommendations as to when each would be applicable, and to compare the methods, when possible, with the usual normal-theory procedures that are avavilable for the Gaussion analog. It is important here to point out the hypotheses that are being tested, the assumptions that are being made, and limitations of the nonparametric procedures. The appropriateness of doing analysis of variance on sample variances are also discussed and studied. This procedure is followed in several NASA simulation projects. On the surface this would appear to be reasonably sound procedure. However, difficulties involved center around the normality problem and the basic homogeneous variance assumption that is mase in usual analysis of variance problems. These difficulties discussed and guidelines given for using the methods.
Fuzzy parametric uncertainty analysis of linear dynamical systems: A surrogate modeling approach
NASA Astrophysics Data System (ADS)
Chowdhury, R.; Adhikari, S.
2012-10-01
Uncertainty propagation engineering systems possess significant computational challenges. This paper explores the possibility of using correlated function expansion based metamodelling approach when uncertain system parameters are modeled using Fuzzy variables. In particular, the application of High-Dimensional Model Representation (HDMR) is proposed for fuzzy finite element analysis of dynamical systems. The HDMR expansion is a set of quantitative model assessment and analysis tools for capturing high-dimensional input-output system behavior based on a hierarchy of functions of increasing dimensions. The input variables may be either finite-dimensional (i.e., a vector of parameters chosen from the Euclidean space RM) or may be infinite-dimensional as in the function space CM[0,1]. The computational effort to determine the expansion functions using the alpha cut method scales polynomially with the number of variables rather than exponentially. This logic is based on the fundamental assumption underlying the HDMR representation that only low-order correlations among the input variables are likely to have significant impacts upon the outputs for most high-dimensional complex systems. The proposed method is integrated with a commercial Finite Element software. Modal analysis of a simplified aircraft wing with Fuzzy parameters has been used to illustrate the generality of the proposed approach. In the numerical examples, triangular membership functions have been used and the results have been validated against direct Monte Carlo simulations.
Parametric studies of penetration events : a design and analysis of experiments approach.
Chiesa, Michael L.; Marin, Esteban B.; Booker, Paul M.
2005-02-01
A numerical screening study of the interaction between a penetrator and a geological target with a preformed hole has been carried out to identify the main parameters affecting the penetration event. The planning of the numerical experiment was based on the orthogonal array OA(18,7,3,2), which allows 18 simulation runs with 7 parameters at 3 levels each. The strength of 2 of the array allows also for two-factor interaction studies. The seven parameters chosen for this study are: penetrator offset, hole diameter, hole taper, vertical and horizontal velocity of the penetrator, angle of attack of the penetrator and target material. The analysis of the simulation results has been based on main effects plots and analysis of variance (ANOVA), and it has been performed using three metrics: the maximum values of the penetration depth, penetrator deceleration and plastic strain in the penetrator case. This screening study shows that target material has a major influence on penetration depth and penetrator deceleration, while penetrator offset has the strongest effect on the maximum plastic strain.
NASA Astrophysics Data System (ADS)
Otanicar, Todd; Chowdhury, Ihtesham; Phelan, Patrick E.; Prasher, Ravi
2010-12-01
The analysis of the combined efficiencies in a coupled photovoltaic (PV)/thermal concentrating solar collector are presented based on a coupled electrical/thermal model. The calculations take into account the drop in efficiency that accompanies the operation of PV cells at elevated temperatures along with a detailed analysis of the thermal system including losses. An iterative numerical scheme is described that involves a coupled electrothermal simulation of the solar energy conversion process. In the proposed configuration losses in the PV cell due to reduced efficiencies at elevated temperatures and the incident solar energy below the PV bandgap are both harnessed as heat. This thermal energy is then used to drive a thermodynamic power cycle. The simulations show that it is possible to optimize the overall efficiency of the system by variation in key factors such as the solar concentration factor, the band gap of the PV material, and the system thermal design configuration, leading to a maximum combined efficiency of ˜32.3% for solar concentrations between 10-50 and a band-gap around 1.5-2.0 eV.
Parametric Analysis of NO2 Gas Sensor Based on Carbon Nanotubes
NASA Astrophysics Data System (ADS)
Naje, Asama N.; Ibraheem, Russul R.; Ibrahim, Fuad T.
2016-06-01
Two types of carbon nanotubes [single walled nanotubes (SWCNTs) and multi walled carbon nanotubes (MWCNTs)] are deposited on porous silicon by the drop casting technique. Upon exposure to test gas mixing ratio 3% NO2, the sensitivity response results show that the SWCNTs' sensitivity reaches to 79.8%, where MWCNTs' is 59.6%. The study shows that sensitivity response of the films increases with an increase in the operating temperature up to 200° and 150° for MWCNTs and SWCNTs. The response and recovery time is about 19 s and 54 s at 200° for MWCNTs, respectively, and 20 s and 56 s at 150° for SWCNTs.
Parametric Analysis of PWR Spent Fuel Depletion Parameters for Long-Term-Disposal Criticality Safety
DeHart, M.D.
1999-08-01
Utilization of burnup credit in criticality safety analysis for long-term disposal of spent nuclear fuel allows improved design efficiency and reduced cost due to the large mass of fissile material that will be present in the repository. Burnup-credit calculations are based on depletion calculations that provide a conservative estimate of spent fuel contents (in terms of criticality potential), followed by criticality calculations to assess the value of the effective neutron multiplication factor (k(sub)eff) for the a spent fuel cask or a fuel configuration under a variety of probabilistically derived events. In order to ensure that the depletion calculation is conservative, it is necessary to both qualify and quantify assumptions that can be made in depletion models.
NASA Astrophysics Data System (ADS)
Wu, Xian-Qian; Wang, Xi; Wei, Yan-Peng; Song, Hong-Wei; Huang, Chen-Guang
2012-06-01
Shot peening is a widely used surface treatment method by generating compressive residual stress near the surface of metallic materials to increase fatigue life and resistance to corrosion fatigue, cracking, etc. Compressive residual stress and dent profile are important factors to evaluate the effectiveness of shot peening process. In this paper, the influence of dimensionless parameters on maximum compressive residual stress and maximum depth of the dent were investigated. Firstly, dimensionless relations of processing parameters that affect the maximum compressive residual stress and the maximum depth of the dent were deduced by dimensional analysis method. Secondly, the influence of each dimensionless parameter on dimensionless variables was investigated by the finite element method. Furthermore, related empirical formulas were given for each dimensionless parameter based on the simulation results. Finally, comparison was made and good agreement was found between the simulation results and the empirical formula, which shows that a useful approach is provided in this paper for analyzing the influence of each individual parameter.
Parametric analysis of synthetic aperture radar data for characterization of deciduous forest stands
NASA Technical Reports Server (NTRS)
Wu, Shih-Tseng
1987-01-01
The SAR sensor parameters that affect the estimation of deciduous forest stand characteristics were examined using data sets for the Gulf Coastal Plain region, acquired by the NASA/JPL multipolarization airborne SAR. In the regression analysis, the mean digital-number values of the three polarization data are used as the independent variables to estimate the average tree height (HT), basal area (BA), and total-tree biomass (TBM). The following results were obtained: (1) in the case of simple regression and using 28 plots, vertical-vertical (VV) polarization yielded the largest correlation coefficients (r) in estimating HT, BA, and TBM; (2) in the case of multiple regression, the horizontal-horizontal (HH) and VV polarization combination yielded the largest r value in estimating HT, while the VH and HH polarization combination yielded the largest r values in estimating BA and TBM. With the addition of a third polarization, the increase in r values is insignificant.
Midgley, S. L. W.; Olsen, M. K.; Bradley, A. S.; Pfister, O.
2010-11-15
We examine the feasibility of generating continuous-variable multipartite entanglement in an intracavity concurrent downconversion scheme that has been proposed for the generation of cluster states by Menicucci et al. [Phys. Rev. Lett. 101, 130501 (2008)]. By calculating optimized versions of the van Loock-Furusawa correlations we demonstrate genuine quadripartite entanglement and investigate the degree of entanglement present. Above the oscillation threshold the basic cluster state geometry under consideration suffers from phase diffusion. We alleviate this problem by incorporating a small injected signal into our analysis. Finally, we investigate squeezed joint operators. While the squeezed joint operators approach zero in the undepleted regime, we find that this is not the case when we consider the full interaction Hamiltonian and the presence of a cavity. In fact, we find that the decay of these operators is minimal in a cavity, and even depletion alone inhibits cluster state formation.